| 1. |
- Koul, Sasha, et al.
(författare)
-
Delay From First Medical Contact to Primary PCI and All-Cause Mortality : A Nationwide Study of Patients With ST-Elevation Myocardial Infarction
- 2014
-
Ingår i: Journal of the American Heart Association. - 2047-9980. ; 3:2, s. e000486-
-
Tidskriftsartikel (refereegranskat)abstract
- Background-Early reperfusion in the setting of an ST-elevation myocardial infarction (STEMI) is of utmost importance. However, the effects of early versus late reperfusion in this patient group undergoing primary percutaneous coronary intervention (PCI) have so far been inconsistent in previous studies. The purpose of this study was to evaluate in a nationwide cohort the effects of delay from first medical contact to PCI (first medical contact [FMC]-to-PCI) and secondarily delay from symptom-to-PCI on clinical outcomes. Methods and Results-Using the national Swedish Coronary Angiography and Angioplasty Register (SCAAR) registry, STEMI patients undergoing primary PCI between the years 2003 and 2008 were screened for. A total of 13 790 patients were included in the FMC-to-PCI analysis and 11 489 patients were included in the symptom-to-PCI analyses. Unadjusted as well as multivariable analyses showed an overall significant association between increasing FMC-to-PCI delay and 1-year mortality. A statistically significant increase in mortality was noted at FMC-to-PCI delays exceeding 1 hour in an incremental fashion. FMC-to-PCI delays in excess of 1 hour were also significantly associated with an increase in severe left ventricular dysfunction at discharge. An overall significant association between increasing symptom-to-PCI delays and 1-year mortality was noted. However, when stratified into time delay cohorts, no symptom-to-PCI delay except for the highest time delay showed a statistically significant association with increased mortality. Conclusions-Delays in FMC-to-PCI were strongly associated with increased mortality already at delays of more than 1 hour, possibly through an increase in severe heart failure. A goal of FMC-to-PCI of less than 1 hour might save patient lives.
|
|
| 2. |
- Bertilsson, Monica, et al.
(författare)
-
Association of stigmatizing attitudes with people's opinion of depression as a valid reason for sickness absence: A Swedish vignette study
- 2022
-
Ingår i: WORK-A JOURNAL OF PREVENTION ASSESSMENT & REHABILITATION. - : IOS Press. - 1051-9815. ; 73:2, s. 495-504
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Depression is a common cause of sickness absence (SA) and also highly associated with stigma. Few studies have addressed the role of stigma in relation to SA. OBJECTIVE: To investigate if attitudes to depression were associated with the public's opinion of depression as a valid reason of SA. METHODS: The study population (n = 2413) originated from a web-based panel of citizens. The survey included a short vignette describing a person with symptoms of depression and the person's work tasks, followed by a question on recommendation of SA. Negative attitudes were measured by the Depression Stigma Scale. Logistic regressions were used to estimate the odds ratios (OR) for the likelihood of not recommending SA, controlling for individual and work-related co-variates. RESULTS: The crude association between negative attitudes and not recommending SA was OR 2.15 (95% CI, 1.76-2.62). In the fully adjusted model the OR was 1.76 (95% CI, 1.40 - 2.21) for not recommending SA. CONCLUSIONS: Participants with negative attitudes to depression were more likely to not consider depression as a valid reason of sickness absence. The study supports theories on layered stigma; attitudes from one arena are related to other arenas. Future studies are needed to confirm our findings.
|
|
| 3. |
|
|
| 4. |
- Carlson, Johan E., et al.
(författare)
-
Calibration of simulation models for ultrasonic transducers based on implicit calibration
- 2009
-
Ingår i: 2008 IEEE Ultrasonics Symposium. - Piscataway, NJ : IEEE Communications Society. - 9781424424283 ; , s. 1528-1531
-
Konferensbidrag (refereegranskat)abstract
- There are numerous software packages available for modeling of the sound pressure fields emitted by ultrasound transducers and transducer arrays. Accurate modeling of a real-world transducer requires knowledge of several parameters that are generally not known. This paper presents an estimation principle that can be used to calibrate such models, based on measurements of the sound field. The model separates the problem into estimation of the transducer's electro-mechanical impulse response and its spatial impulse response. The latter being what the software packages generally model. We demonstrate the principle with measurements of the sound field from a non-focused 5 MHz transducer. The results show that the modeled sound field agrees well with measurements.
|
|
| 5. |
- Carlson, Johan, et al.
(författare)
-
Measurement of methane content in upgraded biogas using pulse-echo ultrasound
- 2008
-
Ingår i: Proceedings of the International Congress on Ultrasonics.
-
Konferensbidrag (refereegranskat)abstract
- In this paper we present an ultrasonic pulseecho technique for estimating the methane (CH4) content in binary mixtures of CH4 and carbon dioxide (CO2). The method is based on parametric estimation of phase velocity and frequency dependent attenuation in combination with Partial Least-Squares Regression (PLSR). The technique is verified using experiments on mixtures with a volume fraction of CO2 in the range of 0 % -10 %. The experiments show that the CH4 content can be accurately estimated with high repeatability.
|
|
| 6. |
- Gustafsson, Silje, et al.
(författare)
-
Influence of self-care advice on patient satisfaction and healthcare utilization
- 2016
-
Ingår i: Journal of Advanced Nursing. - : Wiley. - 0309-2402 .- 1365-2648. ; 72:8, s. 1789-1799
-
Tidskriftsartikel (refereegranskat)abstract
- AimThe aim of this study is to explore the influence of nurse-led self-care advice on healthcare utilization and patients' satisfaction with telephone nursing.BackgroundMany consultations in high-cost settings are for conditions that are manageable through self-care and callers with greater satisfaction with the nurse interaction are nearly four times more likely to engage in self-care.DesignCross-sectional study.MethodsQuestionnaires were sent out to 500 randomly selected callers to the Swedish Healthcare Direct in Northern Sweden during March 2014. Callers were asked about their satisfaction with the consultation, their intended actions prior to consultation, the recommendation given by the nurse and the action undertaken after the call.ResultsYoung callers and persons recommended watchful waiting or recurrence if no improvements were significantly less satisfied with their care. When calling on their own behalf, both men and women rated the severity of their symptoms equally and were advised to self-care to the same extent. Self-care advice had a constricting influence on self-reported healthcare utilization, with 66·1% of cases resulting in a lower level of care than first intended. Feeling reassured after the call was the aspect of nursing care that influenced satisfaction the most.ConclusionReceiving self-care advice rather than referral to a general practitioner influences patient satisfaction negatively. Feeling reassured after consultation is strongly related to satisfaction, which in turn has been found to increase the likelihood of engaging in self-care behaviour.
|
|
| 7. |
- Gustafsson, Silje, et al.
(författare)
-
Need for reassurance in self-care of minor illnesses
- 2018
-
Ingår i: Journal of Clinical Nursing. - : John Wiley & Sons. - 0962-1067 .- 1365-2702. ; 27:5-6, s. 1183-1191
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS AND OBJECTIVES:This study describes people's need for reassurance in self-care of minor illnesses.BACKGROUND:Self-care and active surveillance are advocated as important strategies to manage minor illnesses. Reassurance influences patient satisfaction and confidence in the practicing of self-care.DESIGN:This study is a descriptive and interpretive qualitative study.METHODS:Twelve persons with experience in self-care and receiving self-care advice were recruited, and data were collected using semi-structured interviews between September and December 2014. Data were analyzed using qualitative content analyses.RESULTS:Having previous experience and the ability to actively manage symptoms using self-care interventions was described as reassuring. Participants became stressed and concerned when the symptoms persisted and interventions lacked the desired effect, which often resulted in a decision to consult. Participants wanted to feel that the nurse was an actual person, who was sympathetic, present and understanding, when they received self-care advice. The nurse's assessment and reasoning of the symptoms facilitated care-seekers' assessments of risk, and clear and concrete advice on how to manage the symptoms exerted a calming effect. Patients needed to trust that the nurse understood their situation to embrace the advice, and being invited to return created a feeling that the nurse had listened and taken them seriously.CONCLUSION:Reassurance has the potential to allay doubts and fears to build confidence, which influences self-care and consultation behavior. Personal presence in the encounter, receiving an assessment and an explanation of the symptoms and precise advice are reassuring. This article is protected by copyright. All rights reserved.
|
|
| 8. |
- Gustafsson, Silje, et al.
(författare)
-
Perceptions of needs related to the practice of self-care for minor illness
- 2015
-
Ingår i: Journal of Clinical Nursing. - : Wiley. - 0962-1067 .- 1365-2702. ; 24:21-22, s. 3255-3265
-
Tidskriftsartikel (refereegranskat)abstract
- Aims and objectivesThe aim of this study was to describe people's perceptions of needs to feel confident in self-care for minor illnesses as well as their perceptions about supporting and obstructing factors in the practice of self-care.BackgroundMinor illness constitutes a large part of primary care, and patients' attendance to doctors' appointments for minor illness has been seen to increase future attendance for the same condition. Almost half of the consultations with telenurses result in the provision of self-care advice.DesignA cross-sectional survey.MethodPrimary data were collected using a questionnaire, and the study participants (n = 315) were randomly selected from the national Swedish address register.ResultsHaving knowledge and receiving health care advice and reliable information were perceived to be needs in order for participants to feel confident in self-care. Having family or friends to consult with was perceived to be a positive factor influencing confidence in self-care, especially for persons under the age of 35. Health care services were perceived to support self-care practice by offering easy access to care, giving information about self-care, and offering increased follow-up after consultations. Lack of knowledge, along with difficulties being away from work, were obstructing factors in the practice of self-care.ConclusionsYoung age was the factor influencing people's perceptions of needs and supporting factors the most. Young age and low knowledge scores about minor illnesses were the two factors that had the most influence on perceived obstructing factors.Relevance to clinical practiceNurses play a major role in the promotion of self-care and in the dissemination of self-care advice. If health care services fail to meet the needs of care-seekers with minor illnesses, patients might turn to out-of-hours clinics and emergency departments for help.
|
|
| 9. |
- Hensing, Gunnel, 1956, et al.
(författare)
-
Differences in how women and men in a Swedish population-based sample think about sick leave: A cross-sectional vignette study
- 2024
-
Ingår i: WORK-A JOURNAL OF PREVENTION ASSESSMENT & REHABILITATION. - 1051-9815 .- 1875-9270. ; 77:3, s. 827-838
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Gender differences in attitudes towards depression gives reason to believe that sociocultural gender norms play a role in other areas. OBJECTIVE: The aim was to test (i) if the likelihood to think that sick leave with depression symptoms is not reasonable varies between women and men, and (ii) if the likelihood to think sick leave is not reasonable varies depending on the gender of the individual with depression symptoms. METHODS: A study population of 3147 participants responded to a web-survey with a written case briefly describing a man or woman with symptoms of depression. Respondents were asked if they thought it is reasonable that the person was sick listed for two weeks. Logistic regression was used to analyse the data. RESULTS: After controlling for age, education, self-rated health, and respondent's own experience of sickness absence the adjusted OR was 1.45 (95% CI 1.25-1.67) for men being less likely to think sick-leave was reasonable. Gender difference decreased when adjusting for negative attitudes towards depression (adjusted OR 1.24, 95% CI 1.06-1.44). No difference was found between how women and men thought about sick leave in relation to the gender of the case described in the vignette. CONCLUSION: Men were more likely to think that sick leave was not reasonable with decreased OR after adjustment for negative attitudes towards depression. Gender norms might be part of the explanation for differences but are challenging to test. This study contributes to a bourgeoning research field on gendered attitudes and sick leave, in terms of theoretical reasoning and methodological choice.
|
|
| 10. |
- Hägglund, Fredrik, et al.
(författare)
-
Flaw detection in layered media based on parametric modeling of overlapping ultrasonic echoes
- 2006
-
Ingår i: Proceedings. - Piscataway, NJ : IEEE Communications Society. - 1424402018 ; , s. 136-139
-
Konferensbidrag (refereegranskat)abstract
- In materials consisting of several thin layers, multiple reflections within the structure give rise to received ultrasonic signals composed of overlapping echoes. In this paper we present a parametric model that can be used to decompose such signals into the individual reflections. We derive a Maximum Likelihood Estimator for the the model parameters, which are then used in a Generalized Likelihood Ratio Test (GLRT) to detect flaws in multi-layered structures. We show with simulations how the presence of a thin bonding layer in a three-layer structure can be detected. The probability of detection is shown to be ≈ 96%, for a signal-to-noise ratio (SNR) of 15 dB and a probability of false alarm of 5%.
|
|
| 11. |
- Hägglund, Fredrik, et al.
(författare)
-
Model-based characterization of thin layers using pulse-echo ultrasound
- 2008
-
Ingår i: Proceedings of the International Congress on Ultrasonics.
-
Konferensbidrag (refereegranskat)abstract
- Measurements performed on a thin multilayered structure will imply a received signal waveform consisting of reverberant overlapping echoes. In this paper the multi-layered structure is modeled by a physical model and the Maximum Likelihood Estimator (MLE) is derived for the model parameters. A general recursive expression for the model is given. The model is evaluated using measurements on a thin three-layered structure, where two glass layers are bonded together. We show that measured signal waveforms can be reconstructed using the estimated parameters, and that physical properties can be extracted from the estimated model parameters. Simulations also show that physical parameters can be estimated for thicknesses of the bonding layer down to 50 μm for a wavelength of 200 μm of the ultrasonic pulse.
|
|
| 12. |
|
|
| 13. |
- Hägglund, Fredrik, et al.
(författare)
-
Model-based estimation of thin multi-layered media using ultrasonic measurements
- 2009
-
Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 56:8, s. 1689-1702
-
Tidskriftsartikel (refereegranskat)abstract
- In ultrasonic measurement situations, when dealing with media of multi-layered structures consisting of 1 or more thin layers, analysis of the measured ultrasonic waveform can be difficult because of overlapping and reverberant echoes. Information from the individual layers is then difficult to extract because the individual echoes cannot be detected. In this study, we use a parametric layer model to analyze the multi-layered material in a system identification approach. The parameters of the model are connected to physical properties of the investigated material, e.g., the reflection coefficients, the time-of-flight, and the attenuation. The main advantage using this model is that the complexity of the model is connected to the number of layers rather than the number of observable echoes in the received ultrasonic waveform. A system of linear equations is presented, giving the opportunity to find the model for both pulse-echo and through-transmission measurements. A thorough effort is made on the parameter estimation and optimization algorithm. The model is validated with practical measurements on a 3-layered structure using both pulse-echo and through-transmission techniques. The 3-layered material consists of a thin embedded middle layer with the time-of-flight in that layer shorter than the emitted signal¿s time support, giving rise to overlapping echoes. Finally the relation between the model parameters and physical properties of the material is established.
|
|
| 14. |
- Hägglund, Fredrik, et al.
(författare)
-
Ultrasonic imaging of thin layers within multi-layered structures
- 2008
-
Ingår i: 2008 IEEE International Ultrasonics Symposium. - New York : IEEE Communications Society. - 9781424424283 ; , s. 828-831
-
Konferensbidrag (refereegranskat)abstract
- In the area of process control, non-destructive testing (NDT) using ultrasound is valuable due to its noninvasive properties. In process control, imaging of surface profiles is used to locate defects or problematic areas in order to quickly steer the manufacturing process on track again. This paper presents a method for imaging of parallel thin layers within multi-layered structures. Due to the application in process control a parametric model is used, and all subsequent analysis is performed on the model parameters rather than on the signal waveforms, resulting in a necessary data reduction. The parameters in the model are directly connected to physical properties, such as the reflection coefficients, time-of-flights, and attenuation coefficients. Experimental results shows that the estimated model parameters can be used in imaging of thin layer properties within the material structure. Images of embedded layers with a thickness about the wavelength is shown. Result also show that flaws can be detected in such structures. The results are verified by comparing the images to visual inspections of photographs.
|
|
| 15. |
- Lemlikchi, Safia, et al.
(författare)
-
Parametric estimation of overlapping echoes reflected from coated media
- 2021
-
Ingår i: Applied Acoustics. - : Elsevier. - 0003-682X .- 1872-910X. ; 178
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a parametric modeling strategy was used to investigate ultrasonic signals reflecting from coated structures. The model parameter vector is defined by the combined model consisting of hard and soft modeling. The hard model describes the overlap with pure delays, reflection and transmission coefficients. The soft model copes with a more realistic case when all ultrasonic losses are included. The estimation procedure follows the maximum likelihood approach and uses the Levenberg–Marquardt algorithm for optimizing the objective function. The tested waveforms were reflected from thermally sprayed Diamalloy 4060 coatings deposited on 310SS substrate with increasing degree of overlapping echoes. Measurements were carried out in pulse-echo mode using a 15 MHz nominal frequency transducer. A good prediction of overlapping signals was achieved. Reverberating coating echoes were successfully separated and coating properties (time-of-flight (TOF), ultrasonic velocity and attenuation) were directly deduced. Results show the potential of the method to investigate overlapping ultrasonic signals reflecting from highly attenuating layers such as thermal sprayed coatings. It also shows the ability for the method to make a complete separation of the overlapping echoes, not only between the substrate and the coating echoes, but also between the reverberations in the coating itself that has been neglected for a long time. This allows an accurate characterization of the coating properties.
|
|
| 16. |
- Lemlikchi, Safia, et al.
(författare)
-
Ultrasonic Characterization of Thermally Sprayed Coatings
- 2019
-
Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 28:3, s. 391-404
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the simultaneous determination of the ultrasonic parameters in thermally sprayed coatings. The parameters of interest are the longitudinal wave velocity and the ultrasonic attenuation. The test materials are two cobalt-based coatings (FSX 414 and Diamalloy 4060), both deposited onto stainless steel (310SS) substrates. The ultrasonic measurements were carried out in the pulse-echo configuration using several transducers. The ultrasonic signals reflected from the coatings were successfully estimated using the combined model, together with the maximum likelihood estimation and the Levenberg–Marquardt approach. The best estimate was obtained for 20 MHz measurements. Once the model was validated, the ultrasonic parameters of the thermally sprayed coatings were extracted. Model validation is based on the analysis of the residual between measured and estimated signals. Results showed non-dispersive ultrasonic velocities with average values of (3940±50)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(3940±50)m/s(3940±50)m/s in Diamalloy 4060 and (4260±20)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(4260±20)m/s(4260±20)m/s in FSX 414. High ultrasonic attenuation with a quadratic frequency dependence was observed for both materials. Moreover, it was found that the ultrasonic parameters in thermally sprayed materials are microstructure dependent. For close densities, the harder the coating, the higher the ultrasonic wave velocity and attenuation.
|
|
| 17. |
- Löve, Jesper, 1974, et al.
(författare)
-
Political Ideology and Stigmatizing Attitudes Toward Depression: The Swedish Case
- 2019
-
Ingår i: International Journal of Health Policy and Management. - : Maad Rayan Publishing Company. - 2322-5939. ; 8:6, s. 365-374
-
Tidskriftsartikel (refereegranskat)abstract
- Stigmatizing attitudes toward persons with mental disorders is a well-established and global phenomenon often leading to discrimination and social exclusion. Although previous research in the United States showed that conservative ideology has been related to stigmatizing attitudes toward mental disorders, there is reason to believe that this mechanism plays a different role in the context of a universal welfare state with a multi-party system such as Sweden. Furthermore, “mental disorders” may signify severe psychotic disorders, which may evoke more negative attitudes. This suggests the importance of specific studies focusing on the more common phenomenon of depression. This paper investigates the relationship between political ideology and stigmatizing attitudes toward depression in Sweden. Methods This study is part of the New Ways research program. Data were collected by the Laboratory of Opinion Research (LORE) at the University of Gothenburg in 2014 (N = 3246). Independent variables were political ideology and party affiliation. The dependent variable was the Depression Stigma Scale (DSS). Data were analyzed with linear regression analyses and analyses of variance. Results More conservative ideology (B = 0.68, standard error [SE] = 0.04, P < .001) and more conservative party affiliation (F(8 2920) = 38.45, P < .001) showed more stigmatizing attitudes toward depression. Item-level analyses revealed a difference where the supporters of the conservative party differed (P < .05) from supporters of the liberal party, with a higher proportion agreeing that “people could snap out of” depression if they wanted to; the populist right-wing party differed from the conservative party with a higher proportion agreeing on items displaying people with depression as “dangerous” and “unpredictable.” Even self-stigma was highest among the populist right-wing party with 22.3% agreeing that “if I had depression I wouldn’t tell….” Conclusion Political ideology was associated with stigmatizing attitudes toward depression in Sweden. The results also confirm the need to distinguish between different forms of conservatism by observing social distance as being a more important driver among voters for the populist right-wing party compared with personal agency and responsibility among voters for the more traditional conservative party.
|
|
| 18. |
|
|
| 19. |
- Martinsson, Andreas, et al.
(författare)
-
Inspiratory and end-expiratory effects of lung recruitment in the prone position on dorsal lung aeration – new physiological insights in a secondary analysis of a randomised controlled study in post-cardiac surgery patients
- 2022
-
Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 0007-0912 .- 1471-6771. ; 4:December 2022
-
Tidskriftsartikel (refereegranskat)abstract
- Background Cardiac surgery produces dorso-basal atelectasis and ventilation/perfusion mismatch, associated with infection and prolonged intensive care. A postoperative lung volume recruitment manoeuvre to decrease the degree of atelectasis is routine. In patients with severe respiratory failure, prone positioning and recruitment manoeuvres may increase survival, oxygenation, or both. We compared the effects of lung recruitment in prone vs supine positions on dorsal inspiratory and end-expiratory lung aeration. Methods In a prospective RCT, 30 post-cardiac surgery patients were randomly allocated to recruitment manoeuvres in the prone (n=15) or supine position (n=15). The primary endpoints were late dorsal inspiratory volume (arbitrary units [a.u.]) and left/right dorsal end-expiratory lung volume change (a.u.), prone vs supine after extubation, measured using electrical impedance tomography. Secondary outcomes included left/right dorsal inspiratory volumes (a.u.) and left/right dorsal end-expiratory lung volume change (a.u.) after prone recruitment and extubation. Results The last part of dorsal end-inspiratory volume after extubation was higher after prone (49.1 a.u.; 95% confidence interval [CI], 37.4–60.6) vs supine recruitment (24.2 a.u.; 95% CI, 18.4–29.6; P=0.024). Improvement in left dorsal end-expiratory lung volume after extubation was higher after prone (382 a.u.; 95% CI, 261–502) vs supine recruitment (–71 a.u., 95% CI, –140 to –2; n=15; P<0.001). After prone recruitment, left vs right predominant end-expiratory dorsal lung volume change disappeared after extubation. However, both left and right end-expiratory volumes were higher in the prone group, after extubation. Conclusions Recruitment in the prone position improves dorsal inspiratory and end-expiratory lung volumes after cardiac surgery.
|
|
| 20. |
- Martinsson, Jesper, et al.
(författare)
-
A New Model for the Distribution of Observable Earthquake Magnitudes and Applications to b-Value Estimation
- 2018
-
Ingår i: IEEE Geoscience and Remote Sensing Letters. - : IEEE. - 1545-598X .- 1558-0571. ; 15:6, s. 833-837
-
Tidskriftsartikel (refereegranskat)abstract
- The b-value in the Gutenberg–Richter (GR) law contains information that is essential for evaluating earthquake hazard and predicting the occurrence of large earthquakes. Estimates of b are often based on seismic events whose magnitude exceed a certain threshold, the so-called magnitude of completeness. Such estimates are sensitive to the choice of threshold and often ignore a substantial portion of available data. We present a general model for the distribution of observable earthquake magnitudes and an estimation procedure that takes all measurements into account. The model is obtained by generalizing previous probabilistic descriptions of sensor network limitations and using a generalization of the GR law. We show that our model is flexible enough to handle spatio-temporal variations in the seismic environment and captures valuable information about sensor network coverage. We also show that the model leads to significantly improved b-value estimates compared with established methods relying on the magnitude of completeness.
|
|
| 21. |
- Martinsson, Jesper
(författare)
-
Betydelsen av bortforsling av alger för rekrytering av plattfisk på Gotland
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med projektet var att utvärdera effekten av bortforsling av släke i vikar runt Gotlands kust på tätheten och storleken av juvenil piggvar och flundra som växer upp i denna typ av habitat. Juvenil piggvar och flundra samlades in med landvad i augusti 2014 och 2015 i totalt 19 områden där släke avlägsnades på nio stycken i delprojekt 1. I delprojekt 2 rensades en del av Lausviken medan en annan del av viken var orörd. I denna vik genomfördes flera provtagningar under säsongen medan endast en genomfördes på den regionala skalan i delprojekt 1. Förutom att fånga juvenil plattfisk togs även prover för att uppskatta syrehalt, turbiditet och organisk halt i sedimenten. Tätheten var generellt något högre i de rensade områdena för flundra 2015 i delprojekt 1 och för piggvar i slutet av säsongen i delprojekt 2 2014. Det är dock svårt att utesluta att andra faktorer påverkat de skillnader som uppstått då skillnaderna var små och variationen hög. Det senare speciellt för piggvar. Det fanns ingen skillnad i längd mellan rensade och ej rensade områden. I övrigt var den organiska halten lägre i de rensade områdena 2015 i delprojekt 1 och i delprojekt 2 hade halten minskat i den rensade delen och ökat i den ej rensade 2015 jämfört med året innan. Fler provtagningar behöver göras för att få en högre upplösning i tid och rum av miljövariablerna och för att säkerställa en eventuell trend i den organiska halten samt undersöka om resultaten för plattfisken blir tydligare
|
|
| 22. |
- Martinsson, Jesper
(författare)
-
Compensating distortion effects in repeated measurements under non-stationary conditions
- 2009
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 20:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper a compensation technique is presented for applications using repeated measurements under moderate non-stationary measurement conditions. The assumption is that the measurement conditions are stationary during a single repeated measurement but non-stationary over the entire measurement time. The objective with repeated measurements is often to retrieve an estimate of the (noise reduced) signal and its uncertainties. In order to obtain accurate estimates of these two quantities, stationary measurement conditions must be guaranteed under the measurement time. A condition that in many situations is difficult to achieve, e.g., during long measurement times or in a rapidly changing environment. The proposed method compensates for linear dynamic changes during the measurement time, where the dynamical changes, the underlying signal waveform and the noise covariance are considered unknown. The theoretical effect of moderate non-stationary conditions on repeated measurements is analyzed and experimentally validated. Estimation results using the proposed technique are presented for repeated ultrasonic measurements under non-stationary temperature conditions. The results show accurate signal estimation and noise characterization with uncorrelated normally distributed residuals, in contrast to standard synchronization techniques
|
|
| 23. |
- Martinsson, Jesper, et al.
(författare)
-
Complete post-separation of overlapping ultrasonic signals by combining hard and soft modeling
- 2008
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 48:5, s. 427-443
-
Tidskriftsartikel (refereegranskat)abstract
- In some ultrasonic measurement situations, an adequate signal separation is difficult to achieve. A typical situation is material characterization of thin media using pulse-echo or through-transmission techniques, when the time-of-flight in the media is shorter than the emitted signal's time support. Separated signals are necessary to obtain accurate estimates of material properties and transit times. In this paper a new method is proposed that enables complete post separation of measured coinciding signals. The method is based on a combination of hard physical and soft empirical models, which allows for a description of both known and unknown properties making a complete separation possible. The validity and limitations of the model and the separation results are thoroughly addressed. The proposed technique is verified using real measurements on thin dispersive samples and validated using residual analysis. The experimental results show a complete separation with uncorrelated and normally distributed residuals. The method enables characterization and/or flow analysis in difficult overlapping situations.
|
|
| 24. |
- Martinsson, Jesper, 1981-
(författare)
-
Ecology of juvenile turbot and flounder in the Central Baltic Sea : Implications for recruitment
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our understanding of turbot and flounder ecology in the Baltic Sea is insufficient for sound management decisions. This thesis aims to fill some gaps in current knowledge by providing information of the ecology of turbot and flounder within their juvenile habitat, and to relate these findings to issues assumed relevant for recruitment variation. Main focus is on turbot due to its relatively low abundance and high variability in recruitment. The distribution of both species was studied on different scales, as was environmental effects on food consumption in 0-group turbot. The 0-group turbot display a relatively restricted spatial distribution compared to flounder. This is possibly due to a more specialized diet, which may make them more vulnerable to habitat degradation, especially eutrophication as a strong negative correlation was found with the organic content in the sediment. The species show high temporal and spatial overlap when settling in July-September, with peak abundances in August, and at depths <1 m. Both species display sedentary behavior within the nursery ground. Compared to flounder, turbot was more mobile potentially due to its restricted diet calling for extended searches. For turbot, feeding conditions appear to vary between size groups, which potentially could cause variations in survival between years through size-selective mortality. But, the predation may be low in central Baltic Sea as the abundance of the main predator, brown shrimp are comparatively low during flatfish occupancy. A significant positive relationship was found between the recruitment of turbot and flounder, which suggests that no inter-specific interactions during the juvenile stage affect recruitment. This co-variation also suggests that the recruitment of the species is determined by the same phenomena, potentially by large scale abiotic factors during the egg- and larval stage. For turbot, additional variability is potentially generated during the juvenile stage due to its relatively restricted food and habitat requirements. The specific habitat demands of turbot revealed in this thesis may be used to protect and restore essentially nursery grounds.
|
|
| 25. |
- Martinsson, Jesper
(författare)
-
Effekt av bortforsling av alger på turbiditet och organisk halt i grunda gotländska vikar
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Tång och alger, eller släke, har rensats från gotländska vikar och stränder med hjälp av LOVA-stöd och ideella krafter sedan 2014. Insatserna har följts upp med biologiska undersökningar för att se om vattnets grumlighet (turbiditet) och sedimentens organiska halt har minskat som en effekt av åtgärden.Årets undersökning är en uppföljning av de tidigare biologiska undersökningarna. Syftetmed undersökningen är att ta reda på om det finns några skillnader i turbiditet och sedimentens organiska halt mellan områden där alger tagits bort och i områden där de inte har det för alla provtagningsår 2014-2016. Under 2016 undersöktes även om det fanns någon skillnad i organisk halt innan och efter åtgärden utförts.Prover för mätning av turbiditet och organisk halt togs i totalt 17 områden. Av dessa togsalger bort i åtta. Nisseviken var helt ny i undersökningen. Gnisvärd har varit med tidigare men alger togs bort här för förstra gången 2016Det fanns inga skillnader i turbditet mellan åtgärdade och ej åtgärdade områden för något av åren. För den organiska halten fanns det en skillnad 2015 och 2016. Ingen skillnad före ochefter åtgärden 2016 kunde i övrigt hittas.Det kunde vidare konstateras att det fanns ettsamband mellan organisk halt och exponering till havet. Detta samband var negativt 2014 för alla områden men de andra åren fanns det endast ett negativt samband för vikar där alger ej tagits bort. För de vikar där åtgärden utförts fanns det inget samband alls med exponering.Resultaten från undersökningarna 2014-2016visar att det inte fanns någon effekt på turbiditeten i vattnet av bortforslingen av släke. Den organiska halten var dock lägre i skyddade vikar där alger tagits bort jämfört med skyddade vikar där alger ej tagits bort..
|
|
| 26. |
- Martinsson, Jesper, et al.
(författare)
-
Estimating the underlying signal waveform and synchronization jitter from repeated measurements
- 2006
-
Ingår i: Proceedings. - Piscataway, NJ : IEEE Communications Society. - 1424402018 ; , s. 440-443
-
Konferensbidrag (refereegranskat)abstract
- In this paper we present a synchronization technique, for applications using repeated or periodically excited measurements. The problem with existing techniques is their limitations to specific signal and noise conditions, such as white Gaussian noise or narrowband signals. The proposed method extracts statistical information about the underlying signal and noise in the measurements to obtain good synchronization (asymptotically optimal). The Cramér-Rao lower bound (CRLB) is derived for the synchronization problem, including bounds for the underlying signal waveform and the covariance of the noise. The method, which is the maximum-likelihood estimator for both white and colored Gaussian noise, is compared with standard sub-sample estimation and aligning techniques using Monte Carlo simulations. The results show significant improvements compared to standard synchronization techniques.
|
|
| 27. |
- Martinsson, Jesper
(författare)
-
Estimating the underlying signal waveform, noise covariance and synchronization jitter from unsynchronized measurements
- 2008
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 19:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper a new synchronization technique is presented for applications using repeated measurements or experiments with periodically excited signals. The objective with repeated or periodic measurements is often to retrieve an estimate of the (noise reduced) signal and its uncertainties. However, these measurements need to be synchronized to obtain accurate estimates. Existing synchronization techniques are limited to specific signal and noise conditions, such as white Gaussian noise or narrowband signals, to achieve good performance. The proposed method, not limited by these conditions, extracts statistical information regarding the underlying signal and the noise contained in the measurements, to obtain good synchronization (asymptotically optimal). The Cramér-Rao lower bound (CRLB) is derived for the synchronization problem, including bounds for the underlying signal waveform and the covariance of the measurement noise, both considered unknown. The method, which is shown to be the maximum-likelihood estimator (MLE) in both white and colored Gaussian noise, is compared with the CRLB along with standard sub-sample estimation and aligning techniques using Monte Carlo simulations. The results show significant mean square error (MSE) improvements compared to standard synchronization techniques. Synchronization results using the proposed technique are presented for repeated ultrasonic measurements, to validate the method in a real measurement situation, and to experimentally support theoretical results.
|
|
| 28. |
|
|
| 29. |
- Martinsson, Jesper, et al.
(författare)
-
Model-based phase velocity and attenuation estimation in wideband ultrasonic measurement systems
- 2007
-
Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 54:1, s. 138-146
-
Tidskriftsartikel (refereegranskat)abstract
- A parametric method to estimate frequencydependent phase velocity and attenuation is presented in this paper. The parametric method is compared with standard nonparametric Fourier analysis techniques using numerical simulations as well as real pulse-echo experiments. Approximate standard deviations are derived for bothmethods and validated with numerical simulations. Compared to standard Fourier analysis, the parametric model gives considerably lower variance when estimating attenuation and phase velocity. In contrast to nonparametric techniques, the proposed estimator avoids the phase unwrapping problem because analytical expressions for thecontinuous phase velocity and attenuation can be derived.
|
|
| 30. |
- Martinsson, Jesper, et al.
(författare)
-
Modeling the effects of telephone nursing on healthcare utilization
- 2018
-
Ingår i: International Journal of Medical Informatics. - : Elsevier. - 1386-5056 .- 1872-8243. ; 113, s. 98-105
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundTelephone nursing is the first line of contact for many care-seekers and aims at optimizing the performance of the healthcare system by supporting and guiding patients to the correct level of care and reduce the amount of unscheduled visits. Good statistical models that describe the effects of telephone nursing are important in order to study its impact on healthcare resources and evaluate changes in telephone nursing proceduresObjectiveTo develop a valid model that captures the complex relationships between the nurse's recommendations, the patients’ intended actions and the patients’ health seeking behavior. Using the model to estimate the effects of telephone nursing on patient behavior, healthcare utilization, and infer potential cost savings.MethodsBayesian ordinal regression modelling of data from randomly selected patients that received telephone nursing. Inference is based on Markov Chain Monte Carlo (MCMC) methods, model selection using the Watanabe-Akaike Information Criteria (WAIC), and model validation using posterior predictive checks on standard discrepancy measures.Results and ConclusionsWe present a robust Bayesian ordinal regression model that predicts three-quarters of the patients’ healthcare utilization after telephone nursing and we found no evidence of model deficiencies. A patient's compliance to the nurse's recommendation varies and depends on the recommended level of care, its agreement with and level of the patient's prior intention, and the availability of different care options at the time. The model reveals a risk reducing behavior among patients and the effect of the telephone nursing recommendation is 7 times higher than the effect of the patient's intended action prior to consultation if the recommendation is the highest level of care. But the effect of the nurse's recommendation is lower, or even non-existing, if the recommendation is self-care. Telephone nursing was found to have a constricting effect on healthcare utilization, however, the compliance to nurse's recommendation is closely tied to perceptions of risk, emphasizing the importance to address caller's needs of reassurance
|
|
| 31. |
- Martinsson, Jesper, et al.
(författare)
-
Modelling the Dynamic Relationship Between Mining Induced Seismic Activity and Production Rates, Depth and Size : A Mine-Wide Hierarchical Model
- 2020
-
Ingår i: Pure and Applied Geophysics. - : Springer. - 0033-4553 .- 1420-9136. ; 177:6, s. 2619-2639
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamic properties of mining induced seismic activity with respect to production rate, depth and size are studied in seven orebodies in the same underground iron ore mine. The objective is to understand the relationship between the measured seismic activity and the: seismic decay time, planned production rate, production size and mining depth. This relationship is the first step to individually customise the production rate for each orebody in the mine, make short-term predictions of future seismicity given planned productions, and to find out in what way the available predictors affect the seismicity. The seismic response with respect to the dependent variables is parametrised and the estimated decay times for each orebody, which are of particular interest here, are compared. An autoregressive model is proposed to capture the dynamic relationship between the induced seismic activity, the current production rate and the past seismic activity. Bayesian estimation of the parameters is considered and parameter constraints are incorporated in the prior distributions. The models for all orebodies are tied together and modelled hierarchically to capture the underlying joint structure of the problem, where the mine-wide parameters are learnt together with the individual orebody parameters from the observed data. Comparisons between the parameters from the hierarchical model and independent models are given. Group-level regressions reveal dependencies on size and mining depth. Model validation with posterior predictive checking using several discrepancy measures could not detect any model deficiencies or flaws. Posterior predictive intervals are evaluated and inference of model parameters are presented.
|
|
| 32. |
- Martinsson, Jesper, 1981-, et al.
(författare)
-
Nursery area utilisation by turbot (Psetta maxima) and flounder (Platichthys flesus) at Gotland, central Baltic Sea
- 2011
-
Ingår i: Boreal Environmental Research. - Helsinki : Finnish Environment Institute. - 1239-6095. ; 16:1, s. 60-70
-
Tidskriftsartikel (refereegranskat)abstract
- To reveal the temporal and spatial utilization of a preferred nursery ground habitat by 0-group turbot and flounder in the Baltic Sea, sampling was conducted in six sandy bays in early-mid June to early-mid September 2003-2005 off the cost of Gotland (ICES SD 27 & 28-2). Settlement and peak abundance of turbot occurred from late July-early August to early September and from mid August to early September, respectively. Settlement of flounder occurred from early-mid-July with decreasing numbers over time, except in 2005. Peak abundance of 0-group flounder occurred in late July-ealy August to mid September, suggesting a considerable temporal overlap with 0-group turbot. 0-group turbot and flounder also overlapped in respect to depth with preferences for 0.2 and 0.6 m over 1 m. The spatial and temporal overlap of the species was verified by a logistic regression analysis; the probability of sampling 0-group flounder when 0-group turbot was caught in a haul was 0.84 (0.80-0.87, 95% CI).
|
|
| 33. |
|
|
| 34. |
- Martinsson, Jesper, et al.
(författare)
-
Parametric estimation of ultrasonic phase velocity and attenuation in dispersive media
- 2006
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 44:Supplement 1, s. e991-e994
-
Tidskriftsartikel (refereegranskat)abstract
- In ultrasonic characterization of liquids, gases, and solids, accurate estimation of frequency dependent attenuation and phase velocity is of great importance. Non-parametric methods, such as Fourier analysis, suffers from noise sensitivity, and the variance of the estimated quantities is limited by the signal-to-noise ratio. In this paper we present a parametric method for estimation of these properties. Pulse echo experiments in ethane, oxygen and mixtures of the two show that the proposed method can estimate phase velocity and attenuation with up to 50 times lower variance than standard non-parametric methods.
|
|
| 35. |
- Martinsson, Jesper, et al.
(författare)
-
Parametric modeling of wave propagation in gas mixtures : a system identification approach
- 2005
-
Ingår i: 2005 IEEE Ultrasonics Symposium. - Piscataway, NJ : IEEE Communications Society. - 0780393821 ; , s. 2288-2292
-
Konferensbidrag (refereegranskat)abstract
- In ultrasonic pulse-echo systems, the observable properties are restricted to frequency dependent attenuation and phase velocity, which in turn are related to the material properties of the investigated media. In this paper we present a parametric model of the bulk modulus, composed of the basic physical building blocks of absorption (relaxation blocks). The parametric model is capable of handling the combined effect of the absorption mechanisms present in a gas or gas mixture and captures the experimental variation in the observation. The performance of the parametric model is demonstrated with pulse-echo experiments in oxygen, ethane and mixtures of the two. Compared to standard Fourier analysis techniques, the parametric model gives higher accuracy when estimating attenuation and phase velocity, and physical parameters such as relaxation strengths and relaxation frequencies can be extracted from it.
|
|
| 36. |
|
|
| 37. |
- Martinsson, Jesper, et al.
(författare)
-
Separation of dispersive coinciding signals by combining hard and soft modeling
- 2008
-
Ingår i: Proceedings of the International Congress on Ultrasonics.
-
Konferensbidrag (refereegranskat)abstract
- In some ultrasonic measurement situations, an adequate signal separation is difficult to achieve. A typical situation is material characterization of thin media, relative to the emitted signal's time support. In this paper a new method is proposed that enables accurate signal separation of measured coinciding signals in the postprocessing stage. The method is based on a combination of hard physical and soft empirical models, which allows for a description of both known and unknown dynamics making the separation possible. The proposed technique is verified using real measurements on thin dispersive samples and validated with residual analysis.
|
|
| 38. |
- Martinsson, Jesper
(författare)
-
Statistical tools for ultrasonic analysis of dispersive fluids
- 2006
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the possibility of using ultrasonic measurement techniques for energy gas characterization. The idea is to combine both on-line flow measurements with non-invasive fluid characterization in the same measurement setup using the same sensor(s). The long-term goal of the project is to develop measurement methods based on ultrasonic techniques that can measure; the flow rate, the energy content, detect impurities, and estimate the composition. In this thesis different problems concerning gas characterization and modeling are addressed. The information obtained from ultrasonic measurements are limited to spectral variations in the attenuation and phase velocity. Hence, part of the research is focused on estimating these quantities accurately with low uncertainty. Another area is parametric modeling and identification of the bulk modulus, where a new model structure for gas mixtures with complex dynamic behavior and/or unknown components is presented, capable of handling the combined effect of the absorption mechanisms. Finally, the problem of estimating the composition of a gas mixture is considered. The results show that it is possible to estimate the composition of processed and upgraded biogas, with high accuracy and precision, by combining the developed estimation techniques with multiple linear regression methods. The thesis consists of two parts. The first part includes an introduction to the research area together with a short summary of the contributions. The second part contains a collection of four papers describing the research.
|
|
| 39. |
|
|
| 40. |
- Martinsson, Jesper
(författare)
-
Ultrasonic measurement principles : modeling, identification, and parameter estimation
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents contributions within the fields of ultrasonic modeling and measurement technology, with focus on solutions to difficult modeling and measurement problems. The work is divided into two categories: 1) processing of measurements obtained under non-ideal conditions, such as unsynchronized, distorted, and superimposed signals; 2) estimating acoustic models and parameters from materials, fluids, fluid mixtures, and thin-layered structures. The ultrasonic research field has traditionally been focused on either physical models to describe acoustic properties based on wave propagation experiments, or on statistical/empirical models to describe more complex systems. Physical models have the advantage that the parameters are directly connected to physical properties of the media, enabling an understanding of the underlying dynamics and simplifying the inverse problem. However, their disadvantage is that the derivations are often based on crude approximations and ideal conditions; limitations often leading to correlated residuals, biased parameter estimates, and the necessity of calibration measurements to solve the inverse problem. Conversely, statistical or empirical models often describe the measured data well with uncorrelated residuals, but have the disadvantage that the parameters (or models) are not directly connected to the physical properties of the material or fluid. In this case this connection is often retrieved through calibration. A key ingredient in the work presented in this thesis, is the use of a combination of physical and empirical models. This allows for a description of dynamic elements with both known and unknown structures, and the ability to have both uncorrelated residuals and unbiased parameter estimates related to the physical properties of the media. If sufficient prior knowledge exists of the physical structure and the location of possible non-ideal effects, calibration steps may be avoided or reduced significantly. This combination of hard physical structures with the variability of empirical models inherits advantages and disadvantages from both models. The benefits and limitations of the proposed solutions are analyzed and discussed, and the presented results are supported and validated with real experiments or with combinations of real experiments and simulations
|
|
| 41. |
- Melander, Catharina, et al.
(författare)
-
Measuring Electrodermal Activity to Improve the Identification of Agitation in Individuals with Dementia
- 2017
-
Ingår i: Dementia and Geriatric Cognitive Disorders Extra. - : S. Karger. - 1664-5464. ; 7:3, s. 430-439
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Understanding and interpreting the complexity of agitation in people with dementia is challenging. Objective: To explore whether a sensor measuring electrodermal activity (EDA) can improve the identification of agitation in individuals with dementia. Methods: Nine individuals with dementia wore a sensor that measured EDA. During the same time, assistant nurses annotated the observed behavior of the person with dementia. A binary logistic regression model was applied to assess the relationship between the sensor and the assistant nurses’ structured observations of agitation. Results: The sensor values correlated with the assistant nurses’ observations both at the time of the observation and 1 and 2 h prior to the observation. Conclusion: A sensor measuring EDA can support early detection of agitation in persons with dementia
|
|
| 42. |
- Mishra, Madhav, 1980-, et al.
(författare)
-
Bayesian hierarchical model-based prognostics for lithium-ion batteries
- 2018
-
Ingår i: Reliability Engineering & System Safety. - : Elsevier. - 0951-8320 .- 1879-0836. ; 172, s. 25-35
-
Tidskriftsartikel (refereegranskat)abstract
- To optimise operation and maintenance, knowledge of the ability to perform the required functions is vital. The ability is governed by the usage of the system (operational issues) and availability aspects like reliability of different components. This paper proposes a Bayesian hierarchical model (BHM)-based prognostics approach applied to Li-ion batteries, where the goal is to analyse and predict the discharge behaviour of such batteries with variable load profiles and variable amounts of available discharge data. The BHM approach enables inferences for both individual batteries and groups of batteries. Estimates of the hierarchical model parameters and the individual battery parameters are presented, and dependencies on load cycles are inferred. A BHM approach where the operational and reliability aspects end of life (EoD) and end of life (EoL) is studied where its shown that predictions of EoD can be made accurately with a variable amount of battery data. Without access to measurements, e.g. predicting a new battery, the predictions are based only on the prior distributions describing the similarity within the group of batteries and their dependency on the load cycle. A discharge cycle dependency can also be identified in the result giving the opportunity to predict the battery reliability.
|
|
| 43. |
- Mishra, Madhav, 1980-, et al.
(författare)
-
Bearing Life Prediction with Informed Hyperprior Distribution: A Bayesian Hierarchical and Machine Learning Approach
- 2021
-
Ingår i: IEEE Access. - : IEEE Robotics and Automation Society. - 2169-3536. ; 9, s. 157002-157011
-
Tidskriftsartikel (refereegranskat)abstract
- A Bayesian hierarchical model (BHM) is developed to predict bearing life using envelope acceleration data in combination with a degradation model and prior knowledge of the bearing rating life. The BHM enables the inference of individual bearings, groups of bearings, or bearings operating under certain conditions. The key benefit of the BHM approach is that the relationships between the bearing model parameters and their prior distributions can be expressed at different hierarchical levels. We begin our analysis using a bearing rating life calculation L10h and an estimate of its associated failure time distribution. Realistic variations to constrain our prior distribution of the failure time are then applied before measurements are available. When data become available, estimates more representative of our specific batch and operating conditions are inferred, both on the individual bearing level and the bearing group level. The proposed prognostics methodology can be used in situations with varying amounts of data. The presented BHM approach can also be used to predict the remaining useful life (RUL) of bearings both in situations in which the bearing is considered to be in a healthy state and in situations after a defect has been detected.
|
|
| 44. |
- Mishra, Madhav, 1980-, et al.
(författare)
-
Hierarchical model-based prognostics for Li-ion batteries
- 2018
-
Ingår i: Advances In Engineering. - Ontario, CANADA : Advances In Engineering.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Recent global trend towards a fossil-fuel-free society has yielded the rapid soar in demand of electrically powered systems. Specifically, the demand for battery powered systems has fueled the desire to have better performing batteries with lithium-ion batteries being the most widely used. Presently, for application in unmanned vehicles, exploratory rovers, submarines among others demand a better comprehension of battery performance metrics. Case and point, battery capacity and state of charge have become increasingly vital when it comes to determining the end of discharge. As of now, several techniques have already been established for determining such parameters. Unfortunately, their prognostic capability for determining remaining battery charge is still not optimal. Therefore, there is a need to develop prognostic and health management technology for critical systems (such as Mars rovers) to successfully predict and manage the lifetime of batteries, monitor their health state in real time, evaluate the performance and predict the remaining useful life.To this note, Luleå University of Technology researchers in Sweden: Dr. Madhav Mishra, Dr. Jesper Martinsson, and Dr. Matti Rantatalo in collaboration with Dr. Kai Goebel at NASA in the United States proposed a study whose main objective was to measure the battery discharge and predict the end of discharge considering the operating conditions for lithium ion batteries. To be precise, they purposed on employing a Bayesian Hierarchical Model (BHM)-based end of discharge prognostic for Li-ion batteries. Their work is currently published in the research journal, Reliability Engineering and System Safety.The research technique employed entailed the utilization of two batteries with 16 discharge events with a simplified battery circuit model of the battery. Next, the research team examined the detailed discharge voltage profiles during different discharging cycles with variable load profiles. They then proceeded to demonstrate the BHM approach and group-level dependencies by utilizing more than one battery and more than one discharge cycle.The authors observed that the BHM approach enabled inferences for both individual batteries and groups of batteries. The researchers then recorded the estimates of the hierarchical model parameters and the individual battery parameters after which their dependencies on load cycles were inferred. In addition, they noted that by using the BHM approach the predictions of end of discharge could be made accurately with a variable amount of battery data. Furthermore, this technique was seen to applicable even for new batteries without prior recorded data where the predictions were based only on the prior distributions describing the similarity within the group of batteries and their dependency on the load cycle.In conclusion, the study presented a Bayesian hierarchical model (BHM)-based prognostics approach for Li-ion batteries, where the goal was to analyze and predict the discharge behavior of such batteries with variable load profiles and variable amounts of available discharge data. The results obtained showed that the technique could address cases with or without data. Altogether, the proposed method can capture additional relationships between parameters and use it to improve prognostics. Lastly, the BHM approach has been seen to permit inference at both the individual battery level and group of battery level.
|
|
| 45. |
- Shekhar, Gurmeet, et al.
(författare)
-
Development of an optimal draw control strategy for a sublevel caving operation at Malmberget mine
- 2020
-
Ingår i: Mining Technology. - : Taylor & Francis. - 2572-6668 .- 2572-6676. ; 129:2, s. 104-112
-
Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the identification of the optimal draw control strategy for a sublevel caving (SLC) operation at Malmberget mine in Sweden. Two mathematical models, a probability model and an economic model, were created using five datasets: bucket weights, bucket grades, extraction ratio, mine economics parameters and production constraints. The probability model was used to generate a set of simulated bucket weights and corresponding bucket grades which acts as a ‘virtual mine’ environment. The economic model assesses the economic impact of loading at the draw point. Two approaches to draw control were tested using the ‘virtual mine’ created by the probability model. Based on the results of the simulation tests, an optimal draw control strategy is suggested for a field test at the mine. The new draw control strategy optimises further the loading operation at Malmberget mine. The paper shows a roadmap for optimising draw control strategy for SLC operations.
|
|
| 46. |
- Shekhar, Gurmeet, 1990-
(författare)
-
Draw control strategy for sublevel caving mines : A probabilistic approach
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sublevel caving is an underground mass mining method used for extracting different types of ores from the earth crust. Mines using sublevel caving (SLC) as the primary mining method are generally highly mechanized with standardized and independent unit operations. Different unit operations (drilling, blasting, loading and transportation) are performed in isolation with each other which leads to standardized procedures and safe operation. Loading of the material from the production face in sublevel caving is facilitated by the flow of material under gravity into the production face. A large amount of material is loaded from a limited opening termed as the draw point which creates challenges for the mining method. Material flow in SLC has been studied extensively in the past five decades and different methods have been used to simulate material flow in caving operations. Physical models of different scales has been designed for simulating material flow by using sand, gravel or rocks and studying the movement of material inside the model. Initial physical models showed an ellipsoidal zone above the draw point from which material flowed into the draw point. However, subsequent physical modelling results disagreed with this notion of material flow. Numerical modelling techniques have also been applied to simulate material flow. Currently, marker trials are being used to understand material flow in SLC. Markers (numbered steel rods, RFID enabled markers) are installed in boreholes drilled inside the burden of a production ring and based on the recovery sequence of markers, material flow is predicted. Results from physical models, numerical models and marker trials along with mine experience have been used in the past to optimize mine design and draw control for SLC operation. The results from latest marker trials highlight the chaotic nature of material flow and the unpredictability associated with material flow simulation. In caving operations, draw control deals with the question of when to stop loading and regulates the loading process by providing the information on when to stop loading. The decision to stop loading a blasted ring and proceed to blasting the subsequent ring is a critical decision made in a SLC operation. If a draw point is closed early then ore is lost in the draw point which cannot be conclusively recovered at the lower levels and if delayed the mine faces greater dilution and increased mining costs. A study of the various draw control strategies used in sublevel caving operations globally has also been done to describe the present state-of-art. An analysis of the draw control and loading operations at the Malmberget and Kiirunavaara mines is summarized in the thesis using information collected through interviews, internal documents, meetings, and manuals. An optimized draw control strategy is vital for improving ore recovery and reducing dilution in SLC. Based on the literature review and baseline mapping study, a set of guidelines for designing a new draw control strategy has been listed. In the present scenario of fluctuating metal prices and increasing operational cost a new draw control strategy is needed which is probabilistic in nature and can handle the uncertainties associated with caving operations. A draw control model which is probabilistic in nature provide a scenario based solution and can be used to test different draw control strategy before performing mine test. A framework for a probabilistic draw control model along with its application for draw control optimization has been discussed here. An effective draw control requires a constant monitoring system and a constant calibration of the loading criteria’s through draw point monitoring for reducing dilution and improving ore recovery.
|
|
| 47. |
- Shekhar, Gurmeet, 1990-
(författare)
-
Draw control strategy for sublevel caving mines : A holistic approach
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sublevel caving is an underground mass mining method used for extracting different types of ores from the earth crust. Mines using sublevel caving (SLC) as the primary mining method are generally highly mechanized with standardized and independent unit operations. Different unit operations (drilling, blasting, loading and transportation) are performed in isolation with each other which leads to standardized procedures and safe operation. Loading of the material from the production face in sublevel caving is facilitated by the flow of material under gravity into the production face. A large amount of material is loaded from a limited opening termed as the draw point which creates challenges for the mining method.Material flow in SLC has been studied extensively in the past five decades and different methods have been used to simulate material flow in caving operations. Physical models of different scales has been designed for simulating material flow by using sand, gravel or rocks and studying the movement of material inside the model. Initial physical models showed an ellipsoidal zone above the draw point from which material flowed into the draw point. However, subsequent physical modelling results disagreed with this notion of material flow. Numerical modelling techniques have also been applied to simulate material flow. Currently, marker trials are being used to understand material flow in SLC. Markers (numbered steel rods, RFID enabled markers) are installed in boreholes drilled inside the burden of a production ring and based on the recovery sequence of markers, material flow is predicted. Results from physical models, numerical models and marker trials along with mine experience have been used in the past to optimize mine design and draw control for SLC operation. The results from latest marker trials highlight the chaotic and non-uniform nature of material flow and the unpredictability associated with material flow simulation.In caving operations, draw control deals with the question of when to stop loading and regulates the loading process by providing the information on when to stop loading. The decision to stop loading a blasted ring and proceed to blasting the subsequent ring is a critical decision made in a SLC operation. If a draw point is closed early then ore is lost in the draw point which cannot be conclusively recovered at the lower levels and if delayed the mine faces greater dilution and increased mining costs. A study of the various draw control strategies used in sublevel caving operations globally has also been done to describe the present state-of-art. An analysis of the draw control and loading operations at the Malmberget and Kiirunavaara mines is summarized in the thesis using information collected through interviews, internal documents, meetings, and manuals. Based on the literature review and baseline mapping study, a set of guidelines for designing a new draw control strategy has been listed. A holistic approach to draw control is required which captures the uncertainty and variation associated with loading at the draw point and fulfils the sustainability and economical objectives for the mine. Two mathematical models, a probability model and an economic model, were created using five datasets: bucket weights, bucket grades, extraction ratio, mine economics parameters and production constraints. The probability model was used to generate a set of simulated bucket weights and corresponding bucket grades which acts as a ‘virtual mine’ environment. The economic model assesses the economic impact of loading at the draw point. Two approaches to draw control is tested using the ‘virtual mine’ created by the probability model. Based on the results of the simulation tests, an optimal draw control strategy is suggested for a field test at the mine. The results highlight the importance of dynamic loading control for SLC operations. They also demonstrate the importance of continuous draw point monitoring to optimize SLC operations. The thesis offers a roadmap for mine digitization in which a ‘virtual mine’ model (probability model) is used for simulation and calibration, whilst an online application (economic model) is used at the mine in real time.
|
|
| 48. |
- Trenkwalder, Teresa, et al.
(författare)
-
Effects of the coronary artery disease associated LPA and 9p21 loci on risk of aortic valve stenosis
- 2019
-
Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 276, s. 212-217
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Aortic valve stenosis (AVS) and coronary artery disease (CAD) have a significant genetic contribution and commonly co-exist. To compare and contrast genetic determinants of the two diseases, we investigated associations of the LPA and 9p21 loci, i.e. the two strongest CAD risk loci, with risk of AVS. Methods: We genotyped the CAD-associated variants at the LPA (rs10455872) and 9p21 loci (rs1333049) in the GeneCAST (Genetics of Calcific Aortic STenosis) Consortium and conducted a meta-analysis for their association with AVS. Cases and controls were stratified by CAD status. External validation of findings was undertaken in five cohorts including 7880 cases and 851,152 controls. Results: In the meta-analysis including 4651 cases and 8231 controls the CAD-associated allele at the LPA locus was associated with increased risk of AVS (OR 1.37; 95%CI 1.24–1.52, p = 6.9 × 10−10) with a larger effect size in those without CAD (OR 1.53; 95%CI 1.31–1.79) compared to those with CAD (OR 1.27; 95%CI 1.12–1.45). The CAD-associated allele at 9p21 was associated with a trend towards lower risk of AVS (OR 0.93; 95%CI 0.88–0.99, p = 0.014). External validation confirmed the association of the LPA risk allele with risk of AVS (OR 1.37; 95%CI 1.27–1.47), again with a higher effect size in those without CAD. The small protective effect of the 9p21 CAD risk allele could not be replicated (OR 0.98; 95%CI 0.95–1.02). Conclusions: Our study confirms the association of the LPA locus with risk of AVS, with a higher effect in those without concomitant CAD. Overall, 9p21 was not associated with AVS.
|
|
| 49. |
- Törnman, Wille, et al.
(författare)
-
Reliable automatic processing of seismic events : solving the Swiss cheese problem
- 2020
-
Ingår i: Proceedings of the Second International Conference on Underground Mining Technology. - : University of Western Australia. ; , s. 155-172
-
Konferensbidrag (refereegranskat)abstract
- BEMIS (Bayesian estimation of mining-induced seismicity) is a fully automatic, near real-time, robust and self-learning seismic processing solution for mining-induced seismic events. A prototype solution is tested in parallel with IMS’s routine manual processing in LKAB’s underground mines in Malmberget and Kiruna, providing four times more accurate earthquake locations based on 290 known blasts, 40 times faster processing time that scales with computer power, and the ability to detect and locate up to six times more events given the same input data. In addition to a fully automatic system, BEMIS provides a variety of unique functions such as quality control of all results, self-learning adaptation and calibrations, tomography, and prediction models of future seismicity. In this paper, we summarise the results from different investigations throughout time and discuss the unique approach considered to obtain reliable auto-processing in a challenging, unknown and changing environment.
|
|
| 50. |
- Törnman, Wille, et al.
(författare)
-
Robust Bayesian estimator for S-wave spectra, using a combined empirical Green’s function
- 2021
-
Ingår i: Geophysical Journal International. - : Oxford University Press. - 0956-540X .- 1365-246X. ; 227, s. 403-438
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a new fully automatic and robust Bayesian method to estimate precise and reliable model parameters describing the observed S-wave spectra. All the spectra associated with each event are modelled jointly, using a t-distribution as likelihood function together with informative prior distributions for increased robustness against outliers and extreme values. The model includes the observed noise and a combined empirical Green’s function. It captures source-, receiver-, and path-dependent terms in the description of the observed spectra by combining a physical source and attenuation model with a spatially and event-size dependent empirical compensation. The proposed method propagates estimation uncertainties along the entire processing chain starting from the hypocentre location and delivers reliable uncertainty description of the estimands. The objective is to automatically provide robust and valid descriptions of the observed S-wave spectra generated from an earthquake source in a noisy and heterogeneous environment. The efficiency of the method is tested with synthetic seismograms, and the model is calibrated and cross-validated using 31 640 mining induced seismic events in a iron ore mine (in north of Sweden) with an comprehensive seismic network. The model is evaluated using both posterior predictive checks and residual analysis and we found no evidence that indicates any model deficiencies with respect to central tendency, dispersion, and residual trends.
|
|
