| 1. |
- Ramesh Sagar, Vaishak, 1988, et al.
(författare)
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Investigating the sensitivity of particle size distribution on part geometry in additive manufacturing
- 2020
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Ingår i: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE). ; 2B-2020
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Konferensbidrag (refereegranskat)abstract
- Selective laser melting process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the end product. This paper investigates the effect of PSD on deformation for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder distribution based on the different particle size distribution of the powder. The CFD is used as a virtual test bed to determine thermal parameters such as density, heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to test the sensitivity of the melted zone and distortion using Structural Mechanics. Results showed significant influence of particle size distribution on the packing density, surface height, surface roughness, the stress state and displacement of the melted zone. The results will serve as a catalyst in developing geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.
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| 2. |
- Söderberg, Johan, 1980-, et al.
(författare)
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Haemolysis index : an estimate of preanalytical quality in primary health care!
- 2009
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Ingår i: Clinical Chemistry and Laboratory Medicine. - 1434-6621 .- 1437-4331. ; 47:8, s. 940-944
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Tidskriftsartikel (refereegranskat)abstract
- Background: Haemolysis is usually caused by inadequate specimen collection or preanalytical handling, and is suggested to be a suitable indicator of preanalytical quality. We investigated the prevalence of detectable haemolysis in all routine venous blood samples to identify differences in preanalytical quality.Methods: Haemolysis index (HI) values were obtained from a Vitros 5,1 in the routine clinical chemistry laboratory for samples collected in primary health care centres (PHCs), nursing homes, and a hospital emergency department (ED). Haemolysis was defined as a HI ≥ 15 (detection limit).Results: Samples from the PHC with the highest prevalence of haemolysis were 6.1 times (95% confidence interval (CI) 4.0-9.2) more often haemolysed compared to the centre with the lowest prevalence. Of the samples collected in primary health care, 10.4% were haemolysed compared to 31.1% in the ED (p< 0.001). A notable difference in haemolysed samples was found between the ED section staffed by emergency medicine physicians and the section staffed by primary health care physicians (34.8% vs. 11.3%, p<0.001).Conclusions: The significant variation in haemolysis indices among the investigated units is likely to reflect varying preanalytical conditions. The HI is a valuable tool for estimation and follow-up of preanalytical quality in primary health care.
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| 3. |
- Bergsjö, Dag Henrik, 1980, et al.
(författare)
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Industrial Scale Production of Customized Ceramic Prostheses
- 2014
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Ingår i: Advanced Ceramics for Dentistry, 1st Edition. ; , s. 416-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Today, there are many solutions for dental rehabilitation. A damaged tooth can be replaced with a dental crown, and a toothless patient can be rehabilitated with implants and a corresponding bridge set-up. Traditionally, a dental crown is manufactured by veneering porcelain to a metal surface that is obtained through the use of casting principles. Implant rehabilitations used to rely on a high degree of handcraft by the dentist, where freehand drilling into the jaw- bone was supported by X-ray pictures and was done before implant insertion. Crown and implant rehabilitations can be provided at a much higher degree of industrialization by means of mass customization. The most common dental rehabilitations are crown restorations for single teeth, while full arch implant rehabilitations are the most comprehensive treatments. Trends in industry lean toward a higher degree of automation in production and manufacturing where key characteristics of a well-functioning ceramic prosthesis are cost reduction, patient satisfaction, and quality in both function and perception.
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| 4. |
- Gustavsson, Johan, 1974, et al.
(författare)
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Mode and polarization control in VCSELs using shallow surface structures
- 2007
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Ingår i: IET Optoelectronics. ; 1:5, s. 197-205
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Tidskriftsartikel (refereegranskat)abstract
- Monolithic techniques for mode and polarisation control in vertical-cavity surface emitting lasers (VCSELs) using shallow surface structures are summarized and put in the context with other techniques in terms of performance and manufacturability. The method of using circular-symmetric surface structures for mode control and their combination with a sub-wavelength surface grating for simultaneous mode and polarisation control is described in detail, and adherent experimental results for both 850-nm and 1.3-µm oxide-confined VCSELs are presented.
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| 5. |
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| 6. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Geometry Assurance Integrating Process Variation with Simulation of Spring-in for Composite Parts and Assemblies
- 2014
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Ingår i: Proc. of ASME 2014 International Mechanical Engineering Congress & Exposition. - 9780791846438 ; 2A
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Konferensbidrag (refereegranskat)abstract
- Geometrical variation and deviation in all manufacturing processes affect quality of the final product. Therefore geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites,the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
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| 7. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Geometry Assurance Integrating Process Variation with Simulation of Spring-In for Composite Parts and Assemblies
- 2016
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Ingår i: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2016 by ASME.Geometrical variation and deviation in all the manufacturing processes affect the quality of the final product. Therefore, geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper, we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites, the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
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| 8. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Variation simulation for composite parts and assemblies including variation in fiber orientation and thickness
- 2014
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Ingår i: Procedia CIRP CATS 2014. 5th CATS 2014 - CIRP Conference on Assembly Technologies and Systems. - : Elsevier BV. - 2212-8271. ; 23, s. 235-240
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Konferensbidrag (refereegranskat)abstract
- All manufacturing processes are afflicted by geometrical variation, which can lead to defect products. A simulation tool for geometry assurance analysis is therefore important in the design process. The use of composites has recently increased drastically, but there is still a lack of understanding about the effects of variation in such parts. A method for predicting variation in subassemblies, including variation in fiber orientation and ply thickness for composites is presented. The approach is demonstrated on an industrial case and finite element analysis is used to calculate the deformation. In particular, contribution from variation in material properties to the variation in critical points is analyzed. The results indicate that material uncertainties have a small impact on the geometric variation for the test case.
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| 9. |
- Kero, Timo, 1973, et al.
(författare)
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ASSESSING METHODS FOR MANAGEMENT OF R&D PROCESS INFORMATION
- 2009
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Ingår i: International Association for Management of Technology, IAMOT 2009 Proceedings.
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Konferensbidrag (refereegranskat)abstract
- In this paper a new method incorporating flexible collection of process information along with an intuitive manner of presenting the processes along with the process information is presented and compared to a standard DSM process chart. A prototype tool implementing the proposed method is also presented.A bio-medical process is mapped using interviews and available documentation from Nobel Biocare as the main method to collect process information. The complete model is documented applying a DSM tool. The proposed interactive process modeling (IPM) method has been developed in parallel with the mapped process, along with a prototype process documentation tool, to map the same process and compare the two mapping cases.The studied process contains 101 process activities that have been mapped and described using the two methods (DSM and the new interactive process mapping (IPM)). It has been found that the IPM method enables a more complete approach to process improvement since it can be applied and updated easier because of features such as: version control, higher level of user interactivity, alternative representations of process properties using links between information objects, IT-resources and organizational roles within the process chart.A flexible approach using the IPM method ensures rich and easily accessible process information that is easier to interpret, communicate and maintain over time than the standard DSM model.
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| 10. |
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| 11. |
- Lorin, Samuel C, 1983, et al.
(författare)
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Variation Simulation of Welded Assemblies Using a Thermo-Elastic Finite Element Model
- 2014
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Ingår i: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 14:3, s. Art. no. 031003-
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Tidskriftsartikel (refereegranskat)abstract
- Every series of manufactured products has geometric variation. Variation can lead to products that are difficult to assemble or products not fulfilling functional or aesthetic requirements. In this paper, we will consider the effects of welding in variation simulation. Earlier work that has been combining variation simulation with welding simulation has either applied distortion based on nominal welding conditions onto the variation simulation result, hence loosing combination effects, or has used transient thermo-elasto-plastic simulation, which can be very time consuming since the number of runs required for statistical accuracy can be high. Here, we will present a new method to include the effects of welding in variation simulation. It is based on a technique that uses a thermo-elastic model, which previously has been shown to give distortion prediction within reasonable accuracy. This technique is suited for variation simulations due to the relative short computation times compared to conventional transient thermo-elasto-plastic simulations of welding phenomena. In a case study, it is shown that the presented method is able to give good predictions of both welding distortion and variation of welding distortions compared to transient thermo-elasto-plastic simulations.
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| 12. |
- Mårdberg, Peter, 1980, et al.
(författare)
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Towards Enhanced Functionality and Usability of Giving Manikin Task Instructions in a DHM Tool
- 2023
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Ingår i: Advances in Digital Human Modeling. - Cham : Springer. - 9783031378508 - 9783031378485 ; 744 LNNS, s. 44-51
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Konferensbidrag (refereegranskat)abstract
- There are many approaches on how to make digital manikins replicate how real humans perform tasks. The manikin motions can, for instance, be computed by algorithms based on task instructions from the DHM tool user. In this study, we investigate possibilities for improving the task instruction language used in the DHM software tools. The study focuses on identifying opportunities and challenges for how the task instruction language can be improved, and the goal of the study is to establish research questions and to create a research roadmap. The aims of the research questions and associated research and development are: (i) to make it easier to give task instructions; (ii) to reduce the variance in simulations results between different DHM tool users; and (iii) to improve the trustworthiness of the simulation results, related to issues such as manikin behavior and estimated motion times. The potential approaches that have been identified, and will be elaborated and discussed in this paper, with the DHM software tool IPS IMMA as base, are: (i) to enable the DHM tool user to give task instructions on a higher abstraction level than today; (ii) to incorporate functionality to automatically represent likely human behavior; and (iii) to improve the accuracy of time estimation of task performance.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Söderberg, Emma, 1980, et al.
(författare)
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Suppression of higher order transverse modes and oxide modes in 1.3 µm InGaAs VCSELs by an inverted surface relief
- 2007
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Ingår i: IEEE Photonics Technology Letters. ; 19, s. 327-
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Tidskriftsartikel (refereegranskat)abstract
- It is shown, by a systematic variation of design parameters, that the use of an inverted surface relief is very effective for suppressing higher order transverse modes in oxide confined 1.3-mum InGaAs vertical-cavity surface-emitting lasers (VCSELs). Single-mode emission is achieved for a large variety of oxide aperture and surface relief diameters, with optimum designs, having a surface relief with a diameter half of that of the oxide aperture, producing 1.1-1.3 mW of single-mode power. It is also shown that the anti-phase layer employed to enable the use of an inverted surface relief is effective for suppressing oxide modes that otherwise appear in oxide confined VCSELs with a large detuning between the gain peak and the cavity resonance
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| 17. |
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| 18. |
- Söderberg, Johan, 1980-, et al.
(författare)
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Incident reporting practices in the preanalytical phase : low reported frequencies in the primary health care setting
- 2009
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Taylor & Francis. - 0036-5513 .- 1502-7686. ; 69:7, s. 731-735
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Incident reporting is commonly used to improve patient safety. The preanalytical phase of laboratory testing contains several manual error-prone tasks where mistakes can affect patient outcomes. However, the practical use of incident reports in this area has not been previously investigated in the primary health care setting, where the majority of the patients come in contact with health care.MATERIAL AND METHODS: All staff responsible for venous blood sampling in 70 primary health care centres and in two hospital clinical laboratories (317 respondents, response rate 94%) completed a questionnaire.RESULTS: Of the primary health care staff, 69% reported that they had never filed an incident report regarding venous blood sampling. Barriers for not filing incident reports often/always included lack of time (44%) and a complicated reporting procedure (27%). A higher proportion of staff with re-education (43%) had filed at least one incident report as compared to those without re-education (20%, p < 0.001). No differences in incident reporting practices were found between primary health care and hospital clinical laboratory staff.CONCLUSIONS: The investigated incident reporting system is likely to underreport incidents in the preanalytical phase. Therefore, the ability to discover preventable system vulnerabilities needs refinement.
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| 19. |
- Söderberg, Johan, 1980-, et al.
(författare)
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Preanalytical errors in primary healthcare : a questionnaire study of information search procedures, test request management and test tube labelling
- 2009
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Ingår i: Clinical Chemistry and Laboratory Medicine. - : Walter de Gruyter. - 1434-6621 .- 1437-4331. ; 47:2, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- Background: Most errors in laboratory medicine occur in the preanalytical phase and are the result of human mistakes. This study investigated information search procedures, test request management and test tube labelling in primary healthcare compared to the same procedures amongst clinical laboratory staff.Methods: A questionnaire was completed by 317 venous blood sampling staff in 70 primary healthcare centres and in two clinical laboratories (response rate = 94%).Results: Correct procedures were not always followed. Only 60% of the primary healthcare staff reported that they always sought information in the updated, online laboratory manual. Only 12% reported that they always labelled the test tubes prior to drawing blood samples. No major differences between primary healthcare centres and clinical laboratories were found, except for test tube labelling, whereby the laboratory staff reported better practices. Re-education and access to documented routines were not clearly associated with better practices.Conclusions: The preanalytical procedure in the surveyed primary healthcare centres was associated with a risk of errors which could affect patient safety. To improve patient safety in laboratory testing, all healthcare providers should survey their preanalytical procedures and improve the total testing process with a systems perspective.
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| 20. |
- Söderberg, Johan, 1980-
(författare)
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Sources of preanalytical error in primary health care : implications for patient safety
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background Venous blood tests constitute an important part in the diagnosis and treatment of patients. However, test results are often viewed as objective values rather than the end result of a complex process. This has clinical importance since most errors arise before the sample reaches the laboratory. Such preanalytical errors affect patient safety and are often due to human mistakes in the collection and handling of the sample. The preanalytical performance of venous blood testing in primary health care, where the majority of the patients contact with care occurs, has not previously been reported.Aims To investigate venous blood sampling practices and the prevalence of haemolysed blood samples in primary health care.Methods A questionnaire investigated the collection and handling of venous blood samples in primary health care centres in two county councils and in two hospital clinical laboratories. Haemolysis index was used to evaluate the prevalence of haemolysed blood samples sent from primary health care centres, nursing homes and a hospital emergency department.Results and discussion The results indicate that recommended preanalytical procedures were not always followed in the surveyed primary health care centres. For example, only 54% reported to always use name and Swedish identification number, and 5% to use photo-ID, the two recommended means for patient identification. Only 12% reported to always label the test tubes prior to blood collection. This increases the possibility of sample mix-up. As few as 6% reported to always allow the patient to rest at least 15 minutes before blood collection, desirable for a correct test result. Only 31% reported to have filed an incident report regarding venous blood sampling, indicating underreporting of incidents in the preanalytical phase.Major differences in the prevalence of haemolysed blood samples were found. For example, samples collected in the primary health care centre with the highest prevalence of haemolysed samples were six times (95% CI 4.0 to 9.2) more often haemolysed compared to the centre with the lowest prevalence. The significant variation in haemolysed samples is likely to reflect varying preanalytical conditions.Conclusions This thesis indicates that the preanalytical procedure in primary health care is associated with an increased risk of errors with consequences for patient safety and care. Monitoring of haemolysis index could be a valuable tool for estimating preanalytical sample quality. Further studies and interventions aimed at the preanalytical phase in primary health care are clearly needed.
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| 21. |
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| 22. |
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| 23. |
- Westbergh, Petter, 1981, et al.
(författare)
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Noise, distortion and dynamic range of single mode 1.3 µm InGaAs vertical cavity surface emitting lasers for radio-over-fibre links
- 2008
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Ingår i: IET Optoelectronics. - : Institution of Engineering and Technology (IET). - 1751-8768 .- 1751-8776. ; 2:2, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- The analogue modulation characteristics, including second order harmonic and third order intermodulation distortion, relative intensity noise (RIN) and spurious free dynamic range (SFDR), of single mode, GaAs-based 1.28 μm vertical cavity surface emitting laser (VCSELs) with highly strained InGaAs quantum wells have been investigated. The VCSELs utilise an oxide aperture for current and optical confinement and an inverted surface relief (SR) for suppression of higher order transverse modes. The inverted SR structure also has the advantage of suppressing oxide modes that, otherwise, appear in VCSELs with a large detuning of the cavity resonance with respect to the gain peak, which is needed to extend the emission wavelength. RIN levels comparable with those of single mode VCSELs emitting at 850 nm are demonstrated, with values from 140 to 150 dB/Hz in the 2 5 GHz range. SFDR values of 100 and 95 dBHz2/3 are obtained at 2 and 5 GHz, respectively. These values are in the range of those required in radio-over-fibre links.
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| 24. |
- Westbergh, Petter, 1981, et al.
(författare)
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Single mode 1.3 ÎŒm InGaAs VCSELs for access network applications
- 2008
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Ingår i: Semiconductor Lasers and Laser Dynamics III. - : SPIE. ; 6997, s. 69970Y-1-8-
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Konferensbidrag (refereegranskat)abstract
- GaAs-based VCSELs emitting near 1.3 Όm are realized using highly strained InGaAs quantum wells and a large detuning of the cavity resonance with respect to the gain peak. The VCSELs have an oxide aperture for current and optical confinement and an inverted surface relief for suppression of higher-order transverse modes. The inverted surface relief structure also has the advantage of suppressing oxide modes that otherwise appear in VCSELs with a large detuning between the cavity resonance and the gain peak. Under large signal, digital modulation, clear and open eyes and error free transmission over 9 km of single mode fiber have been demonstrated at the OC-48 and 10 GbE bit rates up to 85°C. Here we review these results and present results from a complementary study of the RF modulation characteristics, including second order harmonic and third order intermodulation distortion, relative intensity noise (RIN), and spurious free dynamic range (SFDR). RIN levels comparable to those of single mode VCSELs emitting at 850 nm are demonstrated, with values from -140 to -150 dB/Hz. SFDR values of 100 and 95 dB·Hz2/3 were obtained at 2 and 5 GHz, respectively, which is in the range of those required in radio-over-fiber systems.
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