| 1. |
- Uhlén, Mathias, et al.
(författare)
-
A human protein atlas for normal and cancer tissues based on antibody proteomics
- 2005
-
Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 4:12, s. 1920-1932
-
Tidskriftsartikel (refereegranskat)abstract
- Antibody-based proteomics provides a powerful approach for the functional study of the human proteome involving the systematic generation of protein-specific affinity reagents. We used this strategy to construct a comprehensive, antibody-based protein atlas for expression and localization profiles in 48 normal human tissues and 20 different cancers. Here we report a new publicly available database containing, in the first version, similar to 400,000 high resolution images corresponding to more than 700 antibodies toward human proteins. Each image has been annotated by a certified pathologist to provide a knowledge base for functional studies and to allow queries about protein profiles in normal and disease tissues. Our results suggest it should be possible to extend this analysis to the majority of all human proteins thus providing a valuable tool for medical and biological research.
|
|
| 2. |
- Allström, Andreas, 1978-, et al.
(författare)
-
A hybrid approach for short-term traffic state and travel time prediction on highways
- 2016
-
Ingår i: TRB 95th annual meeting compendium of papers.
-
Konferensbidrag (refereegranskat)abstract
- Traffic management and traffic information are essential in urban areas, and require a good knowledge about both the current and the future traffic state. Both parametric and non-parametric traffic state prediction techniques have previously been developed, with different advantages and shortcomings. While non-parametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during non-recurring traffic conditions such as incidents and events. Hybrid approaches, combining the two prediction paradigms have previously been proposed by using non-parametric methods for predicting boundary conditions used in a parametric method. In this paper we instead combine parametric and non-parametric traffic state prediction techniques through assimilation in an Ensemble Kalman filter. As non-parametric prediction method a neural network method is adopted, and the parametric prediction is carried out using a cell transmission model with velocity as state. The results show that our hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 minutes into the future, using a prediction horizon of up to 50 minutes ahead in time to allow the journey to be completed.
|
|
| 3. |
- Allström, Andreas, 1978-, et al.
(författare)
-
Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways
- 2016
-
Ingår i: Transportation Research Record. - Washington, DC, USA : The National Academies of Sciences, Engineering, and Medicine. - 0361-1981 .- 2169-4052. ; 2554, s. 60-68
-
Tidskriftsartikel (refereegranskat)abstract
- Traffic management and traffic information are essential in urban areas and require reliable knowledge about the current and future traffic state. Parametric and nonparametric traffic state prediction techniques have previously been developed with different advantages and shortcomings. While nonparametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during nonrecurring traffic conditions, such as incidents and events. Hybrid approaches have previously been proposed; these approaches combine the two prediction paradigms by using nonparametric methods for predicting boundary conditions used in a parametric method. In this paper, parametric and nonparametric traffic state prediction techniques are instead combined through assimilation in an ensemble Kalman filter. For nonparametric prediction, a neural network method is adopted; the parametric prediction is carried out with a cell transmission model with velocity as state. The results show that the hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 min into the future, with a prediction horizon of up to 50 min ahead in time to allow the journey to be completed
|
|
| 4. |
- Allström, Andreas, et al.
(författare)
-
Traffic management for smart cities
- 2016
-
Ingår i: Designing, developing, and facilitating smart cities. - Switzerland : Springer. - 9783319449227 - 9783319449241 ; , s. 211-240
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Smart cities, participatory sensing as well as location data available in communication systems and social networks generates a vast amount of heterogeneous mobility data that can be used for traffic management. This chapter gives an overview of the different data sources and their characteristics and describes a framework for utilizing the various sources efficiently in the context of traffic management. Furthermore, different types of traffic models and algorithms are related to both the different data sources as well as some key functionalities of active traffic management, for example short-term prediction and control.
|
|
| 5. |
- Bree, N, et al.
(författare)
-
Shape Coexistence in the Neutron-Deficient Even-Even Hg182-188 Isotopes Studied via Coulomb Excitation.
- 2014
-
Ingår i: Physical Review Letters. - 1079-7114. ; 112:16
-
Tidskriftsartikel (refereegranskat)abstract
- Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.
|
|
| 6. |
- Bzhalava, Davit, et al.
(författare)
-
Deep sequencing extends the diversity of human papillomaviruses in human skin.
- 2014
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4:Jul 24
-
Tidskriftsartikel (refereegranskat)abstract
- Most viruses in human skin are known to be human papillomaviruses (HPVs). Previous sequencing of skin samples has identified 273 different cutaneous HPV types, including 47 previously unknown types. In the present study, we wished to extend prior studies using deeper sequencing. This deeper sequencing without prior PCR of a pool of 142 whole genome amplified skin lesions identified 23 known HPV types, 3 novel putative HPV types and 4 non-HPV viruses. The complete sequence was obtained for one of the known putative types and almost the complete sequence was obtained for one of the novel putative types. In addition, sequencing of amplimers from HPV consensus PCR of 326 skin lesions detected 385 different HPV types, including 226 previously unknown putative types. In conclusion, metagenomic deep sequencing of human skin samples identified no less than 396 different HPV types in human skin, out of which 229 putative HPV types were previously unknown.
|
|
| 7. |
- Bzhalava, Davit, et al.
(författare)
-
Phylogenetically diverse TT virus viremia among pregnant women
- 2012
-
Ingår i: Virology. - : Elsevier BV. - 1096-0341 .- 0042-6822. ; 432:2, s. 427-434
-
Tidskriftsartikel (refereegranskat)abstract
- Infections during pregnancy have been suggested to be involved in childhood leukemias. We used high-throughput sequencing to describe the viruses most readily detectable in serum samples of pregnant women. Serum DNA of 112 mothers to leukemic children was amplified using whole genome amplification. Sequencing identified one TT virus (TTV) isolate belonging to a known type and two putatively new TTVs. For 22 mothers, we also performed ITV amplification by general primer PCR before sequencing. This detected 39 TTVs, two of which were identical to the Tilts found after whole genome amplification. Altogether, we found 40 TTV isolates, 29 of which were putatively new types (similarities ranging from 89% to 69%). In conclusion, high throughput sequencing is useful to describe the known or unknown viruses that are present in serum samples of pregnant women. (C) 2012 Elsevier Inc. All rights reserved.
|
|
| 8. |
- Bzhalava, Davit, et al.
(författare)
-
Unbiased Approach for Virus Detection in Skin Lesions
- 2013
-
Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:6
-
Tidskriftsartikel (refereegranskat)abstract
- To assess presence of virus DNA in skin lesions, swab samples from 82 squamous cell carcinomas of the skin (SCCs), 60 actinic keratoses (AKs), paraffin-embedded biopsies from 28 SCCs and 72 kerathoacanthomas (KAs) and fresh-frozen biopsies from 92 KAs, 85 SCCs and 92 AKs were analyzed by high throughput sequencing (HTS) using 454 or Ion Torrent technology. We found total of 4,284 viral reads, out of which 4,168 were Human Papillomavirus (HPV)-related, belonging to 15 known (HPV8, HPV12, HPV20, HPV36, HPV38, HPV45, HPV57, HPV59, HPV104, HPV105, HPV107, HPV109, HPV124, HPV138, HPV147), four previously described putative (HPV 915 F 06 007 FD1, FA73, FA101, SE42) and two putatively new HPV types (SE46, SE47). SE42 was cloned, sequenced, designated as HPV155 and found to have 76% similarity to the most closely related known HPV type. In conclusion, an unbiased approach for viral DNA detection in skin tumors has found that, although some new putative HPVs were found, known HPV types constituted most of the viral DNA.
|
|
| 9. |
- Bzhalava, Davit, et al.
(författare)
-
Viremia during pregnancy and risk of childhood leukemia and lymphomas in the offspring: Nested case-control study.
- 2016
-
Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 138:9, s. 2212-2220
-
Tidskriftsartikel (refereegranskat)abstract
- A possible role for infections of the pregnant mother in the development of childhood acute leukemias and lymphomas has been suggested. However, no specific infectious agent has been identified. Offspring of 74,000 mothers who had serum samples taken during pregnancy and stored in a large-scale biobank were followed up to the age of 15 years (750,000 person years) through over-generation linkages between the biobank files, the Swedish national population and cancer registers to identify incident leukemia/lymphoma cases in the offspring. First-trimester sera from mothers of 47 cases and 47 matched controls were retrieved and analyzed using next generation sequencing. Anelloviruses were the most common viruses detected, found in 37/47 cases and in 40/47 controls, respectively (OR: 0.6, 95% CI: 0.2-1.9). None of the detected viruses was associated with leukemia/lymphoma in the offspring. Viremia during pregnancy was common, but no association with leukemia/lymphoma risk in the offspring was found.
|
|
| 10. |
- Castellsague, Xavier, et al.
(författare)
-
Prospective seroepidemiologic study on the role of Human Papillomavirus and other infections in cervical carcinogenesis: Evidence from the EPIC cohort
- 2014
-
Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 135:2, s. 440-452
-
Tidskriftsartikel (refereegranskat)abstract
- To evaluate prospectively the association between serological markers of selected infections, including HPV, and risk of developing cervical cancer (CC) and precancer, we performed a nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC) study that included 184 cases of invasive CC (ICC), 425 cases of cervical intraepithelial neoplasia (CIN) grade 3 or carcinoma in situ (CIS), and 1,218 matched control women. At enrollment participants completed lifestyle questionnaires and provided sera. Subjects were followed-up for a median of 9 years. Immunoassays were used to detect serum antibodies to Human Herpes Virus 2 (HHV-2), Chlamydia trachomatis (CT), Chlamydia pneumoniae, L1 proteins of mucosal and cutaneous HPV types, E6/E7 proteins of HPV16/18, as well as to four polyomaviruses. Adjusted odds ratios (OR) [and 95% confidence intervals (CI)] for CIN3/CIS and ICC risk were respectively: 1.6 (1.2-2.0) and 1.8 (1.1-2.7) for L1 seropositivity to any mucosal HPV type, 1.0 (0.4-2.4) and 7.4 (2.8-19.7) for E6 seropositivity to HPV16/18, 1.3 (0.9-1.9) and 2.3 (1.3-4.1) for CT seropositivity, and 1.4 (1.0-2.0) and 1.5 (0.9-2.6) for HHV-2 seropositivity. The highest OR for ICC was observed for HPV16 E6 seropositivity [OR=10.2 (3.3-31.1)]. Increasing number of sexually transmitted infections (STIs) was associated with increasing risk. Non-STIs were not associated with CC risk. In conclusion, this large prospective study confirms the important role of HPV and a possible contribution of CT and HHV-2 in cervical carcinogenesis. It further identifies HPV16 E6 seropositivity as the strongest marker to predict ICC well before disease development. What's New? Limited data are available from prospective studies concerning the role of past exposure to human papillomavirus (HPV) and other infections in cervical carcinogenesis. This study assessed associations between cervical cancer and pre-cancer and serological markers of exposure to mucosal and cutaneous HPVs, Chlamydia trachomatis (CT), Chlamydia pneumonia, human herpes virus-2 (HHV-2), and polyomaviruses using a nested case-control design within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Associations were found for mucosal HPVs, CT, and HHV-2. A greater number of sexually transmitted diseases further raised the risk of cervical cancer.
|
|
| 11. |
- Cederkäll, Joakim, et al.
(författare)
-
Sub-Barrier Coulomb Excitation of ^110Sn and Its Implications for the ^100Sn Shell Closure
- 2007
-
Ingår i: Physical Review Letters. - 1079-7114. ; 98:17, s. 172501-
-
Tidskriftsartikel (refereegranskat)abstract
- The first excited 2+ state of the unstable isotope 110Sn has been studied in safe Coulomb excitation at 2.82 MeV/u using the MINIBALL array at the REX-ISOLDE post accelerator at CERN. This is the first measurement of the reduced transition probability of this state using this method for a neutron deficient Sn isotope. The strength of the approach lies in the excellent peak-to-background ratio that is achieved. The extracted reduced transition probability, B(E2:0+-->2+)=0.220±0.022e2b2, strengthens the observation of the evolution of the B(E2) values of neutron deficient Sn isotopes that was observed recently in intermediate-energy Coulomb excitation of 108Sn. It implies that the trend of these reduced transition probabilities in the even-even Sn isotopes is not symmetric with respect to the midshell mass number A=116 as 100Sn is approached.
|
|
| 12. |
|
|
| 13. |
- DiJulio, Douglas, et al.
(författare)
-
Coulomb excitation of In-107
- 2013
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:1
-
Tidskriftsartikel (refereegranskat)abstract
- The radioactive isotope In-107 was studied using sub-barrier Coulomb excitation at the REX-ISOLDE facility at CERN. Two gamma rays were observed during the experiment, corresponding to the low-lying 11/2(+) and 3/2(-)states. The reduced transition probability of the 11/2(+) state was determined with the semiclassical Coulomb excitation code GOSIA2. The result is discussed in comparison to large-scale shell-model calculations, previous unified-model calculations, and earlier Coulomb excitation measurements in the odd-mass In isotopes. DOI: 10.1103/PhysRevC.87.017301
|
|
| 14. |
- DiJulio, Douglas, et al.
(författare)
-
Electromagnetic properties of vibrational bands in Er-170
- 2011
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 47:2, s. 25-
-
Tidskriftsartikel (refereegranskat)abstract
- Excited states of the nucleus Er-170 have been studied by Coulomb excitation using the GASP gamma-ray detector system at the Laboratori Nazionali di Legnaro. The ground-state band along with a low-lying K-pi = 0(+) band and gamma-vibrational band were populated during the experiment. Based on the measured gamma-ray yields, a set of interband and intraband matrix elements has been extracted using the Coulomb excitation code GOSIA. The resulting E2 matrix elements are compared to collective model predictions.
|
|
| 15. |
- DiJulio, Douglas, et al.
(författare)
-
Excitation strengths in Sn-109: Single-neutron and collective excitations near Sn-100
- 2012
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 86:3
-
Tidskriftsartikel (refereegranskat)abstract
- A set of B(E2) values for the low-lying excited states in the radioactive isotope Sn-109 were deduced from a Coulomb excitation experiment. The 2.87-MeV/u radioactive beam was produced at the REX-ISOLDE facility at CERN and was incident on a secondary Ni-58 target. The B(E2) values were determined using the known 2(+) -> 0(+) reduced transition probability in Ni-58 as normalization with the semiclassical Coulomb excitation code GOSIA2. The transition probabilities are compared to shell-model calculations based on a realistic nucleon-nucleon interaction and the predictions of a simple core-excitation model. This measurement represents the first determination of multiple B(E2) values in a light Sn nucleus using the Coulomb excitation technique with low-energy radioactive beams. The results provide constraints for the single-neutron states relative to Sn-100 and also indicate the importance of both single-neutron and collective excitations in the light Sn isotopes.
|
|
| 16. |
- DiJulio, Douglas, et al.
(författare)
-
Shell model based Coulomb excitation gamma-ray intensity calculations in Sn-107
- 2012
-
Ingår i: Physica Scripta. - 0031-8949. ; T150
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we present recent shell model calculations, based on a realistic nucleon-nucleon interaction, for the light Sn-107,Sn-109 nuclei. By combining the calculations with the semi-classical Coulomb excitation code GOSIA, a set of gamma-ray intensities has been generated. The calculated intensities are compared with the data from recent Coulomb excitation studies in inverse kinematics at the REX-ISOLDE facility with the nucleus Sn-107. The results are discussed in the context of the ordering of the single-particle orbits relative to Sn-100.
|
|
| 17. |
- DiJulio, Douglas, et al.
(författare)
-
Sub-barrier Coulomb excitation of Sn-107
- 2012
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 381, s. 012073-012073
-
Konferensbidrag (refereegranskat)abstract
- A Coulomb excitation experiment in inverse kinematics has been carried out at the REX-ISOLDE facility in order to study the properties of low-lying excited states in Sn-107. The measured gamma ray spectrum has been compared with predicted gamma ray spectra from a combined shell-model and GOSIA analysis. In this approach, a set of matrix elements, generated within the shell-model framework, based on a realistic nucleon-nucleon interaction and a set of single-particle energies relative to Sn-100, is used as input. Comparison between the calculated and predicted spectra can be used to help identify the placement of the single-neutron states in Sn-101. In particular, the results can potentially provide clues on the ordering of the two lowest-lying orbits; the g(7/2) and d(5/2) states.
|
|
| 18. |
- Diriken, J., et al.
(författare)
-
Coulomb excitation of Ga-73
- 2010
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 82:6
-
Tidskriftsartikel (refereegranskat)abstract
- The B(E2; I-i -> I-f) values for transitions in Ga-71(31)40 and Ga-73(31)42 were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of Ga-71,Ga-73 at the REX-ISOLDE on-line isotope mass separator facility. The emitted gamma rays were detected by the MINIBALL gamma-detector array, and B(E2; I-i -> I-f) values were obtained from the yields normalized to the known strength of the 2(+) -> 0(+) transition in the Sn-120 target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N = 40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N = 40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2(-) spin and parity for the ground state, the extracted results revealed evidence for a 1/2(-), 3/2(-) doublet near the ground state in Ga-73(31)42 differing by at most 0.8 keV in energy.
|
|
| 19. |
- Doornenbal, P., et al.
(författare)
-
Enhanced strength of the 2(1)(+) -> 0(g.s.)(+) transition in Sn-114 studied via Coulomb excitation in inverse kinematics
- 2008
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 78:3
-
Tidskriftsartikel (refereegranskat)abstract
- The 2(1)(+) states of Sn-114,Sn-116 were excited in two consecutive experiments by means of Coulomb excitation in inverse kinematics on a Ni-58 target. A precise determination of the reduced transition probability B(E2; 0(g.s.)(+) -> 2(1)(+)) of Sn-114 relative to the well-known 2(1)(+) excitation strength in Sn-116 was achieved by comparing the relative projectile to target 2(1)(+) -> 0(g.s.)(+) decay intensities. The obtained B(E2 up arrow) value of 0.232(8)e(2)b(2) for Sn-114 confirms the tendency of large B(E2 up arrow) values for the light tin isotopes below the midshell Sn-116 that has been observed recently in various radioactive ion beam experiments. The result establishes most clearly the discrepancy between the current B(E2 up arrow) value predictions from large-scale shell-model calculations and the experimental deviation, which commences already for the stable Sn-114 isotope.
|
|
| 20. |
- Edsjö, Joakim, et al.
(författare)
-
WIMP searches with AMANDA-B10
- 2001
-
Ingår i: The Identification Of Dark Matter. - : World Scientific. - 9789810246020 ; , s. 499-505
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 21. |
- Ekström, Andreas, et al.
(författare)
-
0(gs)+ -->2(1)+ transition strengths in 106Sn and 108Sn.
- 2008
-
Ingår i: Physical Review Letters. - 1079-7114. ; 101:1
-
Tidskriftsartikel (refereegranskat)abstract
- The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.
|
|
| 22. |
- Ekström, Andreas, et al.
(författare)
-
Coulomb excitation of Sn-110 using REX-ISOLDE
- 2006
-
Ingår i: Physica Scripta. - 1402-4896 .- 0031-8949. ; T125, s. 190-191
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we report the preliminary result from the first Coulomb excitation experiment at REX-ISOLDE (Habs et al 1998 Nucl. Instrum. Methods B 139 128) using neutron-deficient Sn-beams. The motivation of the experiment is to deduce the reduced transition probability, B(E2; 2(+) -> 0(+)), for the sequence of neutron deficient, unstable, even-even Sn- isotopes from Sn-110 to ultimately Sn-110. Safe Coulomb excitation using a radioactive beam opens up a new path to study the lifetime of the first excited 2(+) state in these isotopes. The de-excitation path following fusion-evaporation reactions will for the even-even Sn isotopes pass via an isomeric 6(+) state, located at higher energy, which thus hampers measurements of the lifetime of the first excited state using, e. g., recoil-distance methods. For this reason the reduced transition probability of the first excited 2(+) state has remained unknown in this chain of isotopes although the B(E2) value of the stable isotope Sn-112 was measured approximately 30 years ago (see, e. g., Stelson et al 1970 Phys. Rev. C 2 2015). Our experiment is thus the first to accomplish a measurement of this quantity in Sn-110. It is believed that the determination of the B(E2) value in Sn-110 will indicate the turnover point from a trend of increasing B(E2) values for the heavier isotopes to a trend characterized by less collectivity. Our first preliminary result indicates that this assumption may well be correct.
|
|
| 23. |
- Ekström, Andreas, et al.
(författare)
-
Coulomb excitation of the odd-odd isotopes In-106,In-108
- 2010
-
Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 44:3, s. 355-361
-
Tidskriftsartikel (refereegranskat)abstract
- The low-lying states in the odd-odd and unstable isotopes In-106,In-108 have been Coulomb excited from the ground state and the first excited isomeric state at the REX-ISOLDE facility at CERN. With the additional data provided here the pi g(9/2)(-1) circle times nu d(5/2) and pi g(9/2)(-1) circle times nu g7/2 multiplets have been re-analyzed and are modified compared to previous results. The observed gamma-ray de-excitation patterns were interpreted within a shell model calculation based on a realistic effective interaction. The agreement between theory and experiment is satisfactory and the calculations reproduce the observed differences in the excitation pattern of the two isotopes. The calculations exclude a 6(+) ground state in In-106. This is in agreement with the conclusions drawn using other techniques. Furthermore, based on the experimental results, it is also concluded that the ordering of the isomeric and ground state in In-108 is inverted compared to the shell model prediction. Limits on B(E2) values have been extracted where possible. A previously unknown low-lying state at 367 keV in In-106 is also reported.
|
|
| 24. |
- Ekström, Andreas, et al.
(författare)
-
Determination of the isomeric fraction in a postaccelerated radioactive ion beam using the coupled decay-chain equations
- 2010
-
Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 614:2, s. 303-307
-
Tidskriftsartikel (refereegranskat)abstract
- A method based on the coupled decay-chain equations for extracting the isotopic and the isomeric composition of a postaccelerated radioactive ion beam is presented and demonstrated on a data set from a Coulomb excitation experiment. This is the first attempt of analyzing the content of a postaccelerated radioactive ion beam using this technique. The beam composition is required for an absolute normalization of the measurement. The strength of the method, as compared to present online-based methods, lies in the determination of the isomeric fraction of a partially isomeric beam using all data accumulated during the experiment. We discuss the limitations and sensitivity of the method with respect to the gamma-ray detection efficiency and the accumulated flux. (C) 2010 Elsevier B.V. All rights reserved.
|
|
| 25. |
- Ekström, Andreas, et al.
(författare)
-
Electric quadrupole moments of the 2(1)(+) states in Cd-100,Cd-102,Cd-104
- 2009
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:5
-
Tidskriftsartikel (refereegranskat)abstract
- Using the REX-ISOLDE facility at CERN the Coulomb excitation cross sections for the 0(gs)(+)-> 2(1)(+) transition in the beta-unstable isotopes Cd-100,Cd-102,Cd-104 have been measured for the first time. Two different targets were used, which allows for the first extraction of the static electric quadrupole moments Q(2(1)(+)) in Cd-102,Cd-104. In addition to the B(E2) values in Cd-102,Cd-104, a first experimental limit for the B(E2) value in Cd-100 is presented. The data was analyzed using the maximum likelihood method. The provided probability distributions impose a test for theoretical predictions of the static and dynamic moments. The data are interpreted within the shell-model using realistic matrix elements obtained from a G-matrix renormalized CD-Bonn interaction. In view of recent results for the light Sn isotopes the data are discussed in the context of a renormalization of the neutron effective charge. This study is the first to use the reorientation effect for post-accelerated short-lived radioactive isotopes to simultaneously determine the B(E2) and the Q(2(1)(+)) values.
|
|
| 26. |
- Ekström, Andreas, et al.
(författare)
-
Sub-barrier Coulomb excitation of Sn-106,Sn-108,Sn-110
- 2008
-
Ingår i: Frontiers in Nuclear structure, Astrophysics and Reactions - Finustar 2, AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. ; 1012, s. 296-299
-
Konferensbidrag (refereegranskat)abstract
- The reduced transition probabilities between the first excited 2(+) state and the 0(+) ground state, B(E2; 0(+) -> 2(+)), have been measured in Sn-106,Sn-108,Sn-110 using sub-barrier Coulomb excitation in inverse kinematics at REX-ISOLDE. The results are, B(E2;0(+) -> 2(+)) = 0.220(22),0.226(17), and 0.228(32) e(2)b(2), for Sn-110, Sn-108, and Sn-106, respectively. The results for Sn-106,Sn-108 are preliminary. De-excitation gamma-rays were detected by the MINIBALL Ge-array. The B(E2) reveals detailed information about the nuclear wave function. A shell model prediction based on an effective CD-Bonn interaction in the nu(0g(7/2),2s, 1d, 0h(11/2)) model space using e(eff)(nu) =1.0 e follows the experimental values for the neutron rich Sn isotopes, but fails to reproduce the results presented here.
|
|
| 27. |
- Ekström, Joakim, 1982-
(författare)
-
A generalized definition of the polychoric correlation coefficient
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We generalize the polychoric correlation coefficient to a large class of parametric families of bivariate distributions. The generalized definition agrees with the conventional definition on the family of bivariate normal distributions, and with the generalized tetrachoric correlation coefficient for dichotomous variables. Furthermore, we provide some suggestions for goodness-of-fit tests. The theory is illustrated with examples, which show that the distributional assumption can have a substantial impact on the conclusions of the association analysis.
|
|
| 28. |
- Ekström, Joakim, 1982-
(författare)
-
A generalized definition of the tetrachoric correlation coefficient
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We generalize the tetrachoric correlation coefficient to a large class of parametric families of bivariate distributions. We also show that the generalized definition agrees with the conventional definition on the family of bivariate normal distributions. Furthermore, we provide a necessary and sufficient condition for the generalized tetrachoric correlation coefficient to be well defined for a given family of distributions, and some sufficient criteria which can be useful for practical purposes. Moreover, we illustrate with examples how the distributional assumption can have a profound impact on the conclusions of the association analysis. Using S&P 100 stock data, we exemplify the fact that a correct distributional assumption is vitally important for the analysis. Consequently, it is concluded that the tetrachoric correlation coefficient is not robust to changes of the distributional assumption.
|
|
| 29. |
- Ekström, Joakim, 1980-, et al.
(författare)
-
A heuristic method for finding congestion pricing schemes in transportation networks with modal choice
- 2008
-
Ingår i: International conference of Hong Kong society for transportation studies,2008. - Hong Kong, China : Hong Kong Society of Transportation Studies Ltd.. - 9789889884734 ; , s. 773-782
-
Konferensbidrag (refereegranskat)abstract
- In this paper we extend a previously developed heuristic procedure, with a modal choice model, to solve the congestion pricing problem of simultaneously finding the optimal number of toll facilities, their corresponding location and toll levels. When considering a congestion pricing scheme the cost of collecting the tolls can not be disregarded. The objective is where-fore to maximize the net social surplus, which is the social surplus minus the cost of collect-ing the tolls. The heuristic method is an iterative solution procedure, in which the integer part of the objec-tive function is approximated by a continuous function. A version of the Sioux Falls network (76 links) is used to demonstrate the solution procedure. The solution is a congestion pricing scheme which divide the network into four zones, by locating tolls on 27 links. This solution yields a social surplus which is only 13.5% lower than the marginal social cost pricing solu-tion.
|
|
| 30. |
- Ekström, Joakim, 1980-
(författare)
-
A MILP approximation approach for finding optimal toll locations and levels in elastic demand traffic networks
- 2010
-
Ingår i: TRANSPORTATION AND URBAN SUSTAINABILITY. - Hong Kong, China : Hong Kong Society for Transportation Studies. - 9789889884789 ; , s. 107-114
-
Konferensbidrag (refereegranskat)abstract
- The toll design problem (TDP) is to find optimal toll locations and corresponding toll levels in a congestion pricing scheme. The TDP can be formulated as a non-convex mathematical program, in which the road users are assumed to be distributed according to a user-equilibrium with elastic demand. This program is hard to solve due to non-convexity and non-smoothness. In this paper, the TDP is approximated by a mixed integer linear program (MILP), in which the non-linear functions of the TDP are approximated by piecewise linear ones. The MILP can be solved to its global optimal solution by known methods, and its optimal solution will give a lower bound on the optimal solution to the TDP. By iteratively updating the MILP approximation, the error introduced by the approximation is reduced, and for a test network with nine nodes and 18 links, the global optimal solution is obtained.
|
|
| 31. |
- Ekström, Joakim, 1982-
(författare)
-
An empirical polychoric correlation coefficient
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We propose a new measure of association for ordinal variables. The new measure of association, named the empirical polychoric correlation coefficient, builds upon the polychoric correlation coefficient, but relaxes its fundamental assumption so that an underlying distribution is only assumed to exist, not to be of a particular parametric family. The empirical polychoric correlation coefficient has properties that are superior to those of the polychoric correlation coefficient; it rests on weaker assumptions, it is well defined for every contingency table, and it converges almost surely to the correct theoretical polychoric correlation. Consequentially, the empirical polychoric correlation coefficient is theoretically robust to changes of the distributional assumption, unlike the polychoric correlation coefficient. A simulation study confirms that the empirical coefficient is considerably more robust than the polychoric correlation coefficient, and it also indicates that it has lower standard deviation.
|
|
| 32. |
- Ekström, Joakim, 1980-
(författare)
-
Comparison of usage-based congestion pricing schemes
- 2018
-
Ingår i: Proceedings Transportation Research Board 97th Annual Meeting. - Washington D.C..
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates how usage-based pricing can be applied in order to improve the efficiency of the transportation system. Distance-based, travel time-based and delayed-based pricing schemes are investigated, both from a one-link and network perspective. A static modeling framework is adopted, based on user-equilibrium, and a simplified emission model based on the HBEFA emission model is used. Optimal usage-based fees are calculated using a surrogate-based optimization framework, and determination of zone layout is done using k-means clustering. The results for a Stockholm region network show that already with network wide pricing a large proportion of the maximum improvement of social surplus achievable with first-best pricing, can be reached. Delay-based pricing, in which the users are charged based on the excess travel time in comparison to free flow travel times, achieves 99% of the maximum improvement, already with one single fee across the whole network. With clustering of links based on their first-best optimal fees, the benefits of both distance and travel time-based fees can significantly be improved.
|
|
| 33. |
- Ekström, Joakim, 1982-
(författare)
-
Contributions to the Theory of Measures of Association for Ordinal Variables
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we consider measures of association for ordinal variables from a theoretical perspective. In particular, we study the phi-coefficient, the tetrachoric correlation coefficient and the polychoric correlation coefficient. We also introduce a new measure of association for ordinal variables, the empirical polychoric correlation coefficient, which has better theoretical properties than the polychoric correlation coefficient, including greatly enhanced robustness. In the first article, entitled ``On the relation between the phi-coefficient and the tetrachoric correlation coefficient'', we show that under given marginal probabilities there exists a continuous bijection between the two measures of association. Furthermore, we show that the bijection has a fixed point at zero for all marginal probabilities. Consequently, the choice of which of these measures of association to use is for all practical purposes a matter of preference only. In the second article, entitled ``A generalized definition of the tetrachoric correlation coefficient'', we generalize the tetrachoric correlation coefficient so that a large class of parametric families of bivariate distributions can be assumed as underlying distributions. We also provide a necessary and sufficient condition for the generalized tetrachoric correlation coefficient to be well defined for a given parametric family of bivariate distributions. With examples, we illustrate the effects on the polychoric correlation coefficient of different distributional assumptions. In the third article, entitled ``A generalized definition of the polychoric correlation coefficient'', we generalize the polychoric correlation coefficient to a large class of parametric families of bivariate distributions, and show that the generalized and the conventional polychoric correlation coefficients agree on the family of bivariate normal distributions. With examples, we illustrate the effects of different distributional assumptions on the polychoric correlation coefficient. In combination with goodness-of-fit p-values, the association analysis can be enriched with a consideration of possible tail dependence. In the fourth article, we propose a new measure of association for ordinal variables, named the empirical polychoric correlation coefficient. The empirical polychoric correlation coefficient relaxes the fundamental assumption of the polychoric correlation coefficient so that an underlying joint distribution is only assumed to exist, not to be of a particular parametric family. We also provide an asymptotical result, by which the empirical polychoric correlation coefficient converges almost surely to the true polychoric correlation under very general conditions. Thus, the proposed empirical polychoric correlation coefficient has better theoretical properties than the polychoric correlation coefficient.
|
|
| 34. |
- Ekström, Johanna, et al.
(författare)
-
Cutaneous human papillomavirus 88: Remarkable differences in viral load.
- 2008
-
Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 122:2, s. 477-480
-
Tidskriftsartikel (refereegranskat)abstract
- A human papillomavirus (HPV) was cloned from a patient with multiple squamous cell carcinomas (SCCs) and identified as HPV88, recently categorized into a new species within the genus Gamma. The HPV88 viral load in an SCC of the index patient exceeded 1 million copies/cell. By contrast, a survey of 447 skin lesions (79 actinic keratoses, 73 seborrhoeic keratoses, 169 basal cell carcinomas and 126 SCCs) and 362 healthy skin biopsies found detectable HPV88 DNA in only 7 specimens. All these had very low viral loads (<1 copy/10(3) cells) implying extreme biological variability in viral load.
|
|
| 35. |
|
|
| 36. |
- Ekström, Joakim, 1980-, et al.
(författare)
-
Decision support for finding locations and toll levels within a congestion pricing scheme
- 2008
-
Ingår i: Transportation Research Board Annual Meeting,2008. - Washington D.C. : TRB.
-
Konferensbidrag (refereegranskat)abstract
- Designing a congestion pricing scheme involves a number of complex decisions. Focusing on the quantitative parts of a congestion pricing system with link tolls, the problem involves finding the number of tolled links, the link toll locations and their corresponding toll level and schedule. In this paper, we develop and evaluate methods for finding a most efficient design of a congestion pricing scheme in a road network with elastic demand. The design efficiency is measured by the net social surplus, which is computed as the difference between the social surplus and the collection costs (i.e. setup and operation cost) of the congestion pricing system. The problem of finding such a scheme is stated as a combinatorial bi-level optimization problem. On the upper level we maximize the net social surplus and on the lower level we solve a user equilibrium problem with elastic demand, given the toll locations and toll levels, to simulate the user response. We modify a known heuristic procedure for finding the optimal locations and toll levels given a fixed number of tolls to locate, to find the optimal number of tolls to locate as well. A new heuristic procedure is also presented which is based on repeated solutions of a continuous approximation of the combinatorial problem. Numerical results for two small scale test networks are presented. Both methods perform satisfactory on the two networks. Comparing the two methods, the iterative approximation procedure is the one which shows the best results. The results are compared to solutions obtained by an exhaustive search.
|
|
| 37. |
|
|
| 38. |
- Ekström, Joakim, 1980-
(författare)
-
Designing Urban Road Congestion Charging Systems : Models and Heuristic Solution Approaches
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The question of how to design a congestion pricing scheme is difficult to answer and involves a number of complex decisions. This thesis is devoted to the quantitative parts of designing a congestion pricing scheme with link tolls in an urban car traffic network. The problem involves finding the number of tolled links, the link toll locations and their corresponding toll level. The road users are modeled in a static framework, with elastic travel demand.Assuming the toll locations to be fixed, we recognize a level setting problem as to find toll levels which maximize the social surplus. A heuristic procedure based on sensitivity analysis is developed to solve this optimization problem. In the numerical examples the heuristic is shown to converge towards the optimum for cases when all links are tollable, and when only some links are tollable.We formulate a combined toll location and level setting problem as to find both toll locations and toll levels which maximize the net social surplus, which is the social surplus minus the cost of collecting the tolls. The collection cost is assumed to be given for each possible toll location, and to be independent of toll level and traffic flow. We develop a new heuristic method which is based on repeated solutions of an approximation to the combined toll location and level setting problem. Also, a known heuristic method for locating a fixed number of toll facilities is extended, to find the optimal number of facilities to locate. Both heuristics are evaluated on two small networks, where our approximation procedure shows the best results.Our approximation procedure is also employed on the Sioux Falls network. The result is compared with different judgmental closed cordon structures, and the solution suggested by our method clearly improves the net social surplus more than any of the judgmental cordons.
|
|
| 39. |
- Ekström, Johanna, et al.
(författare)
-
Diversity of human papillomaviruses in skin lesions
- 2013
-
Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 447:1-2, s. 300-311
-
Tidskriftsartikel (refereegranskat)abstract
- Pools of frozen biopsies from patients with squamous cell carcinoma (SCC) (n=29) actinic keratosis (AK) (n=31), keratoacanthoma (n=91) and swab samples from 84 SCCs and 91 AKs were analysed with an extended HPV general primer PCR and high-throughput sequencing of amplimers. We found 273 different HPV isolates (87 known HPV types, 139 previously known HPV sequences (putative types) and 47 sequences from novel putative HPV types). Among the new sequences, five clustered in genus Betapapillomavirus and 42 in genus Gammapapillomavirus. Resequencing of the three pools between 21 to 70 times resulted in the detection of 283 different known or putative HPV types, with 156 different sequences found in only one of the pools. Type-specific PCRs for 37 putative types from an additional 296 patients found only two of these putative types. In conclusion, skin lesions contain a large diversity of HPV types, but most appeared to be rare infections. (C) 2013 Elsevier Inc. All rights reserved.
|
|
| 40. |
- Ekström, Joakim, 1982-, et al.
(författare)
-
Exact Probability Distribution for the ROC Area under Curve
- 2023
-
Ingår i: Cancers. - : MDPI. - 2072-6694. ; 15:6
-
Tidskriftsartikel (refereegranskat)abstract
- Simple Summary This contribution allows for the computation of exact p-values and for conducting accurate statistical hypothesis tests of ROC AUC-values. As a result, the development of diagnostic tests is facilitated. This work is illustrated via simulated data and through the development of proteomic blood biomarkers for the early detection of cancer. The Receiver Operating Characteristic (ROC) is a de facto standard for determining the accuracy of in vitro diagnostic (IVD) medical devices, and thus the exactness in its probability distribution is crucial toward accurate statistical inference. We show the exact probability distribution of the ROC AUC-value, hence exact critical values and p-values are readily obtained. Because the exact calculations are computationally intense, we demonstrate a method of geometric interpolation, which is exact in a special case but generally an approximation, vastly increasing computational speeds. The method is illustrated through open access data, demonstrating superiority of 26 composite biomarkers relative to a predicate device. Especially under correction for testing of multiple hypotheses, traditional asymptotic approximations are encumbered by considerable imprecision, adversely affecting IVD device development. The ability to obtain exact p-values will allow more efficient IVD device development.
|
|
| 41. |
|
|
| 42. |
- Ekström, Joakim, 1980-
(författare)
-
Finding second-best toll locations and levels by relaxing the set of first-best feasible toll vectors
- 2014
-
Ingår i: European Journal of Transport and Infrastructure Research. - : Technische Universiteit Delft. - 1567-7133 .- 1567-7141. ; 14:1, s. 7-29
-
Tidskriftsartikel (refereegranskat)abstract
- This paper provides a framework for optimizing toll locations and levels in congestion pricing schemes for large urban road networks, with the objective to maximize the social surplus. This optimization problem is referred to as the toll location and level setting problem (TLLP) and is both non-convex, non-smooth and involves binary decision variables, and is therefore considered as a hard problem to solve. In this paper a solution approach is provided which instead of directly solving the TLLP, makes use of the first-best toll level solution, in which no restrictions are imposed on toll locations or levels. A first-best pricing scheme can be obtained by solving a convex program, and it has previously been shown that for the used routes in the network, the first-best toll levels on a route level are unique. By formulating an optimization problem, which instead of maximizing the social surplus, tries to find the link toll levels which minimize the deviation from first-best route tolls, a mixed integer linear program is obtained, and if the toll locations are predetermined the resulting optimization problem is a linear program.The approach of minimizing the deviation from first--best route tolls is applied for two different network models, and results are provided to show the applicability of the approach, as well as to compare with other approaches. Also, it is shown that for the Stockholm network, virtually the first-best level of social surplus can be obtained with a significantly reduced number of located tolls.
|
|
| 43. |
- Ekström, Joakim, 1980-, et al.
(författare)
-
Heuristic algorithms for a second-best congestion pricing problem
- 2009
-
Ingår i: Netnomics. - : Springer Science and Business Media LLC. - 1385-9587 .- 1573-7071. ; 10:1, s. 85-102
-
Tidskriftsartikel (refereegranskat)abstract
- Designing a congestion pricing scheme involves a number of complex decisions.Focusing on the quantitative parts of a congestion pricing system with link tolls, the problem involves findingthe number of toll links, the link toll locations and their corresponding toll level and schedule.In this paper, we develop and evaluate methods for finding the most efficient design for a congestion pricing scheme in a road network model with elastic demand. The design efficiency is measured by the net social surplus, which is computed as the difference between the social surplus and the collection costs (i.e. setup and operational costs) of the congestion pricing system. The problem of finding such a scheme is stated as a combinatorial bi-level optimization problem. At the upper level, we maximize the net social surplus and at the lower level we solve a user equilibrium problem with elastic demand, given the toll locations and toll levels,to simulate the user response. We modify a known heuristic procedure for finding the optimal locations and toll levels given a fixed number of tolls to locate, to find the optimal number of toll facilities as well. A new heuristic procedure, based on repeated solutions of a continuous approximation of the combinatorial problem is also presented. Numerical results for two small test networks are presented. Both methods perform satisfactorily on the two networks. Comparing the two methods, we find that the continuous approximation procedure is the one which shows the best results.
|
|
| 44. |
- Ekström, Johanna, et al.
(författare)
-
High throughput sequencing reveals diversity of human papillomaviruses in cutaneous lesions.
- 2011
-
Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 129, s. 2643-2650
-
Tidskriftsartikel (refereegranskat)abstract
- There are at least 120 completely characterized human papillomavirus (HPV) types and putative new types are continuously found. Both squamous cell carcinoma of the skin (SCC) and other skin lesions commonly contain multiple cutaneous HPV types. The objective of this study was to achieve an improved resolution of the diversity of HPV types in lesions such as SCCs, actinic keratoses (AKs) and keratoacanthomas (KAs). Fresh frozen biopsies from 37 SCC lesions, 36 AK lesions and 92 KA lesions and swab samples from the top of the lesion from 86 SCCs and 92 AKs were amplified using the general HPV primers FAP and mixed to three pools followed by high throughput sequencing. We obtained 2196 reads with homology to HPV. In the pool of SCC/AK biopsies 48 different HPV types were found. Eighty-three types were found in the pool of SCC/AK swab samples and 64 types in the KA biopsies, respectively. For 9 novel putative HPV types most of the amplimer sequence was obtained, whereas for an additional 35 novel putative HPV types only partial amplimer sequences were obtained. Most of the novel putative types belonged to the genus Gamma. In conclusion, high throughput sequencing was an effective means to identify both known and previously unknown HPV types in putatively HPV-associated lesions and has revealed an extended diversity of HPV types.
|
|
| 45. |
- Ekström, Joakim, et al.
(författare)
-
Metodik för beräkning av emissioner baserat på trafikdata från dynamiska trafikmodeller och trafikmätningar
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet syftade till att ta fram en metod för tillämpning av HBEFA på trafikdata från mätningar och dynamiska trafikmodeller på ett sätt som är konsistent med den tillämpning av HBEFA som idag sker med statisk trafikdata. Projektet fokuserade främst på tillämpningar där lokala emissioner från vägtrafik är av intresse. Exempel på sådana tillämpningar är uppföljning, estimering och prediktering av luftkvalitet. Men även analys av förändring av utsläpp från vägtrafiken över tid, samt före/efter studier vid förändringar av trafikinfrastrukturen. I HBEFA är skattning av trafiktillstånd centralt för estimering av emissioner. I denna studie har vi studerat och jämfört tre olika sätt att definiera trafiktillståndet i HBEFAs trafiksituationer nämligen baserat på:flöde (det som används i nuläget)hastighetdensitetFlödesbaserade definitioner har en inbyggd begränsning i att de inte entydigt kan beskriva trafiksituationen, då lågt flöde kan innebära både låg trängsel och hög trängsel, beroende på hastighet. Detta är inget problem i nuvarande tillämpning av HBEFA med statisk trafikdata, då en förenklad beskrivning av det överbelastade fallet görs, som tillåter flöden över kapaciteten, men som då representerar en efterfrågan snarare än flöde. Undersökningarna i denna studie indikerar att en hastighetsbaserad definition av trafiktillstånd inte är att föredra då hastigheten kan variera relativt mycket mellan olika fordon och över en sträcka vid liknande flödes- och densitetsförhållanden. Hastighetsbaserade gränser mellan trafiktillstånd blir främst problematiskt vid tillämpning på mätdata. Vid hastighetsbaserade gränser blir varje fordonspassage med låg hastighet automatiskt klassade i ett trafiktillstånd som innebär trängsel. Densitet är ett mer stabilt mått vid liknande trafikförhållanden och kan sägas bättre definiera graden av trängsel i trafikteoretisk mening.
|
|
| 46. |
- Ekström, Joakim, 1980-, et al.
(författare)
-
Metodik för beräkning av emissioner baserat på trafikdata från dynamiska trafikmodeller och trafikmätningar
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Dynamiska trafikmodeller förväntas i större utsträckning komplettera och på sikt helt eller delvis ersätta statiska trafikmodeller. Samtidigt blir trafikmätningar mer och mer tillgängliga, och utifrån dessa kan tidsvarierade estimeringar av flöden och hastighet över större områden tas fram. I Sverige används idag HBEFA för estimering av emissioner. HBEFA är en EU-gemensam modell som används i flera europeiska länder för beräkning av luftföroreningar och bränsleförbrukning. Detta projekt syftar till att ta fram en metod för tillämpning av HBEFA på trafikdata från mätningar och dynamiska trafikmodeller på ett sätt som är konsistent med den tillämpning av HBEFA som idag sker med statisk trafikdata. Projektet fokuserar främst på tillämpningar där lokala emissioner från vägtrafik är av intresse. Exempel på sådana tillämpningar är uppföljning, estimering och prediktering av luftkvalitet. Men även analys av förändring av utsläpp från vägtrafiken över tid, samt före/efter studier vid förändringar av trafikinfrastrukturen. Detta kräver att den tillämpade beräkningsmetodiken för utsläpp anpassas för att kunna dra nytta av den rikare information som dynamisk trafikdata innehåller.I HBEFA är skattning av trafiktillstånd centralt för estimering av emissioner. I denna studie har vi studerat och jämfört tre olika sätt att definiera trafiktillståndet i HBEFAstrafiksituationer nämligen baserat på: flöde (det som används i nuläget), hastighet och densitet. Flödesbaserade definitioner har en inbyggd begränsning i att de inte entydigt kan beskriva trafiksituationen, då lågt flöde kan innebära både låg trängsel och hög trängsel, beroende på hastighet. Detta är inget problem i nuvarande tillämpning av HBEFA med statisk trafikdata, då en förenklad beskrivning av det överbelastade fallet görs, som tillåter flöden över kapaciteten, men som då representerar en efterfrågan snarare än flöde. Undersökningarna i denna studieindikerar att en hastighetsbaserad definition av trafiktillstånd inte är att föredra då hastigheten kan variera relativt mycket mellan olika fordon och över en sträcka vid liknande flödes- och densitetsförhållanden. Hastighetsbaserade gränser mellan trafiktillstånd blir främst problematiskt vid tillämpning på mätdata. Vid hastighetsbaserade gränser blir varje fordonspassage med låg hastighet automatiskt klassade i ett trafiktillstånd som innebär trängsel. Densitet är ett mer stabilt mått vid liknande trafikförhållanden och kan sägas bättre definiera graden av trängsel i trafikteoretisk mening. En densitetsbaserad definition kan entydigt bestämma samtliga trafiktillstånd, till skillnad från en flödesbaserad definition som endast kan bestämma icke överbelastade trafiktillstånd entydigt. För de icke överbelastade trafiktillstånden (dvs. 1 och 2) har vi också kunnat visa att en densitetsbaserad definition ger ungefär samma fördelning av trafikarbete mellan trafiktillstånden.För totala emissioner är skillnaden mellan skattade emissioner med nuvarande flödesbaserade definitioner av trafiktillstånd och utvärderad densitetsbaserade definitioner av trafiktillstånd oftast liten. Dock är den densitetsbaserade versionen bättre på att fånga hur emissionerna varierar i tid och rum.
|
|
| 47. |
- Ekström, Joakim, 1982-
(författare)
-
On the relation between the phi-coefficient and the tetrachoric correlation coefficient
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We show existence of a continuous bijection between the tetrachoric correlation coefficient and the phi-coefficient under given marginal probabilities. Implications are that the tetrachoric correlation coefficient can be calculated using the assumptions of the phi-coefficient construction, and the phi-coefficient can be calculated using the assumptions of the tetrachoric correlation construction. As a consequence, whether to use the phi-coefficient or the tetrachoric correlation coefficient is a matter of preference only. The result can also be used to construct a numerical table of tetrachoric correlation coefficients, converted from the marginal probabilities and the phi-coefficient, which is easy to calculate by hand. Moreover, a mathematically rigorous definition of the tetrachoric correlation coefficient is provided, along with a proof that the coefficient is well defined.
|
|
| 48. |
- Ekström, Joakim, et al.
(författare)
-
Optimal Toll Locations and Levels in Congestion Pricing Schemes : a Case Study of Stockholm
- 2014
-
Ingår i: Transportation planning and technology (Print). - : Routledge. - 0308-1060 .- 1029-0354. ; 37:4, s. 333-353
-
Tidskriftsartikel (refereegranskat)abstract
- As congestion pricing has moved from theoretical ideas in the literature to real world implementations, the need for decision support when designing the pricing schemes has become evident. This paper deals with the problem of finding optimal toll levels and locations in a road traffic network, and presents a case study of Stockholm. The optimization problem of finding optimal toll levels, given a predetermined cordon, and the problem of finding both optimal toll locations and levels are presented, and previously developed heuristics are used for solving these problems. For the Stockholm case study, the possible welfare gains of optimizing the toll levels in the current cordon, and optimizing both the toll locations and their corresponding toll levels are evaluated. It is shownthat by tuning the toll levels in the current congestion pricing cordon used in Stockholm, the welfare gain can be significantly increased, and furthermore improved by allowing a toll on the bypass highway “Essingeleden”. It is also shown that by optimizing both the toll locations and levels, a congestion pricing scheme with welfare gain close to what can be achieved by marginal social cost pricing, can be designed with tolls being located on only a forth of the tollable links.
|
|
| 49. |
- Ekström, Joakim, et al.
(författare)
-
Optimal toll locations and toll levels in congestion pricing schemes : a case study of Stockholm
- 2014
-
Ingår i: Transportation planning and technology (Print). - : Informa UK Limited. - 0308-1060 .- 1029-0354. ; 37:4, s. 333-353
-
Tidskriftsartikel (refereegranskat)abstract
- As congestion pricing has moved from theoretical ideas in the literature to real-world implementation, the need for decision support when designing pricing schemes has become evident. This paper deals with the problem of finding optimal toll levels and locations in a road traffic network and presents a case study of Stockholm. The optimisation problem of finding optimal toll levels, given a predetermined cordon, and the problem of finding both optimal toll locations and levels are presented, and previously developed heuristics are used for solving these problems. For the Stockholm case study, the possible welfare gains of optimising toll levels in the current cordon and optimising both toll locations and their corresponding toll levels are evaluated. It is shown that by tuning the toll levels in the current congestion pricing cordon used in Stockholm, the welfare gain can be increased significantly, and furthermore improved by allowing a toll on a major bypass highway. It is also shown that, by optimising both toll locations and levels, a congestion pricing scheme with welfare gain close to what can be achieved by marginal social cost pricing can be designed with tolls being located on only a quarter of the tollable links.
|
|
| 50. |
- Ekström, Joakim, 1980-
(författare)
-
Optimization Approaches for Design of Congestion Pricing Schemes
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, there has been a growing interest in congestion pricing as a tool for solving traffic congestion problems in urban areas. However, the transportation system is complex and to design a congestion pricing scheme, i.e. to decide where and how much to charge the road users, is not trivial. This thesis considers congestion pricing schemes based on road tolls, and the efficiency of a pricing scheme is evaluated by a social welfare measure. To assist in the process of designing congestion pricing schemes, the toll design problem (TDP) is formulated as an optimization problem with the objective function describing the change in social welfare. In the TDP, the road users are assumed to be distributed in the traffic network according to a Wardrop equilibrium. The TDP is a non-convex optimization problem, and its objective function is non-smooth. Thus, the TDP is considered as a hard optimization problem to solve.This thesis aims to develop methods capable of optimizing both toll locations and their corresponding toll levels for real world traffic networks; methods which can be used in a decision support framework when designing new congestion pricing schemes or tuning already implemented ones. Also, this thesis addresses the global optimality of the TDP. 'In this thesis, a smoothening technique is applied which approximates the discrete toll location variables by continuous functions (Paper I). This allows for simultaneous optimization of both toll locations and their corresponding toll levels, using a sensitivity analysis based ascent algorithm. The smoothening technique is applied in a Stockholm case study (Paper II), which shows the potential of using optimization when designing congestion pricing schemes.Global optimality of the TDP is addressed by piecewise linear approximations of the non-linear functions in the TDP (Papers III and IV), resulting in a mixed integer linear program (MILP). The MILP can be solved to global optimality by branch and bound/cut methods which are implemented in commercially available software.
|
|
