| 1. |
- Abbas, Taimoor, et al.
(författare)
-
A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations
- 2015
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877.
-
Tidskriftsartikel (refereegranskat)abstract
- The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading.
|
|
| 2. |
- Abiri, Najmeh, et al.
(författare)
-
Establishing strong imputation performance of a denoising autoencoder in a wide range of missing data problems
- 2019
-
Ingår i: Neurocomputing. - Amsterdam : Elsevier BV. - 0925-2312 .- 1872-8286. ; 365, s. 137-146
-
Tidskriftsartikel (refereegranskat)abstract
- Dealing with missing data in data analysis is inevitable. Although powerful imputation methods that address this problem exist, there is still much room for improvement. In this study, we examined single imputation based on deep autoencoders, motivated by the apparent success of deep learning to efficiently extract useful dataset features. We have developed a consistent framework for both training and imputation. Moreover, we benchmarked the results against state-of-the-art imputation methods on different data sizes and characteristics. The work was not limited to the one-type variable dataset; we also imputed missing data with multi-type variables, e.g., a combination of binary, categorical, and continuous attributes. To evaluate the imputation methods, we randomly corrupted the complete data, with varying degrees of corruption, and then compared the imputed and original values. In all experiments, the developed autoencoder obtained the smallest error for all ranges of initial data corruption.
|
|
| 3. |
- Abiri, Najmeh, et al.
(författare)
-
Variational auto-encoders with Student’s t-prior
- 2019
-
Ingår i: ESANN 2019 - Proceedings : The 27th European Symposium on Artificial Neural Networks, Computational Intelligence and Machine Learning - The 27th European Symposium on Artificial Neural Networks, Computational Intelligence and Machine Learning. - Bruges : ESANN. - 9782875870650
-
Konferensbidrag (refereegranskat)abstract
- We propose a new structure for the variational auto-encoders (VAEs) prior, with the weakly informative multivariate Student’s t-distribution. In the proposed model all distribution parameters are trained, thereby allowing for a more robust approximation of the underlying data distribution. We used Fashion-MNIST data in two experiments to compare the proposed VAEs with the standard Gaussian priors. Both experiments showed a better reconstruction of the images with VAEs using Student’s t-prior distribution.
|
|
| 4. |
- Abrahamsson, Cristian, et al.
(författare)
-
Content, interest and the role of engagement : experienced science teachers discuss
- 2023
-
Ingår i: Physics Education. - Bristol : Institute of Physics Publishing (IOPP). - 0031-9120 .- 1361-6552. ; 58:6
-
Tidskriftsartikel (refereegranskat)abstract
- How do science teachers perceive student engagement and its importance for teaching and what strategies do they use to create it? When 21 experienced science teachers in 4 focus groups discussed these questions, they brought up behavioural aspects, but also less visible emotional and cognitive aspects, as well as reciprocal aspects of teacher and student engagement. One teacher described engagement as 'the oil in the machinery' during lessons. Which role does the curricular content play? Well aware that some topics are seen as more directly interesting by students, teachers connect to these, but also use hooks, including lively demonstrations, role play and connections to the outside world. In this way, they aim to generate situational interest and engagement also in topics that are often viewed as less interesting, including atoms and molecules. These experienced teachers describe how they adapt their teaching to the group also in real time, based on the degree of engagement exhibited by the students. © 2023 The Author(s). Published by IOP Publishing Ltd.
|
|
| 5. |
- Abrahamsson, Cristian, et al.
(författare)
-
En Delfistudie om lärares uppfattning av elevengagemang i NO-undervisningen
- 2019
-
Ingår i: NorDiNa. - Oslo : Naturfagsenteret / Norwegian Centre for Science Education. - 1504-4556 .- 1894-1257. ; 15:2, s. 128-144
-
Tidskriftsartikel (refereegranskat)abstract
- What happens in a science classroom where students are engaged and how do teachers observe and interpret student engagement? This article highlights teachers’ perspective on students’ engagement in science education and to what extent it is connected to the scientific content. This approach complements earlier research which focuses mostly on students’ attitude towards science education and their interest in various topics in science.The findings are based on a three-stage Delphi survey distributed to 39 expert science teachers. The results shows science education with a range of different perspectives and that most teachers do not perceive any direct connection between specific science topics and the students’ engagement. The survey also shows that teachers to a high level interpret students’ emotional expressions and academic behavior as engagement rather than their cognitive behavior.
|
|
| 6. |
- Afram, Basema, et al.
(författare)
-
Predicting institutional long-term care admission in dementia: a mixed-methods study of informal caregivers' reports
- 2015
-
Ingår i: Journal of Advanced Nursing. - Chichester : Wiley. - 0309-2402 .- 1365-2648. ; 71:6, s. 1351-1362
-
Tidskriftsartikel (refereegranskat)abstract
- AimTo investigate agreement between: (1) expected reasons and actual reasons for admission of people with dementia according to informal caregivers; (2) scores on measurement instruments prior to admission and the actual reasons for admission according to informal caregivers. BackgroundTimely admission of people with dementia is a crucial issue. Information is highly warranted on whether informal caregivers are capable of prior identification of causes of admission and, can thus be considered a reliable prospective source on causes of admission. DesignA cohort study among informal caregivers of people with dementia who made a transition to institutional long-term care. MethodsQualitative data on the expected and actual reasons for admission were collected via open-ended questions at baseline and follow-up. Furthermore, at baseline, data were collected using measurement instruments to measure pre-admission characteristics. Interviews took place between November 2010-April 2012. After categorizing the answers, the agreement between the expected and actual reasons was calculated. Furthermore, bivariate associations were calculated between the actual reasons for admission and scores on corresponding measurement instruments. Results/FindingsFor most informal caregivers, there was agreement between their statements on the expected reason and the actual reason for admission. A third of the caregivers showed no conformity. Bivariate associations showed that there is also agreement between the actual reasons for admission and scores on corresponding measurement instruments. ConclusionInformal caregivers can be considered reliable sources of information regarding what causes the admission of a person with dementia. Professional care should anticipate informal caregivers' statements and collaborate with them to strive for timely and appropriate admission.
|
|
| 7. |
- Ageberg, Eva, et al.
(författare)
-
Cocreating injury prevention training for youth team handball : bridging theory and practice
- 2022
-
Ingår i: BMJ Open Sport and Exercise Medicine. - London : BMJ Publishing Group Ltd. - 2055-7647. ; 8:2
-
Tidskriftsartikel (refereegranskat)abstract
- Although it is advocated that end-users are engaged in developing evidence-based injury prevention training to enhance the implementation, this rarely happens. The € Implementing injury Prevention training ROutines in TEams and Clubs in youth Team handball (I-PROTECT)' uses an ecological participatory design incorporating the perspectives of multiple stakeholders throughout the project. Within the I-PROTECT project, the current study aimed to describe the development of holistic injury prevention training specifically for youth handball players through using knowledge from both end-users (coaches and players) and researchers/handball experts. Employing action evaluation within participatory action research, the cyclical development process included three phases: research team preparation, handball expert-based preparation and end-user evaluation to develop injury prevention training incorporating both physical and psychological perspectives. To grow the knowledge of the interdisciplinary research team, rethinking was conducted within and between phases based on participants' contributions. Researchers and end-users cocreated examples of handball-specific exercises, including injury prevention physical principles (movement technique for upper and lower extremities, respectively, and muscle strength) combined with psychological aspects (increase end-user motivation, task focus and body awareness) to integrate into warm-up and skills training within handball practice. A cyclical development process that engaged researchers/handball experts and end-users to cocreate evidence-based, theory-informed and context-specific injury prevention training specifically for youth handball players generated a first pilot version of exercises including physical principles combined with psychological aspects to be integrated within handball practice. © 2022 BMJ Publishing Group. All rights reserved. © 2022 BMJ Publishing Group. All rights reserved.
|
|
| 8. |
- Aghaeipour, Mahtab, et al.
(författare)
-
Comparative study of absorption efficiency of inclined and vertical InP nanowires
- 2017
-
Ingår i: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VI. - Bellingham, WA : SPIE - International Society for Optical Engineering. - 9781510606401 ; 10099
-
Konferensbidrag (refereegranskat)abstract
- Geometrically designed III-V nanowire arrays are promising candidates for optoelectronics due to their possibility to excite nanophotonic resonances in absorption spectra. Strong absorption resonances can be obtained by proper tailoring of nanowire diameter, length and pitch. Such enhancement of the light absorption is, however, accompanied by undesired resonance dips at specific wavelengths. In this work, we theoretically show that tilting of the nanowires mitigates the absorption dips by exciting strong Mie resonances. In particular, we derive a theoretical optimum inclination angle of about 30 degrees at which the inclined nanowires gain 8% in absorption efficiency compared to vertically standing nanowires in a spectral region matching the intensity distribution of the sun. The enhancement is due to engineering the excited modes inside the nanowires regarding the symmetry properties of the nanowire/light system without increasing the absorbing material. We expect our results to be important for nanowire-based photovoltaic applications. © 2017 SPIE.
|
|
| 9. |
- Aghaeipour, Mahtab, et al.
(författare)
-
Considering symmetry properties of inp nanowire/light incidence systems to gain broadband absorption
- 2017
-
Ingår i: IEEE Photonics Journal. - Piscataway : IEEE. - 1943-0655. ; 9:3
-
Tidskriftsartikel (refereegranskat)abstract
- Geometrically designed III-V nanowire arrays are promising candidates for disruptive optoelectronics due to the possibility of obtaining a strongly enhanced absorption resulting from nanophotonic resonance effects. With normally incident light on such vertical nanowire arrays, the absorption spectra exhibit peaks that originate from excitation of HE1m waveguide modes in the constituent nanowires. However, the absorption spectra typically show dips between the absorption peaks. Conventionally, such weak absorption has been counteracted by either making the nanowires longer or by decreasing the pitch of the array, both alternatives effectively increasing the volume of absorbing material in the array. Here, we first study two approaches for compensating the absorption dips by exciting additional Mie resonances: 1) oblique light incidence on vertical InP nanowire arrays and 2) normal light incidence on inclined InP nanowire arrays. We then show that branched nanowires offer a novel route to achieve broadband absorption by taking advantage of simultaneous excitations of Mie resonances in the branches and guided HE1m modes in the stem. Finite element method calculations show that the absorption efficiency is enhanced from 0.72 for vertical nanowires to 0.78 for branched nanowires under normal light incidence. Our work provides new insight for the development of novel efficient photovoltaics with high efficiency and reduced active material volume.
|
|
| 10. |
- Aghaeipour, Mahtab, et al.
(författare)
-
Enhanced broadband absorption in nanowire arrays with integrated Bragg reflectors
- 2018
-
Ingår i: Nanophotonics. - Berlin : Walter de Gruyter GmbH. - 2192-8614. ; 7:5, s. 819-825
-
Tidskriftsartikel (refereegranskat)abstract
- A near-unity unselective absorption spectrum is desirable for high-performance photovoltaics. Nanowire (NW) arrays are promising candidates for efficient solar cells due to nanophotonic absorption resonances in the solar spectrum. The absorption spectra, however, display undesired dips between the resonance peaks. To achieve improved unselective broadband absorption, we propose to enclose distributed Bragg reflectors (DBRs) in the bottom and top parts of indium phosphide (InP) NWs, respectively. We theoretically show that by enclosing only two periods of In0.56Ga0.44As/InP DBRs, an unselective 78% absorption efficiency (72% for NWs without DBRs) is obtained at normal incidence in the spectral range from 300 nm to 920 nm. Under oblique light incidence, the absorption efficiency is enhanced up to about 85% at an incidence angle of 50°. By increasing the number of DBR periods from two to five, the absorption efficiency is further enhanced up to 95% at normal incidence. In this work, we calculated optical spectra for InP NWs, but the results are expected to be valid for other direct band gap III-V semiconductor materials. We believe that our proposed idea of integrating DBRs in NWs offers great potential for high-performance photovoltaic applications.
|
|
