23,535 research outputs found
Modelling Building Usersâ Space Preferences for Group Work: A Discrete-Choice Experiment
Accurate space-use prediction helps architects to optimise space efficiency in buildings, thereby achieving economic and environmental sustainability. However, current space-use prediction models and approaches either disregard or oversimplify the role of building usersâ space preferences in spatial-choice behaviour, thereby compromising prediction accuracy. The aim of this study was thus to develop a space-preference model of spatial choice behaviour with a focus on group work-related activities. A total of 2,464 observations of spatial choices were collected using a discrete-choice experiment. The data were modelled using a conditional logit model and then validated in a predictive success test. The resulting model clearly explains space preferences for group work-related activities and predicts spatial-choice behaviour by generating space-use probabilities for given spaces. The model is compared to a space preference model for individual work-related activities. Lastly, the application of the model was demonstrated in a case example.This work was supported by Hong Kong Polytechnic University: [grant number 1-ZE5H]
A 94-GHz Frequency Modulation Continuous Wave Radar Imaging and Motion Compensation
A compact and lightweight synthetic aperture radar (SAR) that can be loaded on a miniature unmanned aerial vehicle (UAV) was recently developed. The higher the frequency is, the smaller is the antenna size and the microwave characteristics are improved. Thus, a high frequency is favorable for miniaturization and weight reduction. In this chapter, a method of obtaining a radar image through a 94-GHz frequency modulation continuous wave (FMCW) radar is proposed. In addition, a method of motion compensation is described, and the W-band SAR image after motion compensation is confirmed. This kind of SAR imaging can provide geographic information and characteristics of extreme environments, disaster scenes, and information on sites where human access is difficult
Injury Risk Estimation Expertise Assessing the ACL Injury Risk Estimation Quiz
Background: Available methods for screening anterior cruciate ligament (ACL) injury risk are effective but limited in application as
they generally rely on expensive and time-consuming biomechanical movement analysis. A potential efficient alternative to biomechanical
screening is skilled movement analysis via visual inspection (ie, having experts estimate injury risk factors based on
observations of athletesâ movements).
Purpose: To develop a brief, valid psychometric assessment of ACL injury risk factor estimation skill: the ACL Injury Risk Estimation
Quiz (ACL-IQ).
Study Design: Cohort study (diagnosis); Level of evidence, 3.
Methods: A total of 660 individuals participated in various stages of the study, including athletes, physicians, physical therapists,
athletic trainers, exercise science researchers/students, and members of the general public in the United States. The ACL-IQ was
fully computerized and made available online (www.ACL-IQ.org). Item sampling/reduction, reliability analysis, cross-validation,
and convergent/discriminant validity analysis were conducted to optimize the efficiency and validity of the assessment.
Results: Psychometric optimization techniques identified a short (mean time, 2 min 24 s), robust, 5-item assessment with high
reliability (test-retest: r = 0.90) and consistent discriminability (average difference of exercise science professionals vs general
population: Cohen d = 1.98). Exercise science professionals and general population individuals scored 74% and 53% correct,
respectively. Convergent and discriminant validity was demonstrated. Scores on the ACL-IQ were most associated with ACL
knowledge and various cue utilities and were least associated with domain-general spatial/decision-making ability, personality,
or other demographic variables. Overall, 23% of the total sample (40% exercise science professionals; 6% general population)
performed better than or equal to the ACL nomogram.
Conclusion: This study presents the results of a systematic approach to assess individual differences in ACL injury risk factor
estimation skill; the assessment approach is efficient (ie, it can be completed in\3 min) and psychometrically robust. The results
provide evidence that some individuals have the ability to visually estimate ACL injury risk factors more accurately than other
instrument-based ACL risk estimation methods (ie, ACL nomogram). The ACL-IQ provides the foundation for assessing the efficacy
of observational ACL injury risk factor assessment (ie, does simple skilled visual inspection reduce ACL injuries?). It also
provides a representative task environment that can be used to increase our understanding of the perceptual-cognitive mechanisms
underlying observational movement analysis and to improve injury risk assessment performance
LYVE1 Marks the Divergence of Yolk Sac Definitive Hemogenic Endothelium from the Primitive Erythroid Lineage.
The contribution of the different waves and sites of developmental hematopoiesis to fetal and adult blood production remains unclear. Here, we identify lymphatic vessel endothelial hyaluronan receptor-1 (LYVE1) as a marker of yolk sac (YS) endothelium and definitive hematopoietic stem and progenitor cells (HSPCs). Endothelium in mid-gestation YS and vitelline vessels, but not the dorsal aorta and placenta, were labeled by Lyve1-Cre. Most YS HSPCs and erythro-myeloid progenitors were Lyve1-Cre lineage traced, but primitive erythroid cells were not, suggesting that they represent distinct lineages. Fetal liver (FL) and adult HSPCs showed 35%-40% Lyve1-Cre marking. Analysis of circulation-deficient Ncx1-/- concepti identified the YS as a major source of Lyve1-Cre labeled HSPCs. FL proerythroblast marking was extensive at embryonic day (E) 11.5-13.5, but decreased to hematopoietic stem cell (HSC) levels by E16.5, suggesting that HSCs from multiple sources became responsible for erythropoiesis. Lyve1-Cre thus marks the divergence between YS primitive and definitive hematopoiesis and provides a tool for targeting YS definitive hematopoiesis and FL colonization
Role of sea ice on satellite-observed chlorophyll-a concentration variations during spring bloom in the East/Japan sea
The relationship between the spring bloom along the Primorye coast and the sea ice of the Tatarskiy Strait in the northern region of the East/Japan Sea, a semi-enclosed marginal sea in the North Pacific, was investigated using the ten-year SeaWiFS chlorophyll-a concentration data and DMSP/SSMI sea ice concentration data from 1998 to 2007. Year-to-year variations in the chlorophyll-a concentrations in the spring were positively correlated with those of the sea ice concentrations in the Tatarskiy Strait in the previous winter with a correlation coefficient of 0.77. Abrupt increases in nutrients, essential for the spring bloom in the upper ocean during spring, were supplied from sea ice-melted waters. Time series of vertical distributions of the nutrients indicated that phosphate concentrations were extremely elevated in the upper ocean (less than 100 m) without any connection to high concentrations in the deep waters below. The water mass from sea ice provided preferable conditions for the spring bloom through changes in the vertical stratification structure of the water columns. Along-coast ratios of stability parameters between two neighboring months clearly showed the rapid progression of the generation of a shallow pycnocline due to fresh water originating from sea ice. This study addressed the importance of the physical environment for biogeochemical processes in semi-enclosed marginal seas affected by local sea ice. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.1166Ysciescopu
Hydrogenated polymorphous silicon: establishing the link between hydrogen microstructure and irreversible solar cell kinetics during light soaking
This thesis is dedicated to hydrogenated polymorphous silicon (pm-Si:H) and solar cells based on this material. pm-Si:H is a nanostructured thin film deposited by conventional PECVD method. The effects of various deposition parameters (gas flow ratio, pressure, RF power, Ts) on material properties were investigated in order to optimize its quality. The strategy was to combine a wide range of diagnostics (spectroscopic ellipsometry, hydrogen exodiffusion, SIMS, FTIR, AFM, etc.). Due to the contribution of plasma synthesized silicon nanoparticles, the process condition of pm-Si:H shows the difference in contrary to a-Si:H deposition through ionized radicals. Studies on pm-Si:H deposition process allows to fabricate pm-Si:H PIN solar cells with a high initial efficiency of 9.22 % and fill factor of 74.1, but also demonstrate unusual light-induced effects, namely i) a rapid initial degradation, ii) an irreversible degradation, and iii) large macroscopic structural changes. Comprehensive investigation on the light-induced degradation kinetics of pm-Si:H PIN layer stacks reveals a pronounced hydrogen accumulation and delamination at the substrate/p-type layer interface under light-soaking, leading to macroscopic structural changes, e.g., peel-off and solar cell area loss. We have found that a PIN structure leads to facilitated delamination during lightsoaking, which we attribute to hydrogen accumulation at the substrate/p-layer interface, while use of a NIP structure prevents the hydrogen accumulation and delamination. This lead us to fabricate pm-Si:H NIP solar cells showing a high stabilized efficiency of 8.43 %, that shows a small (10 %) light-induced degradation after light-soaking for 500 hours.Cette thĂšse est consacrĂ©e au silicium polymorphe hydrogĂ©nĂ© (pm-Si:H). Elle porte tout d'abord sur une Ă©tude du pm-Si :H puis sur une Ă©tude des cellules photovoltaĂŻques fabriquĂ©es Ă partir de ce matĂ©riau. Le pm-Si:H est formĂ© de couches minces nanostructurĂ©es et peut ĂȘtre dĂ©posĂ© par PECVD conventionnelle. Les effets des diffĂ©rents paramĂštres de dĂ©pĂŽt (mĂ©langes gazeux, pression, puissance RF, tempĂ©rature du substrat) sur les propriĂ©tĂ©s du matĂ©riau ont Ă©tĂ© Ă©tudiĂ©s pour optimiser sa qualitĂ©. La caractĂ©risation des couches a Ă©tĂ© un enjeu primordial. Pour cela, nous avons choisi de combiner une palette trĂšs large de mĂ©thodes de caractĂ©risation (ellipsomĂštrie spectroscopique, exodiffusion d'hydrogĂšne, SIMS, FTIR, AFM, etc...). A cause de la contribution des nanoparticules de silicium dans le plasma, la nature du dĂ©pĂŽt du pm-Si:H montre la diffĂ©rence contrairement au a-Si:H pour lequel le dĂ©pĂŽt se fait par le biais de radicaux ionisĂ©s. L'Ă©tude des conditions du procĂ©dĂ© nous a conduit Ă fabriquer des cellules solaires d'un rendement initial de 9.22 % avec un facteur de forme Ă©levĂ© (74.1), mais aussi de dĂ©montrer des effets de vieillissement inhabituels, tels que i) une dĂ©gradation initiale rapide, ii) une dĂ©gradation irrĂ©versible, et iii) de grands changements structuraux macroscopiques. Nous avons dĂ©couvert que le principal problĂšme se situe entre le substrat et la couche mince de silicium. L'hydrogĂšne molĂ©culaire diffuse et s'accumule Ă l'interface entre le substrat et la couche mince, ce qui introduit un dĂ©laminage local qui a pour consĂ©quence une dĂ©gradation initiale rapide des performances des cellules. Nous avons trouvĂ© que sous Ă©clairement une structure PIN facilite l'accumulation d'hydrogĂšne et le dĂ©laminage Ă l'interface entre le substrat et la couche dopĂ©e p. Cependant, l'utilisation d'une structure NIP empĂȘche l'accumulation d'hydrogĂšne et le dĂ©laminage. Cela nous a permis de fabriquer des cellules solaires pm-Si:H de structure NIP d'un rendement stable de 8.43 %, mais aussi de dĂ©montrer une degradation minimale (10 %) aprĂšs un vieillissement de 500 heures
Nonperturbative Tests of Three-Dimensional Dualities
We test several conjectural dualities between strongly coupled superconformal
field theories in three dimensions by computing their exact partition functions
on a three-sphere as a function of Fayet-Iliopoulos and mass parameters. The
calculation is carried out using localization of the path integral and the
matrix model previously derived for superconformal N = 2 gauge theories. We
verify that the partition functions of quiver theories related by mirror
symmetry agree provided the mass parameters and the Fayet-Iliopoulos parameters
are exchanged, as predicted. We carry out a similar calculation for the mirror
of N = 8 super-Yang-Mills theory and show that its partition function agrees
with that of the ABJM theory at unit Chern-Simons level. This provides a
nonperturbative test of the conjectural equivalence of the two theories in the
conformal limit
- âŠ