91,793 research outputs found
Characterization of GaAs and grown by hydride vapor phase epitaxy
No full text학위논문(석사) - 한국과학기술원 : 물리학과, 1985.2, [ [iii], 64 p. ]한국과학기술원 : 물리학과
Versioning of information goods under the threat of piracy
No full textThe present study investigates the effects of piracy on the quality decisions of a firm that produces two versions of an information good: that is, one version for a consumer with a high willingness to pay and a second version for a consumer with a low willingness to pay. On the assumption that there is no quality difference between the original and the illegal copy and that the cost of the copy is constant across users, we show that the presence of piracy induces the firm to choose a lower level of quality of the former and a higher level of quality of the latter relative to decisions made in the absence of piracy. We also discuss policy implications concerning the socially optimal level of copyright protection. (C) 2010 Elsevier B.V. All rights reserved.We thank Byong-Sam Choi for valuable comments and
encouragement. We are also grateful to the editor, Martin
Peitz and an anonymous referee for their insightful and
constructive comments that greatly improved the exposition
of the paper
노달계산결과로부터 핵연료 집합체내의 출력분포를 재생하는 방법에 관하여
No full textThis paper is a study on an accurate and computationally efficient method for reconstructing pointwise power distributions from coarse-mesh nodal calculations. The modern nodal codes can calculate global reactor power shapes and criticality very efficiently and accurately. But inherent in the nodal procedures, there is inevitable loss of information on local heterogeneous quantities. In this study, an improved form function method which reflects the exponential transition of the thermal flux near the assembly surface is developed for the reconstruction of the heterogeneous fluxes. Use of the new form function method in several pressurized water reactor (PWR) benchmark problems reduces the maximum errors in the reconstructed thermal flux to those in the reconstructed fast flux. Even for assemblies adjacent to the steel baffle in realistic PWR cores, use of this method also results in improved pointwise power reconstruction
노달 계산결과로부터 원자로심내의 출력분포 재생을 위한 방법
No full text학위논문(석사) - 한국과학기술원 : 핵공학과, 1988.2, [ vi, 58, [1] p. ]The objective of this thesis is to develop an accurate and computationally efficient method for reconstruction of pointwise power distributions from coarse-mesh nodalcalculations. Provided that homogenized parameters are properly determined in each node, the analytic nodal method code (ANM) calculates global reactor power shapes and criticality accurately. But inherent in nodal procedures, there is inevitable loss of information on local heterogeneous quantities. Hence a special technique is needed in order to recapture local properties where and when desired. In this study, an improved form function method which reflects the exponential transition of the thermal flux near the assembly surface is developed for the reconstruction of the heterogeneous fluxes. The distinctive feature of the new form function method is that the form function of the thermal flux is dependent on the form function of the fast flux which is approximated by the bi-quadratic polynomials, and the dependency is represented by the hyperbolic functions. Use of the new form function method in several PWR benchmark problems reduces the maximum errors in the reconstructed thermal flux to those in the reconstructed fast flux. In realistic PWER cores, use of this method also results in improved pointwise power reconstruction; the maximum reconstruction errors even for assemblies adjacent to the steel baffle are only half of those obtained by using the conventional bi-quadratic form function method.한국과학기술원 : 핵공학과
Directly Coated Iridium Nickel Oxide on Porous‐Transport Layer as Anode for High‐Performance Proton‐Exchange Membrane Water Electrolyzers
No full textAbstract Developing a high‐performance anode design is important for a low‐cost proton‐exchange membrane water electrolyzer (PEMWE). In this study, an iridium nickel oxide directly coated anode (IrNiOx electrode) for high‐efficient PEMWE is reported. Five IrNiOx electrodes with different Ir‐to‐Ni ratios are developed using co‐electrodeposition. The resulting electrodes contain a thin IrNiOx layer on the carbon substrate. To develop the PEMWE incorporating IrNiOx electrode, the effect of fabrication methods, catalyst compositions, and porous transport layer are investigated. Consequently, the IrNiOx electrode prepared with 7:3 precursor solution (Ir0.5Ni0.5Ox) exhibits higher oxygen evolution reaction activity with a smaller overpotential than the electrode prepared with 10:0 precursor solution (IrOx) and the commercial IrO2. Furthermore, the performance of the PEMWE is higher with the Ir0.5Ni0.5Ox electrode than that with the sprayed electrode with commercial IrO2 nanoparticles. This enhancement is attributed to the high electrochemical surface area caused by introducing Ni in IrOx. Additionally, the performance of the directly coated Ir0.5Ni0.5Ox PEMWE is the highest reported in the literature
A 43.4μW photoplethysmogram-based heart-rate sensor using heart-beat-locked loop
No full textPhotoplethysmogram (PPG) sensors have gained great popularity in recent years as they can easily obtain heart rate (HR) in wearable devices such as smart watches and smart rings. However, one of the biggest problems for PPG sensors is their large power consumption, as wearable devices are highly limited in its battery capacity. The power consumption of a PPG sensor is typically dominated by the LED driver, which requires several to a few tens of mA of current. Thus, many previous works are aimed at reducing the LED driver power [1-5]. The most widely used method is duty-cycling the LED by using a train of discrete pulses instead of always turning on the LED [1-4]. As a PPG signal has low bandwidth, the duty-cycle ratio of the LED can be as low as 1%. Another low-power method is compressive sampling, which exploits the sparse nature of PPG signals [5]. Although it can reduce the effective duty-cycle ratio down to 0.0125%, a critical problem is that a large power consumption is required in reconstructing the compressive-sampled signal. In this work, we present an ultra-low-power PPG sensor with a heartbeat-locked loop (HBLL) that turns on the LED only during the PPG peaks and thus achieves an effective duty cycle of 0.0175%. We also reduce the power consumption of the analog front-end (AFE) by using the HBLL, which is in contrast to previous works where AFE power is not duty-cycled. A prototype implemented in 0.18μm CMOS demonstrates 43.4μW of total power consumption with less than 2.1bpm error in heart rate
Hun Hee Cho, prix de mémoire de diplôme de l'EHESS 2014
No full textLa commission de la scolarité réunie le 16 avril 2015 a attribué Le prix de mémoire de diplôme de l'EHESS 2014 à Hun Hee Cho pour son mémoire intitulé " Les centres commerciaux verticaux : nouveaux lieux marchands dans la société sud-coréenne." dirigé par Valérie Gelézeau. Ci-dessous, rédigé le 05/05/2015 par Hun Hee CHO Mémoire présenté et soutenu en vue du diplôme de l’EHESS par Hun Hee CHO sous la direction de Valérie GELÉZEAU Les centres commerciaux verticaux : nouveaux lieux marchands d..
DOI resolution measurement and error analysis with LYSO and APDs
No full textSpatial resolution degradation in PET occurs at the edge of Field Of View (FOV) due to parallax error. To improve spatial resolution at the edge of FOV, Depth-Of-Interaction (DOI) PET has been investigated and several methods for DOI positioning were proposed. In this paper, a DOI-PET detector module using two 8 x 4 array avalanche photodiodes (APDs) (Hamamatsu, S8550) and a 2cm long LYSO scintillation crystal was proposed and its DOI characteristics were investigated experimentally. In order to measure DOI positions, signals from two APDs were compared. Energy resolution was obtained from the sum of two APDs' signals and DOI positioning error was calculated. Finally, an optimum DOI step size in a 2 cm long LYSO were suggested to help to design a DOI-PET. (c) 2008 Elsevier B.V. All rights reserved
Views of children and young people in foster care survey: education
No full textThis paper explores the educational experiences of children and young people living in foster care in Queensland. Findings are drawn from the responses of 845 children and 1180 young people to the 2011 Views of Children and Young People in Foster Care survey, which is a rich source of information about children’s and young people’s attitudes towards and perceptions of their own education. Findings relate to educational status, key markers of educational disadvantage including suspensions and exclusions, and specific problems children and young people experience at school, as well as children’s and young people’s enjoyment of school and aspirations for the future. Information about educational support, including Educational Support Plans and support provided by Child Safety Officers and Community Visitors are also presented. Where relevant, comparisons are made between the 2011 survey results and prior surveys conducted in 2006, 2007 and 2009. Relationships between key educational measures as well as relationships to other important measures of health and placement stability are also explored.
The findings suggest that children and young people continue to experience educational disadvantage, including high rates of suspension and exclusion and a range of problems at school including problems with schoolwork, bullying and behaviour and that these difficulties can be exacerbated by the child protection system, for example, through placement instability. However, there are reasons for optimism. Children and young people are overwhelmingly likely to report that they enjoy school, expect to complete Year 12 and that their teachers generally like their schoolwork. Furthermore, over time, the proportions of young people reporting that they have an Educational Support Plan have grown, and, importantly, they are more likely to report that these plans are helpful. Analyses in relation to a number of educational variables reveal that young people with a plan they consider to be helpful fare better. Children and young people were also positive about the important role that CSOs and CVs are able to play in supporting their education.
While educational disadvantage is an enduring problem, the survey findings provide evidence of progress in key areas and suggestions for how continued improvements may be made
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