1,298 research outputs found
QJE-STD-18-253.R2-Supplementary_Material – Supplemental material for Development and assessment of the Korean Author Recognition Test
No full textSupplemental material, QJE-STD-18-253.R2-Supplementary_Material for Development and assessment of the Korean Author Recognition Test by Hyosun Lee, Eunjin Seong, Wonil Choi and Matthew W Lowder in Quarterly Journal of Experimental Psychology</p
A Study on the EM Wave Absorber for W-band Navigation Radars
No full textMillimeter wave radars are employed in a wide range of commercial, military and scientific applications for remote sensing, safety, and measurements. But, radar systems suffer from two major problems such as false images and system-to-system interference. False echoes cause driving hazards. These problems can be eliminated through the use of an EM wave absorber. In this dissertation, the EM wave absorbers using Carbon black as a conductive material, TiO2 as a dielectric material, and Permalloy as a magnetic material with CPE were designed and fabricated for W-band navigation radars. First of all, the complex relative permittivity and permeability of three-type absorbing materials are calculated from the S-parameter. The optimum composition ratios of absorbing materials were determined from absorption ability of various composite. The EM wave absorption abilities at different thicknesses are simulated using material properties of the EM wave absorbers, and the EM wave absorbers were fabricated based on the simulated designs. The simulated and measured results agree very well. As a result, the sheet-type absorbers were developed to eliminate false image and system-to-system interference of navigation radars in W-band.Contents i
Nomenclature iii
List of Tables iv
List of Figures v
Abstract x
Abstract translated into korean xiii
Chapter 1 INTRODUCTION 1
1.1 Dissertation Objective 3
1.2 Outline of Remaining Chapters 4
Chapter 2 NAVIGATION RADAR FUNDAMENTAL 6
2.1 History of Radar Development 6
2.2 Radar System Fundamentals 9
2.3 Millimeter Wave Radar 11
2.4 Contributions of EM Wave Absorber 15
Chapter 3 THEORY OF EM WAVE ABSORBER 17
3.1 History of EM Wave Absorber 17
3.2 Electromagnetic Theory 19
3.3 Loss mechanism 26
3.4 Classification of EM Wave Absorber 30
3.5 Application of EM Wave Absorber 33
Chapter 4 DESIGN OF EM WAVE ABSORBER 41
4.1 Introduction 41
4.2 Single-layer Absorber 43
4.3 Multi-layer absorber 47
Chapter 5 MATERIAL PROPERTIES 51
5.1 Introduction 51
5.2 Measurement Techniques of Material Properties 52
5.3 Manufacturing Process of Absorber 59
5.4 Measured Material Properties 62
5.5 SEM Photographs 75
Chapter 6 ABSORPTION ABILITY 79
6.1 Introduction 79
6.2 Measurement Techniques of Absorption Ability 80
6.3 Simulated Absorption Ability 85
6.4 Measured Absorption Ability 94
Chapter 7 CONCLUSIONS 108
References 111
Published papers concerned with this dissertation 116
Acknowledgement 12
Boosting the performance of Zn electrode in aqueous electrolytes via trace amount of organic molecules
No full textVersion of record online: December 20, 2023The poor performance of Zn electrode in aqueous electrolytes prevents the practical application of aqueous zinc-ion batteries (AZIBs). Here, 2-Pyrrolidinone (Pr) is introduced into conventional ZnSO4 electrolytes as additive and only 3 vol.% addition (Pr−to−H2O volume ratio) enables boosted performance. The Pr molecules are preferentially adsorbed on the surface of Zn electrodes to promote the uniform deposition of Zn ions and modulate the solvation structure of Zn2+ to inhibit the side reactions. As a result, the Zn electrode is boosted to run over 1200 h during charge/discharge cycling processes and delivers high average coulombic efficiency (CE) of 99.9 % under 1 mA cm−2, 1 mAh cm−2. Even under harsh testing conditions of 20 mA cm−2 and 20 mAh cm−2, Zn electrode still run over 100 h, which is much longer than that at pristine electrolyte (25 h). Moreover, the Zn||MnO2 full cells with the Pr additive exhibit a high capacity of 201 mAh g−1 and good capacity retention of 89 % after 550 cycles at 0.5 A g−1.Haiji Huang, Yan Wang, Dongmei Xie, Jianyang Sun, Jiachang Zhao, Pinhua Rao, Won Mook Choi, and Jianfeng Ma
An irreducible semigroup of non-negative square-zero operators
No full textWe construct an irreducible multiplicative semigroup of non-negative square-zero operators acting on L-P[0, 1), for 1 less than or equal to p < infinity.PT: J; CR: CHOI MD, 1993, INDIANA U MATH J, V42, P15 DRNOVSEK R, IN PRESS OPERATOR TH DRNOVSEK R, 2000, P EDINBURGH MATH S 1, V43, P43 HADWIN D, 1986, INTEGR EQUAT OPER TH, V9, P739 HALMOS PR, 1950, MEASURE THEORY RADJAVI H, 2000, SIMULTANEOUS TRIANGU RUDIN W, 1986, REAL COMPLEX ANAL TUROVSKII YV, 1999, J FUNCT ANAL, V162, P313 ZHONG Y, 1995, T AM MATH SOC, V347, P3093; NR: 9; TC: 1; J9: INTEGRAL EQUATION OPER THEORY; PG: 12; GA: 533RTSource type: Electronic(1
Three-dimensional clinical handheld photoacoustic/ultrasound scanner
No full textClinical 2D photoacoustic (PA) imaging can be easily implemented in a traditional ultrasound (US) system. However, 3D PA imaging is still preferable because 2D B-mode PA/US imaging suffers from low reproducibility and high-operator dependency. Here, we demonstrate a compact clinical handheld 3D PA/US scanner using an 1D linear array US transducer combined with a mechanical scanning stage working via a Scotch yoke mechanism. The entire scanner measures just 100 × 80 × 100 mm3 and weighs only 950 g, so it can easily be operated by hand. Blood vessels and hemoglobin oxygen saturation images of different parts of the human body (e.g., neck, wrist, thigh, and instep) have been successfully acquired. The system can potentially be used for clinical applications in fields such as oncology, dermatology, nephrology, and internal medicine. © 2020 The Author(s)11Ysciescopu
Increased Excitatory Synaptic Transmission of Dentate Granule Neurons in Mice Lacking PSD-95-Interacting Adhesion Molecule Neph2/Kirrel3 during the Early Postnatal Period
No full textCopy number variants and point mutations of NEPH2 (also called KIRREL3) gene encoding an immunoglobulin (Ig) superfamily adhesion molecule have been linked to autism spectrum disorders, intellectual disability and neurocognitive delay associated with Jacobsen syndrome, but the physiological roles of Neph2 in the mammalian brain remain largely unknown. Neph2 is highly expressed in the dentate granule (DG) neurons of the hippocampus and is localized in both dendrites and axons. It was recently shown that Neph2 is required for the formation of mossy fiber filopodia, the axon terminal structure of DG neurons forming synapses with GABAergic neurons of CA3. In contrast, however, it is unknown whether Neph2 also has any roles in the postsynaptic compartments of DG neurons. We here report that, through its C-terminal PDZ domain-binding motif, Neph2 directly interacts with postsynaptic density (PSD)-95, an abundant excitatory postsynaptic scaffolding protein. Moreover, Neph2 protein is detected in the brain PSD fraction and interacts with PSD-95 in synaptosomal lysates. Functionally, loss of Neph2 in mice leads to age-specific defects in the synaptic connectivity of DG neurons. Specifically, Neph2−/− mice show significantly increased spontaneous excitatory synaptic events in DG neurons at postnatal week 2 when the endogenous Neph2 protein expression peaks, but show normal excitatory synaptic transmission at postnatal week 3. The evoked excitatory synaptic transmission and synaptic plasticity of medial perforant pathway (MPP)-DG synapses are also normal in Neph2−/− mice at postnatal week 3, further confirming the age-specific synaptic defects. Together, our results provide some evidence for the postsynaptic function of Neph2 in DG neurons during the early postnatal period, which might be implicated in neurodevelopmental and cognitive disorders caused by NEPH2 mutations.
Copyright © 2017 Roh, Choi, Cho, Choi, Park, Cutforth, Chung, Park, Lee, Kim, Lee,
Mo, Rhee, Kim, Ko, Choi, Bae, Shen, Kim and Han. This is an open-access article
distributed under the terms of the Creative Commons Attribution License (CC BY).
The use, distribution and reproduction in other forums is permitted, provided the
original author(s) or licensor are credited and that the original publication in this
journal is cited, in accordance with accepted academic practice. No use, distribution
or reproduction is permitted which does not comply with these terms.
© 2017 Roh, Choi, Cho, Choi, Park, Cutforth, Chung, Park, Lee, Kim, Lee,
Mo, Rhee, Kim, Ko, Choi, Bae, Shen, Kim and Han. This is an open-access article
distributed under the terms of the Creative Commons Attribution License (CC BY).
The use, distribution and reproduction in other forums is permitted, provided the
original author(s) or licensor are credited and that the original publication in this
journal is cited, in accordance with accepted academic practice. No use, distribution
or reproduction is permitted which does not comply with these terms.
Frontiers1321sciescopu
CUHK electronic theses & dissertations collection
No full textChoi, Fai Ho.Thesis M.Phil. Chinese University of Hong Kong 2015.Includes bibliographical references (leaves 47-51).Abstracts and appendix also in Chinese.Title from PDF title page (viewed on 08, November, 2016)
Mixed Motives of Simultaneous-move Games in a Mixed Duopoly: Comments and Erratum
No full textIf the public and private firm have mixed motives about payoff in a simultaneous-move game, Choi (2006) analyzes that the resulting equilibrium turns out to be an inefficient level with the monopoly of private firm even if there are Nash equilibria. However, we find that if we use equilibrium profit, we would have solved its unique Nash equilibrium that both firms aim to maximize the relative payoffs.Mixed Duopoly
Bottom-up growth of III-V compound semiconductor nanowires by selective lateral/area epitaxy
No full textSubmission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01The student, Wonsik Choi, accepted the attached license on 2019-12-04 at 16:02.The student, Wonsik Choi, submitted this Dissertation for approval on 2019-12-04 at 16:32.This Dissertation was approved for publication on 2019-12-05 at 17:27.DSpace SAF Submission Ingestion Package generated from Vireo submission #14698 on 2020-02-28 at 17:37:56Bottom-up grown III-V compound semiconductor nanowires (NWs) provide a novel building block for electrical and optical devices. Bottom-up III-V NWs can be synthesized by either a vapor-liquid-solid (VLS) or selective area epitaxy (SAE) mechanism. Under the specific VLS NW growth conditions, planar self-aligned NWs can be grown on top of a substrate under a selective lateral epitaxy (SLE) mechanism.
In this thesis research, first, the realization of lateral multiple p-n junction gallium arsenide (GaAs) SLE NW grown by metal-organic chemical vapor deposition (MOCVD) reactor is presented. Scanning microwave impedance microscopy (sMIM) and infrared scattering-type near-field optical microscopy (IR-SNOM) scans on top of the NW suggested that p-type zinc dopants are accumulated at twin-plane boundaries of NW. The electrical properties of the SLE GaAs lateral p-n junction were analyzed by measuring two-terminal I-V characteristics of arrays of p-n NW diodes. The I-V characteristics of the devices indicated that the lateral p-n junction was successfully realized with a high rectification ratio of ~106.
The gallium phosphide (GaP) SAE NW growth on top of a silicon (Si) substrate will be also introduced. Systemic studies were performed by modulating the following three NW growth conditions: TMGa flow rate, growth temperature, and V/III ratio. By controlling the NW growth parameters, a 97.5% yield of hexagonal NWs was grown on an area of 400 µm × 400 µm. The morphology of the NWs was inspected with a scanning electron microscope (SEM). X-ray diffraction (XRD) analysis was performed on the GaP NWs, and 6.3016 Å of wurtzite (WZ) GaP c-lattice parameter was extracted. Vertical arrays of GaP p-n and p-i-n NW diodes were fabricated. The ideality factor and rectification ratio of p-n GaP NW diode were measured 7 and 10, respectively. The ideality factor and the rectification ratio could be improved to 3.7 and 1000 by introducing an undoped intrinsic layer between n-type and p-type GaP NW.Made available in DSpace on 2020-03-02T22:38:57Z (GMT). No. of bitstreams: 2
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On iso- and nonisothermal crack problems of a layered anisotropic elastic medium
No full textThe iso- and non-isothermal crack problems of layered fiber-reinforced composite materials are investigated within the framework of linear anisotropic thermoelasticity and under the state of generalized plane deformation. The crack is assumed to be parallel to the layer bounding surfaces. By employing the Fourier integral transform technique and the flexibility/stiffness matrix formulation, the current mixed boundary value problems are reduced to solving a set of simultaneous singular integral equations with Cauchy-type kernels. The crack·tip stress intensity factors are then defined in terms of the solution of the integral equations. Numerical results are presented addressing the salient and unique features for a class of crack problems involving highly anisotropic fibrous composite materials. Specifically, the cases of a crack embedded i) within a homogeneous and anisotropic slab, ii) between two bonded dissimilar anisotropic half-spaces and iii) within the matrix-rich interlaminar region of a generally laminated anisotropic slab are considered. The effects of relative crack size, crack location and fiber volume fraction on the stress intensity factors are examined as a function of über angle. For the case of layered composites, the matrix-rich interlaminar region is modeled as a separate interlayer. As the interlayer thickness approaches zero, the interlaminar crack model illustrates no smooth transition to the ideal interface crack model of zero interlayer thickness which exhibits oscillatory stress singularities. The mixed-mode crack tip response is shown to involve the simultaneous presence of three fracture modes. It is demonstrated that the corresponding values of stress intensity factors are strongly influenced by the laminate stacking sequence and layer orientation. In addition, the partially insulated crack surface condition is observed to alleviate the severity of thermally-induced stress fields near the crack tip.Ph. D
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