• 전기학회논문지
• /
• 제62권2호
• /
• pp.228-231
• /
• 2013

This paper proposes a new method that reduces RCS(rader cross section) of the aluminum plate using a oscillation system composed of a VGA(variable gain amplifier) and a phase shifter. Once the oscillation system receives the external-RF signal through a probe on aluminum plate, it makes an amplified signal with a specific phase to cancel the signal reflected from the aluminum plate. The signal transmitted from the oscillation system has the same amplitude and out of phase with the reflected signal. And it can be controlled by the VGA and the phase shifter in the oscillation system. In order to validate the performance of the proposed oscillation system, FEM simulator was used and we measured how much an amplitude of the signal reflected from the aluminum plate rotated in phi direction is reduced in an anechoic chamber.

• 한국산학기술학회논문지
• /
• 제10권7호
• /
• pp.1509-1513
• /
• 2009

본 논문에서는 광대역 통신 시스템을 위한 반원형 (semi-circle) 안테나에 대하여 소개 하였다. 제안된 안테나는 1.5GHz 부터 5GHz (> ${\sim}$110%) 이상의 광대역 주파수 대역에서 전방향성 의 선형 편파를 방사 한다. 반원 안테나의 중심 급전 점으로 부터의 경사각 (tilt angle) 변화에 의하여 발생하는 안테나상의 전류 경로 변화와 이에 따른 동작 주파수 대역 변화에 대하여 조사하였으며, 측정된 안테나의 최대 이득은 동작 주파수 대역에서 2 ${\sim}$3 dBi 이다.

• 한국산학기술학회논문지
• /
• 제10권7호
• /
• pp.1497-1502
• /
• 2009

자동노출은 피사체나 광원의 밝기 변화에 대응하여 카메라로부터 취득된 영상의 노출치를 일정하게 유지시켜주는 기능을 나타내며, CIS 기반 모바일 카메라의 핵심 구성 요소 중의 하나이다. 일반적으로 자동노출 알고리즘은 소프트웨어로 구현되어 CPU와 소프트웨어를 저장하기 위한 ROM을 내장하는 구조를 가지는데, 이는 유연성을 확보하는 대신 CPU와 메모리라는 비용증가로 이어지게 된다. 본 논문에서는 CIS 기반 모바일 카메라를 위하여 임의의 프레임율 가변기능과 아날로그 게인 조정이 가능한 자동 노출 알고리즘을 제안하고, FSM 기반으로 구성된 하드웨어 구조를 제안한다.

• Mass Spectrometry Letters
• /
• 제12권4호
• /
• pp.126-130
• /
• 2021

The mass spectrometry (MS) provides the mass-to-charge ratios of atoms, molecules, stable/metastable complexes, and their fragments. I have taken a long journey with MS to address outstanding issues and problems by experiments and theory and gain insights into underlying principles in chemistry. By looking through the mass-to-charge ratio, I have studied thermochemical problems in silicon chemistry, the infrared multiphoton dissociation spectroscopy of organometallic intermediates, unimolecular dissociations of halotoluene radical cations, and the kinetics of association/dissociation of alkali halide triple ions with Lewis bases. Various MS platforms have been used to characterize non-covalent interactions between porphyrins and fullerenes and those between the group IIB ions and trioctylchalcogenides, and to examine the binding of the group IA, IIA and porphyrin ions to G-quadruplex DNA. Recently, I have focused on mass-balanced H/D isotope dipeptide tags for MS-based quantitative proteomics, a simple chemical modification method for MS-based lipase assay, and the kinetics and dynamics of energy-variable collision-induced dissociation of chemically modified peptides. Now, I see an important role of MS in global issues in the post-COVID era, as the society demands high standards for indoor air quality to contain the airborne-pathogen transmission as well as in-situ monitoring and tracking of carbon emissions to reduce global warming.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권5호
• /
• pp.2400-2413
• /
• 2019

Doubly-selective (DS) fading channel is often occurred in many orthogonal frequency division multiplexing (OFDM) communication systems, such as high-speed rail communication systems and underwater acoustic (UWA) wireless networks. It is challenging to provide an accurate and fast estimation over the doubly-selective channel, due to the strong Doppler shift. This paper addresses the doubly selective channel estimation problem based on complex exponential basis expansion model (CE-BEM) in OFDM systems from the perspective of distributed compressive sensing (DCS). We propose a novel DCS-based improved sparsity adaptive matching pursuit (DCS-IMSAMP) algorithm. The advantage of the proposed algorithm is that it can exploit the joint channel sparsity information using dynamic threshold, variable step size and tailoring mechanism. Simulation results show that the proposed algorithm achieves 5dB performance gain with faster operation speed, in comparison with traditional DCS-based sparsity adaptive matching pursuit (DCS-SAMP) algorithm.

• Nuclear Engineering and Technology
• /
• 제51권4호
• /
• pp.1081-1090
• /
• 2019

Detailed pulse shape analysis of a Geiger-$M{\ddot{u}}ller$ counter is performed to understand the pulse shape dependence on operating voltage. New data is presented to demonstrate that not all pulses generated in a GM counter are identical. In fact, there is a strong correlation between the operating voltage and the pulse shape. Similar to detector deadtime, pulse shapes fall in three distinct regions. For low voltage region, where deadtime was reported to reduce with increasing voltage, pulse generated in this region was observed to have a fixed pulse width with a variable tail. The pulse width and fall time of the tail was observed to be a function of applied voltage; exponentially reducing with increasing voltage with an exponent of negative 6E-04 and 2E-03 respectively. The second region showed a pulse without any significant tail. During this time the detector deadtime was earlier reported to be at its minimum. The highest voltage region demonstrated a different deadtime mechanism where the second pulse was reduced in width. During this time the deadtime seemed to be increasing with increasing voltage. This data allows us to gain some unique insight into the phenomenon of GM detector deadtime not reported thus far.

• Coupled systems mechanics
• /
• 제8권4호
• /
• pp.351-375
• /
• 2019

The present work investigates the use of a rigid rocking block as a tool to reduce vibrations in a frame structure. The study is based on a simplified model composed by a 2-DOF linear system, meant to represent a general M-DOF frame structure, coupled with a rocking rigid block through a linear visco-elastic device, which connects only the lower part of the 2-DOF system. The possibility to restrain the block directly to the ground, by means of a second visco-elastic device, is investigated as well. The dynamic response of the model under an harmonic base excitation is then analysed in order to evaluate the effectiveness of the coupling in reducing the displacements and the drift of the 2-DOF system. The nonlinear equations of motion of the coupled assemblage 2-DOF-block are obtained by a Lagrangian approach and then numerically integrated considering some reference mechanical and geometrical quantities as variable parameters. It follows an extensive parametric analysis, whose results are summarized through behaviour maps, which portray the ratio between the maximum displacements and drifts of the system, with and without the coupling with the rigid block, for several combinations of system's parameters. When the ratio of the displacements is less than unity, the coupling is considered effective. Results show that the presence of the rocking rigid block improves the dynamics of the system in large ranges of the characterizing parameters.

• Journal of Power Electronics
• /
• 제19권1호
• /
• pp.201-210
• /
• 2019

This paper proposes a multimode hybrid control strategy that can achieve zero-voltage switching of primary switches and zero-current switching of secondary rectifier diodes in a wide input voltage range for full-bridge LLC resonant converters. When the input voltage is lower than the rated voltage, the converter operates in Mode 1 through the variable-frequency control strategy. When the input voltage is higher than the rated voltage, the converter operates in Mode 2 through the VF and phase-shift control strategy until the switching frequency reaches the upper limit. Then, the converter operates in Mode 3 through the constant-frequency and phase-shift control strategy. The secondary-side diode current will operate in the discontinuous current mode in Modes 1 and 3, whereas it will operate in the boundary current mode in Mode 2. The current RMS value and conduction loss can be reduced in Mode 2. A detailed theoretical analysis of the operation principle, the voltage gain characteristics, and the realization method is presented in this paper. Finally, a 500 W prototype with 100-200 V input voltage and 40 V output voltage is built to verify the feasibility of the multimode hybrid control strategy.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권1호
• /
• pp.519-529
• /
• 2021

This study aims to investigate the impact of Human Resource Management Practices (HRMP) on improving Employee Performance (EP). The study is accomplished by hypothesizing the impact of HRMP on EP, additionally, this impact is theorized to be mediated through job satisfaction. Employee engagement is also taken into account because of the potential moderating effect it has within the theorized model. Data was collected from 480 questionnaires which were distributed among commercial banks' workers in Jordan and were analyzed using structural equation modeling techniques (SEM), path analysis, and confirmatory factor analysis (CFA). Analysis of a moment structures (AMOS) software version 24 was applied to complete our analysis. The results show that HRMP had a positive impact on EP, as well as job satisfaction and its components (job stability and job enrichment). The mediating role of job satisfaction (enrichment and stability) was discovered. Finally, employee engagement emerged as a moderating variable linking HRMP and EP. The findings of this study show the importance of the role played by job satisfaction and employee engagement in achieving human resources performance goals. Future analysis is recommended to gain deeper insight into the relationship between HRMP, job satisfaction, worker training, and performance appraisal.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권1호
• /
• pp.1009-1016
• /
• 2021

Productive human resources are important assets for companies in facing the global economic competition. The purpose of this study is to examine the effect of economic attitudes toward employees' job satisfaction as well as understanding the impact of economic attitudes toward employee productive behavior at "Sentra Tenun Ikat" in East Java. The research method applied in this study is quantitative research with an explanatory design, which is intended to gain a better understanding of the relationship between variables. The population in this study amounted to 394 participants from SMEs and joint business groups. Meanwhile, the sample was 197 people and collected using a proportional random sampling technique. The variable measurement was carried out by a questionnaire distributed to respondents, which consisted of thirty-five closed questions. Each question item provides five alternative answers. Furthermore, it is calculated using Structural Equation Modeling (SEM) undergoing the LISREL 8.80 program. The findings indicated that there was a positive influence of economic attitudes on employees' job satisfaction. Indeed, the positive value coefficient indicates that there is an effect that is directly proportional to economic attitudes toward employees' productive behavior through employee performance satisfaction, namely, the better the economic attitude taken, the higher the productive behavior of employees.