• Title/Summary/Keyword: channel properties

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PEMFC Optimization Design Using Genetic Algorithm (유전자 알고리즘을 이용한 고분자 전해질 연료전지 최적화 설계)

  • Yang, Woo-Joo;Wang, Hong-Yang;Lee, Dae-Hyung;Kim, Young-Bae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.11
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    • pp.889-897
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    • 2014
  • This paper presents a method for finding an optimized result by using a genetic algorithm (GA) based on a PEMFC analysis result. The conventional analysis method designs fuel cells one-by-one, and each result is compared to obtain the best performance. Because the computational burden of the conventional analysis is enormous, the present optimization process provides an inefficient tool by automatically setting the boundary and material properties and mesh generation. As the change can be reflected automatically in the channel geometry with GA, the fuel cell analysis result with various sizes can be obtained easily. Therefore, the global maximum performance can be obtained through a GA optimization procedure.

Atomic Layer Deposited ZrxAl1-xOy Film as High κ Gate Insulator for High Performance ZnSnO Thin Film Transistor

  • Li, Jun;Zhou, You-Hang;Zhong, De-Yao;Huang, Chuan-Xin;Huang, Jian;Zhang, Jian-Hua
    • Electronic Materials Letters
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    • v.14 no.6
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    • pp.669-677
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    • 2018
  • In this work, the high ${\kappa}$ $Zr_xAl_{1-x}O_y$ films with a different Zr concentration have been deposited by atomic layer deposition, and the effect of Zr concentrations on the structure, chemical composition, surface morphology and dielectric properties of $Zr_xAl_{1-x}O_y$ films is analyzed by Atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and capacitance-frequency measurement. The effect of Zr concentrations of $Zr_xAl_{1-x}O_y$ gate insulator on the electrical property and stability under negative bias illumination stress (NBIS) or temperature stress (TS) of ZnSnO (ZTO) TFTs is firstly investigated. Under NBIS and TS, the much better stability of ZTO TFTs with $Zr_xAl_{1-x}O_y$ film as a gate insulator is due to the suppression of oxygen vacancy in ZTO channel layer and the decreased trap states originating from the Zr atom permeation at the $ZTO/Zr_xAl_{1-x}O_y$ interface. It provides a new strategy to fabricate the low consumption and high stability ZTO TFTs for application.

A study on waterfall classification by form and processes (폭포의 지형학적 분류에 관한 연구)

  • PARK, Kyeong;KIM, Ji Young
    • Journal of The Geomorphological Association of Korea
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    • v.21 no.4
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    • pp.85-96
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    • 2014
  • A waterfall is a channel unit with steep bedrock. No strict criteria for height, water volume, gradient to define waterfalls exist in Korea. The goal of our study is to classify waterfalls based on morphological forms which are the outcomes of developmental processes. The genesis of waterfall depends upon erosional properties of waterfall. The height, gradient, bedrock strength and stream power of waterfalls are regarded as the main factors, by which waterfalls can be classified. We find out that the most important factor for the development of waterfalls is joint system. Development of joint system varies depending on bedrocks. Flow directions and erosional types are decided by the density and direction of joint system in the bedrock, which also decide the height and gradient of stream bed. Joint type decides the gradients of the bed, gradient and height of waterfalls, therefore, decides morphological forms.

Performance of hybrid modulation for digital IoT doorlock system with color grid (컬러그리드기반 디지털 IoT 도어락 시스템을 위한 혼합변조의 성능)

  • Lee, Sun-Yui;Sun, Young-Ghyu;Sim, Issac;Hwang, Yu-Min;Yoon, Sung-Hoon;Cha, Jae-Sang;Kim, Jin-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.6
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    • pp.91-97
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    • 2018
  • This paper presents implementation possibilities of digital IoT doorlock systems via VLC(Visible Light Communication)'s color grid. The color grid-based VLC modulation scheme which are discussed in this paper utilize the straightness of light and abundant frequency resources which are the properties of the light. Performance results in this paper are compared to that of conventional modulations with Bit Error Rate (BER) and Signal to Noise Ratio (SNR) simulations. With respect to a channel model, the proposed modulation schemes select the nearest Line Of Sight (LOS) except Non Line Of Sight (NLOS). Experiments in this paper show error rates of received symbols by changing power dB at a distance of 3m between Tx and Rx in an indoor environment. Through performance results and experiments, this paper demonstrates superiority of the proposed color grid-based modulation schemes.

Onion peel extract and its constituent, quercetin inhibits human Slo3 in a pH and calcium dependent manner

  • Wijerathne, Tharaka Darshana;Kim, Ji Hyun;Kim, Min Ji;Kim, Chul Young;Chae, Mee Ree;Lee, Sung Won;Lee, Kyu Pil
    • The Korean Journal of Physiology and Pharmacology
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    • v.23 no.5
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    • pp.381-392
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    • 2019
  • Sperm function and male fertility are closely related to pH dependent $K^+$ current (KSper) in human sperm, which is most likely composed of Slo3 and its auxiliary subunit leucine-rich repeat-containing protein 52 (LRRC52). Onion peel extract (OPE) and its major active ingredient quercetin are widely used as fertility enhancers; however, the effect of OPE and quercetin on Slo3 has not been elucidated. The purpose of this study is to investigate the effect of quercetin on human Slo3 channels. Human Slo3 and LRRC52 were co-transfected into HEK293 cells and pharmacological properties were studied with the whole cell patch clamp technique. We successfully expressed and measured pH sensitive and calcium insensitive Slo3 currents in HEK293 cells. We found that OPE and its key ingredient quercetin inhibit Slo3 currents. Inhibition by quercetin is dose dependent and this degree of inhibition decreases with elevating internal alkalization and internal free calcium concentrations. Functional moieties in the quercetin polyphenolic ring govern the degree of inhibition of Slo3 by quercetin, and the composition of such functional moieties are sensitive to the pH of the medium. These results suggest that quercetin inhibits Slo3 in a pH and calcium dependent manner. Therefore, we surmise that quercetin induced depolarization in spermatozoa may enhance the voltage gated proton channel (Hv1), and activate non-selective cation channels of sperm (CatSper) dependent calcium influx to trigger sperm capacitation and acrosome reaction.

A Image Search Algorithm using Coefficients of The Cosine Transform (여현변환 계수를 이용한 이미지 탐색 알고리즘)

  • Lee, Seok-Han
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.12 no.1
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    • pp.13-21
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    • 2019
  • The content based on image retrieval makes use of features of information within image such as color, texture and share for Retrieval data. we present a novel approach for improving retrieval accuracy based on DCT Filter-Bank. First, we perform DCT on a given image, and generate a Filter-Bank using the DCT coefficients for each color channel. In this step, DC and the limited number of AC coefficients are used. Next, a feature vector is obtained from the histogram of the quantized DC coefficients. Then, AC coefficients in the Filter-Bank are separated into three main groups indicating horizontal, vertical, and diagonal edge directions, respectively, according to their spatial-frequency properties. Each directional group creates its histogram after employing Otsu binarization technique. Finally, we project each histogram on the horizontal and vertical axes, and generate a feature vector for each group. The computed DC and AC feature vectors bins are concatenated, and it is used in the similarity checking procedure. We experimented using 1,000 databases, and as a result, this approach outperformed the old retrieval method which used color information.

AANet: Adjacency auxiliary network for salient object detection

  • Li, Xialu;Cui, Ziguan;Gan, Zongliang;Tang, Guijin;Liu, Feng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.15 no.10
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    • pp.3729-3749
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    • 2021
  • At present, deep convolution network-based salient object detection (SOD) has achieved impressive performance. However, it is still a challenging problem to make full use of the multi-scale information of the extracted features and which appropriate feature fusion method is adopted to process feature mapping. In this paper, we propose a new adjacency auxiliary network (AANet) based on multi-scale feature fusion for SOD. Firstly, we design the parallel connection feature enhancement module (PFEM) for each layer of feature extraction, which improves the feature density by connecting different dilated convolution branches in parallel, and add channel attention flow to fully extract the context information of features. Then the adjacent layer features with close degree of abstraction but different characteristic properties are fused through the adjacent auxiliary module (AAM) to eliminate the ambiguity and noise of the features. Besides, in order to refine the features effectively to get more accurate object boundaries, we design adjacency decoder (AAM_D) based on adjacency auxiliary module (AAM), which concatenates the features of adjacent layers, extracts their spatial attention, and then combines them with the output of AAM. The outputs of AAM_D features with semantic information and spatial detail obtained from each feature are used as salient prediction maps for multi-level feature joint supervising. Experiment results on six benchmark SOD datasets demonstrate that the proposed method outperforms similar previous methods.

Development of Molecular Dynamics Model for Water Electrolysis Ionomer (수전해용 이오노머 분자동역학 모델 개발)

  • Kang, Hoseong;Park, Chi Hoon;Lee, Chang Hyun
    • Membrane Journal
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    • v.30 no.6
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    • pp.433-442
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    • 2020
  • In this study, in order to build a molecular dynamics simulation model of ionomer for water electrolysis, an ionomer model that reflects the characteristics of a water electrolysis system in which excess water molecules exist was compared to an ionomer built according to the conventional simulation method of the fuel cells membrane. The final ionomer MD models have a strong phase separation and water channel that is one of the important characteristics of the perfluorinated ionomer, and are stable and water-insoluble under excessive water and high temperature conditions. In the ionomer MD models built in this study, the excess water molecules decrease an ion conductivity due to the dilution of ions, but increase a hydrogen diffusivity. Therefore, it is necessary to design the molecular structure of ionomers for water electrolysis in experimental studies as well as molecular dynamics studies according to the characteristics of the water electrolysis system reported in this study.

Concurrency Control with Dynamic Adjustment of Serialization Order in Multilevel Secure DBMS (다단계 보안 데이타베이스에서 직렬화 순서의 동적 재조정을 사용한 병행수행 제어 기법)

  • Kim, Myung-Eun;Park, Seok
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.9 no.1
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    • pp.15-28
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    • 1999
  • In Multilevel Secure Database Management System(MLS/DBMS), we assume that system has a security clearance level for each user and a classification level for each data item in system and the objective of these systems is to protect secure information from unauthorized user. Many algorithms which have been researched have focus on removing covert channel by modifying conventional lock-based algorithm or timestamp-based algorithm. but there is high-level starvation problem that high level transaction is aborted by low level transaction repeatedly. In order to solve this problem, we propose an algorithm to reduce high-level starvation using dynamic adjustment of serialization order, which is basically using orange lock. Because our algorithm is based on a single version unlike conventional secure algorithms which are performed on multiversion, it can get high degree of concurrency control. we also show that it guarantees the serializability of concurrent execution, and satisfies secure properties of MLS/DBMS.

Statistical Analysis of the Springback Scatter according to the Material Strength in the Sheet Metal Forming Process (판재성형공정에서의 소재 강도에 따른 스프링백 산포의 통계분석)

  • Son, Min-Kyu;Kim, Se-Ho
    • Journal of the Korea Convergence Society
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    • v.13 no.4
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    • pp.287-292
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    • 2022
  • In this paper, the stochastic distribution of the springback amount is investigated for the stamping process of a U-channel shaped-product with ultra-high strength steel. Using the reliability-based design optimization technique (RBDO), stochastic distribution of process parameters is considered in the analysis including material properties and process variation. Quantification of the springback scatters is carried out with the statistical analysis method according to the material strength. It is found that the scattering amount of springback decreases while the amount of springback increases as the tensile strength of the blank material increases, which is investigated by analyzing the strain and stress distribution of the punch and die shoulder. It is noted that the proposed scheme is capable of predicting and responding to the unavoidable scattering of springback in the sheet metal forming process.