• Title/Summary/Keyword: 수행성 검증

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Energy Absorption Characteristics and Optimal Welding Space of Square Hat Type Thin-walled Tube (정사각 모자형 박판튜브의 에너지흡수특성 및 최적 용접간격)

  • Lee, Hyung-Yil;Kim, Bum-Joon;Han, Byoung-Kee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.12
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    • pp.2703-2714
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    • 2002
  • In this work, energy absorption characteristics and optimal welding space of spot-welded square hat type tube are investigated via quasi-static crush experiments and finite element (FE) analyses. A FE model reflecting the crush characteristics is established based on the experimentally observed crush mechanisms of specimens with welding spaces (20, 30 & 45 mm) and (25,40 & 55 mm) respectively for two specimen widths (60, 75 mm). The established FE model is then applied to other crush models of widths (50, 60 & 75 mm) with various welding spaces (20, 25, 30, 40, 45, 55, 75, 150, 300 mm) respectively. We examine the energy absorption characteristics with respect to the welding space for each specimen width. The outcome suggests an optimal spot welding space of square hat type thin-walled tube. Energy absorption is also presented in terms of yield strength of base metal, specimen thickness, width, and mean crushing force of spot-welded square hat type thin-walled tube.

A Numerical Study of the Effects of Heat Transfer and Fluid Flow on Tube Insertion Length in Computer-Cooling Radiators (컴퓨터 CPU 냉각용 방열기 튜브 삽입길이에 따른 열유동 해석)

  • Choi, Jin-Tae;Kwon, Oh-Kyung;Yun, Jae-Ho;Kim, Yong-Chan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.2
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    • pp.145-152
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    • 2011
  • The performance of flat-tube radiators with louvered fins was numerically investigated for different tube insertion lengths. The results of numerical analysis using CFX-11 were compared with experimental results. In this study, three types of flat-tube radiators with louvered fins were considered. An experiment was conducted to validate the numerical results. Flow rate ratio (FR) and Stotal were introduced to understand the uniformity of flow distribution easily. The results of numerical analysis revealed that the heat transfer rate and pressure drop increased as the mass flow rate increased. Further, the results showed that the heat transfer rate of sample 3 with h/D = 0.5 was higher than that of the other samples. The pressure drop increased as the insertion length toward the header part increased, and the pressure drop in the case of sample 3 appeared to be the highest. The factor Stotal showed that the uniformity of the flow distribution in the case of sample 1 with h/D = 0 was higher than that in the case of the other samples.

Effects of Self-efficacy on Job Embeddedness, Innovation Behaviors, and Organizational Citizenship Behavior - the Moderating Effect Worked Mainly in the Form- (자기효능감이 직무착근도, 혁신행동과 조직구성원 행동에 미치는 영향 -근무형태에 따른 조절효과 중심으로-)

  • Hong, Hyun-Kyong;Chung, Kyoo-Yup;Kim, Won-Hee
    • The Journal of the Korea Contents Association
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    • v.12 no.5
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    • pp.415-430
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    • 2012
  • Under fastly moving businese circumstance, it is very important to retain par excellence human resource and innovation. The purpose of this study is to find out casual relationship among self-efficacy, job embeddedness, innovative behavior, and organizational citizenship behavior, which is dependent variable. With the help of information technology. To verify hypotheses such statistical analyses as factor analysis, reliability test, and path analysis by AMOS 18.0. The population of this study is employees of super deluxe hotels in korea and they are divided into two categories such as front-of-the-house and back-of-the-house respectively with same numbers. In case of mutual relationship between self-efficacy and innovative behavior, self-control and task difficultness factors significantly influence innovative behavior in case of front-of-the house employees and vice-versa in those of back-of-the-house. In case of interactive relationship between self-efficacy and organizational citizenship behavior, slightly different results are revealed between front-and back-of-the-house employees, employees, i.e. all factors are significantly related in former but not in latter.

Image Quality Evaluation in Computed Tomography Using Super-resolution Convolutional Neural Network (Super-resolution Convolutional Neural Network를 이용한 전산화단층상의 화질 평가)

  • Nam, Kibok;Cho, Jeonghyo;Lee, Seungwan;Kim, Burnyoung;Yim, Dobin;Lee, Dahye
    • Journal of the Korean Society of Radiology
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    • v.14 no.3
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    • pp.211-220
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    • 2020
  • High-quality computed tomography (CT) images enable precise lesion detection and accurate diagnosis. A lot of studies have been performed to improve CT image quality while reducing radiation dose. Recently, deep learning-based techniques for improving CT image quality have been developed and show superior performance compared to conventional techniques. In this study, a super-resolution convolutional neural network (SRCNN) model was used to improve the spatial resolution of CT images, and image quality according to the hyperparameters, which determine the performance of the SRCNN model, was evaluated in order to verify the effect of hyperparameters on the SRCNN model. Profile, structural similarity (SSIM), peak signal-to-noise ratio (PSNR), and full-width at half-maximum (FWHM) were measured to evaluate the performance of the SRCNN model. The results showed that the performance of the SRCNN model was improved with an increase of the numbers of epochs and training sets, and the learning rate needed to be optimized for obtaining acceptable image quality. Therefore, the SRCNN model with optimal hyperparameters is able to improve CT image quality.

An Experimental Study of Synthesis and Characterization of Vanadium Oxide Thin Films Coated on Metallic Bipolar Plates for Cold-Start Enhancement of Fuel Cell Vehicles (연료전지 차량의 냉시동성 개선을 위한 금속 분리판 표면의 바나듐 산화물 박막 제조 및 특성 분석에 관한 연구)

  • Jung, Hye-Mi;Noh, Jung-Hun;Im, Se-Joon;Lee, Jong-Hyun;Ahn, Byung-Ki;Um, Suk-Kee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.6
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    • pp.585-592
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    • 2011
  • The enhancement of the cold-start capability of polymer electrolyte fuel cells is of great importance in terms of the durability and reliability of fuel-cell vehicles. In this study, vanadium oxide films deposited onto the flat surface of metallic bipolar plates were synthesized to investigate the feasibility of their use as an efficient self-heating source to expedite the temperature rise during startup at subzero temperatures. Samples were prepared through the dip-coating technique using the hydrolytic sol-gel route, and the chemical compositions and microstructures of the films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy. In addition, the electrical resistance hysteresis loop of the films was measured over a temperature range from -20 to $80^{\circ}C$ using a four-terminal technique. Experimentally, it was found that the thermal energy (Joule heating) resulting from self-heating of the films was sufficient to provide the substantial amount of energy required for thawing at subzero temperatures.

Design of MRI Spectrometer Using 1 Giga-FLOPS DSP (1-GFLOPS DSP를 이용한 자기공명영상 스펙트로미터 설계)

  • 김휴정;고광혁;이상철;정민영;장경섭;이동훈;이흥규;안창범
    • Investigative Magnetic Resonance Imaging
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    • v.7 no.1
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    • pp.12-21
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    • 2003
  • Purpose : In order to overcome limitations in the existing conventional spectrometer, a new spectrometer with advanced functionalities is designed and implemented. Materials and Methods : We designed a spectrometer using the TMS320C6701 DSP capable of 1 giga floating point operations per second (GFLOPS). The spectrometer can generate continuously varying complicate gradient waveforms by real-time calculation, and select image plane interactively. The designed spectrometer is composed of two parts: one is DSP-based digital control part, and the other is analog part generating gradient and RF waveforms, and performing demodulation of the received RF signal. Each recover board can measure 4 channel FID signals simultaneously for parallel imaging, and provides fast reconstruction using the high speed DSP. Results : The developed spectrometer was installed on a 1.5 Tesla whole body MRI system, and performance was tested by various methods. The accurate phase control required in digital modulation and demodulation was tested, and multi-channel acquisition was examined with phase-array coil imaging. Superior image quality is obtained by the developed spectrometer compared to existing commercial spectrometer especially in the fast spin echo images. Conclusion : Interactive control of the selection planes and real-time generation of gradient waveforms are important functions required for advanced imaging such as spiral scan cardiac imaging. Multi-channel acquisition is also highly demanding for parallel imaging. In this paper a spectrometer having such functionalities is designed and developed using the TMS320C6701 DSP having 1 GFLOPS computational power. Accurate phase control was achieved by the digital modulation and demodulation techniques. Superior image qualities are obtained by the developed spectrometer for various imaging techniques including FSE, GE, and angiography compared to those obtained by the existing commercial spectrometer.

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A Pulse-Echo Testing Model for Partially Damaged Ultrasonic Transducers (부분 손상을 입은 초음파 탐촉자의 펄스-에코 시험 모델)

  • Song, Sung-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.16 no.2
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    • pp.95-108
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    • 1996
  • In ultrasonic testing, flaw signal from which quantitative information on flaws is determined is influenced by 3 factors : (1) the incident wavefield.produced by the transducer, (2) the scattered waves produced by flaws, and (3) the reception of the scattered waves back at the transducer. So even small changes in transducer performance due to aging or unexpected damages can produce the changes in the characteristics of flaw signal and finally the changes in the quantitative information on flaws. Thus a reliable calibration method of transducer performance is desired. Recently, theoretical models for ultrasonic testing have been employed as reference standards for the calibration of transducers which are considered as circular planar piston sources in the most of cases. But this simplification cannot be applied to partially damaged transducer which has lost their symmetry in performance, even not in appearance. Unfortunately there has been no reliable practical model which can be used for the calibration of partially damaged transducers. Here a pulse-echo testing model for partially damaged ultrasonic transducers was developed with experimental verification. The experimental responses agree very well with the theoretical prediction. So we expect that this model can be served as a theoretical reference standards for transducer calibration.

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A Study on Designing an Effective Support Point for After-Stern Tube Bearings Concerning Shaft Alignment (추진축계 정렬시 선미관 베어링 유효지지점 설정에 관한 연구)

  • Lee, Jae-ung;Kim, Yeonwon;Kim, Jung-Ryul
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.6
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    • pp.803-809
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    • 2018
  • Generally, the gap-and-sag method is used in the shipbuilding stage before coupling the shafts to check whether they are installed at the same position as designed and derived from shaft alignment calculation. The primary installed propeller shaft becomes a reference point, the position of the remaining shafts are sequentially determined through the gap-and-sag value derived from the deflection and deflection angle at each shaft flange by own weight. If the reference point varies against the design value, it would have a series of effects on the installation of the remaining shafts. Moreover, after coupling the shafts, even if the bearing reaction forces derived from measurement are satisfied by the allowable limit range, consequently it might have an adverse effect on the stability of the shafting system by not being able to estimate the relative slope angle between the propeller shaft and the after-stern tube bearing. In this paper, to deal with above-mentioned phenomenon, the theoretical calculations related to designing an effective support point of the aft stern tube bearing and analysis by measurement is conducted through a case of open-up inspections. Based on this, a shaft installation guideline is proposed to minimize the misalignment related to preventing wiping damage of the after-stern tube bearing.

A Study on the Application of Spatial Big Data from Social Networking Service for the Operation of Activity-Based Traffic Model (활동기반 교통모형 분석자료 구축을 위한 소셜네트워크 공간빅데이터 활용방안 연구)

  • Kim, Seung-Hyun;Kim, Joo-Young;Lee, Seung-Jae
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.15 no.4
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    • pp.44-53
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    • 2016
  • The era of Big Data has come and the importance of Big Data has been rapidly growing. The part of transportation, the Four-Step Travel Demand Model(FSTDM), a traditional Trip-Based Model(TBM) reaches its limit. In recent years, a traffic demand forecasting method using the Activity-Based Model(ABM) emerged as a new paradigm. Given that transportation means the spatial movement of people and goods in a certain period of time, transportation could be very closely associated with spatial data. So, I mined Spatial Big Data from SNS. After that, I analyzed the character of these data from SNS and test the reliability of the data through compared with the attributes of TBM. Finally, I built a database from SNS for the operation of ABM and manipulate an ABM simulator, then I consider the result. Through this research, I was successfully able to create a spatial database from SNS and I found possibilities to overcome technical limitations on using Spatial Big Data in the transportation planning process. Moreover, it was an opportunity to seek ways of further research development.

Radix-4 Trellis Parallel Architecture and Trace Back Viterbi Decoder with Backward State Transition Control (Radix-4 트렐리스 병렬구조 및 역방향 상태천이의 제어에 의한 역추적 비터비 디코더)

  • 정차근
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.40 no.5
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    • pp.397-409
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    • 2003
  • This paper describes an implementation of radix-4 trellis parallel architecture and backward state transition control trace back Viterbi decoder, and presents the application results to high speed wireless LAN. The radix-4 parallelized architecture Vietrbi decoder can not only improve the throughput with simple structure, but also have small processing delay time and overhead circuit compared to M-step trellis architecture one. Based on these features, this paper addresses a novel Viterbi decoder which is composed of branch metric computation, architecture of ACS and trace back decoding by sequential control of backward state transition for the implementation of radix-4 trellis parallelized structure. With the proposed architecture, the decoding of variable code rate due to puncturing the base code can easily be implemented by the unified Viterbi decoder. Moreover, any additional circuit and/or peripheral control logic are not required in the proposed decoder architecture. The trace back decoding scheme with backward state transition control can carry out the sequential decoding according to ACS cycle clock without additional circuit for survivor memory control. In order to evaluate the usefulness, the proposed method is applied to channel CODEC of the IEEE 802.11a high speed wireless LAN, and HDL coding simulation results are presented.