• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.138-144
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• 2003

Rencentely, the request for the light weight is more incresed in the area of industrial environment and machinery and consistent effort is needed to accomplish high strength of material for the direction of light weight. we got the following characteristic from crack growth test carried out in the range of stress ration of 0.1, 0.3 and 0.6 by means of opening mode displacement. At the content stress ratio, the threshold stress intensity factor crack range ${\Delta}K_{th}$in the early stage of fatigue crack growth (Region I) and dtress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) with an increase in ${\Delta}K$. Fatigue life shows more improvement in the Shot-peened material than in the Un-peening material. And compressive residual stress of surface on the Shot peening processed operate resistance force of fatigue. So we can obtain fallowings. (1) The fatigue crack growth rate on stage II is conspicuous with the size of compressive residual stress and is depend on Paris equation. (2) Although the maxium compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maxium compressive residual stress is formed in surface. (3) The threshold stress intensity factor range is increased with increasing compressive residual stress.

• 한국의류산업학회지
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• 제21권6호
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• pp.697-707
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• 2019

This review paper deals with materials, classification, and a current article investigation on smart textile sensors for wearable vital signs monitoring (WVSM). Smart textile sensors can lose electrical conductivity during vital signs monitoring when applying them to clothing. Because they should have to endure severe conditions (bending, folding, and distortion) when wearing. Imparting electrical conductivity for application is a critical consideration when manufacturing smart textile sensors. Smart textile sensors fabricate by utilizing electro-conductive materials such as metals, allotrope of carbon, and intrinsically conductive polymers (ICPs). It classifies as performance level, fabric structure, intrinsic/extrinsic modification, and sensing mechanism. The classification of smart textile sensors by sensing mechanism includes pressure/force sensors, strain sensors, electrodes, optical sensors, biosensors, and temperature/humidity sensors. In the previous study, pressure/force sensors perform well despite the small capacitance changes of 1-2 pF. Strain sensors work reliably at 1 ㏀/cm or lower. Electrodes require an electrical resistance of less than 10 Ω/cm. Optical sensors using plastic optical fibers (POF) coupled with light sources need light in-coupling efficiency values that are over 40%. Biosensors can quantify by wicking rate and/or colorimetry as the reactivity between the bioreceptor and transducer. Temperature/humidity sensors require actuating triggers that show the flap opening of shape memory polymer or with a color-changing time of thermochromic pigment lower than 17 seconds.

• 대한지역사회영양학회지
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• 제4권3호
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• pp.466-478
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• 1999

A significant gap can exist between what customers expect in foodservice and what service providers deliver to customers. Reducing the gap and enhancing service quality plays a key role in increasing customer satisfaction and repurchase intentions. The purpose of this study was to investigate the personal and operational characteristics that affect the customer perceptions of service quality, to analyze the overall satisfaction and repurchase intention of customers, and to study the service quality gap between customer and foodservice provides. 427 customers and 278 foodservice providers in 82 fast food and family restaurants were surveyed. T-test, ANOVA, Correlation Analysis, and Multiple Regression were used for statistical analysis, The results of this study were as follows: 1) Among the personal characteristics of customers, sex affected the preception of 'General Management' and 'Reputation', and the expense per person showed a correlation with service quality. 2) Among the operational characteristics, the type of restaurant, months since opening, and the number of seats had a significant impact on service quality, while the seat turnover rate showed a negative correlation with service quality. 3) Among the human resource characteristics, the proportion of part-time employees had a negative correlation with service quality, and in general, the training program for full-time employees led to a higher degree of customer perception of service quality. 4) Six dimensions of service quality accounted for 38.39% of customer satisfaction in Multiple Regression. 5) The overall satisfaction of customers willing to repurchase was significantly higher than that of the non-repurchase customers. 6) The operational characteristics explained over 35% for the service quality gap among the customers and the service providers in Multiple Regression.

• Journal of Advanced Marine Engineering and Technology
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• 제35권6호
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• pp.765-772
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• 2011

본 연구에서는 선박 전원용 SOFC 시스템에 대한 HIL(Hardware-In-the-Loop)을 구축하기 위하여 실시간 코드 생성이 가능한 연료전지 시스템 모델을 개발을 하였다. 또한, 메탄을 연료로 사용한 내부개질형 500kW급 고체산화물형 연료전지 시스템에서 연료전지 스택으로 공급되는 애노드와 캐소드 공급가스의 온도 차이를 최소화하기 위하여 연료전지 스택 배기가스의 유량 분배, 연료 및 공기 공급 유량, 공급 공기 온도의 영향이 애노드 및 캐소드 공급 가스의 온도 특성과 연료전지 스택 출력 및 시스템 효율 등에 미치는 영향에 관하여 검토하였다. 그 결과 터빈 출구에 위치한 3-Way 밸브의 위치가 0.839에서 애노드와 캐소드 공급 가스 온도가 약 830K에서 동일하게 유지됨을 알 수 있었다. 또한, 애노드와 캐소드 공급 가스 온도를 높이기 위해서는 연료전지 스택 및 시스템 효율을 충분히 고려하여 메탄 공급 유량을 최적화하는 프로세스가 필요함을 알 수 있었다.

• 대한기계학회논문집A
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• 제38권7호
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• pp.817-822
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• 2014

경춘 복선의 일반 전동열차와 준 고속 열차인 ITX-청춘이 개통된 이래, 서울과 춘천을 오가는 유동인구가 급증하고 있다. 이는 대용량성과 저렴한 요금, 운행의 정시성 및 안전성 측면에서 다른 교통수단에 비해 철도 운송의 경쟁력이 높기 때문이다. 그러나 실내소음 측면에서는 전동 열차에 대한 승객들의 불만이 상당하다. 특히 터널 구간에서 실내소음은 급격히 높아져 대화에도 지장을 줄 정도이다. 본 연구에서는 경춘선 일반 전동 열차와 ITX-청춘 열차를 대상으로 정상 주행 중의 실내소음 특성을 비교 분석한다. 개활지, 터널 및 교량에서의 소음 레벨, 주파수 특성과 음질 지수를 분석하고, 실내 위치에 따른 소음레벨의 차이를 비교하여 소음의 전달 경로를 파악함으로써 향후 전동 열차의 실내소음 향상을 위한 기초 정보를 제공하고자 한다.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.723-735
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• 2020

This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

• 대한환경공학회지
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• 제27권4호
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• pp.438-444
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• 2005

본 연구에서는 가변형 간벽을 설치하고 이 가변형 간벽의 열고 닫음에 따라 하나의 SBR 반응조를 시간적으로 뿐만 아니라 공간적으로도 분리시킴으로써 aerobic, anaerobic 또는 anoxic 상태의 구분을 명확히 하여 탈질 및 탈인 효율을 증대시켰다. 본 연구 결과 $COD_{Cr}$/N ratio 10($BOD_5$/N ratio 5) 정도의 실 플랜트 조건에서 T-N 및 T-P 제거효율은 90.9%와 75%를 나타내었다. 또한 잉여슬러지내 인 함유량 조사결과 기존 처리장에서 발생된 잉여슬러지의 인 함량비율을 100%라 할 때 pilot plant에서 발생된 잉여슬러지의 인 함유율은 생 슬러지의 경우 133.6%, 건조 슬러지의 경우 124.3%로서 기존 처리장의 슬러지내 인 함유율보다 $25{\sim}30%$ 정도 높은 것으로 조사되었다. 따라서 SBR반응조 내에 가변형 간벽을 설치함으로서 명확한 탈질 탈인을 위한 반응조건을 제시해 줄 수 있는 것으로 나타났다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.88-91
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• 1994

It is well known that multipoint and computerized intraoperative mapping systems improve the results of surgery for Wolff-Parkinson-White syndrome and show tremendous potential for opening an entirely new era of surgical intervention for the more common and lethal types of supraventricular tachyarrhythmias such as atrial flutter and atrial fibrillation. In addition, the ability to map and ablate the sometimes fleeting automatic atrial tachycardia is greatly enhanced by computerized mapping systems. In this study, we have developed 64 channel computerized data analysis system using microcomputer (Macintosh IIx) for basic research of electrophysiology and electrical propagation. The bipolar electrogram information is acquired from 64 cardiac sites simultaneously at a sampling rate of 1ksamples/sec with continuous and total data storage of up to 30 seconds. When the reference electrogram is selected and reference point is picked up, delay time from the reference point in displayed on two dimensional diagram of the heart. System design permits easy expansion to almost 256 simultaneous sites, This system is expected to enable us to study pathophysiology of cardiac arrhythmia and to improve the results of diagnosis and surgical treatment for cardiac arrhythmia.

• Journal of Korean Neurosurgical Society
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• 제29권5호
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• pp.659-663
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• 2000

The motality rate of acute subdural hematoma(ASDH) associated with closed head injury is high in spite of recent advances in neurosurgery. Many variables in regard to outcome of ASDH have been assessed. But among them, intracranial pressure(ICP) control and the time interval between injury and operative evacuation are the only things that can be affected by doctor. We introduced a simple method to the management of ASDH for reducing the time interval between injury and operation. When the immediate decompressive operation of ASDH was impossible by any causes, we made a burr hole at the center of hematoma, usually on 2-3cm above temporal squama and 1-2cm behind coronal suture under local anesthesia before main operation. Partial hematoma evacuation was achieved through the burr hole and it was effective in preventing further worsening of patients neurological status before main operation. Prompt hematoma evacuation through the burr hole seemed to be effective in delaying secondary ischemic brain damage and made easy to closing the dura opening and replacement of the bone flap at the end of main decompressive operation. This easy method may reduce the time interval between injury and operation. We represent surgical technique with two cases of ASDH managed with this simple method.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.725-730
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• 2011

우주발사체 추진기관 공급계에서 2-way 솔레노이드밸브는 제어시스템의 명령에 의해 추진제 탱크를 가압하여 탱크내의 압력을 조절한다. 가압용 솔레노이드밸브의 제작에 앞서 설계검증 및 기본적인 작동특성을 분석하기 위해 AMESim상용코드를 이용하여 해석모델을 수립하였다. 입구압력에 따른 작동시간을 시험결과와 비교하여 모델을 검증하였다. 솔레노이드밸브 모델을 이용하여 설계변수인 컨트롤 밸브의 시트 직경, 주 밸브의 시트 직경, 실링 직경 비에 대해 밸브의 동특성 해석을 수행하였다. 해석을 통해 밸브의 개폐작동시간, 작동성능, 개폐압력을 예상하였다. 본 연구 결과는 한국형 발사체 공급계 가압용 솔레노이드밸브의 설계/해석능력을 확보하고 밸브의 개발과정에서 효율성을 높일 수 있으며 파생형 밸브의 설계 및 선행연구에 적용할 수 있을 것으로 판단된다.