• Journal of Power System Engineering
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• v.13 no.6
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• pp.102-109
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• 2009

A retarder, as a supplementary brake system that is not friction-based, is frequently used in heavy-duty vehicles generally to slow the vehicles down on inclines. The electric retarder mainly used in a heavy-duty bus is generally placed between the transmission and the axle. The rotor inside the retarder system is attached to the axle. The operation of the retarder within a driven vehicle generates reverse torque due to coast driving force on hypoid gears in the differential gear system. By the reverse torque, scoring or scuffing on the hypoid gear teeth may directly occur. The scoring may be generated due to excessive contact stresses on the tooth surface. In this study, tooth contact stresses and contact patterns were analysed in order to investigate on the tooth scoring phenomenon using a finite element analysis program T900 in which the Hertzian contact stress formula was taken. Backlash, wear and surface finish were considered in the finite element simulation on the scoring.

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.158-165
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• 2020

Buoys are a necessary component for the safety of vessel traffic. However, if the buoy becomes inoperable from damage and loss, it can have significant impact on vessel traffic safety as well as unexpected budget spending. The purpose of this study was to evaluate the risk of accidental contact by applying the marine traffic assessment index that can reflect the traffic flow in the sea area. First, Busan Port No. 5 fairway, with a high number of buoys and many contact accidents, was set as the sea area for assessment. to investigate the status of accidental contact and evaluate risk of contact accidents based on the IALA Waterway Risk Assessment Programme (IWRAP MkII) and Potential Assessment of Risk Model (PARK Model). As a result, buoys are near the P recautionary Area wherein the traffic flow was complicated by the Masan port vessel and Busan new port vessel, and buoys are near the entrance of the Gadeok waterway, wherein vessels show a pattern of navigation across the fairway and buoys are near the breakwater in the inner fairway were considered as high risk for contact accidents. This study can be used as basic data for establishing an integrated model to evaluate the risk of buoy contact accidents.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.78-78
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• 2021

영상유속분석법은 비접촉식으로 유속을 측정하는 방법으로 특히 홍수시 하천의 표면유속을 안전하게 계측할 수 있어서 경제적이고 안전한 하천유속 측정 방법 중 하나이다. STIV는 영상의 휘도 정보를 시간 방향으로 나열하여 작성된 STI(Space-Time Image)에 나타나는 패턴의 기울기를 이용하여 유속을 산정하는 방법이다. 특히 STIV(Space-Time Image Velocimetry)는 기존 입자군의 상호상관법에 기초한 입자영상유속계와 달리 표식자의 유무와 상관없이 유속을 측정할 수 있어 적용성과 안정성이 확보된다. 하지만 영상의 상태가 불량한 경우 정확한 유속 측정이 난해하며 야간에는 별도의 조명 추가 및 태풍과 같은 악기상에서는 빗방울이 카메라에 맺히거나 수면의 진동, 구조물의 진동에 의한 영상의 상태가 불량하게 되어 측정 정도가 떨어진다. 이처럼 영상을 이용한 유속 계측에 있어 다양한 연구 및 기술개발이 요구되는 시점이다. 따라서 본 연구에서는 영상을 이용한 정확한 유속측정을 위해 STIV와 인공지능을 융합하여 정확한 유속 평가를 목적으로 한다. 우선 기존 STI에 의한 기울기 추정방법을 확장하여 딥러닝(CNN)에 의한 기울기 추정방법을 도입하였다. CNN은 일반적으로 이미지의 특성을 추출하는데 유용한 방법으로서 STI의 2차원 Fourier변환 이미지를 사용하여 패턴의 기울기를 감지하도록 학습하였고 적용 결과 기울기에 대한 인식율은 매우 양호하였으며 이를 이용한 실제 관측 영상에 적용한 결과 유속에 대한 정밀도도 매우 양호하게 나타났다. 또한 딥러닝을 적용한 STIV는 노이즈(진동, 화면 불량 등)가 있는 영상에서도 안정적으로 유속을 산정할 수 있으며 전파유속계를 이용한 실제 하천의 표면유속 관측치와 비교 검토 결과 매우 양호하게 유속을 평가하고 있는 것으로 나타났다.

• Journal of the Mineralogical Society of Korea
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• v.30 no.2
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• pp.71-81
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• 2017

Rock properties and the effects of chemicals that were used for conservation were studied for effective conservation treatment of Seated Buddha rock carving, which is composed of grayish white tuff, at Golguram Hermitage, Gyeongju. The rocks contain 3-5% montmorillonite, a swelling mineral and reacting with water, the d spacing of swelling minerals was increased (1.54-2.69%). On the one hand, the physical properties of the rock samples, such as surface hardness, water absorption rate, and porosity improved after the application of ethyl silicate-based stone strengthener. On the other, the interlayer of swelling minerals decreased and greater the of swelling mineral content, the greater is the extent of swelling (4.23-12.12%). When the ethyl silicate-based stone strengthener was applied after pretreatment with a swelling inhibitor, the physical properties were similar to those of the stone strengthener alone. There was no interlayer spacing change of swelling minerals due to swelling inhibition treatment; however, when the stone strengthener was applied after the swelling inhibitor, interlayer changes were similar to those when only the stone strengthener was treated (4.10-11.85%). Though the peak intensity of swelling minerals in X-ray diffraction pattern decreased, the effect of the swelling inhibitor was almost negligible. Therefore, it is not appropriate to use ethyl silicate-based stone strengthener for Golgulam rock containing swelling minerals and supplementing them with a swelling inhibition system is not effective. Because weathering rapidly progresses when swelling minerals contact moisture, for now, measures to prevent water contact, such as expansion of the canopy, are needed in the lower and side parts of the carving.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.12 s.138
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• pp.1596-1604
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• 2004

Quality Function Deployment(QFD) is a product development tool which ensures that the voice of the customer needs is heard and translated into products. To develop a sensible brassiere for middle-aged women QFD was adopted. In this study the applicability and usefulness of QFD was examined through the engineering design process for a sensible brassiere for middle-aged women. The customer needs for the wear comfort of brassiere was made by one-on-one survey of 100 women who aged 30-40. The customer competitive assessment was generated by wearing tests of 10 commercial brassieres. The subjective assessment was conducted in the enviornmental chamber that was controlled at $28{\pm}1^{\circ}C,\;65{\pm}3\%RH.$ As a results, we developed twenty-one customer needs and corresponding HOWs for the wear comfort of brassiere. The Customer Competitive Assessment was generated by wearing tests of commercial brassiere. The subjective measurement scale and dimension for the evaluation of sensible brassiere were extracted from factor analysis. Four factors were fitting, aesthetic property, pressure sensation, displacement of brassiere due to movement. The most critical design parameter was wire-related property and second one was stretchability of main material of brassiere. Also, wearing comfort of brassiere was affected by the interaction of initial stretchability of wing and support of strap. Engineering design process, QFD was applicable to the development of technical and aesthetic brassieres.