Evaluation of the Structural Safety of a Hydraulic Accumulator used for Marine Diesel Engine According to the Thread Root Radius

A hydraulic accumulator used for marine diesel engine consist of two hemispherical threaded shells, threaded lower shell and threaded upper shell in which liquid and gas are separated by a flexible diaphragm. A hydraulic accumulator can be applied in marine diesel engine with heavy vibration and pressure pulsation so it can damp the sudden pressure shock, pulsation and cushion the pressure spike. During the operation of a hydraulic accumulator, the thread of the lower shell is subjected to concentrated stress. The purpose of this study is to investigate numerically the structural safety of a hydraulic accumulator according to the thread root radius and the friction coefficient using three different models of the lower shells with the thread root radius 0.1 mm, 0.2 mm and 0.4 mm respectively. Charging pressure of a hydraulic accumulator is 300 bar and operating pressure range is from 280 to 300 bar. The primary stress was analyzed by calculating the membrane and bending stress of the lower shell, the upper shell and the thread where stress is concentrated under the pressure condition of 300 bar using finite element method. The mesh test is carried out to ensure reliable analysis result by applying very small element size and the gradient mesh in the thread where stress is concentrated. Even if the thread is not subject to the major deformation, the fatigue life should be evaluated because the peak stress of the thread can cause the fatigue failure. There are three different cases of operating pressure range should be evaluated for the fatigue life according to the service condition of a hydraulic accumulator. First, operating pressure range is from 280 to 300 bar in the normal service condition. Second, operating pressure range is from 250 to 300 bar under the severe service condition. Lastly, operating pressure range is defined as the maximum pressure range of 200 to 300 bar under the abnormal service condition. Alternating stress is calculated with the total stress and the fatigue penalty factor according to the yield strength and the tensile strength of the applied material. The fatigue life is evaluated by applying alternating stress to the fatigue life curve of the applied material. The static analysis result of a hydraulic accumulator shows that the general primary membrane stress and primary bending stress do not exceed the allowable stress in the lower shell, the upper shell and the thread where stress is concentrated under the pressure condition of 300 bar. However the result of evaluation of the fatigue life shows the fatigue life increased as the thread root radius and the friction coefficient increased under the severe service condition and abnormal service condition of a hydraulic accumulator used for marine diesel engine.Abstract ·············································································ⅰ Nomenclature ····································································ⅳ List of Tables ······································································ⅴ List of Figures ···································································· ⅵ 1. 서론 ················································································· 1 1.1 연구 배경 ····································································· 1 1.2 연구 목적 및 내용 ·························································· 2 2. 유압 어큐뮬레이터의 구조해석 및 응력 평가 방법 ·················· 4 2.1 유한요소법 ····································································4 2.2 정적파손이론 : 재료의 항복이론 ····································· 5 2.3 응력 분류 ······································································7 2.3.1 일차 응력 ······························································· 7 2.3.2 이차 응력 ······························································· 8 2.3.3 피크 응력 ······························································· 8 2.4 응력 평가 ······································································8 2.4.1 설계 조건에서의 응력 평가 ········································9 2.4.2 수압 시험 조건에서의 응력 평가 ·································10 3. 유압 어큐뮬레이터의 구조해석 ···············································11 3.1 유한요소 모델링 ·······························································11 3.2 재료 특성 ·········································································13 3.3 요소 생성 및 품질 확인 ······················································14 3.4 경계 조건 및 하중 조건 ······················································18 3.5 나사 골 반경에 따른 쉘 응력 비교 ········································20 3.5.1 나사 골 반경 0.1 mm 구조해석 결과 ·····························22 3.5.2 나사 골 반경 0.2 mm 구조해석 결과 ·····························25 3.5.3 나사 골 반경 0.4 mm 구조해석 결과 ·····························28 3.6 나사 골 반경에 따른 나사 응력 비교 ·····································31 4. 유압 어큐뮬레이터의 피로 수명 평가 ·········································37 4.1 피로 수명 평가 개요 ··························································· 37 4.2 피로 수명 평가 내용 ····························································39 4.3 피로 수명 평가 방법 ····························································40 4.4 작동압력 별 피로 수명 평가 ················································ 44 4.4.1 정상 상태에서의 피로 수명 평가 ·····································44 4.4.2 과부하 상태에서의 피로 수명 평가 ··································50 4.4.3 비정상 상태에서의 피로 수명 평가 ··································55 5. 결론 ······················································································· 60 참고문헌 ······················································································62Maste

Development of touchless fingerprint image acquisition device for 5 fingerprints

생체인식 협동과정/석사[한글]지문을 이용한 인증(Identification)시스템은 크게 센서에 지문을 접촉하여 영상을 획득하는 접촉식 방식과 센서에 지문을 접촉하지 않고 획득하는 비접촉식 방식으로 나눌 수 있다. 기존 접촉식 방식에서는 센서에 지문을 접촉할 때 발생하는 위생상의 문제, 불균일한 압력으로 인한 영상 왜곡 문제, 잔류지문(Latent Fingerprint)의 문제가 발생한다. 또한 손의 구조로 인하여 5손가락의 지문 영상을 한번에 획득하지 못함으로 지문 입력 시 사용자의 불편을 야기하는 문제가 있다. 본 논문에서는 이러한 문제들의 해결을 위하여 비접촉식 5지문 영상획득 장비를 제안한다. 카메라, 모터, 평면 거울 및 LED 조명을 사용하여 사용자가 센서에 접촉하지 않고도 지문 영상을 획득할 수 있도록 하였으며, 5손가락을 입력하여 한번에 5손가락의 지문 영상을 획득할 수 있게 하였다. 또한 제안한 장비에서 카메라의 초점, 조명의 균일도, 손가락의 돌아감(Rolling)을 살펴보고 평가함으로써, 장비 구성 요소 및 장비 완성도를 평가하였다. 유용면적(Possible Region)을 정의함으로 접촉식 장비에서 얻은 지문 영상과의 비교 근거를 마련하였고, 장비간의 간접적인 성능 비교를 시도하였다. 또한 실제 사용자의 지문을 등록하고 정합 실험을 수행함으로써 제안한 장비의 성능을 알아보았다. 결과적으로 제안한 장비에서 획득되는 지문 영상 중 소지를 제외한 나머지 네 개의 지문 영상에서 평균 오류율 4.4%를 확인하였다. 또한 5지 모두를 인식에 사용하였을 경우 최소 오류율이 0% 임을 확인하였다. 이는 제안한 장비가 실제적인 지문 등록 및 인식에 사용 가능함을 보여준다. [영문]Fingerprint recognition systems for identification are divided as touch-based and non touch-based.(touchless) Touch-based Fingerprint Sensors have some problems which are hygienic troubles, image degradations by user’s inconsistent pressure and latent fingerprints. Moreover, there is inconvenience that touch-based fingerprint sensors can not acquire 5 fingerprint images at once because of geometry of hands. So, this thesis proposes touchless fingerprints images acquisition device for 5 fingerprints. The device composes of CCD camera, stepping motor, mirror and Green LED light. This device can solve problems of touch-based fingerprint sensors and get 5 fingerprint images at once. And it is evaluated the completion of device for fingerprint recognition by checking focus, uniformity of illumination and finger rolling. Also it defines possible region so that can compare with touch-based fingerprint images. The recognition performance of device can be measured by enrolling and matching test of users. The matching test result shows that average EER 4.4% when fingerprint images are used individually for recognition except little finger image, and average EER 0% in minimum case when 5 fingerprint images are used for recognition. That results show the proposed device is suitable for enrollment and recognition of fingerprintsope

The methods of analyzing user's relative sensitivities to visual features and applying them to content-based image retrieval

본 발명은 검색 결과에 대한 사용자의 피드백(feedback)을 이용해서 사용자의 각 시각 특징에 대한 상대적인 민감도를 분석하고 분석된 민감도를 그 이후의 검색에 적용하는 사용자의 시각 특징에 대한 상대적인 민감도를 적용한 내용기반 영상 검색방법에 관한 것이다.이러한 본 발명에 따른 내용기반 영상 검색방법은, 임의의 질의에 대한 검색 결과를 이용하여 각 시각 특징에 대한 사용자의 상대적인 민감도를 분석하여 학습하는 제1단계와, 사용자로부터 질의 내용이 주어지는 제2단계, 상기 질의의 각 시각 특징값들을 신경 회로망에 입력하여 각 시각 특징에 대한 상대적인 민감도를 얻어내는 제3단계, 상기 각 시각 특징에 대한 상대적인 민감도가 적용된 두 영상간의 특징 공간에서의 거리를 구하는 식에 상기 질의와 검색 영상을 적용하여, 상대적인 민감도가 적용된 상기 질의와 검색 영상 사이의 특징 공간에서의 거리를 구하는 제4단계, 및 상기 질의와 상기 검색 영상 사이의 특징 공간에서의 거리에 따라 상기 질의와 유사한 검색 영상을 사용자에게 제공하는 제5단계를 포함한다.내용기반 검색, 유클리드 거리, 민감도, 영상검

Development of Motor Vehicle Emission Control Technologies;Development of the Performance Measuring Technique in a Diesel Particulate Trap System

funder : 환경부연구개발내용 및 연구범위 ○ 자료조사 - DPF 장치의 연구 및 개발 동향 : 북미, 일본 및 유럽지역 ○ ECU 작동확인 실험 - ECU에 의한 재생시점 파악 및 입자상물질 퇴적량 측정 - 장치 성능검토를 위한 실험 모우드 설정 ○ 재생조건변경실험 - 구성 장치 구동시간 결정실험 - 재생공기 공급유량 결정을 위한 실험 ○ 디퓨져 설계 및 제작 - 재생잔류량 측정 - 필터 원주 부분의 유동개선을 위한 디퓨져 설계·제작 ○ 고출력 엔진의 제어인자 측정실험 - 230마력급 및 300마력급 엔진 ○ 실차실험 - 장착 및 운행에 대한 문제점 검토Contents and Extents ○ Paper Survey - Trends on worldwide R & D activitives of DPF systems ○ Experiments on Confirmation of ECU function - Measurement of regeneration timing and accumulate soot mass by ECU functioning. - Test mode for system performance ○ Experiments on various regeneration conditions - Experiments for determination of component control timings - Experiments for determination of air flow rate for regeneration - Accumulated soot mass measurements ○ Design of diffuser - Diffuser design for flow imporvement to circumferential part of filter ○ Experimental measurment of ECU control factor for large sized diesel engines - 230 ps & 300 ps engines ○ Vehicle test - Installation - Troubleshootin

A study on analysis and application of user's sensitivity to visual features for the efficient content-based image retrieval

학위논문(석사) - 한국과학기술원 : 전산학과, 1999.2, [ iii, 43 p. ]한국과학기술원 : 전산학과