• 한국정밀공학회지
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• 제31권9호
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• pp.839-846
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• 2014

Recent trends in the miniaturization and weight reduction of portable electronic parts have driven the use of subminiature screws with a micrometer-scale pitch. As both screw length and pitch decrease in subminiature screws, the resulting clamping force becomes diminishes. In this work, Finite element (FE) analysis is performed to evaluate clamping force of a screw assembly, with a comparison with experimental result. To improve clamping force of subminiature screws, a new screw design is considered by modifying screw thread angle: the thread angle is varied as an asymmetric way unlike the conventional symmetric thread angle. FE analyses are then performed to compare the clamping characteristics of each subminiature screw with different thread angle. The effect of thread angles on the clamping force is then discussed in terms of structural safety for both positive and negative screws.

• Journal of Computing Science and Engineering
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• 제7권1호
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• pp.67-80
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• 2013

The worst-case execution time (WCET) of each real-time task in multicore processors with shared caches can be significantly affected by inter-thread cache interferences. The worst-case inter-thread cache interferences are dependent on how tasks are scheduled to run on different cores. Therefore, there is a circular dependence between real-time task scheduling, the worst-case inter-thread cache interferences, and WCET in multicore processors, which is not the case for single-core processors. To address this challenging problem, we present an offline real-time scheduling approach for multicore processors by considering the worst-case inter-thread interferences on shared L2 caches. Our scheduling approach uses a greedy heuristic to generate safe schedules while minimizing the worst-case inter-thread shared L2 cache interferences and WCET. The experimental results demonstrate that the proposed approach can reduce the utilization of the resulting schedule by about 12% on average compared to the cyclic multicore scheduling approaches in our theoretical model. Our evaluation indicates that the enhanced scheduling approach is more likely to generate feasible and safe schedules with stricter timing constraints in multicore real-time systems.

• 대한가정학회지
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• 제20권1호
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• pp.1-10
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• 1982

This experiment was made on the basis of the general observation that silk fabrics is flaccid in sun light. The purpose of this test is to examine efficiency between the processed thread and the unprocessed one after putting the later under the xenon-lit system, which produces continuous spectrum of bright white beam similar to sun light. (i) Color division of silk thread : white, yellow blue (ii) light division and irradiation time : sun lightlongrightarrow210 hrs, Xenonlongrightarrow50,100, 150 hrs. Under the above conditions each object was be tested with and extensometer, TENSILON Type III for the results of (a) the weight-expansibility curve of the silk thread (b) the relationship between cutting in tensity and maximum, weight (c) maximum expansion rate (d) the expansion energy of the tested silk thread (e) the beginning pull-stretch resistance rate of the tested silk thread (f) color difference after processing The results are illustrated in the appropriate tables and figures. Consequently the generalobservation that silk fabrics is flaccid is relevant only in terms of color. So for as Cutting-intensaty is concerned, it turned out to be less flaccid than in color. On the contrary when the untested silk thread was conpared with the xenon-irradiated ones, the latter proved itself to be more flaccid in cutting expansibility than the former. We have learned through this experiment that, after the all rounds of this test, the color tone and chroma of the colored materials remained without significant change, where as their color value changed to a large extent.

• 복식
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• 제67권2호
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• pp.88-100
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• 2017

This study is for the textiles of at Sun Am Temple and characteristic of embroidery. Tak Ui was composed of orange body and green upper cover, and had no strings. The body plate was covered with embroidery, with Gauze base, and upper part was appliqued, by cutting dragon pattern, cloud pattern on satin damask. The thread for embroidery was silk floss, silk twisted thread, rapped gold thread, and rapped silk thread. For padding, it was used cotton thread in the part of dragon's scales. It was used satin stitch, outline stitch, split stitch, couching, and counted stitch, etc. as method of embroidery. In particular, it embroidered counted stitch of diamond shape consecutively on the whole of Tak Ui, it does so with counted stitch of same effect of weaving Brocade in the part of cloud. Besides, it is one of the characteristic for couching rapped silk thread. Such lead embroidery is the popular method in the Ming dynasty of China, in the 16~17 century. The design of Tak Ui is dragon, cloud, and wave in the theme. In the center, 'Seong-su-man-nyeon' was placed on the heads of dragon. This is similar to Dragon Robe of Four-petalled medallion patterns, period of Ming dynasty in China. Therefore, it confirmed that Tak Ui was remodeled the embroidered textiles, made for royal robe, originally, with Tak Ui at temple.

• 한국생산제조학회지
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• 제18권5호
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• pp.514-520
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• 2009

Titanium is one of the most attractive materials due to their superior properties of high specific strength and excellent corrosion resistance. The applications in aerospace and medical industries demand machining process more frequently to obtain more precise products. Machining of titanium is faced with strong challenges such as increased component complexity i.e. airframe components manufacturing processes. The machining cost on titanium have traditionally demanded high cutting tool consumable cost and slow machining cycle times. Similarly, the high wear of the cutting tools restricts the cutting process capabilities. Titanium screws applied to fasten parts In the several corrosion environment. In the thread cutting of titanium alloys, the key point for successful work is to select proper cutting methods and tool materials. This study suggests a guidance fur selecting the cutting methods and the tool materials to improve thread quality and productivity. Some experiments investigate surface roughnesses, cutting forces and tool wear with change of various cutting parameters including tool materials, cutting methods, cutting speed. As the results, the P10 type insert tip was assured of the best for thread cutting of Ti-6Al-4V titanium alloy. Also the initial depth of infeed was desirable to use the value below 0.5mm as the uniform cutting area method is applied.

• 전기전자학회논문지
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• 제21권1호
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• pp.77-80
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• 2017

본 논문에서는 기존의 superscalar GP-GPU 구조와 달리 superscalar issue를 제거하여 GP-GPU성능을 향상하는 방법을 제안한다. superscalar issue를 제거하기 위해 stream processor의 구조를 단순화했다. stream processor의 구조가 단순화 됨에 따라 하드웨어의 크기를 크게 늘리지 않고 thread 개 수가 늘려 성능을 개선하였다. thread 개수가 늘어남에 따라 thread의 묶음인 warp을 관리하는 warp scheduler 구조를 새롭게 제안하였다. 제안하는 warp scheduler는 superscalar issue가 제거 되어 있기 때문에 warp 활성화 정보를 통해 라운드 로빈 스케쥴링을 통해 활성화 된 warp에게 명령어를 전달한다. 성능 비교는 가우시안 필터링 연산을 사용하였으며 기존의 GP-GPU의 비해 7.89배의 성능향상을 보였다.

• 전기전자학회논문지
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• 제21권1호
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• pp.92-95
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• 2017

본 논문에서는 적은 면적의 GP-GPU에서 성능을 향상시키기 위한 방법을 제안한다. 본 논문에서는 superscalar와 같이 과도하게 스케줄링 복잡성을 증가시키지 않는 대신 단순한 코어의 수를 늘려 성능을 극대화 시키는 방법을 제안한다. GP-GPU를 구성하는 Stream Processor의 구조를 단순화한다. 또한, Warp Schedule에서 thread 할당을 어플리케이션에 적합한 방법을 개발하여 성능을 개선한다. 성능을 검증하는 방안으로 neural network의 한 분야인 딥러닝에 대한 스레드 할당방식을 제안한다. Neural Network 알고리즘의 경우 Intel CPU 대비 90%에서 ARM Cortex-A15 4 core 대비 98% 성능 향상을 확인할 수 있었다.

• 소성∙가공
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• 제21권3호
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• pp.179-185
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• 2012

In this paper, it is proposed to produce high precision screws with a diameter of $800{\mu}m$ and a thread pitch of $200{\mu}m$ ($M0.8{\times}P0.2$) by means of a cold thread rolling process. In this part II of the study, the focus is on the production and reliability testing of the prototype $M0.8{\times}P0.2$ micro-screw. Designs for two flat dies were developed with the aid of the literature and previous studies. Process parameters during the cold thread rolling process were established through FE simulations. The simulation results showed that the threads of the micro-screw are completely formed through the rolling process. Prototype $M0.8{\times}P0.2$ micro-screw were fabricated with a high precision thread rolling machine. In order to verify the simulation results, the deformed shape and dimensions obtained from the experiment were compared with those from the simulations. Hardness and failure torque of the fabricated micro-screw were also measured. The values obtained indicate that the CAE based process design used in this paper is very appropriate for the thread rolling of micro-sized screws.

• 한국정보과학회논문지:시스템및이론
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• 제32권1호
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• pp.21-28
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• 2005

웹 서버 혹은 웹 애플리케이션 서버는 급증하는 웹 사용자들의 요구에 효율적으로 대처하기 위하여 일반적으로 다중 쓰레드 모델을 적용하고 있다. 그러나 이러한 다중 쓰레드 모델이 새로운 웹 환경의 특정한 상황에서 다중 프로세스 모델에 비해 오히려 더 나쁜 성능을 보이는 경우가 있다. 본 논문에서는 이러한 문제를 해결하기 위하여 두 가지 접근 방법을 통해 다중 쓰레드 모델의 성능 저하에 대한 원인을 분석한다. 그 중 첫 번째로, 다양한 응용 환경에서의 다중 쓰레드 모델과 프로세스 모델을 비교한다. 두 번째로는 효율성을 위하여 일반적으로 제공되는 프로세스/쓰레드 풀 모델에서 동적인 지시자들의 설정값에 의한 영향을 분석한다. 본 논문에서는 자체 제작한 웹 클라이언트 시뮬레이터와 아파치 엘 서버 2.0을 연동하여 이러한 실험들을 진행하고 결과 및 분석 내용을 제시한다.

• 한국항행학회논문지
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• 제17권2호
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• pp.189-195
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• 2013

작업의 실행요청이 빈번하고 실행시간이 짧은 환경에서, 스레드 생성 및 삭제로 인한 오버헤드를 줄여 작업처리효율을 향상시키기 위해 스레드풀 방법이 자주 사용된다. 그중에서 워터마크 스레드풀 방법은 최대로 필요한 스레드 수 이하의 스레드들을 유지함으로써 자원의 불필요한 사용을 줄인다. 그러나 사용가능한 스레드가 없을 경우에는 지정된 한도 내에서 스레드를 추가로 생성하여 작업들을 처리해야 하므로 스레드 생성으로 인한 시스템 오버헤드가 증가하고 결국 성능 저하 현상이 발생할 수 있다. 본 논문은 이런 성능 저하를 줄이기 위한 방법으로써 히스토리 기반의 동적 스레드풀 방법을 제안한다. 이 방법은 작업처리에 필요한 스레드 수를 측정하고 유지함으로써 스레드 생성 및 삭제로 인한 오버헤드를 줄인다. 실험결과에 따르면, 제안방법은 워터마크 스레드 풀 방식과 비교하여 보유 스레드 수는 평균 33% 증가하나 스레드 생성 수는 평균 62% 감소함으로써 평균 6%의 시스템 처리량 증가를 보인다.