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S-N Fatigue Behavior of Fe25Mn Steel and Its Weld at 298 and 110 K
Hyokyung Sung,Daeho Jeong,Taedong Park,Jongseop Lee,Sangshik Kim 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5
The S-N fatigue behavior of newly developed Fe25Mn steel, including base metal and butt-welded joint, was investigated at 298 and 110 K, and the results were compared to those of previously reported Fe16Mn2Al and STS304L steels. Fe25Mn steel has quite promising fatigue performance at 298 K and even at 110 K, showing comparable resistance to fatigue to STS304L. The S-N fatigue behavior of Fe25Mn steel was dependent on tensile strength at 298 and 110 K, the trend of which well agreed to that of other austenitic steels. The electron backscatter diffraction and micrographic analyses suggested that transformation induced plasticity and twinning induced plasticity effects did not occur in Fe25Mn steel under fatigue loading at room and cryogenic temperatures. The butt-welded Fe25Mn/Fe25Mn and Fe25Mn/STS304L specimens also showed a satisfactory fatigue behavior which was even comparable to that of STS304L/STS304L specimen at 110 K. The S-N fatigue behavior of Fe25Mn steel and its welds was discussed based on the fractographic and microscopic observations.
분산 이질형 객체 환경에서 캐슁 알고리즘의 설계 및 성능 분석
반효경(Hyokyung Bahn),노삼혁(Sam H. Noh),민상렬(Sang Lyul Min),고건(Kern Koh) 한국정보과학회 2000 정보과학회논문지 : 시스템 및 이론 Vol.27 No.6
캐슁 기법은 저장 장치 계층 간의 속도차를 완충시키기 위해 캐쉬 메모리, 페이징 기법, 버퍼링 기법 등으로 널리 연구되어 왔다. 하지만, 최근 웹을 비롯한 다양한 광역 분산 환경의 보편화에 따라 단일 시스템 내의 저장 장치 간에 이루어지는 캐슁 기법 뿐 아니라 타 노드의 객체를 캐슁하는 기법의 중요성이 커지고 있다. 광역 분산 환경에서의 캐슁 기법은 객체의 캐슁에 드는 비용과 캐슁으로 인한 이득이 객체의 근원지 노드의 위치에 따라 이질적이기 때문에 비용 차이를 고려한 캐쉬 교체 알고리즘이 필요하다. 한편, 캐쉬 교체 알고리즘은 온라인 알고리즘으로서 매 시점 교체 대상이 되는 객체를 즉시 선택해야 하기 때문에 알고리즘의 시간 복잡도가 지나치게 높지 않아야 한다. 그러나, 광역 분산 환경에서의 교체 알고리즘에 대한 지금까지의 연구는 객체들의 이질성을 고려하는 문제와 캐쉬 운영의 시간 복잡도 측면 모두에서 만족스러운 결과를 보이지는 못하고 있다. 본 논문은 이러한 점을 극복하여 우수한 성능을 나타내면서 효율적인 구현이 가능한 새로운 교체 알고리즘을 설계하고, 그 우수성을 트레이스 기반 모의 실험을 통해 보여 준다. Caching mechanisms have been studied extensively to buffer the speed gap of hierarchical storages in the context of cache memory, paging system, and buffer management system. As the wide-area distributed environments such as the WWW extend broadly, caching of remote objects becomes more and more important. In the wide-area distributed environments, the cost and the benefit of caching an object is not uniform due to the location of the object; which should be considered in the cache replacement algorithms. For online operation, the time complexity of the replacement algorithm should not be excessive. To date, most replacement algorithms for the wide-area distributed environments do not meet both the non-uniformity of objects and the time complexity constraint. This paper proposes a replacement algorithm which considers the non-uniformity of objects properly; it also allows for an efficient implementation. Trace-driven simulations show that proposed algorithm outperforms existing replacement algorithms.
Secure user identification for consumer electronics devices
Hyejeong Lee,Sang-Ho Lee,Taeseok Kim,Hyokyung Bahn IEEE 2008 IEEE transactions on consumer electronics Vol.54 No.4
<P>With the evolution of consumer electronics technologies, personal information in consumer devices is becoming increasingly valuable. To protect private information from misuses due to loss or theft, secure user identification mechanisms should be equipped into the consumer devices. This paper develops a secure user identification system for consumer electronics devices based on fingerprint identification. The fingerprint identification system is one of the biometric sensor technologies, which provides high accuracy and convenience than other identification techniques. Specifically, the proposed system uses the orientation map and the edit-distance for immediate and accurate identification of users. Experimental results show that the proposed system achieves good performance in terms of the false rejection rate and the false acceptance rate.</P>
Fatigue Crack Propagation Behavior of Fe25Mn and Fe16Mn2Al Steels at Room and Cryogenic Temperatures
Daeho Jeong,Hyokyung Sung,Taedong Park,Jongseop Lee,Sangshik Kim 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.4
The fatigue crack propagation (FCP) behavior of Fe25Mn and Fe16Mn2Al austenitic steels was investigated at 298 and 110 K, and the results were compared with the reported results of Fe24Mn2Cr steel. It was found that the FCP behavior of high-Mn, austenitic steels was largely influenced by the stacking fault energy (SFE) and the grain size. The resistance to FCP of high-Mn steels in this study was enhanced in the near-threshold ΔK regime with decreasing temperature from 298 to 110 K. The improvement for the Fe25Mn and the Fe16Mn2Al specimen was, however, marginal as compared to that of the Fe24Mn2Cr specimen. Other than the change in SFE, the secondary cracking at cryogenic temperature appeared to affect the FCP behavior of high-Mn steels, since the secondary cracks perpendicular to the crack propagating direction could reduce the effective stress intensity factor, decreasing the FCP rates. Sufficiently high stress concentration at grain boundary tended to occur at low temperature for relatively large grain sized Fe24Mn2Cr specimen and cause the secondary cracking, but not for the Fe25Mn and the Fe16Mn2Al specimen.
Clinical analysis and review of literature on pilomatrixoma in pediatric patients
Hu, Ju Long,Yoo, Hyokyung,Kwon, Sung Tack,Kim, Sukwha,Chung, Jee Hyeok,Kim, Hyeonwoo,Kim, Jinhyun,Yu, Na Hee,Kim, Byung Jun Korean Cleft Palate-Craniofacial Association 2020 Archives of Craniofacial Surgery Vol.21 No.5
Background: Pilomatrixoma is a benign tumor that originates from the hair follicle matrix. It usually presents as a hard, slow growing, solitary mass that can be easily misdiagnosed as other skin masses. The aim of this study was to clinically analyze a case series of pilomatrixoma in pediatric patients from Korea. Methods: A total of 165 pediatric patients from 2011 to 2018 with a histological diagnosis of pilomatrixoma were included. A retrospective review was performed using the electronic medical records, including patient demographics, number and location of the mass, clinical and imaging presentation, and postoperative outcomes. Results: There were 61 male and 104 female patients with 152 solitary and 13 multiple pilomatrixomas. Among solitary pilomatrixomas, the lesion commonly occurred in the head and neck (84.2%), followed by upper limbs (11.2%), lower limbs (3.3%), and trunk (1.3%). The pilomatrixoma lesion presented as the following types based on our clinical classification: mass (56.02%), pigmentation (25.31%), mixed (12.65%), ulceration (4.82%), and keloid-like (1.2%). Ultrasonography showed a high positive predictive value (95.56%). There were no specific complications observed except for two cases of recurrence. Conclusion: Pilomatrixoma has various clinical feature presentations and commonly occurs in the head and neck. Ultrasonography is a helpful diagnostic tool. Surgical removal of the lesion is the main treatment method with a low recurrence rate.