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피닝 처리에 따른 304 스테인레스 강의 마모 특성 평가 및 미세구조 분석
정진성(Jine-Sung Jung),이한상(Han-Sang Lee),신기삼(Kee-Sam Shin),김선진(Sun-Jin Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
In most case of materials damages were happened at the surface. The various methods for increasing the fatigue life were existed like as the diffusion coating process, flame hardening, surface rolling and shot peening. The peening of these techniques was applied to the various industries during long times. We investigated on the wear properties and micro-structure before and after shot peening. The 304 stainless steel was used as the test materials. Firstly, the optimum peening condition was determined by the Almen intensity and rotary bending fatigue test. Secondly, the surface roughness and residual compressive stresses were evaluated with the stylus and X-ray diffraction equipment. And then, the wear tests were performed on abrasion and solid particle erosion. Finally, the micro-structure of tested specimens was analyzed using by X-ray diffraction, scanning electron microscope and transmission electron microscope. The residual compressive stress was existed to about 70㎛ depth, the wear properties also was increased and the twins were found in micro-structure.
예측 가능한 실행 시간을 가진 동적 메모리 할당 알고리즘
정성무(Sung Moo Jung),유해영(Hae Young Yoo),심재홍(Jae Hong Shim),김하진(Ha Jine Kimn),최경희(Kyung Hee Choi),정기현(Gi Hyun Jung) 한국정보처리학회 2000 정보처리학회논문지 Vol.7 No.7
This paper proposes a dynamic storage allocation algorithm, QHF(quick-half-fit) for real-time systems. The proposed algorithm manages a free block list per each word size for memory requests of small size, and a free block list per each power of 2 size for memory requests of large size. This algorithm uses the exact-fit policy for small size requests and provides high memory utilization. The proposed algorithm also has the time complexity O(1) and enables us to easily estimate the worst case execution time (WCET). In order to confirm efficiency of the proposed algorithm, we compare the memory utilization of proposed algorithm with that of half-fit and binary buddy system that have also time complexity O(1). The simulation result shows that the proposed algorithm guarantees the constant WCET regardless of the system memory size and provides lower fragmentation ratio and allocation failure ratio than other two algorithms.
이한상 ( Han Sang Lee ),정진성 ( Jine Sung Jung ),유근봉 ( Keun Bong Yoo ),김의현 ( Eui Hyun Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.4
The hot corrosion properties of heat-resistant steels were investigated in an oxidation atmosphere including artificial ash and sulfur dioxide. The heat-resistant steels of T22, T92, T122, T347HFG, Super304H and HR3C were evaluated at 620, 670 and 720℃ for 400 hours. The relationship between the corrosion rate and the temperature followed a bell-shaped curve with a peak rate at around 670℃. The corrosion rates showed a decreasing tendency as the chrome contents of these steels increased from 2.l5 wt.% to 24.5 wt.%, and austenitic steels had a lower corrosion rate than ferritic steels. Sulfidation by SO2 as well as molten salt corrosion also had an effect on the total corrosion rate, especially showing an increase in the corrosion rate in ferritic steels. Regardless of the chrome content in the steels and irrespective of the test temperature, the corrosion scale was composed of an outer oxide and an artificial ash mixed layer, a middle oxide layer andinner sulfide, and amixed oxide layer. As the chrome content increased, the proportion of chrome oxide in the corrosion scale increased. Before spalling of the corrosion scale, voids and cracks were initiated in the sulfide and the mixed oxide layer or at the interface with the substrate. (Received December 16, 2009)
Kamut (Triticum turgidum spp.) 식빵 급여가 고지방식이 유도 비만 C57BL/6 마우스에 미치는 효과
정현기(Hyun Gi Jung),백지윤(Ji Yun Baek),최예정(Ye Jung Choi),강기성(Ki Sung Kang),김현영(Hyun Young Kim),김지현(Ji Hyun Kim),최진상(Jine Shang Choi) 한방비만학회 2021 한방비만학회지 Vol.21 No.2
Objectives: The purpose of this study was to investigate the effect of white pan bread added with Kamut (Triticum turgidum spp.) on high fat diet (HFD)-induced obese C57BL/6 mice. Methods: The white pan bread or white pan bread with Kamut (BK) were administered for 8 weeks in HFD-induced obese C57BL/6 mice. To evaluate the effect and its mechanisms of BK on obese mice, we measured body weight change, serum lipid profiles, histopathological analysis, and protein expression of CCAAT/enhancer binding protein-α (C/EBPα) in the liver. Results: Administration of BK significantly decreased body weight in HFD-induced obese mice. In addition, BK-administered group significantly reduced serum total cholesterol, glucose, and high-density lipoprotein cholesterol levels compared with the HFD-induced control group. The HFD-induced mice had damaged liver tissue and increased the size of adipose tissue, but BK-administered group attenuated liver damage and decreased the size of adipocyte. Furthermore, administration of BK significantly down-regulated C/EBPα in the liver compared with HFD-fed mice. In particular, BK-administered group has higher inhibited body weight, serum lipid profiles, and C/EBPα expressions than white pan bread-administered group. Conclusions: This study demonstrated that administration of BK attenuated HFD-induced obesity by regulation of C/EBPα than consumption of white pan bread. Therefore, BK could be developed as a bread for prevention of obesity.
강명수(Myung Soo kang),정진성(Jine Sung Jung),하정수(Jung Soo Ha) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
In this study the life assessment of low cycle fatigue for 12Cr steel at high temperature arc described. Secondly, comparisons between predicted lives and experimental lives are made for the several sample life prediction models. Two minute hold lime in either tension or compression reduce the number of cycles to failure by about a factor of two. Twenty minute hold time in compression lead to shorter lives than 2 minute hold time in compression. Experiments showed that life predictions from cIassical phenomenological models have limitations. More low cycle fatigue experiments should be pursued to gain understanding of the physical damage mechanisms and to allow the development of physically-based models which can enhance the accuracy of the predictions of components. From a design point-of-view, life prediction has been judged acceptable for these particular loading conditions but extrapolations to thermo-mechanical fatigue loading, for example, require more sophisticated models including physical damage mechanisms.