• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.127-133
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• 2002

The objective of this study is to investigate fatigue life and fatigue crack propagation behavior The experiment of fatigue life for MMC have been carried out for the stress ratio R＝0.1 at 20Hz. Fatigue lift limit of AC4CH alloy is about 70 ㎫ and Fatigue limit of MMC has been increment to 120 ㎫, therefore, fatigue limits of MMC is about 71 % higher than that of AC4CH alloy Crack propagation tests on half-size CT specimen of thickness 12.5mm were conducted by using sinusoidal waveform. The crack length was monitored by compliance method. Test conditions were at 0.1 and 0.05 of load ratio at 10Hz of loading frequency and test load was 2.3kN. The effects of stress ratio on the fatigue crack propagation behavior for MMC was discussed within the Paris law. As the results of this study, Fatigue crack propagation increased with increasing the load ratio.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.3
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• pp.31-39
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• 1996

The objective of this study is to investigate the influence of welding residual stresses on the fatigue crack growth behavior of cracks located transverse to the weld bead. For this purpose, G. T. A (Gas Tungsten Arc) welding was performed on hte Al alloy 1100-O plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base meta respectively. Specimens were used CT(Compact Tension) specimens. Initial welding residual stresses were measured by using strai gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1, It is possible to predict fatigue crack growth behaviors and the fatigue life, using numerical analysis together with distribution of initial residual stress and the values of C and m obtained from $da/dN-{\Delta}K$

• Structural Engineering and Mechanics
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• v.36 no.3
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• pp.343-361
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• 2010

The Discrete Element Method adopting particles for the domain discretization has recently been adopted in fracture studies of non-homogeneous continuous media such as concrete and rock. A model is proposed in which the reinforcement is modelled by 1D rigid-spring discrete elements. The rigid bars interact with the rigid circular particles that simulate the concrete through contact interfaces. The DEM enhanced model with reinforcement capabilities is evaluated using three point bending and four point bending tests on reinforced concrete beams without stirrups. Under three point bending, the model is shown to reproduce the expected final crack pattern, the crack propagation and the load displacement diagram. Under four point bending, the model is shown to match the experimental ultimate load, the size effect and the crack propagation and localization.

• 한국초전도학회:학술대회논문집
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• 2007.07a
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• pp.6-6
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• 2007

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.123-130
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• 1989

In order to investigate the biocompatibility of base metal alloys in dental prosthesis, the 3 types of Ni-Cr alloys and the 3 types of Co-Cr alloys were collected and each alloy was extracted in the culture medium. L-cells derived from the subcutaneous tissue of mouse and extracted medium were cultivated. The relative growth rate of L-cells in the tissue culture was calculated with N-R assay. The obtained results were as follows: 1. In the case of the Co-Cr alloys tested, its cytotoxicity proved weak. 2. In the case of the Ni-Cr alloys tested, there was no significant degree of cytotoxicity, especially 25% Victory was proved noncytotoxicity.

• Journal of applied mathematics & informatics
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• v.27 no.5_6
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• pp.1001-1015
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• 2009

In this paper, two hybrid difference schemes on the Shishkin mesh are constructed for solving a weakly coupled system of two singularly perturbed convection-diffusion second order ordinary differential equations with a small parameter multiplying the highest derivative. We prove that the schemes are almost second order convergence in the supremum norm independent of the diffusion parameter. Error bounds for the numerical solution and its derivative are established. Numerical results are provided to illustrate the theoretical results.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.2
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• pp.197-200
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• 1994

The study was conducted in the Bangladesh Agricultural University campus, Mymensingh, from July 1988 to June 1990. Five grazing fields consisting of five different vegetations were selected for this study. The specimen were collected from this study. The specimen were collected from the grazing fields by dragging method. The results revealed that two species of ticks namely Boophilus microplus and Haemaphysalis bispinosa were collected from five different vegetation. The highest incidence of both B. microplus and H. bispinosa were recorded during winter season and lowest in Monsoon for the year of 1988-89 and 1989-90. These two species were significantly occurred in Winter followed by Monsoon and Autumn.

• Journal of Biosystems Engineering
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• v.19 no.4
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• pp.369-379
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• 1994

A computer vision system consisted of a microscope, a CCD camera, a frame grabber and a personal computer was used to analyze spraying pattern. An algorithm was developed for the system to measure size of droplets including overlapped droplets, to count number of droplets, and to estimate spray deposition in a certain area from the data obtained. A series of experiment was carried out to test validity of the algorithm. The experiment resulted that accuracy of the droplet size measurement, accuracy of counting the number of droplets and the estimation of spray deposition were within an acceptable range. It was concluded from the results that the computer vision system operated by the developed algorithm is very useful tool to analyze spraying pattern.

• Journal of Korean Society on Water Environment
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• v.29 no.5
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• pp.666-673
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• 2013

Chloroform is harmful volatile organics and representatives of Trihalomethane (THM). Well-known removal methods of Chloroform are photo oxidation or OH radical oxidation. Plasma on water surface at slightly vacuum condition (45 torr) can produce OH radical and it will help chloroform removal. 81.5% of chloroform is removed by vacuum and plasma in 10 min.. Plasma can totally oxidize it till 2.8% and partially oxidize chloroform up to 18.5%. Water-surface plasma is good method to remove chloroform in short time.

• Animal Systematics, Evolution and Diversity
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• v.7 no.2
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• pp.233-240
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• 1991

The morphology and ecology of the marine hypotrichous ciliate, Oxytricha saltans (Cohn, 1866) Kahl, 1932 collected from shrimp culturing pond of Qingdao (Tsingtao, 36$^{\circ}$08'N : 120$^{\circ}$43'E) , P.R. China were investigated. collected samples were observed directly and we also observed cultured ones and stained specimens. In relation to this species were described the morphology and infraciliature in detail using protargol method, presented a new diagnosis and discussed some synonyms and the related species, Actinotricha saltans sensu Dragesco, 1963.