• 한국안전학회지
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• 제9권4호
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• pp.17-28
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• 1994

Chip breaking is important in lathe work for maintaining good surface of the products and safety of operator. The purpose of this study is to investigate the performance of chip breaking and chip shape resulted from the carbide inserts with grooved type and obstruction type chip breaker. Experiments have been performed under the following cutting conditions, (1) constant cutting speed with variable depth of cut and feed rate, (2) constant depth of cut with variable cutting speed and feed rate. Also, the flying distance of chip and it's distribution have been investigated. As a results, good performance of chip breaking can be obtained for small radius of curvature and land width of grooved type chip breaker. And the thickness of chip increase with the increase of feed rate and decrease of cutting speed, and the chip breaking becomes easier with the increase of chip thickness due to the large deformation rate. Obstraction type chip breaker shows better performance of surface roughness than the grooved type. The flying distance of the chips over 90% are less than 1 meter, and the distance decreases as the feed rate decreases.

• 한국해안해양공학회지
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• 제2권2호
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• pp.112-117
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• 1990

수면경사가 크거나 수심이 급격하게 변하는 지형에서는 유선의 굴곡으로 인한 연직방향의 가속도가 생겨 정수압과 다른 압력분포를 나타낸다. 따라서 이 경우 이들의 경향을 고려한 Boussinesq식을 사용해야 한다. 여러 가지 방법에 의하여 식을 얻을 수 있으나 여기서는 난류해석을 위한 평균류의 개념을 도입하여 유사한 식을 유도하였으며 기존의 식들과 비교하였다. 또한 실제 수치해석에 의하여 해를 구하고 Boussinesq항의 영향을 검토하였다.

• 천문학회지
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• 제39권4호
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• pp.95-105
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• 2006

We have calculated the cosmic ray(CR) acceleration at young remnants from Type Ia supernovae expanding into a uniform interstellar medium(ISM). Adopting quasi-parallel magnetic fields, gasdynamic equations and the diffusion convection equation for the particle distribution function are solved in a comoving spherical grid which expands with the shock. Bohm-type diffusion due to self-excited $Alfv\acute{e}n$ waves, drift and dissipation of these waves in the precursor and thermal leakage injection were included. With magnetic fields amplified by the CR streaming instability, the particle energy can reach up to $10^{16}Z$ eV at young supernova remnants(SNRs) of several thousand years old. The fraction of the explosion energy transferred to the CR component asymptotes to 40-50 % by that time. For a typical SNR in a warm ISM, the accelerated CR energy spectrum should exhibit a concave curvature with the power-law slope flattening from 2 to 1.6 at $E{\gtrsim}0.1$ TeV.

• 한국표면공학회지
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• 제31권2호
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• pp.91-100
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• 1998

NiCrAlY/YSZ(8wt%$Y_2O_3-ZrO_2$) functionally graded thermal barrier coating (FGC) layers on a Co-base superalloy (HAYNESS 188) substrate were fabstrate were fabicated using Ar shielded single torch air plasma spraying method. Functional grading with the stepwise compositional change throughout layer thickness. Microstructural observation trvealed a successful fabrication of NiCrAlY/YSZ FGC. From the results of the curvature measurement, adhesive strength measurement and thermal shock test for the FGC, it was concluded that the optimum conditions of functionally graded coating layer thinkness and compositional pattern exit to enhance the properties of FGC, which is closely related to the internal residual stess distribution witin it.

• Journal of Plant Biology
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• 제19권2호
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• pp.41-44
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• 1976

Ethylene was found to reverse the direction of gravity-induced lateral auxin transport and to cause an accumulation of auxin in the physically upper sides of horizontally placed pea shoots. The pea shoot displayed a slightly positive (downward) geotropic curvature in the presence of applied ethylene. Golgi bodies were found to be distributed preferentially in the bottom halves of cells as against the top halves following geotropic stimulation, and this pattern of intracellular distribution of dictyosomes was also reversed by ethylene treatment. Intracellular displacement of amyloplsts as a result fo geotropic induction was not reversed by the action of ethylene. In view of a positive correlation between the direction of auxin movement and the displacement patern of dictyosomes, it is suggested that the Golgi bodies are involved in the perception of gravity and/or subsequent redistribution of auxin or differential elongation in geotropism.

• 천문학회지
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• 제36권3호
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• pp.97-103
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• 2003

We now have more than 70 multiple image gravitational lens systems. Since gravitational lensing occurs through gravitational distortions in cosmic space, cosmological informations can be extracted from multiple image systems. Specifically, Hubble constant can be determined by the time delay mea-surement, curvature of the universe can be measured by the distribution of image separations in lens systems, and limits on matter density and cosmological constant can be set by the statistics of gravitationallens systems. Uncertainties, however, still exist in various steps, and results may be taken with some caution. Larger systematic survey and better understanding of galaxy properties would definitely help.

• 자동차안전학회지
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• 제5권1호
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• pp.50-55
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• 2013

When it comes to commercial vehicles, their unique characteristics - center of gravity, size, weight distribution - make them particularly vulnerable to rollover. On top of that, conventional heavy vehicle brake exhibits longer actuation delays caused in part by long air lines from brake pedal to tires. This paper describes rollover prevention algorithm that copes with the characteristics of commercial vehicles. In regard of compensating for high actuating delay, predicted rollover index with short preview time has been designed. Moreover, predicted rollover index with longer preview time has been calculated by using road curvature information based on environment information. When rollover index becomes larger than specific threshold value, desired braking force is calculated in order to decrease the index. At the same time, braking force is distributed to each tire to make yaw rate track desired value.

• Steel and Composite Structures
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• 제18권3호
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• pp.693-709
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• 2015

In this article, nonlinear free vibration behaviour of functionally graded spherical panel is analysed. A nonlinear mathematical model is developed based on higher order shear deformation theory for shallow shell by taking Green-Lagrange type of nonlinear kinematics. The material properties of functionally graded material are assumed to be varying continuously in transverse direction and evaluated using Voigt micromechanical model in conjunction with power-law distribution. The governing equation of the shell panel is obtained using Hamilton's principle and discretised with the help of nonlinear finite element method. The desired responses are evaluated through a direct iterative method. The present model has been validated by comparing the frequency ratio (nonlinear frequency to linear frequency) with those available published literatures. Finally, the effect of geometrical parameters (curvature ratio, thickness ratio, aspect ratio and support condition), power law indices and amplitude of vibration on the frequency ratios of spherical panel have been discussed through numerical experimentations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.93-96
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• 2006

This study represents results of performance-based fragility analysis of reinforced concrete (RC) bridge. Monte carlo simulation is performed to study nonlinear dynamic responses of RC bridge. Two-parameter log-normal distribution function is used to represent the fragility curves. These two-parameters, referred to as fragility parameters, are estimated by the traditional maximum likelihood procedure, which. is treated each event of RC bridge pier damage as a realization of Bernoulli experiment. In order to formulate the fragility curves, five different damage states are described by two practical factors: the displacement and curvature ductility, which are mostly influencing on the seismic behavior of RC bridge piers. Five damage states are quantitatively assessed in terms of these seismic ductilities on the basis of numerous experimental results of RC bridge piers. Thereby, the performance-based fragility curves of RC bridge pier are provided in this paper.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.299-302
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• 2008

The behavior of continuous welded rail tracks is directly affected by the following various parameters: rail size; track curvature; neutral temperature; misalignment; and ballast resistance. Most of these parameters are having the nature of random variables. Therefore, uncertainties exist in the buckling safety assessments. The evaluation of the buckling safety and the maintenance strategy based on the deterministic analysis are very inefficient since the value of deterministic parameters are selected in worst track condition. In this study, the probabilistic approach method were investigated considering the probabilistic distribution of major parameters such as the neutral temperature of rail and the ballast resistance.