• 한국자동차공학회논문집
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• 제25권2호
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• pp.133-139
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• 2017

The timing chain system, which is a typical power transmission technology applied to a vehicle, has been widely used by the automotive industry because it is normally designed to last a car's lifetime. However, the timing chain system may cause some problems due to the shape of the chains and the polygonal behavior on contact between the chain and the sprocket. In addition, noise and vibration caused by transmission error are the most typical problems encountered by major automotive manufacturers and they are considered as the main source of customer complaint. The initial tension of the chain-sprocket system is thought to be the main cause of transmission error, and it is regarded as the source of engine vibration and noise. The initial tension of the chain system should be controlled carefully since a low initial tension can cause twisting, which may lead to a system malfunction, while a high initial tension can reduce the service life due to a worn down contact surface. In this paper, the kinematic analysis model is generated with various initial tensions, which are controlled by changing the shape of the fixed guide with the largest contact surface with chain. The results showed that the transmission error was minimized on a particular range of initial tension, and the tendency showed that the error changed with a higher sensitivity at a lower initial tension.

• 대한임상독성학회지
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• 제7권2호
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• pp.97-104
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• 2009

Purpose: Antivenin is a standard therapy in snakebite victims. While the required antivenin dose can be easily estimated, based on the initial symptoms, this strategy may be unsuccessful if the initial symptoms progressively worsen. The purpose of this study was to identify the progression rate of the initial symptoms following snakebite and its associated factors. Methods: The medical records of 44 patients treated for snakebite from give the actual dates of the study period were retrospectively examined. Thirty-two of these patients were enrolled. Demographic data, local wound grade and local effect score at initial presentation (G-0 and LES-0, respectively) and 12 hours after admission (G-12 and LES-12, respectively) were reviewed, along with laboratory data. Results: The 32 patients had an average age of $54.0{\pm}14.5$ years and were predominantly male (n=26) and presented mainly during summer. Compared to G-0 and LES-0, re-evaluated G-12 and LES-12 were significantly increased despite initial administration of proper antivenin dosage (p=0.001 and p=0.000, respectively). Total amounts of antivenin correlated with LES-12 (correlation co-efficiency 0.558, p<0.05). However, factors associated with symptom progression were not revealed. Conclusion: Initial snakebite symptoms might progressively worsen within hours despite acceptable initial antivenin therapy. Therefore, re-evaluation within several hours must be considered if when the initial snakebite symptoms are minimal or mild.

• 한국전산구조공학회논문집
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• 제25권1호
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• pp.101-108
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• 2012

사장교 시스템의 초기형상해석이라 함은 주형의 수직 처짐과 휨모멘트, 주탑의 수평변위와 휨모멘트를 최소화하면서, 고정하중과 평형을 이룰 수 있는 케이블의 장력과 무응력길이를 결정하는 방법으로 이 때, 케이블이 정착되는 주형의 수평위치, 주탑의 수직위치가 목표형상에 부합할 필요가 있다. 본 연구에서는 고정하중을 받는 사장교의 초기형상을 효율적이고 합리적으로 결정하기 위하여 개선된 초기부재력법과 TCUD법의 비교연구 결과를 제시하고자 한다. 주형과 주탑의 케이블 정착부에서 힘의 평형조건을 이용하여 주형의 수직처짐과 주탑의 수평변위를 효과적으로 제어할 수 있는 절점평형법을 초기 부재력법에 적용하여 초기치에 민감한 기존 초기부재력법을 개선한다. 또한 개선된 TCUD법을 이용한 초기형상해석 수행결과와 비교함으로서 두 방법의 정확성을 입증하고자 한다.

• 의학교육논단
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• 제14권1호
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• pp.51-56
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• 2012

Purpose: Precepted video review (PVR) has been considered one of the methods for the remediation of clinical performance examinations (CPX). This study quantified the effect of brief PVR on CPX scores. Methods: For two years, final-year students (61 students in the 1st year's cohort and 54 in the 2nd year's cohort) participated in CPXs. The scores on the initial CPX were announced to the students shortly after that CPX administration. There was no PVR after the initial CPX in the 1st year. All participants of the 2nd year were notified of the opportunity to voluntarily receive brief PVR after the initial CPX. Several months after the initial CPX, the students took the latter CPX in both years. The differences of scores between initial and latter CPX were compared in good performers and poor performers of the initial CPX. Results: Thirteen poor performers and 8 good performers received PVR in the 2nd year. In the 1st year, history taking (Hx), physical examination, and patient physician interaction (PPI) scores of the good performers of the initial CPX were significantly decreased on the latter CPX. In the 2nd year, the Hx and PPI scores of the good performers of the initial CPX, who received PVR, were significantly decreased at the latter CPX. The Hx and PPI scores of the poor performers of the initial CPX were significantly increased at the latter CPX in both years regardless of PVR. Conclusion: The changes in CPX scores according to PVR did not show any consistent trend. Brief PVR appears to be not sufficient for improving CPX scores.

• 한국정보과학회논문지:소프트웨어및응용
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• 제31권7호
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• pp.859-868
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• 2004

본 논문에서는 능동적 학습이 보다 적은 수의 훈련예제로도 높은 학습성능을 달성할 수 있도록 군집화기법을 이용하여 초기훈련집합을 선정하는 방안을 제안한다. 본 제안 방안은 유사한 예제들보다는 다양한 예제들로 그리고 특수한 예제들보다는 보편적인 예제들로 구성한 집합이 학습에 유리할 것이라는 가정을 바탕으로, 먼저 k-means 군집화 기법으로 예제들을 군집화한 후, 각 군집을 가장 잘 표현하는 대표예제로 개별 군집의 중심점과 가장 가까운 예제를 선정하여 초기훈련집합을 구성한다. 또한 개별 군집의 중심점을 가상의 예제로 가정하여, 이와 연관된 대표예제의 카테고리를 부여함으로써 추가의 훈련예제로 활용하는 방안을 함께 제안한다. 여러 문서 분류 문제를 대상으로 실험한 결과, 본 제안 방안으로 선정한 초기훈련집합에서 출발한 능동적 학습이 임의로 선정한 초기훈련집합에서 출발한 경우에 비해 보다 적은 수의 훈련예제로도 동등한 성능을 달성할 수 있음을 확인하였다.

• Steel and Composite Structures
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• 제30권5호
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• pp.483-492
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• 2019

In the current study, the influence of the initial lateral (sweep) shape and the cross-sectional twist imperfection on the lateral torsional buckling (LTB) response of doubly-symmetric steel I-beams was investigated. The material imperfection (residual stress) was not considered. For this objective, standard European IPN 300 beam with different unbraced span was numerically analyzed for three imperfection cases: (i) no sweep and no twist (perfect); (ii) three different shapes of global sweep (half-sine, full-sine and full-parabola between the end supports); and (iii) the combination of three different sweeps with initial sinusoidal twist along the beam. The first comparison was done between the results of numerical analyses (FEM) and both a theoretical solution and the code lateral torsional buckling formulations (EC3 and AISC-LRFD). These results with no imperfection effects were then separately compared with three different shapes of global sweep and the presence of initial twist in these sweep shapes. Besides, the effects of the shapes of initial global sweep and the inclusion of sinusoidal twist on the critical buckling load of the beams were investigated to unveil which parameter was considerably effective on LTB response. The most compatible outcomes for the perfect beams was obtained from the AISC-LRFD formulation; however, the EC-3 formulation estimated the $P_{cr}$ load conservatively. The high difference from the EC-3 formulation was predicted to directly originate from the initial imperfection reduction factor and high safety factor in its formulation. Due to no consideration of geometric imperfection in the AISC-LFRD code solution and the theoretical formulation, the need to develop a practical imperfection reduction factor for AISC-LRFD and theoretical formulation was underlined. Initial imperfections were obtained to be more influential on the buckling load, as the unbraced length of a beam approached to the elastic limit unbraced length ($L_r$). Mode-compatible initial imperfection shapes should be taken into account in the design and analysis stages of the I-beam to properly estimate the geometric imperfection influence on the $P_{cr}$ load. Sweep and sweep-twist imperfections led to 10% and 15% decrease in the $P_{cr}$ load, respectively, thus; well-estimated sweep and twist imperfections should considered in the LTB of doubly-symmetric steel I-beams.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.255-257
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• 2012

Epoxy resin without any hardener can harden in the presence of hydroxide ions in cement mortars and concretes at ambient temperature. The purpose of present study is to examine the hardening properties of hardener-free epoxy-modified mortars by curing conditions. The hardener-free epoxy-modified mortars using diglycidyl ether of A epoxy resin are prepared with various polymer-cement ratios, and subjected to initial moist/dry curing, initial steam(90℃) curing, initial steam/heat(80℃, 100℃) curing.As a result, degree of hardening of epoxy resin in initial moist/dry cured, initial steam cured and initial steam/heat(80℃) cured hardener-free epoxy-modified mortars is decreased with increasing polymer-cement ratio. However, it is markedly improved with additional dry-curing periods. On the other hand, regardless of the polymer-cement ratio and dry curing periods, degree of hardening of hardener-free epoxy-modified mortars with initial steam/heat(100℃) cure is over 95%.

• 조명전기설비학회논문지
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• 제23권4호
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• pp.72-78
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• 2009

이 논문은 국내 원자력 발전소에서 급수펌프 구동용 소형 터빈의 아날로그 제어시스템을 디지털 방식으로 교체한 후 발전소를 기동하기 전에 최초 제어 파라미터를 설정하는 방법에 대하여 기술하고 있다. 기존 제어시스템의 제어상수가 알려져 있는 경우에는 초기 제어상수를 쉽게 결정할 수 있으나 보통은 아날로그 시스템의 제어상수를 파악할 수 없는 경우가 많으며 이 때 초기 제어상수와 최적 제어상수는 크게 차이가 날 수도 있다. 이런 경우에는 발전소 자체의 기동이 위험한 경우도 발생할 수 있다. 매우 간단한 실험이지만 제어기술자가 플랜트를 기동하기 위해서 매우 유용한 방법과 실제로 이를 적용한 사례에 대하여 기술한다.

• Journal of Biosystems Engineering
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• 제18권3호
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• pp.262-269
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• 1993

Stress relaxation behaviors of the cucumber under bending moment were tested with UTM at three levels of loading rate and initial deflection ratio. Sample cucumber was selected from three cultivars of cucumber, Cheongjangmadi, Baekdadagi, and Gyeousalicheongjang, because these cultivars are the most popular grown cultivars in Korea. When the bending moment was applied to the cucumber sample, the effective span between simple supports was held a constant value of 116mm with consideration of the selected sample length. The objectives of this study were to develop the rheological models such as linear and nonlinear models of the stress relaxation for the cucumber samples, and to investigate the effects of loading rate and initial deflection ratio on the stress relaxation behavior of the cucumber. The results of this study may be summarized as follows : 1. Stress relaxation behavior of the cucumber could be well described by the generalized Maxwell model for each level of deflection ratio. But the stress relaxation behavior of the sample was found to be initial deflection ratio and time dependent, and it was represented the nonlinear viscoelastic model as a function of initial deflection ratio and time. 2. Stress relaxation behavior of the cucumber samples was very highly affected by the loading rate and the initial deflection ratio. The more loading rate and initial deflection ratio resulted in the more initial bending stress and after stress relaxation progressed more rapidly. 3. At the same test conditions, it was found that the stress relaxation rate of Cheongjangmadi was faster than that of other cultivars.

• 한국전기전자재료학회논문지
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• 제17권1호
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• pp.46-51
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• 2004

The cause for the variation of the initial permeability according to the Co substitution of Ni-Zn ferrite used in the LC resonance filter for the power line communication is studied. The initial permeability decreases as the quantity of Co diminishes, and the saturation magnetization increases as the quantity increases. Because the sintering density and the microstructure of ferrite show little change, the variation of the initial permeability can't be explained by the density, microstructure nor the saturation magnetization factor. The magnetocrystalline anisotropy increases, similar with the saturation magnetization, as the quantity of Co increases. The increase of magnetocrystalline anisotropy value makes the domain wall energy grow, which leads to the decrease of the initial permeability, because there's linear law between the magnetocrystalline anisotropy and the domain wall energy. The resonance frequency to Co substitution moved to high frequency band, due to the close relationship with domain wall energy, Initial permeability decreaed a little with an increase of Co contents, but resonace frequency moved to high frequency band. as a result of that, when Co was added 0.05 mol, initial permeability and resonace frequency was 75 and 25 MHz respectively.