• 한국자동차공학회논문집
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• 제17권5호
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• pp.107-114
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• 2009

A Common-Rail Direct Injection (CRDI) system for high speed diesel engines was developed to meet reductions of noise and vibration, emission regulations. High pressure in the common rail with electric control allows the fuel quantity and injection timing to be optimized and controlled throughout a wide range of engine velocity and load conditions. In this study, CRDI system analysis model which includes fuel and mechanical systems was developed using commercial software, AMESim in order to predict characteristics for various fuel injection components. The parameter sensitivity analysis such as throttle size, injection rate, plunger displacement, supply pressure of fuel injection for system design are carried out.

• 대한산업공학회지
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• 제25권3호
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• pp.330-335
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• 1999

The goal of the study is to determine the most sensitive parameter to represent the degree of muscle force and fatigue. Various numerical parameters such as the first coefficient of Autoregressive (AR) Model, Root Mean Square (RMS), Zero Crossing Rate (ZCR), Mean Power Frequency (MPF), Median Frequency (MF) were tested in this study. Ten healthy male subjects participated in the experiment. They were asked to extend their trunk by using the right and left erector spinae muscles during a sustained isometric contraction for twenty seconds. The force levels were 15%, 30%, 45%, 60%, and 75% of Maximal Voluntary Contraction (MVC), and the order of trials was randomized. The results showed that RMS was the best parameter to measure the force level of the muscle, and that the first coefficient of AR model was relatively sensitive parameter for the fatigue measurement at less than 60% MVC condition. At the 75% MVC, however, both MPF and the first coefficient of AR Model showed the best performance in quantification of muscle fatigue. Therefore, the sensitivity of measurement can be improved by properly selecting the parameter based upon the level of force during a sustained isometric condition.

• 한국공작기계학회논문집
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• 제17권6호
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• pp.49-55
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• 2008

Arc welding process is one of the most important technologies to join metal plates. Robotic welding offers the reduced manufacturing cost sought, but its widespread use demands a means of sensing and correcting for inaccuracies in the part, the fixturing and the robot. A number of problems that need to be addressed in robotic arc welding processes include sensing, joint tracking, and lack of adequate models for process parameter prediction and quality control. Problems with parameter settings and quality control occur frequently in the GMA(Gas Metal Arc) welding process due to the large number of interactive process parameters that must be set and accurately controlled. The objectives of this paper are to realize the mapping characteristics of bead width using a sensitivity analysis and develop the neural network and multiple regression method, and finally select the most accurate model in order to control the weld quality(bead width) for fillet welding. The experimental results show that the proposed neural network estimator can predict bead width with reasonable accuracy, and guarantee the uniform weld quality.

• 동력기계공학회지
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• 제21권2호
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• pp.20-26
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• 2017

This study was carried out to investigate the effect of precipitate on the high temperature deformation stability of incoloy 825 alloy. $Cr_{23}C_6$ carbide was precipitated under $950^{\circ}C$, but was not detected over $1,000^{\circ}C$. Most of the precipitation consist of $Cr_{23}C_6$ carbide. Strain-rate sensitivity was the highest in 0.01/s and the lowest in 10/s. Strain-rate sensitivity was decreased sharply below $950^{\circ}C$. In the temperature between $850^{\circ}C{\sim}1,150^{\circ}C$, plastic instable area did not exist. It showed the lowest Ziegler Parameter value of 0.06 Ziegler Parameter was the lowest as 0.06 at $850^{\circ}C$ with 10s-1 of strain. The highest Ziegler Parameter value(0.43) was found in plastic deformation at $1,050^{\circ}C$ with 0.01s-1 of strain. It tends to have an higher resistance to the high temperature deformation under $950^{\circ}C$, due to the precipitation.

• 대한기계학회논문집
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• 제15권3호
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• pp.931-935
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• 1991

본 연구에서는 유효응력확대계수로서 피로크랙 진전수명을 평가할 수 이용되 는 크랙열림비(본 논문에서는 후술하는 최대응력에 대한 크랙 열림응력의 비를 크랙 열림비로 하다)가 진전수명에 미치는 영향을 평가하기 위한것으로서, 제1보에서는 실 험에 의하여 크랙 열림점을 실측한 결과 측정입치에 따라 다른 값을 나타내며 수명평 가법 크랙 선단으로부터 떨어진 곳(크립게이지를 이용한 크랙마우스등)에서 측정한 크 랙 열림점 값을 이용함이 보다 정확함을 밝혔다.본 제2보에서는 크랙열림비가 수명 평가에 미치는 영향을 상기의 파라미터 영향도 평가수법을 이용하여 평가하고자 한다.

• 설비공학논문집
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• 제12권6호
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• pp.599-608
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• 2000

One dimensional numerical modeling was carried out for the melting behavior of dry snow and the unsaturated flow when heat was supplied from the bottom surface. Discrepancy between the previous experimental data and the present numerical results is substantially reduced by considering the density change of water permeation layer due to the infiltration of meltwater. In the parametric study for effective thermal conductivity, it was found that the effect of this parameter to the behavior of snow melting is minor. Sensitivity analysis showed that the melting time is most sensitive to changes in supplied heat flux, snow temperature, and bulk density, whereas snow bulk density and residual saturation have a significant effect on the height of water permeation layer in snow.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1934-1938
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• 1991

This paper proposes a robust model following control systems with nonlinear time varying plant. which realies good properties such as asymptotic stability, disturbance rejection and model-following with reduced sensitivity for plant parameter variation. The schemes do not incorporate any parameter identification algorithms, but the adaptation is realized through signal synthesis in a fixed parameter structure.

• 대한기계학회논문집
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• 제17권1호
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• pp.46-50
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• 1993

본 연구에서는 실제의 하중에서 관찰되는 경우가 많고, 또한, 이론적 취급이 용이한 협대역(narrow band)파형을 대상으로 했으니, 다른 파형의 경우도 대략적인 경 향은 파악할 수 있으리라 생가되며 극치의 확률분포만 주어지면 본 수법과 마찬가지로 동일하게 적용할 수 있다.

• 한국안전학회지
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• 제12권2호
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• pp.17-21
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• 1997

The fatigue crack propagation rate has so far been measured by the effective stress intensity factor range Δ K/sub eff/. But no research has been done to study how much the crack opening ratio influences the expectation of the fatigue crack propagation. Therefore, this paper evaluates of the crack opening ratio on the fatigue crack propagation life by using the method of parameter sensitivity study. Summarizing the result ; ( 1 ) When the crack opening ratio U' is high, the effect of U' gets larger than any other except for the material factor m. But when U' is low, the effect is also diminished. Therefore, the selection of the lowest value possible is desirable in the evaluation of life. (2) When the value of the material factor m is high, the effect of crack opening ratio U' is increased, at the same time the effect of the other parameters also increased wholly. The effect of material factor m itself on life is high, but in case the material factor m is high, that the effect of each parameter on life get higher is unique. In designing, better attention to the material selection should be drawn. (3) In case the stress ratio R gets smaller, the effect of crack opening ratio U' is unchangeable. But the effect of R itself remarkably decreases, and the effect of material factor m somewhat decreases.

• 가정과삶의질연구
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• 제34권4호
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• pp.111-125
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• 2016

The purpose of this study was to model the relations between male and female university students' self-differentiation, rejection sensitivity, and interpersonal anxiety. Questionnaires from 502 university students in Seoul were analysed. The findings are as follows. Firstly, self-differentiation, rejection sensitivity, and interpersonal anxiety were significantly different according to gender. Secondly, the level of differentiation from family regression was higher for both male and female students. And the lower the rejection sensitivity experiencing in vertical relations became, and the lower the rejection sensitivity on horizontal relations was, the lower the interpersonal anxiety became. Thirdly, it was confirmed that for male students, differentiation from family regression affected rejection sensitivity on horizontal relations, and for females, differentiation from emotional reactivity affected ejection sensitivity on both horizontal and vertical relations. Finally, rejection sensitivity played a full mediation parameter when self-differentiation affected interpersonal anxiety, and it was demonstrated differences by gender. This study was meaningful in that it confirmed the relations between male and female university students' self-differentiation, rejection sensitivity, and interpersonal anxiety.