• 한국항만경제학회지
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• 제26권4호
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• pp.207-218
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• 2010

2011년 세계경기는 그리 밝지 않은 것으로 전망되고 있다. 금년 11월 미국 정부가 6,000억 달러라는 천문학적 규모의 양적 완화를 발표하였음에도 별다른 효과를 기대하지 않을 정도로 세계경제에 대한 전망이 흐린 것이다. 글로벌 불균형과 환율문제에서의 국가간 갈등, 국제통화제도의 불안정 등도 경기회복을 더디게 하는 요인으로 지목되고 있다. 그런데 해운경기와 세계경제는 밀접한 연관성을 갖기 때문에 당연히 해운경기에 대한 전망이 밝지 않다. 본고는 2011년의 해운경기를 예측하기 위하여 단변량 모형인 4개의 ARIMA 모형과 6개의 개입ARIMA모형을 이용한다. 먼저 사후적 예측을 하여 10개의 모형의 RMSPE가 비교적 높을 뿐만 아니라 RW 모형의 그것보다 높아 동 모형을 이용한 예측이 부정확할 수 있음을 보인다. 그러나 이러한 점은 예측치에 대한 부정확을 의미하는 것이지 2011년 해운경기의 흐름에 대한 예측을 거부하는 것은 아니다. 사전적 예측을 통해 모형간 예측치가 비교적 큰 차이를 보이나 2011년 내내 침체 상태에 있거나 2011년 후반기에 침체상태로 접어든다는 것을 밝힌다. 해운업계에 어려운 시기가 될 수 있다는 것을 시사한다.

• 제어로봇시스템학회논문지
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• 제20권6호
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• pp.635-640
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• 2014

Detection and diagnosis of incipient bearing fault in an induction motor is important for the prevention of serious motor failure. This paper presents an analysis of the effect of a faulty bearing on the stator current of an induction motor. A bearing fault leads to torque oscillations which result in phase modulation of the stator current. Since the torque oscillations cause specific frequency components at the stator current spectrum to rise sharply, the bearing fault can be detected by checking out the faultrelated frequency. In this paper, a mathematical model of the load torque oscillation caused by a bearing fault is presented. The proposed model can be used to analyze the physical phenomenon of a bearing fault in an induction motor. In order to represent the bearing fault effect, the proposed model is combined with an existing model of vector-controlled induction motors. A set of simulation results demonstrate the effectiveness of the proposed model and represent that bearing fault detection using a stator current is useful for vector-controlled induction motors.

• 한국기계가공학회지
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• 제11권3호
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• pp.182-186
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• 2012

This paper aims to analyze the vibration characteristics of the test equipment that inspects any defects in manufactured semiconductor chips and classifies defective chips. This type of equipment should be robust against any vibrations because such vibrations can cause disruption in the process that requires higher precision. 3D model of the structure of the equipment has been used to configure vibration simulation model. Model analysis have been carried out to analyze which part of the equipment is weak against vibration. To minimize the vibration effect of the equipment, the thickness of the plate consist of the equipment and weights are modified. The results show that thicker plate and higher weight in the equipment can decrease vibration effect.

• 응용통계연구
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• 제27권7호
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• pp.1187-1196
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• 2014

우리나라 대표적인 동계 사료작물인 이탈리안 라이그라스(Italian Ryegrass: IRG)는 사초의 품질과 수량이 높은 반면 내한성이 낮아 중남부 지방에서 주로 재배되고 있다. 본 연구는 우리나라에서 수행된 IRG 연구 자료(n = 375)와 기상청의 기상자료를 이용하여 IRG 수량과 온도, 강수량 등의 기상 변수들과의 인과관계를 분석하였다. 다변량 정규성가정 하에 계절효과를 지닌 구조방정식모형을 고려하여 분석한 결과, 동계작물인 IRG의 수량은 이듬해 봄의 기온에 직접적인 영향을 받고, 이듬해 봄 강수는 다른 요인을 통하여 영향을 미치는 것으로 나타났다. 즉, 저온으로 월동에 문제가 있는 지역에서 IRG 를 이른 봄에 파종하여도 충분히 생산성이 있다는 것을 의미한다. 이번 연구를 통해서 IRG 수량에 대한 보다 구체적이고 종합적인 인과관계를 고찰하는 계기를 마련하였으며, 앞으로 다른 초종에 대해서도 다양한 구조방정식 모형 연구를 통하여 수량증대에 기여할 것으로 사료된다.

• Wind and Structures
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• 제29권5호
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• pp.313-321
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• 2019

The wind blowing at high velocity in an open storage yard leads to wind erosion and loss of material. Fence structures can be constructed around the periphery of the storage yard to reduce the erosion. The fence will cause turbulence and recirculation behind it which can be utilized to reduce the wind erosion and loss of material. A properly designed fence system will produce lesser turbulence and longer shelter effect. This paper aims to show the applicability of Support Vector Machine (SVM) to predict the recirculation length. A SVM model was built, trained and tested using the experimental data gathered from the literature. The newly developed model is compared with numerical turbulence model, in particular, modified $k-{\varepsilon}$ model along with the experimental results. From the results, it was observed that the SVM model has a better capability in predicting the recirculation length. The SVM model was able to predict the recirculation length at a lesser time as compared to modified $k-{\varepsilon}$ model. All the results are analyzed in terms of statistical measures, such as root mean square error, correlation coefficient, and scatter index. These examinations demonstrate that SVM has a strong potential as a feasible tool for predicting recirculation length.

• 대한가정학회지
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• 제32권5호
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• pp.15-28
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• 1994

The purposes of this study are to define the family life events as a input factor of system model and to understand structural characteristics of the family life events in the modern multilateral society have and orientation of the management system leads a satisfactory life. This study attempted through the relation of cause and effect among the components of management system by Deacon & Firebaugh systems theory. The findings of this study are as follows: 1) As for the influence of family life events on the orientation of home management behavior the influential family life event on overall the orientation of home management behavior was social problem of family members($\beta$= -128). 2)Family life events which have influence on the family life satisfaction were financial problem and trouble with husband members problems demand for housework and everyday affairs. 3) The subdivison of home management behavior which influenced on the overall family life satisfaction were communication and decision originality the use of resources and the flexibility of plan. 4) Results of path analysis revealed that relation of cause and effect out of family life events resources the patterns of home management behavior and family life satisfaction the family life events made the family life satisfaction higher because they had negative effect on the family life satisfaction directly but changed total effect into positive one by family management behavior.

• Steel and Composite Structures
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• 제18권3호
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• pp.641-657
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• 2015

Application of reduced web beam section (RWBS) as a sacrificial fuse element has become a popular research field in recent years. Weakening of beam web in these connections may cause local web buckling around the opening area which can affect cyclic behavior of connection including: maximum load carrying capacity, strength degradation rate, dissipated energy, rotation capacity, etc. In this research, effect of local web buckling on the cyclic behavior of RWBS connections is investigated using finite element modeling (FEM). For this purpose, a T-shaped moment connection which has been tested under cyclic loading by another author is used as the reference model. Fracture initiation in models is simulated using Cyclic Void Growth Model (CVGM) which is based on micro-void growth and coalescence. Included in the results are: effect of opening corner radii, opening dimensions, beam web thickness and opening reinforcement. Based on the results, local web buckling around the opening area plays a significant role on the cyclic behavior of connection and hence any parameter affecting the local web buckling will affect entire connection behavior.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1998년도 제34회 추계 학술발표회
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• pp.298-298
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• 1998

The delay on two-lane, Two-way roads is a very important factor which tends to cause relatively high driver loads and too much delay often leads to traffic accidents. In this study a generalized form of delay estimation model was developed based on constant slow moving vehicle speeds, 100% no-passing zone, and flat terrain highway sections. To validate the model, a comparison was made with John Morrall's SMV(Slow Moving Vehicle)model as well as with TWOPAS model. Also a sensitivity analysis was performed to check accuracy of the model. It was found that the model was easy to apply and yet provided reasonable results for experimental conditions specified in the study. It was recommended that speed calculation procedure of the model be improved by further studies, so that the effect of speed acceleration or deceleration according to highway geometries on delay could be analyzed more accurately.

• Environmental Analysis Health and Toxicology
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• 제26권
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• pp.9.1-9.9
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• 2011

Objectives: In order to evaluate which temperature index is the best predictor for the health impact assessment of heat stress in Korea, several indexes were compared. Methods: We adopted temperature, perceived temperature (PT), and apparent temperature (AT), as a heat stress index, and changes in the risk of death for Seoul and Daegu were estimated with $^1{\circ}C$ increases in those temperature indexes using generalized additive model (GAM) adjusted for the non-temperature related factors: time trends, seasonality, and air pollution. The estimated excess mortality and Akaike's Information Criterion (AIC) due to the increased temperature indexes for the $75^{th}$ percentile in the summers from 2001 to 2008 were compared and analyzed to define the best predictor. Results: For Seoul, all-cause mortality presented the highest percent increase (2.99% [95% CI, 2.43 to 3.54%]) in maximum temperature while AIC showed the lowest value when the all-cause daily death counts were fitted with the maximum PT for the $75^{th}$ percentile of summer. For Daegu, all-cause mortality presented the greatest percent increase (3.52% [95% CI, 2.23 to 4.80%]) in minimum temperature and AIC showed the lowest value in maximum temperature. No lag effect was found in the association between temperature and mortality for Seoul, whereas for Daegu one-day lag effect was noted. Conclusions: There was no one temperature measure that was superior to the others in summer. To adopt an appropriate temperature index, regional meteorological characteristics and the disease status of population should be considered.

• 대한기계학회논문집A
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• 제28권8호
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• pp.1075-1086
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• 2004

In this paper, Time Delay Control(TDC) for robot manipulators is analyzed and its problems are founded. In order to remedy the problems, the enhanced controller is proposed and analyzed. The effect of friction associated with TDC is reported and its cause is presented. Through the analysis, simulation and experiment, it is shown that the friction effect causes serious degradation in control performance and that it is a result of the error of Time Delay Estimation(TDE) in TDC. In order to remedy the problems, TDC combined with Internal Model Control(IMC) concept is proposed. The proposed compensator is effective enough to handle the bad effect of friction, and is so simple and efficient as to match positive attribute of TDC. The simulation and experimental results show the effectiveness of proposed controller against the friction of the robot manipulators.