• 한국해양공학회지
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• 제32권6호
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• pp.433-439
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• 2018

An investigation was conducted to determine whether the changes in the maneuvering forces and moments acting on a hull could be affected by changing the vertical center of gravity (VCG) of a tanker. The changes in the hydrodynamic forces and moment acting on a hull according to the restraint conditions of motion were examined using CFD for cases where the VCG was located at the design draught (100% of draught), under the design draught (75% of draught), and at half of the design draught (50% of draught). The following motion restraint conditions were selected: (1) fixed restraints for everything; (2) heave, pitch, and roll free restraint; and (3) heave and pitch free restraints. It was found that restraint condition (2) had the best agreement with the model experiment results. In addition, it was found that the hydrodynamic forces and moment acting on the hull with restraint condition (2) could be greatly affected in the model tests and CFD calculations by the various configurations for the vertical center of gravity of the hull. Finally, it was concluded that the location of the vertical center of gravity of the hull could be an important factor when more accurate hydrodynamic maneuvering forces and moment are estimated.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2006년도 추계공동학술대회
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• pp.523-529
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• 2006

Nowadays, a logistics and distribution center plays an important role in all industries. In addition to its traditional functions as a storage and unloading facility the distribution center serves as an assembly place for information, a source of information, and a turning point for the flow of information. On account of the above-mentioned reasons, each and every industry has increasing need of logistics distribution center. At this juncture, the present author thinks that it is necessary to make a study of the establishment and maximization of a ceramics logistics distribution center as a way for activating the ceramics industry.

• 지구물리와물리탐사
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• 제14권1호
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• pp.88-97
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• 2011

최적화된 4진트리 격자화 기법을 이용한 중력변화율 탐사의 지형 효과 계산 방법을 제시하고자 한다. 제시하고자 하는 방법은 항공탐사의 자료처리를 위하여 지형 자료에 최적화된 빠르고 정확한 지형효과 계산법이다. 각 지점에서의 지형효과 계산에 이용되는 지표 고도 자료는 자동적으로 원하는 정밀도를 제공할 수 있는 최대 크기로 격자화 되어 최대 해상도 자료를 이용하는 방법에 비하여 빠른 계산이 가능하다. 이러한 최적화된 격자 크기는 각 지점에서의 거리와 지표의 고도 변화를 고려하여 구성된다 새로운 접근 방법을 검증하기 위하여 수치모델링과 현장자료에 적용하였다. 현장 자료에 적용한 결과 최적 4 진트리 기법은 최고 해상도 자료를 모두 이용한 방법과 비교하여 중력 변화율 자료에서 1EU(E$\"{o}$tv$\"{o}$s unit)의 정밀도를 유지하면서 계산양은 1/351로 줄일 수 있었다. 또한, 중력탐사 결과의 지형보정에 이용한 결과 모든 DEM자료를 이용한 계산에 비하여 310배나 빠른 계산이 가능하였다.

• 대한조선학회논문집
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• 제46권3호
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• pp.335-342
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• 2009

Motion characteristics of a planing craft are sensitively changed according to its weight and longitudinal center of gravity. In this paper, planing craft model tests were performed in calm water for various test conditions and Froude numbers. Sinkage and trim were measured to analyze the relations between the attitudes of a planing craft and the weight and center of gravity of it. Theoretical formula for the prediction of the attitudes of a prismatic planing hull was modified so that it can be applied to the prediction of the attitudes of a non-prismatic planing hull, and the calculation results by the modified formula were in good agreements with the experimental data.

• International Journal of Advanced Culture Technology
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• 제9권3호
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• pp.23-33
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• 2021

"China's Western Development Policy" has brought multiple opportunities to the development of tourism in Southwest China including Sichuan, Guizhou, Yunnan, Chongqing and Tibet. The 4 provinces and 1 municipality overall show a certain degree of accumulation effect and coordinated development in tourism due to their location, traffic and traditional economic cooperation. This study takes the Southwest China as the research object and utilized the spatial dislocation model and the tourism spatial misalignment index to estimate the mismatch degree between tourism resources and tourism income among provinces and try to find out the internal reason background. The results show that each of the five provinces has its own advantages in index of economy, tourism resources, human resource, and transportation, leading to differences in the center of gravity of the entire region in all aspects. In view of the results of spatial dislocation analysis, suggestions for improvement and optimization are put forward to promote the high-quality development of tourism in Southwest region. development.

• 제어로봇시스템학회논문지
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• 제21권8호
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• pp.758-765
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• 2015

This paper proposes an attitude control system to keep the balance for a two-wheeled mobile manipulator which consists of a mobile platform and a three D.O.F. manipulator. In the conventional control scheme, complicated dynamics of the manipulator need to be derived for balancing control of a mobile manipulator. The method proposed in this paper, however, three links are considered as one body of mass and the dynamics are derived easily by using an inverted pendulum model. One of the best advantage of a sliding mode controller is low sensitivity to plant parameter variations and disturbances, which eliminates the necessity of exact modeling to control the system. Therefore the sliding mode control algorithm has been adopted in this research for the attitude control of mobile platform along the pitch axis. The center of gravity for the whole mobile manipulator is changing depending on the motion of the manipulator. And the orientation variation of center of gravity is used as reference input for the sliding mode controller of the pitch axis to maintain the center of gravity in the middle of robot to keep the balance for the robot. To confirm the performance of controller, MATLAB Simulink has been used and the resulting algorithms are applied to a real robot to demonstrate the superiority of the proposed attitude control.

• 대한산업공학회지
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• 제18권2호
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• pp.1-9
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• 1992

The purpose of this paper is to investigate the dynamic situation of the biomechanical responses of a pilot that occur before the black out during high gravity maneuvering. The computer biodynamic simulations using the Articulated Total Body(ATB) model show the following results : 1) the center of gravity(c. g) offsets of a helmet have significant effects on the head deflection angle which is closely connected with the head down : 2) the average and maximum gravity forces are smaller in the curvilinear type of an acceleration than in the straight type of the acceleration, and it is applied to the case of the head deflection angle. We suggest that the new concept of protective device should be necessary to prevent the head down during high gravity maneuvering.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.833-839
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• 2006

In this paper, roll behavior of three planar half car models are compared. The first model is a simple model whose contact point between a wheel and the ground is assumed to be fixed with a revolute joint. The second model is a modified model of the fIrst model, whose wheel tread width can vary. In this model, the instant center of a wheel with respect to the ground, which is crucial to find the roll center, is assumed to be at the contact point of a wheel and the ground. The last model uses the pole of a wheel with respect to the ground for small displacement as the instant center of a wheel with respect to the ground. Loci of the center of gravity point, the fixed and the moving centrodes which are traces of roll center position in the ground and the body frame respectively, wheel contact points, and instant centers of a wheel with respect to the ground are calculated.

• 무역학회지
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• 제45권3호
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• pp.119-132
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• 2020

In this paper we explore the two analyses to know the urbanization effect on trade. First, the granger causality test to examine the relationship between trade and urbanization. The Granger causality test is a statistical hypothesis test for determining whether one time series is useful for forecasting another. The results indicated that the existence of a bidirectional causality running from trade to urbanization when six lags were applied. When eight lags were applied, we found unidirectional causality running from urbanization to trade. Second, gravity models were used to investigate the urbanization effect on trade. The production cost and specification are affected by the economies of scale, and the economies of scale increased as the greater geographically agglomeration. However, the gravity model to explain the bilateral trade flows ignores the urbanization variables. Therefore we added the urbanization variable represented as the geographically agglomeration into gravity model. The results show that the degree of urbanization of both countries has statistically positive effect on trade (export and import) and the bigger coefficients of trade partner's urbanization. The reason is that the trade share of industrial supplies, intermediate goods and capital goods is much higher than finished consumer goods. The urbanization is more important the improved the efficiency of production than demand market.

• Journal of Biosystems Engineering
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• 제42권3호
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• pp.127-135
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• 2017

Purpose: Purpose: The usability of a mathematical model modified for analysis of the static stability of an asymmetric tractor-harvester system was investigated. Method: The modified asynchronous mathematical model was validated through empirical experiments, and the effects of movements of the center of gravity (CG) coordinates on the stability against lateral overturning were analyzed through simulations. Results: Changes in the lateral overturning angle of the system were investigated when the coordinates of the CG of the system were moved within the variable range. The errors between simulation results and empirical experiments were compared, and the results were -4.7% at the left side overturning and -0.1% at the right side overturning. The asymmetric system was characterized in such a way that the right side overturning had an increase in overturning angle in the (+) variable range, while it had a decrease in overturning angle in the (-) variable range. In addition, the left side overturning showed an opposite result to that of the right side. At the declination angle (296<${\gamma}$<76), the right side overturning had an increase in the maximum overturning angle of 3.6%, in the minimum overturning angle of 20.3%, and in the mean overturning angle of 15.9%. Furthermore, at the declination angle (284<${\gamma}$<64), the left side overturning had a decrease in the maximum overturning angle of 29.2%, in the minimum overturning angle of 44%, and in a mean overturning angle of 39.7%. Conclusion: The modified mathematical model was useful for predicting the overturning angle of the asymmetric tractor-harvester system, and verified that a movement of the CG coordinates had a critical effect on its stability. In particular, the left side overturning was the most vulnerable to stability, regardless of the direction of declination angle.