• Wind and Structures
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• 제25권1호
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• pp.63-77
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• 2017

When railway vehicles run by towers of long span bridges, the railway vehicles might experience a sudden load-off and load-on phenomenon in crosswind conditions. To ensure the running safety of the railway vehicles and the running comfort of the passengers, some studies were carried out to investigate the impacts of sudden changes of aerodynamic loads on moving railway vehicles. In the present study, the aerodynamic coefficients which were measured in wind tunnel tests using a moving train model are converted into the aerodynamic coefficients in the actual scale. The three-component aerodynamic loads are calculated based on the aerodynamic coefficients with consideration of the vehicle movement. A three-dimensional railway vehicle model is set up using the multibody dynamic theory, and the aerodynamic loads are treated as the inputs of excitation varied with time for kinetic simulations of the railway vehicle. Thus the dynamic responses of the railway vehicle passing by the bridge tower can be obtained from the kinetic simulations in the time domain. The effects of the mean wind speeds and the rail track positions on the running performance of the railway vehicle are discussed. The three-component aerodynamic loads on the railway vehicle are found to experience significant sudden changes when the vehicle passes by the bridge tower. Correspondingly, such sudden changes of aerodynamic loads have a large impact on the dynamic performance of the running railway vehicle. The dynamic responses of the railway vehicle have great fluctuations and significant sudden changes, which is adverse to the running safety and comfort of the railway vehicle passing by the bridge tower in crosswind conditions.

• 대한방사선기술학회지:방사선기술과학
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• 제37권4호
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• pp.341-348
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• 2014

쐐기필터는 고선량 부분의 선량분포를 균등하게하기 위해서 사용된다. 금속쐐기필터와 기능강화 동적쐐기필터가 광자선과 상호 작용으로 표면과 선량강화영역 조사면내, 외에 선량변화를 평가하였다. 본 논문에서는 2차원적 조직등가물질로 공간 선량분포가 우수하고, 흡수선량에 따라 현상 없이 실시간으로 광학농도가 변하는 가프크로믹 EBT3 필름을 사용하여 선량평가를 실시하였다. 선형가속기 광자선 에너지는 6 MV, SSD 100 cm, 조사면 $10{\times}10cm^2$으로 고정하고 최대선량점에 400 cGy로 조사하였다. 선량분포는 열린 조사면과 $15^{\circ}$, $30^{\circ}$, 그리고 $45^{\circ}$ 금속쐐기필터와 기능강화 동적쐐기필터를 사용 하였을 때 비교 평가 하였다. $15^{\circ}$ 금속쐐기필터를 사용하면 조사면내 표면선량과 선량증가영역 선량은 기능강화 동적쐐기필터보다 증가하였다. $30^{\circ}$ 금속쐐기필터를 사용하면 조사면내 표면선량과 선량증가영역 선량은 기능강화 동적쐐기필터 보다 감소하였다. $45^{\circ}$ 금속쐐기필터를 사용하면 조사면내 표면선량과 선량증가영역 선량은 많은 차이로 감소하였다. 조사면 주변 반음영 영역에서는 두꺼운 방향은 증가하고 얇은 방향은 감소하였다. 선량분포를 변화하고자 하는 치료 부위에 금속쐐기필터를 적절히 사용하고 유방암 치료와 같이 표면과의 거리가 가까워지지 않으면 표면 및 선량증가영역 선량이 감소하리라 사료된다.

• 한국운동역학회지
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• 제15권3호
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• pp.143-152
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• 2005

The purpose of this study was to predict the failure or success of the Snatch-lifting trial as a consequence of the stand-up phase simulated in Kane's equation of motion that was effective for the dynamic analysis of multi-segment. This experiment was a case study in which one male athlete (age: 23yrs, height: 154.4cm, weight: 64.5kg) from K University was selected The system of a simulation included a multi-segment system that had one degree of freedom and one generalized coordinate for the shank segment angle. The reference frame was fixed by the Nonlinear Trans formation (NLT) method in order to set up a fixed Cartesian coordinate system in space. A weightlifter lifted a 90kg-barbell that was 75% of subject's maximum lifting capability (120kg). For this study, six cameras (Qualisys Proreflex MCU240s) and two force-plates (Kistler 9286AAs) were used for collecting data. The motion tracks of 11 land markers were attached on the major joints of the body and barbell. The sampling rates of cameras and force-plates were set up 100Hz and 1000Hz, respectively. Data were processed via the Qualisys Track manager (QTM) software. Landmark positions and force-plate amplitudes were simultaneously integrated by Qualisys system The coordinate data were filtered using a fourth-order Butterworth low pass filtering with an estimated optimum cut-off frequency of 9Hz calculated with Andrew & Yu's formula. The input data of the model were derived from experimental data processed in Matlab6.5 and the solution of a model made in Kane's method was solved in Matematica5.0. The conclusions were as follows; 1. The torque motor of the shank with 246Nm from this experiment could lift a maximum barbell weight (158.98kg) which was about 246 times as much as subject's body weight (64.5kg). 2. The torque motor with 166.5 Nm, simulated by angular displacement of the shank matched to the experimental result, could lift a maximum barbell weight (90kg) which was about 1.4 times as much as subject's body weight (64.5kg). 3. Comparing subject's maximum barbell weight (120kg) with a modeling maximum barbell weight (155.51kg) and with an experimental maximum barbell weight (90kg), the differences between these were about +35.7kg and -30kg. These results strongly suggest that if the maximum barbell weight is decided, coaches will be able to provide further knowledge and information to weightlifters for the performance improvement and then prevent injuries from training of weightlifters. It hopes to apply Kane's method to other sports skill as well as weightlifting to simulate its motion in the future study.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.690-699
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• 2008

In this paper a conventional approach for design and analysis of subsonic air vehicle is used. First of all subsonic aerodynamic coefficients are calculated using Computational Fluid Dynamics(CFD) tools and then wind-tunnel model was developed that integrates vehicle components including control surfaces and initial data is validated as well as refined to enhance aerodynamic efficiency of control surfaces. Experimental data and limited computational fluid dynamics solutions were obtained over a Mach number range of 0.5 to 0.8. The experimental data show the component build-up effects and the aerodynamic characteristics of the fully integrated configurations, including control surface effectiveness. The aerodynamic performance of the fully integrated configurations is comparable to previously tested subsonic vehicle models. Mathematical model of the dynamic equations in 6-Degree of Freedom(DOF) is then simulated using MATLAB/SIMULINK to simulate trajectory of vehicle. Effect of altitude on range, Mach no and stability is also shown. The approach presented here is suitable enough for preliminary conceptual design. The trajectory evaluation method devised accurately predicted the performance for the air vehicle studied. Formulas for the aerodynamic coefficients for this model are constructed to include the effects of several different aspects contributing to the aerodynamic performance of the vehicle. Characteristic parameter values of the model are compared with those found in a different set of similar air vehicle simulations. We execute a set of example problems which solve the dynamic equations to find the aircraft trajectory given specified control inputs.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.997-1000
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• 2005

Dynamic job shop environment requires not only more flexible capabilities of a CAPP system but higher utility of the generated process plans. In order to meet the requirements, this paper develops an algorithm that can select machines for the machining operations to be performed by predicting the machine loads. The developed algorithm is based on the multiple objective genetic algorithm that gives rise to a set of optimal solutions (in general, known as Pareto-optimal solutions). The objective shows a combination of the minimization of part movement and the maximization of machine utility balance. The algorithm is characterized by a new and efficient method for nondominated sorting, which can speed up the running time, as well as a method of two stages for genetic operations, which can maintain a diverse set of solutions. The performance of the algorithm is evaluated by comparing with another multiple objective genetic algorithm, called NSGA-II.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2006년도 한국컴퓨터종합학술대회 논문집 Vol.33 No.1 (C)
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• pp.46-48
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• 2006

This paper addresses the problem of monitoring continuous k-nearest neighbor (k-NN) queries. Given a set of moving (or static) objects and a set of moving (or static) query points, monitoring continuous k-NN query retrieves and updates the closest k objects to a query point continually. In order to support location based services (LBSs) in highly dynamic environments, where objects and/or queries are frequently moving, monitoring continuous queries require real-time updated results when objects and/or queries change their locations. Thus, it is important to minimize time delay for maintaining up to date the results. In this paper, we present monitoring method to shorten time delay for updating continuous k-NN queries based on the notion of result region and the minimum bounding rectangle enclosing all objects in each cell, referred to as c-MBR, in the grid index structure. Simulations are conducted to show the efficiency of the proposed method.

• 천문학회지
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• 제34권2호
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• pp.111-117
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• 2001

Recently, we have set up a new digital CCD camera system, MicroMax YHS-1300 manufactured by Roper Scientific for Ha observation by Solar Flare Telescope at Bohyunsan Optical Astronomy Observatory. It has a 12 bit dynamic range, a pixel number of 1300$\times$1030, a thermoelectric cooler, and an electric shutter. Its readout speed is about 3 frames per second and the dark current is about 0.05 e-/p/s at $-10^{\circ}C$. We have made a system performance test by confirming the system linearity, system gain, and system noise that its specification requires. We have also developed a data acquisition software which connects a digital camera con-troller to a PC and acquires H$\alpha$ images via Microsoft Visual C++ 6.0 under Windows 98. Comparisons of high quality H$\alpha$ images of AR 9169 and AR 9283 obtained from SOFT with the corresponding images from Learmonth Solar Observatory in Australia confirm that our H$\alpha$ digital observational system is performed properly. Finally, we present a set of H$\alpha$ images taken from a two ribbon flare occurred in AR 9283.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.282-289
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• 2010

A Thomson coil type actuator is applied as the driving unit in an arc eliminator system. To eliminate the arc efficiently, the speed of the actuator is required as fast as possible with certain limit of the exciting current. Therefore, the dynamic characteristics of the Thomson coil type actuator should be analyzed in an effective way. In this paper, a novel solving technique has been developed based on the equivalent circuit model which is set up by dividing the conducting plate into multi segments. To guarantee the calculation accuracy and improve the calculation efficiency, an adaptive refinement algorithm is suggested based on the field continues condition. The proposed method has been verified by the FEM calculation and experiment. The influence of circuit and plate parameters to the performance of the actuator is also investigated, from which a reasonable set of parameters can be found.

• 대한기계학회논문집B
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• 제30권7호
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• pp.612-621
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• 2006

Drawing is a mechanical operation attenuating material thickness to an appropriate level for the next processing or end usage. When the input material has a form of bundle or bundles made of very thin and long shaped wires or fibers, this attenuation operation is called 'bundle drawing' or 'drafting'. Bundle drawing is being used widely in manufacturing micro sized wires or staple yarns. However, the bundle processed by this operation has more or less defects in the evenness of linear density. Such irregularities cause many problems not only for the product quality but also for the efficiency of the next successive processes. In this research a mathematical model for the dynamic behavior of the bundle fluid is to be set up on the basis of general physical laws containing physical variables, i.e. linear density and velocity as the dynamic state variables of the bundle fluid. The governing equations resulting from the modeling show that they appear in a slightly different form from what they do in a continuum fluid. Then, the governing equations system is simplified in a steady state and the bundle dynamics is simulated, showing that the shape of the velocity profiles depends on two model parameters. Experiments confirm that the model parameters are to be well adjusted to show a coincidence with the theoretical analysis. The higher the drawing ratio and drawing speed we, the more sensitive becomes the bundle flow to exogenous disturbances.

• 한국경영정보학회:학술대회논문집
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• 한국경영정보학회 2008년도 춘계학술대회
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• pp.454-471
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• 2008

This study suggests the dynamic pricing model which reveals the organic relationship between ASP (Application Service Provider) price and the related factors, using system dynamics methodology. Basically, we applied the law of supply and demand for analyzing price changes. Then, we deducted ASP price, focusing on fixed cost and variable cost. We also researched the customer's buying behavior according to version differentiation policy. In the version policy, we set up the proposition about customer's satisfaction and willingness-to-pay, using option system. As a result, this research designed the simulation model which analyzes the changes of the sales according to version differentiations and customer's willingness-to-pay. Through this research, we can find effective version differentiation strategies. This paper also found that the larger the number of package, the greater the demand and customer's willingness-to-pay. The increase of the number of package causes the increase of the sales. The increase of the sale is not exactly relative to the number of package. Drawing S-curve, the sales was increased. This dynamic pricing model suggests the ground that the ASP price changes based on the existing version differentiation theory and the demand of customers can affect the changes of the sales. We expect that this model suggests a clear standard of ASP pricing by combining real cases.