• 한국소음진동공학회논문집
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• 제23권3호
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• pp.240-248
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• 2013

자동차 수동변속기 내 래틀과 같은 회전체 진동은 엔진 연소폭발 주기와 연동하여 발생한다. 이러한 충격형 진동 특성은 선형 시간 불변 분석법을 적용하여 살펴볼 수 있다. 기어의 동적 특성을 이해하기 위해, 특정 형태의 앞 바퀴 굴림 방식 수동 변속기에 대한 연구를 수행하였다. 첫째, 동특성 고유값과 주파수 응답함수를 기반으로 자유도를 줄이는 방법을 제시하였는데, 이는 행렬의 크기를 줄이는 효과적인 역할을 한다. 둘째, 단일 질량 플라이휠과 이중 질량 플라이휠의 동적 특성을 비교하였다. 모빌리티 분석을 기반으로 한 이중 질량 플라이휠의 효과를 검토하였는데, 이로부터 진동에 의해 가진되는 충격을 회피하기 위한 기본 개념을 이해 할 수 있다. 마지막으로, 두 단계 클러치 댐퍼로부터 유효 강성 값을 도출하여 선형 불변형 시스템 모델을 연구하였다. 두 단계의 서로 다른 클러치 강성조합을 이용하여 클러치 댐퍼의 동적특성에 대한 관계를 예측할 수 있다.

• Tribology and Lubricants
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• 제30권2호
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• pp.71-76
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• 2014

As the importance of transmission efficiency to reducing fuel consumption and conserving the environment rapidly increases, reducing the drag torque in an automotive wet clutch is emerging as an important issue in the automotive industry. The drag torque in a clutch occurs from viscous drag generated by automatic transmission fluid in the narrow gap between separate friction plates. In this study, the drag torques in an automotive wet clutch are investigated with respect to the angle and density of the grooves between separate friction plates by three-dimensional finite element simulation of a single set of wet clutch disks considering the two-phase flow of air and oil. The simulation results shows that the drag torque generally increases with the rotational speed to a critical point and then decreases at the high-speed regime. The grooves between the plates plays an important role in reducing the drag peak, and the inclined angle of the grooves affects the oil flow. The grooves with an angle of $50^{\circ}$ shows the lowest drag torques at both low and high speeds. The flow vectors inside the $50^{\circ}$ grooves shows clear evidence that the fluid flows out more easily from the grooves compared with the flow vectors inside grooves with lower angles. The simulation results shows that increasing the number of grooves (density of grooves) decreases the drag torque.

• Parasites, Hosts and Diseases
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• 제53권3호
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• pp.355-359
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• 2015

Hydatid disease imposing serious threat on human health and great loss in live-stock pastoralism remains a major public health problem in western China. To assess and monitor the effect of control program on transmission dynamics, we used the prevalence of cystic echinococcosis in slaughtered sheep at slaughterhouse as an indicator during the period of 2007 to 2013 in Emin County, Xinjiang Uygur Autonomous Region, China. The results showed a significant decline trend of prevalence in all age groups during the 7 years when the control program was implemented; particularly, the rate was reduced by 72% after first 3 years. Among the sheep slaughtered, the age distribution evidenced that the prevalence increased significantly as the sheep grew older. The baseline data indicated that the rate was 4.5% at the age <1, 6.7% at age 2~, and reached to the highest 17.9% at age ${\geq}4$ years. Earlier response to the intervention pressure was seen in the sheep at the younger age. Significant decline started from 2008 at the age <1, from 2009 at age of 1~, 2010 at 2~ to 3~, and the latest, in 2012 at age ${\geq}4$. This study demonstrated that the prevalence of cystic echinococcosis in slaughtered sheep may be used as an indicator to assess and monitor the transmission status during and after control program providing information for betterment of performance to sustain control strength.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.882-888
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• 2002

In this paper, an algorithm to increase the shift speed is suggested by increasing the line pressure for a metal belt CVT. In order to control the shift speed, an algorithm to calculate the target shift speed is presented from the modified CVT shift dynamics. In applying the shift speed control algorithm, a criterion is proposed to prevent the excessive hydraulic loss due to the increased line pressure. Simulations are performed based on the dynamic models of the hydraulic control valves, powertrain and the vehicle. It is found from the simulation results that performance of the engine operation can be improved by the faster shift speed, which results in the improved fuel economy by 2% compared with that of the conventional electronic control CVT in spite of the increased hydraulic loss due to the increased line pressure.

• 대한수학회지
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• 제54권3호
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• pp.987-997
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• 2017

A deterministic model for the spread of pine wilt disease with asymptomatic carrier trees in the host pine population is designed and rigorously analyzed. We have taken four different classes for the trees, namely susceptible, exposed, asymptomatic carrier and infected, and two different classes for the vector population, namely susceptible and infected. A complete global analysis of the model is given, which reveals that the global dynamics of the disease is completely determined by the associated basic reproduction number, denoted by $\mathcal{R}_0$. If $\mathcal{R}_0$ is less than one, the disease-free equilibrium is globally asymptotically stable, and in such a case, the endemic equilibrium does not exist. If $\mathcal{R}_0$ is greater than one, the disease persists and the unique endemic equilibrium is globally asymptotically stable.

• 한국자동차공학회논문집
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• 제6권3호
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• pp.45-53
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• 1998

Traction control systems(TCS) improve vehicle acceleration performance and stability, particularly on slippery roads through engine torque and/or brake torque control. This research mainly deals with the engine control algorithm based on adjustment of the engine throttle valve opening. Hardware-in-the-loop simulation(HWILS) is carried out where the actual hardware is used for the engine/automatic transmission and TCS controller, while various vehicle dynamics are simulated on real-time basis. Also, use of the dynamometer is made in order to implement the tractive force that a road applies to the tire. Although some restrictions are imposed mainly due to the capability of the synamometer, simplified HWILS results show that the slip control algorithm can improve the vehicle acceleration performance for low-friction roads.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.410-413
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• 2004

In this paper, a simulator system for Fuel Cell Hybrid Electric Vehicles(FCHEV) is implemented using DSP boards with CAN bus. The subsystems of a FCHEV i.e., the fuel cell system, the battery system, the vehicle dynamics with the transmission mechanism are coded into 3 DSP boards. The power distribution control algorithm and battery SOC control are also coded into a DSP board. The real-time monitoring program is also developed to examine the control performance of power control and SOC control algorithms.

• 한국항만경제학회지
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• 제20권1호
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• pp.43-55
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• 2004

This paper investigates how Japanese economic shocks affect the Korean economy and analyzes the channels through which they are transmitted. Also, the relative importance of domestic and foreign shocks on the dynamics of certain key macro variables is investigated. The techniques of vector autoregression (VAR) are employed to investigate the international transmission of economic disturbances. The VAR methodology is a particularly useful means for characterizing the dynamic relationships among economic variables without imposing certain types of theoretical restrictions. The dynamic effects of Japanese economic shocks on the Korean economy are evaluated by estimating variance decompositions (VDCs) and impulse response functions (IRFs). This study supports the notion of economic dependence of a small open economy such as Korea to a large economy such as Japan.

• 한국경영과학회지
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• 제35권2호
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• pp.53-69
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• 2010

This paper proposes an ant-based routing algorithm, Ant System-Routing in wireless Senor Networks(AS-RSN), for wireless sensor networks. Using a transition rule in Ant System, sensors can spread data traffic over the whole network to achieve energy balance, and consequently, maximize the lifetime of sensor networks. The transition rule advances one of the original Ant System by re-defining link cost which is a metric devised to consider energy-sufficiency as well as energy-efficiency. This metric gives rise to the design of the AS-RSN algorithm devised to balance the data traffic of sensor networks in a decentralized manner and consequently prolong the lifetime of the networks. Therefore, AS-RSN is scalable in the number of sensors and also robust to the variations in the dynamics of event generation. We demonstrate the effectiveness of the proposed algorithm by comparing three existing routing algorithms: Direct Communication Approach, Minimum Transmission Energy, and Self-Organized Routing and find that energy balance should be considered to extend lifetime of sensor network and increase robustness of sensor network for diverse event generation patterns.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.719-724
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• 2002

Impact hammer is widely used as a convenient excitation tool in structural modal testing though, little is known about the dynamic characteristics of its impulse mechanism. Transmission of the impulsive force to the structure depends m the dynamic properties of the impact hammer as well as the stiffness of the tip. In this study an improved dynamic model of the impact hammer is proposed with the consideration of structure to be tested. The deformation masses of hammer tip and structure are as well as their contact stiffness. Numerical results show that this model is useful for the prediction of the impulse duration and the condition of rebounce..