• Tribology and Lubricants
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• 제18권3호
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• pp.181-186
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• 2002

A numerical analysis is undertaken to show the influence of bearing design parameters on the load capacity of air lubricated spiral grooved thrust bearing. The governing equation derived from the mass balance is solved by the finite difference method. Optimal values for various design parameters are obtained to maximize the load capacity. The design parameters are the groove angle, the groove width ratio, the groove height ratio, and the seal ratio.

• The Journal of Korean Physical Therapy
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• 제21권1호
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• pp.19-25
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• 2009

Purpose: We investigated the changes that effects of load stimulation (LS) on static balance and muscle activities in normal healthy elders and chronic stroke patients. Methods: Subjects were instructed twenty normal healthy elders (8 men and 12 women) and ten chronic stroke patients (4 men and 6 women). They were tested while standing on a force platform under two conditions; LS, no LS were applied in random order. Prior to testing, adhesive surface EMG electrodes were fastened to the skin overlying the right (non-paralytic side in stroke patient) bellies of tibialis anterior (TA) and lateral gastrocnemius (LG) muscles. They were assessed on postural sway and %MVC (Maximum voluntary contraction) of TA and LG. Results: Participants showed that the application of LS brought about a decrease in postural sway as expressed by average sway path and velocity. %MVC of TA and LG were increased. The application of LS to normal and stroke patients decreases postural sway during quite stance. Conclusion: These findings the application of LS to normal and stroke patients improves static balance.

• International Journal of Aeronautical and Space Sciences
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• 제1권2호
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• pp.68-74
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• 2000

A comparative wind tunnel testing of an airplane model was performed at the Korea Aerospace Research Institute Low Speed Wind tunnel(KARI LSWT). The model used for the comparative test was a seaplane model from the Glenn L. Martin Wind(GLM) Tunnel of University of Maryland, U.S.A. The 6-component external balance used in force and moment measurement is pyramidal type, which is a precision device that has strain gauge-type load cell inside of balance and the virtual center of the balance coincides with the tunnel centerline. Image method is adopted to eliminate the tare and interference of the model support, and to correct the flow angularity to the model also. Test results from KARI LSWT were compared with the results from GLM tunnel.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2446-2448
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• 2001

In addition to the stabilization of electricity supply and the quality management of electricity, load balance has been an important strategy for achieving high quality load management. Among many techniques for load management, direct load management has been actively studied and applied for increasing the efficiency of power facility and suppressing peak load. In Korea, the highest peak load is demanded in summer rather than in winter, and almost 50% of the peak load comes from cooling load. Currently, applicable systems are limited to air conditioners that have the cooling capacity less than 2kW. This paper describes the development of remote controlled air conditioners and the result of the field test of the new type air conditioner. The technical specification based on the test will be applied to the new model of the remote controlled air conditioner. The wide distribution of the air conditioners to the public will be helpful to control peak demand due to cooling load in summer time. Financial investment to generating, transmission, distribution facilities will be decreased from flatting the seasonal power load.

• 한국정보과학회논문지:정보통신
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• 제34권4호
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• pp.239-245
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• 2007

셀룰러/랜 기반의 중첩 네트워크는 유선 네트워크에 비해 상대적으로 제한된 대역폭을 가지는 특성으로 인해 효율적인 대역폭 관리에 대한 관심이 증가하고 있다. 본 논문에서는 멀티미디어 중첩 네트워크상에서 트래픽의 이동을 통한 온라인 부하분산 알고리즘을 제안하였다. 이 방법은 각 네트워크간 트래픽 부하의 균형을 통해 지역적으로 발생하는, 과부하 현상을 극복하고 높은 대역폭 효율성을 보장한다. 컴퓨터 시뮬레이션을 통하여 대역폭 관리를 위해 제안된 기존의 타 기법들과의 비교, 분석을 수행하여 제안된 방법이 다양한 네트워크 트래픽 상황에서 우수한 성능을 가지는 것을 확인할 수 있었다.

• Environmental Engineering Research
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• 제23권2호
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• pp.150-158
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• 2018

The deteriorating role of Nakdong River due to the Four Major Rivers Project has caused a series of problems, including water pollution, drying streams, aggravation of the hydroecology. Geumho River and Gyeongseong-cheon had a higher concentration index and is believed to impact the water quality of the main stream. The influence index of Geumho River and Nam River between 2015 and 2016, which have a large amount of discharge, was the highest among the tributaries in terms of the load material balance. Showing the highest average concentration and average load in the index assessment, Geumho River is believed to require an intensive management for improving the water quality of the main stream. Furthermore, when the cumulative percentage of the average concentration and average load was compared based on the water quality improvement of the tributaries mixed to Nakdong River, which was set to 60%, Geumho River, Nam River, Topyeong-cheon, and Cha-cheon, which showed the highest ratio in that order, were determined to require a water quality management program as a priority.

• Journal of Power Electronics
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• 제14권6호
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• pp.1178-1188
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• 2014

This study proposes a finite-state model predictive controller to regulate the load current and balance the DC-link capacitor voltages of a four-leg neutral-point-clamped converter. The discrete-time model of the converter, DC-link, inductive filter, and load is used to predict the future behavior of the load currents and the DC-link capacitor voltages for all possible switching states. The switching state that minimizes the cost function is selected and directly applied to the converter. The cost function is defined to minimize the error between the predicted load currents and their references, as well as to balance the DC-link capacitor voltages. Moreover, the current regulation performance is improved by using a two-step prediction horizon. The feasibility of the proposed predictive control scheme for different references and loads is verified through real-time implementation on the basis of dSPACEDS1103.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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• pp.4144-4165
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• 2018

Software-defined networking (SDN) has emerged as a promising technology for network programmability and experiments. In this work, we focus on virtual network embedding in multiple controllers SDN network. In SDN virtualization environment, virtual SDN networks (vSDNs) operate on the shared substrate network and managed by their each controller, the placement and load of controllers affect vSDN embedding process. We consider controller placement, vSDN embedding, controller adjustment as a joint problem, together considering different quality of service (QoS) requirement for users, formulate the problem into mathematical models to minimize the average time delay of control paths, the load imbalance degree of controllers and embedding cost. We propose a heuristic method which places controllers and partitions control domains according to substrate SDN network, embeds different QoS constraint vSDN requests by corresponding algorithms, and migrates switches between control domains to realize load balance of controllers. The simulation results show that the proposed method can satisfy different QoS requirement of tenants, keep load balance between controllers, and work well in the acceptance ratio and revenue to cost ratio for vSDN embedding.

• Journal of Power Electronics
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• 제14권4호
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• pp.661-670
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• 2014

A new DC/DC converter with zero voltage switching is proposed for applications with high input voltage and high load current. The proposed converter has two circuit modules that share load current and power rating. Interleaved pulse-width modulation (PWM) is adopted to generate switch control signals. Thus, ripple currents are reduced at the input and output sides. For high-voltage applications, each circuit module includes two half-bridge legs that are connected in series to reduce switch voltage rating to $V_{in}/2$. These legs are controlled with the use of asymmetric PWM. To reduce the current rating of rectifier diodes and share load current for high-load-current applications, two center-tapped rectifiers are adopted in each circuit module. The primary windings of two transformers are connected in series at the high voltage side to balance output inductor currents. Two series capacitors are adopted at the AC terminals of the two half-bridge legs to balance the two input capacitor voltages. The resonant behavior of the inductance and capacitance at the transition interval enable MOSFETs to be switched on under zero voltage switching. The circuit configuration, system characteristics, and design are discussed in detail. Experiments based on a laboratory prototype are conducted to verify the effectiveness of the proposed converter.

• 한국인터넷방송통신학회논문지
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• 제15권2호
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• pp.255-262
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• 2015

경제급전 최적화 문제를 해결하는 결정론적인 알고리즘에 존재하지 않아 지금까지는 비결정론적인 휴리스틱 알고리즘들이 제안되고 있다. 본 논문은 균형과 교환 방법을 도입하여 경제급전의 최적화 문제를 풀 수 있는 알고리즘을 제안하였다. 제안된 알고리즘은 초기치에 대해 성인걸음수와 아기걸음 수별로 발전량을 감소시켜 ${\Sigma}P_i=P_d$로 균형을 맞추고, 이 때 최소 발전비용을 가진 방법을 선택한다. 다음으로 선택된 방법에 대해 성인걸음-아기걸음 교환과 거인걸음 교환 방법으로 최적화한 값을 구하여 최소값 방법을 선택한다. 마지막으로 선택된 방법에 대해 $P_i{\pm}{\beta}$, (${\beta}=0.1,0.01,0.001,0.0001$)의 교환을 수행하였다. 경제급전 문제의 시험사례로 빈번히 활용되고 있는 3개 데이터에 대해 제안된 알고리즘을 적용한 결과 2개 데이터에서는 성능을 향상시켰으며, 1개 데이터는 기존의 최적해와 동일한 결과를 얻었다. 제안된 알고리즘은 항상 동일한 결과를 얻을 수 있고, 모든 데이터에 적합하므로 경제급전 최적화 알고리즘으로 실제 적용이 가능하다.