• IE interfaces
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• v.21 no.3
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• pp.333-342
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• 2008

Warehouses form an important link in a supply chain network. Among a variety of activities in warehouses, order picking is the process of retrieving a number of items out of storage to meet customer orders. Today, as the transactions through direct sales are wide spread, warehouses often receive a large amount of small orders to be handled within tight time windows, which makes fast and efficient order picking more important than ever. This paper examines a new order picking method where the concept of bucket brigade (BB) is applied. Bucket brigade is a way of dynamically coordinating workers who progressively perform a set of operations along a flow line. In bucket brigades, a worker is not assigned his jobs in a static way. Each worker takes a job from his predecessor when he is free. We identify some considerations when bucket brigades are applied to order picking activities. A new BB picking protocol is presented to improve existing BB picking protocols. Through simulation experiments, the performance of BB order picking is evaluated under various logistics environments.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.21-24
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• 2001

For very large multimedia traffic to be supported successfully in wireless network environment, it is necessary to provide Quality-of-Service(QoS) guarantees between mobile hosts(clients). In order to guarantee the Qos, we have to keep the call blocking probability below target value during handoff session. However, the QoS negotiated between the client and the network may not be guaranteed due to lack of available channels for traffic in the new cell, since mobile clients should be able to continue their on-going sessions. In this paper we propose a efficient load-balancing algorithm based on the adaptive bandwidth reservation scheme for enlarging available channels in a cell. We design a new method to predict the mobility of clients using MPT(mobility profile table). This method is then used to reserve a part of bandwidths for handoff calls to its adjacent cells and this reserved bandwidth can be used for handoff call prior to new connection requests. If the number of free channels is also under a low threshold value, our scheme use a load-balancing algorithm with a adaptive bandwidth reservation. In order to evaluate the performance of our algorithm, we measure the metrics such as the blocking probability of new calls and dropping probability of handoff calls, and compare with other existing schemes.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.441-449
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• 2002

For multimedia traffics to be supported successfully in wireless network environment, it is necessary to provide Qualify-of-Service(QoS) guarantees among mobile hosts(clients). In order to guarantee the QoS, we have to keep the call blocking probability below a target value during hand-off session. However, the QoS negotiated between the client and the network may not be guaranteed due to lack of available channels for traffic of a new cell, since on service mobile clients should be able to continue their sessions. In this paper, we propose an efficient load-balancing algorithm based on the adaptive bandwidth reservation scheme for enlarging available channels in a cell. Proposed algorithm predicts the direction of clients in a cell and adjusts the amount of the channel to be reserved according to the load status of the cell. This method is used to reserve a part of bandwidths of a cell for hand-off calls to its adjacent cells and this reserved bandwidth can be used for hand-off call prior to new connection requests. If the number of free channels is also under a low threshold value, our scheme use a load-balancing algorithm with an adaptive bandwidth reservation. In order to evaluate the performance of our algorithm, we measure metrics such as the blocking probability of new calls and dropping probability of hand-off calls, and compare with those of existing schemes.

• Physical Therapy Korea
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• v.21 no.3
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• pp.45-54
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• 2014

Fall is one of the most intimidating health conditions in elders. Comprehensive assessment is necessary to understand the individual and environmental aspects of the falls such as balancing abilities, depression, and quality of life. The purpose of this study was to compare the balancing ability, depression, and quality of life between elderly fallers and elderly non-fallers. Thirty-two community-dwelling elders (fifteen males and seventeen females between 65 and 83 years old), who have experienced fall on walking during last twelve months, were involved in the elderly fallers group. And twenty-four males and twenty-two females between 65 and 83 years old of community-dwelling elders, who have no experienced fall on walking during last twelve months, were involved in the elderly non-fallers group. Berg balance scale (BBS), timed up and go test (TUG), and functional reach test (FRT), were used to evaluate the ability of the physical balance. 'Beck depression scale in Korean' questionnaire was used to assess the depression. 'Korean version of World Health Organization Quality of Life Assessment Instrument-Bref' questionnaire was used to assess the quality of life. The results were as follows: 1) Balancing abilities measured by the BBS, TUG in the elderly fallers group were meaningfully lower than that of the elderly non-fallers group (p<.05), whereas no significant difference in the FRT was found (p>.05). 2) Depression level in the elderly fallers group was significantly higher than that of the elderly non-fallers group (p<.05). 3) Quality of life in the elderly fallers group was significantly lower than that of the elderly non-fallers group, excluding environment domain (p<.05). Therefore, in order for clinical evaluation of the community-dwelling elders those with reduced balancing ability, it is necessary to evaluate and understand the fall experience, depression, and quality of life.

• Journal of Internet Computing and Services
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• v.6 no.2
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• pp.69-84
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• 2005

As the Internet users are increasing rapidly, a cluster web server system is attracted by many researchers and Internet service providers. The cluster web server has been developed to efficiently support a larger number of users as well as to provide high scalable and available system. In order to provide the high performance in the cluster web server, efficient load distribution is important, and recently many content-aware request distribution techniques have been proposed. In this paper, we propose a new content-aware load balancing technique that can evenly distribute the workload to each node in the cluster web server. The proposed technique is based on the hash histogram transformation, in which each URL entry of the web log file is hashed, and the access frequency and file size are accumulated as a histogram. Each user request is assigned into a node by mapping of (hashed value-server node) in the histogram transformation. In the proposed technique, the histogram is updated periodically and then the even distribution of user requests can be maintained continuously. In addition to the load balancing, our technique can exploit the cache effect to improve the performance. The simulation results show that the performance of our technique is quite better than that of the traditional round-robin method and we can improve the performance more than $10\%$ compared with the existing workload-aware load balancing(WARD) method.

• Journal of International Area Studies (JIAS)
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• v.16 no.2
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• pp.121-146
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• 2012

The purpose of this paper is to study on China's emergence and its influence on international society against the U.S. hegemony. Recently, China's influence has proliferated in Central Asia as well as East Asia at a rapid rate. China, through its soft balancing strategy, increased its influence in Central Asia in response to the U.S. power and behavior. This study analyzes the relationship among China and Central Asia with the view of soft balancing theory. In order to determine whether China's strategy on Central Asia is soft balancing, this paper presents three indicators: 1) Second-tier major power is willing to take a strategy that increase diplomatic cost of hegemony or counter the hegemony influence through using regional and global multilateral cooperation. 2) Second-tier major power is willing to not only increase its influence by strengthening regional economic cooperation, but also check the extension of the hegemony economic influence into its boundary. 3) Second-tier major power intends to prevent expanding hegemony military influence into the region through limited military cooperation and increasing military spending, and denying territory. This paper analyze China's multi-polar strategy, economic and energy cooperation with Central Asia countries, and the military and security cooperation with multilateral organizations such as SCO.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.50-59
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• 1997

This paper is on the generalized singular perturbation approximation (GSPA) preserving the discrete positive real property. We transform the discrete positive real(PR) system into a stochastically banlanced system and get the reduced order discrete system from the GSPA of the full order stochastically balanced system. eSPECIALLY, WHEN THE FREE PARAMETER OF THE gspa IS .+-.1, we show that the reduced order discrete system retains stability, minimality, and positive real and stochstically balancing properties. And we derived the .inf.-norm error bound with the reduced order discrete strictly positive real(SPR) system by the proposed method. Finally, we give an example to ascertain the properties of the proposed reduced order discrete system and to compare with the conventional methods.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.3
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• pp.24-32
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• 1997

This paper is on a discrete controller order reduction with the closed-loop stability and performance guaranteed. to achieve this, after finding the solutionsof two lyapunov inequalities and balancing the full order controller system, we find the reudced order controlers using the balanced truncation (BT) and the balanced singular perturbation approximation (BSPA). When the solutions of the two lyapunov inequalities exist, it is shown that the resulting controllers guarantee the closed-loop stability, and .inf.-norm error bounds are derived for the closed-loop performance region for the BT and in low frequency region for the BSPA. Finally, a numerical example is given to illustrate the validity of the proposed method.

• Journal of Power Electronics
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• v.17 no.2
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• pp.346-357
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• 2017

The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.53-58
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• 2001

This paper presents a high resolution capacitive microaccelerometer for applications to personal information systems. We reduce the mechanical noise level of the microaccelerometer by increasing the proof-mass based on deep RIE process. We reduce the electrical noise level by increasing the amplitude of an AC sense voltage. The high sense voltage is obtained by DC-to-DC voltage multiplier. In order to solve the nonlinearity problem caused by the high sense voltage, we modify the conventional comb electrode of straight finger type into that of branched finger type, resulting in self force-balancing effects for enhanced detection linearity. The proposed branched finger capacitive microaccelerometer was fabricated by the deep RIE process of an SOI wafer. The fabricated microaccelerometer reduces the electrical noise at the level of $2.4{\mu}g/\sqrt{Hz}$ for the sense voltage of l6.5V, which is 10.1 times smaller than the electrical noise level of $24.3{\mu}g/\sqrt{Hz}$ at 0.9V. For the sense voltage higher than 2V, the electrical noise level of the microaccelerometer became smaller than the constant mechanical noise level of $11{\mu}g/\sqrt{Hz}$. Total noise level, including the electrical noise and the mechanical noise, has been measured as $9{\mu}g/\sqrt{Hz}$ for the sense voltage of 16.5V, which is 3.2 times smaller than the total noise of $28.6{\mu}g/\sqrt{Hz}$ for the sense voltage of 0.9V. The self force-balancing effect results in the increased stiffness of 1.98 N/m at the sense voltage of 17.8V, compared to the stiffness of 1.35 N/m at 0V, thereby generating the additional stiffness at the rate of $0.002N/m/V^{2}$.