• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.34-40
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• 2018

In this study, the optimal buffer size is calculated for seamless video playback on a mobile device. Buffer means the memory space for multimedia packet which arrives in mobile device for video play such as VOD service. If the buffer size is too large, latency time before video playback can be longer. However, if it is too short, playback service can be paused because of shortage of packets arrived. Hence, the optimal buffer size insures QoS of video playback on mobile devices. We model the process of buffering into a discret-time queueing model. Mean busy period length and mean waiting time of Geo/G/1 queue with N-policy is analyzed. After then, we uses the main performance measures to present numerical examples to decide the optimal buffer size on mobile devices. Our results enhance the user satisfaction by insuring the seamless playback and minimizing the initial delay time in VOD streaming process.

• Fashion & Textile Research Journal
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• v.20 no.4
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• pp.464-473
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• 2018

The objective of this study is to develop a sizing system of fitness clothing that can properly accommodate various body sizes of Korean senior women. The sizing system of upper and lower fitness clothing was developed in the present study by selection of key variables, identification of size category candidates, and determination of an optimal sizing system. First, key anthropometric dimensions (stature and bust circumference for upper clothing and stature; waist circumference for lower clothing) were identified by factor analysis on the direct body measurements (n = 272) and 3D whole-body scan data (n = 271) of Korean senior women in Size Korea. Second, sizing system candidates based on the key dimensions of upper and lower clothing were explored using a grid method and an optimization method. Lastly, among the sizing system candidates, optimal sizing systems of upper and lower clothing were selected in terms of accommodation rate. Five size categories (short/small, short/medium, tall/small, tall/medium, and tall/large) were selected as the optimal sizing systems of upper and lower clothing with 89% and 78% of accommodation rate, respectively, for the Korean senior women. The anthropometric characteristics of the representative humans of the optimal size categories would be of use in the design of fitness compressive wear for the better fit and effectiveness of exercise and health of Korean senior women.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.834-840
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• 2019

Recently, due to increased tourism and leisure activities, falls by fishers from coastal wave-dissipating blocks (breakwaters) in Korea have been rising. We investigated the optimal mesh size for use in safety nets designed to cover Tetrapod (TTP) breakwaters to prevent casualties from falls. This is a prerequisite for considering the scale and economics of safety net facilities. The optimal mesh size was determined based on the fisher gender and age, and the bodily features of Koreans. The optimal mesh size was found to be 18.6-27.0 cm, derived based on the femoral length and chest circumference.

• The Journal of the Korea Contents Association
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• v.7 no.7
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• pp.39-49
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• 2007

Since the PF scheduling algorithm[13], which is optimal in the hard real-time multiprocessor environments, several scheduling algorithms have been proposed. All these algorithms assume the fixed unit quantum size, and this assumption has problems in the mode change environments. To settle the problem, we already proposed a method for deciding the optimal quantum size[2]. In this paper, we propose improved methods considering the task set whose utilization e is less than or equal to p/3+1. As far as the numbers of computations used to determine the optimal quantum size are concerned, newly proposed methods are proved to be more efficient than our previous ones.

• Journal of Communications and Networks
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• v.16 no.6
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• pp.656-666
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• 2014

In delay tolerant networks (DTNs), delay is inevitable; thus, making better use of buffer space to maximize the packet delivery rate is more important than delay reduction. In DTNs, epidemic routing is a well-known routing protocol. However, epidemic routing is very sensitive to buffer size. Once the buffer size in nodes is insufficient, the performance of epidemic routing will be drastically reduced. In this paper, we propose a buffer scheme to optimize the performance of epidemic routing on the basis of the Lagrangian and dual problem models. By using the proposed optimal buffer scheme, the packet delivery rate in epidemic routing is considerably improved. Our simulation results show that epidemic routing with the proposed optimal buffer scheme outperforms the original epidemic routing in terms of packet delivery rate and average end-to-end delay. It is worth noting that the improved epidemic routing needs much less buffer size compared to that of the original epidemic routing for ensuring the same packet delivery rate. In particular, even though the buffer size is very small (e.g., 50), the packet delivery rate in epidemic routing with the proposed optimal buffer scheme is still 95.8%, which can satisfy general communication demand.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2074-2079
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• 2018

Global state space's optimal policy is used for offline controller in the form of table by using Dynamic Programming. If an optimal policy table has a large amount of control data, it is difficult to use the system in a low capacity system. To resolve these problem, controller using the compressed optimal policy table is proposed in this paper. A DCT is used for compression method and the cosine function is used as a basis. The size of cosine function decreased as the frequency increased. In other words, an essential information which is used for restoration is concentrated in the low frequency band and a value of small size that belong to a high frequency band could be discarded by quantization because high frequency's information doesn't have a big effect on restoration. Therefore, memory could be largely reduced by removing the information. The compressed output is stored in memory of embedded system in offline and optimal control input which correspond to state of plant is computed by interpolation with Inverse DCT in online. To verify the performance of the proposed controller, computer simulation was accomplished with a one link inverted pendulum.

• Journal of Technology Innovation
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• v.25 no.3
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• pp.51-82
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• 2017

In terms of both economic growth and social welfare, this paper discusses the optimal proportion and size of basic research budget by adding knowledge stock to an endogenous growth model. On the basis of the modified endogenous growth model, this paper derived an equation that consists of kinds of parameters and suggested this equation as a criterion for determining whether allocated basic research budget has been appropriate. This paper also found that the theoretical optimal ratio between government investment spending and investment in basic research is equal to the ratio between the partial elasticity of output with respect of public capital stock and the partial elasticity of output with respect of knowledge stock. In addition, after the required parameters were specified based on precedent literatures, this paper estimated an optimum size of the basic research budget using the theoretical optimal ratio with official statistical records and compared the estimated size to its actual size. This paper therefore is expected to contribute to budget planning and allocation regarding establishing basic research policy, because the results of this paper presents a useful criterion for optimum level and an approximate size of investment in basic research. However, it should be noted that although the optimal solution is optimal in a economic sense, it may not be the best solution from a practical perspective.

• Journal of Urban Science
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• v.6 no.2
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• pp.35-47
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• 2017

Tax evasion is increasing, but efficiency of tax administration is evaluated as improving. This is because the taxation cost, which is a measure to judge the efficiency of the tax administration, does not consider the tax evasion effect at all. This method of estimating the cost of taxation is a dispute that neglects the role of taxation authorities in tax evasion. The existing study focuses on the development of a tax evasion model focused on maximizing the utility through the tax evasion of the taxpayer as the tax evasion approaches the individual 's deviant problem. However, this has the aspect of making the role of the tax authorities in tax evasion negative. This study empirically derived the optimal size of tax administration in Korea by using tax collection cost and tax cooperation cost. Also, it is meaningful to consider the role of the taxation authorities in tax evasion and to derive the optimal taxation cost model by estimating the decrease in tax evasion due to the taxation expenditure of the tax authorities. In order to derive the optimal size of tax administration in Korea, taxation cost and tax cooperation cost are derived by classifying tax officials. The optimal taxation cost model was derived by estimating the taxation expenditure related to tax evasion. This study is meaningful to make it possible to emphasize the role of tax authorities in studying future tax evasion by studying the effect of taxation expenditure on tax evasion.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.959-974
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• 2020

High efficiency video coding (HEVC) employs quadtree coding tree unit (CTU) structure to improve its coding efficiency, but at the same time, it also requires a very high computational complexity due to its exhaustive search processes for an optimal coding unit (CU) partition. With the aim of solving the problem, a fast CU size decision optimal algorithm based on neighborhood prediction is presented for HEVC in this paper. The contribution of this paper lies in the fact that we successfully use the partition information of neighborhood CUs in different depth to quickly determine the optimal partition mode for the current CU by neighborhood prediction technology, which can save much computational complexity for HEVC with negligible RD-rate (rate-distortion rate) performance loss. Specifically, in our scheme, we use the partition information of left, up, and left-up CUs to quickly predict the optimal partition mode for the current CU by neighborhood prediction technology, as a result, our proposed algorithm can effectively solve the problem above by reducing many unnecessary prediction and partition operations for HEVC. The simulation results show that our proposed fast CU size decision algorithm based on neighborhood prediction in this paper can reduce about 19.0% coding time, and only increase 0.102% BD-rate (Bjontegaard delta rate) compared with the standard reference software of HM16.1, thus improving the coding performance of HEVC.

• Journal of the Korean Statistical Society
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• v.25 no.1
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• pp.95-110
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• 1996

We consider the question of efficiency of the Bayes sequential procedure with respect to the optimal fixed sample size Bayes procedure in a simple vs. simple testing problem for data coming from a general nonregular density b(.theta.)h(x)l(x < .theta.). Efficiency is defined in two different ways in these caiculations. Also, the minimax sequential risk (and minimax sequential stratage) is studied as a function of the cost of sampling.