• Journal of KIISE:Databases
• /
• v.28 no.4
• /
• pp.688-701
• /
• 2001

Web caching has become an important problem addressing the performance issues in web applications. In this paper we propose a method that enhances the performance of web caching by incorporating the expiration time of web data we introduce the notion of the effective reference probability that incorporates the effect of expiration time into the reference probability used in the existing cache replacement algorithms .We formally define the effective reference probability and derive it theoretically using a probabilistic model. By simply replacing probabilities with the effective reference probability in the existing cache replacement algorithms we can take the effect of expiration time into account The results of performance evaluation through experiments show that the replacement algorithms using the effective reference probability always outperform the existing ones. The reason is that the proposed method precisely reflects the theoretical probability of getting the cache effect, and thus, incorporates the influence of the expiration time more effectively. In particular when the cache fraction is 0.05 and data update is comparatively frequent (i.e. the update frequency is more than 1/0 of the reference frequency) the performance enhancement is more than 30% in LRU-2 and 13% in Aggarwal's method (PSS integrating a refresh overhead factor) The results show that effective reference probability contributes significantly to the performance enhancement of the web cache in the presence of expiration time.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.12B
• /
• pp.1444-1451
• /
• 2009

This paper first proposes diverse C determining models in the Q algorithm which is proposed in the EPCglobal C1 Gen 2 standard and then compares and analyzes its performance. EPCglobal C1 Gen 2 standard proposes the slot-count (Q) selection algorithm for multiple tag identification environment, but there is no such definition for the C value which modifies the Q value depending on collision or no reply. During the tag anti-collision process, the Q algorithm adds C to the Q when there is a collision and reduces the Q by C when there is no reply. The modified Q value updates new slot-counts for tags which determines the tag identification speed, so the C value is an important factor. However, many researches only intend to increase the tag identification speed by proposing a new method or modifying the Q algorithm without any research about the C value. This paper suggests diverse C models which satisfies the EPCglobal C1 Gen 2 and analyzes their performance in the multi tag identification environment. The result of this paper can be used as an index for future researches on EPCglobal C1 Gen 2 C models and multiple tag identification performance.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.4
• /
• pp.19-33
• /
• 2012

Ministry of Land, Transport and Maritime Affairs prepared the method to update traffic connection system by amending "National Transport System Efficiency Act(hereinafter Act)". The key is a development of Intermodal Transfer Center. The law and guideline related with Intermodal Transfer Center requires the installation and operation of transfer information guide facility to improve user's convenience. However, there are no sufficient studies that can be used as references for the method to construct transfer support information system related with user's preference. The study performed the research about user's service satisfaction in relation with transfer support information service, which was embodied in model operation process, on the basis of transfer support information system of Intermodal Transfer Center applied to Gimpo Airport. The analysis result about service preference, importance of each supplied information, service satisfaction and consideration for service embodiment can be used as a guideline to embody the user information service of Intermodal Transfer Center. In addition, through CVM, the study estimated and proposed the service valuation of smart intermodal transfer service that provides customized information to cope with user's situation and traffic means operation status among transfer support information service. It is determined that the study will measure the benefit of Intermodal Transfer Center user by using monetary value when smart intermodal transfer service is supplied and provide the ground to expand high-tech transfer information service with high usefulness and convenience.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.5
• /
• pp.879-886
• /
• 2008

This paper addresses the analysis and the design optimization of differential interconnects for Low-Voltage Differential Signaling (LVDS) applications. Thanks to the differential transmission and the low voltage swing, LVDS offers high data rates and improved noise immunity with significantly reduced power consumption in data communications, high-resolution display, and flat panel display. We present an improved model and new equations to reduce impedance mismatch and signal degradation in cascaded interconnects using optimization of interconnect design parameters such as trace width, trace height and trace space in differential flexible printed circuit board (FPCB) transmission lines. We have carried out frequency-domain full-wave electromagnetic simulations, time-domain transient simulations, and S-parameter simulations to evaluate the high-frequency characteristics of the differential FPCB interconnects. The 10% change in trace width produced change of approximately 6% and 5.6% in differential impedance for trace thickness of $17.5{\mu}m$ and $35{\mu}m$, respectively. The change in the trace space showed a little change. We believe that the proposed approach is very helpful to optimize high-speed differential FPCB interconnects for LVDS applications.

• Korean Journal of Remote Sensing
• /
• v.20 no.2
• /
• pp.65-76
• /
• 2004

This study aims to estimate daily maximum air temperature estimated using satellite-derived surface temperature and Elevation Derivative Database (EDD). The analysis is focused on the establishment of a semi-empirical estimation technique of daily maximum air temperature through the multiple regression analysis. This tests the contribution of EDD in the air temperature estimation when it is added into regression model as an independent variable. The better correlation is shown with the EDD data as compared with the correlation without this data set. In order to provide a progressive estimation technique, we propose and compare three approaches: 1) seasonal estimation non-considering landcover, 2) seasonal estimation considering landcover, and 3) estimation according to landcover type and non-considering season. The last method shows the best fit with the root-mean-square error between 0.56$^{\circ}C$ and 3.14$^{\circ}C$. A cross-validation procedure is performed for third method to valid the estimated values for two major landcover types (cropland and forest). For both landcover types, the validation results show reasonable agreement with estimation results. Therefore it is considered that the estimation technique proposed may be applicable to most parts of South Korea.

• Korean Journal of Comparative Education
• /
• v.27 no.1
• /
• pp.29-49
• /
• 2017

The purpose of this study is to analyze the characteristics and implications of the quality management policy through teachers' entire life in Japan case study. This article composed of four chapters; Implication and problem situation, Backgrounds and streams of the japanese teacher reform policy, Characteristics of the main policies about managing the teacher's quality through their life, and Conclusion(Japanese characteristics and the suggestion for Korea). The main quality management policy means the various teacher recruitment and selection system, Merit system of personnel management, Effective management of a system for teachers performing unsatisfactorily, Professional development for teachers with new and 10 years' experience, and Teacher Certificate Renewal System every ten years. The method of study composed of the literature search and interview. The System Analysis[input-process-output-feedback] is used as a model of the analyze the policy process[backgrounds & T.O-quality management system-japanese teacher's reaction & implications to korea] The Central Council for Education(CCE;2012.8.28) has released "An Outline of Measures for Comprehensively Improving the Quality and Ability of Teachers throughout their career". This report can be regarded as a blueprint for the teacher reform policy in japan. As a conclusion, Ten lessons is proposed for the Korea policy improving the quality and ability of teachers(training, employment, and development).

• Journal of Korea Society of Industrial Information Systems
• /
• v.24 no.5
• /
• pp.115-120
• /
• 2019

In this paper, we present the results of the performance statistical analysis of the multi-robot formation control based on receding horizon particle swarm optimization (RHPSO). The formation control problem of multi-robot system can be defined as a constrained nonlinear optimization problem when considering collision avoidance between robots. In general, the constrained nonlinear optimization problem has a problem that it takes a long time to find the optimal solution. The RHPSO algorithm was proposed to quickly find a suboptimal solution to the optimization problem of multi-robot formation control. The computational complexity of the RHPSO increases as the number of candidate solutions and generations increases. Therefore, it is important to find a suboptimal solution that can be used for real-time control with minimal candidate solutions and generations. In this paper, we compared the formation error according to the number of candidate solutions and the number of generations. Through numerical simulations under various conditions, the results are analyzed statistically and the minimum number of candidate solutions and the minimum number of generations of the RHPSO algorithm are derived within the allowable control error.

• Korean Journal of Construction Engineering and Management
• /
• v.20 no.6
• /
• pp.126-131
• /
• 2019

The estimation of available solar energy at particular locations is critical to find and assess suitable locations of PV sites. The amount of PV power generation is however affected by various geographical factors (e.g., weather), which may make it difficult to identify the complex relationship between affecting factors and power outputs and to apply findings from one study to another in different locations. This study thus undertakes a regression analysis using data collected from 172 PV plants spatially distributed in Korea to identify critical weather conditions and estimate the potential power generation of PV systems. Such data also include solar radiation, precipitation, fine dust, humidity, temperature, cloud amount, sunshine duration, and wind speed. The estimated PV power generation is then compared to the actual PV power generation to evaluate prediction performance. As a result, the proposed model achieves a MAPE of 11.696(%) and an R-squred of 0.979. It is also found that the variables, excluding humidity, are all statistically significant in predicting the efficiency of PV power generation. According, this study may facilitate the understanding of what weather conditions can be considered and the estimation of PV power generation for evaluating and determining suitable locations of PV facilities.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.6
• /
• pp.628-638
• /
• 2017

In response to difficult employment conditions in the maritime industry and a desire to expand their career options, domestic mates are persuing DP operator training at institutions both domestically and abroad based on their shipboard experience. However, since the offshore plant service industry has not yet been established in Korea, those seeking to enter this field have difficulty acquiring qualifications and most seek work overseas for offshore shipping companies. Individuals wishing to work as DP operators are likely to face more conservative recruitment processes with overseas offshore shipping companies, focusing on career language restrictions as they will be non-native speakers relative to the foreign company, difficulty living in a multi-cultural environment, and lack of systematic information on essential job requirements. For these reasons, domestic mates have difficulty seeking jobs. Therefore, this study analyzes the capabilities and qualification required to be a DP operator to provide basic data for developing NCS standards representing a minimum level of competency. These standards can be applied by the government to develop plans for professional training for DP operators. In study, job classifications, competency standards and career development paths for DP operators have been proposed along with joint use of DP training vessels, to train specialized DP instructors. An NCS export model led by the government to activate professional training for DP operators is also presented.

• Journal of the Korea Society of Computer and Information
• /
• v.18 no.12
• /
• pp.123-138
• /
• 2013

This paper was to figure out why online wine purchasing is not activated despite of the many advantages of having online transactions and to fine key determinants of online wine purchasing intention. Thus, the purpose of this study was to identify the determinants of online wine purchase intention, and examines the relationships between the determinants and online wine purchase intention. Data was collected from those who have experienced in using online wine store to purchase wine, and data was used to test the proposed research model. The findings showed that perceived usefulness and social influence(subjective norm, image) were key determinants of online wine site trust, but they were not related to online wine site trust. It also was found that perceived usefulness, perceived ease of use and subjective norm were positively and significantly related to online wine purchase intention whereas it had no relationship with image. In addition, online wine site trust was shown to influence on online wine purchase intention. Finally, the mediating effects were found in the relationships between perceived usefulness, subjective norm, and online wine purchase intention. Based on the results of the study, implications for future research are drawn.