• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1295-1303
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• 2010

In this paper, an effective method has been proposed for selection of white Gaussian noise(WGN) band for radio background noise measurement system under broad band noise environment. MMN which comes from industrial devices and equipment mostly happens in the shape of broad band noise mostly like impulsive noise and this is the main reason for increasing level in the present radio noise measurements. The existing method based on singular value decomposition has weak point that it cannot give good performance for the broad band signal because it uses signal's white property. The proposed method overcomes such a weakness of singular value decomposition based method by using signal's Gaussian property based method in parallel. Moreover, this proposed method hires a modelling based method which uses parameter estimation algorithm like maximum likelihood estimation(MLE) and gives more accurate result than the method using amplitude probability distribution(APD) graph. Experiment results under the natural environment has done to verify feasibility of the proposed method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.1
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• pp.13-25
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• 2005

In general, tunnel ventilation is analyzed with the assumption of equal vehicular speed for both directions in bidirectional traffic tunnels. This practice is likely to result in minimizing the piston effects and cannot take into consideration the effects of real situations, since in most cases, speeds of vehicles moving in opposite directions are not equal. Therefore, The ultimate goal of this study is to review the effects of unequal vehicular speeds on the planning of local bidirectional tunnel ventilation. To apply unequal vehicular speed for the bidirectional tunnel ventilation plan, the following requirements are necessary; (1) Adoption of strict smoke concentration standards for 'free-flow & congested' traffic conditions, (2) Selection of an appropriate ratio of heavy directional traffic volume, and (3) Selection of reasonable stepwised magnitude of speed difference. Based on the importance of research topic, this study aims at comparing the differences of the capacity of ventilation equipment for the cases with equal and unequal vehicular speeds in local bidirectional tunnels.

• The Journal of the Korea Contents Association
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• v.11 no.10
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• pp.301-311
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• 2011

This paper is aimed at providing fundamental data for marketing strategies needed to determine the direction of policy to operate hospitals in an effective way. From the analysis, it was found that: first, expectation toward hospitality of the staff, facilities, environment and administrative service of hospitals for the elderly exercises significantly positive(+) effects on satisfaction of patients; second, trust in and satisfaction with administrative service of hospitals for the elderly exerts significantly positive(+) effects on the intent of patients for revisit and information by word of mouth; and third, the intent for revisit influences positively the intent for information by word of mouth significantly. It is therefore needed to try to understand the motives and tendencies of the elderly in selecting hospitals, to promote their satisfaction and to cultivate the spirit for patient-oriented service. Furthermore, efforts should be made to gain trust of medical staff, effects of medical treatment as well as medical equipment in addition to laborious endeavors to work out marketing strategies backed up by price competitiveness of paradigm.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.640-652
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• 2012

Many studies have investigated the smart grid architecture and communication models in the past few years. However, the communication model and architecture for a smart grid still remain unclear. Today's electric power distribution is very complex and maladapted because of the lack of efficient and cost-effective energy generation, distribution, and consumption management systems. A wireless smart grid communication system can play an important role in achieving these goals. In this paper, we describe a smart grid communication architecture in which we merge customers and distributors into a single domain. In the proposed architecture, all the home area networks, neighborhood area networks, and local electrical equipment form a local wireless mesh network (LWMN). Each device or meter can act as a source, router, or relay. The data generated in any node (device/meter) reaches the data collector via other nodes. The data collector transmits this data via the access point of a wide area network (WAN). Finally, data is transferred to the service provider or to the control center of the smart grid. We propose a wireless cooperative communication model for the LWMN.We deploy a limited number of smart relays to improve the performance of the network. A novel relay selection mechanism is also proposed to reduce the relay selection overhead. Simulation results show that our cooperative smart grid (coopSG) communication model improves the end-to-end packet delivery latency, throughput, and energy efficiency over both the Wang et al. and Niyato et al. models.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.3
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• pp.116-122
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• 2017

Advances in information technology, communication and network technology are radically facilitating digital convergences as the integration of human, equipment, and space in the current industry 4.0 era. In industry 4.0 environment, the vast amount of information with networked computing technology can be simultaneously accessible even in limited physical space. Two main benefit points out of these information are the convenience and efficiency in their online transactions either buying things online or selling online. Even though there exist so many benefits that information technology can create for the people doing business over the internet there is a critical problem to be answered. In spite of many such advantages, however, online transactions have many dysfunctions such as personal information leakage, account hacking, and cybercrime. Without preparing the appropriate protection methods or schema people reluctantly use the transaction or would find some other partners with enhanced information security environment. In this paper we suggested a novel selection criteria that can be used to evaluate the reliable means of authentication against the expected risks under on-going IoT based environment. Our selection criteria consists of 4 steps. The first step is services and risk identification step. The second step is evaluation of risk occurrence step. The third step includes the evaluation of the extent of damage. And the final step is the assessment of the level of risk. With the help of the above 4 step-approach people can systematically identify potential risks hiding in the online transactions and effectively avoid by taking appropriate counter actions.

• Korean Journal of Construction Engineering and Management
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• v.19 no.1
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• pp.32-42
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• 2018

The importance of facility maintenance management cannot be overemphasized in that not only the value but also the performance of the facility is determined by the level of maintenance. The maintenance cost of the facility ranges from 3 to 10 times the initial construction cost depending the type and use of the facility over the life span. This maintenance importance is increased for the group of facilities and even more critical when the facilities compete for the limited budget with the limited resources such as manpower and equipment. This study analyzed sixteen public facility management corporations primarily for three items: 1) facility management system, 2) long-term rehabilitation plan, 3) the rehabilitation selection system. This paper provides and recommends the key elements of the facility maintenance management system based on the analysis of the sixteen corporations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.3
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• pp.151-161
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• 2014

3GPP LTE-Advanced (Release 10) system specifies carrier aggregation (CA) to enable high data rate on using multiple frequency bands, including the variout CA-specific deployment scenarios. Considering one of those scenarios in which the different directional sector antenna is employed by each frequency band, we propose a per-carrier cell selection scheme that can improve the average throughput of the cell-edge users by allowing each user equipment (UE) to select the frequency band of the adjacent cell. Furthermore, a distributed algorithm for inter-cell copperative scheduling in this scheme is proposed to support proportional fairness among the cells. It has been shown that the proposed scheduling algorithm for the per-carrier cell selection scheme improves the cell-edge user throughput roughly by 50% over that of the conventional scheme.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.464-464
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• 2010

A few years ago, for maintaining high stability and production yield of production equipment in a semiconductor fab, on-line monitoring of wafers is required, so that semiconductor manufacturers are investigating a software based process controlling scheme known as virtual metrology (VM). As semiconductor technology develops, the cost of fabrication tool/facility has reached its budget limit, and reducing metrology cost can obviously help to keep semiconductor manufacturing cost. By virtue of prediction, VM enables wafer-level control (or even down to site level), reduces within-lot variability, and increases process capability, $C_{pk}$. In this research, we have practiced VM on $SiO_2$ etch rate with optical emission spectroscopy(OES) data acquired in-situ while the process parameters are simultaneously correlated. To build process model of $SiO_2$ via, we first performed a series of etch runs according to the statistically designed experiment, called design of experiments (DOE). OES data are automatically logged with etch rate, and some OES spectra that correlated with $SiO_2$ etch rate is selected. Once the feature of OES data is selected, the preprocessed OES spectra is then used for in-situ sensor based VM modeling. ICP-RIE using 葰.56MHz, manufactured by Plasmart, Ltd. is employed in this experiment, and single fiber-optic attached for in-situ OES data acquisition. Before applying statistical feature selection, empirical feature selection of OES data is initially performed in order not to fall in a statistical misleading, which causes from random noise or large variation of insignificantly correlated responses with process itself. The accuracy of the proposed VM is still need to be developed in order to successfully replace the existing metrology, but it is no doubt that VM can support engineering decision of "go or not go" in the consecutive processing step.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.30-34
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• 2019

We analyzed how the features in plasma information based virtual metrology (PI-VM) for SiO₂ etching depth with variation of 5% contribute to the prediction accuracy, which is previously developed by Jang. As a single feature, the explanatory power to the process results is in the order of plasma information about electron energy distribution function (PI_EEDF), equipment, and optical emission spectroscopy (OES) features. In the procedure of stepwise variable selection (SVS), OES features are selected after PI_EEDF. Informative vector for developed PI-VM also shows relatively high correlation between OES features and etching depth. This is because the reaction rate of each chemical species that governs the etching depth can be sensitively monitored when OES features are used with PI_EEDF. Securing PI_EEDF is important for the development of virtual metrology (VM) for prediction of process results. The role of PI_EEDF as an independent feature and the ability to monitor variation of plasma thermal state can make other features in the procedure of SVS more sensitive to the process results. It is expected that fault detection and classification (FDC) can be effectively developed by using the PI-VM.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1325-1344
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• 2019

Recently, to satisfy mobile users' increasing data transmission requirement, energy efficiency (EE) resource allocation in distributed antenna systems (DASs) has become a hot topic. In this paper, we aim to maximize EE in DASs subject to constraints of the minimum data rate requirement and the maximum transmission power of distributed antenna units (DAUs) with different density distributions. Virtual cell is defined as DAUs selected by the same user equipment (UE) and the size of virtual cells is dependent on the number of subcarriers and the transmission power. Specifically, the selection rule of DAUs is depended on different scenarios. We develop two scenarios based on the density of DAUs, namely, the sparse scenario and the dense scenario. In the sparse scenario, each DAU can only be selected by one UE to avoid co-channel interference. In order to make the original non-convex optimization problem tractable, we transform it into an equivalent fractional programming and solve by the following two sub-problems: optimal subcarrier allocation to find suitable DAUs; optimal power allocation for each subcarrier. Moreover, in the dense scenario, we consider UEs could access the same channel and generate co-channel interference. The optimization problem could be transformed into a convex form based on interference upper bound and fractional programming. In addition, an energy-efficient DAU selection scheme based on the large scale fading is developed to maximize EE. Finally, simulation results demonstrate the effectiveness of the proposed algorithm for both sparse and dense scenarios.