• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.10
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• pp.435-442
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• 2006

One of the most important topics about the safety of electrical and electronic system is the reliability of the wiring system. The Time-Frequency Domain Reflectometry(TFDR) is a state-of-the-art system for detecting and estimating of the fault on a wiring. In this paper, We've considered the load resistance measurement on a coaxial cable using TFDR in a way of expanded application. The TFDR system was built using commercial Pci extensions for Instrumentation(PXI) and LabVIEW. The proposed real time TFDR system consisted of the reference signal design, signal generation, signal acquisition, algorithm execution and results display part. To implement real time system, all of the parts were programmed by the LabVIEW which is one of the graphical programming languages. Using the application software implemented by the LabVIEW, we were able to design a proper reference signal which is suitable for target cable and control not only the arbitrary waveform generator in the signal generation part but alto the digital storage oscilloscope in the signal acquisition part. By using the TFDR real time system with the terminal resistor on the target cable, we carried out load impedance measurement experiments. The experimental results showed that the proposed system are able not only to detect the location of impedance discontinuity on the cable but also to estimate the load resistance with high accuracy.

• Journal of the Korean Solar Energy Society
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• v.35 no.4
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• pp.1-7
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• 2015

The operation of the natural circulation type solar heating systems with facade integrated collector was analyzed by experiment. Two different types of flat plate solar collectors were used for these experiments. One was for the normal flat plate solar collector with the size of 1m*2m and the other was for the large size solar collector with $4m^2$(1m*4m). The experiments were carried out to investigate the effect of the series or parallel connection method on the performance of the collectors. As a result, the solar thermal system which is installed on the wall or facade would be applicable for the natural circulation type if the system design reflects various parameters, including collector connecting method(series or parallel), to provide enough vertical height between collector and storage tank, and to reduce pressure loss due to collector and piping network, etc. The natural circulation type of solar thermal system as proposed in this study can increase the system reliability by removing or minimizing the use of the components such as pump, controller, sensors which may cause serious troubles of the system for a long-time operation

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.167-173
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• 2007

This study analyzed by simulation using TRNSYS as well as by experiment on the solar district heating system installed for the first time for the district heating system in Bundang. Simulation analysis using TRNSYS focused on the thermal behavior and long-term thermal efficiency of solar system. Experiment carried out for the reliability of simulation system. This solar system where the circuits of two different collectors, flat plate and vacuum tube collector, are connected in series by a collector heat exchanger, and the collection characteristics of each circuit varies. Therefore, these differences must be considered for the system's control. This system uses variable flow rate control in order to obtain always setting temperature of hot water by solar system. Specifically, this is a system that heats returning district heating water (DHW) at approximately $60^{\circ}C$ using a solar collector without a storage tank, up to the setting temperature of approximately $85{\sim}95^{\circ}C$ To realize this, a flat plate collector and a vacuum tube collector are used as separate collector loops. The first heating is performed by a flat plate collector loop and the second by a vacuum tube collector loop. In a gross collector area basis, the mean system efficiency, for 4 years, of a flat plate collector is 33.4% and a vacuum tube collector is 41.2%. The yearly total collection energy is 2,342GJ and really collection energy per unit area ($m^2$) is 1.92GJ and 2.37GJ respectively for the flat plate vacuum tube collector. This result is very important on the share of each collector area in this type of solar district heating system.

• Journal of Korean Society of societal Security
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• v.1 no.1
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• pp.63-67
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• 2008

This study focuses on assessing the security ri sk or the terrorism in chemical process industries. This research modifies conventional method for assessing the terrorism risk. The risk assessment method is developed and it is implemented as software to analyze the possibility of terrorism and sabotage. This program includes five steps; asset characterization, threat assessment, vulnerability analysis, risk assessment and new countermeasures. It is a systematic, risk based approach in which risk is a function of the severity of consequences of an undesired event, the likelihood of adversary attack, and the likelihood of adversary success in causing the undesired event. The reliability of the program is verified using a dock zone case. The case dock zone includes a storage farm, a manufacturing plant, an electrical supply utility, a hydrotreater unit, many containers, and administration buildings. This study represents chemical terrorism response technology, the prevention plan, and new countermeasure to mitigate by using risk assessment methods in the chemical industry and public sector. This study suggests an effective approach to the chemical terrorism response management.

• The Korean Journal of Food And Nutrition
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• v.29 no.2
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• pp.253-266
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• 2016

The current study was conducted to facilitate appropriate hygiene and safety management in children's food service stations, with the ultimate objective of providing sanitary and safe food service to children. In order to develop questionnaire items, literature review was conducted, in addition to detailed interview of working-level personnel at a children's food service management support center. This resulted in a total of thirty questions on personal hygiene management, food materials hygiene management, and facilities hygiene management. Using the questionnaire, seventy-one food service stations for children in District A in Seoul that serve less than one hundred children were surveyed to analyze the reliability, construct validity, and correlation in the developed measurement tool. The developed measurement tool consisted of ten task and environmental hygiene management questions, five personal and cooking hygiene management questions, four food ingredient and storage hygiene management questions, and four food service operation and management question; with a total of twenty-three questions, in four factors stated above. The cumulative distribution of the four factors was 54.698%, and Cronbach's ${\alpha}$ value was 0.672~0.853, which indicated that the study was reliable. The results of the analysis indicated that each of the factors were correlated, the study was satisfactory, and the tool was valid for evaluating hygiene and safety management practices in children's food service stations. Finally, in order to enhance practical utility of the developed measurement tool, the significance and limitations were described.

• Journal of Digital Convergence
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• v.12 no.5
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• pp.263-269
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• 2014

Mobile Cloud Service will provide cloud services through mobile devices. Because storage space constraints and computing process performance limitations of mobile devices, this service will process in the cloud environment after moving works and data that have to process in mobile terminal. The obstacles of mobile cloud service activity will have concerned high about the reliability service, data security, and the confidentiality security. In particular, in convergence of mobile services and cloud services, each threats are expected to be generated complicatedly. In this paper, we define the type of mobile cloud services as well as security threats that can occur in mobile cloud. Also we suggest security countermeasures in mobile app. and enterprises countermeasures. We suggest verification of mobile applications for user information protection about security countermeasures in mobile app. Also we describe the cloud providers responsibility and user responsibility about enterprises countermeasures.

• The Journal of Society for e-Business Studies
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• v.16 no.4
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• pp.1-16
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• 2011

A digital certificate mandated by the Electronic Signature Act has become familiar in our daily lives as 95% of the economically active population hold certificates. Due to upgrades to 256 bit level security that have become effective recently, the security and reliability of digital certificates are expected to increase. Digital certificates based on Public Key Infrastructure (PKI) have been known as "no big problem," but the possibility of password exposure in cases of leaked digital certificates still exists. To minimize this vulnerability, various existing studies have introduced alternative password methods, expansion of certificate storage media, and multiple certification methods. These methods perform enhanced functions but also have limitations including the fact that the secureness of passwords is not guaranteed. This study suggests an alternative method for enhancing the level of password secureness as a way to improve password security. This new method improves security management and enhances the convenience of using digital technologies. The results may be used for developing digital certificate related security technologies and research in the future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4C
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• pp.338-346
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• 2012

Wireless sensor network (WSN) technology provides a variety of medical and healthcare solutions to assist detection and communication of body conditions. However, data reliability inside WSN might be influenced to healthcare routing protocol due to limited hardware resources of computer, storage, and communication bandwidth. For this reason, we have conducted various wireless communication experiments between nodes using parameters such as RF strength, battery status, and deployment status to get a optimal performance of mobile healthcare routing protocol. This experiment may also extend the life time of the nodes. Performance analysis is done to obtain some important parameters in terms of distance and reception rate between the nodes. Our experiment results show optimal distance between nodes according to battery status and RF strength, or deployment status and RF strength. The packet reception rate according to deployment status and RF strength of nodes was also checked. Based on this performance evaluation, the optimized sensor node battery and deployment in the developed our mobile healthcare routing protocol were proposed.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.10
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• pp.413-420
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• 2013

Redundant arrays of independent disks (RAID) without a power-fail-safe component in small and mid-sized business suffers from intolerably long resynchronization time after a unclean power-failure. Data blocks and a parity block in a stripe must be updated in a consistent manner, however a data block may be updated but the corresponding parity block may not be updated when a power goes off. Such a partially modified stripe must be updated with a correct parity block. However, it is difficult to find which stripe is partially updated (inconsistent). The widely-used traditional parity resynchronization manner is a intolerably long process that scans the entire volume to find and fix inconsistent stripes. This paper presents a fast resynchronization scheme with a negligible overhead for small and mid-sized RAIDs. The proposed scheme is integrated into a software RAID driver in a Linux system. According to the performance evaluation, the proposed scheme shortens the resynchronization process from 200 minutes to 5 seconds with 2% overhead for normal I/Os.

• Journal of the Korea Society of Computer and Information
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• v.25 no.2
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• pp.133-140
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• 2020

The IISS(Integrated Interface Storage System) software uses communication methods such as DSS(Data Sharing Service), UDP to perform the function of sending all messages from the Combat Management System to the analytical computer. Because IISS software handles all message used in the Combat Management System, the source code is large and has a highly dependent feature on message changes. Modification of software is a task that requires a lot of labor, such as series of software reliability test. so research has been conducted to reduce software development costs, including minimizing software modifications. In this paper, We study the method of messages receiving and architectural structure improvement to minimize reliance on message changes in the Combat Management System and improve the modifiability. Reduced message dependency by changing the way DSS and UDP protocols are communicated to Packet Sniffing. In addition, Factory Method Pattern were applied to improve the software design. Test comparing existing software and development elements have confirmed that the software has improved its modifiability and reuse.