• Advances in aircraft and spacecraft science
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• v.7 no.5
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• pp.441-458
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• 2020

Rectangular-to-Ellipse Shape Transition (REST) inlets are a class of inward turning inlets designed for hypersonic flight. The aerodynamic design of REST inlets involves very complex flows and shock-wave patterns. These inlets are used in highly integrated propulsive systems. Often the design of these inlets may require many geometrical constraints at different cross-section. In present work a design approach for hypersonic inward-turning inlets, adapted for REST inlets, is coupled with a multi-objective optimization procedure. The automated procedure iterates on the parametric representation and on the numerical solution of a base flow from which the REST inlet is generated by using streamline tracing and shape transition algorithms. The typical design problem of optimizing the total pressure recovery and mass flow capture of the inlet is solved by the proposed procedure. The accuracy of the optimal solutions found is discussed and the performances of the designed REST inlets are investigated by means of fully 3-D Euler and 3-D RANS analyses.

• Asia pacific journal of information systems
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• v.6 no.2
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• pp.107-124
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• 1996

This research studied future directions of Internet technology toward supporting group decision making. From the previous research, this study classified requirements of group decision support systems into three categories which are information transfer, information provision, and communication control. For each of the category, this study analyzed the limits of current Internet functions. Next, this research discussed technological solutions, for each of the OSI 7 layers, toward supporting group decision making. Additional functions in Internet which are required for group supporting are tracing communications, application dependent coding, selection of communication modes, and security handling. For high speed data communication in Internet, this research discussed the potential of cell-switching technology for the lower level link in Internet. The conclusions of this research can be used for designing future group decision support systems and development of Internet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.91-94
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• 2004

Preform design techniques have been investigated in efforts to reduce die wear and forming load and to improve material flow, filing ratio, etc. In hot forging processes, a thin deformed part of a workpiece, known as a flash, is formed in the narrow gap between the upper and lower tools. Although designers make tools that generate a flash intentionally in order to improve flow properties, excessive flash increases die wear and forming load. Therefore, it is necessary to make a preform shape that can reduce the excessive flash without changing flow properties. In this paper, a new preform design technique is proposed to reduce the excessive flash in a metal forging process. After a finite element simulation of the process is carried out with an initial billet, the flow of material in the flash region is traced from the final shape to the initial billet. The region belonging to the flash is then easily found in the initial billet. The finite element simulation is then carried out again with the modified billet from which the selected region has been removed. In several iterations of this technique, the optimal preform shape that minimizes the amount of flash without changing the forgeability can be obtained.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.01a
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• pp.15-17
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• 2012

최근 들어 스마트폰이 급격하게 보급됨에 따라 스마트폰을 이용하여 상대방의 위치를 확인하는 응용 프로그램이 많이 개발되고 있다. 현재 운영중인 위치 추적 서비스는 두 사람이 스마트폰을 소지하고 있는 경우의 서비스 형태와 한 사람만 스마트폰을 소지하고 있는 경우의 서비스 형태로 분류된다. 우리는 스마트폰과 스마트폰 간의 위치 정보 교환을 통해 상대방의 위치를 찾는 방식이 아닌 스마트폰과 GPS모듈 간의 위치 정보 교환을 통하여 어린이나 애완견의 위치를 찾을 수 있도록 GPS 모듈을 개발하고 이 모듈과 통신하는 스마트폰 앱을 개발하였다. 개발된 GPS 모듈은 위치 정보를 받아 전달하는 기능만 가지므로 스마트폰에 비해 매우 저렴하게 구성할 수 있어서 적은 경비로 상대방을 찾을 수 있으며 공중망 대신 무선랜 망을 통해 위치정보를 전달하게 설계되어 추가적인 통신 비용이 들지 않는 장점을 가진다. 하지만 위치추적 서비스가 무선랜 망이 구축된 제한된 구역에서만 가능하다는 단점이 있다. 개발된 위치추적 서비스 방식은 시장이나 놀이공원 같은 특수한 지역에서 유용하게 사용될 수 있을 것으로 생각된다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.929-943
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• 2020

Various methods are being presented to identify the movements of COVID-19 infected persons and to protect personal privacy at the same time. Among them, 'Exposure Notification' released by Apple and Google follows a decentralized approach using Bluetooth. However, the technology must always turn on Bluetooth for use, which can create a variety of security threats. Thus, in this paper, the security assessment of 'Exposure Notification' was performed by applying 'STRIDE' and 'LINDDUN' among the security threat modeling techniques to derive all possible threats. It also presented a new Dell that derived response measures with security assessment results and improved security based on them.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.725-733
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• 2010

A simulator is proposed in this paper for predicting the RF signal level after propagating over sea and land surfaces. Various sea and land types and transmit/receive antenna patterns, as well as the locus of the transmit antenna, are considered for this simulator. At first, microwave reflection characteristics of various sea surfaces have been computed, based on an empirical formula which is developed in this study for the relation between the sea surface roughness and wind speed. Then, microwave reflections from land surfaces such as forests, agricultural areas, and bare surfaces, are computed using the first-order vector radiative transfer theory. Finally, the signal paths over sea and land surfaces are found using the ray tracing technique and the digital elevation model, and the signal level received by a receiving antenna is computed by the using the reflection coefficients of sea and land surfaces and the signal paths.

• Journal of Information Technology Services
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• v.9 no.2
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• pp.179-192
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• 2010

In order to resolve the problems of traditional Enterprise Application Integration (EAI) for system integration and to establish flexible enterprise IT environments, Enterprise Service Bus(ESB) which have distributed architecture and support Service Oriented Architecture(SOA) has introduced. Particularly, JBI which developed by the Java Community Process is most widely used to implement ESB for advantages of Java technology. In ESB based on JBI, reliable message delivery is very important to ensure stability of services and systems because it is a message driven architecture. But, it is difficult to verify messages and trace messages when system fault or service error occurred because JBI specification is not enough to address them. In this paper we has proposed the Message Monitoring Framework for JBI-based ESBs which for using in monitoring messages efficiently. It provides foundations for gathering and tracing message-related information about component installation, message exchange, service deploy by using proxy-based change tracking and delegation mechanism for data processing. The proxy which used in our solutions collects data about message automatically when it changed, and the delegation mechanism provides users flexibility for data processing. Also, we describe the performance evaluation results of our solution which is acceptable. We expect to it enables users to ensure reliability and stability of the JBI-based ESB by systematic monitoring and managing messages being used to interact among components.

• Journal of Internet Computing and Services
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• v.20 no.2
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• pp.29-37
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• 2019

As software development technology evolves, the quality of software has increased. But software created through sophisticated technology is still defective. The developer will be aware of the defect through a bug report and the reported defect must be fixed as soon as possible for the software to function correctly. It is important to know which component of the program is related to the reported defect and should be fixed. However, even though the developer understands the developed software, the task of tracing faults is a time-consuming task and requires effort. Therefore, if there is a way for developers to support tracing faults, they could fix defects more quickly. Because fixing defects rapidly is a factor of software reliability, fault traceability is essential and an effective method is needed. Therefore, in this paper, we propose a model-based fault traceability enhancement technique by using bug report and commit information and verify the effectiveness of the proposed technique.

• Journal of IKEEE
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• v.26 no.4
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• pp.681-685
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• 2022

Including the COVID-19 crisis, humanity is constantly exposed to viral infections, and efforts are being made to prevent the spread of infection by quickly isolating infected people and tracing contacts. Passive epidemiological investigations that confirm contact with an infected person through contact have limitations in terms of accuracy and speed, so automatic tracking methods using various digital technologies are being proposed. This paper verify contact by utilizing Bluetooth Low Energy (BLE) technology and present an algorithm that identifies close contact through analysis and correction of RSSI (Received Signal Strength Indicator) values. Also, propose a system that can prevent the spread of viruses in a centralized server structure.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.505-508
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• 2016

In city, tracing of power transmission lines is difficult due to compound installation of overhead and underground lines, transposition, bad view caused by trees or big buildings. It is hard problem for electrical technician on site to trace power transformers or power lines to serve customers in 3 phase -4 wires power distribution systems. It is necessary that the correct and fast tracing method is required for load balancing among distribution lines. Old technology use to trace lines with high power impulse injection. Our proposed method uses to trace lines with very small power high frequency signal injection. Simulation models for 3-phase power transformers, 3-phase wire lines, and customer loads are described to investigate the transmission characteristics of high frequency power line carrier. Distribution lines have only a limited ability to carry higher frequencies. Typically power transformers in the distribution system prevent propagating the higher frequency carrier signal. The proposed method uses the limited propagation ability to identify the power transformer to serve customers. The system consists of a transmitter and a receiver with power-line communication module. Some experiments are conducted to verify the theoretical concepts in a big commercial building. Also some simulations are done to help and understand the concepts by using MATLAB Simulink simulator.