• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.05a
• /
• pp.611-615
• /
• 2008

The international society under the internet technology have been declining boundaries of the global economy. After this step, a social revolution will be happen from the ubiquitous technology which fives objects intelligence to serve people. And then it is expected that every part of a city competitive power is defined by both in qualify and in quantify of the ubiquitous information unit in the future. On this score, now each nation is trying to set relative services and broadband networks to lead the ubiquitous industry. Therefore this paper analyzed about the progress and prospect of a local U-city plan in our nation Especially we propose a new city development model which use U-city and self-communication network to Improve a city competitive power.

• Journal of the Korea Society of Computer and Information
• /
• v.11 no.6 s.44
• /
• pp.261-267
• /
• 2006

In order to perform a probabilistic safety assessment (PSA), it requires a large number of data for various fields. And the quality of a PSA results have become more important thing of the risk assessment. As part of enhancing the PSA qualify, Korea Atomic Energy Research Institute is developing a full power Human Reliability Analysis (HRA) calculator to manage human failure events (HFEs) and to calculate the diagnosis human error probabilities and execution human error probabilities. This paper introduces the development process and an overview of a standard HRA method for nuclear power plants. The study was carried out in three stages; 1) development of the procedures and rules for a standard HRA method. 2) design of a system structure, 3) development of the HRA calculator.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.11
• /
• pp.1164-1171
• /
• 2014

Bulk Current Injection(BCI) test is a method of injecting current into Integrated Circuit(IC) using a current injection probe to qualify the standards of Electromagnetic Compatibility(EMC). This paper, we propose a microstrip coupler structure that can replace the BCI current injection probe that is used to inject a RF noise in standard IEC 62132-part 3 documented by International Electrotechnical Commission. Conventional high cost BCI probe has mostly been used in testing automotive ICs that use high supply voltage. We propose a compact microstrip coupler which is suitable for immunity testing of low power ICs. We tested its validity to replace the BCI injection probe from 100 MHz to 1,000 MHz. We compared the power[dBm] that is needed to generate the same level of noise between current injection probe and microstrip coupler by sweeping the frequency. Results show that microstrip coupler can inject the same level of noise into ICs for immunity test with less power.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.693-696
• /
• 2008

The systems for mobile communication services of fourth generation use OFDM (Orthogonal Frequency Division Multiplexing) scheme that ran transmit large amounts of data to support the multimedia services, and consist of several types of cell, such as Macro Cell, Pico Cell, Femto Cell to improve the qualify of service. According to subdivision of communication region, superposition of cells in co-channel different from conventional single cell is used, but it cause inter band interference between systems. In particular, an OFDM signal consists of a number of independently modulated subcarriers, and superposition of these subcarriers causes a problem that ran give a large PAPR. Increased PAPR induces signal distortion passing through components such as power amplifier so that inter band interference is caused by out-of-band spectrum radiation. In order to minimize the inter band interference, this paper applies PAPR reduction scheme and analyzes the out-of-band spectrum radiation when the signal passes through nonlinear components such an power amplifier.

• The KSFM Journal of Fluid Machinery
• /
• v.16 no.5
• /
• pp.18-23
• /
• 2013

Thermal aging test is performed to qualify the life time of equipment in thermally aged condition. Due to long life time more than 10 years like as in power plant, the equipment is subjected to the accelerated thermal aging condition which is able to shorten the long aging test period by increasing aging temperature. Normally, conservatism of thermal aging test causes to impose unbalanced and excessive thermal load on components of the equipment, and deformation and damage problems of the components. Additionally, temperature rise of each component through heat generation of the electric equipment leads to long-term problem of the test period. Multi-phase accelerating aging test is to perform thermal aging test in multiple aging conditions after dividing into groups with various components of equipment. The groups might be classified considering various factors such as activation energy, temperature rise, glass transition temperature and melting temperature. In this study, we verify that the multi-phase accelerating aging test method can reduce and equalize the thermal over load of the components and shorten aging test time.

• Journal of Korea Multimedia Society
• /
• v.19 no.12
• /
• pp.2014-2023
• /
• 2016

Web presence is one of the key issues for extensive deployment of Internet-of-Things (IoT). An obstacle to overcome for Web presence is relatively low computing power of IoT devices. In this paper, we present implementation of an IoT platform based on Constrained Application Protocol (CoAP) which is a web transfer protocol proposed by Internet Engineering Task Force (IETF) for the low performance IoT devices such as Wireless Sensor Network (WSN) nodes and micro-controllers. To qualify the performance of CoAP-based IoT system for such an application as smart grid, we designed a test platform consisting of Raspberry Pi2, Kmote WSN node and a desktop PC. Using open source softwares, CoAP was implemented on top of the platform. Leveraging the GET command defined at CoAP specification, performance of the system was measured in terms of round-trip time (RTT) from web application to the Kmote sensor node. To investigate abnormal cases among the test results, hop-by-hop delays were measured to analyze resulting data. The average response time of CoAP-based communication except the abnormal data was reduced by 23% smaller than the previous research result.

• Structural Engineering and Mechanics
• /
• v.19 no.1
• /
• pp.97-106
• /
• 2005

The standard practice is to seismically qualify the safety related equipment and structural components used in the nuclear power plants. Among several qualification approaches the qualification by the analysis using finite element (FE) method is the most common approach used in practice. However the predictions by the FE model for a structure is known to show significant deviations from the dynamic behaviour of 'as installed' structure in many cases. Considering such limitation, few researchers have advocated re-qualification of such structures after installation at site to enhance the confidence in qualification vis-$\grave{a}$-vis plant safety. For such an exercise the validation of FE model with experimental modal data is important. A validated FE model can be obtained by the Model Updating methods in conjugation with the in-situ experimental modal data. Such a model can then be used for qualification. Seismic analysis using the updated FE model and its advantage has been presented through an example of an in-core component - a perforated horizontal tube of a nuclear reactor.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.15 no.2
• /
• pp.51-58
• /
• 2006

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding qualify is 1600W of the laser power, 0.85m/min of welding speed and $4{\ell}/min$ of pressure for shielding gas.

• Journal of Korea Multimedia Society
• /
• v.9 no.1
• /
• pp.51-58
• /
• 2006

In this paper, we evaluated Ultra Wideband MC-CDMA system which is the combination of DS-CDMA and OFDM systems, which have been drafting in current standardization for IEEE802.15.3a. Too many Rake Fingers are demanded in the DS-CDMA system to detect multi-path signals, which results in high system complexity. OFDM system fails to qualify for FCC certification unless frequency hopping is off. MC-CDMA has lower complexity compared to DS-CDMA and shows good performance against frequency selective fading. In addition, for a wide-band communication, less radio power per spectrum is allowed in the MC-CDMA system than in an OFDM system. The MC-CDMA system is analyzed by a numerical formula and compared with DS-CDMA and OFDM by a computer simulation.

• Journal of Drive and Control
• /
• v.15 no.1
• /
• pp.16-27
• /
• 2018

Hydraulic torque load simulator is essential to test and qualify the performance of various angle control systems. Typically a flapper-type second stage servovalve is applied to the load simulator, but here the direct drive servovalve, which is a kind of one-stage valve and affected by the large flow force, is applied. Since the torque load is applied not to the stationary shaft but to the rotating shaft of the angle control system, the controlled torque of load simulator is not accurate due to the rotating speed of the angle control system. A feedforward compensator is designed and applied to minimize the disturbance-like effect. A mathematical model is derived and linearized to analyze the stability, accuracy and responsiveness of the torque load simulator. The parameter effects of a controller, servovalve, hydraulic motor, rotating spring shaft are analyzed and summarized. The goodness of the linear analysis is verified by the digital computer simulations using both the linear and nonlinear mathematical models.