• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.465-471
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• 2013

A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

• The Korean Journal of Nuclear Medicine Technology
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• v.12 no.1
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• pp.33-38
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• 2008

Purpose: The Gated cardiac blood pool scan is non-invasive method that a quantitative evaluation of left ventricular function. Also this scan have shown the value of radionuclide ejection fraction measurements during the course of chemotherapy as a predictor of cardiac toxicity. Therefore a reliable method of monitoring its cardiotoxic effects is necessary. the purpose of this study is to minimize the overestimate of left ventricular ejection fraction (LVEF) by modified body position to reduce the influence of scattered rays from surrounding organs of the heart in the background region of interest. Materials and Methods: Gated cardiac blood pool scan using in vivo $^{99m}Tc$-red blood cell (RBC) was carried out in 20 patients (mean $44.8{\pm}8.6$ yr) with chemotherapy for a breast carcinoma. Data acquisition requires about 600 seconds and 24 frames of one heart cycle by the multigated acquisition mode, Synchronization deteriorates toward the end of the cycle and with the distance from the trigger signal (R-wave) by ECG gating. Gated cardiac blood pool scan was studied with conventional method (supine position and the detector head in $30-45^{\circ}$ left anterior oblique position and caudal $10-20^{\circ}$ tilt) and compared with modified method (left lateral flexion position with 360 mL of drinking water). LVEF analysis was performed by using the automatically computer mode. Results: The ROI counts of modified scan method were lower than LV conventional method ($1429{\pm}251$ versus $1853{\pm}243$, <0.01). And LVEF of modified method was also decrease compared with conventional method ($58.3{\pm}5.6%$ versus $65.3{\pm}6.1%$, <0.01). Imaging analysis indicated that stomach was expanded because of water and spleen position was changed to lateral inferior compared with conventional method. Conclusion: This study shows that the modified method in MUGA reduce the influence of scattered rays from surrounding organs. Because after change the body position to left lateral flexion and drinking water, the location of spleen, left lobe of liver and stomach had changed and they could escaped from background ROI. Therefore, modified method could help to minimize the overestimate LVEF (%).

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.635-648
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• 2018

This study analyzed patent trends of seismic nodal systems and the technical characteristics of core patents of three major companies, including Fairfield, Sercel, and Wireless Seismic, to examine the focus of technology development of each company. From the analysis, the patent application growth rate of seismic nodal systems has steadily increased since early to mid-2000s and has recently shown a higher growth rate. Over the same period, the patent application growth rate of the three major companies examined was higher than that of the global trend, and patent infringement cases was also examined to evaluate market competition in this field. Analysis of the technical characteristics of the three companies' 33 core patents showed that they are generally focused on seismic signal detection. Sub-technologies included improved reliability of data acquisition, data transmission efficiency, and overall operating of the seismic nodal system. New entrants in field of technology development or manufacturing of seismic nodal systems where the market is growing must closely analyze the contents of major companies' products and patents to prevent possible patent disputes or duplicate research.

• Journal of radiological science and technology
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• v.31 no.4
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• pp.355-365
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• 2008

Purpose : This study isto determine the grade of brain tumor and compare the characteristics in each grade using in MRS (MR Spectroscopy). Method : STEAM (Stimulated Echo Acquisition Method) and protocol of PRESS (Point Resolved Spectroscopy) were used in the levels of tumor grade. We classified the pattern of tumor and analysis of the spectrum signals quantitatively from voxel in the brain tumor grade. In accordance with the result, we calculated the accuracy of biochemical. Result : In high-grade tumor, the NAA/Cr showed the signal reduction of 29.4% and 53.9%. However Cho/Cr increased 570% and 711%. However, in low-grade tumor, NAA/Cr downed to 42.6% and 58.1%. Cho/Cr increased to 188% and 195%. Conclusion : The study suggests that the comparative analysis of signals from MR spectroscopy could be useful to evaluate the grade of tumor and find out the characteristics of it. By extension, MR spectroscopy can be used for research with other organs in the human.

• Geophysics and Geophysical Exploration
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• v.8 no.4
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• pp.237-242
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• 2005

A seismic refraction study in estimation of depth to the bedrock demonstrates that 1) the average velocity in the medium is about 250 m/s in the surface layer (< 4 m), 2,500 m/s in the weathered formation, and greater than 3,000 m/s in the bedrock, 2) the depth to the deepest reflector assumed to be the bedrock is about 17 m; however, according to the cores collected in a borehole in study area, the bedrock (granite) occurred at depth 25 m, 3) according to the density and velocity logging, at depth 17 m, a measurable velocity and density increase are observed, and 4) the velocity of the weathered formation is relatively high and therefore, the acquisition offsets ($70{\sim}80m$) are turned out not to be long enough to record the refracted signal from the bedrock at depth 25 m as first arrivals.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.43-48
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• 2006

Recently, many researchers have shown great interest in wind-photovoltaic hybrid generation system which promotes electric power supply safely and progress of energy usage efficiently with complementary cooperation of a wind generation system and photovoltaic generation system. To use this hybrid generation system stably and effectively, we established a system which can acquire, analyse and save data and monitored remotely using internet. We constructed the signal conditioning circuit and used many kinds of converters to measure physical quantities such as wind velocity, intensity of illumination and temperature as well as many kinds of voltage and current for AC and DC. we acquired data from computer with data acquisition board, developed server program and client program which can download data that is monitored and saved in realtime at remote place. We analysed the measured data in relation to many conditions such as time and weather conditions.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1732-1737
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• 2004

This paper proposes Internet-based checking technique for machine-tools with variant CNC (Computerized Numerical Controller). According to the architecture of CNC, CNC is classified into two types such as CAC (Closed Architecture Controller) which is conventional CNC, and OAC (Open Architecture Controller) which is a recently introduced PC-based controller. CAC has a closed architecture and it is dependent on CNC vender specification. Because of this, it has been very difficult for users to implement an application programs in CNC domain. Therefore, an additionally special module is required for Internet-based application such as remote checking. In this case, web I/O embedded module can be efficiently applied for Internet-based checking. The module is directly attached to TCP/IP network for communication. In order to obtain the monitoring data of CNC machines, the I/O signals of the module are assigned to PLC (Programmable Logic Controller) input and output (I/O) signals within CNC domain. On the other hand, OAC has a PC-based open architecture and an additional module is not necessary for the connection with external site. Because of this, a simple DAU is just used for signal sensing and data acquisition without additional communication modules. For Internet-based remote checking of machine-tools with OAC, a user-defined daemon and application programs are implemented as the form of internal function within the PC-based controller. Internet communication is performed between the daemon program in CNC domain and web script programs in external server. Checking points defined in this research are classified into two categories such as structured point and operational point. The formal includes the vibration of bearing, temperature of spindle unit and another periodical management. And the latter includes oil checking, clamp locking/unlocking and machining on/off status.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.111-117
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• 2009

In the wideband code division access (WCDMA) systems, a pilot channel is used to determine WCDMA network coverage, cell identification, synchronization, timing acquisition and tracking, user-set handoff, channel estimation, and so on. A wireless repeater, which is deployed in the urban area for the WCDMA system to meet the growing demand on wireless communication services, has the possibility to receive several pilot signals from a large number of base stations, however, cannot distinguish its service base station's signal among them. This pilot interference results in frequent handoffs in the user equipment, which degrades the radio reception, transmission efficiency, quality of service, and channel capacity and increases the unwanted power consumption. In this paper, thus, we propose a pilot pollution interference cancellation scheme using one of the adaptive estimation algorithms, normalized least mean square (NLMS), which is applicable to a wireless repeater. We carried out link-level and network-level computer simulations to evaluate the performance of the proposed scheme in a wireless repeater. The simulation results verify the bit error rate (BER) improvement in the link level and the call drop probability improvement in the network level.

• The Journal of Korea Robotics Society
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• v.12 no.3
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• pp.350-355
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• 2017

UWB (Ultra Wide Band) refers to a system with a bandwidth of over 500 MHz or a bandwidth of 20% of the center frequency. It is robust against channel fading and has a wide signal bandwidth. Using the IR-UWB based ranging system, it is possible to obtain decimeter-level ranging accuracy. Furthermore, IR-UWB system enables acquisition over glass or cement with high resolution. In recent years, IR-UWB-based ranging chipsets have become cheap and popular, and it has become possible to implement positioning systems of several tens of centimeters. The system can be configured as one-way ranging (OWR) positioning system for fast ranging and TWR (two-way ranging) positioning system for cheap and robust ranging. On the other hand, the ranging based positioning system has a limitation on the number of terminals for localization because it takes time to perform a communication procedure to perform ranging. To overcome this problem, code multiplexing and channel multiplexing are performed. However, errors occur in measurement due to interference between channels and code, multipath, and so on. The measurement filtering is used to reduce the measurement error, but more fundamentally, techniques for removing these measurements should be studied. First, the TWR based positioning was analyzed from a stochastic point of view and the effects of outlier measurements were summarized. The positioning algorithm for analytically identifying and removing single outlier is summarized and extended to three dimensions. Through the simulation, we have verified the algorithm to detect and remove single outliers.

• Investigative Magnetic Resonance Imaging
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• v.22 no.1
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• pp.65-70
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• 2018

The objective of this study was to describe a radiofrequency (RF) coil design for in vivo sodium magnetic resonance imaging (MRI) for use in small animals. Accumulating evidence has indicated the importance and potential of sodium imaging with improved magnet strength (> 7T), faster gradient, better hardware, multi-nucleus imaging methods, and optimal coil design for patient and animal studies. Thus, we developed a saddle-shaped sodium volume coil with a diameter/length of 30/30 mm. To evaluate the efficiency of this coil, bench-level measurement was performed. Unloaded Q value, loaded Q value, and ratio of these two values were estimated to be 352.8, 211.18, and 1.67, respectively. Thereafter, in vivo acquisition of sodium images was performed using normal mice (12 weeks old; n = 5) with a two-dimensional gradient echo sequence and minimized echo time to increase spatial resolution of images. Sodium signal-to-noise ratio in mouse kidneys (renal cortex, medulla, and pelvis) was measured. We successfully acquired sodium MR images of the mouse kidney with high spatial resolution (approximately 0.625 mm) through a combination of sodium-proton coils.