• Analytical Science and Technology
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• v.8 no.3
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• pp.351-358
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• 1995

Oxidation behavior on the surface of Nd-Fe-B ribbon alloy has been studied by X-ray Photoelectron Spectroscopy. In the incipient stage of oxidation on the surface of "as-received" ribbon Nd-oxide film was formed from the fast oxidation of Nd and Fe was metal state in bulk. In process of oxidation time Fe was more abundant in the outmost surface of ribbon from the defused Fe through Nd-oxide film and layer structure of oxidation film was formed.

• Analytical Science and Technology
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• v.8 no.3
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• pp.341-350
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• 1995

$Nd_{14}Fe_{80}B_6$ ribbon alloy was manufactured with using melt-spinning method and analyzed the magnetic properties according to the manufacturing conditions. The microstructure and magnetic properties of melt-spun ribbons are sensitively dependent on the quench rate and annealing conditions. As-quenched $Nd_{14}Fe_{80}B_6$ ribbons with optimum magnetic properties are obtained at wheel speed($v_s$) of about 20m/sec and over quenched ribbons show optimum magnetic properties at $v_s$=22m/see when annealed for 30 minutes at $600^{\circ}C$ under vacuum. The crystallization temperature($T_k$) of $Nd_2Fe_{14}B$ phase is about $595^{\circ}C$ in the DTA analysis.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.39-51
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• 2012

The time-dependent characteristics of mudstone in this study were analyzed by performing creep tests for the mudstone in Pohang. The creep tests were conducted on various boundary conditions to observe the time-dependent behavior of mudstone and the results were compared with values predicted by established visco-elastic model and empirical equations. As a result of analysis for empirical equations proposed by Griggs(1936), Cottrell(1952) and Singh(1975), the creep constants generally tend to increase as increasing the stress level and water content. Moreover, the values predicted by Singh's equation were well fitted for the test results. Therefore, it is expected to be reasonable that creep behavior of mudstone is analyzed using Singh's equation. As a result of analysis for a Burger's model, the predicted values were well fitted for the test results. Therefore, it is expected be reasonable that the creep behavior of mudstone by a rheological model is analyzed using Burger's model.

• Korean Journal of Plant Resources
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• v.10 no.4
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• pp.375-381
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• 1997

This study was conducted to determine the effect of seedling and division nursery stock size on the growth and yield of Wasabia japonica cultivated with cold water from Soyang Dam. As seedling and division nursery stock size were enlarged, their growth and yield were higher. In the case of division nursery stock, the rhizome yield per 10a were 782kg for large one, 723kg form medium one and 567kg for small one, and commercial rates - the percentage of rhizomes that weigh over 40g - were 87% for large one,80% for medium one and 55% for small one. In the case of seedling, large one brought out yield of 575kg/10a while medium and small one brought out low yield of 408kg/10a, and 421kg/10a, respectively. And the commercial rates from seedling were 60% for large one. 13% for medium one and 20% for small one.

• Journal of Korean Society on Water Environment
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• v.34 no.5
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• pp.462-469
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• 2018

There are differences in method and cycle of flow rate survey depending on purpose of the operating department. To verify and use results of flow data according to the purpose, flow data of the directly measured and tele monitoring system were compared to verify validity. Flow measurement in the Ministry of Environment is aimed at setting up a standard flow of target water quality for water quality management and securing flow data of low and normal water level seasons for water quality evaluation. In this study, correlation analysis result ($R^2$) of same time zone data by direct measurement and tele monitoring system (TMS) at Seombon D point, a unit watershed of Seomjin river, for six years ('10 ~ '15) according to implementation of Total Daily Maximum Load (TDML) was wading 0.716, boating 0.962 and on bridge 0.943, and effectiveness of measurement method was verified by characteristics of flow duration as a season of dry and low-water; normal and high water are appropriate for wading, boating, and on bridge respectively. Results revealed it is reasonable to use directly measured results using the wading and boating method for low water level and dry seasons, and TMS data for rainy seasons. It can be used important data for future policy decisions.

• Journal of KIISE:Databases
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• v.37 no.6
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• pp.324-332
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• 2010

The majority of event detection in real-time embedded sensor network systems is based on data fusion that uses noisy sensor data collected from complicated real-world environments. Current research has produced several excellent low-level mechanisms to collect sensor data and perform aggregation. However, solutions that enable these systems to provide real-time data processing using readings from heterogeneous sensors and subsequently detect complex events of interest in real-time fashion need further research. We are developing real-time event detection approaches which allow light-weight data fusion and do not require significant computing resources. Underlying the event detection framework is a collection of real-time monitoring and fusion mechanisms that are invoked upon the arrival of sensor data. The combination of these mechanisms and the framework has the potential to significantly improve the timeliness and reduce the resource requirements of embedded sensor networks. In addition to that, we discuss about a privacy that is foundation technique for trusted embedded sensor network system and explain anonymization technique to ensure privacy.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.156-156
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• 2013

대기압 저온 플라즈마는 간단한 구조 및 제작, 쉬운 조작성, 낮은 온도 특성, 높은 화학적 반응성과 같은 많은 장점에도 불구하고, 플라즈마의 에너지가 낮아 다양한 산업적 응용에 제약을 받아왔다. 이러한 단점을 극복하기 위해서 대기압에서 저온 플라즈마의 에너지를 높이는 여러 시도가 있었으며, 그 중 가까이 인접해 있는 둘 이상의 플라즈마 젯들의 결합 현상(plasma jet-to-jet coupling)을 이용하여 플라즈마 강도를 높이려는 시도가 보고되었다. 본 연구에서는 플라즈마를 발생시키는 유리관을 서로 모아 벌집모양의 배열을 갖는 플라즈마 젯 어레이 장치를 만들어 플라즈마 젯 사이에 상호결합을 유도하여 강한 플라즈마 발광을 발생시켰다. 플라즈마 젯 어레이 장치 중 가운데 위치한 플라즈마 젯은 대기압 플라즈마 젯의 형태를 구현하는 역할을 하고, 가운데를 둘러싼 주변의 여러 플라즈마 젯들은 중앙의 플라즈마 젯에 많은 하전입자를 제공하여 플라즈마 젯의 발광강도를 높이는 역할을 하는 것을 확인했다. 헬륨기체를 사용한 이 플라즈마 젯은 $100^{\circ}C$ 이하의 온도임에도 불구하고 ITO 유리의 유리면을 식각할 만큼 높은 에너지를 가졌다. 이러한 대기압 저온플라즈마 장치에서 플라즈마의 강도를 더 높이기 위해서는 플라즈마 젯 간 결합이 더 많이 일어나는 것이 중요하므로, 이를 위해 주변의 플라즈마 젯의 개수를 높이는 시도를 하였다. 플라즈마 젯 어레이 소자의 중심에 위치한 유리관의 크기를 크게 하고, 주변부의 유리관의 크기를 상대적으로 작게 하여 벌집형태의 배열보다 더 많은 유리관을 주변부에 위치시킨 후 플라즈마를 발생시키고 전기 광학적 특성을 측정하였다. 그 결과, 실험조건에 따라 가운데 플라즈마 젯에서 3배에서 5배 이상 높은 플라즈마의 발광강도를 얻었으며, 플라즈마 젯도 더 안정적으로 발생하였다. 주변부의 유리관의 개수가 증가하면 더 많은 양의 하전 입자들이 플라즈마 결합 과정에 참여하게 되고 결과적으로 더 큰 플라즈마의 발광강도를 나타내는 것이다. 본 실험은 하전입자의 상호작용에 의해 발생하는 서로 인접한 플라즈마 젯 간의 결합이 대기압 저온 플라즈마 젯의 플라즈마 발광강도를 높이는 좋은 방법임을 보였다. 이러한 플라즈마 젯 간의 결합은 대기압 저온 플라즈마의 에너지를 높일 수 있는 쉽고 간단한 방법이며, 이 방법을 이용하여 대기압 저온 플라즈마를 표면처리, 표면개질은 물론, 식각 및 증착, 나아가서는 의료/바이오 분석 기술 등 다양한 학문적, 산업적 응용에도 적용할 수 있을 것으로 기대한다.

• Journal of the Korea Convergence Society
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• v.12 no.9
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• pp.161-168
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• 2021

As the demand for high speed and high precision increases in the field of machine tool, interest in stiffness and vibration of machine tool is increasing. However, it takes a lot of time to develop a detailed design of machine tool based on experience, and it is difficult to design appropriately. Recently, structural optimization using FEM are increasingly used in machine tool design. But, it is difficult to optimize in consideration of the vibration state of the structure since optimization through stress distribution of a structure is mainly used, In this paper, Static structural analysis, mode analysis, and harmonic analysis using FEM were conducted to optimize the head structure that has the most influence on machining in a 5-axis machine tool. It is proposed a topology optimization analysis method that considers both static stiffness and dynamic stiffness using objective function design.

• Journal of IKEEE
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• v.25 no.3
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• pp.517-527
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• 2021

This paper presents the phase-shift full-bridge DC-DC converter using the one-chip micom. The proposed converter primary is the full-bridge power topology that operates with the unipolar pulse-width modulation (PWM) by the phase-shift method, and the secondary is the full-bridge full-wave rectifier composed of four diodes. The control of proposed converter is performed by the one-chip micom and its MOSFET switches are driven by the bootstrap circuit. Thus the total system of proposed converter is simple. The proposed converter achieves high-efficiency using the resonant circuit and blocking capacitor. In this paper, first, the power-circuit operation of proposed converter is explained according to each operation mode. And the power-circuit design method of proposed converter is shown, and the software control algorithm on the micom and the feedback and switch drive circuits operating the proposed converter are described, briefly. Then, the operation characteristics of proposed converter are validated through the experimental results of a designed and implemented prototype converter by the shown design and implementation method in this paper. The highest efficiency in the results was about 92%.

• PNF and Movement
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• v.16 no.3
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• pp.317-332
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• 2018

Purpose: Patients with tibial fractures can have functional problems with balance and gait, as well as lower extremity muscle weakness. This case report aimed to describe the effect of hip joint strengthening exercises using proprioceptive neuromuscular facilitation (PNF) on balance and gait and lower limb function in a patient with tibia fracture. Methods: One patient diagnosed with tibial fracture was treated for seven weeks with the basic procedure, pattern, and technique of PNF for a hip joint strengthening exercise. Results: The results of pre- and post-intervention treatment showed improvements in physical function and structure in the clinical tests, including the manual strength test; the modified Ashworth scale; sensory evaluation; balance, sit-to-stand, and gait performance; and evaluation of lower limb function. Conclusion: Based on the results of this study, it is suggested that the use of theory-based proprioceptive neuromuscular stimulation for hip joint strengthening exercises positively affects patients' functional improvement in tibial fracture patients, and this may be used as a therapeutic exercise method for those with orthopedic problems in the lower extremities. One limitation of this study was that it was performed on only one tibia fracture patient, which makes it difficult to extend the treatment effects to all patients with this condition.