• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.2
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• pp.162-169
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• 2011

The flight control system utilize RSS(Relaxed Static Stability) criteria in both longitudinal axes to achieve performance enhancements and improve stability. The aircraft using digital flight-by-wire flight control system receives aircraft flight conditions such as pitch, roll and yaw rate, normal acceleration from RSA(Rate Sensor Assembly) and ASA(Acceleration Sensor Assembly). These sensors has permissible measurement error related to system safety of an aircraft but, unexpected flight motions are happened by sensing errors such as offset, noise and etc. The unexpected pitch down tendency occurred by ASA sensor bias in 1g level flight with pilot hands-off. This paper addresses the design and verification of flight control law to improve of pitch down or up tendency caused by ASA sensor bias. The result of analysis and flight test reveals that pitch down tendency can be improved by pitch attitude feedback system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.50-60
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• 2015

This paper conducted research on identifying the process of change in fishing gear and organizing the function of periodically-used fishing gear types through net plan and computer simulation by selecting the design of the four types of fishing gear used for the Korea tuna purse seiner in the Western and Central Pacific Ocean, which 1,000 G/T class and whose length over all 60 m class. In the late 1980s, the length of the tuna purse gear was 1,939 m and the design depth was 160 m, but currently, the length and the design depth are 2,515 m and 230 m, respectively. As a result of the simulation, the expansion of the fishing gear increased buoyance, sinking force, sinking depth, surrounded area, and purse wire continuously. Recently, the maximum tension of the currently used purse wire of tuna purse seiner is 23.5 tons and is close to 25.4 tons which is the maximum lift capacity of WS454 winch. The way to improve fishing gear should be proceeded to increase sinking speed rather than expand the size of fishing gear.

• Journal of Powder Materials
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• v.11 no.4
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.39-44
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• 2006

Before applying HTS power cable to the real utility. system analysis should be carried out by some simulation tools . Hereby the electrical power system analysis is very important for practical use of HTS devices. Nowadays PSCAD/EMTDC simulation tool is one of the most popular and useful analysis tool for the electrical power system analysis. Unfortunately the model component for HTS power cable is not provided in the PSCAD/EMTDC simulation tool In this paper. the EMTDC model component for HTS power cable has been developed considering critical current, critical temperature and recovery time constant that depend on the sorts of HTS wire. The numerical model of HTS Power cable in PSCAD/EMTDC was designed by using the real experimented data obtained from the real HTS 1G wire test. The utility application analysis of HTS power cable was also performed using the developed model component and the parameters of the real utility network in this study. The author's got good results. The developed model component for HTS power cable could be variously used when the power system includes HTS power cable, especially it will be readily analyzed by PSCAD/EMTDC in order to obtain the data for the level of fault current power flow, and power losses, and so on.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.2
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• pp.525-536
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• 1996

The purpose of this study was to investigate the effect of electrical anesthesia induced by non-acupuncture point stimulation on inhibition of amplitude of digastric EMG evoked by noxious electrical stimuli in teeth and gingiva. Experiments were performed with dogs anesthetized with intraperitoneal pentobarbital sodium in an initial dose of 30mg/kg. Maintenance doses of 4.0ml/hour were given through a cannula in the femoral vein using a constant infusion pump. Anterior belly of digastric muscle was exposed and a pair of 0.1mm wire electrodes were inserted for E.M.G. recording. Bipolar electrodes were inserted into the labial and lingual surface of upper canine and the labial area of upper gingiva. Noxious stimuli were delivered to the tooth and gingiva through those electrodes by electric stimulator. Non-acupuncture point stimulation of 2Hz was delivered bilaterally to the femoral area. Amplitudes of digastric E.M.G. were measured from the oscilloscope and the monitor connected to amplifier at different intensities of electronic anesthesia of 1 volt, 4 volt and 10 volt. The inhibited rate of the amplitudes of digastric E.M.G. were analysed statistically with paired t-test. The following results were obtained : 1. Non-acupuncture point stimulation with intensities of 1 volt, 4 volt and 10 volt showed the inhibitory effect on pain of 15%, 25% and 16% in teeth and 15%, 18% and 12% in gingiva respectively 2. In tooth, statistical significance was observed between control and each group. In gingiva, there was statistical significance between control and group 1, 2 except group 3 From these results, low frequency electrical stimulation of non-acupuncture point resulted in reducing of dental and gingival pain, it could be used as adjunct to other pain control methods.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.462-466
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• 2010

The purpose of this study is to evaluate the safety of a wire connector fabricated for the effective installation of a lighting fixture including its contact resistance, insulation resistance, withstanding voltage characteristics, etc., and to provide the basis for the analysis and judgment of PL(Product Liability) dispute by presenting a damage pattern due to a general flame and overcurrent. This study applied the Korean Standard (KS) for the incombustibility test of the connector using a general flame and performed an overcurrent characteristics test of the connector using PCITS (Primary Current Injection Test System). The contact resistance of the housing connector was measured using a high resistance meter and the insulation resistance was measured using a multimeter. In addition, a supply voltage of AC 1,500V for testing the withstanding voltage characteristics was applied to both ends of the connector. Measurement was performed on 5 specimens and the measured values were used as a basis for judgment. Since the connector is fabricated in the form of a housing, it can be connected and separated easily and has a structure that allows no foreign material to enter. In addition, since it has a structure that allows wires to be connected only when their polarity is identical, any misconnection that may occur during installation can be prevented. When the incombustibility test was performed by applying a general flame to the connector, it showed outstanding incombustibility characteristics and the blade and blade holder connected to the housing remained firmly secured even after the insulation sheath (PVC) was completely destroyed by fire. In addition, the mechanism of the damaged connecting wire showed a comparatively uniform carbonization pattern and it was found that some residual melted insulation material was attached to both ends. In the accelerated life test (ALT) to which approximately 500% of the rated current was applied, the connector damage proceeded in the order of white smoke generation, wire separation, spark occurrence and carbonization. That is, it could be seen that the connector damaged by overcurrent lost its own metallic color with traces of discoloration and carbonization. The contact resistance of the connector at a normal state was 2.164mV/A on average. The contact resistance measured after the high temperature test was 3.258mV/A. In addition, the insulation resistance after the temperature test was completed was greater than $10G\Omega$ and the withstanding voltage test result showed that no insulation breakdown occurred to all specimens showing stable withstanding voltage and insulation resistance characteristics.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.391-398
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• 2002

During handling unitized products, they are subjected to a variety of environmental hazards. Shock and vibration hazards are generally considered the most damaging of the environmental hazards on a product and it may encounter while passing through the distribution environment. A major cause of shock damage to products is drops during manual handling. The increasing use of unitization of pallets has been resulted in a reduction of the shock hazards. This has caused an increasing interest in research focused on vibration caused dam age. Damage to the product by the vibration most often occurs when a product or a product component has a natural frequency that falls within the range of the forcing frequencies of the particular mode of transportation being used. Transportation vibration is also a major cause of fruit and vegetable quality loss due to mechanical damage. This study was conducted to determine the vibration characteristics of the corrugated fiberboard bones for packages of pears, and to investigate the degree of vibration injury of the pears in the boxes during the simulated transportation environment. The vibration tests were performed on an electrohydraulic vibration exciter. The input acceleration to exciter was fixed at 0.25 G for a single container resonance test and 0.5 G for the vertical stacked container over the frequency range from 3 to 100 Hz. Function generator (HP-33120A) was connected by wire to the vibration exciter for controlling the input acceleration at a continuous logarithmic sweep rate of 1.0 octave per min. The peak frequency and acceleration on the single box test were 22.02 Hz, 1.5425 G respectively, and these values on the vertical stacked boxes were observed from the bottom box 19.02, 18.14, 16.62 and 15.40 Hz and 2.2987, 3.7654. 5.6087, and 7.9582 G, respectively. The pear in the bottom box had a slightly higher damage level than the fruit packed in the other stacked boxes. It is desirable that the package and transportation system has to be so designed that 15∼20 Hz frequency will not occur during the transportation environment.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.897-907
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• 2020

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.127-137
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• 1995

The possibility of new GMAW process using economic shielding gases including CO$_{2}$ gas was investigated on the effect of shielding gas on weldabilty. In the optimum welding condition using 600A power source, FCAW process showed low depositions rate, 114 g/min at 300A, but new GMAW using other mixed shielding gases exhibited high deposition rate, 208-224 g/min at 450A. TIME gas, Ar+CO$_{2}$ gas and Ar+CO$_{2}$+O$_{2}$ gas as a shielding gas were able to be used to the very high welding current(450A), moreover TIME gas and Ar+CO$_{2}$ gas showed the highest arc stability among shielding gases studied in this experiments. The weld penetration was performed by axial spray transfer mode of weld droplet. On the basis of workability, weldability and economic point of view, Ar mixture (80%Ar+20%CO$_{2}$) gas was recommended as a shielding gas for the development and application of new GMAW process. This shielding gas showed the low spatter, good weld quality, stable arc and low cost at the region of high welding current.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2091_2092
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• 2009

지중케이블 시스템에서의 고장은 필연적으로 대전류 현상을 수반하는 경우가 대부분으로서 고장전류는 고장 케이블 자체와 인접해 있는 타 선로 및 통신선 등에 악영향을 미칠 가능성이 크고, 초고압 케이블의 운전전압 레벨이 지속적으로 증가하고 있는 상황에서 사고의 파급 및 위험정도 또한 지속적으로 증가하고 있다. 특히, 단락 고장의 경우 고장전류의 크기도 크지만 고장전류 발생에 따른 전자력을 동반하게 되어 케이블 및 접속함, 각종 금구류에 전기적, 기계적인 스트레스를 야기할 수 있다[1]. 따라서 본 논문에서는 지중케이블의 삼각배열 구간의 단락전자력 영향을 최소화하기 위한 방안을 모색하기 위하여 154kV OF케이블 3상 단락 실증시험을 2회 시행하였고, 유한요소법을 이용하여 단락전자력 발생시 클리트 설치간격에 따른 케이블 변위를 계산함으로써 케이블의 단락 전자력 영향 검토결과를 기술하였다.