• Proceedings of the KWS Conference
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• 1994.10a
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• pp.89-92
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• 1994

According to the industrial development welding technology is necessitated to develop in the direction of full automation, high efficiency, energy saving, and full safety. In this study, thus, a simple holder ampere controller for welding systems is developed and applied to arc welders and its capability is examined and tested. The results are as follows: 1. It has a simple structure, since the primary AC power for the welder can be directly control led using a triac. 2. It can control the electric power strength in several steps as well as on and off easily, since a small-sized variable resistance is installed in the small controller on the welding holder. 3. In real field applications a welding system with this controller increases the working efficiency greatly compare to the conventional arc welders without the system, because the controller can control the ampere onsite far from the main power supply. 4. It can reduce the probability of the electrical mishap due to electrical leakage, since the electricity is disconnected as soon as the switch is off or welding person's hand is taken off from the welder after the work or for rest. 5. It can control the welding depth in the beginning and do the crater treatment well in the ending of welding, since it always supplies the relevent amount of electrical current. Therefore, it can improve the mechanical properties of the welding zone.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.169.1-169.1
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• 2013

산업 및 기술의 발전에 의해 많은 신소재들이 개발되고 있다. 그 중에서 SiC는 고온재료, LED, 반도체 등의 우주선 표면재료, 핵융합로 구조재료, 고온 씰, 히터 등 여러 산업분야에서 관심을 가지면서 다양한 가스를 이용한 합성법이 개발되어 있다. 최근에는 분말의 형태 및 크기를 용도에 맞게 개발해서 사용하고 있는 상황이다. 그런데 각 합성법에 따른 합성원리에 대해서는 여러 가지 주장이 있다. 그 중에서 몇 가지 합성법에 대해서 고찰하고 합성의 원리를 추론한다. 그리고 그 중의 한 가지인 CH3SiCl3 가스를 이용한 SiC 나노분말 합성과 SiC의 결정성장 과정에서 나타나는 whisker의 형성을 확인했다. 정교한 SiC 분말합성은 일반적으로 sol-gel, 플라즈마(DC, AC 및 ICP 등) 등을 이용한 방법이 개발되어 있다. 이와 같이 정교한 SiC 나노분말 등은 실리콘 유기 화합물 중합체(trichloromethylsilane, polycarbosilane 등)의 열분해를 통해 합성 할 수 있으며, 열분해 는 약 1,000{\sim}1,500^{\circ}C의 온도 영역에서 일어난다. 이 과정에서 고분자의 열분해 및 재결합 이 동반되고 부산물로서 HCl, CH4 등의 유해가스를 같이 생성한다. 합성된 SiC 나노분말은 전형적인 ${\beta}-SiC$로 XRD의 관찰결과 (111), (220), (311)의 방향성을 갖는 것을 확인했으며 평균입자의 크기는 약 30 nm 정도다.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.601-607
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• 2011

The study investigated the influence of current density on the corrosion-protection properties of an AZ91 Mg alloy subjected to plasma electrolytic oxidation coating. The present coatings were carried out under an AC condition at three different current densities, i.e., 100, 150, and $200mA/cm^2$. From microstructural observations, the micro cracks connecting each micro pore were pronounced on the oxide surface of the samples coated at current densities higher than $150mA/cm^2$ since increasing the current density in this study led to an increment in the relative volume fraction of the MgO compound. Based on potentio dynamic polarization and immersion tests, the sample coated at a current density of $100mA/cm^2$ showed superior corrosion resistance.

• Korean journal of food and cookery science
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• v.13 no.1
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• pp.64-69
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• 1997

The experiments of rice bread processing were carried out to compare the varietal difference in processing adaptability to rice bread between brown and milled rice flour, and to analyze the interrelations among chemical properties of rice grain and some characteristics relevant to rice bread processing and quality There was varietal difference in adaptability to rice bread processing in both brown and milled rice, but there was not significant adaptability difference between brown and milled rice flours to rice bread processing. However, there was remarkable adaptability difference between brown and milled rice flours to rice bread processing in some rice varieties. Three high-amylose rices AC 27, IR 44, Suweonjo showed high quality of milled rice bread among tested rice materials. Brown rice revealed better adaptability to rice bread processing compared with milled rice in all varieties except the above three varieties. Especially, the glutinous rice Hangangchalbyeo failed to normal formation of rice bread from milled rice flour, but it showed the successful formation of rice bread from brown rice flour. The interrelations among chemical components of rice grain and some characteristics relevant to rice bread processing and quality exhibited quite different tendency between brown and milled rices. In the case of rice bread processing by brown rice flour, the larger volume expansion of dough during fermentation made the more springy rice bread and the more moist rice bread showed the more soft and cohesive physical property. In the case of rice bread processing by milled rice flour, the lower protein of rice flour was closely associated with the more moistness of rice bread and the higher lipid led to the more uniformal air pore distribution, the smaller pore size and the lower springiness of rice bread. Also, the larger volume expansion of dough during fermentation made the better loaf formation and the larger pore size of rice bread. The better loaf formation of rice bread revealed the softer hardness and the lower chewiness, and the lower springiness was closely correlated with the more uniformal size distribution of air pore and the smaller pore size in rice bread.

• Journal of Life Science
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• v.31 no.11
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• pp.995-1003
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• 2021

Chromatin remodeling regulates gene expression through epigenetic mechanisms. Aberrations in histone modification have been associated with depression-like behaviors in animal models. Additionally, growing evidence also indicates that epigenetic modification is associated with depression. p11 (S100A10) has been implicated in the pathophysiology of depression both in human and rodent models. In the present study, we investigated alterations in histone acetylation and methylation at the promoter of the p11 gene in the hippocampus of mice subjected to chronic unpredictable stress (CUS). C57BL/6 mice were exposed to CUS daily for 3 weeks. Depression-like behaviors were measured with the forced swimming test (FST). The levels of hippocampal p11 expression were analyzed by quantitative real-time polymerase chain reaction (PCR) and Western blotting. The levels of acetylated and methylated histone H3 at the promoter of p11 were measured by chromatin immunoprecipitation followed by real-time PCR. CUS-exposed mice displayed depression-like behaviors with prolonged immobility in FST. CUS led to significant decreases in the expression of p11 at both protein and mRNA levels. Meanwhile, there was a decrease in histone H3 acetylation (Ac-H3) and H3-K4 trimethylation (H3K4met3) and an increase in H3-K27 trimethylation (H3K27met3) at the p11 promoter. These results indicate that chronic stress causes the epigenetic suppression of p11 expression in the hippocampus.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.37-44
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• 2010

Recently, urban retrofit and extension, development of new buildings and facilities, and construction of underground structures like subway tunnels in urban areas give rise to significance of site investigation at urban areas. However, ambient electric noises, traffic vibrations, embedded objects work as obstacles to high-quality and accuracy in site investigation at urban areas. In this paper, a new technique called the pseudo-DC resistivity survey (in brief, PDC-R) was proposed to minimize the adverse effect of ambient electrical noises in resistivity survey. PDC-R technique utilizes an AC current with frequency range of 0.1 to 1.0 Hz rather than DC current, which is used for conventional resistivity survey. The motivation of using low-frequency AC current is to avoid 60-Hz components or its multiples in the resistivity survey which ambient noises are mostly composed of. The implementation of PDC-R technique also included the parametric study on skin effect, frequency effect and current-level effect, which led to the determination of optimal values of frequency and current level for PDC-R survey. The reliability and feasibility of PDC-R technique was verified through field tests, accompanied by the comparison with DC resistivity survey and CapSASW tests.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.269-274
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• 2013

To proportionally control the electronic valve position of the actuator, we designed and fabricated PCU, CPT, and rotary absolute optical encoder for the detection of absolute angular position in the actuator. We also designed and constructed the test system by using DAQ hardware and Labview. We designed PCU to convert 1-5 V, 0-5 V, 0-10 V, 2-10 V voltage signals and 4-20 mA current signals to the voltage signals in the common 0.5-2.5 V range. We designed CPT to output 4-20 mA current signals corresponding to the valve positions based on the PWM signal input from the MCU. We also designed 20 bit optical encoder by using infrared LED and infrared transistor and made the serial communication with the main board possible. When we tested PCU and CPT with DAQ hardware and Labview software, they operated correctly with the small errors within ${\pm}0.003$ V and ${\pm}0.01$ mA, respectively, showing that our actuator has the excellent performance to employ as the industrial proportional-valve-actuator. The resolution of the encoder was $11.25^{\circ}$ and the maximum revolution to detect was 32,768.

• Journal of Korean Academy of Nursing
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• v.30 no.4
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• pp.1035-1044
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• 2000

The purpose of this study was to develop and evaluate an internet based program for nursing informatics. The course subject, Nursing Informatics, was made by a computerized instructional module using the internet. The program was developed after taking into consideration the level of competence and knowledge in the subjects. It was based on 10 steps of the CAI module developed by Alessi and Trollip. The subjects consisted of 76 junior nursing students taking a Nursing Informatics course. Two sets of questionnaires were used for this study. First, a questionnaire was administered to 76 students to collect general information on their experience while using computers and the internet. Secondly, another questionnaire was administrated to 76 students after they took the course. They were asked to evaluate the program in terms of easiness of use, precision of contents, freshness of contents, motivation in learning, effectiveness of learning, enhancement of communication, precision of screen, and interest in the contents. IDs and passwords were given to the students. The students were asked to write their IDs and passwords when they connected to Nursing Informatics (http://hallym.ac.kr/~yhyom/ inform.html). They were led the menu page which was categorized into 8 icons (i. e., syllabus, lecture notes, quick test, Q & A board, assignment, on-line test, related web sites and mailing lists) after confirming their IDs and passwords. The students' responses were very positive. This program was a very useful in increasing the effectiveness of learning and motivation in the students. Suggest to be use for other nursing courses.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.470-475
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• 2012

$La_{1-x}Sr_xMnO_3$(LSM,$0{\leq}x{\leq}0.5$) powders as the air electrode for solid oxide fuel cell were synthesized by a glycine-nitrate combustion process. The powders were then examined by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The as-formed powders were composed of very fine ash particles linked together in chains. X-ray maps of the LSM powders milled for 1.5 h showed that the metallic elements are homogeneously distributed inside each grain and in the different grains. The powder XRD patterns of the LSM with x < 0.3 showed a rhombohedral phase; the phase changes to the cubic phase at higher compositions($x{\geq}0.3$) calcined in air at $1200^{\circ}C$ for 4 h. Also, the SEM micrographs showed that the average grain size decreases as Sr content increases. Composite air electrodes made of 50/50 vol% of the resulting LSM powders and yttria stabilized zirconia(YSZ) powders were prepared by colloidal deposition technique. The electrodes were studied by ac impedance spectroscopy in order to improve the performance of a solid oxide fuel cell(SOFC). Reproducible impedance spectra were confirmed using the improved cell, which consisted of LSM-YSZ/YSZ. The composite electrode of LSM and YSZ was found to yield a lower cathodic resistivity than that of the non-composite one. Also, the addition of YSZ to the $La_{1-x}Sr_xMnO_3$ ($0.1{\leq}x{\leq}0.2$) electrode led to a pronounced, large decrease in the cathodic resistivity of the LSM-YSZ composite electrodes.

• Journal of Plant Biotechnology
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• v.6 no.2
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• pp.91-96
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• 2004

The use of liquid-medium-based procedure relative to the solid media led to a 4.5-fold increase in the number of cotyledon-stage embryos. The most efficient system for multiplication and regeneration of somatic embryos was CP6 procedure with the media MSD40/MSD20/MSM6AC/FNL0S3S3GM. However, the rate of regeneration was lower. About 71％ of the embryos with dicotyledon were continued to develop the roots after desiccation treatment and 92％ of the germinated embryos produced shoots in 10 days. Of the four morphologically different types of embryos, dicotyledonous ones showed a high frequency of conversion, while only a few with fused and horn type cotyledon developed shoots. Mature somatic embryos were desiccated in empty petri dishes for 12-72 h. Embryo survival rate was the highest after 12 h of desiccation, but maximal germination was observed at 24 h. After desiccation, they were placed on MS medium without growth regulators for germination. Germinating embryos were transferred to small pots with vermiculite for plant regeneration. The etiolating the plants during the growth was resolved to add 1％ activated charcoal on hormone-free MS medium.