• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.55-60
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• 2017

Capacitor Charging Power Supply(CCPS) is one of the most important components of a pulsed power system. The CCPS is widely used in source of lasers, accelerators and plasma generators. This paper presents design of a dead time control circuit and operation characteristics for stable high repetition rate of high voltage CCPS. The CCPS consists of battery, high voltage transformer and controller with a dead time control circuit. A dead time control circuit was simulated by PSpice. The performance test of the CCPS was carried out with a 7[nF] load capacitor at output voltage of 50[kV] and a pulse repetition frequency of 100[Hz]. As a result, we can verify that charging and discharging waveform is stable at 100[Hz]. The experiment results indicate that 3[ms] dead time made it possible for stable high repetition rate of 100[Hz]. This paper paves the way for designing an advanced CCPS which is more applicable outside experiments.

• Journal of Chest Surgery
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• v.16 no.3
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• pp.272-280
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• 1983

With respect to controversial opinions concerning the nitroglycerin effects on cardiac muscle the direct nitroglycerin actions were thoroughly studied in isolated papillary muscles, atrial preparations and coronary strips of rabbits. Isometric active tension of papillary muscles developed at $35^{\circ}C$ upon electric stimulation at a rate of 60/min, was not affected by nitroglycerin up to a concentration of 10mg/L Higher concentrations of nitroglycerin, however, reduced action tension progressively. This depression of mechanical activity is accompanied by a decrease in oxygen consumption as measured by means of a flow respirometer. Resting oxygen uptake, on the other hand, remained unchanged. Similarly active tension of spontaneously beating atrial preparations also declined at a nitroglycerin concentration of more than 10 mg/L, whereas the sinus frequency did not change up to 40 mg/L. In contrast, rabbit coronary strips are much more sensitive to nitroglycerin and relax in a range of 10-100 ug/L of nitroglycerin concentration. The results indicate that the pharmacologic effects of nitroglycerin in coronary disease are due to vascular actions, because the plasma levels of nitroglycerin attainable in human therapy are not sufficiently high to directly influence the myocardium.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.91-91
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• 2000

a-C:H 혹은 a-SiC:H 박막은 광전소자 및 태양전지 등의 개발에 있어서 중요한 물질이다. 우리는 a-C:H 및 a-SiC:H 박막을 PECVD (plasma-enhanced chemical vapor deposition) 방법으로 증착시키고, 박막의 가열에 따른 스핀밀도의 변화를 ESR (electron spin resonance) 측정을 통하여 조사하였다. PECVD 증착가스는 Ch4, SiH4 가스를 사용하였고, 기판은 Corning 1737glass를 사용하였으며, 기판 온도는 300-40$0^{\circ}C$, 증착 압력은 0.1-0.3 Torr, r.f. 전력은 3-36W 사이에서 변화되었다. ESR 측정은 상온 X-band 영역에서 수행되었고, modulation amplitude는 2.5G, modulation frequency는 100kHz 이었다. a-C:H 혹은 a-SiC:H 박막은 진공상태의 reactor, 혹은 공기중의 furnace 안에서 300-50$0^{\circ}C$ 영역에서 3-8시간 정도 가열되거나, 혹은 상온에서 약 50$0^{\circ}C$ 정도까지 단계적으로 가열되었다. 증착된 a-C:H 박막의 초기 구조는 Raman 측정으로부터 polymer-like Carbon으로 추정되었으며, 300-35$0^{\circ}C$ 가열시 초기 1시간 정도 사이에는 스핀밀도가 증가되었으나, 그 후 8시간 정도까지의 가열의 경우에도 대체로 동일하게 나타났다. 또한 상온으로부터 약 50$0^{\circ}C$까지 단계적으로 온도를 높여주며, 각 단계마다 1시간씩 가열했을 때도 30$0^{\circ}C$ 정도까지는 스핀밀도가 증가하다가 더 높은 온도로 가면서 다시 스핀밀도가 감소함을 볼 수 있었다. 이러한 스핀밀도의 초기 증가 및 감소를 일으키는 메카니즘에 대해서 논의해 볼 것이다.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.100-108
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• 2023

In this study, a neural network model inspired by a one-dimensional convolution U-net is developed to automatically accelerate edge localized mode (ELM) detection from big diagnostic data of fusion devices and increase the detection accuracy regardless of the hyperparameter setting. This model recognizes the input signal patterns and overcomes the problems of existing detection algorithms, such as the prominence algorithm and those of differential methods with high sensitivity for the threshold and signal intensity. To train the model, 10 sets of discharge radiation data from the KSTAR are used and sliced into 11091 inputs of length 12 ms, of which 20% are used for validation. According to the receiver operating characteristic curves, our model shows a positive prediction rate and a true prediction rate of approximately 90% each, which is comparable to the best detection performance afforded by other algorithms using their optimized hyperparameters. The accurate and automatic ELM-burst detection methodology used in our model can be beneficial for determining plasma properties, such as the ELM frequency from big data measured in multiple experiments using machines from the KSTAR device and ITER. Additionally, it is applicable to feature detection in the time-series data of other engineering fields.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.52.1-52.1
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• 2019

Exploring the vicinity of super-massive black holes (SMBHs) is one of the frontiers in astrophysics. KaVA AGN Science WG has launched its Large Program in 2014 focusing on two SMBHs, Sgr A∗ and M87. They are selected based on their large apparent size. Sgr A∗ is the excellent laboratory for studying gas accretion process onto SMBH and M87 is well known as the best case for investigating plasma outflow ultimately driven by SMBH. For Sgr A∗, KaVA and EAVN provides superb UV-coverage on its emitting region and its scattering medium. In the case of M87, we have conducted high cadence dual-frequency (22and 43GHz )VLBI monitoring to clarify the global profile of the M87 jet velocity field and the spectral index map, which should reflect global structure of magnetic fields in the jet. From 2017, the AGN LP is recognized as multi-wavelength EHT project, conducting quasi-simultaneous coherent observations of M87 and Sgr A∗ with the Event Horizon Telescope (EHT) during its campaign observation periods. AGN WG is reviewing and revising its LP to convert it to EAVN LP. We will briefly report our scientific results and future plan which includes even broader international collaboration, namely East-Asia to Italy Nearly Global (EATING) VLBI to reach higher angular resolution.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.407-410
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• 2018

As the operating frequency of an electromagnetic wave increases, the maximum output and wavelength of the wave decreases, so that the size of the circuit cannot be reduced. As a result, the fabrication of a circuit with high power (of the order of or greater than kW range) and terahertz wave frequency band is limited, due to the problem of circuit size, to the order of ${\mu}m$ to mm. In order to overcome these limitations, we propose a source design technique for 0.1 THz~0.3 GW level with cylindrical shape (diameter ~2.4 cm). Modeling and computational simulations were performed to optimize the design of the high-power electromagnetic sources based on Cherenkov radiation generation technology using the principle of plasma wakefield acceleration with ponderomotive force and artificial dielectrics. An effective design guideline has been proposed to facilitate the fabrication of high-power terahertz wave vacuum devices of large diameter that are less restricted in circuit size through objective verification.

• Analytical Science and Technology
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• v.19 no.6
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• pp.535-543
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• 2006

Being used widely in semiconductor and display manufacturing, $NF_3$ is internationally considered as one of the regulated compounds in emission. Numerous companies have been continuously trying to reduce the emissions of $NF_3$ to comply with the global environmental regulation. This work is made to report the destruction and removal efficiency (DRE) of electrically heated scrubbers and the use rate in process chambers installed in three main LCD manufacturing companies in Korea. As the measurement techniques for $NF_3$ emission, mass flow controlled helium gas was continuously supplied into the equipment by which scrubber efficiency is being measured. The partial pressures of $NF_3$ and helium were accurately measured for each sample using a mass spectrometer, as it is emitted from inlet and outlet of the scrubber system. The results show that the DRE value for electrically heated scrubbers installed before 2004 is less than 52 %, while that for the new scrubbers modified based on measurement by scrubber manufacturer has been sigificentely improved upto more than 95 %. In additon, we have confirmed the efficiency depends on such variables as the inlet gas flow rate, water content, heater temperature, and preventative management period. The use rates of $NF_3$ in process chambers were also affected by the process type. The use rate of radio frequency source chambers, built in the $1^{st}$ and $2^{nd}$ generation process lines, was determined to be less than 75 %. In addition, that of remote plasma source chambers for the $3^{rd}$ generation was measured to be aboove 95 %. Therefore, the combined application of improved scrubber and the RPSC process chamber to the semiconductor and display process can reduce $NF_3$ emmision by 99.95 %. It is optimistic that the mission for the reduction of greenhouse gas emission can be realized in these LCD manufacturing companies in Korea.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.7
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• pp.858-868
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• 2008

This study was carried out to investigate the effects of Gastrodiae Rhizoma powder on plasma lipid profiles in elderly volunteers with hyperlipidemia, hypertension, diabetes or heart disease. 32 elderly people, 11 males and 21 females aged $60{\sim}77$ years, were given Gastrodiae Rhizoma powder 15 g twice daily for 6 months. We investigated the antheropometric data, general characteristics and dietary habit by using questionnaires. Fasting blood samples were collected from the subjects before and after this 6 months intervention study. Blood pressure, glucose, hemoglobin and lipid levels of plasma, atherogenic index (AI) and cardiac risk factors (CRF, LHR, HTR) were determined before and after consumption of Gastrodiae Rhizoma powder. The mean body mass index (BMI) of the male and female subjects were 22.4 and 23.6, respectively. The percent of ideal body weight (PIBW) of males and females were 105.6% and 122.3%, respectively. The subjects had decreased intake frequency of fish and meat in their dietary habit. After consumption of Gastrodiae Rhizoma powder, there were no significant differences in blood pressure; however, the blood glucose significantly decreased with Gastrodiae Rhizoma intake in the males. In the subjects, the levels of plasma total cholesterol, triglyceride, and LDL-cholesterol were decreased by the consumption of Gastrodiae Rhizoma powder; while the levels of plasma LDL-cholesterol was significantly decreased in female. Blood pressure and biochemical assessment (blood glucose, hemoglobin, triglyceride, total cholesterol, LDL and HDL-cholesterol) of the subjects were within the normal range. It was found that AI, CRF and LHR were significantly decreased by Gastrodiae Rhizoma intake. The present results indicate that dietary supplementation of Gastrodiae Rhizoma improved lipid metabolism and cardiac risk factor in cardiovascular disease.

• Nutrition Research and Practice
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• v.11 no.3
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• pp.232-239
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• 2017

BACKGROUND/OBJECTIVES: Increased consumption of instant noodles has recently been reported to be positively associated with obesity and cardiometabolic syndrome in South Korea, which has the highest per capita instant noodle consumption worldwide. This study aimed to investigate the association between instant noodle consumption and cardiometabolic risk factors among college students in Seoul. SUBJECTS/METHODS: The study subjects consisted of 3,397 college students (1,782 male; 1,615 female) aged 18-29 years who participated in a health checkup. Information on instant noodle consumption was obtained from the participants' answers to a question about their average frequency of instant noodle intake over the 1 year period prior to the survey. RESULTS: Statistical analysis using a general linear model that adjusted for age, body mass index, gender, family income, health-related behaviors, and other dietary factors important for cardiometabolic risk, showed a positive association between the frequency of instant noodle consumption and plasma triglyceride levels, diastolic blood pressure, and fasting blood glucose levels in all subjects. Compared to the group with the lowest frequency of instant noodle intake (${\leq}1/month$), the odds ratio for hypertriglyceridemia in the group with an intake of ${\geq}3/week$ was 2.639 [95% confidence interval (CI), 1.393-5.000] for all subjects, while it was 2.149 (95% CI, 1.045-4.419) and 5.992 (95% CI, 1.859-21.824) for male and female students, respectively. In female students, diastolic blood pressure was also higher among more frequent consumers of instant noodles. CONCLUSIONS: Our results suggest that frequent consumption of instant noodles may be associated with increased cardiometabolic risk factors among apparently healthy college students aged 18-29 years.

• Biomolecules & Therapeutics
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• v.15 no.1
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• pp.58-64
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• 2007

The previous study reported the biological effect of magnetic field exerted by acting on endocrine and anti-oxidant system. The present study aims to study whether ELF-MF (extremely low frequency magnetic field) affects the physiological endocrine systems such as thyroid and whether ELF-MF affects the defense system against oxidative stress when it alters the function of thyroid. Finally, we correlate the effects of MF on oxidative stress, and adrenal and thyroid with an environmental stress factor. We exposed sham or MF to rats for 5 or 25 days. After the exposure, we determined pain sensitivity, level of TSH, $T_3$ and free $T_4$ in plasma. We also assayed in whole brain, lipid peroxidation, the activity of enzymatic anti-oxidant defense including superoxide dismutase(SOD) and glutathione peroxidase (GPx), and non enzymatic defense such as reduced or oxidized glutathione contents. MF induced the hypersensitivity to thermal stimuli with the reduction of latency. $T_3$ and $T_4$ levels were also increased by the exposure of MF. In addition, we observed the rise of MDA level in rat brain by MF although the MF did not change superoxide dismutase and glutathione peroxidase activity. The effect of MF on both reduced and oxidized glutathione results in decrease in reduced or oxidized glutathione in whole brain. In every experiment, there was no significant difference in MF influence between short term (5 days) and long term (25 days) exposure. Taken together, MF exposure affects the thyroid hormonal control in brain. The elevated thyroid hormone acts on brain, leading to hyper-utilization of oxygen. This phenomenon may be correlated with oxidative stress resulting from MF exposure. In conclusion, we suggest that MF exposure may be an environmental stress by exerting oxidative stress.