• Journal of Power Electronics
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• v.17 no.4
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• pp.942-952
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• 2017

Modular multilevel converters (MMCs) have been receiving extensive research interest in high/medium-voltage applications due to its modularity, scalability, reliability, high-voltage capability, and excellent harmonic performance. Submodule capacitors are usually rather bulky because they have to withstand fundamental frequency voltage fluctuations. To reduce the capacitance of these capacitors, this study proposes a modified MMC with an active power decoupling circuit within each submodule. The modified submodule contains an auxiliary half bridge, with its capacitor split in two. Also, the midpoints of the half bridge and the split capacitors are connected by an inductor. With this modified submodule, the fundamental frequency voltage fluctuation can be suppressed to a great extent. The second-order voltage fluctuation, which is the second most significant component in submodule voltage fluctuations, is removed by the proper control of the second-order circulating current. Consequently, the submodule capacitance is significantly reduced. The viability and effectiveness of the proposed new MMC are confirmed by the simulation and experimental results. The proposed MMC is best suited for medium-voltage applications where power density is given a high priority.

• Korean Journal of Health Education and Promotion
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• v.9 no.2
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• pp.103-120
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• 1992

The purpose of this study was designed for the model development of curriculum of school health education including learning-teaching method, through analysis of results compared between a regular schedule health instruction and irregular health education. And this study is an attempt to give fundamental information for establishing of school health subject as the concept and scope of the school health subject is still not recognized and accepted satisfactorily in Korea. The data were collected by questionnaire from middle school girls and were carried out from 1989 to 1991. The major results obtained from this study were as follows: A Analysis of the case of school health. instruction 1. The responses of students about health eaducation : The positive rate of answers on the 'Health education is very important subject' was 91.2%, and on the 'I can maintain well healthful life : int of selfcare' was 87.1%. 2. The condition on knowledge, attitude and practice about health education: Education group had higher scores than comparison group about all most of questions, especially sex-education and drug abuse prevention education. 3. All the case of disease early founded out during the health instruction were children disease such as bone-tumor, lymphoma, hydrocephalus, and leukemia. B. Model development of school health education 1. Component of the health education subject (1) Healthful Life → Personal Health (2) Physical anatomy and Prevention of disease → Community Health (3) Growth and Development(sex education) → Community Health (4) Environment and Health → Community Health (5) Previntion of drug abuse → Human Health (6) Safety life → Human Health 2. Leanning - teaching method of health instruction (1) A Model of leaning-teaching method : A regular circulating health instruction by the component health subject for 2 hours a month. (2) B Model of leaning-teaching method : A regular schedule health education for hour a week.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1614-1627
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• 2016

The purpose of this paper is to investigate the united Electromagnetic characteristics for the effective monitoring on the static air-gap eccentricity (SAGE) of turbo-generator. Different from other studies, this paper not only studies on the unbalanced magnetic pull (UMP) and the vibration characteristics of the stator and the rotor, but also investigates the harmonic features of the magnetic flux density and the circulating current inside the parallel branches (CCPB). The theoretical calculation, together with the finite-element-method (FEM) simulation and the experiment verification, is taken for a SDF-9 type non-salient generator. It is shown that, when SAGE occurs, apparent double-frequency UMP and vibrations will be produced both on the stator and the rotor, while the CCPB will have an obvious increment at the $1^{st}$ harmonic component. In addition, the amplitude of the magnetic flux density will be of cosine distribution in the circumferential position of the air-gap, while in normal condition it is a constant. Moreover, the pass-band amplitude, together with the $1^{st}$ harmonic of the magnetic flux density, will be enlarged as well. These united electromagnetic characteristics can be used as the diagnosis and monitoring criterion for SAGE.

• Journal of Environmental Science International
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• v.27 no.6
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• pp.467-475
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• 2018

The lifetime of the electrode is one of the most important factors on the stability of the electrode. Since the lifetime of the DSA (Dimensionally stable anode) electrode is long, an accelerated lifetime test is required to reduce the test time. Beacuse there is no basis or standard method for accelerated lifetime testing, many researchers use different methods. Therefore, there is a need for basis and methods for accelerated lifetime testing that other researchers can follow. We designed a reactor system for accelerated lifetime testing and planned specific methods. Reactor system was circulating batch reactor. Reactor volume and cooling water tank were 12.5 L and 100 L, respectively. Electrode size was $2cm{\times}3cm$ (real electrolysis area, $5cm^2$). In order to maintain the harsh conditions, accelerated lifetime test was carried out in a high current density ($0.6A/cm^2$) and low electrolyte concentration (NaCl, 0.068 mol/L). Maintaining a constant temperature was an important operation parameter for exact accelerated lifetime test. As the accelerated lifetime test progressed, the active component of electrode surface was consumed and desorption occurred. At the point of 5 V rise, corrosion of the surface of the base material(titanium) also started.

• Clinical and Experimental Reproductive Medicine
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• v.26 no.2
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• pp.271-274
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• 1999

Activated factor XII (FXIIc: Hageman factor) is a central component of the contact activation system of blood coagulation, fibrinolysis, and kinin formation. Although patients deficient in FXIIc (up to 50% of normal) do not show increased bleeding tendency, thrombotic complications were reported in 8% to 10% among these patients. The reduced generation of bradykinin resulting in diminished release of tissue plasminogen activator is proposed as a cause of thrombosis in factor XII (FXII)-deficient patients. Similarly, in patients with elevated levels of circulating antiphospholipid antibodies, hemostasis may be impaired resulting in excessive thrombophilia. Both vascular and placental thromboses because of antiphospholipid antibodies or FXIIc deficiency have been reported to be associated with recurrent fetal loss. We have experienced a case of factor XII deficiency in woman with recurrent spontaneous abortion. So we report this case with a brief review of literatures.

• CELLMED
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• v.10 no.3
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• pp.24.1-24.6
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• 2020

Kushta Jast (KJ) is a unique herbo-mineral preparation of the Unani System of Medicine (USM) which is prepared by taklis (calcination) and prescribed by the practitioners of USM for the treatment of various ailments, including the respiratory ailments. It is used as muqawwi (tonic) to boost the immunity (Muqawwi-i-badan), and can increase the phagocyte activity of the immune cells, thereby, promoting the growth and spread of lymphocytes and increasing circulating antibodies to neutralize a harmful pathogen and reduce humma or body fever (Dafi'-i-humma). Incidentally, the principal mineral component of KJ, zinc, has been widely acknowledged for its beneficial influence on the immune function, and decrease the risk of developing serious respiratory illnesses. In this manuscript, we provide a glimpse of the literature on KJ and postulate its potential beneficial effects in respiratory infections, including COVID-19.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1639-1649
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• 2016

This paper presents a family of soft-switching DC-DC converters with a simple auxiliary circuit consisting of a coupled winding and a pair of auxiliary switch and diode. The auxiliary circuit is activated in a short interval and thus the circulating conduction losses are small. With the auxiliary circuit, zero-voltage-switching (ZVS) and zero-current-switching are achieved for the main and auxiliary switches respectively, over wide input voltage range and load variation. In addition, the reverse-recovery problem of diodes is significantly alleviated because of the leakage inductor. Furthermore, the coupled inductor simultaneously serves as the main and auxiliary inductors, contributing to reduced magnetic component in comparison with the conventional zero-voltage-transition (ZVT) converters. Experimental results based on a 500 W prototype buck circuit validate the advantages and effectiveness of the proposed magnetic coupling ZVS converter.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.9-13
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• 2004

This paper proposes a modified current differential relay for Y-$\Delta$ transformer protection. The relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. A method to estimate the circulating component of the delta winding current is proposed. To cope with the remanent flux, before saturation, the core-loss current is calculated and used to modify the measured differential current. When the core then enters saturation, the initial value of the flux is obtained by inserting the modified differential current at the start of saturation into the magnetization cure. Thereafter, the core flux is then derived and used in conjunction with the magnetization curve to calculate the magnetizing current. A modified differential current is then derived that compensates for the core-loss and magnetizing currents. The performance of the proposed differential relay was compared against a conventional differential relay. Test results indicate that the modified relay remained stable during severe magnetic inrush and over-excitation because the exciting current was successfully compensated. The relay correctly discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

• International Journal of Industrial Entomology and Biomaterials
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• v.40 no.1
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• pp.16-21
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• 2020

Humans use insects as food and traditional medicine for many years. Hemolymph is the circulating fluid of insects and is a key component of their immune system. However, limited information is available regarding hemolymph identification, development, and differentiation, as well as the related cellular immune responses. In a previous study, hemolymph extracts prepared from Bombyx mori larvae were found to exert anti-inflammatory effects. In this study, we aimed to identify and compare the antioxidant activity of immune-challenged and unchallenged B. mori hemolymph extracts in vitro. For this purpose, human epithelial Caco-2 cells were first exposed to oxidative stress and then treated with various concentrations and incubation times of either immune-challenged or unchallenged B. mori hemolymph extracts. Next, we determined the effect of treatment on the relative expression of GPX-1, SOD-1, and SOD-2 antioxidant marker genes. We found that the expression rates of the three marker genes were markedly higher at a immune-challenged hemolymph extract concentration of 80 ppm compared to those at other concentrations, and the antioxidant effects were enhanced after treatment for 48 hr. Thus, B. mori hemolymph extracts showed antioxidant activity within the limited time and dose. Especially, the immune-challenged B. mori hemolymph extracts showed higher the antioxidant activities than unchallenged one. The activity of silkworm hemolymph extracts could facilitate the development of new types of functional foods, feed additives, and biomaterials with antioxidant properties.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.772-776
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• 2001

The flow structures of turbulent shear layer behind oil fences with different tip configurations were investigated experimentally using flow visualization and PIV velocity field measurement. An oil fence was installed in a circulating water channel and the flow structure around the fence tip was mainly analyzed in this experiment. The four tip configurations tested in this experiment are knife edge; semi-circle edge, circular edge and rectangular edge. The 300 instantaneous velocity fields were measured using the single-frame PIV system and they were ensemble averaged to give the mean velocity field and spatial distribution of turbulent statistics. Free stream velocity was fixed at 10ms/sec and the corresponding Reynolds number based on the fence height was Re=4000. As a result, for the oil fence with rectangular edge, the streamwise velocity component was decreased. On the other hand it was increased for the oil fence with circular edge. For all four fences tested in this study, general flow pattern of the lower shear layer is analogous but the upper layer shows difference depending on the tip configurations. The oil fence with circular edge has more diffusive upper shear layer than that of the others. The shear layer of the oil fence with rectangular edge has relatively thin thickness. The oil fence with circular edge was found to be proper shape for tandem fence.