• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.761-765
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• 2006

At present, harmonic currents cause serious problems in power conversion system using the semiconductor switching device. Also some of the conversion system provokes harmonic currents against to the main power supply system and causes hindrances for the system. Main power impedance of the traditional LC passive filter method, influences on the filter characteristics and amplifies the harmonics when resonance phenomenon is occurred. And the traditional existing 2 level inverter systems show the limit in capacity of voltage and current in case of occurring sudden load change. So, to solve this problem active filter which uses cascaded H-bridge multi level inverter has been designed and ex-filter system circuits were totally investigated. With multi level active filtering system not only the size of filter but also the size of filter for transformer can be reduced by half and so as to the weight, while the capacity of inverter can be double sized and wave forms can be compensated exactly and precisely. Also by the benefit of the increase in rating capacity, the various currents owing to the load fluctuation can be dealt more steadily. In order to simulate the wave form of harmonics based on the measured data on the AC 25kV high speed Domestic Commercial railway, it was simulated with PSCAD/EMTDC and PSIM. Based on the results of this demonstration, the power supply system and inverter system would be more stable and also promoting its efficiency.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.394-403
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• 1994

Chaos characteristics of laser diodes with external optical feedback is investigated. For a FabryPerot resonator laser, optical feedback by external mirror is assumed. The simulation is performed in such a way that a current of $1.3J_{th}$ is injected into the $1.3{\mu}m$wavelength "InGaAsP" buried hetero structure laser. With the increment of K, the system shows the evolution of four steps as follows: i) When the optical feedback coefficient K is very small, the relaxation oscillation is damped and the system reaches the steady state showing the stable operation characteristics. ii) As K increases a little bit, the relaxation oscillation is not damped any more and the system begins to maintain the periodic oscillation. iii) When K is increased further, the oscillation shows the larger amplitude and the long periodic length. iv) When K is increased very large, the system gets unstable and enters into the coherejlce collapse state. state.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.110-123
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• 2016

Since increase in energy consumption and environmental issues started to grab global attention, various countries have had their own supporting policy to promote supply of renewable energy which is a stable and eco-friendly energy source. This study analyses Korean Renewable Portfolio Standard by comparative analysis of current policies in major countries in respect of design components of a pragmatic industrial policy system, such as political leadership, policy coordination and consultative committee discussion, and policy enforcement with responsibility and transparency. This is to identify problems and to present political suggestions for successful management of the standard based on a fundamental concept of the pragmatism industrial policy. It is predicted that the strategic cooperation between a market and a government leads to industry development as the relationships of two parties are regarded not as antagonistic but as complementary.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.4
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• pp.15-26
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• 2013

In recent years, river maintenance projects using natural methods have been continuously implemented in urban areas and methods emphasizing ecology are being developed and constructed in revetment areas. However, there is insufficient technical review on the hydraulic stability of those revetment methods during the event of flood. Therefore, a hydraulic analysis is necessary for the stream where revetments are applied. This study was conducted to develop an objective test method for the hydraulic stability of green revetment media. For this purpose, hydraulic model tests were performed for the green base materials for revetments. Tests were conducted using experimental devices for the hydraulic model which were installed to simulate the rapid current during the flood. Loss of soil by the hydraulic condition was compared and analyzed with that of dry green revetment media, and the evaluations were made on the corrosion resistance, tractive force, and contractile force. Test results showed that green revetment media had higher corrosion resistance in non-vegetation condition compared to dry green revetment media, and the loss of base materials by the rooting of vegetation showed significant reduction by the vegetation. In addition, results of the allowable tractive force of the base material indicated it is relatively stable in vegetation condition but scouring can occur in non-vegetation condition. Therefore, the development of vegetation in revetment areas is anticipated to be effective for the stability of revetment areas by reducing external forces interacting with the corrosion resistance and stream bank. The green revetment media in expected to contribute to the stability of revetment areas.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.95-102
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• 2009

A steam generator (boiler) in thermal power plants, consisting of more than 30,000 parts and components, can lead to the plant shutdown with damage to even the small part of the components; esp., like weld failures on boiler tubes. Consequently it is greatly demanded to improve the quality of the weld on the boiler tube for the stable operation of the power plants. Because of the feature of the welding, which is done past by melting the work pieces and adding a filler material that cools to become a strong coalescence, there is a great possibility that weld failures take place. As a result, it is regulated to make a non-destructive testing, like radiography test, to detect defects and flaws in the weld. The current film radiography test provides a lower image quality exceeding 2.0% of a basic quality level for a penetrameter, it is very likely to fail to detect micro defect. As a result, the prevention for the boiler tube failure has not been made effectively. In this study, computed radiography technology has been applied as a digital radiography test to the boiler tube weld, and Se-75 radiation source was used to improve the image quality, instead of Ir-192 source. As a result of this study, it is proven to save the time and cost for test and to enhance the quality level of penetrameter penetrating image, which enables to upgrade the quality of radiography test to the boiler tube weld.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.4
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• pp.349-355
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• 2018

This study interrogated multi-layer heterojunction anodes were interrogated for potential applications to water treatment. The multi-layer anodes with outer layers of $SnO_2/Bi_2O_3$ and/or $TiO_2/Bi_2O_3$ onto $IrO_2/Ta_2O_5$ electrodes were prepared by thermal decomposition and characterized in terms of reactive chlorine species (RCS) generation in 50 mM NaCl solutions. The $IrO_2/Ta_2O_5$ layer on Ti substrate (Anode 1) primarily served as an electron shuttle. The current efficiency (CE) and energy efficiency (EE) for RCS generation were significantly enhanced by the further coating of $SnO_2/Bi_2O_3$ (Anode 2) and $TiO_2/Bi_2O_3$ (Anode 3) layers onto the Anode 1, despite moderate losses in electrical conductivity and active surface area. The CE of the Anode 3 was found to show the highest RCS generation rate, whereas the multi-junction architecture (Anode 4, sequential coating of $IrO_2/Ta_2O_5$, $SnO_2/Bi_2O_3$, and $TiO_2/Bi_2O_3$) showed marginal improvement. The microscopic observations indicated that the outer $TiO_2/Bi_2O_3$ could form a crack-free layer by an incorporation of anatase $TiO_2$ particles, potentially increasing the service life of the anode. The results of this study are expected to broaden the usage of dimensionally stable anodes in water treatment with an enhanced RCS generation and lifetime.

• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.153-178
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• 2000

Dental prosthetic restoration shows a big difference of cost per itemized unit depending on the size of dental labs, facility standard, manpower, and performance. Even the same dental labs have distinctive cost according to manufacturing performance, inflation, and the number of workers. However, in apite of such a change of circumstances, it appears to be quite stable in the relative cost per itemized unit unless the manufacturing trend of particular item changes dramatically. Therefore, if the relative number of cost per itemized unit, which is produced by costing, is indicated, we are able to utilize it effectively as a standard wage estimate. If the wage of dental prosthetic restoration is determined on the basis of cost, it is desirable that the relative value of cost and that of wage are identical. But, by means of comparative analysis, since the relative value of wage reveals mostly lower than that of cost depending on an item, it is considered that the wage is not reflecting the cost approproately. Due to the subdivision and the profession of medical technology, the new development of wage items for dental prosthetic restoration is required. This means that the need for the establishment of new wage items should be presented as the general concept of dental prothetic restroation changes and the level of pathologic technology increases. The current wage structure has differences in the degree of difficulty accroding to unit items and in the cost factors. Nevertheless, the differences are not reflected enough to the wage, so there is potential to lower the medical quality through the use of low-proce materials to avoid the increase of cost and the work process which skips a manufacturing step. The new items of dental prosthetic restoration also increases, but the development of proper numerical value system is not supported. Thus, the right proce is set mostly by applying to the wage of a similar item. Since most wages are established by an individual agreement between the dental clinic institute and the dental labs, the propriety of wage level lacks. Therefore, it is urgent to provide and promote the system of a fair work charge by a standard cost which can be applied to all medical institute.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.7
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• pp.3213-3218
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• 2012

When patients with advanced breast cancer (ABC) are treated with neoadjuvant chemotherapy (NACT), efficacy is monitored by the extent of tumor shrinkage. Since their publication in 1981, World Health Organization (WHO) guidelines have been widely practiced in clinical trials and oncologic practice, for standardized tumor response evaluation. With advances in cancer treatment and tumor imaging, a simpler criterion based on one-dimensional rather than bi-dimensional (WHO) tumor measurement, named Response Evaluation Criteria in Solid Tumors (RECIST) was introduced in 2000. Both approaches have four response categories: complete response, partial response, stable disease and progressive disease (PD). Bi-dimensional measurement data of 151 patients with ABC were analysed with WHO and RECIST criteria to compare their response categories and inter criteria reproducibility by Kappa statistics. There was 94% concordance and 9/151 patients were recategorized with RECIST including 6/12 PD cases. RECIST therefore under-estimates and delays diagnosis of PD. This is undesirable because it may delay or negate switch over to alternate therapy. Analysis was repeated with a new criteria named RECIST-Breast (RECIST-B), with a lower threshold for PD (${\geq}10%$ rather than ${\geq}20%$ increase of RECIST). This showed higher concordance of 97% with WHO criteria and re-categorization of only 4/151 patients (1/12 PD cases). RECIST-B criteria therefore have advantages of both ease of measurement and calculations combined with excellent concordance with WHO criteria, providing a practical clinical tool for response evaluation and offering good comparison with past and current clinical trials of NACT using WHO guidelines.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.2
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• pp.623-627
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• 2014

Background: Esophagus cancer (EC) is among the five most common cancers in both sexes in Iran, with an incidence rate well above world average. Social rank (SR) of individuals and regions are well-known independent predictors of EC incidence. The aim of current study was to assess gender and social disparities in EC incidence across Iran's provinces through 2003-2009. Materials and Methods: Data on distribution of population at province level were obtained from the Statistical Centre of Iran. Age-standardized incidence rates of EC were gathered from the National Cancer Registry. The Human Development Index (HDI) was used to assess the province social rank. Rate ratios and Kunst and Mackenbach relative indices of inequality ($RII_{KM}$) were used to assess gender and social inequalities, respectively. Annual percentage change (APC) was calculated using joinpoint regression. Results: EC incidence rate increased 4.6% and 6.5% per year among females and males, respectively. There were no gender disparities in EC incidence over the study period. There were substantial social disparities in favor of better-off provinces in Iran. These social disparities were generally the same between males and females and were stable over the study period. Conclusions: The results showed an inverse association between the provinces' social rank and EC incidence rate in Iran. In addition, I found that, in contrast with international trends, women are at the same risk of EC as men in Iran. Further investigations are needed to explain these disparities in EC incidence across the provinces.

• Journal of Microbiology and Biotechnology
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• v.13 no.2
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• pp.217-224
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• 2003

Previously, we developed a CHO cell line (CHO-OTC1-Al9) that expresses the first two enzymes in the urea cycle and exhibits a higher ammonia-removing ability and faster growth rate than a vector-controlled CHO cell line (CHO-neo-5). The current study was undertaken to develop a cell line with an ammonia-removing ability higher than the cell line developed previously. To accomplish this, CHO cell lines expressing the first three, first four, or all five enzymes of the urea cycle were constructed using a stable transfection method. Finally, the CHO-AS-16, CHO-AL-19, and CHO-Arg-11 cell lines expressing the first three, first four, and all five enzymes of the urea cycle, respectively, were selected and found to exhibit higher ammonia-removing ability than the CHO-OTC1-Al9 cell line. Among the three selected cell lines, CHO-AL-19 showed the highest ammonia-removing ability and highest cell viability at a higher cell density, with 40% and 15% lower ammonia concentration in the, culture media than that of CHO-neo-5 and CHO-OTC1-A19 cell lines, respectively. CHO-AL-19 also showed 44% and 10% higher cell viability than the CHO-neo-5 and CHO-OTC-Al9 cell lines, at a higher cell density, respectively. The ammonia concentrations in the culture media were expressed as the ammonia concentration/cell, and the CHO-AL-19 cells revealed 45-60% and 20% lower ammonia concentration/cell than the CHO-neo-5 and CHO-OTC1-Al9 cells, respectively.