• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.75-81
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• 2021

This study analyzes the resonance characteristics caused by the mutual interference between LCL filters and the grid impedance under the parallel operation of the grid-connected inverter using the LCL filter. These characteristics are verified through simulation and experiment. Two inverters are used to connect to the grid in parallel, and the system parameters, including the LCL filter, are set to the same conditions. In the case of inverters running in parallel at the point of common coupling, the presence of grid impedance causes mutual interference between the LCL filters of each inverter, and the deviation of the filter resonance frequency is analyzed to understand the parallel inverter. The correlation between the number of devices and the size of grid impedance is simulated by PSIM and verified by MATLAB. By connecting the real-time digital simulator Typhoon HILS to the DSP 28377 control board, the mutual interference characteristics are tested under the condition of two inverters running in parallel. The experimental and analysis results are the same, indicating the validity of the analysis.

• Journal of Forest and Environmental Science
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• v.37 no.4
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• pp.269-279
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• 2021

This study was carried out to introduce the forest cover types of the Baekdudaegan inhabiting the number of native tree species. In order to understand the vegetation distribution characteristics of the Baekdudaegan, a vegetation survey was conducted on the major 20 mountains of the Baekdudaegan. The vegetation data were collected from 3,959 sample points by the point-centered quarter method. Each mountain was classified into 4-7 forests by using various multivariate statistical methods such as cluster analysis, indicator species analysis, multiple discriminant analysis, and species composition analysis. The forests were classified mainly according to the relative abundance of Quercus mongolica. There was a total of 111 classified forests and these forests were integrated into the following nine forest cover types using the percentage similarity index and by clustering according to vegetation type: 1) Mongolian oak, 2) Mongolian oak and other deciduous, 3) Oaks (Mixed Quercus spp.), 4) Korean red pine, 5) Korean red pine and oaks, 6) ash, 7) mixed mesophytic, 8) subalpine zone coniferous, and 9) miscellaneous forest. Forests grouped within the subalpine zone coniferous and miscellaneous classifications were characterized by similar environmental conditions and those forests that did not fit in any other category, respectively.

• Korean Journal of Adult Nursing
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• v.13 no.4
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• pp.571-580
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• 2001

"Journal of Korean Academy of Adult Nursing" has been published since 1989 and more than 330 articles have been published up 2000. We reviewed all the articles published in this journal to analyze the contents and trend of published articles and to find out the way of improvement both in quantity and quality of studies in this area. The results are as follows; 1) Ninety percent of articles were quantitative studies. Experimental design was used in 16.1% and quasi-experimental design was adapted in 73.6% of articles. Qualitative research were 10.3% of total articles reviewed. 2) Only 5.1% of articles described theoretical framework and 73.6% of experimentally designed articles included research hypotheses. 3) Among experimental studies, only one was true experimental studie design. Eighty nine point three persent had descriptive survey method among non-experimental studies. Amog the thirty four qualitative studies, phenomenologic(73.5%), grounded theory(14.7%), and ethnographic (11.8%) design were used. 4) Most of research subject were patients and few healthy people, healthcare worker, and patient family. 5) Psychosocial data collection method which used questionnaire were 53.7% and interview, physical measurement, observation were used in 22.8%, 8.2%, 5.4% of articles respectively. 6) Total number of keywords were 692, and average number of key words per article was 2.2. Health-related keyword was the most frequently used according to four metaparadigm of nursing (human, health, nursing, and environment). Environment related keyword was rarely appeared. The number and quality of nursing research in "Journal of Korean Academy of Adult Nursing" have been improved continuously. It is difficult to find out special trend or characteristics which is unique in this journal because of relatively short history of adult nursing studies. This review study was performed to analyze adult nursing studies only in the view of quantitative aspect, but it is needed to analyse qualitatively to find philosophical or theoretical trend in nursing.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.35-39
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• 2003

A numerical study is carried out to investigate combustion phenomena in a model SCRamjet engine, which has been experimentally studied at the Australian National University using a T3 free-piston shock tunnel. The Mach number is 3.8, the static pressure 110kPa and the static temperature 1100K in the main air flow. The fuel is hydrogen, which is injected in the cavity. Equivalence ratio is set to either 0.25 or 0.5 to access its effect on the fuel-air mixing combustion phenomena. The results show that the cavity generates several recirculation zones, which increase the fuel-air mixing. Self ignition occurs near the point of fuel injection. The flame is anchored by the cavity and generates the precombustion shock on the step. For a high equivalence ratio, the recirculation zones are bigger and the flame is present throughout the combustor.

• Journal of Environmental Impact Assessment
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• v.14 no.4
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• pp.203-215
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• 2005

Recently, a number of high school, college and university run the School-Based Enterprises(SBE). The purpose of this study is to integrate Education for Sustainable Development(ESD) into the SBE run by vocational high schools. To achieve this goal, this paper takes following research considerations. First of all, this study review the theories of SBE and ESD. Secondly, We extract the factors to analyze from the ESD point of view and integrate them into the SBE in vocational high schools. Thirdly, this study suggests the necessity and methods to integrate ESD into the SBE. ESD could serve important roles to promote the SBE by stimulating the sustainable development and improving human abilities in solving both the environment and development problems.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.401-408
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• 2016

During daylight, the solar array of low earth orbit satellites harvests electrical power to operate satellites. The power conversion of the solar array is carried out by control of the operation point using the solar array regulator when the solar array faces the sunlight. Thus, the design of the solar array should comply with not only the power requirement of satellite system but also the input voltage requirement of the solar array regulator. In this paper, the design requirements of the solar array for low earth orbit satellites are defined, and the means of satisfying these requirements are described. In addition, the architecture of a multi-distributed interface is suggested to maximize the power harvested from a solar array having high temperature deviation between each panel. The power analysis in this paper shows the optimal number of multi-distributed interfaces with a converter.

• Kyungpook Mathematical Journal
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• v.50 no.4
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• pp.509-536
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• 2010

In this paper, we investigate curvature-adapted and proper complex equifocal submanifolds in a symmetric space of non-compact type. The class of these submanifolds contains principal orbits of Hermann type actions as homogeneous examples and is included by that of curvature-adapted and isoparametric submanifolds with flat section. First we introduce the notion of a focal point of non-Euclidean type on the ideal boundary for a submanifold in a Hadamard manifold and give the equivalent condition for a curvature-adapted and complex equifocal submanifold to be proper complex equifocal in terms of this notion. Next we show that the complex Coxeter group associated with a curvature-adapted and proper complex equifocal submanifold is the same type group as one associated with a principal orbit of a Hermann type action and evaluate from above the number of distinct principal curvatures of the submanifold.

• Korean Journal of Mathematics
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• v.25 no.4
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• pp.483-494
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• 2017

In the current manuscript, we investigate the pointwise convergence of the singular integral operators involving power nonlinearity given in the following form: $$T_{\lambda}(f;x)={\int_a^b}{\sum^n_{m=1}}f^m(t)K_{{\lambda},m}(x,t)dt,\;{\lambda}{\in}{\Lambda},\;x{\in}(a,b)$$, where ${\Lambda}$ is an index set consisting of the non-negative real numbers, and $n{\geq}1$ is a finite natural number, at ${\mu}$-generalized Lebesgue points of integrable function $f{\in}L_1(a,b)$. Here, $f^m$ denotes m-th power of the function f and (a, b) stands for arbitrary bounded interval in ${\mathbb{R}}$ or ${\mathbb{R}}$ itself. We also handled the indicated problem under the assumption $f{\in}L_1({\mathbb{R}})$.

• IE interfaces
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• v.17 no.spc
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• pp.62-68
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• 2004

HAPS (High Altitude Platform Station) which is defined as a station located on an object at an altitude of 20 to 50 km and at a specified, nominal, fixed point relative to the earth is a promising technology capable of providing broadband multimedia services. In this study, economical aspects of HAPS service are analyzed by estimating the revenue and costs incurred by the service. To evaluate the profitability of HAPS service, the number of subscribers is estimated and then the net present value (NPV), payback period, and the rate of return on investment (ROI) are calculated under various scenarios.

• Journal of the Korean Professional Engineers Association
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• v.42 no.5
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• pp.29-31
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• 2009

A general practice in software ordering behavior in public sector has been an enormous obstacle standing in development path of Korea's software industry. Standard on software development cost estimation is supposedly based on Function Point, but in general, it is on headcounting (a number of people involved in a project). Moreover, it is difficult to change a contract in an on-going project, since statement of work is not precisely and carefully described. But it has a simple solution. Design and Implementation should be a separate project, as in construction industry, and both power and responsibility for design should be given to an expert with a national-level qualification. Here, there is a simple way for Korea to reborn as one of the strongest software country.