• Journal of Information Technology Services
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• v.9 no.4
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• pp.219-229
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• 2010

The Green's equivalence relations have played a fundamental role in the development of semigroup theory. They are concerned with mutual divisibility of various kinds, and all of them reduce to the universal equivalence in a group. Boolean matrices have been successfully used in various areas, and many researches have been performed on them. Studying Green's relations on a monoid of boolean matrices will reveal important characteristics about boolean matrices, which may be useful in diverse applications. Although there are known algorithms that can compute Green relations, most of them are concerned with finding one equivalence class in a specific Green's relation and only a few algorithms have been appeared quite recently to deal with the problem of finding the whole D or J equivalence relations on the monoid of all $n{\times}n$ Boolean matrices. However, their results are far from satisfaction since their computational complexity is exponential-their computation requires multiplication of three Boolean matrices for each of all possible triples of $n{\times}n$ Boolean matrices and the size of the monoid of all $n{\times}n$ Boolean matrices grows exponentially as n increases. As an effort to reduce the execution time, this paper shows an isomorphism between the R relation and L relation on the monoid of all $n{\times}n$ Boolean matrices in terms of transposition. introduces theorems based on it discusses an improved algorithm for the J relation computation whose design reflects those theorems and gives its execution results.

• Bulletin of the Korean Mathematical Society
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• v.43 no.2
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• pp.353-375
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• 2006

In this paper we establish a counting method for the Green classes of the Birget-rhodes expansion of finite groups. As an application of the results, we derive explicit enumeration formulas for the Green classes for finite groups of order pq and a finite cyclic group of order $p^m$, where p and q are arbitrary given distinct prime numbers.

• Journal of the Korean Society of Combustion
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• v.17 no.4
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• pp.5-10
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• 2012

The reformer system is a chemical device that drives the conversion of hydrocarbon to hydrogen rich gas under high temperature environment($600-1,000^{\circ}C$). Generally, NG(Natural Gas) or AOG(Anode Off Gas) is used as fuel of fuel cell reformer combustion system. The experimental study to analyze the combustion characteristics of a premixed ceramic burner used for 0.5-1.0 kW fuel cell reformer was performed. Ceramic burner experiments using NG and AOG were carried out to investigate the flame stability characteristics by heating capacity, equivalence ratio and different fuels respectively. The results show that surface flames can be classified into green, red, blue and lift-off flames as the equivalence ratio of methane-air mixture decreases. And the stable flames can be established using NG and AOG as reformer fuel in the perforated ceramic burner. In particular, the blue flame is found to be stable at a lean equivalence ratio under different mixture conditions of NG and AOG for the 0.5 to 1.0 kW fuel cell system power range. NOx emission is under 60 ppm between 0.70 to 0.78 of equivalence ratio and CO emission is under 50 ppm between 0.70 to 0.84 of equivalence ratio.

• Journal of Information Technology Services
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• v.7 no.4
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• pp.221-230
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• 2008

Green's relations are five equivalence relations that characterize the elements of a semigroup in terms of the principal ideals. The J relation is one of Green's relations. Although there are known algorithms that can compute Green relations, they are not useful for finding all J relations in the semigroup of all $n{\times}n$ Boolean matrices. Its computation requires multiplication of three Boolean matrices for each of all possible triples of $n{\times}n$ Boolean matrices. The size of the semigroup of all $n{\times}n$ Boolean matrices grows exponentially as n increases. It is easy to see that it involves exponential time complexity. The computation of J relations over the $5{\times}5$ Boolean matrix is left an unsolved problem. The paper shows theorems that can reduce the computation time, discusses an algorithm for efficient J relation computation whose design reflects those theorems and gives its execution results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.9
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• pp.1236-1243
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• 1995

The propagation characteristics of the symmetric and the asymmetric shielded coplanar waveguide with finite metallization thickness is analyzed by boundary integral method employing the equivalence principle. Since the Green's function and the basis functions are composed of sinusoidal functions, the integration in Galerkin's method is solved analytically. The propagation constants of the fundamental and the first higher order mode are obtained and the effects of strip thickness, substrate permittivity, and the asymmetry of the structure are calculated.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.55-63
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• 1995

By employing the concept of superimposing the induced current on partial scattere roled as a secondary source, matrix Green's function was derived. The procedure in the way of derivation presented here was based on the equivalence principle and the induction theorem and applying moment methods to the resulting electric field integral equation. As examples, the induced current on scatterers consisted of wire/plate conductor, the input impedance and gain patterns of corner reflector antenna were calculated. And computing times required for solving matrix equation were compared with those of conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1842-1849
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• 1996

This paper presents a full-wave, moment method analysis of a Moreno directional coupler with tow crossed-slots between two crossed rectangular waveguides. the overall structure is divided into several rectangular waveguides and cavities by the use of the equivalence principle to the complex slot regions. this enables a simple and efficient analysis involving the well-known retangular waveguide/cavity Green's functions. For a numerically efficient simulation, the roof-top basis expansion and line testing is used and an acceleration technique is applied to the series summation in the Green's functions. The numerical results are compared with the measurements to verify the correctness of the present analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.1001-1004
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• 1987

In this study mathematical properties of variational solution and solution of the boundary integral equation of the linear elasticity problem are studied. It is first reviewed that a variational solution for the three-dimensional linear elasticity problem exists in the Sobolev space [ $H^{1}$(.OMEGA.)]$^{3}$ and, then, it is shown that a unique solution of the boundary integral equation is identical to the variational solution in [ $H^{1}$(.OMEGA.)]$^{3}$. To represent the boundary integral equation, the Green's formula in the Sobolev space is utilized on the solution domain excluding a ball, with small radius .rho., centered at the point where the point load is applied. By letting .rho. tend to zero, it is shown that, for the linear elasticity problem, boundary integral equation is valid for the variational solution. From this fact, one can obtain a numerical approximatiion of the variational solution by the boundary element method even when the classical solution does not exist.exist.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.804-808
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• 2010

In this paper, we studied the dielectric breakdown voltage characteristics by the AC withstand voltage test on using green insulation dry air instead of $SF_6$ insulation gas used in the GIB (gas insulated bus) of 362 kV GIS (gas insulated switchgear). The AC withstand voltage test applied to the standard KEPCO's 362 kV GIB with dry air insulation, and the equivalence of dielectric breakdown voltage for dry air and $SF_6$ gas were examined, and the empirical formulas of dielectric breakdown voltage for dry air were calculated, and the criterion of AC withstand voltage test for dry air insulation was derived. Using the criterion, dry air can be used instead of $SF_6$ gas for 362 kV GIB in the factory acceptance test was confirmed.

• Journal of Families and Better Life
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• v.20 no.4
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• pp.89-102
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• 2002

Genetically modified foods may be defined as the foods deemed as safe by current technology among the many kinds of agricultural and stockbreeding products that are now under research and development using contemporary gene-modification techniques. This study examines hotly debated arguments, both for and against genetically modified- foods, in various countries. This study also investigates consumers'rights and responsibilities. Countries that are developing and exporting genetically modified organisms(GMO) have maintained that GMO can help produce more crops while reducing labor and other production-related costs, and that the genetically modified foods signify ″the second green revolution,″ which will solve future food and environmental problems by strengthening specific nutritive substances and extending shelf-life. But consumer groups, environmental organizations. and food-importing countries are more cautious about importing and consuming those foods because the potential dangers of GMO to human bodies and the environment have not been tested thoroughly yet. South Korea, following suit with others such as EU, Japan, Australia, and New Zealand, introduced a law on 'Labeling of Genetically Modified Foods', which went in effect in March, 2001, on the basis of customers'rights to make informed choices. The law takes the ″precautionary principle″ into consideration, rather than stopping at insuring ″substantial equivalence″ in developing and consuming GM foods. The actual impact of the law will depend on the level of citizens'Participation more than on the government's willingness to carry out the law. So far the level of Korean consumers'consciousness about genetically modified foods is very low. Therefore, it is hard to expect consumers to exercise their ″rights not to buy″ foods that are potentially unsafe. The Korean government must devise an effective plan to inform and educate the people about the labeling of genetically modified foods.