• Journal of applied mathematics & informatics
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• 제28권1_2호
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• pp.411-423
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• 2010

In this paper, a numerical method for singular perturbation problems arising in chemical reactor theory for general singularly perturbed two point boundary value problems with boundary layer at one end(left or right) of the underlying interval is presented. The original second order differential equation is replaced by an approximate first order differential equation with a small deviating argument. By using the trapezoidal formula we obtain a three term recurrence relation, which is solved using Thomas Algorithm. To demonstrate the applicability of the method, we have solved four linear (two left and two right end boundary layer) and one nonlinear problems. From the results, it is observed that the present method approximates the exact or the asymptotic expansion solution very well.

• Journal of applied mathematics & informatics
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• 제26권5_6호
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• pp.1273-1287
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• 2008

In this paper, the numerical integration method for general singularly perturbed two point boundary value problems with mixed boundary conditions of both left and right end boundary layer is presented. The original second order differential equation is replaced by an approximate first order differential equation with a small deviating argument. By using the trapezoidal formula we obtain a three term recurrence relation, which is solved using Thomas Algorithm. To demonstrate the applicability of the method, we have solved four linear (two left and two right end boundary layer) and one nonlinear problems. From the results, it is observed that the present method approximates the exact or the asymptotic expansion solution very well.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.682-685
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• 1991

Solvent dependence of the static solution properties of a polymer chain was studied by static light scattering technique for polystyrene in three good solvents, toluene, tetrahydrofuran and $CCl_4$. The molecular parameters such as radius of gyration and second virial coefficients of polystyrene are found to be clearly larger in THF than the other two solvents and they are in the order of tetrahydrofuran > toluene > $CCl_4$. The radius of gyration shows the same order while the difference is smaller. Nontheless, the penetration functions are found to have a comparable value about 0.2, which confirms the universality of the penetration function in high expansion regime over different nature of solvents.

• Journal of applied mathematics & informatics
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• 제39권5_6호
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• pp.655-676
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• 2021

A parameter uniform numerical scheme is proposed for solving singularly perturbed parabolic partial differential-difference convection-diffusion equations with a small delay and advance parameters in reaction terms and spatial variable. Taylor's series expansion is applied to approximate problems with the delay and advance terms. The resulting singularly perturbed parabolic convection-diffusion equation is solved by utilizing the implicit Euler method for the temporal discretization and finite difference method for the spatial discretization on a uniform mesh. The proposed numerical scheme is shown to be an ε-uniformly convergent accurate of the first order in time and second-order in space directions. The efficiency of the scheme is proved by some numerical experiments and by comparing the results with other results. It has been found that the proposed numerical scheme gives a more accurate approximate solution than some available numerical methods in the literature.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.94-102
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• 2001

The thermodynamic second law analysis, which means available energy or exergy analysis, for the indicated performance of Otto cycle engine has been carried out. Each operating process of the engine is simplified and modeled into the thermodynamic cycle. The calculation of the lost work and exergy through each process has been done with the thermodynamic relations and experimental data. The experimental data were measured from the test of single cylinder Otto cycle engine which operated at 2500 rpm, WOT(Wide Open Throttle) and MBT(Minimum advanced spark timing for Best Torque) condition with different fuels: gasoline, methanol and mixture of butane-methanol called M90. Experimental data such as cylinder pressure, air and fuel flow rate, exhaust gas temperature, inlet gas temperature and etc. were used for the analysis. The proposed model and procedure of the analysis are verified through the comparison of the work done in the study with experimental results. The calculated results show that the greatest lost work is generated during combustion process. And the lost work during expansion, exhaust, compression and induction process follows in order.

• International journal of advanced smart convergence
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• 제10권1호
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• pp.117-124
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• 2021

Based on a result of we research and analysis of this study, it was analyzed that the average annual cremators number using E-Haneul Funeral Information System among the five public cremation facilities in Jeollabukdo was 9,713 in total before the opening of public creation facilities in Jeongeup City (2013-2015), while the number was 12,159 after the opening of public cremation facilities in Jeongeup City (2016-2019); the number was increased by 2,446, compared to the opening period (2013-2015), with a large increase rate of 25.2%. In addition, the average annual cremation rate before the opening of public cremation facilities in Jeongeup City (from 2013 to 2015) was 71.6%, but the average annual cremation rate during the period after the opening (from 2016 to 2019) was 81.5%, which was a large increase rate of 9.9% compared to period before the opening of the facilities. Based on research results above, we have presented policy suggestions in order to increase the efficiency of operation and management of public cremation facilities by local governments as follows. First, in order to prepare for the increase in demand for cremation due to the increase in cremators number, a policy promotion for the expansion of "public cremation facilities" should be carried out as soon as possible, focusing on local governments whose supply has reached the limit. Second, in order to support the expansion and construction of public cremation facilities, the government subsidy rate and government subsidy at the level of current 70%, provided by the central government, should be further expanded. Third, overcoming theNIMBY conflict overlocation for public cremation facilities, theutilization rate should be enhanced, through the joint construction and facility operation of the public cremation facilities between local governments, and the ef iciency of the project implementation should be improved through the jointsharing of the facility operation cost.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1996년도 학술발표회
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• pp.57-61
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• 1996

Our goal was to make a cost-effective automatic fire extinguishing system for the engine compartment use of automobiles. We designed this system for the engine compartment. This system consists of 1)foam extinguisher, 2)four nozzles, 3)a pipe arrangement, and 4)an extinguishing device which is equipped with a glass bulb as detector. First and foremost, the extinguishing device was carefully designed to keep the system cost to a minimum. Second, a AFFF foam extinguisher was used because no other fire-fighting agents proved effective against fire in the engine compartment. The AFFF(Aqueous Film Forming Foam) agent which was used in the extinguisher is the 3M company's Light Water. We sought, however, to make other foams by using Halon 1301 and Halon alternatives such as HCFC Blend A, HFC-227ea. We selected these alternatives instead of air in order to raise the expansion ratio of the AFFF agent. By these means we discovered that it is possible to increase the expansion ration of the AFFF agent up to 44:1. We then demonstrated that our automatic fire extinguishing system is the most effective and lowest cost-system yet devised for passenger cars.

• 대한조선학회논문집
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• 제31권4호
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• pp.82-98
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• 1994

본 논문에서는 파중에서 조종운동을 하는 선박에 작용하는 유체력에 대한 수학적 모델을 확립하고, 이에 대한 수치해석을 수행하였다. 파중에서 운항하는 선박은 입사파의 주파수에 의존하는 고주파수 운동과 선박의 조종운동에 따른 저주파수 운동을 하게되므로, two time scale expansion 방법을 적용하여 속도포텐셜에 대한 선형경계치 문제를 정립하였으며, 선박의 조종운동에 미치는 파의 영향은 2차차수 저주파수 표류력만을 조종운동방정식에 포함시켜 고려하였다. 속도포텐셜에 대한 적분방정식의 해는 3차원 파넬방법을 사용하여 구하였으며, 선박에 작용하는 힘은 직접적분법을 사용하여 계산하였다.

• 한국수학교육학회지시리즈A:수학교육
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• 제51권1호
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• pp.1-19
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• 2012

In this study, contents of 'the 2007 revised curriculum handbook' and 16 kinds of mathematics textbooks were analyzed first. The purpose of this study is to examine the understanding state of students at general high schools by making questionnaires to survey the understanding state on contents of chapter of complex number based on above analysis. Results of research can be summarized as follows. First, the content of chapter of complex number in textbook was not logically organized. In the introduction of imaginary number unit, two kinds of marks were presented without any reason and it has led to two kinds of notation of negative square root. There was no explanation of difference between delimiter symbol and operator symbol at all. The concepts were presented as definition without logical explanations. Second, students who learned with textbook in which problems were pointed out above did not have concept of complex number for granted, and recognized it as expansion of operation of set of real numbers. It meant that they were confused of operation of complex numbers and did not form the image about number system itself of complex number. Implications from this study can be obtained as follows. First, as we came over to the 7th curriculum, the contents of chapter of complex number were too abbreviated to have the logical configuration of chapter in order to remove the burden for learning. Therefore, the quantitative expansion and logical configuration fit to the level for high school students corresponding to the formal operating stage are required for correct configuration of contents of chapter. Second, teachers realize the importance of chapter of complex number and reconstruct the contents of chapter to let students think conceptually and logically.

• 복식
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• 제61권6호
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• pp.131-145
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• 2011

The purpose of this study is to provide preliminary data on strategies to create a domestic prestige brand based on Korean traditional designs. This study also deals with how to promote this brand around the world. The two points mentioned above will be accomplished by examining the characteristics of the brand '3.1 Phillip Lim' which succeeded in both design and marketing during a short period of time. The method of the study will be followed. Firstly, the basic design and philosophical background of Phillip Lim was investigated, after reviewing the global luxury market and current status of overseas expansion of Korean designers through paper study and antecedent workups. Secondly, for the practical stage, design characteristics and marketing strategies were reviewed with the collections of '3.1 Phillip Lim'. Three factors found in '3.1 Phillip Lim's design success are as follows: First, practical and simple designs using fabrics of high quality. Second, handcraft elements and interesting details that differentiates his design identity. Third, femininity expressed in the feminine silhouette and color. The marketing elements that made '3.1 Phillip Lim' as a successful brand are: First, differentiated positioning as a luxurious contemporary brand. Second, brand promotion through various collaborations. Third, the gradual expansion of women's, men's, kids' apparel to accessory, lingerie and the stable flagship stores. Thus, '3.1 Phillip Lim' has combined modern and classic styles using high quality fabrics and practical designs with unique details. Through it's differentiated marketing strategy targeting New York's market, which prefers popular 'luxury contemporary brand's rather than high-end luxury brands, this brand's creativity and commercial aspects contributed to make '3.1 Phillip Lim' into a luxury brand that represents New York fashion. Korean designers who seek to enter the global fashion industry should consider applying Korean traditional designs on global designs to make favorable products and localize these products according to regional characteristics.