• Journal for History of Mathematics
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• v.12 no.2
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• pp.15-23
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• 1999

This paper deals with the origin of the concept of lattices in mathematics and its development until 1930's. Although it is purely mathematical, its formation is due to the development of symbolic logic Further, logicians were mostly concerned about how to imitate the methods and duplicate the problems of algebra but not the application to mathematics. The first purely mathematical approach was given by Dedekind and his results were neglected and then reappeared in 1930's.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.121-124
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• 1996

In general, cellular manufacturing system can be constructed by the following two steps. The first step forms machine cells and part families, and the second step determines cell layout based on the result of first step. Cell layout has to be considered when cell is formed becauese the result of cell formation affects it. This paper presents a cell formation algorithm and proposes an integrated mathematical model for cell formation and cell layout. The cell formation algorithm minimizes the number of exceptional element in cellular manufacturing system. New concept for similarity and incapability is introduced, based on machine-operation incidence matrix and part-operation incidence matrix. One is similarity between the machines, the other is similarity between preliminary machine cells and machines. The incapability identifies relations between machine cells and parts. In this procedure, only parts without an exceptional element are assigned to machine cell. Bottleneck parts are considered with cell layout design in an integrated mathematical model. The integrated mathematical model determines cell layout and assigns bottleneck parts to minimize the number of exceptional element and intercell moving distance, based on linearixed 0-1 integer programming. The proposed algorithm is illustrated by using numerical examples.

• Journal of Periodontal and Implant Science
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• v.34 no.2
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• pp.411-424
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• 2004

This study was performed to evaluate bone formation in the calvaria of rabbit by the concept of guided bone regeneration with titanium mesh membrane. Two different titanium meshes with varying number (353, 565) of pore were utilized in the study. Two surgical sites(T353, T565) were evaluated about whether or not the number of pore may have effect on the bone formation. The animal was sacrificed at 10days, 3 weeks, 6weeks, and 8 weeks after the surgery. Non-decalcified specimens were processed for histologic analysis. 1. Titanium mesh was biocompatible and capable of maintaining the spacemaking. 2. At 3 weeks, 6 weeks, and 8 weeks after GBR procedure, bone formation was more in the T353 site than in the T565 site. 3. Soft tissue layer above the regenerated bone was better developed in the T565 site. 4. There was no difference between two membranes in bone maturity with time. Within the above results, titanium mesh with lesser pore in number might be recommended for the early bone formation.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.267-284
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• 1991

Since the concept of a direct contact between bone and implants, without interposed soft- tissue layers, was reported by Dr. $Br{\aa}nemark$, there has been increasing necessity for correct under-standing of bone-implant interface and surrounding tissue response. Beside quality of bone, surgical technique, load applied to implants, one must consider implant materials, design and surface characteristics to obtain osseointegration. In this study HA plasma-sprayed implants, TPS implants and $Al_2O_3$ implants were inserted into the alveolar bone of dog and tissue response was observed with radiograph, stereoscope, light microscope, and scanning electron microscope. Results were as follows : 1. There was rapid and active bone formation in the region adjacent to HA plasma-sprayed implants but in the deep supporting bone only slight bone formation was seen. 2. There was considerable lamella bone formation in the region adjacent to TPS implants and the deep supporting bone became more compact. 3. There was some gap and sclerosing bone formation in the adjacent region of $Al_2O_3$ implants, but there was irregular new bone formation in the deep supporting bone. Therefore, it seems that $Al_2O_3$ is not adequate for osseointegrated implants.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.68-75
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• 2005

By utilizing a semi-empirical soot model, the applicability of the laminar flamelet concept fur simulating the formation and oxidation of soot in the laminar diffusion flame has been studied. The source terms for two transport equations of the soot formation and oxidation are calculated in the mixture fraction/scalar dissipation rate space for laminar flamelets and stored in a library. In this study, emphasis is given to the interaction associated with radiation and soot formation. The radiative heat loss is obtained by solving the radiative transfer equation using the unstructured grid finite volume method with the WSGGM. The calculated temperatures and soot volume fractions agree relatively well with the experimental data and the previous numerical results of Kaplan et al. using the detailed chemistry.

• Korean Management Science Review
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• v.12 no.1
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• pp.1-17
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• 1995

The success of cell manufacturing applications in FMS rests on the effective cell formation to maintain the independent relations both between machine cells and between part families. This paper presents an integrated method for concurrent formation of cells and families with no E.E (Exceptional Element) in FMS with alternative routings. To determine the maximum number of cell and family with no E.E, mathematical conditions and properties are derived. New concept of nonsimilarity is introduced for each machine and part based on machine-operation incidence matrix and part-operation incidence matrix. To concurrently form the cells and families, integer programming based mathematical models are developed. For the predetermined number of cell or family, model I is used to identify whether E.E exists or not. Model II forms cells and families considering only nonsimilarity. But model III can consider nonsimilarity and processing times. The proposed method is tested and proved by using numerical examples.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.123-128
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• 1999

Recently, as a performance based design concept is introduced, assurance of expected performances on serviceability and safety in the whole span of life is exactly requested. So, quantitative assessments about durability related properties of concrete in early-age long term are come to necessary, Especially in early age, deterioration which affects long-term durability performance can be occurred by hydration heat and shrinkage, so development of reasonable hydration heat model which can simulate early age behavior is necessary. The micor-pore structure formation property also affects shrinkage behavior in early age and carbonations and chloride ion penetration characteristic in long term, So, for the quantitative assessment on durability performance of concrete, modelings of early age concrete based on hydration process and micor-pore structure formation characteristics are important. In this paper, a micromechanics based hydration heat evolution model is adopted and a quantitative model which can simulate micro-pore structure development is also verified with experimental results. The models can be used effectively to simulate the early-age behavior of concrete composed of different mix proportions.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.8-16
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• 2017

MILD combustion was first developed to suppress thermal NOx formation in combustor for heating industrial furnaces. In this paper, the effect of co-flow MILD combustor geometry and operating conditions on the formation of MILD combustion was analyzed using 3 dimensional numerical simulation. The numerical simulations were carried out using ANSYS Fluent. The combustion and turbulence flow was modeled using the Eddy Dissipation Concept(EDC) model and realizable $k-{\varepsilon}$ model respectively. The results show that the high temperature region and average temperature decreased due to an increase in the air velocity and decrease the wall thickness of fuel nozzle. In particular, the MILD combustion flame was found to be stable with a combustion flame region at fuel velocity 10 m/s, air velocity 20 m/s, fuel nozzle thickness 1.0 mm, equivalence ratio 0.9, and outlet area ratio 40%.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.44-50
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• 2002

The spray characteristics of GDI(Gasoline Direct Injection) injector affects on engine efficiency and emission of a GDI engine. Thus, many researchers have investigated the spray characteristics and the mixture formation of GDI injector. In this study, it was tried to provide the fundamental data for GDl injector design which effects on the spray macroscopic characteristics such as penetration and spray angle. In addition, the mixture formation analyzed by using entropy analysis. The entropy analysis is based on the concept of statistical entropy, and it identifies the degree of homogeneity in the fuel concentration. The results show that as injection pressure increases but as ambient pressure increases, spray penetration decreases and spray angle doesn't affected by increasing injection pressure and ambient temperature. From the entropy analysis results, we could find that the direct diffusion phenomena is a dominant factor in the formation of a homogeneous mixture at downstream of GDI spray especially in vaporizing conditions.

• Journal of Korean Elementary Science Education
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• v.23 no.2
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• pp.141-151
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• 2004

Pre-service teachers' understandings on magnet was investigated through the questionnaire method. The questionnaire was composed of 17 questions about the strength of magnet, the magnetized object and the direction of magnetic field around magnet. In this investigation study, 225 pre-service teachers were selected through random sampling method, who were sophomores in a National University of Education. The formation rate of the scientific conceptions on the strength of magnet was 30.3% and that on the direction of magnetic field around magnet was 53.9%. The average formation rate of scientific conception of all questions on magnet was 44.13%, which doesn't seem to be high as expected. It shows that many of subjects of the questionnaire don't understand fully the concept of moleclar magnet model and the superposition effects of magnetic field around magnet. The formation rate of the scientific conception on magnet of females who took courses in sciences in high school were higher than that of females who took courses in arts in high school, which had meaningful difference (p<.05).