• 대한기계학회논문집B
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• 제28권10호
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• pp.1264-1270
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• 2004

In this paper research on micro solid propellant thruster is reported. Micro solid propellant thruster has four basic components; micro combustion chamber, micro nozzle, solid propellant and micro igniter. In this research igniter, solid propellant and combustion chamber are focused. Micro igniter was fabricated through typical micromachining and the effect of geometry was evaluated. The characteristic of solid propellant was investigated to observe burning characteristic and to obtain burning velocity. Change of thrust force and the amount of energy loss following scale down at micro combustion chamber were estimated by numerical simulation based on empirical data and through the calculation normalized specific impulses were compared to figure out the efficiency of combustion chamber.

• 한국식품영양학회지
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• 제11권6호
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• pp.667-672
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• 1998

The possibility of solid-substrate fermentation of Lentinus edoes for the productin of protein-boud polysaccharides (PBP) was studied. Zeolite and orchid-pot soil were used as solid materials for the culture because of the desirable physical properties. Sucrose and starch were good carbon sources for the production of PBP by the solid-substrate fermentatin of L. edodes. Among the nitrogen source, bactosoyton was very effective for the PBP production. The optimum pH for solid-substrate fementation for the production of PBP was at pH of 5.5. The PBP production reached to 5∼5.5mg per 100g solid-substrate.

• 소성∙가공
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• 제10권3호
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• pp.214-222
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• 2001

The homogeneous distribution of solid region without liquid segregation is important in terms of high quality component during thixoforming process. In closed die semi-solid forging process, liquid segregation is strongly affected by injection velocity than solid fraction because the material has to travel relatively long distance to fill the cavity through a narrow gate. The designed die by computer simulation data was used to thixoforging process. The thixoforming velocity to prediction the liquid segregation had been determined with strain rate associated with multistage velocity control during compression test of semi-solid material. The optimal forging velocity and die temperature were investigated to produce the near-net-shape compressor component. The mechanical properties of thixoformed component were tested with various die and material temperatures before and after heat treatment.

• 한국CDE학회논문집
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• 제12권2호
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• pp.101-108
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• 2007

As 3D solid modeling has been widely used in designing products, solid models of the products are directly used in various applications such as engineering analysis and process planing. However, the fully-detailed solid models may not be necessary in some application. For example, it is often more efficient to use simplified model of part of engineering analysis. Generation of mesh for the complex original model requires a quite amount of time, and the consequence of finite element analysis may not be desirable due to small and detailed geometry in the model. In this paper, a method to simplify solid models of machined part is presented. This method decomposes the delta volume of machined part, and uses the decomposed volumes to simplify the solid model. Since this method directly recognizes the features to be removed from the final model, it is independent of not only design features of specific CAD system, but also designer's design practice of design sequences.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제19권2호
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• pp.147-169
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• 2012

We introduce a Heaviside-function formulation of the interaction between incompressible two-phase fluid and a non-deformable solid. Fluid and solid interact in two ways : fluid satises the Dirichlet boundary condition imposed by the velocity field of solid, and solid is accelerated by the surface traction exerted by fluid. The two-way couplings are formulated by the Heaviside function to the interface between solid and fluid. The cumbersome treatment of interface is taken care of by the Heaviside function, and the interaction is discretized in a simple manner. The discretization results in a stable and accurate projection method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.670-674
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• 1997

Semi-solid forging is a compound forging technology to deventional forging process. Among several steps of semi-solid forging process, the heating step of a billet prior to semi-solid forging step is necessarily required to obtain globular microstructure. For the forming operation to work properly, it is also important to heat the billet uniformly for the uniformity of solid-liquid distribution. To satisfy these requirements, induction heating has been generally used for a long time. This paper presents the method to find heating condition and the temperature distribution inside of a billet with a induction heating apparatus by comparing the computer simulation with experiment for aluminum alloys Al2024 and A356.

• International Journal of Precision Engineering and Manufacturing
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• 제2권4호
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• pp.23-29
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• 2001

The compression behavior of semi-solid materials is studied from a viewpoint of yield criteria and analysis methods. To describe the behavior of materials in semi-solid state, several theories have been proposed by extending the concept of plasticity of porous compressible materials. In the present work, the upper-bound method and the finite element method are used to model the simple compression process using yield criteria of Kuhn and Doraivelu. Segregation between solid and liquid which cause defect of product is analysed for Sn-15%Pb and A356 alloys during deformation in semi-solid state. The comparison of analyses is made according to yield criteria and analysis methods. In addition, the analysis result for semi-solid dendritic Sn-15%Pb alloy is compared with the experimental result of Charreyron et al..

• 한국정밀공학회지
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• 제14권8호
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• pp.82-91
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• 1997

The major objective of this study is to establish analytical technique in order to analyze the behaviour of semi-solid material considering induction heating of the billet. Induction heating process is analyzed by using commerical finite element software. ANSYS. The finite element program, SFAC2D, for the simulation of deformation in semi-solid state is developed in the present study. The semi-solid behaviour is described by a viscoplastic model for the solid phase, and by the Darcy's law for the liquid flow. Simple compression and closed-die compression process considering induction heating are analyzed, and also it is found that the distribution of initial solid fraction of the billet has an important effect on deformation behaviour of semi-solid material. In order to verify the effectiveness of proposed analytical technique the simulation result is compared with experimental result.

• 한국정밀공학회지
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• 제14권8호
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• pp.15-20
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• 1997

Semi-solid forging is a compound forging technology to develop conventional forging process. Among several steps of semi-solid forging process, the heating step of a billet prior to semi-solid forging step is necessarily required to obtain globular microstructure. For the forming operation to work properly, it is also important to heat the billet uniformly for the uniformity of solid-liquid distribution. To satisfy these requirements, induction heating has been generally used for a long time. This paper presents the method to find heating condition and the temperature distribution inside a billet with a induction heating apparatus by comparing the computer simulation with experiment for aluminium alloys A12024 and A356.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.179-184
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• 1998

Semi-solid forging can be applied in industry only with enough knowledge of the effects of the forming parameters related with the process and their exact control which can be obtained by empirical or numerical methods. In the current study, the effects of process variables on semi-solid forging are discussed based on mainly numerical results. Die preheating temperature, initial solid fraction of the workpiece, and die velocity were selected as process variables, and numerical analyses using a rigid-thermoviscoplastic finite element approach that considered the release of latent heat due to phase change were carried out. In the analyses, a proposed flow stress material characterization and a solid fraction updating algorithm were employed. The obtained results from numerical analysis are discussed and are compared with some experimental observations.