• Interaction and multiscale mechanics
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• v.1 no.1
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• pp.1-31
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• 2008

The present paper presents multiscale modelling via coupling of the discrete and finite element methods. Theoretical formulation of the discrete element method using spherical or cylindrical particles has been briefly reviewed. Basic equations of the finite element method using the explicit time integration have been given. The micr-macro transition for the discrete element method has been discussed. Theoretical formulations for macroscopic stress and strain tensors have been given. Determination of macroscopic constitutive properties using dimensionless micro-macro relationships has been proposed. The formulation of the multiscale DEM/FEM model employing the DEM and FEM in different subdomains of the same body has been presented. The coupling allows the use of partially overlapping DEM and FEM subdomains. The overlap zone in the two coupling algorithms is introduced in order to provide a smooth transition from one discretization method to the other. Coupling between the DEM and FEM subdomains is provided by additional kinematic constraints imposed by means of either the Lagrange multipliers or penalty function method. The coupled DEM/FEM formulation has been implemented in the authors' own numerical program. Good performance of the numerical algorithms has been demonstrated in a number of examples.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.29-35
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• 2004

Fine blanking can be considered as a manufacturing process capable of producing sheet metal parts with completely smooth edges that may be hardly obtained by conventional shear-cutting procedures. This fact, together with the considerable economic advantages offered by this process, has been responsible for the rapid acceptance of fine blanking throughout the manufacturing industry all over the world, and the discovery of many new applications. This study was performed to investigate the effect of clearance and V-ring shape on the quality of sheared surface in a fine blanking process. The critical value needed to apply the normalized Cockcroft-Latham fracture criterion to the simulation of fine blanking is obtained by correlating the result of finite element analysis and that of experiment for the uniaxial tensile test. From finite element analysis of an axisymmetric fine blanking process, it has been found that punch load, die-roll depth, burnish zone size and shape of sheared surface are considerably influenced by clearance and V-ring shape.

• Transactions of Materials Processing
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• v.24 no.5
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• pp.340-347
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• 2015

Multi-pass shape drawing is used to manufacture long products of arbitrary cross-sectional shapes. This process allows smooth surface finishes and closely controlled dimensions of the cross-sectional shape. Tube shape drawing for hollow type products provides material savings and weight reduction. The intermediate die shapes are very important in multi-pass tube shape drawing. In the current paper, the design method for the intermediate dies in a tube shape drawing process is developed using a die offset for corner filling (DOCF) method. Underfill defects are related to the radial velocity distribution of each divided section in the deformation zone. The developed intermediate die shape design was applied to the two-pass tube shape drawing with fixed mandrel for manufacturing a hollow linear motion (LM) guide rail. The proposed design method led to uniform and steady metal flow at each divided section. FE-simulations and experiments were conducted to validate the effectiveness of the proposed method in multi-pass tube shape drawing process.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.1
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• pp.193-195
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• 2001

A radiation-resistant bacterium was isolated from gamma irradiated dried laver (Porphyra tenera) and its microbiological characteristics were examined. As a result of resistance test to gamma irradiation, the isolate was survived $10^{3}$ CFU/mL even at 30 kGy and significant shoulder line zone was shown until 20 kGy. The $D_{10}$ value was 11.27 kGy. The isolate was gram-positive, non-motile coccus and catalase-positive. n culture, the red-pigmented smooth colony was observed. The biochemical test in API (analytical profile index) system showed that the isolate fermented glucose and fructose as the carbon source. Therefore, a radiation-resistant bacterium isolated from laver was potentially identified as Micrococcus roseus sp.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.767-772
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• 2012

Generally, abrasive fluid jet polishing system has been used for polishing of complex shape or freeform surface which has steep local slopes. In the system, abrasive fluid jet is injected through a nozzle at high pressure; however, it is inevitable to lose its coherence as the jet exits a nozzle. This problem causes incorrect polishing results because of unstable and unpredictable workpiece material removal at the impact zone. In order to solve this problem, MR fluid jet polishing method has been developed using a mixture of abrasive and MR fluid which can maintain highly collimated and coherent jet by applied magnetic field. Thus, in this study, an injection nozzle and an electromagnetic module, most important parts in the MR polishing system, were designed and verified by magnetic field and flow analysis. As the results of experiments, it can be confirmed that stable fluid jets for polishing were generated since smooth W-shapes and uniform spot size were observed regardless of standoff distance changes.

• Journal of Plant Biology
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• v.22 no.1_2
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• pp.35-43
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• 1979

The present investigation has been made to study the deficiency symptoms of boron on the formation of cell wall and the development of the individual components of the orchid cell wall. Analytical samples were taken from two sources; one from the individual orchid plants started from an apical meristem culture followed by the generation of the protocorm-like body which was developed into a plant, the other from the plant cultivated in water for 30 days. The amount of boron in the cultrues were controlled and the deficiency symptoms were observed under theelectron microscope, optical microscope with samples taken from the zones of elongation of leaves and compared the dry weight of cell walls and finally the various fractions of the cell wall components. The following results were obtained: (1) The growth of roots and leaves was hampered in the boron deficient plants. (2) In the boron-deficient leaves a severe necrosis and cracks were developed in the tissue of zone of elongation besides the decrease in growth. (3) under the electorn microscope the cell walls of boron-deficient plants showed rough undulated structures unlike the smooth control cell walls. (4) the dry weight of total cells and cell walls of boron deficient plants were higher than the control plants. (5) In the boron deficient plant the amout of pectin and hemicellulose isolated from cell walls were higher and the amount of protein was lower than the controlled plots.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.681-686
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• 2009

Direct laser metal forming technology was applied to restore the damaged mold surface. In order to estimate melting characteristics of the $20{\mu}m$ Fe-Cr-Ni powder, single layer experiments were performed at various levels of heat input. The process window of the $20{\mu}m$ Fe-Cr-Ni powder provided feasible process parameters for the smooth regular surface. The cross hatching scanning strategy on the multiple layer experiment was performed to reduce the thickness non-uniformity of edge portions compared with the one direction scanning. To estimate the coherence between the melted powder and the basematal, the tendency of hardness distribution has been observed. The hardness of the melted and the remelted zone was distributed from 400HV to 600HV. It is over 2 times compared of the hardness of the basemetal. Experimental results show that the mold restoring process using direct laser metal forming can be successfully applied in the mold repair industry.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.7.1-7.1
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• 2009

The use of Duplex stainless steel as a thermo-implant categorizes into two clinical applications: hyperthermia and thermal ablation or destruction. The goal of hyperthermia is to destroy the heat-sensitive abnormal cells and minimize normal cell death maintaining heat between $42^{\circ}C$ and $46^{\circ}C$. Thermal ablation takes place when the local tissue temperature increases greater than $46^{\circ}C$. This elevated temperature denatures protein irreversibly resulting cellular death. The author introduced several thermo-implants such as thermo-rod, thermo-stent, thermo-coil and thermoacupuncture-needle. Those thermo-implants are made of duplex stainless steel which can produce regulated heat by itself within an induction magnetic field. Thermal ablation characteristics of the thermo-rod on tumor hyperthermia depend on configurations of the thermo-rods and the magnitude of the induction magnetic strength. The exothermic properties of the thermo-implants can be characterized using the calorimetric test and the heat affected zone(HAZ) analyses in vitro. Thermal radiation studies using thermo-coils and thermo-stents show the capability of the occlusion of animal blood vessels and inhibiting the proliferation of the abnormal smooth muscle cell growth and inflammatory cell reactions maintaining the heat between $42^{\circ}C$ and $46^{\circ}C$ minimizing a normal cell death in the study on external iliac artery of the New Zealand White (NZW) rabbit. Thermal stimulation study using thermo-acupuncture needles suggests the potential applications of the automated acupunctural therapies.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.173-184
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• 1994

원자력 압력용기강의 탄소성 파괴인성값 $J_IC$를 CT형 시험편을 이용하여 검토하였으며, 평활 시험편 및 측면홈 시험편의 두께는 각각 $B_O$=25.4mm, $B_N$=20.4mm 이다. 측면홈의 깊이는 19.7% 이며, 홈의 각도는 90 .deg.로 가공하였다. 탄소성 파괴인성시험은 ASTM E813-81과 JSME S001-81의 추천방법에 따라 실시하였다. 두 추천방법으로 실험한 결과 ASTM 방법에 의한 $J_IC$값이 과대평가됨으로써 부대조건에 만족되지 못하였지만 JSME방법은 만족되었다. 측면홈 시험편은 R고선법에 의한 ductile tearing의 결정이 평활 시험편보다 용이하였으며, 이에 따른 $J_IC$값의 정확성을 배가 할 수 있었다. 또한 임계 스트레치존 폭($SZW_C$)은 측면홈에 의한 높은 3축응력이 발생되어 평활시험편보다 적게 나타났으며, 이러한 복합적인 원인에 기인하여 스트레치존법에 의한 $J_IC$평가는 R곡선법에 의한 평가보다 약간 과대평가됨을 알 수 있었다.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.351-358
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• 2021

This research project is a program promoted to seek diversification of domestic radioactive waste analysis institutions, and seeks public development, win-win cooperation, and cooperation between the entrusted institution and the entrusted institution. Accordingly, the entrusted institution established a standard analysis procedure for establishing a quality control system for radioactivity analysis, establishing a radiation control zone, obtaining KOLAS accreditation, and performing proficiency tests, which are the performance ranges requested by the entrusted institution, and intersecting the radioactive isotope waste generated at the actual site. Verification was performed to confirm the analysis quality. In addition, facilities and equipment for radioactivity analysis were supplemented and expanded, and the basic technology foundation and technical skills were secured through securing professional technicians and education/training. It is judged that the entrusted institution will contribute to securing radiation safety through the smooth execution of treatment, disposal, and transportation through value creation and analysis of radioactive waste generated by radioactive isotope-using institutions (research institutes, hospitals, industries, etc.) by succeeding in this research project do.