• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.705-709
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• 2002

The spacer grids in nuclear fuel assembly locate and align the fuel rods with respect to each other. They provide axial and lateral restraint against an excessive rod motion mainly caused by coolant flow. It is understood that each rod Is supported by multiple spacer grid. In such a case, it is important to determine spacer grid span so as to avoid resonance between the natural frequency of the fuel rods and excitation frequency. Actually dynamic characteristics of the fuel rods can be improved by assigning adequate spacer grid locations. When a dynamic performance of the structure is to be improved, design sensitivity analysis plays an important role as like many structural redesign problems. In this work, a shape design concept, different from conventional design, was applied to the problem. According to the theory shape can be a design parameter and optimal shape design can be found. This study concentrates on eigenvalue design sensitivity of the fuel rod supported by multiple spacer grids to determine optimal spacer grids positions.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.205-205
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• 2011

The self-assembly of ${\gamma}$-phenylalanine on Au(111) at 150 K was investigated using scanning tunneling microscopy (STM). Phenylalanine can potentially form two-dimensional (2D) molecular networks through hydrogen bonding (through the carboxyl and amino groups) and ${\pi}-{\pi}$ stacking interactions (via aromatic rings). We found that ${\gamma}$-phenylalanine molecules self-assembled on Au(111) surfaces into well-ordered structures such as ring-shaped clusters (at low and intermediate coverages) and 2D molecular domains (intermediate and monolayer coverages), whereas ${\alpha}$-phenylalanine molecules formed less-ordered structure on Au(111). The self-assembly of ${\gamma}$- but not ${\alpha}$-phenylalanine may be related to the flexibility of the carboxyl and amino groups in the molecule. Moreover, as expected, the 2D molecular network of ${\gamma}$-phenylalanine on Au(111) was mediated by a combination of hydrogen bonding and ${\pi}-{\pi}$ stacking interactions.

• Journal of Microbiology
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• v.39 no.4
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• pp.293-299
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• 2001

The nucleocapsid(NP) protein of Newcastle disease virus (NDV) and its derivative (NP$\sub$cfus)containing the myc region and six histidine residues fused to its C-terminus were pcpressed aboundantly in Escherichia coli. The proteins were purified by sucrose gradient centrifugation. Both the NP and NP$\sub$cfus/ proteins self-assem- bled into ring-like particles stacked together to from nucleocapsid-like structure which are heterogeneous in length with a diameter of 20${\pm}$2 nm and central holow of 5${\pm}$1 nm. Only a very small amount of the monomers in the particles was linked by inter-molecular disulfide bonds. Fusion of the C-terminal end to 29 amino acids inclusive of the myc epitope and His tag did not impair ring assembly buy inhibited the formation of the long herringbone structures. Immunogold lableing of the particles with the anti-myc antibody showed that the C-terminus of the NP$\sub$cfus/ protein is exposed on the surface of these ring-like particles.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.4
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• pp.219-225
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• 2010

A structure of line for producing products is variously changing to be automatic and one-person Cell-Line considering the physical burden for workers in manufacturing industry of electronic goods. However, workers tend to still accuse Work-related Musculoskeletal Disorders (including shoulder, waist, hand, wrist, leg etc.) as a simply repeated work by accelerating of the production speed for productivity improvement in the assembly line. Thus manufacturing engineers in charge of changing and set up newly for an assembly line are necessary to the construct of the guideline on human engineering. Especially. There is no standardized engineering-guide and it is difficult to create the exact work environment because the risk factor analysis and the improvement for assembly line are executed once a year on the current situation. I'd like to reduce the physical burden on workers through the effective improvement of processing by the guideline on working environment fit for a characteristic on manufacturing process when the process is changed or newly installed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.7
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• pp.328-334
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• 2002

The DNA chips are devices associating the specific recognition properties of two DNA single strands through hybridization process with the performances of the microtechnology. In the literature, the "Gene chip" or "DNA chip" terminology is employed in a wide way and includes macroarrays and microarrays. Standard definitions are not yet clearly exposed. Generally, the difference between macro and microarray concerns the number of active areas and their size, Macroarrays correspond to devices containing some tens spots of 500$\mu$m or larger in diameter. microarrays concern devices containing thousnads spots of size less than 500$\mu$m. The key technical parameters for evaluating microarray-manufacturing technologies include microarray density and design, biochemical composition and versatility, repreducibility, throughput, quality, cost and ease of prototyping. Here we report, a new method in which minute particles are arranged in a random fashion on a chip pattern using random fluidic self-assembly (RFSA) method by hydrophobic interaction. We intend to improve the stability of the particles at the time of arrangement by establishing a wall on the chip pattern, besides distinction of an individual particle is enabled by giving a tag structure. This study demonstrates the fabrication of a chip pattern, immobilization of DNA to the particles and arrangement of the minute particle groups on the chip pattern by hydrophobic interaction.ophobic interaction.

• International Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.1-8
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• 2018

Military rotorcrafts are constantly exposed to risk from bullet impacts because they operate in a battle environment. Because bullet impact damage can be deadly to crews, the fuel tanks of military rotorcraft must be designed taking extreme situations into account. Fuel tank design factors to be considered include the internal fluid pressure, the structural stress on the part impacted, and the kinetic energy of bullet strikes. Verification testing using real objects is the best way to obtain these design data effectively, but this imposes substantial burdens due to the huge cost and necessity for long-term preparation. The use of various numerical simulation tests at an early design stage can reduce the risk of trial-and-error and improve the prediction of performance. The present study was an investigation of the effects of bullet impacts on a fuel tank assembly using numerical simulation based on SPH (smoothed particle hydrodynamics), and conducted using the commercial package, LS-DYNA. The resulting equivalent stress, internal pressure, and kinetic energy of the bullet were examined in detail to evaluate the possible use of this numerical method to obtain configuration design data for the fuel tank assembly.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.2
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• pp.106-113
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• 2004

The block assembly of ship consists of a certain type of heat processes such as cutting, bending, welding, residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. Systematic and quantitative theoretical works to clarify the effects of various factors on the welding deformation have rarely been found. Therefore, in this paper, the effects of various factors, such as welding process and gravity on the butt welding deformation have been investigated through a number of numerical analyses. In addition, this paper proposes a simplified analysis method to predict the butt welding deformation in actual plate structure. For this purpose, a simple prediction model for butt welding deformations has been derived based on numerical and experimental results through the regression analysis. Based on these results, the simplified analysis method has been applied to some examples to show its validity.

• Nuclear Engineering and Technology
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• v.40 no.2
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• pp.117-126
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• 2008

In this paper, a new reactor core design is proposed on the basis of a mixed core concept consisting of a thermal zone and a fast zone. The geometric structure of the fuel assembly of the thermal zone is similar to that of a conventional thermal supercritical water-cooled reactor(SCWR) core with two fuel pin rows between the moderator channels. In spite of the counter-current flow mode, the co-current flow mode is used to simplify the design of the reactor core and the fuel assembly. The water temperature at the exit of the thermal zone is much lower than the water temperature at the outlet of the pressure vessel. This lower temperature reduces the maximum cladding temperature of the thermal zone. Furthermore, due to the high velocity of the fast zone, a wider lattice can be used in the fuel assembly and the nonuniformity of the local heat transfer can be minimized. This mixed core, which combines the merits of some existing thermal SCWR cores and fast SCWR cores, is proposed for further detailed analysis.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1022-1028
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• 2020

One of the possible options for spent-fuel management in Korea is pyroprocessing, which is a process for electrochemical recycling of spent nuclear fuel. Nuclear material accountancy is considered to be a safeguards measure of fundamental importance, for the purposes of which, the amount of nuclear material in the input and output materials should be measured as accurately as possible by means of chemical analysis and/or non-destructive assay. In the present study, a neutron measurement system based on the fast-neutron energy multiplication (FNEM) and passive neutron albedo reactivity (PNAR) techniques was designed for nuclear material accountancy of a spent-fuel assembly (i.e., the input accountancy of a pyroprocessing facility). Various parameters including inter-detector distance, source-to-detector distance, neutron-reflector material, the structure of a cadmium sleeve around the close detectors, and an air cavity in the moderator were investigated by MCNP6 Monte Carlo simulations in order to maximize its performance. Then, the detector responses with the optimized geometry were estimated for the fresh-fuel assemblies with different ²³⁵U enrichments and a spent-fuel assembly. It was found that the measurement technique investigated here has the potential to measure changes in neutron multiplication and, in turn, amount of fissile material.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.230-230
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• 2012

Graphene have showed promising performance as electrodes of organic devices such as organic transistors, light-emitting diodes, and photovoltaic solar cells. In particular, among various organic materials of graphene-based organic devices, pentacene has been regarded as one of the promising organic material because of its high mobility, chemical stability. In the bottom-contact device configuration generally used as graphene based pentacene devices, the morphology of the organic semiconductors at the interface between a channel and electrode is crucial to efficient charge transport from the electrode to the channel. For the high quality morphology, understanding of initial stages of pentacene growth is essential. In this study, we investigate self-assembly of pentacene molecules on graphene formed on a 6H-SiC (0001) substrate by scanning tunneling microscopy. At sub-monolayer coverage, adsorption of pentacene molecules on epitaxial graphene is affected by $6{\times}6$ pattern originates from the underlying buffer layer. And the orientation of pentacene in the ordered structure is aligned with the zigzag direction of the edge structure of single layer graphene. As coverage increased, intermolecular interactions become stronger than molecule-substrate interaction. As a result, herringbone structures the consequence of higher intermolecular interaction are observed.