• Journal of Life Science
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• v.17 no.3 s.83
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• pp.305-311
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• 2007

Glucocorticoids (GCs) alter metabolism, synaptogenesis, apoptosis, neurogenesis, and dendritic morphology in the hippocampus. To better understand how glucocorticoids regulate these aspects of hippocampal biology, we studied gene expression patterns in the CA3 (Hippocampal pyramidal cell field CA3) and dentate gyrus (DG). Litter-matched Lewis inbred rats treated for 20 days with either 9.5 mg per day sustained-release corticosterone or placebo pellets were compared with high-density oligonucleotide microarray analysis (Rat Neurobiology U34 Arrays, Affymetrix). In placebo-treated rats, 32 genes were expressed at greater levels in CA3 than DG, whereas 3 genes were expressed at great levels in DC than CA3. Regional differences were also apparent in corticosterone-induced changes in the hippocampal transcriptome. Six genes in CA3 and 41 genes in DC were differentially regulated by corticosterone. As per the glucocorticoid effects on gene transcription in the brain, forty three of these genes were upregulated, and 4 genes were downregulated. Genes differentially expressed in hippocampus included those for 13 neurotransmitter proteins, 5 ion channel related proteins, 4 transcription factors, 3 neurotrophic factors, 1 cytokine, 1 apoptosis related protein, and 5 genes involved in synaptogenesis. Interestingly, GCs can have suppressive effects on brain BDNF mRNA transcription, one of the neurotrophic factors. These results indicate the diversity of targets affected by chronic exposure to corticosterone and highlight important regional differences in hippocampal neurobiology.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.8
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• pp.117-124
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• 2009

This paper describes a 3 to 5 GHz frequency synthesizer for MB-OFDM (Multi-Band OFDM) UWB (Ultra- Wideband) application using 0.13 ${\mu}m$ CMOS process. The frequency synthesizer operates in the band group 1 whose center frequencies are 3432 MHz 3960 MHz, and 4488 MHz. To cover the overall frequencies of group 1, an efficient frequency planning minimizing a number of blocks and the power consumption are proposed. And, a high-frequency VCO and LO Mixer architecture are also presented in this paper. A new mixed coarse tuning scheme that utilizes the MIM capacitance, the varactor arrays, and the DAC is proposed to expand the VCO tuning range. The frequency synthesizer can also provide the clock for the ADC in baseband modem. So, the PLL for the ADC in the baseband modem can be removed with this frequency synthesizer. The single PLL and two SSB-mixers consume 60 mW from a 1.2 sV supply. The VCO tuning range is 1.2 GHz. The simulated phase noise of the VCO is -112 dBc/Hz at 1 MHz offset. The die area is 2 ${\times}$ 2mm$^2$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.936-944
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• 2003

In this paper, we propose an AND/XOR-based technology mapping method for field programmable gate arrays (FPGAs). Due to the fixed size of the programmable blocks in an FPGA, decomposing a circuit into sub-circuits with appropriate number of inputs can achieve excellent implementation efficiency. Specifically, the proposed technology mapping method is based on Davio expansion theorem to decompose a given Boolean circuit. The AND/XOR nature of the proposed method allows it to operate on XOR intensive circuits, such as error detecting/correcting, data encryption/decryption, and arithmetic circuits, efficiently. We conduct experiments using MCNC benchmark circuits. When using the proposed approach, the number of CLBs (configurable logic blocks) is reduced by 67.6% (compared to speed-optimized results) and 57.7% (compared to area-optimized results), total equivalent gate counts are reduced by 65.5 %, maximum combinational path delay is reduced by 56.7 %, and maximum net delay is reduced by 80.5 % compared to conventional methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.31-38
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• 2004

Mechanical design process is generally accomplished by design, analysis, and test. Designers use programs fitting purpose, and obtain repeatedly a response of a simulation program, a sub-program for optimization. In this paper, shape optimization using approximate optimization technique is carried out with sequential design domain(SDD). In addition, algorithm executing Pro/Engineer and ANSYS automatically are adopted in the approximate optimization program by SDD. It is difficult for design problem to be approximated accurately for the whole range of design space. However, more or less accurate approximation is constructed if SDD is applied to that case. SDD starts with a certain range which is off-seted from midpoint of an initial design domain and then SDD of the next step is determined by a move limited. Convergence criterion is defined such that optimal point must be located within SDD during the two steps. Also, the PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm is used to solve approximate optimization problems. This algorithm uses the second-order information and the active set strategy, in order to seek the direction of design variables.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.166-176
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• 2010

The output characteristics of photovoltaic(PV) arrays are nonlinear and are affected by the temperature and solar insolation of cells. Maximum power point tracking(MPPT) methods are used to maximize PV array output power by tracking maximum power point(MPP) continuously. To increase the output efficiency of PV system, it is important to have more efficient MPPT. This paper proposes a novel maximum power point tracking(MPPT) control algorithm considering insolation to improve efficiency of PV system. The proposed algorithm is composed perturb and observe(P&O) method and constant voltage(CV) method. The proposed method is simulated under varying operating conditions. The effectiveness of these different MPPT methods is investigated thoroughly by PSIM simulation. The simulation results show that this proposed method provides better performance than conventional methods at a variable insolation without self-excited vibration of the power. By the simulation results, the validity of the proposed HB method is proved.

• Tribology and Lubricants
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• v.30 no.1
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• pp.59-63
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• 2014

Laser Surface Texturing(LST) is a surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact surface. In LST technology, a pulsated laser beam is used to create arranged dimples on a surface by a material ablation process, which can improve such as load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on the bearing steel(AISI 52100) to create arranged dimples. To optimize the surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by combining circles, ellipses and the laser ablation process. The tribological testing of multi-scale textured surface was performed by a flat-on-flat unidirectional tribometer under lubrication and the results compared with that of the non-textured surface. Through an increase in sliding speed, the beneficial effect of multi-scale LST performance was achieved. The multi-scale textured surface had lower friction coefficient performances than the non-textured surface due to the hydrodynamic lubrication effect.

• Korean Journal of Poultry Science
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• v.28 no.2
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• pp.143-153
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• 2001

Using bioinformatic tools for searching the massive genome databases, it is possible to Identify new genes in few minutes for initial discoveries based on evolutionary conservation, domain homology, and tissue expression patterns, followed by further verification and characterization using the bench-top works. The development of high-density two-dimensional arrays has allowed the analysis of the expression of thousands of genes simultaneously in the humans, mice, rats, yeast, and bacteria to elucidate the genes and pathways involved in physiological processes. In addition, rapid and automated protein identification is being achieved by searching protein and nucleotide sequence databases directly with data generated from mass spectrometry. Recently, analysis at the bio-chemical level such as biochemical screening and metabolic profiling (Biochemical genomics) has been introduced as an additional approach for categorical assignment of gene function. To make advantage of recent achievements in computational approaches for facilitated gene discoveries in the avian model, chicken expression sequence tags (ESTs) have been reported and deposited in the international databases. By searching EST databases, a chicken heparanase gene was identified and functionally confirmed by subsequent experiments. Using combination of sub-tractive hybridization assay and Genbank database searches, a chicken heme -binding protein family (cSOUL/HBP) was isolated in the retina and pineal gland of domestic chicken and verified by Northern blot analysis. Microarrays have identified several host genes whose expression levels are elevated following infection of chicken embryo fibroblasts (CEF) with Marek's disease virus (MDV). The ongoing process of chicken genome projects and new discoveries and breakthroughs in genomics and proteomics will no doubt reveal new and exciting information and advances in the avian research.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.134-139
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• 2005

This paper presents a robust design of vehicle interior noise using Taguchi method and a substructure synthesis method with a hybrid model. Firstly, the proposed method identifies the critical process of the concerned interior noise through a TPA (Transfer Path Analysis). Secondly, a strategy for a robust design is discussed, in which the major noise factor among uncertainties in the process is quality distribution of rubber bushes connecting a cradle and a trimmed body. Thirdly, a virtual test model fer the process is developed by applying a substructure synthesis method with a hybrid modeling approach. Fourthly, virtual tests are carried out according to the predefined tables of orthogonal array in Taguchi robust design process. The process was performed under 2 sub-steps. The first step is sensitivity analysis of 31 panels, and the other step is weight optimization of mass dampers on sensitive panels. Finally, two vehicles with the proposed countermeasures were validated. The proposed method reduces 87.5% of trials of measurements due to the orthogonal arrays and increases robustness by 8.6dB of S/N ratio and decreases $5\;dB(A){\sim}10\;dB(A)$ of interior noise in the concerned range of RPM.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.586-592
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• 2009

The preparation of structures with nanosized arrays allows mimicking many different morphologies that exist in nature. In addition, polymer is considered as a material that can be easily applicable to the fabrication of nanostructures and can effectively exhibit nanosize effects since material, synthesis and processing cost is low, and many of polymer structures are well studied. Porous alumina template prepared by anodization of aluminum among nanofabrication methods is the one of promising routes that cost-effectively provides very regularly arrayed nanostructures. In this review, we describe the fabrication of the nanotemplate and template-based polymer nanostructures and their applications.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.191-194
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• 2009

Porous alumina prepared by anodization has been widely studied since it shows very regular nanostructures at inexpensive prices. In this article, porous alumina is obtained by anodization of aluminum in the oxalic acid. After the first formed oxide is selectively removed from the aluminum substrate, the hexagonal nanostructures on the fresh aluminum are converted to nanodots by the second anodization in boric acid. Nanodots are arrayed in the convex of the hexagonal nanostructures. The optimization condition for the fabrication of nanodots with a height of 20 nm is investigated in detail. Subsequently, a gold film is deposited on the nanodots, resulting in the formation of gold nanodots arrays which are probably interesting substrate for biosensor applications.