• 제목/요약/키워드: multi-cells

검색결과 837건 처리시간 0.034초

CAI 엔진 해석을 위한 multi-zone 연소 모델의 개발 (Development of a Multi-zone Combustion Model for the Analysis of CAI Engines)

  • 이경현;임재만;김용래;민경덕
    • 한국자동차공학회논문집
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    • 제16권6호
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    • pp.74-80
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    • 2008
  • A combustion of CAI engine is purely dominated by fuel chemical reactions. In order to simulate the combustion of CAI engine, it should be considered the effect of fuel components and chemical kinetics. So it needs enormous computational power. To overcome this problem reduced problem of needing massive computational power, chemical kinetic mechanism and multi-zone method is proposed here in this paper. A reduced chemical kinetic mechanism for a gasoline surrogate was used in this study for a CAI combustion. This gasoline surrogate was modeled as a blend of iso-octane, n-heptane, and toluene. For the analysis of CAI combustion, a multi-zone method as combustion model for a CAI engine was developed and incorporated into the computational fluid dynamics code, STAR-CD, for computing efficiency. This coupled multi-zone model can calculate 3 dimensional computational fluid dynamics and multi-zoned chemical reaction simultaneously in one time step. In other words, every computational cell interacts with the adjacent cells during the chemical reaction process. It can enhance the reality of multi-zone model. A greatly time-saving and yet still relatively accurate CAI combustion simulation model based on the above mentioned two efficient methodologies, is thus proposed.

Tumorigenicity Evaluation of Umbilical Cord Blood-derived Mesenchymal Stem Cells

  • Park, Sang-Jin;Kim, Hyun-Jung;Kim, Woojin;Kim, Ok-Sun;Lee, Sunyeong;Han, Su-Yeon;Jeong, Eun Ju;Park, Hyun-shin;Kim, Hea-Won;Moon, Kyoung-Sik
    • Toxicological Research
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    • 제32권3호
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    • pp.251-258
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    • 2016
  • Mesenchymal stem cells (MSCs) have been identified in multiple types of tissue and exhibit characteristic self-renewal and multi-lineage differentiation abilities. However, the possibility of oncogenic transformation after transplantation is concerning. In this study, we investigated the tumorigenic potential of umbilical cord blood-derived MSCs (hUCB-MSCs) relative to MRC-5 and HeLa cells (negative and positive controls, respectively) both in vitro and in vivo. To evaluate tumorigenicity in vitro, anchorage-independent growth was assessed using the soft agar colony formation assay. hUCB-MSCs and MRC-5 cells formed few colonies, while HeLa cells formed a greater number of larger colonies, indicating that hUCB-MSCs and MRC-5 cells do not have anchorage-independent proliferation potential. To detect tumorigenicity in vivo, hUCB-MSCs were implanted as a single subcutaneous injection into BALB/c-nu mice. No tumor formation was observed in mice transplanted with hUCB-MSCs or MRC-5 cells based on macro- and microscopic examinations; however, all mice transplanted with HeLa cells developed tumors that stained positive for a human gene according to immunohistochemical analysis. In conclusion, hUCB-MSCs do not exhibit tumorigenic potential based on in vitro and in vivo assays under our experimental conditions, providing further evidence of their safety for clinical applications.

Functional Gene Analysis to Identify Potential Markers Induced by Benzene in Two Different Cell Lines, HepG2 and HL-60

  • Kim, Youn-Jung;Song, Mi-Kyung;Sarma, Sailendra Nath;Choi, Han-Saem;Ryu, Jae-Chun
    • Molecular & Cellular Toxicology
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    • 제4권3호
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    • pp.183-191
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    • 2008
  • Volatile organic compounds (VOCs) are common constituents of cleaning and degreasing agents, paints, pesticides, personal care products, gasoline and solvents. And VOCs are evaporated at room temperature and most of them exhibit acute and chronic toxicity to human. Benzene is the most widely used prototypical VOC and the toxic mechanisms of them are still unclear. The multi-step process of toxic mechanism can be more fully understood by characterizing gene expression changes induced in cells by toxicants. In this study, DNA microarray was used to monitor the expression levels of genes in HepG2 cells and HL-60 cells exposed to the benzene on IC20 and IC50 dose respectively. In the clustering analysis of gene expression profiles, although clusters of HepG2 and HL-60 cells by benzene were divided differently, expression pattern of many genes observed similarly. We identified 916 up-regulated genes and 1,144 down-regulated genes in HepG2 cells and also 1,002 up-regulated genes and 919 down-regulated genes in HL-60 cells. The gene ontology analysis on genes expressed by benzene in HepG2 and HL-60 cells, respectively, was performed. Thus, we found some principal pathways, such as, focal adhesion, gap junction and signaling pathway in HepG2 cells and toll-like receptor signaling pathway, MAPK signaling pathway, p53 signaling pathway and neuroactive ligand-receptor interaction in HL-60 cells. And we also found 16 up-regulated and 14 down-regulated commonly expressed total 30 genes that belong in the same biological process like inflammatory response, cell cycle arrest, cell migration, transmission of nerve impulse and cell motility in two cell lines. In conclusion, we suggest that this study is meaningful because these genes regarded as strong potential biomarkers of benzene independent of cell type.

Effect of Valproic acid, a Histone Deacetylase Inhibitor, on the Expression of Pluripotency and Neural Crest Specific Marker Genes in Murine Multipotent Skin Precursor Cells

  • Hong, Ji-Hoon;Park, Sang-Kyu;Roh, Sang-Ho
    • International Journal of Oral Biology
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    • 제35권4호
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    • pp.209-214
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    • 2010
  • Cells that have endogenous multipotent properties can be used as a starting source for the generation of induced pluripotent cells (iPSC). In addition, small molecules associated with epigenetic reprogramming are also widely used to enhance the multi- or pluripotency of such cells. Skinderived precursor cells (SKPs) are multipotent, sphereforming and embryonic neural crest-related precursor cells. These cells can be isolated from a juvenile or adult mammalian dermis. SKPs are also an efficient starting cell source for reprogramming and the generation of iPSCs because of the high expression levels of Sox2 and Klf4 in these cells as well as their endogenous multipotency. In this study, valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, was tested in the generation of iPSCs as a potential enhancer of the reprogramming potential of SKPs. SKPs were isolated from the back skins of 5-6 week old C57BL/6 X DBA/2 F1 mice. After passage 3, the SKPs was treated with 2 mM of VPA and the quantitative real time RT-PCR was performed to quantify the expression of Oct4 and Klf4 (pluripotency specific genes), and Snai2 and Ngfr (neural crest specific genes). The results show that Oct4 and Klf4 expression was decreased by VPA treatment. However, there were no significant changes in neural crest specific gene expression following VPA treatment. Hence, although VPA is one of the most potent of the HDAC inhibitors, it does not enhance the reprogramming of multipotent skin precursor cells in mice.

고효율 다결정 실리콘 태양전지 제작을 위한 나노크기의 피라미드 텍스쳐 제작 (Nanoscale Pyramid Texture for High Efficiency Multi-Crystalline Silicon Solar Cells)

  • 허종;박민준;지홍섭;김진혁;정채환
    • Current Photovoltaic Research
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    • 제5권1호
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    • pp.25-27
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    • 2017
  • Nanoscale textured black silicon has attracted intensive attention due to its great potential as applications in multicrystalline silicon-based solar cells. It absorbs sunlight over a broad range of wavelengths but introduces large recombination centers, non-uniform doping into cell. In this study, we present a metal-assisted chemical etching technique plus alkaline etching process to fabricate nanoscale pyramid structures with optimized condition. To make the structures, silver nanoparticles-loaded mc-Si wafer was submerged into $H_2O_2/HF$ solution first for nanohole texturing the wafer and textured wafer etched again with KOH solution for making nanoscale pyramid structures. The average reflectivity (350-1050 nm) is about 8.42% with anti-reflection coating.

고분자전해질형연료전지의 가스 채널 최적화를 위한수치적연구(I) -가스 채널 치수가 전류밀도와 HFR 분포에 미치는영향성- (Numerical Study of Land/Channel Flow-field Optimization in Polymer Electrolyte Fuel Cells (PEFCs) (I) -The Effects of Land/Channel Flow-field on Current Density and HFR Distributions-)

  • 주현철
    • 대한기계학회논문집B
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    • 제32권9호
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    • pp.683-694
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    • 2008
  • The performance and durability of Polymer Electrolyte Fuel Cells (PEFCs) are strongly influenced by the uniformity of current density, temperature, species distributions inside a cell In order to obtain uniform distributions in them, the optimal design of flowfield must be a key factor. In this paper, the numerical study of land/channel flowfield optimizations is performed, using a multi-dimensional, multi-phase, non-isothermal PEFC model. Numerical simulations reveal more uniform current density and HFR(High Frequency Resistance) distributions and thus better PEFC performance with narrower land/channel width where the less severe oxygen depletion effect near the land region and more uniform contact resistance variation along the in-plane direction are achieved. The present study elucidates detailed effects of land/channel width and assist in identifying optimal flow-field design strategies for the operation of PEFCs.

Al2O3/Si/Al2O3구조를 이용한 실리콘태양전지 제작 및 특성 (Fabrication and Properties of Silicon Solar Cells using Al2O3/Si/Al2O3 Structures)

  • 김광호
    • 반도체디스플레이기술학회지
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    • 제14권4호
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    • pp.45-49
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    • 2015
  • Using a combined CVD and ALD equipment system, multi-layer quantum well structures of $Al_2O_3/a-Si/Al_2O_3$ were fabricated on silicon Schottky junction devices and implemented to quantum well solar cells, in which the 1~1.5 nm thicknesses of the aluminum oxide films and the a-Si thin film layers were deposited at $300^{\circ}C$ and $450^{\circ}C$, respectively. Fabricated solar cell was operated by tunneling phenomena through the inserted quantum well structure being generated electrons on the silicon surface. Efficiency of the fabricated solar cell inserted with multi-quantum well of 41 layers has been increased by about 10 times that of the solar cell of pure Schottky junction solar cell.

전극의 임피던스 감소를 위해 백금 도금한 ITO 신경신호 검출용 다중 전극 제작 (The fabrication of Pt electroplating on ITO multi-electrode array in neuronal signal detection)

  • 권광민;최준호;이경진;박정호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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    • pp.257-259
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    • 2002
  • In investigating the characteristics of a neural network, the use of planar microelectrode array shows several advantages over normal intracellular recording[1]. A transparent indium tin oxide(ITO) multi-electrode array(MEA) was fabricated and its top surface was insulated with photodefinable polyimide(HD-8001) except the exposed area for interfacing between the ITO electrodes and the neuronal cells. The exposed ITO electrodes were platinized in order to reduce the impedance between the electrodes and electrolyte. The one-minute platinization with $0.99nA/{\mu}m^2$ current density reduced the average impedance of the electrodes from $2.5M\Omega\;to\;90k\Omega$ at 1kHz in normal ringer solution. Cardiac cells were cultured on this MEA as a pilot study before neuron culture. The signals detected by the platinized electrodes had larger amplitudes and improved signal to noise ratio(SNR) compared to non-platinized electrodes. It is clear that microelectrodes need to have lower impedance to make reliable extracellular recordings, and thus platinization is essential part of MEA fabrication. Burst spike of cultured olfactory bulb was also detected with the MEA having platinized electrodes.

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Development and Verification of Make-up Base Containing Aloe

  • Min, Hyejo;Kim, MinJung;Kim, Jeonghee
    • 패션비즈니스
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    • 제19권3호
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    • pp.121-129
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    • 2015
  • Aloe is a popular and effective agent used to cosmetic ingredient. It could replace artificial pigment on make-up base product and it is highly probable that might be useful as ingredients of multi-functional color cosmetic. In this study, we made a makeup base containing aloe extract and tested the effectiveness, safety and stability. Contents of polyphenol and flavonoid from the aloe extract were measured. To determine the antimicrobial effect from the aloe we used the paper disc diffusion method. We assessed the safety of make-up base containing aloe to cultured macrophage RAW 264.7 cells by MTT assay. Polyphenol contents of aloe extract and flavonoid respectively were 48 mg/g and 10 mg/g, in the 10 % concentration aloe extract. In case of aloe make-up base, the clear zone against Stapylococcus epidermidis was 9~11 mm and Stapylococcus aureus was also 9~11 mm. Growth activity of macrophage RAW 264.7 cells was over 80% in all concentration of make-up base containing aloe and general make base product. In conclusion aloe extract may be able to substitute the synthetic pigments and considered to be uses for ingredients multi-functional color cosmetic's ingredient.

Hypergraph Game Theoretic Solutions for Load Aware Dynamic Access of Ultra-dense Small Cell Networks

  • Zhu, Xucheng;Xu, Yuhua;Liu, Xin;Zhang, Yuli;Sun, Youming;Du, Zhiyong;Liu, Dianxiong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제13권2호
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    • pp.494-513
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    • 2019
  • A multi-channel access problem based on hypergraph model in ultra-dense small cell networks is studied in this paper. Due to the hyper-dense deployment of samll cells and the low-powered equipment, cumulative interference becomes an important problem besides the direct interference. The traditional binary interference model cannot capture the complicated interference relationship. In order to overcome this shortcoming, we use the hypergraph model to describe the cumulative interference relation among small cells. We formulate the multi-channel access problem based on hypergraph as two local altruistic games. The first game aims at minimizing the protocol MAC layer interference, which requires less information exchange and can converge faster. The second game aims at minimizing the physical layer interference. It needs more information interaction and converges slower, obtaining better performance. The two modeled games are both proved to be exact potential games, which admit at least one pure Nash Equilibrium (NE). To provide information exchange and reduce convergecne time, a cloud-based centralized-distributed algorithm is designed. Simulation results show that the proposed hypergraph models are both superior to the existing binary models and show the pros and cons of the two methods in different aspects.