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991.
Tin-catalyzed silicon nanowires were synthesized for solar cells application. Voluminous silicon nanowires were fabricated on single crystalline silicon wafer. Optical reflectance and solar cell efficiency of the synthesized silicon nanowires were explored. The reflectance of as-synthesized silicon nanowires was obtained approximately 5% in the short wavelength region (λ < 500 nm). A short circuit current of 2.3 mA/cm2 and open circuit voltage of 520 mV for 1 cm2 SiNWs solar cell was obtained. 相似文献
992.
Sok Won Kim Jaeran Lee Bo-Min Jeon Eun Jung Sang Hyun Lee Kweon Ho Kang Kwon Taek Lim 《International Journal of Thermophysics》2009,30(4):1234-1241
Lead–tin (Pb–Sn) alloys are the dominant solders used for electronic packaging because of their low cost and superior properties
required for interconnecting electronic components. However, increasing environmental and health concerns over the toxicity
of lead, combined with global legislation to limit the use of Pb in manufactured products, have led to extensive research
and development studies of lead-free solders. The Sn–Ag–Cu ternary eutectic alloy is considered to be one of the promising
alternatives. Except for thermal properties, much research on several properties of Sn–Ag–Cu alloy has been performed. In
this study, five Sn–xAg–0.5Cu alloys with variations of Ag content x of 1.0 mass%, 2.5 mass%, 3.0 mass%, 3.5 mass%, and 4.0 mass% were prepared, and their thermal diffusivity and specific heat
were measured from room temperature to 150 °C, and the thermal conductivity was calculated using the measured thermal diffusivity,
specific heat, and density values. Also, the linear thermal expansion was measured from room temperature to 170 °C. The results
show that Sn–3.5Ag–0.5Cu is the best candidate because it has a maximum thermal conductivity and a low thermal expansion,
which are the ideal conditions to be a proper packaging alloy for effective cooling and thermostability. 相似文献
993.
The thermal radiation which generated from the patterned Ta/Pt/Ta thin heater achieved a high temperature up to 1010 °C under applied current of 2.4 A. In order to reduce an electromigration at high current of 2 A, a Ta capping layer was placed on the Pt layer instead of conventional capping layer, such as SiNx and CoWP. Under the thermal radiation at the applied current of 2 A in the Ta/Pt/Ta thin heater, the Ta capping layer enhanced the lifetime of the Pt thin heater up to 5 h. A stamping process for the crystallization of a-Si was performed for 40 samples using the Ta/Pt/Ta thin heater. For all samples, a-Si has been selectively crystallized and Raman peaks were located near 519 cm− 1. These results indicated that the thermal radiation of the Ta/Pt/Ta thin heater was maintained constantly due to the Ta capping. 相似文献
994.
Hardness and thermal stability of TiAlBN coatings prepared by alternating deposition of TiAlN and BN with high rotation speed of substrate holder (∼7 rpm) have been investigated. The TiAlN and BN were deposited by reactive sputtering of Ti0.5Al0.5 and BN targets with N2 and Ar reactive gases, respectively. Despite alternating deposition, the TiAlBN coating did not show layered structure due to high rotation speed of substrate holder. By TEM analysis, the TiAlBN coating was observed to be nanocomposite with grain less than 10 nm in size. Compared to TiAlN coating, the TiAlBN nanocomposite coating showed superior hardness. Furthermore, the hardness of the coating increased after the heat-treatment in N2 atmosphere up to 800 °C. By comparison with TiAlN/BN nanoscale multilayered coating prepared by the same deposition method except the lower rotation speed of substrate holder (∼1 rpm), the hardness enhancement after annealing, ‘self-hardening’, of the TiAlBN nanocomposite coating is believed to be due to the sharpness in chemical composition at the interface between TiAlN and BN phase. 相似文献
995.
Hyung Lee-Kwang Choong Ho Cho 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》1996,26(2):340-344
In this paper, a hierarchical reduction method of hypergraphs is proposed. A macro-vertex in a reduced hypergraph corresponds to an edge of the original hypergraph, and thus a reduced hypergraph can provide a partition of a system. The reduction is realized by the iterations and the sequence of hierarchical reduction gives a sequence of hierarchical partitions. The proposed method allows to reduce and decompose the complexity of the system represented by hypergraphs. 相似文献
996.
Jae Kyoung Mun Jong Won Lim Jae Jin Lee Jeon Wook Yang 《Microelectronics Reliability》1999,39(12):997
The effect of thermal stress on the d.c. parameter degradation of enhancement mode tungsten nitride (WNx) self-aligned gate GaAs MESFETs was investigated. Threshold voltage, source-drain current and transconductance were measured during the tests. The physical properties of the device after thermal stress were analyzed by means of Auger electron spectroscopy (AES), X-ray diffractometry to identify the degradation mechanism. The d.c. failure mode consists of an increase in the threshold voltage and a decrease in the current and transconductance of the FETs. The device simulator was also used for analytical understanding of the d.c. parameter degradation. The simulated results showed that d.c. parameter degradation was mainly attributed to the increase in source and drain ohmic contact resistances. From the AES analysis, we found that the increase of contact resistance was due to carrier compensation, which was caused by Ga outdiffusion and Ni indiffusion under the ohmic contact layer. Therefore the thermally activated carrier compensation effects by trap generation are proposed to be the main failure mechanism for d.c. parameter degradation of enhancement mode WNx self-aligned gate GaAs MESFETs. 相似文献
997.
Soo-Hwan Lim Jong-In Baek Byeong-Min Jeon Jung-Woo Seo Min-Sung Kim Ji-Young Byun Soo-Hoon Park Su-Jin Kim Ju-Young Lee Jun-Hyoung Lee Sun-Chang Kim 《International journal of molecular sciences》2021,22(21)
Protopanaxadiol (PPD), an aglycon found in several dammarene-type ginsenosides, has high potency as a pharmaceutical. Nevertheless, application of these ginsenosides has been limited because of the high production cost due to the rare content of PPD in Panax ginseng and a long cultivation time (4–6 years). For the biological mass production of the PPD, de novo biosynthetic pathways for PPD were introduced in Saccharomyces cerevisiae and the metabolic flux toward the target molecule was restructured to avoid competition for carbon sources between native metabolic pathways and de novo biosynthetic pathways producing PPD in S. cerevisiae. Here, we report a CRISPRi (clustered regularly interspaced short palindromic repeats interference)-based customized metabolic flux system which downregulates the lanosterol (a competing metabolite of dammarenediol-II (DD-II)) synthase in S. cerevisiae. With the CRISPRi-mediated suppression of lanosterol synthase and diversion of lanosterol to DD-II and PPD in S. cerevisiae, we increased PPD production 14.4-fold in shake-flask fermentation and 5.7-fold in a long-term batch-fed fermentation. 相似文献
998.
Kyong-Hwan Chung Sangmin Jeong Heon Lee Sun-Jae Kim Ki-Joon Jeon Young-Kwon Park Sang-Chul Jung 《International Journal of Hydrogen Energy》2017,42(38):24099-24107
Photocatalytic decomposition of acetaldehyde-contained wastewater was assessed for the degradation of pollutants and the production of hydrogen. Liquid phase plasma was applied in the photoreaction as a light source. The evolution of hydrogen and acetaldehyde degradation were characterized by the photocatalytic decomposition system. Ni-loaded TiO2 photocatalysts and various porous materials were introduced to the photocatalytic reaction. The photochemical decomposition by irradiation of the liquid phase plasma without photocatalysts produced some hydrogen evolution with the degradation of acetaldehyde, which was attributed to the decomposition of the reactant by active species generated by the irradiation of liquid phase plasma. The Ni loading on TiO2 brought out an enhancement of acetaldehyde degradation and hydrogen evolution. In the photocatalysis of acetaldehyde-contained wastewater using the liquid phase plasma, hydrogen evolution was accelerated due to the additional hydrogen production by the photocatalytic decomposition of acetaldehyde. The porous materials could be used as an effective photocatalytic support. MCM-41 mesoporous material has acted as a highly efficient photocatalytic support to the TiO2 photocatalyst. 相似文献
999.
Jiyoung Kim Jung Nam Choi Joo Hee Choi Youn Soo Cha Maria John Muthaiya Choong Hwan Lee 《Molecular nutrition & food research》2013,57(10):1886-1891
As a nontargeted metabolomics approach, we investigated changes in the plasma metabolite levels in a mouse model of obesity induced by a high‐fat diet and fermented soybean product diet. We analyzed the plasma samples by using ultra‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry (UPLC‐Q‐TOF‐MS). In the present study, the animals were divided into four groups according to the diet type; normal fat diet control group (ND), high‐fat diet control group (HD), high‐fat diet plus 30% cooked soybean power (HD + S), and high‐fat diet plus 30% 72‐h fermented Cheonggukjang powder (HD + CGJ). To examine the changes in plasma metabolite levels because of high‐fat diet feeding, total cholesterol and triglyceride levels were measured. Total cholesterol and triglyceride levels were lower in the HD + S and HD + CGJ groups than in the ND group. According to partial least‐squares discriminant analysis (PLS‐DA), major metabolites contributing to the discrimination between each group were assigned as lipid metabolites in plasma, e.g., lyso‐phosphatidylcholines and phosphatidylcholines. Therefore, diets containing soy‐based food products, which are rich sources of isoflavonoids, might be helpful for controlling the lipid metabolism under high‐fat diet conditions. 相似文献
1000.
Analysis of 1/f noise in LWIR HgCdTe photodiodes 总被引:2,自引:0,他引:2
Soo Ho Bae Sang Jun Lee Young Ho Kim Hee Chul Lee Choong Ki Kim 《Journal of Electronic Materials》2000,29(6):877-882
We study the 1/f noise currents and dark currents in LWIR HgCdTe photodiodes. The measured dark currents of the diodes processed
by post implantation annealing with different annealing times are analyzed using current model fitting methods. The different
dark current components, such as diffusion current, generation-recombination current, band-to-band tunneling current, and
trap assisted tunneling current, at various bias voltages can be separated from the measured dark currents. By the fitting
analysis, some physical parameters are extracted and different annealing effects can be explained by the parameters. The improvements
in diode characteristics by post implantation annealing can be explained by the changes of trap density, donor concentration,
minority carrier lifetime, and generation lifetime. The 1/f noise currents are measured over a wide range of reverse bias
voltages, and correlated with the extracted dark currents by superposition of the noise generated by the different dark current
mechanisms. It turns out that the band-to-band tunneling has a smaller correlation with the 1/f noise than other current components,
and the trap center seems to be responsible for the 1/f noise characteristics of the LWIR HgCdTe photodiodes. 相似文献