排序方式: 共有38条查询结果,搜索用时 15 毫秒
1.
This paper presents the model of a k-out-of-n: G system with common mode outages. The objective is to analytically derive the mean operating mode between failures for a non-repairable component system. The average system failure time and the system availability are also considered. Then, the model is extended to a system with repairable components and unrestricted repair, in which service times are exponentially distributed. 相似文献
2.
This study employs a relational dialectics approach to gain insights into the nature of relational communication via Cyworld , a Korean social network site. Qualitative analysis of in-depth interview data from 49 users suggests that Cyworld users routinely negotiate multiple dialectical tensions that are created within the online world, transferred from face-to-face contexts, or imposed by interpersonal principles that relate to Korea's collectivistic culture. The interviewees experienced a new relational dialectic of interpersonal relations versus self-relation, analogous to Baxter and Montgomery's (1996) connection-autonomy contradiction. Their responses suggest that Cyworld's design features and functions encourage users to transcend the high-context communication of Korean culture by offering an alternative channel for elaborate and emotional communication, which fosters the reframing of relational issues offline. Cy-Ilchons (online buddies) virtually extend the Korean cultural concept of blood ties, called yons, in ways that intensify the openness-closedness contradiction at early stages of relationship formation. 相似文献
3.
4.
Jae-Wook Lee Kyung-June Hwang Wang-Geun Shim Kyung-Hee Park Hal-Bon Gu Kyu-Hyuk Kwun 《Korean Journal of Chemical Engineering》2007,24(5):847-850
Dye sensitized solar cells (DSSCs) have been receiving significant attention because they have many advantages compared to
conventional organic solar cells. It has been known that the photovoltaic characteristics of DSSC are highly dependent on
the adsorption properties of dyes on TiO2 films. To analyze the surface heterogeneity of TiO2 surfaces, single-phase anatase nanocrystallite titanium films were prepared by sol-gel method using the hydrolysis reaction
of titanium tetraisopropoxide under acidic condition and characterized by XRD, FE-SEM and BET analysis. The adsorption energy
distribution functions were calculated by the generalized nonlinear regularization method. It was found that the shape and
the intensity of the adsorption energy distribution curve determined were highly related with the physical properties (i.e.,
geometrical heterogeneity) and chemical characteristics (i.e., energetic heterogeneity) of nanocrystalline TiO2 for DSSC. 相似文献
5.
6.
Jeon-Hee Kim Seung-Joon Yoo Dong-Heui Kwak Heung-Joe Jung Tae-Young Kim Kyung-Hee Park Jae-Wook Lee 《Nanoscale research letters》2014,9(1):44
Alumina nanofibers were prepared by a technique that combined the sol–gel and electrospinning methods. The solution to be electrospun was prepared by mixing aluminum isopropoxide (AIP) in ethanol, which was then refluxed in the presence of an acid catalyst and polyvinylpyrolidone (PVP) in ethanol. The characterization results showed that alumina nanofibers with diameters in the range of 102 to 378 nm were successfully prepared. On the basis of the results of the XRD and FT-IR, the alumina nanofibers calcined at 1,100°C were identified as comprising the α-alumina phase, and a series of phase transitions such as boehmite → γ-alumina → α-alumina were observed from 500°C to 1,200°C. The pore size of the obtained γ-alumina nanofibers is approximately 8 nm, and it means that they are mesoporous materials. The kinetic study demonstrated that MO adsorption on alumina nanofibers can be seen that the pseudo-second-order kinetic model fits better than the pseudo-first-order kinetic model. 相似文献
7.
Use of biosurfactant to remediate phenanthrene-contaminated soil by the combined solubilization-biodegradation process 总被引:1,自引:0,他引:1
The applicability of the combined solubilization-biodegradation process was examined using soil-packed column. In the solubilization step, 50 pore volumes of 150 mg/l biosurfactants solution was injected and the percentage removal of phenanthrene (mg) was 17.3% and 9.5% from soil with pH 5 and 7, respectively. The highest solubility was detected at pH 5 and this result confirmed that adjusting the pH of the biosurfactants solution injected could enhance the solubility of phenanthrene. Following this, soil samples were completely transferred to batches and incubated for 10 weeks to monitor phenanthrene degradation. The phenanthrene concentration in the soil samples decreased significantly during the biodegradation step in all soil samples, except for the soil sample that was flushed with biosurfactants solution with pH 4. This indicated that the degradation of contaminants by specific species might not be affected by the residual biosurfactants following application of the solubilization process. Moreover, these results suggested that the biosurfactant-enhanced flushing process could be developed as a useful technology with no negative effects on subsurface environments and could be combined with the biodegradation process to increase the removal efficiency. 相似文献
8.
Mu-Hyon Kim Kyeongsoon Park Kyung-Hee Choi Soo-Hong Kim Se Eun Kim Chang-Mo Jeong Jung-Bo Huh 《International journal of molecular sciences》2015,16(5):10324-10336
The authors describe a new type of titanium (Ti) implant as a Modi-anodized (ANO) Ti implant, the surface of which was treated by sandblasting, acid etching (SLA), and anodized techniques. The aim of the present study was to evaluate the adhesion of MG-63 cells to Modi-ANO surface treated Ti in vitro and to investigate its osseointegration characteristics in vivo. Four different types of Ti implants were examined, that is, machined Ti (control), SLA, anodized, and Modi-ANO Ti. In the cell adhesion study, Modi-ANO Ti showed higher initial MG-63 cell adhesion and induced greater filopodia growth than other groups. In vivo study in a beagle model revealed the bone-to-implant contact (BIC) of Modi-ANO Ti (74.20% ± 10.89%) was much greater than those of machined (33.58% ± 8.63%), SLA (58.47% ± 12.89), or ANO Ti (59.62% ± 18.30%). In conclusion, this study demonstrates that Modi-ANO Ti implants produced by sandblasting, acid etching, and anodizing improve cell adhesion and bone ongrowth as compared with machined, SLA, or ANO Ti implants. These findings suggest that the application of Modi-ANO surface treatment could improve the osseointegration of dental implant. 相似文献
9.
Cho Jeong-Yong Jeong Seung-Jae Lee Hee La Park Kyung-Hee Hwang Do Young Park Sun-Young Lee Yu Geon Moon Jae-Hak Ham Kyung-Sik 《Food science and biotechnology》2016,25(6):1701-1708
Food Science and Biotechnology - Ten compounds, including a new guaiane-type sesquiterpene lactone, were isolated from the aerial parts of Artemisia scoparia. The structure of the new compound was... 相似文献
10.
In this study, hybrid silica-conjugated TiO2 photoelectrodes were developed in order to enhance the efficiency of a dye-sensitized solar cell. The relative changes in surface crystallite size and chemical surface states of TiO2 composites were investigated by XRD, XPS, and UV-vis spectroscopy. Therein, the chemical compositions of the nanostructured photoelectrode surfaces were observed to significantly change when the glass powder Si atoms became chemically bonded with the Ti atoms on the photoelectrode surface without appreciable changes to the crystalline structure of TiO2. Furthermore, a significant conversion of Si-Ox into Si-O at the surface of the photoelectrode was observed following the addition of glass powder, which confirms the covalent bonding of Si and Ti atoms into Ti-O-Si. A maximum cell efficiency (η from 5.8% to 8.5%) was observed when 2 wt% of the low-temperature glass powder was added to the TiO2 with a constant amount of dye loading. This observed peak in solar cell efficiently is most likely due to an increase in light harvesting, which is a result of an enhancement of light scattering and the coordination between Ti and Si to establish a Ti-O-Si bond. 相似文献