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1.
This paper reports an alternative method for the growth of GaN epitaxial layer on (0001) Al2O3 substrate by hot-wall vapor phase epitaxy technique. Tris (N,N-dimethyldithiocarbamato)-gallium (III), Ga(mDTC)3 was introduced as a precursor material for the seed layer formation in the growth of GaN. Optimal growth conditions with seed layers formed by the Ga(mDTC)3 concentration of 0.047 mol/L were identified: Growth temperature was found to be 850 °C, and optimal distance between the reactant outlet and substrate was determined to be 12.5 cm. Characterization results showed that this growth method produce high-crystallinity GaN epitaxial layers at a relatively lower growth temperature compared to the existing growth techniques and simplify the growth process.  相似文献   
2.
An inventory model is considered in which inventory is depleted not only by demand, but also by deterioration. Hence, in this paper, we derive the EOQ model for inventory of items that deteriorate at a Weibull-distributed rate, assuming the demand rate with a continuous function of time. Moreover, the proposed model cannot be solved directly in a closed form, thus we used the computer software IMSL MATH/LIBRARY (1989) to find the optimal reorder time. Further, we also find that the optimal procedure is independent from the form of the demand rate. Finally, we also assume that the holding cost is a continuous, non-negative and non-decreasing function of time in order to generalize the EOQ model. Moreover, four numerical examples and sensitivity analyses are provided to assess the solution procedure.  相似文献   
3.
We have successively fabricated inverted bulk heterojunction polymer solar cells employing ZnO and MoO3 as electron and hole selective layers, respectively. The device structure is ITO/ZnO/P3HT: PCBM/MoO3/Al. Differently from conventional polymer solar cells, ITO and Al work as electron and hole collecting electrodes in this inverted structure, respectively. We have found the optimal thickness of ZnO and MoO3 to be 100 nm and 5 nm, respectively. The highest PCE was obtained to be 3.32% under AM 1.5 illumination at 1,000W/m2, which is the highest PCE of inverted solar cells reported previously in the literature.  相似文献   
4.
Maintenance float problems in a flexible manufacturing system structure are intractable. Therefore, there is a need for an enumerative search method to solve such problems. This study presents a novel genetic algorithm to search for the optimal float and capacity of repair stations for FMS maintenance float systems. The proposed algorithm is operated under a feasible set of failure rates to investigate how its performance dominates the enumerative search algorithm. Experimental results indicate that the genetic algorithm is more promising than the enumerative search algorithm in searching for the best approximate solution and in minimizing the execution time.  相似文献   
5.
The study explores the inventory replenishment policies for the cases with time-varying demand, linearly increasing deterioration rate, partial back-ordering, constant service level and equal replenishment intervals over a fixed planning horizon. Since it is difficult to solve the problem directly, we derive the upper bound of replenishment number for a specific planning horizon and find the solution of service level under a given number of replenishment. The optimal solutions of replenishment number and service level are then determined. Numerical examples and sensitivity analyses are also provided to illustrate the solution procedure.  相似文献   
6.
Healthcare today is mainly knowledge-based and the diffusion of medical knowledge is imperative for proper treatment of patients. Our study of the industry explored barriers to knowledge flow using a Cultural Historical Activity Theory framework. Our work was exploratory and qualitative in nature, and consisted of three phases: in-depth interviews to explore medical knowledge flow barriers resulting in a model; a case study using a survey approach to test and modify the model; and a Delphi study to validate the generalizability of the model.  相似文献   
7.
The use of inorganic nano-semiconductor/polymer blend as the active layer for organic bulk hetero-junction solar cell is an alternative to change and improve the device characteristics and performance. Effects of CdSe/P3HT composition in the blend and its loading amount in the solvent on the electrical and structural properties of active layers formed were investigated. The results of atomic force microscopy study indicated that the surface roughness of composite active layer could be controlled below 10 nm for the entire range of composite loading amount investigated in this study. The transmission line method experiments have demonstrated that the electrical percolation pathways could be developed at the critical loading amount of CdSe/P3HT composite, resulting in the abrupt decrease of sheet resistance and significant increase in the power conversion efficiency of ITO/PEDOT:PSS/(CdSe/P3HT)/Al solar cell.  相似文献   
8.
Cadmium selenide (CdSe) nanoparticles of 2–7 nm diameter were synthesized by a hot injection method and their TOPO ligands exchanged with pyridine by a liquid–liquid extraction process. The effects of the ligand exchange on the material properties of the nanoparticles and device performance of the bulk hetero-junction (BHJ) solar cell were systematically investigated. The wavelength shift to a shorter value observed in the PL spectra of the pyridine-capped CdSe indicates that the size of nanoparticles decreased due to the exchange of the surface ligands of the CdSe from TOPO to pyridine. Improvements in the power conversion efficiency of BHJ solar cells made with pyridine-capped CdSe are mainly attributed to the enhanced current collection, Jsc=0.43 mA/cm2 (TOPO) to 1.4 mA/cm2 (pyridine).  相似文献   
9.
We have successfully showed the color mixing between fluorescence and phosphorescence by the incomplete Förster energy transfer. The emission color from fluorescent Rubrene and phosphorescent Ir(ppy)3 was found possible to be mixed for a single-layer device doped with both dyes, maintaining the high luminance efficiency of the phosphorescence. We also found out that the Förster energy transfer was very efficient and independent of the applied voltage with no loss of energy during the transfer.  相似文献   
10.
We prepared a ZnO/TiO2/ZnO multi-layer on quartz glass substrate via electron beam evaporation. Optical and structural properties of the ZnO/TiO2/ZnO multi-layer were investigated. The TiO2 buffer layer is found to improve the crystallinity of the ZnO thin film. A green emission of the ZnO thin film deposited on the TiO2 buffer layer was significantly enhanced due to the increased defect concentration of oxygen vacancy. Photoluminesence spectra measured at 9 K revealed that a violet luminescence at 409 nm was attributed to the draft of the donor's defect levels in the ZnO thin film.  相似文献   
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