Solar cell of 6.3% efficiency employing high deposition rate (8 nm/s) microcrystalline silicon photovoltaic layer

Microcrystalline silicon (μc-Si) films deposited at high growth rates up to 8.1 nm/s prepared by very-high-frequency-plasma-enhanced chemical vapor deposition (VHF-PECVD) at 18–24 Torr have been investigated. The relation between the deposition rates and input power revealed the depletion of silane. Under high-pressure deposition (HPD) conditions, the structural properties were improved. Furthermore, applying μc-Si to n–i–p solar cells, short-circuit current density (J_SC) was increased in accordance with the improvement of microstructure of i-layer. As a result, a conversion efficiency of 6.30% has been achieved employing the i-layer deposited at 8.1 nm/s under the HPD conditions.     

Re‐ignition surge and high‐frequency arc extinction phenomena at 550‐kV shunt reactor current interruption

At substations connected with transmission lines and cables, shunt reactors are sometimes installed to compensate the capacitive current of these lines and cables. It is known that re‐ignitions occur and high‐frequency currents flow during interruption of the shunt reactor currents by switches. When the high‐frequency currents are interrupted immediately after the re‐ignitions (which is called high‐frequency arc extinction), the result is often repetitive re‐ignitions or voltage escalations that produce dangerous overvoltages. The authors investigated the occurrence of high‐frequency arc extinctions in a 550‐kV one‐break SF₆ gas circuit breaker during interruption of a 550‐kV shunt reactor current. Computations for a real 550‐kV substation gave a minimum frequency of 290 kHz for the high‐frequency current. However, 550‐kV reactor current interruption tests showed that high‐frequency arc extinctions did not occur even when this frequency was lowered to 26 kHz. Since high‐frequency arc extinction is generally likely to occur at lower frequencies, it was concluded that high‐frequency arc extinction will not occur in a 550‐kV one‐break SF₆ gas circuit breaker during interruption of shunt reactor current in real substations. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 18–25, 2001     

Prediction of fracture generated by elastic recoveries of tools in multi-level powder compaction using finite element simulation

Fracture initiated in a compact by the difference between the amounts of elastic recovery of tools during the unloading process of multi-level powder compaction is predicted from calculated results by finite element simulation. The loading and unloading processes in the compaction are simulated by the rigid-plastic and elastic finite element methods, respectively. In these simulations, elastic tools are modelled as springs connected with the nodal points on the interfaces between the powder material and tools. This modelling leads to simple treatment of coupling of the tools and compact. The initiation of fracture is evaluated from the maximum principal stress, and the critical stress is measured by means of bending and shearing tests. Two-level compaction operations are simulated by the finite element methods to predict the initiation of fracture. The predicted critical values of relative density for the occurrence of fracture are in good agreement with the experimental ones for iron powder compacts.     

ULVAC research and development of Cat-CVD applications

This paper reports the feasibility for industrial implementation of Cat-CVD (Hot-Wire CVD) technology. Some application examples are shown, and their features and problems are described. Cat-CVD is a unique technology which has a lot of possibilities. Some of them will be commercialized in the near future, but the others need a breakthrough for mass production.     

Agitation requirements for complete solid suspension in an unbaffled agitated vessel with an unsteadily forward–reverse rotating impeller

Background: To develop a new type of solid–liquid apparatus, we have proposed the application of an agitation system with an impeller whose rotation alternates direction unsteadily, i.e., a forward–reverse rotating impeller. For an unbaffled agitated vessel fitted with this system, the suspension of solid particles in a liquid was studied using a disk turbine impeller with six flat blades. Results: The effects of the solid–liquid conditions and geometrical conditions of the apparatus on the minimum rotation rate and the corresponding impeller power consumption were evaluated experimentally for a completely suspended solid. The power consumption for a just suspended solid with this type of vessel was comparable with that for a baffled vessel with a unidirectionally rotating impeller, taking the liquid flow along the vessel bottom into consideration. Conclusion: Empirical relationships to predict the parameters of agitation requirements were found. A comparative investigation demonstrated the usefulness of the forward–reverse rotation mode of the impeller for off‐bottom suspension of solid particles. Copyright © 2007 Society of Chemical Industry     

Simultaneous formation of p- and n-type ohmic contacts to 4H-SiC using the ternary Ni/Ti/Al system

Fabrication procedures for silicon carbide power metal oxide semiconductor field effect transistors (MOSFETs) can be improved through simultaneous formation (i.e., same contact materials and one step annealing) of ohmic contacts on both the p-well and n-source regions. We have succeeded with the simultaneous formation of the ohmic contacts for p- and n-type SiC semiconductors by examining ternary Ni/Ti/Al materials with various compositions, where a slash symbol “/” indicates the deposition sequence starting with Ni. The Ni(20 nm)/Ti(50 nm)/Al(50 nm) combination provided specific contact resistances of 2 × 10⁻³ Ω-cm² and 2 × 10⁻⁴ Ω-cm² for p- and n-type SiC, respectively, after annealing at 800°C for 30 min, where the doping level of Al in the SiC substrate was 4.5 × 10¹⁸ cm⁻³ and the level of N was 1.0 × 10¹⁹ cm⁻³.     

Two-probe electrical measurements in transmission electron microscopes--behavioral control of tungsten microwires

Tungsten microwires have been manipulated and electrically probed inside a transmission electron microscope. Using Au electrodes, the current-voltage characteristics of the W structures were extracted. These showed highly variable behaviors dependent on various factors, the most important of these being orientation and stiffness of the contact. Careful control of loading force and Au-W contact angle enabled a considerable degree of behavior tailoring from nonlinear to Ohmic responses.     

Water flow experiments and analyses on the cross-flow type mercury target model with the flow guide plates

A mercury target is used in the spallation neutron source driven by a high-intensity proton accelerator. In this study, the effectiveness of the cross-flow type mercury target structure was evaluated experimentally and analytically. Prior to the experiment, the mercury flow field and the temperature distribution in the target container were analyzed assuming a proton beam energy and power of 1.5 GeV and 5 MW, respectively, and the feasibility of the cross-flow type target was evaluated. Then the average water flow velocity field in the target mock-up model, which was fabricated from Plexiglass for a water experiment, was measured at room temperature using the PIV technique. Water flow analyses were conducted and the analytical results were compared with the experimental results. The experimental results showed that the cross-flow could be realized in most of the proton beam path area and the analytical result of the water flow velocity field showed good correspondence to the experimental results in the case when the Reynolds number was more than 4.83×10⁵ at the model inlet. With these results, the effectiveness of the cross-flow type mercury target structure and the present analysis code system was demonstrated.     

Effectiveness Evaluation of Pre-review of Software Developed by Novice Engineers in China

This paper quantitatively discusses the pre-review effectiveness of software developed by novice engineers of offshore development companies in China. Pre-review process in a Chinese offshore company is applied to the software developed by novice engineers before the test process for enhancing the quality of the software products. Based on the data collected in 2 years, the relationship between the point rate in pre-review and the bug rate in unit test process is examined from various points of view. It becomes clear that by performing this pre-review, the quality of the software developed by the lower level engineers can be kept at the same level of the middle level engineers. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

PCR-DGGE技术检测双歧杆菌影响因素的探讨

采用PCR-DGGE技术在种及菌株水平上对双歧杆菌进行分类鉴定,筛选到了一组在种和菌株水平上具有良好鉴别能力的引物,并用该引物对14株双歧杆菌菌株进行了鉴定.建立了相应的快速、可靠的双歧杆菌DNA提取方法,并对PCR-DGGE技术中的扩增条件、变构剂浓度、凝胶板的种类及大小等影响PCR-DGGE法检测双歧杆菌的因素进行了探讨.