Analysis of CdS/CdTe devices incorporating a ZnTe:Cu/Ti Contact

High-performance CdS/CdTe photovoltaic devices can be produced using a ZnTe:Cu/Ti back contact deposited onto the CdTe layer. We observe that prolonged exposure of the ZnTe:Cu and Ti sputtering targets to an oxygen-containing plasma significantly reduces device open-circuit voltage and fill factor. High-resolution compositional analysis of these devices reveals that Cu concentration in the CdTe and CdS layers is lower for devices with poor performance. Capacitance-voltage analysis and related numerical simulations indicate that the net acceptor concentration in the CdTe is also lower for devices with poor performance. Photoluminescence analyses of the junction region reveal that the intensity of a luminescent peak associated with a defect complex involving interstitial Cu (Cu_i) and oxygen on Te (O_Te) is reduced in devices with poor performance. Combined with thermodynamic considerations, these results suggest that oxygen incorporation into the ZnTe:Cu sputtering target reduces the ability of sputtered ZnTe:Cu film to diffuse Cu into the CdTe.     

Mode-matched phase diffractive optical element for detecting laser modes with spiral phases

A new type of diffractive optical element for detecting and measuring the power distribution of transverse modes emanating from radially symmetric laser resonators is presented. It is based on a relatively simple straightforward design of a phase-only diffractive optical element that serves as a matched filter, which correlates between specific prerecorded transverse modes with a certain azimuthal mode order and those in the incident laser light. Computer simulations supported by experimental results demonstrate how such elements can accurately detect modes with spiral phases and provide quantitative results on the modal power distribution.     

Analytic design and solutions for resonance domain diffractive optical elements

A model for designing and analyzing complicated surface relief diffractive elements in the resonance domain is developed. It is based on subdividing the complicated diffractive element into many highly efficient local diffraction gratings whose surface relief modulations can be effectively characterized as slanted volume gratings for which closed form analytic solutions exist. The model is illustrated by finding in the resonance domain the local period, effective slant angle, and groove depth at each location on an off-axis cylindrical diffractive lens.     

Seismic isolation design of the San Bernardino County Medical Center replacement project

The San Bernardino County Medical Center Replacement Project, located in Colton, California, consists of six separate building structures containing a total of approximately 920 000 ft² of floor space for hospital and support services. Five of the six buildings will be base isolated. Each of the five base isolated buildings is of different size and configuration, ranging from a six story, 360 000 ft² curved front Nursing Tower to a two story, 24 000 ft² rectangular shaped Central Plant building. The building structures will be framed with structural steel, utilizing concentric braced frames as the lateral force resisting system. The design ground motion for the site, which is located 3 km and 15 km from the San Jacinto and San Andreas faults respectively, is very severe. A base isolation system has been designed for this facility which will provide an essentially elastic building response to the design strong ground motion. The base isolation system is a hybrid passive energy dissipation system consisting of both linear and nonlinear and high damping rubber bearings along with viscous damping devices located at the base of the structure. The high damping rubber bearings provide both lateral stiffness which governs the fundamental period of vibration of the system, and hysteretic damping, while the viscous damping devices provide velocity dependent damping which serves to control overall building displacements. This will maximize the probability that this essential facility will remain fully operational after a major earthquake. Design criteria, structural analysis and design methodologies, and construction details are presented and discussed. The response of one of the base isolated structures is calculated utilizing actual recorded ground motions from the 1994 Northridge earthquake.     

Electrical properties of sub-100 nm Cu films deposited by electroless plating on amino-terminated silicon oxide activated with Au nano-particles

Self-assembled organic monolayers (SAMs) are good coupling agents and diffusion barriers at Cu/SiO₂ and Cu/low-k interfaces and are considered therefore as important elements of future all-wet ULSI metallization with sub-45 nm Cu deposited by electroless plating (ELD). We formed SAM of 3-aminopropyltrimethoxy silane (APTMS) onto SiO₂/Si substrate, activated the surface of APTMS with 5, 8, 15 and 25 nm Au nano-particles (AuNPs), deposited (30-100) nm films of Cu by ELD and measured electrical resistivity ρ of the films in the as-deposited state and after vacuum annealing at 220 C. The size of AuNPs was found to be a key factor in getting low resistance sub-100 nm Cu films by ELD. The resistivity ρ ≈ 4 ± 0.8 μΩ·cm - considerably smaller compared to the previously reported data - was achieved with the use of 5 nm AuNPs. XPS and AFM revealed nano-pores, which can contribute to ρ but do not compromise likely the diffusion barrier properties of the SAM.     

Control strategies for enhanced power smoothing in wind energysystems using a flywheel driven by a vector-controlled induction machine

This paper presents a novel control strategy for power smoothing in wind energy applications, especially those feeding a stand-alone load. The system is based on a vector-controlled induction machine driving a flywheel and addresses the problem of regulating the DC-link system voltage against both input power surges/sags from a wind turbine or sudden changes in load demand. The control is based on a feedforward compensation scheme augmented by a nonlinear controller. Two feedforward compensation schemes are discussed and the limitations and performance of each scheme are analyzed. Experimental results are presented which verify the excellent performance of the feedforward compensation technique     

Drops in Degrees: Comment.

Comments on a table in an article by Lester Recktenwald (see record 2005-07923-012). The author of this comment notes that the data in the table citing the drop in undergraduate degrees from 1950 to 1954 should be interpreted not in an absolute sense, but in the context of the total number of degrees granted in the various years. The author feels this is especially important for these data since the total number of undergraduate degrees granted has declined markedly since 1950. The small number of master's and PhD's in psychology is also mentioned, and the author concludes that the increasing demand for PhD's indicates that every encouragement could be given to qualified students to continue on to the PhD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Colorectal hydrosonography in diagnosis of tumorous and inflammatory diseases of the large intestine

PURPOSE: Evaluation as to whether diagnosis of large bowel disease and TNM staging of colorectal carcinoma are possible by colorectal hydrosonography (HUS). METHOD: 52 patients with suspected neoplastic or inflammatory large bowel disease, underwent HUS. Before performing abdominal ultrasound, the colon was filled with fluid. Morphological alterations of the bowel wall were judged benign or malignant. Colorectal carcinomas were classified according to the TNM system. RESULTS: Laparotomy was performed in 46 of 52 patients. Correlation with surgery and histopathology showed that 77% of morphologic alterations of the colonic wall were detected by HUS. While benign lesions of the colonic wall occasionally mimicked malignant disease, colonic carcinomas were reliably diagnosed by HUS, because destruction and invasion of the bowel wall was visible. Carcinomas of the lower part of the rectum, however, were missed in most cases. Accuracy to determine the infiltration depth of colorectal carcinomas was 89%, but hydrosonographic N-staging was unreliable. Inflammatory disease of the large bowel as well as changes complicating the inflammatory bowel disease were accurately diagnosed by HUS. CONCLUSION: In selected patients, colorectal HUS is suited for diagnosis and staging of colonic tumours. It also helps to evaluate inflammatory bowel disease, because small and large bowel can be reliably distinguished from each other and the degree of stenosis of inflamed colonic segments becomes visible. Furthermore, HUS increases the visibility of fistulas.