PCSIGV: a student-oriented program for calculating the parasitic capacitances for single-level interconnections on GaAs-based VLSI

A microcomputer-efficient algorithm to study the parasitic capacitances associated with high-density single-level interconnections on GaAs-based VLSI is presented and a student-oriented program called PCSIGV is discussed. The algorithm uses the method of moments in conjunction with a Green's function appropriate to the geometry of the interconnections. Results include the fringing fields as well as the effects of shielding due to the presence of the neighboring interconnection lines. PCSIGV has been used to study the dependence of the ground and coupling interconnections capacitances on various interconnection parameters.<>     

Effect of support materials on the performance of direct ethanol fuel cell anode catalyst

Pt–Ru catalysts supported on mesoporous carbon nitride (MCN), multiwall carbon nano tubes (MWCNTs), treated MWCNTs (t-MWCNTS) and Vulcan-XC were prepared using co-impregnation reduction method for the oxidation of ethanol in direct ethanol fuel cell (DEFC) to study the effect of support material. The MCN support was prepared using SBA-15 as template and t-MWCNTs were prepared by refluxing in HNO₃ and H₂SO₄ mixture (1:3) using MWCNTs. XRD shows the formation of Pt–Ru bi-metallic catalyst with size ranges from 7 to 17 nm using different supports. The catalyst and its supports were characterized by physically and electrochemically. Linear sweep voltammetry, cyclic voltammetry and chrono amperometry studies of the above systems reveal that MCN supported Pt–Ru catalyst shows higher electro-catalytic activity towards ethanol oxidation compared to Pt–Ru in treated t-MWCNTs, MWCNts and Vulcan-XC supports. The performance of DEFC based on maximum power density is found to be in the order Pt–Ru/MCN > Pt–Ru/t-MWCNTs > Pt–Ru/MWCNTs > Pt–Ru/Vulcan-XC. The Pt–Ru/MCN shows highest power density of 61.1 mW cm⁻² at 100 °C, 1 bar pressure with catalyst loading of 2 mg cm⁻² using 2 M ethanol feed.     

Structural and thermal characterization of CaO–MgO–SiO2–P2O5–CaF2 glasses

The influence of varying the CaO/MgO ratio on the structure and thermal properties of CaO–MgO–SiO₂–P₂O₅–CaF₂ glasses was studied in a series of eight glass compositions in the glass forming region of diopside (CaMgSi₂O₆)–fluorapatite [Ca₅(PO₄)₃F]–wollastonite (CaSiO₃) ternary system. The melt-quenched glasses were characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q² (Si) species, while phosphorus tends to coordinate in orthophosphate environment. The sintering and crystallization parameters of the glasses were obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass–ceramics were analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite crystallized as the main crystalline phases in all the glass–ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. The implications of structure and sintering behaviour of glasses on their bioactivity were discussed.     

A quantitative assessment of nanometric machinability of major polytypes of single crystal silicon carbide

The influence of polymorphism on nanometric machinability of single crystal silicon carbide (SiC) has been investigated through molecular dynamics (MD) simulation. The simulation results are compared with silicon as a reference material.Cutting hardness was adopted as a quantifier of the machinability of the polytypes of single crystal SiC. 3C-SiC offered highest cutting resistance (～2.9 times that of silicon) followed by the 4H-SiC (～2.8 times that of silicon) whereas 6H-SiC (～2.1 times that of silicon) showed the least. Despite its high cutting resistance, 4H-SiC showed the minimum sub-surface crystal lattice deformed layer depth, in contrast to 6H-SiC. Further analysis of temperatures in the cutting zone and the percentage tool wear indicated that single point diamond turning (SPDT) of single crystal SiC could be limited to either 6H-SiC or 4H-SiC depending upon quality and cost considerations as these were found to be more responsive and amenable to SPDT compared to single crystal 3C-SiC.     

Comparing error estimation measures for polynomial and kriging approximation of noise-free functions

Error estimation measures are useful for assessing uncertainty in surrogate predictions. We use a suite of test problems to appraise several error estimation measures for polynomial response surfaces and kriging. In addition, we study the performance of cross-validation error measures that can be used with any surrogate. We use 1,000 experimental designs to obtain the variability of error estimates with respect to the experimental designs for each problem. We find that the (actual) errors for polynomial response surfaces are less sensitive to the choice of experimental designs than the kriging errors. This is attributed to the variability in the maximum likelihood estimates of the kriging parameters. We find that no single error measure outperforms other measures on all the problems. Computationally expensive integrated local error measures (standard error for polynomials and mean square error for kriging) estimate the actual root mean square error very well. The distribution-free cross-validation error characterized the actual errors reasonably well. While the estimated root mean square error for polynomial response surface is a good estimate of the actual errors, the process variance for kriging is not. We explore a few methods of simultaneously using multiple error measures and demonstrate that the geometric means of several combinations of error measures improve the assessment of the actual errors over individual error measures.     

A Classifiers Based Optimization Technique for Designing Turbine Airfoils

The primary focus of this work is in the development of an evolutionary optimization technique which gets progressively 'smarter' during the optimization process by learning from computed domain knowledge. In the approach, the influence of the design variables on the problem solution is recognized, and the knowledge learned is then generalized to dynamically create or change design rules during optimization. This technique, when applied to a constrained optimization problem, shows progressive improvement in convergence of search, as successive generations of rules evolve by learning from the environment. This method is applied to a complex aerodynamic optimization problem involving turbine airfoil design. In this investigation, the 3D geometry of an airfoil is optimized by simultaneously optimizing multiple 2D slices of the airfoil. Results from the optimization of a low pressure turbine nozzle are presented in the paper. Results obtained using standard numerical optimization techniques are also presented for comparison purposes.     

Compositional and structural analysis of RF magnetron sputtered La3+-modified PZT thin films

In the present work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films in pure perovskite phase by RF magnetron sputtering. For this purpose, a 3-in. diameter target of PLZT (8/60/40) was prepared by conventional solid-state reaction route. The chemical composition of PLZT target was determined using gravimetric analysis followed by UV–vis and flame atomic absorption spectrometry. Various deposition parameters such as target-to-substrate spacing, deposition temperature, post-deposition annealing temperature and time have been optimized to obtain PLZT films in pure perovskite phase. The films prepared in pure argon at 100 W RF power without external substrate heating exhibited pure perovskite phase after rapid thermal annealing (RTA) as confirmed by X-ray diffraction (XRD). Compositional analysis of the PLZT film was performed by secondary ion mass spectroscopy (SIMS) using PLZT target as standard sample. Depth profile of the film shows very good stoichiometric uniformity of all elements of PLZT.     

A protocol to evaluate semi-rigid pedicle screw systems

The objective of the current study was to develop an in vitro testing protocol to evaluate semi-rigid pedicle screw devices. A corpectomy model protocol exists to evaluate rigid spinal implants; however, semi-rigid devices are contraindicated for this condition. This paper describes a technique that simulates more closely the conditions a semi-rigid device would see in vivo. Finally, the new testing protocol is used to evaluate the DDS pedicle screw-cable system. Benefits and shortcomings of the new protocol are discussed.     

A probable explanation for mild extra-articular manifestations in Indian patients of rheumatoid arthritis: a preliminary study

The combination of a total lower lip, chin, and anterior mandibular defect following cancer resection is an extremely complex problem that requires a sequence of operations to optimize functional and aesthetic results. One patient is presented in whom the defect was reconstructed with a free fibular flap followed by a series of ancillary procedures using both modern and traditional techniques. At the time of tumor ablation, the through-and-through oromandibular defect was reconstructed with a fibular osteocutaneous flap. The lower lip and gingivolabial sulcus was reconstructed later with a tongue flap. Tissue expansion was subsequently used to replace the fibular skin with expanded submental hair-bearing skin. A polyethylene implant was added later to the fibular bone for chin augmentation. Subsequently the lower lip was supported with a tendinous graft suspended to the anterior masseter bilaterally. Lastly, the vermilion border was elevated by removing a rim of the tongue flap and covering the secondary wound with a full-thickness skin graft. At the end of the reconstructive procedures, lip seal and oral aperture were good with no drooling and excellent speech.