Measurement of silicon and GaAs/Ge solar cell device parameters

The device parameters (carrier lifetime, ideality factor), and physical parameters (built-in voltage, doping concentration) of silicon (Si) and gallium arsenide (GaAs/Ge) solar cells are measured at different temperatures using time domain technique. Carrier lifetime is calculated from open circuit voltage decay (OCVD). Built-in voltage and doping concentration are derived from the cell capacitance measured at different bias voltages. Ideality factor is derived from the I–V characteristics of solar cell. Carrier lifetime increases while built-in voltage decreases with increase in temperature. Ideality factor of the solar cell decreases with temperature.     

生物抛光染色一浴法工艺

以印度某纺织印染厂的全规模生产为基础,评估了用生物抛光染色一浴法工艺——借助含过氧化氢酶和中性纤维素酶(Novozymes Cellusoft Combi)的复合酶制剂——替代传统3步法工艺的环境影响。结果表明:生物抛光染色一浴法工艺可以节省水资源和能源,减少温室气体排放,同时确保产品质量最优。     

Study of hole-entry hybrid journal bearing system considering combined influence of thermal and elastic effects

A theoretical model is developed to study the performance of a hole-entry hybrid journal bearing system by considering variation of viscosity due to temperature rise of the lubricant in the analysis. The deformation of bush due to fluid-film pressure and temperature has been considered to establish the modified fluid-film profile. The journal temperature is computed on the basis of the fluid-film temperature. The relevant governing equations have been solved using the finite element method and a suitable iterative technique. The thermoelastohydrostatic performance of an orifice compensated symmetric and asymmetric hole-entry hybrid journal bearing configurations has been studied for the chosen bearing operating and geometric parameters. The results presented in the study indicate that the variation of viscosity due to temperature rise of the lubricant fluid-film have a quite appreciable influence on the static and dynamic performance of a hole-entry hybrid journal bearing system.     

An effective density based approach to detect complex data clusters using notion of neighborhood difference

The density based notion for clustering approach is used widely due to its easy implementation and ability to detect arbitrary shaped clusters in the presence of noisy data points without requiring prior knowledge of the number of clusters to be identified. Density-based spatial clustering of applications with noise (DBSCAN) is the first algorithm proposed in the literature that uses density based notion for cluster detection. Since most of the real data set, today contains feature space of adjacent nested clusters, clearly DBSCAN is not suitable to detect variable adjacent density clusters due to the use of global density parameter neighborhood radius N _rad and minimum number of points in neighborhood N _pts . So the efficiency of DBSCAN depends on these initial parameter settings, for DBSCAN to work properly, the neighborhood radius must be less than the distance between two clusters otherwise algorithm merges two clusters and detects them as a single cluster. Through this paper: 1) We have proposed improved version of DBSCAN algorithm to detect clusters of varying density adjacent clusters by using the concept of neighborhood difference and using the notion of density based approach without introducing much additional computational complexity to original DBSCAN algorithm. 2) We validated our experimental results using one of our authors recently proposed space density indexing (SDI) internal cluster measure to demonstrate the quality of proposed clustering method. Also our experimental results suggested that proposed method is effective in detecting variable density adjacent nested clusters.     

Influence of alkali metal (Li and Cs) addition to Mo2N catalyst for CO hydrogenation to hydrocarbons and oxygenates

The aim of this work is to understand the catalytic behaviour of Li and Cs promoted Mo₂N for CO hydrogenation to hydrocarbons and oxygenates at the reaction conditions 275–325 °C, 7 MPa, and 30 000 h^?1 GHSV. Molybdenum nitrides were synthesized via temperature programmed treatment of ammonium heptamolybdate (AHM) and alkali metal (AM) precursors under continuous gaseous ammonia flow. Unpromoted Mo₂N and AM‐Mo₂N catalysts were characterized using BET‐pore size, X‐ray diffraction, TPD‐mass of CO, HR‐TEM, and XPS techniques. Nominal loadings of 1, 5, and 10 wt% of Li and Cs were selected for these studies. At a 10 % CO conversion level, the total oxygenate selectivity of 28, 11, and 6.5 % was observed on 5Cs‐Mo₂N, 5Li‐Mo₂N, and unpromoted Mo₂N, respectively. The decreased oxygenate selectivity for unpromoted Mo₂N was mainly associated with CO dissociative hydrogenation on Mo^δ+ sites. On the other hand, improved molecular CO insertion into ?C_xH_y intermediate accelerates the total oxygenate formation on the Cs‐Mo‐N catalyst. However, during nitridation, crystal structure changes were observed in Li‐Mo‐N and the obtained oxygenates selectivity was attributed to the Li₂MoO₄ phases. At lower AM loadings, the active sites corresponding to oxygenates formation were inadequate, and at higher AM loadings, surface metallic molybdenum decreased the total oxygenate selectivity.

     

Misaligned journal effects in liquid hydrostatic non-recessed journal bearings

The performance characteristics of a capillary-compensated hole-entry hybrid misaligned journal bearing have been studied theoretically. The journal of the bearing is allowed to tilt on an axial plane containing the load vector and on a plane perpendicular to an axial plane containing the load vector. The journal misalignment has been accounted for by defining a pair of misalignment parameters σ and δ. The finite element method has been used to solve Reynold's equation governing the lubricant flow field in the clearance space of the journal bearing. Static and dynamic performance characteristics are presented for the different representative values of the journal misalignment parameters for both hydrostatic and hybrid modes of operation of the bearing. The bearing performance characteristics are also compared for the two hole-entry bearing configurations so as to facilitate the selection of a suitable bearing configuration by the designer. The study suggests that the journal misalignment significantly affects the performance of the hole-entry journal bearing, and for a more accurate prediction of the bearing performance it must be considered in the analysis.     

Electrical transport and current properties of rare-earth dysprosium Schottky electrode on p-type GaN at various annealing temperatures

The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights (BH) of as-deposited and 200℃ annealed SBDs are 0.80 eV (I-V)/0.93 eV (C-V) and 0.87 eV (I-V)/1.03 eV (C-V). However, the BH rises to 0.99 eV (I-V)/ 1.18 eV(C-V) and then slightly deceases to 0.92 eV (I-V)/1.03 eV (C-V) after annealing at 300℃ and 400℃. The utmost BH is attained after annealing at 300℃ and thus the optimum annealing for SBD is 300℃. By applying Cheung''s functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung''s and Ψ_S-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the N_SS decreases up to 300℃ annealing and then slightly increases after annealing at 400℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.     

A novel low‐cost high‐gain antenna design from cuboids and differential strips

This article proposed a novel broadband high‐gain antenna designed by suspended cuboids and differential shorting strips on a circular ground plane. The design structure of the proposed antenna is simple and all its components such as cuboids, strips, and ground plane are fabricated by a copper sheet of thickness 0.5 mm. The proposed antenna has measured ?10 dB impedance bandwidth (IBW) 45% (2.35‐3.7 GHz) with broadside gain of 10.1 ± 0.4 dBi over IBW. The use of differential strips in inner cuboid improved the cross polarization and enhanced the broadside gain. The measured antenna has low cross polarization is below 25 dB in the broadside direction over IBW. The proposed antenna has 1 dB gain‐bandwidth 53% (2.2‐3.8 GHz) in the broadside. The antenna has been fabricated and measured; the results show a good agreement with simulated results.     

Effect of method of preparation on the activity and selectivity of iron phosphate catalyst in the ammoxidation of 2-methyl pyrazine

Ammoxidation of methylpyrazine (MP) to cyanopyrazine (CP) was performed at 633–693 K over iron phosphate catalysts having a P/Fe ratio of 1.2, obtained by adopting different methods of catalyst preparation. The catalysts were characterized by XRD, FTIR, UV-DRS, laser-Raman spectroscopy, TPR, TEM, XPS, acidity by Potentiometric titration and TPD of NH₃. XRD and Raman data suggested predominant formation of quartz phase of iron phosphate. The structure and texture of the catalysts varied with the nature of starting material as well as the preparation method. The catalytic activity depended on the extent of quartz phase formation. Precipitation in the basic medium improved quartz phase formation and enhanced the activity. However, the decreased acid strength caused reduction in nitrile selectivity. A judicious combination of the redox and acid strength properties is required for obtaining maximum yield of CP.     

Hydrothermal synthesis of amorphous MoS2 nanofiber bundles via acidification of ammonium heptamolybdate tetrahydrate

MoS₂ nanofiber bundles have been prepared by hydrothermal method using ammonium molybdate with sulfur source in acidic medium and maintained at 180 °C for several hours. The obtained black crystalline products are characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The PXRD pattern of the sample can be readily indexed as hexagonal 2H-MoS₂. FTIR spectrum of the MoS₂ shows the band at 480 cm⁻¹ corresponds to the γ_as(Mo-S). SEM/TEM images of the samples exhibit that the MoS₂ nanofiber exist in bundles of 120–300 nm in diameter and 20–25 μm in length. The effects of temperature, duration and other experimental parameters on the morphology of the products are investigated.