The demand for energy of modern society is constantly increasing. The desire for environmental-friendly alternative energy resources with the least dependency on fossil fuels is growing. Solar energy is an important technology for many reasons and is worthy of urgent attention. Indeed, it has experienced rapid growth over the last few years. It is expected to become truly main stream when the breakeven of high performance is achieved and its cost becomes comparable with other energy sources. Various approaches have been proposed to enhance the efficiency of solar cells. This paper reviews some current initiatives and critical issues on the efficiency improvement of solar cells from the material sciences and chemistry perspectives. 相似文献
Photofermentative H2 production at higher rate is desired to make H2 viable as cheap energy carrier. The process is influenced by C/N composition, pH levels, temperature, light intensity etc. In this study, Rhodobacter sphaeroides strain O.U 001 was used in the annular photobioreactor with working volume 1 L, initial pH of 6.7 ± 0.2, inoculum age 36 h, inoculum volume 10% (v/v), 250 rpm stirring and light intensity of 15 ± 1.1 W m−2. The effect of parameters, i.e. variation in concentration of DL malic acid, L glutamic acid and temperature on the H2 production was noted using three factor three level full factorial designs. Surface and contour plots of the regression models revealed optimum H2 production rate of 7.97 mL H2 L−1 h−1 at 32 °C with 2.012 g L−1 DL malic acid and 0.297 g L−1 L glutamic acid, which showed an excellent correlation (99.36%) with experimental H2 production rate of 7.92 mL H2 L−1 h−1. 相似文献
The alloy design of WC-10Co cemented carbide, modified with addition of a hard carbide phase, TiC, and with Ni and Mo in the binder phase, has been highlighted by the authors in a number of publications. The present article deals with the fine microstructural features of various phases in such cemented carbides. WC grains in all the investigated cemented carbide compositions appear to develop straight facets during sintering because of their anisotropic nature. In contrast, the TiC phase is characterized by its rounded shape. Dislocations are present in both WC and TiC grains, being of lesser density in the latter. The binder phase is always associated with stacking faults. The nature of the hard phase/binder interfaces has been found to be dependent on the binder phase chemistry. The observed changes in microstructures and mechanical properties have been correlated with the wettability and solubility of the hard phases in the binder melt, and with the different strengthening mechanisms in the binder phase. 相似文献
In this paper, two control allocation algorithms have been proposed for overactuated systems. The algorithms are developed by formulating constrained control allocation problem into an equivalent fixed point framework. The first algorithm follows sequential solving method while the other one involves a zero finding technique by the Newton method. In order to consider limiting constraints, the saturation function has been taken into account that leads to a nonsmooth zero finding problem and the proposed method guarantees superlinear convergence. The second algorithm is easy to implement and faster than the algorithm developed based on the sequential solving technique. To demonstrate the effectiveness of the proposed algorithms, a detail simulation study has been carried out, in which one example considers both the actuator rate and amplitude constraints. 相似文献
This study presents trends, seasonality, hot spots, and anomalies of tropospheric NO2 pollution over four basins of Indus, Ganges, Brahmaputra, and Meghna rivers in South Asia using observations from Ozone Monitoring Instrument (OMI) on-board Aura satellite during 2004–2015. For the first time this area, a highly populated and industrialized region with significant emissions of air pollutants, has been discussed collectively. OMI data reveal significantly elevated NO2 column over the region averaged at (1.9 ± 0.1) × 1015 molecules cm–2 (average ± standard deviation of observations) with an increase of 21.12% (slope (0.036 ± 0.004) × 1015 molecules cm–2, y-intercept (1.705 ± 0.024) × 1015 molecules cm–2, R2= 0.92) during the study period. According to MACCity anthropogenic emissions inventory transportation, energy, residential, and industrial sectors are the major contributors of high NOx emissions. NO2 pollution hot spots are identified and their tendencies have been discussed. The hot spots of megacities Lahore (Pakistan) and Dhaka (Bangladesh) are found to be strengthening and expanding over the time. Eastern Ganges Basin shows the highest NO2 concentration at (2.63 ± 0.22) × 1015 molecules cm–2 and growth rate of 3.22% per year mainly linked to power generation, fossil fuel extraction, mining activities, and biomass burning. NO2 over Indus–Ganges–Brahmaputra–Meghna Basin exhibits seasonal maximum in winter and minimum in monsoon. The highest seasonality is found over Meghna Basin due to large variations in meteorological conditions and large-scale crop-residue burning. Some anomalies in NO2 levels have been detected linked to intense crop-residue burning events. During these anomalies, exceptionally high levels of daily NO2 reaching up to 76.23 × 1015 molecules cm–2 have been observed over some places in Indus and Meghna Basins. 相似文献
Generally in digital communication systems and storage mediums, Reed–Solomon (RS) codes are employed to detect and correct errors. RS code is a promising code for Ultra Wide Band (UWB) which is ideally suitable for wireless application. Design of compact, high-speed and low-power RS(23, 17) code is challenging for today’s wireless communication systems. Here, an optimization algorithm is introduced which is very simple and it is employed to reduce the number of XOR gates required to design constant Galois Field (GF) multipliers. In this paper, a compact RS(23, 17) encoder and decoder circuit is designed and implemented for Ultra Wide Band(UWB) application. The number of two input XOR gates is reduced by 29.27 (20.00) and 56.10 (66.15) % respectively for local and global optimization compared to unoptimized RS encoder (syndrome block) without increasing its delay. The proposed algorithm is also employed to design the RS(204, 188) and RS(255, 223) encoder. All designs are simulated and synthesized for Vertex4 FPGA platform. Proposed algorithm is also used for the design of Chien Search and Forney blocks. Implemented RS(23, 17) codec requires lesser number of slices and LUTs over the unoptimized RS codec. The synthesis results reflect that the proposed design is suitable for resource constraint applications.
\(\upalpha \)-\(\hbox {LiIO}_{3}\) is an excellent optical material exhibiting strong nonlinear optical, piezoelectric and elasto-optic properties. However, its practical applications are limited by the insufficient reproducibility of the mentioned properties caused by the strong influence of the growth conditions, and, in particular, pH of the solution from which \(\upalpha \)-\(\hbox {LiIO}_{3}\) crystal is grown. Herein, we investigate to grow bulk size good quality crystals of \(\upalpha \)-\(\hbox {LiIO}_{3}\) based on the observed problems during its crystallization process. A systematic investigation was carried out to find the effect of pH on solubility, crystal growth, structural, surface and laser damage properties of \(\upalpha \)-\(\hbox {LiIO}_{3}\) single crystals. The structure and phase of \(\hbox {LiIO}_{3}\) were confirmed by powder X-ray diffractometer analysis. The functional groups of the compound were identified using Fourier transform infrared spectroscopy. Surface defects of the grown crystals were studied by etch patterns. The crystal grown at pH 10 showed 10% optical transmission enhancement in comparison to the crystals grown at pH 2. The indirect optical bandgap of the crystal was reinvestigated using ultraviolet–Visible–near-infrared transmittance spectrum. The laser damage threshold studies of the crystals grown at pH 10 reveal the higher optical radiation stability against 532 nm laser. The second-order nonlinear optical behaviour of \(\upalpha \)-\(\hbox {LiIO}_{3}\) crystals grown at different pH conditions have been investigated by using Kurtz and Perry powder technique with Nd:YAG laser pulses at the wavelength of 1064 nm. 相似文献
Despite the recent advancement in graphene oxide (GO) as a host material in energy and environmental sectors, its composite thin films with metal oxides such as nickel oxide (NiO) and its optical, structural, chemical state, and photocatalytic activities have been poorly explored. Herein, we have reported the GO/NiO thin films preparation by a combination of chemical and physical deposition techniques (i.e. spin coating followed by DC/RF sputtering). The as-prepared composites thin films were characterised using Raman spectroscopy, X-ray diffraction/photoelectron spectroscopy scanning electron microscopy, and atomic force microscopy. The surface topography confirmed the uniform deposition of NiO over thin films of GO. The XPS results showed the formation of NiC along with the partial reduction in GO into graphene with their existing four constituents, i.e. NiO, NiC, GO, in the thin film composites. The classical plasmon, Wemple and Didomenico model, was first time applied for GO/NiO to compute energy loss functions, and dispersion energy parameters. The theoretical calculated values for the deposited GO/NiO thin films were found to be in very close agreement to the standard classical plasmon values. The change in spin orbital movement of Ni is considered due to the interaction between its nanoparticles and basal planes of GO. Thin films applied for the photodegradation of recalcitrant organic pollutant 2-chlorophenol (2-CP) revealed the dependence of photocatalytic efficiency on particle size and also on the interaction of GO with NiO rather than the ratio of NiO and GO in the films. 相似文献
With the advent of the digital era, healable electronic devices are being developed to alleviate the propagation of breakdown in electronics due to the mechanical damage caused by bending, accidental cutting or scratching. Meanwhile, flexible transparent electronics, exhibiting high transmittance and robust flexibility, are drawing enormous research efforts due to their potential applications in various integrated wearable electronics. However, the breakdown of flexible transparent electronics seriously limits their reliability and lifetime. Therefore, transparent healable electronics are desired to tackle these problems, yet most of the healable electronics are not transparent nowadays. The combination of high performance, healability, and transparency into electronics is often mutually exclusive. Herein, after a brief introduction of self‐healing materials, healable electronics, and flexible transparent electronics, the recent progress in the healable electronic devices without transparency is reviewed in detail. Then, healable transparent electronic devices with high transparency, robust portability, and reliable flexibility are summarized. They are drawing great attention owing to their potential application in optical devices as well as smart wearable and integrated optoelectronic devices. Following that, the critical challenges and prospects are highlighted for the development of healable transparent electronic devices. 相似文献