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排序方式: 共有2576条查询结果,搜索用时 15 毫秒
31.
A. S. Ibraheam Y. Al-Douri J. M. S. Al-Fhdawi Hamid S. AL-Jumaili K. D. Verma U. Hashim R. M. Ayub A. Rahim Ruslinda M. K. Md Arshad A. H. Reshak S. B. Abd Hamid 《Microsystem Technologies》2016,22(12):2893-2900
The Cu2Zn1?xCdxSnS4 quinternary alloy nanostructures with different Cd contents were grown using spin coating technique on porous silicon (63.93 %) substrate. The structural properties of Cu2Zn1?xCdxSnS4/PS were investigated by X-ray diffraction and field emission-scanning electron microscope (FE-SEM). The optical properties studied through photoluminescence technique, indicated that the band gap is shifted as Cd content increases from 1.84 eV at x = 0 to 1.76 eV at x = 1. The electrical characterization of the Ag/n-PS/Cu2Zn1?xCdxSnS4/Ag diode through current to voltage (I–V) characterization shows the highest photo-response of (value if any) at Cu2Zn0.4Cd0.6SnS4 composition. 相似文献
32.
Md Baharul Islam Wong Lai-Kuan Wong Chee-Onn 《Multimedia Tools and Applications》2017,76(7):9517-9542
The advancement of digital photography and the popularity of photo sharing social media such as Instagram and Facebook have undoubtedly stimulated growing interest in aesthetics quality improvement. One aspect of photography that contributes to high quality photos is image composition; the spatial arrangement of photo subjects in the image frame. Professional photographers often apply a wealth of photographic composition rules, e.g., rule of thirds, visual balance and simplicity to capture compelling photos. In the recent years, aesthetics-driven recomposition that attempts to computationally modify the composition of an image to mimic a professional photo has started to receive considerable research interest. Researchers have proposed numerous recomposition techniques that utilize a single or a combination of multiple image operators, i.e., cropping, warping and patch rearrangement operators, to modify the composition of an image. In this paper, we present a survey on the state-of-the-arts aesthetic-driven image recomposition. We define the image recomposition problem, outline its objectives, and provide a comprehensive review of the existing image recompositoin techniques, together with a detailed analysis of the effectiveness of each technique in achieving the recomposition objectives. This survey is intended as a good reference for researchers interested in image recomposition. 相似文献
33.
The rise of online social media has led to an explosion of metadata-containing user generated content. The tracking of metadata distribution is essential to understand social media. This paper presents two statistical models that detect interpretable topics over time along with their hashtags distribution. A topic is represented by a cluster of words that frequently occur together, and a context is represented by a cluster of hashtags, i.e., the hashtag distribution. The models combine a context with a related topic by jointly modeling words with hashtags and time. Experiments with real-world datasets demonstrate that the proposed models discover topics over time with related contexts effectively. 相似文献
34.
Md. Abdus Sattar 《国际能源研究杂志》1993,17(1):1-7
An analytical study is made of the free and forced convection boundary layer flow past a porous medium bounded by a semi-infinite vertical porous plate. Locally similar solutions are then obtained by a perturbation method for large suction. Solutions for the velocity and temperature distributions are shown graphically for various suction velocities and values of the driving parameter Gr/R, where Gr is the Grashof number and Re is the Reynolds number. The corresponding values of the skin friction coefficient and the Nusselt number are finally shown in tabular form. 相似文献
35.
Salman A. Al‐Shami Md Rawi Che Salmah Siti Azizah Mohd Nor Abu Hassan Ahmad Nur Adibah Mohd Ishadi Hamady Dieng 《河流研究与利用》2013,29(9):1195-1204
Rapid industrialization and urbanization has led to increasing input of chemical contaminants into the aquatic environment of Malaysia. Despite the threat civilization poses to the biota, there are still very few relevant studies on ecotoxicological testing of river ecosystems. To overcome this knowledge gap, we examined lethal and genotoxic effects of sediments from different rivers of the northern Malaysia against Chironomus kiiensis, a group well represented in the aquatic fauna of this region. We exposed the larvae to sediments from Selama River (SR), Permatang Rawa River (PRR) and Kilang Ubi River (KUR) at various durations (0, 6, 12, 24 and 48 h). The larval mortality was monitored, whereas DNA damage in survivors' cells was determined using the comet assay. Pollution level indexed by the amounts of heavy metals and other organic contaminants in the sediment showed progressive increases from SR to PRR to KUR. Highly polluted sediments (PRR to KUR) were detrimental to C. kiiensis larvae, most of which did not survive following exposure for long periods. DNA analyses revealed greater damages in nuclei derived from larvae maintained on polluted sediments, in particular, those from KUR. The effects on the genomic material of C. kiiensis larvae occurred in a time‐dependent manner, with damage level increasing as exposure time progressed. Our results highlight the genotoxic properties of polluted sediments. More importantly, this study showed that C. kiiensis larvae could respond to different levels of pollution with respect to exposure time. It is concluded that C. kiiensis larvae is a potential candidate for river ecotoxicological monitoring. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
36.
Simplified Monthly Hydrology and Irrigation Water Use Model to Explore Sustainable Water Management Options in the Murray-Darling Basin 总被引:1,自引:1,他引:0
We aimed to provide whole-of-basin simulations of flows and diversions in the Murray-Darling Basin for economic and policy analysis. We describe a model based on a subdivision of the basin into 58 catchments. In each catchment, the monthly runoff, river flow and irrigation demand are modelled as lumped processes. This is the first single model of the whole of the Murray-Darling Basin. The model was calibrated using monthly flow and annual diversion records, both by trial and error and using an automated method. We use the model to examine the impact on the flow and diversions in the Murray-Darling Basin of proposed diversion reductions and climate change. The diversion reductions return water to the environment, increasing river flows below the main irrigation areas. However, a middle-of-the-range climate change projection may result in a 13 % decrease in total flows in 2030, which offsets the enhancement to flows gained by diversion reductions. 相似文献
37.
This paper is concerned with an external sorting algorithm with no additional disk space. The proposed algorithm is a hybrid one that uses Quicksort and special merging process in two distinct phases. The algorithm excels in sorting a huge file, which is many times larger than the available memory of the computer. This algorithm creates no extra backup file for manipulating huge records. For this, the algorithm saves huge disk space, which is needed to hold the large file. Also our algorithm switches to special merging process after the first phase that uses Quicksort. This reduces the time complexity and makes the algorithm faster. 相似文献
38.
39.
Jie Li Abul Kalam Ayed Sad Al-Shihri Qingmei Su Guo Zhong Gaohui Du 《Materials Chemistry and Physics》2011
Monodisperse ceria nanospheres have been synthesized by a facile solvothermal method, and their morphology and microstructures have been revealed by a combination of X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and N2 adsorption. It is demonstrated that the as-synthesized powders are highly uniform CeO2 in spherical shape with cubic fluorite structure. HRTEM and XRD studies show that each ceria nanosphere is composed of dozens of nanocrystals with the average size of 8.5 nm. The direct optical band gap of the ceria nanospheres estimated from the ultraviolet–visible absorption spectrum is 2.7 eV, which is evidently red-shifted with respect to the bulk material (Eg = 3.19 eV); the reduced band gap could be resulted from the high concentration of grain boundaries and defects present in the ceria nanospheres. In addition, the ceria nanospheres exhibit a strong blue luminescence at 504 nm and a broad orange luminescence centered at 645 nm. As a result of the large specific surface area, ceria nanospheres are revealed to be an excellent sorbent for the removal of poisonous pollutants present in water, such as chromium ions and rhodamine B. The removal efficiency of chromium ions is as high as ∼94%. 相似文献
40.
Md. Ahamad Mohiddon M. Ghanashyam Krishna G. Dalba F. Rocca 《Materials Science and Engineering: B》2012,177(13):1108-1112
Nickel induced crystallization of amorphous Si (a-Si) films is investigated using transmission electron microscopy. Metal-induced crystallization was achieved on layered films deposited onto thermally oxidized Si(3 1 1) substrates by electron beam evaporation of a-Si (400 nm) over Ni (50 nm). The multi-layer stack was subjected to post-deposition annealing at 200 and 600 °C for 1 h after the deposition. Microstructural studies reveal the formation of nanosized grains separated by dendritic channels of 5 nm width and 400 nm length. Electron diffraction on selected points within these nanostructured regions shows the presence of face centered cubic NiSi2 and diamond cubic structured Si. Z-contrast scanning transmission electron microscopy images reveal that the crystallization of Si occurs at the interface between the grains of NiSi2 and a-Si. X-ray absorption fine structure spectroscopy analysis has been carried out to understand the nature of Ni in the Ni–Si nanocomposite film. The results of the present study indicate that the metal induced crystallization is due to the diffusion of Ni into the a-Si matrix, which then reacts to form nickel silicide at temperatures of the order of 600 °C leading to crystallization of a-Si at the silicide–silicon interface. 相似文献