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排序方式: 共有1791条查询结果,搜索用时 15 毫秒
41.
Sai Rajesh Mahapatro 《传热工程》2018,39(3):252-267
The objective of this study is to predict fluid flow and thermal characteristics associated with forced convection cooling of an array of heat sources mounted in a three-dimensional duct by impinging jets in the presence of cross flow. The equations governing fluid flow and heat transfer are solved using Streamline Upwind / Petrov - Galerkin based finite element method. The role of three dimensional flow structures, horseshoe vortex and counter rotating vortex pair in overall heat transfer distribution is examined. A parametric study is performed to analyze the performance of jets in cross flow for various Reynolds numbers (Re = 100, 250, 500) and velocity ratios (VR = 1.0, 5.0, 10.0). It is observed that with the increase in velocity ratio, the enhancement of heat transfer from heat sources occurs due to increase in the dominance of jet flow accompanied by an unfavorable reduction in heat transfer owing to the increase in size of horseshoe vortex. From numerical studies, it can be concluded that VR = 5.0 exhibits higher overall surface averaged Nusselt number (51.7% over VR = 1.0 and 44.1% over VR = 10.0 for Re = 500) compared to other velocity ratios considered in this study. 相似文献
42.
Wireless Personal Communications - The advancements of technology in the field of communication made WSN based IoT attractive and applicable to various areas. It is comprised IoT nodes that work on... 相似文献
43.
Prapti Chaudhari Satyendra Mishra 《Journal of Materials Science: Materials in Electronics》2018,29(1):117-123
The NiTiO3 nanoparticles with ilmenite phase were synthesized by the sol gel method and investigated for sensing of various volatile organic compounds. The resistive type sensing by NiTiO3 towards LPG was not reported earlier where the sensor showed fair response towards hydrogen sulfide gas, but the sensitivity towards LPG was very high. The response % for 150 ppm of LPG was approximately 3200% at room temperature. The high response towards LPG was due to the presence of some amount of rutile TiO2 in the composites. The response and recovery times of these sensors were very less (about 2 s) which could be attributed to the whiskers like structure of NiTiO3. 相似文献
44.
Neural Computing and Applications - Collaboration among different ad hoc networks allows the formation of efficient guided networks. One of the such collaborative networks is formed between aerial... 相似文献
45.
Lakshmy Rajesh Amina Al-Farsi 《The International journal of environmental studies》2017,74(6):979-990
The paper reports the first study of diversity and distribution of freshwater macrophytes in the wedian (plural of wadi = seasonal river) of the northern Al Hajar Mountain range in Oman. Fifteen lentic habitats in the wedian were surveyed. The number of species, their growth forms and abundance were recorded in the studied habitat of each wadi. In all, 41 species belonging to 14 families and 32 genera were collected. Of these 37 species were emergent and four were submergent. Poaceae was the most diverse emergent family with 17 species. Phragmites australis was the most common emergent followed by Typha domingensis. Among submerged macrophytes, Chara vulgaris had higher frequency of occurrence with low abundance followed by Potamogeton distinctus with relatively high abundance. Floristic diversity was estimated using species richness (Margalef’s D), general diversity (Shannon–Wiener H′), evenness (Pielous’s EH), and dominance (Berger–Parker d) indices for each study habitat. Principal component analysis was used to evaluate the variability using four indices. PC1 and PC2 explained 98.18% of the variability. Some habitats in different watersheds exhibited similar species diversity, but some in the same watershed were different. Baseline data on the freshwater macrophytes in northern Oman are provided here. 相似文献
46.
Fossil fuel depletion and its adverse impact on global warming is a major driving force for a recent upsurge in the development of hybrid electric vehicles technologies. This paper is a conglomeration of the recent literature in the usages of an energy storage system and power conversion topologies in electric vehicles (EVs). An EV requires sources that have high power and energy density to decrease the charging time. Commonly used energy storage devices in EVs are fuel cells, batteries, ultracapacitors, flywheel, and photovoltaic arrays. The power output from energy storage sources is conditioned to match load characteristics with the source for maximum power delivery. A DC-DC converter topology performs this task by way of transforming voltage under the condition of power invariance. In addition, power electronics is also required to power DC/AC motors efficiently with precise control as these motors provide tractive efforts and acts as prime movers. This paper therefore brings out a critical review of the literature on EV's power conversion topologies and energy storage systems with challenges, opportunities and future directions by systematic classification of EVs and energy storage. 相似文献
47.
Murugesan Rajesh Ramu Manikandan Seungil Park Byung Chul Kim Won-Je Cho Kook Hyun Yu C. Justin Raj 《国际能源研究杂志》2020,44(11):8591-8605
Activated carbon, from biomass (pinecone), was synthesized by conventional pyrolysis/chemical activation process and utilized for the fabrication of supercapacitor electrodes. The pinecone-activated carbon synthesized with 1:4 ratio of KOH (PAC4) showed an increase in surface area and pore density with a considerable amount of oxygen functionalities on the surface. Moreover, PAC4, as supercapacitor electrode, exhibited excellent electrochemical performances with specific capacitance value ∼185 Fg−1 in 1 M H2SO4, which is higher than that of nonactivated pinecone carbon and 1:2 ratio KOH-based activated carbon (PAC2) (∼144 Fg−1). The systematic studies were performed to design various forms of devices (symmetric and asymmetric) to investigate the effect of device architecture and operating voltage on the performance and stability of the supercapacitors. The symmetric supercapacitor, designed utilizing PAC4 in H2SO4 electrolyte, exhibited a maximum device-specific capacitance of 43 Fg−1 with comparable specific energy/power and excellent stability (∼96% after 10 000 cycles). Moreover, a symmetric supercapacitor was specially designed using PAC4, as a positive electrode, and PAC2, as a negative electrode, under their electrolytic ion affinity, and which operates in aqueous Na2SO4 electrolyte for a wide cell voltage (1.8 V) and showed excellent supercapacitance performances. Also, a device was assembled with poly(3,4-ethylene dioxythiophene) (PEDOT) nanostructure, as positive electrode, and PAC4, as a negative electrode, to evaluate the feasibility of designing a hybrid supercapacitor, using polymeric nanostructure, as an electrode material along with biomass-activated carbon electrode. 相似文献
48.
49.
Wireless Personal Communications - Wireless sensor network consists of a number of power constrained sensor nodes that sense data from the environment. The collected data is directed to the base... 相似文献
50.
Semiconductors - Zinc Aluminum Oxide thin films were deposited on glass substrates by reactive DC magnetron sputtering method by varying oxygen flow rates from 1 to 4 sccm. Glancing angle X-ray... 相似文献