全文获取类型
收费全文 | 72篇 |
免费 | 3篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 15篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 3篇 |
能源动力 | 8篇 |
轻工业 | 8篇 |
石油天然气 | 3篇 |
无线电 | 9篇 |
一般工业技术 | 3篇 |
原子能技术 | 1篇 |
自动化技术 | 18篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 11篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有75条查询结果,搜索用时 9 毫秒
1.
A numerical study of unsteady natural convection flow during freezing of water in a circular enclosure is presented. Mathematical model for phase change is based on apparent capacity method formulation and the governing equations are discretized on a fixed grid by means of finite element method. Water’s temperature is initially higher than its freezing temperature. Then, the temperature of the enclosure’s boundary is dropped to a temperature lower than freezing temperature. Ice forms at the enclosure boundary while natural convection flow is induced in the liquid region. Calculations have been made for the rate of change of solid fraction and temperature distributions, for conduction and conduction plus convection modes of heat transfer, and density inversion near freezing temperature phenomenon of water is considered. High resolution capturing of solid/liquid moving boundary as well as the details of flow structure is presented. The results indicate that the effect of natural convection is dominant over conduction if the Rayleigh number is higher than 5 × 106 and relatively insignificant if the Rayleigh number is less than 1 × 106. 相似文献
2.
Wi-Fi Direct has become vastly popular in the last few years. Due to its fast network setup and the provision of high transmission rates, it is expected to be the piggyback technology for high speed device-to-device communications in smart cities. The increasing demand on Wi-Fi Direct networks and its co-location in the same band with other Wi-Fi ad-hoc and infrastructure networks have entailed the need for developing new adaptive techniques to utilize the wireless spectrum efficiently. In this paper, we introduce, analyze and implement a self-organizing algorithm designed specifically for pop-up Wi-Fi Direct networks. The algorithm dynamically changes the operating channels of pop-up Wi-Fi Direct networks according to their performance in a non-cooperative manner. It utilizes the spectrum efficiently, reduces congestion and enhances performance. Moreover, the modified Wi-Fi Direct network running the proposed algorithm is interoperable with all other Wi-Fi network modes and setups and does not affect their functionalities. On the contrary, it enhances their performance implicitly. We implement the algorithm using the driver of RTL8188CUS chipset in a Linux environment and conduct experiments to evaluate its performance. The obtained results illustrate the benefits of using the proposed algorithm. 相似文献
3.
Mohammed M. Al-Najjar S. Halim Hamid Esam Z. Hamad 《Polymer Engineering and Science》1996,36(16):2083-2087
Low-molecular-weight polystyrene was nitrated to different levels. The nitrated polystyrene was blended with different molecular weights of poly(acrylic acid), PAA. The glass transition temperatures (Tg) for the mixtures were investigated by differential scanning calorimetry. A single Tg was observed for all blends, indicating single-phase blends. In general, it was found that the Tg increases with molecular weight of PAA. The Tg values of the blends showed a positive deviation from the linear average Tg as a result of strong hydrogen bonding between the segments of the component polymers. The observed Tg values were not adequately represented by simple predictive equations or by single-parameter fitting equations. However, two-parameter fitting equations gave a reasonable representation of the data. 相似文献
4.
A three-phase model for adsorption in zeolite cavities is proposed. The adsorbed molecules are taken to be distributed between a surface layer and a dense phase filling the rest of the cavity volume. This model is a more realistic representation of molecules in zeolite cages especially at high pressures. The equation for the adsorption isotherm, based on this model, has two contributions: a surface term and a dense phase term. The dense phase contribution was estimated from a simple equation that obeys the limiting values at low and high pressures. The surface contribution can be estimated from the existing surface adsorption models. When all model parameters are estimated from molecular and literature data, the combination of the two terms was found to be an improvement over traditional treatment of adsorption data of a number of gases in zeolite-A for a wide range of pressures. However, new models for the adsorbed phase that account for sorbate-sorbate repulsive forces correctly are needed for accurate prediction of adsorption data. 相似文献
5.
Ashraf A. Aly Tamer El Malah Esam A. Ishak Stefan Bräse 《Journal of Sulfur Chemistry》2016,37(2):141-147
Dithiacarbamates reacted with malononitrile dimer to give 1,4-dihydropyridine-2-thiols. The structures of the obtained products were proven by IR, mass, and NMR spectra and elemental analyses. The reaction mechanism is also discussed. 相似文献
6.
Rapid quantitative method for total brominated vegetable oil in soft drinks using ion chromatography
Yousef AA Abbas AB Badawi BSh Al-Jowhar WY Zain EA El-Mufti SA 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2012,29(8):1239-1243
A simple, quantitative and rapid method for total brominated vegetable oil (BVO) using ion chromatography (IC) with suppressed conductivity detection was developed and successfully applied to soft drinks with results expressed as inorganic bromide anion. The procedure involves extraction of BVO with diethyl ether and treatment with zinc dust in a solution of acetic acid, giving recoveries ranging between 92.5 and 98.5%. The calibration curves obtained were linear with correlation coefficients (r (2)) of 0.998, a coefficient of variation (CV) of less than 5% and limit of detection (LOD) and limit of quantification (LOQ) of 250 and 750?μg?l(-1), respectively. The method was successfully applied to the determination of BVO in several commercial soft drinks which were found to contain BVO in the range 1.8-14.510?mg?l(-1). The method has less sources of error compared to previously published methods. 相似文献
7.
The Promise of High-Performance Reconfigurable Computing 总被引:3,自引:0,他引:3
Several high-performance computers now use field-programmable gate arrays as reconfigurable coprocessors. The authors describe the two major contemporary HPRC architectures and explore the pros and cons of each using representative applications from remote sensing, molecular dynamics, bioinformatics, and cryptanalysis. 相似文献
8.
The solution carryover in traditional desiccant regeneration towers is of serious concern in real applications especially when using triethylene glycol (TEG) as a desiccant. In this study, the cellulose rigid media pads are used as the structured packing. The packing arrangements have provided minimum carryover of TEG. A performance study of the simultaneous heat and mass transfer between air and desiccant in a structured packed-stripping tower is conducted. Through the study of the regenerator, important design variables are defined and the regenerator performance is compared with the previous studies. The effects of air and liquid flow rates, air humidity, desiccant temperature and desiccant concentration have been reported on the evaporation rate and humidity effectiveness of the column. It is found that high liquid flow rates do not have a significant effect on the performance variables. 相似文献
9.
Nabih Jaber Kemal E. Tepe Esam Abdel-Raheem Author vitae 《AEUE-International Journal of Electronics and Communications》2011,65(11):924-928
This paper proposes the use of equalization concepts in frequency domain that exploit the frequency domain channel matrix to combat inter-carrier interference (ICI) instead of inter-symbol interference (ISI) in 5.9 GHz Dedicated Short Range Communications (DSRC) systems. The physical layer (PHY) of DSRC is currently being developed by work group of IEEE 802.11p. The conventional system currently assumes static channel characteristics. Channel tracking schemes were investigated and the Viterbi-aided channel estimation scheme was proposed for DSRC systems that did not explicitly exploit the ICI components caused by the time-varying channels. The performance of the DSRC system is investigated for a time-varying channel using a conventional DSRC model, a decision-directed (Viterbi-aided) channel estimation model, and the frequency-domain equalization design. It is shown that the DSRC system with the frequency-domain equalization achieves a considerable performance enhancement compared to both the conventional and the Viterbi-aided channel estimation schemes in terms of both packet error rate (PER) and bit error rate (BER) at relatively high and low velocities. 相似文献
10.
Computationally efficient methods for blind decision feedback equalization of QAM signals 总被引:1,自引:0,他引:1
Kevin Esam Mohammed A.S. 《AEUE-International Journal of Electronics and Communications》2008,62(5):374-385
This paper investigates computationally efficient methods for blind decision feedback equalization (DFE) that reduce the complexity and power requirements of blind equalization algorithms while maintaining their steady-state characteristics for quadrature amplitude modulation (QAM) signals. These include the power-of-two error (POT), selective coefficient update (SCU), and frequency-domain block (FDB) methods. A novel radius-directed stop-and-go (RSG) method is introduced, which selectively adjusts the equalizer tap coefficients based on the equalizer output radius. In addition, a new activation/de-activation method based on the equalizer output radius is utilized to control the feedback equalizer (FBE) of the DFEs. Simulation studies and analysis are provided for empirically derived cable and microwave channels and Ricean fading channels. 相似文献