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1.
With Earth' s power consumption forecast to rocket to new highs in coming decades, one scientist is proposing a suitably far-out solution to the likely energy crunch-power plants on the moon. Prof. David Criswell of the University of Houston' s Institute for Space Systems said that lunar power plants that capture the sun's rays and send them on to Earth as concentrated microwave beams could provide inexpensive, 相似文献
2.
An immune-tabu hybrid algorithm for thermal unit commitment of electric power systems 总被引：1，自引：0，他引：1
This paper presents a new method based on an immune-tabu hybrid algorithm to solve the thermal unit commitment （TUC） problem in power plant optimization. The mathematical model of the TUC problem is established by analyzing the generating units in modem power plants. A novel immune-tabu hybrid algorithm is proposed to solve this complex problem. In the algorithm, the objective function of the TUC problem is considered as an antigen and the solutions are considered as antibodies, which are determined by the affinity computation. The code length of an antibody is shortened by encoding the continuous operating time, and the optimum searching speed is improved. Each feasible individual in the immune algorithm （IA） is used as the initial solution of the tabu search （TS） algorithm after certain generations of IA iteration. As examples, the proposed method has been applied to several thermal unit systems for a period of 24 h. The computation results demonstrate the good global optimum searching performance of the proposed immune-tabu hybrid algorithm. The presented algorithm can also be used to solve other optimization problems in fields such as the chemical industry and the power industry. 相似文献
3.
INTRODUCTION Nitrogen oxide (NOx) is one of the main air pol- lutants found in the flue gases from chemical and power plants belching acid rain and photochemical smog. Over 90 percent of all man-made nitrogen ox- ides that enter our atmosphere are produced by the combustion of various fuels. Compared with the ad- vanced stage of SO2 gas removal technologies devel- opment, the removal of NOx gases is still in the initial stages of development as roughly 90 to 95 percent of NOx emitted i… 相似文献
4.
Utilization of fly ash from coal-fired power plants in China 总被引：2，自引：0，他引：2
The rapidly increasing demand for energy in China leads to the construction of new power plants all over the country. Coal, as the main fuel resource of those power plants, results in increasing problems with the disposal of solid residues from combustion and off gas cleaning. This investigation describes chances for the utilization of fly ash from coal-fired power plants in China. After briefly comparing the situation in China and Germany, the status of aluminum recycling from fly ash and the ad- vantages for using fly ash in concrete products are introduced. Chemical and physical analyses of Chinese fly ash samples, e.g., X-ray diffraction （XRD）, ICP （Inductive Coupled Plasma） and particle size analysis, water requirement, etc. are presented. Rea- sonable amounts of aluminum were detected in the samples under investigation, but for recovery only sophisticated procedures are available up to now. Therefore, simpler techniques are suggested for the first steps in the utilization of Chinese fly ash. 相似文献
5.
A cognitive relay network model is proposed, which is defined by a source, a destination, a cognitive relay node and a primary user. The source is assisted by the cognitive relay node which is allowed to coexist with the primary user by imposing severe constraints on the transmission power so that the quality of service of the primary user is not degraded by the interference caused by the secondary user. The effect of the cognitive relay node on the proposed cognitive relay network model is studied by evaluating the outage probability under interference power constraints for different fading environments. A relay transmission scheme, namely, decode-and-forward is considered. For both the peak and average interference power constraints, the closed-form outage expressions are derived over different channel fading models. Finally, the analytical outage probability expressions are validated through simulations. The results indicate that the proposed model has better outage probability than direct transmission. It is also found that the outage probability decreases with the increase of interference power constraints. Meanwhile, the outage probability under the average interference power constraint is much less than that under the peak interference power constraint when the average interference power constraint is equal to the peak interference power constraint. 相似文献
6.
The definition of reactive power for non-sinusoidal conditions is a controversial issue. The mathematical treatment of nonlinear loads in power systems is also unsettled. This paper starts with the decomposing of apparent power in,the cases of linear and nonlinear loads. When harmonics are present, apparent power is composed of active power, reactive power, and disturbed reactive power. Linear element can be defined as the element without disturbed reactive power. This definition is based on a practical engineering concept which can separate the contribution from the apparent power into utility-duty part and custom-duty part. The field investigation of home-used facilities was conducted. Also the data acquisition in the 0.4 kV distribution systems was completed. Moreover, the loss increase due to the nonlinear loads was estimated. Nonlinear loads can be a dominant effect with respect to reactive power and power factor. Field data from a number of nonlinear load types indicate that the disturbed reactive power can cause significant losses in utility supply systems. 相似文献
7.
INTRODUCTION The most obvious manifestation of gravitys effect on plants is the downward bending of roots and the upward growth of shoots. Gravity is an important factor in plant development (Barlow, 1995). The starch-statolith hypothesis proposed by Haberlandt and Nmec (Audus, 1962) is the most widely accepted view of how plants perceive gravity. Physiological data suggested that the amyloplast containing starch granules act as the statolith in higher plants. Sedimented amyloplasts ar… 相似文献
8.
An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A joint power control algorithm based on service factor is presented to address the TDD-CDMA mobile services in the burst mode according to the Markov modulated Bernoulli process. The joint power control equation is derived. A function model is developed to verify the new algorithm and evaluate its performance. Simulation results show that the new power control algorithm can estimate interference strength more precisely, speed up convergence of power control, and enhance power efficiency and system capacity. It is shown that the proposed algorithm is more robust against link gain changes, and outperforms the reference algorithms. 相似文献
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A method is proposed to monitor and control Hopf bifurcations in multi-machine power systems using the information from wide area measurement systems （WAMSs）. The power method （PM） is adopted to compute the pair of conjugate eigenvalues with the algebraically largest real part and the corresponding eigenvectors of the Jacobian matrix of a power system. The distance between the current equilibrium point and the Hopf bifurcation set can be monitored dynamically by computing the pair of conjugate eigenvalues. When the current equilibrium point is close to the Hopf bifurcation set, the approximate normal vector to the Hopf bifurcation set is computed and used as a direction to regulate control parameters to avoid a Hopf bifurcation in the power system described by differential algebraic equations （DAEs）. The validity of the proposed method is demonstrated by regulating the reactive power loads in a 14-bus power system. 相似文献
10.
A power system with proton exchange membrane fuel cells (PEMFC) was designed for thermal underwater glider.Heat generated by PEMFC is used as the propulsion power of the glider,and the electricity is used in the control and sensor system.An electric energy storage system (ESS) is required which possesses high power density with good cycle life.Ultracapacitors which exhibit high power density and cycle life are considered as energy storage devices.Simulations based on a specific voyage condition indicate that ESS with ultracapacitors has positive effects on reducing the output power demand of PEMFC and lightening the power system.Experimental results show that the state of charge (SOC) is related to the capacitance and resistance in ultracapacitor ESS. 相似文献
11.
温煜东 《晋城职业技术学院学报》2013,(6):59-61
本文设计了一种应用于无线局域网的电磁带隙结构(EBG)的微带天线。通过在微带贴片天线的辐射单元周围加载蘑菇型EBG结构,使得天线的带宽、增益性能得到了显著改善。仿真结果表明,与普通贴片天线相比,加载EBG结构时天线带宽增加了6%,主辐射方向上增益增大了1.98dB。 相似文献
12.
Characteristics of a single-feed dual-frequency bow-tie microstrip antenna are studied. By using the variation method, simple formulas for resonant frequencies of the bow-tie microstrip antenna are derived. It is shown that the dual-frequency ratio can be controlled easily by choosing the parameters of the antenna. This design gives compact antenna size and simple antenna structure. Experimental results are presented, verifying the validity of the design. 相似文献
13.
《校园英语(教研版)》2016,(5)
Square-shaped Split-ring resonator(SRR) lefthand Material(LHM) is proposed in Radio frequency band and S parameter extraction method was used to extract the effective permittivity and permittivity are all negative, hence verifying the nature of its left-hand properties. LHM is put on to dielectric layer of the center frequency of 920 MHZ microstrip patch antenna with 50 Ω coaxial feed. Then the left-hand microstrip patch antenna and conventional antenna are compared, finding that return loss S11 down from- 30 dB to-60 dB. 相似文献
14.
为提高圆形微带贴片天线的性能,提出将一种新型圆柱电磁带隙(EBG)结构应用于天线中,这种柱形EBG基片由两种不同周期单元组成,分别是金属环和接地过孔,形成一种辐射状的圆形周期结构.首先设计了一个圆形微带贴片天线,然后应用电磁仿真软件HFSS对两种周期结构的参数进行了优化分析,最后对加载EBG结构前后微带贴片天线的辐射方向图和回波损耗进行了比较.结果表明,在阻抗匹配良好的前提下,天线增益增强了4.6dB左右,提高了天线的应用性. 相似文献
15.
A low-sidelobe circularly-polarized （CP） microstrip patch array for 2.4 GHz radio frequency identification （RFID） readers is presented. The antenna array with a Chebyshev current distribution is composed of 6 microstrip elements. The CP operation is obtained by the quasi-square patch with difference in lengths of the two sides. The antenna has been investigated numerically and experimentally. Measured results show that the array has a Chebyshev pattern with the sidelobe level of -23 dB, the half-power beamwidth of 16° and an impedance bandwidth （S11 ≥-10 dB） of 130 MHz, which is suitable for RFID reader applications. 相似文献
16.
HUANG Biao YAN Guo-zheng LI Qian-ru 《浙江大学学报(A卷英文版)》2007,8(10):1560-1567
Antenna is very crucial to radiotelemetry capsules which can measure the physiological parameters of the gastroin- testinal (GI) tract. The objective of this paper is to design a novel spiral slots microstrip patch antenna for the radiotelemetry capsules communicating with external recorder at 915 MHz located in ISM (Industry, Science, and Medical) bands. The microstrip patch antenna is designed and evaluated using the finite-difference time-domain (FDTD) method. Return loss characteristics and the effect of the human body on resonant frequency are analyzed, and the performances of radiation patterns at different positions of the human alimentary tract are also estimated. Finally, specific absorption rate (SAR) computations are performed, and the peak 1-g and 10-g SAR values are calculated. According to the peak SAR values, the maximum delivered power for the designed antenna was found so that the SAR values of the antenna satisfy the ANSI (American National Standards Institute) limitations. 相似文献
17.
This paper proposes a compact polarization microstrip antenna based on double-layer structure.The bandwidth of the whole antenna is widened by expanding the top and bottom layers respectively.After the design of antenna structure and adjustment of size,the proposed antenna can achieve both the left-and right-hand circular polarizations in 2.33 GHz-2.97 GHz.Measurement results indicate that the effective bandwidth is 640 MHz in S-band and the relative bandwidth can achieve 24% with 11 S less than 15 dB. 相似文献
18.
本文在基片集成波导腔体结构的基础上,结合共地共面波导结构,提出了一种低剖面带宽增强型背腔缝隙天线．本天线兼具传统金属波导缝隙天线辐射效率高、功率容量大以及传统微带缝隙天线体积较小的优点,同时还具有了低剖面、重量轻、易于与平面电路集成的特点．仿真结果显示,该天线中心工作频率为5．8GHz,最大增益6．9dBi,相对带宽2．25％,完全覆盖5．8GHz频段,适用于RFID应用． 相似文献
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20.
为了实现双频天线的小型化,对平面倒F形天线给出一种改进,在辐射贴片上开一个T形槽．再将它的尾部向内折叠。通过与L形开槽的倒F形天线相比表明：改进后天线的结构更加紧凑,尺寸减小30％以上,且在给定的工作频段具有良好的辐射特性。 相似文献