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991.
Dynamic sectorization of microcells for balanced traffic in CDMA:genetic algorithms approach 总被引:1,自引:0,他引:1
With the increase of cellular users, traffic hot spots and unbalanced call distributions are common in wireless networks. As a solution to this problem, code-division multiple-access techniques enable a base transceiver station to connect microcells with optical fibers and to control the channels by sectorizing the microcells. To solve the load balancing among microcells, we dynamically sectorize the microcells depending on the time-varying traffic. The microcell sectorization problem is formulated as an integer linear programming that minimizes the blocked and handoff calls in the network. In the proposed sectorization, proper, connected, and compact sectors are considered to keep the handoffs as small as possible while satisfying the channel capacity at each sector. Three genetic algorithms (GAs) are proposed to solve the problem: standard GA, grouping GA, and parallel GA. Computational results show that the proposed GAs are highly effective. All three GAs illustrate outstanding performance for small size problems. The parallel GA, which is based on the operators used in grouping GA, demonstrates excellent solution quality in a reasonable time 相似文献
992.
50 nm long MOSFETs with side-gates were optimised in terms of the side-gate length and successfully fabricated with conventional MOS technology. The simulated and fabricated 50 nm long MOSFET shows a reasonable subthreshold swing of 81 mV/dec and a low drain induced barrier lowering of 77 mV 相似文献
993.
Hun-Cheol Lee Seong-Dae Kim 《Electronics letters》2002,38(5):217-218
A simple and fast method to select the assigned number of key frames in a video shot is presented. The algorithm selects the key frames so that the temporal variation of visual content within a video shot is equally distributed to each key frame. Simulation results on a real video sequence are shown to be in agreement with the human visual perception 相似文献
994.
采用真空蒸发的方法交替沉积Ag和TCNQ分子制备了Ag TCNQ金属 有机络合物薄膜 ,并研究了多种外加电压激发下膜的电阻转变特性。发现在转变过程中存在着一种能量效应 ,即当外电压超过某一阈值后 ,完成转变的能量不变。对此现象的可能解释是薄膜内分子在一定的外部电场能量诱导下发生重排 ,致使电导率发生跃变 相似文献
995.
996.
A pilot-scale fluidised pellet bed (FPB) bioreactor, which combines chemical coagulation, biological degradation, particle pelletisation and separation in one unit, was applied for onsite wastewater treatment and reuse. As a result of rational use of inorganic coagulant and organic polymer and moderate mechanical agitation, spherical particles were generated in the upflow column and a well-fluidised bed was formed. With a continuous supply of dissolved oxygen through a recycling loop, an aerobic condition was kept in the bottom section of the FPB column. Under such conditions the pellets in the FPB column showed the following characteristics: (1) compact structure and high density; (2) rich in microorganisms; and (3) high MLSS and MLVSS concentrations. Therefore, the FPB bioreactor achieved more than 90% removal of SS, COD, BOD and TP from raw domestic wastewater within a total hydraulic retention time (HRT) of only about 30 minutes. It also showed nitrification and denitrification ability and the TN removal could be about 50% as the recycling ratio was increased to 1:1. The treated water quality is generally competitive with the secondary effluent from a conventional activated sludge process. With these advantages the FPB bioreactor is recommendable as a compact system for onsite wastewater treatment and reuse. 相似文献
997.
A novel methanol-tolerant oxygen-reduction catalyst, Iridium-selenium (Ir-Se) chalcogenide, was synthesized by chemical precipitation in an organic solvent. Auger electron spectroscopy (AES) analysis confirmed that the synthesized Ir-Se chalcogenide had a chemical formula of Ir4Se. This chalcogenide showed strong catalytic activity towards the oxygen reduction reaction (ORR) and a high methanol tolerance. It was found that most of the oxygen could be directly reduced to water through a four-electron pathway with less than 10% hydrogen peroxide (H2O2) being produced during the ORR. The improvement in catalytic activity of the Ir-Se chalcogenide in comparison with that of pure Ir might be attributed to the effect of a bimetallic interaction. 相似文献
998.
999.
1000.
Robert Leeb Felix Lee Claudia Keinrath Reinhold Scherer Horst Bischof Gert Pfurtscheller 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(4):473-482
The step away from a synchronized or cue-based brain-computer interface (BCI) and from laboratory conditions towards real world applications is very important and crucial in BCI research. This work shows that ten naive subjects can be trained in a synchronous paradigm within three sessions to navigate freely through a virtual apartment, whereby at every junction the subjects could decide by their own, how they wanted to explore the virtual environment (VE). This virtual apartment was designed similar to a real world application, with a goal-oriented task, a high mental workload, and a variable decision period for the subject. All subjects were able to perform long and stable motor imagery over a minimum time of 2 s. Using only three electroencephalogram (EEG) channels to analyze these imaginations, we were able to convert them into navigation commands. Additionally, it could be demonstrated that motivation is a very crucial factor in BCI research; motivated subjects perform much better than unmotivated ones. 相似文献