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81.
An optimum downlink power control that maximizes the user-capacity of a Direct Sequence-Code Division Multiple Access (DS-CDMA) cellular system is proposed based on a convex programming method. First, the downlink beamforming weights for the base-station antenna-array are designed based on the maximum Signal-Interference-Ratio (SIR) criterion. Then by optimizing the downlink power subject to a fixed total transmit power constraint, we further increase the Signal-Interference-Noise-Ratio (SINR) at the mobile terminal, thus increasing the capacity of the system. With the same methodology, we can also minimize the required transmit power while satisfying the SINR threshold constraints. Additionally, a robust downlink power control approach for mitigating the performance degradation due to channel estimates error is also proposed. Computer simulations are given to demonstrate the improvement of downlink capacity, received SINR, robustness, and the minimization of the required transmit power for a DS-CDMA system with antenna-array at the base-station. 相似文献
82.
Influence of ventilation on indoor radon level 总被引:1,自引:0,他引:1
Detailed radon measurements were conducted at different residential units in Hong Kong in winter time when air-conditioners were off and also in summer time when air-conditioners were on. Ventilation rates were measured concurrently to investigate the influence of ventilation on indoor radon level. The ratio of indoor radon level to outdoor radon level was plotted against ventilation rate, and it was found that a critical value existed after which the indoor radon level could be considered identical to the outdoor level. This result is important for use in ventilation design to reduce indoor radon pollution. 相似文献
83.
84.
Yanli Qu Chow W.W.Y. Mengxing Ouyang Tung S.C.H. Li W.J. Xuliang Han 《Nanotechnology, IEEE Transactions on》2008,7(5):565-572
85.
液—固磁场流态化模型及普遍化相图 总被引:3,自引:0,他引:3
本文考察了磁场流态化的基本特征,并结合实验分析了均匀磁场中液-固流态化模型参数的变化规律,对Ma 和 Kwauk 提出的指数模型作了补充,使之与经典流态化加以统一,并在此基础上获得了磁场流态化的普遍化关系图。完善后的模型可根据经典流态化的基础数据直接预示磁场作用下流态化的一些特征,模型计算结果与水-钢丸系统的实验数据吻合较好。 相似文献
86.
The CLAS forward electromagnetic calorimeter 总被引:1,自引:0,他引:1
M. Amarian G. Asryan K. Beard W. Brooks V. Burkert T. Carstens A. Coleman R. Demirchyan Yu. Efremenko H. Egiyan K. Egiyan H. Funsten V. Gavrilov K. Giovanetti R. M. Marshall B. Mecking R. C. Minehart H. Mkrtchan M. Ohandjanyan Yu. Sharabian L. C. Smith S. Stepanyan W. A. Stephens T. Y. Tung C. Zorn 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2001,460(2-3):239-265
The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented individually to form six independent spectrometers. The forward region (8°<θ<45°) of each sector is equipped with a lead–scintillator electromagnetic sampling calorimeter (EC), 16 radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct π° and η decays and detect neutrons. This paper treats the design, construction and performance of the calorimeter. 相似文献
87.
Tung Hsu 《Microscopy research and technique》1987,5(1):75-80
Reflection electron microscopy (REM) is used to calibrate the focusing steps and rotation of electron microscopes. The calibration of focusing steps is done by the direct measurement of the shift on in-focus positions in the REM micrographs. Rotations between the diffraction patterns and images are calibrated in the usual way. By using the REM geometry, the reflection high energy electron diffraction (RHEED) patterns and REM images have no rotation symmetry, thus eliminating the 180° uncertainty. 相似文献
88.
Decision-making in Water Management under Uncertainty 总被引:2,自引:2,他引:0
Decision-making in water management requires the delivery of accurate scientific information. However, the task is challenging
under the situation where a large amount of uncertainty exists in the available information (e.g., model outputs). This paper
investigates the effect of uncertainty on the ranking of options in water management. Different methods for ranking the management
options under uncertainty are reviewed and they account for only partial uncertainty information in model outputs. To consider
the full uncertainty information, a new ranking procedure is proposed in this paper, which is capable of providing more information
to decision makers and at the same time taking their opinions on uncertainty into consideration. The ranking is achieved by
conducting pair-wise comparison of management options, on the basis of the risk defined by the probability of obtaining an
unacceptable ranking and the mean difference in model outputs in pair-wise comparison. An application example is presented
to illustrate the use of the proposed ranking approach. Furthermore, the sensitivity of management option ranking to different
ranking methods and to model uncertainty is also investigated. 相似文献
89.
Thau-Ming Cham Huey-Mee Yu Loong-Chyau Tung 《Drug development and industrial pharmacy》1989,15(14):2441-2454
The counts of microspheres in 20 testing solutions were determined using 2 Coulter Counters (electrical resistance) and 2 HIAC/Royco (light blockage) particle analysers. The mean cumulative number of microspheres (≥2μm) in unit volume of the solutions determined using the Coulter Counters was higher than those determined by HIAC/Royco particle analysers. The mean cumulative counts obtained by the two Coulter Counters are similar; however, t-test analysis shows significant difference for the counts of 8 different types of solutions. The mean cumulative counts obtained by the two HIAC/Royco Counters varied greatly and t-test analysis showed that 18 out of 20 of the solutions gave significant difference 相似文献
90.
In Next-Generation (NG) hybrid wireless networks, Mobile-Controlled Handover (MCHO) is expected to be employed as the handover
control mechanism, in contrast to Network-Controlled Handover (NCHO) used in homogeneous wireless networks. As more independent
network operators get involved in providing Internet access, roaming mobile users would have to deal with complex trust relationships
between heterogeneous network domains. The state-of-the-art handover approaches just take into account Quality of Service
(QoS), but ignore the complexities arising from the coexistence of multiple network operators in the NG networks. The existence
of a complex trust relationship between networks may lead to unnecessary handover attempts in service roaming. In this regard,
this paper introduces a novel approach of dynamically retrieving network trust information, and using it in MCHO. We show
how network trust information can be utilised to obtain a 35% reduction in handover delay, meanwhile retain QoS in a handover.
The proposed scheme does not need bulk storage in mobile handsets, and can react to changes to network topology and trust
relationships dynamically. Analytical results are provided to demonstrate how roaming mobile users make more intelligent and
reliable handover if implementing the proposed handover approach in a multi-operator and multi-technology environment. 相似文献