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191.
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Lun Tang Qianbin Chen Guangyu Wang Xiaoping Zeng Huan Wang 《Telecommunication Systems》2013,52(4):2071-2082
In this paper we have studied the subcarrier and optimal power allocation strategy for OFDM-based cognitive radio (CR) networks. Firstly, in order to protect the primary user communication from the interference of the cognitive user transmissions in fading wireless channels, we design an opportunistic power control scheme to maximize the cognitive user capacity without degrading primary user’s QoS. The mathematical optimization problem is formulated as maximizing the capacity of the secondary users under the interference constraint at the primary receiver and the Lagrange method is applied to obtain the optimal solution. Secondly, in order to limit the outage probability within primary user’s tolerable range we analyze the outage probability of the primary user with respect to the interference power of the secondary user for imperfect CSI. Finally, in order to get the better tradeoff between fairness and system capacity in cognitive radio networks, we proposed an optimal algorithm of jointing subcarrier and power allocation scheme among multiple secondary users in OFDM-based cognitive radio networks. Simulation results demonstrate that our scheme can improve the capacity performance and efficiently guarantee the fairness of secondary users. 相似文献
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本文通过对广州珠江新城关居中心,即将搬迁到东圃花花世界中心商场继续发展的阐述,说明了广州城市化发展下,家具建材商业中心的演化过程,提出城市化发展下,家具建材商业中心新的发展方向以及对人们新生活模式的影响。 相似文献
195.
In this investigation, we propose and experimentally demonstrate the remodulation technique using DPSK format in both downlink and uplink traffics with high extinction ratio (ER) in colorless WDM-PON; together with a simple self-restored architecture against fiber fault. Error free operation was achieved in a 20-km-reach 10-Gb/s WDM-PON without dispersion compensation. Comparison with other wavelength remodulation schemes for WDM-PONs is also performed, showing the proposed scheme can be a potential candidate for next generation wavelength reuse WDM-PONs. In addition, the performance of self-protection has also been discussed and analyzed. 相似文献
196.
Inaccurate early project cost estimates can eliminate investment benefits. This study focuses on assisting estimators who are attempting to enhance the accuracy and reliability of engineering project cost in the pre-conceptual stage. This aim has recently garnered the attention of the transportation communities. Data from the Texas Department of Transportation (TxDOT) were utilized to develop an alternative approach that aids decision makers in terms of probability and confidence level. The proposed procedure comprises heuristic and practical simulation models that can be employed to calculate the probabilistic costs of highway bridge replacement projects. The simulation models utilize independent, correlated, and Latin Hypercube sampling approaches that incorporate major work items, roll-up work items, and project-level engineering contingencies. Cumulative distribution functions (CDFs) are then developed as a user-friendly chart for decision makers and these CDFs can be used to assess project risks during the pre-conceptual stage. Trial runs using these estimating procedures generate reliable pre-conceptual estimates. Additionally, these procedures can be extended to other project types along with programming techniques for developing an engineering project cost decision support system. 相似文献
197.
Distrust hinders disputing parties and mediators from achieving mediation success. Mediators therefore often use different trust-building tactics to generate some degree of trust in themselves and in the mediation process. This paper reports a study that identified the trust-building tactics used by construction mediators and examined the efficacy of these tactics with respect to their outcomes. Three study stages were designed. With reference to the mediation model of Sloan (1998), trust-building tactics and outcomes were first identified in Stage I. Next, the data were collected from accredited mediators with a questionnaire survey in Stage II. The collected data were then validated via reliability assessments in Stage III. With the use of multiple regression analyses, the efficacy of the trust-building tactics was examined by relating these tactics to their outcomes. The findings of this study suggest that the trust-building tactics used in Step 4 (i.e., explore interests) of Sloan’s (1998) mediation model are influential in developing trust among disputing parties and that they can also act as a time-saving tool in the mediation process. Furthermore, it was found that mediators can earn trust by adopting the trust-building tactics used in Step 3 (i.e., issues and trust) of Sloan’s (1998) model. These tactics can also serve to improve the relationships between the disputing parties. The results show that the trust-building tactics used in the final step (i.e., solutions) of Sloan’s (1998) model seem to have low efficacy in developing trust among disputing parties. 相似文献
198.
Yunqi Liu Ho Wai Lee Kin Seng Chiang Tao Zhu Yun Jiang Rao 《Lightwave Technology, Journal of》2009,27(7):857-863
We investigate in detail the process of CO2-laser writing of long-period fiber gratings (LPFGs) in unannealed and annealed boron-doped fiber samples by using repeated scanning of CO2-laser pulses. We find that the writing dynamics depends strongly on the CO2-laser energy density and the annealing temperature of the fiber. Our results from analyzing the writing dynamics reveal the relative importance of various physical effects arising from glass structure changes due to different writing conditions and thus provide a better understanding of the formation and the properties of CO2-laser written LPFGs. 相似文献
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本文以综合医院交通系统与医院功能流线系统研究理论为基础,结合"医院街"设计理念,具体阐述医院交通系统与功能流线混乱问题的解决方案. 相似文献