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31.
Joint Design and Separation Principle for Opportunistic Spectrum Access in the Presence of Sensing Errors 总被引:1,自引:0,他引:1
Yunxia Chen Qing Zhao Swami A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(5):2053-2071
Opportunistic spectrum access (OSA) that allows secondary users to independently search for and exploit instantaneous spectrum availability is considered. The design objective is to maximize the throughput of a secondary user while limiting the probability of colliding with primary users. Integrated in the joint design are three basic components: a spectrum sensor that identifies spectrum opportunities, a sensing strategy that determines which channels in the spectrum to sense, and an access strategy that decides whether to access based on potentially erroneous sensing outcomes. This joint design is formulated as a constrained partially observable Markov decision process (POMDP), and a separation principle is established. The separation principle reveals the optimality of myopic policies for the design of the spectrum sensor and the access strategy, leading to closed-form optimal solutions. Furthermore, it decouples the design of the sensing strategy from that of the spectrum sensor and the access strategy, and reduces the constrained POMDP to an unconstrained one. Numerical examples are provided to study the tradeoff between sensing time and transmission time, the interaction between the physical layer spectrum sensor and the MAC layer sensing and access strategies, and the robustness of the ensuing design to model mismatch. 相似文献
32.
Anandkumar A. Lang Tong Swami A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(7):3175-3181
In this correspondence, the problem of distributed Bayesian estimation is considered in the context of a wireless sensor network. The Bayesian estimation performance is analyzed in terms of the expected Fisher information normalized by the transmission rate of the sensors. The sensors use a communication scheme known as the type-based random access (TBRA) scheme. Under a constraint on the expected transmission energy, an optimal spatio-temporal allocation scheme that maximizes the performance metric is characterized. It is shown that the performance metric is crucially dependent on the fading parameter known as the channel coherence index. For channels with low coherence indices, sensor transmissions tend to cancel each other, and there exists an optimal finite mean transmission rate that maximizes the performance metric. On the other hand, for channels with high coherence indices, there should be as many simultaneous transmissions as allowed by the network. The presence of a critical coherence index where the change from one behavior to another occurs is established. 相似文献
33.
Silicon - Negative Bias Temperature Instability (NBTI) is a key reliability and consistency issue for ultra-scaled Silicon IC technology with substantial consequences on both analog and digital... 相似文献
34.
Discovery of Aporphine Analogues as Potential Antiplatelet and Antioxidant Agents: Design,Synthesis, Structure–Activity Relationships,Biological Evaluations,and in silico Molecular Docking Studies 下载免费PDF全文
Vashundhra Sharma Dr. Pradeep K. Jaiswal Dr. Surendra Kumar Dr. Manas Mathur Dr. Ajit K. Swami Dr. Dharmendra K. Yadav Prof. Sandeep Chaudhary 《ChemMedChem》2018,13(17):1817-1832
To explore the potential of aporphine alkaloids, a novel series of functionalized aporphine analogues with alkoxy (OCH3, OC2H5, OC3H7) functional groups at C1/C2 of ring A and an acyl (COCH3 and COPh) or phenylsulfonyl (SO2Ph and SO2C6H4‐3‐CH3) functionality at the N6 position of ring B of the aporphine scaffold were synthesized and evaluated for their arachidonic acid (AA)‐induced antiplatelet aggregation inhibitory activity and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free‐radical‐scavenging antioxidant activity, with acetylsalicylic acid and ascorbic acid as standard references, respectively. The preliminary structure–activity relationship related to AA‐induced platelet aggregation inhibitory activity results showed that the aporphine analogues 1‐[1,2,9,10‐tetramethoxy‐6a,7‐dihydro‐4H‐dibenzo[de,g]quinolin‐6(5H)‐yl]ethanone and 1‐[2‐(benzyloxy)‐1,9,10‐trimethoxy‐6a,7‐dihydro‐4H‐dibenzo[de,g]quinolin‐6(5H)‐yl]ethanone to be the best compounds of the series. Moreover, the DPPH free‐radical‐scavenging antioxidant activity results demonstrated that the aporphine analogues 1,2,9,10‐tetramethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 2‐ethoxy‐1,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 1‐ethoxy‐2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐1‐propoxy‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, and 1‐(benzyloxy)‐2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline were the best compounds of the series. Moreover, in silico molecular docking simulation studies of the active analogues were also performed. 相似文献
35.
Jeya Jeevahan A. Poovannan V. Sriram R. B. Durai Raj G. Maghwaran G. Britto Joseph 《国际自然能源杂志》2019,40(1):96-100
Stringent emission regulations and health awareness about air pollution have led researchers to find alternative means of minimising emissions in diesel engines. In this article, the influence of oxygen enrichment is discussed to determine the effect on diesel engine performance, emission characteristics and combustion characteristics. Normal diesel and oxygen-enriched diesel are used in this experiment. The increase in oxygen concentration led to complete combustion, producing higher thermal efficiency and low harmful emissions. From the results, it is noted that oxygen-enriched diesel fuel showed reduction of CO, HC and smoke emissions, while NOx emission increased.
Abbreviations/Nomenclature DI: direct injection; NOx: oxides of nitrogen; O2: oxygen; HC: hydrocarbon; PM: particulate matters; CO: carbon monoxide; CO2: carbon dioxide 相似文献
36.
This paper addresses the problem of detecting two spectrally equivalent processes, which are modeled by a noisy AR process and an ARMA process. Higher order statistics (HOS) are shown to be efficient tools for detection. Two HOS-based detectors are derived for the binary hypothesis testing problem (i.e., known signal spectrum): The first detector exploits the asymptotic Gaussianity of the sample estimates of the cumulants. The second detector exploits the singularity of a certain matrix based on HOS. The more general composite hypothesis testing problem (i.e., with unknown signal spectrum) is then considered and a detector proposed. The performances of the different detectors are compared in terms of receiver operating characteristic (ROC) curves. Approximate closed-form expressions are derived for the threshold and the ROCs of the three detectors 相似文献
37.
Aminodi(alkylphenyl) phosphorodithioates have been synthes‐ised by the condensation of di (alkylphenyl) phosphorodithioic acid, which was derived from a renewable, biodegradable, low‐cost, naturally occurring vegetable product, cashew nutshell liquid, with various amines. These ashless aminodi (alkyl‐phenyl) phosphorodithioates have been evaluated as anti‐oxidant, antiwear, friction‐modifying, and extreme‐pressure additives in lubricant compositions. 相似文献
38.
R. Pascal S. Beloglazov S. Bonagiri L. Commin P. Cortes L.M. Giancarli C. Gliss M. Iseli R. Lanza B. Levesy J.-P. Martins J.-C. Nevière L. Patisson D. Plutino W. Shu H.L. Swami 《Fusion Engineering and Design》2012,87(7-8):1347-1351
In the framework of the TBM Program, three ITER vacuum vessel equatorial ports (#16, #18 and #02) have been allocated for the testing of up to six mock-ups of six different DEMO tritium breeding blankets. Each one is called a Test Blanket System (TBS). A TBS consists mainly of the Test Blanket Module (TBM), the in-vessel component facing the plasma, and several ancillary systems, in particular the cooling system and the tritium extraction system. Each port accommodates two TBMs and therefore the two TBSs have to share the corresponding port cell. This paper deals with the design integration aspects of the two TBSs in each port cell performed at ITER Organization (IO) with the corresponding definition of interfaces with other ITER systems. The performed activities have raised several issues that are discussed in the paper and for which design solutions are proposed. 相似文献
39.
40.
Wei Ren Qing Zhao Ram Ramanathan Jianhang Gao Ananthram Swami Amotz Bar-Noy Matthew P. Johnson Prithwish Basu 《Wireless Networks》2013,19(6):1121-1133
We consider the broadcasting problem in multi-radio multi-channel ad hoc networks. The objective is to minimize the total cost of the network-wide broadcast, where the cost can be of any form that is summable over all the transmissions (e.g., the transmission and reception energy, the price for accessing a specific channel). Our technical approach is based on a simplicial complex model that allows us to capture the broadcast nature of the wireless medium and the heterogeneity across radios and channels. Specifically, we show that broadcasting in multi-radio multi-channel ad hoc networks can be formulated as a minimum spanning problem in simplicial complexes. We establish the NP-completeness of the minimum spanning problem and propose two approximation algorithms with order-optimal performance guarantee. The first approximation algorithm converts the minimum spanning problem in simplical complexes to a minimum connected set cover (MCSC) problem. The second algorithm converts it to a node-weighted Steiner tree problem under the classic graph model. These two algorithms offer tradeoffs between performance and time-complexity. In a broader context, this work appears to be the first that studies the minimum spanning problem in simplicial complexes and weighted MCSC problem. 相似文献