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531.
In this work, the secrecy of a typical wireless cooperative dual-hop non-orthogonal multiple access (NOMA)-enabled decode-and-forward (DF) relay network is investigated with the impact of collaborative and non-collaborative eavesdropping. The system model consists of a source that broadcasts the multiplexed signal to two NOMA users via a DF relay, and information security against the eavesdropper nodes is provided by a helpful jammer. The performance metric is secrecy rate and ergodic secrecy capacity is approximated analytically. In addition, a differential evolution algorithm-based power allocation scheme is proposed to find the optimal power allocation factors for relay, jammer, and NOMA users by employing different jamming schemes. Furthermore, the secrecy rate analysis is validated at the NOMA users by adopting different jamming schemes such as without jamming (WJ) or conventional relaying, jamming (J), and with control jamming (CJ). Simulation results demonstrate the superiority of CJ over the J and WJ schemes. Finally, the proposed power allocation outperforms the fixed power allocation under all conditions considered in this work. 相似文献
532.
Naveen Mukhtar Abdul Malik Naheed Riaz Kiran Iqbal RasoolBakhsh Tareen ShamsunNahar Khan SarfrazAhmad Nawaz Juveria Siddiqui M.Iqbal Choudhary 《Helvetica chimica acta》2004,87(2):416-424
Pakistolides A and B, novel dimeric β‐(glucosyloxy)benzoates were isolated from Berchemia pakistanica and assigned structures 1 and 2 on the basis of extensive NMR studies. In addition, the known compounds 7,5′‐dimethoxy‐3,5,2′‐trihydroxyflavone (=3,5‐dihydroxy‐2‐(2‐hydroxy‐5‐methoxyphenyl)‐7‐methoxy‐4H‐1‐benzopyran‐4‐one), 4′,5‐dihydroxy‐3,6,7‐trimethoxyflavone (=5‐hydroxy‐2‐(4‐hydroxyphenyl)‐3,6,7‐trimethoxy‐4H‐1‐benzopyran‐4‐one), 5,6‐dihydroxy‐4,7‐dimethoxy‐2‐methylanthracene‐9,10‐dione, and 1,3,4‐trihydroxy‐6,7,8‐trimethoxy‐2‐methylanthracene‐9,10‐dione were reported for the first time from the genus Berchemia. Both 1 and 2 showed significant α‐glucosidase and lipoxygenase inhibitory activities, while 2 also showed antioxidant potential. 相似文献
533.
The use of very deep submicron technology makes VLSI-based digital systems more susceptible to transient or soft errors, and thus compromises their reliability. This paper proposes an architecture inspired by the human immune system that allows tolerance of such errors. An error in a digital system designed using the proposed architecture is treated as an antigen by the system. Using its distributed defense mechanism the system heals itself from the effect of the error. A major advantage of this architecture is that, the outputs of functional cells are connected to the inputs of other physically adjacent functional cells without having to go through complicated routing. 相似文献
534.
The synthesis of the aza-analogue of diospongin A is described. The key steps in the synthetic sequence are Mitsunobu inversion, cross olefin metathesis and intramolecular aza-Michael addition reactions. The biological activity of this new analogue was also evaluated in the induction of nitric oxide synthase and was found to be better when compared to its natural counterpart. 相似文献
535.
Kiran Singh Rajneesh Mohan Nupinder Kaur N.K. Gaur Manglesh Dixit Vilas Shelke R.K. Singh 《Physica C: Superconductivity and its Applications》2006,450(1-2):124-128
The effects of Cu doping in MgB2 superconductor has been studied at different processing temperatures. The polycrystalline samples of Mg1−xCuxB2 with x = 0.05 were synthesized through the in-situ solid sate reaction method in argon atmosphere at different temperature range between 800–900 °C. The samples were characterized through X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and low temperature R–T measurement techniques for the phase verification, microstructure and superconducting transition temperature, respectively. The XRD patterns of Mg1−xCuxB2 (x = 0.05) do not exhibit any impurity traces of MgB4 or MgB6 and they show the sharp transition in the samples prepared at 850 °C. The onset transition temperature of the prepared samples is around 39 K, which is almost the same as that for the pure MgB2. This indicates that Cu doping in MgB2 does not affect the transition temperature. The SEM micrograph of Mg0.95Cu0.05B2 has shown that the sample is dense with grain size smaller than 1 μm. 相似文献
536.
The need to establish wavelength-routed connections in a service differentiated manner is becoming increasingly important. In the backbone network, support of quality of service (QoS) capabilities at the lightpath level will have to be addressed in the optical domain. Providing a service differentiated connection on an arbitrary virtual topology which does not support any differentiated services will lead to the misuse of network resources. We address the virtual topology design and routing problem, where we minimize congestion in the network. In our work, the service differentiating parameter is bit error rate (BER) in the optical domain. We present a mixed integer linear programming (MILP) formulation for the above problem. We also propose a heuristic based approach to minimize the congestion in the network while satisfying the QoS constraints. These QoS constraints in our case are the differing BER requirements for each connection between each (source, destination) pair. We then present different methods of providing survivability for the virtual topology and compare the performance of these methods. 相似文献
537.
T Kiran. Rajan B.S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(9):2242-2253
We study n-length Abelian codes over Galois rings with characteristic p/sup a/, where n and p are relatively prime, having the additional structure of being closed under the following two permutations: (i) permutation effected by multiplying the coordinates with a unit in the appropriate mixed-radix representation of the coordinate positions and (ii) shifting the coordinates by t positions. A code is t-quasi-cyclic (t-QC) if t is an integer such that cyclic shift of a codeword by t positions gives another codeword. We call the Abelian codes closed under the first permutation as unit-invariant Abelian codes and those closed under the second as quasi-cyclic Abelian (QCA) codes. Using a generalized discrete Fourier transform (GDFT) defined over an appropriate extension of the Galois ring, we show that unit-invariant Abelian and QCA codes can be easily characterized in the transform domain. For t=1, QCA codes coincide with those that are cyclic as well as Abelian. The number of such codes for a specified size and length is obtained and we also show that the dual of an unit-invariant t-QCA code is also an unit-invariant t-QCA code. Unit-invariant Abelian (hence unit-invariant cyclic) and t-QCA codes over Galois field F/sub p//sup l/ and over the integer residue rings are obtainable as special cases. 相似文献
538.
Kiran Prajapati Anuradha Varshney 《Journal of polymer science. Part A, Polymer chemistry》2005,43(24):6524-6533
The free‐radical polymerization of styrene with p‐nitrobenzyl triphenyl phosphonium ylide as an initiator in dioxane at 80 ± 1 °C in a dilatometer under a nitrogen atmosphere for 150 min resulted in a syndiotactic polymer, as evidenced by IR, 1H NMR, and 13C NMR spectroscopy. A 1H NMR spectrum showed methylene protons as triplets; 13C NMR signals of the phenyl ipso carbons were used for the determination of the tacticity. The system followed ideal kinetics. Gel permeation chromatography data were used evaluate the weight‐average molecular weight. The overall activation energy was 47 kJ/mol. Electron spin resonance spectroscopy confirmed the initiation by the phenyl radical obtained by the dissociation of the ylide and the free‐radical mode of polymerization. Differential scanning calorimetry studies showed the glass‐transition temperature of the polymer to be 342 K. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6524–6533, 2005 相似文献
539.
Gowravaram Sabitha G.S.Kiran Kumar ReddyCh.Srinivas Reddy J.S. Yadav 《Tetrahedron letters》2003,44(21):4129-4131
The synthesis of various substituted Hantzsch 1,4-dihydropyridines has been achieved using the classical Hantzsch procedure and modified Hantzsch conditions for the first time at room temperature in the presence of iodotrimethylsilane (TMSI) generated in situ in CH3CN, in excellent yields. 相似文献
540.
Frontispiece: Efficient Synthesis of Dimeric Oxazoles,Piperidines and Tetrahydroisoquinolines from N‐Substituted 2‐Oxazolones 下载免费PDF全文