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Search Results: 1 - 10 of 41314 matches for " Lian Zhao "
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Throughput Maximization Based on Optimal Access Probabilities in Cognitive Radio System  [PDF]
Mohamed Elalem, Lian Zhao
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53024

Well-established fact shows that the fixed spectrum allocation policy conveys to the low spectrum utilization. The cognitive radio technique promises to improve the low efficiency. This paper proposes an optimized access strategy combining overlay scheme and underlay scheme for the cognitive radio. We model the service state of the system as a continuous-time Markov model. Based on the service state, the overlay manner or/and the underlay manner is/are used by the secondary users. When the primary user is not transmitting and only one secondary user has the requirement to transmit, the secondary system adopts the overlay scheme. When the primary user is transmitting and the secondary users want to transmit simultaneously, an underlay scheme with an access probability is adopted. We obtain the optimal access probability in a closed form which maximizes the overall system throughput.

Effective Capacity and Interference Analysis in Multiband Dynamic Spectrum Sensing  [PDF]
Mohamed Elalem, Lian Zhao
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.52011

In this paper, the performance of multichannel transmission in cognitive radio is studied. Both QoS constraints and interference limitations are considered. The activities of the primary users (PU)s are initially detected by cognitive users (CU)s who perform sensing process over multiple channels. They transmit in a single channel at variable power and rates depending on the channel sensing decisions and the fading environment. The cognitive operation is modeled as a state transition model in which all possible scenarios are studied. The QoS constraint of the cognitive users is investigated through statistical analysis. Analytical form for the effective capacity of the cognitive radio channel is found. Optimal power allocation and optimal channel selection criterion are obtained. Impact of several parameters on the transmission performance, as channel sensing parameters, number of available channels, fading and other, are identified through numerical example.

Existence of Unbounded Solutions for a Third-Order Boundary Value Problem on Infinite Intervals
Hairong Lian,Junfang Zhao
Discrete Dynamics in Nature and Society , 2012, DOI: 10.1155/2012/357697
Abstract: We generalize the unbounded upper and lower solution method to a third-order ordinary differential equation on the half line subject to the Sturm-Liouville boundary conditions. By using such techniques and the Schäuder fixed point theorem, some criteria are presented for the existence of solutions and positive ones to the problem discussed.
Poly[[[diisothiocyanatocobalt(II)]-bis[μ-4-tert-butyl-2,6-bis(1,2,4-triazol-1-ylmethyl)phenol]] dimethylformamide disolvate dihydrate]
Zhao-lian Chu
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809005121
Abstract: In the title compound, {[Co(NCS)2(C16H20N6O)2]·2C3H7NO·2H2O}n, each CoII ion located on an inversion center is six-coordinated by four equatorial N atoms from four different 4-tert-butyl-2,6-bis(1,2,4-triazol-1-ylmethyl)phenol (L) ligands, and by two N atoms from two axial thiocyanate anions [Co—N = 2.104 (3)–2.144 (3) ]. The metal centres are connected via the bidentate L ligands into two-dimensional polymeric layers parallel to bc plane. The dimethylformamide and solvent water molecules participate in intermolecular O—H...O and O—H...S hydrogen bonds, which consolidate the crystal packing.
Lian-Peng Zhao
Acta Crystallographica Section E , 2010, DOI: 10.1107/s160053681004568x
Abstract: The complete molecule of the title complex, [Co2(C8H7O3)4(C20H22N4O)2], is a dimer of the paddle-wheel-type generated by crystallographic inversion symmetry. The CoII ion is pentacoordinated by three O atoms from two 4-methoxybenzoate anions (one bidentate and one monodentate) and two N atoms from two 2,2′-bis(2-methyl-1H-benzimidazole)ether ligands. This results in a very distorted trigonal–bipyramidal geometry for the metal ion, with both N atoms in equatorial sites. The dihedral angle between the benzimidazole ring systems in the ligand is 60.04 (8)°. The configuration of the molecule is supported by intramolecular C—H...O hydrogen bonds.
Benzene-1,3,5-tricarboxylic acid–1,10-bis(1,2,4-triazol-1-yl)decane–water (1/1/2)
Lian-Peng Zhao
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810044673
Abstract: In the title 1:1:2 association, C14H24N6·C9H6O6·2H2O, the alkyl chain in the 1,10-bis(1,2,4-triazol-1-yl)decane molecule adopts an extended conformation and the dihedral angle between the aromatic rings is 10.28 (13)°. The benzene-1,3,5-tricarboxylic acid molecule is close to being planar (r.m.s. deviation = 0.052 ). In the crystal, the components are linked by O—H...O and O—H...N hydrogen bonds, generating a layered network.
Triaquachlorido[3-dimethylamino-1-(2-pyridyl)prop-2-en-1-one-κN1]manganese(II) chloride
Zhao-Lian Chu
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809024192
Abstract: In the title compound, [MnCl(C10H12N2O)(H2O)3]Cl, the MnII ion has a distorted octahedral coordination environment formed by one N and one O atom from the chelating 3-dimethylamino-1-(2-pyridyl)prop-2-en-1-one ligand, one chloride anion and three coordinated water molecules. Intermolecular O—H...O and O—H...Cl hydrogen bonds link the cations and anions into layers parallel to the ac plane.
Power Allocation for Amplify-and-Forward Cooperative Transmission Over Rayleigh-Fading Channels
Lian Zhao,Zaiyi Liao
Journal of Communications , 2008, DOI: 10.4304/jcm.3.3.33-42
Abstract: Cooperative transmission has been used to achieve diversity gain through partner to create multiple independent fading channels. It has attracted lots of research attention in recent years. An important question in cooperative communication is power allocation. Given the same total power, how much should be allocated to self-information transmission and how much to relayinginformation transmission. In this paper, we investigate power allocation problem using amplify-and-forward (AF) protocol considering bit error rate (BER) performance of both users and the work region of two cooperative users. We solve cooperative ratio, which is defined as the ratio of power used for cooperative transmission over the total power. We first consider both users applying the same ratio, and then extend to two-dimensional cooperative ratio problem. Our results show that it is sufficient to allocate both users the same ratio. This value is specified by the user with a weaker channel gain to the destination, i.e., bottleneck link.With appropriate selection of the cooperative ratio, the BER performance of both users can be improved significantly. User fairness is also considered in the analysis.
Role of Asp37 in metal-binding and conformational change of ciliate Euplotes octocarinatus centrin  [PDF]
Wen Liu, Lian Duan, Bing Zhao, Ya-Qin Zhao, Ai-Hua Liang, Bin-Sheng Yang
Health (Health) , 2010, DOI: 10.4236/health.2010.23037
Abstract: Centrin is a member of the EF-hand super family that plays critical role in the centrosome duplication and separation. To investigate the role of Asp37 in the process of metal-binding and conformational change of ciliate Euplotes octocarinatus centrin (EoCen), the mutant D37K, in which aspartic acid 37 had been replaced by lysine, was first obtained by the site-directed mutagenesis. Then 2-p-toluidinylnaphthalene-6- sulfonate (TNS) was used as a fluorescence probe to detect the conformational change of the protein. The results show that the metal- binding capability of the site I of EoCen was lost by the mutation of Asp37→Lys. In comparison the Tb3+-saturated EoCen, the hydrophobic surface of D37K, which is exposed by the binding of Tb3+, has shrunk sharply, suggesting that Asp37 plays an important role in maintaining the proper conformation of EoCen in the presence of Tb3+. Meanwhile, the conditional binding constants of TNS with Tb3+-loaded EoCen and D37K were obtained, K(Tb3+-EoCen-TNS)=(7.38 ±0.25)×105 M-1 and K(Tb3+-D37K-TNS)=(1.16± 0.05)×106 M-1.
Nitrogen Use Efficiency under Different Field Treatments on Maize Fields in Central China: A Lysimeter and 15N Study  [PDF]
Jin Zhang, Zhao-Hua Li, Wei Huang, Lian-Hai Sang, Kun Li
Journal of Water Resource and Protection (JWARP) , 2012, DOI: 10.4236/jwarp.2012.48068
Abstract: Nitrogen loss from farmland has caused serious problems all over the world. This field study assessed Nitrogen Use Efficiency1 (NUE) and biomass yield under four different field treatments in the Hubei Province, in central China. Results show that 1) in these four treatments, the maize monoculture plots have the highest rate of fertilizer N losses (69.12%), and the lowest (32.45%) is treated by surface rice straw mulch of maize intercrop with peanut; 2) compared with monoculture, polyculture plots have 36.9 kg·ha–1 and 26.57 kg·ha–1 more nitrogen absorption in the mulched and un-mulched plots respectively, however, polyculture has a lesser effect on NUE; 3) surface straw mulch is an effective way to keep nitrogen in the soil (0 - 100 cm), however it may decrease dry matter yield in monoculture plots; 4) maize intercrop with peanut and surface mulch can keep 47.63% of the fertilizer N in the soil profiles (0 - 100 cm), which is the highest among these four treatments.
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