Coordinated Multi-User Spectrum Sharing in Distributed Antenna-Based Cognitive Radio Systems

Spectrum sharing for efficient reuse of licensed spectrum is an important concept for cognitive radio technologies.In a spectrum-sharing system(SSS),deploying the antennas in a distributed manner can offer a new spatial dimension for the efficient reuse of licensed frequency bands.To improve the whole performance of multiple secondary users(SUs),this paper addresses the problem of coordinated multi-SU spectrum sharing in a distributed antenna-based SSS.By adopting the Hungarian method,the primal decomposition method and pricing policy,we propose a coordinated multi-user transmission scheme,so as to maximize the sum-rate of SUs.Simulation results show that the proposed method can significantly enhance the system performance,and the computational complexity is low.

Climate Characteristics of Thunder and Lightning in Anyang City

The research explored frequencies of different weathers caused by con-vection, characters of thunder and lightning, spatial and temporal changes, move-ment routes, geographical distribution, daily, monthly and annual changes of thunder or lightning, based on 30 years information. Furthermore, a search system of thun-derstorm in history was established, laying foundation for prevention and prepared-ness of thunderstorm in Anyang.

Adaptive impedance matching using quantum genetic algorithm

An adaptive technique adopting quantum genetic algorithm （QGA） for antenna impedance tuning is presented. Three examples are given with different types of antenna impedance. The frequency range of the dual standards is from 1.7 to 2.2 GHz. Simulation results show that the proposed tuning technique can achieve good accuracy of impedance matching and load power. The reflection coefficient and VSWR obtained are also very close to their ideal values. Comparison of the proposed QGA tuning method with conventional genetic algorithm based tuning method is Moreover, the proposed method can be useful for software wireless bands. also given, which shows that the QGA tuning algorithm is much faster. defined radio systems using a single antenna for multiple mobile and

Excess Heat Triggered by Different Current in a D/Pd Gas-Loading System

In order to study the relationship between the triggering current, deuterium pressure and the excess heat, a series of experiments were made in a D/Pd gas-loading system. By comparing the system constants （k = AT//kP） in both nitrogen and deuterium atmosphere we found an optimum current （8 A） and a deuterium pressure （9 x 104 Pa） in which the system could release a maximum excess power （more than 80 W）. The reproducibility was 16/16 and the excess energy released in the longest experiment was about 300 MJ within 40 days, which was corresponding to 104 eV for each palladium atom. Analysis of the palladium surface with a SEM （scanning electron microscopy） and an EDS （energy dispersive spectrometer） revealed that some new surface topographical feature with concentrations of unexpected elements （such as Ag, Sn, Pb and Ca） appeared after the current triggering. The results implied that the excess heat might come from a nuclear transmutation.

Resistivity in Formation and Decomposition of Natural Gas Hydrate in Porous Medium

A new one-dimensional system for resistivity measurement for natural gas hydrate(NGH)exploitation is designed,which is used to study the formation and decomposition processes of NGH.The experimental results verify the feasibility of the measurement method,especially in monitoring the nucleation and growth of the NGH. Isovolumetric formation experiment of NGH is performed at 2°C and 7.8 MPa.Before the NGH formation,the initial resistivity is measured to be 4-7Ω·m,which declines to the minimum value of 2-3Ω·m when NGH begins to nucleate after the pressure is reduced to 3.3 MPa.As the NGH grows,the resistivity increases to a great extent,and finally it keeps at 11-13Ω·m,indicating the completion of the formation process.The NGH decomposition experiment is then performed.When the outlet pressure decreases,NGH begins to decompose,accordingly,the resistivity declines gradually,and is at 5-9Ω·m when the decomposition process ends,which is slightly higher than the resistivity value before the formation of NGH.The occurrence and distribution uniformity of NGH are determined by the distribution and magnitude of the resistivity measured on an one-dimensional sand-packed model.This study tackles the accurate estimation for the distribution of NGH in porous medium,and provides an experimental basis for further study on NGH exploitation in the future.

Rethinking the Power Shortage of China in 2011

As the opening year of the ＂Twelfth Five-Year Plan,＂ driven by the steady and fast economic growth, the year of 2011 saw China＇s rising demand for electricity, resulting in regional power shortages. Sub）ected to multiple factors such as the weather conditions, the contradictions between coal supply and power generation and the structural problems in the power system, power supply shortage across the nation became increasingly critical At the same time, the Northeast and Northwest China, plus Inner Mongolia, often experienced power generation surplus and difficulties in sending power to other regions. This paper reviews the overall situation of the national electric power supply in 2011, elaborates on the current contradictions in the power demand and supply and presents an in-depth analysis of causes and corresponding countermeasures.

Dependency of Electrical Demand of Bangladesh Power System on the Weather of the Country

The variation of electrical demand above its base value is its common characteristic. The weather dependent variation of demand, especially where the weather is severe in nature, requires a significant reserve margin of the generation system. The evaluation of the weather dependent component of the electric demand is the basic tool for the planning of the reserve margin. This paper evaluates the weather dependent portion of the load of BPS （Bangladesh power system）. The evaluation of the weather dependent portion of the demand is based on the EMD （empirical mode decomposition） technique.

Adaptive Energy-Efficient Power Allocation for DAS with Imperfect Channel State Information and Antenna Selection

Considering that perfect channel state information(CSI) is difficult to obtain in practice,energy efficiency(EE) for distributed antenna systems(DAS) based on imperfect CSI and antennas selection is investigated in Rayleigh fading channel.A novel EE that is defined as the average transmission rate divided by the total consumed power is introduced.In accordance with this definition,an adaptive power allocation(PA) scheme for DAS is proposed to maximize the EE under the maximum transmit power constraint.The solution of PA in the constrained EE optimization does exist and is unique.A practical iterative algorithm with Newton method is presented to obtain the solution of PA.The proposed scheme includes the one under perfect CSI as a special case,and it only needs large scale and statistical information.As a result,the scheme has low overhead and good robustness.The theoretical EE is also derived for performance evaluation,and simulation result shows the validity of the theoretical analysis.Moreover,EE can be enhanced by decreasing the estimation error and/or path loss exponents.

Design of a novel finger of DLR/HIT dextrous robot hand based on mechatronic integration

With the idea of mechatronic integration,a novel finger of the dextrous robot hand has been designed. The finger with nice envelop has four joints with three DOFs driven by three brushless DC motors with smaller size and more torque. The use of rigid gear head,bevel gears and linkage in the transmission system makes the finger more rigid. Abundant sensors such as joint angle sensors,joint torque sensors and temperature sensors are located in the finger. Integration and modularization are achieved at most by high integration of finger body,driving system,sensors and electronics.

Impact of Weather Conditions and Dynamic Load Models on Steady State and Dynamic Response of Power System

This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dynamic load models on system stability is also studied. The steady-state and dynamic stability simulation results of a 39 bus system for constant line impedance （the traditional simulation practice） are compared to the results with estimated, but realistic, temperature varied line impedances using PSLF （positive sequence load flow） software. The modulated line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electro-mechanical oscillations at generator buses.