Secrecy outage analysis on underlay cognitive radio using selection combining

Secure data transmission in future high-capacity high-coverage multi-tier hierarchical networks, for which cognitive radio （CR） has emerged as an essential recipe, is of utmost importance. This paper investigates the secrecy outage performance of selection combining （SC） in CR networks （CRNs） over Rayleigh fading channels. In a single-input multiple-output （SIMO） wiretap channel, a secondary user transmits confidential messages to another secondary user, which is equipped with n B （nB ≥1） antennas. Meanwhile, a passive eavesdropper, which is equipped with nE （n E ≥1） antennas, intends to overhear the messages. Both the legal receiver and the eavesdropper adopt SC scheme to process the received multiple signals. The secondary transmitter uses the underlay strategy to guarantee the quality of service of the primary user without spectrum sensing. Compared to the work proposed by Maged Elkashlan et al. in Ref. [ 1 ], we present an alternative method to derive the closed-form expression for the secrecy outage probability （SOP） and develop a simplified SOP when the maximal transmit power at the secondary user is sufficiently high. Our results reveal the impact of the primary network on the secondary network with a multi-antenna wiretap channel and simulations are conducted to validate the accuracy of our proposed analytical models.

Comparisons of Three Recurrent Selection Methods in the Improvement of Maize Populations

The maize population Csyn 4 was improved for three cycles with three recurrent selection methods MS1, MS1-HS, and MHSRRS in northern China. A total of 40 NC Ⅱ testcrosses were made by four testers with Csyn 4 and 10 improved populations, which were evaluated in four environments in the cropping season of 2005. Analysis of variance indicated a significant progress （P〈 0.05） in yield and other chief agronomic traits in the improved populations and testcrosses, demonstrating that the three recurrent selection methods were effective for increasing grain yield of testcrosses and improvement of general combining ability in maize population. The average grain yield increase of population Csyn 4 in MS1, MS1-HS, and MHSRRS recurrent selections was 266.7 kg ha^-1 （5.3%）, 288.0 kg ha^-1 （5.7%）, and 231.3 kg ha^-1 （4.6%） per cycle, while the grain yield of S 1 progeny of population for Csyn 4 was increased by 420.0 kg ha^-1 （10.9%）, 376.0 kg ha^-1 （9.8%）, and 414.7 kg ha^-1 （10.8%） per cycle in MS1, MS1-HS, and MHSRRS recurrent selections, respectively. Linear responses （b） in the MS1, MS1-HS, and MHSRRS recurrent selections were the same as the realized responses of the selection （G） for grain yield increase of Csyn 4 and S1 progeny of the populations. The grain yield of testcrosses increased by 3.3-5.2% on average per cycle. The value of heterosis did not display any differences amongst the different cycles of selections. The GCA for yield component traits of population Csyn 4 was improved significantly by means of three selection methods, whereas the GCA for plant height, ear height, days to silking, and days to pollen did not show significant increase in the recurrent selections. GCA for the number of tassel branches were decreased in the selections, while GCA for the number of plant leaves were increased, but the difference was not significant.

Selection of surgical methods for thoracic ossification of ligamentum flavum combined with cervical spondylotic myelopathy

Objective To investigate the difference between different surgical methods for thoracic ossification of ligamentum flavum(OLF) combined with cervical spondylotic myelopathy(CSM) . Methods From January 1991 to January 2003,56 cases

On the System Performance of Mobile Edge Computing in an Uplink NOMA WSN With a Multiantenna Access Point Over Nakagami-m Fading

In this paper,we study the system performance of mobile edge computing(MEC)wireless sensor networks(WSNs)using a multiantenna access point(AP)and two sensor clusters based on uplink nonorthogonal multiple access(NOMA).Due to limited computation and energy resources,the cluster heads(CHs)offload their tasks to a multiantenna AP over Nakagami-m fading.We proposed a combination protocol for NOMA-MEC-WSNs in which the AP selects either selection combining(SC)or maximal ratio combining(MRC)and each cluster selects a CH to participate in the communication process by employing the sensor node(SN)selection.We derive the closed-form exact expressions of the successful computation probability(SCP)to evaluate the system performance with the latency and energy consumption constraints of the considered WSN.Numerical results are provided to gain insight into the system performance in terms of the SCP based on system parameters such as the number of AP antennas,number of SNs in each cluster,task length,working frequency,offloading ratio,and transmit power allocation.Furthermore,to determine the optimal resource parameters,i.e.,the offloading ratio,power allocation of the two CHs,and MEC AP resources,we proposed two algorithms to achieve the best system performance.Our approach reveals that the optimal parameters with different schemes significantly improve SCP compared to other similar studies.We use Monte Carlo simulations to confirm the validity of our analysis.

Capacity and outage probability analysis of downlink MRT-SC in distributed antenna system

This paper investigates the downlink capacity distribution and the outage probability of the interested area of maximum ratio transmission-selection combining(MRT-SC) scheme in the distributed antenna system(DAS).Composite fading channels are assumed,which include path loss,lognormal shadowing and multi-path Rayleigh fading.Analytical approximations of the capacity's cumulative distribution function(CDF),the outage capacity,the mean capacity,and the outage probability of the interested area are derived by means of moment generation function(MGF) and Gauss-Hermite series expansion based approaches.The influence of antenna number,path loss exponent,and shadowing standard deviation on the capacity distribution are investigated.The simulation results agree with the analytical approximations well,and thus the analytical approximations are able to substitute the time-intensive Monte Carlo simulation for further investigation.

PERFORMANCE ANALYSIS OF TAS/MRC-BASED SCHEME IN TIME-VARYING RAYLEIGH FADING CHANNELS

This paper investigates a Multiple-Input Multiple-Output (MIMO) scheme combining Transmit Antenna Selection and receive Maximal-Ratio Combining (TAS/MRC) in time-varying Rayleigh fading channels. We first present new closed-form expressions for optimal received Signal-to-Noise Ratio (SNR),which is expressed in polynomial form. These are used to analyze ergodic capacity,outage probability and Bit Error Rate (BER) of TAS/MRC systems. Numerical results are presented to validate the theoretical analysis.

N_2O Decomposed by Discharge Plasma with Catalysts

A great deal of attention has been focused on discharge plasma as it can rapidly decompose N2O without additives,which is not only a kind of greenhouse gas but also a kind of damages to the ozone layer.The thermal equilibrium plasma is chosen to combine with catalysts to decompose N2O,and its characteristics are analyzed in the present paper.The results indicate that NO and NO2 were formed besides N2 and O2 during N2O decomposition when N2O was treated merely by discharge plasma.Concentration of NO declined greatly when the discharge plasma was combined with catalysts.Results of Raman spectra analysis on CeO2,Ce（0.75）Zr（0.25）O2and Ce（0.5）Zr（0.5）O2 imply that the products selectivity has been obviously improved in discharge plasma decomposing N2O because of the existence of massive oxygen vacancies over the composite oxide catalysts.

Selection of proper combine harvesters to field conditions by an effective field capacity prediction model

Farmers have to finish their harvesting with high efficiency,because of time and cost.However,farmers are lacking knowledge and information required for selecting suitable combine harvesters and giving the conditions of their rice fields,because both information factors(combine harvester and field condition)impact the field capacity.The field capacity model was generated from combine harvesters with the Thai Hom Mali rice variety(KDML-105).Therefore,this study aimed to determine the prediction model for effective field capacity to combine harvesters when harvesting the Thai Hom Mali rice variety(KDML-105).The methods began by collecting data of 15 combine harvesters,such as field,crop,and machine conditions and operating times;to generate the prediction model for the KDML-105 variety.The prediction model was then validated using 12 combine harvesters that were collected similarly to the model creation.The results showed a root mean square error(RMSE)of 0.24 m^(2)/s for the model.The prediction model can be applied for farmers to select the proper combine harvesters and give their field conditions.

A Novel Strategy of Multi-element Nanocomposite Synthesis for High Performance ZnO-CoSe_(2) Supercapacitor Material Development

Developing multi-eleme nt composites is a promisi ng way for high perform a nee supercapacitor material developme nt,and simplifying the synthesis steps is critical for reducing the preparation costs and successful promotion of the materials.A novel one-step selective reaction strategy is developed,and successfully used to prepare four-element ZnO-CoSe_(2)(ZOCS)nano-spherical composites,to be used as supercapacitor materials.Started form nano-spherical glycerate templates,under the optimal synthesis condition,the obtained ZOCS-0.125 electrode material exhibits a specific capacitance of 450.7 F/g at 1 A/g and a good rate performance by keeping 76.8%capacitance at 20 A/g.Moreover,the ZOCS-0.125 electrode exhibits excellent cycle stability of 114.9%capacitance retention after 5000 cycles at 10 A/g.An asymmetric supercapacitor assembled by ZOCS-0.125 and activated carbon electrodes delivers an energy density of 22.35 Wh/kg at 825 W/kg,and a cycle stability of 105.6%capacitance retention after 5000 cycles.This work not only shows the good potential of the facilely prepared ZnO-CoSe_(2) composite electrode material,but also dem on strates a new strategy for low cost and high performance multielement composite material development,that can be used in a wide range of applications.