Energy Efficiency Analysis of Cellular Networks with Cooperative Relays via Stochastic Geometry

Cooperative relaying is a promising technology that can improve the spectral and energy efficiency of cellular networks. However, the deployed relays consume a lot of energy and system resources. To improve the energy efficiency of the relay-assisted cellular networks, this paper considers the use of energy harvesting(EH) on relay nodes. A random sleeping strategy is also introduced in macro base stations(MBS) as a possible method to reduce energy consumption. In this paper, an analytical model is proposed to investigate the energy efficiency of cellular networks with EH relays and sleep mode strategy. Numerical results confirm a significant energy efficiency gain of the proposed networks comparing to the cellular networks with non-EH relays and MBSs without sleep mode strategy. The effects of the density and transmit power of MBSs on energy efficiency are also given through simulations.

Technical efficiency and its determinants of the various cropping systems in the purple-soiled,hilly region of southwestern China

This study examines the technical efficiency(TE) differences among typical cropping systems of smallholder farmers in the purple-soiled hilly region of southwestern China.Household-,plot-,and crop-level data and community surveys were conducted to explore TE levels and determinants of typical cropping systems by using a translog stochastic frontier production function.Results indicate significant difference in TE and its determinants among cropping systems.The mean TEs of the rice cropping system(R),the rice-rape cropping system(RR),the rice-rape-potato cropping system(RRP),and the oil cropping system(O) are0.86,0.90,0.84,and 0.85,respectively,which are over 1.17 times higher than those of the maize-sweet potato-other crop cropping system(MSO) and the maize-sweet potato-wheat cropping system(MSW) at0.78 and 0.69,respectively.Moreover,Technical inefficiency(TIE) of different cropping systems is significantly affected by characteristics of the household as well as plot.However,the impact of land quality,mechanical cultivation conditions,crop structure,farming system,farm radius,household type,cultivated land area per capita,and annual household income per capitalon TIE vary by cropping system.Additionally,output elasticity of land,labor,and capital,as a group,is greater than the one of agricultural machinery and irrigation.Finally,when household-owned effective agricultural labor is at full farming capacity,optimal plot sizes for the R,RR,RRP,MSO,MSW,and 0 cropping systems are 1.12hm^2,0.35 hm^2,0.25 hm^2,2.82 hm^2,1.87 hm^2,and 1.17hm^2,respectively.

The Extent of Voluntary Information in the Annual Report and the Share Price Volatility： Application of DEA and SFA on the French Market

In the current paper, the authors investigate empirically the relationship between the share price volatility and the amount of voluntary information disclosed in the corporate annual report. The authors use the data envelopment analysis （DEA） and the stochastic frontier analysis （SFA） models on a sample of 50 listed French firms belonging to the Soci6t6s des Bourses Fran^aises （SBF250） index from 2004 to 2008. The authors focus on the extent of voluntary disclosure in the annual reports that have been measure by using a composite disclosure index. Then, the authors study the relevance of disclosure policies through the ability of the voluntary disclosure level to effectively reduce the share price volatility. The findings of DEA and SFA provide, in average, highly efficient scores of the sample, reveal the several dispositions taken by the French Exchange Market authorities and the initiative of French firms to improve the market stability. In addition, the findings highlight, in average, stability of the firms＇ efficiency scores over the studied period. The authors explain these findings by the stability of corporate disclosure policy as suggested in previous literature （e.g., Botosan, 1997）. However, there are some differences between the findings of SFA and DEA models.