高速移动环境中提供QoS保证的跨层调度算法

在高速移动环境中,为了使调度器充分利用信道的时变特性和业务的服务质量(QoS)特性,通过分析业务超时的概率定义了移动效用,给出了业务时延特性、移动速度、中断容量和移动效用的关系.基于移动效用,提出三种调度算法,证明了贪婪算法的最优性,但复杂度较高.为了降低复杂度,基于移动效用的时变特性进一步提出了最大化效用梯度(MG)的调度算法,仿真结果表明,该低复杂度算法在保证系统获得较高吞吐量的同时,显著地提高了高速移动环境下的用户体验.

Mode Selection and Resource Allocation for Deviceto-Device Communications in 5G Cellular Networks

To meet the increasing demand of wireless broadband applications in future 5G cellular networks, Device-to-Device(D2D) communications serve as a candidate paradigm to improve spectrum efficiency. Considering the challenges after D2 D transmission is introduced for future cellular networks, this paper deals with mode selection and resource allocation issues related with D2 D communications. First, we propose a mode selection scheme which aims at guaranteeing the transmission of cellular users and also considering the potential interference. We analyze the condition under which D2 D underlay mode should be used. Second, we answer the question of "how to effectively reuse cellular resource once underlaying mode is adopted". We further present a resource allocation scheme that focuses on minimizing overall interference as well as a power control method to improve the performance of D2 D systems. Simulation results demonstrate that system parameters greatly affect the switching condition of mode selection and probability of choosing underlay mode. Furthermore, for D2 D underlaying scenario, the proposed resource allocation algorithm guarantees the transmission of cellular users with consideration of transmission requirements of D2 D users. Hence, the proposed scheme can achieve better user experience.

Degradation and mineralization of aniline by O_3/Fenton process enhanced using high-gravity technology

The degradation and mineralization of aniline （AN） using ozone combined with Fenton reagent （O3/Fenton） in a rotating packed bed （RPB） was proposed in this study, and the process （RPB-O3/Fenton） was compared with conventional O3/Fenton in a stirred tank reactor （STR-O3/Fenton） or single ozonation in an RPB （RPB-O3）, Effects of high gravity factor, H2O2 dosage, H2O2 dosing method and initial pH on the AN mineralization efficiency were investigated in the RPB-O3/Fenton process, In addition, the behavior of Fe（Ⅱ） was monitored at different H2O2 dosing methods and pH values. Finally, the optimal operation conditions were determined with high gravity factor of 100, initial pH of 5, Fe（Ⅱ） concentration of 0.8 mmol·L-1 and H2O2 dosage of 2.5 ml. Under these conditions, for aniline wastewater at the volume of I L and concentration of 200 mg· L- 1 ,a fast and thorough decay of AN was conducted in 10 min, and the TOC removal efficiency reached 89% in 60 min. The main intermediates of p-benzoquinone, nitrobenzene, maleic acid and oxalic acid were identified by liquid chromatography/mass spectroscopy （LC/MS）, and the degradation pathways of AN in RPB-O3/Fenton system were proposed based on experimental evidence. It could be envisioned that high-gravity technology combined with O3/Fenton processes would be promising in the rapid and efficient mineralization ofwastewater.

Energy Efficiency Optimization for D2D Communications Based on SCA and GP Method

In this paper, we propose an energy-efficient power control scheme for device-to-device(D2D) communications underlaying cellular networks, where multiple D2D pairs reuse the same resource blocks allocated to one cellular user. Taking the maximum allowed transmit power and the minimum data rate requirement into consideration, we formulate the energy efficiency maximization problem as a non-concave fractional programming(FP) problem and then develop a two-loop iterative algorithm to solve it. In the outer loop, we adopt Dinkelbach method to equivalently transform the FP problem into a series of parametric subtractive-form problems, and in the inner loop we solve the parametric subtractive problems based on successive convex approximation and geometric programming method to obtain the solutions satisfying the KarushKuhn-Tucker conditions. Simulation results demonstrate the validity and efficiency of the proposed scheme, and illustrate the impact of different parameters on system performance.

Microbiome analysis and-omics studies of microbial denitrification processes in wastewater treatment: recent advances

Nitrogen pollution is an increasingly severe worldwide problem because of drainage of nitrogen-containing wastewater and intensive application of nitrogen-containing fertilizers. Denitrification, a key process in nitrogen cycles, is commonly employed for nitrogen removal in engineered wastewater treatment systems. Biological denitrification is performed by denitrifying microbes(bacteria) that use nitrate as terminal electron acceptor. Better understanding the functions of diverse microbial populations in denitrification-based wastewater treatment systems, and the interactions of these populations with operating environments, is essential for improving both treatment performance and system stability. Recent advances in "meta-omics"(e.g., genomics, transcriptomics, proteomics, metabolomics), other molecular biology tools, and microbiome analysis have greatly enhanced such understanding. This minireview summarizes recent findings regarding microbial community structure and composition, key functional microbes and their physiology, functional genes involved in nitrogen cycle, and responses of microbes and their genes to changes of environmental factors or operating parameters, in denitrification processes in wastewater treatment systems. Of particular interest are heterotrophic denitrification systems(which require alternative organic carbon sources) and the autotrophic denitrification systems(which do not require an external carbon source). Integrated microbiome and-omics approaches have great future potential for determination of optimal environmental and biotechnological parameters,novel process development, and improvement of nitrogen removal efficiency and system stability.

Equivalent Stiffness of the Saturated Poro-elastic Half Space Interacting with an Infinite Beam to Harmonic Moving Loads

The expression of the equivalent stiffness of the saturated poro-elastic half space interacting with an infinite beam to harmonic moving loads is obtained via the Fourier transformation method in the frequency wave number domain. Based on the obtained equivalent stiffness, the frequency wave number domain solution of the beam-half-space system is obtained by the compatibility condition between the beam and the half space. Critical velocity of harmonic moving loads along an infinite Euler-Bernoulli elastic beam is determined. The time domain solutions for the beam and the saturated poro-elastic half space are derived by means of the inverse Fourier transformation method. Also, the influences of the load speed, frequency and material parameters of the poro-elastic half space on the responses of the beam are investigated. Numerical results show that the frequency corresponding to the maximum deflection and bending moment increases with increasing load speed. Moreover, it can be seen that at higher frequencies, the dynamic response is independent of the load speed. The present results also show that for a beam overlying a saturated poro-elastic half space, there still exist critical velocities even when the load velocity is larger than the shear wave speed of the medium.