人声浊音基频测量谱分析算法

人声基频检测是一个普遍关心的技术问题,目前所采用的方法也很多.利用数字信号处理的方法,通过对人声的浊音部分进行功率谱分析的方式,采用一种检查共振峰位置,进而遏止共振峰,在频域中凸显基波频率的方法,在频域确定信号的频率,从而自动检查出信号的基频.     

一种基于博奕论的功率控制准则

根据微观经济学理论，提出了一种新的功率控制准则。给出了效用函数的定义以及数学表达式。并提出了利用这种算法对WCDMA系统功率控制过程的改进，计算机仿真结果证实了这种新准则的有效性。     

Performance analysis of switch‐and‐stay combining in two‐way relay systems with analog network coding and time‐division broadcast protocols

In this paper, we consider switch‐and‐stay combining (SSC) in two‐way relay systems with two amplify‐and‐forward relays, one of which is activated to assist the information exchange between the two sources. The system operates in either analog network coding (ANC) protocol where the communication is only achieved with the help of the active relay or time‐division broadcast (TDBC) protocol where the direct link between two sources can be utilized to exploit more diversity gain. In both cases, we study the outage probability and bit error rate (BER) for Rayleigh fading channels. In particular, we derive closed‐form lower bounds for the outage probability and the average BER, which remain tight for different fading conditions. We also present asymptotic analysis for both the outage probability and the average BER at high signal‐to‐noise ratio. It is shown that SSC can achieve the full diversity order in two‐way relay systems for both ANC and TDBC protocols with proper switching thresholds. Copyright © 2014 John Wiley & Sons, Ltd.     

Power allocation,relay selection and energy cooperation strategies in energy harvesting cooperative wireless networks

In this paper, optimal power allocation and relay selection strategies in energy harvesting cooperative wireless networks are studied. In particular, signal‐to‐noise ratio (SNR)‐maximizing based power allocation and relay selection without and with energy cooperation—via wireless energy transfer—are considered. Moreover, total relay power minimization subject to target end‐to‐end SNR is investigated. The different optimal strategies are formulated as optimization problems, which are non‐convex. Thus, intelligent transformations are applied to transform non‐convex problems into convex ones, and polynomial‐time solution procedures are proposed. Simulation results illustrate that power allocation strategies achieve higher end‐to‐end SNR than relay selection ones. Finally, energy cooperation is shown to be effective in improving end‐to‐end SNR, while total relay power minimization balances end‐to‐end SNR, transmit power consumption, and harvested energy. Copyright © 2016 John Wiley & Sons, Ltd.     

Selected mapping technique for reducing PAPR of single‐carrier signals

Single‐carrier transmission with frequency‐domain equalization (SC‐FDE) is widely known as a promising transmission technique providing low error probability with low peak‐to‐average power ratio (PAPR) of transmit signal. However, the low‐PAPR property of SC‐FDE cannot be maintained if multi‐level data modulation is introduced. The low‐PAPR property of SC‐FDE can be maintained by applying transmit filtering with roll‐off factor at the expense of spectrum efficiency. In this paper, we propose two types of selected mapping (SLM) to reduce the PAPR of SC‐FDE transmit signal. The first SLM technique is conducted in the frequency domain, where the phase rotation is applied to subcarriers similar to the SLM technique for orthogonal frequency division multiplexing transmission. The second SLM technique is conducted in the time domain, where the phase rotation is applied directly to data‐modulated symbol sequence. Computer simulation confirms that both SLM techniques are able to reduce the PAPR of SC‐FDE signal without significant degradation of bit‐error rate performance and spectrum efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

A ZnO/TiO2 composite nanorods photoanode with improved performance for dye‐sensitized solar cells

A dye‐sensitized solar cell (DSSC) based on ZnO/TiO₂ composite nanorods (NRs) photoanode is fabricated. The power conversion efficiency (PCE) of the ZnO/TiO₂ composite NRs film DSSC is 4.36%, which is obviously higher than that of DSSCs based on pure TiO₂ NRs (0.6%) and ZnO NRs (3.10%). The enhanced performance of ZnO/TiO₂ composite NRs film DSSC can be attributed to the combined effects of ZnO and TiO₂ NRs. In this architecture, the thick ZnO NRs overlayer offers a large surface area for enough dye absorption, while the thin TiO₂ NRs underlayer not only offers a direct and quick pathway for photoinjected electron transfer along the photoanode but also acts as a blocking layer, which effectively hinders the direct contact between the substrate and the electrolyte resulting in lower carrier recombination.     

Global maximum power point tracking based on new extremum seeking control scheme

A new perturbed‐based extremum seeking control (PESC) scheme is proposed in this paper to track the global maximum power point (GMPP). The PESC scheme has two control loops based on power of the photovoltaic (PV) array: the first loop operates as usually to track the maximum power point and the second sweeps all local MPPs to locate the GMPP. Once the GMPP is located based on its uniqueness (after the PV pattern is quickly scanned many times, depending on the PV pattern's profile), the GMPP is accurately tracked based on first control loop. The used PV patterns have the profile of the PV power characteristics obtained for PV array under partially shaded conditions (PSCs). This PESC scheme is proposed to track the GMPP in the PV applications, but also in other multimodal problems from industry, being a good motif to revive the specialists' interest for the extremum seeking control field. The results obtained here are very promising for both search speed and tracking accuracy performances of the GMPP under different PSCs simulated on the PV array. Thus, the energy efficiency of PV array controlled with the proposed PESC scheme will increase with more than 1.2% in comparison with that obtained with the other MPP algorithms because of better performance shown by this PESC scheme. A 99.6% tracking accuracy is obtained here in comparison with a maximum 98.4% tracking accuracy reported in the literature. Furthermore, 100% hit and high search speed are obtained here for the GMPP localization. Copyright © 2015 John Wiley & Sons, Ltd.     

Simulating the variability of dispersed large PV plants

A model to simulate the fluctuations generated by a fleet of dispersed photovoltaic (PV) plants solely based on irradiance data measured at one single location is proposed. This simple model has been satisfactorily tested to quantify the power variability of a generic PV fleet, simply by defining two parameters: mean PV plant size and the number of plants in the PV fleet. Specifically, the model provides series of simulated power outputs that may be used in the grid operator simulation programmes, reproducing critical parameters, such as daily maximum fluctuation or the reserves required to offset these fluctuations. The model is created and validated against experimental 1‐s data collected throughout 2013 at six PV plants in Spain dispersed over 1100 km², totaling 17 MWp. Likewise, the model has been succesfully tested against another irradiance dataset, four sites across the state of Colorado, USA, and spread over 2400 km². Copyright © 2015 John Wiley & Sons, Ltd.     

混合式无线传感器网络动态调度及功率控制方法的研究

无线传感器网络是资源受限网络,研究其动态调度与功率控制对于提高网络性能具有重要意义.基于此,提出了一种无线传感器网络中混合式动态调度与功率控制方法.该方法采用集中式时隙调度与分布式功率控制相结合的思想,避免了介质访问控制(MAC)层传输冲突,并支持各传感器节点综合利用各自的队列状态信息和无线信道信息进行跨层优化传输.该...     

一种基于基波磁通补偿的改进型有源滤波器

提出了一种基于基波磁通补偿的改进型串联混合型有源滤波器,此滤波器具有滤波和单位功率因数校正两种功能。详细分析了其工作原理并进行了仿真实验,仿真结果表明此滤波器具有较好的滤波效果,能进行单位功率因数校正,并且在负载突变时有很快的响应速度,大约在两个基波周期之内就达到稳态。