Calcium deficient hydroxyapatite by precipitation: Continuous process by vortex reactor and semi-batch synthesis

Precipitation of calcium deficient hydroxyapatite nanoparticles in an environmentally benign manner by using only dilute solutions of calcium hydroxide and phosphoric acid without pH adjustment and addition of other chemicals, and water, being the only by-product was investigated by using continuous flow Vortex Reactor (VR) and Semi-Batch Reactor (SBR). The effect of hydrodynamics by changing the Reynolds number of the jets providing residence times of 8.4 ms to 4.37 s for VR, and by changing the stirrer speed between 100 rpm (Re = 2656) and 1000 rpm (Re = 26560) for SBR, on the particle size, particle size distribution, and morphology of the particles was investigated for both systems. It has been shown that it is possible to produce pure phase hydroxyapatite nanoparticles in the desired morphology by changing production system, without resorting to additives. While VR produced rod-like particles with the crystallite size around 4 nm, SBR produced spherical particles with the crystallite size of around 5 nm.     

基于子波变换的涡街流量传感器信号分析

长期以来 ,如何提取潜在噪声下的涡街流量信号一直是个问题。流体流速脉动 ,局部阻力 ,随机振动———所有这些因素都给解决这一问题带来难度。文章应用子波变换消噪理论 ,从软件滤波的角度分析了强噪声干扰下的涡街流量信号 ,并提出了单支重构计数方法。分析结果表明 ,这种方法对低流速流量计量效果很好 ,能够有效地扩展量程下限     

嵌入式数字智能涡街流量计的设计开发

针对目前涡街流重计存在精度不高的问题，采用Toeplitz自相关矩阵近似的准牛顿算法，对涡街传感器输出信号进行数字信号处理。针对客户超低功耗的要求，开发设计以超低功耗的混合信号处理器(MSP430F149)为微处理器，以采用KS0713为控制器的LCD为液晶显示模块，符合HART总线协议的嵌入式智能涡街流量计。     

Pulsating Jet Impingement Heat Transfer Enhancement

This article presents results from a numerical study of pulsating jet impingement heat transfer. The motivation is to seek conditions offering a significant enhancement compared to steady flow impingement drying. The CFD software package FLUENT was used for simulating slot-type pulsating jet impingement flows with confinement. The parameter study included velocity amplitude ratio, mean jet velocity, and pulsation frequency. The distance from nozzle exit to surface was three times the hydraulic diameter of the nozzle. The Reynolds number based on the nozzle hydraulic diameter and jet temperature was 2,460 with a mean jet velocity of 30 m/s, which is the base case of the numerical experiments. Results showed that time-averaged surface heat transfer increased with increasing velocity amplitude for the same mean jet velocity. Large velocity amplitudes helped enhance heat transfer by two mechanisms: high jet velocity during the positive cycle and strong recirculating flows during the negative cycle. For the cases with different mean jet velocities but the same maximum velocity, time-averaged surface heat flux decreased with decreasing mean jet velocity. As for the effects of pulsation frequency, with high-velocity amplitude ratio, time-averaged surface heat fluxes were at the same level regardless of frequency. However, at low-velocity amplitude ratio, high frequency caused stronger recirculating flows resulting in greater heat transfer compared to the cases with a lower frequency.     

多元QoS约束下电力通信无线资源分配的边缘代理调度方法

为满足不同配电通信业务的服务质量要求,BS需要在时变网络条件下实时优化无线资源。提出一种基于级联深度网络的接入网无线资源边缘代理调度方法,将时频资源和发射功率分配给延迟耐受度不同的业务。核心网采用网元功能与专用硬件设备解耦的软切片方法,在保证负荷在规定时长内可靠切除的同时,提高了核心网服务器对不同业务的时空间复用能力。仿真结果表明,多业务并列运行时RTU与协控子站间的接入时延与TD-LTE专网相比降低40.76%,相邻第一第二信道间的功率泄露比均高于45 dB,满足毫秒级负荷切除业务分路整组动作时延和通信可靠性的要求。     

基于隐枚举法的快速分级切负荷优化方法

目前稳控装置广泛采用的穷举法已经很难满足快速、精准切负荷的要求。为了高效地求解切负荷优化问题,为紧急决策争取更多时间,提出了基于隐枚举法的快速分级切负荷优化方法。该方法协调低频和低压切负荷动作轮次,建立切负荷优化模型,通过制定合适的搜索策略和剪枝策略,仅在可行解范围内进行寻优,大大提高了计算最优解的效率。切负荷算例结果表明同等条件下该方法可以节约至少50%以上的计算时间,实现了稳控装置的快速切负荷,保证了紧急情况下电网的安全稳定运行。     

 基于混合模型的优化低频低压减载方法研究

文中以低频低压情况下保证电压稳定的前提下减载为研究内容,提出了一种基于混合模型的优化低频低压减载方法。该混合模型将遗传算法与人工神经网络相结合,在保证电压稳定的情况下选择合适的节点进行负荷切除。实验结果表明,该方法可以在低频低压情况下使负荷减载量达到最小。     

计及灵活性储备的含风电多微电网系统分布式协调调控策略

高比例风电的接入和需求响应技术的应用对分布式架构下的多微电网系统有功功率动态平衡提出了更高的要求,有必要充分利用灵活性资源对系统进行协调调控.提出一种新颖的灵活性电池储备模型对多微电网系统灵活性备用容量进行评估,定义虚拟灵活性电池储备模型对风电场备用与需求响应负荷备用进行评估,充分挖掘其调频的潜在能力.在此基础上,基于一致性算法求解该模型下各微电网的功率分配,提出计及灵活性储备的含风电多微电网系统分布式协调调控策略,实现分布式架构下灵活性资源的协调优化.通过华东某地区实际数据验证了所提策略的有效性.算例结果表明,协调优化源-荷灵活性储备资源在保障风电消纳的同时,实现了分布式架构下系统的动态功率平衡.     

On the modeling of electro-hydrodynamic flow in a wire-plate electrostatic precipitator

Modeling of the flow velocity fields for the electrohydrodynamic (EHD) flow in a wire-to-plate type electrostatic precipitator (ESP) was achieved. Solutions of the steady, two-dimensional Navier-Stokes equations have been computed. The equations were solved in the conservative finite-difference form on a fine uniform rectilinear grid of sufficient resolution to accurately capture the momentum boundary layers. The numerical procedure for differential equations was used by SIMPLEST [Michel, 2002], a derivative of Patankar’s SIMPLE algorithm, to bring rapid convergence. The Phoenics (Version 3.5.1) CFD code, coupled with Poisson’s and ion transport equations and electric body force in the momentum equation, developed in this study, was used for the numerical simulation. From calculations for the flow employing different flow models, the Chen-Kimk-ε turbulent model appeared to be the most appropriate choice to obtain a quantitative image of the resulting mean flow field and downstream wake flow of the rear wire, although this was obtained from a qualitative analysis due to the lack of experimental verification. The flow velocity field pattern showed a strong EHD secondary flow, which was clearly visible in the downstream regions of the corona wire despite the low Reynolds number for the electrode (Re_CW=12.4). Secondary flow vortices were also caused by the EHD with increases in the discharge current     

矩形纵向涡发生器平板强化换热的实验研究

利用热质比拟萘升华技术,在吸入式风洞中对矩形纵向涡发生器平板强化换热进行了实验研究。在雷诺数范围2.3×105~5.4×105内,通过改变涡发生器迎流冲击角β,得到强化换热的效果,并对参数进行优化。