铁矿露天转地下开采的安全问题探讨

露天转地下开采活动中会遇到许多安全问题,需要我们对其安全影响因素进行科学的分析。基于此,在分析露天转地下开采的特点的基础上,仔细分析总结了当前铁矿露天转地下开采的安全问题。     

稳定分析与控制在现代电网发展中面临的挑战及其对策

安全稳定控制装置是保证电力系统安全稳定运行的重要手段,现代电网的发展对稳定分析方法和稳定控制手段提出新的要求。讨论了电力市场化、电网互联和高压直流输电等现代电网发展趋势对电力系统稳定性的影响,分析了电力系统稳定分析与控制在现代电网发展中所面临的挑战,并针对性地给出若干应对措施和建议。最后对电力系统稳定分析和控制技术的发展方向进行了展望。     

大规模风电场对电力系统稳定性影响的研究

风电机组由于其自身特点,风电机组与传统发电机组有不同的稳态和暂态特性,大规模风力发电接入电网后,电网的电压稳定性、暂态稳定性及频率稳定性都会发生变化。主要针对基于普通异步感应电机和基于双馈式感应电机风电机组的风电场对电网稳定性影响进行深入研究,使得对风电场接入电网后,给电网稳定性带来的问题有更全面、更深入的认识,有利于我国风力发电快速、健康发展。     

重油掺水乳化稳定性的实验研究

采用机械搅拌+乳化剂的乳化方法和高温静置的检测方法,对重油进行乳化研究。对比了三种复配乳化剂的乳化效果,确定了影响乳化重油稳定性因素的最佳参数。结果表明:TS-2型乳化剂比其他两种乳化剂乳化效果更好;随着乳化剂含量的增加,乳化油的稳定时间先增大后减小;掺水率越大,乳化油的稳定性越差;搅拌速率增大、乳化时间加长、乳化温度升高,有利于乳化油的稳定,但同时能耗也增加。本实验得出乳化重油的理想工艺条件为:TS-2型乳化剂,乳化剂含量约为0.2%,掺水率为10%～20%,搅拌速率为700～900r/min,乳化时间为30min左右,乳化温度为70～80℃。     

An Experimental Investigation on the Chemical Stability of Selected Formation and Determination of the Proper Type of Water-Base Drilling Fluids. Part 2. Test Results

The objective of this study was to select the proper drilling fluid type and composition for drilling stable holes through the problems of the selected formations. This study was performed on shale samples taken from 10 wells in which hole instability was encountered to various extents during drilling the Germav formation. Both ionic and polymer inhibitions were utilized in formulating the proper drilling for the Germav formation. Ionic inhibition was obtained using KCl and NaCl. Polyanionic polymer (Pac-L) was used for providing the polymer encapsulation. Experimental results indicated that KCl is superior to NaCl in providing ionic inhibition. Both salts lowered the interaction between the drilling fluid and Germav formation, but better results were obtained with KCl. Minimum salt concentration up to 15% yields more inhibitive environment. Polymer inhibition tests indicated that minimum Pac-L concentration required for maintaining the polymer inhibition was about 2 lb/bbl for both systems. In conclusion, KCl/encapsulating polymer system seems to be the most proper water: base drilling fluid available for Germav formation achieving the required wellbore stability. The fluid loss and suspending properties of the proposed system must be controlled using the modified starch and XC polymer.     

滑动轴承转子系统抗扰动稳定裕度的研究

根据Floquent理论关于性周期系数系统解的性质及稳定性条件,定义了非线性非自治系统周期解的稳定度,从动力系统流的概念出发,给出了系统稳态周期解稳定度的数值计算方法,定义了滑动轴承转子系统抗扰动稳定裕度,利用周期稳定度等于零为为确定抗扰动稳定裕度值,该方法既适于自治系统又知于非自治系统。     

基于人工鱼群算法的静态电压稳定评估

提出一种静态电压稳定裕度计算的新方法——人工鱼群算法,该算法就是根据鱼群觅食和生长特点,通过构造人工鱼来模仿鱼群的觅食、聚群及追尾行为,从而实现寻优,能快速寻找到全局最优解,从而求得电压稳定裕度的最大值。运用该算法对IEEE14和IEEE39等节点系统进行仿真计算,计算结果与连续潮流算法和原一对偶内点算法比较,证明此算法的有效性。     

基于BPA软件的地区电网静态电压稳定性分析

电力系统静态电压稳定分析对电力部门的电压稳定控制、调度规划等工作十分重要。基于静态模型提出了求取实际运行电网的功率-电压(P-V)曲线的方法,该方法采用电力系统潮流软件(BPA)作为计算核心,通过设计外部接口实现连续潮流仿真,进行电力系统静态电压稳定裕度分析及绘制P-V曲线。利用该方法对上海电网黄渡分区进行静态电压稳定分析,计算系统的相对电压稳定裕度,找出其存在的电压薄弱点,并提出了进一步提高静态电压稳定水平的若干措施。     

规模化光伏电站与电网暂态交互影响定量分析

在电力系统暂态安全定量分析软件平台FASTEST(Fast Analysis of Stability using the Extended equal areacriterion and Simulation Technologies)上以研究规模化光伏电站接入系统后的稳定性分析为目的,建立了一个完整而且适合系统安全稳定分析的并网光伏电站机电暂态模型。基于FASTEST特有的暂态稳定量化分析功能,对并网光伏电站被浮云遮挡和系统侧发生扰动这2种典型情况进行仿真分析,从对系统暂态功角稳定性、暂态电压稳定性和暂态频率稳定性的影响的角度,探讨光伏电站与常规电源在影响电网运行特性方面的区别。结果表明,光伏电站并网后对系统暂态频率稳定性影响最为严重,相比较于带有励磁和调速系统的同步发电机,光伏电站在网侧故障时的暂态响应特性更为剧烈。     

Linear stability analysis of a fluid-saturated porous layer subjected to time-dependent heating

A theoretical analysis of thermal instability driven by buoyancy forces under the transient temperature fields is conducted in an initially quiescent, fluid-saturated and horizontal porous layer. Darcy’s law is used to explain the characteristics of fluid motion and under the principle of exchange of stabilities, the linear stability theory is employed to derive stability equations. The stability equations are analyzed by the initial value approach with the proper initial conditions. Two stability limits, τ_s and τ_r are obtained under the strong and the relative stability concepts. The critical condition of onset of buoyancy-driven convection is governed by the Darcy–Rayleigh number, as expected. The growth period for disturbances to grow is seemed to be required until the instabilities are detected experimentally. The convective motion can be detected experimentally from a certain time τ₀  4τ_r.     

Studies on novel heat treated sulfonated poly(ether ether ketone) [SPEEK]/diol membranes for fuel cell applications

The paper describes the preparation of membranes based on sulfonated poly(ether ether ketone) [SPEEK] [degree of sulfonation ∼65%] in the presence of varying amounts of poly (ethylene glycol) (molecular weight 200) [PEG-200] and cyclohexane dimethanol [CDM] using water:ethanol (50:50) as solvent. After drying, the membranes were heat treated at 60 °C (2 h), 80 °C (2 h), 100 °C (2 h), 120 °C (2 h) and 135 °C for 16 h. After the heat treatment, samples were insoluble in water:ethanol (50:50) mixture. The membranes thus obtained were characterized by FTIR spectroscopy (structural), water uptake (hydrolytic stability), thermal stability (TG), mechanical stability and proton conductivity. A significant increase in the hydrolytic stability was observed, SPEEK became elastic and fragile whereas the heat-treated SPEEK/PEG and SPEEK/CDM remained stable even after 135 days of water immersion at 35 °C.     

电力系统稳定控制方法综述

现代电力系统的发展使其稳定性问题日趋重要,结合电力系统稳定控制对象,介绍了电力系统稳定的定义及分类,对提高电力系统稳定性的各种控制方法及应用作了综述,包括：基于电力系统线性模型的极点配置、线性最优、线性二次高斯、电力系统非线性控制Lyapunov直接法,映射线性化方法,H∞鲁棒性控制,变结构控制等。最后指出了值得关注的研究方向。     

Storage stability and ageing effect of biodiesel blends treated with different antioxidants

This study investigates the impact of various synthetic phenolic antioxidants on the oxidation stability of biodiesel blends with the employment of the modified Rancimat method. The experimental results revealed that an improvement in oxidation stability could be achieved with all antioxidants tested. Butylated hydroxytoluene (BHT) and butylated hydroxyanisol (BHA) displayed the lowest effectiveness in neat biodiesel, whereas their use in biodiesel blends showed a greater stabilizing potential. Propyl gallate (PG) and pyrogallol (PA) additives showed the strongest effectiveness in both the neat biodiesel and the biodiesel blends. During a naturally ageing process of the biodiesel blends which was conducted for a period of 10 weeks, samples were taken every 2 weeks to measure the oxidation stability, kinematic viscosity and acid value. This process was designed in such manner to simulate the ageing of an automotive biofuel stored in the fuel tank of a vehicle. The results showed a sharp decrease in fuel stability over time. Although limited effects were observed in viscosity, the acid value was significantly increased over time. The addition of antioxidants resulted in some increases in viscosity and acid value of the biodiesel blends.     

On the stability of porous-elastic system with microtemparatures

In this article, we investigate a porous-elastic system with dissipation due to only microtemperatures. It is well-known that such a system with a single damping term lacks exponential stability unless another damping mechanism is added. In this article, however, we prove that the unique dissipation due to the microtemperatures is strong enough to exponentially stabilize the system if and only if the wave speeds of the system are equal. In the case of lack of exponential stability, we show that the solution decays polynomially. Moreover, we show that this rate of decay is optimal. Our result is new and improves previous results in the literature.     

Chemical and mechanical stability of a Silicone gasket material exposed to PEM fuel cell environment

Proton exchange membrane (PEM) fuel cell stack requires gaskets in each cell to keep the reactant gas and liquid within their respective regions. Long-term chemical and mechanical stability and durability of the gaskets are critical to both sealing and the electrochemical performance of the fuel cells. In this paper, the chemical and mechanical degradation of a commercially available elastomeric Silicone material were investigated. A simulated solution at two temperatures, that are close to actual PEM fuel cell environment, was used. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and atomic absorption spectrometer analysis were employed to study the surface chemical degradation of the samples after exposure to the simulated PEM fuel cell environment. Microindentation and dynamic mechanical analysis (DMA) were used to assess the change of mechanical properties of the samples exposed to the environment. The ATR-FTIR results indicate that the surface chemistry of the Silicone material was altered after exposure to the environment over time. In addition, atomic absorption spectrometry detected silicon and Calcium leached from the gasket material into the soaking solution. Microindentation test results show that the sample surface hardening occurred and the elastic modulus increased for the Silicone material exposed to the environment.     

华东电网电压静态稳定性研究

根据华东电网 1995年度运行方式 ,对系统的电压静态稳定性进行分析 ,包括确定电压静态稳定裕度、电压弱稳定区、关键支路和重要发电机组 ,求取对应于给定系统过渡方式的电压静稳极限以及判断系统失稳方式 ,对华东电网电压稳定性的分析及运行监控提供了重要依据。同时 ,计算结果验证了所采用的程序是有实用价值的     

High- and low- temperature behaviors of La0.6Sr0.4Co0.2Fe0.8O3−δ cathode operating under CO2/H2O-containing atmosphere

High- and low- temperature behaviors of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) cathode for solid oxide fuel cells operating under CO₂/H₂O-containing atmosphere are investigated. LSCF shows different stability against CO₂ and H₂O at high and low temperature. LSCF has excellent electrochemical performance and high stability against the corrosion of CO₂ and H₂O at 750 °C due to weak reactivity of LSCF with CO₂. LSCF shows a serious degradation at 600 °C under operation with O₂–CO₂(2.83%)–H₂O(2.64%), which is ascribed to the impeded oxygen activation and oxygen surface diffusion by surface carbonates and SrCO₃ phases on LSCF surface. Under CO₂(5%)–H₂O(2.81%)–He, LSCF reacts with CO₂ to yield SrCO₃ phases in 400–680 °C, and H₂O aggravates the chemical reaction between CO₂ and LSCF. Taking into account of SrCO₃ phase formation on LSCF, LSCF cathode is stable under operation with O₂–CO₂(2.83%)–H₂O(2.64%) in 680–800 °C, whereas it is unstable below 680 °C. LSCF can be subject to degradation caused by CO₂ and H₂O in air during long-term operation below 680 °C.     

Effect of steady deflections on the aeroelastic stability of a turbine blade

This paper deals with effects of geometric non‐linearities on the aeroelastic stability of a steady‐state deflected blade. Today, wind turbine blades are long and slender structures that can have a considerable steady‐state deflection which affects the dynamic behaviour of the blade. The flapwise blade deflection causes the edgewise blade motion to couple to torsional blade motion and thereby to the aerodynamics through the angle of attack. The analysis shows that in the worst case for this particular blade, the edgewise damping can be decreased by half. Copyright © 2010 John Wiley & Sons, Ltd.     

First-principles investigation on the role of interstitial site preference on the hydrogen-induced disproportionation of ZrCo and its doped alloys

There are two phase structures involved in ZrCo hydrides (ZrCoH_x). When x ≤ 1, the α-phase hydride is generated when hydrogen atoms occupy the 3c and 12i sites. When 1 < x ≤ 3, three interstitial sites of 4c₂, 8f₁, and 8e are occupied by H, and in turn the β-phase hydride is formed. There is a disproportionation reaction in β-phase hydrides during hydrogen discharging process to produce the ZrH₂ phase with higher thermal stability, leading to inferior hydrogen storage performance. In this study, the influence of hydrogen storage capacity on thermodynamic and lattice stabilities of α- and β-phase hydrides for each occupancy position is investigated under the framework of the first-principles study. The results indicate that the binding energy in the 3c site is higher compared with the 12i site under the condition of identical hydrogen storage capacity. Similarly, the binding energy is the largest for the 8e site compared with the other two sites, indicating that there is the least energy released in the reaction process. Thus, the 8e site is proved as the most unfavorable site in β-phase ZrCo hydrides, which is due to its degraded thermodynamic stability. Also, comparisons of mechanical properties and total density of states for each site in two hydride phases are presented to demonstrate that compound lattice stability in the 8e site is the poorest, suggesting that it is more likely to produce disproportionation. Furthermore, the dependence of hydrogen storage performance of β-phase hydrides on Ti/Rh doping is examined as well. It is discovered that there is improved thermodynamic stability and lattice stability in the 8e site for Zr_0.875Ti_0.125Co after Zr is partially substituted by Ti, which significantly enhances the disproportionation resistance. In contrast, when Co is partially replaced by Rh, there is a deterioration in the thermodynamic stability of ZrCo_0.875Rh_0.125 in the 8e site, but its lattice stability is somewhat improved.     

大规模风电对电力系统的影响和应对策略

综述了大规模风电接入电网对电力系统带来的影响。阐述了当前风力发电的特点和与风电相关的无功电压问题、暂态稳定性问题、频率问题、电能质量问题。针对不同问题总结了可行的解决方法和研究热点。论述了风力发电2个重要的研究方向：风电场综合控制技术和风电功率预测技术。