Failure evolution and disaster prediction of rock under uniaxial compression based on non-extensive statistical analysis of electric potential

Rock failure can cause serious geological disasters,and the non-extensive statistical features of electric potential(EP)are expected to provide valuable information for disaster prediction.In this paper,the uniaxial compression experiments with EP monitoring were carried out on fine sandstone,marble and granite samples under four displacement rates.The Tsallis entropy q value of EPs is used to analyze the selforganization evolution of rock failure.Then the influence of displacement rate and rock type on q value are explored by mineral structure and fracture modes.A self-organized critical prediction method with q value is proposed.The results show that the probability density function(PDF)of EPs follows the q-Gaussian distribution.The displacement rate is positively correlated with q value.With the displacement rate increasing,the fracture mode changes,the damage degree intensifies,and the microcrack network becomes denser.The influence of rock type on q value is related to the burst intensity of energy release and the crack fracture mode.The q value of EPs can be used as an effective prediction index for rock failure like b value of acoustic emission(AE).The results provide useful reference and method for the monitoring and early warning of geological disasters.

Optimizing Average Electric Power During the Charging of Lithium-Ion Batteries Through the Taguchi Method

In recent times, lithium-ion batteries have been widely used owing to their high energy density, extended cycle lifespan, and minimal self-discharge rate. The design of high-speed rechargeable lithium-ion batteries faces a significant challenge owing to the need to increase average electric power during charging. This challenge results from the direct influence of the power level on the rate of chemical reactions occurring in the battery electrodes. In this study, the Taguchi optimization method was used to enhance the average electric power during the charging process of lithium-ion batteries. The Taguchi technique is a statistical strategy that facilitates the systematic and efficient evaluation of numerous experimental variables. The proposed method involved varying seven input factors, including positive electrode thickness, positive electrode material, positive electrode active material volume fraction, negative electrode active material volume fraction, separator thickness, positive current collector thickness, and negative current collector thickness. Three levels were assigned to each control factor to identify the optimal conditions and maximize the average electric power during charging. Moreover, a variance assessment analysis was conducted to validate the results obtained from the Taguchi analysis. The results revealed that the Taguchi method was an eff ective approach for optimizing the average electric power during the charging of lithium-ion batteries. This indicates that the positive electrode material, followed by the separator thickness and the negative electrode active material volume fraction, was key factors significantly infl uencing the average electric power during the charging of lithium-ion batteries response. The identification of optimal conditions resulted in the improved performance of lithium-ion batteries, extending their potential in various applications. Particularly, lithium-ion batteries with average electric power of 16 W and 17 W during charging were designed and simulated in the range of 0-12000 s using COMSOL Multiphysics software. This study efficiently employs the Taguchi optimization technique to develop lithium-ion batteries capable of storing a predetermined average electric power during the charging phase. Therefore, this method enables the battery to achieve complete charging within a specific timeframe tailored to a specificapplication. The implementation of this method can save costs, time, and materials compared with other alternative methods, such as the trial-and-error approach.

Mechanical and Electrical Properties of Some Sn-Zn Based Lead-Free Quinary Alloys

Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.

Effect of heating rate on the densification of NdFeB alloys sintered by an electric field

This study introduces a novel method of electric field sintering for preparing NdFeB magnets. NdFeB alloy compacts were all sintered by electric fields for 8 min at 1000~C with different preset heating rates. The characteristics of electric field sintering and the effects of heating rate on the sintering densification of NdFeB alloys were also studied. It is found that electric field sintering is a new non-pressure rapid sintering method for preparing NdFeB magnets with fine grains at a relatively lower sintering temperature and in a shorter sintering time. Using this method, the sintering temperature and process of the compacts can be controlled accurately. When the preset heating rate in- creasing from 5 to 2000~C/s the densification of NdFeB sintered compacts gradHally improves. As the preset heating rate is 2000C/s, Nd-rich phases are small, dispersed and uniformly distributed in the sintered compact, and the magnet has a better microstructure than that made by conventional vacuum sintering. Also, the maximum energy product of the sintered magnet reaches 95% of conventionally vacuum sintered magnets.

Effects of the Shading Rate on the Electrical Parameters of CIGS-Based Solar Modules

The aim of this article is to study the effects of the shading rate on the electrical performance parameters of CIGS PV modules. The study concerns a new flexible CIGS type photovoltaic module with a power of 90 W, manufactured by the company Shenzhen Shine Solar Co., Ltd. This module, reference SN-CIGS90, is tested under the initial conditions to ensure its correct operation and to determine the initial values of the electrical parameters before shading. After this characterization test, the module is exposed under the actual operating conditions of the Renewable Energies Study and Research Center (CERER), located in Dakar, then 4 types of shading are performed with the same mask: partial shading 25% partial shading, 50% partial shading, 75% partial shading, and 100% full shading. The variation rates obtained on the experimental values of the 4 types of shading carried out determine that the shading phenomenon constitutes a factor that influences negatively on the electrical parameters of a CIGS-based PV module. Indeed, for 25% of the surface of the shaded module, there is a reduction of 58.139% of the maximum power and of 60.507% of the efficiency and for shading of 100%, the module loses 84.436% of its maximum power and 84.135% of its performance.

Material Removal Rate Prediction of Electrical Discharge Machining Process Using Artificial Neural Network

This article presents an Artificial Neural Network （ANN） architecture to model the Electrical Discharge Machining （EDM） process. It is aimed to develop the ANN model using an input-output pattern of raw data collected from an experimental of EDM process, whereas several research objectives have been outlined such as experimenting machining material for selected gap current, identifying machining parameters for ANN variables and selecting appropriate size of data selection. The experimental data （input variables） of copper-electrode and steel-workpiece is based on a selected gap current where pulse on time, pulse off time and sparking frequency have been chosen at optimum value of Material Removal Rate （MRR）. In this paper, the result has significantly demonstrated that the ANN model is capable of predicting the MRR with low percentage prediction error when compared with the experimental result.

On Some Issues of Assessing the Efficiency of Renewable Energy Power Plants and the Share of Renewables in the World＇s Electricity Generation

The paper considers some issues related to the evaluation of power plants using renewable energy sources： energy efficiency, economic efficiency, the share of renewable energy in the world＇s electricity generation. At one time in the world there was a myth that more energy is expended on the construction of wind and photoelectric power stations, than they produce for the service life. Adherents of this myth are still found in Russia. In response to this myth, numerous studies have been carried out for the manufacturers of wind turbines and photovoltaic modules. It was proved that these power plants spent energy on them are produced within a period of less than a year and the energy consumed by them cannot be taken into account, since it is renewable. The author showed that power plants on organic fuel and existing nuclear plants using depleted fuel with a coefficient less than unity fundamentally cannot compensate for the energy used during their construction. In the world, the concept of the LEC （Levelized Energy Cost） produced by any power plant is widely used to estimate economic efficiency. However, the formula for determining it, in the author＇s opinion, contains an inaccuracy, which is proposed to be eliminated. At present, there are different opinions on the role of RES （Renewable Energy Sources） in the production of electricity. A summary indicator is the share of renewable energy in the world＇s electricity generation. The determination of the actual share of RES and the forecast of its growth is of significant importance for the development of the world economy. The author shows the differences in the estimates and suggests an approach for establishing agreed estimates.

基于PLC技术的联合收割机电气控制系统设计

以联合收割机电气控制系统为研究对象,利用可编程控制器(PLC)对联合收割机电气控制系统进行改进,以提高联合收割机运行效率和可靠性。通过对联合收割机的工作原理和液压作动系统进行分析,基于可编程控制器(PLC)进行联合收割机电气系统整体设计,并对电气系统的运行效果进行测试分析。试验结果表明:系统运行可靠,能够获得良好的收割效果,可将收割损失率控制在2%以内,验证了系统运行过程稳定性。

一种电学控制特性下的变量施肥装置研究

以单片机为基础,设计一种电学控制的变量施肥控制系统装置。工作时,通过系统通信总线接收上位机指令信息和地理环境数据,单片机生成实时指令,对变量施肥装置电液比例系统执行机构进行控制,并对农田中不同位置进行变量施肥控制。系统试验表明:装置进行变量施肥过程中,能够对施肥量进行精准可靠控制,施肥作业过程具有较高的可靠性,施肥控制精度误差小于4%。

基于电气自动化的灌溉水电双控系统设计

针对我国灌溉系统水资源利用率较低的问题,基于电气自动化对灌溉水电双控系统进行了设计。灌溉水电双控系统主要组成包括控制模块、信息采集模块、收费管理模块、执行模块和通信模块。为了实现节水灌溉,提升水利用率,在管理方面对控制系统软件进行设计,在技术方面对控制系统算法进行设计。为了验证灌溉系统的性能,对系统进行了数据计量准确性试验和节水灌溉运行试验。试验结果表明:系统可以准确地测量用电量和用水量,且可自动启动节水灌溉。

计及电-碳交易与综合贡献率的多微网合作运行优化策略

多微网协同互联能够提高系统运行的稳定性与可靠性。针对多微网(multi-microgrids,MMG)系统合作运行过程中由于各微网分属于不同的利益主体而产生的微电网之间的电能交易问题、碳交易问题与利益分配问题,提出一种计及电-碳交易与综合贡献率的多微网合作运行优化策略。首先,分析了含点对点(peer-to-peer,P2P)电-碳交易的多微网合作运行架构,并引入碳捕集系统(carbon capture system,CCS)与电转气(power to gas,P2G)装置,建立了微电网系统及设备模型。其次,在单微网模型构建之后,基于纳什议价理论,构建了含P2P电-碳交易的多微网系统合作运行模型,并将非凸非线性的纳什议价问题转化为易于求解的MMG合作成本最小化与支付收益最大化两个子问题。然后,在合作后的利益分配过程中,量化各微电网对MMG的综合贡献程度并计算出各自的综合贡献率,通过综合贡献率来分配各微网的收益。最后,采用交替方向乘子法(alternating direction multiplier method,ADMM)求解,有效保护了各微网隐私。算例分析与方案对比结果表明,所提策略能够实现微网间的P2P电-碳交易,有效降低MMG总运行成本,减少系统的碳排放量,并且采用的利益分配策略公平合理,能够有效提升各微网参与合作运行的积极性。

多目标优化时域卷积神经网络的窃电行为高准确检测算法

随着当前用户用电行为的多样性及窃电行为隐蔽性的增加,窃电检测检出率高的同时误检率也增加,致使现有算法难以满足高准确窃电稽查的工程实际需求,对此该文提出多目标优化时域卷积神经网络的窃电行为高准确检测算法。首先基于时域卷积神经网络构建深度模型,引入侧输出融合结构提取用户用电信息的高低维特征,并通过注意力机制进行特征融合,提高模型窃电检测准确率;然后通过两阶段训练模型参数,第一阶段基于传统梯度下降算法优化模型权重与阈值,第二阶段基于窃电检测的混淆矩阵建立准确率、检出率与误检率3个维度的目标函数,采用第三代非支配排序遗传算法(non-dominated sorting genetic algorithm,NSGA-Ⅲ)进行模型优化训练,提高窃电检出率并降低误检率,据此建立多目标优化时域卷积神经网络的窃电行为高准确检测算法,并开发窃电检测实验平台实际验证所提算法;最后通过电网实测数据与实验平台验证,结果表明该文所提算法在降低误检率的同时提高10%检出率,比现有算法检出率提高同时误检率降低,更符合当前工程应用高准确窃电的检测实际需求。

高压电脉冲破碎非均质花岗岩数值模拟

对高压电脉冲破碎机制的研究是提高钻井破岩效率和优化电脉冲电参数的关键。利用颗粒流离散元软件及Voronoi划分建立非均匀介电性质的花岗岩模型,从电流场、电路场、电击穿场进行等离子通道生长过程仿真,并分析非均质度对击穿路径的影响;对比不同花岗岩的电破岩效率和电脉冲破岩效果。结果表明:花岗岩的非均质度增大使得初始电场极值增大,相应地降低了电破岩的能量需求;等离子通道的生长方向存在优先发展区域,等离子通道的生长过程体现出通道尖端处电场集中现象强于通道躯干处;花岗岩非均质度的差异使得等离子通道的总长度和平均贯穿深度存在显著差异,在一定非均质度范围内电脉冲破碎效果和非均质度呈正相关;不同非均质度花岗岩的单脉冲电破岩效率差异不大,等离子通道的总长度越长,电破岩效率越高。

国有大型油气企业新能源发电项目经济评价探讨

国有大型油气企业基于减排降碳和可持续健康发展考量,积极探索新能源发电业务,投资项目经济评价方法和参数,成为影响新能源发电业务投资决策和高质量发展的决定性因素。基于经济评价基本原理,根据新能源发电项目技术经济特征,构建新能源发电项目经济评价方法和参数体系。折现现金流法仍然是新能源发电项目经济评价的主要方法,内部收益率和平准化度电成本是衡量项目盈利能力的重要指标。不同类型新能源发电项目经济评价方法具有较高的一致性,但应在投资构成、成本费用估算、收入与税金估算等方面体现差异,重点在营业收入估算中体现项目真正价值。在规制性配置储能要求以及储能收益政策有待落实的情况下,新能源发电项目效益有待提高,建议现阶段适当降低投资回报要求,尤其是出于市场拓展和协同发展目的的战略性新能源发电项目。项目电价和有效利用小时数对新能源发电项目的影响至关重要,应视情况合理选取参数。风光气电融合项目应分业务估算成本。国有大型油气企业应积极开展宏观配套政策和商业模式创新研究,以支撑新能源发电业务的高质量发展。

相干累加与AR滤波相结合的舰船轴频电场信号处理方法

针对采用电场传感器阵列测量舰船电场的应用场景,为提升目标轴频电场的信噪比,提出一种相干累加结合自回归(autoregressive,AR)模型滤波的方法对阵列电场信号进行处理。对测量得到的阵列电场信号进行时延补偿后累加,同时对环境电场信号进行AR建模,并利用AR模型参数构造滤波器,以对累加后的信号实施滤波处理。为验证所提方法在低信噪比条件下的有效性,对实测阵列式电场信号进行处理,结果表明,所提方法能够在信噪比为-25.39 dB的条件下有效压制噪声频谱,保留轴频线谱,处理后信噪比提高约21.92 dB。

城市交通隧道电动汽车火灾安全研究进展

城市电动汽车数量增加给城市交通隧道消防安全带来了新的挑战。论文首先归纳了隧道内电动车辆火灾研究的科学问题和关键技术问题,总结了电动汽车火灾成因及研究手段、火灾燃烧热特性、燃烧产物特性等领域的研究成果,分析了隧道狭长受限空间结构对电动汽车火灾发展过程的影响,探讨了城市交通隧道电动汽车火灾的消防救援。根据现行消防标准规范及隧道消防设计指南,讨论了应对电动汽车火灾交通隧道消防系统设计需要改进的要点。研究表明,新能源车火灾场景比燃油车火灾场景更复杂,主要表现在电池不稳定的喷射火源、持续时间、峰值热释放和峰值温度、汽车带电风险等方面。目前电动汽车火灾实体试验研究主要是在大空间或者开放空间中进行,隧道受限空间对电池燃烧特性影响、电动汽车火灾羽流特性以及有毒烟气蔓延及控制还缺乏系统性研究。研究成果能够为城市交通隧道的消防设计、安全运营以及应急救援预案制定提供参考。

超高功率电弧炉变压器和电抗器技术参数设计

电弧炉变压器主要作用是降低供电电压,产生大电流,在保证供电效率的情况下,适应电弧炉冶炼所需的电弧弧长,保证电弧炉冶炼过程的安全性。同时提供不同挡位的电压和电流,以满足冶炼过程需要。电抗器主要作用是增加线路的无功功率,降低短路电流和功率因数,稳定电弧燃烧。同时提供不同挡位的电抗,以满足冶炼过程不同工况的需要。变压器和电抗器技术参数的合理设计是保证电弧炉稳定冶炼的关键,依据电弧炉所需的冶炼效率及出钢量,系统分析电弧炉变压器和电抗器参数的设计原理。从分析可知,变压器的容量是基于电弧炉的通电时间及出钢量进行确定,而变压器的二次电压、额定电流及电抗器容量等参数是基于电弧冶炼稳定性的约束条件进行计算。计算结果与JB/T 9640-2014参考值进行对比分析,结果匹配度较好。

负离子除尘技术在隧道中的应用与数值模拟研究

以武隆隧道为例,采用便携式负离子发生器进行现场测试,验证了负离子的消耗与除尘的有效性。对武隆隧道中应用负离子净化系统的除尘效果进行了数值模拟。结果表明:隧道内的电场以电极为中心呈环形分布且向外不断扩展;随着粉尘颗粒粒径的增大,荷电量增大,在电场力的作用下粉尘颗粒越容易发生偏移运动;在作用时间为600 s时,对2.5μm与10μm粉尘的除尘率分别为63.57%与99.00%;增大工作电压可以有效提高除尘率。