Fabrication of Graphene/Cu Composite by Chemical Vapor Deposition and Effects of Graphene Layers on Resultant Electrical Conductivity

Graphene(Gr)has unique properties including high electrical conductivity;Thus,graphene/copper(Gr/Cu)composites have attracted increasing attention to replace traditional Cu for electrical applications. However,the problem of how to control graphene to form desired Gr/Cu composite is not well solved. This paper aims at exploring the best parameters for preparing graphene with different layers on Cu foil by chemical vapor deposition(CVD)method and studying the effects of different layers graphene on Gr/Cu composite’s electrical conductivity. Graphene grown on single-sided and double-sided copper was prepared for Gr/Cu and Gr/Cu/Gr composites. The resultant electrical conductivity of Gr/Cu composites increased with decreasing graphene layers and increasing graphene volume fraction. The Gr/Cu/Gr composite with monolayer graphene owns volume fraction of less than 0.002%,producing the best electrical conductivity up to59.8 ×10^(6)S/m,equivalent to 104.5% IACS and 105.3% pure Cu foil.

Void Fraction Measurement in Oil-Gas Transportation Pipeline Using an Improved Electrical Capacitance Tomography System

To measure the void fraction online in oil-gas pipeline, an improved electrical capacitance tomography (ECT) system has been designed. The capacitance sensor with new structure has twelve internal electrodes and overcomes the influence of the pipe wall. The data collection system is improved by using high performance IC (integrated circuit). Static tests of bubble flow, stratified flow and annular flow regime are carried out. Measurements are taken on bubble flow, stratified flow and slug flow. Results show that the new ECT system performs well on void fraction measurement of bubble flow and stratified flow, but the error of measurement for slug flow is more than 10%.

Hamilton formalism and Noether symmetry for mechanico electrical systems with fractional derivatives

This paper presents extensions to the traditional calculus of variations for mechanico-electrical systems containing fractional derivatives. The Euler Lagrange equations and the Hamilton formalism of the mechanico-electrical systems with fractional derivatives are established. The definition and the criteria for the fractional generalized Noether quasi- symmetry are presented. Furthermore, the fractional Noether theorem and conseved quantities of the systems are obtained by virtue of the invariance of the Hamiltonian action under the infinitesimal transformations. An example is presented to illustrate the application of the results.

Influence of the Aggregate Volume on the Electrical Resistivity and Properties of Portland Cement Concretes

The electrical resistivity of concretes with various aggregate volume fractions （Va） of 0%-70% at water/cement （W/C） ratios of 0.4 and 0.5 during 1 day was monitored.It is found that the addition of normal aggregate to cement paste leads to a regular increase in concrete resistivity at each hydration stage and the electrical resistivity has a deeper increase for the lower W/C at a fixed aggregate volume fraction.The number of normalized resistivity （NR） of concrete to its paste matrix was introduced,which is only a function of aggregate volume fraction （Va）.The quantitative relationships give an alternative method for the prediction of aggregate volume in the concrete.A logarithmic relation is established between the elastic modulus of concrete at 7 days or 28 days and the electrical resistivity of concrete at 1 day.The equations are obtained,the compressive strength of concrete at 7 days or 28 days can be determined by the electrical resistivity of concrete at 1 day and the used aggregate content in the concrete.The quantitative relationships give a non-destructive test （NDT） method for prediction of concrete elastic modulus and compressive strength.

Application of silver nanoparticles in electrically conductive adhesives with silver micro flakes

This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a filler loading of 78 wt.%,83 wt.%and 88 wt.%and cured at 150℃and 180℃,respectively.The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature.Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%,because the segregation of NPs enlarged the average distance of silver flakes;while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%,probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes,especially when curing at high temperature of 180℃.

The Integer-Fraction Principle of the Digital Electric Charge for Quarks and Quasiparticles

In the integer-fraction principle of the digital electric charge, individual integral charge and individual fractional charge are the digital representations of the allowance and the disallowance of irreversible kinetic energy, respectively. The disallowance of irreversible kinetic energy for individual fractional charge brings about the confinement of individual fractional charges to restrict irreversible movement resulted from irreversible kinetic energy. Collective fractional charges are confined by the short-distance confinement force field where the sum of the collective fractional charges is integer. As a result, fractional charges are confined and collective. The confinement force field includes gluons in QCD (quantum chromodynamics) for collective fractional charge quarks in hadrons and the magnetic flux quanta for collective fractional charge quasiparticles in the fractional quantum Hall effect (FQHE). The collectivity of fractional charges requires the attachment of energy as flux quanta to bind collective fractional charges. The integer-fraction transformation from integral charges to fractional charges consists of the three steps: 1) the attachment of an even number of flux quanta to individual integral charge fermions to form individual integral charge composite fermions, 2) the attachment of an odd number of flux quanta to individual integral charge composite fermions to form transitional collective integral charge composite bosons, and 3) the conversion of flux quanta into the confinement force field to confine collective fractional charge composite fermions converted from composite bosons. The charges of quarks are fractional, because QCD (the strong force) emerges in the universe that has no irreversible kinetic energy. Kinetic energy emerged in the universe after the emergence of the strong force. The charges of the quasiparticles in the FQHE are fractional because of the confinement by a two-dimensional system, the Landau levels, and an extremely low temperature and the collectivity by high energy magnetic flux quanta. From the integer-fraction transformation from integral charge electrons to fractional charge quarks, the calculated masses of pion, muon and constituent quarks are in excellent agreement with the observed values.

Quantum Theory of Mesoscopic Fractional Electric Fields in a Cavity of Viscous Medium

With conjecture of fractional charge quantization (quantum dipole/multiple moments), Fourier transform stretching, twisting and twigging of an electron quanta and waver strings of electron quanta, the mathematical expressions for mesoscopic fractional electron fields in a cavity of viscous medium and the associated quantum dielectric susceptibility are developed. Agreement of this approach is experimentally evidenced on barite and Fanja site molecular sieves. These findings are in conformity with experimental results of 2012 Physics Nobel prize winning scientists, Serge Haroche and David J. Wineland especially for cavity quantum electro-dynamics electron and its associated mesoscopic electric fields. The mover electron quanta strings lead to warping of space and time following the behaviour of quantum electron dynamics.

不同吸入氧浓度对老年患者腹腔镜前列腺癌根治术后早期肺功能的影响

目的比较术中吸入氧浓度(FiO_(2))30%和80%对老年患者腹腔镜前列腺癌根治术后肺功能的影响。方法选择择期行腹腔镜前列腺癌根治术的老年患者60例,年龄≥65岁,BMI 18~30 kg/m^(2),ASAⅡ或Ⅲ级。采用随机数字表法将患者分为两组:FiO_(2)30%组(L组)和FiO_(2)80%组(H组),每组30例。气管插管后行肺复张,L组调整FiO_(2)为30%直至拔除气管导管。H组调整FiO_(2)为80%直至拔除气管导管。记录入室后5 min(T_(0))、手术开始后1 h(T_(1))、手术开始后2 h(T_(2))、拔管后30 min(T_(3))的HR、MAP,并行动脉血气分析记录PaO_(2)、PaCO_(2),计算氧合指数(OI)。于T_(0)、T_(3)时行电阻抗断层成像(EIT)监测,评估肺通气功能,记录中心通气区(CoV)、依赖静止区(DSS)、非依赖静止区(NSS)的面积百分比。术前1 d、术后第1、3、5天测定第1秒用力呼气容积(FEV_(1))、用力肺活量(FVC)、1秒率(FEV_(1)/FVC)。记录术后5 d内肺不张、呼吸道感染和胸腔积液等肺部并发症的发生情况。结果与H组比较,L组T_(3)时DSS面积百分比明显降低(P<0.05),PaO_(2)与OI明显升高(P<0.05),术后第1天FVC、FEV_(1)和FEV_(1)/FVC均明显升高(P<0.05),术后第3天FEV_(1)/FVC明显升高(P<0.05),术后5 d内肺不张发生率明显降低(P<0.05)。结论与FiO_(2)80%比较,术中FiO_(2)30%可以明显改善老年患者腹腔镜前列腺癌根治术后30 min肺通气、氧合功能与术后早期的肺功能,减少术后肺不张的发生。

水下抛石电阻率特性试验研究

研究旨在利用电阻率技术解决水下抛石坝(隐蔽性工程)隐患探测和质量评价等关键问题。采用四电极法分析了水下抛石在不同供电电压和空隙率条件下的电阻率特性,并建立了电阻率与水下抛石空隙率的经验公式。结果表明:水下抛石电阻率随供电电压(10~60 V)升高呈先衰减后逐渐趋于稳定的变化特征,且供电电压高于30 V时电阻率衰减程度显著降低;水下抛石电阻率随空隙率的增加逐渐减小并趋于稳定(两者间的关系可用递减型幂函数表征),且不同供电电压下电阻率随空隙率的变化规律与此类似;分别选用幂函数、指数函数及对数函数拟合电阻率与空隙率关系,发现幂函数拟合误差最小,考虑供电电压影响最终建立了水下抛石电阻率与空隙率的经验公式;进一步通过水下抛石坝模型试验验证了经验公式的可靠性。该经验公式可有效描述水下抛石分布的密实程度,从而快速识别水下抛石坝内部隐患。

基于分数阶滑模控制的光伏并网模型预测直接功率控制

针对外界扰动情况下的光伏并网模型预测直接功率控制(model predictive direct power control,MPDPC)系统中存在系统抖振、功率跟踪速度慢、并网电流总谐波失真率较高等问题,提出一种改进分数阶滑模电压控制器,该策略在直流侧母线电压外环采用了分数阶微积分理论.首先,构造分数阶非奇异快速终端滑模面函数,削弱系统抖振,提高系统动态性能;然后,构造分数阶双幂次指数趋近律,引入加权积分型增益和饱和函数,有效避免系统在非滑动模态阶段时切换增益的增大,提高系统控制精度;最后,设计新型分数阶电压环控制器并运用于光伏并网系统中.研究结果表明,改进后的分数阶滑模电压控制器能够满足光伏并网MPDPC系统的各项基本需求,抑制系统抖振,提高功率跟踪性能,降低并网电流总谐波失真率,有效解决可再生能源和公共电网电能转化的关键难题,对光伏并网系统高性能控制的理论研究具有重要意义.

基于修正分数Poynting-Thomson模型的高压XLPE海缆绝缘评估

为利用频域介电谱准确评估高压交联聚乙烯(XLPE)海缆的绝缘状态,建立考虑直流电导率的修正分数Poynting-Thomson模型(分数P-T模型)以解析高压XLPE海缆的介电特性。首先,通过加速老化试验制备不同老化程度的高压XLPE海缆试样,并测得各组老化试样的力学、理化和介电数据。然后,应用修正分数P-T模型对实测介电曲线进行拟合,对比修正前后分数P-T模型表征实测介电曲线的效果。最后,通过仿真探究模型参数对介电曲线的影响规律,构建模型参数与绝缘程度之间的联系,将提出的老化特征参数与断裂伸长率(EAB)进行量化研究。研究结果表明,修正分数P-T模型能够准确拟合出不同老化程度高压XLPE海缆试样的介电曲线,提出的老化特征参数α、ε_(a)、ε_(b)和σ_(dc)可实现对高压XLPE海缆绝缘状态的量化评估。

低频交流电压下低密度聚乙烯的空间电荷特性

分频输电技术已逐步成为实现碳中和及海上风电远距离传输的主流方案之一。然而,对高压分频输电背景下的电气设备研究较为欠缺,在频率改变对电缆绝缘材料特性影响方面尚需深入研究。为此,采用具备快速检测能力的脉冲电声测试系统,研究了低密度聚乙烯材料在分频电压下不同电场强度、温度时的空间电荷特性以及频率改变对电荷积聚行为的影响。结果表明:当场强及温度条件较为苛刻时,电荷积聚明显;而随着频率的降低电荷积聚量增加,频率下降至20 Hz后,电荷增长速度显著提高。在此基础上,建立了应用于交变电场下的双极型载流子模型,通过仿真计算对实验观察进行了合理化解释,揭示了电场、温度及频率对空间电荷行为的影响机理。研究方法和结果可为海上风电分频输电系统中的频率选择及线缆绝缘优化设计提供理论支撑。

A Novel Rolling and Fractional-ordered Grey System Model and Its Application for Predicting Industrial Electricity Consumption

Accurate and reasonable prediction of industrial electricity consumption is of great significance for promoting regional green transformation and optimizing the energy structure.However,the regional power system is complicated and uncertain,affected by multiple factors including climate,population and economy.This paper incorporates structure expansion,parameter optimization and rolling mechanism into a system forecasting framework,and designs a novel rolling and fractional-ordered grey system model to forecast the industrial electricity consumption,improving the accuracy of the traditional grey models.The optimal fractional order is obtained by using the particle swarm optimization algorithm,which enhances the model adaptability.Then,the proposed model is employed to forecast and analyze the changing trend of industrial electricity consumption in Fujian province.Experimental results show that industrial electricity consumption in Fujian will maintain an upward growth and it is expected to 186.312 billion kWh in 2026.Compared with other seven benchmark prediction models,the proposed grey system model performs best in terms of both simulation and prediction performance metrics,providing scientific reference for regional energy planning and electricity market operation.

极对数为奇数的分数槽4支路绕组接线设计

三相电机的分数槽绕组通常采用6×60°标准相带进行设计,其并联支路数必须为每相槽数和极数的公因数才能实现三相平衡。据此,当极对数为奇数时不能实现4支路平衡绕组。某些水轮发电机由于并联支路数受此限制而无法设计得具有合理的电磁参数和经济性。本文提出一种新的设计方法—环状相带设计法,可以避免标准相带设计理论中对于并联支路数的限制,在极对数为奇数时仍然能够采用4支路三相平衡绕组,解决了抽水蓄能电站用大容量14极发电电动机的最佳电磁设计问题。文中详细描述了环状相带的电气短距效应的构成方法,给出了包括铁心振动计算所需的分数次谐波在内的所有谐波的分布系数和短距系数的计算公式。

Investigation of oil-air two-phase mass flow rate measurement using Venturi and void fraction sensor

Oil-air two-phase flow measurement was investigated with a Venturi and void fraction meters in this work. This paper proposes a new flow rate measurement correlation in which the effect of the velocity ratio between gas and liquid was considered. With the pressure drop across the Venturi and the void fraction that was measured by electrical capacitance tomography apparatus, both mixture flow rate and oil flow rate could be obtained by the correlation. Experiments included bubble-, slug-, wave and annular flow with the void fraction ranging from 15% to 83%, the oil flow rate ranging from 0.97 kg/s to 1.78 kg/s, the gas flow rate ranging up to 0.018 kg/s and quality ranging nearly up to 2.0%. The root-mean-square errors of mixture mass flow rate and that of oil mass flow rate were less than 5%. Furthermore, coefficients of the correlation were modified based on flow regimes, with the results showing reduced root-mean-square errors.

A Comparative Study of Fractional Order Models on State of Charge Estimation for Lithium Ion Batteries

State of charge(SOC)estimation for lithium ion batteries plays a critical role in battery management systems for electric vehicles.Battery fractional order models(FOMs)which come from frequency-domain modelling have provided a distinct insight into SOC estimation.In this article,we compare five state-of-the-art FOMs in terms of SOC estimation.To this end,firstly,characterisation tests on lithium ion batteries are conducted,and the experimental results are used to identify FOM parameters.Parameter identification results show that increasing the complexity of FOMs cannot always improve accuracy.The model R(RQ)W shows superior identification accuracy than the other four FOMs.Secondly,the SOC estimation based on a fractional order unscented Kalman filter is conducted to compare model accuracy and computational burden under different profiles,memory lengths,ambient temperatures,cells and voltage/current drifts.The evaluation results reveal that the SOC estimation accuracy does not necessarily positively correlate to the complexity of FOMs.Although more complex models can have better robustness against temperature variation,R(RQ),the simplest FOM,can overall provide satisfactory accuracy.Validation results on different cells demonstrate the generalisation ability of FOMs,and R(RQ)outperforms other models.Moreover,R(RQ)shows better robustness against truncation error and can maintain high accuracy even under the occurrence of current or voltage sensor drift.

Measurement of oil volume fraction and velocity distributions in vertical oil-in-water flows using ERT and a local probe

This paper presents the use of a high performance dual-plane electrical resistance tomography (ERT) system and a local dual-sensor conductance probe to measure the vertical upward oil-in-water pipe flows in which the mean oil volume fraction is up to 23.1%. A sensitivity coefficient back-projection (SBP) algorithm was adopted to reconstruct the flow distributions and a cross correlation method was applied to obtain the oil velocity distributions. The oil volume fraction and velocity distributions obtained from both measurement techniques were compared and good agreement was found, which indicates that the ERT tech- nique can be used to measure the low fraction oil-water flows. Finally, the factors affecting measurement precision were discussed.

Closed form soliton solutions of three nonlinear fractional models through proposed improved Kudryashov method

We introduce a new integral scheme namely improved Kudryashov method for solving any nonlinear fractional differential model.Specifically,we apply the approach to the nonlinear space-time fractional model leading the wave to spread in electrical transmission lines(s-tfETL),the time fractional complex Schrödinger(tfcS),and the space-time M-fractional Schrödinger-Hirota(s-tM-fSH)models to verify the effectiveness of the proposed approach.The implementing of the introduced new technique based on the models provides us with periodic envelope,exponentially changeable soliton envelope,rational rogue wave,periodic rogue wave,combo periodic-soliton,and combo rational-soliton solutions,which are much interesting phenomena in nonlinear sciences.Thus the results disclose that the proposed technique is very effective and straight-forward,and such solutions of the models are much more fruitful than those from the generalized Kudryashov and the modified Kudryashov methods.

Melt fractions and medium connectivity in the Himalaya-Tibetan crust

Seismic and magnetotelluric field campaigns carried out across the Himalaya and the Qinghai-Tibetan Plateau show mid-crustal low resistivity and low-velocity zones.Whether these anomalies indicate that there are molten zones present in the Tibet crust is a focus of geophysical and petrological research.Previous interpretations of MT data to infer melt fractions are often based on presumed electrical conductivity values of partial melt.Temperature,pressure,especially water content in the melt influences the melt conductivity and affects the inferred melt fractions in areas of Tibet.So accurate constraints are essential.In addition,a variety of equations have been proposed to model the conductivity of partially molten rocks in Tibetan crust.However,different rock electrical models relate to different lithological parameters of rocks.So we need to find an appropriate rock electrical model that can apply to Tibet crust.In this study,we use a general electrical conductivity model developed by the global fitting of experimental data in previous study and set up a range of temperature,pressure,and water content for five regions in Tibet.What’s more,using three widely used rock electrical models to figure out corresponding melt fractions in areas of Tibet.We find the most applicable rock electrical model in this region and know better about the distribution and morphology of medium in Tibetan crust.

三相逆变并网系统的分数阶建模与控制器设计研究

首先基于分数阶微积分理论分析讨论分抗元件的基本特性,并在Matlab/Simscape平台搭建分抗元件的器件级仿真模块,以实现分数阶逆变系统的器件级仿真;其次建立三相并网逆变器的分数阶高低频数学模型,推导分数阶电流内环的解耦控制结构,并引入分数阶PIλ控制器建立分数阶光伏并网双闭环控制系统。仿真结果表明:所建分抗元件仿真模块能在所选频率段准确模拟分抗元件外特性,分数阶光伏三相逆变器拥有更好的动静态特性,分数阶双闭环控制效果明显优于整数阶双闭环控制。