Solid-state impedance spectroscopy studies of dielectric properties and relaxation processes in Na_(2)O–V_(2)O_(5)–Nb_(2)O_(5)–P_(2)O_(5) glass

Solid-state impedance spectroscopy(SS-IS)was used to investigate the influence of structural modifications resulting from the addition of Nb2O5 on the dielectric properties and relaxation processes in the quaternary mixed glass former(MGF)system 35Na_(2)O–10V_(2)O_(5)–(55-x)P_(2)O_(5)–xNb_(2)O_(5)(x=0–40,mol%).The dielectric parameters,including the dielectric strength and dielectric loss,are determined from the frequency and temperature-dependent complex permittivity data,revealing a significant dependence on the Nb2O5 content.The transition from a predominantly phosphate glass network(x<10,region I)to a mixed niobate–phosphate glass net-work(10≤x≤20,region II)leads to an increase in the dielectric parameters,which correlates with the observed trend in the direct-cur-rent(DC)conductivity.In the predominantly niobate network(x≥25,region III),the highly polarizable nature of Nb5+ions leads to a fur-ther increase in the dielectric permittivity and dielectric strength.This is particularly evident in Nb-40 glass-ceramic,which contains Na_(13)Nb_(35)O_(94) crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz.The relaxation studies,analyzed through modulus formalism and complex impedance data,show that DC conductivity and relaxation processes are governed by the same mechanism,attributed to ionic conductivity.In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus,M″(ω),Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times.The high-frequency peak indicates bulk ionic conductivity,while the additional low-fre-quency peak is associated with the grain boundary effect,confirmed by the electrical equivalent circuit(EEC)modelling.The scaling characteristics of permittivity and conductivity spectra,along with the electrical modulus,validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb_(2)O_(5) incorporation.

Formation and evolution characteristics of bcc phase during isothermal relaxation processes of supercooled liquid and amorphous metal Pb

The formation and evolution characteristics of bcc phase during the isothermal relaxation processes for supercooled-liquid and amorphous Pb were investigated by molecular dynamics simulation and cluster-type index method （CTIM）. It is found that during the relaxation process, the formation and evolution of bcc phase are closely dependent on the initial temperature and structure. During the simulation time scale, when the initial temperature is in the range of supercooled liquid region, the bcc phase can be formed and kept a long time; while it is in the range of glassy region, the bcc phase can be formed at first and then partially transformed into hcp phase; when it decreases to the lower one, the hcp and fcc phases can be directly transformed from the glassy structure without undergoing the metastable bcc phase. The Ostwald＇s ＂step rule＂ is impactful during the isothermal relaxation process of the supercooled and glassy Pb, and the metastable bcc phase plays an important role in the precursor of crystallization.

MULTI-SCALES RELAXATION PROCESSES OF SHORT FIBER OF NEMATIC LIQUID CRYSTALLINE COPOLYMER IN POLYCARBONATE MATRIX

Multi-scales relaxation processes of short fiber of a nematic liquid crystalline copolymer(LCP)in polycarbonate matrix were investigated.First,the structure relaxation of LCP was studied by rheology.The relaxation spectrum of the nematic liquid crystalline copolymer at 295℃was calculated from the combined dynamic modulus.There are three kinds of relaxation mechanisms for nematic liquid crystalline copotymer:the relaxation of chain orientation,the relaxation of deformed polydomains and the coalescence of pol...

Post-seismic relaxation process and vertical deformation following the 2008 Ms8.0 Wenchuan earthquake, China

The post-seismic horizontal and vertical deformations following the 2008 Ms8.0 Wenchuan earth- quake are inferred from GPS and precise leveling data. The post-seismic relaxation process is measured using GPS data from campaign stations located around the Longmenshan fault, and the derived decay time constant is 12 days. The evolution of the post-seismic vertical deformation is obtained from precise leveling data measured near the surface rupture. The results demonstrate that the hanging wall is uplifting and the foot wall is subsi- ding. The amplitude of the post-seismic deformation is lower than that of the co-seismic deformation. The re- gion with the largest post-seismic displacement is located on the leveling route between Maoxian and Beichuan on the hanging wall.

Multi-relaxation-time lattice Boltzmann simulations of lid driven flows using graphics processing unit

Large eddy simulation （LES） using the Smagorinsky eddy viscosity model is added to the two-dimensional nine velocity components （D2Q9） lattice Boltzmann equation （LBE） with multi-relaxation-time （MRT） to simulate incompressible turbulent cavity flows with the Reynolds numbers up to 1 × 10^7. To improve the computation efficiency of LBM on the numerical simulations of turbulent flows, the massively parallel computing power from a graphic processing unit （GPU） with a computing unified device architecture （CUDA） is introduced into the MRT-LBE-LES model. The model performs well, compared with the results from others, with an increase of 76 times in computation efficiency. It appears that the higher the Reynolds numbers is, the smaller the Smagorinsky constant should be, if the lattice number is fixed. Also, for a selected high Reynolds number and a selected proper Smagorinsky constant, there is a minimum requirement for the lattice number so that the Smagorinsky eddy viscosity will not be excessively large.

Decoupling multimode vibrational relaxations in multi-component gas mixtures: Analysis of sound relaxational absorption spectra

Decoupling the complicated vibrational-vibrational （V-V） coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our previous work [Acta Phys. Sin. 61 174301 （2012）], an analytical model to predict the sound absorption from vibrational relaxation in a gas medium is proposed. In this paper, we develop the model to decouple the V-V coupled energy to each vibrationaltranslational deexcitation path, and analyze how the multimode relaxations form the peaks of sound absorption spectra in gas mixtures. We prove that a multimode relaxation is the sum of its decoupled single-relaxation processes, and only the decoupled process with a significant isochoric-molar-heat can be observed as an absorption peak. The decoupling model clarifies the essential processes behind the peaks in spectra arising from the multimode relaxations in multi-component gas mixtures. The simulation validates the proposed decoupling model.

Spin dynamics of the potassium magnetometer in spin-exchange relaxation free regime

The laser-pumped potassium spin-exchange relaxation free （SERF） magnetometer is the most sensitive detector of magnetic field and has many important applications. We present the experimental results of our potassium SERF magne- tometer. A pump-probe approach is used to identify the unique spin dynamics of the atomic ensemble in the SERF regime. A single channel sensitivity of 8 f.THz-1/2 is achieved with our SERF magnetometer.

Low-field NMR inversion based on low-rank and sparsity restraint of relaxation spectra

In this paper,we proposed a novel method for low-field nuclear magnetic resonance(NMR)inversion based on low-rank and sparsity restraint(LRSR)of relaxation spectra,with which high quality construction is made possible for one-and two-dimensional low-field and low signal to noise ratio NMR data.In this method,the low-rank and sparsity restraints are introduced into the objective function instead of the smoothing term.The low-rank features in relaxation spectra are extracted to ensure the local characteristics and morphology of spectra.The sparsity and residual term are contributed to the resolution and precision of spectra,with the elimination of the redundant relaxation components.Optimization process of the objective function is designed with alternating direction method of multiples,in which the objective function is decomposed into three subproblems to be independently solved.The optimum solution can be obtained by alternating iteration and updating process.At first,numerical simulations are conducted on synthetic echo data with different signal-to-noise ratios,to optimize the desirable regularization parameters and verify the feasibility and effectiveness of proposed method.Then,NMR experiments on solutions and artificial sandstone samples are conducted and analyzed,which validates the robustness and reliability of the proposed method.The results from simulations and experiments have demonstrated that the suggested method has unique advantages for improving the resolution of relaxation spectra and enhancing the ability of fluid quantitative identification.

AN INVESTIGATION ON THE LOW TEMPERATURE RELAXATION OF POLYETHERETHERKETONE

The temperature spectra of internal friction of polyetheretherketone (PEEK) are investigated from 130K to 250K with a multi-function torsion pendulum in the frequency range of 0.1 Hz to 5 Hz. A relaxation process, γ relaxation, appears in the temperature range of the measurement. Its relaxation time distribution in terms of a Gaussian distribution, and the relation between molecular motion mechanism and the distribution characteristic are discussed. The element process of γ relaxation is found to be a disordering one.

THE CURIE TEMPERATURE RELAXATION BEHAVIOR OF METGLASES 2826 AND(Fe_(0.1)Co_(0.55)Ni_(0.35))_(78)Si_(8)B_(14) UNDER HIGH PRESSURE

Relaxation behavior of the Curie temperature(TC)of two amorphous alloys Fe40Ni40P14B6 and(Fe0.1Co0.55Ni0.35)78Si8B14 was investigated under high pressure up to 20kbar.Experimental results show that Tc relaxation process was restrained by high pressure.On the other hand,alternative treating sample at different pressures may enhance this process.Based on the expansion of local pressed region in an amorphous structure,a mechanism of relaxation under high pressure was suggested for explaining the above phenomena.

The Role of Water Motion in Natural Processes

A study of the behavior of water during its movements under mechanical shaking is presented. It is shown that rhythmic shaking of water with 1Hz causes the same rhythmic effects in a periodic [H+] growth and products with higher positive potential. This paper discusses the role of water motion in nature.

^(23)Na relaxometry: An overview of theory and applications

^(23)Na is a nuclear magnetic resonance(NMR)-active isotope with a nuclear spin quantum number of 3/2.^(23)Na relaxation phenomenon is at the core of ^(23)Na NMR measurement and analysis.Due to the dominance of quadrupolar interaction,the relaxation behavior of ^(23)Na is physically and mathematically more complex than that of a typical spin-1/2 isotope.In this review,we overview the semi-classical Redfield theory for deriving the formulations of ^(23)Na relaxation.We show that the relaxation behaviors of ^(23)Na can be quantitatively described by constructing the spectral density functions based on the second-order perturbation theory.In addition,we summarize the applications of ^(23)Na relaxometry in different research fields,including biomedicine,sodium ion batteries,and quantum information processing.Because sodium is an essential element in our body,food and industrial materials,the research on sodium by ^(23)Na NMR emerges as important future directions.The theoretical and practical understandings on ^(23)Na relaxation are the step stones for mastering advanced ^(23)Na NMR techniques.

基于半胱氨酸氧化修饰蛋白质组学研究高压处理对冷藏滩羊肉应力松弛特性的影响

通过半胱氨酸(Cys)氧化修饰蛋白质组学探究不同高压处理(200 MPa/500 MPa、18℃、15 min)滩羊(4℃冷藏1、3、7 d)肌肉蛋白半胱氨酸的氧化修饰与应力松弛特性之间的相关性。结果表明:200 MPa和500 MPa高压处理的肌肉硬度和弹性显著高于对照(NT)组(P<0.05);高压处理组应力松弛特性指标普遍高于NT组,贮藏期间,500 MPa高压处理组羰基含量显著高于200 MPa高压处理组,而总巯基含量显著低于200 MPa高压处理组(P<0.05);半胱氨酸氧化修饰蛋白质组学分析结果显示,3组样本中共鉴定出388个显著差异氧化位点(significantly differential oxidation sites,SDOS),其中,15个SDOS与至少1个应力松弛特性指标呈显著相关性(P<0.05、P<0.01),这些位点涉及肌联蛋白(Cys32705、Cys29171、Cys26405、Cys32358)、伴肌动蛋白(Cys5628)、肌球蛋白结合蛋白H(Cys481)、肌球蛋白重链8(Cys403)、膜联蛋白(Cys292)、肌球蛋白重链11(Cys701)、L-乳酸脱氢酶(Cys315)、糖原磷酸化酶(Cys496)、磷酸葡萄糖变位酶1(Cys407、Cys134)、丙酮酸激酶(Cys510)及钙转运ATP酶(Cys651)。综上所述,高压处理可诱导结构蛋白的部分氧化位点发生氧化修饰,使蛋白变性和聚集,进而降低蛋白本身的降解程度,诱导滩羊肉贮藏期间的硬度增加。

针对机械热处理工艺在弛豫控制相变技术中的研究

机械热处理工艺在驰豫控制相变技术中的研究旨在通过调控材料的组织结构和相变行为,改善材料的力学性能和性能稳定性。该研究主要包括加热工艺优化、相变动力学研究、材料结构调控、相变组织演变模拟和相变产物性能调控等方面。通过本研究,找出实现材料性能的优化和稳定性的提高措施。本研究对于提高材料性能和开发新型材料具有重要意义,并在多个领域具有广泛的应用前景。

弛张筛与三产品重介质旋流器分选工艺在选煤厂的应用探讨

针对潘三选煤厂博后筛存在难以达到高效筛分和分级要求的问题,探讨了采用弛张筛和三产品重介质旋流器工艺代替博后筛的几种工艺方案,并利用该厂工艺参数和煤质资料,给出工艺效果的理论值,从整个方案的实施时间、改造难度、产品产率、降灰幅度、系统能力提升等方面进行了详细的对比分析,全面论证了各个方案的优势和弊端,从而为该厂最终工艺改造方案的选择提供了建设性的意见。

0.94(Bi_(0.5)Na_(0.5)TiO_(3))-0.06BaTiO_(3)掺杂铌酸钠基反铁电陶瓷的储能特性研究

利用Bi^(3+)、Ba^(2+)取代A位Na^(+),利用Ti^(4+)取代B位Nb^(5+),以增强NaNbO_(3)基陶瓷的弛豫特性,获得较低的剩余极化强度。同时,Bi^(3+)6s和O^(2-)2p之间的轨道杂化及高极化率的Ba^(2+)的引入有利于陶瓷获得高极化强度,提高其储能特性。在此基础上,设计了(1-x)NaNbO_(3)-x[0.94(Bi_(0.5)Na_(0.5)TiO_(3))-0.06BaTiO_(3)](NN-x(BNT-BT),x=0.20,0.25,0.30,0.35)陶瓷体系,结合轧膜成型工艺,在1140~1160℃保温2 h制备出致密性良好的厚膜陶瓷样品。结果表明,随着BNT-BT掺杂量的增加,陶瓷的击穿强度明显提高。在外加电场为550 kV·cm^(-1)时,NN-0.35(BNT-BT)陶瓷的储能性能达到最优,储能密度和效率分别为6.7 J·cm^(-3)和79.67%。在外加电场为300 kV·cm^(-1)下,25~120℃温度范围内,NN-0.35(BNT-BT)陶瓷的储能密度和效率变化率分别为9%和7%;在10~500 Hz频率范围内,储能密度和效率变化率分别为3%和5%,表现出优异的温度和频率稳定性。此外,NN-0.35(BNT-BT)陶瓷兼具较高的功率密度(261.014 MW·cm^(-3))和较快的放电时间(19 ns),在脉冲电容器领域存在巨大的应用前景。

Hf元素添加对CuZr基非晶合金动态弛豫的影响

考虑到非晶合金具有独特的无序微观结构,其表现出极为复杂的弛豫动力学特性.动态弛豫行为在非晶合金中普遍存在,深刻理解其机制对于解构非晶合金固有的非均匀微观结构至关重要.少量元素的添加是调控非晶合金微观结构有效手段之一.本研究以玻璃形成能力良好的Cu_(46)Zr_(47-x)Hf_(x)Al_(7)(x=0,8)非晶合金为模型合金,运用动态力学分析方法研究复模量随频率和温度的变化,进而探究Hf元素取代Zr元素对动态弛豫的影响.在动态力学频率谱中,借助准点缺陷理论阐明非晶合金在玻璃转变温度T_(g)以下处于等构型状态,准点缺陷浓度保持恒定;而在T_(g)以上,准点缺陷浓度随温度的上升呈线性增加.Hf元素的添加会降低玻璃体系等构型状态下的准点缺陷浓度,并抑制原子迁移能力.通过获取连续和离散的弛豫时间分布,直观展示了非晶合金的动力学非均匀性特征.在动态力学温度谱中,Hf元素的引入增加了玻璃体系的混合焓,抑制了β弛豫强度.进一步从内耗角度表明,Hf元素的引入不仅提高了与β弛豫相关的基本结构单元的激活难度,还增加了整个β弛豫过程的激活能.

基于SVM的配电网新能源接入多元负荷预测误差校正

针对校正配电网新能源接入多元负荷预测误差的目的,提出了基于SVM的配电网新能源接入多元负荷预测误差校正方法。采用SVM方法找出特征空间最大化间隔,消除了异常预测点的影响。引入松弛变量,集成负荷预测误差数据。归一化处理SVM输入数据,计算预测功率、实际功率相对误差,利用SVM支持面设计初步预测误差校正思路,构建损失函数,判断预测值正负,实现配电网新能源接入多元负荷预测误差校正。通过实验结果得出,该方法在第一种和第二种设备故障情况下,针对最高负荷和最低负荷的误差校正结果分别减小了9.797 MW和0.2 MW、5.292 MW和2.363 MW,均能达到有效校正误差的目的。

Tb^(3+)掺杂钒磷酸盐蓝绿发光调控及发光机理研究

本文采用高温固相方法合成了不同掺杂浓度的YVO_(4)∶Tb^(3+)、YPO_(4)∶Tb^(3+)和YV_(1-x)P_(x)O_(4)∶Tb^(3+)系列荧光粉,利用差示扫描量热法(DSC)分析了高温固相合成过程中的化学反应,确定将1 350℃作为高温合成温度。利用XRD表征了材料物相结构,结果显示材料物相单一,均为四方晶系结构。研究了YVO_(4)∶Tb^(3+)、YPO_(4)∶Tb^(3+)和YV_(1-x)P_(x)O_(4)∶Tb^(3+)系列荧光粉室温下的发光性质。受晶体场影响,紫外激发下YVO_(4)∶Tb^(3+)中Tb^(3+)发光主要以^(5)D_(3)→^(7)F_(J)(J=6,5,4,2)跃迁发光为主,发光显示为蓝光;P元素的增加改变了YV_(1-x)P_(x)O_(4)∶Tb^(3+)晶体场环境,增强了基质与^(5)D_(3)、^(5)D_(4)能级间的多声子弛豫及^(5)D_(3)→^(5)D_(4)能级间的交叉弛豫,^(5)D_(4)→^(7)F_(J′)(J′=6,5,4,3)发射逐渐占优,发光呈现蓝、青、绿发光变化;掺杂浓度对YPO_(4)∶Tb^(3+)发光调控作用显著,随着掺杂浓度增加,Tb^(3+)的^(5)D_(3)与^(5)D_(4)能级间的交叉弛豫作用增强,^(5)D_(3)发光减弱,^(5)D_(4)发光增强,通过调整掺杂浓度实现材料发光由青光到绿光的调控。综上,通过基质组分及掺杂浓度调节,可实现Tb^(3+)掺杂钒磷酸盐体系蓝绿发光调控。

基于ABAQUS装配顺序对航空液压产品密封质量的数值分析

为找到国产飞机液压驱动装置在性能试验时发生漏油故障的原因,对密封失效部位的零件进行拆卸、检测、分析,发现拧紧螺栓处有严重划痕,之后应用ABAQUS有限元分析软件模拟手动拧紧螺钉后螺钉发生应力松弛造成的位移,发现应力松弛产生位移会直接导致负载管接孔与阀芯安装后出现偏心现象,间接造成划痕和密封圈失效的问题。最终优化了国产飞机液压驱动装置及类似结构产品的装配工艺方法。