Effective AC response of a nonlinear spherical coated composite

An effective nonlinear response of a nonlinear composite with spherical coated inclusions randomly embedded in a host medium under the action of an external AC electric field, Ea= E1 sin（wt） ＋ E3 sin（3wt）, is investigated using a perturbation method. The local potentials of the composite at higher harmonics are given both in the region of local inclusion particles and in the local host region under the external AC electric field. All effective nonlinear responses of the composite and the relationship between the effective nonlinear responses at the fundamental frequency and third harmonics are also studied for spherical coated inclusion in a dilute limit.

Evaluation of Dielectric Properties of CCTO-BT/Epoxy Composites for Electronic Applications

In the current study,the calcium copper titanate(CCTO)/epoxy,barium titanate(BT)/epoxy and CCTO-BT/epoxy composite samples with variable volume fractions of CCTO and BT are fabricated using hand lay-up and compression moulding process. The composite samples are characterized for the frequency dependence on dielectric properties,conductivity,impedance spectroscopy and electrical modulus.X-ray diffraction(XRD)representation of CCTO-BT/epoxy composite samples confirmed the presence of both CCTO and BT ceramic samples separately. The dielectric characteristics of hybrid CCTO-BT/epoxy composite samples with CCTO∶BT ratio of 40∶60, 60∶40,and 50∶50 was found relatively better than those of single ceramic filler reinforced epoxy composites. AC conductivity analysis shows improvement in the results of hybrid filler-filled CCTO-BT/epoxy composites in comparison with single filler-filled epoxy composite.50∶50 CCTO-BT/epoxy composite shows the best AC conductivity value of~ 2.2 ×10^(-5) ohm^(-1)·m^(-1) at a higher frequency of 1MHz. The impedance analysis confirms the higher insulating properties for hybrid 40∶60 and 60∶40 CCTO-BT/epoxy composites with respect to the single and other hybrid ceramic epoxy composites. The analysis suggests the hybrid CCTO-BT/epoxy composites to be adopted as a potential dielectric material for energy storage devices and other electronic applications.

Effective Response of Nonlinear Spherical Coated Composites Under External AC and DC Electric Field

Under the external AC and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displaeement and electric field, is investigated in the dilute limit by using the perturbation method. The local potentials in inclusion and host regions are derived at all harmonics. Moreover, the formulae of the effective linear and nonlinear responses are given in the dilute limit.

Effective response of nonlinear cylindrical coated composites under external AC and DC electric field

This paper uses the perturbation method to study effective response of nonlinear cylindrical coated composites. Under the external AC and DC electric field Ea （1 ＋sin ωt）, the local potentials of composites at all harmonic frequencies are induced. An effective nonlinear response to composite is given for the cylindrical coated inclusions in the dilute limit.

Effective response in nonlinear spherical coated composites under external AC and DC electric fields

By using the perturbation method, effective nonlinear direct current （DC） and alternating current （AC） responses of nonlinear composites with spherical coated inclusions randomly embedded in a host medium are studied under the action of an external electric field Ea = E0 ＋ E1 sinωt ＋ E3 sin 3ωt with different amplitudes and frequencies. The local potentials of composites at all harmonics are given in the inclusion particles and the host regions. All effective nonlinear responses to composites and the relationship between the effective nonlinear responses at all harmonics are also deduced for the spherical coated inclusions in a dilute limit.

Effective Response of Nonlinear Composite under External AC and DC Electric Field

A perturbation method is used to study effective response of nonlinear Kerr composites, which are subject to the constitutive relation of electric displacement and electric field, Dα=εαE＋xα｜E｜^2E. Under the external AG and DC electric field Eapp = Eα（1 ＋ sinωt）, the effective nonlinear responses and local potentials are induced by the cubic nonlinearity of Kerr materials at all harmonics. As an example in three dimensions, we have investigated this kind of nonlinear composites with spherical inclusions embedded in a host. At all harmonic frequencies, the potentials in inclusion and host regions are derived. Furthermore, the formulae of the effective linear and nonlinear responses are given in the dilute Iimit.

Effective AC and DC Responses of Nonlinear Composites at Higher Concentration

For higher concentration of inclusions, an effective medium approximation （EMA） method is used to investigate the bulk effective response of weakly nonlinear composites, which are subject to the constitutive relation of electric displacement and electric field, Dα = εαE ＋Xα｜E｜^2 E. As an example of three dimensions, under the external AC and DC electric fields Eapp = Eα（1 ＋ sinωt）, we have derived the general effective nonh＇near response of composites by the EMA method for higher concentration of spherical inclusions. Furthermore, the effective nonlinear responses at harmonics are predicted.

Microstructures and mechanical properties of MgAl_2O_4 particle-reinforced AC4C aluminum composites

MgAl2O4 particle-reinforced AC4C based alloy composites were fabricated by the stirring-casting method. The effects of the average sizes and the size distributions of MgAl2O4 particles on the dispersibility were investigated, and the microstructures, strength, and fatigue properties of MgAl2O4 particle-reinforced AC4C based alloy composites were evaluated. Tensile strength in the MgAl2O4 particle-reinforced AC4C based alloy composite was increased by using the classified particles. The fatigue limit at 107 cycles in the MgA1204 particle-reinforced AC4C-Cu composite increased by 27% compared to the unreinforced alloy at 250 ~C. Dislocations were observed in the matrix around the MgAl204 particle which resulted from the mismatch of thermal expansion coefficients between MgAl2O4 and Al, and resisted failure and caused fatigue cracks to propagate around the MgAl2O4 particles, resulting in extensive crack deflection and crack bowing which contributed to the improvement of fatigue strength.

ACES色彩管理流程及其在影视数字合成中的应用

目前,学院颜色编码系统(ACES)已在影视视效制作领域频繁提及并广泛使用。然而,由于ACES的复杂性以及ACES色彩管理流程的专业性,人们对其理解尚不够全面细致。相较于影视数字合成线性工作流(Linear Workflow)的不足,ACES色彩管理流程更具完整性、先进性和前瞻性。本文梳理了同ACES紧密关联的色彩原理和相关概念,总结了ACES的产生原因、优势所在及其在影视数字合成中的具体应用。希望本文有助于视效从业者加深对ACES的全面理解,推进ACES色彩管理流程在剪辑、视效、调色以及虚拟摄制等领域的普及和规范应用。

Effect of Nano Silver Modification on the Dielectric Properties of Ag@TiO_(2)/PVDF Composites

To get a dielectric material with a high dielectric permittivity and suppressed dielectric loss,nano-Ag with a particle size of 20 nm and Ag@TiO_(2)core-shell particles with diameters of approximately 70-120 nm were embedded in polyvinylidene fluoride(PVDF)to fabricate nano-Ag/Ag@TiO_(2)/PVDF composites.After being modified by nano-Ag with 3 vol%optimal amount,the relative permittivity(ε_r)at 100 Hz of 50 vol%Ag@TiO_(2)/PVDF composites was 61,and the dielectric loss can be suppressed to 0.04,almost 96.4%lower than that of unmodified composites,and a higher frequency stability of bothε_r and loss has also been found.The underlying mechanism of the reduced loss was attributed to Maxwell-Wagner polarization and the Coulomb blockade effect caused by the introduction of a small amount of nano-Ag,which will block the movement of electrons between metal nanoparticles and composites.The space charge polarization and conductance loss are weakened at lower and higher Ag@TiO_(2)filling ratios,respectively,thus leading to a very low loss of the composites.

Conduction Mechanism and Conductivity Behaviour of Pure Polypropylene (PP) and Polypropylene-Banana Fiber (PP-B) Composites

Fibers reinforced composite materials offer a combination of strength and modulus that are either comparable to or better than many traditional metallic materials.The research on natural fiber based composite materials fit well into this ecological image.This paper reports the conduction mechanism and ac conductivity,activation energy behavior of Polypropylene and banana fiber reinforced thermoplastic composites.Polypropylene[-CH_(2)-CH_(2)-CH_(2)-]n and different fiber content(wt.%)of polypropylene-banana fibers(natural fiber)composites were fabricated using a hot-press molding system.The optimum fabrication parameters were established(initial pressure,temp.etc.).These composite test samples were fabricated so the short fibers were randomly oriented in the matrix.The detail investigation of the a.c.conductivity and conduction mechanism of polymer composites would provide information about the relaxation processes,activation energy etc.which are dependent on frequency,temperature and time.The activation energy involved in the above processes can also be estimated from this study.The measurements were performed over a wide range of frequency of 60 Hz to 3 MHz and temperature range from 30℃(303°K)to 110℃(383°K).Experimental results of the ac properties of pure polypropylene and polypropylene-natural banana fiber composites were compared.It has been established that the fabricated composition changes its insulating property after adding the natural fibers and gives the better conductivity properties.

荷载作用下UHPC+AC复合试件裂缝发展的分形分析

基于道路及相关材料发展现状,提出UHPC+AC复合式路面,制作UHPC+AC复合小梁试件并开展梯度荷载加载试验,记录得到复合试件表面裂缝的生长过程,利用分形分析方法分别对复合试件AC层、UHPC层裂缝进行量化分析。研究分析发现复合试件AC层裂缝分形维数随荷载增加呈线性关系增加,复合试件UHPC层裂缝分形维数随荷载增加呈指数关系增加,裂缝最终损伤形态分别为网状和线状。研究结论为UHPC+AC复合式路面的设计和维护提供理论依据。

车轮静载下RUHPC+AC复合试件的力学响应分析

为探究RUHPC+AC复合式路面在车轮静载下的应变规律,分别选取AC层不同层位、不同点位的纵向与竖向应变作为主要分析对象,进行车轮静载试验,并用ANSYS有限元软件建模进行验证分析。试验分析结果表明:在车轮静载作用下,同一竖向平面AC层顶的纵向应变大于AC层底的对应值;跨中加载得到的纵向拉应变及竖向压应变均大于1/4点位加载得到的对应值;ANSYS软件分析得到的各力学指标及变化规律与试验数据对应值一致,并且两者差值率基本上在30%以内,为RUHPC+AC复合式路面的设计和力学分析提供参考。

白酒糟中ACE抑制肽提取工艺优化及抗氧化活性

[目的]有效处理白酒糟,研究和开发白酒糟中的高附加值成分,探索其潜在应用途径。[方法]采用超声波辅助碱提酸沉法从白酒糟中提取蛋白质,利用复合酶对白酒糟粗蛋白进行酶解制备血管紧张素转换酶(ACE)抑制肽,通过单因素试验和响应面试验优化ACE抑制肽的提取工艺条件,并对其抗氧化活性进行研究。[结果]采用复合酶法制备ACE抑制肽得到了最佳条件:酶配比(V_(木瓜蛋白酶)∶V_(中性蛋白酶))3∶1,水解温度55.41℃,水解pH 7.72,水解时间2.38 h,该条件下ACE抑制肽水解度为66.62%;复合蛋白酶酶解3 h后得到最高的ACE抑制活性(79.05%);经提取纯化后的ACE抑制肽对DPPH自由基和ABTS自由基的清除率分别为2.078%和3.226%,总抗氧化能力分别为1.161μmol/mL和1.255 mmol。[结论]采用复合酶法从白酒糟中提取ACE抑制肽工艺可行。

MnO_x的掺杂对CeO_2/AC催化剂NH_3选择性催化还原NO_x性能的影响

采用浸渍法制备了MnO_x掺杂的CeO_2/AC催化剂,考察了MnO_x的掺杂对催化剂的低温NH_3选择性催化还原NO_x的性能的影响,并采用了XRD、NH_3-TPD、H_2-TPR对催化剂进行了表征。结果表明,MnO_x的掺杂提高了催化剂的表面酸性和氧化还原性能,从而使催化剂在110℃以下的活性得以提升,但催化剂在120℃以上的活性则随着MnO_x的掺杂量的增加而降低。与其他催化剂相比,Ce/Mn比为4∶1的催化剂在整个温度区间都具有较好的活性,而且该催化剂在210℃下具有较好的抗SO_2中毒能力。

超级电容器用PEDOT/AC复合电极的制备及电化学性能

以对甲苯磺酸铁(Fe(TOS)3)为掺杂剂和氧化剂,采用化学聚合法制备了聚(3,4-乙撑二氧噻吩)/活性炭(PEDOT/AC)复合材料。通过SEM、FT-IR、TGA/DTG等方法分析了复合材料的微观形貌及结构特征。采用循环伏安、恒流充放电、交流阻抗等方法研究了不同配比的复合材料作为卷绕式超级电容器电极的电化学性能。结果表明,PEDOT/AC复合材料具有优良的热稳定性。当AC的含量为EDOT的20%时,复合电极的比容量提高到176.3F/g,经过1 000次恒电流充放电后,容量保持率为83.6%,具有优异的循环稳定性。

TiO_2/wAC复合光催化剂的酸催化水解合成及表征

以TiCl4为钛源,采用酸催化水解法合成了活性炭(AC)复合光催化剂TiO2/wAC(w:AC的质量分数,%).通过对苯酚、甲基橙以及六价铬的光催化降解,考察了AC含量、反应溶液初始pH值、使用次数对TiO2/wAC光催化剂催化活性的影响,并采用重力沉降法测试了催化剂分离性能.采用XRD、DRS、FTIR、SEM、低温液氮吸附等对光催化剂晶相结构、光谱特征、表面结构等进行了表征.结果表明,适宜AC含量的TiO2/wAC(wAC=5%,记为5AC)具有较高的光催化活性.AC掺杂可减小TiO2粒子凝聚,而对TiO2的晶相结构、晶粒大小以及表面性质影响不大,对TiO2能阈结构不产生影响.TiO2与AC结合牢固,接触界面处有Ti—O—C键生成.TiO2/5AC表现出高光催化活性的主要原因是,AC所提供的适宜高浓度环境及对纳米尺寸TiO2团聚的有效抑制.TiO2/5AC的高活性,不易失活,易分离以及活性受pH变化影响较小的特性,使其在实际废水处理方面具有潜在应用价值.

利用牡蛎制备ACE抑制肽的工艺优化

运用正交试验和响应面法优化牡蛎血管紧张素转换酶(angiotensin-Ⅰconverting enzyme,ACE)抑制肽的分步酶解制备工艺。采用复合蛋白酶和碱性蛋白酶对牡蛎进行分步酶解,以十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)分析和ACE抑制率为考核指标优化工艺参数。结果表明,第1步复合蛋白酶最佳工艺参数为:料液比1∶4、加酶量1.2%、pH 7.0、反应温度50℃、酶解时间1 h;第2步碱性蛋白酶最佳工艺参数为:加酶量0.42%、pH 8.3、反应温度53℃、酶解时间73 min。凝胶过滤色谱法测得牡蛎酶解液分子质量在3 000 D以下小肽所占比例为99.72%,其ACE抑制活性IC50为0.8 mg/mL。同时,氨基酸组成分析表明,牡蛎肽中Glu含量最高,Cys含量最低;必需氨基酸和疏水性氨基酸含量分别占总氨基酸的36.6%和37.2%。本研究制备的低分子质量、高ACE抑制活性牡蛎肽,可为牡蛎资源的开发利用提供理论参考。

Mo掺杂MnOx/凹土复合材料在烟气脱汞中的应用

以盐酸活化凹土为载体,采用浸渍法制备Mo掺杂Mn Ox/凹土复合材料(Mo-Mn-ATP),并经负载Mo/Mn Ox后冻干-焙烧变温致孔处理。采用SEM、EDS、FT-IR、XRD及N2吸附-脱附比表面、孔径结构分析进行表征,并在烟气180℃下考察脱除Hg0的效果。结果表明,制得的Mo-Mn-ATP复合材料,在保持凹土原有晶体结构的基础上,随着Mo/Mn摩尔比的减小,材料的比表面积增大。复合材料在180℃对Hg0的脱除性能比酸改性凹土高,其中Mo(1)-Mn(3)-ATP(10%)复合材料的去除率最高,在200 min内Hg0的去除率高达96%。