纳米Mn-Zn软磁铁氧体的制备与性能研究

纳米Mn-Zn软磁铁氧体以硝酸铁、硝酸锌、硝酸锰和柠檬酸为原料,利用溶胶-凝胶凝胶自蔓延燃烧工艺合成纳米级Mn-Zn铁氧体粉体.用X-衍射(XRD)分析了粉体的粒径大小和强度是否符合标准,利用高压投射电子显微镜、振动样品磁强计(VSM)、研究了烧结MnZn铁氧体的成相状态、磁性能.通过分析得到最佳制备条件:Mn:Zn=0.55:0.45、pH值为5、煅烧温度为200℃、煅烧时间为90 min.     

γ-AlOOH纳米棒的制备及其热分解

以氯化铝、氢氧化钠为原料,在反应溶液的pH值为5、反应温度为200℃的条件下用液相法制备薄姆石(γ-AlOOH)纳米棒;对其在不同温度下的煅烧产物及在加热过程的热分解过程进行了分析。结果表明:试验条件下能制备出直径10～30 nm、长度100～300 nm的γ-AlOOH纳米棒;该纳米棒在500～1 200℃下煅烧后转变为γ-Al_2O_3仍保持纳米棒的形貌;在1 250℃下煅烧后转变产物为α-Al_2O_3;在1 300℃下煅烧后转变产物为α-Al_2O_3,纳米棒相互烧结形成团聚体;γ-AlOOH纳米棒的热分解过程分为物理吸附水的脱出、化学吸附水的脱出、结构水脱出并转变为氧化铝中间相、氧化铝中间相中残留羟基的脱出四个阶段。     

添加钴对FeCuNbSiB非晶/纳米晶磁芯软磁性能的影响

在Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9合金成分基础上用硅和钴取代硼,采用单辊快淬法制备了Fe_(73.5)Co_(0.3)Cu_1Nb_3Si_(14.2)B_8合金带,将其绕制成环型磁芯后进行不同温度退火处理,研究了钴的添加对合金带晶化行为及其磁芯软磁性能的影响。结果表明:添加钴对合金带的晶化行为没有显著影响,试验合金带为非晶态结构,经550℃退火处理后磁芯为非晶和纳米晶共存的结构;添加钴后,试验合金非晶/纳米晶磁芯的起始磁导率和饱和磁感应强度分别减小了0.149 9H·m~(-1)和388T,矫顽力增大了0.338 5A·m~(-1),直流软磁性能降低;试验合金非晶/纳米晶磁芯在高频(小于100kHz)下的有效幅值磁导率、电感、品质因数均增大,比总损耗和矫顽力均减小,交流软磁性能提高。     

水热法合成COFe_2O_4纳米颗粒及其磁性能

采用水热法制备尖晶石CoFe_2O_4纳米颗粒,通过改变合成温度(140～200℃)和原料中钴的含量,借助X射线衍射仪、场发射扫描电子显微镜、透射电镜和振动磁强计等研究上述两个因素对合成颗粒结构、形貌及磁性能的影响,并从机制上加以解释。结果表明:水热法合成的CoFe_2O_4纳米颗粒平均粒径在30～40nm之间,提高原料中钴的含量有利于去除α-Fe_2O_3相;随合成温度的升高,该颗粒的饱和磁化强度持续增大,最高为59.694Am~2·kg~(-1),矫顽力先升后降,最高可达1273.28A·m~(-1)。     

脉冲电流加热对纳米晶合金Fe_(73.5)Cu_1Nb_1Mo_2Si_(13.5)B_9组织、磁性与脆性的影响

采用脉冲电流加热纳米晶合金Fe_(73.5)Cu_1Nb_1Mo_2Si_(13.5)B_9,研究了合金纳米晶化后的组织、磁性与脆性的影响。结果表明,脉冲电流加热可制备出晶粒尺寸8～15nm的纳米晶,其软磁性能达到甚至超过等温晶化法制备的纳米晶,且韧性得到明显改善。     

复合电沉积制备纳米钡铁氧体/钴镍合金磁性镀层

采用复合电沉积技术制备了纳米钡铁氧体(BaFe_(12)O_(19))/钴镍合金磁性镀层,研究了纳米钡铁氧铁颗粒对镀层表面形貌及磁性能的影响和镀液中BaFe_(12)O_(19)颗粒含量、电流密度、镀液温度、施镀时间等电沉积工艺参数对复合镀层矫顽力和最大磁能积的影响。结果表明:镀液中加入纳米钡铁氧体颗粒通过优化电沉积工艺可以制备出磁性复合镀层,可明显提高镀层的最大磁能积和矫顽力;以上四种工艺参数对镀层的最大磁能积和矫顽力有明显影响,但影响规律各不相同。     

BaTi03/铁氧体复合材料的制备及性能

采用传统溶胶-凝胶法和改进的柠檬酸盐溶胶-凝胶法制得了钦酸钡,并对其进行了比较.采用柠檬酸-EDTA的联合络合溶胶-凝胶法制得了针状纳米锶铁氧体磁性微粒,并将钛酸钡和锶铁氧体进行了复合.利用XRD对样品的物相进行分析,利用TEM对样品形貌和粒径进行表征,利用振荡样品磁强计(VSM)对样品进行了磁性能研究,并利用矢量网络分析仪对粉末的电磁波吸收性能进行了表征.结果表明,在2～6GHz范围内,钛酸钡质量分数为30%的复合材料在850℃煅烧2h后吸波性能最佳,最大吸收量为28dB,10dB频带宽度为1.7GHz.     

层状前体法制备锰掺杂钴铁氧体的性能

采用层状前体法制备了锰掺杂钴铁氧体Co1-xMnxFe2O4(x分别取0.1,0.2,0.3,0.4),用X射线衍射仪分析了它的物相与结构,用振动样品磁强计测试了它的磁性能,采用自制设备研究了其对巴克豪森信号的接收特性。结果表明:该铁氧体均以单相尖晶石结构存在;掺锰降低了材料的矫顽力,且锰含量越大,矫顽力越小;当x=0.1时材料的饱和磁化强度比钴铁氧体的要大,之后其值随锰含量的增加逐渐减小;Co1-xMnxFe2O4尖晶石铁氧体材料有望作为接收器件应用于巴克豪森磁弹传感器。     

添加CaO对高磁导率Mn-Zn铁氧体磁性能的影响

以MnO、ZnO和Fe_2O_3为基础原料,固定其配比后,添加质量分数在01.0%的CaO,采用传统两步合成工艺制备Mn-Zn铁氧体,研究CaO对铁氧体微观结构和磁性能的影响。结果表明:随着CaO添加量的增加,Mn-Zn铁氧体的平均晶粒尺寸和烧结密度先增大后减小,2.2 MHz频率下的弹性磁导率先增大后急剧减小再略微增大,1T磁场强度下的饱和磁化强度先增大后减小,矫顽力先减小后增大;适量CaO可以改善Mn-Zn铁氧体的微观结构,降低铁心损耗;当CaO质量分数为0.4%时,Mn-Zn铁氧体在1T磁场强度下的饱和磁化强度最大,为46A·m~2·kg~(-1),2.2MHz频率下的弹性磁导率较大,为86.7,损耗功率较低,约为20kW·m~(-3),矫顽力较低,约为183.4kA·m~(-1),Mn-Zn铁氧体的综合磁性能较好。     

BaTiO3/铁氧体复合材料的制备及性能

采用传统溶胶-凝胶法和改进的柠檬酸盐溶胶-凝胶法制得了钛酸钡,并对其进行了比较。采用柠檬酸-EDTA的联合络合溶胶-凝胶法制得了针状纳米锶铁氧体磁性微粒,并将钛酸钡和锶铁氧体进行了复合。利用XRD对样品的物相进行分析,利用TEM对样品形貌和粒径进行表征,利用振荡样品磁强计（VSM）对样品进行了磁性能研究,并利用矢量网络分析仪对粉末的电磁波吸收性能进行了表征。结果表明,在2～6GHz范围内,钛酸钡质量分数为30%的复合材料在850℃煅烧2h后吸波性能最佳,最大吸收量为28dB,10dB频带宽度为1.7GHz。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...