由NiZn—Fe（Ⅱ）-Fe（Ⅲ）层状双金属氢氧化物前体制备NiZnFe2O4尖晶石磁性材料

提出了一种由层状前体合成单一晶相镍锌尖晶石的方法,对NiZn-Fe（Ⅱ）-Fe（Ⅲ）SO4水滑石的制备进行了研究,合成了Ni^2＋、Zn^2＋、Fe^2＋、Fe^3＋摩尔比分别为1：2：5：2,3：3：i0：4,2：1：5;2,5：1：i0：4的系列水滑石层状前体;探讨了合成条件对晶体结构的影响,研究了层状前体焙烧产物的磁学特性。结果表明：四种摩尔比的配方均可制备出晶型较好的水滑石层状前体,焙烧产物为晶相单一的尖晶石铁氧体,其中当摩尔比为3：3：10：4时,产物尖晶石铁氧体的磁学特性较高,比饱和磁化强度高达78．89A·m^2·kg^-1。     

钴酸盐尖晶石的合成与热分析研究

尖晶石是以化学式AB2O4表示的化合物。本文报道了用草酸盐先驱物制备尖晶石型化合物MCo2O4（M＝Mn，Cu，Zn，Cd．Ni，Mg）的方法。用热分析、X-射线粉末衍射和IR光谱证实了尖晶石型化合物MCo2O4的形成；由扫描电镜测得最终产品的颗粒尺寸为1～10μm。先驱物法提供了一个简单可行和有效的合成尖晶石型化合物MCo2O4的方法。     

磁性微晶玻璃连接锂铁氧体接头组织演变及磁性能模拟

锂铁氧体的玻璃连接技术能够克服常规烧结法无法制备复杂结构微波铁氧体构件的困难,并且微晶玻璃能够在铁氧体接头中原位析出磁性微晶相,进而实现连接件结构-功能一体化。设计并制备LFBi5B、LFBi15B、LFBi25B微晶玻璃钎料用于连接锂铁氧体,研究微晶玻璃在锂铁氧体表面的润湿性,钎料成分和连接温度对接头微观组织的影响规律,及锂铁氧体接头中焊缝的磁性来源。结果表明,三种微晶玻璃在铁氧体表面均具有较好的润湿性,锂铁氧体接头中原位析出LiFeO₂晶体;随着连接温度升高,部分析出晶溶解,生成少量钛酸铋晶须。第一性原理模拟结果表明,钎缝中析出的主晶相LiFeO₂总磁矩不等于0,上下自旋能带不对称,态密度图呈现自旋劈裂状态,均证明LiFeO₂晶体具有磁性,其磁性来源为Fe、O原子的p、d态电子交换作用。通过试验与理论相结合,采用微晶玻璃连接锂铁氧体实现了接头中LiFeO₂磁性微晶相的原位形成,验证了LiFeO₂晶体的磁性来源,为磁性接头结构功能一体化设计提供了新思路。     

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。     

共沉淀法制备Ca0．6Mg0．4Zr4（P04）6纳米粉体

采用共沉淀法，以Ca（NO3）2·4H2O、Mg（NO3）2·6H2O、ZrO（NO3）2·8H2O和NH4H2PO4为原料合成Ca0．6Mg0．4Zr4（P04）6（C0．6M0．4ZP）纳米粉体，通过TGDSC、XRD、TEM和纳米粒度／Zeta电位分析手段研究了反应过程pH值、反应物浓度配比和沉淀反应方式等对合成粉体的相组成、平均颗粒尺寸及其分布等的影响。结果表明：将Ca^2＋、Mg^2＋、Zr4＋离子混合溶液加入到不同pH值的NH4H2PO4溶液中，并控制pH=3～11，沉淀物经900℃煅烧3h后，可合成单相的C0．6M0．4ZP纳米粉体；当Zr4十浓度为0．5mol／L、沉淀剂NH4H2PO4浓度为1．0mol／L、pH=9时，合成粉体平均颗粒尺寸和粒径分布范围最小，分别为40nm和20-70nm。     

由NiZn-Fe(Ⅱ)-Fe(Ⅲ)层状双金属氢氧化物前体制备NiZnFe2O4尖晶石磁性材料

提出了一种由层状前体合成单一晶相镍锌尖晶石的方法,对NiZn-Fe(Ⅱ)-Fe(Ⅲ)SO4水滑石的制备进行了研究,合成了Ni2+、Zn2+、Fe2+、Fe3+摩尔比分别为1:2:5:2,3:3:10:4,2:1:5:2,5:1:10:4的系列水滑石层状前体;探讨了合成条件对晶体结构的影响,研究了层状前体焙烧产物的磁学特性.结果表明:四种摩尔比的配方均可制备出晶型较好的水滑石层状前体,焙烧产物为晶相单一的尖晶石铁氧体,其中当摩尔比为3:3:10:4时,产物尖晶石铁氧体的磁学特性较高,比饱和磁化强度高达78.89 A·m2·kg-1.     

液相沉积法制备磁性纳米Fe3O4/SiO2复合粒子

采用液相沉积法在磁性Fe3O4纳米粒子的表面包覆了一层SiO2膜,制备磁性较强的纳米Fe3O4／SiO2复合粒子,采用IR、XPS、XRD、TEM、VSM等方法对复合粒子的性能进行了表征。结果表明：复合粒子的较佳制备条件为正硅酸乙酯(TEOS)的浓度为0．6mol／L,Fe3O4与TEOS物质的数量比为5：1,反应温度为50℃,搅拌速度为800r／min;在此条件下制得的复合粒子的粒径在20nm左右,比饱和磁化强度为60．5emu／g,呈球形且分散均匀。     

制备纳米铁酸锌的一种新方法

利用滚压振动磨在干法室温条件下和化学共沉淀法分别制备了纳米锌和纳米Fe3O4颗粒,再通过锌和Fe3O4水解反应制备纳米ZnFe2O4颗粒;用XRD、TEM以及Mssbauer谱仪等对其进行了表征。结果表明:制得的纳米锌、纳米Fe3O4和纳米ZnFe2O4的颗粒平均粒径分别为40,20,40 nm;当水解反应温度为300℃时,ZnFe2O4颗粒尺寸比较均匀,但明显出现Fe2O3;由Mssbauer谱可知出现了三个六条亚谱。     

用于海洛因检测的低浓度乙酸敏感元件制备和敏感性能研究

文中通过对海洛因毒品的特性分析,提出了采用氧化传感器检测低浓度乙酸气体,间接检测海洛因毒品的技术方案,并对ZnFe2O4、ZnGa2O4气敏材料的制备和气敏性能进行了研究,认为Sb掺杂ZnFe2O4敏感材料适合于乙酸传感器,用于海洛因毒品的检测。     

Fe_3O_4/MnO_2磁性复合颗粒的制备及表征

以纳米Fe3O4颗粒为核,分别采用液相沉积法和溶胶一凝胶法两种方法将MnO2包覆在其上制备了Fe3O4/MnO2磁性复合颗粒,并借助XRD、TEM、FTIR和VSM等手段分别对纳米Fe3O4颗粒和两种复合颗粒进行表征.结果表明:采用液相沉积法进行包覆可生成以多个纳米Fe3O4颗粒为核、粒径约为200 nm的近球形Fe3O4/MnO2磁性复合颗粒,其饱和磁化强度为24.4 kA·m-1;采用溶胶-凝胶法进行包覆则生成以单个纳米Fe3O4颗粒为核、粒径约为50 nm的磁性复合颗粒,包覆层为絮状MnO2,其饱和磁化强度为16.5 kA·m-1.     

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...     

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.     

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.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

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...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.