First-principles investigation of B2 partial disordered structure,martensitic transformation,elastic and magnetic properties of all-d-metal Ni-Mn-Ti Heusler alloys

In this work,the B2 partial disordered structure of the austenitic parent phase,martensitic transformation,elastic and magnetic properties of the Ni8 Mn4+xTi4-x(x=0,1 and 2) Heusler alloys have been systematically investigated by the first-principles calculations.The preferential atomic occupation of B2 structure is one Ti atom exchange with the nearest neighboring Mn atom from the view of lowest energy principle.This disordered exchange sites(Mn-Ti) and the excess Mn atoms occupying the Ti sites(MnTi)could reduce the nearest Mn-Mn distance,resulting in the anti ferromagnetic state in the austenitic and martensitic phases of the alloys.The total magnetic moment of the alloy decreases with the increasing Mn content;it is ascribed to the antiferromagnetic magnetic moments of the excess Mn atoms.When x=0,the alloy does not undergo martensitic transformation since the austenite has absolute phase stability.The martensitic transformation will occur during cooling process for x=1 or 2,owing to the energy difference between the austenite and the martensite could provide the driving force for the phase transformation.The elastic properties of the cubic austenitic phase for the Ni2 MnTi alloy is calculated,and the results reveal the reason why Ni-Mn-Ti alloy has excellent mechanical properties.The origin of martensitic transformation and magnetic properties was discussed based on the electronic density of states.     

耐高温、低导热、韧性中空陶瓷微珠复合材料的制备及其性能

在高速飞行的过程中飞行器温度急速上升,飞行器舱段间的密封材料不仅要具有优异的耐高温性能,同时要具有较低的导热系数辅助参与阻隔舱段间的热量传递,并且要具有优异的力学性能使其不被破坏。以中空陶瓷微球为骨料,加入酚醛树脂及磷酸盐固化体系制备有机/无机杂化耐高温韧性复合材料,并对复合材料进行高温处理,研究复合材料在高温处理前后的变化。通过力学性能测试、SEM观察以及XRD和FT-IR测试对复合材料高温处理前后的抗压强度、压缩形变能力、微观结构以及组分变化进行表征,并通过火焰燃烧对复合材料耐高温性能进行测试。结果表明,所制备的复合材料具有较高的抗压强度以及优异的韧性,1 000℃高温处理600 s复合材料的宏观形貌未受到影响,具有较高的热稳定性。导热系数测试结果表明,中空陶瓷微珠含量的增加、酚醛树脂的添加以及高温处理均会导致复合材料导热系数降低,最低的导热系数低至0.16 W/(m·K)。     

铝钼共掺杂氧化锌粉末的制备及光电性能研究

采用水热法制备了不同含量的铝(Al)单元掺杂及铝(Al)、钼(Mo)共掺杂氧化锌(AZO、AZMO)纳米粉体,利用X射线衍射(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)、荧光分光光度计(PL)、紫外分光光度计(UV-vis)、TG-DTA差热分析、激光粒度分析仪、四探针电阻测试仪等测试手段,探究了Al单元掺杂和Al、Mo共掺对AZO、AZMO粉体结构、形貌及光电性能的影响.结果表明:所制备的AZO和AZMO纳米粉体为结晶度良好的六方纤锌矿结构.Al、Mo掺杂浓度影响纳米氧化锌粉体形貌、晶体结构及光电性能.随着Al、Mo掺杂浓度的增加,粉体的结晶质量降低,晶粒尺寸先减小后增大,光电性能先变好后变差.适度的Al、Mo共掺杂可使氧化锌禁带宽度和电阻率达到最优匹配,改善氧化锌的近紫外发光和蓝色发光特性.在掺杂浓度为m(Al):m(Mo)=1:3时,纳米粉体的综合光电性能最佳,禁带宽度为3.392 eV,电阻率为20.3Ω·m,紫外发光峰强度最大,且出现了蓝移.     

管路-船体耦合振动及水下声辐射研究

充液管路广泛的应用于船舶冷却、输水等多个系统,其振动与水下声辐射一直是学术与工程中的研究热点。基于阻抗综合法,利用耦合点处力与位移的连续边界条件,采用管路解析公式、船体有限元数值计算、管路支撑测试数据三者相结合的方法对管路-船体耦合系统进行振动与水下声辐射工程预报。该综合方法被应用于一个复杂空间管路-船体耦合模型,并与有限元模型结果对比验证了该方法的正确性。     

Understanding the Structure and Properties of Sesqui‐Chalcogenides (i.e., V2VI3 or Pn2Ch3 (Pn = Pnictogen,Ch = Chalcogen) Compounds) from a Bonding Perspective

A number of sesqui‐chalcogenides show remarkable properties, which make them attractive for applications as thermoelectrics, topological insulators, and phase‐change materials. To see if these properties can be related to a special bonding mechanism, seven sesqui‐chalcogenides (Bi₂Te₃, Bi₂Se₃, Bi₂S₃, Sb₂Te₃, Sb₂Se₃, Sb₂S₃, and β‐As₂Te₃) and GaSe are investigated. Atom probe tomography studies reveal that four of the seven sesqui‐chalcogenides (Bi₂Te₃, Bi₂Se₃, Sb₂Te₃, and β‐As₂Te₃) show an unconventional bond‐breaking mechanism. The same four compounds evidence a remarkable property portfolio in density functional theory calculations including large Born effective charges, high optical dielectric constants, low Debye temperatures and an almost metal‐like electrical conductivity. These results are indicative for unconventional bonding leading to physical properties distinctively different from those caused by covalent, metallic, or ionic bonding. The experiments reveal that this bonding mechanism prevails in four sesqui‐chalcogenides, characterized by rather short interlayer distances at the van der Waals like gaps, suggestive of significant interlayer coupling. These conclusions are further supported by a subsequent quantum‐chemistry‐based bonding analysis employing charge partitioning, which reveals that the four sesqui‐chalcogenides with unconventional properties are characterized by modest levels of charge transfer and sharing of about one electron between adjacent atoms. Finally, the 3D maps for different properties reveal discernible property trends and enable material design.     

永磁同步电机矢量控制系统的研究

电机控制技术是实现高性能伺服驱动的核心,也是体现先进制造技术的标志技术之一。基于永磁同步电动机矢量控制理论,介绍了永磁同步电动机的数学模型和基于=0的矢量控制方法,建立了基于空间矢量的永磁同步电动机矢量控制系统Matlab仿真模型,并给出了仿真结果和系统软、硬件设计。硬件系统以TMS320F2812为核心,实现了电流、速度双闭环的矢量控制。仿真结果与理论分析一致,表明设计方案和控制策略的正确性。     

MIS系统中的预警机制

提出在ＭＩＳ系统中引入预警机制的新管理模式并给出了预警管理的实现方案。预警机制的应用,使管理信息系统显示出即时反应的活力,使管理更加智能化、规范化、制度化。实践结果表明,该文给出的解决方案是切实可行的,效果很好。     

熔融挤出接枝法制备HDPE／PA1010增容剂MPE

本文介绍用ＤＣＰＯ作引发剂，通过熔融挤出接枝法制备ＨＤＰＥ／ＰＡ１０１０共混体系增容剂ＭＰＥ的工艺研究。实验结果表明，通过熔融挤出法可将ＭＡＨ单体接枝于ＨＤＰＥ，接枝率和ＭＩ受挤出温度、螺杆转速、ＤＣＰＯ和ＭＡＨ用量的影响，其最佳工艺条件为：挤出温度范围１８０～２２０℃，螺杆转速２５ｒ／ｍｉｎ，ＤＣＰＯ和ＭＡＨ用量分别为０．３份和１．０～１．３份（树脂用量为１００份）。文中还对ＨＤＰＥ融熔挤出接枝     

基于均值查找的快速中值滤波算法

针对传统中值滤波算法时间复杂度高、运行速度慢,难以满足大型图像数据实时处理的问题,提出了一种快速中值滤波算法,将确定中值元素的过程由排序运算转换为基于均值对集合的二分查找,算法不依赖于滤波窗口的形状以及相邻窗口的相关信息,有效提高了中值滤波的执行效率,使传统中值滤波算法的时间复杂度由O(nln n)下降至O(n).实验中,该算法应用于大型图像序列的滤波处理,其运算速度提高到传统中值滤波算法的3倍以上,并且算法运行时间仅随滤波窗口大小线性增长,可以满足大尺度滤波窗口对大型图像数据实时处理的需求,具有显著的实际应用价值.     

Biocompatibility of FGL peptide self-assembly nanofibers with neural stem cells in vitro

In order to study the biocompatibility of self-assembled FGL peptide nanofibers scaffold with neural stem cells (NSCs), FGL pepitide-amphiphile (FGL-PA) was synthesized by solid-phase peptide synthesis technique. The diluted hydrochloric acid was added into FGL-PA solution to reduce the PH value and accordingly induce self-assembly. The morphological features of the assembled material were studied by transmission electron microscope. NSCs were cultured and added with self-assembled FGL-PA. CCK-8 kit was used to test its effect on the proliferation of NSCs. The differentiation of NSCs was also tested after FGL-PA assembled material added. The experimental results showed that FGL-PA could be self-assembled to form a hydrogel. TEM analysis showed the self-assembled hydrogel was nanofibers with diameter of 10–20 nm and length of hundreds nanometers. FGL-PA with concentrations of 50,100, or 200 mg/L could promote the proliferation of NSCs, and absorbance of them was increased (P<0.05). The rate of neurons differentiated from NSCs was improved greatly by FGL-PA assembled material compared with control (P<0.05). The findings suggested that FGL-PA could self-assemble to nanofiber hydrogel, which had good biocompatibility with NSCs.