基于RSM和FEM的辊锻件长度控制技术

以某钩尾框精密辊锻工艺为研究对象,首次应用响应面法(RSM)和有限元数值模拟法(FEM)对精密辊锻件的长度控制问题进行了研究.首先以满足辊锻件长度和降低轧辊最大扭矩为目标,采用FORGE3有限元软件建立了RSM与FEM相结合的二阶分析模型,研究了轧辊间隙、摩擦因子、轧辊转速和坯料温度对辊锻件的长度和轧辊最大扭矩的显著性和影响规律;其次采用优化后的工艺参数对该辊锻工艺进行了再模拟,提出了辊锻件长度的调试原则,利用该原则和点的反追踪技术对辊锻模具进行了再设计,同时分析了设计、模拟和生产辊锻件的长度和辊锻过程的功率耗散和分布.研究结果表明:应用RSM和FEM可准确有效地掌握精密辊锻件的长度控制技术.     

Effect of Ce addition on hot tearing behavior of AZ91 alloy

A small amount of cerium (below 1.0 wt%) addition to AZ91 alloy have been investigated on the hot tearing susceptibility (HTS) at a cooling rate of 1.5Ks^?1. The HTS increased to a maximum value with a cerium addition of 0.6 wt% and then decreased to a stable status as cerium was gradually added. Due to high chemical activity, cerium into the melts can react with aluminum to form an Al₁₁Ce₃ intermetallic compound. X–ray diffraction results also confirmed the existence of Al₁₁Ce₃. The Al₁₁Ce₃ increased with the presence of the needle-like and block morphology. As cerium levels increased, the amount of Mg₁₇Al₁₂ decreased. The variations between Mg₁₇Al₁₂ and Al₁₁Ce₃ resulted in a similar normal distribution of the HTS in AZ91 alloy. The findings were further verified through the microstructure evolution and the surface morphology of fracture.     

基于广义出行成本的出行方案优化

为了使出行成本更加符合出行者的认知规律,运用结构方程建模方法模拟出行成本,个体特征及出行决策之间的影响关系.引入敏感系数调整服务属性在出行成本中的贡献率,利用出行意愿调查数据对敏感系数进行标定.考虑出行者对抵达时刻的选择偏好,假设行程时间服从正态分布条件下,对最佳出发时刻及期望出行成本进行寻优求解,结果表明它取决于期望到达时刻,行程时间的期望值及方差,出行者对早到损失及晚到延误损失时间成本的相对大小.研究成果可为制定个性化及最优化出行决策方案提供依据.     

基于树状分子及炭黑复合纳米材料修饰电极的Cr(VI)电化学检测

用树状分子及炭黑纳米复合材料修饰玻碳电极,并对六价铬Cr(VI)进行电化学测定.采用X射线光电子能谱(XPS)、循环伏安法(CV)、交流阻抗法(EIS)、方波溶出伏安法(SWSV)等方法对修饰电极进行了表征.研究发现多种其他离子如Ni~(2+)、Co~(2+)、Pb~(2+)、Cu~(2+)、Cd~(2+)、NO_3~-、SO_4~(2-)、Cl~-等对六价铬离子的测定没有明显干扰,且Cr(VI)的还原峰电流与Cr(VI)的物质的量浓度在4~60 nmol/L和0.06~500μmol/L范围内呈线性关系,检测限达1 nmol/L.该法具有简便快速,选择性好,线性范围宽,灵敏度高等优点.     

Cobalt doped titanate nanotubes: Synthesis and properties

Cobalt oxide doped titanate nanotubes are synthesized with a simple hydrothermal treatment of mixed Co_3O_4 and TiO_2 powders. The formed tubular nanostructure, chemical composition,and the elemental distribution are analyzed using TEM, BET, FTIR, XRD, and XPS. The electrocatalytic activity towards oxygen evolution reactions and photodegradation against Rhodamine B are investigated. It has been found out that the oxygen evolutions starts at 0.8 V and reaches 0.98 mA ·cm~(–1) at 1.4 V vs. SCE. For photodegradation of Rhodamine B, the concentration decreased to 24% after 1 h irradiation using the sample with a mass percentage of 5% cobalt. The results demonstrate that the cobalt oxide doped titanate nanotubes are good candidates as electrocatalysts and photocatalytic materials.     

C3N4/ZnO复合材料可见光下的甲醛光电气敏性能

以水热法合成的ZnO纳米棒花为载体,将C_3N_4定量负载在其表面,制备C_3N_4/ZnO复合材料.由于C_3N_4与ZnO的能级匹配,可有效促进其光生电荷的分离,降低光生电荷复合率,显著提高载流子浓度,使其光电流明显增加.C_3N_4与ZnO质量比为2%的样品(2%C_3N_4/ZnO)性能最佳,其光电流在370 nm处可达120μA,为纯ZnO的2.4倍.在室温可见光下,2%C_3N_4/ZnO样品对HCHO的光电气敏响应值可达122%,比纯ZnO高4倍左右.结果表明,适量C_3N_4的负载有效延长了光生电荷的寿命,使ZnO材料在可见光区对HCHO气体表现出高效的光电气敏性能.     

基于动态阈值的混凝土裂缝高抗噪提取及识别方法

针对表面布有蜂窝麻面等复杂噪声的混凝土裂缝,提出了一种基于动态阈值的混凝土裂缝高抗噪提取方法.首先,通过灰度变换、高斯滤波、信息增强等技术弱化、去除噪声,增强图像中裂缝的亮度,提高裂缝与背景的对比度;然后,采用OTSU阈值分割算法去除伪裂缝,基于裂缝与干扰噪声面积的差异,引入动态阈值,实现各类型裂缝的提取;最后,基于边缘检测和裂缝骨架细化处理,计算裂缝的长度、宽度和面积3项特征参数.基于室内实验和室外实际桥梁拍摄的4组裂缝图像结果表明,4组裂缝的平均宽度分别为2.01、1.07、1.34、0.97 mm,说明该方法适用于不同背景下各类型裂缝的提取,具有较强的鲁棒性.     

IFT54 regulates IFT20 stability but is not essential for tubulin transport during ciliogenesis

Intraflagellar transport (IFT) is required for ciliogenesis by ferrying ciliary components using IFT complexes as cargo adaptors. IFT54 is a component of the IFT-B complex and is also associated with cytoplasmic microtubules (MTs). Loss of IFT54 impairs cilia assembly as well as cytoplasmic MT dynamics. The N-terminal calponin homology (CH) domain of IFT54 interacts with tubulins/MTs and has been proposed to transport tubulin during ciliogenesis, whereas the C-terminal coiled-coil (CC) domain binds IFT20. However, the precise function of these domains in vivo is not well understood. We showed that in Chlamydomonas, loss of IFT54 completely blocks ciliogenesis but does not affect spindle formation and proper cell cycle progression, even though IFT54 interacts with mitotic MTs. Interestingly, IFT54 lacking the CH domain allows proper flagellar assembly. The CH domain is required for the association of IFT54 with the axoneme but not with mitotic MTs, and also regulates the flagellar import of IFT54 but not IFT81 and IFT46. The C-terminal CC domain is essential for IFT54 to bind IFT20, and for its recruitment to the basal body and incorporation into IFT complexes. Complete loss of IFT54 or the CC domain destabilizes IFT20. ift54 mutant cells expressing the CC domain alone rescue the stability of IFT20 and form stunted flagella with accumulation of both IFT-A component IFT43 and IFT-B component IFT46, indicating that IFT54 also functions in IFT turn-around at the flagellar tip.     

Effect of Graphene Nanoplatelets addition on mechanical properties of pure aluminum using a semi-powder method

In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets(Al/GNPs)composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum(in tension), Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength(+14.7%), ultimate tensile strength(+11.1%) and lower failure strain( -40.6%). Surprisingly, compared to monolithic Al(in compression), Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength(- 7.8%),and lower failure strain(- 20.2%). The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum(+11.8%).Scanning electron microscopy(SEM), Energy-Dispersive X-ray Spectroscopy(EDS) and X-ray diffraction(XRD) were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively.     

基于供应链业务流程改造的模块化设计

首先通过对A公司供应链业务流程现状进行分析,发现存在的问题,然后从模块化的角度对业务流程进行改造,并进一步对改造后的业务流程所涉及的4个模块进行了设计.所提出的供应链模块化设计,可将复杂流程简单化,使供应链管理更加明确、清晰,对于提高供应链的运作效率,缩短对需求响应时间具有重要作用.