Li2AGeO4 (A = Zn,Mg): Two novel low-permittivity microwave dielectric ceramics with olivine structure

Two low-permittivity dielectric materials Li₂AGeO₄ (A?=?Zn, Mg) were prepared via the solid-state reaction method. X-ray diffraction analysis and Rietveld refinement indicated that both ceramics crystallize in an orthorhombic olivine structure with a space group Pmn2₁. Dense ceramics with high relative density and homogeneous microstructure were obtained. Li₂ZnGeO₄ densified at 1200?°C possessed a relative permittivity ε_r?=?6.5, a quality factor Q?×?f?=?35,400?GHz, and a temperature coefficient of resonant frequency. Li₂MgGeO₄ exhibited ε_r?=?6.1, Q?×?f?=?28,500?GHz, and τ_f?=?–74.7?ppm/°C when sintered at 1220?°C. Additionally, the large negative τ_f values of Li₂AGeO₄ (A?=?Zn, Mg) ceramics were successfully adjusted compensated by forming composite ceramics with CaTiO₃ and near-zero τ_f values of +2.9?ppm/°C and +5.8?ppm/°C were achieved in 0.92Li₂ZnGeO₄-0.08CaTiO₃ and 0.90Li₂MgGeO₄-0.10CaTiO₃, respectively.     

Polyurethane/doxorubicin nanoparticles based on electrostatic interactions as pH‐sensitive drug delivery carriers

In order to obtain a pH‐sensitive delivery carrier for doxorubicin (DOX), DOX‐loaded polyurethane (PU·DOX) nanoparticles were readily prepared in water by electrostatic interactions between amphiphilic polyurethane with carboxyl pendent groups (PU‐COOH) and doxorubicin hydrochloride (DOX·HCl). The structures of the products obtained were characterized by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy, gel permeation chromatography, UV–visible spectroscopy, dynamic light scattering and transmission electron microscopy. The average hydrodynamic size of the PU·DOX nanoparticles was around 182 nm with negative surface charge (?1.1 mV) and a spherical or rodlike shape. PU·DOX nanoparticles had a higher drug‐loading content of 14.1 wt%. The in vitro drug release properties of PU·DOX nanoparticles were investigated at pH 4.0, 5.0 and 7.4, respectively. PU·DOX nanoparticles exhibited a good pH‐sensitive drug release property, but there was almost no release of DOX from PU·DOX nanoparticles at pH 7.4. The in vitro cellular uptake assay and the Cell Counting Kit‐8 assay demonstrated that PU·DOX nanoparticles had a higher level of cellular internalization and higher inhibitory effects on the proliferation of human breast cancer (MCF‐7) cells than pure DOX. The enhancement of the inhibition effects resulted from increasing apoptosis‐inducing effects on MCF‐7 cells, which was related to the enhancement of Bax expression and the reduction of Bcl‐2 expression confirmed by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay, real‐time polymerase chain reaction (PCR) assay and western blot assay. © 2018 Society of Chemical Industry     

Isothermal crystallization kinetics and subsequent melting behavior of β‐nucleated isotactic polypropylene/graphene oxide composites with different ordered structure

The effects of ordered structure on isothermal crystallization kinetics and subsequent melting behavior of β‐nucleated isotactic polypropylene/graphene oxide (iPP/GO) composites were studied using differential scanning calorimetry. The ordered structure status was controlled by tuning the fusion temperature (T_f). The results showed that depending on the variation of crystallization rate, the whole T_f range could be divided into three regions: Region I (T_f > 179 °C), Region II (170 °C ≤ T_f ≤ 179 °C) and Region III (T_f < 170 °C). As T_f decreased from Region I to Region III, the crystallization rate would increase substantially at two transition points, due to the variation of the ordered structure status. Calculation of Avrami exponent n indicated that the ordered structure induced the formation of two‐dimensional growing crystallites rather than three‐dimensional growing crystallites. Moreover, in the case of isothermal crystallization, the ordered structure effect (OSE) can also greatly increase the relative content of β‐phase (β_c). In Region II, OSE took place, resulting in evident increase of β_c, achieving 92.4% at maximum. The variation of the isothermal crystallization temperature (T_iso) had little influence on the T_f range (Region II) of the OSE. The higher T_f in Region II was more favorable for the formation of higher β_c. The ordered structure was favorable for the improvement of the nucleating efficiency of β‐nucleating agent (β‐NE), and was more effective for the improvement of lower β‐NE. © 2018 Society of Chemical Industry     

基于TCP协议的WinCC V14与CPU315-2PN/DP通讯建立应用

在实际工业生产中，经常会用到比较重要的第三方专用设备，如立磨、辊压机等，这些专用设备一般会有一些重要的运行参数和控制参数，上位机HMI软件通过读取这些运行数据能够实时了解当前设备的运行状况，通过设置一些控制参数来完成所需要的控制需求。如何读取这些数据以及发送一些控制数据，是相对来说比较困难的问题，对于行业新手来说更是无从下手。     

A dense and compact laser cladding layer with solid metallurgical bonding significantly improved corrosion resistance of Mg alloy for engineering applications

Although Mg alloy attracts great attention for engineering applications because of high specific strength and low density, low corrosion resistance limits its extensive use. In this study, Mg–Al–Zn–Mn alloy was treated via a laser cladding process to generate a dense and compact laser cladding layer with solid metallurgical bonding on the substrate for improving corrosion resistance, effectively hindering the corrosion pervasion into Mg alloy. The corrosion current density declined from 103 μA/cm² for Mg alloy to 13 μA/cm² for the laser cladding layer in NaCl aqueous solution. Moreover, the laser cladding layer was slightly corroded in comparison with Mg alloy in NaCl aqueous solution. Besides, the microhardness of the cladding layer reached a mean value of 170.5 HV, 3.1 times of Mg alloy (56.8 HV) due to the in situ formation of hardening intermetallic phases. Wear resistance of laser cladding layer was also obviously improved. These results demonstrated that the laser cladding layer obviously enhanced anticorrosion property of Mg alloy for engineering applications.     

K2,4,p的点可区别IE-全染色

该文利用色集合事先分配法、构造染色法、反证法讨论了完全三部图K_2,4,p的点可区别IE-全染色问题，确定了K_2,4,p的点可区别IE-全色数。     

K4,4,p的点可区别的IE-全染色(p≥1008)

该文利用色集事先分配法、构造染色法、反证法探讨了完全三部图K_4,4,p (p≥1008)的点可区别IE-全染色问题，确定了K_4,4,p (p≥1008)的点可区别IE-全染色数。     

基于随机场和数学形态学的水泥基材料三维孔隙结构建模研究

孔隙介质在微米及纳米尺度的孔隙结构决定着材料在宏观尺度的物理和力学特征.构建三维孔隙结构数值模型,对于进一步研究水泥基材料的力学及渗流特性有着重要的意义.考虑到传统的基于简单单元的建模方法无法呈现出孔隙分布的随机性和孔隙形状的复杂性,本文采用偏移集理论将连续的高斯随机场阈值化为二相场,并通过多个具有不同相关长度的二相场联合完成模型构建.采用数学形态学图像分析方法分析模型的孔径分布,验证模型构建出满足试验孔径分布曲线的孔隙结构.研究表明,该方法能够使模型孔隙网络的空间形态随机化,且对孔隙率和孔径分布也有着较好的控制.     

基于ANSYS的智能搬运AGV小车下车体结构分析

本文以智能搬运AGV小车下车体机械结构为例，应用ANSYS12.0对智能搬运AGV小车下车体机械结构进行有限元分析，旨在校核该结构的合理性、可靠性；进而为新一代AGV小车车体机械结构的设计提供重要科学性保证。