Effect of annealing atmosphere on the structure and dielectric properties of unfilled tungsten bronze ceramics Ba4PrFe0.5Nb9.5O30

Unfilled tungsten bronze ceramics with the nominal formula Ba₄PrFe_0.5Nb_9.5O₃₀ were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N₂-annealed sample had the largest cell volume. Low-temperature spectrum showed that N₂ annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O₂ annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N₂-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N₂-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder.     

乌鲁木齐机场多普勒天气雷达故障统计分析

文章针对乌鲁木齐机场多普勒天气雷达(以下简称ADWR)2009~2019年发生的故障次数、故障分布以及备件更换情况,逐年统计故障率,深入分析了ADWR系统性能,总结出运行维护中的经验,就如何更好地提高雷达业务运行指标提出建议,以提高ADWR雷达的维护、维修能力,建立有针对性的备件管理,为科学的业务运行管理提供依据。     

起重机自重应力对安全评估中应力测试实验结果的影响

应力测试是起重机安全评估中必须进行的一项检测。目前在安全评估工作中常采用应变电测法来采集起重机工作过程中的应力时程数据,由于该方法只能采集到结构由于载荷变化产生的应力,而无法采集到结构因自重产生的应力,导致应力测试无法获取结构的完整应力。利用起重机金属结构自重应力在总应力中占有的权重,分析其对应力测试实验结果的影响大小,试验结果表明在危险截面自重应力大小占总应力大小可达60%,此时不考虑自重应力进行结构安全性的判定是不全面的。可考虑利用仿真技术获取自重应力[1,2],从而使得安全评估应力测试实验结论更加准确。     

Preparation and properties of Eu and Dy co-doped strontium aluminate long afterglow nanomaterials

The long afterglow nanomaterials of strontium aluminate co-doped by Eu and Dy have been synthesized by co-precipitation combined hydrothermal method. The effects of hydrothermal time, calcination time, pH value, the amount of aluminum nitrate, activator, co-activator and flux H₃BO₃ on the fluorescence properties of the product were investigated by means of single factor optimization experiment. Then the orthogonal experiment was employed to obtain the optimal synthesis conditions that are as follows: n_Dy/n_Eu = 2.5, t_c = 2.5?h, n_Eu/n_Sr = 0.02, t_h = 8?h. Subsequently, the optimal synthesis conditions were verified by three repeated experiments, and the obtained products were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and fluorescence spectrometer. The results showed that the synthesized target products all were the mixed crystal phase of SrAl₂O₄ and Sr₄Al_l4O₂₅. The particles presented regular spherical-like with size ~ 100?nm. The dopants Eu and Dy were confirmed existed in the SrAl₂O₄ powders. The fluorescence and afterglow data of the target products were better than that in the orthogonal experiment scheme. The primary emission spectra band was in the range of 400–600?nm with characteristic peak located at ~ 460?nm corresponding to the transitions of Eu²⁺ ions from 4f⁶5d→4f⁷, and the blue light can be observed by naked eyes. The similar fast-decaying and slow-decaying processes were displayed in all the afterglow curves, and the initial afterglow brightness of the target product is apparently higher than that of products synthesized by the orthogonal experiment. The synthesized target products, which show excellent long afterglow performance, present a great application prospects in the aspects of ceramics, plastics, arts and crafts, ink and coating.     

Allosteric p97 Inhibitors Can Overcome Resistance to ATP-Competitive p97 Inhibitors for Potential Anticancer Therapy

Abstract : A major challenge of targeted cancer therapy is the selection for drug-resistant mutations in tumor cells leading to loss of treatment effectiveness. p97/VCP is central regulator of protein homeostasis and a promising anticancer target because of its vital role in cell growth and survival. One ATP-competitive p97 inhibitor, CB-5083, has entered clinical trials. Selective pressure on HCT116 cells dosed with CB-5083 identified five different resistant mutants. Identification of p97 inhibitors with different mechanisms of action would offer the potential to overcome this class of resistance mutations. Our results demonstrate that two CB-5083 resistant p97 mutants, N660 K and T688 A, were also resistant to several other ATP-competitive p97 inhibitors, whereas inhibition by two allosteric p97 inhibitors NMS-873 and UPCDC-30245 were unaffected by these mutations. We also established a CB-5083 resistant cell line that harbors a new p97 double mutation (D649 A/T688 A). While CB-5083, NMS-873, and UPCDC-30245 all effectively inhibited proliferation of the parental HCT116 cell line, NMS-873 and UPCDC-30245 were 30-fold more potent in inhibiting the CB-5083 resistant D649 A/T688 A double mutant than CB-5083. Our results suggest that allosteric p97 inhibitors are promising alternatives when resistance to ATP-competitive p97 inhibitors arises during anticancer treatment.     

超双疏含氟聚合物的研究进展

超双疏功能性材料在当代化工材料中有着重要的地位，其独特的界面性能使得其在各个领域的应用中大显身手。本文介绍了近年来国内外对含氟聚合物在超双疏领域的研究近况，包括超双疏含氟聚合物的结构特点和合成方法等。含氟聚合物的表面拥有超低的表面能和独特的空间排列方式，通过对比不同结构的含氟聚合物分子与其性能的关系以及对各类含氟聚合物合成方法的调研，发现含氟聚合物作为超双疏涂层材料的使用十分广泛，其结构中含氟单体主要为氟取代丙烯酸酯类，合成方法多为乳液聚合。超疏水含氟聚合物与纳米颗粒材料的结合是当今研究的热点，文中列举了大量研究实例，希望其中的研究方法和合成路线等能对今后该领域的研究起到一定的借鉴作用。     

基于介形类生态特征评价湖南某铀矿山地表水放射性环境

湖南某铀矿为我国一重要铀资源生产基地，长年的矿冶活动使该铀矿冶地域生态环境不可避免地遭到了一定程度破坏。本文以该铀矿冶地域介形类为研究对象，分析其分布与生态特征，并利用该生物评价本矿冶地域地表水放射性污染状况。结果表明，Cypridopsis vidua在溪流与河流中均有分布，Helerocypris incongruens仅发现于河流，两者丰度均不高。利用该两种介形类丰度及总丰度变化可指示水体铀浓度的变化，丰度越小，铀含量越大，反之亦然。Shannon-Wiener物种多样性指数与水体铀浓度呈明显负相关，表明也可利用介形类生物指数指示水体铀浓度。该生物指数明显偏低，说明该铀矿冶地域地表水环境质量需要改善，放射性污染应引起足够重视。     

Fenton 絮凝工艺去除废水中的有机物试验

为了研究废水中有机物的去除问题，针对某企业含有机物废水进行了对比试验，采用了Fenton 絮凝联合工艺去除废水中的COD（化学需氧量）和浊度，考察了初始pH值、H2O2投加量、H2O2与Fe2+投加物质的量比、反应时间、絮凝剂投加量以及絮凝剂投加时的pH值对COD以及浊度去除效果的影响。结果表明，采用最佳工艺参数组合后，浊度去除率和COD的去除率分别为99.32%和97.27%。     

The effect of alkali metal oxide on the properties of borosilicate fireproof glass: Structure,thermal properties,viscosity, chemical stability

The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R₂O–CaO–B₂O₃–SiO₂) systematically. Because the glass would emulsify when Li₂O was added to the glass batch, this article did not discuss Li₂O. The results showed that when the amount of Na₂O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na₂O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased.     

Advances in statistical mechanics of rock masses and its engineering applications

To efficiently link the continuum mechanics for rocks with the structural statistics of rock masses,a theoretical and methodological system called the statistical mechanics of rock masses(SMRM)was developed in the past three decades.In SMRM,equivalent continuum models of stressestrain relationship,strength and failure probability for jointed rock masses were established,which were based on the geometric probability models characterising the rock mass structure.This follows the statistical physics,the continuum mechanics,the fracture mechanics and the weakest link hypothesis.A general constitutive model and complete stressestrain models under compressive and shear conditions were also developed as the derivatives of the SMRM theory.An SMRM calculation system was then developed to provide fast and precise solutions for parameter estimations of rock masses,such as full-direction rock quality designation(RQD),elastic modulus,Coulomb compressive strength,rock mass quality rating,and Poisson’s ratio and shear strength.The constitutive equations involved in SMRM were integrated into a FLAC3D based numerical module to apply for engineering rock masses.It is also capable of analysing the complete deformation of rock masses and active reinforcement of engineering rock masses.Examples of engineering applications of SMRM were presented,including a rock mass at QBT hydropower station in northwestern China,a dam slope of Zongo II hydropower station in D.R.Congo,an open-pit mine in Dexing,China,an underground powerhouse of Jinping I hydropower station in southwestern China,and a typical circular tunnel in Lanzhou-Chongqing railway,China.These applications verified the reliability of the SMRM and demonstrated its applicability to broad engineering issues associated with jointed rock masses.