齿科材料用酸酐类功能单体研究进展

齿科材料用酸酐类功能单体是目前应用最广泛、效果优良的一类齿科材料用功能单体。本文介绍了目前对酸酐类功能单体的结构、合成方法及在不同黏结环境下对黏结强度的提高效果的研究成果，讨论了酸酐类功能单体结构与单体本身性能和树脂黏结性能及其它性能关系，并着重探讨了对功能单体隔离基团结构、黏结性基团与可聚合基团位置及数量与黏结强度提高关系研究的重要性，最后对酸酐类功能单体的研究方向作了筒要的阐述．     

CO2共聚单体及产物改性的研究进展

CO2共聚物的研究开发在环境保护、资源再利用及新材料研究领域中都具有重要的意义。CO2共聚单体是影响其共聚产物结构、性能及成本的重要因素。文中综述了与CO2催化共聚的各类单体的研究进展及产物理化性能的特点,这些单体主要包括环氧化合物、烯类化合物和可再生型环氧烷烃;并介绍了通过三元共聚以调控分子链单元与分子链结构,从而改善聚合产物的理化性能。进一步就今后CO2催化共聚的发展方向进行了探讨。     

含苯乙炔基共轭单体的合成及荧光性能

通过苯乙炔基锂和氯硅烷的偶合反应合成了系列含苯乙炔基共轭单体(PES)。通过红外光谱(FT-IR)、核磁共振(1H-NMR、13C-NMR、29Si-NMR)、质谱分析(MS)和元素分析(EA)对其结构进行了表征,利用紫外光可见分光光谱(UV-Vis)和光致发光光谱(PL)研究了共轭单体的荧光性能,讨论了不同共轭结构与单体性能之间的依赖关系。结果表明,合成得到的共轭单体易溶于常见的有机溶剂(四氢呋喃、氯仿、丙酮、甲苯等)。而且随着单体结构中共轭程度的增大,紫外吸收光谱的最大吸收峰和荧光光谱的发射峰均发生不同程度的红移。其中,四苯乙炔基硅烷(TPES)由于结构极具对称性且共轭程度最高,发射峰红移至368 nm和738 nm处,在可见光范围内发射红光。     

新一代高性能POSS-聚合物材料

描述了多面体聚硅倍半氧烷（Polyhedral Oligomeric Silsesquioxane,POSS)单体的结构与性能,POSS单体改性聚合物在塑料工业,航空与空间等领域的应用现状与前景,并对POSS单体合成技术,成本,POSS单体一步形成串凳式,悬笼式和笼－笼连接式结构作了综合评述。     

高吸油性树脂的合成与性能

以甲基丙烯酸酯为单体，双烯化合物为交联剂，采用悬浮聚合方法合成高吸油性树脂。研究了单体结构、引发剂用量、交联剂用量及共聚单体配比对树脂性能的影响，并考察了高吸油性树脂对水面浮油的回收性能。     

有机氟改性丙烯酸树脂的合成及研究

使用不同的有机氟单体对丙烯酸树脂进行改性,合成了具有低表面能性质的有机氟改性丙烯酸树脂;对树脂进行了红外和分子量检测,并测试了涂膜的附着力、抗冲击力、接触角等各项性能;研究了不同的氟单体种类、氟单体用量以及合成工艺对树脂性能的影响。结果表明,氟单体对丙烯酸树脂进行低表面能改性效果明显,其中含有叔碳原子和甲基结构,分子中含有12个F的G04单体效果最为理想;采用滴加氟单体工艺能够显著增大树脂的接触角;当氟单体G04用量在16.7%时,树脂与水的接触角最大可达104.5°。     

基于咔唑的共轭聚合物材料的合成及性能研究

由咔唑以及3-噻吩甲酸出发,经过合理的化学修饰,合成了单体4,7-二溴正辛基咔唑M1和单体1,5-二(正三正丁基锡)-4,8-二(正十二烷氧基)苯并[1,2-b∶4,5-b’]二噻吩M2,然后单体M1与单体M2通过Suzuki偶联聚合合成了共轭聚合物P1。并对聚合物P1进行了一系列的结构表征和性能测试,结果表明P1的光学能带隙为1.56eV,电化学能带隙为1.57eV,5%热失重温度分别为314℃,显示出了良好的光学性能、热稳定性和电化学氧化还原性能。     

苯胺及吡咯的共聚合研究进展

综述了苯胺及吡咯的共聚合机理、共聚物结构和共聚研究现状。着重讨论了取代基对聚合过程和聚合物性能的影响，以及在与其它共轭单体和非共轭单体共聚时的工艺方法．     

聚N-亚芳基苯并咪唑醚砜的无规共聚与性能表征

选用砜基双苯并咪唑作为第三单体,与砜基二酚以及砜基二氟单体进行亲核取代共聚,将苯并咪唑结构引入聚醚砜主链中,合成了无规共聚聚N-亚芳基苯并咪唑醚砜。对聚合物的涂覆成膜条件进行了探索,并对其表面性能、光学性能、热学性能、溶解性能和力学性能进行了表征。实验结果表明,当砜基二酚单体用量高于砜基双苯并咪唑单体用量时,所得聚合物可以通过涂覆法得到平整而透明的薄膜;双苯并咪唑单体的引入使得聚合物的耐热性有较大提高(玻璃化转变温度和初始分解温度分别升高56℃和44℃),但同时也使得聚合物的在有机溶剂中的溶解性能有所下降;聚合物薄膜具有较好的表面平整性和透光性,双苯并咪唑结构的存在有利于提高薄膜的平整性,但也使得薄膜的透光性有所下降;聚合物薄膜呈现脆性状态,且脆性程度随着双苯并咪唑单体用量的增大而增大,其断裂伸长率为3.1%~7.2%。     

制备超支化聚酰亚胺的研究进展

超支化聚酰亚胺(HBPIs)具有超支化聚合物和聚酰亚胺的综合性能,较高的玻璃化温度和良好的溶解性能。总结了用AB2型单体、A2+B3型单体和A2+B′B2型单体合成HBPIs的方法,并对其性能及应用进行了说明。AB2型单体难以合成,A2+B3型单体聚合虽然具有易制备和可以修饰结构的优点但容易产生凝胶化反应,用A2+B′B2型单体制备HBPIs可避免凝胶化反应,有利于实现HBPIs的大规模生产。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.