六亚甲基二异氰酸酯(HDI)交联壳聚糖与三甲基-烯氯化铵接枝共聚物/聚丙烯腈复合纳滤膜的研究

以壳聚糖与三甲基-烯氯化铵共聚物的水溶液为铸膜液,涂敷在聚丙烯腈超滤膜上,以六亚甲基二异氰酸酯为交联剂,制备了壳聚糖与三甲基一烯基氯化铵共聚物复合阳离子型纳滤膜.着重讨论了交联剂浓度、交联时间、干燥时间等因素的影响,采用单因素实验法确定了最佳的制膜条件:以0.75%(质量分数)的壳聚糖与三甲基-烯氯化铵共聚物水溶液为铸膜液,在50℃下干燥2h.在乙醇、HDI的质量比为50:0.32交联体系中,50℃水浴浸泡交联21h,50℃下热处30min.通过电镜扫描对膜结构进行观察.膜的截留分子量大约为900Da.并且,对该复合膜的性能进行了测试,分别探索了操作压力、料液浓度、料液类型等因素与膜性能的关系.在20℃,流速为30L/h,操作压力为1.2MPa时,对2000mg/L MgCl2、NaCl、MgSO4、CaCl2、Na2SO4、KCl、K2SO4的截留率分别为95.6%、66.4%、80.8%、95.4%、30.7%、53.7%、23.8%;通量分别为6.73、7.35、6.43、6.73、6.12、6.12、6.43L/(h·m-2).对不同类型无机盐的截留顺序为MgCl2≈CaCl2＞ MgSO4＞NaCl＞KCl＞Na2SO4＞K2SO4,呈现阳离子型复合纳滤膜的截留特征.流动电位曲线进一步说明了该复合膜的荷正电性,其电压渗系数β为6.8mV/MPa.     

戊二醛-硫酸混合交联壳聚糖/聚砜复合纳滤膜的结构与性能

以聚砜超滤膜(截留分子量10 000)为基膜,壳聚糖乙酸溶液为铸膜液,使用相转化法制备了戊二醛-硫酸混合交联壳聚糖/聚砜复合纳滤膜,并研究了壳聚糖浓度、戊二醛-硫酸混合交联剂等因素对该膜分离效果的影响.在操作压力1.6 MPa、流量30 L/h、20℃条件下,测得纯水通量为12.84 L/(m2.h),对2 000 mg/L的NaCl、MgCl2、Na2SO4和MgSO4的截留率分别为6.6%,94.5%,34%和80.4%,水通量依次为6.93,11.92,6.95和6.73 L/(m2.h);对分子量不低于280的有机物截留率高于90%;对0.01～0.1 mol/L KCl溶液在0.1～0.7 MPa下测定膜的流动电位为60～6 mV/MPa.电解质离子分离机理取决于膜与电解质离子之间的电荷作用.     

交联壳聚糖渗透蒸发膜分离乙醇—水

对壳聚糖/聚丙烯腈复合膜分别用戊二醛、硫酸、硫酸镍溶液进行了交联改性。交联后,分离选择性(α)大为提高。对戊二醛交联膜进行了乙醇水溶液的分离性能研究,结果表明,50℃、料液中合水率小于45%时,α大于670,渗透通量为100～700g/m~2·h。     

PVA-PAA共混／CA复合膜制备及其分离碳酸二甲酯的性能

研究了聚乙烯醇(PVA)、聚丙烯酸(PAA)共混膜的交联以及铸膜液配方和膜的热处理条件对PVA-PAA共混/CA复合膜渗透汽化(PV)分离碳酸二甲酯(DMC)/水混合物性能的影响.结果表明:交联的PvA-PAA膜在纯水中的溶解率小,改善了膜在长期运行中的稳定性;随着PAA含量、混合交联剂戊二醛和乙二醇的浓度以及热处理条件的变化,水渗透通量JH2O和渗透液的含水量CP-H2O呈规律性变化.在优化条件下制备的PVA-PAA共混/CA复合膜,PV分离DMC/水二元混合物的JH2O为100 g/(m2·h),CP-H2O接近100%,分离DMC/甲醇/水三元混合物时,可同时脱除甲醇和水,当操作温度升高,JH2O和JCH3OH分别增加,CP-DMC始终小于3.6%.     

季铵盐壳聚糖/聚砜复合纳滤膜的制备及性能表征

通过涂敷交联法制备了一种新型荷正电纳滤膜,其中以三甲基壳聚糖酰氯（TMC）为膜材料配制铸膜液,以聚砜超滤膜为基膜,环氧氯丙烷为交联剂.试验在全面考察该复合纳滤膜制备工艺基础上,重点探讨了交联时间对复合纳滤膜性能的影响.结果显示:该方法极大地缩短了交联时间,最优交联时间仅为2 h;同时最优条件所制备纳滤膜的纯水透过系数为14.09L/（m²·h·MPa）,表面粗糙度约为4 nm;对无机盐的截留顺序符合以下规律:MgCl₂>NaCl>MgSO₄>Na₂SO₄,满足荷正电纳滤膜的Donnan平衡模型.     

甲壳素黄原酸酯/聚丙烯腈复合纳滤膜的研究

甲壳素黄原酸酯溶液浇铸在聚丙烯腈超滤膜上,并与戊二醛交联制得一种新型的荷负电复合纳滤膜,研究了复合膜的制备影响因素及操作条件对膜性能的影响.0.4MPa下制备的纳滤膜对1000mg/LNa3PO4、K2SO4、Na2SO4、MgSO4、KCl、NaCl和MgCl2的截盐率分别为90.25%、89.01%、85.15%、36.42%、32.60%、28.90%和15.81%.利用复合膜对PO34-、SO24-有较高的截留率,此膜可用于脱除PO34-、SO24-等阴离子及水的净化.     

交联壳聚糖渗透蒸发膜分离乙醇—水

对壳聚糖/聚丙烯腈复合膜分别用戊二醛、硫酸、硫酸镍溶液进行了交联改性。交联后,分离选择性(α)大为提高。对戊二醛交联膜进行了乙醇水溶液的分离性能研究,结果表明,50°C、料液中合水率小于45％时,α大于670,渗透通量为100～700g/m~2·h。     

PVC/ PVA共混膜的制备及性能研究

采用相转化法制备了聚氯乙烯/聚乙烯醇(PVC/PVA)共混膜,讨论了聚乙烯醇与聚氯乙烯的共混相容性,以及聚乙烯醇含量对共混膜透过性能、亲水性能及机械性能的影响.实验结果表明,聚氯乙烯/聚乙烯醇共混体系为部分相容体系;当铸膜液中聚合物质量分数为12%、聚合物中聚乙烯醇质量分数为10%时,共混膜亲水性较好,水通量可由160.3 L/(m~2·h)增大到298.5 L/(m~2·h),对牛血清蛋白的截留率为82.5%,同时膜的弹性和韧性明显增强;聚乙烯醇可以有效地改善聚氯乙烯超滤膜的亲水性和机械性能,是优良的聚氯乙烯膜共混改性材料.     

戊二醛交联对CCMC/PVA复合膜性能的影响

采用流延成膜工艺制备了CCMC/PVA共混复合膜,研究了戊二醛交联剂对复合膜的透光性能和力学性能的影响。结果表明:交联处理膜的致密性和机械性能显著提高;当戊二醛添加量为2%(质量分数),体系的pH为10,交联反应温度为85℃,交联时间为35 min时,复合膜的拉伸强度可达18.91 MPa,断裂伸长率为226%,透光率为75%。     

不同分子量聚丙烯腈共混膜的制备与表征

将普通分子量聚丙烯腈(C-PAN,Mw=18 000)与超高分子量聚丙烯腈(UHMW-PAN,Mw=1 780 000)共混,采用干-湿相转化法制备不对称共混膜.考察了聚合物浓度、共混比、凝胶浴温度、刮膜厚度、添加剂浓度等对膜结构及性能的影响.采用扫描电镜、纯水通量和BSA截留率等测试手段对所制备膜的结构及性能进行表征.结果表明:共混比及成膜过程对共混膜的结构及性能有重要影响.当铸膜液浓度为12%,C-PAN/UHMW-PAN共混比为2∶3,凝胶浴温度为40℃,刮膜厚度为100μm时,共混膜的纯水通量为580L/(m~2·h),BSA截留率为99.99%.随添加剂浓度增加,交联膜大孔结构减少,海绵状孔结构增加,导致其纯水通量降低,BSA截留率增加,膜的结构可以通过上述因素进行结构调控.     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...