羧甲基甲壳素溶液的流变学性质

研究了羧甲基甲壳素（CMCH）溶液不同状态下的表观黏度,讨论了浓度、温度、外加盐、pH等对CMCH溶液表观黏度的影响,及在不同的溶剂中的触变行为,结果表明,羧甲基甲壳素的溶液是假塑性流体,n=0.70,K=0.50,其溶液的黏流活化能为19.82 kJ/mol;羧甲基甲壳素溶液的表观黏度随着加入盐的不同及加入量的不同而呈复杂变化,其溶液的表观黏度受到pH的影响,在碱性条件下,变化显著,在pH=9.0时达到最大值.其溶液的触变行为受到溶剂的影响,溶剂不同,触变性也不同.     

羧甲基壳聚糖和羧甲基甲壳素的生物学性质研究和比较

制备并纯化出了医用级羧化度为103．14％、脱乙酰度为97．18％的羧甲基壳聚糖和羧化度为96．37％的羧甲基甲壳素，对其对成纤维细胞生长作用和体内外可降解性、生物相容性进行了研究。结果表明，两种多糖均能不同程度地促进成纤维细胞的生长，其中以100μg／ml的羧甲基壳聚糖效果最好。体内外降解实验表明二者均具有良好的可降解性和生物相容性，其中羧甲基甲壳素降解的速度相对较快，而羧甲基壳聚糖的生物相容性更好，在体内降解7d后，已无明显炎症反应。     

一锅连续法制备羧甲基壳聚糖工艺研究

以甲壳素为原料,95%乙醇为反应介质,一锅连续法制备羧甲基壳聚糖的适宜条件为:m(甲壳素)∶m(氢氧化钠)∶m(一氯乙酸)=1∶2.5~3.5∶3~4,脱乙酰化反应温度90℃~100℃;羧甲基化反应温度40℃~50℃,反应时间3 h~4 h,羧甲基壳聚糖产率可达115%(以甲壳素计),羧化度为1.16,4%水溶液的黏度为1662 m Pa.s。该法用碱量小,反应时间短,用水少,无废液排放,顺应环保要求而且产品黏度高。收率大,可降低其生产成本。     

TEMPO/NaClO/NaBr表面改性甲壳素及吸附性能研究

以甲壳素为原料,次氯酸钠为氧化剂,2,2,6,6-四氧基哌啶-1-氧化物自由基和溴化钠为催化剂,制备了氧化甲壳素。通过红外光谱、X射线衍射仪、碳核磁共振图谱和扫描电镜对其结构和形貌进行表征,研究了其对亚甲基蓝的吸附性能。结果表明,氧化改性不改变α-甲壳素晶型,使甲壳素重复结构单元C6位置的部分羟甲基被氧化成羧基,表面由粗糙致密变为光滑结构。氧化甲壳素对亚甲基蓝吸附能够使用Pseudo-Second-order模型和Langmuir等温吸附方程拟合的自发放热反应。相同条件下,氧化甲壳素对亚甲基蓝的吸附能力优于未改性甲壳素和活性炭。     

甲壳胺纤维的制备

一、甲壳胺纤维的结构甲壳素脱去分子中的乙酰基,转变为甲壳胺。甲壳胺的溶解性能较好,故称之为可溶性甲壳素,或称脱乙酰甲壳素、脱乙酰壳多糖、甲壳胺、聚甲壳糖、聚氨基葡糖、黏性甲壳素等。     

基于甲壳素的手性分离材料

甲壳素是一种丰富的可再生资源,将甲壳素在碱性条件下脱去乙酰基得到壳聚糖,甲壳素和壳聚糖分子骨架有大量的手性碳原子存在,且含有较多的羟基、乙酰氨基或氨基活性官能团,容易进行化学改性得到有较好手性识别能力的衍生物,且它们能以膜、纤维、凝胶及微球等不同形式出现,可作为各种手性分离介质。概述了近年来甲壳素衍生物作为手性分离介质的重要研究进展,主要包括甲壳素及其衍生物的色谱手性固定相、手性分离膜、分子印迹聚合物。重点介绍了这些手性分离介质的结构、制备及性能,并展望了甲壳素衍生物手性分离介质的研究前景。     

羧甲基纤维素与丙烯酰胺接枝共聚及共聚物的性能

研究了羧甲基纤维素-丙烯酰胺接枝共聚反应。优化反应条件为:单体浓度20%,引发剂用量300m g/L,初始温度40℃,初始pH值8。通过红外光谱分析、热分析、X射线衍射分析对接枝共聚物结构进行了验证,并对接枝共聚物特性黏数和大分子回旋半径进行了研究。实验得出接枝共聚物回旋半径随聚丙烯酰胺回旋半径与羧甲基纤维素回旋半径变化的关系式,同时证明接枝共聚物在特性黏数、抗温及抗盐性质方面均优于羧甲基纤维素和聚丙烯酰胺。     

羟乙基甲壳素水溶液的流变特性

羟乙基甲壳素是甲壳素的一种水溶性醚化产物，采用气固相制备方法可以得到醚化度高、水溶性好的羟乙基甲壳素。研究了羟乙基甲壳素水溶液在不同温度、不同浓度和不同醚化度下的流变特性，结果表明羟乙基甲壳素水溶液为非牛顿流体，非牛顿指数在0.83～0.98之间，粘流活化能在18-33kJ／mol之间，结构黏度指数在0.47～2.26之间，松弛时间随着剪切速率的增大而逐渐缩短。     

甲壳素与壳聚糖的改性及应用

甲壳素、壳聚糖及其衍生物是一种天然高分子,随着对其研究的深入发展,涉及的内容和应用范围越来越广泛.概述了甲壳素、壳聚糖的结构、性质及其化学改性和共混改性的方法,简单介绍了它们的应用领域.     

甲壳素和壳聚糖的应用研究进展

综述了甲壳素和壳聚糖的应用研究进展。着重介绍了甲壳素和壳聚糖在分析化学、催化、膜材料等领域中的应用。     

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 ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.