真空蒸镀Ag_2O/HDPE膜对奶酪的保鲜性研究

在自制的高密度聚乙烯(HDPE)膜上真空蒸镀氧化银(Ag_2O)得到Ag_2O/HDPE复合膜,考察该膜的抗菌性,并对奶酪进行包装,考察Ag_2O/HDPE膜对奶酪的保鲜性。结果发现,Ag_2O/HDPE膜对大肠杆菌和金黄色葡萄球菌均有强抗菌性。相比于HDPE膜,真空蒸镀Ag_2O/HDPE膜能有效抑制奶酪中微生物的生长、延缓奶酪贮藏期内感官品质的下降,包装7 d的奶酪的pH值更接近标准样,Ag_2O/HDPE膜对奶酪具有一定的保鲜性。此外热重分析结果表明,不同包装材料对奶酪的热分解速率有一定影响,在320℃附近,真空蒸镀Ag_2O/HDPE膜所包装奶酪的热失重比纯HDPE膜所包装奶酪的热失重小。     

表面沉积铜纳米颗粒的细菌纤维素/壳聚糖交联复合膜的制备及其抗菌性能研究

通过戊二醛交联制备了细菌纤维素/壳聚糖复合材料,并采用磁控溅射技术在交联复合膜表面沉积铜(Cu)纳米颗粒。利用扫描电子显微镜观察纳米纤维膜表面形貌,采用傅里叶红外光谱仪、热重分析仪和X射线衍射仪比较交联复合前后以及镀铜前后复合膜基本化学结构、热稳定性和晶面结构的变化。通过能量色散X射线光谱对壳聚糖和铜在复合膜表面的分布情况进行表征。同时借助抗菌实验探究复合膜对金黄色葡萄球菌和大肠杆菌的抗菌能力。结果表明:壳聚糖与细菌纤维素发生了有效交联,改变了细菌纤维素的基本形貌、化学结构、晶体形态以及热学性能,并且镀铜后交联复合膜的抗菌性能得到了明显的提升(膜与细菌接触20min,对金黄色葡萄球菌和大肠杆菌的抗菌效果均达到了99.999%)。     

生物纳米银/聚醚砜复合膜的制备及性能研究

采用生物还原法制备生物纳米银(Bio-Ag~0),通过相转化法制备Bio-Ag~0/聚醚砜(PES)复合膜。扫描电镜分析表明,Bio-Ag~0可以均匀稳定地分散在PES基膜中。纳米银共混可以改善膜断面孔结构,在不影响蛋白质截留率的前提下提高复合膜的纯水通量。采用抑菌环、菌落计数及孔板生物膜培养法研究了Bio-Ag~0/PES复合膜的抗污染性能。结果显示,Bio-Ag~0不仅使纳米复合膜具备良好的抗菌性,而且能有效地抑制细菌在膜表面的粘附及生物膜的形成,显著提高膜材料的抗生物污染性能。     

PET/SiO_x基高阻隔性抑菌膜的制备和表征

分别采用紫外辐照和硅烷偶联剂(KH550)对聚酯(PET)/SiO_x膜的SiO_x镀层进行表面改性以制备PET/SiO_x/壳聚糖-纳米ZnO复合膜。水接触角测试发现,相比于紫外辐照,KH550改性能显著改善SiO_x的表面亲水性,从而成功制备得到PET/SiO_x/壳聚糖和PET/SiO_x/壳聚糖-纳米ZnO复合膜。随后采用电子扫描显微镜(SEM)观测复合膜的微观形态,并对该膜的力学性能、阻隔性和抑菌性进行了表征。SEM照片显示,该复合膜表面光滑,断面呈现层状结构。对该膜的力学性能测试结果发现,表面镀层(SiO_x)使PET膜的力学性能有所改善,但涂层(KH550、壳聚糖和壳聚糖-纳米ZnO)对PET/SiO_x膜的力学性能无显著影响。SiO_x镀层能有效改善PET膜的阻隔性,KH550涂层使PET/SiO_x膜的阻隔性进一步提高,壳聚糖及壳聚糖-纳米ZnO涂膜使复合膜的阻氧性进一步提高,而使其阻水性略有降低。此外,PET/SiO_x/壳聚糖及PET/SiO_x/壳聚糖-纳米ZnO膜对金黄色葡萄球菌及大肠杆菌均有良好的抑菌作用,其中PET/SiO_x/壳聚糖-纳米ZnO膜的抑菌性最强。该类膜有望应用于未来的保鲜包装。     

聚乳酸纳米抗菌复合膜对冷却猪肉保鲜效果的研究

目的 研究添加无机纳米TiO2和无机纳米TiO2+Ag的聚乳酸膜对冷却肉保鲜效果的影响。方法 采用溶剂浇注法,以聚乳酸（PLA）为成膜基质,添加质量分数为9%的柠檬精油（LEO）作为增塑剂和纳米粒子,制备PLA膜、PLA/LEO膜、PLA/LEO/TiO2膜、PLA/LEO/TiO2+Ag膜,用来包装冷却肉,以LDPE膜包装作为对照组,在冷藏温度（4±1）℃下测定其理化指标的变化规律。结果 采用聚乳酸纳米抗菌复合膜保鲜冷却肉的效果均显著大于LDPE膜、PLA膜、PLA/LEO膜（P＜0.05）。聚乳酸纳米抗菌复合膜能够有效地抑制冷却肉表面微生物的生长繁殖,延缓蛋白质和脂肪的氧化,延长冷却肉货架期。结论 聚乳酸纳米抗菌复合膜可以保证冷却肉的品质,以及延长货架期,且PLA/LEO/TiO2+Ag膜包装冷却肉的保鲜效果最佳。     

基于P_2O_5/SiO_2与磺化聚醚醚酮合成的无机/有机复合质子交换膜

采用溶胶-凝胶法制备P2O5/SiO2溶胶与P2O5/SiO2粉末,之后分别与磺化聚醚醚酮(SPEEK)复合,制得无机/有机复合质子交换膜并研究了两种膜的形貌、力学性能以及质子电导率。与纯SPEEK膜相比,P2O5/SiO2无机成分的引入能显著改善复合膜的质子导电性能。同时,P2O5/SiO2的不同引入方式导致复合膜具有不同的结构,进而引起复合膜力学性能与质子导电性能上的差异。在所制备的无机/有机复合膜中,含有40%P2O5/SiO2(质量分数)粉末的复合膜的质子电导率达到1.6×10-2 S/cm,其所组装的单电池的开路电压为0.95V,峰值功率密度达到446mW/cm2。     

基于仿生机理的超疏水有机无机复合膜的制备

采用溶胶-凝胶法制备了粒径分布窄、单分散性好的SiO2颗粒,并用低表面能硅烷偶联剂对其进行改性.改性后的SiO2粒子与聚偏氟乙烯(PVDF)按一定的质量比共混,利用相转化法制备了有机无机复合微孔膜.分析了偶联剂种类及SiO2粒径对微孔膜疏水性的影响,探讨了微孔膜表面能对其疏水性能的影响,并对复合膜的微观形貌进行了表征.研究结果表明:硅烷偶联剂可以有效阻止SiO2溶胶的凝胶作用,降低SiO2的表面能,而表面能对膜的疏水性有显著的影响;制备的复合微孔膜具有良好的有机-无机双微观阶层结构,疏水角达到了151°.     

纳米TiO2固相光催化降解高密聚乙烯

在高密聚乙烯(HDPE)中加入经表面处理的纳米TiO2粒子,用共混法制备HDPE-TiO2纳米复合膜.利用失重、FT-IR、SEM对光照前后的纯膜及复合膜进行表征.实验表明复合膜在空气中能被紫外光有效降解,且其降解速度远远大于纯膜的降解速度.紫外光照780h后,二氧化钛含量为1%的复合膜失重达到了58.1%,而纯膜的光失重率仅为21.2%.     

醋酸纤维素/TiO_2复合膜的制备及性能研究

用溶胶-凝胶法制备纳米TiO2,以纳米TiO2作为无机相添加剂,以醋酸纤维素(CA)作为成膜剂,乙酸甲酯为溶剂,使用流延法制备醋酸纤维素/TiO2复合膜。运用FT-IR、UV-Vis等方法对复合膜进行表征。结果表明,复合膜的热稳定性、耐碱性以及对紫外线的吸收均有所提高。在光照下,对E.coli的抗菌性有所提高。     

膜蒸馏脱盐用超疏水复合膜的研制

通过溶胶凝胶法和表面涂覆法,先后在PVDF中空纤维膜表面引入亲水SiO_2纳米粒子和低表面能PDMS涂层,构建具有高粗糙度、低表面能的超疏水复合膜,并探究SiO_2粒径、SiO_2溶液涂覆时间、PDMS涂覆时间等条件对复合膜性能的影响。SiO_2/PVDF复合膜接触角只有25.8°,而PDMS/SiO_2/PVDF复合膜接触角则达到162.3°,膜蒸馏通量约24.5 kg/(m~2·h);在60 h质量分数3.5%氯化钠盐溶液膜蒸馏测试中性能稳定,截留率始终保持在99.8%以上.     

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 ...