重塑黄土一维应变实验粒子速度测试波形的拉格朗日分析

利用57 mm口径一级轻气炮,飞片选用有机玻璃,对密度1.8 g/cm3、饱和度22%的重塑黄土,进行了一系列一维应变实验。通过在重塑黄土试样内布设多根Π形电磁粒子速度计,直接测得了多个粒子速度波形。该文详细介绍了一维应变条件下Lagrange分析方法的理论推导及求解过程,并对实测粒子速度波形进行了Lagrange分析,得到了加、卸载全过程的应力、应变波形。给出了3发不同压力条件下重塑黄土的应力-应变关系曲线,揭示了重塑黄土介质的本构滞回效应。并使用该应力-应变关系对试样内应力波传播过程进行了反分析,最后对Lagrange分析过程中遇到的问题进行了讨论。     

Evaluation of Microwave Drying for Pharmaceutical Granulations

Abstract

The experiments were designed to compare the granule characteristics following the microwave drying and conventional tray drying. The formulations were designed to study the effect of microwave radiation under different conditions. This later criterion was studied by using granules prepared with different granulating fluids. The granules were prepared by using sulfathiazole as a model drug, lactose as a diluent, and starch as a disintegrating agent. The granulating fluids were 5% solution of PVP in 100% water, 50% water 50% ethanol, and 100% ethanol, respectively. The granules were dried in a microwave oven and in a conventional tray oven at 40±2° C. The loose and bulk densities were measured in a 100 ml glass cylinder. The granule morphology was examined using a scanning electron microscope. Dissolution rates of the granules were monitored using a rotating paddle dissolution apparatus. The loose and tapped bulk densities, the percentage compressibility, hardness, and the time required for 100% dissolution of the granules dried in the microwave oven and in the conventional tray oven were not significantly different (p>0.05). The scanning electron micrographs of the granules also showed no evidence of morphological changes or thermal damage to the granule surface or interior. In conclusion, the microwave radiation has no significant effect on the granules' characteristics.     

Polylactide (PLA)-clay nanocomposites prepared by melt compounding in the presence of a chain extender

Polylactide-layered silicate nanocomposites with and without a chain extender were prepared by melt mixing using a twin-screw extruder. An organo-modified clay, Cloisite® 30B, and a chain extender Joncryl®-ADR 4368F were employed in this study. The effect of the chain extender and processing conditions on the properties of the PLA-clay nanocomposites were investigated for different strategies of mixing. The resulting nanocomposites were characterized by X-ray diffraction (XRD), while their morphology was observed by SEM and TEM. The incorporation of the chain extender could enhance the degree of clay dispersion provided that it is judiciously added to the nanocomposite. The corresponding results revealed that the Joncryl-based nanocomposites, where nanoclay platelets were well-dispersed, exhibited a significantly reduced permeability as compared to others. The mechanical properties of the neat PLA, the PLA and Joncryl-based nanocomposites were also examined. The increased molecular weight in Joncryl-based nanocomposites caused a significant increase in the modulus, drawability and toughness of the samples.     

Cell chip-based monitoring of toxic effects of cosmetic compounds on skin fibroblast cells

The present study estimated the efficacy of electrochemical detection of imidazolidinyl urea-induced cell toxicity in skin human fibroblast cells (HFF cells). The gold nanopunct structures were fabricated through a nanoporous alumina mask, and the structural formations were confirmed via scanning electron microscopy. The HFF cells were allowed to attach to RGD (Arg-Gly-Asp) peptide nanopatterned surfaces, and electrochemical tools were applied to skin cells attached to the chip surface. The HFF cells evidenced inflammation responses to allergens such as imidazolidinyl urea. The cells were subsequently treated with different concentrations of imidazolidinyl urea for 24 h in culture, which induced a change in the cyclic voltammetry (CV) current peak. Treatment with imidazolidinyl urea induced a loss of cell viability and accelerated inflammation in a concentration-dependent manner. The expression level of inflammation-related proteins such as IL-1 beta were increased in imidazolidinyl urea-treated cells. The CV results demonstrated that imidazolidinyl urea significantly reduced the current peaks in a dose-dependent manner. The results showed that the current peak was reduced in accordance with the increases in imidazolidinyl urea-induced inflammation. In conclusion, the results of this study suggest that the electrochemical-based chip provides crucial information for improvements to a cell chip system for drug screening applications.     

Cold model experiment on dynamic behavior of dross in hot dip plating bath

The motions of top and bottom dross in a continuous hot dip plating bath were investigated using a transparent cold model vessel with a reduced scale of one-tenth. The flow field in the model bath was classified into three regions as usual; the entry region, the exit region, and the region enclosed with a belt. This belt was used as a model for a strip. Polystyrene particles were used as models both for the top and bottom dross while NaCl aqueous solutions of different densities were used as models for plating melts. The motions of model particles were observed by eye inspection and by using a high-speed video camera. Local particle frequency and particle holdup were measured with a newly developed sensor. Typical streak lines for the top and bottom dross particles were similar to main stream lines in the bath. Both the top and bottom dross particles were rich in the region enclosed with the belt. A lot of top dross particles floated on the bath surface near the side walls, while many bottom dross particles stayed on the bottom wall in the entry region.     

Statistical Analysis of Macromolecular Chains in the Space Filled by Nanoparticles

The paper presents a combination of worm-like chain numerical models and one with a finite set of nano-particles. The primary objective of the models was to analyze the distribution of space in a system filled by particles. Information on the distribution of space was compared to properties of chains inside the set of particles. The set of nanoparticles was constructed with a tool generating a finite set of particles that is randomly distributed in a given space. The particles have a prescribed volume fraction and uniform size. First, the proportions of chains and particles were compared. The length of chain was expressed in terms of end-to-end length. It was then compared to the size of gaps between two particles. The volume of chain was compared to the volume of space delimited by the particles. Next, a set of 10,000 random chains was generated and these were introduced into the particle set. The contact of a chain with the surface of a particle resulted in the special structural elements of the chain: a chain connecting two different particles, a loop which begins and ends at the same particle, a part of a chain which is completely adhered to the particle surface, a chain attached to a particle with one free end, as well as completely free chains. The chains were classified under three classes: chains which were not in contact with particles, chains which were in contact with one particle, and chains which were in contact with two or more particles. A statistical representation of each class is presented. The contact between chain and particle can influence macroscopic properties such as those that are elastic.     

椰子油制炭微管(英文)

报道了采用可再生的天然前驱体(椰子油),通过化学气相沉积制备一种"高长径比"的新型碳管结构,炭微管(CMTs)的方法。CMTs合成工艺:N2气氛,合成温度1175℃,流速100mL/min,二茂铁为催化剂。合成的CMTs利用SEM,EDX,TEM,和Raman光谱表征。结果表明:合成的CMTs的直径为1.7μm～2.1μm,并具有高的长径比。     

Multidisciplinary in-depth investigations of head-on and left-turn road collisions

To enhance traffic safety, a multidisciplinary Road Accident Investigation Team was established in Denmark for a 2-year trial period. The objective was to conduct in-depth investigations of specific types of accidents, and to identify effective preventive measures. The team consisted of a road engineer, a vehicle inspector, a police superintendent, a psychologist and a physician. Seventeen serious head-on collisions as well as 17 left-turn collisions were analysed. In collecting data, police reports were supplemented by the team's investigation of accident sites and vehicles involved, and interviews were carried out with the involved road users and witnesses. The drivers, to whom the accident factors were primarily related in the head-on collisions, were characterised by their conscious risk-taking behaviour. They were all males; several of them were under age 40 and had earlier traffic and/or drug convictions. The main accident factors were excessive speed, drunk driving and driving under the influence of illegal drugs. In the left-turn accidents, the most common accident factors were attention errors, and it was also noted that elderly drivers ( > 74) were over-represented. The synergy effect of working as a multidisciplinary team proved fruitful. It resulted in a more precise knowledge of the road accident circumstances and of contributing factors leading up to the accidents. Due to the great demand on resources, only a limited number of accidents could be analysed, but the results provide a basis for further and more targeted research.     

Cold model experiment on dynamic behavior of dross in hot dip plating bath

The motions of top and bottom dross in a continuous hot dip plating bath were investigated using a transparent cold model vessel with a reduced scale of one-tenth. The flow field in the model bath was classified into three regions as usual; the entry region, the exit region, and the region enclosed with a belt. This belt was used as a model for a strip. Polystyrene particles were used as models both for the top and bottom dross while NaCl aqueous solutions of different densities were used as models for plating melts. The motions of model particles were observed by eye inspection and by using a high-speed video camera. Local particle frequency and particle holdup were measured with a newly developed sensor. Typical streak lines for the top and bottom dross particles were similar to main stream lines in the bath. Both the top and bottom dross particles were rich in the region enclosed with the belt. A lot of top dross particles floated on the bath surface near the side walls, while many bottom dross particles stayed on the bottom wall in the entry region.     

Effect of oxidizing and coal-slag environments upon the time-dependent strength behaviour of a sintered SiC

The time-dependent variations in the high-temperature mechanical properties of a sintered SiC were investigated. The strength of C-ring specimens was determined as a function of temperature and applied stress in oxidizing atmospheres, and the results indicated that both crackblunting and crack-growth processes were operative when modest stress levels were applied. These results were consistent with the concept of a stress-intensity threshold. In the slag environment, localized reactions between the slag and SiC led to the formation of large surface pits which promoted a time-dependent drop in strength.     

Driving performance of the elderly

While driving on a freeway, visual search patterns, vehicle velocity and voluntary visual occlusion times were recorded for a group of aged and a group of young drivers. The 13 aged drivers were between 60 and 70 years of age; the young drivers were between 21 and 29. In the laboratory all subjects were given a visual search test, an embedded figures test and a motor test. Differences in aged and young performance were found both in freeway driving and the laboratory tests. The results indicate that countermeasures need to be developed in order to aid older drivers.     

Osteochondral tissue engineering using a PLGA–collagen hybrid mesh

Canine bone marrow stromal cells were cultured in a PLGA–collagen hybrid mesh in osteogenic medium in vitro and laminated to construct an osteo layer. Canine articular chondrocytes were cultured in the hybrid mesh in DMEM containing 10% FBS and laminated to construct a chondral layer. The osteo and chondral layers were sutured together and implanted subcutaneously in nude mice. The original round disc shape of the osteochondral constructs was preserved during the implantation. The osteo and chondral layers appeared red and glistening white, respectively. Histological examination of the implant specimens indicated that stromal cells and chondrocytes were evenly distributed throughout the scaffold. The laminated meshes were bound together and the two layers had a distinct interface between them. The cells showed a round morphology in the chondral layer and a spindle morphology in the osteo layer. In the chondral layer, spherical chondrocytes were surrounded by an abundant cartilaginous extracellular matrix. The round morphology and positive stain by safranin-O and toluidine blue, together with the expression of genes encoding type II collagen and aggrecan suggested the formation of neocartilage in the chondral layer. Expressions of genes encoding type I collagen and osteocalcin were detected in the osteochondral implant. These results indicate the formation of osteochondral-like tissue, and the hybrid mesh and lamination method may be useful for osteochondral tissue engineering.     

The development of an inherent safety approach to the prevention of domino accidents

The severity of industrial accidents in which a domino effect takes place is well known in the chemical and process industry. The application of an inherent safety approach for the prevention of escalation events leading to domino accidents was explored in the present study. Reference primary scenarios were analyzed and escalation vectors were defined. Inherent safety distances were defined and proposed as a metric to express the intensity of the escalation vectors. Simple rules of thumb were presented for a preliminary screening of these distances. Swift reference indices for layout screening with respect to escalation hazard were also defined. Two case studies derived from existing layouts of oil refineries were selected to understand the potentialities coming from the application in the methodology. The results evidenced that the approach allows a first comparative assessment of the actual domino hazard in a layout, and the identification of critical primary units with respect to escalation events. The methodology developed also represents a useful screening tool to identify were to dedicate major efforts in the design of add-on measures, optimizing conventional passive and active measures for the prevention of severe domino accidents.     

Use of 8-hydroxyquinoline-chitosan chelating resin in an automated on-line preconcentration system for determination of zinc(II) by F AAS

This study presents the development of an on-line preconcentration system for zinc(II) determination in aqueous samples. The analyte was trapped in a mini-column filled with a chelating resin based on a chitosan biopolymer modified with 8-hydroxyquinoline obtained by the diazotization reaction. Flow and chemical variables of the system, as well as the potential interference ions, were optimized through a multivariate procedure. The factors selected were sample pH, eluent concentration (HNO(3)), and sample and eluent flow rates. It was verified through a full factorial design that the sample pH and eluent flow rate factors were statistically significant at the 95% confidence level. A final optimization of the significant factors was carried out using a Doehlert matrix. The preconcentration system was linear between 2.5 and 75 microgL(-1), with a regression coefficient of 0.9995. The enrichment factor was 17.6. The limits of detection and quantification were 0.8 and 2.5 microgL(-1), respectively. The repeatability and the analytical frequency were, respectively, 2.7 (25.0 microgL(-1), n=8) and 18 samples per hour. Results for recovery tests using mineral water samples were between 85 and 93%. Certified reference materials were analyzed in order to check the accuracy of the proposed method.     

Thermophysical Properties of Solid Phase Hafnium at High Temperatures

The thermophysical properties of several hafnium samples with a content of zirconium below 1% were experimentally studied over a wide temperature range. The specific heat capacity and specific electrical resistivity were measured from 300 to 2340 K, the hemispherical total emissivity from 1000 to 2130 K, while the thermal diffusivity was measured in the range from 300 to 1470 K. The thermal conductivity and Lorentz number were computed from measured properties for the range from 300 to 1470 K. The specific heat capacity, specific electrical resistivity, and hemispherical total emissivity were measured by subsecond pulse calorimetry, and the thermal diffusivity using the laser flash method. Samples in the form of a thin rod or wire, and in the form of a thin disk were used in the first and second methods, respectively. For data reduction and computation of relevant parameters, recent literature values of the linear thermal expansion were used. The results are compared with literature data and discussed.     

锁挡多工位级进模设计

分析了锁挡零件的结构工艺性和冲压工艺,介绍了零件的排样方案、模具总体结构、工作过程、主要零部件的设计,并阐述了模具结构特点.模具结构合理、紧凑,工作平稳,生产效率高,生产的零件质量达到要求.     

Materials characterization and mechanical properties of graded tool steels processed by a new co‐spray forming technique

In order to meet the requirements of micro cold forming tools, a new co‐spray forming process has been applied to produce graded materials from two different tool steels in this study. The two steel melts were atomized and co‐sprayed simultaneously onto a flat substrate, resulting in a flat graded deposit when the two sprays were overlapped. To eliminate porosity and break up carbide network, the graded deposits were further hot rolled. The resultant graded tool steels were investigated with respect to porosity, element distribution, microstructure, hardness, strength, and toughness. The degree of overlapping of the two sprays determined the concentration gradient of the chemical elements in the deposits. The overlapping of the spray cones also contributed to low porosity in the gradient zone of the deposits. The porosity in the graded deposits could be essentially eliminated by means of hot rolling. The carbides and grain structures of the hot rolled tool steels were fine and homogeneous. By means of combining different tool steels in a single deposit, different microstructures and properties were combined.     

Fabrication,Microstructure and Mechanical Properties of TiC/Ti_2AlC/TiAl_3 in situ Composite

This paper described a process for synthesizing a new multiphase TiC/Ti2AlC/TiAl3 composite,in which Ti,Al4C3 and graphite powders were utilized as raw materials,and in situ spark plasma sintering-reactive sintering(SPS-RS) methods were involved.The intermediate phases of Ti3Al and TiAl were found during the reactive sintering process and the reactions for the phase’s formation were proposed.The microstructure and mechanical properties of the composites were investigated.The high-resolution transmission electron microscopy(HRTEM) image of the interface showed that no amorphous phases were detected along the grain boundary.The orientation relationships between the Ti2AlC and the TiC were shown to be(0001)Ti2AlC||(111)TiC and [110]Ti2AlC||[110]TiC.The average hardness,fracture toughness,Young’s modulus and bending strength of the composite were 15.1±0.8 GPa,4.9±0.3 MPa·m 1/2,261±13 GPa and 776±18 MPa,respectively.The toughening mechanism was also discussed.     

TEM研究氢对双相组织的影响

用电镜观察了充氢后双相钢的亚结构,探讨了氢致双相钢机械性能下降的原因。观察表明:充氢后,F相中位错增殖,最后形成胞状亚结构;M相中位错组态变化不明显,但随充氢量增加,裂纹将在M板条界萌生和扩展,有时也横穿M板条;F/M相界充氢后出现宽化现象,并向F相一侧增殖位错,进而界面起裂。M量越多,则此现象越明显。M相与F/M相界起裂对充氢电流密度比充氢时间更为敏感。M相及F/M相界充氢后损伤严重,导致双相钢塑性下降,成为宏观拉伸时易于裂纹萌生和扩展的薄弱部位。     

栉孔扇贝血细胞的吞噬作用及其扫描电镜研究

用透射电镜和扫描电镜技术对栉孔扇贝血细胞的吞噬作用和表面结构进行了研究,结果表明,栉孔扇贝血细胞对大肠杆菌和金黄色葡萄球菌均有很强的吞噬能力,注射细菌15h后,吞噬率分别达25％和27％,小颗粒（嗜中性颗粒）细胞吞噬能力最强,中颗粒（嗜碱性颗粒）细胞吞噬能力较弱,大颗粒（嗜酸性颗粒）细胞无吞噬能力,无颗粒细胞中只有少量较大的细胞具有吞噬能力。吞噬体不断与小空泡（初级溶酶体）融和形成大的吞噬体,并在其内将细菌逐步消化降解,吞噬体中的细菌也可被分散包围成多个小吞噬体后分别被降解。扫描电镜观察栉孔扇贝血细胞的圆形、椭圆形和梭形三种形状,多数血细胞容量变形形成伪足,可形成大量长的纤维状伪足的血细胞具有凝血的功能。