Creep and drying shrinkage of calcium silicate pastes III. A hypothesis of irreversible strains

Irreversible strains, measured on pastes of pure calcium silicates which were loaded without drying, dried to 53% rh without loading, or were loaded and simultaneously dried to 53% rh, are correlated with indications of structural changes occurring within the hydrated pastes. These changes are interpreted in terms of microstructural models of the hydrated pastes. It is assumed that irreversible strains are caused only by changes in the “pore component” and the “CSH component.” In young pastes irreversible shrinkage can be explained by a reduction in pores in the range 40–100 Å diameter. In well-hydrated pastes structural changes in the silicate framework of the “CSH component” dominate irreversibility. Microshearing between CSH particles is thought to occur under load. An increase in degree of silicate polymerization bonding occurs on drying, and this increase is greater when drying takes place under load.     

LIMITING FLUX IN ULTRAFILTRATION OF MACROMOLECULAR SOLUTIONS

The mass transfer equation describing the process of gel polarized ultrafiltration is solved using an integral method. A concentration profile is assumed to be an nth degree polynomial. In conventional integral method, “n”is arbitrarily assigned an integer value. In this paper we have taken the first moment of the convective diffusion equation to determine “n” as a function of the system parameters. The agreement between the closed form integral method solution and the exact numerical solution is excellent while the widely used film theory deviates considerably.     

Physical,Chemical, and Biological Characterization of Veiled Extra Virgin Olive Oil Turbidity for Degradation Risk Assessment

Six different 300 kg batches of olive fruits are processed and the resulting six 20 kg batches of oil are collected at the end of the “decanter.” These batches of oil are subjected to four different water and solid particle separation treatments so as to obtain the following oil samples: veiled oil, filtered oil, “solid particle‐only” oil, and “water‐only” oil. The applied separation treatments show that water content has an important role in the degree of turbidity. High water content values (>0.2% w/w) are related to water activity values of >0.6 which are suitable for chemical and enzymatic reactions. The veiled oil samples are contaminated by microorganisms, but non‐proportional behavior occurs between the microbial cell count and the water and solid particle contents. Practical Applications: The results of this study recommend a multi‐approach method to characterize turbidity, based on control markers such as the degree of turbidity, water content and water activity, solid particle content, microbial contamination, and phenolic compound content. In this way, each degree of turbidity can be associated with a different level of risk of veiled extra virgin olive oil degradation during shelf life.     

基于声发射信号的PE塑料失效PCA预测方法

以聚乙烯(PE)塑料为研究对象,采用声发射监测技术对不同拉伸速度下试样失效过程进行监测,采集相应的声发射信号(持续时间、幅值、事件计数、撞击次数等),通过相关性系数分析确定评价因子,利用三角形隶属函数确定各评语集的失效隶属度,建立了PE塑料失效破坏程度主成分分析(PCA)模糊预测评价模型.另取同型号PE试样进行不同速度...     

Reaction kinetics of polyurethane-polyester interpenetrating polymer network in the bulk polymerization

Kinetics of simultaneous interpenetrating networks (SIN) composed of a polyurethane resin (PU) and an unsaturated polyester resin was studied. A differential scanning calorimeter (DSC) was used to monitor the polymerization course. It was found that increasing the polyester content in a PU-polyester SIN enhanced the polymerization of PU due to the “solvent effect” of polyester. On the other hand, increasing the PU content in the SIN retarded the polymerization of polyester due to the “cage effect” of PU. Polymerization sequence of the SIN could be controlled by employing different initiators for polyester reaction. The degree of crosslinking in each SIN component had a significant effect on the dynamics of the SIN formation and on the limiting conversion of the polyester reartion.     

Thermally stimulated creep of polyethylene,polypropylene, copolymers,and blends

The technique of Thermo Stimulated Creep (TSC) has been applied to the study of anelastic properties of polyethylene, polypropylene, their copolymers and blends. In the temperature range ?200 to 100°C, complex TSC peaks were observed in all samples, namely around 0°C, about the same temperature as for the homopolypolymer polypropylene. By applying “fractional stresses”, with a convenient choice or the loading program, these peaks have been experimentally resolved. Two components can be distinguished: 1. The “low temperature” component is characterized by mechanical retardation times following a compensation law. It has been attributed to microbrownian motions of polypropylene sequences liberated at the glass transition of the “true” amorphous regions. 2. The “high temperature” component which is influenced by thermal treatment has been assigned to microbrownian motions of polypropylene sequences liberated at the glass transition of the “constrained” amorphous regions. In block polymers, an additional TSC peak is observed around ?50°C: it has been associated with the glass transition of ethylene-propylene-rubber (EPR) interphase. The coupling of this interphase with polyethylene and polypropylene phases is insured by diffusion of some ethylene and propylene sequences in-EPR. At about ?140°C, a TSC peak associated with the low temperature component of the glass transition of polyethylene can be distinguished in all the materials studied.     

Cold rolled ABS. Part 2: Rubber morphology and tensile properties of hot stretched and cold rolled ABS

Cold rolling and hot stretching (105°C) both lead to increased failure stress and decreased stress whitening in model ABS composites while hot stretched samples alone retain a tensile yield dip. Further differences between hot stretching and cold rolling are revealed in electron micrographs obtained by the Kato method. In the hot stretched samples the ruber particles appear as elongated “cigar-like” smooth ellipsoids which reflect the observed macroscopic orientation. SAN occlusions within the ruber particles are deformed to the same degree as the rubber. Ruber particles in cold rolled samples, however, exhibit a jagged, “hairy” surface indicating a high degree of shear distortion; and SAN occlusions within the rubber particles are not deformed in rolling. The rubber particles in cold rolled ABS are flattened and disk-like rather than ellipsoidal.     

Modulus development in oriented short-glass-fiber-reinforced polymer composites

The increase in modulus obtained in a short-glass-fiber-reinforced polymer composite as a result of uniaxial deformation may be related to the observed increase in both fiber and matrix orientation. Quantitative measurements of both fiber and matrix orientation are presented for a series of samples of short-glass-fiber-reinforced polyoxymethylene copolymer, processed to various substantial deformation ratios by solid-phase hydrostatic extrusion. The polymer matrix becomes highly oriented at modest deformations, but the glass fibers orient in a slower pseudo-affine manner and dominate the development of modulus in the composite. A simple “law-of-mixtures” model is used to demonstrate that perfect uniaxial orientation of the fibers is not achieved, but a better fit to measured modulus data is obtained by using an “aggregate” model applied to oriented fibers in an oriented matrix. The development of modulus with deformation ratio may be predicted very well if it is assumed that:

• the composite consists of a series-coupled array of sub-units, each containing continuous and fully oriented fibers in a fully oriented matrix; and
• orientation of the sub-units develops with deformation in a pseudo-affine manner.

     

A quantitative theory of the action of microbes attached to a packed column: Relevant to trickling filter effluent purification and to microbial action in soil

A packed column with microorganisms attached is regarded as a series of “theoretical compartments” each separated by a “theoretical film” of biomass. Liquid medium is supposed to pass down the column so that it remains for an equal time in each compartment. The theoretical film of biomass is assumed to have an active layer in contact with the liquid medium, the thickness of the active layer of biomass is estimated from the kinetics of diffusion of the limiting substrate. The efficiency of the column is represented by the number of theoretical compartments per unit length of column. In aerobic processes it is supposed that oxygen will be the rate-limiting nutrient. Expressions are derived for the amounts of substrate that will be consumed in aerated and non-aerated columns. The theory is applied to calculate some of the parameters of a trickling filter for effluent purification. The theory may be readily tested since it involves only measurable and meaningful parameters of a microbial culture.     

基于Fisher判别⁃支持向量机的汽车灯罩显微激光拉曼光谱研究

为实现对司法鉴定工作中经常遇到的汽车灯罩类物证进行数据化、可视化的无损高效率鉴别,采用PCA主成分分析前处理结合FDA-SVM（RBF）组合分析鉴别物证的方法,对获取的“奥迪”“别克”等18个品牌的173组拉曼红外光谱数据进行了实验和理论分析。借助Pearson相关性分析和PCA主成分分析的结果选择特征位移,分别建立基于Fisher判别分析和SVM支持向量机的数据分类模型。结果表明,FDA模型和SVM（RBF）模型对灯罩样本的综合区分准确率分别为97 %和51.85 %,SVM模型对“奔驰”“别克”等8个品牌的区分准确率达到了100 %,FDA与SVM模型互相补充的FDA-SVM（RBF）模型可对不同品牌灯罩拉曼红外光谱进行准确区分,分类效果较好。该方法高效、准确,对侦查破案中借助灯罩物证鉴定缩小侦察范围有一定的参考意义。     

Molecular weight distribution control in a semibatch “living” anionic polymerization. I. Theoretical study

A method to produce homopolymers of preestablished molecular weight distribution (MWD), through “living” anionic polymerizations carried out in homogeneous semibatch reactors is proposed and theoretically justified. In the direct form of the technique, very fast reactions are assumed, and the monomer and “killing” agent feed flows are obtained from the knowledge of the desired MWD, the system spreading function, the total reaction time, the initial reaction volume, and the reagent concentrations. Alternatively, by controlling a reactor outlet flow instead of the “killing” agent feed, an external deactivation of the “living” ends can be implemented. The method can be extended to slow reactions, to more elaborated mechanisms, and to take into account the unwanted deactivation of “living” ends by impurities in the monomer solution feed.     

Shape distinction of particulate materials by laser diffraction pattern analysis

A pattern of a diffraction image depends on the particle shape, while the size of the pattern depends on the sectional area of the particle. In this work, the method to extract differences from the diffraction patterns due to different shapes of non-spherical particles was studied conceptually. In this respect, a radial segment (wedge) photo-detector was assumed as a detector. Diffraction patterns and intensity patterns detected by the radial segment detector were calculated for many kinds of two-dimensional shapes, corresponding to the projections of particles, as a circle, ellipses, triangles, quadrangles, other anonymous shapes, also shapes extracted from real phytoplanktons. From these detected light intensity patterns, we extracted (or define) two indexes: “circular index” and “peak number.” It was shown that various shapes can be distinguished by means of two-dimensional mapping with these parameters. In addition, an applicability of a concentric detector was examined to estimate the particle size when the particle is non-spherical but is a single particle in the measurement. As a result, it was found that the circle equivalent diameter determined with usual scheme agreed well with the sectional area equivalent diameter of the original particle even in any cases of non-spherical samples. From these results, it was shown that the particle size and shape in wide range can be distinguished from the three-dimensional mapping with “circular index”, “peak number” and “particle size”.     

Composition of liver fats of mature and embryo sharks (galeocerdo tigrinus)

1. Two liver fats, one from the “mother” and the other from the “embryo” shark (Galeocerdo tigrinus), have been studied. Their component fatty acids are reported.
2. The mixed fatty acids from each of the fats were first resolved into groups of acids of varying unsaturation by the lithium salt acetone and/or lead salt alcohol methods. The methyl esters of each of these groups of acids were fractionated through the Longenecker's E.H.P. column.
3. The two fats are found to belong to the fourth group of Tsujimoto's classification of the Elasmobranch fish liver fats. The “mother” shark liver fat contains 43.3% saturated and 56.7% unsaturated acids. The “embryo” shark liver fat contains 39.1% saturated and 60.9% unsaturated acids. Palmitic acid was about 25% in both of the fats.
4. A possible explanation for the less unsaturation and the absence of higher polyethenoids in the “embryo” liver fat is given.

     

二元混合物“全回流”间歇精馏的能耗

介绍了在理想操作条件下，“全回流”间歇精馏二元理想混合物量纲1最小操作总时间的数值计算方法.通过举例计算，比较了在理想操作条件下，“全回流”与部分回流间歇精馏二元理想混合物的能耗，得到了“全回流”间歇精馏适合于相对挥发度小、原料中轻组分的浓度低、塔顶产品中轻组分收率要求高而浓度要求低的分离任务的结论.     

Diffusion,swelling, and consolidation in glassy polystyrene microspheres

The effects of prior thermal and swelling history on the kinetics and apparent equilibria of subsequent n-hexane sorption in monodisperse, submicrometer diameter, glassy polystyrene microspheres were studied. Repetitive sorption and desorption cycling was compared with continuous sorption and desorption experiments. The apparent equilibrium uptake of n-hexane in preswollen samples decreased monotonically with the cumulative time under vacuum independent of the cycle frequency or the number of sorption-desorption cycles. This consolidation was modeled as a first order relaxation process with a single characteristic relaxation time. “As-received” samples swelled in the presence of the penetrant and the apparent equilibrium n-hexane content increased monotonically with the time under n-hexane. The Berens-Hopfenberg diffusion-relaxation model accurately describes the cyclic and continuous swelling behavior of the “as-received” sample. At each temperature studied, a true equilibrium n-hexane content was approached asymptotically for the preswollen and “as-received” samples after sufficient time under vacuum or n-hexane, respectively. Whereas the apparent sorption equilibria were controlled by the cumulative time under vacuum or n-hexane for the preswollen and “as-received” samples, respectively, the absorption kinetics are subject to a systematic variation which depends only on the immediate prior vacuum history of the sample. The temperature dependence of the kinetic and equilibrium parameters describing diffusion, consolidation, and swelling suggests a unified molecular interpretation of these diverse glassy-state transport and relaxation processes.     

Residence time distributions of a series of laminar stages

The Residence Time Distribution (RTD) of a series of j cylindrical (and “slit”) geometry vessels with laminar flow is analyzed. Fully transverse mixing at the points of connection between cells and no significant contribution of molecular diffusion to the mixing process are assumed. This model leads to a one-parameter (j) family of RTD curves, which are more asymmetric and long tailed than those predicted by the “ideal back-mix cells in series” and “axial dispersed plug flow” models.     

A comparison of torsional and capillary rheometry for polymer melts: The Cox-Merz rule revisited

Rheological properties of high and low density polyethylene melts (HOPE and LDPE) were measured under two different deformation modes: sinusoidal strain (“dynamic”) and constant rate-of-strain (“steady-state”). For the sinusoidal measurements, a torsional geometry was used, whereas the “steady-state” measurements were carried out in both torsional and capillary flow. The complex and “viscous” components of the “dynamic” viscosity were compared with the “steady-state” viscosities, corrected for both non-Newtonian and end effects. For the HDPEs, the Cox-Merz rule was found to be not valid. The corrected viscosity is closer in magnitude to the “viscous” component, and not to the complex viscosity. However, for the LDPEs, the corrected viscosity is equivalent to the complex viscosity. These results are compared to other correlations found by various authors.     

Modification of natural rubber tubes for biomaterials I. Radiation-induced grafting of N,N-dimethyl acrylamide onto natural rubber tubes

Radiation-induced simultaneous grafting of N,N-dimethyl-acrylamide (DMAA) onto natural rubber (NR) tubes has been studied to improve blood compatibility of the NR tubes. Concerning grafting of DMAA onto NR tubes, it was found that the grafting proceeds effectively in the presence of carbon tetrachloride (CCl₄) as a solvent. The degree of grafting was found to be saturated at about 26 wt%, but a higher degree of grafting can be obtained by either “so called two-step grafting” or “putting a standing time for a while before irradiation.” The initial grafting rate was proportional to 0.85 power of dose rate. The apparent activation energy of the graft-copolymerization was 7.42 kcal/mol. Evaluation of blood compatibility of DMAA-grafted NR tubes has been carried out by ex vivo test. According to the results, significant improvement of blood compatibility was obtained for the samples in which degree of grafting is higher than 30 wt%.     

Study on crystallization of nylon 6 (polycapramide). III. Effect of “crystalline memory” on crystallization kinetics

The effect of the initial degree of crystallinity on the isothermal crystallization kinetics from the melt of nylon 6 has been examined. The investigations were carried out in the conditions which allow to maintain a “crystalline memory.” For the investigations, dilatometric and microscopic methods were used depending on the temperature range used. It has been found that for samples of initial crystallinity up to 15% there exists a possibility of the growth of spherulites either from the sporadic or simultaneous nucleation depending on the crystallization temperature. For samples with initial degree of crystallinity higher than 15% the growth of spherulites occurred always from the predetermined nuclei within the investigated range of the crystallization temperature. The crystallization rate of the samples increased with rise in initial degree of crystallinity of the samples.     

Modelling of the skin effect in catalyst pellets

The “parallel bundle of pores” model for representing the macro-pore structure of a catalyst pellet has been modified to provide a theoretical framework for pellets which have an outer skin of denser macro-pore material. For pellets exhibiting such a “skin-effect” a constricted mouth parallel bundle model has been postulated. In this model any macro-pore is envisaged as passing through the pellet and assumed to have constrictions at each open end. The pore mouth constrictions constitute the skin effect. These skin macro-pores when they are associated with macro-pores of a given size are assumed to be distributed in some way between that macro-pore size and the size of the smallest possible macro-pore.Using this model theoretical expressions have been derived for mercury porosimeter pressuring and depressuring curves. The hysteresis that arises from the skin effect is shown to be a possible approach to characterise a pellet skin. Illustrative results for a typical macro-pore distribution have been obtained for some pore mouth distribution functions representing severe, mild and intermediate skin cases.The consequences of such a skin effect can be a large reduction in internal accessible surface when pore blocking takes place due to the formation of carbonaceous deposits during hydrocarbon catalysis. A quantitative assessment of this effect is presented for the special case when the deposition rate is much faster than the penetration rate.