Brief note on the influence of shape and percentage of gravel on the shear strength of sand and gravel mixtures

The paper records the influence of the shape and the percentage of gravel on the shear strength/frictional angle of sand and gravel mixtures using direct shear tests. The shear strength is mainly derived from the frictional forces developed due to sliding and interlock; they depend on the maximum particle size and shape, the uniformity coefficient, density and the effective normal stress. As the size of material in a mixture is variable, the shear strength also depends upon the ratio of the specimen diameter to the maximum particle size. In this study, two different shapes of limestone were used, angular and rounded, and the maximum gravel size was 6.3 mm in diameter. Air-dried samples were used in the tests. It is concluded that the shape and percentage of gravel have an important influence on the shear strength properties. Electronic Publication     

Shear Property of Kaolin-filled Standard Malaysian Rubber (SMR L) Pressure-sensitive Adhesive

The effect of kaolin loading on the viscosity and shear strength of natural-rubber-based pressure-sensitive adhesive was studied using coumarone-indene resin, toluene, and polyethylene terephthalate as tackifier, solvent, and substrate, respectively. Kaolin loading ranged from 10 to 60 parts per hundred parts of rubber (phr) whereas the tackifier content was fixed at 40 phr. The viscosity and shear strength—from lap shear test—were determined by a Brookfield viscometer and Lloyd adhesion tester, respectively. Results show that viscosity increases with increasing kaolin loading. However, shear strength increases up to 20 phr kaolin loading, after which it decreases with further filler loading. This observation is attributed to the culmination of cohesive strength at the optimum loading of kaolin filler. For a fixed kaolin loading, the shear strength increases with coating thickness and testing rate.     

SGA胶粘剂基组成与性能研究

研究了SGA的基本组成对其固化速度与剪切强度的影响,结果表明,引发剂,促进剂,MAA三者随其用量增大对剪切强度的影响均呈先进后降的趋势,对固化速度的影响依次为先进后降,先升后不变,一直升高,改性材料能提高切强度与固化速度,其中对固化速度的影响是增大体系粘度引起的。恰当的稳定体系可提高胶液的贮存稳定性,较小影响化速度。     

Hydrodynamic Instabilities of Adhering Droplets Due to a Shear Flow in a Rectangular Channel

This paper reports on the hydrodynamic droplet instabilities of different sizes and viscosities due to shear forces in a rectangular channel. Water‐glycerine droplets of different volumes are investigated. A new and nonambiguous definition for the critical velocity of droplet detachment and a new mathematical correlation between the critical velocity v_crit and the fluid properties are presented. The measurements show that v_crit decreases with the droplet volume but at the same time the contour deformation increases. With increasing viscosity of the liquid droplet, i.e., higher glycerine mass fraction, the contour deformation becomes more prominent and an increase in v_crit can be observed. With respect to the fluid properties and droplet volumes, three different motion patterns are detected.     

Rock joint coefficients and their computerized classification

A computerized method for determining rock joint coefficients is presented. Two relative similarity indicators are introduced to classify surface morphology of rock joints. The classification enables to compare investigated and database rock joints. Such a comparison aims at finding the couple of surfaces that are distinguished by the highest dynamical conformity. The first absolute indicator results from the Fourier matrix and evaluates wavy shapes of surfaces. The second absolute indicator quantifies the heights of surface reliefs and is defined as the root mean square height of the surface outline. Numerical reliability of these indicators is tested within the surface analysis of a series of limestone specimens. Besides the computerized assessment, 25 people have performed visual assessment of these limestone specimens.The results of visual assessments have been statistically processed and compared to the results received from the computerized procedure. The newly introduced absolute indicators have proved to be prospective numerical tools for evaluating joint rock coefficients.     

Epoxy Resin Modified with Epoxidized Soybean Rubber

Epoxy resin is widely used for coatings, adhesives, casting, electrical insulation materials, and other applications. However, unsolved problems still remain in these applications. The main problem is low toughness: cured epoxy resin is rather brittle with poor resistance to the propagation of cracks, derived from the internal stress generated from shrinkage in the cooling process from cure temperature to room temperature. To solve this problem epoxidized soybean oil (ESO) has been used to toughen epoxy resin cured with an ambient temperature hardener, Tris-2,4,6-(N,N-dimethyl amino methyl) phenol to reduce the internal stress, by introducing a two-phase structure. The ESO was prepolymerized with the amine hardener to obtain the liquid epoxidized soybean rubber (ESR). The ESR-modified epoxy networks were evaluated for their impact and adhesive properties. The epoxy-ESR compositions were systematically varied to study the effect of modifier concentration on adhesion and impact strength. Optimum properties were obtained at a concentration of 20% ESR polymerized for 60 hr. The scanning electron microscopy analysis indicates phase separation between the epoxy-rich phase and ESO-rich phase.     

我国图书情报类核心期刊信息传播滞后研究

为进一步了解期刊学术论文信息传播滞后情况,以图书情报类核心期刊学术论文信息传播滞后的统计数据状况为例,调查了作者期望。通过比对分析得出:我国图情类核心期刊信息传播滞后时间与作者期望相距甚远,这严重影响了科研成果的快速传播。建议编辑部在保证期刊质量的前提下,应优化审稿、编校和出版流程,尽可能地缩短学术论文信息传播滞后时间,使滞后时间尽可能接近于作者期望。这样,既可加速科研成果的传播速度,也会提升科技期刊的学术影响力。     

分离刚度法测试杨木单板层积材木梁剪切模量的试验研究

目前中国杨木人造板以非结构为主,而在机电包装行业中使用大量实木作为包装材料,从经济成本、资源利用和环境保护等诸多方面都迫切需要以结构人造板替代实木作为机电包装材料。针对厚型单板层积材面内剪切模量测试,从理论上给予推导,并从实践上利用理论指导实际测试,以期为单板层积材的结构设计、性能测试以及使用提供技术基础。     

Social Software in Academic Libraries for Internal Communication and Knowledge Management: A Comparison of Two Reference Blog Implementations

This article investigates the adoption of new innovations for internal reference desk communication and knowledge management in academic libraries, specifically the use of social software tools. Actual implementations of the free blog software Wordpress from two university libraries are described including charts detailing advantages and disadvantages of the methods. In the context of the diffusion of innovation and organizational lag theories, the analyzed outcomes confirm that while social software tools are being used, relatively few institutions have exploited them for improving in-house processes. Without clearly articulated long-term gains, adoption of administrative innovations will follow the pattern of organizational lag.