Shear Strength of Fiber-Reinforced Sands

Soil reinforcement using discrete randomly distributed fibers has been widely investigated over the last 30 years. Several models were suggested to estimate the improvement brought by fibers to the shear strength of soils. The objectives of this paper are to (1) supplement the data available in the literature on the behavior of fiber-reinforced sands; (2) study the effect of several parameters which are known to affect the shear strength of fiber-reinforced sands; and (3) investigate the effectiveness of current models in predicting the improvement in shear strength of fiber-reinforced sand. An extensive direct shear testing program was implemented using coarse and fine sands tested with three types of fibers. Results indicate the existence of a fiber-grain scale effect which is not catered for in current prediction models. A comparison between measured and predicted shear strengths indicates that the energy dissipation model is effective in predicting the shear strength of fiber-reinforced specimens in reference to the tests conducted in this study. On the other hand, the effectiveness of the predictions of the discrete model is affected by the parameters of the model, which may depend on the test setup and the procedure used for mixing the fibers.     

堵水固砂一体化技术研究与应用

针对青海尕斯库勒油田N1-N21油藏地层特点，室内研究了聚合物树脂堵荆配方体系，评价了该堵荆室内模拟实验效果。现场试验结果表明，该聚合物树脂堵剂具有堵水和固砂双重功效，且施工工艺简单，价格便宜，具有较好的推广应用前景。     

Micropatterning of photosensitive glass-ceramic-polymer composite by sand blasting

Abstract

A photosensitive, sandblasted composite was used to achieve a high aspect ratio of barrier ribs. The authors investigated the erosion of the photosensitive composite prepared with two different pastes: normal and photosensitive. The barrier ribs underwent micropatterning with calcium carbonate powder as the sand blasting erodent material. The patterned green barrier ribs were fired in an air atmosphere and the thermal, physical and mechanical properties of the resulting composites were determined by thermal gravimetric analysis, atomic force microscopy, nanoindentation, and peel testing. The photosensitive composite had better adhesion with a dry film resist and showed lower porosity, surface roughness, stiffness and elastic modulus than a normal composite, which was attributed to the remaining polymer. In the process, the developed photosensitive composite and the dry film resist film were able to withstand the impact of the separated particles or clusters. These results support the use of sand blasting to fabricate the micropatterning of barrier ribs with two layers of photosensitive composite.     

Effects of Particle Crushing in Stress Drop-Relaxation Experiments on Crushed Coral Sand

Stress relaxation and stress drop-relaxation tests have been performed to complement a test series performed to study strain rate, creep, and stress drop-creep effects on crushed coral sand. Drained experiments with constant effective confining pressure of 200 kPa were performed in which triaxial specimens of crushed coral sand were loaded to initial stress differences of 500, 700, and 900 kPa, followed by stress drops of 0, 100, 200, 300, and 400 kPa at which points the axial strains were kept constant while the axial stress relaxation and the volumetric strains were observed. The stress drops produced delays in initiation of stress relaxation that were proportional with the magnitudes of the stress drops. The experiments show that sands do not exhibit classic viscous effects, and their behavior is indicated as “nonisotach,” while the typical viscous behavior of clay is termed “isotach.” Thus, there are significant differences in the time-dependent behavior patterns of sands and clay. A mechanistic picture of time effects in sands is proposed.     

Survival of Salmonella spp. in low water activity chicken base paste and powder formulated at different salt levels

Dry flavor ingredients such as black pepper and hydrolyzed vegetable protein (HVP) have been frequently recalled from the supply chain due to contamination with Salmonella. These spices are commonly used in preparation of savory meat flavor bases. This study evaluated the effect of various salt levels on the survival of Salmonella spp. in chicken bases formulated with pepper and HVP, in either paste or powder form. The salt content (% w/w), a_w and pH for regular-salt, 45% reduced-salt and 90% reduced-salt paste formulations were 33.0, 0.686, 5.75; 18.2, 0.691, 5.85; and 3.5, 0.751, 5.96, respectively, and powder formulations were 34.0, 0.254, 6.15; 18.5, 0.290, 6.28; and 3.1, 0.301, 6.50, respectively. To mimic natural contamination, a dry sand inoculation technique was used to prepare the samples. A five serovar cocktail of Salmonella was used and the final inoculation level in the samples was 7.5 ± 0.2 log CFU/g. Inoculated paste samples were stored at 21 °C for up to 12 weeks, and up to 42 weeks for powder formulations. Salmonella counts did not increase in either treatment during storage. The effect of salt levels on Salmonella survival was insignificant. There was a 5.2 ± 0.4 log reduction in paste formulations by 3 week. However, low Salmonella counts (<1.0 log CFU/g) were detected in samples from 6 to 12 weeks. In powder formulations, minimal log reductions of 1.3 ± 0.1 were observed over 42 weeks. When preparing a food product that does not undergo a kill step, it is necessary to ensure the absence of Salmonella in the ingredients, as well as practicing strict adherence to good manufacturing practices including proper environmental monitoring and sanitation in food processing. Furthermore, adequate consumer cooking instructions are important to ensure proper Salmonella lethality during preparation of reconstituted dry products.     

砂—塑复合材料混合团粒设备的分析

本文通过对十种具有混合和团粒功能的砂——塑复合材料团粒设备的初步设计和可行性试验,肯定了以搅拌为主的工作方式.文章建议螺带式团粒机和卧式搅拌团粒机可以作为砂——塑复合材料的预处理设备.     

Bioreduction of Hexavalent Chromium in Flow-Through Quartz Sand Columns

Hexavalent chromium (Cr(VI)) contamination of soil and groundwater is a major environmental concern for some industrial sites and most of the U.S. Department of Energy sites. Cr(VI) is toxic and fairly mobile in groundwater. Bioreduction of Cr(VI) to less toxic and less mobile Cr(III) is considered to be a feasible option. Among the Cr(VI) reducing bacteria, Shewanella oneidensis MR-1 (MR-1) has been shown to be effective in metal reduction under anaerobic conditions. Data on bioreduction of Cr(VI) by MR-1 in a flow-through soil column that better approximates the subsurface condition are not available. The objective of this research project was to study the bioreduction of Cr(VI) by MR-1 in a continuous-flow quartz sand column system. MR-1 was found to be very effective in reducing Cr(VI) to Cr(III) for concentrations ranging from 0.055 mM (2.85?mg/L) to 0.006 mM (0.31?mg/L). The amount of Cr(VI) reduced prior to its breakthrough was found to be inversely proportional to its concentration in the feed due to increased inhibition of microbial activity and a residual reduction of 20–45% of Cr(VI) was observed even after its breakthrough.     

沙尘暴综合预报系统中场特征提取方法的研究

沙尘暴天气频繁发生,严重干扰和影响着人们的正常生活,对社会经济和生活环境均造成一定程度的危害.根据沙尘暴天气的成因及特点,在分析现有特征提取方法弊病的前提下,提出了ANN沙尘暴综合预报系统场特征提取方法.首先进行距平运算数据预处理,获取沙尘暴成因物理场样本;然后利用论文方法进行场特征提取.在此基础上,借助综合预报思想构建并实现了遗传ANN沙尘暴预测系统.仿真结果表明,论文所研究的场特征提取方法在提高沙尘暴预报的准确率方面做出了较大的贡献.