Modeling Compression Behavior of Structured Geomaterials

The influence of the natural (or artificially induced) structure of a geomaterial on its compression behavior is investigated. An approach for modeling this influence for various structured geomaterials is proposed by using the disturbed state concept. An isotropic compression model is formulated on three basic assumptions. A special version of the proposed model is also described for situations where the compression is one-dimensional. The proposed compression model is used to simulate the behavior of a variety of structured geomaterials such as clays, sands, calcareous soils, clay-shale, soft rock, unsaturated soils, and soils artificially treated by adding chemical agents or mechanical reinforcement, and the model is evaluated on the basis of these simulations. A general discussion on the influence of the structure of geomaterials on their mechanical properties is also presented.     

新能源和可再生能源

本文主要综述新能源和可再生能源中的太阳能、风能、燃料电池、海洋温差发电和可燃冰的原理及应用,以及各国的研究现状和发展动态.     

Three-dimensional measurement of ice crystals in frozen beef with a micro-slicer image processing system

A novel technique has been developed for measuring the three-dimensional (3-D) structure and distribution of ice crystals formed in frozen beef by using a micro-slicer image processing system (MSIPS). The system has functions to reconstruct the 3-D image based on the image data of exposed cross-sections obtained by multi-slicing of a frozen sample with the minimum thickness of 1 μm and to display the internal structure as well as an arbitrary cross-section of the sample choosing observation angles. The size and distribution of ice crystals can be determined from the 2-D quantitative information, such as the periphery and area of the crystals. The effects of freezing conditions on the morphology and distribution of the ice crystals were demonstrated quantitatively from the observations of raw beef stained by fluorescent indicator. For the samples frozen at −15 °C, the network structure of ice crystals were observed mainly at intercellular space, having approximately 100 μm in cross-sectional size, while that prepared at −120 °C showed the spherical crystals of 10–20 μm in diameter within the cells. The 3-D image of the sample demonstrated that the growth of ice columns was restricted by the intrinsic structure of muscle fibers. The proposed method provided a new tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.     

冰蓄冷空调控制系统远程监控软件开发

文章采用Visual Basic 6．0开发了冰蓄冷空调控制系统远程监控软件．分析了该监控软件的主要功能．并介绍了该监控软件核心和难点——实时数据采集。     

Fatigue behaviour assessment of flax–epoxy composites

The present study focuses on the characterisation and evaluation of the fatigue behaviour of flax–epoxy composites. A better understanding of this behaviour allows the prediction of long-term properties to assess the viability and long-term durability of these materials. The purpose of this work is to systematically compare the tension–tension fatigue behaviour of flax fibre composites for one random mat, six textile architectures and two laminate configurations, which are used in a wide range of applications. The fibre architecture was found to have a strong effect on the fatigue behaviour, where higher static strength and modulus combinations present the best fatigue characteristics. They have a delayed damage initiation and increased fatigue life as well as a reduced damage propagation rate combined with higher energy dissipation in the early stages of fatigue loading.     

In situ monitoring of structural changes in nonwoven mats under tensile loading using X-ray computer tomography

Changes in the internal structure of nonwoven mats during tensile testing were investigated in situ with micro X-ray computer tomography (CT). Fiber orientation and volume fraction, as well as fiber–fiber contact, were quantitatively characterized at several strain levels. These parameters are apt to change under tensile loading and are important in determining the mechanical properties of nonwoven mats. The reorientation of fibers along the tensile direction was restricted at large deformations due to interlocked structures, which formed as a result of inherent entanglements in the nonwoven mats. In addition, contact efficiency, which describes the relative degree of fiber–fiber contact and was shown to be a suitable geometrical parameter for characterizing the microstructure of nonwoven mats, decreased at low strain and then increased with increasing strain until failure.     

Enumeration and characterization of Listeria monocytogenes in novelty ice cream samples manufactured on a specific production line linked to a listeriosis outbreak

Listeriosis is an invasive illness typically caused by the ingestion of foods contaminated with Listeria monocytogenes. In 2015, an outbreak of listeriosis was linked to ice cream products produced on a specific production line at Facility X. The United States Food and Drug Administration (FDA) obtained samples representing several lots of three products manufactured on that line from May 2014 through January 2015. Two of these products, A and B, while not linked to any reported illnesses, were analyzed to determine the frequency of contamination and the contamination level for risk assessment and dose-response analyses. These enumerations were performed utilizing a Most Probable Number (MPN) method, with a lower detection limit of 0.03 MPN/g, on 344 samples of Product A and 95 samples of Product B. Ten lots of Product A were analyzed and 77% of the samples tested were found to be positive for L. monocytogenes. Five lots of Product B were analyzed and 46% of the tested samples were found to be positive. Additionally, the level of contamination of positive Product B samples was always less than 1 MPN/g. The contamination levels of both products, overall, were low with median values of 0.1 MPN/g and 0.02 MPN/g for Products A and B, respectively. A majority of Product A samples (52%) were contaminated at levels of less than 1 MPN/g and only one sample was above 100 MPN/g. Whole genome sequencing (WGS) of L. monocytogenes isolated from ice cream samples produced in the line suggested minor strain differences related to product type, possibly due to differences in the food matrices and/or differences in the manufacturing equipment. Overall, the data showed a consistent low level of contamination in products produced from a single production line over a nine month period.     

Innovative Ingredients and Emerging Technologies for Controlling Ice Recrystallization,Texture, and Structure Stability in Frozen Dairy Desserts: A Review

Over the past decade, ice cream manufacturers have developed a strong understanding of the functionality of key ingredients and processing, developing effective explanations for the link between structure forming agents, stability mechanisms, and perceived quality. Increasing demand for products perceived as healthier/more natural with minimal processing has identified a number of new tools to improve quality and storage stability of frozen dairy desserts. Ingredients such as dietary fiber, polysaccharides, prebiotics, alternate sweeteners, fat sources rich in unsaturated fatty acids and ice strucsturing proteins (ISP) have been successfully applied as cryoprotective, texturizing, and structuring agents. Emerging minimal processing technologies including hydrostatic pressure processing, ultrasonic or high pressure assisted freezing, low temperature extrusion and enzymatically induced biopolymers crosslinking have been evaluated for their ability to improve colloidal stability, texture and sensory quality. It is therefore timely for a comprehensive review.     

Modeling of degradation processes in historical mortars

The aim of presented paper is modeling of degradation processes in historical mortars exposed to moisture impact during freezing. Internal damage caused by ice crystallization in pores is one of the most important factors limiting the service life of historical structures. Coupling the transport processes with the mechanical part will allow us to address the impact of moisture on the durability, strength and stiffness of mortars. This should be accomplished with the help of a complex thermo-hygro-mechanical model representing one of the prime objectives of this work. The proposed formulation is based on the extension of the classical poroelasticity models with the damage mechanics. An example of two-dimensional moisture transport in the environment with temperature below freezing point is presented to support the theoretical derivations.     

Quantification of effects of stochastic feature parameters of yarn on elastic properties of plain-weave composite – Part 2: Statistical predictions vs. mechanical experiments

This paper presents a linear discretized theoretical model on the basis of the ideal theoretical model to evaluate elastic constants of plain-weave composite by using the statistics of the feature parameters of yarn measured from Micro CT data. A finite element method is utilized to calculate the elastic constants of the composite using the modified and global mean feature parameters of yarn, respectively. Uniaxial tensile and in-plane shear experiments are then completed to measure in-plane elastic constants of the composite. Finally, comparisons among the predictions of two theoretical models, FEM and experimental results are conducted. The results show that the stochastic fluctuations of yarn feature parameters decrease the in-plane elastic moduli and increase the in-plane shear moduli and Poisson’s ratios of the plain-weave composite. The discretized theoretical model with taking account of real yarn stochastic features can predict more accurate elastic constants of the composite than deterministic models.