Damage mechanism of composite cemented backfill based on complex defects influence

In order to reduce mining waste discharge and realize efficient application of tailing material in underground backfilling, the characteristics and mechanism of backfill damage is analyzed, and also the composed behavior and failure characteristic of cemented backfill. Five types of backfills were tested under uniaxial compression loading in SHT4206 electro‐hydraulic servo testing system. Based on the experimental results, the damage constitutive equations of cemented backfills with five cement?tailing ratios were proposed on the basis of damage mechanics and then validated. Research shows that the damage growth rate of backfills with lower cement?tailing is lower before peak value of stress, but it grows more rapidly after that. In addition, four backfill combination schemes were designed for mechanical test. Combining with research results on fracture characteristic of different backfills, a defects coupled constitutive model based on continuum damage mechanics was established. Research shows that the piecewise nonlinear model can well embodies effect of complex defects in backfills on the stress‐strain curve. Accuracy of the model is well verified by measured curve of backfill composite members. The results of this work provide a scientific basis for failure process prediction of backfills and reasonable matching design of framed filling.     

MICROWAVE VACUUM DRYING OF POROUS MEDIA: VERIFICATION OF A SEMI-EMPIRICAL FORMULATION OF THE TOTAL ABSORBED POWER

Vacuum drying experiments were performed on a laboratory scale dryer with two porous materials: a packing of initially saturated glass beads and of unsaturated pharmaceutical granules. Several incident powers and two vacuum pressure levels were tested in order to demonstrate different drying mechanisms. The drying kinetics, temperature of the product and the absorbed power are presented and the coupling between the drying rate and the absorbed power is shown. A semi-empirical formulation of the total absorbed power is proposed taking into account the water content, the temperature and the dielectric properties of each phase. This formulation is based on a quasi-static assumption which allows the local electric field inside the material to be expressed with an analytical equation.     

Impact of stopper type on oxygen ingress during wine bottling when using an inert gas cover

Background and Aims: Many articles evaluating oxygen ingress for different wine stoppers have been published. However, none of these have studied the impact of the stopper type on oxygen ingress during the bottling process. This study tested a range of commercially available stopper types on oxygen entry into headspace during bottling.
Methods and Results: Oxygen concentration in the headspace was measured using the Winkler method. Stopper type significantly ( P  < 0.05) affected oxygen introduced into the headspace. Oxygen concentration correlated well with the volume and the overpressure of the headspace and was also strongly influenced by stopper height. Bottles sealed with natural cork had the lowest headspace oxygen concentration (1.31–2.12 mg/L) despite these stoppers having a lower height (38 mm) than the others tested. Non-cork stoppers were associated with higher oxygen concentrations, probably because they generated higher overpressure. Bottles sealed with screw cap and synthetic stoppers had the highest oxygen concentration (3.29–3.82 mg/L) and, in the case of screw caps, this was probably a result of greater headspace volume. Headspace oxygen concentration for the synthetic stoppers and the screw cap was approximately equivalent to the oxygen entrance through natural cork during the first 8–10 months of ageing.
Conclusions: Stopper type can affect oxygen ingress during bottling because of the changes in headspace volume and overpressure.
Significance of the Study: Along with permeability, stopper selection should also consider the effects of stopper type on the amount of oxygen that initially enters the headspace. If the bottler is not equipped with an efficient vacuum and/or inert gas system, the impact of the stopper type on the entry of oxygen is an important consideration.     

Hidden attribute-based signatures without anonymity revocation

We propose a new notion called hidden attribute-based signature, which is inspired by the recent developments in attribute-based cryptosystem. With this technique, users are able to sign messages with any subset of their attributes issued from an attribute center. In this notion, a signature attests not to the identity of the individual who endorsed a message, but instead to a claim regarding the attributes the underlying signer possesses. Users cannot forge signature with attributes which they have not been issued. Furthermore, signer remains anonymous without the fear of revocation, among all users with the attributes purported in the signature.After formalizing the security model, we propose two constructions of hidden attribute-based signature from pairings. The first construction supports a large universe of attributes and its security proof relies on the random oracle assumption, which can be removed in the second construction. Both constructions have proven to be secure under the standard computational Diffie-Hellman assumption.     

具有圆角的空心圆轴拉伸时的局部应力计算

根据锥形截面假设 ,探讨了一种计算具有圆角的空心圆轴拉伸时局部应力的方法 .文中详细讨论了圆角的半径、圆轴的半径和圆角的深度系数对应力集中的影响 ,并推导出圆轴内、外半径和弹塑性交界面与弹塑性局部应力的关系     

平截面假定及其应用

本文探讨了材料力学中的平截面假定的实质及精确性，并分析了该假定在钢筋砼结构设计、桥梁荷载横向分布计算以及桩基受力计算中的推广应用情况。     

隧道开挖对邻近非连续接口地埋管线的影响分析

隧道开挖引起的地面沉降会引起邻近区域地埋管线的附加受力和变形，甚至会引起管线的开裂破坏。将隧道开挖引起的地面沉降效应作为外界条件施加于地埋管线上，基于改进的Winkler地基模型，并采用虚拟节点以考虑管线接口处的力学特性，提出了刚度非连续接口管线在隧道开挖条件下响应的简化理论分析方法。通过与弹性理论法、离心机试验和实际工程对比，验证了该方法的合理性。并通过与层状弹性理论解的对比，得到了该方法在非均质地基中的适用性。参数分析认为忽略管线接口存在的连续管线假设在分析接口地埋管线有不合理处。     

Development of Numerical Methods for Simulation of Rapid Multi-Phase Interactions

Techniques commonly used in the calculations of multi-phase flow, such as local parameter averaging and continuity phase assumptions, may result in large calculational inaccuracies for phenomena with rapid phase change. For example, with vapor explosions, a large degree of pseudo-diffusion (i.e. numerical diffusion) of components in dispersed states or with discontinuous fronts may occur, and local information, useful for modeling and evaluation of the phenomena, may be lost. Pseudo-diffusion of the components which act as high-temperature heat sources affects component distributions throughout the entire system. Numerical divergence is also often caused by fluctuation of these high-temperature components. In this paper, two treatment methods are proposed to avoid these problems. One method is a dispersed component method, which was developed for dispersed components. This method includes special modeling for some local parameters and some treatments to suppress pseudo-diffusion and numerical divergence. The other is a multi-region scheme, where a calculation domain is divided into an expanding, multi-phase mixture region and the surrounding, single-phase continuum region. The front of the mixture region is tracked using an adaptable grid to accurately follow the interface. By this method, numerical diffusion at the interface can be avoided. The effectiveness of these treatments is demonstrated by numerical simulations.     

Numerical analysis for environmental effects in circular tanks

An efficient numerical method of analysis for environmental (thermal, shrinkage, and swelling) effects in circular, concrete, liquid storage thin-walled tanks under conditions of axial symmetry is outlined. Although the approach is based on individual analyses of wall and plate sub-structures, it yields the global solution that accounts for actual interaction between the wall and plate elements. This interaction between the tank main elements is introduced in a Force Method-type procedure by utilising conditions of compatibility of displacements at the wall-plate junctions. The analysis technique is applicable to a wide range of circular-cylindrical tank systems in contact with a variety of support media. The numerical treatment of the considered environmental effects presented herein extends the approach outlined earlier by the author [1 and 2] and is just a part of design analysis that includes also tank pre-stressing. The effectiveness and usefulness of the proposed method and of the computer software developed are tested with the included examples.     

游离细胞腈水合酶催化丙烯腈水合反应的双稳态反应动力学

腈水合酶是能够催化丙烯腈水合生成丙烯酰胺的一种重要的工业酶。本研究建立了游离细胞腈水合酶催化丙烯腈水合反应的双稳态反应动力学模型,关联了底物浓度、产物浓度和温度等主要因素对反应速率(表观酶活)的影响。在实验研究的基础上,通过麦夸特及全局最优化算法求解了动力学模型。结果表明,游离细胞腈水合酶催化的双稳态反应动力学模型是比较典型的产物抑制型,当产物浓度逐渐增大时,高浓度的产物将抑制腈水合酶的活性。当底物浓度10g·L-1时,由于底物加入反应体系时产生的局部瞬时高浓度,腈水合酶催化的丙烯腈水合反应的表观反应速率不随底物浓度变化。当底物浓度≥10g·L-1时,底物产物浓度对反应速率具有显著影响。温度对酶活的影响也十分显著,相同底物产物浓度下,28℃时的酶催化水合反应速率是15℃时的3.3倍。