一种基于ABE的抗共谋组播方案

基于属性的加密是一种新兴的加密技术,本文在此基础上提出了一个全新抗共谋攻击的组播方案。该方案以属性作为密钥,完成对节点的组播加密。只有当节点拥有符合解密所需要的属性时,才可以解开密文,否则解密失败。本方案不仅能够保证加密解密过程的安全,还能抵御抗共谋攻击,是一个安全而有效的组播方案。     

Separation of butanol from acetone-butanol-ethanol fermentation by a hybrid extraction-distillation process

The alternative fuel butanol can be produced via acetone-butanol-ethanol (ABE) fermentation from biomass. The high costs for the separation of ABE from the dilute fermentation broth have so far prohibited the industrial-scale production of bio-butanol. In order to facilitate an effective and energy-efficient product removal, we suggest a hybrid extraction-distillation downstream process with ABE extraction in an external column. By means of computer-aided molecular design (CAMD), mesitylene is identified as novel solvent with excellent properties for ABE extraction from the fermentation broth. An optimal flowsheet is developed by systematic process synthesis which combines shortcut and rigorous models with rigorous numerical optimization. Optimization of the flowsheet structure and the operating point, consideration of heat integration, and the evaluation of the minimum energy demands are covered. It is shown that the total annualized costs of the novel process are considerably lower compared to the costs of alternative hybrid or pure distillation processes.     

隐藏访问策略的属性基加密机制

在属性基加密方案中,加密者通常把访问策略与密文一起发送给用户,但有时访问策略本身就是敏感信息,需要保密。提出一种新的较高效的匿名访问属性基加密方案,在加密过程中通过隐藏部分子集值以使授权用户有效密文和非授权用户无效密文不可区分,在对称双线性群组的基础上实现了访问匿名。与同类的匿名访问方案比较,新方案减少了双线性对和幂运算的次数,提高了算法的效率,并缩短了分析密文、密钥等的长度。分析结果表明,该算法可以在保持现有公共参数不变的情况下增加新的属性,增强了系统的灵活性。同时可证明新方案在双线性判定性假设下的安全性。     

基于门限属性加密的安全分布式云存储模型

针对云存储存在越来越多的安全问题,设计了一种新的基于门限属性加密的安全分布式云存储模型。该模型由加密、存储、解密三个阶段组成且均具有分布式特点。利用基于属性加密体制不仅提高数据存储的安全性,而且多属性服务器的模式也使得该模型能支持门限解密功能及任意个属性服务器的加入与撤出问题;在存储阶段使用的分布式删除码可充分保障模型的健壮性,且该模型能抵抗共谋攻击。在一些特有云环境中,该模型可向用户提供较好的安全云存储服务。     

基于改进CP ABE算法的移动云计算数据安全访问控制方法

为了提高云计算数据访问的安全性及高效性,采用改进的CP ABE算法来实现移动云计算数据访问控制。该方案将文件按不同的访问权限进行分级管理,将每种访问权限定义为一个权限模型,接着对多个权限模型结构进行整合。这种方案对密文的处理采用分享式的模式,所有权限模型均可共享该密文,有效减少每个权限模型存储密文的时间成本。实验结果显示,提出的分享式密文方案在加密和解密过程中可以有效减少时间开销,具有较强的应用价值。     

Acetone-butanol-ethanol (ABE) fermentation using the root hydrolysate after extraction of forskolin from Coleus forskohlii

The biomass obtained after the extraction of forskolin from the roots of Coleus forskohlii was evaluated as a substrate for the production of acetone-butanol-ethanol (ABE). The spent biomass constituting more than 90% of the raw material showed 50–70% carbohydrates with starch and cellulose being the major constituents. This study was undertaken to optimize enzymatic hydrolysis of C. forskohlii roots for maximum release of fermentable sugars and subsequent fermentation to ABE. The root biomass was hydrolyzed using the Stargen® 002 and Accellerase® 1500. Cocktail of both enzymes (16U Stargen® 002 and 60 FPU Accellerase® 1500) could produce 41.2 g/l of total reducing sugars (glucose equivalent to 32.33 g/l). The production of ABE was optimized in a batch fermentation using Clostridium acetobutylicum NCIM 2877. The maximum ABE production using the root hydrolysates was 0.55 g/l. Pretreatment with lime and Amberlite XAD-4 increased the production of total solvent to 5.33 g/l.     

Quest for sustainable bio‐production and recovery of butanol as a promising solution to fossil fuel

Biobutanol has conventionally been generated by fermentation of carbohydrates derived from biomass (starch or sugar‐based feedstock, such as corn) using Clostridia strains (mainly C. beijerinckii and C. acetobutylicum) under anaerobic conditions in batch mode. Under these premises, it has been tough for the acetone–butanol–ethanol fermentation to compete with petro‐butanol production from an energy efficiency and material consumption standpoint. Challenges for butanol production from biomass comprised high cost of feedstock, scarcity of hyper‐butanol producing bacteria and low butanol yield, volumetric productivity and titre, leading to high water usage and separation‐purification costs. This article is an up‐to‐date review on several under explored sections, such as optimization of fermenter feed, microbial culture responsible for solvent production (co‐culture techniques and electro‐biochemical process), latest recovery techniques and the studies integrating in situ continuous fermentation processes. Biobutanol refinery way forward should build upon the use of low‐cost lignocellulosic matter and zero cost organic wastes and by‐products from food, agriculture, forestry, fermentation and paper industries as feedstock; optimized fermentation of such diversified feed with appropriate hyper‐butanol producing strains in biofilm reactors and integration of fermentation step with hybrid high butanol‐selective recovery techniques. Copyright © 2015 John Wiley & Sons, Ltd.     

Processing of AZ31 magnesium alloy by a new noble severe plastic deformation method

In the present investigation a wrought magnesium alloy (AZ31) has been processed applying the accumulative back extrusion (ABE) method. This was performed through different thermomechanical processing routes (different ABE deformation passes at temperatures of 80-380 °C). The results indicate that AZ31 alloy may successfully be deformed through ABE processing even at temperatures as low as 80 °C. Following the ABE processing a sophisticated microhardness testing was conducted and thorough microstructural observations were undertaken using optical microscopy. The results show that the equiaxed submicron size grains have been achieved. As the number of passes was increased, a more homogeneous microstructure with finer mean grain size was obtained. It was also found that increasing the temperature resulted in larger mean grain size and also higher microstructural homogeneity.