高效可撤销的身份基在线离线加密方案

身份基加密（IBE）需要提供一种有效的成员撤销机制，然而，现有可撤销成员的IBE方案存在密钥更新和加密运算量过大的问题，可能使执行该操作的设备成为系统的瓶颈。将完全子树方法和在线离线技术相结合，通过修改指数逆类型IBE的密钥生成和加密算法，提出了一种高效可撤销的身份基在线离线加密方案。方案利用完全子树方法生成更新钥，使得撤销用户无法获得更新钥，进而失去解密能力；利用在线离线技术，将大部分加密运算在离线阶段进行预处理，使得在线阶段仅执行少量简单计算即可生成密文。与相关知名方案相比，该方案不仅提高密钥生成中心的密钥更新的效率，而且极大减少了轻量级设备的在线加密工作量，适合于轻量级设备保护用户隐私信息。     

A multilevel sampled‐data approach for resilient navigation and control of autonomous systems

Autonomous systems are rapidly becoming an integrated part of the modern life. Safe and secure navigation and control of these systems present significant challenges in the presence of uncertainties, physical failures, and cyber attacks. In this paper, we formulate a navigation and control problem for autonomous systems using a multilevel control structure, in which the high‐level reference commands are limited by a saturation function, whereas the low‐level controller tracks the reference by compensating for disturbances and uncertainties. For this purpose, we consider a class of nested, uncertain, multiple‐input–multiple‐output systems subject to reference command saturation, possibly with nonminimum phase zeros. A multirate output‐feedback adaptive controller is developed as the low‐level controller. The sampled‐data (SD) design of this controller facilitates the direct implementation on digital computers, where the input/output signals are available at discrete time instances with different sampling rates. In addition, stealthy zero‐dynamics attacks become detectable by considering a multirate SD formulation. Robust stability and performance of the overall closed‐loop system with command saturation and multirate adaptive control are analyzed. Simulation scenarios for navigation and control of a fixed‐wing drone under failures/attacks are provided to validate the theoretical findings.     

Cf/C复合材料与纯铜的胶接辅助钎焊连接

采用胶接辅助钎焊方法,以TiH_2粉为活性元素源,环氧树脂为粘性载体,Ag-Cu共晶合金为钎料,Cu箔为应力缓冲层材料,实现了C_f/C复合材料与纯铜的钎焊连接,结果表明,接头界面处产生TiC,TiCu,Ag(s,s),Cu(s,s)等反应产物,其结构可表示为(C_f/C)/TiC+Ag(s,s)+Cu(s,s)+TiCu/Cu。通过钎焊工艺试验得出,在930℃保温25 min钎焊条件下接头的抗剪强度达到最大值30 MPa。     

Isolation and identification of two major acylated anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) by UPLC‐QTOF‐MS/MS and NMR

In recent years, researches on the isolation and preparation of monomeric anthocyanins have intensified because of the requirements of quantitative and structure–bioactivity relationship analyses. However, simple and effective methods about the scale of monomeric anthocyanins from the natural purple sweet potato powder are rarely reported. In this study, high molecular weight acylated monomeric anthocyanins were isolated from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) via the combination of column chromatography and semi‐preparative HPLC technology and identified mainly by ultra‐high‐performance liquid chromatography quadrupole time‐of‐flight tandem mass spectrometry/mass spectrometry (UPLC‐QTOF‐MS/MS) and ¹H and ¹³C nuclear magnetic resonance (NMR). Two major acylated anthocyanins were unambiguously determined as peonidin 3‐O‐(6‐O‐(E)‐caffeoyl‐(2‐O‐(6‐O‐p‐hydroxybenzoyl)‐β‐D‐glucopyranosyl)‐β‐D‐glucopyranoside)‐5‐O‐(β‐D‐glucopyranoside) and peonidin 3‐O‐(6‐O‐(E)‐caffeoyl‐(2‐O‐(6‐O‐(E)‐feruloyl)‐β‐D‐ glucopyranosyl)‐β‐D‐glucopyranoside)‐5‐O‐(β‐D‐glucopyranoside). The results of this study may help promote the purification of high molecular weight acylated anthocyanins from purple sweet potato as well as from other plant materials in nature.     

Mathematical formulation and heuristic algorithms for optimisation of auto-part milk-run logistics network considering forward and reverse flow of pallets

The operational planning of distribution network for automotive industry is complex with many conditions to consider, including heterogeneous fleet, enforcing the feasibility of 3D-packing of pallets into vehicles to address the vehicle's capacity in terms of weight and volume, compatibility of orders in a vehicle, returning empty pallets from assembly-plants backwards to suppliers, and delivery time windows. A mathematical model (MILP) is proposed that takes account of these conditions to minimise total transportation costs. The network structure can be a combination of direct shipment and milk-run for both forward and reverse flow of pallets. The model is solved optimally for small-size problems. For solving larger problems, a heuristic algorithm (in two versions) is proposed that uses a similarity measure to generate a reasonable list of orders. Best/first-fit strategies are employed to generate a feasible solution with the aid of a relaxed version of the proposed MILP. Improvement heuristics are also designed. Unlike most of existing constructive heuristics, our aim for developing the heuristic approach is to force routing decision, with all of its considerations, being made optimal. We also use the proposed best-fit strategy in the body of grouping evolution strategy (GES) algorithm to attain an effective meta-heuristic approach. The effectiveness of heuristics is tested on generated instances which demonstrates they are optimal for small-size problems. They are also tested on the data of daily auto-parts shipments gathered from the largest Iranian automobile company. Results demonstrate there exists a significant potential for cost saving through milk-run strategy compared with the direct shipping strategy.     

异螺距万分尺设计

介绍了一种螺旋万分尺的结构设计。该万分尺的微分筒采用双螺纹,两螺纹的螺旋方向相同,螺距不同。采用V型槽和V型块精确定位来增加量程。测量最小刻度可达0.001 mm,读数精度达0.0001 mm。万分尺采用纯机械结构,结构原理简单,制造安装方便。     

11-苄硒基十一羧酸铵盐的双重刺激响应性质

合成了一种对氧化还原(Redox)和CO_2/N_2具有双重刺激响应的表面活性剂11-苄硒基十一羧酸铵盐(BSeUA),分别利用傅里叶红外光谱、核磁共振和电喷雾质谱等手段研究了BSeUA在Redox和CO_2/N_2刺激响应前后的分子结构变化特征。结果表明,在过氧化氢和水合肼交替作用下,BSeUA分子中二价硒醚基团(-Se-)与相应的四价硒亚砜基团(-Se=O)之间可以氧化还原可逆互变,在CO_2和N_2交替作用下,BSeUA分子中羧酸根(-COO-)与相应的羧酸(-COOH)之间可以可逆互变,从而实现BSeUA对Redox和CO_2/N_2具有双重刺激响应。分别在Redox和CO_2/N_2刺激作用下,由BSeUA稳定的乳液可以在破乳和再乳化2种状态下开关可逆循环至少5次,且乳液粒径和稳定性未发生明显变化。     

固溶处理对TiB2/6061复合材料硬度及耐磨性的影响

采用氟盐法制备了TiB₂质量分数为3%的原位合成TiB₂/6061复合材料,研究了固溶温度和固溶时间对复合材料硬度和耐磨性能的影响。结果表明:TiB₂颗粒弥散分布在6061铝合金基体中,明显细化6061铝合金基体晶粒。当固溶温度一定时,随固溶时间延长,复合材料的硬度和耐磨性可获得明显提高,但固溶时间在6~10 h时,复合材料的性能变化不显著。当固溶时间一定时,随固溶温度升高,复合材料硬度和耐磨性呈现先上升后下降的趋势。3wt%TiB₂/6061复合材料经530 ℃×10 h固溶处理后,硬度和耐磨性能最佳,相较于铸态硬度值提高了79.5％,磨损量减少了59.1%。固溶处理后复合材料的磨损表面犁沟变细变浅,材料脱落现象减少。     

An Atomistic Understanding of Allosteric Inhibition of Glutamate Racemase: a Dampening of Native Activation Dynamics

Glutamate racemases (GR) are members of the family of bacterial enzymes known as cofactor-independent racemases and epimerases and catalyze the stereoinversion of glutamate. D-amino acids are universally important for the proper construction of viable bacterial cell walls, and thus have been repeatedly validated as attractive targets for novel antimicrobial drug design. Significant aspects of the mechanism of this challenging stereoinversion remain unknown. The current study employs a combination of MD and QM/MM computational approaches to show that the GR from H. pylori must proceed via a pre-activation step, which is dependent on the enzyme's flexibility. This mechanism is starkly different from previously proposed mechanisms. These findings have immediate pharmaceutical relevance, as the H. pylori GR enzyme is a very attractive allosteric drug target. The results presented in this study offer a distinctly novel understanding of how AstraZeneca's lead series of inhibitors cripple the H. pylori GR's native motions, via prevention of this critical chemical pre-activation step. Our experimental studies, using SPR, fluorescence and NMR WaterLOGSY, show that H. pylori GR is not inhibited by the uncompetitive mechanism originally put forward by Lundqvist et al.. The current study supports a deep connection between native enzyme motions and chemical reactivity, which has strong relevance to the field of allosteric drug discovery.