Quantization and Event-Triggered Policy Design for Encrypted Networked Control

This paper proposes a novel event-driven encrypted control framework for linear networked control systems(NCSs),which relies on two modified uniform quantization policies,the Paillier cryptosystem,and an event-triggered strategy.Due to the fact that only integers can work in the Pailler cryptosystem,both the real-valued control gain and system state need to be first quantized before encryption.This is dramatically different from the existing quantized control methods,where only the quantization of a single value,e.g.,the control input or the system state,is considered.To handle this issue,static and dynamic quantization policies are presented,which achieve the desired integer conversions and guarantee asymptotic convergence of the quantized system state to the equilibrium.Then,the quantized system state is encrypted and sent to the controller when the triggering condition,specified by a state-based event-triggered strategy,is satisfied.By doing so,not only the security and confidentiality of data transmitted over the communication network are protected,but also the ciphertext expansion phenomenon can be relieved.Additionally,by tactfully designing the quantization sensitivities and triggering error,the proposed event-driven encrypted control framework ensures the asymptotic stability of the overall closedloop system.Finally,a simulation example of the secure motion control for an inverted pendulum cart system is presented to evaluate the effectiveness of the theoretical results.

铜基串联催化剂电催化CO_(2)还原的研究进展

化石燃料的燃烧和其他人类活动排放了大量的CO_(2)气体,引发了诸多环境问题。电催化CO_(2)还原反应(CO_(2)RR)可以储存间歇可再生能源,实现人为闭合碳循环,被认为是获得高附加值化学品和燃料的有效途径。电催化CO_(2)RR涉及多个电子-质子转移步骤,其中^(*)CO通常被认为是关键中间体。铜由于对^(*)CO具有合适的吸附能,已被广泛证明是唯一能够有效地将CO_(2)还原为碳氢化合物和含氧化合物的金属催化剂。然而,纯Cu稳定性差、产品选择性低、过电位高,阻碍了工业级多碳产品的生产。构筑Cu基串联催化剂是提高CO_(2)RR性能的一种有前途的策略。本文首先介绍电催化CO_(2)RR的反应路线和串联机理。然后,系统地总结铜基串联催化剂对电催化CO_(2)RR的最新研究进展。最后,提出合理设计和可控合成新型电催化CO_(2)RR串联催化剂面临的挑战和机遇。

Effects of transection of cervical sympathetic trunk on cerebral infarct volume and oxygen free radical levels in rats with focal cerebral ischemia/reperfusion injury

BACKGROUND: Stellate ganglion block (SGB) plays a protective role on the brain, but the precise mecha- nism of action is not clear. OBJECTIVE: To simulate SGB by transection of the cervical sympathetic trunk (TCST) and to investigate the TCST effects on changes in cerebral infarct volume and oxygen free radical levels in rats with focal cere- bral ischemia/reperfusion injury. DESIGN, TIME AND SETTING: A complete randomized control animal experiment was performed at the Institute of Neurological Diseases of Taihe Hospital, Yunyang Medical College from February to December 2005. MATERIALS: A total of 101 healthy Wistar rats, weighing 280–320 g, of both genders, aged 17–18 weeks, were used in this study. 2, 3, 5-triphenyltetrazolium chloride (TTC) was purchased from Changsha Hongyuan Biological Company. Superoxide dismutase (SOD), malondialdehyde (MDA) and nitric oxide (NO) assay kits were provided by Nanjing Jiancheng Bioengineering Institute. METHODS: Rats were randomly divided into a TCST group, a model group and a sham operation group. Successful models were included in the final analysis, with at least 20 rats in each group. After TCST, rat models of focal cerebral ischemia/reperfusion injury were established in the TCST group by receiving middle cerebral artery occlusion (MCAO) by the intraluminal suture method for 2 hours, followed by 24 hours of reperfusion. Rat models of focal cerebral ischemia/reperfusion injury were made in the model group. Rats in the sham operation group underwent experimental procedures as for the model group, threading depth of 10 mm, and middle cerebral artery was not ligated. MAIN OUTCOME MEASURES: Brain tissue sections of ten rats from each group were used to measure cerebral infarct volume by TTC staining. Brain tissue homogenate of another ten rats from each group was used to detect SOD activities, MDA contents and NO levels. Rat neurological function was assessed by neu- robehavioral measures. RESULTS: Cerebral infarct volume was bigger in the model group than in the TCST group (P < 0.05). Twenty four hours after cerebral ischemia/reperfusion, SOD activities were lower, whereas MDA contents and NO levels were higher in the TCST and model groups, compared with the sham operation group (P < 0.05 or P < 0.01). Compared with the model group, SOD activities were higher, whereas MDA contents and NO lev- els were lower in the TCST group (P < 0.05). CONCLUSION: After TCST, cerebral infarct volume is reduced, SOD activities are increased, and MDA contents and NO levels are decreased compared to the model group in rats with focal cerebral ische- mia/reperfusion injury. These changes may be associated with TCST.

Largeπ-conjugated indium-based metal-organic frameworks for high‐performance electrochemical conversion of CO_(2)

The active site engineering of electrocatalysts,as one of the most economical and technological approaches,is a promising strategy to enhance the intrinsic activity and selectivity towards electrochemical CO_(2)reduction reaction.Herein,an indium-based porphyrin framework(In-TCPP)with a well-defined structure,highly dispersed catalytic center,and good stability was constructed for efficient CO_(2)-to-formate conversion.In-TCPP could achieve a high Faraday efficiency for formate(90%)and a cathodic energy efficiency of 63.8%in flow cells.In situ attenuated total reflectance Fourier transform infrared spectroscopy and density functional theory calculation confirm that the crucial intermediate is*COOH species which contributes to the formation of formate.This work is expected to provide novel insights into the precise design of active sites for high-performance electrocatalysts towards electrochemical CO_(2)reduction reaction.

Two-dimensional covalent organic frameworks for electrocatalysis:Achievements,challenges,and opportunities

Covalent organic frameworks(COFs)represent an emerging class of crystalline porous polymers with high porosity,good stability,and adjustable structure,and their excellent characteristics lay a solid foundation for electrocatalysis.This review systematically introduces the design principles of the catalytic sites in two-dimensional(2D)COF-based electrocatalysts and analyzes the relationship between 2D COF structure and their electrocatalytic performances.In particular,the recent progress in the field of 2D COFs as electrocatalysts is comprehensively summarized.Finally,we discuss the current shortcomings and challenges on tailoring 2D COF for high-performance electrocatalysts in details,and look forward to promoting more researches on 2D COF-based electrocatalysts.

Secure motion control of micro-spacecraft using semi-homomorphic encryption

This paper studies the secure motion control problem for micro-spacecraft systems.A novel semi-homomorphic encrypted control framework,consisting of a logarithmic quantizer,two uniform quantizers,and an encrypted control law based on the Paillier cryptosystem is developed.More specifically,a logarithmic quantizer is adopted as a digitizer to convert the continuous relative motion information to digital signals.Two uniform quantizers with different quantization sensitivities are designed to encode the control gain matrix and digitized motion information to integer values.Then,we develop an encrypted state-feedback control law based on the Paillier cryptosystem,which allows the controller to compute the control input using only encrypted data.Using the Lyapunov stability theory and the homomorphic property of the Paillier cryptosystem,we prove that all signals in the closed-loop system are uniformly ultimately bounded.Different from the traditional motion control laws of spacecraft,the proposed encrypted control framework ensures the security of the exchanged data over the communication network of the spacecraft,even when communication channels are eavesdropped by malicious adversaries.Finally,we verify the effectiveness of the proposed encrypted control framework using numerical simulations.

角速度受限下航天器姿态机动事件触发控制

针对角速度受限和通信资源有限的航天器姿态系统,考虑转动惯量难以精确获得并且存在外部干扰的情况,提出一种基于神经网络的自适应事件触发姿态机动控制算法.该算法首先基于预设性能技术,将角速度受限约束转换为性能边界约束,进一步通过误差转换,建立姿态系统的等效误差模型,将存在角速度约束的航天器姿态系统机动控制问题巧妙地转化为无约束误差系统的状态有界稳定控制问题;然后,选用径向基神经网络设计自适应律,在线逼近系统中由未知转动惯量带来的不确定性项.与此同时,考虑到星载通信资源有限的问题,通过建立触发控制信号与实时控制信号之间的显式关系,设计一个统一的时变事件触发机制,当触发条件满足时同步更新控制器和自适应律,大大减少了控制器和执行器之间频繁的网络信号传输.此外,触发机制中时变项的引入严格保证了触发控制无Zeno现象发生.最后,仿真结果表明了所提出的姿态控制算法不但能够保证航天器高精度、高稳定度、高鲁棒性地完成指定姿态机动任务,而且可以减少大约97.50%的控制信号更新,这大大缓解了航天器的通信负担.

Isolation and phylogenetic study of Rift Valley fever virus from the first imported case to China

Dear Editor,Rift Valley fever(RVF)is an anthropozoonosis caused by Rift Valley fever virus(RVFV).RVFV belongs to the Phlebovirus genus in the family Bunyaviridae,which is circulating among ruminants.Human infection with RVFV is generally asymptomatic,however,minority of patients develop severe RVF diseases like encephalitis

Networking for training Level 3/4 biosafety laboratory staff

Worldwide,public health systems are continually challenged by emerging and re-emerging viruses.It is therefore important that high-containment labs coordinate and communicate globally to share their experiences and lessons to improve their capacity to respond to threats.The National Biosafety(Level 4)Laboratory in Wuhan,CAS,which is the first Level 4 biosafety laboratory(BSL-4)in China,has been certified recently and it is expected to play an important role in the prevention and control of highly infectious agents in future.Trained and experienced staff in such organizations is the most important factor contributing to safety and security.Therefore,it is imperative to develop a standard training program.Accordingly,in the present study,we developed an improved training program and assessment system based on policies and practices developed by BSL-3/4s in other countries.It included the following three components:(1)A flexible modularized theoretical training:This training comprised 14 modularized theoretical topics such that staffs with different backgrounds could take this theoretical training with different topic combinations according to their knowledge and skill levels;(2)A standardized practical training assessment:This comprehensive assessment,which could be used with biosafety laboratory staff before,during,and after training,included standard operation procedures to meet the special requirements of trainees with different scores;and(3)An applicable documentation system:A certification system was established to evaluate the ability of all staff working inside or outside the laboratory,implemented by a special committee.This certification was approved and authorized by the director of the laboratory and was classified into three grades with corresponding minimal requirements.Further,the present study examined the importance of and need for networking for training BSL-3/4 staff.The establishment of rigorous standards for training BSL-3/4 staff will instill confidence in the public,policy makers,and security officials.Additionally,the expanded international network of BSL-3/4s will continue to be operated safely and will pose no risk to scientific staff,local communities,surrounding environment,and host nations.The clarification and coordination of training standards will help develop a highly-qualified biocontainment workforce and will result in a series of programs that will enable scientists to develop measures to deal with existing threat agents and new diseases that emerge.