Online Consensus Control of Nonlinear Affine Systems From Disturbed Data

Dear Editor,In this letter, we introduce a novel online distributed data-driven robust control approach for learning controllers of unknown nonlinear multi-agent systems(MASs) using state-dependent representations.

Mechanically flexible reduced graphene oxide/carbon composite films for high-performance quasi-solid-state lithium-ion capacitors

Practical applications of diverse flexible wearable electronics require electrochemical energy storage(EES)devices with multiple configurations.Moreover,to fabricate flexible EES devices with high energy density and stability,organic integration from electrode design to device assembly is required.To address these challenges,a free-standing reduced graphene oxide(rGO)/carbon film with a unique sandwich structure has been designed via the assistance of vacuum-assistant filtration for lithium-ion capacitors(LICs).The graphene acts as not only a binder to construct a three-dimensional conductive network but also an active material to provide additional capacitive lithium storage sites,thus enabling fast ion/electron transport and improving the capacity.The designed rGO/hard carbon(rGO/HC)and rGO/activated carbon(rGO/AC)free-standing films exhibit enhanced specific capacities(513.7 mA h g^(-1)for rGO/HC and 102.8 mA h g^(-1)for rGO/AC)and excellent stability.Moreover,the integrated flexible quasi-solid-state rGO/AC//rGO/HC LIC devices possess a maximum energy density of 138.3 Wh kg^(-1),a high power density of 11 kW kg^(-1),and improved cycling performance(84.4%capacitance maintained after 10,000 cycles),superior to the AC//HC LIC(43.5%retention).Such a strategy enlightens the development of portable flexible LICs.

Pollination Biology of the Endangered Herbal Medicines Dendrobium chrysotoxum(Orchidaceae)

Pollination biology studies of the endangered herbal medicines Dendrobium chrysotoxum were conducted in natural pollination conditions using flower observation,pollinator observation and artificial pollination experiments.Populations of D.chrysotoxum with fragrance and nectar were pollinated by Ctenoplectra davidi Valhalla(Hymenoptera:Apidae)species.The floral structure of D.chrysotoxum adapted precisely to its pollinators.Flowers had a low capsule setting(0.17%)under natural conditions.However,compared to open pollination,artificial pollination experiments showed a significant increase in capsule setting,and D.chrysotoxum was cross-compatible and self-compatible,but there was pollinator limitation also.This study will provide important information for the preservation of this endangered species.

间苯二酚-双醛淀粉-甲醛共缩聚树脂胶黏剂制备

以玉米淀粉为原料,通过高碘酸钠在酸性条件下氧化得到双醛淀粉。将双醛淀粉与甲醛一起作为醛基给予体,与间苯二酚(R)共缩聚制备间苯二酚-双醛淀粉-甲醛(RDSF)树脂胶黏剂。研究了双醛淀粉用量、共反应p H、共反应温度和共反应时间对RDSF树脂胶黏剂固体含量、黏度、固化时间和胶接强度的影响。结果表明,双醛淀粉加入量为0. 15mol,共反应p H值为9. 0,共反应温度为70℃,共反应时间为90 min时,制得的RDSF树脂胶黏剂综合性能最佳,此时固体含量为42. 59%,黏度为725 m Pa·s,固化时间为53 s,干状胶合强度为1. 38 MPa,湿状胶合强度为1. 17 MPa。傅里叶变换红外光谱测试发现RDSF树脂的结构近似于间苯二酚-甲醛(RF)树脂,表明RDSF树脂可代替RF树脂使用。差示扫描量热分析发现RDSF树脂的固化温度和固化焓值低于RF树脂,固化峰值温度为77. 43℃,固化焓值为-238. 91 J/g,表明其固化能耗更低。

Effects of freeze–thaw cycles on soil N_2O concentration and flux in the permafrost regions of the Qinghai–Tibetan Plateau

Nitrous oxide(N_2 O) is one of the most important greenhouse gases in the atmosphere; freeze–thaw cycles(FTCs) might strongly influence the emission of soil N_2 O on the Qinghai–Tibetan Plateau(QTP). However, there is a lack of in situ research on the characteristics of soil N_2 O concentration and flux in response to variations in soil properties caused by FTCs.Here, we report the effect of FTC-induced changes in soil properties on the soil N_2 O concentration and flux in the permafrost region of the higher reaches of the Shule River Basin on the northeastern margin of the QTP. We measured chemical properties of the topsoil, activities of soil microorganisms, and air temperature(AT), as well as soil N_2 O concentration and flux, over an annual cycle from July 31, 2011, to July 30, 2012. The results showed that soil N_2 O concentration was significantly affected by soil temperature(ST), soil moisture(SM), soil salinity(SS), soil polyphenol oxidase(SPO), soil alkaline phosphatase(SAP), and soil culturable actinomycetes(SCA), ranked as SM>SS>ST>SPO>SAP>SCA, whereas ST significantly increased soil N_2 O flux, compared with SS. Overall, our study indicated that the soil N_2 O concentration and flux in permafrost zone FTCs were strongly affected by soil properties, especially soil moisture, soil salinity, and soil temperature.

Quantum Blockchain: A Decentralized, Encrypted and Distributed Database Based on Quantum Mechanics

Quantum blockchain can be understood as a decentralized, encrypted anddistributed database based on quantum computation and quantum information theory.Once the data is recorded in the quantum blockchain, it will not be maliciously tamperedwith. In recent years, the development of quantum computation and quantum informationtheory makes more and more researchers focus on the research of quantum blockchain. Inthis paper, we review the developments in the field of quantum blockchain, and brieflyanalyze its advantages compared with the classical blockchain. The construction and theframework of the quantum blockchain are introduced. Then we introduce the method ofapplying quantum technology to a certain part of the general blockchain. In addition, theadvantages of quantum blockchain compared with classical blockchain and itsdevelopment prospects are summarized.

Energy evolution and water immersion‑induced weakening in sandstone roof of coal mines

The instability of underground spaces in abandoned coal mines with water-immersed rocks is one of the main hazards hindering the geothermal energy use and ecological restoration of post-mining areas.This study conducted graded cyclic loading–unloading tests of fve groups of sandstone samples with diferent water contents.The evolution of input,elastic,dissipated,damping,and plastic energies were explored,considering the damping efect.The normalized plastic energy serves to characterize the damage evolution of sandstone samples,whose failure characteristics were analyzed from both the macroscopic and microscopic perspectives.X-ray difraction technique and scanning electron microscopy were used to reveal the softening mechanism of sandstone.The results show that under graded cyclic loading,input energy,elastic energy,and dissipated energy all increase gradually,and the fraction of elastic energy increases gradually at frst and then tends to stabilize.The variation in the fraction of dissipated energy is opposite to that of elastic energy.In each cycle,the input energy is stored primarily in the form of elastic energy,whereas the dissipated energy is used primarily to overcome the damping of sandstone.When the normalized number of cycles approached unity,the plastic energy fraction sharply increases,while that of the dampening energy drops abruptly.With increasing water content,the efect of pore water on the lubrication,the water wedge,and dissolution of mineral particles becomes more obvious,reducing the elastic-storage limit of sandstone,meanwhile the sandstone damage factor increases signifcantly under the same cycle and the failure mode changes from brittle to ductile.

Analysis and Improvement of Steganography Protocol Based on Bell States in Noise Environment

In the field of quantum communication,quantum steganography is an important branch of quantum information hiding.In a realistic quantum communication system,quantum noises are unavoidable and will seriously impact the safety and reliability of the quantum steganographic system.Therefore,it is very important to analyze the influence of noise on the quantum steganography protocol and how to reduce the effect of noise.This paper takes the quantum steganography protocol proposed in 2010 as an example to analyze the effects of noises on information qubits and secret message qubits in the four primary quantum noise environments.The results show that when the noise factor of one quantum channel noise is known,the size of the noise factor of the other quantum channel can be adjusted accordingly,such as artificially applying noise,so that the influence of noises on the protocol is minimized.In addition,this paper also proposes a method of improving the efficiency of the steganographic protocol in a noisy environment.

Full-Blind Delegating Private Quantum Computation

The delegating private quantum computation(DQC)protocol with the universal quantum gate set{X,Z,H,P,R,CNOT}was firstly proposed by Broadbent et al.[Broadbent(2015)],and then Tan et al.[Tan and Zhou(2017)]tried to put forward a half-blind DQC protocol(HDQC)with another universal set{H,P,CNOT,T}.However,the decryption circuit of Toffoli gate(i.e.T)is a little redundant,and Tan et al.’s protocol[Tan and Zhou(2017)]exists the information leak.In addition,both of these two protocols just focus on the blindness of data(i.e.the client’s input and output),but do not consider the blindness of computation(i.e.the delegated quantum operation).For solving these problems,we propose a full-blind DQC protocol(FDQC)with quantum gate set{H,P,CNOT,T},where the desirable delegated quantum operation,one of{H,P,CNOT,T},is replaced by a fixed sequence(H,P,CZ,CNOT,T)to make the computation blind,and the decryption circuit of Toffoli gate is also optimized.Analysis shows that our protocol can not only correctly perform any delegated quantum computation,but also holds the characteristics of data blindness and computation blindness.

Quantum Algorithms and Experiment Implementations Based on IBM Q

With the rapid development of quantum theory and technology in recent years,especially the emergence of some quantum cloud computing platforms,more and more researchers are not satisfied with the theoretical derivation and simulation verification of quantum computation(especially quantum algorithms),experimental verification on real quantum devices has become a new trend.In this paper,three representative quantum algorithms,namely Deutsch-Jozsa,Grover,and Shor algorithms,are briefly depicted,and then their implementation circuits are presented,respectively.We program these circuits on python with QISKit to connect the remote real quantum devices(i.e.,ibmqx4,ibmqx5)on IBM Q to verify these algorithms.The experimental results not only show the feasibility of these algorithms,but also serve to evaluate the functionality of these devices.

Cluster mean-field study of spinor Bose-Hubbard ladder:Ground-state phase diagram and many-body population dynamics

We present a cluster mean-field study for ground-state phase diagram and many-body dynamics of spin-1 bosons confined in a two-chain Bose-Hubbard ladder(BHL).For unbiased BHL,we find superfluid(SF)phase and integer filling Mott insulator(Int MI)phase.For biased BHL,in addition to the SF and Int MI phases,there appears half-integer filling Mott insulator(HInt MI)phase.The phase transition between the SF and Int MI phases can be first order at a part of phase boundaries,while the phase transition between the SF and HInt MI phases is always second order.By tuning the bias energy,we report on the change of the nature of SF-MI phase transitions.Furthermore,we study the effect of the spin-dependent interaction on the many-body population dynamics.The spin-dependent interaction can lead to rich dynamical behaviors,but does not influence the particle transfer efficiency.Our results indicate a way to tune the nature of the SF-MI phase transition and open a new avenue to study the many-body dynamics of spinor bosons in optical lattices.

Structural Domain Imaging and Direct Determination of Crystallographic Orientation in Noncentrosymmetric Ca3 Ru2O7 Using Polarized Light Reflectance

The noncentrosymmetricity of a prototypical correlated electron system Ca3Ru2O7 renders extensive interest in the possible polar metallic state,along with multiple other closely competing interactions.However,the structural domain formation in this material often complicates the study of intrinsic material properties.It is crucial to fully characterize the structural domains for unrevealing underlying physics.Here,we report the domain imaging on Ca3Ru2O7 crystal using the reflection of polarized light at normal incidence.The reflection anisotropy measurement utilizes the relative orientation between electric field component of the incident polarized light and the principal axis of the crystal,and gives rise to a peculiar contrast.The domain walls are found to be the interfaces between 90° rotated twin crystals by complementary magnetization measurements.A distinct contrast in reflectance is also found in the opposite cleavage surfaces,owing to the polar mode of the RuO6 octahedra.More importantly,the analysis of the contrast between all inequivalent cleavage surfaces enables a direct determination of the crystallographic orientation of each domain.Such an approach provides an efficient yet feasible method for structural domain characterization,which can also find applications in noncentrosymmetric crystals in general.

A New Spectral Method Using Nonstandard Singular Basis Functions for Time-Fractional Differential Equations

In this paper,we introduce new non-polynomial basis functions for spectral approximation of time-fractional partial differential equations (PDEs). Different from many other approaches,the nonstandard singular basis functions are defined from some generalised Birkhoff interpolation problems through explicit inversion of some prototypical fractional initial value problem (FIVP) with a smooth source term. As such,the singularity of the new basis can be tailored to that of the singular solutions to a class of time-fractional PDEs,leading to spectrally accurate approximation. It also provides the acceptable solution to more general singular problems.

Quantum Algorithm for Appointment Scheduling

Suppose a practical scene that when two or more parties want to schedule anappointment, they need to share their calendars with each other in order to make itpossible. According to the present result the whole communication cost to solve thisproblem should be their calendars’ length by using a classical algorithm. In this work, weinvestigate the appointment schedule issue made by N users and try to accomplish it inquantum information case. Our study shows that the total communication cost will bequadratic times smaller than the conventional case if we apply a quantum algorithm in theappointment-scheduling problem.

Quantum Multi-User Detection Based on Coherent State Signals

Multi-user detection is one of the important technical problems for moderncommunications. In the field of quantum communication, the multi-access channel onwhich we apply the technology of quantum information processing is still an openquestion. In this work, we investigate the multi-user detection problem based on thebinary coherent-state signals whose communication way is supposed to be seen as aquantum channel. A binary phase shift keying model of this multi-access channel isstudied and a novel method of quantum detection proposed according to the conclusionof the quantum measurement theory. As a result, the average interference betweendeferent users is presented and the average error probability of the quantum detection isderived theoretically. Finally, we show the maximum channel capacity of this effectivedetection for a two-access quantum channel.

A Novel Method to against Quantum Noises in Quantum Teleportation

In order to improve the anti-noise performance of quantum teleportation,this paper proposes a novel dynamic quantum anti-noise scheme based on the quantum teleportation which transmits single qubit state using Bell state.Considering that quantum noise only acts on the transmitted qubit,i.e.,the entangled state that Alice and Bob share in advance is affected by the noise,thus affecting the final transmission result.In this paper,a method for dynamically adjusting the shared entangled state according to the noise environment is proposed.By calculating the maximum fidelity of the output state to determine the shared entangled state,which makes the quantum teleportation be affected by the noise as little as possible.This paper calculates the fidelity of teleportation under four kinds of channel noise(amplitude damping,phase damping,bit flip and depolarizing noise).The results show that the scheme has a suppression effect on phase damping,bit flip and depolarizing noise under certain conditions.When the noise intensity is larger,the optimized efficiency is better.

Antibacterial evaporator based on reduced graphene oxide/polypyrrole aerogel for solar-driven desalination

Solar-driven water evaporation is a sustainable method to purify seawater.Nevertheless,traditional volumetric water-evaporation systems suffer from the poor sunlight absorption and inefficient light-to-thermal conversion.Also,their anti-bacterial and antifouling performances are crucial for the practical application.Herein,we introduce reduced graphene oxide(RGO)with broadband absorbance across the entire solar spectrum,and polypyrrole(PPy),an antibacterial polymer with efficient solar absorption and low thermal conductivity,to develop integrated RGO/PPy aerogel as both the solar absorber and evaporator for highly efficient solar-driven steam generation.As a result,the RGO/PPy aerogel shows strong absorption and good photothermal performance,leading to an evaporation rate of 1.44 kg·m^(−2)·h^(−1)and high salt rejection(up to 99.99%)for real seawater,with photothermal conversion efficiency>90%under one sun irradiation.The result is attributed to the localized heat at the air-water interface by the RGO/PPy and its porous nature with functional groups that facilitates the water evaporation.Moreover,the RGO/PPy demonstrates excellent durability and antibacterial efficiency close to 100%for 12 h,crucial characteristics for longterm application.Our well-designed RGO/PPy aerogel with efficient water desalination performance and antibacterial property provides a straightforward approach to improve the solar-driven evaporation performance by multifunctional materials integration,and offers a viable route towards practical seawater desalination.

Cobalt disulfide/carbon nanofibers with mesoporous heterostructure and excellent hydrophilicity for high energy density asymmetric supercapacitor

Herein,a unique mesoporous heterostructure(average pore size:15 nm)cobalt disulfide/carbon nanofibers(CoS_(2)/PCNFs)composite with excellent hydrophilicity(contact angle:23.5°)is prepared using polyethylene glycol(PEG)as a pore-forming agent.The CoS_(2)/PCNF electrode exhibits excellent cycle stability(95.2%of initial specific capacitance at 10 A·g^(-1)after 8000 cycles),good rate performance(46.5%at 10 A·g^(-1)),and high specific capacity(86.1 mAh·g^(-1)at 1 A·g^(-1),about 688.8 F·g^(-1)at 1 A·g^(-1)).Density functional theory(DFT)simulation elucidates that CoS_(2)tends to transfer substantial charges to CNF.As the center of positive charge,CoS_(2)is more likely to capture negative ions in the electrolyte,thus accelerating the ion diffusion process.The excellent properties of the electrode material can not only accelerate the electrochemical reaction kinetics,but also provide abundant redox-active sites and a high Faradaic capacity for the entire electrode due to the synergistic contributions of CoS_(2)nanoparticles,mesoporous heterostructure of PCNF,and admirable hydrophilicity of the composite material.A CoS_(2)/PCNF-0.25//AC(AC:activated carbon)asymmetric supercapacitor is assembled using CoS_(2)/PCNF-0.25 as the positive electrode and AC as the negative electrode,which possesses a high energy density(35.5 Wh·kg^(-1)at a power density of 824 W·kg^(-1))and superior cycling stability(maintaining over 98%of initial capacitance after 2000 cycles).In addition,the unique CoS_(2)/PCNF electrode is expected to be widely used in other electrochemical energy storage devices,such as lithium-ion batteries,sodium-ion batteries,lithium-sulfur batteries,etc.

Hierarchical polypyrrole@cobalt sulfide-based flexible on-chip microsupercapacitors with ultrahigh energy density for selfcharging system

Herein,we prepare the unique hierarchical polypyrrole@cobalt sulfide(PPy-hs@CoS)hollow sphere-based nanofilms as interdigitated electrodes for flexible on-chip micro-supercapacitors(MSC).Benefiting from the excellent flexibility and high electrical conductivity of PPy-hs combined with the great electrochemical activity of CoS,such PPy-hs@CoS composite material can not only inhibit the volume expansion of PPy but also promote the diffusion of the electrolyte ions.The PPy-hs@CoS filmbased electrode delivers a greatly improved specific capacitance and small resistance.Density functional theory calculations infer that OH−prefers to bind to PPy on CoS@PPy and confirms the synergistic effect of each component for enhanced reaction kinetics.A quasi-solid-state on-chip flexible asymmetric MSC based on PPy-hs@CoS and activated carbon(AC)microelectrodes exhibits large areal-specific capacitance(131.9 mF/cm2 at 0.3 mA/cm2),ultrahigh energy density(0.041 mWh/cm2@0.224 mW/cm2 and 25.6 mWh/cm3@140.6 mW/cm3),and long cycle lifespan.We demonstrate the possibility to scale up the PPy-hs@CoS nanofilm microelectrode by arranging two of our asymmetric MSC in series and parallel connections,which respectively increase the output voltage and current.A self-charging system by connecting our asymmetric MSCs with a piece of commercial solar cells is developed as a potential possible mode for future highly durable and high-voltage integrated electronics.

Ce-Ti catalysts modified with copper and vanadium to effectively remove slip NH_(3) and NO_x from coal-fired plants

In this work,V/Ce-Ti catalysts were modified with different kinds of transition metals(Cu,Fe,Co,Mn) by sol-gel and impregnation methods.The NH_(3) oxidation performance of them was tested to select the most active catalyst in NH_(3)-selective catalytic oxidation(NH_(3)-SCO).The effect of NO,SO_(2) and H_(2)O was also investigated.The experimental results indicate that 1% Cu-V/Ce-Ti catalyst exhibits the most significant ability to remove slip ammonia discharged from coal-fired plants and its NH_(3) conversion efficiency reaches90% at 300℃.In additio n,97% NO_x can be removed when NO is introduced in the gas.Cu-V/Ce-Ti catalyst also obtains good resistance to H_(2)O and SO_(2).Based on the characterization experiment,the introduced Cu and V are highly dispersed on Ce-Ti catalyst and they can increase the redox properties and the number of acidic sites.Besides,the redox cycles among Cu,V and Ce species on Cu-V/Ce-Ti catalyst surface are conducive to generating more active oxygen and promoting the oxidation capacity of the catalyst.