A Secure Device Management Scheme with Audio-Based Location Distinction in IoT

Identifying a device and detecting a change in its position is critical for secure devices management in the Internet of Things(IoT).In this paper,a device management system is proposed to track the devices by using audio-based location distinction techniques.In the proposed scheme,traditional cryptographic techniques,such as symmetric encryption algorithm,RSA-based signcryption scheme,and audio-based secure transmission,are utilized to provide authentication,non-repudiation,and confidentiality in the information interaction of the management system.Moreover,an audio-based location distinction method is designed to detect the position change of the devices.Specifically,the audio frequency response(AFR)of several frequency points is utilized as a device signature.The device signature has the features as follows.(1)Hardware Signature:different pairs of speaker and microphone have different signatures;(2)Distance Signature:in the same direction,the signatures are different at different distances;and(3)Direction Signature:at the same distance,the signatures are different in different directions.Based on the features above,amovement detection algorithmfor device identification and location distinction is designed.Moreover,a secure communication protocol is also proposed by using traditional cryptographic techniques to provide integrity,authentication,and non-repudiation in the process of information interaction between devices,Access Points(APs),and Severs.Extensive experiments are conducted to evaluate the performance of the proposed method.The experimental results show that the proposedmethod has a good performance in accuracy and energy consumption.

Understanding the roles of Ti on the structure and electrochemical performances of Li2Ru1-xTixO3 cathode materials for Li-ion batteries

The lattice doping has been widely used to improve the electrochemical performances of Li-rich cathode materials but the roles of the introduced foreign atoms are still not very clear.Herein,a series of Li2Ru1-xTixO3 solid solutions have been synthesized and the roles of Ti doping on the structural and electrochemical properties of Li2RuO3 have been comprehensively investigated.The Rietveld refinement exhibits that the interlayer spacing gradually shortens with increasing Ti content.This shrinkage is favorable to the layered structure stability but increases the lithium diffusion barrier.Galvanostatic measurements show that Li2Ru0.8Ti0.2O3 possesses the best cyclability with 196.9 and 196.1 m Ah g-1for charge and discharge capacity retaining after 90 cycles,respectively.Cyclic voltammetry scanning indicates that Ti dopant promotes the formation of more peroxo-or superoxo-like species but reduces the initial coulumbic efficiency.Results of electrochemical impedance spectroscopy display that Ti doping reduces the charge transfer impedance,which facilitates the lithium-ion diffusion across the electrolyteelectrode interface and improves the electronic conductivity.Li2Ru0.8Ti0.2O3exhibits the best electrochemical performance owing to the balance among all the factors discussed above.This study also offers some new insights into optimizing the electrochemical performances of Li-rich cathode materials through the lattice doping.

Evolution process of rock mass engineering system using systems science

The rock mass engineering system （RMES） basically consists ofrock mass engineering （RME）, water system and surroundingecological environments, etc. The RMES is characterized by nonlinearity,occurrence of chaos and self-organization （Tazaka, 1998;Tsuda, 1998; Kishida, 2000）. From construction to abandonmentof RME, the RMES will experience four stages, i.e. initial phase,development phase, declining phase and failure phase. In thiscircumstance, the RMES boundary conditions, structural safetyand surrounding environments are varied at each phase, so arethe evolution characteristics and disasters （Wang et al., 2014）.

Discriminative Features of Abnormities in a Spiral Groove Gas Face Seal Based on Dynamic Model Considering Contact

It is a difficult task to root the cause of the failure of a gas face seal because different causes may result in similar observations.In the work being presented,the discrimination of multiple types of abnormities in a spiral groove gas face seal is studied.A dynamic model is employed to analyze groups of cases in order to uncover the dynamic behaviors when the face contact is induced by different mixtures of abnormities,whose discriminative features when motion and contact are monitored are studied and uncovered.A circumferential-pattern-related oscillation phenomenon is discovered,which is extracted from contact information and implies the relative magnitude of the moment on stator and the rotor tilt.The experimental observation shows consistent results.It means that the grooves(or other circumferential patterns)generate useful informative features for monitoring.These results provide guidance for designing a monitored gas face seal system.

Recent progress and perspective on electrocatalysis in neutral media:Mechanisms,materials,and advanced characterizations

Electrocatalysis,which involves oxidation and reduction reactions with direct electron transfer,is essential for a variety of clean energy conversion devices.Currently,the vast majority of studies regarding electrocatalysis reactions focus on strong acidic or alkaline media because of the higher catalytic activity.Nevertheless,some inherent drawbacks,including the corrosive environment,expensive proton exchange membranes,and side effects,are still hard to break through.A sustainably promising way to overcome these shortcomings is to deploy neutral/near-neutral electrolytes for electrocatalysis reactions.Unfortunately,insufficient research in this area due to the lack of attention to related issues has slowed down the development process.In this review,we systematically review the catalytic reaction mechanisms,neutral electrolytes,electrocatalysts,and modification strategies carried out in neutral media on the three most common electrocatalytic reactions,that is,hydrogen evolution reaction,oxygen reduction reaction,and oxygen evolution reaction.Furthermore,the advanced characterization tools for guiding catalyst synthesis and mechanistic studies are also summarized.Eventually,we propose some challenges and perspectives on electrocatalysis reactions in neutral media and hope it will attract more research interest and provide guidance in neutral electrocatalysis.

Tuning the Oxygen Anionic Redox Reversibility in Na_(0.67)Mn_(0.8)Fe_(0.1)Co_(0.1)O_(2)Through Sn Doping

Oxygen anion redox chemistry in layered oxide cathodes for sodium-ion batteries has attracted great interest.However,the release of lattice oxygen caused by the irreversible anionic redox and Jahn–Teller effect accelerates the structural distortion and electrochemical degradation.Herein,we rationally construct a stable crystal lattice to enhance the reactivity and reversibility of oxygen redox and inhibit the Jahn–Teller effect by Sn doping.The stronger binding energy of Sn–O enhances the structural stability of the cathode,which is favorable to suppress the oxygen release and Jahn–Teller effect.Thus,the reversibility of oxygen redox and the stability of the layered structure are enhanced.The expansion of the interlayer spacing decreases the energy barriers for Na+ion intercalation,improving the rate performance of the electrode.Benefitting from the rational design,the electrode delivers an enhanced rate performance and cycling stability.This work offers some insights into tuning the oxygen anion redox chemistry as well as suppressing the Jahn–Teller effect by lattice modulation.

Friction Characteristics of Impregnated and Non-Impregnated Graphite against Cemented Carbide under Water Lubrication

The friction behavior of resin-impregnated and non-impregnated graphite sliding against a cemented carbide in dry, oil, and water environments using a ring–ring configuration was investigated. Friction coefficients were recorded at various speeds. The results showed that the impregnated graphite exhibited much better friction properties under water or oil lubrication than non-impregnated graphite, and the impregnated graphite could remain in the stable friction regime under high pressure × velocity（pv）.Based on scanning electron microscopy and Raman spectroscopy analyses, the different characteristics between impregnated and non-impregnated graphite were able to be attributed to the structure of the graphite and wettability of the lubricants.

Tuning anionic/cationic redox chemistry in a P2-type Na0.67Mn0.5Fe0.5O2 cathode material via a synergic strategy

The anionic redox chemistry(O^2-→O^-)in P2-type sodium-ion battery cathodes has attracted much attention.However,determining how to tune the anionic redox reaction is still a major challenge.Herein,we tune the activity and reversibility of both the anionic and cationic redox reactions of Na0.67Mn0.5Fe0.5O2 though an integrated strategy that combines the advantages of Li2SiO3 coating,Li doping and Si doping,and the initial capacity,rate performance and cycling stability are significantly improved.The in-depth modulation mechanism is revealed by means of neutron diffraction,X-ray absorption spectroscopy,in situ X-ray diffraction,electron paramagnetic resonance spectroscopy,first-principles calculations and so on.The Li2SiO3 coating alleviates the side reactions and enhances the cycling stability.Si^4+doping lowers the Na^+diffusion barrier due to the expanded interlayer spacing.Additionally,Si^4+doping improves the structural stability,oxygen redox activity and reversibility.Li^+doping in Na sites further increases the structure stability.The electron density maps confirm the greater activity of Na and O in the modified sample.Nuclear density maps and bond-valence energy landscapes identify the Na^+migration pathway from Nae site to Naf site(the positions of the Na ions in the crystal structure).The proposed insights into the modulation mechanism of the anionic and cationic redox chemistry are also instructive for designing other oxide-based cathode materials.

Wear behavior of WC-Ni sliding against graphite under water lubrication

Wear of hard materials in contact with softer materials is a neglected area of research. However, we observed considerable wear phenomenon at a hard WC-Ni surface sliding over soft graphite under water lubrication. The influences of applied load and the application history on the wear of surface were addressed in our experimental design. Wear of both graphite and WC-Ni surfaces increased with a greater applied load and repeated sliding. The topographies of the worn surfaces showed clear micro-scratches on the hard WC-Ni surface. Scanning electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the abrasive wear of the WC-Ni surface could be attributed to hard WC particles embedded in the graphite surface. These hard particles were formed by shearing of sharp WC-Ni asperities under certain conditions and intrinsic defects of the WC-Ni surface could accelerate this wear process.

Truncated separation method for characterizing and reconstructing bi-Gaussian stratified surfaces

Existing ISO segmented and continuous separation methods for differentiating the two components contained within a bi-Gaussian stratified surface were developed based on the fit of the probability material ratio curve.In the present study,because of the significant effect of the plateau component on tribological behavior such as asperity contact,wear and friction,a truncated separation method is proposed based on the truncation of the upper Gaussian component defined by zero skewness.The three separation methods are applied to real worn surfaces.Surface-separation and surface-reconstruction results show that the truncated method accurately captures the upper component identically to the ISO and continuous ones.The identification of the lower component characteristics requires performing a curve fit procedure on the data left after truncation.However,the truncated method fails in identifying the upper component when the material ratio of the transition is less than 9％.

Significant friction reduction of high-intensity pulsed ion beam irradiated WC-Ni against graphite under water lubrication

Two types of commercial WC-Ni samples were irradiated with the High-intensity pulsed ion beam(HIPIB).Both the surface characteristics and tribo-characteristics of the non-irradiated and irradiated WC-Ni samples,sliding against graphite under water lubrication,were compared.Quite low steady friction coefficients(approximately of 0.02) of the irradiated WC-Ni were observed.The surface topographies and components were investigated.The quite low friction of the irradiated WC-Ni samples was ascribed to the higher fluid retention capability of the latter and the tribofilm formed during sliding.

Designing a durable high-rate K_(0.45)Ni_(0.1)Fe_(0.1)Mn_(0.8)O_(2) cathode for K-ion batteries:A joint study of theory and experiment

K-ion batteries(KIBs)hold great promise for large-scale energy storage.However,the absence of suitable cathode materials limits their practical application.Meanwhile,rationally designing advanced cathode materials for KIBs remains an open question.In this work,based on density functional theory calculations,we find that the bond stability of Fe–O is higher than that of Co–O in layered transitional metal(TM)oxides.Additionally,the K-ion migration in the Fe-based layered TM oxide has a significantly lower activation energy barrier than that in the Co-based one.Based on this theoretical prediction,we successfully synthesized a low-cost K_(0.45)Ni_(0.1)Fe_(0.1)Mn_(0.8)O_(2)cathode,which shows excellent structural stability and superior K-storage properties,including durable cycle life and high-rate capability.Moreover,the designed K_(0.45)Ni_(0.1)Fe_(0.1)Mn_(0.8)O_(2)cathode possesses a great full-cell performance with a discharge capacity of~75 mA h g^(-1) and capacity retention of~80%after 100 cycles.The results show that Fe has better structural stability and K-ion diffusion than high-cost Co in layered oxide cathodes,and this finding provides new insights into the design of low-cost and high-performance KIB layered cathodes.This work highlights the feasibility of a theory-guided experiment in screening promising battery materials.

Method for solving the nonlinear inverse problem in gas face seal diagnosis based on surrogate models

Physical models carry quantitative and explainable expert knowledge.However,they have not been introduced into gas face seal diagnosis tasks because of the unacceptable computational cost of inferring the input fault parameters for the observed output or solving the inverse problem of the physical model.The presented work develops a surrogate-model-assisted method for solving the nonlinear inverse problem in limited physical model evaluations.The method prepares a small initial database on sites generated with a Latin hypercube design and then performs an iterative routine that benefits from the rapidity of the surrogate models and the reliability of the physical model.The method is validated on simulated and experimental cases.Results demonstrate that the method can effectively identify the parameters that induce the abnormal signal output with limited physical model evaluations.The presented work provides a quantitative,explainable,and feasible approach for identifying the cause of gas face seal contact.It is also applicable to mechanical devices that face similar difficulties.