This paper proposes and implements a model-free open-loop iterative learning control(ILC)strategy to realize the speed control of the single-phase flux switching motor(FSM)with an asymmetrical rotor.Base on the propos...This paper proposes and implements a model-free open-loop iterative learning control(ILC)strategy to realize the speed control of the single-phase flux switching motor(FSM)with an asymmetrical rotor.Base on the proposed winding control method,the asymmetrical rotor enables the motor to generate continuous positive torque for positive rotation,and relatively small resistance torque for negative rotation.An initial iteration coefficient and variable iteration coefficient optimized scheme was proposed based on the characteristics of the hardware circuit,thereby forming the model-free strategy.A series of prototype experiments was carried out.Experimental results verify the effectiveness and practicability of the proposed ILC strategy.展开更多
This study provides a comprehensive analysis of collision and impact problems’ numerical solutions, focusing ongeometric, contact, and material nonlinearities, all essential in solving large deformation problems duri...This study provides a comprehensive analysis of collision and impact problems’ numerical solutions, focusing ongeometric, contact, and material nonlinearities, all essential in solving large deformation problems during a collision.The initial discussion revolves around the stress and strain of large deformation during a collision, followedby explanations of the fundamental finite element solution method for addressing such issues. The hourglassmode’s control methods, such as single-point reduced integration and contact-collision algorithms are detailedand implemented within the finite element framework. The paper further investigates the dynamic responseand failure modes of Reinforced Concrete (RC) members under asymmetrical impact using a 3D discrete modelin ABAQUS that treats steel bars and concrete connections as bond slips. The model’s validity was confirmedthrough comparisons with the node-sharing algorithm and system energy relations. Experimental parameterswere varied, including the rigid hammer’s mass and initial velocity, concrete strength, and longitudinal and stirrupreinforcement ratios. Findings indicated that increased hammer mass and velocity escalated RC member damage,while increased reinforcement ratios improved impact resistance. Contrarily, increased concrete strength did notsignificantly reduce lateral displacement when considering strain rate effects. The study also explores materialnonlinearity, examining different materials’ responses to collision-induced forces and stresses, demonstratedthrough an elastic rod impact case study. The paper proposes a damage criterion based on the residual axialload-bearing capacity for assessing damage under the asymmetrical impact, showing a correlation betweendamage degree hammer mass and initial velocity. The results, validated through comparison with theoreticaland analytical solutions, verify the ABAQUS program’s accuracy and reliability in analyzing impact problems,offering valuable insights into collision and impact problems’ nonlinearities and practical strategies for enhancingRC structures’ resilience under dynamic stress.展开更多
In the digital age, the data exchanged within a company is a wealth of knowledge. The survival, growth and influence of a company in the short, medium and long term depend on it. Indeed, it is the lifeblood of any mod...In the digital age, the data exchanged within a company is a wealth of knowledge. The survival, growth and influence of a company in the short, medium and long term depend on it. Indeed, it is the lifeblood of any modern company. A companys operational and historical data contains strategic and operational knowledge of ever-increasing added value. The emergence of a new paradigm: big data. Today, the value of the data scattered throughout this mother of knowledge is calculated in billions of dollars, depending on its size, scope and area of intervention. With the rise of computer networks and distributed systems, the threats to these sensitive resources have steadily increased, jeopardizing the existence of the company itself by drying up production and losing the interest of customers and suppliers. These threats range from sabotage to bankruptcy. For several decades now, most companies have been using encryption algorithms to protect and secure their information systems against the threats and dangers posed by the inherent vulnerabilities of their infrastructure and the current economic climate. This vulnerability requires companies to make the right choice of algorithms to implement in their management systems. For this reason, the present work aims to carry out a comparative study of the reliability and effectiveness of symmetrical and asymmetrical cryptosystems, in order to identify one or more suitable for securing academic data in the DRC. The analysis of the robustness of commonly used symmetric and asymmetric cryptosystems will be the subject of simulations in this article.展开更多
In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of ro...In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of the doubly-fed generator is proposed.When the power grid voltage drops symmetrically,the generator approximate equation under steady-state conditions is no longer applicable.Considering the dynamic process of stator current excitation,according to the change of stator flux and the depth of voltage drop,the system can dynamically provide reactive power support for parallel nodes and suppress the rise of DC side voltage and rotor over-current.When the grid voltage drops asymmetrically,the positive and negative sequence components are separated in the rotating coordinate system.The doubly fed generator model is established to suppress the rotor positive sequence current and negative sequence current respectively.At the same time,the output voltage limit of the converter is discussed,and the reference value is adjusted within the allowable output voltage range.In order to adapt to the occurrence of different types of power grid faults and complex operating conditions,a fast switching module of fault type detection and rotor control mode is designed to detect the type of power grid faults and voltage drop depth in real time and switch the rotor side control mode dynamically.Finally,the simulation model of the doubly fed wind turbine is constructed in Matlab/Simulink.The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetric voltage drop of the power grid and identify the power grid fault type and provide the correct control strategy.展开更多
The initial copper with large grain sizes of 60-100 μm was processed by six passes asymmetrical accumulative rolling-bond （AARB） and annealing, the ultra-fine-grained （UFG） copper with grain size of 200 nm was ob...The initial copper with large grain sizes of 60-100 μm was processed by six passes asymmetrical accumulative rolling-bond （AARB） and annealing, the ultra-fine-grained （UFG） copper with grain size of 200 nm was obtained, and the microstructures and properties were studied. The results show that there are large sub-structures and also texture component C for the UFG copper obtained by six passes AARB, possessing high strength and microhardness in company with poor elongation and conductivity. Thereafter, the UFG copper was annealed at 220 °C for 35 min, in which the sub-structures disappear, the grain boundaries are composed of big angle grain boundaries, and the textures are composed of a variety of texture components and parts of twins. Compared with the UFG copper obtained by six passes AARB, the tensile strength and yield strength for the UFG copper obtained by six passes AARB and annealing at 220 °C for 35 min are decreased slightly, the elongation and conductivity are improved obviously.展开更多
This paper presents an experimental study of the characterisation of local materials used in the construction and thermal insulation of buildings. These materials are compressed earth bricks stabilised with cement and...This paper presents an experimental study of the characterisation of local materials used in the construction and thermal insulation of buildings. These materials are compressed earth bricks stabilised with cement and sawdust. The thermal conductivity, diffusivity, effusivity, and specific heat of earth-based materials containing cement or sawdust have been determined. The results show that the blocks with earth + sawdust are better thermal insulators than the blocks with simple earth. We observe an improvement in thermal efficiency depending on the presence of sawdust or cement stabilisers. For cement stabilisation, the thermal conductivity increases (λ: 1.04 to 1.36 W·m<sup>-1</sup>·K<sup>-1</sup>), the diffusivity increases (from 4.32 × 10<sup>-7</sup> to 9.82 × 10<sup>-7</sup> m<sup>2</sup>·s<sup>-1</sup>), and the effusivity decreases (1404 - 1096 J·m<sup>-2</sup>·K<sup>-1</sup>·s<sup>-1/2</sup>). For sawdust stabilisation, the thermal conductivity decreases (λ: 1.04 to 0.64 W·m<sup>-1</sup>·K<sup>-1</sup>), the diffusivity increases (from 4.32 × 10<sup>-7</sup> to 5.9 × 10<sup>-7</sup> m<sup>2</sup>·s<sup>-1</sup>), and the effusivity decreases (1404 - 906 J·m<sup>-2</sup>·K<sup>-1</sup>·s<sup>-1/2</sup>). Improving the structural and thermal efficiency of BTC via stabilisation with derived binders or cement is beneficial for the load-bearing capacity and thermal performance of buildings.展开更多
Simultaneous anterior and posterior traumatic dislocations of both hips are very rare. Only 33 cases have been previously reported in the English language literature. Although they were all due to high-energy injuries...Simultaneous anterior and posterior traumatic dislocations of both hips are very rare. Only 33 cases have been previously reported in the English language literature. Although they were all due to high-energy injuries, they were hemodynamically stable and had a stable pelvic ring. We report a unique case of asymmetrical hip dislocations with an unstable pelvic ring and hemodynamic instability. A 40-year-old man was injured in a high-energy motor vehicle accident. He was hemodynamically unstable when he presented in the emergency department. Radiolographs showed asymmetrical dislocations of both hips with an unstable pelvic ring. Under general anesthesia, he had closed reduction of the dislocations of both hips, followed by temporary stabilization with an external fixator. Transcatheter arterial embolization was performed to stop active pelvic bleeding. Delayed open reduction and internal fixation was performed 12 d later with anterior and posterior plates. The patient recovered well with an uneventful post-operative course. Asymmetrical bilateral hip dislocations with pelvic ring instability caused by trauma, as presented in this case, is very rare and potentially life threatening. Prompt treatment can give a good outcome.展开更多
Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural e...Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}<1ī2>+{112}<11ī> texture component disappears and turns into{122}<212>cube twin texture component.展开更多
The directed motion of a Brownian particle in a Bashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the...The directed motion of a Brownian particle in a Bashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the steady current J of the particle is calculated via Langevin simulation. The results show that the optimal cycle period (Tm), which takes the maximum of J, is shifted to a small value when the transition probability A from the potential on to the potential off decreases, the maximal current appears in the case of the average waiting time in the potential on being longer than in the potential off, and the direction of current depends on the ratio of the average times waiting in two states.展开更多
Based on NCEP/CFSR 0.5° reanalysis data and the best track data from the Japan Tokyo Typhoon Center,composite and comparative analyses demonstrate the asymmetrical structures of the temperature and humidity in tr...Based on NCEP/CFSR 0.5° reanalysis data and the best track data from the Japan Tokyo Typhoon Center,composite and comparative analyses demonstrate the asymmetrical structures of the temperature and humidity in tropical cyclones over the Western North Pacific and the South China Sea from 1979 to 2010.The results are shown as follows.(1) With intensifying tropical cyclones,the flow field tends to become gradually more axisymmetric;however,the asymmetry of the specific humidity in the outer regions is more obvious.(2) In general,tropical cyclones have a non-uniform,vertical, "double warm-core" structure.The "warm-cores" in the lower level of weak tropical cyclones and in the higher level of strong tropical cyclones are the stronger of the two.(3) The distribution area of a "warm-core" is enhanced with cyclone intensification and tends to become more axisymmetric.At 200 hPa,the "warm-core" of a weak cyclone has a weak anticyclone in the center,whereas that of a strong cyclone has a weak cyclone in the center.(4)The "wet-core" of a tropical cyclone is primarily located in the lower level(700-850 hPa).With the cyclone's intensification,the intensity of the "wet-core" increases and the scope of the 0.8 g kg^(-1) specific humidity anomaly tends to expand to higher levels.(5) With the cyclone's deepening,the pseudo-equivalent potential temperature at different levels in different regions increases.In addition,the largest warming rates at each intensity level in the different regions occur in the core area,followed in turn by the envelope and outer areas.展开更多
Quantum cryptography and quantum search algorithm are considered as two important research topics in quantum information science.An asymmetrical quantum encryption protocol based on the properties of quantum one-way f...Quantum cryptography and quantum search algorithm are considered as two important research topics in quantum information science.An asymmetrical quantum encryption protocol based on the properties of quantum one-way function and quantum search algorithm is proposed.Depending on the no-cloning theorem and trapdoor one-way functions of the publickey,the eavesdropper cannot extract any private-information from the public-keys and the ciphertext.Introducing key-generation randomized logarithm to improve security of our proposed protocol,i.e.,one privatekey corresponds to an exponential number of public-keys.Using unitary operations and the single photon measurement,secret messages can be directly sent from the sender to the receiver.The security of the proposed protocol is proved that it is informationtheoretically secure.Furthermore,compared the symmetrical Quantum key distribution,the proposed protocol is not only efficient to reduce additional communication,but also easier to carry out in practice,because no entangled photons and complex operations are required.展开更多
We present the analytic solution of an asymmetrical crack in a strip from which the stress intensity factors are determined.The results have important application in earthquake source physics and provide information c...We present the analytic solution of an asymmetrical crack in a strip from which the stress intensity factors are determined.The results have important application in earthquake source physics and provide information concerning the instability of faults and the detection of earthquake precursors.展开更多
The structural characteristics of 2004 typhoon Aere's precipitation are analyzed using the high-resolution data from the Tropical Rainfall Measuring Mission(TRMM) of the National Aeronautics Space Administration(N...The structural characteristics of 2004 typhoon Aere's precipitation are analyzed using the high-resolution data from the Tropical Rainfall Measuring Mission(TRMM) of the National Aeronautics Space Administration(NASA).It is found that the typhoon's characteristics vary at different stages of its development.To analyze the asymmetric causation of precipitation distribution,data from the National Center for Environmental Prediction(NCEP) reanalysis are used to calculate the vertical integral of the water vapor flux vector.The results show that because of this process,along with the unique phenomenon of twin-typhoon circulation,the easterly air current of the typhoon's northern side and the southwesterly air current of its southern side play a joint role in transporting water vapor.Furthermore,its transport effects vary greatly at the different stages of development,showing the peculiarity of the water source for this typhoon process.The distributions of the typhoon convection area—characterized by heavy precipitation and a maximum-value area of the water vapor flux,as well as a strong ascending-motion area—differ at different stages of the typhoon's development.The non-uniform distribution of water vapor flux and the vertical motion bring about asymmetrical distribution of the typhoon precipitation.展开更多
Axisymmetric bogus vortexes at sea level are usually used in the traditional bogus data assimilation （BDA） scheme. In the traditional scheme, the vortex could not accurately describe the specific characteristics of ...Axisymmetric bogus vortexes at sea level are usually used in the traditional bogus data assimilation （BDA） scheme. In the traditional scheme, the vortex could not accurately describe the specific characteristics of a typhoon, and the evolving real typhoon is forced to unreasonably adapt to this changeless vortex. For this reason, an asymmetrical typhoon bogus method with information blended from the analysis and the observation is put forward in this paper, in which the impact of the Subtropical High is also taken into consideration. With the fifth-generation Penn State/NCAR Mesoscale Model （MM5） and its adjoint model, a four-dimensional variational data assimilation （4D-Var） technique is employed to build a dynamic asymmetrical BDA scheme to assimilate different asymmetrical bogus vortexes at different time. The track and intensity of six surmner typhoons much influenced by the Subtropical High are simulated and the results are compared. It is shown that the improvement in track simulation in the new scheme is more significant than that in the traditional scheme. Moreover, the periods for which the track cannot be simulated well by the traditional scheme can be improved with the new scheme. The results also reveal that although the simulated typhoon intensity in the new scheme is generally weaker than that in the traditional scheme, this trend enables the new scheme to simulate, in the later period, closer-to-observation intensity than the traditional scheme. However, despite the fact that the observed intensity has been largely weakened, the simulated intensity at later periods of the BDA schemes is still very intensive, resulting in overly development of the typhoon during the simulation. The limitation to the simulation effect of the BDA scheme due to this condition needs to be further studied.展开更多
The dynamic thermal process during double-sided asymmetrical TIG backing welding of large thick plates （ 1 000 mm×700 mm×50 mm） is numerically simulated using MSC. MARC. The effect of arc distance on the t...The dynamic thermal process during double-sided asymmetrical TIG backing welding of large thick plates （ 1 000 mm×700 mm×50 mm） is numerically simulated using MSC. MARC. The effect of arc distance on the thermal cycle in weld zone during double-sided asymmetrical T1G backing welding is investigated. The results show that the workpiece experiences double-peak thermal cycle in double-sided asymmetrical TIG backing welding. On the one hand, the fore arc has the pre- heating effect on the rear pass, and the pre-heating temperature depends on the distance between the double arcs, the heat input of fore arc, and the initial temperature of workpiece. On the other hand, the rear arc has the post-heating effect on the fore pass. The mutual effects of two heat sources decrease with the increase of arc distance.展开更多
Cross sections of the 10B(n,α)7Li reaction(including the total,the“leaking”alpha,forward alpha and backward alpha parts)at En=4.0 and 5.0 MeV were measured using an asymmetrical twin gridded ionization chamber and ...Cross sections of the 10B(n,α)7Li reaction(including the total,the“leaking”alpha,forward alpha and backward alpha parts)at En=4.0 and 5.0 MeV were measured using an asymmetrical twin gridded ionization chamber and two back−to-back 10B samples.Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University.Monoenergetic neutrons were produced through the ^(2)H(d,n)3He reaction with a deuterium gas target.Absolute neutron flux was determined by a ^(238)U sample set inside the gridded ionization chamber and a BF_(3) long counter was employed as a neutron flux monitor and for normalization.The present results are compared with previous measurements and evaluations.展开更多
As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the...As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the SynRM,the torque ripple is a big issue and a great of work could been done on reducing it.In this paper,asymmetrical magnetic flux barriers in the SynRM rotor were studied comprehensively,including angle and width of each layer and each side of the magnetic barrier.The SynRMb with asymmetrical and parallel magnetic flux barrier was found as the best way to design SynRM based on the multi-objective design optimization method.Moreover,each parameter was studied to show the design rule of the asymmetrical magnetic flux barrier.As the average torque will be reduced with the asymmetrical barrier is used,the grain-oriented silicon steel is used on stator teeth of the SynRMb(SynRMbG)was proposed and studied.The analysis results show that the proposed new method can make the SynRM have better performance.展开更多
In previous studies about the synchronization of vibrators,the restoring forces of springs are mainly treated as linear directly,whereas the nonlinear features are rarely considered in vibrating systems.To make up thi...In previous studies about the synchronization of vibrators,the restoring forces of springs are mainly treated as linear directly,whereas the nonlinear features are rarely considered in vibrating systems.To make up this drawback,a dynamical model of a nonlinear vibrating mechanical system with double rigid frames(RFs),driven by two vibrators,is proposed to explore the synchronization and stability of the system.In this paper,the nonlinearity is reflected in nonlinear restoring forces of springs characterized by asymmetrical piecewise linear,where the nonlinear stiffness of springs is linearized equivalently using the asymptotic method.Based on the average method and Hamilton’s principle,the theory conditions to achieve synchronization and stability of two vibrators are deduced.After the theory analyses,some numerical qualitative analyses are given to reveal the coupling dynamical characteristics of the system and the relative motion properties between two RFs.Besides,some experiments are carried out to examine the validity of the theoretical results and the correctness of the numerical analyses results.Based on the comparisons of the theory,numeric and experiment,the ideal working regions of the system are suggested.Based on the present work,some new types of vibrating equipment,such as vibrating discharging centrifugal dehydrators/conveyers/screens,can be designed.展开更多
This paper studies a simple asymmetrically evolved community network with a combination of preferential attachment and random properties. An important issue about community networks is to discover the different utilit...This paper studies a simple asymmetrically evolved community network with a combination of preferential attachment and random properties. An important issue about community networks is to discover the different utility increments of two nodes, where the utility is introduced to investigate the asymmetrical effect of connecting two nodes. On the other hand, the connection of two nodes in community networks can be classified as two nodes belonging to the same or to different communities. The simulation results show that the model can reproduce a power-law utility 1 distribution P（u） - u^-σ, σ = 2 ＋1/p, which can be obtained by using mean-field approximation methods. Furthermore, P the model exhibits exponential behaviour with respect to small values of a parameter denoting the random effect in our model at the low-utility region and a power-law feature with respect to big values of this parameter at the high-utility region, which is in good agreement with theoretical analysis. This kind of community network can reproduce a unique utility distribution by theoretical and numerical analysis.展开更多
A new aromatic asymmetrical ether diamine, 1,4-bis（3＇,4’-diaminophenoxy）benzene 3 was synthesized in three steps, using hydroquinone as starting material. A new aromatic polyimide containing asymmetrical diaryl et...A new aromatic asymmetrical ether diamine, 1,4-bis（3＇,4’-diaminophenoxy）benzene 3 was synthesized in three steps, using hydroquinone as starting material. A new aromatic polyimide containing asymmetrical diaryl ether segments was prepared from the resulting diamine with 4,4＇-oxydiphthalic anhydride （ODPA） via a conventional two-step thermal or chemical imidization method. The resulting polyimide exhibits high thermal resistance, excellent solubility, film-forming capability, high mechanical strength and modulus.展开更多
文摘This paper proposes and implements a model-free open-loop iterative learning control(ILC)strategy to realize the speed control of the single-phase flux switching motor(FSM)with an asymmetrical rotor.Base on the proposed winding control method,the asymmetrical rotor enables the motor to generate continuous positive torque for positive rotation,and relatively small resistance torque for negative rotation.An initial iteration coefficient and variable iteration coefficient optimized scheme was proposed based on the characteristics of the hardware circuit,thereby forming the model-free strategy.A series of prototype experiments was carried out.Experimental results verify the effectiveness and practicability of the proposed ILC strategy.
基金the authority of the National Natural Science Foundation of China(Grant Nos.52178168 and 51378427)for financing this research work and several ongoing research projects related to structural impact performance.
文摘This study provides a comprehensive analysis of collision and impact problems’ numerical solutions, focusing ongeometric, contact, and material nonlinearities, all essential in solving large deformation problems during a collision.The initial discussion revolves around the stress and strain of large deformation during a collision, followedby explanations of the fundamental finite element solution method for addressing such issues. The hourglassmode’s control methods, such as single-point reduced integration and contact-collision algorithms are detailedand implemented within the finite element framework. The paper further investigates the dynamic responseand failure modes of Reinforced Concrete (RC) members under asymmetrical impact using a 3D discrete modelin ABAQUS that treats steel bars and concrete connections as bond slips. The model’s validity was confirmedthrough comparisons with the node-sharing algorithm and system energy relations. Experimental parameterswere varied, including the rigid hammer’s mass and initial velocity, concrete strength, and longitudinal and stirrupreinforcement ratios. Findings indicated that increased hammer mass and velocity escalated RC member damage,while increased reinforcement ratios improved impact resistance. Contrarily, increased concrete strength did notsignificantly reduce lateral displacement when considering strain rate effects. The study also explores materialnonlinearity, examining different materials’ responses to collision-induced forces and stresses, demonstratedthrough an elastic rod impact case study. The paper proposes a damage criterion based on the residual axialload-bearing capacity for assessing damage under the asymmetrical impact, showing a correlation betweendamage degree hammer mass and initial velocity. The results, validated through comparison with theoreticaland analytical solutions, verify the ABAQUS program’s accuracy and reliability in analyzing impact problems,offering valuable insights into collision and impact problems’ nonlinearities and practical strategies for enhancingRC structures’ resilience under dynamic stress.
文摘In the digital age, the data exchanged within a company is a wealth of knowledge. The survival, growth and influence of a company in the short, medium and long term depend on it. Indeed, it is the lifeblood of any modern company. A companys operational and historical data contains strategic and operational knowledge of ever-increasing added value. The emergence of a new paradigm: big data. Today, the value of the data scattered throughout this mother of knowledge is calculated in billions of dollars, depending on its size, scope and area of intervention. With the rise of computer networks and distributed systems, the threats to these sensitive resources have steadily increased, jeopardizing the existence of the company itself by drying up production and losing the interest of customers and suppliers. These threats range from sabotage to bankruptcy. For several decades now, most companies have been using encryption algorithms to protect and secure their information systems against the threats and dangers posed by the inherent vulnerabilities of their infrastructure and the current economic climate. This vulnerability requires companies to make the right choice of algorithms to implement in their management systems. For this reason, the present work aims to carry out a comparative study of the reliability and effectiveness of symmetrical and asymmetrical cryptosystems, in order to identify one or more suitable for securing academic data in the DRC. The analysis of the robustness of commonly used symmetric and asymmetric cryptosystems will be the subject of simulations in this article.
基金The authors highly acknowledge the technology financial assistance provided by Jiangsu Frontier Electric Technology Co.,Ltd.(KJ202003).
文摘In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of the doubly-fed generator is proposed.When the power grid voltage drops symmetrically,the generator approximate equation under steady-state conditions is no longer applicable.Considering the dynamic process of stator current excitation,according to the change of stator flux and the depth of voltage drop,the system can dynamically provide reactive power support for parallel nodes and suppress the rise of DC side voltage and rotor over-current.When the grid voltage drops asymmetrically,the positive and negative sequence components are separated in the rotating coordinate system.The doubly fed generator model is established to suppress the rotor positive sequence current and negative sequence current respectively.At the same time,the output voltage limit of the converter is discussed,and the reference value is adjusted within the allowable output voltage range.In order to adapt to the occurrence of different types of power grid faults and complex operating conditions,a fast switching module of fault type detection and rotor control mode is designed to detect the type of power grid faults and voltage drop depth in real time and switch the rotor side control mode dynamically.Finally,the simulation model of the doubly fed wind turbine is constructed in Matlab/Simulink.The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetric voltage drop of the power grid and identify the power grid fault type and provide the correct control strategy.
基金Project (50804018) supported by the National Natural Science Foundation of ChinaProject (ZDS2010015C) supported by Key Lab of Advanced Materials in Rare and Precious and Non-ferrous Metals, Ministry of Education, KMUST, ChinaProject (2010DH025) supported by Yunnan Province Construction Plans of Scientific and Technological Conditions, China
文摘The initial copper with large grain sizes of 60-100 μm was processed by six passes asymmetrical accumulative rolling-bond （AARB） and annealing, the ultra-fine-grained （UFG） copper with grain size of 200 nm was obtained, and the microstructures and properties were studied. The results show that there are large sub-structures and also texture component C for the UFG copper obtained by six passes AARB, possessing high strength and microhardness in company with poor elongation and conductivity. Thereafter, the UFG copper was annealed at 220 °C for 35 min, in which the sub-structures disappear, the grain boundaries are composed of big angle grain boundaries, and the textures are composed of a variety of texture components and parts of twins. Compared with the UFG copper obtained by six passes AARB, the tensile strength and yield strength for the UFG copper obtained by six passes AARB and annealing at 220 °C for 35 min are decreased slightly, the elongation and conductivity are improved obviously.
文摘This paper presents an experimental study of the characterisation of local materials used in the construction and thermal insulation of buildings. These materials are compressed earth bricks stabilised with cement and sawdust. The thermal conductivity, diffusivity, effusivity, and specific heat of earth-based materials containing cement or sawdust have been determined. The results show that the blocks with earth + sawdust are better thermal insulators than the blocks with simple earth. We observe an improvement in thermal efficiency depending on the presence of sawdust or cement stabilisers. For cement stabilisation, the thermal conductivity increases (λ: 1.04 to 1.36 W·m<sup>-1</sup>·K<sup>-1</sup>), the diffusivity increases (from 4.32 × 10<sup>-7</sup> to 9.82 × 10<sup>-7</sup> m<sup>2</sup>·s<sup>-1</sup>), and the effusivity decreases (1404 - 1096 J·m<sup>-2</sup>·K<sup>-1</sup>·s<sup>-1/2</sup>). For sawdust stabilisation, the thermal conductivity decreases (λ: 1.04 to 0.64 W·m<sup>-1</sup>·K<sup>-1</sup>), the diffusivity increases (from 4.32 × 10<sup>-7</sup> to 5.9 × 10<sup>-7</sup> m<sup>2</sup>·s<sup>-1</sup>), and the effusivity decreases (1404 - 906 J·m<sup>-2</sup>·K<sup>-1</sup>·s<sup>-1/2</sup>). Improving the structural and thermal efficiency of BTC via stabilisation with derived binders or cement is beneficial for the load-bearing capacity and thermal performance of buildings.
基金Zhejiang Scientific and Technological Plan of Traditional Chinese Medicine,No.2018ZB033Zhejiang Medical and Health Science and Technology Project,No.2018234792
文摘Simultaneous anterior and posterior traumatic dislocations of both hips are very rare. Only 33 cases have been previously reported in the English language literature. Although they were all due to high-energy injuries, they were hemodynamically stable and had a stable pelvic ring. We report a unique case of asymmetrical hip dislocations with an unstable pelvic ring and hemodynamic instability. A 40-year-old man was injured in a high-energy motor vehicle accident. He was hemodynamically unstable when he presented in the emergency department. Radiolographs showed asymmetrical dislocations of both hips with an unstable pelvic ring. Under general anesthesia, he had closed reduction of the dislocations of both hips, followed by temporary stabilization with an external fixator. Transcatheter arterial embolization was performed to stop active pelvic bleeding. Delayed open reduction and internal fixation was performed 12 d later with anterior and posterior plates. The patient recovered well with an uneventful post-operative course. Asymmetrical bilateral hip dislocations with pelvic ring instability caused by trauma, as presented in this case, is very rare and potentially life threatening. Prompt treatment can give a good outcome.
基金Projects(50804018,50564005)supported by the National Natural Science Foundation of ChinaProject(2003E0003Z)supported by the Key Science Foundation of Yunnan Province,China+1 种基金Project(08Y0055)supported by Scientific Research Fund of Yunnan Provincial Education Department,ChinaProject(2008-055)supported by Talents Cultivation Foundation of Kunming University of Science and Technology,China
文摘Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}<1ī2>+{112}<11ī> texture component disappears and turns into{122}<212>cube twin texture component.
文摘The directed motion of a Brownian particle in a Bashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the steady current J of the particle is calculated via Langevin simulation. The results show that the optimal cycle period (Tm), which takes the maximum of J, is shifted to a small value when the transition probability A from the potential on to the potential off decreases, the maximal current appears in the case of the average waiting time in the potential on being longer than in the potential off, and the direction of current depends on the ratio of the average times waiting in two states.
基金Major State Basic Research Program of China(2013CB430305)National Natural Science Foundation of China(41475060,41275067,41305049)Public Benefit Research Foundation of China(GYHY201406010)
文摘Based on NCEP/CFSR 0.5° reanalysis data and the best track data from the Japan Tokyo Typhoon Center,composite and comparative analyses demonstrate the asymmetrical structures of the temperature and humidity in tropical cyclones over the Western North Pacific and the South China Sea from 1979 to 2010.The results are shown as follows.(1) With intensifying tropical cyclones,the flow field tends to become gradually more axisymmetric;however,the asymmetry of the specific humidity in the outer regions is more obvious.(2) In general,tropical cyclones have a non-uniform,vertical, "double warm-core" structure.The "warm-cores" in the lower level of weak tropical cyclones and in the higher level of strong tropical cyclones are the stronger of the two.(3) The distribution area of a "warm-core" is enhanced with cyclone intensification and tends to become more axisymmetric.At 200 hPa,the "warm-core" of a weak cyclone has a weak anticyclone in the center,whereas that of a strong cyclone has a weak cyclone in the center.(4)The "wet-core" of a tropical cyclone is primarily located in the lower level(700-850 hPa).With the cyclone's intensification,the intensity of the "wet-core" increases and the scope of the 0.8 g kg^(-1) specific humidity anomaly tends to expand to higher levels.(5) With the cyclone's deepening,the pseudo-equivalent potential temperature at different levels in different regions increases.In addition,the largest warming rates at each intensity level in the different regions occur in the core area,followed in turn by the envelope and outer areas.
基金This work was supported in part by the program for Innovation Team Building at Institutions of Higher Education in Chongqing under Grant No.KJTD201310，the Scientific and Technological Research Program of Chongqing Municipal Education Commission of China under Grant KJ120513，Natural Science Foundation Project of CQ CSTC of P.R.China under Grant No.cstc2011jjA40031
文摘Quantum cryptography and quantum search algorithm are considered as two important research topics in quantum information science.An asymmetrical quantum encryption protocol based on the properties of quantum one-way function and quantum search algorithm is proposed.Depending on the no-cloning theorem and trapdoor one-way functions of the publickey,the eavesdropper cannot extract any private-information from the public-keys and the ciphertext.Introducing key-generation randomized logarithm to improve security of our proposed protocol,i.e.,one privatekey corresponds to an exponential number of public-keys.Using unitary operations and the single photon measurement,secret messages can be directly sent from the sender to the receiver.The security of the proposed protocol is proved that it is informationtheoretically secure.Furthermore,compared the symmetrical Quantum key distribution,the proposed protocol is not only efficient to reduce additional communication,but also easier to carry out in practice,because no entangled photons and complex operations are required.
基金Supported by Doctorate Station Foundation of State Educational Commission of China。
文摘We present the analytic solution of an asymmetrical crack in a strip from which the stress intensity factors are determined.The results have important application in earthquake source physics and provide information concerning the instability of faults and the detection of earthquake precursors.
基金A key project of National Foundation of Natural Science (40533015)Foundation for Meteorological Research of Jiangsu Province (K200715)a project of Foundation for Fundamental Theoretic Research of Institute of Meteorology,PLA University of Science and Technology
文摘The structural characteristics of 2004 typhoon Aere's precipitation are analyzed using the high-resolution data from the Tropical Rainfall Measuring Mission(TRMM) of the National Aeronautics Space Administration(NASA).It is found that the typhoon's characteristics vary at different stages of its development.To analyze the asymmetric causation of precipitation distribution,data from the National Center for Environmental Prediction(NCEP) reanalysis are used to calculate the vertical integral of the water vapor flux vector.The results show that because of this process,along with the unique phenomenon of twin-typhoon circulation,the easterly air current of the typhoon's northern side and the southwesterly air current of its southern side play a joint role in transporting water vapor.Furthermore,its transport effects vary greatly at the different stages of development,showing the peculiarity of the water source for this typhoon process.The distributions of the typhoon convection area—characterized by heavy precipitation and a maximum-value area of the water vapor flux,as well as a strong ascending-motion area—differ at different stages of the typhoon's development.The non-uniform distribution of water vapor flux and the vertical motion bring about asymmetrical distribution of the typhoon precipitation.
基金Natural Science Foundation of China (10871099 40805046+2 种基金 40830958)Specialized Projects of Public Welfare Industry (Meteorological Sector) (GYH(QX)2007-6-15)973 Program of National Key Foundamental Research and Development (2009CB421502)
文摘Axisymmetric bogus vortexes at sea level are usually used in the traditional bogus data assimilation （BDA） scheme. In the traditional scheme, the vortex could not accurately describe the specific characteristics of a typhoon, and the evolving real typhoon is forced to unreasonably adapt to this changeless vortex. For this reason, an asymmetrical typhoon bogus method with information blended from the analysis and the observation is put forward in this paper, in which the impact of the Subtropical High is also taken into consideration. With the fifth-generation Penn State/NCAR Mesoscale Model （MM5） and its adjoint model, a four-dimensional variational data assimilation （4D-Var） technique is employed to build a dynamic asymmetrical BDA scheme to assimilate different asymmetrical bogus vortexes at different time. The track and intensity of six surmner typhoons much influenced by the Subtropical High are simulated and the results are compared. It is shown that the improvement in track simulation in the new scheme is more significant than that in the traditional scheme. Moreover, the periods for which the track cannot be simulated well by the traditional scheme can be improved with the new scheme. The results also reveal that although the simulated typhoon intensity in the new scheme is generally weaker than that in the traditional scheme, this trend enables the new scheme to simulate, in the later period, closer-to-observation intensity than the traditional scheme. However, despite the fact that the observed intensity has been largely weakened, the simulated intensity at later periods of the BDA schemes is still very intensive, resulting in overly development of the typhoon during the simulation. The limitation to the simulation effect of the BDA scheme due to this condition needs to be further studied.
文摘The dynamic thermal process during double-sided asymmetrical TIG backing welding of large thick plates （ 1 000 mm×700 mm×50 mm） is numerically simulated using MSC. MARC. The effect of arc distance on the thermal cycle in weld zone during double-sided asymmetrical T1G backing welding is investigated. The results show that the workpiece experiences double-peak thermal cycle in double-sided asymmetrical TIG backing welding. On the one hand, the fore arc has the pre- heating effect on the rear pass, and the pre-heating temperature depends on the distance between the double arcs, the heat input of fore arc, and the initial temperature of workpiece. On the other hand, the rear arc has the post-heating effect on the fore pass. The mutual effects of two heat sources decrease with the increase of arc distance.
基金by the National Natural Science Foundation of China under Grant No 10875006the National Basic Research Program of China under Grant No 2008CB717803China Nuclear Data Center and the Science and Technology on Nuclear Data Laboratory.
文摘Cross sections of the 10B(n,α)7Li reaction(including the total,the“leaking”alpha,forward alpha and backward alpha parts)at En=4.0 and 5.0 MeV were measured using an asymmetrical twin gridded ionization chamber and two back−to-back 10B samples.Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University.Monoenergetic neutrons were produced through the ^(2)H(d,n)3He reaction with a deuterium gas target.Absolute neutron flux was determined by a ^(238)U sample set inside the gridded ionization chamber and a BF_(3) long counter was employed as a neutron flux monitor and for normalization.The present results are compared with previous measurements and evaluations.
基金the National Natural Science Foundation of China under Project 52007047,in part by the National Natural Science Foundation of China under Project 51877065,and in part by Natural Science Foundation of Hebei Province under Project E2019202220.
文摘As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the SynRM,the torque ripple is a big issue and a great of work could been done on reducing it.In this paper,asymmetrical magnetic flux barriers in the SynRM rotor were studied comprehensively,including angle and width of each layer and each side of the magnetic barrier.The SynRMb with asymmetrical and parallel magnetic flux barrier was found as the best way to design SynRM based on the multi-objective design optimization method.Moreover,each parameter was studied to show the design rule of the asymmetrical magnetic flux barrier.As the average torque will be reduced with the asymmetrical barrier is used,the grain-oriented silicon steel is used on stator teeth of the SynRMb(SynRMbG)was proposed and studied.The analysis results show that the proposed new method can make the SynRM have better performance.
基金National Natural Science Foundations of China(Grant No.52075085)Fundamental Research Funds for the Central Universities of China(Grant No.N2103019).
文摘In previous studies about the synchronization of vibrators,the restoring forces of springs are mainly treated as linear directly,whereas the nonlinear features are rarely considered in vibrating systems.To make up this drawback,a dynamical model of a nonlinear vibrating mechanical system with double rigid frames(RFs),driven by two vibrators,is proposed to explore the synchronization and stability of the system.In this paper,the nonlinearity is reflected in nonlinear restoring forces of springs characterized by asymmetrical piecewise linear,where the nonlinear stiffness of springs is linearized equivalently using the asymptotic method.Based on the average method and Hamilton’s principle,the theory conditions to achieve synchronization and stability of two vibrators are deduced.After the theory analyses,some numerical qualitative analyses are given to reveal the coupling dynamical characteristics of the system and the relative motion properties between two RFs.Besides,some experiments are carried out to examine the validity of the theoretical results and the correctness of the numerical analyses results.Based on the comparisons of the theory,numeric and experiment,the ideal working regions of the system are suggested.Based on the present work,some new types of vibrating equipment,such as vibrating discharging centrifugal dehydrators/conveyers/screens,can be designed.
基金supported by National Basic Research Program of China (Grant No 2006CB705500)Chang-jiang Scholars and Innovative Research Team in University (Grant No IRT0605)National Natural Science Foundation of China (Grant No 70631001)
文摘This paper studies a simple asymmetrically evolved community network with a combination of preferential attachment and random properties. An important issue about community networks is to discover the different utility increments of two nodes, where the utility is introduced to investigate the asymmetrical effect of connecting two nodes. On the other hand, the connection of two nodes in community networks can be classified as two nodes belonging to the same or to different communities. The simulation results show that the model can reproduce a power-law utility 1 distribution P（u） - u^-σ, σ = 2 ＋1/p, which can be obtained by using mean-field approximation methods. Furthermore, P the model exhibits exponential behaviour with respect to small values of a parameter denoting the random effect in our model at the low-utility region and a power-law feature with respect to big values of this parameter at the high-utility region, which is in good agreement with theoretical analysis. This kind of community network can reproduce a unique utility distribution by theoretical and numerical analysis.
文摘A new aromatic asymmetrical ether diamine, 1,4-bis（3＇,4’-diaminophenoxy）benzene 3 was synthesized in three steps, using hydroquinone as starting material. A new aromatic polyimide containing asymmetrical diaryl ether segments was prepared from the resulting diamine with 4,4＇-oxydiphthalic anhydride （ODPA） via a conventional two-step thermal or chemical imidization method. The resulting polyimide exhibits high thermal resistance, excellent solubility, film-forming capability, high mechanical strength and modulus.
