In this paper,the distributed fuzzy fault-tolerant tracking consensus problem of leader-follower multi-agent systems(MASs)is studied.The objective system includes actuator faults,mismatched parameter uncertainties,non...In this paper,the distributed fuzzy fault-tolerant tracking consensus problem of leader-follower multi-agent systems(MASs)is studied.The objective system includes actuator faults,mismatched parameter uncertainties,nonlinear functions,and exogenous disturbances under switching communication topologies.To solve this problem,a distributed fuzzy fault-tolerant controller is proposed for each follower by adaptive mechanisms to track the state of the leader.Furthermore,the fuzzy logic system is utilized to approximate the unknown nonlinear dynamics.An error estimator is introduced between the mismatched parameter matrix and the input matrix.Then,a selective adaptive law with relative state information is adopted and applied.When calculating the Lyapunov function’s derivative,the coupling terms related to consensus error and mismatched parameter uncertainties can be eliminated.Finally,a numerical simulation is given to validate the effectiveness of the proposed protocol.展开更多
The design of servo controllers for flexible ball screw drives with matched and mismatched disturbances and uncertainties is focused to improve the tracking performance and bandwidth of ball screw drives.A two degrees...The design of servo controllers for flexible ball screw drives with matched and mismatched disturbances and uncertainties is focused to improve the tracking performance and bandwidth of ball screw drives.A two degrees of freedom mass model is established based on the axial vibration characteristics of the transport ball screw,and the controller of an adaptive integral sliding mode is proposed combining the optimal design of state feedback gain matrix K to restrain the vibration and the matched disturbances and uncertainties.Then for the counteraction of the mismatched disturbances and uncertainties,a nonlinear disturbance observer is also developed.The trajectory tracking performance experiments and bandwidth analysis were conducted on experimental setup with the proposed control method.It is proved that the adaptive integral sliding mode controller has a high tracking performance and bandwidth especially for the axial vibration characteristics model of ball screw drives.And the ball screw tracking accuracy also has a considerable improvement with the application of the proposed nonlinear disturbance observer.展开更多
In this paper, an adaptive full order sliding mode （FOSM） controller is proposed for strict feedback nonlinear systems with mismatched uncertainties. The design objective of the controller is to track a specified tr...In this paper, an adaptive full order sliding mode （FOSM） controller is proposed for strict feedback nonlinear systems with mismatched uncertainties. The design objective of the controller is to track a specified trajectory in presence of significant mismatched uncertainties. In the first step the dynamic model for the first state is considered by the desired tracking signal. After the first step the desired dynamic model for each state is defined by the previous one. An adaptive tuning law is developed for the FOSM controller to deal with the bounded system uncertainty. The major advantages offered by this adaptive FOSM controller are that advanced knowledge about the upper bound of the system uncertainties is not a necessary requirement and the proposed method is an effective solution for the chattering elimination from the control signal. The controller is designed considering the full-order sliding surface. System robustness and the stability of the controller are proved by using the Lyapunov technique. A systematic adaptive step by step design method using the full order sliding surface for mismatched nonlinear systems is presented, Simulation results validate the effectiveness of the proposed control law.展开更多
This paper proposes a discrete-time robust control technique for an uncertain nonlinear system. The uncertainty mainly affects the system dynamics due to mismatched parameter variation which is bounded by a predefined...This paper proposes a discrete-time robust control technique for an uncertain nonlinear system. The uncertainty mainly affects the system dynamics due to mismatched parameter variation which is bounded by a predefined known function. In order to compensate the effect of uncertainty, a robust control input is derived by formulating an equivalent optimal control problem for a virtual nominal system with a modified costfunctional. To derive the stabilizing control law for a mismatched system, this paper introduces another control input named as virtual input. This virtual input is not applied directly to stabilize the uncertain system, rather it is used to define a sufficient condition. To solve the nonlinear optimal control problem, a discretetime general Hamilton-Jacobi-Bellman(DT-GHJB) equation is considered and it is approximated numerically through a neural network(NN) implementation. The approximated solution of DTGHJB is used to compute the suboptimal control input for the virtual system. The suboptimal inputs for the virtual system ensure the asymptotic stability of the closed-loop uncertain system. A numerical example is illustrated with simulation results to prove the efficacy of the proposed control algorithm.展开更多
This letter delnonstrates the structure of the passive radar using TV signals. Because the TV signal is a kind of pseudoperiodic signal, the matched filtering of color TV signals would yield high sidelobes which cause...This letter delnonstrates the structure of the passive radar using TV signals. Because the TV signal is a kind of pseudoperiodic signal, the matched filtering of color TV signals would yield high sidelobes which cause the range ambiguity. To overcome this problem, the mismatched filter is proposed to suppress the correlation sidelobcs of matched filtering of TV signals. By utilizing the iteration process, this method could achieve the required peak sidclobc level. The impacts of the noise and target movement on mismatched filtering are also analysed, Simulation results are included to demonstrate the effectiveness of the proposed technique.展开更多
An idealized tri-material assumption is established to describe the constitutive relationship of mismatched welded joints by considering the influence of heat affected zone（HAZ）.The fracture parameters Jand C＊are e...An idealized tri-material assumption is established to describe the constitutive relationship of mismatched welded joints by considering the influence of heat affected zone（HAZ）.The fracture parameters Jand C＊are estimated for mismatched welded joints with HAZ cracks by finite element analysis with ABAQUS.A middle crack tension（M（T））specimen is utilized in the analysis for different material properties and geometries of the weldment.The influence of mechanical property and geometry on the fracture parameters Jand C＊of the specimen is discussed for the welded joints with HAZ crack.The results suggest that the HAZ property is a significant factor in the estimation of Jand C＊for the mismatched welded joint with HAZ crack.展开更多
Based on the scatter matrix of the four-port lossless mismatched circulator, the phase differential equation of the injection-locked magnetron is derived by comparing different effects of the mismatched and perfect ci...Based on the scatter matrix of the four-port lossless mismatched circulator, the phase differential equation of the injection-locked magnetron is derived by comparing different effects of the mismatched and perfect circulator on the injection ratio. Besides, the locking range of the injection-locked magnetron with the mismatched circulator is deduced by functional operation. In addition, the phase differential equation and the locked bandwidth of the injection-locked system with a mismatched circulator are compared with those of the small injection-ratio case with a perfect circulator. The in- fluence of the circulator reflection coefficient on the injection-locked magnetron is also analyzed by numerical calculation. Theoretical analysis shows that the decrement of the locked bandwidth is less than 1% and decrement of the stable phase difference is less than 1.2% when the reflection coefficient is less than 0.1.展开更多
A two-layer switching architecture and a two-layer switching rule for stabilization of switched linear control systems are proposed, under which the mismatched switching between switched systems and their candidate hy...A two-layer switching architecture and a two-layer switching rule for stabilization of switched linear control systems are proposed, under which the mismatched switching between switched systems and their candidate hybrid controllers can be allowed. In the low layer, a state-dependent switching rule with a dwell time constraint to exponentially stabilize switched linear systems is given; in the high layer, supervisory conditions on the mismatched switching frequency and the mismatched switching ratio are presented, under which the closed-loop switched system is still exponentially stable in case of the candidate controller switches delay with respect to the subsystems. Different from the traditional switching rule, the two-layer switching architecture and switching rule have robustness, which in some extend permit mismatched switching between switched subsystems and their candidate controllers.展开更多
Study of radiation properties of mismatched microstrip termination is carried out in warm ionized electron plasma medium. Linearised hydrodynamic theory coupled with vector wave technique is used to investigate radiat...Study of radiation properties of mismatched microstrip termination is carried out in warm ionized electron plasma medium. Linearised hydrodynamic theory coupled with vector wave technique is used to investigate radiation patterns and radiated power of a microstrip mismatched termination in one component electron plasma media for different plasma to source frequencies .These properties are used to compare the performance of an open circuit discontinuity with those of matched microstrip termination. Matched terminations are found more suitable for applications at higher frequencies than an open circuit discontinuity in the plasma medium though in free space they are less suitable.展开更多
Nowadays, in a household PV （photovoltaic） generation system, it is generally connecting PV modules in series and then output to the power-conditioner. However, when PV modules are mismatched, it will lead to a wron...Nowadays, in a household PV （photovoltaic） generation system, it is generally connecting PV modules in series and then output to the power-conditioner. However, when PV modules are mismatched, it will lead to a wrong MPPT （maximum power point tracking） to all modules and a power decreasing of the whole system. Aiming at this problem, this paper presents the idea which improves the MPPT without changing the conventional power-conditioner, by adding a Buck type DC-DC （direct current） converter behind each module. Simulations of PSIM （power simulation） and experiments are taken to prove this theory. The result shows that, by this idea, the generated power of the conventional PV generation system can be greatly increased under the condition of mismatch.展开更多
The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conv...The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.展开更多
Welding of high strength low alloy steels (HSLA) involves usage of low, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the avail...Welding of high strength low alloy steels (HSLA) involves usage of low, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the filler material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0).A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.展开更多
A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes(μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency(EQE) and the optical power. In this...A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes(μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency(EQE) and the optical power. In this work, we propose and fabricate a polarization mismatched p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure for 445 nm GaN-based μLEDs with the size of 40 × 40 μm^(2), which serves as the hole injection layer. The polarization-induced electric field in the p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure provides holes with more energy and can facilitate the non-equilibrium holes to transport into the active region for radiative recombination. Meanwhile, a secondary etched mesa for μLEDs is also designed, which can effectively keep the holes apart from the defected region of the mesa sidewalls, and the surface nonradiative recombination can be suppressed. Therefore, the proposed μLED with the secondary etched mesa and the p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure has the enhanced EQE and the improved optical power density when compared with the μLED without such designs.展开更多
Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the la...Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions,respectively.Taking the Si and III-V systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and III-V semiconductors along different directions,it is found that the band offsets of Si/InAs and Si/InSb systems in[100],[110]and[111]directions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.展开更多
In quantum key distribution(QKD),the passive decoy-state method can simplify the intensity modulation and reduce some of side-channel information leakage and modulation errors.It is usually implemented with a heralded...In quantum key distribution(QKD),the passive decoy-state method can simplify the intensity modulation and reduce some of side-channel information leakage and modulation errors.It is usually implemented with a heralded single-photon source.In Wang et al 2016(Phys.Rev.A 96032312),a novel passive decoy-state method is proposed by Wang et al,which uses two local detectors to generate more detection events for tightly estimating channel parameters.However,in the original scheme,the two local detectors are assumed to be identical,including the same detection efficiency and dark count rate,which is often not satisfied in the realistic experiment.In this paper,we construct a model for this passive decoy-state QKD scheme with two mismatched detectors and explore the effect on QKD performance with certain parameters.We also take the finite-size effect into consideration,showing the performance with statistical fluctuations.The results show that the efficiencies of local detectors affect the key rate more obviously than dark count rates.展开更多
Metal-on-metal hip resurfacing has gained popularity as a feasible treatment option for young and active patients with hip osteoarthritis and high functional expectations.This procedure should only be performed by sur...Metal-on-metal hip resurfacing has gained popularity as a feasible treatment option for young and active patients with hip osteoarthritis and high functional expectations.This procedure should only be performed by surgeons who have trained specifically in this technique.Preoperative planning is essential for hip resurfacing in order to execute a successful operation and preview any technical problems.The authors present a case of a man who underwent a resurfacing arthroplasty for osteoarthritis of the left hip that was complicated by mismatched implant components that were revised three days afterwards for severe pain and leg length discrepancy.Such mistakes,although rare,can be prevented by educating operating room staff in the size and colour code tables provided by the companies on their prostheses or implant boxes.展开更多
The paper presents finite element modeling of crack tip blunting for numerical estimation of fracture parameter of a Mode I crack, in weak alloy steel, which is near and normal to the interface of elastically identica...The paper presents finite element modeling of crack tip blunting for numerical estimation of fracture parameter of a Mode I crack, in weak alloy steel, which is near and normal to the interface of elastically identical but stronger maraging steel. The bimetallic body is subjected to monotonic load in K dominated regime. Crack tip yield zone across the interface, treated as Dugdale’s cohesive zone, is isolated from the bimetallic domain and is modeled alone under the action of respective cohesive stress over yield zones for obtaining the contribution of mismatch between yield strength of the steels in crack energy release rate component, Jinterface. Effect of far field load on Jinterface is found separately from a theoretical model. Numerical and theoretical results of Jinterface are in good agreement.展开更多
The finite element analysis of mismatched welded jo ints with a 30°groove angle was performed to study the mechanical behavior of D MWJs (dissimilar metal welded joints). It is concluded that the distribution of...The finite element analysis of mismatched welded jo ints with a 30°groove angle was performed to study the mechanical behavior of D MWJs (dissimilar metal welded joints). It is concluded that the distribution of stress triaxiality in the DMWJs is uneven, especially near the fusion lines. The degree of creep strength mismatch has remarkable effect on the distribution. Th e higher the level of mismatch is, the more uneven the distribution is and the e asier for premature failure to occur in the joint.展开更多
Characteristics of Mode I crack near the interface of elasticity matched but plasticity and strength mismatched materials differ from those of the crack in a homogenous body. Interface body of different strength influ...Characteristics of Mode I crack near the interface of elasticity matched but plasticity and strength mismatched materials differ from those of the crack in a homogenous body. Interface body of different strength influences the plastic or cohesive zone at the crack tip in parent body. The mathematical model for load line opening of the crack near the interface in linear elastic regime involves singular integrals. The paper presents explicit solution of these integrals with the help of Cauchy’s principal value theorem. Cases of thin and thick welds between the materials are investigated. Solutions of the integrals are well substantiated. Final results are provided in a consolidated form.展开更多
Facile and ultrasensitive detection of Pb^(2+)in water for remote or resource-limited environments remains challenging.DNAzyme-based colorimetric nanobiosensors have been extensively studied to regulate the assembly o...Facile and ultrasensitive detection of Pb^(2+)in water for remote or resource-limited environments remains challenging.DNAzyme-based colorimetric nanobiosensors have been extensively studied to regulate the assembly of functionalized gold nanoparticles(AuNPs).However,these nanobiosensors have been criticized for their low sensitivity owing to the difficulty of dissociating DNAzyme embedded in AuNP aggregates.To address this issue,we rationally designed a DNAzyme by introducing an adenine-cytosine(A-C)mismatch to strengthen the disassembly of DNAzyme-linked nanostructures.As proof of concept,a“turn on”colorimetric nanobiosensor integrated with mismatched DNAzyme and functionalized AuNPs was first developed for Pb^(2+)detection.Under the optimal detection conditions,the obtained typical calibration curve shows a detection limit of 8.6 nmol/L,with an approximately 11-fold sensitivity improvement in Pb^(2+)detection compared with unmismatched DNAzyme,and a linear response range from 10 to 300 nmol/L.This nanobiosensor demonstrated robust selectivity and satisfactory recovery rates between 86.5%and 106.4%for Pb^(2+)in spiked environmental water samples.Additionally,the detection process is user-friendly and can be completed within 30 min,requiring only a simple water sample addition step.Considering the extensive applications of DNAzyme in conjunction with nanoparticles,this study provides a valuable reference for designing other DNAzyme-powered nanoparticle assemblies in biosensing systems.展开更多
基金This work was supported by Tianjin Natural Science Foundation of China(20JCYBJC01060,20JCQNJC01450)the National Natural Science Foundation of China(61973175)Tianjin Postgraduate Scientific Research and Innovation Project(2020YJSZXB03,2020YJSZXB12).
文摘In this paper,the distributed fuzzy fault-tolerant tracking consensus problem of leader-follower multi-agent systems(MASs)is studied.The objective system includes actuator faults,mismatched parameter uncertainties,nonlinear functions,and exogenous disturbances under switching communication topologies.To solve this problem,a distributed fuzzy fault-tolerant controller is proposed for each follower by adaptive mechanisms to track the state of the leader.Furthermore,the fuzzy logic system is utilized to approximate the unknown nonlinear dynamics.An error estimator is introduced between the mismatched parameter matrix and the input matrix.Then,a selective adaptive law with relative state information is adopted and applied.When calculating the Lyapunov function’s derivative,the coupling terms related to consensus error and mismatched parameter uncertainties can be eliminated.Finally,a numerical simulation is given to validate the effectiveness of the proposed protocol.
基金Project(2013ZX04008011)supported by the National Science and Technology Major Projects of ChinaProject(51675100)supported by the National Natural Science Foundation of China
文摘The design of servo controllers for flexible ball screw drives with matched and mismatched disturbances and uncertainties is focused to improve the tracking performance and bandwidth of ball screw drives.A two degrees of freedom mass model is established based on the axial vibration characteristics of the transport ball screw,and the controller of an adaptive integral sliding mode is proposed combining the optimal design of state feedback gain matrix K to restrain the vibration and the matched disturbances and uncertainties.Then for the counteraction of the mismatched disturbances and uncertainties,a nonlinear disturbance observer is also developed.The trajectory tracking performance experiments and bandwidth analysis were conducted on experimental setup with the proposed control method.It is proved that the adaptive integral sliding mode controller has a high tracking performance and bandwidth especially for the axial vibration characteristics model of ball screw drives.And the ball screw tracking accuracy also has a considerable improvement with the application of the proposed nonlinear disturbance observer.
文摘In this paper, an adaptive full order sliding mode （FOSM） controller is proposed for strict feedback nonlinear systems with mismatched uncertainties. The design objective of the controller is to track a specified trajectory in presence of significant mismatched uncertainties. In the first step the dynamic model for the first state is considered by the desired tracking signal. After the first step the desired dynamic model for each state is defined by the previous one. An adaptive tuning law is developed for the FOSM controller to deal with the bounded system uncertainty. The major advantages offered by this adaptive FOSM controller are that advanced knowledge about the upper bound of the system uncertainties is not a necessary requirement and the proposed method is an effective solution for the chattering elimination from the control signal. The controller is designed considering the full-order sliding surface. System robustness and the stability of the controller are proved by using the Lyapunov technique. A systematic adaptive step by step design method using the full order sliding surface for mismatched nonlinear systems is presented, Simulation results validate the effectiveness of the proposed control law.
文摘This paper proposes a discrete-time robust control technique for an uncertain nonlinear system. The uncertainty mainly affects the system dynamics due to mismatched parameter variation which is bounded by a predefined known function. In order to compensate the effect of uncertainty, a robust control input is derived by formulating an equivalent optimal control problem for a virtual nominal system with a modified costfunctional. To derive the stabilizing control law for a mismatched system, this paper introduces another control input named as virtual input. This virtual input is not applied directly to stabilize the uncertain system, rather it is used to define a sufficient condition. To solve the nonlinear optimal control problem, a discretetime general Hamilton-Jacobi-Bellman(DT-GHJB) equation is considered and it is approximated numerically through a neural network(NN) implementation. The approximated solution of DTGHJB is used to compute the suboptimal control input for the virtual system. The suboptimal inputs for the virtual system ensure the asymptotic stability of the closed-loop uncertain system. A numerical example is illustrated with simulation results to prove the efficacy of the proposed control algorithm.
文摘This letter delnonstrates the structure of the passive radar using TV signals. Because the TV signal is a kind of pseudoperiodic signal, the matched filtering of color TV signals would yield high sidelobes which cause the range ambiguity. To overcome this problem, the mismatched filter is proposed to suppress the correlation sidelobcs of matched filtering of TV signals. By utilizing the iteration process, this method could achieve the required peak sidclobc level. The impacts of the noise and target movement on mismatched filtering are also analysed, Simulation results are included to demonstrate the effectiveness of the proposed technique.
基金Sponsored by National High Technology Research and Development Program of China(2012AA040106)
文摘An idealized tri-material assumption is established to describe the constitutive relationship of mismatched welded joints by considering the influence of heat affected zone（HAZ）.The fracture parameters Jand C＊are estimated for mismatched welded joints with HAZ cracks by finite element analysis with ABAQUS.A middle crack tension（M（T））specimen is utilized in the analysis for different material properties and geometries of the weldment.The influence of mechanical property and geometry on the fracture parameters Jand C＊of the specimen is discussed for the welded joints with HAZ crack.The results suggest that the HAZ property is a significant factor in the estimation of Jand C＊for the mismatched welded joint with HAZ crack.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB328901)the National Natural Science Foundation of China(Grant No.11305177)
文摘Based on the scatter matrix of the four-port lossless mismatched circulator, the phase differential equation of the injection-locked magnetron is derived by comparing different effects of the mismatched and perfect circulator on the injection ratio. Besides, the locking range of the injection-locked magnetron with the mismatched circulator is deduced by functional operation. In addition, the phase differential equation and the locked bandwidth of the injection-locked system with a mismatched circulator are compared with those of the small injection-ratio case with a perfect circulator. The in- fluence of the circulator reflection coefficient on the injection-locked magnetron is also analyzed by numerical calculation. Theoretical analysis shows that the decrement of the locked bandwidth is less than 1% and decrement of the stable phase difference is less than 1.2% when the reflection coefficient is less than 0.1.
基金supported by the National Natural Science Foundation of China(No.61233002)the Fundamental Research Funds for the Central Universities(No.N120404019)
文摘A two-layer switching architecture and a two-layer switching rule for stabilization of switched linear control systems are proposed, under which the mismatched switching between switched systems and their candidate hybrid controllers can be allowed. In the low layer, a state-dependent switching rule with a dwell time constraint to exponentially stabilize switched linear systems is given; in the high layer, supervisory conditions on the mismatched switching frequency and the mismatched switching ratio are presented, under which the closed-loop switched system is still exponentially stable in case of the candidate controller switches delay with respect to the subsystems. Different from the traditional switching rule, the two-layer switching architecture and switching rule have robustness, which in some extend permit mismatched switching between switched subsystems and their candidate controllers.
文摘Study of radiation properties of mismatched microstrip termination is carried out in warm ionized electron plasma medium. Linearised hydrodynamic theory coupled with vector wave technique is used to investigate radiation patterns and radiated power of a microstrip mismatched termination in one component electron plasma media for different plasma to source frequencies .These properties are used to compare the performance of an open circuit discontinuity with those of matched microstrip termination. Matched terminations are found more suitable for applications at higher frequencies than an open circuit discontinuity in the plasma medium though in free space they are less suitable.
文摘Nowadays, in a household PV （photovoltaic） generation system, it is generally connecting PV modules in series and then output to the power-conditioner. However, when PV modules are mismatched, it will lead to a wrong MPPT （maximum power point tracking） to all modules and a power decreasing of the whole system. Aiming at this problem, this paper presents the idea which improves the MPPT without changing the conventional power-conditioner, by adding a Buck type DC-DC （direct current） converter behind each module. Simulations of PSIM （power simulation） and experiments are taken to prove this theory. The result shows that, by this idea, the generated power of the conventional PV generation system can be greatly increased under the condition of mismatch.
基金supported by the project of Large Research Infrastructures"China initiative Accelerator-Driven System"(No.2017-000052-75-01-000590)"Studies of intelligent LLRF control algorithms for superconducting RF cavities"(No.E129851YR0)the National Natural Science Foundation of China(No.12205344).
文摘The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.
文摘Welding of high strength low alloy steels (HSLA) involves usage of low, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the filler material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0).A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.
基金supported in part by the National Natural Science Foundation of China (Grant Nos.62074050 and 61975051)Research Fund by State Key Laboratory of Reliability and Intelligence of Electrical Equipment,Hebei University of Technology (Grant Nos.EERI PI2020008 and EERI_PD2021012)Joint Research Project for Tunghsu Group and Hebei University of Technology (Grant No.HI1909)。
文摘A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes(μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency(EQE) and the optical power. In this work, we propose and fabricate a polarization mismatched p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure for 445 nm GaN-based μLEDs with the size of 40 × 40 μm^(2), which serves as the hole injection layer. The polarization-induced electric field in the p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure provides holes with more energy and can facilitate the non-equilibrium holes to transport into the active region for radiative recombination. Meanwhile, a secondary etched mesa for μLEDs is also designed, which can effectively keep the holes apart from the defected region of the mesa sidewalls, and the surface nonradiative recombination can be suppressed. Therefore, the proposed μLED with the secondary etched mesa and the p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure has the enhanced EQE and the improved optical power density when compared with the μLED without such designs.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2018YFB2200100)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB22)+1 种基金the National Natural Science Foundation of China(Grant No.118764347,11614003,11804333)H.X.D.was also supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2017154).
文摘Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions,respectively.Taking the Si and III-V systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and III-V semiconductors along different directions,it is found that the band offsets of Si/InAs and Si/InSb systems in[100],[110]and[111]directions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.
基金We gratefully acknowledge the financial support from the National Key R&D Program of China(2018YFA0306400,2017YFA0304100)the National Natural Science Foundation of China(12074194,11774180,U19A2075,12104240,62101285)+2 种基金the Leading-edge technology Program of Jiangsu Natural Science Foundation(BK20192001)Natural Science Foundation of Jiangsu Province(BK20210582)NUPTSF(NY220122,NY220123).
文摘In quantum key distribution(QKD),the passive decoy-state method can simplify the intensity modulation and reduce some of side-channel information leakage and modulation errors.It is usually implemented with a heralded single-photon source.In Wang et al 2016(Phys.Rev.A 96032312),a novel passive decoy-state method is proposed by Wang et al,which uses two local detectors to generate more detection events for tightly estimating channel parameters.However,in the original scheme,the two local detectors are assumed to be identical,including the same detection efficiency and dark count rate,which is often not satisfied in the realistic experiment.In this paper,we construct a model for this passive decoy-state QKD scheme with two mismatched detectors and explore the effect on QKD performance with certain parameters.We also take the finite-size effect into consideration,showing the performance with statistical fluctuations.The results show that the efficiencies of local detectors affect the key rate more obviously than dark count rates.
文摘Metal-on-metal hip resurfacing has gained popularity as a feasible treatment option for young and active patients with hip osteoarthritis and high functional expectations.This procedure should only be performed by surgeons who have trained specifically in this technique.Preoperative planning is essential for hip resurfacing in order to execute a successful operation and preview any technical problems.The authors present a case of a man who underwent a resurfacing arthroplasty for osteoarthritis of the left hip that was complicated by mismatched implant components that were revised three days afterwards for severe pain and leg length discrepancy.Such mistakes,although rare,can be prevented by educating operating room staff in the size and colour code tables provided by the companies on their prostheses or implant boxes.
文摘The paper presents finite element modeling of crack tip blunting for numerical estimation of fracture parameter of a Mode I crack, in weak alloy steel, which is near and normal to the interface of elastically identical but stronger maraging steel. The bimetallic body is subjected to monotonic load in K dominated regime. Crack tip yield zone across the interface, treated as Dugdale’s cohesive zone, is isolated from the bimetallic domain and is modeled alone under the action of respective cohesive stress over yield zones for obtaining the contribution of mismatch between yield strength of the steels in crack energy release rate component, Jinterface. Effect of far field load on Jinterface is found separately from a theoretical model. Numerical and theoretical results of Jinterface are in good agreement.
文摘The finite element analysis of mismatched welded jo ints with a 30°groove angle was performed to study the mechanical behavior of D MWJs (dissimilar metal welded joints). It is concluded that the distribution of stress triaxiality in the DMWJs is uneven, especially near the fusion lines. The degree of creep strength mismatch has remarkable effect on the distribution. Th e higher the level of mismatch is, the more uneven the distribution is and the e asier for premature failure to occur in the joint.
文摘Characteristics of Mode I crack near the interface of elasticity matched but plasticity and strength mismatched materials differ from those of the crack in a homogenous body. Interface body of different strength influences the plastic or cohesive zone at the crack tip in parent body. The mathematical model for load line opening of the crack near the interface in linear elastic regime involves singular integrals. The paper presents explicit solution of these integrals with the help of Cauchy’s principal value theorem. Cases of thin and thick welds between the materials are investigated. Solutions of the integrals are well substantiated. Final results are provided in a consolidated form.
基金supported by the Basic Research Project of Shanxi Province,China(202203021222086)the start-up foundation of Taiyuan University of Technology,China(RY2400000583).
文摘Facile and ultrasensitive detection of Pb^(2+)in water for remote or resource-limited environments remains challenging.DNAzyme-based colorimetric nanobiosensors have been extensively studied to regulate the assembly of functionalized gold nanoparticles(AuNPs).However,these nanobiosensors have been criticized for their low sensitivity owing to the difficulty of dissociating DNAzyme embedded in AuNP aggregates.To address this issue,we rationally designed a DNAzyme by introducing an adenine-cytosine(A-C)mismatch to strengthen the disassembly of DNAzyme-linked nanostructures.As proof of concept,a“turn on”colorimetric nanobiosensor integrated with mismatched DNAzyme and functionalized AuNPs was first developed for Pb^(2+)detection.Under the optimal detection conditions,the obtained typical calibration curve shows a detection limit of 8.6 nmol/L,with an approximately 11-fold sensitivity improvement in Pb^(2+)detection compared with unmismatched DNAzyme,and a linear response range from 10 to 300 nmol/L.This nanobiosensor demonstrated robust selectivity and satisfactory recovery rates between 86.5%and 106.4%for Pb^(2+)in spiked environmental water samples.Additionally,the detection process is user-friendly and can be completed within 30 min,requiring only a simple water sample addition step.Considering the extensive applications of DNAzyme in conjunction with nanoparticles,this study provides a valuable reference for designing other DNAzyme-powered nanoparticle assemblies in biosensing systems.
