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摘要:Tunneling wounds create passageways underneath the skin surface with varying sizes and shapes and can have twists and turns,making their treatment extremely *** wound care solutions only cater to superficial wounds,and untreated tunneling wounds pose major health *** study aims to fulfill this challenge by fabricating tunnel wound fillers(TWFs)made of natural polymers that mimic the dermal extracellular *** this study,cellulose microfibers(CMFs)derived from banana stem and fish skin-derived collagen were used to formulate bio-inks with varying CMF contents(25,50,and 75 mg).Tri-layered(CMFs,primary and secondary collagen coatings),drug-eluting(Baneocin),and cell-laden(human mesenchymal stem cells)TWFs were three-dimensional(3D)-printed and extensively *** showed the most suitable rheological properties for 3D printing at 50 mg *** Alamar Blue data showed significantly increased cell proliferation from Day 1 to Day 7,and scratch tests used to evaluate in vitro wound healing revealed that the best coverage of the wound area was achieved using CMFs in combination with collagen and ***,the TWF showed promising capability and tunability in terms of wound shape and size upon testing on a chicken tissue *** results demonstrate the tremendous potential of TWFs in treating deep tunneling wounds with unique advantages,such as patient-specific customization,good wound exudate absorption capability while releasing wound healing drugs,and the inclusion of stem cells for accelerated healing and tissue regeneration.
摘要:Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium(5.0wt%–10.0wt%) and chromium(up to 9.0wt%) contents. The alloys were quenched at 920℃. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides(M7C3) and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%–10.0wt% for V and 2.5wt%–4.5wt% for Cr, which corresponds to the alloys containing 9vol%–15vol% spheroidal VC carbides, 8vol%–16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9–2.3 times that of the traditional 12wt% V–13wt% Mn spheroidal carbide cast iron.
摘要:Wind power is one of the most reliable renewable energy sources and internationally installed capacity is increasing radically every *** wind power has been favored by the public in general,the problem with the impact of wind turbine noise on people living in the vicinity of the turbines has been *** noise wind turbine design is becoming more and more important as noise is spreading more adverse effect of wind turbine to *** paper demonstrates the design of 10 kW class wind turbines,each of three blades,a rotor diameter 6.4 m,a rated rotating speed 200 r/min and a rated wind speed 10 m/*** optimized airfoil is dedicated for the 75% spanwise position because the dominant source of a wind turbine blade is trailing edge noise from the outer 25% of the *** computations are performed for incompressible flow and for Mach number at 0.145 and for Reynolds numbers at 1.02×106 with a lift performance,which is resistant to surface contamination and turbulence *** objectives in the design process are to reduce noise emission,while sustaining high aerodynamic *** broadband noise sources are predicted by semi-empirical formulas composed of the groundwork by Brooks et *** Lowson associated with typical wind turbine operation *** the airfoil redesign process,the aerodynamic performance is analyzed to reduce the wind turbine power *** results obtained from the design process show that the design method is capable of designing airfoils with reduced noise using a commercial 10 kW class wind turbine blade airfoil as a ***,the new optimized airfoil showing 2.9 dB reductions of total sound pressure level(SPL) and higher aerodynamic performance are achieved.
摘要:Much research effort has been devoted to economic design of X & S control charts,however,there are some problems in usual *** the one hand,it is difficult to estimate the relationship between costs and other model parameters,so the economic design method is often not effective in producing charts that can quickly detect small shifts before substantial losses occur;on the other hand,in many cases,only one type of process shift or only one pair of process shifts are taken into consideration,which may not correctly reflect the actual process *** improve the behavior of economic design of control chart,a cost & loss model with Taguchi's loss function for the economic design of X & S control charts is embellished,which is regarded as an optimization problem with multiple statistical *** optimization design is also carried out based on a number of combinations of process shifts collected from the field operation of the conventional control charts,thus more hidden information about the shift combinations is mined and employed to the optimization design of control *** the same time,an improved particle swarm optimization(IPSO) is developed to solve such an optimization problem in design of X & S control charts,IPSO is first tested for several benchmark problems from the literature and evaluated with standard performance *** results show that the proposed algorithm has significant advantages on obtaining the optimal design parameters of the *** proposed method can substantially reduce the total cost(or loss) of the control charts,and it will be a promising tool for economic design of control charts.
摘要:Shape memory polymers(SMPs)are a promising class of materials for biomedical applications due to their favorable mechanical properties,fast response,and good ***,it is difficult to achieve controllable sequential shape change for most SMPs due to their high deformation temperature and the simplex deformation ***,shape memory composites based on polylactic acid(PLA)matrix and semi-crystalline linear polymer polycaprolactone(PCL)are fabricated using 4D printing *** with pure PLA,with the rise of PCL content,the 4D-printed PLA/PCL composites show decreased glass transition temperature(Tg)from 67.2 to 55.2°*** the precise control of the deformation condition,controllable sequential deformation with an outstanding shape memory effect can be achieved for the PLA/PCL shape memory *** response time of shape recovery is less than 1.2 s,and the shape fixation/recov-ery rates are above 92%.In order to simulate sequential petal opening and sequential drug releasing effects,a double-layer bionic flower and a drug release device,respectively,are presented by assembling PLA/PCL samples with different PLA/PCL *** results indicate the potential applications of 4D-printed PLA/PCL composites in the field of bio-inspired robotics and biomedical devices.
摘要:Conducting polymers(CPs),including poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS),are promising coating materials for neural ***,the weak adhesion of CP coatings to substrates such as platinum-iridium is a significant challenge that limits their practical *** address this issue,we used femtosecond laser-prepared hierarchical structures on platinum-iridium(Pt-Ir)substrates to enhance the adhesion of PEDOT:PSS ***,we used cyclic voltammetry(CV)stress and accelerated aging tests to evaluate the stability of both drop cast and electrodeposited PEDOT:PSS coatings on Pt-Ir substrates,both with and without hierarchical *** results showed that after 2000 CV cycles or five weeks of aging at 60℃,the morphology and electrochemical properties of the coatings on the Pt-Ir substrates with hierarchical structures remained relatively *** contrast,we found that smooth Pt-Ir substrate surfaces caused delamination of the PEDOT:PSS coating and exhibited both decreased charge storage capacity and increased ***,enhancing the stability of PEDOT:PSS coatings used on common platinum-iridium neural electrodes offers great potential for improving their electrochemical performance and developing new functionalities.
摘要:This work investigates the machining temperatures of ultra-fine-grained titanium(UFG Ti),prepared by equal channel angular extrusion,through analytical *** Ti has great usefulness in biomedical applications because of its high mechanical strength,sufficient manufacturability,and high *** temperatures were predicted using a physics-based predictive model based on material constitutive relation and mechanics of the orthogonal cutting *** minimization between the stress calculated using Johnson–Cook constitutive model and the same stress calculated using mechanics model yields the estimation of machining temperatures at two deformation *** agreements are observed upon validation to the values reported in the *** machinability of UFG Ti is investigated by comparing its machining temperature to that of Ti–6Al–4V alloy under the same cutting *** lower temperatures are observed in machining UFG *** computational efficiency of the presented model is investigated by comparing its average computational time(~0.5 s)to that of a widely used modified chip formation model(8900 s)with comparable prediction *** work extends the applicability of the presented temperature model to a broader class of materials,specifically ultra-fine-grained *** high computational efficiency allows the in situ temperature prediction and optimization of temperature condition with process parameters planning.
摘要:Aiming at dealing with the difficulty for traditional emergency rescue vehicle(ECV)to enter into limited rescue scenes,the electro-hydraulic steer-by-wire(SBW)system is introduced to achieve the multi-mode steering of the *** overall structure and mathematical model of the SBW system are described at *** fractional order proportional-integral-derivative(FOPID)controller based on fractional calculus theory is designed to control the steering cylinder’s movement in SBW *** anti-windup problem is considered in the FOPID controller design to reduce the bad influence of *** parameters of the FOPID controller are optimized using the genetic algorithm by maximizing the fitness function which involves integral of time by absolute value error(ITAE),peak overshoot,as well as settling *** time-domain simulations are implemented to identify the performance of the raised FOPID *** simulation results indicate the presented FOPID controller possesses more effective control properties than classical proportional-integral-derivative(PID)controller on the part of transient response,tracking capability and robustness.
摘要:Traditional simulation methods are unable to meet the requirements of lunar takeo simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have the advantages of high payload to weight ratio, potentially large workspace, and high-speed motion, these mechanisms have the potential to be used for lunar takeo simulations. Thus, this paper presents a parallel mechanism driven by nine cables. The purpose of this study is to optimize the dimensions of the cable-driven parallel mechanism to meet dynamic workspace requirements under cable tension constraints. The dynamic workspace requirements are derived from the kinematical function requests of the lunar takeo simulation equipment. Experimental design and response surface methods are adopted for building the surrogate mathematical model linking the optimal variables and the optimization indices. A set of dimensional parameters are determined by analyzing the surrogate mathematical model. The volume of the dynamic workspace increased by 46% after optimization. Besides, a force control method is proposed for calculating output vector and sinusoidal forces. A force control loop is introduced into the traditional position control loop to adjust the cable force precisely, while controlling the cable length. The e ectiveness of the proposed control method is verified through experiments. A 5% vector output accuracy and 12 Hz undulation force output can be realized. This paper proposes a cable-driven parallel mechanism which can be used for lunar takeo simulation.
摘要:The hypersonic vehicle model is characterized by strong coupling,nonlinearity,and acute changes of aerodynamic parameters,which are challenging for control system *** study investigates a novel compound control scheme that combines the advantages of the Fractional-Order Proportional-Integral-Derivative(FOPID)controller and Linear Active Disturbance Rejection Control(LADRC)for reentry flight control of hypersonic vehicles with actuator ***,given that the controller has adjustable parameters,the frequency-domain analysis-method-based parameter tuning strategy is utilized for the FOPID controller and LADRC method(FOLADRC).Then,the influences of the actuator model on the anti-disturbance capability and parameter tuning of the FOLADRC-based closed-loop control system are ***,the simulation results indicate that the proposed FOLADRC approach has satisfactory performance in terms of rapidity,accuracy,and robustness under the normal operating condition and actuator fault condition.
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