REDUCTION APPROACHES FOR VIBRATION CONTROL OF REPETITIVE STRUCTURES

The reduction approaches are presented for vibration control of symmetric, cyclic periodic and linking structures. The condensation of generalized coordinates, the locations of sensors and actuators, and the relation between system inputs and control forces are assumed to be set in a symmetric way so that the control system posses the same repetition as the structure considered. By employing proper transformations of condensed generalized coordinates and the system inputs, the vibration control of an entire system can be implemented by carrying out the control of a number of sub-structures, and thus the dimension of the control problem can be significantly reduced.

A NEW METHOD FOR STRESS ANALYSIS OF A CYCLICALLY SYMMETRIC STRUCTURE

In this paper, a computational method for finite element stress analysis of a cyclically symmetric structure subjected to arbitrary loads is provided. At first, using discrete Fourier transformation technique, the complete structure is analyzed by considering only one sector with appropriate complex constraints on its boundary with the adjacent sectors. Next, an imaginary structure which is composed of two identically overlapping sectors is constructed, and that the complex constraints mentioned above can be equivalently replaced by a set of real constraints on this imaginary structure is proved. Therefore, the stress analysis of a cyclically symmetric structure can be solved conveniently by most of finite element programs.

ON DECENTRALIZED STABILIZATION OF LINEAR LARGE SCALE SYSTEMS WITH SYMMETRIC CIRCULANT STRUCTURE

The decentralized stabilization of continuous and discrete linear large scale systems with symmetric circulant structure was studied.A few sufficient conditions on decentralized stabilization of such systems were proposed.For the continuous systems,by introducing a concept called the magnitude of interconnected structure,a very important property that the decentralized stabilization of such systems is fully determined by the structure of each isolated subsystem that is obtained when the magnitude of interconnected structure of the overall system is given.So the decentralized stabilization of such systems can be got by only appropriately designing or modifying the structure of each isolated subsystem,no matter how complicated the interconnected structure of the overall system is.A algorithm for obtaining decentralized state feedback to stabilize the overall system is given.The discrete systems were also discussed.The results show that there is a great dfference on decentralized stabilization between continuous case and discrete case.

The effect of the horizontal structure for symmetric tropical cyclones on their movement

In this paper, using Holland's method, the effect of the horizontal structure of tropical cyclones on their motion is investigated. The 'characteristic radius', r0 characterized as the horizontal structure of a tropical cyclone,in which m and p are the parameters of the vortex, has been found by the author. And then it has been shown that there is but one 'characteristic radius' for each cyclone with horizontal structure. Two direct analytic solutions for the uniform and non-uniform basic flows in steady situations are presented with rc Results show that the change in the horizontal structure of the tropical cyclone itself will have obvious effect on the cyclone motion, on both its direction and speed. Therefore it must be considered in the research on the tropical cyclone motion.

A Novel Three-dimensional Mn(Ⅱ) Coordination Polymer Constructed from Biphenyl-3,3',5,5'-tetracarboxylic Acid and Water

The title Mn（Ⅱ） coordination polymer,poly{[heptaaqua-（μ4-bi-phenyl-3,3？,5,5？-tetracarboxylate）-bimanganese（Ⅱ）] pentahydrate},[Mn_2（bpta）（H_2O）_7]_n·5n H_2O（I）,is crystallized from a mixture of biphenyl-3,3？,5,5？-tetracarboxylic acid（H_4bpta） and MnCl_2·4H_2O in waterethanol under room temperature. Its asymmetric unit consists of one and two halves of crystallographically independent Mn（Ⅱ） cations,one fully deprotonated H4 bpta ligand,seven coordinated water molecules and five solvent water as guest molecules. In I,each Mn（Ⅱ） atom is octahedrally coordinated by six oxygen atoms from bpta^（4-） anions and coordinated water molecules. In the Mn（Ⅱ） cations,one half Mn（Ⅱ） ion of them located at a 2-fold axis generating a trinuclear [Mn_3（H_2O）_2（RCOO）_2] linker by μ1,1-O（water） and μ1,3-O,O？（carboxylate） bridges and another half Mn（Ⅱ） ion with an inversion is a mononuclear linker. These neighbouring trinuclear and mononuclear Mn（Ⅱ） cations are linked together by biphenyl-3,3？,5,5？-tetracarboxylates to form a three-dimensional framework with a（42.84） topology of a（4,4）-connected net,in which the positions of the trinuclear [Mn_3（H_2O）_2（R-COO）_2] linker as a 4-connector linking four bpta^（4-） ligands in I reproduce an eagle-shaped arrangement. The polymeric structure exhibits a water channel with an accessible void of 797.1 ？~3,amounting to 15.7% of the total unit-cell volume. Each of the cavities in the network is occupied by solvent water molecules.

Mechanical design and analysis of a novel variable stiffness actuator with symmetrical pivot adjustment

The safety of human-robot interaction is an essential requirement for designing collaborative robotics.Thus,this paper aims to design a novel variable stiffiiess actuator(VSA)that can provide safer physical human-robot interaction for collaborative robotics.VS A follows the idea of modular design,mainly including a variable stiffiiess module and a drive module.The variable stiffiiess module transmits the motion from the drive module in a roundabout maimer,making the modularization of VS A possible.As the key component of the variable stiffiiess module,a stiffness adjustment mechanism with a symmetrical structure is applied to change the positions of a pair of pivots in two levers linearly and simultaneously,which can eliminate the additional bending moment caused by the asymmetric structure.The design of the doubledeck grooves in the lever allows the pivot to move freely in the groove,avoiding the geometric constraint between the parts.Consequently,the VSA stiffiiess can change from zero to infinity as the pivot moves from one end of the groove to the other.To facilitate building a manipulator in the future,an expandable electrical system with a distributed structure is also proposed.Stiffiiess calibration and control experiments are performed to evaluate the physical performance of the designed VSA.Experiment results show that the VSA stiffiiess is close to the theoretical design stiffness.Furthermore,the VSA with a proportional-derivative feedback plus feedforward controller exhibits a fast response for stiffiiess regulation and a good performance for position tracking.

Achieving excellent bandwidth absorption by a mirror growth process of magnetic porous polyhedron structures

A symmetrical Fe2O3/BaCO3 hexagonal cone structure having a height of 10 um and an edge length of -4um is reported, obtained using a common solvothermal process and a mirror growth process. Focused ion beam and high-resolution transmission electron microscopy techniques revealed that α-Fe2O3 was the single crystal feature present. Ba ions contributed to the formation of symmetrical structures exhibited in the final composites. Subsequently, porous magnetic symmetric hexagonal cone structures were used to study the observed intense electromagnetic wave interference. Electromagnetic absorption performance studies at 2-18 GHz indicated stronger attenuation electromagnetic wave ability as compared to other shapes such as spindles, spheres, cubes, and rods. The maximum absorption frequency bandwidth was at 7.2 GHz with a coating thickness d = 1.5 mm. Special structures and the absence of BaCO3 likely played a vital role in the excellent electromagnetic absorption properties described in this research.

The Symmetric Banzhaf Value for Fuzzy Games with a Coalition Structure

In this paper,a generalized form of the symmetric Banzhaf value for cooperative fuzzy games with a coalition structure is proposed.Three axiomatic systems of the symmetric Banzhaf value are given by extending crisp case.Furthermore,we study the symmetric Banzhaf values for two special kinds of fuzzy games,which are called fuzzy games with multilinear extension form and a coalition structure,and fuzzy games with Choquet integral form and a coalition structure,respectively.

Hypothesis Testing for Independence Under Blocked Compound Symmetric Covariance Structure

One type of covariance structure is known as blocked compound symmetry.Recently,Roy et al.(J Multivar Anal 144:81–90,2016)showed that,assuming this covariance structure,unbiased estimators are optimal under normality and described hypothesis testing for independence as an open problem.In this paper,we derive the distributions of unbiased estimators and consider hypothesis testing for independence.Representative test statistics such as the likelihood ratio criterion,Waldstatistic,Rao’s score statistic,and gradient statistic are derived,and we evaluate the accuracy of the test using these statistics through numerical simulations.The power of the Wald test is the largest when the dimension is high,and the power of the likelihood ratio test is the largest when the dimension is low.

Design and Experimentation of a Novel Separable Vibration-Assisted Stage

In this paper,a novel,separable two-degrees-of-freedom stage with high-precision motion and resolution is proposed for the application of vibration-assisted micromilling.A separable design was realized on the basis of the detachable structure of the platform.Flexible stages with different dimensions and types can be utilized in the devices.A circular-fillet hinge is selected as the flexible unit with a parallel structure to realize output decoupling and reduce the coupling error between the two vibration directions.Analytical modeling is conducted to explore the static and dynamic characteristics of the stage.Results reveal a good agreement with the finite element simulation result.A series of experiments were conducted to assess the static and dynamic performances of the flexible stage,encompassing tests such as amplitude response,motion trajectory,and coupling trajectory.The results of these tests revealed that the designed vibration-assisted system exhibits precise movement capabilities.

Small-signal switch model of GaN HEMTs for MMIC applications

Gallium nitride （GaN） high electron mobility transistor （HEMT） with symmetrical structure as a control device is discussed in this paper. The equivalent circuit model is proposed on the basis of physical and electrical properties of the GaN HEMT device. A transistor with 0.5 μm gate length and 6 x 125 gm gate width is fabricated to verify the model, which can be treated as a single pole single throw （SPST） switch due to the ON state and OFF state. The measurement results show a lzood agreement with the simulation results, which demonstrates the effectiveness of the proposed model.

Combined kinematic and static analysis of an articulated lower limb traction device for a rehabilitation robotic system

This paper presents a design of an articulated lower limb traction device(ALLTD) with joint torque generators for a cable-driven parallel rehabilitation robotic system(CDPRRS). An earlier version of the ALLTD uses a rigid link to model the lower limbs of a patient. This paper extends this scenario to include articulations in the lower limbs and analyzes the resulting two-link mechanism. Due to the force-displacement coupled structure, the inverse and forward kinematics of the ALLTD model are analyzed in combination with the requirement for static force balance. Examples using the limb parameters of Chinese adults are provided to show the efficacy of our model. The workspaces and cable tensions of the model indicate that the ALLTD could satisfy the rehabilitation training needs of patients with various lengths of lower limbs.

Singular PT-symmetry broken point with infinite transmittance and reflectance--a classical analytical demonstration

To demonstrate the existence of singularparity-time symmetry(PT-symmetry)broken point inoptics system,we designed a one-dimensional PT symmetricstructure including N unit-cell with loss and gainmaterials in half.We performed an analytical deduction toobtain the transmittance and reflectance of the structurebasing on Maxwell’s equations.We found that with theexact structure unit-cell number and the imaginary part ofrefraction index,the transmittance and reflectance are bothclose to infinite.Such strict condition is called the singularpoint in this study.At the singular point position,both thetransmission and reflection are direction-independent.Away from the singular point,the transmittance andreflectance become finite.In light of classical wave optics,the single unit and total structure both become theresonance units.The infinite transmittance and reflectanceresult from the resonance matching of single unit and totalstructure.In light of quantum theory,the singular pointcorresponds to the single eigenvalue of electromagneticscattering matrix.The infinite transmittance and reflectancemean a huge energy transformation from pumpingsource to light waves.Numerical calculation and softwaresimulation both demonstrate the result.