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## Preparation of Branched Polymers Using a Polymerizable RAFT Agent

### Advanced Graphic Communications and Media Technologies (2017-01-01) 417: 1171-1176 , January 01, 2017

A reversible addition-fragmentation chain transfer (RAFT) agent, 2-((2-(((dodecylthio)carbonothioyl)thio)propanoyl)oxy)ethyl acrylate (DTEA), was synthesized through the condensation reaction of 2-(dodecylthio-carbonothioylthio) propanoic acid with 2-hydroxyethyl acrylate. DTEA is a bifunctional molecule which is characterized by having one double bond and one thiocarbonylthio group. Branched poly(methyl acrylate)s (BPMAs) were prepared through one-step radical polymerization of methyl acrylate (MA) in the presence of DTEA. ^{1}H NMR spectra of the polymers were used to study the degree of branching (DB). The DB values of the three prepared BPMAs were calculated to be 0.46, 0.18 and 0.087, respectively. It was found that the DB value could be adjusted by controlling the ratio of MA to DTEA.

## Decision Aided Uplink Compressive Channel Estimation for Massive MIMO Systems

### Wireless Personal Communications (2017-09-01) 96: 153-162 , September 01, 2017

Thank to the observation that in massive multi-input multi-output systems, the channels associated with different base station antennas may share common sparse support, the significant path delays can be accurately captured by only few pilots, leading to a reduction of pilot overhead. However, when the number of pilots is small, the path gains can not be accurately estimated and this limits the system performance. To solve this problem, in this paper we propose a decision aided compressive sensing based channel estimation scheme, which utilizes the decoded data to refine the channel estimation. This scheme can effectively improve the channel estimation without increasing the length of pilot sequence, which is confirmed by both analyses and simulation results.

## A superconvergent isogeometric formulation for eigenvalue computation of three dimensional wave equation

### Computational Mechanics (2016-06-01) 57: 1037-1060 , June 01, 2016

A superconvergent isogeometric formulation is presented to compute the eigenvalues for three dimensional wave equation. This three dimensional superconvergent isogeometric formulation is characterized by a higher order mass matrix formulation with particular reference to the quadratic basis functions. The three dimensional higher order mass matrix is built upon an optimal combination of the reduced bandwidth mass matrix and the consistent mass matrix. The frequency error associated with the isogeometric discretization of three dimensional wave equation is derived in detail. In particular, the optimal mass combination parameter for higher order mass matrix is devised as a function of the two spatial wave propagation angles, which enables that arbitrary frequency corresponding to a given wave propagation direction can be computed in a superconvergent way. Two extra orders of accuracy, i.e., 6th order of accuracy, are attained by the proposed higher order mass matrix than the consistent mass matrix for the frequency computation of three dimensional wave equation. The dispersion property of the present three dimensional higher order mass matrix formulation is examined as well. The accuracy of the proposed three dimensional superconvergent isogeometric formulation is testified by several numerical examples.

## Inverse dynamics of the HALF parallel manipulator with revolute actuators

### Nonlinear Dynamics (2007-10-01) 50: 1-12 , October 01, 2007

Recursive matrix relations for kinematics and dynamics of the HALF parallel manipulator are presented in this paper. The prototype of this robot is a spatial mechanism with revolute actuators, which has two translation degrees of freedom and one rotation degree of freedom. The parallel manipulator consists of a base plate, a movable platform and a system of three connecting legs, having wide application in the fields of industrial robots, simulators, parallel machine tools and any other manipulating devices where high mobility is required. Supposing that the position and the motion of the moving platform are known, an inverse dynamics problem is solved using the principle of virtual powers. Finally, some iterative matrix relations and graphs of the torques and powers for all actuators are analysed and determined. It is shown that this approach is an effective means for kinematics and dynamics modelling of parallel mechanisms.

## Research on Autobody Panels Developmental Technology Based on Reverse Engineering

### Proceedings of the 2012 International Conference on Communication, Electronics and Automation Engineering (2013-01-01) 181: 747-753 , January 01, 2013

For finding the shortest path in GIS (geographic information system), an algorithm of the approximate shortest path between two points on arbitrary triangular model is proposed in this paper. Its efficiency and better control accuracy are suitable to search for the shortest path. And three-dimensional visualization of the algorithm can be implemented by OpenGL with Visual C ^{ + + } 9.0.

## Hopf Bifurcation

### Bifurcation and Chaos in Engineering (1998-01-01): 176-229 , January 01, 1998

Periodic vibration phenomena can be found in many non-conservative systems in nature. Hopf bifurcation theory is a theory that studies the modern development of period vibration phenomena. In this chapter we introduce the method of studying the Hopf bifurcation of autonomous systems by the normal form theory.

## A Multitarget Passive Recognition and Location Method Fusing SVM and BSS

### Electrical Power Systems and Computers (2011-01-01) 99: 73-81 , January 01, 2011

A multitarget passive recognition and location method which fuses SVM and blind signal processing technique is proposed in this paper. Its characters are: Sampling data via multitarget information receiving array at first; And then getting separated signal and matrix by blind signal separation (BSS) to these data; Completing classification of each separated signal by using decision tree support vector machine (SVM) multitarget recognition process to the separated signal; Obtaining direction information of each signal by blind deconvolution location algorithm based on array model to the separated matrix at the same time; Finally, realizing target recognition and location by synthesizing targets information of the classification and direction. This paper studies technique principle of this method, gives a detailed implement step and proves its validity by multitarget recognition and location experiment of measured ship-radiated noise.

## Observer-based fault-tolerant control for an air-breathing hypersonic vehicle model

### Nonlinear Dynamics (2014-04-01) 76: 409-430 , April 01, 2014

This paper focuses on controller and observer design for the longitudinal model of an air-breathing hypersonic vehicle (AHV) subject to actuator faults and limited measurements of the states. The feedback linearization method is firstly employed for a modified AHV model with actuator faults, and dynamic effect caused by the actuator faults on the linearized model is analyzed. Based on full state information, an adaptive controller is designed using the Lyapunov method, which guarantees reference command tracking of the AHV under actuator faults. Next, to estimate the unmeasurable states used in the adaptive controller, a sliding observer is designed based on the sliding control method and the Filippov’s construction of the equivalent dynamics (FCED). Finally, the adaptive controller is combined with the sliding observer to generate the observer-based adaptive controller, which relies only on partial state information. Simulations demonstrate that the observer-based adaptive controller achieves desired tracking performance and good robustness in the presence of actuator faults.

## Fiber Based Radio Frequency Dissemination Scheme to Multiple Users

### China Satellite Navigation Conference (CSNC) 2015 Proceedings: Volume III (2015-01-01) 342: 379-386 , January 01, 2015

High-precision time and frequency signals play an important role in many areas such as modern communication, navigation, and baseline interferometry. Optical fiber based time and frequency networking not only has a higher precision which can meet the demand of new generation time and frequency standard but also constructs to the ground based time and frequency network as a complementary choice of satellite based methods. As a consequence, we propose a fiber based radio frequency dissemination scheme to multiple users with a tree-like topology. The noise compensation system acquiring the noise information by measuring multiple reflection signal is put in remote terminals, which allow users to access the frequency signal along the fiber without affecting others. With this scheme, a high precise frequency transfer experiment is demonstrated along a 60 km fiber link to multiple users. The frequency stability of 7.1 × 10^{−14} @1 s and 6.8 × 10^{−17}@10^{4 }s are obtained. Furthermore, the influence induced by adding or cancelling a new terminal is tested when other terminals are operating. The result shows that the stability of radio frequency networking scheme which is robust and flexible can fulfil most atomic clock that is currently used and would bring benefit to establish a national or even continental ultra-stable frequency dissemination network.

## Effects of tension on vortex-induced vibration (VIV) responses of a long tensioned cylinder in uniform flows

### Acta Mechanica Sinica (2017-02-01) 33: 1-9 , February 01, 2017

The effects of tension on vortex-induced vibration (VIV) responses for a tension-dominated long cylinder with an aspect ratio of 550 in uniform flows are experimentally investigated in this paper. The results show that elevated tension suppresses fluctuations of maximum displacement with respect to flow velocity and makes chaotic VIV more likely to appear. With respect to periodic VIV, if elevated tension is applied, the dominant vibration frequency in the in-line (IL) direction will switch from a fundamental vibration frequency to twice the value of the fundamental vibration frequency, which results in a ratio of the dominant vibration frequency in the IL direction to that in the cross-flow direction of 2.0. The suppression of the elevated tension in the fluctuation of the maximum displacement causes the axial tension to become an active control parameter for the VIV maximum displacement of a tension-dominated long riser or tether of an engineering structure in deep oceans. However, the axial tension must be optimized before being used since the high dominant vibration frequency due to the elevated tension may unfavorably affect the fatigue life of the riser or tether.