Stabilization of fixed modes in expansions of LTI systems

The objective of this note is to propose a method for stabilization of structurally fixed modes in expansions of LTI dynamic systems in the scope of overlapping decentralized control design based on the expansion/contraction framework, enabling successful design for a broader class of problems than considered so far. The method is based on a judicious choice of complementary matrices in the expanded space. Numerical examples are provided to illustrate simplicity and efficiency of the proposed approach.     

On decentralized stabilization and structure of linear large scale systems

Connective stabilizability of large-scale systems, which are composed of interconnected subsystems, is considered using decentralized feedback. Both analytical and graph-theoretic conditions are derived directly in terms of the interconnection structure, which ensure that stability of the overall closed-loop system is invariant under the structural perturbations caused by disconnections and reconnections of links among the subsystems. The conditions characterize a large class of decentrally stabilizable systems, which includes all classes of connectively stabilizable interconnected systems considered so far.     

形变热处理对烧结Cu-Au合金性能与微观组织的影响(英文)

研究Cu-4%Au合金的硬度、显微硬度、导电性和微观组织在形变热处理过程中的变化。在加工硬化后,再对轧制合金在60～350°C温度下退火。由于退火硬化效应,合金的强度增大。结果表明:Cu-Au合金性能在两个阶段都得到改善;合金进行变形量为40%的热轧后,在260°C退火能得到最佳的综合性能。合金的微观组织也在形变热处理过程中发生显著变化。     

Characterisation of melt spun Ni-Ti shape memory Ribbons’ microstructure

NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-K?? radiation at room temperature.     

Self‐Assembly: I‐Motif Nanospheres: Unusual Self‐Assembly of Long Cytosine Strands (Small 8/2011)

The synthesis and characterization of novel DNA structures based on tetraplex cytosine (C) arrangements, known as i‐motifs or i‐tetraplexes, is reported. Atomic force microscopy (AFM) investigation shows that long C‐strands in mild acidic conditions form compact spherically shaped nanostructures. The DNA nanospheres are characterized by a typical uniform shape and narrow height distribution. Electrostatic force microscopy (EFM) measurements performed on the i‐motif spheres clearly show their electrical polarizability. Further investigations by scanning tunneling microscopy (STM) at ultrahigh vacuum reveals that the structures exhibit an average voltage gap of 1.9 eV, which is narrower than the voltage gap previously measured for poly(dG)–poly(dC) molecules in similar conditions.     

COUPLED PROBLEM OF THERMODIFFUSION IN VISCOELASTIC BODIES

This paper deals with the effect of the process of thermodiffusion in viscoelastic bodies. The basic linear coupled equations of the problem are derived, and possibilities for their simplification are indicated. A method for their solution is demonstrated and then applied to the case of a viscoelastic layer.     

Jacobi and Gauss-Seidel Iterations for Polytopic Systems: Convergence via Convex M-Matrices

A natural generalization of the Jacobi and Gauss-Seidel iterations for interval systems is to allow the matrices to reside in convex polytopes. In order to apply the standard convergence criteria involving M-matrices to iterations for polytopic systems, we derive conditions for a convex polytope of matrices to be a polytope of M-matrices in terms of its vertices. We show the conditions are used in the convergence analysis of iterations for block and nonlinear polytopic systems.     

Evaluation of the effect of reaction and mass transfer on the growth of polymer particles in olefin polymerization

The process of the growth of polymer particles in olefin polymerization is studied. The regions of the possible overheating of particles due to the polymerization reaction in the gas and liquid phases of a monomer and in a solvent are estimated. It is shown how the rates of external mass transfer, internal diffusion, and reaction in the polymer particle vary with its growth. The cause of unusual transition of the reaction from the diffusion region to the kinetic one with the growth of particles is clearly explained. A model for the dynamics of the polymerization process is proposed that takes into account the diffusion of active component ions of a catalyst (chlorine in Ti _x Cl _y and oxygen in Cr _x O _y ). The results of the study are used in the application of high-activity catalysts to the slurry process of propylene polymerization.     

Roll forming of branched profiles

Due to the new mass forming process “linear flow splitting” forming of branched profiles in integral style out of sheet metal without joining, lamination of material or heating of the semi-finished part becomes feasible. Since the resulting flanges provide extra stiffness without increasing the weight of the semi-finished product, split profiles are suitable especially for lightweight applications. The combination of the linear flow splitting process with a following roll-forming process enables the continuous production of one- or multi-chambered profiles with free flanges. In this paper phenomena occurring during roll forming of branched profiles are described and discussed.