一类时滞差分方程解的性态

对于一类差分方程,通过把一类有理递归序列线性化,利用线性差分方程的有关结论,去讨论一类有理递归序列解的性质,给出了此差分方程在不同情况下解的稳定性的条件,所得的结论推广了已有的相关结果.     

一类高阶差分方程的全局渐进稳定性(英文)

作者研究了一类高阶非线性时滞有理差分方程的渐进稳定性问题.应用线性化方程与方程平衡点的局部渐进稳定性的相关理论,以及相关函数的单调性与序列的迭代关系,作者证明了方程平衡点的全局渐进稳定性.所得结果推广了一些已知结果.     

一类高阶方程的动力学行为

研究了一类非线性有理差分方程的动力学行为.利用差分方程的定性和稳定性理论及不等式技巧等,详细研究了平衡点的稳定性和吸引性.     

一类非线性差分方程的全局行为

研究了一类非线性有理差分方程的全局行为.利用差分方程的定性和稳定性理论及不等式技巧等,详细研究了平衡点的稳定性和吸引性.     

一类非线性高阶差分方程的全局吸引性

借助于极限理论、单调性分析方法考虑高阶差分方程.针对不变区间的不同的类形给出了全局吸引子的若干充分条件,并将这些结论应用于有理递归序列,对G.Ladas提出的公开问题进行了有益的探讨,给出了部分回答.     

高阶有理差分方程单半环解的存在性

作者研究了一类一般性的高阶有理差分方程的单半环解的存在性问题.应用线性化方程理论、方程平衡点的性质和非线性差分方程的包含定理, 作者证明了该方程单半环解的存在性.该结果推广了一些已知的结果.     

一类非线性差分方程的全局行为

利用差分方程的定性和稳定性理论及不等式技巧等研究了一类非线性有理差分方程的全局行为.     

一类有理差分方程的全局渐近稳定性

运用子序列分析法研究一类高阶有理差分方程得到该方程的半环轨道结构和正平衡点全局渐近稳定性的充分条件,推广相关的已知结果.     

一类非线性有理差分方程的全局渐近稳定性

运用建立辅助方程的方法研究一类非线性有理差分方程正平衡点的全局渐近稳定性,得到一个充分条件.证明一个猜想,对复杂高阶有理差分方程稳定性的研究提供新的思路.     

一类特殊的三阶有理差分系统的动力学行为研究

对一类特殊的三阶有理差分系统的定性行为进行了研究。利用差分方程的基本理论,考虑了系统中平衡点的存在性和稳定性;进而讨论了系统解的周期性问题,得到了阶-2周期解存在的条件,并分析了系统解序列收敛到平凡平衡点的收敛速度;最后,通过数值模拟验证了所得结论的正确性。     

Adaptive and local analysis of climate data

This paper focuses on how to extract physically meaningful information from climate data, with em- phases placed on adaptive and local analysis. It is argued that many traditional statistical analysis methods with rigorous mathematical footing may not be efficient in extracting essential physical information from climate da- ta; rather, adaptive and local analysis methods that agree well with fundamental physical principles are more ca- pable of capturing key information of climate data. To illustrate the improved power of adaptive and local analy- sis of climate data, we also introduce briefly the empirical mode decomposition and its later developments.     

Subsurface macro-inclusions and solidified hook character in aluminum-killed deep-drawing steel slabs

Subsurface macro-inclusions and hooks are detrimental to the surface quality of deep-drawing steel sheets. However, little is known about the relationship between macro-inclusions and hooks. Thus, in this work, two ultralow carbon (ULC) steel slabs and two low carbon (LC) aluminum-killed steel slabs were sampled to study the relationship between hooks and subsurface macro-inclusions, which were detected on the cross-sections of steel samples with an area of 56058 mm2 using an automated scanning electron microscopy/energy-dispersive X-ray spectroscopy system. Results show that subsurface inclusions larger than 200 μm were almost entrapped by hook structures, whereas the location of other inclusions smaller than 200 μm had no obvious dependence on the location of solidified hooks. Furthermore, the number density (ND) of subsurface inclusions larger than 200 μm decreased from 0.02 to 0 cm-2 in ULC steel as the mean hook depth decreased from 1.57 to 1.01 mm. Similar trends were also observed in LC steel. In addition, the detected inclusions larger than 200 μm were concentrated in the region near the slab center (3/8 width-5/8 width), where hook depths were also larger than those at any other locations. Therefore, minimizing the hook depth is an effective way to reduce inclusion-induced sliver defects in deep-drawing steels.     

Effects of basicity and MgO content on the viscosity of the SiO2-CaO-MgO-9wt%Al2O3 slag system

The effects of basicity and MgO content on the viscosity of SiO2-CaO-MgO-9wt%Al2O3 slags with basicity from 0.4 to 1.0 and MgO content from 13wt%to 19wt%were investigated using the rotating cylinder method. A correlation between the viscosity and the slag structure was determined by Fourier transform infrared （FTIR） spectroscopy. It is indicated that the complex network structure of the slag melt is depolymerized into simpler network units with increasing basicity or MgO content, resulting in a continuous decrease in viscosity of the slag. The viscosity is strongly dependent on the combined action of basic oxide components in the slag. Under the present experimental conditions, increasing the basicity is found to be more effective than increasing the MgO content in decreasing the viscosity of the slag. At higher temperatures, the increase of basicity or MgO content does not appreciably decrease the viscosity of the slag, as it does at lower tem-peratures. The calculated activation energy of viscous flow is between 154 and 200 kJ＆#183;mol-1, which decreases with an increase in basicity from 0.4 to 1.0 at a fixed MgO content in the range of 13wt%to 19wt%.     

Influence of Te doping on the dielectric and optical properties of InBi crystals grown by directional freezing

Stoichiometric pure and tellurium (Te) doped indium bismuthide (InBi) were grown using the directional freezing technique in a fabricated furnace. The X-ray diffraction profiles identified the crystallinity and phase composition. The surface topographical features were observed by scanning electron microscopy and atomic force microscopy. The energy dispersive analysis by X-rays was performed to identify the atomic proportion of elements. Studies on the temperature dependence of dielectric constant (?), loss tangent (tanδ), and AC conductivity (σ_ac) reveal the existence of a ferroelectric phase transition in the doped material at 403 K. When InBi is doped with tellurium (4.04 at%), a band gap of 0.20 eV can be achieved, and this is confirmed using Fourier transform infrared studies. The results thus show the conversion of semimetallic InBi to a semiconductor with the optical properties suitable for use in infrared detectors.     

Cache performance optimization of irregular sparse matrix multiplication on modern multi-core CPU and GPU

This paper focuses on how to optimize the cache performance of sparse matrix-matrix multiplication （SpGEMM）.It classifies the cache misses into two categories：one is caused by the irregular distribution pattern of the multiplier-matrix,and the other is caused by the multiplicand.For each of them,the paper puts forward an optimization method respectively.The first hash based method removes cache misses of the 1 st category effectively,and improves the performance by a factor of 6 on an Intel 8-core CPU for the best cases.For cache misses of the 2nd category,it proposes a new cache replacement algorithm,which achieves a cache hit rate much higher than other historical knowledge based algorithms,and the algorithm is applicable on CELL and GPU.To further verify the effectiveness of our methods,we implement our algorithm on GPU,and the performance perfectly scales with the size of on-chip storage.     

A study on the characterization of smoke movement in shafts with different fire source positions

In this study, experimental and numerical simulation methods were combined to simulate the changing course of the temperature and velocity fields in nine different fire scenes. The characteristics of smoke movement in shafts with different fire source position factors （h/H） were quantitatively investigated, and the non-dimensional fitting function between the fire source position factors and the maximum temperature was deduced. The results showed that the location of the neutral plane moved upward as the fire source rose, and all the generated smoke spread to the upper areas; however, there was barely any smoke in the lower areas. The maximum temperature was inversely proportional to the fire source position factor; the higher the source position is, i.e. the higher the ra- tio factor is, the lower the maximum temperature is in the shaft. The experimental verification of the fire dynamics simulator （FDS） showed good results.     

Full-scale model tests and nonlinear analysis of prestressed concrete simply supported box girders

Full-scale model tests were carried out on a 30 m span prestressed concrete box girder and a 20 m span prestressed concrete hollow slab. Failure models were prestressed reinforcement tensile failure and crashing of roof concrete, respectively. The ductility indexes of the box girder and hollow slab were 1.99 and 1.23, respectively, according to the energy viewpoint. Based on the horizontal section hypothesis, the nonlinear computation procedure was established using the limited banding law, and it could carry out the entire performance analysis including the unloading, mainly focusing on the ways to achieve the unloading curves computation through stress-strain, moment-curvature and load-displacement curves. Through the procedure, parameters that influence on the bearing capacity, deformation performance and ductility of the structures were analyzed. Those parameters were quantity of prestressed reinforcement and tension coefficients of prestressed reinforcement. From the analysis, some useful conclusions can be obtained.     

Microstructure and mechanical properties of （Ti,AI,Zr）N/（Ti,AI,Zr,Cr）N films on cemented carbide substrates

（Ti,Al,Zr）N/（Ti,Al,Zr,Cr）N bilayer films were deposited on cemented carbide （WC-8%Co） substrates by multi-arc ion plating （MAIP） using two Ti-AI-Zr alloy targets and one pure Cr target. To investigate the composition, morphology, and crystalline structure of the bilayer films, a number of complementary methods of elemental and structural analysis were used, namely, scanning electron microscopy （SEM）, energy disperse X-ray spectroscopy （EDS）, and X-ray diffraction （XRD）. Adhesive strength and mechanical properties of the films were evaluated by scratch testing and Vickers microindentation, respectively. It is shown that the resulting films have a TiN-type face-centered cubic （FCC） structure. The films exhibit fully dense, uniform, and columnar morphology. Furthermore, as the bias voltages vary from -50 to -200 V, the microhardness （max. Hv001 4100） and adhesive strength （max. 〉 200 N） of the bilayer films are superior to those of the （Ti,Al,Zr）N and （Ti,Al,Zr, Cr）N monolayer films.     

The HITCR-I： Evaluation on a free gait generation method for the hexapod robot on irregular terrain

The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage mechanism and with force sensors in the tip of legs,distributed hardware structure and a modular software structure of the control system.Based on a set of local rules between adjacent legs,finite state machine （FSM） model is built to control the coordination of legs.An automatic smooth transition of gait pattern is achieved through deriving the mathematical relation between gait pattern and locomotion parameters.The disordered inter-leg phase sequence is adjusted to a regular state smoothly and quickly by the local rules based FSM,and the gait pattern can transform automatically adapting to irregular terrain.The experiment on HITCR-I has demonstrated that it can walk through irregular terrain reliably and expeditiously with the free gait controller designed in this paper.     

Influence of Rare Earth Elements on Mechanical Properties and Corrosion Resistance of Cu-15Ni Alloy

In order to improve the mechanical property and Cl-+S2-corrosion resistance of B15 copper-nickel alloy,Cu-15Ni-xRE(x:0-0.1%by weight)alloy was prepared by adding rare earth(RE)in melted Cu-15Ni alloy using metal mould casting method.Optical microscopy(OM),electronic tensile testing machine,X-ray diffraction(XRD),scanning electron microscope(SEM),and electrochemical testing system were used to analyze mechanical property,corrosion resistance property,and surface microstructure of different treatment samples.The results of OM and tensile testing show that the RE addition can effectively deoxidize the alloy melt and the microstructure of the alloy changes from coarse dendrite to small equiaxed grain.By addition of 0.05%RE,the tensile strength and elongation of Cu-15Ni alloys are improved from 294 MPa to 340MPa,and 8%to 33.5%respectively.The results of electrochemical testing show that the corrosion resistance of Cu-15Ni alloy is greatly improved by adding proper amount of RE,whereas excess addition of RE worsens the corrosion resistance.The optimum RE content was about 0.05%by weight.In comparison with the alloy without RE,the corrosion potential and corrosion current density of Cu-15Ni alloy containing proper RE decreased by about-0.28 V and 70A/cm2,respectively.