不同应变率加载下硅的高压相变行为

高压相变是凝聚态物理、地球与行星科学、材料科学等领域关注的核心问题之一,而加载应变率是相变动力学过程的重要影响因素。由于动态加载下物质相结构原位诊断技术的不足以及宽广加载应变率下物质高压相变系统实验研究的缺失,难以开展基于原子尺度物理机制的相变动力学过程建模和数值模拟研究。由于硅的高压相极其丰富,且拥有大量亚稳相,动力学因素在其高压相变过程中发挥着至关重要的作用,因此,硅是研究高压相变动力学的理想材料,对普适相变动力学过程的理论建模具有重要意义。以硅为例,介绍其在准静态、中等应变率和高应变率加载下的相变行为,探讨加载应变率对其高压相变行为的影响。

Small-Signal Equivalent Circuit Modeling of a Photodetector Chip

A small-signal equivalent circuit model and the ted. The equivalent lumped circuit, which takes the main extraction techniques for photodetector chips are presen- factors that limit a photodetector＇s RF performance into consideration,is first determined based on the device＇s physical structure. The photodetector＇s S parameters are then on-wafer measured, and the measured raw data are processed with further calibration. A genetic algorithm is used to fit the measured data, thereby allowing us to calculate each parameter value of the model. Experimental resuits show that the modeled parameters are well matched to the measurements in a frequency range from 130MHz to 20GHz, and the proposed method is proved feasible. This model can give an exact description of the photodetector chip＇s high frequency performance,which enables an effective circuit-level prediction for photodetector and optoelectronic integrated circuits.

Large-scale manufacturing of aluminum alloy plate extruded from subsize billet by new porthole-equal channel angular processing technique

To manufacture plate by the combination of equal channel angular processing （ECAP） and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing （P-ECAP）, was studied. Extrusion of AL6005A plate used for the bullet train plate was investigated by finite element method. The relevant porthole dies involving ECAP technique in channels were designed. Dimensional changes in the scrap part of the extrudate obtained after extrusion from the P-ECAP die, with different channel angles, were predicted. Effects of the channel angle and extrusion speed on the maximum temperature of the workpiece and other field variables were evaluated. At the channel angle of 160° of P-ECAP dies, the extrudate exhibited the optimal performance and the least amount of extrudate scrap was obtained. The optimal extrusion speed was 3-5 mm/s. Moreover, with the increase in ram speed from 1 to 9 mm/s, the peak extrusion load increased by about 49% and the maximum temperature was increased by about 70 ℃. The effective strain exhibited ascending trend in the comer of the ECAP deformation zone. In the solder seam and the side of die bearing of extrudate, the maximum principal stresses were tensile stress.

Abstraction of Small Signal Equivalent Circuit Parameters of Enhancement-Mode InGaP/AlGaAs/InGaAs PHEMT

An extraction method of the component parameter values of an enhancement-mode InGaP/AIGaAs/In-GaAs PHEMT small signal equivalent circuit is presented,and these component parameter values are extracted by using the EEHEMT1 model of IC-CAP software. The extraction results are verified by ADS software,and the DC I-V curves and S parameters simulated by ADS are basically accordant with those of the test results. These results indicate that the EEHEMT1 model can be used for extracting the component parameters of an enhancement-mode PHEMT.

Searching scheme in P2P system based on semantic overlay network

In consideration of the limitation of super-peer overlay network, the semantic information was introduced into the super-peers＇ organization. A novel P2P （peer-to-peer） searching model, SSP2P, was put forward. The peers in the model were organized in a natural area autonomy system （AAS） based on the smallworld theory. A super-peer was selected in each AAS based on power law; and all the super-peers formed different super-peer semantic networks. Thus, a hierarchical super-peer overlay network was formed. The results show that the model reduces the communication cost and enhances the search efficiency while ensuring the system expansibility. It proves that the introduction of semantic information in the construction of a super-peer overlay is favorable to P2P system capability.

Isolation and Characterization of Mlo and NBS-LRR-like Gene Sequences in Wheat

Based on both cDNA sequence of barley powdery mildew resistance control element Mlo and DNA sequence of the known putative disease resistance gene from Triticum monococcum L., we designed some primers to amplify resistant homologous sequences in the near isogenic lines (NILs) of powdery mildew resistance using RT-PCR method. Two expressed cDNA fragments were isolated from wheat genome. One showed 83% homology to the Mlo gene of barley. The other contained two possible open reading frames (ORFs). NBS conservative domains 2, 3 of disease resistance gene and 13 LRR structures similar to rice Pib protein terminal were found respectively in the two ORFs. It indicated that the latter fragment belongs to NBS-LRR-like genes. The obvious difference of RT-PCR products was observed between the before challenged and the challenged for 72 h by Blumeria graminis f. sp. tritici, which, implied that this sequence could be associated with disease resistance of wheat. Using nulli-tetrasomic lines of 'Chinese Spring', the NBS-LRR-like gene had been located on chromosome 1D.

Effect of gap size on microstructure of transient liquid phase bonded IN-738LC superalloy

In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.

Plasma and platelet serotonin levels in patients with liver cirrhosis

AIM: To analyze the relationship between plasma and platelet serotonin levels and the degree of liver insufficiency. METHODS: The prospective study included 30 patients with liver cirrhosis and 30 healthy controls. The degree of liver failure was assessed according to the Child-Pugh classification. Platelet and platelet poor plasma serotonin levels were determined. RESULTS: The mean plasma serotonin level was higher in liver cirrhosis patients than in healthy subjects (215.0 ± 26.1 vs 63.1 ± 18.1 nmol/L; P < 0.0001). The mean platelet serotonin content was not significantly different in patients with liver cirrhosis compared with healthy individuals (4.8 ± 0.6; 4.2 ± 0.3 nmol/platelet; P > 0.05). Plasma serotonin levels were significantly higher in Child- Pugh grade A/B than in grade C patients (246.8 ± 35.0 vs 132.3 ± 30.7 nmol/L; P < 0.05). However, platelet serotonin content was not significantly different between Child-Pugh grade C and grade A/B (4.6 ± 0.7 vs 5.2 ± 0.8 nmol/platelet; P > 0.05). CONCLUSION: Plasma serotonin levels are significantly higher in patients with cirrhosis than in the controls and represent the degree of liver insufficiency. In addition, platelet poor plasma serotonin estimation is a better marker for liver insufficiency than platelet serotonin content.

Microsatellites underestimate genetic divergence in the Green-backed Tit (Parus monticolus)

Although a growing number of both sequence-based and microsatellite nuclear loci have been used to infer genetic structures, their relative efficiencies remain poorly understood. In our study, we used the Green-backed Tit (Parus monticolus) to explore the resolving ability of these two types of markers. The south-western and central mitochondrial DNA (mtDNA) phylogroups were divergent to some extent in sequence-based nuclear data, while mixed together in microsatellites data. The F ST values among clades were about four times lower in microsatellite loci than those in sequence-based nuclear loci. We are of the opinion that size homoplasy may have contributed to the inability of microsatellites to uncover differentiation. Our results suggest that sequence-based nuclear loci outperformed microsatellite loci in detecting population structures, especially those focused on populations with large effective population sizes. There was no significant correlation between F ST values and allelic size variability, which suggested that the efficiency of microsatellite loci in detecting genetic structure may be independent of their polymorphism. F ST is better than R ST in detecting intraspecific divergence due to the high variance of R ST . In agreement with sequence-based nuclear loci, microsatellite loci did resolve the genetic distinctness of the Taiwan Residents phylogroup. The genetic differentiation between the Taiwan Residents and continental clades may involve allopatric divergence without gene flow.

SOME RESULTSON R_2-EDGE-CONNECTIVITY OF EVEN REGULAR GRAPHS

Let Gbe a connected k(≥3)-regulargraph w ith girth g. A setSofthe edgesin G is called an R2-edge-cutifG- Sis disconnected and contains neither an isolated vertex nor a one- degree vertex. The R2-edge-connectivity of G, denoted by λ″(G), is the m inim um cardinality over allR2-edge-cuts, w hich is an im portantm easure for fault-tolerance of com puter intercon- nection netw orks. In this paper, λ″(G)= g(2k- 2) for any 2k-regular connected graph G(≠ K5) that is either edge-transitive or vertex-transitive and g≥5 is given.

Biomarkers for radiation-induced small bowel epithelial damage:An emerging role for plasma Citrulline

Reduction of cancer treatment-induced mucosal injury has been recognized as an important target for improving the therapeutic ratio as well as reducing the economic burden associated with these treatment related sequellae. Clinical studies addressing this issue are hampered by the fact that specif ic objective parameters, which enable monitoring of damage in routine clinical practice, are lacking. This review summarizes pros and cons of currently available endpoints for intestinal injury. The metabolic background and characteristics of plasma citrulline, a recently investigated biomarker specifically for small intestinal injury, are discussed in more detail.

On Infinitesimal Ⅱ-isometry of Surfaces

In this paper,we try to discuss the conjecture which says that infinitesimal Ⅱ-isome try of surface is infintesimal Ⅰ -isometry. i. e, infinitesimal rigid.Under some weakly suppositions of Guass curvature,some new results are worked out They are generalizations of known theories.

A Theorem on Infinitesimal I-isometry of Surfaces Immersed in a Space with Constant Curvature

In this paper we discuss the infinitesimal I-isometric de formations of surfaces immersed in a space with constant curvature. We obtain a sufficient condition for the de formation vector field to be zero vector field which is generalization of the results in [1] and [2].

Rank-size Distributions of Chinese Cities: Macro and Micro Patterns

A large number of studies have been conducted to find a better fit for city rank-size distributions in different countries. Many theoretical curves have been proposed, but no consensus has been reached. This study argues for the importance of examining city rank-size distribution across different city size scales. In addition to focusing on macro patterns, this study examines the micro patterns of city rank-size distributions in China. A moving window method is developed to detect rank-size distributions of cities in different sizes incrementally. The results show that micro patterns of the actual city rank-size distributions in China are much more complex than those suggested by the three theoretical distributions examined(Pareto, quadratic, and q-exponential distributions). City size distributions present persistent discontinuities. Large cities are more evenly distributed than small cities and than that predicted by Zipf′s law. In addition, the trend is becoming more pronounced over time. Medium-sized cities became evenly distributed first and then unevenly distributed thereafter. The rank-size distributions of small cities are relatively consistent. While the three theoretical distributions examined in this study all have the ability to detect the overall dynamics of city rank-size distributions, the actual macro distribution may be composed of a combination of the three theoretical distributions.

A minimal axiom group for rough set based on quasi-ordering

Rough set axiomatization is one aspect of rough set study to characterize rough set theory using dependable and minimal axiom groups. Thus, rough set theory can be studied by logic and axiom system methods. The classic rough set theory is based on equivalent relation, but rough set theory based on reflexive and transitive relation (called quasi-ordering) has wide applications in the real world. To characterize topological rough set theory, an axiom group named RT, consisting of 4 axioms, is proposed. It is proved that the axiom group reliability in characterizing rough set theory based on similar relation is reasonable. Simultaneously, the minimization of the axiom group, which requires that each axiom is an equation and each is independent, is proved. The axiom group is helpful for researching rough set theory by logic and axiom system methods.

Time Dependent Gaussian Equivalent Linearization of Duffing Oscillator Using Continuous Wavelet Transform

Evolutionary response analysis of Duffing oscillator using Gaussian equivalent linearization in wavelet based time-frequency frame work is presented here. Cubic （i.e., odd type） non-linearity associated with stiffness and damping is modeled. The goal of this research is to develop the mathematical model of an equivalent linear system which is applicable for different non-stationary input processes （i.e., either summation of amplitude modulated stationary orthogonal processes or digitally simulated non-stationary processes）. The instantaneous parameters of the ELTVS （equivalent linear time varying system） are evaluated by minimizing the error between the displacements of non-linear and equivalent linear systems in wavelet domain. For this purpose, three different basis functions （i.e., Mexican Hat, Morlet and a modified form of Littlewood-Paley） are used. The unknown parameters （i.e., natural frequency and damping） of the ELTVS are optimized in stochastic least square sense. Numerical results are presented for different types of input to show the applicability and accuracy of the proposed wavelet based linearization technique.

Pellet Injection Experiments in the HL-2A Tokamak

The advantages of pellet injection as a competitive means of fuelling a tokamak are well known. They include： （ 1 ） deep deposition of fuel, （ 2 ） better fuelling efficiency, （ 3 ） purer plasma, and so on. Meanwhile, improving plasma performance by pellet injection has been proven in many tokamak experiments. The deposition of pellet particles following pellet injection causes a temporal change of the local plasma temperature and density gradients which affects the transport properties of the plasma, so pellet injection can be used as a method of studying the transport process as well.

Effect of Particle＇s Size on the Structural and Dynamical Properties in 2D Dusty Plasma

In a two-dimensional （219） dusty plasma system, the size of particles is considered under two different interparticle potentials （Yukawa potential and Dressed potential）. The structural and dynamical characters are investigated by molecular dynamics simulation respectively. The results show that the 2D systems via Yukawa and Dressed potentials have a different critical coupling constant F corresponding to the systems beginning to coagulate and exhibit different crystal configurations. Also we find that the size of particles has little influence on the 2D system＇s structure characters.

A Case Study of Affordable Housing in a Medium-Sized City in Central China

The main task of this paper is to explore the housing condition and housing policy in the vast but long-neglected middle-sized cities in China. Under the requirement of ＂Construction of 10 Million Units in 2011＂ from the central government, the affordable housing has started its nationwide building. Medium-sized cities are facing different developing periods but applying same housing policy as big cities. The paper examines the economic and social condition of the case city to find out the housing problems. It concludes that houses are affordable in these medium-sized cities, but housing policies are not implemented well. The paper proposed that housing affordability in medium-sized city is not about quantity but about quality. To keep houses affordable in these medium-sized cities, housing market, legislation, urban planning, public participation and intensive developments are all important.

Characterization of New Allelic Variation for Glutenin in EMS-Mutant Durum Wheat Population （Triticum turgidum L. subsp, durum （Desf.））

The High Molecular Weight HMW-GS and Low-Molecular-Weight LMW-GS Glutenin Subunits are major determinants of wheat dough processing qualities. Tilling populations was generated by EMS mutagenesis from Chaml durum variety. Protein quality was investigated by SDS sedimentation, protein content, gluten content and thousand kernel weights. 21 mutants were selected from 1,500 lines of tilling population depending on the variations of their electrophoresis profiles. The analysis of Glu-B 1 HMW-GS has showed two types of profiles： lines deficient on Bx7 and lines with expression of new protein between （Bx7-ByS） allelic pair combination. The majority of these mutant lines have showed quality compounds associated with bad technological characteristics like the parent Cham l with the exception of two mutant lines expressing new protein that have significantly stronger gluten properties an one mutant deficient on Bx7 HMW-GS that developed high value of SDS. For Glu-B3 LMW-GS coding for LMW glutenin type 1 and 2, new mutant line showing expression of new protein pattern. The mutant showing over-expression of bands on gel SDS-PAGE for LMW typel like Chaml, have produced the highest protein and gluten content, while the new mutant showing new profile have showed high value of Gluten and SDS.