Electron quantum path tuning and isolated attosecond pulse emission driven by a waveform-controlled multi-cycle laser field

We investigate high-order harmonic emission and isolated attosecond pulse (IAP) generation in atoms driven by a two-colour multi-cycle laser field consisting of an 800 nm pulse and an infrared laser pulse at an arbitrary wavelength. With moderate laser intensity, an IAP of similar to 220 as can be generated in helium atoms by using two-colour laser pulses of 35 fs/800 nm and 46 fs/1150 nm. The discussion based on the three-step semiclassical model, and time-frequency analysis shows a clear picture of the high-order harmonic generation in the waveform-controlled laser field which is of benefit to the generation of XUV IAP and attosecond electron pulses. When the propagation effect is included, the duration of the IAP can be shorter than 200 as, when the driving laser pulses are focused 1 mm before the gas medium with a length between 1.5 mm and 2 mm.

Structure analysis of CCR5 from human and primates

It is well known that the chemokine receptor CCR5 plays very important roles in HIV-1 virus infection. A three-dimensional molecular model of human CCR5 was generated by SYBYL, a distance geometry-based homologous modeling package, using the corresponding transmembrane domain of bacteriorhodopsin as the template. On the basis of human CCR5 model, we also built 18 3D molecular models of CCR5 in primates from Pongo pygmaeus, Pygathrix nemaeus, Macaca assameniss, Trachy-pithecus phayrei, T. francoisi, M. arotoides, Rhinopithecus roxellance, R, bieti, R. avunculus, Hylobates leucogenys, Pan troglodytes, Gorilla gorilla, Cercopithecus aethiops 1, C. aethiops 2, Papio hamadryas M. mulatta, M. fascicularis and M. nemestrina. Structural analyses and statistics results suggested that the main-chains of the primate CCR5 were similar to that of the human CCR5 and that the fit-RMS deviation values of these primate CCR5 were less than 0.1 Angstrom. Moreover, the structures of these CCR5 proteins, except those of the African green monkey 1 (C.aet1), do not have a remarkable difference. It is proved that the 14th residue is possibly very important in the inhibition infections by M-tropic HIV-1, and it is also demonstrated that the 13th residue of human CCR5 was changed from asparagine into aspartic acid in all these primates. It means that the primate CCR5 no longer depend on CD4 for efficient entry, but human CCR5 may have evolved subsequently due to the use of CD4 as a receptor, allowing the high-affinity chemokine receptor-binding site of HIV to be sequestered from host immune surveillance. (C) 2000 Elsevier Science B.V. All rights reserved.

Thermal quenching of luminescence from buried and surface InGaAs self-assembled quantum dots with high sheet density

Variable-temperature photoluminescence (PL) spectra of Si-doped self-assembled InGaAs quantum dots (QDs) with and without GaAs cap layers were measured. Narrow and strong emission peak at 1075 nm and broad and weak peak at 1310 nm were observed for the buried and surface QDs at low temperature, respectively. As large as 210 meV redshift of the PL peak of the surface QDs with respect to that of the buried QDs is mainly due to the change of the strain around QDs before and after growth of the GaAs cap layer. Using the developed localized-state luminescence model, we quantitatively calculate the temperature dependence of PL peaks and integrated intensities of the two samples. The results reveal that there exists a large difference in microscopic mechanisms of PL thermal quenching between two samples. (c) 2005 American Institute of Physics.

Thermal redistribution of localized excitons and its effect on the luminescence band in InGaN ternary alloys

Temperature-dependent photoluminescence measurements have been carried out in zinc-blende InGaN epilayers grown on GaAs substrates by metalorganic vapor-phase epitaxy. An anomalous temperature dependence of the peak position of the luminescence band was observed. Considering thermal activation and the transfer of excitons localized at different potential minima, we employed a model to explain the observed behavior. A good agreement between the theory and the experiment is achieved. At high temperatures, the model can be approximated to the band-tail-state emission model proposed by Eliseev et al. [Appl. Phys. Lett. 71, 569 (1997)]. (C) 2001 American Institute of Physics.

Influence of polarization orientation of violet light on the diffraction efficiency of bacteriorhodopsin

When a grating is recorded in a bacteriorhodopsin film by two linear parallel polarized beams together with anauxiliary violet light, the diffraction efficiency has a dependence on the polarization orientation of the violet light as well as its intensity. A method for calculating the diffraction efficiency of gratings in bacteriorhodopsin is proposed based on the two-state photochromic model, considering the saturation effect and the polarization status of all the involved lights. It is found that the polarization orientation of the violet light produces an approximate-cosine and an approximate-sine modulation on the steady-state diffraction efficiency separately at low and high intensities, respectively. The parallel polarized violet light can improve the steady-state diffraction efficiency to a larger degree than the perpendicularly polarized violet light when both are at their optimal intensities. The optimal intensity for the parallel polarized violet light is lower than that of the perpendicular polarized one. Thus, the improvement of the steady-state diffraction efficiency is less sensitive to the intensity of perpendicular polarized violet light than to that of parallel polarized violet light. (C) 2008 Optical Society of America.

干湿交替过程中土壤胀缩特征的实验研究

土壤胀缩是土壤在干燥、湿润交替变化过程中所表现出的土壤容积随含水量改变的现象。本文通过测定4种土壤脱水和吸水过程中的土柱高度和直径的变化,分析了胀缩过程中土壤容积与含水量的关系及土壤的胀缩特征。结果显示:三直线模型能够很好地拟合4种土壤的收缩、膨胀过程;土壤收缩、膨胀曲线各段的特征值均小于1,这说明土壤胀缩过程中土壤容积的变化速率小于含水量的变化速率;4种土壤胀缩过程中几何因子rs大于1而小于3,且收缩初期几何因子rs等于1,表明土壤的胀缩是各向异性的,并且在土壤收缩的最初阶段只有垂直收缩。

Critical behavior of multifragmentation in finite nuclei and extraction of critical exponents

Using a phenomenological asymmetric nuclear equation of state, we obtained pressure-density isotherms of the finite nucleus Sn-112 simulated in r-space and in p-space and constructed the nuclear fragments by using the coalescence model. After correlatively analysing the fragments, the signal of critical behavior has been found and critical exponents were also extracted.

Numerical Simulation of Reactive Extrusion Processes for Activated Anionic Polymerization

In order to deal with the complicated relationships among the variables of the reactive extrusion process for activated anionic polymerization, a three-dimensional equivalent model of closely intermeshing co-rotating twin screw extruders was established. Then the numerical computation expressions of the monomer concentration, the monomer conversion, the average molecular weight and the fluid viscosity were deduced, and the numerical simulation of the reactive extrusion process of Styrene was carried out. At last, our simulated results were compared with Michaeli's simulated results and experimental results. (C) 2007 Elsevier B.V. All rights reserved

Kinetics and Statistical Distributions of Single-Molecule Conformational Dynamics

We developed a coarse-grained yet microscopic detailed model to study the statistical fluctuations of single-molecule protein conformational dynamics of adenylate kinase. We explored the underlying conformational energy landscape and found that the system has two basins of attractions, open and closed conformations connected by two separate pathways. The kinetics is found to be nonexponential, consistent with single-molecule conformational dynamics experiments. Furthermore, we found that the statistical distribution of the kinetic times for the conformational transition has a long power law tail, reflecting the exponential density of state of the underlying landscape. We also studied the joint distribution of the two pathways and found memory effects.

INTERFACIAL BEHAVIOR OF COMPATIBILIZERS IN POLYMER BLENDS

From an analysis of the literature and our experimental results, we have established that interfacial tension is a function of the concentration of a compatibilizer, and put forward a 'three-stage' physical model to account for the compatibilizing behavio

Application of forecasting structural cracks technique of 3D move in Chengdao buried hill

3DMove software, based on the three-dimension structural model of geologic interpretation, can forecast reservoir cracks from the point of view of formation of the structural geology, and analyze the characteristics of the cracks. 3DMove software dominates in forecasting cracks. We forecast the developments and directions of the cracks in Chengbei buried hill with the application of forecasting technique in 3DMove software, and obtain the chart about strain distributing on top in buried hill and the chart about relative density and orientation and the chart about the analysis of crack unsealing. In Chengbei 30 buried hill zone, north-west and north-east and approximately east-west cracks in Cenozoic are very rich and the main directions in every fault block are different. Forecasting results that are also verified by those of drilling approximately accord with the data from well logging, the case of which shows that the technique has the better ability in forecasting cracks, and takes more effects on exploration and exploitation of crack reservoir beds in ancient buried hill reservoirs.

Numerical simulation on the process of saltwater intrusion and its impact on the suspended sediment concentration in the Changjiang (Yangtze) estuary

To study the relationship between sediment transportation and saltwater intrusion in the Changjiang (Yangtze) estuary, a three-dimensional numerical model for temperature, salinity, velocity field, and suspended sediment concentration was established based on the ECOMSED model. Using this model, sediment transportation in the flood season of 2005 was simulated for the Changjiang estuary. A comparison between simulated results and observation data for the tidal level, flow velocity and direction, salinity and suspended sediment concentration indicated that they were consistent in overall. Based on model verification, the simulation of saltwater intrusion and its effect on sediment in the Changjiang estuary was analyzed in detail. The saltwater intrusion in the estuary including the formation, evolution, and disappearance of saltwater wedge and the induced vertical circulation were reproduced, and the crucial impact of the wedge on cohesive and non-cohesive suspended sediment distribution and transportation were successfully simulated. The result shows that near the salinity front, the simulated concentrations of both cohesive and non-cohesive suspended sediment at the surface layer had a strong relationship with the simulated velocity, especially when considering a 1-hour lag. However, in the bottom layer, there was no obvious correlation between them, because the saltwater wedge and its inducing vertical circulation may have resuspended loose sediment on the bed, thus forming a high-concentration area near the bottom even if the velocity near the bottom was very low during the transition phase from flood to ebb.

一种输电线路巡检机器人控制系统的设计与实现

介绍了一种超高压输电线路巡检机器人控制系统的设计与实现方法.根据巡检作业任务的要求,采用遥控与局部自主相结合的控制模式实现巡检机器人沿线行走及跨越障碍.设计了巡检机器人有限状态机模型,实现了机器人遥控与局部自主控制的有机结合.采用基于激光传感器定位的方法实现了巡检机器人的自主越障控制.实验结果表明,该机器人可实现沿线行走及自主跨越障碍,从而验证了控制系统设计的有效性与合理性.

大陆地壳岩石结构重建：方法与实例

The composition of the continental crust has long been a subject of interest to earth scientists as it can provide key information about the crustal growth and evolution of the continents. In this paper we make a comparative study on the lithological discrimination schemes featuring with the use of different seismic attributes, such as P-wave velocity, P- to S-wave velocity ratio, acoustic or elastic impedances, Lame impedances and high-sensitive identification factors. The results demonstrate that Lame impedances have more powerful constrains than other seismic attributes. In order to fully take the advantage of make the best of the different seismic response of crustal rock, we firstly use seismic attribute that have weak distinguish power to construct loose constrained lithological model, then use seismic attributes that have stronger distinguish power to tighten the constrains of lithological discrimination. We propose a joint scheme (chain constrain technique) by combing all available constrains to reduce the non-uniqueness in mapping rock distribution. We adopt chain constrain technique to construct lithological model beneath Tunxi-Wenzhou transect, Southeastern China, Manzhouli-Suifenhe transect, Northeastern China, and geophysical profile in Bohai Bay Basin, North China. The results can be suumarized as the follows: (1) We compare the sensitivity of different seismic factor constraints on rock types, and conclude that Lame impedances have tighter constrains than seismic velocity, Vp/Vs, density. (2) We propose chain constrains to construct lithological model from integrated geophysical data, and reduce the non-uniqueness in mapping rock distribution. (3) We reconstruct crustal lithological model beneath Tunxi-Wenzhou transect, Southeastern China. The results suggested that Jiangshan-Shaoxing fault is a crust-scale, and it is the boundary between Cathaysia and Yanthze blocks. (4) We construct crustal lithological model beneath Manzhouli-Suifenhe transect, Northeastern China. (5) We map the petrologic distribution along a geophysical profile in Bohai Bay Basin, North China, and construct a three-layered petrology model from the depth 2 km to about 10 km, consisted of basalt (the first layer), pelitic siltstone (the second layer), and silty mudstone and fine sandstone (the third layer).

特大地震激发地球自由振荡的数值模拟研究

Large earthquakes, such as the Chile earthquake in 1960 and the Sumatra-Andaman earthquake on Dec 26, 2004 in Indonesia, have generated the Earth’s free oscillations. The eigenfrequencies of the Earth’s free oscillations are closely related to the Earth’s internal structures. The conventional methods, which mainly focus on calculating the eigenfrequecies by analytical ways, and the analysis on observations can not easily study the whole processes from earthquake occurrence to the Earth’s free oscillation inspired. Therefore, we try to use numerical method incorporated with large-scale parallel computing to study on the Earth’s free oscillations excited by giant earthquakes. We first give a review of researches and developments of the Earth’s free oscillation, and basical theories under spherical coordinate system. We then give a review of the numerical simulation of seismic wave propagation and basical theories of spectral element method to simulate global seismic wave propagation. As a first step to study the Earth’s free oscillations, we use a finite element method to simulate the propagation of elastic waves and the generation of oscillations of the chime bell of Marquis Yi of Zeng, by striking different parts of the bell, which possesses the oval crosssection. The bronze chime bells of Marquis Yi of Zeng are precious cultural relics of China. The bells have a two-tone acoustic characteristic, i.e., striking different parts of the bell generates different tones. By analysis of the vibration in the bell and the spectrum analysis, we further help the understanding of the mechanism of two-tone acoustic characteristics of the chime bell of Marquis Yi of Zeng. The preliminary calculations have clearly shown that two different modes of oscillation can be generated by striking different parts of the bell, and indicate that finite element numerical simulation of the processes of wave propagation and two-tone generation of the chime bell of Marquis Yi of Zeng is feasible. These analyses provide a new quantitative and visual way to explain the mystery of the two-tone acoustic characteristics. The method suggested by this study can be applied to simulate free oscillations excited by great earthquakes with complex Earth structure. Taking into account of such large-scale structure of the Earth, small-scale low-precision numerical simulation can not simply meet the requirement. The increasing capacity in high-performance parallel computing and progress on fully numerical solutions for seismic wave fields in realistic three-dimensional spherical models, Spectral element method and high-performance parallel computing were incorporated to simulate the seismic wave propagation processes in the Earth’s interior, without the effects of the Earth’s gravitational potential. The numerical simulation shows that, the results of the toroidal modes of our calculation agree well with the theoretical values, although the accuracy of our results is much limited, the calculated peaks are little distorted due to three-dimensional effects. There exist much great differences between our calculated values of spheroidal modes and theoretical values, because we don’t consider the effect the Earth’ gravitation in numerical model, which leads our values are smaller than the theoretical values. When , is much smaller, the effect of the Earth’s gravitation make the periods of spheroidal modes become shorter. However, we now can not consider effects of the Earth’s gravitational potential into the numerical model to simulate the spheroidal oscillations, but those results still demonstrate that, the numerical simulation of the Earth’s free oscillation is very feasible. We make the numerical simulation on processes of the Earth’s free oscillations under spherically symmetric Earth model using different special source mechanisms. The results quantitatively show that Earth’s free oscillations excited by different earthquakes are different, and oscillations at different locations are different for free oscillation excited by the same earthquake. We also explore how the Earth’s medium attenuation will take effects on the Earth’s free oscillations, and take comparisons with the observations. The medium attenuation can make influences on the Earth’s free oscillations, though the effects on lower-frequency fundamental oscillations are weak. At last, taking 2008 Wenchuan earthquake for example, we employ spectral element method incorporated with large-scale parallel computing technology to investigate the characteristics of seismic wave propagation excited by Wenchuan earthquake. We calculate synthetic seismograms with one-point source model and three-point source model respectively. Full 3-D visualization of the numerical results displays the profile of the seismic wave propagation with respect to time. The three-point source, which was proposed by the latest investigations through field observation and reverse estimation, can better demonstrate the spatial and temporal characteristics of the source rupture processes than one-point source. Primary results show that those synthetic signals calculated from three-point source agree well with the observations. This can further reveal that the source rupturing process of Wenchuan earthquake is a multi-rupture process, which is composed by at least three or more stages of rupture processes. In conclusion, the numerical simulation can not only solve some problems concluding the Earth’s ellipticity and anisotropy, which can be easily solved by conventional methods, but also finally solve the problems concluding topography model and lateral heterogeneity. We will try to find a way to fully implement self-gravitation in spectral element method in future, and do our best to continue researching the Earth’s free oscillations using the numerical simulations to see how the Earth’ lateral heterogeneous will affect the Earth’s free oscillations. These will make it possible to bring modal spectral data increasingly to bear on furthering our understanding of the Earth’s three-dimensional structure.