S-curve networks and an approximate method for estimating degree distributions of complex networks

In the study of complex networks almost all theoretical models have the property of infinite growth,but the size of actual networks is finite.According to statistics from the China Internet IPv4(Internet Protocol version 4) addresses,this paper proposes a forecasting model by using S curve(logistic curve).The growing trend of IPv4 addresses in China is forecasted.There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6.Based on the laws of IPv4 growth,that is,the bulk growth and the finitely growing limit,it proposes a finite network model with a bulk growth.The model is said to be an S-curve network.Analysis demonstrates that the analytic method based on uniform distributions(i.e.,Barab’asi-Albert method) is not suitable for the network.It develops an approximate method to predict the growth dynamics of the individual nodes,and uses this to calculate analytically the degree distribution and the scaling exponents.The analytical result agrees with the simulation well,obeying an approximately power-law form.This method can overcome a shortcoming of Baraba’si-Albert method commonly used in current network research.     

基于6LoWPAN技术的气体环境监控系统

针对日趋严重的大气污染问题,提出了一种基于6LoWPAN技术的大气环境监测方案。通过IPv6通信协议组建的6LoWPAN星型网络,能够实现大规模传感控制网络,解决了IPv4 地址枯竭、各厂商协议不统一等问题。各个PAN采集到的数据通过路由器发送给监控终端,使用Labview为开发平台进行数据汇总后实现对环境中有害气体的实时监控,并通过以太网进行数据共享。实验结果表明,该系统数据采集准确无误,并对环境污染起到了预防作用,可保证社会的可持续发展。     

Modeling the IPv6 internet AS-level topology

To measure the IPv6 internet AS-level topology, a network topology discovery system, called Dolphin, was developed. By comparing the measurement result of Dolphin with that of CAIDA’s Scamper, it was found that the IPv6 Internet at AS level, similar to other complex networks, is also scale-free but the exponent of its degree distribution is 1.2, which is much smaller than that of the IPv4 Internet and most other scale-free networks. In order to explain this feature of IPv6 Internet we argue that the degree exponent is a measure of uniformity of the degree distribution. Then, for the purpose of modeling the networks, we propose a new model based on the two major factors affecting the exponent of the EBA model. It breaks the lower bound of degree exponent which is 2 for most models. To verify the validity of this model, both theoretical and experimental analyses have been carried out. Finally, we demonstrate how this model can be successfully used to reproduce the topology of the IPv6 Internet.     

Evolution of IPv6 Internet topology with unusual sudden changes

The evolution of Internet topology is not always smooth but sometimes with unusual sudden changes. Consequently, identifying patterns of unusual topology evolution is critical for Internet topology modeling and simulation. We analyze IPv6 Internet topology evolution in IP-level graph to demonstrate how it changes in uncommon ways to restructure the Internet. After evaluating the changes of average degree, average path length, and some other metrics over time, we find that in the case of a large-scale growing the Internet becomes more robust; whereas in a top-bottom connection enhancement the Internet maintains its efficiency with links largely decreased.     

Ab initio study of oxygen-vacancy LaAlO3（001） surface

Density functional theory is used to investigate the surface structures and the energies of two possible terminated LaAlO3 （001） surfaces with oxygen vacancies, i.e. LaO- and AlO2-terminated surfaces. The large displacements of ions, deviated from their crystalline sites, can lead to the formation of the surface rumpling. From thermodynamics analysis, the AlO2-terminated surface with oxygen-vacancies is less stable than the LaO-terminated one. Some states in the gap lie under the Fermi level by about -1eV in the LaO-terminated surface with oxygen vacancies. For the AlO2- terminated oxygen-vacancy surface, some O 2p states move into the mid-gap region and become partially unoccupied. The two types of termination surfaces exhibit conduction related to oxygen vacancies. Our results can contribute to the application of LAO films to high dielectric constant materials.     

Fermion states on domain-wall junctions and the flavor number

In this paper we address the problem of localizing fermion states on stable domain-wall junctions. The study focus on the consequences of intersecting six independent 8d domain walls to form 4d junctions in a ten-dimensional spacetime. This is related to the mechanism of relaxing to three space dimensions through the formation of domain-wall junctions. The model is based on six bulk real scalar fields, the φ ⁴ model in its broken phase, the prototype of the Higgs field, and is such that the fermion and scalar modes bound to the domain walls are the zero mode and a single massive bound state, which can be regarded as a two-level system, at least at sufficiently low energy. Inside the junction, we use the fact that some states are statistically more favored to address the possibility of constraining the flavor number of the elementary fermions.     

Perceptual learning and generalization resulting from training on an auditory amplitude-modulation detection task

Fluctuations in sound amplitude provide important cues to the identity of many sounds including speech. Of interest here was whether the ability to detect these fluctuations can be improved with practice, and if so whether this learning generalizes to untrained cases. To address these issues, normal-hearing adults (n = 9) were trained to detect sinusoidal amplitude modulation (SAM; 80-Hz rate, 3-4 kHz bandpass carrier) 720 trials/day for 6-7 days and were tested before and after training on related SAM-detection and SAM-rate-discrimination conditions. Controls (n = 9) only participated in the pre- and post-tests. The trained listeners improved more than the controls on the trained condition between the pre- and post-tests, but different subgroups of trained listeners required different amounts of practice to reach asymptotic performance, ranging from 1 (n = 6) to 4-6 (n = 3) sessions. This training-induced learning did not generalize to detection with two untrained carrier spectra (5 kHz low-pass and 0.5-1.5 kHz bandpass) or to rate discrimination with the trained rate and carrier spectrum, but there was some indication that it generalized to detection with two untrained rates (30 and 150 Hz). Thus, practice improved the ability to detect amplitude modulation, but the generalization of this learning to untrained cases was somewhat limited.     

Superstrings with tensor degrees of freedom

We add antisymmetric tensor degrees of freedom to the usual superstring coordinates. We show that super and kappa symmetries are only achieved for the spacetime dimensionD=4. We also address problems related to the quantization of the model and discuss the influences of this extended spacetime in the usual quantum field theory.     

Stationary ‘V’ States for Preferred Motions of Many Particles

We use the discrete kinetic theory with the free-orientation parameter being fixed () to derive the macroscopic velocity field for many particles flowing through a microdomain. Our results resemble qualitatively other hydrodynamical solutions. The V-shaped velocity field changes as the dominant physical parameter (Knudsen number) varies. We also briefly discuss the possible mechanism due to the entropy production along the boundaries.The only author's address after 2007-Aug. is: P.O. Box 30-15, Shanghai 200030, PR China     

iC多型体X射线定量分析的Rietveld方法

鉴于SIC多型体的主要衍射线完全重叠，用常规X射线粉末衍射方法确定SiC陶瓷材料中多型体含量的分布是非常困难的．提出以X射线粉末衍射全谱拟合的Rietveld方法进行SiC多型体定量分析，阐述了原理及方法．对含3C，4H，6H和15R4种多型体衍射数据的定量分析结果表明：Rietveld方法可对SiC材料中常见多型体的定量分析给出准确的结果．还给出了各自的标准偏差，并估计了该方法对各多型体能给出精确结果的最低含量     

Autler--Townes doublet in novel sub-Doppler spectra with caesium vapour cell

With a coupling laser locked to caesium 6S$_{1 / 2}$ $F_{\rm g}$=4--6P$_{3 / 2}$ $F_{\rm e}$=5 cycling transition and a co-propagating probe laser scanned across 6S$_{1 / 2}$ $F_{\rm g}$=4--6P$_{3 / 2}$ $F_{\rm e}$=3, 4 and 5 transitions, a novel scheme for sub-Doppler spectra in Doppler-broadened V-type three-level system is demonstrated by detecting the transmission of the coupling laser through a caesium vapour cell. The Autler--Townes doublet in the sub-Doppler spectra of the coupling laser is clearly observed. The effects of coupling laser intensity on the splitting and linewidth of the Autler--Townes doublet are experimentally investigated and the results agree well with theoretical predictions. Taking the multiple hyperfine levels of caesium atom into account, a brief analysis is presented.     

The next detectors for gravitational wave astronomy

This paper focuses on the next detectors for gravitational wave astronomy which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves. The next detectors will need to have greater sensitivity, while also enabling the world array of detectors to have improved angular resolution to allow localisation of signal sources. Sect. 1 of this paper begins by reviewing proposals for the next ground based detectors,and presents an analysis of the sensitivity of an 8 km armlength detector, which is proposed as a safe and cost-effective means to attain a 4-fold improvement in sensitivity. The scientific benefits of creating a pair of such detectors in China and Australia is emphasised. Sect. 2 of this paper discusses the high performance suspension systems for test masses that will be an essential component for future detectors, while sect. 3 discusses solutions to the problem of Newtonian noise which arise from fluctuations in gravity gradient forces acting on test masses. Such gravitational perturbations cannot be shielded, and set limits to low frequency sensitivity unless measured and suppressed. Sects. 4 and 5 address critical operational technologies that will be ongoing issues in future detectors. Sect. 4 addresses the design of thermal compensation systems needed in all high optical power interferometers operating at room temperature. Parametric instability control is addressed in sect. 5. Only recently proven to occur in Advanced LIGO, parametric instability phenomenon brings both risks and opportunities for future detectors. The path to future enhancements of detectors will come from quantum measurement technologies. Sect. 6 focuses on the use of optomechanical devices for obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum measurement options.     

1-W, high-repetition-rate room temperature operation of mid-infrared optical parametric oscillator based on periodically poled MgO-doped LiNbO

In this paper a high-repetition-rate mid-infrared （mid-IR） optical parametric oscillator based on periodically poled MgO-doped LiNbO3 （PPMgLN） at room temperature was demonstrated. The maximum average mid-IR output power at 3.63μm was 1.02 W with the repetition rate of 60kHz and corresponding efficiency from the pump to the idler was 26.7%. The temperature tuning and the period tuning characteristics were also discussed.     

The Time-Resolved Fluorescence Stokes Shift of Cucurbit[6]Uril Complexes with a Pyridinium Styryl Dye

The time-resolved Stokes shift of fluorescence of styryl dye, trans-4-[4-(dimethylamino)-styryl]-1-methylpyridinium iodide (DASPI), and its host-guest complexes with cucurbit[6]uril (CB[6]) was studied by up-conversion technique on a 5 ps time scale. In all cases, the solvation time correlation function – that describes relaxation of the fluorescent state - contains two components. The time constant of the first component, which is related to the vibrational relaxation of the dye cation, increases from 118 fs without CB[6] to 224 fs in the presence CB[6]. It suggests the production of CB[6] complexes to disturb the hydrogen-bond net in the vicinity of DASPI cation. The time constant of the second component, which is associated with solvation, changes from 0.81 ps without CB[6] to 1.15 ps in the presence of the cavitand. The observed increase can be related to the displacement of the dye cation deeper into CB[6] that allows considering DASPI-CB[6] complexes as a light-controlled molecular machine with a response time on the picosecond scale.     

Supersymmetric descendants of self-adjointly extended quantum mechanical Hamiltonians

We consider the descendants of self-adjointly extended Hamiltonians in supersymmetric quantum mechanics on a half-line, on an interval, and on a punctured line or interval. While there is a 4-parameter family of self-adjointly extended Hamiltonians on a punctured line, only a 3-parameter sub-family has supersymmetric descendants that are themselves self-adjoint. We also address the self-adjointness of an operator related to the supercharge, and point out that only a sub-class of its most general self-adjoint extensions is physical. Besides a general characterization of self-adjoint extensions and their supersymmetric descendants, we explicitly consider concrete examples, including a particle in a box with general boundary conditions, with and without an additional point interaction. We also discuss bulk-boundary resonances and their manifestation in the supersymmetric descendant.     

Design of 0.25 μm 2.7 V 2T2C 4 Mb asynchronous ferroelectric random access memory (FRAM) for mobile applications

In order to fabricate nonvolatile 4 Mb ferroelectric random access memory (FRAM) for the application to portable electronic devices, we proposed two noble techniques; (1) shared sense amplifier arrangement structure for reducing a chip size, active current, and power consumption, and (2) address transition detection (ATD) control scheme for asynchronous operation and limited address skew-free. We successfully developed 4 Mb FRAM with the address access time of 90 ns, read/write cycle time of 100 ns, and limited address skew-free of 20 ns at 2.7 V and 85 °C.     

Effect of upward ion on field-aligned currents in the near-earth magnetotail

A 3-dimensional resistive MHD simulation was carried out to study the effect of the upward ions on the field-aligned currents (FACs) in the near-earth magnetotail. The simulation results show that the up-flow ions originating from the nightside auroral oval would drift into the center plasma sheet along the magnetic field lines in the plasma sheet boundary, and have an important effect on the field-aligned currents. The main conclusions include that: 1) the upward-ions mainly affect the field-aligned currents in the near-earth magnetotail (inside 15 Re); 2) the generated FACs in the near-earth region have two types, i.e., Region 1 FAC in the high-latitude and Region 2 FAC in the low-latitude; 3) FACs increase with the enhancement of the upward ion flux; 4) with the same flux of the upward ions, FACs enhance with the increase of the velocity of the up-flow ions; 5) the intensification of FACs is also closely related with the latitude of the upward ions, and the ions from the closed field line region generate larger FACs; 6) the generation of FACs is closely related with B _y created by the upward ions. Supported by the National Natural Science Foundation of China (Grant Nos. CNSF-40474058 and CNSF-40536030)     

Excited-state dynamics of Yb in LiCaAlF6 single crystal

Single crystals of Yb²⁺-doped LiCaAlF₆ were grown by the Czochralski technique under CF₄ atmosphere. Photoluminescence, thermally stimulated luminescence and decay kinetics of Yb²⁺ centre in the LiCaAlF₆ host were measured in the 4–300 K temperature interval. Phenomenological two excited-state-level model is introduced to obtain quantitative characteristics of the excited state dynamics of Yb²⁺. The role of Yb²⁺ centre in trapping processes is discussed. Moreover, defect centres related to LiCaAlF₆ host were found.     

天然萤石的阴极射线发光谱研究

本文报导产自我国几个主要萤石矿床中若干萤石样品的阴极射线发光谱.除样品Mo-25以外,所研究样品发光谱的主要谱线均来源于取代Ca2+的Dy3+和Sm3+离子的f-f跃迁.此外,还观察到几条Er3+、Pr3+和Tb3+离子的发光谱线.谱线的相对强度与样品中各种稀土离子的相对含量有关.群论分析表明,萤石中Dy3+离子的局部对称性低于立方,或者存在着一种以上的Dy3+环境.在稀土含量最低的样品(Mo-25)的谱中,可见区只观察到一条中心在490nm处的宽带,它可能是Mn2+离子的4T1g(G)→4A1g(G)跃迁产生的.由于萤石中Mn2+的晶场分裂参量Dq反常地低,故能产生八配位Mn2+离子少见的绿色发光.     

Vertical rotation effect on turbulence characteristics in an open channel flow

This paper solves the three-dimensional Navier-Stokes equation by a fractional-step method with the Reynolds number Reτ=194 and the rotation number Nτ=0-0.12. When Nτ is less than 0.06, the turbulence statistics relevant to the spanwise velocity fluctuation are enhanced, but other statistics are suppressed. When Nτ is larger than 0.06, all the turbulence statistics decrease significantly. Reynolds stress budgets elucidate that turbulence kinetic energy in the vertical direction is transferred into the streamwise and spanwise directions. The flow structures exhibit that the bursting processes near the bottom wall are ejected toward the free surface. Evident change of near-surface streak structures of the velocity fluctuations are revealed.