Research on Bearing Capacity Calculation Method of Large Diameter Cylinder in Soft Clay

A large diameter cylinder inserted in soils is a new type of engineering structures used in offshore and port engineering. The mechanism of its bearing capacity and the analysis of its stability are important to its design and applications. In this paper, the finite element method is used to analyze the reacting forces of the soft soil foundation on the structure under the wave action. A simplified method is proposed, based on the plastic limit method, for the safety and stability analysis. Our analysis shows that the assumptions made in this paper and the mechanism used are reasonable, and the results obtained are appropriate. The calculation method is very efficient and can be used to evaluate main parameters of the structure in its preliminary designs.

Prevalence Of Shear Banding In Compression Of Zr41Ti14Cu12.5Ni10Be22.5 Pillars As Small As 150 Nm In Diameter

Recently, the size dependence of mechanical behaviors, particularly the yield strength and plastic deformation mode, of bulk metallic glasses (BMG) has created a great deal of interest. Contradicting conclusions have been drawn by different research groups, based on various experiments on different BMG systems. Based on in situ compression transmission electron microscopy (TEM) experiments on Zr41Ti14Cu12.5Ni10Be22.5 (Vit 1) nanopillars, this paper provides strong evidence that shear banding still prevails at specimen length scales as small as 150 nm in diameter. This is supported by in situ and ex situ images of shear bands, and by the carefully recorded displacement bursts under load control its well as load drops under displacement control. Finite element modeling of the stress state within the pillar shows that the unavoidable geometry constraints accompanying such experiments impart a strong effect on the experimental results, including non-uniform stress distributions and high level hydrostatic pressures. The seemingly improved compressive ductility is believed to be due to such geometry constraints. Observations underscore the notion that the mechanical behavior of metallic glasses, including strength and plastic deformation mode, is size independent at least in Vit 1. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The near wall velocity measurements in microchannels with different diameter particles by microPIV/PTV. 8th International symposium on PIV

In near wall measurements with microPIV/PTV, whether seeding particles can be effectively used to detect local fluid velocity is a crucial problem. This talk presents our recent measurements in microchannels [1][2]. Based on measured velocity profiles with 200nm and 50nm in pure water, we found that the measured velocity profiles are agreed with the theoretical values in the middle of channel, but large deviations between measured data and theoretical prediction appear close to wall (0.25mm

Sessile Drop in Microgravity: Creation, Contact Angle and Interface

We present in this paper the results obtained from a parabolic flight campaign regarding the contact angle and the drop interface behavior of sessile drops created under terrestrial gravity (1g) or in microgravity (mu g). This is a preliminary study before further investigations on sessile drops evaporation under microgravity. In this study, drops are created by the mean of a syringe pump by injection through the substrate. The created drops are recorded using a video camera to extract the drops contact angles. Three fluids have been used in this study : de-ionized water, HFE-7100 and FC-72 and two heating surfaces: aluminum and PTFE. The results obtained evidence the feasibility of sessile drop creation in microgravity even for low surface tension liquids (below 15 mN m (-aEuro parts per thousand 1)) such as FC-72 and HFE-7100. We also evidence the contact angle behavior depending of the drop diameter and the gravity level. A second objective of this study is to analyze the drop interface shape in microgravity. The goal of the these experiments is to obtain reference data on the sessile drop behavior in microgravity for future experiments to be performed in an French-Chinese scientific instrument (IMPACHT).

Finite element analysis on a circular wedge prism with 400 mm diameter

The paper comprehensively analyzes the distortions of a circular wedge prism with 400 mm diameter in a scanner by method of optical-mechanical-thermal integrating analysis. The structure and intensity of the prism assembly is verified and checked, and the surface deformations of the prism under gravity load, as well as the thermo-elastic distortions of the prism, are analyzed in detail and evaluated, which is finally contrasted with the measured values of Zygo Mark interferometer. The results show: the maximal distortion of the prism assembly is 10 nm magnitude and the maximal stress is 0.441 Mpa, which has much tolerance to the precision requirement of structure and the admissible stress of material; the influence of heat effect on the surface deformations of prism is proved to be far greater than the influence of gravity load, so some strict temperature-controlled measures are to be considered when the scanner is used. (c) 2006 Elsevier GmbH. All rights reserved.

Field and dispersion properties of subwavelength-diameter hollow optical fiber

We have investigated the basic properties of subwavelength-diameter hollow optical fiber with exact solutions of Maxwell's equations. The characteristics of modal field and waveguide dispersion have been studied. It shows that the subwavelength-diameter hollow optical fibers have interesting properties, such as enhanced evanescent field, local enhanced intensity in the hollow core and large waveguide dispersion that are very promising for many miniaturized high performance and novel photonic devices. (C) 2007 Optical Society of America.

Field enhancement and power distribution characteristics of subwavelength-diameter terahertz hollow optical fiber

Fields in subwavelength-diameter terahertz hollow optical fiber (STHOF) can be intensified by large discontinuity of the electric field at high index contrast interfaces. The influences of fiber geometry and refractive index of the dielectric region on the fiber characteristics, such as power distribution, enhancement factor, have been discussed in detail. By appropriate design, the intensity in the central region of STHOF may be enhanced by a factor of greater than 1.5 compared with subwavelength-diameter terahertz fiber without the central hole and the loss can be reduced. For its compact structure and simple fabrication process, the fiber may be very useful in many miniaturized high performance and novel terahertz photonic devices. (c) 2007 Elsevier B.V. All rights reserved.

纳米ZnO粉末中随机激光现象

实验采用三倍频Nd：YAG（波长355nm，脉宽8ns，频率30Hz）脉冲激光器作为抽运光源，在ZnO纳米粉末（直径～100nm）中发现了类似激光现象．并用环形腔理论模拟了ZnO的颗粒密度对平均自由程的影响，从理论上证明在纳秒级激光器的抽运下，ZnO纳米粉末也可以发射激光．

Enhanced luminescence from transparent Ni2+-doped MgO-Al2O3-SiO2 glass ceramics by Ga2O3 addition

Transparent Ni2+-doped MgO-Al2O3-SiO2 glass ceramics without and with Ga2O3 were synthetized. The precipitation of spinel nanocrystals, which was identified as solid solutions in the glass ceramics, could be favored by Ga2O3 addition and their sizes were about 7.6 nm in diameter. The luminescent intensity of the Ni2+-doped glass ceramics was largely enhanced by Ga2O3 addition which could mainly be caused by increasing of Ni2+ in the octahedral sites and the reduction of the mean frequency of phonon density of states in the spinel nanocrystals of solid solutions. The full width at half maximum (FWHM) of emissions for the glass ceramics with different Ga2O3 content was all more than 200 nm. The emission lifetime increased with the Ga2O3 content and the longest lifetime is about 250 mu s. The Ni2+-doped transparent glass ceramics with Ga2O3 addition have potential application as broadband optical amplifier and laser materials. (C) 2007 Elsevier Ltd. All rights reserved.

Isolation of a novel cyanophage infectious to the filamentous cyanobacterium Planktothrix agardhii (Cyanophyceae) from Lake Donghu, China

A previously unknown cyanophage, PaV-LD (Planktothrix agardhii Virus isolated from Lake Donghu), which causes lysis of the bloom-forming filamentous cyanobacterium P. agardhii, was isolated from Lake Donghu, Wuhan, China. PaV-LD only lysed P. agardhii strains isolated from Lake Donghu and not those isolated from other lakes. The PaV-LD particle has an icosahedral, non-tailed structure, ca. 70 to 85 nm (mean +/- SD = 76 +/- 6 nm) in diameter. PaV-LD was stable at freezing temperature, but lost its infectivity at temperatures >50 degrees C. Lysis of host cells was delayed about 3 d after the PaV-LD treatment with chloroform, and the virus was inactivated by exposure to low pH (<= 4). The latent period and burst size of the PaV-LD were estimated to be 48 to 72 h and about 340 infectious units per cell, respectively. The regrowth cultures of surviving host filaments were not lysed by the PaV-LD suspension. To our knowledge, this is the first isolation and cultivation of a virus infectious to the filamentous bloom-forming cyanobacterium Planktothrix from a freshwater lake.

Sinibrama longianalis, a new cyprinid species (Pisces : Teleostei) from the upper Yangtze River basin in Guizhou, China

Sinibrama longianalis, a new cyprinid species from the Wu Jiang (upper Yangtze River basin) in Guizhou, China is distinguished from other congeners in having the following combination of characters: last simple dorsal-fin ray well-ossified; a snout shorter than eye diameter; eye diameter 27.1-31.6% HL; lateral line scales 56-64 (mean 59.5); circumpeduncular scales 18-21; anal fin with 24-28 (mean 25.2) branched rays, originating opposite to or slightly in advance of posterior end of dorsal-fin base, basal length 27.0-31.1% SL; pectoral fin reaching to or slightly beyond pelvic-fin insertion.

Room-temperature highly anisotropic ferromagnetism and uniaxial spin amplification in (In,Mn)As quantum dots

The hole-mediated ferromagnetism in (In,Mn)As quantum dots is investigated using the k center dot p method and the mean field model. It is found that the (In,Mn)As quantum dot can be ferromagnetic at room temperature when there is one hole in the dot. For the spherical quantum dots, the Curie temperature decreases as the diameter increases, and increases as the effective composition of magnetic ions increases. It is interesting to find that the (In,Mn)As oblate quantum dot has highly anisotropic Zeeman splitting and ferromagnetism due to the spin-orbit coupling effect, which can be used as an uniaxial spin amplifier. (c) 2008 American Institute of Physics.

An internally-matched GaN HEMTs device with 45.2 W at 8 GHz for X-band application

Optimized AlGaN/AlN/GaN high electron mobility transistor (HEMT) with high mobility GaN channel layer structures were grown on 2-in. diameter semi-insulating 6H-SiC substrates by MOCVD. The 2-in. diameter GaN HEMT wafer exhibited a low average sheet resistance of 261.9 Omega/square, with the resistance un-uniformity as low as 2.23%. Atomic force microscopy measurements revealed a smooth AlGaN surface whose root-mean-square roughness is 0.281 nm for a scan area of 5 x 5 mu m. For the single-cell HEMTs device of 2.5-mm gate width fabricated using the materials, a maximum drain current density of 1.31 A/mm, an extrinsic transconductance of 450 mS/mm, a current gain cutoff frequency of 24 GHz and a maximum frequency of oscillation 54 GHz were achieved. The four-cell internally-matched GaN HEMTs device with 10-mm total gate width demonstrated a very high output power of 45.2 W at 8 GHz under the condition of continuous-wave (CW), with a power added efficiency of 32.0% and power gain of 6.2 dB. To our best knowledge, the achieved output power of internally-matched devices are the state-of-the-art result ever reported for X-band GaN-based HEMTs. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

Stone-Wales defects created by low energy recoils in single-walled silicon carbide nanotubes

The defect creation at low energy events was studied using density functional theory molecular dynamics simulations in silicon carbide nanotubes, and the displacement threshold energies determined exhibit a dependence on sizes, which decrease with decreasing diameter of the nanotubes. The Stone-Wales (SW) defect, which is a common defect configurations induced through irradiation in nanotubes, has also been investigated, and the formation energies of the SW defects increase with increasing diameter of the nanotubes. The mean threshold energies were found to be 23 and 18 eV for Si and C in armchair (5,5) nanotubes. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3238307]