伺服控制土石混合体压力渗透仪研究

土石混合体渗流特性的研究对于工程建设、土石混合体滑坡的防治有重要意义。总结了前人对于堆石料渗透试验仪的研究,其特点在于渗透筒的大尺寸、供水系统、供水压力的控制;透水板、制样方法、筒壁防渗对于试验的影响。周中等自制的常水头渗透仪,主要对土石混合体渗透系数及其影响因素进行研究。本文研制的伺服控制土石混合体压力渗透仪能够准确伺服控制供水压力和供水速度,提供不超过2MPa的高水压,调节试样渗流速度,操作方便,能够有针对性的研究土石混合体的渗流特性。     

Numerical investigation of ice breaking by a high-pressure bubble based on a coupled BEM-PD model

In this paper, by combining the boundary element method (BEM) and peridynamics (PD), a bubble-ice interaction model is established, which can investigate the dynamic interactions between a high-pressure bubble and an ice plate with particular focus on the mechanical behaviors of ice breaking. The bubble dynamics are solved by BEM based on the potential flow theory. Ice cracks initiation and propagation are simulated by the bond-based peridynamics which is validated by a three-point bending test. The fluid–structure interaction (FSI) is achieved by matching the normal velocity and hydrodynamic loads at the fluid–structure interface. To validate the proposed FSI model, an experiment is carried out in which an oscillating bubble is generated under an ice plate by underwater discharge system. The whole interaction process is captured by a Phantom V711 high-speed camera. Qualitative agreements are achieved between the numerical and experimental results. The underlying mechanism of cracks initiation, propagation, branching, and coalescence of the ice plate is found to highly depend on three parameters, i.e., bubble–ice distance, ice thickness and bubble size. The present study is expected to provide further assists in the understanding of ice breaking problems.     

Pressure-Induced Enhancement of the Photoluminescence in Ca 1−x Sr x F 2 :Mn 2+

The surprising disappearance of the Mn 2+ photoluminescence (PL) on passing from CaF 2 to SrF 2 through the Ca 1 m x Sr x F 2 :Mn 2+ series is investigated through pressure spectroscopy, and as a function of the temperature. The PL quenching which is observed along the series is explained on the basis of multiphonon relaxation mechanisms, which are described by a thermally activated process. In non-luminescent crystals, PL can be recovered by applying pressure. The results are accounted for through an universal equation relating the PL lifetime as a function of P (or V ) and T , using an activation energy and a transition rate that are strongly dependent on the lattice parameter (crystal volume).     

Shock Hugoniot for Biological Materials

This paper presents shock Hugoniot compression data for several bio-related materials by using flat plate impact experiments. Shock pressure covered in this study ranges at least up to 1 GPa. It is emphasized here that spatial and temporal uniformity of pressure distribution behind a shock wave front is very important and it can be realized in these materials by the impact method, and their precise shock propagation characteristics have been obtained by the application of the procedure developed previously by our group. Hugoniot measurements for different and systematic data for various samples are compared with shock Hugoniot curve for water. Samples used in the experiment include water gel of gelatin, NaCl aqueous solution, and finally chicken breast meat. Several samples with different initial density were used for gelatin and NaCl solution. Shock Hugoniot function for all the specimens tested can be summarized as u _s =A+B u _p , B ~ 2Value of the intercept of the relationship, A, which has the meaning of the sound velocity, is apparently dependent on the material and ambient temperature. Physical meanings of the obtained results have been discussed.     

Experimental investigation on the self-ignition of pressurized hydrogen released by the failure of a rupture disk through tubes

Hydrogen is expected to be used as a clean energy carrier. However, when high-pressure hydrogen is suddenly released into the air through tubes, self-ignition can occur by a diffusion ignition mechanism. In this paper, the phenomena of self-ignition and flame propagation during the sudden release of high-pressure hydrogen were investigated experimentally. Experimental results show that self-ignition can occur when bursting pressure is sufficiently high in spite of the shortness of the tube. For example, self-ignition was observed at a bursting pressure as high as 23.5 MPa with 50 mm long tube. When self-ignition successfully occurs, a hydrogen jet flame is produced by the ignition. The flame is then stabilized at the tube outlet. From photodiode signals and flame images, the propagation of a flame inside the tube is confirmed and the flame is detected near the rupture disk as the bursting pressure increases. When the tube length is not long enough to produce self-ignition, a hydrogen flame is observed in the only boundary layer at the end of tube and it quenches after the flame exits the tube. Consequently, the formation of a complete flame across the tube is important to initiate self-ignition, which sustains a diffusion flame after jetting out of the tube into the air. Also, in order to establish a complete flame across the tube, it is necessary to have sufficient length such that the mixing region is generated by multi-dimensional shock–shock interactions.     

Measurement of laser-induced breakdown threshold intensities of high-pressure gasses and water droplets to determine the number density of an aerosol

The laser-induced breakdown threshold intensities of high-pressure gasses as a function of pressure were measured. The breakdown threshold intensity of N₂ gas was found to be much higher than those of He and Ar gasses at a gas pressure of 2.0 MPa. It was also 7 to 11 times higher than that of aerosol droplets, and is sufficiently high to allow the number density of droplets to be measured in a high-pressure aerosol by laser-induced breakdown.     

High-pressure synthesis and structures of lanthanide germanides of LnGe5 (Ln=Ce, Pr, Nd, and Sm) isotypic with LaGe5

A series of lanthanide penta-germanides LnGe₅ (Ln=Ce, Pr, Nd and Sm) has been prepared by high-pressure (5–13 GPa) and high-temperature (500–1200 °C) reaction. CeGe₅ crystallizes in an orthorhombic unit cell (S.G. Immm (71)) with a=4.000(5) Å, b=6.192(5) Å, c=9.86(1) Å, and V=244.1(5) Å³. The new germanides are isotypic with LaGe₅ consisting of a Ge covalent network with tunnels where guest ions Ln³⁺ are situated. The network is composed of sublayers with edge-sharing Ge six-membered rings with only boat conformation. The sublayers are connected by rare eight-coordinated Ge atoms. The cell volume of the compounds systematically decreases from La to Sm compounds, except for CeGe_5, owing to the lanthanide contraction. The lattice constants of CeGe₅ are smaller than those of the Pr compound because it contains Ce⁴⁺ ions. CeGe₅ is paramagnetic above 2 K, but does not obey the Curie–Weiss law. PrGe₅ and NdGe₅ are Curie–Weiss type paramagnets with Weiss temperatures of –3.3 and –18.4 K. SmGe₅ shows an antiferromagnetic transition at 10.4 K.     

Functional form of the repulsive potential in the high pressure region

The present work is devoted to the analysis of the functional form of the repulsive potential in the framework of soft-sphere model. We used two different approaches which were based on the treatment of an equation of state and spectra of molecular light scattering at large shifts of frequencies. In particular, it has been shown that the density dependence of pressure at P>10³ MPa allowed to calculate the steepness exponent of the repulsive potential as a fitting parameter of the equation of state which possesses reliable extrapolation properties under extrapolating experimental PVT data in the high-pressure region. Processing of experimental data on a base of the statistical equation of state reveals the temperature dependence of the steepness parameter. The similar situation is also typical for the light scattering spectra. So for argon the value of this parameter varies from 15 to 10 in the gas phase and up to 24–28 in the liquid phase. The results obtained with the help of the equation of state and molecular light scattering spectra correlate well.     

Homogeneous ignition of CH4/air and H2O and CO2-diluted CH4/O2 mixtures over Pt; an experimental and numerical investigation at pressures up to 16 bar

The homogeneous ignition of CH₄/air, CH₄/O₂/H₂O/N₂, and CH₄/O₂/CO₂/N₂ mixtures over platinum was investigated experimentally and numerically at pressures 4 bar p 16 bar, temperatures 1120 K T 1420 K, and fuel-to-oxygen equivalence ratios 0.30 0.40. Experiments have been performed in an optically accessible catalytic channel-flow reactor and included planar laser induced fluorescence (LIF) of the OH radical for the determination of homogeneous (gas-phase) ignition and one-dimensional Raman measurements of major species concentrations across the reactor boundary layer for the assessment of the heterogeneous (catalytic) processes preceding homogeneous ignition. Numerical predictions were carried out with a 2D elliptic CFD code that included elementary heterogeneous and homogeneous chemical reaction schemes and detailed transport. The employed heterogeneous reaction scheme accurately captured the catalytic methane conversion upstream of the gaseous combustion zone. Two well-known gas-phase reaction mechanisms were tested for their capacity to reproduce measured homogeneous ignition characteristics. There were substantial differences in the performance of the two schemes, which were ascribed to their ability to correctly capture the p–T– parameter range of the self-inhibited ignition behavior of methane. Comparisons between measured and predicted homogeneous ignition distances have led to the validation of a gaseous reaction scheme at 6 bar p 16 bar, a pressure range of particular interest to gas-turbine catalytically stabilized combustion (CST) applications. The presence of heterogeneously produced water chemically promoted the onset of homogeneous ignition. Experiments and predictions with CH₄/O₂/H₂O/N₂ mixtures containing 57% per volume H₂O have shown that the validated gaseous scheme was able to capture the chemical impact of water in the induction zone. Experiments with CO₂ addition (30% per volume) were in good agreement with the numerical simulations and have indicated that CO₂ had only a minor chemical impact on homogeneous ignition.     

微波高压消解-火焰原子吸收光谱法测定精神病患者头发中微量元素

本文提出微波高压消解-火焰原子吸收光谱法（FAAS）测定痕量铜、锌、铁和锰的方法。该方法检检出限CU^2 、Zn^2 、Mn^2 为0.001μg/mL和Fe^3 为0.005μg/ml。Mn^2 、Fe^3 、Cu^2 和Zn^2 的含量分别在0.1-1.0、0.1-5.0、0.1-2.5和0.1-2.5μg/mL范围内测定。线性关系良好，相关系数为0.9997-0.9999，此法巳成功用于人发样中铜、锌、铁和锰含量的测定。