外压对饱和蒸气压的影响

讨论了外压对液体饱和蒸气压的影响,并利用毛细现象中力学平衡条件和等温气压公式对此作了推导.     

Radiation pressure

Formulae for the radiation pressure of electromagnetic and of sound waves are reviewed. The pressure on an obstacle in the path of the waves can be calculated from the momenta of the incident and scattered trains, and it is now well established that any train of waves of intensity J propagated with speed v has momentum J/v ² per unit volume. A general proof of this result is proposed, independent of the nature of the waves.     

Ruby under pressure

The ruby luminescence method is widely used for pressure measurement in the diamond anvil cell and other optically transparent pressure cells. With this application in mind, we briefly review the ground-state physical properties of corundum (α-Al₂O₃) with some emphasis on its behavior under high pressure, survey the effects of temperature and stress on the R-line luminescence of ruby (Cr-doped corundum), and address the recent efforts towards an improved calibration of the R-line shift under hydrostatic pressures beyond the 50 GPa mark.     

Ruby-spheres as pressure gauge for optically transparent high pressure cells

Abstract

Ruby is widely used as an in siru pressure gauge for optically transparent pressure cells up to the megabar range. Usually ruby chips cut from bulk crystals are used which are ill-characterized and inconvenient to handle and to identify visually. Here we present a systematic study on corundum samples doped with Cr³⁺ ions with concentration from 60 to 23500 ppm to determine the optimal conditions for the use as an accurate pressure marker. The influence of the excitation wavelength on the luminescence spectra was investigated. These studies led to the synthesis of small (1–50 micrometer) ruby spheres with 3000 ppm chromium concentration. After annealing and a heat treatment to avoid internal strains we find reproducible values of the position and the width of the fluorescence lines. These ruby spheres are not only well suited for a reliable and accurate pressure determination in experiments using diamond anvil cells, but can also be used as an in sihr micro-thermometer in high pressure-low temperature studies.     

Ultra-high pressure apparatus

This review applies to static pressure apparatus capable of developing pressures over about 25 kbar for purposes of scientific measurements of the physical and chemical behavior of matter, and in some cases for the high-pressure, high-temperature, synthesis of materials like diamond and cubic boron nitride. A brief history is presented, and major emphasis is given to geometry and stress/strain analysis and the properties of materials that are useful in ultra-high pressure (UHP) apparatuses. Examples are given, and analyzed, of various kinds of UHP apparatuses which have been used extensively in actual service. Finally there is an assessment of the future possibilities for realizing pressures greater than those that have been attained to date.     

Water under pressure

Water under pressure is investigated by first principles molecular dynamics, with a focus on the changes in hydrogen bonding and the oxygen network in the nondissociative regime. At a pressure of 10 GPa and a temperature of 600 K, which is close to the freezing point, no appreciable molecular dissociation is observed in the simulations. However, the structure of water is substantially altered from that at ambient conditions. The liquid exhibits a much larger coordination of oxygen atoms, an essential weakening of hydrogen bonding, and sizable changes in the density of electronic states close to the Fermi level. Our results provide new structural data for direct comparison with future experiments.     

六面顶压机立方压腔内压强的定量测量及受力分析

将六面顶压机立方压腔内置入电路,采用原位电阻测量确定Bi,Tl,Ba相变的方法,标定了压腔内不同位置的压力(强).通过标定立方压腔顶锤表面的压力并结合计算,分别得到了外部加载与压腔密封边受力以及合成腔体受力的对应关系.实验分析结果表明,随着外部加载的增加,当腔体压力达到5 GPa时,消耗在压腔密封边上的加载急剧上升,消耗在合成腔体的加载趋于不变,从而导致立方压腔压力达到上限.利用实验结果,分析了立方压腔在高压下的受力状态,解释了立方压腔的压力难以超过7 GPa的原因.结合立方压腔的几何结构,通过理论分析,提出了采用高体弹模量的物质作为传压介质,同时采用低体弹模量的物质作为密封边提高立方压腔压力上限的可行方案.通过定量标定叶腊石压腔轴向的压力梯度,给出了压腔内沿对称轴不同位置压力值的计算方法,此方法可为高压实验提供更精确的压力数据.     

Impact of acoustic pressure on ambient pressure estimation using ultrasound contrast agent

Local blood pressure measurements provide important information on the state of health of organs in the body and can be used to diagnose diseases in the heart, lungs, and kidneys. This paper presents an approach for investigating the ambient pressure sensitivity of a contrast agent using diagnostic ultrasound. The experimental setup resembles a realistic clinical setup utilizing a single array transducer for transmit and receive. The ambient pressure sensitivity of SonoVue (Bracco, Milano, Italy) was measured twice using two different acoustic driving pressures, which were selected based on a preliminary experiment. To compensate for variations in bubble response and to make the estimates more robust, the relation between the energy of the subharmonic and the fundamental component was chosen as a measure over the subharmonic peak amplitude. The preliminary study revealed the growth stage of the subharmonic component to occur at acoustic driving pressures between 300 and 500 kPa. Based on this, the pressure sensitivity was investigated using a driving pressure of 485 and 500 kPa. At 485 kPa, a linear pressure sensitivity of 0.42 dB/kPa was found having a linear correlation coefficient of 0.94. The second measurement series at 485 kPa showed a sensitivity of 0.41 dB/kPa with a correlation coefficient of 0.89. Based on the measurements at 500 kPa, this acoustic driving pressure was concluded to be too high causing the bubbles to be destroyed. The pressure sensitivity for these two measurement series were 0.42 and 0.25 dB/kPa with linear correlation coefficients of 0.98 and 0.93, respectively.     

高压电导研究

高压下物质结构和性质会发生很大的改变，电导对于认识压力的作用效应和寻找新的导电材料具有重要意义．高压电导研究所采用的设备主要有金刚石压腔、超高压大腔体装置(大压机)以及高压电导池三种．金刚石压腔可达550GPa压力；超高压大腔体装置压力一般在30GPa以下，可以提供较大体积的样品；高压电导池主要进行流体的电导研究，压力在400MPa以下，有静止和流动两种类型，流动式高压电导池是近年来才发展起来的，其准确方便．文章对目前高压电导的研究进行简单的介绍和分析．     

Triangular dynamics under pressure

Three planar classical particles interact via a potential proportional to the area of the triangle they form. This system is equivalent to two oscillators attached to the origin, the nearest being repelled by and the other being attracted to it (piecewise integrable Hamiltonian). Numerical simulations show two types of trajectories: those apparently escaping to infinity, and those in confined quasiperiodic orbits. Adiabatic theories lead to discrete recurrence relations and allow for the second type only. A general method allowing prediction of first return time of the slow motion as well as a short/long-period relation is presented. The issue of the possibly metastable nature of escaping trajectories is raised.Dedicated to Prof. Philippe Choquard.     

Fiber ringdown pressure sensors

An exploratory study on a novel fiber ringdown pressure sensor is presented. With this technique, pressure measurements are achieved in a time domain by measurement of ringdown times. The proof-of-concept device consists of a diode laser light source, two 2 x 1 fiber couplers, a section of fused-silica single-mode fiber, a photodetector, and an electronic control. The sensor's performance in the areas of stability, repeatability, and dynamic range is explored. The results demonstrate the new concept of fiber pressure sensors and the technical feasibility of developing a new generation of fiber sensors for pressure measurements.     

Casimir zero-point radiation pressure

We analyze some consequences of the Casimir-type zero-point radiation pressure. These include macroscopic "vacuum" forces on a metallic layer in between a dielectric medium and an inert [epsilon(omega)=1] one. Ways to control the sign of these forces, based on dielectric properties of the media, are thus suggested. Finally, the large positive Casimir pressure, due to surface plasmons on thin metallic layers, is evaluated and discussed.     

A high pressure Raman study of KTP and pressure induced phase transitions

Potassium titanate orthrophosphate KTiOPO₄ (KTP) has been studied by high pressure Raman technique to 17 GPa using a diamond cell. The Raman data reveal that two phase transitions occur in the system: one near 5.5 GPa and another near 10 GPa. The Lower-pressure transition is definitely first-order but appears to be driven by the phonon mode near 56 cm⁻¹, which exhibits marked softening. A mean field-like behavior is observed. It is hypothesized that this transition is likely to be from ferroelectric (FE) to an antiferroelectric (AF) phase. The 10 GPa transition may be due to AF-PE (paraelectric) transition driven by pressure from high temperature to room temperature. From the larger pressure responce of the PO₄ vibrational modes it is believed that the PO₄ polyhedral compression is larger than the TiO₆ polyhedral compression. leading to polyhedral tilt transitions.     

Gold under high pressure

Abstract

First principle predictions for the equation of state of gold using solid and liquid state theories are compared up to combined pressures and temperatures of 600 GPa and 17 000 K with static diamond anvil cell compression, ultrasonic measurements and shock Hugoniot data which include a recent laser driven shock Hugoniot points at 600 GPa. Excellent agreement between theoretical and experimental data is observed. The theoretically estimated 300 K isotherm agrees to within 2 GPa with the isotherm that has been measured to 70 GPa using the diamond anvil cell. The structural energy estimates show that the normal f.c.c. phase remains stable under pressure. The estimate of the shock Hugoniot temperature of gold at 600 GPa based on a liquid state model is consistent with the measurements of laser induced shock luminescence, which in fact provides an experimental determination of the temperature of gold above its Hugoniot melting point. The powerful means provided by theory in the prediction of material properties of gold at ultra high pressures and temperatures is significant because gold is an efficient converter of laser energy into soft X-rays and is a potential candidate as a standard for high pressure, high temperature work.     

Accurate measurement of pressure

This paper briefly describes the fundamental principles of the instruments used for accurate measurement of hydrostatic pressure and in particular the use of piston gauges as primary pressure standards. Different methods for the calibration of secondary standards have been discussed and in particular, emphasis has been given to the calibration of secondary piston gauges against the primary standards by the cross-float method along with the evaluation of uncertainties attached to different correction factors associated with the measurement of pressure from these gauges. The importance of secondary pressure standards in the region 0.1 GPa to several GPa has also been defined.     

GaP at ultrahigh pressure

An x-ray diffraction experiment has been carried out on GaP compressed in a quasi-hydrostatic pressurizing medium to 296 ± 5 kbar. The transformation pressure was found to be increased from the value of 220 kbar (22 GPa) reported in a less hydrostatic environment, since two phases of GaP (I and II) were found in coexistence at 250 ± 5 kbar. No evidence of disproportionation was found at this pressure, or 296 kbar, where sharp lines of phase II were found (body centered tetragonal). No evidence of amorphization was found on release of pressure.     

Birefringent fibre-optic pressure sensor

In this paper a birefringent optical fibre sensor is used to measure the external wall pressure of a pressurized resilient tube. In the design presented here, the sensing polarization-maintaining fibre is external to the tube and the interaction alters the polarization state of the guided light which can easily be measured by conventional techniques.