The vapor pressure over a binary ordered ferromagnetic alloy

The saturated vapor pressure over a binary alloy in which both atomic and magnetic ordering can occur has been calculated. The temperature dependence of the pressure exhibits special features at the magnetic and structural transformation points. From a knowledge of the temperature dependence of the vapor pressure in the high-temperature range, a number of physical characteristics of the alloy can be determined experimentally.     

Einstein's paradox and a new mixing paradox

A study is made of Einstein's paradox for the isothermal mixing of ideal quantum gases and also of a new paradox when such gases are mixed adiabatically. Both paradoxes are resolved.     

The dynamics of a vapor bubble containing a hot particle in pressure wave

The dynamics and heat and mass exchange in the pressure wave of a vapor bubble containing a hot particle was investigated parametrically. The influence of the particle size and temperature, of the liquid temperature and static pressure, and the wave amplitude on the dynamics of such a two-phase bubble was studied. A procedure is proposed to estimate the least value of the thickness of a vapor layer around the particle. The work was supported financially by the President of Russian Federation (NSh-7055.2006.1).     

The law of corresponding states for the saturation vapor pressure of a liquid

Graphical examination of Maxwell's rule is employed with Van der Waals' equations to give a graphical relation of saturation vapor pressure to temperature from the law of corresponding states. An analytic approximation is compared with experiment and with an approximation for the experimental mean curve. Phenomenological arguments are employed to derive the latent heat of evaporation of the liquid and the critical temperature of the vapor in terms that are correct to a first approximation for all substances.     

制冷系统的广义预测控制方法研究

制冷系统的蒸发器过热度的控制对于制冷系统稳定、高效运行具有重要作用。文中通过实验辨识了基于过热度和蒸发温度的制冷系统多输入多输出模型,并采用广义模型预测控制方法,针对制冷系统的变负荷运行工况下进行了实验研究。结果表明,该方法很好的适应了制冷系统变过热度、变蒸发温度的控制要求,相比常规的单输入单输出PID控制,跟踪性能良好、动态控制精度高,可以适应制冷系统负荷大范围变动的控制需求。     

Water vapor overtones pressure line broadening and shifting measurements

By using a spectrometer having as source a commercial etherostructure Al _x Ga_{1 − x} As diode laser operating in “free-running mode”, line shape parameters of some water vapor ro-vibrational overtones at 820–830 nm have been measured at room temperature. These weak absorption lines have been detected by using the wavelength modulation spectroscopy technique with second-harmonic detection. The broadening and shifting coefficients have been obtained by fitting the collected second-harmonic absorption features while varying the pressure of different foreign gases.     

On a paradox of probability theory

Costa de Beauregard's proposal concerningretrocausality is formulated in terms of conditional probabilities. In its current formulation his proposal reveals a paradox intrinsic to elementary probability theory. The paradox is perhaps related to the nonlocal causality revealed through Bell's theorem.     

Characteristics of the Na/beta-alumina/Na cell as a sodium vapor pressure sensor

The EMF and voltage-current characteristics for a galvanic cell with the configuration Na vapor (P₁)/sodium beta-alumina/Na vapor (P₂) were studied. It was verified that the EMF followed the Nernst relation over a wide pressure range. For example, when P₁ = 2 × 10^-2 mm Hg and beta-alumina temperature = 340°C, the measured EMF agreed with the calculated value in P₂ range from 10^-5 to 10^-2 mm Hg. At lower pressure range, the measured EMF showed a negative deviation. Coexisting argon gas did not influence the cell EMF characteristic. In an atmosphere containing oxygen, the measured EMF was very high at first. Then it decreased and finally approached a value which agreed with the Nernst equation after several hours. At low beta-alumina temperatures, current saturation was observed in the voltage versus current relation with the anode on the P₂ side. Although the sodium pressure could be determined from saturating current measurement, the measurable pressure range was narrower than that for EMF measurement. At high beta-alumina temperature, current saturation was not clear. Values of 6 × 10^-6 (Ω cm)^-1 for the electron conductivity and 6 × 10^-10 (Ω cm)^-1 for the hole conductivity at 340° were obtained for beta-alumina from the voltage-current characteristics at low sodium pressure.     

Mathematical simulation of the compression process of a vapor bubble at a pressure increase in the surrounding liquid

The thermophysical and hydrodynamic processes in a spherical vapor bubble and the surrounding liquid at increasing external pressure are investigated by using a numerical simulation method. The investigation is performed on the basis of a new mathematical model belonging to the class of models of homobaric bubbles (the pressure in the bubble is homogeneous at nonhomogeneous temperature and density). The model takes into account the following main physical effects: the viscosity of the liquid, the heat conductivity of the liquid and vapor, the surface tension, and the phase transitions at the bubble surface. An energy equation taking into account convective heat transfer and viscous dissipation in the liquid is used to calculate the temperature fields in the liquid and vapor. The model also takes into account the dependence of the thermophysical properties on the temperature. A distinctive feature of the proposed model is that the integral conservation law of the system’s total energy (including the kinetic energy of the liquid, the surface energy, and the internal energy of the liquid and vapor) is exactly satisfied (without allowance for the kinetic energy of the vapor). As a result of the numerical simulation of the compression of vapor bubbles in water, we obtained data for the major characteristics of the process at considerable degrees of compression. It is shown that the heat and mass transfer between the vapor in a bubble and the surrounding liquid considerably slow down the temperature increase in the bubble.     

蒸气压对激光辐照靶材烧蚀速率的影响

研究了强激光辐照碳/碳复合材料靶材引起的烧蚀现象及蒸气压对烧蚀速率的影响。基于傅里叶定律,建立了强激光辐照靶材的热传导模型,模拟了忽略蒸气压影响时烧蚀速率随功率的变化;通过Mott-smith近似方法描述了Knudsen层间断区域,分析了间断两侧表面粒子状态参数;结合质量连续方程和蒸气压与温度关系方程,并由气体状态方程描述蒸气流状态,对蒸气压条件下激光烧蚀碳/碳复合材料靶材的速率随功率变化的关系进行了数值模拟。结果表明,在高能激光对靶材的烧蚀过程中,蒸气压力变化会导致靶材的饱和蒸气温度发生变化,进而影响烧蚀速率且使其随功率呈非线性变化,与忽略蒸气压作用时的线性变化规律相差较大,从理论上解释了忽略蒸气压导致的实验数据与理论结果的差异。     

Spectroscopy of output pressure dependences of water vapor passed through adsorbent

The output concentration pressure dependences of the water vapor passed in portions through a layer of MN-200 adsorbent whose delay and shape drastically depend on the parameters of introduced portions are determined using diode-laser spectroscopy. A model describing the experimental data and demonstrating the important role of interphase mass-exchange lag in the process of water vapor propagation in a porous-granular medium is proposed.     

Influence of the iodine vapor pressure on the output characteristics of a UV low-pressure gas-discharge lamp

The influence of the iodine vapor pressure on the output characteristics of a UV lamp pumped by a longitudinal glow discharge is studied. The lamp is filled with a helium-iodine mixture to a pressure of 100–1500 Pa. In the spectral range 320–360 nm, the I₂(D′ → A′) band with a peak at 342 nm prevails, while in the bactericidal range, iodine atomic lines at 183.0 and 206.2 nm dominate. The power of the UV lamp is optimized according to the iodine vapor pressure and working mixture composition by numerical simulation.     

On the pressure dependent sensitivity of a photoacoustic water vapor detector using active laser modulation control

A detailed study on the pressure dependent sensitivity of a wavelength modulated diode laser based photoacoustic (PA) water vapor detection system is presented. It is shown that the pressure dependence of sensitivity is primarily determined by the pressure dependence of the microphone’s sensitivity and the quality factor of the excited acoustic resonance of the PA cell. Effort was made to improve the system’s sensitivity for the whole pressure range (from 200 mbar to 1000 mbar) of operation typical in atmospheric research, while maintaining the inherent fast response time of the PA system. For this purpose active control of modulation based on the continuous adjustment of the unmodulated and modulated parts of the laser current in accordance with the actual gas pressure was introduced, with which a minimum detectable water vapor concentration (3σ) of 300 ppb at 200 mbar and 188 ppb at 1000 mbar was achieved. The system’s sensitivity improves slightly at the lower end of the pressure range and increases by a factor of more than two at the higher end, when compared with that of our PA system currently on board of a commercial aircraft within the framework of an atmospheric research project (CARIBIC—Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container). Test measurements proved the feasibility of the implementation of the developed modulation method within the framework of the CARIBIC project.     

Low pressure chemical vapor deposition of niobium coating on silicon carbide

Nb coatings were prepared on a SiC substrate by low pressure chemical vapor deposition using NbCl₅. Thermodynamic calculations were performed to study the effect of temperature and partial pressure of NbCl₅ on the final products. The as-deposited coatings were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The Nb coatings are oriented and grow in the preferred (2 0 0) plane and (2 1 1) plane, at 1173 K and 1223-1423 K, respectively. At 1123-1273 K, the deposition is controlled by the surface kinetic processes. The activation energy is found to be 133 kJ/mol. At 1273-1373 K, the deposition is controlled by the mass transport processes. The activation energy is found to be 46 kJ/mol. The growth mechanism of the chemical vapor deposited Nb is also discussed based on the morphologies and the deposition rates.     

Measurements of near-IR water vapor absorption at high pressure and temperature

Tunable diode lasers (TDLs) are used to measure high resolution (0.1 cm^-1), near-infrared (NIR) water vapor absorption spectra at 700 K and pressures up to 30 atm within a high-pressure and -temperature optical cell in a high-uniformity tube furnace. Both direct absorption and wavelength modulation with second harmonic detection (WMS-2f) spectra are obtained for 6 cm^-1 regions near 7204 cm^-1 and 7435 cm^-1. Direct absorption measurements at 700 K and 10 atm are compared with simulations using spectral parameters from HITRAN and a hybrid database combining HITRAN with measured spectral constants for transitions in the two target spectral regions. The hybrid database reduces RMS error between the simulation and the measurements by 45% for the 7204 cm^-1 region and 28% for the 7435 cm^-1 region. At pressures above 10 atm, the breakdown of the impact approximation inherent to the Lorentzian line shape model becomes apparent in the direct absorption spectra, and measured results are in agreement with model results and trends at elevated temperatures reported in the literature. The wavelength-modulation spectra are shown to be less affected by the breakdown of the impact approximation and measurements agree well with the hybrid database predictions to higher pressures (30 atm). PACS 33.20.Ea; 42.62.Fi; 52.25.Os     

Klein paradox in a kerr geometry

The crossing of the classical positive and negative energy states E⁺ and E^? introduced by Christodoulou-Ruffini and interpreted within the framework of a relativistic quantum field theory by Deruelle and Ruffini, leads to a Klein paradox. It has been shown by Euler and Heisenberg that when the transmission coefficient T² through the barrier between the E⁺ and E^? states is small it is proportional to the probability of pair creation. Numerical computations show that, in the case of a small Kerr black hole (GM/c² ??/muc), the probability of pair creation of particles of mass μ is maximum when $\text{E ～ ?Ω}$, where E is the energy of the created particles and Ω and M the angular velocity and the mass of the back hole.