Development of finite fluctuations in local density, velocity, and temperature for real fluids

Analytical expressions for large-scale finite local fluctuations of temperature and collective velocity valid for all states of real fluids are presented. Models for the probability distribution of finite density and temperature fluctuations are proposed. It is demonstrated that a fluctuating fluid consists of two fractions. The basic properties of the fractions are established, and the role of each faction in the makeup of the physical and chemical properties of the fluid is specified. It is shown that the development of large-scale finite fluctuations is not an inherent feature of the critical state: it is characteristic of a wide range of states of real fluids.     

Submillimeter test of the gravitational inverse-square law: a search for "large" extra dimensions

Motivated by higher-dimensional theories that predict new effects, we tested the gravitational 1/r(2) law at separations ranging down to 218 microm using a 10-fold symmetric torsion pendulum and a rotating 10-fold symmetric attractor. We improved previous short-range constraints by up to a factor of 1000 and find no deviations from Newtonian physics.     

引入热力学温标的一种方案

提供了一种引入热力学温标的简易方案.     

Simulation of a morning air temperature inversion break-up in complex terrain and the influence on sound propagation on a local scale

A mesoscale atmospheric model is used to model the break up of a morning air-temperature inversion during a clear weather situation with low wind speeds at ground. Modified slope-radiation parameterization in the model results in more realistic predicted air temperature profiles when compared to profiles measured with a tethered balloon. A wave number integration code is used to demonstrate how the modelled atmospheric profiles can be used to predict the reduction of sound level along ground during inversion break-up.     

Ice shielding in the large scale GENIUS experiment for double beta decay and dark matter search

We suggest here the use of ice as shielding material in the large scale GENIUS experiment for the ultimate sensitive double beta decay and dark matter search. The idea is to pack a working volume of several tons of liquid nitrogens, which contains the “naked” Ge detectors, inside an ice shielding. Very thin plastic foil would be used in order to prevent leakage of the liquid nitrogen. Due to the excellent advantages of ice shielding (high purity and low cost, self-supporting ability, thermo-isolation and optical properties, safety) this could be another possible way of realization of the GENIUS project. Received: 30 July 1998     

Spontaneous Raman scattering: a useful tool for investigating the afterglow of nanosecond scale discharges in air

Nanosecond scale discharges are considered an interesting way for assisting combustion by enhancing either flame stabilization or ignition. Better understanding of energy deposit and radical species production processes is still required under pressure conditions normally encountered in combustion. The purpose of the present paper is to show that spontaneous Raman scattering, seldom used to investigate nanosecond pulsed discharges, is a useful measurement method for investigating the energy deposit of these discharges. The advantage of spontaneous Raman scattering is described by analyzing N₂ and O₂ spectra during the post-discharge of a filamentary nanosecond air discharge under atmospheric pressure, using phase-locked average spectra. The main advantages of spontaneous Raman scattering measurements are that they allow line-wise probing of different species with the same experimental setup and the determination of vibrational distribution by comparison with theoretical modeling over a wide range of vibrational levels (from v=0 to v=20 for N₂). The model proposed takes into account the high level of vibrational excitation and the strong non-equilibrium observed, allowing the characterization of the vibrational relaxation over the complete post-discharge duration. Although the rotational structure is not resolved, the rotational temperature and thus translational temperature are determined with a moderate uncertainty for T above 500 K.     

On the time variation of the surface air temperature in Genoa, Italy

Summary The annual averages of the maximum, minimum and mean daily temperatures measured at the Genoa University Observatory from 1833 to 1986 are examined. All maxima lie between 20.0°C and 17.2°C and the minima between 14.7°C and 11.5°C; while the mean values lie between 17.1°C and 13.2°C. The smallest value of every series was recorded in 1956, the coldest of the last 154 years. The courses show sequences of years with increasing and decreasing temperatures and oscillations with different amplitudes and periods. The time occurrences of the sequences and the sign of the variations agree very well with those observed in many European places while differences concerning the amount of the variations were found. The comparison between the annual mean values of the minima in Genoa and in a rural site (Mt. Cappellino) during the last 30-year period shows a smaller increase of their differences. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Effect of the stagnation temperature on supersonic flow parameters: Application for air in nozzles

When the stagnation temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this temperature. The gas remains perfect and its state equation always remains valid, except it will be called a calorically imperfect gas. The aim of this research is to develop the relations of the necessary thermodynamics and geometrical ratios and to study the supersonic flow at high temperature (lower than the threshold of dissociation). The results are found by the resolution of nonlinear algebraic equations and integration of complex analytical functions where the exact calculation is impossible. The dichotomy method is used to solve the nonlinear equation, and the Simpson algorithm is used for the numerical integration of the found integrals. A condensation of the nodes is used, since the functions to be integrated have a high gradient at the extremity of the interval of integration. A comparison is made with a calorifcally perfect gas to determine the error of this. An application is made for air in a supersonic nozzle. The text was submitted by the authors in English.     

Acoustic method for measuring air temperature and humidity in rooms

A method is proposed to determine air temperature and humidity in rooms with a system of sound sources and receivers, making it possible to find the sound velocity and reverberation time. Nomograms for determining the air temperature and relative air humidity are constructed from the found sound velocity and time reverberation values. The required accuracy of measuring these parameters is estimated.     

草地下垫面地表温度与近地面气温的对比研究

地表温度是气候系统中的关键参数,它与近地面气温的差异极大地影响着地-气界面上能量和水汽通量的交换。根据大气辐射国际联合观测网合肥站2002年9月至2005年8月三年期间无云晴天的地面观测资料,研究了该地区草地下垫面的地表温度(辐射测温法)和近地面气温的年变化、季节变化和日分布特征。着重讨论了两者差值的变化情况以及两者的相关性,提出了基于近地面气温的地表温度的经验计算方法。研究发现,当地表比辐射率ε的取值范围为0.94～1.00时,ε每改变0.01,草地地表温度的平均变化小于0.2 K。该研究结果可为卫星资料的地面验证提供参考。     

The search for ultrashort bursts of cosmic ray intensity on the Andyrchi air shower array

A new data acquisition system that makes it possible to measure the count rate of each detector of the Andyrchi air shower array every millisecond is described. This new detection system allows us to search for ultrashort bursts of cosmic ray intensity when operating the array in the single-component detection mode. The method of data acquisition and analysis is discussed.     

Low temperature electrical resistivity studies and search for superconductivity in Ti-B system

Resistivity of TiB_x alloy has been measured for three different compositions. The alloys contain the three known phases TiB₂, TiB and Ti₃B₄ and unknown phase/phases. Resistivity measurements between room temperature and 77 K show that there is no superconducting transition in this range of temperature contrary to some recent reports. Resistivity shows a small anomaly at low temperature which is attributed to the unknown phase.     

A study of the assessment of air temperature, and sensible-and latent-heat fluxes from sonic-anemometer observations

Summary In the past ten years, use of sonic anemometers to provide fast-response wind sensing in the atmospheric surface layer became more and more intensive, due to their increasing availability, decreasing cost and increasing number of publications regarding their data treatment. In this paper, we present an algorithm we have developed in order to analyse the data of one of the most diffused types of sonic anemometer,i.e. the Gill sonic anemometer. Our software allows to evaluate the air temperature and the sensible- and latent-heat fluxes if also low-response measurements of air humidity at the same level of sonic anemometer, and of net radiation and ground surface flux are available. We let our software the option of evaluating the fluxes along the mean local streamline (thus the turbulent fluxes are associated with transport across mean streamline surfaces). By using the data gathered in two field experiments, we discuss the applications of the proposed formulations and check the accuracy of our method by comparing the evaluated fluxes with those measured by fluxmeter.     

Comparison of scale factor estimators for ultrasonic temperature monitoring: Application to structural health monitoring

In Structural Health Monitoring (SHM) of materials, estimating the effects of environmental and operational conditions such as temperature is important. Indeed, temperature changes induce modifications of the mechanical properties of the material and therefore cause a dilation of the acoustic signals characterized by a scale factor. This paper described four scale factor estimators able to monitor changes in temperature: The short-time cross-correlation (STXC) method, the stretching method (STRE), the Minimum Variance Based Estimator method (MVBE) and the Scale Transform Based Estimator method (STBE). The first two methods have already been assessed in the literature while the latter two have been specifically developed for this study. First, closed-form for the Cramer-Rao bound on the estimates of the scale factor, from a simplified deterministic signal, are derived and simplified expressions are given. Then, a statistical evaluation of the quality of estimates is conducted through Monte-Carlo simulations using synthetic signals, based on a model taking into account the influence of temperature. A raw estimate of the computational complexity of signal processing methods also completes this evaluation phase. Finally, the experimental validation of estimation methods is conducted on an aluminum plate subjected to temperatures variations in a controlled thermal environment. The temperature estimates are then faced with an analytical model describing the material behavior.     

两种非等温送风恒温恒湿机的实验研究

恒温恒湿机的用途之一是通过给机电设备机房降温,完成对电子设备的降温.去掉中间的降温媒介,直接对电子设备发热截面进行吹风降温,可以减掉机房照明和维护结构的发热量,从而节省电能.对于各部位发热量不同的设备发热截面,可以通过非等温送风型恒温恒湿机,实现从冷却设备到被冷却设备的点对点降温.对于两台发热量不同的电子设备,可以应用...