Use Of Precise Measurements Research Articles

Tracing the gravitational potential using cosmic voids

The properties of large underdensities in the distribution of galaxies in the Universe, known as cosmic voids, are potentially sensitive probes of fundamental physics. We use data from the MultiDark suite of N-body simulations and multiple halo occupation distribution mocks to study the relationship between galaxy voids, identified using a watershed void-finding algorithm, and the gravitational potential $\Phi$. We find that the majority of galaxy voids correspond to local density minima in larger-scale overdensities, and thus lie in potential wells. However, a subset of voids can be identified that closely trace maxima of the gravitational potential and thus stationary points of the velocity field. We identify a new void observable, $\lambda_v$, which depends on a combination of the void size and the average galaxy density contrast within the void, and show that it provides a good proxy indicator of the potential at the void location. A simple linear scaling of $\Phi$ as a function of $\lambda_v$ is found to hold, independent of the redshift and properties of the galaxies used as tracers of voids. We provide an accurate fitting formula to describe the spherically averaged potential profile $\Phi(r)$ about void centre locations. We discuss the importance of these results for the understanding of the evolution history of voids, and for their use in precision measurements of the integrated Sachs-Wolfe effect, gravitational lensing and peculiar velocity distortions in redshift space.

Study of different mathematical approaches in determining the dynamic rating of overhead power lines and a comparison with real time monitoring data

Electricity generation is changing as new, renewable and smaller generation facilities are created, and classic topologies have to accommodate this distributed generation. These changes lead to the creation of smart grids in which advanced generation, information and communication technologies are needed.Information metering is important, and one of the most important grid parameters to be measured and controlled is the temperature of overhead conductors due to their relation to the maximum allowable sag of the line.The temperature and current of an overhead conductor and the weather conditions surrounding the cable are measured every 8min for more than a year. With these data, the accuracies of the different algorithms presented in the standards (CIGRE TB601 and IEEE 738) are studied by implementing them in MATLAB®.The use of precise measurements of solar radiation and low wind speeds with ultrasonic anemometers, improves the accuracy of the estimated temperature compared with the real measured conductor temperature. Additionally, using dynamic algorithms instead of assuming a steady state analysis increases the accuracy. However, an equilibrium between the accuracy and mathematical complexity should be obtained depending on the specific needs.

Critical Crossover Functions for Simple Fluids: Non-Analytical Scaling Determination of the Ising-Like Crossover Parameter

A non-analytical scaling determination of the Ising-like crossover parameter is proposed considering the critical isochore of a simple fluid at finite distance from its critical temperature. The mean crossover functions, estimated from the bounded results of the massive renormalization scheme in field theory applied to the $$\left( \Phi ^{2}\right) _{d}^{2}\left( n\right) $$ model in three dimensions ( $$d=3$$ ) and scalar order parameter ( $$n=1$$ ), are used to formulate the corresponding scaling equations valid in two well-defined temperature ranges from the critical temperature. The validity range and the Ising-like nature of the corresponding crossover description are discussed in terms of a single Ising-like scale factor characterizing the critical isochore. The asymptotic value of this scale factor can be predicted within the Ising-like preasymptotic domain. Unfortunately, the absence of precise experimental data in such a close vicinity of the critical point leads the direct testing impossible. A contrario, from our scaling equations and the use of precise measurements performed at finite distance from the critical point, its local value can be estimated beyond the Ising-like preasymptotic domain. This non-analytical scaling determination only needs to make reference to the universal features estimated from the mean crossover functions and to introduce a single master dimensionless length common to all the simple fluids. This latter parameter guaranties the uniqueness of the physical length unit used for the theoretical crossover functions and the fluid singular properties when the generalized critical coordinates of the vapor-liquid critical point of each fluid are known. Xenon case along its critical isochore is considered as a typical example to demonstrate the singleness of the Ising-like crossover parameter. With the measurements at finite temperature range of the effective singular behaviors of the isothermal compressibility in the homogeneous domain, and the vapor-liquid coexisting densities in the non homogeneous domain, our scaling equations provide the local estimate of this crossover parameter as a function of the temperature distance from the critical temperature. Our results compare favorably with the single asymptotic value calculated only using four critical coordinates of xenon.

Gravitational “Constant” G as a Function of Quantum Vacuum Energy Density and its Dependence on the Distance from Mass

In a previous paper the author has shown the gravitational constant ruling Newton’s law can be expressed as a function of quantum variables related to Zero Point Field as Planck’s time and quantum vacuum energy density. On the other hand the quantum vacuum energy density has been proved to be modified by the presence of a mass within the volume occupied by the mass itself and in the space surrounding it. Furthermore, according to the Einstein’s Theory of General Relativity the same mass determines a gravitational potential that alters the speed of light, the clock’s rate and the particle size as a function of the distance the distance from the center of mass. All these considerations strongly suggest that also the constant G could be expressed as a function of quantum vacuum energy density somehow depending on the distance from the mass whose presence modifies the Zero Point Field energy structure. In this paper, starting from the idea of inertial mass of a body as the seat of standing waves of Zero Point Field and from the picture of a fluid-like model of space, it has been established a model in which the gravitational constant G is expressed as a function of Quantum Vacuum energy density in turn depending on the radial distance from center of the mass originating the gravitational field, supposed as spherically symmetric. The proposed model suggests the gravitational “constant” G could be not truly unchanging but varying as a function of the distance from the mass originating gravitational potential itself, whose approximate analytic expression has been also found and discussed. Finally a possible experimental test of the model, making use of precise measurements on a satellite has been outlined. The proposed theoretical model could be able to give valuable insights into a deeper understanding of the true origin and dynamics of gravity as well as the theoretical basis for unthinkable applications related, for example, to the field of gravity control and space propulsion.

Experimental investigation of models of sound wave propagation in air-saturated porous media

Several theoretical models of sound wave propagation in air-saturated porous material are studied making use of precise measurements of both physical (porosity, flow resistivity, tortuosity) and acoustical (characteristic impedance, propagation constant) parameters. The aspects covered include the use of shape factors and the adequacy of frequency-dependent dynamic viscosity functions. Experimental results on both model materials and real material are used, with special attention to the low-frequency/high-flow resistivity regime for solid frame porous materials.

Digital scattering angle pre-processors

Designs are presented for two pre-processors to analyze scattering angles measured with drift-chamber systems for use in precision measurements of channeling effects at high energies.

Galileo and the Problem of Free Fall

There can be little doubt that 1973 will remain notable as a year in which knowledge of Galileo's mechanics increased dramatically. Professor Stillman Drake's publication, in May, of some of Galileo's early work on the law of free fall was followed in the autumn by the publication of a number of important manuscripts clearly indicating Galileo's use of precise measurement. From a discussion of these manuscripts and Thomas Settle's performance of Galileo's inclined plane experiment, Drake implies that a clear view of Galileo's use of experiment is now emerging. Added emphasis was given to Drake's thesis that doubts concerning Galileo's use of experiment were largely unfounded, by James MacLachlan's realization of a Galilean experiment which was previously described as ‘imaginary’ by Koyré. The purpose of this paper is to suggest that, while it cannot be doubted that Galileo used experiment and precise measurement, his attitude to observation may well have been far more complex than Drake has supposed. My point of departure is James MacLachlan's remark that continuing disagreement over Galileo's use of experiment should lead to further examination of Galileo's experimental claims. I shall indicate that more than one view of Galileo's use of experiment may prove capable of explaining our present knowledge—a corollary of this being that alternative explanations may be proposed for the manuscripts recently published by Drake.

Gas Thermal-Conductivity Studies at High Temperature. Line-Source Technique and Results in N2, CO2, and N2-CO2 Mixtures

A new technique for measuring the thermal conductivity of gases over a fairly wide temperature range is described. The method makes use of precise measurements of the thermal-wake widths downstream of a steady line source of heat in a uniform laminar flow of the test gas. The theory and practice of the method are discussed, and it is shown to have advantages over conventional methods in that it is an absolute technique requiring measurement only of distance, gas velocity, and relative temperature differences. The technique has been tested on N2 and CO2 over the range 300–1100°K with results that agree well with previously reported work done by conventional means. Measurements on N2-CO2 mixtures covering the entire composition range and in the same temperature interval are also presented. These are compared with kinetic-theory calculations using the best available input data. The results are then used to predict the thermal conductivity of N2, CO2, and N2-CO2 mixtures up to 2000°K with what is believed to be the most reliability which is presently possible.

New Germanium Standard Wavelengths in the Region from 1998 A to 1630 A*

The application of interferometric and grating measurements in the long wavelength region of the germanium arc spectrum in connection with the extended analysis of this spectrum permits the calculation of precise wavelengths of 69 Ge i lines in the vacuum ultraviolet region on the basis of Ritz’s combination principle. This furnishes a welcome enrichment and extension of the list of Ge i vacuum ultraviolet standards obtained by VanVeld and Meissner on the same basis by the use of precision measurements in the short wavelength region. Most of these lines can be recommended as reliable secondary standards in the vacuum region.

Precise geodetic measurements and their relation to seismological investigations

The use of precise measurements is becoming more general in efforts to interpret the phenomena connected with changes in the Earth's surface. It may be that the use of these precise measurements will eventually lead to a more exact knowledge as to how the Earth s surface originally became so irregular with great areas standing high, as continents, and other areas depressed, as ocean basins.The science of seismology is adding much to our exact data. The locations of the epicenters of earthquakes and the determination of their intensity and the rate of transmission of the earthquake‐shocks through the Earth's materials at different depths furnish information of the highest value.