Search

We derive the mass-temperature relation using an improved top-hat model and a continuous formation model which takes into account the effects of the ordered angular momentum acquired through tidal-torque interaction between clusters, random angular momentum, dynamical friction, and modifications of the virial theorem to include an external pressure term usually neglected. We show that the mass-temperature relation differs from the classical self-similar behavior, $M \propto T^{3/2}$, and shows a break at $3--4$ keV, and a steepening with a decreasing cluster temperature. We then compare our mass-temperature relation with those obtained in the literature with $N$-body simulations for $f(R)$ and symmetron models. We find that the mass-temperature relation is not a good probe to test gravity theories beyond Einstein's general relativity, because the mass-temperature relation of the $\Lambda$CDM model is similar to that of the modified gravity theories., Comment: 11 pages; 2 figures; matches the published Phys. Rev. D version

Researchers and engineers use the voltage–temperature ( $V$ – $T$ ) relation to calculate the maximum temperature of electric contacts from contact voltage drop and thus evaluate their performance. However, researchers found deviations from the $V$ – $T$ relation for large contact systems when heat dissipation to the environment becomes significant. We investigated the applicability of the $V$ – $T$ relation to high-power contact systems with spring-loaded contact elements. Such connections with rated normal currents of several kiloamperes and short-time withstand currents of several tens of kiloamperes are used in high-voltage switchgear. We loaded a connector cooled by a potent variable water cooling system with continuous ac up to 6.7 kA to create a multitude of thermally symmetric and asymmetric steady-state operating points. However, temperature differences in the contact system remained below 20 K. Temperature differences calculated with the $V$ – $T$ relation were 23% higher than the measured values, but nevertheless deliver an assessment of the maximum contact system temperature valid for engineering purposes. In the case of a 1-s, 20-kA short-circuit current, a transient temperature rise occurs in the contact system. We numerically calculated the development of the spatial temperature distribution over time and found significant differences to the electric–thermal steady state. While contacts react very quickly and even oscillate with twice the line frequency on ac load, the contact element and conductor continuously heat up and do not reach the steady state.

The viscosity of glass is the most important technological property to glass manufactures and various applications. Practically, finding an accurate equation to express the glass viscosity behavior in the entire glass transition temperature range is tremendously challenge because it spans more than ten orders of magnitude. After a brief review of existing empirical viscosity equations, this work focuses on the correlating silica viscosity behavior with the evolution of glass medium-range structure, based on the recently proposed nanoflake model. From this new model, a new equation is constructed, which correctly describes the Arrhenius-type behavior of silica viscosity η above the melting temperature Tm, and non-Arrhenius-type behavior from Tm to a critical temperature Tc. At temperature lower than Tc, the equation predicts Arrhenius-type behavior again for the viscous flow with increased activation energy. The new equation agrees with experimental data in the entire temperature spanned from extremely high to extremely low. The application of the new equation is shown to extend to sodium silicate glasses as well.

In work results of a numerical research of influence of viscosity-temperature relation on structure of a convective Couette flow of thermoviscous liquid are presented in ring area between two coaxial cylinders under a condition when one of them has more high temperature. Comparison of a convective Couette flow of model liquid with non-monotone temperature dependence of viscosity and liquid with constant viscosity is carried out. Depending on parameters of viscosity anomaly the steady and oscillation flow regimes both with periodic and with not repeating fluctuations of vortex structures are found. The number of time-constant vortex structures also depends on parameters of viscosity anomaly.

Measured yields and ion temperatures inferred from the fusion product energy spectra can be used as metrics for the performance of an ICF implosion. This can be used to infer species separation, thermal decoupling, flows, or other effects that can cause the inferred ion temperatures to deviate from the true underlying thermal temperature and the yield ratio to deviate from the expected value. Direct inference of the impact of these effects on observed temperatures and yields can be difficult to uncover due to the underlying dependence on the shape and time evolution of the temperature and density profiles of the fusing plasma. Due to differences in the temperature dependence of the reactivities, different fusion products are emitted from different regions and times within the implosion. In order to properly account for this, a second-order analytical expression relating the apparent temperatures and yield ratios is developed. This expression can be coupled to models of yield and/or temperature altering effects to infer their burn-averaged impact on an implosion. The second-order expression shows significant improvement over lower-order expressions in synthetic data studies. Demonstrations of its applications to synthetic data coupled with models of ion thermal decoupling and radial flows are presented. In the case of thermal decoupling, both first and second-order expressions show reasonable levels of accuracy. To consistently infer the amplitude of radial flow with a

Observations and numerical simulations have shown that the relation between the mass scaled with the critical density of the universe and the X-ray temperature of galaxy clusters is approximately represented by $M_\Delta \propto T_X^{3/2}$ (e.g. $\Delta=500$). This relation is often interpreted as evidence that clusters are in virial equilibrium. However, the recently discovered fundamental plane (FP) of clusters indicates that the temperature of clusters primarily depends on a combination of the characteristic mass $M_s$ and radius $r_s$ of the Navarro-Frenk-White profile rather than $M_\Delta$. Moreover, the angle of the FP revealed that clusters are not in virial equilibrium because of continuous mass accretion from the surrounding matter. By considering both the FP and the mass dependence of the cluster concentration parameter, we show that this paradox can be solved and the relation $M_\Delta \propto T_X^{3/2}$ actually reflects the central structure of clusters. We also find that the intrinsic scatter in the halo concentration-mass relation can largely account for the spread of clusters on the FP. We also show that X-ray data alone form the FP and the angle and the position are consistent with those of the FP constructed from gravitational lensing data. We demonstrate that a possible shift between the two FPs can be used to calibrate cluster masses obtained via X-ray observations., Comment: Published on ApJ. Matched to published version

We introduce a new test to study the Cosmological Principle with galaxy clusters. Galaxy clusters exhibit a tight correlation between the luminosity and temperature of the X-ray-emitting intracluster medium. While the luminosity measurement depends on cosmological parameters through the luminosity distance, the temperature determination is cosmology-independent. We exploit this property to test the isotropy of the luminosity distance over the full extragalactic sky, through the normalization $a$ of the $L_X-T$ scaling relation and the cosmological parameters $\Omega_m$ and $H_0$. We use two almost independent galaxy cluster samples: the ASCA Cluster Catalog (ACC) and the XMM Cluster Survey (XCS-DR1). Interestingly enough, these two samples appear to have the same pattern for $a$ with respect to the Galactic longitude. We also identify one sky region within $l\sim (-15^o,90^o)$ (Group A) that shares very different best-fit values for $a$ for both samples. We find the deviation of Group A to be $2.7\sigma$ for ACC and $3.1\sigma$ for XCS-DR1. This tension is not relieved after excluding possible outliers or after a redshift conversion to the CMB frame is applied. Using also the HIFLUGCS sample, we show that a possible excess of cool-core clusters in this region, cannot explain the obtained deviations. Moreover, we tested for a dependence of the $L_X-T$ relation on supercluster environment. We indeed find a trend for supercluster members to be underluminous compared to field clusters. However, the fraction of supercluster members is similar in the different sky regions. Constraining $\Omega_m$ and $H_0$ via the redshift evolution of $L_X-T$ and the luminosity distance, we obtain approximately the same deviation amplitudes as for $a$. The observed behavior of $\Omega_m$ for the sky regions that coincide with the CMB dipole is similar to what was found with other cosmological probes as well., Comment: 18 pages, 15 figures, accepted for publication in A&A

Urban areas exhibit a variable land surface temperature (LST) pattern that can be linked to albedo variations. In this work, different spaceborne and airborne sensors have been considered to infer the albedo-LST relation in two urban areas (the cities of Perugia and Aprilia, in Central Italy), in July. Also, an in situ campaign for the measurement of albedo and LST values was carried out in Perugia. The study reveals the expected “inverse” relation albedo-LST (growing LST with decreasing albedo), with surfaces having albedo around 0.10 that can produce an average surface heating greater than 60 °C in July. The observations provide an indication of the global variability of these parameters and their relation in space and time. Furthermore, an analysis at different times can point out an average albedo variation for the same built-up area that could be ascribed to the materials used for new settlements and for existing construction refurbishment

We measure the evolution of the velocity dispersion--temperature ($\sigma_{\rm v}$--$T_{\rm X}$) relation up to $z = 1$ using a sample of 38 galaxy clusters drawn from the \textit{XMM} Cluster Survey. This work improves upon previous studies by the use of a homogeneous cluster sample and in terms of the number of high redshift clusters included. We present here new redshift and velocity dispersion measurements for 12 $z > 0.5$ clusters observed with the GMOS instruments on the Gemini telescopes. Using an orthogonal regression method, we find that the slope of the relation is steeper than that expected if clusters were self-similar, and that the evolution of the normalisation is slightly negative, but not significantly different from zero ($\sigma_{\rm v} \propto T^{0.86 \pm 0.14} E(z)^{-0.37 \pm 0.33}$). We verify our results by applying our methods to cosmological hydrodynamical simulations. The lack of evolution seen in our data is consistent with simulations that include both feedback and radiative cooling., Comment: Accepted to MNRAS (3 August 2016); Paper: 15 pages, 12 figures; Appendix A: 1 table; Appendix B: 34 Tables; Appendix C: 2 Figures

We present \Chandra\ observations of 23 galaxy groups and low-mass galaxy clusters at $0.03, Comment: 14 pages, 11 figures, 7 tables

The XXL Survey is the largest homogeneous survey carried out with XMM-Newton. Covering an area of 50 deg$^{2}$, the survey contains several hundred galaxy clusters out to a redshift of $\approx$2 above an X-ray flux limit of $\sim$5$\times10^{-15}$ erg cm$^{-2}$ s$^{-1}$. This paper belongs to the first series of XXL papers focusing on the bright cluster sample. We investigate the luminosity-temperature (LT) relation for the brightest clusters detected in the XXL Survey, taking fully into account the selection biases. We investigate the form of the LT relation, placing constraints on its evolution. We have classified the 100 brightest clusters in the XXL Survey based on their measured X-ray flux. These 100 clusters have been analysed to determine their luminosity and temperature to evaluate the LT relation. We used three methods to fit the LT relation, with two of these methods providing a prescription to fully take into account the selection effects of the survey. We measure the evolution of the LT relation internally using the broad redshift range of the sample. Taking into account selection effects, we find a slope of the bolometric LT relation of B$_{\rm LT}=3.08\pm$0.15, steeper than the self-similar expectation (B$_{\rm LT}$=2). Our best-fit result for the evolution factor is $E(z)^{1.64\pm0.77}$, consistent with "strong self-similar" evolution where clusters scale self-similarly with both mass and redshift. However, this result is marginally stronger than "weak self-similar" evolution, where clusters scale with redshift alone. We investigate the sensitivity of our results to the assumptions made in our model, finding that using an external LT relation as a low-z baseline can have a profound effect on the measured evolution. However, more clusters are needed to break the degeneracy between the choice of likelihood model and mass-temperature relation on the derived evolution., Comment: 16 pages, 9 figures. Accepted for publication in A&A

We propose that the mass-temperature relation of galaxy clusters is a prime candidate for testing gravity theories beyond Einstein's general relativity, for modified gravity models with universal coupling between matter and the scalar field. For non-universally coupled models we discover that the impact of modified gravity can remain hidden from the mass-temperature relation. Using cosmological simulations, we find that in modified gravity the mass-temperature relation varies significantly from the standard gravity prediction of $M \propto T^{1.73}$. To be specific, for symmetron models with a coupling factor of $\beta=1$ we find a lower limit to the power law as $M\propto T^{1.6}$; and for f(R) gravity we compute predictions based on the model parameters. We show that the mass-temperature relation, for screened modified gravities, is significantly different from that of standard gravity for the less massive and colder galaxy clusters, while being indistinguishable from Einstein's gravity at massive, hot galaxy clusters. We further investigate the mass-temperature relation for other mass estimates than the thermal mass estimate, and discover that the gas mass-temperature results show an even more significant deviations from Einstein's gravity than the thermal mass-temperature., Comment: Updated, submitted to A&A

Experimental results suggest that the mechanical properties of mild steel at elevated temperatures are affected by the cyclic load history previously applied to the material. This has great implications when it comes to post-earthquake fire analyzes. Therefore, it is desirable to establish the relationship for each mechanical property, not only as a function of temperature but also the damage induced by the cyclic load history. To achieve this goal, a special class of functions known as Bezier curves have been utilized in this research. These functions are used for the construction of stress–strain curves that depend on temperature and the amplitude of the previously applied strain cycles. Actual experimental results are used throughout the process for calibration and validation purposes. The proposed model proves to be highly versatile in the sense that it can successfully take the effect of temperature and pre-induced strain cycles into account, making it applicable to post-earthquake fire analyzes.

Casting simulation results are only useful to a foundry if they reflect reality, which requires accurate material datasets for the alloys being simulated. Material datasets include property data such as density, specific heat and thermal conductivity as functions of temperature, as well as latent heat of solidification and a solid fraction–temperature relation. Unfortunately, there are a significant number of commonly used metal alloys for which no reliable material data are available. The present study focuses on five such corrosion resistant alloys: superaustenitic stainless steel CN3MN, duplex stainless steels CD3MN and CD4MCuN and nickel based alloys CW6MC and N3M. Initial alloy material datasets are generated using thermodynamic simulation software. Comparisons of temperatures measured in full scale sand castings made from these alloys with temperatures predicted in computer simulations revealed that these initial datasets are inadequate. Therefore, an iterative method is developed to adjust the datasets (in particular the solid fraction–temperature relation and latent heat) in order to match measured and predicted temperatures and cooling rates. Uncertainties in the simulation are effectively eliminated through parametric studies. Although more tedious, the present iterative method to determine the solid fraction–temperature relation and latent heat is believed to be more accurate than traditional cooling curve analysis using small experimental castings.

Based on the dynamics of vitrification process driven by the configurational entropy, a novel expression of viscosity- temperature relation with the form of Fermi-type function is deduced below melting temperature by supposed an exponential function of average aggregation energy with temperature. The ‘molecular rearrangement’ to form aggregated regions at temperatures below the melting temperature is major contribution to the aggregation energies for describing vitrification process. The expression of relaxation time or viscosity is confirmed with several super-cooled liquids in broad temperature region. The expression contains the Vogel-Fulcher relation in limited temperature region and can avoid Kauzmenn paradox. The derived fragility shows that a reduced temperature may be a common structural variable in comparing various glassy liquids.

We derive constraints on the mass-temperature relation of galaxy clusters from their observed luminosity-temperature relation and X-ray temperature function. Adopting the isothermal gas in hydrostatic equilibrium embedded in the universal density profile of dark matter halos, we compute the X-ray luminosity for clusters as a function of their hosting halo mass. We find that in order to reproduce the two observational statistics, the mass-temperature relation is very tightly constrained as T_{gas} = (1.5~2.0)keV (M_{vir}/10^{14}h_{70}^{-1}M_\odot)^{0.5~0.55}, and a simple self-similar evolution model (T_{gas} \propto M_{vir}^{2/3}) is strongly disfavored. In the cosmological model that we assume (a \Lambda CDM universe with \Omega_0=0.3, \lambda_0=0.7 and h_{70}=1), the derived mass-temperature relation suggests that the mass fluctuation amplitude \sigma_8 is 0.7--0.8., Comment: 25 pages, 10 figures. Omission of scaling of 1/h**2 in several figures is corrected. Conclusions remain unchanged. ApJ 2003 June 10 issue, in press

An attempt to select the most suitable force-distance relation between a dislocation and the agglomerate (trimer) of impurity-vacancy dipoles in annealed KCl:Sr2+ (SrCl2 0.050 mol% in the melt) single crystals was conducted among the four models: the Fleischer’s model, a square, a parabolic, and a triangular force-distance relations. These models are taken into account the Friedel relation between the effective stress and the average dislocation segments. This was carried out on the basis of the temperature dependence of p1 τ , which reveals the force-distance profile. Unfortunately, there is no difference in the linear p1 τ -temperature relation for the four models. Therefore, it is difficult to select the most suitable model of the four from the linear plots of effective stress vs. temperature.

The evolution of the properties of the hot gas that fills the potential well of galaxy clusters is poorly known, since models are unable to give robust predictions, and observations lack a sufficient redshift leverage and are affected by selection effects. Here, with just two high-redshift, z≈ 1.8, clusters avoiding selection biases, we obtain a significant extension of the redshift range and we begin to constrain the possible evolution of the X-ray luminosity versus temperature relation. The two clusters, JKCS 041 at z= 2.2 and ISCS J1438+3414 at z= 1.41, are, respectively, the most distant and the second most distant clusters, overall, that can be used for studying scaling relations. Their location in the X-ray luminosity versus temperature plane, with an X-ray luminosity five times lower than expected, suggests at the 95 per cent confidence level that the evolution of the intracluster medium has not been self-similar in the last three-quarters of the age of the Universe. Our conclusion is reinforced by data on a third, X-ray-selected, high-redshift cluster, too faint for its temperature when compared to a sample of similarly selected objects. Our data suggest that non-gravitational effects, such as the baryon physics, influence the evolution of galaxy clusters. Precise knowledge of evolution is central for using galaxy clusters as cosmological probes in planned X-ray surveys, such as WFXT or JDEM.

A new relation for the Ms temperature prediction is proposed. The composition ranges covered by the new model are enlarged compared to the classical relations. This new relation is obtained from a data base of almost 1000 different compositions. The predictive ability of this new relation is compared to the classical ones.

A single-sinker magnetic suspension densimeter based on Archimedes’ buoyancy principle is described. Density measurements on high-purity nitrogen demonstrate the performance of the densimeter. Comprehensive (p, ρ, T) measurements at low densities on a gaseous mixture with mole fraction of (0.8977CH4 + 0.1023N2) were carried out on this densimeter at six temperatures from (170.586 to 270.054) K and at pressures ranging from (0.1333 to 1.5945) MPa. The overall uncertainty in density is estimated to be 0.1%. The uncertainty in temperature is estimated to be 5 mK and that in pressure is 250 Pa for (0 to 1.5) MPa and 390 Pa for (1.5 to 3) MPa, respectively. The experimental results of the (methane + nitrogen) mixture were compared with REFPROP 9.0, which used GERG-2008 and AGA8 equations of state to predict thermophysical properties of natural gas. The absolute relative deviations of density measurements are all within 0.1%. Meanwhile the experimental results were correlated using the virial equation of state (Virial EOS) with three different mixing rules. The calculated results using the virial EOS combined with VDW mixing rule show good agreement with the experimental data.

We measure the evolution of the X-ray luminosity-temperature (L_X-T) relation since z~1.5 using a sample of 211 serendipitously detected galaxy clusters with spectroscopic redshifts drawn from the XMM Cluster Survey first data release (XCS-DR1). This is the first study spanning this redshift range using a single, large, homogeneous cluster sample. Using an orthogonal regression technique, we find no evidence for evolution in the slope or intrinsic scatter of the relation since z~1.5, finding both to be consistent with previous measurements at z~0.1. However, the normalisation is seen to evolve negatively with respect to the self-similar expectation: we find E(z)^{-1} L_X = 10^{44.67 +/- 0.09} (T/5)^{3.04 +/- 0.16} (1+z)^{-1.5 +/- 0.5}, which is within 2 sigma of the zero evolution case. We see milder, but still negative, evolution with respect to self-similar when using a bisector regression technique. We compare our results to numerical simulations, where we fit simulated cluster samples using the same methods used on the XCS data. Our data favour models in which the majority of the excess entropy required to explain the slope of the L_X-T relation is injected at high redshift. Simulations in which AGN feedback is implemented using prescriptions from current semi-analytic galaxy formation models predict positive evolution of the normalisation, and differ from our data at more than 5 sigma. This suggests that more efficient feedback at high redshift may be needed in these models.

A testing device for the resistivity of high-temperature melt was adopted to measure the l resistivity of In–Bi system melts at different temperatures. It can be concluded from the analysis and calculation of the experimental results that the resistivity of In x Bi 100− x ( x = 0–100) melt is in linear relationship with temperature within the experiment temperature range. The resistivity of the melt decreases with the increasing content of In. The fair consistency of resistivity of In–Bi system melt is found in the heating and cooling processes. On the basis of Novakovic's assumption, we approximately estimated the content of InBi atom clusters in In x Bi 100− x melts with the resistivity data by equation ρ ≈ ρ InBi x InBi + ρ m (1 − x InBi ). In the whole components interval, the content corresponds well with the mole fraction of InBi clusters calculated by Novakovic in the thermodynamic approach. The mole fraction of InBi type atom clusters in the melts reaches the maximum at the point of stoichiometric composition In 50 Bi 50 .

We investigate the form and evolution of the X-ray luminosity-temperature (LT) relation of a sample of 114 galaxy clusters observed with Chandra at 0.1 0.5 and discuss the effect of this on measurements of the evolution in the LT relation.

An attempt to select the most suitable force-distance relation between a dislocation and the monovalent cation impurity in KCl:Li+ (LiCl 0.5 mol% in the melt) and KCl:Na+ (NaCl 0.5 mol% in the melt) was conducted among the three models: a square, a parabolic, and a triangular force-distance relations. These models are taken into account the Friedel relation. The grope for the most suitable model was carried out at 80-300 K by roportionality of ∆H(T) . The ∆H(T) is the activation enthalpy for the interaction between a dislocation and an impurity as a function of temperature. As a result, the square force-distance relation seemed to be the most suitable of the three for KCl:Na+. However, it was difficult to select that for KCl:Li+. ∆H (Tc) was further obtained on the three force-distance relations for both the pecimens. ∆H (Tc) corresponds to the activation enthalpy for overcoming the strain field with cubic distortion around the substitutional impurity by a dislocation without an applied stress.

A gas-controlled heat-pipe is used at the Italian National Research Institute of Metrology (INRIM) to realise the mercury (liquid + vapour) equilibrium from (450 to 700) K. The pressure in the heat pipe is controlled between (5 and 200) kPa by means of an innovative computer-driven system having a pressure sensitivity of a few parts per million. The vapour pressure of 0.9999999 pure mercury has been measured between (500 and 665) K. A standard pressure balance and a standard platinum resistance thermometer (SPRT) calibrated at the ITS-90 fixed points, were used. The experimental data obtained are fitted to a semi-empirical relationship between vapour pressure and temperature. The basic features of gas-controlled heat pipes and the metrological quality of the temperature and pressure measurements available in the laboratory, allowed the determination of the mercury vapour pressure at the level of a few parts in 10 −5 . The paper reports the acquired data and the evaluated relationship, together with the uncertainty budget of the associated measurements. A complete description of the mercury heat-pipe, the gas controlled system, the measuring instruments involved and the temperature and pressure data acquisition and processing is also presented. The relationship between temperature and pressure of the mercury liquid–vapour transition has then been derived and it is here reported together with the mathematical and experimental uncertainty budgets. An accurate comparison with the existing data is also reported.