Measurement of thermal conductivities of polymer films with the TC-1000 thermal comparator

The single-probe, direct reading thermal comparator has been used extensively to measure the thermal conductivity of bulk solids, liquids, and gases. With the use of an analytical heat flow model based on the work of Dryden1 and the work of Carslaw and Jeager2, the comparator can also be used to obtain an in-situ measurement of the thermal conductivity of a film while attached to a substrate. The purpose of this paper is to test this model by measuring the thermal conductivities of commercially available polymer films (DuPont Kapton and Teflon). The values obtained with the comparator were found to be 0.24 .02 (W/mK) for the Kapton film and to be 0.22 .03 (W/mK) for the Teflon film. Our results are consistent with the conductivity values issued by DuPont. The systematic uncertainty on our measurements is 45% and is mainly due to an inability to accurately estimate a model parameter called the heat flow radius . This is the radius of the effective heat flow contact area between the probe tip and the film. The TC-1000 thermal comparator technique is also reviewed in this thesis. An attempt is made to explain in detail both the calibration and operating procedures for the thermal comparator

Nuclear stopping and sideward-flow correlation from 0.35A to 200A GeV

The correlation between the nuclear stopping and the scale invariant nucleon sideward flow at energies ranging from those available at the GSI heavy ion synchrotron (SIS) to those at the CERN Super Proton Synchrotron (SPS) is studied within ultrarelativistic quantum molecular dynamics (UrQMD). The universal behavior of the two experimental observables for various colliding systems and scale impact parameters are found to be highly correlated with each other. As there is no phase transition mechanism involved in the UrQMD, the correlation may be broken down by the sudden change of the bulk properties of the nuclear matter, such as the formation of quark-gluon plasma (QGP), which can be employed as a QGP phase transition signal in high-energy heavy ion collisions. Furthermore, we also point out that the appearance of a breakdown of the correlation may be a powerful tool for searching for the critical point on the QCD phase diagram.Comment: 5 pages, 4 figure

Spatial damping of propagating sausage waves in coronal cylinders

Sausage modes are important in coronal seismology. Spatially damped propagating sausage waves were recently observed in the solar atmosphere. We examine how wave leakage influences the spatial damping of sausage waves propagating along coronal structures modeled by a cylindrical density enhancement embedded in a uniform magnetic field. Working in the framework of cold magnetohydrodynamics, we solve the dispersion relation (DR) governing sausage waves for complex-valued longitudinal wavenumber $k$ at given real angular frequencies $\omega$. For validation purposes, we also provide analytical approximations to the DR in the low-frequency limit and in the vicinity of $\omega_{\rm c}$, the critical angular frequency separating trapped from leaky waves. In contrast to the standing case, propagating sausage waves are allowed for $\omega$ much lower than $\omega_{\rm c}$. However, while able to direct their energy upwards, these low-frequency waves are subject to substantial spatial attenuation. The spatial damping length shows little dependence on the density contrast between the cylinder and its surroundings, and depends only weakly on frequency. This spatial damping length is of the order of the cylinder radius for $\omega \lesssim 1.5 v_{\rm Ai}/a$, where $a$ and $v_{\rm Ai}$ are the cylinder radius and the Alfv\'en speed in the cylinder, respectively. We conclude that if a coronal cylinder is perturbed by symmetric boundary drivers (e.g., granular motions) with a broadband spectrum, wave leakage efficiently filters out the low-frequency components.Comment: 6 pages, 2 figures, to appear in Astronomy & Astrophysic