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Numerical Method for Simulation of Physical Processes Represented by Weakly Singular Fredholm, Volterra, and Volterra-Fredholm Integral Equations
Published in Seshu Kumar Damarla, Madhusree Kundu, Fractional Order Processes, 2018
Seshu Kumar Damarla, Madhusree Kundu
A fluid with zero viscosity is called superfluid, which was discovered by Pyotr Leonidovich Kapitsa. The superfluidity property of fluid allows it to flow without friction past any surface, thus the fluid continues to circulate over hindrances and through openings in containers which hold it, subject only to its own inertia. This phenomenon is generally observed in helium-3 and helium-4 when they are liquefied by cooling to cryogenic temperatures. The helium-4 acts as a normal and colorless liquid (which is called Helium I) below its boiling point (4.21 K) and above a temperature of 2.1768 K (the lambda point of helium). When the helium-4 is cooled below the lambda point, a part of it enters state called helium II which is a superfluid, and when the helium-4 is further cooled, increasing parts of it are converted to the superfluid state.
Phase Transitions
Published in Teunis C. Dorlas, Statistical Mechanics, 2021
Note that for T>Tc the gas cannot be condensed into liquid no matter how high the pressure! This is no problem for water since Tc(H2O)=647K=374° C, but it does present a problem for the liquefaction of air for instance: Tc(O2)=154K=−119° C and Tc(N2)=126K=−147° C. The problem is even greater for helium. Normal helium-4 (4He) has a critical temperature of 5.2 K and the isotope 3He has an even lower critical temperature of 3.3 K. To liquefy these latter gases, one needs to attain very low temperatures therefore. How this is done will be discussed further in chapter 11.
Ultra-accurate thermophysical properties of helium-4 and helium-3 at low density. I. Second pressure and acoustic virial coefficients
Published in Molecular Physics, 2021
In 2017, Przybytek et al. [6] reported a new pair potential for the interactions between helium atoms. Their high-level calculations on potential energies account for both the Born–Oppenheimer (BO) component and various post-BO effects. As a result, the accuracy of the 2017 potential is improved by an order of magnitude relative to their previous best determination in 2010 [7]. The 2017 potential by Przybytek et al. is represented by a form like, which will be applied to study the B and of helium-4 and helium-3 in this work. The complete information of the potential as well as its fitting coefficients in Equation (1) is provided in the supplementary materials of Ref. [6] and will not be duplicated in our paper.
Evolution of Rutherford’s ion beam science to applied research activities at GNS Science
Published in Journal of the Royal Society of New Zealand, 2021
John V. Kennedy, William Joseph Trompetter, Peter P. Murmu, Jerome Leveneur, Prasanth Gupta, Holger Fiedler, Fang Fang, John Futter, Chris Purcell
The New Zealand Department of Scientific and Industrial Research (DSIR) was founded in 1926 by Ernest Marsden after calls from Ernest Rutherford for the New Zealand government to support education and research (Atkison 1976). Ernest Marsden was a former Rutherford student who conducted the famous Geiger–Marsden experiment, also called the gold foil experiment, together with Hans Geiger under Rutherford's supervision. Marden came to New Zealand in 1915 on Rutherford’s recommendation to be a Professor of Physics at Victoria University in Wellington and then the 1st director of DSIR in 1926. During this time, he championed nuclear science and technology in New Zealand leading to isotope and nuclear physics research activities starting within the Chemistry Division and the Physics & Engineering Laboratory of DSIR. In 1959, the nuclear science teams were consolidated into the Institute of Nuclear Sciences (INS) located at Gracefield in Lower Hutt as a new division of the DSIR with T.A. Rafter as the 1st director. In 1992 the INS group became part of the Institute of Geological and Nuclear Sciences when the crown research institutes (CRI) were formed and was later branded as GNS Science. As the first major research tool, a 3.7 meter 3MV single-ended Van de Graaff accelerator from High Voltage was acquired and commissioned in 1966 (Atkison 1976; Priestly 2012). This machine has been modified and upgraded over the years produces single charged positive ion beams of hydrogen (1H+), deuterium (2H+) and helium (4He+) for IBA. Inside the machine, the high voltage terminal is charged via a belt-based system and powerful electric fields accelerate and focus a continuous stream of charged particles (ion beam). An analysing magnet allows the selection of specific ion species with well-defined ion energy to enter one of the two beam lines used for broad beam and microprobe ion beam analysis experiments (Purcell 1987). Guided by beam optic components, the ion beam is shot onto targets to produce scattered particles and generate reaction products that are used for IBA (Markwitz and Kennedy 2005).