Spelling suggestions: "subject:"matematerials at low temperatures."" "subject:"datenmaterials at low temperatures.""
11 |
The magnetic susceptibility of dilute copper-iron alloys at low temperature.Raudorf, Thomas Walter. January 1967 (has links)
No description available.
|
12 |
Prediction of the temperature distribution in asphalt pavement samplesBurger, Marco 04 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The convection heat transfer coefficient between an infinite, horizontal surface and the natural
environment is determined experimentally. It is shown that, during daytime, heat is
transferred due to natural and forced convection, while during nighttime heat is transferred
due to conduction and forced convection. Equations that correlate the daytime and nighttime
convective heat transfer coefficients respectively, are presented. The results are compared
with values obtained by other investigators.
The equations for the convection heat transfer coefficient are then used to predict the surface
temperature and the temperature at depth of asphalt pavement samples using a simulation
model. It is found that there is good agreement between the measured and the predicted
asphalt pavement sample temperatures. / AFRIKAANSE OPSOMMING: Die konveksie warmteoordrags-koëffisiënt tuseen 'n oneindige, horisontale oppervlak en die
natuurlike omgewing is eksperimenteel bepaal. Daar word getoon dat warmte, tydens die
dag, oorgedra word deur natuurlike en geforseerde konveksie, terwyl warmte tydens die nag
oorgedra word deur geleiding en geforseerde konveksie. Die resultate word vergelyk met die
resultate van ander navorsers. Vergelykings wat die konveksie warmteoordrags-koëffisiënt
gedurende die dag en nag onderskeidelik korreleer word voorgestel.
Die vergelykings vir die konveksie warmteoordrags-koëffisiënt word dan gebruik in 'n
simulasiemodel om die oppervlaktemperatuur en die temperatuur onder die oppervlakte van
asfalt-padoppervlakmonsters te voorspel.
|
13 |
Silicon-germanium devices and circuits for cryogenic and high-radiation space environmentsWilcox, Edward 08 April 2010 (has links)
This work represents several years' research into the field of radiation hardening by design. The unique characteristics of a SiGe HBT, described in Chapter 1, make it ideally suitable for use in extreme environment applications.
Chapter 2 describes the total ionizing dose effects experienced by a SiGe HBT, particularly those experienced on an Earth-orbital or lunar-surface mission. In addition, the effects of total dose are evaluated on passive devices.
As opposed to the TID-hardness of SiGe transistors, a clear vulnerability to single-event effects does exist. This field is divided into three chapters. First, the very nature of single-event transients present in SiGe HBTs is explored in Chapter 3 using a heavy-ion microbeam with both bulk and SOI platforms [31]. Then, in Chapter 4, a new device-level SEU-hardening technique is presented along with circuit-design techniques necessarily for its implementation. In Chapter 5, the circuit-level radiation-hardening techniques necessarily to mitigate the effects shown in Chapter 3 are developed and tested [32].
Finally, in Chapter 6, the performance of the SiGe HBT in a cryogenic testing environment is characterized to understand how the widely-varying temperatures of outer space may affect device performance.
Ultimately, the built-in performance, TID-tolerance, and now-developing SEU-hardness of the SiGe HBT make a compelling case for extreme environment electronics. The low-cost, high-yield, and maturity of Si manufacturing combine with modern bandgap engineering and modern CMOS to produce a high-quality, high-performance BiCMOS platform suitable for space-borne systems.
|
14 |
Transient processing and characterizatin of advanced materials /Moussa, Sherif Omar Hassan, January 2003 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 160-167). Also available on the Internet.
|
15 |
Transient processing and characterizatin of advanced materialsMoussa, Sherif Omar Hassan, January 2003 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 160-167). Also available on the Internet.
|
16 |
Modeling of minority carrier recombination and resistivity in sige bicmos technology for extreme environment applicationsMoen, Kurt Andrew 19 November 2008 (has links)
This work presents a summary of experimental data and theoretical models that characterize the temperature-dependent behavior of key carrier-transport parameters in silicon down to cryogenic temperatures. In extreme environment applications such as space-based electronics, accurate models of carrier recombination, carrier mobility, and incomplete ionization of dopants form a necessary foundation for the development of reliable high-performance devices and circuits. Not only do these models have a wide impact on the simulated DC and AC performance of devices, but they also play a critical role in predicting the behavior of important phenomena such as single event upset in digital logic circuits. With this motivation, an overview is given of SRH recombination theory, addressing in particular the dependence of recombination lifetime on temperature and injection level. Carrier lifetime measurement methods are reviewed, and experiments to study carrier lifetimes in the substrate of a commercial SiGe BiCMOS process are presented. The experimental data is analyzed and leveraged in order to develop calibrated TCAD-relevant models. Similarly, an overview of low-temperature resistivity in silicon is presented. Modeling of resistivity over temperature is discussed, addressing the prevailing theoretical models for both carrier mobility and incomplete ionization of dopants. Experimental measurements of the temperature dependence of resistivity in both p-type and n-type silicon are presented, and calibrated TCAD-relevant models for carrier mobility and incomplete ionization are developed. Finally, the ability to integrate these calibrated models within commercial TCAD software is demonstrated. In addition, applications for these accurate temperature-dependent models are discussed, and future directions are outlined for research into cryogenic modeling of fundamental physical parameters.
|
17 |
Periodic flow physics in porous media of regenerative cryocoolersPathak, Mihir Gaurang 20 September 2013 (has links)
Pulse tube cryocoolers (PTC) are a class of rugged and high-endurance refrigeration systems that operate without moving parts at their low temperature ends, and are capable of reaching temperatures down to and below 123 K. PTCs are particularly suitable for applications in space, guiding systems, cryosurgery, medicine preservation, superconducting electronics, magnetic resonance imaging, weather observation, and liquefaction of gases. Applications of these cryocoolers span across many industries including defense, aerospace, biomedical, energy, and high tech. Among the challenges facing the PTC research community is the improvement of system efficiency, which is a direct function of the regenerator component performance. A PTC implements the theory of oscillatory compression and expansion of the gas within a closed volume to achieve desired refrigeration. An important deficiency with respect to the state of art models dealing with PTCs is the limited understanding of the hydrodynamic and thermal transport parameters associated with periodic flow of a cryogenic fluid in micro-porous structures. In view of the above, the goals of this investigation include: 1) experimentally measuring and correlating the steady and periodic flow Darcy permeability and Forchheimer’s inertial hydrodynamic parameters for available rare-Earth ErPr regenerator filler; 2) employing a CFD-assisted methodology for the unambiguous quantification of the Darcy permeability and Forchheimer’s inertial hydrodynamic parameters, based on experimentally measured steady and periodic flow pressure drops in porous structures representing recently developed regenerator fillers; and 3) performing a direct numerical pore-level investigation for steady and periodic flows in a generic porous medium in order to elucidate the flow and transport processes, and quantify the solid-fluid hydrodynamic and heat transfer parameters. These hydrodynamic resistances parameters were found to be significantly different for steady and oscillatory flows.
|
Page generated in 0.1279 seconds