Search results for "Heat"
showing 10 items of 2717 documents
Atkārtojums Semjuela Beketa dramaturģiskajā darbā “Luga”
2016
Semjuela Beketa dramatiskais darbs “Luga” ir gan netradicionāls, gan unikāls. Luga uzrakstīta 1963.gadā un atšķiras no citiem darbiem ar bezemocionāliem un neizteiksmīgiem personāžiem. Uz skatuves atrodas trīs personāži, kuri nespēj ne kustēties, ne runāt izteiksmīgi, ne paust emocijas, ne izmantot mīmiku. Lai izprastu šo lugu, jāizpēta tas, kas jau dots – mākslinieciskie izteiksmes līdzekļi. Atkārtojums ir viens no visvairāk izmantotajiem līdzekļiem un katrs personāžs to izmanto citādāk, lai panāktu noteiktu efektu uz klausītāju. Katrs atkārtojums var tikt grupēts atšķirīgās kategorijās un katram no tiem ir sava funkcija dramatiskajā darbā. Visbiežāk atkārtojums izmantots, lai pabeigtu dom…
Derivation of a Homogenized Two-Temperature Model from the Heat Equation
2014
This work studies the heat equation in a two-phase material with spherical inclusions. Under some appropriate scaling on the size, volume fraction and heat capacity of the inclusions, we derive a coupled system of partial differential equations governing the evolution of the temperature of each phase at a macroscopic level of description. The coupling terms describing the exchange of heat between the phases are obtained by using homogenization techniques originating from [D. Cioranescu, F. Murat: Coll\`ege de France Seminar vol. 2. (Paris 1979-1980) Res. Notes in Math. vol. 60, pp. 98-138. Pitman, Boston, London, 1982.]
Inverse estimation of model parameters for newborn brain cooling process simulations
2019
In this work, a three-dimensional simplified computational model was built to simulate the passive thermo-physiological response of part of a newborn’s head for neonate’s selective brain cooling. Both metabolicheat generation and blood perfusion were considered. The set of model parameters was selected anda sensitivity study was carried out. Analysis of dimensionless sensitivity coefficients showed that the mostimportant are: the contact thermal resistance between the cool-cap and skin, the thermal resistance ofthe plastic wall material, and deep (arterial) blood temperature. The function specification method wasapplied to estimate the value of the contact resistance. Two, four and six comp…
A study of the optical effect of plasma sheath in a negative ion source using IBSIMU code
2020
A plasma sheath inside an ion source has a strong focusing effect on the formation of an ion beam from the plasma. Properties of the beam depend on the shape and location of the plasma sheath inside the source. The most accessible experimental data dependent on the plasma sheath are the beam phase space distribution. Variation of beam emittance is a reflection of the properties of the plasma sheath, with minimum emittance for the optimal shape of the plasma sheath. The location and shape of the plasma sheath are governed by complex physics and can be understood by simulations using plasma models in particle tracking codes like IBSimu. In the current study, a model of the D-Pace’s TRIUMF lic…
Modeling self-sustaining waves of exothermic dissolution in nanometric Ni-Al multilayers
2016
Abstract The self-sustained propagating reaction occurring in nanometric metallic multilayers was studied by means of molecular dynamics (MD) and numerical modeling. We focused on the phenomenon of the exothermic dissolution of one metallic reactant into the less refractory one, such as Ni into liquid Al. The exothermic character is directly related to a negative enthalpy of mixing. An analytical model based on the diffusion-limited dissolution [1] coupled with heat transfer was derived to account for the main aspects of the process. Together, several microscopic simulations were carried out. The first series were set up to obtain all the parameters governing the process, including the heat…
Space charge accumulation in undersea HVDC cables as function of heat exchange conditions at the boundaries – water-air interface
2020
Transmission lines with undersea HVDC cables are an interesting technological solution for the supply of electrical energy to islands. The accumulation of space charge inside the dielectric layer of a HVDC cable is one of the most important element to consider in its design and during operation. The formation of space charge is due to various factors including the high dependence on the temperature of the electrical conductivity of the insulation and the establishment of a thermal gradient under load conditions. This research is focused on the space charge accumulation phenomenon around a section of a HVDC cable half dipped in water and half in air. Due to the high difference in thermal con…
Numerical modelling for the diameter increase of silicon crystals grown with the pedestal method
2021
Abstract The pedestal method is one of crucible-free crystal growth methods, that has been less researched than the well-known floating zone (FZ) method. However, the pedestal method may be a cost-effective alternative to FZ, if large diameter feed rods are available. The investigated system contains two electromagnetic inductors: high-frequency inductor for pedestal top surface melting and middle-frequency inductor for pedestal side heating. The present work describes recent advances in numerical modelling of heat transfer and phase boundaries in axially symmetrical approximation, neglecting the melt flow. The shape of high-frequency inductor was optimized with the algorithm of gradient de…
Validation of a 3D mathematical model for feed rod melting during floating zone Si crystal growth
2019
Abstract A mathematical model of global 3D heat transfer in floating zone silicon single crystal growth process is used to predict the shape of the open melting front of the feed rod. The model is validated using measurement data from research-scale growth experiments. Shape profiles of the open melting front are obtained from the feed rod leftover using a movable dial gauge. Azimuthal asymmetry of the rim of the open melting front is revealed in both simulations and measurements, quantitatively indicating the influence of the main slit of the inductor.
Application of enthalpy model for floating zone silicon crystal growth
2017
Abstract A 2D simplified crystal growth model based on the enthalpy method and coupled with a low-frequency harmonic electromagnetic model is developed to simulate the silicon crystal growth near the external triple point (ETP) and crystal melting on the open melting front of a polycrystalline feed rod in FZ crystal growth systems. Simulations of the crystal growth near the ETP show significant influence of the inhomogeneities of the EM power distribution on the crystal growth rate for a 4 in floating zone (FZ) system. The generated growth rate fluctuations are shown to be larger in the system with higher crystal pull rate. Simulations of crystal melting on the open melting front of the pol…
Deviation of H− beam extraction simulation model
2018
Negative hydrogen ion source extraction system development is dependent on accurate and fast simulation methods for modelling the behaviour of ion and electron beams. Traditionally this type of work has been done using ray-tracing extraction codes, such as IBSimu. The plasma extraction model in IBSimu has been observed to under-estimate the charge density near the plasma sheath, leading to incorrect prediction of the current at which the system produces the optimum emittance. It is suspected that this deviation results from the approximations made by the model, neglecting the magnetic field and collisional effects near the sheath region. Results and comparisons to simulations are presented …