No description available.

In this dissertation we use Lie symmetry analysis to obtain invariant solutions for certain soil water equations. These solutions are invariant under two-parameter symmetry groups obtained by the group classification of the governing equation. We also obtain all nontrivial conservation laws for a class of (2+1) nonlinear evolution partial differential equations which are related to the soil water equations. It is shown that nontrivial conservation laws exist for certain classes of equations which admit point symmetries. We note that one cannot invoke Noether's theorem here as there is no Lagrangian for these partial differential equations. / (M.Sc.) North-West University, Mafikeng Campus, 2003

A Flash Unit to supply a pulsed source of continuum radiation has been constructed to provide the light required for the study of absorption spectra of plasmas. The unit which contains the plasma has been designed to produce a gas of high purity. Several transitions in the excited neon were seen in absorption. At least two have not been reported previously. A preliminary determination of transition temperatures has been made. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

L'étude porte sur les écoulements et les transferts en convection naturelle au sein d'empilements de produits alimentaires et plus particulièrement dans des réfrigérateurs ménagers. L'approche est à la fois expérimentale et numérique. Une première étude a été effectuée dans un empilement ordonné de sphères soumis à une convection à faible vitesse d'air (u<0.2 ms-1). L'intensité des échanges convectifs entre les objets et l'air ainsi qu'entre la paroi de la cavité et l'air a été caractérisée en fonction de la position et de la vitesse. Par ailleurs, les résultats ont montré que les autres modes de transfert (conduction et rayonnement entre les objets et avec les parois) sont du même ordre de grandeur que la convection. Des mesures de vitesse d'air (par vélocimétrie par images de particules) et de température ont été effectuées dans une enceinte fermée représentant une maquette d'un réfrigérateur ménager (à l'échelle 1) dans différentes configurations (maquette vide, maquette chargée d'empilement de produits inertes thermiquement et de produits échangeant de la chaleur). Des instationnarités dans le bas de l'enceinte vide ont été mis en évidence (Ra" 3´108). La présence d'empilements d'objets (même inerte thermiquement) modifie de façon importante les écoulements et les transferts. Les simulations numériques effectuées avec un logiciel de mécanique de fluide pour les différentes configurations étudiées sur la maquette et dans le cas d'un réfrigérateur réel ont donné des prédictions satisfaisantes en comparaison avec les mesures expérimentales. Mots clés: milieu macro-poreux, convection naturelle, coefficient de transfert convectif, conduction, rayonnement, réfrigérateur ménager, simulations numérique (CFD).

We have conducted a detailed experimental and theoretical study of nonlinear absorption in semiconductors. Experimental measurements were made on a variety of materials at wavelengths of 1.06 and 0.53 microns using a picosecond Nd:YAG laser. Both two- and three-photon processes were investigated. Values of nonlinear absorption coefficients extracted from these measurements show excellent agreement with recent theory and scaling rules. Our theoretical investigation has been carried out for two-, three-,and n-photon absorption, for both continuous and pulsed sources. Expressions are obtained for the transmission of the sample in terms of the incident irradiance for each case. The physical interpretation of these results is discussed. We have also considered the effects of the photogenerated carriers on the measurements. Equations are developed that include linear absorption by these carriers. We have observed severe distortions on the transmitted beam, caused by changes in the refractive index of the material, due to the presence of these carriers. We present a model that accurately describes these effects in terms of the photogenerated carrier density. We have developed several novel techniques for monitoring nonlinear absorption. In particular, we have adapted the photoacoustic technique to the measurement of nonlinear absorption in semiconductors. We have also developed a technique employing irradiance modulation to greatly enhance the sensitivity to nonlinear processes and simultaneously discriminate against linear background signals. A related technique has been used to observe coherent mixing effects in semiconductors with cw, modelocked dye lasers.

<p>Detta examensarbete handlar om mag-tarmkanalen och är uppdelat i två avsnitt. Den första delen handlar om mag-tarmkanalens uppbyggnad, rent anatomiskt men också hur den ser ut histologiskt. Histologin är bara ytligt behandlad då den endast är med som förklaring till vissa händelser inom fysiologin. Den andra delen, fysiologidelen handlar om de olika delarna i mag-tarmkanalen, deras funktioner och vad som reglerar dessa. I fysiologiavsnittet behandlas också nedbrytning och absorption av de olika näringsämnena.</p>

Detta examensarbete handlar om mag-tarmkanalen och är uppdelat i två avsnitt. Den första delen handlar om mag-tarmkanalens uppbyggnad, rent anatomiskt men också hur den ser ut histologiskt. Histologin är bara ytligt behandlad då den endast är med som förklaring till vissa händelser inom fysiologin. Den andra delen, fysiologidelen handlar om de olika delarna i mag-tarmkanalen, deras funktioner och vad som reglerar dessa. I fysiologiavsnittet behandlas också nedbrytning och absorption av de olika näringsämnena.

Kauno miesto miškų medžių absorbcinės gebos įvertinimas buvo atliktas i-tree programos UFORE techniniu modeliu. Taip pat šia programa įvertinta Kleboniškio, Panemunės, Romainių, Ąžuolyno miesto parko absorbcinė geba. Airviro programos pagalba nustatytos oro teršalų koncentracijos mieste, pavaizduota grafiškai emisijų sklaida. Nustatyta procentinė dalis oro taršos sumažėjimo, kurią lemia Kauno miesto miško želdiniai. Duomenis apie želdinius Kauno mieste ir pasirinktuose analizuoti parkuose naudoti remiantis Kauno miesto savivaldybės teritorijoje esančių miškų taksoraščiu (VĮ Valstybinis miškotvarkos institutas, miškų inventorizacija 2003/2004) bei atliktais matavimais Kleboniškio, Panemunės, Romainių ir ��žuolyno parkuose. Meteorologinius duomenis oro taršai nustatyti pateikė VŠĮ „Kauno aplinkos kokybės tyrimai“. Rezultatai parodė, kad Kauno miesto miško medžiai per metus pašalina 328 tonas pagrindinių atmosferos teršalų: 97,7 t ozono, kietųjų dalelių pašalinta 87,3 t, azoto dioksido 81 t, sieros dioksido 42,4 t, anglies monoksido 19,3 t. Pagal procentinę sudėtį ozono tarp pagrindinių pašalintų atmosferos oro teršalų yra 29,9 %, kietųjų dalelių 26,6 %, azoto dioksido 24,7 %, sieros dioksido 12,8%, anglies monoksido 6%. Didžiausias teršalų kiekis pašalinamas Kleboniškio miško parke - 38,7 tonos (39 % bendro analizuojamų parkų pašalintų teršalų kiekio), toliau seka panemunės miško parkas - 35,7 tonos (36%), Romainių miško parkas - 20,4 tonos ( 20 %) ir Ąžuolynas - 5 tonos (5%)... [toliau žr. visą tekstą] / Assessment of Kaunas Urban forest effects and air pollution mitigation was done using i-tree program UFORE model. During the study four different city parks were analyzed – Kleboniskis, Panemune, Romainiai, Azuolynas. Kaunas city air pollution concentrations were counted with Airviro program. Data required for this study was used from Kaunas city trees inventory book 2004, as well field data has been collected from city parks in random sample of fixed area plots in April of 2008. VŠĮ “Kauno aplinkos kokybės tyrimai “delivered meteorogical data about Kaunas city. Results showed, that Kaunas city forest remove about 328 metric tones of atmospheric air pollutants per year. In addition these trees remove 97,7 metric tones of O3, 87,3 metric tones of particulate matter, NO2 – 81 metric tones, SO2 – 42,4 metric tones, CO – 19,3 metric tones. The biggest part of pollutants have been removed in the park of Kleboniskis – 38,7 metric tones (39% of total air pollutants removed in the analyzed city parks), Panemune park removed 35,7 metric tones (36%), Romainiai park - 20,4 metric tones (20%), ąžuolynas- 5 metric tones ( 5 %). Results presented, that Kaunas city urban forest are able to sequestrate 3365 metric tones of Carbon per year, all Kaunas urban forest trees could storage 237210 metric tones of carbon. The city parks carbon storage are: Panemune park trees - 25 metric tones, Kleboniskis park trees -13 metric tones, Romainiai park trees -12,5 metric tones, Ąžuolynas park... [to full text]

The Shubnikov-de Haas magneto-resistance oscillations and photoconductivity were experimentally studied in order to investigate the interaction of CO laser radiation with n-InSb at liquid helium temperatures. The roles of various absorption mechanisms on these effects were considered, particularly near the intrinsic band edge. From these measurements an effective electron temperature Tₑ was defined that increased or decreased under illumination, depending upon the strength of the applied electric field.