A numerical study of Bi-periodic binary diffraction gratings for solar cell applications

In this paper, a numerical study is made of simple bi-periodic binary diffraction gratings for solar cell applications. The gratings consist of hexagonal arrays of elliptical towers and wells etched directly into the solar cell substrate. The gratings are applied to two distinct solar cell technologies: a quantum dot intermediate band solar cell (QD-IBSC) and a crystalline silicon solar cell (SSC). In each case, the expected photocurrent increase due to the presence of the grating is calculated assuming AM1.5D illumination. For each technology, the grating period, well/tower depth and well/tower radii are optimised to maximise the photocurrent. The optimum parameters are presented. Results are presented for QD-IBSCs with a range of quantum dot layers and for SSCs with a range of thicknesses. For the QD-IBSC, it is found that the optimised grating leads to an absorption enhancement above that calculated for an ideally Lambertian scatterer for cells with less than 70 quantum dot layers. In a QD-IBSC with 50 quantum dot layers equipped with the optimum grating, the weak intermediate band to conduction band transition absorbs roughly half the photons in the corresponding sub-range of the AM1.5D spectrum. For the SSC, it is found that the optimised grating leads to an absorption enhancement above that calculated for an ideally Lambertian scatterer for cells with thicknesses of 10 ?m or greater. A 20um thick SSC equipped with the optimised grating leads to an absorption enhancement above that of a 200um thick SSC equipped with a planar back reflector.

Rammed earth walls in the late middle age castles in the actual province of Soria, Spain

This paper analyzed the building techniques based in the use of rammed earth in the Late Medieval fortifications in the province of Soria, Spain. The manorial castles of Serón de Nágima and Yanguas were built completely with rammed earth. However, these techinques are different. Through the study of the constructive signals, we can reconstruct the constructive process and made an hypothesis of the auxiliary scaffolding necessary for the construction. After, other four cases in which there is presence of rammed earth are described: Ágreda, Arcos de Jalón, Caracena and the tower of Martín González or castle of La Raya (the Border). Rammed earth is used in some secondary architectural elements and also as a filling of the masonry walls, but somtimes there are ancient rammed earth walls overlaid with stone masonry.

A subgrid viscosity Lagrance-Galerkin method for convection-diffusion problems

We present and analyze a subgrid viscosity Lagrange-Galerk in method that combines the subgrid eddy viscosity method proposed in W. Layton, A connection between subgrid scale eddy viscosity and mixed methods. Appl. Math. Comp., 133: 14 7-157, 2002, and a conventional Lagrange-Galerkin method in the framework of P1⊕ cubic bubble finite elements. This results in an efficient and easy to implement stabilized method for convection dominated convection diffusion reaction problems. Numerical experiments support the numerical analysis results and show that the new method is more accurate than the conventional Lagrange-Galerkin one.

Integração morfológica e modularidade em crânios das espécies do grupo Rhinella granulosa

Os conceitos e métodos provindos das teorias de integração morfológica e de genética quantitativa formam o arcabouço teórico para o estudo da evolução de estruturas complexas, compostas de múltiplos caracteres que interagem entre si. Nesse trabalho, utilizamos o crânio como modelo de estrutura complexa e estudamos sua diversificação nas espécies de sapo do grupo Rhinella granulosa. As perguntas do trabalho foram: (1) A organização da (co)variação é similar entre as espécies?; (2) A organização da (co)variação é modular nas espécies, conforme expectativas baseadas em desenvolvimento ou função?; (3) Fatores externos, como filogenia e clima, estruturam a similaridade no padrão de covariação entre as espécies?; (4) A diversificação da morfologia média do crânio se deu por deriva ou seleção natural?; (5) A divergência na morfologia média do crânio está associada à variação climática entre as espécies?; e finalmente (6) Restrições evolutivas atuaram na divergência entre as espécies? Os espécimes foram escaneados e validamos o uso de imagens 3D para a mensuração de 21 distâncias lineares. Os crânios das espécies foram representados como matrizes fenotípicas (P) de covariância e de correlação entre as distâncias. A similaridade entre as P das espécies é alta. As P de todas as espécies se conformam a um padrão modular compatível com interações funcionais entre ossos. As diferenças entre as P concentram-se no rostro e são associadas a diferenças no clima entre as espécies. Detectamos sinal de seleção natural nos nós mais basais da filogenia e variação local no crânio está associada à variação na sazonalidade da chuva entre as espécies. Restrições evolutivas atuaram na diversificação do crânio das espécies, defletindo as respostas evolutivas para tamanho. Concluímos que tanto seleção estabilizadora e direcional, conectadas à variação climática, quanto restrições evolutivas atuaram na diversificação do crânio das espécies

Meteorological measurements from 8 dropsondes released during POLAR 4 flight on 1993-03-04 along a track orthogonal to the pack ice edge north west of Svalbard

Different parameterizations of subgrid-scale fluxes are utilized in a nonhydrostatic and anelastic mesoscale model to study their influence on simulated Arctic cold air outbreaks. A local closure, a profile closure and two nonlocal closure schemes are applied, including an improved scheme, which is based on other nonlocal closures. It accounts for continuous subgrid-scale fluxes at the top of the surface layer and a continuous Prandtl number with respect to stratification. In the limit of neutral stratification the improved scheme gives eddy diffusivities similar to other parameterizations, whereas for strong unstable stratifications they become much larger and thus turbulent transports are more efficient. It is shown by comparison of model results with observations that the application of simple nonlocal closure schemes results in a more realistic simulation of a convective boundary layer than that of a local or a profile closure scheme. Improvements are due to the nonlocal formulation of the eddy diffusivities and to the inclusion of heat transport, which is independent of local gradients (countergradient transport).

Observatory [Lake Angelus]

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940. On verso: Kodatone; Nov - 7 1935; Eastman Kodak Stores; Detroit

Observatory [Lake Angelus]

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940. On verso: Kodatone; Nov - 7 1935; Eastman Kodak Stores; Detroit

Observatory [Lake Angelus]

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940. Several people in image. On verso: Kodatone; Nov - 7 1935; Eastman Kodak Stores; Detroit

Observatory [Lake Angelus]

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940. On verso: Kodatone; May 16, 1936; Eastman Kodak Stores; Detroit

McMath-Hulbert Observatory

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940.

McMath-Hulbert Observatory

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940.

McMath-Hulbert Observatory [Lake Angelus, MI]

Observatory is near Lake Angelus, Mich. (five miles north of Pontiac). 24" reflecting telescope began operations in July 1930; also included a 10 1/2" reflector. Established and deeded to the university by Robert R. McMath, Francis McMath, and Judge Henry S. Hulbert. An additional 50' tower telescope was added in 1935/ 1946 and 70' tower telescope and office building added in 1940. Image is photograph of a painting.

Computer simulation of liquid flow patterns on distillation trays

This thesis describes work carried out to improve the fundamental modelling of liquid flows on distillation trays. A mathematical model is presented based on the principles of computerised fluid dynamics. It models the liquid flow in the horizontal directions allowing for the effects of the vapour through the use of an increased liquid turbulence, modelled by an eddy viscosity, and a resistance to liquid flow caused by the vapour being accelerated horizontally by the liquid. The resultant equations are similar to the Navier-Stokes equations with the addition of a resistance term.A mass-transfer model is used to calculate liquid concentration profiles and tray efficiencies. A heat and mass transfer analogy is used to compare theoretical concentration profiles to experimental water-cooling data obtained from a 2.44 metre diameter air-water distillation simulation rig. The ratios of air to water flow rates are varied in order to simulate three pressures: vacuum, atmospheric pressure and moderate pressure.For simulated atmospheric and moderate pressure distillation, the fluid mechanical model constantly over-predicts tray efficiencies with an accuracy of between +1.7% and +11.3%. This compares to -1.8% to -10.9% for the stagnant regions model (Porter et al. 1972) and +12.8% to +34.7% for the plug flow plus back-mixing model (Gerster et al. 1958). The model fails to predict the flow patterns and tray efficiencies for vacuum simulation due to the change in the mechanism of liquid transport, from a liquid continuous layer to a spray as the liquid flow-rate is reduced. This spray is not taken into account in the development of the fluid mechanical model. A sensitivity analysis carried out has shown that the fluid mechanical model is relatively insensitive to the prediction of the average height of clear liquid, and a reduction in the resistance term results in a slight loss of tray efficiency. But these effects are not great. The model is quite sensitive to the prediction of the eddy viscosity term. Variations can produce up to a 15% decrease in tray efficiency. The fluid mechanical model has been incorporated into a column model so that statistical optimisation techniques can be employed to fit a theoretical column concentration profile to experimental data. Through the use of this work mass-transfer data can be obtained.