The purposes of the study were as follows: first, to study the literature in the field of teaching drafting with special reference to the use of instructional aides in presenting orthographic projection concerning the use of a projection box; second, to ascertain the value of the use of a tri-color projection box in teaching orthographic projection to an experimental group of students at the R. L. Turner High School, Carrollton, Texas; and third, to determine if an analysis of these data indicates a justification for the use of this type of an instructional aid in teaching orthographic projection.

Aerosols contribute the largest uncertainty to estimates of radiative forcing of the Earth’s atmosphere, which are thought to exert a net negative radiative forcing, offsetting a potentially significant but poorly constrained fraction of the positive radiative forcing associated with greenhouse gases. Aerosols perturb the Earth’s radiative balance directly by absorbing and scattering radiation and indirectly by acting as cloud condensation nuclei, altering cloud albedo and potentially cloud lifetime. One of the major factors governing the uncertainty in estimates of aerosol direct radiative forcing is the poorly constrained aerosol single scattering albedo, which is the ratio of the aerosol scattering to extinction. In this thesis, I describe a new instrument for the measurement of aerosol optical properties using photoacoustic and cavity ring-down spectroscopy. Characterisation is performed by assessing the instrument minimum sensitivity and accuracy as well as verifying the accuracy of its calibration procedure. The instrument and calibration accuracies are assessed by comparing modelled to measured optical properties of well-characterised laboratory-generated aerosol. I then examine biases in traditional, filter-based absorption measurements by comparing to photoacoustic spectrometer absorption measurements for a range of aerosol sources at multiple wavelengths. Filter-based measurements consistently overestimate absorption although the bias magnitude is strongly source-dependent. Biases are consistently lowest when an advanced correction scheme is applied, irrespective of wavelength or aerosol source. Lastly, I assess the sensitivity of the direct radiative effect of biomass burning aerosols to aerosol and cloud optical properties over the Southeast Atlantic Ocean using a combination of offline radiative transfer modelling, satellite observations and global climate model simulations. Although the direct radiative effect depends on aerosol and cloud optical properties in a non-linear way, it appears to be only weakly dependent on sub-grid variability.

Made available in DSpace on 2015-05-14T13:21:35Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5352516 bytes, checksum: 794641cb921c8b2deee06ca5e6ee12ed (MD5) Previous issue date: 2014-04-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / A portable and low-cost photometer is proposed in this work. The instrument uses a tri-color light emitting diode (LED) as its radiation source in maximum emission wavelengths of 480 (blue), 534 (green) and 630 nm (red). It employs a phototransistor with spectral sensitivity in the visible region, as well as an Arduino microcontroller. Its analytical performance was evaluated by means of quantitative analysis (analytical curves), whose models were validated by analysis of variance (ANOVA). The instrument was applied to determine sunset yellow dye in energy drinks and sodas, and potassium permanganate pills. For comparison purposes, a commercial spectrophotometer was used to construct the calibration curves for the reference method. Applying the paired t-test at a 95 % confidence level for the concentration results obtained with the two instruments, we observed no statistically significant difference. Furthermore, accurate concentration estimates were obtained for the analytes as confirmed by the low relative standard deviation range of 0.2 and 0.5%, respectively, for both the dye and the permanganate. The proposed photometer might be an economically viable alternative to spectroscopic analysis, especially in teaching laboratories with limited financial resources or lacking in highly qualified personnel. / Um fotômetro portátil e de baixo custo é proposto neste trabalho. Esse instrumento utiliza um diodo emissor de luz (LED-Light Emitting Diode) tricolor como fonte de radiação nos comprimentos de onda do máximo de emissão de 480 (azul), 534 (verde) e 630 nm (vermelho). Além disso, emprega um fototransistor com sensibilidade espectral na região do visível como fototransdutor, bem como um microcontrolador Arduino como unidade de controle. Seu desempenho analítico foi avaliado por meio de análises quantitativas baseadas em curvas analíticas, cujos modelos foram validados por meio da Análise de Variância (ANOVA). O instrumento foi aplicado à determinação do corante amarelo crepúsculo em amostras de refrigerantes e bebidas energéticas e de permanganato de potássio em amostras de medicamentos. Para fins de comparação, um espectrofotômetro comercial foi empregado para construir as curvas analíticas do instrumento de referência. Aplicando o teste t-emparelhado ao nível de 95% de confiança para os resultados de concentração obtidos com os dois instrumentos, observa-se que não houve diferença estatisticamente significativa. Ademais, resultados precisos nas estimativas das concentrações dos analitos foram obtidos sendo atestado pelo baixo desvio padrão relativo conjunto de 0,2 e 0,5%, respetivamente, para o corante e permanganato. O fotômetro proposto pode ser uma alternativa economicamente viável para análises espectrométricas, sobretudo, em laboratórios de ensino com poucos recursos financeiros e carentes de pessoal altamente qualificado.