Estudo Comparativo dos Custos de Aquecedores de Passagem Individual a Gás e um Sistema de Aquecimento Centralizado a Gás com Apoio Solar para Aquecimento de Água em Edifícios Residenciais Multifamiliares

TCC (graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Engenharia Civil.O presente trabalho tem por objetivo o estudo comparativo de custos de implantação e operação de dois sistemas de aquecimento em edificações residenciais existentes, um a gás de passagem individual e o outro um sistema de aquecimento centralizado a gás com apoio solar. São analisados os benefícios de economia de energia que o sistema com apoio solar tem em relação ao aquecimento dos aquecedores de passagem através do comparativo do histórico de compra de gás para as duas edificações. Com base no estudo comparativo de custos de instalação e operação dos sistemas, foi possível verificar qual o tempo de retorno do investimento no sistema de aquecimento centralizado a gás com apoio solar. Adicionalmente, foi feita uma análise de satisfação com os moradores do edifício com aquecimento de apoio solar para verificar se o projeto atende a demanda de água quente solicitada pela edificação. Os resultados demonstram viabilidade econômica na agregação da energia solar térmica com relação ao aquecimento utilizando somente o gás como fonte de energia./The present project aims to compare two different forms of water heating used in real apartment buildings located in Florianópolis-SC. One of them consists of individual, apartment-based, gas burner equipped with ignition system that provides hot water for householders. The other one is basically a central gas heating system, backed up by solar heating panels. There will be analyzed different points related to the benefits brought by the central gas system plus solar heating compared to the individual heaters, such as energy economy and performance. The economical analysis was made through the survey of gas expenses throughout the years, as well installation and maintenance costs, which made possible to make assumptions about how long would it take for the best system to pay off its costs. In addition to that, a costumer satisfaction survey was conducted asking the proprietors to determine the level of satisfaction with the central heating plus solar system. The following results demonstrates the economic viability of adding solar panels as support to central heating system that uses gas as main fuel

High Frame-rate Imaging Based Photometry, Photometric Reduction of Data from Electron-multiplying Charge Coupled Devices (EMCCDs)

The EMCCD is a type of CCD that delivers fast readout times and negligible readout noise, making it an ideal detector for high frame rate applications which improve resolution, like lucky imaging or shift-and-add. This improvement in resolution can potentially improve the photometry of faint stars in extremely crowded fields significantly by alleviating crowding. Alleviating crowding is a prerequisite for observing gravitational microlensing in main sequence stars towards the galactic bulge. However, the photometric stability of this device has not been assessed. The EMCCD has sources of noise not found in conventional CCDs, and new methods for handling these must be developed. We aim to investigate how the normal photometric reduction steps from conventional CCDs should be adjusted to be applicable to EMCCD data. One complication is that a bias frame cannot be obtained conventionally, as the output from an EMCCD is not normally distributed. Also, the readout process generates spurious charges in any CCD, but in EMCCD data, these charges are visible as opposed to the conventional CCD. Furthermore we aim to eliminate the photon waste associated with lucky imaging by combining this method with shift-and-add. A simple probabilistic model for the dark output of an EMCCD is developed. Fitting this model with the expectation-maximization algorithm allows us to estimate the bias, readout noise, amplification, and spurious charge rate per pixel and thus correct for these phenomena. To investigate the stability of the photometry, corrected frames of a crowded field are reduced with a PSF fitting photometry package, where a lucky image is used as a reference. We find that it is possible to develop an algorithm that elegantly reduces EMCCD data and produces stable photometry at the 1% level in an extremely crowded field.Comment: Submitted to Astronomy and Astrophysic

The Domain Chaos Puzzle and the Calculation of the Structure Factor and Its Half-Width

The disagreement of the scaling of the correlation length xi between experiment and the Ginzburg-Landau (GL) model for domain chaos was resolved. The Swift-Hohenberg (SH) domain-chaos model was integrated numerically to acquire test images to study the effect of a finite image-size on the extraction of xi from the structure factor (SF). The finite image size had a significant effect on the SF determined with the Fourier-transform (FT) method. The maximum entropy method (MEM) was able to overcome this finite image-size problem and produced fairly accurate SFs for the relatively small image sizes provided by experiments. Correlation lengths often have been determined from the second moment of the SF of chaotic patterns because the functional form of the SF is not known. Integration of several test functions provided analytic results indicating that this may not be a reliable method of extracting xi. For both a Gaussian and a squared SH form, the correlation length xibar=1/sigma, determined from the variance sigma^2 of the SF, has the same dependence on the control parameter epsilon as the length xi contained explicitly in the functional forms. However, for the SH and the Lorentzian forms we find xibar ~ xi^1/2. Results for xi determined from new experimental data by fitting the functional forms directly to the experimental SF yielded xi ~ epsilon^-nu} with nu ~= 1/4 for all four functions in the case of the FT method, but nu ~= 1/2, in agreement with the GL prediction, in the the case of the MEM. Over a wide range of epsilon and wave number k, the experimental SFs collapsed onto a unique curve when appropriately scaled by xi.Comment: 15 pages, 26 figures, 1 tabl

Processor Allocation for Optimistic Parallelization of Irregular Programs

Optimistic parallelization is a promising approach for the parallelization of irregular algorithms: potentially interfering tasks are launched dynamically, and the runtime system detects conflicts between concurrent activities, aborting and rolling back conflicting tasks. However, parallelism in irregular algorithms is very complex. In a regular algorithm like dense matrix multiplication, the amount of parallelism can usually be expressed as a function of the problem size, so it is reasonably straightforward to determine how many processors should be allocated to execute a regular algorithm of a certain size (this is called the processor allocation problem). In contrast, parallelism in irregular algorithms can be a function of input parameters, and the amount of parallelism can vary dramatically during the execution of the irregular algorithm. Therefore, the processor allocation problem for irregular algorithms is very difficult. In this paper, we describe the first systematic strategy for addressing this problem. Our approach is based on a construct called the conflict graph, which (i) provides insight into the amount of parallelism that can be extracted from an irregular algorithm, and (ii) can be used to address the processor allocation problem for irregular algorithms. We show that this problem is related to a generalization of the unfriendly seating problem and, by extending Tur\'an's theorem, we obtain a worst-case class of problems for optimistic parallelization, which we use to derive a lower bound on the exploitable parallelism. Finally, using some theoretically derived properties and some experimental facts, we design a quick and stable control strategy for solving the processor allocation problem heuristically.Comment: 12 pages, 3 figures, extended version of SPAA 2011 brief announcemen