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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Técnica de localização em ambientes fechados utilizando padrões de redes sem fio. / Indoor location technique with wireless fingerprint.

Costa, Lucas Juliano Spinola 05 December 2014 (has links)
Localizar objetos ou pessoas no interior de um edifício é de grande interesse. Contudo, diferentemente do que ocorre no exterior de edificações, não há metodologia consagrada para a determinação da posição desses entes nos edifícios. Para o posicionamento em locais abertos existem tecnologias consolidadas, como GNSS (Global Navigation Satellite System), a dificuldade em fazê-lo em interiores é maior. Nesses casos, o GNSS não pode ser utilizado, pois os sinais de rádio dos satélites não conseguem penetrar através das estruturas, enquanto que outras tecnologias são apenas incipientes nesse quesito. Abordagens habituais para a resolução dessa demanda têm se baseado na utilização de propagadores das ondas de rádio do GNSS, no uso da potência de sinais de redes sem fio ou, ainda, no emprego de transmissores infravermelhos. No entanto, uma técnica diferente pode ser empreendida para essa finalidade. Usando-se a assinatura das potências de rádio das redes sem fio nas imediações e no interior da edificação, é possível criar um mapa com base nesses sinais, permitindo a determinação da posição de um objeto. No presente trabalho foram desenvolvidos um sistema para geração do mapa de sinais, com critério de parada e um método de cálculo de posicionamento. Procedeu-se, também, à análise de quatro critérios para o cálculo final da posição do objeto, baseados no uso da distância euclidiana com os conjuntos de roteadores disponíveis. Concluiu-se que, quando o mapa de sinais é pequeno, o posicionamento fracassou. Entretanto, quando a quantidade de sinais geradores do mapa aumenta, os resultados apresentaram melhora significativa, com resultados próximos a 100% de assertividade. Desse modo foi possível determinar uma estimativa boa para o número mínimo de roteadores presentes na base e estabelecer um critério de parada para a fase de criação do mapa de sinais. / Locate objects or person inside a building is a subject that matters. Although what occurs outdoor of a building, there is no consolidate methodology to define a position in an indoor environment. For outdoor positioning there is the GNSS (Global Navigation Satellite System) a consolidate technology for outdoor usage with a lot of challenges to make this work in an indoor environment. In such cases, the GNSS cannot be used due to the lack of the sattelite radio signal, which cannot penetrate the walls and buildings structures, meanwhile other technologies are just incipient. Usual approaches using this approach are based in propagation of the GNSS radio signal, wi-fi based location or infrared transmitter. A different technique can be applied for indoor positioning. Using the wireless fingerprint in an indoor environment we created a radio map based on those signals, allowing the location of a mobile station. In the present research, we developed a system that generates a radio map (with a stop criteria) and a positioning calculation method. We concluded that when the radio map is small (with only a few measurements) the method cannot calculate accurately. However, with more measurements, the method succeeded and have a performance near a 100% of precision. In this way it was posible to estimate a number of access points needed for a building\'s range and define the stop criteria used in the radio map phase.
72

Chemical oxidation of tryptic digests to improve sequence coverage in peptide mass fingerprint protein identification

Lucas, Jessica Elaine 30 September 2004 (has links)
Peptide mass fingerprinting (PMF) of protein digests is a widely-accepted method for protein identification in MS-based proteomic studies. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) is the technique of choice in PMF experiments. The success of protein identification in a PMF experiment is directly related to the amount of amino acid sequence coverage. In an effort to increase the amount of sequence information obtained in a MALDI PMF experiment, performic acid oxidation is performed on tryptic digests of known proteins. Performic acid was chosen as the chemical oxidant due to the ease of use and to the selective oxidation of cysteine, methionine, and tryptophan residues. In experiments performed in our laboratory, performic acid oxidation either increased or did not affect protein sequence coverage in PMF experiments when oxidized tryptic digests were analyzed by MALDI. Negative mode MALDI data were acquired, as well as positive mode MALDI data, due to the enhanced ionization of cysteic acid-containing peptides in negative mode. Furthermore, the confidence in a protein match is increased by observation of mass shifts indicative of cysteine, methionine, and/or tryptophan in oxidized peptide ion signals when comparing MALDI spectra prior to performic acid oxidation and after oxidation due to the low abundance of these residues in the majority of all known and hypothetical proteins.
73

Microbial community dynamics in long-term no-till and conventionally tilled soils of the Canadian prairies

Helgason, Roberta Lynn 15 January 2010
Adoption of no-till (NT) and reduced tillage management is widespread on the Canadian prairies and together form the basic platform of soil management upon which most crop production is based. Elimination of tillage in cropping systems changes the physical and chemical characteristics of the soil profile and can affect crop growth and ultimately yield. As such, understanding how soil biota, as drivers of nutrient turnover, adapt to NT is important for maximizing crop productivity and mitigating environmental damage in agroecosystems. This work aims to achieve a greater understanding of microbial community structure and function in long-term NT versus conventionally tilled (CT) soils. Community phospholipid and DNA fingerprinting did not reveal any consistent tillage-induced shifts in microbial community structure, but demonstrated a clear influence of depth within the soil profile. While tillage did not result in broad changes in the community structure, total, bacterial and fungal biomass was consistently greater near the surface of NT soils. Further examination at one site near Swift Current, SK revealed differences in microbial biomass and community structure in NT and CT in field-formed aggregate size fractions. Measurement of mineralization and nitrification at the same site indicated that differences in the early-season turnover of N may be related to physical rather than microbial differences in NT and CT soils. Potential nitrification was higher prior to seeding than mid-season, was not affected by tillage and was correlated with ammonia oxidizer population size of archaea, but not bacteria. This work indicates that edaphic soil properties and spatial distribution of resources in the soil profile, rather than tillage management, are the primary factors driving microbial community structure in these soils.
74

Fingerprint Segmentation

Jomaa, Diala January 2009 (has links)
In this thesis, a new algorithm has been proposed to segment the foreground of the fingerprint from the image under consideration. The algorithm uses three features, mean, variance and coherence. Based on these features, a rule system is built to help the algorithm to efficiently segment the image. In addition, the proposed algorithm combine split and merge with modified Otsu. Both enhancements techniques such as Gaussian filter and histogram equalization are applied to enhance and improve the quality of the image. Finally, a post processing technique is implemented to counter the undesirable effect in the segmented image. Fingerprint recognition system is one of the oldest recognition systems in biometrics techniques. Everyone have a unique and unchangeable fingerprint. Based on this uniqueness and distinctness, fingerprint identification has been used in many applications for a long period. A fingerprint image is a pattern which consists of two regions, foreground and background. The foreground contains all important information needed in the automatic fingerprint recognition systems. However, the background is a noisy region that contributes to the extraction of false minutiae in the system. To avoid the extraction of false minutiae, there are many steps which should be followed such as preprocessing and enhancement. One of these steps is the transformation of the fingerprint image from gray-scale image to black and white image. This transformation is called segmentation or binarization. The aim for fingerprint segmentation is to separate the foreground from the background. Due to the nature of fingerprint image, the segmentation becomes an important and challenging task. The proposed algorithm is applied on FVC2000 database. Manual examinations from human experts show that the proposed algorithm provides an efficient segmentation results. These improved results are demonstrating in diverse experiments.
75

Microbial community dynamics in long-term no-till and conventionally tilled soils of the Canadian prairies

Helgason, Roberta Lynn 15 January 2010 (has links)
Adoption of no-till (NT) and reduced tillage management is widespread on the Canadian prairies and together form the basic platform of soil management upon which most crop production is based. Elimination of tillage in cropping systems changes the physical and chemical characteristics of the soil profile and can affect crop growth and ultimately yield. As such, understanding how soil biota, as drivers of nutrient turnover, adapt to NT is important for maximizing crop productivity and mitigating environmental damage in agroecosystems. This work aims to achieve a greater understanding of microbial community structure and function in long-term NT versus conventionally tilled (CT) soils. Community phospholipid and DNA fingerprinting did not reveal any consistent tillage-induced shifts in microbial community structure, but demonstrated a clear influence of depth within the soil profile. While tillage did not result in broad changes in the community structure, total, bacterial and fungal biomass was consistently greater near the surface of NT soils. Further examination at one site near Swift Current, SK revealed differences in microbial biomass and community structure in NT and CT in field-formed aggregate size fractions. Measurement of mineralization and nitrification at the same site indicated that differences in the early-season turnover of N may be related to physical rather than microbial differences in NT and CT soils. Potential nitrification was higher prior to seeding than mid-season, was not affected by tillage and was correlated with ammonia oxidizer population size of archaea, but not bacteria. This work indicates that edaphic soil properties and spatial distribution of resources in the soil profile, rather than tillage management, are the primary factors driving microbial community structure in these soils.
76

A New Minutiae Method Based on Partial Fingerprints

Lin, Chin-Hung 23 August 2006 (has links)
As information technologies advanced greatly in recent years, the security problem of information networks becomes all the more important. As a result, biometric identification techniques have been given considerable attention. Fingerprint-related techniques, due to these desirable properties, i.e., universality, perpetuity, collectability and particularity, are most widely applied and documented. However, in practice, collected fingerprint images are not always of good quality. They often are noisy or are even partial images. Therefore, in this research, we propose a new minutiae matching method, while using a coefficient of variation of orientation difference, a coefficient of frequency correlation, along with other image features to obtain a match based on only partial fingerprints. By the proposed method, when a score is arrived at and the test image and the database image have five minutia points matched, we have both FRR and FAR values close to 29%, and the correctness of matching reaches 70.56%.
77

Methods for Locating Distinct Features in Fingerprint Images / Methods for Locating Distinct Features in Fingerprint Images

Nelson, Jonas January 2002 (has links)
<p>With the advance of the modern information society, the importance of reliable identity authentication has increased dramatically. Using biometrics as a means for verifying the identity of a person increases both the security and the convenience of the systems. By using yourself to verify your identity such risks as lost keys and misplaced passwords are removed and by virtue of this, convenience is also increased. The most mature and well-developed biometric technique is fingerprint recognition. Fingerprints are unique for each individual and they do not change over time, which is very desirable in this application. There are multitudes of approaches to fingerprint recognition, most of which work by identifying so called minutiae and match fingerprints based on these. </p><p>In this diploma work, two alternative methods for locating distinct features in fingerprint images have been evaluated. The Template Correlation Method is based on the correlation between the image and templates created to approximate the homogenous ridge/valley areas in the fingerprint. The high-dimension of the feature vectors from correlation is reduced through principal component analysis. By visualising the dimension reduced data by ordinary plotting and observing the result classification is performed by locating anomalies in feature space, where distinct features are located away from the non-distinct. </p><p>The Circular Sampling Method works by sampling in concentric circles around selected points in the image and evaluating the frequency content of the resulting functions. Each images used here contains 30400 pixels which leads to sampling in many points that are of no interest. By selecting the sampling points this number can be reduced. Two approaches to sampling points selection has been evaluated. The first restricts sampling to occur only along valley bottoms of the image, whereas the second uses orientation histograms to select regions where there is no single dominant direction as sampling positions. For each sampling position an intensity function is achieved by circular sampling and a frequency spectrum of this function is achieved through the Fast Fourier Transform. Applying criteria to the relationships of the frequency components classifies each sampling location as either distinct or non-distinct. </p><p>Using a cyclic approach to evaluate the methods and their potential makes selection at various stages possible. Only the Circular Sampling Method survived the first cycle, and therefore all tests from that point on are performed on thismethod alone. Two main errors arise from the tests, where the most prominent being the number of spurious points located by the method. The second, which is equally serious but not as common, is when the method misclassifies visually distinct features as non-distinct. Regardless of the problems, these tests indicate that the method holds potential but that it needs to be subject to further testing and optimisation. These tests should focus on the three main properties of the method: noise sensitivity, radial dependency and translation sensitivity.</p>
78

Visualization of Wine Attributes

Mei, Yuanxun January 2009 (has links)
<p>As the development of the Internet and the rapid increase of data, information visualization is becoming more and more popular. Since human eyes receive visual information very quick and easy, the visualization can make complex and large data more understandable.</p><p>Describing sensory perceptions, such as taste, is a challenging task. For a customer, the visualization of the taste of a specific wine together with the other wine attributes such as color and grape type would help him/her choose the right one.    In the thesis, two suitable representations of wine attributes are implemented. And, the final system contains two parts. One is a user interface generating his/her fingerprint based on the two representations. The other one is generating the fingerprints of all wines in a database, and save these fingerprints as images. If the user compares his/her wine fingerpr</p>
79

Biometri vid fysisk access : En jämförande studie mellan ansiktsigenkänning och fingeravtrycksavläsning

Hanner, Martin, Björk, Tobias January 2006 (has links)
<p>In today’s society, people often find themselves in situations where they need to be identified;for example when we buy alcohol, need to use an ATM or log on to our e-mail account. The most common methods today that are used for these kinds of matters are antiquated, and in</p><p>the meantime, criminals all over the world get more sophisticated. Companies invest billions every day in order to protect their interests. Maybe it’s time that we finally give biometrics the</p><p>attention that it deserves.</p><p>This essay aims to describe the biometric methods that are available today, find some of the most effective when it comes to physical access and make a comparison. Face recognition and fingerprint scanning will be described more thoroughly. Pros and cons will be analyzed and the theory will be linked to interviews with three Swedish organisations.</p> / <p>I dagens samhälle hamnar vi människor regelbundet i situationer där vi blir tvungna att identifiera oss. Det kan till exempelvis vara när vi köper alkohol, tar ut pengar eller loggar in på vårt e-mailkonto. De vanligaste metoderna, som idag används för dessa identifieringar, har funnits länge och är föråldrade och i takt med detta blir brottslingar världen allt mer sofistikerade. Dagligen investerar företag världen över miljarder för att skydda exempelvis</p><p>data med hjälp av koder och andra mjukvaruinstallationer. Kanske är det istället dags för att vi ger biometrin en ordentlig chans.</p><p>Den här uppsatsen syftar till att redogöra för de biometriska säkerhetsmetoder som finns tillgängliga, identifiera några av de effektivaste när det gäller fysisk access och jämföra dessa med varandra. Det är framförallt ansiktsigenkänning och fingeravtrycksavläsning som kommer att ges mycket plats i studien. För- och nackdelar kommer att tas upp och teorin kommer att kopplas till intervjuer gjorda med tre svenska företag.</p>
80

Chemical oxidation of tryptic digests to improve sequence coverage in peptide mass fingerprint protein identification

Lucas, Jessica Elaine 30 September 2004 (has links)
Peptide mass fingerprinting (PMF) of protein digests is a widely-accepted method for protein identification in MS-based proteomic studies. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) is the technique of choice in PMF experiments. The success of protein identification in a PMF experiment is directly related to the amount of amino acid sequence coverage. In an effort to increase the amount of sequence information obtained in a MALDI PMF experiment, performic acid oxidation is performed on tryptic digests of known proteins. Performic acid was chosen as the chemical oxidant due to the ease of use and to the selective oxidation of cysteine, methionine, and tryptophan residues. In experiments performed in our laboratory, performic acid oxidation either increased or did not affect protein sequence coverage in PMF experiments when oxidized tryptic digests were analyzed by MALDI. Negative mode MALDI data were acquired, as well as positive mode MALDI data, due to the enhanced ionization of cysteic acid-containing peptides in negative mode. Furthermore, the confidence in a protein match is increased by observation of mass shifts indicative of cysteine, methionine, and/or tryptophan in oxidized peptide ion signals when comparing MALDI spectra prior to performic acid oxidation and after oxidation due to the low abundance of these residues in the majority of all known and hypothetical proteins.

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