Made available in DSpace on 2014-06-12T17:40:49Z (GMT). No. of bitstreams: 2 arquivo7042_1.pdf: 3910655 bytes, checksum: 9a5e52d2535f94f8e232ee5d957d91ee (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / Recentemente, foram desenvolvidos algoritmos iterativos de compressão destinados à transmissão de imagens estáticas via rede tais como: JPEG progressivo, JPEG2000 progressivo, PNG entrelaçado e GIF entrelaçado. Esses algoritmos decompõem a imagem e a transmitem de forma não seqüencial. O propósito desta dissertação consiste em efetuar um estudo comparativo desses algoritmos. A metodologia adotada consiste em fazer uma análise das imagens parciais obtidas para cada formato. Em cada etapa, faz-se uma inspeção visual da imagem e mede-se o PSNR (Peak Signal-to-Noise Ratio) em relação à imagem final, um fator objetivo de qualidade de imagens. Parâmetros como tamanho do arquivo parcial, natureza da imagem e inspeção visual também são alvo de estudo. Através de uma análise detalhada das imagens parciais obtidas somos capazes de definir então qual algoritmo é mais apropriado em cada etapa da transmissão de acordo com a natureza da imagem analisada

This survey study on students attitudes towards science was conducted in Papua New Guinea. It involved 200 randomly selected grade six students in eight selected community (primary) schools (4 urban and 4 rural) of four provinces. There were six research questions to focus the study. The instruments consisted of 9 Students Background Questions, 9 interview questions, 43 Students Science Attitude Questionnaire Items, and a 20-item cognitive test. The former three sets of instruments were trialled in two schools. The test questions were not trialled as they were trialled previously in several schools within PNG. The 43 Likert-type items were divided into five categories - curiosity, enjoyment, science learning, perceived achievement, and relevance. Each category was assigned 10 items, with the exception of perceived achievement which had three items. About half of the the statements in a category were negatively worded. A student had to put a tick in a box next to a statement according to his or her feelings. The choices were given by the five-point scale - Strongly Agree (SA), Agree (A), Hot Sure (NS), Disagree (D), and Strongly Disagree (SD) along with three laces (smiling, uncertain and frowning) which were added as interest, From the twenty five students in a study school, a group of 6 students (3 males and 3 females) was randomly selected for face to face interview. The responses in the items associated with the five categories (dependent variables) were used to assess various student characteristics (independent variables) of parent and home background (i.e. parent educational levels and language use at home), gender (male and female), biogeographical location (urban and rural), and level of performance in standardized cognitive test (above average, average and below average). Statistical techniques of correlation coefficient, analysis of variance and factor analysis were used in analysing the responses but the results were not clear due insufficient trialling and test of reliability with the limited period in which the data had to be collected. As consequence, chi-square test (contingency tables) was used as alternative statistical test to determine significant differences in responses to the items at 0.05 level. With the exception of perceived achievement, student responses to the items on the categories were generally and satisfactorily positive. The mean levels of attitudes in the categories were not as high as one may expect (Table 5.1). Relatively, few of the items associated with student independent variables showed significant differences. There was generally no significant differences in parent and home backgrounds (i.e. language use and parent educational background). Urban students tended to be more positive than the rural students, but. this not could be generalised due to a small number of items with significant differences. Male students showed more positive attitudes to science than female students, but this was limited to a small number of items. The students with above average scores in the cognitive test showed more positive attitudes to science than those of average and below verage scores. However, the number of items were quite small, and therefore could not be generalised. Points of improvement in the practice of teaching and future research in attitudes to science are recommended. For instance, the present officially prescribed time of 40 minutes per week for science should be changed to 1.5 to 2 hours after further investigation. The reason for this is that it requires some preparation before actual lessons begin (e.g. collecting materials by groups) and the students are generally slow.

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The study combined qualitative methods (observation, interview and case study techniques) and quantitative methods (use of questionnaire and survey instruments) methods to (a) identify and describe current teaching practices in Papua New Guinea (PNG) secondary science laboratory classrooms; (b) investigate the effect of specific teaching practices on academic success on an external science achievement examinaton; and (c) investigate whether an educational productivity model for investigating factors associated with learning is applicable to a developing country context, namely, PNG. Analysis of data from 3,182 Papua New Guinea secondary students, generated revealed similar science laboratory learning environments across most high schools with Open-Endedness having the lowest score. Overall students' attitudes towards science were favourable, with boys having a more favourable attitudes than girls. Multivariate analyses showed that science academic achievement, science practical achievement and attitudes were related to quality and quantity of instruction, the science laboratory learning environment and gender. As in similar studies in other countries, male students performed significantly better than female students in external science achievement examinations. But female students achieved significantly better on a practical science process test. Finally, the study identified some specific aspects of current teaching practices in a developing country context, involving science learning environments and students' attitudes towards science.

Guided missiles are among the most effective threats against air platforms. Aircraft and helicopter losses in the last decades were mostly due to guided missiles, 70% of which were infrared guided missiles. Today, there are as many as 500,000 shoulder-fired missiles in military arsenals around the world, whose guidance algorithms enable them to track the desired trajectories very precisely. In this thesis, main focus is on defining infrared missile guidance and control algorithms in order to study on various target-missile scenarios for the effectiveness of these algorithms. First, a mathematical model of a generic missile is given. Then the flight control system of the missile is created by using LQR and PID controllers. Different kinds of PNG algorithms applied to an infrared missile are presented. The seeker part of the infrared missile is also discussed. The effectiveness of guidance algorithms are studied based on different target &ndash / missile scenarios and the responses of them to IR countermeasures are also observed. This study shows that different guidance algorithms can be used for different scenarios. If suitable algorithms are combined and suitable constants are applied, the guided missile can track the target very precisely. In addition, the seeker part has to be improved with tracking algorithms in order to recognize IR-countermeasures and not to follow them.

Signal compression is necessary part for ECG scanning, because of relatively big amount of data, which must be transmitted primarily wirelessly for analysis. Because of the wireless sending it is necessary to minimize the amount of data as much as possible. To minimize the amount of data, lossless or lossy compression algorithms are used. This work describes an algorithm SPITH and newly created experimental method, based on PNG, and their testing. This master’s thesis there is also a bank of ECG signals with parallel sensed accelerometer data. In the last part, modification of SPIHT algorithm, which uses accelerometer data, is described and realized.

This thesis deals with development of guidance laws for advanced applications. Two class of guidance problems, namely, impact angle constrained guidance and pulsed guidance for exo-atmospheric engagements, are considered here. Three impact angle constrained guidance schemes are developed using (i) Proportional navigation guidance (PNG), (ii) State Dependent Riccati Equation (SDRE) technique and (iii) geometric concepts, respectively. A collision course based pulsed guidance law is presented for exo-atmospheric interceptors. Proportional Navigation Guidance (PNG) law is the most widely used guidance law because of its ease of implementation and efficiency. However, in its original form, it achieves only a limited set of impact angles. A two stage PNG law is presented for achieving all impact angles against a stationary target. In the first phase of guidance, an orientation PNG command is used. The orientation navigation constant (N ) is a function of the initial engagement geometry and has a lower value (N less than 2). It is proved that following the orientation trajectory, the interceptor can switch to N = 2 and achieve the desired impact angle. Simulations, with a constant speed and with a realistic interceptor model, show successful interception of the target with all desired impact angles. Feedback implementation of the guidance law results in negligible errors in impact angle with uncompensated autopilot delays. The idea of a two-stage PNG law with impact angle constraint is further used to develop a guidance law for intercepting moving targets. Following the orientation trajectory, the interceptor can switch to N = 3 and achieve the desired impact angle. It is proved that the guidance achieves all impact angles in a surface-to-surface engagement scenario with receding and approaching targets, respectively. In a air-to-surface engagement scenario, it is proved that the guidance law achieves all impact angles in a deterministic set. Constant speed and realistic interceptor models are used for simulations. Results show negligible error in impact angle and miss distance for moving targets. The guidance law, in its feedback implementation form, achieves the desired impact angle for interceptors with delay and with a maneuvering target. The impact angle errors are low with negligible errors in miss distance. Next, the impact angle constrained guidance problem against a stationary target is solved as a non-linear regulator problem using the SDRE technique. The interceptor guidance problems are of finite time nature. As the main contribution of this part of the work, we solve a finite time interceptor guidance problem with infinite horizon SDRE formulation by choosing the state weighting matrix as a function of time-to-go. Numerical simulations are carried out both for a constant speed interceptor model and a realistic interceptor model. Simulations for both the models are carried out for various impact angles and firing angles. Robustness of the proposed guidance law with respect to autopilot lag is also verified by simulations. Results obtained show the efficiency of the SDRE approach for impact angle constrained missile guidance. A geometric guidance scheme is proposed for lateral interception of targets in a planar engagement scenario in the absence of line-of-sight rate information. A kill-band is defined for target initial positions capturable by an arc maneuver, followed by a straight line path by the interceptor. Guidance law for capturing targets inside the kill-band is presented and is further modified for targets outside the kill-band. Based on analytical studies on the kill-band, a guidance law is proposed for lateral interception of maneuvering targets. Simulations are carried with for typical low speed engagements. The concept of kill-band provides an inherent robustness to the proposed guidance law with respect to uncompensated system delays and target maneuver. As the final part of the work, an interceptor endgame pulsed guidance law for exoatmospheric engagements is derived by using the notion of collision heading. The proposed guidance law is derived in steps by (i) Obtaining the collision heading based on the collision triangle engagement geometry and then (ii) Computing the width of the pulse fired by the divert thruster to attain the collision heading. It is shown that this strategy is more effective than the existing zero effort miss (ZEM) based guidance laws for intercepting targets with higher heading angles off the nominal head-on collision course. A result on pulse firing sequence is also presented showing that firing pulses in quick succession results in minimum pulse widths and hence minimum control effort for a desired miss distance. Simulations are carried out for various engagement scenarios. Results show better miss-distance and divert thrust performance as compared to the existing ZEM based law.

The flow of genetic information from genes to proteins is mediated through proteins which interact with the nucleic acids at several stages to successfully transmit the information from the nucleus to the cell cytoplasm. Unlike in the case of protein-protein interactions, the principles behind protein-nucleic acid interactions are still not very (Pabo and Nekludova, 2000) and efforts are still underway to arrive at the basic principles behind the specific recognition of nucleic acids by proteins (Prabakaran et al., 2006). This is mainly due to the innate complexity involved in recognition of nucleotides by proteins, where, even within a given family of DNA binding proteins, different modes of binding and recognition strategies are employed to suit their function (Luscomb et al., 2000). Such difficulties have also not made possible, a thorough classification of DNA/RNA binding proteins based on the mode of interaction as well as the specificity of recognition of the nucleotides. The availability of a large number of structures of protein-nucleic acids complexes (albeit lesser than the number of protein structures present in the PDB) in the past few decades has provided the knowledge-base for understanding the details behind their molecular mechanisms (Berman et al., 1992). Previously, studies have been carried out to characterize these interactions by analyzing specific non-covalent interactions such as hydrogen bonds, van der Walls, and hydrophobic interactions between a given amino acid and the nucleic acid (DNA, RNA) in a pair-wise manner, or through the analysis of interface areas of the protein-nucleic acid complexes (Nadassy et al., 1998; Jones et al., 1999). Though the studies have deciphered the common pairing preferences of a particular amino acid with a given nucleotide of DNA or RNA, there is little room for understanding these specificities in the context of spatial interactions at a global level from the protein-nucleic acid complexes. The representation of the amino acids and the nucleotides as components of graphs, and trying to explore the nature of the interactions at a level higher than exploring the individual pair-wise interactions, could provide greater details about the nature of these interactions and their specificity. This thesis reports the study of protein-nucleic interactions using graph and network based approaches. The evaluation of the parameters for characterizing protein-nucleic acid graphs have been carried out for the first time and these parameters have been successfully employed to capture biologically important non-covalent interactions as clusters of interacting amino acids and nucleotides from different protein-DNA and protein-RNA complexes. Graph and network based approaches are well established in the field of protein structure analysis for analyzing protein structure, stability and function (Kannan and Vishveshwara, 1999; Brinda and Vishveshwara, 2005). However, the use of graph and network principles for analyzing structures of protein-nucleic acid complexes is so far not accomplished and is being reported the first time in this thesis. The matter embodied in the thesis is presented as ten chapters. Chapter 1 lays the foundation for the study, surveying relevant literature from the field. Chapter 2 describes in detail the methods used in constructing graphs and networks from protein-nucleic acid complexes. Initially, only protein structure graphs and networks are constructed from proteins known to interact with specific DNA or RNA, and inferences with regard to nucleic acid binding and recognition were indirectly obtained . Subsequently, parameters were evaluated for representing both the interacting amino acids and the nucleotides as components of graphs and a direct evaluation of protein-DNA and Protein-RNA interactions as graphs has been carried out. Chapter 3 and 4 discuss the graph and network approaches applied to proteins from a dataset of DNA binding proteins complexed with DNA. In chapter 3, the protein structure graphs were constructed on the basis of the non-covalent interactions existing between the side chains of amino acids. Clusters of interacting side chains from the graphs were obtained using the graph spectral method. The clusters from the protein-DNA interface were analyzed in detail for the interaction geometry and biological importance (Sathyapriya and Vishveshwara, 2004). Chapter 4 also uses the same dataset of DNA binding proteins, but a network-based approach is presented. From the analysis of the protein structure networks from these DNA binding proteins, interesting observations relating the presence of highly connected nodes(or hubs) of the network to functionally important amino acids in the structure, emerged. Also, the comparison between the hubs identified from the protein-protein and the protein-DNA interfaces in terms of their amino acid composition and their connectivity are also presented (Sathyapriya and Vishveshwara, 2006) Chapter 5 and 6 deal with the graph and network applications to a specific system of protein-RNA complex (aminoacyl-tRNA synthetases) to gain insights into their interface biology based on amino acid connectivity. Chapter 5 deals with a dataset of aminoacyl-tRNA synthetase (aaRS) complexes obtained with various ligands like ATP, tRNA and L-amino acids. A graph based identification of side chain clusters from these ligand-bound aaRS structures has highlighted important features of ligand-binding at the catalytic sites of the two structurally different classes of aaRS (Class I and Class II). Side chain clusters from other regions of aaRS such as the anticodon binding region and the ligand-activation sites are discussed. A network approach is used in a specific system of aaRS(E.coli Glutaminyl-tRNA synthetase (GlnRS) complexed with its ligands, to specifically understand the effects of different ligand binding., in chapter 6. The structure networks of E.coli GlnRS in the ligand-free and different ligand-bound states are constructed. The ligand-free and the ligand-bound complexes are compared by analyzing their network properties and the presence of hubs to understand the effect of ligand-binding. These properties have elegantly captured the effects of ligand-binding to the GlnRS structure and have also provided an alternate method for comparing three dimensional structures of proteins in different ligand-bound states (Sathyapriya and Vishveshwara, 2007). In contrast to protein structure graphs (PSG), both the interacting amino acids and nucleotides (DNA/RNA) form the components of the protein-nucleic acid graphs (PNG) from protein-nucleic acid complexes. These graphs are constructed based on the non-covalent interactions existing between the side chains of the amino acids and nucleotides. After representing the interacting nucleotides and amino acids as graphs, clusters of the interacting components are identified. These clusters are the strongly interacting amino acids and nucleotides from the protein-nucleic acid complexes. These clusters can be generated at different strengths of interaction between the amino acid side chain and the nucleotide (measured in terms of its atomic connectivity) and can be used for detecting clusters of non-specific as well as specific interactions of amino acids and nucleotides. Though the methodology of graph construction and cluster identification are given in chapter 2, the details of the parameters evaluated for constructing PNG are given in chapter 7. Unlike in the previous chapters, the succeeding chapters deal exclusively with results that are obtained from the analyses of PNG. Two examples of obtaining clusters from a PNG are given, one each for a protein-DNA and a protein-RNA complex. In the first example, a nucleosome core particle is subjected to the graph based analysis and different clusters of amino acids with different regions of the DNA chain such as phosphate, deoxyribose sugar and the base are identified. Another example of aminoacyl-tRNA synthetase complexed with its cognate tRNA is used to illustrate the method with a protein-RNA complex. Further, the method of constructing and analyzing protein-nucleic acid graphs has been applied to the macromolecular machinery of the pre-translocation complex of the T. thermophilus 70S ribosome. Chapter 8 deals exclusively with the results identified from the analysis of this magnificent macromolecular ensemble. The availability of the method that can handle interactions between both amino acids and the nucleotides of the protein-nucleic acid complexes has given us the basis fro evaluating these interactions in a level higher than that of analyzing pair-wise interactions. A study on the evaluation of short hydrogen bonds(SHB) in proteins, which does not fall under the realm of the main objective of the thesis, is discussed in the Chapter 9. The short hydrogen bonds, defined by the geometrical distance and angle parameters, are identified from a non-redundant dataset of proteins. The insights into their occurrence, amino acid composition and secondary structural preferences are discussed. The SHB are present in distinct regions of protein three-dimensional structures, such that they mediate specific geometrical constraints that are necessary for stability of the structure (Sathyapriya and Vishveshwara, 2005). The significant conclusions of various studies carried out are summarized in the last chapter (Chapter 10). In conclusion, this thesis reports the analyses performed with protein-nucleic acid complexes using graph and network based methods. The parameters necessary for representing both amino acids and the nucleotides as components of a graph, are evaluated for the first time and can be used subsequently for other analyses. More importantly, the use of graph-based methods has resulted in considering the interaction between the amino acids and the nucleotides at a global level with respect to their topology of the protein-nucleic acid complexes. Such studies performed on a wide variety of protein-nucleic acid complexes could provide more insights into the details of protein-nucleic acid recognition mechanisms. The results of these studies can be used for rational design of experimental mutations that ascertain the structure-function relationships in proteins and protein-nucleic acid complexes.