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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.
161

Resolução de problemas matemáticos aditivos : possibilidades da ação docente

Justo, Jutta Cornelia Reuwsaat January 2009 (has links)
Que influência tem um programa de formação continuada dos professores em exercício na escola e um programa de ensino sobre o campo conceitual aditivo no desempenho dos alunos em problemas matemáticos aditivos? Para buscar respostas a essa questão foi realizado um estudo experimental nos Anos Iniciais do Ensino Fundamental de duas escolas, uma pública e outra privada. Com o objetivo de aprimorar o desempenho dos alunos dos Anos Iniciais na resolução de problemas matemáticos aditivos, implementou-se um programa de formação continuada junto a um grupo de professores das duas escolas para proporcionar a eles avanços no conhecimento do processo de ensino e aprendizagem do campo conceitual aditivo; e construir com eles um programa de ensino que levasse em conta a construção de significados das operações de adição e subtração, a compreensão das relações semânticas encontradas nos problemas matemáticos aditivos, o ensino de procedimentos, de representações e de habilidades metacognitivas. O estudo não tratou de comparar a escola pública e a privada. A pesquisa envolveu a avaliação do desempenho em problemas aditivos de um total de 320 estudantes dos Anos Iniciais do Ensino Fundamental. Desses, 167 alunos também participaram de um programa de ensino dos problemas aditivos. No estudo desenvolvido, a maioria das turmas experimentais evidenciou um pico no desempenho em comparação às turmas controle. A taxa de acertos mais acentuada das turmas experimentais pôde ser explicada pelo programa de formação continuada de suas professoras e pelo programa de ensino proposto a esse grupo de estudantes por intermédio delas, indo ao encontro do que várias pesquisas na área da eficácia escolar atualmente estão apontando: o professor tem um efeito maior do que anteriormente se pensava no desempenho do aluno. Os resultados evidenciam a importância de políticas e de ações de formação continuada de professores em exercício no próprio âmbito escolar, em que o coletivo dos professores esteja envolvido. Considera-se que mudanças em algumas escolas possam ser um passo inicial para a ampliação de transformações que atinjam, com o tempo, mais escolas, qualificando o ensino e a aprendizagem e desmitificando a ideia de que o conhecimento matemático só é para alguns. / What influence does a program of continued formation for teachers in exercise in a school have? And concerning a program of education on the additive conceptual field in the performance of the pupils in additive mathematical problems, what influence can this program have? To answer these questions an experimental study in the initial years of Elementary School was developed, and two schools were studied, a private and a public one. With the objective to improve the performance of the pupils of the initial years in the resolution of additive mathematical problems, a program of continued formation for a group of teachers from the two schools was implemented to provide advances in the knowledge of the teaching and learning processes related to the additive conceptual field; to construct with these teachers an educational program that took in consideration the construction of meanings of the operations of addition and subtraction, the understanding of the semantic relations found in the additive mathematical problems, the teaching process of procedures, representations and metacognitive abilities. The study did not compare the public school and the private one, but involved the evaluation of the performance in additive problems of a total of 320 students from the initial years of Elementary School. From these 320, 167 pupils had also joined a program on teaching process of the additive problems. In this study, the majority of the experimental groups evidenced a higher improvement in their performance in comparison to the control groups. The most relevant tax of accuracy on the experimental groups could be explained by the program of continued formation which their teacher joined, as well as the program of education in which these students took part and was presented to them by their teachers. All these results are similar to other studies’ results in the area, which are related to school effectiveness on how the teacher affects more than what was previously expected, in relation with the performance of their pupils. These results evidence the importance of politics and action of continued formation of teachers in their own school and where all the teachers are involved. Those changes in some schools can be an initial step considering the improvement of the transformations that will, after a period of time, happen in more schools, what will qualify the teaching and the learning processes, what will change the idea that the mathematical knowledge is only possible for some students.
162

Análise de dificuldades de alunos com o algoritmo da subtração

Mello, Elisabete Marcon 11 September 2008 (has links)
Made available in DSpace on 2016-04-27T16:58:43Z (GMT). No. of bitstreams: 1 Elisabete Marcon Mello.pdf: 3017114 bytes, checksum: 16fd1525b6ecfe454ef3f00ca9c10565 (MD5) Previous issue date: 2008-09-11 / Secretaria da Educação do Estado de São Paulo / This research analyzed the difficulties that students from Basic Education face up to the use of the algorithm of the borrowing (decomposition of the minuend) to solve subtractions operations. Therefore, it was made a comparison between the algorithm of the borrowing and algorithm of the compensation (addition of equal quantities in the minuend and the subtrahend) in order to check if using the algorithm of compensation it could diminish their mistakes. Once in the diagnosis study we found out that students make many mistakes when they have to use the algorithm of the borrowing, mainly when it is necessary to proceed some borrowings to solve the operation. This difficulty was found out in all grades from Basic Education 2 and sometimes it extends to High School level. It was analyzed sixty didactic books and five pedagogical publications from private schools systems of the second grade and we realized the use of the algorithm of the borrowing to solve the subtractions with reserve in all of them. Besides, we analyzed six books for teacher s formation and the same procedure was adopted. Most of teachers who were interviewed recognized that students have difficulties with the subtractions that involve some borrowings. We applied a didactic sequence for fifth grade students in order to introduce the use of the algorithm of the compensation. Based on results of our research, we believed that the use of the algorithm of the compensation could be more efficient for the subtraction problems faced to the students. Our research is based on the Theory of the conceptual fields of Gerard Vergnaud and on the Theory of the Situations of Brousseau / Neste trabalho levantamos as dificuldades enfrentadas por alunos do Ensino Fundamental com o uso do algoritmo do empréstimo (decomposição do minuendo) para efetuar subtrações. Fazemos uma comparação entre o algoritmo do empréstimo e o algoritmo da compensação (adição de quantidades iguais no minuendo e no subtraendo) a fim de saber se, com esse último, poderíamos diminuir as dificuldades dos alunos. Por meio de um estudo diagnóstico constatamos que os alunos cometem muitos erros ao utilizar o algoritmo do empréstimo, principalmente quando são necessários vários empréstimos para efetuar a subtração. Verificamos que essa dificuldade é encontrada em todas as séries do Ensino Fundamental II e se estende ao Ensino Médio. Verificamos sessenta títulos de livros didáticos e cinco apostilas de sistemas educacionais de segunda série do Ensino Fundamental e todos propõem o uso do algoritmo do empréstimo para efetuar as subtrações com reserva. Os seis títulos destinados à formação de professores, que analisamos, também privilegiam o uso do algoritmo do empréstimo. A maioria dos professores analisados reconhece que os alunos têm dificuldades com as subtrações que envolvem vários empréstimos. Aplicamos uma seqüência didática a alunos de quinta série do Ensino Fundamental a fim de introduzir o uso do algoritmo da compensação. Baseados nos resultados de nossa pesquisa, acreditamos que o uso do algoritmo da compensação poderia ser mais eficiente do que o uso do algoritmo do empréstimo, contornando problemas que os alunos enfrentam para efetuar subtrações. Nossa pesquisa está fundamentada na teoria dos campos conceituais de Gerard Vergnaud e na Teoria das Situações Didáticas de Brousseau
163

Esquema de auxílio ao diagnóstico de reabsorção óssea periodontal através de subtração digital de radiografias odontológicas / Aided diagnosis scheme for periodontal bone resorption through odontological digital subtraction radiography

Rodrigues, Eveline Batista 09 August 2006 (has links)
A radiografia é uma das ferramentas primárias de auxílio ao diagnóstico e monitoração do tratamento das doenças periodontais. Porém, a análise subjetiva dessas radiografias feita pelo dentista só consegue identificar lesões quando o quadro clínico apresenta perda acima de 30% do conteúdo mineral do osso, levando um sério desafio ao exercício da odontologia. Em muitas situações clínicas, o dentista também precisa ser capaz de quantificar o tamanho de uma lesão para determinar a taxa de progressão ou cura da doença. A técnica de subtração digital de radiografias provê a detecção de mudanças ósseas sutis, de cerca de 5%, levando ao diagnóstico precoce da doença e aumentando assim o sucesso de seu tratamento. Desta forma, o esquema de auxílio ao diagnóstico de reabsorção óssea periodontal através de subtração digital de radiografias odontológicas proposto no presente trabalho emprega a técnica de subtração digital de radiografias, onde duas radiografias odontológicas, tiradas em intervalos de tempos planejados, são subtraídas para obter uma nova imagem onde serão visíveis somente estruturas que mudaram de uma imagem em relação à outra. Será gerada uma imagem que auxiliará o dentista a efetuar um diagnóstico precoce e instituir o melhor plano de tratamento, e assim acompanhar a resposta do tratamento a partir de novas imagens subtraídas. Na fase anterior à subtração, é necessário o alinhamento, para garantir que estruturas idênticas em ambas imagens estejam no mesmo local, e evitando que o resultado da subtração seja errôneo. O alinhamento consiste na marcação de 4 pontos em regiões de alto contraste em ambas as imagens para que a imagem subseqüente seja alinhada em translação e em rotação em relação à primeira. Posteriormente, uma técnica de correção de contraste é utilizada para corrigir eventuais diferenças de contraste. A subtração fornecerá três formas de visualização, na imagem subtraída, da área onde ocorreu uma reabsorção ou ganho ósseo. Uma delas é a subtração qualitativa, cujas áreas onde as imagens se mantiveram idênticas são mostradas em preto, e áreas onde ocorreram mudanças, em branco. A segunda é a subtração quantitativa, que gera a imagem subtraída em níveis de cinza, mostrando em tons de cinza uniformes áreas onde as imagens se mantiveram idênticas; em tons de cinza escuros, onde ocorreu reabsorção óssea; e em tons de cinza claros, onde ocorreu ganho ósseo. Além destas duas subtrações, há uma terceira subtração, a subtração quantitativa porcentagem-colorida, que mostrará a porcentagem de reabsorção ou ganho ósseo através de áreas coloridas na imagem. O intervalo de porcentagens poderá ser escolhido pelo dentista e a este intervalo poderá ser atribuída uma cor para visualização. Intervalos de porcentagens negativas indicam reabsorção óssea e intervalos de porcentagens positivas, ganho ósseo. Os testes realizados encontraram um erro médio de 7,5% no resultado da subtração, sendo que deste total, 3,5% é o erro introduzido pelo digitalizador. É importante ressaltar que esta taxa representa o erro não somente do algoritmo desenvolvido, mas também a propagação do erro em todas as etapas do processo, ou seja, aquisição, digitalização, alinhamento e subtração. Portanto, o erro da subtração deduzido do erro do digitalizador é de somente 4,0%. / Radiography is one of the primary features to help diagnose and monitor the treatment of periodontal diseases. However, the subjective analysis of these radiographs by the dentist only can identify lesions above 30% of mineral bone loss, leading to a serious challenge for the practice of odontology. In many clinical situations, the dentist needs to quantify the size of a lesion to determine the rate of progression or healing the disease. The digital subtraction radiography technique provides the detection of subtle bone changes, i.e., changes of around 5%, leading to an early diagnosis and enlarging the success of its treatment. The aided diagnosis scheme for periodontal bone resorption through odontological digital subtraction radiography proposed in this work employees the digital subtraction radiography technique, where two odontologic radiographs taken at intervals of planned times are subtracted to obtain a new image where only structures that have been changed from one image to the other will be visible. It will generate an image to help the dentist make an early diagnosis and establish the best treatment plan, besides accompanying the treatment’s response starting from new subtracted images. In the stage previous to the subtraction, the lining up is necessary to assure that identical structures on both images are in the same place, avoiding an erroneous result of the subtraction. It consists in marking 4 points in places with high contrast on both images for the subsequent image to be first lined up in translation and then in rotation in relation to the first one. Then, a contrast correction technique is used to correct possible contrast differences. The subtraction will provide three ways of visualization in the subtracted image of the area where a bone resorption or gain occurred. One of them is the qualitative subtraction, where areas kept identical are showed in black and areas where changes occurred are showed white. The second is the quantitative subtraction, which generates a subtracted image in gray levels, showing in uniform gray levels the areas where the images remained identical, in dark gray levels the areas where there was bone resorption and in light gray levels the area with bone gain. The third subtraction is called colored-percentage quantitative subtraction, which shows the percentage of bone resorption or gain through colored areas on the radiograph. The intervals of percentage can be chosen by the dentist and he/she can attribute a color for visualization to this interval. Negative percentage intervals indicate bone resorption and positive percentage intervals correspond to bone gain. The tests performed found a mean error of 7.5% in the result of the subtraction, of which 3.5% correspond to the error introduced by the digitalizer. It is important to stress that this rate represents the error not only for the algorithm developed, but the spreading of the error to all process stages, such as acquisition, digitalization, lining up and subtraction. Therefore, the subtraction error deduced from the digitalizer error is only 4,0%.
164

An investigation of instruction in two-digit addition and subtraction using a classroom teaching experiment methodology, design research, and multilevel modeling

Tabor, Pamela D Unknown Date (has links)
In his keynote address to the National Council of Teachers of Mathematics research pre-session, Sloane (2006b) challenged mathematics education researchers to ‘quantify qualitative insights’. This quasi-experimental study used blended methods to investigate the development of two-digit addition and subtraction strategies. Concurrent classroom teaching experiments were conducted in two intact first grade classrooms (n = 41) in a mid-Atlantic American public school. From a pragmatic emergent perspective, design research (Gravemeijer & Cobb, 2006) was used to develop local instructional theory. An amplified theoretical framework for early base-ten strategies is explicated. Multilevel modelling for repeated measures was used to evaluate the differences in strategy usage between classes across occasions and the association of particular pedagogical practices with the emergence of incrementing and decrementing by ten (N10) or decomposition (1010) strategies (Beishuizen, Felix, & Beishuizen, 1990).The two matched classes were not different in terms of gender, poverty, race, pre-assessment performance, and special education services. After the first unit of instruction with differentiated pedagogical tools, the collection class was significantly (p = .001) more likely to use 1010 than the linear class. No difference was demonstrated during the post-assessment. Students in both classes were more likely to use N10 during the last structured interview than in the first (p < .0001). Furthermore, there was no difference between the two classes in using any advanced strategy; however, students in both classes were more likely to use an advanced strategy at the conclusion of the study than they were initially (p = .033). The order of emergence of 1010 and N10 was not associated with the ability to develop both strategies, but there was an association (p < .001) between use of an advanced strategy and success on a district-mandated written assessment of two-digit addition and subtraction.Two original instructional sequences of contextually-based investigations are presented. Protocols transcribed from videotaped lessons and dynamic assessment interviews are presented to illuminate specific constructs detected and to illustrate the pedagogical techniques. An amplified framework for early place value constructs is proposed. Recommendations for future studies, curricular changes, and the need of early intervention are discussed.
165

Visual Detection And Tracking Of Moving Objects

Ergezer, Hamza 01 November 2007 (has links) (PDF)
In this study, primary steps of a visual surveillance system are presented: moving object detection and tracking of these moving objects. Background subtraction has been performed to detect the moving objects in the video, which has been taken from a static camera. Four methods, frame differencing, running (moving) average, eigenbackground subtraction and mixture of Gaussians, have been used in the background subtraction process. After background subtraction, using some additional operations, such as morphological operations and connected component analysis, the objects to be tracked have been acquired. While tracking the moving objects, active contour models (snakes) has been used as one of the approaches. In addition to this method / Kalman tracker and mean-shift tracker are other approaches which have been utilized. A new approach has been proposed for the problem of tracking multiple targets. We have implemented this method for single and multiple camera configurations. Multiple cameras have been used to augment the measurements. Homography matrix has been calculated to find the correspondence between cameras. Then, measurements and tracks have been associated by the new tracking method.
166

Multiple Target Tracking Using Multiple Cameras

Yilmaz, Mehmet 01 May 2008 (has links) (PDF)
Video surveillance has long been in use to monitor security sensitive areas such as banks, department stores, crowded public places and borders. The rise in computer speed, availability of cheap large-capacity storage devices and high speed network infrastructure enabled the way for cheaper, multi sensor video surveillance systems. In this thesis, the problem of tracking multiple targets with multiple cameras has been discussed. Cameras have been located so that they have overlapping fields of vision. A dynamic background-modeling algorithm is described for segmenting moving objects from the background, which is capable of adapting to dynamic scene changes and periodic motion, such as illumination change and swaying of trees. After segmentation of foreground scene, the objects to be tracked have been acquired by morphological operations and connected component analysis. For the purpose of tracking the moving objects, an active contour model (snakes) is one of the approaches, in addition to a Kalman tracker. As the main tracking algorithm, a rule based tracker has been developed first for a single camera, and then extended to multiple cameras. Results of used and proposed methods are given in detail.
167

Implementation and Evaluation of Spectral Subtraction with Minimum Statistics using WOLA and FFT Modulated Filter Banks

Rao, Peddi Srinivas, Sreelatha, Vallabhaneni January 2014 (has links)
In communication system environment speech signal is corrupted due to presence of additive acoustic noise, so with this distortion the effective communication is degraded in terms of the quality and intelligibility of speech. Now present research is going how effectively acoustic noise can be eliminated without affecting the original speech quality, this tends to be our challenging in this current research thesis work. Here this work proposes multi-tiered detection method that is based on time-frequency analysis (i.e. filter banks concept) of the noisy speech signals, by using standard speech enhancement method based on the proven spectral subtraction, for single channel speech data and for a wide range of noise types at various noise levels. There were various variants have been introduced to standard spectral subtraction proposed by S.F.Boll. In this thesis we designed and implemented a novel approach of Spectral Subtraction based on Minimum Statistics [MinSSS]. This means that the power spectrum of the non-stationary noise signal is estimated by finding the minimum values of a smoothed power spectrum of the noisy speech signal and thus circumvents the speech activity detection problem. This approach is also capable of dealing with non-stationary noise signals. In order to analyze the system in time frequency domain, we have implemented two different filter bank approaches such as Weighted OverLap Added (WOLA) and Fast Fourier Transform Modulated (FFTMod). The proposed systems were implemented and evaluated offline using simulation tool Matlab and then validated their performances based on the objective quality measures such as Signal to Noise Ratio Improvement (SNRI) and Perceptual Evaluation Speech Quality (PESQ) measure. The systems were tested with a pure speech combination of male and female sampled at 8 kHz, these signals were corrupted with various kinds of noises at different noise power levels. The MinSSS algorithm implemented using FFTMod filter bank approach outperforms when compared the WOLA filter bank approach.
168

Απεικόνιση των ενδοκρανιακών αγγείων με την ψηφιακή αγγειογραφία (DSA) συγκριτικά με την CT αγγειογραφία (CTA) / Demonstration of the intracranial vessels using digital subtraction angiography (DSA) in comparison to CT angiography (CTA)

Καραμεσίνη, Μαρία 25 June 2007 (has links)
Η CT αγγειογραφία εγκεφάλου (CTA) είναι μέθοδος καθιερωμένη για την διερεύνηση και την θεραπεία των ενδοκρανιακών ανευρυσμάτων. Σκοπός της μελέτης μας ήταν η σύγκριση των ευρημάτων της ψηφιακής αγγειογραφίας (DSA) με αυτά της CTA και με τα χειρουργικά ευρήματα σε ασθενείς με οξεία υπαραχνοειδή αιμορραγία, καθώς επίσης και η αξιολόγηση της κλινικής χρησιμότητας της μεθόδου. Κατά την διάρκεια τριών ετών, 82 ασθενείς προσήλθαν με κλινική εικόνα και σημειολογία συμβατή με υπαραχνοειδή αιμορραγία. Η CTA έγινε αμέσως μετά την απλή CT, ενώ η DSA εντός των πρώτων 48 ωρών από την εισαγωγή. Όλα τα ανευρύσματα που ευρέθησαν με τις δύο μεθόδους υπεβλήθησαν σε χειρουργική αποκατάσταση ή ενδαγγειακό εμβολισμό. Σε όσους ασθενείς βρέθηκε αρνητικό αποτέλεσμα και με τις δύο μεθόδους, έγινε επαναληπτική DSA 15 ημέρες μετά το επεισόδιο με σκοπό την επιβεβαίωση της απουσίας ανευρύσματος. Οι CTA εξετάσεις καθώς και οι κλασσικές αγγειογραφίες μελετήθηκαν από μια ομάδα δύο ακτινολόγων για κάθε τεχνική, οι οποίοι έπρεπε να καταγράψουν την ύπαρξη ή μη ανευρύσματος, να περιγράψουν τα χαρακτηριστικά του και να αξιολογήσουν την μέθοδο. Χειρουργική ή και ενδαγγειακή θεραπεία έγινε σε 45 ασθενείς και ανευρέθησαν 53 ανευρύσματα. Χρησιμοποιώντας την CTA, ευρέθησαν 47 ανευρύσματα σε 42 ασθενείς. Η DSA ανίχνευσε 43 ανευρύσματα σε 39 ασθενείς. Η ευαισθησία της CTA για τον εντοπισμό όλων των ανευρυσμάτων με βάση το χειρουργικό/θεραπευτικό αποτέλεσμα ήταν 88,7%, η ειδικότητα 100%, η θετική προβλεπτική αξία (PPV) 100%, η αρνητική προβλεπτική αξία (NPV) 80,7% και η ακρίβεια 92,3%. Αντίστοιχα, η ευαισθησία της DSA ήταν 87,8%, η ειδικότητα 98%, η PPV 97,7%, η NPV 89,1% και η ακρίβεια 92,9%. Όσον αφορά στα ανευρύσματα ≥3 mm, η CTA είχε ευαισθησία που κυμαινόταν μεταξύ 93,3 έως 100%, ίση με αυτή της DSA. Η CTA εμφάνισε τα ίδια ποσοστά ευαισθησίας με αυτά της DSA σε ανευρύσματα ≥3 mm. Εμφάνισε επίσης 100% ποσοστό ανίχνευσης σε ανευρύσματα της πρόσθιας αναστομωτικής και του διχασμού της μέσης εγκεφαλικής αρτηρίας, ενώ μερικές εντοπίσεις όπως η οπίσθια αναστομωτική αρτηρία παραμένουν προβληματικές. 80 Κατά την διάρκεια της παρούσας μελέτης προσπαθήσαμε να δημιουργήσουμε μια τεχνική προσομοίωσης της διεγχειρητικής εικόνας των ραγέντων ενδοκρανιακών ανευρυσμάτων, με τη χρήση volume rendering techniques σε εικόνες που προκύπτουν από CT αγγειογραφία. Η τρισδιάστατη κατασκευή των εικόνων προέκυψε από την συνεργασία μιας ομάδας αποτελούμενης από τέσσερις ακτινολόγους, έναν νευροχειρουργό και έναν ιατρικό φυσικό. Το αποτέλεσμα αυτής της συνεργασίας ήταν η παραγωγή μιας εικόνας οριοθετημένης στο χώρο, με οδηγά σημεία που εύκολα μπορούσαν να αναπαραχθούν κατά την διάρκεια του χειρουργείου. Οι εικόνες χειρουργικής προσομοίωσης ενός ανευρύσματος είναι πιθανώς χρήσιμο εργαλείο για τον προεγχειρητικό σχεδιασμό των ενδοκρανιακών ανευρυσμάτων. / Cerebral CT angiography is an established method applied to both the detection and treatment planning of intracranial aneurysms. The aim of our study was to compare DSA to CTA findings and with the surgical results mainly in patients with acute SAH and to evaluate the clinical usefulness of CTA. During the last three years, 82 consecutive patients were admitted under clinical symptoms and signs suggestive of harbouring an intracranial aneurysm. CT angiography performed immediately afterwards the plain CT, while DSA was performed within the first 48 hours of admission. All aneurysms detected, were confirmed during surgery or endovascular embolization. Repeat DSA was performed in all patients having both the initial CTA and the DSA 15 days after the onset of symptoms negative. CT angiograms and conventional angiographies were studied by a consensus of two radiologists for each technique, who performed aneurysm detection, morphological features characterization and evaluation of the technique. Surgical or/and endovascular treatment was performed in 45 patients and 53 aneurysms were confirmed. Using 3D-CT angiography we detected 47 aneurysms in 42 patients. Conventional angiography depicted 43 aneurysms in 39 patients. The sensitivity of CTA for the detection of all aneurysms versus surgery was 88.7%, the specificity 100%, the positive predictive value (PPV) 100%, the negative predictive value (NPV) 80.7% and the accuracy 92.3%. Consequently, the sensitivity of DSA was 87.8%, the specificity 98%, the PPV 97.7%, the NPV 89.1% and the accuracy 92.9%. Considering the aneurysms ≥ 3 mm, CTA showed a sensitivity ranging from 93.3% to 100%, equal to that of DSA. Cerebral CT angiography has an equal sensitivity to DSA in the detection of intracranial aneurysms greater than 3 mm. It has also 100% detection rate in AcoA and MCA bifurcation aneurysms, while some locations like posterior communicating artery aneurysms remain problematic. The delineating features of each aneurysm are better depicted with CTA due to 3D visualization. The use of Digital Subtraction Angiography as a diagnostic tool can be limited in equivocal cases. A supplement to the above work is our effort to describe a technique for simulating the surgical view of ruptured intracranial aneurysms, using volume 82 rendering techniques in spiral CT angiography data. The 3D rendered images were assessed by a team consisted of four radiologists, one neurosurgeon and one medical physicist. The resultant ‘surgical view’ image was standardized in space using a three-dimensional coordinate system, which allowed for its reproduction in the operating theatre. The surgical views are easily reproducible and αποτελούν a useful tool for the surgical planning of intracranial aneurysms.
169

Beyond-mean-field corrections and effective interactions in the nuclear many-body problem

Moghrabi, Kassem 12 September 2013 (has links) (PDF)
Mean-field approaches successfully reproduce nuclear bulk properties like masses and radii within the Energy Density Functional (EDF) framework. However, complex correlations are missing in mean-field models and several observables related to single-particle and collective nuclear properties cannot be predicted accurately. The necessity to provide a precise description of the available data as well as reliable predictions in the exotic regions of the nuclear chart motivates the use of more sophisticated beyond-mean-field models. Correlations and higher-order corrections (beyond the leading mean-field order) are introduced. A crucial aspect in these calculations is the choice of the effective interaction to be used when one goes beyond the leading order (available effective interactions are commonly adjusted at the mean-field level). In the first part, we deal with the equation of state of nuclear matter evaluated up to the second order with the phenomenological Skyrme force. We analyze the ultraviolet divergence that is related to the zero range of the interaction and we introduce Skyrme-type regularized interactions that can be used at second order for matter. Cutoff regularization and dimen- sional regularization techniques are explored and applied. In the latter case, connections are naturally established between the EDF framework and some techniques employed in Effective Field Theories. In the second part, we check whether the regularized interactions introduced for nuclear matter can be employed also for finite nuclei. As an illustration, this analysis is performed within the particle- vibration model that represents an example of beyond mean-field models where an ultraviolet divergence appears if zero-range forces are used. These first applications suggest several directions to be explored to finally provide regularized interactions that are specially tailored for beyond- mean-field calculations for finite nuclei. Conclusions and perspectives are finally illustrated.
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An investigation of instruction in two-digit addition and subtraction using a classroom teaching experiment methodology, design research, and multilevel modeling

Tabor, Pamela D Unknown Date (has links)
In his keynote address to the National Council of Teachers of Mathematics research pre-session, Sloane (2006b) challenged mathematics education researchers to ‘quantify qualitative insights’. This quasi-experimental study used blended methods to investigate the development of two-digit addition and subtraction strategies. Concurrent classroom teaching experiments were conducted in two intact first grade classrooms (n = 41) in a mid-Atlantic American public school. From a pragmatic emergent perspective, design research (Gravemeijer & Cobb, 2006) was used to develop local instructional theory. An amplified theoretical framework for early base-ten strategies is explicated. Multilevel modelling for repeated measures was used to evaluate the differences in strategy usage between classes across occasions and the association of particular pedagogical practices with the emergence of incrementing and decrementing by ten (N10) or decomposition (1010) strategies (Beishuizen, Felix, & Beishuizen, 1990).The two matched classes were not different in terms of gender, poverty, race, pre-assessment performance, and special education services. After the first unit of instruction with differentiated pedagogical tools, the collection class was significantly (p = .001) more likely to use 1010 than the linear class. No difference was demonstrated during the post-assessment. Students in both classes were more likely to use N10 during the last structured interview than in the first (p < .0001). Furthermore, there was no difference between the two classes in using any advanced strategy; however, students in both classes were more likely to use an advanced strategy at the conclusion of the study than they were initially (p = .033). The order of emergence of 1010 and N10 was not associated with the ability to develop both strategies, but there was an association (p < .001) between use of an advanced strategy and success on a district-mandated written assessment of two-digit addition and subtraction.Two original instructional sequences of contextually-based investigations are presented. Protocols transcribed from videotaped lessons and dynamic assessment interviews are presented to illuminate specific constructs detected and to illustrate the pedagogical techniques. An amplified framework for early place value constructs is proposed. Recommendations for future studies, curricular changes, and the need of early intervention are discussed.

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