This degree project was performed in collaboration with the division of nuclear physics at the department of physics, KTH Royal Institute of Technology. A partial goal of the project was to create a simulation model, where the relationship be- tween the multiplication of electrons that occurs in an ionization chamber and the different pressures of air in the detector could be visualized. The main goal was then to use this model in order to examine the behaviour of electron multiplication for different geometries of the simulated ionization chamber. The simulation was performed in Python 3.7 (Python Soft- ware Foundation, DE, United States), and geometry was modified by increasing and decreasing the simulated inner and anode wire radius of the chamber. Results showed that the peak of the multiplication curve occurred at different pressures for different geometries. When the anode wire radius was fixed, the peak occurred at a lower pressure for an increase of the inner radius, whereas, when the inner radius was fixed, the peak occurred at a higher pressure for an increase of the anode wire radius. The number of created electrons are dependent of Townsend’s coefficent, α, which in turn is dependent of the relationship between pressure and electric field strength. The electric field strength within an ionization chamber varies for different geometries, and therefore is the relationship between pressure and electric field that results in the max- imum value of α, and thus the maximum peak of the multiplication factor, consequently given by different pressures for different chamber geometries. If the results from the simulations in this project are to correspond with actual experimental data, the knowledge of this geometry-dependence may be used to include or exclude the multiplication peak in further measurements depending upon preference.

Distal radius fracture (DRF) is the most common fracture encountered in clinical practice. Every year, more than 20000 people in Sweden suffer from this injury. It has been shown that there is a correlation between malalignment and function following distal radial fractures and malunion may cause persistent pain and disability. A problem has been in making a correct initial assessment of the fracture. Many fractures are unstable despite an acceptable position on the initial radiographic examination or following a successful closed fracture reduction. Numerous classification systems have been developed for evaluation of DRF in order to predict the outcome. However, the values of these are limited since they have not shown satisfactory reliability. Furthermore, the utility of these systems to predict radiographic or clinical outcome is not yet proven. These shortcomings may be one reason why optimal DRF management is still controversial. Requests for a new classification system of DRF, predictive of outcome and easy to use, have been made. Improvement in initial assessment of DRF will benefit a large group of patients, as well as the society, by reducing persistent symptoms and disability. Study I: In this study we evaluated the interobserver and intraobserver reliability of a new classification system (the Buttazzoni classification). Two hundred and thirty-two patients with acute DRF were blindly evaluated using the new classification by three orthopaedic surgeons twice with a 1-year interval. The new classification showed fair to substantial interobserver and intraobserver reliability, i.e., results comparable with other commonly used classification systems. Study II: This was a prospective multicenter study of fracture stability in 428 DRF. The study investigated whether cortical comminution and intra-articular involvement, as well as the new classification system, could predict displacement in DRF. Logistic regression analysis showed that initial position of the fracture and volar or dorsal comminution predicted later displacement, while intra-articular involvement did not. Volar comminution was the strongest predictor of displacement. The new classification system, which is the first to include volar comminution as a separate parameter, was highly predictive of fracture instability. Furthermore we found that it is quite common for non-operatively treated fractures to displace at a later stage than two weeks. Study IV: In study II it was found that late displacement of DRF, still in acceptable radiologic position after 10-14 days, occurred in approximately 1/3 of cases. Despite this, we have not been able to find any study focusing on evaluating the clinical outcome in patients with late displacement. Two hundred and nine unilateral DRF from study II were still in good position after 10-14 days and were included in the study. One hundred and seventy five patients had radiographs taken at a minimum of 3 months and a clinical examination 1 year after the fracture. Late displaced distal radius fractures had significantly higher loss of ROM and grip strength compared to fractures that didn’t displace. No significant differences were seen in subjective outcome. In conclusion, initial position of the fracture predicted later displacement and was the most important parameter in predicting clinical outcome. Comminution of the fracture also affected radiological stability and clinical outcome. Volar comminuted fractures are highly unstable and need surgical intervention if displacement is to be avoided. Intra-articular involvement affected clinical outcome. Late displacement is common in DRF and may result in loss of range of motion and grip strength. To detect late displacement, DRF should be followed for more than 2 weeks. The new classification system had a moderate reliability and reproducibility. The classification was found predictive of radiologic and objective clinical outcome. However, it was not predictive of subjective outcome. The classification system was also predictive of fractures at risk for late displacement.

Clustering gene expression data such that the diameters of the clusters formed are no greater than a specified threshold prompted the development of the Quality Threshold Clustering (QTC) algorithm. It iteratively forms clusters of non-increasing size until all points are clustered; the largest cluster is always selected first. The QTC algorithm applies in many other domains that require a similar quality guarantee based on cluster diameter. The worst-case complexity of the original QTC algorithm is (n5). Since practical applications often involve large datasets, researchers called for more efficient versions of the QTC algorithm. This dissertation aimed to develop and evaluate efficient variations of the QTC algorithm that guarantee a maximum cluster diameter while producing partitions that are similar to those produced by the original QTC algorithm. The QTC algorithm is expensive because it considers forming clusters around every item in the dataset. This dissertation addressed this issue by developing methods for selecting a small subset of promising items around which to form clusters. A second factor that adversely affects the efficiency of the QTC algorithm is the computational cost of updating cluster diameters as new items are added to clusters. This dissertation proposed and evaluated alternate methods to meet the cluster diameter constraint while not having to repeatedly update the cluster diameters. The variations of the QTC algorithm developed in this dissertation were evaluated on benchmark datasets using two measures: execution time and quality of solutions produced. Execution times were compared to the time taken to execute the most efficient published implementation of the QTC algorithm. Since the partitions produced by the proposed variations are not guaranteed to be identical to those produced by the original algorithm, the Jaccard measure of partition similarity was used to measure the quality of the solutions. The findings of this research were threefold. First, the Stochastic QTC alone wasn’t computationally helpful since in order to produce partitions that were acceptably similar to those found by the deterministic QTCs, the algorithm had to be seeded with a large number of centers (ntry ≈ n). Second, the preprocessed data methods are desirable since they reduce the complexity of the search for candidate cluster points. Third, radius based methods are promising since they produce partitions that are acceptably similar to those found by the deterministic QTCs in significantly less time.

No description available.

Wireless Networks is a very growing market. However, the security measures are not strong enough; the WEP security protocol is flawed. The 802.11 Task Group I is working on new security measures in order to strengthen the access control of users, the privacy and the integrity of data. We will describe the WEP flaws and the new security measures of 802.11 Task Group I. Finally, we will propose a new architecture to improve user identification for the wireless network of our department.

In 1994 there was an earthquake occurred in Northridge, California which caused damage in structures built with Steel Moment Frames (SMF) due to the brittle fractures in the beam and column connections. It has led to the major modifications and improvements in the connection detailing prior to the earthquake occurred in the Northbridge. These changes came up with better materials for welding and introduced the use of cover plate and Reduced Beam Section (RBS). RBS connections are the most widely used connection today and it allows the SMF systems to yield extensively and deform plastically by avoiding brittle fracturing at connections. The most important factors that affect the response along with the design of Steel Moment Frames (SMF) and Reduced Beam Section (RBS) connections are connection strength, stiffness, connection type, use of deep columns and phenomena associated with its instability, the strength of ductility of the column panel zone-beam instability.

O procedimento de dimensionamento de uma linha lateral de irrigação localizada necessita ser avaliado com precisão, devido às perdas de carga tanto distribuídas na tubulação como nas inserções dos emissores com os tubos. Devido a isso, desenvolveu-se uma metodologia para a determinação da perda de carga localizada mediante a formulação de um modelo matemático a partir do índice de obstrução. Estas perdas localizadas podem ser significativas quando comparadas com as perdas de carga totais, devido ao grande número de emissores instalados ao longo da linha lateral. O experimento foi junto ao Departamento de Engenharia Rural (ESALQ-USP) e ajustado para valores número de Reynolds (R), no intervalo de 7.480 a 32.597 para proporcionar fluxo turbulento e velocidade máxima de 2,0 m s-1. A pesquisa foi conduzida em duas etapas: 1) ajuste do fator f para um seguimento de 0,5 m de tubo,sendo realizada 10 repetições, com o intuito de validação da metodologia empregada comparando-se o ajuste dos dados encontrados com os trabalhos existentes na literatura, 2) determinação da perda de carga (hf) em um seguimento de tubo de 1 m de comprimento com emissor devidamente vedado, portanto, pela diferença entre a hf do tubo mais o emissor e a hf do tubo obtido na primeira etapa, obteve-se a perda de carga localizada do emissor (hfe). Além disso, com a determinação da geometria do emissor, pelo projetor ótico HB 400, formulou-se uma equação que permitiu o cálculo da perda de carga localizada utilizando-se as características geométricas do emissor (comprimento do emissor, índice de obstrução e coeficiente de contração). Pelos resultados obtidos para 4 modelos utilizados, o modelo estimou satisfatoriamente para 2 modelos, e também verificou-se que o modelo apresentou um desempenho classificado como \'ótimo\', portanto, podendo ser empregado para estimativa de perda de carga localizada provocada por emissores integrados não coaxiais com geometria semelhante ao emissor Uniram e Drip Net. / The design of a lateral line of trickle irrigation requires an accurate evaluation of head losses in not only the pipe but the emitters as well. A procedure was developed to determine localized head losses within the emitters by the formulation of a mathematical model accounting for the obstruction caused by the insertion point. These localized losses can be significant when compared with the total head losses within the system, due to the large number of emitters typically installed along the lateral line. An experiment was carried out by altering flow characteristics to create Reynolds Number (R) in the interval from 7480 to 32597 to provide turbulent flow and a maximum velocity of 2.0 m s-1. The geometry of the emitter point was determined by an optical projector and sensor. An equation was formulated that allows the localized head loss calculation using the geometric characteristics of the emitter (emitter length, obstruction index and the contraction coefficient). The obtained results for 4 used models, the model esteemed satisfactorily for 2 models, and was also verified that the model presents an acting classified as \'great\', therefore, could be used to estimate localized head loss provoked by non coaxial emitters inserted in polyethylene pipe with similar geometry as the Uniram and Drip Net emitters.

The work presented in this thesis studies acoustic perturbations in slowly varying pipes. The slow variation is introduced in the form of a small parameter ${\epsilon}$ and through this in turn gives rise to a slow axial scale $X$ such that $X = {\epsilon}x$ where $x$ is the normal axial coordinate. This allows an asymptotic approach and the WKB method is used to solve the subsequent mathematical problems. The first deals with the existence of a trapped mode in a hard-walled pipe of varying radius conveying fluid. For the derived leading order propagating mode solution, its amplitude becomes singular at transition points $X_{t}$ and $X_{t'}$ where $X_{t} > 0$ and $X_{t'} < 0$ and thus is unable to propagate past these points. Because of the break down in the solution, this leads to the theory that in the neighbourhood of these points there exists a boundary layer in which the original assumption about having slow variation does not hold. By first seeking the thickness of the layer, valid solutions can then be derived and then matched to the outer solutions in order to produce a uniform solution which holds for the entire axial domain. Once this is achieved, it is then used to derive trapped mode solutions. In this case, the theory used is that of two single turning points which are then combined to obtain the full solution. It is illustrated through consideration of examples and the dependence on ${\epsilon}$ is also shown through various plots. This problem will be considered for a symmetric and asymmetric duct and for differing duct parameters. Problems may arise when the two turning points lie close together and so we seek to improve on the method used by deriving a solution to trapped modes encompassing both turning points, which will be proposed together with some illustrations in order to justify its use and reliability. Next, the case of mode propagations on a thin elastic shell of varying radius conveying fluid is studied. The acoustic solutions of a straight shell in vacuo are first briefly reviewed and then built up by the addition of radius variation and the presence of a stationary fluid. The work presented first outlines the analysis for wave propagation in a slowly-varying thin elastic shell in vacuo. It is found that the shell and the fluid terms are coupled through the fluid pressure term, which is added to the equation governing the radial shell displacements since the pressure is assumed to affect radial motion only. Once the newly corrected equation for the radial shell displacements has been obtained, together with the axial and azimuthal displacements equations, this new system of governing equations is then separated into leading order ${\epsilon}^{0}$ and first order ${\epsilon}^{1}$ systems. In order to simplify the calculations, only the zeroth azimuthal order $m = 0$ will be studied here. With this simplification, a notable result is that the solutions of the torsional motion is decoupled from the axial and radial solutions. Once the dispersion equation is extracted from the leading order system, it can be seen that the axial and radial solutions are in fact coupled. The solution to the in vacuo with varying radius problem is first briefly presented and it is then followed by the solution to the fluid inclusion problem with varying radius, which makes up the main part of this section. The solution is studied for various frequencies and at various points along the shell. In addition, the axial and radial components of the first three modes are examined along with their amplitudes and energy distributions. Finally, mean flow is added and the same analysis is carried out, paying particular attention to the differences which arise in comparison to the stationary flow case.

In CO2 storage sites, seal has a vital role in inhibiting migration of the supercritical CO2 to other geological strata. The major difficulties in studying seals include two aspects: lack of available samples (especially for saline aquifers), and the difficulty to study over geological time and spatial scales. The analysis of natural analogue has been chosen to overcome these difficulties. Hydrocarbon fields are used to investigate the pore throat radii, which is the major factor for capillary sealing of caprocks, using newly established statistics model. Natural CO2 springs at Green River, Utah are used to study how the long-term CO2 charge triggers chemical reactions and migration in shales. One of the major sealing mechanism of caprocks is capillary sealing. Pore throat radius, as the main factor to decide the capillary sealing, has been investigated in this study. As an alternative to the traditional method of mercury injection porosimetry, a statistical model for effective pore throat radii determination has been established. The cumulative percentage and the probability distribution of the effective pore throat radii of the shale caprocks in the UK North Sea oil fields are obtained, which would be used as a reference for the saline aquifers in CO2 storage siting in the future work. Monte Carlo simulation is utilised to get the distribution of the effective pore throat radii. The cumulative distribution from this study has been compared with the distribution by Yang and Aplin (1998). The distribution by the statistical model enables to narrow down the range of effective pore throat radii to 37nm~1700nm, and help to make a better prediction on the pore throat radii. The correlation between the controlling factors of faulting, burial depth, caprock thickness and the pore throat radii have been examined. Good correlation between the depth less than 3000m and the effective pore throat radii indicates clay diagenesis should be the major factor for shallowly buried caprocks. Faulting and caprock thickness present no significant correlation with the effective pore throat radii. Crystal Geyser is used as an ideal natural analogue to study the Mancos Shale alteration. The interacted fluid that deposited travertine is important for the study. Hence, carbonate veins and reduction zones that associated with the activity of the main fault are used as records of the geochemistry of the paleo-fluid, the features of which are compared to the present spring water. The result shows the paleo-fluid was much more saline than the present fluid, with greater flow-rate. The decreased flow-rate might be owing to the self-healing of the fault during the time. Mancos shales outcropped in the hanging wall of the Little Grand Wash fault were sampled to investigate on the alterations triggered by the CO2-charged fluid from the fault and fractures. The result shows the alteration radius of the Mancos has limited within the distance of 20m away from the fault. CO2-rich fluid could interact with deformed shale (both dissolution and precipitation might happen), but no evidence shows the intact Mancos has been altered. The calcite cements in Mancos derived from CO2 sequestration could reach up to 27% (%weight of the whole rock) at 15m away from the fault. The conclusion facilitates the carbon storage siting criteria by Chadwick et al., (2009), who proposed the cautionary thickness of the caprock to be 20m.

As fraturas da extremidade distal do rádio são muito comuns em nosso meio, sendo a mais freqüente do punho. Inúmeras pesquisas já foram realizadas sobre o tema e é conhecida a importância da redução anatômica das fraturas intra-articulares; porém, a causa de insucesso no seu tratamento pode ser a associação de outras lesões, envolvendo partes moles e cartilagem. O objetivo foi realizar uma avaliação artroscópica para analisar a incidência das lesões ligamentares e condrais associadas às fraturas intraarticulares da extremidade distal do rádio, correlacionado-a com classificação AO/ASIF. Trinta pacientes, com idade entre 20 a 50 anos, portadores de fratura fechada dos grupos B e C da classificação AO/ASIF foram selecionados. Todos eles foram submetidos à artroscopia do punho, para abordar as lesões intra-articulares e para redução e osteossíntese da fratura. Observou-se uma alta incidência de lesões intra-articulares, sendo que 76,7% deles apresentavam lesão do complexo da fibrocartilagem triangular, 36,6% do ligamento intrínseco escafo-semilunar, 6,6% do ligamento intrínseco semilunar-piramidal e 33,3% com lesão da cartilagem articular maior que três milímetros. Pacientes portadores de fraturas tipo C da classificação AO/ASIF apresentam uma incidência maior de lesões ligamentares associadas. Não houve relação entre a presença de lesão cartilaginosa e a classificação AO/ASIF das fraturas nesta casuística. / Fractures of the distal end of the radius are very frequent in our country and the most common is that of the wrist. Much research was carried out on the subject and the importance of the anatomical reduction of intra-articular fractures is well known, however the cause of unsuccessful treatment may be the association of other injuries involving soft tissues and cartilage. The purpose here was to perform an arthroscopic evaluation to analyze the incidence of ligament and chondral injuries associated to intra-articular fractures of the distal end of the radius, for correlation with the AO/ASIF classification. Thirty patients ranging from 20 to 50 years of age, bearers of closed fractures of groups B and C of the AO/ASIF classification were selected. They were submitted to wrist arthroscopy to treat the intra-articular injuries for fracture reduction and osteosynthesis. A high incidence of intraarticular injuries was noted, 76.7% of them presenting injury of the triangular fibrocartilage complex, 36.6% of the intrinsic scapholunate ligament, 6.6% of the intrinsic lunotriquetral ligament and 33.3% of an injury of the articular cartilage larger than three millimeters. Patients bearers of a type C fracture in the AO/ASIF classification present with a higher incidence of associated ligament injuries. No relation between presence of cartilage injury and AO/ASIF Classification was found in this casuistry.