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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.
1

Criteria of design improvement of shaped charges used as oil well perforators

Elshenawy, Tamer Abdelazim January 2012 (has links)
In addition to its various military applications, shaped charges have been used in oil industry as an oil well perforator (OWP) to connect oil and gas to their reservoirs. The collapse of the liner material under the explosive load produces a hypervelocity jet capable of achieving a deep penetration tunnel into the rock formation. The achieved penetration depends on the OWP design, which includes the geometry and the material of the explosive and the liner as well as the initiation mode and the casing of the shaped charge. The main purpose of this research is to assess the performance of OWP with different design aspects in terms of its penetration depth into concrete material.This research employed the Autodyn finite difference code to model the behaviour of OWPs in the stages of liner collapse, jet formation and jet penetration. The design parameters of OWPs were studied quantitatively to identify the effect of each individual parameter on the jet characteristics and the jet penetration depth into concrete material according to the API-RP43 standard test configuration. In order to validate the Autodyn jetting analysis, this research compared the jetting simulation results of copper OWP liners with those obtained from flash x-ray measurements while the numerical jet penetration into the laminated concrete target was validated experimentally by the static firing of OWPs. Above-mentioned experiments were designed and performed in this project.The validated hydrocode was implemented in this research to study the effects of the concrete target strength, the liner material and the liner shape on the jet penetration depth into concrete targets.For the target strength, the traditional virtual origin (VO) penetration model was modified to include a strength reduction term based on Johnson’s damage number and the effect of the underground confinement pressure using Drucker-Prager model. The VO analytical model is also implemented in the liner material study to account for the jet density reduction phenomena and its induced reduction of jet penetration capability. The jets obtained from machined copper and zirconium liners and from copper-tungsten powder liner all exhibited the density reduction phenomena. The modified VO model considers the non-uniform distribution of jet density based on the jet profile analysis using Autodyn and the experimental soft recovery for some tested liners. The results lead to a modified VO penetration model including the non-uniform jet density effect.For zirconium liner material, numerical and analytical studies were conducted for different flow velocities and different collapse angles in order to determine the boundaries between the jetting and non-jetting phases and whether a coherent or a non-coherent jet will form. This study indicated that the suggested four different liner shapes (i.e. the conical, the biconical, the hemispherical and the bell) will produce coherent jet when the zirconium is used as OWP liner.The validated Autodyn hydrocode is also used in this thesis to calculate the velocity difference between two neighbouring zirconium jet fragments. The velocity difference is related directly to the breakup time of an OWP jet, and thus, it is calculated for a range of zirconium liners with different liner wall thicknesses. The calculated values of velocity difference gave a clear insight for the breakup time formulae for zirconium jet in terms of the liner thickness and the charge diameter.
2

"Estudo anatômico do retalho perfurante ântero-lateral da coxa" / Anatomic study of the anterolateral thigh flap

Ishida, Luiz Carlos 17 August 2006 (has links)
INTRODUÇÃO: O retalho ântero-lateral da coxa é baseado em vasos perfurantes do ramo descendente da artéria circunflexa lateral femoral. Este retalho tem características muito interessantes para a cirurgia reparadora, como a pequena espessura, pedículo longo e excelente área doadora. No entanto, existem muitas controvérsias na literatura quanto aos vasos perfurantes e ao trajeto do pedículo deste retalho. Neste trabalho procurou-se estabelecer alguns parâmetros anatômicos e esclarecer estas controvérsias. MÉTODO: Estudaram-se 100 coxas de 50 cadáveres quanto aos seguintes aspectos: 1- Número e localização de perfurantes encontrados, 2- Trajeto do pedículo perfurante, 3- Trajetória intramuscular, 4- Comprimento do trajeto intramuscular, 5- Comprimento total do pedículo, 6- Diâmetro dos vasos e 7- Espessura do retalho. RESULTADOS: 1- Encontraram-se de 0 a 4 perfurantes por coxa estudada, todas em um raio de até 6cm do ponto médio entre a espinha ilíaca ântero-superior e a borda lateral da patela. 2- Os vasos perfurantes tinham trajeto músculo-cutâneo em 75,76% das coxas e septo-cutâneo em 24,24%. 3- Dos pedículos perfurantes com trajeto músculo-cutâneo, 86,67% possuíam trajetória indireta contra 13,33% com trajetória direta. 4- O comprimento médio do trajeto intramuscular dos pedículos foi de 3,67 ± 2,01 cm. 5- O comprimento médio do pedículo total foi de 11,31 ± 3,12 cm. 6- O diâmetro médio da artéria na origem do ramo descendente da artéria circunflexa femoral foi de 2,21 ± 0,85 mm e para as veias no mesmo local de 2,66 ± 1,33 mm e 2,10 ± 1,11 mm. 7- A espessura da tela subcutânea foi de 8,98 ±6,23 mm e da pele de 1,60 ± 0,76 mm. CONCLUSÕES: 1- Existiu uma pequena possibilidade de não haver pedículos perfurantes. 2- Quando presentes, os pedículos perfurantes do ramo descendente da artéria circunflexa lateral femoral eram encontrados em numero de 1 a 4, sempre em um raio de 6 cm a partir do ponto médio entre a espinha ilíaca ântero-superior e a borda lateral da patela. 3- Os trajetos dos pedículos perfurantes eram predominantemente músculo-cutâneos. 4- A trajetória intramuscular encontrada foi predominantemente indireta. 5- O comprimento do trajeto intramuscular correspondeu a 31,69% do comprimento total do pedículo. 6- O comprimento total do pedículo se mostrou adequado tanto para transferências locais como à distancia por técnicas microcirúrgicas. 7- Os diâmetros dos vasos, tanto da artéria quanto das veias, se mostraram adequados para a realização de anastomoses microcirúrgicas. 8- A espessura do retalho encontrada foi significantemente maior nas coxas de indivíduos femininos, mas tanto nos homens quanto nas mulheres a espessura foi relativamente fina. / INTRODUCTION: The anterolateral thigh flap is based on the perforator vessels of the descending branch of the lateral circumflex femoral artery. This flap has very interesting characteristics for the reconstructive surgery, like the small thickness, long pedicle and excellent donor site. On the other hand, there are many controversial data on the literature about the perforator vessels and the pedicle course of this flap. The aims of this study are to establish some anatomical parameters and clear some controversies. METHOD: A hundred thighs of 50 cadavers were studied for: 1- The number and location of the perforator vessels. 2- The course of the perforator pedicles. 3- The intramuscular course. 4- The length of the intramuscular course. 5- The total length of the vascular pedicle. 6- The diameter of the vessels. and 7- The thickness of the flap. RESULTS: 1- There were found from 0 to 4 perforators per thigh, all in a 6cm radius from the mid point between the anterosuperior iliac spine and the lateral border of the patella. 2- The pedicles was musculocutaneous in 75,76% of the thighs and septocutaneous in 24,24%. 3- Among the musculocutaneous pedicles, 86,67% had a direct intramuscular course, and 13,33% had indirect course. 4- The mean length of the intramuscular course was 3,67 ± 2,01 cm. 5- The mean total pedicle length was 11,31 ± 3,12 cm. 6-The mean artery diameter on the origin of the descending branch of the lateral circumflex femoral artery was 2,21 ± 0,85 mm and the mean vein diameter on the same spot was 2,66 ±1,33 mm and 2,10 ± 1,11 mm. 7- The mean subcutaneous fat tissue thickness was 8,98 ± 6,23 mm and the mean skin thickness was e 1,60 ± 0,76 mm. CONCLUSIONS: 1- There was a possibility of finding no perforators of the descending branch of the lateral circumflex femoral artery. 2- When present, the perforators pedicles were found in numbers between 1 to 4, always in a 6cm radius from the mid point between the anterosuperior iliac spine and the lateral border of the patella. 3- The perforators pedicles courses were predominantly musculocutaneous. 4- The intramuscular courses were mainly indirect. 5- The intramuscular length was responsible for 31,69% of the total length of the vascular pedicle. 6- The total length of the pedicle was adequate for either local or microsurgical transfers. 7- The arterial and venous diameters were adequate for microsurgical anastomosis. 8- The female cadavers had significantly thicker flaps, but both in the male and the female cadavers the flap was considerably thin.
3

"Estudo anatômico do retalho perfurante ântero-lateral da coxa" / Anatomic study of the anterolateral thigh flap

Luiz Carlos Ishida 17 August 2006 (has links)
INTRODUÇÃO: O retalho ântero-lateral da coxa é baseado em vasos perfurantes do ramo descendente da artéria circunflexa lateral femoral. Este retalho tem características muito interessantes para a cirurgia reparadora, como a pequena espessura, pedículo longo e excelente área doadora. No entanto, existem muitas controvérsias na literatura quanto aos vasos perfurantes e ao trajeto do pedículo deste retalho. Neste trabalho procurou-se estabelecer alguns parâmetros anatômicos e esclarecer estas controvérsias. MÉTODO: Estudaram-se 100 coxas de 50 cadáveres quanto aos seguintes aspectos: 1- Número e localização de perfurantes encontrados, 2- Trajeto do pedículo perfurante, 3- Trajetória intramuscular, 4- Comprimento do trajeto intramuscular, 5- Comprimento total do pedículo, 6- Diâmetro dos vasos e 7- Espessura do retalho. RESULTADOS: 1- Encontraram-se de 0 a 4 perfurantes por coxa estudada, todas em um raio de até 6cm do ponto médio entre a espinha ilíaca ântero-superior e a borda lateral da patela. 2- Os vasos perfurantes tinham trajeto músculo-cutâneo em 75,76% das coxas e septo-cutâneo em 24,24%. 3- Dos pedículos perfurantes com trajeto músculo-cutâneo, 86,67% possuíam trajetória indireta contra 13,33% com trajetória direta. 4- O comprimento médio do trajeto intramuscular dos pedículos foi de 3,67 ± 2,01 cm. 5- O comprimento médio do pedículo total foi de 11,31 ± 3,12 cm. 6- O diâmetro médio da artéria na origem do ramo descendente da artéria circunflexa femoral foi de 2,21 ± 0,85 mm e para as veias no mesmo local de 2,66 ± 1,33 mm e 2,10 ± 1,11 mm. 7- A espessura da tela subcutânea foi de 8,98 ±6,23 mm e da pele de 1,60 ± 0,76 mm. CONCLUSÕES: 1- Existiu uma pequena possibilidade de não haver pedículos perfurantes. 2- Quando presentes, os pedículos perfurantes do ramo descendente da artéria circunflexa lateral femoral eram encontrados em numero de 1 a 4, sempre em um raio de 6 cm a partir do ponto médio entre a espinha ilíaca ântero-superior e a borda lateral da patela. 3- Os trajetos dos pedículos perfurantes eram predominantemente músculo-cutâneos. 4- A trajetória intramuscular encontrada foi predominantemente indireta. 5- O comprimento do trajeto intramuscular correspondeu a 31,69% do comprimento total do pedículo. 6- O comprimento total do pedículo se mostrou adequado tanto para transferências locais como à distancia por técnicas microcirúrgicas. 7- Os diâmetros dos vasos, tanto da artéria quanto das veias, se mostraram adequados para a realização de anastomoses microcirúrgicas. 8- A espessura do retalho encontrada foi significantemente maior nas coxas de indivíduos femininos, mas tanto nos homens quanto nas mulheres a espessura foi relativamente fina. / INTRODUCTION: The anterolateral thigh flap is based on the perforator vessels of the descending branch of the lateral circumflex femoral artery. This flap has very interesting characteristics for the reconstructive surgery, like the small thickness, long pedicle and excellent donor site. On the other hand, there are many controversial data on the literature about the perforator vessels and the pedicle course of this flap. The aims of this study are to establish some anatomical parameters and clear some controversies. METHOD: A hundred thighs of 50 cadavers were studied for: 1- The number and location of the perforator vessels. 2- The course of the perforator pedicles. 3- The intramuscular course. 4- The length of the intramuscular course. 5- The total length of the vascular pedicle. 6- The diameter of the vessels. and 7- The thickness of the flap. RESULTS: 1- There were found from 0 to 4 perforators per thigh, all in a 6cm radius from the mid point between the anterosuperior iliac spine and the lateral border of the patella. 2- The pedicles was musculocutaneous in 75,76% of the thighs and septocutaneous in 24,24%. 3- Among the musculocutaneous pedicles, 86,67% had a direct intramuscular course, and 13,33% had indirect course. 4- The mean length of the intramuscular course was 3,67 ± 2,01 cm. 5- The mean total pedicle length was 11,31 ± 3,12 cm. 6-The mean artery diameter on the origin of the descending branch of the lateral circumflex femoral artery was 2,21 ± 0,85 mm and the mean vein diameter on the same spot was 2,66 ±1,33 mm and 2,10 ± 1,11 mm. 7- The mean subcutaneous fat tissue thickness was 8,98 ± 6,23 mm and the mean skin thickness was e 1,60 ± 0,76 mm. CONCLUSIONS: 1- There was a possibility of finding no perforators of the descending branch of the lateral circumflex femoral artery. 2- When present, the perforators pedicles were found in numbers between 1 to 4, always in a 6cm radius from the mid point between the anterosuperior iliac spine and the lateral border of the patella. 3- The perforators pedicles courses were predominantly musculocutaneous. 4- The intramuscular courses were mainly indirect. 5- The intramuscular length was responsible for 31,69% of the total length of the vascular pedicle. 6- The total length of the pedicle was adequate for either local or microsurgical transfers. 7- The arterial and venous diameters were adequate for microsurgical anastomosis. 8- The female cadavers had significantly thicker flaps, but both in the male and the female cadavers the flap was considerably thin.

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