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Papers by Juan huane giraldo

Research paper thumbnail of Tomografía computarizada por rayos X: fundamentos y actualidad

Este articulo presenta una revision de los fundamentos de la tomografia computarizada, empezando ... more Este articulo presenta una revision de los fundamentos de la tomografia computarizada, empezando por un recuento de los inicios y progresos de esta tecnica a traves del tiempo, y continuando con una descripcion de los principios fisicos que rigen la produccion de los rayos X. El articulo tambien discute las bases matematicas para la reconstruccion de las imagenes a partir de proyecciones utilizando metodos analiticos o iterativos. En una seccion independiente, se revisan los conceptos mas importantes relacionados con los riesgos de la radiacion ionizante y se discuten investigaciones recientes, algunas polemicas, acerca de los beneficios y riesgos asociados con la tomografia computarizada y como estos afectan los protocolos de adquisicion de las imagenes. Finalmente, con base en los avances cientificos y tendencias mas recientes, el articulo propone las areas que, presumiblemente, continuaran siendo el centro de atencion de la tomografia computarizada de rayos X en los proximos anos.

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Research paper thumbnail of Diseño y construcción de una cámara de combustión para una microturbina de gas

Las microturbinas son dispositivos que encuentran aplicaciones no solo en la generacion de electr... more Las microturbinas son dispositivos que encuentran aplicaciones no solo en la generacion de electricidad, sino tambien en usos menos comunes como la generacion de calor, aeromodelismo, unidades de potencia pico, aviacion, plantas motrices y automoviles. Uno de los elementos que hace parte de la microturbina es la camara de combustion. En el presente trabajo se resume el diseno y construccion de una camara de combustion para una microturbina de gas. Ademas se busca desarrollar una base teorica para el diseno y construccion de este tipo de dispositivos.

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Research paper thumbnail of Masa y trauma

Se intentara demostrar que el sujeto que se inscribe en los vinculos sociales contemporaneos esta... more Se intentara demostrar que el sujeto que se inscribe en los vinculos sociales contemporaneos esta mas expuesto al trauma como resultado de la declinacion de la imagen mnemica del padre de la infancia.

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Research paper thumbnail of Subjective and objective heterogeneity scores for differentiating small renal masses using contrast-enhanced CT

Abdominal Radiology, 2016

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Research paper thumbnail of A family-focused oral-health toy library: Towards a new direction in oral health education

Revista Facultad De Odontologia Universidad De Antioquia, Jun 1, 2012

Introduction: discovering strategies to promote motivation of personal skills must be a permanent... more Introduction: discovering strategies to promote motivation of personal skills must be a permanent task of oral health professionals. The purpose of this program was to create a place, within the toy library, devoted to strengthening oral health habits, with the guidance of trained personnel such as toy librarians and dentists, who developed ludic strategies for teaching and reinforcing oral health knowledge among children and their families Methods: this was a pre-experimental community intervention program, which evaluated 99 children between 4 and 12 years of age. Surveys were conducted in order to assess the students', parents', and guardians' knowledge before and after their interaction with the ludic material; also, caries and dental plaque indexes were measured. Results: this training program allowed improving the knowledge level among parents and children by 21 and 29% respectively. The average percentage of dental plaque was 38.2 ± 18.9 showing a difference of 18.3% with respect to the initial exam. Among the surfaces with caries history, those which had been restored were predominant (1.5 ± 2.6). The qualitative analysis of the children's perception of the games revealed that they found them positive, nice, fun, and educational. Conclusions: establishing an oral health toy library, as a constructive environment that involves innovative strategies aimed at health education, allowed socialization of the studied population as well as promotion of healthy oral habits and reinforcement of self-care among this population.

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Research paper thumbnail of Las prácticas de mercadeo, un aporte a la competitividad de las pequeñas empresas de servicios en la ciudad de Medellín

Tesis (Maestria en Mercadeo). Universidad de Manizales. Facultad de Ciencias Contables, Economica... more Tesis (Maestria en Mercadeo). Universidad de Manizales. Facultad de Ciencias Contables, Economicas y Administrativas, 2013

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Research paper thumbnail of Saluteca oral con enfoque familiar: hacia una nueva orientación en educación de la salud bucal

Revista Facultad De Odontologia Universidad De Antioquia, Jun 20, 2012

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Research paper thumbnail of In Vivo Discrimination of Nonuric Acid Kidney Stone Types

PURPOSE To evaluate the use of an advanced dual energy processing algorithm to improve the abilit... more PURPOSE To evaluate the use of an advanced dual energy processing algorithm to improve the ability of dual energy CT (DECT) protocol to differentiate non-uric acid (NUA) renal stone types in a patient cohort. METHOD AND MATERIALS We evaluated data from 81 patients that received a non-enhanced DECT scan prior to surgical removal of kidney stones and subsequent stone composition analysis by infrared spectroscopy (IR). DECT scans were performed using a dual-source CT scanner (Somatom Definition Flash, Siemens Healthcare), 100 kV and 140 kV with tin filtration, and 240 and 185 mAs quality reference mAs values for the low and high energy tubes, respectively. Images were reconstructed with medium smooth kernel (D30) and 1 mm thickness. Only relatively pure kidney stones (≥90% of a single composition, as determined by IR) were included in this analysis (n=44 stones). A Matlab-based processing algorithm was developed to semiautomatically segment kidney stones and predict stone composition u...

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Research paper thumbnail of Determination of Kidney Stone Composition Using Dual Energy CT in a Cohort of Patients with Medium to Large Body Size

PURPOSE Patients with medium to large body sizes may be unable to receive dual-energy CT (DECT) e... more PURPOSE Patients with medium to large body sizes may be unable to receive dual-energy CT (DECT) exams for the purpose of determining renal stone composition due to increased image noise when using 80/140 kV protocols resulting in reduced diagnostic accuracy. In this study, we determined the accuracy of 100/140 kV DECT protocols for kidney stone composition analysis in a patient cohort having medium to large body size. METHOD AND MATERIALS A retrospective chart review identified 81 patients with lateral abdominal size above 35 cm who were scanned using a dual-source system for clinical indications, with subsequent surgical stone removal. A 100/140kV DECT protocol was used, with a tin filter on the 140 kV tube to increase separation of the x-ray spectra. Automatic exposure control was used to adapt the tube current to patient size, and average scanner x-ray output was recorded (volume CT dose index, CTDIvol).After surgical extraction, stone composition was determined using infrared sp...

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Research paper thumbnail of Improved Discrimination of Calcium Oxalate and Apatite Kidney Stones with Dual Energy CT and Clinical Information

PURPOSE Differentiating between calcium oxalate and apatite stones using dual-energy CT (DECT) ha... more PURPOSE Differentiating between calcium oxalate and apatite stones using dual-energy CT (DECT) has been difficult in previous studies. In this study, we propose to improve the accuracy of non-invasive characterization of these two stone types by combining dual-energy CT and clinical information. METHOD AND MATERIALS Patients referred for clinically-indicated dual-energy CT for stone composition analysis whose stones were subsequently surgically removed were enrolled in this IRB-approved study. Removed stones were evaluated using infrared microscopy to determine elemental composition. Dual-energy CT images were processed using a custom-developed software tool that evaluated the ratio of CT numbers between the low- and high-energy images. Stones were segregated into four groups according to the thresholds established in our previous study. Clinical information, including patient age, gender, family history, dietary habit, and comorbidities, as well as lab results including: serum elec...

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Research paper thumbnail of A Biological Liver Phantom to Evaluate the Impact of Radiation Dose Reduction on the Accuracy of CT Perfusion Imaging

PURPOSE Physical phantoms that realistically mimic human vasculature and microvasculature are dif... more PURPOSE Physical phantoms that realistically mimic human vasculature and microvasculature are difficult, if not impossible, to design and build. The purpose of this study was to evaluate the feasibility of using a fixed ex vivo porcine liver to systematically evaluate dose reduction strategies in perfusion computed tomography (PCT). METHOD AND MATERIALS A fresh porcine liver was perfused with formalin to preserve the specimen and ensure patency of the vascular structures. The portal vein was connected to a continuous flow pump, allowing control of input pressure and flow. The liver was submerged in a 32 cm wide, body-shaped acrylic phantom filled with water. The phantom was scanned four times, with a PCT protocol using 80 kVp and 400, 400, 100 and 20 mAs. 4 cc of iodine (300 mg/ml) was injected at 1 cc/sec for each scan and images were acquired for 50 sec, 2 sec after injection at each dose level. We compared percent root mean square (RMS) error between time attenuation curves (TACs...

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Research paper thumbnail of Accuracy Improvement in Low Dose Dual-Energy CT for Renal Stone Composition Differentiation

PURPOSE To improve the accuracy of dual energy stone composition classification with low dose CT ... more PURPOSE To improve the accuracy of dual energy stone composition classification with low dose CT using a noise reduction technique - HighlY constrained backPRojection (HYPR) - while maintaining the spatial resolution and noise texture. METHOD AND MATERIALS A total of 80 kidney stones with 18 pure uric acid (UA) stones and 62 non-uric acid (NUA) stones were included in this study. Each stone was placed in a water filled plastic container and placed in 2 water phantoms with lateral width measured at 30 and 35 cm. Phantoms were scanned on a dual-source CT system (Definition FLASH, Siemens Healthcare, Forchheim, Germany) operating in dual energy mode with 80 kV and 140 kV with an added tin filter. Scans were conducted at three dose levels: 100, 50 and 25% of a clinical dose level (18 mGy for a standard size patient). Images were reconstructed using commercial filtered backprojection (FBP) algorithm and HYPR. Image noise was measured and HYPR noise reduction calculated. Stone composition...

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Research paper thumbnail of Dynamic Analysis of Heat Transfer Through a Fin of Constant Cross-Sectional Area: Specified Fin Tip Temperature

Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer, 2009

A dynamic analysis is performed for heat transfer through a fin with constant cross-sectional are... more A dynamic analysis is performed for heat transfer through a fin with constant cross-sectional area and with a specified fin tip temperature. The process starts with a dynamic energy balance around the fin. Laplace transforms and the Bromwich Integral are used to solve analytically the resulting partial differential equation. The final purely analytical solution is compared to the well known steady state solution. The two match exactly as time approaches infinity. Furthermore it is shown that the steady-state and dynamic characteristics of the fin are directly tied to the Biot number.© 2009 ASME

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Research paper thumbnail of A Semantic-Based Approach for the Management of Digital Documents

2008 11th IEEE International Conference on Computational Science and Engineering - Workshops, 2008

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Research paper thumbnail of Physiological Mechanisms Underlying the Seasonality of Leaf Senescence and Renewal in Seasonally Dry Tropical Forest Trees

Seasonally Dry Tropical Forests, 2011

Seasonality in the presence and production of leaves is the defining characteristic of seasonally... more Seasonality in the presence and production of leaves is the defining characteristic of seasonally dry tropical forest (SDTF) ecosystems and has important implications for their functioning. Temporal patterns of shoot activity influence photosynthetic carbon gain and thus affect competition between tree phenological types (Givnish 2002), the seasonal rhythms of tree-herbivore interactions (Leigh 1999; Dirzo and Boege 2009), and the annual ecosystem carbon uptake and energy fluxes (Kucharik et al. 2006). The impact of leaf phenology on tree carbon return is associated with its effect on the length of leaf exposure to herbivore and pathogen damage, the timing of leaf loss for water balance, and the energy investment in leaf construction (Franco et al. 2005). The timing and the length of leaf presence in tropical forests has also been suggested to play a key role in maintaining tree diversity by regulating the abundance of pest pressures (Leigh et al. 2004).

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Research paper thumbnail of La gestión del mercadeo: un aporte a la competitividad de las pequeñas empresas del sector servicios en Medellín

Revista científica Pensamiento y Gestión, 2014

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Research paper thumbnail of Procesos psicológicos básicos incluidos en publicaciones científicas sobre comportamiento alimentario en niños: revisión sistemática

Revista chilena de nutrición, 2014

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Research paper thumbnail of Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation

Plant, Cell & Environment, 2009

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Research paper thumbnail of Nonconvex prior image constrained compressed sensing (NCPICCS): Theory and simulations on perfusion CT

Medical Physics, 2011

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Research paper thumbnail of Comparison of spinal anesthesia with combined sciatic-femoral nerve block for outpatient knee arthroscopy

Journal of Clinical Anesthesia, 2008

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Research paper thumbnail of Tomografía computarizada por rayos X: fundamentos y actualidad

Este articulo presenta una revision de los fundamentos de la tomografia computarizada, empezando ... more Este articulo presenta una revision de los fundamentos de la tomografia computarizada, empezando por un recuento de los inicios y progresos de esta tecnica a traves del tiempo, y continuando con una descripcion de los principios fisicos que rigen la produccion de los rayos X. El articulo tambien discute las bases matematicas para la reconstruccion de las imagenes a partir de proyecciones utilizando metodos analiticos o iterativos. En una seccion independiente, se revisan los conceptos mas importantes relacionados con los riesgos de la radiacion ionizante y se discuten investigaciones recientes, algunas polemicas, acerca de los beneficios y riesgos asociados con la tomografia computarizada y como estos afectan los protocolos de adquisicion de las imagenes. Finalmente, con base en los avances cientificos y tendencias mas recientes, el articulo propone las areas que, presumiblemente, continuaran siendo el centro de atencion de la tomografia computarizada de rayos X en los proximos anos.

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Research paper thumbnail of Diseño y construcción de una cámara de combustión para una microturbina de gas

Las microturbinas son dispositivos que encuentran aplicaciones no solo en la generacion de electr... more Las microturbinas son dispositivos que encuentran aplicaciones no solo en la generacion de electricidad, sino tambien en usos menos comunes como la generacion de calor, aeromodelismo, unidades de potencia pico, aviacion, plantas motrices y automoviles. Uno de los elementos que hace parte de la microturbina es la camara de combustion. En el presente trabajo se resume el diseno y construccion de una camara de combustion para una microturbina de gas. Ademas se busca desarrollar una base teorica para el diseno y construccion de este tipo de dispositivos.

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Research paper thumbnail of Masa y trauma

Se intentara demostrar que el sujeto que se inscribe en los vinculos sociales contemporaneos esta... more Se intentara demostrar que el sujeto que se inscribe en los vinculos sociales contemporaneos esta mas expuesto al trauma como resultado de la declinacion de la imagen mnemica del padre de la infancia.

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Research paper thumbnail of Subjective and objective heterogeneity scores for differentiating small renal masses using contrast-enhanced CT

Abdominal Radiology, 2016

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Research paper thumbnail of A family-focused oral-health toy library: Towards a new direction in oral health education

Revista Facultad De Odontologia Universidad De Antioquia, Jun 1, 2012

Introduction: discovering strategies to promote motivation of personal skills must be a permanent... more Introduction: discovering strategies to promote motivation of personal skills must be a permanent task of oral health professionals. The purpose of this program was to create a place, within the toy library, devoted to strengthening oral health habits, with the guidance of trained personnel such as toy librarians and dentists, who developed ludic strategies for teaching and reinforcing oral health knowledge among children and their families Methods: this was a pre-experimental community intervention program, which evaluated 99 children between 4 and 12 years of age. Surveys were conducted in order to assess the students', parents', and guardians' knowledge before and after their interaction with the ludic material; also, caries and dental plaque indexes were measured. Results: this training program allowed improving the knowledge level among parents and children by 21 and 29% respectively. The average percentage of dental plaque was 38.2 ± 18.9 showing a difference of 18.3% with respect to the initial exam. Among the surfaces with caries history, those which had been restored were predominant (1.5 ± 2.6). The qualitative analysis of the children's perception of the games revealed that they found them positive, nice, fun, and educational. Conclusions: establishing an oral health toy library, as a constructive environment that involves innovative strategies aimed at health education, allowed socialization of the studied population as well as promotion of healthy oral habits and reinforcement of self-care among this population.

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Research paper thumbnail of Las prácticas de mercadeo, un aporte a la competitividad de las pequeñas empresas de servicios en la ciudad de Medellín

Tesis (Maestria en Mercadeo). Universidad de Manizales. Facultad de Ciencias Contables, Economica... more Tesis (Maestria en Mercadeo). Universidad de Manizales. Facultad de Ciencias Contables, Economicas y Administrativas, 2013

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Research paper thumbnail of Saluteca oral con enfoque familiar: hacia una nueva orientación en educación de la salud bucal

Revista Facultad De Odontologia Universidad De Antioquia, Jun 20, 2012

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Research paper thumbnail of In Vivo Discrimination of Nonuric Acid Kidney Stone Types

PURPOSE To evaluate the use of an advanced dual energy processing algorithm to improve the abilit... more PURPOSE To evaluate the use of an advanced dual energy processing algorithm to improve the ability of dual energy CT (DECT) protocol to differentiate non-uric acid (NUA) renal stone types in a patient cohort. METHOD AND MATERIALS We evaluated data from 81 patients that received a non-enhanced DECT scan prior to surgical removal of kidney stones and subsequent stone composition analysis by infrared spectroscopy (IR). DECT scans were performed using a dual-source CT scanner (Somatom Definition Flash, Siemens Healthcare), 100 kV and 140 kV with tin filtration, and 240 and 185 mAs quality reference mAs values for the low and high energy tubes, respectively. Images were reconstructed with medium smooth kernel (D30) and 1 mm thickness. Only relatively pure kidney stones (≥90% of a single composition, as determined by IR) were included in this analysis (n=44 stones). A Matlab-based processing algorithm was developed to semiautomatically segment kidney stones and predict stone composition u...

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Research paper thumbnail of Determination of Kidney Stone Composition Using Dual Energy CT in a Cohort of Patients with Medium to Large Body Size

PURPOSE Patients with medium to large body sizes may be unable to receive dual-energy CT (DECT) e... more PURPOSE Patients with medium to large body sizes may be unable to receive dual-energy CT (DECT) exams for the purpose of determining renal stone composition due to increased image noise when using 80/140 kV protocols resulting in reduced diagnostic accuracy. In this study, we determined the accuracy of 100/140 kV DECT protocols for kidney stone composition analysis in a patient cohort having medium to large body size. METHOD AND MATERIALS A retrospective chart review identified 81 patients with lateral abdominal size above 35 cm who were scanned using a dual-source system for clinical indications, with subsequent surgical stone removal. A 100/140kV DECT protocol was used, with a tin filter on the 140 kV tube to increase separation of the x-ray spectra. Automatic exposure control was used to adapt the tube current to patient size, and average scanner x-ray output was recorded (volume CT dose index, CTDIvol).After surgical extraction, stone composition was determined using infrared sp...

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Research paper thumbnail of Improved Discrimination of Calcium Oxalate and Apatite Kidney Stones with Dual Energy CT and Clinical Information

PURPOSE Differentiating between calcium oxalate and apatite stones using dual-energy CT (DECT) ha... more PURPOSE Differentiating between calcium oxalate and apatite stones using dual-energy CT (DECT) has been difficult in previous studies. In this study, we propose to improve the accuracy of non-invasive characterization of these two stone types by combining dual-energy CT and clinical information. METHOD AND MATERIALS Patients referred for clinically-indicated dual-energy CT for stone composition analysis whose stones were subsequently surgically removed were enrolled in this IRB-approved study. Removed stones were evaluated using infrared microscopy to determine elemental composition. Dual-energy CT images were processed using a custom-developed software tool that evaluated the ratio of CT numbers between the low- and high-energy images. Stones were segregated into four groups according to the thresholds established in our previous study. Clinical information, including patient age, gender, family history, dietary habit, and comorbidities, as well as lab results including: serum elec...

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Research paper thumbnail of A Biological Liver Phantom to Evaluate the Impact of Radiation Dose Reduction on the Accuracy of CT Perfusion Imaging

PURPOSE Physical phantoms that realistically mimic human vasculature and microvasculature are dif... more PURPOSE Physical phantoms that realistically mimic human vasculature and microvasculature are difficult, if not impossible, to design and build. The purpose of this study was to evaluate the feasibility of using a fixed ex vivo porcine liver to systematically evaluate dose reduction strategies in perfusion computed tomography (PCT). METHOD AND MATERIALS A fresh porcine liver was perfused with formalin to preserve the specimen and ensure patency of the vascular structures. The portal vein was connected to a continuous flow pump, allowing control of input pressure and flow. The liver was submerged in a 32 cm wide, body-shaped acrylic phantom filled with water. The phantom was scanned four times, with a PCT protocol using 80 kVp and 400, 400, 100 and 20 mAs. 4 cc of iodine (300 mg/ml) was injected at 1 cc/sec for each scan and images were acquired for 50 sec, 2 sec after injection at each dose level. We compared percent root mean square (RMS) error between time attenuation curves (TACs...

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Research paper thumbnail of Accuracy Improvement in Low Dose Dual-Energy CT for Renal Stone Composition Differentiation

PURPOSE To improve the accuracy of dual energy stone composition classification with low dose CT ... more PURPOSE To improve the accuracy of dual energy stone composition classification with low dose CT using a noise reduction technique - HighlY constrained backPRojection (HYPR) - while maintaining the spatial resolution and noise texture. METHOD AND MATERIALS A total of 80 kidney stones with 18 pure uric acid (UA) stones and 62 non-uric acid (NUA) stones were included in this study. Each stone was placed in a water filled plastic container and placed in 2 water phantoms with lateral width measured at 30 and 35 cm. Phantoms were scanned on a dual-source CT system (Definition FLASH, Siemens Healthcare, Forchheim, Germany) operating in dual energy mode with 80 kV and 140 kV with an added tin filter. Scans were conducted at three dose levels: 100, 50 and 25% of a clinical dose level (18 mGy for a standard size patient). Images were reconstructed using commercial filtered backprojection (FBP) algorithm and HYPR. Image noise was measured and HYPR noise reduction calculated. Stone composition...

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Research paper thumbnail of Dynamic Analysis of Heat Transfer Through a Fin of Constant Cross-Sectional Area: Specified Fin Tip Temperature

Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer, 2009

A dynamic analysis is performed for heat transfer through a fin with constant cross-sectional are... more A dynamic analysis is performed for heat transfer through a fin with constant cross-sectional area and with a specified fin tip temperature. The process starts with a dynamic energy balance around the fin. Laplace transforms and the Bromwich Integral are used to solve analytically the resulting partial differential equation. The final purely analytical solution is compared to the well known steady state solution. The two match exactly as time approaches infinity. Furthermore it is shown that the steady-state and dynamic characteristics of the fin are directly tied to the Biot number.© 2009 ASME

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Research paper thumbnail of A Semantic-Based Approach for the Management of Digital Documents

2008 11th IEEE International Conference on Computational Science and Engineering - Workshops, 2008

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Research paper thumbnail of Physiological Mechanisms Underlying the Seasonality of Leaf Senescence and Renewal in Seasonally Dry Tropical Forest Trees

Seasonally Dry Tropical Forests, 2011

Seasonality in the presence and production of leaves is the defining characteristic of seasonally... more Seasonality in the presence and production of leaves is the defining characteristic of seasonally dry tropical forest (SDTF) ecosystems and has important implications for their functioning. Temporal patterns of shoot activity influence photosynthetic carbon gain and thus affect competition between tree phenological types (Givnish 2002), the seasonal rhythms of tree-herbivore interactions (Leigh 1999; Dirzo and Boege 2009), and the annual ecosystem carbon uptake and energy fluxes (Kucharik et al. 2006). The impact of leaf phenology on tree carbon return is associated with its effect on the length of leaf exposure to herbivore and pathogen damage, the timing of leaf loss for water balance, and the energy investment in leaf construction (Franco et al. 2005). The timing and the length of leaf presence in tropical forests has also been suggested to play a key role in maintaining tree diversity by regulating the abundance of pest pressures (Leigh et al. 2004).

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Research paper thumbnail of La gestión del mercadeo: un aporte a la competitividad de las pequeñas empresas del sector servicios en Medellín

Revista científica Pensamiento y Gestión, 2014

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Research paper thumbnail of Procesos psicológicos básicos incluidos en publicaciones científicas sobre comportamiento alimentario en niños: revisión sistemática

Revista chilena de nutrición, 2014

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Research paper thumbnail of Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation

Plant, Cell & Environment, 2009

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Research paper thumbnail of Nonconvex prior image constrained compressed sensing (NCPICCS): Theory and simulations on perfusion CT

Medical Physics, 2011

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Research paper thumbnail of Comparison of spinal anesthesia with combined sciatic-femoral nerve block for outpatient knee arthroscopy

Journal of Clinical Anesthesia, 2008

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