Djenane Pamplona - Academia.edu (original) (raw)
Papers by Djenane Pamplona
International journal of …, 2003
This paper investigates the non-linear dynamic behavior and stability of the internal membrane of... more This paper investigates the non-linear dynamic behavior and stability of the internal membrane of a ventricular assist device (VAD). This membrane separates the blood chamber from the pneumatic chamber, transmitting the driving cyclic pneumatic loading to blood flowing from the left ventricle into the aorta. The membrane is a thin, nearly spherical axi-symmetric shallow cap made of polyurethane and reinforced
Proceedings do 6º Encontro Nacional de Engenharia Biomecânica
Journal of Mechanical Engineering and Biomechanics
One internal pressure measuring devices, with data recording capability, was developed and built ... more One internal pressure measuring devices, with data recording capability, was developed and built for medical applications, to assist physicians acquiring data for the purpose of studying the pressure decay in subsequent infusions and subcutaneous implants. Such as infiltrations in skin expanders, and monitoring breast implants.
Revista Brasileira de Cirurgia Plástica (RBCP) – Brazilian Journal of Plastic Sugery
Introduction: Skin expansion is a physiological process defined as the ability of human skin to i... more Introduction: Skin expansion is a physiological process defined as the ability of human skin to increase its superficial area in response to a stress or given deformation. In reconstructive surgery, skin expanders are implanted beneath the skin and periodically infiltrated with a saline solution to provide an extra flap of skin. When the prescribed internal volume of the expander is reached, reconstructive surgery is performed. Methods: A semiautomatic and portable device was developed and built to facilitate a skin expansion procedure. The device aims to simplify the infiltration process, providing mobility and independence to the patient and assuring the physician of the infiltration quality and precision. The device also enables continuous expansion in hospitalized patients. Results: Using a code, the doctor accesses the menu of the device and sets the maximum pressure and/or value for each expander of the patient. The patient can control the infiltration velocity and reverse or stop the operation. All data are recorded on a simcard and include date, time, initial and final volumes, and initial and final pressures of each procedure for each expander. Conclusions: The device motorizes and optimizes the expansion, allowing the doctor to prescribe a maximum infiltration pressure or volume. All data are recorded to provide an important database of skin behavior related to sex, race, age, and expansion site.
International Journal of Non-Linear Mechanics
Structural Engineering and Mechanics, 2006
ABSTRACT In this paper the buckling and post-buckling behavior of slender bars under self-weight ... more ABSTRACT In this paper the buckling and post-buckling behavior of slender bars under self-weight are studied. In order to study the post-buckling behavior of the bar, a geometrically exact formulation for the non-linear analysis of uni-directional structural elements is presented, considering arbitrary load distribution and boundary conditions. From this formulation one obtains a set of first-order coupled nonlinear equations which, together with the boundary conditions at the bar ends, form a two-point boundary value problem. This problem is solved by the simultaneous use of the Runge-Kutta integration scheme and the Newton-Raphson method. By virtue of a continuation algorithm, accurate solutions can be obtained for a variety of stability problems exhibiting either limit point or bifurcational-type buckling. Using this formulation, a detailed parametric analysis is conducted in order to study the buckling and post-buckling behavior of slender bars under self-weight, including the influence of boundary conditions on the stability and large deflection behavior of the bar. In order to evaluate the quality and accuracy of the results, an experimental analysis was conducted considering a clamped-free thin-walled metal bar. As this kind of structure presents a high index of slenderness, its answers could be affected by the introduction of conventional sensors. In this paper, an experimental methodology was developed, allowing the measurement of static or dynamic displacements without making contact with the structure, using digital image processing techniques. The proposed experimental procedure can be used to a wide class of problems involving large deflections and deformations. The experimental buckling and post-buckling behavior compared favorably with the theoretical and numerical results.
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
Siggraph, 1996
Nowadays a wide variety of warping applications is known, like educational ones and entertainment... more Nowadays a wide variety of warping applications is known, like educational ones and entertainment ones. The method presented in this work modifies conventional warping techniques in order to applicate it in ageing facial manipulation. We used ageing curves of facial region to show forward and backward ageing face.
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
International Journal of Solids and Structures, 2001
This paper investigates the large deformations of an extended fluid-filled cylindrical membrane. ... more This paper investigates the large deformations of an extended fluid-filled cylindrical membrane. The static case and the behaviour of the membrane rotating at a constant angular velocity are both considered. A detailed experimental analysis was carried out involving different geometries, and initial axial forces and the influence of the axial force and the fluid volume were investigated. An apparatus was
ABSTRACT This paper describes a mathematical and graphical model for face aging. It considers the... more ABSTRACT This paper describes a mathematical and graphical model for face aging. It considers the possibility of predicting the aging process by offering an initial quantification of this process as it applies to the face. It is concerned with physical measurements and a general law of time dependence. After measuring and normalizing a photograph of a person, one could predict, with a known amount of error, the appearance of that person at a different age. The technique described has served its purpose successfully, with a representative amount of patient data behaving sufficiently near the general aging curve of each parameter. That model uses a warping technique to emulate the aging changes on the face of women. Frequently the warping methods are based on the interpolation between images or general mathematical functions to calculate the pixel attributes. The implemented process considers the age features of selected parts of a face such as the face outline and the shape of the lips. These age features were obtained by measuring the facial regions of women that have been photographed throughout their lives. The present work is first concerned with discussing a methodology to define the aging parameters that can be measured, and second with representing the age effects graphically.
Simplified Facial Rejuvenation, 2008
Journal of Medical Imaging and Health Informatics, 2014
ABSTRACT
Skin Research and Technology, 2014
Skin expansion is a physiological process that is defined as the ability of the human skin to inc... more Skin expansion is a physiological process that is defined as the ability of the human skin to increase its superficial area in response to stress or to a given deformation. Skin expanders are silicon bags that are implanted underneath the skin. Because the skin presents creep or relaxation, the resulting stress decreases after a time due to the imposed deformation. Skin expansions are used to reconstruct burned areas and breasts after a mastectomy or to hide scars. The question that constantly arises during skin expansion is whether it creates a sufficient amount of skin or, in other words, whether the achieved expansion is sufficient to resurface the defect. These questions are answered with information about how much new tissue is required to achieve the reconstruction in a given context and calculating the required tissue (surface area) in relationship with the volume infiltrated. Surface formulas for round and rectangular, and finite elements method for crescent skin expanders are used to calculate the relation between infiltrated volume and surface area. Those results were corrected or validated by an experimental work using 3D scanners to calculate the relation between surface area and internal volumes for the three types of expanders in question. The research provides information to determine the type, number, and volume of skin expanders necessary to obtain an extra amount of skin to repair a specific medical condition and to determine the amount of skin obtained even in cases when the expansion does not come to term. fci, Correcting factor, which corrects the mathematical formulas using the experimental results, for i skin expander; i, geometry of the expander, round (c), rectangular (r), or crescent (cresc/cr); Sd , surface of the defect; Sds , surface area of the donor site; Sfi, surface area obtained using a mathematical calculation for the i skin expander; S¯fi, surface area obtained experimentally for the i skin expander; Sfi∗, corrected surface area obtained using a mathematical calculation for the i skin expander corrected by the correcting factor; S¯fi∗∗ extra flap of skin obtained by expansion for the i skin expander; Vii, internal volume infiltrated in the i skin expander; Vni, nominal internal volume of the i skin expander.
Journal of the Mechanical Behavior of Biomedical Materials, 2014
This article discusses skin expansion without considering cellular growth of the skin. An in vivo... more This article discusses skin expansion without considering cellular growth of the skin. An in vivo analysis was carried out that involved expansion at three different sites on one patient, allowing for the observation of the relaxation process. Those measurements were used to characterize the human skin of the thorax during the surgical process of skin expansion. A comparison between the in vivo results and the numerical finite elements model of the expansion was used to identify the material elastic parameters of the skin of the thorax of that patient. Delfino's constitutive equation was chosen to model the in vivo results. The skin is considered to be an isotropic, homogeneous, hyperelastic, and incompressible membrane. When the skin is extended, such as with expanders, the collagen fibers are also extended and cause stiffening in the skin, which results in increasing resistance to expansion or further stretching. We observed this phenomenon as an increase in the parameters as subsequent expansions continued. The number and shape of the skin expanders used in expansions were also studied, both mathematically and experimentally. The choice of the site where the expansion should be performed is discussed to enlighten problems that can lead to frustrated skin expansions. These results are very encouraging and provide insight into our understanding of the behavior of stretched skin by expansion. To our knowledge, this study has provided results that considerably improve our understanding of the behavior of human skin under expansion.
Journal of Mechanics of Materials and Structures, 2012
This study characterized human skin of the lower leg and scalp during the surgical process of ski... more This study characterized human skin of the lower leg and scalp during the surgical process of skin expansion. To our knowledge, this is the first study in this field, which has provided results that considerably improve our understanding of human skin. A detailed in vivo analysis was carried out involving four different patients that allowed for observation during the relaxation process. A comparison between the in vivo and numerical finite elements model of the expansion was used to identify the material elastic parameters of the skin. After a comprehensive search of constitutive equations for describing skin, Delfino's constitutive equation was chosen to model the in vivo results. We considered skin as an isotropic, homogeneous, hyperelastic, and incompressible membrane. The parameters of Delfino's exponential function obtained for the first skin stretch process were a = 40.0 KPa and b = 20.2. As skin is extended, such as with expanders or in other procedures that tighten the skin, the collagen fibers are also extended and cause stiffening in the skin, which results in it being more and more resistant to expansion or further stretching. We observed this phenomenon as an increase in parameters a and b as subsequent expansions continued. The results of this study allow for the quantification of stiffening of the skin after several stretches, when the skin becomes more and more inelastic. These results are very encouraging and provide insight into our understanding of the behavior of stretched skin and maybe other biological tissues, as swollen artery and veins.
Journal of Biomechanical Engineering, 2005
In the classical "first approximation" theory of thin-shell structures, the con... more In the classical "first approximation" theory of thin-shell structures, the constitutive relations for a generic shell element--i.e. the elastic relations between the bending moments and membrane stresses and the corresponding changes in curvature and strain, respectively-are written as if an element of the shell is flat, although in reality it is curved. In this theory it is believed that discrepancies on account of the use of "flat" constitutive relations will be negligible provided the ratio shell-radius/thickness is of sufficiently large order. In the study of drawing of narrow, cylindrical "tethers" from liposomes it has been known for many years that it is necessary to use instead a constitutive law which explicitly describes a curved element in order to make sense of the mechanics; and indeed such tethers are generally of "thick-walled" proportions. In this paper we show that the proper constitutive relations for a curved element must also be used in the study, by means of shell equations, of the buckling of initially spherical thin-walled giant liposomes under exterior pressure: these involve the inclusion of what we call the "Mkappa" terms, which are not present in the standard "first-approximation" theory. We obtain analytical expressions for both the bifurcation buckling pressure and the slope of the post-buckling path, in terms of the dimensions and elastic constants of the lipid bi-layer, and also the initial state of bending moment in the vesicle. We explain physically how the initial bending moment can affect the bifurcation pressure, whereas it cannot in "first-approximation" theory. We use these results to map the conditions under which the vesicle buckles into an oblate, as distinct from a prolate ("rugby-ball") shape. Some of our results were obtained long ago by the use of energy methods; but our aim here has been to identify precisely what is lacking in "first-approximation" theory in relation to liposomes, and so to put the "shell equations" approach onto a firm footing in mechanics.
International journal of …, 2003
This paper investigates the non-linear dynamic behavior and stability of the internal membrane of... more This paper investigates the non-linear dynamic behavior and stability of the internal membrane of a ventricular assist device (VAD). This membrane separates the blood chamber from the pneumatic chamber, transmitting the driving cyclic pneumatic loading to blood flowing from the left ventricle into the aorta. The membrane is a thin, nearly spherical axi-symmetric shallow cap made of polyurethane and reinforced
Proceedings do 6º Encontro Nacional de Engenharia Biomecânica
Journal of Mechanical Engineering and Biomechanics
One internal pressure measuring devices, with data recording capability, was developed and built ... more One internal pressure measuring devices, with data recording capability, was developed and built for medical applications, to assist physicians acquiring data for the purpose of studying the pressure decay in subsequent infusions and subcutaneous implants. Such as infiltrations in skin expanders, and monitoring breast implants.
Revista Brasileira de Cirurgia Plástica (RBCP) – Brazilian Journal of Plastic Sugery
Introduction: Skin expansion is a physiological process defined as the ability of human skin to i... more Introduction: Skin expansion is a physiological process defined as the ability of human skin to increase its superficial area in response to a stress or given deformation. In reconstructive surgery, skin expanders are implanted beneath the skin and periodically infiltrated with a saline solution to provide an extra flap of skin. When the prescribed internal volume of the expander is reached, reconstructive surgery is performed. Methods: A semiautomatic and portable device was developed and built to facilitate a skin expansion procedure. The device aims to simplify the infiltration process, providing mobility and independence to the patient and assuring the physician of the infiltration quality and precision. The device also enables continuous expansion in hospitalized patients. Results: Using a code, the doctor accesses the menu of the device and sets the maximum pressure and/or value for each expander of the patient. The patient can control the infiltration velocity and reverse or stop the operation. All data are recorded on a simcard and include date, time, initial and final volumes, and initial and final pressures of each procedure for each expander. Conclusions: The device motorizes and optimizes the expansion, allowing the doctor to prescribe a maximum infiltration pressure or volume. All data are recorded to provide an important database of skin behavior related to sex, race, age, and expansion site.
International Journal of Non-Linear Mechanics
Structural Engineering and Mechanics, 2006
ABSTRACT In this paper the buckling and post-buckling behavior of slender bars under self-weight ... more ABSTRACT In this paper the buckling and post-buckling behavior of slender bars under self-weight are studied. In order to study the post-buckling behavior of the bar, a geometrically exact formulation for the non-linear analysis of uni-directional structural elements is presented, considering arbitrary load distribution and boundary conditions. From this formulation one obtains a set of first-order coupled nonlinear equations which, together with the boundary conditions at the bar ends, form a two-point boundary value problem. This problem is solved by the simultaneous use of the Runge-Kutta integration scheme and the Newton-Raphson method. By virtue of a continuation algorithm, accurate solutions can be obtained for a variety of stability problems exhibiting either limit point or bifurcational-type buckling. Using this formulation, a detailed parametric analysis is conducted in order to study the buckling and post-buckling behavior of slender bars under self-weight, including the influence of boundary conditions on the stability and large deflection behavior of the bar. In order to evaluate the quality and accuracy of the results, an experimental analysis was conducted considering a clamped-free thin-walled metal bar. As this kind of structure presents a high index of slenderness, its answers could be affected by the introduction of conventional sensors. In this paper, an experimental methodology was developed, allowing the measurement of static or dynamic displacements without making contact with the structure, using digital image processing techniques. The proposed experimental procedure can be used to a wide class of problems involving large deflections and deformations. The experimental buckling and post-buckling behavior compared favorably with the theoretical and numerical results.
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
Siggraph, 1996
Nowadays a wide variety of warping applications is known, like educational ones and entertainment... more Nowadays a wide variety of warping applications is known, like educational ones and entertainment ones. The method presented in this work modifies conventional warping techniques in order to applicate it in ageing facial manipulation. We used ageing curves of facial region to show forward and backward ageing face.
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
International Journal of Solids and Structures, 2001
This paper investigates the large deformations of an extended fluid-filled cylindrical membrane. ... more This paper investigates the large deformations of an extended fluid-filled cylindrical membrane. The static case and the behaviour of the membrane rotating at a constant angular velocity are both considered. A detailed experimental analysis was carried out involving different geometries, and initial axial forces and the influence of the axial force and the fluid volume were investigated. An apparatus was
ABSTRACT This paper describes a mathematical and graphical model for face aging. It considers the... more ABSTRACT This paper describes a mathematical and graphical model for face aging. It considers the possibility of predicting the aging process by offering an initial quantification of this process as it applies to the face. It is concerned with physical measurements and a general law of time dependence. After measuring and normalizing a photograph of a person, one could predict, with a known amount of error, the appearance of that person at a different age. The technique described has served its purpose successfully, with a representative amount of patient data behaving sufficiently near the general aging curve of each parameter. That model uses a warping technique to emulate the aging changes on the face of women. Frequently the warping methods are based on the interpolation between images or general mathematical functions to calculate the pixel attributes. The implemented process considers the age features of selected parts of a face such as the face outline and the shape of the lips. These age features were obtained by measuring the facial regions of women that have been photographed throughout their lives. The present work is first concerned with discussing a methodology to define the aging parameters that can be measured, and second with representing the age effects graphically.
Simplified Facial Rejuvenation, 2008
Journal of Medical Imaging and Health Informatics, 2014
ABSTRACT
Skin Research and Technology, 2014
Skin expansion is a physiological process that is defined as the ability of the human skin to inc... more Skin expansion is a physiological process that is defined as the ability of the human skin to increase its superficial area in response to stress or to a given deformation. Skin expanders are silicon bags that are implanted underneath the skin. Because the skin presents creep or relaxation, the resulting stress decreases after a time due to the imposed deformation. Skin expansions are used to reconstruct burned areas and breasts after a mastectomy or to hide scars. The question that constantly arises during skin expansion is whether it creates a sufficient amount of skin or, in other words, whether the achieved expansion is sufficient to resurface the defect. These questions are answered with information about how much new tissue is required to achieve the reconstruction in a given context and calculating the required tissue (surface area) in relationship with the volume infiltrated. Surface formulas for round and rectangular, and finite elements method for crescent skin expanders are used to calculate the relation between infiltrated volume and surface area. Those results were corrected or validated by an experimental work using 3D scanners to calculate the relation between surface area and internal volumes for the three types of expanders in question. The research provides information to determine the type, number, and volume of skin expanders necessary to obtain an extra amount of skin to repair a specific medical condition and to determine the amount of skin obtained even in cases when the expansion does not come to term. fci, Correcting factor, which corrects the mathematical formulas using the experimental results, for i skin expander; i, geometry of the expander, round (c), rectangular (r), or crescent (cresc/cr); Sd , surface of the defect; Sds , surface area of the donor site; Sfi, surface area obtained using a mathematical calculation for the i skin expander; S¯fi, surface area obtained experimentally for the i skin expander; Sfi∗, corrected surface area obtained using a mathematical calculation for the i skin expander corrected by the correcting factor; S¯fi∗∗ extra flap of skin obtained by expansion for the i skin expander; Vii, internal volume infiltrated in the i skin expander; Vni, nominal internal volume of the i skin expander.
Journal of the Mechanical Behavior of Biomedical Materials, 2014
This article discusses skin expansion without considering cellular growth of the skin. An in vivo... more This article discusses skin expansion without considering cellular growth of the skin. An in vivo analysis was carried out that involved expansion at three different sites on one patient, allowing for the observation of the relaxation process. Those measurements were used to characterize the human skin of the thorax during the surgical process of skin expansion. A comparison between the in vivo results and the numerical finite elements model of the expansion was used to identify the material elastic parameters of the skin of the thorax of that patient. Delfino's constitutive equation was chosen to model the in vivo results. The skin is considered to be an isotropic, homogeneous, hyperelastic, and incompressible membrane. When the skin is extended, such as with expanders, the collagen fibers are also extended and cause stiffening in the skin, which results in increasing resistance to expansion or further stretching. We observed this phenomenon as an increase in the parameters as subsequent expansions continued. The number and shape of the skin expanders used in expansions were also studied, both mathematically and experimentally. The choice of the site where the expansion should be performed is discussed to enlighten problems that can lead to frustrated skin expansions. These results are very encouraging and provide insight into our understanding of the behavior of stretched skin by expansion. To our knowledge, this study has provided results that considerably improve our understanding of the behavior of human skin under expansion.
Journal of Mechanics of Materials and Structures, 2012
This study characterized human skin of the lower leg and scalp during the surgical process of ski... more This study characterized human skin of the lower leg and scalp during the surgical process of skin expansion. To our knowledge, this is the first study in this field, which has provided results that considerably improve our understanding of human skin. A detailed in vivo analysis was carried out involving four different patients that allowed for observation during the relaxation process. A comparison between the in vivo and numerical finite elements model of the expansion was used to identify the material elastic parameters of the skin. After a comprehensive search of constitutive equations for describing skin, Delfino's constitutive equation was chosen to model the in vivo results. We considered skin as an isotropic, homogeneous, hyperelastic, and incompressible membrane. The parameters of Delfino's exponential function obtained for the first skin stretch process were a = 40.0 KPa and b = 20.2. As skin is extended, such as with expanders or in other procedures that tighten the skin, the collagen fibers are also extended and cause stiffening in the skin, which results in it being more and more resistant to expansion or further stretching. We observed this phenomenon as an increase in parameters a and b as subsequent expansions continued. The results of this study allow for the quantification of stiffening of the skin after several stretches, when the skin becomes more and more inelastic. These results are very encouraging and provide insight into our understanding of the behavior of stretched skin and maybe other biological tissues, as swollen artery and veins.
Journal of Biomechanical Engineering, 2005
In the classical "first approximation" theory of thin-shell structures, the con... more In the classical "first approximation" theory of thin-shell structures, the constitutive relations for a generic shell element--i.e. the elastic relations between the bending moments and membrane stresses and the corresponding changes in curvature and strain, respectively-are written as if an element of the shell is flat, although in reality it is curved. In this theory it is believed that discrepancies on account of the use of "flat" constitutive relations will be negligible provided the ratio shell-radius/thickness is of sufficiently large order. In the study of drawing of narrow, cylindrical "tethers" from liposomes it has been known for many years that it is necessary to use instead a constitutive law which explicitly describes a curved element in order to make sense of the mechanics; and indeed such tethers are generally of "thick-walled" proportions. In this paper we show that the proper constitutive relations for a curved element must also be used in the study, by means of shell equations, of the buckling of initially spherical thin-walled giant liposomes under exterior pressure: these involve the inclusion of what we call the "Mkappa" terms, which are not present in the standard "first-approximation" theory. We obtain analytical expressions for both the bifurcation buckling pressure and the slope of the post-buckling path, in terms of the dimensions and elastic constants of the lipid bi-layer, and also the initial state of bending moment in the vesicle. We explain physically how the initial bending moment can affect the bifurcation pressure, whereas it cannot in "first-approximation" theory. We use these results to map the conditions under which the vesicle buckles into an oblate, as distinct from a prolate ("rugby-ball") shape. Some of our results were obtained long ago by the use of energy methods; but our aim here has been to identify precisely what is lacking in "first-approximation" theory in relation to liposomes, and so to put the "shell equations" approach onto a firm footing in mechanics.