Hung Truong - Academia.edu (original) (raw)

Papers by Hung Truong

Theoretical and Applied Mechanics Letters

EDITOR'S RECOMMENDATION The flight of insects has enlightened the flying dream of human being... more EDITOR'S RECOMMENDATION The flight of insects has enlightened the flying dream of human beings for centuries. Wing flexibility is often used by insects to increase their flight efficiencies. However, the mechanism of the increased efficiencies still remains mysterious. Prof. Kai Schneider's group studies the aerodynamics of a tethered flapping bumblebee using a mass-spring fluid-structure interaction numerical solver. It indicates that a higher flight efficiency or a larger lift-to-power ratio can be achieved by flapping insects with optimal mechanical properties of the flexible wings. The novel understanding of insects’ body structure and flying behavior will benefit the design of micro-air vehicles (MAVs). ABSTRACT The sophisticated structures of flapping insect wings make it challenging to study the role of wing flexibility in insect flight. In this study, a mass-spring system is used to model wing structural dynamics as a thin, flexible membrane supported by a network of veins. The vein mechanical properties can be estimated based on their diameters and the Young's modulus of cuticle. In order to analyze the effect of wing flexibility, the Young's modulus is varied to make a comparison between two different wing models that we refer to as flexible and highly flexible. The wing models are coupled with a pseudo-spectral code solving the incompressible Navier–Stokes equations, allowing us to investigate the influence of wing deformation on the aerodynamic efficiency of a tethered flapping bumblebee. Compared to the bumblebee model with rigid wings, the one with flexible wings flies more efficiently, characterized by a larger lift-to-power ratio.

Cartesian CFD Methods for Complex Applications, 2020

Wing flexibility plays an essential role in the aerodynamic performance of insects due to the con... more Wing flexibility plays an essential role in the aerodynamic performance of insects due to the considerable deformation of their wings during flight under the impact of inertial and aerodynamic forces. These forces come from the complex wing kinematics of insects. In this study, both wing structural dynamics and flapping wing motion are taken into account to investigate the effect of wing deformation on the aerodynamic efficiency of a bumblebee in tethered flight. A fluid-structure interaction solver, coupling a mass-spring model for the flexible wing with a pseudospectral code solving the incompressible Navier-Stokes equations, is implemented for this purpose. We first consider a tethered bumblebee flying in laminar flow with flexible wings. Compared to the rigid model, flexible wings generate smaller aerodynamic forces but require much less power. Finally, the bumblebee model is put into a turbulent flow to investigate its influence on the force production of flexible wings.

Summary: Due to the increasing availability of large unstructured point clouds from lasers cannin... more Summary: Due to the increasing availability of large unstructured point clouds from lasers canning and photogrammetry, there is a growing demand for automatic evaluation methods. Given the complexity of the underlying problems, several new methods resort to using semantic knowledge in particular for object detection and qualification support. In this paper, we present a novel approach which makes use of advanced algorithms, and benefits from intelligent knowledge management strategies for the processing of 3D point clouds and object qualification in a scanned scene. In particular, our method extends the use of semantic knowledge to all stages of the processing, including the guidance of the 3D processing algorithms. The complete solution consists of a multi- stage, iterative, concept based on three factors: the modeled knowledge, the package of algorithms, and the qualification engine. Zusammenfassung: Automatische Detektion und Qualifizierung von Objekten in Punktwolken unter Nutzu...

The reconstruction of 3D objects from point clouds and images is a major task in many application... more The reconstruction of 3D objects from point clouds and images is a major task in many application fields. The processing of such spatial data, especially 3D point clouds from terrestrial laser scanners, generally consumes time and requires extensive interaction between a human and the machine to yield a promising result. Presently, algorithms for an automatic processing are usually datadriven and concentrate on geometric feature extraction. Robust and quick methods for complete object extraction or identification are still an ongoing research topic and suffer from the complex structure of the data, which cannot be sufficiently modelled by purely numerical strategies. Therefore, the intention of our approach is to take human cognitive strategy as an example, and to simulate these processes based on available knowledge for the objects of interest. Such processes will first, introduce a semantic structure for the objects and second, guide the algorithms used to detect and recognize obj...

Bioinspiration & Biomimetics, 2021

Insect wings can undergo significant deformation during flapping motion owing to inertial, elasti... more Insect wings can undergo significant deformation during flapping motion owing to inertial, elastic and aerodynamic forces. Changes in shape then alter aerodynamic forces, resulting in a fully coupled Fluid-Structure Interaction (FSI) problem. Here, we present detailed three-dimensional FSI simulations of deformable blowfly (Calliphora vomitoria) wings in flapping flight. A wing model is proposed using a multi-parameter mass-spring approach, chosen for its implementation simplicity and computational efficiency. We train the model to reproduce static elasticity measurements by optimizing its parameters using a genetic algorithm with covariance matrix adaptation (CMA-ES). Wing models trained with experimental data are then coupled to a high-performance flow solver run on massively parallel supercomputers. Different features of the modeling approach and the intra-species variability of elastic properties are discussed. We found that individuals with different wing stiffness exhibit similar aerodynamic properties characterized by dimensionless forces and power at the same Reynolds number. We further study the influence of wing flexibility by comparing between the flexible wings and their rigid counterparts. Under equal prescribed kinematic conditions for rigid and flexible wings, wing flexibility improves lift-to-drag ratio as well as lift-to-power ratio and reduces peak force observed during wing rotation.

Computers & Fluids, 2020

The secret to the spectacular flight capabilities of flapping insects lies in their wings, which ... more The secret to the spectacular flight capabilities of flapping insects lies in their wings, which are often approximated as flat, rigid plates. Real wings are however delicate structures, composed of veins and membranes, and can undergo significant deformation. In the present work, we present detailed numerical simulations of such deformable wings. Our results are obtained with a fluidstructure interaction solver, coupling a mass-spring model for the flexible wing with a pseudo-spectral code solving the incompressible Navier-Stokes equations. We impose the no-slip boundary condition through the volume penalization method; the time-dependent complex geometry is then completely described by a mask function. This allows solving the governing equations of the fluid on a regular Cartesian grid. Our implementation for massively parallel computers allows us to perform high resolution computations with

Videometrics, Range Imaging, and Applications XII; and Automated Visual Inspection, 2013

ABSTRACT The modeling of real-world scenarios through capturing 3D digital data has been proven a... more ABSTRACT The modeling of real-world scenarios through capturing 3D digital data has been proven applicable in a variety of industrial applications, ranging from security, to robotics and to fields in the medical sciences. These different scenarios, along with variable conditions, present a challenge in discovering flexible appropriate solutions. In this paper, we present a novel approach based on a human cognition model to guide processing. Our method turns traditional data-driven processing into a new strategy based on a semantic knowledge system. Robust and adaptive methods for object extraction and identification are modeled in a knowledge domain, which has been created by purely numerical strategies. The goal of the present work is to select and guide algorithms following adaptive and intelligent manners for detecting objects in point clouds. Results show that our approach succeeded in identifying the objects of interest while using various data types.

Fluid Mechanics and Its Applications

Eighth International Multi-Conference on Systems, Signals & Devices, 2011

Object reconstruction is an important task in many fields of application as it allows to generate... more Object reconstruction is an important task in many fields of application as it allows to generate digital representations of our physical world used as base for analysis, planning, construction, visualization or other

2009 IEEE International Symposium on Assembly and Manufacturing, 2009

Abstract Elevator button (EB) detection is a very important research issue in home service roboti... more Abstract Elevator button (EB) detection is a very important research issue in home service robotics area, this paper describes an effective method for EB detection with mirroring effects in completely reflective surfaces. Line features and other local features (such as corner, ...

2012 11th International Conference on Information Science, Signal Processing and their Applications (ISSPA), 2012

ABSTRACT In this paper we present a novel approach for 3D point cloud processing with the aim of ... more ABSTRACT In this paper we present a novel approach for 3D point cloud processing with the aim of annotating objects in a scanned scene. Our method is based on human cognition to guide the 3D processing algorithms and uses semantic knowledge to manage data and identify immediate situation-dependent objectives. In particular, we have built a system that allows an automatic and flexible selection of algorithms. The selection strategy exploits knowledge to identify the geometrical features to be detected as well as the objects to be annotated at each stage of the 3D processing of the point cloud.

2008 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems, 2008

Exploiting geometric features, such as points, straight or curved lines and corners, plays an imp... more Exploiting geometric features, such as points, straight or curved lines and corners, plays an important role in object recognition. In this paper, we present a model-based recognition of 3D objects using intersecting lines. We concentrate on using perpendicular line pairs to test recognition of a parallelepiped model and represent the visible face of the object. From 2D images and point clouds, first, 3D line segments are extracted, and then intersecting lines are selected from them. By estimating the coverage ratio, we find the most accurate matching between detected perpendicular line pairs and the model database. Finally, the position and the pose of the object are determined. The experimental results show the performance of the proposed algorithm.

PROCEEDINGS OF HYDRAULIC ENGINEERING, 2007

We numerically simulate "bedload transport" of noncohesive sediment by a turbulent liquid flow ov... more We numerically simulate "bedload transport" of noncohesive sediment by a turbulent liquid flow over an erodible bed using a "fictitious domain" simulation method that employs a fixed Cartesian grid. We report here on comparison with a challenging dense-phase particulate flow, namely a rotating drum partially-filled with spherical particles, through which oil flows to form a free-surface flow. Overall agreement between experimental and simulated values for bed and free-surface angles is found to be quite satisfactory..

PROCEEDINGS OF HYDRAULIC ENGINEERING, 2007

A simple correction model for "subgrid" lubrication force is proposed for fictitious-domain simul... more A simple correction model for "subgrid" lubrication force is proposed for fictitious-domain simulation of solid-liquid flow employing the Variable-density Implicit Volumetric forcing. The model is to compensate the unresolved lubrication force for gaps of few grid spacings between the solid surfaces, and is validated with the examination of velocity history and fluid force acting on spherical particles falling under gravity towards a plane wall. The peak particle Reynolds number is from 7 to 58, and relative density between the fluid and the solid is up to 2.9. Excellent agreements have been observed among the simulation results, the experimental ones, and predictions from an analytical model which consists of the lubrication force proposed by Cox & Brenner (1967), the added mass force proposed by Milne-Thomson (1968), and the history term proposed by Mei & Adrian (1992).

PROCEEDINGS OF HYDRAULIC ENGINEERING, 2006

To numerically simulate "bedload transport" of sediment by a turbulent flow over an erodible bed,... more To numerically simulate "bedload transport" of sediment by a turbulent flow over an erodible bed, our group has been developing "fictitious domain" methods to handle dense-phase particulate flow in turbulent flow of liquid. We report on efforts to check our simulation method against experiment for a dense-phase particulate flow in liquid, namely a rotating drum half-filled with spherical particles. Overall agreement between experimental and simulated values of static and dynamic angle of repose is found to be quite satisfactory, both in air and in oil.

The Journal of Urology, 2008

DVC loose knot/inaccurate plane (n=9), bladder neck too large (n=10), posterior bladder neck plan... more DVC loose knot/inaccurate plane (n=9), bladder neck too large (n=10), posterior bladder neck plane inaccurate (n=2), sewing error: broken needle/stitch (n=7), and prostate capsule violation (n=1).

Journal of Urology, 2011

Purpose: Tisseel® is used to control minor bleeding during laparoscopic procedures. The DuploSpra... more Purpose: Tisseel® is used to control minor bleeding during laparoscopic procedures. The DuploSpray MIS™ spray system allows thin, even application over a larger surface area. We use sprayed Tisseel as the sole agent to control hemorrhage and seal the renal collecting system after severe porcine laparoscopic partial nephrectomy. Methods and Materials: We performed staged bilateral severe laparoscopic partial nephrectomy in 12 Yucatan pigs using a longitudinal cut from upper to lower pole through the entire collecting system. In each pig 1 kidney was harvested immediately while the other was harvested after 4 weeks. After hilar clamping laparoscopic partial nephrectomy was done with cold scissors in 6 pigs while LigaSure™ was used in the other 6. Sprayed Tisseel was applied, and bleeding and urinary leakage were evaluated. Additional Tisseel was applied for repeat bleeding. We performed retrograde pyelogram (chronic) and burst pressure testing of the arterial and collecting systems. Results: All animals survived 4 weeks. One urinoma was seen on retrograde pyelogram in the cold cut group. Average hilar clamp time was similar in the acute and chronic study arms. Average estimated blood loss was significantly less in the LigaSure group (p ϭ 0.0045). Average arterial burst pressure was significantly different in the chronic and acute groups (605.8 vs 350.4 mm Hg, p ϭ 0.008) but average collecting system burst pressure was similar (186.3 and 149.5 mm Hg, respectively). Conclusions: Sprayed Tisseel without suturing effectively sealed the arterial and collecting system after severe laparoscopic partial nephrectomy in the porcine model.

The Journal of Urology, 2012

Journal of Endourology, 2010

Introduction: Laparoscopic partial nephrectomy (LPN) has not received widespread clinical applica... more Introduction: Laparoscopic partial nephrectomy (LPN) has not received widespread clinical application because of its technical challenge. Bovine serum albumin glutaraldehyde (BSAG) is a hemostatic agent that is independent of the clotting cascade. We evaluated the use of BSAG as the sole agent for parenchymal and collecting system closure during LPN in a survival porcine model. Methods: Eighteen pigs underwent hilar clamping and LPN by longitudinal excision of the lateral one-third of the right kidney. The opened collecting system was covered with oxidized cellulose to prevent BSAG seepage into the urinary tract. BSAG was allowed to set for 10 or 5 minutes. Twelve animals underwent survival LPN BSAG only closure; six control pigs were acutely studied using saline. Urinary extravasation was evaluated by injection of furosemide and indigo carmine, and then evaluating the renal surface and bladder catheter drainage for dye. A subjective bleeding score was assigned after hilum unclamping. At 6 weeks, BSAG kidneys were harvested for burst pressure testing and histopathological analysis. Results: All 12 pigs survived for 6 weeks. No pigs had urinary extravasation. Mean percentage of kidney removed by weight was 19%. Mean warm ischemia time was 29 minutes. Five pigs required a second BSAG application to achieve a bleeding score of 0. Mean arterial and collecting system burst pressures were 301.8 and 322.4 mm Hg, respectively. Mean postoperative creatinine increase was 0.07 mg=dL. Conclusion: BSAG for completely sutureless LPN in a survival porcine model was feasible.

Theoretical and Applied Mechanics Letters

EDITOR'S RECOMMENDATION The flight of insects has enlightened the flying dream of human being... more EDITOR'S RECOMMENDATION The flight of insects has enlightened the flying dream of human beings for centuries. Wing flexibility is often used by insects to increase their flight efficiencies. However, the mechanism of the increased efficiencies still remains mysterious. Prof. Kai Schneider's group studies the aerodynamics of a tethered flapping bumblebee using a mass-spring fluid-structure interaction numerical solver. It indicates that a higher flight efficiency or a larger lift-to-power ratio can be achieved by flapping insects with optimal mechanical properties of the flexible wings. The novel understanding of insects’ body structure and flying behavior will benefit the design of micro-air vehicles (MAVs). ABSTRACT The sophisticated structures of flapping insect wings make it challenging to study the role of wing flexibility in insect flight. In this study, a mass-spring system is used to model wing structural dynamics as a thin, flexible membrane supported by a network of veins. The vein mechanical properties can be estimated based on their diameters and the Young's modulus of cuticle. In order to analyze the effect of wing flexibility, the Young's modulus is varied to make a comparison between two different wing models that we refer to as flexible and highly flexible. The wing models are coupled with a pseudo-spectral code solving the incompressible Navier–Stokes equations, allowing us to investigate the influence of wing deformation on the aerodynamic efficiency of a tethered flapping bumblebee. Compared to the bumblebee model with rigid wings, the one with flexible wings flies more efficiently, characterized by a larger lift-to-power ratio.

Cartesian CFD Methods for Complex Applications, 2020

Wing flexibility plays an essential role in the aerodynamic performance of insects due to the con... more Wing flexibility plays an essential role in the aerodynamic performance of insects due to the considerable deformation of their wings during flight under the impact of inertial and aerodynamic forces. These forces come from the complex wing kinematics of insects. In this study, both wing structural dynamics and flapping wing motion are taken into account to investigate the effect of wing deformation on the aerodynamic efficiency of a bumblebee in tethered flight. A fluid-structure interaction solver, coupling a mass-spring model for the flexible wing with a pseudospectral code solving the incompressible Navier-Stokes equations, is implemented for this purpose. We first consider a tethered bumblebee flying in laminar flow with flexible wings. Compared to the rigid model, flexible wings generate smaller aerodynamic forces but require much less power. Finally, the bumblebee model is put into a turbulent flow to investigate its influence on the force production of flexible wings.

Summary: Due to the increasing availability of large unstructured point clouds from lasers cannin... more Summary: Due to the increasing availability of large unstructured point clouds from lasers canning and photogrammetry, there is a growing demand for automatic evaluation methods. Given the complexity of the underlying problems, several new methods resort to using semantic knowledge in particular for object detection and qualification support. In this paper, we present a novel approach which makes use of advanced algorithms, and benefits from intelligent knowledge management strategies for the processing of 3D point clouds and object qualification in a scanned scene. In particular, our method extends the use of semantic knowledge to all stages of the processing, including the guidance of the 3D processing algorithms. The complete solution consists of a multi- stage, iterative, concept based on three factors: the modeled knowledge, the package of algorithms, and the qualification engine. Zusammenfassung: Automatische Detektion und Qualifizierung von Objekten in Punktwolken unter Nutzu...

The reconstruction of 3D objects from point clouds and images is a major task in many application... more The reconstruction of 3D objects from point clouds and images is a major task in many application fields. The processing of such spatial data, especially 3D point clouds from terrestrial laser scanners, generally consumes time and requires extensive interaction between a human and the machine to yield a promising result. Presently, algorithms for an automatic processing are usually datadriven and concentrate on geometric feature extraction. Robust and quick methods for complete object extraction or identification are still an ongoing research topic and suffer from the complex structure of the data, which cannot be sufficiently modelled by purely numerical strategies. Therefore, the intention of our approach is to take human cognitive strategy as an example, and to simulate these processes based on available knowledge for the objects of interest. Such processes will first, introduce a semantic structure for the objects and second, guide the algorithms used to detect and recognize obj...

Bioinspiration & Biomimetics, 2021

Insect wings can undergo significant deformation during flapping motion owing to inertial, elasti... more Insect wings can undergo significant deformation during flapping motion owing to inertial, elastic and aerodynamic forces. Changes in shape then alter aerodynamic forces, resulting in a fully coupled Fluid-Structure Interaction (FSI) problem. Here, we present detailed three-dimensional FSI simulations of deformable blowfly (Calliphora vomitoria) wings in flapping flight. A wing model is proposed using a multi-parameter mass-spring approach, chosen for its implementation simplicity and computational efficiency. We train the model to reproduce static elasticity measurements by optimizing its parameters using a genetic algorithm with covariance matrix adaptation (CMA-ES). Wing models trained with experimental data are then coupled to a high-performance flow solver run on massively parallel supercomputers. Different features of the modeling approach and the intra-species variability of elastic properties are discussed. We found that individuals with different wing stiffness exhibit similar aerodynamic properties characterized by dimensionless forces and power at the same Reynolds number. We further study the influence of wing flexibility by comparing between the flexible wings and their rigid counterparts. Under equal prescribed kinematic conditions for rigid and flexible wings, wing flexibility improves lift-to-drag ratio as well as lift-to-power ratio and reduces peak force observed during wing rotation.

Computers & Fluids, 2020

The secret to the spectacular flight capabilities of flapping insects lies in their wings, which ... more The secret to the spectacular flight capabilities of flapping insects lies in their wings, which are often approximated as flat, rigid plates. Real wings are however delicate structures, composed of veins and membranes, and can undergo significant deformation. In the present work, we present detailed numerical simulations of such deformable wings. Our results are obtained with a fluidstructure interaction solver, coupling a mass-spring model for the flexible wing with a pseudo-spectral code solving the incompressible Navier-Stokes equations. We impose the no-slip boundary condition through the volume penalization method; the time-dependent complex geometry is then completely described by a mask function. This allows solving the governing equations of the fluid on a regular Cartesian grid. Our implementation for massively parallel computers allows us to perform high resolution computations with

Videometrics, Range Imaging, and Applications XII; and Automated Visual Inspection, 2013

ABSTRACT The modeling of real-world scenarios through capturing 3D digital data has been proven a... more ABSTRACT The modeling of real-world scenarios through capturing 3D digital data has been proven applicable in a variety of industrial applications, ranging from security, to robotics and to fields in the medical sciences. These different scenarios, along with variable conditions, present a challenge in discovering flexible appropriate solutions. In this paper, we present a novel approach based on a human cognition model to guide processing. Our method turns traditional data-driven processing into a new strategy based on a semantic knowledge system. Robust and adaptive methods for object extraction and identification are modeled in a knowledge domain, which has been created by purely numerical strategies. The goal of the present work is to select and guide algorithms following adaptive and intelligent manners for detecting objects in point clouds. Results show that our approach succeeded in identifying the objects of interest while using various data types.

Fluid Mechanics and Its Applications

Eighth International Multi-Conference on Systems, Signals & Devices, 2011

Object reconstruction is an important task in many fields of application as it allows to generate... more Object reconstruction is an important task in many fields of application as it allows to generate digital representations of our physical world used as base for analysis, planning, construction, visualization or other

2009 IEEE International Symposium on Assembly and Manufacturing, 2009

Abstract Elevator button (EB) detection is a very important research issue in home service roboti... more Abstract Elevator button (EB) detection is a very important research issue in home service robotics area, this paper describes an effective method for EB detection with mirroring effects in completely reflective surfaces. Line features and other local features (such as corner, ...

2012 11th International Conference on Information Science, Signal Processing and their Applications (ISSPA), 2012

ABSTRACT In this paper we present a novel approach for 3D point cloud processing with the aim of ... more ABSTRACT In this paper we present a novel approach for 3D point cloud processing with the aim of annotating objects in a scanned scene. Our method is based on human cognition to guide the 3D processing algorithms and uses semantic knowledge to manage data and identify immediate situation-dependent objectives. In particular, we have built a system that allows an automatic and flexible selection of algorithms. The selection strategy exploits knowledge to identify the geometrical features to be detected as well as the objects to be annotated at each stage of the 3D processing of the point cloud.

2008 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems, 2008

Exploiting geometric features, such as points, straight or curved lines and corners, plays an imp... more Exploiting geometric features, such as points, straight or curved lines and corners, plays an important role in object recognition. In this paper, we present a model-based recognition of 3D objects using intersecting lines. We concentrate on using perpendicular line pairs to test recognition of a parallelepiped model and represent the visible face of the object. From 2D images and point clouds, first, 3D line segments are extracted, and then intersecting lines are selected from them. By estimating the coverage ratio, we find the most accurate matching between detected perpendicular line pairs and the model database. Finally, the position and the pose of the object are determined. The experimental results show the performance of the proposed algorithm.

PROCEEDINGS OF HYDRAULIC ENGINEERING, 2007

We numerically simulate "bedload transport" of noncohesive sediment by a turbulent liquid flow ov... more We numerically simulate "bedload transport" of noncohesive sediment by a turbulent liquid flow over an erodible bed using a "fictitious domain" simulation method that employs a fixed Cartesian grid. We report here on comparison with a challenging dense-phase particulate flow, namely a rotating drum partially-filled with spherical particles, through which oil flows to form a free-surface flow. Overall agreement between experimental and simulated values for bed and free-surface angles is found to be quite satisfactory..

PROCEEDINGS OF HYDRAULIC ENGINEERING, 2007

A simple correction model for "subgrid" lubrication force is proposed for fictitious-domain simul... more A simple correction model for "subgrid" lubrication force is proposed for fictitious-domain simulation of solid-liquid flow employing the Variable-density Implicit Volumetric forcing. The model is to compensate the unresolved lubrication force for gaps of few grid spacings between the solid surfaces, and is validated with the examination of velocity history and fluid force acting on spherical particles falling under gravity towards a plane wall. The peak particle Reynolds number is from 7 to 58, and relative density between the fluid and the solid is up to 2.9. Excellent agreements have been observed among the simulation results, the experimental ones, and predictions from an analytical model which consists of the lubrication force proposed by Cox & Brenner (1967), the added mass force proposed by Milne-Thomson (1968), and the history term proposed by Mei & Adrian (1992).

PROCEEDINGS OF HYDRAULIC ENGINEERING, 2006

To numerically simulate "bedload transport" of sediment by a turbulent flow over an erodible bed,... more To numerically simulate "bedload transport" of sediment by a turbulent flow over an erodible bed, our group has been developing "fictitious domain" methods to handle dense-phase particulate flow in turbulent flow of liquid. We report on efforts to check our simulation method against experiment for a dense-phase particulate flow in liquid, namely a rotating drum half-filled with spherical particles. Overall agreement between experimental and simulated values of static and dynamic angle of repose is found to be quite satisfactory, both in air and in oil.

The Journal of Urology, 2008

DVC loose knot/inaccurate plane (n=9), bladder neck too large (n=10), posterior bladder neck plan... more DVC loose knot/inaccurate plane (n=9), bladder neck too large (n=10), posterior bladder neck plane inaccurate (n=2), sewing error: broken needle/stitch (n=7), and prostate capsule violation (n=1).

Journal of Urology, 2011

Purpose: Tisseel® is used to control minor bleeding during laparoscopic procedures. The DuploSpra... more Purpose: Tisseel® is used to control minor bleeding during laparoscopic procedures. The DuploSpray MIS™ spray system allows thin, even application over a larger surface area. We use sprayed Tisseel as the sole agent to control hemorrhage and seal the renal collecting system after severe porcine laparoscopic partial nephrectomy. Methods and Materials: We performed staged bilateral severe laparoscopic partial nephrectomy in 12 Yucatan pigs using a longitudinal cut from upper to lower pole through the entire collecting system. In each pig 1 kidney was harvested immediately while the other was harvested after 4 weeks. After hilar clamping laparoscopic partial nephrectomy was done with cold scissors in 6 pigs while LigaSure™ was used in the other 6. Sprayed Tisseel was applied, and bleeding and urinary leakage were evaluated. Additional Tisseel was applied for repeat bleeding. We performed retrograde pyelogram (chronic) and burst pressure testing of the arterial and collecting systems. Results: All animals survived 4 weeks. One urinoma was seen on retrograde pyelogram in the cold cut group. Average hilar clamp time was similar in the acute and chronic study arms. Average estimated blood loss was significantly less in the LigaSure group (p ϭ 0.0045). Average arterial burst pressure was significantly different in the chronic and acute groups (605.8 vs 350.4 mm Hg, p ϭ 0.008) but average collecting system burst pressure was similar (186.3 and 149.5 mm Hg, respectively). Conclusions: Sprayed Tisseel without suturing effectively sealed the arterial and collecting system after severe laparoscopic partial nephrectomy in the porcine model.

The Journal of Urology, 2012

Journal of Endourology, 2010

Introduction: Laparoscopic partial nephrectomy (LPN) has not received widespread clinical applica... more Introduction: Laparoscopic partial nephrectomy (LPN) has not received widespread clinical application because of its technical challenge. Bovine serum albumin glutaraldehyde (BSAG) is a hemostatic agent that is independent of the clotting cascade. We evaluated the use of BSAG as the sole agent for parenchymal and collecting system closure during LPN in a survival porcine model. Methods: Eighteen pigs underwent hilar clamping and LPN by longitudinal excision of the lateral one-third of the right kidney. The opened collecting system was covered with oxidized cellulose to prevent BSAG seepage into the urinary tract. BSAG was allowed to set for 10 or 5 minutes. Twelve animals underwent survival LPN BSAG only closure; six control pigs were acutely studied using saline. Urinary extravasation was evaluated by injection of furosemide and indigo carmine, and then evaluating the renal surface and bladder catheter drainage for dye. A subjective bleeding score was assigned after hilum unclamping. At 6 weeks, BSAG kidneys were harvested for burst pressure testing and histopathological analysis. Results: All 12 pigs survived for 6 weeks. No pigs had urinary extravasation. Mean percentage of kidney removed by weight was 19%. Mean warm ischemia time was 29 minutes. Five pigs required a second BSAG application to achieve a bleeding score of 0. Mean arterial and collecting system burst pressures were 301.8 and 322.4 mm Hg, respectively. Mean postoperative creatinine increase was 0.07 mg=dL. Conclusion: BSAG for completely sutureless LPN in a survival porcine model was feasible.