Wiroj Limtrakarn - Academia.edu (original) (raw)

Papers by Wiroj Limtrakarn

Research paper thumbnail of Fluid Temperature at the Corneal Endothelium during Phacoemulsification: Comparison of an Ophthalmic Viscosurgical Device and Balanced Salt Solution Using the Finite Element Method

Ophthalmic Research, 2010

The purpose of this study was to estimate and compare the temperatures of two different anterior ... more The purpose of this study was to estimate and compare the temperatures of two different anterior chamber solutions at the corneal endothelial level during phacoemulsification. An ophthalmic viscosurgical device (OVD) and balanced salt solution (BSS) were compared using the finite element method (FEM). The thermal properties of an OVD (IAL-F) and BSS were studied in an experimental setting. A computer-aided design model of ocular anatomy was created in two dimensions. The phaco needle was considered to be the only source of heat generation. Then, the FEM was used to demonstrate the transient temperature distribution in the two ocular models at 10, 20, 30, 40, 50 and 60 s. In these models, the anterior chamber was filled with IAL-F (IAL-F model) or BSS (BSS model). The heat generation rate of the phaco needle was 0.0004 cal/s/mm(2). The maximum corneal endothelial temperatures for the two models at 60 s were 52.67 and 41.57 degrees C, respectively. The experimental IAL-F model showed fewer changes in temperature for any given time and location. At larger distances from the heat source, less temperature variation was detected. Phacoemulsification is a potential heat-generating procedure performed between the delicate anterior chamber structures. During this procedure, IAL-F protects the endothelium against heat better than BSS.

Research paper thumbnail of Nodeless Finite Element Method for 2d Potential flow Problems

Thammasat International Journal of Science and Technology, 2005

Research paper thumbnail of The Effectiveness of Mirror Therapy to Upper Extremity Rehabilitation in Acute Stroke Patients

Rehabilitation is a crucial part of stroke recovery to help them regain use of their limb. The ai... more Rehabilitation is a crucial part of stroke recovery to help them regain use of their limb. The aim of this article was to compare the effectiveness of long-term training of mirror therapy with conventional rehabilitation therapy on neurological and recovery of upper limb in acute stroke patients. In this randomized and assessor-blinded control study, 20 acute stroke patients were analyzed in this study and allocated to a case (n = 10, 50.6 ± 17.90 years) and control group (n = 10, 55.9 ± 11.25 years). All the participants performed daily home exercise during 12 weeks. The patients in the control group were treated with conventional therapy (CT) and a group of cases were treated with mirror therapy (MT) alone program. The outcome measurements were assessed by a therapist blinded assessor using Fugl-Meyer Assessment (FMA) upper extremity score, Brunnstrom recovery stages (BRS), Modified Ashworth Scale (MAS) and Muscle Strength to evaluate upper limb motor function and motor recovery. ...

Research paper thumbnail of Stress Analysis On Crack Tip Using Q8 And Adaptive Meshes

Thammasat International Journal of Science and Technology, 2005

Research paper thumbnail of Whole blood viscosity modeling using power law, Casson, and Carreau Yasuda models integrated with image scanning U-tube viscometer technique

This study presented the image scanning U-tube viscometer technique to measure the whole blood vi... more This study presented the image scanning U-tube viscometer technique to measure the whole blood viscosity. Two different constitutive models, power law and Casson, were selected to calculate blood viscosity. Results were compared with rotating viscometer. They had a good agreement at higher shear rates. Three constitutive models power law, Casson and Carreau Yasuda models were applied to blood viscosity data and used to simulate transient blood height in the U-tube. Comparison of the U-tube simulation and the actual experiment showed that Carreau Yasuda model is the most accurate model for whole blood viscosity measurement.

Research paper thumbnail of Thermal Damage Improvement of Slider Fixture in Ion Mill Heatless Etching Process by FEM

Thammasat International Journal of Science and Technology, 2012

This paper presents thermal deformation of slider fixture in ion mill heatless etching process by... more This paper presents thermal deformation of slider fixture in ion mill heatless etching process by the finite element method. The research objective is to reduce thermal damage of the ion mill heatless etching process. First the process parameters and slider burn defect of the ion mill heatless etching process are studied. Next, a CAD model and mesh are constructed. Boundary conditions for heat transfer analysis are applied on the mesh. Temperature distribution is calculated and set as thermal load for thermal stress analysis. Then thermal deformation is computed. A new model of slider fixture is designed. The thermal deformation of the new model is computed. The results show that the new model reduces thermal deflection 3% and increases real clamp force 2.5 times the old model. The new model will reduce: the burned area on a slider’s surface or permanent bending deformation. Keywords: Thermal Damage, Ion Mill Heatless Etching Process, Finite Element Method

Research paper thumbnail of Mirror Therapy Rehabilitation for Lower Limb of Acute Stroke Patients

This paper aims to study the effectiveness of mirror therapy (MT) having treated to acute stroke ... more This paper aims to study the effectiveness of mirror therapy (MT) having treated to acute stroke patients. The subjects of 20 acute stroke patients, who possessed the ability to respond to verbal instructions were randomly blinded and allocated to a control group (n = 10, 59.2 ± 2.28 years) and a mirror group (n = 10, 53.8 ± 6.14 years). Both groups were treated by intervention of traditional rehabilitation therapy comparing with mirror therapy. Intervention of mirror therapy was taken 60 minutes per day, 5 days per week for 12 weeks. Measures of intervention effectiveness were taken before treatment and after treatment by therapist using Brunnstrom stages, Fugl-Meyer Assessment (FMA) lower extremity score and Brunnel Balance Assessment (BBA) balance. Data were analyzed using independent sample t-test. The results revealed that, after 12 weeks of treatment, subjects of both groups gained statistically significant improvements in all variables measure (p < 0.05). Having compared w...

Research paper thumbnail of Adaptive Finite Element Method to Determine Ki and Kii of Crack Plate with Different Einclusion/Eplate Ratio

Transactions of the Canadian Society for Mechanical Engineering

An adaptive finite element method is presented to determine the KI and KII stress intensity facto... more An adaptive finite element method is presented to determine the KI and KII stress intensity factors of crack plate with different inclusions. The paper starts from describing two-dimensional fracture mechanics theory, an adaptive finite element formulation and the reflection photoelastic technique. An adaptive finite element method is evaluated by analyzing two examples. A single edge cracked plate made from polycarbonate. The second example is the slant edge 45° cracked plate subjected to a uniform uniaxial tensile stress. The KI and KII results are found to be function of the crack length per width and the inverse function of E ratio. These examples demonstrate the efficiency of the adaptive finite element method to provide accurate solutions as compared to those from the reflection photoelastic technique.

Research paper thumbnail of Stress Intensity Factor KI and Crack–hard Inclusion Interaction Study of a Single Edge Cracked Plate by Adaptive Remeshing and Photoelasticity

Applied Science and Engineering Progress

An adaptive remeshing and photoelasticity techniques are presented to determine the stress intens... more An adaptive remeshing and photoelasticity techniques are presented to determine the stress intensity factors K I and crack-hard inclusion interaction of a single edge cracked plate for two-dimensional fracture mechanics problems. The paper starts from describing two-dimensional linear fracture mechanics theory and an adaptive remeshing H method using the quadrilateral and triangular elements. The computational procedure and related finite element equations are explained. The photoelastic theory and its experimental procedure with the use of the stress optic laws are then described. The photoelasticity prototype is designed and built. Performance of adaptive remeshing method is evaluated by analyzing a single edge cracked plate made from polycarbonate. A crack plate with a hard inclusion is then studied for stress intensity factor and crack-hard inclusion interaction. The hard inclusion is made from aluminum. The K I stress intensity factor is found to be a function of the crack length per width. The results of adaptive remeshning method and the photoelasticity technique are compared with Brown's study. This example demonstrates the efficiency of the adaptive remeshing method to provide accurate solutions as compared to those from the photoelastic technique. Then, crack-hard inclusion interaction is studied by varying stress intensity ratio and E ratio. The crack-hard inclusion interaction behavior is formulated in exponential equation, i.e. cracking tip shielding function. The cracking tip shielding function shows that maximum stress intensity ratio reduces rapidly if E ratio increases. The normalized stress intensity factor is as a convergence exponential function of E ratio.

Research paper thumbnail of Comparison in the Stress Analysis of 2D Solid Mechanics Problems of Finite Element Method and Photoelasticity

วารสารวิจัยและพัฒนา มจธ, 2005

Finite Element Method and photoelasticity technique are presented to predict the stress distribut... more Finite Element Method and photoelasticity technique are presented to predict the stress distributionfor solid mechanics problems. The paper first describes 2D solid mechanics theory. Finiteelement formulation, the computational procedure and its boundary conditions are then represented.Photoelasticity theory and its procedure are described. The validated examples of both techniquesare four-point bending problem and chain-gear contact problem. The solutions show the efficiency offinite element method and have a good agreement with the photoelasticity results. Keywords : Finite Element Method / Photoelasticity

Research paper thumbnail of Fluid–Thermal Interaction of High–Speed Compressible Viscous Flow Past Uncooled and Cooled Structures by Adaptive Mesh

Research paper thumbnail of Capability Enhancement in Sheet Metal Stamping Technology

Research paper thumbnail of Effect of Residual Stress on Fatigue Failure of Carbonitrided Low-Carbon Steel

Journal of Materials Engineering and Performance, 2008

Research paper thumbnail of J-5 TEMPERATURE DISTRIBUTION IN ANTERIOR EYE DURING PHACOEMULSIFICATION BY FINITE ELEMENT METHOD (Session: Interface/FEM/CAE)

Research paper thumbnail of Computational Fluid Dynamics Modeling to Improve Natural Flow Rate and Sweet Pepper Productivity in Greenhouse

Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simul... more Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective of this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure for the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal project foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor variation of temperature inside the greenhouse. The measured temperature data were used as the boundary conditions for the CFD analysis. A new greenhouse model with two-step roof shape was designed and the air flow behavior was simulated by using CFD. Regarding CFD results the air flow rate of the new model is about 39% higher than that of old model. The maximum temperature of the new model is lower than that of the old one. The sweet paper growths in both greenhouse models were measured and compared. Results show that the new model obtains 4 • C lower maximum temperature in day time, 97% in number and 90% in weight higher the first grade pepper productivity than the old one.

Research paper thumbnail of Nodeless Variables Finite Element Method for 2D Heat Transfer Problems

... 3. Dechaumphai, P., 2004, Finite Element Method in Engineering, Third Ed., ChulalongkornUnive... more ... 3. Dechaumphai, P., 2004, Finite Element Method in Engineering, Third Ed., ChulalongkornUniversity Press, Bangkok, Thailand. ... 10, No. 4, pp. 41 – 47. 5. Limtrakarn, W., Reepolmaha, S., and Uthaisang, W., 2007, Application of 3D Finite Element Method to Reduce Cornea ...

Research paper thumbnail of Comparison of Finite Element Solution and Photoelastic Results for 2-D Contact Mechanics Problems

The finite element method and photoelasticity technique are presented to predict displacementand ... more The finite element method and photoelasticity technique are presented to predict displacementand stress distribution for contact mechanics problems. The paper first describes 2D contactmechanics theory. The finite element formulations based on Lagrange multiplier and Penalty methodare presented, The computational procedure and its boundary conditions are then described. Thephotoelasticity theory and its procedure are also explained. To evaluate the efficiency of bothtechniques, the displacement and stress distribution for two circular plates contact problem andcircular-flat plate contact problem are used to compare the finite element solutions and those fromphotoelasticity technique and Hertz solution. The solutions show that the stress distributionspredicted by finite element method are in good agreement with the photoelasticity results and Hertzsolutions. Keywords : Finite Element Method / Photoelasticity / Contact Mechanics

Research paper thumbnail of The Effect of Temperature of Eye Irrigation Solution to Reduce Corneal Endothelial Cell Loss during Phacoemulsification: An In Vitro Model Study

To compare the efficiency of eye irrigation solution (balanced salt solution: BSS) stored in a re... more To compare the efficiency of eye irrigation solution (balanced salt solution: BSS) stored in a refrigerator and air-conditioned room to reduce the number of corneal endothelial cell loss during the process of phacoemulsification. Porcine corneal endothelial cells (PCEC) isolated from porcine eyes were used as a model. The porcine eyes were obtained from a local slaughterhouse within 6 h after death and PCEC were cultured as standard method. The percentage of cell survival was evaluated by MTT assay. The PCEC was successfully grown in the standard culturing system. The growth curve of PCEC demonstrated that log phase was reached in 3-6 days. The evaluation of heat effect (40-60 degrees C) to PCEC survival was shown that cells death was found at 55 and 60 degrees C which the percentage of cell survival reduced to 30% at 60 degrees C, 180 sec. Further observation on the efficiency of BSS stored in different conditions, refrigeration (8 degrees C) and air-conditioned room (25 degrees C) to PCEC survival was revealed that the number of cell survival increased from 40% to almost 70% when using refrigerated BSS as irrigation solution, while from air-conditioned BSS only at 55%. From using PCEC as a model and mimic the process of irrigation in phacoemulsification, it was found that the eye irrigation solution (balanced salt solution: BSS) stored in the refrigerator had a better result in helping protection the corneal endothelial cell loss from heat damaged than BSS stored in air-conditioned room.

Research paper thumbnail of Transient temperature distribution on the corneal endothelium during ophthalmic phacoemulsification: a numerical simulation using the nodeless variable element

Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into ... more Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into the anterior chamber of eye. Then, heat is generated by the oscillation of the phaco needle, which may injury the corneal endothelial cells. There are no data available for temperature responses at the corneal endothelium to heat from the phaco needle during phacoemulsification. Objective: Investigate temperature distribution on the corneal endothelium during ophthalmic phacoemulsification using numerical simulation, and compare the transient temperature response to heat between balanced salt solution (BSS) and ophthalmic viscoelastic device (OVD), Viscoat ®. Methods: Heat flux from a phaco needle was measured with thermal properties of BSS and AVS in an experimental setting. Then, nodeless variable finite element method was applied to predict temperature changes in the eye by the phaco needle inserted into the anterior chamber. The transient temperature distribution on the corneal endothelium was calculated at 10, 20, and 30 seconds after heat generation by the needle. Results: The heat generation of phaco needle without sleeve cover was 1.6 kW/m 2. The numerical simulation showed that the maximum temperature occurs on the wound location at all times after heat generation by the phaco needle. Especially, at time 30 seconds, it was 49.2 and 41.7 o C in BSS and OVD, respectively. The temperature elevation by the phaco needle was lower in OVD than BSS. Conclusion: Phacoemulsification is a heat-generating procedure performed between the anterior chamber structures of eye. During this procedure, OVD may protect the corneal endothelium against heat better than BSS.

Research paper thumbnail of Biomechanics Study of Knee Ligament

This research studies biomechanics of ligament on knee. The purpose is to calculate stress and st... more This research studies biomechanics of ligament on knee. The purpose is to calculate stress and strain distribution on knee ligament while walking. First, study anatomy of knee. Ligament is tested to obtain mechanical properties, which are used for knee behavior simulation. Next, cad model and finite element model are constructed. The stress and strain on knee's ligament while walking are calculated by finite element method. The research output is ligament behavior while walking. The maximum stress and strain occur on a top of ligament while extend leg are 33.82 MPa and 0.16 mm/mm, respectively, for 1 hamstring bundle. The maximum stress is 41.87 MPa and maximum strain is 0.18 mm/mm for 2 hamstring bundles. The advantage is to understand the biomechanics of the knee ligaments while walking. And this research result can help patients who have tear problem of an Anterior Cruciate Ligaments (ACL) and be developed for further research about force and behaviors of the other ligament and muscle in body.

Research paper thumbnail of Fluid Temperature at the Corneal Endothelium during Phacoemulsification: Comparison of an Ophthalmic Viscosurgical Device and Balanced Salt Solution Using the Finite Element Method

Ophthalmic Research, 2010

The purpose of this study was to estimate and compare the temperatures of two different anterior ... more The purpose of this study was to estimate and compare the temperatures of two different anterior chamber solutions at the corneal endothelial level during phacoemulsification. An ophthalmic viscosurgical device (OVD) and balanced salt solution (BSS) were compared using the finite element method (FEM). The thermal properties of an OVD (IAL-F) and BSS were studied in an experimental setting. A computer-aided design model of ocular anatomy was created in two dimensions. The phaco needle was considered to be the only source of heat generation. Then, the FEM was used to demonstrate the transient temperature distribution in the two ocular models at 10, 20, 30, 40, 50 and 60 s. In these models, the anterior chamber was filled with IAL-F (IAL-F model) or BSS (BSS model). The heat generation rate of the phaco needle was 0.0004 cal/s/mm(2). The maximum corneal endothelial temperatures for the two models at 60 s were 52.67 and 41.57 degrees C, respectively. The experimental IAL-F model showed fewer changes in temperature for any given time and location. At larger distances from the heat source, less temperature variation was detected. Phacoemulsification is a potential heat-generating procedure performed between the delicate anterior chamber structures. During this procedure, IAL-F protects the endothelium against heat better than BSS.

Research paper thumbnail of Nodeless Finite Element Method for 2d Potential flow Problems

Thammasat International Journal of Science and Technology, 2005

Research paper thumbnail of The Effectiveness of Mirror Therapy to Upper Extremity Rehabilitation in Acute Stroke Patients

Rehabilitation is a crucial part of stroke recovery to help them regain use of their limb. The ai... more Rehabilitation is a crucial part of stroke recovery to help them regain use of their limb. The aim of this article was to compare the effectiveness of long-term training of mirror therapy with conventional rehabilitation therapy on neurological and recovery of upper limb in acute stroke patients. In this randomized and assessor-blinded control study, 20 acute stroke patients were analyzed in this study and allocated to a case (n = 10, 50.6 ± 17.90 years) and control group (n = 10, 55.9 ± 11.25 years). All the participants performed daily home exercise during 12 weeks. The patients in the control group were treated with conventional therapy (CT) and a group of cases were treated with mirror therapy (MT) alone program. The outcome measurements were assessed by a therapist blinded assessor using Fugl-Meyer Assessment (FMA) upper extremity score, Brunnstrom recovery stages (BRS), Modified Ashworth Scale (MAS) and Muscle Strength to evaluate upper limb motor function and motor recovery. ...

Research paper thumbnail of Stress Analysis On Crack Tip Using Q8 And Adaptive Meshes

Thammasat International Journal of Science and Technology, 2005

Research paper thumbnail of Whole blood viscosity modeling using power law, Casson, and Carreau Yasuda models integrated with image scanning U-tube viscometer technique

This study presented the image scanning U-tube viscometer technique to measure the whole blood vi... more This study presented the image scanning U-tube viscometer technique to measure the whole blood viscosity. Two different constitutive models, power law and Casson, were selected to calculate blood viscosity. Results were compared with rotating viscometer. They had a good agreement at higher shear rates. Three constitutive models power law, Casson and Carreau Yasuda models were applied to blood viscosity data and used to simulate transient blood height in the U-tube. Comparison of the U-tube simulation and the actual experiment showed that Carreau Yasuda model is the most accurate model for whole blood viscosity measurement.

Research paper thumbnail of Thermal Damage Improvement of Slider Fixture in Ion Mill Heatless Etching Process by FEM

Thammasat International Journal of Science and Technology, 2012

This paper presents thermal deformation of slider fixture in ion mill heatless etching process by... more This paper presents thermal deformation of slider fixture in ion mill heatless etching process by the finite element method. The research objective is to reduce thermal damage of the ion mill heatless etching process. First the process parameters and slider burn defect of the ion mill heatless etching process are studied. Next, a CAD model and mesh are constructed. Boundary conditions for heat transfer analysis are applied on the mesh. Temperature distribution is calculated and set as thermal load for thermal stress analysis. Then thermal deformation is computed. A new model of slider fixture is designed. The thermal deformation of the new model is computed. The results show that the new model reduces thermal deflection 3% and increases real clamp force 2.5 times the old model. The new model will reduce: the burned area on a slider’s surface or permanent bending deformation. Keywords: Thermal Damage, Ion Mill Heatless Etching Process, Finite Element Method

Research paper thumbnail of Mirror Therapy Rehabilitation for Lower Limb of Acute Stroke Patients

This paper aims to study the effectiveness of mirror therapy (MT) having treated to acute stroke ... more This paper aims to study the effectiveness of mirror therapy (MT) having treated to acute stroke patients. The subjects of 20 acute stroke patients, who possessed the ability to respond to verbal instructions were randomly blinded and allocated to a control group (n = 10, 59.2 ± 2.28 years) and a mirror group (n = 10, 53.8 ± 6.14 years). Both groups were treated by intervention of traditional rehabilitation therapy comparing with mirror therapy. Intervention of mirror therapy was taken 60 minutes per day, 5 days per week for 12 weeks. Measures of intervention effectiveness were taken before treatment and after treatment by therapist using Brunnstrom stages, Fugl-Meyer Assessment (FMA) lower extremity score and Brunnel Balance Assessment (BBA) balance. Data were analyzed using independent sample t-test. The results revealed that, after 12 weeks of treatment, subjects of both groups gained statistically significant improvements in all variables measure (p < 0.05). Having compared w...

Research paper thumbnail of Adaptive Finite Element Method to Determine Ki and Kii of Crack Plate with Different Einclusion/Eplate Ratio

Transactions of the Canadian Society for Mechanical Engineering

An adaptive finite element method is presented to determine the KI and KII stress intensity facto... more An adaptive finite element method is presented to determine the KI and KII stress intensity factors of crack plate with different inclusions. The paper starts from describing two-dimensional fracture mechanics theory, an adaptive finite element formulation and the reflection photoelastic technique. An adaptive finite element method is evaluated by analyzing two examples. A single edge cracked plate made from polycarbonate. The second example is the slant edge 45° cracked plate subjected to a uniform uniaxial tensile stress. The KI and KII results are found to be function of the crack length per width and the inverse function of E ratio. These examples demonstrate the efficiency of the adaptive finite element method to provide accurate solutions as compared to those from the reflection photoelastic technique.

Research paper thumbnail of Stress Intensity Factor KI and Crack–hard Inclusion Interaction Study of a Single Edge Cracked Plate by Adaptive Remeshing and Photoelasticity

Applied Science and Engineering Progress

An adaptive remeshing and photoelasticity techniques are presented to determine the stress intens... more An adaptive remeshing and photoelasticity techniques are presented to determine the stress intensity factors K I and crack-hard inclusion interaction of a single edge cracked plate for two-dimensional fracture mechanics problems. The paper starts from describing two-dimensional linear fracture mechanics theory and an adaptive remeshing H method using the quadrilateral and triangular elements. The computational procedure and related finite element equations are explained. The photoelastic theory and its experimental procedure with the use of the stress optic laws are then described. The photoelasticity prototype is designed and built. Performance of adaptive remeshing method is evaluated by analyzing a single edge cracked plate made from polycarbonate. A crack plate with a hard inclusion is then studied for stress intensity factor and crack-hard inclusion interaction. The hard inclusion is made from aluminum. The K I stress intensity factor is found to be a function of the crack length per width. The results of adaptive remeshning method and the photoelasticity technique are compared with Brown's study. This example demonstrates the efficiency of the adaptive remeshing method to provide accurate solutions as compared to those from the photoelastic technique. Then, crack-hard inclusion interaction is studied by varying stress intensity ratio and E ratio. The crack-hard inclusion interaction behavior is formulated in exponential equation, i.e. cracking tip shielding function. The cracking tip shielding function shows that maximum stress intensity ratio reduces rapidly if E ratio increases. The normalized stress intensity factor is as a convergence exponential function of E ratio.

Research paper thumbnail of Comparison in the Stress Analysis of 2D Solid Mechanics Problems of Finite Element Method and Photoelasticity

วารสารวิจัยและพัฒนา มจธ, 2005

Finite Element Method and photoelasticity technique are presented to predict the stress distribut... more Finite Element Method and photoelasticity technique are presented to predict the stress distributionfor solid mechanics problems. The paper first describes 2D solid mechanics theory. Finiteelement formulation, the computational procedure and its boundary conditions are then represented.Photoelasticity theory and its procedure are described. The validated examples of both techniquesare four-point bending problem and chain-gear contact problem. The solutions show the efficiency offinite element method and have a good agreement with the photoelasticity results. Keywords : Finite Element Method / Photoelasticity

Research paper thumbnail of Fluid–Thermal Interaction of High–Speed Compressible Viscous Flow Past Uncooled and Cooled Structures by Adaptive Mesh

Research paper thumbnail of Capability Enhancement in Sheet Metal Stamping Technology

Research paper thumbnail of Effect of Residual Stress on Fatigue Failure of Carbonitrided Low-Carbon Steel

Journal of Materials Engineering and Performance, 2008

Research paper thumbnail of J-5 TEMPERATURE DISTRIBUTION IN ANTERIOR EYE DURING PHACOEMULSIFICATION BY FINITE ELEMENT METHOD (Session: Interface/FEM/CAE)

Research paper thumbnail of Computational Fluid Dynamics Modeling to Improve Natural Flow Rate and Sweet Pepper Productivity in Greenhouse

Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simul... more Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective of this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure for the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal project foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor variation of temperature inside the greenhouse. The measured temperature data were used as the boundary conditions for the CFD analysis. A new greenhouse model with two-step roof shape was designed and the air flow behavior was simulated by using CFD. Regarding CFD results the air flow rate of the new model is about 39% higher than that of old model. The maximum temperature of the new model is lower than that of the old one. The sweet paper growths in both greenhouse models were measured and compared. Results show that the new model obtains 4 • C lower maximum temperature in day time, 97% in number and 90% in weight higher the first grade pepper productivity than the old one.

Research paper thumbnail of Nodeless Variables Finite Element Method for 2D Heat Transfer Problems

... 3. Dechaumphai, P., 2004, Finite Element Method in Engineering, Third Ed., ChulalongkornUnive... more ... 3. Dechaumphai, P., 2004, Finite Element Method in Engineering, Third Ed., ChulalongkornUniversity Press, Bangkok, Thailand. ... 10, No. 4, pp. 41 – 47. 5. Limtrakarn, W., Reepolmaha, S., and Uthaisang, W., 2007, Application of 3D Finite Element Method to Reduce Cornea ...

Research paper thumbnail of Comparison of Finite Element Solution and Photoelastic Results for 2-D Contact Mechanics Problems

The finite element method and photoelasticity technique are presented to predict displacementand ... more The finite element method and photoelasticity technique are presented to predict displacementand stress distribution for contact mechanics problems. The paper first describes 2D contactmechanics theory. The finite element formulations based on Lagrange multiplier and Penalty methodare presented, The computational procedure and its boundary conditions are then described. Thephotoelasticity theory and its procedure are also explained. To evaluate the efficiency of bothtechniques, the displacement and stress distribution for two circular plates contact problem andcircular-flat plate contact problem are used to compare the finite element solutions and those fromphotoelasticity technique and Hertz solution. The solutions show that the stress distributionspredicted by finite element method are in good agreement with the photoelasticity results and Hertzsolutions. Keywords : Finite Element Method / Photoelasticity / Contact Mechanics

Research paper thumbnail of The Effect of Temperature of Eye Irrigation Solution to Reduce Corneal Endothelial Cell Loss during Phacoemulsification: An In Vitro Model Study

To compare the efficiency of eye irrigation solution (balanced salt solution: BSS) stored in a re... more To compare the efficiency of eye irrigation solution (balanced salt solution: BSS) stored in a refrigerator and air-conditioned room to reduce the number of corneal endothelial cell loss during the process of phacoemulsification. Porcine corneal endothelial cells (PCEC) isolated from porcine eyes were used as a model. The porcine eyes were obtained from a local slaughterhouse within 6 h after death and PCEC were cultured as standard method. The percentage of cell survival was evaluated by MTT assay. The PCEC was successfully grown in the standard culturing system. The growth curve of PCEC demonstrated that log phase was reached in 3-6 days. The evaluation of heat effect (40-60 degrees C) to PCEC survival was shown that cells death was found at 55 and 60 degrees C which the percentage of cell survival reduced to 30% at 60 degrees C, 180 sec. Further observation on the efficiency of BSS stored in different conditions, refrigeration (8 degrees C) and air-conditioned room (25 degrees C) to PCEC survival was revealed that the number of cell survival increased from 40% to almost 70% when using refrigerated BSS as irrigation solution, while from air-conditioned BSS only at 55%. From using PCEC as a model and mimic the process of irrigation in phacoemulsification, it was found that the eye irrigation solution (balanced salt solution: BSS) stored in the refrigerator had a better result in helping protection the corneal endothelial cell loss from heat damaged than BSS stored in air-conditioned room.

Research paper thumbnail of Transient temperature distribution on the corneal endothelium during ophthalmic phacoemulsification: a numerical simulation using the nodeless variable element

Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into ... more Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into the anterior chamber of eye. Then, heat is generated by the oscillation of the phaco needle, which may injury the corneal endothelial cells. There are no data available for temperature responses at the corneal endothelium to heat from the phaco needle during phacoemulsification. Objective: Investigate temperature distribution on the corneal endothelium during ophthalmic phacoemulsification using numerical simulation, and compare the transient temperature response to heat between balanced salt solution (BSS) and ophthalmic viscoelastic device (OVD), Viscoat ®. Methods: Heat flux from a phaco needle was measured with thermal properties of BSS and AVS in an experimental setting. Then, nodeless variable finite element method was applied to predict temperature changes in the eye by the phaco needle inserted into the anterior chamber. The transient temperature distribution on the corneal endothelium was calculated at 10, 20, and 30 seconds after heat generation by the needle. Results: The heat generation of phaco needle without sleeve cover was 1.6 kW/m 2. The numerical simulation showed that the maximum temperature occurs on the wound location at all times after heat generation by the phaco needle. Especially, at time 30 seconds, it was 49.2 and 41.7 o C in BSS and OVD, respectively. The temperature elevation by the phaco needle was lower in OVD than BSS. Conclusion: Phacoemulsification is a heat-generating procedure performed between the anterior chamber structures of eye. During this procedure, OVD may protect the corneal endothelium against heat better than BSS.

Research paper thumbnail of Biomechanics Study of Knee Ligament

This research studies biomechanics of ligament on knee. The purpose is to calculate stress and st... more This research studies biomechanics of ligament on knee. The purpose is to calculate stress and strain distribution on knee ligament while walking. First, study anatomy of knee. Ligament is tested to obtain mechanical properties, which are used for knee behavior simulation. Next, cad model and finite element model are constructed. The stress and strain on knee's ligament while walking are calculated by finite element method. The research output is ligament behavior while walking. The maximum stress and strain occur on a top of ligament while extend leg are 33.82 MPa and 0.16 mm/mm, respectively, for 1 hamstring bundle. The maximum stress is 41.87 MPa and maximum strain is 0.18 mm/mm for 2 hamstring bundles. The advantage is to understand the biomechanics of the knee ligaments while walking. And this research result can help patients who have tear problem of an Anterior Cruciate Ligaments (ACL) and be developed for further research about force and behaviors of the other ligament and muscle in body.