Dr. Po Ting Lin is a Professor in the Department of Mechanical Engineering at National Taiwan University of Science and Technology, Taipei, Taiwan. His research interests include design optimization, reliability analysis, machine learning, machine vision, robotics and vehicle designs.
Journal of Thermal Science and Engineering Applications, Oct 21, 2013
Multiple microchannel heat transfer systems have been developed for the urge of rapid and effecti... more Multiple microchannel heat transfer systems have been developed for the urge of rapid and effective cooling of the electronic devices, which have become smaller and more powerful but also produced more heat. Two different types of single-phase liquid cooling, including the straight and U-shaped microchannel heat sinks, have been utilized to reduce the temperature of the electronic chips. The cooling performances however depend on the preferences of different factors such as the thermal resistances, the pressure drops, and the heat flows at the solid-fluid interfaces. Lower thermal resistance represents higher temperature reduction; lower pressure drop means lower usage of the pumping power; and higher heat flows indicates more effective cooling between the heat spreader and the liquid. In this paper, an optimization strategy based on the prioritized performances has been developed to find the optimal design variables for multiple objectives: minimal thermal resistances, minimal pressure drops and maximal heat flows. The fuzzy and correlated preferences are modeled by the Gaussian membership functions with respect to different levels of the objective function values. The overall performances are formulated based on the prioritized preferences and maximized on the Pareto-optimal solution set to find the solutions for various preference conditions. Two case studies have been discussed. The first case considered the prioritized preferences based on uni-objective function values while the second one focused on the preferences of the thermal resistances and the efficiency measures, correlatively evaluated by the flow rates, pressure drops, and heat flows.
This paper describes a non-destructive detection method for identifying cable defects using K-mer... more This paper describes a non-destructive detection method for identifying cable defects using K-mer frequency encoding. The detection methodology combines magnetic leakage detection equipment with artificial intelligence for precise identification. The cable defect identification process includes cable signal acquisition, K-mer frequency encoding, and artificial intelligence-based identification. A magnetic leakage detection device detects signals via sensors and records their corresponding positions to obtain cable signals. The K-mer frequency encoding method consists of several steps, including cable signal normalization, the establishment of K-mer frequency encoding, repeated sampling of cable signals, and conversion for comparison to derive the K-mer frequency. The K-mer frequency coding method has advantages in data processing and repeated sampling. In the identification step of the artificial intelligence identification model, an autoencoder model is used as the algorithm, and t...
Recently, human activity recognition (HAR) techniques have made remarkable developments in the fi... more Recently, human activity recognition (HAR) techniques have made remarkable developments in the field of machine learning. In this paper, we classify human gestures using data collected from a curved piezoelectric sensor, including elbow movement, wrist turning, wrist bending, coughing, and neck bending. The classification process relies on data collected from a sensor. Machine learning algorithms enabled with K-mer are developed and optimized to perform human gesture recognition (HGR) from the acquired data to achieve the best results. Three machine learning algorithms, namely support vector machine (SVM), random forest (RF), and k-nearest neighbor (k-NN), are performed and analyzed with K-mer. The input parameters such as subsequence length (K), number of cuts, penalty parameter (C), number of trees (n_estimators), maximum depth of the tree (max_depth), and nearest neighbors (k) for the three machine learning algorithms are modified and analyzed for classification accuracy. The pro...
In this paper the process of Chemical Vapor Deposition (CVD) in a vertical impinging reactor is s... more In this paper the process of Chemical Vapor Deposition (CVD) in a vertical impinging reactor is simulated and optimized using the reliability based Performance Measure Approach (PMA) for the deposition of a thin film of silicon from silane. The key focus is on the rate of deposition and on the quality of the thin film produced. Proper control of the governing transport processes results in large area film thickness and composition uniformity. The effect of important design parameters and operating conditions are studied using numerical simulations. Response surfaces are generated for deposition rate and uniformity of the deposited film using Compromise Response Surface Method (CRSM) for the range of design variables considered. The resulting response surfaces are used to optimize the CVD system by considering the uncertainty in the design variables.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2012
The network of delivering commodities has been an important design problem in our daily lives and... more The network of delivering commodities has been an important design problem in our daily lives and many transportation applications. The delivery performance is evaluated based on the system reliability of delivering commodities from a source node to a sink node in the network. The system reliability is thus maximized to find the optimal routing. However, the design problem is not simple because (1) each path segment has randomly distributed attributes; (2) there are multiple commodities that consume various path capacities; (3) the optimal routing must successfully complete the delivery process within the allowable time constraints. In this paper, we want to focus on the design optimization of the Multi-State Flow Network (MSFN) for multiple commodities. We propose an efficient approach to evaluate the system reliability in the MSFN with respect to randomly distributed path attributes and find the optimal routing subject to the allowable time constraints. The delivery rates, also kn...
Compliance mechanisms have been used in the design of soft grippers or flexible mechanisms, whose... more Compliance mechanisms have been used in the design of soft grippers or flexible mechanisms, whose mobilities came from the flexibility of their members rather than the rigid parts in the mechanisms. Compliance linkage mechanisms, that are composed of multiple straight linkages, are simple to manufacture and could be easily applied to the desired gripper designs. One way to synthesize the compliance linkage mechanisms is Topology Optimization (TO). TO methods have been well developed for structural and multidisciplinary designs in terms of finding the optimal objective functions subject to constraints of loading conditions and other design requirements. In practical uses, clear black-and-white optimal designs (i.e. structural design with nonfuzzy distribution of elemental members) are desired but may not be delivered at the end of the TO procedures. Therefore, many additional treatments such as regularization and filtering have been developed to produce black-and-white designs. Some ...
Computational design procedures have been more widely accepted during the past decades due to the... more Computational design procedures have been more widely accepted during the past decades due to the improvements in computing technologies. Together with this, rapid advancements in the algorithms and automated design procedures have flourished. This paper focuses on topology optimization as one of the most viable and active research areas for automated designs. Topology optimization is an automated, “best material lay-out” process which follows the governing equations of one or more physics taken under consideration under a user-defined set of conditions and limitations. This paper does not intend to provide a technical overview of the said topic but rather it reviews several applications on the design of consumer products and structures. This paper would also tackle on how designers could benefit from the generated designs and how creativity can still be practiced despite the automation of the design. The idea of co-creation and maker movement is then explored with the insights on h...
Topology Optimization (TO) methods have been well developed for structural and multidisciplinary ... more Topology Optimization (TO) methods have been well developed for structural and multidisciplinary designs in terms of finding the optimal objective functions subject to constraints of loading conditions and other design requirements. In practical uses, clear black-and-white optimal designs are desired but may not be delivered at the end of the TO procedures. Therefore, many additional treatments such as regularization and filtering have been developed to produce black-and-white designs. Some of the said procedures were also found in the fields of computer vision and image processing. This paper presents a method to automatically generate truss designs by applying image-processing techniques to TO designs. The presented post-processing procedure includes noise removal, pattern thinning, and automatic determination of truss nodes linages. Several numerical examples were shown to demonstrated the presented methodology for automatic truss designs.
1. Abstract Various Reliability-Based Design Optimization (RBDO) methods have been developed and ... more 1. Abstract Various Reliability-Based Design Optimization (RBDO) methods have been developed and widely used to solve design optimization problems with the existence of design uncertainties. The general problem formulation states that the objective function is minimized while the failure probabilities of the performance constraints are subjected to the allowable probability levels. RBDO algorithms derive and formulate various approximate probabilistic constraints with respect to the means of the randomly distributed design variables in replace of the evaluations of failure probabilities using the integral of joint probability density functions. However, there is a huge diversity of approximate probabilistic formulations from various RBDO algorithms. The goodness of fit of each approximate model is problem dependent but highly affects the accuracy and efficiency of the optimization process. In this paper, a Unified Reliability Formulation (URF) is derived from the fundamental aspect ...
The heat sink designs using impinging liquid jets, which form stagnation flows, feature uniform h... more The heat sink designs using impinging liquid jets, which form stagnation flows, feature uniform heat transfer coefficients, and provide thin thermal boundary layers, are studied to reduce the heat from GPUs. Three different designs using central, micro, and uniform-crosssection (UCS) central jets are studied and simulated in COMSOL. The efficiency factors, defined as the ratio of total removed energy over inlet pumping energy, are measured to quantitatively represent the heat transfer performances. The central and micro jet designs consume smaller amounts of pumping powers but form vortexes and thicker thermal boundary layers near the outlets. The UCS central jet design not only avoids the vortex formations but also maintains the thermal boundary layer thickness; therefore, higher efficiency has been achieved.
1. Abstract Several Reliability-Based Design Optimization (RBDO) algorithms have been developed t... more 1. Abstract Several Reliability-Based Design Optimization (RBDO) algorithms have been developed to solve engineering optimization problems under design uncertainties. Some existing methods transform the random design space to standard normal design space to estimate the reliability assessment for the evaluation of the failure probability. When the random variable is arbitrarily distributed and cannot be properly fitted to any known form of probability density function, the existing RBDO methods, however, cannot perform reliability analysis either in the original design space or in the standard normal space. This paper proposes a novel method, Ensemble of Gradient-based Transformed Reliability Analyses (EGTRA), to evaluate the failure probability of arbitrarily distributed random variables in the original design space. The arbitrary distribution of the random variable is approximated by a merger of multiple Gaussian kernel functions. Each Gaussian kernel function is transformed to a ...
Airflow stability plays a vital role in optimizing the spray dryer operation; wherein the airflow... more Airflow stability plays a vital role in optimizing the spray dryer operation; wherein the airflow patterns present inside the drying chamber are considered as the primary factors that influences the histories of the product particle. In this paper, the optimum drying parameters that would produce a higher yield of powdered egg while retaining its quality parameter such as moisture content and water activity were determined by means of Euler-Lagrange Discrete Phase Modeling (DPM) numerical method present in the ANSYS-Fluent ver. 14.5 CFD solver. During the computational simulation, the flow pattern of the air was first identified using the Eulerian method then the results were coupled using the Lagrangian-Discrete Phase Modeling to track the particle histories of the disperse phase inside the tall-form spray drying chamber. Results showed that the optimum inlet air velocity and temperature are 8.87 m/s and 444 K respectively. At these conditions, the particle trajectories simulated exhibited that the calculated final moisture content and water activity for the dried egg powder are 1.09 % and 0.012, respectively.
Increasing trends and improvements in numerical modeling has been evident in the past years espec... more Increasing trends and improvements in numerical modeling has been evident in the past years especially for the HVAC&R industry where airflow and temperature profiles are being predicted. The purpose of this paper is to build a numerical model using ANSYS Fluent Software to predict the velocity profiles and flow distribution caused by the Underfloor Air Distribution (UFAD) module inside the Philippine Society of Ventilation, Air-conditioning and Refrigeration Engineers (PSVARE) Air-conditioning Laboratory in Mapua Institute of Technology. The model had been compared with the data obtained from the original commissioning report and air-balancing data obtained when the project was completed. The said facility will be renovated and used for experiments requiring numerical models and this study presents the baseline of such.
Journal of Thermal Science and Engineering Applications, Oct 21, 2013
Multiple microchannel heat transfer systems have been developed for the urge of rapid and effecti... more Multiple microchannel heat transfer systems have been developed for the urge of rapid and effective cooling of the electronic devices, which have become smaller and more powerful but also produced more heat. Two different types of single-phase liquid cooling, including the straight and U-shaped microchannel heat sinks, have been utilized to reduce the temperature of the electronic chips. The cooling performances however depend on the preferences of different factors such as the thermal resistances, the pressure drops, and the heat flows at the solid-fluid interfaces. Lower thermal resistance represents higher temperature reduction; lower pressure drop means lower usage of the pumping power; and higher heat flows indicates more effective cooling between the heat spreader and the liquid. In this paper, an optimization strategy based on the prioritized performances has been developed to find the optimal design variables for multiple objectives: minimal thermal resistances, minimal pressure drops and maximal heat flows. The fuzzy and correlated preferences are modeled by the Gaussian membership functions with respect to different levels of the objective function values. The overall performances are formulated based on the prioritized preferences and maximized on the Pareto-optimal solution set to find the solutions for various preference conditions. Two case studies have been discussed. The first case considered the prioritized preferences based on uni-objective function values while the second one focused on the preferences of the thermal resistances and the efficiency measures, correlatively evaluated by the flow rates, pressure drops, and heat flows.
This paper describes a non-destructive detection method for identifying cable defects using K-mer... more This paper describes a non-destructive detection method for identifying cable defects using K-mer frequency encoding. The detection methodology combines magnetic leakage detection equipment with artificial intelligence for precise identification. The cable defect identification process includes cable signal acquisition, K-mer frequency encoding, and artificial intelligence-based identification. A magnetic leakage detection device detects signals via sensors and records their corresponding positions to obtain cable signals. The K-mer frequency encoding method consists of several steps, including cable signal normalization, the establishment of K-mer frequency encoding, repeated sampling of cable signals, and conversion for comparison to derive the K-mer frequency. The K-mer frequency coding method has advantages in data processing and repeated sampling. In the identification step of the artificial intelligence identification model, an autoencoder model is used as the algorithm, and t...
Recently, human activity recognition (HAR) techniques have made remarkable developments in the fi... more Recently, human activity recognition (HAR) techniques have made remarkable developments in the field of machine learning. In this paper, we classify human gestures using data collected from a curved piezoelectric sensor, including elbow movement, wrist turning, wrist bending, coughing, and neck bending. The classification process relies on data collected from a sensor. Machine learning algorithms enabled with K-mer are developed and optimized to perform human gesture recognition (HGR) from the acquired data to achieve the best results. Three machine learning algorithms, namely support vector machine (SVM), random forest (RF), and k-nearest neighbor (k-NN), are performed and analyzed with K-mer. The input parameters such as subsequence length (K), number of cuts, penalty parameter (C), number of trees (n_estimators), maximum depth of the tree (max_depth), and nearest neighbors (k) for the three machine learning algorithms are modified and analyzed for classification accuracy. The pro...
In this paper the process of Chemical Vapor Deposition (CVD) in a vertical impinging reactor is s... more In this paper the process of Chemical Vapor Deposition (CVD) in a vertical impinging reactor is simulated and optimized using the reliability based Performance Measure Approach (PMA) for the deposition of a thin film of silicon from silane. The key focus is on the rate of deposition and on the quality of the thin film produced. Proper control of the governing transport processes results in large area film thickness and composition uniformity. The effect of important design parameters and operating conditions are studied using numerical simulations. Response surfaces are generated for deposition rate and uniformity of the deposited film using Compromise Response Surface Method (CRSM) for the range of design variables considered. The resulting response surfaces are used to optimize the CVD system by considering the uncertainty in the design variables.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2012
The network of delivering commodities has been an important design problem in our daily lives and... more The network of delivering commodities has been an important design problem in our daily lives and many transportation applications. The delivery performance is evaluated based on the system reliability of delivering commodities from a source node to a sink node in the network. The system reliability is thus maximized to find the optimal routing. However, the design problem is not simple because (1) each path segment has randomly distributed attributes; (2) there are multiple commodities that consume various path capacities; (3) the optimal routing must successfully complete the delivery process within the allowable time constraints. In this paper, we want to focus on the design optimization of the Multi-State Flow Network (MSFN) for multiple commodities. We propose an efficient approach to evaluate the system reliability in the MSFN with respect to randomly distributed path attributes and find the optimal routing subject to the allowable time constraints. The delivery rates, also kn...
Compliance mechanisms have been used in the design of soft grippers or flexible mechanisms, whose... more Compliance mechanisms have been used in the design of soft grippers or flexible mechanisms, whose mobilities came from the flexibility of their members rather than the rigid parts in the mechanisms. Compliance linkage mechanisms, that are composed of multiple straight linkages, are simple to manufacture and could be easily applied to the desired gripper designs. One way to synthesize the compliance linkage mechanisms is Topology Optimization (TO). TO methods have been well developed for structural and multidisciplinary designs in terms of finding the optimal objective functions subject to constraints of loading conditions and other design requirements. In practical uses, clear black-and-white optimal designs (i.e. structural design with nonfuzzy distribution of elemental members) are desired but may not be delivered at the end of the TO procedures. Therefore, many additional treatments such as regularization and filtering have been developed to produce black-and-white designs. Some ...
Computational design procedures have been more widely accepted during the past decades due to the... more Computational design procedures have been more widely accepted during the past decades due to the improvements in computing technologies. Together with this, rapid advancements in the algorithms and automated design procedures have flourished. This paper focuses on topology optimization as one of the most viable and active research areas for automated designs. Topology optimization is an automated, “best material lay-out” process which follows the governing equations of one or more physics taken under consideration under a user-defined set of conditions and limitations. This paper does not intend to provide a technical overview of the said topic but rather it reviews several applications on the design of consumer products and structures. This paper would also tackle on how designers could benefit from the generated designs and how creativity can still be practiced despite the automation of the design. The idea of co-creation and maker movement is then explored with the insights on h...
Topology Optimization (TO) methods have been well developed for structural and multidisciplinary ... more Topology Optimization (TO) methods have been well developed for structural and multidisciplinary designs in terms of finding the optimal objective functions subject to constraints of loading conditions and other design requirements. In practical uses, clear black-and-white optimal designs are desired but may not be delivered at the end of the TO procedures. Therefore, many additional treatments such as regularization and filtering have been developed to produce black-and-white designs. Some of the said procedures were also found in the fields of computer vision and image processing. This paper presents a method to automatically generate truss designs by applying image-processing techniques to TO designs. The presented post-processing procedure includes noise removal, pattern thinning, and automatic determination of truss nodes linages. Several numerical examples were shown to demonstrated the presented methodology for automatic truss designs.
1. Abstract Various Reliability-Based Design Optimization (RBDO) methods have been developed and ... more 1. Abstract Various Reliability-Based Design Optimization (RBDO) methods have been developed and widely used to solve design optimization problems with the existence of design uncertainties. The general problem formulation states that the objective function is minimized while the failure probabilities of the performance constraints are subjected to the allowable probability levels. RBDO algorithms derive and formulate various approximate probabilistic constraints with respect to the means of the randomly distributed design variables in replace of the evaluations of failure probabilities using the integral of joint probability density functions. However, there is a huge diversity of approximate probabilistic formulations from various RBDO algorithms. The goodness of fit of each approximate model is problem dependent but highly affects the accuracy and efficiency of the optimization process. In this paper, a Unified Reliability Formulation (URF) is derived from the fundamental aspect ...
The heat sink designs using impinging liquid jets, which form stagnation flows, feature uniform h... more The heat sink designs using impinging liquid jets, which form stagnation flows, feature uniform heat transfer coefficients, and provide thin thermal boundary layers, are studied to reduce the heat from GPUs. Three different designs using central, micro, and uniform-crosssection (UCS) central jets are studied and simulated in COMSOL. The efficiency factors, defined as the ratio of total removed energy over inlet pumping energy, are measured to quantitatively represent the heat transfer performances. The central and micro jet designs consume smaller amounts of pumping powers but form vortexes and thicker thermal boundary layers near the outlets. The UCS central jet design not only avoids the vortex formations but also maintains the thermal boundary layer thickness; therefore, higher efficiency has been achieved.
1. Abstract Several Reliability-Based Design Optimization (RBDO) algorithms have been developed t... more 1. Abstract Several Reliability-Based Design Optimization (RBDO) algorithms have been developed to solve engineering optimization problems under design uncertainties. Some existing methods transform the random design space to standard normal design space to estimate the reliability assessment for the evaluation of the failure probability. When the random variable is arbitrarily distributed and cannot be properly fitted to any known form of probability density function, the existing RBDO methods, however, cannot perform reliability analysis either in the original design space or in the standard normal space. This paper proposes a novel method, Ensemble of Gradient-based Transformed Reliability Analyses (EGTRA), to evaluate the failure probability of arbitrarily distributed random variables in the original design space. The arbitrary distribution of the random variable is approximated by a merger of multiple Gaussian kernel functions. Each Gaussian kernel function is transformed to a ...
Airflow stability plays a vital role in optimizing the spray dryer operation; wherein the airflow... more Airflow stability plays a vital role in optimizing the spray dryer operation; wherein the airflow patterns present inside the drying chamber are considered as the primary factors that influences the histories of the product particle. In this paper, the optimum drying parameters that would produce a higher yield of powdered egg while retaining its quality parameter such as moisture content and water activity were determined by means of Euler-Lagrange Discrete Phase Modeling (DPM) numerical method present in the ANSYS-Fluent ver. 14.5 CFD solver. During the computational simulation, the flow pattern of the air was first identified using the Eulerian method then the results were coupled using the Lagrangian-Discrete Phase Modeling to track the particle histories of the disperse phase inside the tall-form spray drying chamber. Results showed that the optimum inlet air velocity and temperature are 8.87 m/s and 444 K respectively. At these conditions, the particle trajectories simulated exhibited that the calculated final moisture content and water activity for the dried egg powder are 1.09 % and 0.012, respectively.
Increasing trends and improvements in numerical modeling has been evident in the past years espec... more Increasing trends and improvements in numerical modeling has been evident in the past years especially for the HVAC&R industry where airflow and temperature profiles are being predicted. The purpose of this paper is to build a numerical model using ANSYS Fluent Software to predict the velocity profiles and flow distribution caused by the Underfloor Air Distribution (UFAD) module inside the Philippine Society of Ventilation, Air-conditioning and Refrigeration Engineers (PSVARE) Air-conditioning Laboratory in Mapua Institute of Technology. The model had been compared with the data obtained from the original commissioning report and air-balancing data obtained when the project was completed. The said facility will be renovated and used for experiments requiring numerical models and this study presents the baseline of such.
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Papers by Po Ting Lin