Ming C. Leu

Ming C. Leu
National Taiwan University | NTU · Department of Mechanical Engineering

About

362
Publications
187,972
Reads
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13,558
Citations
Citations since 2017
81 Research Items
8867 Citations
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201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500

Publications

Publications (362)
Preprint
Full-text available
Assembly activity recognition and prediction help to improve productivity, quality control, and safety measures in smart factories. This study aims to sense, recognize, and predict a worker's continuous fine-grained assembly activities in a manufacturing platform. We propose a two-stage multi-modal network for workers' fine-grained activity recogni...
Preprint
Full-text available
The powder spreading is a vital step of powder-based Additive Manufacturing (AM) processes. The quality of spread powder can considerably influence the properties of fabricated parts. Poorly-packed powder beds with high surface roughness result in printed part layers with large porosity and low dimensional accuracy, leading to poor mechanical prope...
Article
Ceramic On-Demand Extrusion (CODE) is a direct ink writing process which allows for the creation of near theoretically dense ceramic components with large cross-sections due to oil-assisted drying. Yttria-stabilized zirconia (YSZ) colloidal pastes were used in CODE to produce dense (multi-road infill and ≳ 98% relative density), large continuous vo...
Poster
Full-text available
In this poster, we explain the real-time human-robot collaboration using gestures and speech, including I)•Design a real-time, multi-modal communication HYC system based on gesture and speech recognition. II)• Design and recognize dynamic gestures for communication between a human to an industrial robot. II)• Understand human speech and integrate t...
Article
Thickening electrodes is one effective approach to increase active material content for higher energy and low‐cost lithium‐ion batteries, but limits in charge transport and huge mechanical stress generation result in poor performance and eventual cell failure. This paper reports a new electrode fabrication process, referred to as µ‐casting, enablin...
Article
The laser powder bed fusion (LPBF) process is strongly influenced by the characteristics of the powder layer, including its thickness and thermal transport properties. This paper investigates in-situ characterization of the powder layer using thermographic inspection. A thermal camera monitors the temperature history of the powder surface immediate...
Article
Full-text available
As artificial intelligence and industrial automation are developing, human-robot collaboration (HRC) with advanced interaction capabilities has become an increasingly significant area of research. In this paper, we design and develop a real-time, multi-model HRC system using speech and gestures. A set of sixteen dynamic gestures is designed for com...
Article
Full-text available
Particles of AISI 304L stainless steel powder were spheroidized by the induction plasma spheroidization process (TekSphero-15 spheroidization system) to assess the effects of the spheroidization process on powder and part properties. The morphology of both as-received and spheroidized powders was characterized by measuring particle size and shape d...
Article
Purpose This paper aims to present the development and experimental study of a fully automated system using a novel laser additive manufacturing technology called laser foil printing (LFP), to fabricate metal parts layer by layer. The mechanical properties of parts fabricated with this novel system are compared with those of comparable methodologie...
Article
Future action anticipation aims to infer future actions from the observation of a small set of past video frames. In this paper, we propose a novel Jointly-learnt Action Anticipation Network (J-AAN) via Self-Knowledge Distillation (Self-KD) and cycle consistency for future action anticipation. In contrast to the current state-of-the-art methods whi...
Preprint
Full-text available
Human Activity Recognition (HAR) using wearable devices such as smart watches embedded with Inertial Measurement Unit (IMU) sensors has various applications relevant to our daily life, such as workout tracking and health monitoring. In this paper, we propose a novel attention-based approach to human activity recognition using multiple IMU sensors w...
Article
The use of gas-atomized powder as the feedstock material for the laser powder bed fusion (LPBF) process is common in the additive manufacturing (AM) community. Although gas-atomization produces powder with high sphericity, its relatively expensive production cost is a downside for application in AM processes. Water atomization of powder may overcom...
Article
Full-text available
Real-time Action Recognition (ActRgn) of assembly workers can timely assist manufacturers in correcting human mistakes and improving task performance. Yet, recognizing worker actions in assembly reliably is challenging because such actions are complex and fine-grained, and workers are heterogeneous. This paper proposes to create an individualized s...
Article
We Introduce a simple yet effective network that embeds a novel Discriminative Feature Pooling (DFP) mechanism and a novel Video Segment Attention Model (VSAM), for video-based human action recognition from both trimmed and untrimmed videos. Our DFP module introduces an attentional pooling mechanism for 3D Convolutional Neural Networks that attenti...
Chapter
Virtual Reality (VR) technologies provide a realistic, safe, and controllable environment for novice surgeons to practice surgical operations, allowing them to make mistakes without serious consequences, which have been changing the world of surgical training and practice. This book chapter focuses on methodologies and applications of utilizing VR...
Article
Full-text available
The success of laser-foil-printing (LFP) additive manufacturing depends critically on the laser welding of sheet metals onto the substrate or the previous layer during the part fabrication process. The welding can be generally categorized into two modes: conduction mode and keyhole mode. In this study, 304L stainless steel parts fabricated by the L...
Conference Paper
Full-text available
With the development of industrial automation and artificial intelligence, robotic systems are developing into an essential part of factory production, and the human-robot collaboration (HRC) becomes a new trend in the industrial field. In our previous work, ten dynamic gestures have been designed for communication between a human worker and a robo...
Article
The Ceramic On-Demand Extrusion (CODE) process has been recently proposed for additive manufacturing of dense, strong ceramic components via extrusion with uniform layered drying. This study focuses on enabling CODE to fabricate functionally graded ceramics. A controlled volumetric flowrate for each ceramic paste was used to achieve a gradient betw...
Article
This study aims at sensing and understanding the worker’s activity in a human-centered intelligent manufacturing system. We propose a novel multi-modal approach for worker activity recognition by leveraging information from different sensors and in different modalities. Specifically, a smart armband and a visual camera are applied to capture Inerti...
Article
Laser Powder-Bed Fusion (L-PBF), often called selective laser melting (SLM), is a powder-bed fusion process in Additive Manufacturing (AM) that uses a laser beam to selectively fuse layers of powder into near net-shape components with little porosity. However, inconsistencies in the part properties due to the presence of defects in as-built compone...
Conference Paper
Full-text available
Human-robot collaboration (HRC) is a challenging task in modern industry and gesture communication in HRC has attracted much interest. This paper proposes and demonstrates a dynamic gesture recognition system based on Motion History Image (MHI) and Convolutional Neural Networks (CNN). Firstly, ten dynamic gestures are designed for a human worker to...
Article
Assembly carries paramount importance in manufacturing. Being able to support workers in real time to maximize their positive contributions to assembly is a tremendous interest of manufacturers. Human action recognition has been a way to automatically analyze and understand worker actions to support real-time assistance for workers and facilitate w...
Article
Cellularized scaffolds fabricated with hydrogel do not possess sufficient strength to act as stand-alone implant devices for hard tissue repair and regeneration. A thermoplastic polymer support structure typically provides the structural integrity to scaffolds while cells and growth factors in hydrogel provide biological stimulation for tissue form...
Article
Full-text available
The pore geometry of scaffold intended for the use in the bone repair or replacement is one of the most important parameters in bone tissue engineering. It affects not only the mechanical properties of the scaffold but also the amount of bone regeneration after implantation. Scaffolds with five different architectures (cubic, spherical, x, gyroid,...
Article
Quality and efficiency are crucial indicators of any manufacturing company. Many companies are suffering from a shortage of experienced workers across the production line to perform complex assembly tasks. To reduce time and error in an assembly task, a worker-centered system consisting of multi-modal Augmented Reality (AR) instructions with the su...
Article
Ceramic On‐Demand Extrusion (CODE) process has been recently proposed for additive manufacturing of strong ceramic components via extrusion. This paper focuses on fabricating 3 mol% yttria‐stabilized zirconia (3YSZ) components using this process, and enabling CODE to produce parts with support structures. A colloidal suspension of 3YSZ was develope...
Article
Full-text available
Fabrication of dense aluminum (Al-1100) parts (>99.3% of relative density) by our recently developed laser-foil-printing (LFP) additive manufacturing method was investigated as described in this paper. This was achieved by using a laser energy density of 7.0 MW/cm2 to stabilize the melt pool formation and create sufficient penetration depth with 30...
Article
Full-text available
In a human-centered intelligent manufacturing system, every element is to assist the operator in achieving the optimal operational performance. The primary task of developing such a human-centered system is to accurately understand human behavior. In this paper, we propose a fog computing framework for assembly operation recognition, which brings c...
Article
Full-text available
The global escalating cases of skin donor shortage for patients with severe wounds warn the vital need for alternatives to skin allografts. Over the last three decades, research in the skin regeneration area has addressed the unmet need for artificial skin substitutes. 3D bioprinting is a promising innovative technology to accurately fabricate skin...
Article
The performance of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) is highly dependent on the flow distribution and pressure of reactant gases, which are controlled by flow field design. The relative importance of differing supply pressure requirements of flow field designs in PEMFCs is considered here. A First-Law analysis of the auxiliary system...
Preprint
Full-text available
In a human-centered intelligent manufacturing system, sensing and understanding of the worker's activity are the primary tasks. In this paper, we propose a novel multi-modal approach for worker activity recognition by leveraging information from different sensors and in different modalities. Specifically, a smart armband and a visual camera are app...
Article
Full-text available
Training and on-site assistance is critical to help workers master required skills, improve worker productivity, and guarantee the product quality. Traditional training methods lack worker-centered considerations that are particularly in need when workers are facing ever-changing demands. In this study, we propose a worker-centered training & assis...
Article
In this study we demonstrate that the mechanical properties of 304L stainless steel (304L SS) parts fabricated by the laser-foil-printing (LFP) additive manufacturing process can be enhanced as compared to parts fabricated by the selective laser melting (SLM) technology. The tensile test results indicate that the LFP fabricated parts achieve ˜15% a...
Chapter
Full-text available
Virtual Reality (VR) and Augmented Reality (AR) technologies have been well researched for decades, and recently they have been introduced to the consumer market and are being applied to many fields. This chapter focuses on utilizing VR/AR technologies for assembly simulations in advanced manufacturing. First, some basic terminologies and concepts...
Article
Full-text available
Three-dimensional (3D) bioprinting technologies have shown great potential in the fabrication of 3D models for different human tissues. Stem cells are an attractive cell source in tissue engineering as they can be directed by material and environmental cues to differentiate into multiple cell types for tissue repair and regeneration. In this study,...
Article
Full-text available
In today’s competitive production era, the ability to identify and track important objects in a near real-time manner is greatly desired among manufacturers who are moving towards the streamline production. Manually keeping track of every object in a complex manufacturing plant is infeasible; therefore, an automatic system of that functionality is...
Article
Full-text available
Production innovations are occurring faster than ever. Manufacturing workers thus need to frequently learn new methods and skills. In fast changing, largely uncertain production systems, manufacturers with the ability to comprehend workers’ behavior and assess their operation performance in near real-time will achieve better performance than peers....
Article
Full-text available
Bioactive glasses have recently gained attention in tissue engineering and three-dimensional (3D) bioprinting because of their ability to enhance angiogenesis. Some challenges for developing biological tissues with bioactive glasses include incorporation of glass particles and achieving a 3D architecture mimicking natural tissues. In this study, we...
Article
One of the polymer additive manufacturing processes commonly used today is fused deposition modelling (FDM). FDM is the process of manufacturing three-dimensional structure through the use of a layer-by-layer printing of the polymer filament. Due to the anisotropic nature of FDM parts, the orientation of the rasters and the build orientation have a...
Article
The application of bulk metallic glasses (BMGs) has been traditionally limited to parts with small dimensions and simple geometries, due to the requirement of fast cooling during the conventional process of casting. This research exemplifies a promising additive manufacturing method, i.e., laser-foil-printing (LFP), to fabricate high-quality BMG pa...
Preprint
Full-text available
Additive manufacturing (AM) components fabricated by the selective laser melting (SLM) process are used increasingly more in industrial applications. This is mainly due to the SLM ability to fabricate complicated parts geometry coupled with restricted tolerances and the availability of a wide range of alloy compositions. Although there is much prog...
Article
Purpose The purpose of this paper is to study the flexural behavior of additively manufacture Ultem 1010 parts. Fused deposition modeling (FDM) process has become one of most widely used additive manufacturing methods. The process provides the capability of fabricating complicated shapes through the extrusion of plastics onto a print surface in a...
Preprint
Full-text available
American Sign Language (ASL) alphabet recognition by computer vision is a challenging task due to the complexity in ASL signs, high interclass similarities , large intraclass variations, and constant occlusions. This paper describes a method for ASL alphabet recognition using Convolutional Neural Networks (CNN) with multiview augmentation and infer...
Conference Paper
Full-text available
Ceramic On-Demand Extrusion (CODE) is an extrusion-based additive manufacturing process recently developed for fabricating dense, functional ceramic components. Presented in this paper is a further development of this process focusing on fabrication of functionally graded materials (FGM). A dynamic mixing mechanism was developed for mixing constitu...
Conference Paper
Full-text available
Digital-Twins simulate physical world objects by creating as-is virtual images in a cyberspace. In order to create a well synchronized digital-twin simulator in manufacturing, information and activities of a physical machine need to be virtualized. Many existing digital-twins stream read-only data of machine sensors and do not incorporate operation...
Conference Paper
Full-text available
Lattice structures fabricated by Additive Manufacturing (AM) processes are promising for many applications, such as lightweight structures and energy absorbers. However, predicting and controlling of their mechanical behaviors is challenging due to the complexity of modeling and the uncertainties exist in the manufacturing process. In this paper, w...
Conference Paper
Full-text available
In a smart manufacturing system involving workers, recognition of the worker's activity can be used for quantification and evaluation of the worker's performance, as well as to provide onsite instructions with augmented reality. In this paper, we propose a method for activity recognition using Inertial Measurement Unit (IMU) and surface electromyog...
Article
Cloud manufacturing yields insights of manufacturing services over cyberspace based on the integration of advanced manufacturing with cloud computing. However, the different communication standards between the different system levels are the main challenge for the integration without conflicting communication. Ethernet appears to be the best soluti...
Conference Paper
Full-text available
Recognition of American Sign Language (ASL) alphabet not only could bring benefits to the ASL users, but also could provide solutions for natural human-computer/robot interactions in many applications. In this paper, we propose a method for ASL alphabet recognition with use of a Leap Motion Controller (LMC). The skeleton data from the native LMC AP...
Article
Welding of dissimilar metals is challenging, particularly between crystalline metals and metallic glasses (MGs). In this study, Zr65.7Cu15.6Ni11.7Al3.7Ti3.3 (wt%) MG structures were built on 304 stainless steel (SS) substrates by laser-foil-printing (LFP) additive manufacturing technology in which MG foils were laser welded layer-by-layer onto the...
Article
When data collisions happen in Radio‐Frequency Identification (RFID) networks, inaccurate tag's information or the communication between the RFID reader and the RFID tag occur. Although recent technological advances have improved the inquiry capacity performance of RFID readers, the performance of RFID networks can still be affected by collisions....
Article
The Ceramic On-Demand Extrusion (CODE) process is a novel additive manufacturing method for fabricating dense (~99% of theoretical density) ceramic components from aqueous, high solids loading pastes (>50 vol%). In this study, 3 mol% Y2O3 stabilized zirconia (3YSZ) specimens were fabricated using the CODE process. The specimens were then dried in a...
Article
Full-text available
Three-dimensional (3D) bioprinting is an emerging technology in which scaffolding materials and cell-laden hydrogels may be deposited in a pre-determined fashion to create 3D porous constructs. A major challenge in 3D bioprinting is the slow degradation of melt deposited biopolymer. In this paper, we describe a new method for printing poly-caprolac...
Book
Full-text available
This self-guided tutorial provides a step-by-step approach for users to learn NX 12. It is intended for those with no previous experience with NX. However, users of previous versions of NX may also find this tutorial useful for them to learn the new user interfaces and functions. The user will be guided from starting an NX 12 session to creating mo...
Article
Through using Zr intermediate layers, Zr65.7Ti3.3Al3.7Ni11.7Cu15.6 metallic glass (MG) parts are successfully built on Ti-6Al-4V substrates by laser-foil-printing (LFP) additive manufacturing technology in which MG foils are laser welded layer-by-layer onto the substrate. The printed MG part is free of porosity, cracking and crystallization; additi...
Conference Paper
Full-text available
Ceramic On-Demand Extrusion (CODE) is an extrusion-based additive manufacturing process recently developed for fabricating dense, functional ceramic components. This paper presents a further development of this process and focuses on fabricating 3 mol% yttria-stabilized zirconia (3YSZ) components that cannot be fabricated without using support stru...
Article
Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bone is limited due to their poor mechanical properties in comparison to human bone. This work investigates the freeform extrusion fabrication of bioactive silicate 13–93 glass scaffolds reinforced with titanium...
Article
Full-text available
Critical to the selection requirements for additive manufacturing (AM) is the need for appropriate materials. Materials requirements for AM include the ability to produce the feedstock in a form amenable to the specific AM process, suitable processing of the material by AM, capability to be acceptably post-processed to enhance geometry and properti...
Article
This paper describes a further development of the novel Ceramic On-Demand Extrusion (CODE) process, with focus on fabricating ceramic components that have external/internal features and cannot be fabricated without the use of support structures. The minimum angle of a wedge-shaped part that can be fabricated using Al2O3 (alumina) paste without a su...
Article
In laser-foil-printing additive manufacturing, 3D metallic glass structures can be built by laser welding of amorphous foils, layer by layer, upon a crystalline metal substrate. In this paper, weldability studies for laser welding of Zr52.5Ti5Al10Ni14.6Cu17.9 amorphous foils onto a Ti-6Al–4 V (Ti 6-4) or Zr 702 substrate are conducted. After laser...
Article
An extrusion-based additive manufacturing process, called the Ceramic On-Demand Extrusion (CODE) process, for producing three-dimensional ceramic components with near theoretical density is introduced in this paper. In this process, an aqueous paste of ceramic particles with a very low binder content (<1 vol%) is extruded through a moving nozzle at...