Browsing by Author "Chang, Chia-Ming"

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A Hierarchical Task Assignment for Manual Image Labeling
(2019-01-01)
Chang, Chia-Ming
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Mishra, Siddharth Deepak
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Igarashi, Takeo
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傳播與科技學系
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Department of Communication and Technology
Manual image labeling (selecting an appropriate "category" for an image) is very tedious and time consuming especially when selecting labels from a large number of categories. In this study, we propose a hierarchical assignment of labeling tasks where the labelers recursively classify images in a category group into sub category groups, working on a single level at a time. This significantly makes each labeler's task easier, reducing the number of choices from 1,000 to 27 on average. In the user study, we compared our hierarchical assignment to a normal (non-hierarchical) assignment for a labeling task. The results show that the hierarchical assignment requires less total time to complete the labeling task. In addition, the learning effect in the labeling process is more profound in the hierarchical assignment.
A large bistable negative lens by integrating a polarization switch with a passively anisotropic focusing element
(2014-06-02)
Chen, Hung-Shan
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Lin, Yi-Hsin
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Srivastava, Abhishek Kumar
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Chigrinov, Vladimir Grigorievich
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Chang, Chia-Ming
A bistable negative lens with a large aperture size (similar to 10mm) by integrating a polarization switch of ferroelectric liquid crystals (FLCs) with a passively anisotropic focusing element is demonstrated. The proposed lens not only exhibits electrically tunable bistability but also fast response time of sub-milliseconds. The tunable lens power is from 0 to -1.74 Diopters. The electro-optical properties and imaging performances are demonstrated. The impact of this study is to provide a solution of electrically bistable liquid crystal lenses for the applications of portable devices, wearable devices and colored ophthalmic lenses. (C) 2014 Optical Society of America
A liquid crystal and polymer composite film for liquid crystal lenses
(2015-01-01)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Wang, Yu-Jen
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Chang, Chia-Ming
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光電工程學系
Liquid crystal (LC) lenses offer novel opportunities for applications of ophthalmic lenses, camera modules, pico projectors, endoscopes, and optical zoom systems owing to electrically tunable lens power. Nevertheless, the tunable lens power and the aperture size of LC lenses are limited by the optical phase resulting from limit birefringence of LC materials. Recently, we developed a liquid crystal and polymer composite film (LCPCF) as a separation layer and an alignment layer for a multi-layered structure of LC lenses in order to enlarge the polarization-independent optical phase modulation. However, the physical properties and mechanical properties of the LCPCF are not clearly investigated. In this paper, we show the mechanical and physical properties of the LCPCF. The anchoring energy of the LCPCF is comparable with the standard rubbing-induced alignment layer. The transmission efficiency is around 97% neglecting the Fresnel reflection. The surface roughness is under 2 nm by using AFM scanning. The bending strength test indicates that the LCPCF can hold the LC material with reasonable deformation. We believe this study provides a deeper insight to the LC lens structure embedded with LCPCF.
A polarized bifocal switch based on liquid crystals operated electrically and optically
(2015-01-28)
Chen, Hung-Shan
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Lin, Yi-Hsin
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Chang, Chia-Ming
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Wang, Yu-Jen
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Srivastava, Abhishek Kumar
A polarized bifocal switch based on liquid crystals (LC) operated electrically and optically is demonstrated. The bifocal switch mainly consists of two parts: a LC layer as a polarization switch and two polymeric layers for modulation of polarization dependent spatial phase difference which results in a positive or a negative lensing effect. The orientations of the LC molecules in the polarization switch are manipulated either in electrically switching (ES) mode or optically rewritten (ORW) mode. The bifocal switch with an aperture size of 10mm exhibits two discrete lens powers (-1.39 Diopter and +0.7 Diopter) with different polarization states no matter in ES mode or in ORW mode. ORW mode is also a bistable mode. The related mechanism and electro-optical performance are discussed and demonstrated. Such a versatile optical switch is capable of not only switching between a positive lens power and a negative lens power, but also switching between two linear polarization states which can be useful in optical systems. The potential applications are for optical systems, wearable devices and ophthalmic lenses. (C) 2015 AIP Publishing LLC.
A polarized liquid crystal lens with electrically switching mode and optically written mode
(2015-01-01)
Chen, Hung-Shan
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Lin, Yi-Hsin
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Chang, Chia-Ming
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Wang, Yu-Jen
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Srivastava, Abhishek Kumar
A polarized liquid crystal (LC) lens composed of a LC layers as a polarization switch and a liquid crystal and polymer composites lens (LCPC lens) is demonstrated with electrically switching (ES) mode and optically rewritten (ORW) mode. The lens power of LCPC lens is related to a polarization state of light modulated by the LC layer whose orientations are manipulated either electrically or optically. As a result, the LC lens is not only electrically switchable, but also optically rewritable. Each mode, ES mode or ORW mode, exhibits two discrete lens powers (-1.39 Diopter and +0.7 Diopter). The demonstrated aperture size is 10 mm. The detail optical mechanism is also discussed. The Modulation Transfer Function (so-called MTF) of the lens is measured as well. In addition, the image performance and the dispersion of the LC lens are investigated. Such a polarized LC lens could be a special switch in optical systems due to dual operation modes.
A Polarizer-Free Liquid Crystal Lens Exploiting an Embedded-Multilayered Structure
(2015-04-15)
Chen, Hung-Shan
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Wang, Yu-Jen
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Chang, Chia-Ming
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Lin, Yi-Hsin
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光電工程學系
Development of liquid crystal (LC) lenses is limited by the power law. The aperture size of LC lenses is traded for the lens power. In this letter, we prove theoretically and experimentally that the aperture size is not limited by the power law based on a polarizer-free LC lens exploiting an embedded-multilayered structure. By adding numbers of LC layers, the aperture size of the LC lens can be enlarged without lowering the tunable lens power. The optical theory of the polarization independence of the LC lens is derived. The wavefronts are measured after light propagates through the LC lens to discuss the polarization independence and image adjustment. The impact of this study is to show the possibility of LC lenses with large aperture size for wearable devices and ophthalmic applications.
A SERVER LOAD BALANCING DESIGN FOR PEER-TO-PEER NETWORK
(2011)
Liaw, Der-Cherng
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Chiu, Cheng-Hsiang
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Yeh, Chia-Wei
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Chang, Chia-Ming
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Hsieh, Hsiao-Jen
A novel scheme is proposed for server load balancing. It is known that load balancing plays a critical role in network-based information service. Although lots of methods have been recently proposed, however, most of those schemes might not be able to make the loading of all servers evenly. Thus, server system might encounter the risk of being over-loaded and/or out of function. In this paper, we propose a distribution scheme to prevent the server from being over-loaded and save the power consumption of all server system for low loading request. It is shown in the paper that the proposed scheme can make the load distribution more efficiently without being over-loaded. Experimental results demonstrate the success of the proposed design.
A Server Load Balancing Design for Peer-To-Peer Network
(2010)
Liaw, Der-Cherng
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Chiu, Cheng-Hsiang
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Yeh, Chia-Wei
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Chang, Chia-Ming
;
Hsieh, Hsiao-Jen
A novel scheme is proposed for server load balancing. It is known that load balancing plays a critical role in network-based information service. Although lots of methods have been recently proposed, however, most of those schemes might not be able to make the loading of all servers evenly. Thus, server system might encounter the risk of being over-loaded and/or out of function. In this paper, we propose a distribution scheme to prevent the server from being overloaded and save the power consumption of all server system for low loading request. It is shown in the paper that the proposed scheme can make the load distribution more efficiently without being over-loaded. Experimental results demonstrate the success of the proposed design.
An optical image stabilization using a droplet manipulation on a liquid crystal and polymer composite film
(2015-01-01)
Wang, Yu-Jen
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Chang, Chia-Ming
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Tsou, Yu-Shih
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Chen, Ming-Syuan
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Chen, Hung-Shan
Motion blur is one of the major factors decreasing the image quality of a hand-held optical imaging system while the system is under shakes or vibrations during exposure. Optical image stabilization (OIS) is a technique to reduce such a blurring. The basic principle of OIS is to stabilize the recorded image in a camera by varying the optical path to the sensor under vibrations during exposure. In this paper, we demonstrate optical image stabilization (OIS) for an imaging system using a droplet manipulation on a liquid crystal and polymer composite film (LCPCF) that reduces the motion blur. The mechanism is based on manipulation of position of the liquid lens on LCPCF by means of electrically adjusting orientations of liquid crystals. The change of the position of the liquid lens compensates the deviation of light when the image system is under a handshake vibration. Therefore, the imaging system forms a clear image with a droplet on different position to overcome handshake vibration. The concept in this paper can also be extended to design other optical components for modulating the direction of light.
An optical system adopting liquid crystals with electrical tunability of wavelength and energy density for low level light therapy
(2015-01-01)
Chang, Chia-Ming
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Wang, Yu-Jen
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Chen, Hung-Shan
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Lin, Yi-Hsin
;
Srivastava, Abhishek Kumar
We have developed a bistable negative lens by integrating a polarization switch of ferroelectric liquid crystals (FLCs) with a passively anisotropic focusing element. The proposed lens not only exhibits electrically tunable bistability but also fast response time of sub-milliseconds, which leads to good candidate of optical component in optical system for medical applications. In this paper, we demonstrate an optical system consisting of two FLC phase retarders and one LC lenses that exhibits both of electrically tunable wavelength and size of exposure area. The operating principles and the experimental results are discussed. The tunable spectrum, exposure area size and tunable irradiance are illustrated. Compared to conventional lenses with mechanical movements in the medical light therapy system, our electrically switchable optical system is more practical in the portable applications of light therapy (LLLT).
An optical system via liquid crystal photonic devices for photobiomodulation
(2018-03-09)
Chang, Chia-Ming
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Lin, Yi-Hsin
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Srivastava, Abhishek Kumar
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Chigrinov, Vladimir Grigorievich
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光電工程學系
Photobiomodulation or low-level light therapy (LLLT) has extensive applications based on light-induced effects in biological systems. Photobiomodulation remains controversial because of a poorly understood biochemical mechanism limited by the well-known biphasic dose response or Arndt-Schulz curve. The Arndt-Schulz curve states that an optimal dose of light is a key factor for realizing a therapeutic effect. In this report, we demonstrate a tunable optical system for photobiomodulation to aid physicians in overcoming the constraints of light due to biphasic dose response. The tunable optical system is based on a white light-emitting diode and four liquid crystal (LC) photonic devices: three LC phase retarders, and one LC lens. The output light of the tunable optical system exhibits electrical tunability for the wavelength, energy density and beam size. The operating principle is introduced, and the experimental results are presented. The proposed concept can be further extended to other electrically tunable photonic devices for different clinical purposes for photobiomodulation.
Applications of neural network models for structural health monitoring based on derived modal properties
(2018-12-01)
Chang, Chia-Ming
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Lin, Tzu-Kang
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Chang, Chih-Wei
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土木工程學系
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Department of Civil Engineering
Structural health monitoring is required to interpret damaged structures in terms of locations and severity, even remaining performance of the damaged members. Therefore, this study proposes a new artificial intelligence-based structural health monitoring strategy based on neural network modeling. A neural network model is developed in accordance with a numerical model which is derived from the identified modal properties under ambient vibrations. The stochastic subspace system identification is first implemented to derive the natural frequencies and mode shapes of a healthy structure. These natural frequencies and mode shapes are then employed to derive a simplified model of this structure, allowing changing stiffness terms to construct various damage patterns. A neural network model is trained and built by the modal properties of the structure with these damage patterns. After a critical event occurs (e.g., earthquakes), this neural network model can be employed to estimate the damage patterns in terms of stiffness reduction. In this study, a numerical example consisting of two damage scenarios is carried out. This example studies a seven-story building with a single and multiple damaged columns in order to evaluate performance of the proposed structural health monitoring strategy. Moreover, the proposed structural health monitoring strategy is also applied to an experimental test of a scaled twin-tower building with weak braces in some floors. Partially modal properties of the structure are obtained from the stochastic subspace system identification, while a simplified model is developed in accordance to the identified modal properties of the healthy building. Then, a neural network model is established based on this simplified model. After seismic events, this neural network model is employed to carry damage detection of this building in terms of damage locations and levels. As a result, the proposed artificial intelligence-based structural health monitoring strategy is quite effective to locate damage if the identified modal properties are relatively accurate.
BalloonFAB: Digital Fabrication of Large-Scale Balloon Art
(2019-01-01)
Xie, Haoran
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Peng, Yichen
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Chen, Naiyun
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Xie, Dazhao
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Chang, Chia-Ming
We propose an interactive system that allows common users to build large-scale balloon art based on a spatial augmented reality solution. The proposed system provides fabrication guidance to illustrate the differences between the depth maps of the target three-dimensional shape and the current work in progress. Instead of using color gradients for depth difference, we adopt a high contrast black and white projection of the numbers in considering balloon texture. In order to increase user immersion in the system, we propose a shaking animation for each projected number. Using the proposed system, the unskilled users in our case study were able to build large scale balloon art.
Behavioral Therapy for Phobias Using Immersive Virtual Reality Technology
(2020-04-01)
Trappey, Amy J. C.
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Trappey, Charles V.
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Chang, Chia-Ming
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Govindarajan, Usharani Hareesh
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Shih, Xyuan-Yu
Mental disorders are difficult to diagnose and treat. Global economic growth, changing social organizations, and urban conditions affect mental health resulting in increased costs, limited benefits, and fewer facilities for behavioral treatment. Virtual reality-based behavioral treatments for mental illness offer benefits to supplement conventional therapies. Virtual Reality Treatment (VRT) let patients confront phobias using a virtual environment with a therapist. A therapist observes and coaches the patient through increasingly difficult levels of confrontation to desensitize patient phobias. This research presents a generic framework and discusses the related behavioral therapy. A VRT for confronting fear of spiders is the case used for the technology development and data collection processes which establish the basis for future clinical trials and analysis. The preliminary trial of the arachnophobia VRT platform with eight scenario levels has produced accurate bio-feedback results. The system demonstrates promise for rapid VRT application development for clinical behavioral psychotherapy.
Effect of Thermal Annealing on a-plane GaN Grown on r-plane Sapphire
(2014)
Ko, Tsung-Shine
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Lu, Tien-Chang
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Chen, Jung-Ron
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Ou, Sin-Liang
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Chang, Chia-Ming
The crystal quality improvement of a-plane GaN grown on r-plane sapphire was demonstrated by applying thermal annealing on as-grown samples in nitrogen ambient. The root mean square roughness of the 1000 degrees C-annealed a-plane GaN was only 0.4 nm measured by atomic force microscopy. Transmission electron microscopy results further indicate threading dislocations were decreased from 5x10(10) cm(-2) to 1.5x10(10) cm(-2) along [0001] GaN and stacking faults were decreased from 8.7x 10(5) cm(-1) to 4.8x 10(5) cm(-1) after the sample was annealed at 1000 degrees C. Room temperature photo luminescence measurements showed band edge emission intensity was enhanced up to 2.6 folds compared to the regular a-plane GaN film. Furthermore, corresponding cathode luminescence images reveal larger emission area for a-plane GaN with annealing than those without annealing, which was attributed to reduction of the nonradiative recombination centers. A series of experiments confirm this annealing process could be useful for further applications of GaN-based optoelectric devices.
Effects of Negative Electrodes Coated by ZnO with Different Morphologies on Electrochemical Performances and Safety of Lithium Ion Batteries
(2019-02-01)
Chang, Chia-Ming
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Lin, Hsiu-Fen
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Liao, Shih-Chieh
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Chiu, Hsin-Tien
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Liu, Chia-Erh
To improve the safety of lithium-ion batteries, this study applied topographically different ZnO to the surface of negative graphite electrodes to serve as heat-resistant layers and explored the effects of these layers on a battery's electrochemical and safety features. The results indicate that when using a tetrapod ZnO (T-ZnO) particle coating as a heat-resistant layer on a negative graphite electrode, ion diffusion is improved because T-ZnO has a three-dimensional network structure and forms highly porous layers. This causes batteries to retain excellent electrochemical characteristics even if they contain inactive substances. Moreover, the results of overcharge and penetration tests were satisfactory, suggesting that the batteries are highly safe.
Effects of Negative Electrodes Coated by ZnO with Different Morphologies on Electrochemical Performances and Safety of Lithium Ion Batteries
(2019-01-01)
Chang, Chia-Ming
;
Lin, Hsiu-Fen
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Liao, Shih-Chieh
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Chiu, Hsin-Tien
;
Liu, Chia-Erh
To improve the safety of lithium-ion batteries, this study applied topographically different ZnO to the surface of negative graphite electrodes to serve as heat-resistant layers and explored the effects of these layers on a battery's electrochemical and safety features. The results indicate that when using a tetrapod ZnO (T-ZnO) particle coating as a heat-resistant layer on a negative graphite electrode, ion diffusion is improved because T-ZnO has a three-dimensional network structure and forms highly porous layers. This causes batteries to retain excellent electrochemical characteristics even if they contain inactive substances. Moreover, the results of overcharge and penetration tests were satisfactory, suggesting that the batteries are highly safe.
Highly efficient blue organic electroluminescent devices
(2005)
Chang, Chia-Ming
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Lee, Meng-Ting
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Chen, Chin H.
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應用化學系
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Department of Applied Chemistry
We have synthesized a highly efficient blue dopant based on the amino-substituted distyrylarylene (DSA-amine) fluorescent dye. Doped in the stable diphenyanthracene type of blue host material 2-(methyl)-9,10-di(2-naphthyl)anthrace (MADN), it achieved a luminance yield of 9.1 cd/A at 20 mA/cm(2) with a CIEx,y color coordinate of [0.16, 0.28] and a maximum external quantum efficiency of 4.7%.
Iminodibenzyl-substituted distyrylarylenes as dopants for blue and white organic light-emitting devices
(2008-02-01)
Ho, Meng-Huan
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Chang, Chia-Ming
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Chu, Ta-Ya
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Chen, Teng-Ming
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Chen, Chin H.
A series of highly efficient blue materials based on iminodibenzyl-substituted distyrylarylene (IDB-series) fluorescent dyes using the concept of steric-compression have been designed and synthesized by means of a rigidized and over-sized ring. The steric-compression effect can shorten the effective conjugation length (chromophore) of the molecule and the added phenyl moiety in the core can alleviate the propensity for molecular aggregation. These materials also possess high glass transition temperature over 100 degrees C. The blue IDB-Ph device achieved a maximum external quantum efficiency of 4.8% with a Commission Internationale de I'Eclairage (CIEx,y) coordinate of (0.16, 0.28). When applied in two-element white OLED system, the IDB-Ph doped device achieved a luminance efficiency of 11.0 cd/A with a CIEx,y color coordinate of (0.29, 0.36). (c) 2007 Elsevier B.V. All rights reserved.
Large aperture and polarizer-free liquid crystal lenses for ophthalmic applications
(2014-01-01)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Chang, Chia-Ming
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Wang, Yu-Jen
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光電工程學系
Large aperture and polarizer-free liquid crystal lenses (LC lenses) based on a double-layered structure for ophthalmic applications are demonstrated. The polarizer-free LC lens functions as both of a positive lens and a negative lens with large aperture size of 10mm. The lens power is electrically and continuously tunable ranging from -1.32 Diopter to 1.83 Diopter. To demonstrate the polarization independency, the wavefronts of the LC lenses under different polarized light were measured and discussed. The detail operations of the applied voltage and frequency are also discussed. The imaging performance of the LC lens is also evaluated. This study provide a detail understanding of the polarizer-free LC lenses based on a double-layered structure.