Browsing by Author "Tsai, Yu-Ting"

Now showing 1 - 19 of 19

Adaptive sampling approach for volumetric shadows in dynamic scenes
(2013-11-01)
Lin, Hsiang-Yu
;
Chang, Chin-Chen
;
Tsai, Yu-Ting
;
Way, Der-Lor
;
Shih, Zen-Chung
Ray marching is an important technique to generate volumetric lighting effects. However, it is very expensive for each pixel on the screen, especially in dynamic scenes. The authors propose an adaptive approach to reduce samples for volumetric shadows in the time domain. In dynamic scenes, shadow volumes of moving objects are created and are rasterised to decide pixels that cannot be reused. The authors use a stencil buffer to maintain the information of screen pixels by recomputing or just using the previous information. Experimental results show that the proposed approach is simple to implement. Moreover, compared to the previous method, the proposed approach achieves a specific speedup and maintains similar visual quality.
All-frequency precomputed radiance transfer using spherical radial basis functions and clustered tensor approximation
(2006-07-01)
Tsai, Yu-Ting
;
Shih, Zen-Chung
;
資訊工程學系
;
Department of Computer Science
This paper introduces a new data representation and compression technique for precomputed radiance transfer (PRT). The light transfer functions and light sources are modeled with spherical radial basis functions (SRBFs). A SRBF is a rotation-invariant function that depends on the geodesic distance between two points on the unit sphere. Rotating functions in SRBF representation is as straightforward as rotating the centers of SRBFs. Moreover, high-frequency signals are handled by adjusting the bandwidth parameters of SRBFs. To exploit inter-vertex coherence, the light transfer functions are further classified iteratively into disjoint clusters, and tensor approximation is applied within each cluster. Compared with previous methods, the proposed approach enables real-time rendering with comparable quality under high-frequency lighting environments. The data storage is also more compact than previous all-frequency PRT algorithms.
Carrier Transport and Multilevel Switching Mechanism for Chromium Oxide Resistive Random-Access Memory
(2011)
Chen, Shih-Cheng
;
Chang, Ting-Chang
;
Chen, Shih-Yang
;
Li, Hung-Wei
;
Tsai, Yu-Ting
This article investigates the carrier transport phenomenon and multilevel switching mechanism of Cr(2)O(3)-based resistive random access memory (RRAM) with Pt/Cr(2)O(3)/TiN structure. Before the forming process, the interfacial Schottky barrier dominates the carrier transport. The barrier heights of Pt/Cr(2)O(3) and Cr(2)O(3)/TiN are 0.7 and 0.96 eV, respectively. After the forming process, RRAM at a low resistance state follows the Ohmic conduction. While RRAM is switched to a high resistance state during the reset process, the Frenkel-Poole emission becomes a dominant conduction mechanism. The multilevel resistance states were achieved by applying corresponding reset voltages to the device for controlling the trap levels of the Cr(2)O(3) layer. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3518710] All rights reserved.
Clip Space Sample Culling for Motion Blur and Defocus Blur
(2015-05-01)
Wu, Yi-Jeng
;
Way, Der-Lor
;
Tsai, Yu-Ting
;
Shih, Zen-Chung
;
多媒體工程研究所
Motion blur and defocus blur are two common visual effects for rendering realistic camera images. This paper presents a novel clip space culling for stochastic rasterization to render motion and defocus blur effects. Our proposed algorithm reduces the sample coverage using the clip space information in camera lens domain (UV) and time domain (T). First, samples outside the camera lens were culled in stage I using the linear relationship between camera lens and vertex position. Second, samples outside the time bounds were culled in stage II using the triangle similarity in clip space to find the intersection time. Each pixel was computed within two linear bounds only once. Our method achieves good sample test efficiency with low computation cost for real-time stochastic rasterization. Finally, the proposed method is demonstrated by means of various experiments, and a comparison is made with previous works. Our algorithm was able to handle these two blur effects simultaneously and performed better than others did.
Deformation Simulation Based on Model Reduction with Rigidity Sampling
(2017-01-01)
Chien, Shuo-Ting
;
Hu, Chen-Hui
;
Huang, Cheng-Yang
;
Tsai, Yu-Ting
;
Lin, Wen-Chieh
Deformation simulation based on model reduction with rigidity-guided sampling
(2018-06-01)
Chien, Shuo-Ting
;
Hu, Chen-Hui
;
Huang, Cheng-Yang
;
Tsai, Yu-Ting
;
Lin, Wen-Chieh
The deformation results of previous model reduction methods with external forces applied show noticeable differences from full-scale finite element method (FEM) simulation. We found that data-driven approaches, specifically proper orthogonal decomposition, can be a solution to this nonlinear deformation simulation problem in the subspace. Nevertheless, off-line FEM simulation with an infinite number of possible input forces at different locations makes it infeasible if no prior information is given. We propose rigidity-guided sampling to efficiently select the points of application of forces (force sample points) to construct more effective and compact subspace bases, thereby improving the simulation accuracy of reduced deformable models with applied external forces and still retaining fast run-time performance. The key idea of our approach is that distinct deformations of an object at different force sample points can be estimated prior to FEM simulation. By selecting the force sample points with distinct deformations, the computational cost of off-line FEM simulation can be reduced significantly. Our run-time deformation results are much closer to the full-scale FEM simulation with external forces applied, compared to the results of using only the modal derivative bases while the speedup over full-scale simulation is still substantial.
Development and Fabrication of AlGaInP-Based Flip-Chip Micro-LEDs
(2018-01-01)
Horng, Ray-Hua
;
Chien, Huan-Yu
;
Chen, Ken-Yen
;
Tseng, Wei-Yu
;
Tsai, Yu-Ting
The fabrication of AlGaInP-based flip-chip micro light-emitting-diodes (LED; emitting area: 4.5 mil x 5 mil) with horizontal electrodes is reported in this paper. The thickness of the epitaxial layer of the thin LED structure was reduced to 50% of that of the traditional thick LED, whereas carrier concentration in the n-type GaAs contact layer was increased to 5 x 10(18) cm(-3) to meet the Ohmic contact requirement. At a current injection of 5 mA, the thin LED exhibited a forward voltage, output power, and external quantum efficiency of 1.8 V, 1.9 mW, and 19%, respectively. The optoelectronic performance of the thin LED was as good as that of the traditional thick red LED. The technique proposed by this paper can be used to integrate AlGaInP-based LEDs with nitride LEDs for full-color display applications.
Developments in nanocrystal memory
(2011-12-01)
Chang, Ting-Chang
;
Jian, Fu-Yen
;
Chen, Shih-Cheng
;
Tsai, Yu-Ting
;
電子工程學系及電子研究所
Since the 1990s, portable electronic products have been a prominent part of our daily lives; and many of these devices require flash memories. The floating-gate (FG) structure, invented by Sze and Kahng at Bell Labs in 1967, forms the primary technology necessary to construct flash memories(1), Fig. 1a. In order to meet the demands of product miniaturization, the shrinking of transistors has evolved as a method to not only pack more devices into a given area, but also improve the switching speed. In such a situation, conventional nonvolatile memory (FG) suffers from certain physical limitations, such as an insufficient tunneling oxide thickness from the continual scaling down of the device structures(2). Because the floating gate (as a charge storing layer) is conductive, all charge will be lost if a leakage path appears in the tunneling oxide, resulting in a serious reliability issue for memory applications. Discrete nanocrystal memory was first proposed by IBM in 1995, and by the early 2000s researchers were already considering it to be a promising candidate for the solution of the scaling problem(3) (Fig. 1b). In addition, nanocrystal memory has a two bit per cell storage capability due to its discrete electron storing center. This means that more data can be stored in one memory cell, which readily increases the memory density(4).
Effect of Top Electrode Material on Resistive Switching Characteristics in MnO2 Nonvolatile Memory Devices
(2011)
Tsai, Yu-Ting
;
Chang, Ting-Chang
;
Lin, Chao-Cheng
;
Chiang, Lan-Shin
;
Chen, Shih-Cheng
The influence of top electrode material on the resistive switching properties of MnO2-based memory film using Pt as a bottom electrode was investigated in this study. In comparison with Pt/MnO2/Pt and Al/ MnO2/Pt devices, the Ti/ MnO2/Pt device exhibits resistive switching current-voltage (I-V) curve, which can be traced and reproduced more than 10(5) times only showing a little decrease of resistance ratio between high and low resistance states. Furthermore, transmission electron microscopy analyses are used to confirm the crystalline structure of MnO2 on Pt bottom electrode. Secondary ion mass spectrometry reveals a change of oxygen distribution in MnO2 thin film due to material characteristic of variant top electrodes. We suggest that the interface between MnO2 and electrodes play an important role on the resistive switching behaviors.
Exemplar-based freckle retouching and skin tone adjustment
(2019-02-01)
Lin, Tsung-Ying
;
Tsai, Yu-Ting
;
Huang, Tsung-Shian
;
Lin, Wen-Chieh
;
Chuang, Jung-Hong
This paper presents a novel system for freckle retouching and skin tone adjustment based on a set of exemplar image pairs obtained before and after cosmetic laser therapy. Our key observation is that cosmetic laser therapy relies on decomposing and adjusting melanin and hemoglobin to change skin appearance, and the reflectance properties of the two pigments can greatly influence human skin color. We thus retouch freckles and adjust skin tone in a query image by changing the densities of melanin and hemoglobin to match the variation of those in the exemplar image pairs. Based on the proposed system, we can easily and intuitively generate an output image that looks similar to the results of cosmetic laser therapy. Our system also can detect more skin flaws and define their regions more accurately than previous retouching methods. (C) 2018 Elsevier Ltd. All rights reserved.
Generating Pointillism Paintings Based on Seurat's Color Composition
(2013-06-01)
Wu, Yi-Chian
;
Tsai, Yu-Ting
;
Lin, Wen-Chieh
;
Li, Wen-Hsin
;
資訊工程學系
This paper presents a novel example-based stippling technique that employs a simple and intuitive concept to convert a color image into a pointillism painting. Our method relies on analyzing and imitating the color distributions of Seurat's paintings to obtain a statistical color model. Then, this model can be easily combined with the modified multi-class blue noise sampling to stylize an input image with characteristics of color composition in Seurat's paintings. The blue noise property of the output image also ensures that the color points are randomly located but remain spatially uniform. In our experiments, the multivariate goodness-of-fit tests were adopted to quantitatively analyze the results of the proposed and previous methods, further confirming that the color composition of our results are more similar to Seurat's painting style than that of previous approaches. Additionally, we also conducted a user study participated by artists to qualitatively evaluate the synthesized images of the proposed method.
Importance sampling of products from illumination and BRDF using spherical radial basis functions
(2008-07-01)
Tsai, Yu-Ting
;
Chang, Chin-Chen
;
Jiang, Qing-Zhen
;
Weng, Shr-Ching
;
資訊工程學系
In this paper, a new approach for the importance sampling of products from a complex high dynamic range (HDR) environment map and measured bidirectional reflectance distribution function (BRDF) data using spherical radial basis functions (SRBFs) is presented. In the pre-process, a complex HDR environment map and measured BRDF data are transformed into a scattered SRBF representation by using a non-uniform and non-negative SRBF fitting algorithm. An initial guess is determined for the fitting operation. In the run-time rendering process, after the product of the two SRBFs is evaluated, this is used to guide the number of samples. The sampling is done by mixing samples from the various "product" SRBFs using multiple importance sampling. Hence, the proposed approach efficiently renders images with multiple HDR environment maps and measured BRDFs.
Influence of Nanocrystals on Resistive Switching Characteristic in Binary Metal Oxides Memory Devices
(2011)
Tsai, Yu-Ting
;
Chang, Ting-Chang
;
Lin, Chao-Cheng
;
Chen, Shih-Cheng
;
Chen, Chi-Wen
The resistive random access memory has attracted much attention for nonvolatile memory application in recent years. However, there is an issue about variations of switching parameters such as set voltage and conductivity of resistance state in resistive switching memory. The variations may cause not only switching error but also reading error during operation. We investigated the switching performance of binary metal oxide as a resistive switching layer embedded with and without metal nanocrystals. Compared with the conventional memory structure, the memory embedded with metal nanocrystals shows better stability, preferable uniformity for the next generation nonvolatile memory application. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3531843] All rights reserved.
Investigation for coexistence of dual resistive switching characteristics in DyMn(2)O(5) memory devices
(2011-08-29)
Tsai, Yu-Ting
;
Chang, Ting-Chang
;
Huang, Wei-Li
;
Huang, Chih-Wen
;
Syu, Yong-En
Dual bipolar resistive switching characteristics were observed in the Pt/DyMn(2)O(5)/TiN memory devices. The typical switching effect could be attributed to the formation and rupture of the conducting filament in DyMn(2)O(5) films. The parasitic switching behavior can be observed in the specific operation condition. Dual bipolar resistance switching behaviors of filament-type and interface-type can coexist in the devices by appropriate voltage operation. The operating current can be significantly decreased (100 times) by parasitic switching operation for portable electronic product application. In addition, the relationship between filament-type and interface-type switching behaviors were studied in this paper. (C) 2011 American Institute of Physics. [doi:10.1063/1.3629788]
Investigation for coexistence of dual resistive switching characteristics in DyMn2O5 memory devices
(2011-08-29)
Tsai, Yu-Ting
;
Chang, Ting-Chang
;
Huang, Wei-Li
;
Huang, Chih-Wen
;
Syu, Yong-En
Dual bipolar resistive switching characteristics were observed in the Pt/DyMn2O5/TiN memory devices. The typical switching effect could be attributed to the formation and rupture of the conducting filament in DyMn2O5 films. The parasitic switching behavior can be observed in the specific operation condition. Dual bipolar resistance switching behaviors of filament-type and interface-type can coexist in the devices by appropriate voltage operation. The operating current can be significantly decreased (100 times) by parasitic switching operation for portable electronic product application. In addition, the relationship between filament-type and interface-type switching behaviors were studied in this paper. (C) 2011 American Institute of Physics. [doi:10.1063/1.3629788]
K-Clustered Tensor Approximation: A Sparse Multilinear Model for Real-Time Rendering
(2012-05-01)
Tsai, Yu-Ting
;
Shih, Zen-Chung
;
資訊工程學系
;
Department of Computer Science
With the increasing demands for photo-realistic image synthesis in real time, we propose a sparse multilinear model, which is named K-Clustered Tensor Approximation (K-CTA), to efficiently analyze and approximate large-scale multidimensional visual datasets, so that both storage space and rendering time are substantially reduced. K-CTA not only extends previous work on Clustered Tensor Approximation (CTA) to exploit inter-cluster coherence, but also allows a compact and sparse representation for high-dimensional datasets with just a few low-order factors and reduced multidimensional cluster core tensors. Thus, K-CTA can be regarded as a sparse extension of CTA and a multilinear generalization of sparse representation. Experimental results demonstrate that K-CTA can accurately approximate spatially varying visual datasets, such as bidirectional texture functions, view-dependent occlusion texture functions, and biscale radiance transfer functions for efficient rendering in real-time applications.
Modeling Bidirectional Texture Functions with Multivariate Spherical Radial Basis Functions
(2011-07-01)
Tsai, Yu-Ting
;
Fang, Kuei-Li
;
Lin, Wen-Chieh
;
Shih, Zen-Chung
;
資訊工程學系
This paper presents a novel parametric representation for bidirectional texture functions. Our method mainly relies on two original techniques, namely, multivariate spherical radial basis functions (SRBFs) and optimized parameterization. First, since the surface appearance of a real-world object is frequently a mixed effect of different physical factors, the proposed sum-of-products model based on multivariate SRBFs especially provides an intrinsic and efficient representation for heterogenous materials. Second, optimized parameterization particularly aims at overcoming the major disadvantage of traditional fixed parameterization. By using a parametric model to account for variable transformations, the parameterization process can be tightly integrated with multivariate SRBFs into a unified framework. Finally, a hierarchical fitting algorithm for bidirectional texture functions is developed to exploit spatial coherence and reduce computational cost. Our experimental results further reveal that the proposed representation can easily achieve high-quality approximation and real-time rendering performance.
Study of Electric Faucet Structure by Embedding Co Nanocrystals in a FeOx-Based Memristor
(2012)
Chang, Yao-Feng
;
Tsai, Yu-Ting
;
Syu, Yong-En
;
Chang, Ting-Chang
;
電子工程學系及電子研究所
The electric faucet concept was realized and demonstrated by embedding cobalt nanocrystals in a TiN/SiO2/FeOx/FePt structure. The thermal annealing induced cobalt nanocrystals in silicon oxide would shrink both the operation voltage and variation as well as improves the electric faucet stability. The thickness effect and area size effect would be discussed, which indicated the optimized design and possible resistive switching mechanism for the FeOx-based memristor. The improvement of resistive switching stabilities and switching power characteristics show that the embedded nanocrystals in the insulating layer would localize the electric faucet formation and rupture at interface region. Importantly, a proposed mathematical model to describe the compliance current effect shows that the electric faucet was grown in two dimensions. These electrical results not only provide a possible physical picture to image the dynamic characteristics of the electric faucet's growth, but also introduce a possible mathematical method to quantify the electric faucet properties. (C) 2012 The Electrochemical Society. All rights reserved.
Study of Resistive Switching Characteristics on a Temperature-Sensitive FeOx-Transition Layer in a TiN/SiO2/FeOx/Fe Structure
(2012)
Chang, Yao-Feng
;
Tsai, Yu-Ting
;
Chang, Geng-Wei
;
Syu, Yong-En
;
Tai, Ya-Hsiang
Thermal annealing effect and high temperature electrical measurement were studied on a temperature-sensitive FeOx-transition layer of a TiN/SiO2/FeOx/Fe structure, including bipolar switching behaviors, statistics of set and reset electrical characteristics, endurance and retention. Increase of the thermal budget on the structure shrinks both the operation voltage and variation as well as improving the device operation stability and power dissipation. Cross-sectional image, crystallinity and chemical composition analyzes of the FeOx-transition layer were examined by transmission electron microscope, X-ray diffraction and X-ray photon-emission spectra depth profiles, respectively. In addition, for the temperature-sensitive FeOx-containing structure, the resistive switching behaviors and characteristics were also investigated at room temperature and 85 degrees C. These resistive switching behaviors indicate the possible resistive switching mechanism and electrical characteristics, providing a better understanding for the temperature-sensitive FeOx-based memristors. (C) 2012 The Electrochemical Society. All rights reserved.