Browsing by Author "Wang, Wei"

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A Novel Anti-Spoofing Solution for Iris Recognition Toward Cosmetic Contact Lens Attack Using Spectral ICA Analysis
(2018-03-01)
Hsieh, Sheng-Hsun
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Li, Yung-Hui
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Wang, Wei
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Tien, Chung-Hao
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光電工程學系
In this study, we maneuvered a dual-band spectral imaging system to capture an iridal image from a cosmetic-contact-lens-wearing subject. By using the independent component analysis to separate individual spectral primitives, we successfully distinguished the natural iris texture from the cosmetic contact lens (CCL) pattern, and restored the genuine iris patterns from the CCL-polluted image. Based on a database containing 200 test image pairs from 20 CCL-wearing subjects as the proof of concept, the recognition accuracy (False Rejection Rate: FRR) was improved from FRR = 10.52% to FRR = 0.57% with the proposed ICA anti-spoofing scheme.
Assessment of ESD Robustness in High Power Light-Emitting Diodes
(2010)
Yang, Shih-Chun
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Lin, Pang
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Fu, Han-Kuei
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Wang, Chien-Ping
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Chen, Tzung-Te
The capability of high-power nitride-based light-emitting diodes (HPLED) to withstand electrostatic discharge (ESD) is very important key index due to the horizontal structure of the insulating property of the sapphire substrate. However, it is difficult to real-time monitor the damage caused by the ESD stress because it occurred in a very short period. Current-voltage (I-V) curves and electroluminescence (EL) spectrum were applied to study the change during the series ESD stress. Time-resolved optical beam induced current (TR-OBIC) was used to analyze the characteristics of the delay time between normal region and the defect point caused by ESD stress. Transmission electron microscopy (TEM) was used to compare to the difference in the distribution of damage region and investigate the failure modes. During the series ESD stresses, V-shaped pits suffered from the high electrical field and the distance from multi-quantum well (MQW). The bottom of V-shaped defect would be one of index to assess the ESD endurance of LED chips.
Biogenesis mechanisms of circular RNA can be categorized through feature extraction of a machine learning model
(2019-12-01)
Liu, Chengyu
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Liu, Yu-Chen
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Huang, Hsien-Da
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Wang, Wei
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生物資訊及系統生物研究所
Motivation: In recent years, multiple circular RNAs (circRNA) biogenesis mechanisms have been discovered. Although each reported mechanism has been experimentally verified in different circRNAs, no single biogenesis mechanism has been proposed that can universally explain the biogenesis of all tens of thousands of discovered circRNAs. Under the hypothesis that human circRNAs can be categorized according to different biogenesis mechanisms, we designed a contextual regression model trained to predict the formation of circular RNA from a random genomic locus on human genome, with potential biogenesis factors of circular RNA as the features of the training data. Results: After achieving high prediction accuracy, we found through the feature extraction technique that the examined human circRNAs can be categorized into seven subgroups, according to the presence of the following sequence features: RNA editing sites, simple repeat sequences, self-chains, RNA binding protein binding sites and CpG islands within the flanking regions of the circular RNA back-spliced junction sites. These results support all of the previously reported biogenesis mechanisms of circRNA and solidify the idea that multiple biogenesis mechanisms co-exist for different subset of human circRNAs. Furthermore, we uncover a potential new links between circRNA biogenesis and flanking CpG island. We have also identified RNA binding proteins putatively correlated with circRNA biogenesis.
Constructing exact tolerance intervals for the exponential distribution based on record values
(1970-01-01)
Guo, Baocai
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Zhu, Naifan
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Wang, Wei
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Wang, Hsiuying
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統計學研究所
Recently, with the wide application of tolerance intervals (TIs), especially in quality management, the construction of TIs has attracted increasing attention. However, TIs applied to record data have not been well established as they have been for complete data. In many industrial stress tests, only record data are stored instead of complete data, which leads to the fact that the developments of methods based on record data are as important as those based on complete data. In this paper, we propose the exact two-sided TIs for the exponential distribution based on record values from the frequentist and Bayesian perspectives. The accuracy of each type of TIs is quantified. The results show that the Bayesian approach is superior to the frequentist approach in terms of the accuracy. A real data example is used to illustrate the constructions and implementations of the proposed TIs.
Exact two-sided tolerance interval controlling tail proportions for sample variances
(1970-01-01)
Guo, Baocai
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Zhu, Naifan
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Wang, Wei
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Song, Yurong
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Wang, Hsiuying
Tolerance intervals (TIs) for variances are useful when we are interested in the precision of the quality characteristic. They can provide a deeper understanding of the process variability corresponding to process improvement and deterioration. In this paper, we consider the exact two-sided TI for sample variances that simultaneously controls the proportions in each of the two tails of the distribution. The minimum number of subgroups required to achieve a specified level of precision is also computed. Moreover, we minimize the width of the TI through adjusting the tolerance factors, and the performance of the adjusted TI shows some improvement, especially when the amount of reference data is small. Finally, a real application is used to illustrate the construction and implementation of the proposed TIs.
Impedance Matched GaN LD Package for Direct OFDM Communication at 14 Gbps
(2016)
Huang, Yu-Fang
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Wu, Tsai-Chen
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Chi, Yu-Chieh
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Tsai, Cheng-Ting
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Wang, Wei
A transmission line aided impedance matching package for 450-nm GaN laser diode is employed to increase the directly encoded 16-QAM OFDM transmission up to 14-Gbps over 7 m in free-space after modulation throughput intensity optimization.
Modeling of switching speed and retention time in volatile resistive switching memory by ionic drift and diffusion
(2019-01-01)
Wang, Wei
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Covi, Erika
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Lin, Yu-Hsuan
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Ambrosi, Elia
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Ielmini, Daniele
The understanding of the dynamic mechanism of volatile resistive switching memory devices is of paramount importance to further increase the switching speed. It is also of great value for future neuromorphic applications which use such devices in temporal domain In this work, we investigate the switching speed and retention time of metallic filamentary volatile resistive switching devices. We find that the switching speed can be quantitatively described by the ionic mobility, while the retention time can be quantitatively described by the surface ionic diffusion following the gradient descent of surface atomic concentration. Further analysis reveals that the ionic mobility and surface diffusivity can be connected with Einstein relation. Finally, evidences supporting this relation and experimental data showing the competition of the ionic drift and diffusion are collected and shown.
Neutrino physics with JUNO
(2016-03)
An, Fengpeng
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An, Guangpeng
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An, Qi
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Antonelli, Vito
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Baussan, Eric
The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multipurpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy (MH) as a primary physics goal. The excellent energy resolution and the large fiducial volume anticipated for the JUNO detector offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. In this document, we present the physics motivations and the anticipated performance of the JUNO detector for various proposed measurements. Following an introduction summarizing the current status and open issues in neutrino physics, we discuss how the detection of antineutrinos generated by a cluster of nuclear power plants allows the determination of the neutrino MH at a 3-4 sigma significance with six years of running of JUNO. The measurement of antineutrino spectrum with excellent energy resolution will also lead to the precise determination of the neutrino oscillation parameters sin(2) theta(12), Delta m(21)(2), and vertical bar Delta m(ee)(2)vertical bar to an accuracy of better than 1%, which will play a crucial role in the future unitarity test of the MNSP matrix. The JUNO detector is capable of observing not only antineutrinos from the power plants, but also neutrinos/antineutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, and solar neutrinos. As a result of JUNO\'s large size, excellent energy resolution, and vertex reconstruction capability, interesting new data on these topics can be collected. For example, a neutrino burst from a typical core-collapse supernova at a distance of 10 kpc would lead to similar to 5000 inverse-beta-decay events and similar to 2000 all-flavor neutrino-proton ES events in JUNO, which are of crucial importance for understanding the mechanism of supernova explosion and for exploring novel phenomena such as collective neutrino oscillations. Detection of neutrinos from all past core-collapse supernova explosions in the visible universe with JUNO would further provide valuable information on the cosmic star-formation rate and the average core-collapse neutrino energy spectrum. Antineutrinos originating from the radioactive decay of uranium and thorium in the Earth can be detected in JUNO with a rate of similar to 400 events per year, significantly improving the statistics of existing geoneutrino event samples. Atmospheric neutrino events collected in JUNO can provide independent inputs for determining the MH and the octant of the theta(23) mixing angle. Detection of the Be-7 and B-8 solar neutrino events at JUNO would shed new light on the solar metallicity problem and examine the transition region between the vacuum and matter dominated neutrino oscillations. Regarding light sterile neutrino topics, sterile neutrinos with 10-(5) eV(2) < Delta m(41)(2) < 10(-2) and a sufficiently large mixing angle theta(14) could be identified through a precise measurement of the reactor antineutrino energy spectrum. Meanwhile, JUNO can also provide us excellent opportunities to test the eV-scale sterile neutrino hypothesis, using either the radioactive neutrino sources or a cyclotron-produced neutrino beam. The JUNO detector is also sensitive to several other beyondthe-standard-model physics. Examples include the search for proton decay via the p -> K++ <(v)over bar> decay channel, search for neutrinos resulting from dark-matter annihilation in the Sun, search for violation of Lorentz invariance via the sidereal modulation of the reactor neutrino event rate, and search for the effects of non-standard interactions. The proposed construction of the JUNO detector will provide a unique facility to address many outstanding crucial questions in particle and astrophysics in a timely and cost-effective fashion. It holds the great potential for further advancing our quest to understanding the fundamental properties of neutrinos, one of the building blocks of our Universe.
Pepsin-inspired polyurethanes containing a tyrosine-fumaric acid-tyrosine segment
(2012)
Lu, Haoxiang
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Wang, Wei
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Zheng, Zhen
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Sun, Peiyu
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Wang, Xinling
Two kinds of novel peptide mimetic pepsin-inspired degradable polyurethanes were synthesized and characterized. A synthetic pseudo tripeptide acted as chain extender and provided active sites for pepsin biodegradation. In vitro degradation behavior was investigated in simulated gastric fluid containing pepsin, and assessed by H-1 NMR, mass loss and SEM. The results indicated that the pseudo peptide bonds in polyurethanes were effectively digested by the action of pepsin. Furthermore, the rate and degree of pepsin-inspired polyurethanes in simulated gastric fluid containing pepsin could be controlled by alteration of the soft segments and activity of pepsin. The influence of the polymers on human umbilical vein endothelial cells was evaluated by WST-1 assay. The results indicated that the polymers sustained much higher cell viability than the controls.
THE EQUITABLE CHROMATIC THRESHOLD OF THE CARTESIAN PRODUCT OF BIPARTITE GRAPHS IS AT MOST 4
(2014-06-01)
Yan, Zhidan
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Lin, Wu-Hsiung
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Wang, Wei
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應用數學系
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Department of Applied Mathematics
A graph G is equitably k-colorable if its vertex set can be partitioned into k independent sets, any two of which differ in size by at most 1. We prove a conjecture of Lin and Chang which asserts that for any bipartite graphs G and H, their Cartesian product G square H is equitably k-colorable whenever k >= 4.
Volatile Resistive Switching Memory Based on Ag Ion Drift/Diffusion Part I: Numerical Modeling
(2019-09-01)
Wang, Wei
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Laudato, Mario
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Ambrosi, Elia
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Bricalli, Alessandro
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Covi, Erika
Resistive-switching random access memory (RRAM) devices based on filamentary switching are attracting widespread interest for their unique properties, such as high ON-OFF ratio, ultrasteep slope, good endurance, and low-current operation. Recently, volatile RRAMs based on Ag drift and diffusion were also demonstrated for possible applications such as crosspoint array selectors and neuromorphic computing. However, the mechanism of the volatile switching, namely, the spontaneous dissolution of the Ag filament, is still not clear. A deep understanding of the metallic filament formation and spontaneous disruption would strongly help the engineering of the device for optimized performances. Here, we present a numerical physics-based drift/diffusion modeling framework to describe the threshold switching, I-V characteristics, and morphological evolution of the metallic filament. The model can support TCAD-type device simulations for scaling, reliability, and variability studies.
Volatile Resistive Switching Memory Based on Ag Ion Drift/Diffusion-Part II: Compact Modeling
(2019-09-01)
Wang, Wei
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Laudato, Mario
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Ambrosi, Elia
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Bricalli, Alessandro
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Covi, Erika
Resistive-switching random access memory (RRAM) based on Cu or Ag filament is a promising selector device for high-density crosspoint arrays. These devices display high ON-OFF ratio, volatile switching, high switching speed, and long endurance, supporting the adoption in large memory arrays. However, the mechanism of volatile switching is not clear yet, which prevents the development of compact models for circuit design and simulation. Based on an extensive study of the switching mechanism, we report an analytical model that captures all electrical characteristics of the device, including switching, recovery, and their dependence on the applied voltage. We use the analytical model to simulate the circuit-level behavior of the device as long/short term memory synapse.