Browsing by Author "Liu, Yang"

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110 GHz hybrid mode-locked fiber laser with enhanced extinction ratio based on nonlinear silicon-on-insulator micro-ring-resonator (SOI MRR)
(2016-03)
Liu, Yang
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Hsu, Yung
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Chow, Chi-Wai
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Yang, Ling-Gang
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Yeh, Chien-Hung
We propose and experimentally demonstrate a new 110 GHz high-repetition-rate hybrid mode-locked fiber laser using a silicon-on-insulator microring-resonator (SOI MRR) acting as the optical nonlinear element and optical comb filter simultaneously. By incorporating a phase modulator (PM) that is electrically driven at a fraction of the harmonic frequency, an enhanced extinction ratio (ER) of the optical pulses can be produced. The ER of the optical pulse train increases from 3 dB to 10 dB. As the PM is only electrically driven by the signal at a fraction of the harmonic frequency, in this case 22 GHz (110 GHz/5 GHz), a low bandwidth PM and driving circuit can be used. The mode-locked pulse width and the 3 dB spectral bandwidth of the proposed mode-locked fiber laser are measured, showing that the optical pulses are nearly transform limited. Moreover, stability evaluation for an hour is performed, showing that the proposed laser can achieve stable mode-locking without the need for optical feedback or any other stabilization mechanism.
2.333-Tbit/s bi-directional optical mobile networks using optical wireless communication (OWC)
(2020-11-15)
Wei, Liang-Yu
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Chen, Shu-, I
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Yeh, Chien-Hung
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Liu, Yang
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Chen, Guan-Hong
We propose and experimentally demonstrate a 2.333-Tbit/s bi-directional optical mobile network using optical wireless communication (OWC). The proposed network architecture is divided into: fronthaul network con-necting between the distributed-unit (DU) and the remote-radio-unit (RRU); and midhaul network connecting between the central unit (CU) and the DU. At the midhaul, an aggregated 2.333-Tbit/s transmission is achieved using wavelength division multiplexed (WDM) infrared (IR) based invisible light communication (IVLC). For the link between the RRU and user-equipment (UE), 2.7 Gbit/s white-light visible-light-communication (VLC) transmission is achieved for indoor 1.5 m transmission. It can provide communication and lighting simultaneously. A gateway (GW) is also proposed acting as the interface between the IVLC and VLC transmissions. In the proposed architecture, about 400 VLC end-users can be supported.
A fracture energy based damage-plasticity interfacial constitutive law for discrete finite element modelling of masonry structures
(2019-08-01)
Yuen, Terry Y. P.
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Deb, Trissa
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Zhang, Hanhui
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Liu, Yang
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土木工程學系
The robust structural design relies on the accuracy of the response analysis to different loadings. Strut-and-tie models and continuum models are often used for the design of masonry structures but they are generally not able to simulate detailed damage and progressive collapse. To this regard, this paper presents a new and robust interfacial constitutive law, which couples the damage and plastic deformation with fracture energy-based softening rules, for the discrete finite element modelling (DFEM) of masonry structures. The model has 14 required parameters and 2 optional parameters of which calibration methods using the standard test data and physical rules are provided in details. It was demonstrated that the comprehensive mechanical behaviour including the pressure-dependent fracture, wearing-off of the friction, dilatation, stiffness degradation, shear retention, and component disintegration can be well captured. The model validation studies were performed with various material and structural tests including shear-compression and uniaxial tension tests on the joints, and horizontal loading and shake-table tests on large-scale masonry structures. Good agreements between the simulated and experimental results could be observed. Comparing to conventional modelling approaches, the DFEM with the interfacial constitutive law can also simply the meshing work and better control the mesh quality. (C) 2019 Elsevier Ltd. All rights reserved.
Activity and Metabolic Versatility of Complete Ammonia Oxidizers in Full-Scale Wastewater Treatment Systems
(2020-03-01)
Yang, Yuchun
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Daims, Holger
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Liu, Yang
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Herbold, Craig W.
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Pjevac, Petra
The recent discovery of complete ammonia oxidizers (comammox) contradicts the paradigm that chemolithoautotrophic nitrification is always catalyzed by two different microorganisms. However, our knowledge of the survival strategies of comammox in complex ecosystems, such as full-scale wastewater treatment plants (WWTPs), remains limited. Analyses of genomes and in situ transcriptomes of four comammox organisms from two full-scale WWTPs revealed that comammox were active and showed a surprisingly high metabolic versatility. A gene cluster for the utilization of urea and a gene encoding cyanase suggest that comammox may use diverse organic nitrogen compounds in addition to free ammonia as the substrates. The comammox organisms also encoded the genomic potential for multiple alternative energy metabolisms, including respiration with hydrogen, formate, and sulfite as electron donors. Pathways for the biosynthesis and degradation of polyphosphate, glycogen, and polyhydroxyalkanoates as intracellular storage compounds likely help comammox survive unfavorable conditions and facilitate switches between lifestyles in fluctuating environments. One of the comammox strains acquired from the anaerobic tank encoded and transcribed genes involved in homoacetate fermentation or in the utilization of exogenous acetate, both pathways being unexpected in a nitrifying bacterium. Surprisingly, this strain also encoded a respiratory nitrate reductase which has not yet been found in any other Nitrospira genome and might confer a selective advantage to this strain over other Nitrospira strains in anoxic conditions. IMPORTANCE The discovery of comammox in the genus Nitrospira changes our perception of nitrification. However, genomes of comammox organisms have not been acquired from full-scale WWTPs, and very little is known about their survival strategies and potential metabolisms in complex wastewater treatment systems. Here, four comammox metagenome-assembled genomes and metatranscriptomic data sets were retrieved from two full-scale WWTPs. Their impressive and-among nitrifiers-unsurpassed ecophysiological versatility could make comammox Nitrospira an interesting target for optimizing nitrification in current and future bioreactor configurations.
Adaptive filtering for white-light LED visible light communication
(2017-01)
Hsu, Chin-Wei
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Chen, Guan-Hong
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Wei, Liang-Yu
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Chow, Chi-Wai
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Lu, I-Cheng
White-light phosphor-based light-emitting diode (LED) can be used to provide lighting and visible light communication (VLC) simultaneously. However, the long relaxation time of phosphor can reduce the modulation bandwidth and limit the VLC data rate. Recent VLC works focus on improving the LED modulation bandwidths. Here, we propose and demonstrate the use of adaptive Volterra filtering (AVF) to increase the data rate of a white-light LED VLC system. The detailed algorithm and implementation of the AVF for the VLC system have been discussed. Using our proposed electrical frontend circuit and the proposed AVF, a significant data rate enhancement to 700.68 Mbit/s is achieved after 1-m free-space transmission using a single white-light phosphor-based LED. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Adaptive filtering for white-light LED visible light communication
(2017-01-01)
Hsu, Chin-Wei
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Chen, Guan-Hong
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Wei, Liang-Yu
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Chow, Chi-Wai
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Lu, I-Cheng
White-light phosphor-based light-emitting diode (LED) can be used to provide lighting and visible light communication (VLC) simultaneously. However, the long relaxation time of phosphor can reduce the modulation bandwidth and limit the VLC data rate. Recent VLC works focus on improving the LED modulation bandwidths. Here, we propose and demonstrate the use of adaptive Volterra filtering (AVF) to increase the data rate of a white-light LED VLC system. The detailed algorithm and implementation of the AVF for the VLC system have been discussed. Using our proposed electrical frontend circuit and the proposed AVF, a significant data rate enhancement to 700.68 Mbit/s is achieved after 1-m free-space transmission using a single white-light phosphor-based LED. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Analysis of Non-Hermitian symmetry (NHS) IFFT/FFT size efficient OFDM for multiple-client non-orthogonal multiple access (NOMA) visible light communication (VLC) system
(2020-10-01)
Adnan, Assaidah
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Liu, Yang
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Chow, Chi-Wai
;
Yeh, Chien-Hung
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交大名義發表
Orthogonal-frequency-division-multiplexing (OFDM) format is widely deployed in visible-light-communication (VLC) systems due to its high spectral efficiency. To produce real-valued OFDM signal for VLC, Hermitian-symmetry (HS) is needed during the inverse-fast-Fourier-transform (IFFT) encoding process. However the HS requirement doubles the IFFT/FFT size and increase the encoding complexity. Non-Hermitian symmetry (NHS)-OFDM schemes are proposed, but they have different limitations. In this work, we propose and investigate a non-orthogonal multiple access (NOMA) VLC network serving 2, 3 or 4 clients simultaneously using NHS-OFDM IFFT/FFT size efficient (SE) OFDM format. Numerical analysis of signal amplitude effect to the bit-error-ratio (BER) performance for different users are performed, showing that the BER < 7% forward-error-correction (FEC) limit can be achieved as long as the required signal amplitude ratio of each user is fulfilled. We also compare the proposed system with a typical example of HS-OFDM modulation, i.e. direct-current optical (DCO)-OFDM NOMA-VLC system.
Angle-of-Arrival (AOA) Visible Light Positioning (VLP) System Using Solar Cells With Third-Order Regression and Ridge Regression Algorithms
(2020-06-01)
Hong, Chong-You
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Wu, Yu-Chun
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Liu, Yang
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Chow, Chi-Wai
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Yeh, Chien-Hung
We put forward and demonstrate a angle-of-arrival (AOA) based visible-light-positioning (VLP) system using quadrant-solar-cell (QSC) and third-order ridge regression machine learning (RRML) to improve the positioning accuracy.
CMOS camera based visible light communication (VLC) using grayscale value distribution and machine learning algorithm
(2020-01-20)
Hsu, Ke-Ling
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Wu, Yu-Chun
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Chuang, Yu-Cheng
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Chow, Chi-Wai
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Liu, Yang
We demonstrate a visible light communication (VLC) system using light emitting diode (LED) backlight display panel and mobile-phone complementary-metal-oxide-semiconductor (CMOS) camera. The panel is primarily used for displaying advertisements. By modulating its backlight, dynamic contents (i.e. secondary information) can be transmitted wirelessly to users based on rolling shutter effect (RSE) of the CMOS camera. As different display content will be displayed on the panel, the VLC performance is significantly limited if the noise-ratio (NR) is too high. Here, we propose and demonstrate a CMOS RSE pattern demodulation scheme using grayscale value distribution (GVD) and machine learning algorithm (MLA) to significantly enhance the demodulation. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Comparison of thresholding schemes for visible light communication using mobile-phone image sensor
(2016-02-08)
Liu, Yang
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Chow, Chi-Wai
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Liang, Kevin
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Chen, Hung-Yu
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Hsu, Chin-Wei
Based on the rolling shutter effect of the complementary metal-oxide-semiconductor (CMOS) image sensor, bright and dark fringes can be observed in each received frame. By demodulating the bright and dark fringes, the visible light communication (VLC) data logic can be retrieved. However, demodulating the bright and dark fringes is challenging as there is a high data fluctuation and large extinction ratio (ER) variation in each frame due. Hence proper thresholding scheme is needed. In this work, we propose and compare experimentally three thresholding schemes; including third-order polynomial curve fitting, iterative scheme and quick adaptive scheme. The evaluation of these three thresholding schemes is performed. (C) 2016 Optical Society of America
Cost-Effective Mobile Backhaul Network Using Existing ODN of PONs for the 5G Wireless Systems
(2015-12-01)
Sung, Jiun-Yu
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Chow, Chi-Wai
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Yeh, Chien-Hung
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Liu, Yang
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Chang, Gee-Kung
An optical distribution network (ODN) sharing scheme to integrate mobile backhaul networks with the existing passive optical network (PON) systems is proposed and demonstrated. With the ODN sharing scheme, the expense of building new fibers for the next-generation fifth-generation (5G) mobile backhaul networks can be reduced. As many wavelengths are allocated to the already deployed PON systems, there remain limited wavelengths for the mobile backhaul systems. Hence, to efficiently increase the serving cell sites of the 5G systems, spectral-efficient orthogonal frequency-division multiplexing (OFDM) is adopted in the mobile backhaul systems. In order to reduce the latency of the system, adaptive adjustment of the OFDM signals for different transmission distances is averted. The OFDM signals are transmitted only using specific available bandwidth. The available bandwidth for each wavelength is studied according to the power fading relationship between the transmission distances and the chirp induced from signal modulation. A proof-of-concept demonstration experiment has been performed. In our results, 20.17 Gb/s with a bit error rate (BER) lower than 3.8 x 10(-3) was realized with a split ratio of 256 and a 40-km transmission distance of the PON ODN. Hence, each wavelength can support about 20, six, and two nodes for the IMT-advanced, current Long-Term Evolution-Advanced (LTE-A) systems, and the expected 5G systems, respectively.
Demonstration of Non-Hermitian Symmetry (NHS) IFFT/FFT Size Efficient OFDM Non-Orthogonal Multiple Access (NOMA) for Visible Light Communication
(2020-06-01)
Assaidah, Assaidah
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Liu, Yang
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Chow, Chi-Wai
;
Yeh, Ching-Hua
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交大名義發表
We propose and experimentally demonstrate a non-orthogonal multiple access (NOMA) visible light communication (VLC) system using non-Hermitian symmetry (NHS) inverse-fast-Fourier-transform (IFFT)/FFT size efficient (SE) orthogonal frequency division multiplexing (OFDM). Fix power allocation and successive interference cancellation (SIC) algorithms are realized. The power ratio between different users, transmission distance, network cell coverage are investigated. The proposed scheme is also compared with the HS based direct-current optical (DCO)-OFDM NOMA-VLC system.
Demonstration of Using Digital FIR Filter and Matched Filter to Increase Data Rate in Visible Light Communication
(2013)
Liu, Yu-Feng
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Yeh, Chien-Hung
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Chow, Chi-Wai
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Huang, Po-Yen
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Liu, Yang
Using digital-filters in time domain are demonstrated to enhance the modulation-speed of 1 MHz bandwidth white LED communication. Digital FIR filter and matched filtering are used to reduce the inter-symbol-interference (ISI). Hence, 20-Mbps is achieved by using 4-ASK modulation.
Digital Signal Processing for Visible Light Communication Applications
(2019-01-01)
Chow, Chi-Wai
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Chen, Guan-Hong
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Peng, Ching-Wei
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Wei, Liang-Yu
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Yeh, Chien-Hung
We reviewed our resent works using digital-signal-processing (DSP) techniques to improve visible-light-communication (VLC). A rolling-shutter-effect (RSE) light-panel and CMOS image-sensor based VLC and a visible-light-positioning (VLP) system using machine learning are discussed.
Efficient demodulation scheme for rolling-hutter-patterning of CMOS image sensor based visible light communications
(2017-10-02)
Chen, Chia-Wei
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Chow, Chi-Wai
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Liu, Yang
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Yeh, Chien-Hung
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光電工程學系
Recently even the low-end mobile-phones are equipped with a high-resolution complementary-metal-oxide-semiconductor (CMOS) image sensor. This motivates using a CMOS image sensor for visible light communication (VLC). Here we propose and demonstrate an efficient demodulation scheme to synchronize and demodulate the rolling shutter pattern in image sensor based VLC. The implementation algorithm is discussed. The bit-error-rate (BER) performance and processing latency are evaluated and compared with other thresholding schemes. (C) 2017 Optical Society of America
High Speed Imaging 3 x 3 MIMO Phosphor White-Light LED Based Visible Light Communication System
(2016-12-01)
Hsu, Chin-Wei
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Chow, Chi-Wai
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Lu, I-Cheng
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Liu, Yen-Liang
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Yeh, Chien-Hung
The phosphor light-emitting diode (LED) has been widely used not only for indoor illumination but for the optical transmitter (Tx) as well in visible light communication (VLC). However, the transmission data rate is significantly limited by the modulation bandwidth of LED because of the low-speed response of phosphor. In order to enhance the data rate of the VLC system, we demonstrate a 3 x 3 imaging multiple-input multiple-output (MIMO) VLC system. Besides, the pre-equalizer circuit is used to extend the bandwidth of the LED Tx. Orthogonal frequency division multiplexing (OFDM) with bit-loading algorithm is used. By using the proposed scheme, the original 1 MHz bandwidth commercially available phosphor white light LED can achieve 1 Gbps data rate over 1-m free-space transmission distance.
Leveraging Strategic Detection Techniques for Smart Home Pricing Cyberattacks
(2016-03-04)
Liu, Yang
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Hu, Shiyan
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Ho, Tsung-Yi
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資訊工程學系
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Department of Computer Science
In this work, the vulnerability of the electricity pricing model in the smart home system is assessed. Two closely related pricing cyberattacks which manipulate the guideline electricity prices received at smart meters are considered and they aim at reducing the expense of the cyberattacker and increasing the peak energy usage in the local community. A single event detection technique which uses support vector regression and impact difference for detecting anomaly pricing is proposed. The detection capability of such a technique is still limited since it does not model the long term impact of pricing cyberattacks. This motivates us to develop a partially observable Markov decision process based detection algorithm, which has the ingredients such as reward expectation and policy transfer graph to account for the cumulative impact and the potential future impact due to pricing cyberattacks. Our simulation results demonstrate that the pricing cyberattack can reduce the cyberattacker\'s bill by 34.3 percent at cost of the increase of others\' bill by 7.9 percent, and increase the peak to average ratio (PAR) by 35.7 percent. Furthermore, the proposed long term detection technique has the detection accuracy of more than 97 percent with significant reduction in PAR and bill compared to repeatedly using the single event detection technique.
Light Encryption Scheme Using Light-Emitting Diode and Camera Image Sensor
(2016-02-01)
Liu, Yang
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Liang, Kevin
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Chen, Hung-Yu
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Wei, Liang-Yu
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Hsu, Chin-Wei
Visible light communication (VLC) is regarded as relatively secure communication when compared with other wireless communications using radio frequency (RF). However, due to the visual nature, the VLC signals are still subject to eavesdropping when they are emitted by the light source. Here, we propose a light encryption scheme using devices having light-emitting diode (LED) and a camera image sensor, such as a mobile phone. The original visible signal sending from the lamp can be first received by the proposed light encrypter. The information can be encrypted and then emitted. The light encrypter acts as an encryption gateway for signals in optical domain. The rolling shutter effect of the complementary metal-oxide semiconductor (CMOS) camera in the mobile phone can be used. By demodulating the rolling shutter pattern, the data information can be obtained. We also propose and demonstrate using the Otsu thresholding scheme to define the data logic in the rolling shutter pattern. We show that the Otsu scheme is effective for estimating the bit error rate (BER). The optimum number of intervals (segmentations) and the process time of the Otsu method are also studied.
Long distance non-line-of-sight (NLOS) visible light signal detection based on rolling-shutter-patterning of mobile-phone camera
(2017-05-01)
Wang, Wei-Chung
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Chow, Chi-Wai
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Wei, Liang-Yu
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Liu, Yang
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Yeh, Chien-Hung
We propose and demonstrate a long distance non-line-of-sight (NLOS) visible light signal detection based on the rolling shutter patterning using commercial mobile phone camera. By using our improved rolling shutter pattern demodulation algorithm, such as the background compensation (BC) blooming mitigation, extinction-ratio (ER) enhancement and Bradley adaptive thresholding, a 1.5 m NLOS visible signal (at low illumination of 145 lux) can be retrieved. (C) 2017 Optical Society of America
Metagenomic and metatranscriptomic analyses reveal activity and hosts of antibiotic resistance genes in activated sludge
(2019-08-01)
Liu, Zongbao
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Klumper, Uli
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Liu, Yang
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Yang, Yuchun
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Wei, Qiaoyan
Wastewater treatment plants (WWTPs) are a source and reservoir for subsequent spread of various antibiotic resistance genes (ARGs). However, little is known about the activity and hosts of ARGs in WWTPs. Here, we utilized both metagenomic and metatranscriptomic approaches to comprehensively reveal the diversity, abundance, expression and hosts of ARGs in activated sludge (AS) from three conventional WWTPs in Taiwan. Based on deep sequencing data and a custom-made ARG database, a total of 360 ARGs associated with 24 classes of antibiotics were identified from the three AS metagenomes, with an abundance range of 7.06 x 10(-1)-1.20 x 10(-4) copies of ARG/copy of 16S rRNA gene. Differential coverage binning analysis revealed that > 22 bacterial phyla were the putative hosts of the identified ARGs. Surprisingly, genus Mycobacterium and family Burkholderiaceae were observed as multi-drug resistant harboring 14 and 50 ARGs. Metatranscriptome analysis showed 65.8% of the identified ARGs were being expressed, highlighting that ARGs were not only present, but also transcriptionally active in AS. Remarkably, 110 identified ARGs were annotated as plasmid-associated and displayed a close to two-fold increased likelihood of being transcriptionally expressed compared to those ARGs found exclusively within bacterial chromosomes. Further analysis showed the transcript abundance of aminoglycoside, sulfonamide, and tetracycline resistance genes was mainly contributed by plasmid-borne ARGs. Our approach allowed us to specifically link ARGs to their transcripts and genetic context, providing a comprehensive insight into the prevalence, expression and hosts of ARGs in AS. Overall, results of this study enhance our understanding of the distribution and dissemination of ARGs in WWTPs, which benefits environmental risk assessment and management of ARB and ARGs.