Browsing by Author "Chen, Yu-Wen"

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A 94% Efficiency Near-Constant Frequency Self-Oscillating Class-D Audio Amplifier with Voltage Control Resistor
(2013)
Ng, Shao Siang
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Lin, Kuei-Liang
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Chen, Ke-Horng
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Chen, Yu-Wen
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電控工程研究所
A self-oscillating constant frequency class-D audio amplifier with voltage control resistor (VCR) technique is proposed for system-on-a-chip (SoC) applications. The VCR control circuit is used to ensure stable switching frequency over a wide range of the modulation index. The proposed method also improves the THD performance at high output power condition. The proposed self-oscillating class-D amplifier can have extremely good performance since the carrier distortion is avoided and the intrinsic harmonic can be attenuated by the second-order loop filter. The VCR control can dynamically adjust the switching frequency according to distinct modulation index. In addition, stable frequency operation can reduce the switching frequency at low output amplitude to improve power efficiency. Experimental results demonstrate that the proposed class-D amplifier can delivers 1.4W to the 8 Omega load with a 5V supply. The power efficiency is achieved over 95% and the output THD can be smaller than 0.001%.
A Low Power Hearing Aid Computing Platform Using Lightweight Processing Elements
(2012)
Chang, Kuo-Chiang
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Chen, Yu-Wen
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Kuo, Yu-Ting
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Liu, Chih-Wei
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電子工程學系及電子研究所
This paper presents a power-efficient computing platform for hearing aids. The proposed platform composes four heterogeneous processing elements. Each processing element includes one tiny RISC processor and several power-efficient hardwired accelerators. The hardwired accelerators integrate static floating-point and truncated multiplier to improve signal-to-noise ratio and reduce computational complexity. Compared to the post-truncate multiplication in FIR filter, the proposed static floating-point datapath reduces 50.8% area and improves 2.2 dB SNR simultaneously.
A Single-Inductor Dual-Output Converter with Switchable Digital-or-Analog Low-Dropout Regulator for Ripple Suppression and High Efficiency Operation
(2012)
Lee, Yu-Huei
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Chen, Wei-Chung
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Chiu, Chao-Chang
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Peng, Shen-Yu
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Chu, Kuan-Yu
a single-inductor dual-output (SIDO) converter with the switchable digital-or-analog (D/A) low-dropout (LDO) regulator achieves an analog dynamic voltage scaling (ADVS) function for ripple suppression and high efficiency in system-on-achip (SoC). The ADVS function helps dynamically adjust the dropout voltage of the switchable D/A LDO regulator with analog operation for ripple suppression according to the load current. On other hand, the switchable D/A LDO regulator activates the digital operation for high efficiency at light loads since the dropout voltage of the LDO regulator can be further reduced. Besides, the bidirectional asynchronous signal pipeline (BASP) can realize the 50nA quiescent current in digital LDO regulator. This chip was fabricated by the 40 nm CMOS process. Experimental results demonstrate the switchable LDO regulator operation with the peak efficiency of 92% and the 7 mV output voltage ripple at 200 mA load because of the ripple suppression. The efficiency can be kept higher than 83% even the load current is 1 mA.
Adaptive and secure VCSEL FSO based on simple dual-polarized architecture for short distance transmission
(2020-09-01)
Yeh, Chien-Hung
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Yang, Yun-Cheng
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Hsu, Tzu-An
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Chen, Yu-Wen
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Chow, Chi-Wai
In this study, using dual-polarized-multiplexing VCSEL based free space optical (FSO) transmission system is demonstrated experimentally. Two orthogonal polarizers (POLs), a beam splitter (BS) and a reflected mirror (M) are applied in the FSO transmitter (Tx) side to combine dual FSO signals into one for data security without code encryption. In the receiver (Rx) side, two blended FSO channels can be decoded adaptively by applying a POL with properly polarization status. Furthermore, when we add two corresponding POLs with orthogonal polarization in the Rx side, the FSO capacity also can double by the presented dual-polarized FSO architecture. Here, the relationships of the detected FSO powers and rotating angle between two POLs are also experimentally discussed.
Application of System Dynamics on Shallow Multipurpose Artificial Lakes: A Case Study of Detention Pond at Tainan, Taiwan
(2010-06-01)
Chu, Hone-Jay
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Chang, Liang-Cheng
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Lin, Yu-Pin
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Wang, Yung-Chieh
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Chen, Yu-Wen
This study designs a multipurpose urban shallow artificial lake, including water supply, flood detention, and water environment preservation. It is expected to not only preserve a healthy water environment but to also retain water conservation and flood detention. This study adopts system dynamics (SD) to analyze the relationship between different purposes of water resources utilization. Furthermore, different operation strategies effects can be simulated by SD through a proposed urban multipurpose shallow artificial lake system. The results demonstrate the dynamic effects of strategies managers propose such as demand analysis, inflow control, and water quality improvement in this case study for Taiwan. SD aids lake system prediction and understanding temporally in sequential planning for water supply, environmental preservation, and flood detention. The SD model will hopefully serve as a reference to study different features before artificial lakes constructing.
Applying Multiobjective Genetic Algorithm to Analyze the Conflict among Different Water Use Sectors during Drought Period
(2010-09-01)
Chang, Liang-Cheng
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Ho, Chih-Chao
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Chen, Yu-Wen
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土木工程學系
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Department of Civil Engineering
Water deficits often occur during the drought season and may cause water conflicts among various water use sectors. The reservoir rule curve operation is commonly used to avoid extreme water shortage during droughts in Taiwan. When applying the rule curve operation, the water supply discounting ratio for different sectors implies a trade-off of water deficit impact among sectors. This study therefore develops a multiobjective water resource management model to evaluate the trade-off curve of water deficit impact between irrigation and public sectors to facilitate negotiation between the sectors for obtaining acceptable discounting ratios. The study uses the shortage index to assess water deficit impact. The proposed model integrates operating rules, the stepwise optimal water allocation model, and the convex hull multiobjective genetic algorithm to solve the multiobjective regional water allocation planning problem. The computed trade-off curve, noninferior solutions, provides relevant information to facilitate negotiating water-demand transfer. The results reveal that when decision makers prefer specified water use, the discounting ratio of another competing water use at the low buffer zone should be limited on the lower bound.
Automatic Loading Detection (ALD) Technique for 92% High Efficiency Interleaving Power Factor Correction (PFC) Over a Wide Output Power of 180W
(2012)
Tsai, Jen-Chive
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Chen, Chun-Yen
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Chen, Yi-Ting
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Ni, Chia-Lung
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Su, Yi-Ping
the proposed automatic loading detection (ALD) technique keeps high efficiency in interleaving power factor correction (PFC) over a wide load range. With the advantages of small input/output filter and output ripple in the interleaving mechanism, the improved efficiency by the ALD technique at light loads due to reduced switching loss can be widely used in the adapter of portable electronics. The ALD technique can calculate the power by the detection of peak input voltage to reduce the switching loss since the slave channel can be completely turned off for power saving at light loads. Therefore, the boundary control mode (BCM) control can simultaneously provide high power and keep high conversion efficiency both at light and heavy loads. The highly integrated PFC controller fabricated in TSMC 800V UHV process shows high efficiency of 92% over a wide output power of 180 W.
Developing a Conjunctive Use Optimization Model for Allocating Surface and Subsurface Water in an Off-Stream Artificial Lake System
(2016-08-01)
Pan, Chen-Che
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Chen, Yu-Wen
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Chang, Liang-Cheng
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Huang, Chun-Wei
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土木工程學系
This work develops a rule curve-based conjunctive use management model for optimizing the operating rules for a lake-groundwater system with off-stream storage lakes. The proposed procedure is a simulation-optimization approach that embeds an Artificial Neural Network ( ANN) instead of a groundwater numerical model into a genetic algorithm ( GA). The direct physical exchange between lake water with groundwater is simulated using the ANN model, which is a reduced version of a full numerical model, MODFLOW with an LAK3 module. By applying the ANN model, the proposed procedure can reduce the computational burden that is induced by the nonlinear exchange. An operating rule-based optimal conjunctive use management model for the Gaopin Artificial lakes system in Taiwan was thus developed using the proposed framework. A set of optimal solutions involves rule curves and a discount ratio. Simulation results demonstrate that the embedded ANN model can accurately simulate the nonlinear exchange of a lake with groundwater. The embedded ANN model is less computationally complex than the numerical model. This work demonstrates a methodology for reducing the computational burden of the optimal conjunctive use management model that is associated with an internal nonlinear system by using the ANN reduced model. Specifically, the concept of, and results obtained using the developed operating rule-based model incorporating five artificial lakes and considering the nonlinear exchange of those lakes with the groundwater system provides a valuable practical reference for solving related conjunctive use problems.
Elastic and cost-effective data carrier architecture for smart contract in blockchain
(2019-11-01)
Liu, Xiaolong
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Muhammad, Khan
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Lloret, Jaime
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Chen, Yu-Wen
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Yuan, Shyan-Ming
Smart contract, which could help developer deploy decentralized and secure blockchain application, is one of the most promising technologies for modern Internet of things (IoT) ecosystem today. However, Ethereum smart contract lacks of ability to communicate with outside IoT environment. To enable smart contracts to fetch off-chain data, this paper proposes a data carrier architecture that is cost-effective and elastic for blockchain-enabled IoT environment. Three components, namely Mission Manager, Task Publisher and Worker, are presented in the data carrier architecture to interact with contract developer, smart contract, Ethereum node and off-chain data sources. Selective solutions are also proposed for filtering smart contract event and decoding event log to fit different requirements. The evaluation results and discussions show the proposed system will decrease about 20USD deployment cost in average for every smart contract, and it is more efficient and elastic compared with Oraclize Oracle data carrier service. (C) 2019 Elsevier B.V. All rights reserved.
Groundwater Simulations and Uncertainty Analysis Using MODFLOW and Geostatistical Approach with Conditioning Multi-Aquifer Spatial Covariance
(2017-03-01)
Lin, Yu-Pin
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Chen, Yu-Wen
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Chang, Liang-Cheng
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Yeh, Ming-Sheng
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Huang, Guo-Hao
This study presents an approach for obtaining limited sets of realizations of hydraulic conductivity (K) of multiple aquifers using simulated annealing (SA) simulation and spatial correlations among aquifers to simulate realizations of hydraulic heads and quantify their uncertainty in the Pingtung Plain, Taiwan. The proposed approach used the SA algorithm to generate large sets of natural logarithm hydraulic conductivity (ln(K)) realizations in each aquifer based on spatial correlations among aquifers. Moreover, small sets of ln(K) realizations were obtained from large sets of realizations by ranking the differences among cross-variograms derived from the measured ln(K) and the simulated ln(K) realizations between the aquifer pair Aquifer 1 and Aquifer 2 (hereafter referred to as Aquifers 1-2) and the aquifer pair Aquifer 2 and Aquifer 3 (hereafter referred to as Aquifers 2-3), respectively. Additionally, the small sets of realizations of the hydraulic conductivities honored the horizontal spatial variability and distributions of the hydraulic conductivities among aquifers to model groundwater precisely. The uncertainty analysis of the 100 combinations of simulated realizations of hydraulic conductivity was successfully conducted with generalized likelihood uncertainty estimation (GLUE). The GLUE results indicated that the proposed approach could minimize simulation iterations and uncertainty, successfully achieve behavioral simulations when reduced between calibration and evaluation runs, and could be effectively applied to evaluate uncertainty in hydrogeological properties and groundwater modeling, particularly in those cases which lack three-dimensional data sets yet have high heterogeneity in vertical hydraulic conductivities.
GROUP AUTHENTICATION METHOD
(2009-02-26)
Chen, Yu-Wen
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Wang, Jui-Tang
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Tseng, Chien-Chao
A group authentication method adaptable to a communication system is disclosed. The communication system includes a user group, a serving network, and a home network. The user group includes at least one mobile station. The home network pre-distributes a group authentication key to itself and all the mobile stations in the same user group and generates a mobile station authentication key for each mobile station. The home network generates a group list for recording related information of the user group. The home network has a database for recording the group list. The serving network has a database for recording the group list and a group authentication data received from the home network. The group authentication method includes following steps. The serving network performs an identification action to a mobile station. The communication system performs a full authentication action or a local authentication action according to the result of the identification action.
Group-Based Authentication and Key Agreement
(2012-02-01)
Chen, Yu-Wen
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Wang, Jui-Tang
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Chi, Kuang-Hui
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Tseng, Chien-Chao
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資訊工程學系
This paper presents an authentication and key agreement protocol to streamline communication activities for a group of mobile stations (MSs) roaming from the same home network (HN) to a serving network (SN). In such a roaming scenario, conventional schemes require the SN to interact with the HN for authenticating respective MSs, at the cost of repeated message exchanges and communication delay. Instead, in our design, when the first MS of a group visits, the SN performs full authentication with the concerned HN and thereby obtains authentication information for the MS and other members. Thus when any other MS of the same group visits, the SN can authenticate locally without subsequent involvement of the HN, so as to simplify protocol operations. We will show that our scheme does not trade performance for security and robustness to the extent that security requirements are unduly weakened. Both qualitative and quantitative discussions indicate that our proposed scheme lends itself to pragmatic settings.
High Recharge Areas in the Choushui River Alluvial Fan (Taiwan) Assessed from Recharge Potential Analysis and Average Storage Variation Indexes
(2015-04-01)
Tsai, Jui-Pin
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Chen, Yu-Wen
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Chang, Liang-Cheng
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Kuo, Yi-Ming
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Tu, Yu-Hsuan
High recharge areas significantly influence the groundwater quality and quantity in regional groundwater systems. Many studies have applied recharge potential analysis (RPA) to estimate groundwater recharge potential (GRP) and have delineated high recharge areas based on the estimated GRP. However, most of these studies define the RPA parameters with supposition, and this represents a major source of uncertainty for applying RPA. To objectively define the RPA parameter values without supposition, this study proposes a systematic method based on the theory of parameter identification. A surrogate variable, namely the average storage variation (ASV) index, is developed to calibrate the RPA parameters, because of the lack of direct GRP observations. The study results show that the correlations between the ASV indexes and computed GRP values improved from 0.67 before calibration to 0.85 after calibration, thus indicating that the calibrated RPA parameters represent the recharge characteristics of the study area well; these data also highlight how defining the RPA parameters with ASV indexes can help to improve the accuracy. The calibrated RPA parameters were used to estimate the GRP distribution of the study area, and the GRP values were graded into five levels. High and excellent level areas are defined as high recharge areas, which composed 7.92% of the study area. Overall, this study demonstrates that the developed approach can objectively define the RPA parameters and high recharge areas of the Choushui River alluvial fan, and the results should serve as valuable references for the Taiwanese government in their efforts to conserve the groundwater quality and quantity of the study area.
Monitoring and estimating the flow conditions and fish presence probability under various flow conditions at reach scale using genetic algorithms and kriging methods
(2011-02-10)
Lin, Yu-Pin
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Wang, Cheng-Long
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Yu, Hsiao-Hsuan
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Huang, Chung-Wei
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Wang, Yung-Chieh
The combination of current velocity and water depth influences stream flow conditions, and fish activities prefer particular flow conditions. This study develops a novel optimal flow classification method for identifying types of stream flow based on the current velocity and the water depth using a genetic algorithm. It is applied to the Datuan stream in northern Taiwan. Fish were sampled and their habitat investigated at the study site during the spring, summer, fall and winter of 2008-2009. The current velocity, water depth and maps of the presence probability of fish were estimated by ordinary and indicator kriging. The optimal classification results were compared with the classification results obtained using the Froude number and empirical methods. The flow classification results demonstrate that the proposed optimal flow classification method that considers depth-velocity and optimally identified criteria for classifying flow types, yields a current velocity and water depth of 0.32 (m/s) and 0.29 (m), respectively, and classifies the flow conditions in the study area as pool, run, riffle and slack The variography results of the current velocity and the water depth data reveal that seasonal flows are not spatially stationary among seasons in the study area. Kriging methods and a two-dimensional hydrodynamic model (River 2D) with empirical and optimal flow classification methods are more effective than the Froude number method in classifying flow conditions in the study area. The flow condition classifications and probability maps were generated by River 2D, ordinary kriging and indicator kriging, to quantify the flow conditions preferred by Sicyopterus japonicus in the study area. However, the proposed optimal classification method with kriging and River 2D is an effective alternative method for mapping flow conditions and determining the relationship between flow and the presence probability of target fish in support of stream restoration. (C) 2010 Elsevier B.V. All rights reserved.
Off-chain Data Fetching Architecture for Ethereum Smart Contract
(2018-01-01)
Liu, Xiaolong
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Chen, Riqing
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Chen, Yu-Wen
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Yuan, Shyan-Ming
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資訊工程學系
Ethereum smart contract makes developers can deploy decentralized applications to inherit features from blockchain, such as decentralization and openness. Although Ethereum provided a decentralized platform, Ethereum Virtual Machine for smart contracts, it lacks of ability to fetch off-chain data. The general solution is Oracle data carrier. However, Oracle results in rising deployment costs. It requires Ethereum smart contract developers to follow format in programing contract, this constraint decreases the readability of smart contract. This paper proposes an off-chain data fetching architecture which is cost-effective and highly elastic for smart contract. It also compatible with exited contract, which makes Ethereum smart contract owner able to automate the reply process.
Optimizing system capacity expansion schedules for groundwater supply
(2009-07-10)
Chang, Liang-Cheng
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Chen, Yu-Wen
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Yeh, Ming-Sheng
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土木工程學系
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Department of Civil Engineering
Groundwater plays a vital role in regional water resources management. In conventional design, a full-scale network system is installed initially to use groundwater resources. However, the system capacity may exceed water demand in the early stages because water demand generally increases with time. Therefore, this work proposes a novel optimal capacity expansion model capable of determining an optimal schedule to expand system capacity according to increasing water demand. The proposed algorithm hybridizes a genetic algorithm (GA) and constrained differential dynamic programming (CDDP). The chromosomes of the GA represent a possible design alternative, a groundwater network with capacity that expands with time. The CDDP algorithm is then used to compute the optimal pumping policy associated with the chromosome. Simulation results indicate that the capacity expansion model saves more total present value cost than conventional designs for the same annual interest rate and water demand. Results of this study demonstrate promise for the proposed model in facilitating a cost-effective groundwater network design with capacity expansion for regional groundwater supply.
Real-Time Instruction-Cycle-Based Dynamic Voltage Scaling (iDVS) Power Management for Low-Power Digital Signal Processor (DSP) with 53% Energy Savings
(2012)
Peng, Shen-Yu
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Lee, Yu-Huei
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Wu, Chun-Hsien
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Huang, Tzu-Chi
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Chen, Ke-Horng
this paper presents an instruction-cycle-based dynamic voltage scaling (iDVS) power management strategy for a low-power processor design. The iDVS technique is fully compatible with conventional DVS scheduler algorithms. Furthermore, an additional iDVS design flow embedded in the standard cell lib flow is proposed to implement the iDVS-based DSP. In addition, the fast-response bidirectional asynchronous wave-pipeline (BAWP) digital low-dropout (LDO) regulator is also presented to improve the iDVS performance. The iDVS-based DSP chip implemented in an HH-NEC 0.18 mu m standard CMOS process demonstrates 53% energy savings over that without the iDVS technique.
Security optical data storage in Fourier holograms
(2012-03-20)
Su, Wei-Chia
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Chen, Yu-Wen
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Chen, Yu-Jen
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Lin, Shiuan-Huei
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Wang, Li-Karn
We have proposed and demonstrated a holographic security storage system that is implemented with a shift multiplexing technique. The security function of this storage system is achieved by using a micro-diffuser (MD) for random phase encoding of the reference beams. The apparatus of random phase encoding in this system offers an additional and flexible function during the recording processes. The system can generate holographic security memory or nonsecurity holographic memory via using the MD or not. The storage capacity and the average signal-to-noise value of the security storage system are 16 bits/mu m(2) and 3.5, respectively. Lateral shifting selectivity in this holographic security storage system is theoretically analyzed and experimentally investigated. (C) 2012 Optical Society of America
Survivable and Reliable WDM-PON System With Self-Protected Mechanism Against Fiber Fault
(2019-01-01)
Yeh, Chien-Hung
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Luo, Chien-Ming
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Xie, Yue-Ru
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Chow, Chi-Wai
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Chen, Yu-Wen
In the paper, we present and design a self-restored wavelength multiplexing division passive optical network (WDM-PON) configuration to prevent the fiber failure and data disconnection. Here, the new remote node (RN) and optical network unit (ONU) are proposed in the fiber network to provide the protection behavior to increase the network reliability and flexibility. Moreover, the network performances of WDM signals are also analyzed and discussed.
The assessment of high recharge areas using DO indicators and recharge potential analysis: a case study of Taiwan\'s Pingtung plain
(2015-03-01)
Tsai, Jui-Pin
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Chen, Yu-Wen
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Chang, Liang-Cheng
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Chen, Wen-Fu
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Chiang, Chung-Jung
Identifying high groundwater recharge areas is important for the conservation of groundwater quality and quantity. A common practice used by previous studies is to estimate groundwater recharge potential (GRP) using recharge potential analysis (RPA) under different environments. These studies use the estimated GRP to identify the high potential groundwater recharge sites. However, the RPA parameters are subjectively defined for these previous studies. To remove the supposition, this study proposes a systematic approach that defines the RPA parameter values based on the theory of parameter identification. This study uses dissolved oxygen (DO) indicators to calibrate the RPA parameters. This calibration improves the correlation coefficient between the DO indicators and computed GRP values from 0.63 to 0.87. By comparing the initial values, these results indicate that the estimated RPA parameters better represent the field infiltration characteristic. This result also indicates that defining the RPA parameter values based on DO indicators is necessary and important for accuracy. These calibrated parameters are used to estimate the GRP distribution of Taiwan\'s Pingtung Plain. The GRP values are delineated into five levels. High and excellent GRP areas are defined as high recharge areas, which compose about 26.74 % of the study area. Based on the proposed method, the estimated GRP distribution can accurately represent the study area\'s field recharge characteristics. These study results can be a good reference for groundwater recharge analyses, specifically if well data is limited or difficult to obtain.