Browsing by Author "Chang, Chia-Wei"

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A low-power CMOS voltage reference circuit based on subthreshold operation
(2007)
Chang, Chia-Wei
;
Lo, Tien-Yu
;
Chen, Chia-Min
;
Wu, Kuo-Hsi
;
Hung, Chung-Chih
A low power CMOS Voltage Reference Circuit was designed and implemented by TSMC 0.18-mu m CMOS process. The voltage reference circuit uses the V-GS difference between two MOSFETs operating in the weak-inversion region to generate the voltage with positive temperature coefficient The reference voltage can be obtained by combining the weighted V-GS difference with weak-inversion V-GS voltage, which has a negative temperature coefficient. This circuit provides a nominal reference voltage of 621 mV, a temperature coefficient of 11.5 ppm/degrees C in [-20 degrees C-120 degrees C] from a 1.5 V supply voltage. The line regulation of the reference voltage is 6 mV/V when the supply voltage is increased from 1.5 V to 3 V. The chip area is 0.132 mm(2) and dissipates 17.25 mu W at room temperature. By connecting a 0.22 mu F loading capacitor, the measured noise density at 100 Hz and 100 kHz is 0.14 mu V/root Hz and 22.2 mu V/root Hz, respectively.
A systematic bit-wise decomposition of M-ary symbol metric
(2006-10-01)
Chang, Chia-Wei
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Chen, Po-Ning
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Han, Yunghsiang S.
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電信工程研究所
;
Institute of Communications Engineering
In this paper, we present a systematic recursive formula for bit-wise decomposition of M-ary symbol metric. The decomposed bit metrics can be applied to improve the performance of a system where the information sequence is binary-coded and interleaved before M-ary modulated. A traditional receiver designed for certain system is to de-map the received M-ary symbol, into its binary isomorphism so as to facilitate the subsequent bit-based manipulation, such as hard-decision decoding. With a bit-wise decomposition of M-ary symbol metric, a soft-decision decoder can be used to achieve a better system performance. The idea behind the systematic formula is to decompose the symbol-based maximum-likelihood (ML) metric by equating a number of specific equations that are drawn from squared-error criterion. It interestingly yields a systematic recursive formula that can be applied to some previous work derived from different standpoint. Simulation results based on IEEE 802.11a/g standard show that at bit-error-rate of 10(-5), the proposed bit-wise decomposed metric can provide 3.0 dB, 3.9 dB and 5.1 dB improvement over the concatenation of binary-demapper, deinterleaver and hard-decision decoder respectively for 16QAM, 64QAM and 256QAM symbols, in which the in-phase and quadrature components in a complex M-2-QAM symbol are independently treated as two real M-PAM symbols. Further empirical study on system imperfection implies that the proposed bit-wise decomposed metric also improves the system robustness against gain mismatch and phase imperfection. In the end, a realization structure that avails the recursive nature of the proposed bit-decomposed metric formula is addressed.
A vision-based blind spot warning system for daytime and nighttime driver assistance
(2013-04-01)
Wu, Bing-Fei
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Huang, Hao-Yu
;
Chen, Chao-Jung
;
Chen, Ying-Han
;
Chang, Chia-Wei
This paper proposes an effective blind spot warning system (BSWS) for daytime and nighttime conditions. The proposed BSWS includes camera models of a dynamic calibration and blind spot detection (BSD) algorithms for the daytime and nighttime. Under daytime conditions, the proposed system presents the Horizontal Edge and Shadow Composite Region (HESCR) method to extract the searching region and to acquire the shadow location of the targeted vehicles. Additionally, to detect vehicles at nighttime road scenes, the proposed system extracts bright objects and recognizes the paired headlights of the targeted vehicles for the BSD. The BSWS is implemented on a DSP-based embedded platform. The results of the BSWS are obtained by conducting practical experiments on our camera-assisted car on a highway in Taiwan under both nighttime and daytime conditions. Experimental results show that the proposed BSWS is feasible for vehicle detection and collision warning in various daytime and nighttime road environments. (C) 2013 Elsevier Ltd. All rights reserved.
Adjustable Extended Discontinuous Reception Cycle for Idle-State Users in LTE-A
(2016-11)
Chang, Chia-Wei
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Chen, Jyh-Cheng
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資訊工程學系
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Department of Computer Science
In the long term evolution advanced, a user in idle state can activate the discontinuous reception (DRX) to save its energy, and the 3GPP extends the length of a DRX cycle. Therefore, how to configure the extended DRX (eDRX) cycle is a tradeoff between the tracking area update (TAU) cost (the cost of updating a user\'s location) and the paging cost (the cost of waking up a user). In this letter, we analyze the tradeoff and determine the optimal length for the eDRX cycle under the latency constraint. The objective function is to minimize the total signaling cost considering the tradeoff between TAU cost and paging cost. The analytical and simulation results demonstrate that the proposed mathematical model can mitigate the signaling cost for the networks.
Congestion Control for Machine-Type Communications in LTE-A Networks
(2016-01-01)
Chang, Chia-Wei
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Lin, Yi-Hao
;
Ren, Yi
;
Chen, Jyh-Cheng
;
資訊工程學系
Collecting data from a tremendous amount of Internet-of-Things (IoT) devices for next generation networks is a big challenge. A large number of devices may lead to severe congestion in Radio Access Network (RAN) and Core Network (CN). 3GPP has specified several mechanisms to handle the congestion caused by massive amounts of devices. However, detailed settings and strategies of them are not defined in the standards and are left for operators. In this paper, we propose two congestion control algorithms which efficiently reduce the congestion. Simulation results demonstrate that the proposed algorithms can achieve 20 similar to 40% improvement regarding accept ratio, overload degree and waiting time compared with those in LTE-A.
Design and Implement a Mobile Badminton Stroke Classification System
(2017-01-01)
Lin, Juyi
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Chang, Chia-Wei
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Wang, Chih-Hao
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Chi, Hong-Chuan
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Yi, Chih-Wei
The use of the badminton stroke strategy in the evenly matched game is often the key to victory. In this work, a smart racket based on wearable seusors is proposed to collect the data of swing of badminton. A cell phone APP with machine learning techniques is implemented to record stroke types automatically. In each stroke hit event, this prototype system uses Bluetooth earphone to collect the sound for detecting the accuracy time. It uses the data of IMU in each stroke for determining stroke type. Compared to IMU only solution, the system will reduce the false count of stroke hit. Using cloud techniques could record the training and game record in a long period. Overall the accuracy of stroke hit event is almost 100% by using voice print. The data of IMU is classified by Random Forest or SMO. The accuracy for personal model is 95.91 %, and it is 79.32% for general model. We develop a stroke record system which is combined with Wearable sensor, Mobile platform and Cloud service.
Design of multifold Ge/Si/Ge composite quantum-dot heterostructures for visible to near-infrared photodetection
(2015-05-15)
Kuo, Ming-Hao
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Lai, Wei-Ting
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Lee, Sheng-Wei
;
Chen, Yen-Chun
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Chang, Chia-Wei
We demonstrate an effective approach to grow high-quality thin film (>1 mu m) ofmultifold Ge/Si/Ge composite quantum dots ( CQDs) stacked heterostructures for near infrared photodetection and optical interconnect applications. An otherwise random, self-assembly of variable-fold Ge/Si CQDs has been grown on Si through the insertion of Si spacer layers to produce micron-scale-thick, stacked Ge/Si CQD layers with desired QD morphology and composition distribution. The high crystalline quality of these multifold Ge CQD heterostructures is evidenced by low dark current density of 3.68 pA/mu m(2), superior photoresponsivity of 267 and 220 mA/W under 850 and 980 nm illumination, respectively, and very fast temporal response time of 0.24 ns measured on the Ge/Si CQD photodetectors. (C) 2015 Optical Society of America
Dual Functionality of BODIPY Chromophore in Porphyrin-Sensitized Nanocrystalline Solar Cells
(2012-05-17)
Shrestha, Maheshwar
;
Si, Liping
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Chang, Chia-Wei
;
He, Hongshan
;
Sykes, Andrew
A new organic dye (BET) was synthesized and coadsorbed on TiO2 nanoparticles to make mixed BET/porphyrirf-sensitized solar cells (DSCs). The BET is a boron dipyrromethene compound with one benzoic acid group attached to the meso position for its binding to the TiO2 nanoparticles and two ethyl groups in the 3 and 3' positions of pyrrolic units to broaden its absorption. Two ethyl groups are in the cis position, as revealed by its single-crystal X-ray diffraction analysis. The BET exhibits strong absorption in the green light region with an absorption maximum at 528 nm in CH2Cl2, which is complementary to the absorption spectrum of porphyrin dyes. When the BET coadsorbs on the TiO2 nanoparticles with porphyrin dyes (TMPZn and LD12), the power conversion efficiencies increase from 1.09% to 2.90% for TMPZn-sensitized solar cells and from 6.65% to 7.60% for LD12-sensitized solar cells, respectively. The IPCE of the devices in the green light region increases dramatically due to the cosensitizing effect of BET. The fluorescence of BET in solution is partially quenched and that of porphyrin is enhanced in the presence of BET dye, indicating an intermolecular energy transfer from BET to the porphyrin dyes. The direct electron injection from BET to the TiO2 conduction band was rather poor; only negligible photocurrent was observed. Comparative studies of absorption spectra on the TiO2 nanoparticle films and electrochemical impedance at the dye/TiO2 interface also indicate that the BET is an excellent coadsorber to prevent the aggregation of porphyrin dyes. An intermolecular energy transfer model is proposed to account for the observed photovoltaic enhancement of the cosensitization system.
Electricity Generation Using Biogas From Swine Manure for Farm Power Requirement
(2015-01-01)
Chang, Chia-Wei
;
Lee, Tsung-Han
;
Lin, Wei-Tsung
;
Chen, Chiun-Hsun
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機械工程學系
This study conducted 30 kW-generator experiments at a small biogas plant on a swine farm to serve as a preliminary study for the construction of a 300-kW power plant for a larger scale biogas plant in the near future. The experimental results showed that the optimum biogas flow rate for the engine was around 240 to 260 L/min, and the maximum power generation, the corresponding thermal efficiency, and the percentage of consumed CH4 were 26.8 kW, 28.7%, and 95.4%, respectively, at a biogas supply rate of 260 L/min. With 3% oxygen-enriched air, the maximum power generation, thermal efficiency, and percentage of consumed CH4 increased up to 28.2 kW, 30.2%, and approximately 100%, respectively, for a biogas supply rate of 260 L/min, and the engine can operate normally at a lower limited fuel supply rate of 220 L/min. The heat exchanger could recover 923 kJ/min of heat from the flue gas, leading to an overall efficiency of 47.3%, at a biogas supply rate of 240 L/min. With the total swine population (around 4.3 million heads) from the farm scale of over 1,000 heads of pigs in Taiwan, the estimation, based on the data obtained from this study, shows the economic benefits of using biogas, including an annual electricity generation of 2.67 x 10(8) kWh(e) (corresponding to electricity charge savings of US$ 26.7 million), where natural gas charge savings total US$ 8.7 million, and the carbon dioxide reduction totals 180,000 tons.
Embedded Weather Adaptive Lane and Vehicle Detection System
(2008)
Wu, Bing-Fei
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Chen, Chao-Jung
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Kao, Chih-Chung
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Chang, Chia-Wei
;
Chiu, Shen-Ting
In this paper, the lane and vehicle detection with distance estimation algorithm is proposed by using a CCD camera mounted behind the windshield of our experimental car, TAIWAN iTS-1. The gray level and gradient value are applied for the lane marking detection. The lane marking information is utilized in vehicle detection algorithm. The front vehicles are recognized by comparing the gray level value and Sobel edge pixels. Then, the image coordinate model is utilized for the distance estimation with the located approaching vehicles. The verified effective distance is 50m in front of the host vehicle. This approach has been successfully implemented on the DSP system which is designed by us for the real-time detection. This system will be integrated into the lane departure warning and collision avoidance system with the visual and audio alerts to warn the careless drivers.
Enabling High-Injection Current Light-Emitting Diodes Prepared on 10-mu m-Thick GaN Films Grown by Hydride Vapor Phase Epitaxy
(2015-09-01)
Chen, Yu-An
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Chang, Chia-Wei
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Kuo, Cheng-Huang
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照明與能源光電研究所
;
Institute of Lighting and Energy Photonics
In this paper, we successfully introduced the sputtered AlN/patterned sapphire substrate template into hydride vapor phase epitaxy (HVPE) using a two-step growth method. This method simplified the procedure, realized uninterrupted growth, and improved the crystal quality of GaN films. The effects of light-emitting diodes (LEDs) grown on a 10-mu m-thick GaN film through HVPE were also compared with those of the LEDs grown on a 2.4-mu m-thick GaN film through metal organic chemical vapor deposition (MOCVD). Compared with the LEDs grown on the 2.4-mu m-thick GaN film through MOCVD, the LEDs grown on the 10-mu m-thick GaN film through HVPE had significantly enhanced light output power (3.24-4.79 mW) and extended saturation current (300-355 mA). These improvements of the LEDs were attributed to the better thermal conductivities and better crystal quality of the 10-mu m-thick GaN film through HVPE than those of the 2.4-mu m-thick GaN film through MOCVD.
Enhanced photovoltaic performance with co-sensitization of porphyrin and an organic dye in dye-sensitized solar cells
(2012-04-01)
Lan, Chi-Ming
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Wu, Hui-Ping
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Pan, Tsung-Yu
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Chang, Chia-Wei
;
Chao, Wei-Shan
We designed a stepwise approach for co-sensitization of a zinc porphyrin sensitizer (LD12) with a spirally configured organic dye (CD5) for dye-sensitized solar cells. The co-sensitized LD12 + CD5 device showed significantly enhanced V-OC and J(SC) relative to its individual single-dye sensitized devices. Upon optimization, the device made of the LD12 + CD5 system yielded J(SC)/mA cm(-2) = 16.7, V-OC/V = 0.74, FF = 0.73 and eta = 9.0%; this performance is superior to that of either individual device made from LD12 (eta = 7.5%) and CD5 (eta = 5.7%) under the same conditions of fabrication. To understand the effects of the potential shift and charge recombination on the cell performance, we measured charge-extraction (CE) and intensity-modulated photovoltage spectra (IMVS). Upon sensitization with each dye, the TiO2 potentials are similar, but co-sensitization causes the potential to shift down (cathodic shift). Charge recombination was significantly retarded for the co-sensitized system relative to each individual dye-sensitized system, to account for the enhanced V-OC for the former relative to the latter. A test of stability indicates a systematic trend between the LD12 + CD5 and LD12 devices; the performance of the co-sensitized device degraded only similar to 15% and remained stable during the period of 500-1000 h near 295 K.
Enveloping porphyrins for efficient dye-sensitized solar cells
(2012-05-01)
Wang, Chin-Li
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Lan, Chi-Ming
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Hong, Shang-Hao
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Wang, Yi-Fen
;
Pan, Tsung-Yu
A series of porphyrins bearing alkoxyl and/or alkyl chains were prepared to investigate the roles of alkoxyl/alkyl chains in the enhanced photovoltaic performance of the dyes. Based on the experimental results and the molecular simulations, we demonstrated that suitable long alkoxyl chains are capable of wrapping the porphyrin core, thus resulting in decreased dye aggregation, elevated excited states and LUMOs, and improved photovoltaic performance.
FetalCare: A Mobile Cardiotocograph System
(2015)
Chang, Chia-Wei
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Tsai, Hsin-Hsi
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Yi, Chih-Wei
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Wang, Yi-Chang
;
Kuo, Jen-Yau
Due to the increasing of elderly primigravidae, the demand of the tocolysis is more than before. In this project, NCTU and ITRI worked together to improve the Maya Tocolytic System at Mackay Memorial Hospital by augmenting remote real-time physiological data transmission and display on smartphones. Doctors can have real-time physiological data to make diagnosis and provide advice remotely by leverage mobile technologies.
MicroRNA-30a increases tight junction protein expression to suppress the epithelial-mesenchymal transition and metastasis by targeting Slug in breast cancer
(2016-03-29)
Chang, Chia-Wei
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Yu, Jyh-Cherng
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Hsieh, Yi-Hsien
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Yao, Chung-Chin
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Chao, Jui-I
The epithelial-to-mesenchymal (EMT) transition is a prerequisite for conferring metastatic potential during tumor progression. microRNA-30a (miR-30a) expression was significantly lower in aggressive breast cancer cell lines compared with non-invasive breast cancer and non-malignant mammary epithelial cell lines. In contrast, miR-30a overexpression reversed the mesenchymal appearance of cancer cells to result in a cobblestone-like epithelial phenotype. We identified Slug, one of the master regulators of EMT, as a target of miR-30a using in silico prediction. Reporter assays indicated that miR-30a could bind to the 3'-untranslted region of Slug mRNA. Furthermore, we linked miR-30a to increased expression of claudins, a family of tight junction transmembrane proteins. An interaction between Slug and E-box in the claudin promoter sequences was reduced upon miR-30a overexpression, further leading to reduction of filopodia formation and decreased invasiveness/metastasis capabilities of breast cancer cells. Consistently, delivery of miR-30a in xenografted mice decreased tumor invasion and migration. In patients with breast cancer, a significantly elevated risk of the miR-30a(low)/CLDN2(low)/FSCNhigh genotype was observed, linking to a phenotypic manifestation of larger tumor size, lymph node metastasis, and advanced tumor stage among patients. In conclusion, the miR-30a/Slug axis inhibits mesenchymal tumor development by interfering with metastatic cancer cell programming and may be a potential target for therapy in breast cancer.
MicroRNA-30a inhibits cell migration and invasion by downregulating vimentin expression and is a potential prognostic marker in breast cancer
(2012-08-01)
Cheng, Chun-Wen
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Wang, Hsiao-Wei
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Chang, Chia-Wei
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Chu, Hou-Wei
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Chen, Cheng-You
"Tumor recurrence and metastasis result in an unfavorable prognosis for cancer patients. Recent studies have suggested that specific microRNAs (miRNAs) may play important roles in the development of cancer cells. However, prognostic markers and the outcome prediction of the miRNA signature in breast cancer patients have not been comprehensively assessed. The aim of this study was to identify miRNA biomarkers relating to clinicopathological features and outcome of breast cancer. A miRNA microarray analysis was performed on breast tumors of different lymph node metastasis status and with different progression signatures, indicated by overexpression of cyclin D1 and beta-catenin genes, to identify miRNAs showing a significant difference in expression. The functional interaction between the candidate miRNA, miR-30a, and the target gene, Vim, which codes for vimentin, a protein involved in epithelial-mesenchymal transition, was examined using the luciferase reporter assay, western blotting, and migration and invasion assays. The association between the decreased miR-30a levels and breast cancer progression was examined in a survival analysis. miR-30a negatively regulated vimentin expression by binding to the 3'-untranslated region of Vim. Overexpression of miR-30a suppressed the migration and invasiveness phenotypes of breast cancer cell lines. Moreover, reduced tumor expression of miR-30a in breast cancer patients was associated with an unfavorable outcome, including late tumor stage, lymph node metastasis, and worse progression (mortality and recurrence) (p < 0.05). In conclusion, these findings suggest a role for miR-30a in inhibiting breast tumor invasiveness and metastasis. The finding that miR-30a downmodulates vimentin expression might provide a therapeutic target for the treatment of breast cancer."
Morphological control of platinum nanostructures for highly efficient dye-sensitized solar cells
(2012)
Li, Lu-Lin
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Chang, Chia-Wei
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Wu, Hsin-Hui
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Shiu, Jia-Wei
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Wu, Po-Ting
Cyclic electro-deposition (CED) is a cost-effective tool to synthesize nanostructures with a solution process, controllable morphology and high purity. Here we report novel platinum nanostructures fabricated according to CED at room temperature in solution containing H2PtCl6 precursor and NaNO3. Remarkable Pt nanostructures-from nanoclusters, nanosheets, nanograsses to nanoflowers-were produced through morphological control via variation of either period of CED scans or concentration of the precursor. Pt films with uniform nanograss structures have great electrocatalytic performance (electron-transfer resistance = 0.3 Omega) and intrinsic light-scattering (reflectivity similar to 50%), perfectly suitable for use as counter-electrodes for dye-sensitized solar cells (DSSCs). The DSSC device made with the Pt-nanograss counter-electrode and N719 dye attained efficiency eta = 9.61% of power conversion, which is 12% enhanced from that fabricated according to a conventional thermal decomposition method (eta = 8.55%) under similar experimental conditions. When the devices were further optimized with a thick TiO2 film (17 + 5 mu m) sensitized by Z907 dye using the CED-Pt counter-electrode, we obtained J(SC) (mA cm(-2)) = 19.44, V-OC (V) = 0.742, and FF = 0.736, giving an exceptional power conversion efficiency of 10.62%.
Numerical Simulation and Experimental Analysis of Current Spreading Length in Nitride-Based Light-Emitting Diodes Prepared on 10-mu m-Thick n-GaN Template
(2015-11-01)
Chen, Yu-An
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Chang, Chia-Wei
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Kuo, Cheng-Huang
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照明與能源光電研究所
;
Institute of Lighting and Energy Photonics
Numerical and experimental demonstrations were performed in this letter to enhance the current spreading length of nitride-based light-emitting diodes (LEDs) with a 10-mu m-thick n-GaN template on an AlN/high-aspect ratio patterned sapphire substrate template via hydride vapor phase epitaxy. At an injection current of 20 mA, the output powers were 4.34 and 6.39 mW for a conventional LED and an LED with a 10-mu m-thick n-GaN template, respectively. The larger LED output power is attributed to the enhanced current spreading length, which improved the heat dissipation ability and the improved crystal quality.
Scattering Random-Access Intensity in LTE Machine-to-Machine (M2M) Communications
(2013-01-01)
Chang, Chia-Wei
;
Chen, Jyh-Cheng
;
Chen, Chien
;
Jan, Rong-Hong
;
資訊工程學系
Supporting a large number of devices in LTE Machine-to-Machine (M2M) communications is a big challenge. The large number of devices will try to access radio resource in a short period of time which may result in severe congestion to the Radio Access Network (RAN). Hence, how to scatter the devices, which are always trying to access to a same eNBs (evolved Node B), to other eNBs has become an important issue. In other words, balancing the random access intensity among eNBs will reduce the congestion of an RAN and improve the network utilization. Nevertheless, how to select an eNB to attach to during the initial access in a way that will balance overall access intensity in the network is a key challenge. Unfortunately, from the perspective of eNB, an eNB is unaware of how many devices will access to the eNB. Thus, an eNB cannot release the information about the access intensity in advance. In this paper, therefore, we propose four effective eNB selection algorithms to estimate the access intensity of an eNB. Simulation results show that the proposed algorithms perform better than conventional approach.
Size-dependent field-emission characteristics of ZnO nanowires grown by porous anodic aluminum oxide templates assistance
(2010-10-01)
Lai, Chun-Hung
;
Chang, Chia-Wei
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The field-emission electrical properties of hydrothermally synthesized zinc-oxide nanowires grown on SiO(2)-Si substrate are reported. Vertically aligned single-crystalline emitters with distinct length L and diameter D are realized by controlling the assisted growth of porous anodic aluminum oxide (AAO) templates. Field-emission measurement revealed that these field emitters exhibited controllable turn-on field E(to) and the field enhancement factor beta. Sample with feature size of L = 500 nm and D = 80 nm was prepared and then used as a basis for examining the size effect. Lower E(to) and higher beta were observed consistently for increasing the aspect ratio LID. The enhanced properties of E(to) = 1.48 V/mu m and beta up to 6100 are achieved for L/D = 53 (L = 1600 nm and D = 30 nm). Optimal characterizing parameters of E(to) and beta will be reached while pursuing extreme L/D practically. Factors such as the geometric limit of AAO template manufacture and the filling efficiency of ZnO into AAO pores will exert influence on the size-dependent effect. (C) 2010 Elsevier B.V. All rights reserved.