Browsing by Author "Liu, CH"

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A 9 kb/s CAPDM speech coder based on pitch synchronous substitution for wireless PCN applications
(2000)
Liu, CH
;
Huang, CC
;
電信工程研究所
;
Institute of Communications Engineering
This paper describes a low data rate speech coder, which is based on CAPDM (Controlled Adaptive Prediction Delta Modulation) algorithm [2] and operates at about 9 kb/s. It combines the features of one-step looking forward decision, syllabic companding, instantaneous companding, pitch detection, and adaptive prediction. A packet-based CAPDM speech coder for PCN applications, which operates at 16 kb/s, was presented previously and showed near toll quality performance [3]. In this paper, the data rate of CAPDM is further reduced by exploiting the quasi-periodic property of speech vowel waveform and by dropping speech samples every other pitch period. The dropped speech samples are recovered at receiver by duplicating the decoded speech samples according to the pitch periods. The MOS listening test results of the 9 kb/s CAPDM coder are compared with those of the 16 kb/s continuous variable slope delta modulation (CVSD), 16 kb/s CAPDM, and 32 kb/s ADPCM.
A low-power group-based VLD design
(2004)
Liu, CH
;
Shieh, BJ
;
Lee, CY
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, a low power variable length code decoder with group-based scheme [10] is proposed. It can save at most 70% power dissipation while maintaining the same throughput rate as the conventional one. This proposal mainly consists of look-up table (LUT) partitioning and group-based memory storing, where the former is used to reduce the power wasted on looking-up unnecessary code-words due to a large LUT, especially those code-words with low probability; the latter is used to reduce the storage space of VLC tables and maintain the flexibility of our hardware decoder.
A new controlled adaptive prediction delta coder for wireless PCN applications
(1996)
Liu, CH
;
Huang, CC
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
A median-rate speech delta coder with low complexity is presented in this paper. It combines the features of one-step looking forward decision, syllabic companding, instantaneous companding, and adaptive prediction. This coder uses not only short-term prediction filter but also long-term prediction filter to estimate the current speech sample. The performance for this coder with and without pitch prediction is compared by computer simulation. Comparisons between the performance of this coder and the performance of CVSD are also included.
A packet-based CAPDM speech coder for PCN applications
(2000-05-01)
Liu, CH
;
Huang, CC
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we present a median-rate speech coder, the controlled adaptive prediction delta modulation coder (CAPDM), which operates at 16 kb/s with good speech quality and low algorithm complexity [15], The coder is dedicated to personal communication network (PCN) applications and transmits speech samples on the basis of packets. It combines the features of one-step looking forward decision, syllabic companding, instantaneous companding, and adaptive prediction. In addition to the use of a short-term prediction filter, CAPDM also exploits the pitch property to predict speech waveform explicitly. With the aid of a pitch prediction filter, the performance of a CAPDM codec improves about 3 dB in segmental signal-to-noise ratio (SEGSNR), The average SEGSNR of CAPDM.FF is about 21 dB, which is 7 dB over traditional CVSD at 16 kb/s, We also utilize an adaptive postfilter (APF) to enhance the perceptual quality of the decoded speech. The mean opinion score (MOS) listening test of CAPDM.FF with APF shows that its average score achieves 4.19, which is as good as G.728 16-kb/s LD-CELP and is comparable with CCITT G.721 32-kb/s ADPCM, The complexity of CAPDM.FF is evaluated to be 8 MIPS, which Is much lower than that of LD-CELP and could be further reduced by adopting a smaller correlation window for pitch detection. To solve the problem of packet loss, we developed a packet-based waveform substitution method by reinitializing the codec parameters at the beginning of each packet. The simulation results show that CAPDM.FF could tolerate 5% of packet loss and still keep an SEGSNR at 10 db and an MOS at about 3.0.
A priority MAC protocol to support real-time traffic in ad hoc networks
(2004-01-01)
Sheu, JP
;
Liu, CH
;
Wu, SL
;
Tseng, YC
;
資訊工程學系
Carrier sense multiple access and its variants have been widely used in mobile ad hoc networks. However, most existing access mechanisms cannot guarantee quality for real-time traffic. This paper presents a distributed medium access control protocol that provides multiple priority levels for stations to compete for the wireless channel. One common channel is assumed to be shared by all stations. Stations are assumed to be able to hear each other (i.e., the network is fully connected). The channel is accessed by stations according to their priorities, and for stations with the same priority, they send frames in a round robin manner. The channel access procedure is divided into three stages: priorities classification period, ID initialization period, and transmission period. Simulation results indicate that our protocol provides high channel utilization and bounded delays for real-time frames.
An effictive and efficient hierarchical fuzzy rule based classifier
(2003)
Tsai, CH
;
Lin, SY
;
Cheng, MH
;
Horng, SC
;
Liu, CH
In this paper, we propose a hierarchical fuzzy rule based classifier (HFRBC) for the classification problem with large number of classes and continuous attributes. A hierarchical clustering concept is introduced to achieve a finer fuzzy partition. Critical attributes are used to perform the cluster splitting and generate a cluster splitting tree. The effective attributes for the terminal clusters in the cluster splitting tree are picked so as to reduce the size of the fuzzy-rule set and hence reduce the computational complexity. The fuzzy rule generation procedures and classification procedures of the proposed HFRBC are simple and easily implemented. We have successfully applied the HFRBC to the classification problem of the working wafers in an ion implanter.
Application of selective liquid-phase deposition to fabricate contact holes without plasma damage
(1999-06-01)
Yeh, CF
;
Liu, CH
;
Su, JL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work develops an alternative method, selective liquid-phase deposition (S-LPD), to fabricate contact holes instead of reactive ion etching. In preliminary experiments, deep n(+)/p junction diodes with contact holes prepared by S-LPD exhibit much less reverse current, unity ideality factor, larger forward current, lower contact resistance, and higher thermal stability than those prepared by reactive ion etching. Further superiority of plasma damage-free near-surface regions is also investigated using Schottky and ultrashallow junction diodes. Experimental results indicate that S-LPD can be applied to the submicron contact-hole process. The data after reverse bias temperature stress reveals the satisfactory reliability of S-LPD contact holes. This work demonstrates that the S-LPD technology is a highly promising means of replacing reactive ion etching processes to form submicron contact holes as reliably as those by wet-etching. (C) 1999 The Electrochemical Society. S0013-4651(98)08-119-1. All rights reserved.
Applying selective liquid-phase deposition to create contact holes in plasma damage-free process
(1998)
Yeh, CF
;
Liu, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We apply an alternative plasma damage-free process -- the selective liquid-phase deposition (S-LPD), instead of the conventional RIE to form metal/semiconductor contact holes. This paper studies the performance comparison between S-LPD and RIE to form contact hole in n(+)/p junction diode, Schottky diode, and ohmic contact. In our experiments, if the plasma-free S-LPD technique is adopted, there is excelled performance including lower reverse current, lower ideality factor, higher forward current, high Schottky barrier, lower contact resistance and better thermal stability in these devices.
Biotreatment of hydrogen sulfide- and ammonia-containing waste gases by fluidized bed bioreactor
(2001-02-01)
Chung, YC
;
Huang, CP
;
Liu, CH
;
Bai, HL
;
環境工程研究所
Gas mixtures of H2S and NH3 are the focus of this study of research concerning gases generated from animal husbandry and treatments of anaerobic wastewater lagoons. A heterotrophic microflora (a mixture of Pseudomonas putida for H2S and Arthrobacter oxydans for NH3) was immobilized with Ca-alginate and packed into a fluidized bed reactor to simultaneously decompose H2S and NH3. This bioreactor was continuously supplied with H2S and NH3 separately or together at various ratios. The removal efficiency, removal rate, and metabolic product of the bioreactor were studied. The results showed that the efficiency remained above 95% when the inlet H2S concentration was below 30 ppm at 36 L/hr. Furthermore, the apparent maximum removal and the apparent half-saturation constant were 7.0 x 10(-8) gS/cell/day and 76.2 ppm, respectively, in this study. The element sulfur as a main product prevented acidification of the biofilter, which maintained the stability of the operation. As for NH3, the greater than 90% removal rate was achieved as long as the inlet concentration was controlled below 100 ppm at a flow rate of 27 L/hr. In the NH3 inlet, the apparent maximum removal and the apparent half-saturation constant were 1.88 x 10(-6) g-N/cell/day and 30.5 ppm, respectively. Kinetic analysis showed that 60 ppm of NH3 significantly suppressed the H2S removal by Pseudomonas putida, but H2S in the range of 5-60 ppm did not affect NH3 removal by Arthrobacter oxydans. Results from bioaerosol analysis in the bioreactor suggest that the co-immobilized cell technique applied for gas removal creates less environmental impact.
Efficiency evaluation of PTA wastewater treatment with the ultrasound/H2O2 process
(1997)
Liu, CH
;
Ma, YS
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Lin, JG
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交大名義發表
;
環境工程研究所
In this study, we used the ultrasound/hydrogen peroxide (H2O2) process to treat the pure terephaltic acid (PTA) industrial wastewater. The BOD5 and TOC of raw PTA wastewater were 13,200 and 6,390 mg/L, respectively. Several semi-and non-volatile organics, such as benzoic acid, 4-methyl benzaldehyde, phenyl acetic acid, and 4-ethyl benzoic acid were detected in PTA wastewater by GCD (HP GCD 1800A). In the present paper, we discussed the effect of ultrasound/H2O2 process with various concentrations of H2O2 and pH values on mineralization and biodegradability of PTA wastewater. Mineralization of PTA wastewater was evaluated by the ratio of TOC removal and biodegradability by real residual BOD5 over theoretical residual BOD5. The results show that the lower the initial pH value and the higher the concentration of H2O2, the higher ratio of mineralization was found. During the reaction time, the ORP value at pH 3 was greater than at pH 7 and 11. The pH value affected ORP value more significantly than H2O2 dosage in this work. The biodegradability increased with the amount of TOC removal by ultrasound/H2O2 process but decreased with the amount of TOC removal by ultrasound only. The optimum condition to pretreat PTA wastewater with ultrasound/H2O2 process before biological treatment was pH 3 and H2O2 200 mg/L. However, when ultrasound/H2O2 process was used as a sole treatment without biological treatment, the optimum pH value was also controlled at 3, but the concentration of H2O2 must increase upto 500 mg/L. Under such conditions, the ratio of mineralization was 70%.
Efficiency of supercritical fluid extraction for determining 4-nonylphenol in municipal sewage sludge
(1999-04-23)
Lin, JG
;
Arunkumar, R
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Liu, CH
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環境工程研究所
;
Institute of Environmental Engineering
When the sewage sludge containing the persistent, lipophilic, metabolite 4-nonylphenol (4-NP) has been disposed of in the environment it's toxic nature can lead to serious health risks to human beings and can also affect plants and aquatic organisms. Supercritical fluid extraction (SFE) is a new and powerful technique for extracting the organic contaminants from the solid phase. The present study was conducted to investigate optimal conditions for the quantitative extraction of 4-NP by SFE and to determine the concentration of 4-NP in municipal sewage sludge. The effect of several parameters such as temperature, pressure, static extraction time, dynamic extraction time, CO2 flow-rate, sample mass and modifier on the extraction were investigated. The optimal conditions for die extraction of the spiked sample were fluid pressure 97 bar, temperature 40 degrees C, flow-rate 3.0 ml/min, static extraction time 2 min, dynamic extraction time 5 min and modifier methanol (0.5 ml). Extracts were analyzed by gas chromatography-mass spectrometry. Concentration of 4-NP in the anaerobically degraded sludge of the De-flaw Sewage Treatment plant in Taiwan was found to be 243.9 mg/kg. The extraction efficiency of the SFE method was compared with the conventional Soxhlet extraction method. The overall recovery of the SFE method was found to be greater and the results indicate that SFE is an efficient method for extracting 4-NP from sewage sludge. (C) 1999 Elsevier Science B.V. All rights reserved.
Estimating coefficients of volume compressibility from compression of strata and piezometric changes in a multiaquifer system in west Taiwan
(2004-09-01)
Liu, CH
;
Pan, YW
;
Liao, JJ
;
Hung, WC
;
土木工程學系
This paper estimates the coefficients of volume compressibility from variation in compressible! layer thickness and changes in piezometric heads by using detail ground surface surveys and a multilayer monitoring well at a selected site (Shigang) within the Choshui River alluvial fan in west Taiwan. The paper integrates various types of in situ monitoring tools, including leveling surveys, continuous global position system (GPS) stations, multilevel layer compression and groundwater pressure head-monitoring wells, to investigate the situation and progress of the subsidence problem in the region. The results from the cross-analyses of the measured data show that surface settlement caused by the compression of strata is between the depths of 60 and 210 m where the clayey stratum within 120-180 m was most pronounced and contributes up to 53% of the total compression. The results indicate that the clayey stratum is under normal consolidation. The results also reflect the fact that 20% of settlement contribution comes from the sandy stratum within 90-120 m; the elasto-plastic behavior of this sandy stratum is clear. The coefficients of volume compressibility of the clayey and sandy stratum analysed from the stratum's compression records; they were 6.38 x 10(-8) and 5.71 x 10(-9) m(2)/N, respectively. Ultimately, this parameter estimation would permit to control and predict land subsidence based on change in pressure head which are related to groundwater extraction. (C) 2004 Elsevier B.V. All rights reserved.
Fault detection and isolation for plasma etching using model-based approach
(2003)
Cheng, MH
;
Huan-Shin, L
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Lin, SY
;
Liu, CH
;
Lee, WY
A fault detection and isolation system using model-based approach for the chamber pressure of plasma etching is developed. The dynamics of chamber pressure is modeled as a linear multiple-input-single-output closed-loop system and the model parameters are extracted by the system identification technique. The obtained parameters are then converted to physically meaningful features for detecting and isolating faults. The fuzzy inference and Dempster-Shafer evidence combining techniques are employed to detect and isolate fault from the features. The system has been evaluated by the measured data that are collected via SECS-II from the employed Lam-490 plasma etcher for processing practical products. The test results are satisfactory for a large amount of practical data and extensive computer simulations.
Feasibility of fluidized-bed bioreactor for remediating waste gas containing H2S or NH3
(2001)
Chung, YC
;
Liu, CH
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
Pseudomonas putida for H2S and Arthrobacter oxydans for NH3 were immobilized with Ca-alginate and packed inside glass columns to form fluidized-bed bioreactors. The feasibility of the lab-scale bioreactor for the treatment of H2S or NH3 was examined. Phosphate salt, being added to the nutrient solution as buffer solution, may chelate with Ca2+ in the Ca-alginate beads, resulting in the disintegration of gel structure. When the buffer capacity of the phosphate solution was over the critical point of 33.5 mM/pH, all calcium ions in the bead were released and beads were broken. Increasing liquid flowrate and inlet gas concentration favored to H2S and NH3 removal. Carbon source addition was essential and Facilitated malodorous removal for this system. Removal capacity increased with inlet concentration. However, increasing pattern was dependent of H2S or NH3. The result clearly indicated that bioreactor was suitable to be applied for the industry of livestock farm for removing wastegas containing H2S or NH3.
Forward gated-diode measurement of filled traps in high-field stressed thin oxides
(2000-08-01)
Chen, MJ
;
Kang, TK
;
Huang, HT
;
Liu, CH
;
Chang, YJ
The forward gated-diode monitoring technique can find its potential applications in assessing the filled traps in MOSFET thin oxides, which are subjected to high-field stressing and then followed by hot-electrons filling scheme. Our measurement of the gate voltage shift associated with the forward current peak produces a power lan relation between the filled trap density and the electron stress fluence, indeed in close agreement with that obtained by MOSFET threshold voltage shift.
Hierarchical instruction encoding for VLIW digital signal processors
(2005)
Liu, CH
;
Lin, TJ
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Chao, CM
;
Hsiao, PC
;
Lin, LC
VLIW-based architectures are very popular in high-performance DSP processors, for their relatively simpler implementations and more predictable execution times. But they need more program memory because of (1) the fixed-length instruction encoding, (2) NOP insertion due to limited parallelism, and (3) repetitive codes for loop unrolling. This paper describes a novel hierarchical instruction encoding that address these three problems to improve the VLIW code density. In our simulations, the proposed encoding scheme saves 61.4%-66.9% code sizes in highly parallel DSP kernels, and more savings can be expected for general programs. Besides, a simple decoding architecture is proposed and has been integrated into a 4-way VLIW DSP processor. The prototype is implemented in the 0.18um CMOS technology with its operating frequency at 208MHz.
Highly reliable liquid-phase deposited SiO2 with nitrous oxide plasma post-treatment for low temperature processed poly-Si TFT's
(1998)
Yeh, CF
;
Chen, DC
;
Lu, CY
;
Liu, C
;
Lee, ST
Low temperature (similar to 300 degrees C) N2O plasma annealing for liquid-phase deposited (LPD) gate oxide has been proposed for the first time. Physicochemical and electrical characterizations show that the N2O-treated LPD-SiO2 improves breakdown field, interface state density, and Si-rich phenomenon. This novel technology has been also successfully applied to LTP poly-Si TFT's, which reveal excellent characteristics and reliability. It is believed that the N2O plasma post-treatment not only improves the oxide quality, but also passivates the trap states in poly-Si channel.
Highly reliable liquid-phase-deposited SiO2 with nitrous oxide plasma post-treatment for low-temperature-processed polysilicon thin film transistors
(2002-10-01)
Yeh, CF
;
Chen, DCH
;
Lu, CY
;
Liu, C
;
Lee, ST
Low-temperature ( similar to 300 C) N2O-plasma post-treatment for liquid-phase-deposited (LPD) gate oxide has been proposed for the first time. This treatment successfully takes the place of conventional furnace annealing in O-2 ambient. Results of physicochemical and electrical characteristics shock that N2O-plasma post-treated LPD-SiO2 has a high electrical breakdown field and low interface State density. In addition. N2O-plasma treatment also improves the Si-rich phenomenon of LPD-SiO2. From the comparison with pure N2O-plasma oxidation film, LPD-SiO2 with its short re-oxidation time in N2O plasma plays an important role in relieving interfacial stress. Finally, the novel technology is applied to the gate oxide of low-temperature-processed (LTP) polysilicon thin film transistors (poly-Si TFTs). The device performance reveals excellent electrical characteristics, and the reliability shows a satisfactory result. as well as the gate oxide reliability. It is believed that the N2O-plasma post-treatment not only improves the oxide quality, but also effectively passivates the trap states of poly-Si TFTs.
Low-frequency noise in n-channel metal-oxide-semiconductor field-effect transistors undergoing soft breakdown
(2001-01-01)
Chen, MJ
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Kang, TK
;
Lee, YH
;
Liu, CH
;
Chang, YJ
For 3.3-nm thick gate oxide n-channel metal-oxide-semiconductor field-effect transistors subject to a stress gate voltage of 5.5 V, three distinct events are encountered in the time evolution of the gate current: stress-induced leakage current (SILC), soft breakdown (SBD), and hard breakdown (HBD). The localization of SBD and HBD paths, as well as their developments with the time, is determined electrically, showing random distribution in nature. At several stress times, we interrupt the stressing to measure the drain current low-frequency noise power S-id. As expected, S-id follows up the spontaneous changes at the onset of SBD and HBD. The S-id spectra measured in fresh and SILC mode are reproduced by a literature model accounting for the carrier number and surface mobility fluctuations in the channel, and, as a result, both preexisting and newly generated trap densities are assessed. The post-SBD S-id does originate from current fluctuations in the SBD percolation paths, which can couple indirectly to drain via underlying channel in series, or directly to drain if the SBD path is formed close to drain extension. In particular, a fluctuation in S-id itself in the whole SBD duration is observed. This phenomenon is very striking since it indeed evidences the dynamic percolation origin concerning the trapping-detrapping processes in and around the SBD paths. The subsequent HBD duration remarkably features a flat S-id, indicating the set-up of a complete conductive path prevailing over the trapping-detrapping processes. (C) 2001 American Institute of Physics.
Novel contact hole fabrication using selective liquid-phase deposition instead of reactive ion etching
(1999-01-01)
Yeh, CF
;
Liu, CH
;
Su, JL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work forms a contact hole utilizing the selectively liquid-phase deposited (S-LPD) silicon-oxide technique instead of the conventional reactive ion etching (RIE), The n(+)/p junction diode with contact hole formed by S-LPD exhibits one order less reverse current, larger forward current, smaller ideality factor, and better thermal stability than that formed by RIE. The Schottky junction with S-LPD contact hole also possesses several excellent characteristics, including ideality factor, reverse current and barrier height, even without sintering treatment. These characteristics confirm the effectiveness of S-LPD technique in replacing conventional RIE to form contact holes, particularly for the ultra-shallow junction in future.