Browsing by Author "Yu, YH"

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A COMM baseband processor with robust synchronization for high-speed WLAN applications
(2004)
Liu, HY
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Yu, YH
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Lin, CC
;
Chung, CC
;
Hsu, TY
in this paper, a high-performance and low-cost COFDM baseband processor is presented. With algorithm exploration in channel estimation and phase error tracking, synchronization becomes more robust to enhance system performance. And better design SNR (1.35similar to7.16 dB) can be achieved compared to current solutions. Moreover through architectural exploration, the proposed baseband processor designed in 0.18 um CMOS process contains only 370 K logic gates and 3.3 K byte memory. Measurement results show that better hardware efficiency and performance enhancement is achieved for high-speed WLAN applications.
A dynamic model of ozone disinfection in a bubble column with oxygen mass transfer
(2002-05-01)
Chen, YH
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Chang, CY
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Yu, YH
;
Chiang, PC
;
Chiu, CY
The dynamic process of disinfection with ozone in a bubble column is studied for model establishment. Bubble columns have been widely used for ozone disinfection in plants and laboratories. Ozone is produced by passing oxygen-enriched gas through an ozone generator, and introduced into the bottom of a column equipped with a gas-diffuser. There certainly exists a temporary and unsteady period before the ozone disinfection system reaches steady state. Available ozone disinfection models employed to describe dissolved ozone and surviving microorganism profiles have commonly been developed for steady state. Moreover, oxygen mass transfer has usually been neglected in previous ozone disinfection models. However, this information is desirable for the proper operation of ozone disinfection in a bubble column. Thus, the objective of this study was to model and investigate the dynamic ozone disinfection process in a bubble column with oxygen mass transfer. A dynamic axial dispersion model is proposed and was employed to predict the variation of the ozone, microorganism and oxygen concentrations along the column. The results of prediction were obtained based on the conditions of Marinas et al. (1993). E. coli was chosen as the model microorganism. The dynamic model of ozone inactivation is useful for proper prediction of the variables of an ozone disinfection system in a bubble column.
A model-based rate allocation mechanism for wavelet-based embedded image and video coding
(2005)
Yu, YH
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Tsai, CJ
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資訊工程學系
;
Department of Computer Science
In wavelet-based embedded coding for still images and/or videos, a trade-off between scalability and coding efficiency is achieved via layered-packetization of the embedded bitstreams optimized for several target operating bitrate points. This process is called rate allocation (tier-2 coding). The typical rate allocation mechanism is formulated as a rate-distortion optimization problem and a simple searching method with slow convergence rate is used. In this paper, a highly efficient model-based rate allocation mechanism is proposed. The algorithm is base on the adaptive analysis of the relationship between rate and distortion of the image/video data. Experiments conducted on a scalable video codec show that the time to obtain the optimal solution is greatly reduced. The techniques can be applied to various wavelet-based embedded image and video coding schemes, such as JPEG2000 and scalable video coding.
A novel visual distortion sensitivity analysis for video encoder bit allocation
(2004)
Tang, CW
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Chen, CH
;
Yu, YH
;
Tsai, CJ
;
資訊工程學系
A novel video bit allocation technique adopting a visual distortion sensitivity model for better rate-visual distortion coding control is proposed in this paper. Instead of applying complicated semantic understanding, the proposed automatic distortion sensitivity analysis process analyzes both the motion and the texture structures in the video sequences in order to achieve better bit allocation for rate-constrained video coding This analysis evaluates the tolerable perceptual distortions on a macroblock basis, and allocates fewer bits to regions permitting large perceptual distortions for rate reduction. The proposed algorithm can be incorporated into any existing video coding rate control schemes to achieve same Visual quality at greatly reduced bitrate. Experiments based on H.264 show that this technique achieves bit-rate saving of up to 40% with no perceptual quality degradations. The experiments also demonstrate the inadequacy Of using PSNR as a distortion measure in a video coding framework.
A refined model for ozone mass transfer in a bubble column
(1998-01-01)
Huang, WH
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Chang, CY
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Chiu, CY
;
Lee, SJ
;
Yu, YH
The mathematical model proposed by Marinas et ai. (1993) for a bubble column gas-liquid contactor is refined to described the mass transfer of ozone absorption and decomposition in the aqueous solution with the decomposition rate expression of general reaction orders (not necessarily integers). Three system equations are employed to describe the ozone concentrations in the bulk liquid (C-ALb), the hold-up gas (C-AGb), and the superficial gas rise velocity (u(G)), respectively. The variation of u(G) and the effect of ozone decomposition on the mass transfer, which is reflected by the enhancement factor (E-r) defined as the ratio of chemical to pure physical mass fluxes according to the film model of gas liquid absorption, are considered in the refined model. This analysis thus extends the applicability of the model of Marinas et al. (1993) and is of special importance for the ozone mass transfer in the cases of basic solutions and of low mass transfer coefficients, in which the effect of decomposition on absorption is significant. An example of such case is the cyanide wastewater treatment in the strong basic condition.
A refined model for ozone mass transfer in a bubble column
(1998-01-01)
Huang, WH
;
Chang, CY
;
Chiu, CY
;
Lee, SJ
;
Yu, YH
The mathematical model proposed by Marinas et ai. (1993) for a bubble column gas-liquid contactor is refined to described the mass transfer of ozone absorption and decomposition in the aqueous solution with the decomposition rate expression of general reaction orders (not necessarily integers). Three system equations are employed to describe the ozone concentrations in the bulk liquid (C-ALb), the hold-up gas (C-AGb), and the superficial gas rise velocity (u(G)), respectively. The variation of u(G) and the effect of ozone decomposition on the mass transfer, which is reflected by the enhancement factor (E-r) defined as the ratio of chemical to pure physical mass fluxes according to the film model of gas liquid absorption, are considered in the refined model. This analysis thus extends the applicability of the model of Marinas et al. (1993) and is of special importance for the ozone mass transfer in the cases of basic solutions and of low mass transfer coefficients, in which the effect of decomposition on absorption is significant. An example of such case is the cyanide wastewater treatment in the strong basic condition.
A refined model for ozone mass transfer in a semibatch stirred vessel
(1997-11-01)
Chiu, CY
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Chang, CY
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Huang, WH
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Lee, SJ
;
Yu, YH
The mathematical model proposed by Anselmi et al. (1984) for a semibatch stirred gas-liquid contactor is refined to describe the mass transfer of ozone absorption and decomposition in aqueous solution with the decomposition rate expression of general reaction orders (not necessarily integers). Three system equations are employed to describe the ozone concentrations in the bulk liquid (C-ALb), the hold-up gas (C-AGi), and the outlet gas in the free volume above the liquid surface (C-AGe), respectively. The effect of ozone decomposition on the mass transfer, which is reflected by the enhancement factor (E-r) defined as the ratio of mass absorbed per unit area in time t with chemical reaction (r) to that without chemical reaction or of the purely physical absorption, is considered in the refined model. Furthermore, the refined model also takes into account the variation of E-r with C-ALb, which changes with time during the course of gas-liquid contacting. Thus this analysis extends the applicability of the model of Anselmi et al. (1984) and is of special importance for ozone mass transfer in the cases of basic solutions and of low mass transfer coefficients, in which the effect of decomposition on absorption is significant, and in the system with variable liquid phase ozone concentration.
Adaptive rate-distortion optimization using perceptual hints
(2004)
Tsai, CJ
;
Tang, CW
;
Chen, CH
;
Yu, YH
;
資訊工程學系
A novel video coding approach that performs adaptive rate-distortion optimization guided by perceptual hints is proposed in this paper The key idea is to adaptively adjust the Lagrange multipliers of the RDO coder control module based on visual attention analysis. The observation is that human vision is sensitive to movement of well structured objects while tolerates large distortion in moving areas with random structure (texture-wise and motion-wise). The proposed algorithm analyzes permissible perceptual distortions and, accordingly, assigns larger Lagrange multipliers to regions that are perceptually less sensitive to distortion so that rate-reduction is weighted more than distortion reduction in these regions. Experiments show that this scheme achieves bit-rate saving of 5-7% with virtually same perceptual quality and is very promising for practical systems.
Catalytic decomposition of ozone in the presence of water vapor
(1998)
Tsai, WT
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Chang, CY
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Jung, FH
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Chiu, CY
;
Huang, WH
The catalytic decomposition of ozone in the presence of water vapor at the relative humidity (RH) of about 90 % was investigated by using a tubular fixed-bed reactor. The performance tests and reaction kinetic studies were conducted for catalyst, i.e., Pt/gamma-Al2O3 (symbolized as Dash-220). The experiments were carried out at various constant reaction temperatures (298 similar to 323 K) and space velocities (24,000 similar to 44,000 hr(-1)). About 75 % decomposition efficiencies of ozone with inlet concentration of about 0.17 mol/m(3) was achieved at catalyst contact time of 015 sec (space velocity of 24,000 hr(-1)), reaction temperature of 323 K and RH of about 90 % for the Dash-220 catalyst. However, about 97 % decomposition efficiencies of ozone without the presence of water vapor at the same reaction conditions. The results indicated that the Dash-220 catalyst with the presence of water vapor gave lower performance of ozone decomposition than without the presence of water vapor can be achieved at the same reaction conditions. For the reaction kinetics, it was found that the pseudo-first-order chemical reaction rate equation was appropriate for the catalytic decomposition of ozone in the presence of water vapor investigated in this study. The apparent activation energies for the decomposition reaction of ozone using the Dash-220 catalyst in the presence of water vapor at RH of 90 % is 19.32 kJ mol(-1). The corresponding pre-exponential factor is 0.0041 mol/(s g-catalyst (mol/m(3))).
Combined absorption and self-decomposition of ozone in aqueous solutions with interfacial resistance
(1996-05-01)
Chang, CY
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Chiu, CY
;
Lee, SJ
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Huang, WH
;
Yu, YH
A theoretical analysis is performed employing the film model for the isothermal absorption and self-decomposition of ozone in aqueous solutions with interfacial resistance, which is inversely proportional to the interfacial mass transfer coefficient k(g). A closed-form solution has been obtained. The effects of system parameters on the ozone mass transfer rate are examined. These parameters include the interfacial resistance (1/k(g)),the acidic and basic self-decomposition reaction rate parameters (M(m)(0.5), M(n)(0.5); M(m) = [2D(A)k(m)C(Ai)(m-1)/((m+1)]/k(L)(0))(2), M(n) = (2D(A)k(n)C(Ai)(n-1)/(n+1))/k(L)(0))(2), the reaction orders (m,n), the pH value of solution, and the liquid-phase mass transfer coefficient (k(L)(0)). The results indicate that the reduction effect of the interfacial resistance on the absorption rate is most significant for the situation with the larger values of M(m) and M(n) as well as with higher pH values. Also, for any particular finite value of k(L)(0)/k(g), the reduction effect encountered is greater for a gas liquid contactor with a lower k(L)(0). The reduction effect should be avoided in order to maintain a higher mass transfer rate of ozone in aqueous solution. This analysis is of importance for the efficient use of ozone in water/wastewater treatment processes in the presence of interfacial resistance substances such as surface active agents. For some known special cases (for example, cases with no interfacial resistance), the present solution reduces to the previous works of other investigators.
Combining adaptive smoothing and decision-directed channel estimation schemes for OFDM WLAN systems
(2003)
Liu, HY
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Yu, YH
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Hung, CJ
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Hsu, TY
;
Lee, CY
In this paper, a new channel estimation method for OFDM WLAN systems is proposed. This proposal mainly consists of smoothing filtering and decision-directed tracking loop schemes, where the former is used to enhance performance at low SNR and the latter is exploited to enhance performance at high SNR respectively. Together with an adaptive channel management, better performance in terms of MSE and PER can be achieved. Simulation shows the proposed method (1) achieves better 9.0dB similar to 13.0dB gain in MSE than zero forcing criterion and better 2.0dB gain in MSE than conventional approaches in BPSK transmission, and (2) contributes 0.8dB similar to 2.0dB gain in SNR for 10% PER in different transmission modes.
Decomposition of 2-mercaptothiazoline in aqueous solution by ozonation
(2004-07-01)
Chen, YH
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Chang, CY
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Chen, CC
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Chiu, CY
;
Yu, YH
This study investigates the ozonation of 2-mercaptothiazoline (2-MT). The 2-MT is one of the important organic additives for the electroplating solution of the printed wiring board industry and has been widely used as a corrosion inhibitor in many industrial processes. It is of concern for the aquatic pollution control especially in the wastewaters. Semibatch ozonation experiments in the completely stirred tank reactor are performed under various concentrations of input ozone. The concentrations of 2-MT, sulfate, and ammonium are analyzed at specified time intervals to elucidate the decomposition of 2-MT during the ozonation. In addition, the time variation of the dissolved ozone concentration (C-ALb) is continuously monitored in the course of experiments. Total organic carbon (TOC) is chosen and measured as a mineralization index of the ozonation of 2-MT. The results indicate that the decomposition of 2-MT is efficient, while the mineralization of TOC is limited via the ozonation only. Simultaneously, the yield of sulfate with the maximum value of about 47% is characterized by the increases of TOC removal and ozone consumption. These results can provide some useful information for assessing the feasibility of the treatment of 2-MT in the aqueous solution by the ozonation. (C) 2004 Elsevier Ltd. All rights reserved.
Decomposition of 2-naphthalenesulfonate in aqueous solution by ozonation with UV radiation
(2002-09-01)
Chen, YH
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Chang, CY
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Huang, SF
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Chiu, CY
;
Ji, D
This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined With ultraviolet (UV) radiation, Naphthalenesulfonic acids are of importance as dye intermediates for the dye and textile auxiliary industries. Its derivatives, such as 2-NS. have been found in rivers and tannery effluents causing Pollution problems. Thus, the 2-NS is of concern for the aquatic pollution control especially in the surface and waste waters. Ozonation combined with UV radiation is employed for the removal of 2-NS in the aqueous solution. Semibatch ozonation experiments were proceeded under different reaction conditions to studs the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS and sulfate are analyzed at specified time internals to elucidate the decomposition of 2-NS. In addition, values of pH and oxidation reduction potential are continuously Measured in the course of experiments. Total organic carbon is chosen as a mineralization index of the ozonation of 2-NS, The mineralization of 2-NS via the ozonation is remarkably enhanced by the UV radiation. These results can provide useful information for the proper removal of 2-NS in the aqueous solution by the ozonation with UV radiation. (C) 2002 Published by Elsevier Science Ltd.
Dynamic behavior of ozonation with pollutant in a countercurrent bubble column with oxygen mass transfer
(2003-06-01)
Chen, YH
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Chang, CY
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Chiu, CY
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Yu, YH
;
Chiang, PC
The dynamic behavior of ozonation with pollutants in a countercurrent bubble column is studied for the model establishment. Bubble columns have been widely used for an ozonation system in the plants and laboratories. In addition, a countercurrent bubble column has been commonly recommended than a cocurrent one because it has a higher ozone transfer efficiency. Therefore, the investigation of this paper focuses on the countercurrent bubble column. As an ozonation process starts, the gas mixture of ozone and oxygen is introduced into the bottom of a column, and then transferred into the liquid. The pollutants in the wastewater are eliminated subsequently via oxidation by the dissolved ozone. There certainly exists a temporary and unsteady period before the ozonation system reaches steady state. However, available ozonation models employed to describe ozone and pollutant profiles have commonly been developed for steady state. The treating qualities of wastewater in the early stage of ozonation are usually not predicted, and the time required for the steady-state establishment remains to be determined. Moreover, oxygen mass transfer is usually neglected in previous ozonation models so that the increase of dissolved oxygen is uncertain. These information is desirable for the proper design and operation of ozonation system in a bubble column. Thus, the aim of this study is to model and investigate the dynamic processes of ozonation with pollutants including oxygen mass transfer. The dynamic axial dispersion model proposed is employed to predict the variation of the ozone, pollutant, and oxygen concentrations profiles. The validity of the model was demonstrated by comparing the predicted results with the experimental data. The o-cresol was chosen as the model pollutant. The temporal concentration variations of the residual o-cresol and dissolved oxygen in the effluent liquid, and the off-gas ozone in the free volume were measured accordingly. Furthermore, the variation of the enhancement factor of ozone and the amount of off-gas were predicted. Note that it usually needs 2-5 hydraulic retention times to approach steady state under the conditions of this study. Further, the effects of dimensionless system parameters on the performance of the ozonation processes are examined. As a result, the proposed dynamic model of ozonation with pollutants is useful for proper prediction of the variables of an ozonation system in a countercurrent bubble column. (C) 2003 Elsevier Science Ltd. All rights reserved.
Dynamic model of ozone contacting process with oxygen mass transfer in bubble columns
(2002-11-01)
Chen, YH
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Chang, CY
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Chiu, CY
;
Huang, WH
;
Yu, YH
The dynamic process of the dissolution of ozone in a countercurrent bubble column is studied for model establishment. Bubble columns have been used widely for ozone contacting in the plant and laboratory. Ozone is produced by oxygen-enriched gas through an ozone generator, and introduced into the bottom of the column equipped with the gas diffuser. The ozone contacting system proceeds for a temporary and unsteady period before reaching steady state. The available ozone dissolution models employed for the description of the dissolved ozone profiles were commonly developed for the steady state. Moreover, oxygen mass transfer is usually neglected in the preceding ozone dissolution models. However, this information is desirable for proper operation of ozone dissolution in a bubble column. Thus, the objective of this study is to model and investigate the dynamic ozone dissolution process in a bubble column with the oxygen mass transfer. The dynamic axial dispersion model proposed is employed to predict the variations of ozone and oxygen concentrations along the column, and the amount of off-gas. The validity of the model is demonstrated by comparing the predicted results with the experimental data. The dynamic model of ozone dissolution is useful and referable for proper prediction of the variables of the ozone contacting system in a bubble column.
Kinetics of decomposition of polyethylene glycol in electroplating solution by ozonation with UV radiation
(2001-10-01)
Chang, CY
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Chen, YH
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Li, H
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Chiu, CY
;
Yu, YH
The kinetics of the ozonation of polyethylene glycol (PEG) with ultraviolet (UV) radiation in the acid-based electroplating solution of the printed wiring board industry is studied. The substrate prescription of a typical electroplating solution is with pH of 0. 18-0.42, [CuSO4 . 5H(2)O] of 200 g/L, [H2SO4] of 60 g/L, and [Cl-] of 0.03 g/L. Certainly, the discarded electroplating solution is hard to treat with the common chemical and biological processes because of its acidic and metallic compositions. In addition, it contains valuable substances suitable for recovery and reutilization. One of the most important processes for reviving it is to remove the aged organic additives such as PEG. A two-step reaction mechanism in terms of ozone A and total organic carbon is proposed to express the reaction kinetics of PEG ozonation with UV radiation with intensity [I-uv]. The initial concentration of PEG is 30 mg/L, according to the recipe of a typical electroplating solution, which is equivalent to total organic carbon of 16.3 mg/L. The reaction rate r expressions of the concentrations of the liquid phase ozone C-ALb, PEG C-BLb, and intermediates C-ILb are r(A) (=dC(ALb)/dt) = -(k(Am) + k(t)[I-uv)C-ALb (k(R1) + k(RI1)[I-uv])CALbCBLb - (k(R2) + k(RI2)[I-uv])CALbCILb, r(B) (=dC(BLb)/dt) = -(k(R1) + k(RI1)[I-uv])CALbCBLb, r(int) (=dC(ILb)/dt) (k(R1) + k(RI1)[I-uv])CALbCBLb - (k(R2) + k(RI2)[I-uv])CALbCILb, with k(Am) = 0.0036 s(-1), k(1) = 4.654 X 10(-5)s(-1)/(Wm(-2)), k(R1) = 13.525 M(-1)s(-1), k(R2) = 0.751 M(-1)s(-1), k(RI1) = 0.683 M(-1)s(-1)/(Wm(-2)), and k(RI2) = 0.042 M(-1)s(-1)/(Wm(-2)). These reaction kinetic expressions are useful and referable for the proper design of an ozonation system with UV radiation for the treatment of PEG in the printed wiring board electroplating solution.
Modeling ozone mass transfer with combined effects of ozone decomposition and reaction with pollutants in a bubble column
(2001-09-01)
Huang, WH
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Chang, CY
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Chiu, CY
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Chen, YH
;
Yu, YH
This paper analyzes the countercurrent single-stage bubble column reactor (BCR) for gas-liquid ozonation systems. The effects of system variables on ozonation performance are examined. The aspects of ozonation performance considered include the efficiency of ozone utilization, the efficiency of pollutant removal, and the emission concentration of ozone gas. This analysis takes into account the effects of ozone decomposition and the ozonation of pollutants on the ozone mass transfer (i. e., enhancement factror, E-r), the variation of pressure (P) and of gas velocity (U-G) along the column, and dispersion effects (Pe(G), Pe(L)). The obtained detailed single-stage BCR model may be used in further development of multi-stage BCR model in the future. The results of this study can provide useful information for rational design of a BCR ozonation contactor, and are important with respect to the treatment of pollutants via ozonation. For the simplified case without ozonation of pollutants, this analysis reduces to that of Huang et al. (1998).
Visual sensitivity guided bit allocation for video coding
(2006-02-01)
Tang, CW
;
Chen, CH
;
Yu, YH
;
Tsai, CJ
;
資訊工程學系
A video bit allocation technique adopting a visual distortion sensitivity model for better rate-visual distortion Coding control is proposed in this paper. Instead of applying complicated semantic understanding, the proposed automatic distortion sensitivity analysis process analyzes both the motion and the texture structures in the video sequences in order to achieve better bit allocation for rate-constrained video coding. The proposed technique evaluates the perceptual distortion sensitivity on a macroblock basis, and allocates fewer bits to regions permitting large perceptual distortions for rate reduction. The proposed algorithm can be incorporated into existing video coding rate control schemes to achieve same visual quality at reduced bitrate. Experiments based on H.264 JM7.6 show that this technique achieves bit-rate saving of up to 40.61%. However, the conducted subjective viewing experiments show that there is no perceptual quality degradation.