Browsing by Author "Wu, JR"

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Decomposition of 2-chlorophenol in aqueous solution by ultrasound/H2O2 process
(1996)
Lin, JG
;
Chang, CN
;
Wu, JR
;
環境工程研究所
;
Institute of Environmental Engineering
Several authors have indicated that ultrasound is effective in oxidizing organic contaminants in water and in wastewater either as the sole means of treatment or in combination with ozonation and UV irradiation. In this work we decomposed 2-chlorophenol (2-cp) in aqueous solution with ultrasound and H2O2. The experiment was conducted with a sonicator (Microson XL-2020) operated at 20 kHz. The double amplitude at the tip of the standard horn (12.7 mm) was adjusted to 0, 72 and 120 mu m, corresponding to power input 0, 125 and 160 W. The initial concentration of aqueous 2-cp solution was 100 mg/l, treated in the system with 0, 100, 200 and 500 mg/l H2O2 individually. The volume of solution was 11 in a mixing flask, and was circulated to the sonication cell at the rate 500 mL/min. Oxygen was continuously purged into the flask. The temperature of solution was kept constant at 25 degrees C and pH was controlled at 3, 5, 7, 9 and 11. The results showed the decomposition of 2-cp was effective at increased amplitude of ultrasound and concentration of H2O2, and smaller pH. At reaction duration 360 min, 2-cp decomposition with 500 mg/l H2O2 was found with 57% improvement over the control, i.e. without H2O2 addition. The pH, controlled below the pKa of 2-cp (8.49 at 25 degrees C), had significantly better decomposition of 2-cp than at greater values. The decomposition rate of 100 mg/l 2-cp was 99% at 120 mu m double amplitude with H2O2 (200 mg/L) and pH 3, after 360 min of reaction. The removal of total organic carbon was found to be only 63%. From analysis of the experimental results, the data on 2-cp decomposition appeared to follow pseudo-first-order reaction kinetics. The squared correlation coefficient, R2, of the model was greater than 0.9 for various pH values. Copyright (C) 1996 IAWQ.
Effective mechanisms to reduce the overhead of migratory sharing for linked-based cache coherence protocols in clustering multiprocessor architecture
(1998)
Pean, DL
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Wu, JR
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Chen, C
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資訊工程學系
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Department of Computer Science
Migratory-sharing data references will incur many cache misses that can be reduced by merging the invalidation/update requests and the cache misses. This paper presents effective software and hardware techniques to reduce the overhead of migratory-sharing references for the linked-based cache coherence protocols. The software scheme combines both compiler labeling and run time detection techniques. The hardware scheme uses the special access patterns in the linked-based protocols to detect migratory data objects. We have evaluated the performance on the linked-based program-driven simulation environment by using a set of SPLASH benchmarks. According to the simulation results, our software and hm du are methods effectively enhanced the system performance up to 29% and 23% respectively by reducing the overhead of the migratory-sharing references.
Enhancement of decomposition of 2-chlorophenol with ultrasound/H2O2 process
(1996)
Lin, JG
;
Chang, CN
;
Wu, JR
;
Ma, YS
;
環境工程研究所
We investigated the effects of pH, ionic strength, catalyst, and initial concentration on both decomposition of 2-chlorophenol (2-cp) and removal of total organic carbon (TOC) in aqueous solution with ultrasonic amplitude 120 mu m and H2O2 (200 mg/l). When the initial concentrations of 2-cp was 100 mg/l and the pH was controlled at 3, the rate of 2-cp decomposition was enhanced up to 6.6-fold and TOC removal up td 9.8-fold over pH controlled at 11. At pH 3, the efficiency of decomposition of 2-cp was 99% but the removal of TOC was only 63%; a similar situation applied at pH 7 and 11. Hence intermediate compounds were produced and 2-cp was not completely mineralized. When the concentration of ionic strength was increased from 0.001 to 0.1 M, the rate of 2-cp decomposition was enhanced only 0.3-fold, whereas the TOC removal was not enhanced. In comparison of the effects of pH and ionic strength, pH had greater influence on both 2-cp decomposition and TOC removal than ionic strength. The effect of a catalyst (FeSO4) on decomposition of 2-cp was insignificant comparing with direct addition of H2O2 The reaction rate at a smaller initial concentration of 2-cp (10 mg/l) was more rapid than at a greater one (100 mg/l). The rate of 2-cp decomposition and TOC removal appeared to follow pseudo-first-order reaction kinetics. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.
Harmonic injection-locking behavior of frequency-detuned optical pulse in erbium-doped fiber laser
(2004-08-01)
Lin, GR
;
Liao, YS
;
Wu, JR
;
光電工程學系
;
Department of Photonics
The harmonic injection-locking dynamics of a gain-switched laser diode (GSLD) pulse-injection-locked Erbium-doped fiber amplifier-based laser (EDFL) are studied. Under GSLD injection with a pulsewidth and an average power of 17.6ps and 0.2 mW, respectively, at a repetition frequency corresponding to the 223rd harmonic (996.8635971 MHz) of the EDFL, the pulsewidth, peak power, and phase noise of the injection-locked EDFL are broadening from 34.3 ps to 130 ps, decreasing from 1.8 W to 500 mW, and increasing from - 101.5 dBc/Hz to -86 dBc/Hz, respectively, as the repetition frequency detunes toward the injection-locking margin. The injection-locking range is from -13 kHz to +27 kHz. The peak power of the broadened pulses is greatly reduced to one third of that at the zero-detuning condition even with a detuning frequency of 5 kHz. The injection-locked EDFL pulse-train eventually disappears as the repetition frequency of the GSLD detuned beyond the injection-locking bandwidth. The timing jitter of the GSLD harmonic injection-locked EDFL remains unchanged (<0.5ps) within a positive detuning frequency of <25kHz, which is less stable at a negatively frequency-detuned regime.
Linewidth reduction and wavelength tuning of an erbium-doped fiber laser by use of a single-mode-selected and side-mode-suppressed Fabry-Perot laser diode
(2003-09-20)
Lin, GR
;
Wu, JR
;
光電工程學系
;
Department of Photonics
A single-mode and highly side-mode-suppressed 1.55-mum Fabry-Perot laser diode (FPLD) is achieved by feedback injection with an erbium-doped fiber laser (EDFL). For selection of the strongest longitudinal mode from the gain spectrum of the FPLD for lasing in the EDFL, the FPLD is operated at just below the threshold condition and is feedback injected by 0.02% of the EDFL output power. The lasing mode and center wavelength of the proposed single-mode FPLD source are decided by cross-correlated gain profiles of the EDFL and the FPLD; however, the effect of FPLD injection modes is found to be more pronounced. The optimized lasing linewidth (system limitation) and side-mode suppression ratio of 0.01 nm and >49 dB are obtained, which are far better than those of a FPLD at free-running condition. The worst linewidths at 3- and 10-dB decay are observed to be at approximately 0.016 and 0.05 nm, respectively. Linear wavelength tuning of as much as 4.5 nm (from 1558.7 to 1563.2 nm) by adjustment of the temperature of the FPLD from 10 degreesC to 40 degreesC at just below threshold is reported. The wavelength-tuning slope is approximately 0.14 nm/degreesC under temperature accuracy of 0.1 degreesC. (C) 2003 Optical Society of America.
Optical-pulse-injection-iniduced 40 GHz photonic frequency multiplication in erbium-doped fiber laser
(2004-08-01)
Lin, GR
;
Lin, GC
;
Wu, JR
;
光電工程學系
;
Department of Photonics
The generation of a 40 GHz regeneratively amplified and frequency-multiplied optical pulse train from an erbium-doped fiber ring laser is demonstrated. This is achieved by seeding a I GHz gain-switched Fabry-Perot laser diode and detuning its repetition frequency to coincide with the harmonic resonant cavity mode. The peak power of frequency-multiplied erbium-doped fiber lasers (EDFL) pulses increases from 80 mW to 230 mW as the modulation level of the Fabry-Perot laser diode (FPLD) increases from 18 dBm to 30 dBm. The pulsewidth and peak power are 10 ps and 5 mW at a repetition rate of 40 GHz. The EDFL longitudinal mode frequency fluctuation is within +/-2.5 kHz during 2 h. The frequency-multiplied EDFL pulses exhibit relatively low phase noises of -95 dBc/Hz and -120 dBc/Hz at offset frequencies of 10 kHz and I MHz, respectively. The associated timing jitter of the EDFL pulses exponentially increases from 0.6 ps to beyond 5.8 ps as the frequency multiplication order increases from I to 40.
Rational harmonic mode-locking of erbium-doped fiber laser at 40 GHz using a loss-modulated Fabry-Perot laser diode
(2004-08-01)
Lin, GR
;
Chang, YC
;
Wu, JR
;
光電工程學系
;
Department of Photonics
Rational harmonic mode-locking of an Erbium-doped fiber ring laser (EDFL) at repetition frequency of 40 GHz is demonstrated by using a purely loss-modulated Fabry-Perot laser diode (FPLD) at 1 GHz. The FPLD is neither lasing nor gain-switching, which requires a threshold modulation power of 18 dBm to initiate harmonic mode-locking of the EDFL. After chirp compensation, the nearly transform-limited pulsewidth And spectral linewidth of 3 ps and 1.3 mn are obtained at repetition frequency of 40 GHz, which corresponds to a time-bandwidth product of 0.31. The EDFL gradually evolves from harmonic mode-locking to injection-locking mode as the FPLD changes from loss-modulation to gain-switching mode by increasing its dc driving current.
Tenth-order rational-harmonic frequency multiplication and detuning of optical pulse injection-locked erbium-doped fiber laser
(2005-04-20)
Lin, GR
;
Wu, JR
;
光電工程學系
;
Department of Photonics
The jitter and frequency-detuning dynamics of a 10-GHz rational-harmonic frequency-multiplied pulse train generated from an erbium-doped fiber laser (EDFL) is studied. The EDFL is self-feedback seeded and optically injection locked by a gain-switched laser diode (GSLD) with a pulse width and an average power of 1.7.6 ps and 0.2 mW, respectively, at a repetition frequency of 1 GHz. The repetition frequency of the optical pulse train can be tenth-order multiplied by a slight detuning of the repetition frequency of the GSLD to match the rational-harmonic injection-locked condition of the EDFL. As the repetition frequency is multiplied from 1 to 10 GHz, the peak power, the pulse width, and the frequency-detuning bandwidth of the injection-locked EDFL pulses decrease from 1.2 to 0.3 W, from 40 to 21 ps, and from 40 to 9 kHz, respectively. The timing jitter of the injection-locked EDFL repeated at 1 GHz remains unchanged (< 0.5 ps) within the detuning bandwidth, which inevitably increases to 1.2 ps after tenth-order multiplication. (c) 2005 Optical Society of America.
Tunable single-mode fiber laser with a low-cost active Fabry-Perot filter of ultra-narrow-linewidth and high side-mode-suppressing ratio
(2002)
Lin, GR
;
Wu, JR
;
光電工程學系
;
Department of Photonics
We demonstrate a novel approach for generating a narrow-linewidth and highly side-mode suppressed Erbium-doped fiber laser (EDFL) by combining it with an intracavity feedback-injected 1.55mum Fabry-Perot laser diode (FPLD) via optical couplers. To help selecting the strongest longitudinal mode from the gain-spectrum of FPLD for lasing in the EDF ring cavity, the intracavity FPLD is operated at just below threshold condition associated with an intracavity feedback optical power ratio of <1%. The lasing mode and center wavelength of the proposed EDFL source are decided by both the cross-correlated gain profile of EDFA and FPLD, however, the effect of FPLD injection modes is found to be more pronounced. The optimized lasing linewidth (system limitation) and side-mode suppression ratio of 0.01 nm and > 49 dB are obtained. The worst linewidth at 3-dB and 10-dB decay are observed to maintain at about 0.016 nm and 0.05 nm, respectively. Linear wavelength tuning of up to 6 nm (from 1551.5 nm to 1557.7 nm) by adjusting temperature of FPLD from 10 degreesC to 50 degreesC at just below threshold is reported. The wavelength-tuning slope is about 0.155 nm/degreesC under temperature accuracy of 0.1 degreesC.