The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Clyde G. Bethea - One of the best experts on this subject based on the ideXlab platform.
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Steady state Model for facet heating leading to thermal runaway in semiconductor lasers
Journal of Applied Physics, 1994Co-Authors: Richard Schatz, Clyde G. BetheaAbstract:A steady state Model is presented which provides new insight into the thermal runaway process that leads to catastrophic damage of semiconductor lasers. We show that thermal runaway is preceded by a situation where two self consistent thermal steady state solutions exist at low output power, one stable and one unstable. When the output power is increased, the two solutions degenerate and disappear which means that the laser will enter thermal runaway. The steady state Model consists of two parts: a three dimensional thermal Model and a one dimensional Model for the carrier diffusion towards the facet. The temperature dependence of both the heat sources and the thermal conductivity play the crucial role. Also ordinary bulk heating is shown to be an important factor. Both 0.88 μm GaAs lasers and 1.5 μm InGaAsP lasers are discussed and minimum values of surface recombination and output power needed for thermal runaway are given. Thermal runaway in GaAs lasers can be explained by the Model for realistic value...
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Steady state Model for facet heating leading to thermal runaway in semiconductor lasers
Journal of Applied Physics, 1994Co-Authors: Richard Schatz, Clyde G. BetheaAbstract:A steady state Model is presented which provides new insight into the thermal runaway process that leads to catastrophic damage of semiconductor lasers. We show that thermal runaway is preceded by a situation where two self consistent thermal steady state solutions exist at low output power, one stable and one unstable. When the output power is increased, the two solutions degenerate and disappear which means that the laser will enter thermal runaway. The steady state Model consists of two parts: a three dimensional thermal Model and a one dimensional Model for the carrier diffusion towards the facet. The temperature dependence of both the heat sources and the thermal conductivity play the crucial role. Also ordinary bulk heating is shown to be an important factor. Both 0.88 μm GaAs lasers and 1.5 μm InGaAsP lasers are discussed and minimum values of surface recombination and output power needed for thermal runaway are given. Thermal runaway in GaAs lasers can be explained by the Model for realistic values of surface recombination. However, the calculated values of needed output power are significantly higher than what is experienced in reality. Possible explanations for this discrepancy are given.
R. Brenot - One of the best experts on this subject based on the ideXlab platform.
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Wideband Steady-State Model of a Strained InGaAsP MQW-SOA
Journal of Lightwave Technology, 2016Co-Authors: M. Connelly, Simone Mazzucato, Hélène Carrère, Xavier Marie, Thierry Amand, M. Achouche, C. Caillaud, R. BrenotAbstract:A Steady-State Model of a strained MQW-SOA is described. Least-squares fitting of the Model to experimental polarization resolved amplified spontaneous emission spectra is used to obtain difficult to measure Model parameters such as the linebroadening lineshape parameters, Auger recombination, bandgap shrinkage, and intervalence band absorption coefficients. Well capture and escape processes are Modeled by a carrier density dependent net escape time which accounts for barrier effects. Simulations and comparisons with experimental data are given which demonstrate the accuracy and versatility of the Model.
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Wideband Steady-State Model of a strained MQW-SOA
2014Co-Authors: M. Connelly, Simone Mazzucato, Hélène Carrère, Xavier Marie, Thierry Amand, M. Achouche, C. Caillaud, R. BrenotAbstract:A wideband Steady-State Model of a MQW-SOA is described. Least-squares fitting of the Model to experimental polarization resolved amplified spontaneous spectra were used to obtain difficult to measure Model parameters such as the intraband broadening energy, Auger recombination coefficient and the bandgap shrinkage coefficient. Simulations and comparisons with experiment are given which demonstrate the accuracy and versatility of the Model.
Richard Schatz - One of the best experts on this subject based on the ideXlab platform.
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Steady state Model for facet heating leading to thermal runaway in semiconductor lasers
Journal of Applied Physics, 1994Co-Authors: Richard Schatz, Clyde G. BetheaAbstract:A steady state Model is presented which provides new insight into the thermal runaway process that leads to catastrophic damage of semiconductor lasers. We show that thermal runaway is preceded by a situation where two self consistent thermal steady state solutions exist at low output power, one stable and one unstable. When the output power is increased, the two solutions degenerate and disappear which means that the laser will enter thermal runaway. The steady state Model consists of two parts: a three dimensional thermal Model and a one dimensional Model for the carrier diffusion towards the facet. The temperature dependence of both the heat sources and the thermal conductivity play the crucial role. Also ordinary bulk heating is shown to be an important factor. Both 0.88 μm GaAs lasers and 1.5 μm InGaAsP lasers are discussed and minimum values of surface recombination and output power needed for thermal runaway are given. Thermal runaway in GaAs lasers can be explained by the Model for realistic value...
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Steady state Model for facet heating leading to thermal runaway in semiconductor lasers
Journal of Applied Physics, 1994Co-Authors: Richard Schatz, Clyde G. BetheaAbstract:A steady state Model is presented which provides new insight into the thermal runaway process that leads to catastrophic damage of semiconductor lasers. We show that thermal runaway is preceded by a situation where two self consistent thermal steady state solutions exist at low output power, one stable and one unstable. When the output power is increased, the two solutions degenerate and disappear which means that the laser will enter thermal runaway. The steady state Model consists of two parts: a three dimensional thermal Model and a one dimensional Model for the carrier diffusion towards the facet. The temperature dependence of both the heat sources and the thermal conductivity play the crucial role. Also ordinary bulk heating is shown to be an important factor. Both 0.88 μm GaAs lasers and 1.5 μm InGaAsP lasers are discussed and minimum values of surface recombination and output power needed for thermal runaway are given. Thermal runaway in GaAs lasers can be explained by the Model for realistic values of surface recombination. However, the calculated values of needed output power are significantly higher than what is experienced in reality. Possible explanations for this discrepancy are given.
George A. Ekama - One of the best experts on this subject based on the ideXlab platform.
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sani process realizes sustainable saline sewage treatment steady state Model based evaluation of the pilot scale trial of the process
Water Research, 2012Co-Authors: George A. Ekama, Jiang Feng, Mark C M Van Loosdrecht, Guanghao ChenAbstract:Abstract A steady state Model was developed for evaluating the sulfur cycle based SANI® process. The Model comprises: 1) a COD-based anaerobic hydrolysis kinetics Model to determine removal of biodegradable COD and sulfate under different hydraulic retention time (HRT) and sludge retention time (SRT), 2) an element (C, H, O, N, P, S), COD and charge mass balanced stoichiometric part for prediction of the concentrations of alkalinity ( H 2 CO 3 ∗ alkalinity + H2S alkalinity), COD, sulfate, sulfide, nitrate and free saline ammonia in anaerobic sulfate reduction, anoxic autotrophic denitrification and aerobic autotrophic nitrification, and 3) an inorganic carbon ( HCO 3 − ) and sulfide (H2S/HS−) mixed weak acid/base chemistry part for pH prediction. Through characterization of the sewage organic matter and determination of the anaerobic hydrolysis kinetic rate and other relevant parameters, the steady state Model was calibrated to a pilot plant for the SANI® process. The Model predictions agreed well with the experimental data of the pilot-scale trial, demonstrating that the Model developed from this study can explain the causes and conditions for the different bioprocesses and minimal sludge production in the SANI® process.
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biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed reactor part 5 steady state Model
SA Journal of Radiology, 2010Co-Authors: Johann Poinapen, George A. EkamaAbstract:This paper describes the development of a Steady-State anaerobic digestion Model for biological sulphate reduction using primary sewage sludge (PSS) as substrate. The Model comprises: a chemical oxygen demand (COD) based hydrolysis kinetics part in which the PSS biodegradable COD and sulphate removals are calculated for given hydraulic and sludge retention times; a C, H, O, N, P, S, COD and charge mass balance stoichiometry part in which the alkalinity generated (from both the HCO3- and HS-) is determined from the COD and sulphate removals; and an inorganic carbon (CO2) and sulphide mixed weak acid/base chemistry part in which the digester pH is calculated from the HCO3- and HS- species formed. From the stoichiometry, it was found that the PSS is carbon limited in that it does not generate sufficient HCO3- alkalinity for the sulphate reduction, i.e., its COD/C ratio is too high which accounts for the observed zero gas (CO2) generation. The H2S/HS- system provides the alkalinity shortfall and establishes the system pH. Once developed and calibrated, the Model results were compared with experimental data from 2 laboratory-scale upflow anaerobic sludge bed reactors (operated at 35oC and 20°C respectively) fed PSS and sulphate. The predicted COD and sulphate removals, alkalinity and digester pH correspond very well to the measured data. The Model assists in identifying design and operation parameters sensitive to the system and provides a basis for developing an integrated biological, chemical and physical process dynamic Model.Keywords: biological sulphate reduction, primary sewage sludge, upflow anaerobic sludge bed reactor, steady state Model, kinetics, stoichiometry, mixed weak acid/base chemistry
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A steady state Model for anaerobic digestion of sewage sludges
Water SA, 2006Co-Authors: Sw Sötemann, Ne Ristow, M. C. Wentzel, George A. EkamaAbstract:A steady state Model for anaerobic digestion of sewage sludge is developed that comprises three sequential parts – a kinetic part from which the % COD removal and methane production are determined for a given retention time; a stoichiometry part from which the gas composition (or partial pressure of CO,sub>2 ), ammonia released and alkalinity generated are calculated from the %COD removal; and a carbonate system weak acid/base chemistry part from which the digester pH is calculated from the partial pressure of CO 2 and alkalinity generated. From the stoichiometry and weak acid base chemistry parts of the Model, for a given % COD removal, the digester gas composition, ammonia released, alkalinity generated and digester pH are com¬pletely defined by the influent sludge composition, i.e. X, Y, Z and A in CXHYOZNA of the hydrolysable organics; volatile fatty acid (VFA) concentration; and pH. For the kinetic part of the Model, four hydrolysis kinetic equations were calibrated against 7 to 60 d retention time anaerobic digesters treating two different sewage sludge types, viz. first order; first order specific; Monod; and saturation. Once calibrated against the two sludge type data sets and taking into account experimental error in effluent COD concentration and gas production (i.e. COD mass balance error), each of the four hydrolysis kinetic equa¬tions predicted the % COD removal versus retention time equally well, and predicted COD removal and methane production compared well with measured data. For the different sewage sludge types, viz. a primary and humus sludge mixture from a trickling filter plant, and a “pure” primary sludge, different kinetic rate constants were obtained indicating that the “pure” primary sludge hydrolysed faster and had a lower unbiodegradable particulate COD fraction (f PS'up = 0.33) than the primary and humus sludge mixture (0.36). With the %COD removal known from the hydrolysis part of the Model, and again taking experimental error into account (i.e. C and N mass balances error), the stoichiometry and weak acid base chemistry parts of the Model predicted the gas composition, effluent free and saline ammonia (FSA) concentration, alkalinity generated and digester pH well for a primary and humus sludge composition of C 3.5 H 7 O 2 N 0.196 . From independent measurement of primary sludge CHON composition, this Model estimated composition is within 96%, 100%, 95% and 99% of the average measured composition of C 3.65 H 7 O 1.97 N 0.190 lending strong support to the developed steady state Model. Keywords : Anaerobic digestion, steady state Model, sewage sludge, hydrolysis kinetics, biodegradability Water SA Vol. 31(4) 2005: 511-528
M. Connelly - One of the best experts on this subject based on the ideXlab platform.
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Wideband Steady-State Model of a Strained InGaAsP MQW-SOA
Journal of Lightwave Technology, 2016Co-Authors: M. Connelly, Simone Mazzucato, Hélène Carrère, Xavier Marie, Thierry Amand, M. Achouche, C. Caillaud, R. BrenotAbstract:A Steady-State Model of a strained MQW-SOA is described. Least-squares fitting of the Model to experimental polarization resolved amplified spontaneous emission spectra is used to obtain difficult to measure Model parameters such as the linebroadening lineshape parameters, Auger recombination, bandgap shrinkage, and intervalence band absorption coefficients. Well capture and escape processes are Modeled by a carrier density dependent net escape time which accounts for barrier effects. Simulations and comparisons with experimental data are given which demonstrate the accuracy and versatility of the Model.
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Wideband Steady-State Model of a strained MQW-SOA
2014Co-Authors: M. Connelly, Simone Mazzucato, Hélène Carrère, Xavier Marie, Thierry Amand, M. Achouche, C. Caillaud, R. BrenotAbstract:A wideband Steady-State Model of a MQW-SOA is described. Least-squares fitting of the Model to experimental polarization resolved amplified spontaneous spectra were used to obtain difficult to measure Model parameters such as the intraband broadening energy, Auger recombination coefficient and the bandgap shrinkage coefficient. Simulations and comparisons with experiment are given which demonstrate the accuracy and versatility of the Model.
