The Experts below are selected from a list of 2880 Experts worldwide ranked by ideXlab platform
Mike Hettich - One of the best experts on this subject based on the ideXlab platform.
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all optical control of comb like coherent acoustic phonons in multiple quantum well structures through double pump pulse pump probe experiments
Optics Express, 2019Co-Authors: V Gusev, Thomas Dekorsy, Mike HettichAbstract:We present an advancement in applications of ultrafast optics in picosecond laser ultrasonics - laser-induced comb-like coherent acoustic phonons are optically controlled in a In0.27Ga0.73As/GaAs multiple quantum well (MQW) structure by a high-speed asynchronous optical sampling (ASOPS) system based on two GHz Yb:KYW lasers. Two successive pulses from the same pump laser are used to excite the MQW structure. The second pump light pulse has a tunable time delay with respect to the first one and can be also tuned in intensity, which enables the amplitude and phase modulation of acoustic phonons. This yields rich temporal acoustic patterns with suppressed or enhanced amplitudes, various Wave-packet shapes, varied Wave-packet widths, reduced Wave-packet periods and varied phase shifts of single-period oscillations within a Wave-packet. In the frequency domain, the amplitude and phase shift of the individual comb component present a second-pump-delay-dependent Cosine-Wave-like and sawtooth-Wave-like variation, respectively, with a modulation frequency equal to the comb component frequency itself. The variations of the individual component amplitude and phase shift by tuning the second pump intensity exhibit an amplitude valley and an abrupt phase jump at the ratio around 1:1 of the two pump pulse intensities for certain time delays. A simplified model, where both generation and detection functions are assumed as a Cosine stress Wave enveloped by Gaussian or rectangular shapes in an infinite periodic MQW structure, is developed in order to interpret acoustic manipulation in the MQW sample. The modelling agrees well with the experiment in a wide range of time delays and intensity ratios. Moreover, by applying a heuristic-analytical approach and nonlinear corrections, the improved calculations reach an excellent agreement with experimental results and thus enable to predict and synthesize coherent acoustic Wave patterns in MQW structures.
Shaban G Gouda - One of the best experts on this subject based on the ideXlab platform.
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model selection for accurate daily global solar radiation prediction in china
Journal of Cleaner Production, 2019Co-Authors: Shaban G Gouda, Zakia Hussein, Shuai Luo, Qiaoxia YuanAbstract:Abstract Solar energy can share with a big percentage in solving in the environmental pollution and energy crisis in China. For the most application of solar energy, an accurate information of solar radiation amount received by a horizontal surface is the first step. In this study, nine-day of the year based models are calibrated and evaluated to estimate the daily global solar radiation (DGSR) on a horizontal surface using long-term data of 84 stations all over China. After dividing China into five solar climatic zones, the highest performance model for each zone is chosen to be a general day of the year based models and then calibrate and evaluated at each solar zone. Based on statistical indicator; the root mean square error (RMSE), the mean absolute bias error (MABE), coefficient of determination (R2) and the correlation coefficient (r) and the uncertainty based on a 95% confidence level (U95) and Taylor diagram, results show that the models perform best in the solar zones that receive a high amount of solar radiation and the performance decreases with decreasing of the daily solar radiation incidence. The hybrid sine and Cosine Wave day of the year based models exhibit the best performance, model D7 is the best for zone I and model D8 for zones II and IV. For zones II and V, the Gaussian form model (D3 model) and the 4th order polynomial model (D4 model) yield high performance, respectively. Whereas, the two Gaussian form model is the worth performance for all zones. The developed general day of the year based models for each zone in this study can be used with high accuracy to estimate the (DGSR) on a horizontal surface in areas where there is no data or the data is missing all over China.
V Gusev - One of the best experts on this subject based on the ideXlab platform.
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all optical control of comb like coherent acoustic phonons in multiple quantum well structures through double pump pulse pump probe experiments
Optics Express, 2019Co-Authors: V Gusev, Thomas Dekorsy, Mike HettichAbstract:We present an advancement in applications of ultrafast optics in picosecond laser ultrasonics - laser-induced comb-like coherent acoustic phonons are optically controlled in a In0.27Ga0.73As/GaAs multiple quantum well (MQW) structure by a high-speed asynchronous optical sampling (ASOPS) system based on two GHz Yb:KYW lasers. Two successive pulses from the same pump laser are used to excite the MQW structure. The second pump light pulse has a tunable time delay with respect to the first one and can be also tuned in intensity, which enables the amplitude and phase modulation of acoustic phonons. This yields rich temporal acoustic patterns with suppressed or enhanced amplitudes, various Wave-packet shapes, varied Wave-packet widths, reduced Wave-packet periods and varied phase shifts of single-period oscillations within a Wave-packet. In the frequency domain, the amplitude and phase shift of the individual comb component present a second-pump-delay-dependent Cosine-Wave-like and sawtooth-Wave-like variation, respectively, with a modulation frequency equal to the comb component frequency itself. The variations of the individual component amplitude and phase shift by tuning the second pump intensity exhibit an amplitude valley and an abrupt phase jump at the ratio around 1:1 of the two pump pulse intensities for certain time delays. A simplified model, where both generation and detection functions are assumed as a Cosine stress Wave enveloped by Gaussian or rectangular shapes in an infinite periodic MQW structure, is developed in order to interpret acoustic manipulation in the MQW sample. The modelling agrees well with the experiment in a wide range of time delays and intensity ratios. Moreover, by applying a heuristic-analytical approach and nonlinear corrections, the improved calculations reach an excellent agreement with experimental results and thus enable to predict and synthesize coherent acoustic Wave patterns in MQW structures.
Kasra Mohammadi - One of the best experts on this subject based on the ideXlab platform.
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prediction of daily global solar radiation by day of the year in four cities located in the sunny regions of iran
Energy Conversion and Management, 2013Co-Authors: Hossein Khorasanizadeh, Kasra MohammadiAbstract:Abstract In this study, by using long-term global solar radiation data, 6 day of the year based empirical models were tested for prediction of daily global solar radiation in four Iranian cities of Bandarabass, Isfahan, Kerman and Tabass. The statistical non-linear regression technique was utilized to establish the models then their accuracy evaluated using the statistical indicators of mean absolute percentage error, mean absolute bias error, root mean square error and coefficient of determination. In Bandarabass, Kerman and Tabass, the hybrid sine and Cosine Wave model and in Isfahan the 4th order polynomial model provided the highest accuracy. To assess the performance of the models in different days of the year a further statistical analysis was performed using the relative percentage error. The number of days falling in its acceptable interval of −10% to 10% for the best models in Bandarabass, Isfahan, Kerman, and Tabass were 346, 322, 334 and 328, respectively. Making comparison with the predictions of some existing monthly averaged models stated the superiority of the newly established day of the year based models. Hence, they can be utilized swimmingly to estimate daily insolation in the corresponding cities and a vast similar climate region around them.
Qiaoxia Yuan - One of the best experts on this subject based on the ideXlab platform.
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model selection for accurate daily global solar radiation prediction in china
Journal of Cleaner Production, 2019Co-Authors: Shaban G Gouda, Zakia Hussein, Shuai Luo, Qiaoxia YuanAbstract:Abstract Solar energy can share with a big percentage in solving in the environmental pollution and energy crisis in China. For the most application of solar energy, an accurate information of solar radiation amount received by a horizontal surface is the first step. In this study, nine-day of the year based models are calibrated and evaluated to estimate the daily global solar radiation (DGSR) on a horizontal surface using long-term data of 84 stations all over China. After dividing China into five solar climatic zones, the highest performance model for each zone is chosen to be a general day of the year based models and then calibrate and evaluated at each solar zone. Based on statistical indicator; the root mean square error (RMSE), the mean absolute bias error (MABE), coefficient of determination (R2) and the correlation coefficient (r) and the uncertainty based on a 95% confidence level (U95) and Taylor diagram, results show that the models perform best in the solar zones that receive a high amount of solar radiation and the performance decreases with decreasing of the daily solar radiation incidence. The hybrid sine and Cosine Wave day of the year based models exhibit the best performance, model D7 is the best for zone I and model D8 for zones II and IV. For zones II and V, the Gaussian form model (D3 model) and the 4th order polynomial model (D4 model) yield high performance, respectively. Whereas, the two Gaussian form model is the worth performance for all zones. The developed general day of the year based models for each zone in this study can be used with high accuracy to estimate the (DGSR) on a horizontal surface in areas where there is no data or the data is missing all over China.
