The Experts below are selected from a list of 188970 Experts worldwide ranked by ideXlab platform
Shibin Jiang - One of the best experts on this subject based on the ideXlab platform.
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Efficient Operation of diode pumped single frequency thulium doped fiber lasers near 2 μm
Optics Letters, 2007Co-Authors: Jihong Geng, Shibin JiangAbstract:Efficient Operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber. At 1893 nm, the single-frequency fiber laser has a pump threshold of 30 mW, a slope efficiency of 35%, and maximum output power of 50 mW with respect to the launched power of single-mode pump diodes at 805 nm. To the best of our knowledge, this is the highest lasing efficiency achieved in single-frequency fiber lasers operating near 2 micro m. Frequency noise of the single-frequency fiber laser at 1893 nm has been characterized and compared with that of single-frequency fiber lasers at 1 and 1.55 micro m.
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Efficient Operation of diode pumped single frequency thulium doped fiber lasers near 2 micro m
Optics Letters, 2007Co-Authors: Jihong Geng, Shibin JiangAbstract:Efficient Operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber. At 1893 nm, the single-frequency fiber laser has a pump threshold of 30 mW, a slope efficiency of 35%, and maximum output power of 50 mW with respect to the launched power of single-mode pump diodes at 805 nm. To the best of our knowledge, this is the highest lasing efficiency achieved in single-frequency fiber lasers operating near 2 micro m. Frequency noise of the single-frequency fiber laser at 1893 nm has been characterized and compared with that of single-frequency fiber lasers at 1 and 1.55 micro m.
Jihong Geng - One of the best experts on this subject based on the ideXlab platform.
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Efficient Operation of diode pumped single frequency thulium doped fiber lasers near 2 μm
Optics Letters, 2007Co-Authors: Jihong Geng, Shibin JiangAbstract:Efficient Operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber. At 1893 nm, the single-frequency fiber laser has a pump threshold of 30 mW, a slope efficiency of 35%, and maximum output power of 50 mW with respect to the launched power of single-mode pump diodes at 805 nm. To the best of our knowledge, this is the highest lasing efficiency achieved in single-frequency fiber lasers operating near 2 micro m. Frequency noise of the single-frequency fiber laser at 1893 nm has been characterized and compared with that of single-frequency fiber lasers at 1 and 1.55 micro m.
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Efficient Operation of diode pumped single frequency thulium doped fiber lasers near 2 micro m
Optics Letters, 2007Co-Authors: Jihong Geng, Shibin JiangAbstract:Efficient Operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber. At 1893 nm, the single-frequency fiber laser has a pump threshold of 30 mW, a slope efficiency of 35%, and maximum output power of 50 mW with respect to the launched power of single-mode pump diodes at 805 nm. To the best of our knowledge, this is the highest lasing efficiency achieved in single-frequency fiber lasers operating near 2 micro m. Frequency noise of the single-frequency fiber laser at 1893 nm has been characterized and compared with that of single-frequency fiber lasers at 1 and 1.55 micro m.
Tao Tang - One of the best experts on this subject based on the ideXlab platform.
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a subway train timetable optimization approach based on energy Efficient Operation strategy
IEEE Transactions on Intelligent Transportation Systems, 2013Co-Authors: Shuai Su, Xiang Li, Tao TangAbstract:Given rising energy prices and environmental concerns, train energy-Efficient Operation techniques are paid more attention as one of the effective methods to reduce Operation costs and energy consumption. Generally speaking, the energy-Efficient Operation technique includes two levels, which optimize the timetable and the speed profiles among successive stations, respectively. To achieve better performance, this paper proposes to optimize the integrated timetable, which includes both the timetable and the speed profiles. First, we provide an analytical formulation to calculate the optimal speed profile with fixed trip time for each section. Second, we design a numerical algorithm to distribute the total trip time among different sections and prove the optimality of the distribution algorithm. Furthermore, we extend the algorithm to generate the integrated timetable. Finally, we present some numerical examples based on the Operation data from the Beijing Yizhuang subway line. The simulation results show that energy reduction for the entire route is 14.5%. The computation time for finding the optimal solution is 0.15 s, which implies that the algorithm is fast enough to be used in the automatic train Operation (ATO) system for real-time control.
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Energy-Efficient Operation of Subway Systems
2013Co-Authors: Yinhi Wang, B. De Schutter, T.j.j. Van Den Boom, Tao TangAbstract:To reduce the Operational costs and to improve the Operational efficiency, people are paying more and more attention to the energy-Efficient Operation of subway systems. In this paper, the authors present and compare two algorithms for determining the energy-Efficient speed profile for trains of subway systems. Firstly, they formulate a mixed integer linear programming (MILP) model to get the optimal speed profile. Secondly, they present an integrated algorithm for optimizing the timetable for the entire route together with the speed profiles between successive stations, which is called integrated timetable. Finally, based on the data from the Beijing YiZhuang subway line, they give some numerical examples to illustrate the validity, and to compare the optimality of the algorithms. The results show that both algorithms can get a good performance in saving energy, but the MILP approach gives a better energy-Efficient performance, and the integrated algorithm needs a shorter computation time.
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A Subway Train Timetable Optimization Approach Based on Energy-Efficient Operation Strategy
2012 Joint Rail Conference, 2012Co-Authors: Tao TangAbstract:With the rising energy prices and environment concerns, energy-Efficient Operation is paid more and more attention in the subway systems, which is one of the effective ways to reduce the Operation cost and then improve the Operation efficiency. There are many researches for energy-Efficient Operation on designing a reasonable timetable or optimizing the speed profile, but all of them are studied separately. To achieve a better performance on energy saving, we present an integrated algorithm for optimizing the timetable for the entire route together with the speed profiles between successive stations, which is named as integrated timetable. First, we give an analytical algorithm to get the optimal switching points for each section by using the Pontryagin maximum principle. For dealing with the variable speed limits, we calculate the reserve time, i.e., the difference between the pre-determined trip time and the minimum trip time, and then design an algorithm to distribute it among different sections with constant speed limits. Finally, we extend the algorithm to solve the integrated timetable. We also give some numerical examples to illustrate the validity of the algorithm based on the data from the Beijing YiZhuang subway line in China. It is recorded that the energy consumption for interstation trip can be reduced by 10.3% on average, and the total energy reduction for the entire trip is 14.5% by using the integrated timetable. Besides, it takes about 0.15 seconds to generate the integrated timetable, which means that the algorithm is quick enough to be used in the automatic train Operation (ATO) system for real-time control.Copyright © 2012 by ASME
John E Seem - One of the best experts on this subject based on the ideXlab platform.
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extremum seeking control for Efficient Operation of hybrid ground source heat pump system
Renewable Energy, 2016Co-Authors: Bin Hu, Yaoyu Li, Baojie Mu, Shaojie Wang, John E SeemAbstract:The Hybrid Ground Source Heat Pump (GSHP) systems combine the renewable geothermal energy and cooling tower for rejecting the cooling load, which is often adopted for high cooling demand. Model based control can be limited due to variations in ambient conditions, ground-loop heat exchanger (GHE) and equipment characteristics, cost and reliability of sensors. A self-optimizing control scheme is proposed for Efficient Operation of the hybrid GSHP based on Extremum Seeking Control (ESC), with feedback of the total power consumption and the control inputs of the relative flow rate of cooling tower and the water pump speed. The cooling capacity of the heat pump regulates the evaporator leaving water at 7 °C. A Modelica based dynamic simulation model is developed for a Hybrid GSHP system, with the vertical GHE model adopted from Modelica Buildings Library. The transient heat transfer is implemented with a finite volume method inside and outside the borehole. The proposed ESC scheme is evaluated under the scenarios of fixed cooling load, ramp change in the evaporator inlet water temperature, diurnal sinusoidal cycle of air wet-bulb temperature, and realistic ambient and cooling load condition. Simulation results show the proposed ESC strategy effectively achieves nearly optimal efficiency without the need for plant model.
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Experimental Study on Extremum Seeking Control for Efficient Operation of Air-side Economizer
2014Co-Authors: John E SeemAbstract:The air-side economizers have been developed as a major class of energy-saving equipment to enhance the energy efficiency of central air-conditioning systems by taking advantage of outdoor air during cool or cold weather. In current practice, the outdoor air damper is controlled to maintain either the maximum or minimum opening by comparing the outdoor air temperature/enthalpy with the setpoint temperature/enthalpy or return-air temperature/enthalpy. However, in practice many economizers do not behave as expected or even waste more energy due to the erroneous damper actions because of the inaccurate or failed temperature and/or relative humidity (RH) sensors. Recently, a self-optimizing controller based on extremum seeking control (ESC) has been proposed in an earlier study by Li et al. (2010) for Efficient Operation of an air-side economizer. This paper presents two experimental studies of the ESC air-side economizer control: one is a laboratory setup with a direct-expansion air conditioning unit, and the other is a chilled-water based air handling unit (AHU) facility at Iowa Energy Center. Experimental results from both studies validate the effectiveness of the ESC scheme as a model free optimal control strategy for air-side economizer Operation.
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Self-optimizing control of cooling tower for Efficient Operation of chilled water systems.
2012Co-Authors: John E SeemAbstract:The chilled-water systems, mainly consisting of electric chillers and cooling towers, are crucial for the ventilating and air conditioning systems in commercial buildings. Energy Efficient Operation of such systems is thus important for the energy saving of commercial buildings. This paper presents an extremum seeking control (ESC) scheme for energy Efficient Operation of the chilled-water system, and presents a Modelica based dynamic simulation model for demonstrating the effectiveness of the proposed control strategy. The simulated plant consists of a water-cooled screw chiller and a mechanical-draft counter-flow wet cooling tower. The ESC scheme takes the total power consumption of the chiller compressor and the tower fan as feedback, and uses the fan speed setting as the control input. The inner-loop controllers for the chiller Operation include two proportional-integral (PI) control loops for regulating the evaporator superheat and the chilled water temperature. Simulation was conducted on the dynamic simulation model of the whole plant including the screw chiller and the cooling tower for different scenarios. The simulation results demonstrated the effectiveness of the proposed ESC strategy in searching for the optimal tower fan speed set-point under tested circumstances, and the potential for energy saving is also evaluated.
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ACC - Extremum seeking control of cooling tower for self-optimizing Efficient Operation of chilled water systems
2012 American Control Conference (ACC), 2012Co-Authors: John E SeemAbstract:This paper presents an extremum seeking control (ESC) scheme for energy Efficient Operation of chilled-water system, and Modelica based dynamic simulation models for demonstrating the effectiveness of the proposed control strategy. The simulated plant consists of a water-cooled screw chiller and a mechanical-draft counter-flow wet cooling tower. The ESC scheme takes the total power consumption of chiller compressor and tower fan as feedback, and uses the fan speed setting as control input. The inner-loop controllers for the chiller Operation include two PI control loops for regulating the evaporator superheat and the chilled water temperature. Simulation was conducted for different scenarios. The simulation results demonstrated the effectiveness of the proposed ESC strategy, and the potential for energy saving is also evaluated. Also investigated is the ESC windup issue caused by the limitation of the fan's maximum Operation speed. A back-calculation anti-windup ESC scheme is applied and its effectiveness is validated by simulation results.
W. Nakwaski - One of the best experts on this subject based on the ideXlab platform.
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Thermal aspects of Efficient Operation of vertical-cavity surface-emitting lasers
Optical and Quantum Electronics, 1996Co-Authors: W. NakwaskiAbstract:Thermal aspects of Efficient Operation of vertical cavity surface-emitting lasers (VCSELs) are reviewed and discussed. The effects of temperature on VCSEL Operation characteristics are considered, including the temperature dependence of their longitudinal mode spectra, their threshold current, and their transverse-mode structure. The principles of Operation of ‘temperature-insensitive’ VCSELs are explained. A comparison between the behaviour of VCSELs and that of conventional edgeemitting lasers is emphasized.
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Thermal aspects of Efficient Operation of vertical-cavity surface-emitting lasers
Optical and Quantum Electronics, 1996Co-Authors: W. NakwaskiAbstract:Thermal aspects of Efficient Operation of vertical cavity surface-emitting lasers (VCSELs) are reviewed and discussed. The effects of temperature on VCSEL Operation characteristics are considered, including the temperature dependence of their longitudinal mode spectra, their threshold current, and their transverse-mode structure. The principles of Operation of ‘temperature-insensitive’ VCSELs are explained. A comparison between the behaviour of VCSELs and that of conventional edgeemitting lasers is emphasized.
