An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar ...An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.展开更多
A part load operation by turning the burner on and off intermittently is effective for a small scale direct fired absorption chiller. The dynamic performance of the system has been investigated. The relationship betwe...A part load operation by turning the burner on and off intermittently is effective for a small scale direct fired absorption chiller. The dynamic performance of the system has been investigated. The relationship between pressure, temperature and concentration of the lithium bromide solution have been analyzed. The result obtained indicates that the pressure of the high pressure generator and the temperature of the exhausted smoke are the most sensitive parameters. It is also found that the transition time from a full load to a part load condition is quite long, and part load relative cooling capacity is almost near the intermittent running time ratio and oil consumption ratio.展开更多
A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels i...A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water. A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol?L–1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm;effective filtering diameter, 35 mm) at a flow rate of 80 - 100 mL?min–1 to preconcentrate seven analytes. The IED was dried at 100?C for 20 min in an electric oven, and 110 - 145 small disks, each 2 mm in diameter, were punched out from the IED. A small disk was introduced into the graphite furnace and atomized according to a heating program. For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances. Calibration was performed using aqueous standard solutions. The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg·L–1 for Co, 0.12 μg·L–1 for Ni, 0.40 μg·L–1 for Cu, 0.077 μg·L–1 for Cd, 0.92 μg·L–1 for Sn, 0.61 μg·L–1 for Pb, and 0.80 μg·L–1 for Bi with an enrichment factor of 140 using a 100-mL water sample. A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% - 108%).展开更多
The nonlinear absorption properties of direct (GaN) and indirect (CdI2) band gap crystals have been studied by using an open aperture Z-scan technique under fundamental (1064 nm) and frequency doubled (532 nm) wavelen...The nonlinear absorption properties of direct (GaN) and indirect (CdI2) band gap crystals have been studied by using an open aperture Z-scan technique under fundamental (1064 nm) and frequency doubled (532 nm) wavelength respectively with 10 ns or 60 ps pulse durations. Direct band gap crystal exhibits two and three photon absorption at all input irradiances. On the other hand, at low input irradiance the indirect band gap crystal exhibits saturable absorption (SA). At higher input irradiances two and three photon absorption becomes dominant. A monotonic increase of the nonlinear absorption coefficients with increasing laser pulse duration from 60 ps to 10 ns is observed for GaN and CdI2 crystals.展开更多
Nanofluids based direct absorption solar collectors(DASCs) are considered as the important alternative for further improve the utilization of solar energy. However the low-quality energy and aggregation of nanoparticl...Nanofluids based direct absorption solar collectors(DASCs) are considered as the important alternative for further improve the utilization of solar energy. However the low-quality energy and aggregation of nanoparticles obstructs their large-scale application. In this work, a new method of using magnetic nanofluids in DASCs is proposed. By this method, not only high-quality energy is got as well as the problems of blockage and corrosion in heat exchanger are well avoided. The result shows that the maximum temperature can reach 98℃ under 3 solar irradiations and the photothermal conversion efficiency can be further increased by 12.8% when the concentration is 500 ppm after adding an external rotating magnetic field. The highest viscosity of working fluid reduced by 21% when the concentration is 500 ppm at 95℃ after separating the Fe_(3)O_(4)@C nanoparticles from the nanofluids via magnetic separation technology. Meanwhile, the obtained pure base liquids with high temperature flow to heat exchanger, which also reduces the flow resistance in pipeline and avoids the problems such as blockage and corrosion in heat exchanger. This research promotes a new way for the efficient utilization of solar energy.展开更多
In this study, a novel model of photothermal conversion in a direct absorption solar collector based on the Monte Carlo and finite volume methods was built and validated and the temperatures of the novel and tradition...In this study, a novel model of photothermal conversion in a direct absorption solar collector based on the Monte Carlo and finite volume methods was built and validated and the temperatures of the novel and traditional solar collectors were compared. The sensitivity of the parameters to the radiative heat loss was investigated. Finally, the radiative heat transfer characteristics were discussed using the radiative exchange factor. The results of this study validated the advantages of the novel solar collector at both the surface and fluid temperatures. Under the conditions used in this study, the maximum temperature difference of the novel solar collector was 30 K, compared with 193 K for the traditional solar collector. Furthermore, the collector was divided into several units along the flow direction. The radiative exchange factor indicated that with an increase in the attenuation coefficient, the percentage of radiation intensity in the total solar radiation absorbed by the corresponding unit increased.Simultaneously, it decreased with an increase in the incident angle and scattering albedo. These results provide a reference for addressing the low efficiency and thermal damage caused by traditional solar collectors at high temperatures.展开更多
The optical absorption of exciton interstate transition in Zn1-xlMgxlO/ZnO/Zn1-xcMgxcO/ZnO/Zn1-xrMgxrO asymmetric double quantum wells(ADQWs)with mixed phases of zinc-blende and wurtzite in Zn1-xMgxO for 0.37<x<...The optical absorption of exciton interstate transition in Zn1-xlMgxlO/ZnO/Zn1-xcMgxcO/ZnO/Zn1-xrMgxrO asymmetric double quantum wells(ADQWs)with mixed phases of zinc-blende and wurtzite in Zn1-xMgxO for 0.37<x<0.62 is discussed.The mixed phases are taken into account by our weight model of fitting.The states of excitons are obtained by a finite difference method and a variational procedure in consideration of built-in electric fields(BEFs)and the Hartree potential.The optical absorption coefficients(OACs)of exciton interstate transition are obtained by the density matrix method.The results show that Hartree potential bends the conduction and valence bands,whereas a BEF tilts the bands and the combined effect enforces electrons and holes to approach the opposite interfaces to decrease the Coulomb interaction effects between electrons and holes.Furthermore,the OACs indicate a transformation between direct and indirect excitons in zinc-blende ADQWs due to the quantum confinement effects.There are two kinds of peaks corresponding to wurtzite and zinc-blende structures respectively,and the OACs merge together under some special conditions.The computed result of exciton interband emission energy agrees well with a previous experiment.Our conclusions are helpful for further relative theoretical studies,experiments,and design of devices consisting of these quantum well structures.展开更多
The laser frequency could be linked to an radio frequency through an external cavity by the combination of Pound-Drever-Hall and Devoe-Brewer locking techniques.A stable and tunable optical frequency at wavelength of ...The laser frequency could be linked to an radio frequency through an external cavity by the combination of Pound-Drever-Hall and Devoe-Brewer locking techniques.A stable and tunable optical frequency at wavelength of 1.5μm obtained by a cavity with high finesse of 96000 and a fiber laser has been demonstrated,calibrated by a commercial optical frequency comb.The locking performances have been analyzed by in-loop and out-loop noises,indicating that the absolute frequency instability could be down to 50 kHz over 1 s and keep to less than 110 kHz over 2.5 h.Then,the application of this stabilized laser to the direct absorption spectroscopy has been performed.With the help of balanced detection,the detection sensitivity,in terms of optical density,can reach to 9.4×10^(-6).展开更多
The γ-ray radiation will speed up the discharge of the storedcharge in nonvolatile MNOS structure. The radiation absorptionmechanism to enhance the discharge is discussed. A direct radiationemission model from the in...The γ-ray radiation will speed up the discharge of the storedcharge in nonvolatile MNOS structure. The radiation absorptionmechanism to enhance the discharge is discussed. A direct radiationemission model from the interface traps distributing both in energylevel and in space is given. The theoretical results based on thismodel are in good agreement with experimental measurements.展开更多
常规的碳捕集与封存技术和碳捕集、利用与封存技术多针对固定源排放CO_(2),直接空气捕集CO_(2)(Direct Air Capture,DAC)技术作为一种新兴的负碳排放技术可对分布源排放的CO_(2)进行捕集,进一步降低全球大气CO_(2)体积分数。介绍了DAC...常规的碳捕集与封存技术和碳捕集、利用与封存技术多针对固定源排放CO_(2),直接空气捕集CO_(2)(Direct Air Capture,DAC)技术作为一种新兴的负碳排放技术可对分布源排放的CO_(2)进行捕集,进一步降低全球大气CO_(2)体积分数。介绍了DAC典型液体吸收工艺、固体吸附工艺的发展过程及相关示范项目建设情况,分析了新兴DAC工艺的技术特点,探讨了现有DAC工艺关键装置方案和未来发展趋势。DAC液体吸收工艺具有吸收剂原料成本较低、选择性较高的特点,可实现大规模连续化捕集,但再生过程中能耗较高。DAC固体吸附工艺具有模块化、投资成本较低的特点,且再生过程能耗相对较低,但需要定期对吸附材料更换和吸附设备维护,适用于较小规模的DAC应用场景。对2种典型DAC工艺吸收/吸附材料进行了概述。DAC电振荡吸附工艺中CO_(2)在固体电极中发生化学反应被捕集,并通过外加电场改变固体电极极性实现CO_(2)脱附,该工艺具有比基于热量或压力的分离过程更高的效率。空气中CO_(2)选择透过DAC分离膜从而实现了高效碳捕集。DAC变湿吸附工艺通过湿度的改变实现CO_(2)的吸脱附,突破了常规变温/变压吸附的高能耗限制等问题。DAC生物吸收工艺通过藻类生物的光合作用将CO_(2)吸收固定。基于双功能催化剂的DAC工艺可以在一个综合过程中实现CO_(2)的捕集与催化,节省了CO_(2)捕集后的运输与存储成本。DAC液体吸收工艺的关键装置为空气接触器、颗粒反应器、煅烧炉和熟化器,其中空气接触器开发的核心在于提高气液接触效率,减少喷淋过程中的水分损失和减轻设备腐蚀,颗粒反应器和熟化器开发的关键在于提高固液两相物料的接触效率以及反应后的固液分离效率。DAC固体吸附工艺由引风模块、吸附/再生模块、供能再生模块和CO_(2)压缩模块组成的模块化装置组成,其中优化吸附模块的核心在于提高气固传质速率、调谐CO_(2)捕集效率、降低压降;并基于不同应用场景工艺需求选择合适的再生系统或利用清洁能源,优化DAC工艺过程和开发高性能的DAC核心装置至关重要。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11272338)the Science and Technology on Scramjet Key Laboratory Funding,China(Grant No.STSKFKT 2013004)the China Scholarship Council
文摘An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.
文摘A part load operation by turning the burner on and off intermittently is effective for a small scale direct fired absorption chiller. The dynamic performance of the system has been investigated. The relationship between pressure, temperature and concentration of the lithium bromide solution have been analyzed. The result obtained indicates that the pressure of the high pressure generator and the temperature of the exhausted smoke are the most sensitive parameters. It is also found that the transition time from a full load to a part load condition is quite long, and part load relative cooling capacity is almost near the intermittent running time ratio and oil consumption ratio.
文摘A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water. A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol?L–1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm;effective filtering diameter, 35 mm) at a flow rate of 80 - 100 mL?min–1 to preconcentrate seven analytes. The IED was dried at 100?C for 20 min in an electric oven, and 110 - 145 small disks, each 2 mm in diameter, were punched out from the IED. A small disk was introduced into the graphite furnace and atomized according to a heating program. For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances. Calibration was performed using aqueous standard solutions. The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg·L–1 for Co, 0.12 μg·L–1 for Ni, 0.40 μg·L–1 for Cu, 0.077 μg·L–1 for Cd, 0.92 μg·L–1 for Sn, 0.61 μg·L–1 for Pb, and 0.80 μg·L–1 for Bi with an enrichment factor of 140 using a 100-mL water sample. A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% - 108%).
文摘The nonlinear absorption properties of direct (GaN) and indirect (CdI2) band gap crystals have been studied by using an open aperture Z-scan technique under fundamental (1064 nm) and frequency doubled (532 nm) wavelength respectively with 10 ns or 60 ps pulse durations. Direct band gap crystal exhibits two and three photon absorption at all input irradiances. On the other hand, at low input irradiance the indirect band gap crystal exhibits saturable absorption (SA). At higher input irradiances two and three photon absorption becomes dominant. A monotonic increase of the nonlinear absorption coefficients with increasing laser pulse duration from 60 ps to 10 ns is observed for GaN and CdI2 crystals.
基金supported by National Natural Science Foundation of China(51590901&51876112&51906132&51906123)Shanghai Municipal Natural Science Foundation(Grant No.17ZR1411000)+1 种基金the Key Subject of Shanghai Polytechnic University(Material Science and engineeringGrant Nos.XXKZD1601 and EGD18YJ0042)。
文摘Nanofluids based direct absorption solar collectors(DASCs) are considered as the important alternative for further improve the utilization of solar energy. However the low-quality energy and aggregation of nanoparticles obstructs their large-scale application. In this work, a new method of using magnetic nanofluids in DASCs is proposed. By this method, not only high-quality energy is got as well as the problems of blockage and corrosion in heat exchanger are well avoided. The result shows that the maximum temperature can reach 98℃ under 3 solar irradiations and the photothermal conversion efficiency can be further increased by 12.8% when the concentration is 500 ppm after adding an external rotating magnetic field. The highest viscosity of working fluid reduced by 21% when the concentration is 500 ppm at 95℃ after separating the Fe_(3)O_(4)@C nanoparticles from the nanofluids via magnetic separation technology. Meanwhile, the obtained pure base liquids with high temperature flow to heat exchanger, which also reduces the flow resistance in pipeline and avoids the problems such as blockage and corrosion in heat exchanger. This research promotes a new way for the efficient utilization of solar energy.
基金supported by the National Natural Science Foundation of China (Grant No. 52041601)Hebei Natural Science Foundation (Grant No. E202203156)+1 种基金Chinese Scholarship Council (Grant No. 202106120167)partly funded the research activities—Enabling cooperation of the Harbin Institute of Technology with the Technical University of Denmark。
文摘In this study, a novel model of photothermal conversion in a direct absorption solar collector based on the Monte Carlo and finite volume methods was built and validated and the temperatures of the novel and traditional solar collectors were compared. The sensitivity of the parameters to the radiative heat loss was investigated. Finally, the radiative heat transfer characteristics were discussed using the radiative exchange factor. The results of this study validated the advantages of the novel solar collector at both the surface and fluid temperatures. Under the conditions used in this study, the maximum temperature difference of the novel solar collector was 30 K, compared with 193 K for the traditional solar collector. Furthermore, the collector was divided into several units along the flow direction. The radiative exchange factor indicated that with an increase in the attenuation coefficient, the percentage of radiation intensity in the total solar radiation absorbed by the corresponding unit increased.Simultaneously, it decreased with an increase in the incident angle and scattering albedo. These results provide a reference for addressing the low efficiency and thermal damage caused by traditional solar collectors at high temperatures.
基金Project supported by the National Natural Science Foundation of China(Grant No.61764012).
文摘The optical absorption of exciton interstate transition in Zn1-xlMgxlO/ZnO/Zn1-xcMgxcO/ZnO/Zn1-xrMgxrO asymmetric double quantum wells(ADQWs)with mixed phases of zinc-blende and wurtzite in Zn1-xMgxO for 0.37<x<0.62 is discussed.The mixed phases are taken into account by our weight model of fitting.The states of excitons are obtained by a finite difference method and a variational procedure in consideration of built-in electric fields(BEFs)and the Hartree potential.The optical absorption coefficients(OACs)of exciton interstate transition are obtained by the density matrix method.The results show that Hartree potential bends the conduction and valence bands,whereas a BEF tilts the bands and the combined effect enforces electrons and holes to approach the opposite interfaces to decrease the Coulomb interaction effects between electrons and holes.Furthermore,the OACs indicate a transformation between direct and indirect excitons in zinc-blende ADQWs due to the quantum confinement effects.There are two kinds of peaks corresponding to wurtzite and zinc-blende structures respectively,and the OACs merge together under some special conditions.The computed result of exciton interband emission energy agrees well with a previous experiment.Our conclusions are helpful for further relative theoretical studies,experiments,and design of devices consisting of these quantum well structures.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.61875107,61905136,61905134,62175139)+1 种基金Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(Grant No.2019L0062)Opening Foundation of Key Laboratory of Laser&Infrared System(Shandong University)。
文摘The laser frequency could be linked to an radio frequency through an external cavity by the combination of Pound-Drever-Hall and Devoe-Brewer locking techniques.A stable and tunable optical frequency at wavelength of 1.5μm obtained by a cavity with high finesse of 96000 and a fiber laser has been demonstrated,calibrated by a commercial optical frequency comb.The locking performances have been analyzed by in-loop and out-loop noises,indicating that the absolute frequency instability could be down to 50 kHz over 1 s and keep to less than 110 kHz over 2.5 h.Then,the application of this stabilized laser to the direct absorption spectroscopy has been performed.With the help of balanced detection,the detection sensitivity,in terms of optical density,can reach to 9.4×10^(-6).
文摘The γ-ray radiation will speed up the discharge of the storedcharge in nonvolatile MNOS structure. The radiation absorptionmechanism to enhance the discharge is discussed. A direct radiationemission model from the interface traps distributing both in energylevel and in space is given. The theoretical results based on thismodel are in good agreement with experimental measurements.
文摘常规的碳捕集与封存技术和碳捕集、利用与封存技术多针对固定源排放CO_(2),直接空气捕集CO_(2)(Direct Air Capture,DAC)技术作为一种新兴的负碳排放技术可对分布源排放的CO_(2)进行捕集,进一步降低全球大气CO_(2)体积分数。介绍了DAC典型液体吸收工艺、固体吸附工艺的发展过程及相关示范项目建设情况,分析了新兴DAC工艺的技术特点,探讨了现有DAC工艺关键装置方案和未来发展趋势。DAC液体吸收工艺具有吸收剂原料成本较低、选择性较高的特点,可实现大规模连续化捕集,但再生过程中能耗较高。DAC固体吸附工艺具有模块化、投资成本较低的特点,且再生过程能耗相对较低,但需要定期对吸附材料更换和吸附设备维护,适用于较小规模的DAC应用场景。对2种典型DAC工艺吸收/吸附材料进行了概述。DAC电振荡吸附工艺中CO_(2)在固体电极中发生化学反应被捕集,并通过外加电场改变固体电极极性实现CO_(2)脱附,该工艺具有比基于热量或压力的分离过程更高的效率。空气中CO_(2)选择透过DAC分离膜从而实现了高效碳捕集。DAC变湿吸附工艺通过湿度的改变实现CO_(2)的吸脱附,突破了常规变温/变压吸附的高能耗限制等问题。DAC生物吸收工艺通过藻类生物的光合作用将CO_(2)吸收固定。基于双功能催化剂的DAC工艺可以在一个综合过程中实现CO_(2)的捕集与催化,节省了CO_(2)捕集后的运输与存储成本。DAC液体吸收工艺的关键装置为空气接触器、颗粒反应器、煅烧炉和熟化器,其中空气接触器开发的核心在于提高气液接触效率,减少喷淋过程中的水分损失和减轻设备腐蚀,颗粒反应器和熟化器开发的关键在于提高固液两相物料的接触效率以及反应后的固液分离效率。DAC固体吸附工艺由引风模块、吸附/再生模块、供能再生模块和CO_(2)压缩模块组成的模块化装置组成,其中优化吸附模块的核心在于提高气固传质速率、调谐CO_(2)捕集效率、降低压降;并基于不同应用场景工艺需求选择合适的再生系统或利用清洁能源,优化DAC工艺过程和开发高性能的DAC核心装置至关重要。
