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Temperature dependence photoluminescence properties of ZnSe-based core-shell quantum dots

Optics Express 2025年第11期33卷 22588-22597页

作者： Zhang, Tingting Ma, Qing Li, Qingping Huang, Lanting Feng, Yuqiong Duan, Hongwei Chen, Xinlei Li, Qinghua Jin, Xiao Bai, Jinke Xu, Bing Key Laboratory of Environmentally Friendly Functional Materials and Devices School of Physics Science and Technology Lingnan Normal University Guangdong Zhanjiang524048 China School of Energy and Power Engineering Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Department of Materials and Chemical Engineering Taiyuan University Taiyuan030032 China

Heavy metal-free ZnSe-based core-shell quantum dots (QDs) are promising emitting material for achieving violet-blue luminescence. Investigating the temperature-dependent variations in the photoluminescence (PL) properties of ZnSe-based QDs will enhance our understanding of the intrinsic factors that influence their diverse luminescence characteristics. Here we select the optimally synthesized ZnSe core QDs with three diameters (4.1, 5.2, and 8.3 nm) and ZnSe/ZnS core-shell QDs to study their temperature-dependent photoluminescence properties. As the sample temperature is increased, the PL intensity decreases, the emission energy redshifts, and the spectral become broader. We observe a reduction in the exciton-longitudinal optical (LO)-phonon coupling constant from 21.7 meV to 16.1 meV as the diameter of ZnSe core QDs increased from 4.1 nm to 8.3 nm. This decrease is associated with a narrower homogeneous broadening of the emission spectrum. Besides, the epitaxial growth of a ZnS wide bandgap shells onto the ZnSe core QDs can effectively isolate the photogenerated excitons away from the inorganic-organic interface, thus reducing the PL peak width and increasing the exciton binding energy of the QDs. Our research provides a valuable addition to the existing studies on the photoluminescence properties of ZnSe-based core-shell QDs. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Atomic emission spectroscopy

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Depth from Defocus Technique for High Number Densities and Non-Spherical Particles

SSRN

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SSRN 2024年

作者： Xu, Rixin Huang, Zuojie Gong, Wenchao Zhou, Wu Tropea, Cameron School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering Shanghai China Institute for Fluid Mechanics and Aerodynamics Technical University of Darmstadt Darmstadt Germany

The Depth from Defocus (DFD) imaging technique for measuring the size and number concentration of particles in a dispersed two-phase flow has up to now been restricted to relatively sparse particle densities and to identifying only spherical particles. The present study examines two advancements to the technique, widening its range of application significantly. The first advancement introduces an image processing procedure which can identify and size particle images which are overlapping. This increases the tolerable number concentration of particles which can be identified and processed within the measurement volume. The second advancement explores the possibility of determining the size and position of non-spherical particles within an observation volume. These enhancements are experimentally validated using a dedicated apparatus in which particles of known size, shape and degree of overlapping images can be systematically varied. This experimental setup provides benchmark data to quantify the accuracy and limitations of the processing algorithms. © 2024, The Authors. All rights reserved.

关键词： Two phase flow

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Enhanced catalytic activity for simultaneous removal of PCDD/Fs and NO over carbon nanotubes modified MnO_(x)-CeO_(2)/TiO_(2)catalyst at low temperatu

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Waste Disposal and Sustainable Energy 2021年第1期3卷 63-71页

作者： Qiulin Wang Zhuping Jiang Jianjian Zhou Jin Jing School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Henan Diesel Engine Industry Co LtdLuoyang 471000China

Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem caused during waste incineration.A novel catalyst with excellent low-temperature activity towards PCDD/Fs catalytic decomposition,as well as selective catalytic reduction(SCR)of NO with NH_(3)is urgently needed to simultaneously control PCDD/Fs and NO ***-cerium composite oxides supported on titanium dioxide(MnO_(x)-CeO_(2)/TiO_(2))or TiO_(2)and carbon nano-tubes(CNTs)composite carrier(MnO_(x)-CeO_(2)/TiO_(2)-CNTs)were prepared using sol-gel method,and their catalytic activity towards simultaneous abatement of ortho-dichlorobenzene(o-DCBz,model molecular to simulate PCDD/Fs)and NO was *** comparison with their removal,the simultaneous removal efficiencies of o-DCBz and NO over MnO_(x)-CeO_(2)/TiO_(2)catalyst are lowered to 27.9%and 51.3%at 150℃under the gas hourly space velocity(GHSV)of 15,000 h−1,due to the competition between the reactants for the limited surface acid sites and surface reactive oxygen *** addition improves the catalytic activity for their simultaneous *** optimum condition occurs on MnO_(x)-CeO_(2)/TiO_(2)combined with 20 wt.%CNTs that above 70%of o-DCBz and NO are removed *** results reveal that MnO_(x)-CeO_(2)/TiO_(2)-CNTs catalyst with proper CNTs content has larger Brunauer-Emmet-Teller surface area and greatly improved surface acidity property,which are beneficial to both o-DCBz and NO ***,the relatively higher surface atomic concentration of Mn^(4+)as well as the existence of abundant surface Ce^(3+)atom accelerates the redox cycle of the catalyst and enriches the surface reactive oxygen *** the above factors alleviate the competition effect between o-DCBz catalytic oxidation and NH_(3)-SCR reaction and are conducive to the simulta

关键词： o-DCBz catalytic oxidation Simultaneous removal MnO_(x)-CeO_(2)catalyst Composite carrier Carbon nanotube

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The proposal and calculation method of the annular domain weight function for the electromagnetic flowmeter under annular conductivity distribution

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flow MEASUREMENT AND INSTRUMENTATION 2024年 100卷

作者： Yang, Yang Yang, Biaohu Zhang, Chao Yang, Bin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Researching on the characteristic of weight function distribution under non-uniform conductivity distribution is of significant importance for expanding the engineering applications of electromagnetic flowmeter. In this paper, the characteristic of weight function distribution is firstly explored for annular conductivity distribution where the center and outer ring are both conductive. The research results indicate an important finding that the average value of the weight function within any small annular domain of the center or outer ring remains constant as the radial position changes. Therefore, the concept of 'annular domain weight function' is then innovatively proposed. Furthermore, the relationship is studied between the ratio of the annular domain weight function of the center and outer ring and the annular feature parameters. Ultimately, the correlations are obtained for calculating the annular domain weight functions of the center and outer ring.

关键词： Electromagnetic flowmeter Weight function Annular conductivity distribution Annular domain weight function

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High-efficiency reactor and its tandem module with Au-Co-CoOx-coated glass beads for continuous-flow reduction of dyeing wastewater

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REACTION CHEMISTRY & engineering 2023年第8期8卷 1981-1992页

作者： Sun, Li Sun, Mengying Zhi, Yuan Zhang, Hua Shan, Yuejin Dou, Binlin Chen, Jian Zhang, Lixin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Jun Gong Rd 516 Shanghai 200093 Peoples R China Shanghai Minrula Biotechnol Co Ltd R&D Dept Bldg 15 Haji Sixth Rd 218 Shanghai 201306 Peoples R China Utsunomiya Univ Dept Mat & Environm Chem Res Div Funct Mat Design Yoto 7-1-2 Utsunomiya 3218585 Japan

The continuous-flow (C-F) reduction process has been limitedly applied in the treatment of dyeing wastewater owing to the weak catalytic performance of the reactors employed. In this work, a small tubular packed reactor and its module are designed, fabricated and used for the C-F reduction of nitro and azo compounds in dyeing wastewater. Here, Au-Co-CoOx-coated glass beads with superior catalytic activity are chosen as packing materials, prepared without any toxic chemical agents. By means of the reactor, 4-nitrophenol (4-NP) can be completely removed and its removal rate is determined to be 100 & mu;mol h(-1). After that, a novel strategy for the tandem module is proposed to further enhance the removal rate of 4-NP. Based on the tandem module, the removal rate of 4-NP can be dramatically boosted to 1900 & mu;mol h(-1). Meanwhile, the rate constant for the C-F reduction of 4-NP can reach up to 0.44 s(-1). Furthermore, the tandem module displays satisfactory operating stability, reusability and reliability in real water samples. In addition, the tandem module first achieves the C-F reduction of 2-nitrophenol, 3-nitrophenol, methyl red and methyl orange. Clearly, the reactor and its module can effectively extend the application of the C-F reduction process in dyeing wastewater treatment.

关键词： Wastewater treatment

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Structural optimization of a latent heat storage unit with the fractal fin

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NUMERICAL heat transfer PART A-APPLICATIONS 2023年第8期84卷 921-939页

作者： Zhao, Ming Yao, Li Ye, Wenlan Fang, Qiang Univ Shanghai Sci & Technol Coll Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China

The fractal structure was applied to the fin optimization of latent heat storage (LHS) technology based on the fractal principle. By numerical simulation, the performances of LHS units with fractal tree-shaped fins were compared with those with traditional plate fins, and the effects of fin structure parameters based on the fractal principle on heat storage and release performances were studied. The results show that the heat storage performance and heat release performance of LHS units with fractal tree-shaped fins are clearly improved, and the optimal fractal structure parameters allow the LHS units to achieve optimal performance. A nonlinear surface fitting function method was used to obtain the functional relation between the branching angle and length index and the heat storage time of the LHS unit. In fractal tree-shaped fins, the optimal length index is 1.141, the optimal width ratio is 1, and the branching angle is 73.55 degrees. In comparison to the LHS unit with traditional plate fins, the LHS unit with the optimum fractal structure parameters has a 35.85% faster melting rate and a 63.39% faster heat release rate. The least entransy dissipation, least thermal resistance and best reversibility are all characteristics of the LHS unit with the optimal fractal structure parameters.

关键词： Entransy dissipation fractal structure latent heat storage (LHS) technology tree-shaped fins

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Experimental Investigation on heating Performance of Newly Designed Air Source heat Pump System for Electric Vehicles

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JOURNAL OF THERMAL SCIENCE AND engineering APPLICATIONS 2021年第2期13卷 021020页

作者： Li, Kang Yu, Jun Yu, Rong Su, Lin Fang, Yidong Yang, Zhongcheng Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai 200093 Peoples R China

Utilizing the heat from air source with heat pump system in electric vehicles shows a significant advantage from thermoelectric heat source for heat supply in cold climate. It could improve the driving range of electric vehicles considerably in winter and replace the positive temperature coefficient (PTC) heater with an acceptable cost and reliability. In this work, a newly designed heat pump system was first introduced with less components and cost. Second, experiments were conducted to investigate its cooling performance, and subsequent heating performance from -10 to 10 degrees C. The typical heat transfer and flow characteristics of refrigerant were recorded, and the behavior of each component including compressor, evaporator, condenser, and outside heat exchanger were analyzed and interpreted. The results showed that the heating and cooling performance of the new heat pump system could almost remain the same with traditional air-conditioning system in automobile and surely satisfy with the heat requirement of electric vehicles. In the heating mode, the maximum heating capacity increases by 13% at 400 m(3)/h air volume from 300 m(3)/h at the ambient temperature -10 degrees C, while the outlet air temperature decreases by 4-6%. In addition, using a heat pump system showed an increase in the driving range of electric vehicles by 25-31% as compared to PTC heaters.

关键词： air source heat pump driving range heat capacity electric vehicle energy efficiency energy systems thermal systems

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The effect of heat flux on enhancement heat transfer mechanism in copper metal foam composite paraffin wax during melting process: Experimental and simulation research

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INTERNATIONAL JOURNAL OF heat AND MASS transfer 2024年 226卷

作者： Wang, Zilong Gui, Jintao Zhu, Liucan Zhang, Hua Dou, Binlin Yu, Guoxin Song, Mengjie Jiang, Lianyong Xiao, Xin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China QINGDAO HAIER SMART TECHNOL R&D CO LTD 1 Haier Rd Qingdao Shandong Peoples R China Beijing Inst Technol Sch Mech Engn Dept Energy & Power Engn Beijing 100081 Peoples R China Shanghai Jiao Tong Univ Xinhua Hosp Sch Med Dept Cardiothorac Surg Shanghai 200092 Peoples R China Donghua Univ Coll Environm Sci & Engn Shanghai 201620 Peoples R China

To investigate the effect of heat flux on the enhanced heat transfer in phase change materials (PCMs) composed of copper metal foam (CMF) and paraffin wax (PX), a semi-cylindrical visualized heat storage device with a varied heat flux of 7.3 kW/m2, 8.5 kW/m2, 9.7 kW/m2, and 10.9 kW/m2 was established in this paper. Moreover, a 3-D mathematical model of composite phase change materials (CPCMs) was established using hybrid grid to study the temperature distribution, imbalance effect, flow, heat transfer mechanisms, and heat storage performance during the melting process. The results showed that the melting time of the CPCMs decreased as the heat flux increased. Compared with a heat flux of 7.3 kW/m2, the melting time was shortened by 10.05 %, 20.71 %, and 27.21 %, respectively. In addition, the Rayleigh number (Ra) increased with the increase in heat flux, and the amplitudes of Ra were 1.45x108,1.54x108,1.61x108, and 1.74x108, respectively, which indicated that the higher the heat flux, the larger the amplitudes. Moreover, the heat transfer mechanism during the melting process was dominated by conduction;however, with the increase in heat flux, the maximum flow velocity of the liquid paraffin increased, which caused the proportion of natural convection to increase from 27.80 % to 31.30 %. Hence, the integrated heat transfer coefficient of CPCMs increased from 5.69 W/(m & sdot;K) to 5.81 W/(m & sdot;K). However, the temperature imbalance effect of the CPCMs was exacerbated, as evidenced by the increased maximum temperature difference in the vertical direction of the center of the CPCMs from 24.7 K to 35.6 K. Besides, the heat storage performance was enhanced. Compared with a heat flux of 7.3 kW/m2, the heat storage capacities of the CPCMs increased by 4.21%, 9.46%, and 12.66 % with increasing heat flux, and the heat storage rates of the CPCMs increased by 15.3 %, 34.9 %, and 52.3 %, respectively. Furthermore, the relative error of the overall melting time was 3.4 %, in

关键词： heat flux Phase change materials Copper metal foam Numerical simulation heat transfer mechanism

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An polymorphic firefly algorithm with self-adaptation strategy for process system heat integration

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CASE STUDIES IN THERMAL engineering 2023年 47卷

作者： Chen, Jiaxing Cui, Guomin Shen, Shuqi Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Parameter setting effecting on solving efficiency is problematic and challenge of heuristic algorithm in engineering optimization. To reinforce the algorithm optimization, self-adaptation strategy of optical absorption coefficient based on dynamical spatial distribution of individual information is provided for parameter adjustment of Polymorphic firefly algorithm. This method is utilized to test and calculate three different scale heat exchanger network examples in public literature. More economic networks of lower total annualized cost are obtained, and the three cases are all calculated in about 1 h, which shows the higher convergence efficiency of this method.

关键词： Polymorphic firefly algorithm Self-adaptation strategy Process system heat integration heat exchanger network synthesis

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Wetting States and Departure Diameters of Bubbles on Micro-/Nanostructured Surfaces

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LANGMUIR 2022年第10期38卷 3180-3188页

作者： Li, Junyang Gong, Shuai Zhang, Lenan Cheng, Ping Ma, Xiaojing Hong, Fangjun Shanghai Jiao Tong Univ Sch Mech Engn Shanghai 200240 Peoples R China MIT Dept Mech Engn Cambridge MA 02139 USA North China Elect Power Univ Beijing Key Lab Multiphase Flow & Heat Transfer L Beijing 102206 Peoples R China Suzhou Univ Sci & Technol Jiangsu Key Lab Micro & Nano Heat Fluid Flow Tech Suzhou 215009 Jiangsu Peoples R China

Wetting states for droplets have been extensively investigated in the past. As the counter phase of the droplets, bubbles' wetting states have rarely been systematically explored. The wetting state of a bubble is closely related to its departure diameter, which plays significant roles in bubble-generated processes in boiling heat transfer and gas-evolving reactions. Based on the principle of minimum surface energy, we explicitly define three equilibrium wetting states (hemi-wicking state, Wenzel state, and Cassie-Baxter state) for bubbles on micro-/nanostructured surfaces in this paper. We analyze the three-phase contact line profiles for bubbles under these wetting states and propose theoretical models for predicting departure diameters of hemi-wicking-state bubble and Wenzel-state bubble on micro-/nanostructured surfaces. We identify competing effects of bubble departure in Wenzel state: the augmentation of contact line length due to the roughness, which would delay bubble departure, and the decrease of contact line length due to the reduced apparent contact angle, which would facilitate bubble departure. We demonstrate that hemi-wicking-state bubble exhibits a much smaller departure diameter on the textured surfaces. These findings are supported by numerical simulations by the three-dimensional (3D) multiple-relaxation-time lattice Boltzmann method. It is found that the length of the outermost contact lines instead of all contact lines determines the departure diameter of hemi-wicking-state bubble based on bubble detachment processes captured by our 3D numerical simulations. This work offers an avenue for the accurate prediction and control of bubble departure behaviors from micro-/nanostructured surfaces, and therefore can guide optimal designs of micro-/nanostructured surfaces in a variety of applications in boiling, desalination, and hydrogen production by electrolysis.

关键词： Bubbles Contact angle Liquids Equilibrium Wetting

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