15,642 results on '"rate equation"'
Search Results
2. Revisiting the measured luminescence lifetimes in Yb3+,Er3+-co-doped upconversion nanocrystals
- Author
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Wen, Chenqing, Shi, Mei, and Feng, Wei
- Published
- 2025
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3. Charge Transport in Interband Cascade Lasers: An Ab‐Initio Self‐Consistent Model.
- Author
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Windischhofer, Andreas, Opačak, Nikola, and Schwarz, Benedikt
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RATE equation model , *CONDUCTION bands , *TRANSPORT equation , *NUMERICAL analysis , *LASERS - Abstract
Interband cascade lasers (ICLs) stand out due to their low threshold current and minimal power consumption, rendering them viable sources for compact and mobile devices in the mid‐infrared. Since their first demonstration, they experienced major performance improvements. Mostly they originate from either improved material quality or the outcomes of numerical analysis of secluded parts. Encouraged by the impact of secluded models, an ICL‐specific simulation tool can lead to performance breakthroughs and a better comprehension of governing mechanisms. Drawing from an evaluation of existing tools designed for quantum cascade structures, a self‐consistent density matrix rate equation model is implemented to simulate the transport in both conduction and valence band heterostructures. Albeit the extensive inclusion of the quantum effects, special care was taken to maintain a high numerical efficiency. The charge transport model additionally considers optical field calculations, allowing for predictive calculations of light–current–voltage curves. The model is benchmarked against well‐established ICL designs and demonstrate reliable performance predictability. Additionally, detailed insights into device characteristics extracted from the model are provided. This ultimately allows to deepen the understanding of ICL and not only refine existing ones but also generate novel optimized designs. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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4. Mathematical modeling of breakthrough curves in dynamic column adsorption: analytical solutions and validation.
- Author
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Dima, Jimena B., Ferrari, Mariano A., and Zaritzky, Noemi
- Abstract
Water pollution is a critical global problem. The fixed- bed continuous adsorption column provides the most practical application in the industry for wastewater treatment. The mass transfer process in the column can be described using a mass balance differential equation, and a sorbate–adsorbent interaction rate equation. The objective of this work was to describe the mass transfer in an adsorption column, analyzing the differential equations of the process and their analytical solutions. A general rate equation with four parameters was proposed, adding a zero-order parameter. The general model was solved using Laplace Transform method. The model proposed was applied to describe the adsorption of hexavalent chromium on chitosan biopolymer. The theoretical solution found was satisfactory to estimate the experimental breakthrough curves, and the estimated parameters allowed to predict other curves with different operational conditions. The zero-order parameter added relates to the baseline height of the breakthrough curve. The general model proposed generalizes already known plug flow models based on a single rate equation. The present model uses the information obtained from the column and from the equilibrium batch isotherm, which constitutes a useful tool for describing the dynamic adsorption process and to make decisions on column design. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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5. An encompassed representation of timescale hierarchies in first-order reaction network.
- Author
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Yutaka Nagahata, Masato Kobayashi, Mikito Toda, Satoshi Maeda, Tetsuya Taketsugu, and Tamiki Komatsuzaki
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CLAISEN rearrangement , *DIFFERENTIAL equations , *VINYL ethers , *EQUILIBRIUM - Abstract
Complex networks are pervasive in various fields such as chemistry, biology, and sociology. In chemistry, first-order reaction networks are represented by a set of firstorder differential equations, which can be constructed from the underlying energy landscape. However, as the number of nodes increases, it becomes more challenging to understand complex kinetics across different timescales. Hence, how to construct an interpretable, coarse-graining scheme that preserves the underlying timescales of overall reactions is of crucial importance. Here, we develop a scheme to capture the underlying hierarchical subsets of nodes, and a series of coarse-grained (reduceddimensional) rate equations between the subsets as a function of time resolution from the original reaction network. Each of the coarse-grained representations guarantees to preserve the underlying slow characteristic timescales in the original network. The crux is the construction of a lumping scheme incorporating a similarity measure in deciphering the underlying timescale hierarchy, which does not rely on the assumption of equilibrium. As an illustrative example, we apply the scheme to four-state Markovian models and Claisen rearrangement of allyl vinyl ether (AVE), and demonstrate that the reduced-dimensional representation accurately reproduces not only the slowest but also the faster timescales of overall reactions although other reduction schemes based on equilibrium assumption well reproduce the slowest timescale but fail to reproduce the second-to-fourth slowest timescales with the same accuracy. Our scheme can be applied not only to the reaction networks but also to networks in other fields, which helps us encompass their hierarchical structures of the complex kinetics over timescales. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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6. Effect of shorter section length on the performance of bisection gain lever transistor laser.
- Author
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Ranjith, R. and Piramasubramanian, S.
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TRANSISTORS , *LASERS , *LEVERS - Abstract
The effects of different shorter to longer section length ratio on the performance of dual section transistor laser is analyzed numerically by solving the coupled rate equations. Dual section transistor laser is configured in common emitter configuration and biased in the active region. The DC and gain levering characteristics of bisection transistor laser is analyzed for different shorter to longer section length ratio ranging from 3:97 to 30:70. The shorter and longer section threshold current are found increase with increase in the shorter to longer section length ratio. A minimum shorter section threshold current of 3 µA is estimated for longer section bias current of 1.6 mA with shorter to longer section length ratio of 3:97. Higher slope efficiency is observed between an optical power and bias current of bisection transistor laser. A maximum gain lever of 9.87 dB is predicted for the shorter to longer section length ratio of 3:97 and gain levering decreases for increase in the ratio. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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7. Kinetics of indium and indium–tin soldering materials in vacuum volatilization
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Jian Pang, Lingxin Kong, Bin Yang, Zhicheng Yang, Hai Wu, Wei Zhao, Jiapeng Zhang, Junjie Xu, and Baoqiang Xu
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In–Sn ,Kinetic model ,Lead-free soldering material ,Rate equation ,Vacuum volatilization ,Mining engineering. Metallurgy ,TN1-997 - Abstract
Vacuum volatilization is a clean and efficient method for metal purification, alloy separation, and comprehensive recovery of secondary resources. The evaporation kinetics of In and In–Sn alloys were investigated to better understand the evaporation mechanism during the vacuum volatilization of In. The evaporation rates of the In and In–Sn alloys at 1173–1373 K and 5 Pa increased significantly with increasing temperature in accordance with the equation ω = e(a+b∙T). The evaporation rates at 1323 K and 5 Pa decreased with increasing crucible depth in accordance with the equation ω = a2+(a1-a2)/(1+e(h-b)/c). For In and In–Sn, the total mass-transfer coefficients of In were obtained at different temperatures and crucible depths. A theoretical kinetic model of In was established and limiting links were obtained vacuum volatilization of In and In–Sn.
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- 2023
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8. A Kinetic Study of Oxidation of New [Co(L)2(H2O)2] Complex by N-bromosuccinimide (NBS).
- Author
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Ellakwa, Takwa E., Basry, A. A. H., and El Hassan, Sawsan M. Abu
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FREE radical reactions , *OXIDATION kinetics , *CHARGE exchange , *POLYMERIZATION - Abstract
The kinetics of the oxidation of the [Co(L)2(H2O)2] complex by N-bromosuccinimide (NBS) in aqueous media (L = bidentate ligand mono deprotonated anion derived from methyl salicylaldehyde and sulfacetamide) were investigated over a pH range of 4.2-5.4, temperatures ranging from 25°C to 40°C, and an ionic strength of 0.1 mol/l-0.4 mol/l for both NBS and complex concentrations. The reaction rate over the studied pH ranges was predicted to be first order NBS and complex dependent and to rise with decreasing [H+]. It was compatible with the experimental rate law to say that a process in which the complex's dehydrogenated form is greater reactivity compared to its conjugate acid. Acrylonitrile polymerisation was tested for its abundance of free radicals in the reaction admixture. It was supposed that transfer of electrons and formation of initial cobalt(III) products, which were eventually were tardily transformed into the final cobalt(III) products, occurred by an inner-sphere mechanism. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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9. Nonlinear dynamics of Kerr optical microresonators with spatially fluctuating loss.
- Author
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Dikandé, Alain Moïse
- Subjects
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GROUP velocity dispersion , *NONLINEAR differential equations , *SOLITONS , *PHASE modulation , *SPATIAL variation - Abstract
Dissipative soliton crystals (the so-called soliton combs) form in Kerr microresonators as a result of the competition between the group-velocity dispersion and the Kerr nonlinearity on one hand, and the balance of cavity loss by an external pump on the other hand. In some physical contexts, the loss can fluctuate within the microresonator cavity, inducing a saturable-absorption process which impacts the dynamics of the optical field. In this study, dissipative soliton crystals are investigated in a Kerr optical microresonator with spatially fluctuating loss. The underlying mathematical model consists of a modified Lugiato–Lefever equation with a space-dependent loss, coupled to a rate equation for the fluctuating loss. Adopting an ansatz that describes the optical-field envelope as a complex function of real amplitude and real phase with a characteristic modulation frequency, the mathematical model is reduced to a set of first-order nonlinear ordinary differential equations which are solved numerically. Simulations suggest that when the homogeneous cavity loss is small enough, the impact of loss fluctuation on the soliton-comb profile is rather moderate. The effect of loss fluctuations becomes noticeable when the homogeneous loss is sizable, with the recovery time of the induced saturable-absorption process being reasonably long to promote a slow saturable absorption. An analysis of the influence of the detuning on the amplitude and phase of the dissipative soliton crystal, as well as on the spatial variation of the loss for a fixed value of the characteristic frequency, is taken into consideration in the study. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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10. Reusable palladium–quinolyl benzimidazole complex immobilized on a polymer for the hydrogenation of organic substrates.
- Author
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Lakshminarayana, Shilpa Madhugiri, Boregowda, Roopashree, and Virupaiah, Gayathri
- Abstract
2-(2'-quinolyl) benzimidazole (QBIMH) anchored on to the crosslinked polymer beads of chloromethylated poly (styrene-co-divinyl benzene) (PSDVB) was reacted with sodium tetrachloropalladate (Na
2 PdCl4 ) to form polymer-supported palladium complex. The immobilized palladium complex was treated with sodium borohydride and activated. Multifarious approach supported the characterization of polymer-anchored [2-(2'-quinolyl) benzimidazole]palladium complex (PSDVB-QBIM-PdCl2 ) and its activated form. The optimal activated complex catalyzed the hydrogenation of olefins, Schiff bases and nitro compounds under ambient conditions. The kinetic studies were carried out for the hydrogenation of certain olefins. The recycling ability of the supported and the unsupported catalysts was showcased. [ABSTRACT FROM AUTHOR]- Published
- 2023
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11. Chemical Durability of Glasses
- Author
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Conradt, Reinhard, Öchsner, Andreas, Series Editor, da Silva, Lucas F. M., Series Editor, Altenbach, Holm, Series Editor, Annapurna, K., editor, and Molla, Atiar Rahaman, editor
- Published
- 2022
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12. A DFT-based kinetic model for Cu-Al oxygen carrier material in chemical looping with oxygen uncoupling.
- Author
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Liu, Lei, Li, Kexin, Liu, Hanzi, and Sun, Zhiqiang
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CARBON sequestration , *CHEMICAL-looping combustion , *OXYGEN carriers , *COUPLING reactions (Chemistry) , *TRANSPORT equation - Abstract
• DFT-based microkinetic rate equation was established based on the DFT results. • Successfully predict oxygen uncoupling kinetics without fitting experimental data. • MFB-MS experiments were carried out to verify the kinetic rate equation. • The theory is a powerful tool to screen and optimize oxygen carrier for CLOU. Chemical looping with oxygen uncoupling is a promising technology for efficient fuel conversion with inherent CO 2 capture. The oxygen uncoupling reaction of oxygen carrier determines the burning rate of reacting gases with decomposed O 2 in the fuel reactor. However, the existing modeling methods to study the oxygen uncoupling reactions generally ignore the mechanisms, which limits the development of oxygen carrier materials. In this article, density functional theory (DFT) calculations were applied to identify the pathways of oxygen coupling of a Cu-Al-based oxygen carrier. It was found the oxygen coupling reaction fa two-step mechanism involving surface reactions and subsequent O 2 desorption with the energy barrier of 2.42 eV and 0.72 eV respectively. The kinetic rate constants were determined using the Transition State Theory. A rate equation informed by DFT, encompassing energies and frequencies, was formulated. The equation was then incorporated into both the particle model and the reactor model through a series of transport equations. Experiments were executed using a micro-fluidized bed mass spectrometer to collect kinetic data on the oxygen uncoupling of the Cu-Al material. The oxygen uncoupling kinetics of the Cu–Al oxygen carrier at 1000 ℃ in pure inert argon atmosphere is ∼2 times faster than that at 925 ℃, confirming the significant effect of temperature. The simulation results demonstrated that the model accurately forecasts the oxygen uncoupling kinetics under high temperatures (925–1000 °C) and varying oxygen partial pressures (0–8 vol%). The developed theory serves as a potent instrument for the screening and optimizing oxygen carrier materials. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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13. Research on collinear double pulse generation method of electro-optical Q-switched Nd:YAG laser.
- Author
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Dai, Shoujun, He, Jianguo, Wang, Hui, Liu, Yang, Yu, Jiaqi, Zhao, Haidong, Meng, Jingjing, Yuan, Hong, and Huang, Min
- Abstract
This letter introduces the collinear double-pulse generation method of the electro-optical Q-switched Nd:YAG laser and the rate equations describing its pulse formation dynamics. The two pulses share the same resonator and thus have a natural and highly coaxial characteristic. The effect of the voltage applied on the electro-optic crystal on the pulse energy and temporal waveform was studied. The time interval of the double-pulse laser can be tuned from 80 ns to 10 μ s, thus satisfying the needs of a general double-pulse laser. This method is ideal for obtaining a collinear double-pulse laser and can be extended to other lasers. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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14. Rate-equation approach for multi-level quantum systems.
- Author
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Liul, M. P. and Shevchenko, S. N.
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SIMPLICITY - Abstract
Strong driving of quantum systems opens opportunities for both controlling and characterizing their states. For theoretical studying of these systems properties we use the rate-equation formalism. The advantage of such approach is its relative simplicity. We used the formalism for description of a two-level system with further expanding it on a case of a multi-level system. Obtained theoretical results have good agreement with experiments. The presented approach can also be considered as one more way to explore properties of quantum systems and underlying physical processes such as, for instance, Landau–Zener–Stückelberg–Majorana transitions and interference. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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15. How Micelles Influence the Optical Limiting Properties of Zinc Porphyrins and J-Aggregates for Picosecond Pulse Trains.
- Author
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Miao, Quan, Sun, Erping, and Xu, Yan
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OPTICAL limiting , *PICOSECOND pulses , *MICELLES , *SODIUM dodecyl sulfate , *CETYLTRIMETHYLAMMONIUM bromide , *METALLOPORPHYRINS , *ZINC porphyrins - Abstract
In this work, we studied nonlinear dynamics and optical limiting (OL) effects of pulse trains in zinc porphyrins meso-tetrakis methylpyridiniumyl (Zn 2 + TMPyP) and meso-tetrakis sulfonatophenyl (Zn 2 + TPPS) and porphyrin J-aggregates. The environments of zinc porphyrins were selected as aqueous solutions and micelles of sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB). Our numerical results show that both Zn 2 + TMPyP and Zn 2 + TPPS are good optical limiters in all solutions. Zn 2 + TPPS in aqueous solutions shows the best OL effect. Micelles of SDS and CTAB produced less OL effects than the aqueous solutions. The main reason lies in the first excited singlet state and intersystem crossing depending on the electronic structures in different environments. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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16. Parameter Extraction For Quantum Well DFB Lasers Based on 1D Traveling Wave Model
- Author
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Jiewen Chi, Chuanning Niu, and Jia Zhao
- Subjects
DFB lasers ,parameter extraction ,1D TWM ,rate equation ,Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
Extracting the parameters of a laser from the measured results is critical for laser design, modeling and optimization. This work presents a parameter extraction method for quantum well distributed feedback (DFB) lasers based on the one-dimensional traveling wave model (1D TWM). Facet reflectivities, grating coupling coefficient and the other parameters can be extracted by fitting the lasing spectrum, light-current (L-I) curve, intensity modulation (IM) response and large-signal chirp. During the extraction progress, the 1D TWM is simplified to improve the extraction efficiency. The feasibility of this extraction method is verified by extracting parameters from preset simulation results and experimental results, respectively. The 1D TWM can reflect the physical properties of the laser profoundly and the parameter extraction method based on 1D TWM will be a valuable tool for laser design, optimization or processing improvement.
- Published
- 2022
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17. Parameter Extraction For Quantum Well DFB Lasers Based on 1D Traveling Wave Model.
- Author
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Chi, Jiewen, Niu, Chuanning, and Zhao, Jia
- Abstract
Extracting the parameters of a laser from the measured results is critical for laser design, modeling and optimization. This work presents a parameter extraction method for quantum well distributed feedback (DFB) lasers based on the one-dimensional traveling wave model (1D TWM). Facet reflectivities, grating coupling coefficient and the other parameters can be extracted by fitting the lasing spectrum, light-current (L-I) curve, intensity modulation (IM) response and large-signal chirp. During the extraction progress, the 1D TWM is simplified to improve the extraction efficiency. The feasibility of this extraction method is verified by extracting parameters from preset simulation results and experimental results, respectively. The 1D TWM can reflect the physical properties of the laser profoundly and the parameter extraction method based on 1D TWM will be a valuable tool for laser design, optimization or processing improvement. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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18. Accelerating gain and phase recovery in Quantum-Dot reflective Semiconductor optical Amplifier: Unraveling the influence of inhomogeneous broadening and pumping power for enhanced performance.
- Author
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Safari, Khalil, Matloub, Samiye, and Connelly, Michael J.
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SEMICONDUCTOR optical amplifiers , *OPTICAL pumping , *QUANTUM states , *QUANTUM wells , *OPTICAL distortion - Abstract
• This study delves into the intricate interplay between inhomogeneous broadening (IHB) and pumping power on the gain and phase recovery dynamics of Quantum-Dot (QD) Reflective Semiconductor Optical Amplifiers (RSOAs), offering a thorough comparative analysis of their static and dynamic characteristics. • Utilizing an improved QD-RSOA model, incorporating coupled rate equations and considering IHB effects and amplified spontaneous emission, the research provides a sophisticated framework for modeling and comparing ultrafast gain and phase recovery responses in QD-SOAs and QD-RSOAs under different pumping schemes. • Analysis of the contributions from QD states and Quantum Well (QW) carrier reservoirs to phase changes yields valuable insights, demonstrating that a reduction in IHB leads to an accelerated phase response by diminishing slow phase recovery components, particularly for the QD ground and excited states. • The study reveals that, across all pumping schemes, QD-RSOAs exhibit more pronounced phase recovery acceleration compared to QD-SOAs, highlighting the crucial role of optical pumping schemes in achieving enhanced phase recovery without introducing distortion. • By providing insights into the design and performance of QD-SOAs and QD-RSOAs, this research paves the way for advancements in optical communication technologies, emphasizing the importance of controlling phase recovery for optimizing device performance. This investigation examines the complex interaction between inhomogeneous broadening (IHB) and pumping power concerning the gain and phase recovery dynamics of Quantum-Dot (QD) Reflective Semiconductor Optical Amplifiers (RSOAs). An improved QD-RSOA model, employing coupled rate equations and incorporating IHB effects and amplified spontaneous emission is used to model and compare ultrafast gain and phase recovery responses in QD-SOAs and QD-RSOAs for an electrical and two single-color optical pumping schemes. Analysis of the contributions from QD states and Quantum Well (QW) carrier reservoirs to phase changes provides valuable insights. A reduction in IHB leads to an accelerated phase response by diminishing the slow phase recovery components for the QD ground and excited states, and so reducing the contributions from slow phase recovery in carrier reservoirs. Across all pumping schemes, the QD-RSOA exhibits more pronounced phase recovery acceleration. Despite achieving ultrafast gain and phase recovery responses observed in QD-RSOAs when subjected to electrical pumping, a significant overshoot in the phase recovery response is observed. This overshoot leads to a potentially significant chirping and distortion in amplified optical pulses. The study suggests that in long QD-SOAs and QD-RSOAs with higher gain, optical pumping schemes offer a promising strategy for achieving phase recovery acceleration without introducing distortion, which is important for applications of QD-SOAs. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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19. A Rectified Linear Unit Model for Diagnosing VCSEL’s Power Output
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Wang, Li, Chen, Wenhao, Filipe, Joaquim, Editorial Board Member, Ghosh, Ashish, Editorial Board Member, Kotenko, Igor, Editorial Board Member, Prates, Raquel Oliveira, Editorial Board Member, Zhou, Lizhu, Editorial Board Member, Barbosa, Simone Diniz Junqueira, Founding Editor, He, Jing, editor, Yu, Philip S., editor, Shi, Yong, editor, Li, Xingsen, editor, Xie, Zhijun, editor, Huang, Guangyan, editor, Cao, Jie, editor, and Xiao, Fu, editor
- Published
- 2020
- Full Text
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20. Performance tunable passively Q-switched fiber laser based on single-walled carbon nanotubes.
- Author
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Zheng, Jiancheng, He, Chongjun, Wen, Ying, and Li, Hongxiang
- Subjects
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Q-switched lasers , *FIBER lasers , *CARBON nanotubes , *PULSE frequency modulation , *METERING pumps , *OPTICAL communications , *SIGNAL-to-noise ratio - Abstract
Passively Q-switched fiber laser (PQFL) has great potential applications in remote sensing, ranging, and optical communications. However, the PQFLs were seldom studied in view of both theory and experiment. This paper is dedicated to make up for this shortcoming. On the one hand, by describing the coupling rate equations of the PQFL system, the Q-switched pulse output with a modulation frequency of 17.61 kHz and a modulation period of 56.8 μs was obtained at 140 mW pump power. On the other hand, an erbium-doped PQFL whose performance is tunable by controlling the pump power and polarization state was constructed by using a single-walled carbon nanotube (SWCNT) as the saturable absorber (SA). The Q-switched pulse with a repetition rate of 17.61 kHz and a signal-to-noise ratio of 50.2 dB was output at a pump power of 140 mW. The theoretical simulation results were in good agreement with the experimental results. It was also verified from such two aspects that the repetition rate of the output pulse of PQFL was approximately proportional to the pump power. This research promotes the theory and design of PQFL. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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21. Theoretical Modeling and Analysis of Blue Laser Characteristics of Continuous-Wave Single-Wavelength Two-Photon Pumped Rb-Vapor Laser.
- Author
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Ji, Yanhui, He, Yang, Wan, Haohua, Wang, Jiamin, and Chen, Fei
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BLUE lasers , *LASER pumping , *CONTINUOUS wave lasers , *SEMICONDUCTOR lasers , *INFRARED lasers , *PHOTON detectors - Abstract
Based on an analysis of kinetic processes in the continuous-wave (CW) single-wavelength two-photon pumped Rb-vapor laser (Rb-TPAL), a three-dimensional computational model is established using the rate equation. Based on the application of the model to cavity-enhanced Rb-TPAL [Yuan et al., Optics Express 29, 4858 (2021)], the calculated and measured dependences of the laser power on the pump power show good agreement. We simulate the Rb-TPAL pumped by a high-power CW laser diode and analyze the effects of temperature, vapor cell length, pump waist, vapor cell transmission, and output mirror reflectance on the characteristics of the blue laser. The results suggest that the output power and efficiency of blue laser can be improved by optimizing the above parameters; however, the particles in the $5^{2}\text{D}_{5/2}$ level face difficulty to transition to the $6^{2}\text{P}_{3/2}$ level, and this limits the further improvement of blue laser efficiency; therefore, an approach is proposed to improve the efficiency of Rb-TPAL. This study can be useful for designing a two-photon pumped alkali metal laser with high-power output. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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22. Quantum cutting properties in KYF4:Tb3+, Yb3+ phosphors: Judd-Ofelt analysis, rate equation models and dynamic processes
- Author
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Biao Zheng, Jinquan Hong, Bohao Chen, Ying Chen, Ruoqian Lin, Chunlei Huang, Cheng Zhang, Jun Wang, Lin Lin, and Zhiqiang Zheng
- Subjects
Spectroscopic properties ,Rate equation ,Dynamic analysis ,Quantum cutting ,Energy transfer ,Physics ,QC1-999 - Abstract
Spectroscopic properties play a significant role during the design and development of novel luminescent materials. In this work, quantum cutting (QC) luminescent materials KYF4:Tb3+,Yb3+ phosphors were successfully synthesized by sol–gel method. The crystal structure, morphology, fluorescence spectra, and decay curves were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM) and spectrofluorometer. The Judd-Ofelt (J-O) parameters, Ωλ (λ = 2, 4, 6), were directly derived from the emission spectra and decay curves, attributed to the transition intensities of Tb3+ ions were dependent on the J-O parameters. Then, the radiative and nonradiative transition rates, fluorescent branching ratios, cross-relaxation rates and lifetimes of QC luminescence were calculated based on the obtained J-O parameters. Moreover, the rate equation models of QC luminescence were established and the time-dependent population densities in excited levels of Tb3+ ions and Yb3+ ions were simulated. Finally, the dynamic processes of QC luminescence were discussed carefully and the corresponding theoretical quantum efficiency was estimated. Our studies would provide an insight into the QC luminescence and give theoretical guidance for developing novel luminescent materials.
- Published
- 2021
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- View/download PDF
23. Investigations on saturable absorption characteristic of PdS2 and its application to high-peak-power sub-nanosecond intracavity OPO.
- Author
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Han, Chao, Chu, Hongwei, Feng, Tianli, Zhao, Shengzhi, Li, Dechun, Zhao, Jia, and Huang, Weiping
- Subjects
- *
MODE-locked lasers , *OPTICAL parametric oscillators , *Q-switched lasers , *NONLINEAR optical materials , *OPTICAL materials , *ABSORPTION , *PULSED lasers - Abstract
In this work, a unique pentagonal TMD material, palladium disulfide (PdS 2) nanosheets were fabricated by the liquid-phase exfoliation (LPE) process, and the physical characteristics were also investigated. The nonlinear transmittance is measured by the power scanning method and the modulation depth is fitted to be 15.3%. Based on the transmittance curve, the saturable absorption parameters of PdS 2 are calculated, including 5.85 × 10−19 cm2 ground-state absorption cross-section, 1.63 × 10−19 cm2 excited-state absorption cross-section, and 683.5 μs excited-state lifetime. By employing both PdS 2 as a saturable absorber (SA) and an acousto-optic modulator (AOM), a doubly Q-switched and mode-locked (QML) laser-pumped intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) was realized. The pulse energy and the pulse width of the Q-switched envelope for signal wave have been measured. At higher pump power, the high-peak-power low-repetition-rate sub-nanosecond mode-locking pulse of signal wave is generated, in which there is only one mode-locked pulse underneath a Q-switched envelope. The measured shortest signal pulse duration is 530 ps, corresponding to a peak power of 337 kW, at an incident pump power of 9.81 W and an acousto-optic modulator (AOM) repetition rate of 1 kHz. In addition, by considering the Gauss distribution of intracavity photon density, a set of coupled rate equations for a doubly QML laser-pumped intracavity OPO was given and the numerical simulations agreed with the experimental results. These results indicate that PdS 2 is a promising nonlinear optical material for optical applications in the near-infrared (NIR) region. • The PdS 2 nanoflakes was fabricated by liquid-phase exfoliation and characterized. • Palladium disulfide nanomaterials performed well for pulsed laser generation. • Applying the PdS 2 SA, a dual-loss-modulated QML IOPO was realized. • The rate equations for IOPO with PdS 2 were numerically solved. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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24. A theoretical description for competitive adsorption at the Solid/Solution interface.
- Author
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Bashiri, Hadis, Hassani Javanmardi, Alireza, and Soltani, Zeinab
- Subjects
DIFFERENTIAL forms ,LANGMUIR isotherms ,ANALYTICAL solutions ,ADSORPTION kinetics - Abstract
[Display omitted] • A new rate equation for competitive adsorption is obtained. • The first analytical solution of the Langmuir kinetics model of competitive adsorption is provided. • The new equation for competitive adsorption is an exponential kinetic model. Wastewaters usually contain several solutes, and the adsorption process for removing pollutants from the solutions is usually competitive. Kinetic modeling of adsorption systems is a useful tool to obtain some information about the behavior of the system at the same time or in the future. The provided rate equations for binary adsorption are in differential form, and their solutions are approximated numerically using computers. In the present work, the kinetics of competitive adsorption at the solid/solution interface is studied. The new equation shows an exponential relation between time and surface coverage. This new equation is the first analytical solution of the kinetics Langmuir model of competitive adsorption. The simulated and experimental data confirm the provided equation is suitable to study the rate of binary adsorption. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
25. Sub-nanosecond single mode-locking pulse generation in an intracavity KTP optical parametric oscillator with a few-layer Bi2Te3 topological insulator saturable absorber.
- Author
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Han, Chao, Chu, Hongwei, Feng, Tianli, Zhao, Shengzhi, Li, Dechun, Zhao, Jia, Feng, Chuansheng, and Huang, Weiping
- Subjects
- *
OPTICAL parametric oscillators , *Q-switching , *TOPOLOGICAL insulators , *QUARTZ crystals , *Q-switched lasers - Abstract
• The Bi 2 Te 3 nanoflakes was fabricated by liquid-phase exfoliation and characterized. • Applying the Bi 2 Te 3 SA, a dual-loss-modulated QML IOPO laser was realized, resulting in the generation of sub-nanosecond single mode-locking pulses. • The rate equations for IOPO driven by the QML laser with Bi 2 Te 3 SA were numerically solved. By utilizing the ultrasound-assisted liquid phase exfoliation process, Bi 2 Te 3 nanosheets are synthesized and deposited onto a quartz plate to form a saturable absorber (SA), in which nonlinear absorption characteristics around 1 μm are investigated with a home-made Q-switched laser. With the as-prepared Bi 2 Te 3 SA employed, a sub-nanosecond KTiOPO 4 (KTP) based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched and mode-locked (QML) laser is successfully realized. With a short duration of sub-nanosecond and a repetition rate of several kilohertz (kHz), the signal wave's single mode-locking pulse existed underneath a Q-switched envelope can be formed. At an incident pump power of 8.92 W and an acousto-optic modulator (AOM) repetition rate of 2 kHz, a signal wave's single mode-locking pulse underneath a Q-switching envelope with a measured minimum pulse duration of 520 ps is accomplished. It is the first demonstration of such Bi 2 Te 3 SA utilized in a solid-state QML IOPO laser, to the best of our knowledge. According to the experimental results, this provides an efficient and straightforward approach to acquire sub-nanosecond OPO signal wave pulses. Additionally, the relevant coupled rate equations are established, and the simulation results match the experimental results, revealing the potential of Bi 2 Te 3 as a nanomaterial for optoelectronic applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
26. The kinetics of carbon monoxide reduction of magnetite concentrate particles through CFD modelling.
- Author
-
Fan, De-Qiu, Elzohiery, Mohamed, Mohassab, Yousef, and Sohn, H. Y.
- Subjects
- *
CARBON monoxide , *MAGNETITE , *COMPUTATIONAL fluid dynamics , *DISCONTINUOUS precipitation , *PARTIAL pressure , *ACTIVATION energy - Abstract
The kinetics of CO reduction of magnetite concentrate particles was investigated in drop-tube reactors (DTR) to obtain a rate equation for the design and analysis of a flash ironmaking reactor. The effect of CO partial pressure was determined and temperature was varied from 1473 K to 1873 K in few seconds of residence time similar to that in a typical flash reactor. The experimental data were divided into two temperature ranges, below 1623 K and above where the magnetite concentrate melts. The reduction degrees achieved at temperatures below 1623 K were under 50%, while significant reduction degrees (higher than 85%) were achieved at higher temperatures. Computational fluid dynamics (CFD) analysis was employed to improve the accuracy of the rate expressions. It was determined that the nucleation and growth kinetics best describes the investigated reaction. The activation energy was 451 and 88 kJ mol−1, respectively, below and above 1623 K. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
27. Kinetics of hydrogen reduction of magnetite concentrate particles at 1623–1873 K relevant to flash ironmaking.
- Author
-
Elzohiery, Mohamed, Fan, Deqiu, Mohassab, Yousef, and Sohn, H. Y.
- Subjects
- *
MAGNETITE , *COMPUTATIONAL fluid dynamics , *PARTIAL pressure , *DISCONTINUOUS precipitation , *ACTIVATION energy , *HYDROGEN - Abstract
The reduction of magnetite concentrate particles by H2 has been investigated in drop-tube reactor (DTR) to obtain a rate equation that can be applied to the design and analysis of an ironmaking flash reactor. The temperature range in this work is 1623 to 1873 K, where the magnetite concentrate particles become molten droplets. Full reduction of the magnetite concentrate is achieved at a residence time greater than 4 s and H2 partial pressure of 0.15 atm within the temperature range investigated. Computational fluid dynamics analysis is used to improve the accuracy of the obtained rate expressions where the variation of particle temperature is taken into consideration. The reduction of magnetite concentrate particles in this temperature range is best described by the nucleation and growth model with an Avrami parameter n = 1 and a first-order dependence on the partial pressure of H2. The activation energy of reaction is 180 kJ mol−1. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
28. Kinetics models of transesterification reaction for biodiesel production: A theoretical analysis.
- Author
-
Ezzati, Rohollah, Ranjbar, Shahram, and Soltanabadi, Azim
- Subjects
- *
TRANSESTERIFICATION , *BASE catalysts , *ANALYTICAL mechanics , *CHEMICAL kinetics - Abstract
The kinetics of the transesterification reaction has been explored theoretically. A general rate equation (GRE) was obtained for kinetics modeling of transesterification at the entire time of reaction based on a three-step mechanism. It has been shown that the GRE model converts to a Second-Order (SO) model at short initial times of reaction and it converts to Pseudo-First-Order (PFO) model at short initial times of reaction and high concentration of alcohol. Also, a modified form of the Second-Order model (MSO) was derived when the reaction is spontaneous (at Δ r G ≪ 0 conditions or at short initial times of reaction). The accuracy of theoretical models and our assumptions was evaluated by three sets of experimental data selected at literature. It has been shown that the accuracy of PFO, SO, and MSO models followed the order of MSO > SO > PFO at short initial times while the GRE model is a suitable kinetics model at the entire times of reaction. Also, our research, contrary to what has been reported so far in published papers, shows that pseudo-first-order and second-order models are only accurate for kinetics modeling of the transesterification reaction at short initial times of reaction. Image 1 [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
29. Estimation of 177Lu activity produced from direct and indirect routes in Indian research reactors
- Author
-
Singh, Tej, Banerjee, Shantanab, Mishra, Abhishek, Chakraborty, Sudipta, and Chakravarty, Rubel
- Published
- 2022
- Full Text
- View/download PDF
30. Optimal design of composite Nd:YAG/Cr4+: YAG passive Q-switched microchip laser.
- Author
-
LIU Ruike, WANG Chaochen, NIU Changdong, JIN Duo, BAI Zhenxu, WANG Yulei, and LU Zhiwei
- Abstract
Laser diode ( LD) pumped passively Q-switched microchip laser has important applications in the field of industry, military, and medical treatment. To improve the output performance and system integration of LD pumped pulse microchip lasers, the Runge-Kutta method was used to solve the passively Q-switched laser rate equation, and the output parameters of LD end-pumped bonded Nd:YAG/Cr
4+ :YAG microchip laser was numerically simulated. The results show that with a 1mm/1. 5mm bonded Nd: YAG/Cr4+ : YAG as the gain medium, when the initial transmittance of Cr :YAG is 75%, the transmittance of output mirror is 30%, and the radii of the pump and fundamental mode are 100µm, a 0. 7W average power with pulse-width of 174ps at 16. 1kHz can be obtained under the 4. 5W pumping. This study has theoretical significance for the optimization and application of the passively Q-switched microchip laser. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
31. High fidelity readout and protection of a 43Ca+ trapped ion qubit
- Author
-
Szwer, David James and Lucas, David M.
- Subjects
530.0724 ,Atomic and laser physics ,ion trap ,decoherence ,dephasing ,readout ,measurement ,hyperfine ,qubit ,shelving ,quantum computing ,quantum computation ,rate equation ,dynamical decoupling ,Uhrig - Abstract
This thesis describes theoretical and experimental work whose main aim is the development of techniques for using trapped
43 Ca⁺ ions for quantum information processing. I present a rate equations model of43 Ca⁺, and compare it with experimental data. The model is then used to investigate and optimise an electron-shelving readout method from a ground-level hyperfine qubit. The process is robust against common experimental imperfections. A shelving fidelity of up to 99.97% is theoretically possible, taking 100 μs. The laser pulse sequence can be greatly simplified for only a small reduction in the fidelity. The simplified method is tested experimentally with fidelities up to 99.8%. The shelving procedure could be applied to other commonly-used species of ion qubit. An entangling two-qubit quantum controlled-phase gate was attempted between a40 Ca⁺ and a43 Ca⁺ ion. The experiment did not succeed due to frequent decrystallisation of the ion pair, and strong motional decoherence. The source of the problems was never identified despite significant experimental effort, and the decision was made to suspend the experiments and continue them in an improved ion trap which is under construction. A sequence of pi-pulses, inspired by the Hahn spin-echo, was derived that is capable of greatly reducing dephasing of any qubit. If the qubit precession frequency varies with time as an nth-order polynomial, an (n+1) pulse sequence is theoretically capable of perfectly cancelling the resulting phase error. The sequence is used on a 43Ca+ magnetic-field-sensitive hyperfine qubit, with 20 pulses increasing the coherence time by a factor of 75 compared to an experiment without any spin-echo. In our ambient noise environment the well-known Carr-Purcell-Meiboom-Gill dynamic-decoupling method was found to be comparably effective.- Published
- 2009
32. Stability and Strong Convergence for Spatial Stochastic Kinetics
- Author
-
Engblom, Stefan and Holcman, David, editor
- Published
- 2017
- Full Text
- View/download PDF
33. Chemical Kinetics
- Author
-
Teixeira-Dias, José J. C. and Teixeira-Dias, José J. C.
- Published
- 2017
- Full Text
- View/download PDF
34. Multi-Objective Laser Rate Equation Based Parameter Extraction Using VCSEL Small Signal Response and RIN Spectra.
- Author
-
Melgar, Alirio, Thomas, Varghese A., and Ralph, Stephen E.
- Abstract
Rate equation parameters used to simulate semiconductor lasers must be carefully chosen in order to accurately model high-speed laser characteristics in optical link simulations. Previous parameter extraction methods have largely characterized these lasers through their small signal frequency response. We show that capturing both the small signal frequency response and relative intensity noise (RIN) spectrum of the laser is crucial for accurate parameter extraction. We present a multi-objective parameter extraction method alongside a stochastic rate equation model to account for a vertical cavity surface emitting laser's (VCSEL's) bandwidth and RIN characteristics. A genetic algorithm extracts VCSEL parameters from a set of experimentally measured small signal responses and RIN spectra at multiple drive currents. Through Pareto sorting we can extract a single set of parameters which accurately captures the laser's BW and RIN characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
35. Kinetic modelling and simulation studies for the esterification process with Amberlyst 16 resin.
- Author
-
Mekala, Mallaiah and Chimmiri, Venkateswarlu
- Subjects
- *
ESTERIFICATION , *METHYL acetate , *ACETIC acid , *METHANOL , *BATCH reactors - Abstract
Methyl acetate has been synthesized by the reaction between acetic acid and methanol in an experimental batch reactor. The reaction has been carried out homogeneously without using any catalyst and heterogeneously by using Amberlyst 16 resin catalyst. The reaction is performed using different temperatures in the range of 318.15-333.15 K. The reaction catalyzed by Amberlyst 16 is found faster than the uncatalyzed reaction and the influence of process parameters such as catalyst loading, reaction mixture temperature, initial reactant mole ratio, catalyst size, agitation speed on acetic acid conversion has been investigated experimentally for the catalyzed reaction. Further, pseudo-homogeneous kinetic models have been developed for the catalyzed reaction and the uncatalyzed reaction. The reaction rate expressions of catalyzed reaction and uncatalyzed reaction are used to derive the reaction rate equation influenced by the catalyst alone. This rate equation is useful to examine the influence of catalyst alone in the heterogeneously catalyzed methanol esterification reaction. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
36. Effect of pulse irradiation on the evolution of damage structure.
- Author
-
Yoshiie, T. and Kinomura, A.
- Subjects
- *
DISLOCATION loops , *IRRADIATION , *NEUTRON irradiation , *PARTICLE beams - Abstract
Charged particle beams from accelerators driven by radiofrequency or with beam scanners possess time structures (i.e., pulse beam operations). However, it is not clear whether the irradiation effects of these pulse beam operations are the same as those of continuous beams, although the average damage rate is the same in both cases. In this study, the difference between continuous beams and pulse beams, and the effect of the repetition frequency and pulse duration on the defect accumulation are evaluated by the rate equation analysis for Al and Fe. The growth rate of interstitial type dislocation loops in Al is simulated with fixed duty ratios (constant pulse duration over the irradiation period) at 453 K. The effect of pulse duration on a constant period of 1 s is simulated in Fe, changing the pulse duration from 1 to 10−6 s, while the damage (dpa) caused by one pulse remains the same. The results are analyzed and the effects of pulse duration and repetition rate on the damage structure evolution are demonstrated in relation to materials parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
37. Life cycle of scientific publications in the field of high social impact.
- Author
-
Ruggiero, B., Amato, U., Franco, B., De Petrocellis, L., Vettoliere, A., Granata, C., Silvestrini, S., Bonavolontà, C., Valentino, M., Brocchieri, J., and Silvestrini, P.
- Subjects
- *
SOCIAL impact , *QUANTUM transitions , *NANOELECTRONICS , *TECHNOLOGICAL innovations - Abstract
In a previous work, we have presented an innovative theoretical model to describe the evolution of the life cycle of a new technology. We have proposed a mathematical approach based on a rate equation, similar to that used to describe quantum level transitions. The model is able to describe the hype curve evolution in many relevant conditions, which can be associated with various external parameters. In this article, we apply this model to describe the evolution of the number of publications in some different research fields that are very current and extremely advanced in terms of social impact. The applications have been chosen in the fields of biomolecular chemistry, genetics and superconducting nanoelectronics. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
38. Self-Raman Nd-doped vanadate laser: a pump source of organic crystal based difference frequency generation.
- Author
-
Liu, Pengxiang, Qi, Feng, Li, Weifan, Liu, Zhaoyang, Wang, Yelong, Ding, Xin, and Yao, Jianquan
- Subjects
- *
LASER pumping , *ORGANIC bases , *SUBMILLIMETER waves , *VANADATES , *GENERATIONS , *LASERS - Abstract
We analyse a method of high repetition rate, efficient terahertz wave difference frequency generation (DFG) by using a self-Raman Nd-doped vanadate laser to pump 4'-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). A semi-analytical model is introduced that combines the rate equations (for the self-Raman dual-wavelength laser) and the coupled-wave equations (for the DAST-based DFG). Calculations were performed on a diffusion-bonded Nd:YVO4-YVO4 laser with an acousto-optic Q-switch. Parameters (including transmittances at output mirror and crystal lengths) were optimized to obtain high output. Sub-milliwatt average power is predicted under current pump condition. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
39. Kinetics of indium separation and recovery from In–Sn alloys in ITO waste target products via vacuum evaporation.
- Author
-
Pang, Jian, Dong, Chaowei, Xu, Baoqiang, Wu, Hai, Kong, Lingxin, and Yang, Bin
- Subjects
- *
MASS transfer coefficients , *INDIUM , *MASS transfer , *WASTE recycling - Abstract
The environmentally friendly recycling of ITO waste material to regenerate indium resources is crucial for sustainability. The hydrogen reduction process, particularly the green and low-carbon technique of vacuum distillation, is crucial in the production of In–Sn alloys. However, a thorough examination of the mechanics underlying its evaporation throughout this process has yet to be performed. These mechanics are investigated in the present study for 92In–8Sn alloys under specific conditions, including temperatures between 1173 and 1373 K, pressure of 5 Pa, and crucible depth of 25 mm. The relationship between temperature and the rate of volatilization is mathematically represented as ω = e (a+b∙ T). Furthermore, the equation ω = A 2 + (A 1 -A 2)/(1 + e(h -h0)/ dh ) was used to predict the dependency of the volatilization rate on crucible depth, ranging from 25 to 65 mm at 1323 K and 5 Pa. The mass transfer coefficients for the alloy at different temperatures were calculated, and a theoretical kinetic model for evaporation behavior indicated that vapor-phase mass transfer is the limiting step in the process of vacuum distillation of this alloy. This study presents a theoretical basis for the retrieval of In from the In–Sn alloy using vacuum distillation. • A new method for sustainable recovery In–Sn alloy in ITO waste target products is presented. • Actual volatilization rates of 92In–8Sn alloys were studied for the first time. • Kinetic model for vacuum volatilization of In was developed. • Volatile mass transfer of In was associated with M-MIVM. • Limiting link for the vacuum volatilization of In was evaluated. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
40. Modeling and analysis of buffer gas effect on 52S1/2→52D5/2 and 52S1/2→72S1/2 broadened two-photon pumped Rb vapor lasers.
- Author
-
Ji, Yanhui, He, Yang, Pan, Li, Wang, Jiamin, and Chen, Fei
- Subjects
- *
GAS analysis , *LASERS , *ABSORPTION spectra , *VAPORS , *BLUE lasers , *PUMPING machinery - Abstract
• Three-dimensional theoretical model of Rb-TPAL is established, incorporating the spectra of pump and absorption with He. • Theoretical prediction regarding He pressure-induced broadening of 52S 1/2 → 52D 5/2 transition agrees with experimental findings. • Adding a small amount of He contributes to the output of Rb-TPAL, consistent with experimental findings. • 52S 1/2 → 72S 1/2 transition in the Rb-TPAL has been proven to have the potential to achieve higher efficiency. The study introduces helium (He) as a buffer gas to theoretically investigate the characteristics of two-photon pumped Rb vapor laser (Rb-TPAL) in order to enhance the pumping absorption efficiency of Rb-TPAL and consequently achieve high-power laser output. The analysis is based on a three-dimensional computational model, incorporating the spectral distribution of pump and absorption, as well as the influence of He on the absorption spectrum. The theoretical calculation of the dependence of the 52S 1/2 → 52D 5/2 transition broadened as a function of the pressure of He has good agreement with experimental results. We also simulated the influence of the pump linewidth and pressure of He on the output characteristics when 52S 1/2 → 52D 5/2 and 52S 1/2 → 72S 1/2 transitions in Rb-TPAL. A comparative analysis revealed that opting for the 52S 1/2 → 72S 1/2 transition can achieve higher optical–optical efficiency. The results also substantiate that the addition of a small amount of He has a positive impact on the laser output, consistent with experimental findings. Our study is crucial for designing the high-power multi-wavelength output Rb-TPAL system. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
41. The Limitation of the Combination of Transition State Theory and Thermodynamics for the Reactions of Proteins and Nucleic Acids
- Author
-
Nobuo Shimamoto
- Subjects
chemical ratchet ,kinetics ,reaction theory ,rate equation ,transition-state theory ,detailed balance ,Microbiology ,QR1-502 - Abstract
When a reaction is accompanied by a change with the speed close to or slower than the reaction rate, a circulating reaction flow can exist among the reaction states in the macroscopic stationary state. If the accompanying change were at equilibrium in the timescale of the relevant reaction, the transition-state theory would hold to eliminate the flow.
- Published
- 2021
- Full Text
- View/download PDF
42. Generation of High Peak Power Mode-Locked Green Pulses Based on WS2 and EOM: Experiment and Theory
- Author
-
Wenjing Tang, Wanggen Sun, Jing Wang, Kai Jiang, Wei Xia, and Shengzhi Zhao
- Subjects
solid-state ,frequency modulated ,mode-locked pulses ,high peak power ,rate equation ,Organic chemistry ,QD241-441 - Abstract
Based on an as-prepared high-quality WS2 film and an electro-optic modulator (EOM), a dual-loss-modulated low repetition rate mode-locking laser at 0.53 μm with high peak power is presented for the first time. The laser characteristics versus the pump power are investigated experimentally and theoretically. At a pump power of 10.67 W, the shortest pulse duration of 305 ps can be measured, corresponding to the highest peak power of 931 kW, which is much higher than those of the single passive modulated lasers with WS2-SA. A simple rate equation simulation was used to describe this dual-loss-modulated mode-locking green laser based on WS2 and EOM. The results of the numerical simulation are basically in accordance with the experimental values.
- Published
- 2021
- Full Text
- View/download PDF
43. Inevitable Approximations
- Author
-
Lente, Gábor and Lente, Gábor
- Published
- 2015
- Full Text
- View/download PDF
44. Rates and Rate Equations
- Author
-
Lente, Gábor and Lente, Gábor
- Published
- 2015
- Full Text
- View/download PDF
45. Rate Equations
- Author
-
Witelski, Thomas, Bowen, Mark, Chaplain, M.A.J., Series editor, Erdmann, K., Series editor, MacIntyre, Angus, Series editor, Süli, Endre, Series editor, Tehranchi, M R, Series editor, Toland, J.F., Series editor, Witelski, Thomas, and Bowen, Mark
- Published
- 2015
- Full Text
- View/download PDF
46. Multiple Interactions: Essential Activation and Liberation
- Author
-
Baici, Antonio and Baici, Antonio
- Published
- 2015
- Full Text
- View/download PDF
47. MULTI-HOP GENERALIZED CORE PERCOLATION ON COMPLEX NETWORKS.
- Author
-
SHANG, YILUN
- Subjects
- *
FIRST-order phase transitions , *PERCOLATION , *GENERATING functions , *PHASE transitions , *KERNEL (Mathematics) - Abstract
Recent theoretical studies on network robustness have focused primarily on attacks by random selection and global vision, but numerous real-life networks suffer from proximity-based breakdown. Here we introduce the multi-hop generalized core percolation on complex networks, where nodes with degree less than k and their neighbors within L -hop distance are removed progressively from the network. The resulting subgraph is referred to as G (k , L) -core, extending the recently proposed G k -core and classical core of a network. We develop analytical frameworks based upon generating function formalism and rate equation method, showing for instance continuous phase transition for G (2 , 1) -core and discontinuous phase transition for G (k , L) -core with any other combination of k and L. We test our theoretical results on synthetic homogeneous and heterogeneous networks, as well as on a selection of large-scale real-world networks. This unravels, e.g., a unique crossover phenomenon rooted in heterogeneous networks, which raises a caution that endeavor to promote network-level robustness could backfire when multi-hop tracing is involved. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
48. Efficiency Droop and Effective Active Volume in GaN-Based Light-Emitting Diodes Grown on Sapphire and Silicon Substrates.
- Author
-
Ryu, Han-Youl, Ryu, Geun-Hwan, and Onwukaeme, Chibuzo
- Subjects
SAPPHIRES ,RATE equation model ,DIODES ,ELECTRON distribution ,QUANTUM wells ,SILICON - Abstract
We compared the efficiency droop of InGaN multiple-quantum-well (MQW) blue light-emitting diode (LED) structures grown on silicon(111) and c-plane sapphire substrates and analyzed the efficiency droop characteristics using the rate equation model with reduced effective active volume. The efficiency droop of the LED sample on silicon was observed to be reduced considerably compared with that of the identical LED sample on sapphire substrates. When the measured external quantum efficiency was fitted with the rate equation model, the effective active volume of the MQW on silicon was found to be ~1.45 times larger than that of the MQW on sapphire. The lower efficiency droop in the LED on silicon could be attributed to its larger effective active volume compared with the LED on sapphire. The simulation results showed that the effective active volume decreased as the internal electric fields increased, as a result of the reduced overlap of the electron and hole distribution inside the quantum well and the inhomogeneous carrier distribution in the MQWs. The difference in the internal electric field of the MQW between the LED on silicon and sapphire could be a major reason for the difference in the effective active volume, and consequently, the efficiency droop. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
49. Derivation of rate equations for equilibrium limited gas-solid reactions.
- Author
-
Wenzel, Marcus and Sundmacher, Kai
- Subjects
- *
GAS phase reactions , *SOLID-liquid equilibrium , *EQUILIBRIUM reactions , *EQUILIBRIUM , *EQUATIONS - Abstract
Highlights • A general derivation for equilibrium limited gas-solid reactions is proposed. • Piecewise-defined rate equation allows for a change in the rate expression. • Case studies highlight the importance of the piecewise-defined reaction rate expression. • Numerical stability problems are discussed and possible solutions proposed. Abstract In this work the differences between the formulation of reaction rate equations for equilibrium limited reactions in homogeneous and heterogeneous systems are investigated. A rigorous derivation for equilibrium limited gas-solid reactions is proposed based on the core ideas of homogeneous gas phase reactions. The resulting reaction rate expression allows for two distinct reaction rate mechanisms for the forward and reverse reaction direction and is, therefore, valid in both reaction directions. The thermodynamic consistency and the validity of the proposed reaction rate expression is shown using a simple reactor model. The results are compared to traditional reaction rate expressions and it is explained why they are not able to appropriately describe the true reaction behavior in some cases. The implications and use cases for process modeling are investigated and suggestions are proposed for solving numerical challenges associated with the proposed reaction rate equations. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
50. Experimental and theoretical investigation on Q-switched Nd:LuLiF4 laser.
- Author
-
Li, Shixia, Xia, Feng, and Kong, Weijin
- Subjects
- *
Q-switched lasers , *RATE equation model , *GAUSSIAN distribution - Abstract
A diode-pumped continuous-wave (CW) and passively Q-switched Nd:LuLiF 4 laser was investigated. Under an incident pump power of 11.2 W, an output power of up to 1.92 W was generated, corresponding to a slope efficiency of 17.4%. By using a Cr4+:YAG wafer as saturable absorber, stable Q-switched pulse trains with an average output power of 1.13 W and a pulse duration of 13.8 ns were captured at a repetition rate of 32.5 kHz, delivering a pulse energy of 36.4 μJ. A rate equation model was further introduced to theoretically analyze the dynamical mechanism, in which the Gaussian spatial distribution theory was taken into account. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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