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Analysis of optical and thermal factors’ effects on the transient performance of parabolic trough solar collectors
摘要： Solar resources are inherently unsteady and their energy density on the earth is low. Thereby, when the solar energy is converted into thermal energy through concentrating the sunlight, how to predict the transient performance of parabolic trough solar collectors under the operating conditions is necessary for the steady useful output and the efficient use of the energy. So this paper describes a mathematical model of the transient thermal behaviors of parabolic trough solar collectors. Then, to validate this transient model, its numerical results are compared with the experimental data. These data were collected from a utility-scale loop of parabolic trough solar collectors. The comparison between the model predictions and the experimental data shows a consistent and reasonable agreement. Furthermore, the primary interest of this study is to determine how the temperature distributions of the absorber, the glass envelope and the heat transfer fluid evolve from initial conditions with specified optical and thermal parameters. Thus, this model is used to carry out parametric studies to make analyses of essential impact factors on transient behaviors of parabolic trough solar collectors. These factors include the temperature of the heat transfer fluid at the inlet, the initial conditions, and the optical efficiency. Moreover, this model has the function of continuous adjustment of the flow rate to satisfy the requirement of the temperature of the heat transfer fluid at the outlet according to varying boundary conditions. Hence, another analysis is performed to investigate transient processes when the flow rate is continuously adjusted at various DNI ramp rates.
关键词： Concentrating solar power,Transient model,Parabolic trough solar collector,Solar heating and cooling
更新于2025-09-23 15:23:52
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Reproduction of surface-enhanced resonant Raman scattering and fluorescence spectra of a strong coupling system composed of a single silver nanoparticle dimer and a few dye molecules
摘要： The spectral changes in surface-enhanced resonant Raman scattering (SERRS) and surface enhanced fluorescence (SEF) of single silver nanoparticle dimers adsorbed by near-single dye molecules are reproduced under strong coupling regimes. For the reproduction, the enhancement and quenching factors in SERRS and SEF are derived from the Purcell factors including both radiative and nonradiative plasmon modes. The Purcell factors are estimated using the coupling energies obtained by analyzing the spectral changes in plasmon resonance during SERRS and SEF decay processes on the basis of a classical hybridization model. The model is composed of a plasmon and a molecular exciton with phonon replicas accurately representing the molecular multi-level system. The reproduced SERRS spectral changes are consistent with the experimental ones. Furthermore, the calculated SEF spectral changes can reproduce the experimental ones by phenomenologically assuming transitions from ultra-fast SEF to conventional SEF with decreasing coupling energies.
关键词： strong coupling,hybridization model,silver nanoparticle dimer,dye molecules,Purcell factors,surface enhanced fluorescence,surface-enhanced resonant Raman scattering
更新于2025-09-23 15:23:52
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Pay-As-You-Go financing: A model for viable and widespread deployment of solar home systems in rural India
摘要： Decentralised Solar Home Systems (SHSs) are established as an effective strategy to connect the ‘last mile’ without electricity access and leapfrog communities to clean energy solutions. According to the World Bank, the Pay-As-You-Go (PAYG) model has emerged as one of the effective commercially viable solutions to provide decentralised energy access to rural and remote communities in developing nations. The paying ability of households is a critical challenge for energy enterprises, and PAYG, with its easy payment schemes makes solar units affordable and allows households to gradually own these systems. The model also offers user training, ongoing maintenance, and service blocking functionality that minimises investment risk. The PAYG model has demonstrated huge success in Sub-Saharan Africa where Kenya pioneered the model as a cost competitive modern alternative for kerosene. One in five people in India lack access to electricity, and grid-connected rural communities often face frequent blackouts. With the advancement in distributed solar technologies and growing penetration of the mobile telecommunications network in India, PAYG could advance into a successful model to electrify communities living off the grid. Our analysis involves a two-dimensional approach where a systematic review of PAYG literature including case studies from Kenya and India was performed, followed by three expert interviews to further augment learnings and opportunities to deploy PAYG SHSs in India. This analysis finds that India's socio-political context seems suited for increased PAYG penetration, including utilising the opportunity provided by the country's Unified Payments Interface. This paper offers insights for practitioners and policymakers to consider the PAYG model to deploy clean electricity to households and rural micro-enterprises.
关键词： Public-private partnership,Decentralised renewable energy,Flexible repayment,Energy access,Rural electrification,Pay-As-You-Go model (PAYG)
更新于2025-09-23 15:23:52
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Experimental studies and mathematical simulation of intermittent infrared and convective drying of sweet potato (Ipomoea batatas L.)
摘要： Intermittent infrared and convective drying (IIRCD) is a novel drying method that can enhance energy efficiency and quality of dried product. The mechanism of drying using this method is not yet fully understood. Mathematical models that describe the drying process of IIRCD for agricultural crops do not exist. In this study, a physics based mathematical model was developed to understand the mechanism of drying sweet potato using IIRCD. The model was based on shrinkage dependent diffusivity and evaporation phenomenon. COMSOL Multiphysics finite element software was employed for the model simulation. The simulation results of moisture and temperature distribution were validated by experimental drying data. The results fitted closely with experimental data. Drying of sweet potato using IIRCD was found to be more efficient in terms of final product quality compared to convective hot-air drying method.
关键词： quality of dried products,COMSOL,Physics-based model,modelling and simulation
更新于2025-09-23 15:23:52
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Monte Carlo based model for diffuse reflectance from turbid media for the diagnosis of epithelial dysplasia
摘要： Diffuse reflectance from biological tissue has been widely used in diagnostic oncology for characterizing biochemical and morphological changes in epithelial tissue. However, computational complexity and time consumption involved in the extraction of absorption and scattering properties of tissues from diffuse reflectance reduce its potentiality for the effective diagnosis in a clinical setup. In this regard, a simple and accurate empirical equation for diffuse reflectance from a turbid medium was developed. A diffuse reflectance lookup table was generated using Monte Carlo simulations of all the optical properties typical of soft tissues in the visible and near infrared region of the spectrum for a semi-infinite medium. The generated lookup table was used to extract an empirical equation for diffuse reflectance using the surface fitting method. The proposed equation was tested with simulations and tissue phantom validation studies. The accuracy of the proposed empirical equation is tenfold higher than the diffusion approximation method. The uniqueness of the present method lies in its reliability even at extremities.
关键词： turbid medium,empirical model,Monte Carlo,epithelial dysplasia,diffuse reflectance
更新于2025-09-23 15:23:52
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Bright optical solitons for Lakshmanan–Porsezian–Daniel model with spatio-temporal dispersion by improved Adomian decomposition method
摘要： This paper conducts numerical studies of optical solitons with Lakshmanan–Porsezian–Daniel model having spatio-temporal dispersion. A newly proposed version of the well-known Adomian's decomposition method is applied to secure numerical simulations of the recently reported analytical soliton solutions. The focus of this paper stays with bright soliton solutions to the model.
关键词： improved Adomian decomposition method,Lakshmanan–Porsezian–Daniel model,Optical Soliton,Kerr law nonlinearity
更新于2025-09-23 15:23:52
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Infrared Spectroscopy of Triatomics for Space Observation || Clathrate Nano-Cages
摘要： Determining the presence and evolution of molecular species and their physicochemical environment in astrophysical media makes high-resolution infrared spectroscopy a powerful investigative tool that would provide a great deal of information on how these molecules behave in their environments. In this chapter, we describe the theoretical models developed to analyze the absorption spectra of a triatomic molecule trapped in a clathrate nano-cage at very low temperatures. The Lakhlifi–Dahoo extended inclusion model allows the determination of the trapping site (cage structure type), position and movements of the molecule in its site. Frequency shifts due to the solid environment can be interpreted using an atom–atom potential model to describe the interaction between the clathrate matrix and the trapped molecule. Moreover, this inclusion model makes it possible to determine the IR spectra and the couplings with the atoms or molecules forming the nano-cage.
关键词： clathrate,nano-cage,inclusion model,infrared spectroscopy,astrophysical media,triatomic molecule
更新于2025-09-23 15:23:52
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Generating a hyperspectral digital surface model using a hyperspectral 2D frame camera
摘要： Miniaturised 2D frame format hyperspectral camera technology that is suitable for small unmanned aerial vehicles (UAVs) has entered the market, making the generation of hyperspectral digital surface models (HDSMs) feasible. HDSMs offer a rigorous approach to capturing the target spectral and 3D geometric data. The main objective of this investigation was to study and develop techniques for the generation of HDSMs in forest areas using novel hyperspectral 2D frame camera technologies. An approach based on object-space image matching was developed, adapting the traditional vertical line locus (VLL) method for HDSM generation; this was then named the hyperspectral VLL (HVLL) approach. Additionally, image classification was introduced into the processing chain in order to adapt the matching parameters, based on different classes. We also proposed a method for extracting the spectral and viewing angle information of the points. An empirical study was carried out using UAV datasets from tropical and boreal forests using 2D format hyperspectral cameras, based on tuneable Fabry-Pérot interferometer (FPI) technology. Quality assessment was performed using DSMs based on state-of-the-art commercial software and airborne laser scanning (ALS). The results showed that the proposed technique generated a high-quality HDSM in both tested environments. The HDSM had higher deviations over the continuous canopy cover than the digital surface models (DSMs) generated using commercial software. The method using image classification information outperformed the commercial approach with respect to the ability to measure ground points in shadowed areas and in canopy gaps. The proposed method is of great interest in supporting automated interpretations of novel multi- and hyperspectral imaging technologies, especially when applied complex objects, such as forests.
关键词： Forest,Hyperspectral 2D frame camera,Image matching,Hyperspectral digital surface model
更新于2025-09-23 15:23:52
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Large scale image retrieval with DCNN and local geometrical constraint model
摘要： Image retrieval, which refers to browse, search and retrieve the images of the same scene or object from a large database of digital images, has attracted increasing interests in recent years. This paper proposes a coarse-to-fine method for fast indexing with Deep Convolutional Neural Network(DCNN) and Local Geometrical Constraint Model. We first use a vector quantized DCNN feature descriptors and exploit enhanced Locality-sensitive hashing(LSH) techniques for fast coarse-grained retrieval. Then, we focus on obtaining high-precision preserved matches for fine-grained retrieval. This is formulated as a maximum likelihood estimation of a Bayesian model with latent variables indicating whether matches in the putative set are inliers or outliers. We impose the non-parametric global geometrical constraints on the correspondence using Tikhonov regularizers in a reproducing kernel Hilbert space. To ensure the well-posedness of the problem, we develop a local geometrical constraint that can preserve local structures among neighboring feature points, and it is also robust to a large number of outliers. The problem is solved by using the Expectation Maximization algorithm. Extensive experiments on real near-duplicate images for both feature matching and image retrieval demonstrate that the results of the proposed method outperform current state-of-the-art methods.
关键词： Image retrieval,Coarse-to-fine,Local geometrical constraint model,DCNN
更新于2025-09-23 15:23:52
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Influence of In Doping on the Electronic Transport Properties of n-Type Cu0.008Bi2Te2.7Se0.3
摘要： Doping is an effective approach to enhance the thermoelectric figure of merit (zT) of thermoelectric alloys by modifying their electronic structure. In this study, we investigated the influence of In doping on the electronic and thermal transport properties of n-type Cu0.008Bi2-xInxTe2.7Se0.3 (x = 0, 0.005, 0.01, and 0.015) polycrystalline alloys. The electrical conductivity of the alloys showed a moderate decreased by In doping. The Seebeck coefficient also decreased slightly. The bandgap Eg of the alloys widened slightly according to the Goldsmid–Sharp Eg formula. The band parameters of the conduction and valence bands were estimated using a two-band model. In the case of the In-doped samples, the concentration and mobility of electrons decreased simultaneously, resulting in a reduction in the electrical conductivity. However, the level of bipolar conduction remained unchanged even after doping because of the compensation of Eg widening and the band parameter modification. Meanwhile, the effect of In doping on the thermal conductivity of n-type Cu0.008Bi2Te2.7Se0.3 was found to be insignificant. Consequently, the zT of the alloy increased slightly to 1.12 at x = 0.05, while it decreased at higher doping levels.
关键词： bipolar conduction,Thermoelectrics,single parabolic band model,bismuth telluride
更新于2025-09-23 15:23:52