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Evaluation of Factors, Influencing the Accuracy of the Digital Model, Obtained by Laser Scanning
摘要： Measurements in terrestrial laser scanning (TLS) are not perfect and are subject to errors caused by various factors affecting the quality of the capture process and the resulting final product. Careful consideration of all these factors and errors provides a good basis for assessing the quality of the data and the information received. The accuracy of the 3D model obtained from laser scanning is influenced by the density of the measurements and the modelling methods. 3D modelling algorithms allow accuracy to be improved, but modelling software cannot solve all the problems, and it is impossible to achieve high quality 3D modelling without taking into account the factors that affect the accuracy of the measurements. The investigation of error sources in TLS measurements is rather complicated due to the large number of influencing factors that are interconnected. In addition to angular and longitudinal measurements, most scanning systems also offer a measure of the intensity of the reflected signal. Because the TLS is a non-reflective geodetic technology, it means that the measurement results are highly dependent on the reflectivity of the materials. The energy of the reflected signal depends on the following physical factors: object material properties, surface colour of the object, surface temperature, surface humidity, illumination. From the experimental studies it has been confirmed that the illumination and humidity of the scanned surfaces have a significant impact on their reflecting ability and the density of the received point cloud. Evaluation of digital model accuracy is made with а plane approximation and comparison with control points. Areas with different point densities were created in order to analyse the accuracy of 3D model and to determine the optimum scanning density.
关键词： accuracy,illumination,humidity,terrestrial laser scanning,TLS,point cloud,3D model,reflectivity
更新于2025-09-16 10:30:52
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In situ laser reflectivity to monitor and control the nucleation and growth of atomically-thin 2D materials
摘要： The growth of atomically-thin two-dimensional (2D) layered and other quantum materials is typically performed without in situ monitoring or control. Here, a simple laser reflectivity approach is demonstrated to provide in situ control over sub-monolayer thickness and growth kinetics during pulsed laser deposition (PLD) of MoSe2 layers. First, the general technique is presented with emphasis on designing the maximum sensitivity of the optical contrast through consideration of Fresnel’s equations with proper choice of layer thickness, substrate, and laser monitoring wavelength, incidence angle, and laser polarization. Then the 633 nm optical reflectivity of MoSe2 layers on SiO2/Si substrates was predicted and compared with in situ monitoring of MoSe2 growth by PLD under actual growth conditions using a probe HeNe laser beam. The measurements showed high sensitivity and excellent agreement with MoSe2 surface coverages calculated from atomic resolution STEM analysis of 2D layers deposited in arrested growth experiments. Growth kinetics revealed by these measurements showed sigmoidal nucleation and growth stages in the formation of the 2D MoSe2 layers that are described by a simple model, indicating the promise of the laser reflectivity technique for in situ monitoring and control of 2D materials deposition.
关键词： pulsed laser deposition (PLD),MoSe2,kinetic modeling,in situ reflectivity,2D materials
更新于2025-09-16 10:30:52
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Performance Improvement of Trough Concentrating Photovoltaic Thermal System: A Review
摘要： This paper presents an overview on the performance improvement of trough concentrating photovoltaic thermal system by optimizing different components and operating parameters of the system and has been put forwarded. Initially, the performance of four types of solar cell arrays was studied, in that triple junction GaAs cells possessed good performance characteristics. Subsequently the importance of increasing the concentrator reflectivity for improving the performance of TCPV/T system is presented by increasing the mirror reflectivity from 0.69 to 0.92 and consequently the maximum power of the cell array got increased. Then, the role of receiver shape like rectangle and triangle for the maximum utilization of solar radiation is also presented.
关键词： Concentrator reflectivity,GaAs,PV cells,trough collector,Heat transfer
更新于2025-09-12 10:27:22
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Chirped and chirp–free solitons in optical fiber bragg gratings with dispersive reflectivity having parabolic law nonlinearity by Jacobi’s elliptic function
摘要： Optical solitons and other solutions in fiber Bragg gratings having dispersive reflectivity with parabolic form of nonlinearity are recovered in this paper. The new Jacobi elliptic functions expansion has been utilized. Chirped as well as chirp–free pulses are recovered.
关键词： chirp,dispersive reflectivity,Bragg gratings,solitons
更新于2025-09-12 10:27:22
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High-performance and -stability graphene quantum dots-mixed conducting polymer/porous Si hybrid solar cells with titanium oxide passivation layer
摘要： Recently, conducting polymer/Si hybrid solar cells (HSCs) based on simple fabrication processes are highly attractive due to their low cost, but low conductivity of the polymer, high reflection index of Si, and large recombination loss on the Si back contact are major drawbacks that should be solved for the practical applications. Here, we first report HSCs composed of graphene quantum dots (GQDs)-mixed poly (3,4-ethylenedioxythiophene) (PEDOT:GQDs)/porous Si (PSi)/n-Si/titanium oxide (TiOx, back passivation layer). Maximum power conversion efficiency (PCE) of 10.49 % is obtained from the HSCs at an active area of 5 mm2, resulting from the enhanced conductivity of the PEDOT:GQDs, the reduced reflectivity of Si (the increased absorption) by the formation of PSi, and the prevented recombination loss at the Si backside due to the passivation. In addition, the HSCs of 16 mm2 active area maintain ~78 % (absolutely from 8.03 to 6.28 %) of the initial PCE even while kept under ambient conditions for 15 days.
关键词： conducting polymer,passivation,hybrid solar cell,titanium oxide,porous Si,reflectivity,graphene quantum dot
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Moving Gap Solitons in a Coupled Nonuniform Fiber Bragg Grating with Cubic-Quintic Nonlinearity
摘要： The existence and stability of moving gap solitons in a coupled fiber Bragg gratings with dispersive reflectivity in a cubic-quintic nonlinear medium are investigated. The effect of dispersive reflectivity on the stability of solitons is analyzed.
关键词： dispersive reflectivity,Gap soliton,cubic-quintic nonlinearity
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - Dynamics of Colliding Solitons in a Coupler with Separated Nonuniform Bragg Grating and Nonlinearity
摘要： In this paper we present the systematic analysis of the collisions of counter-propagating gap solitons in a linearly coupled dual-core system where one core has only Kerr nonlinearity and the other core is linear which contains a nonuniform Bragg grating with dispersive reflectivity.
关键词： dispersive reflectivity,Gap soliton,Bragg grating
更新于2025-09-11 14:15:04
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Thickness-Dependent Swelling Behavior of Vapor-Deposited Smart Polymer Thin Films
摘要： In this contribution, the temperature-dependent swelling behavior of vapor-deposited smart polymer thin films is shown to depend on cross-linking and deposited film thickness. Smart polymers find application in sensor and actuator setups and are mostly fabricated on delicate substrates with complex nanostructures that need to be conformally coated. As initiated chemical vapor deposition (iCVD) meets these specific requirements, the present work concentrates on temperature-dependent swelling behavior of iCVD poly(N-isopropylacrylamide) thin films. The transition between swollen and shrunken state and the corresponding lower critical solution temperature (LCST) was investigated by spectroscopic ellipsometry in water. The films’ density in the dry state evaluated from X-ray reflectivity could be successfully correlated to the position of the LCST in water and was found to vary between 1.1 and 1.3 g/cm3 in the thickness range 30?330 nm. This work emphasizes the importance of insights in both the deposition process and mechanisms during swelling of smart polymeric structures.
关键词： X-ray reflectivity,spectroscopic ellipsometry,vapor-deposited,smart polymers,iCVD,LCST,film thickness,swelling behavior,cross-linking
更新于2025-09-11 14:15:04
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Microstructure-Stabilized Blue Phase Liquid Crystals
摘要： We show that micron-scale two-dimensional (2D) honeycomb microwells can significantly improve the stability of blue phase liquid crystals (BPLCs). Polymeric microwells made by direct laser writing improve various features of the blue phase (BP) including a dramatic extension of stable temperature range and a large increase both in reflectivity and thermal stability of the reflective peak wavelength. These results are mainly attributed to the omnidirectional anchoring of the isotropically oriented BP molecules at the polymer walls of the top and bottom substrates. This leads to an omnidirectional stabilization of the entire BPLC system. This study not only provides a novel insight into the mechanism for the BP formation in the 2D microwell but also points to an improved route to stabilize BP using 2D microwell arrays.
关键词： honeycomb microwells,temperature range,stability,thermal stability,reflectivity,blue phase liquid crystals
更新于2025-09-11 14:15:04
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Stability of Multilayered Ag/Ag<inf>3</inf>Sn/Sn Films Noncyanide Electroplateded for high-reflective back-electrode
摘要： Due to the problems of environmental pollution and energy consumption, the design of high-reflective back-electrode (HRBE) was proposed and applied to flip-chip and vertical-packaged high-power LED packaging processes. The working reliability of the Ag-based reflective electrode material is a key technical bottleneck in the development of a HRBE that has a simple structure, a low manufacturing cost, and a high reliability in a complicated working environment. In this work, multilayered Ag/Ag3Sn/Sn films were prepared by non-cyanide electrodeposition and annealing and we studied their properties. Multilayered Ag/Ag3Sn/Sn exhibited reflectance superior high compared to pure Ag films. After immersing in 2 ml/L (NH4)2Sx solution for 60min, the multilayered Ag/Ag3Sn/Sn films still maintained the initial reflectivity, and the pure Ag film decreased significantly. In addition, the contact resistance of the pure Ag film increases significantly with the increase of the immersing time and eventually fails. These results show that Ag/Ag3Sn/Sn films have excellent reflectivity and sulfidation resistance, paving the way for the preparation of efficient HRBE.
关键词： reflectivity,electrodeposition,Ag/Ag3Sn/Sn layers,sulfidation resistance
更新于2025-09-10 09:29:36