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The effect of grain-size on fracture of polycrystalline silicon carbide: A multiscale analysis using a molecular dynamics-peridynamics framework
摘要： A robust atomistic to mesoscale computational multiscale/multiphysics modeling framework that explicitly takes into account atomic-scale descriptions of grain-boundaries, is implemented to examine the interplay between grain-size and fracture of polycrystalline cubic silicon carbide (3C-SiC). A salient feature of the developed framework is the establishment of scale-parity between the chosen atomistic and the mesoscale methods namely molecular dynamics (MD) and peridynamics (PD) respectively, which enables the ability to model the effect of the underlying microstructure as well as obtain relevant new insights into the role of grain-size on the ensuing mechanical response of 3C-SiC. Material properties such as elastic modulus, and fracture toughness of single crystals and bicrystals of various orientations are obtained from MD simulations, and using appropriate statistical analysis, MD derived properties are interfaced with PD simulations, resulting in mesoscale simulations that accurately predict the role of grain-size on failure strength, fracture energy, elastic modulus, fracture toughness, and tensile toughness of polycrystalline 3C-SiC. In particular, it is seen that the fracture strength follows a Hall-Petch law with respect to grain-size variations, while mode-I fracture toughness increases with increasing grain-size, consistent with available literature on brittle fracture of polycrystalline materials. Equally importantly, the developed MD-PD multiscale/multiphysics framework represents an important step towards developing materials modeling paradigms that can provide a comprehensive and predictive description of the microstructure-property-performance interplay in solid-state materials.
关键词： Peridynamics,Polycrystalline,Multiscale modeling,3C-SiC,Grain boundaries,Molecular dynamics
更新于2025-09-23 15:22:29
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Deciphering controls for debris-flow erosion derived from a LiDAR-recorded extreme event and a calibrated numerical model (Ro?bichelbach, Germany)
摘要： Debris flows are among the most destructive and hazardous mass movements on steep mountains. An understanding of debris-flow erosion, entrainment and resulting volumes is a key requirement for modelling debris-flow propagation and impact, as well as analysing the associated risks. As quantitative controls of erosion and entrainment are not well understood, total volume, runout and impact energies of debris flows are often significantly underestimated. Here, we present an analysis of geomorphic change induced by an erosive debris-flow event in the German Alps in June 2015. More than 50 terrestrial laser scans (TLS) of a 1.2 km long mountain torrent recorded geomorphic change in comparison to an airborne laser scan (ALS) performed in 2007. Errors were calculated using a spatial variable threshold based on the point density of ALS and TLS and the slope of the digital elevation models. Highest erosion rates approach 5.0 m3/m2 (mean 0.6 m3/m2). During the event 9,550 ± 1,550 m3 was eroded whereas only 650 ± 150 m3 was deposited in the channel. Velocity, flow pressure, momentum and shear stress were calculated using a carefully calibrated RAMMS Debris Flow model including material entrainment. Here we present a linear regression model relating debris-flow erosion rates to momentum and shear stress with an R2 up to 68 %. Channel transitions from bedrock to loose debris sections cause excessive erosion up to 1 m3/m2 due to previously unreleased random kinetic energy now available for erosion.
关键词： erosion,numerical modeling,debris flow,geomorphic change,RAMMS,LiDAR
更新于2025-09-23 15:22:29
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Prediction of Second-Order Nonlinear Optical Properties of D–π–A Compounds Containing Novel Fluorene Derivatives: A Promising Route to Giant Hyperpolarizabilities
摘要： Herein, ?rst attempt has been made to utilize ?uorene-based dye-sensitized solar cell (DSSCs) dye JK-201 as potential nonlinear optical (NLO) material and for the theoretical designing of novel NLO chromophores JK-D1–JK-D12. DFT/TDDFT calculations were performed to compute the effect of p-linkers and acceptors-steered modulation on electronic, photophysical and NLO properties of JK-201 and JK-D1–JK-D12. Results illustrate that computed kmax (484.74 nm) and experimentally calculated kmax (481 nm) of JK-201 was found in good agreement. Maximum red shifted absorption spectrum was observed in JK-D12 with 599.38 nm. JK-D1–JK-D12 showed narrow energy gap and broader absorption spectrum as compared to JK-201. NBO analysis con?rmed the formation of charge separation state due to robust range of electrons/charge transfer from donor to acceptor via p-bridge. Giant NLO response was observed in all compounds. Particularly, JK-D12 displayed surprisingly large hai and btot computed 1376.74 (a.u.) and 405,731.84 (a.u.) respectively. Although literature is ?ooded with D–p–A compounds investigated for their DSSCs properties, but research reports on their NLO properties and utilization as NLO materials are completely deserted. Our research will open new horizons to explore DSSCs materials for NLO applications. This theoretical framework also exposed that ?uorene-substituted chromophores are excellent NLO candidates for modern hi-tech applications.
关键词： D–p–A organic chromophores,Acceptor units,Molecular modeling,Density functional theory,NLO response properties,p-Conjugated linkers
更新于2025-09-23 15:22:29
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[IEEE 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Novosibirsk, Russia (2018.10.2-2018.10.6)] 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Students' Project Developments of Wave Optics Virtual Labs
摘要： The author organized the project activity of computer modeling in teaching physics of IT students. The students' teams develop software products – virtual laboratories. The article presents some examples of the students' developments of virtual laboratories of Wave Optics.
关键词： computer modeling of physical processes,project training,virtual labs
更新于2025-09-23 15:22:29
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An analytical method to create patient-specific deformed bone models using X-ray images and a healthy bone model
摘要： Generation of patient-specific bone models from X-ray images is useful for various medical applications such as total hip replacement, implant manufacturing, knee kinematic studies and deformity correction. These models may provide valuable information required for a more reliable operation. In this work, we propose a new algorithm for generating patient-specific 3D models of femur and tibia with deformity, using only a generic healthy bone model and some simple measurements taken on the X-ray images of the diseased bone. Using the X-ray measurements, an interpolation function (a polynomial or a cubic spline) is fit to the mid-diaphyseal curve of the actual bone and the generic bone model is deformed in the guidance of this function with free form deformation method. The created models are intended to be used mainly for the visualization of fixation procedure in software-supported external fixation systems. An error measure is defined to quantify the error in this matching procedure. The method is found to be capable of producing deformed tibia models that satisfactorily reflect the actual bones, as confirmed by two orthopaedic surgeons who use software-supported external fixation systems regularly.
关键词： Deformity,3D bone modeling,Free form deformation,External fixation,Patient-specific bone models,Mathematical modeling
更新于2025-09-23 15:21:21
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Evaluation method for the performance of light screen array measurement system based on semi-physical simulation
摘要： The paper presents a method to evaluate the performance of light screen array measurement system (LSA for short) objectively and scienti?cally. We put forward the scheme of semi-physical veri?cation platform based on arbitrary waveform generator (AWG), and this instrument is used as a substitute for light screen detector in the LSA. according to some main characteristics of dynamic signal, the waveform ?les of two simulation signals with a certain time interval are compiled and created through con?guring some options through a signal waveform edition software. Furthermore, these waveform ?les are downloaded into the AWG to generate two channel simulation signals. Then, the time interval of these two signals can be measured in the signal acquisition & processing module of LSA. Finally, we can compare the di?erence between true values and measured results. Through experiment and analysis, the proposed method can meet the requirement of performance evaluation on the LSA, and it is superior to the other previous methods.
关键词： Semi-physical simulation,Noise environment,Waveform modeling and editing,Photoelectric measurement,Dynamic signal generation
更新于2025-09-23 15:21:21
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Integrated adsorption and photocatalytic degradation of volatile organic compounds (VOCs) using carbon-based nanocomposites: A critical review
摘要： Volatile organic compounds (VOCs) are harmful for human and surrounding ecosystem, and a great number of VOC abatement technologies have been developed during the past few decades. However, the single method has some problems such as high energy consumption, unfriendly environment, and low removal efficiency. Recently, the integration of adsorption and photocatalytic degradation of VOCs is considered as a promising one. Carbon material, with large surface area, high adsorption capacity, and fast electron transfer ability, is widely used in integrated adsorptive-photocatalytic removal of VOCs. It is thus crucial to digest and summarize recent research advances in carbon-based nanocomposites as the adsorbent-photocatalyst for VOC removal. To satisfy this need, this work provides a critical review of the related literature with focuses on: (1) the advantages and disadvantages of various carbon-based nanocomposites for the applications of VOC adsorption and photocatalytic degradation; (2) models and mechanisms of adsorptive-photocatalytic removal of VOCs according to the material properties; and (3) major factors controlling adsorption-photocatalysis processes of VOCs. The review is aimed to establish the "structure-property-application" relationships for the development of innovative carbon-supported nanocomposites and to promote future research on the integrated adsorptive and photocatalytic removal of VOCs.
关键词： Modeling,Photocatalytic degradation,VOC abatement,Carbon-based nanocomposite,Adsorption
更新于2025-09-23 15:21:21
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Polarization Dependence in the Carbon K-edge Photofragmentation of MAPDST Photoresist: an Experimental and Theoretical Study
摘要： The use of tunable soft X-rays from synchrotron radiation (SR) opens the possibility of inducing selective chemical bond scission due to its high localization in a chemical bond. The selective fragmentation of a potential extreme ultraviolet (EUV) resist, poly(4-(methacryloyloxy) phenyldimethylsulfoniumtriflate (MAPDST), was examined using inner shell polarized SR excitation. Selective bond dissociation processes were studied using a combination of carbon K-edge excitation, angle-resolved irradiation, and NEXAFS spectroscopy. Detailed theoretical calculations carried out with the FEFF9 modeling program allowed the interpretation of all the observed experimental features. NEXAFS results indicated that the aromatic group of the polymer lies parallel to the substrate surface. FEFF9 theoretical calculations confirmed the origin of the splitting of the main C 1s →π*C=C resonances observed. The transition C1s → πα*C=C (285.3 eV) can be associated with the four internal carbons of the aromatic ring. The transition C1s → πβ*C=C (286.9 eV) was assigned to the carbon atoms attached to the oxygen and sulfur atoms. According to the theoretical calculations, the origin of the splitting is due to the different absolute energy of C1s. The results showed a strong selective dissociation effect when the excitation energy was tuned to C1s → πα*C=C transition and the electric field vector of the photon was perpendicular to the substrate plane (grazing angle). On the contrary, other transitions were in general less affected. When the SR irradiation angle changed from grazing to normal incidence, the intensity of the C1s → π*C=C transitions was almost unaffected by 285.3 eV photons. The experimental results suggest that site-specific core excitation combined with the direction of the electric field vector of the incidence SR, can efficiently control the localization of the photon energy to produce selective bond dissociation in MAPDST thin films. The results presented here can also be useful to guide new processing lithographic methods for EUVL using the polarization properties of light in ordered polymeric thin films.
关键词： NEXAFS spectroscopy,FEFF9 modeling,selective bond dissociation,synchrotron radiation,polarization dependence,MAPDST photoresist
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Evaluation of Tidal Effect On Water Constituent Variations Using Optical Observations And Tide Gauge Records in the Dutch Wadden Sea
摘要： In this study, the effect of tide on the variation of concentrations of Chlorophyll-a (Chla) and Suspended Particulate Matters (SPM), retrieved from a complete dataset of diurnal close-range hyperspectral observations recorded at the NIOZ jetty station (NJS) located at the Marsdiep inlet in the Dutch part of the Wadden Sea, was evaluated. The two-stream radiative transfer model 2SeaColor was inverted to retrieve Chla and SPM concentrations per each hyperspectral observation of the quality-controlled dataset. Concurrently with these diurnal observations, tidal information was obtained from the Den Helder station located at 3.7 km from the NJS. From the performed analysis and evaluation of this study, we concluded that the tide has little observable effects on the diurnal changes of SPM concentration at the NJS located in the Dutch part of the Wadden Sea. The results of this evaluation and the favorable location of the NJS, which is not influenced by the tidal phase, will contribute to a better understanding of the seasonal variability of the retrieved Chla and SPM concentration values using diurnal optical observations at the NJS. These long-term retrievals can be used later to do the phenological analysis of Chla concentration values in this region.
关键词： tidal effect,the NIOZ jetty station,2SeaColor model,hyperspectral observations,Radiative transfer modeling (RTM)
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Using Multi-Frequency Insar Data to Constrain Ground Deformation of Ischia Earthquake
摘要： In this study, multi-frequency Synthetic Aperture Radar Interferometry (InSAR) data are used to constrain the ground deformation due to the August 21st, 2017, Ischia earthquake. InSAR results are the input data to infer the source model of the seismic event. C-band Sentinel-1 and X-band COSMO-SkyMed? InSAR results show a displacement pattern in the epicentral area, with a maximum value of ~3.5 cm and a dominant vertical component. Preliminary analytical and numerical models suggest that the retrieved InSAR ground displacements are due to the combination of two phenomena: the tectonic dislocation caused by the slip on the fault plane and the surficial displacement caused by the triggering of shallow landslides.
关键词： InSAR,Ischia earthquake,Landslides,Deformations,Modeling
更新于2025-09-23 15:21:21