Thermal Features Research Articles

Calculation of thermal features in welding and additive manufacturing

This paper summarizes multiple engineering expressions that enable the prediction of thermal magnitudes of interest associated with moving heat sources. The expressions use only fundamental parameters available before performing any experiments, and their calculation is algebraic, without the need for numerical methods. All expressions are based on the fundamental governing equations of heat transfer in the solid. The magnitudes predicted include maximum width and its location, maximum penetration, thickness of HAZ, maximum temperature and its location, leading and trailing edge of an isotherm, heating and cooling rate, aspect ratio of an isotherm, melting efficiency, cooling time from 800°C to 500°C, solidification time, and maximum distribution of a heat source to reach a target temperature. Parameters involved include heat source power and speed, thermal conductivity and diffusivity of the substrate material, temperature of interest and preheat or interpass temperature. Temperature-dependent properties are accounted for by the use of effective properties. The expressions proposed can be extended into sophisticated geometries for welding and specific additive manufacturing cases.

Research on foil thermal features of hydrodynamic air foil bearing with the Three-dimensional heat transfer model

Research on foil thermal features of hydrodynamic air foil bearing with the Three-dimensional heat transfer model

AQUADA PLUS: Automated damage inspection of cyclic-loaded large-scale composite structures using thermal imagery and computer vision

This study develops and demonstrates a new method to locate and track multiple fatigue damages in large-scale composite structures subject to cyclic loads using thermography and computer vision. Progressive damages generate thermal features due to material friction, allowing efficient detection using passive thermography. Automated damage localization and evaluation are done by thermal image processing incorporated with thermodynamics principles. The proposed new method, AQUADA PLUS, is demonstrated on two composite wind turbine blades in which artificial defects are introduced to trigger damage growth when subject to cyclic loading. Multiple damage sites are located, tracked, and evaluated automatically despite the complex thermal background that changes considerably when the thermal videos are taken. A pioneering drone-based field test has been conducted to demonstrate the possibility of field application where complex environmental conditions and varying thermal backgrounds are present. The associated challenges are identified and the possible solutions are discussed for the further development of the proposed method toward real-world application. All original thermal videos presented in this study are shared with the public for future study.

The Expectations and Prospects for Quantitative Volcanology in the Upcoming Surface Biology and Geology (SBG) Era

AbstractThe Surface Biology and Geology (SBG) mission is part of the National Aeronautics and Space Administration's planned Earth System Observatory. The mid/thermal infrared (MIR/TIR) portion of SBG will deliver high spatial and temporal resolution data designed (in part) to answer fundamental volcano science questions, as outlined in the 2018 Decadal Survey (DS). The planned 60 m spatial resolution, high TIR saturation temperature (∼500 K), and addition of two high temperature MIR bands (∼800–1200 K) will improve thermal feature and spatial variability detection across all volcanic surfaces, as well as limit data saturation over high temperature targets such as lava flows. However, the MIR/TIR part of the mission also has design aspects that will hinder volcanic science. The ability to derive accurate spectral information of volcanic, and indeed other geologic surfaces, is a function of the number and placement of the TIR bands. The originally proposed five TIR bands do not advance these diagnostic investigations beyond what is currently available. In fact, it may hinder them. Six or more TIR bands are vital for accurate assessment of mineral and glass abundances in volcanic deposits. The SBG MIR/TIR mission temporal resolution (3–5 days) will improve repeat coverage of volcanic systems, aiding in longer‐term monitoring, but observations of highly dynamic processes will not be possible, despite their importance in the 2018 DS. Most problematic is the proposed local overpass time of 12:30, which will result in cloudier scenes (especially in tropical/lower latitude regions) and complicate atmospheric corrections compared to the traditional morning overpass times of earlier TIR missions.

Chiral diketopyrrolo[3,4-c]pyrrole-1,2,3-1H-triazole dyes with highly tunable properties in solution and thin films.

We studied the impact of achiral substituents on the chiral supramolecular architectures of diketopyrrolo[3,4-c]pyrrole-1,2,3-1H-triazole (DPP) dyes. We decorated the same chiral DPP motif with substituent groups on the nitrogen atoms of the lactam moiety: the hydrophobic n-octyl alkyl chain, the hydrophilic triethylene glycol (TEG) chain and the thermo-cleavable t-butoxycarbonyl (t-Boc) carbamate group. In spite of identical conjugated chromophore and chiral appendage, in aggregated form the three dyes displayed profoundly different optical, chiroptical, electrochemical and thermal features. ECD measurements revealed differences in the aggregation modes, which would be inaccessible by most other techniques. We found strong chiroptical features, which would have major implications in the context of chiral organic opto-electronics and in the development of other highly innovative technological applications.

Thermal Stabilization of Nafion with Nanocarbon Materials.

The stability of Nafion-carbon composites is important for the efficient functioning of fuel cells. The thermal decomposition of Nafion, nanostructured carbon materials, such as multi-walled carbon nanotubes, graphene-like materials, and their composites, have been studied using constant heating rate thermogravimetry in air. Materials were characterized by quantitative and qualitative analysis methods, such as thermogravimetry, X-ray photoelectron spectroscopy, scanning, and transmission electron microscopy with field emission. In Nafion-carbon composites, an increase in the thermal stability of the Nafion polymer is observed due to the formation of surface compounds at the Nafion-carbon interface. In this case, the degree of stabilization is affected by both the component composition of the composite and the structure of the nanocarbon material. The greatest effect was obtained in the case of using thermally expanded graphite (few-layer graphene). Nafion is distributed to a greater extent over the surface of the carbon material due to its high structural accessibility. The most thermally stable composite is Nafion-graphene in a mass ratio of components 1:4 with one stage Nafion degradation at 422 °C, whereas the degradation of pristine Nafion occurs in three stages at 341, 413, and 430 °C. The dependences of thermal stability and features of thermal degradation on the composition and structure of composites are discussed.

Performance and microstructural investigations of processed lateritic fine aggregates in blended cement mortars exposed to elevated temperatures

PurposeIn recent years, fire accidents in engineering structures have often been reported worldwide, leading to a severe risk to life and property safety. The present study is carried out to evaluate the performance of Ground Granulated Blast Furnace Slag (GGBS) and fly ash–blended laterized mortars at elevated temperatures.Design/methodology/approachThis test program includes the replacement of natural river sand with lateritic fine aggregates (lateritic FA) in terms of 0, 50 and 100%. Also, the ordinary Portland cement (OPC) was replaced with fly ash and GGBS in terms of 10, 20, 30% and 20, 40 and 60%, respectively, for producing blended mortars.FindingsThis paper presents results related to the determination of residual compressive strengths of lateritic fine aggregates-based cement mortars with part replacement of cement by fly ash and GGBS exposed to elevated temperatures. The effect of elevated temperatures on the physical and mechanical properties was evaluated with the help of microstructure studies and the quantification of hydration products.Originality/valueA sustainable cement mortar was produced by replacing natural river sand with lateritic fine aggregates. The thermal strength deterioration features were assessed by exposing the control specimens and lateritic fine aggregates-based cement mortars to elevated temperatures. Changes in the mechanical properties were evaluated through a quantitative microstructure study using scanning electron microscopy (SEM) images. The phase change of hydration products after exposure to elevated temperatures was qualitatively analyzed by greyscale thresholding of SEM images using Image J software.

Double diffusion and Hall effects on MHD sinusoidal natural convection flow of silver water-based nanofluid from a porous vertical plate

This paper scrutinizes Hall current, Soret and Dufour impacts on natural convective flow of nanofluid attributable to variation in sinusoidal surface temperature over a vertical plate through a porous medium with strong transverse magnetic field applied normally to the flow. In this regard, the silver metal is considered as nanoparticles with water as base fluid. The overlapping multi-domain bivariate spectral local linearization method (OMD-BSLLM) has been utilized to solve the dimensionless governing equations which are attained by means of appropriate transformations. The obtained results are portrayed via graphical and tabular formations to inspect flow fields, shear stresses, heat and mass transmission characteristics for varying thermo-physical parameters. We found that there is an enhancement in the flow fields, shear stresses and heat transportation with the use of silver nanoparticles. Thermal and concentration boundary layer thickness enhance by using porous material, whereas diminish with improvement in Hall effect and ratio of buoyancy forces. The flow characteristics decline with the inclusion of porous medium while elevates with increment in Hall parameter. Moreover, an upgrade in thermal-diffusion correspond to a substantial growth in concentration field along with mass transfer rate. Current analysis can be useful in MHD energy generators, and industrial applications such as heating and cooling procedures owing to the involvement of nanoparticles having superior thermal conductivity features.

Hydrodynamic evolution of Sgr A East: the imprint of a supernova remnant in the Galactic Centre

ABSTRACT We perform three-dimensional numerical simulations to study the hydrodynamic evolution of Sgr A East, the only known supernova remnant (SNR) in the centre of our Galaxy, to infer its debated progenitor supernova (SN) type and its potential impact on the Galactic Centre environment. Three sets of simulations are performed, each of which represents a certain type of SN explosion (SN Iax, SN Ia, or core-collapse SN) expanding against a nuclear outflow of hot gas driven by massive stars, whose thermodynamical properties have been well established by previous work and fixed in the simulations. All three simulations can simultaneously roughly reproduce the extent of Sgr A East and the position and morphology of an arc-shaped thermal X-ray feature, known as the ‘ridge’. Confirming previous work, our simulations show that the ridge is the manifestation of a strong collision between the expanding SN ejecta and the nuclear outflow. The simulation of the core-collapse SN, with an assumed explosion energy of 5 × 1050 erg and an ejecta mass of 10 M⊙, can well match the X-ray flux of the ridge, whereas the simulations of the SN Iax and SN Ia explosions underpredict its X-ray emission, due to a smaller ejecta mass. All three simulations constrain the age of Sgr A East to be ≲1500 yr and predict that the ridge should fade out over the next few hundred years. We address the implications of these results for our understanding of the Galactic Centre environment.

Environmental and economic management study of phase change material integrated bifacial photovoltaic thermal-greenhouse drying system: A thermal approach

Environmental and economic analysis of any technology is essential for long-term sustainability. The present article explores the environmental and economic aspects of phase change material-integrated bifacial photovoltaic thermal greenhouse drying system (BIPVTGDPCM). The literature discusses that poor operating hours and self-sustainability are key problems with the greenhouse drying system (GD). Along with the performance issue, lack of information available on the environmental and economic impact of GD. The BIPVTGDPCM is designed to minimize all defined problems with the assurance of environmental quality. The designed system is tested at the geographical location of Rohtak, Haryana, India. The study's outcome shows that the integration of PCM (Lauric acid) runs the system even after sunset. The CO2 emission and the carbon credit earned by the system are 49,851 kg and 498,514 US$, respectively. The energy back time was found to be 2.14 years, whereas the cost payback time is 2.6 years. The system recovers energy and money invested quickly and runs with minimal cost after the payback period. The BIPVTGDPCM save almost 90121₹ (1192.94 US$) in a life span of 25 years. The thermal, electrical, environmental, and economic features of the BIPVTGDPCM make it future-ready environment-friendly food preservation technology.

Iceline variations driven by protoplanetary disc gaps

ABSTRACT The composition of forming planets is strongly affected by the protoplanetary disc’s thermal structure. This thermal structure is predominantly set by dust radiative transfer and viscous (accretional) heating and can be impacted by gaps – regions of low dust and gas density that can occur when planets form. The effect of variations in dust surface density on disc temperature has been poorly understood to date. In this work, we use the radiative transfer code MCMax to model the 2D dust thermal structure with individual gaps corresponding to planets with masses of 0.1 MJ –5 MJ and orbital radii of 3, 5, and 10 au. Low dust opacity in the gap allows radiation to penetrate deeper and warm the mid-plane by up to 16 K, but only for gaps located in the region of the disc where stellar irradiation is the dominant source of heating. In viscously heated regions, the mid-plane of the gap is relatively cooler by up to 100 K. Outside of the gap, broad radial oscillations in heating and cooling are present due to disc flaring. These thermal features affect local dust–gas segregation of volatile elements (H2O, CH4, CO2, and CO). We find that icelines experience dramatic shifts relative to gapless models: up to 6.5 au (or 71 per cent) closer to the star and 4.3 au (or 100 per cent) closer to the mid-plane. While quantitative predictions of iceline deviations will require more sophisticated models, which include transport, sublimation/condensation kinetics, and gas–dust thermal decoupling in the disc atmosphere, our results suggest that planet-induced iceline variations represent a potential feedback from the planet on to the composition of material it is accreting.

Isolation of cellulose microfibers and nanofibers by mechanical fibrillation in a water-free solvent

Cellulose from vegetable sources is the most abundant biopolymer on earth. In plants, cellulose is a reinforcement element that conforms to a hierarchical structure. Cellulose micro-/nanofibers can be isolated from the cell wall by top-down strategies involving mechanical processes to be used in applications as a reinforcing material. Nonetheless, its use has been limited as its extraction in an aqueous medium is unfavorable when employed in low-hydrophilic matrices. Therefore, this work proposes a novel homogenization route in which cellulose micro-/nanofibers are directly obtained and dispersed in propylene glycol (PG), which generates more possibilities for these (nano) structures in applications that require water-free environments. Moreover, the influence on the cycle numbers in the morphological, chemical, thermal, and rheological properties was researched. Thus, the obtained micro-/nanofibers presented TEM diameters even below 20 nm. XRD analysis evidenced crystalline planes located at 1overline{1 }0, 110, and 200, and crystallinity degree values up to 80%. Also, FTIR spectra bands in 3340 cm−1, 2890 cm−1, 1314 cm−1, and in the fingerprint region corresponded to native cellulose Iβ. FTIR and TGA confirmed no influence of mechanical cycles on cellulose fibers’ chemical and thermal properties. Furthermore, the increase in the cycle number evidenced a shear-thinning rheological behavior of the suspensions. Considering the above results, it was concluded that the proposed high-pressure homogenization within PG is an approach for vegetable nanocellulose homogenization while maintaining high crystallinity, thermal, and chemical features with huge importance for subsequent processes in the development of nanocomposites with hydrophilic matrices for industrial applications.Graphical abstract

Experimental and simulation analysis of thermal behavior of large‐span roof system under solar radiation

SummaryThe large‐span metal roof systems can produce a significant nonuniform temperature effect under solar radiation, leading to potential safety hazards. An experiment is conducted to study the nonuniform thermal behavior of a small‐scale continuous welded stainless steel roof (CWSSR) system under solar radiation. The small‐scale CWSSR system considered different roof slopes and sunward side and nightside. The efficiency of the numerical analysis of the thermal behavior of the roof slab is verified in comparison with the experimental results. Based on the numerical and experimental results, the thermal effect of a full‐scale CWSSR system is studied under different orientations, wind speeds, and atmospheric temperature. Through the analysis of research results, the nonuniform thermal features of the CWSSR system are significant and cannot be overlooked. The temperature difference between the sunward side and nightside roof slab is positively correlated with the roof slope. The thermal behavior of the CWSSR system is greatly influenced by wind speeds but is less affected by orientations and atmospheric temperature.

Evaluation of design information disclosure through thermal feature extraction in metal based additive manufacturing

Manufacturing-as-a-Service (MaaS) can accelerate additive manufacturing (AM) process-defect modeling by augmenting training data to all collaborating users via a data sharing network. However, sharing process data may disclose product design information. This paper aims to evaluate design information disclosure of various thermal history-based feature extraction methods for metal-based AM anomaly detection. This is accomplished by evaluating the design information (i.e., printing orientation) retained, and the overall data usability (i.e., anomaly detection) preserved in the extracted features for various state-of-the-art feature extraction methods. The evaluation results indicate that there are urgent needs in privacy preserving data sharing for additive MaaS (AMaaS).

HAFNet: Hierarchical Attentive Fusion Network for Multispectral Pedestrian Detection

Multispectral pedestrian detection via visible and thermal image pairs has received widespread attention in recent years. It provides a promising multi-modality solution to address the challenges of pedestrian detection in low-light environments and occlusion situations. Most existing methods directly blend the results of the two modalities or combine the visible and thermal features via a linear interpolation. However, such fusion strategies tend to extract coarser features corresponding to the positions of different modalities, which may lead to degraded detection performance. To mitigate this, this paper proposes a novel and adaptive cross-modality fusion framework, named Hierarchical Attentive Fusion Network (HAFNet), which fully exploits the multispectral attention knowledge to inspire pedestrian detection in the decision-making process. Concretely, we introduce a Hierarchical Content-dependent Attentive Fusion (HCAF) module to extract top-level features as a guide to pixel-wise blending features of two modalities to enhance the quality of the feature representation and a plug-in multi-modality feature alignment (MFA) block to fine-tune the feature alignment of two modalities. Experiments on the challenging KAIST and CVC-14 datasets demonstrate the superior performance of our method with satisfactory speed.

Prediction and optimization of mechanical properties of Ni based and Fe–Ni based super alloys via neural network approach with alloying composition parameter

The Optimization of super alloy through alloying element composition control is very challenging since it contains more than ten type of elements. Generally, the optimization process of the mechanical properties of super alloy by composition alteration was performed via trial-and-error which is time consuming and expensive. In this study, the artificial neural network was successfully employed to reveal the correlation between alloying element and the hardness, tensile strength, and melting point of Ni based and Fe–Ni based super alloy. The model showed a good accuracy between predicted and actual values, especially for hardness and melting temperature, with R2 and RMSE values were found to be above 95% and below 3%, respectively. The Pearson Correlation Coefficient and Feature Importance revealed the linear and non-linear correlation of elements in the matrix. The validation of mathematical expression derived from symbolic regression displayed a high reliability associated with RMSE values of approaching 0%. The feature importance derived from atomic and thermal features characterization on Fe–Ni based super alloy as selected sample revealed the dominant effect of Ni matrix on the mechanical properties of the alloy. These results show the potential of our model to assist in the designing of super alloy for industry.

Thermal and Acoustic Features of Lightweight Concrete Based on Marble Wastes and Expanded Perlite Aggregate

A large amount of industrial solid waste is generated from industrial activities worldwide. One such waste is marble waste, a waste generated from quarries which is generated in larger amount which needs attention. It is proved that this waste has a significant impact both on the people health and on the environment. Hence, research works are directed towards addressing usage of waste marble power, the aim of this experimental investigation is to study the usability of sand obtained by crushing marble waste (MWS) on the mixing of lightweight concrete based on expanded perlite aggregate (EPA). First, the mechanical, chemical, and physical properties of marble waste sand and expanded perlite aggregate were determined after which different mixtures of concrete are prepared by varying the percentage of EPA (0, 20, 40, 60, 80, and 100%), in order to find the optimum mixture focussing on obtaining best hydraulic properties. Also, in this work, the thermal and acoustic properties (thermal conductivity, thermal diffusivity, specific heat capacity and sound reduction index at different frequencies) of the tested concrete samples were investigated. Results shows that it is possible to obtain thermal and acoustic insulation lightweight concrete by using sand obtained by crushing marble wastes. Also, addition of more than 20% of EPA aggregate in concrete, develops a thermal insulating lightweight concrete which possess capacity to store heat and produce better thermal performance. Concrete blend with a percentage of more than of 20% of EPA aggregate can be placed in the category of acoustic insulation lightweight concrete. In summary, cement based on MWs and EPA provides better workability and energy saving qualities, which are economical and environmentally beneficial and may result in decreased construction budget and improve a long-term raw materials sustainability.

Thermal performance improvement of a LS-2 parabolic trough solar collector using porous disks

This study presents a thorough numerical investigation of a LS-2 parabolic trough collector (PTC) to introduce a manufacturable structure with high performance. This is done by considering all influential parameters such as possible design shapes (full, upward half, and downward half), diameters, spacings, and PPI (pores per inch) of porous materials along with thermal and fluidic features of heat transfer fluid used inside the absorber pipe. It is found that the full-disk cases perform better than half-disk options. Moreover, the thermal efficiency of PTC improves by increasing PPI and the diameter of porous disks, as well as by reducing the space gaps between the disks. Studying the effects of volumetric flow rate and inlet flow temperature shows that the thermal efficiency diminishes by increasing inlet temperature and decreasing flow rate. In addition, the variations of Nusselt number and friction factor for all mentioned parameters are studied, and performance evaluation criteria are developed to assess the simultaneous effects of enhancing heat transfer against increasing the pumping power.

Ligand field parameters, optical, thermal, magnetic, and structural features of ZnO containing cobalt-borate glasses

This article presents a study of cobalt speciation in borate glass samples, with up to 20 mol. % of zinc oxide. The samples were prepared by the melt-quenching method. The glass properties were presented utilizing a set of complementary investigations of all samples to evaluate structural, optical, thermal, and magnetic properties. XRD technique was exploited to scrutinize the structural nature of samples. Macrostructural modifications were demonstrated using Archimedes’ principle. FT-IR was utilized to probe the internal components of the glass network. Thermograms analysis was used to determine the thermal stability of the samples, which is required for applications. Optical band gap energy was decreased while the Urbach energy was enhanced. Using ligand field theory of cobalt ions, the optical absorption transitions were studied of Co2+ ions. Astonishingly, the usability of ligand field theory to evaluate the optical parameters was presented, in addition to their relation to the structural changes was demonstrated. Non-linearity aspects were enhanced with ZnO addition. Finally, ESR signals confirmed the existence of Co2+ ions in octahedral and tetrahedral symmetry, with a possibility of tetrahedral ions converting to octahedral symmetry. Based on the evaluation of ligand field parameters, besides the structural, optical, thermal, and magnetic features due to ZnO addition, our study reveals a significant potential for utilizing Zn-BNC glass for different optoelectronic purposes.

Field-scale yield prediction of winter wheat under different irrigation regimes based on dynamic fusion of multimodal UAV imagery

Field-scale crop yield prediction is critical to site-specific field management, which has been facilitated by recent studies fusing unmanned aerial vehicles (UAVs) based multimodal data. However, these studies equivalently stacked multimodal data and underused canopy spatial information. In this study, multimodal imagery fusion (MIF) attention was proposed to dynamically fuse UAV-based RGB, hyperspectral near-infrared (HNIR), and thermal imagery. Based on the MIF attention, a novel model termed MultimodalNet was proposed for field-scale yield prediction of winter wheat. To compare multimodal imagery-based and multimodal features-based methods, a stacking-based ensemble learning model was built using UAV-based canopy spectral, thermal, and texture features. The results showed that the MultimodalNet achieved accurate results at the reproductive stage and performed better than any single modality in the fusion. The MultimodalNet performed best at the flowering stage, with a coefficient of determination of 0.7411 and a mean absolute percentage error of 6.05%. The HNIR and thermal imagery were essential in yield prediction of winter wheat at the reproductive stage. Compared to equivalent stacking fusion, dynamic fusion through adaptively adjusting modality attention improved the model accuracy and adaptability across winter wheat cultivars and water treatments. Equivalently stacking more modalities did not necessarily yield improved performance than dynamically fusing fewer modalities. Methods using multimodal UAV imagery with rich spatial information were more applicable than methods using multimodal features to field-scale yield prediction. This study indicates that the MultimodalNet makes a powerful tool for field-scale yield prediction of winter wheat.