Thermal Model Research Articles

A ConvLSTM-based model for predicting thermal damage during laser interstitial thermal therapy.


Accurate prediction of thermal damage extent is essential for effective and precise thermal therapy, especially in brain laser interstitial thermal therapy (LITT). Immediate postoperative contrast-enhanced T1-weighted imaging (CE-T1WI) is the primary method for clinically assessing in vivo thermal damage after image-guided LITT. CE-T1WI reveals a hyperintense enhancing rim surrounding the target lesion, which serves as a key radiological marker for evaluating the thermal damage extent. Although widely used in clinical practice, traditional thermal damage models rely on empirical parameters from in vitro experiments, which can lead to inaccurate predictions of thermal damage in vivo. Additionally, these models predict only two tissue states (damaged or undamaged), failing to capture three tissue states observed on post-CE-T1WI images, highlighting the need for improved thermal damage prediction methods. This study proposes a novel Convolutional Long Short-Term Memory (ConvLSTM)-based model that utilizes intraoperative temperature distribution history data measured by magnetic resonance temperature imaging (MRTI) during LITT to predict the enhancing rim on post-CE-T1WI images. This method was implemented and evaluated on retrospective data from 56 patients underwent brain LITT.
Main results:
The proposed model effectively predicts the enhancing rim on postoperative images, achieving an average Dice Similarity Coefficient (DSC) of 0.82 (±0.063) on the test dataset. Furthermore, it generates real-time predicted thermal damage area variation trends that closely resemble those of the traditional thermal damage model, suggesting potential for real-time prediction of thermal damage extent. This method could provide a valuable tool for visualizing and assessing intraoperative thermal damage extent.&#xD.

Three-dimensional inversion algorithm of magnetotelluric data based on solution space dimensionality reduction technique

The magnetotelluric (MT) method is highly advantageous in geothermal resource exploration because of its deep probing capability, low cost, and sensitivity to key geothermal system elements such as heat sources, reservoirs, and caprocks. To address the challenge of balancing the MT inversion resolution and computational efficiency, we propose a Gauss–Newton optimization inversion algorithm based on the solution space dimensionality reduction technique. This algorithm uses solution space dimensionality reduction to establish algebraic mapping relationships between the edges of grid cells, effectively reducing the degrees of freedom in the linear equation system required for forward and pseudo-forward modeling, thereby saving computational costs. In addition, during the inversion process, a multiple right-hand direct–iterative hybrid solver is employed to solve the dimensionally reduced linear equation s, further enhancing the computational efficiency of the inversion. We then validate and analyze the accuracy and efficiency of the forward and inversion algorithms using various synthetic models. Finally, we apply this inversion strategy to field MT data from the Dabie Mountain geothermal area in eastern China. On the basis of the inversion results, we then analyze the thermal genesis model of the region, providing technical support for the exploration and development of deep geothermal resources.

Analysis of magnetic field formulation for transferred arc thermal plasma modelling

Abstract Thermal plasma modelling of arc plasma systems offers an efficient way to understand the arc dynamics inside the torch and the plume characteristics. Extensive usage of these plasma models necessitates the efforts to improve its fidelity to simulate the actual arc environment. Since the arc dynamics is highly influenced by the self-induced magnetic field, the choice of magnetic field formulations incorporated in the plasma model plays a crucial role. Existing magnetic field formulations based on Ampere’s law, referred as potential vector formulation (PVF), and Biot-Savart law lack accuracy and computational efficiency, respectively. Integration of Biot-Savart law with PVF, referred as mixed formulation (MF), improves the accuracy but still lack computational efficiency. Extended domain based magnetic field formulation (EDF) has the tendency to offer both accuracy and computational efficiency but rarely incorporated in arc plasma system simulations. The present work studies the influence of different magnetic formulations on the self-induced magnetic field prediction in a 2.6 kW transferred arc plasma system. It is inferred that EDF predicts the magnetic field close to that of MF in most of the regions when compared to PVF. Analysing the effect of predicted magnetic field by different formulations on plasma characteristics revealed minimal influence in the considered transferred arc plasma system due to the static arc behaviour. The incorporation of EDF is expected to have significant importance on the scenario with transient arc behaviour.

Towards model-driven heat pump control in a multi-story building

Domestic heating systems exhibit significant energy flexibility when integrated with heat pumps and hot-water buffer tanks, especially with fluctuating day-ahead energy prices. However, optimizing these systems in large buildings with shared resources poses crucial challenges. While most existing methods target single-room or single-family houses, this study delves into complexities within a three-story building housing six apartments. The building's heating system comprises a hot water buffer tank, mixing loop, floor heaters, and a Ground Source Heat Pump (GSHP) controlled by a weather-compensated control strategy (WCS). Our approach aims to tackle challenges like integrating real sensor data, scalability, varying weather effects, and diverse resident heat use preferences. We employ CTSMR software to identify thermal behaviour and use reinforcement learning to design an intelligent Uppaal Stratego controller. Our results reveal a 43% reduction in energy costs while maintaining comfort levels compared to WCS. The temporal validity of estimated thermal models is also analyzed.

An Analytical Model for the Steady-State Thermal Analysis of Façade-Integrated PV Modules Cooled by a Solar Chimney

This paper proposes a steady-state thermal model for the passive cooling of photovoltaic (PV) modules integrated into a vertical building façade by means of a solar chimney, including an empirical correlation for turbulent free convection from a vertical isothermal plate. The proposed analytical model estimates the air velocities at the inlet and at the outlet of the ventilation channel of such a cooling system and the average temperature of the façade-integrated PV modules. A configuration composed of a maximum of six vertically installed PV modules and one solar chimney is considered. The air velocities at the inlet and at the outlet of the ventilation channel obtained for the case of installing PV modules on the building façade are compared with those calculated for the case where the PV modules are integrated into the roof with a slope of 37°. By comparing each of the solutions with one PV module to the corresponding one with six PV modules, it was found that the increase in the air velocity due to the effects of the solar irradiance and the height difference between the two openings of the ventilation channel ranges between 41.05% in the case of “Roof” and 141.14% in the case of “Façade”. In addition, it was obtained that an increase in the solar chimney height of 1 m leads to a decrease in the average PV section temperature by 1.95–7.21% and 0.65–2.92% in the cases of “Roof” and “Façade”, respectively. Finally, the obtained results confirmed that the use of solar chimneys for passive cooling of façade-integrated PV modules is technically justified.

Navajo Sandstone concretions record extended magnetic chronology.

This study investigates iron oxide concretions from the Jurassic Navajo Sandstone in Utah as potential recorders of long-term magnetic field variations. Using a combination of alternating field and thermal demagnetization, physical abrasion, chemical analysis, and magnetic modeling, we reveal multiple magnetic components with contrasting directions within individual concretions. Finite Element Magnetic Modelling demonstrates the sensitivity of magnetic signatures to small changes in layer thickness. X-Ray Fluorescence spectrometry confirms high iron concentrations in concretion crusts. Our results support a two-stage formation model involving initial iron hydroxide precipitation followed by progressive transformation to hematite. This extended formation process suggests these concretions may record paleomagnetic field changes, though their reliability as magnetic recorders need to be verified in more details. The identification of both goethite and hematite phases, coupled with their distinct magnetic behaviors, has implications for understanding similar concretionary structures observed on Mars. However, environmental differences between terrestrial and Martian settings require careful consideration when making such comparisons.

Part-scale numerical simulation for laser-powder directed energy deposition: experimental calibration

Abstract To increase the environmental sustainability of products, the repair and refurbishment of damaged or obsolete components can be carried out using additive manufacturing (AM) processes. The Laser-powder directed energy deposition (LP-DED) process is an interesting candidate due to its many potential applications, particularly for the repair of metal parts. For a more thorough knowledge and understanding of the process, numerical approaches are necessary to avoid extensive and costly experimental campaigns. In this work, an original 3D thermal FEM model is proposed to predict the temperature during the LP-DED process at the macroscopic scale. The numerical simulation was based on the layer-by-layer method using an equivalent volumetric heat source and then using the superlayer method. The predicted temperature is compared with experimental temperature measurements during the deposition of stainless steel (316L) single-bead walls and multi-layer squares. The experimental results showed the influence of process parameters and deposition strategy on the temperature, which reached a maximum around 220 °C. The numerical simulation showed an overestimation of the temperature of about 120 to 200 °C compared to the experiments for all the tests carried out. A correction factor was applied to the numerical heat source which allowed to reduce the discrepancies to 50 °C. Finally, the superlayer approach led to a reduction of computational time at the expense of accuracy. Current limitations highlighted the importance of the definition of the equivalent heat source definition and boundary conditions. The chosen approach (layer-by-layer vs. superlayer) depends on the applications and the studied geometry.

Investigation on the quench characteristics of parallel high temperature superconducting tapes

Abstract The thermal load on high-temperature superconducting (HTS) tapes during quenching poses a threat to the stable operation of superconducting magnets. To protect superconducting coils and cables, this paper investigates the quench characteristics of HTS tapes as a basis. First, coupled with a reduced-dimensional thermal model and current redistribution model, a finite element method (FEM) model based on the 3D T-A formulation for a single HTS tape was built. Taking into account the terminal resistances and circuit inductances, the quench characteristics of parallel HTS tapes can be further analyzed by the field-circuit model. Then, a platform for detecting local quenches was constructed to verify the simulation results, and the experimental procedure was explained in detail, along with the test samples. Finally, we present the quench characteristics of single HTS tape, parallel HTS tapes, and stacked HTS tapes, which were found to be consistent with the simulation results. The parallel structure significantly reduces the risk of local quench compared to a single HTS tape. Due to contact resistances, the quench time of parallel tapes is longer than stacked tapes.

Absorption measurements of optical coatings at 1.1 µm and 1.5 µm with Lock-In Thermography and associated thermal model

Absorption measurements of optical coatings at 1.1 µm and 1.5 µm with Lock-In Thermography and associated thermal model

Thermal and Micro-segregation Model Applied to Fusion-Based Additive Manufacturing of Ni-Based Superalloy Haynes 282

Thermal and Micro-segregation Model Applied to Fusion-Based Additive Manufacturing of Ni-Based Superalloy Haynes 282

Laser-induced thermal size effects in micro-Raman thermal conductivity measurements

Thermal conductivity measurements of submicrometer structures are at the core of the efficient power design of semiconductor devices. Micro-Raman spectroscopy measures thermal conductivity in a fast, nondestructive, and non-contact manner. However, the focused laser heating in micro-Raman experiments may cause drastic thermal size effects. To date, the role of such effects in the accuracy and limitations of the measurement has not been addressed. Here, we present an advanced thermal model to capture the role of material properties, laser power, and film thickness in the thermal size effects, based on the three-dimensional (3D) gray phonon Boltzmann transport equation. Recalling that laser-induced thermal size effects can lead to unexpectedly high local temperatures, even damaging the measured materials, our advanced 3D model gains particular importance for the accurate measurements of directional thermal conductivities in submicrometer structures using future high-resolution optical pump–probe techniques.

A new thermal conductivity model of dry natural sands considering particle morphology

A new thermal conductivity model of dry natural sands considering particle morphology

Design and evaluation of a dilute flow particle-to-air heat exchanger for energy storage applications

Design and evaluation of a dilute flow particle-to-air heat exchanger for energy storage applications

Application of artificial intelligence brain structure-based paradigm to predict the slip condition impact on magnetized thermal Casson viscoplastic fluid model under combined temperature dependent viscosity and thermal conductivity

Application of artificial intelligence brain structure-based paradigm to predict the slip condition impact on magnetized thermal Casson viscoplastic fluid model under combined temperature dependent viscosity and thermal conductivity

Thermo‐Tectonic History of the Qilian Shan and Adjacent Areas: New Insights From Apatite U‐Pb and Fission Track Thermochronology

AbstractThe Qilian Shan is situated along the northeastern margin of the Tibetan Plateau, and has undergone multiple episodes of tectonic deformation since the Paleozoic. Strikingly, tectonic deformation in the Qilian Shan and adjacent areas encompasses newly formed and inherited lithospheric and crustal structures. This study presents the Mesozoic‐Cenozoic post‐orogenic thermo‐tectonic histories of these active tectonic units utilizing an integrated approach combining apatite U‐Pb and fission track thermochronometers. The apatite U‐Pb dates are dominantly Paleozoic, mainly recording post‐magmatic cooling of the sampled granitoid rocks. The apatite fission track data record Late Triassic to Cretaceous cooling ages (central ages between ∼223 and ∼88 Ma), and most of the measured mean track lengths are between ∼13 and ∼12 μm. The apatite fission track results and thermal history models revealed that the Qilian Shan, Longshou Shan and Beida Shan experienced various moderate to rapid basement cooling episodes during the Late Triassic to Early Cretaceous, which we interpret as a far‐field response to a series of distant tectonic events including the Paleo‐Asian Ocean's closure, Qiangtang collision, Tethys‐deformation and Lhasa collision. During this period, these fault‐bounded tectonic units displayed different exhumation patterns, with the North Qilian Shan exhibiting a late Early Cretaceous rapid denudation while others preserved uplifted apatite partial annealing zones.

Current and future thermal effects and spatial optimization modelling of urban greenspace in megacity

Current and future thermal effects and spatial optimization modelling of urban greenspace in megacity

Comparative analysis of axial effective thermal conductivity models and their impact on ammonia synthesis process

Comparative analysis of axial effective thermal conductivity models and their impact on ammonia synthesis process

A Review on High-speed Electric Spindle Dynamics Modeling and Vibration Response Research

Background: One of the main directions of modern technology in the field of precision machining is high-speed operation. The spindle system is commonly utilized in this kind of operation, and the electric spindle is the main preference among high-speed machine tool spindles. Objective: High-speed electric spindle vibration characteristics affect the machining accuracy of the machine tool and the quality of the workpiece, so the research on high-speed electric spindle vibration characteristics has important engineering practical significance. Methods: The research status of high-speed electrospindle at home and abroad has been summarized in this paper. Combined with the patents related to the dynamics modelling of electrospindle, the research on the dynamics modelling of high-speed electrospindle is analyzed. On this basis, the computational and analytical methods for the vibration modelling of the electrospindle, including the transfer matrix method and the finite element method, are investigated, the theoretical foundations of these methods are discussed in depth, and the advantages and disadvantages of the methods are evaluated. The applicability and limitations of the two methods are also compared. Results: The analysis has shown that the current research on the vibration characteristics of highspeed electrospindle is mainly based on mechanical modal analysis and electromagnetic analysis. At present, the dynamic modeling of the electrospindle mainly includes bearing modeling, shaft bearing modeling, spindle-case modeling, electrospindle electromechanical coupling modeling, electrospindle thermal coupling modeling, etc. The correctness of the modelling theory is verified through experimental and simulation results. Although these models tend to be perfected, they are still insufficient in the case of multiple influencing factors coupling and need further development. Conclusion: Finally, through the analysis of the patent and dynamic characteristics related to the high-speed electric spindle, thermal deformation, magnetic tension, material, and other factors should be considered comprehensively, and these factors should be coupled to establish an overall dynamics model for the vibration characteristics analysis. The dynamic modelling, vibration modelling method, and vibration characteristics of the high-speed electric spindle have been summarized in this study, and the outlook is presented.

Revealing the contribution of flame spread to vertical thermal runaway propagation for energy storage systems

Revealing the contribution of flame spread to vertical thermal runaway propagation for energy storage systems

Impact analysis of uncertainty in thermal resistor-capacitor models on model predictive control performance

Impact analysis of uncertainty in thermal resistor-capacitor models on model predictive control performance