Thermal Constraints Research Articles

Ice Shell Structure of Ganymede and Callisto Based on Impact Crater Morphology

AbstractUnderstanding the thermal structure of the ice shells around Ganymede and Callisto remains a critical step in unraveling the geologic histories of the moons. The depth‐diameter (d‐D) trends of pristine craters on each surface have an inflection point in crater morphology at approximately 26 km diameter, at which point observed crater depths transition from craters deepening with increasing crater diameter to craters shallowing with increasing crater diameter. In this work, we use iSALE‐2D to simulate impact crater formation in ice shells. We test conductive thermal gradients between 5 and 15 K/km and convective ice temperatures between 240 and 260 K in a modeled ice shell to determine if these observed d‐D trends correlate to specific thermal parameters. We find that the conductive thermal gradient has a more pronounced effect than the temperature of the underlying convective ice on reproducing the d‐D trends of craters up to 100 km in diameter, and that the inflection point in the observed crater depth trend on both Ganymede and Callisto is replicated in ice shells with a conductive thermal gradient of ∼10 K/km. With this conductive thermal gradient, the conductive ice was approximately 12–14 km thick on each body at the time they accrued these unmodified craters. The similar thermal constraints for both moons suggest that there are other differences between Ganymede and Callisto responsible for their divergent evolutionary paths, such as an increased proportion of strong impurities in Callisto's ice shell.

Exact solutions for buckling loads of nanobeams under thermal effect based on local/nonlocal mixture integral models with bi-Helmholtz kernel

In this work, we present predictive models of the buckling loads of Bernoulli-Euler nanobeams under a uniformly thermal environment based on strain-/stress-driven local/nonlocal mixture theories. The constitutive equation is expressed in local/nonlocal mixture integral form with the bi-Helmholtz kernel. The temperature effect is equivalent to a thermal load induced by the thermal expansion and boundary constraint, while the local/nonlocal mixture effects on the thermal load are taken into account. Using Laplace transform methods, the integral governing equations derived using different local/nonlocal mixture models are solved directly and exact solutions for critical buckling loads are obtained. We provide a series of numerical examples in which we present predictions of the size-effects on beams with various boundary edges. Moreover, the influence of considering the size-dependent thermal loads is also examined.

The post-Caledonian thermo-tectonic evolution of Fennoscandia

The evolution of Fennoscandia following the early Devonian collapse of the Caledonian mountains is a matter of debate, due largely to the scarcity of post-Caledonian cover rocks. The preserved geological record therefore provides only partial documentation of the geological evolution. A more complete understanding is obtained by also considering evidence of rocks that were formerly present but have since been removed. We report apatite fission track data and associated thermal history constraints in 331 samples of Precambrian basement, younger sedimentary cover, Paleozoic and Mesozoic igneous rocks from outcrops and boreholes (up to 6 km depth) across Fennoscandia, which define thirteen phases of cooling (each representing kilometre-scale exhumation) over the last 1100 Myr. Key post-Caledonian episodes began in the intervals 311–307 Ma (late Carboniferous), 245–244 Ma (Middle Triassic), 170–167 Ma (Middle Jurassic), 102–92 Ma (mid-Cretaceous) and 23–21 Ma (early Miocene). These episodes, varying in magnitude, are recognised across Fennoscandia, and their effects are documented in the stratigraphic record and as prominent regional peneplains. The results define a history involving repeated episodes of regional burial and exhumation. Major offsets in Mesozoic paleotemperatures over short distances define kilometre-scale differential vertical displacements, emphasising the tectonic nature of the history. Results from Finland record the same events recognised in Norway and Sweden (though less pronounced), and are not consistent with long-term cratonic stability. The lack of preserved Phanerozoic sedimentary cover in Finland is interpreted to be due to complete removal during multiple episodes of denudation. In southern Norway and Sweden, early Miocene exhumation led to creation of a peneplain, which in Pliocene times was uplifted and dissected, producing the modern landscape. Post-Caledonian exhumation episodes defined here are broadly synchronous with similar events in Greenland, the British Isles and North America. Far-field transmission of plate-tectonic stress and/or mantle processes may explain the vertical movements described here.

Thermal Aeroelastic Tailoring for Laminated Panel with Lamination Parameters and JAYA Algorithm

This work investigates thermal aeroelastic tailoring of a laminated composite panel with a lamination parameter-based method. Equivalent membrane and bending coefficients of thermal expansions for symmetric laminated panel are derived and represented with lamination parameters using Classical Laminated Plate Theory. The relationship between thermal flutter behavior and lamination parameters is examined. The optimization process is split into two stages. In the first stage, lamination parameters and laminate thicknesses are as design variables to minimize the structure mass, subject to thermal flutter behavior and feasible region constraints of lamination parameters. In the second-stage, instead of using conventional genetic algorithm, the enhanced JAYA method is extended to search the laminate configuration to target the optimal lamination parameters. The effectiveness of the presented method is demonstrated through a thermal aeroelastic tailoring problem.

Conductive SnO2-x thin films deposited by thermal ALD with H2O reactant

In this study, SnO2-x films were deposited by a thermal atomic layer deposition (ALD) method with H2O as a reactant. The electrical property of the films was assessed with the intention of applying them as a channel for a back-end-of-line (BEOL) compatible transistor. Under the thermal budget constraint (<450 °C) required for a BEOL transistor, the effect of ALD process parameters and post-annealing conditions on the carrier concentration and mobility of the films was investigated. While the as-deposited films were amorphous, more distinctive recrystallization could be observed with the deposition temperature of 200 °C combined with the annealing ambient of N2. As a result, the mobility of 21.55 cm2/Vs and 3.3 × 1019 cm−3 carrier concentration were achieved with an 18-nm thick n-type SnO2-x film. However, it was also observed the mobility of the N2-annealed SnO2-x decreased by ∼50% of an initial value upon exposure to humidity for 2–3 days. 5-Nm Al2O3 on SnO2-x as a capping layer could prevent the degradation, suggesting the presence of a more conductive path near the surface. This work demonstrates SnO2-x deposited by a thermal ALD can exhibit an excellent electrical property suitable for various electronic devices such as a BEOL compatible transistor.

The role of block-type support structure design on the thermal field and deformation in components fabricated by Laser Powder Bed Fusion

Successful production of overhang features, with no underlying deposited layers or substrate, in a Laser Powder Bed Fusion (LPBF) process requires sacrificial structures, known as support structures. However, these structures add extra time and cost to the manufacturing process of a component. Optimisation of support structure design should reduce materials waste (which affects the time and cost of the build process) while minimising bleed-throughs and residual deformation. Optimisation of support structure design requires an understanding of their impact on the thermal field and mechanical constraints. In this research, a combination of experiments and numerical modelling was used to quantify the contribution of various support structure design elements on component deformation. The results indicate that the total contact area of teeth and the total support base area alter thermal fields within the produced components. Increasing the area for heat conduction to the start plate was found to reduce the peak temperature in the cantilevered plate. Additionally, increasing the contact area between teeth and the cantilevered plate reduces the peak temperature and the vertical temperature gradient in the overhang platform, both of which are consistent with reducing in-situ plastic strain accumulation and residual part deformation.

Design of robust and low‐loss 3‐D printed double‐ridged waveguide to microstrip transition

In this paper, we present a new microstrip to waveguide transition design for interfacing printed circuit board (PCB) microstrip transmission lines with 3-D printed metallised-plastic waveguide components. Compared with traditional metal waveguides, interfacing with plastic-based waveguides are challenging due to thermal and mechanical constraints. Despite the development of 3-D printing technology, the precision of 3-D printed waveguides is not as good as the machined metal counterparts. This is critical for microwave components and must be considered in the design process. To minimise the effect of non-ideal waveguide components, a design methodology minimising sensitivity to geometrical variations in the 3-D printed parts is proposed. By sandwiching the PCB between two waveguide sections and optimising the waveguide impedance transformation geometry, the design shows very low insertion loss. It is mechanically robust, cost effective and simple to manufacture. In full system integration, this transition design eliminates the need for expensive microwave cabling and connectors by directly mounting the waveguide to the microwave transceiver PCB. The proof-of-concept transition structure presented in this paper is suitable for microwave applications where low cost and low weight are critical, for example, drone-based radars for remote sensing and space-born satellites. The fabricated structure is characterised using two sets of waveguide components manufactured with different 3-D printing technology and metallisation process': conductive spray painted Fused Deposition Modelling—Polylactic Acid (PLA Painted) and copper electroplated Stereolithography (SLA Plated). Scattering parameters for both types are measured in a short and back-to-back configuration, obtaining the reflection coefficient and insertion loss. Measurements indicate good agreement with modelling and measured performance exceeding prior art. The measured operation band of the Copper-SLA version is 2.9–7.2 GHz with <−10 dB reflection coefficient (S11) and with an insertion loss (S21) of <0.7 dB. With the reduced metallisation and surface quality of the Spray-PLA model, the band is shifted to 3.0–8.0 GHz with an increased S21 of <1.8 dB. The results demonstrate the importance of adopting new transition structures for 3-D printed microwave components where the surface roughness, metallisation quality, and mechanical properties are less optimal. By combining the proposed design with 3-D printed metallised microwave components, very light weight and cost-effective antenna systems can be implemented. Radiation measurements of a 3-D printed double ridge horn antenna connected to the waveguide and used as a feed are also presented, where the operation band is measured to 3–10 GHz with a gain of 5–10 dBi.

Solar Energy Compensation for Building Energy Saving with Thermal Comfort in a Cold Climate

This paper proposes an energy-saving strategy with assistance from solar thermal compensation for building energy systems. The target of the control strategy was to minimize energy consumption under thermal comfort constraints in buildings. First, the factors influential to indoor temperature in building environments were analyzed. Secondly, the internal and external factors, such as building materials; building orientation; window size; heating, ventilation, and air conditioning (HVAC) facilities; blinding device; solar irradiation; wind speed; and outdoor temperature were used to construct a building model on the platform ENERGYPLUS (E+). A controller aiming to regulate the amount of solar irradiation was developed with the Building Controls Virtual Test Bed (BCVTB) tool. Afterward, the building performance under different strategies was tested by co-simulation using both the computational platforms, E+ and BCVTB. The optimum scheme achieved 30.6% energy savings while meeting the same comfort criterion of its competition strategy. The study verified that the proposed strategy of combined heating, ventilation, and air conditioning and blind control could realize the energy savings and comfort satisfaction at the same time. The proposed method provides a reference to the development of low-/zero-energy building concepts in the field.

Adaptive Model Predictive Control Including Battery Thermal Limitations for Fuel Consumption Reduction in P2 Hybrid Electric Vehicles

The primary objective of a hybrid electric vehicle (HEV) is to optimize the energy consumption of the automotive powertrain. This optimization has to be applied while respecting the operating conditions of the battery. Otherwise, there is a risk of compromising the battery life and thermal runaway that may result from excessive power transfer across the battery. Such considerations are critical if factoring in the low battery capacity and the passive battery cooling technology that is commonly associated with HEVs. The literature has proposed many solutions to HEV energy optimization. However, only a few of the solutions have addressed this optimization in the presence of thermal constraints. In this paper, a strategy for energy optimization in the presence of thermal constraints is developed for P2 HEVs based on battery sizing and the application of model predictive control (MPC) strategy. To analyse this approach, an electro-thermal battery pack model is integrated with an off-axis P2 HEV powertrain. The battery pack is properly sized to prevent thermal runaway while improving the energy consumption. The power splitting, thermal enhancement and energy optimization of the complex and nonlinear system are handled in this work with an adaptive MPC operated within a moving finite prediction horizon. The simulation results of the HEV SUV demonstrate that, by applying thermal constraints, energy consumption for a 0.9 kWh battery capacity can be reduced by 11.3% relative to the conventional vehicle. This corresponds to about a 1.5% energy increase when there is no thermal constraint. However, by increasing the battery capacity to 1.5 kWh (14s10p), it is possible to reduce the energy consumption by 15.7%. Additional benefits associated with the predictive capability of MPC are reported in terms of energy minimization and thermal improvement.

ОПТИМІЗАЦІЙНИЙ ПІДХІД ДО ВИЗНАЧЕННЯ КОНСТРУКТИВНИХ ПАРАМЕТРІВ ЛІНІЙНОГО МАГНІТОЕЛЕКТРИЧНОГО ДВИГУНА ВІБРАЦІЙНОЇ ДІЇ

The constructional parameters of the linear permanent magnet vibratory motor in accordance with the set optimization criteria (minimum cost, force to volume ratio and efficiency) and mechanical load parameters are substantiated in the work. To do this, a computer model was developed, which is based on magnetic and electrical equivalent circuits with lumped parameters. The magnetic circuit of the model is built taking into account the saturation of the magnetic material, magnetic losses and leakage fluxes. The electromagnetic force amplitude of the motor is determined on the basis of the fundamental component of the Fourier series expansion of the air-gap flux density. The mechanical part of the model is constructed using the electromechanical analogy method, according to which, induced armature EMF is represented by a voltage drop on the equivalent mechanical resistance. The problem of choosing the constructional parameters for the given mechanical load characteristics is considered in conjunction with the nonlinear connections of the system and subject to thermal, magnetic and electrical constraints. Using the gradient descent method, the motor parameters were optimized and the most effective designs that meet the selected criteria were determined. References 8, figures 5, tables 2.

Control of grid side converters under constraints in unbalanced operating conditions. A Lyapunov framework

This work presents a Lyapunov-based control of a grid side converter of distributed energy systems. The analysis focuses on the constraints imposed by unbalanced operation and thermal limits. On one side, the proposal, which considers symmetrical components, allows controlling the converter in such a way that it is able to deliver constant real power to the grid in the presence of highly unbalanced voltages. On the other side, to solve the operation under thermal constraints, the references in control loops are adapted. Both issues, unbalanced operation but also thermal constraints, are considered in a sole Lyapunov function, formed by the union of a set of Lyapunov ones. This ensures the stability of the whole system by using simple PI controllers. Finally, different scenarios, strong disturbances and reaching current limits are explored in simulation results.

Topology optimization of thermo‐elastic structures considering stiffness, strength, and temperature constraints over a wide range of temperatures

AbstractThis article proposes a thermo‐elastic topology optimization with stiffness, strength, and temperature constraints involving a wide range of temperatures. The state equations for the linear elasticity and heat conduction are considered. Formulations involving minimum volume with compliance, stress and temperature limits under multiple thermal conditions are presented. The global stress and regional temperature metrics adopting the corrected aggregation function are used to evaluate the maximal stress and temperature, respectively. The stress stabilizing scheme is utilized to overcome the iteration oscillation stemming from highly nonlinear behavior of thermal stress constraints for multiple thermal conditions. To achieve clear optimized topologies under design‐dependent loads, a continuation strategy for the relaxed Heaviside function is developed. Two 2D numerical examples are employed to illustrate the validity and practicability of the proposed approach. The results show that the optimized structures designed by a certain temperature may be damaged or have thermal deformations once the ambient temperature changes due to the thermal residual stress. The designs covering wide temperature range achieved by neglecting stiffness or strength constraints can result in stiffness reduction or strength failure. It is therefore imperative for the optimization to adopt a multi‐physics model involving multi‐constraints over a wide temperature range.

Role of reliability assessment in Si-based non-Isolated DC-DC power electronic converters

Electrical energy is one of the majorly adaptable sources of energy available today due to the advancement of power electronics in recent decades. Nonetheless, designing proper power electronic converters is not an easy task: it normally encompasses minimization of several competing factors, such as power losses and mass, while adhering to a variety of technical and thermal constraints. Power electronic systems are becoming essential in power quality enhancement, grid integration; variable drives systems, energy storage systems, and electrical vehicles (EVs). Power electronic technologies provide lightweight and high-efficiency power transfer solutions. DC-DC converters are those devices that convert voltage from one level to another level as per the application or requirement. Reliability is known as the tendency that a system or subsystem facilitates the essential function for the specified duration of the period under given operational and environmental conditions. In this paper, the role of reliability assessment has been addressed in the context of complementary metal–oxidesemiconductor (CMOS) technology-oriented silicon (Si)-based non-isolated DC-DC converters. Here, Impacts of parasitic elements on reduced reliability have been analyzed using MATLAB® Simulink. Further various reliability prediction matrices, failure modes, and other factors have been presented that clearly show that reliability assessment is a necessary condition for reliable design and operation management of Non-isolated DC-DC converters.

Multi-Stage Real-Time Operation of a Multi-Energy Microgrid With Electrical and Thermal Energy Storage Assets: A Data-Driven MPC-ADP Approach

This paper studies the multi-stage real-time stochastic operation of grid-tied multi-energy microgrids (MEMGs) via the hybrid model predictive control (MPC) and approximate dynamic programming (ADP) approach. In the MEMG, practical power and thermal network constraints, heterogeneous energy storage devices, and distributed generations are involved. Given the relatively large thermal inertia and slow thermal energy fluctuation, only uncertainties of renewable energy sources and active/reactive power loads are considered. Then, historical data are adopted as training scenarios for the MPC-ADP method to acquire empirical knowledge for dealing with all the diverse uncertainties. Further, piecewise linear functions are used to approximate value functions with respect to the operation status of energy storage assets, which enables sequentially solving the Bellman’s equation forward through time to minimize MEMG operation cost. Finally, numerical case studies are conducted to illustrate the effectiveness and superiority of the proposed MPC-ADP approach. Simulation results indicate that with sufficient information embedded, the MPC-ADP approach could obtain good-enough real-time operation solutions with the successively updated forecast. Further, it outperforms alternative real-time operation benchmarks in terms of optimality and convergence for various application scenarios.

Active-matrix micro-light-emitting diode displays driven by monolithically integrated dual-gate oxide thin-film transistors

We present the first monolithic fabrication of a-IGZO TFTs on a GaN-based micro-LED array at a low temperature to overcome the weak thermal endurance constraint of the organic planarization layer for high resolution and stable low-cost LED displays.

Temperatures of canonical condensation: Constraints from CAIs

The analogy between Al_8/3O₄ – MgAl₂O₄ spinels and AgSbS₂ − PbS galenas is explored. Although the spinel observed in calcium-aluminum-rich inclusions in carbonaceous chondrites (CAIs) is nearly pure MgAl₂O₄ and the galena found in hydrothermal ore deposits is nearly pure PbS, in both occurrences a very strong case may sometimes be made that these phases originally crystallized as solid solutions with substantially higher abundance of these minor components, Al_8/3O₄ in CAI spinel and AgSbS₂ in hydrothermal galena. It is shown that a few retrograde net-transport reactions accompanying Al_8/3O₄ breakdown in Al_8/3O₄ − MgAl₂O₄ spinels can account for several important features of spinel-rich CAIs including reverse zoning of åkermanite−gehlenite melilites, the production of Al-rich diopside and the depletion of anorthite in reaction rims, and the scarcity of grossite despite its previous presence as a high temperature condensate. AgSbS₂ in galena is analogous, because galenas in ore deposits today have an undetectable amount of AgSbS₂ (for example, Knowles,1983), yet, for example, the galena-rich ore deposits from the Coeur d9Alene mining district (ID) were responsible for the largest recorded number of ounces of Ag produced in the world until recently. Accordingly, it is appropriate that the primary Al_8/3O₄ contents of spinels in CAIs are reconstructed following methods analogous to those employed by Sack and others (2002,2005) to reconstruct the primary AgSbS₂ contents of galenas from the Coeur d9Alene ores, if CAIs spinels are to be used to constrain temperatures, and hence pressures, of canonical condensation. Several examples are given to demonstrate the thermal constraints which may be obtained from reconstructed primary spinel Al_8/3O₄ concentrations starting with the Al_8/3O₄ -rich CAI spinels reported by Yurimoto and others (2021) and El Goresy and others (1984). The compositions of spinels which form rims around corundum and corundum-hibonite aggregates in CAIs from the Murchison and Murray chondrites (Makide and others,2013) are then used to prove that Al_8/3O₄ in Al_8/3O₄ − MgAl₂O₄ spinels from CAIs are completely analogous to AgSbS₂ in AgSbS₂ − PbS galenas from hydrothermal ore deposits.

Hybrid Physics-based and Data-driven Model Predictive Control for Multi-Zone Building's Thermal Comfort Under Disjunctive Uncertainty

This paper develops a hybrid approach that utilizes the distributional information of the disjunctive uncertainty sets and incorporates them into the model predictive control (MPC). This approach aims at the multi-zone building control to the thermal comfort, and it's robust to the uncertain weather forecast errors. The control objective is to maintain each zone's temperature and relative humidity within the specified ranges using the minimum cost of energy of the underlying heating system. The hybrid model is constructed using a physics-based and regression method for the temperature and relative humidity of each zone in the building. The uncertainty space is based on historical weather forecast error data, which are captured by a group of disjunctive uncertainty sets using k-means clustering algorithm. Machine learning approaches based on principal component analysis and kernel density estimation are used to construct each basic uncertainty set and reduce the conservatism of resulting robust control action under disturbances. A robust MPC framework is developed based on the proposed hybrid model and data-driven disjunctive uncertainty set. An affine disturbance feedback rule is employed to obtain a tractable approximation of the robust MPC problem. A case study of controlling temperature and relative humidity of a multi-zone building in Ithaca, New York, USA, is presented. The results demonstrate that the proposed hybrid approach can reduce 9.8% to 17.9% of total energy consumption compared to conventional robust MPC approaches. Moreover, the proposed hybrid approach can essentially satisfy the thermal constraints that certainty equivalent MPC and robust MPC largely violate.

Distinct temperature stressors acting on multiple ontogenetic stages influence the biogeography of Atlantic blue crabs

To understand and predict shifts in species distribution in a changing climate, it is important to consider the exposure and sensitivity of multiple life history stages, particularly for marine species with complex life cycles. In this study, we examined spatio-temporal trends in the abundance of the blue crab Callinectes sapidus and how different temperature stressors acting on multiple ontogenetic stages may affect the species’ current and future distribution across the Atlantic coast of the USA. Since 1975, crab abundance has remained constant or increased in the northeast and northern mid-Atlantic regions but declined in the southern mid-Atlantic and southeast. In the northeast, abundance changes and the location of the northern range boundary appear to be dictated primarily by lower thermal constraints on summer larval stages and may be reinforced by chronic winter cold stress on juveniles and adults. In the mid-Atlantic, acute winter cold stress on juveniles and adults may regulate crab abundance, whereas in the southeast, temperature stress is likely not limiting or directly driving abundance declines. Temperature projections suggest a potential for northward range expansion and increased abundance in the northeast. In the northern mid-Atlantic, however, changes in the duration, magnitude, and phenology of summer temperatures may have complex effects on crab reproduction. Our results highlight how past and future changes in environmental suitability can vary non-uniformly both within and beyond a species’ current range, and the value of examining multiple life history stages and aspects of temperature stress.

Room-temperature deposition of ZnS antireflection coatings for MIR-LWIR applications

Integration of unconventional materials on established CMOS platforms requires to fulfill tight thermal budget constraints. However, low temperature processing may result in poor mechanical properties of the deposited films, which can exhibit stress-induced degradation of the optical properties or even delamination. This work focuses on a CMOS-compatible low-temperature deposition process for ZnS films on silicon and its use for the realization of an antireflection coating (ARC) operating in the medium infrared (MIR)–longwave infrared (LWIR) range. A thin interlayer of Al2O3 is employed to achieve good adhesion of a ZnS film deposited on Si by e-beam evaporation at room temperature. Numerical simulations are carried out to optimize the performance of single- and double-side ARC structures, quantifying the impact of the Al2O3 interlayer and of the fabrication tolerances on the optical transmission. Experimental results on an 8” silicon wafer demonstrate a peak transmittance of 66% for single-side ARC and 89% for a double-side ARC at a wavelength of 10 µm, resulting in an average transmission of 76.2% for black body radiation at 36 °C in the 6–20 μm wavelength range.

A Design Technique of Traction Motor for Efficiency Improvement Based on Multiobjective Optimization

With the increasing demand of driving range of new energy vehicle (NEV), design optimization for energy efficiency of traction motors became more important. However, traction motor design is complex since multiple objectives should be satisfied, such as the required torque-speed operating range and package and thermal constraints. This dramatically increases the computation time of the design optimization process, while the additional energy efficiency objective of the whole driving cycle. This paper proposes an equivalent driving cycle points extraction method, based on energy consumption equivalence to facilitate the design optimization of traction motors. This paper presents necessary rules of multiobjective optimization methods, and then gives an optimization process and proves the effectiveness.