Central Temperature Research Articles

Solar prominence diagnostics and their associated estimated errors from 1D NLTE Mg II h&k modelling

Aims. We present further development of the rolling root mean square (rRMS) algorithm. These improvements consist of an increase in computational speed and an estimation of the uncertainty on the recovered diagnostics. This improved algorithm is named the cross root mean square (xRMS) algorithm. Methods. We used the quantile method to recover the statistics of the line profiles in order to study the evolution of the prominence observed by IRIS on 1 October 2019. We then introduced the improvements to rRMS. These improvements greatly increased the computational speed, and this increase in speed allowed us to use a large model grid. Thus, we utilised a grid of 23 940 models to recover the thermodynamic diagnostics. We used the “good” (but not “best”) fitting models to recover an estimate of the uncertainty on the recovered diagnostics. Results. The maximum line-of-sight (LOS) velocities were found to be 70 km s−1. The line widths were mostly 0.4 Å, with the asymmetries of most pixels around zero. The central temperature of the prominence was found to range from 10 kK to 20 kK, with uncertainties of approximately ±5 to ±15 kK. The central pressure was around 0.2 dyn cm−2, with uncertainties of ±0.2 to ±0.3 dyn cm−2. The ionisation degree ranged from 1 to 1000, with uncertainties mostly in the range ±10 to ±100. The electron density was mostly 1010 cm−3, with uncertainties of mostly ±109. Conclusions. The new xRMS algorithm finds an estimation of the errors of the recovered thermodynamic properties. To our knowledge, this is the first attempt at systematically determining the errors from forward modelling. The large range of errors found may hint at the degeneracies present when using a single ion and/or species from forward modelling. In the future, co-aligned observations of more than one ion and/or species should be used to attempt to constrain this problem.

ENN's roadmap for proton-boron fusion based on spherical torus

ENN Science and Technology Development Co., Ltd. (ENN) is committed to generating fusion energy in an environmentally friendly and cost-effective manner, which requires abundant aneutronic fuel. Proton-boron (p-11B or p-B) fusion is considered an ideal choice for this purpose. Recent studies have suggested that p-B fusion, although challenging, is feasible based on new cross section data, provided that a hot ion mode and high wall reflection can be achieved to reduce electron radiation loss. The high beta and good confinement of the spherical torus (ST) make it an ideal candidate for p-B fusion. By utilizing the new spherical torus energy confinement scaling law, a reactor with a major radius R0=4 m, central magnetic field B0=6 T, central temperature Ti0=150 keV, plasma current Ip=30 MA, and hot ion mode Ti/Te=4 can yield p-B fusion with Q>10. A roadmap for p-B fusion has been developed, with the next-generation device named EHL-2. EHL stands for ENN He-Long, which literally means “peaceful Chinese Loong.” The main target parameters include R0≃1.05 m, A≃1.85, B0≃3 T, Ti0≃30 keV, Ip≃3 MA, and Ti/Te≥2. The existing ST device EXL-50 was simultaneously upgraded to provide experimental support for the new roadmap, involving the installation and upgrading of the central solenoid, vacuum chamber, and magnetic systems. The construction of the upgraded ST fusion device, EXL-50U, was completed at the end of 2023, and it achieved its first plasma in January 2024. The construction of EHL-2 is estimated to be completed by 2026.

Observations of airflow around a supertall curved building and its impact on temperature and humidity in Houston's urban center

Characterization of realistically shaped skyscrapers embedded in non-uniform neighbourhoods experiencing intricate weather patterns remains inadequately investigated. Aiming to close this gap, the Center for Multiscale Applied Sensing team deployed its mobile observatory in the street canyons around the curved Wells Fargo Plaza skyscraper in downtown Houston, TX. Three deployments allowed airflow observations under different inflow wind and thermodynamic stability conditions. Doppler lidar measurements reveal that when inflow hits the curved wall of the skyscraper, perpendicular canyons experience similar vortex configurations creating two windward and two leeward circulations. Windsond measurements support that buoyancy within the deep street canyons can generate thermal updrafts as strong as 2 m s−1 which is sufficient to overturn the mechanical downwash under gentle wind conditions. Canyons experiencing venting during the daytime were observed to be more thermodynamically stable at night while thermodynamically stable canyons during the day were observed to be more thermodynamically unstable at night owing to the accumulation of heat near street-level. Fourier decomposition of the vertical velocity measurements shows that in all cases flow exhibited high Reynolds numbers and was composed of turbulent eddies of predominantly 6 and 15 min periods. This observational dataset provides insights to assess wind load, pedestrian comfort, urban air mobility, and natural ventilation and may be used as a benchmark for numerical model and wind tunnel studies attempting to represent realistically complex urban conditions.

A 300-year tree-ring δ18O-based precipitation reconstruction for the South American Altiplano highlights decadal hydroclimate teleconnections

Tropical South American climate is influenced by the South American Summer Monsoon and the El Niño Southern Oscillation. However, assessing natural hydroclimate variability in the region is hindered by the scarcity of long-term instrumental records. Here we present a tree-ring δ18O-based precipitation reconstruction for the South American Altiplano for 1700–2013 C.E., derived from Polylepis tarapacana tree rings. This record explains 56% of December–March instrumental precipitation variability in the Altiplano. The tree-ring δ18O chronology shows interannual (2–5 years) and decadal (~11 years) oscillations that are remarkably consistent with periodicities observed in Altiplano precipitation, central tropical Pacific sea surface temperatures, southern-tropical Andean ice core δ18O and tropical Pacific coral δ18O archives. These results demonstrate the value of annual-resolution tree-ring δ18O records to capture hydroclimate teleconnections and generate robust tropical climate reconstructions. This work contributes to a better understanding of global oxygen-isotope patterns, as well as atmospheric and oceanic processes across the tropics.

A new chronology of Cedrela fissilis (Meliaceae) for Southern Brazil: Combining classical dendrochronology and radiocarbon dating

Cedrela fissilis is a tree species widely distributed in the tropical biomes of South America. This species has visible annual growth rings and can live for several centuries. The present study aims to (i) develop a chronology of C. fissilis to the Southern Brazilian Plateau using traditional dendrochronological methods, (ii) validate the dendrochronological dating using the radiocarbon (14C) bomb pulse method, and (iii) determine the influence of temperature and precipitation variations and their teleconnections with the tropical Pacific Ocean temperatures on the annual radial growth of this species. The ring width chronology was developed using 24 C. fissilis trees. The Schulman years of 1957, 1962, 1963, 1966, 1969 and 1974 were independently dated using the 14C bomb pulse methodology by accelerator mass spectrometry (AMS). Tree-ring indices were compared with temperature and precipitation records from stations around the study forest. The chronology covers the period 1907–2018 (111 years) and is well replicated (> 10 trees) from 1941 onwards. Statistics commonly used in dendrochronology indicate that the chronology is highly reliable and of good quality (mean series intercorrelation r = 0.49; Rbar = 0.30; EPS = 0.86; MSI = 0.40). The 14C bomb pulse of selected calendar years showed that the trees were accurately dated using the classical cross-dating approach. Precipitation from November to December (wet period) is positively correlated with tree growth (r = 0.36, n = 49; p<0.05). In addition, variations in temperature from May to July are positively correlated with ring width (r = 0.39, n = 49; p<0.05), suggesting that C. fissilis growth is favored by abundant rainfall during the growing season and above-average winter temperatures. Interannual variation in the chronology is partially modulated by El Niño 3.4 (East Central Tropical Pacific Sea Surface Temperature) during Oct-Dec (r = 0.27, n = 68, p<0.05). The growth of C. fissilis trees is directly dependent on climate variability, suggesting that more abundant precipitation and higher winter temperatures, as projected for the future climate of southern Brazil, will have a positive effect on tree growth. However, prolonged droughts and high temperatures during the growing season will have a negative impact on tree growth, even in humid forests with high soil moisture content.

Development of multi-cross-linking, rapid curing, and easy cleaning, edible hydrogels for meat preservation

The design and development of a food preservation coating material with rapid curing and stable performance to shorten the coating process time and reduce quality changes caused by temperature fluctuations in cold chain is highly desirable in fresh meat preservation applications. In this study, a series of multi-cross-linked edible hydrogels were designed based on gelatin and k-carrageenan through the self-assembly triple-helix of gelatin and the potassium ion-mediated k-carrageenan double-helix structure. The tannic acid with phenolic hydroxyl groups was employed to enable the dynamic bond cross-linking between two polymers, endowing the composite hydrogel with rapid curing ability at low-temperature and a uniform molecular network structure. The hydrogel with a concentration of gelatin was 16% (GCBG-16) achieved the optimal combination properties, including 73.41% of elongation at break, 71.59 kJ/m2 of toughness, 27.73% of swelling ratio, and 50.73% of DPPH· scavenging rate. The hydrogels could be rapidly washed within 30 min at 40 °C by water, as well as possessing a certain self-healing and anti-freezing capabilities. The hydrogel GCBG-16 had a great capacity for protecting meat with a E value of 50.4 and 17.53 N of shear force even placed in a 37 °C environment, which showed no significant difference (p > 0.05) compared to the initial value. Furthermore, the fresh meats with coating showed delayed central temperature increase speed after leaving from the cold chain and placed in a 37 °C environment. The research results demonstrated that the proposed hydrogel has great potential in preserving fresh meat, which can serve as a matrix material combined with other active additives for extending the shelf life of meat products.

Study of dynamic performance of PEMFC-based CCHP system in a data center based on real-time load and a novel synergistic control method with variable working conditions

In this paper, the dynamic performance of Proton Exchange Membrane Fuel Cell-based Combined Cooling Heating and Power (PEMFC-based CCHP) system combined with a data center real-time load is studied. A novel synergistic control method is proposed to achieve optimization of energy flow between system units under fluctuating load. First, the off-design working condition models of PEMFC-based CCHP system are constructed. The delay in the changes of data center temperature is considered because of the thermal inertia under dynamic conditions. Second, the dynamic performance of PEMFC-based CCHP system to step changes of data center load is analyzed. Third, to further reveal the energy flow between units, the units output under varying load conditions are compared under the constraints of power and refrigeration supply. Finally, the dynamic performance of PEMFC-based CCHP system under the traditional control method of following electric load are revealed. A novel synergistic control method for the PEMFC-based CCHP system is proposed by refining the traditional method to optimize the energy flow between units. The result presents that the average energy efficiency reaches 78.29 %. Compared with the following electric load method, the energy efficiency is increased by 6.02 %. The response time of synergistic control method is 27.0 ms. Improved energy efficiency and fast response have been achieved.

Evaluating innovative collective heating and cooling concepts by incorporating occupants' preferences for conflicting performance indicators

Various Collective Heating and Cooling Systems (CHCS) have emerged as promising low-carbon energy solutions for buildings. However, the absence of tailored decision guidelines often hinders decision-makers from identifying the optimal system for any given case. This research introduces a novel methodology for comprehensive evaluation of different CHCS under diverse case-specific boundary conditions, leading to informed recommendations. The proposed methodology integrates occupants' preferences for thermal comfort and costs into a holistic Key Performance Indicator (KPI) score, i.e. a weighted sum of normalised indicators including indoor thermal comfort, domestic hot water comfort, and levelised cost of energy. By applying this methodology to evaluate three advanced central change-over temperature CHCS across various building sizes and family types, our study demonstrates the effectiveness of this approach. The results suggest that 4-pipe systems are preferable when prioritising thermal comfort, whereas decentralised booster heat pumps are recommended for cost reduction. Notably, for small apartment buildings inhabited by working families, a 2-pipe system with decentralised storage might be preferred. These insights underscore the importance of incorporating occupants' preferences into multi-objective decision-making. Furthermore, the holistic KPI score methodology can assess different control strategies and provide valuable insights for policymakers when extended with additional indicators.

Topology optimization and bionic analysis of heat sink fin configuration based on additive manufacturing technology

Fins are extensively employed in heat sinks for high heat flux components. In this study, three distinct objective functions, namely temperature gradient minimization (TO-I type fin), average temperature minimization (TO-II type fin), and entransy dissipation minimization (TO-III type fin), are established for topology optimization design of the heat sink fin structure to effectively minimize the temperature of the heat source. By conducting a comparative analysis of the configuration features and thermal performance of optimized fins with different objective functions, it is evident that the TO-I type fin exhibits superior thermal performance. When the fin volume fraction φ is 0.3, the heat source center temperature of TO-I type fin is 2.67 K and 4.55 K lower than that of TO-II type fin and TO-III type fin, respectively. Meanwhile, the bionic analysis of the optimized fins under different objective functions using fractal theory reveals that the fractal dimension of the TO-I type fin is 1.4038, which is the closest to the average fractal dimension of many kinds of leaf veins in nature (D¯f= 1.3762), which indicates that the optimized fins have the bionic characteristics most similar to those of the leaf blade. Finally, the three topology optimization fins were fabricated using boundary-filtering optimization 3D printing technology. Comparative tests verified the advantage of minimizing the temperature gradient as the objective function of topology optimization and demonstrated its potential for thermal performance and lightweighting applications, especially under high heat source operating conditions.

FAUST. XIV. Probing the Flared Disk in L1527 with Sulfur-bearing Molecules

IRAS04368+2557 in L1527 is a Class 0/I protostar with a clear disk-envelope system revealed by previous Atacama Large Millimeter/submillimeter Array (ALMA) observations. In this paper, we discuss the flared structure of this source with observed sulfur-bearing molecules included in the FAUST ALMA large program. The analyses of molecular distributions and kinematics have shown that CS, SO, and OCS trace different regions of the disk-envelope system. To evaluate the temperature across the disk, we derive rotation temperature with the two observed SO lines. The temperature profile shows a clear, flared “butterfly” structure with the higher temperature being ∼50 K and the central lower temperature region (<30 K) coinciding with the continuum peak, suggesting dynamically originated heating rather than radiation heating from the central protostar. Other physical properties, including column densities, are also estimated and further used to demonstrate the vertical structure of the disk-envelope system. The “warped” disk structure of L1527 is confirmed with our analyses, showing that sulfur-bearing molecules are not only effective material probes but also sufficient for structural studies of protostellar systems.

Achieving stationary high performance plasmas at Wendelstein 7-X

This work reports on recent results on the search for high performance plasma scenarios at the magnetically confined stellarator fusion device Wendelstein 7-X. In four new designed scenarios, the development from transient toward stationary plasmas of improved performance has been realized. In particular, a high performance duration of up to 5 s, an energy confinement time of 0.3 s, a diamagnetic energy of 1.1 MJ, a central ion temperature of 2.2 keV, and a fusion triple product of 3.4×1019m−3· keV · s have been achieved, and previously observed limitations of the machine have been overcome, regarding both the performance and its duration. The two main experimental techniques for stationary high performance are neutral beam injection core fueling on the one hand and the use of a magnetic field configuration with internal islands on the other hand. Two of the developed scenarios are expected to be extendable straightforward toward a duration of several tens of seconds, making use of the long pulse operation capabilities of W7-X.

Nonlinear combination resonance analysis of parametric-forced excitation for an axially moving piezoelectric rectangular thin plate in thermal- electromechanical coupling field

In this paper, the combination resonance of parametric-forced excitation characteristics for an axially moving rectangular piezoelectric plate under a thermal-electromechanical field is studied. Based on Kirchhoff-Love plate theory and Von Karman theory, the transverse vibration governing equations are derived from Hamilton's principle. The equations are discretized to ordinary differential equations by the Galerkin method. Then, the multiple scales method is applied to solve the system combination resonance equation, two different resonance states and corresponding amplitude-frequency response equations are obtained by eliminating the secular term, respectively. Additionally, the stability of the steady-state responses is analyzed by Lyapunov stability. Based on the numerical analysis, the influence of axial velocity, external voltage, central temperature difference, structural damping, and other parameters on nonlinear combination resonance response are investigated. The effect of parameter variation on period-doubling bifurcation and the chaotic motion of the system are also discussed by the system global bifurcation diagram.

Numerical study of the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics

Helical fuel is a promising nuclear fuel proposed to improve the core power density and safety margin. In this study, the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics in helical fuel annuli has been investigated. The volumetric energy source is applied to the fuel pin, and coupled walls are used at the coolant-cladding and cladding-fuel interfaces. The numerical method with SST k-ω turbulence model has been validated with the results of bare annulus. The flow field, fuel central temperature, friction factor, and the circumferential distribution of swirl intensity, heat flux and wall temperature are obtained based on the numerical simulation. The increase in R2/R1 will result in broadening transverse flow region, reducing the gradient of surface heat flux and wall temperature, lowering the maximum wall temperature, but increasing the fuel central temperature and has no significant effect on the friction resistance. The decrease of helical pitch increases the swirl intensity and friction factor, but worsens the heat transfer at the blade roots.

A multifunctional flexible composite phase-change film with excellent solar driven thermal management

The development of multifunctional films with integrated temperature regulation, photothermal conversion, and bendability is urgently needed for personal thermal management products. In this paper, aminated multi-walled carbon nanotubes modified phase-change microcapsules (ACNTs-PCMC) were synthesized. Subsequently, a flexible polyvinyl alcohol (PVA)/graphene/ACNTs-PCMC composite film (PGAMF) with a three-dimensional sandwich structure was prepared by a simple tape-casting method. The obtained PGAMF films possessed a phase-change enthalpy of 45.5 ± 0.7 J/g. The designed sandwich structure can fix the ACNTs-PCMC microcapsules inside the PGAMF films through the bonding effect of the PVA to prevent them from falling off and sliding, so that the PGAMF composite films have the proper mechanical properties and excellent flexibility. More importantly, the PGAMF composite films had a high photothermal conversion efficiency of 88.8 %. In the cold environment, the center temperature of the PGAMF composite film adhered to the fiber fabric driven by a low solar radiation was 14.5 ± 0.5 °C higher than that of the fiber fabric without the PGAMF composite film. Therefore, the multifunctional composite films with flexibility, heat storage and solar-to-heat conversion prepared in this study have broad application scenarios in heat preservation in low temperature areas and solar-driven thermal management engineering.

Thermal hazard evaluation of 18650 lithium-ion batteries at various discharge rates

Lithium-ion batteries (LIB) provide high energy density, low self-discharge rate, long cycle life, and superior suitability for a wide range of applications, such as portable electronic devices, electric vehicles, and renewable energy systems. In this investigation, we prepared 18650 LIB cells with various discharging rates (1C, 2C, 3C, and 4C) using specified conditions for static discharging experiment, and recorded the battery discharge current (Idis), discharge time (tdis), central surface maximum temperature (Tmax), temperature fluctuation, discharge capacity (Cdis), discharge energy (Wdis), and voltage at different time intervals. We studied the association between the discharge rate and the thermal stability of LIB specimens. In the discharge process, it was observed that operating at an increased discharge rate exhibited a direct correlation with a higher temperature rise. The findings indicate that batteries prepared with a higher discharge rate exhibit greater instability in terms of inherent property. During the 4C discharge rate, the Tmax, Cdis, and Wdis values were 96.6 °C, 3.117 Ah, and 9.021 Wh, respectively. These results indicate that a discharging rate of 4C is inappropriate for batteries, while the discharging rates of 1C, 2C, and 3C are suitable in terms of thermal stability.

Emergent constraint on the projected central equatorial Pacific warming and northwestern Pacific monsoon trough change

The northwestern Pacific monsoon trough (NWPMT) deeply impacts socio-economic development and human security over East Asia by supplying moisture to the summer monsoon rainfall and modulating tropical cyclone activities. However, considerable inter-model spreads in the coupled model inter-comparison project phase 6 models make the future projection of the NWPMT less reliable. Here, we find that the inter-model spread of the NWPMT change is significantly correlated with the central equatorial Pacific sea surface temperature change, and mainly determined by the equatorial thermocline sharpness in the historical simulations. According to the emergent constraint method, the central equatorial Pacific SST would warm up about 6% slower than the multi-model mean with 56% uncertainty reduced. Correspondingly, the NWPMT would slacken westward with 36% uncertainty reduced. Results here emphasize the importance of examining and reducing systematic model biases in simulating thermocline sharpness that have been overlooked in past literatures, before achieving more reliable future projections.

Experimental study on scaled-down pads for nuclear main pump thrust bearing

The lubrication performance of thrust bearings is essential for the efficient, economical, and safe operation of nuclear main pumps. In this paper, a test system for scaled-down tilting pad thrust bearings was designed and built, and the feasibility of the scaled-down scheme was verified. The test results show that: with the increase of loading force, the pressure and temperature at different measurement points gradually increase. The influence of lubricant temperature on oil film pressure under the same loading force is small. During the rotor start process, the oil film pressure shows a trend of first increasing and then gradually stabilizing, and the temperature of each pad center gradually increases. During the rotor stop process, the oil film pressure initially increases slightly and then drops sharply with the reduction of speed, while the temperature at the center of the pad gradually decreases and the rate of decrease gradually increases.

Energy transfer in compressible channel flows with two-dimensional sinusoidal rough walls

We perform direct numerical simulations to investigate the effect of two-dimensional sinusoidal roughness in the compressible channel flows with varying roughness height at Mach numbers M0=0.8 and 1.5. We observed the strong oblique shock waves and alternating compression/expansion regions are generated due to the roughness at higher Mach number, which also results in higher temperature in the channel center. The effects of roughness height on the transfer between the kinetic and internal energies are analyzed in detail. We found that the roughness significantly enhances the production of the turbulent kinetic energy while the Mach number has little influence on this term. The transfer terms between kinetic and internal energies are pressure- and viscosity-related, and is dominated by the viscous terms. The roughness-induced shock waves strongly affect the local distributions of the pressure-related terms, but its spatial average is only slightly modified. The energy transfer from the mean kinetic energy to both the internal energy and the turbulent kinetic energy is amplified by the roughness through the viscous terms. The average effect of roughness is intensified as the roughness height increases, but is insensitive to the Mach number variation.

Effects of grilling conditions on heterocyclic amines and quality attributes of grilled grass carp

SummaryThe effects of different grilling temperatures (220 °C, 250 °C, 280 °C, 310 °C) reaching the central temperature of 70 °C on heterocyclic amines (HAs) formation, moisture content, cooking loss, texture, colour, and sensory properties of grilled grass carp (Ctenopharyngodon idella) were investigated. The grilling condition significantly (P &lt; 0.05) affected cooking loss, moisture content, heterocyclic amines (HAs) formation, texture, colour and sensory properties. The results showed that 5 kinds of free and 9 kinds of protein‐bound heterocyclic amines were detected. The total amount of protein‐bound heterocyclic amines was much higher than that of the free state. Harman and Norharman, belonging to β‐carboline, constituted over 80% of the total content of heterocyclic amines. Considering the HAs formation and quality attributes, when the grilling condition was 280 °C for 10 min, the total content of HAs was the lowest, and the fish had moderate moisture content, firm texture, bright colour, and high sensory evaluation score.

Enhancing sustainability with waste hemp-shive and phase change material: Novel gypsum-based composites with advanced thermal energy storage properties

This study addresses the rising demand for sustainable construction by introducing composite materials from natural and renewable resources: gypsum, hemp, and phase change materials (PCMs). These materials cater to the growing preference for eco-friendly building solutions. Incorporating hemp enhances sustainability while integrating PCMs into the porous hemp structure ensures adequate thermal energy storage and release without leakage. Firstly, the agricultural waste hemp shives and lauryl alcohol (LA) PCM were mixed to create shape-stabilized hemp/PCM composites. The highest PCM ratio was determined in shape-stabilized composites exhibiting non-leakage properties, which was 45 wt %. These composites were then incorporated into gypsum materials at loadings of 7.5 %, 15 %, 22.5 %, and 35 wt % to produce the final composites. Morphological, thermal, and chemical characteristics of shape-stabilized composites were examined using SEM, TGA, and DSC, while the solar thermoregulation tests assessed the gypsum matrix composites. The phase change temperature of PCM was determined as 20.24 °C with a melting enthalpy value of 224.4 J/g. The hemp/PCM shape-stabilized composites demonstrated an impressive melting enthalpy value of 100.2 J/g, with only a slight reduction to 99.5 J/g after 750 test cycles. When the ambient temperature exceeded 50 °C, the central temperature of the cabins containing PCM composites was found to be at least 4 °C cooler than those containing only gypsum. Conversely, when the ambient temperature dropped to around 20 °C, it was observed that the central temperature of the cabins with PCM composites was approximately 2 °C warmer than those with only gypsum. This study introduces a novel approach to creating environmentally friendly gypsum/hemp/PCM composites for thermal energy storage systems.