| 1. |
- Lu, Longyu, et al.
(författare)
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Tunable Magnetism in Atomically Thin Itinerant Antiferromagnet with Room-Temperature Ferromagnetic Order
- 2024
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Ingår i: Nano Letters. - 1530-6984. ; 24:20, s. 5984-5992
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Tidskriftsartikel (refereegranskat)abstract
- Addressing the need for modulated spin configurations is crucial, as they serve as the foundational building blocks for next-generation spintronics, particularly in atomically thin structures and at room temperature. In this work, we realize intrinsic ferromagnetism in monolayer flakes and tunable ferro-/antiferromagnetism in (Fe0.56Co0.44)5GeTe2 antiferromagnets. Remarkably, the ferromagnetic ordering (≥1 L) and antiferromagnetic ordering (≥4 L) remain discernible up to room temperature. The TC (∼310 K) of the monolayer flakes sets a record high for known exfoliated monolayer van der Waals magnets. Within the framework of A-type antiferromagnetism, a notable odd-even layer-number effect at elevated temperatures (T = 150 K) is observed. Of particular interest is the strong ferromagnetic order in even-layer flakes at low temperatures. The intricate interplay among magnetic field strength, layer number, and temperature gives rise to a diverse array of phenomena, holding promise not only for new physics but also for practical applications.
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| 2. |
- Li, Xueqiang, et al.
(författare)
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Key factors affecting the performance of the multi-stream heat exchanger for CO2 condensation
- 2023
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Ingår i: International journal of thermal sciences. - : Elsevier Masson s.r.l.. - 1290-0729 .- 1778-4166. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- The multi-stream heat exchanger (MS-HEX) is an important equipment in CO2 capture processes, especially for CO2 condensation. By now, little attention has been paid to thoroughly investigating its performance. To provide insights for optimizing the design and operation of the MS-HEX, this paper evaluated the impacts of some key factors, such as the flow arrangement and the content of non-condensable (NC) gases, on the performances of the MS-HEX, including the exit vapor fraction, the pressure drop, the heat transfer coefficient (HTC), and the sub-cooling degree. A 3D CFD model was developed and validated. Based on simulations, it was found that the flow arrangement can clearly affect the performance of the MS-HEX, and there existed an optimal one, which can give the highest sub-cooling degree. Moreover, increasing the volume fraction of NC gases can lead to a decrease of the HTC and the sub-cooling degree; and Ar showed the biggest impact, followed by O2 and N2. For instance, compared to condensing a stream containing 5 vol % N2, condensing a stream containing 5 vol % Ar led to a lower HTC and a lower sub-cooling degree, which can be up to 27.3% and 4 K, respectively.
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| 3. |
- Li, Xueqiang, et al.
(författare)
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Optimizing cooling electronic chips at high altitude with consideration of solar radiation
- 2023
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Ingår i: International journal of thermal sciences. - : Elsevier. - 1290-0729 .- 1778-4166. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining a proper working environment for electronic chips is challenging for airships, as the ambient parameters at high altitude are largely different from those on the ground, which can influence the performance of cooling. This work aims to optimize the finned sink to minimize the weight with the consideration of the impact of solar radiation. By using a validated 3D model, it was found that the ignorance of the solar radiation can lead to a temperature deviation of 4.1 °C for electronic chips at 20 km when the solar radiation intensity was 1400 W/m2 and the wind speed was 10 m/s. Meanwhile, compared to the solar radiation intensity and the emissivity, the direction of solar radiation showed more impacts. In addition, even though the solar radiation doesn't influence the optimal fin height, fin number, and fin thickness, it would clearly affect the optimal heat transfer area ratio. As a result, it can clearly change the optimized weight, which was 5.7% higher if the solar radiation was not considered. © 2022 The Authors
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| 4. |
- Liu, Shengchun, et al.
(författare)
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Alternative positions of internal heat exchanger for CO2 booster refrigeration system : Thermodynamic analysis and annual thermal performance evaluation
- 2021
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Ingår i: International journal of refrigeration. - : ELSEVIER SCI LTD. - 0140-7007 .- 1879-2081. ; 131, s. 1016-1028
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Tidskriftsartikel (refereegranskat)abstract
- Refrigeration systems running on transcritical CO2 cycle are considered an alternative to phase-down the use of hydrofluorocarbons (HFCs) in response to the Kigali Amendment. Responding to the need to improve the efficiency of CO2 booster systems and to identify optimum system designs, thermodynamic models of three booster systems are proposed with the use of an internal heat exchanger (IHX). Findings from this study suggest that placing the IHX with a low-temperature fluid side at the suction line of high pressure stage compressor and high-temperature fluid side at the outlet of gas cooler represents the most optimal approach in improving the coefficient of performance (COP) of the booster system. When operating in the transcritical conditions, the COP values can be improved by 6.35% at the IHX thermal effectiveness of 0.8 and by 6.48% at the ratio of medium temperature load to low temperature load of 6. Using IHX can significantly reduce the compressor discharge pressure, which can be reduced by 0.55 MPa at the ambient temperature of 40 degrees C. Furthermore, by adding IHX, the annual performance factor of CO2 system can be improved significantly by 1.68% and the annual total power consumption can be decreased by 6.48% in the tropical climate. It can be concluded that IHX can improve the COP values of a booster system when operating in the subtropical and tropical regions.
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| 5. |
- Yang, Sheng‐Chun, et al.
(författare)
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The ENUF method—Ewald summation based on nonuniform fast Fourier transform : Implementation, parallelization, and application
- 2020
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Ingår i: Journal of Computational Chemistry. - : John Wiley & Sons. - 0192-8651 .- 1096-987X. ; 41:27, s. 2316-2335
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Forskningsöversikt (refereegranskat)abstract
- Computer simulations of model systems are widely used to explore striking phenomena in promising applications spanning from physics, chemistry, biology, to materials science and engineering. The long range electrostatic interactions between charged particles constitute a prominent factor in determining structures and states of model systems. How to efficiently calculate electrostatic interactions in simulation systems subjected to partial or full periodic boundary conditions has been a grand challenging task. In the past decades, a large variety of computational schemes has been proposed, among which the Ewald summation method is the most reliable route to accurately deal with electrostatic interactions between charged particles in simulation systems. In addition, extensive efforts have been done to improve computational efficiencies of the Ewald summation based methods. Representative examples are approaches based on cutoffs, reaction fields, multi‐poles, multi‐grids, and particle‐mesh schemes. We sketched an ENUF method, an abbreviation for the Ewald summation method based on the nonuniform fast Fourier transform technique, and have implemented this method in particle‐based simulation packages to calculate electrostatic energies and forces at micro‐ and mesoscopic levels. Extensive computational studies of conformational properties of polyelectrolytes, dendrimer‐membrane complexes, and ionic fluids demonstrated that the ENUF method and its derivatives conserve both energy and momentum to floating point accuracy, and exhibit a computational complexity of with optimal physical parameters. These ENUF based methods are attractive alternatives in molecular simulations where high accuracy and efficiency of simulation methods are needed to accelerate calculations of electrostatic interactions at extended spatiotemporal scales.
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| 6. |
- Zhang, Huilin, et al.
(författare)
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Exposure to polycyclic aromatic hydrocarbons (PAHs) in outdoor air and respiratory health, inflammation and oxidative stress biomarkers : A panel study in healthy young adults
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 899
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Tidskriftsartikel (refereegranskat)abstract
- Exposure to polycyclic aromatic hydrocarbons (PAHs) can be associated with different types of health effects. However, the systemic changes of health effects between fluctuations of PAHs exposure have not been established. In this study, urinary hydroxylated PAHs (OH-PAHs) and 12 biomarkers were determined among 36 students from the urban to the suburb in Taiyuan in 2019. The concentration of & sigma;12OH-PAHs in urban areas (28.2 and 21.4 & mu;g/g Cr) was significantly higher than that in suburban area (16.8 & mu;g/g Cr). The regression showed that hydroxy-phenanthrene (OH-Phe, 1/2/3/4/9-OH-Phe) was significantly positively correlated with lung function (PEF25 and PEF50), 8-hydroxydeoxyguanosine (8-OHdG), interleukin-8 (IL-8), and fractional exhaled nitric oxide (FeNO). Moreover, there were negative associations of 2-hydroxyfluorene (2-OH-Flu) with FVC and FEV1. 1 unit increase of 1-hydroxypyrene (1-OH-Pyr) was negatively associated with 18.8% FVC, 17.3% FEV1, and 26.4% PEF25 in the suburban location, respectively. During urban2, each unit change of 2-OH-Flu was associated with 10.9% FVC and 10.5% FEV1 decrease, which were higher than those in suburban location. 8-OHdG decreased by 32.0% with each unit increase in 3-hydroxyfluorene (3-OH-Flu) during urban2 (p < 0.05), while 1.9% in the suburban location. During the suburban period, the increase in OH-Phe was correlated with the decrease in malondialdehyde (MDA). The respiratory damage caused by PAHs in the urban disappeared after backing to the urban from the suburban area. Notably, despite the total significant liner mixed regression association of FeNO with multiple OH-PAHs, the association of FeNO with OH-PAHs was not significant during different periods except for 2-OH-Flu. Our findings suggested that short-term exposure to different concentrations of PAHs might cause changes in health effects and called for further research to investigate possible alterations between health effects and PAH exposure.
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