We demonstrate that a field-effect transistor (FET) made of few-layer black phosphorus (BP) encapsulated in hexagonal boron nitride (h-BN) in vacuum exhibits a room-temperature hole mobility of 5200 ...cm2/(Vs), being limited just by the phonon scattering. At cryogenic temperatures, the FET mobility increases up to 45 000 cm2/(Vs), which is five times higher compared to the mobility obtained in earlier reports. The unprecedentedly clean h-BN–BP–h-BN heterostructure exhibits Shubnikov–de Haas oscillations and a quantum Hall effect with Landau level (LL) filling factors down to v = 2 in conventional laboratory magnetic fields. Moreover, carrier density independent effective mass of m * = 0.26 m 0 is measured, and a Landé g-factor of g = 2.47 is reported. Furthermore, an indication for a distinct hole transport behavior with up- and down-spin orientations is found.
In this article, a miniaturized antenna is proposed for 4G/5G multiple input, multiple output (MIMO) applications for smartphones. The proposed antenna is composed of an inverted L-shaped antenna ...with decoupled elements to cover 4G (2000-2600 MHz), and a planar inverted-F antenna (PIFA) with a J-slot to cover 5G (3400-3600 MHz and 4800-5000 MHz). Furthermore, to achieve the purposes of miniaturization and decoupling, the structure adopts a feeding stub, shorting stub, and outstanding floor, additionally adding the slot to the PIFA, to generate additional frequency bands. Due to the advantages such as multiband operation, MIMO configuration for 5G communications, high isolation, and a compact structure, the proposed antenna design is attractive for 4G/5G smartphones. The antenna array is printed on an FR4 dielectric board, measuring 140 × 70 × 0.8 mm
, with the 4G antenna located on a top 15 mm-long headroom.
TNFR-associated factors (TRAFs) and receptor-interacting protein kinases (RIPKs) are important immunological linker molecules in mammals and play important roles in the TNFα, TLR and IFN signaling ...pathways. However, the evolutionary origins of these genes in vertebrates have not previously been described in lampreys. In this study, we searched the genomes of
, and
for genes encoding
and
and performed homologous sequence alignment, phylogenetic tree, functional domain, conserved motif, gene structure, and synteny analyses to determine their evolutionary relationships. The distribution of the lamprey
and
families and the immune response of the gene families in lampreys stimulated by different pathogens were also demonstrated, suggesting a role of structural changes in expression and functional diversification. Additionally, the dual luciferase reporter gene assay showed that the addition of exogenous immunomodulator (TNFα or IFN) to the overexpression of LjLRIPK1a or LjTRAF3/6 significantly downregulated NF-κB or ISRE activation. LjRIPK1a can significantly enhance caspase-8 activity, and overexpression of LjRIPK1a or LjTRAF3a/6 in HEK293T cells results in cell apoptosis. In summary, this study makes an important contribution to the understanding of the
and
gene families in different vertebrates. Our results also provide new evidence for the evolution of vertebrate TRAFs and RIPKs and their impacts on immune regulation.
The microstructure evolution of boron-bearing high speed steel roll materials after casting and tempering was investigated. The results indicate that as-cast boron-bearing high speed steel consists ...of martensitic matrix, retained austenite and different borocarbides. The as-cast alloy has a hardness above 64 HRC, and the borocarbides distribute along the grain boundaries. After RE-Mg-Ti compound modification treatment, obvious necking and broken network appear in the grain boundaries. The hardness of boron-bearing high speed steel roll materials reduces gradually with the increase of tempering temperature. Under the same conditions, the toughness of the modified roll material is higher than that of the unmodified roll material. Wear tests show that the wear resistance of boron-bearing high-speed steel modified by RE-Mg-Ti compound modification treatment is better.
A lattice Boltzmann method (LBM) two-dimensional (2D) mesoscopic model is presented for studying the frost crystal nucleation process involved in liquid-solid phase change on a cold surface. In order ...to make the simulation more realistic, the actual frost crystal nucleus deformation process is considered in this model. The simulation results agree well with our experimental results. Detailed analysis was made on the dynamic behavior of liquid-solid phase change and heat transfer happening in the frost crystal nucleation process. Results are presented for the evolution law of frost crystal nucleus deformation, dynamic solid-liquid phase change process as well as the dynamic distribution of frost nucleus interior temperature during frost crystal nucleation. In addition, the occurrence of frost crystal nucleus deformation is explained by the theory of crystal growth. Finally, where and why the initial position of frost crystal growth happens is also revealed. Furthermore, the reason why the hydrophobic surface can delay the droplet freezing and why the frost growth is faster on the hydrophobic surface after the droplet is frozen is analyzed based on this model.
This study numerically examines the effect of actual gas turbine operating conditions on heat transfer characteristics in a ribbed passage with mist/steam cooling. A 60° ribbed passage with aspect ...ratio of 1/1 was investigated at Reynolds number of 300,000, and steam cooling was used to provide a contrast. Three main factors were considered: coolant temperature, operating pressure, and wall heat flux density. The heat transfer enhancement mechanism of mist/steam cooling was explored, and the results showed that the heat transfer performance of mist/steam cooling was superior to steam cooling. When the coolant temperature varied from 300 to 500 °C, the average Nusselt number of mist/steam cooling decreased by 26.6%, and the heat transfer enhancement ratio dropped from 15% to 10%. As operating pressure increased, the heat transfer performance factor of mist/steam firstly increased and then decreased. At an operating pressure of 1.5 MPa, the heat transfer achieved its optimal performance, and the heat transfer enhancement ratio achieved its maximum value of 15.9%. Larger wall heat flux density provided less heat transfer enhancement. When the heat flux density increased from 100,000 to 300,000 W·m−2, the average Nusselt number of mist/steam cooling decreased by 13.8%, while the heat transfer enhancement ratio decreased from 25.3% to 12.6%.
A numerical investigation of frost growth on a cold flat surface was presented based on two-dimensional Lattice Boltzmann model. This model has been validated to have less prediction error by past ...experiments. According to the results, it is shown that average frost density appears different at an increasing rate at different frosting stages. In addition, cold surface temperature has great influence on frost growth parameters such as frost crystal deposition mass, frost deposition rate, and frost crystal volume fraction. It was found that the frost crystal deposition mass, frost crystal volume, and the deposition rate first increase rapidly, then gradually slow down, finally remaining unchanged while the cold surface temperature decreases. The further away from the cold surface, the more sparser the frost layer structure becomes due to the smaller frost crystal volume fraction.
•The impacting-freezing behavior of ellipsoidal water droplet is numerically studied.•Increasing aspect ratio can increase the spreading range of water droplets.•The effect of surface wettability on ...the first peak of impact force is smaller.•Heat transfer between water droplet and cold surface is increased with aspect ratio.
A two-dimensional numerical model that investigates the freezing behavior of ellipsoidal impacting water droplets on cold surfaces was established in this paper, focusing on the spreading behavior, impact force evolution and heat transfer behavior of ellipsoidal water droplets. For cold surfaces with a higher temperature, reducing aspect ratio can reduce the contact time of water droplets on the superhydrophobic surface, which is useful for the rebound of impacting water droplets. Increasing aspect ratio can increase the spreading range of water droplets, especially for hydrophilic surfaces. The evolution of impact force of ellipsoidal water droplets on superhydrophobic surfaces exhibits a double-peak feature. With increase of aspect ratio, the first peak of impact force is gradually decreased, while the second peak is gradually increased. The effect of surface wettability on the first peak of impact force is smaller. The feature of the second peak of impact force decreases with increase of surface wettability and finally disappears. Although water droplet with higher aspect ratio has smaller peak of heat transfer rate, the heat transfer between it and cold surface is greater than that with lower aspect ratio. The stronger the surface wettability, the more obvious this phenomenon is. For some applications where the rapid freezing of impacting water droplets is required, increasing aspect ratio of water droplets seems to be a good choice.
Microstructure, mechanical properties, and wear resistance of B-bearing high-speed steel (HSS) roll material containing 0.90-1.00% C, 1.3-1.5% B, 0.8-1.5% W, 0.8-1.5% Mo, 4.6-5.0% Cr, 1.0-1.2% V, and ...0.15-0.20% Ti were studied by means of the optical microscopy (OM), the scanning electron microscopy (SEM), x-ray diffraction (XRD), hardness, impact toughness, and pin-on-disk abrasion tests. The results showed that as-cast structure of B-bearing HSS consisted of α-Fe-, M
23
(B,C)
6
-, M
3
(B
0.7
C
0.3
)-, and M
2
(B,C)-type borocarbides, a small quantity of retained austenite, and a small amount of TiC. The hardness and impact toughness values of as-cast B-bearing HSS reached 65-67 HRC and 80-85 kJ/cm
2
, respectively. There were many M
23
(B,C)
6
-precipitated phases in the matrix after tempering, and then, with increasing temperature, the amount of precipitated phases increased considerably. Hardness of B-bearing HSS gradually decreased with the increasing tempering temperature, and the change of tempering temperature had no obvious effect on impact toughness. B-bearing HSS tempered at 500 °C has excellent wear resistance, which can be attributed to the effect of boron.
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