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Owing to the existence of high-order motion parameters and vertical velocity, severe range-azimuth coupling and two-dimensional spatial variability of the imaging parameters degrade the image quality of high-squint synthetic aperture radar (SAR) mounted on manoeuvring platforms. To accommodate these issues, a novel sub-aperture SAR imaging algorithm based on keystone transform (KT) and azimuth sub-region deramp is proposed. In the range dimension processing, a correction function is constructed based on the scene centre to realise non-spatial-variant range cell migration (RCM) correction and range-azimuth decoupling, and then the residual spatial-variant RCM is removed by the KT. In the azimuth dimension processing, considering the impact of the range distortion on the azimuth modulated phase, accurate analytical formula of the signal in the azimuth time domain is deduced. On this basis, a fast azimuth compression method based on the azimuth sub-region deramp is proposed, and the theoretical effective imaging area is analysed. The theoretical analysis and the simulations show that the proposed imaging algorithm has high computational efficiency and can effectively expand the imaging area of high-squint SAR mounted on manoeuvring platforms.

Occurrence of various travel trajectories poses a challenge in synthetic aperture radar (SAR) imaging. A method is proposed to solve this problem. After distance compression, the range equation is ...

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 paper presents a new compact circular-polarized Huygens source antenna with low profile. A circular-ring that can generate electric and magnetic resonances is employed to complete this design. The operating principle of the Huygens source is introduced. The input power with 90° phased differences is provided by a coupled feeding system. A low profile with a thickness of $\mathbf{0.046}\ \lambda_{\mathbf{0}}(\lambda_{\mathbf{0}}$ is the wavelength in free space at the center work-frequency) is achieved. The -10 dB operating bandwidth is 3.7%, which covers 1.57 GHz to 1.63 GHz. The fractional 3 dB axial ratio bandwidth is 2.75%. In addition, the maximum gain and the half-power beamwidth are 2.85 dBi and 128°, respectively. Finally, good simulated performances validate this concept.

A compact circular-polarization discriminator is presented in this paper. The proposed structure is composed of three simple layers, which are connected by air spacers. The first and third layers act as circular polarisers (CPs), and the second one is a linear polarizer (LP). By combing the three layers together, the right-handed circularly-polarized wave (RHCPW) can be reflected, while the left-handed circularly-polarized wave (LHCPW) can be transmitted through the proposed structure. Within the operating band, the insertion loss is lower than 2.5 dB. Finally, the proposed design is validated by both simulated and measured results.

Traditional imaging algorithms of uniform motion SAR are not suitable for maneuvering imaging. Time-domain algorithm is too computational to be suitable for realtime imaging. Frequency domain algorithm mainly relies on the solution of two-dimensional spectrum. It is usually suitable for SAR imaging in a single motion mode, and its applicability is poor. A maneuvering SAR imaging algorithm based on the separation of azimuthal motion information is proposed. The algorithm breakes through the limitation that the traditional frequency domain imaging algorithm can only be applied to a single motion state. Through simulation, the applicability of the algorithm in the traditional uniform motion, three-dimensional uniform motion, three-dimensional uniform acceleration motion and other motion states is verified. The algorithm is simple, stable and applicable.

In this paper, a new kind of composite continuous wave signal modulated by pseudorandom code family is designed aiming at solving the problem of group targets resolution with high dynamic: more quantity, larger speed variation, larger distribution and higher resolution. With a thumbtacked ambiguity, the new composite signal retained the advantage of pseudo code signal with high 2 dimensional resolution of speed and range. Furthermore, a new single demodulation method is proposed for this modulated signal. This method brings the characteristic of multi-resolution for the composite signal. Single demodulation method has been proved to be feasible through the correlation analysis and fuzzy characteristics analysis of sub-signal from the composite signal. Meanwhile, the realization process of signal multiresolution is illustrated by an example. At last, recommendations pertaining to signal selection, number option and usage are put forward for this signal modulated by pseudo-code family and this single demodulation method. The study of this paper is helpful for group targets resolution and is also of great importance to improve complex waveform design and performance.

For the impacting-freezing process of the droplet on cold surfaces, more studies have focused on stationary surfaces, while moving surfaces have received less attention. Here, a three-dimensional numerical model based on the VOF model and the Solidification/Melting model is established to numerically study the impacting-freezing process of the droplet on a lateral moving cold superhydrophobic surface, and focusing on the morphology evolution of the droplet and the initial freezing location. For the lateral moving surface, five different morphology distributions were observed during the impacting-freezing process of the droplet: full rebound, near full rebound, partial rebound, near full adhesion and full adhesion. The initial freezing location of the droplet preferentially appears on the upstream side of the droplet. The freezing on the downstream side of the droplet lags behind that of the upstream side due to the cooling effect of the cold surface, and the lagging effect is strongly influenced by the cold surface temperature. Moreover, the effects of cold surface temperature, supercooling degree and impacting Weber number on the spreading factor during the impacting-freezing process of the droplet are also discussed. The effect of the cold surface temperature on the spreading factor is greater than that of the supercooling degree. And a unified morphology distribution map of rebound and adhesion of the droplet is plotted based on the weighted average temperature and the impacting Weber number, which can show the competitive relationship between droplet impact hydrodynamics and droplet solidification.

A two-dimensional Lattice Boltzmann model was established to study the dynamic physical process of frost growth on a cold flat surface. It is verified that the theoretical results are in good agreement with the experiment data with better accuracy. The frost morphology is explored by showing two-dimension density distribution with different cold surface temperatures. The results also include dynamic characteristics of frost properties such as thickness, deposition weight, volume fraction, density, temperature. According to the results, it is found that the nearer it is from the cold flat plate, the larger of frost crystal volume fraction and density are. The frost surface temperature increases rapidly at the early period of frosting and then increases gradually towards the triple point temperature of the water. The frost internal temperatures rise in a linear tendency with the frost thickness and decrease at the same frost layer location with frost growth. Super-saturation degree of moist air has non-negligible effect on frost growth parameters such as frost thickness, frost crystal deposition mass, frost deposition rate and frost crystal volume fraction.

A droplet can bounce in a short contact time after impacting on superhydrophobic surfaces (SHSs), which is of benefit to the applications like anti-icing, anti-frosting and self-cleaning. In this study, we numerically investigate the fast droplet bouncing induced by asymmetric spreading on the concave SHS with a trapezoidal cross-section and focus on the droplet morphology evolution and contact time variation. A preferential transport at the both sides of the droplet from the inclined part to the flat part will occur because of the concave structure feature. The droplet will exhibit asymmetric spreading behavior. Moreover, the effects of structure parameters and impact velocity on the droplet contact time are explored. Within this concave structure, the droplet contact time is less influenced by the impact velocity and more influenced by the structural parameters. The presence of the tangential momentum can enhance the droplet asymmetric spreading, but it is not always beneficial to the droplet contact time reduction. Therefore, there will be an optimal structure to achieve the minimum droplet contact time. A concave SHS structure with the structure width w = 1–1.2r and the inclination angle of 45° is a more desirable choice, which is expected to reduce the droplet contact time by 40~45%.

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 Lampetra japonicum, Lethenteron reissneri, and Petromyzon marinus for genes encoding trafs and ripks 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 traf and ripk 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 traf and ripk 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.

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&deg, 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 &deg, 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&middot, m&minus, 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%.

Serine protease inhibitors (serpins) are a large protein family that is involved in various physiological processes and is known to regulate innate immunity pathways. However, research for the functional study of serpins in lamprey is limited. In the present study, a serpin gene was cloned and characterized from Lampetra japonica at molecular, protein and cellular levels, named L-serpin which belongs to family F serine protease inhibitors (serpin family). The L-serpin includes a serpin domain in the N-terminus. The mRNA transcript of L-serpin was extensively expressed in kidney, supraneural body, intestine, liver, heart, gill and the highest expression in leukocytes. The mRNA expression level of L-serpin increased significantly after Vibrio anguillarum, Staphylocccus aureus and Poly I:C stimulation and dramatically peak at 8 h. It is demonstrated that the L-serpin protected cells from lethal Gram-negative endotoxemia through associating with inhibition of lipopolysaccharide (LPS)-triggered cell death and inflammatory factors expression. Surface plasmon resonance (SPR) and the microbe binding assay were used to determine that L-serpin interacts directly with LPS (KD = 6.14 × 10−7 M). Furthermore, we confirmed L-serpin is a major inhibitor of complement activation by inactivating lamprey-C1q protein (KD = 2.06 × 10−6 M). Taken together, these findings suggest that L-serpin is a endogenous anti-inflammatory factor to defend against Gram-negative bacterial challenge and involved in lamprey innate immunity.

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 m0 is measured, and a Lande 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.

The navigation, positioning and imaging of blind area (unknown area) has always been one of the research focuses in the field of unmanned and intelligent development. It is known that the choice of the grid where the sub-images are computed is a key point of the fast factorized back projection (FFBP, can be adopted to obtain images with arbitrary trajectories) algorithm. The grid partition of blind area may result in the loss of information in the imaging area due to the unpredictability. The same loss also exists when the angle of existence deviates from the ideal imaging angle. In this paper, a new echo signal processing method for blind area imaging of synthetic aperture radar (SAR) is proposed. It is presented that a method of describing irregular echoes by using generalized array. The definition and operation principle of generalized array are introduced, as well as the relationship between the echo described by generalized array and traditional echo. Finally, the simulation results show that the proposed method is beneficial to imaging processing, and the method has great significance to range migration correction in frequency domain and imaging grid generation of BP algorithm.

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.

In this paper, we design and prepare five kinds of high-boron high-speed steel roll materials. The microstructure, mechanical property and wear resistance of high-boron high-speed steel roll materials were studied by means of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and hardness measurement, impact test and abrasion test. The results show that as-cast microstructure of high-boron high-speed steel consists of martensite, retained austenite and borocarbide. Hardness of as-cast high-boron high-speed steel excels 64 HRC. In unmodified high-boron high-speed steel, eutectic borocarbide is distributed in a network along the grain boundary. With the addition of RE-Mg-Ti compound modifier, the networks of borocarbide is broken. The hardness of high-boron high-speed steel gradually decreased with the increase of tempering temperature. Under the same conditions, the impact toughness of unmodified high-boron high-speed steel roll material is slightly lower than that of modified steel. The wear resistance of modified high-boron high-speed steel roll material is greater than that of high-carbon high-vanadium high-speed steel roll.

We investigate the re-entrant tetragonal phase in the iron-based superconductor Ba 0 .76 K 0.24 Fe 2 As 2 by DC magnetization and thermoelectrical measurements. The reversible magnetization confirms by a thermodynamic method that the spin alignment in the re-entrant C 4 phase is out-of-plane, in agreement with an itinerant double- Q magnetic order [Allred et al., Nat. Phys. 12 , 493 (2016)]. The Nernst coefficient shows the typical unusually large negative value in the stripe-type spin density wave (SDW) state owing to the Fermi surface reconstruction associated with SDW and nematic order. At the transition into the re-entrant C 4 tetragonal phase it hardly changes, which could indicate that instead of a complete vanishing of the associated charge order, the spin reorientation could trigger a redistribution of the charges to form a secondary charge order, e.g. in form of a chequerboard-like pattern that no longer breaks the rotational C 4 symmetry.

We fabricate high-mobility p-type few-layer WSe_{2} field-effect transistors and surprisingly observe a series of quantum Hall (QH) states following an unconventional sequence predominated by odd-integer states under a moderate strength magnetic field. By tilting the magnetic field, we discover Landau level crossing effects at ultralow coincident angles, revealing that the Zeeman energy is about 3 times as large as the cyclotron energy near the valence band top at the Γ valley. This result implies the significant roles played by the exchange interactions in p-type few-layer WSe_{2}, in which itinerant or QH ferromagnetism likely occurs. Evidently, the Γ valley of few-layer WSe_{2} offers a unique platform with unusually heavy hole carriers and a substantially enhanced g factor for exploring strongly correlated phenomena.

We fabricate high-mobility p-type few-layer WSe_{2} field-effect transistors and surprisingly observe a series of quantum Hall (QH) states following an unconventional sequence predominated by odd-integer states under a moderate strength magnetic field. By tilting the magnetic field, we discover Landau level crossing effects at ultralow coincident angles, revealing that the Zeeman energy is about 3 times as large as the cyclotron energy near the valence band top at the Γ valley. This result implies the significant roles played by the exchange interactions in p-type few-layer WSe_{2}, in which itinerant or QH ferromagnetism likely occurs. Evidently, the Γ valley of few-layer WSe_{2} offers a unique platform with unusually heavy hole carriers and a substantially enhanced g factor for exploring strongly correlated phenomena.

We report measurements of the specific heat and electrical resistivity of $\mathrm{C}{\mathrm{a}}_{3}{(\mathrm{I}{\mathrm{r}}_{0.91}\mathrm{C}{\mathrm{o}}_{0.09})}_{4}\mathrm{S}{\mathrm{n}}_{13}$ in comparison to $\mathrm{C}{\mathrm{a}}_{3}\mathrm{I}{\mathrm{r}}_{4}\mathrm{S}{\mathrm{n}}_{13}$. The Co substitution was chosen to suppress the structural anomaly ${T}^{*}=38\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ reported in $\mathrm{C}{\mathrm{a}}_{3}\mathrm{I}{\mathrm{r}}_{4}\mathrm{S}{\mathrm{n}}_{13}$. While the superconducting transition temperature of $\mathrm{C}{\mathrm{a}}_{3}{(\mathrm{I}{\mathrm{r}}_{0.91}\mathrm{C}{\mathrm{o}}_{0.09})}_{4}\mathrm{S}{\mathrm{n}}_{13}$ is slightly higher than in the stoichiometric parent compound $\mathrm{C}{\mathrm{a}}_{3}\mathrm{I}{\mathrm{r}}_{4}\mathrm{S}{\mathrm{n}}_{13}$, and it displays a stronger superconducting coupling strength, the absence of a structural phase transition allows us to determine the spectral distribution of phonon states and its relation to superconductivity. The phonon density of states $F$(\ensuremath{\omega}) and the spectral electron-phonon scattering function ${{a}_{tr}}^{2}F(\ensuremath{\omega})$ are determined by deconvolution of the specific heat and electrical resistivity, respectively. A dominant mode appears in both histograms at $\ensuremath{\hbar}\ensuremath{\omega}=12\phantom{\rule{0.16em}{0ex}}\mathrm{meV}$, which indicates that this phonon mode is responsible for the superconductivity in $\mathrm{C}{\mathrm{a}}_{3}{(\mathrm{I}{\mathrm{r}}_{0.91}\mathrm{C}{\mathrm{o}}_{0.09})}_{4}\mathrm{S}{\mathrm{n}}_{13}$. The data suggest that superconductivity in this material class can be conclusively explained within a conventional strong -coupling phonon-mediated scenario.

The hole doped Fe-based superconductors $\mathrm{B}{{\mathrm{a}}_{1}}_{\ensuremath{-}x}{A}_{x}\mathrm{F}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2}$ (where $A=\mathrm{Na}$ or K) show a particularly rich phase diagram. It was observed that an intermediate reentrant tetragonal phase, in which the ${C}_{4}$ fourfold rotational symmetry is restored, forms within the orthorhombic antiferromagnetically ordered stripe-type spin density wave state above the superconducting transition [S. Avci et al., Nat. Commun. 5, 3845 (2014); A. E. B\"ohmer et al., Nat. Commun. 6, 7911 (2015)]. A similar intermediate phase was reported to appear if pressure is applied to underdoped $\mathrm{B}{{\mathrm{a}}_{1}}_{\ensuremath{-}x}{\mathrm{K}}_{x}\mathrm{F}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2}$ [E. Hassinger et al., Phys. Rev. B 86, 140502(R) (2012)]. Here we report data of the electric resistivity, Hall effect, specific heat, and the thermoelectric Nernst and Seebeck coefficients measured on a $\mathrm{B}{\mathrm{a}}_{0.85}{\mathrm{K}}_{0.15}\mathrm{F}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2}$ single crystal under pressure up to 5.5 GPa. The data reveal a coexistence of the intermediate phase with filamentary superconductivity. The Nernst coefficient shows a large signature of nematic order that coincides with the stripe-type spin density wave state up to optimal pressure. In the pressure-induced intermediate phase the nematic order is removed, thus confirming that its nature is a reentrant tetragonal phase.

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-, M23(B,C)6-, M3(B0.7C0.3)-, and M2(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/cm2, respectively. There were many M23(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.

The effects of quenching temperature on microstructure and performance of Al-bearing cast boron steel (ACBS) containing 0.25–0.45%C, 1.5–1.8%B and 1.4–1.6%Al were investigated by means of the optical microscopy (OM), the scanning electron microscopy (SEM), X-ray diffraction (XRD), Rockwell hardness and Vickers micro-hardness tester. The results show that the solidification structures of cast steel consist of high hardness boride, ferrite, pearlite and a small quantity of martensite when 1.5–1.8%B and 1.4–1.6%Al are added into the carbon steel. The metallic matrix of ACBS changes into single martensite from the mixed structure of ferrite, pearlite and martensite along with the increase of quenching temperature. The increase of quenching temperature also leads to the transformation of boride from continuous shape to isolated shape. Moreover, the micro-hardness of matrix and macroscopical hardness increase with the increase of quenching temperature. When the quenching temperature excels 1000°C, the hardness has a slight decrease. ACBS has good comprehensive properties after heat treatment at 1000°C.

We demonstrate that encapsulation of atomically thin black phosphorus (BP) by hexagonal boron nitride (h-BN) sheets is very effective for minimizing the interface impurities induced during fabrication of BP channel material for quantum transport nanodevices. Highly stable BP nanodevices with ultrahigh mobility and controllable types are realized through depositing appropriate metal electrodes after conducting a selective etching to the BP encapsulation structure. Chromium and titanium are suitable metal electrodes for BP channels to control the transition from a p-type unipolar property to ambipolar characteristic because of different work functions. Record-high mobilities of 6000 $cm^2V^{-1}s^{-1}$ and 8400 $cm^2V^{-1}s^{-1}$ are respectively obtained for electrons and holes at cryogenic temperatures. High-mobility BP devices enable the investigation of quantum oscillations with an indistinguishable Zeeman effect in laboratory magnetic field., Comment: 14 pages, 3 figures