Search

Beam scanning antenna brings new opportunities to reduce the data collision of multi-node communication in the Internet of Things (IoT). This paper proposes a new type antenna design scheme that can be used for IoT relay communication. A programmable beam scanning antenna without phase shifters operating in the X-band is designed to evaluate the feasibility of this scheme. The integrated design of excitation source and phasemodulated structure greatly reduces the profile of the antenna and improves the integrated degrees of freedom with other equipment. By switching the state of the PIN diode loaded on each element, different radiators can be selected and the direction of current polarization on elements can be adjusted to change the radiation phase. Furthermore, the diode states are encoded by the holographic antenna theory and controlled by the FPGA controller to realize programmable beam scanning. One element, two-element and 1-D array containing 32 elements are fabricated and measured. Experimental results are in good agreement with the simulation data. The operating bandwidth is 7.5% at 10GHz while the beam scanning range of the array is -60∘ 60∘, with a good scanning accuracy and stability. The proposed low-profile beam scanning antenna can provide stable communication services to multiple users and smart devices as a new type of beam scanning array antenna solution for the IoT application, which is beneficial to this field.

In this paper, a broadband tri-polarization reconfigurable antenna applied to polarization diversity is proposed. A partially reflective surface (PRS) is designed to form an air-filled resonator cavity. The reflection phase of the PRS has a positive phase gradient in order to achieve the characteristics of the proposed antenna gain enhancement in the wideband. A metal patch of a four-arm meander structure is used as the radiation structure and the feeding is realized through a four-channel rotating feeding network with equal amplitude and 90∘ phase difference. The feeding network is connected to the radiation structure through four metallized vias. In order to realize the polarization reconfigurability, the PIN diodes and the corresponding DC bias circuit are integrated in the rotating feeding network. The characteristics of horizontal polarization (HP), vertical polarization (VP) and right-hand circular polarization (RHCP) are realized by changing the ON/OFF states of PIN diodes integrated in the feeding network. In order to verify the performance of the proposed antenna, fabrication and testing were carried out. The measurement results show that the -10 dB impedance bandwidths of HP, VP, RHCP are 11% (12.5-14 GHz), 6.4% (13.7-14.6 GHz) and 20% (12.2-14.9 GHz), and the peak realized gains are 9.1, 9.2 and 11.5 dBi, respectively. For RHCP mode, the 3-dB axial ratio bandwidth reaches about 17% (12.35-13.4 GHz and 13.6-14.9 GHz).

The implantable antenna is an important part of the wireless capsule endoscopy (WCE) system to achieve wireless communication. This paper designed an ultra-wideband flexible implantable antenna for wireless capsule endoscopy system. With a very wide bandwidth, the antenna can completely cover the industrial, scientific, and medical frequency bands (ISM, 2.4-2.48 GHz) and Wireless Medical Telemetry Service (WMTS, 1.395-1.4 GHz). The expanded size of the proposed antenna is 18mm× 10mm× 0.1mm. The conformal technology of the antenna has further reduced the space of the system and achieved miniaturization. The capsule antenna in this paper is a compact planar monopole antenna fed by a coplanar waveguide, and it uses a flexible material as a dielectric substrate to achieve the conformal shape of the antenna. U-shaped ground branch (UGB) and a loaded split ring resonator (SRR) structure were used to further improve the antenna performance. Simulation and measurement results were basically the same. On the premise of radiation safety and miniaturization of the antenna, the ultra-wideband operation of the antenna was realized. This antenna design provided reference value for the design and application of the capsule antenna.

The available experimental self-diffusion coefficients of twenty-two liquid elements near their melting temperatures are compared with the calculated data by the first-principal dynamics simulation. The holistic evaluation shows that the calculated self-diffusion coefficients are in reasonable agreement with the experimental data. For liquid metals with loose-packed structure, the self-diffusion coefficient decreases in general with the increase of packing fraction. For liquid metals with close-packed structure in which the coordination number is larger than 11.5, the self-diffusion coefficient fluctuates around 2.0×10-9 m2s-1, except for liquid Al, Ti and Li of which the self-diffusion coefficients are anomalously large. The packing fraction can only partially account for the self-diffusion coefficient of liquid metals.

The origin of β-relaxation in metallic glasses is still not fully understood, and the guidance of slow atoms for caged dynamics and β-relaxation is rarely mentioned. Using molecular dynamics simulations, we reveal the bridging role of slow atoms on unusual caged dynamics and β-relaxation. In the stage of unusual caged dynamics, slow atoms are bounded by neighboring atoms. It is difficult for the slow atoms to break the cage, producing more high-frequency vibration, which causes more atoms to jump out of the cage randomly in the next stage. Precisely, the movement of the slow atoms changes from individual atoms vibrating inside the cage and gradually breaking out of the cage into a string-like pattern. The string-like collective atomic jumps cause decay of the cages, inducing β-relaxation. This situation generally exists in binary systems with the large atomic mass difference. This work offers valuable insights for understanding the role of slow atoms in unusual caged dynamics and β-relaxation, complementing studies on the origin of β-relaxation in metallic glasses and their glass-forming liquids.

Understanding the mixing properties of liquids is important to design new materials; however, the mechanism of mixing effect is unclear. In this work, the mixing effect of Zr–Cu metallic liquids has been investigated via molecular dynamics simulations. Various mixing properties including mixing enthalpy, (ΔH m) mixing volume (ΔV m), mixing coordination number (ΔZ m) and mixing diffusion coefficient (ΔD m) are studied in this work. Remarkably, it is found that all the mixing properties (ΔP m) can be described by a common equation, ΔP m = [aP (T) + bP (T)* (c Zr − c Cu)]*c Zr*c Cu. In addition, it is found that all the fitting coefficients of aP (T) and most of bP (T) show a quadratic dependence of temperature. Moreover, it is found that ΔH m, ΔV m and ΔD m show linear correlations with each other at high temperatures, revealing close correlation between the thermodynamic and dynamic properties in metallic liquids. Our results are helpful to understand the mixing effects in metallic liquids.

International audience; Based on the time-temperature-transformation interpretation, a new criterion for glass forming ability, Z = [(Tx-Tg)/(Tl-Tg)][(Tl–Tl(c))/(Tl-Tg)]0.556, is proposed, where Tg, Tx, Tl and Tl(c) respectively denote the glass transition temperature, the onset crystallization temperature upon heating, the liquidus temperature and the onset solidification temperature of the liquid upon cooling. The Z parameter jointly considers the stability of the liquid and the devitrification of glassy phases. A non-linear relationship between the parameter Z and the critical glassy size dc has been found to be log (dc)cal = 0.1392 + 17.0616Z - 41.985(Z)2, showing stronger correlation than other earlier reported parameters. The advantage of using Z as a GFA parameter is that it roughly reflects the relative influences of the thermodynamics and kinetics of the systems on glass formation. In addition, the parameter describes the stability of liquid in the course of being quenched from above liquidus temperature.

Bond breaking related with plastic deformation in a deformed metallic glass Zr50Cu50 is investigated by molecular dynamics simulations. The results show that the spatial distributions of broken bonds are closely correlated with local shear strains, and the clustering behaviors of atoms with broken bonds (flow defects) are characterized with different stages of plastic deformation. The average distance among those clusters of flow defects decreases as the strains increase, which follows the curvature quadrupole model for flow defects in ideal amorphous solids. For the first time, the features of bond breaking processes are quantitatively measured with the chemical composition, bond length and orientation, bond pairs, local five-fold symmetry and quasi-nearest atoms, whose threshold values are important factors that could characterize the flow defects in metallic glasses under plastic deformation. The shape, orientation and energetics of flow defects quantitatively characterized by the bond breaking analysis thus facilitate our understanding on the deformation mechanisms in metallic glasses.

Other than Fe–based amorphous alloys, the atomic configurations of amorphous pure Fe exhibit abundant topological local structures and exclude chemical effects on the local magnetic moment of a Fe atom. We thus employed amorphous pure Fe to investigate the structural–magnetic properties relationship by ab initio molecular dynamics simulations. Our results showed that the decreased volume leads to a reduction of absolute values of both positive and negative magnetic moments, which agrees with earlier investigations. Further, we employed the minimum coordination polyhedrons with the coordination number of 5–10 to depict the local structures, and found that there is a strong correlation between the minimum coordination polyhedrons and local magnetic moments. The local magnetic moments increase with the coordination number of the minimum coordination polyhedron; the larger distortion of the minimum coordination polyhedron corresponds to larger average magnetic moments.

An attempt is carried out to design metallic glasses by modifying the local structure of icosahedral quasicrystals. A series of metallic glasses are prepared by introducing beryllium to the quasicrystal former, Zr40Ti40Ni20, and the maximum diameter of the glasses reaches 20 mm. A phase transformation diagram is constructed for the alloys of (Zr40Ti40Ni20)100-xBex, revealing the transition from stable crystal to quasicrystal and then to metallic glasses with the increased Be content. This study shows a connection between the formation of metallic glasses and the specific thermodynamics of the initially precipitated quasicrystals. Interestingly, both improvements in the forming ability for glasses and quasicrystals are observed over a wide composition range. Ab initio molecular dynamic simulations show the evolution of the structural features of the metallic melts for the optimised glass forming region, which guarantee the primary precipitation of quasicrystal.

Hydrogenation properties of two five-component Mg60Ce10Ni20Cu5X5 (X = Co, Zn) metallic glasses have been studied. Using high-pressure differential scanning calorimetery (HP-DSC) under hydrogen atmosphere and hydrogenation kinetics study, it is demonstrated that alloying with Zn shows negligible impact on the hydrogenation kinetics and storage capacity of the Mg Ce Ni Cu metallic glass, however, alloying with Co remarkably improves the hydrogenation kinetics and storage capacities. Apparent activation energies for hydrogenation are calculated to be 64.4 kJ/mol, and 107.2 kJ/mol, for the Mg60Ce10Ni20Cu5Co5 and Mg60Ce10Ni20Cu5Zn5 metallic glasses, respectively. Theoretical calculations are performed to understand the atomic structure of the five-component metallic glasses. It shows that the overall, Mg Mg pair and Mg Ni pair distribution functions (PDFs) of the Mg60Ce10Ni20Cu5Co5 and Mg60Ce10Ni20Cu5Zn5 metallic glasses are almost the same, indicating that geometry issue is not a key factor on influencing the hydrogenation properties of the studied Mg-based metallic glasses. It is proposed that chemical composition is the key to improve the hydrogenation properties of Mg-based metallic glasses.

The atomic structures of Zr50Cu50 metallic glasses (MGs) under high pressures from 0 GPa to 150 GPa are investigated via molecular dynamics simulations. We found that as pressure and density increase, local structural parameters such as coordination number, five-fold symmetry and quasi-nearest atom reach maxima (or minima) at 60 GPa, rather than monotonous pressure dependence. Atomic structure analyses uncover unexpected shortening of Zr-Zr bonding of Zr50Cu50 MGs under high pressures, responsible for the change of atomic packing in Zr50Cu50 MGs from dense to loose while pressure increasing. Furthermore, composition segregation is observed at high pressures, resulted from the new finding that the Zr-Zr and Cu-Cu bonding are much easier to decrease than Zr-Cu under high pressures. The results help to understand the behaviors of metallic glasses under extreme conditions.

We observed the transition of medium-range orders (MROs) and physical properties in liquid Fe–Al alloys by using ab initio molecular dynamics simulation. Above 66 at. % Al, only Fe–Fe MRO exists, while in other binary Fe–Al alloys studied Fe–Fe and Al–Al MROs coexist, and below 50 at. % Al, Al–Al MRO turns to be dominant. The curve of short-range order around Fe atoms versus Al content also shows a juncture at 66 at. % Al above which polyhedron type increase significantly, correspondingly a significant decrease of the average magnetic moment per Fe atom is observed. In addition, the self-diffusion coefficient of Al atom increases sharply above 66 at. % Al.

The atomic structure and corrosion behavior of Fe87-xB13Nbx (x = 0, 7, 10 and 13) metallic glasses were investigated using various experimental techniques and simulations. The netlike (Fe, Nb)23B6 structure units, which took root in the Nb-contained amorphous matrix, emerged after annealing and raised markedly corrosion resistance of as-spun amorphous samples as cNb > 7 at.%, such as the occurrence of wider passive platform in the potentiodynamic polarization plots and the transformation from the porous holes to stable passive films on corrosion surfaces.

Rejuvenation is the structural excitation of metallic glasses that can significantly increase the enthalpy and free volume. Here, the rejuvenation in Zr46Cu46Al8 metallic glasses with pressure preloading was studied by molecular dynamics simulation. As the strain gradually increases, high-density deformation units in different regions are formed in the rejuvenated Zr46Cu46Al8 metallic glass with pressure preloading, but they do not form the shear bands that cause brittle fracture. In terms of the microstructure, the pressure preloading increases the degree of the short range order, but decreases the medium range order. 3-atom connections in the medium range order of icosahedra and other clusters are proposed to represent the level of rejuvenation. The decrease of 3-atom connections in the medium range order can lower the energy barrier and decrease the elastic modulus, improving the level of the rejuvenation. With the weakening of the 3-atom connections, the rejuvenated metallic glass possesses the features of high density, high energy, high Poisson's ratio, high defects and low localization. These findings open an avenue to evaluate the level of rejuvenation and provide a strong foundation for metallic glass design. Keywords: Metallic glass, Rejuvenation, Pressure, Plasticity, Molecular dynamic simulation

In this paper, we present a frequency reconfigurable microstrip array antenna with four PIN diodes. The 1x4 microstrip array antenna is designed by combining the microstrip patch antennas that connected by quarter-to-four power-division feed network. Four PIN diodes are integrated in each element of the microstrip array antenna. By controlling the on and off of the four diodes at the same time, the microstrip array antenna can exhibit radiation characteristics with reconfigurable frequencies. When diodes are turn off, the operating frequency band of the antenna is 12.1-12.SGHz with the maximum radiation gain of 11.8dB. When the diode is turn on, the operating frequency band of the antenna is 13.1-13.8GHz, the maximum radiation gain is 11.6dB. The frequency reconfigurable microstrip array antenna we designed has good frequency control performance at dual-band frequency, that it is guiding significance for the reconfigurable design of the array antenna. And there is a wide range of application prospects.

With the advantages of low profile, light weight, flexible design and low cost, metasurface reflectors are widely used in beam control, polarization transformation and RCS Reduction. In this paper, the influence of element reflection phase deviation on the pattern of beam deflection metasurface reflector array is simulated and analyzed. It is concluded that the general phase deviation will only affect part of the array elements, not the main deflection direction and gain of the array pattern, but will slightly increase the side lobe.

The antenna is an important component to realize the wireless communication between the wireless capsule endoscope system inside the human body and the outside world. This paper designs an ultra-wideband conformal capsule antenna with the volume of 18mm3, which uses in wireless capsule endoscopy systems. The antenna is a coplanar waveguide-fed compact planar slotted microstrip antenna, which uses flexible materials to achieve conformal antennas, and is used in the industrial, scientific, and medical frequency bands of 2.45-2.48 GHz (ISM). Under the premise of satisfying radiation safety, while ensuring the performance of the antenna, the ultrawideband operation of the antenna is realized with a bandwidth of 108.9%, and the gain of the antenna at 2.45GHz is −25.4dBi. The research results provide an important reference for the development and application of conformal capsule antennas.

A biplanar microstrip quasi-Yagi antenna at 5.8GHz is proposed with novel directors to adjust the beam tilt angel. Different from directors in other directional microstrip yagi antenna which are placed with the spacing of 1/4λ 0 along the radiation direction, the directors we present are made up with a bending strip and a rectangular patch to reduce the size of the antenna and enlarge the beam tilt angle. Optimized antenna provides 4.45dBi gain with beam tilt angle of 45°. The -10dB impedance bandwidth covers from 5.3 to 6.0GHz about 12% relatively. The size of the yagi antenna is 42mm×38mm×1.575mm, and total efficiency over the operating band is above 87%. The compact antenna is suitable for a non-endfire directional wireless communication.

A ridged TEM horn wideband antenna is designed to operate in the VHF band. Inspired by the fishtail structure and the classic ridged structure, the antenna's operating bandwidth at low frequencies is extended through a unique curved structure design. Compared with the conventional TEM horn antenna, the antenna designed in this paper achieve stronger directivity and widened frequency by using a unique shape structure and dielectric loading technology. Furthermore, we optimize the main structural parameters of the antenna. It can be seen from the simulation results that the antenna satisfies S11 less than -10dB in the ultra-short wave VHF operating frequency range 65 ~ 308MHz, and the antenna's radiation pattern and gain are wonderful. The result indicates that the antenna has potential for application in ultra-short wave systems.

A dynamically tunable metasurface element in the K-band is proposed. The element consists of a circular complementary resonator patterned into the upper microstrip line and excited through by guided waves. Different from the rectangular resonator, the introduction of the circular structure increases the current distribution area on the resonator, which can reduce the ohmic loss on the element, therefore improves the radiation efficiency. By loading PIN diodes on the element, the dynamic reconfigurability of the element and the combination of abilities of radiation and adjustment are achieved. No external excitation antenna is required, which facilitates low-profile design. This element can be used to design RF devices such as reconfigurable metasurface antennas, and has potential application prospects in dynamic beam-forming, microwave imaging, and security screening.

This paper proposes a cable bundle simplification modeling method to analyze the motor drive system’s radiated electromagnetic interference(EMI). Firstly, the common-mode interference mechanism and propagation is established. Then, the key components’ models in conducted interference path are explored. After that, each part circuit model of interference source and key components are connected on the basis of the system’s actual combination and the radiated EMI prediction model is obtained. Finally, a numerical simulation method is applied to validate the proposed prediction model.

A small and compact CPW-fed dual-frequency implantable antenna with a size of 10mm × 10mm × 1.27mm is designed for medical telemetry. The antenna is used for medical implant communication services (MICS) Frequency band (402 ~ 405MHz) and Wireless Medical Telemetry Service (WMTS) frequency band (1.427 ~ 1.432GHz). The use of a high dielectric constant and a folded meandering monopole structure reduces the size of the antenna. On the premise of meeting the SAR value standard, both the size is reduced, and a high gain is obtained. The gains at the resonant frequencies in the two frequency bands are -31.68dBi and -17.98dBi, respectively, ensuring the performance of the antenna. The research results provide an important reference for the development and application of implantable antennas.

We reassessed the structural transition regions along the liquidus of Fe–Si alloys by using ab initio molecular dynamics simulation. Except for 50 at.% Si, structural transition compositions are found at both 30 at.% Si and 67 at.% Si (FeSi2) which are eutectic alloys. We demonstrated that the liquid structure in the sub-region of 0∼30 at.% Si is close-packed, and in the sub-region of 67∼100 at.% Si liquid alloys have very open structure. From 30 at.% Si to 67 at.% Si, the close-packed structure gradually change into open one. These structure transition sub-regions are also supported by the formation enthalpy of liquid alloys. Furthermore, the predicted enthalpy change between 1585 K and 1873 K is so large that there is probably liquid–liquid transition with temperature at FeSi2 alloy which is an important thermoelectric material. Discussions have been made on the materials phenomenon of several Fe–Si alloys based on the structural information.

In practical engineering, impedance surface design can be carried out by selecting impedance units with corresponding characteristics according to the function and the performance requirements of microwave RF modules. Therefore, firstly, the paper analyzes the structure and the electromagnetic modulation principle of the metasurface, designing three different types of impedance units, and extract the dispersive curves corresponding to different parameters of impedance units. Secondly, to analyze the influence of dispersion characteristics on surface waves propagation, and extract the impedance curves of three kinds of impedance units based on them. The three impedance units are designed to have different application scenarios, which has direct guiding value for the application of impedance units, and has good application prospects in the fields of planar lens and impedance surface holographic antenna design as well as microwave imaging systems.

Structural and bonding transformation of the Al0.67CrCoFeNi high-entropy alloys (HEA) during quenching is investigated by molecular dynamics simulations. At a high cooling rate, some short-ranged ordered clusters, such as FCC, HCP and BCC crystalline clusters are already present in the almost amorphous HEAs. When the cooling rate decreases, the atoms become packed more orderly and ultimately form a nano-polycrystalline structure dominated by FCC structures. The BCC structures appear only as an intermediate state acting on the course of crystallization, while the HCP structure can be viewed as the precursor of the malposed FCC structure due to the identical first neighbor distances. In liquid HEAs, the low-symmetry and low-coordination bond pairs, either transform to high-symmetry and high-coordination 1551 bond pairs, or transform to 1(5,4)41 bond pairs for FCC structure and 1661 bond pairs for an HCP structure, depending on the cooling rates. This study will contribute to a better understanding of the essential phase change in HEAs.

Minor alloying addition of Ag improves the hydrogen storage capacity and reduces the dehydrogenation temperature of the amorphous Mg65Cu25Y10 alloy. Hydrogen storage capacity is increased from 2.1 wt% to 3.2 wt% when substituting Mg by only 1 at% of Ag. After hydrogenation, the amorphous Mg-Cu-Y(-Ag) alloys decompose into two types of sites for hydrogen occupations: i.e. a new amorphous Mg-Cu(-Ag) hydride clusters and YH3 nanocrystals. This study shows a simple method to tailor hydrogen storage properties of amorphous Mg65Cu25Y10 alloy.

The quasi-crystal-forming alloys with adjustable compositions were prepared by element-addition to a pre-existing pure quasi-crystalline system. The protocol alloy Zr40Ti40Ni20 was chosen as the parent alloy, and beryllium was used as the additive element. The quasi-crystal forming ability was found to be enhanced with Be content within a wide composition range of (Zr40Ti40Ni20)100-xBex (0 ≤ x ≤ 16). A maximum size of up to 10 mm in diameter of pure quasi-crystalline rod was attained at a composition of (Zr40Ti40Ni20)84Be16. Structural analyses show that Be-addition continuously reduces the interplanar spacing. The mechanism of the enhanced quasi-crystal forming ability was also discussed.

In this paper, a novel decoupling technique both in pattern diversity (PD) and defected ground structure (DGS) is proposed for planar Yagi multiple-input multiple-output (MIMO) antenna arrays. The proposed planar Yagi antenna (PYA) is composed of two symmetrical printed dipoles and U-/V-shape directors. Based on the redirection effect of the directors, the desired pattern diversity and isolation improvement are achieved. DGS is added outside the excitation dipoles for closely packed elements, which achieves decoupling and better impedance matching. Through the whole frequency bandwidth (5.5–6.1 GHz), the mutual coupling between two-ports Yagi antenna elements is lower than −25 dB, and the stable gain is above 8 dBi with the variation of 1 dBi. Moreover, the validation of the proposed decoupling method is carried out on three and four-ports MIMO antenna arrays. By combining two kinds of directors and asymmetric DGS, the imbalance problem of the multi-port antennas is solved. The simulated and measured results validate the effectiveness of PD-DGS in MIMO directional antenna systems with high isolation and gain for 5.8 GHz WLAN application.

The atomic dynamics of a Zr50Cu50 metallic glass-forming liquid has been investigated in isothermal compression by using molecular dynamics simulations. It is found that the mean square displacement (MSD) for Zr is unexpectedly larger than that for Cu under super-high pressures. This interesting result challenges our understanding that the Cu atoms are always faster than Zr atoms in normal liquids, suggesting that the atomic dynamics for Zr becomes extraordinary under super-high pressure. We found that the shorter-bonded Zr atoms can be formed under-super high pressure because of the remarkable softness of Zr-Zr bonding ways. Further studies suggest that this special local structure is responsible for the unexpected atomic dynamics of Zr. These results shed light on the understanding of the inimitable dynamics in Zr-based metallic glass-forming liquids under super-high pressure.

The correlation between local structures and dynamics of the central Al atoms of the icosahedral clusters in the Al90Sm10 super-cooled liquid was investigated by classic molecular dynamics simulations. Three typical order parameters (i.e. the chemical composition, cluster penetration, and quasi-nearest atom) of the Al-centered icosahedral clusters were calculated and we demonstrated that the correlation between each of these parameters and dynamic propensities of the central Al atoms of the icosahedral clusters is weak. Then a simple combined parameter including these three parameters was proposed and it is found that there is a strong correlation between this new parameter and dynamic propensities of the central Al atoms of the icosahedral clusters. The present observations imply that the dynamic property of icosahedral clusters was mainly determined by multiple structural features of local structures. Our results are helpful to understand the relationship between atomic structures and dynamics in super-cooled liquids.

In this paper, the gradient elliptical slots (ES) are designed to enhance the operating bandwidth of the Vivaldi antenna (VA) in the relatively low frequency band. The antenna EVA is implemented by integrating the elliptical slots to the edge of the VA, which extends the low frequency operating point from 7.4 GHz to 5.4 GHz while obtaining the miniaturized design of the antenna. To address the problem of the gain deterioration, we design ultra-wideband metasurface lens (ML) and integrate it into the aperture of the EVA. The lens has a simple structure that can perform dual polarization modulation on electromagnetic waves. The propagation path of the electric field at the aperture of the EVA loaded with the ML is extended, and the electric field behaves more planar. We simulate and analyze the conventional VA, EVA, and ML integrated EVA (MLEVA). The VA and the proposed MLEVA are fabricated and measured. The results match those of the simulations. The operating bandwidth of the proposed antenna is 5.4–18 GHz that has been expanded compared with the VA. And the gain has increased by approximately 0.3–3.2 dB without changing the overall antenna sizes. The sidelobe level is significantly reduced at the same time. Generally, miniaturization and performance enhancement of the VA is achieved in the proposed MLEVA.

The structural evolution of liquid Mg–Al alloys has been investigated with composition variation from pure Mg to Al at 973 K using ab initio molecular dynamics simulation. The local structures are characterized in terms of pair correlation functions, coordinate numbers, and bond pairs. The atomic interactions are evaluated by the electronic structures to reveal the formation mechanism of the liquid structures. As a result of the fact that the formation of Mg–Al bonds is actually restrained by Al–Al bonds with lower energy, the initial local structures around Mg trend to be maintained as the fragments during the structural evolution, and the discrete Al atoms transforms to be segregated around Mg in the composition region from 18.75 to 31.25 at.% Al. Based on these structural characteristics, the liquid structures are modeled as the Al bonded networks surrounding Mg fragments. Further, the dynamical properties are reflected by the self-diffusion coefficients. The results show that the diffusion of Mg atoms is actually limited by Al bonded networks, which confirm the reliability of the model. It is also worth expecting that the structure model may provide a new viewpoint for further study on the complex metallic alloys in solid Mg–Al system.

Athermal quasi-static compressive deformation for a model metallic glass is investigated by molecular dynamics simulations. A new structural parameter, quasi-nearest atom (QNA), is used to characterize local atomic packing of initial structure. We find that regions with higher nonaffine displacement have more atoms with more QNA. The coarse grained number of QNAs exhibits significant spatial heterogeneities and these structural fluctuations show close correlation with the nonaffine displacement. The correlation between the coarse grained number of QNA and nonaffine displacement does not decrease as the strain increases but show the maximum at a certain strain, indicating that strain localized regions are activated individually. Therefore, our results provide a direct evidence of the correlation between atomic structure and deformation in metallic glass.

The mechanism of refinement of eutectic Si with Sb additions in an Al–10 wt.% Si alloy is studied. The increased holding time designates a transition of the eutectic nucleation temperature from a decreased value to an increased one, accompanied by a morphological transformation of eutectic Si from lamellar to a shorter, rod-like shape. By ab initio molecular dynamics simulation, the chemical short-range order of −0.002 demonstrates weak affinity in the Al–Sb pair, which does not favor the existence of AlSb clusters in the melts. Sb–Sb segregation and the Sb–Si repulsive force are revealed, which promote the formation of Al-enriched precursors and the accumulation of Si atoms adjacent to precursors, inducing precursor nucleation. Continuous attachment of precursors and individual Si atoms during Si growth results in the high number-density nano-particles and suppresses the formation of twin grains within eutectic Si. Keywords: Al–Si alloys, High number-density nano-particle, Precursor-assisted nucleation, Atomic structure, Eutectic Si refinement