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High-pressure phase diagrams of the La–N binary system were systematically constructed using the CALYPSO method and first-principles calculations. In addition to the pressure-induced La–N compounds reported previously, we have uncovered a hitherto unknown LaN9 structure in Pm3¯ symmetry stabilized within a narrow pressure range of 20–24.5 GPa. Notably, LaN9 stands as the first thermodynamically stable metal nine-nitrogen compound, featuring centrosymmetric linear N3 anion units and an edge-sharing LaN12 icosahedron. Charge transfer between the La and N atoms plays a crucial role in facilitating structural stability. Furthermore, we identified a novel Cm phase for LaN8, which has a lower enthalpy compared to the previously reported phase. N atoms in Cm LaN8 are polymerized into infinite N∞ chains. Calculations demonstrate the potential recoverability of LaN9 and Cm LaN8 under atmospheric conditions while preserving their initial polynitrogen configuration. From the perspective of detonation pressure and detonation velocity, LaN9 and Cm LaN8 exhibit excellent explosive performance in comparison to TNT and HMX, with estimated energy densities of 0.9 and 1.54 kJ g−1, respectively, indicating their potential utility as high-energy-density materials. [ABSTRACT FROM AUTHOR]

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Let L n (x) denote the largest digit of the first n terms in the Lüroth expansion of x ∈ (0 , 1 ]. Shen, Yu and Zhou, A note on the largest digits in Luroth expansion, Int. J. Number Theory 10 (2014) 1015–1023 considered the level sets E (γ) = x ∈ (0 , 1 ] : lim n → ∞ log L n (x) log n = γ , γ ≥ 0 , and proved that each E (γ) has full Hausdorff dimension. In this paper, we investigate the Hausdorff dimension of the following refined exceptional set: E (α , β) = x ∈ (0 , 1 ] : liminf n → ∞ log L n (x) log n = α , limsup n → ∞ log L n (x) log n = β and show that E (α , β) has full Hausdorff dimension for each pair (α , β) with 0 ≤ α < β ≤ + ∞. Combining the two results, (0 , 1 ] can be decomposed into the disjoint union of uncountably many sets with full Hausdorff dimension. [ABSTRACT FROM AUTHOR]

Low-profile shared-structure dual-polarized (DP) Yagi–Uda antennas are proposed, which are formed by three kinds of basic components, namely DP driven element, DP director, and DP reflector. An open-cavity dipole is utilized as the DP driven element to generate DP endfire radiations. The quarter-wave resonance mode for vertical polarization (VP) and half-wave dipole resonance mode for horizontal polarization (HP) are excited by differential feeding structures in the DP driven element. The open-cavity element is adopted as the DP director or reflector to enhance endfire gain. For the proposed design, two polarization radiators are integrated into one structure, realizing structure sharing, and thus a low profile. Three-element (Ant. 1) and seven-element (Ant. 2) antennas with a profile of 0.1 λ0 are designed, fabricated, and measured. The measured overlapped bandwidth of the Ant. 1 is from 4.11 to 4.83 GHz (16%) with ports isolation higher than 30 dB, and the measured VP and HP gains are from 5 to 6 dBi and 5 to 7 dBi, respectively. The Ant. 2 further increases the DP endfire gain by 2–3 dBi at the overlapped bandwidth of 16.3%. [ABSTRACT FROM AUTHOR]

Metal borides are of significant interest because of their high strength, high melting point, superconductivity and magnetism. Here, a combination of swarm-intelligence structural search and first-principle calculations propose a pressure-stabilized hitherto unknown manganese boride, MnB6, that is recoverable under ambient conditions and exhibits versatile properties. MnB6 contains unique B∞ ribbons along the c-axis, which are linked to each other in the a-b plane by B–B bonds to form open channels filled with Mn atoms. MnB6 is ferromagnetic at its onset energetically stable pressure of 127 GPa and undergoes a transition from magnetic to superconducting at 160 GPa, with an estimated superconducting critical temperature of 15.9 K. Under ambient pressure, MnB6 exhibits increased ferromagnetism with a magnetic moment of 1 μB per Mn atom and a Curie temperature as high as 520 K. Moreover, MnB6 possesses good mechanical properties with an estimated Vickers hardness of 25 GPa and high ductility, which stems from the peculiar structural arrangements in MnB6 driven by the ability of boron to form unusually versatile bonding states. [ABSTRACT FROM AUTHOR]

Element B in binary metal borides forms various polymetric configurations due to its electron-deficient nature. Here we predict a new pressure-stabilized boron clathrate structure, LaB8, that is recoverable under ambient conditions. Crystal structure searches and first-principles calculations predict a series of thermodynamically stable La–B compounds at high pressures. Besides known LaB4 and LaB6 compounds, trigonal LaB8 is predicted to be thermodynamically stable above 70 GPa. Its B atoms construct face-sharing B26 cages, each surrounding a central La atom. The compound can be recovered to ambient conditions with the B26 cages well preserved. Electron–phonon coupling calculations suggest that it is potentially superconducting with an estimated Tc of 5 K at 70 GPa, which increases to ∼20 K at ambient pressure. The enhanced Tc is attributed to the increased B-derived electronic density of states at the Fermi level and to the softened Eu mode related to vibration of the B26 cages. [ABSTRACT FROM AUTHOR]

The recent discovery of superconductivity near room temperature in highly compressed superhydrides highlights the key role of the hydrogen cage structure in determining the high superconducting critical temperature. Here, we propose a hitherto unknown metastable cage boron allotrope possessing high superconductivity at ambient pressure. Using first-principles calculations with structure searching, we have predicted various dynamically stable structures for MnB12 that can be possibly synthesized at high pressures and high temperatures. Among these structures the tetragonal t-MnB12 contains unique B16 cages, which are linked to each other to form open channels filled with Mn atoms. The removal of Mn atoms leads to the formation of a tetragonal cage boron allotrope t-B, which possesses partial ionicity due to the slight charge transfer between two inequivalent B atoms. t-B is a potential superconductor with an estimated critical temperature of 43 K, the highest value in elemental superconductors at ambient pressure. [ABSTRACT FROM AUTHOR]

Considering that pressure-induced formation of short, strong covalent bonds in light-element compounds can produce superhard materials, we employ structure searching and first-principles calculations to predict a new class of boron nitrides with a stoichiometry of BN2, which are stable relative to alpha-B and alpha-N2 at ambient pressure. At ambient pressure, the most stable phase has a layered structure (h-BN2) containing hexagonal BN layers between which there are intercalated N2 molecules. At 25 GPa, a three-dimensional P42/mmc structure with single N–N bonds becomes the most stable. Dynamical, thermal, and mechanical stability calculations reveal that this structure can be recovered under ambient conditions. Its calculated stress-strain relations demonstrate an intrinsic superhard nature with an estimated Vickers hardness of ∼43 GPa. This structure has a potentially high energy density of ∼4.19 kJ/g. [ABSTRACT FROM AUTHOR]

An annular array antenna is proposed in this letter. The proposed low-profile antenna produces an enhanced gain with omnidirectional vertically polarized radiation patterns. Center-fed via-shorted circular patch antenna with omnidirectional radiation pattern can be low profile and wide bandwidth but suffers from tilted beam leading to a low gain in the azimuth plane. To improve the azimuth gain, instead of the traditional way of increasing the profile, a low-profile omnidirectional director is exploited, which is basically a passive magnetic dipole consisting of an annular side-coupling open-cavity. Several directors cooperating with the driven element form the proposed antenna, whose working principle is similar to the Yagi–Uda antenna. A prototype with a low profile of 0.11 ${\lambda _0}$ is designed and fabricated. Measured results show that the prototype can realize −10-dB impedance bandwidth of 13% (4.72–5.42 GHz) and gain of 3.72 dBi at 5.34 GHz with good omnidirectivity. Compared with that of the driven element only, the omnidirectional azimuth gain is significantly improved within the bandwidth, with the maximum gain being enhanced from −4.2 to 3.72 dBi at 5.34 GHz. The proposed antenna is designed for a portable 5G sub-6 GHz wireless channel measurement application. [ABSTRACT FROM AUTHOR]

Nanoporous atom-thick two-dimensional materials with uniform pore size distribution and excellent mechanical strength have been considered as the ideal membranes for hydrogen purification. Here, our first-principles structure search has unravelled four porous boron nitride monolayers (m-BN, t-BN, h′-BN and h′′-BN) that are metastable relative to h-BN. Especially, h′-BN consisting of B6N6 rings exhibits outstanding selectivity and permeability for hydrogen purification, higher than those of common membranes. Importantly, h′-BN possesses the mechanical strength to sustain a stress of 48 GPa, which is two orders of magnitude higher than that (0.38 GPa) of a recently reported graphene-nanomesh/single-walled carbon nanotube network hybrid membrane. The excellent selectivity, permeability and mechanical strength make h′-BN an ideal candidate for hydrogen purification. [ABSTRACT FROM AUTHOR]

In this paper, a decoupling multivariable control strategy for linear time‐invariant (LTI) multi‐input/multi‐output (MIMO) systems is proposed. The strategy includes a multivariable disturbance observer (MDOB) and a decoupling controller. This MDOB is introduced to improve the system performances when the system encounters severe external disturbances. H2 optimal scheme is utilized to design the MDOB filter. The controller is developed based on an inverse control method, through which the design process can be simplified. Simulation results certify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

The multivariable coal-fired power plants (CFPPs) are characterized by several interconnected nonlinear subsystems of varying time lags making the whole system stiff, and thereby attaining multitime-scale property. In this case, controls based on singular perturbation and time-scale theories provide superior results than conventional one. This brief aims to develop an integral state feedback controller with an observer using three-time-scale approach for CFPP. The integral action assures zero steady-state error, an observer determines states, and a three-time-scale technique provides flexibility to design independent subsystem controls. First, a state space model is obtained with state feedback integral action in three-time-scale form. Second, three-stage feedback control is proposed by an innovative two-time-scale separation so as to reduce design complexity and computations. Finally, an observer is constructed again by time-scale decoupling. It is then examined on the practical model of 300-MW CFPP for investigating plant behavior under various transients. In comparison, the performance of the suggested controller is found to be superior to a recently published controller. [ABSTRACT FROM AUTHOR]

In this brief, a sliding mode controller (SMC) established via a new adaptive reaching law is proposed for discrete-time systems. To guarantee a smaller width of the quasi-sliding mode domain (QSMD), disturbance of the system is estimated based on the second-order difference of historical observation information, and the reaching law is designed on the choice of a negative power term that adapts to the variations of the switching function. Dynamics of the controlled system both outside and within the QSMD are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents the circuit design and magnetic integration of push–pull class-E inverters for wireless power transfer (WPT) up to megahertz. The design criterion for achieving zero-voltage switching (ZVS) of a class-E inverter with coupled windings is derived mathematically. The approaches of magnetic integration for push–pull class-E inverters are analyzed and compared. Then, a new magnetic structure with hybrid magnetic materials is proposed to build the integrated inductors with either coupled windings or uncoupled windings. A 3-MHz WPT system is built to verify the analysis. The detailed comparison of the class-E inverters with magnetic integration is presented in terms of switch voltage, efficiency, harmonic currents, and thermal distribution. In the optimized design example, the switches keep ZVS over the entire load range without using any closed-loop control. The system efficiency reaches 87.1% at 350-W output power. [ABSTRACT FROM AUTHOR]

The search for two-dimensional superconductors has attracted increasing interest because of their potential applications in constructing nanoscale superconducting devices. Through swarm-intelligence based CALYPSO method and the first-principles calculations, we have identified a monolayer structure for yttrium sulfide (t-YS), which is energetically and dynamically stable. The application of biaxial strain turns t-YS to a Bardeen–Cooper–Schrieffer superconductor, which mainly originates from the softening of in-plane modes of Y atoms. The superconducting critical temperature increases monotonously with strain, which reaches 6 K at a maximum strain of 10%. Calculations show that doping at 0.3 holes per unit cell based on a strain of 10% could further enhance the superconductivity to 7.3 K. Simulations have helped to propose a candidate substrate with ∼8.3% lattice mismatch to obtain superconductive t-YS experimentally. The findings will enrich two-dimensional superconductors and stimulate immediate experimental interest. [ABSTRACT FROM AUTHOR]

In this study, a new adaptive controller is introduced for the induction motors (IMs) based on immersion and invariance (I&I) technique. The dynamics of the IM system are perturbed by some disturbances such as time‐varying rotor resistance and load torque. Accordingly, an adaptive controller is designed and the uncertain parameters are online estimated. The adaptation laws are obtained from the stability analysis based on I&I method. The simulation results verified the effectiveness of the proposed control method. It is revealed that the outputs of the IM could track the desired signals in the presence of the mentioned disturbances. Also, the results are compared with the conventional control methods and it is concluded that the proposed control approach resulted in better performance. [ABSTRACT FROM AUTHOR]

Materials possessing both superhard and metallic properties are beneficial for the creation of multifunctional devices under extreme conditions. Here, we report the formation of a new metallic superhard boron nitride at high pressure with stoichiometry B2N3 through first-principles calculations and structure searching. At ambient pressure, B2N3 has layered structures (h-B2N3) consisting of hexagonal B4N4 layers intercalated by triply bonded N2 molecules. With the pressure increasing to ∼10 GPa, h-B2N3 transforms to a three-dimensional tetragonal structure (t-B2N3) with the formation of single N–N bonds. Calculations reveal that t-B2N3 can be recovered under ambient conditions in view of the dynamical, thermal and mechanical stability. Interestingly, t-B2N3 is proposed to be a superhard material with an estimated Vicker's hardness of ∼52 GPa by performing stress–strain calculations. More importantly, electronic calculations show unique two-dimensional metallicity in t-B2N3, which originates from the π orbitals of N–N bonds spreading in the ab plane. In addition, the energy density of ∼2.95 kJ g−1 makes t-B2N3 a potential high-energy density material. [ABSTRACT FROM AUTHOR]

This paper presents an output feedback indirect dynamic inversion (IDI) approach for a class of uncertain nonaffine systems with input unmodelled dynamics. Compared with previous approaches to achieve performance recovery, the proposed method aims at dealing with a broader class of nonaffine-in-control systems with triangular structure. An IDI state feedback law is designed first, in which less knowledge of the model plant is needed compared to earlier approximate dynamic inversion methods, thus yielding more robust performance. After that, an extended high-gain observer is designed to accomplish the task with output feedback. Finally, we prove that the designed IDI controller is equivalent to an adaptive proportional-integral (PI) controller, with respect to both time response equivalence and robustness equivalence. The conclusion implies that for the studied strict-feedback non-affine systems with unmodelled dynamics, there always exits a PI controller to stabilise the systems. The effectiveness and benefits of the designed approach are verified by three examples. [ABSTRACT FROM PUBLISHER]

This study presents a new observer‐based electronic line‐shafting (ELS) control scheme as motion synchronisation solution for motor drives in the industrial manufacturing process. To achieve better speed control performance for each ac motor drive, a sliding mode controller is proposed. This controller is designed based on a non‐linear reaching law, which helps to settle the reaching time/chattering dilemma in the conventional sliding mode control (SMC) approach. In addition, a sliding mode observer is proposed to estimate lumped disturbances for the motor drives. Disturbance estimation results are fed forward as compensation parts for the SMC controller; in the meantime, they are transmitted to the virtual line‐shafting drive to accurately reflect total system disturbances, thus to achieve high motor speed synchronisation precision. Effectiveness of the proposed ELS control scheme is verified by simulation results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two hitherto unknown N 2 F and N 10 F compounds are predicted at high pressure. • Both N 2 F and N 10 F contain N 6 rings, but connected in different ways. • N 2 F and N 10 F are recovered under ambient pressure with high-energy density. • Polymeric nitrogen mC 10-N can be obtained after the removal of F from N 10 F at ambient pressure. • mC 10-N has an energy density of 11.20 kJ/g. Polymeric nitrogen possessing ambient quench recoverability is considered to be the most powerful and green high-energy density material, which has triggered extensive interest. Herein, we predicted two hitherto unknown nitrogen-rich nitrogen fluorine compounds with stoichiometries N 2 F and N 10 F using structure searching method and first-principles calculations. N 2 F and N 10 F are thermodynamically stable relative to ε-N and fluorine at 67–110 and 87–110 GPa, respectively. Both N 2 F and N 10 F encompass N 6 rings, forming one-dimensional N ∞ ribbons by edge-sharing and three-dimensional channel-like open framework by edge-sharing and two N atoms-bridging, respectively. Phonon spectra calculations and molecular dynamics simulations demonstrate the ambient-pressure quench recoverability of the two predicted phases. Interestingly, after the removal of F atoms from open channel in N 10 F, the polymeric nitrogen framework mC 10-N is retained at ambient conditions with the energy density of 11.20 kJ/g, rendering it a remarkable high-energy density material. [ABSTRACT FROM AUTHOR]

Abstract This research explores the eudaimonic environmental pursuit of Generation Zers. Although how they can contribute to the environment has gained traction, extant tourism research in this regard largely lags behind. Drawing on self-determination and self-efficacy theories, this inquiry fills this void by proposing a model that delineates a motivation–behavior–goal mechanism to illuminate how pursuits for environmental sustainability can develop into self-actualization. Using an explanatory sequential design, we first undertook a survey-based investigation with data acquired through purposive sampling to sample Generation Zers who had attended a minimum of one green volunteer trip in the prior year. Results first unravel how eudaimonic environmental motivation can induce green travel involvement, leading to environmental citizenship. Exhibiting environmental citizenship presents an avenue to foster environmental goal attainment and subsequent self-actualization, synthesizing a path that depicts behavior-goal-actualization of oneself. The moderating effect of environmental self-efficacy is also warranted. A post-hoc study was followed using semistructured interviews to explore Generation Zers’ eudaimonic environment pursuits and goal attainment. Our findings pave the way for a better understanding of behavioral engagement and pursuits of this rising cohort towards a greener tomorrow. It lays the groundwork to bring personal growth needs for environmental goal attainment to light. [ABSTRACT FROM AUTHOR]

High-pressure phase diagrams of the La-N binary system were systematically constructed using the CALYPSO method and first-principles calculations. In addition to the pressure-induced La-N compounds reported previously, we have uncovered a hitherto unknown LaN 9 structure in Pm 3̄ symmetry stabilized within a narrow pressure range of 20-24.5 GPa. Notably, LaN 9 stands as the first thermodynamically stable metal nine-nitrogen compound, featuring centrosymmetric linear N 3 anion units and an edge-sharing LaN 12 icosahedron. Charge transfer between the La and N atoms plays a crucial role in facilitating structural stability. Furthermore, we identified a novel Cm phase for LaN 8 , which has a lower enthalpy compared to the previously reported phase. N atoms in Cm LaN 8 are polymerized into infinite N ∞ chains. Calculations demonstrate the potential recoverability of LaN 9 and Cm LaN 8 under atmospheric conditions while preserving their initial polynitrogen configuration. From the perspective of detonation pressure and detonation velocity, LaN 9 and Cm LaN 8 exhibit excellent explosive performance in comparison to TNT and HMX, with estimated energy densities of 0.9 and 1.54 kJ g -1 , respectively, indicating their potential utility as high-energy-density materials.

Two-dimensional materials with a negative Poisson's ratio, known as auxetic materials, are of great interest owing to their improved mechanical properties, which enable plenty of advanced nanomechanical devices. Here, by first-principles swarm-intelligence structural search methods, we predict a thermodynamically stable Si 2 S monolayer, which has a puckered 2D lattice in which the S atoms are adsorbed on the top of a distorted tetragonal silicene layer. The puckered 2D lattice makes the Si 2 S monolayer exhibit in-plane negative Poisson's ratios of -0.05 and -0.069 along the x and y directions, respectively. Moreover, electronic structure calculations reveal that the Si 2 S monolayer is a semiconductor with a quasi-direct band gap of 1.81 eV, which can be converted into a direct gap semiconductor of 1.43 eV by applying a low tensile strain (∼2%). The Si 2 S monolayer has a large visible light absorption coefficient of 10 5 cm -1 . The hole (electron) mobility is 200 (81) cm 2 V -1 s -1 along the y direction, 3.4 (1.5) times that along the x direction, comparable to MoS 2 . Moreover, the Si 2 S monolayer has the good ability of oxidation resistance. We provide a possible route to experimentally grow a Si 2 S monolayer on a suitable substrate such as the Cu(100) surface. The versatile properties render the Si 2 S monolayer potential for advanced application in nanodevices.

Two-dimensional materials with a planar lattice, suitable direct band gap, and high and highly anisotropic carrier mobility are desirable for the development of advanced field-effect transistors. Here we predict three thermodynamically stable B-rich 2D B-N compounds with the stoichiometries of B 2 N, B 3 N, and B 4 N using a combination of crystal structure searches and first-principles calculations. Among them, B 2 N has an ultraflat surface and consists of eight-membered B 6 N 2 and pentagonal B 3 N 2 rings. The eight-membered B 6 N 2 rings are linked to each other through both edge-sharing (in the y direction) and bridging B 3 N 2 pentagons (in the x direction). B 2 N is a semiconductor with a direct band gap of 1.96 eV, and the nature of the direct band gap is well preserved in bilayer B 2 N. The hole mobility of B 2 N is as high as 0.6 × 10 3 cm 2 V -1 s -1 along the y direction, 7.5 times that in the x direction. These combined novel properties render the B 2 N monolayer as a natural example in the field of two-dimensional functional materials with broad application potential for use in field-effect transistors.