Double Slab Research Articles

Crystal structures of the R1.33Ni3Ga8 (R = Tb, Ho, Er, Tm, Lu) compounds

The existence of five new ternary compounds with Gd1.33Pt3Al8-type structure (Pearson symbol hR51, space group R-3m) was established by means of X-ray powder diffraction and energy-dispersive X-ray spectroscopy: Tb1.33Ni3Ga8 (а = 4.2056(1), с = 37.8913(9) Å), Ho1.33Ni3Ga8 (а = 4.19666(9), с = 37.7882(9) Å), Er1.33Ni3Ga8 (a = 4.19290(8), c = 37.7446(8) Å), Tm1.33Ni3Ga8 (a = 4.18819(7), c = 37.6980(7) Å), and Lu1.33Ni3Ga8 (a = 4.1826(1), c = 37.647(1) Å). The structures of the ternary R1.33Ni3Ga8 compounds belong to a family of linear-intergrowth structures with the general formula R0.67TnM2n + m and are built from atom layers of the composition R0.67Ga (R0.67M), separated by single or double NiGa2 slabs (TM2). The layers containing the rare-earth metal atoms are characterized by a disordered distribution of rare-earth metal atoms and Ga-atom triangles.

Characteristic frequencies of transverse electric modes in a double negative slab waveguide with Kerr-type nonlinearity

The evolution equation for guided transverse electrical modes in a slab waveguide having a double negative core is derived for the electrical field. Special solutions of the dispersion equation for the case with double positive symmetric cladding are searched for. Relevant eigenmodes are formulated in terms of characteristic frequencies as a new method, and these frequencies corresponding to the oscillating guided modes are found for different wave numbers and core widths assuming the lossless Drude model can be used for the core medium with a Kerr-type nonlinearity. Results show that normalized characteristic frequencies increase with increasing wave numbers and mode numbers.

Bayesian optimization of periodic multilayered slabs for passive absorptivity control

A vanadium dioxide (VO2) film grown on a titanium oxide crystal shows a metal–insulator transition at room temperature with drastically changed optical properties. A multilayered slab with a sub-micron scale VO2 film was proposed to utilize its unique properties for passive intensity control of sunlight absorption and radiative cooling. Its optimal geometries were numerically explored using the Bayesian optimization (BO) method. BO was applied for three types of multilayered slabs, those having one, two, or three isolated slabs of different widths. For each type of multilayered slab, BO could optimize geometric variables with practical calculation times considering the total number of possible combinations of variables, which is subsequently referred to as the total number of candidates. Optimization results revealed that two isolated slabs had the most suitable spectral absorptivity in both hot and cold environments. The infrared absorptivity of the double slab was kept low in cold conditions to suppress radiative cooling. However, the double slab exhibited good radiative cooling performance under hot conditions. Electromagnetic energy density surrounding the slab illustrated that metallic VO2 and gold placed in a parallel manner excited the coupled mode of surface plasmon polaritons to enhance absorptivity. Radiative cooling faded for the triple slab because each slab could couple with radiation propagating only across a portion of the cross-sectional area. Through three BO trials, improvement of the VO2 visible reflectivity was recognized as a future issue for further development of passive sunlight absorption control.

Structural Performance of Reinforced Concrete Double Layer Bamboo Bubble Slab Under Uniformly Distributed Load

The architectural use areas in the structure are formed by reinforced concrete (RC) slabs, which transport vertical loads to the beams, columns, load-bearing walls, and shear walls. The slab is an important structural member of reinforced concrete building structures and concrete-intensive parts of structural members. . The slab deflects significantly when the load acting on the slab or the clear span between columns is large. As a result, the slab's thickness increases to accommodate the load received. Since this slab's self-weight increases as the thickness increases, the slabs get heavier and causes the slab unable to withstand the load and to produce cracks on the surface. At the turn of the twentieth and twenty-first centuries, the creation of the bubble deck slab became an innovation to replace conventional slab. This study used bamboo as the bubble material in reinforced concrete bubble slab. This study examined and assessed the mechanical properties and structural behaviour of bamboo as a bubble in supported reinforced concrete double-layer bamboo bubble slab under a uniformly distributed load. In this research, 500 mm x 1250 mm x 175 mm supported reinforced concrete slabs C25 (1 sample) and C30 (1 sample) with double layer (DL) bamboo bubble slabs were constructed. Both samples were compared with the control sample (CS) for each slab type. It was found that the maximum displacement occurred at the centre of the slab, with 6.45 mm for DL25 and 6.89 mm for DL30. According to stress-strain analysis, the double layer bamboo slab produced a lower stress value than the control sample. Since the values were smaller than 2, DL25 and DL30 slab performed better for the ductility factor than CS25 and CS30. As a result, the displacement, ductility and section capacity were improved by employing bamboo as a bubble material in a reinforced concrete slab.

Mechanistic insights into the deprotonation of methanol by facile synthesized 3D flower-like BiOX (X= Cl, Br, I) catalysts for rapid hydrogen generation from NaBH4 methanolysis: The ‘X’ factor

Bismuth oxyhalides (BiOX, X = Cl, Br, I) have been showing promising catalytic activity in various applications due to their electronic properties and unique layered structure. However, their catalytic potential for hydrogen generation from chemical hydrides is unrevealed. Herein, BiOX (X = Cl, Br, I) catalysts were prepared via a simple co-precipitation method. The physical and chemical characteristics of the as-prepared samples were then duly characterized using various techniques such as X-ray diffractometer spectroscopy (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Nitrogen adsorption-desorption, and Scanning electron microscope (SEM). The catalysts were then applied to NaBH4 methanolysis for the production of hydrogen. Among the BiOX catalysts, BiOCl exhibits excellent performance which is attributed to the highest electronegativity possessed by the Cl− halogens clinging onto the catalytic layers, simply overriding the substitution reactions. Subsequently, superior performances were depicted with rapid generation of hydrogen, High rate of hydrogen generation, HGR = 42,740 mL H2 g−1min−1, and calculated activation energy of Ea = 43.5 kJ/mol with stability for over 5 successive cycles. Withal, a plausible mechanism based on the exchange reactions promoted by the BiOX catalysts, which comprises interlacing [Bi2O2] slabs with double halogen slabs coupled with a strong ionic nature is illustrated in line with the experimental results.

Innovative hybrid coupled wall systems to resist seismic action – HYCAD

AbstractThis article summarizes the research carried out in the ongoing HYCAD project, which aims to improve the performances of a hybrid coupled wall (HCW) system for buildings in seismic areas, by further developing the HCW originally studied in the RFCS project INNO‐HYCO. This HCW system consisted of a reinforced concrete (RC) wall coupled with two steel side‐columns via steel coupling links. Encouraging outcomes were obtained such as: controlled post‐elastic ductile behaviour under medium‐ and high‐intensity earthquakes, suitable lateral stiffness, seismic energy dissipation concentrating in the easily‐replaceable steel links and very limited damage in the RC wall. However, advanced studies were required to bring this system into practice, addressing issues and develop advancements in the analysis, design, and detailing. This article summarizes the primary steps taken towards that purpose. Five new components were chosen in order to improve the performance of the HCW system: (1) Link‐to‐wall connections using post‐tensioned tendons; (2) Composite walls with encased steel profiles instead of a conventional RC wall; (3) Rocking coupled wall system; (4) Dissipating devices as links and (5) Precast double slab wall systems. Combining these components, four new HCW systems were developed, pre‐designed and analysed through numerical and experimental studies. Advanced yet simple techniques were proposed for the numerical analyses while test specimens are used to characterize local and global behaviour.

Improved voice acquisition using acoustic metamaterials

Voice acquisition and recognition are important, because sound is the most convenient and efficient media to realize seamless and hands-free human–machine interaction. Many applications, such as smart phones, humanoid robots, smart home, autonomous vehicles, and Internet of Things, demand for high-quality voice acquisition, especially in a noisy environment. In this report, we show that the evanescent portion of human voice can be amplified by setting an acoustic metamaterial in front of a microphone; thus, the signal to noise ratio can be enhanced remarkably. Such an effect is demonstrated through a double negative acoustic metamaterial slab with simultaneous negative density and bulk modulus induced by coexisting and coupled Helmholtz and Fabry–Pérot resonances. This work provides a passive and physical means, rather than the traditional active and algorithmic method, to improve the quality of voice sound acquisition.

Superstructures and Chemical Bonding in Rare Earth Metal Polytellurides RETe2‐δ (RE=La−Nd; Sm−Tm; 0≤δ≤0.2)

AbstractPolychalcogenides REX2‐δ (X=S, Se, Te; 0≤δ≤0.2) of trivalent rare earth metals RE have been investigated in recent years to shed light on the structural diversity as a function of compositional, metric, thermodynamic, and electronic situation. Whereas the former aspects have comparable influence on the structures of all polychalcogenides REX2‐δ, the bonding situation was assumed different for tellurides due to tellurium's higher tendency to delocalize electrons. The crystal structures generally contain puckered [REX] double slabs and planar [X] layers, the latter hosting different distortions from a square‐like arrangement. The distortion patterns of sulfides and selenides can be understood by a Zintl‐type approach; they are dominated by localization of valence electrons in mono‐ (X2−) or dinuclear (X22−) anions only. This review discusses crystal structures of some rare‐earth metal polytellurides RETe2‐δ (0≤δ≤0.2) and bonding features in the chalcogenide layers and relates them to their sulfide and selenide counterparts.

Architectural-archaeological research and the hypothesis of the development of pre-local Drohobych in the XII-XIII centuries

Architectural and archaeological studies of preserved architectural monuments emphasise the continuity of development, succession, and originality of the culture of each nation. The research aims to highlight the results of architectural and archaeological surveys at the foundations of the wooden architectural monument - the Church of the Exaltation of the Holy Cross in Drohobych, as well as to develop the hypothesis of the city's urban genesis. According to the analysis of literary sources, seven construction periods have been identified since the church was built in 1613. The sounding method showed that the first foundations were standards, which were installed in pits on the cut surface of the continent, often with stone slabs, and covered with soil. The system of double slabs fixed under the altar crown of the log house is considered archaic. During the third and fourth construction periods, some of the stands were replaced, and a stone foundation supported by a wide base of slabs was built under the northwestern corner of the main log cabin. In 1823, the altar log cabin and the southern façade of the building were supported by a ribbon structure of stone foundations. No banded foundations were found under the western base of the chancel and the northern base of the nave. The lower gallery of the nineteenth and early twentieth centuries is supported by a system of foundations and smaller stands. Within the fourth probe, a deep archaeological site was localised with a ceramic sherd in the fill dating to the princely period. The analysis of several features and stratigraphic features of the fill gives grounds to interpret the object as the remains of a semi-hut of this period. Based on the location of the first immovable object, an attempt is made to clarify one of the hypotheses of the urban development of Drohobych from the unfortified initial settlement of salt workers on the right bank of the Pobuk in the twelfth and thirteenth centuries, through its gradual development into a proto-city settlement of the thirteenth and early fourteenth centuries in the present Zvarytske suburb to the foundation of a new locational centre in the fourteenth/fifteenth centuries on the free adjacent territory

A metamaterial‐incorporated wireless power transmission system for efficiency enhancement

SummaryIn this paper, an efficient wireless power transmission (WPT) system that incorporates a new negative permeability metamaterial is presented. The operating principle of the metamaterial with negative permeability is first analyzed. To improve transmission efficiency of the WPT system at the operating frequency of 13.56 MHz, a new metamaterial with three open rings is designed. By respectively placing a single metamaterial slab and double metamaterial slabs at different positions between transmitting coil and receiving coil, the performance of the proposed WPT system is evaluated by simulation work. The corresponding magnetic field distribution is also analyzed. Besides, comparison is made with the conventional WPT system without metamaterial. It is found that transmission efficiency of the proposed WPT system is obviously improved when incorporating the metamaterial since the designed metamaterial effectively focuses magnetic field towards the receiving coil. Comparing with the conventional system, the results also show that the proposed WPT system is more robust to lateral and angular misalignment of the receiving coil. With the designed metamaterial, it is found that the proposed system with double metamaterial slabs performs better than that with a single metamaterial slab.

Reduced Slit Rolling Power in Rebar Steel Production

The rolling process of rebar steel production is one of the well established manufacturing processes; however, it should be subjected to revision and redesign for productivity enhancement and power reduction throughout the slit rolling process. In this work, slitting passes are extensively reviewed and modified for the attainment of better rolling stability and reduction in power consumption. The study has been applied for grade B400B-R Egyptian rebar steel, which is equivalent to steel grade ASTM A615M, Grade 40. Traditionally, the rolled strip in the rolling pass is edged before implementing a slitting pass using grooved rolls; this produces a single barreled strip. This single barrel form causes instability in the next slitting stand on the pressing by the slitting roll knife. Multiple industrial trials are attempted to achieve the deformation of the edging stand using a grooveless roll. As a result, a double barreled slab is produced. In parallel, finite element simulations of the edging pass are performed using grooved and grooveless rolls, and similar slab geometry with single and double barreled form are produced. In addition, further finite element simulations of the slitting stand are execute using idealized single barreled strips. The power calculated by the FE simulations of the single barreled strip is (245 kW), which is in acceptable agreement with the experimental observations in the industrial process (216 kW). This result validates the FE modeling parameters such as material model and boundary conditions. The FE modeling is extended to the slit rolling stand of a double barreled strip, which was previously produced by the grooveless edging rolls. It is found that the power consumption is (165 kW) 12% lower than the power consumed (185 kW) for slitting the single barreled strip.

Numerical Analysis on the Structure Design of Precast Cement Concrete Pavement Slabs

The performance of cast-in-place cement concrete pavement can be greatly influenced by the surrounding environment and the quality of construction, and it requires longer curing time before opening to the traffic. The precast cement concrete pavement has the potential to address the disadvantages of using the cast-in-place cement concrete as the pavement surface material, and it also provides an alternative solution for the rapid repair of pavement damage. The current study aimed to assess the influences of geometry of full-scaled precast concrete slabs with various load transfer joint types. A numerical analysis was conducted using the finite element method to analyze the mechanical responses of the single and double slabs in accordance with the elastic thin-plate theory and the Specifications for Design of Highway Cement Concrete Pavement. Under the premise of determining the most unfavorable load position for different mechanical parameters, the mechanical response regularity under the critical loads was determined. The precast concrete pavement slab with dimensions 4 m long, 3 m wide and 0.28 m thick exhibited better mechanical responses when considering the maximum deflection and flexural stress as the evaluation index. The results indicated that the variation of joint forms has marginal influences on the maximum deflection and displacement transfer coefficient. When considering the maximum flexural stress and load transfer coefficient of the precast slabs, the circular tongue-and-groove joint form was recommended for application.

Research on the Residual Bearing Capacity of a Rib Beam Bridge Carriageway Slab Based on Fatigue Cumulative Damage

In order to study the residual bearing capacity of the carriageway slab of a reinforced concrete rib beam bridge after fatigue damage, a double T-beam carriageway slab model with a high degree of symmetry was designed and fatigue tests were carried out. Based on the fatigue cumulative damage theory, the fatigue residual strength equation of concrete was improved and a constitutive fatigue model of a steel bar and concrete with arbitrary loading times was established. Because the carriageway slabs are highly symmetrical, we used a ratio of length to width and a ratio of width to height to express the dimensional changes in the carriageway slabs. Abaqus general analysis program was used to create a symmetrical T-beams model and analyze the influence of the fatigue load level, the ratio of width to height of the roadway slab, and the ratio of length to width on the remaining bearing capacity of the roadway slab. Finally, the 1stOpt fitting software was employed to fit the roadway slab’s residual bearing capacity evaluation model. The fatigue test results show that the fatigue failure form of the roadway slab is punching failure, and the development law of fatigue damage can be divided into three stages, accounting for 6.25%, 56.25%, and 37.5% of the total fatigue life. The finite element analysis results showed that the length–width ratio of the roadway slab is positively correlated with its relative residual bearing capacity, and the residual bearing capacity of the two-way slab is higher than that of the one-way slab. The fatigue load level and the aspect ratio of width to height are negatively correlated with their relative residual bearing capacity.

Reconstructions of effective parameters for a metamaterial antenna via 3D-printed components

This study presents the reconstruction of effective medium parameters for a double negative metamaterial slab from the knowledge of the measured/simulated S-matrix. The structure initially has been designed to embed into a patch antenna for a radar application. To observe the medium characteristics, we locate the slab in a rectangular waveguide for various orientations. The waveguide-based retrieval method is applied to find parameters regarding the biaxial anisotropic medium. Fundamental mode is used for the excitation. Additive printing technology is employed to manufacture a rectangular waveguide and its adapters for the experiments. The metallization is achieved by coating the printed structures with conductive thin layers. Experimental setups for each orientation are simulated as well. We illustrate good agreements between simulation and measurements under the fabrication tolerances. The feasibility and applicability of the additive printing technology for the investigations of the metamaterial anisotropic/bianisotropic nature is reported.

Experimental study on the buckling behavior of double steel plate concrete composite slabs with stiffening ribs and tie plates

Double steel plate concrete (DSC) composite slabs consist of two outside steel plates and a concrete core that are connected by welded studs or cross tie bars. If weak restraints are designed for the interface between the steel plates and concrete core, the surface steel plate of the DSC slabs may suffer local buckling when subjected to a compressive load. In this paper, a new type of DSC slab with stiffening ribs and tie plates (SDSC slab) is proposed to improve the stability of surface steel plates. Two groups of bending tests are carried out to investigate the buckling behavior of both SDSC slabs and ordinary DSC slabs (ODSC slabs). Furthermore, the influence of the B/t ratio, that is, the ratio between the stud spacing and the steel plate thickness, is intensively analyzed. The experimental results reveal that compared with that of the ODSC slabs, the buckling behavior of steel plates in the SDSC slabs is delayed or even prevented owing to the additional stiffening ribs and tie plates. Thus, the bending capacity and ductility of SDSC slabs are both enhanced. According to the test results, calculation formulas are derived to predict the bending capacity of the ODSC slabs and SDSC slabs, respectively. In addition, design models for buckling analysis are proposed to determine the buckling stress and critical B/t ratio for different types of DSC slabs. The accuracy of the theoretical methods is validated against the test data, and two examples are provided in detail to illustrate the design process of the steel plate in SDSC slabs.

Structure and electron affinity of the 4H–SiC (0001) surfaces: a methodological approach for polar systems

The ability to accurately and consistently determine the surface electronic properties of polar materials is of great importance for device applications. Polar surface modelling is fundamentally limited by the spontaneous polarisation of these materials in a periodic boundary condition scheme. Surface data are sensitive to supercell parameters, including slab and vacuum thicknesses, as well as the non-equivalence of surface adsorbates on opposite surfaces. Using 4H–SiC as a specific case, this study explores calculation of electron affinities (EAs) of (000) and (0001) surfaces varying chemical termination as a function of computational parameters. We report the impact in terms of band-gap, electric fields across the vacuum and slab for single and double cell slab models, where the latter is constructed with inversional symmetry to eliminate the electric field in the vacuum regions. We find that single cells are sensitive to both slab and vacuum thickness. The band-gap narrows with slab thickness, ultimately vanishing and inducing charge transfer between opposite surfaces. This has a consequence for predicted EAs. Adsorbate species are found to play a crucial role in the rate of narrowing. Back to back cells with inversional symmetry have larger electric fields present across the slab than the single slab cases, resulting in a greater band-gap narrowing effect, but the vacuum thickness dependence is completely removed. We discuss the relative merits of the two approaches.

Design method for radar absorbing structures using reliability-based design optimization of the composite material properties

Functional composites dispersed with nanofillers are used to enhance the characteristics of radar absorbing structures (RAS). In this study, the relative permittivity of the RAS substrate is measured under various environmental conditions of temperature and humidity. The probability distributions of the dielectric materials used for RAS are determined using maximum likelihood estimation based on raw data. With the determined distributions, 107 samples are generated and sampling-based reliability-based design optimization (RBDO) for reflection loss of a double slab RAS is performed based on transmission line theory. Two objectives considering absorption properties and bandwidth that represent the performance of the RAS are presented. The results of deterministic optimization (DO) and RBDO are compared considering the failure probability of the application system under operating conditions. Although the total thickness increases slightly, the RBDO provides a significant reduction in the failure probability.

7 kHz sub-nanosecond microchip laser amplified by a grazing incidence double pass slab amplifier

To obtain short pulse width and high peak power laser, a 7 kHz sub-nanosecond microchip laser amplified by a grazing incidence double pass slab amplifier is experimentally demonstrated in this Letter. We use a compact side-pumped Nd:YVO4 bounce amplifier with grazing incidence beam for achieving high gains and power extraction. Laser output power of 7.37 W at 7 kHz, 1.2 MW pulse peak power with 877 ps duration and 1.05 mJ energy, 25 pm spectral width, and near diffraction limited mode beam quality are achieved, and the optical-to-optical efficiency is 18%. The laser is packaged in a volume of 356 mm × 226 mm × 84 mm and may be used for applications such as laser altimeters and ladar systems.

Energetic spin-polarized proton beams from two-stage coherent acceleration in laser-driven plasma.

We propose a scheme to overcome the great challenge of polarization loss in spin-polarized ion acceleration. When a petawatt laser pulse penetrates through a compound plasma target consisting of a double layer slab and prepolarized hydrogen halide gas, a strong forward moving quasistatic longitudinal electric field is constructed by the self-generated laser-driven plasma. This field with a varying drift velocity efficiently boosts the prepolarized protons via a two-stage coherent acceleration process. Its merit is not only achieving a highly energetic beam but also eliminating the undesired polarization loss of the accelerated protons. We study the proton dynamics via Hamiltonian analyses, specifically deriving the threshold of triggering the two-stage coherent acceleration. To confirm the theoretical predictions, we perform three-dimensional PIC simulations, where unprecedented proton beams with energy approximating half GeV and polarization ratio ∼ 94% are obtained.

Understanding the nano-photonics absorption limit in both front-side and front/rear-side textured slabs

Surface texturing is one of the main techniques to enhance light absorption in solar cells. In thin film devices, periodic texturing can be used to excite the guided resonances supported by the structure. Therefore, total absorption is enhanced largely due to the excitation of these resonances. Although the maximum absorption enhancement limit in both bulk and photonic structures is known already, the weight of each resonance type in this limit is not yet clear. In this contribution, we extend the temporal couple-mode theory, deriving a closed formula to distinguish the contribution of Fabry-Perot and wave-guided modes within the absorption limit for 1-D grating structures. Secondly, using this analytical approach, we can clearly address cases of bulk and thin absorber thicknesses. Our results, supported by rigorous electromagnetic calculation, show that absorption enhancement in a 1-D grating structure can be much higher than the nano-photonic limit (2πn) reported by Yu et al. Thirdly, beyond the framework put forward by Yu et al., we extended our theory to describe the absorption enhancement in double side textured slabs. We have found that when the periods of top and bottom gratings are aliquant, absorption is enhanced in a wider frequency range. We provide rigorous numerical calculations to support our theoretical approach.