Double-deck Structure Research Articles

Double-Deck Structure in a Fluid Flow Induced by a Uniformly Rotating Disk with Small Irregularities: the Nonsymmetric Case

Double-Deck Structure in a Fluid Flow Induced by a Uniformly Rotating Disk with Small Irregularities: the Nonsymmetric Case

Modeling of fluid flow along a small heated irregularity on the plate surface in the framework of double-deck boundary layer structure

Modeling of fluid flow along a small heated irregularity on the plate surface in the framework of double-deck boundary layer structure

A Double-decker Flux Rope Model for the Solar Eruption on 2012 March 10

We present a magnetic configuration of a compound solar eruption observed on 2012 March 10, from NOAA AR 11429 near the disk center, which displayed a soft X-ray sigmoid before the eruption. We constructed a series of magnetic field models, including double-decker flux rope configurations, using the flux rope insertion method. This produces three-dimensional coronal magnetic field models constrained by the photospheric magnetogram and observed EUV coronal structures. We used different combinations of flux rope paths. We found that two flux ropes sharing the same path at different heights quickly experience a partial merging in the initial iteration of the magnetofrictional relaxation process. Different paths with less than 30% overlap allowed us to construct stable double-decker structures. The high spatial and temporal resolution of the Solar Dynamics Observatory/Atmospheric Imaging Assembly facilitated the selection of a best-fit model that matches the observations best. Moreover, by varying fluxes in this validated nonlinear force-free field double-decker configuration, we successfully reproduce all three scenarios of eruptions of double-decker configurations: (i) eruption due to the instability of higher flux rope; (ii) eruption due to rising lower flux rope and merging with higher flux rope; and (iii) eruption due to the instability of both flux ropes. This demonstrates that magnetofrictional simulation can capture the large-scale magnetic structure of eruptions for a realistic field configuration at eruption onset.

Prandtl System of Equations with Self-Induced Pressure for the Case of Non-Newtonian Fluid: Dynamics of Boundary Layer Separation

The problem of flow of a non-Newtonian viscous fluid with power-law rheological properties along a semi-infinite plate with a small localized irregularity on the surface is considered for large Reynolds numbers. The asymptotic solution with double-deck structure of the boundary layer is constructed. The numerical simulation of the flow in the region near the surface was performed for different fluid indices. The results of investigations of the flow properties depending on the fluid index are presented. Namely, the boundary layer separation is investigated for different fluid indices, and the dynamics of vortex formation in this region is shown.

Study of Rail Structure Interaction on Double-Decker integrated bridge with Metro and Highway Structure

In the metro rail system, Long Welded Rails (LWR) have been used for less maintenance, smooth & safe ride at higher speeds. The arrangement of connecting rail and deck system causes an interaction effect in force transfer. The study of this effect in the structure is Rail Structure Interaction (RSI) analysis. In this study, the behavior of double-decker integrated structure, rail stresses and relative deformation are studied due to the bending behavior of the deck, bearing articulation & support stiffness with the proposed geometrical arrangement of the bridge and applicable loading as per standards. The effect of RSI analysis and limitations of additional stresses are referred with the guidance of UIC standards & RDSO guidelines. The double-decker elevated viaduct structure is proposed with a first level highway deck carrying highway loading and second level metro system carrying metro loading. In highway bridge deck, the decks are proposed with four span continuous to avoid discomfort due to more number of expansion joints and thereby provide smooth riding for passengers. The effect of RSI is studied in this paper by considering the above complexity of two-level superstructure with a different type of superstructure at the metro level due to the track requirement like U girder deck system at each track, I girder deck system as a single deck for both the tracks at the cross over / pocket track locations and I girder deck system at highway level with deck continuity. A finite element analysis is performed using the analytical tool MIDAS CIVIL software to study the interaction mechanism for this double-decker bridge structure. For this study, rail and deck (unballasted) are linked with a multilinear elastic spring as recommended in UIC 774-3R and other boundary conditions as per IRS & IRC standards. This paper discusses the behavior of structure from the results of the rail stresses and forces to the substructure due to thermal and live load effects at both level Metro Rail system and Highway Road systems.

Modeling of melting-freezing of ice in problem of fluid flow along a small irregularity

In this paper, we study the phase transition in a fluid flow along an ice surface with a small localized irregularity for large Reynolds numbers. In the framework of the double-deck structure of the boundary layer, a mathematical modelbased on the phase field system is constructed that describes the dynamics of the phase transition, and the results of numerical simulation are presented.

The strain regulation of atomic structure and properties on ultra-stable monolayer butylammonium-based halide perovskites: Insight from density functional theory

The two-dimensional (2D) monolayer butylammonium (BA)-based halide perovskites are applied for perovskite solar cells (PSCs) due to ultra-stable and highly crystalline. However, the systematic analysis has not been well conducted for 2D monolayer (BA)2BX4 (BPb, Sn; X = I, Br, Cl) perovskites. Here we systematically investigated the photoelectric and mechanical properties using density functional theory (DFT), further revealing the effect and mechanism of the direct and doping-modulated strain induced by external strain(stress) and pre-strain treatment technology. (BA)2PbI4, (BA)2SnI4 and (BA)2SnBr4 have excellent properties for PSCs. Based on the direct strain regulation, (BA)2SnBr4 exhibits smaller bandgaps and more stable atomic evolution than (BA)2PbI4, and better mechanical properties and smaller electrostatic macroscopic average potential difference (ΔP) than (BA)2SnI4. Based on the doping-modulated strain regulation on 2D (BA)2(Pb1-xSnx)X4, lower Pb-doping ratio induces the nonlinear dependence of bandgaps, which mainly originating from the local compressive strain effect on Sn crystal structure induced by larger Pb-atomic radius. Especially, the double-decker structure (Sn2Pb2-p) obtains excellent stability due to stress relaxation induced by in-inorganic layer homogeneity. We anticipate this work will provide the sufficient guidance for designing and fabricating green 2D or 2D/3D halide junction PSCs to improve both PCE and stability.

Synthesis, Structure, and Magnetic Properties of Homometallic Mono-, Penta-, and Hexanuclear Dysprosium Complexes

Regulation of the complex structure is greatly significant for the preparation of single-molecule magnets (SMMs). A Schiff base ligand, having suitably flexible coordination pockets, is usually designed to construct SMMs. In this text, three new homometallic complexes ([Dy(HL)2](NO3)·2H2O (Dy1), [Dy5(L)4(CH3CO2)6](CH3CO2)·6MeOH·H2O (Dy5), and [Dy6(L)2(L1)2(u3-OH)4(CF3SO3)6(EtOH)4]·2EtOH (Dy6)) were synthesized based on a Schiff base ligand, 6,6′-dimethoxy-2,2′-[4,5-dimethyl-o-phenylenebis(nitrilomethylidyne)]-diphenol (H2L), which has an N2O2 pocket and a certain extent of steric hindrance. Their structures are characterized by single-crystal X-ray diffraction, and their magnetic properties are also explored. Complex Dy1 is a double-decker structure in which the Dy ion is sandwiched by two HL– ligands. Complex Dy5 displays a helical quadruple-decker structure which can be regarded as the structural extension of complex Dy1 but this is terminated by the coordination of acetate groups. Complex Dy6 is a centrosymmetric hexanuclear structure in which three Dy(III) ions construct an independent triangular plane. The new ligand L12– (H2L1 = 2-(hydroxymethyl)-6-methoxyphenol) in complex Dy6 is produced in situ from H2L under hydrothermal conditions. Magnetic studies on these complexes revealed that both Dy1 and Dy6 are typical SMMs, with a Ueff/kB value of 38.4 K for Dy1 and 33.6 K for Dy6, respectively, and complex Dy5 also shows SMM behavior under a zero dc field.

An Improved Evolutionary Structure Optimization Method for Smooth Topology Design of Structures

To meet the needs of industrial production, an improved evolution structural optimization (ESO) method with high efficiency is proposed. The optimized design variables with intermediate density were designed using the windowed evolution structural optimization (WESO) method to increase the stability of the algorithm. The efficient calculation method of the element node sensitivity was established, which realizes the establishment of level set functions, smooth topological design of structures and the updating of design variables. The stability of the proposed algorithm was verified by the Zhou–Rozvany problem, two- and three-dimensional (3D) numerical results. The effectiveness and efficiency of the proposed algorithm was further verified by numerical comparison with other topology optimization frameworks. Lastly, the improved windowed ESO method was applied to the initial configuration design of the double-deck bridge structure, which not only provides guidance for its initial design but also demonstrates the applicability of the method in complex structural systems.

Numerical Simulations of the Influence on the Temperature Fields of Large-Sized Nd-Glass Slab with Designed Edge-Cladding Materials, Methods, and Structures

The good cladding of a large-sized Nd-doped phosphate glass slab as a laser amplifier requires not only the amplified spontaneous emission and parasitic oscillation to be fully absorbed, to hold up the small signal gain coefficient of the Nd ions, but also the absorbed heat energy to be appropriately dissipated to extend a uniform temperature field for the larger laser beam aperture of the edge-cladded Nd–glass slab. In the present work, numerical simulations were performed based on the developed feasible edge-cladding designs for a 786 × 436 × 40 mm3 Nd–glass slab, including the following alterations: optical absorptivity, quantum-dot absorption centers, ceramics with higher thermal diffusivity, glasses with lower and higher specific heat values, 3D printing edge-cladding methods, double-deck edge-cladding structure with transparent strips as a buffer layer, and thickening of the edge-cladding. All of these designed edge-cladding materials, methods, and structures satisfy both requirements of sufficiently absorbing and precisely matching with the refractive index, as emphasized by the edge-cladding for the Nd–glass. Some of the designed edge-claddings resulted in a much more uniform temperature field than the composite polymer–glass edge-cladding as the standard for comparison, which could be utilized to extend the effective laser aperture of the Nd–glass slab, thus being beneficial to the laser beam size and laser energy in the optics recycle loop strategy.

A Double-decker Filament Formation Driven by Sunspot Rotation and Magnetic Reconnection

In this paper, through analyzing data from the Solar Dynamics Observatory (SDO) and the Global Oscillation Network Group (GONG), we present a study on the formation of a double-decker filament in NOAA Active Region 12665 from 2017 July 8 to 14. We find that magnetic reconnection occurs between two smaller filaments to form a longer filament. According to the evolution of the leading sunspot, it is obvious that the sunspot experiences a continuous rotation around its umbra. During the period from 03:00 UT on July 11 to 10:00 UT on July 14, the average speed of sunspot rotation is about 3.°7 hr–1. The continuous rotation of sunspot stretches the filament and results in the formation of a reversed S-shaped filament. Due to the motion of the magnetic field and internal magnetic reconnection, the filament splits into two branches and forms a double-decker filament structure. In the process of filament separation, internal magnetic reconnection can also accelerate the filament separation. Nonlinear force-free field extrapolation indicates that there are two magnetic flux ropes, which are consistent with the observed results. Eventually, the upper filament erupts and produces an M-class flare and a halo coronal mass ejection.

Double–deck structure in the fluid flow induced by a uniformly rotating disk with small symmetric irregularities on its surface

The stationary problem of a uniformly rotating disk with slightly perturbed surface immersed in a viscous fluid is considered. The asymptotic solutions with double-deck structure of the boundary layer are constructed for the symmetric periodic and localized types of irregularities on the disk surface for large Reynolds numbers. The numerical simulation of the flow near the surface shows that the radial component of the velocity prevails and the qualitative behavior of the flow depends on the amplitude of irregularities. Namely, the separation of the boundary layer from the streamlined surface occurs when a certain critical value of the amplitude of irregularities is exceeded and a laminar flow with a stationary vortex is observed in this case.

Self-floating Ti3C2 MXene-coated polyurethane sponge with excellent photothermal conversion performance for peroxydisulfate activation and clean water production

• MXene@PU photothermal conversion module reached 140 °C interfacial temperature. • Thermal activation of PDS significantly enhanced the degradation of organic pollutants. • Abundant recycled water was produced in photothermal conversion process. The self-floating Ti 3 C 2 MXene-coated polyurethane sponge (MXene@PU module) was prepared via the simple coating operation for thermal activation of peroxydisulfate (PDS) and production of clean water. Coating MXene on the surface of PU significantly improved the degradation of model pollutant carbamazepine (CBZ) compared with PU alone under simulated solar radiation. Because of the excellent photothermal conversion performance of Ti 3 C 2 MXene and the unique double-deck structure of MXene@PU module, the interfacial temperature of MXene@PU module reached about 140 °C, far higher than that of PU (about 82 °C). Radical identification experiments demonstrated that both hydroxyl radical and sulfate radical contributed to the degradation of organic pollutant. Addition of Cl − , HPO 4 2− , HCO 3 − and natural organic matter in solution generated inhibitory effect on CBZ degradation. The prepared MXene@PU module exhibited excellent stability after long-time experiment. Importantly, the interfacial evaporation process produced abundant recycled water and no pollutant was detected in recycled water. This study provides a feasible way to utilize the renewable solar energy for removal of organic pollutants and production of clean water.

100-μm-Scale High-Detectivity Infrared Detector With Thermopile/Absorber Double-Deck Structure Formed in (111) Silicon

This article presents a 96 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times $ </tex-math></inline-formula> 106 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> sized single-crystalline silicon (SC-Si) /Au thermopile infrared (IR) detector, with the thermopile and IR absorber located at different layers of a double-deck micromechanical structure for improving detectivity. In order to enhance IR-heat absorption within such a tiny device size, an umbrella-shaped SiN IR absorbing membrane instead of traditional plane IR-absorbing film occupies the whole area of the top layer structure. The umbrella-shaped IR absorber is suspended on top of the IR-detecting thermopile layer, with a central umbrella-stick to support the suspending and conducting the absorbed IR-heat to the bottom thermopile layer. The bottom thermopile layer consists of six pairs of spiral-shaped SC-Si/Au thermocouples that feature several times higher Seebeck coefficient compared to the traditional polysilicon/metal thermocouples. By combining surface-micromachining technique with a specific bulk-micromachining process performed in (111) silicon wafer, the double-deck structured IR-detector is successfully fabricated only from the front side of a single (111) silicon wafer for IC-foundry compatible low-cost manufacturing. Testing results show that this device of about 100-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> scale achieves an ultrahigh IR detectivity of 1.01 <inline-formula> <tex-math notation="LaTeX">$\times \,\,10^{{8}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>Hz<inline-formula> <tex-math notation="LaTeX">$^{{{1}/{2}}}\cdot \text{W}^{-{1}}$ </tex-math></inline-formula>, which is two times improvement compared to the recently reported thermopile IR detectors, though the counterparts had larger device area. Featuring tiny size and batch fabrication capability, the proposed high-performance IR-detector is promising in both single-point detection and multipixel arrayed temperature imaging applications.

Partial Eruption, Confinement, and Twist Buildup and Release of a Double-decker Filament

Abstract We investigate the failed partial eruption of a filament system in NOAA AR 12104 on 2014 July 5, using multiwavelength EUV, magnetogram, and Hα observations, as well as magnetic field modeling. The filament system consists of two almost co-spatial segments with different end points, both resembling a C shape. Following an ejection and a precursor flare related to flux cancellation, only the upper segment rises and then displays a prominent twisted structure, while rolling over toward its footpoints. The lower segment remains undisturbed, indicating that the system possesses a double-decker structure. The erupted segment ends up with a reverse-C shape, with material draining toward its footpoints, while losing its twist. Using the flux rope insertion method, we construct a model of the source region that qualitatively reproduces key elements of the observed evolution. At the eruption onset, the model consists of a flux rope atop a flux bundle with negligible twist, which is consistent with the observational interpretation that the filament possesses a double-decker structure. The flux rope reaches the critical height of the torus instability during its initial relaxation, while the lower flux bundle remains in stable equilibrium. The eruption terminates when the flux rope reaches a dome-shaped quasi-separatrix layer that is reminiscent of a magnetic fan surface, although no magnetic null is found. The flux rope is destroyed by reconnection with the confining overlying flux above the dome, transferring its twist in the process.

A Double-Deck Structure of Reduced Graphene Oxide Modified Porous Ti3C2Tx Electrode towards Ultrasensitive and Simultaneous Detection of Dopamine and Uric Acid.

Considering the vital physiological functions of dopamine (DA) and uric acid (UA) and their coexistence in the biological matrix, the development of biosensing techniques for their simultaneous and sensitive detection is highly desirable for diagnostic and analytical applications. Therefore, Ti3C2Tx/rGO heterostructure with a double-deck layer was fabricated through electrochemical reduction. The rGO was modified on a porous Ti3C2Tx electrode as the biosensor for the detection of DA and UA simultaneously. Debye length was regulated by the alteration of rGO mass on the surface of the Ti3C2Tx electrode. Debye length decreased with respect to the rGO electrode modified with further rGO mass, indicating that fewer DA molecules were capable of surpassing the equilibrium double layer and reaching the surface of rGO to achieve the voltammetric response of DA. Thus, the proposed Ti3C2Tx/rGO sensor presented an excellent performance in detecting DA and UA with a wide linear range of 0.1–100 μM and 1–1000 μM and a low detection limit of 9.5 nM and 0.3 μM, respectively. Additionally, the proposed Ti3C2Tx/rGO electrode displayed good repeatability, selectivity, and proved to be available for real sample analysis.

Ultra-high-performance heat spreader based on a graphite architecture with three-dimensional thermal routing

To meet the increasing demand for highly efficient heat dissipation in power electronics, a heat spreader that has significantly greater isotropic thermal conductivity than the commonly used copper (400 W/m·K) should be developed. Although graphite is a promising candidate because of its high basal-plane thermal conductivity, its application is restricted by its low c axis thermal conductivity. This issue can be resolved by transforming graphite into an isotropic thermal conductor by building a structure that can effectively route heat in all three dimensions. Herein, we develop a double-decker structure with differently oriented graphite layers to realize high heat dissipation from a local heat source. The critical issue of bonding the graphite layers is overcome by a high-temperature process using Cu as the binding layer. The graphite/Cu composite efficiently dissipates heat nearly isotropically and performs as well as an isotropic conductor with a thermal conductivity of 900 W/m·K. Anisotropic thermal conduction of graphite is overcome by 3D thermal routing Isotropic heat dissipation is realized by a double-decker structure of graphite blocks Performance comparable to isotropic materials with thermal conductivity of 900 W/m·K In this paper by Xu et al., the anisotropic heat conduction of graphite is overcome by assembling graphite blocks into a double-decker structure, which provides effectively isotropic heat dissipation comparable to isotropic materials with thermal conductivity as high as 900 W/m·K. This is more than twice the value of the typically used copper.

On the Plasmonic Properties of Double-Deck Graphene Nanoribbon Structure in Mid-Infrared Regime

In this work, a double-deck structure consisting of graphene nanoribbons is proposed, and the plasmonic properties of the system is investigated at mid-infrared wavelengths. In the structure, two graphene nanoribbon arrays with different parameters are coated on both sides of a glass substrate. With respectively varying the Fermi energies, the layer numbers of the graphenes, and the widths of the ribbons, the light transmittance is studied in the wavelength region from 5 to 30\(\mu\)m, via the finite difference time domain method. Multiple plasmonic resonances are revealed in the double-deck graphenes. It is shown that the plasmonic resonance properties including the resonance wavelengths, the peak intensities, and the peak widths can be adjusted by changing the parameters of the graphenes. The double-deck graphene nanoribbon structure proposed in this work may be implemented in designs of plasmonic devices in mid-infrared regime.

Double-deck structure in the fluid flow problem over plate with small irregularities of time-dependent shape

An asymptotic solution with double-deck boundary layer structure is constructed for the problem of an incompressible fluid flow over a semi-infinite plate with small localized or periodic (fast-oscillating) irregularities on the surface whose shape depends on time. Numerical simulation of flow in the near-plate region is presented for two types of the shape change: oscillations of the amplitude of irregularities and the motion of the irregularity in the upstream and downstream directions. The influence of the time-dependent shape on the flow behavior (including the vortex formation process) is shown in detail.

Self-contained Janus Aerogel with Antifouling and Salt-Rejecting Properties for Stable Solar Evaporation.

Janus structural interfacial vaporization by separating the solar absorber from the bulk working fluid has attracted tremendous attention due to its low heat losses and high solar conversion efficiency for desalination, water purification, energy generation, etc. However, a totally separated double-deck structure with a discontinuous interfacial transition and inefficient photothermic materials undermines its long-term use and large-scale practical exploitation. Herein, a low-cost Janus monolithic chitosan aerogel with continuous aligned run-through microchannels has been demonstrated to have a highly efficient photothermic effect on seawater desalination and wastewater purification. The top solar absorber layer enhances broadband light absorption and photothermal conversion efficiency via the multiple internal reflection of incident light in the aligned microchannels. Moreover, the insulating/hydrophilic bottom layer promotes water transportation and heat localization, and simultaneously prevents salt/fouling accumulation. As a result, a long-term solar vaporization rate of ∼1.76 kg m-2 h-1 is achieved, corresponding to a light-to-vapor efficiency of ∼91% under 1 sun irradiation. Notably, the large-vessel microchannels throughout the aerogel and favorable swelling property provide sufficient water replenishment and storage for completely isolating self-contained evaporation, illustrating an enhanced and time-extended self-contained solar steam generation. Such a low-cost bilayer aerogel with remarkable cycling stability in various fluids offers potential opportunities for freshwater production in remote rural areas.