Vertical Interface Research Articles

Thermal characterization of vertical interface by scanning photothermal radiometry.

In this work, scanning photothermal radiometry is used for imaging and to characterize a submicron crack. From the thermal images, the evolution of the crack is mapped in the space with micrometer resolution. A vertical contact interface at the steel-steel junction is used to represent a micro-crack with a thickness less than 0.5μm. The thermal quadrupole approach is used to model the heat transfer within the semi-infinite vertical crack. Then, using the phase mapping and that calculated from the model, the estimation of both the equivalent thermal boundary resistance of the interface and the average interface thickness was done.

Enhancement of tunneling electroresistance in metal/two-dimensional ferroelectric tunnel junctions: route for polarization-modulated interface transport

In fabricating ferroelectric tunnel junction (FTJ) devices, it is essential to employ low-resistance metals as electrodes interfacing with two-dimensional (2D) ferroelectric materials. For FTJs with a top contact configuration, two interfaces for charge transport are present, namely the vertical interface between the metal electrode and the 2D ferroelectric material, and the lateral interface between the electrode and the central scattering region. These interfaces significantly influence the tunneling electroresistance (TER) of FTJs. However, there exists a notable deficiency in comprehension concerning the physics of charge transport at the interface. In this work, we explore the interface transport properties in FTJs featuring a top contact configuration between metal and the typicalα-In2Se3monolayer. By employing the non-equilibrium Green's function method, we observe a TER ratio of1.15×105% for the Pd top contact interfacing with anα-In2Se3monolayer. The significant TER effect is attributed to polarization-controlled interface transport, which is further elucidated through an analysis of the transport mechanisms influenced by the out-of-plane polarization ofα-In2Se3at the vertical interface and the in-plane polarization at the lateral interface. This investigation of the fundamental physical mechanisms of polarization-controlled interface transport demonstrates significant potential for enhancing non-volatile memory devices.

Broadband and low-reflection mid-infrared grating coupler for a perfectly vertical fiber-chip interface.

Short-wavelength mid-infrared (SWMIR) silicon photonics has gained significant attention due to its applications in sensing, spectroscopy, and communications. A perfectly vertical grating coupler is a valuable packaging technique that is convenient for chip-to-chip optical interconnects and has low risks of mechanical failure during testing. However, SWMIR grating couplers have fewer periods to tailor the diffracted light, hindering the improvement of bandwidths and backreflections. Herein, we demonstrate a perfectly vertical subwavelength grating coupler by using a modified inverse design approach. The device exhibits a coupling efficiency of -5.9 dB with a 1-dB bandwidth of ∼122 nm and a low backreflection of -19.2 dB at 2200 nm wavelengths. Besides, the device also exhibits exceptional spatial fiber misalignment tolerance. The study underscores the effectiveness of the inverse design strategy in subwavelength grating couplers, charting a path to advance the mid-infrared silicon photonic packaging.

Study on damage of CRTS II slab tracks in coated-uncoated transition zones subjected to temperature and train loads

The CRTS II ballastless track is sensitive to temperature due to its longitudinal continuity. The application of reflective insulation coating can efficiently lower the temperature of the track slab, thereby decelerating track deterioration. Given the considerable length of high-speed railway lines, the application of reflective insulation coatings leads to numerous transitions between coated and uncoated sections. This study investigates the influence of reflective insulation coatings on the structural damage of coated-uncoated transition zones in railways. To this end, a CRTS II slab track model involving the bilinear cohesive zone model and the concrete plastic damage model is established. The model examines the combined impact of high temperature and train loading, aiming to investigate the damage patterns within the coated-uncoated transition zone of the track. The results indicate: (1) During high temperature loading, the center of the track slab layer is predisposed to warping compared to the sides. (2) If the cohesion parameter falls below 0.04 MPa, augmenting the cohesion model parameter effectively alleviates track slab arching. (3) In instances where the track slab lacks complete coverage of reflective insulation coatings, train loading may shift the location of the maximum vertical displacement and interface failure mode.

Application of Slip Interface Conditions in the Elastic Parabolic Equation

The parabolic equation method is the most effective approach for solving wave propagation problems in environments with strong vertical variations and gradual horizontal variations. This approach efficiently provides accurate solutions for problems involving sloping fluid-fluid interfaces, sloping solid-solid interfaces, and sloping solid boundaries. There remains a need for improvement for the case of sloping fluid-solid interfaces. The most promising approach to date is the combination of a single-scattering approximation and the treatment of part of the fluid layer as a solid layer with low shear speed. This is a singular perturbation, which results in rapid oscillations near the interface between the low-speed layer and the true solid layer. It is demonstrated here that the rapid oscillations may be eliminated by using slip conditions at the interface between the low-speed layer and the true solid layer. Stability problems were encountered when attempting to directly implement the slip conditions, but this problem was resolved by using an equivalent condition involving the normal derivative of the tangential displacement. This progress does not fully resolve the case of the sloping fluid-solid interface. There remains a need to find a vertical interface condition that is compatible with the slip conditions and that provides accurate results for problems involving sloping fluid-solid interfaces.

Exploring the Structural Stability of 1T-PdO2 and the Interface Properties of the 1T-PdO2/Graphene Heterojunction.

Motivated by a recent study on the air stability of PdSe2, which also reports the metastability of the PdO2 monolayer [Hoffman A. N.. npj 2D Mater. Appl.2019, 3( (1), ), 50.], in this work, we use density functional theory (DFT) to further explore the thermal, dynamic, and mechanical stability of monolayer PdO2 and study its structural and electronic properties. We further studied its vertical heterojunction composed of 1T-PdO2 and graphene monolayers. We show that both the monolayer and the heterojunction are energetically and dynamically stable with no negative frequencies in the phonon spectrum and belong to the vdW-type. 1T-PdO2 is an indirect-band-gap semiconductor with band-gap values of 0.5 eV (GGA) and 1.54 eV (HSE06). The interface properties of the heterojunction show that the n-type Schottky barrier height (SBH) becomes negative at the vertical interface in the PdO2/graphene contact, forming an Ohmic contact and mainly suggesting the potential of graphene for efficient electrical contact with the PdO2 monolayer. However, at the same time, a negative band bending occurs at the lateral interface based on the current-in-plane model. Moreover, the optical absorption of the PdO2/graphene heterojunction under visible-light irradiation is significantly enhanced compared to the situation in their free-standing monolayers.

Laser powder bed fusion of 316L stainless steel and K220 copper multi-material

ABSTRACT Multi-material additive manufacturing holds immense potential for performance and functionality enhancement. Past research efforts primarily focused on the horizontal interface (perpendicular to the sample build direction) during the laser-powder bed fusion (LPBF) of multi-materials, whereas a few studies demonstrated that the vertical interface (parallel to the sample build direction) is in fact the main obstacle towards high-integrity multi-material fabrication in a three-dimensional space. In this work, facilitated by our own patented powder spreading device, we explored the mechanisms behind defect formation along both the horizontal and vertical interfaces during the LPBF production of 316L stainless steel and K220 copper multi-materials. High-fidelity fluid dynamics simulations were also conducted to rationalise the experimental observations. A practical process parameter optimisation approach is also proposed at the end, with the aim of mitigating those large defects currently occurring near the vertical interface.

Measuring human perception of residential built environment through street view image and deep learning

As an important part of the urban built environment, streets exploring the influence mechanism between the built environment and human perception. It is one of the issues in building healthy cities. In this study, the residential streets of Zhongshan Distict, Dalian were selected as the study site, including Mountain Low-rise Neighborhood, Old Mid-rise Neighborhood, and Modern High-rise Neighborhood. Meanwhile, spatial measurement and human perception perception evaluation of the street environment were based on Deep learning and street view image (SVI). The study used human perceptions as dependent variables, and physical features as the independent variables. Finally, two regression models of positive and negative perceptions were established to analyze the relationship between them. The results showed that in the three types of neighborhood, positive perception was mainly focused on Mountain Low-rise Neighborhood; Negative perception was mainly focused on Old Mid-rise Neighborhood. Greenness, Openness, Natural Landscape, Natural to artificial ratio of the horizontal interface, and Natural to artificial ratio of the vertical interface had a positive influence on positive perception. Pedestrian occurrence rate, Enclosure, and Vehicle Occurrence rate had a negative influence on negative emotive. Greenness was the physical feature that most affected human perception. This study provided a method for objectively evaluating the quality of the street built environment. It is important for promoting the quality of residential streets and public mental health.

Studies on effect of failure modes on mechanical properties of staggered composites

Biological materials such as bone, nacre, antler, and teeth are gifted with excellent mechanical properties that have inspired the development of synthetic composites. These superior properties are attributed to the geometrical as well as the material properties of the constituents at a small scale. This paper is focused on the influence of failure modes over the mechanical properties including stiffness, strength, and toughness, after the failure of different interfaces in staggered bio-inspired structures such as regular and stairwise staggered arrangements where stiff platelets are embedded in a pliant matrix. In order to find these properties, this article develops a novel analytical model for stress transfer and effective Young’s modulus of a stairwise staggered composite based on composite micro-mechanics principles. The results indicate that the failure sequence indeed influences mechanical characteristics such as stiffness, strength, and toughness. Also, the results from the present study is capable of quantifying the major contribution of toughness that is obtained from the vertical interface failure, which is ignored in previous studies for estimating the toughness. The results indicate that a toughness contribution as high as 56% from the inclusion of the first failure can be obtained in a stairwise staggered composite. The influence of significant parameters like Young’s moduli ratio between the platelet and matrix ( Ep/Em ) over the strength at different modes of failure showed that the strength at first and second failures increases as the Ep/Em ratio increases. The findings of this study hold significant potential for predicting the failure sequences with their quantified contributions towards the mechanical properties of a bio-inspired staggered composite.

The Effect of Touchscreen Layout Division on the Usability and Driving Safety of In-Vehicle Information Systems

Compared to traditional physical controls, in-vehicle touchscreen interaction relies more on vision. Irrational In-Vehicle Information System (IVIS) interface layout design can lead to decreased driver performance and even serious traffic accidents. This study investigated the impact of IVIS layouts on usability and driving safety. We extracted and analyzed the current mainstream IVIS homepage layouts in the market and summarized four different layout structures. An experiment was conducted on a driving simulator to examine the usability of the IVIS layout design based on task reaction time, error rate, NASA-TLX (a subjective workload assessment scale developed by NASA), and subjective preference (PREF). The safety issues of IVIS layout design were also examined based on standard deviation lane position (SDLP), speed variation (SV), mean glance time, mean number of glances, and blink frequency. This study recorded and evaluated the driving performance of 40 participants during real driving tasks at four speeds (0, 60, 90, and 120 km/h). Results showed that there were significant differences in task reaction time, NASA-TLX, PREF, mean glance time, SDLP, and SV among the four layouts. Furthermore, we observed that these four layouts had varying effects on usability and driving safety at four speeds. In the stationary state, the three-partition layouts were more efficient, while the two-partition layouts had more advantages during driving. Meanwhile, the horizontal dock bar layout interfaces have more advantages compared to the vertical dock bar interface. The study provides empirical evidence for optimizing the IVIS interface layout design for enhanced usability and driving safety.

Anti‐plane stress analysis for V‐notch in a piezomagnetic half space under SH wave

AbstractIn this paper, the anti‐plane stress analysis of a V‐notch with complex boundary conditions in a piezomagnetic half space is studied. Firstly, SH wave is considered as an external load acting on piezomagnetic half space, on the basis of repeated image superposition, the analytical expression of scattering wave is conducted, which satisfies the boundary conditions on the boundary of the half space. Then, the analytical expression of standing wave is established, which satisfies the stress free and magnetic insulation conditions on the boundaries of V‐notch by the fractional Bessel function expansion method and Graf addition theorem. Finally, Green's function method is applied, the half space is divided into two parts along the vertical interface, a pair of in‐plane magnetic field and out‐plane forces are applied on the vertical interface, and the first kind of Fredholm integral equations are set up and solved by applying orthogonal function expansion technique and effective truncation. Results clarified the influence on the dynamic stress concentration factor and magnetic field intensity concentration factor under proper conditions. Besides, the analytical solutions are compared with the finite element solutions to verify the accuracy of the conclusions in this article.

Bond-slip model of headed bar and its application to component-based model for precast concrete joints under accidental loads

This study focused on investigating bond-slip behaviour of headed bars embedded in well-confined concrete. Test results based on eight pull-out specimens under displacement-controlled incremental loading showed that recommended development lengths from ACI318–19 are conservative in developing ultimate strength of headed bars associated with smaller slips than straight bars. Moreover, it was found that different (but sufficiently long) embedment lengths had a significant effect on the free-end slip but negligible effect on the loaded-end slip of headed bars. Additionally, the study highlighted the significance of head bearing in anchorage formation, especially during inelastic stage when bond strength had deteriorated. To address inaccuracy in predicting structural behaviour caused by inadequate anchorage strength of headed bars, a macro bond-slip model was proposed based on correlation in strain distribution obtained from the pull-out tests. Subsequently, the proposed model was incorporated into a component-based model (CBM) and validated against test results of PC joints under seismic loading. A numerical investigation using the validated CBM was conducted to study behaviour of exterior PC joints with headed bars and special detailing. These included Type X joint with X-bent bars and plastic hinge relocation (PHR), and Type A joint with an additional bar layer (ABL) in the beam-joint region, subjected to extreme loads such as seismic action or progressive collapse. The results revealed that seismic behaviour of exterior joints was governed by ductile failure of the beam at the PHR and vertical joint interface in Type X and Type A joints, respectively. Progressive collapse was primarily caused by column failure, with flexural and catenary action effectively preventing collapse. Notably, under both loading conditions, presence of ABL in Type A joint and X-bent bars with PHR in Type X joint improves flexural strength of beams at critical sections and joint shear strength, ultimately enhancing structural performance of joints. Design recommendations include replacing hooked bars with headed bars as well as implementing X-bent bars with PHR and ABL in PC joints. The authors advocate the strong-column-weak-beam design approach as an effective measure to prevent progressive collapse.

EHD instability of a cylindrical interface separating two couple-stress fluids

This article is an attempt at examining the axi-symmetric and asymmetric streaming flows described by the CSF framework. A liquid that has microfibers implanted in it, like a fiber-reinforced composite substance, is so-called CSF. It is a system that consists of an endless vertical cylindrical interface that separates the two CSF structure. The CSFs are increasingly growing significant in modern manufacturing and technology, necessitating greater research into these fluids. An axial EF acts over the cylindrical contact in addition to the influence of CSF. The VPT is employed for the sake of convenience to minimize mathematical complexity. Combining the elementary linear equations of motion and the proper linear related BCs is the major procedure of the linear technique. A collection of physically dimensionless numbers is produced using a non-dimensional process. Subsequently, the requirements for hypothetical linear stability are developed. With the aid of the Gaster's theorem, the MS is applied in computing the dispersion relationships. After carefully examining a variety of effects on the stability investigation of the system at issue, it has been shown that the system is more unstable when a porous material is present than it would be without one. The resulting axisymmetric disturbance situation is more unstable. The linear techniques are depicted throughout a number of graphs.

Lateral hysteretic behavior of precast concrete shear walls with unjointed vertical distribution bars and opening

Precast concrete shear walls with unjointed vertical distribution bars have desirable lateral resistance compared with cast in situ concrete shear walls and much less construction cost as no sleeve splicing joint is needed. However, the influence of opening in the precast panels on their lateral hysteretic behavior has not been fully investigated. This study presents the results of cyclic loading tests of three full size precast concrete shear walls with unjointed vertical bars and opening. The test results showed that these shear walls had similar failure modes as a cast in situ concrete shear wall, such as cracking in the corners of the opening and the concrete and steel bars crushing at the bottom corners of the shear walls. The peak load of the positive and negative loading cycles and the stiffness of the unjointed shear wall with a window opening were 14.6%, 4.3% and 1.3%, respectively, smaller and the ductility ratio was 37.6% higher, than an otherwise the same cast in situ shear wall. The lateral stiffness of the unjointed shear wall with a door opening was 35% smaller than that of the one with a window opening, due to the stiffness contribution of the wall segment underneath the window opening. The development of the longitudinal strains of concrete and steel strain along the height of the wall limbs generally met the plane section assumption. However, those next to the vertical joint interface were affected by the development length of the shear force after the bedding mortar cracked under tension. The determination of the development length needs to consider the influence of the stiffness of the link beam and the wall segment underneath the opening.

Enhanced Memristive Performance via a Vertically Heterointerface in Nanocomposite Thin Films for Artificial Synapses.

Memristors can be used to mimic synaptic behavior in artificial neural networks, which makes them a key component in neuromorphic computing and holds promise for advancing the field. In this study, a memory artificial synaptic device based on ZnO-BaTiO3 (ZnO-BTO) vertically aligned nanocomposite thin films was prepared. The vertical interface between the two phases can be used as a conduit for oxygen vacancy (OV) accumulation and a channel for OV movement, which greatly optimizes the resistive switching performance of the device and has the potential for multistage storage. By applying different pulse sequences to the device, the conductance of the device is adjusted from multiple angles, and a variety of synaptic functions are simulated, such as paired-pulse facilitation, spike-timing-dependent plasticity, short-term plasticity to long-term plasticity (STP-LTP), and long-term potentiation/depression (LTP/LTD). Finally, we construct a neural network for image recognition, and the recognition accuracy can reach 91%. Our study demonstrates the feasibility of using composite thin-film vertical interface to regulate the resistive performance of memristors and its great potential in artificial synaptic simulation and neuromorphic computing.

Analysis on scattering characteristics of SH guided wave due to V-notch in a piezoelectric bi-material strip

In this paper, the problem of a V-notch with complex boundary conditions in a piezoelectric bi-material strip is studied. First, SH guided wave is considered as an external load acting on the piezoelectric bi-material strip; on the basis of repeated image superposition, the analytical expression of scattering wave is conducted, which satisfies the stress-free and electric insulation conditions on the upper and lower horizontal boundaries of the strip. Then, the analytical expression of standing wave is established, which satisfies the stress-free and electric insulation conditions on the boundaries of V-notch by the fractional Bessel function expansion method and Graf addition theorem. Finally, Green’s function method is applied, the bi-material strip is divided into two parts along the vertical interface, a pair of in-plane electric field and out-plane forces is applied on the vertical interface, and the first kind of Fredholm integral equations is set up and solved by applying the orthogonal function expansion technique and effective truncation. Results clarified the influence on the dynamic stress concentration factor and electric field intensity concentration factor under proper conditions. Besides, the analytical solutions are compared with the finite element solutions to verify the accuracy of the conclusions in this article.

Contact evaluation of the penta-PdPSe/graphene vdW heterojunction: tuning the Schottky barrier and optical properties.

In this work, we design a van der Waals heterojunction composed of semiconducting penta-PdPSe and semi-metallic graphene (G) monolayers based on state-of-the-art theoretical calculations. Our results show that both monolayers well preserve their intrinsic features and possess an n-type near Ohmic Schottky contact with a low Schottky barrier height of 0.085 eV for the electrons at the vertical interface. The electronic band alignment suggests a negative band bending of -1.47 eV at the lateral interface, implying electrons as the major transport carriers. Moreover, the transmission gap closely mirrors the heterojunction's band gap, indicating a subtle yet profound interaction between graphene and penta-PdPSe monolayers, which leads to enhanced optical absorption coefficient reaching 106 cm-1 and strong conductivity spanning the visible to ultraviolet region. In addition, our study demonstrates the ability to modify the penta-PdPSe/G heterojunction interface, switching between p-type as well as Ohmic contacts by applying external electric fields. These properties render the penta-PdPSe/G heterojunction promising for optoelectronic applications.

Dynamic analysis for V-notch in a piezomagnetic bi-material strip under SH guided wave

In this paper, the problem of a V-notch with complex boundary conditions in a piezomagnetic bi-material strip is studied. Firstly, SH guided wave is considered as an external load acting on piezomagnetic bi-material strip, on the basis of repeated image superposition, the analytical expression of scattering wave is conducted, which satisfies the stress free and magnetic insulation conditions on the upper and lower horizontal boundaries of the strip. Then, the analytical expression of standing wave is established, which satisfies the stress free and magnetic insulation conditions on the boundaries of V-notch by the fractional Bessel function expansion method and Graf addition theorem. Finally, Green’s function method is applied, the bi-material strip is divided into two parts along the vertical interface, a pair of in-plane magnetic field and out-plane forces are applied on the vertical interface, and the first kind of Fredholm integral equations are set up and solved by applying orthogonal function expansion technique and effective truncation. Results clarified the influence on the dynamic stress concentration factor and magnetic field intensity concentration factor under proper conditions. Besides, the analytical solutions are compared with the finite element solutions to verify the accuracy of the conclusions in this article.

Exploring the application of virtual space in spatial design in the era of artificial intelligence

Abstract The development of the Internet era acts on every change brought by spatial design so that the application of virtual reality technology in spatial design solutions begins to emerge. In this paper, firstly, combining the general process of visualization and the characteristics of visual variables, seven visual variables are selected for preliminary 3D visual representation, and their applicability under virtual reality space is analyzed. The HSV color space is also used for visual coding. According to the intuitive nature of visual perception of spatial design, a multiple visual variables mapping model based on VR is proposed. Considering the sequential characteristics of spatial design, PCA-LSTM spatial design classification model is proposed, and virtual space is applied in spatial design by local changes of the top surface, ground surface, and vertical interface. The simulation experiments are conducted by selecting SVM, BP neural network, and LSTM network as the comparison algorithms, and the results show that the accuracy of both the training set and the test set is found to be improved based on the PCA-LSTM classification model for spatial design classification, which is 4.9% and 9.49% higher than the traditional LSTM algorithm, respectively, verifying the PCA-LSTM for spatial design The effectiveness of PCA-LSTM for spatial design classification is verified. This study cleverly uses the design technique of virtual space to better apply virtual space in spatial design.

Flexural behavior of long-term loaded RC beams strengthened by ultra-high performance concrete

This study aims to investigate the flexural behavior of reinforced concrete (RC) beams strengthened with ultra-high-performance concrete (UHPC) after being loaded with long-term sustained loads for more than 20 years. Seven RC beams, originally fabricated in 1998, are categorized as the one-time pouring unnotched beam (Overall beam), one-time pouring notched beam (Notched beam), and two-time pouring beam (Repaired beam). These RC beams were firstly tested under the effect of long-term sustained loads which lasted 23.6 years. Subsequently, notched beams were strengthened using UHPC (hereafter named as Strengthened beam), which are tested under four-point bending test to investigate the significance of strengthening using the UHPC. Long-term load effects on the flexural performance of RC beams, including creep, cracking, concrete carbonization, and steel rebar corrosion were tested and analyzed. Test results showed that the maximum carbonization depth was less than the concrete cover depth and the steel rebars corrosion was among 1.51–2.47%, which indicates that the steel rebars inside the beam are well protected and are almost free of rust. The bearing capacity of the strengthened beams were increased by 24.6–48.6% compared with that of the Notched beam, which emphasizes the significance of strengthening using the UHPC. The displacement ductility of the strengthened beams was decreased by 82–94% compared with that of the Overall beam, however no brittle failure was observed during the test. It is worth mentioning that the internal changes, caused by the long-term sustained loading, could not be completely changed by adopting UHPC strengthening, while the stiffness reduction caused by long-term loading considerably influenced the flexural behavior of the UHPC strengthened beams. In addition, more attention shall be paid to the UHPC-NC vertical interface which remarkably affected the flexural performance of the Strengthened beams.