Arrangement Of Pillars Research Articles

Research on reasonable coal pillar staggered distance in shallow multi-seam mining

In shallow buried closely spaced multi-seam mining in Jurassic Coalfield in western China, due to specific reasons, it is inevitable that the lower and upper coal seam working faces and coal pillars are overlapped, resulting in stress concentration, uneven subsidence of the ground surface, the deformation and damage of the roadway intensified. In order to decrease surface damage and stress concentration, combined with physical simulation, engineering practices and theoretical analyses, reasonable coal pillar staggered distance in shallow multi-seam mining is investigated. The evolution properties of three-field (stress field, displacement field and fracture field) based on coal pillar staggered distance (CPSD) were analyzed, the determination method of rational CPSD was put up. Research findings reveal that concentrated stress results from upper and lower pillar stress superposition, and the lower pillar should be arranged in the low-stress zone. Through rational pillar arrangement, the uneven subsidence of surface is reduced, and the concentrated fractures of overlying strata and surface are decreased. For No. 1–2 and No. 2–2 coal seam mining, as CPSD is increased, subsidence above the upper coal pillar increases and the uneven subsidence of surface decreases, the concentrated stress reduced by 25%, the width of surface fractures reduced 81.1%. Consequently, rational CPSD on the basis of coupling control of three-field can be determined, the reasonable CPSD is 40–55 m. It can provide a method to realize underground safe mining and ground surface green mining in shallow multi-seam mining.

Optimizing implant lattice design for large distal femur defects: Stimulating interface bone growth to enhance osseointegration

Large bone defects in the distal femur present a significant challenge due to the lack of inherent self-healing capabilities. Traditional approaches, such as utilizing polymethyl methacrylate (PMMA) in conjunction with a plate for distal femur reconstruction, have shown unsatisfactory osseointegration outcome, which leads to complications. To address this challenge, this study focuses on developing a lattice-structured implant for reconstructing distal femoral bone defects. The lattice geometry is based on the cuboctahedron lattice, with its design optimized through the adjustment of pillar diameter and arrangement angle. The lattice structure is designed to stimulate the surrounding bone, ultimately enhancing osseointegration in distal femur reconstruction. Finite element analysis revealed that for promoting bone ingrowth toward the implant, setting the optimal lattice structure parameters, i.e., a 45° arrangement angle and a 0.8 mm pillar diameter, is required. Fabricated using state-of-the-art metal three-dimensional printing, the implant underwent rigorous validation through biomechanical testing, in vitro biological assays, and animal experiments. The comprehensive results affirmed the bioactivity of the lattice-structured implant, underscoring its capability to improve osseointegration in distal femoral defect reconstruction.

Dislodgement of Hydrogen Bubbles in Microchannels with Embedded Pillars: An Analytical, Experimental, and Numerical Study.

Microchannels with integrated pillars have enhanced the production capabilities and performance of various applications due to their high surface-to-volume ratio. However, emerging gas bubbles can become trapped, potentially limiting the functionality or efficiency of the device when scaled down to the low-micrometer scale. Understanding the conditions required to dislodge these bubbles is thus critical for optimizing microfluidic devices with complex physical behaviors. Here an analytical model is presented that outlines the dislodgment conditions and driving forces for such gas-liquid flows. These terms are derived from the gas-liquid interface properties, geometry, and processing parameters. As the density of the pillar arrangement is scaled down, the resistance to bubble dislodgment typically increases. Nevertheless, the bubble is compelled to dislodge at lower pressure loads when critical volumes are reached. This newly discovered effect is particularly noticeable in densely packed arrays and can be explained by the interplay of increased surface tension, geometrical restrictions, and volume-preserving forces. The analytical terms and effects are validated through novel experimental and numerical methods tailored for microchannels in the low-micrometer scale, showing strong agreement.

Design method for large-scale wide field-of-view monochromatic metalenses

We propose a novel design method for wide field-of-view monochromatic metalenses. The proposed technique partitions the outer region of a metalens into supercells, which are generated by dividing the outer region into intervals along the radial direction, where the target phase changes by 2π, and along the angular direction with a constant angular periodicity. Therefore, the shape of each supercell can be approximated as a rectangle with its size comparable to a wavelength. The arrangement of pillars within this supercell is determined by metagrating optimization via the adjoint method. The optimization process considers both inter-pillar couplings and the range of incidence angles. This makes the design of large-scale wide field-of-view high-efficiency metalenses more tractable than the conventional unit-cell-based method, which is prone to efficiency decrease especially near the lens periphery. Furthermore, it has a potential advantage in terms of computational cost over other recently proposed optimization-based methods.

Sensitivity and optimization analysis of pillar arrangement on the thermal–hydraulic performance of vapor chamber

A vapor chamber with pillar columns is imperative for heat management in high-powered electronic devices. Previous investigations presented a trade-off between the thermal transfer and flow pressure drop within the parameters of the pillar arrangement. However, the parameters of pillar arrangement at millimeter scale are not thoroughly considered, and this trade-off has yet to be addressed in the complete VC-P device. In this work, we optimized the parameters of pillar arrangement at millimeter scale within the complete VC-P, which was conducted by ANSYS Workbench with optiSLang. The multi-objective minimization strategy was the maximum temperature difference on the condenser surface (ΔTc,max), total thermal resistance (R), and total pressure drop (ΔPtotal). The three key parameters of optimizing pillar arrangement were the horizontal (X) and vertical (Y) pitch of pillar columns, and the diameter of pillar columns. First, a prediction model utilizing a response surface methodology derived from a central composite design was established. The results found that a critical pitch of pillar columns is approximately 15 mm. High sensitivity value (0.84) indicate that the diameter of pillar columns has a crucial impact on ΔTc,max and R. Using strength Pareto evolutionary algorithm 2, Part of these optimized VC-P exhibits reduce ΔPvc significant up to 40–60 %, while incurring a marginal increase in R and ΔTc,max higher less than 4–13 % and 1–8 % compared to the vapor chamber without pillar columns. Finally, the final optimal solution has been selected using the TOPSIS analysis method. The case study presented can offer valuable insights into the application of the same methodologies for the analysis of scenarios involving non-circular pillars.

백제 웅진기 건물지의 구조분석

Since the building site during the Ungjin period of Baekje is different from the Hanseong period pit-house building site in that it has an above-ground structure, it is very important data in understanding the form and changes of the Baekje building site and the changes in the cultural base. The shape of the building site can be examined focusing on Gongsanseong Castle, a royal castle during the Ungjin period, and the ruins of Jeongjisan Mountain, a national ceremonial site, and most of the building site shows the structure of a Byeokju-building site.
 In order to analyze the structure of the building sites during the Ungjin period of Baekje, an attempt was made to analyze the floor plan, scale, entrance facilities, windows, pillar arrangement, walls, roof type, and living aspects of the building sites identified at the Gongsanseong Castle and Jeongjisan Mountain ruins.
 The structure of the building site during the Ungjin period of Baekje shows a square and rectangular plane, and is judged to be a single-room building composed of a single room with a wall made of mixed mud & wood. The scale is about 6m in both length and width, and the concept of a compartment is believed to be expressed through side expansion, which is believed to be due to the development of wooden furniture technology and thus the stabilization of above-ground building site.
 Therefore, the structural characteristics of building site during the Ungjin period of Baekje, can be understood as the above-ground of the living plane of the building site and the standardization of the scale, as well as the spatial composition of the building with compartments based on wooden structures.

Multifunctional Composite Material with Efficient Microwave Absorption and Ultra-High Thermal Conductivity

The increasing demands for electronic devices to achieve high miniaturization, functional integration, and wide bandwidth will exacerbate the heat generation and electromagnetic interference, which hinders the further development of electronic devices. Therefore, both the issues of microwave absorption and heat dissipation of materials need to be addressed simultaneously. Herein, a multifunctional composite material is proposed by periodic arrangement of copper pillars in a matrix, based on the wave-absorbing material. As a result, the equivalent thermal conductivity of the composite structure is nearly 35 times higher than the wave-absorbing matrix, with the area filling proportion of the thermal conductivity material being 3.14%. Meanwhile, the reflectivity of the composite structure merely changes from −15.05 dB to −13.70 dB. It is proved that the designed composite structure possesses both high thermal conduction and strong microwave absorption. The measured results accord well with the simulation results, which demonstrates that the thermal conductivity of the composite structure can reach more than 10W⋅m−1⋅K−1 without significant deterioration of the absorption performance.

Numerical Analysis, Optimization, and Multi-Criteria Design of Vacuum Insulated Glass Composite Panels.

The subject of this study is Vacuum Insulated Glass (VIG) panels, which consist of two glass panes with an evacuated space and evenly distributed micro-support pillars between them. The deflection of panes towards the centre of the structure caused by atmospheric pressure is a mechanical problem that occurs in this type of structure. The aim of this study was to extend previous research on the optimal arrangement of support pillars in terms of eigenfrequencies and dynamics to include aesthetic aspects. Using Abaqus/CAE v2017 software, a large number of numerical models were created and subjected to a comprehensive multi-criteria analysis. Fractal analysis was employed to automatically assess the aesthetics of the proposed solutions. The study presents theoretical solutions that could be implemented in industrial production. The presented study shows that it is possible to effectively extend the criteria for optimizing the arrangement of pillars with new design criteria. Most studies focus on pillar placement, amount, or shape in terms of panes thermal or mechanical properties. Due to the increasing number of VIG panels applications in places exposed to external vibrations, other design criteria for VIG panels are also required and are provided by the following study.

Role of Interfacial Evaporation Process in Thin Vapor Chambers With Variable Pillar Spacing and Nonuniform Heat Flux

This paper reports the results of our numerical studies on the performance of thin film evaporation, mostly seen in the evaporator of a thin vapour chamber, using micropillar arrays of varying pitch and under both uniform and non-uniform heat flux conditions. The dry-out heat flux and evaporator surface temperature have been used as the performance metrics. A numerical model has been formulated to solve the fluid flow and phase change heat transfer considering the capillary pumping action (wicking action). The model is next exercised to study the performance of the evaporator with variable pitch of the micropillar array and with both uniform and non-uniform heat flux at the base. The pitch variations are done either by maintaining the mean pitch to be constant (same number of pillars) or by keeping the limiting pitch (maximum) equal to the uniform pitch scenario. The results show that a linearly decreasing pillar spacing arrangement along the downstream direction, i.e., along the flow direction (+ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> direction), results in significant enhancement of the cooling limit up to 1.5 times along with the reduction in overall evaporator surface temperature when compared to uniform pillar spacing where increase in cooling limit is accompanied with increase in overall evaporator surface temperature. In addition, the interplay of variable spacing and non-uniform heat flux results in design guidelines for pillar arrangements for given power maps while throwing new insights into the complex fluid flow and heat transfer phenomena encountered in this process. A higher concentration of pillars is found to result in lower evaporator surface temperatures, thereby recommending more number of pillars in high heat flux zones.

A Numerical Study on the Erythrocyte Flow Path in I-Shaped Pillar DLD Arrays

Erythrocyte enrichment is needed for blood disease diagnosis and research. DLD arrays with an I-shaped pillar (I-pillar) sort erythrocytes in a unique, accurate, and low-reagent method. However, the existing I-shaped pillar DLD arrays for erythrocyte sorting have the drawbacks of higher flow resistance and more challenging fabrication. A two-dimensional erythrocyte simulation model and the arbitrary Lagrangian–Euler equations at the cell–fluid boundary were built based on the fluid–solid coupling method to investigate the influencing factors of the erythrocyte flow path in an I-pillar DLD array and find its optimization method. Three different sizes of I-pillars were built and multiple sets of corresponding arrays were constructed, followed by finite element simulations to separately investigate the effects of these arrays on the induction of erythrocyte motion paths. This work demonstrates the motion paths of erythrocyte models in a series of I-pillar arrays with different design parameters, aiming to summarize the variation modes of erythrocyte motion paths, which in turn provides some reference for designing and optimizing the pillar size and array arrangement methods for I-pillar array DLD chips.

Fluidic-chemical characteristics of electroless copper deposition of ordered mass-fabricated pillars in a microchannel for chip packaging applications

The trend of chip-packaging in the semiconductor industry is pointing towards 3D integrated circuits and scaling down to attain devices with enhanced efficiency and performance. To overcome the reassimilating challenges, we propose the usage of an electroless plated deposition layer to connect pillar bumps and create high-density interconnections. The substrates and pillar arrangements encompass our microchannel with the height of 50 µm or 25 µm where in between the electrolyte is forced with a superficial velocity of 0.3 to 300 mm s−1 in our experiments. The results are compared to a numerical multi-physics model which simulates idealized plating conditions without any disruptions to characterize and quantify the different flow regimes and undesired side-effects. In the low-velocity regime, hydrogen bubbles cannot be dislodged and remain in the microchannel which is accompanied with the formation of extraneous deposition on the resist surface. The mid-velocity regime shows a good match to the simulation model and is considered as optimal plating condition. The chemical reaction slows down for high velocities.

Heat transfer enhancement in a rectangular channel with pillars

This paper numerically studied the heat transfer performance of water flowing in a rectangular channel with pillar structures. We systematically investigated the influence of the pitch, inclination angle, shape, and pillar arrangement on the flow and heat transfer characteristics. The results show that adopting spacing with S/d=2 can improve heat transfer performance sufficiently for a low Reynolds number case. Meanwhile, the noticeable enhancement can also be observed by making the pillar inclination direction consistent with the flow direction or staggered rhombic-shaped.

Study of the Classical Cassie Theory and Wenzel Theory Used in Nanoscale

Recently, there are hesitations in the application scope of the classical Cassie theory and Wenzel theory. In this paper, Molecular Dynamics (MD) simulations are used to study these two theories used in the nanoscale and find their limitations. The effect of parameters including solid fractions (or roughness factors), arrangement of pillars (with same solid fractions), pillar height, and droplet size on contact angles was investigated. It shows that the Cassie equation is suitable for droplets on uniform pillared surfaces including different solid fractions, arrangement of pillars and pillar height, when there is no meniscus of droplets. The Wenzel equation is also suitable for droplets on uniform pillared surfaces including different roughness factors, arrangement of pillars and pillar heights. Moreover, whether the droplet size has an influence on the contact angle depends on the pinned place of the contact line. In the Wenzel state, the contact line is pinned although increasing the droplet size, resulting in increasing the contact angle, while the contact angle decreases to the initial value again when the droplet size increases enough to allow the contact line moving to the next pillar. The results provide insights toward the wettability of droplets on surfaces in nanoscale.

New Test Structure Development for Pattern Collapse Evaluations

Test structure development is critical for single wafer pattern collapse evaluations. A good test vehicle not only allows optimization and benchmarking of different processes, but also facilitates understanding of the underlying mechanism. For high aspect ratio silicon nanopillar arrays, by increasing the gap distance in one direction while keeping the other direction constant, an unexpected higher collapse rate is found. This preliminary finding is contradictory to the prevalent models that are based on equilibrium force balance between capillary and mechanical interactions. It is postulated that the asymmetric arrangement of pillars facilitates the formation of liquid bridge and thus more pattern collapse. Such test structures can bring useful insights to understand the dynamic mechanism of pattern collapse.

Terahertz Spoof Surface Plasmonic Logic Gates.

SummaryLogic gates are important components in integrated photonic circuitry. Here, a series of logic gates to achieve fundamental logic operations based on linear interference in spoof surface plasmon polariton waveguides are demonstrated at terahertz frequencies. A metasurface-based plasmonic source is adopted to couple free-space terahertz radiation into surface waves, followed by a funnel-shaped metasurface to efficiently couple the surface waves to the waveguides built on a domino structure. A single Mach-Zehnder waveguide interferometer can work as logic gates for four logic functions: AND, NOT, OR, and XOR. By cascading two such interferometers, NAND and NOR operations can also be achieved. Experimental investigations are supported by numerical simulations, and good agreement is obtained. The logic gates have compact sizes and high intensity contrasts for the output “1” and “0” states. More complicated functions can be envisioned and will be of great value for future terahertz integrated computing.

Nonlinear higher-order polariton topological insulator.

We address the resonant response and bistability of the exciton-polariton corner states in a higher-order nonlinear topological insulator realized with a kagome arrangement of microcavity pillars. Such states are resonantly excited and exist due to the balance between pump and losses, on one hand, and between nonlinearity and dispersion in inhomogeneous potential landscape, on the other hand, for pump energy around eigen-energies of corresponding linear localized modes. Localization of the nonlinear corner states in a higher-order topological insulator can be efficiently controlled by tuning pump energy. We link the mechanism of corner state formation with symmetry of the truncated kagome array. Corner states coexist with densely packed edge states but are well isolated from them in energy. Nonlinear corner states persist even in the presence of perturbations in a corner microcavity pillar.

Bifunctional superlens for simultaneous flexural and acoustic wave superfocusing

Superfocusing of acoustic and elastic waves is generally achieved by the combination of negative refraction and the enhancement of the evanescent waves. Here, we numerically and experimentally demonstrate the bifunctionality of a superlens that can simultaneously focus acoustic and flexural waves beyond the diffraction limit. The designed structure is composed of a two-dimensional arrangement of pillars that act as rigid scatterers for the sound waves and as resonant scatterers for the flexural waves. The band structure presents modes with negative dispersion bands allowing negative refraction for both types of waves within the frequency range of 6.9–7.4 kHz, which is induced by the Bragg scattering effect. Edge modes that enhance the evanescent waves through resonant coupling appear around 7.2 kHz for the flexural and sound wave. The simultaneous superlensing is then observed at this frequency. Our finding will enlighten multiphysical and multifunctional wave manipulations and could have pragmatic applications involving multiwave devices.

Wetting behavior of textured silicon surfaces- an experimental study

The behavior of a liquid on a solid surface has shown great interest in a variety of applications related to surfaces and its interfaces. In this paper, the wetting behavior of DI water on micropatterned silicon surfaces fabricated through photolithography and deep reactive ion etching (DRIE) is investigated. Micro pillars of both solid and hollow geometries at a varying pitch and its arrangement in an array has been examined with static contact angle measurement. However, the results concluded that the arrangement of pillars in an array plays an important role as hollow geometries in the case of chain type arrangement provide both hydrophilic and hydrophobic surface properties, while the same hollow geometries in case of zig-zag orientation experiences only hydrophobicity at a varying pitch. Decreased WCA with increased pitch has been observed in the case of a zig-zag arrangement, due to the effect of capillary and gravitation forces. Also the existence of air pockets at sharp corner in the case of hollow square assists in providing maximum contact angle (WCA = 144°) as compared to hollow circle and solid geometries; thus a non-sticky behavior would be possible between the droplet and the patterned surface, due to less adhesion force.

Investigating fouling at the pore-scale using a microfluidic membrane mimic filtration system

The work investigates fouling in a microfluidic membrane mimic (MMM) filtration system for foulants such as polystyrene particles and large polymeric molecules. Our MMM device consists of a staggered arrangement of pillars which enables real-time visualization and analysis of pore-scale phenomena. Different fouling scenarios are investigated by conducting constant-pressure experiments. Fouling experiments are performed with three different types of foulants: polystyrene particle solution (colloidal fouling), polyacrylamide polymer solution (organic fouling) and a mixture of these two solutions (combined fouling). Four major categories of microscopic fouling are observed: cake filtration (upstream), pore blocking (inside the pores), colloidal aggregation (downstream) and colloidal streamer fouling (downstream). Our microfluidic experiments show that downstream colloidal aggregation and streamer fouling have a significant effect on overall membrane fouling which were not studied before.

Beech wood cross sections as natural templates to fabricate superhydrophobic surfaces

Inspired by the hierarchical and porous wood microstructure, polydimethylsiloxane (PDMS)-positive replicas of beech (Fagus sylvatica) cross sections, with superhydrophobic properties, were fabricated. Microtomed transverse sections of beech wood were directly used as templates, and an accurate replication of the anatomical wood features (vessels and fibers) was obtained. The resulting PDMS-positive replicas show an arrangement of pillars, contributing to surface structuration. By adjusting the PDMS pre-curing time, the extent of PDMS penetration could be controlled inside the wood capillaries, inducing the formation of pillars with various aspect ratios. The wettability of the templated surfaces as a function of the different pillars heights was studied, and the optimal pillar aspect ratio was identified to enhance the hydrophobicity of the PDMS structured surfaces (reaching a water contact angle of 156°). Fagus sylvatica wood cross sections are therefore simple, scalable, and inexpensive templates to manufacture structured surfaces, with the possibility to adjust wettability according to application needs.