Hollow Square Research Articles

Bi-directional seismic behavior of steel beam-column connections with outer annular stiffener

This paper investigates the seismic behavior of steel beam-column connections with outer annular stiffener under bi-directional cyclic loadings. Five welded three-dimensional beam-column connections configurated by hollow square structural steel (HSS) column sections, H-shaped steel beams, and outer annular stiffener was tested. The main parameters considered in this experimental study include loading protocols (anti-symmetric bidirectional and unidirectional cyclic reversals), beam depths, and the leg size of fillet weld between the outer annular stiffener and column. Moment versus rotation hysteretic responses, skeleton curves, stiffness degradation, and the associated energy-dissipating capacity were analyzed. The hysteretic loops of all specimens show a stable and ductile performance indicating a good energy-dissipating capacity. The ultimate flexural strength under the uni-directional cyclic reversals was found to be 20% higher than that under the corresponding bi-directional loading history. As the fillet weld leg size increases from 6 mm to 10.2 mm, the ultimate flexural capacity of the beam ends is slightly enhanced. The beam depth is a major factor that controls the elastic stiffness and strength capacity of the outer annular stiffener. The ductile failure mode can be achieved by using the proposed equations for the strength calculation of ring stiffeners.

Square structured photonic crystal fiber based THz sensor design for human body protein detection

In this manuscript, a squared hollow-core photonic crystal fiber-sensor is introduced, which can be used for efficient amino acid investigations using THz waves. Amino acid identification is crucial in medical science, particularly in the drug discovery. The performance analysis has been conducted using the finite element method (FEM) based the COMSOL MULTIPHYSICS software package, and important waveguide properties have been assessed elaborately for five essential amino acids in a wide range of THz frequencies at different core dimensions. The analysis shows that the proposed model exhibits an extraordinarily high sensitivity of 99.98% and remarkably low confinement loss of 4.72 × 10–22 cm−1 for tryptophan, the rarest of the essential amino acids found in proteins. The excellent sensing capabilities are achieved by introducing two hollow square air cavities surrounded by four rectangular air channels in the cladding. The fabrication of the sensor is achievable using the extrusion technique with 3D printing, which is also discussed in detail.

Transient combined volumetric radiation and free convection in a chamber with a hollow heat-generating solid body

The present investigation numerically scrutinizes the generated heat removal in some electronic devices both to prevent overcooling and keep the uniformity of environmental temperature with the goal of increasing the operating life. For this purpose, conjugate combined convective-radiative energy transport is studied in a square shape and tilted chamber containing a hollow square shell solid block as a second cavity with a uniform heat generation which is placed in the central zone of the chamber. The finite-difference method is employed to solve the governing equations. Also, for considering the gas radiation effect, the radiating computations are based on the numerical solution of the radiation transfer equation and solved by the discrete ordinate method. The effects of Plank number, the inclination angle of the cavity, the gas optical thickness, and surface emissivity of the boundaries on the flow and the thermal characteristics of the system and on controlling the working temperature near to the optimal set point is studied. The results show that by using the radiating filling gas with low optical thickness, high Plank number, and applying higher surface emissivity, more cooling rate can be achieved at the transient period up to 38%, 85%, and 50% respectively.

Influence of Scanning Strategy on the Performances of GO-Reinforced Ti6Al4V Nanocomposites Manufactured by SLM

In this work, the effects of line (L-scanning strategy), stripe (S-scanning strategy), hollow square (H-scanning strategy) and chess board partition (C-scanning strategy) on the performances of graphene oxide reinforced Ti6Al4V matrix nanocomposites (GO/TC4) as fabricated by selective laser melting (SLM) were investigated. Numerical temperature field simulation of four different scanning strategies was utilized to investigate the effects of thermal concentration on SLM-processed GO/TC4 nanocomposites, linking to its micro-voids, surface roughness, porosity, microhardness and tribological properties. The proposed simulation scheme is validated by comparing the simulated thermal analysis with experimental results. Simulation results show that the thermal concentration effects of a part during SLM process is distinctive under different scanning strategies, with the slowest cooling rate of 64,977.5 °C/s that is achieved by C-scanning strategy specimen. The experimental results indicate that the performances of the L-scanning strategy or S-scanning strategy sample are seriously affected by the thermal concentration, causing a large number of micro-voids and defects. All the experimental results suggest that the sample using C-scanning strategy exhibits the optimal performance of all investigated specimens, which closely correlates with its lowest temperature gradients. This study highlights the importance of using a partition scanning strategy during SLM process, which can be easily extended to other powder bed fusion process.

Levantamento fitossociológico na cultura do amendoim

A identificação das espécies de plantas daninhas que infestam as áreas agrícolas é importante para a tomada de decisão durante a escolha do método de controle. Diante disto, o objetivo do trabalho foi identificar e quantificar as principais espécies de plantas daninhas presentes em área de produção de amendoim no município de Jaboticabal – SP. O delineamento experimental foi em blocos casualizados. As avaliações foram realizadas aos 15, 30, 45, 75, 90, 105 e 130 dias após a semeadura, utilizando-se o método do quadrado vazado. Em cada avaliação foram realizadas 2 amostragens/parcela, totalizando 8 amostragens por tratamento. As plantas coletadas foram seccionadas rente ao solo, identificadas, acondicionadas em estufa de circulação de ar a 70ºC e, após 96 horas, foi determinada a massa seca das plantas. Com base nas informações obtidas nas amostragens, foram estimados os parâmetros fitossociológicos, frequência, frequência relativa, densidade, densidade relativa, abundância, abundância relativa, dominância, dominância relativa e determinou-se o índice de valor de importância. Verificou-se que a comunidade infestante na cultura do amendoim apresentou 17 espécies, em 17 gêneros e 9 famílias. O maior número de plantas daninhas foi encontrado na família Poaceae. Concluiu-se que nesta área, as espécies que predominaram foram Alternanthera tenella Colla, Digitaria sp. e Amaranthus sp.

Generation of uniform-intensity light beams with controllable spatial shapes

We present the generation of high-quality light beams of controllable spatial shapes with uniform-intensity distribution based on diffractive optical elements (DOEs) designed by an iterative method that involves spatial Fourier filtering. The Gaussian input beam illuminates the DOEs, and after propagating certain distance transforms into desired uniform-intensity output beams with square, annular, rectangular, hollow square, and plus spatial shapes. We have performed a detailed robustness analysis on the quality of shaped output beams against various types of imperfections in an input beam. It is found that the quality of shaped output beams can be further improved by using additional spatial filtering. Furthermore, we have shown that the quality of shaped output beams remains excellent even when DOE (designed for a specific wavelength) is illuminated by input beam with different wavelengths over a broad range.

Cross-Sectional Performance of Hollow Square Prisms with Rounded Edges

Hollow-section columns are one of the mechanically superior structures with high buckling resistance and high bending stiffness. The mechanical properties of the column are strongly influenced by the cross-sectional shape. Therefore, when evaluating the stability of a column against external forces, it is necessary to reproduce the cross-sectional shape accurately. In this study, we propose a mathematical method to describe a polygonal section with rounded edges and vertices. This mathematical model would be quite useful for analyzing the mechanical properties of plants and designing plant-mimicking functional structures, since the cross-sections of the actual plant culms and stems often show rounded polygons.

Hollow Square RodLike Microtubes Composed of Anatase Nanocuboids with Coexposed {100}, {010}, and {001} Facets for Improved Photocatalytic Performance.

In this study, hollow square rodlike microtubes composed of anatase nanocuboids with coexposed {100}, {010}, and {001} facets were successfully synthesized via a mild hydrothermal treatment method in the presence of NH4F by using layered H2Ti3O7 ribbons as the precursor. The precursor H2Ti3O7 ribbons were prepared from H+/Na+ ion-exchanged Na2Ti3O7. The suspension solution of protonated H2Ti3O7 ribbons was adjusted to desired pH values (0.5–13.0) prior to hydrothermal treatment. The elongated direction of the microtubes is along the b axis, according to the profile of the H2Ti3O7 ribbons. The transformation from staggered [Ti3O7]2– sheets to hollow square rodlike microtubes contained the formation and recombination of the dispersed octahedral [Ti(OH)2(OH2)4]2+ monomers, the formation and growth of the initial anatase nuclei, and the reassembly of the anatase nanocuboids along the b-axis direction during the continuous hydrothermal process. The degradation rate of pH 0.5-TiO2 was the highest at 1.66 × 10–2 min–1, which was 1.3, 1.5, 2.0, 2.3, and 18.4 folds higher than that of pH 3.0-TiO2 (1.27 × 10–2 min–1), pH 7.0-TiO2 (1.11 × 10–2 min–1), pH 5.0-TiO2 (0.83 × 10–2 min–1), P25–TiO2 (0.73 × 10–2 min–1), and the blank sample (0.09 × 10–2 min–1), respectively. Compared with P25–TiO2 and the other anatase TiO2 samples, pH 0.5-TiO2 exhibited the best photocatalytic activity, which was mainly attributed to its larger proportion of {010} (or {100}) facets, smaller crystalline size, higher band gap, and larger specific surface area.

Flow topology downstream of the hollow square cylinder with slots

Flow patterns downstream of the hollow square cylinder with slots are experimentally investigated to show effect of the slot ratio on the wake flow characteristics and turbulence statistics at Reynolds number of Re = 6000 using the particle image velocimetry (PIV) technique. Proper orthogonal decomposition (POD) analyses indicate that the self-issuing jet dramatically changes the mechanism of vortex shedding interaction. Penetration of the self-issuing jet into the wake region leads to increasing of the vortex formation length for low slot ratios. On the other hand, the self-issuing jet penetrates further downstream due to increasing momentum coefficient of the jet and splits the wake region in half for high slot ratios. Strouhal number increases with the increasing slot ratio and it attains approximately the twofold of the solid cylinder case, since the self-issuing jet accelerates the vortex shedding process. However, turbulence statistics are significantly reduced for all slot ratios. Distributions of the spectral density in the wake region of the cylinder indicate that the vortex shedding instability could be reduced considerably by the slotted cylinder. Drag coefficient, which is estimated from PIV data, reduces up to 42% in comparison with the solid cylinder model.

Analytical, Numerical, and Experimental Investigations on Transverse Bending Responses of CFRP Square Tube Filled with Aluminum Foam

In order to explore the transverse bending responses of carbon fiber-reinforced polymer (CFRP) square tubes filled with aluminum foam, the three-point bending tests were carried out on an INSTRON machine, the full-field deformation measurement was performed using a 3D-DIC test system, the numerical model was established by ABAQUS/Explicit, and the bending stiffness was calculated by the improved analytical model based on shear-deformable beam theory. The discrepancies of experimental data, numerical results, and analytical predictions were acceptable, which were within 5%. The failure modes and mechanical properties of the filled tubes were experimentally captured and numerically predicted. Due to the filling effect of aluminum foam, the ultimate load, bending stiffness, and energy absorption of the filled CFRP square tubes increased, comparing to those of the hollow CFRP square tubes. With the increase of the aluminum foam density, the ultimate load, bending stiffness, and energy absorption of the filled tubes increased, while the specific ultimate load, specific bending stiffness, and specific energy absorption decreased.

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.

Neonatal Management During the Coronavirus Disease (COVID-19) Outbreak: The Chinese Experience.

Novel coronavirus infection is a disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and was named COVID-19 by the World Health Organization on January 7, 2020. In early December 2019, a number of pneumonia cases of unknown origin emerged in Wuhan, Hubei province, China. (1)(2) The disease then spread rapidly throughout China and has now become a global pandemic. As of March 23, 2020, more than 340,000 cases have been reported in more than 150 countries. Because the disease is primarily an airborne respiratory infection and is documented to have a strong human-to-human transmission, the pediatric and neonatal populations are vulnerable to this disease. However, the incidence and clinical presentations of pediatric COVID-19 infections are varied and differ from those found in adult patients. The atypical clinical presentations and 2 potential modes of transmission in neonates (ie, maternal-fetal or maternal-neonatal) have led to diagnostic and management challenges. In this perspective, we would like to share some published information from Chinese pediatric and neonatal societies about their approach to handling the 2019-2020 COVID-19 outbreak in China. Since the COVID-19 outbreak in December 2019, more than 81,000 confirmed cases have been reported in China (as of March 23, 2020). Most of these cases occurred between late January and early February 2020. The diagnosis of COVID-19 is based on the epidemiologic history of contact with an infected person, typical clinical features such as fever and respiratory distress, and a positive real-time polymerase chain reaction to the SARS-CoV-2 RNA test. The nucleic test is considered the gold standard for confirmation. As of February 8, 2020, 731 confirmed pediatric cases were reported in China, mainly from Wuhan city. (3) Relative to the total number of cases (n=34,664) reported in China, on February 8, 2020, the pediatric COVID-19 population accounted for 2.1% …

Experimental Flexural Behavior of Composite Beam using Cold Formed Hollow Square Section

Structural hollow sections have excellent properties for resisting static loads, with regard to buckling, bi-axial bending and torsion. Structural hollow sections are generally used for truss components, considering greater stiffness and lateral strength. A square hollow section truss has about two third of surface area of same size I section. Hollow section truss may have smaller members as a result of higher structural efficiency. Construction of composite beam commonly includes I section. This paper deals with comparison of commonly used hot rolled or welded I composite section with cold formed hollow RHS and SHS composite section with respect to flexure and shear. Flexural tests were conducted to evaluate the structural behavior of the proposed composite beams. Two different steel sections were used for this study with nominal concrete strength of 30 MPa. The composite beams were tested under concentrated two points loading. The test results were plotted and compared with analytical results. The mid span deflections and slip were recorded for both composite beams. Buckling modes for both composite beams were identified. comparisons have been carried out between predicted beam strength as provided by Eurocode -4 and experimental test results. Sectional properties are checked for cold formed hollow square section using EN 1993-1-3.

Experimental studies on thread-fixed one-side bolted connection of beam to hollow square steel tube under static bending moment

Test results on the Thread-fixed One-side Bolted Connection (TOBC) of a beam to a Hollow Square Steel Tube (HSST) under static bending moment were presented and corresponding design methods were proposed. In order to enhance the initial stiffness and bending moment capacity of the TOBC, different strengthening methods to the connection, including backing plate and H-shaped stiffener, were investigated. Four TOBCs were tested under monotonic loading and a traditional Nut-fixed Double-sides Bolted Connection (NDBC) was tested for comparison. Failure modes, bending moment-rotation curves, and strain evolution curves measured from tests were presented. Test results indicated that the yielding bending moment, the ultimate bending moment and the ultimate rotation of a TOBC strengthened with backing plate were only a little lower than those of a NDBC, but the initial stiffness was improved. The yielding bending moment, the ultimate bending moment and the initial stiffness of a TOBC strengthened with H-shaped stiffener were higher than those of a NDBC, but the ultimate rotation decreased. All TOBCs tested met the seismic ductility requirement of not less than 30 mrad, suggested by the US seismic code FEMA-350. Based on the experimental results, design methods for calculating the bending moment capacity of TOBCs under failure modes of the hole threads failure, the endplate yielding and the column wall yielding were proposed, respectively. The calculated yielding bending moment capacity of a TOBC agreed well with the test result.

ANALYSIS OF A CANTILEVER COLUMN SUBJECTED TO CYCLIC LOADING

In a seismic incident, the structural steel columns are commonly damaged with local buckling formulation at either the top or bottom ends. This study analyzes and simulates the hysteretic behavior of a hollow square steel column under cyclic loading by adopting the fiber-element approach. This method discretizes the hinge zone into a series of fibers and considers buckling behavior of those fibers along the column wall. The analytical result was achieved in good agreement with the component test.

An experimental/numerical hydrothermal analysis on natural convection and TiO2-SiO2/W-EG nanofluid’s properties in a hollow/finned cavity

Purpose This paper aims to provide an experimental/numerical analysis of free convection within a hollow/finned cavity. Design/methodology/approach The hollow square cavity is equipped with eight active fins which have a similar configuration and different temperatures. Furthermore, four different thermal arrangements are considered to determine the order of temperature for each fin. The coupled lattice Boltzmann method is used, which not only maintains the considerable advantages of standard lattice Boltzmann method such as accuracy but also enhances the stability of this method. Findings The cavity is filled with TiO2-SiO2/Water-Ethylene Glycol nanofluid. The thermal conductivity and dynamic viscosity of nanofluid are experimentally measured using high-precision devices in six concentrations of the nanoparticle. In this study, some main parameters, including a range of Rayleigh number (103 < Ra < 106), the concentration of nanofluid (0.5 to 3 Vol.%) and thermal arrangements of fins, are considered. The effects of these main parameters on the flow, isotherms, heat transfer performance and entropy generation are studied. Originality/value The originality of this paper is combining the numerical simulation (lattice Boltzmann method) using a modern approach with experimental observations of nanofluid’s properties.

"Within Thy Circling Pow'r I Stand": Immersive Video from Sacred Harp's Hollow Square

"Within Thy Circling Pow'r I Stand": Immersive Video from Sacred Harp's Hollow Square

Evaluation of Weed Incidence and Biomass in Coffee Intercropped with Oil Palm in Avenue and Hollow Square Arrangement in Nigeria

Weed incidence and biomass in tree crop plantations are mainly influenced by environmental, farm management practices and cropping systems. Manipulation of intercropping systems to improve weed management in coffee intercropped with oil palm requires a better understanding of spatial and temporal dynamics of weeds. To evaluate the effect of weed incidence and biomass in coffee intercropped with oil palm in avenue and hollow square arrangement, a study was carried out in Cocoa Research Institute of Nigeria (CRIN) in two locations. The locations are Idi-Ayunre (7°25'N, 3°24'E) (an alfisol) and Uhonmora (6°5'N, 5°50'E) (ultisol) in rainforest and derived savannah parts of Nigeria respectively. The experiment had three treatments comprising coffee sole (control), coffee with oil palm (Hollow square) arrangement and coffee with oil palm (Avenue) planting. Coffee was planted 3.0 m apart while oil palm was planted 9 m apart. Equal size of land area was used for coffee in each treatment. The experimental design was Randomized Complete Block (RCBD) with three replicates. Data on vegetative growth of coffee, weed incidence and biomass were taken at three-monthly intervals. The result showed that coffee/oil palm (Hollow Square) had the least weed incidence and biomass closely followed by coffee/oil palm (Avenue) planting. The control had the highest weed biomass which was significantly different from Hollow square and Avenue planting at P ≤ 0.05. The morphological parameters on coffee followed the same pattern but Hollow square arrangement was significantly higher than Avenue and control at P ≤ 0.05.

Experimental Study on Flexural Behaviour of Reinforced Foamed Concrete Square Hollow Beam

Nowadays construction industry continuously looking for new, better and efficient construction material and method due to environmental impact. This research reported the effect of reinforced foamed concrete square hollow beam in order to reduce the effect of the application of concrete materials. Foamed concrete with density of 1600kg/m³ is now widely used as a structural component like slab and wall due to it lighter than the normal concrete. Meantime, it helps in saving cost and reduce the use of formwork. The hollow section also can reduce the dead loads which contribute to seismic effect in high rise buildings. In addition, the Processed Spent Bleaching Earth (PSBE) is an industry waste which possess a good pozzolanic reaction is used as partial cement replacement in order to make it more environmentally friendly. The experimental program consists of casting and testing of foamed concrete beams of size 150 x 200 x 1500 mm with and without square hollow section. To study the flexural behaviour, all beams are tested after 28 days of curing subjected to four-points bending test in order to analyse the effect of the reinforcement of hollow section on the strength, deflection and mode of failure of foamed concrete beam. The performance of reinforced foamed concrete hollow square beam (RHB) under flexural shows better when compared with conventional solid beam (CSB) and hollow square beam without reinforcement (HB). The RHB exhibited greater strength with lesser deflection and cracking.

Effect of convective heat transfer coefficient on estimation of effective thermal conductivity of two-phase material

Two-phase materials are involved in applications of day to day life, the reason being it is having discrete properties like firmness, required thermal conductivity, durability as well as good impact properties, etc. Thermal conductivity of two-phase material is a basic property to envision its evaluation in engineering. Distinct geometry for example cylinder, spherical, random size particles are being proposed by researchers for computation of effective thermal conductivity (ETC) of material like two-phase. This paper includes a two-dimensional two-phase system with hollow square geometry which is being considered for mathematically deriving an algebraic equation for computing ETC with the inclusion of the convective heat transfer coefficient. A unit cell approach is considered for deriving the equations. The obtained results are validated with the basic available models for distinctive types of two-phase materials. Hollow square model with Ψ = 0.3 gives approximate reasonable agreement for predicting ETC having a mean percentage error of 5.73% which is acceptable.