Short Wall Research Articles

General solution for shear strength estimate of RC elements based on panel response

The capacity of structural systems subjected to shear loads commonly distinguished by discontinuities such as point loads or supports, or abrupt changes of cross section, where complex fields of stresses and strains are generated, is vital information for design. Four structural systems that present stress concentration due to applied shear loads are commonly short walls, deep beams, corbels and beam-column joints. In the present work a model is developed to predict the shear capacity of these elements based on a panel model that considers average strain and stresses in a reinforced concrete orthotropic material, which covers the section of the structural element subjected to stress concentration. In addition, the panel element complies with the longitudinal equilibrium, by equalizing the applied axial load with the internal stresses of the structural element, requiring constitutive material laws for both concrete and steel reinforcement. The original model that has shown good shear strength prediction requires solving the non-linear equation of vertical equilibrium. Thus, this work eliminates the need to solve the iterative problem for the capacity estimation of four possible limit states (failure of concrete in tension and compression, and yielding of longitudinal web and boundary reinforcement). For that, an expression is calibrated for the strain of the model with respect to relevant parameters, for each limit state, that allow the generation of a non-iterative model. The model results in an average predicted capacity over experimental capacity ratio, Vmodel/Vtest, of 1.0 and a COV of 0.25, with similar performance for all four structural systems. When comparing these results with the general model that requires an iterative method, a similar performance is observed, with an average strength ratio and COV of 0.98 and 0.23, respectively. Likewise, in comparison with the ACI 318, the latter shows worse predictions (on average 24% lower) and with greater scatter (on average 28% higher). The expression in AASHTO code presents better correlation than ACI with predictions closer the proposed model.

A Rat Model of Orthotopic Liver Transplantation Using a Novel Magnetic Anastomosis Technique for Suprahepatic Vena Cava Reconstruction.

The rat model of orthotopic liver transplantation (OLT) is essential for transplant research. It is a very sophisticated animal model and requires a steep learning curve. The introduction of the cuff technique for anastomosis of the portal vein (PV) and infrahepatic vena cava (IHVC) has significantly simplified the transplant procedure in rats. However, due to the short anterior wall of the recipients' suprahepatic vena cava (SHVC), the cuff technique is very difficult to use for the reconstruction of the SHVC. Most researchers in this field still use the hand-suture technique for SHVC reconstruction, which makes it the bottleneck step in rat orthotopic liver transplantation. The magnetic anastomosis technique (i.e., magnamosis) is a method of connecting two vessels using the attractive force between two magnets. Our recent study has shown that the magnetic anastomosis technique is superior to the hand-suture technique for SHVC reconstruction in rats. In this article, we show a step-by-step protocol for SHVC reconstruction in rats using the novel magnetic anastomosis technique. In this model, the reconstruction of the PV and IHVC was performed by the standard cuff technique, while the reconstruction of the bile duct (BD) was performed by a stent technique. The hepatic re-arterialization was not performed. The magnetic anastomosis technique made SHVC reconstruction much easier and significantly shortened the anphepatic phase. After a reasonable learning curve, even researchers without advanced microsurgical skills can produce reliable and reproducible results using this rat model of OLT.

Experimental study on seismic behavior of Un-Reinforced Masonry (URM) brick walls strengthened with shotcrete

In this study, the efficiency of conventional shotcrete technique for strengthening of Un-Reinforced Masonry (URM) walls was shown using an experimental program. In addition, in this program the possible benefit of using anchors for connecting the shotcrete reinforcement layer to the R/C foundation was studied. The experimental program consisted of testing five full scale specimens with two different height-to-length aspect ratios and so different failure modes, under in-plane cyclic loading conditions. Two specimens were tested as reference and others were strengthened on a single-face using shotcrete layer. According to the results, strengthening of URM walls using traditional shotcrete approach created a completely stiff panel and prevented the formation of cracks. The failure mode in both reference and strengthened short length walls was rocking and the shotcrete layer could increase the strength capacity, energy dissipation, and stiffness of wall due to yielding and rupture of steel bars anchored to the foundation. On the other hand, in strengthened long length walls, shotcrete layer increased the shear sliding capacity with no or small increasing in their rocking capacity. Therefore, the failure mode of strengthened walls converted from shear sliding to rocking, even in the specimen with anchorage system. The distributed type of anchorage system could not improve the strength capacity of long length wall. Anchorage system was able to improve the out-of-plane performance of strengthened walls.

STUDY ON FEEDING HABIT AND FEED SPECTRUM OF GOLDEN TANK GOBY Glossogobius aureus Akihito & Meguro, 1975

Glossogobius aureus Akihito & Meguro, 1975 is a fish with good flesh, which has brought about high economic value. The study on feeding habit and feed spectrum of G. aureus was conducted from January to December 2013 at the coastal area of Ben Tre province. The results have showed that the mouth of thisfish is wide, tongue is bilobate, teeth on faws develop well. The gill rakers are sparse, short and hard. The esophagus and the intestine are short, the stomach and intestinal walls are thick. The Relative Length Gut index (RLG) of G. aureus was less than 1. The results also indicated that G. Aureus are fed mainly on small fish (46.3%) and crustaceans (40.5%). The result showed that G. aureus is the carnivorous species

Codesigned High-Efficiency Single-Layered Substrate Integrated Waveguide Filtering Antenna With a Controllable Radiation Null

This letter proposes a codesigned substrate integrated waveguide (SIW) filtering slot antenna with a controllable radiation null in gain response. The antenna is composed of a single-layered SIW cavity, four metalized posts, a transverse slot, and a vertical SMA connector. Four metalized posts are introduced to split the cavity into two TE 110-mode resonators. The transverse slot is utilized not only to generate radiation, but also to further split one TE110-mode resonator into two half-mode resonators. The bandpass filtering performance is achieved by the couplings between three resonators and the slot. One radiation null has been introduced for selectivity enhancement, and it will occur at the frequency where the slot is placed at about quarter-wavelength from the shorted wall of the cavity. So by changing the position of the slot, frequency of radiation null can be easily controlled, even from one side to another side of the passband. For demonstration, one antenna with a lower out-of-band radiation null and another one with an upper out-of-band radiation null have been designed, fabricated, and measured. Experimental results show that the antennas have the merits of high efficiency, high selectivity, and easily controllable radiation null.

High-Efficiency, Broadband Converter From A Rectangular Waveguide TE10Mode to A Circular Waveguide TM01Mode for Overmoded Device Measurement

To accurately measure the performance of overmoded devices used in high-power microwave systems, a novel structure that effectively converts the TE10 mode in a rectangular waveguide to a high-purity TM01 mode in a circular waveguide is proposed. The circular TM01 mode is excited by a hybrid rectangular E-T waveguide structure, which uses a circular waveguide as the E element. Convex slots loaded at the rectangular waveguide, axially symmetric about the cylindrical waveguide, are introduced to suppress the competing lower order TE11 mode. A tuning stub loaded at the rectangular short wall is used to increase the frequency tuning range. The scattering matrix technique was used to study the mode converter along with the microwave network analysis method using some generalizations of the input port reflection and conversion efficiency, which were verified by the numerical full-wave simulation. Based on the theoretical analysis, an X-band TM01 mode generator is designed and measured. Low-power tests show that, when the length of the tuner increases from 5.7 to 11.7 mm, a wide frequency tuning range of ~500 MHz is obtained with a conversion efficiency of ~99%. Measured results and the theoretical analysis are in good agreement.

Substrate integrated low-profile dual-band magneto-electric dipole antenna

In this article, a novel substrate integrated low-profile dual-band magneto-electric (ME) dipole antenna is proposed. The entire antenna is constructed by four-layer printed circuit boards (PCBs). Consequently, the height of the proposed antenna is decreased from 0.25λ0 to 0.11λ0 (λ0 is the free-space wavelength at 5.5 GHz). By introducing rectangular patches with different sizes as electric dipoles, dual operating bands are achieved. Meanwhile, for the purpose of improving the impedance matching at the lower frequency band, a pair of complementary split-ring resonators (CSRRs) is etched on the larger rectangular patches. Moreover, the short walls composed of plated through holes operate as a magnetic dipole. The antenna is fed by an equivalent wideband microstrip-to-parallel stripline balun. The results show that the antenna obtains dual bandwidths of 4.31-4.71 GHz (8.8%) and 5.07-5.89 GHz (14.9%) with VSWR <2, which can be applied for C-band and 5G WiFi. Over the dual operating bands, stable gain and unidirectional radiation patterns with low polarization and low back lobe are also obtained.

Fracture resistance and failure modes of polymer infiltrated ceramic endocrown restorations with variations in margin design and occlusal thickness

PurposeThe purpose of this in vitro study was to assess the effect of varying the margin designs and the occlusal thicknesses on the fracture resistance and mode of failures of endodontically treated teeth restored with polymer infiltrated ceramic endocrown restorations. MethodsRoot canal treated mandibular molars were divided into four groups (n=8) and were prepared to receive Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) fabricated polymer infiltrated ceramic endocrowns (ENAMIC blocks). Group B2 represents teeth prepared with a butt joint design receiving endocrowns with 2mm occlusal thickness and the same for group B3.5 but with 3.5mm occlusal thickness. Group S2 represents teeth prepared with 1mm shoulder finish line receiving endocrowns with 2mm occlusal thickness and the same for group S3.5 but with 3.5mm occlusal thickness. After cementation and thermal aging, fracture resistance test was performed and failure modes were observed. ResultsGroup S3.5 showed the highest mean fracture load value (1.27±0.31kN). Endocrowns with shoulder finish line had significantly higher mean fracture resistance values than endocrowns with butt margin (p<0.05). However, the results were not statistically significant regarding the restoration thickness. Evaluation of the fracture modes revealed no statistically significant difference between the modes of failure of tested groups. ConclusionsFor the restoration of endodontically treated teeth, adding a short axial wall and shoulder finish line can increase the fracture resistance. However, further investigations, especially the fatigue behavior, are needed to ensure this effect applies with small increases of restoration thickness.

Parametric analysis of laminar pulsating flow in a rectangular channel

Pulsating flow has potential for enhanced cooling of future electronics and photonics systems. To better understand the mechanisms underlying any heat transfer enhancement, it is necessary to decouple the mechanical and thermal problems. The current work performs a parametric analysis of the flow hydrodynamics using particle image velocimetry (PIV) measurements, CFD simulations and analytical solutions, reorganised in terms of amplitude and phase values using complex notation. To the best of the authors’ knowledge, the frequency-dependent behaviour of amplitude and phase of wall shear stress has not been studied in a two-dimensional channel. For laminar flow, the amplitudes are directly proportional to pressure. The amplitudes of various local and mean wall shear stress measures are augmented with frequency compared to steady flow, especially near the short walls and corners. The phases of wall shear stress differ at each wall at moderate frequencies – with the bulk-mean values at the short wall leading those at the long wall – and tend to π/4 in the limit of high frequency. The amplitudes of pressure gradient increase more significantly than wall shear stress magnitudes due to accelerative forces. The boundaries to the quasi-steady, intermediate and inertia-dominated regimes are estimated at Womersley number W o = 1.6 and 27.6 in a rectangular channel, based on the contribution of viscous and inertial terms.

Optimum Design Of Silo Structures

This paper deals with the problem of optimal design of reinforced concrete silos using genetic algorithms and minimizing the maximum objective method. The study provides two types of concrete silos circular and rectangular. Janssen theory method is used to analyze the structure design of silos. The cost function represents the cost of concrete, steel, and form work for the silos. The design variables are taken such as diameter, long wall, short wall, height of cylinder and box for circular &amp; rectangular silo respectively with free board,depth of the hopper, thickness of the wall, dimensions of ring beam, thickness of slab, angles of incline of the hopper and the amounts of reinforcement for silos. The formulation of the problem is according to ACI (313-97) code and is carried out by using a toolbox of MATLAB program. The change of design capacity related to total cost approximately linearly. The effect of the change of the concrete grade, unit price of steel and concrete, and finally the unit cost of form work leads to increasing the total cost, while changing the steel grade leads to decreasing the total cost of both types of silo.

Residuos Inertes para la Preparación de Ladrillos con Material Reciclable: Una Práctica para Protección del Ambiente

El desarrollo industrial y el crecimiento poblacional están generando la sobreproducción de residuos. En ocasiones estos residuos, aunque inertes, se disponen a cielo abierto causando alteraciones al ambiente, particularmente en el paisaje. Llantas, sobrantes de construcción como pedazos de tubería y tierra, material de poda de arreglos de zonas verdes, bolsas plásticas, son ejemplos de algunos de los residuos que pueden llegar a encontrarse. En este trabajo se evaluó el uso de estos residuos en la preparación de muestras de mampuestos de concreto y de tierra que fueron ensayados a compresión mediante la construcción de muretes. Los resultados demostraron que los especímenes de concreto aligerados presentaron una mayor resistencia a compresión que los especímenes en tierra modificada. Se enfatiza en la importancia de tomar medidas ambientales para aprovechamiento de residuos con el fin de disminuir los impactos ambientales generados por la inadecuada disposición de estos.

Coaxial Feed Pyramidal Horn Antenna with High Efficiency

ABSTRACTIn this paper, a short pyramidal horn antenna with coaxial feed has been designed and fabricated with 52% bandwidth, which covers CDMA and GSM 900 bands. The total length of the antenna including coaxial feed is approximately 0.85λ at the lowest usable frequency. The effect of coaxial probe length, probe radius, and its location from the short wall of the waveguide on the resonance frequency, impedance matching, and bandwidth of the horn antenna have been analysed using CST Microwave studio software. Also, parametric analyses have been done by varying the horn length and aperture dimensions to study radiation characteristics of the horn antenna. The horn length has been optimized to obtain maximum efficiency for a fixed aperture. Simulation results show that as the frequency increases from 700 to 1130 MHz, the gain monotonically increases from 8.4 to 12.6 dBi with maximum efficiency of 80% at 850 MHz and it varies between 72% and 80% over this band. The pyramidal horn antenna has been fabricated and measured results are in good agreement with the simulated results.

Relationship between swim start wall contact time and final performance in backstroke events in international swimming championships

The purpose of this study was to investigate the association between race-start wall contact time and final performance for each sex as a function of classification and anti-slip start-device use (with or without) in backstroke events of international competitions. Twenty-one international competitions covering a 10-year period (2006–2015) were analysed, retrospectively. The data corresponded to the competition histories of 1723 swimmers. For the contact-time data of each event (50-m, 100-m and 200-m), two-way ANOVAs (sex × classification and sex × start device use) were performed. The Bonferroni post-hoc test was used to compare means, and Pearson’s simple correlation coefficient to determine possible correlations between wall contact times and final performance. The results showed the men to have shorter wall contact times than the women in the 50-m and 100-m events, and that, for the women medallists, their wall contact times were positively correlated with final performance in all events except the 200-m swim without the start device.

Cultural differences in room size perception.

Cultural differences in spatial perception have been little investigated, which gives rise to the impression that spatial cognitive processes might be universal. Contrary to this idea, we demonstrate cultural differences in spatial volume perception of computer generated rooms between Germans and South Koreans. We used a psychophysical task in which participants had to judge whether a rectangular room was larger or smaller than a square room of reference. We systematically varied the room rectangularity (depth to width aspect ratio) and the viewpoint (middle of the short wall vs. long wall) from which the room was viewed. South Koreans were significantly less biased by room rectangularity and viewpoint than their German counterparts. These results are in line with previous notions of general cognitive processing strategies being more context dependent in East Asian societies than Western ones. We point to the necessity of considering culturally-specific cognitive processing strategies in visual spatial cognition research.

MHD convection and entropy generation of nanofluid in a porous enclosure with sinusoidal heating

A numerical study of heat transfer and entropy generation of a magneto-hydrodynamic (MHD) nanofluid flow inside an enclosure filled with a fluid saturated porous medium is presented. The flow is influenced by time periodic discrete heat sources along the short side walls. A detailed physical insights of time dependent flow and heat transfer is presented based on various flow governing parameters such as Grashof number (104–106), Hartmann number (1–50), Darcy number (0.001–1.0) and nanoparticle volume fraction (0.0–0.20) with a fixed Prandtl number (6.2). The resulting energy flux vectors are simulated to analyze the convection generated heat transfer ratio. Entropy generation and Bejan number are used to study the performance of the system.

Características estructurales de escuelas colombianas de hormigón reforzado con mampostería no reforzada

La evaluación de la vulnerabilidad sísmica del inventario de edificaciones de una región es de vital importancia para poder estimar el riesgo sísmico del lugar. Las escuelas constituyen una importante clase estructural porel alto número de personas que albergan, su rol social y la posibilidad de ser usadas como centros de atención en eventuales emergencias. En este artículo se presenta el análisis de las características de 77 edificios pertenecientes a 28 escuelas de los municipios de Medellín, Itagüí y Sabaneta(Colombia). Cada edificio es una estructura de pórticos de hormigón reforzado con muros de mampostería no reforzada. Dentro de los parámetros analizados se encuentra el número de pisos, altura de la edificación, área en planta, irregularidades en planta y en altura, presencia de columnas cortas, materiales de muros, dimensiones de columnas y muros, tipo desuelo, carga lateral de diseño, nivel de mantenimiento, año de construcción y existencia de daños o intervenciones de repotenciación. El análisis presentado constituye información valiosa que puede usarse para fines de estimación de la vulnerabilidad de este grupo estructural y, por lo tanto,de su riesgo sísmico.

Broadband Characterization of Circularly Polarized Waveguide Antennas Using L-Shaped Probe

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

The Motion of a Neutrally Buoyant Ellipsoid Inside Square Tube Flows

AbstractThe motion and rotation of an ellipsoidal particle inside square tubes and rectangular tubes with the confinement ratio R/a∈(1.0,4.0) are studied by the lattice Boltzmann method (LBM), where R and a are the radius of the tube and the semi-major axis length of the ellipsoid, respectively. The Reynolds numbers (Re) up to 50 are considered. For the prolate ellipsoid inside square and rectangular tubes, three typical stable motion modes which depend on R/a are identified, namely, the kayaking mode, the tumbling mode, and the log-rolling mode are identified for the prolate spheroid. The diagonal plane strongly attracts the particle in square tubes with 1.2≤R/a&lt;3.0. To explore the mechanism, some constrained cases are simulated. It is found that the tumbling mode in the diagonal plane is stable because the fluid force acting on the particle tends to diminish the small displacement and will bring it back to the plane. Inside rectangular tubes the particle will migrate to a middle plane between short walls instead of the diagonal plane. Through the comparisons between the initial unstable equilibrium motion state and terminal stable mode, it is seems that the particle tend to adopt the mode with smaller kinetic energy.

Ecoanatomía de la madera de dos taxa mexicanos del género Mimosa (Leguminosae-Mimosoideae)

Antecedentes y Objetivos: Los estudios ecoanatómicos permiten estimar la respuesta de los taxa a distintos factores ambientales. Considerando la relevancia biológica y ecológica del género Mimosa, se estimaron las posibles respuestas adaptativas de dos taxa endémicos de México, M. aculeaticarpa var. aculeaticarpa y M. luisana, a través de un análisis ecoanatómico de su madera, para evaluar su resistencia y tolerancia a cambios en la precipitación.Métodos: Se recolectaron tres árboles de talla y cobertura similar por taxon. Se cortaron cubos de madera de 1 × 1 cm, ablandados a reflujo. Se hicieron secciones transversales, tangenciales y radiales, con grosor de 20 µm. Se tiñeron con safranina-verde rápido y se montaron en resina sintética. La descripción y el análisis de los caracteres anatómicos de la madera se basaron en la nomenclatura propuesta por la IAWA.Resultados clave: Mimosa aculeaticarpa var. aculeaticarpa presenta porosidad anular, mientras que M. luisana tiene porosidad difusa. Mimosa aculeaticarpa var. aculeaticarpa muestra vasos con diámetro tangencial mediano en madera temprana y pequeño en madera tardía y M. luisana presenta vasos con diámetro tangencial pequeño. Ambos tienen placa de perforación simple, punteaduras intervasculares areoladas, alternas y pequeñas, y ornamentadas en M. luisana. Mimosa aculeaticarpa var. aculeaticarpa posee principalmente parénquima axial paratraqueal vasicéntrico, mientras que en M. luisana es vasicéntrico y unilateral. En M. aculeaticarpa var. aculeaticarpa, los radios son uniseriados y en M. luisana biseriados. Las fibras son de longitud corta, diámetro fino y pared gruesa. Los índices de vulnerabilidad (IV) y de mesomorfía (IM) más altos se encontraron en M. aculeaticarpa var. aculeaticarpa (4.05 y 729.05, respectivamente), lo que indica que este taxon es más vulnerable a la sequía, mientras que los valores más bajos de IV y de IM correspondieron a M. luisana (1.42 y 226.71, respectivamente), sugiriendo que éste es más resistente a la sequía.Conclusiones: Se propone que M. aculeaticarpa var. aculeaticarpa es apta para restaurar lugares mésicos y M. luisana lo es para ambientes secos.

ESS Smelting Technology

The envirosteel smelter is a rectangular furnace with a large free board volume and multiple channel inductors mounted below the hearth. The raw materials are charged against the back wall forming an inclined heap sloping toward the front long wall. The feed blend is spread in thin layers over the surface of the heap and is heated by exposure to radiation from the free board. Reducing conditions in the top layer of the heap permit gas–solid reduction. Metal, in the hearth of the furnace, flows into the channel inductor where it is heated. The heated metal flows back against the front long wall to under the heap. The bottom of the heap is continuously melted by energy transferred from the metal layer. The two off-gas ducts are located in the short end walls. The combustion air is heated to around 800°C by a furnace gas in an external heat exchanger.