Search results for: capping beam

Authors: Mai A. Aljaberi

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The anchorage of fibre-reinforced polymer (FRP) sheets is the most effective solution to prevent or delay debonding failure; this system has proven to get better levels of FRP utilization. Unfortunately, the related design information is still unclear. This shortcoming limits the widespread use of the anchorage system. In order to minimize the knowledge gap about the design of U-wrap anchors, this paper reports the results of tested beams which were strengthened with carbon fiber-reinforced polymer (CFRP) sheets at their tension sides and secured with U-wrap anchors at each end of the longitudinal CFRP. The beams were tested under four-point loading until failure. The parameters examined include the compressive strength of the concrete and the number of longitudinal CFRP. It is concluded that these parameters have a considerable effect on the debonding of the strain. The greatest improvement in the strain was 55.8% over the control beam.

Keywords: CFRP, concrete strengthening, debonding failure, debonding strain, U-wrap anchor

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Authors: Areeg Shermaddo, Abedulgader Baktheer

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Solar updraft power plants (SUPPs) made from reinforced concrete (RC) are an innovative technology to generate solar electricity. An up to 1000 m high chimney represents the major part of each SUPP ensuring the updraft of the warmed air from the ground. Numerical simulation of nonlinear behavior of such large mega shell concrete structures is a challenging task, and computationally expensive. A general finite element approach to simulate reinforced concrete bearing behavior is presented and verified on a simply supported beam, as well as the technique of submodeling. The verified numerical approach is extended and consecutively transferred to a more complex chimney structure of a SUPP. The obtained results proved the reliability of submodeling technique in analyzing critical regions of simple and complex mega concrete structures with high accuracy and dramatic decrease in the computation time.

Keywords: ABAQUS, nonlinear analysis, submodeling, SUPP

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Authors: Igor Shardakov, Anton Bykov, Alexey Shestakov, Irina Glot

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This article focuses on the cycle of experimental studies of the formation of cracks and debondings in the concrete reinforced with carbon fiber. This research was carried out in Perm National Research Polytechnic University. A series of CFRP-strengthened RC beams was tested to investigate the influence of preload and crack repairing factors on CFRP debonding. IRT was applied to detect the early stage of IC debonding during the laboratory bending tests. It was found that for the beams strengthened under load after crack injecting, СFRP debonding strain is 4-65% lower than for the preliminary strengthened beams. The beams strengthened under the load had a relative area of debonding of 2 times higher than preliminary strengthened beams. The СFRP debonding strain is weakly dependent on the strength of the concrete substrate. For beams with a transverse wrapping anchorage in support sections FRP debonding is not a failure mode.

Keywords: IC debonding, infrared thermography, non-destructive testing methods, quality control, strengthening

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Authors: Byeong-Sam Kim, Kyeongwoo Park

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In this study, induced structural optimization is performed to compare the trade-off between wing weight and induced drag for wing panel extensions, construction of wing panel and winglets. The aerostructural optimization problem consists of parameters with strength condition, and two maneuver conditions using residual stresses in panel production. The results of kinematic motion analysis presented a homogenization based theory for 3D beams and 3D shells for wing panel. This theory uses a kinematic description of the beam based on normalized displacement moments. The displacement of the wing is a significant design consideration as large deflections lead to large stresses and increased fatigue of components cause residual stresses. The stresses in the wing panel are small compared to the yield stress of aluminum alloy. This study describes the implementation of a large wing panel, aerostructural analysis and structural parameters optimization framework that couples a three-dimensional panel method.

Keywords: wing panel, aerostructural optimization, FEM, structural analysis

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Authors: Pavel Chmelar, Martin Dobrovolny

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Laser projection or laser footprint detection is today widely used in many fields of robotics, measurement, or electronics. The system accuracy strictly depends on precise laser footprint detection on target objects. This article deals with the laser line detection based on the RGB segmentation and the component labeling. As a measurement device was used the developed optical rangefinder. The optical rangefinder is equipped with vertical sweeping of the laser beam and high quality camera. This system was developed mainly for automatic exploration and mapping of unknown spaces. In the first section is presented a new detection algorithm. In the second section are presented measurements results. The measurements were performed in variable light conditions in interiors. The last part of the article present achieved results and their differences between day and night measurements.

Keywords: color segmentation, component labelling, laser line detection, automatic mapping, distance measurement, vector map

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Authors: B. G. Patel, A. K. Desai, S. G. Shah

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The main of objective of this paper is to develop new measurement technique without touching the object. DIC is advance measurement technique use to measure displacement of particle with very high accuracy. This powerful innovative technique which is used to correlate two image segments to determine the similarity between them. For this study, nine geometrically similar beam specimens of different sizes with (steel fibers and glass fibers) and without fibers were tested under three-point bending in a closed loop servo-controlled machine with crack mouth opening displacement control with a rate of opening of 0.0005 mm/sec. Digital images were captured before loading (unreformed state) and at different instances of loading and were analyzed using correlation techniques to compute the surface displacements, crack opening and sliding displacements, load-point displacement, crack length and crack tip location. It was seen that the CMOD and vertical load-point displacement computed using DIC analysis matches well with those measured experimentally.

Keywords: Digital Image Correlation, fibres, self compacting concrete, size effect

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Authors: E. Ebru Demirci, Remzi Şahin

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The purpose of this study is to compare Self Compacting Concrete (SCC) and Conventional Concrete (CC) in terms of their capillary water absorption. During the comparison of SCC and CC, the effects of two different factors were also investigated: concrete strength class and curing condition. In the study, both SCC and CC were produced in three different concrete classes (C25, C50 and C70) and the other parameter (i.e curing condition) was determined as two levels: moisture and air curing. It was observed that, for both curing environments and all strength classes of concrete, SCCs had lower capillary water absorption values than that of CCs. It was also detected that, for both SCC and CC, capillary water absorption values of samples kept in moisture curing were significantly lower than that of samples stored in air curing. Additionally, it was determined that capillary water absorption values for both SCC and CC decrease with increasing strength class of concrete for both curing environments.

Keywords: capillary water absorption, curing condition, reinforced concrete beam, self-compacting concrete

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Authors: Mahdi Amne Elahi, Marcus Koch, Peter Plapper

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Due to the demand of miniaturizing in automotive industry, the application of laser welding is quite promising. The current study focused on laser micro-welding of CuSn6 bronze and nickel wire for a miniature electromechanical hybrid component. Due to the advantages of laser welding, the welding can be tailored specifically for the requirements of the part. Scanning electron and optical microscopy were implemented to study the microstructure and tensile-shear test was selected to represent the mechanical properties. Different welding sides, beam oscillations, and speeds have been investigated to optimize the tensile-shear load and microstructure. The results show that the mechanical properties and microstructure of the joint is highly under the influence of the mentioned parameters. Due to the lack of intermetallic compounds, the soundness of the joint is achievable by manipulating the geometry of the weld seam and minimize weld defects.

Keywords: bronze, laser micro-welding, microstructure, nickel, tensile shear test

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Authors: Syfur Rahman, Mohammad J. Khattak

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Every year a huge quantity of recycling concrete aggregate (RCA) is generated in the United States of America. Utilization of RCA can solve the storage problem, prevent environmental pollution, and reduce the construction cost. However, due to the overall low strength and durability characteristics of RCA, its usages are limited to a certain area like a landfill, low strength base material, replacement of a few percentages of virgin aggregates in Portland cement concrete, etc. This study focuses on the improvement of the strength and durability characteristics of RCA by introducing the concept of roller-compacted geopolymer concrete. In this research, developed roller-compacted geopolymer concrete (RCGPC) and roller-compacted cement concrete (RCC) mixtures containing 100% recycled concrete aggregate were evaluated and compared. Several selected RCGPC mixtures were investigated to find out the effect of mixture variables, including sodium hydroxide (NaOH) molar concentration, sodium silicate (Na₂SiO₃), to sodium hydroxide (NaOH) ratio on the strength, stiffness and durability characteristics of the developed RCGPC. Sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) were mixed in different ratios to synthesize the alkali activator. American Concrete Pavement Association (ACPA) recommended RCC gradation was used with a maximum nominal aggregate size of 19 mm with a 4% fine particle passing 0.075 mm sieve. The mixtures were made using NaOH molar concentration of 8M and 10M along with, Na₂SiO₃ to NaOH ratio of 0 and 1 by mass and 15% class F fly ash. Optimum alkali content and moisture content were determined for each RCGPC and RCC mixtures, respectively, using modified proctor test. Compressive strength, semi-circular bending beam strength, and dynamic modulus test were conducted to evaluate the mechanistic characteristics of both mixtures. To determine the optimum curing conditions for RCGPC, effects of different curing temperature and curing duration on compressive strength were also studied. Sulphate attack and freeze-thaw tests were also carried out to assess the durability properties of the developed mixtures. X-ray diffraction (XRD) was used for morphology and microstructure analysis. From the optimum moisture content results, it was found that RCGPC has high alkali content, which was mainly due to the high absorption capacity of RCA. It was found that the mixtures with Na₂SiO₃ to NaOH ratio of 1 yielded about 60% higher compressive strength than the ratio of 0. Further, the mixtures using 10M NaOH concentrations and alkali ratio of 1 produced about 28 MPa of compressive strength, which was around 33% higher than 8M NaOH mixtures. Similar results were obtained for elastic and dynamic modulus of the mixtures. On the other hand, the semi-circular bending beam strength remained the same for both 8 and 10 molar NaOH geopolymer mixtures. Formation of new geopolymeric compounds and chemical bonds in the newly formed novel RCGPC mixtures were also discovered using XRD analysis. The results of mechanical and durability testing further revealed that RCGPC performed similarly to that of RCC mixtures. Based on the results of mechanical and durability testing, the developed RCGPC mixtures using 100% recycled concrete could be used as a cost-effective solution for the construction of pavement structures.

Keywords: roller compacted concrete, geopolymer concrete, recycled concrete aggregate, concrete pavement, fly ash

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Authors: Lei Qi, Rongxin Yan, Lichen Sun

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With the increasing of human space activities, the number of space debris has increased dramatically, and the possibility that spacecrafts on orbit are impacted by space debris is growing. A method is of the vital significance to real-time detect and assess spacecraft damage, determine of gas leak accurately, guarantee the life safety of the astronaut effectively. In this paper, acoustic sensor array is used to detect the acoustic signal which emits from the damage of the spacecraft on orbit. Then, we apply the time difference of arrival and beam forming algorithm to locate the damage and leakage. Finally, the extent of the spacecraft damage is evaluated according to the nonlinear ultrasonic method. The result shows that this method can detect the debris impact and the structural damage, locate the damage position, and identify the damage degree effectively. This method can meet the needs of structural damage detection for the spacecraft in-orbit.

Keywords: acoustic sensor array, spacecraft, damage assessment, leakage location

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Authors: J. A. Sawicki, C. Ebrahimi

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The first geochemical, petrological, X-ray diffraction, Raman, Mössbauer, and oxygen isotopic analyses of very intriguing 13-kg Sooke #1 stone covered in 70% of its surface with black fusion crust, found in and recovered from Sooke Basin, near Juan de Fuca Strait, in British Columbia, were reported as poster #2775 at LPSC52 in March. Our further analyses reported in poster #6305 at 84AMMS in August and comparisons with the Mössbauer spectra of Martian meteorite MIL03346 and Martian rocks in Gusev Crater reported by Morris et al. suggest that Sooke #1 find could be a stony achondrite of Martian polymict breccia type ejected from early watery Mars. Here, the Raman spectra of a carbon-rich ~1-mm² fossil-like white area identified in this rock on a surface of polished cut have been examined in more detail. The low-intensity 532 nm and 633 nm beams of the InviaRenishaw microscope were used to avoid any destructive effects. The beam was focused through the microscope objective to a 2 m spot on a sample, and backscattered light collected through this objective was recorded with CCD detector. Raman spectra of dark areas outside fossil have shown bands of clinopyroxene at 320, 660, and 1020 cm-1 and small peaks of forsteritic olivine at 820-840 cm-1, in agreement with results of X-ray diffraction and Mössbauer analyses. Raman spectra of the white area showed the broad band D at ~1310 cm-1 consisting of main mode A1g at 1305 cm⁻¹, E2g mode at 1245 cm⁻¹, and E1g mode at 1355 cm⁻¹ due to stretching diamond-like sp3 bonds in diamond polytype lonsdaleite, as in Ovsyuk et al. study. The band near 1600 cm-1 mostly consists of D2 band at 1620 cm-1 and not of the narrower G band at 1583 cm⁻¹ due to E2g stretching in planar sp2 bonds that are fundamental building blocks of carbon allotropes graphite and graphene. In addition, the broad second-order Raman bands were observed with 532 nm beam at 2150, ~2340, ~2500, 2650, 2800, 2970, 3140, and ~3300 cm⁻¹ shifts. Second-order bands in diamond and other carbon structures are ascribed to the combinations of bands observed in the first-order region: here 2650 cm⁻¹ as 2D, 2970 cm⁻¹ as D+G, and 3140 cm⁻¹ as 2G ones. Nanodiamonds are abundant in the Universe, found in meteorites, interplanetary dust particles, comets, and carbon-rich stars. The diamonds in meteorites are presently intensely investigated using Raman spectroscopy. Such particles can be formed by CVD process and during major impact shocks at ~1000-2300 K and ~30-40 GPa. It cannot be excluded that the fossil discovered in Sooke #1 could be a remnant of an alien carbon organism that transformed under shock impact to nanodiamonds. We trust that for the benefit of research in astro-bio-geology of meteorites, asteroids, Martian rocks, and soil, this find deserves further, more thorough investigations. If possible, the Raman SHERLOCK spectrometer operating on the Perseverance Rover should also search for such objects in the Martian rocks.

Keywords: achondrite, nanodiamonds, lonsdaleite, raman spectra

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Authors: Azad A. Mohammed, Dunyazad K. Assi, Alan S. Abdulrahman

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Current ACI 318 Code provides two limits for minimum steel ratio for concrete beams. When concrete compressive strength be larger than 31 MPa the limit of √(fc')/4fy usually governs. In this paper shortcomings related to using this limit was fairly discussed and showed that the limit is based on 90% safety factor and was derived based on modulus of rupture equation suitable for concretes of compressive strength lower than 31 MPa. Accordingly, the limit is nor suitable and critical for concretes of higher compressive strength. An alternative equation was proposed for minimum steel ratio of rectangular beams and was found that the proposed limit is accurate for beams of wide range of concrete compressive strength. Shortcomings of the current ACI 318 Code equation and accuracy of the proposed equation were supported by test data obtained from testing six reinforced concrete beams.

Keywords: concrete beam, compressive strength, minimum steel ratio, modulus of rupture

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Authors: Guray Arslan, Riza Secer Orkun Keskin

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Numerical investigations were conducted to study the influence of flexural reinforcement ratio on the diagonal cracking strength and ultimate shear strength of reinforced concrete (RC) beams without stirrups. Three-dimensional nonlinear finite element analyses (FEAs) of the beams with flexural reinforcement ratios ranging from 0.58% to 2.20% subjected to a mid-span concentrated load were carried out. It is observed that the load-deflection and load-strain curves obtained from the numerical analyses agree with those obtained from the experiments. It is concluded that flexural reinforcement ratio has a significant effect on the shear strength and deflection capacity of RC beams without stirrups. The predictions of the diagonal cracking strength and ultimate shear strength of beams obtained by using the equations defined by a number of codes and researchers are compared with each other and with the experimental values.

Keywords: finite element, flexural reinforcement, reinforced concrete beam, shear strength

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Authors: G. K. S. Prakash, Rao K. Srinivasa

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MEMS plays an important role in wide range of applications like biological, automobiles, military and communication engineering. This paper mainly investigates on capacitive shunt RF MEMS switch with low actuation voltage and low insertion losses. To trim the pull-in voltage, a step structure has introduced to trim air gap between the beam and the dielectric layer with that pull in voltage is trim to 2.9 V. The switching time of the proposed switch is 39.1μs, and capacitance ratio is 67. To get more isolation, we have used aluminum nitride as dielectric material instead of silicon nitride (Si₃N₄) and silicon dioxide (SiO₂) because aluminum nitride has high dielectric constant (εᵣ = 9.5) increases the OFF capacitance and eventually increases the isolation of the switch. The results show that the switch is ON state involves return loss (S₁₁) less than -25 dB up to 40 GHz and insertion loss (S₂₁) is more than -1 dB up to 35 GHz. In OFF state switch shows maximum isolation (S₂₁) of -38 dB occurs at a frequency of 25-27 GHz for K band applications.

Keywords: RF MEMS, actuation voltage, isolation loss, switches

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Authors: Ahmad Seiar Yasser

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Sediment is an important habitat for organisms and act as a store house for nutrients in aquatic ecosystems. Hydrogen sulfide is produced by microorganisms in the water columns and sediments, which is highly toxic and fatal to benthic organisms. However, the irons have the capacity to regulate the formation of sulfide by poising the redox sequence and to form insoluble iron sulfide and pyrite compounds. Therefore, we conducted two experiments aimed to evaluate the remediation efficiency of iron application to organically enrich and improve sediments environment. Experiments carried out in the laboratory using intact sediment cores taken from Mikawa Bay, Japan at every month from June to September 2017 and October 2018. In Experiment 1, after cores were collected, the iron powder or iron hydroxide were applied to the surface sediment with 5 g/ m2 or 5.6 g/ m2, respectively. In Experiment 2, we experimentally investigated the removal of hydrogen sulfide using (2mm or less and 2 to 5mm) of the steelmaking slag. Experiments are conducted both in the laboratory with the same boundary conditions. The overlying water were replaced with deoxygenated filtered seawater, and cores were sealed a top cap to keep anoxic condition with a stirrer to circulate the overlying water gently. The incubation experiments have been set in three treatments included the control, and each treatment replicated and were conducted with the same temperature of the in-situ conditions. Water samples were collected to measure the dissolved sulfide concentrations in the overlying water at appropriate time intervals by the methylene blue method. Sediment quality was also analyzed after the completion of the experiment. After the 21 days incubation, experimental results using iron powder and ferric hydroxide revealed that application of these iron containing materials significantly reduced sulfide release flux from the sediment into the overlying water. The average dissolved sulfides concentration in the overlying water of the treatment group was significantly decrease (p = .0001). While no significant difference was observed between the control group after 21 day incubation. Therefore, the application of iron to the sediment is a promising method to remediate contaminated sediments in a eutrophic water body, although ferric hydroxide has better hydrogen sulfide removal effects. Experiments using the steelmaking slag also clarified the fact that capping with (2mm or less and 2 to 5mm) of slag steelmaking is an effective technique for remediation of bottom sediments enriched organic containing hydrogen sulfide because it leads to the induction of chemical reaction between Fe and sulfides occur in sediments which did not occur in conditions naturally. Although (2mm or less) of slag steelmaking has better hydrogen sulfide removal effects. Because of economic reasons, the application of steelmaking slag to the sediment is a promising method to remediate contaminated sediments in the eutrophic water body.

Keywords: sedimentary, H2S, iron, iron hydroxide

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Authors: Nasruddin Junus

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CFTR column is one of the improvements CFT columns by inserting reinforcing steel bars into infill concrete. The presence of inserting reinforcing steel bars is increasing the excellent structural performance of the CFT column, especially on the fire-resisting performance. Investigation on the mechanical behavior of CFTR column connection is summarized in the three parts; column to column joint, column to beam connection, and column base. Experiment that reported in this paper is concerned on the mechanical behavior of CFTR column joint under pull out testing, especially on its stress transfer mechanism. A number series of the pull out test on the CFT with inserting reinforcing steel bar are conducted. Ten test specimens are designed, constructed, and tested to examine experimentally the effect of the size of square steel tube, size of the bearing plate, length of embedment steel bars, kind of steel bars, and the numbers of rib plate.

Keywords: CFTR column, pull out, stress, transfer mechanism

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Authors: Mohanad Talal Alfach

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This paper concerns the seismic behaviour of soil-piles-bridge reinforced by additional micropiles. The analysis carried out by three-dimensional finite element modelling using the FE software ABAQUS. The soil behaviour is assumed to be elastic with Rayleigh damping, while the micropiles are modeled as 3D elastic beam elements. The bridge deck slab was represented by a concentrated mass at the top of the pier column. The interaction between the added micropiles and the existing piles as well as the performance of the retrofitted soil-pile-superstructure system were investigated for different configurations of additional micropiles (number, position, inclination). Numerical simulation results show that additional micropiles constitute an efficient retrofitting solution. Analysis of results also shows that spacing between existing piles and retrofitting micropiles has little effect; while it is observed a substantial improvement (in case of weak piles/micropiles - soil interface) with reducing the inclination angle of retrofitting micropiles.

Keywords: retrofitting, seismic, finite element, micropiles, elastic

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Authors: Aleksandra Boldyreva, Alexander Golubnichiy, Artem Abakumov

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Various perovskite materials have surprisingly high resistance towards high-energy electrons, protons, and hard ionization, such as X-rays and gamma-rays. Superior radiation hardness makes a family of perovskite semiconductors an attractive candidate for single- and multijunction solar cells for the space environment and as X-ray and gamma-ray detectors. One of the methods to study the radiation hardness of different materials is by exposing them to gamma photons with high energies (above 500 keV) Herein, we have explored the recombination dynamics and defect concentration of a mixed cation mixed halide perovskite Cs0.17FA0.83PbI1.8Br1.2 with 1.74 eV bandgap after exposure to a gamma-ray source (2.5 Gy/min). We performed an advanced STEM EDX analysis to reveal different types of defects formed during gamma exposure. It was found that 10 kGy dose results in significant improvement of perovskite crystallinity and homogeneous distribution of I ions. While the absorber layer withstood gamma exposure, the hole transport layer (PTAA) as well as indium tin oxide (ITO) were significantly damaged, which increased the interface recombination rate and reduction of fill factor in solar cells. Thus, STEM analysis is a powerful technique that can reveal defects formed by gamma exposure in perovskite solar cells. Methods: Data will be collected from perovskite solar cells (PSCs) and thin films exposed to gamma ionisator. For thin films 50 μL of the Cs0.17FA0.83PbI1.8Br1.2 solution in DMF was deposited (dynamically) at 3000 rpm followed by quenching with 100 μL of ethyl acetate (dropped 10 sec after perovskite precursor) applied at the same spin-coating frequency. The deposited Cs0.17FA0.83PbI1.8Br1.2 films were annealed for 10 min at 100 °C, which led to the development of a dark brown color. For the solar cells, 10% suspension of SnO2 nanoparticles (Alfa Aesar) was deposited at 4000 rpm, followed by annealing on air at 170 ˚C for 20 min. Next, samples were introduced into a nitrogen glovebox for the deposition of all remaining layers. Perovskite film was applied in the same way as in thin films described earlier. Solution of poly-triaryl amine PTAA (Sigma Aldrich) (4 mg in chlorobenzene) was applied at 1000 rpm atop of perovskite layer. Next, 30 nm of VOx was deposited atop the PTAA layer on the whole sample surface using the physical vapor deposition (PVD) technique. Silver electrodes (100 nm) were evaporated in a high vacuum (10-6 mbar) through a shadow mask, defining the active area of each device as ~0.16 cm2. The prepared samples (thin films and solar cells) were packed in Al lamination foil inside the argon glove box. The set of samples consisted of 6 thin films and 6 solar cells, which were exposed to 6, 10, and 21 kGy (2 samples per dose) with 137Cs gamma-ray source (E = 662 keV) with a dose rate of 2.5 Gy/min. The exposed samples will be studied on a focused ion beam (FIB) on a dual-beam scanning electron microscope from ThermoFisher, the Helios G4 Plasma FIB Uxe, operating with a xenon plasma.

Keywords: perovskite solar cells, transmission electron microscopy, radiation hardness, gamma irradiation

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Authors: Khalid A. Rabaeh, Belal Moftah, Ahmed A. Basfar, Akram A. Almousa

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Polymer gel dosimeters are tissue equivalent martial that fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of absorbed radiation dose. Polymer gel dosimeters can uniquely record the radiation dose distribution in three-dimensions (3D). A novel composition of normoxic polymer gel dosimeters based on radiation-induced polymerization of N-(Hydroxymethyl)acrylamide (NHMA) is introduced in this study for radiotherapy treatment planning. The dosimeters were irradiated by 10 MV photon beam of a medical linear accelerator at a constant dose rate of 600 cGy/min with doses up to 30 Gy. The polymerization degree is directly proportional to absorbed dose received by the polymer gel. UV/Vis spectrophotometer was used to investigate the degree of white color of irradiated NHMA gel which is associated to the degree of polymerization of polymer gel dosimeters. The absorbance increases with absorbed dose for all gel dosimeters in the dose range between 0 and 30 Gy. Dose rate , energy of radiation and the stability of the polymerization after irradiation were investigated. No appreciable effects of these parameters on the performance of the novel gel dosimeters were observed.

Keywords: dosimeter, gel, spectrophotometer, N-(Hydroxymethyl)acrylamide

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Authors: A. Shooshtari, A. R. Masoodi, S. Heyrani Moghaddam

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Free vibration analysis of a gabled frame with elastic support and semi-rigid connections is performed by using a program in OpenSees software. Natural frequencies and mode shape details of frame are obtained for two states, which are semi-rigid connections and elastic supports, separately. The members of this structure are analyzed as a prismatic nonlinear beam-column element in software. The mass of structure is considered as two equal lumped masses at the head of two columns in horizontal and vertical directions. Note that the degree of freedom, allocated to all nodes, is equal to three. Furthermore, the mode shapes of frame are achieved. Conclusively, the effects of connections and supports flexibility on the natural frequencies and mode shapes of structure are investigated.

Keywords: natural frequency, mode shape, gabled frame, semi-rigid connection, elastic support, OpenSees software

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Authors: Luciano Roberto Fernandez-Sola, Cesar Augusto Arredondo-Velez, Miguel Angel Jaimes-Tellez

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This paper explores the modifications on peak acceleration, velocity and displacement profiles over the structure due to dynamic soil-structure interaction (DSSI). A shear beam model is used for the structure. Soil-foundation flexibility (inertial interaction) is considered by a set of springs and dashpots at the structure base. Kinematic interaction is considered using transfer functions. Impedance functions are computed using simplified expressions for rigid foundations. The research studies the influence of the slenderness ratio on the value of the peak floor response. It is shown that the modifications of peak floor responses are not the same for acceleration, velocity and displacement. This is opposite to the hypothesis used by methods included in several building codes. Results show that modifications produced by DSSI on different response quantities are not equal.

Keywords: peak floor intensities, dynamic soil-structure interaction, buildings with flexible base, kinematic and inertial interaction

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Authors: Bhavana Gulaty, Arshia Chaudhri

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Great civic projects contribute integrally to a city, and every city undergoes a recurring cycle of urban transformations and regeneration by their insertion. The M.I.C.E. (Meetings, Incentives, Convention and Exhibitions) industry is the forbearer of one category of such catalytic civic projects. Through a specific focus on M.I.C.E. destinations, this paper illustrates the multifarious dimensions that urban catalysts impact the city on S.P.U.R. (Seed. Profile. Urbane. Reflections), the theoretical framework of this paper aims to unearth these dimensions in the realm of the COEX (Convention & Exhibition) biosphere. The ‘COEX Biosphere’ is the filter of such catalysts being ecosystems unto themselves. Like a ripple in water, the impact of these strategic interventions focusing on art, culture, trade, and promotion expands right from the trigger; the immediate context to the region and subsequently impacts the global scale. These ripples are known to bring about significant economic, social, and political and network changes. The COEX inventory in the Asian context has one such prominent addition; the proposed India International Convention and Exhibition Centre (IICC) at New Delhi. It is envisioned to be the largest facility in Asia currently and would position India on the global M.I.C.E map. With the first phase of the project scheduled to open for use in the end of 2019, this flagship project of the Government of India is projected to cater to a peak daily footfall of 3,20,000 visitors and estimated to generate 5,00,000 jobs. While the economic benefits are yet to manifest in real time and ‘Good design is good business’ holds true, for the urban transformation to be meaningful, the benefits have to go beyond just a balance sheet for the city’s exchequer. This aspect has been found relatively unexplored in research on these developments. The methodology for investigation will comprise of two steps. The first will be establishing an inventory of the global success stories and associated benefits of COEX projects over the past decade. The rationale for capping the timeframe is the significant paradigm shift that has been observed in their recent conceptualization; for instance ‘Innovation Districts’ conceptualised in the city of Albuquerque that converges into the global economy. The second step would entail a comparative benchmarking of the projected transformations by IICC through a toolkit of parameters. This is posited to yield a matrix that can form the test bed for mapping the catalytic trajectory for projects in the pipeline globally. As a ready reckoner, it purports to be a catalyst to substantiate decision making in the planning stage itself for future projects in similar contexts.

Keywords: catalysts, COEX, M.I.C.E., urban transformations

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Authors: Abdur Rosyid, Mohamed El-Madany, Mohanad Alata

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Due to simplicity and low cost, rotordynamic system is often modeled by using lumped parameters. Recently, finite elements have been used to model rotordynamic system as it offers higher accuracy. However, it involves high degrees of freedom. In some applications such as control design, this requires higher cost. For this reason, various model reduction methods have been proposed. This work demonstrates the quality of model reduction of rotor-bearing-support system through substructuring. The quality of the model reduction is evaluated by comparing some first natural frequencies, modal damping ratio, critical speeds and response of both the full system and the reduced system. The simulation shows that the substructuring is proven adequate to reduce finite element rotor model in the frequency range of interest as long as the numbers and the locations of master nodes are determined appropriately. However, the reduction is less accurate in an unstable or nearly-unstable system.

Keywords: rotordynamic, finite element model, timoshenko beam, 3D solid elements, Guyan reduction method

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Authors: Yusuf Ziya Halefoğlu

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Phosphorescence, classically, excitation effects (radiation, electron beam, electric field, temperature, etc.) is the name given after the elimination of materials that glow in the visible region. This event continues to glow after the elimination of the effect of excitation is called phosphorescence. In this study were synthesized by the method of the combustion lanthanide doped alkaline earth aluminates. High temperature and long reaction time required and the sol-gel method of combustion according to the methods of solid state synthesis temperature lower than the short reaction time, a small particle size, convenience, and is superior in terms of being secured. Their microstructures and its effect on the photoluminescence properties were studied. Phosphorescence is derived in the dark when produced materials are held in sunlight or under ultraviolet light typically at 365-520 nm wavelength range. In this study, the optimal ratio of rare earth elements, in terms of brightness and glow duration was examined by SEM, XRD and photoluminescence analysis.

Keywords: persistence luminescence, phosphorescence, trap depth, combustion method

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Authors: Philip Rose, Markus Linke, David Busquets

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The distinction between interlaminar and intralaminar fracture toughness has already been investigated by several authors. For loading mode I, the double cantilever beam specimens were often used for the interlaminar fracture toughness and the compact tension specimen for the intralaminar fracture toughness. In order to minimize the influence of the different specimen geometries, a method was developed which allows the determination of both the interlaminar and the intralaminar fracture toughness on an almost identical specimen geometry. However, as this method is not applicable to prepreg semi-finished products, a further modification was developed, which is also suitable for prepreg laminates. After the successful application for the investigation of mode I with this method, the application of the method for loading mode II is presented in this paper. In addition to manufacturing differences, due to an additional fiber ply in which the controlled crack growth takes place, the adapted test procedure is also explained. By comparing the test results of standardized end-notched flexure (ENF) specimens with those of the modified ENF specimen, the difference between the interlaminar and intralaminar fracture toughness of the material Hexply 8552/IM7 is shown.

Keywords: ENF, fracture toughness, interlaminar, mode II

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Authors: Seyed Mahdi Rafiaei

Abstract:

In this investigation, firstly Eu3+ doped YVO4 phosphor was synthesized using solid-state method. Then silica was coated on the surface of particles via sol-gel method. To study the influence of SiO2 addition on microstructure and photoluminescence characteristics of YVO4:4% Eu3+ phosphor materials, we employed X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), High-Resolution Transmitted Electron Microscope (HRTEM), Focused Ion Beam (FIB), Brunauer Emmett Teller (BET), Inductively coupled plasma (ICP), Electron Spin Resonance (ESR) and Photoluminescence (PL) equipments. The XPS characterization confirmed the formation of Y–O–Si and V-O-Si bondings between YVO4:Eu3+ phosphor particle and SiO2 coating. In addition, it was found that although the amounts of added SiO2 were not remarkable, but it resulted in enhancement of emission intensity of the phosphors. Finally by employing ESR analysis, it was shown that surface oxygen vacancies, result in reduction of V5+ to the lower valence state of V4+.

Keywords: solid state, sol-gel, silica, coating, photoluminescence

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Authors: Tran Trong Thang, Nguyen Phan Kien, Trinh Quang Duc

Abstract:

The phased-array ultrasound transducer types are utilities for medical ultrasonography as well as optical imaging. However, their discontinuity characteristic limits the applications due to the artifacts contaminated into the reconstructed images. Because of the effects of the ultrasound pressure field pattern to the echo ultrasonic waves as well as the optical modulated signal, the side lobes of the focused ultrasound beam induced by discontinuity of the phased-array ultrasound transducer might the reason of the artifacts. In this paper, a simple method in approach of numerical simulation was used to investigate the limitation of discontinuity of the elements in phased-array ultrasound transducer and their effects to the ultrasound pressure field. Take into account the change of ultrasound pressure field patterns in the conditions of variation of the pitches between elements of the phased-array ultrasound transducer, the appropriated parameters for phased-array ultrasound transducer design were asserted quantitatively.

Keywords: phased-array ultrasound transducer, sound pressure pattern, discontinuous sound field, numerical visualization

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Authors: Mehrdad Azimzadeh, Seyed Mohammadreza Jabbari, Mohammadreza Hosseinzadeh Alherd

Abstract:

This paper includes experimental results and analytical studies about increasing resistance of single-span reinforced concreted frames against impact factor and their modeling according to optimization methods and optimizing the behavior of these frames under impact loads. During this study, about 30 designs for different frames were modeled and made using specialized software like ANSYS and Sap and their behavior were examined under variable impacts. Then suitable strategies were offered for frames in terms of concrete mixing in order to optimize frame modeling. To reduce the weight of the frames, we had to use fine-grained stones. After designing about eight types of frames for each type of frames, three samples were designed with the aim of controlling the impact strength parameters, and a good shape of the frame was created for the impact resistance, which was a solid frame with muscular legs, and as a bond away from each other as much as possible with a 3 degree gradient in the upper part of the beam.

Keywords: optimization, reinforced concrete, optimization methods, impact load, earthquake

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Authors: G. Vinitha, A. Ramalingam

Abstract:

In view of a possible application in optical data storage devices, diffraction grating efficiency of an organic dye, Acid Fuchsin doped in PMMA matrix was studied under excitation with CW diode pumped Nd: YAG laser at 532 nm. The open aperture Z-scan of dye doped polymer displayed saturable absorption and the closed aperture Z-scan of the samples exhibited negative nonlinearity. The diffraction efficiency of the grating is the ratio of the intensity of the first order diffracted power to the incident read beam power. The dye doped polymer films were found to be good media for recording. It is observed that the formation of gratings strongly depend on the concentration of dye in the polymer film, the intensity ratios of the writing beams and the angle between the writing beams. It has been found that efficient writing can be made at an angle of 20° and when the intensity ratio of the writing beams is unity.

Keywords: diffraction efficiency, nonlinear optical material, saturable absorption, surface-relief-gratings

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Authors: Diane Ghanem, Arjun Gupta, Rohan Vijayan, Ali Uneri, Babar Shafiq

Abstract:

Introduction: Ankle sprains and fractures often result in syndesmosis injuries. Unstable syndesmotic injuries result from relative motion between the distal ends of the tibia and fibula, anatomic juncture which should otherwise be rigid, and warrant operative management. Clinical and radiological evaluations of intraoperative syndesmosis stability remain a challenging task as traditional 2D fluoroscopy is limited to a uniplanar translational displacement. The purpose of this pilot cadaveric study is to compare the 2D fluoroscopy and 3D cone beam computed tomography (CBCT) stress-induced syndesmosis displacements. Methods: Three fresh-frozen lower legs underwent 2D fluoroscopy and 3D CIOS CBCT to measure syndesmosis position before dissection. Syndesmotic injury was simulated by resecting the (1) anterior inferior tibiofibular ligament (AITFL), the (2) posterior inferior tibiofibular ligament (PITFL) and the inferior transverse ligament (ITL) simultaneously, followed by the (3) interosseous membrane (IOM). Manual external rotation and Cotton stress test were performed after each of the three resections and 2D and 3D images were acquired. Relevant 2D and 3D parameters included the tibiofibular overlap (TFO), tibiofibular clear space (TCS), relative rotation of the fibula, and anterior-posterior (AP) and medial-lateral (ML) translations of the fibula relative to the tibia. Parameters were measured by two independent observers. Inter-rater reliability was assessed by intraclass correlation coefficient (ICC) to determine measurement precision. Results: Significant mismatches were found in the trends between the 2D and 3D measurements when assessing for TFO, TCS and AP translation across the different resection states. Using 3D CBCT, TFO was inversely proportional to the number of resected ligaments while TCS was directly proportional to the latter across all cadavers and ‘resection + stress’ states. Using 2D fluoroscopy, this trend was not respected under the Cotton stress test. 3D AP translation did not show a reliable trend whereas 2D AP translation of the fibula was positive under the Cotton stress test and negative under the external rotation. 3D relative rotation of the fibula, assessed using the Tang et al. ratio method and Beisemann et al. angular method, suggested slight overall internal rotation with complete resection of the ligaments, with a change < 2mm - threshold which corresponds to the commonly used buffer to account for physiologic laxity as per clinical judgment of the surgeon. Excellent agreement (>0.90) was found between the two independent observers for each of the parameters in both 2D and 3D (overall ICC 0.9968, 95% CI 0.995 - 0.999). Conclusions: The 3D CIOS CBCT appears to reliably depict the trend in TFO and TCS. This might be due to the additional detection of relevant rotational malpositions of the fibula in comparison to the standard 2D fluoroscopy which is limited to a single plane translation. A better understanding of 3D imaging may help surgeons identify the precise measurements planes needed to achieve better syndesmosis repair.

Keywords: 2D fluoroscopy, 3D computed tomography, image processing, syndesmosis injury

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