Seismic Rehabilitation of Corner RC Beam-Column Joints Using CFRP Composites

In this paper, efficiency and effectiveness of carbon fiber reinforced polymers (CFRPs) in upgrading the shear strength and ductility of seismically deficient corner or knee reinforced concrete beam-column joints have been studied. For this purpose, four as-built corner/knee joints were constructed with no transverse reinforcement, representing extreme case of preseismic code design construction practice of joints and encompassing many existing beam-column corner joints. Out of these four as-built specimens, two specimens were used as baseline specimens (control specimens) and other two were strengthened with CFRP sheets under two different schemes (strengthened specimens). In the first scheme, CFRP sheets were epoxy bonded to joint, beams, and part of the column regions. In the second scheme, however, sheets were epoxy bonded to joint region only but they were effectively prevented against any possible debonding through mechanical anchorages. All these four subassemblages were subjected to cyclic lateral load histories to simulate loading due to earthquake and provide the equivalent of severe earthquake damage. The damaged control specimens were then repaired by filling their cracks through epoxy and externally bonding them with CFRP sheets under the same above two schemes. These repaired specimens were subjected to the similar cyclic lateral load history and their response histories were obtained. Response histories of control, repaired, and strengthened specimens were then compared. The results were compared through hysteretic loops, load-displacement envelopes, column profiles, ductility, and stiffness degradation. The comparison shows that CFRP sheets are very effective in improving shear resistance and deformation capacity of the corner beam-column joints and delaying their stiffness degradation. Shear capacities of control, repaired, and strengthened specimens were also predicted using writers’ published formulation. The predicted shear capacities were in a good agreement with the experimental values.     

Inkjet printing of polyimide insulators for the 3D printing of dielectric materials for microelectronic applications

In this article, we report the first continuous fabrication of inkjet‐printed polyimide films, which were used as insulating layers for the production of capacitors. The polyimide ink was prepared from its precursor poly(amic) acid, and directly printed on to a hot substrate (at around 160 °C) to initialize a rapid thermal imidization. By carefully adjusting the substrate temperature, droplet spacing, droplet velocity, and other printing parameters, polyimide films with good surface morphologies were printed between two conducting layers to fabricate capacitors. In this work, the highest capacitance value, 2.82 ± 0.64 nF, was achieved by capacitors (10 mm × 10 mm) with polyimide insulating layers thinner than 1 μm, suggesting that the polyimide inkjet printing approach is an efficient way for producing dielectric components of microelectronic devices. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43361.     

Effect of the delignification of wood fibers on the mechanical properties of wood fiber–polypropylene composites

The effect of the delignification of hornbeam fibers on the mechanical properties of wood fiber–polypropylene (PP) composites was studied. Original fibers and delignified fibers at three levels of delignification were mixed with PP at a weight ratio of 40:60 in an internal mixer. Maleic anhydride (0.5 wt %) as the coupling agent and dicumyl peroxide (0.1 wt %) as the initiator were applied. The produced composites were then hot‐pressed, and specimens for physical and mechanical testing were prepared. The results of the properties of the composite materials indicate that delignified fibers showed better performance in the enhancement of tensile strength and tensile modulus, whereas the hardness of the composites was unaffected by delignification. Delignified fibers also exhibited better water absorption resistance. Notched impact strength was higher for delignified fiber composites, but it was reduced at higher delignification levels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4759–4763, 2006     

Optical properties of thermally crystallized poly(ethylene terephthalate)

The optical properties of thermally crystallized polyethylene terephthalate (PET) were investigated using the methods of small-angle light scattering, density, and haze measurements. The results indicate that the haze in crystallized PET results from scattering due to crystalline aggregates called spherulites. The formation of spherulites can lead to high levels of haze even at very low levels of crystallinity. A detailed analysis of polarized light-scattering patterns was employed in order to define the various structural parameters responsible for haze. The relationships between haze, crystallinity, spherulite size, and volume fraction of spherulites were developed for PET.     

Fatigue Reduction in Tubular Web Connections in Semi-deep Beams

In this paper, the experimental and numerical results of a new type of Reduced Beam Section (RBS) connection called (abbreviated of Holed Tubular Web), are investigated. The HTW-RBS connection is a kind of accordion-web RBS connection by which contribution of the web to the flexural capacity of the beam would be reduced. In HTW-RBS connection, a steel tube is used instead of part of the beam web to place the plastic hinge in the expected location and also holes are created on the beam web. Similar to the corrugated webs, HTW-RBS connection has also adequate shear capacity but has little contribution to the flexural stiffness and capacity. Specimens of semi-deep beams with HTW-RBS connections are prepared and tested under cyclic loading. Results of proposed connection (HTW-RBS), indicated that the fatigue caused by stress concentration at the connection of the tube and beam is decreased and no fracture and cracking occurred at this area. Holes as second fuse actuated After the tube (primary fuse) and the length of plastic hinge is increased. Specimens provide at least 7% story drift, without any significant strength loss, which is more than current requirements for qualifying connections in special moment frames. Finally, the HTW-RBS specimen is simulated by finite element software and the results are compatible with the experimental results.

     

Automatic plagiarism detection in obfuscated text

Pattern Analysis and Applications - Plagiarism is a serious problem in education, research, publishing and other fields. Automatic plagiarism detection systems are crucial for ensuring the...     

Detection of Impact Damage in Carbon Fiber Composites Using an Electromagnetic Sensor

This article presents a comprehensive experimental study of impact damage detection for carbon fiber-reinforced polymer (CFRP) composites using an electromagnetic (EM) sensor with coupled spiral inductors (CSI). Two representative types of damage are detected and evaluated, i.e., barely visible impact damage (BVID) and delamination. A multifrequency inspection is performed, where the resultant images indicate the potential of the CSI sensor in the characterization of damage extent. The accuracy and efficiency of the CSI sensor are compared with the open-ended waveguide imaging, near-field microwave microscopy, microwave time-domain reflectometry, the complementary split-ring resonator, and ultrasonic scanning. Applications and limitations of these nondestructive testing (NDT) methods for identifying impact damage are discussed. There is a free edge effect on the electromagnetic signal, which is illustrated for the first time with the proposed EM technique. Detection of the air gap produced by inserting a thin piece into a machined subsurface groove is carried out. It is found that the developed CSI sensor is able to accurately resolve the location and extent of the air gap. The experimental results demonstrate that the sensor could offer an alternative relatively low cost method that can be fully automated for structural monitoring of aircraft and other composite structures.     

Performance Evaluation of 5G Modulation Techniques

Wireless Personal Communications - Higher data rate, increased capacity, higher mobility, lower latency and better quality are the mobile communication prime objectives need to improve in the near...