NiCoTi spinel ferrite, SrCoTi hexagonal ferrite and copper microparticles were coated with polypyrrole (PPY) using in situ chemical oxidative method. The resulted microwave absorbing material was introduced into polyurethane matrix. XRD patterns indicated the successful preparation of spinel and hexagonal ferrites. SEM micrographs showed the semi-spherical morphology of the prepared composite. The magnetic properties have been investigated using VSM. The microwave absorber with 20%w/w loading percentage exhibits the best microwave absorption performance (bandwidth under −10 dB of 3 GHz and reflection loss of −24 dB at the matching frequency 9.75 GHz and thickness of 1.8 mm). The measurements of permittivity and permeability reveal that the dielectric loss mechanism is the predominant in the current absorber. The measured reflection loss using free space method also indicates the superior performance of the sample with 20%w/w loading percentage.
<p>The horizontal web reinforcement arranged along the depth of the web was proposed as integrated shear reinforcement with stirrups. According the plane-section assumption, the shear strength provided by compression stresses in the concrete at ultimate stage can be calculated. A series of model girders with horizontal reinforcement in webs were fabricated and tested. The tests show that the horizontal web reinforcements can not only carry the horizontal component of the</p><p>diagonal-tension stress, but also delay the occurrence of diagonal cracking, and reduce the width of diagonal cracks, and increase the rigidity and shear strength of beams effectively.</p>
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