Experimental study on flexural behavior of concrete T-beams strengthened with externally prestressed tendons.

To investigate effect of the number of deviators, the tension method, and the tendon profile on the flexural behaviour of reinforcement concrete (RC) T-beams strengthened with externally prestressed tendons, seven identical RC T-beams strengthened with external prestressing tendons were tested under four-point loading. Of these, one beam was ordinary RC beam without strengthening, another six beams were classified into three groups termed G1, G2 and G3. Two beams in G1 had identical straight external tendons with a different number of deviators, two beams in G2 had identical V shape external tendons with different tension method, and two beams in G3 had identical U shape external tendons with different tension method. The failure mode, deflection, strain, load carrying capacity and ductility of the specimens under loading were recorded and analyzed. Test results indicated that strengthening with external prestressing tendons is a very effective method to improve the load carrying capacity and stiffness of the RC beam. Provision of two deviators at the loading points led to satisfactory service load behavior (deflection, cracking, and concrete strain) and a higher load carrying capacity compared to the case where one deviator or no deviators were provided. In addition, tension method of the external tendon nearly had no effect on the load carrying capacity and mechanical behaviour of the RC beams.

Fast optical cooling of nanomechanical cantilever with the dynamical Zeeman effect.

We propose an efficient optical electromagnetically induced transparency (EIT) cooling scheme for a cantilever with a nitrogen-vacancy center attached in a non-uniform magnetic field using dynamical Zeeman effect. In our scheme, the Zeeman effect combined with the quantum interference effect enhances the desired cooling transition and suppresses the undesired heating transitions. As a result, the cantilever can be cooled down to nearly the vibrational ground state under realistic experimental conditions within a short time. This efficient optical EIT cooling scheme can be reduced to the typical EIT cooling scheme under special conditions.