Current Issue : October - December Volume : 2018 Issue Number : 4 Articles : 5 Articles
This work proposes a 3D shaped optic fiber sensor for ultrasonic stress waves detection\nbased on the principle of a Machââ?¬â??Zehnder interferometer. This sensor can be used to receive\nacoustic emission signals in the passive damage detection methods and other types of ultrasonic\nsignals propagating in the active damage detection methods, such as guided wave-based methods.\nThe sensitivity of an ultrasonic fiber sensor based on the Machââ?¬â??Zehnder interferometer mainly\ndepends on the length of the sensing optical fiber; therefore, the proposed sensor achieves the\nmaximum possible sensitivity by wrapping an optical fiber on a hollow cylinder with a base.\nThe deformation of the optical fiber is produced by the displacement field of guided waves in the\nhollow cylinder. The sensor was first analyzed using the finite element method, which demonstrated\nits basic sensing capacity, and the simulation signals have the same characteristics in the frequency\ndomain as the excitation signal. Subsequently, the primary investigations were conducted via a\nseries of experiments. The sensor was used to detect guided wave signals excited by a piezoelectric\nwafer in an aluminum plate, and subsequently it was tested on a reinforced concrete beam, which\nproduced acoustic emission signals via impact loading and crack extension when it was loaded to\nfailure. The signals obtained from a piezoelectric acoustic emission sensor were used for comparison,\nand the results indicated that the proposed 3D fiber optic sensor can detect ultrasonic signals in the\nspecific frequency response range....
In this study, we proposed a U-shaped optical fiber probe fabricated using a flame heating\nmethod. The probe was packaged in glass tube to reduce human factors during experimental testing\nof the probe as a glucose sensor. The U-shaped fiber probe was found to have high sensitivity in\ndetecting the very small molecule. When the sensor was dipped in solutions with different refractive\nindexes, its wavelength or transmission loss changed. We used electrostatic self-assembly to bond\ngold nanoparticles and glucose oxidase (GOD) onto the sensor�s surface. The results over five cycles of\nthe experiment showed that, as the glucose concentration increased, the refractive index of the sensor\ndecreased and its spectrum wavelength shifted. The best wavelength sensitivity was 2.899 nm/%,\nand the linearity was 0.9771. The best transmission loss sensitivity was 5.101 dB/%, and the linearity\nwas 0.9734. Therefore, the proposed U-shaped optical fiber probe with gold nanoparticles and GOD\nhas good potential for use as a blood sugar sensor in the future....
Through remote forces, levitating micro-actuators completely eliminate mechanical\nattachment between the stationary and moving parts of a micro-actuator, thus providing\na fundamental solution to overcoming the domination of friction over inertial forces at the micro-scale.\nEliminating the usual mechanical constraints promises micro-actuators with increased operational\ncapabilities and low dissipation energy. Further reduction of friction and hence dissipation by means\nof vacuum leads to dramatic increases of performance when compared to mechanically tethered\ncounterparts. In order to efficiently employ the benefits provided by levitation, micro-actuators are\nclassified according to their physical principles as well as by their combinations. Different operating\nprinciples, structures, materials and fabrication methods are considered. A detailed analysis of the\nsignificant achievements in the technology of micro-optics, micro-magnets and micro-coil fabrication,\nalong with the development of new magnetic materials during recent decades, which has driven the\ncreation of new application domains for levitating micro-actuators is performed....
This paper presents all the significant nonlinearities that exist in the description of an\nelectro hydraulic actuator for flexible nozzle thrust vector control. Starting from practical possibilities\nof the theory of a nonlinear system (which are based on the analyses of one nonlinearity or one\nequivalent nonlinearity in the proximity of the linear description of an actuator), this paper explores\nthe possibilities of additional analyses of a nonlinear electro hydraulic actuator for flexible nozzle\nthrust vector control. These explored possibilities can provide information that is useful for the design\nof the control algorithm, as well as for the general design of a flexible nozzle and actuator system....
A repeater coil is used to extend the detection distance of a passive wireless multi-parameter sensing system. The passive wireless\nsensing system has the ability of simultaneously monitoring three parameters by using backscatter modulation together with\nchannel multiplexing. Two different repeater coils are designed and fabricated for readout distance enhancement of the sensing\nsystem: one is a PCB (printed circuit board) repeater coil, and the other is a copper wire repeater coil. Under the conditions of\nfixed voltage and adjustable voltage, the maximum readout distance of the sensing system with and without a repeater coil is\nmeasured. Experimental results show that larger power supply voltage can help further increase the readout distance. The\nmaximum readout distance of the sensing system with a PCB repeater coil has been extended 2.3 times, and the one with a\ncopper wire repeater coil has been extended 3 times. Theoretical analysis and experimental results both indicate that the high Q\nfactor repeater coil can extend the readout distance more. With the copper wire repeater coil as well as a higher power supply\nvoltage, the passive wireless multi-parameter sensing system finally achieves a maximum readout distance of 13.5 cm....
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