Applied Mechanics and Materials Vols. 738-739

Abstract: This paper presents the development and fabrication of fiber Bragg grating hydrogen sensor by using magnetron sputtering method to overcome the problem of hydrogen embrittlement.With compact, smooth and high quality thin films deposited by magnetron sputtering, two layers have been sputtered around the fiber cladding: titanium (Ti) layer (20nm) and palladium (Pd) layer (500nm). Between the two layers, Ti is acted as adhesive coatings to ensure connection between fiber and Pd film. Finally, the performance of the developed FBG hydrogen sensor was tested in the laboratory under low hydrogen concentration. The results prove that the fabricated hydrogen sensor has a high sensitivity of 22.67pm/%H₂.

Abstract: In this paper, the electric impendence sensor is simulated calculation with COMSOL Multiphysics. The relationship between impedance and x-displacement of air cavity, the relationship between impedance and y-displacement of air cavity, and the relationships between impedance and radius of air cavity are obtained.

Abstract: Most optical hydrogen sensors are based on light intensity measurement and light intensity detection is vulnerable to the light source output and the optical fiber arrangement. To overcome the shortcomings, an optical fiber based sensor based on fiber Bragg grating (FBG) technique which is capable to measure the concentration of hydrogen dissolved is described in this paper. To examine the availability of monitoring initial hydrogen generation, a needle-to-plate partial discharge (PD) model was setup in the lab. The results between wavelength shifts of optical hydrogen sensor well agreed with conventional dissolved gas analysis (DGA), proving a potential utilization in the detection of dissolved hydrogen in power transformer.

Abstract: This paper develops a multiple membranes fiber Bragg grating (FBG) hydrogen sensor and investigates the relationship between wavelength of FBG hydrogen sensor and ambient hydrogen concentration. A physical and mathematical model is built to explain the sensor behavior when it is subjected to the changes in hydrogen concentration and in temperature. The shifts in Bragg wavelengths of the Pd-coated FBG hydrogen sensor as a function of hydrogen partial pressure is obtained. Thus the developed FBG hydrogen sensor has a linear response to hydrogen in the low concentration range. Tests were carried on to prove the relationship between wavelength shift and hydrogen concentration.

Abstract: Nowadays, extending the service life of the WSN and reducing energy consumption are very important in the research of sensor networks. This paper proposes LEACH-ICE (LEACH Inner Cluster Election) algorithm based on LEACH algorithm. By adjusting the threshold function of the node selected to be cluster head and communicating with base station when node is closer to the base station, LEACH-ICE elects new cluster head inside the cluster when the resident energy of the former cluster head is lower than standard in order to improve the clustering mechanism. Simulation results show that the algorithm achieves saving energy and extending the service life of the WSN.

Abstract: We propose a tapered fiber-optic based surface plasmon resonance (SPR) sensor. The plasmonic sensing is designed by coating the waist of tapered fiber-optic with gold. The transmission spectrum of SPR wavelength were investigated by 2D finite element method (FEM). The calculation shows that the dips of the resonance wavelength shift toward long wave direction with the thickness of gold film decreasing. And increasing the diameters of the waist core of tapered fiber-optic also makes the resonance wavelength shift long wave direction. Furthermore, changing the refractive index of the external samples from 1.333 to 1.343 with step of ~0.002, the SPR wavelength shifts linearly from 575.05nm to 472.5nm. Owing to its compact and simple configuration, it also provides a feasible program for the refractive index high sensitivity detection.Keywords: surface plasmon resonance (SPR); tapered fiber-optic sensor; surface plasma; finite element method (FEM); optical fiber sensor

Abstract: Hexagonal (β)-phase NaYF₄:Yb³⁺, Er³⁺ upconversion nanoparticles (UCNPs) with and without an inert (undoped NaYF₄) shell have been successfully synthesized and the effects of shell thickness on the upconversion luminescence (UCL) and temperature sensing properties were systematically investigated. It was found that the NaYF₄ shell and its thickness do not affect the R_HS values and thermal sensitivity, but can obviously improve the UCL intensity of NaYF₄:Yb³⁺, Er³⁺ UCNPs. It implies that the core-shell structured NaYF₄:Yb³⁺, Er³⁺@NaYF₄ UCNPs with excellent UCL properties have great potential to be used as temperature sensing probes in biomedical fields, without considering the influences of the shell thickness on their temperature sensing properties.

Abstract: In this paper, we demonstrated a gold nanoparticle based two-photon photoluminescence (TPPL) assay for the detection of dopamine with the detection limit of 0.3 μM. Protonated dopamine molecules can bind bidentately to surface of gold atoms through the catechol group. The adsorption of dopamine displaces the stabilizing agent of citrate groups, and neutralizes the charge of solution, resulting in non-cross linking aggregation of Au NPs. Aggregation of Au NPs could induce significantly enhanced TPPL. Thus, a simple TPPL assay was designed. We have shown that when Au NPs solution was mixed with dopamine, TPPL intensity increased by about 47 times. The mechanism of sensing assay has been discussed. In addition, the TPPL assay was highly selective to dopamine and it can distinguish from uric acid, ascorbic acid and metal ions.

Abstract: This paper summarizes the application situation of the ultra-high frequency (UHF) method in gas insulated switchgear (GIS) partial discharge detection, as well as the differences between internal and external UHF sensors. The performance indicators of internal sensors are introduced, and five main types of internal sensors are discussed and evaluated. In addition, several problems to be solved are posed for researchers.