We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears i...We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears in the conductance-frequency curve.With gradually increasing liquid density,the additional peak moves from low to high frequency region then disappears.The frequency of the additional resonant peak is sensitive to the change in liquid density.The frequency shift of the additional peak is linear with the liquid density in a given range.For a 5 MHz PQC with a reflection distance of 16 mm for longitudinal wave,the sensitivity to liquid density is 2.61×10^6 Hz g^-1 cm^3.The overlap between the primary resonant peak and the additional resonant peak causes a decrease in the intensity of the former and an increase in the intensity of the latter.In a combined impedance analysis method,the changes in surface mass loading,density and viscosity of the liquid were monitored simultaneously by a PQC sensor.展开更多
The optimization of network performance in a movement-assisted data gathering scheme was studied by analyzing the energy consumption of wireless sensor network with node uniform distribution. A theoretically analytica...The optimization of network performance in a movement-assisted data gathering scheme was studied by analyzing the energy consumption of wireless sensor network with node uniform distribution. A theoretically analytical method for avoiding energy hole was proposed. It is proved that if the densities of sensor nodes working at the same time are alternate between dormancy and work with non-uniform node distribution. The efficiency of network can increase by several times and the residual energy of network is nearly zero when the network lifetime ends.展开更多
A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems （MEMS） technology. The sensor measures fluid density through the relationship between the density and the resonant frequ...A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems （MEMS） technology. The sensor measures fluid density through the relationship between the density and the resonant frequency of the cantilever im-mersed in the fluid. To improve the sensitivity of the sensor, the modal and harmonic response analyses of trapezoidal and rec-tangular cantilevers are simulated by ANSYS software. The higher the resonant frequency of the cantilever immersed in the fluid, the higher the sensitivity of the sensor; the higher the resonant strain value, the easier the detection of the output signal of the sensor. Based on the results of simulation, the trapezoidal cantilever is selected to measure the densities of dimethyl silicone and toluene at the temperature ranges of 30 to 55 ℃ and 26 cantilever density sensor has a good performance. to 34 ℃, respectively. Experimental results show that the trapezoidal cantilever density sensor has a good pertbrmance.展开更多
基金supported by the National Natural Science Foundation of China(Nos.20775045,20975063)open foundation of the State Key Laboratory of Chemo/Biosensing and Chemometrics,Hunan University(No.2008012)
文摘We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears in the conductance-frequency curve.With gradually increasing liquid density,the additional peak moves from low to high frequency region then disappears.The frequency of the additional resonant peak is sensitive to the change in liquid density.The frequency shift of the additional peak is linear with the liquid density in a given range.For a 5 MHz PQC with a reflection distance of 16 mm for longitudinal wave,the sensitivity to liquid density is 2.61×10^6 Hz g^-1 cm^3.The overlap between the primary resonant peak and the additional resonant peak causes a decrease in the intensity of the former and an increase in the intensity of the latter.In a combined impedance analysis method,the changes in surface mass loading,density and viscosity of the liquid were monitored simultaneously by a PQC sensor.
基金Project(60873081)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0787)supported by Program for New Century Excellent Talents in UniversityProject(11JJ1012)supported by the Natural Science Foundation of Hunan Province,China
文摘The optimization of network performance in a movement-assisted data gathering scheme was studied by analyzing the energy consumption of wireless sensor network with node uniform distribution. A theoretically analytical method for avoiding energy hole was proposed. It is proved that if the densities of sensor nodes working at the same time are alternate between dormancy and work with non-uniform node distribution. The efficiency of network can increase by several times and the residual energy of network is nearly zero when the network lifetime ends.
基金Project supported by the National Natural Science Foundation of China (Nos. 50836004,50905139,and 90923001)the Fundamental Research Funds for the Central Universities (No. xjj20100140)+2 种基金the Science and Technology Research Project of Shaanxi Province (No. 2012KJXX-01)the Program of Changjiang Scholars and Innovative Research Team in University (No. IRT1033)the 111 Program (No. B12016),China
文摘A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems （MEMS） technology. The sensor measures fluid density through the relationship between the density and the resonant frequency of the cantilever im-mersed in the fluid. To improve the sensitivity of the sensor, the modal and harmonic response analyses of trapezoidal and rec-tangular cantilevers are simulated by ANSYS software. The higher the resonant frequency of the cantilever immersed in the fluid, the higher the sensitivity of the sensor; the higher the resonant strain value, the easier the detection of the output signal of the sensor. Based on the results of simulation, the trapezoidal cantilever is selected to measure the densities of dimethyl silicone and toluene at the temperature ranges of 30 to 55 ℃ and 26 cantilever density sensor has a good performance. to 34 ℃, respectively. Experimental results show that the trapezoidal cantilever density sensor has a good pertbrmance.
