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Four-stage main helicopter transmission system occupies several strong points like good carrying capacity and is addressed by many scholars. However, the influence of variable parameters on natural characteristics in a three-engine helicopter, is not to be investigated, according to the limited published issues. Thus, in the study, a vibration model of the four-stage main helicopter transmission system is established through the lumped mass method. In the model, many factors, including time-varying meshing stiffness and torsional stiffness of gear shaft are considered. The differential equation of the system is solved via the Fourier method, 27-orders natural frequency and modal shape corresponded by each degree of freedom (DOF) of the system are obtained. The influence of the shaft torsional stiffness on the first five orders of the system natural frequency is studied. Besides, the impact of the matching relationship of key shafts’ torsional stiffness on the system stability is analyzed. These contributions would improve modification developments of four-stage deceleration helicopter in future.

The hydroacoustic transponder based on the principle of laser interferometry is investigated, which consists of three parts: 1) the front-end module, which is a signal receiving and pre-processing module, and consists of a laser interferometric receiver and a filter group; 2) the signal processing module, which consists of the data acquisition module and a data processing system; 3) the back-pulse module, which consists of an automatic gain adjustment module, a transmitter module and a back-transducer. We give the detailed designing flow charts of the hardware and software programs.

The design on distributed controller of underwater profile monitoring vehicle is investigated. We foucs on the characteristics on voltage transmission, communication and motion control precision of the vehicle, and then design a distributed controller on Underwater Profile Monitoring Vehicle. Experiment results show the effectiveness of the proposed control scheme.

Planar sensor of SrTi(1-x)Fe(x)O3-delta, x = 0.4 and 0.6, with perovskite structure was fabricated on alumina substrate using thick film technology. Electrical resistance was measured as a function of thermal treatment conditions, atmosphere, time and temperature. Sensing property was also measured as a function of temperature and the gases of O2, CH4, CO, CO2, NO and NO2. The resistance of SrTi(1-x)Fe(x)O3-delta is lower than those of SrTiO3 or SrFeO3. TCR (temperature coefficient of resistance) of zero over 550 degrees C was measured for the composition of SrTi(1-x)Fe(x)O3-delta after thermal treatment at 1100 degrees C in air atmosphere only. The perovskite SrTi(1-x)Fe(x)O3-delta didn't show any response to CH4, CO, CO2, NO and NO2, but an excellent response and recovery characteristics with oxygen concentration.

In order to fabricate 8YSZ thick film by silk screen printing, YSZ(yttria-stabilized zirconia) commercial powder was used as starting materials. Paste for screen printing was made by mixing 8YSZ powder and organic vehicles. 8YSZ thick film was formed on Al₂O₃ substrate. The crystal structure, and microstructure were investigated. Grain size of 8YSZ was increased with increasing calcination temperature and rapid grain growth was shown after calcination at 1300℃. Microstructure showed the mixture of large and small grain size after 1400℃ sintering. Shrinkage rate of 8YSZ thick film sintered at 1400℃ was more than 40%.

The fractional quantitative computed tomography (fQCT) to determine both quantity and distribution of bone mineral was evaluated based on the mechanical properties of trabecular bone. Using quantitative computed tomography (QCT), bone mineral density was measured at 46 areas from 5 bovine tibias. Subsequently, fQCT was measured by the proportion of pixels showing a bone mineral density greater than 290 mg/ml. Based on the mechanical properties of the bone specimens, the QCT and the fQCT were compared. The fQCT showed a significant correlation with the compressive strength with superiority to the QCT.

Perovskite-structure thick films, in which x is 0.4 or 0.6, were prepared by normal ceramic process on alumina substrate. Electrical resistance was measured as a function of thermal treatment condition including atmosphere, time, and temperature. The resistance of films is lower than those of or films. The temperature coefficient of resistance over was measured to be 0 for the films after thermal treatment at in air. The sensing property of the films was also measured as a function of temperature and gas such as , CO, , NO and . films showed a good sensing property for , but no sensing signal for CO, , NO and .

The physicochemical and electrical properties of Pd-deposited WO3 thin films were investigated as a function of Pd thickness, annealing temperature, and operating temperature for application as a hydrogen gas sensor. WO3 thin films were deposited on an insulating material using a thermal evaporator. X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to evaluate the crystal structure, microstructure, surface roughness, and chemical property of the films, respectively. The deposited films grew into polycrystalline WO3 with a rhombohedral structure after annealing at 500 °C. Adding Pd had no effect on the crystallinity, but suppressed the growth of WO3 grains. The Pd was scattered as isolated small spherical particles of PdO2 on the WO3 thin film after annealing at 500 °C, while it agglomerated as irregular large particles or diffused into the WO3 after annealing at 600 °C. PdO2 reduction under H2 and reoxidation under air were dependent on both the Pd deposition thickness and annealing conditions. The WO3 thin film with a 2-nm-thick Pd deposit showed a good response and recovery to H2 gas at a 250 °C operating temperature.

In these potentiometric sensors, a mixed binary carbonate sensing material consisting of 90 mol% Li 2 CO 3 and 10 mol% BaCO 3 was modified by adding ceramic oxide materials such as SiO 2 , B 2 O 3 , La 2 O 3 , Bi 2 O 3 , CeO 2 and In 2 O 3 in different mol% concentrations. Various sensors mixed with these external oxides have shown good performance at operating temperatures below 300 °C. Scanning electron microscopy reveals that a glassy sensing phase is formed in the sensing bi-carbonate by the addition of ceramic oxides and sintered at 600 °C for 1 h. The sensor mixed with SiO 2 :B 2 O 3 :Bi 2 O 3 in 1:2:1 mol% showed an excellent response and recovery characteristics and followed a fair Nernstian behavior with a ΔEMF/dec value of −48.18 at as low as 150 °C. The decrease in operating temperature is attributed to the enhanced lithium ion migration through the glassy sensing phase of the sensing electrode.