Applied Mechanics and Materials Vols. 148-149

Abstract: Improving spectrometer detection limit using statistical principle and signal-processing technique are described simply in this work. In the detection of gas photoacoustic(PA) signal, accurate partitions of the sampled data affect on the detection limit to some extent although Lock-in amplification technique with high SNR and microphone sensor with high sensitivity have been used. A model and the resulting algorithm are proposed from PA-signal samples. The techniques are validated at ppb level on PA spectrometer for NH3 breath detection in high concentration of CO2 and H2O based on tunable erbium-doped fiber laser (TEDFL) or for multicomponent trace gas detection based on waveguide CO2 laser or on other laser source.

Abstract: This paper presents the effect of using a modified air pump to compress the mixture of air and biogas into a single cylinder diesel engine. The crankshafts of both were modified such that two equal size sprockets could be fastened to them. A toothed belt was used to synchronize the crank positions of the pump and diesel engine. By adjusting the angular positions of the crankshaft of the pump at 205 degrees in advance compared to the angular positions of the crankshaft of the diesel engine, the maximum volumetric efficiency of 99.95% could be achieved at 1200 rpm. And when supplementing diesel fuel with biogas via the large venturi, the consumption of 50 cc. of diesel extended to 194.18% at 1200 rpm as compared to running the engine with 50 cc. of diesel alone.

Abstract: The rotor vibration of the unit is sensitive to the running conditions for the turbine group low head, high flow characteristics. It easily lead the rotor bracket of oblique arm structure to crack. The reason of rotor bracket cracks is proved by ANSYS analysis and its repair program have been identified. Running for some time after repair, the main parameters, such as air-gap and other unit operation , have been analyzed. The results are satisfactory, which verifies that the analysis of the rotor bracket crack repair is objective and reasonable.

Abstract: Surface modification treatment on rubber used in lubricating environment can reduce the friction coefficient, friction temperature and wear loss, thereby increase the service life of rubber products. The effect of Sulfuration treatment on wear behavior of NBR was investigated using a reciprocating tester under water lubricating sliding. The hardness and morphology of samples were measured using Shore sclerometer and stereo microscope, respectively. The results showed that immersion loss of rubber in different sulfuration solution increased with immersion time. The immersion loss of rubber immersed in 60% and 70% sulfuration solution remarkably increased after immersing for 4 and 3 days, respectively. The Shore hardness of rubber immersed in sulfuration solution was higher than that untreated sample. The Shore hardness of rubber increased with the increasement of sulfuration concentration and immersing time. Better resistance of NBR in water lubricating sliding could be obtained when NBR is immersed in lower sulfuration solution for longer time or in high sulfuration solution for shorter time.

Abstract: The issue of optimization of LDPC Coded IDMA system is studied. The iterative decoding process of LDPC code is called inner iteration, and the iterative process between LDPC code and elementary signal estimator (ESE) is called outer iteration. The performance of the system is shown by BER and the complexity is indicated by iteration number. Check matrix is constructed randomly based on the obtained degree profile and simulations are made. The results show that performance of the system improves as the iteration number increases, either inner or outer iteration number. On the other hand, the performance gain of the system decreases with the increase of iteration number. Besides, the performance can be improved by reasonable setting of iteration number with the same complexity.

Abstract: In the paper, the fuzzy control algorithm was studied in turbofan engine. The turbofan engine models of “little deflection” model and “large deflection” model were built based on component level model. Then, a fuzzy controller, including the fuzzy-integral mixed controller, smith forecast and compensation, was designed with the fuzzy rules were optimized by improved genetic algorithm. The simulation results show that the designed control system responds fast, has no overshoot or oscillation, and the control precision is high. The controller can effectively solve time delay influence with a great control effect for “little deflection” model and acceleration model.

Abstract: BaO-Sm2O3-4TiO2 (abbreviated BST) ceramic powder was prepared by the conventional solid-state reaction method. The effects of doping ZnO-2B2O3-7SiO2 (abbreviated ZBS) glass by sol-gel method on the sintering behaviors, microstructure, phase composition and dielectric properties of BST ceramics were investigated. The experimental results reveal that the main phase of samples doped with ZBS glass is tungsten bronze structure type BaSm2Ti4O12 phase, a litter Sm2Ti2O7 phase is also observed. The sintering tenperature of BST ceramics is remarkably reduced from 1350°C to 1050°C and the good dielectric properties of εr=60.2，tanδ=0.004，τf=-7.9ppm/°C were obtained for BST ceramics doped with 6wt% ZBS glass by sol-gel method sintered at 1050°C for 3h.

Abstract: ECE R29 regulation has legally claimed that the survival space must be guaranteed for the safety for driver and front seat passenger in event of crash during design of truck cabin. In this paper, a finite element model of a high-top cabin of a heavy truck with a manikin on the driver seat was built with commercial code Hypermesh, The explicit finite element program Ls-Dyna was used to simulate the frontal pendulum impact on the high-top cab in the light of ECE R29 regulation. Deformation of the truck cabin and the survival space of the dummy were analyzed and discussed. Also, some suggestions were given to solve the contact possibility between steering column and the knees of manikin.

Abstract: TWIP steels are high manganese steel (Mn: 17% - 35%) which are used for shaping car bodies. The structure of this kind of steels remains austenite even in room temperature. Due to low SFE (Stacking Fault Energy) twinning of grains is governing reformation mechanism in this kind of steels which strengthen TWIP steel. Regarding heat treatment influences on mechanical properties of TWIP steels, in this paper we discuss twinning phenomenon resulting from this kind of treatment. For this, following casting and hot rolling processes, we anneal the steel at 1100°C and different time cycles and study its microstructure using light microscope. The results showed that with decreasing grain size the number of twin annealing added And four types of annealing twin in the microstructure, in the end they all become one twin and then turn into grain.

Abstract: The rail irregularity and other factors often cause vehicle vertical vibration when the vehicle is running. When the vibration intensity reaches a certain limit, the passenger in the vehicle will feel very uncomfortable. The excessive vibration will also affect the service life of the vehicle and operation stability. So the good cushioning and vibration isolation performance are need to people when the vehicle is running. A vibration experiment test system is designed according to the urban rail vehicle characteristics and the vehicle vibration characteristics during running. The parameters can becalculated and the 1Hz to 3Hz square and sine wave vibration characteristics test can be completed in the system. Using the system we can evaluate the vehicle vibration characteristics and ride comfort better .So the test results have a certain value.