Applied Mechanics and Materials Vols. 105-107

Abstract: With the rapid development of industry and transportation, air pollution is worsening, therefore, monitoring of air pollution components is more and more heeded. In this study, based on the measurement model and the composition of the air quality monitoring system on line, the mathematical model of the measurement system value transmission was analyzed, and the uncertainty components were calculated respectively, a conclusion that the main factor of the overall system uncertainty is the uncertainty of system itself in the existing air quality monitoring system was drawn, so measurement uncertainty of the calibration system was focused on the research. The effects of the Zero-gas, calibration gases and gas mass flow controller on the uncertainty of the calibration system was experimented and analyzed, and measurement uncertainty of the dynamic calibration system was evaluated.

Abstract: A new algorithm which is “the minimum zone evaluation for sphericity error based on the dichotomy approximating” has been presented with the geometric characteristics and research situation of sphericity error and through the understanding of the definition and the evaluation problem of the sphericity. The principle of the algorithm is that based on finding the initial point of the ball as the base, around which the side decorates cube by certain length, calculating the distance of the points on the sphere to the cube measuring points of the eight vertex and the initial point, by comparing and judging to find a new beginning starting point, and arrange new cube repeatedly until meets the requirement. The sphericity error value of corresponding evaluation method (Minimum Zone Sphere method (MZS)) was obtained according to that. The mathematical formula、program flowchart and example verification were given. The example verification results show that the sphericity error can be evaluated effectively and exactly with this algorithm.

Abstract: The simulation level of prototypes mimicking torsional wave propulsion is low at present. A new prototype which uses a combination of crank and rocker mechanisms and pleated-skirt-pattern membrane is presented in this paper. The prototype’s dorsal fin is of high fidelity, the waveform looks pretty smooth and the wave amplitude can reach 85 degrees. In still pool, measurement of thrust and lateral force of dorsal fin were performed with a one-component balance. The experimental results show: 1. the thrust on the dorsal fin has periodic variation, and the frequency of thrust variation is twice the fin frequency. 2. The lateral force on the dorsal fin also has periodic variation, and the frequency of lateral force variation is the same as the fin frequency. 3. The periodic mean thrust on the dorsal fin is proportional to the square of fin frequency, and the influence of fin frequency on dorsal fin is stronger as wave number increases. 4. The computed results of large-amplitude EBT coincide qualitatively with experimental result, but our computed propulsive forces are quantitatively smaller. (This work was supported by the National Natural Science Foundation of China (10572151).)

Abstract: The sanitary sewage is treated with four different vegetation types by means of artificial surface runoff. Results show soil+ Cynodon dactylon L. + Festuca arundinacea Schreb is the best vegetation type in treating the sanitary sewage, and the total removal of it is 80.24% TN, 62.99% TP, 74.85% BOD₅, 39.73% COD and 58.64% TOC respectively in the course of trial, which indicates that the mixed vegetation type made up of plants and soil is better than the pure soil vegetation type, and the complementary collocation of complex plants is better than the single plant.Five water-quality indexes of the sanitary sewage removed by the single vegetation type are also studied, and it shows that there are some differences among them from high to low as follows: TN>BOD₅>TP>TOC>COD.

Abstract: The principle of stochastic resonance in bistable system is introduced firstly. The medium-low-frequency periodic signal and multi-frequency harmonic signal (the large parameter signal) are common in mechanical failure, but it is difficult to achieve stochastic resonance in these signals detection. The signal modulation characteristic is used in this paper to transform the various frequency components into small parameter signals which satisfy the adiabatic approximation theory. On the basis of that, weak signal detection based on stochastic resonance theory is realized. Then a mixing circuit system based on stochastic resonance is designed, the circuit first makes a frequency selection processing with a mixer on the mixed signal between the measurable signal and a scanning signal, and then it is input to the nonlinear bistable system to realize signal detection based on stochastic resonance. At last, the MATLAB simulation result shows that the circuit can realize the stochastic resonance and detection of weak periodic signal in medium-low frequency from noise background.

Abstract: In the Automatic License Plate Recognition (ALPR) system, the License Plate Location (LPL) is the key step before the final recognition. This paper proposed an improved LPL algorithm for Vietnam vehicle license plates (LP). The proposed algorithm consists of three main modules: Pre-processing (convert RGB image to grayscale image, adjust grayscale image intensity, image binarization use Otsu method), LP candidates location (morphology opening to remove noises & dilation operation, measure properties of image regions to find candidates), LP exactly location (finding the LP angle & rotating LP, cut exactly LP region). We implemented test for 350 Vietnam vehicle images, which obtained from the actual system, the average rate of accuracy of our method is 98.64%, our results are more exactly presented methods.

Abstract: Based on the experimental data acquired from natural circulation experiment, critical heat flux (CHF) was detected through applying Fourier transform and wavelet transform firstly. Then, the technology of edge detection was applied in detecting CHF regions under different heating powers from the photos which were taken in experiment. Results showed that wavelet transform could detect the occurrence of CHF much more accurate than Fourier transform. The apply of wavelet transform using of db1 wavelet and edge detection technology using of Canny algorithm could accurately distinguish the singularity of CHF in one-dimensional temperature signal and dry patch regions that represented CHF phenomena in two-dimensional photographs respectively, which can provide a new approach in the analysis of CHF experimental studies of natural circulation.

Abstract: To correctly acquire steel strain and deformation of SRC during construction process, one SRC transfer storey used in ultra high connected structure is chose. By nonlinear finite element method and field measurement, research on steel beam strain and deformation of the SRC connected structure in the whole construction process is performed. Based on practical construction method, the numerical analysis model for the construction process is established. Combined with time-variation mechanics and nonlinear finite element method, construction mechanics of the SRC transfer storey is analyzed, considering temporary support and construction load in each construction stage. Meanwhile, the field measurement of SRC transfer storey is carried out, and then the comparison between calculate result and measured value. The results show that, calculate result tallies closely with measured value, the steel beam is in a low stress state in the whole construction process, and the deformation of SRC structure varies linearly. The conclusion is that, mechanical behavior of the SRC transfer storey in the whole construction process can be grasped by nonlinear finite element method, and also the reliability of such structures in construction period and service life.

Abstract: In order to ensure the prestress establishment of large-span suspendome, research on the measure-control methods for large-span suspendome during prestress construction process is performed, by summarizing the existing measure and test methods. According to engineering practice at present, the paper classifies the measure-control content of large-span suspendome during prestress construction period into two parts: internal force of cable-strut and deformation of steel structure. Taking practical project of a gymnasium as an example, the axial forces of hoop cables, radial steel tie rods and struts are measured, and also the verticality of struts. The test results are analyzed, and compared with the calculated value. The results show that, the internal forces of cable-strut and verticality of struts can both meet the design requirement, by mechanical analyzing and precise monitoring of the whole prestress construction process. The conclusion is that, before the prestress construction of large-span suspendome, construction mechanics analysis must be carried out in details to determine the control content and its target value, right measure-control methods are chosen, and then the effective establishment of prestress can be achieved.

Abstract: A new optical metrology method for measuring soil landslide displacement is presented in this paper. Under the optical experimental system, the soil micro-displacement field can be measured by obtaining the digital images of the soil specimen under water load and searching the gray value in sub-pixels by digital image surface fitting technology. The results show that through the optical system, this nondestructive testing method can improve the measurement accuracy, and has a very good prospect of application in the study of soil landslide. The experimentation can provide useful data for disaster prevention and mitigation research and actual construction. In addition, if using a CCD with higher resolution and more effective record area, or using synthetic aperture technology to increase effective record area, the accuracy of the experiment are expected to be further enhanced.