Applied Mechanics and Materials Vols. 333-335

Abstract: As an important part of the aero engine, the quality of the blade seriously affects the engine performance, so the inspection method of the blade is significant. Based on the research of the HB 5647-98<<to mark dimensions, tolerances of the vane type and the surface roughness of the blade body>> , this paper concludes different evaluation methods of the blade. The main evaluated parameters include the leading and trailing edge radius, the chord length, the maximum thickness of blade profile, the mean camber line, and the surface twist and so on. Here we mainly discuss the previous three terms. The least square method is adopted to fit the arc of the leading and trailing edge; introduce the projection method to calculate the chord length; at last, we employ the spline fitting method to get the mean line and then obtain the maximum thickness of the blade section.

Abstract: When measuring the thermal conductivities of poor conductor with steady-state method, some errors should be introduced through the process of the experimental principle derivation to the experimental data measurement. To satisfy the need of measurement, this study aims to improve the structure of the “TC-I1 Type thermal conductivity measuring apparatus” correspondingly: we placed two fans at the side of the cooling plate, thus effectively control the stability of the strong-force convection cooling environment. This study chose digital thermometer of UT325 Type to collect temperature signals, storing the data on computer and putting such data under fitting process with the software Matlab. Compared with the traditional measurement, the post-modification apparatus successfully achieves lower errors in the coefficient of heat conductivity measurement and thus the results are closer to the inherent attribute values of the sample plate. It’s very satisfactory to the requirements of teaching and scientific research oriented measurements.

Abstract: The paper presents an investigation of deformation in the active region of GaAs laser diodes under operating conditions.Since the properties of bulk material and manufactured diode are not identical,a study of the spectral splitting and polarisation changes caused by mechanical stress in the diode is made.These results are used to calibrate instruments for a study of the deformation due to thermal stress in the diode under operating conditions.This thermal stress can exceed the shear stress required for dislocation motion in the active region of the diode.

Abstract: This paper investigated the relationship of the nuclear quadrupole resonance (NQR) signal amplitudes with nitrogen contents and frequencies of explosive simulants based on the NQR explosive detection principle. The NQR signals of urea, urotropine and sodium nitrite were detected by experiment at room temperature, and the signal spectra of the nitrogenous compounds with different weights were obtained. The results indicate that the NQR signal amplitudes of the same mimic are increasing linearly with the increase of weights under the same experimental conditions, meanwhile, the higher the frequency, the greater the signal amplitude. The NQR signal amplitudes of different mimics do not rely on the nitrogen contents, but depend on the other internal factors such as relaxation times, NQR frequencies and so on. The experimental data are consistent with the theoretical predictions. The results will be of value to the detection of NQR signals in explosives and the research on how to improve the signal-to-noise ratio (SNR).

Abstract: Azimuth estimate is easily affected by noise and multipah during acoustic transmission in Ultra Short Base Line (USBL). To solve this problem, a new array with eight hydrophones and signal processing method are presented and analyzed. With the help of redundant hydrophones, various results could be obtained. Compared with the standard deviations of various results, correct one would be picked out. Lake experiment proved that wrong azimuth estimate was effectively eliminated and the positioning performance was improved.

Abstract: An evaluation is conducted to the uncertainty measurement with contact type interferometer after intellectualized improvement. CMOS sensing photographing technology and computer technology are applied to the improvement of contact type interferometer. A mathematical modeling is established by taking pixel number as reading unit and gauge block length comparative measurement method as means. The purpose is to analyze the source of measurement uncertainty, estimate the standard uncertainty of input, evaluate and set forth the expanded uncertainty. The result of evaluation is superior to the level of measurement uncertainty before improvement.

Abstract: With the operation of giant unit of hydroelectric plant represented by the Three Gorges Power Station, the vibration problem of hydraulic turbine set unit is increasingly outstanding, especially the vibration of structure induced by pressure fluctuation. In order to guarantee the normal operation of unit, model test is more important in the respect of predicting performance, increasing stability and avoiding vibration. The pressure fluctuation measurement system based on LabVIEW according to pressure fluctuation model test was designed in this paper. The system is applied to the hydro-turbine model test-bed of HEC so that real-time automatic test with the characteristics of high stability and precision is implemented successfully. It plays an important role in respects of mastering the operation characteristics collecting and analyzing pressure fluctuation signals. Moreover it is meaningful to the hydraulic engineering.

Abstract: The pulverized coal concentration in blast pipe in front of firebox is one key parameter in coal boiler used in a power plant; it will affect the state of burning in firebox. This paper proposes a new digital correlation method to measure the time delay of ultrasonic for measuring the pulverized coal concentration. The principle of measurement is discussed in detail and the measuring system is designed.

Abstract: One of the key technologies to make shield tunnel successful is to ensure that the subway tunnel can through exactly according to design requirements. This paper conducts theoretical analysis of shield tunnel through errors sources, reasonable distribution of its limits for plane control measurement in different stages and illuminates layout principles and limits optimization of ground control point in long and large shield zone.

Abstract: In order to solve the problem of monitoring dust concentration, the paper applies the charge induction method in the design of the monitoring sensor. Specifically, the dust concentration can be characterized by the induction voltage of the sensor which is located in the high-voltage alternating electric field. In particular, the paper introduces the structure of the sensor and analyses the basic principles and feasibility of the measuring equipment. Furthermore, couples of simulation test is conducted based on the test platform. According to the test results, the monitoring sensor performs well when the dust concentration is between 0.81g/m3 and 1.99g/m3, in which the maximum measurement error is only 1.8%. Undoubtedly, the method used for the dust concentration monitoring has a wide prospect in industrial application.