Study on Various Rectifiers for Fan-Filter Units

The face velocities of the high efficiency particulate air filters and the ultra low penetration airfilters in fan filter units (FFUs) have large relative standard deviation and turbulivity. It seriously affects the unidirectivity of the flow in the unidirectional flow clean zone and cleanroom. The cross contamination in this kind of unidirectional flow area is hardly controlled. It is significant to find optional method for keeping the face velocity uniformity of FFU and reducing the face velocity turbulivity of FFU, furthermore, to keep the cleanliness level under FFUs. The normal and easy method is to add flow rectifiers under filters. FFUs with various flow rectifiers have been tested. The uniformity and turbulivity of facevelocity under the FFU are presented in this paper. The influence of the facevelocity uniformity and turbulivity on the contamination boundary of the unidirectional flow is studiedas well.

Micro-failure process and failure mechanism of brittle rock under uniaxial compression using continuous real-time wave velocity measurement

In this study,the micro-failure process and failure mechanism of a typical brittle rock under uniaxial compression are investigated via continuous real-time measurement of wave velocities.The experimental results indicate that the evolutions of wave velocities became progressively anisotropic under uniaxial loading due to the direction-dependent development of micro-damage.A wave velocity model considering the inner anisotropic crack evolution is proposed to accurately describe the variations of wave velocities during uniaxial compression testing.Based on which,the effective elastic parameters are inferred by a transverse isotropic constitutive model,and the evolutions of the crack density are inversed using a self-consistent damage model.It is found that the propagation of axial cracks dominates the failure process of brittle rock under uniaxial loading and oblique shear cracks develop with the appearance of macrocrack.

Work characteristic analysis of single-rod symmetric cylinders

Hydraulic cylinders are divided into single-rod asymmetric cylinders and double-rod symmetric cylinders. The single-rod asymmetric cylinder has the advantages of small size and simple structure,but its speed characteristic is not symmetric. The double rod symmetric cylinder has the characteristic of symmetric speed,but it cannot be used in some special occasions. In this paper,one special hydraulic cylinder,a single-rod symmetric cylinder,is developed. Firstly,characters of this type of cylinder are introduced. Then,the system model is constructed by using one software which is Simulation X. Moreover,one single rod asymmetric cylinder is designed and the test rig using the symmetric valve to control single-rod symmetric or asymmetric cylinder is constructed. Both of the simulation and experimental results show that the symmetric valve control single-rod symmetric cylinder servo system is of symmetric speed characteristic,which can be used in practical occasion.

Effect of vertical overturning circulation scale and moist static energy tendency on MJO phase speed

The combined effects of vertical overturning circulation(VOC) zonal length scale and moist static energy(MSE)tendency zonal asymmetry on MJO phase speed were investigated based on diagnosis of ERA-Interim data over a 40-year period(1979-2019).In a key region(80°-100°E),128 MJO events were selected.It was found that the larger the VOC zonal length scale,the faster the MJO eastward propagation.The correlation coefficient between them was 0.52,exceeding the 99% confidence level.A significant positive correlation(0.59) was also identified between the phase speed and MSE tendency zonal asymmetry.A linear regression model based on the aforementioned two parameters was constructed,and the phase speed could be estimated based on the model.The correlation coefficient between the reconstructed phase speed and its observed counterpart was 0.73,exceeding the 99% confidence level with an F-test.A composite analysis of the fast and slow groups indicated that the VOC zonal length scale was modulated by the background state.An El Nino(La Ni?a)-like SST pattern and associated precipitation anomalies promoted a larger(smaller) VOC zonal length scale and thus a faster(slower)propagation speed.A sensitivity test with a reference point in a different longitudinal zone(120°-140°E) was conducted.Again,there were significant relationships between the MJO phase speed and the two parameters.The correlation between the reconstructed and observed phase speed was 0.67,exceeding the 99% confidence level.

A new compensation method for angular rate estimation of non-gyro inertial measurement unit

A new compensation method for angular rate estimation of non-gyro inertial measurement unit （NGIMU） is proposed in terms of the existence of aecelerometer mounting error, which seriously affects the precision of navigation parameter estimation. Using the accelerometer output error function, the algorithm compensates the posture parameters in the traditional algorithm of angular rate estimation to reduce the accelerometer mounting error. According to the traditional aceelerometer configurations, a novel nine-accelerometer confi-guration of NGIMU is presented with its mathematic model constructed. The semi-hardware simulations of the proposed algorithm are investigated based on the presented NGIMU configuration, and the results show the effectivity of the new algorithm.

利用共振辐射压力获得准单一速度原子束

报道了利用行波场的并振辐射压力获得准单一速度原子束的实验研究结果，并进行了理论分析．实验上利用外入射失谐为－１００ＭＨｚ行波光声并振作用原子束可使准单—速度原子束偏转１．７ｍｍ，速度宽度小于５８ｍ／ｓ．