Theoretical and Experimental Study on the Performance of Hermetic Diaphragm Squeeze Film Dampers for Gas-Lubricated Bearings

Low damping characteristics have always been a key sticking points in the development of gas bearings.The application of squeeze film dampers can significantly improve the damping performance of gas lubricated bearings.This paper proposed a novel hermetic diaphragm squeeze film damper(HDSFD)for oil-free turbomachinery supported by gas lubricated bearings.Several types of HDSFDs with symmetrical structure were proposed for good damping performance.By considering the compressibility of the damper fluid,based on hydraulic fluid mechanics theory,a dynamic model of HDSFDs under medium is proposed,which successfully reflects the frequency dependence of force coefficients.Based on the dynamic model,the effects of damper fluid viscosity,bulk modulus of damper fluid,thickness of damper fluid film and plunger thickness on the dynamic stiffness and damping of HDSFDs were analyzed.An experimental test rig was assembled and series of experimental studies on HDSFDs were conducted.The damper fluid transverse flow is added to the existing HDSFD concept,which aims to make the dynamic force coefficients independent of frequency.Although the force coefficient is still frequency dependent,the damping coefficient at high frequency excitation with damper fluid supply twice as that without damper fluid supply.The results serve as a benchmark for the calibration of analytical tools under development.

An Experimental Study of Bulge-Forming Polycarbonate (PC)Semisphere Shell Parts

In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form polycarbonate part. But the wall thickness distribution of the bulged specimen by this method is not so even.

Clinical and Experimental Study on Effect of Garlicin in Treating Angina Pectorls

Objective: To observe the effect and mechanism of Garlicin in treating coronary heart disease (CHD) with angina pectoris. Methods: Clinical study: 55 patients were selected and randomized into the Garlicin group and the nitroglycerin group. To Garlicin group, 60 mg of Garlicin was given by adding in 5% glucose solution for intravenous dripping once per day, the therapeutic course

An Experimental Study on Atmospheric Pressure Glow Discharge in Different Gases

Usually, the electrical breakdown of dielectric barrier discharge (DBD) at atmo-spheric pressure leads to a filamentary non-homogeneous discharge. However, it is also possible to obtain a diffuse DBD in homogeneous form, called atmospheric pressure glow discharge (APGD). We obtained a uniform APGD in helium and in the mixture of argon with alcohol, and studied the electrical characteristics of helium APGD. It is found that the relationship between discharge current and source frequency is different depending on the difference in gas gap when the applied voltage is kept constant. The discharge current shows an increasing trend with the increased frequency when gas gap is 0.8 cm, but the discharge current tends to decrease with the increased frequency when the gas gap increases. The discharge current always increases with the increased applied voltage when the source frequency is kept constant. We also observed a glow-like discharge in nitrogen at atmospheric pressure.

Numerical and Experimental Study of the 3D Effect on Connecting Arm of Vertical Axis Tidal Current Turbine

Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the pressure distribution along the span of the turbine blade, herein we call it 3D effect. However, so far the effect is rarely reported in the research, moreover, in numerical simulation. In the present study, a 3D numerical model of the turbine with the connecting arm was developed by using FLUENT software compiling the UDF（User Defined Function） command. The simulation results show that the pressure distribution along the span of blade with the connecting arm model is significantly different from those without the connecting arm. To facilitate the validation of numerical model, the laboratory experiment has been carried out by using three different types of NACA aerofoil connecting arm and circle section connecting arm. And results show that the turbine with NACA0012 connecting arm has the best start-up performance which is 0.346 m/s and the peak point of power conversion coefficient is around 0.33. A further study has been performed and a conclusion is drawn that the aerofoil and thickness of connecting arm are the most important factors on the power conversion coefficient of the vertical axis tidal current turbine.

An Experimental Study of Thermophysical Properties for Quinary High-Entropy NiFeCoCrCu/Al Alloys

Two quinary high-entropy alloys （HEAs） with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning cMorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face- centered cubic high-entropy phase plus a minor interdendritic （Cu） phase and display a lower entropy of fasion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubie high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are signitieantly larger than those of the latter At-doped M1oy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860-912 K.

Ideas for Hypertensive Experimental Study Prevented and Treated by TCM

Hypertensive ex—perimental studies pre—vented and treated byTCM are matured re|e—rant studies of westernmedicine for reference,such as the hypotensiveeffect and elucidating itstherapeutic mechanism.Comprehension in allliteratures,most simpleherbs and compound

The Influence of Blending Learning on Undergraduates’Critical Thinking Disposition:A Quasi Experimental Study

Objective:To explore the influence of blending learning on the critical thinking disposition among undergraduates.Methods:Two undergraduate classes majoring in Applied Psychology with similar level of critical thinking disposition were selected as the research subjects.Class A(106 students)was the experimental class,and class B(131 students)was the control class.During the research period of one semester(four months),the following measures were implemented for the two classes.The control class studied Developmental Psychology under the conventional teaching methods and procedures,while the experimental class studied Developmental Psychology according to the requirements and procedures of blending learning.The two classes were investigated with Critical Thinking Disposition Inventory-Chinese Version(CTDI-CV)at the beginning and end of the course.Results:At the beginning of the course,the total scores of CTDI-CV of the two classes were(217.33±14.90)and(218.31±16.29),respectively,with no significant difference(P>0.05).At the end of the course,the total scores of CTDI-CV of the experimental class and the control class were(237.84±17.53)and(224.22±17.52),respectively,and the difference was statistically significant(P<0.001).Conclusion:Blending learning may have a positive effect in improving the critical thinking disposition in undergraduates.

An experimental study of the relations between bispectra and nonlinear apparent features of wind waves

To investigate the nonlinear properties of wind waves, experiments are carried out in a wind-wave flume with slope bottom at different wind speeds and fetches. Both the internal structure and apparent features of the nonlin-earity of wind waves are studied by using bispectral and statistical analysis of surface elevations. The relations between bispectra and nonlinear apparent characteristics of wind waves are established and confirmed.

An Experimental Study of CIRC in English Classroom in Vocational Colleges

CIRC is short for Cooperative Integrated Reading and Composition.It is to help improve students' English proficiency by integrating writing into reading.In order to verify the results of the method,the author made an experimental study in Nanning College for Vocational Technology.She designed a small teaching cycle of "7 phases with 12 steps"and applied CIRC in her English class.One of the results is that CIRC can improve students'academic achievements.

Simulation Analysis and Experimental Study of Defect Detection Underwater by ACFM Probe

This article studies the application of the alternating current field measurement （ACFM） method in defect detection for underwater structures. Numerical model of the ACFM system is built for structure surface defect detection in seawater environment. Finite element simulation is performed to investigate rules and characteristics of the electromagnetic signal distribution in the defected area. In respect of the simulation results, underwater artificial crack detection experiments are designed and conducted for the ACFM system. The experiment results show that the ACFM system can detect cracks in underwater structures and the detection accuracy is higher than 85%. This can meet the engineering requirement of underwater structure defect detection. The results in this article can be applied to establish technical foundation for the optimization and development of ACFM based underwater structure defects detection system.

An experimental study on preventive effect of continuous irrigation from peridural adhesion after laminectomy

Objective To observe the preventive effect of continuous irrigation with sodium hyaluronate injection from peridural adhesionaminectomy.Methods Larninectomies were performed in L1,L4,L7 of 25 New Zealand rabbits respectively with 3

A field experimental study of lignin sand stabilizing material(LSSM) extracted from spent-liquor of straw pulping paper mills

A new technique was introduced for sand stabilization and re-vegetation by use of lignin sand stabilizing material(LSSM). LSSM is a reconstructed organic compound with lignin as the most dominant component from the extracts of black-liquor issued by straw pulp paper mills. Unlike the polyvinyl acetate or foamed asphalt commonly used for dune stabilization, the new material is plant-friendly and can be used with virescence actions simultaneously. The field experimental study was conducted since 2001 in China's Northwest Ningxia Hui Autonomous Region and has been proved that LSSM is effective in stabilizing the fugitive dunes, making the arenaceous plants survive and the bare dune vegetative. The advisable solution concentration is 2% and the optimal field spraying quantity is 2 5 L/m^2 The soil nutrients of the stabilized and greened dune, such as organic matter, available phosphorous and total nitrogen are all increased compared with the control treatment, which is certainly helpful to the growth of arenaceous plants. The technique is worthwhile to be popularized because it is provided not only a new method for desertification control but also an outlet for cleaning contaminants issued from the straw paper mills.

Design and Experimental Study of an 80C196KC-Based SRD System Controller

Aim To design and experimentally study an 80C196KC-based SRD (switched re- luctance motor drive drive sytem) controller,Methods with the guidelines of the digitized SRD system controller,the circuit design and software programming were completed,and a relevantexperimental system was PUT forward to test the newly designed controller.Result The experi-mental study showed that the newlydesigned controller had good speed-adjusting characteristicfor a switched reluctance motor ,its stable error was less than 5% and its full-load startingtime was shorter than 1.8s .Conclusion The new controller has reasonable circuit design and suitable controlling algorithm,and it is a feasible SRD system controller design scheme.

Dynamic experimental study on rock meso-cracks growth by digital image processing technique

A new meso-mechanical testing scheme based on SEM was developed to carry out the experiment of microfracturing process of rocks. The microfracturing process of the pre-crack marble sample on surrounding rock in the immerged Long-big tunnel in Jinping Cascade II Hydropower Station under uniaxial compression was recorded by using the testing scheme. According to the stereology theory, the propagation and coalescent of cracks at meso-scale were quantitatively investigated with digital technology. Therefore, the basic geometric information of rock microcracks such as area, angle, length, width, perimeter, was obtained from binary images after segmentation. The failure mechanism of specimen under uniaxial compression with the quantitative information was studied from macro and microscopic point of view. The results show that the image of microfracturing process of the specimen can be observed and recorded digitally. During the damage of the specimen, the distribution of microcracks in the specimen is still subjected to exponential distribution with some microcracks concentrated in certain regions. Finally, the change law of the fractal dimension of the local element in marble sample under different external load conditions is obtained by means of the statistical calculation of the fractal dimension.

CO hydrogenation combined with water-gas-shift reaction for synthetic natural gas production:a thermodynamic and experimental study

The hydrogenation of CO to synthetic natural gas (SNG) needs a high molar ratio of H2/CO (usually large than 3.0 in industry), which consumes a large abundant of hydrogen. The reverse dry reforming reaction (RDR, 2H2 + 2CO←→CH4 + CO2), combining CO methanation with water-gas-shift reaction, can significantly decrease the H2/CO molar ratio to 1 for SNG production. A detailed thermodynamic analysis of RDR reaction was carried out based on the Gibbs free energy minimization method. The effect of temperature, pressure. H2/CO ratio and the addition of H2O, CH4, CO2, O2 and C2H4 into the feed gas on CO conversion, CH4 and CO2 selectivity, as well as CH4 and carbon yield, are discussed. Experimental results obtained on homemade impregnated Ni/Al2O3 catalyst are compared with the calculations. The results demonstrate that low temperature (200-500 °C), high pressure (1-5 MPa) and high H2/CO ratio (at least 1) promote CO conversion and CH4 selectivity and decrease carbon yield. Steam and CO2 in the feed gas decrease the CH4 selectivity and carb on yield, and enhance the CO2 con tent. Extra CH4 elevates the CH4 content in the products, but leads to more carbon formation at high temperatures. O2 significantly decreases the CH4 selectivity and C2H4 results in the generation of carbon.

AN EXPERIMENTAL STUDY OF SHEET EROSION IN GRANITIC REGION OF WUHUA COUNTY,GUANGDONG PROVINCE

The relationships between rainfall, runoff and erosion in South China granitic weathering red soil region were studied by using data collected from 7 experimental plots in Wuhua County, Guangdong Province. Results showed that when rainfall is less than 50 mm, small volumes of runoff were produced. Rainfall intensity might be the main factor in controlling runoff. When rainfall exceeds 50 mm, because of its large volume and high intensity, runoff and the produced amount of erosion increased with raimfall quickly. Analysis of the relationship bebeen runoff and erosion suggsted that runoff of 30 mm (corresponding to about 50 mm rainfall might be taken as a threshold at which wter on land surface was sufficient to start the larg amount of soil particles. Vegtation cover is very effective in protection soil from being eroded. When vegetation coverag increases from 0 to 80 percent,runoff and soil loss decrease from 179.34mm/a to 126.36mm/a and 6262.15T/a km2 to 368.02 T/a km2, respectively.

An Experimental Study on the Effect of the Side Hull Symmetry on the Resistance Performance of a Wave‑Piercing Trimaran

This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.