Advanced Materials Research Vols. 383-390

Abstract: For the existing drawbacks in the crucible rotation vertical drop method, the control system is improved. Developed a new control system, overcome the drawbacks of original crystal growth control system, and improve the control precision, and simplify the programming program. Use to prove it reliable, stable, a more perfect crystal growth control system. Now has been formally put into use.

Abstract: In order to improve the sinusoidal level of air gap magnetic field of the traditional surface PMSM, reduce its harmonic losses and fully reflect its energy-saving advantages, this paper introduces a type of sinusoidal pole width modulation permanent magnet synchronous motor. The surface magnetic poles of the rotor iron core constitute by a number of small array magnets, which makes the air gap magnetic field more sinusoidal. Placing starting winding in remaining space between array magnets of rotor outer surface to make surface-mounted permanent magnet synchronous motor add self-starting function. The sine wave distortion rate of air gap magnetic field of sinusoidal pole width modulation structure was compared with traditional surface-mounted structure by electromagnetic field calculation and experiment. The copper starting winding and aluminum starting winding were placed in sinusoidal pole width modulation structure motor respectively, and then the paper analyzes dynamic torque and rotational speed of self-starting progress. Finally the analysis is verified by experiments.

Abstract: The influence of the microwave propagation in the evaporation duct is studied by solving wide angle parabolic equation using Fast-Fourier transform method. Then, the result under smooth surface is compared with the simple and complex obstacle on the surface. It is shown that the propagation loss of electromagnetic wave will increase in evaporation duct with increase of the propagation path and the height obstacle, which effectively improves its remote propagation in waveguide after diffracting.

Abstract: In this paper, the performances of natural refrigerant R290/CO2 cascaded refrigeration system using R290 as high temperature cycle refrigerant and CO2 as low temperature cycle refrigerant were investigated experimentally. The test results show that both CO2 compressor and R290 compressor start up stably and present good running performance. The start-up power and start-up electric current of CO2 compressor are higher than that of R290 compressor. The COP (Coefficient of performance) of R290/CO2 cascaded system enhances with the increase of cooling water mass flow rate and the decrease of cooling water inlet temperature. The effect of CO2 refrigerant charge on the COP of cascaded system is obvious; however, the effect of R290 refrigerant charge on the COP of cascaded system is not obvious. Hence, the hermetic scroll type compressor is urgent to be developed and used in CO2 cycle for ensuring run safely and reliably, the value of cooling water mass flow rate and the cooling water inlet temperature must be selected reasonability for saving water resource and energy, as well as the charge amount must be determined by experiment for obtaining the optimum refrigerant charge.

Abstract: The ultimate relative slip between reinforced polymer (FRP) and concrete on their bond interface is a key parameter to analyze the debonding failure of FRP strengthened reinforced concrete beams. Lots of simple shear test specimens have been used to test the slip-shear stress relationship on the bond interface. However, the ultimate FRP-concrete slip has not been obtained directly from these experiments. Based on different theoretical considerations some ultimate slip values have been predicted. These values differ from one another to a large extent. The lower limit of the maximal slip between FRP and concrete in the span of strengthened beams is derived through a set of simple assumptions. Example calculations show that at loads exceeding 80% of the designed loads most maximal slips would reach 0.2mm or greater. The fact that most experimental beams at such loads do not exhibit debonding failure manifests that the ultimate slip should be greater than 0.2mm.

Abstract: An experimental loop was established with API X52 steel pipes to investigate the effect of drag-reducing polymer on heat transfer in gas-liquid two-phase flow. The inner diameter of the steel pipe is forty millimeter and the test loop has four different test sections such as horizontal, inclined upward, inclined downward and vertical upward sections. The experimental results were presented. The relationship between the drag reduction efficiency and heat transfer reduction was analyzed. When the drag reduction induced by drag-reducing polymer is about 60~70%, the heat transfer between the fluid and the pipe wall obviously decreases. The heat transfer reduction can reach up to 80~90%, which is greater than the drag reduction. A new method is proposed for characterizing the effect of drag reducing polymer on the heat transfer in two-phase flow with Stanton Number.

Abstract: Strong anion exchange (SAX) columns and oasis HLB cartridges were combined to extract trace level oxytetracycline(OTC) and high performance liquid chromatography(HPLC) UV-detector were used to measure it in wastewater sample. The effect of mobile phase was investigated. Under the best analysis conditions, linear calibration equations were established for OTC. The linearity were in the range of 0.1-10g/mL, Correlation coefficient (R2) is about 0.9997. The recovery factors ranged from 82-92% with a relative standard deviation of 4.8-6.4%.Lab-scale experiments were conducted to investigate the sorption behavior of OTC by anaerobic sludge. Starch in the mixed liquor can decrease the adsorption capacity of OTC.

Abstract: Bubbling absorption experiments of ammonia water(NH3/H2O) solution added with FeO nano-particles were carried out in some conditions. The results showed that the absorption effect of the ammonia-water solution with the nano-particles was improved. The several key factors affecting the absorption process, such as preparing of nanofluid, absorption pressure, solution temperature and the flow rate of cooling water, were also analyzed, repectively, and finally it was pointed out that there exist certain possible coupling relations between these influencing factors.

Abstract: Objective of the present work is to model EDM process using ANSYS software, and to investigate the effects of most significant machining parameters (pulse current and pulse duration) on the residual stresses developed in the beneath the spark produced by a single spark. The workpiece material is AISI D2 tool steel. The FEA model is then used to study the relation between these parameters and maximum temperature attended at the end of heating cycle along with residual stress produced at the end of cooling cycle. To establish the residual stresses in the work piece during EDM, the temperature distribution at the end of pulse duration in the work piece has to be estimated first, latter on after cooling the residual stress is determined. In addition, residual stress which is the main aspect responsible for component failure, and the location of tensile peak stress, at the end of cooling cycle are investigated.

Abstract: Joining of dissimilar materials is of increasing interest for a wide range of industrial applications like nuclear, thermal power. The automotive industry, in particular, views dissimilar materials joining as a gateway for the implementation of lightweight materials. Friction welding of tube to tube plate using an external tool is an innovative friction welding process and is capable of producing high quality leak proof weld joints. In the present study, friction welding of steel tube to commercial aluminum tube plate using an external tool with and without tube projection have been performed. The joints were evaluated by mechanical testing and metallurgical analysis. The results of bonding interface hardness and joint strength reveal that steel tube with projection are better than the steel tube without projection.