Papers by Keyword: Asymmetric

Abstract: Usually the angle steel is attached to the bracket to withstand tensile or compressive forces. The single-angle steel section is an asymmetrical section, and the nature of the section involves a complex analysis. The load is transmitted to the single-angle steel through the steel plate, thus causing eccentric load behaviour. The eccentric load will cause the single angle steel to bear the action of the axial pressure and the bending moment. The process of design and analysis is difficult based on the asymmetry of single angle steel. The behaviour of axial force and bending moment involves warping and torsion, and the analysis and design process is complicated. The eccentric load behaviour of single angle steel is based on complex formula analysis, and the 2010 AISC specification [1] also provides a table lookup function. This study collated the analytical formula of a single angle steel with complex eccentric loads. According to the theory of beam-column interaction, different lengths and positions are considered. The article provides a reference for the correct analysis of the user and improves the correctness of the analysis of the single angle steel.

Abstract: Accurate prediction for the deformation of the roll system is a key to improve the accuracy of the preset model and on-line control model of strip cold rolling processes. A non-linear finite element contact model to simulate the roll system deformation has been developed for4h cold strip rolling mill. Roll process of 4-high cold strip mill is simulated and analyzed by 3D elastic-plastic FEM on the bases of software ANSYS. In the model, the elastic deformation of work roll and backup roll, the plastic deformation of the strip and the pressure of strip and the work and the backup roll were taken into account. Results show that the work roll HYPERLINK "javascript:showjdsw ('showjd_0','j_0')" asymmetric bending is the most effective mean in these strip shape controlling means. The calculated roll gap profile is close to the measured values. This model can improve the accuracy of final products through a correct preset model and on-line control model of strip.

Abstract: Alumina hollow fiber membrane with asymmetric structure has been developed using phase inversion technique followed by sintering process. The formation of asymmetric alumina hollow fiber was influenced by a phenomenon known as hydrodynamically unstable viscous fingering. A desired morphology of the ceramic hollow fiber membrane, that consists of 52 % of finger-like and the rest is sponge-like structure, is tailored by controlled parameters during membrane fabrication process. The result shows that the ratio of alumina/PESf should be reduced to 6. At this ratio, the finger-like structure can be easily formed with inner and outer diameters were 1.11 mm and 2.05 mm respectively. From the given thickness, approximately 243 µm of finger-like length can be developed originating from the lumen of hollow fiber.

Abstract: Cascaded H-Bridge (CHB) multilevel inverter (MLI) is among the most preferred topology in solar PV systems. While traditional asymmetric CHB MLI is easy to achieve higher number of output voltage levels compared to traditional symmetric CHB MLI, charge balancing between the voltage sources remains a challenge for asymmetric CHB MLI. This drawback results in unsteady DC voltage levels due to unbalanced power drawn from each voltage sources. Besides that, in battery powered applications, unbalanced power drawn results in unequal discharged among the batteries. In this paper, an asymmetric half H-bridge (HHB) MLI topology is presented which is easy to modularize as for symmetric CHB MLI while maintaining the ease in charge balancing control. The performance of this proposed asymmetric HHB MLI with charge balance control has been evaluated using PSIM software.

Abstract: A piezoceramic actuator is widely employed in micropositioning and MEMS. However, the piezoceramic actuators are limited due to the natural hysteresis nonlinearity which affect the accuracy of the actuators in applications. In order to revise the hysteresis nonlinearity, lots of hysteresis models have been proposed such as the Preisach model, the classical Prandtl—Ishlinskii model and so on. While some drawbacks still exist with these models, a generalized hysteresis model for asymmetric hysteresis basing on the classical Prandtl—Ishlinskii model is devised. In the modified model, the exponential functions which contain the amplitude and the frequency of the input voltage and its gain factor are introduced into the NLPO (nonlinearity play operator). As a result, the generalized model in this paper applies to modeling asymmetric hysteresis. This model was identified and simulated using the experimental data by other researchers. At last, the validity and the accuracy of the given model were tested through the experiment of the piezoceramic control.

Abstract: Asymmetric 2-p-nitrophenyl-5-naphthylmethylene-1,3,4-oxadiazole and 2-p-aminophenyl-5-naphthylmethylene-1,3,4-oxadiazole were synthesized and characterized by IR、¹HNMR and MS analysis, and their optical properties were detected using UV-vis absorption spectroscopy and fluorescence spectroscopy. The existence of electron-withdrawing oxadiazole units causes a significant bathochromic shift of the UV absorption maximum. The largest UV-absorption peak of target compounds is in the range of 298-317 nm, and a new emission band at 402 nm is formed. The fluorescence intensity is gradually enhanced, which strengthens the intramolecular charge transfer effect between the electron-withdrawing oxadiazole and electron-donating aniline.

Abstract: The deformation load is the most important parameter in the press design as it affects the structure and the general integrity of the final product. Therefore, every other parameter such as die shape, friction, type of process (hot or cold), and speed considered in modeling is optimized to cut back on the metal forming load. The flow of metal is largely influenced by the geometry of the die and hence the geometric shape of the tools is the main factor by which an optimum load can be evaluated. In extrusion process the strain distribution, resulting from deformation load, and other important variables that influence material structure, such as a hydrostatic stress, are strongly dependent on the geometry of the die. In the present investigation using linearly converging die profiles, the extrusion of symmetric and asymmetric polygons such as circular, square, triangular, hexagonal, heptagonal, octagonal, and L-, T-and H-, respectively sections from round billet have been numerically simulated. Mathematical equations describing the die profiles were derived, and then using MATLAB R2009b the co-ordinate of the die profiles was evaluated. A solid CAD model for the linearly converging die profile was made using Autodesk Inventor 2013 software and numerical analysis using DEFORM software for extrusion of the above sections from round billet was then performed to predict, for dry and lubricated condition, the extrusion load during deformation. It is found that the predictive loads for asymmetric shapes are found to be higher than that of the symmetric shapes. While there is no marked difference between the predictive loads for symmetric shapes that of the asymmetric shapes is significant where L-section has the highest extrusion load, followed by T-section and the H-section given the least pressure.

Abstract: The article based on the valve driving servo system of 125MN hydraulic press extruder, aimed at solving the unconformity of the dynamic property in electromechanical integration equipment or control system. It analyzed the mathematical model of the system, the influencing parameter and the regularity related to the asymmetric characteristics, when the cylinder moving forward and reverse direction. According the application in industry field, it adopts the methods by adjusting the ratio of the proportion parameters to remove the asymmetric characteristics in different direction and different loads.

Abstract: In order to expand cross wedge rolling technology applications further and improving the quality of asymmetric shaft parts, this paper predicts the position of center defect location of Cross Wedge Rolling asymmetric shaft parts based on Parity Wedge by Normalized C & L criteria. On this basis, it conducted a systematic study on the effect of forming angle on quality of rolling core part. It has found that, during the forming process of Cross Wedge Rolling shaft parts, rolling center region was more prone to damage, and achieved the regularity of process parameters on the quality of core part. The study results lay the theoretical foundation for preventing defects effectively and improving quality of rolling core part.

Abstract: Four cinchona alkaloid-silyl ether derivatives have been used to catalyze the asymmetric “interrupted” Feist-Bénary reaction of ethyl bromopyruvate/substituted bromo-ketoesters and 1,3-Cyclohexadione. The corresponding hydroxydihydrofurans have been obtained in excellent yields (85-96%) with high enantiomeric excess (ee) values of up to 90%.