Papers by Author: J. Liu

Abstract: A planar cam theoretical profile can be considered as cycloid of the roller center. There is singular point on the cycloid when the roller center is located on the instantaneous axis. Then, the curvature of the cycloid at the singular point is likely to be infinite and interference may be inevitable. Thus, avoiding such singular point is imperative in cam profile design. But, in analyzing the characteristics of the tangent vector and curvature at such singular point, it reveals that the curvature may be finite, even zero, if the cycloid fulfills some condition at the singular point. This leads to a very important property that at the singular point the tangent of the cycloid is parallel to the normal of the instantaneous center curve. The pressure angle is very small even zero. These results would be very efficacious in planar cam mechanism applications. The characteristics of singular point on cycloid are detailed in this paper. As application, a novel kind of parallel indexing cam mechanism is developed. Its configuration and principle are described.

Abstract: Based on the shortcoming and deficiency of deep hole machining, a grinding wheel spindle with squeeze film damper—SFD is design based on squeeze film damped theory. The motion differential equation of SFD grinding wheel spindle is constituted according to D’ Ale mbert principle，and a lot of simulated research has been carried out about the locus of grinding wheel spindle affect by SFD. Founded on the simulated result, the SFD grinding wheel spindle of internal grinder have designed, and the grinding experiments have been performed. Experimental result indicate that the rationality of design for SFD can make the vibration of the grinding wheel spindle reduce 25% , and make machining precision of hole improve 20% , make work efficiency of the grinder raise 15%.

Abstract: In this paper the modeling method of object entity in the environment of virtual is introduced and the three-dimensional simulation model of grinding wheel is established in Visual C++ programming language and OpenGL tool. The simulated experiment is made, which can indicate the effect of different parameters to grinding process. It proved the reliability and practicability of virtual wheel through comparing the simulation results and experimental data.

Abstract: The precise face grinding and lapping technology with abrasive or abrasive tool has been widely used in the field of the precise manufacture and ultraprecise manufacture. It has become an essential technology in the manufacture of many components. The planetary lapping machine is typical equipment for face grinding or lapping process. And the relative motions between the workpieces and grinding wheel will affect the formation of wear profiles of the tools, furthermore, the work result will be affected directly by the cutting path of this relative motions. In this paper, the kinematic principle of face grinding process on lapping machines has been analyzed. By means of the concept of pitch point and pitch circles, the complicated grinding process has been converted into two kinds of rotations with the fixed center distance. Two kinds of path curves, i.e. workpiece against grinding wheel and grinding wheel against workpiece, and their relations are analyzed. The geometrical analyses and the manufacture quality of the workpiece are linked with the aid of the cutting velocity, the range of the rotational angle of the cutting traces and the rate of the change of the rotational angle with time. The optimal path curve and kinematic parameters are achieved, and these results are corresponding to the experimental results.

Abstract: The objective of this study was to evaluate the in vivo characteristics of poly (ethylene glycol)-poly (lacticacid-co-glycolicacid)-poly (ethylene- glycol) (PELGE) copolymers as drug carriers. In order to test this circulation time, mitoxantrone (DHAQ) was used as a model drug in this study. DHAQ nanoparticles (DHAQ-NP) were prepared, subsequently the DHAQ-NP were evaluated by measuring the drug concentration in plasma after intravenous administration via the tail vein of mice. The circulation time of the DHAQ-NP were tested. The results showed prolonged mitoxantrone (DHAQ) residence in systemic blood circulation.

Abstract: The regular spherical poly-D, L-lactic acid (PDLLA) nanoparticles containing DNR are produced using a double-emulsion solvent evaporation process. The products morphology is characterized by a laser light-scattering particle size analyzer and scanning electron microscopy. Results show a mean diameter in 546.9 nm with narrow size distribution and homogeneous particle production. The encapsulation efficiency is evaluated by UV spectra. The results indicate that drug contents and loading efficiency are 14.34% and 72.9% respectively, and the drug release profile shows a biphasic phenomenon.