4,954 research outputs found
A Preliminary Study on Reorganization of the Shipping Goods Market Department of Guangdong Province in Late Ming Dynasty
In the Ming Dynasty, the China overseas trade management administrations, the shipping goods market departments, declined. However, historical materials show that the shipping goods market department of Guangdong Province had been especially enhanced in the overall decline trend. At present, the academia has not paid enough attention to this phenomenon. Based on the historical materials, a preliminary analysis shows that the chief tax inspector Li Feng was in charge of the taxes of Guangdong Province in the late Wanli period (from September 4, 1573 to August 18, 1620) in the Ming Dynasty, and he forced to change the original power structure of the shipping goods market department. The change of the original power structure was one of key factors which strengthened the shipping goods market department of Guangdong Province. The deeper reason was the change of Guangdong overseas trade situation in the late Ming Dynasty. The change made the shipping goods market department to do corresponding adjustments of its management mechanism
Study on radiative decays of and into by means of LFQM
The observed resonance peak around 2.86 GeV has been carefully reexamined by
the LHCb collaboration and it is found that under the peak there reside two
states and which are considered as
and with slightly different masses and
total widths. Thus, the earlier assumption that the resonance
was a state should not be right. We suggest to measure the partial widths
of radiative decays of and to confirm their
quantum numbers. We would consider as or a pure
state, or their mixture and respectively calculate the corresponding
branching ratios as well as those of . The future precise
measurement would provide us information to help identifying the structures of
those resonances .Comment: 8 pages, 4 figures, 1 tabl
Investigation into the dispensing-based fabrication process for tissue scaffolds
Tissue engineering is a multidisciplinary subject aimed at producing the immunologically tolerant ‘artificial’ tissues/organs to repair or replace damaged ones. In this field, tissue scaffold plays a key role to support cell growth and new tissue regeneration. For fabrication of tissue scaffolds with individual external geometry and predefined inner structure, rapid prototyping (RP) systems based on fluid dispensing techniques have proved to be very promising. The present research conducted a comprehensive study on the dispensing-based fabrication process. First of all, the scaffold materials are characterized in terms of their biocompatibility and flow behaviour. The biocompatibility of biomaterials of PLLA, PCL, collagen, chitosan, and gelatine is evaluated in terms of supporting neuron cells’ adhesion and outgrowth. Chitosan solution (2% w/v) in acetic acid is shown to be the most promising among the examined biomaterials for the fabrication of nerve tissue scaffolds. Its non-Newtonian flow behaviour is identified by using a commercial rheometer. In the fabrication process, the flow rate of biomaterials dispensed, the profile of strand cross-sections, and the scaffold porosity are very important and must be precisely controlled. A model is developed to represent the flow rate of biomaterials dispensed under the assumptions that the flow is incompressible, steady, laminar, and axisymmetric. Also, the profile and size of line strands at different layers and portions are modeled based on the Young-Laplace equation. Thus the dispensing-based fabrication process can be predicted in terms of the flow rate and the scaffold porosity. The effects of operation conditions on the fabrication result are identified theoretically and experimentally. Simulation result shows that a higher driving pressure, a higher temperature, and a larger needle diameter will result in a larger size of the strand cross-sections and lower scaffold porosity. The change pattern, however, is nonlinear, which is affected by the fluid surface tension and non-Newtonian flow behaviour of scaffold biomaterials. To verify the effectiveness of the developed models, experiments were carried out on a commercial dispensing system (C-720, Asymtek, USA). To avoid the possible error derived from the temperature difference between the dispensing system and the rheometer, a new method is presented to characterize the fluid properties used for model predictions. Experimental results illustrate that the developed models, combined with the new identification method, are very promising to predict the dispensing-based fabrication process
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