Papers by Author: Qian Peng

Abstract: Based on more than three hundred transformer accidents and some statistics data related, this paper manages to draw a standard classification table of transformer failure. 5 degrees of failure possibilities are classified in the paper: extremely high, high, general, low, extremely low. Besides, 4 major factors that affects risk of transformer failure severity are studied: direct lossmonitoring levelmaintenance cost and maintenance period. Also, failure severity of each risk source are classified into 5 levels: not serious, mild, ordinary, less serious, and serious, and Extensional Analytic Hierarchy Process (EAHP) and Extensional Project Appraisal Methods are used to evaluate the severity of risk of transformer failures. Last but not least, risk matrix has been built and divided into four parts: high risk area, critical risk area, medium risk area and low risk area. On that top, some maintenance strategies are proposed accordingly.

Abstract: The interconnected porous scaffolds are crucial to support the attachment, differentiation, proliferation of cells so to construct 3-dimensional (3-D) tissues. Up to now, there are several approaches to prepare porous scaffolds. In our experiments, we designed a novel porous bioceramic scaffold, called the hydroxyapatite (HA) spherule scaffold, by accumulating HA spherules in an HA porous tube to establish an interconnected porous structure which can be reconstructed exactly. The porous HA tube was manufactured by polymer sponge template while HA spherules were prepared by sol-gel process. In the animal experiment, the HA spherule scaffolds were implanted at 2 different non-osseous sites such as muscle and abdominal cavity in dogs. The new bone growth was investigated after six months. The preliminary results demonstrated that the proliferation of osteocytes on the scaffolds in muscle was obviously better than in abdominal cavity, and about ten times more blood vessels (BVs) were appeared in the former site than those in the latter site. This study presents an alternative way to reveal the relationship between the porous structure of scaffolds and ectopia bone growth because the interconnection and porosity can be controlled easily by the size and porosity of HA spherules.

Abstract: This study was aimed to estimate the cell-activity after culture of the cell-material composite and to evaluate the feasibility of constructing tissue-engineered bone using this novel material. Hollow HA mcirospheres (H-HAMs), porous PLA\HA tube，polyurethane plunger were prepared respectively. Mesenchymal stem cells (MSCs), which were derived from rat bone marrow were utilized as seed cells.Two different methods were used to integrate the seed cells and scaffold materials. Group A: H-HAMs were filled into porous HA tube, and porous polyurethane plungers were used to cover onto the ends of HA/PLA tubes as a whole, Then MSCs were cultured on the composite scaffolds; Group B: MSCs were compounded with H-HAMs completely first, then the pre-seeded composite of H-HAMs and cells was put into the porous PLA\HA tube which was then sealed with the polyurethane plunger. 1,3,5,7 and 9 days after cell-material composites were cultured, the growing status and adhesions of seed cells were observed. The viability of cells was quantified and increased over time in different methods, but was significantly higher in Group B after 9 days of culture. SEM detection revealed that more cells were detected on the PLA\HA tube and the outer layer of H-HAMs; growth of cells was more widespread and more cells were detected on H-HAMs in Group B. However, cells on H-HAMs seem to diminish over time in both groups. As a novel 3-D Hydroxyapatite scaffold, its H-HAMs are more easy to be integrated with seed cells, to be shaped according to clinical needs because of its semi-liquidity. However, the growth of cells especially in the inner core of the integrated material needs further research.

Abstract: Hydroxyapatite (HA) which has excellent biocompatibility and osteoconductivity is limited in the load-bearing repair because of its brittleness. Applying appropriate sintering additives for HA is a possible way to improve its mechanical properties. Systematic studies have has been performed to investigate the effect of LiCl as an additive on the microstructure and sinterability of HA and the relationship to its mechanical properties. The densification of HA containing different LiCl contents was completed through a special sintering process with the highest temperature of 1280°C. Microhardness was tested as a short cut to evaluate the changes of mechanical properties affected by the microstructure of HA doped with LiCl. The results of the experiment showed that LiCl is an effective sintering agent which causes neither decomposition of HA nor formation of other undesired phases with the increase of its microhardness.

Abstract: Hollow hydroxyapatite microspheres (H-HAMs) with controlled characteristic mesoporous structure on the shell were successfully fabricated by using core template technology and sol-gel process. The fabrication of H-HAMs mainly included three distinct steps: the preparation of core template spheres of chitin by emulsifying chitin solution in oil, the formation of core-shell composite spheres of chitin-HA/chitin after a layer of chitin/HA solution coated on the surface of chitin core templates by means of a gelling process of chitin solution with the help of water in the cores, and the harvest of H-HAMs through a special sintering procedure to remove chitin. The size and shape of H-HAMs were chiefly determined by the size and morphology of core templates. The thickness of shells was easily controlled by altering water content of the starting template particles, and the characteristic mesoporous structure on the shell was related to the proportion of chitin in the chitin/HA composite solution and the sintering temperature. H-HAMs with characteristic mesoporous architecture on the shell have many potential applications such as used as a carrier for sustained release of drugs in the therapy of hard tissue system.

Abstract: A porous composite scaffold for tissue engineering had been developed through a novel gel-casting approach with needle-like nano hydroxyapatite (HA) crystallites and chitin. The freeze-dried nano-HA powder was firstly dispersed in the chitin solvent before chitin dissolves in its solvent completely. The composite solution was evenly mixed with a selected porosifier and poured into a mold in which it became a composite gel under the reaction of water molecules in atmosphere. Subsequently, the composite gel was subjected to the simultaneous extraction of the porosifier and chitin solvent in distilled water. After the drying process the porous composite scaffold was obtained. The morphological analysis showed that the manufactured scaffold had uniform and isotropic porous structure with controlled, fully interconnected pores. In vitro experiments indicated that the bone-like apatite layer formed easily on the walls of the porous n-HA/chitin composite scaffold.

Abstract: Hydroxyapatite (HA) spherulites had been fabricated successfully through a novel approach including chitin emulsion and geletion processes. The freeze-dried nano-HA powder was firstly dispersed in the chitin solvent before chitin dissolves in its solvent completely. The chitin sol containing nano-HA particles was dropped into oil and emulsified making use of liquids immiscibility effect between oil and chitin sol by stirring. The n-HA/Chitin sol spherulites gelled in situ with the existence of water molecules. Subsequently, the spherular gel granules were rinsed in distilled water to leach the solvent and dried in room circumstance. Finally, special sintering routines were carried to harvest spherular HA granules. The size and porosity of HA spherulites were controlled by the rate of nano-HA to chitin, the chitin concentration in the starting slurry, the stirring rate and the temperature of oil etc. In addition porosifier such as sugar was used in order to adjust the macro- and micro-porous structures in the HA spherulites. The morphological observation showed that the HA spherulites had good sphericity and characteristic microporous structure which were favorable for medical application.