Aim The piezoelectric properties and cytotoxicity of a porous lead-free piezoelectric ceramic for use as a direct bone substitute were investigated. Methodology Cold isostatic pressing （CIP） was applied to fabricate...Aim The piezoelectric properties and cytotoxicity of a porous lead-free piezoelectric ceramic for use as a direct bone substitute were investigated. Methodology Cold isostatic pressing （CIP） was applied to fabricate porous lithium sodium potassium niobate （Li0.06Na0.5K0.44） NbO3 specimens using a pore-forming method. The morphologies of the CIP-processed specimens were characterized and compared to those of specimens made by from conventional pressing procedures. The effects of the ceramic on the attachment and proliferation of osteoblasts isolated from the cranium of 1-day-old Sprague- Dawley rats were examined by a scanning electron microscopy （SEM） and metbylthiazol tetrazolium （MTT） assay. Results The results showed that CIP enhanced piezoelectricity and biological performance of the niobate specimen, and also promoted an extracellular matrix-like topography of it. In vitro studies showed that the CIP-enhanced material had positive effects on the attachment and proliferation of osteoblasts. Conclusion Niobate ceramic generated by CIP shows a promise for being a piezoelectric composite bone substitute.展开更多
Background: For over a hundred thirty years, consecutive Ethiopian regimes have denied the Oromo people the right to develop free media. In this paper I explore how this denial has affected the development of public h...Background: For over a hundred thirty years, consecutive Ethiopian regimes have denied the Oromo people the right to develop free media. In this paper I explore how this denial has affected the development of public health conditions in Oromia. Methods: Using the “upstream” public health metaphor as the framework of thinking, in this paper I explore how the denial of free media has hindered the development of better public health conditions. Finding: Although media and public health are distinct social organizations, many of their functions overlap, with the former significantly supporting the development of the latter. Media informs, educates, entertains, molds opinion, advocates, provides a framework of thinking, connects people and ideas, and records events. The foundation of public health rests on the study of risks to population health and identifying health promotion as well as disease prevention (primary, secondary and tertiary) tools. Media facilitates knowledge construction and its dissemination. It supports the efforts societies make in establishing and maintaining the social conditions that will ensure the best public health outcomes possible. Conclusion: Since media facilitates knowledge construction and knowledge dissemination, it can help produce knowledgeable and critical citizens who are equipped with problem-solving skills. Denying the Oromo people the right to develop their own free media is hindering them from having people with skills who are critically needed in transforming their society and developing better public health conditions.展开更多
The reliability and robustness of the electro-hydraulic servo control system for heavy-duty forging machine play an important role in forging processes. A mathematic model of 50 MN water press for free forging was cre...The reliability and robustness of the electro-hydraulic servo control system for heavy-duty forging machine play an important role in forging processes. A mathematic model of 50 MN water press for free forging was created in this research. The dynamic robust compensator integrating with PID control method is designed and applied to the mathematical model simulation. The simulated results approved that the dynamic robust compensator application restrains interference from extra load and improves the electro-hydraulic position servo control system accuracy and stability.展开更多
基金supported by the National Natural Science Foundation of China (59972020)
文摘Aim The piezoelectric properties and cytotoxicity of a porous lead-free piezoelectric ceramic for use as a direct bone substitute were investigated. Methodology Cold isostatic pressing （CIP） was applied to fabricate porous lithium sodium potassium niobate （Li0.06Na0.5K0.44） NbO3 specimens using a pore-forming method. The morphologies of the CIP-processed specimens were characterized and compared to those of specimens made by from conventional pressing procedures. The effects of the ceramic on the attachment and proliferation of osteoblasts isolated from the cranium of 1-day-old Sprague- Dawley rats were examined by a scanning electron microscopy （SEM） and metbylthiazol tetrazolium （MTT） assay. Results The results showed that CIP enhanced piezoelectricity and biological performance of the niobate specimen, and also promoted an extracellular matrix-like topography of it. In vitro studies showed that the CIP-enhanced material had positive effects on the attachment and proliferation of osteoblasts. Conclusion Niobate ceramic generated by CIP shows a promise for being a piezoelectric composite bone substitute.
文摘Background: For over a hundred thirty years, consecutive Ethiopian regimes have denied the Oromo people the right to develop free media. In this paper I explore how this denial has affected the development of public health conditions in Oromia. Methods: Using the “upstream” public health metaphor as the framework of thinking, in this paper I explore how the denial of free media has hindered the development of better public health conditions. Finding: Although media and public health are distinct social organizations, many of their functions overlap, with the former significantly supporting the development of the latter. Media informs, educates, entertains, molds opinion, advocates, provides a framework of thinking, connects people and ideas, and records events. The foundation of public health rests on the study of risks to population health and identifying health promotion as well as disease prevention (primary, secondary and tertiary) tools. Media facilitates knowledge construction and its dissemination. It supports the efforts societies make in establishing and maintaining the social conditions that will ensure the best public health outcomes possible. Conclusion: Since media facilitates knowledge construction and knowledge dissemination, it can help produce knowledgeable and critical citizens who are equipped with problem-solving skills. Denying the Oromo people the right to develop their own free media is hindering them from having people with skills who are critically needed in transforming their society and developing better public health conditions.
文摘The reliability and robustness of the electro-hydraulic servo control system for heavy-duty forging machine play an important role in forging processes. A mathematic model of 50 MN water press for free forging was created in this research. The dynamic robust compensator integrating with PID control method is designed and applied to the mathematical model simulation. The simulated results approved that the dynamic robust compensator application restrains interference from extra load and improves the electro-hydraulic position servo control system accuracy and stability.
