The phenomenon of anti-symmetrical bifurcation of periodic solutionsoccurring near an integral manifold is the intrinsic cause resulting in harmonic resonanceover-voltage in power systems. Due to this discovery, the p...The phenomenon of anti-symmetrical bifurcation of periodic solutionsoccurring near an integral manifold is the intrinsic cause resulting in harmonic resonanceover-voltage in power systems. Due to this discovery, the principle of eliminating resonance byusing anti-bifurcation technique is presented, which makes that the theoretical bases of verymeasure to eliminate resonance are unified firstly from a point of view of basic theory. Ourdiscussion models depend on a class of nonlinear control model. Using the direct Lyapunov method, acomplete theoretical proof is given in accordance with the measure of eliminating resonance byconnecting nonlinear resistor in series to the neutral point of P. T., and the feedback control lawbeing applied. It comprises the action of parameters of resistor to eliminate resonance and theactual process of eliminating resonance, i.e., to go against bifurcation process which forces thebig harmonic solutions to retreat to the integral manifold gradually and disappear eventually, whichby using the nonlinear controllers. This makes it sure that the intrinsic cause of resonance iseliminated thoroughly. The obtained theory results and computing results are better than thepresented results.展开更多
The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders...The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders were investigated.It is found that Arabic gum can better adsorb on silver particles via chemical adsorption,and it shows the best dispersive effect among all the selected dispersants.The particle size of silver powders can be finely tuned from 0.34 to 4.09μm by adjusting pH values,while the morphology of silver powders can be tuned by changing the temperature.The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8-70°C.Especially,the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50°C.The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.展开更多
Objective Cystic meningiomas are quite rare. There is a great controversy concerning the management of the cystic wall. We reported six peritumoral cystic meningiomas and reviewed the literature to discuss the managem...Objective Cystic meningiomas are quite rare. There is a great controversy concerning the management of the cystic wall. We reported six peritumoral cystic meningiomas and reviewed the literature to discuss the management of the cystic wall. Methods Six cases of peritumoral cystic meningiomas were retrospectively analyzed. Results Gadolinium-enhanced Tl-weighted magnetic resonance imaging scans disclosed the solid tumor enhancement in 3 cases, the cystic wall enhancement in 2 cases. One case only showed the cystic lesion. All the tumors were totally removed （ including the involved dura and partial cystic wall）. Histopathological examination showed 3 meningiotheliomatous meningiomas, 2 microcystic meningiomas, 1 mucoid degeneration. After operation, all the patients recovered well and demonstrated no neurological deficit. During the follow-up time, no tumor was recurrence. Conclusion Magnetic resonance imaging with contrast enhancement can provide information regarding whether surgical removal of the cystic wall is indicated. Peripheral enhancement of the cystic wall strongly indicates the presence of tumor infiltration. The removal of the entire cystic wall should be performed, excessive damage to brain be prevented.展开更多
According to the construction method of Taizhou Bridge, numerical simulation is conducted to analyze the vibration of caisson under wind and water flows to determine the main factors of the caisson vibration. Meanwhil...According to the construction method of Taizhou Bridge, numerical simulation is conducted to analyze the vibration of caisson under wind and water flows to determine the main factors of the caisson vibration. Meanwhile, the localization system of caissons and anchors of Taizhou Bridge is modeled in order to summarize the vibration mechanism of caissons under deep-water and jet-flow condition, and further pertinent vibration-control measures are proposed. The obtained results are well verified in engineering practice, and consequently the safety risk of positioning the caisson is reduced.展开更多
文摘The phenomenon of anti-symmetrical bifurcation of periodic solutionsoccurring near an integral manifold is the intrinsic cause resulting in harmonic resonanceover-voltage in power systems. Due to this discovery, the principle of eliminating resonance byusing anti-bifurcation technique is presented, which makes that the theoretical bases of verymeasure to eliminate resonance are unified firstly from a point of view of basic theory. Ourdiscussion models depend on a class of nonlinear control model. Using the direct Lyapunov method, acomplete theoretical proof is given in accordance with the measure of eliminating resonance byconnecting nonlinear resistor in series to the neutral point of P. T., and the feedback control lawbeing applied. It comprises the action of parameters of resistor to eliminate resonance and theactual process of eliminating resonance, i.e., to go against bifurcation process which forces thebig harmonic solutions to retreat to the integral manifold gradually and disappear eventually, whichby using the nonlinear controllers. This makes it sure that the intrinsic cause of resonance iseliminated thoroughly. The obtained theory results and computing results are better than thepresented results.
基金Project(2014DFA90520)supported by the International Cooperation Program of Ministry of Science and Technology of ChinaProject(2013A090100003)supported by the Production,Teaching and Research Program of Guangdong Province,ChinaProject(2013DY048)supported by the Science and Technology Cooperation Program of Daye Nonferrous Metals Group,China
文摘The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders were investigated.It is found that Arabic gum can better adsorb on silver particles via chemical adsorption,and it shows the best dispersive effect among all the selected dispersants.The particle size of silver powders can be finely tuned from 0.34 to 4.09μm by adjusting pH values,while the morphology of silver powders can be tuned by changing the temperature.The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8-70°C.Especially,the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50°C.The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.
文摘Objective Cystic meningiomas are quite rare. There is a great controversy concerning the management of the cystic wall. We reported six peritumoral cystic meningiomas and reviewed the literature to discuss the management of the cystic wall. Methods Six cases of peritumoral cystic meningiomas were retrospectively analyzed. Results Gadolinium-enhanced Tl-weighted magnetic resonance imaging scans disclosed the solid tumor enhancement in 3 cases, the cystic wall enhancement in 2 cases. One case only showed the cystic lesion. All the tumors were totally removed （ including the involved dura and partial cystic wall）. Histopathological examination showed 3 meningiotheliomatous meningiomas, 2 microcystic meningiomas, 1 mucoid degeneration. After operation, all the patients recovered well and demonstrated no neurological deficit. During the follow-up time, no tumor was recurrence. Conclusion Magnetic resonance imaging with contrast enhancement can provide information regarding whether surgical removal of the cystic wall is indicated. Peripheral enhancement of the cystic wall strongly indicates the presence of tumor infiltration. The removal of the entire cystic wall should be performed, excessive damage to brain be prevented.
基金National Science and Technology Support Program of China ( No. 2009BAG15B02) Key Programs for Science and Technology Development of Chinese Transportation Industry( No. 2008-353-332-150)
文摘According to the construction method of Taizhou Bridge, numerical simulation is conducted to analyze the vibration of caisson under wind and water flows to determine the main factors of the caisson vibration. Meanwhile, the localization system of caissons and anchors of Taizhou Bridge is modeled in order to summarize the vibration mechanism of caissons under deep-water and jet-flow condition, and further pertinent vibration-control measures are proposed. The obtained results are well verified in engineering practice, and consequently the safety risk of positioning the caisson is reduced.
