This paper deals with a digest on electrical treeing degradation in nanocomposite of magnesium oxide(MgO) added to a low-density polyethylene(LDPE).The objective is to elucidate the"visual"aspects of runaway...This paper deals with a digest on electrical treeing degradation in nanocomposite of magnesium oxide(MgO) added to a low-density polyethylene(LDPE).The objective is to elucidate the"visual"aspects of runaway stage of final treeing breakdown mechanisms,and to ensure that the existence of MgO filler itself is responsible for this aspect instead of voltage application changes.The"visual"aspect of treeing breakdown was investigated by applying ac ramp voltage with continuous rising speed of 0.5 kV/s.As soon as tree had been incepted,the voltage was kept constant to observe the tree propagation until breakdown.The tree propagations were also described by their fractal dimension. To ensure the responsibility of MgO filler on the"visual"aspect results,the experiment was repeated using the same rate of ac ramp voltage.However,as soon as tree had been incepted,the voltage was either increased or decreased to a constant value of mean tree inception voltage obtained from the preceding results to observe its propagation to breakdown. As a result,the tree inception voltage was increased with the filler concentration in LDPE.The filler is considered not only acted as a physical obstacle for tree to propagate,but also as a chemical obstacle in which the free electron might be trapped to cause difficulties for electron avalanche occurrence.This consideration could also be valid for tree propagation up to breakdown.During propagation,due to the filler,the tree structure is accompanied by more branches.Since the branches are closely placed each other,the tree tips become relatively uniform field compares to pure LDPE.This would produce the higher local breakdown strength at the tree tips,leads to the suppression of propagation.The"visual"aspect of breakdown could be achieved by applying voltage exactly at the inception level. After bridging the tree would not breakdown until a short period of time lag.Within this period,the tree channel will be eroded by internal flashover(IFO) and become thicker.MgO filler could still restrain the IFO at the small diameter; however there will be a maximum diameter above which the effect of MgO would be very small.Lastly,it is confirmed that the MgO filler itself excels to suppress the tree degradation instead of the voltage application changes.The polymer nanocomposite appears to be more resistive to treeing degradation than their base material.展开更多
Collinear Holography was proposed by OPTWARE Corporation, in which the information and reference beams were aligned co-axially and modulated by the same SLM. With this unique configuration the optical pickup can be de...Collinear Holography was proposed by OPTWARE Corporation, in which the information and reference beams were aligned co-axially and modulated by the same SLM. With this unique configuration the optical pickup can be designed as small as the DVD ′ s, and can be placed on one side of the recording disc. A 2-dimensional digital page data format was used and the shift-multiplexing method was employed to increased recording density of HVD. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disc in the recording and the reconstructing process, a vibration isolator is no longer necessary. In HVD, the pre-formatted meta-data reflective layer was used for the focus/tracking servo and reading address information, and the dichroic mirror layer was used for detecting holographic recording information without interfering with the preformatted information.Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. HVD will be compatible with existing disc storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems.展开更多
基金Supported by the Ministry of Education,Culture, Sports,Science,and Technology(Monbukagakusho) Japanthe 21st Century COE Program"Intelligent Human Sensing",Toyohashi University of Technology,Japan
文摘This paper deals with a digest on electrical treeing degradation in nanocomposite of magnesium oxide(MgO) added to a low-density polyethylene(LDPE).The objective is to elucidate the"visual"aspects of runaway stage of final treeing breakdown mechanisms,and to ensure that the existence of MgO filler itself is responsible for this aspect instead of voltage application changes.The"visual"aspect of treeing breakdown was investigated by applying ac ramp voltage with continuous rising speed of 0.5 kV/s.As soon as tree had been incepted,the voltage was kept constant to observe the tree propagation until breakdown.The tree propagations were also described by their fractal dimension. To ensure the responsibility of MgO filler on the"visual"aspect results,the experiment was repeated using the same rate of ac ramp voltage.However,as soon as tree had been incepted,the voltage was either increased or decreased to a constant value of mean tree inception voltage obtained from the preceding results to observe its propagation to breakdown. As a result,the tree inception voltage was increased with the filler concentration in LDPE.The filler is considered not only acted as a physical obstacle for tree to propagate,but also as a chemical obstacle in which the free electron might be trapped to cause difficulties for electron avalanche occurrence.This consideration could also be valid for tree propagation up to breakdown.During propagation,due to the filler,the tree structure is accompanied by more branches.Since the branches are closely placed each other,the tree tips become relatively uniform field compares to pure LDPE.This would produce the higher local breakdown strength at the tree tips,leads to the suppression of propagation.The"visual"aspect of breakdown could be achieved by applying voltage exactly at the inception level. After bridging the tree would not breakdown until a short period of time lag.Within this period,the tree channel will be eroded by internal flashover(IFO) and become thicker.MgO filler could still restrain the IFO at the small diameter; however there will be a maximum diameter above which the effect of MgO would be very small.Lastly,it is confirmed that the MgO filler itself excels to suppress the tree degradation instead of the voltage application changes.The polymer nanocomposite appears to be more resistive to treeing degradation than their base material.
基金Grant in AidforScientificResearchfromTheJapanSocietyforthePromotionofScience(JSPS) ,Grant in AidforYoungScientistsfromTheMinistryofEducation ,Culture ,Sports ,ScienceandTechnology (MEXT)
文摘Collinear Holography was proposed by OPTWARE Corporation, in which the information and reference beams were aligned co-axially and modulated by the same SLM. With this unique configuration the optical pickup can be designed as small as the DVD ′ s, and can be placed on one side of the recording disc. A 2-dimensional digital page data format was used and the shift-multiplexing method was employed to increased recording density of HVD. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disc in the recording and the reconstructing process, a vibration isolator is no longer necessary. In HVD, the pre-formatted meta-data reflective layer was used for the focus/tracking servo and reading address information, and the dichroic mirror layer was used for detecting holographic recording information without interfering with the preformatted information.Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. HVD will be compatible with existing disc storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems.
