Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer ...Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.展开更多
Calotropis procera(Aiton)W.T.Aiton,belonging to the family Apocynaceae,is C3 evergreen plant species in arid and semi-arid areas of the Punjab Province,Pakistan.It grows in a variety of habitats like salt affected and...Calotropis procera(Aiton)W.T.Aiton,belonging to the family Apocynaceae,is C3 evergreen plant species in arid and semi-arid areas of the Punjab Province,Pakistan.It grows in a variety of habitats like salt affected and waterlogged area,desert/semi-desert,roadside,wasteland,graveyard,forest,crop field,coastline,and river/canal bank.A total of 12 populations growing in different ecological regions were sampled to evaluate their growth,physio-biochemical,and anatomical responses to specific environmental condition.Population adapted to desert/semi-desert showed vigorous growth(plant height,shoot length,and number of leaves),enhanced photosynthetic level(chlorophyll a,chlorophyll b,carotenoids,and total chlorophyll),and apparent anatomical modifications such as increased stem radius,cuticle thickness,storage parenchyma tissues(cortex and pith),and vascular bundles in stems,while the maximum of midrib and lamina thickness,epidermal cells,cuticle thickness,cortical proportion,abaxial stomatal density,and its area in leaves.There was high plasticity in structural and functional features of these populations,which enable them to survive and tolerate under such hot and dry desert environment.Population of saline areas exhibited very critical modifications to sustain under salt prone environment.At physiological level,it possesses the maximum amount of organic osmolytes(glycine betaine and proline)and antioxidants(superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)),while at anatomical level,it showed intensive sclerification,large phloem region(inner and outer),pith parenchyma cells,and metaxylem vessels in stems and leaves.The population of dry mountains showed very distinctive features,such as increased shoot ionic contents(K+and Ca2+),collenchyma and sclerenchyma thickness in stems,trichomes size,and numerous small stomata on abaxial surface of leaves.It is concluded that no definite or precise single character can be taken as a yardstick for adjudging the biomass production in this rubber bush weed population.展开更多
The failure rate of crankpin bearing bush of diesel engine under complex working conditions such as high temperature,dynamic load and variable speed is high.After serious wear,it is easy to deteriorate the stress stat...The failure rate of crankpin bearing bush of diesel engine under complex working conditions such as high temperature,dynamic load and variable speed is high.After serious wear,it is easy to deteriorate the stress state of connecting rod body and connecting rod bolt,resulting in serious accidents such as connecting rod fracture and body damage.Based on the mixed lubrication characteristics of connecting rod big endbearing shell of diesel engine under high explosion pressure impact load,an improved mixed lubrication mechanism model is established,which considers the influence of viscoelastic micro deformation of bearing bush material,integrates the full film lubrication model and dry friction model,couples dynamic equation of connecting rod.Then the actual lubrication state of big end bearing shell is simulated numerically.Further,the correctness of the theoretical research results is verified by fault simulation experiments.The results show that the high-frequency impact signal with fixed angle domain characteristics will be generated after the serious wear of bearing bush and the deterioration of lubrication state.The fault feature capture and alarm can be realized through the condition monitoring system,which can be applied to the fault monitoring of connecting rod bearing bush of diesel engine in the future.展开更多
The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carr...The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carried out.Based on the experimental data,a ternary quadratic regression equation was established by orthogonal experiment.The Ramberg-Osgood constitutive model of tin-bronze connecting rod bushing was obtained.Referred to the constitutive relation of macroscopic incremental,the incremental elastoplastic constitutive relation of spinning parts was deduced based on the Mises yield criterion and kinematic hardening model.The results can be applied to the elastoplastic analysis in finite element numerical simulation.展开更多
Design and optimization of bushing at present mainly use the traditional experience method.The relevant research that adopts computer simulation to carry on the operation behavior of the bushing has appeared in recent...Design and optimization of bushing at present mainly use the traditional experience method.The relevant research that adopts computer simulation to carry on the operation behavior of the bushing has appeared in recent years.How to use the finite element method to research bushing was introduced in the article.Physics fields and many relevant parameters of one real bushing were calculated.Through the results of calculation,it indicate that the finite element method is very useful in bushing research of designing and optimizing.展开更多
Presents the study on the pressure and friction fields of the lubricant film on the surface of a large thrust elastic metal plastic bearing bush in a hydraulic turbine using the method of finite element analysis and t...Presents the study on the pressure and friction fields of the lubricant film on the surface of a large thrust elastic metal plastic bearing bush in a hydraulic turbine using the method of finite element analysis and the stress and displacement fields in the vertical direction of the bush surface obtained to provide a theoretical basis for the design of contour lines and investigation into the causes for destruction of bushes, and concludes with test results that 1) the stress on the surface of the bush is not uniform; 2) a tension stress tends to occur near the oil ingress and egress edges but it is minor; 3) the biggest displacement in the vertical direction appears where x=84 and Y=1 153 and has a value of 0.022 mm; 4) the deformation of the bearing bush is harmful to the maintenance of lubricant film.展开更多
In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radi...In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radial stiffness coefficient. The obtained theoretical result is consistent with previous research results in both long rubber bushes and short rubber bushes. The simulation case was conducted by the finite element method to verify the correctness of the theory. The axial compression experiment was conducted to obtain the parameters needed in the simulation. The result shows that the percentage difference between the theoretical result and the simulation one is only 2.75%. A series of simulations were conducted to compare with previous work, and the largest magnitude of the percentage difference is only about 5%. Finally, the radial stiffness experiment was conducted by using a dynamic vibration absorber, and the influence of the structural parameters of the rubber bush on its radial stiffness is obtained. The result shows that the radial stiffness of the rubber bush increases with the increase in the length and the inner radius, but decreases with the increase in the outer radius.展开更多
The temperature of bush inner surface temperature is measured by using infrared thermometer and transparent bearing,and temperature rise is measured by using thermocouple. The influence of rotating speed and axial loc...The temperature of bush inner surface temperature is measured by using infrared thermometer and transparent bearing,and temperature rise is measured by using thermocouple. The influence of rotating speed and axial location on the bush inner surface temperature is studied,and the influence of supply pressure and rotating speed on the temperature rise is analyzed. The results show the bush inner surface temperature and temperature rise of spiral oil wedge hydrodynamic bearing increase with the increase of rotation speed. In axial direction,the temperature is higher around the oil return hole. The temperature rise decreases with the increase of supply pressure. The highest temperature of bush inner surface and temperature rise are higher at higher speed,so the temperature rise is the fundamental reason which restricts the increase of rotation speed for high speed sleeve bearing.展开更多
The numerical simulation for temperature distribution of Pt-Rh alloy bushing was carried out using a thermal-electric module in ANSYS Workbench finite element analysis software.The effects of side wall thickness,plug ...The numerical simulation for temperature distribution of Pt-Rh alloy bushing was carried out using a thermal-electric module in ANSYS Workbench finite element analysis software.The effects of side wall thickness,plug thickness,the angle of two side walls and electrode structure on the uniformity of temperature distribution were investigated.Meanwhile,the contrastive analysis results of bushing with and without glass melt were discussed.The simulation results show that,when the homogeneous glass melt flows through bushing,the temperature difference between the center and both ends of bushing is decreased significantly,but the temperature distribution at both ends of bushing is still affected by heating non-uniformity of bushing.Compared with side wall thickness,plug thickness and the angle of two side walls,electrode structure plays a greater role in adjusting heating uniformity of bushing.展开更多
AISn8Pb2Si25Cu0.8Cr0.2(ASP) is a new bush material with high performance, but its bad plasticity limits itsapplication. By studying the effect of silicon content on the performance of this bush material, it was found ...AISn8Pb2Si25Cu0.8Cr0.2(ASP) is a new bush material with high performance, but its bad plasticity limits itsapplication. By studying the effect of silicon content on the performance of this bush material, it was found that the alloyperformance and the distribution of tin and lead were affected by the silicon content. When the silicon content was 2.5%,most of the silicon precipitated along the grain boundary, and most of the lead and tin located along the grain boundarycontinuously, this resulted in the decrease of the bush material’s performance. When the silicon content decreased to 1.0%,it distributed more uniformly, the tin and lead phases were spheroidized and became discontinuous, the performance ofASP material was then greatly increased.展开更多
In this paper,glass fibers were prepared by centrifugal-spinneret-blow(CSB) process.The molten glass got different flow rate from 390 kg/h to 270 kg/h by adjusting the electric current of platinum/10 rhodium alloy bus...In this paper,glass fibers were prepared by centrifugal-spinneret-blow(CSB) process.The molten glass got different flow rate from 390 kg/h to 270 kg/h by adjusting the electric current of platinum/10 rhodium alloy bushing.The diameter and microstructure of glass fibers have been investigated by scanning electron microscopy(SEM) and vertical optical microscope(VOM).The results indicated that the flow rate of molten glass was proportional to the diameter of glass fibers when the molten glass got main flow rate of 330 kg/h.The lower the flow rate was,the finer the average diameter was.展开更多
A design of a slot bushing with a volumetric field has been developed, which allows to produce continuous fibers from melts with difficult processing characteristics in order to produce fibers with better operating ch...A design of a slot bushing with a volumetric field has been developed, which allows to produce continuous fibers from melts with difficult processing characteristics in order to produce fibers with better operating characteristics. The operability of the design was confirmed when solving two problems of special technological complexity. 1. 400 and 800 orifice bushings for production of continuous fibers from the basalt melt have been developed and recommended for manufacture. 2. The process of production of continuous fibers from standard glass using 2400 orifice bushing with perforated plates instead of orifice tips without air cooling, has been realized for the first time.展开更多
Exploitation of equipment with cross linked polyethylene (XLPE ) insulation requires its condition monitoring and diagnostic. Traditionally diagnostics of insulation is carried out by means of partial discharge detect...Exploitation of equipment with cross linked polyethylene (XLPE ) insulation requires its condition monitoring and diagnostic. Traditionally diagnostics of insulation is carried out by means of partial discharge detection. However, such identification of a defect, for example, void, inclusion or treeing, does not say about its danger from a point of view of full insulation gap breakdown and insulation construction failure. For this purpose a 29 kV CN-CV cable sample is studied. The experiment is based on research for determination of the dependencies between PD characteristics in XLPE upon time and three dimension PD patterns of corresponding treeing. The investigations were carried out by means of electrical measurement of PD current and simultaneous optical recording of treeing image. The needleplane electrode is applied as the electrode. As a result, -q-n PD patterns which are used as the bases to bush tree initialization and growth can be obtained. Test results show that PD pattern recognition can be applied as a powerful tool for recognizing electrical tree initialization and growth. This can make a good basis for on-line condition monitoring of high voltage power cable.展开更多
Background: Soft song is a low-amplitude song produced by many birds. Recent studies have confirmed that soft song is an aggressive signal. For example, the Brownish-flanked Bush Warblers Cettia fortipes use soft song...Background: Soft song is a low-amplitude song produced by many birds. Recent studies have confirmed that soft song is an aggressive signal. For example, the Brownish-flanked Bush Warblers Cettia fortipes use soft song in male-male conflicts, particularly prior to attacks. Although stable signaling systems require that signals be honest on average,models predict that cheating is an acceptable strategy for some individuals or in some contexts.Methods: This study aimed to test the reliability of soft song as an aggressive signal in the brownish-flanked bush warbler. We used mounted specimens accompanied by broadcast songs or soft songs to simulate a male attempting to invade an existing territory.Results: We found the mounted specimen that coupled playback of soft songs suffered more and quicker attacks from the territory owner and that the relationship between soft song and subsequent attack in the territory owner was far from perfect. We observed territory owners that both over-signaled(i.e., produced soft song but did not attack) and under-signaled(i.e., attacked without producing soft song). Under-signaling territory owners were relatively more commonly than were over-signaling territory owners, particularly in simulated intrusion that coupled playback of soft song with a mount specimen.Conclusions: We discuss the cost of producing soft song and the potential benefit of the unreliable use of soft song and propose a new hypothesis for under-signaling with soft song; i.e., under-signaling territory owners might benefit from taking the initiative in fights.展开更多
In recent years, the deficiencies of ceramic insulators along with their high maintenance costs have resulted in the replacement of ceramic insulators with silicon type in the pollution area. This idea has been employ...In recent years, the deficiencies of ceramic insulators along with their high maintenance costs have resulted in the replacement of ceramic insulators with silicon type in the pollution area. This idea has been employed for more than two decades in the polluted areas. Humidity of the weather in the south of Iran and the presence of pollutants in the air have made special conditions for construction and maintenance of some equipment including transformer bushings. Usual ceramic bushings, due to their ability in absorbing pollution and the rapid reduction of creepage distance (in a limited time period), have reduced transformer disconnection severely as a result of earth fault. Additionally, they are costly to be washed regularly. Therefore, using intelligent materials in designing bushing can increase the reliability of network and consequently reduction of costs. In this regard, this paper investigates the use of silicon bushings in the distribution systems and proposes operational ideas for the optimal operation of these devices in the polluted areas. The sample bushing was evaluated based on the IEC60137 standard test.展开更多
基金National Natural Science Foundation of China under Grant No.51878508。
文摘Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.
文摘Calotropis procera(Aiton)W.T.Aiton,belonging to the family Apocynaceae,is C3 evergreen plant species in arid and semi-arid areas of the Punjab Province,Pakistan.It grows in a variety of habitats like salt affected and waterlogged area,desert/semi-desert,roadside,wasteland,graveyard,forest,crop field,coastline,and river/canal bank.A total of 12 populations growing in different ecological regions were sampled to evaluate their growth,physio-biochemical,and anatomical responses to specific environmental condition.Population adapted to desert/semi-desert showed vigorous growth(plant height,shoot length,and number of leaves),enhanced photosynthetic level(chlorophyll a,chlorophyll b,carotenoids,and total chlorophyll),and apparent anatomical modifications such as increased stem radius,cuticle thickness,storage parenchyma tissues(cortex and pith),and vascular bundles in stems,while the maximum of midrib and lamina thickness,epidermal cells,cuticle thickness,cortical proportion,abaxial stomatal density,and its area in leaves.There was high plasticity in structural and functional features of these populations,which enable them to survive and tolerate under such hot and dry desert environment.Population of saline areas exhibited very critical modifications to sustain under salt prone environment.At physiological level,it possesses the maximum amount of organic osmolytes(glycine betaine and proline)and antioxidants(superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)),while at anatomical level,it showed intensive sclerification,large phloem region(inner and outer),pith parenchyma cells,and metaxylem vessels in stems and leaves.The population of dry mountains showed very distinctive features,such as increased shoot ionic contents(K+and Ca2+),collenchyma and sclerenchyma thickness in stems,trichomes size,and numerous small stomata on abaxial surface of leaves.It is concluded that no definite or precise single character can be taken as a yardstick for adjudging the biomass production in this rubber bush weed population.
基金Supported by the National Natural Science Foundation of China(No.52101343)the Aeronautical Science Foundation(No.201834S9002).
文摘The failure rate of crankpin bearing bush of diesel engine under complex working conditions such as high temperature,dynamic load and variable speed is high.After serious wear,it is easy to deteriorate the stress state of connecting rod body and connecting rod bolt,resulting in serious accidents such as connecting rod fracture and body damage.Based on the mixed lubrication characteristics of connecting rod big endbearing shell of diesel engine under high explosion pressure impact load,an improved mixed lubrication mechanism model is established,which considers the influence of viscoelastic micro deformation of bearing bush material,integrates the full film lubrication model and dry friction model,couples dynamic equation of connecting rod.Then the actual lubrication state of big end bearing shell is simulated numerically.Further,the correctness of the theoretical research results is verified by fault simulation experiments.The results show that the high-frequency impact signal with fixed angle domain characteristics will be generated after the serious wear of bearing bush and the deterioration of lubrication state.The fault feature capture and alarm can be realized through the condition monitoring system,which can be applied to the fault monitoring of connecting rod bearing bush of diesel engine in the future.
基金Project(2012011023-2)supported by the Natural Science Foundation of Shanxi Province,China
文摘The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carried out.Based on the experimental data,a ternary quadratic regression equation was established by orthogonal experiment.The Ramberg-Osgood constitutive model of tin-bronze connecting rod bushing was obtained.Referred to the constitutive relation of macroscopic incremental,the incremental elastoplastic constitutive relation of spinning parts was deduced based on the Mises yield criterion and kinematic hardening model.The results can be applied to the elastoplastic analysis in finite element numerical simulation.
基金National Science Foundation of China Yunnan United Foundation.(U0837601)the Natural Science Foundation of Yunnan Province,China(2010CF126)
文摘Design and optimization of bushing at present mainly use the traditional experience method.The relevant research that adopts computer simulation to carry on the operation behavior of the bushing has appeared in recent years.How to use the finite element method to research bushing was introduced in the article.Physics fields and many relevant parameters of one real bushing were calculated.Through the results of calculation,it indicate that the finite element method is very useful in bushing research of designing and optimizing.
文摘Presents the study on the pressure and friction fields of the lubricant film on the surface of a large thrust elastic metal plastic bearing bush in a hydraulic turbine using the method of finite element analysis and the stress and displacement fields in the vertical direction of the bush surface obtained to provide a theoretical basis for the design of contour lines and investigation into the causes for destruction of bushes, and concludes with test results that 1) the stress on the surface of the bush is not uniform; 2) a tension stress tends to occur near the oil ingress and egress edges but it is minor; 3) the biggest displacement in the vertical direction appears where x=84 and Y=1 153 and has a value of 0.022 mm; 4) the deformation of the bearing bush is harmful to the maintenance of lubricant film.
基金The Scientific Innovation Research of Graduate Students in Jiangsu Province(No.KYLX16-0186)the National Science and Technology M ajor Project(No.2013ZX04012032)
文摘In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radial stiffness coefficient. The obtained theoretical result is consistent with previous research results in both long rubber bushes and short rubber bushes. The simulation case was conducted by the finite element method to verify the correctness of the theory. The axial compression experiment was conducted to obtain the parameters needed in the simulation. The result shows that the percentage difference between the theoretical result and the simulation one is only 2.75%. A series of simulations were conducted to compare with previous work, and the largest magnitude of the percentage difference is only about 5%. Finally, the radial stiffness experiment was conducted by using a dynamic vibration absorber, and the influence of the structural parameters of the rubber bush on its radial stiffness is obtained. The result shows that the radial stiffness of the rubber bush increases with the increase in the length and the inner radius, but decreases with the increase in the outer radius.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51305242)the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents(Grant No.2013RCJJ014)
文摘The temperature of bush inner surface temperature is measured by using infrared thermometer and transparent bearing,and temperature rise is measured by using thermocouple. The influence of rotating speed and axial location on the bush inner surface temperature is studied,and the influence of supply pressure and rotating speed on the temperature rise is analyzed. The results show the bush inner surface temperature and temperature rise of spiral oil wedge hydrodynamic bearing increase with the increase of rotation speed. In axial direction,the temperature is higher around the oil return hole. The temperature rise decreases with the increase of supply pressure. The highest temperature of bush inner surface and temperature rise are higher at higher speed,so the temperature rise is the fundamental reason which restricts the increase of rotation speed for high speed sleeve bearing.
基金Funded by the State Key Laboratory of Silicate Materials for Architectures(Wuhan University of Technology)(No.SYSJJ2019-21)the National Key Research and Development Program of China(No.2016YFB0303700)。
文摘The numerical simulation for temperature distribution of Pt-Rh alloy bushing was carried out using a thermal-electric module in ANSYS Workbench finite element analysis software.The effects of side wall thickness,plug thickness,the angle of two side walls and electrode structure on the uniformity of temperature distribution were investigated.Meanwhile,the contrastive analysis results of bushing with and without glass melt were discussed.The simulation results show that,when the homogeneous glass melt flows through bushing,the temperature difference between the center and both ends of bushing is decreased significantly,but the temperature distribution at both ends of bushing is still affected by heating non-uniformity of bushing.Compared with side wall thickness,plug thickness and the angle of two side walls,electrode structure plays a greater role in adjusting heating uniformity of bushing.
文摘AISn8Pb2Si25Cu0.8Cr0.2(ASP) is a new bush material with high performance, but its bad plasticity limits itsapplication. By studying the effect of silicon content on the performance of this bush material, it was found that the alloyperformance and the distribution of tin and lead were affected by the silicon content. When the silicon content was 2.5%,most of the silicon precipitated along the grain boundary, and most of the lead and tin located along the grain boundarycontinuously, this resulted in the decrease of the bush material’s performance. When the silicon content decreased to 1.0%,it distributed more uniformly, the tin and lead phases were spheroidized and became discontinuous, the performance ofASP material was then greatly increased.
文摘In this paper,glass fibers were prepared by centrifugal-spinneret-blow(CSB) process.The molten glass got different flow rate from 390 kg/h to 270 kg/h by adjusting the electric current of platinum/10 rhodium alloy bushing.The diameter and microstructure of glass fibers have been investigated by scanning electron microscopy(SEM) and vertical optical microscope(VOM).The results indicated that the flow rate of molten glass was proportional to the diameter of glass fibers when the molten glass got main flow rate of 330 kg/h.The lower the flow rate was,the finer the average diameter was.
文摘A design of a slot bushing with a volumetric field has been developed, which allows to produce continuous fibers from melts with difficult processing characteristics in order to produce fibers with better operating characteristics. The operability of the design was confirmed when solving two problems of special technological complexity. 1. 400 and 800 orifice bushings for production of continuous fibers from the basalt melt have been developed and recommended for manufacture. 2. The process of production of continuous fibers from standard glass using 2400 orifice bushing with perforated plates instead of orifice tips without air cooling, has been realized for the first time.
基金The project supported by the Science and Engineering Reserch Fund of Southwest JiaotongUniversity(1999 XM02) and the Startup F
文摘Exploitation of equipment with cross linked polyethylene (XLPE ) insulation requires its condition monitoring and diagnostic. Traditionally diagnostics of insulation is carried out by means of partial discharge detection. However, such identification of a defect, for example, void, inclusion or treeing, does not say about its danger from a point of view of full insulation gap breakdown and insulation construction failure. For this purpose a 29 kV CN-CV cable sample is studied. The experiment is based on research for determination of the dependencies between PD characteristics in XLPE upon time and three dimension PD patterns of corresponding treeing. The investigations were carried out by means of electrical measurement of PD current and simultaneous optical recording of treeing image. The needleplane electrode is applied as the electrode. As a result, -q-n PD patterns which are used as the bases to bush tree initialization and growth can be obtained. Test results show that PD pattern recognition can be applied as a powerful tool for recognizing electrical tree initialization and growth. This can make a good basis for on-line condition monitoring of high voltage power cable.
基金supported by National Natural Science Foundation of China (No.31172098)the China Postdoctoral Science Foundation (No.2014 M550026)
文摘Background: Soft song is a low-amplitude song produced by many birds. Recent studies have confirmed that soft song is an aggressive signal. For example, the Brownish-flanked Bush Warblers Cettia fortipes use soft song in male-male conflicts, particularly prior to attacks. Although stable signaling systems require that signals be honest on average,models predict that cheating is an acceptable strategy for some individuals or in some contexts.Methods: This study aimed to test the reliability of soft song as an aggressive signal in the brownish-flanked bush warbler. We used mounted specimens accompanied by broadcast songs or soft songs to simulate a male attempting to invade an existing territory.Results: We found the mounted specimen that coupled playback of soft songs suffered more and quicker attacks from the territory owner and that the relationship between soft song and subsequent attack in the territory owner was far from perfect. We observed territory owners that both over-signaled(i.e., produced soft song but did not attack) and under-signaled(i.e., attacked without producing soft song). Under-signaling territory owners were relatively more commonly than were over-signaling territory owners, particularly in simulated intrusion that coupled playback of soft song with a mount specimen.Conclusions: We discuss the cost of producing soft song and the potential benefit of the unreliable use of soft song and propose a new hypothesis for under-signaling with soft song; i.e., under-signaling territory owners might benefit from taking the initiative in fights.
文摘In recent years, the deficiencies of ceramic insulators along with their high maintenance costs have resulted in the replacement of ceramic insulators with silicon type in the pollution area. This idea has been employed for more than two decades in the polluted areas. Humidity of the weather in the south of Iran and the presence of pollutants in the air have made special conditions for construction and maintenance of some equipment including transformer bushings. Usual ceramic bushings, due to their ability in absorbing pollution and the rapid reduction of creepage distance (in a limited time period), have reduced transformer disconnection severely as a result of earth fault. Additionally, they are costly to be washed regularly. Therefore, using intelligent materials in designing bushing can increase the reliability of network and consequently reduction of costs. In this regard, this paper investigates the use of silicon bushings in the distribution systems and proposes operational ideas for the optimal operation of these devices in the polluted areas. The sample bushing was evaluated based on the IEC60137 standard test.
