There is nonradiative recombination in waveguide region owing to severe carrier leakage,which in turn reduces output power and wall-plug efficiency.In this paper,we designed a novel epitaxial structure,which suppresse...There is nonradiative recombination in waveguide region owing to severe carrier leakage,which in turn reduces output power and wall-plug efficiency.In this paper,we designed a novel epitaxial structure,which suppresses carrier leakage by inserting n-Ga_(0.55)In_(0.45)P and p-GaAs_(0.6)P_(0.4) between barriers and waveguide layers,respectively,to modulate the energy band structure and to increase the height of barrier.The results show that the leakage current density reduces by 87.71%,compared to traditional structure.The nonradiative recombination current density of novel structure reduces to 37.411 A/cm^(2),and the output power reaches 12.80 W with wall-plug efficiency of 78.24%at an injection current density 5 A/cm^(2) at room temperature.In addition,the temperature drift coefficient of center wavelength is 0.206 nm/℃at the temperature range from 5℃to 65℃,and the slope of fitted straight line of threshold current with temperature variation is 0.00113.The novel epitaxial structure provides a theoretical basis for achieving high-power laser diode.展开更多
The calculation model was established by k-ε turbulence stress which reflects the change of indoor gas leak's volume fraction,and the CFD software was used to numerically simulate the volume fraction of gas after...The calculation model was established by k-ε turbulence stress which reflects the change of indoor gas leak's volume fraction,and the CFD software was used to numerically simulate the volume fraction of gas after the gas of continuity leakage,at the same time the changes of gas leak were studied. The results show that the process of gas leakage is different with the change of conditions of indoor and outdoor. Because of the different influencing factors,when the gas leak reaches a certain stable value,the volume fraction,velocity and the explosion of regional are different in the same state indoor. In some regions the gas will explode which meets the fire even if the mean volume fraction of the gas cannot achieve the explosion limit.展开更多
The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null positio...The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null position,thereby affecting high-precision control and stability of the servo system.This paper investigates the effects of the clearance structure on leakage behavior at null position of the HESV.A numerical approach was employed to evaluate the effects,and then a mathematical model was established to obtain the variation law of leakage flow rate at null position.The results indicate that the leakage flow rate at null position varies linearly with supply pressure and rounded corner radius,and is nonlinear as a quadratic concave function with annular clearance.The leakage flow rate of the annular clearance and the rounded corner varies with the valve opening in an invariable−nonlinear−linear trend.A test rig system of leakage behavior at null position of the HESV was built to confirm the validity of the numerical model,which agrees well with the conducted experimental study.展开更多
For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic...For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic theory of leakage detection and location was introduced. Then the physical relationship between instantaneous energy and structural state variation of a system was analyzed theoretically. With HILBERT-HUANG transformation (HHT), the instantaneous energy distribution feature of an unstable acoustic signal was obtained. According to the relative contribution method of the instantaneous energy, the noise in signal was eliminated effectively. Furthermore, in order to judge the leakage, the typical characteristic of the instantaneous energy of signal in the input and output end was discussed using correlative analysis. A number of experiments were carried out to classify the leakage from normal operations, and the results show that the leakages are successfully detected and the average recognition rate reaches 93.3% among three group samples. It is shown that the method using acoustic technique with IED and correlative analysis is effective and it may be referred in other pipelines.展开更多
In the leakage current test, through the high speed data collection and digital filtering to the output voltage of the human body impedance network, leakage current test that is in accordance with many kinds of electr...In the leakage current test, through the high speed data collection and digital filtering to the output voltage of the human body impedance network, leakage current test that is in accordance with many kinds of electrical safety standards can be realized, and the frequency distribution information of the leakage current can be got as well, which can be used to much more completely evaluate the possible damage degree of the leakage current to the human body and analyze the reason for the appearance of the leakage current in the electric equipment.展开更多
The tire blowout or severe leakage real-time monitoring is one of key technologies for developing a tire blowout automatic braking system.An indirect real-time monitoring method to fuse analyses of tire vibration and ...The tire blowout or severe leakage real-time monitoring is one of key technologies for developing a tire blowout automatic braking system.An indirect real-time monitoring method to fuse analyses of tire vibration and effective radius is provided in this paper,and a monitoring system is developed.The calibration and related test results showthat the system can detect the tire blowout in low and middle vehicle speeds and the severe leakage in all speeds timely and accurately.展开更多
The belief rule-based(BRB)system has been popular in complexity system modeling due to its good interpretability.However,the current mainstream optimization methods of the BRB systems only focus on modeling accuracy b...The belief rule-based(BRB)system has been popular in complexity system modeling due to its good interpretability.However,the current mainstream optimization methods of the BRB systems only focus on modeling accuracy but ignore the interpretability.The single-objective optimization strategy has been applied in the interpretability-accuracy trade-off by inte-grating accuracy and interpretability into an optimization objec-tive.But the integration has a greater impact on optimization results with strong subjectivity.Thus,a multi-objective optimiza-tion framework in the modeling of BRB systems with inter-pretability-accuracy trade-off is proposed in this paper.Firstly,complexity and accuracy are taken as two independent opti-mization goals,and uniformity as a constraint to give the mathe-matical description.Secondly,a classical multi-objective opti-mization algorithm,nondominated sorting genetic algorithm II(NSGA-II),is utilized as an optimization tool to give a set of BRB systems with different accuracy and complexity.Finally,a pipeline leakage detection case is studied to verify the feasibility and effectiveness of the developed multi-objective optimization.The comparison illustrates that the proposed multi-objective optimization framework can effectively avoid the subjectivity of single-objective optimization,and has capability of joint optimiz-ing the structure and parameters of BRB systems with inter-pretability-accuracy trade-off.展开更多
Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspens...Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.展开更多
In order to investigate the physical mechanism of metal magnetic memory testing, both the influences of earth magnetic field and applied stress on magnetic domain structure were discussed. Static tension and fatigue t...In order to investigate the physical mechanism of metal magnetic memory testing, both the influences of earth magnetic field and applied stress on magnetic domain structure were discussed. Static tension and fatigue tests for low carbon steel plate specimens were carried out on hydraulic servo testing machine of MTS810 type and magnetic signals were measured during the processes by the type of EMS-2003 instrument. The results indicate that the initial magnetic signals of specimens are different before loading. The magnetic signals curves are transformed from initial random to regular pattern due to the effect of two types of loads. However, the shape and distribution of magnetic signal curves in the elastic region are different from that of plastic region in tension test. While in fatigue test those magnetic signals curves corresponding to different cycles are similar. The H_p(y) value of magnetic signals on the fracture zone increases dramatically at the breaking transient time and positive-negative magnetic poles occur on the two parts of fracture zone.展开更多
The anti——icing and de·-icing methods of insulator strings are still under laboratory studies while many technologies are applied in operation to overhead conductors.The anti—icing method using semiconducting ...The anti——icing and de·-icing methods of insulator strings are still under laboratory studies while many technologies are applied in operation to overhead conductors.The anti—icing method using semiconducting silicone rubber coating applied to the bottom side of the insulators could get good results in a climate chamber.However,the resistance of the coating is an important factor influencing the anti—icing performance of the coated insulators.Thus the coating resistance should be determined.展开更多
Background Cotton(Gossypium hirsutum L.),adapted to tropical and subtropical regions of the world,is highly sensitive to low temperatures throughout its life cycle.The objective of this study was to evaluate the mitig...Background Cotton(Gossypium hirsutum L.),adapted to tropical and subtropical regions of the world,is highly sensitive to low temperatures throughout its life cycle.The objective of this study was to evaluate the mitigating effects of different doses of animal-derived(0.25%,0.50%,and 1.00% Isabion■),seaweed-based(0.165%,0.330%,and 0.660% Proton■)biostimulants,as well as a copper(Cu)-containing fungicide application,on cotton cultivar Lazer seedlings at the four true leaves(V4)stage.The plants were exposed to a low temperature of 5℃for 48 h,and the changes in morphological(seedling fresh and dry weight,plant height,and stem diameter)and physiological parameters(leaf temperature,chlorophyll content,relative water content,electrolyte leakage,and relative injury)were examined.Results The results revealed that chilling stress reduced plant growth,while biostimulants helped protect the plants and overcome the adverse effects of chilling.Under chilling stress,there was a considerable reduction in seedling fresh weight(SFW),seedling dry weight(SDW),plant height(PH),stem diameter(SD),leaf temperature(LT),and relative water content(RWC).Cotton seedlings treated with the animal-derived biostimulants showed significantly enhanced SFW,SDW,PH,SD,LT,chlorophyll content(Chl),electrolyte leakage(EL),and relative injury(RI),although there were no positive changes in RWC.No significant differences in the morphological traits were observed among the doses of seaweed biostimulants.For SDW,PH,EL,and RI,the best results were obtained with the application of a fungicide containing copper.Conclusion These results show the efficiency of the biostimulant and fungicide treatments in mitigating low-temperature stress in cotton seedlings.Applying a copper-containing fungicide to cotton seedlings helped to counteract the negative effects of low-temperature stress and to protect the plants from damage by maintaining electrolyte balance.Among the biostimulant applications,all levels of animal-derived biostimulant applications,as well as the 0.660% level of the seaweed-derived biostimulant,led to increased tolerance of cotton plants to chilling stress.展开更多
文摘There is nonradiative recombination in waveguide region owing to severe carrier leakage,which in turn reduces output power and wall-plug efficiency.In this paper,we designed a novel epitaxial structure,which suppresses carrier leakage by inserting n-Ga_(0.55)In_(0.45)P and p-GaAs_(0.6)P_(0.4) between barriers and waveguide layers,respectively,to modulate the energy band structure and to increase the height of barrier.The results show that the leakage current density reduces by 87.71%,compared to traditional structure.The nonradiative recombination current density of novel structure reduces to 37.411 A/cm^(2),and the output power reaches 12.80 W with wall-plug efficiency of 78.24%at an injection current density 5 A/cm^(2) at room temperature.In addition,the temperature drift coefficient of center wavelength is 0.206 nm/℃at the temperature range from 5℃to 65℃,and the slope of fitted straight line of threshold current with temperature variation is 0.00113.The novel epitaxial structure provides a theoretical basis for achieving high-power laser diode.
基金Supported by the National Natural Science Foundation of China(11371368,11071254,61305076)the Natural Science Foundation of Hebei Province of China(A2014506015)
基金Projects(50704041, 50838009, 50678179) supported by the National Natural Science Foundation of ChinaProjects(2006BAJ02A09, 2006BAJ02A13-4) supported by the National Key Technologies R & D Program of China+1 种基金Project(CSTC2008BB6347) supported by the Natural Science Foundation Project of ChongqingProject(20080430752) supported by the Postdoctoral Science Foundation of China
文摘The calculation model was established by k-ε turbulence stress which reflects the change of indoor gas leak's volume fraction,and the CFD software was used to numerically simulate the volume fraction of gas after the gas of continuity leakage,at the same time the changes of gas leak were studied. The results show that the process of gas leakage is different with the change of conditions of indoor and outdoor. Because of the different influencing factors,when the gas leak reaches a certain stable value,the volume fraction,velocity and the explosion of regional are different in the same state indoor. In some regions the gas will explode which meets the fire even if the mean volume fraction of the gas cannot achieve the explosion limit.
基金Project(51705164)supported by the National Natural Science Foundation of China。
文摘The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null position,thereby affecting high-precision control and stability of the servo system.This paper investigates the effects of the clearance structure on leakage behavior at null position of the HESV.A numerical approach was employed to evaluate the effects,and then a mathematical model was established to obtain the variation law of leakage flow rate at null position.The results indicate that the leakage flow rate at null position varies linearly with supply pressure and rounded corner radius,and is nonlinear as a quadratic concave function with annular clearance.The leakage flow rate of the annular clearance and the rounded corner varies with the valve opening in an invariable−nonlinear−linear trend.A test rig system of leakage behavior at null position of the HESV was built to confirm the validity of the numerical model,which agrees well with the conducted experimental study.
基金Project(51004005) supported by the National Natural Science Foundation of ChinaProject supported by Open Research Fund Program of Beijing Engineering Research Center of Monitoring for Construction Safety (Beijing University of Civil Engineering and Architecture), China
文摘For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic theory of leakage detection and location was introduced. Then the physical relationship between instantaneous energy and structural state variation of a system was analyzed theoretically. With HILBERT-HUANG transformation (HHT), the instantaneous energy distribution feature of an unstable acoustic signal was obtained. According to the relative contribution method of the instantaneous energy, the noise in signal was eliminated effectively. Furthermore, in order to judge the leakage, the typical characteristic of the instantaneous energy of signal in the input and output end was discussed using correlative analysis. A number of experiments were carried out to classify the leakage from normal operations, and the results show that the leakages are successfully detected and the average recognition rate reaches 93.3% among three group samples. It is shown that the method using acoustic technique with IED and correlative analysis is effective and it may be referred in other pipelines.
文摘In the leakage current test, through the high speed data collection and digital filtering to the output voltage of the human body impedance network, leakage current test that is in accordance with many kinds of electrical safety standards can be realized, and the frequency distribution information of the leakage current can be got as well, which can be used to much more completely evaluate the possible damage degree of the leakage current to the human body and analyze the reason for the appearance of the leakage current in the electric equipment.
基金Sponsored by the Applied Foundation Research Project of Suzhou(SYFG0932)
文摘The tire blowout or severe leakage real-time monitoring is one of key technologies for developing a tire blowout automatic braking system.An indirect real-time monitoring method to fuse analyses of tire vibration and effective radius is provided in this paper,and a monitoring system is developed.The calibration and related test results showthat the system can detect the tire blowout in low and middle vehicle speeds and the severe leakage in all speeds timely and accurately.
基金supported by the National Natural Science Foundation of China(71901212)the Science and Technology Innovation Program of Hunan Province(2020RC4046).
文摘The belief rule-based(BRB)system has been popular in complexity system modeling due to its good interpretability.However,the current mainstream optimization methods of the BRB systems only focus on modeling accuracy but ignore the interpretability.The single-objective optimization strategy has been applied in the interpretability-accuracy trade-off by inte-grating accuracy and interpretability into an optimization objec-tive.But the integration has a greater impact on optimization results with strong subjectivity.Thus,a multi-objective optimiza-tion framework in the modeling of BRB systems with inter-pretability-accuracy trade-off is proposed in this paper.Firstly,complexity and accuracy are taken as two independent opti-mization goals,and uniformity as a constraint to give the mathe-matical description.Secondly,a classical multi-objective opti-mization algorithm,nondominated sorting genetic algorithm II(NSGA-II),is utilized as an optimization tool to give a set of BRB systems with different accuracy and complexity.Finally,a pipeline leakage detection case is studied to verify the feasibility and effectiveness of the developed multi-objective optimization.The comparison illustrates that the proposed multi-objective optimization framework can effectively avoid the subjectivity of single-objective optimization,and has capability of joint optimiz-ing the structure and parameters of BRB systems with inter-pretability-accuracy trade-off.
文摘Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.
文摘In order to investigate the physical mechanism of metal magnetic memory testing, both the influences of earth magnetic field and applied stress on magnetic domain structure were discussed. Static tension and fatigue tests for low carbon steel plate specimens were carried out on hydraulic servo testing machine of MTS810 type and magnetic signals were measured during the processes by the type of EMS-2003 instrument. The results indicate that the initial magnetic signals of specimens are different before loading. The magnetic signals curves are transformed from initial random to regular pattern due to the effect of two types of loads. However, the shape and distribution of magnetic signal curves in the elastic region are different from that of plastic region in tension test. While in fatigue test those magnetic signals curves corresponding to different cycles are similar. The H_p(y) value of magnetic signals on the fracture zone increases dramatically at the breaking transient time and positive-negative magnetic poles occur on the two parts of fracture zone.
文摘The anti——icing and de·-icing methods of insulator strings are still under laboratory studies while many technologies are applied in operation to overhead conductors.The anti—icing method using semiconducting silicone rubber coating applied to the bottom side of the insulators could get good results in a climate chamber.However,the resistance of the coating is an important factor influencing the anti—icing performance of the coated insulators.Thus the coating resistance should be determined.
文摘Background Cotton(Gossypium hirsutum L.),adapted to tropical and subtropical regions of the world,is highly sensitive to low temperatures throughout its life cycle.The objective of this study was to evaluate the mitigating effects of different doses of animal-derived(0.25%,0.50%,and 1.00% Isabion■),seaweed-based(0.165%,0.330%,and 0.660% Proton■)biostimulants,as well as a copper(Cu)-containing fungicide application,on cotton cultivar Lazer seedlings at the four true leaves(V4)stage.The plants were exposed to a low temperature of 5℃for 48 h,and the changes in morphological(seedling fresh and dry weight,plant height,and stem diameter)and physiological parameters(leaf temperature,chlorophyll content,relative water content,electrolyte leakage,and relative injury)were examined.Results The results revealed that chilling stress reduced plant growth,while biostimulants helped protect the plants and overcome the adverse effects of chilling.Under chilling stress,there was a considerable reduction in seedling fresh weight(SFW),seedling dry weight(SDW),plant height(PH),stem diameter(SD),leaf temperature(LT),and relative water content(RWC).Cotton seedlings treated with the animal-derived biostimulants showed significantly enhanced SFW,SDW,PH,SD,LT,chlorophyll content(Chl),electrolyte leakage(EL),and relative injury(RI),although there were no positive changes in RWC.No significant differences in the morphological traits were observed among the doses of seaweed biostimulants.For SDW,PH,EL,and RI,the best results were obtained with the application of a fungicide containing copper.Conclusion These results show the efficiency of the biostimulant and fungicide treatments in mitigating low-temperature stress in cotton seedlings.Applying a copper-containing fungicide to cotton seedlings helped to counteract the negative effects of low-temperature stress and to protect the plants from damage by maintaining electrolyte balance.Among the biostimulant applications,all levels of animal-derived biostimulant applications,as well as the 0.660% level of the seaweed-derived biostimulant,led to increased tolerance of cotton plants to chilling stress.
