In this paper, two-dimensional （2D） transient simulations of an A1GaN/GaN high-electron-mobility transistor （HEMT） are carded out and analyzed to investigate the current collapse due to trapping effects. The coupl...In this paper, two-dimensional （2D） transient simulations of an A1GaN/GaN high-electron-mobility transistor （HEMT） are carded out and analyzed to investigate the current collapse due to trapping effects. The coupling effect of the trapping and thermal effects are taken into account in our simulation. The turn-on pulse gate-lag transient responses with different quiescent biases are obtained, and the pulsed current-voltage （l-V） curves are extracted from the transients. The experimental results of both gate-lag transient current and pulsed I-V curves are reproduced by the simulation, and the current collapse due to the trapping effect is explained from the view of physics based on the simulation results. In addition, the results show that bulk acceptor traps can influence the gate-lag transient characteristics of A1GaN/GaN HEMTs besides surface traps and that the thermal effect can accelerate the emission of captured electrons for traps. Pulse transient simulation is meaningful in analyzing the mechanism of dynamic current collapse, and the work in this paper will benefit the reliability study and model development of GaN-based devices.展开更多
Five different trapping treatments, spraying attractant on bottle surface and spraying attractant inside the bottles with 0, 50,100 and 200 mL water, were set to trap Bactrocera dorsalis and B. cucurbitae in guava （P...Five different trapping treatments, spraying attractant on bottle surface and spraying attractant inside the bottles with 0, 50,100 and 200 mL water, were set to trap Bactrocera dorsalis and B. cucurbitae in guava （Psidium guajava） park. The results showed that when the usage of attractant was 1 g, both Haonian and Wende had trapping effect on B. dorsalis and B. cucurbitae. The trapping effect of Haonian on B. dorsalis was better than that of Wende, while their trapping effects on B. cucurbitae was just the opposite. The trapping effects of different treatments had great difference. The trapping effect of Haonian on two species of fruit flies enhanced with the increasing volume of water, and reached the ma^mum value as the water volume was 200 mL. With the increasing volume of water, the trap- ping effect of Wende on two species of fruit flies first increased, and then decreased, which reached the maximum value as the water volume was 50 mL. Different treatments with attractants spraying inside bottles had better trapping effects on two species of fruit flies than that spraying on bottle surface.展开更多
The key application technology for sex pheromone of Grapholitha molesta was studied from the aspects of different hanging heights and orientations, dif- ferent doses and types of traps through the tests on trapping qu...The key application technology for sex pheromone of Grapholitha molesta was studied from the aspects of different hanging heights and orientations, dif- ferent doses and types of traps through the tests on trapping quantity of G. molesta in fields. The results showed that the trapping effect was enhanced when the hanging height was increased, and the trapping effect was the best in west direction. The trapping effect was enhanced when the dosage was increased. When it was up to 6 lures, the trapping effect was the best with 38.75 head/trap; the next was 2 lures with 31.00 head/trap. All types of traps had trapping ability to G. mo- lesta, among which triangle trapper was the best, followed by self-made bottle trap. Their trapping effects were 138.75 and 100.25 head/trap, respectively.展开更多
Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes dev...Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.展开更多
Trivalent rare-earth ions （La3＋,Pr3＋,Nd3＋,Sm3＋,Gd3＋,Tb3＋,Dy3＋,Ho3＋,Er3＋,Tm3＋,and Yb3＋） were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS：Eu2＋ in order to enha...Trivalent rare-earth ions （La3＋,Pr3＋,Nd3＋,Sm3＋,Gd3＋,Tb3＋,Dy3＋,Ho3＋,Er3＋,Tm3＋,and Yb3＋） were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS：Eu2＋ in order to enhance the fluorescence properties.It was found that Sm3＋ and Tb3＋ had the best photoluminescence stimulated luminescence （PSL） effect among the selected trivalent rare-earth ions.All the SrS：Eu2＋ samples doped by different trivalent rare-earth ions could be stimulated by 980 nm laser after being exposed to the conventional sunlight,and they emitted PSL with the peak located at 615 nm.The result also indicated that some co-doped rare earth ions could increase fluorescence intensities of the traditional electron trapping materials SrS：Eu2＋.展开更多
The trapping effects of yellow, blue, green, cyan and white sticky traps on adult Bradysia odoriphaga Yang et Zhang were studied in the field during its peak occurrence period. The results showed that yellow sticky tr...The trapping effects of yellow, blue, green, cyan and white sticky traps on adult Bradysia odoriphaga Yang et Zhang were studied in the field during its peak occurrence period. The results showed that yellow sticky trap received the best trapping effect on adult B. odoriphaga, follow by blue and green sticky traps, while cyan and white sticky traps received worse effects. The yellow sticky trap settled at south position was most attractive to adult B. odoriphaga, which had significant differences with tho^e placed at east and north positions （P 〈 0.05 ） ; the yellow sticky trap at hanging height of 0 cm showed significantly higher attractive- ness than those at heights of 20 and 40 cm.展开更多
[Objective]The paper was to study the control effect of pheromone insect-attracting board on tea green leafhopper（Empoasca vitis Gothe）in fields. [Method]Pheromone insect-attracting board and ordinary insect-attract...[Objective]The paper was to study the control effect of pheromone insect-attracting board on tea green leafhopper（Empoasca vitis Gothe）in fields. [Method]Pheromone insect-attracting board and ordinary insect-attracting board were used to trap tea green leafhopper in fields,and control efficacies were studied.[Result]The daily trapping effect of pheromone insect-attracting board on tea green leafhopper was 19.0 insect/grid,while that of ordinary insect-attracting board was 13.8 insect/grid.The highest control effect of pheromone insect-attracting board and ordinary insect-attracting board were 71.6% and 63. 6%,respectively.The distribution of tea green leafhopper in two types of boards showed the following regularities：more in upper edge and less in lower edge of boards,more on both sides and less in the middle of boards.The mean values of control effects of two insect-attracting boards were significantly different（t =5.66展开更多
A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting...A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting magneto–optic rotation effect,a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained.The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order,and the ability to detect weak magnetic fields is extended one-fold.Therefore,the proposed scheme is suited to realize a pocket-size CPT magnetometer.展开更多
A new serials of Er^3＋/Yb^3＋ co-doped tellurite-silicate glasses were prepared by the technique of high-temperature mehing. The thermal stability, absorption spectra, emission spectra and upconversion spectra were m...A new serials of Er^3＋/Yb^3＋ co-doped tellurite-silicate glasses were prepared by the technique of high-temperature mehing. The thermal stability, absorption spectra, emission spectra and upconversion spectra were measured and investigated. It is found that these kinds of glasses have good thermal stability, broad FWHM and large stimulated emission cross-section. The three upconversion emission at 525, 546, 658 nm, corresponding to the ^2H11/2→^4Ⅰ15/2, ^4S3/2→4^Ⅰ15/2 and ^F9/2→^4Ⅰ15/2 transitions of Dr^3＋ ions,展开更多
A new model of hydrogen diffusion in metals has been developed,it is more efficient to describe the hydrogen diffusion with trapping in metals.In the model newly developed an impli- cit dependence on time of hydrogen ...A new model of hydrogen diffusion in metals has been developed,it is more efficient to describe the hydrogen diffusion with trapping in metals.In the model newly developed an impli- cit dependence on time of hydrogen diffusion coefficient in metals with trapping was firstly built and it is shown that hydrogen diffusion coefficient will be different at different posi- tions in a dynamic process of hydrogen diffusion in a metal. Numerical solutions of the present model were obtained by finite difference method.By changing the parameters in the model the diffusion of hydrogen in a metal and the effect of trapping were described and discussed.And the comparison between the well known McNabb and Foster's model and the present model was also made.展开更多
The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The co...The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The code is suitable for various auxiliary heating and current drive schemes in tokamak plasmas. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized. It is shown that, as an electrostatic force, the lower hybrid wave causes some of the trapped electrons to be untrapped and lose their energy, which can cut the LHCD efficiency by about 30%. The ITER scaling law is also used to estimate the trapped electron effects.展开更多
The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped parti...The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized.展开更多
Check dams have been used worldwide for a variety of purposes.With increasing age,check dams gradually lose their sediment trapping function via the continuous deposition of material carried by debris flows and flash ...Check dams have been used worldwide for a variety of purposes.With increasing age,check dams gradually lose their sediment trapping function via the continuous deposition of material carried by debris flows and flash floods,and eventually,check dams become unable to perform the designed mitigation function.In this paper,the sediment deposit evolution in a dam with multiple debris flow surges and its influence on the sediment trapping effect were investigated.The results showed that the debris flow deposition process can be divided into three phases:the backwater-controlled deposition phase,landform-controlled deposition phase,and quasi-equilibrium phase.The sediment trapping ratio of the check dam gradually decreased as the deposit volume increased and was linearly negatively correlated with the sediment deposition rate.Moreover,a mathematical model describing the negative feedback between deposit volume and sediment trapping ratio was established,and the physical meanings of the coefficients in the model and their empirical values were clarified.Furthermore,the deposit distribution,which satisfied the Weibull distribution in the longitudinal direction,was revealed.In the cross-sectional direction,the distribution of deposition gradually became uneven with increasing sediment filling rate.展开更多
In this paper,drain current transient characteristics ofβ-Ga2O3 high electron mobility transistor(HEMT)are studied to access current collapse and recovery time due to dynamic population and de-population of deep leve...In this paper,drain current transient characteristics ofβ-Ga2O3 high electron mobility transistor(HEMT)are studied to access current collapse and recovery time due to dynamic population and de-population of deep level traps and interface traps.An approximately 10 min,and 1 h of recovery time to steady-state drain current value is measured under 1 ms of stress on the gate and drain electrodes due to iron(Fe)–dopedβ-Ga2O3 substrate and germanium(Ge)–dopedβ-Ga2O3 epitaxial layer respectively.On-state current lag is more severe due to widely reported defect trap EC–0.82 e V over EC–0.78 e V,-0.75 e V present in Iron(Fe)-dopedβ-Ga2O3 bulk crystals.A negligible amount of current degradation is observed in the latter case due to the trap level at EC–0.98 e V.It is found that occupancy of ionized trap density varied mostly under the gate and gate–source area.This investigation of reversible current collapse phenomenon and assessment of recovery time inβ-Ga2O3 HEMT is carried out through 2 D device simulations using appropriate velocity and charge transport models.This work can further help in the proper characterization ofβ-Ga2O3 devices to understand temporary and permanent device degradation.展开更多
Based on molecular dynamics simulations,we have studied the wetting behaviors of water on the talc-like surface with different surface polarity by modifying the charge distribution of surface hydroxyl(–OH)groups.With...Based on molecular dynamics simulations,we have studied the wetting behaviors of water on the talc-like surface with different surface polarity by modifying the charge distribution of surface hydroxyl(–OH)groups.With the change of the charge of the hydrogen atom(denoted asδq)in–OH group,the contact angle decreases from 91°to 50°and then remains constant.On the surfaces with the larger charge of hydrogen atoms(δ_(q)≥0.2 e),a water droplet is formed above a water monolayer,which is exactly contacted on the surface.Each water molecule in the monolayer forms one hydrogen bond(H bond)with surface–OH groups,without participating in any H bond with the water molecules within the monolayer or with the water molecules above the monolayer.The polarity of the–OH group also has a great influence on the dynamic behaviors of the interface water,such as residence time,hydrogen bond lifetime and selfdiffusion coefficient.The diffusion of water molecules in the water monolayer near the highly polar surface is greatly suppressed,and the residence time of water molecules in the water monolayer even exceeds 12 ns.展开更多
Surface-enhanced Raman scattering(SERS) has been widely used as an effective technique for lowconcentration molecules detections in the past decades. This work proposes a rapid and accessible process to fabricate SERS...Surface-enhanced Raman scattering(SERS) has been widely used as an effective technique for lowconcentration molecules detections in the past decades. This work proposes a rapid and accessible process to fabricate SERS-active substrates with high uniformity and controllability based on two-step laser ablation. Laser beams directly ablate the surface of Si, concurrently creating microstructures and ejecting molten materials caused by the thermal effect that nucleate in ambient air. The nuclei grow into nanoparticles and deposit over the surface. These nanoparticles,together with microstructures, improve the light collection efficiency of the SERS-active substrates. Especially after Au thin film deposition, these nanoparticles can provide nanogaps as hotspots for SERS. By orthogonal experiment design,laser processing parameters for better performances are determined. Compared with substrates fabricated by single 1064 nm master oscillator power amplifier(MOPA) laser ablation, substrates ablated by the primary 1064 nm MOPA laser and secondary UV pulsed laser show more uniform nanoparticles’ deposition over the surface. The optimized largearea substrate has a SERS detection limit of 10^(-8)mol/L for 4-aminothiophenol(4-ATP), indicating the potential realworld applications for trace detection.展开更多
AlGaN/GaN high-electron-mobility transistors(HEMTs)with postpassivation plasma treatment are demonstrated and investigated for the first time.The results show that postpassivation plasma treatment can reduce the gate ...AlGaN/GaN high-electron-mobility transistors(HEMTs)with postpassivation plasma treatment are demonstrated and investigated for the first time.The results show that postpassivation plasma treatment can reduce the gate leakage and enhance the drain current.Comparing with the conventional devices,the gate leakage of Al Ga N/Ga N HEMTs with postpassivation plasma decreases greatly while the drain current increases.Capacitance-voltage measurement and frequencydependent conductance method are used to study the surface and interface traps.The mechanism analysis indicates that the surface traps in the access region can be reduced by postpassivation plasma treatment and thus suppress the effect of virtual gate,which can explain the improvement of DC characteristics of devices.Moreover,the density and time constant of interface traps under the gate are extracted and analyzed.展开更多
A two-dimensional electrical SiC MOS interface model including interface and near-interface traps is established based on the relevant tunneling and interface Shockley–Read–Hall model. The consistency between simula...A two-dimensional electrical SiC MOS interface model including interface and near-interface traps is established based on the relevant tunneling and interface Shockley–Read–Hall model. The consistency between simulation results and measured data in the different temperatures shows that this interface model can accurately describe the capture and emission performance for near-interface oxide traps, and can well explain the hysteresis-voltage response with increasing temperature, which is intensified by the interaction between deep oxide traps and shallow oxide traps. This also indicates that the near-interface traps result in an increase of threshold-voltage shift in SiC MOSFET with increasing temperature.展开更多
The Fokker Planck package which without the relativity effect has been developed in 2002. The package with relativity effect, which induced from Italy, is now developed. It conrains relativity effect, and is bounce a...The Fokker Planck package which without the relativity effect has been developed in 2002. The package with relativity effect, which induced from Italy, is now developed. It conrains relativity effect, and is bounce averaged. It can deal with such as the trapping effect, wave heating, neutral beam injecting, and particle losses. It is very useful for our HL-2A experimental results analysis.展开更多
Sand protection systems are widely used to shelter roads from blowing sand.Therefore,it's very important to evaluate their effectiveness.To provide some insights,we used field investigations,measurements of accumu...Sand protection systems are widely used to shelter roads from blowing sand.Therefore,it's very important to evaluate their effectiveness.To provide some insights,we used field investigations,measurements of accumulated sand,work logs from sand-removal workers,and wind speed data to analyze a system's performance using China's CekeeEjina expressway as a case study.Our results demonstrated that the critical wind speed required to deposit sand on the expressway was 8.6 m s^(-1)(cumulative frequency 12.1%)before implementing the sand protection system.After implementing the system,the critical wind speed required to deposit sand on the road increased to 14.8 m s^(-1)(0.3%).However,the critical wind speed decreased to 11.1 m s^(-1)(3.5%)the next year.Additional work,such as digging ditches,increasing the fence height,and planting shrubs,would help the sand protection system retain its function.Nonetheless,the system continued to function well.The volume of sand removed decreased from ca.10,000 m^(3) in 2015 to ca.100 m^(3) in 2020.Our results quantify the effectiveness of the sand protection system and reveal how its effectiveness decreases over time.They therefore provide an empirical basis for improving the design and maintenance of sand protection systems.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61306113)
文摘In this paper, two-dimensional （2D） transient simulations of an A1GaN/GaN high-electron-mobility transistor （HEMT） are carded out and analyzed to investigate the current collapse due to trapping effects. The coupling effect of the trapping and thermal effects are taken into account in our simulation. The turn-on pulse gate-lag transient responses with different quiescent biases are obtained, and the pulsed current-voltage （l-V） curves are extracted from the transients. The experimental results of both gate-lag transient current and pulsed I-V curves are reproduced by the simulation, and the current collapse due to the trapping effect is explained from the view of physics based on the simulation results. In addition, the results show that bulk acceptor traps can influence the gate-lag transient characteristics of A1GaN/GaN HEMTs besides surface traps and that the thermal effect can accelerate the emission of captured electrons for traps. Pulse transient simulation is meaningful in analyzing the mechanism of dynamic current collapse, and the work in this paper will benefit the reliability study and model development of GaN-based devices.
基金Supported by Special Fund for Agro-scientific Research in the Public Interest( 201103026-1)
文摘Five different trapping treatments, spraying attractant on bottle surface and spraying attractant inside the bottles with 0, 50,100 and 200 mL water, were set to trap Bactrocera dorsalis and B. cucurbitae in guava （Psidium guajava） park. The results showed that when the usage of attractant was 1 g, both Haonian and Wende had trapping effect on B. dorsalis and B. cucurbitae. The trapping effect of Haonian on B. dorsalis was better than that of Wende, while their trapping effects on B. cucurbitae was just the opposite. The trapping effects of different treatments had great difference. The trapping effect of Haonian on two species of fruit flies enhanced with the increasing volume of water, and reached the ma^mum value as the water volume was 200 mL. With the increasing volume of water, the trap- ping effect of Wende on two species of fruit flies first increased, and then decreased, which reached the maximum value as the water volume was 50 mL. Different treatments with attractants spraying inside bottles had better trapping effects on two species of fruit flies than that spraying on bottle surface.
基金Supported by Special Fund for Agro-scientific Research in the Public Interest( 201103024)
文摘The key application technology for sex pheromone of Grapholitha molesta was studied from the aspects of different hanging heights and orientations, dif- ferent doses and types of traps through the tests on trapping quantity of G. molesta in fields. The results showed that the trapping effect was enhanced when the hanging height was increased, and the trapping effect was the best in west direction. The trapping effect was enhanced when the dosage was increased. When it was up to 6 lures, the trapping effect was the best with 38.75 head/trap; the next was 2 lures with 31.00 head/trap. All types of traps had trapping ability to G. mo- lesta, among which triangle trapper was the best, followed by self-made bottle trap. Their trapping effects were 138.75 and 100.25 head/trap, respectively.
基金supported by the Large Research Infrastructures China initiative Accelerator Driven System(No.2017-000052-75-01-000590)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022422)+1 种基金the Young Scientists of National Natural Science Foundation of China(No.12005275)the Advanced Energy Science and Technology Guangdong Laboratory(No.HND22PTZZYY)。
文摘Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.
基金Project supported by the National Natural Science Foundations of China (20876002, 20976002)the Beijing Natural Science Foundation (2091002)Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality
文摘Trivalent rare-earth ions （La3＋,Pr3＋,Nd3＋,Sm3＋,Gd3＋,Tb3＋,Dy3＋,Ho3＋,Er3＋,Tm3＋,and Yb3＋） were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS：Eu2＋ in order to enhance the fluorescence properties.It was found that Sm3＋ and Tb3＋ had the best photoluminescence stimulated luminescence （PSL） effect among the selected trivalent rare-earth ions.All the SrS：Eu2＋ samples doped by different trivalent rare-earth ions could be stimulated by 980 nm laser after being exposed to the conventional sunlight,and they emitted PSL with the peak located at 615 nm.The result also indicated that some co-doped rare earth ions could increase fluorescence intensities of the traditional electron trapping materials SrS：Eu2＋.
基金Supported by Special Fund for Agro-scientific Research in the Public Interest(201303027)
文摘The trapping effects of yellow, blue, green, cyan and white sticky traps on adult Bradysia odoriphaga Yang et Zhang were studied in the field during its peak occurrence period. The results showed that yellow sticky trap received the best trapping effect on adult B. odoriphaga, follow by blue and green sticky traps, while cyan and white sticky traps received worse effects. The yellow sticky trap settled at south position was most attractive to adult B. odoriphaga, which had significant differences with tho^e placed at east and north positions （P 〈 0.05 ） ; the yellow sticky trap at hanging height of 0 cm showed significantly higher attractive- ness than those at heights of 20 and 40 cm.
基金Supported by Science and Technology Promotion Project of Ningbo Forestry Bureau "Application Research and Extension of Insect Pheromone in Tea Garden"(2010L05)
文摘[Objective]The paper was to study the control effect of pheromone insect-attracting board on tea green leafhopper（Empoasca vitis Gothe）in fields. [Method]Pheromone insect-attracting board and ordinary insect-attracting board were used to trap tea green leafhopper in fields,and control efficacies were studied.[Result]The daily trapping effect of pheromone insect-attracting board on tea green leafhopper was 19.0 insect/grid,while that of ordinary insect-attracting board was 13.8 insect/grid.The highest control effect of pheromone insect-attracting board and ordinary insect-attracting board were 71.6% and 63. 6%,respectively.The distribution of tea green leafhopper in two types of boards showed the following regularities：more in upper edge and less in lower edge of boards,more on both sides and less in the middle of boards.The mean values of control effects of two insect-attracting boards were significantly different（t =5.66
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304362 and 61434005)
文摘A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting magneto–optic rotation effect,a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained.The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order,and the ability to detect weak magnetic fields is extended one-fold.Therefore,the proposed scheme is suited to realize a pocket-size CPT magnetometer.
文摘A new serials of Er^3＋/Yb^3＋ co-doped tellurite-silicate glasses were prepared by the technique of high-temperature mehing. The thermal stability, absorption spectra, emission spectra and upconversion spectra were measured and investigated. It is found that these kinds of glasses have good thermal stability, broad FWHM and large stimulated emission cross-section. The three upconversion emission at 525, 546, 658 nm, corresponding to the ^2H11/2→^4Ⅰ15/2, ^4S3/2→4^Ⅰ15/2 and ^F9/2→^4Ⅰ15/2 transitions of Dr^3＋ ions,
文摘A new model of hydrogen diffusion in metals has been developed,it is more efficient to describe the hydrogen diffusion with trapping in metals.In the model newly developed an impli- cit dependence on time of hydrogen diffusion coefficient in metals with trapping was firstly built and it is shown that hydrogen diffusion coefficient will be different at different posi- tions in a dynamic process of hydrogen diffusion in a metal. Numerical solutions of the present model were obtained by finite difference method.By changing the parameters in the model the diffusion of hydrogen in a metal and the effect of trapping were described and discussed.And the comparison between the well known McNabb and Foster's model and the present model was also made.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10675043, 10575031 and 10675042）.
文摘The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The code is suitable for various auxiliary heating and current drive schemes in tokamak plasmas. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized. It is shown that, as an electrostatic force, the lower hybrid wave causes some of the trapped electrons to be untrapped and lose their energy, which can cut the LHCD efficiency by about 30%. The ITER scaling law is also used to estimate the trapped electron effects.
基金Supported by the National Natural Science Foundation of China （10675043, 10575031 and 10675042）
文摘The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized.
基金supported by the National Natural Science Foundation of China(No.41925030)the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK0904)+1 种基金the Chinese Academy of Sciences“Light of West China”ProgramSupport from the Dongchuan Debris Flow Observation and Research Station(DDFORS),Chinese Academy of Sciences,is acknowledged.
文摘Check dams have been used worldwide for a variety of purposes.With increasing age,check dams gradually lose their sediment trapping function via the continuous deposition of material carried by debris flows and flash floods,and eventually,check dams become unable to perform the designed mitigation function.In this paper,the sediment deposit evolution in a dam with multiple debris flow surges and its influence on the sediment trapping effect were investigated.The results showed that the debris flow deposition process can be divided into three phases:the backwater-controlled deposition phase,landform-controlled deposition phase,and quasi-equilibrium phase.The sediment trapping ratio of the check dam gradually decreased as the deposit volume increased and was linearly negatively correlated with the sediment deposition rate.Moreover,a mathematical model describing the negative feedback between deposit volume and sediment trapping ratio was established,and the physical meanings of the coefficients in the model and their empirical values were clarified.Furthermore,the deposit distribution,which satisfied the Weibull distribution in the longitudinal direction,was revealed.In the cross-sectional direction,the distribution of deposition gradually became uneven with increasing sediment filling rate.
基金an outcome of the collaborative R&D work undertaken in the project under the Visvesvaraya PhD Scheme of Ministry of Electronics&Information Technology,Govt.of India,being implemented by Digital India Corporation。
文摘In this paper,drain current transient characteristics ofβ-Ga2O3 high electron mobility transistor(HEMT)are studied to access current collapse and recovery time due to dynamic population and de-population of deep level traps and interface traps.An approximately 10 min,and 1 h of recovery time to steady-state drain current value is measured under 1 ms of stress on the gate and drain electrodes due to iron(Fe)–dopedβ-Ga2O3 substrate and germanium(Ge)–dopedβ-Ga2O3 epitaxial layer respectively.On-state current lag is more severe due to widely reported defect trap EC–0.82 e V over EC–0.78 e V,-0.75 e V present in Iron(Fe)-dopedβ-Ga2O3 bulk crystals.A negligible amount of current degradation is observed in the latter case due to the trap level at EC–0.98 e V.It is found that occupancy of ionized trap density varied mostly under the gate and gate–source area.This investigation of reversible current collapse phenomenon and assessment of recovery time inβ-Ga2O3 HEMT is carried out through 2 D device simulations using appropriate velocity and charge transport models.This work can further help in the proper characterization ofβ-Ga2O3 devices to understand temporary and permanent device degradation.
基金supported by the National Natural Science Foundation of China(Grant No.12022508,12074394,11674345)the Key Research Program of Chinese Academy of Sciences(Grant No.QYZDJ-SSW-SLH019)the Sichuan Science and Technology Program(Grant No.2017YJ0174)。
文摘Based on molecular dynamics simulations,we have studied the wetting behaviors of water on the talc-like surface with different surface polarity by modifying the charge distribution of surface hydroxyl(–OH)groups.With the change of the charge of the hydrogen atom(denoted asδq)in–OH group,the contact angle decreases from 91°to 50°and then remains constant.On the surfaces with the larger charge of hydrogen atoms(δ_(q)≥0.2 e),a water droplet is formed above a water monolayer,which is exactly contacted on the surface.Each water molecule in the monolayer forms one hydrogen bond(H bond)with surface–OH groups,without participating in any H bond with the water molecules within the monolayer or with the water molecules above the monolayer.The polarity of the–OH group also has a great influence on the dynamic behaviors of the interface water,such as residence time,hydrogen bond lifetime and selfdiffusion coefficient.The diffusion of water molecules in the water monolayer near the highly polar surface is greatly suppressed,and the residence time of water molecules in the water monolayer even exceeds 12 ns.
基金Project(2020H0006) supported by the Fujian Provincial Science and Technology ProgrammeChina+2 种基金Project(62175203) supported by the National Natural Science Foundation of ChinaProject(RD2020050301) supported by the Innovation Laboratory for Science and Technology of Energy Materials of Fujian Province Applied Research ProjectChina。
文摘Surface-enhanced Raman scattering(SERS) has been widely used as an effective technique for lowconcentration molecules detections in the past decades. This work proposes a rapid and accessible process to fabricate SERS-active substrates with high uniformity and controllability based on two-step laser ablation. Laser beams directly ablate the surface of Si, concurrently creating microstructures and ejecting molten materials caused by the thermal effect that nucleate in ambient air. The nuclei grow into nanoparticles and deposit over the surface. These nanoparticles,together with microstructures, improve the light collection efficiency of the SERS-active substrates. Especially after Au thin film deposition, these nanoparticles can provide nanogaps as hotspots for SERS. By orthogonal experiment design,laser processing parameters for better performances are determined. Compared with substrates fabricated by single 1064 nm master oscillator power amplifier(MOPA) laser ablation, substrates ablated by the primary 1064 nm MOPA laser and secondary UV pulsed laser show more uniform nanoparticles’ deposition over the surface. The optimized largearea substrate has a SERS detection limit of 10^(-8)mol/L for 4-aminothiophenol(4-ATP), indicating the potential realworld applications for trace detection.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61674130 and 61804139)。
文摘AlGaN/GaN high-electron-mobility transistors(HEMTs)with postpassivation plasma treatment are demonstrated and investigated for the first time.The results show that postpassivation plasma treatment can reduce the gate leakage and enhance the drain current.Comparing with the conventional devices,the gate leakage of Al Ga N/Ga N HEMTs with postpassivation plasma decreases greatly while the drain current increases.Capacitance-voltage measurement and frequencydependent conductance method are used to study the surface and interface traps.The mechanism analysis indicates that the surface traps in the access region can be reduced by postpassivation plasma treatment and thus suppress the effect of virtual gate,which can explain the improvement of DC characteristics of devices.Moreover,the density and time constant of interface traps under the gate are extracted and analyzed.
基金Supported by the Science Challenge Project under Grant No TZ2018003
文摘A two-dimensional electrical SiC MOS interface model including interface and near-interface traps is established based on the relevant tunneling and interface Shockley–Read–Hall model. The consistency between simulation results and measured data in the different temperatures shows that this interface model can accurately describe the capture and emission performance for near-interface oxide traps, and can well explain the hysteresis-voltage response with increasing temperature, which is intensified by the interaction between deep oxide traps and shallow oxide traps. This also indicates that the near-interface traps result in an increase of threshold-voltage shift in SiC MOSFET with increasing temperature.
文摘The Fokker Planck package which without the relativity effect has been developed in 2002. The package with relativity effect, which induced from Italy, is now developed. It conrains relativity effect, and is bounce averaged. It can deal with such as the trapping effect, wave heating, neutral beam injecting, and particle losses. It is very useful for our HL-2A experimental results analysis.
基金funded by“Gansu Provincial Science and Technology Planning Project(23ZDFA018)”“The Major Science and Technology Projects of Inner Mongolia Autonomous Region(2021ZD0008)”.
文摘Sand protection systems are widely used to shelter roads from blowing sand.Therefore,it's very important to evaluate their effectiveness.To provide some insights,we used field investigations,measurements of accumulated sand,work logs from sand-removal workers,and wind speed data to analyze a system's performance using China's CekeeEjina expressway as a case study.Our results demonstrated that the critical wind speed required to deposit sand on the expressway was 8.6 m s^(-1)(cumulative frequency 12.1%)before implementing the sand protection system.After implementing the system,the critical wind speed required to deposit sand on the road increased to 14.8 m s^(-1)(0.3%).However,the critical wind speed decreased to 11.1 m s^(-1)(3.5%)the next year.Additional work,such as digging ditches,increasing the fence height,and planting shrubs,would help the sand protection system retain its function.Nonetheless,the system continued to function well.The volume of sand removed decreased from ca.10,000 m^(3) in 2015 to ca.100 m^(3) in 2020.Our results quantify the effectiveness of the sand protection system and reveal how its effectiveness decreases over time.They therefore provide an empirical basis for improving the design and maintenance of sand protection systems.
