As salinity stratification is necessary to form the barrier layer (BL), the quantification of its role in BL interannual variability is crucial. This study assessed salinity variability and its effect on the BL in t...As salinity stratification is necessary to form the barrier layer (BL), the quantification of its role in BL interannual variability is crucial. This study assessed salinity variability and its effect on the BL in the equatorial Pacific using outputs from Beijing Normal University Earth System Model (BNU-ESM) simulations. A comparison between observations and the BNU-ESM simulations demonstrated that BNU-ESM has good capability in reproducing most of the interannual features observed in nature. Despite some discrepancies in both magnitude and location of the interannual variability centers, the displacements of sea surface salinity (SSS), barrier layer thickness (BLT), and SST simulated by BNU-ESM in the equatorial Pacific are realistic. During E1 Nifio, for example, the modeled interannual anomalies of BLT, mixed layer depth, and isothermal layer depth, exhibit good correspondence with observations, including the development and decay of E1 Nifio in the central Pacific, whereas the intensity of the interannual variabilities is weaker relative to observations. Due to the bias in salinity simulations, the SSS front extends farther west along the equator, whereas BLT variability is weaker in the central Pacific than in observations. Further, the BNU-ESM simulations were examined to assess the relative effects of salinity and temperature variability on BLT. Consistent with previous observation-based analyses, the interannual salinity variability can make a significant contribution to BLT relative to temperature in the western-central equatorial Pacific.展开更多
Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and Bay of Bengal(BoB)are examined using monthly Argo data sets during 2002–2017.The B...Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and Bay of Bengal(BoB)are examined using monthly Argo data sets during 2002–2017.The BLT during November–January(NDJ)in the EEIO shows strong IAV,which is associated with the Indian Ocean dipole mode(IOD),with the IOD leading the BLT by two months.During the negative IOD phase,the westerly wind anomalies driving the downwelling Kelvin waves increase the isothermal layer depth(ILD).Moreover,the variability in the mixed layer depth(MLD)is complex.Affected by the Wyrtki jet,the MLD presents negative anomalies west of 85°E and strong positive anomalies between 85°E and 93°E.Therefore,the BLT shows positive anomalies except between 86°E and 92°E in the EEIO.Additionally,the IAV in the BLT during December–February(DJF)in the BoB is also investigated.In the eastern and northeastern BoB,the IAV in the BLT is remotely forced by equatorial zonal wind stress anomalies associated with the El Ni?o-Southern Oscillation(ENSO).In the western BoB,the regional surface wind forcing-related ENSO modulates the BLT variations.展开更多
In this study rectangular AlGaN/AlN/GaN heterostructure field-effect transistors(HFETs) with 22-nm and 12-nm AlGaN barrier layers are fabricated, respectively. Using the measured capacitance–voltage and current–volt...In this study rectangular AlGaN/AlN/GaN heterostructure field-effect transistors(HFETs) with 22-nm and 12-nm AlGaN barrier layers are fabricated, respectively. Using the measured capacitance–voltage and current–voltage characteristics of the prepared devices with different Schottky areas, it is found that after processing the device, the polarization Coulomb field(PCF) scattering is induced and has an important influence on the two-dimensional electron gas electron mobility.Moreover, the influence of PCF scattering on the electron mobility is enhanced by reducing the AlGaN barrier thickness.This leads to the quite different variation of the electron mobility with gate bias when compared with the AlGaN barrier thickness. This mainly happens because the thinner AlGaN barrier layer suffers from a much stronger electrical field when applying a gate bias, which gives rise to a stronger converse piezoelectric effect.展开更多
We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetratin...We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the BOB.Prior to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky condition.Meanwhile,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave radiation.On the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed layer.As the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation mechanism.However,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB SST.In other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.展开更多
The multilevel storage capability of nonvolatile resistive random access memory(ReRAM)is greatly de-sired to accomplish high functioning memory density.In this study,Ta_(2)O_(5) thin film with different thick-nesses(2...The multilevel storage capability of nonvolatile resistive random access memory(ReRAM)is greatly de-sired to accomplish high functioning memory density.In this study,Ta_(2)O_(5) thin film with different thick-nesses(2,4,and 6 nm)was exploited as an appropriate interfacial barrier layer for limiting the formation of the interfacial layer between the 10 nm thick sputtering deposited resistive switching(RS)layer and Ta ohmic electrode to improve the switching cycle endurance and uniformity.Results show that lower form-ing voltage,narrow distribution of SET-voltages,good dc switching cycles(10^(3)),high pulse endurance(10^(6) cycles),long retention time(10^(4) s at room temperature and 100℃),and reliable multilevel resis-tance states were obtained at an appropriate thickness of∼2 nm Ta_(2)O_(5) interfacial barrier layer instead of without Ta_(2)O_(5) and with∼4 nm,and∼6 nm Ta_(2)O_(5) barrier layer,ZrO_(2)-based memristive devices.Besides,multilevel resistance states have been scientifically investigated via modulating the compliance current(CC)and RESET-stop voltages,which displays that all of the resistance states were distinct and stayed stable without any considerable deprivation over 10^(4) s retention time and 104 pulse endurance cycles.The I-V characteristics of RESET-stop voltage(from−1.7 to−2.3 V)of HRS are found to be a good linear fit with the Schottky equation.It can be seen that Schottky barrier height rises by increasing the stop-voltage during RESET-operation,resulting in enhancing the data storage memory window(on/offratio).Moreover,RESET-voltage and CC control of HRS and LRS revealed the physical origin of the RS mecha-nism,which entails the formation and rupture of conducting nanofilaments.It is thoroughly investigated that proper optimization of the barrier layer at the ohmic interface and the switching layer is essential in memristive devices.These results demonstrate that the ZrO_(2)-based memristive device with an optimized∼2 nm Ta_(2)O_(5) barrier layer is a promising candidate for multilevel data storage memory applications.展开更多
A relationship between oceanic conditions in the northwestern equatorial Atlantic (NWEA) and the seasonal rainfall over the northern part of Brazilian Northeast (NNEB) allows large climate events to be forecasted with...A relationship between oceanic conditions in the northwestern equatorial Atlantic (NWEA) and the seasonal rainfall over the northern part of Brazilian Northeast (NNEB) allows large climate events to be forecasted with a delay of a few months. Observed sea surface variables (sea surface temperature, wind stress and latent heat flux) and reanalyzed temperature and salinity profiles at depths of 0 - 150 m are used during 1974-2008. Perturbations in the Wind-Evaporation-SST mechanism over the NWEA during the last months of the year and the first months of the following year are of primary importance in evaluating the risk that strong climate events will affect the subsequent seasonal rainfall (in March-April) over the NNEB. Especially interesting are the Barrier Layer Thickness (BLT) and Ocean Heat Content (OHC) in the NWEA region from August-September through the subsequent months, during which a slow and steady evolution is apparent, with the highest signal occurring in October-November. Through their relationship with the local surface dynamic conditions, such BLT and OHC perturbations during the last months of the year can be used as a valuable indicator for forecasting wet or dry events over the NNEB during the subsequent rainfall season. A proposal is discussed to deploy additional temperature/conductivity sensors down to a depth of 140 m at three PIRATA moorings located in the NWEA region. That will be necessary if the BLT and other parameters of energy exchange between the ocean and atmosphere are to be estimated in real time and with a sufficiently high vertical resolution.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41376039,41376019 and 41421005)the NSFC-Shandong Joint Fund for Marine Science Research Centers(Grant No.U1406401)+1 种基金the IOCAS through the CAS Strategic Priority Project[the Western Pacific Ocean System(WPOS)]the WPOS in the "Strategic Priority Research Program" of the Chinese Academy of Sciences(Grant No.XDA11010304)
文摘As salinity stratification is necessary to form the barrier layer (BL), the quantification of its role in BL interannual variability is crucial. This study assessed salinity variability and its effect on the BL in the equatorial Pacific using outputs from Beijing Normal University Earth System Model (BNU-ESM) simulations. A comparison between observations and the BNU-ESM simulations demonstrated that BNU-ESM has good capability in reproducing most of the interannual features observed in nature. Despite some discrepancies in both magnitude and location of the interannual variability centers, the displacements of sea surface salinity (SSS), barrier layer thickness (BLT), and SST simulated by BNU-ESM in the equatorial Pacific are realistic. During E1 Nifio, for example, the modeled interannual anomalies of BLT, mixed layer depth, and isothermal layer depth, exhibit good correspondence with observations, including the development and decay of E1 Nifio in the central Pacific, whereas the intensity of the interannual variabilities is weaker relative to observations. Due to the bias in salinity simulations, the SSS front extends farther west along the equator, whereas BLT variability is weaker in the central Pacific than in observations. Further, the BNU-ESM simulations were examined to assess the relative effects of salinity and temperature variability on BLT. Consistent with previous observation-based analyses, the interannual salinity variability can make a significant contribution to BLT relative to temperature in the western-central equatorial Pacific.
基金The National Key R&D Program of China under contract No.2018YFA0605702the National Natural Science Foundation of China under contract Nos 41522601,41876002 and 41876224the Fundamental Research Funds for the Central Universities under contract Nos 2017B04714 and 2017B4114。
文摘Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and Bay of Bengal(BoB)are examined using monthly Argo data sets during 2002–2017.The BLT during November–January(NDJ)in the EEIO shows strong IAV,which is associated with the Indian Ocean dipole mode(IOD),with the IOD leading the BLT by two months.During the negative IOD phase,the westerly wind anomalies driving the downwelling Kelvin waves increase the isothermal layer depth(ILD).Moreover,the variability in the mixed layer depth(MLD)is complex.Affected by the Wyrtki jet,the MLD presents negative anomalies west of 85°E and strong positive anomalies between 85°E and 93°E.Therefore,the BLT shows positive anomalies except between 86°E and 92°E in the EEIO.Additionally,the IAV in the BLT during December–February(DJF)in the BoB is also investigated.In the eastern and northeastern BoB,the IAV in the BLT is remotely forced by equatorial zonal wind stress anomalies associated with the El Ni?o-Southern Oscillation(ENSO).In the western BoB,the regional surface wind forcing-related ENSO modulates the BLT variations.
基金supported by the National Natural Science Foundation of China(Grant Nos.61306113 and11174182)
文摘In this study rectangular AlGaN/AlN/GaN heterostructure field-effect transistors(HFETs) with 22-nm and 12-nm AlGaN barrier layers are fabricated, respectively. Using the measured capacitance–voltage and current–voltage characteristics of the prepared devices with different Schottky areas, it is found that after processing the device, the polarization Coulomb field(PCF) scattering is induced and has an important influence on the two-dimensional electron gas electron mobility.Moreover, the influence of PCF scattering on the electron mobility is enhanced by reducing the AlGaN barrier thickness.This leads to the quite different variation of the electron mobility with gate bias when compared with the AlGaN barrier thickness. This mainly happens because the thinner AlGaN barrier layer suffers from a much stronger electrical field when applying a gate bias, which gives rise to a stronger converse piezoelectric effect.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA20060502)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0306)+4 种基金the National Natural Science Foundation of China(Nos.41776023,41731173,41521005,41676013,41775052,41506003)the Rising Star Foundation of the South China Sea Institute of Oceanology(No.NHXX2018WL0201)the Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences(No.ISEE2018PY06)the Independent Research Project Program of State Key Laboratory of Tropical Oceanography(No.LTOZZ1802)the Basic Scientifi c Research and Operation Foundation of the CAMS(Nos.2018Z006,2017R001)。
文摘We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the BOB.Prior to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky condition.Meanwhile,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave radiation.On the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed layer.As the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation mechanism.However,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB SST.In other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.
基金supported in part by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No.2021R1C1C1004422)the Dongguk University Research Fund of 2020supported through the National Research Foundation of Korea (NRF) funded by the Ministry of Science,ICT & Future Planning (Nos.NRF2020M3F3A2A02082449 and NRF-2016R1A6A1A03013422)。
文摘The multilevel storage capability of nonvolatile resistive random access memory(ReRAM)is greatly de-sired to accomplish high functioning memory density.In this study,Ta_(2)O_(5) thin film with different thick-nesses(2,4,and 6 nm)was exploited as an appropriate interfacial barrier layer for limiting the formation of the interfacial layer between the 10 nm thick sputtering deposited resistive switching(RS)layer and Ta ohmic electrode to improve the switching cycle endurance and uniformity.Results show that lower form-ing voltage,narrow distribution of SET-voltages,good dc switching cycles(10^(3)),high pulse endurance(10^(6) cycles),long retention time(10^(4) s at room temperature and 100℃),and reliable multilevel resis-tance states were obtained at an appropriate thickness of∼2 nm Ta_(2)O_(5) interfacial barrier layer instead of without Ta_(2)O_(5) and with∼4 nm,and∼6 nm Ta_(2)O_(5) barrier layer,ZrO_(2)-based memristive devices.Besides,multilevel resistance states have been scientifically investigated via modulating the compliance current(CC)and RESET-stop voltages,which displays that all of the resistance states were distinct and stayed stable without any considerable deprivation over 10^(4) s retention time and 104 pulse endurance cycles.The I-V characteristics of RESET-stop voltage(from−1.7 to−2.3 V)of HRS are found to be a good linear fit with the Schottky equation.It can be seen that Schottky barrier height rises by increasing the stop-voltage during RESET-operation,resulting in enhancing the data storage memory window(on/offratio).Moreover,RESET-voltage and CC control of HRS and LRS revealed the physical origin of the RS mecha-nism,which entails the formation and rupture of conducting nanofilaments.It is thoroughly investigated that proper optimization of the barrier layer at the ohmic interface and the switching layer is essential in memristive devices.These results demonstrate that the ZrO_(2)-based memristive device with an optimized∼2 nm Ta_(2)O_(5) barrier layer is a promising candidate for multilevel data storage memory applications.
文摘A relationship between oceanic conditions in the northwestern equatorial Atlantic (NWEA) and the seasonal rainfall over the northern part of Brazilian Northeast (NNEB) allows large climate events to be forecasted with a delay of a few months. Observed sea surface variables (sea surface temperature, wind stress and latent heat flux) and reanalyzed temperature and salinity profiles at depths of 0 - 150 m are used during 1974-2008. Perturbations in the Wind-Evaporation-SST mechanism over the NWEA during the last months of the year and the first months of the following year are of primary importance in evaluating the risk that strong climate events will affect the subsequent seasonal rainfall (in March-April) over the NNEB. Especially interesting are the Barrier Layer Thickness (BLT) and Ocean Heat Content (OHC) in the NWEA region from August-September through the subsequent months, during which a slow and steady evolution is apparent, with the highest signal occurring in October-November. Through their relationship with the local surface dynamic conditions, such BLT and OHC perturbations during the last months of the year can be used as a valuable indicator for forecasting wet or dry events over the NNEB during the subsequent rainfall season. A proposal is discussed to deploy additional temperature/conductivity sensors down to a depth of 140 m at three PIRATA moorings located in the NWEA region. That will be necessary if the BLT and other parameters of energy exchange between the ocean and atmosphere are to be estimated in real time and with a sufficiently high vertical resolution.