Drinking good quality water is essential for better health. It is therefore essential to assess the radiological quality of all water consumed in the District of Abidjan in order to prevent related hazards. Thus, the ...Drinking good quality water is essential for better health. It is therefore essential to assess the radiological quality of all water consumed in the District of Abidjan in order to prevent related hazards. Thus, the objective of this study was to assess the risk of cancer due to the ingestion of alpha and beta emitting radionuclides in the different types of water consumed in the region. A total of 63 water samples with 43 tap water samples, 5 bottled mineral water and 15 sachet water samples was collected and taken to GAEC laboratory for analysis. The low background Gas-less Automatic Alpha/Beta counting system (Canberra iMatic<sup>TM</sup>) was used to determine alpha and beta activity concentrations. Activity concentrations of both gross alpha and gross beta obtained in water sample were respectively lower than the WHO recommended limits of 0.1 Bq/l and 1 Bq/l. Also, the annual effective dose and total equivalent effective dose found in mineral bottled water samples were higher than in other types of water. The assessment of radiological lifetime risk has shown values of cancer risk due to ingestion alpha and beta emitters lower than recommended limit. These results indicate that there is no health hazard associated to consumption of water in the District of Abidjan.展开更多
Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible substrates.The QD radiative recombination lifetime has attracted eno...Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible substrates.The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes.However,the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle.This article presents a novel explanation that recon-ciles this controversy.Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window.Further,we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states.Each of the contradictory size-dependent patterns reflects this trend in a specific size range.As the optical band gap increases,the radiative lifetime decreases in larger QDs,increases in smaller QDs,and is weakly depend-ent on size in the intermediate energy region.This study addresses the inconsistencies in the scaling law of the exciton life-time and gives a unified interpretation over a widened framework.Moreover,it provides valuable guidance for carrier separa-tion in the thin film solar cell of CdSe QDs.展开更多
Employing the advanced relativistic configuration interaction(RCI)combined with the many-body perturbation theory(RMBPT)method,we report energies and lifetime values for the lowest 35 energy levels from the(1s^(2))nl ...Employing the advanced relativistic configuration interaction(RCI)combined with the many-body perturbation theory(RMBPT)method,we report energies and lifetime values for the lowest 35 energy levels from the(1s^(2))nl configurations(where the principal quantum number n=2–6 and the angular quantum number l=0,...,n-1)of lithium-like iron Fe XXIV,as well as complete data on the transition wavelengths,radiative rates,absorption oscillator strengths,and line strengths between the levels.Both the allowed(E1)and forbidden(magnetic dipole M1,magnetic quadrupole M2,and electric quadrupole E2)ones are reported.Through detailed comparisons with previous results,we assess the overall accuracies of present RMBPT results to be likely the most precise ones to date.Configuration interaction effects are found to be very important for the energies and radiative properties for the ion.The present RMBPT results are valuable for spectral line identification,plasma modeling,and diagnosing.展开更多
An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0....An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T.The decay photons emitted from 3d^(9) ^(2)D_(3/2) level are subsequently recorded via a cooled photomultiplier tube.Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes,we have determined the lifetime of Mo^(15+)3d^(9)2D_(3/2)metastable level to be 2.83(22)ms.The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches.展开更多
Thermal oxidation and hydrogen annealing were applied on a 100μm thick Al-doped p-type 4H-Si C epitaxial wafer to modulate the minority carrier lifetime,which was investigated by microwave photoconductive decay(μ-PC...Thermal oxidation and hydrogen annealing were applied on a 100μm thick Al-doped p-type 4H-Si C epitaxial wafer to modulate the minority carrier lifetime,which was investigated by microwave photoconductive decay(μ-PCD).The minority carrier lifetime decreased after each thermal oxidation.On the contrary,with the hydrogen annealing time increasing to3 hours,the minority carrier lifetime increased from 1.1μs(as-grown)to 3.14μs and then saturated after the annealing time reached 4 hours.The increase of surface roughness from 0.236 nm to 0.316 nm may also be one of the reasons for limiting the further improvement of the minority carrier lifetimes.Moreover,the whole wafer mappings of minority carrier lifetimes before and after hydrogen annealing were measured and discussed.The average minority carrier lifetime was up to 1.94μs and non-uniformity of carrier lifetime reached 38%after 4-hour hydrogen annealing.The increasing minority carrier lifetimes could be attributed to the double mechanisms of excess carbon atoms diffusion caused by selective etching of Si atoms and passivation of deep-level defects by hydrogen atoms.展开更多
In Wireless Sensor Network(WSN),scheduling is one of the important issues that impacts the lifetime of entire WSN.Various scheduling schemes have been proposed earlier to increase the lifetime of the network.Still,the...In Wireless Sensor Network(WSN),scheduling is one of the important issues that impacts the lifetime of entire WSN.Various scheduling schemes have been proposed earlier to increase the lifetime of the network.Still,the results from such methods are compromised in terms of achieving high lifetime.With this objective to increase the lifetime of network,an Efficient Topology driven Cooperative Self-Scheduling(TDCSS)model is recommended in this study.Instead of scheduling the network nodes in a centralized manner,a combined approach is proposed.Based on the situation,the proposed TDCSS approach performs scheduling in both the ways.By sharing the node statistics in a periodic manner,the overhead during the transmission of control packets gets reduced.This in turn impacts the lifetime of all the nodes.Further,this also reduces the number of idle conditions of each sensor node which is required for every cycle.The proposed method enables every sensor to schedule its own conditions according to duty cycle and topology constraints.Central scheduler monitors the network conditions whereas total transmissions occurs at every cycle.According to this,the source can infer the possible routes in a cycle and approximate the available routes.Further,based on the statistics of previous transmissions,the routes towards the sink are identified.Among the routes found,a single optimal route with energy efficiency is selected to perform data transmission.This cooperative approach improves the lifetime of entire network with high throughput performance.展开更多
Amber can emit room temperature phosphorescence(RTP)under the well-known 365 nm fluorescence ultraviolet light.This paper is devoted to the phosphorescence study of 20 pieces of amber materials from the Dominican Repu...Amber can emit room temperature phosphorescence(RTP)under the well-known 365 nm fluorescence ultraviolet light.This paper is devoted to the phosphorescence study of 20 pieces of amber materials from the Dominican Republic,Mexico,Baltic sea,Myanmar,and Fushun,China.The results show that amber from the same geographic origin has similar shape in phosphorescence spectra.However,the shape of the amber phosphorescence spectra varies depending on their different localities.Burmite(amber from Myanmar)and Fushun amber have a bright yellow phosphorescence with a long lifetime,while the Dominican and Mexican ones are weaker and last shorter.The irradiation of Baltic amber becomes faint or even inert.Phosphorescence spectral Gaussian fitting results suggest an emission maximum near 550 nm in most amber samples.Their phosphorescence lifetime,analyzed through the exponential function fitting,is up to 1 second in Burmite and Fushun samples,shorter in the Dominican and Mexican ones,about 0.230 s,and the shortest in Baltic amber,close to 0.151 s.These variations of phosphorescence lifetime and intensity are related to the relative geological ages of these amber.It indicated that the phosphorescence agent was probably formed during the long geological time.While the anomaly occurred in Baltic amber,the only one found in a sea secondary deposit form,it demonstrated that the terrestrial geological environment these amber preserved has prevented the phosphorescence agent to be deactivated.展开更多
The air continues to be an extremely substantial part of survival on earth.Air pollution poses a critical risk to humans and the environment.Using sensor-based structures,we can get air pollutant data in real-time.How...The air continues to be an extremely substantial part of survival on earth.Air pollution poses a critical risk to humans and the environment.Using sensor-based structures,we can get air pollutant data in real-time.However,the sensors rely upon limited-battery sources that are immaterial to be alternated repeatedly amid extensive broadcast costs associated with real-time applications like air quality monitoring.Consequently,air quality sensor-based monitoring structures are lifetime-constrained and prone to the untimely loss of connectivity.Effective energy administration measures must therefore be implemented to handle the outlay of power dissipation.In this study,the authors propose outdoor air quality monitoring using a sensor network with an enhanced lifetime-enhancing cooperative data gathering and relaying algorithm(E-LCDGRA).LCDGRA is a cluster-based cooperative event-driven routing scheme with dedicated relay allocation mechanisms that tackle the problems of event-driven clustered WSNs with immobile gateways.The adapted variant,named E-LCDGRA,enhances the LCDGRA algorithm by incorporating a non-beacon-aided CSMA layer-2 un-slotted protocol with a back-off mechanism.The performance of the proposed E-LCDGRA is examined with other classical gathering schemes,including IEESEP and CERP,in terms of average lifetime,energy consumption,and delay.展开更多
For the product degradation process with random effect(RE), measurement error(ME) and nonlinearity in step-stress accelerated degradation test(SSADT), the nonlinear Wiener based degradation model with RE and ME is bui...For the product degradation process with random effect(RE), measurement error(ME) and nonlinearity in step-stress accelerated degradation test(SSADT), the nonlinear Wiener based degradation model with RE and ME is built. An analytical approximation to the probability density function(PDF) of the product's lifetime is derived in a closed form. The process and data of SSADT are analyzed to obtain the relation model of the observed data under each accelerated stress. The likelihood function for the population-based observed data is constructed. The populationbased model parameters and its random coefficient prior values are estimated. According to the newly observed data of the target product in SSADT, an analytical approximation to the PDF of its residual lifetime(RL) is derived in accordance with its individual degradation characteristics. The parameter updating method based on Bayesian inference is applied to obtain the posterior value of random coefficient of the RL model. A numerical example by simulation is analyzed to verify the accuracy and advantage of the proposed model.展开更多
GaN-based continuous-wave operated blue-violet laser diodes(LDs) with long lifetime are demonstrated, which are grown on a c-plane GaN substrate by metal organic chemical vapor deposition with a 10 × 600 μm^2 ri...GaN-based continuous-wave operated blue-violet laser diodes(LDs) with long lifetime are demonstrated, which are grown on a c-plane GaN substrate by metal organic chemical vapor deposition with a 10 × 600 μm^2 ridge waveguide structure.The electrical and optical characteristics of a blue-violet LD are investigated under direct-current injection at room temperature(25 °C). The stimulated emission wavelength and peak optical power of the LD are around 413 nm and over 600 mW, respectively.In addition, the threshold current density and voltage are as small as 1.46 kA/cm^2 and 4.1 V, respectively. Moreover, the lifetime is longer than 1000 hours under room-temperature continuous-wave operation.展开更多
For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency ...For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency of the parameters estimation are not high, and the current degradation state of the target device is not accurately estimated. In this paper, a nonlinear Wiener degradation model with random effect is proposed and the corresponding probability density function(PDF) of the first hitting time(FHT)is deduced. A parameter estimation method based on modified expectation maximum(EM) algorithm is proposed to obtain the estimated value of fixed coefficient and the priori value of random coefficient in the model. The posterior value of the random coefficient and the current degradation state of target device are updated synchronously by the state space model(SSM) and the Kalman filter algorithm. The PDF of RL with random effect is deduced. A simulation example is analyzed to verify that the proposed method has the obvious advantage over the existing methods in parameter estimation error and RL prediction accuracy.展开更多
Aging diagnosis of batteries is essential to ensure that the energy storage systems operate within a safe region.This paper proposes a novel cell to pack health and lifetime prognostics method based on the combination...Aging diagnosis of batteries is essential to ensure that the energy storage systems operate within a safe region.This paper proposes a novel cell to pack health and lifetime prognostics method based on the combination of transferred deep learning and Gaussian process regression.General health indicators are extracted from the partial discharge process.The sequential degradation model of the health indicator is developed based on a deep learning framework and is migrated for the battery pack degradation prediction.The future degraded capacities of both battery pack and each battery cell are probabilistically predicted to provide a comprehensive lifetime prognostic.Besides,only a few separate battery cells in the source domain and early data of battery packs in the target domain are needed for model construction.Experimental results show that the lifetime prediction errors are less than 25 cycles for the battery pack,even with only 50 cycles for model fine-tuning,which can save about 90%time for the aging experiment.Thus,it largely reduces the time and labor for battery pack investigation.The predicted capacity trends of the battery cells connected in the battery pack accurately reflect the actual degradation of each battery cell,which can reveal the weakest cell for maintenance in advance.展开更多
Cyber-physical-system（CPS） has been widely used in both civil and military applications.Wireless sensor network（WSN） as the part and parcel of CPS faces energy problem because sensors are battery powered,which res...Cyber-physical-system（CPS） has been widely used in both civil and military applications.Wireless sensor network（WSN） as the part and parcel of CPS faces energy problem because sensors are battery powered,which results in limited lifetime of the network.To address this energy problem,we take advantage of energy harvesting device（EHD） and study how to indefinitely prolong oil pipeline monitoring network lifetime by reasonable selecting EHD.Firstly,we propose a general strategy worst case-energy balance strategy（WC-EBS）,which defines worst case energy consumption（WCEC） as the maximum energy sensor node could expend for oil pipeline monitoring WSN.When the energy collected by EHD is equal or greater than WCEC,network can have an unlimited lifetime.However,energy harvesting rate is proportional to the price of EHD,WC-EBS will cause high network cost.To reduce network cost,we present two optimization strategies,optimization workloadenergy balance strategy（OW-EBS） and optimization first nodeenergy balance strategy（OF-EBS）.The main idea of OW-EBS is to cut down WCEC by reducing critical node transmission workload;OF-EBS confirms critical node by optimizing each sensor node transmission range,then we get the optimal energy harvesting rate in OF-EBS.The experimental results demonstrate that OF-EBS can indefinitely extend network lifetime with lower cost than WC-EBS and OW-EBS,and energy harvesting rate P in each strategy satisfies Pof-EBS≤P（OW-EBS）≤PWC-EBS.展开更多
New-generation synchrotron light sources are being designed and operated worldwide to provide brighter radiation by reducing the beam emittance to X-ray diffraction limits.Intra-beam scattering(IBS)and Touschek scatte...New-generation synchrotron light sources are being designed and operated worldwide to provide brighter radiation by reducing the beam emittance to X-ray diffraction limits.Intra-beam scattering(IBS)and Touschek scattering in such facilities are significant and require attention because of their ultra-low emittance.Therefore,cure strategies need to be carefully studied to obtain highquality photon beams.For the Shanghai Synchrotron Radiation Facility Upgrade(SSRF-U),a candidate lattice of the storage ring,reaching the soft X-ray diffraction limit,was designed and presented for the first time in this study.The emittance growth and beam lifetime in the SSRF-U storage ring were studied using particle simulations for a series of different machine configurations.The gains with RF frequencies of 100 MHz and 500 MHz were compared.Along with a better filling pattern,a more suitable RF frequency was adopted in the SSRF-U.The variations in the equilibrium beam emittance with beam coupling and bunch-lengthening were identified using simulations.Optimal beam coupling and required bunch-lengthening for the SSRF-U storage ring were thus determined.The fitness of the beam energy in the SSRF-U was subsequently assessed using the obtained parameters.Additionally,the Touschek scattering and beam lifetime were calculated,and an acceptable total beam lifetime was obtained.展开更多
Continuous tracking of bunch charges is the key to maintain stable operations in a storage ring in top-up mode. Recently, a precise bunch-by-bunch beam-current measurement (BCM) system has been developed at the Shangh...Continuous tracking of bunch charges is the key to maintain stable operations in a storage ring in top-up mode. Recently, a precise bunch-by-bunch beam-current measurement (BCM) system has been developed at the Shanghai Synchrotron Radiation Facility. To avoid the influence of longitudinal oscillation on the amplitudes of the sampling points, a method called two-point equilibrium sampling is introduced. The results, obtained during routine operation time, show that the relative resolution of the measurement of the bunch charges is better than 0.02%. With this high resolution, the new BCM system is able to monitor the bunch-by-bunch beam lifetime. By using the filling pattern information, the Touschek lifetime and the vacuum lifetime can also be calculated. In this paper, the principle of the new method and the experiments is presented in detail.展开更多
Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) in order to simplify and understand the LB films of fluorescent probe labeling proteins. Its monolayer and multilaye...Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) in order to simplify and understand the LB films of fluorescent probe labeling proteins. Its monolayer and multilayers in the absence and presence of stearic acid were deposited by LB technique. Fluorescence spectra and lifetimes of the fluorescent products were studied to elucidate the microenvironment of molecules in the LB films.展开更多
In order to ascertain the key factors affecting the lifetime of the triple grids in the LIPS-300 ion thruster,the thermal deformation,upstream ion density and component lifetime of the grids are simulated with finite ...In order to ascertain the key factors affecting the lifetime of the triple grids in the LIPS-300 ion thruster,the thermal deformation,upstream ion density and component lifetime of the grids are simulated with finite element analysis,fluid simulation and charged-particle tracing simulation methods on the basis of a 1500 h short lifetime test.The key factor affecting the lifetime of the triple grids in the LIPS-300 ion thruster is obtained and analyzed through the test results.The results show that ion sputtering erosion of the grids in 5 kW operation mode is greater than in the case of 3 kW.In 5 kW mode,the decelerator grid shows the most serious corrosion,the accelerator grid shows moderate corrosion,and the screen grid shows the least amount of corrosion.With the serious corrosion of the grids in 5 kW operation mode,the intercept current of the acceleration and deceleration grids increases substantially.Meanwhile,the cold gap between the accelerator grid and the screen grid decreases from 1 mm to 0.7 mm,while the cold gap between the accelerator grid and the decelerator grid increases from 1 mm to 1.25 mm after 1500 h of thruster operation.At equilibrium temperature with 5 k W power,the finite element method(FEM)simulation results show that the hot gap between the screen grid and the accelerator grid reduces to 0.2 mm.Accordingly,the hot gap between the accelerator grid and the decelerator grid increases to 1.5 mm.According to the fluid method,the plasma density simulated in most regions of the discharge chamber is 1?×?10^(18)-8?×?10^(18)m^(-3).The upstream plasma density of the screen grid is in the range 6?×?10^(17)-6?×?10^(18)m^(-3)and displays a parabolic characteristic.The charged particle tracing simulation method results show that the ion beam current without the thermal deformation of triple grids has optimal perveance status.The ion sputtering rates of the accelerator grid hole and the decelerator hole are 5.5?×?10^(-14)kg s^(-1)and 4.28?×?10^(-14)kg s^(-1),respectively,while after the thermal deformation of the triple grids,the ion beam current has over-perveance status.The ion sputtering rates of the accelerator grid hole and the decelerator hole are 1.41?×?10^(-13)kg s^(-1)and 4.1?×?10^(-13)kg s^(-1),respectively.The anode current is a key factor for the triple grid lifetime in situations where the structural strength of the grids does not change with temperature variation.The average sputtering rates of the accelerator grid and the decelerator grid,which were measured during the 1500 h lifetime test in5 k W operating conditions,are 2.2?×?10^(-13)kg s^(-1)and 7.3?×?10^(-13)kg s^(-1),respectively.These results are in accordance with the simulation,and the error comes mainly from the calculation distribution of the upstream plasma density of the grids.展开更多
A thermal fatigue lifetime prediction model of ceramic ball grid array(CBGA)packages is proposed based on the Darveaux model.A finite element model of the CBGA packages is established,and the Anand model is used to de...A thermal fatigue lifetime prediction model of ceramic ball grid array(CBGA)packages is proposed based on the Darveaux model.A finite element model of the CBGA packages is established,and the Anand model is used to describe the viscoplasticity of the CBGA solder.The average viscoplastic strain energy density increment △Wave of the CBGA packages is obtained using a finite element simulation,and the influence of different structural parameters on theWave is analyzed.A simplified analytical model of the △Wave is established using the simulation data.The thermal fatigue lifetime of CBGA packages is obtained from a thermal cycling test.The Darveaux lifetime predictionmodel ismodified based on the thermal fatigue lifetime obtained fromthe experiment and the corresponding △Wave.A validation test is conducted to verify the accuracy of the thermal fatigue lifetime prediction model of the CBGA packages.This proposed model can be used in engineering to evaluate the lifetime of CBGA packages.展开更多
文摘Drinking good quality water is essential for better health. It is therefore essential to assess the radiological quality of all water consumed in the District of Abidjan in order to prevent related hazards. Thus, the objective of this study was to assess the risk of cancer due to the ingestion of alpha and beta emitting radionuclides in the different types of water consumed in the region. A total of 63 water samples with 43 tap water samples, 5 bottled mineral water and 15 sachet water samples was collected and taken to GAEC laboratory for analysis. The low background Gas-less Automatic Alpha/Beta counting system (Canberra iMatic<sup>TM</sup>) was used to determine alpha and beta activity concentrations. Activity concentrations of both gross alpha and gross beta obtained in water sample were respectively lower than the WHO recommended limits of 0.1 Bq/l and 1 Bq/l. Also, the annual effective dose and total equivalent effective dose found in mineral bottled water samples were higher than in other types of water. The assessment of radiological lifetime risk has shown values of cancer risk due to ingestion alpha and beta emitters lower than recommended limit. These results indicate that there is no health hazard associated to consumption of water in the District of Abidjan.
基金supported by the National Key Research and Development Program of China under Grant No.2021YFB2800304.
文摘Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible substrates.The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes.However,the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle.This article presents a novel explanation that recon-ciles this controversy.Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window.Further,we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states.Each of the contradictory size-dependent patterns reflects this trend in a specific size range.As the optical band gap increases,the radiative lifetime decreases in larger QDs,increases in smaller QDs,and is weakly depend-ent on size in the intermediate energy region.This study addresses the inconsistencies in the scaling law of the exciton life-time and gives a unified interpretation over a widened framework.Moreover,it provides valuable guidance for carrier separa-tion in the thin film solar cell of CdSe QDs.
基金Project supported by the Research Foundation for Higher Level Talents of West Anhui University(Grant No.WGKQ2021005)。
文摘Employing the advanced relativistic configuration interaction(RCI)combined with the many-body perturbation theory(RMBPT)method,we report energies and lifetime values for the lowest 35 energy levels from the(1s^(2))nl configurations(where the principal quantum number n=2–6 and the angular quantum number l=0,...,n-1)of lithium-like iron Fe XXIV,as well as complete data on the transition wavelengths,radiative rates,absorption oscillator strengths,and line strengths between the levels.Both the allowed(E1)and forbidden(magnetic dipole M1,magnetic quadrupole M2,and electric quadrupole E2)ones are reported.Through detailed comparisons with previous results,we assess the overall accuracies of present RMBPT results to be likely the most precise ones to date.Configuration interaction effects are found to be very important for the energies and radiative properties for the ion.The present RMBPT results are valuable for spectral line identification,plasma modeling,and diagnosing.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1602500)the National Natural Science Foundation of China(Grant No.12274352)。
文摘An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T.The decay photons emitted from 3d^(9) ^(2)D_(3/2) level are subsequently recorded via a cooled photomultiplier tube.Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes,we have determined the lifetime of Mo^(15+)3d^(9)2D_(3/2)metastable level to be 2.83(22)ms.The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches.
基金Project supported by Key Area Research and Development Project of Guangdong Province,China(Grant No.2020B010170002)the Science Challenge Project(Grant No.TZ2018003-1-101)+4 种基金the Natural Science Foundation of Fujian Province of China for Distinguished Young Scholars(Grant No.2020J06002)the Science and Technology Project of Fujian Province of China(Grant No.2020I0001)the Fundamental Research Funds for the Central Universities(Grant Nos.20720190049 and 20720190053)the Science and Technology Key Projects of Xiamen(Grant No.3502ZCQ20191001)the National Natural Science Foundation of China(Grant No.51871189)。
文摘Thermal oxidation and hydrogen annealing were applied on a 100μm thick Al-doped p-type 4H-Si C epitaxial wafer to modulate the minority carrier lifetime,which was investigated by microwave photoconductive decay(μ-PCD).The minority carrier lifetime decreased after each thermal oxidation.On the contrary,with the hydrogen annealing time increasing to3 hours,the minority carrier lifetime increased from 1.1μs(as-grown)to 3.14μs and then saturated after the annealing time reached 4 hours.The increase of surface roughness from 0.236 nm to 0.316 nm may also be one of the reasons for limiting the further improvement of the minority carrier lifetimes.Moreover,the whole wafer mappings of minority carrier lifetimes before and after hydrogen annealing were measured and discussed.The average minority carrier lifetime was up to 1.94μs and non-uniformity of carrier lifetime reached 38%after 4-hour hydrogen annealing.The increasing minority carrier lifetimes could be attributed to the double mechanisms of excess carbon atoms diffusion caused by selective etching of Si atoms and passivation of deep-level defects by hydrogen atoms.
文摘In Wireless Sensor Network(WSN),scheduling is one of the important issues that impacts the lifetime of entire WSN.Various scheduling schemes have been proposed earlier to increase the lifetime of the network.Still,the results from such methods are compromised in terms of achieving high lifetime.With this objective to increase the lifetime of network,an Efficient Topology driven Cooperative Self-Scheduling(TDCSS)model is recommended in this study.Instead of scheduling the network nodes in a centralized manner,a combined approach is proposed.Based on the situation,the proposed TDCSS approach performs scheduling in both the ways.By sharing the node statistics in a periodic manner,the overhead during the transmission of control packets gets reduced.This in turn impacts the lifetime of all the nodes.Further,this also reduces the number of idle conditions of each sensor node which is required for every cycle.The proposed method enables every sensor to schedule its own conditions according to duty cycle and topology constraints.Central scheduler monitors the network conditions whereas total transmissions occurs at every cycle.According to this,the source can infer the possible routes in a cycle and approximate the available routes.Further,based on the statistics of previous transmissions,the routes towards the sink are identified.Among the routes found,a single optimal route with energy efficiency is selected to perform data transmission.This cooperative approach improves the lifetime of entire network with high throughput performance.
基金the financial support from the National Key R&D Program of China(2018YFF0215400)grants from the Gemmological Institute of the China University of Geosciences in Wuhan。
文摘Amber can emit room temperature phosphorescence(RTP)under the well-known 365 nm fluorescence ultraviolet light.This paper is devoted to the phosphorescence study of 20 pieces of amber materials from the Dominican Republic,Mexico,Baltic sea,Myanmar,and Fushun,China.The results show that amber from the same geographic origin has similar shape in phosphorescence spectra.However,the shape of the amber phosphorescence spectra varies depending on their different localities.Burmite(amber from Myanmar)and Fushun amber have a bright yellow phosphorescence with a long lifetime,while the Dominican and Mexican ones are weaker and last shorter.The irradiation of Baltic amber becomes faint or even inert.Phosphorescence spectral Gaussian fitting results suggest an emission maximum near 550 nm in most amber samples.Their phosphorescence lifetime,analyzed through the exponential function fitting,is up to 1 second in Burmite and Fushun samples,shorter in the Dominican and Mexican ones,about 0.230 s,and the shortest in Baltic amber,close to 0.151 s.These variations of phosphorescence lifetime and intensity are related to the relative geological ages of these amber.It indicated that the phosphorescence agent was probably formed during the long geological time.While the anomaly occurred in Baltic amber,the only one found in a sea secondary deposit form,it demonstrated that the terrestrial geological environment these amber preserved has prevented the phosphorescence agent to be deactivated.
文摘The air continues to be an extremely substantial part of survival on earth.Air pollution poses a critical risk to humans and the environment.Using sensor-based structures,we can get air pollutant data in real-time.However,the sensors rely upon limited-battery sources that are immaterial to be alternated repeatedly amid extensive broadcast costs associated with real-time applications like air quality monitoring.Consequently,air quality sensor-based monitoring structures are lifetime-constrained and prone to the untimely loss of connectivity.Effective energy administration measures must therefore be implemented to handle the outlay of power dissipation.In this study,the authors propose outdoor air quality monitoring using a sensor network with an enhanced lifetime-enhancing cooperative data gathering and relaying algorithm(E-LCDGRA).LCDGRA is a cluster-based cooperative event-driven routing scheme with dedicated relay allocation mechanisms that tackle the problems of event-driven clustered WSNs with immobile gateways.The adapted variant,named E-LCDGRA,enhances the LCDGRA algorithm by incorporating a non-beacon-aided CSMA layer-2 un-slotted protocol with a back-off mechanism.The performance of the proposed E-LCDGRA is examined with other classical gathering schemes,including IEESEP and CERP,in terms of average lifetime,energy consumption,and delay.
基金supported by the National Defense Foundation of China(71601183)
文摘For the product degradation process with random effect(RE), measurement error(ME) and nonlinearity in step-stress accelerated degradation test(SSADT), the nonlinear Wiener based degradation model with RE and ME is built. An analytical approximation to the probability density function(PDF) of the product's lifetime is derived in a closed form. The process and data of SSADT are analyzed to obtain the relation model of the observed data under each accelerated stress. The likelihood function for the population-based observed data is constructed. The populationbased model parameters and its random coefficient prior values are estimated. According to the newly observed data of the target product in SSADT, an analytical approximation to the PDF of its residual lifetime(RL) is derived in accordance with its individual degradation characteristics. The parameter updating method based on Bayesian inference is applied to obtain the posterior value of random coefficient of the RL model. A numerical example by simulation is analyzed to verify the accuracy and advantage of the proposed model.
基金supported by the National Key R&D Program of China (Nos. 2016YFB0401801, 2016YFB0400803)the Science Challenge Project (No. TZ2016003)+1 种基金the National Natural Science Foundation of China (Nos. 61674138, 61674139, 61604145, 61574135, 61574134, 61474142, 61474110)the Beijing Municipal Science and Technology Project (No. Z161100002116037)
文摘GaN-based continuous-wave operated blue-violet laser diodes(LDs) with long lifetime are demonstrated, which are grown on a c-plane GaN substrate by metal organic chemical vapor deposition with a 10 × 600 μm^2 ridge waveguide structure.The electrical and optical characteristics of a blue-violet LD are investigated under direct-current injection at room temperature(25 °C). The stimulated emission wavelength and peak optical power of the LD are around 413 nm and over 600 mW, respectively.In addition, the threshold current density and voltage are as small as 1.46 kA/cm^2 and 4.1 V, respectively. Moreover, the lifetime is longer than 1000 hours under room-temperature continuous-wave operation.
基金supported by the National Defense Foundation of China(71601183)the China Postdoctoral Science Foundation(2017M623415)
文摘For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency of the parameters estimation are not high, and the current degradation state of the target device is not accurately estimated. In this paper, a nonlinear Wiener degradation model with random effect is proposed and the corresponding probability density function(PDF) of the first hitting time(FHT)is deduced. A parameter estimation method based on modified expectation maximum(EM) algorithm is proposed to obtain the estimated value of fixed coefficient and the priori value of random coefficient in the model. The posterior value of the random coefficient and the current degradation state of target device are updated synchronously by the state space model(SSM) and the Kalman filter algorithm. The PDF of RL with random effect is deduced. A simulation example is analyzed to verify that the proposed method has the obvious advantage over the existing methods in parameter estimation error and RL prediction accuracy.
基金Supported by National Natural Science Foundation of China(Grant Nos.51875054,U1864212)Graduate Research and Innovation Foundation of Chongqing+2 种基金China(Grant No.CYS20018)Chongqing Municipal Natural Science Foundation for Distinguished Young Scholars of China(Grant No.cstc2019jcyjjq X0016)Chongqing Science and Technology Bureau of China。
文摘Aging diagnosis of batteries is essential to ensure that the energy storage systems operate within a safe region.This paper proposes a novel cell to pack health and lifetime prognostics method based on the combination of transferred deep learning and Gaussian process regression.General health indicators are extracted from the partial discharge process.The sequential degradation model of the health indicator is developed based on a deep learning framework and is migrated for the battery pack degradation prediction.The future degraded capacities of both battery pack and each battery cell are probabilistically predicted to provide a comprehensive lifetime prognostic.Besides,only a few separate battery cells in the source domain and early data of battery packs in the target domain are needed for model construction.Experimental results show that the lifetime prediction errors are less than 25 cycles for the battery pack,even with only 50 cycles for model fine-tuning,which can save about 90%time for the aging experiment.Thus,it largely reduces the time and labor for battery pack investigation.The predicted capacity trends of the battery cells connected in the battery pack accurately reflect the actual degradation of each battery cell,which can reveal the weakest cell for maintenance in advance.
基金partially supported by National Natural Science Foundation of China(61472072)National Basic Pre-research Program of China(2014CB360509)
文摘Cyber-physical-system（CPS） has been widely used in both civil and military applications.Wireless sensor network（WSN） as the part and parcel of CPS faces energy problem because sensors are battery powered,which results in limited lifetime of the network.To address this energy problem,we take advantage of energy harvesting device（EHD） and study how to indefinitely prolong oil pipeline monitoring network lifetime by reasonable selecting EHD.Firstly,we propose a general strategy worst case-energy balance strategy（WC-EBS）,which defines worst case energy consumption（WCEC） as the maximum energy sensor node could expend for oil pipeline monitoring WSN.When the energy collected by EHD is equal or greater than WCEC,network can have an unlimited lifetime.However,energy harvesting rate is proportional to the price of EHD,WC-EBS will cause high network cost.To reduce network cost,we present two optimization strategies,optimization workloadenergy balance strategy（OW-EBS） and optimization first nodeenergy balance strategy（OF-EBS）.The main idea of OW-EBS is to cut down WCEC by reducing critical node transmission workload;OF-EBS confirms critical node by optimizing each sensor node transmission range,then we get the optimal energy harvesting rate in OF-EBS.The experimental results demonstrate that OF-EBS can indefinitely extend network lifetime with lower cost than WC-EBS and OW-EBS,and energy harvesting rate P in each strategy satisfies Pof-EBS≤P（OW-EBS）≤PWC-EBS.
基金The authors would like to thank Dr.Na Wang and Sai-Ke Tian in IHEP for their useful discussions.
文摘New-generation synchrotron light sources are being designed and operated worldwide to provide brighter radiation by reducing the beam emittance to X-ray diffraction limits.Intra-beam scattering(IBS)and Touschek scattering in such facilities are significant and require attention because of their ultra-low emittance.Therefore,cure strategies need to be carefully studied to obtain highquality photon beams.For the Shanghai Synchrotron Radiation Facility Upgrade(SSRF-U),a candidate lattice of the storage ring,reaching the soft X-ray diffraction limit,was designed and presented for the first time in this study.The emittance growth and beam lifetime in the SSRF-U storage ring were studied using particle simulations for a series of different machine configurations.The gains with RF frequencies of 100 MHz and 500 MHz were compared.Along with a better filling pattern,a more suitable RF frequency was adopted in the SSRF-U.The variations in the equilibrium beam emittance with beam coupling and bunch-lengthening were identified using simulations.Optimal beam coupling and required bunch-lengthening for the SSRF-U storage ring were thus determined.The fitness of the beam energy in the SSRF-U was subsequently assessed using the obtained parameters.Additionally,the Touschek scattering and beam lifetime were calculated,and an acceptable total beam lifetime was obtained.
基金supported by the National Natural Science Foundation of China(No.11575282)the Ten Thousand Talent Program
文摘Continuous tracking of bunch charges is the key to maintain stable operations in a storage ring in top-up mode. Recently, a precise bunch-by-bunch beam-current measurement (BCM) system has been developed at the Shanghai Synchrotron Radiation Facility. To avoid the influence of longitudinal oscillation on the amplitudes of the sampling points, a method called two-point equilibrium sampling is introduced. The results, obtained during routine operation time, show that the relative resolution of the measurement of the bunch charges is better than 0.02%. With this high resolution, the new BCM system is able to monitor the bunch-by-bunch beam lifetime. By using the filling pattern information, the Touschek lifetime and the vacuum lifetime can also be calculated. In this paper, the principle of the new method and the experiments is presented in detail.
基金the National Natural Science Foundation of China (296333010) and The President Science Foundation of the Chinese Academy of Scie
文摘Octadecylamine was derivatized with dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride) in order to simplify and understand the LB films of fluorescent probe labeling proteins. Its monolayer and multilayers in the absence and presence of stearic acid were deposited by LB technique. Fluorescence spectra and lifetimes of the fluorescent products were studied to elucidate the microenvironment of molecules in the LB films.
基金supported by the fund of National Key Laboratory of Science and Technology on Vacuum Technology and Physics (Grant No. 6142207030103)
文摘In order to ascertain the key factors affecting the lifetime of the triple grids in the LIPS-300 ion thruster,the thermal deformation,upstream ion density and component lifetime of the grids are simulated with finite element analysis,fluid simulation and charged-particle tracing simulation methods on the basis of a 1500 h short lifetime test.The key factor affecting the lifetime of the triple grids in the LIPS-300 ion thruster is obtained and analyzed through the test results.The results show that ion sputtering erosion of the grids in 5 kW operation mode is greater than in the case of 3 kW.In 5 kW mode,the decelerator grid shows the most serious corrosion,the accelerator grid shows moderate corrosion,and the screen grid shows the least amount of corrosion.With the serious corrosion of the grids in 5 kW operation mode,the intercept current of the acceleration and deceleration grids increases substantially.Meanwhile,the cold gap between the accelerator grid and the screen grid decreases from 1 mm to 0.7 mm,while the cold gap between the accelerator grid and the decelerator grid increases from 1 mm to 1.25 mm after 1500 h of thruster operation.At equilibrium temperature with 5 k W power,the finite element method(FEM)simulation results show that the hot gap between the screen grid and the accelerator grid reduces to 0.2 mm.Accordingly,the hot gap between the accelerator grid and the decelerator grid increases to 1.5 mm.According to the fluid method,the plasma density simulated in most regions of the discharge chamber is 1?×?10^(18)-8?×?10^(18)m^(-3).The upstream plasma density of the screen grid is in the range 6?×?10^(17)-6?×?10^(18)m^(-3)and displays a parabolic characteristic.The charged particle tracing simulation method results show that the ion beam current without the thermal deformation of triple grids has optimal perveance status.The ion sputtering rates of the accelerator grid hole and the decelerator hole are 5.5?×?10^(-14)kg s^(-1)and 4.28?×?10^(-14)kg s^(-1),respectively,while after the thermal deformation of the triple grids,the ion beam current has over-perveance status.The ion sputtering rates of the accelerator grid hole and the decelerator hole are 1.41?×?10^(-13)kg s^(-1)and 4.1?×?10^(-13)kg s^(-1),respectively.The anode current is a key factor for the triple grid lifetime in situations where the structural strength of the grids does not change with temperature variation.The average sputtering rates of the accelerator grid and the decelerator grid,which were measured during the 1500 h lifetime test in5 k W operating conditions,are 2.2?×?10^(-13)kg s^(-1)and 7.3?×?10^(-13)kg s^(-1),respectively.These results are in accordance with the simulation,and the error comes mainly from the calculation distribution of the upstream plasma density of the grids.
文摘A thermal fatigue lifetime prediction model of ceramic ball grid array(CBGA)packages is proposed based on the Darveaux model.A finite element model of the CBGA packages is established,and the Anand model is used to describe the viscoplasticity of the CBGA solder.The average viscoplastic strain energy density increment △Wave of the CBGA packages is obtained using a finite element simulation,and the influence of different structural parameters on theWave is analyzed.A simplified analytical model of the △Wave is established using the simulation data.The thermal fatigue lifetime of CBGA packages is obtained from a thermal cycling test.The Darveaux lifetime predictionmodel ismodified based on the thermal fatigue lifetime obtained fromthe experiment and the corresponding △Wave.A validation test is conducted to verify the accuracy of the thermal fatigue lifetime prediction model of the CBGA packages.This proposed model can be used in engineering to evaluate the lifetime of CBGA packages.
