Estimation of leaf chlorophyll content(LCC) by proximal sensing is an important tool for photosynthesis evaluation in high-throughput phenotyping. The temporal variability of crop biochemical properties and canopy str...Estimation of leaf chlorophyll content(LCC) by proximal sensing is an important tool for photosynthesis evaluation in high-throughput phenotyping. The temporal variability of crop biochemical properties and canopy structure across different growth stages has great impacts on wheat LCC estimation, known as growth stage effects. It will result in the heterogeneity of crop canopy at different growth stages, which would mask subtle spectral response of biochemistry variations. This study aims to explore spectral responses on the growth stage effects and establish LCC models suited for different growth stages. A total number of 864 pairwise samples of wheat canopy spectra and LCC values with 216 observations of each stage were sampled at the tillering, jointing, booting and heading stages in 2021. Firstly, statistical analysis of LCC and spectral response presented different distribution traits and typical spectral variations peak at 470, 520 and 680 nm. Correlation analysis between LCC and reflectance showed typical red edge shifts. Secondly, the testing model of partial least square(PLS) established by the entire datasets to validate the predictive performance at each stage yielded poor LCC estimation accuracy. The spectral wavelengths of red edge(RE) and blue edge(BE) shifts and the poor estimation capability motivated us to further explore the growth stage effects by establishing LCC models at respective growth periods.Finally, competitive adaptive reweighted sampling PLS(CARS-PLS), decision tree(DT) and random forest(RF) were used to select sensitive bands and establish LCC models at specific stages. Bayes optimisation was used to tune the hyperparameters of DT and RF regression. The modelling results indicated that CARS-PLS and DT did not extract specific wavelengths that could decrease the influences of growth stage effects. From the RF out-of-bag(OOB) evaluation, the sensitive wavelengths displayed consistent spectral shifts from BE to GP and from RE to RV from tillering to heading stages. Compared with CARS-PLS and DT,results of RF modelling yielded an estimation accuracy with deviation to performance(RPD) of 2.11, 2.02,3.21 and 3.02, which can accommodate the growth stage effects. Thus, this study explores spectral response on growth stage effects and provides models for chlorophyll content estimation to satisfy the requirement of high-throughput phenotyping.展开更多
The Schottky photodetector was fabricated on GaN epilayers grown by metalorganic chemical vapour deposition (MOCVD). The spectral response of the Schottky photodetector was characterized. A new model is proposed to ...The Schottky photodetector was fabricated on GaN epilayers grown by metalorganic chemical vapour deposition (MOCVD). The spectral response of the Schottky photodetector was characterized. A new model is proposed to interpret the characteristic of the spectral response curve of the Schottky photodetectors by introducing a penetrating distance of an incident light at a certain wavelength in the current continuity equation and the interface recombination at the metal-semiconductor rectifying contact. The expressions for the spectral response of the Schottky photodetector are deduced and used successfully to fit the experimental data.展开更多
This work introduces the branching ratio(BR) method for determining relative spectral responses,which are needed routinely in laser induced breakdown spectroscopy(LIBS). Neutral and singly ionized Ti lines in the 250...This work introduces the branching ratio(BR) method for determining relative spectral responses,which are needed routinely in laser induced breakdown spectroscopy(LIBS). Neutral and singly ionized Ti lines in the 250–498 nm spectral range are investigated by measuring laser-induced micro plasma near a Ti plate and used to calculate the relative spectral response of an entire LIBS detection system. The results are compared with those of the conventional relative spectral response calibration method using a tungsten halogen lamp, and certain lines available for the BR method are selected. The study supports the common manner of using BRs to calibrate the detection system in LIBS setups.展开更多
A four-channel 400 GHz channel spacing InP-based arrayed waveguide grating with a flattened wavelength re- sponse by employing a multimode interference coupler at the input waveguide of the filter is prepared. The fab...A four-channel 400 GHz channel spacing InP-based arrayed waveguide grating with a flattened wavelength re- sponse by employing a multimode interference coupler at the input waveguide of the filter is prepared. The fabricated devices show a flattened spectral response with a broadened 3-dB bandwidth up to 3.5 nm, interchan- nel non-uniformity of 〈0. 7dB and excellent match to the simulation results.展开更多
We report our results on the modeling of the spectral response of the near-infrared(NIR) lattice-matched p-n-p In_(0.53)Ga_(0.47)As/InP heterojunction pbototransistors(HPTs).The spectral response model is deve...We report our results on the modeling of the spectral response of the near-infrared(NIR) lattice-matched p-n-p In_(0.53)Ga_(0.47)As/InP heterojunction pbototransistors(HPTs).The spectral response model is developed from the solution of the steady state continuity equations that dominate the excess optically generated minority-carriers in the active regions of the HPTs with accurate boundary-conditions.In addition,a detailed optical-power absorption profile is constructed for the device modeling.The calculated responsivity is in good agreement with the measured one for the incident radiation at980 nm,1310 nm,and 1550 nm.Furthermore,the variation in the responsivity of the device with the base region width is analyzed.展开更多
General Research Institute for Non-ferrous Metals in cooperation with Changchun Instituteof Optical and Fine Mechanics prepared an automatic measurement instrument for spectral re-sponse test of solar cells. This inst...General Research Institute for Non-ferrous Metals in cooperation with Changchun Instituteof Optical and Fine Mechanics prepared an automatic measurement instrument for spectral re-sponse test of solar cells. This instrument having enough accuracy can measure at AM1.5 condi-tion. It meets the needs for measurement of spectral response for silicon, gallium arsenide solarcells.展开更多
Hyper-and multi-spectral image fusion is an important technology to produce hyper-spectral and hyper-resolution images,which always depends on the spectral response function andthe point spread function.However,few wo...Hyper-and multi-spectral image fusion is an important technology to produce hyper-spectral and hyper-resolution images,which always depends on the spectral response function andthe point spread function.However,few works have been payed on the estimation of the two degra-dation functions.To learn the two functions from image pairs to be fused,we propose a Dirichletnetwork,where both functions are properly constrained.Specifically,the spatial response function isconstrained with positivity,while the Dirichlet distribution along with a total variation is imposedon the point spread function.To the best of our knowledge,the neural network and the Dirichlet regularization are exclusively investigated,for the first time,to estimate the degradation functions.Both image degradation and fusion experiments demonstrate the effectiveness and superiority of theproposed Dirichlet network.展开更多
Dynamically engineering the optical and electrical properties in two-dimensional(2D)materials is of great signifcance for designing the related functions and applications.The introduction of foreign-atoms has previous...Dynamically engineering the optical and electrical properties in two-dimensional(2D)materials is of great signifcance for designing the related functions and applications.The introduction of foreign-atoms has previously been proven to be a feasible way to tune the band structure and related properties of 3D materials;however,this approach still remains to be explored in 2D materials.Here,we systematically demonstrate the growth of vanadium-doped molybdenum disulfde(V-doped MoS_(2))monolayers via an alkali metal-assisted chemical vapor deposition method.Scanning transmission electron microscopy demonstrated that V atoms substituted the Mo atoms and became uniformly distributed in the MoS_(2)monolayers.This was also confrmed by Raman and X-ray photoelectron spectroscopy.Power-dependent photoluminescence spectra clearly revealed the enhanced B-exciton emission characteristics in the V-doped MoS_(2)monolayers(with low doping concentration).Most importantly,through temperature-dependent study,we observed efcient valley scattering of the B-exciton,greatly enhancing its emission intensity.Carrier transport experiments indicated that typical p-type conduction gradually arisen and was enhanced with increasing V composition in the V-doped MoS_(2),where a clear n-type behavior transited frst to ambipolar and then to lightly p-type charge carrier transport.In addition,visible to infrared wide-band photodetectors based on V-doped MoS_(2)monolayers(with low doping concentration)were demonstrated.The V-doped MoS_(2)monolayers with distinct B-exciton emission,enhanced p-type conduction and broad spectral response can provide new platforms for probing new physics and ofer novel materials for optoelectronic applications.展开更多
As an important rice disease, rice bacterial leaf blight (RBLB, caused by the bacterium Xanthomonas oryzae pv.oryzae), has become widespread in east China in recent years. Significant losses in rice yield occurred as ...As an important rice disease, rice bacterial leaf blight (RBLB, caused by the bacterium Xanthomonas oryzae pv.oryzae), has become widespread in east China in recent years. Significant losses in rice yield occurred as a result ofthe disease’s epidemic, making it imperative to monitor RBLB at a large scale. With the development of remotesensing technology, the broad-band sensors equipped with red-edge channels over multiple spatial resolutionsoffer numerous available data for large-scale monitoring of rice diseases. However, RBLB is characterized by rapiddispersal under suitable conditions, making it difficult to track the disease at a regional scale with a single sensorin practice. Therefore, it is necessary to identify or construct features that are effective across different sensors formonitoring RBLB. To achieve this goal, the spectral response of RBLB was first analyzed based on the canopyhyperspectral data. Using the relative spectral response (RSR) functions of four representative satellite or UAVsensors (i.e., Sentinel-2, GF-6, Planet, and Rededge-M) and the hyperspectral data, the corresponding broad-bandspectral data was simulated. According to a thorough band combination and sensitivity analysis, two novel spectralindices for monitoring RBLB that can be effective across multiple sensors (i.e., RBBRI and RBBDI) weredeveloped. An optimal feature set that includes the two novel indices and a classical vegetation index was formed.The capability of such a feature set in monitoring RBLB was assessed via FLDA and SVM algorithms. The resultdemonstrated that both constructed novel indices exhibited high sensitivity to the disease across multiple sensors.Meanwhile, the feature set yielded an overall accuracy above 90% for all sensors, which indicates its cross-sensorgenerality in monitoring RBLB. The outcome of this research permits disease monitoring with different remotesensing data over a large scale.展开更多
A two-dimensional model of a 4H-SiC metal-semiconductor-metal(MSM) ultraviolet photodetector has been established using a self-consistent numerical calculation method.The structure-dependent spectral response of a 4...A two-dimensional model of a 4H-SiC metal-semiconductor-metal(MSM) ultraviolet photodetector has been established using a self-consistent numerical calculation method.The structure-dependent spectral response of a 4H-SiC MSM detector is calculated by solving Poisson's equation,the current continuity equation and the current density equation.The calculated results are verified with experimental data.With consideration of the reflection and absorption on the metal contacts,a detailed study involving various electrode heights(H),spacings (S) and widths(W) reveals conclusive results in device design.The mechanisms responsible for variations of responsivity with those parameters are analyzed.The findings show that responsivity is inversely proportional to electrode height and is enhanced with an increase of electrode spacing and width.In addition,the ultraviolet (UV)-to-visible rejection ratio is 103.By optimizing the device structure at 10 V bias,a responsivity as high as 180.056 mA/W,a comparable quantum efficiency of 77.93%and a maximum UV-to-visible rejection ratio of 1875 are achieved with a detector size of H = 50 nm,S =9μm and W = 3μm.展开更多
We study,by means of numerical simulation,the impact of doping and traps on the performance of the"solar blind"ultraviolet Schottky detector based on AlGaN.We implemented physical models and AlGaN material propertie...We study,by means of numerical simulation,the impact of doping and traps on the performance of the"solar blind"ultraviolet Schottky detector based on AlGaN.We implemented physical models and AlGaN material properties taken from the literature,or from the interpolation between the binary materials(GaN and AlN) weighted by the mole fractions.We found that doping and traps highly impact the spectral response of the device,and in particular a compromise in the doping concentration must be reached in order to optimize the spectral response of the detector.These results give us a powerful tool to quantitatively understand the impact of elaboration and processing conditions on photodetector characteristics,and thus identify the key issues for the development of the technology.展开更多
Based on transmission theory, a 17 x 17 polymer arrayed waveguide grating (AWG) multiplexer para meter optimization is performed, and the influence of the fabrication results on the transmission characteristics are ...Based on transmission theory, a 17 x 17 polymer arrayed waveguide grating (AWG) multiplexer para meter optimization is performed, and the influence of the fabrication results on the transmission characteristics are analyzed. In this paper, we mainly discuss three of the main errors in the fabrication of polymer AWG devices. One is 3n 1, which is caused by the tuning of the core refractive index n 1, the second is 8b, which results from the rotating-coating of the core thickness b, and the other is the non-ideal core cross-section, which is caused by steam redissolution. The effects of the above fabrication errors on the transmission characteristics of the AWG device are investigated, and compensation techniques are proposed. By comparing the theoretical simulation and experimental results, the shift in the transmission spectrum is reduced by 0.028 nm, the 3 dB bandwidth is increased by about 0.036 nm, the insertion loss is reduced by about 3 dB for the central channel and 4.5 dB for the edge channels, and the crosstalk is reduced by 1.5 dB.展开更多
Arrayed waveguide grating(AWG) is a key device in the wavelength-division multiplexing(WDM) system, and the flat spectral response of the AWG device is required.In this paper,the RIE process has been improved.By u...Arrayed waveguide grating(AWG) is a key device in the wavelength-division multiplexing(WDM) system, and the flat spectral response of the AWG device is required.In this paper,the RIE process has been improved.By using the steam-redissolution technique,the insertion loss and the crosstalk have been reduced.Experimental results show that the central wavelength is 1550.86 nm,the channel spectral response flatness is about 1.5 dB,3-dB bandwidth is about 0.478 nm,insertion loss is 10.5 dB,and crosstalk is about-22 dB.The insertion loss of an AWG device is reduced by about 3 dB for the central channel and 4.5 dB for the edge channels,and the crosstalk is reduced by 2.5 dB after the steam-redissolution.展开更多
A retrofit procedure for existing buildings called the "weakening and damping technique" (WED) is presented in this paper. Weakening of structures can limit the maximum response accelerations during severe ground ...A retrofit procedure for existing buildings called the "weakening and damping technique" (WED) is presented in this paper. Weakening of structures can limit the maximum response accelerations during severe ground motions, but leads to an increase in the displacements or inter-story drifts. Added damping by using viscous dampers, on the other hand, reduces the inter-story drifts and has no significant effect on total accelerations, when structures behave inelastically. The weakening and damping technique addresses the two main causes for both structural and nonstructural damage in structures. The weakening retrofit is particularly suitable for structures that have overstressed components and weak brittle components. In this paper, the advantages of the WeD are verified by nonlinear dynamic analysis and simplified spectral approach that has been modified to fit structures with additional damping devices. A hospital structure located in the San Fernando Valley in California is selected as a case study. The results from both analyses show that the retrofit solution is feasible to reduce both structural acceleration and displacement. A sensitivity analysis is also carried out to evaluate the effectiveness of the retrofitting method using different combinations of performance thresholds in accelerations and displacements through fragility analysis.展开更多
The present paper addresses the comparative study of three adjacent single-degree-of freedom structures for elastic and inelastic system with and without pounding under seismic excitations. For the gap between three a...The present paper addresses the comparative study of three adjacent single-degree-of freedom structures for elastic and inelastic system with and without pounding under seismic excitations. For the gap between three adjacent structures, the simulation is done by using linear spring element without damping. The entire numerical simulation is done in time domain by considering the inputs of four real ground motions. The results of the study show that the response of elastic system is much different to that of response of inelastic system in the absence and presence of pounding, especially in lighter or more flexible structures. Elastic structures show much severe pounding response than inelastic structures. Modeling of colliding structures behaving inelastically is really needed in order to obtain the accurate structural pounding involved response under seismic excitation.展开更多
Si-based optical position-sensitive detectors(PSDs)have stimulated the interest of researchers due to their wide range of practical applications.However,due to the rigidity and fragility of Si crystals,the application...Si-based optical position-sensitive detectors(PSDs)have stimulated the interest of researchers due to their wide range of practical applications.However,due to the rigidity and fragility of Si crystals,the applications of flexible PSDs have been limited.Therefore,we presented a flexible broadband PSD based on a WS_(2)/Si heterostructure for the first time.A scalable sputtering method was used to deposit WS_(2)thin films onto the etched ultrathin crystalline Si surface.The fabricated flexible PSD device has a broad spectral response in the wavelength range of 450-1350 nm,with a high position sensitivity of~539.8 mV·mm^(−1)and a fast response of 2.3μs,thanks to the strong light absorption,the built-in electrical field at the WS_(2)/Si interface,and facilitated transport.Furthermore,mechanical-bending tests revealed that after 200 mechanical-bending cycles,the WS_(2)/Si PSDs have excellent mechanical flexibility,stability,and durability,demonstrating the great potential in wearable PSDs with competitive performance.展开更多
Solar cell technology comes with unique temperature coefficients. These temperature coefficients are important and temperature of the solar cell has direct influence on the power output of a photovoltaic cells. CdTe i...Solar cell technology comes with unique temperature coefficients. These temperature coefficients are important and temperature of the solar cell has direct influence on the power output of a photovoltaic cells. CdTe is a very robust and chemically stable material and for this reason its related solar cell. Thin film photovoltaic technology is now the only thin film technology in the first top 10 producers in the world. The strong improvement in efficiency in the last 7 years was obtained by a new redesign of the CdTe solar cell device reaching a single solar cell. In this paper, we describe the fabrication process following the history of the solar cell as it was developed in the early years up to the latest development and changes. The configuration of fabricated cell is n-CdTe/NaOH (0.15 M) + S (0.15 M) + Na<sub>2</sub>S (0.15 M)/C<sub>(graphite)</sub>. The junction ideality factor was found to be 2.63, 2.13, and 1.89. The flat band potential is found to be -0.400, -0.450, -0.501 V. The barrier height value was found to be 0.523, 0.487, and 0.436 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency were found to be 120 mV, 24.2 μA, 32.68%, 26.18%, and 19.73% and 0.63%, 0.37%, and 0.23%, respectively. The lighted ideality factor was calculated and found to be 3.26, 1.87, and 1.17. Spectra attain maximum value of current at λ = 580 nm and decrease with increase in wavelength. The photovoltaic cell characterization of the thin films is carried out by studying current-voltage characteristics in dark, capacitance-voltage in dark, barrier height measurements, power output characteristics.展开更多
In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics o...In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature.The results show that the photodetector has a good rectifying character and a good response to near-infrared light.Interface states should be minimized to obtain a lower reverse leakage current.The response spectrum of the β-FeSi2/4H-SiC detector,which consists of a p-type β-FeSi2 absorption layer with a doping concentration of 1×1015cm-3 and a thickness of 2.5 μm,has a peak of 755 mA/W at 1.42 μm.The illumination of the SiC side obtains a higher responsivity than that of the β-FeSi2 side.The results illustrate that the β-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices.展开更多
GaInP/GaAs/Ge triple-junction solar cells were irradiated with 50 keV and 100 keV protons at fluences of 5 × 10^10 cm^-2, 1 × 10^11 cm^-2,1 × 10^12 cm^-2, and 1 × 10^13 cm^-2. Their performance deg...GaInP/GaAs/Ge triple-junction solar cells were irradiated with 50 keV and 100 keV protons at fluences of 5 × 10^10 cm^-2, 1 × 10^11 cm^-2,1 × 10^12 cm^-2, and 1 × 10^13 cm^-2. Their performance degradation is analyzed using current-voltage characteristics and spectral response measurements, and then the changes in Isc, Voc, Pmax and the spectral response of the cells are observed as functions of proton irradiation fluence and energy. The results show that the spectral response of the top cell degrades more significantly than that of the middle cell, and 100 keV proton-induced degradation rates of Isc, Voc and Pmax are larger compared with 50 keV proton irradiation.展开更多
An optimization method for the consistent evaluation of two Rayleigh damping coefficients is proposed. By minimizing an objective function such as an error term of the peak displacement of a structure, the two coeffic...An optimization method for the consistent evaluation of two Rayleigh damping coefficients is proposed. By minimizing an objective function such as an error term of the peak displacement of a structure, the two coefficients can be determined with response spectral analysis. The optimization method degenerates into the conventional method used in current practices when only two modes of vibration are included in the objective function. Therefore, the proposed method with all significant modes included for simplicity in practical applications results in suboptimal damping coefficients. The effects of both spatial distribution and frequency content of excitations as well as structural dynamic characteristics on the evaluation of Rayleigh damping coefficients were investigated with a five-story building structure. Two application examples with a 62-story high-rise building and a 840 m long cable-stayed bridge under ten earthquake excitations demonstrated the accuracy and effectiveness of the proposed method to account for all of the above effects.展开更多
基金supported by the National Key Research and Development Program (2019YFE0125500)University-Locality Integrative Development Project of Yantai (2020XDRHXMPT35)+1 种基金the National Natural Science Foundation of China (31971785 and41801245)the Graduate Training Project of China Agricultural University (JG2019004, JG202026, YW2020007, QYJC202101, and JG202102)。
文摘Estimation of leaf chlorophyll content(LCC) by proximal sensing is an important tool for photosynthesis evaluation in high-throughput phenotyping. The temporal variability of crop biochemical properties and canopy structure across different growth stages has great impacts on wheat LCC estimation, known as growth stage effects. It will result in the heterogeneity of crop canopy at different growth stages, which would mask subtle spectral response of biochemistry variations. This study aims to explore spectral responses on the growth stage effects and establish LCC models suited for different growth stages. A total number of 864 pairwise samples of wheat canopy spectra and LCC values with 216 observations of each stage were sampled at the tillering, jointing, booting and heading stages in 2021. Firstly, statistical analysis of LCC and spectral response presented different distribution traits and typical spectral variations peak at 470, 520 and 680 nm. Correlation analysis between LCC and reflectance showed typical red edge shifts. Secondly, the testing model of partial least square(PLS) established by the entire datasets to validate the predictive performance at each stage yielded poor LCC estimation accuracy. The spectral wavelengths of red edge(RE) and blue edge(BE) shifts and the poor estimation capability motivated us to further explore the growth stage effects by establishing LCC models at respective growth periods.Finally, competitive adaptive reweighted sampling PLS(CARS-PLS), decision tree(DT) and random forest(RF) were used to select sensitive bands and establish LCC models at specific stages. Bayes optimisation was used to tune the hyperparameters of DT and RF regression. The modelling results indicated that CARS-PLS and DT did not extract specific wavelengths that could decrease the influences of growth stage effects. From the RF out-of-bag(OOB) evaluation, the sensitive wavelengths displayed consistent spectral shifts from BE to GP and from RE to RV from tillering to heading stages. Compared with CARS-PLS and DT,results of RF modelling yielded an estimation accuracy with deviation to performance(RPD) of 2.11, 2.02,3.21 and 3.02, which can accommodate the growth stage effects. Thus, this study explores spectral response on growth stage effects and provides models for chlorophyll content estimation to satisfy the requirement of high-throughput phenotyping.
文摘The Schottky photodetector was fabricated on GaN epilayers grown by metalorganic chemical vapour deposition (MOCVD). The spectral response of the Schottky photodetector was characterized. A new model is proposed to interpret the characteristic of the spectral response curve of the Schottky photodetectors by introducing a penetrating distance of an incident light at a certain wavelength in the current continuity equation and the interface recombination at the metal-semiconductor rectifying contact. The expressions for the spectral response of the Schottky photodetector are deduced and used successfully to fit the experimental data.
基金supported by the National Key Scientific Instrument and Equipment Development Projects of China (2014YQ120351)National Natural Science Foundation of China (11704372)Anhui Provincial Natural Science Foundation (1708085QF130)
文摘This work introduces the branching ratio(BR) method for determining relative spectral responses,which are needed routinely in laser induced breakdown spectroscopy(LIBS). Neutral and singly ionized Ti lines in the 250–498 nm spectral range are investigated by measuring laser-induced micro plasma near a Ti plate and used to calculate the relative spectral response of an entire LIBS detection system. The results are compared with those of the conventional relative spectral response calibration method using a tungsten halogen lamp, and certain lines available for the BR method are selected. The study supports the common manner of using BRs to calibrate the detection system in LIBS setups.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61274046,61201103,61335009 and61320106013the National Basic Research Program of China under Grant No 2013AA014202
文摘A four-channel 400 GHz channel spacing InP-based arrayed waveguide grating with a flattened wavelength re- sponse by employing a multimode interference coupler at the input waveguide of the filter is prepared. The fabricated devices show a flattened spectral response with a broadened 3-dB bandwidth up to 3.5 nm, interchan- nel non-uniformity of 〈0. 7dB and excellent match to the simulation results.
基金Project supported by the National Natural Science Foundation of China(Grant No.61307044)the National Basic Research Program of China(Grant No.2012CB619200)+4 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20130321)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20133201120009)the Open Project of Key Laboratory of Infrared Imaging Materials and Detectors,Chinese Academy of Sciences(IIMDKFJJ-15-06)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of Chinathe Research Innovation Program for College Graduates of Jiangsu Province,China(Grant No.SJLX15-0600)
文摘We report our results on the modeling of the spectral response of the near-infrared(NIR) lattice-matched p-n-p In_(0.53)Ga_(0.47)As/InP heterojunction pbototransistors(HPTs).The spectral response model is developed from the solution of the steady state continuity equations that dominate the excess optically generated minority-carriers in the active regions of the HPTs with accurate boundary-conditions.In addition,a detailed optical-power absorption profile is constructed for the device modeling.The calculated responsivity is in good agreement with the measured one for the incident radiation at980 nm,1310 nm,and 1550 nm.Furthermore,the variation in the responsivity of the device with the base region width is analyzed.
文摘General Research Institute for Non-ferrous Metals in cooperation with Changchun Instituteof Optical and Fine Mechanics prepared an automatic measurement instrument for spectral re-sponse test of solar cells. This instrument having enough accuracy can measure at AM1.5 condi-tion. It meets the needs for measurement of spectral response for silicon, gallium arsenide solarcells.
基金the Postdoctoral ScienceFoundation of China(No.2023M730156)the NationalNatural Foundation of China(No.62301012).
文摘Hyper-and multi-spectral image fusion is an important technology to produce hyper-spectral and hyper-resolution images,which always depends on the spectral response function andthe point spread function.However,few works have been payed on the estimation of the two degra-dation functions.To learn the two functions from image pairs to be fused,we propose a Dirichletnetwork,where both functions are properly constrained.Specifically,the spatial response function isconstrained with positivity,while the Dirichlet distribution along with a total variation is imposedon the point spread function.To the best of our knowledge,the neural network and the Dirichlet regularization are exclusively investigated,for the first time,to estimate the degradation functions.Both image degradation and fusion experiments demonstrate the effectiveness and superiority of theproposed Dirichlet network.
基金supported by the National Key R&D Program of China(No.2022YFA1204300)the National Natural Science Foundation of China(Grant Nos.62104066,52372146,U22A20138,52221001 and 62090035)+2 种基金the Open Project Program of Wuhan National Laboratory for Optoelectronics(No.2020WNLOKF016)the Science and Technology Innovation Program of Hunan Province(Nos.2021RC3061 and 2020RC2028)the National Postdoctoral Program for Innovative Talents(No.BX2021094).
文摘Dynamically engineering the optical and electrical properties in two-dimensional(2D)materials is of great signifcance for designing the related functions and applications.The introduction of foreign-atoms has previously been proven to be a feasible way to tune the band structure and related properties of 3D materials;however,this approach still remains to be explored in 2D materials.Here,we systematically demonstrate the growth of vanadium-doped molybdenum disulfde(V-doped MoS_(2))monolayers via an alkali metal-assisted chemical vapor deposition method.Scanning transmission electron microscopy demonstrated that V atoms substituted the Mo atoms and became uniformly distributed in the MoS_(2)monolayers.This was also confrmed by Raman and X-ray photoelectron spectroscopy.Power-dependent photoluminescence spectra clearly revealed the enhanced B-exciton emission characteristics in the V-doped MoS_(2)monolayers(with low doping concentration).Most importantly,through temperature-dependent study,we observed efcient valley scattering of the B-exciton,greatly enhancing its emission intensity.Carrier transport experiments indicated that typical p-type conduction gradually arisen and was enhanced with increasing V composition in the V-doped MoS_(2),where a clear n-type behavior transited frst to ambipolar and then to lightly p-type charge carrier transport.In addition,visible to infrared wide-band photodetectors based on V-doped MoS_(2)monolayers(with low doping concentration)were demonstrated.The V-doped MoS_(2)monolayers with distinct B-exciton emission,enhanced p-type conduction and broad spectral response can provide new platforms for probing new physics and ofer novel materials for optoelectronic applications.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA28010500)National Natural Science Foundation of China(Grant Nos.42371385,42071420)Zhejiang Provincial Natural Science Foundation of China(Grant No.LTGN23D010002).
文摘As an important rice disease, rice bacterial leaf blight (RBLB, caused by the bacterium Xanthomonas oryzae pv.oryzae), has become widespread in east China in recent years. Significant losses in rice yield occurred as a result ofthe disease’s epidemic, making it imperative to monitor RBLB at a large scale. With the development of remotesensing technology, the broad-band sensors equipped with red-edge channels over multiple spatial resolutionsoffer numerous available data for large-scale monitoring of rice diseases. However, RBLB is characterized by rapiddispersal under suitable conditions, making it difficult to track the disease at a regional scale with a single sensorin practice. Therefore, it is necessary to identify or construct features that are effective across different sensors formonitoring RBLB. To achieve this goal, the spectral response of RBLB was first analyzed based on the canopyhyperspectral data. Using the relative spectral response (RSR) functions of four representative satellite or UAVsensors (i.e., Sentinel-2, GF-6, Planet, and Rededge-M) and the hyperspectral data, the corresponding broad-bandspectral data was simulated. According to a thorough band combination and sensitivity analysis, two novel spectralindices for monitoring RBLB that can be effective across multiple sensors (i.e., RBBRI and RBBDI) weredeveloped. An optimal feature set that includes the two novel indices and a classical vegetation index was formed.The capability of such a feature set in monitoring RBLB was assessed via FLDA and SVM algorithms. The resultdemonstrated that both constructed novel indices exhibited high sensitivity to the disease across multiple sensors.Meanwhile, the feature set yielded an overall accuracy above 90% for all sensors, which indicates its cross-sensorgenerality in monitoring RBLB. The outcome of this research permits disease monitoring with different remotesensing data over a large scale.
基金Project supported by the Pre-Research Foundation from the National Ministries and Commissions(Nos.51323040118,513080302)
文摘A two-dimensional model of a 4H-SiC metal-semiconductor-metal(MSM) ultraviolet photodetector has been established using a self-consistent numerical calculation method.The structure-dependent spectral response of a 4H-SiC MSM detector is calculated by solving Poisson's equation,the current continuity equation and the current density equation.The calculated results are verified with experimental data.With consideration of the reflection and absorption on the metal contacts,a detailed study involving various electrode heights(H),spacings (S) and widths(W) reveals conclusive results in device design.The mechanisms responsible for variations of responsivity with those parameters are analyzed.The findings show that responsivity is inversely proportional to electrode height and is enhanced with an increase of electrode spacing and width.In addition,the ultraviolet (UV)-to-visible rejection ratio is 103.By optimizing the device structure at 10 V bias,a responsivity as high as 180.056 mA/W,a comparable quantum efficiency of 77.93%and a maximum UV-to-visible rejection ratio of 1875 are achieved with a detector size of H = 50 nm,S =9μm and W = 3μm.
文摘We study,by means of numerical simulation,the impact of doping and traps on the performance of the"solar blind"ultraviolet Schottky detector based on AlGaN.We implemented physical models and AlGaN material properties taken from the literature,or from the interpolation between the binary materials(GaN and AlN) weighted by the mole fractions.We found that doping and traps highly impact the spectral response of the device,and in particular a compromise in the doping concentration must be reached in order to optimize the spectral response of the detector.These results give us a powerful tool to quantitatively understand the impact of elaboration and processing conditions on photodetector characteristics,and thus identify the key issues for the development of the technology.
基金supported by the National Natural Science Foundation of China(No.11254001)the Science and Technology Development of Jilin Province of China(Nos.20110320,201201078)
文摘Based on transmission theory, a 17 x 17 polymer arrayed waveguide grating (AWG) multiplexer para meter optimization is performed, and the influence of the fabrication results on the transmission characteristics are analyzed. In this paper, we mainly discuss three of the main errors in the fabrication of polymer AWG devices. One is 3n 1, which is caused by the tuning of the core refractive index n 1, the second is 8b, which results from the rotating-coating of the core thickness b, and the other is the non-ideal core cross-section, which is caused by steam redissolution. The effects of the above fabrication errors on the transmission characteristics of the AWG device are investigated, and compensation techniques are proposed. By comparing the theoretical simulation and experimental results, the shift in the transmission spectrum is reduced by 0.028 nm, the 3 dB bandwidth is increased by about 0.036 nm, the insertion loss is reduced by about 3 dB for the central channel and 4.5 dB for the edge channels, and the crosstalk is reduced by 1.5 dB.
基金Project supported by the National Natural Science Foundation of China(No.60576045).
文摘Arrayed waveguide grating(AWG) is a key device in the wavelength-division multiplexing(WDM) system, and the flat spectral response of the AWG device is required.In this paper,the RIE process has been improved.By using the steam-redissolution technique,the insertion loss and the crosstalk have been reduced.Experimental results show that the central wavelength is 1550.86 nm,the channel spectral response flatness is about 1.5 dB,3-dB bandwidth is about 0.478 nm,insertion loss is 10.5 dB,and crosstalk is about-22 dB.The insertion loss of an AWG device is reduced by about 3 dB for the central channel and 4.5 dB for the edge channels,and the crosstalk is reduced by 2.5 dB after the steam-redissolution.
基金MCEER, Through a Grant from the Earthquake Engineering Research Centers Program of the National Science Foundation Under Grant No. EEC-9701471
文摘A retrofit procedure for existing buildings called the "weakening and damping technique" (WED) is presented in this paper. Weakening of structures can limit the maximum response accelerations during severe ground motions, but leads to an increase in the displacements or inter-story drifts. Added damping by using viscous dampers, on the other hand, reduces the inter-story drifts and has no significant effect on total accelerations, when structures behave inelastically. The weakening and damping technique addresses the two main causes for both structural and nonstructural damage in structures. The weakening retrofit is particularly suitable for structures that have overstressed components and weak brittle components. In this paper, the advantages of the WeD are verified by nonlinear dynamic analysis and simplified spectral approach that has been modified to fit structures with additional damping devices. A hospital structure located in the San Fernando Valley in California is selected as a case study. The results from both analyses show that the retrofit solution is feasible to reduce both structural acceleration and displacement. A sensitivity analysis is also carried out to evaluate the effectiveness of the retrofitting method using different combinations of performance thresholds in accelerations and displacements through fragility analysis.
文摘The present paper addresses the comparative study of three adjacent single-degree-of freedom structures for elastic and inelastic system with and without pounding under seismic excitations. For the gap between three adjacent structures, the simulation is done by using linear spring element without damping. The entire numerical simulation is done in time domain by considering the inputs of four real ground motions. The results of the study show that the response of elastic system is much different to that of response of inelastic system in the absence and presence of pounding, especially in lighter or more flexible structures. Elastic structures show much severe pounding response than inelastic structures. Modeling of colliding structures behaving inelastically is really needed in order to obtain the accurate structural pounding involved response under seismic excitation.
基金supported by the National Natural Science Foundation of China(No.51972341)the Shandong Natural Science Foundation,China(No.ZR2020MA069).
文摘Si-based optical position-sensitive detectors(PSDs)have stimulated the interest of researchers due to their wide range of practical applications.However,due to the rigidity and fragility of Si crystals,the applications of flexible PSDs have been limited.Therefore,we presented a flexible broadband PSD based on a WS_(2)/Si heterostructure for the first time.A scalable sputtering method was used to deposit WS_(2)thin films onto the etched ultrathin crystalline Si surface.The fabricated flexible PSD device has a broad spectral response in the wavelength range of 450-1350 nm,with a high position sensitivity of~539.8 mV·mm^(−1)and a fast response of 2.3μs,thanks to the strong light absorption,the built-in electrical field at the WS_(2)/Si interface,and facilitated transport.Furthermore,mechanical-bending tests revealed that after 200 mechanical-bending cycles,the WS_(2)/Si PSDs have excellent mechanical flexibility,stability,and durability,demonstrating the great potential in wearable PSDs with competitive performance.
文摘Solar cell technology comes with unique temperature coefficients. These temperature coefficients are important and temperature of the solar cell has direct influence on the power output of a photovoltaic cells. CdTe is a very robust and chemically stable material and for this reason its related solar cell. Thin film photovoltaic technology is now the only thin film technology in the first top 10 producers in the world. The strong improvement in efficiency in the last 7 years was obtained by a new redesign of the CdTe solar cell device reaching a single solar cell. In this paper, we describe the fabrication process following the history of the solar cell as it was developed in the early years up to the latest development and changes. The configuration of fabricated cell is n-CdTe/NaOH (0.15 M) + S (0.15 M) + Na<sub>2</sub>S (0.15 M)/C<sub>(graphite)</sub>. The junction ideality factor was found to be 2.63, 2.13, and 1.89. The flat band potential is found to be -0.400, -0.450, -0.501 V. The barrier height value was found to be 0.523, 0.487, and 0.436 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency were found to be 120 mV, 24.2 μA, 32.68%, 26.18%, and 19.73% and 0.63%, 0.37%, and 0.23%, respectively. The lighted ideality factor was calculated and found to be 3.26, 1.87, and 1.17. Spectra attain maximum value of current at λ = 580 nm and decrease with increase in wavelength. The photovoltaic cell characterization of the thin films is carried out by studying current-voltage characteristics in dark, capacitance-voltage in dark, barrier height measurements, power output characteristics.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60876050 and 51177134)
文摘In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature.The results show that the photodetector has a good rectifying character and a good response to near-infrared light.Interface states should be minimized to obtain a lower reverse leakage current.The response spectrum of the β-FeSi2/4H-SiC detector,which consists of a p-type β-FeSi2 absorption layer with a doping concentration of 1×1015cm-3 and a thickness of 2.5 μm,has a peak of 755 mA/W at 1.42 μm.The illumination of the SiC side obtains a higher responsivity than that of the β-FeSi2 side.The results illustrate that the β-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices.
基金supported by National Natural Science Foundation of China(Nos.10675023,11075018)the Fundamental Research Funds for the Central Universities of China
文摘GaInP/GaAs/Ge triple-junction solar cells were irradiated with 50 keV and 100 keV protons at fluences of 5 × 10^10 cm^-2, 1 × 10^11 cm^-2,1 × 10^12 cm^-2, and 1 × 10^13 cm^-2. Their performance degradation is analyzed using current-voltage characteristics and spectral response measurements, and then the changes in Isc, Voc, Pmax and the spectral response of the cells are observed as functions of proton irradiation fluence and energy. The results show that the spectral response of the top cell degrades more significantly than that of the middle cell, and 100 keV proton-induced degradation rates of Isc, Voc and Pmax are larger compared with 50 keV proton irradiation.
基金National Natural Science Foundation of China under Grant No.51078032the Visiting Scholar Foundation of China Scholarship Councilthe Center for Infrastructure Engineering Studies at Missouri University of Science and Technology
文摘An optimization method for the consistent evaluation of two Rayleigh damping coefficients is proposed. By minimizing an objective function such as an error term of the peak displacement of a structure, the two coefficients can be determined with response spectral analysis. The optimization method degenerates into the conventional method used in current practices when only two modes of vibration are included in the objective function. Therefore, the proposed method with all significant modes included for simplicity in practical applications results in suboptimal damping coefficients. The effects of both spatial distribution and frequency content of excitations as well as structural dynamic characteristics on the evaluation of Rayleigh damping coefficients were investigated with a five-story building structure. Two application examples with a 62-story high-rise building and a 840 m long cable-stayed bridge under ten earthquake excitations demonstrated the accuracy and effectiveness of the proposed method to account for all of the above effects.