Federated learning is a decentralized model training paradigm with significant potential.However,the quality of Federated Network’s client updates can vary due to non-IID data distributions,leading to suboptimal glob...Federated learning is a decentralized model training paradigm with significant potential.However,the quality of Federated Network’s client updates can vary due to non-IID data distributions,leading to suboptimal global models.To address this issue,we propose a novel client selection strategy called FedPA(Performance-Based Federated Averaging).This proposed model selectively aggregates client updates based on a predefined performance threshold.Only clients whose local models achieve an F1 score of 70%or higher after training are included in the aggregation process.Clients below this threshold receive the updated global model but do not contribute their parameters.In this way,the low-performance clients are still in the process of learning and,after some rounds,will be able to contribute.If no client meets the performance threshold in a given round,the system falls back to standard FedAvg aggregation.This ensures the global model continues to improve even when most clients perform poorly.We evaluate FedPA on a subset of the MURA dataset for abnormality detection in radiographs of four bone types.Compared to baseline federated learning algorithms such as Federated Averaging(FedAvg),Federated Proximal(FedProx),Federated Stochastic Gradient Descent(FedSGD),and Federated Batch Normalization(FedBN),FedPA consistently ranks first or second across key performance metrics,particularly in accuracy,F1 score,and recall.Moreover,FedPA demonstrates notable efficiency,achieving the lowest average round time(≈2270 s)and minimal memory usage(≈645.58 MB),all without relying on GPU resources.These results highlight FedPA’s effectiveness in improving global model quality while reducing computational overhead,positioning it as a promising approach for real-world federated learning applications in resource-constrained environments.展开更多
In the performance based navigation（PBN）,the flight technical error（FTE）and the navigation system error（NSE）are two main parts of total system error（TSE）.The implementation of PBN requires pre-flight predictio...In the performance based navigation（PBN）,the flight technical error（FTE）and the navigation system error（NSE）are two main parts of total system error（TSE）.The implementation of PBN requires pre-flight prediction and en-route short-term dynamical prediction of TSE.Once the sum of predicted FTE and NSE is greater than the specified PBN value,PBN cannot operate.Thus,it requires accurate modeling and thorough analysis of the two main contributors.Multiple-input multiple-output（MIMO）longitudinal flight control system of ARIC model is designed using the linear quadratic Gaussian and loop transfer recovery（LQG/LTR）method,and FTE in symmetrical plane of aircraft is analyzed during the turbulence disturbed approach.The error estimation mapping function of FTE in symmetrical plane and its bound estimation model are proposed based on the singular value theory.The model provides an approach based on the forming mechanism of FTE,rather than the costly flight test and the data fitting.Real-data based simulation validates the theoretical analysis of FTE in symmetrical plane.It also shows that FTE is partially caused by the turbulence fluctuation disturbance when the automatic flight control system（AFCS）is engaged and increases with escalating the environmental turbulence intensity.展开更多
Flight technical error （FTE） combined with navigation system error （NSE） is the main part of total system error （TSE） in performance based navigation （PBN）. The implementation of PBN requires pre-flight predic...Flight technical error （FTE） combined with navigation system error （NSE） is the main part of total system error （TSE） in performance based navigation （PBN）. The implementation of PBN requires pre-flight prediction and en-route short-term dynamical prediction of the TSE. Once the sum of predicted lateral FTE and NSE is greater than the specified PBN value, the PBN cannot operate. Thus, accurate modeling and thorough analysis of lateral FTE are indispensible. Multiple-input multiple-output （MIMO） lateral track control system of a transport aircraft is designed using linear quadratic Gaussian and loop transfer recovery （LQG/LTR） method, and the lateral FTE of a turbulence disturbed approach operation is analyzed. The error estimation mapping function of latera FTE and its bound estimation algorithm are proposed based on singular value theory. According to the forming mechanism of lateral FTE, the algorithm considers environmental turbulence fluctuation disturbance, aircraft dynamics and con- trol system parameters. Real-data-based Monte-Carlo simulation validates the theoretical analysis of FTE. It also shows that FTE is mainly caused by turbulence fluctuation disturbance when automatic flight control system （AFCS） is engaged and would in- crease with escalating environmental turbulence intensity.展开更多
Purpose: The main goal of this study is to outline and analyze the Danish adoption and translation of the Norwegian Publication Indicator. Design/methodology/approach: The study takes the form of a policy analysis mai...Purpose: The main goal of this study is to outline and analyze the Danish adoption and translation of the Norwegian Publication Indicator. Design/methodology/approach: The study takes the form of a policy analysis mainly drawing on document analysis of policy papers, previously published studies and grey literature. Findings: The study highlights a number of crucial factors that relate both to the Danish process and to the final Danish result underscoring that the Danish BFI model is indeed a quite different system than its Norwegian counterpart. One consequence of these process-and design differences is the fact that the broader legitimacy of the Danish BFI today appears to be quite poor. Reasons for this include: unclear and shifting objectives throughout the process; limited willingness to take ownership of the model among stakeholders; lack of communication throughout the implementation process and an apparent underestimation of the challenges associated with the use of bibliometric indicators. Research limitation: The conclusions of the study are based on the authors’ interpretation of a long drawn and complex process with many different stakeholders involved. The format of this article does not allow for a detailed documentation of all elements, but further details can be provided upon request. Practical implications: The analysis may feed into current policy discussions on the future of the Danish BFI. Originality/value: Some elements of the present analysis have previously been published in Danish outlets, but this article represents the first publication on this issue targeting a broader international audience.展开更多
A Schottky barrier diode with low-barrier is presented, based on which a terahertz waveguide detector working at 500-600 GHz is designed and fabricated. By using the InGaAs/InP material system, the feature of the low ...A Schottky barrier diode with low-barrier is presented, based on which a terahertz waveguide detector working at 500-600 GHz is designed and fabricated. By using the InGaAs/InP material system, the feature of the low barrier is obtained which greatly improves the performance of the detector. The measured typical voltage responsivity is about 900 V/W at 50-560 OHz and is about 400 V/W at 560 600 GHz. The proposed broadband waveguide detector has the characteristics of simple structure, compact size, low cost and high performance, and can be used in a variety of applications such as imaging, moleeuIar spectroscopy and atmospheric remote sensing.展开更多
The objective of Performance-Based Earthquake Engineering （PBEE） is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increas...The objective of Performance-Based Earthquake Engineering （PBEE） is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increasing levels of strong ground motion having decreasing annual probabilities of exceedance. The development of this methodology includes three steps： （1） evaluation of the distribution of ground motion at a site; （2） evaluation of the distribution of system response; （3） evaluation of the probability of exceeding decision variables within a given time period, given appropriate damage measures. The work has taken a systematic approach to determine the impact of increasing levels of detail in site characterization on the accuracy of ground motion and site effects predictions. Complementary studies have investigated the use of the following models for evaluating site effects： （1） amplification factors defined on the basis of generalized site categories, （2） one-dimensional ground response analysis, and （3） two-dimensional ground response analysis for surface topography on ground motion. The paper provides a brief synthesis of ground motion and site effects analysis procedures within a Performance-Based Design framework. It focuses about the influence on the evaluation of site effects in some active regions by different shear waves velocity measurements Down Hole （D-H）, Cross Hole （C-H）, Seismic Dilatometer Marchetti Test （SDMT） and by different variation of shear modulus and damping ratio with strain level and depth from different laboratory dynamic tests for soil characterization： Resonant Column Test （RCT）, Cyclic Loading Torsional Shear Test （CLTST）.展开更多
Impact of band-engineering to the performance of charge trapping memory with HfO2/Ta2O5/HfO2 （HTH） as the charge trapping layer is investigated. Compared with devices with the same total HfO2 thickness, structures w...Impact of band-engineering to the performance of charge trapping memory with HfO2/Ta2O5/HfO2 （HTH） as the charge trapping layer is investigated. Compared with devices with the same total HfO2 thickness, structures with Ta2O5 closer to substrates show larger program/erase window, because the 2nd HfO2 （next to blocking oxide） serving as part of blocking oxide reduces the current tunneling out of/in the charge trapping layer during program and erase. Moreover, trapped charge centroid is modulated and contributed more to the fiat-band voltage shift. Further experiments prove that devices with a thicker 2nd HfO2 layer exhibit larger saturate fiat-band shift in both program and erase operation. The optimized device achieves a 7 V memory window and good reliability characteristics.展开更多
Ring oscillators based on indium gallium zinc oxide thin film transistors are fabricated on glass substrates. The oscillator circuit consists of seven delay stages and an output buffer inverter. The element inverter e...Ring oscillators based on indium gallium zinc oxide thin film transistors are fabricated on glass substrates. The oscillator circuit consists of seven delay stages and an output buffer inverter. The element inverter exhibits a voltage gain higher than -6 V/V and a wide output swing close to 85% of the full swing range. The dynamic performance of the ring oscillators is evaluated as a function of supply voltage and at different gate lengths. A maximum oscillation frequency of 0.88MHz is obtained for a supply voltage of 50V, corresponding to a propagation delay of less than 85 ns/stage.展开更多
The performance and morphology stability of polymer bulk heterojunetion solar cells based on poly（3-hexylthiophene） （P3HT） as the donor and indene-C6o bisadduct （ICBA） or methanofullerene [6,6]-phenyl C61-butyri...The performance and morphology stability of polymer bulk heterojunetion solar cells based on poly（3-hexylthiophene） （P3HT） as the donor and indene-C6o bisadduct （ICBA） or methanofullerene [6,6]-phenyl C61-butyric acid methyl ester （PCBM） as the aeceptor are compared. Effect of the different donor and aeeeptor weight ratios on photo- voltaic performance of the P3HT：ICBA device is studied. The optimal device achieved power conversion emeiency of 5.51~o with dso of l0.86mA/cm2, Voc of 0.83 V, and fill factor （FF） of 61.1 % under AM 1.5G （lOOmW/cm2） simulated solar illumination. However, the stability measurement shows that cells based on P3HT：ICBA are less stable than those of the device based on P3HT：PCBM. Atomic force microscope results reveal that the morphol- ogy of the P3HT：ICBA film changed considerably during the storage periods due to unstable interpenetrating D-A network. This observation can be explained by the fact that there is lack of intermolecular hydrogen bonds in the P3HT：ICBA system. However, in the P3HT：PCBM system the molecules in the blend film are firmly held together in the solid state by means of intermoleeular hydrogen bonds originating from C-H. ~. Os bonds （where Os comes from the singly-bonded 0 atom of PCBM）, forming a stable three-dimensional network. The measured PL decay lifetimes for P3HT：PCBM and P3HT：ICBA systems are 33.66 ns and 35.34 ns, respectively, indicating that the P3HT：ICBA system has a less efficient exciton separation eftleiency than that of P3HT：PCBM, which may result in the interracial photogenerated charges accumulated on the D： A interface. Such progressive phase segregation between P3HT and ICBA eventually leads to the degradation in performance and deteriorates the stability of the device. We also present an approach to enhance the stability of P3HT：ICBA systems by adding PCBM as the second acceptor. Our results show that by carefully tuning the contents of PCBM as the second acceptor, more stable polymer solar cells can be obtained.展开更多
Roads are the major asset of any country and to conserve them maintenance is essential. The delay of maintenance works can lead the road in the stage of expensive rehabilitation and reconstruction. In Nepal, Departmen...Roads are the major asset of any country and to conserve them maintenance is essential. The delay of maintenance works can lead the road in the stage of expensive rehabilitation and reconstruction. In Nepal, Department of Roads (DoR) is responsible for maintenance of strategic roads of country. The maintenance practice of the road under Department of Road is predominantly based on Strengthen Maintenance Division Process where several maintenance activities like Routine maintenance, Recurrent Maintenance, Periodic Maintenance and Emergency Maintenance are planned and carried out. The maintenance work is based on traditional quantity and unit price based short term maintenance contracts, where maintenance of physical works is outsourced. Client demands the contractor what work is to be done, when to be do it and the extent of the work. The contractor is paid on the basis of a defined output or quantity accomplished, and the schedule of the rates. DoR engineers required full time supervision of work. Pilot based performance based maintenance practice of road started in Nepal in 2003. The study assesses performance road maintenance practices of road maintenance in Nepal on the basis of the framework of cost efficiency, level of service effectiveness and quality of service. The study concluded that implementation of Performance Based Maintenance Contract (PBMC) was not successful in Nepal as Road Asset condition was not maintained to performance standard. One of the reasons is the weak service delivery of contractor alongside weak contract enforcement from the road agency.展开更多
The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore...The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore speed-correcting coefficients of the tool are given. On the basis of thework, a data base for coated carbide tools has been built on a microcomputer. It consists of fivemodules. essential data base, tools' comparison and inquiry, recommending cutting regimes, exper.imental curve base and an expert system for tool selection.展开更多
Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and...Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and stoppers have been installed on bridges to prevent unseating and excessive displacements, respectively. Alternatively, column jacketing has also been proven to be effective. However, the enhanced shear strength may result in extra retrofitting works on the footing. For bridges damaged in the Chi-Chi earthquake, investigations revealed that most bridge columns experienced none-to-minor damage in the longitudinal direction. The reason for this unexpected performance was the construction practice of using a rubber bearing, which is an unbolted design that may slide under large lateral forces. In this paper, parametric studies on simply-supported bridges retrofitted by a restrainer or concrete shear key along the longitudinal and transverse axes were carried out. The research focuses on finding suitable combinations of the design force and gap spacing so the restrainer and concrete shear key can be used as an unseating prevention device, with respect to the allowable column damage in terms of displacement ductility under near-fault type earthquakes. A two-lane PCI-girder bridge was selected as the benchmark model. In the longitudinal direction, a total of nine combinations considering yielding strength and gap spacing for the restrainer were analyzed; while parameters for the concrete shear key were divided into three shear force levels and three gap spacings. In the transverse direction, a similar approach was adapted, except smaller gap spacing was used. For each of the above mentioned earthquakes, seven input ground motions were selected and their PGAs were adjusted to 0.36g and 0.45g as the Design earthquake and Maximum Considerable Earthquake, respectively. Based on the results of nonlinear time history analyses, proper parameters to design the restrainers and concrete shear keys are obtained. Responses obtained from numerical simulations under the Chi-Chi earthquake leaded to new implications to design those devices. Restrainer should not exceed its breaking strain and sufficient unseating length will be needed always. Concrete Shear key was determined by considering both displacement demand of the superstructure and displacement ductility of the column at the same time. Further study is needed to provide optimal design parameters for use in performance based bridge design.展开更多
Composites of a nickel based compound incorporated with graphene sheets （NiBC-GS） are prepared by a simple flocculation, using hydrazine hydrate as flocculant and reductant, from a homogeneous intermixture of nickel...Composites of a nickel based compound incorporated with graphene sheets （NiBC-GS） are prepared by a simple flocculation, using hydrazine hydrate as flocculant and reductant, from a homogeneous intermixture of nickel dichloride and graphene oxide dispersed in N,N-dimethylformamide. Morphology, microstructure and thermal stability of the obtained products were characterized by field-emission scanning electron microscopy, X-ray diffraction and thermal gravimetric analysis. Furthermore, the electrochemical properties of NiBC-GS, as electrode materials for supercapacitors, were studied by cyclic voltammetry and galvanostatic charge]discharge in 2 mol L 1 KOH solution. It was determined that for NiBC-GS annealed at 250 ~C, a high specific capacitance of 2394 F g 1 was achieved at a current density of 1 A g^-1, with 78% of the value （i.e., 1864 F g^-1） retained after 5000 times of repeated galvanostatic charge/discharge cycling. The high specific capacitance and available charge/discharge stability indicate the synthesized NiBC-GS250 composite is a good candidate as a novel electrode material for supercapacitors.展开更多
Performance-Based Design （PBD） is a more rational approach, particularly in seismic environments. In this approach it is relevant the performance required to structures and to geotechnical works, as well as the geot...Performance-Based Design （PBD） is a more rational approach, particularly in seismic environments. In this approach it is relevant the performance required to structures and to geotechnical works, as well as the geotechnical constitutive models used to predict the performance. The parameters of the constitutive models are related in turn to soil properties. So soil properties are a key point for Performance-Based Design. Questions arising are： （i） which are the more relevant soil properties to solve a specific PBD geotechnical problem？ （ii） which are the more relevant model parameters and how they can be evaluated and/or correlated to soil properties？ （iii） which is the role of the soil parameters uncertainty in Performance-Based Design？ An answer to these questions is given in this paper, outlining the potential offered by the new advanced in-situ and laboratory tests and discussing the performance required by some geotechnical works.展开更多
Carbon-based HTM-free perovskite solar cells(C-PSCs)have received extensive attention due to their low cost and high stability.However,some issues with regard to their relatively low efficiency and toxicity still need...Carbon-based HTM-free perovskite solar cells(C-PSCs)have received extensive attention due to their low cost and high stability.However,some issues with regard to their relatively low efficiency and toxicity still need to be addressed before their commercialization.For the first time,a high-efficiency carbonbased planar perovskite solar cell was prepared based on TiO_(2)combined with PC_(61)BM as the electrontransport layer.PC_(61)BM could passivate the interface between the perovskite film layer and the TiO_(2)film layer;at the same time,it also exhibited the function of an additive to improve the crystal quality of the perovskite.Planar C-PSC was successfully fabricated with an open voltage(Voc)of 1.005 V,which represented~2.6%enhancement compared to that of the device with a mesoporous structure,and power conversion efficiency(PCE)of 14.37%.Moreover,stability was also investigated;3%degradation appeared in the PCE of the planar C-PSC after being stored for 1900 h in the dark.This methodology of introducing PC_(61)BM to reduce the recombination probability of electrons and holes and improve the crystal quality of perovskites has universal significance for the further development of planar C-PSCs.展开更多
A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its...A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l1, 2 × l1, 22 ×l1, 23 ×l1, 24 ×l1, ..., 2N-4 × l1, 15 × 2N-7 ×l1, 10 × 2N-6 × l1 and 2N-2 ×l1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can achieve 170-nm tuning range, -50-dB crosstalk, bandpass width applicable to 25-GHz channel spacing and 1 dB insert loss.展开更多
A method based on the diffraction theory for estimating the three-dimensional (3D) focusing performance of the compound refractive X-ray lenses is presented in this paper. As a special application, the 3D X-ray intens...A method based on the diffraction theory for estimating the three-dimensional (3D) focusing performance of the compound refractive X-ray lenses is presented in this paper. As a special application, the 3D X-ray intensity distribution near the focus is derived for a plano-concave compound refractive X-ray lens. Moreover, the computer codes are developed and some results of 3D focusing performance for a compound refractive X-ray lens with Si material are shown and discussed.展开更多
An objective visual performance evaluation with visual evoked potential （VEP） measurements was first inte- grated into an adaptive optics （AO） system. The optical and neural limits to vision can be bypassed throug...An objective visual performance evaluation with visual evoked potential （VEP） measurements was first inte- grated into an adaptive optics （AO） system. The optical and neural limits to vision can be bypassed through this system. Visual performance can be measured electrophysiologically with VEP, which reflects the objective func- tion from the retina to the primary visual cortex. The VEP ts without and with AO correction were preliminarily carried out using this system, demonstrating the great potential of this system in the objective visual performance evaluation. The new system will provide the necessary technique and equipment support for the further study of human visual function.展开更多
With increasing demand to reduce the carbon emission of buildings,it is crucial to quantify the life cycle envi-ronmental impact of new buildings,including the environmental impact due to natural hazards,such as earth...With increasing demand to reduce the carbon emission of buildings,it is crucial to quantify the life cycle envi-ronmental impact of new buildings,including the environmental impact due to natural hazards,such as earth-quakes.This study presents a novel comprehensive probabilistic framework to quantify the environmental impact of buildings,including uncertainties in the material extraction and production,transportation,construction,seis-mic exposure and aging(including deterioration),and end-of-life stages.The developed framework is used to quantify the environmental impact of a 3-story residential building located in Vancouver,Canada.The results show that there is a significant variation in the environmental impact of the prototype building in each stage of the life cycle assessment.If the prototype building is hit by the design level earthquake,it is expected that the median environmental impact of the prototype will be further increased by 42%.In addition,by accounting for the probability of occurrence of different earthquakes within a 50-year design life of the prototype building,the earthquake related damage will result in an additional 5%of the initial carbon emission of the building.This shows the importance of including earthquake hazard and deterioration in whole building life cycle assessments.展开更多
Evaluating the expected sliding distance of a vertical slit caisson breakwater is proposed. Time history for the wave load to a vertical slit caisson is made. It consists of two impulsive wave pressures followed by a ...Evaluating the expected sliding distance of a vertical slit caisson breakwater is proposed. Time history for the wave load to a vertical slit caisson is made. It consists of two impulsive wave pressures followed by a smooth sinusoidal pressure. In the numerical analysis, the sliding distance for an attack of single wave was shown and the expected sliding distance during 50 years was also presented. Those results were compared with a vertical front caisson breakwater without slit. It was concluded that the sliding distance of a vertical slit caisson may be over-estimated if the wave pressure on the caisson is evaluated without considering vertical slit.展开更多
文摘Federated learning is a decentralized model training paradigm with significant potential.However,the quality of Federated Network’s client updates can vary due to non-IID data distributions,leading to suboptimal global models.To address this issue,we propose a novel client selection strategy called FedPA(Performance-Based Federated Averaging).This proposed model selectively aggregates client updates based on a predefined performance threshold.Only clients whose local models achieve an F1 score of 70%or higher after training are included in the aggregation process.Clients below this threshold receive the updated global model but do not contribute their parameters.In this way,the low-performance clients are still in the process of learning and,after some rounds,will be able to contribute.If no client meets the performance threshold in a given round,the system falls back to standard FedAvg aggregation.This ensures the global model continues to improve even when most clients perform poorly.We evaluate FedPA on a subset of the MURA dataset for abnormality detection in radiographs of four bone types.Compared to baseline federated learning algorithms such as Federated Averaging(FedAvg),Federated Proximal(FedProx),Federated Stochastic Gradient Descent(FedSGD),and Federated Batch Normalization(FedBN),FedPA consistently ranks first or second across key performance metrics,particularly in accuracy,F1 score,and recall.Moreover,FedPA demonstrates notable efficiency,achieving the lowest average round time(≈2270 s)and minimal memory usage(≈645.58 MB),all without relying on GPU resources.These results highlight FedPA’s effectiveness in improving global model quality while reducing computational overhead,positioning it as a promising approach for real-world federated learning applications in resource-constrained environments.
基金Supported by the National Basic Research Program of China("973"Program)(2010CB731805)theFoundation for Innovative Research Groups of the National Natural Science Foundation of China(60921001)+1 种基金the National Key Technologies R&D Program of China(2011BAH24B02)the Basic Scientific Research Fundation of Central Institutions of Higher Education(ZXH2009D006)~~
文摘In the performance based navigation（PBN）,the flight technical error（FTE）and the navigation system error（NSE）are two main parts of total system error（TSE）.The implementation of PBN requires pre-flight prediction and en-route short-term dynamical prediction of TSE.Once the sum of predicted FTE and NSE is greater than the specified PBN value,PBN cannot operate.Thus,it requires accurate modeling and thorough analysis of the two main contributors.Multiple-input multiple-output（MIMO）longitudinal flight control system of ARIC model is designed using the linear quadratic Gaussian and loop transfer recovery（LQG/LTR）method,and FTE in symmetrical plane of aircraft is analyzed during the turbulence disturbed approach.The error estimation mapping function of FTE in symmetrical plane and its bound estimation model are proposed based on the singular value theory.The model provides an approach based on the forming mechanism of FTE,rather than the costly flight test and the data fitting.Real-data based simulation validates the theoretical analysis of FTE in symmetrical plane.It also shows that FTE is partially caused by the turbulence fluctuation disturbance when the automatic flight control system（AFCS）is engaged and increases with escalating the environmental turbulence intensity.
基金National High-tech Research and Development Program of China(2006AA12A103)National Basic Research Program of China(2010CB731803)Basic Scientific Research Fund of Central Institutions of Higher Education(ZXH2009D006,YWF-10-02-02)
文摘Flight technical error （FTE） combined with navigation system error （NSE） is the main part of total system error （TSE） in performance based navigation （PBN）. The implementation of PBN requires pre-flight prediction and en-route short-term dynamical prediction of the TSE. Once the sum of predicted lateral FTE and NSE is greater than the specified PBN value, the PBN cannot operate. Thus, accurate modeling and thorough analysis of lateral FTE are indispensible. Multiple-input multiple-output （MIMO） lateral track control system of a transport aircraft is designed using linear quadratic Gaussian and loop transfer recovery （LQG/LTR） method, and the lateral FTE of a turbulence disturbed approach operation is analyzed. The error estimation mapping function of latera FTE and its bound estimation algorithm are proposed based on singular value theory. According to the forming mechanism of lateral FTE, the algorithm considers environmental turbulence fluctuation disturbance, aircraft dynamics and con- trol system parameters. Real-data-based Monte-Carlo simulation validates the theoretical analysis of FTE. It also shows that FTE is mainly caused by turbulence fluctuation disturbance when automatic flight control system （AFCS） is engaged and would in- crease with escalating environmental turbulence intensity.
文摘Purpose: The main goal of this study is to outline and analyze the Danish adoption and translation of the Norwegian Publication Indicator. Design/methodology/approach: The study takes the form of a policy analysis mainly drawing on document analysis of policy papers, previously published studies and grey literature. Findings: The study highlights a number of crucial factors that relate both to the Danish process and to the final Danish result underscoring that the Danish BFI model is indeed a quite different system than its Norwegian counterpart. One consequence of these process-and design differences is the fact that the broader legitimacy of the Danish BFI today appears to be quite poor. Reasons for this include: unclear and shifting objectives throughout the process; limited willingness to take ownership of the model among stakeholders; lack of communication throughout the implementation process and an apparent underestimation of the challenges associated with the use of bibliometric indicators. Research limitation: The conclusions of the study are based on the authors’ interpretation of a long drawn and complex process with many different stakeholders involved. The format of this article does not allow for a detailed documentation of all elements, but further details can be provided upon request. Practical implications: The analysis may feed into current policy discussions on the future of the Danish BFI. Originality/value: Some elements of the present analysis have previously been published in Danish outlets, but this article represents the first publication on this issue targeting a broader international audience.
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2011AA010203the National Basic Research Program of China under Grant Nos 2011CB201704 and 2010CB327502the National Natural Science Foundation of China under Grant No 61434006
文摘A Schottky barrier diode with low-barrier is presented, based on which a terahertz waveguide detector working at 500-600 GHz is designed and fabricated. By using the InGaAs/InP material system, the feature of the low barrier is obtained which greatly improves the performance of the detector. The measured typical voltage responsivity is about 900 V/W at 50-560 OHz and is about 400 V/W at 560 600 GHz. The proposed broadband waveguide detector has the characteristics of simple structure, compact size, low cost and high performance, and can be used in a variety of applications such as imaging, moleeuIar spectroscopy and atmospheric remote sensing.
文摘The objective of Performance-Based Earthquake Engineering （PBEE） is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increasing levels of strong ground motion having decreasing annual probabilities of exceedance. The development of this methodology includes three steps： （1） evaluation of the distribution of ground motion at a site; （2） evaluation of the distribution of system response; （3） evaluation of the probability of exceeding decision variables within a given time period, given appropriate damage measures. The work has taken a systematic approach to determine the impact of increasing levels of detail in site characterization on the accuracy of ground motion and site effects predictions. Complementary studies have investigated the use of the following models for evaluating site effects： （1） amplification factors defined on the basis of generalized site categories, （2） one-dimensional ground response analysis, and （3） two-dimensional ground response analysis for surface topography on ground motion. The paper provides a brief synthesis of ground motion and site effects analysis procedures within a Performance-Based Design framework. It focuses about the influence on the evaluation of site effects in some active regions by different shear waves velocity measurements Down Hole （D-H）, Cross Hole （C-H）, Seismic Dilatometer Marchetti Test （SDMT） and by different variation of shear modulus and damping ratio with strain level and depth from different laboratory dynamic tests for soil characterization： Resonant Column Test （RCT）, Cyclic Loading Torsional Shear Test （CLTST）.
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00602the National Key Scientific and Technological Project under Grant No 2013ZX01032001-001-003
文摘Impact of band-engineering to the performance of charge trapping memory with HfO2/Ta2O5/HfO2 （HTH） as the charge trapping layer is investigated. Compared with devices with the same total HfO2 thickness, structures with Ta2O5 closer to substrates show larger program/erase window, because the 2nd HfO2 （next to blocking oxide） serving as part of blocking oxide reduces the current tunneling out of/in the charge trapping layer during program and erase. Moreover, trapped charge centroid is modulated and contributed more to the fiat-band voltage shift. Further experiments prove that devices with a thicker 2nd HfO2 layer exhibit larger saturate fiat-band shift in both program and erase operation. The optimized device achieves a 7 V memory window and good reliability characteristics.
基金Supported by the National Basic Research Program of China under Grant Nos 2011CB301900 and 2011CB922100the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Ring oscillators based on indium gallium zinc oxide thin film transistors are fabricated on glass substrates. The oscillator circuit consists of seven delay stages and an output buffer inverter. The element inverter exhibits a voltage gain higher than -6 V/V and a wide output swing close to 85% of the full swing range. The dynamic performance of the ring oscillators is evaluated as a function of supply voltage and at different gate lengths. A maximum oscillation frequency of 0.88MHz is obtained for a supply voltage of 50V, corresponding to a propagation delay of less than 85 ns/stage.
基金Supported by the Tianjin Natural Science Foundation under Grant Nos 13JCYBJC18900 and 13JCZDJC26700the National High Technology Research and Development Program of China under Grant No 2013AA014201
文摘The performance and morphology stability of polymer bulk heterojunetion solar cells based on poly（3-hexylthiophene） （P3HT） as the donor and indene-C6o bisadduct （ICBA） or methanofullerene [6,6]-phenyl C61-butyric acid methyl ester （PCBM） as the aeceptor are compared. Effect of the different donor and aeeeptor weight ratios on photo- voltaic performance of the P3HT：ICBA device is studied. The optimal device achieved power conversion emeiency of 5.51~o with dso of l0.86mA/cm2, Voc of 0.83 V, and fill factor （FF） of 61.1 % under AM 1.5G （lOOmW/cm2） simulated solar illumination. However, the stability measurement shows that cells based on P3HT：ICBA are less stable than those of the device based on P3HT：PCBM. Atomic force microscope results reveal that the morphol- ogy of the P3HT：ICBA film changed considerably during the storage periods due to unstable interpenetrating D-A network. This observation can be explained by the fact that there is lack of intermolecular hydrogen bonds in the P3HT：ICBA system. However, in the P3HT：PCBM system the molecules in the blend film are firmly held together in the solid state by means of intermoleeular hydrogen bonds originating from C-H. ~. Os bonds （where Os comes from the singly-bonded 0 atom of PCBM）, forming a stable three-dimensional network. The measured PL decay lifetimes for P3HT：PCBM and P3HT：ICBA systems are 33.66 ns and 35.34 ns, respectively, indicating that the P3HT：ICBA system has a less efficient exciton separation eftleiency than that of P3HT：PCBM, which may result in the interracial photogenerated charges accumulated on the D： A interface. Such progressive phase segregation between P3HT and ICBA eventually leads to the degradation in performance and deteriorates the stability of the device. We also present an approach to enhance the stability of P3HT：ICBA systems by adding PCBM as the second acceptor. Our results show that by carefully tuning the contents of PCBM as the second acceptor, more stable polymer solar cells can be obtained.
文摘Roads are the major asset of any country and to conserve them maintenance is essential. The delay of maintenance works can lead the road in the stage of expensive rehabilitation and reconstruction. In Nepal, Department of Roads (DoR) is responsible for maintenance of strategic roads of country. The maintenance practice of the road under Department of Road is predominantly based on Strengthen Maintenance Division Process where several maintenance activities like Routine maintenance, Recurrent Maintenance, Periodic Maintenance and Emergency Maintenance are planned and carried out. The maintenance work is based on traditional quantity and unit price based short term maintenance contracts, where maintenance of physical works is outsourced. Client demands the contractor what work is to be done, when to be do it and the extent of the work. The contractor is paid on the basis of a defined output or quantity accomplished, and the schedule of the rates. DoR engineers required full time supervision of work. Pilot based performance based maintenance practice of road started in Nepal in 2003. The study assesses performance road maintenance practices of road maintenance in Nepal on the basis of the framework of cost efficiency, level of service effectiveness and quality of service. The study concluded that implementation of Performance Based Maintenance Contract (PBMC) was not successful in Nepal as Road Asset condition was not maintained to performance standard. One of the reasons is the weak service delivery of contractor alongside weak contract enforcement from the road agency.
文摘The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore speed-correcting coefficients of the tool are given. On the basis of thework, a data base for coated carbide tools has been built on a microcomputer. It consists of fivemodules. essential data base, tools' comparison and inquiry, recommending cutting regimes, exper.imental curve base and an expert system for tool selection.
文摘Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and stoppers have been installed on bridges to prevent unseating and excessive displacements, respectively. Alternatively, column jacketing has also been proven to be effective. However, the enhanced shear strength may result in extra retrofitting works on the footing. For bridges damaged in the Chi-Chi earthquake, investigations revealed that most bridge columns experienced none-to-minor damage in the longitudinal direction. The reason for this unexpected performance was the construction practice of using a rubber bearing, which is an unbolted design that may slide under large lateral forces. In this paper, parametric studies on simply-supported bridges retrofitted by a restrainer or concrete shear key along the longitudinal and transverse axes were carried out. The research focuses on finding suitable combinations of the design force and gap spacing so the restrainer and concrete shear key can be used as an unseating prevention device, with respect to the allowable column damage in terms of displacement ductility under near-fault type earthquakes. A two-lane PCI-girder bridge was selected as the benchmark model. In the longitudinal direction, a total of nine combinations considering yielding strength and gap spacing for the restrainer were analyzed; while parameters for the concrete shear key were divided into three shear force levels and three gap spacings. In the transverse direction, a similar approach was adapted, except smaller gap spacing was used. For each of the above mentioned earthquakes, seven input ground motions were selected and their PGAs were adjusted to 0.36g and 0.45g as the Design earthquake and Maximum Considerable Earthquake, respectively. Based on the results of nonlinear time history analyses, proper parameters to design the restrainers and concrete shear keys are obtained. Responses obtained from numerical simulations under the Chi-Chi earthquake leaded to new implications to design those devices. Restrainer should not exceed its breaking strain and sufficient unseating length will be needed always. Concrete Shear key was determined by considering both displacement demand of the superstructure and displacement ductility of the column at the same time. Further study is needed to provide optimal design parameters for use in performance based bridge design.
基金financially supported by National Natural Science Foundation of China(No.51075384)
文摘Composites of a nickel based compound incorporated with graphene sheets （NiBC-GS） are prepared by a simple flocculation, using hydrazine hydrate as flocculant and reductant, from a homogeneous intermixture of nickel dichloride and graphene oxide dispersed in N,N-dimethylformamide. Morphology, microstructure and thermal stability of the obtained products were characterized by field-emission scanning electron microscopy, X-ray diffraction and thermal gravimetric analysis. Furthermore, the electrochemical properties of NiBC-GS, as electrode materials for supercapacitors, were studied by cyclic voltammetry and galvanostatic charge]discharge in 2 mol L 1 KOH solution. It was determined that for NiBC-GS annealed at 250 ~C, a high specific capacitance of 2394 F g 1 was achieved at a current density of 1 A g^-1, with 78% of the value （i.e., 1864 F g^-1） retained after 5000 times of repeated galvanostatic charge/discharge cycling. The high specific capacitance and available charge/discharge stability indicate the synthesized NiBC-GS250 composite is a good candidate as a novel electrode material for supercapacitors.
文摘Performance-Based Design （PBD） is a more rational approach, particularly in seismic environments. In this approach it is relevant the performance required to structures and to geotechnical works, as well as the geotechnical constitutive models used to predict the performance. The parameters of the constitutive models are related in turn to soil properties. So soil properties are a key point for Performance-Based Design. Questions arising are： （i） which are the more relevant soil properties to solve a specific PBD geotechnical problem？ （ii） which are the more relevant model parameters and how they can be evaluated and/or correlated to soil properties？ （iii） which is the role of the soil parameters uncertainty in Performance-Based Design？ An answer to these questions is given in this paper, outlining the potential offered by the new advanced in-situ and laboratory tests and discussing the performance required by some geotechnical works.
基金supported by the National Natural Science Foundation of China(No.51572025)the National Foundation of China(No.41422050303)+1 种基金the Program of Introducing Talents of Discipline to Universities(B14003the Beijing Municipal Science&Technology Commission and the Fundamental Research Funds for Central Universities.
文摘Carbon-based HTM-free perovskite solar cells(C-PSCs)have received extensive attention due to their low cost and high stability.However,some issues with regard to their relatively low efficiency and toxicity still need to be addressed before their commercialization.For the first time,a high-efficiency carbonbased planar perovskite solar cell was prepared based on TiO_(2)combined with PC_(61)BM as the electrontransport layer.PC_(61)BM could passivate the interface between the perovskite film layer and the TiO_(2)film layer;at the same time,it also exhibited the function of an additive to improve the crystal quality of the perovskite.Planar C-PSC was successfully fabricated with an open voltage(Voc)of 1.005 V,which represented~2.6%enhancement compared to that of the device with a mesoporous structure,and power conversion efficiency(PCE)of 14.37%.Moreover,stability was also investigated;3%degradation appeared in the PCE of the planar C-PSC after being stored for 1900 h in the dark.This methodology of introducing PC_(61)BM to reduce the recombination probability of electrons and holes and improve the crystal quality of perovskites has universal significance for the further development of planar C-PSCs.
文摘A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l1, 2 × l1, 22 ×l1, 23 ×l1, 24 ×l1, ..., 2N-4 × l1, 15 × 2N-7 ×l1, 10 × 2N-6 × l1 and 2N-2 ×l1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can achieve 170-nm tuning range, -50-dB crosstalk, bandpass width applicable to 25-GHz channel spacing and 1 dB insert loss.
基金This work was supported by the National Natural Science Foundation of China (No. 10174079)the fund for the qualified researchers in the Zhejiang University of Technology, P. R. China.
文摘A method based on the diffraction theory for estimating the three-dimensional (3D) focusing performance of the compound refractive X-ray lenses is presented in this paper. As a special application, the 3D X-ray intensity distribution near the focus is derived for a plano-concave compound refractive X-ray lens. Moreover, the computer codes are developed and some results of 3D focusing performance for a compound refractive X-ray lens with Si material are shown and discussed.
基金supported by the National Natural Science Foundation of China (No. 61378064)the National High Technology Research and Development Program of China (No. 2015AA020510)
文摘An objective visual performance evaluation with visual evoked potential （VEP） measurements was first inte- grated into an adaptive optics （AO） system. The optical and neural limits to vision can be bypassed through this system. Visual performance can be measured electrophysiologically with VEP, which reflects the objective func- tion from the retina to the primary visual cortex. The VEP ts without and with AO correction were preliminarily carried out using this system, demonstrating the great potential of this system in the objective visual performance evaluation. The new system will provide the necessary technique and equipment support for the further study of human visual function.
文摘With increasing demand to reduce the carbon emission of buildings,it is crucial to quantify the life cycle envi-ronmental impact of new buildings,including the environmental impact due to natural hazards,such as earth-quakes.This study presents a novel comprehensive probabilistic framework to quantify the environmental impact of buildings,including uncertainties in the material extraction and production,transportation,construction,seis-mic exposure and aging(including deterioration),and end-of-life stages.The developed framework is used to quantify the environmental impact of a 3-story residential building located in Vancouver,Canada.The results show that there is a significant variation in the environmental impact of the prototype building in each stage of the life cycle assessment.If the prototype building is hit by the design level earthquake,it is expected that the median environmental impact of the prototype will be further increased by 42%.In addition,by accounting for the probability of occurrence of different earthquakes within a 50-year design life of the prototype building,the earthquake related damage will result in an additional 5%of the initial carbon emission of the building.This shows the importance of including earthquake hazard and deterioration in whole building life cycle assessments.
基金supported by the Human Resources Development Program(Grant No.20144030200590)of the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea Government Ministry of Knowledge Economythe Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(Grant No.NRF-2016R1A6A1A03013567)
文摘Evaluating the expected sliding distance of a vertical slit caisson breakwater is proposed. Time history for the wave load to a vertical slit caisson is made. It consists of two impulsive wave pressures followed by a smooth sinusoidal pressure. In the numerical analysis, the sliding distance for an attack of single wave was shown and the expected sliding distance during 50 years was also presented. Those results were compared with a vertical front caisson breakwater without slit. It was concluded that the sliding distance of a vertical slit caisson may be over-estimated if the wave pressure on the caisson is evaluated without considering vertical slit.
