Helper-thread of a task can hide the memory access time of irregular data on the chip muhi-core processor （CMP）. For constructing a compiler that effectively supports the helper-thread of a task in the multi-core sc...Helper-thread of a task can hide the memory access time of irregular data on the chip muhi-core processor （CMP）. For constructing a compiler that effectively supports the helper-thread of a task in the multi-core scenario based on the last level shared cache, this paper studies its performance stable condi- tions. Unfortunately, there is no existing model that allows extensive investigation of the impact of stable conditions, we present the base of pre-computation that is formalized by our degraded task-pair 〈 T, T＇ 〉 with the helper-thread, and its stable conditions are analyzed. Finally, a novel performance model and a constructing method of pre-computation based on our positive degraded task-pair are proposed. The efficient results are shown by our experiments. If we further exploit memory level parallelism （MLP） for our task-pair, the task-pair 〈 T, T＇ 〉 can reach better performance.展开更多
Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for...Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for the inlet-diffuser system,pri-mary/secondaryflow interaction,and pressure feedback matching,was developed for operating characteristics studies and multi-objective optimization analysis of the ejector mode of an actual RBCC engine.A series of three-dimensional simulations of separate inlet and fullflowpath was completed to validate the modeling study and provide further insight into the operating charac-teristics.The primary/secondary equilibrium pressure ratio functions a significant effect on ejector mode performance,a higher performance augmentation can be obtained by lower rocket pressure ratio,larger mixing section area ratio,smaller throttling throat and higher equivalence ratio,within an appropriate range.The positive performance augmentation can be realized at lowflight Mach conditions,the coordination and trade-off relationships between specific im-pulse,performance augmentation ratio and thrust-to-area ratio during ejector mode are present by the Pareto-front from MOP analysis.It is further verified by CFD simulation that,the operating back-pressure at the exit of inlet-diffuser system functions a decisive influence on the airbreathing characteristics,the pressure feedback and matching should be well-controlled for secondaryflowrate and performance augmentation.The thermodynamic modeling analysis re-sults are basically consistent with those of numerical simulation,to validate the rationality and effectiveness of the modeling method.展开更多
Today, in the field of computer networks, new services have been developed on the Internet or intranets, including the mail server, database management, sounds, videos and the web server itself Apache. The number of s...Today, in the field of computer networks, new services have been developed on the Internet or intranets, including the mail server, database management, sounds, videos and the web server itself Apache. The number of solutions for this server is therefore growing continuously, these services are becoming more and more complex and expensive, without being able to fulfill the needs of the users. The absence of benchmarks for websites with dynamic content is the major obstacle to research in this area. These users place high demands on the speed of access to information on the Internet. This is why the performance of the web server is critically important. Several factors influence performance, such as server execution speed, network saturation on the internet or intranet, increased response time, and throughputs. By measuring these factors, we propose a performance evaluation strategy for servers that allows us to determine the actual performance of different servers in terms of user satisfaction. Furthermore, we identified performance characteristics such as throughput, resource utilization, and response time of a system through measurement and modeling by simulation. Finally, we present a simple queue model of an Apache web server, which reasonably represents the behavior of a saturated web server using the Simulink model in Matlab (Matrix Laboratory) and also incorporates sporadic incoming traffic. We obtain server performance metrics such as average response time and throughput through simulations. Compared to other models, our model is conceptually straightforward. The model has been validated through measurements and simulations during the tests that we conducted.展开更多
Intelligent maintenance of roads and highways requires accurate deterioration evaluation and performance prediction of asphalt pavement.To this end,we develop a time series long short-term memory(LSTM)model to predict...Intelligent maintenance of roads and highways requires accurate deterioration evaluation and performance prediction of asphalt pavement.To this end,we develop a time series long short-term memory(LSTM)model to predict key performance indicators(PIs)of pavement,namely the international roughness index(IRI)and rutting depth(RD).Subsequently,we propose a comprehensive performance indicator for the pavement quality index(PQI),which leverages the highway performance assessment standard method,entropy weight method,and fuzzy comprehensive evaluation method.This indicator can evaluate the overall performance condition of the pavement.The data used for the model development and analysis are extracted from tests on two full-scale accelerated test tracks,called MnRoad and RIOHTrack.Six variables are used as predictors,including temperature,precipitation,total traffic volume,asphalt surface layer thickness,pavement age,and maintenance condition.Furthermore,wavelet denoising is performed to analyze the impact of missing or abnormal data on the LSTM model accuracy.In comparison to a traditional autoregressive integrated moving average(ARIMAX)model,the proposed LSTM model performs better in terms of PI prediction and resiliency to noise.Finally,the overall prediction accuracy of our proposed performance indicator PQI is 93.8%.展开更多
Visual question answering(VQA)is a multimodal task,involving a deep understanding of the image scene and the question’s meaning and capturing the relevant correlations between both modalities to infer the appropriate...Visual question answering(VQA)is a multimodal task,involving a deep understanding of the image scene and the question’s meaning and capturing the relevant correlations between both modalities to infer the appropriate answer.In this paper,we propose a VQA system intended to answer yes/no questions about real-world images,in Arabic.To support a robust VQA system,we work in two directions:(1)Using deep neural networks to semantically represent the given image and question in a fine-grainedmanner,namely ResNet-152 and Gated Recurrent Units(GRU).(2)Studying the role of the utilizedmultimodal bilinear pooling fusion technique in the trade-o.between the model complexity and the overall model performance.Some fusion techniques could significantly increase the model complexity,which seriously limits their applicability for VQA models.So far,there is no evidence of how efficient these multimodal bilinear pooling fusion techniques are for VQA systems dedicated to yes/no questions.Hence,a comparative analysis is conducted between eight bilinear pooling fusion techniques,in terms of their ability to reduce themodel complexity and improve themodel performance in this case of VQA systems.Experiments indicate that these multimodal bilinear pooling fusion techniques have improved the VQA model’s performance,until reaching the best performance of 89.25%.Further,experiments have proven that the number of answers in the developed VQA system is a critical factor that a.ects the effectiveness of these multimodal bilinear pooling techniques in achieving their main objective of reducing the model complexity.The Multimodal Local Perception Bilinear Pooling(MLPB)technique has shown the best balance between the model complexity and its performance,for VQA systems designed to answer yes/no questions.展开更多
Precipitous Arctic sea-ice decline and the corresponding increase in Arctic open-water areas in summer months give more space for sea-ice growth in the subsequent cold seasons. Compared to the decline of the entire Ar...Precipitous Arctic sea-ice decline and the corresponding increase in Arctic open-water areas in summer months give more space for sea-ice growth in the subsequent cold seasons. Compared to the decline of the entire Arctic multiyear sea ice,changes in newly formed sea ice indicate more thermodynamic and dynamic information on Arctic atmosphere–ocean–ice interaction and northern mid–high latitude atmospheric teleconnections. Here, we use a large multimodel ensemble from phase 6 of the Coupled Model Intercomparison Project(CMIP6) to investigate future changes in wintertime newly formed Arctic sea ice. The commonly used model-democracy approach that gives equal weight to each model essentially assumes that all models are independent and equally plausible, which contradicts with the fact that there are large interdependencies in the ensemble and discrepancies in models' performances in reproducing observations. Therefore, instead of using the arithmetic mean of well-performing models or all available models for projections like in previous studies, we employ a newly developed model weighting scheme that weights all models in the ensemble with consideration of their performance and independence to provide more reliable projections. Model democracy leads to evident bias and large intermodel spread in CMIP6 projections of newly formed Arctic sea ice. However, we show that both the bias and the intermodel spread can be effectively reduced by the weighting scheme. Projections from the weighted models indicate that wintertime newly formed Arctic sea ice is likely to increase dramatically until the middle of this century regardless of the emissions scenario.Thereafter, it may decrease(or remain stable) if the Arctic warming crosses a threshold(or is extensively constrained).展开更多
This paper describes an innovative adaptive algorithmic modeling approach, for solving a wide class of e-business and strategic management problems under uncertainty conditions. The proposed methodology is based on ba...This paper describes an innovative adaptive algorithmic modeling approach, for solving a wide class of e-business and strategic management problems under uncertainty conditions. The proposed methodology is based on basic ideas and concepts of four key-field interrelated sciences, i.e., computing science, applied mathematics, management sciences and economic sciences. Furthermore, the fundamental scientific concepts of adaptability and uncertainty are shown to play a critical role of major importance for a （near） optimum solution of a class of complex e-business/services and strategic management problems. Two characteristic case studies, namely measuring e-business performance under certain environmental pressures and organizational constraints and describing the relationships between technology, innovation and firm performance, are considered as effective applications of the proposed adaptive algorithmic modeling approach. A theoretical time-dependent model for the evaluation of firm e-business performances is also proposed.展开更多
This paper presents the theory,method,and application of performance-based pavement needs assessment at a state level,using the Pennsylvania Interstate System as an example.First,a general framework is presented for t...This paper presents the theory,method,and application of performance-based pavement needs assessment at a state level,using the Pennsylvania Interstate System as an example.First,a general framework is presented for the pavement asset management and a general optimization model is established for the pavement maintenance and rehabilitation needs assessment.Also,the bundling of pavement segments for the project implementation is discussed.Using the examples of Statewide Transportation Improvement Plan and Long Range Transportation Plan for Pennsylvania Interstate System,the application of performance-based pavement needs assessment is demonstrated.It is shown that unconstrained analysis can help decision-makers investigate the real maintenance and rehabilitation needs;financially-constrained analysis can help decision-makers select projects for implementation and examine the corresponding future pavement conditions.Trade-off analysis can help decision-makers investigate the outcomes of different investment levels on pavement maintenance and rehabilitation and make the final decision on the investment level.The proposed case study provides a good example of performance-based pavement needs assessment for developing countries.展开更多
Revealing regional climate changes is vital for policymaking activities related to climate change adaptation and mitigation.South China is a well-developed region with a dense population,but the level of uncertainty i...Revealing regional climate changes is vital for policymaking activities related to climate change adaptation and mitigation.South China is a well-developed region with a dense population,but the level of uncertainty in climate projections remains to be evaluated in detail.In this study,we comprehensively assessed the historical simulations and future projections of climate change in South China based on CMIP5/CMIP6 models.We show evidence that CMIP5/CMIP6 models can skillfully reproduce the observed distributions of annual/seasonal mean temperature but show much lower skill for precipitation.CMIP6 outperforms CMIP5 in the historical simulations,as evidenced by more models with lower bias magnitude and higher skill scores.During 2021–2100,the annual mean temperature over South China is projected to increase significantly at a rate of 0.53(0.42–0.63)and 0.59(0.52–0.66)℃(10 yr)^(-1),while precipitation is projected to increase slightly at a rate of 0.78(0.15–1.56)and 1.52(0.91–2.30)%(10 yr)^(-1),under the RCP8.5 and SSP5-8.5 scenarios,respectively.CMIP6 models project larger annual/seasonal mean temperature and precipitation trends than CMIP5 models under equivalent scenarios.The temperature in South China is projected to increase robustly by more than1.5℃during 2041–2060 under RCP4.5 and SSP2-4.5,but by 4.5℃during 2081–2100,under RCP8.5 and SSP5-8.5 with respect to 1850–1900.The uncertainty in temperature projections is mainly dominated by model uncertainty and scenario uncertainty,while internal uncertainty contributes some of the uncertainty during the near-term.The uncertainty in precipitation projection stems mainly from internal uncertainty and model uncertainty.For both the temperature and precipitation projection uncertainty,the relative sizes of contributions from the main contributors vary with time and show obvious seasonal differences.展开更多
For short-term PV power prediction,based on interval type-2 Takagi-Sugeno-Kang fuzzy logic systems(IT2 TSK FLS),combined with improved grey wolf optimizer(IGWO)algorithm,an IGWO-IT2 TSK FLS method was proposed.Compare...For short-term PV power prediction,based on interval type-2 Takagi-Sugeno-Kang fuzzy logic systems(IT2 TSK FLS),combined with improved grey wolf optimizer(IGWO)algorithm,an IGWO-IT2 TSK FLS method was proposed.Compared with the type-1 TSK fuzzy logic system method,interval type-2 fuzzy sets could simultaneously model both intra-personal uncertainty and inter-personal uncertainty based on the training of the existing error back propagation(BP)algorithm,and the IGWO algorithm was used for training the model premise and consequent parameters to further improve the predictive performance of the model.By improving the gray wolf optimization algorithm,the early convergence judgment mechanism,nonlinear cosine adjustment strategy,and Levy flight strategy were introduced to improve the convergence speed of the algorithm and avoid the problem of falling into local optimum.The interval type-2 TSK FLS method based on the IGWO algorithm was applied to the real-world photovoltaic power time series forecasting instance.Under the same conditions,it was also compared with different IT2 TSK FLS methods,such as type I TSK FLS method,BP algorithm,genetic algorithm,differential evolution,particle swarm optimization,biogeography optimization,gray wolf optimization,etc.Experimental results showed that the proposed method based on IGWO algorithm outperformed other methods in performance,showing its effectiveness and application potential.展开更多
This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of ...This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). It is a spectral model truncated at R42(2.8125°long×1.66°lat) resolution and with nine vertical levels, and referred to as R42L9/LASG hereafter. It is also the new version of atmospheric component model R15L9 of the global ocean-atmosphere-land system (GOALS/LASG). A 40-year simulation in which the model is forced with the climatological monthly mean sea surface temperature is compared with the 40-year (1958-97) U.S. National Center for Environmental Prediction (NGEP) global reanalysis and the 22-year (1979-2000) Xie-Arkin monthly precipitation climatology. The mean DJF and JJA geographical distributions of precipitation, sea level pressure, 500-hPa geopotential height, 850-hPa and 200-hPa zonal wind, and other fields averaged for the last 30-year integration of the R42L9 model are analyzed. Results show that the model reproduces well the observed basic patterns, particularly precipitation over the East Asian region. Comparing the new model with R15L9/LASG, the old version with coarse resolution (nearly 7.5°long×4.5°lat), shows an obvious improvement in the simulation of regional climate, especially precipitation. The weaknesses in simulation and future improvements of the model are also discussed.展开更多
Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in...Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.展开更多
In order to assess the effects of calibration data series length on the performance and optimal parameter values of a hydrological model in ungauged or data-limited catchments （data are non-continuous and fragmental ...In order to assess the effects of calibration data series length on the performance and optimal parameter values of a hydrological model in ungauged or data-limited catchments （data are non-continuous and fragmental in some catchments）, we used non-continuous calibration periods for more independent streamflow data for SIMHYD （simple hydrology） model calibration. Nash-Sutcliffe efficiency and percentage water balance error were used as performance measures. The particle swarm optimization （PSO） method was used to calibrate the rainfall-runoff models. Different lengths of data series ranging from one year to ten years, randomly sampled, were used to study the impact of calibration data series length. Fifty-five relatively unimpaired catchments located all over Australia with daily precipitation, potential evapotranspiration, and streamflow data were tested to obtain more general conclusions. The results show that longer calibration data series do not necessarily result in better model performance. In general, eight years of data are sufficient to obtain steady estimates of model performance and parameters for the SIMHYD model. It is also shown that most humid catchments require fewer calibration data to obtain a good performance and stable parameter values. The model performs better in humid and semi-humid catchments than in arid catchments. Our results may have useful and interesting implications for the efficiency of using limited observation data for hydrological model calibration in different climates.展开更多
In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign met...In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.展开更多
The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. B...The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed.Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance,and it establishes a theoretical basis for studies and engineering applications.展开更多
To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster an...To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV＇s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.展开更多
Reliable national estimates of CH_4 emissions from natural wetlands depend on model validation based on site observations.We therefore evaluated the performance of the CH_4 MODwetlandmodel in simulating CH_4 emissions...Reliable national estimates of CH_4 emissions from natural wetlands depend on model validation based on site observations.We therefore evaluated the performance of the CH_4 MODwetlandmodel in simulating CH_4 emissions from 11 representative wetland sites in five regions of China.Model performance analysis showed that this method effectively simulates differences in the CH_4 fluxes between different sites and regions.The model efficiency for estimating the daily CH_4 fluxes in the northeastern China（NE）,Inner Mongolia and northwestern China（NW）,the North China plain and the Middle-Lower Yangtze Plain（E） and the Qinghai Tibetan Plateau（SW） was 0.51,0.20,0.52 and 0.65,respectively.The efficiency for estimating the annual mean CH_4 fluxes in southern China（S） was 0.99.Systematic negative deviation between the simulated and observed CH_4 emissions existed in all regions,especially in the NW region,which had a mean deviation（RMD） value of-36.7%.On the national scale,the root mean square error（RMSE）,the RMD,the model efficiency（EF）between the simulated and observed seasonal values were 28.7%,-7.8% and 0.93,respectively.The CH_4 emissions showed the highest sensitivity to air temperature in the NE and SW regions,and to water table depth in the E region.Based on the sensitivity analysis,future climate warming and wetting are likely to increase the wetland CH_4 emissions at different levels in all regions of China.展开更多
Performance models provide insightful perspectives to predict performance and to propose optimization guidance.Although there has been much researches,pinpointing bottlenecks of various memory access patterns and reac...Performance models provide insightful perspectives to predict performance and to propose optimization guidance.Although there has been much researches,pinpointing bottlenecks of various memory access patterns and reaching high accurate prediction of both regular and irregular programs on various hardware configurations are still not trivial.This work proposes a novel model called process-RAM-feedback(PRF)to quantify the overhead of computation and data transmission time on general-purpose multi-core processors.The PRF model predicts the cost of instruction for singlecore by a directed acyclic graph(DAG)and the transmission time of memory access between each memory hierarchy through a newly designed cache simulator.By using performance modeling and feedback optimization method,this paper uses PRF model to analyze and optimize convolution,sparse matrix-vector multiplication and sn-sweep as case study for covering with typical regular kernel to irregular and data dependence.Through the PRF model,it obtains optimization guidance with various sparsity structures,algorithm designs,and instruction sets support on different data sizes.展开更多
IEEE 802.11 distributed coordination function （DCF） is a distributed medium access scheme based on carrier sense multiple access with collision avoidance （CSMA/CA） protocol. Many literatures have analyzed the perf...IEEE 802.11 distributed coordination function （DCF） is a distributed medium access scheme based on carrier sense multiple access with collision avoidance （CSMA/CA） protocol. Many literatures have analyzed the performance of IEEE802.11 DCF. However, such literatures either used simulation methods or built the analytical models under the assumption that the saturation condition was satisfied. To overcome such a problem, in this paper, a hi-dimensional Markovian model has been introduced to depict the DCF mechanism. The proposed model introduced an idle stage and a discrete time M/G/1 queue to deduce the channel throughput under finite load traffic. Simulation results proved the accuracy of the proposed model.展开更多
Electrodynamic tethered deorbit technology is a novel way to remove abandoned spacecrafts like upper stages or unusable satellites. This paper investigates and analyses the deorbit performance and mission applicabilit...Electrodynamic tethered deorbit technology is a novel way to remove abandoned spacecrafts like upper stages or unusable satellites. This paper investigates and analyses the deorbit performance and mission applicability of the electrodynamic tethered system. To do so, the electrodynamic tethered deorbit dynamics with multi-perturbation is firstly formulated, where the Earth magnetic field, the atmospheric drag, and the Earth oblateness effect are considered. Then, the key system parameters, including payload mass, tether length and tether type, are analyzed by numerical simulations to investigate their influences on the deorbit performance and to give the setting principles for choosing system parameters. Based on this and given an appropriate group of system parameters, numerical simulations are undertaken to study the impact of the mission parameters, including orbit height and orbit inclination, and thus to investigate the mission applicability of the electrodynamic tethered deorbit technology.展开更多
文摘Helper-thread of a task can hide the memory access time of irregular data on the chip muhi-core processor （CMP）. For constructing a compiler that effectively supports the helper-thread of a task in the multi-core scenario based on the last level shared cache, this paper studies its performance stable condi- tions. Unfortunately, there is no existing model that allows extensive investigation of the impact of stable conditions, we present the base of pre-computation that is formalized by our degraded task-pair 〈 T, T＇ 〉 with the helper-thread, and its stable conditions are analyzed. Finally, a novel performance model and a constructing method of pre-computation based on our positive degraded task-pair are proposed. The efficient results are shown by our experiments. If we further exploit memory level parallelism （MLP） for our task-pair, the task-pair 〈 T, T＇ 〉 can reach better performance.
基金supported by the National Natural Science Foundation of China (Grant No.52076094).
文摘Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for the inlet-diffuser system,pri-mary/secondaryflow interaction,and pressure feedback matching,was developed for operating characteristics studies and multi-objective optimization analysis of the ejector mode of an actual RBCC engine.A series of three-dimensional simulations of separate inlet and fullflowpath was completed to validate the modeling study and provide further insight into the operating charac-teristics.The primary/secondary equilibrium pressure ratio functions a significant effect on ejector mode performance,a higher performance augmentation can be obtained by lower rocket pressure ratio,larger mixing section area ratio,smaller throttling throat and higher equivalence ratio,within an appropriate range.The positive performance augmentation can be realized at lowflight Mach conditions,the coordination and trade-off relationships between specific im-pulse,performance augmentation ratio and thrust-to-area ratio during ejector mode are present by the Pareto-front from MOP analysis.It is further verified by CFD simulation that,the operating back-pressure at the exit of inlet-diffuser system functions a decisive influence on the airbreathing characteristics,the pressure feedback and matching should be well-controlled for secondaryflowrate and performance augmentation.The thermodynamic modeling analysis re-sults are basically consistent with those of numerical simulation,to validate the rationality and effectiveness of the modeling method.
文摘Today, in the field of computer networks, new services have been developed on the Internet or intranets, including the mail server, database management, sounds, videos and the web server itself Apache. The number of solutions for this server is therefore growing continuously, these services are becoming more and more complex and expensive, without being able to fulfill the needs of the users. The absence of benchmarks for websites with dynamic content is the major obstacle to research in this area. These users place high demands on the speed of access to information on the Internet. This is why the performance of the web server is critically important. Several factors influence performance, such as server execution speed, network saturation on the internet or intranet, increased response time, and throughputs. By measuring these factors, we propose a performance evaluation strategy for servers that allows us to determine the actual performance of different servers in terms of user satisfaction. Furthermore, we identified performance characteristics such as throughput, resource utilization, and response time of a system through measurement and modeling by simulation. Finally, we present a simple queue model of an Apache web server, which reasonably represents the behavior of a saturated web server using the Simulink model in Matlab (Matrix Laboratory) and also incorporates sporadic incoming traffic. We obtain server performance metrics such as average response time and throughput through simulations. Compared to other models, our model is conceptually straightforward. The model has been validated through measurements and simulations during the tests that we conducted.
基金supported by the National Key Research and Development Program of China(No.2021YFB2600300).
文摘Intelligent maintenance of roads and highways requires accurate deterioration evaluation and performance prediction of asphalt pavement.To this end,we develop a time series long short-term memory(LSTM)model to predict key performance indicators(PIs)of pavement,namely the international roughness index(IRI)and rutting depth(RD).Subsequently,we propose a comprehensive performance indicator for the pavement quality index(PQI),which leverages the highway performance assessment standard method,entropy weight method,and fuzzy comprehensive evaluation method.This indicator can evaluate the overall performance condition of the pavement.The data used for the model development and analysis are extracted from tests on two full-scale accelerated test tracks,called MnRoad and RIOHTrack.Six variables are used as predictors,including temperature,precipitation,total traffic volume,asphalt surface layer thickness,pavement age,and maintenance condition.Furthermore,wavelet denoising is performed to analyze the impact of missing or abnormal data on the LSTM model accuracy.In comparison to a traditional autoregressive integrated moving average(ARIMAX)model,the proposed LSTM model performs better in terms of PI prediction and resiliency to noise.Finally,the overall prediction accuracy of our proposed performance indicator PQI is 93.8%.
文摘Visual question answering(VQA)is a multimodal task,involving a deep understanding of the image scene and the question’s meaning and capturing the relevant correlations between both modalities to infer the appropriate answer.In this paper,we propose a VQA system intended to answer yes/no questions about real-world images,in Arabic.To support a robust VQA system,we work in two directions:(1)Using deep neural networks to semantically represent the given image and question in a fine-grainedmanner,namely ResNet-152 and Gated Recurrent Units(GRU).(2)Studying the role of the utilizedmultimodal bilinear pooling fusion technique in the trade-o.between the model complexity and the overall model performance.Some fusion techniques could significantly increase the model complexity,which seriously limits their applicability for VQA models.So far,there is no evidence of how efficient these multimodal bilinear pooling fusion techniques are for VQA systems dedicated to yes/no questions.Hence,a comparative analysis is conducted between eight bilinear pooling fusion techniques,in terms of their ability to reduce themodel complexity and improve themodel performance in this case of VQA systems.Experiments indicate that these multimodal bilinear pooling fusion techniques have improved the VQA model’s performance,until reaching the best performance of 89.25%.Further,experiments have proven that the number of answers in the developed VQA system is a critical factor that a.ects the effectiveness of these multimodal bilinear pooling techniques in achieving their main objective of reducing the model complexity.The Multimodal Local Perception Bilinear Pooling(MLPB)technique has shown the best balance between the model complexity and its performance,for VQA systems designed to answer yes/no questions.
基金supported by the Chinese–Norwegian Collaboration Projects within Climate Systems jointly funded by the National Key Research and Development Program of China (Grant No.2022YFE0106800)the Research Council of Norway funded project,MAPARC (Grant No.328943)+2 种基金the support from the Research Council of Norway funded project,COMBINED (Grant No.328935)the National Natural Science Foundation of China (Grant No.42075030)the Postgraduate Research and Practice Innovation Program of Jiangsu Province (KYCX23_1314)。
文摘Precipitous Arctic sea-ice decline and the corresponding increase in Arctic open-water areas in summer months give more space for sea-ice growth in the subsequent cold seasons. Compared to the decline of the entire Arctic multiyear sea ice,changes in newly formed sea ice indicate more thermodynamic and dynamic information on Arctic atmosphere–ocean–ice interaction and northern mid–high latitude atmospheric teleconnections. Here, we use a large multimodel ensemble from phase 6 of the Coupled Model Intercomparison Project(CMIP6) to investigate future changes in wintertime newly formed Arctic sea ice. The commonly used model-democracy approach that gives equal weight to each model essentially assumes that all models are independent and equally plausible, which contradicts with the fact that there are large interdependencies in the ensemble and discrepancies in models' performances in reproducing observations. Therefore, instead of using the arithmetic mean of well-performing models or all available models for projections like in previous studies, we employ a newly developed model weighting scheme that weights all models in the ensemble with consideration of their performance and independence to provide more reliable projections. Model democracy leads to evident bias and large intermodel spread in CMIP6 projections of newly formed Arctic sea ice. However, we show that both the bias and the intermodel spread can be effectively reduced by the weighting scheme. Projections from the weighted models indicate that wintertime newly formed Arctic sea ice is likely to increase dramatically until the middle of this century regardless of the emissions scenario.Thereafter, it may decrease(or remain stable) if the Arctic warming crosses a threshold(or is extensively constrained).
文摘This paper describes an innovative adaptive algorithmic modeling approach, for solving a wide class of e-business and strategic management problems under uncertainty conditions. The proposed methodology is based on basic ideas and concepts of four key-field interrelated sciences, i.e., computing science, applied mathematics, management sciences and economic sciences. Furthermore, the fundamental scientific concepts of adaptability and uncertainty are shown to play a critical role of major importance for a （near） optimum solution of a class of complex e-business/services and strategic management problems. Two characteristic case studies, namely measuring e-business performance under certain environmental pressures and organizational constraints and describing the relationships between technology, innovation and firm performance, are considered as effective applications of the proposed adaptive algorithmic modeling approach. A theoretical time-dependent model for the evaluation of firm e-business performances is also proposed.
基金The National Key Research and Development Program of China(No.2018YFB1601202)the Natural Science Foundation of Shaanxi Province(No.2019JM-228)+1 种基金the National Natural Science Foundation of China(No.51308335)the Fundamental Research Funds for the Central Universities of Chang’an University(No.300102218401)
文摘This paper presents the theory,method,and application of performance-based pavement needs assessment at a state level,using the Pennsylvania Interstate System as an example.First,a general framework is presented for the pavement asset management and a general optimization model is established for the pavement maintenance and rehabilitation needs assessment.Also,the bundling of pavement segments for the project implementation is discussed.Using the examples of Statewide Transportation Improvement Plan and Long Range Transportation Plan for Pennsylvania Interstate System,the application of performance-based pavement needs assessment is demonstrated.It is shown that unconstrained analysis can help decision-makers investigate the real maintenance and rehabilitation needs;financially-constrained analysis can help decision-makers select projects for implementation and examine the corresponding future pavement conditions.Trade-off analysis can help decision-makers investigate the outcomes of different investment levels on pavement maintenance and rehabilitation and make the final decision on the investment level.The proposed case study provides a good example of performance-based pavement needs assessment for developing countries.
基金jointly supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U2242203)the National Natural Science Foundation of China(Grant No.41905070)+4 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021A1515011421,2023A1515240067,2023B1515020009)the National Key R&D Program of China(Grant No.2018YFC1505801)supported by the Guangdong Provincial Marine Meteorology Science Data Center(2024B1212070014)the China Meteorology Administration Key Innovation Team of Tropical Meteorology(Grant No.CMA2023ZD08)State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences(Project No.LTO2311)。
文摘Revealing regional climate changes is vital for policymaking activities related to climate change adaptation and mitigation.South China is a well-developed region with a dense population,but the level of uncertainty in climate projections remains to be evaluated in detail.In this study,we comprehensively assessed the historical simulations and future projections of climate change in South China based on CMIP5/CMIP6 models.We show evidence that CMIP5/CMIP6 models can skillfully reproduce the observed distributions of annual/seasonal mean temperature but show much lower skill for precipitation.CMIP6 outperforms CMIP5 in the historical simulations,as evidenced by more models with lower bias magnitude and higher skill scores.During 2021–2100,the annual mean temperature over South China is projected to increase significantly at a rate of 0.53(0.42–0.63)and 0.59(0.52–0.66)℃(10 yr)^(-1),while precipitation is projected to increase slightly at a rate of 0.78(0.15–1.56)and 1.52(0.91–2.30)%(10 yr)^(-1),under the RCP8.5 and SSP5-8.5 scenarios,respectively.CMIP6 models project larger annual/seasonal mean temperature and precipitation trends than CMIP5 models under equivalent scenarios.The temperature in South China is projected to increase robustly by more than1.5℃during 2041–2060 under RCP4.5 and SSP2-4.5,but by 4.5℃during 2081–2100,under RCP8.5 and SSP5-8.5 with respect to 1850–1900.The uncertainty in temperature projections is mainly dominated by model uncertainty and scenario uncertainty,while internal uncertainty contributes some of the uncertainty during the near-term.The uncertainty in precipitation projection stems mainly from internal uncertainty and model uncertainty.For both the temperature and precipitation projection uncertainty,the relative sizes of contributions from the main contributors vary with time and show obvious seasonal differences.
基金supported by National Natural Science Foundation of China(No.12172157)Key Project of Natural Science Foundation of Gansu Province(No.25JRRA150)Key Research and Development Planning Project of Gansu Province(No.23YFWA0007).
文摘For short-term PV power prediction,based on interval type-2 Takagi-Sugeno-Kang fuzzy logic systems(IT2 TSK FLS),combined with improved grey wolf optimizer(IGWO)algorithm,an IGWO-IT2 TSK FLS method was proposed.Compared with the type-1 TSK fuzzy logic system method,interval type-2 fuzzy sets could simultaneously model both intra-personal uncertainty and inter-personal uncertainty based on the training of the existing error back propagation(BP)algorithm,and the IGWO algorithm was used for training the model premise and consequent parameters to further improve the predictive performance of the model.By improving the gray wolf optimization algorithm,the early convergence judgment mechanism,nonlinear cosine adjustment strategy,and Levy flight strategy were introduced to improve the convergence speed of the algorithm and avoid the problem of falling into local optimum.The interval type-2 TSK FLS method based on the IGWO algorithm was applied to the real-world photovoltaic power time series forecasting instance.Under the same conditions,it was also compared with different IT2 TSK FLS methods,such as type I TSK FLS method,BP algorithm,genetic algorithm,differential evolution,particle swarm optimization,biogeography optimization,gray wolf optimization,etc.Experimental results showed that the proposed method based on IGWO algorithm outperformed other methods in performance,showing its effectiveness and application potential.
文摘This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). It is a spectral model truncated at R42(2.8125°long×1.66°lat) resolution and with nine vertical levels, and referred to as R42L9/LASG hereafter. It is also the new version of atmospheric component model R15L9 of the global ocean-atmosphere-land system (GOALS/LASG). A 40-year simulation in which the model is forced with the climatological monthly mean sea surface temperature is compared with the 40-year (1958-97) U.S. National Center for Environmental Prediction (NGEP) global reanalysis and the 22-year (1979-2000) Xie-Arkin monthly precipitation climatology. The mean DJF and JJA geographical distributions of precipitation, sea level pressure, 500-hPa geopotential height, 850-hPa and 200-hPa zonal wind, and other fields averaged for the last 30-year integration of the R42L9 model are analyzed. Results show that the model reproduces well the observed basic patterns, particularly precipitation over the East Asian region. Comparing the new model with R15L9/LASG, the old version with coarse resolution (nearly 7.5°long×4.5°lat), shows an obvious improvement in the simulation of regional climate, especially precipitation. The weaknesses in simulation and future improvements of the model are also discussed.
基金National Natural Science Foundation of China (Grant No.52178393)the Science and Technology Innovation Team of Shaanxi Innovation Capability Support Plan (Grant No.2020TD005)Science and Technology Innovation Project of China Railway Construction Bridge Engineering Bureau Group Co.,Ltd.(Grant No.DQJ-2020-B07)。
文摘Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.
基金supported by the National Basic Research Program of China (the 973 Program,Grant No.2010CB951102)the National Supporting Plan Program of China (Grants No.2007BAB28B01 and 2008BAB42B03)the National Natural Science Foundation of China (Grant No. 50709042),and the Regional Water Theme in the Water for a Healthy Country Flagship
文摘In order to assess the effects of calibration data series length on the performance and optimal parameter values of a hydrological model in ungauged or data-limited catchments （data are non-continuous and fragmental in some catchments）, we used non-continuous calibration periods for more independent streamflow data for SIMHYD （simple hydrology） model calibration. Nash-Sutcliffe efficiency and percentage water balance error were used as performance measures. The particle swarm optimization （PSO） method was used to calibrate the rainfall-runoff models. Different lengths of data series ranging from one year to ten years, randomly sampled, were used to study the impact of calibration data series length. Fifty-five relatively unimpaired catchments located all over Australia with daily precipitation, potential evapotranspiration, and streamflow data were tested to obtain more general conclusions. The results show that longer calibration data series do not necessarily result in better model performance. In general, eight years of data are sufficient to obtain steady estimates of model performance and parameters for the SIMHYD model. It is also shown that most humid catchments require fewer calibration data to obtain a good performance and stable parameter values. The model performs better in humid and semi-humid catchments than in arid catchments. Our results may have useful and interesting implications for the efficiency of using limited observation data for hydrological model calibration in different climates.
基金Projects(50875090,50905063) supported by the National Natural Science Foundation of ChinaProject(2009AA04Z111) supported by the National High Technology Research and Development Program of China+2 种基金Project(20090460769) supported by China Postdoctoral Science FoundationProject(2011ZM0070) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(S2011010001155) supported by the Natural Science Foundation of Guangdong Province,China
文摘In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.
基金supported by the National Natural Science Foundation of China (Grant 51375035)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant 20121102110021)
文摘The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed.Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance,and it establishes a theoretical basis for studies and engineering applications.
基金Supported by the National Natural Science Foundation of China under Grant No.50909025
文摘To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV＇s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.
基金supported by the Chinese Academy of Sciences(CAS) strategic pilot technology special funds(No.XDA05020204)the National Natural Science Foundation of China(Nos.31000234,41321064 and 41573069)the Climate Change Special Foundation of China Meteorological Administration(No.CCSF201604)
文摘Reliable national estimates of CH_4 emissions from natural wetlands depend on model validation based on site observations.We therefore evaluated the performance of the CH_4 MODwetlandmodel in simulating CH_4 emissions from 11 representative wetland sites in five regions of China.Model performance analysis showed that this method effectively simulates differences in the CH_4 fluxes between different sites and regions.The model efficiency for estimating the daily CH_4 fluxes in the northeastern China（NE）,Inner Mongolia and northwestern China（NW）,the North China plain and the Middle-Lower Yangtze Plain（E） and the Qinghai Tibetan Plateau（SW） was 0.51,0.20,0.52 and 0.65,respectively.The efficiency for estimating the annual mean CH_4 fluxes in southern China（S） was 0.99.Systematic negative deviation between the simulated and observed CH_4 emissions existed in all regions,especially in the NW region,which had a mean deviation（RMD） value of-36.7%.On the national scale,the root mean square error（RMSE）,the RMD,the model efficiency（EF）between the simulated and observed seasonal values were 28.7%,-7.8% and 0.93,respectively.The CH_4 emissions showed the highest sensitivity to air temperature in the NE and SW regions,and to water table depth in the E region.Based on the sensitivity analysis,future climate warming and wetting are likely to increase the wetland CH_4 emissions at different levels in all regions of China.
基金Supported by the National Key Research and Development Program of China(No.2017YFB0202105,2016YFB0201305,2016YFB0200803,2016YFB0200300)the National Natural Science Foundation of China(No.61521092,91430218,31327901,61472395,61432018).
文摘Performance models provide insightful perspectives to predict performance and to propose optimization guidance.Although there has been much researches,pinpointing bottlenecks of various memory access patterns and reaching high accurate prediction of both regular and irregular programs on various hardware configurations are still not trivial.This work proposes a novel model called process-RAM-feedback(PRF)to quantify the overhead of computation and data transmission time on general-purpose multi-core processors.The PRF model predicts the cost of instruction for singlecore by a directed acyclic graph(DAG)and the transmission time of memory access between each memory hierarchy through a newly designed cache simulator.By using performance modeling and feedback optimization method,this paper uses PRF model to analyze and optimize convolution,sparse matrix-vector multiplication and sn-sweep as case study for covering with typical regular kernel to irregular and data dependence.Through the PRF model,it obtains optimization guidance with various sparsity structures,algorithm designs,and instruction sets support on different data sizes.
文摘IEEE 802.11 distributed coordination function （DCF） is a distributed medium access scheme based on carrier sense multiple access with collision avoidance （CSMA/CA） protocol. Many literatures have analyzed the performance of IEEE802.11 DCF. However, such literatures either used simulation methods or built the analytical models under the assumption that the saturation condition was satisfied. To overcome such a problem, in this paper, a hi-dimensional Markovian model has been introduced to depict the DCF mechanism. The proposed model introduced an idle stage and a discrete time M/G/1 queue to deduce the channel throughput under finite load traffic. Simulation results proved the accuracy of the proposed model.
文摘Electrodynamic tethered deorbit technology is a novel way to remove abandoned spacecrafts like upper stages or unusable satellites. This paper investigates and analyses the deorbit performance and mission applicability of the electrodynamic tethered system. To do so, the electrodynamic tethered deorbit dynamics with multi-perturbation is firstly formulated, where the Earth magnetic field, the atmospheric drag, and the Earth oblateness effect are considered. Then, the key system parameters, including payload mass, tether length and tether type, are analyzed by numerical simulations to investigate their influences on the deorbit performance and to give the setting principles for choosing system parameters. Based on this and given an appropriate group of system parameters, numerical simulations are undertaken to study the impact of the mission parameters, including orbit height and orbit inclination, and thus to investigate the mission applicability of the electrodynamic tethered deorbit technology.
