检索结果-南通市图书馆

On the Current Error Based Sampled-data Iterative Learning Control with Reduced Memory Capacity

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2015年第3期12卷 307-315页

作者： chiang-Ju chien Yu-Chung hung rong-hu chi Department of Electronic Engineering Huafan University School of Automation and Electrical Engineering Qingdao University of Science and Technology

The design of iterative learning controller(ILC) requires to store the system input, output or control parameters of previous trials for generating the input of the current trial. In order to apply the iterative learning controller for a real application and reduce the memory size for implementation, a current error based sampled-data proportional-derivative(PD) type iterative learning controller is proposed for control systems with initial resetting error, input disturbance and output measurement noise in this *** proposed iterative learning controller is simple and effective. The first contribution in this paper is to prove the learning error convergence via a rigorous technical analysis. It is shown that the learning error will converge to a residual set if a forgetting factor is introduced in the controller. All the theoretical results are also shown by computer simulations. The second main contribution is to realize the iterative learning controller by a digital circuit using a field programmable gate array(FPGA) chip applied to repetitive position tracking control of direct current(DC) motors. The feasibility and effectiveness of the proposed current error based sampleddata iterative learning controller are demonstrated by the experiment results. Finally, the relationship between learning performance and design parameters are also discussed extensively.

关键词： Iterative learning control current error sampled-data system memory capacity field programmable gate array(FPGA) chip.

Automated regression test method for scientific computing libraries:Illustration with SPHinXsys

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2024年第3期36卷 466-478页

作者： Bo Zhang chi Zhang Xiangyu hu TUM School of Engineering and Design Technical University of MunichMunichGermany

Scientific computing libraries,whether in-house or open-source,have witnessed enormous progress in both engineering and scientific ***,it is important to ensure that modifications to the source code,prompted by bug fixing or new feature development,do not compromise the accuracy and functionality that have been already validated and *** paper introduces a method for establishing and implementing an automatic regression test environment,using the open-source multi-physics library SPHinXsys as an illustrative ***,a reference database for each benchmark test is generated from observed data across multiple *** comprehensive database encapsulates the maximum variation range of metrics for different strategies,including the time-averaged,ensemble-averaged,and dynamic time warping *** accounts for uncertainties arising from parallel computing,particle relaxation,physical instabilities,and ***,new results obtained after source code modifications undergo testing based on a curve-similarity comparison against the reference *** the source code is updated,the regression test is automatically executed for all test cases,providing a comprehensive assessment of the validity of the current *** regression test environment has been successfully implemented in all dynamic test cases within SPHinXsys,including fluid dynamics,solid mechanics,fluid-structure interaction,thermal and mass diffusion,reaction-diffusion,and their multi-physics couplings,and demonstrates robust capabilities in testing different *** is noted that while the current test environment is built and implemented for a particular scientific computing library,its underlying principles are generic and can be easily adapted for use with other libraries,achieving equal effectiveness.

关键词： Scientific computing open-source library verification and validation regression test automatic test environment curve similarity comparison smoothed particle hydrodynamics

Coupled conditional nonlinear optimal perturbations and their application to ENSO ensemble forecasts

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science china Earth Sciences 2024年第3期67卷 826-842页

作者： Wansuo DUAN Lei hu rong FENG LASG Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of chinese Academy of Sciences Beijing 100049China

Limitations are existed in current ensemble forecasting initial perturbation methods for describing the interactions among various spheres of the Earth system. In this study, a new method is proposed, namely, the coupled conditional nonlinear optimal perturbation(C-CNOP) method, which incorporates multisphere interactions much appropriately. The El Nino-Southern Oscillation(ENSO) is a typical ocean-atmosphere “coupling”(or “interaction”) phenomenon. The C-CNOP method is applied to ensemble forecasting of ENSO. It is demonstrated that the C-CNOP method can generate coupled initial perturbations(CPs) that appropriately consider initial ocean-atmosphere coupling uncertainty for ENSO ensemble forecasts. Results reveal that the CPs effectively improve the ability of ENSO ensemble-mean forecasts in both temporal variability of Nio3.4 sea surface temperature anomalies(SSTAs) and spatial variability of ENSO mature-phase SSTAs. Notably, despite the weakest ocean-atmosphere coupling strength in the tropical Pacific occurring during the boreal spring and summer, CPs still capture the uncertainties of this weak coupling when ENSO predictions are initialized at these seasons. This performance of CPs significantly suppresses the rapid increase of ENSO prediction errors due to the high ocean-atmosphere coupling instability during these seasons, and thus effectively extends the lead time of skillful ENSO forecasting. Hence, the C-CNOP method is a suitable initial perturbation approach for ENSO ensemble forecast that can describe initial ocean-atmosphere coupling uncertainty. It is expected that the CCNOP method plays a significant role in predictions of other high-impact climate phenomena, and even future Earth system predictions.

关键词： Ensemble forecast Multisphere interaction Initial perturbations ENSO

Impact of Carbon Chain Structures in the Backbone on the Flexibility of Modified Polyarylene Sulfide Resins: Molecular Dynamics Simulations and Mesoscopic Analysis

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Polymer Science 2024年第4期42卷 544-557页

作者： chi Zhang rong Liu Jing-Yuan Liu Wen-Wei Jiang Key Laboratory of Fine Chemical Engineering and Functional Materials School of Chemical EngineeringSichuan UniversityChengdu610065China

In the domain of high-performance engineering polymers, the enhancement of mechanical flexibility in poly(phenylene sulfide) (PPS) resins has long posed a significant challenge. A novel molecular structure, designated as PP-He-IS, wherein imide rings and an aliphatic hexylene chain are covalently incorporated into the PPS backbone to enhance its flexibility, is introduced in this study. Molecular dynamics (MD) simulations are employed to systematically explore the effects of diversifying the backbone chain structures by substituting phenyl units with alkyl chains of varying lengths, referred to as PP-A-IS where “A” signifies the distinct intermediary alkyl chain configurations. Computational analyses reveal a discernable decrement in the glass transition temperature (Tg) and elastic modulus, counterbalanced by an increment in yield strength as the alkyl chain length is extended. Notably, the PP-He-IS variant is shown to exhibit superior yield strength while simultaneously maintaining reduced elastic modulus and Tg values, positioning it as an advantageous candidate for flexible PPS applications. Mesoscopic analyses further indicate that structures such as PP-He-IS, PP-Pe-IS, and PP-Bu-IS manifest remarkable flexibility, attributable to the presence of freely rotatable carbon-carbon single bonds. Experimental validation confirms that a melting temperature of 504 K which is lower than that of conventional PPS, and lower crystallinity are exhibited by PP-He-IS, thereby affording enhanced processability without compromising inherent thermal stability. Novel insights into the strategic modification of PPS for mechanical flexibility are thus furnished by this study, which also accentuates the pivotal role played by molecular dynamics simulations in spearheading high-throughput investigations in polymer material modifications.

关键词： Molecular dynamics simulations Polyarylene Sulfide Main-chain modifications Flexibility Aliphatic hexylene chain

An impact sensitivity assessment method of spacecraft based on virtual exterior wall

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第1期31卷 142-157页

作者： Runqiang chi Yuyan Liu Diqi hu Baojun Pang Hypervelocity Impact Research Center Harbin Institute Of TechnologyHarbin150080China

The impact sensitivity assessment of spacecraft is to obtain the probability of spacecraft encountering the OD/M(orbital debris or meteoroid),which is a prerequisite for survivability assessment of on-orbit *** impact sensitivity assessment method of spacecraft based on virtual exterior wall was proposed to improve the computational *** method eliminates determination of the outermost surface elements of the spacecraft before generating the debris rays,which are assumed to originate from a non-concave virtual wall that completely wraps the *** Dist Mesh method was adopted for the generating of the virtual wall to ensure its mesh *** influences of the sizes,mesh densities,shapes of the virtual wall on the efficiency and accuracy were considered to obtain the best combination of the size and mesh density of the wall and *** results of this method were compared with those of S3DE(Survivability of Spacecraft in Space Debris Environment),BUMPER,MDPANTO,ESABASE2/Debris to verify the feasibility of the *** PchiP(Piecewise Cubic Hermite Interpolating Polynomial)was used to fit the size *** relationship of the space debris to acquire the impact probability of OD/M with arbitrary size on the spacecraft.

关键词： Sensitivity OD/M Spacecraft Virtual exterior wall

Capillary Property of Entangled Porous Metallic Wire materials and Its Application in Fluid Buffers:Theoretical Analysis and Experimental Study

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第1期31卷 400-416页

作者： Yu Tang Yiwan Wu hu Cheng rong Liu Engineering Research Center for Metal Rubber School of Mechanical Engineering and AutomationFuzhou UniversityFuzhou 350156China AECC Guizhou Liyang Aviation Power Co. LTDGuiyang 550014China College of Computer and Information Sciences Fujian Agriculture and Forestry UniversityFuzhou 350156China

Strong impact does serious harm to the military industries so it is necessary to choose reasonable cushioning material and design effective buffers to prevent the impact of *** on the capillary property entangled porous metallic wire materials(EPMWM),this paper designed a composite buffer which uses EPMWM and viscous fluid as cushioning materials under the low-speed impact of the recoil force device of weapon equipment(such as artillery,mortar,etc.).Combined with the capillary model,porosity,hydraulic diameter,maximum pore diameter and pore distribution were used to characterize the pore structure characteristics of *** calculation model of the damping force of the composite buffer was *** low-speed impact test of the composite buffer was *** parameters of the buffer under low-speed impact were identified according to the model,and the nonlinear model of damping force was *** test results show that the composite buffer with EPMWM and viscous fluid can absorb the impact energy from the recoil movement effectively,and provide a new method for the buffer design of weapon equipment(such as artillery,mortar,etc.).

关键词： Entangled porous metallic wire materials Capillary property Viscousfluid Low-speed impact Damping force

Shock-induced chemical reaction characteristics of PTFE-Al-Bi_(2)O_(3)reactive materials

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第6期36卷 1-12页

作者： Chunlan Jiang rong hu Jingbo Zhang Zaicheng Wang Liang Mao State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

A ternary system of PTFE/Al/Bi_(2)O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive *** effects of Bi_(2)O_(3)in the PTFE/Al/Bi_(2)O_(3)on both mechanical properties and the energy release were investigated through various tests such as thermogravimetry-differential scanning calorimetry,adiabatic oxygen bomb test and split Hopkinson pressure bar *** microstructure observed through scanning electron microscope and Xray diffraction results are used to analyze the ignition and reaction mechanism of PTFE/Al/Bi_(2)O_(3).The results indicate that the PTFE/Al/Bi_(2)O_(3)are capable of triggering the exothermic reaction of molten PTFE/Bi_(2)O_(3)and Al/Bi_(2)O_(3)over the PTFE/Al reactive materials,thereby promoting *** excessive aluminum in the ternary system is beneficial for increasing energy *** ignition of shock-induced chemical reactions in PTFE/Al/Bi_(2)O_(3)is closely related to the material *** dominant mechanism for hot-spot generation under Split Hopkinson Pressure Bar test is the frictional temperature rise at the microcrack after failure.

关键词： PTFE/Al/Bi_(2)O_(3) Shock-induced chemical reaction Energy release

Mechanism investigation of A-site doping on modulating electronic band structure and photocatalytic performance towards CO_(2) reduction of LaFeO_(3) perovskite

在线全文

学校读者我要写书评

暂无评论

Nano Research 2024年第5期17卷 3733-3744页

作者： chi Cao Jinshuo Li Yang hu Lin Zhang Wensheng Yang State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of ChemistryJilin UniversityChangchun 130012China Engineering Research Center for Nanomaterials Henan UniversityKaifeng 475004China

Three kinds of metal atoms with different valence electronic configurations,Bi(6s^(2)6p^(3)),Y(4d^(1)5s^(2)),and Ce(4f^(1)5d^(1)6s^(2)),were selected to investigate the effect of A-site(La^(3+))doping on electronic band structure,photoelectric properties,and photocatalytic performance of LaFeO_(3) *** was identified that the Bi doped LaFeO_(3) presented significantly improved photocatalytic activity towards the reduction of CO_(2),while the Y or Ce doped LaFeO_(3) displayed decreased photocatalytic activity compared to the pristine LaFeO_(3).It was revealed that doping of all the three metal atoms resulted in narrowed band gap and thus extended light absorption of LaFeO_(3) by lowering its conduction band minimum(CBM).The recombination rate and mobility of the charge carriers were represented by the relative effective mass(D)between holes and electrons for pristine and A-site doped LaFeO_(3).The doping of Bi resulted in increased D value,attributed to the Bi 6s electron states at the valence band maximum(VBM),and thus promoted separation and transfer of the charge carriers and improved photocatalytic activity of LaFeO_(3).In contrast,the doping of Ce resulted in significantly decreased D value,induced by the highly localized Ce 4f hole states at the CBM,and thus higher recombination rate of the charge carriers and decreased photocatalytic activity of LaFeO_(3).Furthermore,the Y doped LaFeO_(3) with a slightly decreased D value presented slightly increased recombination rate of the charge carriers and thus decreased photocatalytic *** a work provides new insights into the A-site doping in LaFeO_(3) perovskite,which should be helpful for optimizing the electronic band structure and activity of perovskite-type photocatalysts at atomic level.

关键词： A-site doping electronic band structure charge carrier behavior photocatalytic CO_(2)reduction perovskite-type photocatalytsts

Synergistic Interdecadal Evolution of Precipitation over Eastern china and the Pacific Decadal Oscillation during 1951-2015

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2024年第1期41卷 53-72页

作者： Minmin WU rong-hua ZHANG Junya hu Hai ZHI Key Laboratory of Ocean Circulation and Waves Institute of OceanologyChinese Academy of SciencesQingdao 266071China School of Marine Sciences Nanjing University of Information Science and TechnologyNanjing 210044China Laosan Laboratory Qingdao 266237China School of Atmospheric Sciences Nanjing University of Information Science and TechnologyNanjing 210044China University of chinese Academy of Sciences Beijing 100029China

By using the multi-taper method(MTM)of singular value decomposition(SVD),this study investigates the interdecadal evolution(10-to 30-year cycle)of precipitation over eastern china from 1951 to 2015 and its relationship with the North Pacific sea surface temperature(SST).Two significant interdecadal signals,one with an 11-year cycle and the other with a 23-year cycle,are identified in both the precipitation and SST *** show that the North Pacific SST forcing modulates the precipitation distribution over china through the effects of the Pacific Decadal Oscillation(PDO)-related anomalous Aleutian low on the western Pacific subtropical high(WPSH)and Mongolia high(MH).During the development stage of the PDO cold phase associated with the 11-year cycle,a weakened WPSH and MH increased the precipitation over the Yangtze River Basin,whereas an intensified WPSH and MH caused the enhanced rain band to move northward to North china during the decay *** the development stage of the PDO cold phase associated with the 23-year cycle,a weakened WPSH and MH increased the precipitation over North china,whereas an intensified WPSH and the weakened MH increased the precipitation over South china during the decay *** 11-year and 23-year variabilities contribute differently to the precipitation variations in the different regions of china,as seen in the 1998flooding *** 11-year cycle mainly accounts for precipitation increases over the Yangtze River Basin,while the 23-year cycle is responsible for the precipitation increase over Northeast *** results have important implications for understanding how the PDO modulates the precipitation distribution over china,helping to improve interdecadal climate prediction.

关键词： MTM-SVD PDO SST anomalies interdecadal variability precipitation over china