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41.
An analogue method(AM) is a nonparametric approach that has been applied to predict the future states of a dynamic system by following the evolution of the analogues in the historical archive. In this study, we proposed a hidden Markov model(HMM)framework for a modified analogue forecasting(MAF) approach for meteorological droughts in Korea. The unobservable(hidden) state process in the framework aims to model the underlying drought state, while the observation process was formed from the time series of the standardized precipitation index(SPI) as a drought index. Within the framework, the likelihood estimator was used as the measure of similarity between past SPI analogues and current data. The MAF approach was conducted on the selected analogues to make forecasts at lead times of one and three months. The proposed model was applied to five selected stations in Korea using the SPI data from 1973 to 2016. The forecasting performance of the proposed model was tested during the validation period(2003–2016) using several statistical criteria and it was compared to a persistence-based benchmark model. The results showed significant improvement in the forecasting capacity, and satisfactory performance for numerical SPI forecasting and categorical drought forecasting. The results also suggested that the proposed model was able to provide useful information for determining future drought categories for early drought warning with a lead time of up to three months. 相似文献
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Pulse electrochemical polishing (PECP) was used to improve the mechanical properties,such as surface roughness and corrosion resistance,of conductive metallic materials.PECP can provide a smooth,bright,reflective,and deburred surface that exhibits superior corrosion resistance.In this work,stainless steel was used as the anode,and copper was used as the cathode due to their low electrical resistances.The surface roughness of the PECP sample was measured by atomic force microscopy (AFM).A scanning electron microscope (SEM) was used to observe surface characteristics,and an Auger electron spectroscope (AES) was used to analyze the metallurgical composition and thickness of the passive film.The aim of this research was to compare the corrosion resistance rates of the unprocessed and PECP-processed stainless steel. 相似文献
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This work demonstrates high-performance and current crowding-free InGaN/GaN light-emitting diodes (LEDs) using an electrically-reverse-connected Schottky diode (SD) and an Mg-delta (δ) doped layer.Poss... 相似文献
46.
The relative wear of a single point diamond, defined in terms of the grinding force, was determined for a group of A12O3 and Si3N4. It was found that the wear rate is directly related to the mechanical properties of the workpiece and the grinding environment. 相似文献
47.
A major hurdle in the development of intelligent robots is that we still do not possess efficient computational and representational methodologies for emulating knowledge and expectation driven behaviour so basic to human cognition and problem solving. Even if we use techniques such as geometric modelling for representing objects in the robot world, we are still lacking in methods for linking such representations with sensory feedback. In this paper, we have proposed the use of intermediate representations—we call them sensor-tuned representations—for linking CSG based solid modelling with sensory information. We also discuss how sensor-tuned representations are constructed from range data and how object recognition can be done with sensor-tuned representations. Finally, we show results of manipulation experiments produced by the current implementation of the system. 相似文献
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In this paper, two algorithms are developed for the determination of pickup and delivery point locations for an AGV system. The first algorithm is applicable to general layout configurations and seeks solutions until the local optimum is reached by comparing relative locations of pickup and delivery points. The second algorithm generates solutions with a minimal amount of computational time due to its exploitation of the structural feature of departmental layouts. Computational results are provided to check the quality of solutions from each algorithm. 相似文献
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The microstructure and mechanical properties of Mg-xCe-0.5Zn(x=0.5,1.5,2.5,molar fraction,%) alloys were examined using a nano-indentation technique.The alloys were fabricated using a vacuum induction melting method under an argon atmosphere. The microstructures of Mg-xCe-0.5Zn alloys mainly consist ofα-Mg and eutectic Mg12Ce phase.The volume fraction and size of the eutectic Mg12Ce phase increase with increasing Ce contents.Nano-indentation test results show that the indentation hardness and elastic modulus of the eutectic Mg12Ce phase are higher than those of theα-Mg matrix.In addition,the mean indentation hardness and elastic modulus of the Mg-xCe-0.5Zn alloys increase with the Ce addition amount increasing. 相似文献