278 research outputs found

    Generalized Coupled-line All-Pass Phasers

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    Generalized coupled-line all-pass phasers, based on transversally-cascaded (TC), longitudinally-cascaded (LC) and hybrid-cascaded (HC) coupled transmission line sections, are presented and demonstrated using analytical, full-wave and experimental results. It is shown that for N commensurate coupled-line sections, LC and TC phasers exhibit N group delay peaks per coupled-line section harmonic frequency band, in contrast to the TC configuration, which exhibits only one peak within this band. It is also shown that for a given maximum achievable coupling-coefficient, the HC configuration provides the largest group delay swing. A wave-interference analysis is finally applied to the various coupled-line phasers, explaining their unique group delay characteristics based on physical wave-propagation mechanisms.Comment: 10 pages, 11 figure

    Cathode Materials for Lithium Sulfur Batteries: Design, Synthesis, and Electrochemical Performance

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    With the rapid development of electronic devices, portable electronics, and electric vehicles, the energy density and cycle life of LIBs are insufficient for the demands. Based on the reaction mechanisms, lithium-sulfur (Li-S) batteries have a high specific capacity of 1672 mAh/g, with a theoretical energy density up to 2600 Wh/Kg. However, the sulfur cannot serve as cathode individually because of its isolation nature and soluble compounds, which necessitates a second component as a conducting matrix and sulfur host. Thus, sulfur cathodes have diversified through microstructure designing with various materials, including inorganic compounds, polymers, carbon materials, and their hybrids, which should be satisfied several essential requirements, such as high stable incorporation with sulfur, high electrical conductivity of electrode materials, and loose framework to suffer the volume expansion of cathode during charge-discharge process. These investigations may provide the effective routes to prepare different new cathode materials with unique structures and morphologies for Li-S batteries, which improve cycling stability, coulombic efficiency, and rate capacity of the electrode at higher current density

    Modeling production configuration using nested colored object-oriented Petri-nets with changeable structures

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    Configuring production processes based on process platforms has been well recognized as an effective means for companies to provide product variety while maintaining mass production efficiency. The production processes of product families involve diverse variations in manufacturing and assembly processes resulted from a large variety of component parts and assemblies. This paper develops a multilevel system of nested colored object-oriented Petri nets with changeable structures to model the configuration of production processes. To capture the semantics associated with production configuration decisions, some unique modeling mechanisms are employed, including colored Petri nets, object-oriented Petri nets, changeable Petri net structures, and net nesting. The modeling formalism comprises resource nets, manufacturing nets, assembly nets and process nets. The paper demonstrates how these net definitions are applied to the specification of production process variants at different levels of abstraction. Also reported is a case study in an electronics company. The system model is further analyzed with focus on conflict prevention and deadlock detection

    Nested coloured timed Petri nets for production configuration of product families

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    International audienceProduction configuration is as an effective technique to deal with product variety while maintaining production stability and efficiency. It involves a diverse set of process elements (e.g., machines, operations), a high variety of component parts and assemblies and many constraints arising from product and process variety. Production configuration entails the selection and subsequent arrangement of process elements into complete production processes and the final evaluation of configured multiple alternatives. To better understand production configuration and its implementation, we study the underlying logic for configuring production processes using a dynamic modeling and visualization approach. This is accomplished through developing a new formalism of nested colored timed Petri nets (PNs). In view of the inherent modeling difficulties, in the formalism three types of nets - process nets, assembly nets and manufacturing nets - together with a nested net system are defined. Using an industrial example of vibration motors, we show how the proposed formalism can be applied to specify production processes at different levels of abstraction to achieve production configuration

    The Role of Paragus quadri-fasciatus Meigen on Aphid Control and the Observations of its Biological Characteristics

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    Four-strip small syrphid fly, Paragus quadri-fasciatus Meigen is the important natural enemy of aphids in our region. A fly can eat about 800 aphids during its whole life. There are more than 10 kinds of aphids can be food of this fly, such as soybean aphid, Chinese sorghum aphid and radish aphid etc. The fly has 3~4 generations each year in Tonghua county, Jilin province. The adult of the first generation appears after the last ten-day period of April each year. It takes 30~35 days to complete one generation. The fly can oviposit 84~124 eggs in its whole life. Major natural enemies of the fly are ichneumon wasps, spiders, lacewings and etc.Originating text in Chinese.Citation: Gao, Junfeng, Jiang, Lianfeng, Zhang, Guangxin, Li, Chunshan, Zhao, Guangquan. (1996). The Role of Paragus quadri-fasciatus Meigen on Aphid Control and the Observations of its Biological Characteristics. Journal of Jilin Agricultural Sciences, 5(2), 60-61

    PROCESS PLATFORM FORMATION FOR PRODUCT FAMILIES

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    ABSTRACT In accordance with the product families, process platforms have been recognized as a promising tool for companies to configure optimal, yet similar, production processes for producing different products. This paper tackles process platform formation from large volumes of production data available in companies' production systems. A data mining methodology based on text mining and tree matching is developed for the formation of process platforms. A case study of high variety production of vibration motors for mobile phones is reported to prove the feasibility and potential of forming process platforms using text mining and tree matching
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