The objective of this paper is to quantify the variability in emissions of off-road equipment using a portable emission measurement system.A total of 53 commonly used equipment for agriculture,base construction,paving...The objective of this paper is to quantify the variability in emissions of off-road equipment using a portable emission measurement system.A total of 53 commonly used equipment for agriculture,base construction,paving construction,and material handling were selected.Time-based and fuel-based emissions were quantified by different duty and engine modes.Three duty modes(idling,moving,and working)were used.Ten engine modes were defined based on normalized engine revolutions-per-minute and manifold absolute pressure,respectively.Composite emission factors taking into account both duty modes and its corresponding time percentage during a typical duty cycle were estimated.Results showed that there existed a large off-road equipment variability in emissions.Depending on duty and engine modes,time-based NO emissions ranged from 3.1 to 237.9,29.1‒1475.6,83.2‒681.6,and 3.2‒385.2 g/h for agriculture,base construction,paving construction and material handling equipment,respectively while for fuel-based NO emissions these ranges were 5.3‒52.0,11.7‒69.0,4.8‒30.8,and 11.0‒54.6 g/kg,respectively.Furthermore,emission factors derived from this study exhibited a much larger variability compared to those used in NONROAD by US EPA and National Guideline for Off-road Equipment of China.This implied that localized measurements of emissions are needed for improvement of accuracy of emission inventory.Furthermore,both equipment types and operations should be considered for development of emission inventory and control strategy.展开更多
在三维系统中实时渲染二维图层是实现紧密型二三维结合GIS的关键。该文在二三维结合实现三维GIS的基础上,提出了基于LOD(Level of Detail)的二维图层与三维地形叠加的渲染构架和紧密型二三维结合GIS的初步系统构架,并利用ArcGIS Engine...在三维系统中实时渲染二维图层是实现紧密型二三维结合GIS的关键。该文在二三维结合实现三维GIS的基础上,提出了基于LOD(Level of Detail)的二维图层与三维地形叠加的渲染构架和紧密型二三维结合GIS的初步系统构架,并利用ArcGIS Engine开发包与World Wind开源软件实现了该原型系统。系统运行结果表明,该构架完全能够满足紧密型二三维结合GIS对渲染效果和效率的要求,成功解决了紧密型二三维结合系统的关键问题。展开更多
In this paper, first studied are the distribution characteristics of user behaviors based on log data from a massive web search engine. Analysis shows that stochastic distribution of user queries accords with the char...In this paper, first studied are the distribution characteristics of user behaviors based on log data from a massive web search engine. Analysis shows that stochastic distribution of user queries accords with the characteristics of power-law function and exhibits strong similarity, and the user' s queries and clicked URLs present dramatic locality, which implies that query cache and 'hot click' cache can be employed to improve system performance. Then three typical cache replacement policies are compared, including LRU, FIFO, and LFU with attenuation. In addition, the distribution character-istics of web information are also analyzed, which demonstrates that the link popularity and replica pop-ularity of a URL have positive influence on its importance. Finally, variance between the link popularity and user popularity, and variance between replica popularity and user popularity are analyzed, which give us some important insight that helps us improve the ranking algorithms in a search engine.展开更多
The amount of information on the web is growing rapidly and search engines that rely on keyword matching usually return too many fow quality matches. To improve search results, a challenging task for search engines is...The amount of information on the web is growing rapidly and search engines that rely on keyword matching usually return too many fow quality matches. To improve search results, a challenging task for search engines is how to effectively calculate a relevane ranking for each web page. This paper discusses in what order a search engine should return the URLs it has produced in response to a user's query so as to show more relevant pages first. Emphasis is given on the ranking functions a-dopted by WebGather that take link structure and user popularity factors into account. Bxperimental results are also presented to evaluate the proposed strategy.展开更多
基金This work was supported by the Public Environmental Service Project of the Ministry of Environmental Protection of PRC(No.201409012)the Research Project of the Bureau of Science and Technology of Sichuan(No.2019YFS0498)。
文摘The objective of this paper is to quantify the variability in emissions of off-road equipment using a portable emission measurement system.A total of 53 commonly used equipment for agriculture,base construction,paving construction,and material handling were selected.Time-based and fuel-based emissions were quantified by different duty and engine modes.Three duty modes(idling,moving,and working)were used.Ten engine modes were defined based on normalized engine revolutions-per-minute and manifold absolute pressure,respectively.Composite emission factors taking into account both duty modes and its corresponding time percentage during a typical duty cycle were estimated.Results showed that there existed a large off-road equipment variability in emissions.Depending on duty and engine modes,time-based NO emissions ranged from 3.1 to 237.9,29.1‒1475.6,83.2‒681.6,and 3.2‒385.2 g/h for agriculture,base construction,paving construction and material handling equipment,respectively while for fuel-based NO emissions these ranges were 5.3‒52.0,11.7‒69.0,4.8‒30.8,and 11.0‒54.6 g/kg,respectively.Furthermore,emission factors derived from this study exhibited a much larger variability compared to those used in NONROAD by US EPA and National Guideline for Off-road Equipment of China.This implied that localized measurements of emissions are needed for improvement of accuracy of emission inventory.Furthermore,both equipment types and operations should be considered for development of emission inventory and control strategy.
文摘在三维系统中实时渲染二维图层是实现紧密型二三维结合GIS的关键。该文在二三维结合实现三维GIS的基础上,提出了基于LOD(Level of Detail)的二维图层与三维地形叠加的渲染构架和紧密型二三维结合GIS的初步系统构架,并利用ArcGIS Engine开发包与World Wind开源软件实现了该原型系统。系统运行结果表明,该构架完全能够满足紧密型二三维结合GIS对渲染效果和效率的要求,成功解决了紧密型二三维结合系统的关键问题。
基金This work was supported by the National Grand Fundamental Research of China ( Grant No. G1999032706).
文摘In this paper, first studied are the distribution characteristics of user behaviors based on log data from a massive web search engine. Analysis shows that stochastic distribution of user queries accords with the characteristics of power-law function and exhibits strong similarity, and the user' s queries and clicked URLs present dramatic locality, which implies that query cache and 'hot click' cache can be employed to improve system performance. Then three typical cache replacement policies are compared, including LRU, FIFO, and LFU with attenuation. In addition, the distribution character-istics of web information are also analyzed, which demonstrates that the link popularity and replica pop-ularity of a URL have positive influence on its importance. Finally, variance between the link popularity and user popularity, and variance between replica popularity and user popularity are analyzed, which give us some important insight that helps us improve the ranking algorithms in a search engine.
基金the National "9th Five-Year Plan)" Key Technology Project (No. 96-743-01-05-01) and the NKBRSF of China (No. G1999032706).
文摘The amount of information on the web is growing rapidly and search engines that rely on keyword matching usually return too many fow quality matches. To improve search results, a challenging task for search engines is how to effectively calculate a relevane ranking for each web page. This paper discusses in what order a search engine should return the URLs it has produced in response to a user's query so as to show more relevant pages first. Emphasis is given on the ranking functions a-dopted by WebGather that take link structure and user popularity factors into account. Bxperimental results are also presented to evaluate the proposed strategy.
