Applications of sketches in network traffic measurement: A survey

Accurate and timely network traffic measurement is essential for network status monitoring, network fault analysis, network intrusion detection, and network security management. With the rapid development of the network, massive network traffic brings severe challenges to network traffic measurement. However, existing measurement methods suffer from many limitations for effectively recording and accurately analyzing big-volume traffic. Recently, sketches, a family of probabilistic data structures that employ hashing technology for summarizing traffic data, have been widely used to solve these problems. However, current literature still lacks a thorough review on sketch-based traffic measurement methods to offer a comprehensive insight on how to apply sketches for fulfilling various traffic measurement tasks. In this paper, we provide a detailed and comprehensive review on the applications of sketches in network traffic measurement. To this end, we classify the network traffic measurement tasks into four categories based on the target of traffic measurement, namely cardinality estimation, flow size estimation, change anomaly detection, and persistent spreader identification. First, we briefly introduce these four types of traffic measurement tasks and discuss the advantages of applying sketches. Then, we propose a series of requirements with regard to the applications of sketches in network traffic measurement. After that, we perform a fine-grained classification for each sketch-based measurement category according to the technologies applied on sketches. During the review, we evaluate the performance, advantages and disadvantages of current sketch-based traffic measurement methods based on the proposed requirements. Through the thorough review, we gain a number of valuable implications that can guide us to choose and design proper traffic measurement methods based on sketches. We also review a number of general sketches that are highly expected in modern network systems to simultaneously perform multiple traffic measurement tasks and discuss their performance based on the proposed requirements. Finally, through our serious review, we summarize a number of open issues and identify several promising research directions.     

How do project management competencies change within the project management career model in large Chinese construction companies?

Due to the increasing complexity and flexibility of business activities, project-based organizations have become common. In such organizations, project management competencies, which refer to a collection of knowledge, personal attitudes, skills, and relevant experience, are core assets that must be taken seriously. Formalized project management career paths have been widely implemented in the construction industry. However, most recent studies treat project management competencies as static constructs and fail to consider their dynamic changes as a career path advances. To fill this gap in the literature, this study conducted an empirical examination of project management competencies integrated with a career model for the construction industry. First, key project management competencies are identified through a literature review. Then, a project management career model for large Chinese construction companies is developed based on an empirical investigation of six large Chinese construction companies from various sectors. Moreover, a quantitative analysis is performed to explore how these competencies dynamically change as position levels rise in the career model. The research findings indicate that significant differences in project management competencies exist at different levels of the career model. However, the distribution remains steady at different project management position levels for conceptual and organizational competencies, human competencies, and technical competencies.     

GIS method for characterizing fire flow capacity

There are numerous methods currently used to calculate required water flow rates for sprinklered and non-sprinklered buildings. The aim of this study is provide a flexible automated procedure for indentifying locations lacking adequate fire flow. To accomplish this objective, this research uses a GIS procedure to determine the spatial relationships between fire hydrants and historical fire incidences, and integrates the recommended hydrant spacing and building type specifications from the International Fire Code. This method was tested in two communities in eastcentral Michigan, USA. The results indicate an ability to define clusters of fires, determine the availability of hydrants, and assess the suitability of the available fire flow, including areas of potential extra capacity. Using these same data, additional GIS analyses can optimize hydrant location, ascertain the frequencies of different categories of fires, and identify the patterns of building types prone to fires.     

兼容二元:中国县镇乡发展的基本判断与路径选择

新型城镇化的国家战略对于县、镇、乡是一次新的发展机遇。通过更大数量和更基层的县城、镇等的发展,将城市资本与数量众多的县、镇、乡的土地、劳动力等资源集合起来,能够进一步生产和扩大市场,维持社会稳定。结合城乡关系过程的政治经济分析和历史讨论,作者提出县镇乡"兼容二元"的发展路径。但县、镇、乡的发展不仅仅与市场有关,它们的发展也不仅仅是被整合入全球经济生产链的问题。它们的开放或内生性发展对于地方的文化发展、大地景观、生活方式与价值理念、环境状况等都将有巨大影响,这仍然需要进一步讨论。     

Effectiveness of PEMFC historical state and operating mode in PEMFC prognosis

As a high efficiency and environmental friendly energy conversion technique, proton exchange membrane fuel cell (PEMFC) system faces challenges of limited durability and performance decay during long-term operation. Prognosis estimates the remaining useful life (RUL) of the system, from which maintenance policy can be scheduled to extend its useful life. However, parameters related to either PEMFC historical state or operating mode are used in most existing PEMFC prognostic studies, while their effects on PEMFC predictions are not clarified, this brings great challenge in selecting appropriate parameters for reliable PEMFC prognosis in practical applications subjected to complex operating conditions. In this paper, the effectiveness of PEMFC historical behavior and operating mode on PEMFC future performance at both static and non-static conditions are investigated, using back propagation neural network (BPNN) and adapted neural fuzzy inference system (ANFIS), respectively. From the findings, PEMFC historical state and operating mode make varying contributions to PEMFC prognostic results at different operating scenarios. At static operating condition, PEMFC predictions are dominated by its historical state, since constant operating mode is applied in this scenario, thus reliable prediction can be made by using only parameters representing PEMFC historical state. However, at non-static operating condition, the varying operating mode makes more contribution to the PEMFC predictions, and accurate prognosis should be provided by including variables representing varying operating mode in the prognostic analysis. The results can be beneficial in selecting appropriate parameters in prognostic analysis at practical PEMFC applications, where complex operating conditions may be experienced.     

Recent Developments in Integrated Solar Combined Cycle Power Plants

Global concern for depleting fossil fuel reserves have been compelling for evolving power generation options using renewable energy sources. The solar energy happens to be a potential source for running the power plants among renewable energy sources. Integrated Solar Combined Cycle(ISCC) power plants have gained popularity among the thermal power plants. Traditional ISCC power plants use Direct Steam Generation(DSG) approach. However, with the DSG method, the ISCC plant’s overall thermal efficiency does not increase significantly due to variations in the availability of solar energy. Thermal Energy Storage(TES) systems when integrated into the solar cycle can address such issues related to energy efficiency, process flexibility, reducing intermittency during non-solar hours. This review work focuses and discusses the developments in various components of the ISCC system including its major cycles and related parameters. The main focus is on CSP technologies, Heat Transfer Fluid(HTF), and Phase Change Material(PCM) used for thermal energy storage. Further, study includes heat enhancement methods with HTF and latent heat storage system. This study will be beneficial to the power plant professionals intending to modify the solar-based Combined Cycle Power Plant(CCPP) and to retrofit the existing Natural Gas Combined Cycle(NGCC) plant with the advanced solar cycle.     

Hydrogen refuelling stations in the Netherlands: An intercomparison of quantitative risk assessments used for permitting

As of 2003, 15 hydrogen refuelling stations (HRSs) have been deployed in the Netherlands. To become established, the HRS has to go through a permitting procedure. An important document of the permitting dossier is the quantitative risk assessment (QRA) as it assesses the risks of the HRS associated to people and buildings in the vicinity of the HRS. In the Netherlands, a generic prescribed approach exists on how to perform a QRA, however specific guidelines for HRSs do not exist. An intercomparison among the QRAs of permitted HRSs has revealed significant inconsistencies on various aspects of the QRA: namely the inclusion of HRS sub-systems and components, the HRS sub-system and component considerations as predefined components, the application of failure scenarios, the determination of failure frequencies, the application of input parameters, the consideration of preventive and mitigation measures as well as information provided regarding the HRS surroundings and the societal risk. It is therefore recommended to develop specific QRA guidelines for HRSs.     

云南沿边境地带小流域LUCC遥感监测试验研究

通过对1990年和2004年两期Landsat TM影像LUCC信息提取方法的处理,揭示了14年间畹町河流域土地利用/土地覆盖的动态变化情况,并对其数量变化和空间特征进行了分析。研究表明,1990-2004年间流域内林地和水域面积显著减少,城镇沿公路大量向外扩张,耕地和未利用土地面积有所增加,草地面积相对持平。     

单位职工社区中的集体主义生活——东北老工业区居住建筑格局的变迁

在“一五”期间，国家对工业布局进行了大的调整，随着苏联援建的156个建设项目,东北工业基地的建设也拉开了帷幕。为了配合工业项目的开展,受苏联规划模式与规划思想的影响，厂前生活区的规划呈现出前所未有的全新的居住形态。50多年过去了，生活在其中的人们的社会关系以及对居住空间的需求都发生了很大改变。这些老建筑能否适应社会的新要求？它们又留给这个城市什么样的历史记忆？这种居住模式对我们今天的生活是否值得借鉴？这些都值得我们深入研究。     

匠事留痕——记敦煌壁画里的建筑施工

敦煌石窟保存下几方古代工匠施工场面的壁画。客观上再现了一千多年或几百年以前工匠操作的场景。北周第296窟窟顶上画有两处表现建筑施工的壁画，一者建塔，一者建屋。隋代第302窟有一伐木建塔图。初唐第321窟有两个施工场面，一建屋，一建塔。五代第72窟有一个修塑佛像的画面。北周和隋代两幅画里有工人手持矩尺的形象。这些壁画为研究建筑史学具有一定意义。