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试论影响项目工程经济效益的条件 总被引:2,自引:0,他引:2
众所周知,影响项目工程经济效益的因素包括成本控制、变更索赔、合同风险、降低能效等方面。本文着重从项目工程在施工前应当具备的"几大条件"出发,进行深入分析,并从引入具体实例——城际高速铁路中选择两大方面进行论述。 相似文献
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根据绿色效能的一级、二级指标值与指标权重值,从资源节约和环境保护影响两个方面,对天府机场进行了绿色能效评估,计算出了天府机场的绿色效能值,以探讨绿色机场建设的重要性及其意义。 相似文献
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就成都地区开展空调蓄能能效电厂项目进行可行性分析,认为该项目的研究及实施将有利于政府解决电力短缺和能源可持续利用问题,更有利于企业降低成本,提高竞争力。 相似文献
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确保基坑安全的关键是土压力的准确计算。结合近年的工程研究成果,对土压力的一些影响因素进行了简单分析,简要归纳了目前工程师对这些影响因素的认识。据此提出一点建议:把握岩土基本概念,注重理论与实际相联系,综合各种因素解决问题。 相似文献
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论述了森林资源有偿使用的等价交换原则,以林价为补偿手段,强调了诸多基础性工作都是关系林价计算能否准确的关键性因素。 相似文献
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指出了水质检测工作的开展,离不开诸多先进技术手段的支撑,要确保化学需氧量测定的精准性,就必须保障化学需氧量测定结果的合理与准确。结合工作经验,分析了测定化学需氧量原理及操作,总结了测定过程中的影响性因素,并在实验方法的运用下,提出了为其结果的合理与准确提供充分的外在条件。 相似文献
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以临安市为研究案例,根据2003-2013年的统计年鉴数据,借鉴IPCC提供的碳排放相关数据及估算法,计算得出临安市近11年的工业碳排放量呈坡形曲线变化、先升后降,表明前5年的工业迅速增长及后6年的碳减排已收到成效;利用LMDI模型进行碳排放影响因素分解,结果表明总人口数、人均生产总值、能源利用效率是临安市工业碳排放的推进因素,工业化率、能源结构是临安市工业碳排放的衰减因素;结合计算结果的图表分析提出,作为一个中等城市,临安市应控制城市人口规模,加强能源结构调整,推进农村建设和产业结构优化,使工业碳减排成为城市良性发展的主要动力。 相似文献
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基于非集计理论的思路,利用灰关联分析方法确定公交出行的主要影响因素。该方法对数据的样本量需求小,可以分析出公交特征、个体出行特征和个体特性等因素的变化对公交出行行为的影响。最后采用苍南县城乡公交规划中的数据,通过此种方法得到主要影响因素,再通过SPSS对分组数据进行非线性回归分析,拟合出影响因素与公交分担率之间的函数关系。文章中使用的方法与结论可以为公交系统规划、方案评价、政府及相关部门决策提供参考和支持。 相似文献
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Negative air ions are natural components of the air we breathe Forests are the main continuous natural source of negative air ions (NAI). The spatio-temporal patterns of negative air ions were explored in Shanghai, based on monthly monitoring in 15 parks from March 2009 to February 2010. In each park, sampling sites were selected in forests and open spaces. The annual variation in negative air ion concentrations (NAIC) showed peak values from June to October and minimum values from December to January. NAIC were highest in summer and autumn, intermediate in spring, and lowest in winter. During spring and summer, NAIC in open spaces were significantly higher in rural areas than those in suburban areas. However, there were no significant differences in NAIC at forest sites among seasons. For open spaces, total suspended particles (TSP) were the dominant determining factor of NAIC in sum- mer, and air temperature and air humidity were the dominant determining factors of NAIC in spring, which were tightly correlated with Shanghai's ongoing urbanization and its impacts on the environment. R is suggested that urbanization could induce variation in NAIC along the urban-rural gradient, but that may not change the temporal variation pattern. Fur- thermore, the effects of urbanization on NAIC were limited in non-vegetated or less-vegetated sites, such as open spaces, but not in well-vegetated areas, such as urban forests. Therefore, we suggest that urban greening, especially urban forest, has significant resistance to theeffect of urbanization on NAIC. 相似文献
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以绿道建构城乡绿地生态网络是一种构筑完整连续的生态系统的重要方法,其于结构、功能及系统层面建立起人类与自然保护之间的连接,是生态向着城乡演进的一种空间战略、发展模式与生态策略。文中侧重从生态视角解析绿道由本体、边缘区、影响辐射区3个要素构成,提出绿道在生态网络建构过程中体现出的统领性、生态性、系统性3大特性,并分别从其与城乡的空间形态演进、系统耦合关系及价值驱动机制3个方面分析绿道及绿网对于城乡发展的意义与价值,为探知、建构合理高效的城乡绿地生态空间提供了新的视角。
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Urbanization is accelerating across the globe, elevating the importance of studying urban ecology. Urban environments exhibit several factors affecting plant growth and function, including high temperatures (particularly at night), CO(2) concentrations and atmospheric nitrogen deposition. We investigated the effects of urban environments on growth in Quercus rubra L. seedlings. We grew seedlings from acorns for one season at four sites along an urban-rural transect from Central Park in New York City to the Catskill Mountains in upstate New York (difference in average maximum temperatures of 2.4 °C; difference in minimum temperatures of 4.6 °C). In addition, we grew Q. rubra seedlings in growth cabinets (GCs) mimicking the seasonal differential between the city and rural sites (based on a 5-year average). In the field experiment, we found an eightfold increase in biomass in urban-grown seedlings relative to those grown at rural sites. This difference was primarily related to changes in growth allocation. Urban-grown seedlings and seedlings grown at urban temperatures in the GCs exhibited a lower root: shoot ratio (urban ~0.8, rural/remote ~1.5), reducing below-ground carbon costs associated with construction and maintenance. These urban seedlings instead allocated more growth to leaves than did rural-grown seedlings, resulting in 10-fold greater photosynthetic area but no difference in photosynthetic capacity of foliage per unit area. Seedlings grown at urban temperatures in both the field and GC experiments had higher leaf nitrogen concentrations per unit area than those grown at cooler temperatures (increases of 23% in field, 32% in GC). Lastly, we measured threefold greater (13)C enrichment of respired CO(2) (relative to substrate) in urban-grown leaves than at other sites, which may suggest greater allocation of respiratory function to growth over maintenance. It also shows that lack of differences in total R flux in response to environmental conditions may mask dramatic shifts in respiratory functioning. Overall, our findings indicating greater seedling growth and establishment at a critical regeneration phase of forest development may have important implications for the ecology of urban forests as well as the predicted growth of the terrestrial biosphere in temperate regions in response to climate change. 相似文献
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基于EDA技术的自动立木整枝机无线遥控发射系统 总被引:4,自引:0,他引:4
立木整枝是优质工业用材林定向抚育的重要环节,采用自动立木整枝机是实现高效、高质量和安全可靠整枝的有效途径。本文综合运用电子电路设计及优化技术、无线遥控及通信编解码技术,创造性地研制了基于CPLD的无线数字编码抗干扰自动立木整枝机无线遥控发射系统,通过优化CPLD内部逻辑电路有效消除了逻辑竞争冒险、降低了噪声干扰,确保了系统逻辑设计的正确性。该系统具有可靠、节能、抗干扰、工作效率高等优点。本研究成果及方法为推进其他林业机械的自动化与智能化进程提供了一种有效的新思路。 相似文献
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折扇是传统扇子的改良型产品,既具有消暑降温、避阳取风的实用功能,也具有很高的文化价值和艺术价值,是传统民间器具中重要的一员。文中介绍了折扇的发展历史、制作工艺,从设计的角度分析了折扇的设计思想,即简洁实用的设计功能、折叠便携的设计理念和雅俗共赏的设计文化。 相似文献
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Since the electric tools are increasingly entering the field of forestry, the aim of this study was to establish the consequences of using electric powered chainsaws on work and its energy efficiency, as well as health of workers. For this purpose, 40 trees were felled in two young spruce stands, half with a cordless electric chainsaw and one half with a petrol chainsaw. Results showed that electric chainsaws are a good alternative to petrol chainsaws for use in small-scale forestry, since in terms of work efficiency their use is comparable to petrol chainsaws and they provide a lower level of energy consumption, and lower exposure of fellers to noise and hand-arm vibrations. Similar to other fields, the results confirmed a positive impact of hand toll electrification on man and environment. The development of electric tools for forestry is expected to intensify with the development of more powerful batteries which are currently still regarded as the major bottleneck. 相似文献