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991.
利用线性拟合、Mann—Kendall方法、小波分析对石羊河流域五个测站空间平均的近50年来的逐日风速资料进行了倾向、周期、突变等特性分析。研究结果表明:1959年至2008年间,整个石羊河流域风速呈减小趋势,变化率约为-0.004m/(s.a).而上游风速呈现明显的上升趋势。四个季节中冬季风速降低速度最大,而夏季风速呈现上升趋势。风速的长期变化还具有一定的突变性,年平均风速在1988年出现了由高到低的突变,表明风速开始下降。复值Morlet小波分析的结果显示,风速变化存在6a、13a、19a、25a四个峰值。其中19a的时间尺度为第一主周期。 相似文献
992.
Kostanjsek R Lapanje A Drobne D Perović S Perović A Zidar P Strus J Hollert H Karaman G 《Environmental science and pollution research international》2005,12(6):361-368
- Goal, Scope, Background. Lake Skadar is the largest lake in Balkan Peninsula, located on the Montenegro-Albanian border. The
unique features of the lake and wide range of endemic and rare or endangered plant and animal species resulted in the classification
of the Skadar as a wetland site of international significance. In spite of its importance the Lake is influenced by inflowing
waters from river Morača and other regional rivers contaminated by the industry, municipal and agricultural activities in
the area. Therefore, the Lake has been subject of various physical, chemical, biological and toxicological examinations. However,
community-level analyses are most relevant to assess the effect of stressors on aquatic ecosystems. In the present study bacterial
community structure among differently polluted sites of the lake was compared by genetic fingerprinting technique.
Methods Water and sediment samples were collected from five differently polluted sampling sites on the Lake Skadar in spring and
autumn of the same year. The bacterial community structure in the samples was characterized and compared by temporal temperature
gel electrophoresis (TTGE) analysis of polymerase chain reaction-amplified bacterial 16S rRNA genes.
Results and Discussion The TTGE analysis resulted in many distinguishable and reproducible band patterns, allowing reliable comparison of bacterial
communities among sampling sites. Results on the bacterial community structure revealed that three of the selected locations
can be considered as sites that have not shown any pollution degradation determined by our method, due to similar structure
of bacterial community in the sediment samples. On the other hand, significant shifts in bacterial community structure in
the mouth of the river Morača and Plavnica were shown. Since the results coincide with some of the bioassays and chemical
analysis performed previously, the changes in bacterial community structure are explained as an effect of antropogenic pollution
on the lake ecosystem by waters of river Morača and stream Plavnica.
Conclusion The TTGE has proven to be an efficient and reliable method to monitor bacterial dynamics and community shifts in aquatic
environment, especially in the sediments. Within the variety of environmental quality assessments the use of TTGE analyses
of bacterial community is strongly recommended, particularly as an initial investigation. However, in any conclusion on the
state of the environment, the TTGE results should be combined to some other biological, chemical and hydrological data.
Recommendation and Outlook Since prokaryotes are a crucial group of organisms in the biosphere, the ecosystem function studies are largely based on
bacterial communities. Therefore, bacterial community structure analysis should be a part of an integrated weight of evidence
approach in pollution assessment. In case of Triad approach, consisting of chemical analyses, bioassays, and community studies
in the field, the TTGE bacterial community structure analyses should be placed in the later Triad leg. In comparison to other
community studies, based on various biotic indices, the TTGE bacterial community analysis has proven to be very sensitive,
reliable and less time consuming. 相似文献
993.
In 1988 the Toronto World Conference on the Changing Atmosphere called for a reduction of CO2 emissions of the industrialized countries by approximately 20% by the year 2005 as compared with 1988. A stabilization of
CO2 concentrations would require an eventual emissions reduction of more than 50% of present levels. Model runs were performed
with the Dutch Integrated Model for the Assessment of the Greenhouse Effect (IMAGE) to put these figures into perspective.
It was found that the suggested emissions reduction levels could indeed be adequate to prevent global temperature change from
moving beyond past climate experience. However, this would only be the case when these reduced levels of emissions were achieved
at a global scale and maximum emission control for the other greenhouse gases was implemented. A delayed response analysis
shows that the policies of the coming decades are crucial for the eventual control of the greenhouse effect. 相似文献
994.
995.
为了持续监测燃气工业加热炉燃烧状况,保障锅炉运行安全,根据燃气火焰的特点,利用数字图像处理技术,设计了相应的燃气加热炉火焰视频监控系统。通过图像预处理、火焰特征提取、火焰特征分析三个步骤,可实现对炉膛火焰燃烧状态进行实时判定,包括火焰燃烧或熄灭、燃烧是否充分、是否稳定。仿真实验结果表明,该系统能准确地从监控视频中检测和识别火焰燃烧状态,并能将燃烧特征量和特征分析结果存储到数据库以供事后查询。 相似文献
996.
人民生活水平的提高使人民对室内环境的舒适程度提出了更高要求 ,室内装饰织物的用量迅速增加 ,室内装饰织物在燃烧时会释放出大量有毒物质和热量 ,对人及环境构成了巨大危害。因此 ,研究装饰织物的燃烧特性非常重要。笔者利用热重 -差热 (TG -DTA)分析仪对纯棉、棉麻和腈纶这几种典型的装饰织物在不同的氧气浓度 (10 % ,15 % ,2 1% )和升温速率 (10K/min ,30K/min)条件下进行了热重分析 (TG)和差热分析 (DTA)实验 ,研究了它们的燃烧特性 ,并着重进行了不同氧浓度下的对比研究 ,发现试样的燃烧分为两个阶段。建立了以一级反应模型为主的动力学方程 ,并得出了各阶段的动力学参数、表观活化能和频率因子。 相似文献
997.
998.
999.
Alberico Zeppetella 《Journal of Environmental Planning and Management》1988,31(2):103-109
The paper attempts to conceptualise a range of problems arising from project appraisals. The author presents some general considerations concerning the role of social appraisal in territorial planning, the theoretical weaknesses of cost‐benefit analysis in assessing the effects of projects on territorial resources and some questions relating to assessment methodologies and the welfare foundations of social appraisal within planning practices. The author moves away from evaluation as a technical process towards one which also incorporates ‘practical’ knowledge in a process of argumentation. 相似文献
1000.