排序方式: 共有31条查询结果,搜索用时 15 毫秒
11.
Summary The major objective of the design of safe crowded transmitting antenna sites is not only to determine a safe zone around each
individual antenna; rather, to establish safety areas at the antenna site itself, as well as, at the neighboring areas. The
requirement is to ascertain the safety regions by considering the following parameters at each Test Point (TP) (or area segment):
the contribution of N co-located radiating antennas to the total radiation incident at the TP, the radiation pattern of each antenna, the near/far
field region of each antenna, and most importantly, the different Permissible Exposure Limits (PELs) associated with each
operating frequency at the antenna site. Implementation of all the above-mentioned aspects in a suitable computer requires
resources that only expert knowledgeable organizations possess. The graphically aided tool presented in this paper facilitates
the calculation of a “safety zone” for RADHAZ around a crowded antenna site from the knowledge of the “safety ranges” which
correspond to the individual transmitting antennas comprising it. 相似文献
12.
13.
Héctor Miguel Aviña Jiménez Gabriel León de los Santos Miguel Ángel Benítez Torreblanca 《International Journal of Sustainable Engineering》2017,10(2):90-98
In this article, the comparison of the energetic performance of a binary cycle and a modified binary cycle with flash evaporation is presented, both using a low-enthalpy geothermal resource. The comparative analysis is based on two main discourses: the first one evaluates a conventional binary cycle (CBC) with isopentane as working fluid in order to validate and compare the generated data with those reported in similar studies; the second one uses the same input parameters for both cycles, obtaining the cases in which the modified binary cycle is the most viable choice to use. In addition to the above, several aspects are considered when selecting the most suitable working fluid, and the use of water as working fluid is introduced. When the temperature of the geothermal resource is below 140 °C, and the ambient temperature is 25 °C, the flash evaporation binary cycle, using water as working fluid, shows an improved performance compared to a CBC, with a theoretical output over 1000 kWe. This may encourage new areas of opportunity for power generation, not only with low- and medium-enthalpy geothermal energy, but also with other renewable energy sources such as solar. 相似文献
14.
The effects of disturbance based management on the dynamics of Mediterranean vegetation: A hierarchical and spatially explicit modeling approach 总被引:1,自引:0,他引:1
Avi Bar Massada Yohay Carmel Gili Koniak Imanuel Noy-Meir 《Ecological modelling》2009,220(19):2525-2535
The eastern Mediterranean region has been subjected to intensive human disturbance in the past 10,000 years, mainly in the forms of agro-pastoral activities such as grazing, shrub clearing, and prescribed burning. This disturbance history resulted in the formation of highly heterogeneous landscapes, characterized by high biodiversity. Recent changes in human activities have resulted in a decrease of landscape heterogeneity, leading to decreasing biodiversity and increasing fire risk. To conserve heterogeneity, land managers apply disturbance based management practices, using the same activities that created and maintained landscape heterogeneity in the past. However, the long-term and large-scale outcomes of these disturbances are often unknown, due to the complex response of Mediterranean vegetation to disturbance. Here we report on a spatially explicit, hybrid, and spatially hierarchical ecological model developed by us. The model attempts to predict the outcome of various disturbance based management activities on the long-term spatio-temporal dynamics of five common Mediterranean vegetation types. The model uses a spatially explicit state and transition formulation, with continuous transition functions. Model simulations were conducted on a Mediterranean landscape in Northern Israel, incorporating various disturbance practices that are common in the region. Simulation results highlight the potential of disturbance based management as a tool for conserving landscape heterogeneity, as well as the complex interactions between disturbances and the spatial structure of the landscape in Mediterranean regions. 相似文献
15.
Oz Barazani Avi Golan-Goldhirsh 《Environmental science and pollution research international》2009,16(7):855-861
Background, aim, and scope
It can be learned from the Pistacia spp. germplasm collection () that the growth of Salsola inermis is inhibited in the vicinity of the evergreen Pistacia lentiscus, but not in the surroundings of the deciduous Pistacia atlantica and Pistacia chinensis. Irrigation of trees during the summer months increases soil salinity around the trees. It was therefore hypothesized that inhibition of S. inermis around P. lentiscus is related to depletion of salt in the vicinity of the latter species. 相似文献16.
Schröder P Navarro-Aviñó J Azaizeh H Goldhirsh AG DiGregorio S Komives T Langergraber G Lenz A Maestri E Memon AR Ranalli A Sebastiani L Smrcek S Vanek T Vuilleumier S Wissing F 《Environmental science and pollution research international》2007,14(7):490-497
Goal, Scope and Background One of the burning problems of our industrial society is the high consumption of water and the high demand for clean drinking
water. Numerous approaches have been taken to reduce water consumption, but in the long run it seems only possible to recycle
waste water into high quality water. It seems timely to discuss alternative water remediation technologies that are fit for
industrial as well as less developed countries to ensure a high quality of drinking water throughout Europe.
Main Features The present paper discusses a range of phytoremediation technologies to be applied in a modular approach to integrate and
improve the performance of existing wastewater treatment, especially towards the emerging micro pollutants, i.e. organic chemicals
and pharmaceuticals. This topic is of global relevance for the EU.
Results Existing technologies for waste water treatment do not sufficiently address increasing pollution situation, especially with
the growing use of organic pollutants in the private household and health sector. Although some crude chemical approaches
exist, such as advanced oxidation steps, most waste water treatment plants will not be able to adopt them. The same is true
for membrane technologies.
Discussion Incredible progress has been made during recent years, thus providing us with membranes of longevity and stability and, at
the same time, high filtration capacity. However, these systems are expensive and delicate in operation, so that the majority
of communities will not be able to afford them. Combinations of different phytoremediation technologies seem to be most promising
to solve this burning problem.
Conclusions To quantify the occurrence and the distribution of micropollutants, to evaluate their effects, and to prevent them from passing
through wastewater collection and treatment systems into rivers, lakes and ground water bodies represents an urgent task for
applied environmental sciences in the coming years.
Recommendations Public acceptance of green technologies is generally higher than that of industrial processes. The EU should stimulate research
to upgrade existing waste water treatment by implementing phytoremediation modules and demonstrating their reliability to
the public. 相似文献
17.
18.
19.
Alan E. Donnenfeld MD Johanna van de Woestune Frank Craparo Catherine S. Smith Avi Ludomirsky Stuart Weiner 《黑龙江环境通报》1991,11(4):235-244
Experience with three prenatally diagnosed pregnancies complicated by an acardiac twin reveals that ultrasonography and echocardiography are helpful in detecting early signs of in-utero congestive heart failure in the normal twin. The use of Doppler blood flow analysis to determine direction of blood flow, post-mortem placental and fetal angiography, and umbilical cord blood gas determination provided proof that retrograde arterial perfusion occurs in the acardiac fetus. In a fourth pregnancy, an experimental approach to occlude the acardiac twin's umbilical cord was attempted, but was unsuccessful. 相似文献