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171.
172.
The present study reports the synthesis of a novel ionophore, calix[4]azacrown ( 5 ) bearing two amino groups at the lower rim along with its oligomeric analogue ( 6 ). The liquid‐liquid extraction properties of these compounds towards selected metal cations and dichromate anions have been evaluated. It is observed that ( 5 ) and ( 6 ) are good extractants for the selected metal cations. However, in the case of dichromate anion, only species ( 5 ) shows remarkable extraction properties at low pH, whereas species ( 6 ) shows poor extraction behavior. The results have importance especially in wastewater treatment to obtain environmentally safe industrial effluent and they should also assist supramolecular chemists in designing and synthesizing more sophisticated host molecules for the removal of toxic pollutants. 相似文献
173.
With increasing uncertainties associated with climate change, precipitation characteristics pattern are receiving much attention these days. This paper investigated the impact of climate change on precipitation in the Kansabati basin, India. Trend and persistence of projected precipitation based on annual, wet and dry periods were studied using global climate model (GCM) and scenario uncertainty. A downscaling method based on Bayesian neural network was applied to project precipitation generated from six GCMs using two scenarios (A2 and B2). The precipitation values for any of three time periods (dry, wet and annual) do not show significant increasing or decreasing trends during 2001–2050 time period. There is likely an increasing trend in precipitation for annual and wet periods during 2051–2100 based on A2 scenario and a decreasing trend in dry period precipitation based on B2 scenario. Persistence during dry period precipitation among stations varies drastically based on historical data with the highest persistence towards north‐west part of the basin. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
174.
?brahim Kü?ük ?pek üler ?ükriye ?z Sedat Onay Ali R?za ?zdemir Mehmet Gül?en Mikail Sar?kaya Nazl? Derya Dag?tekin Ferhat Fikri ?zeren 《Experimental Astronomy》2012,33(1):1-26
Selecting the future site for a large Turkish radio telescope is a key issue. The National Radio Astronomy Observatory is now in the stage of construction at a site near Karaman City, in Turkey. A single-dish parabolic radio antenna of 30?C40 m will be installed near a building that will contain offices, laboratories, and living accommodations. After a systematic survey of atmospheric, meteorological, and radio frequency interference (RFI) analyses, site selection studies were performed in a predetermined location in Turkey during 2007 and 2008. In this paper, we described the experimental procedure and the RFI measurements on our potential candidate??s sites in Turkey, covering the frequency band from 1 to 40 GHz. 相似文献
175.
Atila Yildiz Ahmet Aksoy Gul Nilhan Tug Cemil Islek Dilek Demirezen 《Journal of Atmospheric Chemistry》2008,60(1):71-81
The objective of this study was to determine the air pollution level of Ankara and to generate the air pollution map of this
city by using Pseudevernia furfuracea (L.) Zopf as a biomonitor. Lichen samples were collected from unpolluted area at Yaprakli Mountains, Cankiri in November
2002 and transplanted to 27 localities in Ankara. Lichen samples were retrieved following an exposure of 3 and 6 months. Heavy
metal, Cu, Mn, Ni, Pb and Zn, contents were determined by using inductively coupled plasma spectrometry (ICP). The chlorophyll
a and b contents were determined by using DMSO method. The increase in Ni, Pb, Zn and chlorophyll a content of the specimens
were statistically important. All the increases and decreases in the variables could be explained by the environmental stress
like pollution, but it is hard to say that this is the only reason of these changes, also climatic conditions, seasons, strength
of the light and the physiological status of the plant itself effective on these changes. According to the results of heavy
metal analysis Pseudevernia furfuracea continued to accumulate heavy metals and worked well as a biomonitor. The air pollution level of Ankara shows great variations
because of the great area of the city. 相似文献
176.
Oya Algan M. Namk Yaln Mehmet
zdoan sak Ylmaz Erol Sar Elmas Krc-Elmas Demet Ongan
zlem Bulkan-Yeiladal Yücel Ylmaz smail Karamut 《Quaternary Research》2009,72(3):457-461
The sedimentary sequence discovered at archaeological excavations in ancient Theodosius Harbour at İstanbul contains the records of sea level, environmental changes and the cultural history of the region. The cobbles at the base of the sequence include archaeological remnants of Neolithic culture that settled in the area between 8.4 and 7.3 14C ka BP, and are located at 6 m below the present sea level. The sediments representing a coastal environment indicate that the area was used as a harbour from AD 4th to at least the 11th century and were filled by the sediments derived from Lykos Stream after 11th century. 相似文献
177.
Hydrogeochemical factors effecting the scaling problem in Balçova geothermal field,İzmir, Turkey 总被引:1,自引:0,他引:1
Reservoir fluid compositions have been assessed from analytical data on water samples collected from thermal and cold waters in Balçova geothermal field. The results of mineral equilibrium modelling indicate that the waters, with some exceptions, are systematically supersaturated with respect to calcite, aragonite, dolomite, chalcedony and quartz, but undersaturated with respect to amorphous silica, celestite, anhydrite and gypsum and undersaturated or supersaturated with respect to barite, low-albite, K-feldspar, gibbsite and Fe(OH)3(a). Calculation of mineral saturation states and geochemical analyses of scale and field observations show that carbonate minerals (calcite, aragonite and dolomite) are most likely to be precipitated as a scale type. Besides carbonates, scale formation risk of amorphous silica, Fe(OH)3(a), anhydrite, barite and celestite minerals should be taken into account in some wells and surface equipment. Most of the waters, with some exceptions, have carbonate scaling risk at all temperatures, whereas the other scaling risks only exist over a limited temperature range. While silica, Fe(OH)3(a) and barite show a scaling tendency at low temperatures, anhydrite and celestite scaling occurs at higher temperatures. 相似文献
178.
179.
Mehmet Ali Hindistan Abdullah Erhan Tercan Bahtiyar Ünver 《International Journal of Coal Geology》2010,81(3):139-150
The coal quality is an important aspect of coal mine planning. This paper presents a case study in which an underground coal mine is faced with severe penalty cost because it does not consider in situ coal quality control at all. To help short term planning of the coal production the mean calorific values of the blocks inside the production panels are estimated by kriging. The estimated calorific values are compared with those obtained from actual production. The ratio of the calorific values of actual production to estimated values is found to be 0.73 in average due to adverse effect of dilution on the quality of run-of-mine coal. This study reveals the importance of geostatistical block modelling in short term mine planning. 相似文献
180.
The effect of reservoir length on seismic performance of gravity dams to near- and far-fault ground motions 总被引:1,自引:1,他引:0
In this article, the effect of reservoir length on seismic performance of gravity dams to near- and far-fault ground motions
is investigated. For this purpose, four finite element models of dam–reservoir–foundation interaction system are prepared
by using the Lagrangian approach. In these models, the reservoir length varies from H to 4H (H: the height of dam). The Folsom gravity dam is selected as a numerical application. Two different ground motion records of
1989 Loma Prieta earthquake are used in the analyses. One of ground motions is recorded in near fault; the other is recorded
in far fault. Also, the two records have the same peak ground acceleration. The study mainly consists of three parts to assess
the effects of reservoir length on the seismic performance of the concrete gravity dam. In the first part, the linear time-history
analyses of the four finite element models prepared for the Folsom gravity dam are performed. In the second part, the seismic
performance of the dam is evaluated according to demand–capacity ratio and cumulative inelastic duration. Finally, the nonlinear
time-history analyses of the finite element models of the dam are carried out by using Drucker–Prager yield criteria for dam
concrete. It is seen from the analyses results that the seismic behavior of the concrete gravity dams is considerably affected
from the length of the reservoir. The reservoir length of 3H is adequate for concrete gravity dams. The selection of ground motion is on of the important parts of seismic evaluation
of gravity dams. Also, the frequency characteristics of the ground motion having the same peak ground acceleration affect
the seismic performance of the dam. The near-fault ground motions are generally creates more stress on the dam body than far-fault
ground motions. The used performance approach provides a systematic methodology for assessment of the seismic performance
and necessity of nonlinear analyses for dam systems. 相似文献