排序方式: 共有22条查询结果,搜索用时 781 毫秒
11.
The paper studies and applies the approaches to forecast long-term (LT) real prices of iron ore. This price is crucial for valuation of investments in Greenfield iron ore projects on the horizon of more than 5 years. The forecast is obtained by three different approaches which are usually used by investment bank analysts: marginal costs approach and 2 approaches based on calculation of incentive price. The paper concludes that there has been a structural shift on the iron ore market and LT iron ore prices will be higher by 20–30% than the average of industry forecasters suggest. This is related to the 2 key factors which were taken into account in this study—depletion of existing iron ore deposits and targeted return on investments for new projects. In addition, escalated industry costs inflation is claimed to be the factor which will bolster nominal iron ore prices at high levels in the long-term. Using a Monte-Carlo simulation approach, confidence interval for future iron ore price was estimated. 相似文献
12.
In addition to encoding referential information and information about the sender’s motivation, mammalian alarm calls may encode
information about other attributes of the sender, providing the potential for recognition among kin, mates, and neighbors.
Here, we examined 96 speckled ground squirrels (Spermophilus suslicus), 100 yellow ground squirrels (Spermophilus fulvus) and 85 yellow-bellied marmots (Marmota flaviventris) to determine whether their alarm calls differed between species in their ability to encode information about the caller’s
sex, age, and identity. Alarm calls were elicited by approaching individually identified animals in live-traps. We assume
this experimental design modeled a naturally occurring predatory event, when receivers should acquire information about attributes
of a caller from a single bout of alarm calls. In each species, variation that allows identification of the caller’s identity
was greater than variation allowing identification of age or sex. We discuss these results in relation to each species’ biology
and sociality. 相似文献
13.
Environmental monitoring of aquatic systems is needed to estimate the quality of the systems, to evaluate standards and to
study stressor–response relationships. Monitoring programs often focus on the collection of biological, chemical and physical
measures of the system. An important concern is the effect of chemical and physical stressors on the biological community.
Evaluation of relationships may be difficult as the extent of the relationship is not known. From a management perspective,
interest is on what factors affect the biological community and where these factors have an influence. The focus of this paper
is on the use of regression based cluster analysis as a tool for finding relationships between a single biological response
and a suite of environmental stressors. The approach to cluster analysis uses a penalized regression classification likelihood
and Markov Chain Model Composition Monte Carlo. This approach allows for simultaneous development of regression models and
clustering of the regression models. The method is applied to the analysis of a data set describing stressors/response relationship
in Ohio. 相似文献
14.
The aim is to fill a water storage with potable water of a given quality, for subsequent treatment and distribution to a water
conveying system. During a given period, a set of several pumping stations is working to deliver water from different sources
at different locations. A multi-stage control process is considered whereby the total pumping time is divided into short sampling
intervals. The intensity of pumping as a function of time is the control variable. It is assumed that there exists a reliable
forecast of every pollutant as a function of time and water source. The amount of the pollutants are constrained in the final
mass of water in the storage. The mass of water at the end of the operation period should be maximized. A linear programming
(LP) model of the problem is described, and an algorithm of the reduction of its dimensionality is presented. An illustrative
example is shown.
A short conference version of this paper has been presented at 14th IEEE Mediterranean Conference on Control Automation, June
28–30 2006, Polytechnical University of Ancona, Ancona, Italy. 相似文献
15.
Wetlands are a vital resource, particularly in Africa where livelihoods are closely linked to natural capital. In recent years,
extensive drainage has occurred to make way for agriculture. To gain insight into whether drainage is justified, we review
the value of African wetlands dominated by Cyperus papyrus in relation to use, conservation and conversion. Evidence suggests that the value derived from low-intensity, multifunctional
wetland use far exceeds the value derived from swamp reclamation and generally exceeds that of conservation. At a local level,
the main driver of wetland misuse appear to be a breakdown in collaborative management regimes and the main constraint on
wetland use, the value of labor and selling-times. Local drivers are linked to regional factors such as the lack of coordinated
wetland policies and difficulties in ensuring that legislation is absorbed by all sectors of society. We highlight opportunities
for ensuring more effective collaborative management and legislation communication, which capitalize on existing governance
structures. In contrast to predictions by Hardin’s Tragedy of the Commons model, we argue that effective wetland management
is best achieved by preventing privatization and promoting common property management regimes. We also argue that poverty
and income inequity are more important drivers of unsustainable resource use than environmental managers commonly acknowledge. 相似文献
16.
17.
Evans Meredydd Legro Susan Popov Ilya 《Mitigation and Adaptation Strategies for Global Change》2000,5(4):319-336
Joint implementation (JI) can provide flexibility in meetingKyoto Protocol commitments, and 44 nations have already participated inthe U.N. Framework Convention on Climate Change – Activities Implemented Jointly (AIJ) pilot. Thispaper surveys JI policy and projects in three countries – Russia, Ukraine,and Poland – over the past five years and examines the effects of domesticinstitutions, foreign policy, and investment trends on JI in each country.The institutional and economic situation in the three nations differs greatly,and these distinctions have resulted in very different circumstances for AIJprojects, affecting both their number and scope. Poland has a well-definedset of rules and procedures for JI and its economy is quite strong. Ukrainehas not yet established criteria or clear procedures for AIJ project reviewsalthough it does have an Interagency Commission on Climate Change.Ukraine's economy declined by over 40% in the 1990s. Russia'seconomy has also declined, to a lesser extent. Russia does have aprocedure for reviewing AIJ projects, though it has temporarily halted thesereviews. Countries seeking JI investment can take several steps to improve thenumber and quality of AIJ projects that they receive. In the long term,governments can create macroeconomic stability and a solid legalinvestment basis to attract investment for JI and other areas. In the shortterm, however, governments can undertake several simple and inexpensivesteps to promote JI. Establishing clear rules and procedures for AIJprojects is an important step. So too are clearly delegating responsibilityfor AIJ project review and providing a single JI point of contact in thegovernment to which investors and project developers can turn. Gainingmore experience in implementing AIJ projects now is important preparationfor fully implementing the Kyoto Protocol beginning in 2008. 相似文献
18.
Vera A. Matrosova Ilya A. Volodin Elena V. Volodina Andrey F. Babitsky 《Behavioral ecology and sociobiology》2007,62(2):181-191
In most mammals, larger adult body size correlates with lower fundamental frequency and more closely spaced formants in vocalizations
relative to juveniles. In alarm whistles of two free-living rodents, the speckled ground squirrel Spermophilus suslicus and yellow ground squirrel S. fulvus, these cues to body size were absent despite prominent differences in body weight and skull and larynx sizes between juveniles
and adults. No significant correlations were found between the individual maximum fundamental frequency and body weight, both
within age classes and for pooled samples of all animals within species. Furthermore, the mean alarm whistle maximum fundamental
frequencies did not differ significantly between age classes (juvenile versus adult) in the speckled squirrel and were even
significantly lower in juvenile yellow squirrels. We discuss the hypothesis that the obfuscation of vocal differences between
juvenile and adult squirrels may represent a special adaptation of pup vocal behaviour—a form of “vocal mimicry,” resulting
in imitation of adult vocal pattern to avoid infanticide and age-dependent predation risk. 相似文献
19.
Jason W. Kelsey Ilya B. Slizovskiy Richard D. Peters Adam M. Melnick 《Environmental pollution (Barking, Essex : 1987)》2010,158(6):2251-2257
Laboratory experiments were conducted to assess the effects of soil sterilization on the bioavailability of spiked p,p′-DDE and anthracene to the earthworms Eisenia fetida and Lumbricus terrestris. Physical and chemical changes to soil organic matter (SOM) induced by sterilization were also studied. Uptake of both compounds added after soil was autoclaved or gamma irradiated increased for E. fetida. Sterilization had no effect on bioaccumulation of p,p′-DDE by L. terrestris, and anthracene uptake increased only in gamma-irradiated soils. Analyses by FT-IR and DSC indicate sterilization alters SOM chemistry and may reduce pollutant sorption. Chemical changes to SOM were tentatively linked to changes in bioaccumulation, although the effects were compound and species specific. Artifacts produced by sterilization could lead to inaccurate risk assessments of contaminated sites if assumptions derived from studies carried out in sterilized soil are used. Ultimately, knowledge of SOM chemistry could aid predictions of bioaccumulation of organic pollutants. 相似文献
20.
K. Devi C. S. Vijaya Lakshmi M. C. Raicy P. Srinivasan S. G. N. Murthy S. M. Hussain Ilya Buynevich Rajesh R. Nair 《Journal of Coastal Conservation》2013,17(1):167-178
The refraction of the 2004 Indian Ocean tsunami waves caused drastic devastation along East coast of India, mainly in the area of investigation. Here, we appraise and integrate the sedimentary characteristics and microfossil studies of the area. The gigantic tsunami waves caused the landward fining of sediments that were carried as suspended load. Tsunami sediments have distinctive characteristics, like fine-to-medium grained sand, moderately to poorly sorted sediments which indicating sudden winnowing followed by tranquil flood. Positively skewed grain size distribution indicating unidirectional transport, and mesokurtic to platykurtic character implying poorly sorted single source origin. The species of benthonic foraminifers and ostracods reside in marine environment indicating shallow water origin of sediments. The onshore deposits are vertically divided into three depositional units interpreted from Ground Penetrating Radar (GPR) signatures—Unit 1 is a relatively continuous parallel layer indicative of calm environment; Unit 2 has paleochannels and burial scarps, seen as oblique reflections that might be indicative of an intense erosional environment; Unit 3 is interpreted as 2004 tsunami layer, has three subunits. Each main units have been separated by Heavy Mineral Concentrated (HMC) layers, deposited by continuous wave action (~?20 cm) and by the tsunami (>?30 cm) activity, evidenced by low magnetic susceptibility values at the bottom compared to the top of the HMC layers. GPR has been effectively utilized in this paper as subsurface imaging tool for the interpretation and reconstruction of stratigraphy, and also helped to unearth the erosional and depositional environments. 相似文献