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1.
《Atmósfera》2014,27(4):429-449
This paper proposes a new methodology for generating climate change scenarios at the local scale based on multivariate time series models and restricted forecasting techniques. This methodology offers considerable advantages over the current statistical downscaling techniques such as: (i) it provides a better representation of climate at the local scale; (ii) it avoids the occurrence of spurious relationships between the large and local scale variables; (iii) it offers a more appropriate representation of variability in the downscaled scenarios; and (iv) it allows for compatibility assessment and combination of the information contained in both observed and simulated climate variables. Furthermore, this methodology is useful for integrating scenarios of local scale factors that affect local climate. As such, the convenience of different public policies regarding, for example, land use change or atmospheric pollution control can be evaluated in terms of their effects for amplifying or reducing climate change impacts.  相似文献   

2.
The complex mobilities of homeless people in rural England   总被引：2，自引：0，他引：2  
Paul Cloke 《Geoforum》2003,34(1):21-35
This paper explores the interconnected issues of mobility, power and meaning in the context of rural homelessness. It explores two common assumptions relating to these interconnections: that rural homeless people move to cities thereby transposing homelessness into an urban problem; and that mobility is deeply implicated in the mapping of moral codes in rural areas. Drawing on a range of interviews with homeless people, and workers with homelessness agencies in the rural areas of Gloucestershire and Somerset, the paper discusses four types of movement: ‘local’ homeless people moving out of rural areas; ‘local’ homeless people moving within rural areas; homeless ‘incomers’ moving to rural areas; and itinerant/transient homeless people moving through rural areas. The complex mobilities of rural homeless people influence common ideas about where homelessness occurs and how it is experienced. These mobilities also affect how homelessness is ‘made known’ in rural areas, as different elements of the mobility of homeless people are discursively scattered amongst identity labels and policy arenas other than homelessness. Finally, homeless mobilities problematise the adequacy and nature of policy responses to homelessness in rural areas.  相似文献   

3.
Acid-base titrations and electrophoretic mobility measurements were conducted on the thermophilic bacteria Anoxybacillus flavithermus and Geobacillus stearothermophilus at two different growth times corresponding to exponential and stationary/death phase. The data showed significant differences between the two investigated growth times for both bacterial species. In stationary/death phase samples, cells were disrupted and their buffering capacity was lower than that of exponential phase cells. For G. stearothermophilus the electrophoretic mobility profiles changed dramatically. Chemical equilibrium models were developed to simultaneously describe the data from the titrations and the electrophoretic mobility measurements. A simple approach was developed to determine confidence intervals for the overall variance between the model and the experimental data, in order to identify statistically significant changes in model fit and thereby select the simplest model that was able to adequately describe each data set. Exponential phase cells of the investigated thermophiles had a higher total site concentration than the average found for mesophilic bacteria (based on a previously published generalised model for the acid-base behaviour of mesophiles), whereas the opposite was true for cells in stationary/death phase. The results of this study indicate that growth phase is an important parameter that can affect ion binding by bacteria, that growth phase should be considered when developing or employing chemical models for bacteria-bearing systems.  相似文献   

4.
In this paper, we report a detailed study of helium (He) incorporation and diffusion pathways in the perfect and defective zircon lattice. Ab initio methods based on Density Functional Theory (DFT) were used to calculate the structural features, the solution energies in interstitial sites in the perfect zircon and in vacancy sites of the defective lattice and He diffusion pathways in these systems. We show that the mode of He incorporation in the perfect zircon is influenced mainly by the topological features of the lattice, promoting site preference of He towards accommodation in the interstitial sites present in the middle of c cylinder channels. The presence of defect species in the form of lattice vacancies and interstitials has a significant effect on He solubility and diffusivity in the lattice, where the ability of lattice vacancies to act as physical traps or repulsive sites depends greatly on the electronic nature of the vacancy, which can enhance solubility of He in the lattice and affect the kinetics of He mobility in zircon mineral.  相似文献   

5.
The study of life course has become a central feature of geographical and other social science approaches to youth and migration. It has offered scholars possibilities to explore the timing of events, experiences of time and in the context of migration, the opportunity to analyse mobility patterns in relation to life stages and transitions. Yet, despite this emphasis, much life-course research rests on a limited understanding of time characterised as a linear or even static entity that regulates life in a way that occludes the complex directionality and rhythms of time. In this paper we seek to push beyond these limitations of life course research by developing broader theoretical understandings of time in migration. In particular, we develop a Heideggerian analysis of the migration stories of western English teachers in South Korea, an example of migration as part of a youth–adult transition. Our analysis reveals that the mobilities of English teachers need to be understood in much more complex and relational ways and we draw attention to their more-than-subjective temporalities, questions of attunement to being (affect) and temporal openness in migration. Through this discussion the paper highlights three key areas for further development of scholarly understandings of time in migration: the situatedness of migrants, the holistic character of migration as a happening in the world, and the eventfulness of migration, always characterised by an openness of possibility for emergent spatio-temporal differentiation.  相似文献   

6.
Diamondback terrapins (Malaclemys terrapin) drown in blue crab (Callinectes sapidus) pots throughout their range. The objectives of this study were to test if bycatch mortality of diamondback terrapins in commercial crab pots is reduced by using bycatch reduction devices (BRDs) and to determine if BRDs affect crab catch in Florida by comparing sex, size, and number of blue crabs captured in standard crab pots with those captured in pots equipped with BRDs. We fished 15 standard crab pots (controls) and 15 crab pots with bycatch reduction devices (experimentals) for 10-d periods at two sites per year from 2002 through 2005. Study sites were located in eight Florida counties with one sample period per county. Pots were checked daily and baited on alternate days. We determined sex and size of captured terrapins and blue crabs to evaluate if BRDs affected the size of either species. Thirty-seven terrapins were caught in control pots and four in experimentals. Eleven terrapins were small enough that they would not have been prevented from entering either pot treatment, but we found that 73.2% of the terrapins in this study could have been prevented from entering crab pots with functional BRDs. There were no significant differences between the sex, measurements, or number of legal-sized crabs captured in control and experimental pots at any of the study sites. We recommend that the Florida Fish and Wildlife Conservation Commission devise and adopt regulations that require the use of 4.5×12 cm BRDs on all commercial and recreational crab pots in Florida without delay.  相似文献   

7.
The radiation resistance of zircon (ZrSiO4) was comparatively tested with computer simulations of four different sets of parameters of interatomic potentials. The energies of Frenkel pairs (FP) for Zr, Si, and O atoms were calculated using the Mott-Littleton method in approximation of isolated defects. The difference between the FP energies calculated for four potentials and the FP energies obtained ab initio is the least in the one of the four calculated potentials that takes into account the ab initio data for Zircon 3. The formation of an atomic displacement cascade (ADC) after the passage of the initially knocked-out Th atom with energy of 20 keV was investigated using the molecular dynamics method. The number of FP in ADC reaches 5300 to 61 900, depending on the chosen potential. The number of FP at the end of the simulation varies from 480 to 4970. The distribution of internodal oxygen atoms in zircon has been studied. It is shown that within a time (t) interval of 0?C0.1 ps (ballistic stage), the internodal oxygen atoms knocked-out from the initial equilibrium site are predominant (O1 defects). Thereby the Si-O bond is ruptured. The mean displacement of those defects is 2?C3 ?. The probability of their survival is 34?C73% depending on the chosen potential. After t = 0.1 ps (onset of the thermal stage), many SiO4 tetrahedra in zircon are displaced with formation of a great amount of internodal oxygen atoms, because the Si-O bond is not ruptured. The mean displacement of those O2 defects is 1 ?; the probability of their survival is insignificant: 1.5?C3.0% depending on the chosen potential. The total amount of internodal oxygen atoms consists of O2 defects (19?C25%) and largely of O1 defects. A parameter characterizing that part of the energy of the initially knocked-out atom, which is consumed for FP, has been introduced. The physically acceptable values of this parameter (<1) are obtained only for Zircon 3 potential. The results show that a substantial discrepancy in relative amounts of Si and O atoms with displacements for 0.3?C0.5 ? from the equilibrium site exists for different potentials. In particular, the number of FP in zircon diminishes with decrease in mobility of atoms. It has been established that the lower the mobility of atoms, the lower the number of FP, and the most reasonable consistency with the preset conditions of the computer simulation is provided by Zircon 3 potential.  相似文献   

8.
Tailings generated during processing of sulfide ores represent a substantial risk to water resources. The oxidation of sulfide minerals within tailings deposits can generate low-quality water containing elevated concentrations of SO4, Fe, and associated metal(loid)s. Acid generated during the oxidation of pyrite [FeS2], pyrrhotite [Fe(1−x)S] and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate, (oxy)hydroxide, and silicate minerals. The extent of acid neutralization and, therefore, pore-water pH is a principal control on the mobility of sulfide-oxidation products within tailings deposits. Metals including Fe(III), Cu, Zn, and Ni often occur at high concentrations and exhibit greater mobility at low pH characteristic of acid mine drainage (AMD). In contrast, (hydr)oxyanion-forming elements including As, Sb, Se, and Mo commonly exhibit greater mobility at circumneutral pH associated with neutral mine drainage (NMD). These differences in mobility largely result from the pH-dependence of mineral precipitation–dissolution and sorption–desorption reactions. Cemented layers of secondary (oxy)hydroxide and (hydroxy)sulfate minerals, referred to as hardpans, may promote attenuation of sulfide-mineral oxidation products within and below the oxidation zone. Hardpans may also limit oxygen ingress and pore-water migration within sulfide tailings deposits. Reduction–oxidation (redox) processes are another important control on metal(loid) mobility within sulfide tailings deposits. Reductive dissolution or transformation of secondary (oxy)hydroxide phases can enhance Fe, Mn, and As mobility within sulfide tailings. Production of H2S via microbial sulfate reduction may promote attenuation of sulfide-oxidation products, including Fe, Zn, Ni, and Tl, via metal-sulfide precipitation. Understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings.  相似文献   

9.
We introduce new estimators for fracture trace intensity, trace density and mean trace length that exploit the use of circles as efficient sampling tools. A fracture trace is the commonly observed surface expression of a fracture, i.e. the intersection of a fracture with an exposed surface such as a rock pavement or a mine drive wall. Trace intensity, trace density and mean trace length estimators are derived and shown to form a self-consistent set of two-dimensional fracture abundance measures. The intensity estimator n/4r uses the number, n, of intersections between fracture traces and a circular scanline of radius r. The density estimator m/2πr2 uses the number, m, of trace endpoints inside a circular window. The mean trace length estimator (n/m)πr/2 uses the ratio of the number of trace intersections on the circle to the number of endpoints in the circle.The circular sampling tools and estimators described here eliminate most sampling biases due to orientation and also correct many errors due to censoring and length bias that plague established scanline and areal measurement techniques. Performance of the estimators is demonstrated by comparison with areal samples of a synthetic fracture trace population with known intensity, density and mean trace length. The estimators are also applied successfully to a natural rock pavement with two orthogonal fracture sets, one of which is severely censored. Because the new circle-based estimators only require counts of trace–circle intersections and/or trace endpoints, they are more time-efficient than current methods for estimating geometric characteristics of fracture traces.  相似文献   

10.
Citric acid is found along with uranyl in the subsurface of former nuclear facilities because of its use as a decontamination agent in the nuclear industry. Citrate’s metal chelating properties affect the mobility of uranyl in the subsurface and consequently, citrate biodegradation may significantly impact uranyl fate and transport. Under the non-growth conditions considered, low (micromolar) uranyl concentrations inhibit the biodegradation of citrate by Pseudomonas fluorescens, a common subsurface denitrifying bacterium. Additionally, uranyl is found readily associated with the cell envelope of P. fluorescens. The observed inhibition appears to be linked to the binding of uranyl to the cell surface and is reversible by desorbing cell-bound uranyl. This study establishes a link between uranyl association with the cell surface and the observed inhibitory effect of uranyl on cell metabolism.  相似文献   

11.
Response of sand ripples to change in oscillatory flow   总被引：3，自引：1，他引：3  
Ripples take time to evolve to a new equilibrium state in response to a change in wave-generated oscillatory flow. The paper presents results from flow tunnel experiments designed to examine oscillatory flow transient ripple processes under controlled, full-scale laboratory conditions. The experiments include study of the growth of ripples from flat bed and the evolution of existing ripples to new equilibrium ripples in response to a step change in the flow. In general, ripples evolve through a combination of two main processes: (i) from a flat bed or from a bed consisting of ripples that are smaller than the equilibrium ripples through a combination of 'slide' and 'merge'; (ii) from a bed consisting of ripples that are larger than the equilibrium ripples through a combination of 'split' and 'merge'. The experimental results show that equilibrium ripple geometry is independent of initial bed morphology while the time to reach equilibrium is largely independent of the initial bed and the equilibrium ripple size. The time to reach equilibrium depends strongly on the mobility number, and a new empirical equation relating mobility number and the number of flow cycles to equilibrium is proposed. This equation is combined with a simple exponential function for ripple height growth or decay to produce a new empirical model for ripple height evolution, which gives a reasonably good overall agreement with the measurements. The model is based on experiments involving one sediment size only and further work is needed to develop the model for other sand sizes.  相似文献   

12.
Fred Gray  Martin Boddy 《Geoforum》1979,10(1):117-127
The paper looks in detail at one particular interpenetration of academic theory and state policy making — filtering theory in urban geography. While household mobility and turnover are important processes in the housing system, they are extended in filtering theory to form a universal explanatory model embracing the entire housing system. In this model idealised concepts of the operation of the housing market—valid only under conditions that do not occur in practice — are used to legitimate a laissez-faire natural-market view of how the housing system should operate. Translated into government policy, used to justify the dominant private interests in housing, and supported by academic explanation, the theory then comes to legitimate the persistence of gross inequalities in housing provision and to maintain the allocation of resources away from those most in need. This paper reviews this use of filtering theory both in Britain and the United States, and makes a variety of empirical and theoretical criticism of its validity.  相似文献   

13.
Cyclic mobility is a mechanism of ground failure due to lateral spreading of soils during an earthquake that usually occurs in soft or medium stiff saturated soils. The simplified procedures developed by the researchers give a factor of safety for judging the cyclic mobility potential. However, the simplified procedures do not take into account the uncertainty in the parameters required to estimate the cyclic stresses in the soil. In this study, a reliability framework based on the simplified procedure, considering the parameter uncertainty, has been proposed for computing the probability of cyclic mobility of clay deposits for a metro city of India, i.e., Mumbai city (latitudes 18°53′N–19°19′N and longitudes 72°47′E–72°58′E). Extensive geotechnical borehole data from 1028 boreholes across 50 locations in the city area of 390 km2 and laboratory test data are collected and analyzed thoroughly. A correlation between undrained shear strength (Su) and other parameters such as natural water content (w), SPT N value, liquid limit (LL) and plasticity index (PI) has been established for Mumbai city and has been used in the proposed approach. The sensitivity analysis of the proposed approach predicts that Su has significant influence in the evaluation of the cyclic mobility. Cyclic mobility hazard maps are prepared using the geo-statistical analysis tool in GIS, and it shows that the clayey soils at few locations have a 60–90 % probability of cyclic mobility for a moment magnitude (M w) of an earthquake of 7.5. These hazard maps can be used by the geotechnical engineers for the cyclic mobility hazard assessment of Mumbai city.  相似文献   

14.
What does it mean to reflect upon space in connection to telecommunications? If we start with a conception of urban space as being fully integrated, including on an equal footing both information and communication technologies (ICT) and mobility techniques, as well as the founding notion of copresence that we find at the heart of all urban organization, we might then be able to examine the notion of the ‘digital divide’ in a new light. This clearly experimental approach is conducted by a research group called ‘Urbatic’, which is composed of geographers who, for the last three years, have been conducting theoretical research whose objective is to take into account two fields of social science: the theory of urbanity and the theory of telecommunication. Surveys conducted in this perspective focus on the analysis of the choices people make between the different means they can use to cope with distances (copresence, mobility and telecommunication) with a view to constructing their own space. The analysis of these choices leads us to propose a new theorized interpretation of the ‘digital divide’.  相似文献   

15.
Landslides triggered by rainfall can be foreseen by modeling the relationship between the time occurrence of landslides and rainfall. This paper deals with the argument by adopting a hydrological model called Forecasting of Landslides Induced by Rainfall (FLaIR). The model is applicable for forecasting recurrent landslides and it is based on the identification of a mobility function Y(.) that links the occurrence of a slope movement to the antecedent rainfall. Once the mobility function is defined, it is possible to define its critical values, the exceeding of which indicates that new mobilizations could occur. The FLaIR model has been used to study some phenomena that happened in Lanzo Valleys, a Western Alps sector of the Piedmont region (Northern Italy) where slope debris flows are the predominant landslide type. The study has led to the development of an early warning system, called MoniFLaIR, for real-time monitoring and forecasting of slope hazard. This article describes some details of the system and its performance.  相似文献   

16.
The nuclear reaction 19F(1H, αγ) 16O has been used to determine the hydrogen concentration in natural and synthetic quartz samples. The depth-profile of the hydrogen concentration in these samples has been determined in detail for the smoky and X o quartzes. These profiles exhibit a region of high hydrogen concentration in the near surface region (down to a depth of ～2000Å), with a lower concentration in the bulk of the sample. The results provide a plausible explanation for the substantial disagreement between previous hydrogen analysis in these quartzes by other techniques. Evidence for hydrogen mobility in crystalline quartz under ion beam bombardment is presented and discussed.  相似文献   

17.
This paper explores young people’s experiences and perceptions of mobility and mobility constraints in poorer urban areas of Ghana, Malawi and South Africa within the specific context of inter-generational relations. Drawing principally on qualitative research findings from a study involving both adult and child researchers, our aim is to chart the diversities and commonalities of urban young people’s mobility experiences in the everyday - how they use and experience the city - developing a comparative perspective across three urban study sites which links young people’s mobility with the power relations that operate to shape their movements in individual locations. In particular, we consider how positive and negative images of young people’s mobility play out in terms of the inter-generational frictions and negotiations generated by their mobility performances. We also reflect on the developmental implications, in terms of young people’s access to services and income and their participation in the social networks and peer culture which may shape their life trajectories. Three themes are explored in detail: mobility as challenge, mobility as temptation and mobility control.  相似文献   

18.
Along with the applicability of optimization algorithms, there are lots of features that can affect the functioning of the optimization techniques. The main purpose of this paper is investigating the significance of boundary constraint handling (BCH) schemes on the performance of optimization algorithms. To this end, numbers of deterministic and probabilistic BCH approaches are applied to one of the most recent proposed optimization techniques, named interior search algorithm (ISA). Apart from the implementing different BCH methods, a sensitivity analysis is conducted to find an appropriate setting for the only parameter of ISA. Concrete cantilever retaining wall design as one of the most important geotechnical problems is tackled to declare proficiency of the ISA algorithm, on the one hand, and benchmark the effect of BCH schemes on the final results, on the contrary. As results demonstrate, various BCH approaches have a perceptible impact on the algorithm performance. In like manner, the essential parameter of ISA can also play a pivotal role in this algorithm's efficiency. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

19.
In this paper soft computing techniques, self-organizing maps and fuzzy clustering techniques have been proposed to isolate different layers in stratified soil based on available cone penetration test results. The results have been compared with that obtained from cone classification chart, hierarchical and K-mean clustering techniques. It was observed that variation in result with self-organizing map (SOM) and fuzzy clustering for isolating soil layers is marginal. These techniques are found to be efficient compared to hierarchical clustering technique. The results of K-mean clustering show that the identified soil strata are similar to that obtained from cone classification chart, SOM and fuzzy clustering.  相似文献   

20.
The aim of this paper is to investigate the behavior of laterally loaded pile groups in sands with a rigid head and correlate the response of a pile group it to that of a single pile. For this purpose, a computationally intensive study using 3-D nonlinear numerical analysis was carried out for different pile group arrangements in sandy soils. The responses of the pile groups were compared to that of the single pile and the variation of the displacement amplification factor Ra was then quantified. The influence of the number of piles, the spacing, and the deflection level on the group response is discussed. A relationship for predicting the response of a pile group, based on its configuration and the response of a single pile, has been formulated allowing also for soil shear strength which was found to affect the group response. The relationship provides a reasonable prediction for various group configurations in sandy soils.  相似文献   

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