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11.
Joni Mäkinen 《Sedimentology》2003,50(2):327-360
ABSTRACT Evidence of conspicuous repeated seasonal to annual deposition of glaciofluvial and glaciolacustrine sequences within a structurally complex interlobate esker segment in SW Finland is presented. The time‐transgressive, overlapping depositional sequences consist of deposits from two successive melt seasons, including three vertically stacked lithofacies associations: (1) massive to stratified coarse gravels = summer deposits; (2) trough and ripple cross‐stratified fine‐grained deposits = autumn to winter deposits; and (3) sandy stratified beds = spring deposits. The depositional environment of each lithofacies association involves a transition from subglacial or submarginal tunnel to a subaqueous re‐entrant environment, which then passes to a proglacial glaciolacustrine environment. The study also presents evidence of headward extension of subglacial tunnel deposits, related to the rapid shifting of a tunnel expansion point during the increasing spring discharge, which occupied the old tunnel exit: this mode of annual deposition has not been reported previously in esker studies. The good preservation of the rhythmic lithofacies associations is suggested as resulting from interlobate depositional conditions associated with rapidly decaying icestreams. Therefore, the depositional model may provide a key to recognizing time‐transgressive interlobate eskers that form an important geomorphological and sedimentological record of meltwater activity during the last deglaciation of the Fennoscandian and Laurentide ice sheets. The identification of time‐transgressive interlobate eskers and associated palaeo‐icestream behaviour is an essential step forward for more accurate models of ice sheet behaviour and palaeoclimatic reconstructions. 相似文献
12.
Joni Seager 《The Professional geographer》2000,52(4):709-721
The academic job search process, and the applications and reference letters that are constitutive elements of that process, are central to the creation and re‐creation of a discipline. Disciplines and departments renew and re‐create themselves — or do not, and merely replicate themselves — through hirings. A job search process can serve to hinder changes in the membership, culture, “look,” and the norms of the discipline, or it can facilitate dramatic and often rapid transformations. Job search materials thus provide an insight into the prevailing norms and conventions of a discipline. A review of a recent set of such materials reveals subtle gendered and racialized differences in the job search process. Such differences are apparent in the composition of referee committees, in the evocation of marital status both by applicants and by referees, and in the surprising persistence of themes of robust manhood. The referee pool, the applicant pool, and the search committee pool in an academic discipline are interlocked constituencies, and the job search process plays a “gatekeeping” role. The extent to which gender or racial differences are inserted into the job process thus has a bearing on the long term social construction of the discipline. 相似文献
13.
Landsat MSS imagery is employed to assess the aquatic complexes of the regulated Lake Kemijärvi and the adjoining small natural lakes in Northern Finland.Ground data were collected from within the hydrolittoral areas to allow the evaluation and revision of the computer-aided Landsat MSS classification. The major developments reported here are: (1) the utilization of the computer-aided technique for surveying natural and regulated aquatic areas, (2) the recognition of different aquatic units and complexes defined by depth relations, bottom quality, vegetation coverage or flooding stage, and (3) the presentation of the lower limit of satellite data applicability for mapping small-sized and complicated areas.Although the low spectral and ground resolution levels place restrictions on the use of computeraided Landsat MSS data remote sensing for the parametric mapping of all aquatic phenomena, such data are still of value under circumstances in which ground data collected from a small number of reference areas can be extrapolated to apply to the surrounding lakes and aquatic areas within a single MSS frame. Studies of this kind also facilitate the multitemporal inspection of changing regulated lake environments, due to the long-term nature of the Landsat project. 相似文献
14.
The water quality data collected on the ground by the Water District Office in Oulu was subjected to statistical analyses together with Landsat data to display a few interactions and the possibilities of exploiting remote sensing methods in water area surveying. Correlations between the Landsat data statistics and some water quality measurements were identified. The small size of the studied lakes does not allow any clear calibration to be made but there could be possibilities to develop remote sensing methods for the evaluation of environmental variables and the detection of productivity and the eutrophication stage.The remote sensing procedure could also be useful in portraying temporal variations within lakes as well as relative variations between lakes by classifying each lake on a pixel-by-pixel basis. Although the remote sensing method is not able to supersede ground truth information for lake studies, it has value in regions where many lakes are to be found within a restricted small area. Under these circumstances the collection of information on the ground for a small number of test lakes and the generalization of this data, with the aid of machine-pressing remote sensing, would result in considerably less field work and cost savings. 相似文献
15.
The method for mapping the pixel-scale and larger ruggednesses of the Martian ridged plains within Solis Planum is described by assuming the Lommel-Seeliger's reflection law. This method allows surface tilt angles towards and away from the Sun to be estimated and topographic elevations to be displayed by the aid of monoscopic digital image data. The restrictions of this method are also discussed. 相似文献
16.
The location of new homes defines the urban–rural fringe and determines many facets of the urban–rural interaction set in
motion by construction of new homes in previously rural areas. Home, neighborhood and school district characteristics play
a crucial role in determining the spatial location of new residential construction, which in turn defines the boundary and
spatial extent of the urban–rural fringe. We develop and apply a spatial hedonic variant of the Blinder (J Hum Resour 8:436–455,
1973) and Oaxaca (Int Econ Rev 9:693–709, 1973) price decomposition to newer versus older home sales in the Columbus, Ohio metropolitan area during the year 2000. The preferences
of buyers of newer homes are compared to those who purchased the nearest neighboring older home located in the same census
block group, during the same year. Use of the nearest older home purchased in the same location represents a methodology to
control for various neighborhood, social–economic-demographic and school district characteristics that influence home prices.
Since newer homes reflect current preferences for home characteristics while older homes reflect past preferences for these
characteristics, we use the price differentials between newer and older home sales in the Blinder–Oaxaca decomposition to
assess the relative significance of various house characteristics to home buyers.
相似文献
| Joni S. CharlesEmail: |
17.
The network K‐function in context: examining the effects of network structure on the network K‐function 
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下载免费PDF全文 The flaws of using traditional planar point‐pattern analysis techniques with network constrained points have been thoroughly explored in the literature. Because of this, new network‐based measures have been introduced for their planar analogues, including the network based K‐function. These new measures involve the calculation of network distances between point events rather than traditional Euclidean distances. Some have suggested that the underlying structure of a network, such as whether it includes directional constraints or speed limits, may be considered when applying these methods. How different network structures might affect the results of the network spatial statistics is not well understood. This article examines the results of network K‐functions when taking into consideration network distances for three different types of networks: the original road network, topologically correct networks, and directionally constrained networks. For this aim, four scenarios using road networks from Tampa, Florida and New York City, New York were used to test how network constraints affected the network K‐function. Depending on which network is under consideration, the underlying network structure could impact the interpretation. In particular, directional constraints showed reduced clustering across the different scenarios. Caution should be used when selecting the road network, and constraints, for a network K‐function analysis. 相似文献
18.
Alicia Correa Christian Birkel Jason Gutierrez Joni Dehaspe Ana María Durán-Quesada Chris Soulsby Ricardo Sánchez-Murillo 《水文研究》2020,34(25):4776-4793
Pristine tropical forests play a critical role in regional and global climate systems. For a better understanding of the eco-hydrology of tropical “evergreen” vegetation, it is essential to know the partitioning of water into transpiration and evaporation, runoff and associated water ages. For this purpose, we evaluated how topography and vegetation influence water flux and age dynamics at high temporal (hourly) and spatial (10 m) resolution using the Spatially Distributed Tracer-Aided Rainfall-Runoff model for the tropics (STARRtropics). The model was applied in a tropical rainforest catchment (3.2 km2) where data were collected biweekly to monthly and during intensive monitoring campaigns from January 2013 to July 2018. The STARRtropics model was further developed, incorporating an isotope mass balance for evapotranspiration partitioning into transpiration and evaporation. Results exhibited a rapid streamflow response to rainfall inputs (water and isotopes) with limited mixing and a largely time-invariant baseflow isotope composition. Simulated soil water storage showed a transient response to rainfall inputs with a seasonal component directly resembling the streamflow dynamics which was independently evaluated using soil water content measurements. High transpiration fluxes (max 7 mm/day) were linked to lower slope gradients, deeper soils and greater leaf area index. Overall water partitioning resulted in 65% of the actual evapotranspiration being driven by vegetation with high transpiration rates over the drier months compared to the wet season. Time scales of water age were highly variable, ranging from hours to a few years. Stream water ages were conceptualized as a mixture of younger soil water and slightly older, deeper soil water and shallow groundwater with a maximum age of roughly 2 years during drought conditions (722 days). The simulated soil water ages ranged from hours to 162 days and for shallow groundwater up to 1,200 days. Despite the model assumptions, experimental challenges and data limitation, this preliminary spatially distributed model study enhances knowledge about the water ages and overall young water dominance in a tropical rainforest with little influence of deeper and older groundwater. 相似文献
19.
Joni T. Backstrom Derek W.T. Jackson J. Andrew G. Cooper 《Continental Shelf Research》2009,29(11-12):1361-1372
A 2-year investigation into shoreface morphodynamic behaviour off a high-energy headland-embayment coast in Northern Ireland reveals important process–response mechanisms that cannot be explained solely by existing conceptual models. Fourteen sequential bathymetric surveys, conducted every 1–2 months, show that morphologic (seabed) change is not directly related to oceanographic forcing—extensive nearshore and shoreface accretion and erosion occurs under fair-weather, modal and high-energy conditions. The main factors which seem to cause significant change are long-duration (swell) events coupled with onshore winds, availability of (recently) introduced sediment, surges and elapsed time between storms and the next scheduled survey. Several high-energy events over a short time period (<30 days) did not result in extensive seafloor changes, contrary to expectations. Net seabed change over 2 years shows an average to 0.6 m m?2 of shoreface accretion from the nearshore to 24 m depth. Net erosion was not observed anywhere, including the subaerial beach. Geologic evidence strongly suggests that the source of the significant volume (7.7×105 m3) of sediment introduced into the study area must have been derived from the lower shoreface and/or inner shelf, beyond 24 m depth. 相似文献
20.
There have been a number of flume tests of flow round bends with idealized geometry and recently hydraulic simulations of such experiment. However, studies of hydraulic models in natural river bend are rather limited because of greater complexity of the flow characteristics and lack of detailed data. In this article, we study how 2D hydraulic model and raster‐based hydraulic parameter calculations predict flow characteristics on the natural point bar environment. We will compare calculations of various hydraulic parameters (velocity, bed shear stress and stream power) by the 2D model and the associated sedimentology of the point bars. As a result of comparison, the usability of the 2D model for flow‐form‐product relationship predictions will be evaluated in natural river bend environment. The study shows that the 2D model can be generally utilized to predict the flood‐generated flow‐form‐product relationship in coarse‐grained and structurally complex point bar environments with sand‐dominated bedload. For example, point bar sections submerged in water depths greater than 50 cm showed a relatively good match laterally between the model and sedimentological estimations. Furthermore, this approach allows us to estimate flood processes on a local scale in similar point bar environments with width–length ratio. The flow direction estimates of the 2D model coincided relatively well with the sedimentological estimations on the bar head. However, flow directions on the downstream section could not be modelled because the 2D model cannot handle the helicoidal flow of the river bend. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献