REGIONAL AND TEMPORAL TRENDS IN POWER PLANT UNIT SITING, 1912–1978*     

Robert Q. Hanham  Frank J. Calzonetti 《The Professional geographer》1983,35(4):416-426

Regional trends in the siting of U.S. coal, gas, oil, and nuclear power plant units from 1912 to 1978 are examined. Results of a multivariate statistical analysis indicate that while these trends are comparatively individualistic, they tend to be governed more by factors affecting the choice of fuel than by regional differences in the siting process.  相似文献   

荒漠植物种子萌发研究进展   总被引：62，自引：22，他引：62  

张勇  薛林贵  高天鹏  晋玲  安黎哲 《中国沙漠》2005,25(1):106-112

 对种子自身结构,水分、温度、光照、沙埋深度等对荒漠植物种子萌发的影响进行了综述。硬实种子的不透水性、不透气性以及物理障碍是影响种子萌发的重要因素,通过热水浸种、擦破种皮或果皮、浓硫酸浸泡、低温或辐射处理可以破除硬实的影响。有些荒漠植物果皮或种皮外包有粘液层,这种结构对种子的萌发及幼苗生长有促进作用;部分植物的种胚覆盖物含有生长抑制物质而抑制种子萌发;胚休眠与后熟是影响胚萌发的重要生理因素。雨量大小、分布,降雨次数及土壤湿度是决定荒漠植物种子萌发的重要生态因子;温度影响种子的萌发,变温促进萌发;部分荒漠植物种子的萌发需要光照,有些要在暗中萌发,有些则对光无特异的需求;沙埋深度可调节光照、土壤湿度和土壤温度,从而调节种子萌发。应重视荒漠植物种子对严酷环境适应的研究,从分子水平上阐述其对严酷生境的适应机制。  相似文献   

Support for the Giant Wave Hypothesis: evidence from submerged terraces off Lanai,Hawaii     

Jody M. Webster  David A. Clague  Juan Carlos Braga 《International Journal of Earth Sciences》2007,96(3):517-524

The origin of subaerial coral conglomerate deposits on the Hawaiian islands of Lanai and Molokai is controversial, primarily because these deposits are difficult to interpret and the vertical motion of these islands is poorly constrained. Based on bathymetry, dive observations, sedimentary and radiocarbon data from coralline algal dominated deposits from two submerged terraces at −150 and −230 m off Lanai, Lanai has experienced relatively little vertical movement over the last 30 ka. Using internally consistent age versus depth relationships, paleowater depths, and published sea level data, we estimate that Lanai has experienced maximum rates of uplift of 0.1 m/kyr or subsidence of 0.4 m/kyr over this period. Our analysis of possible uplift mechanisms, published geophysical, numerical modelling, and recent tide data suggests that this is also the maximum uplift rate for the last several hundred thousand years. Taken together these data support the interpretation that coral conglomerates at elevations higher than +35 m on Lanai are tsunami deposits with a minimum wave run up > 170 m, rather than shoreline deposits formed during the last two interglacials, then uplifted to their present elevations.  相似文献   

Mapping soil salinity using a combined spectral response index for bare soil and vegetation: A case study in the former lake Texcoco, Mexico   总被引：3，自引：0，他引：3  

N. Fernndez-Buces  C. Siebe  S. Cram  J.L. Palacio 《Journal of Arid Environments》2006,65(4):644-667

Mapping soil salinity is difficult due to its large spatial and temporal variability. Remote sensing is widely used to lower survey costs, but existing studies usually analyze bare soils and make little reference to the halophytic plants and their role as salinity indicators.This paper aims to correlate soil characteristics (electric conductivity in saturation extract (EC_e) and sodium absorption ratio (SAR) with the spectral response of plant species and bare soils, integrating an algorithm to allow multi-scale mapping using remote sensors.Ground radiance was measured on different plant species and bare soils. A Combined Spectral Response Index (COSRI) was calculated for bare soils and vegetation by adjusting the normalized difference vegetation index (NDVI). EC_e and SAR were determined in surface soil samples. Correlation coefficients between COSRI and soil salinity were obtained and a model was adjusted to predict soil salinity. Landsat-ETM and airborne digital images were used to calculate raster maps of COSRI, and EC_e and SAR were estimated using adjusted models. Correlation between COSRI and EC_e and SAR was of −0.885 and −0.857, respectively. Variance accounted for by exponential models for EC_e and SAR was of 82.6% and 75.1%, respectively. It may be concluded that the method is an easy, low-cost procedure to map salt-affected areas.  相似文献   

Perceptions of Local People toward Wild Edible Plant Gathering and Consumption: Insights from the Q-method in Hani Terraces     

DING Lubin  HE Siyuan  MIN Qingwen  LI Heyao  MA Nan  LI Wenhua 《资源与生态学报(英文版)》2021,12(4):462-470

Wild edible plants (WEPs) can provide a variety of provisioning services and cultural services but they are currently under-utilized. Understanding farmers’ perceptions of the collection and consumption of wild edible plant resources is essential for promoting local socio-ecological system resilience and local wild plant resource use. This paper uses the Q-method to investigate the main perspectives of farmers toward collecting and consuming wild edible plants in the Honghe Hani Terraces region of Yunnan Province. This analysis identified four main perspective types among the farmers, including market-driven, household user-driven, cultural service seekers, and tradition followers. It revealed the main factors that limit and facilitate farmers’ WEP collection and consumption, including limitations due to loss of traditional knowledge, and changes in socioeconomic conditions that negatively affect WEP collection and consumption; while, on the other hand, the demand for WEP-related cultural services and the presence of a strong culture slowed down changes in dietary structure, which in turn have maintained WEP collection and consumption. The Q-method can help in identifying the relationship between community residents and local wild plant resource use in rapidly transitioning areas and in identifying the barriers that affect the resilience of local socio-ecological systems.  相似文献   

Analysis of modern and fossil plant cuticles by Curie point Py-GC and Curie point Py-GC-MS: Recognition of a new, highly aliphatic and resistant biopolymer     

M. Nip  E.W. Tegelaar  H. Brinkhuis  J.W. De Leeuw  P.A. Schenck  P.J. Holloway 《Organic Geochemistry》1986,10(4-6)

This paper investigates to what extent the chemical constituents of plant cuticles (waxes and cutin) can survive diagenesis. Recent and fossil plant cuticles were analyzed by means of Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry. Recent cuticles were analyzed without treatment, after solvent extraction and after cutin depolymerization. Extensive series of straight-chain alkanes, alk-1-enes and α,ω)-alkadienes dominate the pyrolysates, especially after removal of the wax and cutin. ¹³C-NMR spectroscopy of the residue after removal of the cutin confirmed the presence of a new, highly aliphatic biopolymer and a polysaccharide fraction.The abundance of straight-chain alkanes, alk-1-enes and α,ω-alkadienes in the fossil plant cuticles indicates the chemical resistence of the biopolymer to diagenesis and may explain the occurrence of straight-chain aliphatic moieties in organic-matter-rich sediments and coals as revealed by “C-NMR spectroscopy and flash pyrolysis methods. The highly aliphatic biopolymer may function as an important oil precursor.  相似文献   

Turbulence characteristics of flow past submerged vanes     

《国际泥沙研究》2020,35(1):42-56

Submerged vanes are hydrofoils utilized to manage the sediment transport through the river by generating the turbulence in the flow in the form of helical currents.The vanes are placed in the flow with respect to its direction at angle of 10°to 40°.In the current study,an attempt has been made to study the effect of the introduction of vanes in form of rows on parameters like turbulence intensities,Reynolds stresses,turbulent kinetic energy,anisotropy index,and the velocity profile of the flow.It is observed that the profile of variation of turbulence intensities,turbulent kinetic energy,vertical Reynolds stress and velocity over three different marked verticals on a transect are nearly identical whereas a large scatter is observed in the variation of transverse Reynolds stress over the vertical of the aforementioned vertical locations.This observation suggests that flow turbulence is homogeneous over the vertical while scattering in the variation of the transverse Reynolds stress component may be attributed to the presence of secondary currents in the flow.After introducing rows of submerged vanes,the bed turbulence is reduced,hence,helping reduce many scour related phenomenon.It is also observed that a vortex occurred at 0.85 times the height of the vane and the variation of turbulence quantities in the presence of vanes shows the existence of a peak in these quantities.It is observed that as flow moves away from the vane rows,due to the interaction of vortices and the action of vorticity,vortices dampens down and the flow regains homogeneity.After the introduction of submerged vane rows,bed shear stress reduces as fluid from the surface replaces the slow-moving fluid near the bed due to the secondary currents generated by the vanes leading to reduction in the magnitude of turbulence intensities,Reynolds stresses,and turbulent kinetic energy near the bed.The anisotropy index is observed to increase near the bed as induced secondary currents enhanced the turbulence production in the near bed region.All the profiles of parameters obtained in the current study show the existence of a peak or inflexions at a height of 0.85 H from bed(Where,H is the height of the submerged vane).Profiles of parameters obtained in the current study suggest that as the vorticity dampens the vane-generated secondary currents,the scattering in the profiles along the vertical reduces and profiles are observed to regain the variation which they had before the introduction of vane rows,suggesting that flow turbulence has regained its homogeneity.  相似文献   

Numerical modeling of local scour due to submerged wall jets using a strict vertex-based,terrain conformal,moving-mesh technique in OpenFOAM     

《国际泥沙研究》2020,35(3):237-248

This study presents the implementation and validation of a new sediment-scour model with a strict vertex-based,terrain conformal,moving-mesh technique within the framework of OpenFOAM.OpenFOAM lacks the ability to simulate large-amplitude motion needed for analysis of sediment-scour problems,and,thus,its application normally is restricted to small-amplitude cases to prevent computational divergence due to mesh deterioration.The proposed simple,moving-mesh technique in OpenFOAM is implemented to overcome the shortcomings of the conventional automatic mesh-motion techniques in handling large-amplitude moving geometries.The model is used to simulate a simple case of prescribed boundary motion,a previous experiment in the literature,and a new laboratory experiment for local scour due to submerged wall jets.The results are compared with both the experimental and other numerical results.The comparisons demonstrate that the proposed model has the novel advantage of allowing for more severe topographic variations,and can provide more reliable predictions for the key characteristics and evolution of the bed profiles in wall jet scour problems.Furthermore,to improve the practice of modeling wall jet scour,various turbulence modeling approaches and bedload equations also are evaluated and compared.  相似文献   

Evaluation of a Movie Theater Advertisement Campaign to Promote Behaviors that Prevent Spread of Aquatic Invasive Species     

Bret R. Shaw  Allison Howell  Ken Genskow 《社会与自然资源》2014,27(7):768-776

One of the primary causes of the spread of aquatic invasive species (AIS) is boaters and anglers who move between bodies of water. Engaging with recreational boaters and anglers to encourage preventative behaviors is crucial for managing the spread of AIS. The use of cinema advertising for disseminating pro-environmental messages is a relatively novel and understudied outreach strategy. To explore this approach, an AIS-related public service announcement was placed in the preshow advertising at a movie theater in north central Wisconsin. Movie patrons were surveyed as they left the theater to determine demographic, AIS awareness, advertising exposure, and recall information. The results of this study suggest movie theater advertising is a potentially efficacious medium for pro-environmental outreach efforts.  相似文献   

Detecting subcanopy invasive plant species in tropical rainforest by integrating optical and microwave (InSAR/PolInSAR) remote sensing data,and a decision tree algorithm     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

In this paper, we propose a decision tree algorithm to characterize spatial extent and spectral features of invasive plant species (i.e., guava, Madagascar cardamom, and Molucca raspberry) in tropical rainforests by integrating datasets from passive and active remote sensing sensors. The decision tree algorithm is based on a number of input variables including matching score and infeasibility images from Mixture Tuned Matched Filtering (MTMF), land-cover maps, tree height information derived from high resolution stereo imagery, polarimetric feature images, Radar Forest Degradation Index (RFDI), polarimetric and InSAR coherence and phase difference images. Spatial distributions of the study organisms are mapped using pixel-based Winner-Takes-All (WTA) algorithm, object oriented feature extraction, spectral unmixing, and compared with the newly developed decision tree approach. Our results show that the InSAR phase difference and PolInSAR HH–VV coherence images of L-band PALSAR data are the most important variables following the MTMF outputs in mapping subcanopy invasive plant species in tropical rainforest. We also show that the three types of invasive plants alone occupy about 17.6% of the Betampona Nature Reserve (BNR) while mixed forest, shrubland and grassland areas are summed to 11.9% of the reserve. This work presents the first systematic attempt to evaluate forest degradation, habitat quality and invasive plant statistics in the BNR, and provides significant insights as to management strategies for the control of invasive plants and conversation in the reserve.  相似文献