中国城市(包括辖县)的工业职能分类——理论、方法和结果   总被引：18，自引：0，他引：18  

周一星  R.布雷德肖 《地理学报》1988,(4)

在城市发展的经济基础理论的指导下,作者提出城市工业职能的概念包括城市的专业化部门、职能强度和职能规模三个要素。城市工业职能分类就是按照上述三要素的相似性和差异性对城市进行分类。本研究曾采用主因素分析、聚类分析和纳尔逊的统计分析等多种方法。最后以沃德误差法的聚类分析结果作为分类的基础,稍加修正,并以纳尔逊法分析结果作补充。中国1984年的295个城市被分成三个大类、十九个亚类和五十四个职能组。  相似文献   

MAVIS–an upper crustal seismic refraction experiment in the Midland Valley of Scotland     

M. C. Dentith  J. Hall 《Geophysical Journal International》1989,99(3):627-643

The results of the Midland Valley Investigation by Seismology (MAVIS) are described. The experiment consists of three refraction profiles of between 80 and 100 km length across the Upper Palaeozoic basins of the Scottish Midland Valley.
Three refractors are recognized, thus defining four upper crustal layers. The top two layers are interpreted as Carboniferous plus Upper Old Red Sandstone, and Lower Old Red Sandstone plus Lower Palaeozoic. The structure of the refractor, an unconformity, separating the two layers mirrors surface structure. Deeper refractors, associated with Midland Valley crystalline basement, show no correlation with surface structure. The MAVIS survey allows the refinement of earlier gross interpretation of upper crustal structure in the Midland Valley, but confirms the existence of anomalously shallow (6.4 km s^–1) basement, and shows, in conjunction with results of previous work, that a large area of the central and southern Midland Valley is characterized by one velocity signature, probably indicative of a single terrane.  相似文献   

An explanation for USGS Station 6 record, 1979 Imperial Valley earthquake: a caustic induced by a sedimentary wedge     

J. A. Rial  V. Pereyra  G. L. Wojcik 《Geophysical Journal International》1986,84(2):257-278

Summary. The largest earthquake-induced acceleration yet recorded occurred at the United States Geological Survey's (USGS) Strong Motion Array Station 6 during the 1979 October 15, Imperial Valley, California earthquake. This large acceleration (1.74 g, vertical component) is anomalously strong considering the low magnitude of the event ( M = 6.4), and the fact that receivers in the immediate neighbourhood of Station 6 recorded much lower accelerations. Previous studies of the records by other investigators have suggested a number of explanations for the anomaly, several of which implicate the near-receiver geological structure.
We present a detailed time and frequency domain analysis of the acceleration records at Stations 6, 5, 7, 8 and Diff Array to suggest that the anomalous acceleration is the consequence of the focusing of the incoming body waves by the lens-like effect of the sedimentary wedge between Imperial Valley and Brawley faults. The analyses include a detailed comparison of observed particle motions between neighbouring stations. Narrow band-pass filtered particle motions at Station 6 reveal the interaction of multipath arrivals as well as the frequency-dependent interference between them. Three-dimensional ray tracing experiments confirm the fact that the faulted sedimentary wedge is capable of focusing P -waves near Station 6. The interpretation that best combines theoretical and observed results is that amplification was due to the formation of an elliptic umbilic caustic with focus near the surface.  相似文献   

INDUSTRY-GOVERNMENT-ACADEMIC COOPERATION: POSSIBLE BENEFITS FOR GEOGRAPHY     

Glen A. Marotz 《The Professional geographer》1983,35(4):407-415

Some current developments outside of academe and their relationship to geography are presented; comments are based on experience from a three year National Science Foundation Faculty Fellowship. Suggestions for improving our educational efforts are discussed, including new roles for the AAG, changes in teaching methods, establishment of advisory boards, and closer ties with industry and government.  相似文献   

Optimization of grid-drilling using computer simulation     

J. William Miller Jr. 《Mathematical Geology》1991,23(2):201-218

A computer simulation method has been developed to find efficient drilling grids for mineral deposits. A well-known ore deposit is used as a model to develop an efficient pattern for undiscovered ore bodies in the same area or in other prospects where similar geometry is suspected. The model for this study is the Austinville, Virginia deposit, a Mississippi Valley-type deposit composed of 17 ore bodies totaling 34 million short tons (30 million metric tons). The method employs a computer program that simulates drilling the model deposit with different patterns, including various levels of follow-up drilling. Follow-up holes are drilled in fences at one half the original spacing around holes in the grid that show ore-grade mineralization. Each pattern is drilled 100 times from random starting locations to provide a range of outcomes of drilling, including the best, worst, and most likely. For this study, patterns of 100 drill holes were composed of 10 fences spaced 1000–5000 feet (305–1524 m) apart, each with 10 holes spaced 200–1000 feet (61–305 m) apart. In all, 25 grids were used with zero to three levels of follow-up drilling. The 600/2000 grid, with drill holes spaced 600 feet (183 m) apart in fences spaced 2000 feet (610 m) apart, was compared with the 200/5000 grid because they represented contrasting outcomes. The 600/2000 grid penetrated many ore bodies consistently but with few multiple hits to individual ore bodies; whereas the 200/5000 grid inconsistently penetrated few ore bodies with many multiple hits. The 600/2000 grid was more efficient than the 200/5000 grid at hitting large ore bodies of 1,000,000 short tons or greater (900,000 metric tons or greater) and was made more effective by adding one cycle of follow-up drilling. The 600/2000 grid had a 97% chance of hitting one or more large ore bodies with at least one drill hole per ore body, and the 200/5000 grid had a 64% chance. Once hit, there was an 82% chance that the largest ore body would be penetrated by three or more holes when using the 600/2000 grid and an 88% chance using the 200/5000 grid.  相似文献   

Do benthic biofilters contribute to sustainability and restoration of the benthic environment impacted by offshore cage finfish aquaculture?     

Aguado-Giménez F  Piedecausa MA  Carrasco C  Gutiérrez JM  Aliaga V  García-García B 《Marine pollution bulletin》2011,62(8):1714-1724

Benthic biofilters were deployed under a cage fish farm and in two reference locations to assess the influence of the farm on the biofilters and the surroundings, as well as to verify the usefulness of this technology as a mitigation tool. The biofilters underneath the farm recruited a fouling community practically identical to that of the control biofilters, which included a variety of trophic strategies. The former showed a higher ¹⁵N enrichment, indicating that fouling beneath the farm was benefiting from the farm waste. The waste retention efficiency was low (0.02 g N m⁻² month⁻¹) beneath the farm. Benthic biofilters aggregated demersal wild fish around and within them. Pelagic wild fish also frequently used the biofilters beneath the farm, forming compact shoals around them. The increased complexity of the habitat below the fish farm enhanced biodiversity, but this improvement did not lead to the recovery of the sediments around the biofilters.  相似文献   

Mesofossil flora from the Late Cretaceous of New Zealand     

David J. Cantrill  Livia Wanntorp  Andrew N. Drinnan 《Cretaceous Research》2011,32(2):164-173

This study presents the first report of mesofossils of flowers, fruits and seeds found in the Cretaceous of New Zealand. The specimens were recovered from the Late Cretaceous (Maastrichtian, ca. 70 Ma) at Kai Point Mine, South Island in a sequence of floodplain sediments sampled just below the Barclay Coal Seam. Angiosperm flowers, fruits and seeds occur in the sample. The most common form is an actinomorphic flower with two whorls of three tepals. Anther bases are preserved and the ovary develops into a drupe, all features that are consistent with placement in the Lauraceae. Reproductive structures including seeds of conifers are also described, with some allied to the Podocarpaceae. This contrasts with interpretations of the flora based on macrofossils that indicate abundant Araucariaceae and highlights the different perspectives that mesofossil floras give to any assemblage. The results of the present study support a Late Cretaceous flora at this site mainly dominated by conifers with affinities to Podocarpaceae but also including lauraceous angiosperms.  相似文献   

Bioavailability and toxicity of aluminium in a model planktonic food chain (Chlamydomonas-Daphnia) at neutral pH     

P. Quiroz-Vázquez  K.N. White 《Limnologica》2010,40(3):269-709

Dissolved aluminium (Al) is generally at low concentrations in neutral freshwater due to its insolubility. However, a fall in pH resulting from acid deposition and mining alters the mobility of Al and so entry to adjacent neutral waters. The present study examines the environmental behaviour, cell-associated surface adsorption/absorption and toxicity of Al at neutral pH to the alga Chlamydomonas gigantea in the presence and absence of the key Al-binding ligand silica. We then examined transfer of Al from C. gigantea to the planktonic crustacean Daphnia pulex. Finally, the effect of Al on the elemental composition (and hence nutritional value) of the two organisms was compared to unexposed controls. C. gigantea increased the amount of Al in the algal culture medium. Binding of Al to extracellular glycoprotein is probably the reason why only one-third of the biosorbed Al was absorbed (accumulated) by C. gigantea. Aluminium concentrations between 50 and 500 μg l⁻¹ reduced growth of C. gigantea at 16 days exposure to the metal. Silica reduced biosorption, accumulation and toxicity of Al by C. gigantea. The concentration of Al in D. pulex fed Al-contaminated C. gigantea for 16 days did not differ from those fed alga grown in the absence of added Al. C. gigantea contaminated with Al contained less sulphur, magnesium, potassium and sodium although only sulphur fell in D. pulex subsequently fed the contaminated alga. Chloride, calcium, iron and silicon were significantly higher in D. pulex.  相似文献   

Preliminary model of nitrogen loads from southern bluefin tuna aquaculture   总被引：1，自引：0，他引：1  

Fernandes M  Lauer P  Cheshire A  Angove M 《Marine pollution bulletin》2007,54(9):1321-1332

Farming of wild tuna in coastal areas is a relatively new aquaculture industry and little is known about the magnitude of nutrient discharges to the environment. In this work we present a preliminary model of nitrogen loads from southern bluefin tuna (Thunnus maccoyii) aquaculture in lower Spencer Gulf, South Australia. The model was developed based on feed inputs, estimates of fish metabolism and environmental data. Two pens were monitored over a full grow-out season to determine nitrogen sedimentation fluxes, remineralization at the sediment-water interface and accumulation in the sediments. The model suggests that the high metabolic rates of tuna lead to low retention of nitrogen in fish tissues (7-12% of feed inputs) and high environmental losses (260-502kg Ntonne(-1) growth). Considering Australian annual production of 4380tonnes over initial stocked biomass, total loads can reach 1137tonnes N per year, 86-92% lost as dissolved wastes. The nature of wastes suggests low localized impacts at current stocking densities and holding periods.  相似文献   

大数据环境下地理信息产业发展的几点思考     

周顺平  徐枫 《测绘软科学研究》2014,(1):45-50

大数据背景下地理信息产业的发展有了新的驱动力,通过思考这种驱动力对产业发展可能产生的影响,分析指出了大数据在地理信息产业中的中心地位和重要价值,综述了大数据给地理信息产业的涵盖范围、关键技术和服务模式所带来的重大变革,探讨了大数据技术对于GIS传统技术优化升级的几个着力点,并剖析了大数据技术在地理信息产业的相关应用中所面临的制约因素。  相似文献