首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到16条相似文献,搜索用时 15 毫秒
1.
This article describes a new model that simulates the spread of post-earthquake urban fires. Adapting and integrating compartment fire models, this new model explicitly represents: (1) the evolution of fire within a room or roof; (2) room-to-room spread within a building through doorways, by burning through walls and ceilings, and by leapfrogging between windows; and (3) building-to-building spread by window flame impingement; radiation from window flames, room gas, and roof flames; and branding. The model can be used to explore how much, how fast, where, and by what modes fires will spread, and what factors influence fire spread.  相似文献   

2.
This article introduces a new time-varying model to generate synthetic non-stationary acceleration records using the modified Kanaii-Tajimi model with time-variant parameters. The proposed method can capture two different dominant frequencies per time which makes it suitable for synthesizing the near-field no-pulse earthquake records. A number of closed-form relationships are developed to describe the frequency dependent time-domain level crossings of the simulated records under white noise excitation. The model parameters are optimized using the crossing and Arias intensity properties of the synthetic and target records. The efficiency of the proposed model is demonstrated using a data base of 106 near-field records.  相似文献   

3.
As in traditional societies today ancient societies probably selected different fuels to meet specific heat requirements. Char and ash, the end products of fire, are often found in abundance in archaeological contexts. These end products can provide information regarding (i) the original fuel resource and type, (ii) the characteristics of the fire and (iii) combined with other archaeological evidence shed further light on possible socio-economic activity(-ies) associated with that fire. The three main fuel resources would have been (i) modern vegetation, (ii) fossil fuel and (iii) animal by-products. Local availability and abundance would have influenced the choice made.In this study an experimental approach was adopted to try and distinguish between the three different fuel resources that are known to have been used by ancient societies (and continue to be used by traditional societies today) from their char and ash remains to help determine original fuel-type and understand the relative heating properties. For this end one fuel-type from each fuel resource listed above, namely wood, peat and cow dung, was chosen.  相似文献   

4.
Assessing the impact of prehistoric sites on their local environment is difficult to accomplish with standard archaeological methods. Simulation modeling offers a solution to this issue, but it is first necessary to delimit a site catchment, or “zone of impact”, around archaeological sites in which to carry out human–environment interaction modeling. To that end, I have developed a new method for GIS-based catchment reconstruction and distilled it into a custom module (r.catchment) for GRASS GIS, which calculates catchments of a given area based on anisotropic travel costs from a point of origin. One method of applying this new module in exploratory catchment modeling is discussed using the pastoral economy of the Late Neolithic period in Wadi Ziqlâb, Northern Jordan as a test case. A model of Late Neolithic herding economy and ecology is constructed, which combines data from archaeology, phytogeography, range science, agronomy, and ethnohistory. Four sizes of pastoral catchments are then derived using r.catchment, and the herd ecology model is used to estimate the stocking-rate (carrying capacity) of mixed goat and sheep herds for each catchment. The human populations these herd numbers could support (between 3 and 630 people in the Wadi) are then compared with human population estimates derived from household architectural analyses (between 18 and 54 people in the Wadi) to determine the most probable catchment configurations. The results indicate that the most probable zone of impact around the known Late Neolithic sites in Wadi Ziqlâb was somewhere between 9 and 20 square kilometers, delineated by 3 and 4.5 km pasture radii respectively.  相似文献   

5.
The role of natural processes in the formation of the Bed I and II sites at Olduvai Gorge (Tanzania) remains the subject of much debate, five decades after their original excavation. Preferred orientation of items is indicative of water disturbance, but compass bearings were not available in Mary Leakey's (1971) study. Using GIS methods, we have vectorized maps from 1960s excavations at Olduvai, and applied a range of statistical techniques to calculate items strike. The GIS analysis suggests strongly preferred orientation patterns in Bed I, and more heterogeneous angular histograms in Bed II. Two complementary lines of evidence support these results. Firstly, modelling of potential mapping errors provides a large interval of confidence for preferred orientation patterns. Second, the GIS study was extended to photographs of the earlier excavations and to maps from recent fieldwork at Olduvai; both yielded patterned arrangement of lithics and bones, and are consistent with results based on the analysis of the 1960s maps, i.e. a large number of the Bed I and II assemblages are preferentially oriented. These results highlight the potential of GIS applications to the analysis of imagery in Stone Age studies, and bear important implications for the understanding of the role of natural agents in site formation processes at Olduvai.  相似文献   

6.
20世纪的中国史学有两大流派,即实证主义史学和马克思主义史学。韩儒林先生是一位掌握实证史学方法、努力用马克思主义观点解释历史现象的史学家。他在元史和边疆史地研究方面取得了丰硕成就,成为一代学术大师。  相似文献   

7.
Provenance studies can tell us which sources of lithic raw material were used in the past, but can they tell us why? After all, many factors can have entered into a person’s choice to use one source rather than another. Those factors can be grouped into two categories, the geologic/geographic characteristics of the source itself (quality, abundance, size of pieces, etc.), and the human factors (direction of travel, time available, social restrictions, etc.). This paper demonstrates how the geologic/geographic characteristics can be quantified and calculated together to give one value, the attractiveness of the source, which can then be used in a gravity model approach to predict which sources ‘should’ have been used more than others. Deviations from the predicted pattern point to situations where the human factors were of greater or lesser importance. The values are also used to delineate geographical areas within which particular sources would be likely to be used (‘areas of influence’), which gives us a useful new way of understanding the landscape within which the prehistoric group lived.  相似文献   

8.
The recent advances in computer-based modelling of pollen dispersal and deposition through the POLLANDCAL (POLlen-LANDscape CALibration) network have enabled landscape simulations to be constructed and tested, both to validate the theoretical models, and to validate modelled landscapes using empirical data. This paper presents the first attempt to develop simulations based on real landscapes, by placing distinct vegetation communities using reclassified digital elevation models (combined slope and altitude data). The approach is tested by modelling a palynological signature for the expansion of mixed agriculture into an upland margin, and the results for 49 simulated pollen deposition sites, across an altitudinal range for a series of landscape scenarios, is compared with existing empirical data. The broad trends within the two data sets are in general accordance, and variation between them is attributed to local variation in vegetation heterogeneity. The results show that the POLLANDCAL models offer a new and exciting method by which sub-fossil pollen assemblages can be examined, theoretical models of landscape use tested, and will offer a significant tool in the interpretation of environmental data in archaeology, in particular when combined with GIS-based models of the physical environment.  相似文献   

9.
The taphonomic study of Petit-Bost, Croix-de-Canard and Cantalouette II, three Palaeolithic sites that were recently discovered near Périgueux and Bergerac (Dordogne, France) in a colluvial context, has enlightened the difficulty of adequately appreciating the relative role of cultural and natural processes in site spatial patterning. Periglacial solifluction was thought to have played a significant role in site formation. Because the nature of the modifications induced by solifluction was still poorly understood, a simulation was made using data of soil movement recorded at La Mortice (French Southern Alps, 3100 m in elevation) in a modern periglacial environment. The results show that, for a knapping location, the first steps of deformation are typified both by a downslope translation of the location center and by an anisotropic diffusion of the artifacts. The knapping spot becomes elongated along the slope, with a dense relic concentration of artifacts in the upslope portion. This type of pattern has been obtained after 100–200 years of simulated displacement according to the climatic and soil conditions that characterise the La Mortice site. The ultimate stages of deformation show that the artifact distribution tends to homogenise on larger surfaces and resemble a random distribution. The ability of the simulated patterns to closely fit those observed in archaeological contexts is evaluated at three sites from Southwestern France. At Petit-Bost, the hypothesis of limited solifluction explains accurately the association of both cultural (artifact concentrations) and natural (artifact preferred orientation) features. At Croix-de-Canard, long-term solifluction can be proposed. By contrast, the simulated patterns do not describe the structures observed on the steeper slopes at Cantalouette II, where the knapping spot transforms into distinct solifluction lobes.  相似文献   

10.
从传道之师到大学教员:现代学术研究职业化趋向   总被引:1,自引:0,他引:1  
左玉河 《安徽史学》2007,3(1):47-53
近代知识人的学术研究出现了职业化趋向.所谓学术职业化,就是将学术研究作为一种谋生的职业,学术研究者成为职业学者.随着清末民初现代学术教育体制的建立、科学家群体的形成、专门科研机构的创建、科研成就的取得与科学交流系统的建成,近代学者的社会职业角色开始形成,学术研究逐渐呈现一种职业化趋向,不仅出现了以知识生产和传授为谋生手段的社会职业,而且这种学术研究职业为一定的制度所保障.学术职业化是现代学术体制的重要特征.职业化学者被纳入近代分科化、专门化之学术体制中.现代学术体制以有形之场地和无形之规范,直接限定着学者之学术活动,并间接影响着学者之学术思想.职业化之知识人多遵从现代学术体制从事知识生产,甚至将知识作为稻粱谋,而不再执着于思想之道.这是职业化体制下学术研究的特点及知识人的特色.  相似文献   

11.
Abstract

The disparity between men and women in science is a hot topic in gender studies and a relevant target of scientific policies. The leaky pipeline metaphor illustrates the decreasing number of women along senior positions in academia; however many questions remain unanswered. What factors progressively diminish the number of women in scientific careers and why do they appear to be less successful than their male colleagues? In order to discover new insight, this work compares men’s and women’s career paths by taking into account academic and family milestones achieved throughout the life course. An innovative and interdisciplinary methodology (from bibliometrics, statistics, and sociology) has been constructed to examine men’s and women’s trajectories. Findings display gender differences in scientists’ trajectories. The evolution of scientists’ careers reveals linear careers for males, whilst women develop non-linear careers. Motherhood emerges as a problem for developing linear careers. And collegiate decisions of gatekeepers seem to systematically disfavour women scientists’ careers.  相似文献   

12.
程圩  隋丽娜 《旅游科学》2007,21(1):7-12
本项研究调查了近千名长三角地区潜在游客对韩国旅游形象的感知,运用多元统计技术手段分析探讨了刺激因素、个体因素和形象感知三者之间的关系,研究表明,刺激因素(一手信源和二手信源)与个体因素(旅游动机和社会人口统计特征)差异会影响旅游形象的感知,是旅游形象的前因变量.  相似文献   

13.
Identifying tools by means of morphological attributes are widely used in lithic studies to categorize retouched artifacts from different archaeological periods. This procedure has facilitated the exchange of information between separate researchers and has improved the comparison of different assemblages. In these classifications, denticulates and notched tools have been regularly interpreted as analogues and chronologically unvaried in different and vast territories. Based on the definitions developed by Bordes, the denticulate category has become a catchall for any kind of tool bearing concavities. In this paper a new quantitative approach to the classification of denticulates and notched tools is proposed. The new methodology is based on measuring the length of notches and their distribution on the perimeter of the blank. Analyzing the lithic series of the Abric Romaní rock-shelter (Spain) and Grotta Maggiore di San Bernardino (Italy) led to the identification of 11 redundant forms: eight denticulates and three notched tools. Moreover, the application of Kuhn’s Geometric Index of Unifacial Reduction brought local manufacturing trends to light, calling into question the presumed geographical uniformity of these categories of artifacts.  相似文献   

14.
This study investigates preferences of visitors to the Discovery Museum (in North East England) with respect to opportunities to develop social capital. The extent to which museums generate social capital is largely unknown, but museums have potential opportunities to develop this type of capital. This study uses a stated preference choice experiment (CE) technique to estimate museum visitor preferences towards social capital opportunities. The findings indicate that visitors have a preference for visiting a museum with another individual(s); and that the provision of participatory activities, extended opening hours and locally related displays would generate more social capital among visitors and in society.  相似文献   

15.
A subterranean, stone‐built, sediment‐filled culvert discovered during excavations at the Agora (Athens, Greece) was dated to the Roman period on the basis of its characteristic construction and associated finds, including coins. The location of the culvert relative to other adjacent watercourses and an ancient river bed suggested that the structure was a sewer. This was confirmed through a multi‐molecular biomarker approach based on analysis of the bile acids associated with sediment filling the sewer, using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The acid fraction contained predominantly deoxycholic and lithocholic acids, while the neutral steroid fraction comprised a complex mixture of Δ5 sterol and 5β‐ and 5α‐stanols, dominated by coprostanol, suggesting the presence of faecal matter of predominantly human origin. The concentrations of neutral and acidic faecal biomarkers were observed to vary in tandem, with the highest concentrations being found in the sediment at the base of the fill in the culvert. A reduction in concentration occurred with decreasing depth of the fill, with concentrations in the uppermost samples being little different from control samples of sediment taken beyond the confines of the culvert. The enhanced concentration of bile acids relative to 5β‐stanols compared with fresh human faeces must reflect the enhanced diagenetic stability of the former, thereby making bile acids the possibly preferred biomarker for this type of study. The quantitative data obtained suggest that the culvert fell rapidly out of use, possibly coinciding with the Slavic incursion in AD 582–3.  相似文献   

16.
Boron isotope ratios of reservoir minerals and fluids can be a useful geothermometer and monitor of fluid–rock interactions. In Cold Lake oil sands of northern Alberta, there is a large variation in δ11B of the produced waters generated during steam injection and recovery of oil and water. The higher temperature waters (~ 200 °C) have isotopically light δ11B values (+ 3‰ to + 14‰) and high B contents (~150 p.p.m.). It is inferred that the range of δ11B values of the hydrothermal fluids results from reaction with the reservoir rock, and is a function of the temperature of the fluid–rock interaction. The distinct B geochemistry of the produced waters can be used to show that there is no detectable mixing of the oil recovery waters with the regional formation waters or shallow groundwater aquifers containing potable water. Examination of B isotope ratios of reservoir minerals, before and after steam injection, allows the evaluation of sources of B in the reservoir. The only significant phase containing B is pumice. It shows generally positive δ11B values before steam injection and negative values after steam, with δ11B as low as ? 28‰. Other possibly reactive phases include clay minerals and organic matter, but their abundance is not great enough to impact on the isotopic composition of the produced waters. This information makes it possible to evaluate the boron isotope fractionation equation derived from experimental data ( Williams LB (2000) Boron isotope geochemistry during burial diagenesis. PhD Dissertation. The University of Calgary, Alberta, Canada; Williams LB, Hervig RL, Holloway JR, Hutcheon I (2001a) Boron isotope geochemistry during diagenesis: Part 1. Experimental determination of fractionation during illitization of smectite. Geochimica et Cosmochimica Acta, in press). The results show that the fractionation curve predicts the difference between δ11B of the pumice and hydrothermal fluids in the Cold Lake reservoir. This not only indicates that the reservoir fluids have approached boron isotope equilibrium with the reservoir rock, but also shows that B isotopes provide a useful geothermometer for hydrothermally stimulated oil reservoirs.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号