基于三维扫描模型的兵马俑足踝有限元分析

利用三维扫描技术获取兵马俑残片的三维点云数据,结合Geomagic Studio和Hypermesh建立高精度的兵马俑足踝残片三维实体网格模型。通过基于ABAQUS的重力作用下的有限元分析,研究足踝部分的Von Mises应力和变形特征,以确定足踝处的受力薄弱部位。为进一步探究模型各残片的最佳点云简化比例,采用点云简化模型进行相同工况的有限元分析,以验证点云简化的可靠性。结果表明:结构在重力作用下可保持安全稳定的状态,相对薄弱部位位于左腿足踝处;对于大部分残片,其最佳简化比例在60%～70%,简化后可有效缩短模型实体化处理时间;采用简化模型得到的有限元结果,其最大Mises应力相比于原始模型的误差小于15%,且应力云图和变形图形状接近,模型简化具有可靠性。     

Mortality date estimation using fetal pronghorn remains

Pronghorn (Antilocapra americana) fetal remains are sometimes recovered from archaeological contexts. Pronghorn have consistent reproductive schedules so their remains may provide information on seasonality of site occupation and number of mortality events. To investigate the reliability of fetal remains for seasonality and mortality event assessment, bone size and tooth eruption were measured in a sample of modern fetal pronghorn remains with known mortality dates. Results indicate a strong correlation between bone size and mortality date, but no significant correlation between tooth eruption level and mortality date. Fetal bone size was used to estimate a late April or early May mortality date at both the Oyster Ridge (48UT35) and Trappers Point (48SU1006) archaeological sites. The number of mortality events at Trappers Point was also investigated. Copyright © 2007 John Wiley & Sons, Ltd.     

A Modified Capacity Spectrum Method with Direct Calculation of Seismic Intensity of Points on Capacity Curve

A direct methodology for solving the seismic intensity of each point on the capacity curve is proposed. By utilizing the procedure, a continuous curve between the structural response and the seismic intensity, the structural response function, can be easily generated. Unlike previous procedures that search for the performance point of a determined seismic intensity, the proposed methodology easily draws the full curve without iterations. The procedure is applicable to both a smooth design spectrum and an actual response spectrum. Examples indicate the methodology is accurate and fast, and convenient to be combined with existing procedures, such as Modal Pushover Analysis.     

Poverty Point Objects Reconsidered

In this paper we examine the enigmatic but plentiful hand-molded, baked-clay objects known as Poverty Point Objects (PPOs) from a number of different facets. Although the vast majority of these Terminal Archaic artifacts are found in the Lower Mississippi Valley, they also are found at sites as far north as Clarksville, Indiana, and as far east as the Atlantic Coast of Florida. Although most archaeologists generally assume PPOs were used primarily for roasting food, we consider a variety of other possible functions, including their use in boiling water and as symbolic tokens linking the far-flung Poverty Point culture area. We demonstrate that even though a few other archaeological cultures in the world used round clay balls for cooking, the Poverty Point culture was unique in the care, variety, and standardized forms of its baked-clay objects. We discuss the various PPO types and their possible functions in nine distinct regions in the southeastern United States and, based on our thin-section analyses of 66 samples, we demonstrate that PPOs circulated among different sites in these regions.     

The Mechanism and Kinetics of In Situ Conservation of Iron Cannon on Shipwreck Sites

Analysis of the pre‐disturbance values of the in situ corrosion parameters on historic iron shipwrecks and artefacts has established that the arithmetic product of the pH and corrosion potential is dependent on the burial environment and provides a unique insight into the objects' state of decay. The value of the product changes during in situ conservation treatment with sacrificial anodes, and reaches a minimum at which point the treatment is completed. Treatment times vary with water‐depth, being faster on shallower sites and shorter for more extensively corroded artefacts. The model was developed using data from the Duart Point wreck (1653), the Monitor‐styled warship HMVS Cerberus (1926) and a series of wrecks in Australia and the USA.     

Addressing seasonal site use through ancient DNA species identification of Pacific salmon at Dionisio Point,Galiano Island,British Columbia

We use ancient DNA analysis to identify Pacific salmon vertebrae to species in order to provide an important line of evidence that helps to establish the timing of seasonal residence at a Pacific Northwest Coast village site. Ancient DNA results from House 2 at Dionisio Point allow a characterization of the salmon fishery. Ten of eleven randomly selected smaller-sized salmon vertebrae were positively identified as sockeye salmon (Oncorhynchus nerka) while only a single pink salmon (Oncorhynchus gorbuscha) was identified. Of the 322 whole salmon vertebrae identified from House 2 occupation deposits during zooarchaeological analysis, 58 percent measure less than 8.0 mm and 70 percent are less than 8.5 mm in maximum transverse diameter. Together with documented aspects of the material record from Dionisio Point, most notably the vertebrate fauna from House 2, the indication that sockeye was the primary focus of the Dionisio Point salmon fishery suggests the site was inhabited during the spring and summer. This approach to the identification of season-specific site occupation has the potential for application over much of the Northeast Pacific.     

Formal analyses and functional accounts of groundstone “plummets” from Poverty Point, Louisiana

Groundstone plummets of magnetite or hematite are commonly found artifacts of the Late Archaic period in Louisiana. While often assumed to have functioned as weights for fishnets or as thrown objects used to catch waterfowl, relatively little empirical evidence has been generated to explain their form and features relative to hypothesized performance in prehistoric behavior. To address this deficiency, we provide a morphometric analysis of the variability in plummet shape as a means for studying the performance constraints inherent to their use. Based on our analyses, we find that plummet form is well explained as a component of weighted looms, supporting the early use weaving technology in the Late Archaic of Eastern North America.     

Field Measurements and Numerical Simulation of Debris Flows from Dolomite Slopes Destabilized during the 2005 Kashmir Earthquake,Pakistan

A devastating earthquake occurred in Kashmir, Pakistan on October 8, 2005. This earthquake resulted from reactivation of a known active fault later defined as the Balakot–Bagh fault, which caused widespread slope failure throughout its stretch, particularly around Muzaffarabad, the provincial capital of Azad Jammu and Kashmir. This slope failure resulted in a huge amount of debris material which flows in deeply incised creeks during monsoon and hits the inhabitants along the valley in Muzaffarabad. Two GPS measurements are carried out along with channel morphometric parameters and observed changes to investigate the effect of debris flows along these creeks during monsoon. Other than the physical measurements, actual debris flow is simulated using the Depth Average Material Point Method (DAMPM) after carrying out parametric study and calibrating the model for subject topographical and geological settings. The generalized effect of different input parameters of the model on debris flow runout features is studied and discussed in detail. After ensuring validation of the numerical tool, the contribution of a single closed-type check dam to decrease runout intensity to its downstream reach is also investigated for different locations to obtain optimized selection.     

Tetrahedron baked-clay objects from an early woodland context at the Jaketown site,Mississippi

Excavations undertaken in 1951 at the Jaketown site revealed a dense deposit of fragmented and intact pyramid-shaped baked-clay objects (BCOs) at the base of Mound A. This deposit was associated with the site’s Early Woodland component. Recent fieldwork at Jaketown also encountered the same tetrahedron deposit and identified an additional and distinct pit feature filled with the objects. In this article, we present the results of analyses that examine the production, composition, chronology, and function of these enigmatic baked-clay artifacts. Following a hiatus associated with massive flooding in the Mississippi Valley ca. 3200–2850 cal B.P., Jaketown was re-occupied by people who shared ceramic affinities with groups to the south and to the east and, who like many contemporaries, used BCOs as a part of their cooking technology. The tetrahedron deposit represents one of the earliest dated Tchula contexts at ca. 2600 cal B.P., and was used over a short time for a social purpose that brought populations together for food consumption as a means of encouraging cooperation.     

从"第四点计划"到和平队:美国对发展中国家援助理论与实践的转变

肯尼迪政府组建和平队,以志愿者的形式,向不发达国家提供所谓“中等人力资源”,进行技术援助,实际上是对战后美国对外援助工作反思的结果,同时也为美国对外援助注入了新的内容。它所涉及的更为深层的考虑,则是广大不发达国家未来的发展道路问题,即这些国家以什么样的方式实现现代化,是以美国为代表的资本主义发展模式,还是以苏联或中国为代表的社会主义发展模式。肯尼迪政府希望,通过和平队的工作,向第三世界国家展示美国的现代化经验和技术,诱导第三世界国家走美国式的现代化道路。