Green cities? Urbanization,trade, and the environment

Is urbanization good for the environment? This paper establishes a simple core–periphery model with monocentric cities, which comprises key forces that shape the structure and interrelation of cities to study the impact of the urban evolution on the environment. We focus on global warming and the potential of unfettered market forces to economize on emissions. The model parameters are chosen to match the dichotomy between average “large” and “small” cities in the urban geography of the United States, and the sectoral greenhouse gas emissions recorded for the United States. Based on numerical analyzes we find that a forced switch to a system with equally sized cities reduces total emissions. Second, any city driver which pronounces the asymmetry between the core and the periphery drives up emissions in the total city system, too, and the endogenous adjustment of the urban system accounts for the bulk of the change in emissions. Third, none of the city drivers gives rise to an urban environmental Kuznets curve according to our numerical simulations. Finally, the welfare‐maximizing allocation tends to involve dispersion of cities and the more so the higher is the marginal damage from pollution.     

Lichenometric constraints on the age of the Huashan Grottoes, East China

Lichenometry is a method of dating that has been widely used in glaciated areas for determining the minimum age of exposure of a geomorphic landform during the late Holocene. This paper presents a regional calibration data set of lichen thallus sizes versus rock surface ages for the Huashan area, East China, based on measurements of yellow-green Rhizocarpon lichens on the known-age substrates at eight sites. An empirical relationship between thallus sizes and rock surface ages was established using both the traditional regression and the Bayesian approaches. Using the Bayesian calibration, the minimum age of the Huashan Grottoes was dated from 450 ± 60 to 330 ± 60 years ago, corresponding to the late Ming Dynasty (AD 1477–1632). These dates are generally consistent with those predicted from the regression-based linear growth curve. Our results suggest that applications of this technique can be safely extended to the non-glaciated areas.     

14C测定判别武王克商年代范围始末

武王克商年代是我国古代编年中的一个关键点,近年来^14C测定技术有了重要发展,我国^14C测年界在此基础上探讨了^14C方法应用于商周历史纪年的希望。1996年夏商周断代工程正式立项,利用^14C测定判别武王克商年代范围的任务得以实施。1998年初两个常规^14C实验室以3‰测定精度,前后开始对陕西丰镐遗址出土样品^14C测定,并于1998年10月6－7日先后公布了^14C数据,提出武王克商代范围应判别在公元前1050－1020年间。1998年下半年AMS室开始测定。三室测定数据对比结果基本相合,利用殷墟,琉璃河等遗址出土的样品系列作^14C测定得出的结果,与上述年代范围一致。1998年11月30日公布了天计算结果,与测定结果不谋而合,经多方面反复验证,历时近二年,都无法动摇已有的判别结果,具有较高的可信度。     

青铜文物缓蚀剂效率及封护剂抗腐蚀能力的比较研究

为评价青铜文物缓蚀剂效率及封护剂抗腐蚀能力进行了两项电化学实验。一是利用直流腐蚀的极化电阻法对缓蚀效率评价,二是应用恒电位交流阻抗法对涂层的抗腐蚀效率评价。实验表明,复合缓蚀剂的缓蚀效率优于单一缓蚀剂如AMT、BTA,在模拟中性土壤介质的水溶液中各自缓蚀效率分别为88.7%、94.6%,两者组成复合缓蚀剂后其缓蚀效率高达98.8%,这是发挥其缓蚀剂各组分的协同效应的结果。应用恒电位交流阻抗实验,可以更好地理解附着有封护层时复杂的腐蚀过程。结果表明,石蜡涂层样品的Nyquist谱图出现扩散过程引起的阻抗特征;聚乙烯醇缩丁醛涂层、Paraloid B72涂层、空白样(缓蚀层BTA)三种样品Nyquist谱图均是由于涂层微孔引起的阻抗特征,在同一浓度下其抗腐蚀性能排序呈依次递减趋势。     

顶杆热膨胀法测定古陶瓷烧成温度的应用研究

目前,顶杆热膨胀法在测定古陶瓷烧成温度中应用最为广泛。本研究首先对该方法研究现状进行了详细梳理,再通过中国古代陶器、白瓷、黑瓷的具体应用实例,详细分析了它们的热膨胀曲线特征,并结合对高铁胎的模拟实验研究,提出应从800℃以下的早期低温陶器样品、800℃以上且具有明显收缩转折点样品和高温没有收缩只有膨胀转折点样品这3种类型来进行具体分析。利用切线计算烧成温度只有在800℃以上且具有收缩转折点情形下正确率较高,而高温阶段的膨胀转折点温度只能作为参考;同时,也要利用较完整的烧结步骤曲线从化学组成等方面研究其原料特性,并结合吸水率等物理性能指标来进行验证。这些结果为该方法的进一步应用提供了参考依据。     

浙江仙居岩画的微腐蚀断代

微腐蚀测年通过观测矿物晶体上的"石亏"来获知岩画的制作年代,是一种无损的"直接断代法"。仙居岩画的测年工作主要在送龙山和小方岩两处地点开展,经过观测,研究人员从岩画刻槽中取得了十一组石亏微腐蚀数据,以及两组来自吴芾墓附属石刻的校准数据。由校准后的年代计算结果可知,小方岩岩画的制作开始于东吴末年,贯穿了两晋及南北朝时期,一直延续至唐初,而送龙山岩画则为唐代作品。     

ON THE SEISMIC VULNERABILITY OF EXISTING UNREINFORCED MASONRY BUILDINGS

A large part of the building population in Switzerland is made of unreinforced masonry. For the assessment of the seismic risk the evaluation of the seismic vulnerability of existing unreinforced masonry buildings is therefore crucial. In this paper a method to evaluate existing buildings, which was developed for the earthquake scenario project for Switzerland, is briefly introduced and discussed in more detail for unreinforced masonry buildings. The method is based on a non-linear static approach where the seismic demand on the building is compared with the capacity of the building. In-plane and out-of-plane behaviour are considered. Comparisons with test results from model buildings show that the proposed method suitably forecasts the capacity of a building. Finally, a numerical example of the application of the method to a building in the city of Basel is given.     

Radiocarbon calibration curves,summed probability distributions,and early Paleoindian population trends in North America

Archaeologists increasingly examine summed probability distributions of radiocarbon dates to search for temporal trends in ancient human populations, including early North American population trends across the onset of the Younger Dryas climatic period (10,900 BC). We use both IntCal04 and IntCal09 to simulate and calibrate sequences of radiocarbon dates that represent evenly spaced calendar ages from 12,000 to 9000 BC and use IntCal09 to simulate two different demographic processes across this interval. The shapes of the calibrated summed probability distribution from our first set of simulations mirror many trends that have been interpreted in demographic terms and this shape shows clear links to the shape of the radiocarbon calibration curve. This is true for both IntCal04 and IntCal09, although these different curves produce different probability distributions. The shapes of the calibrated summed probability distribution from our second set of simulations differ somewhat but show virtually identical trends at points where the actual frequencies of calendar dates are very different. We conclude that changing frequencies of radiocarbon dates over time probably do contain demographic information, but that extracting this information is more difficult than archaeologists have acknowledged.     

Demography and the intensity of cultural activities: an evaluation of Funnel Beaker Societies (4200–2800 cal BC)

The Early and Middle Neolithic in Northern Central Europe and Southern Scandinavia is characterised by substantial changes in economic technology as well as in material culture in different periods. One of the main drivers for social development, but also for anthropogenic changes in the environment, is surely shifts in population density. To evaluate group sizes and population density we need archaeological proxies. Similar to other studies, we use ¹⁴C dates to reconstruct the intensity of prehistoric activities. A comparison of the human impact from pollen data with a quantification based on ¹⁴C dates proves a correlation which supports our appreciation of the value of sum-calibrated probabilities of radiometric measurements as a proxy for demographic developments. The large amount of usable dates in this study not only enables us to draw general conclusions on a supraregional level, but also makes it possible for us to compare the character of different areas on a regional scale. As a result, we reconstruct a significant rise in population between 4100 and 3500 cal BC and a degression around 3350–3100 cal BC, followed by a reiterated increase for the Funnel Beaker West and North Groups. On the Danish Isles, as well as in the Funnel Beaker North Eastern Group, different tendencies are observable.     

Calibration of an Advanced Constitutive Model for Babolsar Sand Accompanied by Liquefaction Analysis

In our research, we apply numerical modeling for prediction of liquefaction of sands during and after dynamic loading. In numerical modeling, to properly simulate the generation, redistribution, and dissipation of excess pore water pressure during and after dynamic loading, it is important to use a suitable constitutive model for soil. In this article, Dafalias and Manzari’s model [2004] (a critical state bounding surface plasticity model) was used to model the behavior of saturated sand due to relatively simple of formulations and a unique set of input parameters for a wide range of initial stress and void ratio. The attention in this article is on Babolsar sand. After calibration model parameters for Babolsar sand, the analysis of liquefaction using the modeling of a centrifuge test and predictions of model was carried out. The results indicate a reasonable performance of the model for prediction of behavior of types of sands. Also, Babolsar sand has more prone to dilatancy than Nevada and Toyoura sands.