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.     

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。     

Deletion/Substitution/Addition (DSA) model selection algorithm applied to the study of archaeological settlement patterning

This paper introduces GIS-based statistical methods for the study of settlement patterning in an archaeological context. The main aspect is an improvement over suboptimal stepwise statistical model selection procedures, with the introduction of a Deletion/Substitution/Addition (DSA) algorithm, a systematic model selection algorithm that provides an optimal model choice. The paper also introduces the combined use of Receiving Operator Characteristic (ROC) curves, and variable ranking as key tools aimed at an understanding of settlement patterning causation. An illustrative case study is provided whereby both a purely environmental and a mixed environmental/historical model (based on settlement hierarchy considerations) are investigated.     

SEISMIC BEHAVIOUR OF A R/C WALL: NUMERICAL SIMULATION AND EXPERIMENTAL VALIDATION

This paper describes the numerical simulation of the seismic behaviour of a mock-up of a six-floor building, constituted by two parallel R/C walls and experimentally tested on a shaking table. Within the scope of an international benchmark the mock-up was submitted to three earthquakes with intensities up to 0.71 g, which induced nonlinear behaviour in the concrete and reinforcement. For the numerical simulations concrete is discretised with 2D finite elements, and its behaviour reproduced via a constitutive model with two scalar damage variables. Steel rebars are discretised with 2-noded truss elements, and their constitutive behaviour under cyclic conditions reproduced by the Menegottb-Pinto model. Specific attention is devoted to Rayleigh damping, focusing on two different strategies: (i) disregarding the damping contribution, or (ii) adopting a damping matrix that takes into account the stiffness changes during the nonlinear analyses. Main results and strategies for simulating the benchmark axe presented, with emphasis on the comparison between the numerical and the experimental results, which show good agreement when the damping contribution is neglected.     

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。     

Object-based landform delineation and classification from DEMs for archaeological predictive mapping

In this paper we report the results of an experiment with automated landform delineation and classification from digital elevation models (DEMs) using object-based image analysis (OBIA). Archaeologists rely on accurate and detailed geomorphological maps to predict and interpret the location of archaeological sites. However, they have been using high-resolution DEMs primarily for visual interpretation and expert-judgement classification of landform. OBIA can perform these classifications much faster and in a more objective fashion. The method was tested on a study area in the south east of the Netherlands. It is concluded that OBIA is a suitable technique for quick and objective delineation of landform, but needs an improved conceptual framework adapted to the local situation and archaeological questions to better identify and interpret the derived landform objects.     

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.     

INTEGRATED PASSIVE-ACTIVE SYSTEM FOR SEISMIC PROTECTION OF A CABLE-STAYED BRIDGE

This paper presents an integrated passive-active (i.e. hybrid) system for seismic response control of a cable-stayed bridge. Since multiple control devices are operating, a hybrid control system could alleviate some of the restrictions and limitations that exist when each system is acting alone. Lead rubber bearings are used as passive control devices to reduce the earthquake-induced forces in the bridge and hydraulic actuators are used as active control devices to further reduce the bridge responses, especially deck displacements. In the proposed hybrid control system, a linear quadratic Gaussian control algorithm is adopted as a primary controller. In addition, a secondary bang-bang type (i.e. on-off type) controller according to the responses of lead rubber bearings is considered to increase the controller robustness. Numerical simulation results show that control performances of the integrated passive-active control system are superior to those of the passive control system and are slightly better than those of the fully active control system. Furthermore, it is verified that the hybrid control system with a bang-bang type controller is more robust for stiffness perturbation than the active controller with a μ-synthesis method, and there are no signs of instability in the over-all system whereas the active control system with linear quadratic Gaussian algorithm shows instabilities in the perturbed system. Therefore, the proposed hybrid protective system could effectively be used for seismically excited cable-stayed bridges.