浅谈初中信息技术课教学模式和方法

初中计算机教学主要目的是激发学生学习和使用计算机的兴趣,巩固学生学习计算机的热情,让学生初步掌握计算机的基本操作技能并应用于实践,注重培养学生的信息素质和创新思维以及自学能力,为达此目的在教学中应根据学生实况采取灵活多样的教学模式和方法。     

A Bayesian C chronology of Early and Middle Bronze Age in Sicily. Towards an independent absolute dating

This paper proposes a Bayesian model for the ¹⁴C chronology of Sicilian Early and Middle Bronze Age, with a specific focus on the northeastern sector of the island. Building on the available ¹⁴C determinations, the model allows addressing a number of chronological questions left open in literature, making a first step towards an independent absolute chronology. The analysis put the start of the earlier part of Early Bronze Age (Capo Graziano 1-Casa Lopez phase) between 2400 and 2175 cal BC, and the end at about 1960 cal BC. The advanced stage of the same period (Capo Graziano 1-Filo Braccio phase) is likely to have started and ended around 1960 and 1730 cal BC respectively. The model indicates that the time slot with the highest posterior probability for the start of the Middle Bronze Age–Milazzese (Portella phase) is between 1490 and 1460 cal BC. This turns up to be earlier than held to date. Notably, the model enables for the first time to bracket the development of the later stage of Early Bronze (Capo Graziano 2-M. di Capo Graziano phase) between 1730 (end of Filo Braccio phase) and 1490/60 cal BC (start of Middle Bronze Age–Portella phase). The latter date is earlier than usually held for the end of Capo Graziano 2. The existence of a narrow gap between the end of the latter and the start of Middle Bronze Age-Portella phase is tentatively proposed only on stratigraphic grounds. Further, the analysis enables for the first time to pinpoint and quantify the lag that is likely to have existed between the start of those Sicilian prehistoric phases and the appearance of Late Helladic imports. The comparison with the Aegean ¹⁴C Bayesian chronology indicates that a time lag (about 45 yr) is likely to have occurred between the start of Capo Graziano 2 and of the Late Helladic period. A time lag between 20 and 70 yr is likely to have existed between the start of the Sicilian Middle Bronze Age and of the Late Helladic III. Arguments tentatively supporting the narrower interval are also discussed.     

Applying new approaches to modeling diet and status: isotopic evidence for commoner resiliency and elite variability in the Classic Maya lowlands

Classic Maya states were characterized by a high degree of socioeconomic stratification. This paper investigates the degree to which status, as defined by grave goods and tomb construction, influenced dietary patterns of elites and commoners throughout the Classic Period (200–900/1000 AD) of the southern lowlands. We compile a database (N = 102) of previously-published stable isotope ratios (δ¹³C collagen, δ¹³C apatite, and δ¹⁵N collagen) from Maya bone mineral and collagen, and interrogate these data through two new isotopic modeling techniques: a simple carbon isotope model ( Kellner and Schoeninger, 2007; Froehle et al., 2010) and a multivariate isotope model ( Froehle et al., 2012). We find that Maya elite diet varied significantly through time in terms of maize consumption and trophic level, while commoner diet remained remarkably stable. These findings provide new information relevant to studies of ancient Maya class structure and to studies of subsistence strategies of the pre-Columbian Americas.     

Cacao consumption during the 8th century at Alkali Ridge,southeastern Utah

Theobroma cacao was detected in the ceramic assemblage at the 8th century Site 13, Alkali Ridge, southeastern Utah. The presence of this Mesoamerican beverage during the Pueblo I period is the earliest reported use of cacao in the northern American Southwest, coming centuries earlier than the recently documented Pueblo II consumption of cacao in cylinder jars, sharp-shouldered pitchers and shallow bowls at Pueblo Bonito, Chaco Canyon. Analogous to the situation at Chaco, cacao was found at Site 13 in a new vessel form decorated with a distinctive design system that contrasted markedly with designs and vessel forms in the local black-on-white ceramic assemblage. We postulate that Abajo R/O at Site 13 represents a ceramic tradition brought by one of the many groups moving into the northern Southwest. The detection of cacao in their ceramic vessels represents new evidence for the migration model that for centuries brought people with Mesoamerican beliefs, ritual practices and a new subsistence lifeway into the American Southwest.     

A Geospatial Analysis of China's Exports, 1991-2008

Three Taiwan-based economists employ a range of exploratory spatial data analysis tools (e.g., Moran's I and LISA statistics) to investigate trends in the growth of China's exports over the period 1991-2008. A particular focus is on the detection of spatial correlations between China and 40 export destination countries in major world regions. Emphasis in the paper on the key years of 1991, 2001, 2006, and 2008 has enabled the authors to analyze the impacts on China's trade of such major events as the country's accession to the World Trade Organization and the global economic crisis of 2008-2009. The results of the spatial analysis reveal the continuing importance of the U.S. and Asian countries in China's export trade (despite changes in the character of trade relations) and identify the spatial outliers (e.g., in Latin America) that may serve as the basis for new export markets for China in the future.     

Mechanisms Shaping the Transition to Farming in Europe and the North American Woodland

Despite the fact that Europe and Eastern North America both have similar woodland environments, the emergence of agriculture in these areas proceeded very differently varying in timing, speed, and mechanism. To analyze the different subsistence paths the Global Land Use and Technological Evolution Simulator was used, a numerical model for simulating demography, innovation, domestication, migration and trade within the geoenvironmental context. I demonstrate how Europe receives a large package of foreign domesticates and converts rapidly. In contrast, trajectories relating to Eastern North America exhibit a gradual transition in which hunting and gathering and agropastoralism coexist for a long period of time, and agriculture is integrated slowly into the existing subsistence scheme. I deduce from this a qualitative economic difference in the two regional transitions: limited population size in Europe, limited resources in Eastern North America.     

A Genetic Approach to the Subdivision of Tropical Soils,Regolith and their Products of Redeposition

A soil classification based on the genetic principles of Russia's Dokuchayev school is proposed for the tropical setting of Cuba. In view of the heavy degradation of the island's original forest and savanna soils, leaving fully developed soil profiles only in a few areas, such a genetic classification of Cuban soils must incorporate both the few fully developed soils proper and the various types of subsoil, consisting both of parent material and of its products of redeposition. The following types of parent material are distinguished: (a) quartz-allitic-ferritic, on acid crystalline rocks; (b) kaol-inite-allitic-ferritic, on schists; (c) zeolitic, on basic volcanics; (d) ferro-zeolitic, on ultrabasics, and (e) terra rossa, on crystalline limestones. These primary types of parent material, developed on crystalline rocks, have their secondary equivalents on sedimentary rocks.     

新时期国内旅游抗周期性及双对数需求弹性分析

2000年以来,我国人均收入超过1000美元,国内旅游进入快速增长期,呈现抗周期性的新特征。本文在形态指标分析的基础上,界定了旅游业抗周期的概念及两种表现形式。相关统计数据实证检验发现,2003年SARS危机后,2004年国内旅游强力反弹,2009年国民经济进入低谷期后国内旅游率先恢复,形成一种受短期波动影响较小的惯性增长。同时,本文依据1994年～2012年时间序列数据建立了双对数模型,分析全国及城市居民国内旅游收入弹性和价格弹性,结果显示,收入需求弹性大于价格需求弹性,收入增长对居民国内旅游的推动作用大于价格的限制,形成了“刚性”的旅游需求,这是新时期国内旅游迅猛增长及抗周期性形成的根本原因。