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321.
遗产区域:一种大尺度文化景观保护的新方法   总被引:2,自引:0,他引:2  
遗产区域是美国国内针对大尺度文化景观保护的一种较新的方法。该方法重视人与土地之间的互动关系。强调通过对地方历史文化、自然和游憩资源的综合保护与利用。实现遗产保护、经济发展、重建区域身份、提供游憩机会等多重目标。从美国历史保护运动的发展背景出发。回顾了遗产区域的发展历程,从定义、特征与分类三个方面评述了其概念内涵,并对遗产区域保护中的几个关键问题进行了讨论。最后针对遗产区域保护方法在中国的发展与应用提出了相关建议。  相似文献   
322.
主要结合多年民航系统设备设施的雷电防护建设实践,在符合国家和民航局相关规定、技术规范的前提下,理论结合实际说明民航通信、导航、监视设施雷电防护的特点。  相似文献   
323.
根据胶东半岛及附近海域地震活动性参数的研究,对2012年存在的地震活动性异常演化情况进行跟踪分析,对2013年度出现的新地震异常进行分析,获得大震孕震过程时、空综合变化结果,提出胶东半岛及附近海域的震情趋势判定意见。  相似文献   
324.
火焰原子吸收光度法测定水中铝的方法改进   总被引:1,自引:0,他引:1  
研究了在盐酸介质中,壬基酚聚氧乙烯-7醚(NP-7)活化下,火焰原子吸收光度法测定环境水体中铝的方法改进。在25mL容量瓶中,加入5.0mL体积分数为50%的盐酸、2.0mL质量浓度为0.01g/mL NP-7和4.0mL质量浓度为75.0μg/mL的铝标准溶液,在原子吸收分光光度计的最佳测定条件下测定吸光度。根据吸光度与铝质量浓度绘制了工作曲线,线性范围3.0~24.0μg/mL,检出限1.32μg/mL。该法用于环境水体中铝含量的测定,加标回收率为94.4%~101.4%,最大相对标准偏差5.8%,方法对比最大相对误差4.1%。  相似文献   
325.
包头境内的白云鄂博矿是一座资源丰富的大型矿山,已为我国大型钢铁稀土联合企业开采利用40余年,白云鄂博原矿平均伴生天然,在矿物资源的开发利用中,对环境造成放射性污染。本文从白云鄂博矿资源、资源特殊性,开发利用,放射性废渣及钍核素排放等方面进行论述,并提出防治控制管理措施。  相似文献   
326.
甘肃省作物布局演变及其对区域气候变暖的响应   总被引:2,自引:1,他引:1  
根据甘肃省1985-2005年的气候资料和同时期主要作物播种面积等统计资料,利用快速聚类分析方法分析了气候变暖背景下甘肃省主要作物的种植格局和种植界限演变情况。结果表明:过去20 a里特别是进入20世纪90年代,在河西地区,玉米和棉花播种范围扩张趋势明显,种植面积比重显著增加,春小麦种植面积比重快速降低,种植范围大幅向祁连山浅山区退缩,种植结构的这种调整使玉米和棉花逐渐取代小麦成为河西主要作物,并最终导致该区主要作物种植格局从以小麦为主转变为以玉米和棉花为主;在中部地区,春小麦面积逐年缩小,冬小麦和杂粮种植扩张,玉米的种植比例逐年上升,马铃薯种植逐渐形成规模,形成了以小麦和玉米为主的种植格局;在东南部地区,春小麦和冬小麦面积逐年缩小,玉米、冬油菜和其他喜温的经济作物种植比例逐年上升。相关分析表明,上述作物种植格局的变化与气候变暖带来的积温增加及积温带北移东扩密切相关。  相似文献   
327.
A new air exchange rate (AER) monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs (0.1-10.0 hr-1). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO2 sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr-1 in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr??1 in fall, and 0.12 to 1.39 hr-1 in winter with a median AER of 1.15.  相似文献   
328.
In recent years, with the wide applications and mineral exploitation of rare earth elements, their potential environmental and health effects have caused increasing public concern. Effect of rare earth elements La and Yb on the morphological and functional development of zebrafish embryos were studied. The embryos were exposed to La3+ or Yb3+ at 0, 0.01, 0.1, 0.3, 0.5 and 1.0 mmol/L, respectively. Early life stage parameters such as egg and embryo mortality, gastrula development, tail detachment, eyes, somite formation, circulatory system, pigmentation, malformations, hatching rate, length of larvae and mortality were investigated. The results showed La3+ and Yb3+ delayed zebrafish embryo and larval development, decreased survival and hatching rates, and caused tail malformation in a concentration-dependent way. Moreover, heavy rare-earth ytterbium led to more severe acute toxicity of zebrafish embryo than light rare-earth lanthanum.  相似文献   
329.
The reaction mechanism of ozone (O3) addition to the double bonds of gas phase keto-limonene was investigated using ab initio methods. Two different possibilities for O3 addition to the double bond were considered and two corresponding van derWaals complexes (Complex 1 and Complex 2) were found for 1-endo and 2-endo. The rate constants were calculated using the transition state theory at the CCSD(T)/6-31G(d) + CF//B3LYP/6-31G(d,p) level. The high-pressure limit of the total rate constant at 298 K was 3.51 × 10-16 cm3/(molecule sec), which was in a good agreement with the experimental data.  相似文献   
330.
The vertical distribution of aerosols was directly observed under various atmospheric conditions in the free troposphere using surface micro-pulse lidar (MPL4) at the Zhangye Station (39.08°N, 100.27°E) in western China in the spring of 2008. The study shows that the aerosol distribution over Zhangye can be vertically classified into upper, middle and lower layers with altitudes of 4.5 to 9 km, 2.5 to 4.5 km, and less than 2.5 km, respectively. The aerosol in the upper layer originated from the external sources at higher altitude regions, from far desert regions upwind of Zhangye or transported from higher atmospheric layers by free convection, and the altitude of this aerosol layer decreased with time; the aerosols in the middle and lower layers originated from both external and local sources. The aerosol extinction coefficients in the upper and lower layers decreased with altitude, whereas the coefficient in the middle layer changed only slightly, which suggests that aerosol mixing occurs in the middle layer. The distribution of aerosols with altitude has three features: a single peak that forms under stable atmospheric conditions, an exponential decrease with altitude that occurs under unstable atmospheric conditions, and slight change in the mixed layer. Due to the impact of the top of the atmospheric boundary layer, the diurnal variation in the aerosol extinction coefficient has a single peak, which is higher in the afternoon and lower in the morning.  相似文献   
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