高分散性、粒度高正态分布氢氧化镁的制备研究进展          下载免费PDF全文

郑小刚  李海民 《盐湖研究》2010,18(4)

近年来Mg(OH)2的改性研究受到广泛重视;对水热处理技术和表面改性手段处理Mg(OH)2的研究现状进行概述,并讨论制备超细粉体改性Mg(OH)2的影响因素。  相似文献   

基于ACCRBF网络的多层砖房震害预测   总被引：1，自引：1，他引：0  

杨秀萍  程运平  陈克珩  丁大勇 《震灾防御技术》2013,8(1):90-96

针对传统震害预测方法逐栋抽样计算建筑物抗震性能的不足,本文提出了一种基于蚁群聚类径向基(ACCRBF)网络模型的建筑物震害预测方法。依据不同地震动峰值加速度下多层砖房的实际震害资料,对模型进行训练,在模型的输入和输出之间建立映射关系,并利用这种映射关系对未知样本进行分类,实现对多层砖房的震害分析和预测。模型的输入为反映结构的震害影响因子,输出为给定的地震动峰值加速度下结构震害等级。研究表明,基于ACCRBF网络模型的多层砖房震害预测结果与震害实例基本吻合,具有推广应用价值。  相似文献   

鄂尔多斯盆地下石盒子组盒8段储集砂体发育控制因素及沉积模式研究   总被引：6，自引：0，他引：6  

田景春  吴琦  王峰  林小兵  张锦泉  曹桐生 《岩石学报》2011,27(8):2403-2412

以鄂尔多斯盆地二叠系下石盒子组盒8段储集砂体为研究对象,在众多前人研究成果的基础上,综合研究了盆地内下石盒子组盒8段沉积演化过程中储集砂体发育特征,主要表现为:岩石类型多样,包括含砾粗砂岩、中粒砂岩、细粒砂岩等;成因复杂:包括冲积扇砂体、河流砂体、辫状河三角洲砂体等;分布广泛:具有广覆式大面积分布特征。在上述基础上,系统深入分析了控制盒8大面积砂体分布的关键因素,主要包括:强物源、多物源供给是基础,多水系发育是前提,平缓古地貌是背景,高流速河流是动力。其中,强物源、多物源不仅为盆地内提供了丰富碎屑物质,而且控制着盆地内不同区域储集砂体的岩性特征;多水系发育为形成大面积砂体分布提供了条件,发源于物源区向盆地内搬运陆源碎屑物质的六条水浅流急的辫状河道在盆地中部汇合交叉控制着单层砂体厚度及其连片性。平缓古地貌控制着多河道发育和长距离搬运过程中河道摆动、迁移频繁,并相互叠置交叉。高流速河流控制着平缓古地形上发育的多河道不断交叉、复合。并定量计算了盒8段储集砂体沉积时的地形古坡度,平均坡降为1.10m·km^-1,平均坡度为0.063°;古河流水体平均流速为8.31m·s^-1。进而,结合盆地内钻井实际建立了下石盒子组盒8段独具特色的"强物源供给的缓坡浅水辫状河三角洲沉积模式"。  相似文献   

民勤绿洲1971-2010年沙尘暴特征及影响因素分析     

赵明瑞 《沙漠与绿洲气象(新疆气象)》2013,7(3):35-39

根据1971～2010年民勤近40a气象资料、民勤周边县市沙尘暴资料,详细分析了民勤绿洲沙尘暴变化特征及影响因素,结果表明：①绿洲以局地性沙尘暴为主,但区域性沙尘暴无论是持续时间、伴随的大风强度和成灾性均大于局地性沙尘暴。②一日中局地性和区域性沙尘暴主要出现在下午和傍晚;月际变化除3月份外其它月份局地性均较区域性沙尘暴多,6～8月份偏多明显,各季局地性均比区域性沙尘暴多,夏季偏多明显;年际局地和区域性沙尘暴均为显著减少趋势,年代际为明显减少趋势。③干旱气候、丰富的沙源是民勤多沙尘暴的自然原因,气候的变化和下垫面状况的改善使沙尘暴减少。分析表明气候变暖使大风日数减少、风力减小,从而影响局地和区域性沙尘暴减少,气候变暖使日照时数增长、蒸发增大,从而影响区域性沙尘暴减少,而对局地性沙尘暴的减少影响不大。  相似文献   

Deforestation dynamics and drivers in different forest types in Latin America: Three decades of studies (1980–2010)     

《Global Environmental Change》2017

Over the last decades there have been a considerable number of deforestation studies in Latin America reporting lower rates compared with other regions; although these studies are either regional or local and do not allow the comparison of the intraregional variability present among countries or forest types. Here, we present the results obtained from a systematic review of 369 articles (published from 1990 to 2014) about deforestation rates for 17 countries and forest types (tropical lowland, tropical montane, tropical and subtropical dry, subtropical temperate and mixed, and Atlantic forests). Drivers identified as direct or indirect causes of deforestation in the literature were also analysed. With an overall annual deforestation rate of −1.14 (±0.092 SE) in the region, we compared the rates per forest type and country. The results indicate that there is a high variability of forest loss rates among countries and forest types. In general, Chile and Argentina presented the highest deforestation rates (−3.28 and −2.31 yearly average, respectively), followed by Ecuador and Paraguay (−2.19 and −1.89 yearly average, respectively). Atlantic forests (−1.62) and tropical montane forests (−1.55) presented the highest deforestation rates for the region. In particular, tropical lowland forests in Ecuador (−2.42) and tropical dry forests in Mexico (−2.88) and Argentina (−2.20) were the most affected. In most countries, the access to markets and agricultural and forest activities are the main causes of deforestation; however, the causes vary according to the forest types. Deforestation measurements focused at different scales and on different forest types will help governments to improve their reports for international initiatives, such as reducing emissions from deforestation and forest degradation (REDD+) but, more importantly, for developing local policies for the sustainable management of forests and for reducing the deforestation in Latin America.  相似文献   

马里亚纳海槽区岩芯中浮游有孔虫和CaCO_3溶解及其影响溶解的因素     

高建西  周希林  鞠晓华 《海洋科学进展》1993,(2)

本文从浮游有孔虫壳体保存,数量,分异度值,底栖类/浮游类比率和CaCO_3含量诸方面讨论马里亚纳海槽区岩芯中溶解及其影响溶解的因素。  相似文献   

Mooring system reliability in tropical cyclone and North Sea winter storm environments     

《Applied Ocean Research》2019

The characteristics of waves, winds and currents in a tropical cyclone environment differ significantly from those in a winter storm environment, like the North Sea. This can have a significant effect on the reliability of a mooring system that is designed to satisfy 100 yr conditions with specified Factors of Safety in accordance with ISO19901-7 or API RP 2SK. This paper presents reliability analysis of the mooring system of a permanently connected Floating LNG vessel, placed at two locations: (a) a tropical cyclone environment of the North West Shelf of Australia and (b) a winter storm environment of the North Sea. It is demonstrated that as a result of differences in the long term distribution of environmental parameters (waves, winds) between a North Sea environment and a tropical cyclone environment, the long term distribution of the mooring line response differs significantly in these two locations.This paper shows that a mooring system which is designed in accordance with ISO (or API), in these two environments, will achieve very different reliability levels because of the significant differences in environmental characteristics. In order to achieve the same reliability for the mooring system at these two geographical locations, Factors of Safety for use with 100 yr environmental conditions (Ultimate Limit State) were derived to achieve the same target probability of failure of 10⁻⁴/annum. It was found that for the North Sea environment, a factor of 1.5 is required for both the mooring chain and the pile, while for the tropical cyclone environment the required Factor of Safety has to be increased to 2.1. These differences are very significant and design standards need to be revised to reflect these findings.  相似文献   

五台山积雪变化趋势及其影响因素     

范强  刘楠  任天晨 《水文》2023,43(4):111-115

基于MODIS积雪产品与微波遥感数据,分析五台山2000—2019水文年积雪时空分布、变化趋势及与影响因素的Pearson相关性,结果表明：（1）五台山积雪期为10月至翌年4月,年内呈单峰型变化趋势,积雪集中于西北部。（2）积雪面积和积雪日数的年际变化呈显著减少趋势（p<0.05）。（3）积雪面积和积雪日数与海拔正相关,积雪面积在北坡高于南坡。（4）积雪面积与气温相关程度高于降水量,积雪面积在年内与气温和降水量日值呈显著负相关（p<0.05）,在年际与气温年均值呈显著负相关（p<0.05）。  相似文献   

四川盆地农业区的形成历史与地理因素分析     

陈家其 《云南地理环境研究》1993,5(2):52-61

四川盆地农业区最早的农业至少可追溯到新石器时代中期。在其以后的发展过程中,秦汉、隋唐、北宋是三个农业发展的高潮时期。复杂多样的农业自然条件使农业历史悠久且类型多样,而水利建设在不同历史时期的土地开发和农业发展中,都起着先导作用。明末战乱和自然灾害将农业破坏几尽。清康雍时期,外省移民纷至沓来,促进了农业区的全面恢复和发展。  相似文献   

莫索湾地区侏罗系三工河组储集层沉积及成岩作用特征   总被引：2，自引：0，他引：2  

德勒达尔  张有平  帕尔哈提  王安生 《新疆地质》2003,21(3):269-273

主要根据5口评价井，莫101、莫102、莫103、莫104、莫105井及盆5、盆6井的取心资料、电测曲线、综合录井资料以及地震资料分析研究，得出研究区侏罗系三工河组J1s2^2；地层的岩石学特征，认为储层的岩石类型为细中粒岩屑砂岩及不等粒岩屑砂岩，细粒岩屑砂岩少量．沉积相为三角洲前缘亚相，并指出它们在纵向上的沉积序列特征及砂体展布特征．通过大量的分析化验数据分析了成岩作用类型，划分了其成岩序列及成岩阶段．指出压实作用、粘土矿物及敏感性及软碎屑等因素不同程度的影响了储集层。  相似文献