西藏高原农户的投资行为——以达孜县为例   总被引：7，自引：0，他引：7  

王慎强  刘伟 《山地学报》2001,19(3):243-247

根据农户调查资料和有关的统计数据对西藏达孜县农户的投资行为进行了研究。结果表明：该县农户的投资主要以直接投资为主，间接投资所占的比重较低；在直接投资中，又以家庭经营投资和固定资产投资为主；农户对科技教育、文化娱乐方面的投资较少，而对宗教信仰方面的投资相对较多；其投资资金来源主要是自有资金。其次是银行贷款和其他资金，国家财政拨款所占的比重不大；受投资结构等因素的影响，该县农户的投资效益基本上呈农年降低趋势。  相似文献   

无人机航测技术在风电场测图中的应用     

黄小兵 《北京测绘》2020,(5):700-704

本文提出了一种利用无人机航空摄影测量技术完成风电场测图的方法,利用该方法可以实现测区1∶2000地形图数据的生产。首先根据航摄区域和航线规划布设控制点、像控点、检查点,利用飞马F300无人机进行航摄作业获取航测数据,然后对数据进行预处理,按照标准格式导入Context Capture软件建立三维倾斜模型,通过EPS2016立体量测软件基于三维倾斜模型完成地形图数据的采集,对于模型变形的区域,利用MapMatrix软件进行数据采集与校核。利用安徽宿州风电场测图项目验证了该方法满足1∶2000大比例尺地形图精度要求。  相似文献   

退耕还林政策实施的农户水土保持行为响应研究--以江西省丰城市梅林镇为例     

翟文侠  黄贤金 《云南地理环境研究》2006,18(2):33-39

农户水土保持行为与生态环境变化关系密切，分析农户水土保持行为响应机理对退耕还林政策的实施具有重要意义。通过对江西省丰城市梅林镇多元回归模型分析，结果表明：（1）农户水土保持行为与退耕还林实施力度、退耕地收入与退耕还林后补偿比重成正相关，与退耕补偿年限成负相关；（2）农户水土保持投入减少反映农户家庭收入结构发生变化：从农业为主的收入阶段向以非农业或农业与非农业收入为主的阶段转变；（3）退耕还林政策实施农户水土保持行为响应以效益引导型为主。据此，提出相关建议。  相似文献   

Asteroid Mean Elements: Higher Order and Iterative Theories     

Andrea Milani  Zoran Knežević 《Celestial Mechanics and Dynamical Astronomy》1998,71(1):55-78

Mean orbital elements are obtained from osculating ones by removing the short periodic perturbations. Large catalogues of asteroid mean elements need to be computed, as a first step in the computation of proper elements, used to study asteroid families. The algorithms for this purpose available so far are only accurate to first order in the masses of the perturbing planet; the mean elements have satisfactory accuracy for most of the asteroid belt, but degraded accuracy in the neighbourhoods of the main mean motion resonances, especially the 2:1. We investigate a number of algorithms capable of improving this approximation; they belong to the two classes of Breiter-type methods and iterative methods. The former are obtained by applying some higher order numerical integration scheme, such as Runge–Kutta, to the differential equation whose solution is a transformation removing the fast angular variables from the equations; they can be used to compute a full second order theory, however, only if the full second order determining function is explicitly computed, and this is computationally too cumbersome for a complicated problem such as the N-body. The latter are fixed point iterative schemes, with the first order theory as an iteration step, used to compute the inverse map from mean to osculating elements; formally the method is first order, but because they implement a fixed frequency perturbation theory, they are more accurate than conventional single iteration methods; a similar method is already in use in our computation of proper from mean elements. Many of these methods are tested on a sample of asteroid orbits taken from the Themis family, up to the edge of the 2:1 resonance, and the dispersion of the values of the computed mean semimajor axis over 100 000 years is used as quality control. The results of these tests indicate that the iterative methods are superior, in this specific application, to the Breiter methods, in accuracy and reliability. This is understood as the result of the cancellations occurring between second order perturbation terms: the incomplete second order theory, resulting from the use of a Breiter method with the first order determining function only, can be less accurate than complete, fixed frequency theories of the first order. We have therefore computed new catalogues of asteroid mean and proper elements, incorporating an iterative algorithm in both steps (osculating to mean and mean to proper elements). This new data set, significantly more reliable even in the previously degraded regions of Themis and Cybele, is in the public domain. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

论土地整理概念的科学界定   总被引：26，自引：3，他引：23  

姜爱林  姜志德 《地域研究与开发》1998,17(1):1-4

土地整理是土地利用的一种发展趋势,目前已成为社会关注的焦点。然而,从国内外的研究情况来看,土地整理的概念、内容都不尽一致。理论上的混乱无疑会给实际工作造成诸多的困扰。本文从分析比较国内外对土地整理的不同观念出发,并结合我国实际,科学地提出了土地整理的经济学概念及确定这一要概念必须遵循的规律。  相似文献   

作物水分生产函数与农田非充分灌溉研究述评   总被引：36，自引：4，他引：36       下载免费PDF全文

沈荣开  张瑜芳 《水科学进展》1995,6(3):248-254

介绍作物水分生产函数国内外研究现状,把目前通用的各类模型归纳为最终产量模型和动态产量模型两大类,分析评述两类模型的特点及适用条件.此外,对作物水分生产函数的试验方法和试验处理设计作了介绍.  相似文献   

Women in agriculture: advocates for a gendered sustainable agriculture     

Ruth Liepins 《The Australian geographer》1995,26(2):118-126

A gendered consideration of rural geography has been barely discernible within Australian and New Zealand literature. The notable exceptions in this case have illustrated the complexity and merit of studying the gender patterns and relations of rural life. Outside geography, there is an expanding literature on rural women in Australia. These works parallel significant developments in the lives and politics of rural and agricultural women themselves. This paper reports selected findings from a study of the women in agriculture movement in Australia. As such, it illustrates the increased awareness of the gendered conditions of farming. The women in agriculture movement works to increase the recognition of women's contribution to agriculture. In doing so it affirms the legitimacy of women farmers’ voices and perspectives. There will be no sustainable rural systems while half the rural population is unseen or unheard. Women in agriculture demonstrate a social dimension of sustainability. They highlight the need to integrate gender equity and a ‘wider‐than‐economic’ conceptualisation of sustainable agriculture. Their actions can stimulate rural geographers to further consider the social and political aspects of rural sustainability beyond the conventional farm/industry and community service sites we usually consider.  相似文献   

从中国东部若干重要矿区看花岗岩类的成矿专属性     

张师 《地球科学》1985,(2)

本文着重讨论中国东部与铁、铜、钨、相及锡矿床有关的花岗岩类的岩石化学特征:铁矿成矿母岩通常为SiO_2 52—63%,Fe_2O_3 FeO 5.2—10%,K_2O Na_2O 5—10%。正常系列。S=62—72,b=10—20,σ=3—5。当PH_2O=500～1000巴时,初始结晶温度≥820°C。铜矿成矿母岩通常为SiO_2 61—70%,Fe_2O_3 FeO 2—5.2%,K_2O Na_2O5—7％。正常或铝过饱和系列。S=70—80.5,b=6—12,σ≤3。当PH_2O=500—1000巴时,初始结晶温度为780—820°C。钨、钼和锡矿成矿母岩SiO_2 70—77%,Fe_2O_3 FeO<5％,K_2O Na_2O 7—10%。铝过饱和系列。S=77—83,b=1—9,σ≤3。当PH_2O=300—1000巴时,初始结晶温度<780°C。  相似文献   

台湾与广州观光农园对比研究   总被引：4，自引：1，他引：4  

余国扬 《热带地理》2002,22(4):341-344,366

台湾观光农园（台湾称休闲农场）是农业生产适应休闲旅游发展的产物，是利用农业生产项目的第一过程进行“包装”推销、提供游观赏、参与、体验、品尝与购物等旅游活动，从而使农业生产与休闲旅游形成发展链。广州发展观光农业的条件基础不逊色于台湾，但现实上是落后了。为此，广州要以农业土特产生产为观光农业突破口，对观光农园进行科学化规划、基地化建设、规模化经营，重点建设3个多样性、规模性、多品种、示范性农业土特产观光农园，从而带动促进广州观光农园全面发展。  相似文献   

测绘人员智能家居系统设计探讨     

余家树  张忠  张仁杰 《地理空间信息》2010,8(1):117-118

分析了智能家居的内涵;阐述了智能家居系统的设计目的;指出了智能家居的核心和特点是数字化、网络化、智能化;提出了智能家居系统的实现方法:由智能家居应用集成系统、家庭网关、家庭网络联网技术等组成。  相似文献