Implications of land use transitions on soil nitrogen in dynamic landscapes in Tanzania

Land use transitions are rated among the leading sources of greenhouse gas emissions in the tropics. They significantly challenge the functioning of ecosystems and affect multi-temporal stability of greenhouse gases such as N₂O and soil properties. Studies on dynamics in nitrogen balances are essential in understanding greenhouse gas emissions such as N₂O and to manage their impacts on productivity. In this study, multi-temporal Landsat images (1975, 1995 and 2012) were classified to determine land use transitions and potential drivers. The classified images were categorized into degraded and non-degraded lands and eighty sampling plots generated within the entire study area. Soil samples were then collected at 0–15, 15–30 and 30–60 cm depths on each plot and soil nitrogen determined. A regression analysis was developed to determine the influence of forest and grassland degradation on soil nitrogen. Results indicated a significant change in major land use and land cover types. Specifically, there was a decrease in areas covered by forests, woodland and grassland, however, area covered by less dense forest increased. Results also indicated variability in mean nitrogen content between degraded and non-degraded areas and depths. Furthermore, levels of degradation influence nitrogen content up to a soil depth of 30 cm. The present study is relevant in the detailed assessment of the extent of damage and threats posed to biodiversity hotspots in sub-Saharan Africa. These results are transferable to other parts of the world characterized by dynamic ecological transformation.     

黑土典型区有机质高光谱预测模型

土壤有机质(SOM)是鉴别土壤肥力的重要指标,是土壤肥力的物质基础,其含量预测模型研究对于土壤肥力评价、土壤碳库估算、土壤资源利用与保护具有重要意义。该文以黑龙江省黑土带典型区为例,采集区域土壤样本,基于有机质含量与土壤反射率的定量关系,对光谱反射率进行一阶微分和倒对数的处理,建立偏最小二乘法模型(PLSR)、一元线性回归模型和多元线性逐步回归模型。结果表明:(1)土壤有机质敏感波段位于650-750nm。(2)通过比较建模样本与检验样本的决定系数(R2)和均方根误差(RMSE)的大小,得到反射率和倒对数处理后的数据最优模型都为PLSR模型,一阶微分处理后的最优模型为多元线性逐步回归模型。(3)PLSR模型的建模效果优于回归模型,但其预测效果却并不理想。该研究将为改进土壤理化参数、遥感反演、土地质量评价等工作方法提供理论与技术支持。     

Urban Sensing by Crowdsourcing: Analysing Urban Trip behaviour in Zurich

The research on which this essay is based sought to provide a deeper understanding of live urban activities. The main idea was to obtain in‐depth trip information by integrating sensing technology with crowdsourcing‐based methods. Location and acceleration sensors embedded in smartphones can deliver useful trip information. Research had previously been conducted to find an accurate data analysis algorithm for high‐level data mining, an efficient sensing method for power saving. As a proof of concept, this essay presents a case study of Zurich that successfully implemented previous research achievements in the real environment. It established that urban travel behaviour can, in fact, be collected by sensors embedded in mobile devices, and that the data thus obtained can be used to measure the characteristics of trip behaviour in cities by means of an advanced classifying algorithm and analysis. The strength of this research is its pioneering role in clearing the ground for future urban data collection methods and planning strategies. Specifically, this study could provide answers to the following key questions: How can crowdsourcing be applied to the collection of urban transportation data? What kinds of information can be extracted from the crowdsourced mobile sensing platform? What kinds of knowledge, within the transportation domain, can be derived from the above?     

农业水循环与水环境遥感应用研究进展

农业生产受环境因素影响大,进入农耕文明以来,农业对气候的高度依赖局面没有得到根本性的改变,频繁的自然灾害给我国的农村经济发展造成了极大的困难。遥感技术是运用各类非接触的主被动的探测设备,对地面目标物的电磁波辐射与反射特性进行探测,通过其特性分析,探明其物体性质、特征及状态的综合性探测技术。它具有覆盖面积广、空间分辨率高、获取信息大、重访周期短等优点,适用于农业资源调查与自然灾害监测等农业相关领域的研究,对农业生产的指导与相关部门的决策管理意义重大。文章主要针对国内遥感技术在农业水循环与水环境的发展、应用现状进行综述与分析,并对遥感技术在农业水资源领域的发展趋势进行展望。     

基于光谱吸收的光纤瓦斯气体传感系统分析

根据瓦斯气体在一定波段对光有吸收的特性,通过对煤矿瓦斯气体吸收光谱的分析,研究了一种光纤传感瓦斯气体系统。     

污染地域环境水文地质勘查技术应用浅探

随着时代的发展,科技水平的不断进步,社会对水文地质勘察技术的关注程度越来越高,其应用范围也越来越广。     

论PLC实现路口交通信号灯远程智能控制的设计

对如何应用PLC实现十字路口交通信号灯远程智能控制,论述了通过对PLC控制系统的软、硬设计,分析对交通信号灯的控制要求,同时将PLC的逻辑控制、数据运算、数据比较、数据传送,通过程序有机地结合起来,既远程控制交通灯的变化,同时对应的时间显示。     

电力配网线损管理系统的研究与开发

研究和开发电力配网线损管理系统能够有效解决我国电力配网线损问题。文中的电力配网线损管理系统采用了融合B/S结构和C/S结构的三层系统结构模式;同时,该线损管理系统充分利用了现今非常发达的通信技术,通过公共通信网络(GPRS、CDMA以及GSM等)传输各种电力信息和数据,有效杜绝了传统信息传输方式高成本、难维护和低时效的问题,利用远方检测终端设备便可实时检测用端的用电情况。     

M2M消防远程监控系统的应用

文章把M2M的概念引入消防远程监控系统中应用,消防远程监控系统通过运营商网络将各建筑物内独立的火灾自动报警系统联网,在监控中心内对所有联网建筑物的火灾报警情况进行实时监测,对消防设施进行集中管理。     

基于“北斗一代”的Zigbee无线网关设计

为了解决野外多点数据采集无供电、布线复杂和通信困难的问题,提出了一种基于“北 斗一代”的Zigbee无线网关设计方案。采用MSP430F6438、CC2341微处理器和一体化的RDSS “北斗”射频芯片完成低功耗、小成本的硬件设计。通过增加SIM卡的数量,将网关转发“ 北斗”数据的频率降至最低的5 s,提高了网关的通信速率。通过软件设计实现了Zigbee无 线传感网络和“北斗一代”系统之间数据的透明交换。该方法已成功应用于野外油气井远程 监控系统中。