一种由铣刀刃形求螺旋槽形状方法的探讨

根据无瞬心包络原理,用向量法推导一种由已知铣刀刃形求螺旋槽形状的简便计算公式和方法.     

下沉剂沉降堵水规律的研究

根据苏里格西区上气下水型储层的气水分布特征,该区适合下沉剂堵水压裂工艺。目前常用的下沉剂控缝高技术是在压裂时先将下沉剂通过携带液带入裂缝,随着下沉剂的下沉在裂缝的尖端处形成低渗透或不渗透的人工隔层,增加裂缝末梢的阻抗值,降低裂缝尖端的扩展应力,从而有效控制裂缝的垂向延伸。因此研究下沉剂在牛顿流体、非牛顿流体及裂缝内的沉降规律,通过合理的工艺优化设计,有利于提高堵水增气的效果。     

Global forest conservation initiatives as spaces for participation in Colombia and Costa Rica

This paper investigates the spaces for participation that have been created by readiness preparations launched in connection with the international initiative “Reduced Emissions from Deforestation and Forest Degradation” (REDD+) in Colombia and Costa Rica. I analyse the emergence of these spaces and who is leading the process in each country. My findings indicate that in Costa Rica, the public sector is leading preparation activities and creating the public spaces for participation in REDD to which private actors are invited. In Colombia on the other hand, NGOs, development assistance agencies and other private actors are leading the process and the state is the invited actor. I identify four factors that determine the scope of different actors’ possibilities to participate in the REDD+ spaces. These are (a) control of key resources, (b) ideological affinity, (c) the creation and dissemination of information and knowledge, and (d) the creation of norms to validate REDD+ pilot initiatives. The separation between these factors is not clear-cut and consequently they reinforce each other at different levels. The research presented here contributes to a better understanding of the implications that national REDD+ politics may have in the future functioning of the programme.     

A new methodology for measuring coastline recession using buffering and non‐linear least squares estimation

Coastline recession is one of the best indicators of coastal erosion. Three methods for computing coastline recession – the baseline approach, the dynamic segmentation approach and the area‐based approach – have been used, each of which has one or more drawbacks. To overcome these problems, a new methodology for measuring coastline recession is proposed, using buffering and non‐linear least squares estimation. The proposed method was compared with the three existing methods with respect to two simulated cases and two real coastlines. Test results confirmed that the new method is more reliable than the three other methods, all of which are susceptible to variability of recession, scale, number of line segments, length of coastlines and direction of the baseline. The proposed method, incorporating two physically meaningful values – magnitude and variability of coastline recession according to the mean and standard deviation of coastline offsets, respectively – presents itself as an effective alternative method of assessing coastline recession.     

Predicting Diel,Diurnal and Nocturnal Dynamics of Dissolved Oxygen and Chlorophyll‐a Using Regression Models and Neural Networks

Human‐induced and natural interruptions with continuous streams of observational data necessitate the development of gap‐filling and prediction strategies towards better understanding, monitoring and management of aquatic systems. This study quantified the efficacy of multiple non‐linear regression (MNLR) versus artificial neural network (ANN) models as well as the temporal partitioning of diurnal versus nocturnal data for the predictions of chlorophyll‐a (chl‐a) and dissolved oxygen (DO) dynamics. The temporal partitioning increased the predictive performances of the best MNLR models of diurnal DO by 45% and nocturnal DO by 4%, relative to the best diel MNLR model of diel DO ($r_{{\rm adj}}^{2} = 68.8\%$ ). The ANN‐based predictions had a higher predictive power than the MNLR‐based predictions for both chl‐a and DO except for diurnal DO dynamics. The best ANNs based on independent validations were multilayer perceptron (MLP) for diel chl‐a, generalized feedforward (GFF) for diurnal and nocturnal chl‐a, MLP for diel DO, GFF for diurnal DO, and MLP for nocturnal DO.     

山西省多普勒雷达非降水回波应用研究

本文研究了多普勒天气雷达速度图上非降水回波（不包括地物回波）的空间结构，并对太原雷达站业务运行以来多普勒天气雷达观测到的“非降水回波”的速度特征进行了深入、系统的分析。发现由大气湍流和云滴后向散射所致的非降水回波，虽然强度很弱，但其速度回波却代表了环境风的三维结构，对临近预报有5h～7h的提前量，为临近预报提供了一种新的有效手段。     

城市地表饮用水源保护研究进展

城市水资源短缺和地表饮有水污染已成为全球范围的重大问题和人类社会共同关注的焦点。城市地表饮用水源的保护已越来越受到人们的重视,它的研究应该在城市地表饮用水源的科学管理和保护中发挥重要的作用。对国内外地表饮用水源保护研究现状和地表饮用水源保护现状进行综述,同时重点分析和讨论了国内外研究存在的不足,提出城市地表饮用水源保护的未来研究重点。     

水汽场初值调整及其对华南降水预报贡献的研究

该文利用GMS多通道气象卫星资料推导得到的降水资料估算出的加热率, 作为非绝热的非线性正规模初始化过程中的非绝热强迫项, 进行风压场的初值调整, 再采用一个与模式中的对流参数化方案相反的逆运算方案, 进行水汽场的初值调整.以保证初始时刻按模式的物理参数化方案计算得到的加热率与由卫星推导的加热率一致. 这一方法在非绝热的非线性正规模初值化的框架中, 使初始时刻的水汽场得到调整.既实现了传统的初始化目标, 又提高了模式对降水的短时预报效果.对华南的两个个例的试验结果表明该文的方法是有效的.