防潮减灾中几个重要问题的探讨与建议

本文就防潮减灾中四个重要问题进行了深入探讨。即：(1)历史文献记述及历史潮灾调查;(2)可能最大风暴潮：(3)防潮减灾预案;(4)新形势、新灾情、新问题。最后并提出四点建议。     

Predicting the capability-polar-plots for dynamic positioning systems for offshore platforms using artificial neural networks

As the capability of polar plots becomes better understood, improved dynamic positioning (DP) systems are possible as the control algorithms greatly depend on the accuracy of the aerodynamic and hydrodynamic models. The measurements and estimation of the environmental disturbances have an important role in the optimal design and selection of a DP system for offshore platforms. The main objective of this work is to present a new method of predicting the Capability-Polar-Plots for offshore platforms using the combination of the artificial neural networks (NNs) and the capability polar plots program (CPPP). The estimated results from a case study for a scientific drilling vessel are presented. A trained artificial NN is designed in this work and is able to predict the maximum wind speed at which the DP thrusters are able to maintain the offshore platform in a station-keeping mode in the field site. This prediction for the maximum wind speed will be a helpful tool for DP operators in managing station-keeping for offshore platforms in an emergency situation where the automation of the DP systems is disabled. It is obvious from the obtained results that the developed technique has potential for the estimation of the capability-polar-plots for offshore platforms. This tool would be suitable for DP operators to predict the maximum wind speed and direction in a very short period of time.     

Analysis of suspended sediment yields after low impact forest harvesting

Disturbances to forest catchments have profound effects on the environment of headwater streams and have an impact on suspended sediment (SS) management. Forest harvesting is a dominant factor in increasing SS yields. Road construction, skidder activity and ploughing associated with harvesting cause serious soil disturbance that results in SS increases. However, few studies have shown whether harvesting itself increases SS yields. This study examined how harvesting influenced SS yields in a steep forested area. During harvesting, soil surface disturbance was prevented as much as possible by using skyline logging treatments and piling branches and leaves at selected locations in the watershed. Using these methods, the representative SS rating curve did not change significantly after harvesting. The results also show that the characteristics of SS transport were related to the SS source area, and reveal that the riparian zone/stream bank was a dominant SS source area at the study site. Annual SS yields did not increase despite increasing annual water yields after harvesting. The limited water capacity of the soil at the study site likely led to only slight differences in pre‐ and post‐harvest water discharge from heavy rainfall events. Most SS was transported during heavy rainfall events, and increases in SS yields were not detected after harvesting. We concluded that it is possible to prevent post‐harvest SS increases by performing careful, low‐impact harvesting procedures. Copyright © 2007 John Wiley & Sons, Ltd.     

A comparison of techniques for generating forest ownership spatial products

To fully understand forest resources, it is imperative to understand the social context in which the forests exist. A pivotal part of that context is the forest ownership. It is the owners, operating within biophysical and social constraints, who ultimately decide if the land will remain forested, how the resources will be used, and by whom. Forest ownership patterns vary substantially across the United States. These distributions are traditionally represented with tabular statistics that fail to capture the spatial patterns of ownership. Existing spatial products are not sufficient for many strategic-level planning needs because they are not electronically available for large areas (e.g., parcels maps) or do not provide detailed ownership categories (e.g., only depict private versus public ownership). Thiessen polygon, multinomial logit, and classification tree methods were tested for producing a forest ownership spatial dataset across four states with divergent ownership patterns: Alabama, Arizona, Michigan, and Oregon. Over 17,000 sample points with classified forest ownership, collected as part of the USDA Forest Service, Forest Inventory and Analysis (FIA) program, were divided into two datasets, one used as the dependent variable across all of the models and 10 percent of the points were retained for validation across the models. Additional model inputs included a polygon coverage of public lands from the Conservation Biology Institute’s Protected Areas Database (PAD) and data representing human population pressures, road densities, forest characteristics, land cover, and other attributes. The Thiessen polygon approach predicted ownership patterns based on proximity to the sample points in the model dataset and subsequent combining with the PAD ownership data layer. The multinomial logit and classification tree approaches predicted the ownership at the validation points based on the PAD ownership information and data representing human population, road, forest, land cover, and other attributes. The percentage of validation points across the four states correctly predicted ranged from 76.3 to 78.9 among the methods with corresponding weighted kappa values ranging from 0.73 to 0.76. Different methods performed slightly, but statistically significantly, better in different states Overall, the Thiessen polygon method was deemed preferable because: it has a lower bias towards dominant ownership categories; requires fewer inputs; and is simpler to implement.     

From Community Forest Management to Polycentric Governance: Assessing Evidence from the Bottom Up

Decentralization of governance is an emerging trend in many natural resource sectors in both developed and developing countries. Despite the normative agenda of community-based natural resource management for social and ecological outcomes, a shift to multilevel or polycentric theorizing is warranted. Polycentric governance recognizes the importance of cross-scale interactions, as well as the horizontal and vertical institutional linkages of authority, networks, and markets in which community institutions are embedded. Based on qualitative community forestry research in Revelstoke, British Columbia, Canada, this article explores the themes of livelihood and local economy, collaborative forest planning and participation, and environmental governance. Bottom-up empirical evidence suggests that viewing community forestry through a polycentric governance network is necessary for theorizing complex cross-scale dynamics. Incentivizing policies that encourage the development of polycentric systems for natural resource governance is important for maintaining local benefits, while increasing adaptive capacity to deal with complex social–ecological challenges.     

A MULTIBLOCK PARTIAL LEAST SQUARES ALGORITHM FOR INVESTIGATING COMPLEX CHEMICAL SYSTEMS

The details of a general multiblock partial least squares(PLS)algorithm based on one originallypresented by Wold et al.have been developed and are completely presented.The algorithm can handlemost types of relationships between the blocks and constitutes a significant advancement in the modelingof complex chemical systems.The algorithm has been programmed in FORTRAN and has been testedon two simulated multiblock problems,a three-block and a five-block problem.The algorithm combinesthe score vectors for all blocks predicting a particular block into a new block.This new block is used topredict the predicted block in a manner analogous to the two-block PLS.In a similar manner if one blockpredicts more than one other block,the score vectors of all predicted blocks are combined to form a newblock,which is then predicted by the predictor block as in the two-block PLS.Blocks that both predictand are predicted are treated in such a way that both of these roles can be taken into account whencalculating interblock relationships.The results of numerical simulations indicate that the computerprogram is operating properly and that the multiblock PLS produces meaningful and consistent results.     

GIS程序符号的设计与实现

提出了一种程序符号设计与管理方案,解决了复杂符号的制作问题,利用GIS软件Geostar5.0开发了程序符号系统,验证了该方案的可行性与实用性。     

短周期笔绘记录地震仪常数计算程序

结合本台实际情况，应用BASIC语言编写了本程序，运用于台站实际工作，减轻了台站观测人员的工作量，输出图表与规范要求的短周期笔绘 记录地震仪常数测算表一致，计划结果的精度与取位符合规模要求。     

Variations of the Treescape in Relation to Urban Development in a Chinese City: The Case of Nanjing*

Urban trees, as prominent and pertinent landscape elements of cities, are increasingly studied by both practitioners and academics. Trees in Chinese cities have hitherto received little detailed analysis from the viewpoint of urban forestry or landscape analysis. This study attempts a comprehensive evaluation of the tree population in Nanjing, focusing on the association between urban development and treescape attributes. Six districts, covering the main built‐up area of 130 km², formed the study area. Nine land‐use types with varied urban morphology and three urban zones with different development history were identified, within which subareas and trees were sampled for field study of tree dimensions, tree performance, and site characteristics. Statistical analyses on the 6,527 surveyed trees verify that tree performance is significantly associated with land use, site condition, and related human activities. Treescape is associated with housing ownership, town planning, and the history of urban expansion. The relationship between treescape and urban landscape units can furnish hints for improved urban forest planning and management and better coordination between planners and landscape professionals.     

THE POLITICAL ECONOMY OF FOREST POLICY IN MEXICO AND CHILE

Widespread agreement exists on the broad outlines of the concept of sustainable development for developing countries. This calls for a development model capable of meeting basic needs without depleting natural resources at a rate that robs future generations of their use. In this regard, citizen participation is also considered key to legitimise such policy choices. However, there is considerable disagreement over the substance and meaning of the major components of the concept and the relationship between them. This paper argues that positions in policy disputes over the sustainable development of the forest cluster in two distinct approaches: market‐friendly initiatives and grassroots development. Since market economies prevail almost everywhere, the question that is posed concerns the conditions under which the grassroots development approach is included as a significant complement to market‐friendly initiatives. This is a political question, requiring an examination of actors, interests and power resources. The paper thus applies a political economy framework to a paired comparison of Mexico, where grassroots development approaches (community forestry) had notable successes, and Chile, where market‐friendly forest policy crowded out alternatives.