Knowledge-based spatiotemporal linear abstraction

We present a theoretical framework and a case study for reusing the same conceptual and computational methodology for both temporal abstraction and linear (unidimensional) space abstraction, in a domain (evaluation of traffic-control actions) significantly different from the one (clinical medicine) in which the method was originally used. The method, known asknowledge-based temporal abstraction, abstracts high-level concepts and patterns from time-stamped raw data using a formal theory of domain-specific temporal-abstraction knowledge. We applied this method, originally used to interpret time-oriented clinical data, to the domain of traffic control, in which the monitoring task requires linear pattern matching along both space and time. First we reused the method for creation of unidimensional spatial abstractions over highways, given sensor measurements along each highway measured at the same time point. Second, we reused the method to create temporal abstractions of the traffic behaviour, for the same space segments, but during consecutive time points. We defined the corresponding temporal-abstraction and spatial-abstraction domain-specific knowledge. Our results suggest that (1) the knowledge-base temporal-abstraction method is reusable over time and unidimensional space as well as over significantly different domains; (2) the method can be generalised into a knowledge-based linear-abstraction method, which solves tasks requiring abstraction of data along any linear distance measure; and (3) a spatiotemporal-abstraction method can be assembled, from two copies of the generalised method and a spatial-decomposition mechanism, and is applicable to tasks requiring abstraction of time-oriented data into meaningful spatiotemporal patterns over a linear, decomposable space, such as traffic over a set of highways.     

Reinforcement learning on explicitly specified time scales

In recent years hierarchical concepts of temporal abstraction have been integrated in the reinforcement learning framework to improve scalability. However, existing approaches are limited to domains where a decomposition into subtasks is known a priori. In this article we propose the concept of explicitly selecting time scale related abstract actions if no subgoal related abstract actions are available. This concept is realised with multi-step actions on different time scales that are combined in one single action set. We exploit the special structure of the action set in the MSA-Q-learning algorithm. This approach is suited for learning optimal policies in unstructured domains where a decomposition into subtasks is not known in advance or does not exist at all. By learning different explicitly specified time scales simultaneously, we achieve a considerable improvement of learning speed, which we demonstrate on several benchmark problems.     

Hierarchical Processing for Evolving Recursive and Modular Programs Using Higher-Order Functions and Lambda Abstraction

We present a novel approach using higher-order functions and abstraction to evolve recursive and modular programs. Moreover, a new term structure abstraction is introduced to describe the property emerged from the higher-order function program structure. We test this technique on the general even-parity problem. The results indicate that this approach is very effective with the general even-parity problem due to the appropriate selection of the foldr higher-order function. Initially, foldr structure abstraction identify the promising area of the search space at generation zero. Once the population is within the promising area, foldr structure abstraction provides hierarchical processing for search. Consequently, solutions to the general even-parity problem are found very efficiently. We identify the limitations of this new approach and conclude that only when the appropriate higher-order function is selected that the benefits of structure abstraction show.     

小波全分量层相乘滤波及其在GPR反射目标提取中的应用

从GPR工程实践需求出发,提出了一种新的保留小波分解系数的方法,即全分量层相乘滤波,主要包括2个步骤:对GPR剖面作小波分解,分量层对应相乘得到空间滤波器;用得到的滤波器与各分量层的小波系数直接相乘,得到滤波后的小波系数,重构得到处理后的剖面.依据分量层相乘办法的不同可分为分量层递推相乘(DM1)和全分量层相乘(DM2).DM2在提取GPR剖面目标反射中的实际应用表明,该方法能突出有用信号,进行目标提取.     

Incremental hierarchical construction of modular supervisors for discrete-event systems

Adoption of the supervisory control framework introduced by Ramadge and Wonham has been slowed somewhat by the problem of state space explosion that arises in systems of the scale common to most industrial applications. Hierarchical and modular approaches have been explored historically as means for addressing this problem. The limitations of these approaches include that a ‘consistent’ hierarchy is often difficult to achieve, and that modular supervisors often conflict with each other when acting in conjunction. This paper offers an approach that addresses some of these issues by incrementally building modular supervisors that are nonconflicting by construction. Abstractions are employed to make the procedure more computationally feasible. Proof is given showing the set of modular supervisors generated in this manner meet given specifications without blocking. Furthermore, examples are provided that demonstrate the reduction in complexity that this approach provides.     

Use of mesohabitat‐specific relationships between flow velocity and river discharge to assess invertebrate minimum flow requirements

The benthic macroinvertebrate community in the sixth order lowland River Spree (Germany) was investigated in order to assess ecological effects of a flow reduction. The benthic habitat was composed of visually distinguishable mesohabitats. Eight mesohabitats were delineated, Dreissena‐bank, unionid mussel bed, rip‐rap, coarse woody debris (CWD), alder roots, stable sand, shifting sand and mud. The mesohabitats differed in their physical structure and hydraulic nature. These functional habitats were partly inhabited by distinct invertebrate assemblages. The use of mesohabitat‐specific relationships between flow velocity and discharge seemed the most appropriate approach in order to assess the impact of flow reduction on lotic fauna. In combination with the species‐specific optima and tolerances for flow velocity, this approach can be used to develop a minimum flow level that mitigates the effects of flow reduction and enables the persistence of rheophilic invertebrates in their specific mesohabitat. Copyright © 2001 John Wiley & Sons, Ltd.     

流域水资源配置方法研究

流域水资源配置解决的主要问题是确定不同天然来水情况下的省际规划出境水量,以及平原地下水规划开采量和入海水量.省际规划出境水量是流域水资源管理的基础指标,平原地下水规划开采量和入海水量是反映生态状况的指标.结合严重缺水的海河流域,研究并提出采用典型年法进行水资源配置的技术路线,提出2010规划水平年满足各项控制指标条件下省际配置分区经济社会发展的可利用水量.     

Tradeable Rights for Water Abstraction

The Environment Agency has a statutory duty to secure the proper use of water resources, which is now considered inter alia to include an economically efficient allocation of resources as far as is possible within the current legislation. This paper considers the practical extent to which water rights can be traded within the existing system of regulation as a means of (a) improving the economic efficiency of resource allocation, and (b) satisfying customer demand for additional supplies. Outline proposals are also made for deregulation of current legislation to encourage further trading through less restrictive regulation.     

Conversion of simulation processes to pascal constructs

Although the expressive power of retentive control is widely accepted, languages possessing such control forms are not always available. In this paper, we present an implementation technique to extend a recursive language to one containing simulation processes. In particular, we report on the design of a preprocessor that translates SimCal, a language that combines Pascal and the process abstraction of Simula, into Pascal. The translation is done automatically by the preprocessor without additional information from the user. The preprocessor has been implemented for a microcomputer using Turbo Pascal, which is also used as the target language. SimCal has been found to be useful for teaching simulation and for programming simulation applications.     

丝绸图案设计中的抽象手法

现代真丝绸作为一种出口高档消费品,必然要更多地反映当代文化,抽象图案就是其中之一。本文阐述了丝绸图案从写实花卉走向抽象几何形的历史过程,并系统地论述了丝绸图案中几种抽象手法的运用。