Fuzzy expert systems in civil engineering

Imperial Users onl

Aided diagnosis of structural pathologies with an expert system

Sustainability and safety are social demands for long-life buildings. Suitable inspection and maintenance tasks on structural elements are needed for keeping buildings safely in service. Any malfunction that causes structural damage could be called pathology by analogy between structural engineering and medicine. Even the easiest evaluation tasks require expensive training periods that may be shortened with a suitable tool. This work presents an expert system (called Doctor House or DH) for diagnosing pathologies of structural elements in buildings. DH differs from other expert systems when it deals with uncertainty in a far easier but still useful way and it is capable of aiding during the initial survey 'in situ', when damage should be detected at a glance. DH is a powerful tool that represents complex knowledge gathered from bibliography and experts. Knowledge codification and uncertainty treatment are the main achievements presented. Finally, DH was tested and validated during real surveys.Peer ReviewedPostprint (author's final draft

Characterising bias in regulatory risk and decision analysis: An analysis of heuristics applied in health technology appraisal, chemicals regulation, and climate change governance

In many environmental and public health domains, heuristic methods of risk and decision analysis must be relied upon, either because problem structures are ambiguous, reliable data is lacking, or decisions are urgent. This introduces an additional source of uncertainty beyond model and measurement error – uncertainty stemming from relying on inexact inference rules. Here we identify and analyse heuristics used to prioritise risk objects, to discriminate between signal and noise, to weight evidence, to construct models, to extrapolate beyond datasets, and to make policy. Some of these heuristics are based on causal generalisations, yet can misfire when these relationships are presumed rather than tested (e.g. surrogates in clinical trials). Others are conventions designed to confer stability to decision analysis, yet which may introduce serious error when applied ritualistically (e.g. significance testing). Some heuristics can be traced back to formal justifications, but only subject to strong assumptions that are often violated in practical applications. Heuristic decision rules (e.g. feasibility rules) in principle act as surrogates for utility maximisation or distributional concerns, yet in practice may neglect costs and benefits, be based on arbitrary thresholds, and be prone to gaming. We highlight the problem of rule-entrenchment, where analytical choices that are in principle contestable are arbitrarily fixed in practice, masking uncertainty and potentially introducing bias. Strategies for making risk and decision analysis more rigorous include: formalising the assumptions and scope conditions under which heuristics should be applied; testing rather than presuming their underlying empirical or theoretical justifications; using sensitivity analysis, simulations, multiple bias analysis, and deductive systems of inference (e.g. directed acyclic graphs) to characterise rule uncertainty and refine heuristics; adopting “recovery schemes” to correct for known biases; and basing decision rules on clearly articulated values and evidence, rather than convention

Knowledge Based Systems: A Critical Survey of Major Concepts, Issues, and Techniques

This Working Paper Series entry presents a detailed survey of knowledge based systems. After being in a relatively dormant state for many years, only recently is Artificial Intelligence (AI) - that branch of computer science that attempts to have machines emulate intelligent behavior - accomplishing practical results. Most of these results can be attributed to the design and use of Knowledge-Based Systems, KBSs (or ecpert systems) - problem solving computer programs that can reach a level of performance comparable to that of a human expert in some specialized problem domain. These systems can act as a consultant for various requirements like medical diagnosis, military threat analysis, project risk assessment, etc. These systems possess knowledge to enable them to make intelligent desisions. They are, however, not meant to replace the human specialists in any particular domain. A critical survey of recent work in interactive KBSs is reported. A case study (MYCIN) of a KBS, a list of existing KBSs, and an introduction to the Japanese Fifth Generation Computer Project are provided as appendices. Finally, an extensive set of KBS-related references is provided at the end of the report

Development of a decision support system for assessment of mobile bridges

The development of a prototype Decision Support System (DSS) for the condition assessment of the Armored Vehicle Launched Bridge (AVLB) has been demonstrated in the current work. AVLB is a mobile bridge that has been used by the US Army for tank and assault vehicle crossing. It is employed for spanning short gaps of 50 feet or less in the terrain. The condition assessment of such bridges, to ensure safety of personnel and tank, is of strategic importance. The methodology of the prototype DSS is based on a refined visual inspection procedure and a previously established vibration measurement technique.;Conforming to the design requirements, the DSS has been developed as an Internet based, interactive application, and is integrated with an automated vibration measurement system. The web-based DSS, which incorporates an expert system and a database system, can be run from a web-browser. The development of the system, as described in this thesis, involved: identification of important visual and vibration inspection parameters; development of an expert system for bridge condition assessment, based on these parameters; and design of a database for storing important inspection data and other vital bridge records. The prototype system has been validated through limited test runs. Discussion on further verification and validation issues has also been put forth in this work.;The unique feature of this DSS is its accessibility through the Internet, which is practical considering that the AVLB is deployed worldwide. With a central database, this system provides a useful research tool for further study of the AVLB behavior and damage mechanisms, and can be used to establish failure prediction model and remaining life assessment

Invisible Hand in the Process of Making Economics or on the Method and Scope of Economics

As a social science, economics cannot be reduced to simply an a priori science or an ideology. In addition economics cannot be solely an empirical or a historical science. Economics is a research field which studies only one dimension of human behavior, with the four fields of mathematics, econometrics, ethics and history intersecting one another. The purpose of this paper is to discuss the two parts of the proposition above, in connection with the controversies surrounding the method and the scope of economics: economics as an applied mathematics and economics as a predictive/empirical science.Invisible hand, Scope and method in economics, Economics as an applied mathematics, Economics as an empirical science, Economics as ideology.

Use of fuzzy risk assessment in FMEA of offshore engineering systems

This paper proposes a novel framework for analysing and synthesising engineering system risks on the basis of a generic Fuzzy Evidential Reasoning (FER) approach. The approach is developed to simplify the inference process and overcome the problems of traditional fuzzy rule based methods in risk analysis and decision making. The framework, together with the FER approach has been applied to model the safety of an offshore engineering system. The benchmarking between the new model and a well-established Rule based Inference Methodology using the Evidential Reasoning (RIMER) is conducted to demonstrate its reliability and unique characteristics. It will facilitate subjective risk assessment in different engineering systems where historical failure data is not available in their safety practice

An Inference about Interference: A Surprising Application of Existing International Law to Inhibit Anti-Satellite Weapons

This article presents a thesis that most readers will find surprising, in an effort to develop a novel, simultaneous solution to three urgent, complex problems related to outer space. The three problems are: a) the technical fact that debris in outer space (the accumulated orbital junk produced by decades of space activities) has grown to present a serious hazard to safe and effective exploration and exploitation of space; b) the strategic fact that many countries (notably the United States, China and Russia, but others, too) continue to demonstrate a misguided interest in pursuing anti-satellite weapons, which can jeopardize the security of space; and c) the political fact that attempts to provide additional legal regulation of outer space (via new bilateral or multilateral international agreements) have failed, with little prospect for prompt conclusion of meaningful new accords. The proposed solution is to adapt existing international law in an unforeseen way. Specifically, numerous current and historical arms control treaties provide for verification of parties’ compliance via “national technical means” (NTM) of verification, which prominently include satellite-based sensory and communications systems. These treaties routinely provide protection for those essential space assets by requiring parties to undertake “not to interfere” with NTM. The argument developed here is that additional tests in space of debris-creating anti-satellite weapons would already be illegal, even without the conclusion of any dedicated new treaty against further weaponization of space, because in the current crowded conditions of space, a new cloud of orbital debris would, sooner or later, impermissibly interfere with NTM satellites. If sustained, this thesis can provide a new rationale for opposition to the development, testing, and use of anti-satellite weapons. It a legal reinforcement for the political instincts to avoid activities that further undercut the optimal usability of outer space, and it demonstrates how creative re-interpretation of existing legal provisions can promote the advancement of the rule of international law, even in circumstances where the articulation of new treaties is blocked

An " expert system building tool" incorporated with fuzzy concepts.

by Lam Wai.Thesis (M.Ph.)--Chinese University of Hong Kong, 1988.Bibliography: leaves 216-220

Generalized Probabilistic Reasoning and Empirical Studies on Computational Efficiency and Scalability

Expert Systems are tools that can be very useful for diagnostic purposes, however current methods of storing and reasoning with knowledge have significant limitations. One set of limitations involves how to store and manipulate uncertain knowledge: much of the knowledge we are dealing with has some degree of uncertainty. These limitations include lack of complete information, not being able to model cyclic information and limitations on the size and complexity of the problems to be solved. If expert systems are ever going to be able to tackle significant real world problems then these deficiencies must be corrected. This paper describes a new method of reasoning with uncertain knowledge which improves the computational efficiency as well as scalability over current methods. The cornerstone of this method involves incorporating and exploiting information about the structure of the knowledge representation to reduce the problem size and complexity. Additionally, a new knowledge representation is discussed that will further increase the capability of expert systems to model a wider variety of real world problems. Finally, benchmarking studies of the new algorithm against the old have led to insights into the graph structure of very large knowledge bases