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Modular fuzzy-reinforcement learning approach with internal model capabilities for multiagent systems.

To date, many researchers have proposed various methods to improve the learning ability in multiagent systems. However, most of these studies are not appropriate to more complex multiagent learning problems because the state space of each learning agent grows exponentially in terms of the number of partners present in the environment. Modeling other learning agents present in the domain as part of the state of the environment is not a realistic approach. In this paper, we combine advantages of the modular approach, fuzzy logic and the internal model in a single novel multiagent system architecture. The architecture is based on a fuzzy modular approach whose rule base is partitioned into several different modules. Each module deals with a particular agent in the environment and maps the input fuzzy sets to the action Q-values; these represent the state space of each learning module and the action space, respectively. Each module also uses an internal model table to estimate actions of the other agents. Finally, we investigate the integration of a parallel update method with the proposed architecture. Experimental results obtained on two different environments of a well-known pursuit domain show the effectiveness and robustness of the proposed multiagent architecture and learning approach.

Journal Article↗

Expert-system-based fuzzy control of arterial pressure by drug infusion.

This paper proposes a new type of fuzzy controller which is based on the general-purpose Fuzzy LOgic Production System shell FLOPS [1, 2, 7, 12, 13]. Human mean arterial pressure was controlled by the proposed fuzzy controller, in digital computer stimulation, by regulating the infusion rate of the drug, sodium nitroprusside. Under nonstationary arterial background pressure noise, mean arterial pressures of different patients with different sensitivities to sodium nitroprusside were controlled satisfactorily. Furthermore, the effects of changing the adjustable parameters of the proposed fuzzy controller on the control results were studied. Finally, the performance of the proposed fuzzy controller was compared to that of a fine-tuned Proportional-Integral (PI) controller by using a first-order linear model.

Blood Pressure↗

[Logic and analogy in psychiatry. Their "common root"].

Logic and analogy pose a fundamental problem in psychiatry. The latter is at the moment renewed by the existence of fuzzy logics. The authors put forward the hypothesis of a common root using the systemal method, an original strategy and a particular test. Several questions are tackled: definitions, hierarchy, linking, linearity or circularity, closed of open aspect of thought process, integration, separation or continuity, ways of appearance, discrete organization or organization in networks, different or common origin, importance of modal and non monotonous logics. A discussion and the consequences of this hypothesis are specified.

Humans↗

POPFNN: A Pseudo Outer-product Based Fuzzy Neural Network.

A novel fuzzy neural network, called the pseudo outer-product based fuzzy neural network (POPFNN), is proposed in this paper. The functions performed by each layer in the proposed POPFNN strictly correspond to the inference steps in the truth value restriction method in fuzzy logic [[Mantaras (1990)] Approximate reasoning models, Ellis Horwood]. This correspondence gives it a strong theoretical basis. Similar to most of the existing fuzzy neural networks, the proposed POPFNN uses a self-organizing algorithm ([Kohonen, 1988], Self-organization and associative memories, Springer) to learn and initialize the membership functions of the input and output variables from a set of training data. However, instead of employing the popularly used competitive learning [[Kosko (1990)] IEEE Trans. Neural Networks, 3(5), 801], this paper proposes a novel pseudo outer-product (POP) learning algorithm to identify the fuzzy rules that are supported by the training data. The proposed POP learning algorithm is fast, reliable, and highly intuitive. Extensive experimental results and comparisons are presented at the end of the paper for discussion. Copyright 1996 Elsevier Science Ltd.

Journal Article↗

Industrial application of fuzzy control to large-scale recombinant vitamin B2 production.

A fuzzy control system featuring the identification of culture phases by fuzzy logic was applied to the large-scale recombinant vitamin B2 (VB2) production at the Fukuroi factory of Nippon Roche, Fukuroi. Prior to actual operation, the knowledge base for fuzzy control was tuned and verified by a simulation system. Only four rules, formulated as IF approximately THEN instructions and membership functions for state variables, are employed to control the feed rate and pH of the fed-batch culture. By applying fuzzy control, total VB2 production and VB2 yield was increased by 6-16% and 4-11% compared with conventional control, respectively. Operating stability was also improved. The large-scale fermentor used for VB2 production has been successfully operated under the control of the fuzzy system for more than 2 years.

Journal Article↗

Production of highly concentrated xylitol by Candida magnoliae under a microaerobic condition maintained by simple fuzzy control.

Microbial production of xylitol from xylose was investigated using Candida magnoliae. In particular, the effect of the oxygenation condition on the xylitol production yield was examined and the significance of maintaining a microaerobic condition was demonstrated. A simple system of fuzzy logic control (FLC) was devised to maintain the microaerobic condition in the xylitol production phase by regulating the proportion of air (air flow rate) supplied to the fermentor. The input variables to the fuzzy control system were the dissolved oxygen (DO) concentration in the culture broth and the CO2 concentration in the exit gas. A batch cultivation test using the FLC system confirmed the importance of maintaining a constant microaerobic condition throughout the xylitol production phase, and indicated it would be advantageous for this phase to be prolonged. An intermittent fed-batch culture was therefore carried out. The FLC system allowed a constant microaerobic condition to be maintained, resulting in minimal cell mass production and constant xylitol accumulation in the culture medium. As a consequence, a very high xylitol concentration of 356 g/dm3 could be attained. The xylitol yield in the fed-batch culture was 0.75, which corresponded to 82% of the theoretical yield.

Journal Article↗

CADIAG: approaches to computer-assisted medical diagnosis.

CADIAG-1 is a medical expert system, based on a symbolic logic representation of medical relationships. Strong relationships such as confirming, excluding or obligatory occurrence are applied to confirm or exclude diagnoses. Weak relationships are represented by facultative and not confirming relationships (FN-relationships). Diagnostic hypotheses are established by systematic combination of symptoms showing FN-relationships. CADIAG-2, a medical expert system based on fuzzy set theory and fuzzy logic, allows detailed specification of medical relationships. Here the diagnostic process also provides confirmed and excluded diagnoses as well as diagnostic hypotheses. Hypotheses are calculated by considering fuzzy relationships between medical entities. 426 cases with rheumatic and 47 cases with pancreatic diseases were tested. For CADIAG-1, the overall accuracy for confirmation and hypothesis generation is calculated with 91.1% for rheumatic diseases and 100% for pancreatic diseases. CADIAG-2 reached an overall accuracy of 93.7% for rheumatic cases and 91.5% for pancreatic cases.

Artificial Intelligence↗

Computational functions in biochemical reaction networks.

In prior work we demonstrated the implementation of logic gates, sequential computers (universal Turing machines), and parallel computers by means of the kinetics of chemical reaction mechanisms. In the present article we develop this subject further by first investigating the computational properties of several enzymatic (single and multiple) reaction mechanisms: we show their steady states are analogous to either Boolean or fuzzy logic gates. Nearly perfect digital function is obtained only in the regime in which the enzymes are saturated with their substrates. With these enzymatic gates, we construct combinational chemical networks that execute a given truth-table. The dynamic range of a network's output is strongly affected by "input/output matching" conditions among the internal gate elements. We find a simple mechanism, similar to the interconversion of fructose-6-phosphate between its two bisphosphate forms (fructose-1,6-bisphosphate and fructose-2,6-bisphosphate), that functions analogously to an AND gate. When the simple model is supplanted with one in which the enzyme rate laws are derived from experimental data, the steady state of the mechanism functions as an asymmetric fuzzy aggregation operator with properties akin to a fuzzy AND gate. The qualitative behavior of the mechanism does not change when situated within a large model of glycolysis/gluconeogenesis and the TCA cycle. The mechanism, in this case, switches the pathway's mode from glycolysis to gluconeogenesis in response to chemical signals of low blood glucose (cAMP) and abundant fuel for the TCA cycle (acetyl coenzyme A).

Biochemistry↗

Problems in establishing the medical expert systems CADIAG-1 and CADIAG-2 in rheumatology.

CADIAG-1 and CADIAG-2 are medical expert systems with applications in rheumatology, gastroenterology, and hepatology. CADIAG-1 is based on a symbolic logic representation of medical relationships between symptoms, signs, or findings and diseases. Definite relationships (obligatory occurrence, confirming, and excluding) as well as uncertain relationships (facultative occurrence and not confirming) are applied to confirm or exclude diagnoses and to establish diagnostic hypotheses. CADIAG-2 employs fuzzy set theory and fuzzy logic to formalize medical entities and relationships. The medical concept of confirming or excluding diagnoses is identical to that of CADIAG-1, but diagnostic hypotheses are generated differently. Here, a documentation of medical relationships allowing gradual transitions from "always" to "never" for the frequencies of occurrence of symptoms with and from "strong" to "weak" for their strengths of confirmation for diseases leads to strongly or weakly supported diagnostic hypotheses in the actual case. Tests with 322 real patient cases from a rheumatological hospital, each including between 500 and 700 symptoms, signs, and findings, were carried out. The percentage of cases diagnosed correctly is about 80%. Problems and pitfalls that became apparent in the evaluation of the cases are shown and discussed.

Adult↗

Intelligent control of a cryogenic cooling plant based on blackboard system architecture.

Intelligent system techniques have been rapidly assimilating into process control engineering, with many applications reported in the last decade. Intelligent control is bringing a new perspective as well as new challenges to process control. In this paper, a software architecture for a Blackboard for Integrated Intelligent Control Systems (BIICS) is described. The system is designed to simultaneously support multiple heterogeneous intelligent methodologies, such as neural networks. expert systems, fuzzy logic, neural networks and genetic algorithms. It will be shown how such methodologies can be readily assimilated into the software architecture. The BIICS system represents a multi-purpose platform for design and simulation of intelligent control paradigms for different kinds of processes. Currently the system utilizes intelligent control techniques (neuro-fuzzy and genetic optimization) for controlling a cryogenic plant used for superconductor testing at temperatures below 100 K.

Journal Article↗

Multi-sensor integration for on-line tool wear estimation through radial basis function networks and fuzzy neural network.

On-line tool wear estimation plays a very critical role in industry automation for higher productivity and product quality. In addition, appropriate and timely decision for tool change is significantly required in the machining systems. Thus, this paper is dedicated to develop an estimation system through integration of two promising technologies, artificial neural networks (ANN) and fuzzy logic. An on-line estimation system consisting of five components: (1) data collection; (2) feature extraction; (3) pattern recognition; (4) multi-sensor integration; and (5) tool/work distance compensation for tool flank wear, is proposed herein. For each sensor, a radial basis function (RBF) network is employed to recognize the extracted features. Thereafter, the decisions from multiple sensors are integrated through a proposed fuzzy neural network (FNN) model. Such a model is self-organizing and self-adjusting, and is able to learn from the experience. Physical experiments for the metal cutting process are implemented to evaluate the proposed system. The results show that the proposed system can significantly increase the accuracy of the product profile.

Journal Article↗

Fuzzy assessment of sleep-disordered breathing during continuous positive airway pressure therapy.

We propose a new method of quantifying sleep-disordered breathing (SDB) for the purpose of automating continuous positive airway pressure (CPAP) titration. Our algorithm, based on fuzzy logic, emulates the less-than-crisp kind of decision-making generally employed at the human level. Three input variables were first derived on a breath-by-breath basis from respiratory airflow measurements. These were: (1) the relative duration of inspiratory flow limitation in each breath; (2) the degree of hypopnea relative to the past 15 breaths; and (3) the intensity of snoring. Using these descriptors as inputs, our fuzzy inference algorithm produced a "severity index" (SI) quantifying the degree of SDB. Severity index was determined in CPAP titration procedures conducted on one normal snorer and 12 patients with moderate-to-severe obstructive sleep apnea. SI computed over the last 6 minutes of each CPAP level was compared against other more-conventional indices of SDB, such as total pulmonary resistance (RL), the number of apneas and hypopneas (NAH), and the number of arousals (NAr). In all but one of the subjects, the correlation coefficients for SI vs each of RL, NAH, and NAr were significantly different from zero, but not different from each other. The group correlation coefficients for SI vs RL, NAH, and NAr were 0.89, 0.86, and 0.87, respectively, demonstrating that SI accurately quantifies SDB. SI collapses multiple features of the airflow pattern into a single index and, therefore, may be useful as a "feedback" variable for the automatic control of CPAP therapy.

Adult↗

Expert systems in histopathology. V. DS theory, certainty factors and possibility theory.

Uncertainty management for the evaluation of evidence based on linguistic and conceptual data is taking advantage of developments in the Dempster-Shafer (DS) theory of evidence, possibility theory and fuzzy logic. The DS theory offers the capability to assess the uncertainty of different subsets of assertions in a domain and the way in which uncertainty is affected by accumulating evidence. The DS theory goes beyond probability theory in its ability to represent ignorance about certain aspects of a situation. However, the theory is very sensitive to the numerical assessments provided by users and can lead to intuitively unexpected and even undesirable results. Certainty factors are widely used in various expert systems. Their definition and updating may follow either a probabilistic model or fuzzy set theoretic concept.

Data Interpretation, Statistical↗

[Development of fuzzy blood pressure control system].

Fuzzy blood pressure control system has been developed to regulated blood pressure by using vaso-active drugs, which aims the medical treatment of the patient. Fuzzy logic is used to convert heuristic control rules as a physician's knowledge into an automatic control strategy. Usually, a physician decides infusion rate based on referring ideal pressure trajectory during control. To emulate such a physician's heuristic control, the controller refer an ideal pressure trajectory, for example, from the normal level to the target level. One of Inputs to the controller is a difference between real pressure and ideal pressure, where another is a rate of its pressure difference. An output from the controller is the change in drug infusion rate. Both of inputs and output are transformed into fuzzy sets, whose membership functions are predefined. Twenty one physician's control rules are converted into fuzzy control rules. The fuzzy control procedure consists of three steps: (1) computing both input values and finding their appropriate membership values (grade), (2) finding applied rules and applying fuzzy composition to infer weighted output fuzzy sets, (3) inferring the change in drug infusion rate by taking the center of mass of the membership function of output. Nine animal experiments are performed to evaluate the developed system by using rats with vasopressor drug. Angiotensin II Blood pressure was elevated from normal pressure (around 100 mmHg) to 150 mmHg. Satisfactory blood pressure control was realized on eight experiments and effectiveness of the controller was confirmed confirmed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Beyond self and nonself: fuzzy recognition of the immune system.

Self-nonself discrimination of the immune system is a widely accepted principle of immunology; however, abundant existing and physiologic functions of harmless autoimmunity as well as degeneracy of antigen recognition expose the over-simplification of the two-valued doctrine. Here, based on infinite-value fuzzy logic, we propose that the immune repertoire, as a consequence of central tolerance, is able to recognize both self and nonself antigens to a certain degree, compensating for the inadequacy of the two-valued self-nonself doctrine. Subthreshold recognition of self antigens is necessary for the generation of regulatory T cells, survival of both naive and memory T cells and other physiologic functions. The kind and magnitude of the immune response depend on the affinity between the antigen (self and foreign) and the T-cell receptor, and microenvironmental and cellular threshold. The outcome of self-nonself discrimination is influenced fundamentally by central tolerance and further dynamic regulation of threshold molecules both in time and space. Understanding the fuzzy feature of the immune system may shed light on mechanisms of autoimmune diseases, cancers and other chronic diseases, and lead to the design of novel vaccines or immunotherapies.

Abatacept↗

Visualization of nerve fiber orientation in gross histological sections of the human brain.

Diffusion weighted magnetic resonance imaging (DWMRI) allows visualization of the orientation of the nervous fibers in the living brain. For comparison, a method was developed to examine the orientation of fibers in histological sections of the human brain. Serial sections through the entire human brain were analyzed regarding fiber orientation using polarized light. Direction of fibers in the cutting plane was obtained by measuring the azimuth with the lowest intensity value at each point, and inclination of fibers in the section was evaluated using fuzzy logic approximations. Direction and inclination of fibers revealing their three-dimensional orientation were visualized by colored arrows mapped into the images. Using this procedure, various fiber tracts were identified (pyramidal tract, radiatio optica, radiatio acustica, arcuate fascicle, and 11 more). Intermingled fibers could be separated from each other. The orientation of the fiber tracts derived from polarized light microscopy was validated by confocal laser scanning microscopy in a defined volume of the internal capsule, where the fiber orientation was studied in four human brains. The polarization method visualizes the high degree of intermingled fiber bundles in the brain, so that distinct fiber pathways cannot be understood as solid, compact tracts: Neighbouring bundles of fibers can belong to different systems of fibers distinguishable by their orientation.

Aged↗

Pattern recognition strategies for molecular surfaces. II. Surface complementarity.

Fuzzy logic based algorithms for the quantitative treatment of complementarity of molecular surfaces are presented. Therein, the overlapping surface patches defined in article I1 of this series are used. The identification of complementary surface patches can be considered as a first step for the solution of molecular docking problems. Standard technologies can then be used for further optimization of the resulting complex structures. The algorithms are applied to 33 biomolecular complexes. After the optimization with a downhill simplex method, for all these complexes one structure was found, which is in very good agreement with the experimental results.

Journal Article↗

Free food or earned food? A review and fuzzy model of contrafreeloading

Animals will work (e.g. lever press) for 'earned' food even though identical 'free' food can easily be obtained from a nearby dish. This phenomenon, called contrafreeloading, appears to contradict a basic tenet of most learning, motivation and optimal foraging theories; namely that animals strive to maximize the ratio of reward, or benefit, to effort, or cost. This paper reviews the factors that have been found to affect the level of contrafreeloading, to try to explain the behaviour. In experiments involving intensive training, contrafreeloading may be explained on the basis of secondary reinforcement and/or differential exposure to the alternative food sources. However, contrafreeloading also occurs without prior training. Contrafreeloading declines with increasing hunger and with increases in the effort required to obtain the earned food: it also has an inverted-U relationship with the degree of stimulus change associated with the earned food. A fuzzy logic model is developed to predict the outcome of interactions between these factors. The model successfully simulates previous empirical findings and provides novel, testable predictions. It is argued that contrafreeloading does not contradict reinforcement theory, provided that the sensory reinforcement obtained from stimuli associated with the earned food is also taken into account. A functional explanation of why such stimuli are reinforcing, and of contrafreeloading itself, is based upon the advantage of gathering information for animals living in changing environments (i.e. an information primacy model). Animals work for earned food in order to update their estimate of a currently sub-optimal food source because, in the longer term, it may unpredictably become the optimal place to feed. Contrafreeloading is therefore a behaviour that, under natural conditions, is adaptive.

Journal Article↗