29850435
Linguistic hedges on trapezoidal fuzzy sets: a revisit
Trapezoidal fuzzy sets (including triangular ones) are most commonly used in fuzzy modelling for computational simplicity. Applications of conventional linguistic hedges over such sets, however, often fail to result in significant changes of the sets definition. The paper presents an improved version of more effective hedges specifically devised for trapezoidal fuzzy sets, to be applied to dilate or concentrate a given set by expanding or shrinking its constituent parts. It also introduces three new hedges, named UPPER, LOWER and MID. Simulation results are provided to demonstrate the advantages of utilising the revised and newly introduced hedges for assisting fuzzy modelling, in comparison to the use of conventional ones.
14492081
Linguistic Bayesian Networks for reasoning with subjective probabilities in forensic statistics
Recent work in forensic statistics has shown how Bayesian Networks (BNs) can be used to infer the probability of defence and prosecution statements based on forensic evidence. This is an important development as it helps to quantify the meaning of forensic expert testimony during court proceedings, for example, that there is "strong support" for the defence or prosecution position. Due to the lack of experimental data, inferred probabilities often rely on subjective probabilities provided by experts. Because these are based on informed guesses, it is very difficult to express them accurately with precise numbers. Yet, conventional BNs can only employ probabilities expressed as real numbers. To address this issue, this paper presents a novel extension of probability theory. This allow the expression of subjective probabilities as fuzzy numbers, which more faithfully reflect expert opinion. By means of practical a example, it will be shown that the accurate representation of this lack of precision in reasoning with subjective probabilities has important implications for the overall result.
14802627
Fuzzy Sets and Rough Sets for Scenario Modelling and Analysis
Both fuzzy set theory and rough set theory play an important role in data-driven, systems modelling and analysis. They have been successfully applied to building various intelligent decision support systems (amongst many others). This paper presents an integrated utilisation of some recent advances in these theories for detection and prevention of serious crime (e.g. terrorism). It is shown that the use of these advanced theories offers an effective means for the generation and assessment of plausible scenarios which can each provide an explanation for the given intelligence data. The resulting systems have the potential to facilitate rapid response in devising and deploying preventive measures. The paper also suggests a number of important further challenges in consolidating and refining such systems.
25318357
Towards Fuzzy Compositional Modelling
Compositional modelling (CM) has been applied to synthesize automatically plausible scenarios in many problem domains with promising results. However, it is assumed that the generic and reusable model fragments within the knowledge base can all be expressed by precise and crisp information. This paper presents an initial attempt to extend the existing CM work to allow the generation of scenario spaces which are capable of representing, storing and supporting inference about imprecise or ill-defined data, by the use of fuzzy sets. A knowledge representation formalism for both fuzzy parameters and fuzzy constraints is incorporated into the representation of conventional model fragments. The applicability of the proposed method is illustrated by means of a simple worked example for supporting crime investigation.
2587320
Dynamic Flexible Constraint Satisfaction
Existing techniques for solving constraint satisfaction problems (CSPs) are largely concerned with a static set of imperative, inflexible constraints. Recently, work has addressed these shortcomings of classical constraint satisfaction in the form of two separate extensions known as flexible and dynamic CSP. Little, however, has been done to combine these two approaches in order to bring to bear the benefits of both in solving more complex problems. This paper presents a new integrated algorithm, Flexible Local Changes, for dynamic flexible problems. It is further shown how the use of flexible consistency-enforcing techniques can improve solution re-use and hence the efficiency of the core algorithm. Empirical evidence is provided to support the success of the present approach.
30104568
Rough set-aided keyword reduction for text categorization
The volume of electronically stored information increases exponentially as the state of the art progresses. Automated information filtering (IF) and information retrieval (IR) systems are therefore acquiring rapidly increasing prominence. However, such systems sacrifice efficiency to boost effectiveness. Such systems typically have to cope with sets of vectors of many tens of thousands of dimensions. Rough set (RS) theory can be applied to reducing the dimensionality of data used in IF/IR tasks, by providing a measure of the information content of datasets with respect to a given classification. This can aid IF/IR systems that rely on the acquisition of large numbers of term weights or other measures of relevance. This article investigates the applicability of RS theory to the IF/IR application domain and compares this applicability with respect to various existing TC techniques. The ability of the approach to generalize, given a minimum of training data is also addressed. The background of RS theory is presented, with an illustrative example to demonstrate the operation of the RS-based dimensionality reduction. A modular system is proposed which allows the integration of this technique with a large variety of different IF/IR approaches. The example application, categorization of E-mail messages, is described. Systematic experiments and their results are reported and analyzed.
7724198
Admission Control for Providing QoS in Wireless Mesh Networks
An admission control algorithm should be properly designed to guarantee the quality of service (QoS) in wireless mesh networks (WMNs). Based on channel business ratio, an admission control algorithm (ACA) is proposed to provide QoS for realtime and non-realtime traffic. For realtime traffic, all the nodes on a route make the admission control decision based on the estimation of available bandwidth. For non-realtime traffic, a rate adaption algorithm is proposed to adjust the sending rates of the source nodes to prevent a network from entering a saturated status. Finally, we demonstrate the effectiveness by simulations in NS-2.
15138853
A Cluster Warhead Projection-Time Self-Adaptive Algorithm and Simulation
This paper proposes a self-adaptive algorithm for the projection-time of the cluster warhead, which is applicable to the realization of the engineering project with low cost. On the basis of keeping the simplified correction strategy that keeps the constant distance of the projection points and through detecting the deviation of the actual trajectory data at a specific time with respect to the pre-determined trajectory data, this algorithm adopts the simple functional relationship to calculate the correction of the projection time. It adopts Monte Carlo computer simulation method to verify. The circular probable error of the projection point, caused by this algorithm, at the horizontal distance is 8.2 meters. The working content and the flow procedures for the setter and the fuze projection-time self-adaptive controller, which adopts this algorithm, are finally concluded. While being free from influencing the precision, this algorithm can effectively simplify the design of the projection-time self-adaptive projection controller, can reduce the volume and the circuit power consumption, and is applicable to be used on the fuze.
15141835
Design of Range Correction Fuze Trajectory Calculation and Control Device
For a range correction fuze of a rocket range-extended projectile, a DSP-based trajectory calculation and correction controller that is cooperated with MCU is designed to examine the axial acceleration during the flying of a projectile, and to perform the trajectory calculation and the start-up time calculation of a correction mechanism, and to control the action of a resistance-correction mechanism. When designing the hardware and the software, the tasks for DSP and MCU are reasonably assigned. The DSP mainly completes the collection of the acceleration data, the trajectory calculation and the start-up time calculation of the resistance-correction mechanism, while MCU mainly completes the time counting and controls the startup of the resistance-correction mechanism according to the time calculated by DSP. This device also can store the flying acceleration measurement data of the projectile, the trajectory calculation results, etc., which can be adopted as the basic data for analyzing the working correctness of the range correction fuse at the research stage. It is proved in the range test that this device can resist the high-impact overloading during the emission, and can normally complete the tasks such as the trajectory calculation and the resistance-correction mechanism startup control during the flying of the projectile.
4966601
Power controlled network protocols for Multi-Rate ad hoc networks
In this paper, we propose for multi-rate ad hoc networks a cross-layer design using power control, called MRPC. MRPC consists of two parts. First, we propose a multi-rate power controlled MAC protocol, called MRPC-MAC. By carefully controlling the transmission power, it can enable concurrent transmissions, which is otherwise impossible for the IEEE 802.11 standard. Second, we propose a multi-rate power controlled routing protocol, called MRPC-Routing. Different from traditional routing protocols, MRPC-Routing is not intended to find end-to-end paths, rather, it determines the next hop right before transmitting packets at the MAC layer. In this protocol, it uses the effective transport capacity as the routing metric such that short links with high bandwidth are preferred and more concurrent transmissions can be enabled. Having these coupled power controlled MAC protocol and routing protocol, MRPC can greatly improve the spatial reuse and the network throughput. Simulation results also show MRPC-MAC, MRPC-routing, and especially MRPC, can improve the network throughput significantly.
16916124
Improving throughput by tuning carrier sensing in 802.11 wireless networks
In this paper, we study the impacts of physical carrier sensing and channel rate on the throughput of 802.11 wireless networks with chain topology. Firstly, we show that by adopting different carrier sensing thresholds for the RTS and CTS transmissions, the blocking problem caused by exposed terminals can be greatly alleviated. In 802.11 wireless networks with this modification, the spatial reuse ratio under certain channel rates can be increased to 13, which is the highest value to our best knowledge. Secondly, in multi-rate networks, we demonstrate that 13 is still the best value of spatial reuse ratio in terms of maximizing the achievable data rate under certain conditions. Thirdly, this paper proposes a new method to address the intra-flow contention by decreasing the carrier sensing threshold of the source node. This method requires less response time than that of the traditional method which adjusts the backoff window size. Finally, extensive simulations are implemented in NS2 and the results show that our scheme significantly improves the throughput of 802.11 wireless networks with chain topology.