Elvin J. Moore

Traffic Sign Recognition System for Roadside Images in Poor Condition

Traffic sign detection and recognition is a difficult task, especially if we aim at detecting and recognizing signs in images captured under poor conditions. Complex backgrounds, obstructing objects, inappropriate distance of signs, shadow, and other lighting-related problems may make it difficult to detect and recognize signs in both rural and urban areas. In this paper we propose and test a system that employs image pre-processing, color filtering, color segmentation for traffic sign detection at the detection stage, feature extraction and trained neural networks for unique identification of signs at the recognition stage. The traffic sign detection and recognition system has been tested on actual roadside images taken under poor conditions. The images were selected in order to test the efficiency of the system under challenging conditions of inappropriate distance, traffic sign size, poor lighting and complex background. Suggestions are made for improving the performance of the system.

SYNTHESIS OF ACTIVATED CARBON FROM JATROPHA SEED COAT AND APPLICATION TO ADSORPTION OF IODINE AND METHYLENE BLUE

This article provides evidence that jatropha seed coat residues can be used as a carbon source for preparing activated carbons that have good adsorption properties for iodine and methylene blue. Activated carbons were prepared using three different methods of activation, physical, chemical, and physico-chemical, for a range of activation temperatures (600°, 700°, 800°, and 900°C) and activation hold times (1, 2, and 3 h). The highest BET surface area (1479 m2 g−1) and the highest iodine adsorption (1511 mg g−1) were obtained with physico-chemical activation at a temperature of 900°C and a hold time of 2 h. This activated carbon gave higher BET surface area and iodine adsorption than commercial activated carbon (1169.1 m2 g−1 and 1076 mg g−1). The activated carbons prepared by physico-chemical activation at 900°C and 2 h were then tested for adsorption of methylene blue at a range of concentrations of methylene blue (100, 200, 300, 400, and 500 mg L−1). It was found that a Langmuir isotherm gave a better fit (R 2 = 0.999) to the observed adsorptions than a Freundlich isotherm (R 2 = 0.884). For the adsorption kinetics, a pseudo-second-order model gave a better fit (R 2 > 0.998, Δq e = 3.7%) than a pseudo-first-order model (R 2 ≈ 0.95, Δq e = 85.6%). These results suggest that chemisorption is the rate-controlling step for the adsorption of methylene blue. The experimental results show that jatropha seed coat is a lignocellulosic waste precursor for preparation of activated carbon that is an alternative source for preparation of commercial-grade activated carbons.

A bifurcation path to chaos in a time-delay fisheries predator-prey model with prey consumption by immature and mature predators

Stage-structure models have been extensively applied in predator-prey systems. In this paper, we consider an application to fisheries. We assume that there is a single prey population and a predator population that can be separated by reproduction ability into an immature and a mature stage, with a time delay for the immature to mature transition. Our model includes the new assumption that both predators are able to hunt the same prey, although at different rates. It is proved that the system has three nonnegative equilibrium points, namely, a trivial point with all populations zero, a predator-free equilibrium point, and a coexistence equilibrium point with all three populations non-zero. It is proved that the trivial equilibrium point is always unstable, that the predator-free equilibrium point is stable if and only if the coexistence equilibrium point does not exist, and that the coexistence point can either be stable for all time delays or become unstable if a Hopf bifurcation exists at a critical time delay. Numerical simulations show that the behavior of the system can become extremely complicated as the time delay is increased, with the long-time behavior changing from a stable coexistence equilibrium, to a limit cycle with one local maximum and minimum per cycle (Hopf bifurcation), to limit cycles with an increasing number of local maxima and minima per cycle, and finally to chaotic-type solutions.

Traffic sign recognition by color segmentation and neural network

An algorithm is proposed for traffic sign detection and identification based on color filtering, color segmentation and neural networks. Traffic signs in Thailand are classified by color into four types: namely, prohibitory signs (red or blue), general warning signs (yellow) and construction area warning signs (amber). A color filtering method is first used to detect traffic signs and classify them by type. Then color segmentation methods adapted for each color type are used to extract inner features, e.g., arrows, bars etc. Finally, neural networks trained to recognize signs in each color type are used to identify any given traffic sign. Experiments show that the algorithm can improve the accuracy of traffic sign detection and recognition for the traffic signs used in Thailand.

A Delay Differential Equation Model for Dengue Fever Transmission in Selected Countries of South‐East Asia

Dengue Fever is a dangerous viral disease that is transmitted by female Aedes mosquitoes and is common in more than 100 countries in the world and in all countries of South‐East Asia. Mathematical models of Dengue Fever transmission are useful for studying the causes of the spread of the disease and to try to develop methods for reducing the spread of the disease. In this paper, a mathematical model for Dengue fever is analyzed consisting of a system of four nonlinear differential equations with two time delays. The model includes infected humans, infectious humans, infected mosquitoes and infectious mosquitoes. The model has disease‐free and endemic equilibrium points. The asymptotic stability of the equilibrium points are studied analytically. The Matlab computer program is used to obtain numerical solutions of the model for both zero and nonzero time delays for a range of parameter values. It is found that for some reasonable estimates of parameter values the endemic equilibrium point is asymptotically...

Generalized reproduction numbers, sensitivity analysis and critical immunity levels of an SEQIJR disease model with immunization and varying total population size

Abstract An SEQIJR model of epidemic disease transmission which includes immunization and a varying population size is studied. The model includes immunization of susceptible people (S), quarantine (Q) of exposed people (E), isolation (J) of infectious people (I), a recovered population (R), and variation in population size due to natural births and deaths and deaths of infected people. It is shown analytically that the model has a disease-free equilibrium state which always exists and an endemic equilibrium state which exists if and only if the disease-free state is unstable. A simple formula is obtained for a generalized reproduction number R g where, for any given initial population, R g < 1 means that the initial population is locally asymptotically stable and R g > 1 means that the initial population is unstable. As special cases, simple formulas are given for the basic reproduction number R 0 , a disease-free reproduction number R d f , and an endemic reproduction number R e n . Formulas are derived for the sensitivity indices for variations in model parameters of the disease-free reproduction number R d f and for the infected populations in the endemic equilibrium state. A simple formula in terms of the basic reproduction number R 0 is derived for the critical immunization level required to prevent the spread of disease in an initially disease-free population. Numerical simulations are carried out using the Matlab program for parameters corresponding to the outbreaks of severe acute respiratory syndrome (SARS) in Beijing, Hong Kong, Canada and Singapore in 2002 and 2003. From the sensitivity analyses for these four regions, the parameters are identified that are the most important for preventing the spread of disease in a disease-free population or for reducing infection in an infected population. The results support the importance of isolating infectious individuals in an epidemic and in maintaining a critical level of immunity in a population to prevent a disease from occurring.