Identification of Frequency Ranges for Subharmonic Oscillations in a Relay Feedback System

This paper examines the behaviour of a single loop relay feedback system (RFS) which is driven by an external signal. It is well known that such a RFS exhibits a variety of oscillation patterns including forced and subharmonic oscillations (SO). This paper focuses on the conditions for SO. It will be shown that for an external signal with a fixed amplitude, it is possible for SO with different orders to occur simply by changing the frequency of the external signal. Similarly, for an external signal with a fixed frequency, it is possible for SO with different orders to occur when the amplitude of the external signal is varied. The conditions under which these different scenarios will occur are explored. An analysis of these conditions identifies the frequency ranges where certain orders of SO are possible for a given amplitude of the external signal. The effects of the initial conditions on the SO are illustrated and discussed. Simulation studies are presented to illustrate the result

Efficient transport and economic development: A transport survey analysis

Efficient transport and economic growth in a city or country are inter-related. The overall focus of the survey conducted was to find the travel habits of the residents in the city of Kuching (Malaysia), so as to weigh the prospects of economic development in future. The three objectives were to evaluate the efficiency of the local bus transportation system, to confirm on the usage of car as the preferred mode of transport, and to identify areas of improvement to the system as well as analyzing the need for an alternative mode(s) of transportation. The quantitative and qualitative analysis is done on data to find the relationships between various variables measured. Car has been confirmed to be the popular mode of transport across the age groups, across the income groups and across the professions, whereas the bus transport was really not significant. The study identified the important characteristics and priorities in the travel behavior of Kuching residents. The results of the study will be significant in the planning of new economic developments that encourages the use of public transportation in Kuching city

A novel approach for the adsorption of cadmium ions in aqueous solution by dead calcareous skeletons

Heavy metal contamination in water causes problems to the environment and the deterioration of human health. Various types of water remediation methods have been conducted to counter this problem and to reduce the toxicity risk in water. As the conventional treatment process does not completely remove pollutants in the water, alternative purification methods have been studied to improve the treatment process. In this present study, batch experiments were conducted to evaluate the ability of dead calcareous skeleton in removing cadmium ions (Cd(II)) from aqueous solution. The factors affecting adsorption were evaluated in respect of adsorbent size, contact time, adsorbent dosage, pH, and initial concentration to determine the optimum conditions for Cd(II) removal. The optimum size of CS was 710 μm and the equilibrium was achieved at 600 min. The most favorable dosage concentration was 20 g/L. The optimum pH for the Cd(II) adsorption was 6.42, which is the initial pH of Cd(II) solution. The adsorption capacity of CS appeared to be higher when the initial concentration Cd(II) increased above 1 mg/L. The experimental data fitted better in the Freundlich isotherm than in the Langmuir isotherm but the bonding was rather weak. The results from this study demonstrate that dead calcareous skeletons have considerable potential in water treatment applications for the metal removal process. In addition, the cost of chemical usage can be reduced due to the natural characteristics of adsorbents, which are able to alter the pH of the solution so that it is favorable for optimum adsorption capacity

A Review of Network Models for Internet of Vehicles

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An experimental approach on the removal of Cd (II) and Pb (II) ions from aqueous solutions by using dead calcareous skeletons

Calcareous skeletons were studied to determine its ability in removing cadmium (Cd (II)) and lead ions (Pb (II)) from aqueous solutions. The factors affecting adsorption were evaluated with respect to adsorbent size, contact time, adsorbent dosage, pH, and initial concentration to determine the optimum conditions for Cd (II) and Pb (II) removal. The optimum dosage for removal of Cd (II) and Pb (II) were 20 and 10 g/L, respectively. The pH of both metal solutions had shifted from acidic to alkali condition after equilibrating with the adsorbent. The adsorption capacity of CS appeared to be higher when the initial metal concentrations increased above 1 mg/L. This investigation has proved that CS has a great potential for removing metal contamination in acidic water

Effective removal of lead (II) ions by dead calcareous skeletons: sorption performance and influencing factors

Dead calcareous skeletons (CSs) as low-cost adsorbents were studied to remove lead ions (Pb (II)) in an aqueous solution. Factors influencing the efficiency of CSs were evaluated by adsorbent size, contact time, initial concentration, dosage concentration and pH. The optimum CS size for removal of Pb (II) was 710 μm at an equilibrium time of 720 min. The best dosage of CS was 10 g/L for a 99% removal efficiency without pH adjustment. Pb (II) ions were effectively removed in the initial pH of the metal solution. CS was able to remove a high concentration (100 mg/L) of Pb (II) at a removal efficiency of 99.92% and at an adsorption capacity of 13.06 mg/g. Our results demonstrated the potential of CS as a metal adsorbent in the aqueous phase with a high-removal efficiency and distinct physical characteristics

Cross-Cultural Variations in Naïve Psychology among 2-year-olds: A Comparison of Children in the United Kingdom and Singapore

Children's understanding of naïve psychology is the main focus of this study. Research evidence suggests that 2- and 3-year-olds understand some aspects of naïve psychology. By 4 years, they develop internal representations of mental states. Previous studies have also reported cross-cultural variations in naïve psychology development. The majority of this research has focused on Western individualistic societies such as Australia, Europe and North America, and Eastern collectivism societies such as China and Japan. Singapore with its blend of Eastern and Western values represents a unique case for comparison with Western societies. This paper reports a cross-cultural study of young children's developing understanding of naïve psychology in Edinburgh, UK and Singapore. It addresses three main questions: (a) Are there cross-cultural differences in the development of naïve psychology?; (b) What are children's performance sequences on naïve psychology tasks?; and (c) Are naïve psychology concepts coherent? The participants were 87 children from the UK (n=43, mean age 2 years 4 months) and Singapore (n=44, mean age 2 years 5 months). This study incorporated several established tasks of pretence, desires, emotions, perceptions, appearance-reality and false-beliefs to investigate children's understanding of non-representational and representational mental states. The results showed no gross cross-cultural differences. However, significant cultural differences in performance on two tasks and differences in the coherence of naïve psychology concepts were identified. The results highlight the importance of considering subtle cultural influences on children's developing understanding of various aspects of naïve psychology. © 2010 Brill

A review on economically adsorbents on heavy metals removal in water and wastewater

Heavy metals contamination in water has been an issue to the environment and human health. The persisting contamination level has been observed and concerned by the public due to continuous deterioration of water quality. On the other hand, conventional treatment system could not completely remove the toxic metals in the water, thus alternative purification methods using inexpensive materials were endeavor to improve the current treatment process. Wide ranges of low cost adsorbents were used to remove heavy metal in aqueous solution and wastewater. The low cost adsorbents were usually collected from agricultural waste, seafood waste, food waste, industrial by-product and soil. These adsorbents are readily available in a copious amount. Besides, the pretreatment are not complicated to be conducted on the raw products, which is economically sound for an alternative treatment. The previous studies have provided much evidence of low cost adsorbents’ efficiency in removing metal ions from aqueous solution or wastewater. In this review, several low cost adsorbents in the recent literature have been studied. The maximum adsorption capacity, affecting factors such as pH, contact times, temperature, initial concentration and modified materials were revised and summarized in this review for further reference. Comparisons of the adsorbent between the modified and natural products were also demonstrated to provide a clear understanding on the kinetic uptake of the selected adsorbents. Some of the natural adsorbents appeared as good heavy metal removal, while some were not and require further modifications and improvements to enhance the adsorption capacity. SWOT analysis (strength, weakness, opportunities, threat) was also performed on the low cost adsorbents to identify the advantages of using low cost adsorbents and solve the weaknesses encountered by the utilization of low cost materials. This tool helps to determine the potential quality of low cost materials in the application for water and wastewater treatment