Switched-capacitor filters

A novel technique for building active filters using switched-capacitor (SC) circuits is proposed. Principles of operation, methods of control, analysis, and design of a typical SC filter are presented. To assess its effectiveness, the technique is used to control input current harmonics in a phase-controlled converter. It is shown that a wide range of harmonics can be controlled using a single filter     

Thermal analysis of ME—TVC+MEE desalination systems

Thermal analysis of three different configurations of a multi-effect thermal vapor compression desalting system is presented: conventional ME—TVC,ME—TVC with regenerative feed heaters (ME—TVC,FH) and ME—TVC coupled with a conventional MEE system (ME—TVC+MEE). The analysis is based on the First and Second Law of Thermodynamics. A parametric study was carried out to investigate the impact of motive steam pressure, temperature difference per effect, top brine temperature, feed seawater temperature and motive steam flow rate on the system's performance for each configuration. The exergy analysis showed that irreversibilities in the steam ejector and evaporators are the main sources of exergy destruction in the three configurations. When steam is supplied directly from the boiler to all configurations, results showed that the first effect was responsible for about 50% of the total effect exergy destruction. The study also showed that the decrease in exergy destruction is more pronounced than the decrease in the gain ratio at lower values of motive steam pressure. Lowering the temperature difference across the effects, by increasing the surface area, decreases the specific heat consumption. On the other hand, exergy losses are small at low temperature differences and low top brine temperature. The analysis showed that the third configuration (ME—TVC+MEE) has two main features compared to ME—TVC and ME—TVC, FH. First it has a lower compression ratio, which makes the motive steam capable of compressing larger amounts of the entrained vapor; as a result, the amount of motive steam is reduced. Second, the configuration can be used for large-scale production.     

Comparative study on breast milk of mothers delivering preterm and term infants--protein, fat and lactose

Milk samples were collected from 35 mothers delivering preterm infants and from 35 mothers delivering term infants at 3 time intervals over the first 3 weeks of lactation. The samples were collected by manual expression from both breasts into polyethylene containers and were frozen at -20 degrees C and stored for analysis. The protein content of preterm milks during the first and second weeks is higher than that of term milk (P less than 0.05). The fat and lactose contents during the first week are slightly more in term milk than in preterm milk. During the third week the fat content of preterm milk is higher but its lactose content was lower. All these differences are not significant. These results are discussed.     

Photodegradation of phenol red in the presence of oxyhydroxide of Fe(III) (Goethite) under artificial and a natural light

The (α‐FeOOH) Goethite composite is a stable and an efficient catalyst in aqueous suspension under irradiation at 365 nm and by solar light. The photocatalytic activities of this composite were evaluated using Phenol Red (PR) dye (phenolsulfonphthalein class). In the dark, controlling factors, such as the pH and the adsorption of PR on Goethite surface were evaluated (before starting the photochemical experiments). It was found that the system PR‐Goethite present a small decrease in the main band of the dye (435 nm) which was explained by the low rate of adsorption of this dye on the Goethite. Also, we note that 40% of PR decolourisation was obtained after 200 min by the system PR‐Goethite‐hydrogen peroxide (H₂O₂) in dark due to the formation of ^?OH by thermal decomposition of H₂O₂ on the surface of Goethite. The effects of various experimental parameters, such as initial dye concentration, pH, photocatalyst amount, tert‐Butyl alcohol effect and H₂O₂ addition were investigated in the study of photodegradation of the dye. The results showed that the photodegradation of PR under UV‐A (365 nm) irradiation could be enhanced greatly in the presence of H₂O₂. Natural radiation tests (under sunlight) showed that degradation was faster comparing with that obtained using the artificial one at 365 nm. Studies of the mineralization using total organic carbon method under naturel light certify that this method, compatible with the environment, may be considered in the treatment of wastewater and generally in the process of removal of this kind of pollutant.     

Integrated electrokinetic-soil flushing to remove mixed organic and metal contaminants

The integrated use of hydraulic flushing and electrokinetic treatment was investigated for the remediation of silty sand contaminated by both PAHs and heavy metals. The soil was collected from a polluted former manufactured gas plant (MGP). Four bench-scale experiments were conducted to analyze the ability of the combined hydraulic flushing and the electrokinetic treatment for the simultaneous removal of PAHs and heavy metals. Sequential flushing with ethylenediaminetetraacetic acid (EDTA) or Igepal CA-720 were tested with or without the simultaneous application of a low intensity direct electric field (1 VDC cm⁻¹). The best results were obtained with 0.2 M EDTA flushing in two stages (without and with voltage gradient, 1 VDC cm⁻¹), followed by 5% Igepal flushing in two stages (without and with 1 VDC cm⁻¹). Heavy metals were removed mainly during the EDTA flushing, with removal efficiencies of about 60% for Zn, 80% for Pb, and 30% for Cu. During Igepal flushing, no heavy metals were removed, but PAHs were removed, including 40% phenanthrene, 30% pyrene, and 20% benzo[a]pyrene. Overall, this study showed that a carefully designed sequential hydraulic flushing scheme with selected chelant and surfactant is needed for the removal of both heavy metals and PAHs from MGP silty sands. Combining electrokinetics with hydraulic flushing may not necessarily improve contaminant removal from such soils.     

Operations research/management science in the Arab world: historical development

This study aims to review the related literature on operations research (OR)/management science (MS) in the Arab world published during the last three decades. Owing to the nature of this study, an extensive survey of the related literature was conducted and inferences were drawn. The inferences drawn from the literature survey on OR/MS in the Arab world were first, there is a paucity of published real‐world applications of OR/MS. Second, there is a lack of published survey‐type studies in most Arab countries, except in Jordan, Lebanon, Palestine, Syria, and the United Arab Emirates. Third, the majority of published works on OR/MS were of a conceptual nature. A few papers concerned with OR/MS in the Arab world were published during the 1980s, with a special emphasis on conceptual issues rather than on applied or survey‐type studies. The 1990s witnessed an increased number of publications on both survey‐type and conceptual studies. Since 2000, the number of publications has increased substantially, mainly through conceptual studies. This study has a number of implications for both practitioners and researchers. Practitioners will be made aware of the applications of OR/MS in the Arab world and the type of problems that have been addressed. This, in turn, might motivate the decision makers and the managers to adopt OR/MS approaches in solving their organizations' problems. As a result, this might increase the usage of OR/MS in this part of the world. Researchers will be able to identify the OR/MS research areas that need more attention in the Arab world. The study mainly covers the studies that are written in English and indexed in non‐Arabic databases. Although the Arabic works were not surveyed exhaustively, the author reviewed and included some available OR/MS works written in Arabic. This study is considered as the first work of its type in surveying the scholarly publications pertaining to OR/MS in the Arab world since the 1980s.     

A multi-verse optimizer approach for feature selection and optimizing SVM parameters based on a robust system architecture

Neural Computing and Applications - Support vector machine (SVM) is a well-regarded machine learning algorithm widely applied to classification tasks and regression problems. SVM was founded based...     

An analytical simulator for deploying IP telephony

Deploying IP telephony or voice over IP (VoIP) is a major and challenging task. This paper describes an analytical design and planning simulator to assess the readiness of existing IP networks for the deployment of VoIP. The analytical simulator utilizes techniques used for network flows and queuing network analysis to compute two key performance bounds for VoIP: delay and bandwidth. The simulator is GUI‐based and has an interface with drag‐and‐drop features to easily construct any generic network topology. The simulator has an engine that automates and implements the analytical techniques. The engine determines the number of VoIP calls that can be sustained by the constructed network while satisfying VoIP QoS requirements and leaving adequate capacity for future growth. As a case study, the paper illustrates how the simulator can be utilized to assess the readiness to deploy VoIP for a typical network of a small enterprise. We have made the analytical simulator publicly available in order to improve and ease the process of VoIP deployment. Copyright © 2008 John Wiley & Sons, Ltd.     

Statistical models for spot welding of commercial aluminium sheets

The present paper reports experimental investigations on the spot welding of commercial aluminium sheets. Experiments were carried out to study the influence of spot welding parameters (welding current, welding time, electrode force and sheet thickness) on the strength of spot welded aluminum sheets with commercial purity. Experiments were planned on the basis of response surface methodology (RSM) technique. The mathematical models (failure load and nugget area) correlating process parameters and their interactions with response parameters have been established. These models have been used in selecting the optimum process parameters for obtaining the desired spot welding quality at the least possible consumed power.