A variable neighborhood binary particle swarm algorithm for cell layout problem

In this paper, a new mathematical model is proposed for inter- and intra-cell layout problem in cellular manufacturing system. A binary particle swarm optimization algorithm with a new heuristic approach for satisfying the constraints of model is implemented to solve the proposed model. Also, a variable neighborhood search is applied for finding better local optimal solutions. Some sensitivity analyses are carried out to find the best values of PSO parameters. To prove the efficiency of the proposed algorithm, various numerical examples in small, medium, and large sizes in both perfect geometric shapes and random placements are generated and solved.     

The importance of hydrodynamics in UV advanced oxidation reactors.

The flow field of UV reactors was characterised experimentally using particle image velocimetry (PIV) and modelled with computational fluid dynamics (CFD). The reactor flow was integrated with the radiation fluence rate and photolysis kinetics to calculate the overall conversion of photo-reactant components in annular UV reactors with an inlet parallel and perpendicular to the reactor axis. The results indicated that the fluid flow distribution within the reactor volume affects photo-reactor performance.     

Simulation of UV photoreactor for water disinfection in Eulerian framework

A novel computational fluid dynamic (CFD) modeling procedure was developed in order to simulate ultraviolet (UV) photoreactors in the Eulerian framework. In this procedure, the governing equations of radiation distribution, mass conservation, momentum conservation, and species mass conservation are solved together in order to determine the radiant energy field, velocity field, and the concentration profile of microorganisms at steady state conditions. The general method presented can be employed to derive the volumetric inactivation rate and the theoretical efficiency of a UV photoreactor. The integrated CFD model of UV photoreactor performance was successfully evaluated with experimental biodosimetry results. The verified procedure can be applied to the simulation and design optimization of UV photoreactors with different geometries and operating conditions.     

Effect of freezing on the dynamic mechanical response of hardened cement paste down to −60°C

The dynamic mechanical response (the internal friction, tanδ, and the E-modulus) in the temperature range from −60°C to 0°C reveals a sharp modulus change and a shallow tanδ peak. This “capillary transition” occurs only in specimens suspected of having capillary water; its strength is both a function of moisture content and the pore structure. The E-T curve in the transition region for a number of saturated specimens is fitted by an empirical equation; the parameters of this equation are correlated with the capillary porosity, defined in the conventional manner. One of these parameters is interpreted in terms of a maximum pore size. A theory is outlined for interpreting the E-T curve in terms of thermodynamic, composite mechanics, and pore structure parameters. The discovery of the “capillary transition” has made available a new technique for investigating the various, rather complicated aspects of the process of freezing within a porous solid.     

The Impact of Ventilation Rate and Partition Layout on the VOC Emission Rate: Time-Dependent Contaminant Removal

A numerical study has been carried out to predict the indoor air quality in a newly painted partitioned office and to assess the effect of ventilation rate and partition layout on the pre-ventilation time required to allow the contaminant concentration level to drop to an acceptable level. The air-flow pattern, the time history of the average contaminant concentration level in the occupied zone, and the pre-ventilation time were computed by a CFD code with a K-ε turbulence model. A displacement ventilation system, with different operating conditions, was used to remove contaminants in the office. The VB emission model, developed by Guo and Tichenor (1992), has been improved to include the influence of non-uniform concentration distribution on contaminant emission rate from the paints. The average contaminant (VOC) concentration levels in the occupied zone and in each chamber were recorded hourly until the average concentrations in the office were less then 0.0005 g/m³. It has been found that the non-uniform concentration distri- bution greatly influences the decay rate of VOC emissions. The time required for the average concentration in each chamber to reach the threshold level is different, since they are non-uniform. The time differences between the chambers having the highest and lowest concentrations were 3 to 8 hours. The results also show that the time required to reduce the concentration in the occupied zone to the threshold level is dependent on the partition layout. For the same ventilation rate, the required time is approximately 4-8 hours longer when using a side layout than when using a central layout.     

Characterization of medical waste from hospitals in Tabriz, Iran

Medical waste has not received enough attention in recent decades in Iran, as is the case in most economically developing countries. Medical waste is still handled and disposed of together with domestic waste, creating great health risks to health-care stuff, municipal workers, the public, and the environment. A fundamental prerequisite for the successful implementation of any medical waste management plan is the availability of sufficient and accurate information about the quantities and composition of the waste generated. The objectives of this study were to determine the quantity, generation rate, quality, and composition of medial waste generated in the major city northwest of Iran in Tabriz. Among the 25 active hospitals in the city, 10 hospitals of different size, specializations, and categories (i.e., governmental, educational, university, private, non-governmental organization (NGO), and military) were selected to participate in the survey. Each hospital was analyzed for a week to capture the daily variations of quantity and quality. The results indicated that the average (weighted mean) of total medical waste, hazardous-infectious waste, and general waste generation rates in Tabriz city is 3.48, 1.039 and, 2.439 kg/bed-day, respectively. In the hospital waste studied, 70.11% consisted of general waste, 29.44% of hazardous-infectious waste, and 0.45% of sharps waste (total hazardous-infectious waste 29.89%). Of the maximum average daily medical waste, hazardous-infectious waste, and general waste were associated with N.G.O and private hospitals, respectively. The average composition of hazardous-infectious waste was determined to be 35.72% plastics, 20.84% textiles, 16.70% liquids, 11.36% paper/cardboard, 7.17% glass, 1.35% sharps, and 6.86% others. The average composition of general waste was determined to be 46.87% food waste, 16.40% plastics, 13.33% paper/cardboard, 7.65% liquids, 6.05% textiles, 2.60% glass, 0.92% metals, and 6.18% others. The average bulk densities of total medical waste, hazardous-infectious waste, and general waste were determined to be 99.58, 96.16 and 101.26 kg/m³, respectively. Significant differences were observed between the medical waste characteristics of the hospitals studied here and those reported in other studies. In conclusion, the characteristics of generated medical waste, current environmental problems and strict budgets necessitate that the implementation of efficient management, training, and segregation program be top priorities if we are to minimize the treatment and disposal costs and reduce the risks of hazardous-infectious waste in Tabriz city.     

Optimization of ventilation systems in office environment,Part II: Results and discussions

Whether one considers the issues related to office workers' well-being and productivity or the issues from an energy and environmental perspective, there are clear evidences in favor of improving the quality of office environment. Part I of this paper proposed a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop. In this part, the results from data preparation for ANN model construction, ANN training and testing, and sensitivity analysis (regarding the impact of weighting factors in the objective function on the optimization results) are presented. Final optimization results indicate that the present choices of objective function and optimization approach are able to result in great improvement in the design and operation of ventilation systems in an office environment, with the goal of enhancing the thermal comfort and indoor air quality (IAQ) without sacrificing the energy costs of ventilation.