A mathematical model has been proposed to simulate unsteady state SIMULTANEOUS heat and mass transfer in an aggregative fluidized bed of porous particles. This model could be used in the design of a fluidized bed dryer for the drying of solids or gases. An implicit finite difference method is used to solve the partial differential equations that describe the model. A computer program is written to solve the model and by using this program the effect of mass transfer on heat transfer is studied by comparing two examples in a fluidized bed dryer for the drying of air by silica-gel particles. To test the proposed model, the experimental results obtained by a pilot-scaled fluidized bed dryer were compared with those predicted by the model. A good agreement has been observed between the results.

Background and Objective: The purpose of this paper is SIMULATIONg of gasification and steam cycle of Tehran waste power plant in order to achieve and identify the parameters affecting the efficiency and output of power plant. The information obtained through this SIMULATION, in addition to being used to increase the productivity and efficiency of Tehran power plant, can be used as valuable information in other waste power plants of the country should also be employed. Method: By considering the obtained data from Process Flow Diagram, actual operation condition of this plant, the analyses of Tehran’ s urban waste and using Aspen plus software as the simulating and modeling tool. The developed SIMULATION model has been validated by using actual operating condition of the plant and also the experimental results of the verified papers. Findings: The result shows that the moisture content and the composition of the inlet MSW have significant impact on the output power of this plant. The findings indicate that a 10% reduction in the moisture content of inlet MSW cause an increase of 30% in output power. Also, by increasing the wood and the green waste in the combination of inlet MSW, the output power will be reduced. Discussion and Conclusion: Generally, MSW has low thermal value due to its high percentage of biological ingredients. Therefore, identifying the factors which are affecting the efficiency and power output of the power plant is essential and important. In this regard, the SIMULATION shows that the high percentage of wood-containing compounds and green waste in the input waste will reduce the output power of this plant. As a result, implementing necessary measures to reduce the amount of moisture content of incoming waste as well as achieving the combination with the least amount of wood and green waste will increase the efficiency and the output power of this plant.

In this article, a modeling of the SIMULTANEOUS heat and mass transfer processes in force convection for a laboratory system is provided. Solution of large sets of non-linear algebraic equations reveals that the mass transfer has an immense effect on the heat flux and this effect is greatly enhanced in present of condensation, evaporation and absorption. SIMULATION results about the effect of mass transfer on heat transfer coefficient and total heat flux for various systems such as water vapor condensation from humid air, evaporation of water into dry air and SIMULTANEOUS water vapor evaporation into air containing ammonia and ammonia absorption from air to water, have been completely investigated.

Introduction: Musculoskeletal problems are the common complaints of patients refer to internal medicine clinics and the pain is the most important of them. There are different physiotherapy methods for reduction of pain and action potential SIMULATION therapy (APS therapy) is one of newest methods. The aim of this study was to determine reduction of pain with APS therapy. Materials & Methods: In 47 patients with different musculoskeletal pain APS therapy performed in 6 days each for 16 minutes and with current of 0.7-1.2 mA. Pain (VAS), Global functional status (ACR) and relief of pain (VAS) before and after study compared.Results: APS therapy reduced pain (p<0.001) and increased Global functional status (p<0.001) and increased relief of pain (p<0.005) but there was not any correlation between this reduction of pain with APS therapy and educational status and past history of physiotherapy and duration of illness in these patients.Conclusion: APS therapy is a useful physiotherapy modality for reduction of pain in musculoskeletal problems.

SIMULTANEOUS effect of salinity and drought stresses and their critical limits imposed on cv. Hashemi (most common rice cultivar in Guilan province) was investigated. Also the best model to estimate the reduction of plant's water absorption due to SIMULTANEOUS interaction of salinity and water stresses was identified. Experimental treatments consisted of three levels of irrigation; continuous flood irrigation (3 cm water height) and two intermittent irrigation (4 and 8 days intervals) and five levels of salinity by using irrigation water with electric conductivity of 1, 2, 3, 4 and 5 dS.m-1applied in factorial based randomized block design with four replications. Results indicated that for rice plant yield loss threshold due to drought stress occurred at soil moisture about 80% of saturation. Salinity threshold for this cultivar was at soil extraction of 2.83 dS.m-1 which implies it’s sensitivity to salinity. Among the evaluated models, the best model for predicting the reduction of plant's water absorption due to SIMULTANEOUS effect of salinity and water stresses is Homaee and Feddes for rice. In this model, by subtraction of yield reduction threshold osmotic pressure from the soil water pressure in permanent wilting point, SIMULTANEOUS effect of salinity and water stresses assumed to be less than total or product of these stresses. It is concluded that under conditions when drought and salinity stresses are not balance, predictions by this model are closer to observation and the prediction of relative low grain yield is possible.

Ventilation is essential to provide a smoke-free path for safe passenger evacuation and effective rescue services in case of a tunnel fire, because the closure tunnels increase consequences of accidents significantly. In the present study, the SIMULTANEOUS use of longitudinal ventilation and smoke extraction from the ceiling in fires inside tunnels and physical phenomena has been investigated. Fire dynamics simulator will be used as a CFD tool. This SIMULATION was performed to investigate the effect of the longitudinal distance of the smoke extraction system from the fire source on the smoke back-layering length and the maximum temperature in the two operating conditions used by this system downstream and upstream the fire source. In the present work, the smoke extraction system is located on the ceiling of the tunnel. The results show that using a smoke extraction system upstream of the fire source will increase the maximum temperature, but using the same system downstream will reduce the temperature throughout the tunnel and prevent smoke back-layering. However, attention to the smoke extraction velocity prevents the plug-holding phenomenon. The results also show that the SIMULTANEOUS use of two smoke extraction systems at the upstream or downstream of the fire source will have a better result and The maximum temperature is reduced by 10%.

Transport and transformation of urea, nitrate, and ammonium in the soil take place as a sequential decay chain reactions which should be considered altogether for more precise management of water and fertilizer in agricultural farms. In this study, HYDRUS-2D model was evaluated to predict distribution of water, nitrate and ammonium under furrow and ridge during the growing period of maize. Thus, maize was planted in the treatments with nitrogen rates of 0, 150, and 250 kg ha-1. The amounts of nitrogen uptake, soil water, nitrate, and ammonium concentrations during the growing season, before and after fertilization, and after harvesting were measured over different depths under ridges and furrows.  Results showed suitable agreement between predicted and measured water, nitrate and ammonium distribution in soil during validation stage. NRMSE and R2 as evaluation indexes for the predicted soil water were calculated as 0.772 and 4.37%, respectively. Besides, these indexes were calculated for the predicted ammonium concentration under furrow and ridge for all treatments and were found to be in the range of 0.645-0.798 and 14.23%-29.4%, and for the predicted nitrate concentration, they were in the range of 0.716- 0.829 and 23.57%- 25.2%, respectively. According to the results of this study, the HYDRUS model is a useful tool for management of water and fertilizer in furrow irrigation.

The accurate prediction of soil water movement and root uptake are very important to provide optimal root zone moisture conditions for increasing plant yield. In this study, soil water movement and sugar beet root uptake were SIMULTANEOUSly simulated, using HYDRUS 3D software, and the effect of extraction methods of input parameters on the accuracy of SIMULATION were evaluated. For this purpose, sugar beet was cultivated in three lysimeters with identical soil texture. Irrigation was performed twice a week (8 on Sunday and 16 on Wednesday). Volumetric water content and drainage water volume from lysimeters were measured before and after each irrigation, respectively. The volume of drainage water from the lysimeters at different times, was selected as objective function. Using measurement, calculation or SIMULATION, the hydrus 3D software input parameters including initial moisture (with two methods), saturated moisture (with three methods), residual moisture (with two methods) and saturated hydraulic conductivity (with two methods), extracted and SIMULATION were completed. The results showed that if the residual moisture derived from measurement (by pressure plate method), saturated moisture derived from RETC software, initial moisture derived from measurement (measured by weighing method) and hydraulic conductivity derived from Rosetta software, were used in the SIMULATION, the SIMULATION accuracy will be highest. The values of relative error, root mean square error, mean absolute error, geometric mean error ratio and coefficient of determination are 17.58%, 0.759 liters, 0.866, 0.777 and 0.885, respectively. Values of GMER parameter, also, showed that in most SIMULATIONs the model is underestimated.

Introduction: The goal of SPECT is determining activity distribution inside the patient body. To achieve this goal a rotating gamma camera acquires many projections around the patient. These projections are later used by reconstruction algorithms to reconstruct the slices corresponding to activity bio distribution. The primary assumption of these algorithms is that Radon transform is a suitable model for image formation. Therefore Filtered Back Projection (FBP) which used inverse Radon transform is the main method for reconstruction; however this model doesn’t consider the effect of attenuation and non-ideal collimation. Therefore the final reconstructed slices degrade due to the effect of photons attenuation and are blurred due to collimator and detector response (CDR) which is the main cause of resolution degradation. In this study a more suitable model contains the effect of both attenuation and CDR is introduced and used during reconstruction by iterative OSEM algorithm to correct for their degrading effects.Methods: at first a point source of Tc-99m is modeled and placed in different distances from the face of collimator. SIMIND Monte Carlo simulator is used to create projections from this activity source. After finding suitable models, a digital brain phantom (ZUBAL) with a typical Tc99m-ECD distribution is used to validate the ability of our algorithm. The effect of attenuation and CDR were modeled in both projection/backprojection of the OSEM algorithm.Results: qualitatively, better match between activity phantom and reconstructed images are found in comparison with conventional reconstruction algorithms. Quantitatively, a dramatic increase in amount of activity in different parts of brain image is found. The contrast of gray to white matter is increased more than 30%. SNR is also increased by factor of 2. The FWHM of final reconstructed image of point source of activity is also reduced from 7mm at center of field of view to less than 4mm by suggested algorithm which shows a considerable improvement in image resolution.Conclusion: by using more suitable models for image formation it is possible to reconstruct images with much higher quantitative and qualitative accuracy which is essential in both diagnostic and image guided therapy procedures.