A. Pasban; M. Mohebbi; H. Sadrnia; S. A. Shahidi
Abstract
Introduction Convective air drying is one of the oldest and most popular drying methods. Designing and controlling the convective air drying needs the mathematical description of the moisture transfer during the drying process, known as drying kinetics. Fick’s second law of diffusion can be used ...
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Introduction Convective air drying is one of the oldest and most popular drying methods. Designing and controlling the convective air drying needs the mathematical description of the moisture transfer during the drying process, known as drying kinetics. Fick’s second law of diffusion can be used for modelling the moisture distribution inside the moist object during drying process. Mathematical modeling of drying process is a very important tool, as it contributes to understand better moisture distributions inside the product which helps designing, improving and controlling drying operation in the food industry. Implementation of the partial differential equations subject to the correspondent initial and boundary conditions is one of the main methods of mathematical modeling to describe the physical phenomena such as moisture transfer during drying. In the recent decades, considerable number of research works have been devoted to numerical solution of mass transfer phenomena during convective drying of food products by using the common numerical solution such as FDMs, FEMs and FVMs. The spectral collocation (pseudospectral) methods is a powerful tool for the numerical solutions of smooth PDEs like mass transfer equations. Pseudospectral methods are able to achieve the high precision with using a small number of discretization points compared to FDMs and FEMs and with low computational time and computer memory. The objective of present research is to simulate the mass transfer phenomena in one dimension during convective drying of apple slices. The validation of the presented numerical model was done by comparing experimental drying data taken from Kaya et al. (2007) and Zarein et al. (2013). For more confirming the numerical approach, a numerical example with the exact solution is provided and the related errors were evaluated. Materials and Methods Estimation of mass transfer coefficients The convective mass transfer coefficient in the surface of the apple slice was obtained according to the relationship presented by Paitil (1988) and Janjai et al. (2008). (1) Estimation of effective moisture diffusivity coefficient Fick’s second law of diffusion was applied to obtain the effective moisture diffusivity coefficient of the apple slices. The analytical solution of this equation can be written as follows (Crank, 1975): (2) In this study, we consider the Pseudospectral methods for solving 1D mass transfer equation. In order to develop the model, the following common assumptions are considered: negligible heat changes during drying process, moisture is transferred inside the slices by diffusion, one-dimensional mass transfer in apple slices, non-shrinkage and non-deformation of the slice. Results and Discussion In the field of numerical analysis, the main advantage of pseudospectral methods compared to others such as FDMs and FEMs are exponential convergence and sufficient accuracy (Sun et al., 2012). The values of parameters and coefficients of mathematical model are summarized in Table 1. The comparisons between the predicted average moisture content and the experimental data are shown in Fig. 1 & 2. It can be seen, the numerical results are in good agreement with the experimental data. The values of the correlation coefficient and the root mean square error from comparison of numerical result with experimental data taken from Zarein et al. (2013) and Kaya et al. (2007) were 0.9996, 0.0729 and 0.997, 0.1561 respectively. Moreover, the running time for solving 1D mass transfer equations was about 3 seconds. This result is the evident that the presented model is successful for predicting the moisture content history during drying process. Moreover, by using the considered numerical method the approximate solutions of defined numerical example for different discretizing points was evaluated and the associated error history are shown in Figure 3. It can be seen that the values of errors are very low and about 10-3 and 10-5, that confirms the high accuracy, robustness and efficiency of the suggested numerical approach. Conclusion Spectral collocation (pseudospectral) method is presented to solve mass transfer equation in one dimensional in during convective drying process approximately. The model was validated by the reported experimental data from convective drying of apple slices. Also, a numerical example, which had an exact solution in a closed form, was provided to illustrate the high accuracy of the proposed method. The results of statistical computations (r and RMSE) and numerical example showed the efficiency, applicability and robustness of the presented approach.
S. Mollazehi; H. Sadrnia; M. R. Bayati
Abstract
Introduction In recent decays, the microwave heating treatment is one of the best ways for the pest control. It is difficult to determine temperature in different parts of materials by Thermometer, but we can solve this problem by Comsol Multiphysics Software. In a research, results of a farm test were ...
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Introduction In recent decays, the microwave heating treatment is one of the best ways for the pest control. It is difficult to determine temperature in different parts of materials by Thermometer, but we can solve this problem by Comsol Multiphysics Software. In a research, results of a farm test were consistent with laboratory data and high temperature area was belonged to the outer part of wooden piece (Massa et al., 2015). The numerical simulation of Microwave heating was successfully done for fruits and compared with experimental measurement in two cylindrically and spherically states by Zhao et al. (2011). The results indicated that, the temperature prediction in a wooden piece under heating of a Microwave system was in conformity with experimental infra-red rays data (Rattanadecho, 2006). The outer part of the piece was impressed by inspired heating and the inner part by transmission of heating (Massa et al., 2011). A high frequency structure simulator software, a radiant trumpet shaped antenna with 2.45GHz frequencies, 100 watt electric power were the tools that were used to predict the temperature at a Date Palm Wooden piece at 10, 12, 14 and 16 centimeters (Al Shwear and Remili, 2016). Microwave pretreatment was studied with two factors of Microwave radiation (170, 450, and 850 W) and Microwave duration (2, 6, and 10 min). It can be concluded that the Ozonolysis is the most effective pretreatment regarding to saccharification percentage of sugarcane bagasse (Eqra et al., 2015). This study has been done with the aim of fighting with Rhynchophorus ferrugineus blight by microwave and removing toxins in crops. Materials and Methods Samples features such as physical, mechanical and magnetic once were established in both Tehrans Material and Energy lab and Polymer and Petrochemical Research Center, Then it was simulated by Time_ Temperature profile software. For simulating research by Comsol Multiphysics software, at first sample and chamber sizes were determined and the type of material, meshing, 2.45GHz frequencies and the time duration of heating were measured, respectively. Finally the research was analyzed and Time_Temperature profile which was one of the outcomes of Multiphysics software was determined. A cubic piece of wood (103×86×78 mm) (Fig. 1), a Digital Thermometer and a Microwave are the tools which the researcher used in this sample. The temperature was measured at three different parts of cub diagonal by Thermometer. At first, the wooden sample was divided in two equal parts and a sensor was placed in the middle of it and then it was placed in the Microwave. The primary temperature of sample and Microwaves was 27°C. We turn the Microwave on for a period of 10 minutes, after that we check the wooden piece temperature by Thermometer at 20 seconds intervals. Results and Discussion T-test was used to compare statistical results achieved by simulated and experimental temperature of cubic diagonal. According to T mark at 5 percent level, we can say that there is a significant difference between simulated and experimental temperature at point1, however, there is no such a significant difference at 2 and 3 points. In the following phase, the temperature was compared at two simulated and experimental states by variance analysis test. There was significant difference at 1, 2 and 3 points according to data are shown at figure 4. Moreover, Duncan Post hoc test is shown at figures 5 and 7 that experimental temperature shows no difference at 1 and 3 points but it makes difference at 1, 2 and 2, 3 points. Conclusion Results show that the simulation model can predict the temperature in different parts of a wooden sample. The temperature will be higher as much as the points will be closer to the wave producer resource. In order to control pests in the trunk of a tree, we should use several wave generator systems, instead of ones. It is recommended that cylindrical microwave should be simulated and designed instead cubic ones, because it is better adjusted with tree stock and the wave generator system is placed on this surface so that the temperature will be distributed symmetrically along the diagonal.
R. Goudarzi; H. Sadrnia; A. Rohani; M. Nouribaygi
Abstract
Introduction The demand of pre-determined optimal coverage paths in agricultural environments have been increased due to the growing application of field robots and autonomous field machines. Also coverage path planning problem (CPP) has been extensively studied in robotics and many algorithms have been ...
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Introduction The demand of pre-determined optimal coverage paths in agricultural environments have been increased due to the growing application of field robots and autonomous field machines. Also coverage path planning problem (CPP) has been extensively studied in robotics and many algorithms have been provided in many topics, but differences and limitations in agriculture lead to several different heuristic and modified adaptive methods from robotics. In this paper, a modified and enhanced version of currently used decomposition algorithm in robotics (boustrophedon cellular decomposition) has been presented as a main part of path planning systems of agricultural vehicles. Developed algorithm is based on the parallelization of the edges of the polygon representing the environment to satisfy the requirements of the problem as far as possible. This idea is based on "minimum facing to the cost making condition" in turn, it is derived from encounter concept as a basis of cost making factors. Materials and Methods Generally, a line termed as a slice in boustrophedon cellular decomposition (BCD), sweeps an area in a pre-determined direction and decomposes the area only at critical points (where two segments can be extended to top and bottom of the point). Furthermore, sweep line direction does not change until the decomposition finish. To implement the BCD for parallelization method, two modifications were applied in order to provide a modified version of the boustrophedon cellular decomposition (M-BCD). In the first modification, the longest edge (base edge) is targeted, and sweep line direction is set in line with the base edge direction (sweep direction is set perpendicular to the sweep line direction). Then Sweep line moves through the environment and stops at the first (nearest) critical point. Next sweep direction will be the same as previous, If the length of those polygon's newly added edges, during the decomposition, are less than or equal to the base edge, otherwise a search is needed to choose a new base edge. This process is repeated until a complete coverage. The second modification is cutting the polygon in the location of the base edge to generate several ideal polygons beside the base edges. The algorithm was applied to a dataset (including 18 cases, ranging from simple-shaped to complex-shaped polygons) gathered from other studies and was compared with a split-merge algorithm which has been used in some other studies. The M-BCD algorithm was coded in C++ language using Microsoft Visual Studio 2013 software. Algorithm was run on a laptop with 2.5 GHz Intel(R) core™ i5-4200M CPU, processor with 4 GB of RAM. Also Split-merge algorithm provided by Driscoll (2011) was coded. Two algorithms were applied to the dataset. Cost of coverage plan was calculated using cost function of U-shaped turns in study Jin and Tang (2010). In this paper machine-specific parameters were working width 10 m and minimum turning radius 5 m. Results and Discussion Based on the results, the proposed algorithm has low computational time (below 100 ms in dataset and runs many times (on average 75 times) faster than split-merge algorithm. Algorithm resulted in a calculated savings up to 12% and on average 2% than the split-merge algorithm. Another consequence from parallelization method was effectiveness of multi-optimal direction coverage pattern than a single-optimal direction coverage; a calculated savings up to 14% and 2% on average than a single optimal direction achieved. Algorithm was evaluated on several test cases in detail. Based on the results, it is possible to loose optimal solutions especially in the case of simple shaped environments (in terms of number of convex points and internal obstacles), for example case 10 in dataset, is a case with a number of orthogonal edges. Reviewing the algorithm and Figure 4 demonstrate that sweep line moves down from the first longest edge in top of the polygon, and it doesn't stop during the process until the whole area is covered with a single coverage path direction (parallel to the longest edge). As it can be seen, no decomposition is proposed, because sweep line has faced no critical points. Based on the results in Table 2, there is 8% (equal to 88m) more cost (in term of the non-effective distance) in this case than an optimal direction and the split-merge algorithm. There are similar cases in the dataset: number 9, 12 and 13. This condition rarely occurs in complex environments, but in general it can be prevented by using an evaluation step at the end of the decomposition process. Ideally, the cost of coverage plan must be significantly less than related costs of a single optimal direction. Unlike the simple cases, algorithm returns near the optimal solution, especially in the case of complex environments. A good example of this ability of the algorithm can be seen in Figure 6. This field is case 17 in the dataset. It has many edges (almost 90 edges) and several non-convex points and an internal irregular shaped obstacle. M-BCD algorithm in a very short time (87 ms) generated several near to ideal shaped sub-regions around the field. Algorithm resulted in a calculated saving of 5% than an optimal direction with minimum non-effective distance. We can see the solution of split-merge algorithm by Oksanen and Visala (2009) in Figure 6, it can be clearly seen that coverage pattern by M-BCD is very close to the high time-consuming and optimal split-merge algorithm by Oksanen and Visala (2009). It verifies that M-BCD is efficient and optimal. There are similar test cases as hard cases in which considerable savings has been achieved (cases 6, 8 and 14). Conclusion In this paper a modified decomposition algorithm as a main part of path planning systems in agricultural environments was presented. Proposed algorithm uses method of parallelization of the edges of polygon. This method is based on encounter concept and "minimum facing to cost making condition". Although the general problem had been proved to be NP-hard problem, the method has limited the search space correctly and effectively which resulted close to the optimal solutions quickly. Another advantage of the method is suitability of the solutions for any kind of machine and any polygonal flat field (and those which can be considered as flat fields).
H. Sadrnia; M. Khojastehpour; H. Aghel; A. Saiedi Rashk Olya
Abstract
Introduction The high energy consumption is one of the serious problems in poultry industry. The poultry industry consume about five percent of total energy sources in different countries, with consideration of losses, it increases up to 16-20%. In the year 2003 also, the Iranian chicken meat consumption ...
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Introduction The high energy consumption is one of the serious problems in poultry industry. The poultry industry consume about five percent of total energy sources in different countries, with consideration of losses, it increases up to 16-20%. In the year 2003 also, the Iranian chicken meat consumption per capita was 13.3 kg, while in the year 2013 it increased to 25.9 kg (FAO, 2014). It shows that in the diet of Iranian people, the chicken meat has become a strategic food. Poultry industry is one of the biggest and most developed industries in Iran. In the past two decays, mainly due to population growth and increase demand of white meats, it is necessary to change and improve energy efficiency in this industry. Technical efficiency of broiler farms in the central region of Saudi Arabia was analyzed through stochastic frontier approach (Alrwis and Francis, 2003). They reported that many farms under study work lower than their total capacity. In the research, the output was chicken meat weight in the term of the kilogram per one period and the inputs were the number of chicks, feed, the total of all variable expenses and fixed input except chicks and feed and the total cost of fixed inputs including building, equipment and machinery used for the broiler houses. They found that the small and large size broiler farms in the Central Region of Saudi Arabia were produced chicken with mean technical efficiency 83 and 88%, respectively (Alrwis and Francis, 2003). Efficiency measurement of broiler production units in Hamadan province was investigated by Fotros and Solgi (2003). They reported that the minimum, maximum and mean technical efficiency under variable return to scale were 12.7, 100 and 64.4%, respectively. Their results showed that technical efficiency at 16.5 (14 units) and 42.35% (24 units) of farms were more than 90 and 70%, respectively (Fotros and Salgi, 2003). Khorasan Razavi province after Esfahan and Mazandaran provinces is the third largest producer of broilers in Iran. This research was performed because it is necessary to have energy consumption status; also there is a few data about broiler’s energy consumption in Mashhad. In this research, the data of Mashhad’s broilers was analyzed by Data Envelopment Analysis Method. The other objectives of this study were to separate efficient and inefficient units to use energy resource efficiently and determine total energy saving. Materials and Methods This study was performed in 2013 in Mashhad, Iran. The data were collected through interviews and questionnaires from 36 poultry farmers for a growing period of April to May. Input energies were the feed, fuel (gas and gas oil), electricity, labor, equipment and chicken, and the output energies were the chicken meat and the manure. The energy consumption for each element was calculated by multiplied amount of inputs/outputs to energy equivalents. Results and Discussion The total of input and output energies were obtained 125.2, 24.9 GJ/1000Birds, respectively. Energy indices such as energy ratio, energy efficiency and specific energy were determined to be 0.2, 0.019 kg/MJ and 52.55 MJ/kg, respectively. The highest share of energy consumption were 50.84 and 42.43%, for fuel (natural gas and diesel fuel) and feed respectively, the lowest share among the input energies were 0.39 and 0.06%, for chicken and labor respectively. Comparison of energy in three levels of farm sizes (≤15000, 15000-30000 and ≥30000 chicks) showed the energy ratio for large farms were higher than the other levels. Data Envelopment Analysis (DEA) was used to evaluate the poultry efficiency. The results showed that 13 poultry units had average technical efficiency (0.93) in the definition of Constant Returns to Scale (CRS), and 21 poultry units had pure technical efficiency (0.99) in the definition of Variable Returns to Scale (VRS). Conclusion The Fuel (natural gas and diesel fuel) consumption energy had the highest shares of energy consumption; it is because of the low efficient heating equipment in poultry houses and low fuel prices in Iran. Energy efficiency of broiler farms in Mashhad was obtained 0.2 that show low energy efficiency. Improvements in energy efficiency could be achieved by increasing yield or reducing inputs energies.
A. Kosari Moghaddam; H. Sadrnia; H. Aghel; M. Bannayan Aval
Abstract
Introduction
The working day is an important component in selection and analysis of farm machinery systems. The number of working days is affected by various factors such as climate, soil characteristics and type of operation. Daily soil moisture models based on weather long-term data and soil characteristics ...
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Introduction
The working day is an important component in selection and analysis of farm machinery systems. The number of working days is affected by various factors such as climate, soil characteristics and type of operation. Daily soil moisture models based on weather long-term data and soil characteristics were almost used for calculating probability of working days. The goal of this study was to develop a simulation model to predict the number of working days for secondary tillage and planting operation in fall at 50, 80 and 90% probability levels.
Materials and Methods
A Simulation model was developed using 21 years weather data and soil characteristics for calculate daily soil moisture content in Research Station of Ferdowsi University of Mashhad. So soil moisture was calculated using daily soil water equation for top 25 centimeter of soil depth. Moisture equal or lower than 85% of soil field capacity and precipitation lower than 4 millimeter (local data) were considered as soil workability criteria. Then the working days were determined for secondary tillage and planting operation at 50, 80 and 90% probability levels in falls. The number of days at 50% probability was the mean over 21 years and the number of days at 80% and 90% were determined for each two weeks period as the average number of working days minus the product of t value and standard deviation of those numbers.
Model Evaluation
Evaluation of model included a comparison of predicted and the observed the number of working days in Research Station of Ferdowsi University of Mashhad during 2002-2010 and sensitivity analysis was implemented to test the effect of changes in soil workability criterion (80, 90, 95 and 100% of soil field capacity), drainage coefficient (25 % decrease and increase) and soil field capacity (40% increase) on simulation results.
Results and Discussion
Comparison of predicted and observed days showed that correlation coefficient was 0.998 and the difference between the simulated data and observed data was not significant at the 5% level.
Results from sensitivity analysis in Table 3 showed that when soil workability, drainage coefficient and field capacity increased, the number of working days increased, but model sensitivity was very low to drainage coefficient and soil field capacity. In general, the most important factor is precipitation in this weather conditions.
The number of working days for secondary tillage and planting operation for each period in fall are shown in Table 4.
Conclusions
A simulation model was developed for predicting the number of working days for secondary tillage and planting operation in fall. This model was based on weather long-term data and soil characteristics for the Research Station of Ferdowsi University of Mashhad. The most important factor was precipitation and the model had low sensitivity to drainage coefficient and soil field capacity. The number of working days in 50%, 80% and 90% probability levels for period of ten days was on average 9.94, 9.21, 8.57 days for 23th September to 22th October and 9.77, 8.02, 6.41 days for 23th October to 21th November and 9.68, 7.48 and 5.24 for 22th November to 21th December, respectively.
H. Sadrnia; H. Monfared; M. Khojastehpour
Abstract
Drying is one of the oldest methods to preserve agricultural products and hence expanding the food market. By drying, the agricultural products can be stored and transferred to the market throughout the year. One of the most important and nutritious vegetables is turnip which can be used by drying in ...
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Drying is one of the oldest methods to preserve agricultural products and hence expanding the food market. By drying, the agricultural products can be stored and transferred to the market throughout the year. One of the most important and nutritious vegetables is turnip which can be used by drying in out of season. In this research, the hot air and vacuum drying methods of turnip were compared. The effect of independent factors including temperature and vacuum, on dependent factors such as the shrinkage, rehydration and rate of electric energy consumption on final products of turnip were investigated. A randomized completely design for hot air dryer and a factorial experiment based on completely randomized design for drying under vacuum condition were used. Results showed that the temperature and vacuum have affected the shrinkage, rehydration and electricity consumption. Shrinkage parameter is more depend on the final humidity of product and the energy consumption of the devices depends on time. The best quality of dried turnip was achieved from hot air drying device with final humidity of 14±1%, shrinkage of 39.98%, rehydration of 4.45 and consumed electricity of 32.36 kWh kg-1 of DM in 60˚C. For the vacuum drying device the best quality of produce achieved with shrinkage of 38.12%, rehydration of 4.87 and consumed electricity of 30.58 kWh kg-1 of DM in vacuum condition of 10 kPa in 60˚C. Comparison of results showed that the vacuum dryer is more appropriate than the hot air dryers for drying turnip with better quality and lower power consumption.
M. Saadatinia; B. Emadi; H. Sadrnia
Abstract
One of the nondestructive methods for assessing the internal quality of some fruits is the processing and analyzing the sound signals generated by an impact on the fruit. In this regard determining the location and the suitable impact levels for a certain fruit is required. In this study, the selected ...
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One of the nondestructive methods for assessing the internal quality of some fruits is the processing and analyzing the sound signals generated by an impact on the fruit. In this regard determining the location and the suitable impact levels for a certain fruit is required. In this study, the selected Crimson sweet variety of watermelon was used for the acoustic tests by imposing the impact force on samples. Acoustic tests were conducted using two independent variables including impact location (two sides of the symmetrical line of watermelon and the opposite of the stem end) and impact levels (12.09, 15.08 and 17.11 kg mm s-1) on the generated sound signals, to evaluate the stiffness of the fruit. The relation between the acoustic signals and the texture of both peel and flesh was examined using puncture test. The results showed that the variation of location and levels of impact on the obtained values of acoustic tests were significant
M. Jafarian; H. Sadrnia; M. H. Aghkhani
Abstract
Today, the use of coatings is common to maintain the quality of fruits in storage period. Previous studies have shown that the calcium compounds can improve and preserve the strength of fruit’s cell wall. In this research, the effect of calcium chloride dehydrate (CaCl2*2H2O) concentration on two ...
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Today, the use of coatings is common to maintain the quality of fruits in storage period. Previous studies have shown that the calcium compounds can improve and preserve the strength of fruit’s cell wall. In this research, the effect of calcium chloride dehydrate (CaCl2*2H2O) concentration on two varieties of apple (Golden Delicious and Red Delicious), was studied. The apples were immersed in the calcium chloride dihydrate solution and then transferred to a cold storage. The effect of three concentration levels: 0, 3 and 6 percent, and three storage durations: no storage, one month and two months, were investigated on the apples mechanical properties such as failure stress, failure strain, modulus of elasticity and toughness. Statistical factorial experiments in the form of completely randomized design were used to analyze the obtained results. The ANOVA results showed that the effect of calcium chloride concentration was significant on the modulus of elasticity (P
