دانشگاه فردوسي مشهد
دانشگاه فردوسي مشهد
دانشگاه فردوسي مشهد
دانشگاه فردوسي مشهد
گروه آموزشی زراعت
Microwave heating is an environmentally friendly method for killing pest insects and here its efficacy in the control of a pest species of dried fig and raisin was assessed. Dried fig and raisin samples were infested with Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) larvae and heated in a microwave oven at power outputs of 450, 720, and 900 W for 20, 30, 40, and 50 s. Following exposure to the microwave treatments, larval mortality and changes to organoleptic properties, which indicate consumer preference and include aroma, color, sweetness, acerbity, fragility, stiffness, and overall acceptability, were assessed. Our results showed mortality rates were greatest with the highest degree and duration of microwave exposure, where 100% mortality was recorded at 900 W with an exposure time of 50 s. The sensory evaluations of the fruit showed that microwave heating had some effect on aroma, color, fragility, sweetness, and overall acceptability, but no effect on acerbity and stiffness in dried fig, whereas in raisin, there were no impacts on acerbity, stiffness, or sweetness, but aroma, color, fragility, and overall acceptability were affected. We conclude that application of lower intensities of microwave treatment may provide acceptable levels of pest control in stored dried fruit without an associated trade-off in the reduction in quality of sensory attributes.
روش المان محدود براى مدل سازى انتقال هم زمان جرم و حرارت در نمونه هاى استوانه اى موز مورد استفاده قرار گرفت. در مدل ارائه شده خواص ترموفیزیکى محصول به صورت تابعى از رطوبت و دماى محصول در طول فرایند در نظر گرفته شد. مدل سازى به کمک نرم افزار تجارى COMSOLنسخه 5/1و به صورت تقارن محورى انجام شد. از روش اویلر لاگرانژ دلخواه ) (ALEبراى تعریف مرز متحرک جهت احتساب چروکیدگى در مدل استفاده شد. براى راستى آزمایى مدل، نمونه هاى موز در شرایط مختلف خشک شدند و تغییرات دما در مرکز نمونه و میانگین محتوى رطوبت نمونه ها با مقادیر پیش بینى شده توسط مدل مقایسه شدند. نتایج نشان داد درصد میانگین خطاى نسبى براى تخمین رطوبت و دما به ترتیب در محدوده % 4/23-8/83و % 1/12-1/82 بود. بنابراین مدل ارائه شده قادر است محتوى رطوبت و دماى مرکز نمونه را در طول فرایند خشک شدن به طور موفقیت آمیزى پیش بینى کند. با توجه به اهمیت پیش بینى تغییرات دما و رطوبت، مدل ارائه شده مى تواند به عنوان ابزار مفیدى در جهت بهینه کردن فرایند خشک کردن موز از نظر بازده آن وکیفیت محصول مورد استفاده قرار گیرد. انتظار مى رود که مدل مذکور به راحتى قابل تعمیم براى خشک کردن محصول هاى مشابه با شکل استوانه اى باشد
Grading which results in easier fruit packaging not only reduces the waste but also increases the marketing value of agricultural products. The knowledge on existing relationship among the mass, length, width, thickness, volume and projected areas of fruits is useful for proper design of grading machines. The aim of this study was mass modeling of two major cultivars of Iranian cantaloupes (Tile Magasi and Tile Shahri) based on geometrical attributes. Models were classified into three: 1 – univariate and multivariate models based on the outer dimensions of fruit. 2 – Univariate and multivariate models based on the projected areas of fruit. 3 – Univariate models based on the actual volume, volume of the fruit assumed as prolate and oblate spheroid shapes. The results indicated that the models based on the fruit width, third projected area and assumed oblate spheroid volume have the highest determination coefficient (R2) and the lowest standard error of estimate (SEE). It was finally concluded that cantaloupe mass modeling based on the volume of fruit assumed as oblate spheroid shape with a nonlinear relation; , R2 = 0.986 these values were suitable for grading systems.
In this study, the mechanical properties of the skin and flesh of cantaloupe were determined by individual experiments and then finite element simulation was developed for cantaloupe fruit under compression loading. The applied deformations were equal to 10, 20 and 30% of rupture deformation or 4.5, 9 and 13.5 mm, respectively. The results showed that the internal tissue of fruit reached to yield point in 20% of whole deformation or in force 90 N and the internal failure occurred with no visibility. The statistical comparison of finite element method results with experimental data was performed. The results showed finite element method was able to determine the force threshold of internal bruising for cantaloupe.
Knowledge about the safety of agricultural machines can be useful for reducing the physical damages and financial losses incurred by the farmers. In this study, VisualNastran desktop software was used to analyze the mechanism of three-point hitch in MF-285 tractor. Two different load cases (lifting a usual plow and maximum hydraulic lifting capacity) were studied. Neither accidental nor exceptional load cases were examined here. The finite element method was used to estimate the stress distribution and factor of safety of lift arm in SolidWorks software. The FEA results show that the maximum values of the von MISES equivalent stress for both examinated load cases are, respectively, 79 and 367 Mpa for lifting a usual plow (500 kg) and maximum hydraulic lifting capacity (2230 kg). The lift arm is safe enough for lifting of a usual plow but it may be failed when the three-point hitch works with maximum hydraulic lifting capacity. It is recommended to revise the design and construction process of the lift arm or limit the lifting capacity to 1430 kg weight.
The effect of microwave power levels on drying characteristics of basil (Ocimum basilicum L.) in microwave dryer was investigated in this study. The microwave power levels of 90, 270, 450, 720 and 900W were used to dry 30 g of basil leaves. The initial moisture content of the samples was 7.25 g water per g dry base. In order to determine the kinetic parameters, experimental data were fitted to seven different models based on the ratios of differences between the initial and final moisture contents and equilibrium moisture content. The energy consumption and the effective moisture diffusivity were determined for different microwave power levels. The results showed that increasing microwave power in the range of 90‐900W leads to the decrease of drying time in the range of 35‐6 minutes. The comparison of proposed models showed that the logarithmic model of MR= a.exp(‐k.t)+b was the best fit for all microwave powers due to the highest coefficient of determination (R2), the lowest chi‐square (χ2) and the lowest root mean square error (RMSE). Therefore the mentioned model can be used to estimate the moisture in basil leaves at any time during the microwave‐drying process. The maximum and minimum values of consumed energy for drying in 90 and 450 W microwave powers were 52.5 and 99 W.h, respectively. The effective diffusivity of basil leaves were in the range of 1.624×10−10 to 7.652×10−10 m2s‐1 for different microwave powers.
Engine cooling system plays an important role in the engine’s efficiency and its damage prevention. Radiator as a heat exchanger is a part of this system. The aim of this study was to determine the optimal working conditions of radiator. The finite element method (FEM) and computational fluid dynamics (CFD) were used simultaneously to analyse the heat transfer in U650 tractor radiator in Flow Simulation package. The boundary conditions were defined as cooling water flow rates; 50, 60, 70 and 80 L/min and its temperature; 80, 93 and 100 ° C. In all cases, the cooling air flowed with the velocity of 2 m/s and the temperature of 25 °C through the radiator. The amount of temperature loss in the radiator was considered as the parameter for determination of heat transfer value. The results showed that the thermal performance of radiator improved with increase of water temperature or decrease of its flow rate. Actually, the maximum values of heat transfer was for flow rate of 50 L/min and coolant temperature of 100 °C and the minimum value was for flow rate of 80 L/min and coolant temperature of 80 °C . Also the distributions of temperature and heat flux were obtained in different parts of the fluid, copper pipes and fins.
در میوۀ طالبی بهدلیل پوست نسبتاً سخت و گوشت نرم آن، لهیدگی بافتهای داخلی شایعترین نوع آسیب مکانیکی است که در ظاهر قابلتشخیص نیست و پیشبینی آن به روشهای تحلیلی سخت است. از حل غیرخطی مسئلۀ بارگذاری استاتیکی میوه در جهت طولی بین دو صفحۀ موازی با روش المان محدود و با نرمافزار آباکوس ) (ABAQUSبرای پیشبینی لهیدگی داخلی طالبی استفاده شد. تغییر شکلهای اعمالشده به مدل ،11 ،5/5و 16/5میلیمتر معادل ،10 ،20و 30درصد تغییر شکل تخریب بود. تحلیل تنشهای وارد بر پوست و گوشت میوه نشان داد که بافت داخلی میوه در 20درصد تغییر شکل تخریب یا نیروی معادل 90نیوتن به حد تسلیم رسیده است و گسیختگی داخلی آغاز میشود و این حالت در ظاهر میوه قابل رؤیت نیست. رابطۀ قوی بین نیروی پیشبینیشده توسط مدل المان محدود و نیروی FEMاعتبار مدل ) (R2=0.983واقعی را تصدیق کرد
The finite element method was employed to model the simultaneous heat and mass transfer in cylindrical samples of banana during convective drying. The Arbitrary Lagrangian–Eulerian (ALE) approach was implemented to incorporate the axial and radial shrinkage effects in the FEM model. The results showed that the FEM model was satisfactorily able to predict the moisture content (R2 > 0.97) and core temperature (R2 > 0.98). Therefore, the proposed model can be used as a promising tool to optimise the drying process of banana from quality and efficiency points of view. Also, the model can be easily extended for drying of similar products with cylindrical shape.
Color and shrinkage are two main quality attributes of dried banana. In this study, a hot air dryer equipped with a computer vision system (CVS) was employed for online monitoring of quality changes of banana during drying. Banana slices were dried at temperatures of 80, 90 and 100 °C and air velocities of 1.0 and 1.5 m/s. Drying took place entirely in the falling rate period. The results showed that the system could successfully measure and monitor the color and shrinkage evolutions of banana during drying. Air temperature had significant effect on drying time. For all temperatures, drying followed by decrease of the lightness (L*) and increase in the redness (a*) of banana samples but with no clear tendency of the yellowness (b*). It was found the total color difference (ΔE*) has a direct relation with drying temperature. Shrinkage showed almost a linear correlation with moisture ratio. Drying at higher temperatures led to more color changes but less shrinkage. Air velocity in the studied range had no significant effect on both color change and sample shrinkage.
In this study, microwave heating was employed for controlling Oryzaephilus surinamensis adult beetles infesting stored Iranian dried figs. The dried fig samples were artificially infested with O. surinamensis and then heated in a microwave oven (2,450 MHz) at power outputs of 450, 720, and 900 W for 20, 30, 40, and 50 s. Changes in the color of the samples after these microwave applications were evaluated for lightness (ΔL*), redness (Δa*), and yellowness (Δb*) using an image processing technique. Both parameters of microwave power and exposure time had significant effects on beetle mortality (P , 0.01). A direct positive relationship was found between the mortality rate and microwave power. Complete mortality was achieved at 900 W and for 50 s. The color parameters of the dried fig samples did not change significantly. These results indicate that microwave irradiation can be introduced as an appropriate alternative to chemical fumigants without affecting product quality