An Analytical Method for Crack Detection of Beams with Uncertain Boundary Conditions by a Concentrated Test Mass

The aim of this study is to introduce a method for crack detection and simultaneously assessing boundary conditions in beams. This study suggests a method based on the effect of a concentrated test mass on the natural frequency that is defined as a stationary mass, which can be located in different positions of the beam and cannot be separated from the beam. Timoshenko beam theory is used to calculate the frequencies. In this method, a beam with the desired number of cracks is modeled. The beam is divided into separated parts at crack section which are joined together by elastic weightless torsion springs, to avoid non-linearity effects, it is assumed that the crack is always open. At the first step, equations for a cracked beam are extracted by considering the spring boundary conditions. Then, to verify the equations, numerical finite element model is used. In this way, a new method is also applied to model the torsion springs in supports and it is shown that suggested model is acceptable. Eventually, the obtained responses are evaluated and the sources of errors are identified. To correct the existing errors, a modifying function is suggested. Finally, the inverse problem is solved

Design, Fabrication and Evaluation A New Mechanism to Automatic Weight Transfer Control System on A Tractor

Increasing tractor weight during agricultural operations is one of ways to optimization the performance of tractor tires interacting with soil. One of these methods is adding weight on the front of the tractor, which leads to better engagement of front tires with soil. In four-wheel drive tractors also causes better steering wheel drive tractors, in addition it prevents from weight transfer to the rear of the tractor, which causes overturning. In this research, a new approach has been proposed that proves automatic weight transfer is possible by putting some lightweight instead of main weights on the front of the tractor. To do this, a number of weights to a specified amount were added on the front of the tractor which could be moved by using a mechanical joint and a hydraulic jack (considering working condition and ground conditions). Traction force and slop of land that have the most impact on weight transfer were measured by a dynamometer and an inclinometer. Also the critical values of these parameters were controlled by an electronic circuit. Results prove that the applied system on the tractor was able to control dynamic weight transfer also the longitudinal balance on the tractor was investigated by performing an experiment on a sloping surface, and good results were detained

Moisture-Dependent Some Engineering Properties of Soybean Grains

This study was carried out to evaluate the effect of moisture content on some physical properties and mechanical behaviour under compression load of soybean grains. Four levels of moisture content ranging from 6.92 to 21.19% d.b. were used. The average length, width, thickness, arithmetic and geometric mean diameter, surface area, thousand grains mass and angle of repose increased as the moisture content increased from 6.92 to 21.19%. As the moisture content increased from 6.92 to 21.19% d.b., the bulk density and true density were found to decrease from 650.95 to 625.36 kg/m3 and 1147.86 to 1126.43 kg/m3 respectively, while the porosity was found to increase from 43.29 to 44.48%. The static coefficient of friction of soybean increased linearly against various surfaces as the moisture content increased from 6.92 to 21.19% d.b. The rupture energy of the grains increased in magnitude with an increase in moisture content, while rupture force decreased

Evaluation of different sensing approaches concerning to nondestructive estimation of leaf area index (LAI) for winter wheat

Different approaches of non-destructive estimation of the LAI in winter wheat were compared. Plant height had weak relation with the LAI, while estimated biomass showed high logarithmic relationship (R2=0.839). NDRE and REIP were logarithmically well related to the LAI (R2=0.726 and 0.779 respectively). Saturation effect of NDRE and REIP was less than NDVI. Some RGB-based indices also showed good potential to estimate the LAI. Among the indices, Gm, GMB, RMB, and NRMB were better related to the LAI. The results indicated that digital cameras can be used as an affordable and simple approach for assessment of the LAI of crops

Investigation on new low cost electronically controlled fuel metering systems for small gas turbine engines

This work introduces two new lost cost, electronically controlled fuel metering systems for small gas turbine engines, particularly applicable in remotely piloted vehicles. The first one incorporates a diaphragm operated flat-seat bypass valve to maintain a constant differential pressure across the metering valve, which is actuated by a digital linear actuator. In the second one, both the metering and the bypass valves are controlled by two independently operated digital linear actuators. The mathematical models for the first fuel metering system, were created and used for computer simulation. Next, after preparing the experimental test set-up, the manufactured prototype was tested and the models for both the steady state and the dynamic response were validated. Three design optimization criteria, fuel flow linearity, low sensitivity to the design parameters changes and fast dynamic response were examined to improve the performance of the proposed fuel metering system. Finally, a multi-objective optimization technique was developed and implemented to obtain the best design parameters of the system. For the second fuel metering system, first the mathematical models for both the steady state and dynamic response were developed. Next, due to the flexibility offered by this system, different control strategies for controlling the digital linear actuators during the normal operation mode of the actuators and also during the back-up operation modes were introduced and investigated. Finally, to investigate the impact of different control strategies on the dynamic response of the engine, a dynamic model for the engine was also developed and used. At the end, four available fuel metering systems, including the two new ones, were compared regarding their deviation from the fuel flow linearity, dynamic response and the cost

Comparison of Mechanical Properties of Wheat and Barley Straw

The objective of this work was to compare the mechanical properties of wheat and barley straw. The experiments were conducted at moisture contents of 10.24% and 10.76% w.b. for wheat and barley straw, respectively, and three internode positions down from the ear. The average shear strength for wheat and barley straw varied from 6.81 to 7.12 MPa and 3.90 to 4.49 MPa, respectively. The specific shearing energy of wheat and barley straw increased from 21.85 to 25.74 mJ/mm2 and 18.79 to 19.85 mJ/mm2, respectively, towards the third internode position. The bending stress and Young’s Modulus of wheat and barley straw increased towards the first internode position. The results showed that the mechanical properties of wheat and barley straw were statistically different

Effect of Moisture Content and Loading Rate on the Shearing Characteristics of Barley Straw by Internode Position

This research was conducted to evaluate the effect of moisture content, internode position and loading rate on the shearing characteristics of barley straw in terms of shear strength and shearing energy. The characteristics were determined at three moisture levels: 10, 15 and 20 % w.b., three loading rates: 5, 10 and 15 mm/min and three internodes: first, second and third internode. The results showed that both the shear strength and shearing energy increased with an increase in moisture content and loading rate and towards the third internode position. The average shear strength was obtained as 5.08 MPa varying from 3.68 to 6.18 MPa, while the average shearing energy was calculated as 100.93 mJ ranging from 65.17 to 131.06 mJ. The shear strength of the barley straw increased from 4.09 to 5.03 MPa, 4.84 to 5.25 MPa and 5.15 to 5.94 MPa for the first, second and third internodes, respectively, as the moisture content increased. The shearing energy of the straw also varied from 70.44 to 99.82 mJ, 92.46 to 121.25 mJ and 102.33 to 122.09 mJ for the first, second and third internodes, respectively

Modified Atmosphere Packaging: A Progressive Technology for Shelf-Life Extension of Fruits and Vegetables

Packaging and storage are the final phases in the food industry. Quality preservation, improving safety and reduction of postharvest losses waste are some objectives of the packaging engineering. One of techniques that widely used in packaging of fruits and vegetables are modified atmosphere packaging (MAP). In MAP for fresh fruits and vegetable the air of packaging headspace replaces with a predetermined atmospheric gases different in proportion from that of air. Oxygen, carbon dioxide and nitrogen are the main gases used in MAP for injection to the headspace of pack. The choice and ratio of gases are very dependent upon the material that being packed. respiration rate of crop, O2 and CO2 permeability of package material, volume of headspace present inside the package and storage temperature are some factors that affect the quality of MA packaging. Polymeric films are widely used in MAP engineering. The most application of polymeric films for MAP are in flexible package structures. In many cases the plastic packaging films are combined with one another or with other materials such as paper or aluminum through coating, lamination, coextrusion and metallization processes. The equipment used in MAP is divided into two main categories: pillow wrap and chamber. Flexible pillow wrapping machines are composed of Horizontal Form-Fill-Seal (HFFS) machines and Vertical Form-Fill-Seal (VFFS) systems. This paper reviews some recent developments in MAP technology applied for fruits and vegetables

Using online image processing technique for measurement the browning in banana during drying (a new and automatic method)

Determination and controlling of quality parameters can be useful for ordering and marketing of fruits.  Color is the first and the most important parameter in the visual appearance of fruits, specifically in banana.  The aim of this study is to use image-processing technique (online operation) to measure and analyze the color change of banana slices during thin layer drying.  Using online-image-processing technique resulted in designing a machine vision system to control the color change of products automatically.  The results show a linear relation with high correlation coefficient for L*, a* and b* (0.967, 0.962 and 0.991 respectively) between the data of the image-processing technique and the hold-hand colorimeter.  In this study, parameters of chroma, hue and browning index were determined to describe the kinetics of color change in banana slices.  The change of chroma was not significant, but hue was decreased and browning index was increased during drying time.  In addition, the experimental data of the L* and ∆E was fitted using zero and first order models with high correlation coefficient (0.80-0.97).   Keywords: image processing, machine vision, online, banan

Evaluation of an electronic nose system for characterization of pomegranate varieties

The electronic nose (e-nose) would simulate the human sense (smell) to identify and realize the complex aromas by employing a chemical sensors array. One of the most common sensors used in electronic nose systems are metal oxide semiconductor (MOS) sensors. In this research, a low cost e-nose system based on six metal oxide semi-conductor (MOS) sensors as a non-destructive instrument for recognition pomegranate varieties is investigated. Principal component analysis (PCA) and linear discriminant analysis (LDA) techniques are used for this purpose. The proposed e-nose has a capability of demonstrating a clear difference in aroma fingerprint of pomegranate by PCA and LDA analysis. Using LDA analysis, it is possible to identify and to categorize the difference between pomegranate varieties, and based on the results, the classification accuracy of 95.2% was obtained. Sensor array capabilities for classification of pomegranate varieties using loading analysis were investigated too. Results showed high ability of e-nose for distinguishing between the varieties of pomegranates