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Arthropods were sampled on an early- and late-season crop of watermelon in the 2016 cropping season using motorized suction sampler swept along 5m length of the middle row of 20 experimental plots at Federal University Wukari. Specimens were sorted to morphotypes, feeding guilds and as dominant based on percentage relative abundance (RA) and frequency of occurrence (FO). Different species diversity indices were computed. The collections made on the early- and late-sown crops were compared using Jaccard’s Similarity index (C_j). Spatial distribution pattern of the dominant arthropods were determined using Taylor’s power law and Iwao’s patchiness regression. Results showed that collections on both crops were similar (C_j= 0.83). A total of 14,466 specimens sorted to 1 order (Araneae) in the class Arachnida and 64 species in 41 families and 8 orders in the class Hexapoda were collected. Data showed moderately high species diversity (H = 2.8-3.0), richness (R = 6.0-7.2), but low evenness (E = 0.26-0.39). Coleopterous insects (22 species), dominated by chrysomelids, were the most diverse and species-rich followed by hymenopterans, mainly formicids. Dominant arthropods (RA≥1.0 and FO≥25.0%) included Asbecesta nigripennis, Aulacophora africana, Philanthus triangulum (parasitoid of bee), Pheidole sp., Camponotus sp., Rhynocoris nitidulus and spiders. Most dominant arthropods were aggregated; dispersion varied with model used and crop season. Only 27.3% of the diverse and rich arthropods on watermelon at Wukari require pest management intervention and validation of their dispersion pattern in large-scale watermelon production.

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One of the remarkable concerns in Shallow arches’ behavior under lateral loading is snap through, a phenomenon which can make the structure collapse or displace to another stable configuration. Introducing functionally graded materials in recent years led to some interesting results, for instance, using functionally graded materials in shallow arches can give structures with favorable stability properties. In this work, we investigate dynamic stability of the pined-pined functionally graded sinusoidal shallow arch under impulsive loading. Material properties vary through the thickness by power law function. Nonlinear governing equations are derived using Euler-Bernoulli beam assumption and equations of motion are expressed by a nonlinear differential-integral equation. The solution utilizes a Fourier form of response. The procedure to analyze dynamic stability followed here uses total energy of the system and Lyapunov function in the phase space. We find the stable region against dynamical snap through under material properties’ variation through the thickness of shallow arch. We also proceed to find the sufficient critical load in order to make the dynamical snap through occur. The results are analyzed in detail and illustrated in some diagrams.

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Today, oil journal bearings are widely used as an efficient support for rotary systems in various industries. When these bearings are used by loading in high speed conditions, whirling disturbances in the rotor motion status leading to collisions and abrasion is probable. Designing specific geometric shapes or applying industrial lubricants with different new combinations can affect the journal bearings ability to maintain their dynamic stability in critical situations. From this view, the use of non-circular bearings and non-Newtonian fluids in the field of lubrication has recently been heavily taken into consideration. In the present study by choosing non-Newtonian lubricant simulated by power law fluid model, the effects of design parameters such as eccentricity ratio, aspect ratio and power law index on dynamic stability of noncircular two, three and four lobe bearings are investigated. For this purpose, assuming the limited cycle oscillations of the rotor around the equilibrium point after damping the effects of initial imposed disturbances and using finite element numerical method to solve the governing equations, stability range of the system in form of linear dynamic analysis characteristics is determined based on the whirl frequency ratio and critical mass parameter. The results indicate that by increasing the power law index and decreasing aspect ratio, the dynamic range of bearing support will be developed. Also, by increasing the number of noncircular bearings lobes with power law lubricant and providing the system's positioning conditions in high values of eccentricity ratio, more ability to damping dynamic disturbances can be achieved.

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Free convection heat transfer of a non-Newtonian thickening power law fluid in a closed asymmetrical enclosure with fixed aspect ratio was investigated in this study. Many of the previous studies, addressed the case with symmetrical heat transfer enclosure and for a given inclination. The governing equations were established by the finite volume method and solved by the SIMPLEC algorithm. In order to evaluate the code, its results were compared to those of other papers in the field of Newtonian and non-Newtonian fluids. The impact of the enclosure inclination and the Rayleigh number on the heat transfer and the flow field were investigated. It was found that for Rayleigh numbers smaller than , inclination has little impact on heat transfer, while at Rayleigh numbers larger than , the lowest heat transfer was observed at an angle of . Moreover, the results pertaining to Newtonian and non-Newtonian thickening fluids were compared. The results show that heat transfer by thickening non-Newtonian fluids, in addition to other parameters, depends on the parameter (n) and in the case of the angle of inclination , the heat transfer of Newtonian and non-Newtonian thickening fluids is equal. Considering the non-Newtonian behavior of the fluid and nondimensionalization of the problem, a new dimensionless number known as the extended Prandtl number 〖(Pr〗^*) appeared in the equations that depends on fluids characteristics, flow geometry, and the power law exponent . Its optimal value was observed at 〖(Pr〗^*=0.07) where heat transfer from the enclosure was at maximum.

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Guar gum is a biopolymer that is used in the food industry as a thickener, stabilizer, and edible coating. The aqueous solution of this gum has high viscosity and pseudoplastic behavior. This research aimed to analyze the impacts of sonication at different intensities (0, 75, and 150 W) and time intervals (0, 5, 10, 15, and 20 min) on the viscosity and rheological behavior of guar gum solution. The results showed that the apparent viscosity of guar gum solution (untreated sample) reduced from 0.070 to 0.030 Pa.s with increasing shear-rate from 12.2 s^-1 to 134.5 s^-1. Also, the apparent viscosity of guar gum solution reduced from 0.046 to 0.021 Pa.s with increasing the sonication time from 0 to 20 min (shear-rate=49 s^-1 and power= 150 W). Various rheological equations (Power law, Bingham, Herschel-Bulkley, Casson, and Vocadlo) were employed to fit the empirical values, and the findings of the current study confirmed that the Power law model was the best fit to explain the flow behavior of guar gum solution s. The consistency coefficient of guar gum solution significantly reduced from 0.202 Pa.sⁿ to 0.063 Pa.sⁿ (p<0.05) with increasing sonication time from 0 to 20 min. Furthermore, the consistency coefficient of guar gum solution decreased considerably (p<0.05) while the ultrasonic power enhanced. The flow behavior index of guar gum solution increased significantly (p<0.05) while the intensity and duration of ultrasound treatment increased.

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Cereal leaf miner, Syringopais temperatella Led. (Lep., Gelechiidae), is an important wheat pest in many regions of the world, including Iran. Fixed precision sequential sampling plan, a cost-efficient method for estimating pest population density, has been used for developing a successful IPM program. In this study, the fixed precision sequential sampling plan of S. temperatella larvae was developed on wheat, cultivar Verinac^®, during 2017-2019 growing seasons in Iran. For this purpose, first, spatial distribution of the larvae on wheat leaves was determined using Taylor's power law and Iwao's patchiness regression. The spatial distribution of the larvae was aggregative on the wheat leaves. Taylor’s power law provided a better fit for the data than Iwao’s patchiness regression. Therefore, Green's model was used for developing the fixed precision sequential sampling plan. The optimum sample sizes of the larvae ranged from 5- 68 plants and 12- 189 plants according to the average of larval density at precision levels D= 0.25 and D= 0.1, respectively. Estimated stop lines showed that the sampling must be continued until the cumulative number of the pest larvae reaches 3.45 (D= 0.25) and 83.76 (D= 0.1) per plant. Accuracy of the sampling plan was validated by RVSP software.

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In this research, the dielectric barrier discharge plasma driven channel flow with the applied magnetic field has been proposed for use as a thruster in propulsion applications and studied experimentally. Measurements of the thrust and consumed power of thruster for different values of the barrier thickness have been performed and the data have been compared with the corresponding ones without magnetic field. It is found that consumed power and thrust of the thruster in the presence of magnetic field are respectively little reduced and increased than that without the magnetic field. The measurements show that the effectiveness increases to a maximum and then drops as the operating voltage monotonically increases over a range from 12 to 26 kV. A power law analysis for revealing the relationships among the effectiveness, thrust, consumed power, and operating voltage has been presented for the thruster with and without the magnetic field. It is seen that the applied magnetic field and thicker dielectric barrier can lead to a higher effectiveness at the point of transition from the glow regime to the filamentary regime. The effects of micro-discharge channels on the effectiveness in the both regimes have been discussed. The observations indicate that in the presence of magnetic field, the additional micro-discharge channels are generated and develop along the magnetic field lines and the diffuse background emission of the discharge is stronger in plasma. The underlying physical mechanisms of mentioned phenomena have been explained and mainly ascribed to the enhanced ionization by applying the magnetic field.

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Worldwide, Iran is the first producer of pistachio, which is one of the most economically important agricultural products for this country. Idiocerus stali Fieber (Hemiptera: Cicadellidae) is one of the most important pests of this plant. Adults and nymphs pest feed on leaf tissues and fruit clusters, and they cause damage by sucking the sap. This pest has one generation per year. In this research, population fluctuations of the pistachio leafhopper associated to the temperature and humidity changes and its spatial distribution, using both statistical and geostatistical methods were studied in 2018-2019. The spatial distribution of all life stages in both years was cumulative according to Iwao model, whereas considering Taylor's power law model it was cumulative in 2018 and random in 2019. Considering coefficients' values, both models of Taylor's power law (R²= 0.93) and Iwao model (R²= 0.92) are appropriate for estimating the type of spatial distribution for this pest, however, Taylor model showed a better data fitting. Concerning geostatistics models, Kriging interpolation method was more accurate than Inverse Distance Weighting (IDW) and it was used to produce pest distribution maps. The movement process of adults, nymphs, and the sites of laying areas per week was precisely determined. Hence, contamination foci can be identified and used to apply appropriate management methods at the right time at a low cost.

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The nut scale, Eulecanium tiliae (L.) is a potential pest, infesting deciduous trees in Iran, where it is common in urban horticultural areas and usually present in high population on some stone fruit trees, such as Prunus spp., including Prunus cerasus. It has higher occurrence and population in sustainable orchards. This pest has one generation per year and second nymphs overwinter on one or two-years old branches. High populations of this pest can cause death of branches, twigs and degeneration of leaves chloroplasts. In this research, the spatial distribution pattern and population fluctuation for all stages of E. tiliae were investigated in a cherry orchard of Kermanshah region during two studied seasons from 2016 to 2018. Four different methods were used to calculate distribution pattern including index of dispersion, Morisita’s index and regression methods (Taylor’s and Iwao’s). Sample size was determined for the first time, according to a primary sampling date and corrected for other sampling dates according to the data of the previous sampling date. Data analysis was performed using Minitab16 and Office Excel 2016 statistical softwares. Most used methods revealed aggregated distribution pattern of the pest in both years. The results obtained from the Morisita’s index during activity showed the random distribution of the second nymphs (in 16 April 2016, Z= -1.218, I_б= 0.440) (in 16 April 2017, Z= -0.179, I_б= 0.942) (-1.96< Z< 1.96). These changes showed that the spatial distribution could change during the season. Knowledge of the pest spatial distribution pattern can be used to arrange sampling program in pest management.

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 The date palm dust mite Oligonychus afrasiaticus (McGregor) is one of the most important pests of the date palms Phoenix dactylifera L. around the world. This pest causes reduction in the economic value of the product, and sometimes its damage reaches up to 100% in the southern provinces of Iran. The population fluctuations and spatial distribution of this pest on two more common varieties (Sayer and Barhi) were investigated in Ramshir City, Khuzestan Province, southwestern Iran. For this purpose, two date palm plantations of 2 ha that had those two varieties of date palm trees were selected, and 10 trees of each variety in each orchard were selected randomly. Sampling was done from North, South, East, and West of each date palm every four days from mid-May to early November, during 2020 and 2021. The results showed that the spider mite appeared on the clusters of two varieties from the beginning of June, and the peak population of mites on both varieties was recorded in September, in both years. Significant difference was observed between different sampling times during those two years and the two varieties: Sayer (F₁._{916, 9.580}= 183. 695, P< 0.0001) and (F_{2.344, 11.720}= 58. 104, P< 0.0001) and Barhi (F_{1.541, 4.622}= 89.010, P< 0.0001) and (F_{1.688, 5.065}= 31. 137, P