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BLUNT CRACK-TIP ELASTOPLASTIC ZONE OF MIXED MODE FRACTURE

Acta Mechanica Solida Sinica 2014年第5期27卷 531-541页

作者： mehdi khojastehpour Department of Biosystems Engineering Ferdowsi University of Mashhad

This article discusses the characterization of fracture process zone at the tip of a blunt crack in elastoplastic materials under mixed mode loading. The analysis includes the description of elastoplastic zone geometry around the blunt crack tip for predicting crack growth direction. The deformed zone appearing at the crack front is described by presenting a criterion based on the subloading surface concept falling within the framework of unconventional plasticity. The mixed mode crack propagates along the minimum value of the elastoplastic region. The present solutions are reduced to those previously reported in literature, when the elastic perfectly plastic material is considered.

关键词： crack fracture elastic plastic materials stress concentration

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Sensitivity analysis of energy inputs and economic evaluation of pomegranate production in Iran

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Information Processing in Agriculture 2018年第1期5卷 114-123页

作者： mehdi Esmailpour Troujeni mehdi khojastehpour Adel Vahedi Bagher Emadi Department of Biosystems Engineering Ferdowsi University of MashhadMashhadIran Agricultural Engineering Research Institute(AERI) Agricultural Research Education and Extension Organization(AREEO)KarajIran

The aim of this research was to investigate the energy use and costs of pomegranate production in Behshahr city(Mazandaran province)of *** required data were gathered by questionnaire and face to face interviews with 83 pomegranate ***-Douglas model and sensitivity analysis were employed for energy flows modeling of the production *** total energy inputs and energy output of production were determined to be 11195.06 and 13276.56 MJ ha1,and two inputs of diesel fuel and chemical fertilizers with the shares of 45.81 and 23.47%,were the highest energy consumers for pomegranate *** use efficiency,energy productivity and net energy were 1.18,2081.50 MJ ha1 and 0.62 kg MJ1,*** results of Cobb-Douglas model showed that the effect of the energy inputs including human labor,biocides,chemical fertilizers,farmyard manure,electricity and water for irrigation on pomegranates yield were positive,while the effects of diesel fuel and agricultural machinery were negative on the pomegranate *** sensitivity analysis results of energy inputs showed that with the increase of one MJ in the energy input of water for irrigation and chemical fertilizers,the yield was increased to 3.12 and 1.42 kg,*** with the increase of one MJ in diesel fuel and agricultural machinery inputs,the yield was decreased to 0.67 and 0.47 kg,*** fuel as the most used energy input in the production accounted for 0.85%of variable costs and the benefit to cost ratio was determined to be 5.57.

关键词： Benefit to cost Cobb-Douglas Energy modeling Energy pattern Pomegranate

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Life Cycle Assessment modeling of milk production in Iran

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Information Processing in Agriculture 2015年第2期2卷 101-108页

作者： Hamzeh Soltanali Bagher Emadi Abbas Rohani mehdi khojastehpour Amin Nikkhah Department of Biosystems Engineering Ferdowsi University of MashhadAzadi SquareMashhadIran Young Researchers and Elite Club Rasht BranchIslamic Azad UniversityRashtIran

Livestock units are known as one of the most influential sectors in the environment ***,the aim of this study was to investigate the environmental impacts of milk production in Guilan province of Iran through Life Cycle Assessment(LCA)*** primary data were collected from 45 units of milk production through a field survey with the help of a structured *** reliability was assessed using Cronbach’s alpha coefficient and was estimated an acceptable value of *** consumption of resources and emissions were allocated to a functional unit(FU)of one ton of *** of emissions in five impact categories of global warming,acidification,eutrophication,photochemical oxidation and depletion of resources were *** results showed that the characterization index for these impact categories were 1831 kg CO2 eq,7.97 kg SO2 eq,3.42 kg PO4^-3 eq,0.21 kg C2H4 eq and 838.39 MJ,*** indices for these impact categories were calculated as 0.24,0.28,0.076,0.017 and 0.046,*** index(EcoX)and resources depletion index(RDI)were obtained 0.61 and 0.04,*** this study,the highest potential for environmental impacts of production revealed for acidification and followed by global warming impact category.

关键词： Acidification Dairy farm Environmental impact Global warming

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Ergonomic assessment of drivers in MF285 and MF399 tractors during clutching using algometer

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Information Processing in Agriculture 2016年第1期3卷 54-60页

作者： Hossein Fallahi Mohammad Hossein Abbaspour-Fard Amin Azhari mehdi khojastehpour Amin Nikkhah Department of Biosystems Engineering Ferdowsi University of MashhadMashhadIran Orthopedic Research Center Mashhad University of Medical SciencesMashhadIran

Tractor as one of the most widely used agricultural machinery should be considered from different *** frequent application of clutch and brake pedals and also the steering wheel within farms,along with the unfavorable working conditions,cause negative effects on the occupational health of the tractor ***,in this research,the imposed forces on three engaged muscles including:Gastrocnemius,Trapezius and Quadrate’s lumborum of the tractor drivers during clutching have been *** this regard,algometer device was used to determine the applied forces on selective muscles of drivers during clutching of MF285 and MF399 *** experiments were performed employing sample of 30 drivers and were conducted on two Iranian frequently used tractors including:MF285 and MF399 *** results showed that the clutching forces for MF285 and MF399 tractors were 340 N and 290 N,*** knee angle of the drivers of the two tractors was statistically different at the one percent level of *** reduction of pain threshold after 30 and 60 s clutching and also 60 s rest after clutching in MF285 tractor,for all three muscles,were more than those of MF399 *** impact of clutching on the average decreases of pain threshold,for all drivers and all clutching periods,during and after clutching,in the Quadratus lumborum muscle was more than the other two muscles,in both *** order to reduce the clutching force for MF285 tractor some modifications is *** this regard the force transfer joint between the pedal and the clutch release linkage may be replaced with one made of cast iron.

关键词： Algometer Ergonomic Muscle Operator Tractor

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