Wyniki wyszukiwania - Biblioteka Nauki

1

A study on thermal drying of wood

100%

Haghi A. K. , Haghi R. K.

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2007

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tom Vol. 12, no 3

865-873

EN

Drying is a complex operation involving transient transfer of heat and mass along with several rate processes, such as physical or chemical transformations, which in turn, may cause changes in product quality. This article surveys the impacts of convective, infrared and microwave drying on the strength of dried wood. The effects of drying methods on mechanical properties have been studied for many materials, but wood products have seldom been the subject. Spruce wood samples (length = 140 mm and diameter = 21.0 mm) were dried using the following drying regimes: convective (1000 C and 400 C), microwave (480, 790, and 1000 W power) and infrared (100% power). The dried sampies were then subjected to tensile loading in order to evaluate the mechanical properties. It is concluded that the microwave drying can improve the strength of dried samples significantly.

2

Investigation on the influence of the electron radiation on the appearance of fibers

100%

Mohammadi K. , Haghi A. K.

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2007

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tom Vol. 12, no 3

875-877

EN

In this paper, the influences of electron radiation on the appearance of microwave-dried fibers were studied. Previously dried fibers with different properties are radiated by the electron beam of an electron microscope. Variable magnifications, processing time and voltage are applied. Using electron microscopy photographs, fibers inflations or deflations are measured precisely. It is observed that the electron energy can have significant effects on the fibers surface layer properties.

3

Experimental study on combined infrared and microwave drying of porous media with particular application in wood industry

100%

Haghi A. K. , Ghanadzadeh H.

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2006

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tom Vol. 11, no 4

985-991

EN

Porous materials such as wood have microscopic capillaries and pores which cause a mixture of transfer mechanisms to occur simultaneously when subjected to heating. Infrared and microwave heating of wood products has not been used to a larger extent by the wood industries and manufactures. This could be explained by the insufficient knowledge of the complex interaction between a porous material and process parameters during drying. This article uses the drying experiments to study the effects of drying modes, density and moisture content on wood hardness. Brinell hardness is measured on wood surfaces of Guilan spruce at two angles to the grain.

4

Mechanical properties of cement based composite containing Rice-Husk Ash

100%

Sadrmomtazi A. , Haghi A. K.

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2009

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tom Vol. 14, no 2

501-508

EN

Different mix designs of cement based composites with a varying amount of rice-husk ash as a pozzolan, water-cement ratio and super plasticizer were investigated. Composite properties were then studied using the Slump-Flow test, L-Box test, V-Funnel test in order to evaluate bleeding, resistance to segregation and workability. The physical and mechanical properties of Self-Compacting Concrete (SCC) were studied and compared with a reference normal concrete (NC). 48 cubic moulds were made and their compressive strength at the ages of 3, 7, 14, 28, 60, 90 and 120 days determined. In this survey to determine tensile strength, shrinkage and modulus of elasticity, 12 prismatic moulds, 6 prismatic and 3 cylinders moulds were prepared. These samples cured in three different environmental conditions such as water, humidity and air. The results show higher compressive strength in SCC, while shrinkage does not differ from that of NC. We found that the modulus of elasticity and Poisson's ratio are slightly improved in SCC.

5

Post buckling modelling and optimization of sandwich panels with corrugated cores

80%

Gorji M. , Ashouri D. , Asadi H. , Haghi A. K.

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2009

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tom Vol. 14, no 4

949-964

EN

In the present study, analytical expressions for critical loads are derived and eigenvalue and post buckling analyses are performed on the panels, using the finite element method, and the commercial software ABAQUS. A genetic algorithm is used for optimization of sandwich panels with periodic, open-cell cores. Yielding and buckling in components are treated as optimization constraints. Then minimum weights for some load capacities are determined. Design variables and cost function are defined as non-dimensional and optimal results are shown by diagrams.

6

ANAFIS and neural network for modeling and prediction of ship squat in shallow waters: a new approach

80%

Zeraatgar H. , Akbari Vakilabadi K. , Salmalian K. , Haghi A. K.

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2011

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tom Vol. 16, no 1

211-231

EN

The reduction of the distance between ship floor and seabed, while the ship is moving forward, is called squat. In this research, squat is determined for vessels with Series-60 hull forms in various depths by experimental methods and then different numerical methods are employed for squat modeling. For this reason, a set of facilities for testing the ship movement in shallow waters is prepared. A series of models of the vessel is manufactured and many tests are carried out. The aim of the present study is to demonstrate the usefulness of an adaptive-network-based fuzzy inference system (ANFIS) for modeling and predicting the squat parameter for ships in shallow waters. It is also shown how dimensionless squat (S*) varies with the variation of important parameters, namely: block coefficient (CB), dimensionless distance between the seabed and ship floor […] and hydraulic Froude Number (Fnh). The results obtained through the ANFIS are also compared with those of a multiple linear regression and GMDH-type neural network with multi-layered feed forward back propagation algorithm. The results show that the ANFIS-based squat has higher predictability function than other numerical methods.