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Showing 47 results for Bond


Volume 5, Issue 19 (11-2012)
Abstract

As a Pioneer story writer, Jamalzadeh by bringing together Western and Eastern techniques in Yeki bud yeki nabud[1] founded a new style that became famous as “short story.” “Veylân od-Dowleh” with a different structure from the other five story of this collection poses the subject of joblessness which is similar to the “Le Vagabond,” the work of French writer, Guy de Maupassant. In these two stories, the joblessness is discussed from two different angles: voluntary joblessness, by emphasizing on the mystical observation, and involuntary unemployment. By posing this question that whether Jamalzadeh, in the writing of this story, was influenced by Maupassant or not, I investigate comparatively these two works, looking at the subject and style of expression. Accordingly, drawing on some textual examples from these two stories, I have investigated the views of the two writers about the subject of unemployment through a study of the personalities, actions, and reactions of the two protagonists struggling with the inner-self and the outside world. [1] Once Upon a Time

Volume 11, Issue 3 (11-2011)
Abstract

Abstract: Cement based material such as mortar and concrete are brittle in nature and crack under low tensile stress and strain levels. Adding discontinuous fibers as reinforced concrete remedy some concern related to cement based material brittleness and poor resistance to crack growth. After cracking the fibers arrest between two crack faces and provide mechanisms that abate their unstable propagation []. Fibers bridging force is achieved by transmission of the bond interfacial stress between the fiber and surrounding matrix. The resistance of the section to further crack opening depends largely on the fiber pullout mechanisms and related possibilities including complete fiber pullout or fiber fracture []. The high levels of interfacial shear strength may prevent fibers from complete debonding and result in fiber fracture. Although the strength of composite may increase, its toughness reduces significantly and failure is brittle. On contrary the low interfacial shear strength causes complete fiber debonding from matrix and fiber pullout. The effectiveness of fiber is often assessed by using single fiber pullout test. The experiments have shown that in improving the pullout resistance, hook-end fiber is more effective than straight fiber [, ,].The pullout process of hooked-end fibers is more complex than that of straight steel fibers and there is one additional deformation mechanism because of mechanical anchorage. So the analytical models for straight fiber are not valid for the fibers having mechanical anchorage. The main objective of this paper is to develop an analytical model for hook-end steel fiber pullout behavior. In this model the concept of bond shear stress versus slip relation between fiber and matrix has been used to develop fiber force and bond stress. Also the interfacial stress has been supposed that to be distributed uniformly. Based on two mentioned assumption a theoretical relation have been developed for aligned straight fiber at first. Then this relation is promoted for hook ended steel fiber pullout response. In order to do this, the effect of hooks on force and stress distribution has been analyzed along the fiber length and utilized for developing the pullout response of hook ended steel fiber. Based on obtained relation, the hooks change the fiber along the fiber length at the hooks and this force will be decreased with constant coefficient which is the function of fiber geometry. Despite that a normal force and its frictional force will be occurred at the hook bent. Decreasing the fiber force and creating a normal force at the hook bend are the factors that create an extra resistance force against the pullout in hook-end fiber. This study investigates these factors and develops the relations in order to calculating the maximum load required for pulling out the hook-end fiber. Finally the model has been validated by experimental results on the hook-end steel fiber. Proposed model is able to estimate the main pullout mechanism due to mechanical anchorage of hooks.

Volume 12, Issue 3 (8-2012)
Abstract

In this research, the effects of different parameters on simulation of Young’s modulus of a Graphene sheet are studied. In simulation of Young’s modulus of Graphene sheet, different parameters such as the thickness of a single layer of Graphene, type of loading and boundary conditions, effects of interactions non-neighbor atoms, type of element for carbon-carbon bond, mechanical properties of carbon-carbon bond and the size of the Graphene sheet influence the results. It was found that the thickness of a single layer Graphene and the type of element are effective parameters. Moreover, the type of loading and boundary conditions did not influence the Young’s modulus of the Graphene sheet. Therefore, the Graphene sheet can be considered as an isotropic material. Considering the effects of interactions of non-neighbor atoms increases the run-time and improves the accuracy of calculations. Mechanical properties of carbon-carbon bond are important parameters and must be chosen carefully. Also, it has been observed that when the length and width of the Graphene sheet are smaller than one nanometer, the size of Graphene sheet has a great influence on the Young’s modulus.

Volume 12, Issue 3 (10-2012)
Abstract

Steel is considered to be one of the desirable materials used for reinforcing concrete structural members. However, the corrosion of steel bars has been always a threat for the service life of reinforced concrete members in corrosive environments. Fiber Reinforced Polymer (FRP) bars can be used as reinforcing materials due to their corrosion resistance. FRP reinforcing bars are available in different grades of tensile strength and modulus of elasticity. These bars have high tensile strength and durability and display linear elastic behavior up to their failure. The behavior of concrete beams reinforced with FRP bars is different from that of steel reinforced concrete beams. Concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars exhibit large deflections and crack widths as compared with steel reinforced concrete beams due to the low modulus of elasticity of GFRP. In addition, the bond between concrete and FRP bars is different from steel bars because of the difference in their surface geometries and mechanical characteristics. This paper proposes an equation for the bond strength of lap-spliced concrete beams reinforced with FRP bars. First, equations for displacement modulus and local bond strength of FRP bars are formulated by pullout test results, tested by other researchers. Then, using the local bond strength equation and based on the experimental results of lap-spliced FRP reinforced concrete beams, an equation for bond strength of splices is derived. In the formulation of this equation, the non-uniform distribution of the bond stress along the splice length is considered. The effects of concrete cover and transverse reinforcement are also taken into account in the proposed equation. Transverse reinforcement has an important role in the bond strength of beams with spliced bars. Transverse reinforcement confines developed and spliced bars by limiting the progression of splitting cracks and increases the uniformity of bond stress distribution along the splice length and thus, increasing the bond strength. The bond strengths calculated by the proposed equation are compared with the experimental values. The comparison shows that the proposed equation predicts the splice strength accurately. Also, calculated bond strengths are compared with the values predicted by different code provisions and other models. The average and standard deviation of the experimental over calculated bond strength ratios obtained by the proposed equation are 1.00 and 0.14, respectively. These ratios are 0.65 and 0.19 for the ACI440.1R-06 code, 0.55 and 0.15 for the CAN/CSA-S6-00, 0.67 and 0.16 for the CAN/CSA S806-02 code and 0.99 and 0.36 for the Aly equation. Compared to Aly equation and design guidelines, the proposed equation for calculating the bond strength shows better agreement with experimental values. In addition, code equations overestimate the bond strength of GFRP bars in splices of beams.

Volume 13, Issue 4 (12-2009)
Abstract

In the aftermath of the Islamic Revolution and due to doubts cast on the usurious character of interests on debenture bonds, the Iranian legislator was led to replace the latters by the so-called profit-sharing securities (ORAGHE MOSHAREKAT). The enactment, of the law and regulation, (in 1997 and 1998) concerning the issuing of profit-sharing securities has given rise to doctrinal discussions regarding the mechanism and legal nature of these kinds of securities. In fact, the question is whether or not these new sorts of securities are identical in nature to the old debenture bonds. The objective of the present article is to consider, firstly the mechanism and secondly the legal nature of the profit-sharing securities.

Volume 14, Issue 4 (9-2023)
Abstract

Aim: Follistatin-like protein 1 (FSTL1) is a secreted glycoprotein that plays an important role in regulating cell survival, proliferation, differentiation, migration, inflammation, and modulating the immune system. The FK domain in FSTL1 has 10 conserved cysteine residues that form 5 disulfide bonds. Despite extensive studies on the function of FSTL1, limited structural information is available about this biologically important molecule.
Materials and Methods:Using the SWISS-MODEL server and using the crystal structure of the FK domain of the mouse FSTL1 protein with the code (PDB: 6jzw) as a template, structural models of the FK domain of the human FSTL1 protein were prepared. In the next step, the resulting structures were checked using Swiss-PDB Viewer 4.10, Chimera 1.12 software, Ramachandaran diagram and PDBSUM server, in terms of the distance between two cysteine residues, the modeling error range, and the formation of disulfide bonds. Molecular dynamics simulations were performed using the AMBER software package with the ff14SB force field.
Results: The results showed that the FK domain without disulfide bond has root mean square deviations (RMSD) and root mean square fluctuations (RMSF), higher than the native FK domain. In addition, the radius of gyration in domain without disulfide bonds is significantly lower than that of native FK domain. The results show that the disulfide bonds of the FK domain play a role in the stability of the structural folding of the FK domain and the removal of these bonds increases the structural flexibility of this domain.
 

Volume 14, Issue 6 (9-2014)
Abstract

Abstract: In the papers published on compressible fluid using Pseudo Bond Graph approach, isentropic flow is assumed. However in a converging- diverging nozzle, for a specific pressure ratio, the assumption of isentropic flow is invalid. For the purpose of considering normal shock effects, this paper introduces a new field (NIKE-field) to the pseudo bond graph. The output of the new field can be also used to determine normal shock position and to extract momentum equation as well. In the following, the methodology developed in this paper has been applied a simple pedagogic example. Simulation result is validated by comparison with the analytical result. As the new field can be modeled non-isentropic flow, it can be used to for modeling rockets motors and thrusters in transient state. One of another advantage of new field (NIKE-field) is that it can be easily used in many software applications like MS1, SYMBOLS2000 and 20SIM®; therefore, With regard to the systematic derivation of a mathematical model from a bond graph in these softwares, there is no need to derive any state equations and their solutions.

Volume 14, Issue 15 (3-2015)
Abstract

Spin-bonding is a method for fabrication of bilayer tubes based on flow-forming process. This new method is a process with high potential in production of seamless thin-walled tubes. Utilizing this process, aluminum tube (as the inner layer or clad layer) has been bonded into steel tube (as the outer layer) to fabricate tubular laminate composites. As important parameters for creating a suitable bond, effects of thickness reduction, initial aluminum thickness and strength on bonding strength were investigated. The bond strength was evaluated by peel test and the peeled surfaces were examined using scanning electron microscopy (SEM). The results indicated that thickness reduction has great influence on strength and quality of the bond. After a threshold reduction (about 35%) the bond strength increases rapidly with the amount of deformation, until it approaches the weaker metal strength, and samples fracture from the base metal in the peel test. Approaching the strength of the two metals and decreasing the initial thickness of the clad layer, with a high amount of deformation increased the bonding strength. Fracture surface images showed that the surface fraction of bonding area was increased when deformation increased. It was also increased with the reduction of the initial thickness of the clad layer and when the strength of the two layers approached each other. Additionally, distribution and shape of the fracture area changed from a disordered fibril structure to approximately straight area, with an increase in the deformation.

Volume 15, Issue 1 (5-2015)
Abstract

One of the strengthening methods in reinforced concrete frame buildings is improving seismic behavior of such structures by means of steel bracing. When influenced by compressive stresses, traditional steel braces would buckle and are free of any ductility. As a result, efforts in order to restrain buckling problem for steel braces has led to creation of steel unbonded brace. In these braces, Eulerian buckling of central steel core is controlled by placing in a steel tube full of mortar. In this paper, RC buildings of 6, 12 and 18 stories are first designed based on standard 2800 and then controlled based on the rehabilitation regulation and the third edition of standard 2800. After analyzing and in order to improve seismic behavior, these buildings are strengthened by the use of common braces and steel unbonded braces and the columns of braced frames are also reinforced by concrete jacket. Totally, 42 models were analyzed by nonlinear static analysis (pushover analysis). The results indicate that structures with traditional braces have weakness in high level of drifts due to buckling of compressive braces and the energy absorption in 12 and 18 stories structures is even lower than non-strengthened structures. Nevertheless, this defect is removed by applying unbounded braces because of somehow identical behavior in extension and pressure as well as utilizing total capacity of these kinds of brace. Also, in comparison with structures with traditional braces and non-strengthened structures, a high level of energy absorption will be obtained. One of the strengthening methods in reinforced concrete frame buildings is improving seismic behavior of such structures by means of steel bracing. When influenced by compressive stresses, traditional steel braces would buckle and are free of any ductility. As a result, efforts in order to restrain buckling problem for steel braces has led to creation of steel unbonded brace. In these braces, Eulerian buckling of central steel core is controlled by placing in a steel tube full of mortar. In this paper, RC buildings of 6, 12 and 18 stories are first designed based on standard 2800 and then controlled based on the rehabilitation regulation and the third edition of standard 2800. After analyzing and in order to improve seismic behavior, these buildings are strengthened by the use of common braces and steel unbonded braces and the columns of braced frames are also reinforced by concrete jacket. Totally, 42 models were analyzed by nonlinear static analysis (pushover analysis). The results indicate that structures with traditional braces have weakness in high level of drifts due to buckling of compressive braces and the energy absorption in 12 and 18 stories structures is even lower than non-strengthened structures. Nevertheless, this defect is removed by applying unbounded braces because of somehow identical behavior in extension and pressure as well as utilizing total capacity of these kinds of brace. Also, in comparison with structures with traditional braces and non-strengthened structures, a high level of energy absorption will be obtained.

Volume 15, Issue 2 (8-2015)
Abstract

In this paper, a new model for degradation has been introduced to cover multiple dynamics for prognostics purposes. Firstly, Augmented Global Analytical Redundancy Relations (AGARRs) have been introduced to track system’s health constantly. Whenever an inconsistency appears, the proposed algorithm checks the Mode Change Signature Matrix (MCSM) and decides if inconsistency is due to a change in modes or an existence of a faulty component. Using Mode Dependent Fault Signature Matrix (MD-FSM), a Set of Candidate Faults will be generated and fed into PF part to estimate the actual fault and parameters of the degradation model. Finally, by applying obtained degradation model, Remaining Useful Lifetime (RUL) will be estimated.

Volume 15, Issue 5 (7-2015)
Abstract

Cold spin bonding is a new invented method for producing layered composite tubes based on flow-forming process. Bonding strength in this process is dependent to parameters such as initial thickness, rate of deformation, bonding temperature, initial strength, heat treatment temperature, duration of heat treatment and also production parameters like feed rate and spindle RPM. In the present work, effect of rate on thickness reduction, heat treatment temperature and duration of heat treatment on bonding strength of steel and aluminum have been studied. The strength of bonding which produced by cold spin bonding has been measured by peel test and structure investigation has been done by scanning electron microscopy. Among the parameters, heat treatment temperature and after that thickness reduction rate have the most effects on bonding strength and heat treatment duration has less effect in comparison. The results show that the increase of heat treatment temperature up to a certain level increase bonding strength, but above that level the strength will decrease. . This study also has shown that the best condition occur in %50 thickness reduction, heat treatment temperature of 475 degree and 120 minutes of heat treatment in which bonding strength reaches to yield strength of base metal.

Volume 15, Issue 7 (9-2015)
Abstract

Applications of aluminium and magnesium castings have been increased, as a result of increasing demand for the light weight components in various sectors of industries, in recent years. In this work an Al/Mg bimetal was prepared by casting Al melt into a cylindrical Mg bush, with 35 mm height and 76 and 84 inner and outer inner diameter, rotating at 1200 and 1600 revolutions per minute (rpm), 0.9, 1.6 and 2.7 melt-to-solid volume ratio and 30, 120, 150 and 200 oC preheating temperature, respectively. Vertical centrifugal casting process was selected for producing samples. In this process melt is under effect of centrifugal, coriolis and gravity forces during filling. Difference between shrinkage of Al and Mg led to the formation of mechanical bond in the interface. The results of scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis showed that concentration gradient changes from Mg to Al side in such a way that three sub layers including Al3Mg2 and Al12Mg17 intermetallics plus eutectic microstructure (Al12Mg17 and δ), were formed, based on aluminium and magnesium phase diagram, in the interface

Volume 16, Issue 1 (3-2016)
Abstract

Adding particles and fibers to the adhesive layer is a method suggested to improve the stress distribution and to increase the strength and toughness of adhesive joints. In this paper, the effects of adding the metal fibers and also the reduction of fiber horizontal distance on distribution of peel stress and shear stress toward longitudinal and transverse directions were studied using finite element analysis. The obtained results showed that the reduction of the horizontal distance between the metal fibers in the longitudinal direction improves the distribution of the peel stress and shear stress and leads to a significant reduction in their maximum values in the joint length with respect to the non-reinforced adhesive. Meanwhile, reduction of the horizontal distance between the metal fibers in the transverse direction first degrades the peel stress and then improves it. Despite the trend observed for the peel stress with the transverse direction, the distribution of the shear stress with reduction of the horizontal distance between the metal fibers becomes more uniform and the maximum values of shear stress regularly decreases in the joint length due to considerable load sharing of the metal fibers in the adhesive layer. In addition to the analyses carried out on the distribution of stress in the joints length, the distribution of peel stress and shear stress were also investigated in joint width, which was indicative of a significant effect of the metal fibers in the transverse configuration.
Mansur Zarra Nezhad, Sayed Amin Mansouri,
Volume 16, Issue 3 (11-2016)
Abstract

The main purpose of this study is to examine the household’s behavior in response to the kinds of the wealth and the estimation of marginal propensity to consume out of wealth. By using Ando-Modigliani consumption model and applying Engle-Granger co-integration strategy, marginal propensity to consume out of wealth is estimated in Iran during 1982-2008. The various forms of wealth as durable good, housing, bonds, savings, combinative and normal good are considered. Results show that households respond to kinds of wealth differently. This study finds that the marginal propensities to consume (MPCs) out of labor income and wealth, in the form of durable good, are 0.93 and 0.012, respectively. In addition, the MPCs out of labor income and wealth in the form of housing are 0.8 and 0.027, respectively. Regarding bonds as wealth, the corresponding MPCs are 0.67 and 0.055, respectively. For savings, the corresponding MPCs are 0.58 and 0.081, respectively. In combinative form of wealth, the computed MPCs are 0.7 and 0.04, respectively. Finally, considering normal goods as wealth, this study reaches the MPCs of orders 0.59 and 0.16, respectively. The long-run relationship shows that individuals’ MPC is about 0.79 apart from what types of wealth they hold. One important finding is liquidity allocation by individuals facing various kinds of wealth. This study indicates the fastest velocity of liquidation of savings and the lowest velocity of liquidation of durable goods.

Volume 16, Issue 6 (8-2016)
Abstract

Sever plastic deformation process in one of the important methods to produce nanostructures materials that is highly regarded in two past decades. Accumulative press bonding (APB) is a novel variant of severe plastic deformation processes (SPD), which is devised to produce materials with ultra-fine grain (UFG). In the present work, effect of APB technique on mechanical properties and microstructural of AA1100 alloy, were investigated. The study of the microstructure of AA1100 alloy was performed via optical microscopy. This article revealed that the grain size of the produced samples decreased to 950 nm, after six passes of APB process. The yield strength of AA1100 alloy after six passes of the process increased up to 264 MPa, which is three times higher than that of the as-cast material (89 MPa). After six passes, microhardness values of AA1100 alloy increased from 38 to 61 HV. Furthermore, the results showed that the behavior of variations in mechanical properties are in accordance with the microstructural changes and it can be justified by using the Hall-Patch equation. Moreover, the rise in the yield strength can be attributed to the reduction of the grain size and strain hardening phenomenon.

Volume 16, Issue 6 (8-2016)
Abstract

Molecular Dynamics (MD) method is a computer simulation for studying the physical movements of atoms and molecules of a N-body system by solving classical equations of motion. Here, this method is used to investigate the structural changes of a vital molecular bond in the body. This bond is created by the interaction of P-selectin, expressed on activated endothelium, and its counterpart P-selectin glycoprotein ligand-1 (PSGL-1) which is expressed on leukocytes. Frequent association and dissociation of these bonds allow the leukocyte to roll on the endothelium layer which is a pivotal step in inflammatory responses. Understanding the mechanism underlying the dissociation process of this bond is helpful in pathological researches. Here this process is simulated with MD method using the program NAMD and Visual Molecular Dynamics (VMD). The results indicate that the hydrogen bonds between ion Ca2+ and residue fucose of glycan group of PSGL-1 and also between sulfated tyrosine residues are the most effective bonds in binding.

Volume 17, Issue 2 (3-2017)
Abstract

Accumulative press bonding (APB) process is one of the newest approaches of SPD processes in which the applying of strain in materials lead to the substantial plastic deformation and microscopic changes. In this study, APB method was used to production of Al/Cu composite and AA1100 and pure commercial Copper sheets used as matrix and reinforcement respectively. Microstructure evolutions samples proceeding by APB process were studied by Scan Electron Microscopy (SEM) and Optical Microscopy (OM). Mechanical characteristics were accomplished by conducting standard tensile and microhardness tests. The microscopic analysis indicates that as the number of APB passes increased, the reinforcement phase (Cu) dispersion be improved and result in Cu continues layers discrete in to shorter layers. As well, by increasing the number of APB passes up to 3 the ultimate strength, microhardness and elongation had been increased so that, the ultimate strength is raised to 375Mpa, it about 3.1 and 2.7 times is more than as Al and Cu respectively. Under the 3 cycles of APB, the hardness of Al and Cu were reached to 62 and 152.6 HV respectively which are 1.6 and 2.6 times greater than those of corresponding pure materials. Furthermore, SEM observations demonstrated the failure mode in Al/Cu composite proceeding by APB process is shear ductile rupture.

Volume 17, Issue 6 (8-2017)
Abstract

In this paper, transient liquid phase (TLP) bonding process between Inconel 718 alloy and Inconel 600 alloy using a BNi-2 interlayer with 50 μm thickness was investigated. Transient liquid phase bonding process was performed at 1050 °C for 5, 25 and 45 min. Microstructure evaluation was carried out through optical microscopy, field emission scanning electron microscopy (FE-SEM). Also, bonding shear strength was measured. The results showed that the joint microstructure was formed of three zones including isothermal solidification zone (ISZ), thermal solidification zone (ASZ) and diffusion affected zone (DAZ). At the time of 5 min, boride intermetallic compounds in thermal solidification zone were formed. Isothermal solidification was completed and thermal solidification zone was vanished by increasing the bonding time from 5 to 45 min. Diffusion affected zone of the Inconel 718 alloy was persistent and expanded by increasing the time and diffusion of B element to parent metals, but this region in Inconel 600 alloy was vanished and the homogenization process was occurred by increasing the bonding time. Also, because of remove of boride intermetallic compounds, changes of hardness in joint region were more smoothly and the hardness value of joint region was about 280 HV. The results of shear strength showed that the bonding strength was increased from 250 MPa to 410 MPa with increasing the bonding time from 5 to 45 min, respectively.

Volume 17, Issue 7 (9-2017)
Abstract

Some appropriate characteristics like corrosion resistance, higher strength, and higher thermal and electrical conductivities cause that applications of clad sheets have been recently increased significantly in industries like production of electrical and electronic switches. In this paper, an analytical solution based on the slab method analysis is presented to investigate the asymmetrical rolling of unbonded clad sheet. Roll radii, roll speeds, friction condition between surfaces, as well as the yield stress ratio of material of sheets are parameters of the asymmetrical rolling that considered in this paper. The non-uniformity of the shear stresses and the uniformity of the normal stresses at the vertical sides of each slab across the portion of the deformation material is taken into account through the plastic region. The behavior of material in plastic region is considered to be rigid-perfectly plastic. The main goal of this paper is to investigate the simultaneous effect of back and front tension and asymmetrical parameters on normal stresses and pressure distributions along the contact area of rolls and sheets for the first time in order to decrease pressure and force in the process. The effects of these parameters on the positions of the neutral points on the upper and lower rolls are also investigated. Moreover, the maximum back and front tensions to avoid slipping of the sheet are determined. The results show that by applying the proper amounts of tensions to the sheet at the entry and exit of deformation zone, pressure and force values could be reduced, considerably.

Volume 17, Issue 9 (11-2017)
Abstract

In this study, the effect of accumulative roll bonding (ARB) process on microstructure and hardness of cast A356/titanium carbide composite produced by semi-solid processing evaluated. ARB process up to 4 cycles on the composite containing 10 vol.% titanium carbide with an average particle size less than 10 μm performed at ambient temperature. Microstructural examination by optical microscope and harness tests including macrohardness and microhardness performed. The results showed that by increasing the number of process cycles, the distribution of the Si and TiC in the aluminum matrix homogenized, the particles became finer and more spheroidal. On the other hand, particle free zones removed and the quality of the bond between the particles and the matrix improved. In addition, the porosity in the casting structure significantly decreased. It was found that the hardness in the first two cycles greatly increased, and then the number of cycles had less effect on the hardness value. In general, the microstructure of the composite after 4 cycles of ARB process considerably refined so that the increased hardness of the composite was 170% compared to the cast. The results showed that by increasing the number of ARB cycles, the amount of fluctuation in the thickness of the composite decreased.

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