• Computers and Concrete
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• v.25 no.6
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• pp.485-495
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• 2020

This paper, presents the dynamic and stability analysis of the simply supported single walled Carbon Nanotubes (SWCNT) reinforced concrete beam on elastic-foundation using an integral first-order shear deformation beam theory. The condition of the zero shear-stress on the free surfaces of the beam is ensured by the introduction of the shear correction factors. The SWCNT reinforcement is considered to be uniform and variable according to the X, O and V forms through the thickness of the concrete beam. The effective properties of the reinforced concrete beam are calculated by employing the rule of mixture. The analytical solutions of the buckling and free vibrational behaviors are derived via Hamilton's principle and Navier method. The analytical results of the critical buckling loads and frequency parameters of the SWCNT-RC beam are presented in the form of explicit tables and graphs. Also the diverse parameters influencing the dynamic and stability behaviors of the reinforced concrete beam are discussed in detail.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.621-631
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• 2018

In this paper, an exact analytical solution is developed for the analysis of the post-buckling non-linear response of simply supported deformable symmetric composite beams. For this, a new theory of higher order shear deformation is used for the analysis of composite beams in post-buckling. Unlike any other shear deformation beam theories, the number of functions unknown in the present theory is only two as the Euler-Bernoulli beam theory, while three unknowns are needed in the case of the other beam theories. The theory presents a parabolic distribution of transverse shear stresses, which satisfies the nullity conditions on both sides of the beam without a shear correction factor. The shear effect has a significant contribution to buckling and post-buckling behaviour. The results of this analysis show that classical and first-order theories underestimate the amplitude of the buckling whereas all the theories considered in this study give results very close to the static response of post-buckling. The numerical results obtained with the novel theory are not only much more accurate than those obtained using the Euler-Bernoulli theory but are almost comparable to those obtained using higher order theories, Accuracy and effectiveness of the current theory.

• Analytical Science and Technology
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• v.12 no.2
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• pp.130-135
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• 1999

A graphite furnace atomic absorption spectrometry (GFAAS) with matrix modification has been used to determine trace amounts of arsenic, lead and selenium in rice flour samples. A mixed solution of palladium and magnesium nitrate was used as a matrix modifier to convert the analyte elements into a phase of higher thermostability and to increase the volatility of concomitants in graphite furnace. Matrix modification effects by the mixed solution were investigated for several elements (As, Cd, Cu, Pb, Se, Zn). It has been found that the matrix modifier substantially increase the pyrolysis and atomization temperature, and absorbance for As, Pb and Se. The concentration of As, Pb and Se in rice flour samples were determined by standard addition method with Zeeman background correction after microwave acid digestion. In this method the characteristic concentrations of As, Pb and Se are 26 ng/g, 18 ng/g, 24 ng/g on the basis of dry sample respectively.

• Analytical Science and Technology
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• v.7 no.2
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• pp.173-179
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• 1994

The point of present study was focused on developing the method for the determination of dissociation constant by means of FIA conjunction with Diode Array Spectrphotometry or spectrophotometry along with small amount of Bromocresol Green(mg order) within short time. On the calculation with computer, the indicator with pK=7 has been shown the most sensitive reaction when little amount of base or acid has been added. The pKa of Bromothymol Blue and Bromocresol Green were measured as 7.31 and 4.82 respectively with spectrophotometry after activity correction by Kielland method (Reported value by Bishop, 7.30 and 4.79). The pKa of Bromocresol Green by FIA was obtained as 4.78 and was comparable with other values determined by other methods.

• Computers and Concrete
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• v.26 no.2
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• pp.185-201
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• 2020

This research is devoted to investigate the bending and free vibration behaviour of laminated composite/sandwich plates and shells, by applying an analytical model based on a generalized and simple refined higher-order shear deformation theory (RHSDT) with four independent unknown variables. The kinematics of the proposed theoretical model is defined by an undetermined integral component and uses the hyperbolic shape function to include the effects of the transverse shear stresses through the plate/shell thickness; hence a shear correction factor is not required. The governing differential equations and associated boundary conditions are derived by employing the principle of virtual work and solved via Navier-type analytical procedure. To verify the validity and applicability of the present refined theory, some numerical results related to displacements, stresses and fundamental frequencies of simply supported laminated composite/sandwich plates and shells are presented and compared with those obtained by other shear deformation models considered in this paper. From the analysis, it can be concluded that the kinematics based on the undetermined integral component is very efficient, and its use leads to reach higher accuracy than conventional models in the study of laminated plates and shells.

• Analytical Science and Technology
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• v.26 no.1
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• pp.51-60
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• 2013

The geometrical parameters, vibrational frequencies, and adiabatic electron affinities (AEAs) for c-$C_nF_{2n}$ (n=8, 9) and $C_{10}F_{18}$ (perfluorodecalin) have been investigated using various quantum mechanical techniques. The possible structures for the neutrals and anions of c-PFA are fully optimized and electron affinities are predicted using energy difference between the neutral and anion. The harmonic vibrational frequencies are also determined and zero-point vibrational energies (ZPVEs) are considered for the better prediction of the electron affinities. The electron affinities are predicted to be 1.18 eV for c-$C_8F_{16}$ (ortho), 1.37 eV for c-$C_9F_{18}$, and 1.38 eV for $C_{10}F_{18}$ (perfluorodecalin) at the MP2 level of theory after ZPVE correction.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.38-47
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• 1989

A purely analytical model for HEMT's based on a two dimensional charge control simul-ation[4] is proposed. In this model proper treatment of diffusion effect of electron transport along a 2-DEG (two dimensional electron gas) channel is perfoemed. This diffusion effect is shown to effectively increase the bulk mibility and threshold voltage of the I-V curves compared to the existing models. The channel thickness and gate capacitance are expressed as functions of gate voltages covering subthreshold characteristics of HEMT's analytically. By introducing the finite channel opening and an effiective channel-length modulation, the solpe of the saturation region of the I-V curves ws modeled. The smooth transition of the I-V curves at linear-to-saturation regions of the I-V curves was possible using the continuous Troffimenkoff-type of field dependent mobility. Furthermore, a correction factor f was introduced to account for the finite transition section forming between a GCA and a saturated section. This factor removes large discrepancies in the saturation region of the I-V curve predicted by existing l-dimensional models.

• Steel and Composite Structures
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• v.36 no.3
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• pp.355-367
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• 2020

The current work, present dynamic analysis of the FG-sandwich plate seated on elastic foundation with various kinds of support using refined shear deformation theory. The present analytical model is simplified which the unknowns number are reduced. The zero-shear stresses at the free surfaces of the FG-sandwich plate are ensured without introducing any correction factors. The four equations of motion are determined via Hamilton's principle and solved by Galerkin's approach for FG-sandwich plate with three kinds of the support. The proposed analytical model is verified by comparing the results with those obtained by other theories existing in the literature. The parametric studies are presented to detect the various parameters influencing the fundamental frequencies of the symmetric and non-symmetric FG-sandwich plate with various boundary conditions.

• Journal of Environmental Health Sciences
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• v.18 no.2
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• pp.82-91
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• 1992

The examination of the pollutants originated from domestic sewage, industrial and agricutural activities the existences of some toxic heavy metals, organic matters and pathogenic microorganisms. A recent report of WHO brought out that such pollutants are in existence with above roughly 2,000 kinds of chemical substances and amongst them about 750 chemicals have been indentified by drinking water. And above 600 kinds of them are organic pollutants and in addition these include carcinogenic mutagenic and poisonous substances. This is not intended to embody a study of broad confined to various approaches on organic materials, and therefore will be THM produced on injection of chlorine at water filtration plant. To specify the relations between THM and factors having an effect upon THM such as TOC, Cl$_{2}$, Temperature, pH and reaction time, first of all the recovery ratio for analytical methods of THM (Head sapce, purge and trap, Liquid/ Liquid Extraction methods) was investigated. Provided that by using it,the correction coefficients are obtained, the accuracy of data might be able to be enhanced through analysis.The result of the experiments are given in the followings. 1) Among three kinds of analytical methods, recovery rate was higher in order of purge and trap Liquid/Liquid Extraction, Head space. There is no great difference in recovery rate among three methods. 2) The higher the concentration of TOC, the more the amount of THM. 3) The higher the reaction temperature, the more the amount of THM. 4) The longer the reaction time, the more the amount of THM. 5) The higher the pH, the more the amount of THM. 6) The higher the concectration of chlorine, the more the amount of THM.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.75-86
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• 1982

The degeneration of two classes of thick beam elements has been conducted, one (DB6) based on the conventional Timoshenko beam assumptions whereas the other (DB7) based on the assumed cubic axial displacement profile. While an adjustable shear correction factor is required for the DB 6 element to compensate for the unrealistic distribution of shear strain across the thickness, the DB 7 element assumes the more realistic quadratic profile of shear strain at the outset. With the plane-stress continuum solution as reference, solutions obtained by these two element models are compared with the analytical Timoshenko solution, the analytical thin beam solution and several available solutions of other existing beam elements. The result indicates that the performance of the higher order beam element DB 7 is consistently superior to any others. This is true for the whole range of aspect ratios of beam, in both static and free vibration analyses.