• Journal of the Korean Chemical Society
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• v.56 no.2
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• pp.207-211
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• 2012

Using Carnahan-Starling equation for hard spheres and a lattice model with an attractive potential, a new twoparameter equation of state for pure gases is derived. Using this equation, compressibility factors are calculated and compared with Nelson-Obert generalized compressibility factor charts. The results show that the agreement of this equation with the experimental Nelson-Obert charts is similar to that of Redlich-Kwong equation in the average. But parameters and terms of the new equation have physical meanings which are more definite than those of Redlich-Kwong equation.

• Journal of applied mathematics & informatics
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• v.15 no.1_2
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• pp.447-456
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• 2004

In this paper we investigate the Hyers-Ulam-Rassias stability of a 4-dimensional quadratic functional equation (equation omitted).

• Journal of applied mathematics & informatics
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• v.33 no.3_4
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• pp.261-273
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• 2015

We consider the hyperelastic rod equation describing nonlinear dispersive waves in compressible hyperelastic rods. We investigate the existence of certain traveling wave solutions to this equation. We also determine whether two other equations(the b-family equation and the modified Camassa-Holm equation) have our solution type.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.14.1-14.14
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• 2022

Background: Although spirometry results can be interpreted differently depending on the reference equation used, there are no established criteria for selecting reference equations as part of the special health examinations for Korean workers. Thus, it is essential to examine the current use of reference equations in Korea, quantify their impact on result interpretation, and propose reference equations suitable for Korean workers, while also considering the environmental conditions of special health examination facilities. Methods: The 213,640 results from the special health examination database were analyzed to identify changes in the ratio of measured values to reference values of lung capacity in Korean workers with changes in age or height, and changes in the agreement of interpretations with the reference equation used. Data from 238 organizations that participated in the 2018-2019 quality control assessment by the Korea Occupational Safety and Health Agency were used to identify the spirometer model and reference equations used in each special health examination facility. Results: Korean special health examination facilities used six reference equations, and the rate of normal or abnormal ventilatory diagnoses varied with the reference equation used. The prediction curve of the Global Lung Function Initiative 2012-Northeast Asian (GLI2012) equation most resembled that of the normal group, but the spirometry model most commonly used by examination facilities was not compliant with the GLI2012 equation. With a scaling factor of 0.95 applied to the Dr. Choi equation, the agreement with the GLI2012 equation was > 0.81 for men and women. Conclusions: We propose the GLI2012 equation as reference equation for spirometry in Korean workers. The GLI2012 equation exhibited the most suitable prediction curve against the normal lung function group. For devices that cannot use the GLI2012 equation, we recommend applying a scaling factor of 0.95 to the Dr. Choi equation.

• Korean Journal of Crystallography
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• v.13 no.2
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• pp.86-90
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• 2002

The structure of N-(Diphenylmethylene)aminomethylphosphonate has been determined by X-ray diffraction methods. The crystal system is triclinic, space group P(equation omitted), unit cell constants, a＝8.967(2) (equation omitted), b＝9.309(2) (equation omitted), c＝ 10.981(2) (equation omitted), α＝101.42(2)°, β＝92.22(2)°, γ＝92.23(2)°, V=896.8(3) (equation omitted), T＝296 K, Z＝2, D/sub c/＝1.227 Mgm/sup -3/. The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with graphite monochromated MoKα radiation (λ＝0.7107(equation omitted)). The molecular structure was solved by direct methods and refined by full-matrix least-squares to a final R＝7.3% for 979 unique observed F/sub o/>4σ(F/sub o/) refections and 209 parameters.

• Bulletin of the Korean Mathematical Society
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• v.41 no.2
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• pp.319-326
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• 2004

In this article, we investigate invertible interpolation problems in Alg(equation omitted) : Let(equation omitted) be a subspace lattice on a Hilbert space H and let X and Y be operators acting on H. When does there exist an invertible operator A in Alg(equation omitted) such that AX = Y?

• Communications of the Korean Mathematical Society
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• v.37 no.3
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• pp.881-891
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• 2022

In the present paper, we have studied Miao-Tam equation on three dimensional almost coKähler manifolds. We have also proved that there does not exist non-trivial solution of Miao-Tam equation on the said manifolds if the dimension is greater than three. Also we give an example to verify the deduced results.

• Journal of applied mathematics & informatics
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• v.28 no.1_2
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• pp.383-395
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• 2010

In the present paper, we construct the traveling wave solutions involving parameters of nonlinear evolution equations in the mathematical physics via the (3+1)- dimensional potential- YTSF equation, the (3+1)- dimensional generalized shallow water equation, the (3+1)- dimensional Kadomtsev- Petviashvili equation, the (3+1)- dimensional modified KdV-Zakharov- Kuznetsev equation and the (3+1)- dimensional Jimbo-Miwa equation by using a simple method which is called the ($\frac{G'}{G}$)- expansion method, where $G\;=\;G(\xi)$ satisfies a second order linear ordinary differential equation. When the parameters are taken special values, the solitary waves are derived from the travelling waves. The travelling wave solutions are expressed by hyperbolic, trigonometric and rational functions.

• Journal of applied mathematics & informatics
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• v.13 no.1_2
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• pp.117-123
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• 2003

For an n ${\times}$ n real matrix X, let ${\Phi}$(X) = X o (X$\^$-1/)$\^$T/, where o stands for the Hadamard (entrywise) product. Suppose A, B, G and D are n ${\times}$ n real nonsingular matrices, and among them there are at least one solutions to the equation (equation omitted). An equivalent condition which enable (equation omitted) become a real solution ot the equation (equation omitted), is given. As application, we get new real solutions to the matrix equation (equation omitted) by applying the results of Zhang. Yang and Cao [SIAM.J.Matrix Anal.Appl, 21(1999), pp: 642-645] and Chen [SIAM.J.Matrix Anal.Appl, 22(2001), pp:965-970]. At the same time, all solutions of the matrix equation (equation omitted) are also given.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.3 no.2
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• pp.206-214
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• 2003

In this paper, we propose a method to avoid obstacles that have unstable limit cycles in a chaos trajectory surface. We assume all obstacles in the chaos trajectory surface have a Van der Pol equation with an unstable limit cycle. When a chaos robot meets an obstacle in an Arnold equation or Chua's equation trajectory, the obstacle reflects the robot. We also show computer simulation results of Arnold equation and Chua's equation and random walk chaos trajectories with one or more Van der Pol obstacles and compare the coverage rates of each trajectory. We show that the Chua's equation is slightly more efficient in coverage rates when two robots are used, and the optimal number of robots in either the Arnold equation or the Chua's equation is also examined.