• Food Science of Animal Resources
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• v.30 no.5
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• pp.730-738
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• 2010

We developed predictive growth models for Staphylococcus aureus and Bacillus cereus on various food matrices consisting primarily of ready-to-eat (RTE) foods. A cocktail of three S. aureus strains, producing enterotoxins A, C, and D, or a B. cereus strain, were inoculated on sliced bread, cooked rice, boiled Chinese noodles, boiled bean sprouts, tofu, baked fish, smoked chicken, and baked hamburger patties at an initial concentration of 3 log CFU/g and stored at 8, 10, 13, 17, 24, and $30^{\circ}C$. Growth kinetic parameters were determined by the Gompertz equation. The square-root and Davey models were used to determine specific growth rate and lag time values, respectively, as a function of temperature. Model performance was evaluated based on bias and accuracy factors. S. aureus and B. cereus growth were most delayed on sliced bread. Overall, S. aureus growth was significantly (p<0.05) more rapid on animal protein foods than carbohydrate-based foods and vegetable protein foods. The fastest growth of S. aureus was observed on smoked chicken. B. cereus growth was not observed at 8 and $10^{\circ}C$. B. cereus growth was significantly (p<0.05) more rapid on vegetable protein foods than on carbohydrate-based foods. The secondary models developed in this study showed suitable performance for predicting the growth of S. aureus and B. cereus on various food matrices consisting of RTE foods.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.509-518
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• 2002

In order to perform the spatial buckling and static analysis of the nonsymmetric thin-walled beam-column element, improved exact static stiffness matrices were evaluated using equilibrium equation and force-deformation relationships. This numerical technique was obtained using a generalized linear eigenvalue problem, by introducing 14 displacement parameters and system of linear algebraic equations with complex matrices. Unlike the evaluation of dynamic stiffness matrices, some zero eigenvalues were included. Thus, displacement parameters related to these zero eigenvalues were assumed as polynomials, with their exact distributions determined using the identity condition. The exact displacement functions corresponding to three loadingcases for initial stress-resultants were then derived, by consistently combining zero and nonzero eigenvalues and corresponding eigenvectors. Finally, exact static stiffness matrices were determined by applying member force-displacement relationships to these displacement functions. The buckling loads and displacement of thin-walled beam were evaluated and compared with analytic solutions and results using ABAQUS' shell element or straight beam element.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.195-202
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• 2012

Two nonlinear frame elements taking into account geometric nonlinearity is presented and compared based on the Lagrangian co-rotational formulation. The first frame element is believed to be geometrically-exact because not only tangent stiffness matrices is exactly evaluated including stiffness matrices due to initial deformation but also total member forces are directly determined from total deformations in the deformed state. Particularly two exact tangent stiffness matrices based on total Lagrangian and updated Lagrangian formulation, respectively, are verified to be identical. In the second frame element, the deformed curved shape is regarded as the polygon and current flexural deformations in iteration process are neglected in evaluating tangent stiffness matrices and total member forces. Two numerical examples are given to demonstrate the accuracy and the good performance of the first frame element compared with the second element. Furthermore it is shown that the first frame element can be used in tracing nonlinear behaviors of cable members.

• Journal of the Korea Society of Computer and Information
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• v.15 no.5
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• pp.13-21
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• 2010

The Optimal results of Kalman Filtering on the Inverted Pendulum System requires an effective factor such as the noise covariance matrix Q, the measurement noise covariance matrix R and the initial error covariance matrix $P_0$. We present a special case where the optimality of the filter is not destroyed and not sensitive to scaling of these covariance matrix because these factors are unknown or are known only approximately in the practical situation. Moreover, the error covariance matrices issued by this method predict errors in the state estimate consistent with the scaled covariance matrices and not the issued state estimates. Various results using the scalar gain $\delta$ are derived to described the relations among the three covariance matrices, Kalman Gain and the error covariance matrices. This paper is described as follows: Section III a brief overview of the Inverted Pendulum system. Section IV deals with the mathematical dynamic model of the system used for the computer simulation. Section V presents a various simulation results using the scalar gain.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.12
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• pp.1266-1269
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• 2008

We propose an integral sliding mode control for robot manipulators guaranteeing that sliding motion exists starting from an initial time. Also, we prove the asymptotic stability for robot manipulators using three important properties in the robot dynamics: skew-symmetry, positive-definiteness, and boundedness of robot parameter matrices. From illustrative examples, we show that the proposed method effectively controls for robot manipulators.

• Communications of the Korean Mathematical Society
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• v.36 no.3
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• pp.413-422
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• 2021

The Study determinant is known as one of replacements for the determinant of matrices with entries in a noncommutative ring. In this paper, we give a generalization of the Study determinant and show its relationship with the Cayley-Dickson process. We also give some properties of a non-associative ring obtained by the Cayley-Dickson process with a not necessarily commutative, but associative ring as the initial ring.

• Archives of Pharmacal Research
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• v.26 no.10
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• pp.880-885
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• 2003

Research in this paper focuses on the kinetic evaluation of swelling of the liquid crystalline phases of glyceryl monooleate (GMO). Swelling of the lamellar and cubic liquid crystalline phases of GMO was studied using two in vitro methods, a total immersion method and a Franz cell method. The swelling of the lamellar phase and GMO having 0 %w/w initial water content was temperature dependent. The swelling ratio was greater at $20^{\circ}^C than 37^{\circ}^C$ . The water uptake increased dramatically with decreasing initial water content of the liquid crystalline phases. The swelling rates obtained using the Franz cell method with a moist nylon membrane to mimic buccal drug delivery situation were slower than the total immersion method. The swelling was studied by employing first-order and second-order swelling kinetics. The swelling of the liquid crystalline phases of GMO could be described by second-order swelling kinetics. The initial stage of the swelling (t < 4 h) followed the square root of time relationship, indicating that this model is also suitable for describing the water uptake by the liquid crystalline matrices. These results obtained from the current study demonstrate that the swelling strongly depends on temperature, the initial water content of the liquid crystalline phases and the methodology employed for measuring the swelling of GMO.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.4
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• pp.231-237
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• 1999

A geometric non-linear finite element formulation of spatial ocean cable under currents is presented using multiple noded curved cable elements. Tangent stiffness and mass matrices for the isoparametric cable ele¬ment are derived and the initial equilibrium state of ocean cable subjected to self-weights, buoyancy, and current as well as support motions is determined using the load incremental method. Free vibration analysis of ocean cables is performed based on the initial equilibrium configuration. Numerical examples are presented and discussed in order to demonstrate the feasibility of the present finite element method and investigate dynamic characteristics of ocean cables.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.319-324
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• 1999

This study is to investigate the properties on the load-deflection and fracture behaviors of the steel fiber reinforced concrete(SFRC) slab model specimens, Steel fibers of indent, crimp, and end hook shape were considered to reinforce the matrix under various mixing conditions and proportions. Initial cracking load, maximum load, and energy absorption capacity(load carrying capacity) of SFRC panel specimen increased with increase of steel fiber contents. And the plain concrete slab was fractured abruptly after maximum load but SRFC slabs were fractured smoothly by steel fibers in concrete matrix operated as cracking resistance force after maximum load. Indent, crimp and end hook shape steel fibers were effective in reinforcing the matrices but end hook type fiber were superior to indent and crimp type fibers.

• Structural Engineering and Mechanics
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• v.27 no.6
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• pp.683-696
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• 2007

This article is concerned with the presentation of a time-domain BEM approach applied to the solution of the scalar wave equation for 2D problems. The basic idea is quite simple: the basic variables of the problem at time $t_n$ (potential and flux) are computed with the results related to the potential and to its time derivative at time $t_{n-1}$ playing the role of "initial conditions". This time-marching scheme needs the computation of the potential and its time derivative at all boundary nodes and internal points, as well as the entire discretization of the domain. The convolution integrals of the standard time-domain BEM formulation, however, are not computed; the matrices assembled, only at the initial time interval, are those related to the potential, flux and to the potential time derivative. Two examples are presented and discussed at the end of the article, in order to verify the accuracy and potentialities of the proposed formulation.