• Kyungpook Mathematical Journal
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• v.49 no.4
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• pp.605-618
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• 2009

A stage-structured predator-prey system with time delay and Beddington-DeAngelis functional response is considered. By analyzing the corresponding characteristic equation, the local stability of a positive equilibrium is investigated. The existence of Hopf bifurcations is established. Formulae are derived to determine the direction of bifurcations and the stability of bifurcating periodic solutions by using the normal form theory and center manifold theorem. Numerical simulations are carried out to illustrate the theoretical results.

• Applied Biological Chemistry
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• v.14 no.3
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• pp.207-212
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• 1971

An enzyme preparation from a newly isolated Candida that showed a high lipase activity was subjected to examination of its reaction rate under various conditions. The original and a diluted enzyme solutions showed the zero order curve starting at the point of 50 minutes in time. When PVA was used as an emulsifyer more activity was observed than the case of gum arabic. The optimal temperature and pH were $37{\sim}40^{\circ}C$ and 7.0, respectively. Oleic acid as a fatty acid conferred on the enzyme an inhibitory action while calcium ion a positive one. Sodium cholate yielded an increase in reaction rate at the first stage.

• Journal of Ginseng Research
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• v.9 no.2
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• pp.170-178
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• 1985

Korean red ginseng tails was extracted with solutions having various ethanol concentration at the temperature range of 70-100 $^{\circ}C$. Extraction was carried out for 1-5 times of 8 hours at given temperature. The results obtained on physicochemical properties of yields, saponins, sugars, minerals, color and viscosity were analyzed statistically to find the correlation with extracting conditions. A very high positive correlation was found between extraction time and cumulative values of yields of chemical components. Increase in ethanol concentration affected negatively on viscosity, absorbencies and yields of soluble solids and minerals. Some of the properties also showed a high correlation with temperature increase. Equations were also derived from the significant results on correlation analysis.

• Journal of the Korean Applied Science and Technology
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• v.28 no.2
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• pp.247-250
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• 2011

The excess volumes of mixing of benzyl alcohol and halothane in vesicle and in suspensions of several lipids have been determined at $25^{\circ}C$ it using a excess volume dilatometer. The potency of general anesthetics has long been known to correlate with lipid solubility. Denaturations of the vesicle, which is a sole membrane protein in the purple membrane of Halobacteriun Halobium, were studied by absorption changes at 280 nm and fluorescence changes at 330 nm and excess volume dilatometer. The particle size analysis of viscous polymer solutions by diffusional interchange is the key step by measurement. The excess volume of mixing in chitosan was found to be negative, whereas them of purple membrane, Halobacteriun Halobium and red membrane were positive in benzyl alcohol and halothane. This result was confirmed as Miller's supposition.

• Kyungpook Mathematical Journal
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• v.56 no.3
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• pp.831-844
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• 2016

In this paper, we consider a discrete predator-prey system with Watt-type functional response and impulsive controls. First, we find sufficient conditions for stability of a prey-free positive periodic solution of the system by using the Floquet theory and then prove the boundedness of the system. In addition, a condition for the permanence of the system is also obtained. Finally, we illustrate some numerical examples to substantiate our theoretical results, and display bifurcation diagrams and trajectories of some solutions of the system via numerical simulations, which show that impulsive controls can give rise to various kinds of dynamic behaviors.

• Journal of the Korean earth science society
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• v.25 no.3
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• pp.129-141
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• 2004

A peer assessment method was implemented as part of an action research project where the primary goal was to create constructivist science classrooms. Student reflective writings, which had been created in the process of action research, were analyzed to examine the perceptions of the students concerning the peer assessment method employed in their earth science classrooms. Five perception categories and thirteen statements were developed from the student writings. These indicated that the students appreciated the positive nature of peer assessment and the effects of it as an alternative method for promoting learning. It was also revealed, however, that some students displayed inappropriate behaviors toward peer assessment which led to negative perceptions of the new assessment method. Implications for future use of peer assessment in science classrooms are discussed. Limitations founded in the present study as well as possible solutions are provided.

• Journal of Family Resource Management and Policy Review
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• v.6 no.1
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• pp.135-147
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• 2002

The purpose of this study was to achieve regarding the environmental problem due to excessive economic development for human being's continous life and to try to enhance the quality of life. The major findings of this study are as followings: 1) Environmental consciousness and activity are closely correlated and also postively related to quality of life. Accordingly, environmental consciousness should be inspired and the environmental activities performed successfully to enhance the quality of life so that we can lead higher quality of life. 2) Income takes the highest position in the life-influncing factor with the following sequence of environmental consciousness, preservation acitivity, housekeeper's education level and age. So, earlier and steady education are important in raising the education level to have people equipped with environmental consciousness and activity. Moreover, we should be able to create income through education to enhance the quality of life. Accordingly, we should take a positive measure for enhancing environmental preservation and quality of life to meet two solutions, such as mankind's continuous development and value-oriented life.

• Journal of applied mathematics & informatics
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• v.28 no.5_6
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• pp.1285-1304
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• 2010

The purpose of this paper is to establish some sufficient conditions for oscillation of solutions of the second-order functional dynamic equation of Emden-Fowler type $\[a(t)x^{\Delta}(t)\]^{\Delta}+p(t)|x^{\gamma}(\tau(t))|\|x^{\Delta}(t)\|^{1-\gamma}$ $sgnx(\tau(t))=0$, $t\;{\geq}\;t_0$, on a time scale $\mathbb{T}$, where ${\gamma}\;{\in}\;(0,\;1]$, a, p and $\tau$ are positive rd-continuous functions defined on $\mathbb{T}$, and $lim_{t{\rightarrow}{\infty}}\;{\tau}(t)\;=\;\infty$. Our results include some previously obtained results for differential equations when $\mathbb{T}=\mathbb{R}$. When $\mathbb{T}=\mathbb{N}$ and $\mathbb{T}=q^{\mathbb{N}_0}=\{q^t\;:\;t\;{\in}\;\mathbb{N}_0\}$ where q > 1, the results are essentially new for difference and q-difference equations and can be applied on different types of time scales. Some examples are worked out to demonstrate the main results.

• The Journal of Fisheries Business Administration
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• v.51 no.1
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• pp.67-79
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• 2020

The purpose of this study is to propose a policy improvement plan by analysis of the extinction risk factors reflecting the specificity of fishing villages, fishing village support policies, and settlement conditions of fishing villages as one of the solutions to the immediate problem of fishing village extinction. The results of the study show the higher the level of number of fishing ports, number of returning rural population, and housing diffusion rate, the dependent variable extinction risk index was a positive effect while vacant house ratio and aged house ratio was analyzed to be in was a negative (-) relationship with the dependent variable.The policy implications through this study were to prepare an effective policy to reduce the risk of extinction, to improve urgent settlement conditions, and to prepare a condition to convert returning rural population into fishery population.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.151-156
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• 1998

This paper presents an $H_{\infty)$ output feedback controller design method for linear systems with delayed state, delayed control input, and delayed masurement output. Using a Lyapunov functional, the stability for delayed systems is discussed independently of delays. Also, sufficient condition for the existence of $H_{\infty)$ controllers of any order is given in terms of three linear matrix inequalities(LMIs). Based on positive definite solutions of their LMIs, we briefly explain the way to construct $H_{\infty)$ controller, which stabilizes time-delay systems independently of delays and guarantees an $H_{\infty)$norm bound.