• East Asian mathematical journal
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• v.36 no.3
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• pp.365-376
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• 2020

Nonalcoholic fatty liver is a type of fatty liver in which fat accumulates in the liver without alcohol. In the accumulation, Nrf1 and miR-378 genes play very important role, so called negative feedback loop, in which the two genes suppress the other's production. In other words, Nrf1 activates fatty acid oxidation which promotes fat consumption in the liver, while miR-378 deactivates fatty acid oxidation. Thus, both genes regulate nonalcoholic fatty liver. In this paper, the negative feedback loop of Nrf1 and miR-378 are expressed by a system of ordinary differential equations. And, bifurcation simulation shows the change in the amount of each gene with significant parameter range changes. Bifurcation simulation has also used to determine the thresholds for transit between disease and steady state.

• Research in Mathematical Education
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• v.13 no.2
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• pp.109-122
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• 2009

This study investigates the change in two theoretical constructs, attitudes toward mathematics and mathematics self-efficacy, among college students involved in a learning community model. The case of this study was a developmental mathematics class offered at a historically black college located in the southeastern United States. Subjects included 31 students enrolled in an introductory mathematics course, some of whom participated in a learning community (treatment group). The participants completed mathematics attitudes and mathematics efficacy instruments twice: at the beginning of the semester and again at the end. Data was analyzed using descriptive statistics and a non-parametric statistic. The results showed that students' attitudes toward mathematics and mathematics self-efficacy are strongly correlated; the mathematical problem-solving efficacy changed significantly over time and it is significantly higher in the treatment group than in the control group; and the treatment group produced better outcomes. These findings indicate that a learning community model can increase students' mathematics self-efficacy beliefs. It is recommended that mathematics self-efficacy and attitudes toward mathematics be measured over an extended period of time when a learning community is implemented.

• Journal for History of Mathematics
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• v.20 no.1
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• pp.33-44
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• 2007

This paper examines a historical case- the French Revolution- of conceptual change in mathematics. The case that is a space of possibility gave birth to a new community of mathematical practitioners. Carnot and Monge shared the particular conceptions of the problems, aims, and methods of a field and contributed to found Ecole Polytechnique. I intend to show how Carnot's and Monge's mathematical endeavours responded to social, political and technological developments in French society.

• Research in Mathematical Education
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• v.8 no.1
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• pp.31-37
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• 2004

This study explores the relations between mathematics and the natural human language. At the very outset, a general definition of language was, given while it was attempted to make some comparisons between the words of natural language and mathematical symbols at that. Besides, the occupation of natural language functions within mathematics was handled. Consequently, it was tried to manifest that the language of mathematics enjoys the features of natural language as well. Mathematics makes use of many functional and structural features. The fact that fundamental ingredient of mathematics is symbols does not change this reality.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1296-1302
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• 2002

A mathematical model for cold rolling and temper rolling process of thin steel strip has been developed using the influence function method. By solving the equations describing roll gap phenomena in a unique procedure and considering more influence factors, the model offers significant improvements in accuracy, robustness and generality of the solution for the thin strip cold and temper rolling conditions. The relationship between the shape of the roll profile and the roll force is also discussed. Calculation results show that any change increasing the roll force may result in or enlarge the central flat region in the deformation zone. Applied to the temper rolling process, the model can well predict not only the rolling load but also the large forward slip. Therefore, the measured forward slip, together with the measured roll force, was used to calibrate the model. The model was installed in tile setup computer of a temper rolling mill to make parallel setup calculations. The calculation results show good agreement with the measured data and the validity and precision of the model are proven.

• Bulletin of the Korean Mathematical Society
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• v.40 no.2
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• pp.327-340
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• 2003

We are devoted to dealing with the conformal theory of a Rizza manifold with a generalized Finsler metric $G_{ij}$ (x,y) and a new conformal invariant non-linear connection $M^{i}$ $_{j}$ (x,y) constructed from the generalized Cern's non-linear connection $N^{i}$ $_{j}$ (x,y) and almost complex structure $f^{i}$ $_{j}$ (x). First, we find a conformal invariant connection ( $M_{j}$ $^{i}$ $_{k}$ , $M^{i}$ $_{j}$ , $C_{j}$ $^{i}$ $_{k}$ ) and conformal invariant tensors. Next, the nearly Kaehlerian (G, M)-structures under conformal change in a Rizza manifold are investigate.

• Bulletin of the Korean Mathematical Society
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• v.55 no.1
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• pp.239-250
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• 2018

A knot complement admits a pseudo-hyperbolic structure by solving Thurston's gluing equations for an octahedral decomposition. It is known that a solution to these equations can be described in terms of region variables, also called w-variables. In this paper, we consider the case when pinched octahedra appear as a boundary parabolic solution in this decomposition. The w-solution with pinched octahedra induces a solution for a new knot obtained by changing the crossing or inserting a tangle at the pinched place. We discuss this phenomenon with corresponding holonomy representations and give some examples including ones obtained from connected sum.

• Bulletin of the Korean Mathematical Society
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• v.55 no.2
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• pp.561-572
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• 2018

In this paper we consider the concept of statistical causality in continuous time between flows of information, represented by filtrations. Then we relate the given concept of causality to the equivalent change of measure that plays an important role in mathematical finance. We give necessary and sufficient conditions, in terms of statistical causality, for extremality of measure in the set of martingale measures. Also, we have considered the extremality of measure which involves the stopping time and the stopped processes, and obtained similar results. Finally, we show that the concept of unique equivalent martingale measure is strongly connected to the given concept of causality and apply this result to the continuous market model.

• The Mathematical Education
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• v.52 no.3
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• pp.335-361
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• 2013

The purpose of this study is to analyze effects on storytelling materials of statistics in the middle school classroom lesson. For this purpose, a story is developed by the Zazkis & Liljedahl's model and applied to the 7th graders of 4 classes in a middle school. After the comparison between 5 hours of storytelling lessons and ordinary lessons, the following research findings are obtained. First, storytelling material brings a positive effect on student's academic achievement. It is also shown by the qualitative analysis that this result was caused by cognition of data observation, data transformation, and unification of data with context. Second, storytelling material brings a positive effect on student's affective attitude. It is also validated by the qualitative analysis that students show the positive change in mathematical value cognition and the interests in the lesson.

• Bulletin of the Korean Mathematical Society
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• v.53 no.5
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• pp.1497-1530
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• 2016

External barrier options are two-asset options with stochastic variables where the payoff depends on one underlying asset and the barrier depends on another state variable. The barrier state variable determines whether the option is knocked in or out when the value of the variable is above or below some prescribed barrier level. This paper derives the explicit analytic solution of the chained option with an external single or double barrier by utilizing the probabilistic methods - the reflection principle and the change of measure. Before we do this, we examine the closed-form solution of the external barrier option with a single or double-curved barrier using the methods of image and double Mellin transforms. The exact solution of the external barrier option price enables us to obtain the pricing formula of the chained option with the external barrier more easily.