• Proceedings of the KSME Conference
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• 2000.04b
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• pp.108-112
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• 2000

This paper presents a mathematical model and simulation of the micro-actuator based on thermally induced liquid-vapor phase-change in a partially-filled closed cavity. The volume expansion by liquid-vapor Phase change can generate considerable forces and displacement $({\sim}50{\mu}m)$ required for commercial use. For optimum operation involving many cycles within the closed chamber, active(thermoelectric) heating and cooling is used. The optimization of the system is conducted according to the parameters such as input power and response time. The optimized performance of micro-actuator is reasonable compared to other actuators.

• Korean Institute of Interior Design Journal
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• no.21
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• pp.10-16
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• 1999

Mathematics is considered to the beginning of designing thinking because of the sense of logical order system. In this study, it was regarded the mathematics as the logic and the measurement of design system. as is often the case in history, mathematics, it is regard as conceptual model of architectural though, as aesthetic proportional measure and the mirror of thought. The direction of this study is rather multi-sided approaching to the spatial concept than one-sided plane. It is multi-acceptable way to apply mathematical principle to the pace and to be a flexible one. And boundary of interpretation of the flexibility means potential use-ability, and the strictly meaning of flexibility means that the acception of the various Secession and the Change of space. And the various interpretation of the flexibility only can expressed in the relation of opposite concept: the assembly and the disassembly, the expand and the decease, the open and the close and the construct and the de-construct. Mathematics provide the resonable way in architectural thinking and endow the order as logical organizatiov. Regarding these facts, this research is for making it possible to consider the expression property of interior space combination as the way of understanding the accepting of the changes of the times with the mathematical induction, using the rational method like the mathematical arrangement organizatiov.

• Journal of the Korean School Mathematics Society
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• v.13 no.1
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• pp.163-184
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• 2010

In this paper, we study the effects on mathematical communication and disposition for the writing mathematics letters in secondary mathematics education. For this purpose we construct a experimental class and then analyse the students' change in those aspects after applying writing mathematics letters made some significant changes on the students communication in mathematics and disposition. First. the results for this purpose on regarding the enhancement of mathematical communication are effective. Second, the results on regarding the improvement of disposition are effective.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.3080-3087
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• 2000

We obtain the mathematical model of the hard disk drive actuator system the system response data of the finite element analysis or experimental results. The model is base on the Rayleigh-Ritz method to approximate the dynamic response of the actuator system. The basic idea is to use the curve-fit technique to obtain the approximation coefficients. It allows the dynamic analysis of the actuator system without resort to the repetitive finite element modeling work. Even though the dynamic characteristics of the system of the system are affected somewhat by the structural modification and the change of the material properties, we can use the modified size and dynamic properties of the actuator system in the mathematical model to some extent. In this study, we express the mathematical model of the simplified rectangular plate first and then proceed to the actual hard disk drive actuator system.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1280-1290
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• 2016

This paper presents an advanced estimation method for obtaining the probability density functions of a damage parameter for valve leakage detection in a reciprocating pump. The estimation method is based on a comparison of model data which are simulated by using a mathematical model, and experimental data which are measured on the inside and outside of the reciprocating pump in operation. The mathematical model, which is simplified and extended on the basis of previous models, describes not only the normal state of the pump, but also its abnormal state caused by valve leakage. The pressure in the cylinder is expressed as a function of the crankshaft angle, and an additional volume flow rate due to the valve leakage is quantified by a damage parameter in the mathematical model. The change in the cylinder pressure profiles due to the suction valve leakage is noticeable in the compression and expansion modes of the pump. The damage parameter value over 300 cycles is calculated in two ways, considering advance or delay in the opening and closing angles of the discharge valves. The probability density functions of the damage parameter are compared for diagnosis and prognosis on the basis of the probabilistic features of valve leakage.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.374-384
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• 1995

The mathematical adjoint solution of the Analytic Function Expansion (AFEN) method is found by solving the transposed matrix equation of AFEN nodal equation with only minor modification to the forward solution code AFEN. The perturbation calculations are then performed to estimate the change of reactivity by using the mathematical adjoint The adjoint calculational scheme in this study does not require the knowledge of the physical adjoint or the eigenvalue of the forward equation. Using the adjoint solutions, the exact and first-order perturbation calculations are peformed for the well-known benchmark problems (i.e., IAEA-2D benchmark problem and EPRI-9R benchmark problem). The results show that the mathematical adjoint flux calculated in the code is the correct adjoint solution of the AFEN method.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.474-479
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• 1998

In this paper, we present a mathematical model of the piezoelectric pump and its application to the automobile brake system. The piezoelectric pump consists of a multi-layered piezoelectric element a diaphragm, pumping values, resonant pipes and accumulators, and the maximum pumping power of 62W nab obtained in the previous experiments by using the piezoelectric element of 22mm diameter and 55.5mm length. A detailed mathematical model of the pump is derived here by considering the compressibility of the working oil, nonlinear characteristics of piezoelectric element, the time delay of pumping values' action and be on. The validity of the model is illustrated by comparing the experimental data and the simulation results. Using the mathematical model of the piezoelectric pump, a brake system for automobile disk brake is also simulated in this paper. The brake system consists of a piezoelectric pump as a power source, calipers and its piston to generate brake force, and a three position solenoid value to change the brake situation. It is shown that 15mm/sec of piston speed and 20kN of piston force are obtained by using the piezoelectric element of 33mm diameter and 55.5mm length.

• The Mathematical Education
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• v.51 no.3
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• pp.301-321
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• 2012

Since research has barely been done on the minority with low-achievement & low-SES in probability, this research attempted to search the change of their thinking level in the classes of probability and motivate them on the mathematical learning to feel confident in mathematics. We can say that the problems of the educational discriminations are due to the overlook on the individual conditions, situations, and environments. Therefore, in order to resolve some discrimination, 4 students who belonged to the minority group, engaged in the research, based on 10 units of the instructional materials designed for the research. As a result, for the student's thinking level, it was observed that they were improved from the 1st to the 3rd level in probability. Also, the researcher found that the adequate use of the encouragement, the praise, the direct explanation, and the scaffolding enabled them to prompt their learning motives and the increased responsibility on the learning. As time passed, the participants could share their mathematical knowledge and its concept with others, in the increased confidence.

• Research in Mathematical Education
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• v.14 no.4
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• pp.361-380
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• 2010

Some 400 Secondary One (i.e. seventh-grade) students from 10 schools were provided with non-routine mathematical problems in their normal mathematics classes as exercises for one academic year. Their attitudes toward mathematics, their conceptions of mathematics and their problem-solving performance were measured both in the beginning and at the end of the year. Hierarchical regression analyses revealed that the introduction of an appropriate dose of non-routine problems would generate some effects on the students' conceptions of mathematics. A medium dose of non-routine problems (as reported by the teachers) would result in a change of the students' conception of mathematics to perceiving mathematics as less of "a subject of calculables." On the other hand, a high dose would lead students to perceive mathematics as more useful and more as a discipline involving thinking. However, with a low dose of non-routine problems, students found mathematics more "friendly" (free from fear). It is therefore proposed that the use of non-routine mathematical problems to an appropriate extent can induce changes in students' "lived space" of mathematics learning and broaden their conceptions of mathematics and mathematics learning.

• The Mathematical Education
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• v.53 no.2
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• pp.239-261
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• 2014

The purpose of this study is to analyze the influences of discussion-based learning of mathematics using smart phone application on the middle school students' mathematics learning. For this purpose, we selected 6 open problems suitable for learning mathematical reasoning and five 3rd grade middle school students as participants who expected to participate in 6 lessons of discussion-based learning of mathematics using smart phone application. From the analysis of 6 lessons, we found the following results. First, attending the lessons of discussion-based learning of mathematics using smart phone application makes students more interested in mathematics and change their mathematics learning attitudes more positively. Second, the lessons of discussion-based learning of mathematics using smart phone application facilitate students' mathematical communication with the help of various communication methods using many functions of smart phone applications. Third, the lessons of discussion-based learning of mathematics using smart phone application provide teachers with teaching-learning environment where teachers can easily give their students consultation about mathematics learning or daily life.