• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.81-86
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• 2016

Three hundred years ago, the fractional differential equation that is one of concept of fractional calculus released. Now, many researchers continue to try best effort applying into the control engineering, mathematics and physics. In this paper, the dynamics equation which is represented by Van der Pol, represent integer order and fractional order that having real order. Then this paper performs the comparisons between integer and real order as time series and phase portrait according to variation of parameter value for real order.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.731-742
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• 2010

We propose an incremental relaying protocol in conjunction with opportunistic communication for differential modulation with an aim to make efficient use of the degrees of freedom of the channels by exploiting a imited feedback signal from the destination. In particular, whenever the direct link from the source to the destination is not favorable to decoding, the destination will request the help from the opportunistic relay (if any). The performance of the proposed system is derived in terms of average bit error probability and achievable spectral efficiency. The analytic results show that the system assisted by the opportunistic relaying can achieve full diversity at low SNR regime and exhibits a 30㏈ gain relative to direct transmission, assuming single-antenna terminals. We also determine the effect of power allocation on the bit error probability BEP) performance of our relaying scheme. We conclude with a discussion on the relationship between the given thresholds and channel resource savings. Monte-Carlo simulations are performed to verify the analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.327-332
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• 1998

Drying shrinkage means the reduction of volume of concrete because of the loss of water in concrete. This shirinkage can cause tensile stresses, crack formations at the exposure surfaces in concretes. The purpose of this paper is to apply differential shrinkage model which uses moisture diffusion equation and to calculate more reasonable shrinkage quantity, the stresses of concretes. The result of this papar is that the mean value of differential shrinkage is similar to the existing result but at exposures surface the shrinkage strains are more large. From this result the possiblility of crack formation can take place. Thus a resonable counterplan for tensile stresses in exposure surfaces is necessary.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.221-225
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• 2004

Evaluation of turbulence models is performed for a better prediction of thermal stratification in an upper plenum of a liquid metal reactor by applying them to the experiment conducted at JNC. The turbulence models tested in the present study are the two-layer model, the $\kappa-\omega$ model, the v2-f model and the low-Reynolds number differential stress-flux model. When the algebraic flux model or differential flux model are used for treating the turbulent heat flux, there exist little differences between turbulence models in predicting the temporal variation of temperature. However, the v2-f model and the low-Reynolds number differential stress-flux model better predict the steep gradient o( temperature at the interface of thermal stratification, and only the v2-f model predicts properly the oscillation of temperature. The LES Is needed for a better prediction of the amplitude and frequency of the temperature fluctuation.

• Communications of Mathematical Education
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• v.18 no.2 s.19
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• pp.79-92
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• 2004

This paper offers an analysis of how students reasoned with the dynamic parameter time to support their mathematical activity and deepen their understandings of mathematical concepts. This mathematical thinking occurred as they participated in a differential equations class before, during, and instruction on solutions to linear systems of differential equations. Students participated in the following identified mathematical practices related to parametric reasoning during this time period: reasoning simultaneously in a qualitative and quantitative manner, reasoning by moving from discrete to continuous imaging of time, and reasoning by imagining the motion. Examples of this reasoning are provided in this report. Implications of this research include the possibility that instructional activities can build on this reasoning to help students learn about the mathematics of change at the middle school, high school, and the university.

• The Plant Pathology Journal
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• v.26 no.3
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• pp.260-263
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• 2010

Scald, caused by Rhynchosporium secalis has been the major yield-reducing factor for barley production during the last decade. In this study, pathogenic groups of R. secalis were identified to obtain a global picture of the assembly of isolates involved in Syrian populations which is essential for the development of scald-resistant barley cultivars. To identify a number of pathogenic groups, 49 isolates collected over ten years from major barley growing areas in Syria were evaluated on five differential barley genotypes. Genotypes presented a continuous range of response from highly susceptible to moderately resistant, but none were immune to the disease. A cluster analysis placed isolates in six distinct differential pathogenic groups. Mean disease rating of 39.24% was the separation point between avirulent and virulent reactions. Isolate Rs46 exhibited distinct differential virulence patterns associated with high frequency across all genotypes. Hence, the data presented here provides crucial information for future selection of isolates to develop durable barley scald resistance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.575-578
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• 2008

In this paper, the purpose is to investigate the stability and variation of natural frequency of a Timoshenko cantilever beam subjected to follower force and tip mass. In addition, an analysis of the flutter instability(flutter critical follower force) of a cantilever beam as slenderness ratio is investigated. The governing differential equations of a Timoshenko beam subjected to an end tangential follower force is derived via Hamilton;s principle. The two coupled governing differential equations are reduced to one fourth order ordinary differential equation in terms of the flexural displacement. Finally, the influence of the slenderness ratio and tip mass on the critical follower force and the natural frequency of a Timoshenko beam are investigated.

• Coupled systems mechanics
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• v.3 no.3
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• pp.291-304
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• 2014

Paper discusess a dynamic engineering problem of a mass attached to a pendulum sliding along a cable. In this problem the pendulum mass and the cable are coupled together in a model described by a system of differential algebraic equations (DAE). In the paper we have presented formulation of the system of differential equations that models the problem and determination of the initial conditions. The developed model is general in a sense of free choice of support location, elastic cable properties, pendulum length and inclusion of braking forces. Examples illustrate and validate the model.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.5
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• pp.17-27
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• 2000

In a SCH(separate confinement heterostructure) QW(quantum well) laser, we calculated the optical gain, the differential gain and recombination current in the QW and derived the bulk carrier density in the SCH region as a function of the QW current by using the analytical capture escape model. Based upon above relations, we found the optical gain and the differential gain correspond to the ratios of carrier and current injected into the QW.

• Journal of Engineering Education Research
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• v.23 no.4
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• pp.37-51
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• 2020

This study examined the differential effects of High-Impact Practices(HIPs) on the career aspiration of STEM college students by gender. Through the theoretical lens of Social Cognitive Career Theory(SCCT), a two-level model analysis was conducted. A sample of 2,101 third- and fourth-year undergraduate students majoring in STEM at 38 universities, which had been collected from the National Survey on College Student Experiences and Learning Outcomes funded by the Korea Research Foundation, was used. This study found that the three HIP domains(learning with peers, faculty support, content relevancy) had different influences depending on gender. These findings suggest that HIPs can benefit the development of female students' career aspiration and have gender-differential effects on students in STEM majors. Based on those findings, this study also deduced implications about the roles of faculty members and higher-education institutions that might foster the retention of women in STEM.