• Journal of the Korea Convergence Society
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• 제8권12호
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• pp.369-378
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• 2017

This study is devoted to investigating participation motivations of billiard players who join games through open-ended questionnaires, and identify the difference of participation motivations in the game according to age and experience. Thus, 696 original data on participation motivations was obtained from 267 billiard players in Gyeonggi-do based on open-ended questionnaires. Results from inductive analysis are as follows. First, their participation motivations included 10 general sectors such as interests, objective achievement motive, competition, interpersonal relationship, mental health, job, gambling, sport competence, suggestion by others, and university admission. Second, enjoyment showed the highest percents among participation motivations according to participants' age. Third, interest showed the highest percents among participation motivations in less than five years of their experiences. Objective achievement motive was the highest portion for more than five years. These outcomes will be used as a basic data to understand the relationship of billiard players who participate in the game and further create better billiard game culture.

• Journal of the Korean association of regional geographers
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• 제20권1호
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• pp.141-151
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• 2014

This study is to explain understanding types about the concept of a 'Region' in the 3rd grade high school students(39) through open-ended questionnaires and describe the pedagogical utilizations for this. Students' understanding types about the concept of a 'Region' are compared and then determined through two meaning agreement and association between meaning of students' understanding which is collected through open-ended questionnaires and meaning of a 'Region' which is described in high school curriculum. The results are as in the following. First, Students' understanding types about the concept of a 'Region' were divided into four categories: full, partial, ambiguous, and converted understanding. Second, The degree of right meaning agreement and association existing between two meanings is rising steadily by converted, ambiguous, partial, and full understanding. For this reason, This result can make sure the understanding degree about the concept of a 'Region' is different depending on the students. Third, Students' partial understanding, ambiguous understanding and converted understanding on region concept could be judged as misconception not fully corresponded to region concept in the curriculum explanation. Fourth, Teachers can achieve conceptual change through this misconception as a subject matter of educational dialogue for meaning change.

• Journal of the Korean Geosynthetics Society
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• 제16권2호
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• pp.67-77
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• 2017

This study analyzes behavior of bearing capacity of open-ended pipe pile from laboratory experiment results. Unlike the conventional pipe piles, cone penetration is implemented into the inside of the pipe pile. During the cone penetration, cone driving energy helps densification of plugged soils and soils below the pile end. Sand pluviator was used to obtain homogeneous soil layers. Two kinds of piles with different pile outer surface roughness were prepared, and two different drop heights of pile driving were applied. Eight experimental cases varying pile outer surface roughness, pile driving energy for conventional and cone penetration implemented piles were conducted. From the experiments, ultimate load of the pile increased approximately by 70% for increased pile driving height, and it increased by 21% for rougher surface pile. When cone penetration is implemented, the ultimate load increased by 40% in average.

• Geotechnical Engineering
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• 제9권4호
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• pp.7-16
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• 1993

Calibration chamber tests were conducted on open -ended model piles driven into dried siliceous sands with different soil conditions in order to clarify the effect of soil conditions on plug capacity, The model pile used in the test series was devised so that the bearing capacity of an open -ended pile could be measured out into three components , outside shaft resistance. plug resistance and tip resistance. Under several assumption, the value of earth pressure coefficient in the soil plug is calculated. It is gradually reduced with increase in the longitudinal distance from the pile tip. At the bottom of soil plug, it tends to decrease with increase in the penetration depth and relative density, and to increase with the increase of ambient pressure. In comparison of measured and calculated plug capacities using the one -dimensional analysis, we note that API code and one -dimensional analysis combined with P suggested by Randolph et al. and O'Neill et al. result in great underestimation of the plug capacity. Therefore, based on the test results, an empirical equation was suggested to compute the earth pressured coefficient to be used in the calculation of plug capacity using the one -dimensional analysis. and it produces proper plug capacities for all soil conditions.

• Journal of the Korean Geotechnical Society
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• 제32권5호
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• pp.27-36
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• 2016

This paper presents the investigation of the major influence factors on the degree of soil plugging for open-ended piles based on the Coupled Eulerian-Lagrangian (CEL) numerical technique. The main objective of this study was to investigate the effect of soil plugging on the response of piles in various conditions. Through comparison of the results of field load tests, the CEL methodology was found to be in good agreement with the general trend observed by in situ measurement. Additionally, the parametric studies were performed by controlling the soil conditions, soil elastic moduli, end-bearing conditions and multi layers. It was found that the degree of soil plugging for sand layers was greater than that of clay layers. Also, the degree of soil plugging increased with an increase in both the soil stiffness and length of pile embedded in the bearing layer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제18권1호
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• pp.7-14
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• 2007

In this paper, the scan characteristics of phased array antenna consisted of rectangular open-ended waveguide with a triangular grid are investigated. An infinite array structure is analyzed by numerically solving the integral equation for the electric field over the waveguide aperture using waveguide mode function and Floquet mode function. Next, SEP(Scan Element Pattern) and SI(Scan Impedance) characteristics are simulated by CST's MWS(Microwave Studio) and Ansoft's HFSS(High Frequency Structure Simulator) for the finite and infinite array structures. Also, validity of these approaches is verified by comparing the calculated and simulated results with the measured ones for an $8{\times}8$ subarray. Within 10.5 % fractional bandwidth in the X-band, the fabricated subarray showed the flat gain characteristic in the scan range of ${\pm}45^{\circ}C$ in the E-plane(azimuth) and ${\pm}20^{\circ}C$ in the H-plane(elevation), and also showed the return loss characteristic of less than -10 dB.

• Journal of the Korean Geotechnical Society
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• 제40권4호
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• pp.145-154
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• 2024

This study used the discrete element method (DEM) to model the driving process of open-ended piles and investigate the behavior of soil plug during pile penetration. The developed DEM model was verified by comparing model pile test results and numerical analysis, particularly using a contact model considering rolling resistance between soil particles. The study successfully simulated soil compression inside the pile by adjusting the relative density and penetration velocity, and it was confirmed that the soil plug tended to be more compressed as the initial penetration velocity decreased. Soil plug length measurements, plug length ratio, and incremental filling ratio were analyzed and validated against experimental results. The developed DEM model aims to reduce trial and error in further studies by detailing the modeling and verification process.

• Journal of Practical Engineering Education
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• 제15권3호
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• pp.539-547
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• 2023

In recent years, university education has emphasized a learner-centered education model with a change in educational paradigm. This study aims to explore students' diverse opinions and improve the quality of education by analyzing the open-ended responses of university lecture evaluations using topic modeling. To this end, a total of 45,001 open-ended responses based on the results of lecture evaluations from 2017 to 2022 in non-metropolitan universities were divided into majors and liberal arts, and a short-form optimized Biterm Topic Modeling (BTM) analysis was conducted. As a result of the analysis, major lectures were divided into "attitude toward non-face-to-face classroom experience", "attitude toward questions and discussions", "attitude toward attendance and grading", "attitude toward practical activities and presentations", and "attitude toward communication and collaboration", while liberal arts lectures were divided into "attitude toward non-face-to-face classroom experience", "attitude toward grades and evaluations", "attitude toward attendance and syllabus", "attitude toward academic knowledge and interest", and "attitude toward communication and questions". The results of this study, which analyzed various feedback from students, provide insights that can be used to compare the characteristics of majors and liberal arts courses and improve teaching and learning experiences.

• Clean Technology
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• 제30권3호
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• pp.228-238
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• 2024

Electrolytes are one of the essential components of a lithium-ion battery. They determine the battery's lifespan and cell characteristics. The dielectric constant is a key thermophysical property for determining how much salt can be dissociated and solvated in a solution. Hence, fast and reliable dielectric constant measurement is essential when formulating an electrolyte solution. This work implemented an open-ended coaxial probe (OECP) station as a quick and reliable tool to measure the complex permittivity spectra of electrolyte solutions. The capability of the OECP station was tested by measuring the complex permittivity of propylene carbonate (PC), dimethyl carbonate (DMC), and their mixtures from 0.1 to 8 GHz at 288.15, 298.15, and 308.15 K. The obtained dielectric spectra were then interpreted based on dielectric relaxation models and thermodynamic theories. The measured static dielectric constant data agreed well with the data from previous studies. They were also correlated using the Wang-Anderko thermodynamic model, showing approximately a 1% deviation from the experimental data. In addition, the relaxation characteristics, including the relaxation time and the Cole-Davidson exponent, showed that the microstructure of the solution significantly changes at the propylene carbonate mole fraction of 0.4. These results and methodologies are expected to contribute to the further understanding of electrolyte solutions and ultimately lead to the optimization of electrolyte formulation for lithium-ion batteries.

• Journal of Educational Research in Mathematics
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• 제8권2호
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• pp.405-423
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• 1998

This study aims to reflect the origin and the meaning of open education and to derive pedagogical principles for open mathematics education. Open education originates from Socrates who was the founder of discovery learning and has been developed by Locke, Rousseau, Froebel, Montessori, Dewey, Piaget, and so on. Thus open education is based on Humanism and Piaget's psychology. The aim of open education consists in developing potentials of children. The characteristics of open education can be summarized as follows: open curriculum, individualized instruction, diverse group organization and various instruction models, rich educational environment, and cooperative interaction based on open human relations. After considering the aims and the characteristics of open education, this study tries to suggest the aims and the directions for open mathematics education according to the philosophy of open education. The aim of open mathematics education is to develop mathematical potentials of children and to foster their mathematical appreciative view. In order to realize the aim, this study suggests five pedagogical principles. Firstly, the mathematical knowledge of children should be integrated by structurizing. Secondly, exploration activities for all kinds of real and concrete situations should be starting points of mathematics learning for the children. Thirdly, open-ended problem approach can facilitate children's diverse ways of thinking. Fourthly, the mathematics educators should emphasize the social interaction through small-group cooperation. Finally, rich educational environment should be provided by offering concrete and diverse material. In order to make open mathematics education effective, some considerations are required in terms of open mathematics curriculum, integrated construction of textbooks, autonomy of teachers and inquiry into children's mathematical capability.