• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.699-708
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• 2001

This paper presents a new approach to the AFR (Air-to-Fuel Ratio) control problem, which is based on the wide-band oxygen sensor output. The dedicated nonlinear controller is based on the feedback lineaization technique. It is well known that the feedback linearizing control technique requires an exact model of the plant for the cancellation of plant nonlinearities. A sliding mode control scheme is applied which can effectively compensate the modeling uncertainties. The measurement time delay of an oxygen sensor limits the gain of the feedback controller. Hence, time delay compensation procedure is necessary for the improvement of control performance. The Smith predictor is adopted to compensate the effects of time delay. The simulation and experimental results show that the proposed controllers can effectively reduce the transient peaks of AFR in spite of fast tip-in and tip-out maneuvers of the throttle.

• Journal of Engineering Education Research
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• v.11 no.4
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• pp.58-63
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• 2008

This thesis investigated way of employment, education course of a training school of electrical company. And student more than. Faced a human power demand in an education demand and a field rehearsal student demand and and analyzed it. The sample extraction used industrial classification, work of scale, Assignment sample extraction way (quota Sampling). All data called at a silver phone and, and the investigated, The data parser analyzed the statistics that used Microsoft Excel.

• Journal of Information Display
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• v.8 no.3
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• pp.11-16
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• 2007

Theoretical simulations of spatial distribution of charge carriers and recombination rate, and J-V characteristics of the multi-layer organic light emitting diodes are carried out. Drift-diffusion current transport, field-dependent carrier mobility, exponential and Gaussian trap distribution, and Langevin recombination models are included in this computer model. The simulated results show good agreement with the experimental data confirming the validity of the physical models for organic light emitting diodes.

• Research in Mathematical Education
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• v.27 no.1
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• pp.129-150
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• 2024

This study utilized South Korean elementary and middle school student data to examine the longitudinal change trajectories of learning motivation types according to the longitudinal change trajectories of mathematics academic achievement. Growth mixture modeling, latent growth model, and multiple indicator latent growth model were used to examine various change trajectories for longitudinal data. As a result of the analysis, it was classified into 4 subgroups with similar longitudinal change trajectories of mathematics academic achievement, and the characteristics of the mathematics subject, which emphasize systematicity, appeared. Furthermore, higher mathematics academic achievement was associated with higher self-determination and higher academic motivation. And as the grade level increases, amotivation increases and self-determination decreases. This study suggests that teaching and learning support using this is necessary because the level of learning motivation according to self-determination is different depending on the level of mathematics academic achievement reflecting the characteristics of the student.

• Research in Mathematical Education
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• v.25 no.2
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• pp.99-115
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• 2022

This study examined difficulties middle school students have in learning mathematics and proposed a flipped classroom consisting of Khan Academy activities, small-group problem solving, and mathematical modeling to help improve their learning. A mixed-method approach was used to identify difficulties students have in learning mathematics, explore how the flipped classroom helped them reduce the learning difficulties identified, and examine if there were differences in students' mathematics achievement and their affective characteristics after participating in the flipped classroom. Qualitative analyses showed that students had difficulties in understanding mathematical concepts and finding effective ways to learn as well as negative views towards learning mathematics. This study also found that each activity of the flipped classroom had a different impact on student learning. Before class, the Khan Academy activities were most likely to help students understand mathematical concepts. In class, small-group problem solving activities were most helpful for students who had trouble finding effective learning methods and environments. Mathematical modeling activities were most likely effective in changing students' negative views towards mathematics. A quantitative analysis showed that the flipped classroom not only significantly improved the students' mathematics achievement, but also positively affected their confidence and motivation and how much they valued learning mathematics.

• Korean small business review
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• v.39 no.3
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• pp.57-76
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• 2017

While the unemployment rate is rising rapidly due to recent economic recession at home and abroad, university students' reluctance to apply for jobs in Small and Medium Enterprises (SME's) causes instability in manpower supply and demand and social unrest. To provide insights for solving the problem, this study explores how beliefs and attitudes of university students influence their intention to apply for jobs in SME's using Theory of Planned Behavior proposed by Icek Ajzen. This study followed the 2-stage survey methodology suggested by Ajzen. In the first stage of pilot study, a small sample of university students was used to illicit readily accessible behavioral outcomes, normative referents, and control factors. In the second stage of main study, the standard questionnaire was designed and administered and data were collected and analysed using the PLS Structural Equation Modeling (SEM) technique. PLS-SEM was used instead of Covariance Based (CB)- SEM considering the exploratory nature of this study. In overall, the results showed that TPB is very effective in explaining and predicting the university student's intention to apply for jobs in SEM's. Gender turned out to be a significant moderator variable in the relations between intention and its influence factors. Student's scholastic performance showed a negative correlation with intention. More research efforts need to be exerted to better understand university student's job seeking behavior.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.163-166
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• 2007

본 연구에서는 우수 학생을 알아보기 위해 학생들의 학습 성과 및 과외활동을 바탕으로 평가모형을 설계하고 AHP(Analytic Hierarchy Process) 기법을 통해 분석하였다. 대부분의 대학에서 시행되고 있는 장학금 제도는 평가 기준이 해당 학기 평점으로 장학금 혜택을 받는 학생들이 일부 학생으로 제한되는 경우가 생기기도 한다. 실제로 평점뿐 아니라 다른 평가 기준을 가지고 학생들을 평가하여 학생들의 다양한 특성을 키워 줄 필요가 있다 평점만으로 학생을 평가하는 방식이 아닌 다양한 기준의 평가 모형을 가지고 학생들을 평가하는 새로운 방식의 학생평가모델을 제안하고자 한다.

• Korean Journal of Veterinary Research
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• v.47 no.2
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• pp.259-263
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• 2007

The choice of input distribution in quantitative risk assessments modeling is of great importance to get unbiased overall estimates, although it is difficult to characterize them in situations where data available are too sparse or small. The present study is particularly concerned with accommodation of uncertainties commonly encountered in the practice of modeling. The authors applied parametric and non-parametric bootstrap simulation methods which consist of re-sampling with replacement, in together with the classical Student-t statistics based on the normal distribution. The implications of these methods were demonstrated through an empirical analysis of trade volume from the amount of chicken and pork meat imported to Korea during the period of 1998-2005. The results of bootstrap method were comparable to the classical techniques, indicating that bootstrap can be an alternative approach in a specific context of trade volume. We also illustrated on what extent the bias corrected and accelerated non-parametric bootstrap method produces different estimate of interest, as compared by non-parametric bootstrap method.

• Journal of The Korean Association For Science Education
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• v.34 no.6
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• pp.583-592
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• 2014

The purpose of this study is to investigate the impact of argument-based modeling strategy using scientific writing on student's modeling ability. For this study, 66 students (three classes) from the 7th grade were selected and of these, 43 students (two classes) were assigned to two experimental groups while the other 23 students (one class) were assigned to comparative group. In the experimental groups, one group (22 students) was Argument-based multimodal Representation and Modeling (AbRM), and the other group (21 students) was Argument-based Modeling (AbM). Modeling ability consisted of identifying the problem, structuring of scientific concepts, adequacy of claim and evidence and index of multimodal representation. As for the modeling ability, AbRM group scored significantly higher than the other groups, AbM group was significantly higher than comparative group. The four sub-elements of modeling ability in the AbRM group was significantly higher than the other groups statistically and AbM group scored significantly higher than comparative group. From these results, the argument-based modeling strategy using scientific writing was effective on students' modeling ability. Students organized or expressed the model and evaluated or modified it through the process of argument-based modeling using scientific writing and the exchange of opinions with others by scientific language as argument and writing.

• Communications of Mathematical Education
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• v.35 no.3
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• pp.295-322
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• 2021

This study was conducted for one semester through one group pretest-posttest design with 49 first-year middle school students to explore the effects of mathematics-centered STEAM class experiences on students' mathematical modeling abilities. The main results of this study are as follows: First, the results of the pre and post-mathematical modeling ability tests showed that the average score of posttest was improved compared to the pretest, and that the experiences of mathematics-centered STEAM classes provided in this study had a positive effect on improving the mathematical modeling ability of first-year middle school students. Second, STEAM classes were more effective in solving mathematical modeling problems that require students' creative and divergent thinking. Third, the content analysis of student responses for each subquestion showed that STEAM classes were especially more helpful in activating students' mathematical model construction and validating steps.