• Journal of Elementary Mathematics Education in Korea
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• v.17 no.1
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• pp.67-86
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• 2013

The purpose of this study is to analyze selection of factors of Schoenfeld's problem solving behavior shown in problem solving process of mathematically gifted students based on brain preference of the students and to present suggestions related to hemispheric lateralization that should be considered in teaching such students. The conclusions based on the research questions are as follows. First, as for problem solving methods of the students in the Gifted Education Center based on brain preference, the students of left brain preference showed more characteristics of the left brain such as preferring general, logical decision, while the students of right brain preference showed more characteristics of the right brain such as preferring subjective, intuitive decision, indicating that there were differences based on brain preference. Second, in the factors of Schoenfeld's problem solving behavior, the students of left brain preference mainly showed factors including standardized procedures such as algorithm, logical and systematical process, and deliberation, while the students of right brain preference mainly showed factors including informal and intuitive knowledge, drawing for understanding problem situation, and overall examination of problem-solving process. Thus, the two types of students were different in selecting the factors of Schoenfeld's problem solving behavior based on the characteristics of their brain preference. Finally, based on the results showing that the factors of Schoenfeld's problem solving behavior were differently selected by brain preference, it may be suggested that teaching problem solving and feedback can be improved when presenting the factors of Schoenfeld's problem solving behavior selected more by students of left brain preference to students of right brain preference and vice versa.

• Journal of the Korean Data and Information Science Society
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• v.28 no.2
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• pp.349-359
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• 2017

In this paper, we conducted survival analyses by fitting the Cox proportional hazards model to stage III proximal colon cancer data obtained from the Surveillance, Epidemiology, and End Results program of the National Cancer Institute. We investigated the effect of covariates on the hazard function for death from proximal colon cancer in stage III with surgery performed and estimated the survival probability for a patient with specific covariates. We showed that the proportional hazards assumption is satisfied for covariates that were used to analyses, using a test based on the Schoenfeld residuals and plots of the Schoenfeld residuals and $log[-log\{{\hat{S}}(t)\}]$. We evaluated the model calibration and discriminatory accuracy by calibration plot and time-dependent area under the ROC curve, which were calculated using 10-fold cross validation.

• Communications of Mathematical Education
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• v.15
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• pp.207-214
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• 2003

수학교육에서 학생들이 학습을 통하여 습득하여할 중요한 주제는 수학 지식과 수학을 다루는 인지적 조작 기술일 것이다. 특히 수학지식과 지식의 활용은 문제해결을 통한 학습에서 의미 있게 학생에게 나타나며 이를 통하여 수학 학습 동기를 강화하고 수학의 가치를 느끼게 한다는 점에서 중요한 의의를 갖는다. 대학수준의 수학교육과정에서도 문제해결은 중요한 수학교육의 중심 수단으로서 목적으로서 선언되어 있지만 실제 수업에서 잘 다루고 있지 못하다. 문제해결 지도에 대한 접근 방식으로 1950년대의 문제해결전략을 다룬 Polya, 1990년대의 메타인지적 접근을 강조한 Schoenfeld 및 최근의 여러 연구자들의 활발한 연구가 이어지고 있다. 본 논문에서 대학 수준의 문제해결 수업의 접근 방법을 소개함으로 문제해결 수업을 구현할 수 있는 지식을 제공한다. 특히 Schoenfeld의 문제해결 수업 모델은 수학 교육의 교실 수업으로의 구현 측면에서 갖는 다양한 함의를 제시한다.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.1
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• pp.441-447
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• 2014

Background: Multi-state models are appropriate for cancer studies such as gastrectomy which have high mortality statistics. These models can be used to better describe the natural disease process. But reaching that goal requires making assumptions like Markov and homogeneity with time. The present study aims to investigate these hypotheses. Materials and Methods: Data from 330 patients with gastric cancer undergoing surgery at Iran Cancer Institute from 1995 to 1999 were analyzed. To assess Markov assumption and time homogeneity in modeling transition rates among states of multi-state model, Cox-Snell residuals, Akaikie information criteria and Schoenfeld residuals were used, respectively. Results: The assessment of Markov assumption based on Cox-Snell residuals and Akaikie information criterion showed that Markov assumption was not held just for transition rate of relapse (state 1 ${\rightarrow}$ state 2) and for other transition rates - death hazard without relapse (state 1 ${\rightarrow}$ state 3) and death hazard with relapse (state 2 ${\rightarrow}$ state 3) - this assumption could also be made. Moreover, the assessment of time homogeneity assumption based on Schoenfeld residuals revealed that this assumption - regarding the general test and each of the variables in the model- was held just for relapse (state 1 ${\rightarrow}$ state 2) and death hazard with a relapse (state 2 ${\rightarrow}$ state 3). Conclusions: Most researchers take account of assumptions such as Markov and time homogeneity in modeling transition rates. These assumptions can make the multi-state model simpler but if these assumptions are not made, they will lead to incorrect inferences and improper fitting.

• Journal of the Korean School Mathematics Society
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• v.9 no.1
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• pp.105-120
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• 2006

The Seventh Curriculum makes sure that those students who don't have a proper understanding of contents required at a certain stage take a remedial course. But a trend contrary to the intention is formed since there is no systematic education for such a course and thus more students get to fall into the group of low achievement. In particular, solving a simultaneous equation in a rote way without understanding influences negatively students' achievement. Schoenfeld introduced the basic elements of one's own mathematical problem solving process and behavior, referred to Polya's. Employing Schoenfeld's strategy, this study aimed to induce students' active participation in math classes, as well as to focus on a mathematical problem solving process during the study. Two students were selected from a remedial course at 00 Middle School and administered with a qualitative case study method over 17 lessons, each of which lasted for 30 minutes. In the beginning, they used such knowledge as facts and definitions a lot. There was a tendency of their resorting to intuitive knowledge more when they lacked basic knowledge or met with a difficult question. As the lessons were given, however, they improved their ability to implement algorithm procedures and used more familiar ones with the developed common procedures in the area of resources.

• Journal of Educational Research in Mathematics
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• v.14 no.3
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• pp.239-266
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• 2004

This article presents new perspectives for analysing and diagnosing students' mathematical errors on the basis of Pascaul-Leone's neo-Piagetian theory. Although Pascaul-Leone's theory is a cognitive developmental theory, its psychological mechanism gives us new insights on mathematical errors. We analyze mathematical errors in the domain of proof problem solving comparing Pascaul-Leone's psychological mechanism with mathematical errors and diagnose misleading factors using Schoenfeld's levels of analysis and structure and fuzzy cognitive map(FCM). FCM can present with cause and effect among preconceptions or misconceptions that students have about prerequisite proof knowledge and problem solving. Conclusions could be summarized as follows: 1) Students' mathematical errors on proof problem solving and LC learning structures have the same nature. 2) Structures in items of students' mathematical errors and misleading factor structures in cognitive tasks affect mental processes with the same activation mechanism. 3) LC learning structures were activated preferentially in knowledge structures by F operator. With the same activation mechanism, the process students' mathematical errors were activated firstly among conceptions could be explained.

• The Mathematical Education
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• v.61 no.1
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• pp.83-108
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• 2022

This research is a case study in which teachers tried to improve classes through online class analysis and self-evaluation in elementary school mathematics classes using a checklist of class reflection based on fair access, autonomy, initiative, and evaluation areas in the TRU analysis framework of Schoenfeld (2016). As a result, it was confirmed that the teacher's fair participation, student autonomy, initiative, feedback, and evaluation areas improved teaching methods during the short time. Therefore, if you want to improve classes in relatively short period of time, you can see the effect of some improvement only by self-evaluation. However, continuous improvement of teaching methods require the help of a teacher communities including experts or critical colleagues, and a longer-term case study.

• Journal of the Korean Statistical Society
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• v.23 no.2
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• pp.379-402
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• 1994

Graphical and numerical methods for checking the assumption of proportional hazards of Cox model for censored survival data are discussed. The strenths and weaknessess of several goodness of fit tests for the propotional hazards for the two-sample problem are evaluated with Monte Carlo simulations, and the tests of Schoenfeld (1980), Andersen (1982), Wei (1984), and Gill and Schumacher (1987) are considered. The goodness of fit methods are illustrated with the survival data of patients who had chronic liver disease and had been treated with the endoscopy injection sclerotheraphy. Two other examples of data known to have nonpropotional hazards are also used in the illustration.

• Communications for Statistical Applications and Methods
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• v.24 no.6
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• pp.583-604
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• 2017

The most popular regression model for the analysis of time-to-event data is the Cox proportional hazards model. While the model specifies a parametric relationship between the hazard function and the predictor variables, there is no specification regarding the form of the baseline hazard function. A critical assumption of the Cox model, however, is the proportional hazards assumption: when the predictor variables do not vary over time, the hazard ratio comparing any two observations is constant with respect to time. Therefore, to perform credible estimation and inference, one must first assess whether the proportional hazards assumption is reasonable. As with other regression techniques, it is also essential to examine whether appropriate functional forms of the predictor variables have been used, and whether there are any outlying or influential observations. This article reviews diagnostic methods for assessing goodness-of-fit for the Cox proportional hazards model. We illustrate these methods with a case-study using available R functions, and provide complete R code for a simulated example as a supplement.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.124-127
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• 2004

W/n-GaN Schottky diodes were irradiated with $^{60}Co\;{\gamma}-rays$ to doses up to 315Mrad. The barrier height obtained from current-voltage (I-V) measurements showed minimal change from its estimated initial value of ${\sim}0.4eV$ over this dose range, though both forward and reverse I-V characteristics show evidence of defect center introduction at doses as low as 150 Mrad. Post irradiation annealing at $500^{\circ}C$ increased the reverse leakage current, suggesting migration and complexing of defects. The W/GaN interface is stable to high dose of ${\gamma}-rays$, but Au/Ti overlayers employed for reducing contact sheet resistance suffer from adhesion problems at the highest doses.