• Communications for Statistical Applications and Methods
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• 제27권2호
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• pp.211-224
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• 2020

Sensitivity and specificity are popular measures described by the receiver operating characteristic (ROC) curve. There are also two other measures such as the positive predictive value (PPV) and negative predictive value (NPV); however, the PPV and NPV cannot be represented by the ROC curve. Based on the total operating characteristic (TOC) curve suggested by Pontius and Si (International Journal of Geographical Information Science, 97, 570-583, 2014), explanatory methods are proposed to geometrically describe the PPV and NPV by the TOC curve. It is found that the PPV can be regarded as the slope of the right-angled triangle connecting the origin to a certain point on the TOC curve, while 1 - NPV can be represented as the slope of the right-angled triangle connecting a certain point to the top right corner of the TOC curve. When the neutral zone exists, the PPV and 1-NPV can be described as the slopes of two other right-angled triangles of the TOC curve. Therefore, both the PPV and NPV can be estimated using the TOC curve, whether or not the neutral zone is present.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.113-116
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• 2006

In this paper, the fairing effects on the aerodynamics stability of basic plate-girder sections are investigated trough wind tunnel tests. As basis sections, two types of $\pi$-type shape sections with aspect ratios(D/B) of 1/5 and 1/10 are employed as the basic sections. And three types of triangular fairings are applied such as right-angled triangle(F1), inverted right-angled triangle(F2) and regular triangle(F3). The effects of attack angle on the dynamic response of each section are also investigated. As the results of experiments, fairings F2 is most effective to suppress flutter phenomenon or vortex induced vibration among three types of fairings.

• 한국수학사학회지
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• 제15권1호
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• pp.57-68
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• 2002

Mathematical problems are classified into two families, i.e. the solvable ones and the others. There are some such problems in the documentary records of tile Chosun Dynasty ages. In those days, a ‘normal right triangle’ whose ratio of the three sides in the triangle is 3 : 4 : 5 was defined and had been used tacitly. This paper intends to introduce the problems having errors.

• Anatomy and Cell Biology
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• 제56권3호
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• pp.350-359
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• 2023

The suboccipital triangle (ST) is a clinically relevant landmark in the posterior aspect of the neck and is used to locate and mobilize the horizontal segment of the third part of the vertebral artery before it enters the cranium. Unfortunately, this space is not always a viable option for vertebral artery exposition, and consequently a novel triangle, the inferior suboccipital triangle (IST) has been defined. This alternative triangle will allow surgeons to locate the artery more proximally, where its course is more predictable. The purpose of this study was to better define the anatomy of both triangles by measuring their borders and calculating their areas. Ethical clearance was obtained from the University of Pretoria (reference number: 222/2021) and both triangles were subsequently dissected out on both the left and right sides of 33 formalin-fixed human adult cadavers. The borders of each triangle were measured using a digital calliper and the areas were calculated using Herons Formula. The average area of the ST is 969.82±153.15 mm², while the average area of the IST is 307.48±41.31 mm². No statistically significant differences in the findings were observed between the sides of the body, ancestry, or sex of the cadavers. Measurement and analysis of these triangles provided important anatomical information and speak to their clinical relevance as surgical landmarks with which to locate the vertebral artery. Of particular importance here is the IST, which allows for mobilisation of this artery more proximally, should the ST be occluded.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제20권2호
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• pp.163-175
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• 2017

본 연구는 평면 도형의 도형 분류하기 과제를 제시할 때 길이와 각의 표기 여부가 도형의 개념 이해에 어떤 영향을 주는지 알아보는데 목적이 있다. 이를 위해, 초등학교 4학년 학생 33명을 대상으로 분류하기 과제 해결 과정을 Eye-tracker를 통해 녹화하고 정답률과 Gaze Duration을 중심으로 분석하였다. 그 결과, 이등변삼각형과 정삼각형의 분류하기에서는 길이를 제시하였을 때 정답률이 증가하고 Gaze Duration은 감소하였다. 예각삼각형과 둔각삼각형 과제에서도 직각을 표기했을 때 정답률이 증가하고 Gaze Duration이 감소하였다. 이러한 결과로 볼 때, 평면도형을 분류하는 과제를 제시할 때는 길이와 각을 표기하여 학생들이 어림하여 도형을 분류하기 보다는 도형의 개념 이해를 바탕으로 분류하는 것을 측정하는 데 초점을 두어야 할 것이다.

• 한국수학사학회지
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• 제30권4호
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• pp.221-232
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• 2017

In this paper, we discuss how ancient Egyptians find out the area of the circle based on $\ll$Ahmose Papyrus$\gg$. Vogel and Engels studied the quadrature of the circle, one of the basic concepts of ancient Egyptian mathematics. We look closely at the interpretation based on the approximate right triangle of Robins and Shute. As circumstantial evidence for Robbins and Shute's hypothesis, Egyptians prior to the 12th dynasty considered the perception of a right triangle as examples of 'simultaneous equation', 'unit of length', 'unit of slope', 'Egyptian triple', and 'right triangles transfer to Greece'. Finally, we present a method to utilize the squaring the circle by ancient Egyptians interpreted by Robbins and Shute as the dynamic symmetry of Hambidge.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.641-642
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• 2010

삼각함수는 직각삼각형에서 한 각의 크기가 일정하면, 이들 변의 비의 값은 삼각형의 크기에는 관계없이 일정하다는 가장 단순하고 독특한 성질에 기초를 둔 학문이다. 직삼각형의 밑변의 길이와 건물을 올려다본 각이 있다면 건물의 높이를 삼각함수를 이용하여 구할 수 있다. 이는 차를 타고 이동하면서 건물의 높이를 가늠할 수 있는 좋은 방법이라고 볼 수 있다.

• 한국의류학회지
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• 제47권2호
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• pp.392-408
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• 2023

This study concerns the flower-shaped silver crown ornament and inverted triangle-shaped crown ornament of Baekje, which were worn frequently during the Sabi period. The purpose of this study is to present a new estimated shape of the crown and ornaments. Individual excavation cases and archaeological data were analyzed. The flower-shaped silver crown ornament appears as a thin silver plate with buds on the center and side branches and is symmetrically bent from the center to form a ∧ shape. The inverted triangle-shaped crown ornament resembles two right-angle triangles that are back-to-back. The crown to which the two ornaments were added appears to be a triangular crown that was made by covering birch bark of with fabric. Both ornaments were believed to have been located on the front of crown, but that is incorrect. The flower-shaped silver crown ornament was inserted on the front of the crown, and the inverted triangle-shaped crown ornament was fixed with a tip at the top of the crown and then obliquely on the crown's side. The inferred design was confirmed with real reproductions. This study is significant in that it identifies the crown of Baekje during the Sabi period.

• 한국수학사학회지
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• 제26권5_6호
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• pp.345-353
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• 2013

Some teachers do not regard the computation of the sum of the angles of a triangle by using a cut-and-paste or paper-folding method as providing a proof that the sum of the angles of a triangle is equal to two right angles. Some even think that this way of working is not mathematics but more like an experiment in physics. Some see the method as no better than measurement of the angles by a protractor. The author will examine this issue in the teaching and learning of school geometry and more generally as a specific example from the perspective of HPM (History and Pedagogy of Mathematics).

• 한국수학사학회지
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• 제18권3호
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• pp.25-38
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• 2005

이 글에서는 중국의 산학서에 나타난 직각 삼각형의 풀이에 관한 연구 결과를 역사적으로 간략히 알아본다. 그리고 직각 삼각형에 관한 문제만을 다룬 조선의 산학서 [유씨구고술요도해]를 중심으로 직각 삼각형의 풀이에 관한 문항들을 분석하고, 문제 풀이를 위한 다항 방정식 작성 방법을 예시하며, 각 문항에서 이용한 피타고라스 삼조들을 조사한다.