• Journal for History of Mathematics
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• v.22 no.2
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• pp.99-116
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• 2009

In this paper we study errors related with constructing regular polygons in the book 'Method of Ruler and Compass' written three hundreds years ago. It is well known that regular heptagon and regular nonagon are not constructible using compass and ruler. But in this book construction methods of these regular polygons is suggested. We show that the construction methods are incorrect, it include some errors.

• Physical Therapy Korea
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• v.6 no.2
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• pp.43-55
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• 1999

In today's society, many women wear high-heeled shoes, but the effect of heel height on lumbar lordosis has not been clearly defined. The objective of this study was to identify the influence of heel height and general characteristics of subjects on lumbar lordosis. The subjects of this study were 40 healthy women who were students of the Department of Physical Therapy, College of Rehabilitation Science, Taegu University. Flexible ruler measurement was used to measure the lumbar lordosis at barefoot, 3 cm and 7 cm high-heeled standing positions. The results were as follows: 1) Significant statistical decrease in lumbar lordosis was observed as heel heights were increased from barefoot to 7 cm high heel. 2) There were no statistically significant differences between lumbar lordosis according to three different heel heights and weight, body mass index. 3) Lumbar lordosis measured at different heel heights was related to subject's height. With increasing subject's height, lumbar lordosis that measured from each heel height was significantly decreased. As heel heights were increased from barefoot to 7 cm high heel, significant statistical decrease in lumbar lordosis was observed in the subjects whose height were 151~160 cm. 4) Intrarater reliability on lumbar lordosis taken with a flexible ruler was good, with Cronbach ${\alpha}$ values of 0.8971 for barefoot, 0.8107 for 3 cm and 0.9002 for 7 cm high-heeled standing positions.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.21.1-21.3
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• 2019

Background: Treatment planning the correction of a transverse maxillary occlusal plane cant often involves a degree of qualitative "eyeballing", with the attendant possibility of error in the estimated judgement. A simple chair side technique permits quantification of the extent of asymmetry and thereby quantitative measurements for the correction of the occlusal plane cant. Methods: A measuring instrument may be constructed by soldering the edge of a stainless steel dental ruler at 90° to the flat surface of a similar ruler. With the patient either standing in natural head position, or alternatively seated upright in the dental chair, and a dental photographic retractor in situ, the flat under-surface of the horizontal part of this measuring instrument is placed on a unilateral segment of a bilateral structure, e.g. the higher maxillary canine orthodontic bracket hook. The vertical ruler is held next to the contralateral canine tooth, and the vertical distance measured directly from the canine bracket to the flat under-surface of the horizontal part of the measuring instrument. Results: This vertical distance quantifies the overall extent of movement required to level the maxillary occlusal plane. Conclusions: This measuring instrument and simple chair side technique helps to quantify the overall extent of surgical levelling required and may be a useful additional technique in our clinical diagnostic armamentarium.

• Korean Journal of Computational Design and Engineering
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• v.6 no.2
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• pp.78-88
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• 2001

In order to adopt feature-based parametric modeling, CAD/CAM applications must have a geometric constraint solver that can handle a large set of geometric configurations efficiently and robustly. In this paper, we describe a graph constructive approach to solving geometric constraint problems. Usually, a graph constructive approach is efficient, however it has its limitation in scope; it cannot handle ruler-and-compass non-constructible configurations and under-constrained problems. To overcome these limitations. we propose an algorithm that isolates ruler-and-compass non-constructible configurations from ruler-and-compass constructible configurations and applies numerical calculation methods to solve them separately. This separation can maximize the efficiency and robustness of a geometric constraint solver. Moreover, the solver can handle under-constrained problems by classifying under-constrained subgraphs to simplified cases by applying classification rules. Then, it decides the calculating sequence of geometric entities in each classified case and calculates geometric entities by adding appropriate assumptions or constraints. By extending the clustering types and defining several rules, the proposed approach can overcome limitations of previous graph constructive approaches which makes it possible to develop an efficient and robust geometric constraint solver.

• Journal of Applied Reliability
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• v.13 no.2
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• pp.141-151
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• 2013

The study of environmental stress cracking (ESC) by contact with plastic rulers and PVC erasers which was artificially added to the external stress was carried out in order to accelerate the chemicals crack. To analyze a blooming plasticizer that migrates from the inside of blended eraser to the surface of the eraser, the ESC experiments were carried out at room temperature and $50^{\circ}C$ conditions. The chemicals crack shape caused by the plasticizer and the brittle fracture shape resulted from the external stress were observed in consequence with the cross-sectional surface analysis of the ruler crack by the ESC. The bending strength of the plastic rulers were fractured prior to the yield point and it had low bending flexure stress. We presented that ESC of polymer materials was affected by the polarity of the chemicals and polymer, the exposure time to chemicals, the exposure temperature and the level of strain on the polymer.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.149-156
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• 2013

With a rapid growth of smartphone technologies, various applications are developed and diffused actively nowadays. Especially, interesting applications using camera module in a smartphone are developed continuously, mobile users are able to use various useful mobile services in humdrum life. In this paper, we design and implement measurement algorithms which precisely measure the object taken by the camera module in a smartphone. We use 3-axis gyro accelerometer sensor in a smartphone to get the distance, incline and rotation angle in a real time when we take a picture of shooting object and can obtain precise size of it in the picture image. The measurement algorithms proposed in this paper are analyzed and evaluated by a simulation study.

• Journal of the Korean Institute of Rural Architecture
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• v.1 no.2
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• pp.133-144
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• 1999

This paper is a study of rural settlement and housing planning in North-Korea. All the housing facilities belong to the government in North-Korea. which leads to the system in which the North-Korea government controls all the housing problems. The North-Korea government actively engages in the settlement of housing problems have close relations with and effects on the urban housing ones. The government has designed to make the rural areas self-sufficient in matters of the rural housing arrangement. They try to make an axis in the middle of each village uniformly and heighten its symbolism of the rural. They place all the symbolic structures in the center to express the ideas of the ruler's. thus making the whole village a study hall where the villagers are forced to learn the ruler's ideas as a way of brainwashing the people.

• Journal of the Korean School Mathematics Society
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• v.6 no.2
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• pp.39-53
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• 2003

We study the dynamic geometry software suitable for the Internet Environment. First, we look into the necessity of dynamic geometry software and compare the functions and the features of commercial softwares, GSP, Cabri and Cinderella. Secondly, we introduce the process of development and the structure of the new software DRC(Digital Ruler and Compass) designed by authors and discuss the learning program with DRC and Internet, and view the upgrade of the software in the future.

• 한국기계연구소 소보
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• s.19
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• pp.81-92
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• 1989

This paper presents a simple identification method of the actual kinematic parameters for the robot with parallel joints. It is known that Denavit-Hartenberg's coordinate system is not useful for nearly parallel joints. In this paper, the coordinate frames are reassigned to model the kinematic parameter between nearly parallel joints by four parameters. The proposed identification method uses a straight ruler about 1m long. A robot hand is placed by using a teaching pendant at the prescribed points on the ruler, and corresponding error function is defined. The identified kinematic parameters which make the error function zero are obtained by iterative least square error method based on the singular value decomposition. In the compensation of joint angles, only the position is considered because the usual applications of robot do not require a precise orientation control.

• Korean Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.211-222
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• 1998

Parametric design is an important modeling paradigm in CAD/CAM applications, enabling efficient design modifications and variations. One of the major issues in parametric design is to develop a geometric constraint solver that can handle a large set of geometric configurations efficiently and robustly. In this appear, we propose a new approach to geometric constraint solving that employs a graph-based method to solve the ruler-and-compass constructible configurations and a numerical method to solve the ruler-and-compass non-constructible configurations, in a way that combines the advantages of both methods. The geometric constraint solving process consists of two phases: 1) planning phase and 2) execution phase. In the planning phase, a sequence of construction steps is generated by clustering the constrained geometric entities and reducing the constraint graph in sequence. in the execution phase, each construction step is evaluated to determine the geometric entities, using both approaches. By combining the advantages of the graph-based constructive approach with the universality of the numerical approach, the proposed approach can maximize the efficiency, robustness, and extensibility of geometric constraint solver.