• Journal of Mechanical Science and Technology
• /
• v.17 no.12
• /
• pp.1835-1843
• /
• 2003

This paper introduces the development of the caliper system for a geometry PIG (Pipeline Inspection Gauge). The objective of the caliper system is to detect and measure dents, wrinkles, and ovalities affect the pipe structural integrity. The developed caliper system consists of a finger arm, an anisotropic permanent magnet, a back yoke, pins, pinholes and a linear hall effect sensor. The angle displacement of the finger arm is measured by the change of the magnetic field in sensing module. Therefore the sensitivity of the caliper system mainly depends on the magnitude of the magnetic field inside the sensing module. In this research, the ring shaped anisotropic permanent magnet and linear hall effect sensors were used to produce and measure the magnetic field. The structure of the permanent magnet, the back yoke and pinhole positions were optimized that the magnitude of the magnetic field range between a high of 0.1020 Tesla and a low of zero by using three dimensional nonlinear finite element methods. A simulator was fabricated to prove the effectiveness of the developed caliper system and the computational scheme using the finite element method. The experimental results show that the developed caliper system is quite efficient for the geometry PIG with good performance.

• The Journal of Korea Robotics Society
• /
• v.1 no.1
• /
• pp.17-24
• /
• 2006

Though the final goal of mobile robot navigation is to be autonomous, operators' intelligent and skillful decisions are necessary when there are many scattered obstacles. There are several limitations even in the camera-based tele-operation of a mobile robot, which is very popular for the mobile robot navigation. For examples, shadowed and curved areas cannot be viewed using a narrow view-angle camera, especially in bad weather such as on snowy or rainy days. Therefore, it is necessary to have other sensory information for reliable tele-operations. In this paper, sixteen ultrasonic sensors are attached around a mobile robot in a ring pattern to measure the distances to obstacles. A collision vector is introduced in this paper as a new tool for obstacle avoidance, which is defined as a normal vector from an obstacle to the mobile robot. Based on this collision vector, a virtual reflection force is generated to avoid the obstacles and then the reflection force is transferred to an operator who is holding a joystick to control the mobile robot. Relying on the reflection force, the operator can control the mobile robot more smoothly and safely. For this bi-directional tele-operation, a master joystick system using a hall sensor was designed to resolve the existence of nonlinear sections, which are usual for a general joystick with two motors and potentiometers. Finally, the efficiency of a force reflection joystick is verified through the comparison of two vision-based tele-operation experiments, with and without force reflection.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.21 no.4
• /
• pp.135-141
• /
• 2021

Interest is growing in the design and development of square wave driven BLDC permanent magnet motors suitable for industrial automation, and the development of position detection circuits and drivers. However, this motor is somewhat limited in its application despite the price and functional advantages due to the decrease in efficiency due to switching loss and vibration and noise. In the process of designing and assembling a BLDC motor, the magnetic pole angle is not uniform or the magnetic flux distribution is distorted due to problems in magnetic circuit design or product non-uniformity in the assembly process. Therefore, these things cause position detection deviation and deteriorate the motor characteristics. In addition, the sine wave driven BLDC system can operate stably only when the signal generated from the position sensor is accurately fed back to the driver. However, since the generated signal cannot perform stable position detection due to the occurrence of DC offset component due to magnetic flux density deviation or magnetization technology, which is an external influence, this study intends to study the proposed circuit that can remove the DC offset component.

• Journal of architectural history
• /
• v.31 no.6
• /
• pp.59-68
• /
• 2022

This paper is an architectural historical study on Chimi of Hwangnyongsa Temple. In this research, the shape and cross-section of the chimi are reviewed. The results of the study are as follows. The chimi is a form in which the head part facing the maru is omitted, and the upper and lower body are separated. The upper and lower bonds are assembled into a two types of joint throughout the side of the torso, and then bound with an iron strap. Because of the absence of ridge line in the front, and the narrow curved surface which makes the side plate close to the plane, the entire cross-section is triangular, and the rear plate maintains the shape of the chimi. The naerimmaru connected to the side of the chimi has a slope, so it is clear that the chimi was used on the woojingak-jibung(hipped-roof), and the wing part and back of the chimi are erected on the side roof. The height of the yongmaru and chunyeomaru is about the same and the roofing tiles of those are in contact. The roofing tiles of chunyemaru should be cut to fit the angle of the contacting part. The maru is 30 stories high of roofing tiles as a result of the on-board survey. Based on reference on the shape and timing of the production of chimi, the height of chimi, and the maru is believed to have been built before the Unified Silla Period and used in buildings with at least seven-kan frontage. Buildings corresponding to these construction conditions can be seen as Central hall and East hall in Hwangnyongsa temple.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.3
• /
• pp.201-210
• /
• 2013

The purpose of this study was to examine the species of 117 wooden elements which were used in the Daewungjeon Hall (National Treasure No. 805, constructed in A. D. 1659) of Bukjijangsa Temple, Daegu, Korea. Pillars were identified as 5 red pines (hard pines; most likely, Pinus densiflora S. et Z.), 2 Cerris section of subgenus Lepidobalanus (deciduous oaks) and 3 Tsuga spp. Hwalju columns were 3 Abies spp. and 1 red pine. Head-penetrating ties were 8 red pines and 1 Cerris sp.; Pyeongbang, 3 red pines and 6 Cerris spp. Purlins were identified as 17 red pines, 16 Cerris spp. and 1 Tsuga sp. Angle rafters were 3 red pines and 1 Cerris sp., and end angle rafters, 2 red pines, 1 Zelkova serrata and 1 exotic hard pine. All of brackets (31 woods), jangyeo (4) and deot-chunyeo (2) were identified as red pines. As a whole, red pines (70.1%) and Cerris (22.2%) were major species used in the Daewungjeon Hall of Bukjijangsa Temple. Tsuga, Abies and exotic hard pines seem imported woods used for recent repairs.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.11
• /
• pp.1645-1650
• /
• 2015

This paper presents the 3-dimensional electromagnetic field analysis method and correction of sensor distortion that is used by a motor speed sensor. The magnetic sensors are being expanded due to lower price than the other speed sensors such as resolver and encoder. Magnetic sensor generates sine and cosine waves when the motor rotates. However, the sine and cosine signals are distorted due to magnetic noise, which makes the angle error of the sensor, generated near by the Hall element. This paper defines an optimal design variables by using the Taguchi method to minimize output distortion of the magnetic sensor and permanent magnet. To enhance reliability of the magnetic position sensor from sensitivity error, assembly amplitude mismatch and the electrical angle, 3-Dimensional electromagnetic finite element method and correction algorithm errors were performed in due of the magnetic sensor in order to improve the quality of the initial production model.

• The Journal of Korean Physical Therapy
• /
• v.33 no.3
• /
• pp.148-154
• /
• 2021

Purpose: This study covered the effect of shoulder stabilization exercise on muscle activity, postural alignment and self-efficacy of the elderly people with round shoulders by visiting village hall in rural area. Methods: 40 elderly people with round shoulders were recruited for this study (experimental group: 20 subjects and control group: 20 subjects). The experimental group was asked to perform shoulder stabilization exercise 60 minutes per one time for 8 weeks and three times in a week and the control group was asked to receive education related to pain management for the initial one time. Before and after the experiment, we measured the subjects' muscle activity of upper trapezius, serratus anterior, infraspinatus, pectoralis major and the lower trapezius, then postural alignment of craniovertebral angle and round shoulder posture. In addition, self-efficacy is measured through the questionnaire. Results: Compared to the control group, the experimental group showed significant differences in the muscle activity of all muscles, posture alignment of the craniovertebral angle. round shoulder posture, and improvement of self-efficacy. Conclusion: We found that shoulder stabilization exercise is effective in muscle activity, postural alignment and self-efficacy of the elderly people through visit-rehabilitation service. This study can be used for improving the physical and mental abilities through active visit-rehabilitation service for areas where have poor medical benefits. It is considered that systematic visit rehabilitation service should have institutional framework ultimately.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.34 no.2
• /
• pp.99-104
• /
• 2021

Ion-beam sputtering (IBS) was used to deposit semiconducting IZTO (indium zinc tin oxide) thin films onto heavily-doped Si substrates using a sintered ceramic target with the nominal composition In0.4Zn0.5Sn0.1O1.5, which could work as a channel layer for oxide TFT (oxide thin film transistor) devices. The crystallization behavior and electrical properties were examined for the films in terms of deposition parameters, i.e. target tilt angle and substrate temperature during deposition. The thickness uniformity of the films were examined using a stylus profilometer. The observed difference in electrical properties was not related to the degree of crystallization but to the deposition temperature which affected charge carrier concentration (n), electrical resistivity (ρ), sheet resistance (Rs), and Hall mobility (μH) values of the films.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.10
• /
• pp.37-42
• /
• 2014

This paper discusses study of sensorless control of a variable speed switched reluctance motor (SRM) for electric AC compressors on electrical vehicles. A typical SRM drive requires a position sensor such as an encoder or hall sensor to measure the angular rotor position. However, harsh environment in electrical AC compressors for electric vehicles makes it difficult to use the position sensor in their motor drive system. Therefore, a sensorless control scheme for electric compressor motors utilizing magnetic characteristics of SRM with respect to position angle and phase current is proposed. The overall variable speed SRM drive with position sensorless control scheme has been modeled using Matlab/Simulink software and closed loop current control simulation is presented to validate the proposed sensorless drive control.

• Transactions of Materials Processing
• /
• v.19 no.7
• /
• pp.416-422
• /
• 2010

The $\{10\bar{1}2\}$ twinning characteristics, such as active twin variants, volume fraction of twins with strain, twin morphology, twin texture and angle relationship between twins, were dependent on the activation mode (i.e., tension parallel to the caxis or compression perpendicular to the c-axis). The selection criterion of active twin variants was governed by the Schmid law. This activation of selected twin variants depending on the activation mode consequently caused a totally different plastic deformation behavior in two activation modes. The differences in the deformation characteristics, such as flow stress and work hardening rate, between both activation modes were explained in relation with activation stresses for slips and twinning, relative activities of twinning and slips during plastic deformation, grain refining effect by twin boundaries (Hall-Petch effect), and twinning-induced change in activities of slips.