• Publications of The Korean Astronomical Society
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• 제36권3호
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• pp.65-78
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• 2021

Jagyeokru, an automatic striking water clock described in the Sejong Sillok (Veritable Records of King Sejong) is essentially composed of a water quantity control device and a time-signal device, with the former controlling the amount or the flow rate of water and the latter automatically informing the time based on the former. What connects these two parts is a signal generating device or a power transmission device called the 'Jujeon' system, which includes a copper rod on the float and ball-racked scheduled plates. The copper products excavated under Gongpyeong-dong in Seoul include a lot of broken plate pieces and cylinder-like devices. If some plate pieces are put together, a large square plate with circular holes located in a zigzag can be completed, and at the upper right of it is carved 'the first scheduled plate (一箭).' Cylinder-like devices generally 3.8 cm in diameter are able to release a ball, and have a ginkgo leaf-like screen fixed on the inner axis and a bird-shaped hook of which the leg fixes another axis and the beak attaches to the leaf side. The lateral view of this cylinder-like device appears like a trapezoid and mounts an iron ball. The function of releasing a ball agrees with the description of Borugak Pavilion, where Jagyeokru was installed, written by Kim Don (1385 ~ 1440). The other accounts of Borugak Pavilion's and Heumgyeonggak Pavilion's water clocks describe these copper plates and ball releasing devices as the 'Jujeon' system. According to the description of Borugak Pavilion, a square wooden column has copper plates on the left and right sides the same height as the column, and the left copper plate has 12 drilled holes to keep the time of a 12 double-hours. Meanwhile, the right plate has 25 holes which represent seasonal night 5-hours (Kyeong) and their 5-subhours (Jeom), not 12 hours. There are 11 scheduled plates for seasonal night 5-hours made with copper, which are made to be attached or detached as the season. In accordance with Nujutongui (manual for the operation of the yardstick for the clepsydra), the first scheduled plate for the night is used from the winter solstice (冬至) to 2 days after Daehan (大寒), and from 4 days before Soseol (小雪) to a day before the winter solstice. Besides the first scheduled plate, we confirm discovering a third scheduled plate and a sixth scheduled plate among the excavated copper materials based on the spacing between holes. On the other hand, the width of the scheduled plate is different for these artifacts, measured as 144 mm compared to the description of the Borugak Pavilion, which is recorded as 51 mm. From this perspective, they may be the scheduled plates for the Heumgyeonggak Ongru made in 1438 (or 1554) or for the new Fortress Pavilion installed in Changdeokgung palace completed in 1536 (the 31^st year of the reign of King Jungjong) in the early Joseon dynasty. This study presents the concept of the scheduled plates described in the literature, including their new operating mechanism. In addition, a detailed model of 11 scheduled plates is designed from the records and on the excavated relics. It is expected that this study will aid in efforts to restore and reconstruct the automatic water clocks of the early Joseon dynasty.

• The Transactions of the Korean Institute of Electrical Engineers D
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• 제53권1호
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• pp.32-39
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• 2004

The color-based vision systems have been used to recognize our team robots, the opponent team robots and a ball in the robot soccer system. The color-based vision systems have the difficulty in that they are very sensitive to color variations brought by brightness changes. In this paper, a neural network trained with data obtained from various illumination conditions is used to classify colors in the modified YUV color space for the robot soccer vision system. For this, a new method to measure brightness is proposed by use of a color card. After the neural network is constructed, a look-up-table is generated to replace the neural network in order to reduce the computation time. Experimental results show that the proposed color classification method is robust under illumination variations.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 한국퍼지및지능시스템학회 2000년도 추계학술대회 학술발표 논문집
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• pp.448-451
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• 2000

Fuzzy control has been researched for application of industrial processes which have no accurate mathematical model and could not controlled by conventional methods because of a lack of quantitative input-output data. Intelligent control approach based on fuzzy logic could directly reflex human thinking and natural language to controller comparing with conventional methods. In this paper, the tested system is constructed for sending a ball to the goal position using wind from two DC motors in the path. This system contains non-linearity and uncertainty because of the characteristic of aerodynamics inside the path. The system used in this experiment could be hardly modeled by mathematic methods and could not be easily controlled by linear control manners. The controller, in this paper could control the system containing non-linearity and uncertainty because it is designed based on the input-output data and experimental knowledge obtained by trials.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.416-421
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• 2002

The purpose of t his paper is to database each factors from experimental results and develop the servo-controlled feeding system on these database. At first, spring back and bending farce are analyzed by basic theory of bending processing. In database, through practical experiment by the expert various types of bending angel and thickness of plate are tested and classified with SB34P and Aluminum. For the development of servo-controlled feeding system, automatic feeding system is designed and manufactured with ball screw and LM guide and performance of the developed feeding system is tested under condition of standard machine tool examination. Also, Mechanical consideration of mainframe in press brake, development of controller based on NC, program for servo-control are studied. Finally, based on experimental data, the system is operated and compared with theoretical data

• Journal of the Korean Society of Manufacturing Technology Engineers
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• 제22권3호
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• pp.380-387
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• 2013

In this study, two finite element (FE) models were developed to evaluate the thermal characteristics of a feeding axis of a CNC lathe. One was used for analysis of heat transfer to identify the temperature distribution of the feeding axis and then, the other was used for analysis of thermal deformation to evaluate its structural behavior based on the temperature distribution. The FE models were based on the test standard for the axial thermal displacement. The feeding velocity was composed of three steps: the ascending, constant, and descending velocities. Therefore, the heat generation and convection coefficient were calculated for each velocity and applied to the thermal FE model. The convection coefficient for the ball screw rotation was based on an experimental equation. The result of the analytical thermal displacement was compared with that of the experimental displacement to verify the finite element models.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.882-887
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• 2005

The paper describes Quasi-simultaneous recognition of plural targets and motion control of robot based on the recognition. The method searches for targets by model-based matching method using the hybrid GA, and the motion of the robot is generated based on the targets' positions on the image. The method is applied to a soccer robot, and targets are a ball, a goal, and an enemy in the experiment. The Experimental results show robustness and reliability of the proposed method.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.494-499
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• 2003

This paper concerns the static, dynamic and thermal characteristics analysis of a high-speed spindle system for horizontal machining centers with 45mm x50,000rpm. The spindle system is designed based on the angular contact ceramic ball bearings, built-in motor, oil-air lubrication method and oil jacket cooling method. The structural and thermal analysis models of spindle system are constructed by the finite element method. The static and dynamic characteristics are estimated based on the static deformation, modal parameter, mode shape and frequency response function, and the thermal characteristics are estimated based on the temperature rise, temperature distribution and thermal deformation. The analysis results illustrate that the designed spindle system has excellent structural and thermal stabilities

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.333-334
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• 2023

Interest in the commercialization of research results is increasing according to the recent social atmosphere. In the field of construction, new technologies are also being actively commercialized. Pre-analysis of products is an important procedure for future market entry. This study aims to conduct a product-based importance-performance analysis as one of the preliminary analysis methods for the commercialization of technologies developed in the field of construction and to explore their applicability. This study conducts a survey on those involved by setting the categories of product quality, convenience, and usability for the commercialization of previously developed pipeline inspection product. Based on this, we would like to present an analysis that calculates importance and performance of the product and helps to set the development direction through interrelationship analysis.

• Journal of Powder Materials
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• 제27권5호
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• pp.414-419
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• 2020

In the present study, we investigated the austenite stability of a sintered Fe-based nanocrystalline alloy. The volume fraction of austenite was measured based on the X-ray diffraction data of sintered Fe-based nanocrystalline alloys, which were prepared by high-energy ball milling and spark plasma sintering. The sintered alloy samples showed a higher volume fraction of austenite at room temperature as compared to the equilibrium volume fraction of austenite obtained using thermodynamic calculations, which resulted from the nanosized crystalline structure of the sintered alloy. It was proved that the austenite stability of the sintered Fe-based alloy increased with a rise in the amount of austenite stabilizing elements such as Mn, Ni, and C; however, it increased more effectively with a decrease in the actual grain size. Furthermore, we proposed a new equation to predict the martensite starting temperature for sintered Fe-based alloys.

• Journal of Power System Engineering
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• 제11권1호
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• pp.121-126
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• 2007

This study aims at investigating the effect of heat treatment conditions on the dry sliding wear behavior of thermally sprayed Ni-based self-flux alloy coatings. Ni-based self-flux alloy powders were sprayed onto a carbon steel substrate and then heat-treated at 700, 800, 900 and $1000^{\circ}C$ for 30 minutes in a vacuum furnace. Dry sliding wear tests were performed using sliding speed of 0.4 m/s and applied load of 6 N. AISI 52100 ball(diameter 8 mm) was used as counterparts. Microstructure and wear behavior of both as-sprayed and heat-treated Ni-based self-flux alloy coatings were studied using a scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDX), electron probe micro-analysis(EPMA) and X-ray diffraction(XRD). It was revealed that microstructure and wear behavior of thermally sprayed Ni-based self-flux alloy coatings were much influenced by heat treatment conditions.