• Journal of Biosystems Engineering
• /
• v.33 no.4
• /
• pp.217-223
• /
• 2008

In this study, a garlic clove planter which is capable of planting holes in soil and planting a clove at the same time was designed and tested for film mulched beds. Planting characteristics of the planter were measured through field experiment. Some characteristics were analyzed with multibody dynamic simulation software. Simulation was performed on opening time of the planting hopper. Measured characteristics were position, angle, and reposition amount of garlic in sowing hole. Experiment results showed that the planted position of garlic in planting was 23.0 mm from the hole wall. The reposition amount of garlic was varied with its position and angle when the planted garlic was pressed by an angled compaction wheel. In case of type II position, the position movement of garlic was larger than type I. Average position movement of type II was 11.5 mm at $20^{\circ}$ of compaction wheel angle. These data suggest that cutting diameter of film opening must be larger than 33 mm to provide enough space for garlic sprouting. Also, simulation results showed that the maximum opening time of the planting hopper was 0.26 second.

• Journal of Aerospace System Engineering
• /
• v.12 no.4
• /
• pp.18-25
• /
• 2018

The head frame structure of a machine tool for aircraft parts, which requires machining precision and machining of difficult-to-cut materials is required to be light-weighted for precision high-speed machining and to minimize possible deformation by cutting force. To achieve high stiffness and for light-weight structure optimization design, a preliminary model was designed based on finite element analysis. The topology optimization design of light-weight, high stiffness, and low vibration frame structure were performed by minimizing compliance. As a result, the frame weight decreased by 17.3%, the maximum deflection was less than 0.007 mm, and the natural frequency increased by 30.6%. The static stiffness was increased in each axis direction and the dynamic stiffness exhibited contrary results according to the axis. Optimized structure with the high stiffness of low vibration in topology optimization design was confirmed.

• 한국터널공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.233-247
• /
• 2005

Most tunnel lining material which has been used in the domestic is a concrete. But many problems as the construction period, the cost, and the crack occurrence for the design, construction, and management were happened in the concrete lining. For this reason, many research institutes like the Korea Highway Corporation recognize the necessity of an alternate material development and grow on the interest for that. So in this study, the seismic behaviour characteristics for the application of the Corrugated Steel Plate Lining in cut-and-cover tunnel are evaluated as several conditions for the backfill height, the cutting slope, and the relative density of backfill soil are changed. The compressive stress which is calculated in the Corrugated Steel Plate Lining by the seismic load is decreased as the backfill height increases and the cut slope grows gentle. Also, the moment shows the tendency of decrease according to the increase of the backfill height. But in the case of the relative density of the backfill soil is small, the moment increases according to the increase of the backfill height and affects the dynamic behaviour characteristic. So it is considered that the relative density of the backfill soil is also the important point. As the result in analyzing the seismic response characteristics of the reinforcement spacing of the Corrugated Steel Plate, the variation in the compressive force is hardly happened, but the moment and the shear force increase on the reinforcement spacing being narrow.

• Journal of Gifted/Talented Education
• /
• v.18 no.3
• /
• pp.465-496
• /
• 2008

With leadership and speciality, creativity is cutting a fine figure among major values of human resource in 21C knowledge-based society. In the 7th school curriculum much emphasis is put on the importance of creativity by pursuing the image of human being based on creativity based on basic capabilities'. Also creativity is one of major factors of giftedness, and developing one's creativity is the core of the program for gifted education. Doing mathematics requires high order thinking and knowledgeable understandings. Thus mathematical creativity is used as a measure to test one's flexibility, and therefore it is the basic tool for creativity study. But theoretical study for mathematical creativity is not common. In this paper, we discuss mathematical creativity applied to 6 approaches suggested by Sternberg and Lubart in educational theory. That is, mystical approaches, pragmatical approaches, psycho-dynamic approaches, cognitive approaches, psychometric approaches and scio-personal approaches. This study expects to give useful tips for understanding mathematical creativity and understanding recent research results by reviewing various aspects of mathematical creativity.

• Journal of Computational Design and Engineering
• /
• v.1 no.1
• /
• pp.27-36
• /
• 2014

Similar to the essential components of many mechanical systems, the geometrical properties of the teeth of spiral bevel gears greatly influence the kinematic and dynamic behaviors of mechanical systems. Logarithmic spiral bevel gears show a unique advantage in transmission due to their constant spiral angle property. However, a mathematical model suitable for accurate digital modeling, differential geometrical characteristics, and related contact analysis methods for tooth surfaces have not been deeply investigated, since such gears are not convenient in traditional cutting manufacturing in the gear industry. Accurate mathematical modeling of the tooth surface geometry for logarithmic spiral bevel gears is developed in this study, based on the basic gearing kinematics and spherical involute geometry along with the tangent planes geometry; actually, the tooth surface is a parametric surface defined on a parallelogrammic domain. Equivalence proof of the tooth surface geometry is then given in order to greatly simplify the mathematical model. As major factors affecting the lubrication, surface fatigue, contact stress, wear, and manufacturability of gear teeth, the differential geometrical characteristics of the tooth surface are summarized using classical fundamental forms. By using the geometrical properties mentioned, manufacturability (and its limitation in logarithmic spiral bevel gears) is analyzed using precision forging and multiaxis freeform milling, rather than classical cradle-type machine tool based milling or hobbing. Geometry and manufacturability analysis results show that logarithmic spiral gears have many application advantages, but many urgent issues such as contact tooth analysis for precision plastic forming and multiaxis freeform milling also need to be solved in a further study.

• Journal of the Institute of Convergence Signal Processing
• /
• v.13 no.2
• /
• pp.70-76
• /
• 2012

In this paper, an automatic extraction method of glomerulus region from human renal tissue image is presented. The important information reflecting the state of kidneys richly included in the glomeruli, so it should be the first step to extract the glomerulus region from the renal tissue image for the further quantitative analysis of the renal condition. Especially, there is no clear difference between the glomerulus and other tissues, so the glomerulus region can not be easily extracted from its background by the existing segmentation methods. The outer edge of a glomerulus region is regarded as a common property for the regions of this kind ; a two- dimensional Gaussian distribution is used to convolve with an original image first and then the image is thresholded at this blurred image ; a closed curve corresponding to the outer edge can be obtained by usual pattern processing skills like thinning, branch-cutting, hole-filling etc., Finally, the glomerulus region can be obtained by extracting the area in the original image surrounded by the closed curve. The glomerulus regions are correctly extracted by 85 percentages and experimental results show the proposed method is effective.

• Earthquakes and Structures
• /
• v.17 no.2
• /
• pp.175-189
• /
• 2019

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.6
• /
• pp.98-105
• /
• 2019

In order to improve the fuel economy and dynamic behavior of automobiles, the weight reduction tendency of automobile parts is obvious. Also, in order to maximize assembly and maintenance convenience, various parts are integrated and modularized. Multi-piece methods require many manufacturing processes and become a factor of lowering the strength of parts. It is advantageous to overcome the disadvantages by integrally manufacturing to reduce the processing steps and ensure the strength of the parts. However, when it is necessary to process in a narrow space inside the part, it is impossible to process with the existing spindle. The angle head spindle is only a component of a machine tool, but it is a core part that requires high technology and is highly utilizable in products requiring high precision machining. Therefore, various and continuous studies needs for angle head spindles in areas such as vibration absorption, operational safety, excellent dimensional stability, and strength. In this paper, we propose an optimal design for angle head spindle by performing structural analysis and shape optimization for angle head spindle gear and case.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.1 s.53
• /
• pp.88-96
• /
• 2009

This study proposes a wireless measurement system that is a new safety management system by using an FBG sensor and a PDA. The sensor part has many advantages of implementing a wireless measurement system, and the study emploies an FBG-LVDT sensor, FBG-STRAIN sensor, FBG-TEMP sensor, and FBG-ACC sensor, using FBG sensors. Also, the study show a configuration of a signal process system for operating a wireless transmission system of FBG sensors applied to the signal process system, and engrafted the cutting edge information technology industry in order to display from a remote distance using a PDA. In order to verify the applicability of the developed FBG sensors and wireless measurement monitoring system to the field, their accuracy, and usability, the study has conducted a static and dynamic test to a bridge in the field. The study made an assessment of service for the vibration of the bridge by applying dynamic data measured by an FBG-LVDT sensor and FBG-ACC sensor to Meister's curve and prepared methods for assessing the vibration of the bridge by proposing a standard of vibration limitation given the service of vibration of the bridge. As a follow up for this study, it would be necessary to set up an overall model for the standard of service assessment established in this study.

• Restorative Dentistry and Endodontics
• /
• v.32 no.2
• /
• pp.130-137
• /
• 2007

This in vitro study examined the effect of surface defects on cutting blades on the extent of the cyclic fatigue fracture of HEROShaper Ni-Ti rotary files using fractographic analysis of the fractured surfaces. A total of 45 HEROShaper (MicroMega) Ni-Ti rotary flies with a #30/.04 taper were divided into three groups of 15 each. Group 1 contained new HEROShapers without any surface defects. Group 2 contained HEROShapers with manufacturing defects such as metal rollover and machining marks. Croup 3 contained HEROShapers that had been clinically used for the canal preparation of 4-6 molars A fatigue-testing device was designed to allow cyclic tension and compressive stress on the tip of the instrument whilst maintaining similar conditions to those experienced in a clinic. The level of fatigue fracture time was measured using a computer connected the system. Statistical analysis was performed using a Tukey's test. Scanning electron microscopy (SEM) was used for fractographic analysis of the fractured surfaces. The fatigue fracture time between groups 1 and 2, and between groups 1 and 3 was significantly different (p<0.05) but there was no significant difference between groups 2 and 3 (p>0.05). A low magnification SEM views show brittle fracture as the main initial failure mode At higher magnification, the brittle fracture region showed clusters of fatigue striations and a large number of secondary cracks. These fractures typically led to a central region of catastrophic ductile failure. Qualitatively, the ductile fracture region was characterized by the formation of microvoids and dimpling. The fractured surfaces of the HEROShapers in groups 2 and 3 were always associated with pre-existing surface defects. Typically, the fractured surface in the brittle fracture region showed evidence of cleavage (transgranular) facets across the grains, as well as intergranular facets along the grain boundaries. These results show that surface defects on cutting blades of Ni-Ti rotary files might be the preferred sites for the origin of fatigue fracture under experimental conditions. Furthermore this work demonstrates the utility of fractography in evaluating the failure of Ni-Ti rotary flies.