• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.445-456
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• 2005

The research concentrates on improving the in-hole seismic probe, which has been developed in past five years, to be used in stiffness measurements of tunnel-face materials. The probe was down-sized to be fit in 45-mm diameter holes(or BX) drilled by a jumbo-drill, which is used to drill holes to install explosives for tunneling. Also trigger system was improved by using a down-speeding motor for operating convenience and air packing system was replaced with a set of plate-springs to eliminate supply of compressed air. These modifications are to adjust the probe for the unfavourable environment inside of tunnels and to test without any further drilling cost. The probe and testing procedure were successfully adopted with horizontal holes drilled by a jumbo-drill at a tunnel-face to evaluate the stiffness of rock mass. The measured shear wave velocities can be used to estimate deformation properties of rock mass for tunnel analyses.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.217-224
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• 1994

The combination of both phase-shifting convolution and 2-bit quantization smoothing filter was used to reduce speckle noise from saw-tooth speckle fringes phase map, obtained in phase-shifting speckle interferometer. The phase-shifting convolution showed the noise reduction capability of speckle fringe without destroying edge information across 271 jump. Also, it was shown that the 2-bit quantization smoothing filter was superior to average, low-pass filter and median filter in speeding up smoothing process and enhancing SIN ratio. Finally, a path dependent unwrapping algorithm was used to unwrap a noise reduced 271 modulo speckle phasemap. semap.

• Tribology and Lubricants
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• v.29 no.4
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• pp.242-247
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• 2013

This study aims to establish the fundamental basis for the design of materials used in high-speed trains, by using a lab-scale dynamometer to evaluate the characteristic behavior of metallic sintered friction materials in relation to the shape of graphite. The test results clearly demonstrate that when flake graphite and granular graphite are added equivalently, the average coefficient of friction is much lower, and it is less influenced by speed variation; moreover, friction wear is observed to be insignificantly low. Adding flake graphite increases the coefficient of friction, which leads to higher friction wear. In addition, the roughness of the disc surface was equivalent regardless of the shape of the graphite.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.753-758
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• 2000

Heat engine and fluid machinery in the plant have to linked with various ducts network and the corresponding design have to be concerned about effectiveness and stability of system of plant. To optimum control and design system concerning stability, economization, operating effectiveness we have to exact analysis flow properties of a duct applying to fluid machinery, heat exchanger, cooling machine, air conditioning equipment. therefore, it is necessary to research the duct, heat transfer equipment, for increasing overall effectiveness of air conditioning system by suggesting basic data of the duct resulting from organic research. So we can contribute to technical development of the duct. In case of speeding up the flow rate of the duct, lots of wave velocity components are occurred the value of boundary layer resulting from developing the boundary layer at both walls of duct.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.358-365
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• 2005

In induction machine drive without a speed sensor, the estimation of the motor flux and speed often becomes deteriorated at low speeds with low back EMF. Our analysis shows that, in addition to the state resistance variation, the estimated value of field orientation angle is often corrupted by accumulative errors from the integration of voltage variables at motor terminals that have low signal/noise ratio at low frequencies. A repetitive loop path of integration in the feedback can amplify this type of error, thus speeding up the degradation process. The control system runs into information starvation due to the loss of correct field orientation. The machine's spiral vectors are controlled only in a reduced dimension in this situation. A novel control scheme is developed to improve the control performance of motor's current, torque and speed at low frequencies. The scheme gains a full-dimensional vector control and is less sensitive to the combined effect of the error sources at the low frequencies. Experimental tests demonstrate promising performances are achievable even below 0.5 Hz.

• Journal of the Korean Professional Engineers Association
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• v.42 no.2
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• pp.41-48
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• 2009

The Government declared 'Low-Carbon Green Growth' as the new national vision for future development to improve economic growth and quality of life through higher energy efficiency, less energy consumption, wider use of renewable energy, etc. Korea can no longer delay participating in international efforts against global warming by reducing carbon dioxide and other greenhouse gas emissions. Thus low-carbon green growth is not a matter of choice, and it becomes indispensible to sustaining the nation's economic development. The Government is determined to take the initiative in speeding up economic recovery by carrying out the large scale investment projects such as the Korean version of a 'Green New Deal. The 49 trillion-won projects include river improvement, eco-friendly transportation networks, advanced information infrastructure, water resources & dam construction, green cars & clean energy development, etc. which will create nearly one million new jobs over the next four years.

• International Journal of Contents
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• v.5 no.4
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• pp.55-61
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• 2009

In this paper, we propose a hierarchical method for segmenting a given 3D mesh, which hierarchically clusters sharp vertices of the mesh using the metric of geodesic distance among them. Sharp vertices are extracted from the mesh by analyzing convexity that reflects global geometry. As well as speeding up the computing time, the sharp vertices of this kind avoid the problem of local optima that may occur when feature points are extracted by analyzing the convexity that reflects local geometry. For obtaining more effective results, the sharp vertices are categorized according to the priority from the viewpoint of cognitive science, and the reasonable number of clusters is automatically determined by analyzing the geometric features of the mesh.

• Journal of the Korean Statistical Society
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• v.32 no.4
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• pp.401-409
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• 2003

We consider a particle walking on the nonnegative integers and each unit of time it makes, given it is at site k, either a jump of size m distance units to the right with probability $p_{k}$ or it goes back (falls down) to its starting point 0, a retaining barrier, with probability $v_{k}\;=\;1\;-\;p_{k}$. This is a Markov chain on the integers $mZ^{+}$. We show that if $v_{k}$ has a nonzero limit, then the Markov chain is positive recurrent. However, if $v_{k}$ speeds to 0, then we may get transient Markov chain. A critical speeding rate to zero is identified to get transience, null recurrence, and positive recurrence. Another type of random walk on $Z^{+}$ is considered in which a particle moves m distance units to the right or 1 distance unit to left with probabilities $p_{k}\;and\;q_{k}\;=\;1\;-\;p_{k}$, respectively. A necessary condition to having a stationary distribution and positive recurrence is obtained.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.77-80
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• 2010

The demand for human security significantly promotes the development of surveillance applications using a multi-sensor integrated UAV system. For more sophisticated operations, the system should provide a sequence of images rectified in a ground coordinate system in realtime. This rectification requires accurate position and attitude of the camera at the time of exposure of each image, which can be estimated through an Aerial Triangulation process using the GPS/INS data and tie points between adjacent images. In this work, the KLT tracker is utilized to obtain the tie points. To satisfy the realtime requirements, we present an approach to speed up the tracker by supplying the initial guessed positions of tie points based on the exterior orientation. The experimental results show that, when the guessed positions are supplied, the KLT tracker consumed less computational time than the ordinary KLT which is more suitable to be incorporated into the realtime image georeferencing process.

• Journal of the Korea Society of Computer and Information
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• v.22 no.10
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• pp.93-100
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• 2017

Current internet has evolved from the sharing and efficiency aspects of information, it is still vulnerable to the fact that the Internet is not secure in terms of security and is not safe to secure of security mechanism. Repeating patches on continuous hacking are continuously demanding additional resources for network or system equipment, and consequently the costs continue to increase. Businesses and individuals alike are speeding up the damage caused by crime like of ransomware, not jusy simple attacks, and businesses and individuals need to respond to cyber security. In addition, the ongoing introduce of security device, and separate of networks for secure transmission of contents in the existing TCP/IP system, but it is still lacking in security. To complement the security implications of this existing TCP/IP Internet Protocol, we intend to propose a Secure Contents Transport System (SCTS) on the network using the CCN concept.