• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.102-112
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• 2005

In this work, we developed fully integrated broadband MMIC chip set employing CSP(Chip Size Package) for K/Ka band applications. By utilizing an ACF for the RF-CSP, the fabrication process for the packaged amplifier MMIC could be simplified and made cost effective. $STO(SrTi_{3})$ capacitors were employed to integrate the DC biasing components on the MMIC, and LC parallel circuits were employed for DC feed and ESD protection. A pre-matching technique and RC parallel circuit were used to achieve a broadband matching and good stability fer the amplifier MMIC in K/Ka band. The amplifier CSP MMIC exhibited good RF performance over a wide frequency range in K/Ka band. This work is the first report of a fully integrated CSP amplifier MMIC successfully operating in the K/Ka band.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1091-1098
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• 2009

In this paper, we designed the authentication system for home network service and applied it to actual sensor nodes. The pair-wise pre-distribution key skim is applied for prevention of authentication key from sniffing on the wireless sensor networks. The authentication key and data are encrypted by using the CBC mode RC5 algorithm based on the SPINS. The experimental environment consists of a base station (BS)and sensor nodes and each sensor node sends both sensing data and the encrypted authentication key to the BS. For simulations we set up some what-if scenarios of security menaces in home network service.Slightly modified the TOS_Msg data arrays of TinyOS is suggested to store 8-byte authentication key which can enable data encryption and authentication at the each sensor node. As a result, malfunction caused by communication between BS and nodes of other groups of added nodes having malicious purpose can be protected. Also, we confirmed that a critical data of home networking service like vital signal can be transmitted securely through this system by encryption technique.

• Journal of Biosystems Engineering
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• v.34 no.4
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• pp.278-285
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• 2009

Navigation system is applied in variety of fields including the simple location positioning, autopilot navigation of unmanned robot tractor, autonomous guidance systems for agricultural vehicles, construction of large field works that require high precision and map making process. Particularly utilization of GPS (Global Positioning System) is very common in the present navigation system. This study introduces a navigation system for autonomous field robot that travels to the pre-input path using GPS information. Performance of the GPS- based navigation is highly depended on its receiving rate because GPS receivers do not acquire any navigation information in the period between the refresh intervals. So this study presents an algorithm that improves an accuracy of the navigation by estimation the positional information during the blind period of a low rate GPS receiver. In fact the algorithm calculated the robot's heading in a 50 Hz rate, so the blind period of an 1 Hz GPS receiver is extensively covered. Consequently implementation of the algorithm to the GPS based navigation showed an improvement in guidance accuracy. The conventional field robot directly carried an expensive control computer and sensors onboard, therefore the miniaturization and weight reduction of the robot was limited. In this paper, the field robot carried only communication equipments such as GPS module, normal RC receiver, and bluetooth modem. This enabled the field robot to be built in an economic cost and miniature size.

• Journal of Ginseng Research
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• v.31 no.3
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• pp.159-174
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• 2007

Pharmacology of Korean Red ginseng gives us unique possibility to develop new class of antiepileptic drugs today and to improve one's biological activity. The chemical structures of ginsenosides (GS) have some principal differences from well-known antiepileptic new generation drugs. The antiepileptic effect of GS was also demonstrated in all models of epilepsy in rats (young and adult), which have studied, in all models of epilepsy including status epilepticus (SE), induced by lithium - pilocarpine. In our experiments in rats new evidences on protective effects were exerted as a result of premedication by GS. Pre-treatment of several GS could induce decrease of the seizures severity and brain structural damage (by MRI), neuronal degeneration in hippocampus. Wave nature of severity of motor seizures during convulsive SE was observed during lithium-pilocarpine model of SE in rats (the first increase of seizures was 30 min after the beginning of SE and the second - 90 min after. The efficacy of treatment on SE by ginsenoside as expected was observed after no less 3 weeks by daily GS i.p. administration. It is blocked SE or significantly decrease the severity of seizures during SE. The implication of presented data is that combination of ginsenosides from Korean Red ginseng and ginseng cell culture Dan25 that could be applied for prevention of epileptical status development. However, a development of optimal ratio of different ginsenosides $(Rb_1$ Rc, Rg, Rf,) should consummate in the new antiepileptic drug development.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1429-1435
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• 2004

In this work, high performance broadband amplifier MMIC including all the matching and biasing components, and electrostatic discharge (ESD) protection circuit was developed for K/Ka band applications. Therefore, external biasing or matching components were not required for the operation of the MMIC. STO (SrTiO3) capacitors were employed to integrate the DC biasing components on the MMIC, and miniaturized LC parallel ESD protection circuit was integrated on MMIC, which increased ESD breakdown voltage from 10 to 300 V. A pre-matching technique and RC parallel circuit were used for the broadband design of the amplifier MMIC. The amplifier MMIC exhibited good RF performances and good stability in a wide frequency range. The chip size of the MMICs was $1.7{\pm}0.8$ mm2.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.21-34
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• 2008

An improved optimum design method for reinforced concrete frames using integrated genetic algorithm(GA) with direct search method is presented. First, various sets of initially assumed sections are generated using GA, and then, for each resultant design member force condition optimum solutions are selected by regression analysis and direct search within pre-determined design section database. In advance, global optimum solutions are selected from accumulated results through several generations. Proposed algorithm makes up for the weak point in standard genetic algorithm(GA), that is, low efficiency in convergence causing the deterioration of quality of final solutions and shows fast convergence together with improved results. Moreover, for the purpose of elevating economic efficiency, optimum design based on the nonlinear structural analysis is performed and therefore makes all members resist against given loading condition with the nearest resisting capacity. The investigation for the effectiveness of the introduced design procedure is conducted through correlation study for example structures.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.368-372
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• 2007

Recently, construction companies prefer to use large scale system forms to prepare for lacking of skilled workers, aging and the chances of application of pre-build&post-sale policy. In result of the effort and interest, the duration for framework of domestic high rise buildings has been accomplished to 3-4days per floor but for the apartment housing which form over 90% of the domestic construction industry, and especially the middle story RC apartments which is the main part, the duration for framework is only about 6-8days per level. This is only about 50% of the duration per level of RC residential buildings in North America. In previous researches elementary technology, which has potential of duration reduction, was proposed and this research suggest the applicability in construction sites and ways to improve it using elementary technology applied Mock-up Test. Furthermore, we analyze the productivity and T/C usage rate of the 6day-Cycle and suggest an improved model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.56-64
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• 2019

Various defects that occur in the maintenance stage are connected to all kinds of wasted resources and economic losses as additional investments are made. Residents are harmed temporally, materially, and psychologically, and businesses suffer not only monetary losses but also reduced credit ratings. The aim of this study was to increase the efficiency of quality management and minimize defect disputes by estimating the importance of the defect type considering the defect frequency and severity in apartment buildings. For this, 7,548 defect items for 48 apartment buildings were examined. The analysis confirmed that defects are concentrated on RC, finishing and MEP work. In addition, defects with high importance are identified as broken, incorrect installation, missing tasks, and water problems. In addition, the exterior wall/roof, the Internal wall, ceiling, and floor, which are constructed in the field, are more important than the furniture and MEP equipment installed in the field.

• Computers and Concrete
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• v.24 no.2
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• pp.159-172
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• 2019

This paper presents an investigation into the flexural behavior of reinforced concrete (RC) beams retrofitted by ultra-high performance fiber-reinforced concrete (UHPFRC) layers. The experimental study has been conducted in two parts. In the first part, four methods of retrofitting with UHPFRC layers in both the up and down sides of the beams have been proposed and their efficiency in the bonding of the normal concrete and ultra-high performance fiber-reinforced concrete has been discussed. The results showed that using the grooving method and the pre-casted UHPFRC layers in comparison with the sandblasting method and the cast-in-place UHPFRC layers leads to increase the load carrying capacity and the energy absorption capacity and causes high bond strength between two concretes. In the second part of the experimental study, the tests have been conducted on the beams with single UHPFRC layer in the down side and in the up side, using the effective retrofitting method chosen from the first part. The results are compared with those of non-retrofitted beam and the results of the first part of experimental study. The results showed that the retrofitted beam with two UHPFRC layers in the up and down sides has the highest energy absorption and load carrying capacity. A finite element analysis was applied to prediction the flexural behavior of the composite beams. A good agreement was achieved between the finite element and experimental results. Finally, a parametric study was carried out on full-scale retrofitted beams. The results indicated that in all retrofitted beams with UHPFRC in single and two sides, increasing of the UHPFRC layer thickness causes the load carrying capacity to be increased. Also, increases of the normal concrete compressive strength improved the cracking load of the beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.311-318
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• 2006

This paper presents experimental studies on investigating the seismic retrofit performance of reinforced concrete circular columns with poor lap-splice details using GFRP wrapping. Five full-scale model columns have been tested. The prototype structure is an existing circular reinforced concrete bridge piers designed following the pre-seismic codes and constructed in South Korea in 1979. The as-built column will be expected to suffer brittle failure due to the bond failure of lap-spliced longitudinal reinforcement. The retrofitted columns using GFRP wrapping showed significant improvement of seismic performance. However, the predicted flexural failure mode was not achieved and the longitudinal bars were not yielded. Failure modes of the retrofitted columns are considered to be the gradually delayed bond slip in lap-spliced longitudinal reinforcement. Suggested retrofit design methods using GFRP were validated experimentally.