• Smart Structures and Systems
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• v.14 no.5
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• pp.917-942
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• 2014

Multivariate statistics based damage detection algorithms employed in conjunction with novel sensing technologies are attracting more attention for long term Structural Health Monitoring of civil infrastructure. In this study, two practical data driven methods are investigated utilizing strain data captured from a 4-span bridge model by Fiber Bragg Grating (FBG) sensors as part of a bridge health monitoring study. The most common and critical bridge damage scenarios were simulated on the representative bridge model equipped with FBG sensors. A high speed FBG interrogator system is developed by the authors to collect the strain responses under moving vehicle loads using FBG sensors. Two data driven methods, Moving Principal Component Analysis (MPCA) and Moving Cross Correlation Analysis (MCCA), are coded and implemented to handle and process the large amount of data. The efficiency of the SHM system with FBG sensors, MPCA and MCCA methods for detecting and localizing damage is explored with several experiments. Based on the findings presented in this paper, the MPCA and MCCA coupled with FBG sensors can be deemed to deliver promising results to detect both local and global damage implemented on the bridge structure.

• Smart Structures and Systems
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• v.26 no.5
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• pp.641-656
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• 2020

The finite element solutions of thermal buckling load values of the graded sandwich curved shell structure are reported in this research using a higher-order kinematic model including the shear deformation effect. The numerical buckling temperature has been computed using an in-house specialized code (MATLAB environment) prepared in the framework of the current mathematical formulation. In addition, the mathematical model includes the excess structural distortion under the influence of elevated environment via Green-Lagrange nonlinear strain. The corresponding eigenvalue equation has been solved to predict the critical buckling temperature of the graded sandwich structure. The numerical stability and the accuracy of the current solution have been confirmed by comparing with the available published results. Thereafter, the model is extended to bring out the influences of structural parameters i.e. the curvature ratio, core-face thickness ratio, support conditions, power-law indices and sandwich types on the thermal buckling behavior of graded sandwich curved shell panels.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.375-380
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• 2014

To enhance biocompatibility between the orthopedic implant stem and obsteoblast cells, bone-forming cells, micro-size holes are patterned in Ti plate surface. Initially, the house built laser power stabilization system is applied to the laser micro patterning machine to convince repeatable result. Various pulse widths are irradiated Ti plate and relationship between diameters of patterned holes and pulsed width is derived. Effect of multi pulse is observed and optimal pulse number is considered to avoid heat affected zone. After MG-63 osbeoblast cells are cultured, micro patterned Ti plates are compared with control plates. In SEM image, cells are well aligned and aggregation is observed in both 60, and $100{\mu}m$ patterned plates. Finally, free form surface stem model is prepared to test micro hole patterning.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.576-578
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• 2015

Interest in a comfortable living space is increasing as the home monitoring technology advances. This paper proposes design and implementation of home monitoring and controlling system using arduino and smartphone. To collect environmental data in home, various sensors are installed in the house. A user can monitor the sensed data and can send controlling message through the smartphone.

• Smart Structures and Systems
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• v.18 no.2
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• pp.293-315
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• 2016

Seismic isolation is often used in protecting mission-critical structures including hospitals, data centers, telecommunication buildings, etc. Such structures typically house vibration-sensitive equipment which has to provide continued service but may fail in case sustained accelerations during earthquakes exceed threshold limit values. Thus, peak floor acceleration is one of the two main parameters that control the design of such structures while the other one is peak base displacement since the overall safety of the structure depends on the safety of the isolation system. And in case peak base displacement exceeds the design base displacement during an earthquake, rupture and/or buckling of isolators as well as bumping against stops around the seismic gap may occur. Therefore, obtaining accurate peak floor accelerations and peak base displacement is vital. However, although nominal design values for isolation system and superstructure parameters are calculated in order to meet target peak design base displacement and peak floor accelerations, their actual values may potentially deviate from these nominal design values. In this study, the sensitivity of the seismic performance of structures equipped with linear and nonlinear seismic isolation systems to the aforementioned potential deviations is assessed in the context of a benchmark shear building under different earthquake records with near-fault and far-fault characteristics. The results put forth the degree of sensitivity of peak top floor acceleration and peak base displacement to superstructure parameters including mass, stiffness, and damping and isolation system parameters including stiffness, damping, yield strength, yield displacement, and post-yield to pre-yield stiffness ratio.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.33-42
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• 2020

Emission factors for ammonia and particulate matters (PMs) from livestock buildings are of increasing importance in view of the environmental protection. While the existing emission factors were determined based on the emission inventory of other countries, in situ measurement of emission factors is required to construct an accurate emission inventory for Korea. This study is to report measurements of ammonia and PMs emissions from mechanically-ventilated pig houses, which are common types of pig barns in Korea. Ventilation rates and concentrations of ammonia and PMs were measured at the ventilation outlets of a weaner unit, a growing pig unit and a fattening pig unit to calculated the emission factors. The PMs emission was characterized with different aerodynamic diameters (PM_2.5, PM₁₀, and total suspended particulates (TSP)). The measured ammonia emission factors for weaners, growing pigs and fattening pigs were 0.225, 0.869 and 1.679 kg animal^-1 yr^-1, respectively, showing linear increase with pigs' age. The PMs emission factors for three growing stages were 0.023, 0.237 and 0.241 kg animal^-1 yr^-1, respectively for TSP, 0.017, 0.072 and 0.223 kg animal^-1 yr^-1, respectively for PM₁₀, and 0.011, 0.016 and 0.151 kg animal^-1 yr^-1, respectively for PM_2.5. PMs emissions were increased with pigs' age due to increasing feed supply and animal movement. The measured emission factors were smaller than those of the existing emission inventory indicating that the existing ones overestimate the emissions from pig buildings and also suggesting that long-term in situ monitoring at various livestock buildings is required to construct the accurate emission inventory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.871-874
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• 2010

Needs for Smart Grid development are increasing all over the world as a solution to its problem according to depletion of energy resources, climatic and environmental rapidly change and growing demand for electrical power. Especially decentralized power is attracting world's attention. In this mood a new era for a unit scale of decentralized power environment is on its way in building. However there is a problem to have to be solved in the uniformity of power quality because the amount of power generated from renewable energy resources such as wind power and solar light is very sensitive to climate fluctuation. And thus this paper tries to suggest an energy management method on basis of real time monitoring for meteorological data. In the current situation of lacking in USN-based killer application in Smart Grid field, this paper proposes the USN-based DER management system which collects the meteorological data and control power system througout utilizing wireless sensor network technique this business. This communication technique is regarded to be efficient in aspects of installation cost and tits maintenance cost. The proposed EMS model embodies the method for predicting the power generation by monitoring and analyzing the climatic data and controling the efficient power distribution between the renewable energy and the existing power. The ultimate goal of this paper is to provide the technological basis for achieving zero-energy house.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.396-402
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• 2010

The tracking of current location of residents is an essential requirement for context-aware service of smart houses. This paper presents a wireless sensor network system which could detect location transition such as entrance and exit to a room and also identify the user who passed the room, without duty of wearing any sort of tag. We designed new sensor node to solve the problem of short operation lifetime of previous work[1] which has two pyroelectric infrared (PIR) sensors and an ultrasonic sensor, as well as a 2.4 GHz radio frequency wireless transceiver. The proposed user identification method is to discriminate a person based on his/her height by using an ultrasonic sensor. The detection idea of entering/exiting behavior is based on order of triggering of two PIR sensors. The topology of the developed wireless sensor network system is simple star structure in which each sensor node is connected to one sink node directly. We evaluated the proposed sensing system with a set of experiments for three subjects in a model house. The experimental result shows that the averaged recognition rate of user identification is 81.3% for three persons. and perfect entering/exiting behavior detection performance.

• Journal of Korean Society of Transportation
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• v.32 no.1
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• pp.27-38
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• 2014

Recently, urban and transportation planning for Transit Oriented Development(TOD) has become a major issue. For the effective policy implementation of TOD, it is important to understand the travel behavior of residents in housing areas. In this study, we compared the travel behaviors of residents by housing types based on 'the 2010 Household Travel Survey Data' focusing on metropolitan areas. By building an estimation model for subway trip frequency by housing types, it was identified that the factors influencing subway trips and ultimately suggested implications to increase the use of the subway. The highest share of bus mode was for detached house residents with 22.8%, whereas the share of subway mode was highest by efficiency apartment residents with 17.5%. Walking distance to the subway from efficiency apartment and row house were verified as 661meters and 749meters. As the residents of each housing type have more cars and bicycles, their subway trips were decreased. It was also found that subway trips were increased when the population density of residence was high with good accessibility to subway stations and poor accessibility to bus service. In this study, the statistical findings to differentiate the planning factors of public transportation by housing types were also provided. The results of this study would be used for urban design considering the travel behaviors of residents by housing types and can also be utilized for promoting the patronage of public transportation. Some limitations and a future research agenda have also been discussed.

• Journal of Digital Contents Society
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• v.16 no.5
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• pp.783-793
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• 2015

TV display which existed only in house started to show up out of house around us and now it found naturally its place in everywhere like street, bus, subway and elevator. It is called digital signage which showed up through digitalization of sign, that is, sign board and bulletin board. The distinction of digital sign from existing signs is that the latter one should go through physical process like removal after installation every time its contents are changed but the former one can produce its various outputs flexibly once it is installed. Also existing sign may be static image or 2 or 3 pieces of image to express simple motion while digital sign can contain multi media contents luxurious in design and motion. This paper confined the range of contents in digital signage in bus and subway. It needs to analyze characteristics of mass transportation-people of use, consumer by place and time, accommodation environment for consumer etc and arrange planned contents along with time and place. Developments of dedicated contents suitable to those digital signages will harmonize with place and time and promote the realm of digital signage which provides variety of experience to consumer and with which communication is possible and which is distinctive. Furthermore we may expect the birth of smart signage as a new media, in which fun and art are combined.