• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1252-1261
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• 2006

This paper summarizes theoretical work on the multichannel decentralized feedback control of sound radiation from aircraft trim panels using piezoceramic actuators. The aircraft trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. It is motivated by the localization of reduction in vibration of single channel active trim panels. 12-channel decentralized feedback control systems are investigated in terms of the reduction of noise and vibration for three configurations of sensor actuator pairs. Local coupling of the closely-spaced sensor and actuator pairs was modeled using single degree of freedom systems. The multichannel control system is characterized using the state-space model. For the stability point of view, the relative stability or robustness is evaluated by comparing the real part of eigenvalues of the system matrix for the three configurations. The control performance is also evaluated and compared for the three configurations. It is found that the multichannel system can lead to the globalization of the reduction in vibration and radiated noise. It does not appear to yield a significant improvement in the vibration because of decreased gain margin. However, the reduction in the radiated noise is remarkably improved due to the variation of the vibration pattern with the actuation configurations.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2033-2038
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• 2003

This paper describes an integrated navigation strategy for the autonomous service robot PSR. The PSR is under development at the KIST for service tasks in indoor public environments. The PSR is a multi-functional mobile-manipulator typed agent, which works in daily life. Major advantages of proposed navigation are as follows: 1) Structured control architecture for a systematic integration of various software modules. A Petri net based configuration design enables stable control flow of a robot. 2) A range sensor based generalized scheme of navigation. Any range sensor can be selectively applied using the proposed navigation scheme. 3) No need for modification of environments. (No use of artificial landmarks.) 4) Hybrid approaches combining reactive behavior as well as deliberative planner, and local grid maps as well as global topological maps. A presented experimental result shows that the proposed navigation scheme is useful for mobile service robot in practical applications.

• KSBB Journal
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• v.26 no.5
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• pp.422-426
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• 2011

Alginate bead has been supplemented with various polymers to control permeability and to enhance mechanical strength. In this report, fibroin-reinforced alginate hydrogel was prepared, in which spatial localization of fibroin molecules was investigated. Confocal laser scanning microscopy revealed that fibroin molecules formed a fibrous network in the alginate-fibroin beads, which was expected to enhance mechanical strength as same as in many composite materials. Uniaxial compression test showed that fibroin-reinforced alginate beads had increased mechanical strength only after methanol treatment that caused ${\beta}$-sheet formation among fibroin molecules. Simultaneous curing and dialysis of alginate beads were carried out to remove excesscalcium but to retain fibroin in the dialysis chamber, which fabricated beads without internal fibrous fluorescent stains. Fibroin molecules were only found beneath the surface of the beads. The fibroin-diffused shell was further processed to form a thick wall after drying or was mobilizedto the centre of the bead by methanol treatment. Accordingly, the structure analyses provide processing methods of fibroin to form a wall or center clumps, which could be applied to design controlled delivery device.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.497-502
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• 2010

The accurate estimation of position and direction of the mobile robot is essential for preparing precise movement and works in the inner complex environment. In this paper, we propose a robust estimation method of location and direction using the velocity of mobile robot in the inner GPS environment. The estimation using the inner GPS with ultrasonic sensors have to consider with various acoustic noise and sensor errors. We design a robust estimation method using a membership function based on uncertainty of the obtained information and robot velocity. The simulation results of the proposed method show effectiveness in the contaminated environment with position errors.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.632-637
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• 2017

Even though the potential for an accident in nuclear power plants is very low, multiple emergency plans are necessary because the impact of such an accident to the public is enormous. One of these emergency plans involves a robotic system for investigating accidents under conditions of high radiation and contaminated air. To develop a robot suitable for operation in a nuclear power plant, we focused on eliminating the three major obstacles that challenge robots in such conditions: the disconnection of radio communication, falling on uneven floors, and loss of localization. To solve the radio problem, a Wi-Fi extender was used in radio shadow areas. To reinforce the walking, we developed two- and four-leg convertible walking, a floor adaptive foot, a roly-poly defensive falling design, and automatic standing recovery after falling methods were developed. To allow the robot to determine its location in the containment building, a bar code landmark reading method was chosen. When a severe accident occurs, this robot will be useful for accident condition monitoring. We also anticipate the robot can serve as a workman aid in a high radiation area during normal operations.

• Korean Journal of Audiology
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• v.24 no.1
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• pp.1-9
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• 2020

Auditory scene analysis is defined as a listener's ability to segregate a meaningful message from meaningless background noise in a listening environment. To gain better understanding of auditory perception in terms of message integration and segregation ability among concurrent signals, we aimed to systematically review the size of auditory scenes among individuals. A total of seven electronic databases were searched from 2000 to the present with related key terms. Using our inclusion criteria, 4,507 articles were classified according to four sequential steps-identification, screening, eligibility, included. Following study selection, the quality of four included articles was evaluated using the CAMARADES checklist. In general, studies concluded that the size of auditory scene increased as the number of sound sources increased; however, when the number of sources was five or higher, the listener's auditory scene analysis reached its maximum capability. Unfortunately, the score of study quality was not determined to be very high, and the number of articles used to calculate mean effect size and statistical significance was insufficient to draw significant conclusions. We suggest that study design and materials that consider realistic listening environments should be used in further studies to deep understand the nature of auditory scene analysis within various groups.

• Journal of Audiology & Otology
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• v.24 no.1
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• pp.1-9
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• 2020

Auditory scene analysis is defined as a listener's ability to segregate a meaningful message from meaningless background noise in a listening environment. To gain better understanding of auditory perception in terms of message integration and segregation ability among concurrent signals, we aimed to systematically review the size of auditory scenes among individuals. A total of seven electronic databases were searched from 2000 to the present with related key terms. Using our inclusion criteria, 4,507 articles were classified according to four sequential steps-identification, screening, eligibility, included. Following study selection, the quality of four included articles was evaluated using the CAMARADES checklist. In general, studies concluded that the size of auditory scene increased as the number of sound sources increased; however, when the number of sources was five or higher, the listener's auditory scene analysis reached its maximum capability. Unfortunately, the score of study quality was not determined to be very high, and the number of articles used to calculate mean effect size and statistical significance was insufficient to draw significant conclusions. We suggest that study design and materials that consider realistic listening environments should be used in further studies to deep understand the nature of auditory scene analysis within various groups.

• Journal of Korea Ship Safrty Technology Authority
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• s.21
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• pp.66-77
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• 2006

Stainless steel has been stably used closed by passivity oxidation films(Cr₂O₃) is made by neutral atmospheric environment. However, passivity oxidaton films of the surface of stainless steel occasionally comes to be destroyed in seawater which is influenced by an environment having galogen ion like Cl‾, then, localization corrosion comes to occur Stainless steel 304 for shaft system material of the small-size FRP fishing boat on seawater environments made an experiment on simulation of sacrifical anode(Al, Zn). Through these experiment and study, following results have been obtained ; According to the field inspection and corrosion simulation, the corrosion on the 2nd class stainless steel shaft(STS304) in FRP fishing boat has been verified to occur by crevice corrosion and galvanic corrosion etc., According to the comparison and analysis of Stainless steel 304 was severely corroded, but, protected shaft specimen was not totallay corroded. This result is assumed to be made by the facts that anodic reaction, Fe → fe²+＋ 2e¯, has been restricted by the cathodic protection current of sacrificial anode material.

• 한국정보컨버전스학회:학술대회논문집
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• 2008.06a
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• pp.199-204
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• 2008

Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad-hoc method of deployment. Considerable research has been focused at overcoming these deficiencies through faster media accessing, more energy efficient routing, localization algorithms and system design. Our research attempts to provide a method of improvement MAC performance in these issues. We show that traditional carrier-sense multiple access(CSMA) protocols like IEEE 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size, We present more efficient method of a medium access for real-time wireless sensor networks. Proposed MAC protocol is a randomized CSMA protocol, but unlike previous legacy protocols, does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, it carefully decides a fixed-size contention window, non-uniform probability distribution of transmitting in each slot within the window. We show that it can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely used simulator ns-2. We, finally show that proposed MAC scheme comes close to meeting bounds on the best latency achievable by a decentralized CSMA-based MAC protocol for real-time wireless sensor networks which is sensitive to latency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.654-661
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• 2011

RTLS (Real-time locating systems) are used for tracking the location of people or assets in real time. In this system, RTLS readers continuously communicate with RTLS tags for measuring time or ranges and location engine tries to calculate accurate location of tags. However, when we attempt to apply this system to real world, the non-line-of-sight(NLOS) problem can be critical to the system performance because of the obstacles. In this paper, we suggest a new location estimation method for an NLOS environment using a reader-selection strategy. We have implemented all components of the locating system and carried out experiments in a test-bed. The accuracy of the system is 50% better than that of the existing general locating system.