• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.154-156
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• 2006

These days wireless sensor networks receive much attention from industry and researchers on various fields. The challenge is that wireless sensor networks have limited resources. Nevertheless, the route discovery in ZigBee sensor networks is performed by simple flooding when the original racket is rebroadcasted at least once by every node in a network. Such uncontrolled flooding generates an excessive number of packets competing for the media and causes a high collision rate. In this article, we propose a suitable packet Time-To-Live value to solve problems of uncontrolled flooding in ZigBee networks. It is shown that more sufficient route discovery in a ZigBee network can save network resources and lengthen the life of a sensor network.

• Journal of Applied Reliability
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• v.3 no.2
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• pp.103-116
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• 2003

We carry out reliability tests and investigate the failure mechanisms. of the wafer level vacuum packaged MEMS gyroscope sensor using an accelerated degradation test. The accelerated degradation test (ADT) is used to evaluate reliability (and/or life) of the MEMS vacuum package and to select the accelerated test conditions, which reduce the reliability testing time. Using the failure distribution model and stress-life model, we are able to estimate the average life time of the vacuum package, which is well agreed with the measured data. After improving several package reliability issues such as prevention of gas diffusion through package, we carry out another set of accelerated tests at the chosen acceleration level. The results show that reliability of the vacuum packaged gyroscope has been greatly improved and can survive without degradation of performance, which is the Q-factor in gyroscope sensor, during environmental stress reliability tests.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.6
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• pp.127-134
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• 2016

WBSN (Wireless Body Sensor Network), also called WBAN (Wireless Body Area Networks) generally, is a kind of WSN (Wireless Sensor Network) applications, which is composed of the various sensor nodes residing in human body embodied or in wearable way. The measured data at each sensor node in WBSN requires being synchronized at sink node for exact analysis for status of human body, which is like WSN. Although many time synchronization protocols for WSN has been already developed, they are not appropriate to WBSN. In this paper, a new time synchronization protocol for WBSN considering the characteristics of WBSN is proposed. The proposed scheme is not only simple, but also consumes less power, leading to increasing network life time. We will show that the proposed scheme is appropriate to WBSN by evaluating its performance by simulation.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.364-371
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• 2017

TPMS is a vehicle electric system that measures the air pressure of a tire, and informs the driver of current tire states. The TPMS sensor typically uses unidirectional communication for small size, light weight, and low power. The transmission period of the sensor indicates the service quality of monitoring the tire. In order to determine the optimal transmission period, frame collision probability and the life time of the sensor should be analyzed. In this paper, collision probability model using Venn diagram is designed in low power TPMS with the normal and warning mode. And the life time and a collision probability were analyzed with the ratio(n) of the normal mode to warning mode transmission period. As a result, $T_{nP}=31sec$ and $T_{wP}=2.4sec$ at 5 years, and $T_{nP}=71sec$ and $T_{wP}=2.5sec$ at 7 years.

• Journal of Digital Convergence
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• v.11 no.10
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• pp.419-429
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• 2013

The Wireless sensor network(WSN) consisting of a large number of sensors aims to gather data in a variety of environments. The sensor nodes operate on battery of limited power. so, To extend network life time is major goals of research in the WSN. In this paper, we state the key point of a energy consumption with minimum&load balancing. The proposed protocol guarantee balance of number of cluster member nodes using the node memory threshold and optimization of distribution of cluster head using the optimized clustering method. The results show that the proposed protocol could support the load balancing and high energy efficiency by distributing the clusters with a reasonable number of member nodes. The simulation results show that our schme ensure longer life time in WSN as compare with existing schemes such as LEACH and CBLM.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.1
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• pp.1-9
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• 2023

The skin structure of sensor pod mounted on the exterior of aircraft can be exposed to the acoustic dynamic load and static load such as aerodynamic pressure and inertial load during flight. Fatigue life prediction of structural model under acoustic load should be performed and also differential stiffness of model modified by static load should be considered. The acoustic noise test spectrum of MIL-STD-810G was applied to the structural model and the stress response power spectral density (PSD) was calculated. The frequency response analysis was performed with or without prestress induced by inplane static load, and the response spectrum was compared. Time series data was generated using the calculated PSD, and the time and frequency domain fatigue life were predicted and compared. The variation of stress response spectrum due to static load and predicted fatigue life according to the different structural model considering mean stress were examined and decreasing fatigue life was observed in the model with prestress of compressive static load.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1022-1027
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• 1997

The grinding operation is an important machining process for machining of final surface. However. grinding process has inevitable troubles such as loading and glazing for grinding wheel. It is, therefore, an essential research theme to determine the wheel life and the dressing timefor efficient grinding. In this study, AE signals (AEavg) generated in thc grinding operation were measured and the dressing time was determined from the analysis of the AEavg value. To verify the propriety of the obtained result. the AE signals measured on the grinding and the dressing operation were compared with the grinding force signals and the dressing force which were measured at same time. From the obtained result, it was confirmed that the determination of the wheel life and the dressing time by the AE measurement technique proposed in this study can be practically used.

• Geomechanics and Engineering
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• v.38 no.5
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• pp.529-539
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• 2024

A high-level nuclear waste (HLW) repository is designed for the long-term disposal of high-level waste. Positioned at depths of 500-1000 meters, it offers an alternative to the insufficient storage space for spent fuels, providing a long-term solution. High-level waste emits heat and radiation, causing structural deterioration, including strength reduction and cracks. Therefore, the use of piezoelectric sensors for structural health monitoring is essential for evaluating the safety of the structure over time. Unlike other structures, the HLW repository restricts human access after the disposal of HLW, rendering sensor replacement impossible. Therefore, it is necessary to assess both the lifespan and suitability of sensors under the disposal conditions in the HLW repository. This study employed an accelerated life test (ALT) to assess the sensor's lifespan under disposal conditions. Failure modes, failure mechanisms, and operational limits were analyzed through accelerated stress test (AST). Additionally, the parameters of the Weibull life probability distribution and the Arrhenius accelerated life model were estimated through statistical methods, including the likelihood ratio test, maximum likelihood estimation, and hypothesis testing. Results confirmed that the sensor's lifespan decreases significantly with the increase in the temperature limit of the HLW repository. The findings of this study can be used for improving sensor lifespan through shielding, development of alternative sensors, or lifespan evaluation of alternative monitoring sensors.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.405-410
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• 2016

Elevator industry is a field that is mechanical, electrical and electronic technology and constantly requires inspection and maintenance considering various applications and various types. Recently, various elevator control and monitoring technologies with IT are developing for elevators on land. But technologies with IT have been hardly done in marine elevator that is consistently assured safety and reliability of life cycle for its parts in poor environment. In this paper, we implemented embedded main controller, floor controller and car controller that meet the requirements and use NMEA network protocol by analyzing home and abroad integrated elevator operation and management systems. Especially, we secured reliability of maintenance by real-time fault diagnosis and control that was implemented with limit switch, gyro sensor, temperature/humidity/barometric pressure sensor and fire detection sensor thinking over the environmental conditions of terrestrial and marine elevator.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.167-172
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• 2017

Mobile nodes are used for prolonging the life-time of the entire wireless sensor networks and many studies that use drones to collected data have been actively conducted with the development of drone related technology. In case of associating a drone and tactical wireless sensor networks, real-time feature and efficiency are improved. The previous studies so focus on reducing drone's flight distance that the energy consumption of sensor nodes is unbalanced. This unbalanced energy consumption accelerates the network partition and increases drone's flight distance. In this paper, we proposed a new selection scheme considered drone's flight distance and nodes' life-time to solve this problem when rendezvous nodes that collect data from their cluster and directly communicate with a drone are selected.