• Structural Monitoring and Maintenance
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• v.4 no.4
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• pp.301-329
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• 2017

Impedance-based damage detection method has been known as an innovative tool with various successful implementations for structural health monitoring of civil structures. To monitor the local critical area of a structure, the impedance-based method utilizes the high-frequency impedance responses sensed by piezoelectric sensors as the local dynamic features. In this paper, current advances and future challenges of the impedance-based structural health monitoring are presented. Firstly, theoretical background of the impedance-based method is outlined. Next, an overview is given to recent advances in the wireless impedance sensor nodes, the interfacial impedance sensing devices, and the temperature-effect compensation algorithms. Various research works on these topics are reviewed to share up-to-date information on research activities and implementations of the impedance-based technique. Finally, future research challenges of the technique are discussed including the applicability of wireless sensing technology, the predetermination of effective frequency bands, the sensing region of impedance responses, the robust compensation of noise and temperature effects, the quantification of damage severity, and long-term durability of sensors.

• The Journal of the Korea Contents Association
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• v.11 no.11
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• pp.42-48
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• 2011

This paper presents a bridge road surface frost prediction and monitoring system. The node sensing hardware comprises microprocessor, temperature sensors, humidity sensors and Zigbee wireless communication. A software interface is implemented the control center to monitor and acquire the temperature and humidity data of bridge road surface. A bridge road surface frost occurs when the bridge deck temperature drops below the dew point and the freezing point. Measurement data was used for prediction of road surface frost occurrences. The actual alert is performed at least 30 minutes in advance the road surface frost. The road surface frost occurrences data are sent to nearby drivers for traffic accidents prevention purposes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.69-78
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• 1993

A testing system has been developed to evaluate the seasonal variation of the resilient modulus of granular subgrade soils. Two sites were successfully instrumented with soil moisture-temperature cells to monitor over a period of one year, the field temperature and moisture content underneath the pavement. Multiple regression equations were developed to determine the resilient modulus under environmental conditions. It is noted that the use of the effective resilient modulus at the location of the Average Depth of Significant Stress (ADSS) provides a reasonable basis for determining subgrade properties. In addition, a theoretical model has been developed to predict the resilient modulus due to the change of temperature and moisture condition.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.77-82
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• 1999

Resistance spot welding process is completed in very short time and there are many factors affecting on the generation of heat. It is difficult to control these experimental factors and monitor distribution of the temperature and stresses in the experimental analysis case. and too much time and expense are required for the experimental trials to fine proper welding condition. So numerical analyses have been attempted steadily, but most numerical analyses on the resistance spot welding are mainly focused on thermal behavior. Therefore, in this paper, the numerical analysis of mechanical behavior as well as heat conduction is carried out for the spot welding process. For this numerical analysis, axial symmetric computer program for the spot welding analysis by F.E.M. has been developed considering heat conduction and thermal elastic-plastic theory. Material properties depending on temperature such as density, heat conductivity, heat expansion coefficient, specific heat, yield stress, elastic modulus, and specific resistance are considered. Using the results of temperature distribution obtained from heat conduction analysis, the thermal elastic-plastic analysis is carried out to clarify mechanical behavior of spot welded specimen. In order to evaluate the effect of residual stresses, numerical analyses are carried out under tension-shear load in two cases respectively; one with residual stress, the other without residual stresses.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.90-99
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• 1992

In resent year Laser Speckle and its development have enabled surface deformation of engineering components and materials to be interferometrically examined. Laser Speckle- Pettern Interferometry Method is a very useful method for measuring In-plane components of displacement. In measuring thermal expansion coefficient, the various problems generated were established, and the measuring limitation examined. Metarial INCONEL 601 was used in experiments. Specimen was heated to the high temperature(100$0^{\circ}C$) by diong current to the direct two specimen. Then, those problems appear to the influence of back-ground radiation by the heated specimen, the influence by air turbulence, the oxidation of specimen. The color monitor and interference filter prevented the back-ground radiation by rad heat. The oxidation occuring in specimen itself was not generated by the being acid-proof excellence of material INCONEL 601. Yet, in this experiments, the serious problems are the oxidation of specimen and influence by air turbulence. By more reserching these problems forward, it is helpful that the thermal expansion coefficient of many materials is directly measured under high temperature.

• Journal of Sensor Science and Technology
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• v.15 no.6
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• pp.417-424
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• 2006

An ubiquitous healthcare monitoring system for elderly person at home was designed for continuous healthy monitoring of elderly person or patients. Human vital signals, such as ECG and body temperature, were monitored by terminal PC or PDA via ECG and temperature sensor nodes on the patient's body. From the ECG data, the heart rate, tachycardia, bradycardia and arrhythmia were diagnosed on the terminal PC or PDA to assist doctor's or nurse's aid or patient itself to monitor the patient's condition and give medical examination. Artificial judgement support system was designed in server computer and the system support a doctor or nurser for management or treatment of the patient. This system can be applied to vital signal monitoring system for solitude elderly person at self house or home health care service part. And this ubiquitous healthcare system can reduce the medical expenses in coming aging or aged society.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.12
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• pp.1395-1402
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• 2015

An electric heat tracing system manages the temperature of pipes used in a plant. We propose a Zigbee-based wireless system so called the TESCON(: TEmperature Sensing and CONtrol) to monitor and control the electric heat tracing system in an integrated way. Simulations have been done to analyze the performance of the TESCON system. The performance of the TESCON system is validated by obtaining similar results via testbed operation. We also suggest an extension method of the TESCON system based on the hierarchical tree topology by adopting techniques such as network partition, channel reuse and frame aggregation.

• Journal of the Korean Society of Safety
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• v.22 no.3 s.81
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• pp.7-12
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• 2007

This paper presents the development of an electrical fire detection system using digital temperature and current detectors in order to sound for electrical fire in advance. As the demand for electricity is increasing and industrial facilities are getting more complex and larger in size, the losses of human life and property are on the increase by electrical fires. In order to prevent electrical fires, it is required to find out fire signatures, or electric signal of the overcurrent and overheating. Therefore, in this paper, developed is an electrical fire detection system based on the detection of signal for overcurrent and overheating to prevent electrical accidents in advance that happen in electrical wires. The developed system gives an alarm by computer monitor, speaker system and mobile phone before electrical fires occur and give severe damages to human beings and properties, and the system can be implemented and supplied for business and residental buildings at a low price. The usefulness and validity of the system, also, verified in this paper by case study and experiments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1027-1029
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• 2015

Heat exchange ventilation facility is using for heating the inflow outside-air with warm outflow inside-air. Energy cost is saved and respiratory disease caused by temperature difference of air is prevented. In this paper, system for remote control and monitoring of heat exchange ventilation facility is developed. This system is applied in chicken breeding farm, and verification test of performance such as temperature and humidity control and monitoring is conducted. From verification test, temperature control error is measured as under 2degrees around the chicken breeding farm.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.922-925
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• 2007

In the usual dry etching process for the TFT-LCD fabrication, it is hard to monitor the basic plasma parameters such as density and temperature. However, the basic parameters are easily monitored during the dry etching process. We have simultaneously measured the electric characteristics and basic plasma parameters of the dry etching chamber during the process, analyzed them to interpret plasma parameters. For the Ar plasma discharge case, we could obtain the density and temperature from the electric characteristics using a simple simple sheath model.