• Computers and Concrete
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• v.21 no.4
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• pp.367-376
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• 2018

This study reports the results of nondestructive monitoring of macro void developments in mortars manufactured with both ordinary Portland cement and sulfate resistant cement. Two types of curing were utilized; tap water curing and another curing environment that contains 5% $Na_2(SO_4)$ solution. Being the primary objective of this study, macro void developments of the mortar specimens were monitored by X-ray Medical Computerized Tomography. Compressive strength tests and water absorption tests were conducted on specimens that were kept in both curing environments for a duration of 560 days. Data analyses yielded consistent results among the three tests used in this experimental study. Macro void ratios of mortars decreased at the beginning of experiments for a certain period; afterwards, macro void ratios increased. The objective of this study was accomplished as anticipated since X-CT image analysis was able to nondestructively monitor macro void development process in cement mortars.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.3
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• pp.253-262
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• 1995

A study has been performed on the characteristics of rural and urban surface ozone concentration for the period of March 1992 to February 1993. The monitoring station of rural ozone is located at Kosan, Cheju and other urban monitoring stations are located at Seoul, Pusan and Kwangju. Rural's and urban's ozone data exhibit a distinct features in many ways. First, annual mean of rural ozone concentration os very high(42 ppbv) but urban's are very low(10 .sim.15 ppbv). Second, rural ozone data shows a seasonal variation with it's maximum in spring, and minimum in summer, but urban's show a seasonal variation with it's maximum in spring, and minimum in winter. Third, diurnal variation of rural data is very small but that of urban's are very large. Fourth, urban's data are extremely low(< 3 ppbv) and have no seasonal variations.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E4
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• pp.169-181
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• 2001

To test the compatibility of differential optical absorption spectroscopy (DOAS) and conventional in-situ monitoring technique we conducted a comparative analysis of the two systems using hourly measurement data sets of three criteria pollutants including No$_{2}$O$_{3}$, and SO$_{2}$ collected in months between April and June of 2001 at Sung Man city, Kyung Gi Province, Korea. The results of our comparative analysis were useful to evaluate the various aspects of DOAS performance, of particular the level of agreement with the counterpart method through computation of percent differences and correlation analysis. Interpretation of the mixing ratio data for those chemical species was however confined in terms of explaining the differences affected by the changes in environmental conditions because measurements of important meteorological parameters were limited during most of the study period. Nevertheless, the overall results of this study strongly demonstrated that the mixing ratio of major pollutants measured by the two different systems maintain strong compatibility from various respects.

• Ecology and Resilient Infrastructure
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• v.5 no.1
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• pp.54-58
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• 2018

Diet composition of amphibians usually reflects the distribution of potential prey within habitats, as well as their diet preference. We identified the diet items of Japanese tree frog (Hyla japonica) using a stomach flushing method in a rice paddy for the establishment of bio-monitoring systems of landscape changes. During the reproductive period, 71% of calling males had empty stomachs. All prey items in the stomachs belonged to the phylum Arthropoda, from eight orders of Insecta and one order of Arachnida. Among insect prey, the most common items in the stomachs were adults of beetles, flies and bugs, and larvae of butterflies and moths. There was a significant positive correlation between the body mass of Japanese tree frogs and the volume of prey items. Our results can provide a basic framework to guide the monitoring systems using prey identification of Japanese tree frogs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.469-474
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• 2016

Abnormal sound was heard from a heat exchanger of condensate water system in a nuclear power plant, which was identified as impact sound of a loose part later. Nuclear power plants are normally equipped with loose part monitoring system for primary water system, but not for secondary water system. The abnormal sound was analyzed by using the impact signal-processing methodology based on the Hertz theory. The predicted results for impact location and size of the loose part showed good agreement with those of the actual loose part found during the overhaul period in the plant. So, this analysis methodology for the impact signal will be widely utilized for the primary and secondary side of the nuclear power plant.

• Journal of Communications and Networks
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• v.13 no.2
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• pp.125-131
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• 2011

Rapid strides are being made to bring to reality the technology of wearable sensors for monitoring patients' physiological data.We study the problem of automatically detecting anomalies in themeasured blood glucose levels. The normal daily measurements of the patient are used to train a hidden Markov model (HMM). The structure of the HMM-its states and output symbols-are selected to accurately model the typical transitions in blood glucose levels throughout a 24-hour period. The learning of the HMM is done using historic data of normal measurements. The HMM can then be used to detect anomalies in blood glucose levels being measured, if the inferred likelihood of the observed data is low in the world described by the HMM. Our simulation results show that our technique is accurate in detecting anomalies in glucose levels and is robust (i.e., no false positives) in the presence of reasonable changes in the patient's daily routine.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.262-263
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• 2019

In this study, a sensor for detecting corrosion of rebar embedded in reinforced concrete structures was fabricated and its performance was verified. In order to monitor the open circuit potential(OCP) of the rebar embedded in reinforced concrete, a concrete embedded solid electrode was constructed as a sensor using MnO2. The OCP of the rebar could be observed using a sensor and a data logger. The decrease of the OCP to -510mV (vs.MnO2) or less was judged to be corrosion of the rebar. Since it is a solid-mediated sensor, it is more stable and durable than an electrode using an aqueous solution, and it is considered that the corrosion state of the rebar can be monitored for a long period of time.

• Structural Engineering and Mechanics
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• v.41 no.1
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• pp.139-155
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• 2012

Structural health monitoring systems are often installed on bridges to provide assessments of the need for structural maintenance and repair. Damage or deterioration may be detected by observation of changes in bridge characteristics evaluated from measured structural responses. However, construction materials such as concrete and steel cables exhibit certain time-dependent behaviour, which also results in changes in structural characteristics. If these are not accounted for properly, false alarms may arise. This paper proposes a systematic and efficient method to study the time-dependent effects on the dynamic properties of cable-stayed bridges. After establishing the finite element model of a cable-stayed bridge taking into account geometric nonlinearities and time-dependent behaviour, long-term time-dependent analysis is carried out by time integration. Then the dynamic properties of the bridge after a certain period can be obtained. The effects of time-dependent behaviour of construction materials on the dynamic properties of typical cable-stayed bridges are investigated in detail.

• Wind and Structures
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• v.16 no.4
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• pp.393-409
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• 2013

This paper uses ten years of on-site monitoring data for the Confederation Bridge to derive wind loads and investigate whether the bridge has experienced its design wind force effects since its completion in 1997. The load effects derived using loads from the on-site monitoring data are compared to the load effects derived using loads from the 1994 and 2009 wind tunnel aerodynamic model tests. The research shows, for the first time, that the aerodynamic model-based methodology originally developed in 1994 is a very accurate method for deriving wind loads for structural design. The research also confirms that the bridge has not experienced its specified (i.e., unfactored) wind force effects since it was opened to traffic in 1997, even during the most severe event that has occurred during this period.

• Journal of Biomedical Engineering Research
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• v.27 no.5
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• pp.260-266
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• 2006

Due to damaged vertebrae nerves, serious disease and aging, patients who have to lie down for long period of time need to exercise to maintain up-right standing position and recover their paralytic leg. This study describes a development of an intellectual tilt table which can provide a patient with rehabilitating condition. This can be possible by measuring and displaying the hee bent angle and pressure for each foot during exercise in real time. It is expected that the patient's exercising effect can increase by monitoring these two values during exercise.