• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.328-338
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• 2007

One of main advantages of composite using smart material as reinforcement can be controlled cracks behavior inside the composite. If the smart composite is applied as part of the structure, the use of the shape memory effect of the smart material is the best way to protect the propagation of cracks generated in the structure while use. In this study, the optical manufacturing conditions for the smart composite were derived. In order to evaluate the shape memory effect by shape memory alloy, the tensile load was applied to the smart composite and stress distribution was inspected. And then, the smart composite was heated to a certain temperature and the shape memory alloy would shrink to the original shape. Finally, at this point the recovering status of stress using photoelastic instrument was discussed.

• Corrosion Science and Technology
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• v.12 no.2
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• pp.93-101
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• 2013

The object of this work is to establish an electrochemical noise(EN) measurement technique combined with a direct current potential drop(DCPD) method for monitoring of localized corrosion cracking of nickel-based alloy, and to analyze its mechanism. The electrochemical current and potential noises were measured under various conditions of applied stress to a compact tension specimen in a simulated primary water chemistry of a pressurized water reactor. The amplitude and frequency of the EN signals were evaluated in both time and frequency domains based on a shot noise theory, and then quantitatively analyzed using statistical Weibull distribution function. From the spectral analysis, the effect of the current application in DCPD was found to be effectively excluded from the EN signals generated from the localized corrosion cracking. With the aid of a microstructural analysis, the relationship between EN signals and the localized corrosion cracking mechanism was investigated by comparing the shape parameter of Weibull distribution of a mean time-to-failure.

• Geomechanics and Engineering
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• v.7 no.1
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• pp.75-85
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• 2014

The application of the mechanized tunnelling has been extended in recent years. There are at present different approaches that are used in the design of segmental tunnel linings supported in mechanized tunnels. Even though segmental lining is utilized for mechanized tunnels, its behaviour is still quite unclear under in situ stress and there is a lack of data regarding the distribution of stresses inside segmental linings. So far no single effective calculation method exists for segmental lining design. The lack of clear solutions makes the use of segmental lining to be more expensive due to the adoption of greater safety factors. Therefore, a particular attention must be given in order to obtain data from monitored tunnels which permits to validate design methods. In this study, strain measurements, which were conducted during the construction of twin tunnels in the Bologna-Florence railway line, have been presented. The behaviour of segmental lining during the excavation and the influence of a new tunnel excavation on an existing tunnel have been shown through the measured data. The data are then compared with the results obtained with Einstein and Schwartz's method and Duddeck and Erdmann's method, which permits to highlight the fact that the two analytical methods underestimate structural forces induced in the segmental lining and then must be used with caution.

• Structural Engineering and Mechanics
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• v.72 no.5
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• pp.643-652
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• 2019

Protection of cultural heritage and carrying it to the future are at the top of the significant topics of research and implementation in engineering in the 21st century. There are several historical structures in the district of Ahlat located in the east of Turkey on the Lake Van Basin that has harbored many civilizations. Some of such works are the gravestones that are found in the Ahlat Seljuk Cemetery, which is the oldest and largest cemetery in the district. This study firstly provides information about the Ahlat Seljuk Cemetery and the gravestones found in it. Observation-based structural analyses were carried out on these gravestones that are found in this area that are known to have belonged to different civilizations based on their physical and constructional characteristics. These stones were built out of Ahlat stone as single pieces. Information is provided on the damages that have occurred on the gravestones in time and their causes. In general, losses of mass, abrasions, separations, collapses and calcifications due to natural conditions, as well as vegetative formations, were observed in the gravestones. To provide an example of other gravestones within the context of the study, the gravestone that is known to belong to the person named Nureddin Ebu Hasan was selected. As a result of the modeling that was carried out for this gravestone by using the finite elements method, modal analyses were carried out. With these analyses, for the gravestone, period, effective mass participation rates and stress values were calculated. The stress values that were obtained in this study were compared to the material safety stress values that were obtained in previous studies. Additionally, QR code application was created for the gravestone that was selected as an example in the study, and information on this gravestone was transferred to an electronic environment. The QR code application includes different language options, visuals of the gravestone and information on the gravestone. The QR application was also supported with a video of the cemetery where the gravestone is located. With this application, access to information about gravestones will be possible by using tablets and smartphones. With a QR code to be created for each gravestone, these gravestones will obtain identity cards.

• Mass Spectrometry Letters
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• v.14 no.3
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• pp.91-103
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• 2023

As one of the most common mood disorders, numerous studies have shown depression is the main risk factor for non-suicidal self-harm. The pathogenesis of depression is complex, and a comprehensive and rapid measurement of monoamine neurotransmitters and their metabolites will be very helpful in understanding the pathogenesis of depression. Therefore, a rapid and sensitive underivatized liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous monitoring of the levels of ten neurotransmitters and their metabolites in rat serum and limbic system and successfully applied to quantify the changes of neurotransmitter levels in chronic unpredictable mild stress-induced rats. The analytes studied were mainly involved in tyrosine metabolism, tryptophan metabolism, and glutamate cycling pathways, which are important in the pathogenesis of depression. It had been verified the method was sensitive and effective, with satisfactory linearity, and met the requirements of biological sample determination. Levels of neurotransmitters in rat serum, hippocampus, amygdala, prefrontal cortex, striatum, and hypothalamus were determined via the method. The results showed serotonin, dopamine, norepinephrine, and their metabolites were decreased, glutamine was increased, and glutamate was disturbed in chronic unpredictable mild stress-induced depression rats. This method provides a new approach to studying the pathogenesis of depression and other neurological disorders.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.46-52
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• 1998

The author conducted new back analysis method using monitoring data to a landslide which occurred around portal. In this case, because the tunnel being located under the sliding plane of the landslide, calculated value from the ordinary back analysis in which considered only stress release by the tunnel excavation didn't fit the measured value. Then, in the new method, a body force as the movement of the landslide mass was added to the ordinary back analysis and good results were obtained. Furthermore, the author carried out stability analysis of the landslide with the data of the back analysis and examined the loosened area and decreasing og the sliding plane strength due to the tunnel excavation.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.985-994
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• 2004

The application of the reinforced retaining wall has increased in the last 10 years in Korea. The height of reinforced wall is generally limited to less than 15m. It has been reported that the reinforced wall higher than 10m should have higher strength reinforcement or should reduce the lateral earth pressure of the reinforced wall to secure the stability of the wall. In this study, the reinforced retaining wall was constructed 14m high, backfilled by a mixture of soil and cement and instrumented on the reinforcement elements. The instrumented reinforced wall was monitored during and after construction. Field monitoring result shows that a backfill by a mixture of soil and cement reduced the tensile stress developed on the reinforcing elements and the reinforced wall backfilled by a mixture of soil and cement performed successful.

• Environmental Engineering Research
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• v.14 no.2
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• pp.120-125
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• 2009

Water stress has become a major concern in agriculture. Korea suffers from limited agricultural water supply, and wastewater reuse has been recommended as an alternative solution.A study was performed to examine the effects of microorganism concentration in the ponded-water of a paddy rice field with reclaimed-water irrigation for evaluating the microbial risk to farmers and neighborhoodchildren.Most epidemiological studies were performed based on an upland field, and they may not directly applicable to paddy fields. Beta-Poisson model was used to estimate the microbial risk of pathogen ingestion. Their risk value increased significantly high level after irrigation and precipitation.It implies that agricultural activities such as plowing, and fertilizing, and precipitation need be practiced a few days after irrigation considering health risks. The results about field application of the microbial risk assessment using E. coli showed difference according to monitoring time and treatment plot. Result of the microbial risk assessment showed that risk values of ground-water and reclaimed secondary waste water irrigation were lower than directly use of wastewater treatment plants' effluent. This paper should be viewed as a first step in the application of quantitative microbial risk assessment of E. coli to wastewater reuse in a paddy rice farming.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.613-620
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• 2002

Sand Compaction Pile(SCP) is a soil improvement method that a sand charge is introduced into the pipe, and the pipe is withdrawn part away while the sand pile is compacted and its diameter is enlarged. The sand used in this method should be of good quality. In Korea, crushed stone and washed sea sand are used frequently in SCP. However, use of these materials is restricted because of environmental problem and deficiency of supply. In the copper smelting process, about 0.7 million tons of copper slag are produced in Korea. The range of particle size distribution of copper slag is from 0.15mm to 5mm, so it can be a substitute for sand, and the relatively high specific gravity compared with the sand, is its characteristic. Copper slag is hyaline and so stable environmentally that in foreign country, such as Japan, Germany etc., it is widely used in harbor, revetment and offshore structure construction works. Therefore, in this study, the several laboratory tests were peformed to evaluate the applicability of copper slag as a substitute for sand of SCP. From the mechanical property test, the characteristics of sand and copper slag were compared and analyzed, and from laboratory model test, the strength of composite ground was compared and analyzed by monitoring the stress and ground settlement of clay, SCP and copper slag compaction pile. Specially, this study focused on the application of copper slag as sand substitute in SCP pilot tests based on laboratory tests results.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.10a
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• pp.43-51
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• 2008

Currently an increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). For rational management of tunnels from planning to construction and maintenance stages, prediction, control and monitoring of displacements of and around the tunnel have to be performed with high accuracy. Computational method tools, such as finite element method, have been and are indispensable tool for tunnel engineers for many years. It is, however, a commonly acknowledged fact that determination of input parameters, especially material properties exhibiting nonlinear stress-strain relationship, is not an easy task even for an experienced engineer. Use and application of the acquired tunnel information is important for prediction accuracy and improvement of tunnel behavior on construction. Artificial Neural Network (ANN) model is a form of artificial intelligence that attempts to mimic behavior of human brain and nervous system. The main objective of this paper is to perform the deformation analysis in NATM tunnel by means of numerical simulation and artificial neural network (ANN) with field database. Developed ANN model can achieve a high level of prediction accuracy.