• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.479-493
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• 2023

The need for safety management has arisen due to the increasing number of years of operated underground structures, such as tunnels and utility tunnels, and accidents caused by those aging infrastructures. However, in the case of privately managed underground utility ducts, there is a lack of detailed guidelines for facility safety and maintenance, resulting in inadequate safety management. Furthermore, the absence of basic design information and the limited space for safety assessments make applying currently used non-destructive testing methods challenging. Therefore, this study suggests non-destructive inspection methods using ultrasonic and impact-echo techniques to assess the quality of underground structures. Thickness, presence of rebars, depth of rebars, and the presence and depth of internal defects are assessed to provide fundamental data for the safety assessment of box-type general underground structures. To validate the proposed methodology, different conditions of concrete specimens are designed and cured to simulate actual field conditions. Applying ultrasonic and impact signals and collecting data through multi-channel accelerometers determine the thickness of the simulated specimens, the depth of embedded rebar, and the extent of defects. The predicted results are well agreed upon compared with actual measurements. The proposed methodology is expected to contribute to developing safety diagnostic methods applicable to general underground structures in practical field conditions.

• Steel and Composite Structures
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• v.50 no.6
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• pp.705-720
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• 2024

Analyzing the collapse behavior of thin-walled steel structures holds significant importance in ensuring their safety and longevity. Geometric imperfections present on the surface of metal materials can diminish both the durability and mechanical integrity of steel shells. These imperfections, encompassing local geometric irregularities and deformations such as holes, cavities, notches, and cracks localized in specific regions of the shell surface, play a pivotal role in the assessment. They can induce stress concentration within the structure, thereby influencing its susceptibility to buckling. The intricate relationship between the buckling behavior of these structures and such imperfections is multifaceted, contingent upon a variety of factors. The buckling analysis of thin-walled steel shell structures, similar to other steel structures, commonly involves the determination of crucial material properties, including elastic modulus, shear modulus, tensile strength, and fracture toughness. An established method involves the emulation of distributed geometric imperfections, utilizing real test specimen data as a basis. This approach allows for the accurate representation and assessment of the diversity and distribution of imperfections encountered in real-world scenarios. Utilizing defect data obtained from actual test samples enhances the model's realism and applicability. The sizes and configurations of these defects are employed as inputs in the modeling process, aiding in the prediction of structural behavior. It's worth noting that there is a dearth of experimental studies addressing the influence of geometric defects on the buckling behavior of cylindrical steel shells. In this particular study, samples featuring geometric imperfections were subjected to experimental buckling tests. These same samples were also modeled using Finite Element Analysis (FEM), with results corroborating the experimental findings. Furthermore, the initial geometrical imperfections were measured using digital image correlation (DIC) techniques. In this way, the response of the test specimens can be estimated accurately by applying the initial imperfections to FE models. After validation of the test results with FEA, a numerical parametric study was conducted to develop more generalized design recommendations for the stainless-steel shell structures with the initial geometric imperfection. While the load-carrying capacity of samples with perfect surfaces was up to 140 kN, the load-carrying capacity of samples with 4 mm defects was around 130 kN. Likewise, while the load carrying capacity of samples with 10 mm defects was around 125 kN, the load carrying capacity of samples with 14 mm defects was measured around 120 kN.

• Journal of Korean Society of Water and Wastewater
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• v.37 no.4
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• pp.215-229
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• 2023

In this study, non-destructive technologies that can be applied to evaluate the integrity of valve materials, safety against internal pressure caused by corrosion, and the blocking function of large-diameter water valves during operation without requiring specimen collection or manpower entering the inside of the valve were tested to assess the reliability of the technologies and their suitability for field application. The results showed that the condition of the graphite structure inside the valve body can be evaluated directly through the optical microscope in the field without specimen collection for large-diameter water butterfly valves, and the depth of corrosion inside the valve body can be determined by array ultrasound and the tensile strength can be measured by instrumented indentation test. The reliability of each of these non-destructive techniques is high, and they can be widely used to evaluate the condition of steel or cast iron pipes that are significantly smaller in thickness than valves. Evaluation of blocking function of the valves with mixed gas showed that it can be detected even when a very low flow rate of mixed gas passes through the disk along with the water flow. Finally, as a result of evaluating the field applicability of non-destructive technologies for three old butterfly valves installed in the US industrial water pipeline, it was found that it is possible to check the material and determine the suitability of large-diameter water valves without taking samples, and to determine the corrosion state and mechanical strength. In addition, it was possible to evaluate safety through the measurement results, and it is judged that the evaluation of the blocking function using mixed gas will help strengthen preventive response in the event of an accident.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.361-371
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• 2005

The objective of study was to diagnose integrative ecological health of Daejeon Stream, one of the tributaries of Guem River, during May 2004 ${\sim}$ April 2005. The research approach was primarily based on a Qualitative Habitat Evaluation Index (QHEI) and the Index of Biological Integrity (IBI) using fish assemblage. These outcomes were compared with conventional chemical dataset. For the experiment, four sampling sites were chosen from Daejeon Stream and long-term water quality data during 1995 ${\sim}$ 2004 (obtained from the Ministry of Environment) were analyzed in the spatial and temporal aspects. For the biological health assessment, we developed a stream health assessment model (SHA model) far regional applications. We found that current water quality conditions, based on the COD, BOD, TN and TP, were enhanced by 1.6 ${\sim}$ 5.3 fold over the period of 1995 ${\sim}$ 2004 and that the parameters showed a typical longitudinal decline from the upstream to downstream reach. The differences of water quality between the two reaches were more than 4.4 times, indicating a large spatial variations within the stream. The health conditions, based on the SHA model, averaged 23 and varied from 20 to 26 depending on the sampling stations. Values of the QHEI varied from 39 (Poor condition) to 124 (Cood condition)and values of QHEI in the reach of S2 ${\sim}$ S4 had significantly lower than in the headwater site (S1). Also, biological stream health, based on the criteria of US EPA (1993), was judged as 'Poor condition', in the S4 where TN, TP, BOD and COD were highest. In the meantime, maximum value of SHA (26) was found in the upstream reach (S1) where the water quality and QHEI were best. We also found that compositions of sensitive species showed a linear function with water quality conditions and this pattern was evident in the tolerant species. Thus, the biological stream health, based on the SHA model, matched well water chemistry. Overall outcomes suggest that the biological health impact was a function of chemical degradation and physical habitat quality in the stream.

• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.130-142
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• 2007

This study was to examine impacts of turbid water on fish community in the downstream of Yongdam Dam during the period from June to October 2006. For the research, we selected six sampling sites in the field: two sites were controls with no influences of turbid water from the dam and other remaining four sites were the stations for an assessment of potential turbid effects. We evaluated integrative health conditions throughout applications of various models such as necropsy-based fish health assessment model (FHA), Index of Biological Integrity (IBI) using fish assemblages, and Qualitative Habitat Evaluation Index (QHEI). Laboratory tests on fish exposure under 400 NTU were performed to find out impact of turbid water using scanning electron microscope (SEM). Results showed that fine solid particles were clogging in the gill in the treatments, while particles were not found in the control. This results indicate that when inorganic turbidity increases abruptedly, fish may have a mechanical abrasion or respiratory blocking. The stream health condition, based on the IBI values, ranged between 38 and 48 (average: 42), indicating a "excellent" or "good" condition after the criteria of US EPA (1993). In the mean time, physical habitat condition, based on the QHEI, ranged 97 to 187 (average 154), indicating a "suboptimal condition". These biological outcomes were compared with chemical dataset: IBI values were more correlated (r=0.526, p<0.05, n=18) with QHEI rather than chemical water quality, based on turbidity (r=0.260, p>0.05, n=18). Analysis of the FHA showed that the individual health indicated "excellent condition", while QHEI showed no habitat disturbances (especially bottom substrate and embeddeness), food-web, and spawning place. Consequently, we concluded that the ecological health in downstream of Yongdam Dam was not impacted by the turbid water.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.527-533
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• 2004

One clinical technique recommended for improving marginal integrity is "rebonding" or application of unfilled resins to the surface of composite restoration. But continuously the restorations are affected with occlusal load. There is room for doubt that the rebonding agent has the positive effect on microleakage in spite of the stress generated by the occlusal load. This study determined the effect of rebonding on microleakage of Class V resin composite restorations under load cycling. Class V cavities were prepared on the buccal surface of 40 sound extracted premolars and restored with a hybrid light-cured resin composite according to manufacturers' directions. They were randomly divided into two groups consisting of 20 samples: a control(group I), without surface sealing, and the other group(group II) in which margins were etched and rebonded. After thermocycling, each of groups was divided into subgroups(group A, B), and load cycling(total 100,000 cycles with 4-100N load at a rate of 1 Hz) were applied on the group B. Assessment of microleakage utilized methylene blue dye penetration. The following results were obtained: 1. In the occlusal region, no significant difference was noted in the scores regardless of whether or not the rebonding agent was used(group TA-IIA, IB-IIB)(p>0.05). 2. In the cervical region, the control group with rebonding(group IIA) showed the better result than the group without rebonding(group IA)(p<0.05). 3. In the cervical region, the rebonded group with load cycling(group IIB) showed similar results to the group without rebonding(group IB) and no significant difference was noted(p>0.05).

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.183-191
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• 2009

This study was to evaluate ecological health of Dongjin River in October 2007. The ecological health assessments was based on the Index of Biological Integrity (IBI), Qualitative Habitat Evaluation Index (QHEI), and water chemistry. For the study, the models of IBI and QHEI were modified as 8 and 11 metric attributes, respectively. We also analyzed spatial patterns of chemical water quality over the period of 2005${\sim}$2008, using the water chemistry dataset, obtained from the Ministry of Environment, Korea. In Dongjin River, values of IBI averaged 19 (n=3), which is judged as a "Fair" condition after the criteria of Barbour et al. (1999). There was a distinct spatial variation. IBI score at Site 1 was estimated as 28, indicating a "Good" condition whereas, IBI at Site 2 and Site 3 were as 18 and 12, indicating "Fair" and "Poor" condition, respectively. Habitat analysis showed that QHEI values in the river averaged 117 (n=3), indicating a "Fair${\sim}$Good" condition after the criteria of Barbour et al. (1999). Values of BOD and COD averaged 2.3 mg $L^{-1}$ (scope: 0.1${\sim}$8.9 mg $L^{-1}$) and 5.5 mg $L^{-1}$ (scope: 1.8${\sim}$12.6 mg $L^{-1}$), respectively during the study. Total nitrogen (TN) and total phosphorus (TP) averaged 2.7mg $L^{-1}$ and 0.127mg $L^{-1}$, respectively, and the nutrients showed large longitudinal gradients between the upper and lower reach. Overall, dataset of IBI, QHEI, and water chemistry showed that river health was a gradual decline at upstream to downstream. So, Dongjin River should be protected from habitat disturbance and chemical pollutions.

• Management & Information Systems Review
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• v.39 no.2
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• pp.113-126
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• 2020

This study suggested implications by dividing the concept of brand origin into national image and manufacturing capacity image, verifying the direct impact of these variables on brand trust and brand loyalty, and verifying the difference between products with the effect on brand trust of brand origin, which is the result of verification. The specific implications of this paper are as follows. First, brand origin does not directly affect brand loyalty, but it can have a direct impact on the preceding variable, brand loyalty. This study may conclude that it is desirable to define the factors that affect the purchase selection indirectly through the assessment of product properties or positive effects on brand image rather than having a direct impact on product purchase or selection. Second, the difference in brand origin influence by product characteristics was very evident. Past studies were limited to a few products, so pan-product testing was not conducted, and the empirical power was judged to be limited, so this study included a variety of products and tried to detect differences between products through actual empirical research. Involvement and self-congruity have been presented with results that can be judged as important variables for brand origin to affect brand performance and variables. Looking at the role of the brand origin for each product characteristic by distinguishing between product characteristics and whether or not products related to quality, history, authenticity, etc., the product recognized as high quality and the product recognized as having high integrity showed higher effect of the brand origin, but history was a product characteristic that did not show the effect of the brand origin.

• Journal of Life Science
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• v.16 no.2 s.75
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• pp.352-356
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• 2006

Quantity of protein, amino acid, and sugar leaked from seeds was greater as the viability of seeds was dropped by the time elapsed of seed aging treatment. In the seeds with the artificial aging treatment for 20 days, 35.8 mg of protein was leaked on the 4th day after soaking, which was 6.9 times higher than that of control. Leakage of amino acid was also higher from low quality seeds treated with the aging treatment. In the seeds with the aging treatment for 20 days, $36.5{\mu}g$ fig of sugar was leaked on the 4th day after soaking, which was 2.8 times higher than that of control. The leakage of inorganic compound was higher from the low quality seeds, and leakage of total protein, amino acid, and sugar. According to .the quantity of leakage, water soluble compounds, which can be used for the assessment of seed quality without any destruction, were protein and potassium. Germination rate and percentage of seeds were dropped with the seed aging treatment, and the seed viability could be recovered by priming treatment. This phenomenon was very clear when the low quality seeds were germinated at low temperature.

• Korean Journal of Environmental Biology
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• v.31 no.2
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• pp.96-104
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• 2013

The objectives of this study were to analyze chemical the water quality related to the fish community and to evaluate the ecosystem health based on the faunal composition and guild structure in 2007 in Baekma River. Mean concentrations of biological oxygen demand (BOD) and chemical oxygen demand (COD) were 2.8 and $4.0mg\;L^{-1}$, respectively and total nitrogen (TN) and total phosphorus (TP) were $5.0mg\;L^{-1}$ and $158{\mu}g\;L^{-1}$, which is indicating that the river is in an eutrophic state. Especially, organic pollution and eutrophication occurred in the downstream reach of Baekma River. A total of 19 fish species were collected during the study and the most dominant species was Opsariichthys uncirostris amurensis accounted 48% of the total abundances. The proportion of sensitive species was low (2.3%), compared with that of tolerant species (71.8%). These results suggest that tolerant species and the biotic quality of the fish community was severely degraded. According to the multi-metric model, the Index of Biological Integrity (IBI), the mean model value of the fish community in Baekma River was estimated as 14.8 indicating a "poor" condition. The minimum values of the IBI were observed in the downstreams, and this was mainly attributed to chemical pollutions of nutrients (N, P) and organic matters.