• Journal of the Korea Institute of Building Construction
• /
• v.23 no.3
• /
• pp.315-326
• /
• 2023

The design principles and implementation of rebar lap splice in architectural structures are governed by building regulations. Nevertheless, the minimization of rebar-cutting waste (RCW) is often impeded by the mandatory requirements pertaining to the rebar lapping zone as prescribed in design codes. In real-world construction scenarios, compliance with these rules often falls short due to hurdles concerning productivity, quality, safety, time, and cost. This discrepancy between code stipulations and on-the-ground construction practices necessitates an academic exploration. The goal of this research was to delve into the effect of rebar lap splice placement on the robustness and constructability of building edifices. The study initially took on a review of the computation of rebar lapping length and the rules revolving around the lapping zone. Following this, a structural robustness and constructability examination was undertaken, focusing on adherence to the lap splice zone. The interpretations and deductions of the research led to the following insights: (1) the efficacy of rebar lap splice is not solely contingent on the moment, and (2) the implementation of rebar lap splice beyond the specified zone can match the structural integrity and robustness of those confined within the designated area. As a result, the constraints on the rebar lapping zone ought to be revisited and possibly relaxed. The conclusions drawn from this research are anticipated to reconcile the disconnect between building codes and practical construction conditions, furnishing invaluable academic substantiation to further the endeavor of achieving near-zero RCW.

• Computers and Concrete
• /
• v.31 no.5
• /
• pp.395-403
• /
• 2023

The paper investigates the effect of two parameters - sand content (SC) and grain migration during shearing - on the mechanical properties of gravel-sand mixtures. Consolidated undrained (CU) triaxial tests were carried out on eight series of mixtures containing gravel (1<d<16 mm) and sand (0.1<d<1 mm). The prepared mixtures have sand contents of 0, 10, 15, 20, 40, 54, 94 and 100%, and a relative density of 60%. The transition sand content (TSC) is experimentally defined and marks the transition from gravel-driven to sand-driven behavior. For SC<TSC, the dry density of the mixture increases with SC. This induces an increase in undrained peak strength and dilative trend. The slope and position of the critical state line (CSL) are also deeply dependent on SC. At SC=TSC, the mixtures exhibit the largest dry density and yield the highest undrained peak strength and the largest dilative trend. During shearing, large internal migration of grains was observed at the TSC, causing heterogeneity in the sample. Analysis of the CSL deduced from the final points of the triaxial tests shows that, at the TSC, failure appears to correspond to the behavior of the coarsest fraction of the soil. This fraction is located in the upper part of the sample, where the sand particles had been eliminated by suffusion. On the other hand, in the more stable materials, the CSL is consistent with the bulk grain size distribution of the soil.

• Journal of Environmental Science International
• /
• v.31 no.2
• /
• pp.149-169
• /
• 2022

Hwapocheon stream is located in Gimhae-si, Gyeongsangnam-do, and a part was declared a protected wetland area in 2017. In 2020 and 2021, we investigated the community structure of benthic macroinvertebrates of the Hwapocheon stream to provide ecological information for the management of the wetland. As a result, 4 phyla, 6 classes, 20 orders, 51 families, 83 species, and 2,621 individuals of benthic macroinvertebrates were identified. The average indices of diversity, richness, and evenness were the highest in the midstream area, whereas the highest average index of dominance was observed upstream. Seven biological water quality evaluations based on the distribution of benthic macroinvertebrates showed that the Biological Monitoring Working Party was an extremely suitable method for environmental evaluation of the Hwapocheon stream. Regarding functional feeding groups, the number of species of predators and gathering-collectors was the highest, and considering habitual dwelling groups, the number of species of clingers and sprawlers was the highest. The species number of Odonata, Hemiptera, and Coleoptera increased toward the downstream area, whereas the community loss index was the highest upstream. We also investigated relative resistance and resilience based on the distribution of aquatic insects and found that community stability was the highest downstream, whereas the lowest upstream.

• Journal of Environmental Science International
• /
• v.33 no.2
• /
• pp.139-160
• /
• 2024

The community structure of benthic macroinvertebrates in the Madongho Wetland protected area and inflow river located in Goseong-gun, Gyeongsangnam-do, was investigated in 2022 and 2023. We collected and identified 3,582 individuals belonging to 7 classes, 23 orders, 51 families, and 78 species over the 2 years from six sites. Gnorimosphaeroma naktongense was the dominant species with a ratio of 20%, and Caridina denticulata denticulata was the subdominant species with a ratio of 13.32%. Predators and gathering collectors were the most abundant in the functional feeding group, while sprawlers were the most diverse and numerous in the habitual dwelling group. Diversity, richness, dominance, and evenness were calculated as the biological indices. In addition, various biological water quality indices were calculated. Most insects in the inflow rivers belonged to group I in evaluating relative resistance and resilience, showing high colony stability. The results of analyzing the correlation between salinity and substrate particle size with brackish water species showed that Gnorimosphaeroma naktongense and Hediste japonica had a significant positive correlation with salinity, while Assiminea lutea and Neomysis awatschensis had a significant positive correlation with substrate particle size. Additionally, Sinelobus kisui was found to be a new record of Korean Tanaididae in this study.

• KDI Journal of Economic Policy
• /
• v.46 no.1
• /
• pp.21-51
• /
• 2024

Since the Global Financial Crisis of 2008-2009, the importance of nonbank financial institutions in macroprudential management has increased significantly. Consequently, major countries and international financial institutions have been actively discussing and implementing macroprudential supervision and regulation for non-bank financial institutions (NBFI). In this context, this paper analyzes the systemic risk of both banks and non-bank sectors (securities firms and insurance companies) in South Korea over different time periods. Using the widely recognized ΔCoVaR methodology for measuring systemic risk, the analysis reveals that systemic risk increased substantially across all three sectors (banks, securities firms, and insurance companies) during the Global Financial Crisis, the European Sovereign Debt Crisis, and the COVID-19 pandemic. Although the banking sector exhibited relatively high systemic risk compared to the securities and insurance sectors, the relative differences in systemic risk varied across the different crisis periods. Notably, during the margin call crisis in March of 2020, the gap in systemic risk between the banking and securities sectors decreased significantly compared to that during both the Global Financial Crisis and the European Sovereign Debt Crisis, indicating that securities firms had a more substantial impact on risk in the overall financial system during this period. Furthermore, I analyze the impact of the issuance of equity-linked securities (ELS) by financial institutions on systemic risk, as measured by ΔCoVaR, finding that an increase in the outstanding balance of ELS issuance by financial institutions had an impact on increasing ΔCoVaR during the three crisis periods. These findings underscore the growing importance of non-bank financial institutions in relation to South Korea's macroprudential management and supervision. To address this evolving landscape, enhanced monitoring and regulatory measures focusing on non-bank systemic risk are essential components of maintaining financial stability in the country.

• Geomechanics and Engineering
• /
• v.36 no.6
• /
• pp.527-543
• /
• 2024

In the implementation of most civil structures, especially underground, deep excavations with a vertical slope are required. Using flexible retaining walls is applied as one of the ways to stabilize vertical holes. Therefore, it is necessary to know the parameters affecting the performance of such walls in reducing their horizontal movement. In this research, by building a suitable laboratory model, the parameters of the amount of flexibility, the embedment depth of the wall, the type and number of tieback in the wall were investigated for 42 static laboratory models. The purpose of this research is to study the flexible retaining wall with helical tieback compared to simple tieback at different heights, which shows the best performance in terms of reducing horizontal displacement in proportion to increasing or decreasing flexibility. On the other hand, one of the parameters affecting the flexibility of the wall, which is its bending stiffness, was extracted by numerical software outputs and studied on the results such as relative flexibility, stiffness, safety and numerical stability of the wall.The results of this study show that among the parameters, in the first place, the effect of the type of tieback is inhibited and in the second place, the ratio of thickness to wall height is known as the most important parameter. the best performance for walls with the helical tiebacks in reducing their horizontal displacement can be economically, flexibly and stability assigned to a wall that tiebacks is in the range of H2/t to H4/t and its flexibility ratio is 2/3.

• Journal of the Korean earth science society
• /
• v.42 no.5
• /
• pp.496-503
• /
• 2021

By analyzing the characteristics of atmospheric stability in the southern coastal region of the Korean Peninsula in the summer of 2019, a quantitative threshold of atmospheric instability indices was derived for predicting rainfall events in the Korean Peninsula. For this analysis, we used data from all of the 243 radiosonde intensive observations recorded at the Boseong Standard Weather Observatory (BSWO) in the summer of 2019. To analyze the atmospheric stability of rain events and mesoscale atmospheric phenomena, convective available potential energy (CAPE) and storm relative helicity (SRH) were calculated and compared. In particular, SRH analysis was divided into four levels based on the depth of the atmosphere (0-1, 0-3, 0-6, and 0-10 km). The rain events were categorized into three cases: that of no rain, that of 12 h before the rain, and that of rain. The results showed that SRH was more suitable than CAPE for the prediction of the rainfall events in Boseong during the summer of 2019, and that the rainfall events occurred when the 0-6 km SRH was 150 m² s^-2 or more, which is the same standard as that for a possible weak tornado. In addition, the results of the atmospheric stability analysis during the Changma, which is the rainy period in the Korean Peninsula during the summer and typhoon seasons, showed that the 0-6 km SRH was larger than the mean value of the 0-10 km SRH, whereas SRH generally increased as the depth of the atmosphere increased. Therefore, it can be said that the 0-6 km SRH was more effective in determining the rainfall events caused by typhoons in Boseong in the summer of 2019.

• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.2
• /
• pp.191-204
• /
• 2005

Building and furnishing materials and consumer product are important sources of volatile organic compounds(VOCs) and other aldehydes in the indoor environment. Some available evidence indicates that VOCs can cause adverse health effects to the building occupants and contribute to some of the symptoms of what we call, 'Sick House Syndrome' in Korea. The aims of this study were to evaluate the efficiency of emission system and to investigate comparison of the emission characteristics of different building materials such as wall-papers, paints, and adhesives. The emission of VOCs from building materials were determined in the small chambers defining the temperature, relative humidity, and ventilation rate in this study. VOCs were sampled for 20 minutes using Tenax-TA tubes and analysed by GC-MS with thermal desorption. The stability of conditions for temperature and relative humidity in this small chamber system showed that the fluctuation of temperature was between 25.4$\pm$0.3$^{\circ}C$ and that of relative humidity was 50.2$\pm$0.6$\%$ under the airflow rate of 167 mL/min. The emission tests from building materials resulted in TVOC emission rates of 0.011 $\~$ 3.108 mg/m$^{2}$h after 7 days. The general wall-papers emitted toluene abundantly and the natural wall-papers mainly emitted n-butanol and a minor amount of alkanes compound such as n -tetradecane. The remainder consisted of toluene, m,p -xylene, and styrene. The paints mainly emitted toluene and the adhesives mainly emitted chloroform as well as toluene. As a result, this study is expected to suggest meaningful data for future studies in exposure control through selecting healthy building materials and for the establishment of guidelines for various building materials in Korea.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.6
• /
• pp.78-86
• /
• 2014

In this paper, a novel intensity-based fiber optic vibration sensor using a mass-spring structure, which consists of four serpentine flexure springs and a rectangular aperture within a proof mass, is proposed and its feasibility test is given by the simulation and experiment. An optical collimator is used to broaden the beam which is modulated by the displacement of the rectangular aperture within the proof mass. The proposed fiber optic vibration sensor has been analyzed and designed in terms of the optical and mechanical parts. A mechanical structure has been designed using theoretical analysis, mathematical modeling, and 3D FEM (Finite Element Method) simulation. The relative aperture displacement according to the base vibration is given using FEM simulation, while the output beam power according to the relative displacement is measured by experiment. The simulated sensor sensitivity of $15.731{\mu}W/G$ and detection range of ${\pm}6.087G$ are given. By using reference signal, the output signal with 0.75% relative error shows a good stability. The proposed vibration sensor structure has the advantages of a simple structure, low cost, and multi-point sensing characteristic. It also has the potential to be made by MEMS (Micro-Electro-Mechanical System) technology.

• Food Science and Biotechnology
• /
• v.15 no.5
• /
• pp.698-703
• /
• 2006

We investigated how the addition of polypeptides to instant fried noodle dough affects the dough properties, starch gelatinization, and textural properties of cup-type instant fried noodles. After comparing farinograph results of 100% wheat flour with 1% wheat flour substituted with gluten, there was a small difference in the mechanical dough properties. However, in the case of 1% wheat flour substituted with gluten peptides, the dough development time increased, dough stability decreased, and weakness increased. On the other hand, when gluten or gluten peptides were added, starch gelatinization did not change significantly. At the steaming stage, substitution with gluten peptides or soybean peptides markedly changed the molecular weight distributions of extractable polypeptides. Especially in the case of wheat flour substituted with 1% gluten peptides, the relative portion of low Mw extractable polypeptides (2.5-50 kDa) decreased more compared to a control. Also, the hardness and chewiness decreased in cooked cup-type instant fried noodles containing gluten peptides. This suggests that the addition of gluten peptides can reduce the rehydration time of cup-type instant fried noodles.