• Journal of Korea Water Resources Association
• /
• v.54 no.7
• /
• pp.485-493
• /
• 2021

Groundwater is an important water resource that can be used along with surface water. In particular, in the case of island regions, research on groundwater level variability is essential for stable groundwater use because the ratio of groundwater use is relatively high. Researches using artificial intelligence models (AIs) for the prediction and analysis of groundwater level variability are continuously increasing. However, there are insufficient studies presenting evaluation criteria to judge the appropriateness of groundwater level prediction. This study comprehensively analyzed the research results that predicted the groundwater level using AIs for various regions around the world over the past 20 years to present the range of allowable groundwater level prediction errors. As a result, the groundwater level prediction error increased as the observed groundwater level variability increased. Therefore, the criteria for evaluating the adequacy of the groundwater level prediction by an AI is presented as follows: less than or equal to the root mean square error or maximum error calculated using the linear regression equations presented in this study, or NSE ≥ 0.849 or R² ≥ 0.880. This allowable prediction error range can be used as a reference for determining the appropriateness of the groundwater level prediction using an AI.

• Korean Journal of Ichthyology
• /
• v.33 no.2
• /
• pp.74-83
• /
• 2021

Distribution status, habitat characteristics, and extinction threat evaluation of the endangered species, Brachymystax lenok tsinlingensis were investigated in 2015 and 2019. Historical distribution reports of B. l. tsinlingensis were divided into before 1990, 1997~2006, 2000~2011, and 2010~2019. Among the 150 sampling sites investigated during the study period, number of individuals of B. l. tsinlingensis were collected 542 individuals from 67 sites. The streams inhabited of B. l. tsinlingensis were Naerincheon (11 stations), Odaecheon (11 stations), Bukcheon (10 stations), Bangtaecheon (8 stations), Songjeongricheon (4 stations), Suipcheon (3 stations), Inbukcheon (3 stations), Hyeondongcheon (3 stations) etc. The main habitat of B. l. tsinlingensis was upstream of the river with a high altitude of more than 400 m, 4~20 m water flow width, 1~2 m water depth, and high ratio (70~80%) boulder bottoms. The main reasons for the decline in population size were assumed as river works, construction of reservoirs and bridges, discharge of contaminated water into the river, the inflow of summer vacationers, and weir. Compared to our results there exists evidence that states a 20.7% reduction in occupancy within 10 years, in a small appearance range (7,732 km²) and occupancy area (268 km²), number of disconnected locations (15 locations), and a decline in habitat quality. Therefore, B. l. tsinlingensis is now considered as Near Threatened (NT) based on the results (Near meets VU A2acd, B1b(i,ii,iii)+B2b(i,ii,iii)) of IUCN Red List categories and criteria.

• Korean Journal of Ichthyology
• /
• v.34 no.1
• /
• pp.34-43
• /
• 2022

A distribution survey was conducted from March to August 2021 to evaluate the distribution status, habitat characteristics, and threat of extinction of the Korean cold-water fish Ladislabia taczanowskii Dybowski (Cypriniformes, Cyprinidae). Historical distribution reports were divided into 1997~2005, 2006~2012, 2013~2019, and distribution surveyed 169 sampling sites, and 1,040 individuals were collected from 72 sites. Areas where the habitat was confirmed were Namhan River (27 stations), Han River (17 stations), Bukhan River (16 stations), Samcheok Osipcheon (4 stations), Yeongokcheon (3 stations), Gangneung Namdaecheon (2 stations), Jeoncheon (1 station), Chucheon (2 stations). The main habitat of L. taczanowskii was upstream of the river with a high altitude of more than 300 m, 2~30 m water flow width, 0.3~1.5 m water depth, and high ratio (50~90%) boulder bottoms. The main reasons for the decline in population size were assumed as river works, construction of reservoirs and bridges, discharge of contaminated water into the river, the inflow of summer vacationers, and weir. Compared to our results there exists evidence that states a 36.1% reduction in occupancy within 10 years, in a small appearance range (7,820 km²) and occupancy area (288 km²), number of disconnected locations (19 locations), and a decline in habitat quality. Therefore, L. taczanowskii is now considered as Vulnerable (VU) based on the results (VU A2ac, Near meets B1b (i, ii, iii)+B2b (i, ii, iii)) of IUCN Red List categories and criteria. Lastly, the conservation plan of Ladislabia taczanowskii was discussed.

• Wind and Structures
• /
• v.34 no.1
• /
• pp.115-125
• /
• 2022

The high-Reynolds number flow around a rectangular cylinder, having streamwise to crossflow length ratio equal to 5 is analyzed in the present paper. The flow is characterized by shear-layer separation from the upstream edges. Vortical structures of different size form from the roll-up of these shear layers, move downstream and interact with the classical vortex shedding further downstream in the wake. The corresponding mean flow is characterized by a recirculation region along the lateral surface of the cylinder, ending by mean flow reattachment close to the trailing edge. The mean flow features on the cylinder side have been shown to be highly sensitive to set-up parameters both in numerical simulations and in experiments. The results of 21 Large Eddy Simulations (LES) are analyzed herein to highlight the impact of the lateral mean recirculation characteristics on the near-wake flow features and on some bulk quantities. The considered simulations have been carried out at Reynolds number Re=DU_∞/ν=40 000, being D the crossflow dimension, U_∞ the freestream velocity and ν the kinematic viscosity of air; the flow is set to have zero angle of attack. Some simulations are carried out with sharp edges (Mariotti et al. 2017), others with different values of the rounding of the upstream edges (Rocchio et al. 2020) and an additional LES is carried out to match the value of the roundness of the upstream edges in the experiments in Pasqualetto et al. (2022). The dimensions of the mean recirculation zone vary considerably in these simulations, allowing us to single out meaningful trends. The streamwise length of the lateral mean recirculation and the streamwise distance from the upstream edge of its center are the parameters controlling the considered quantities. The wake width increases linearly with these parameters, while the vortex-shedding non-dimensional frequency shows a linear decrease. The drag coefficient also linearly decreases with increasing the recirculation length and this is due to a reduction of the suctions on the base. However, the overall variation of C_D is small. Finally, a significant, and once again linear, increase of the fluctuations of the lift coefficient is found for increasing the mean recirculation streamwise length.

• Journal of Bio-Environment Control
• /
• v.32 no.1
• /
• pp.34-39
• /
• 2023

Growth modeling in plant factories can not only control stable production and yield, but also control environmental conditions by considering the relationship between environmental factors and plant growth rate. In this study, using the expolinear function, we modeled perilla [Perilla frutescens (L.) Britt.] cultivated in a plant factory. Perilla growth was investigated 12 times until flower bud differentiation occurred after planting under light intensity, photoperiod, and the ratio of mixed light conditions of 130 μmol·m^-2·s^-1, 12/12 h, red:green:blue (7:1:2), respectively. Additionally, modeling was performed to predict dry and fresh weights using the expolinear function. Fresh and dry weights were strongly positively correlated (r = 0.996). Except for dry weight, fresh weight showed a high positive correlation with leaf area, followed by plant height, number of leaves, number of nodes, leaf length, and leaf width. When the number of days after transplanting, leaf area, and plant height were used as independent variables for growth prediction, leaf area was found to be an appropriate independent variable for growth prediction. However, additional destructive or non-destructive methods for predicting growth should be considered. In this study, we created a growth model formula to predict perilla growth in plant factories.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.37 no.5
• /
• pp.431-435
• /
• 1992

This experiment was carried out to evaluate Korean red rices as useful genetic resource. Semi-wild red rices were collected from farmer's field of the Korean peninsula from 1988 to 1991. The collected red rices were classified into two groups according to length /width ratio of paddy rice and ecological characters. One was long grain red rice and the other was short grain red rice. Those were evaluated in yield components, culm length and panicle length. Mean number of panicles per hill of collected long grain red rices was 21.5 and that of short grain was 11.8. Number of spikelets per panicile of the long and short grain red rices were 86.1 and 108.7, respectively. 1000 grains weight of long grain was 20.1g and that of short grain was 20.2g. Spikelet fertility of long and short grain were 80.4% and 79.4%, respectively. Culm length of long grain was 103.6cm and that of short grain was 94.8cm. Panicle length of long and short grain were 22.1cm and 21.3cm, respectively. Number of panicles per hill, number of spikelets per panicle and culm length were significantly different between the two groups, however no differences, in panicle, length and seed fertility were found between the two groups.

• Journal of Periodontal and Implant Science
• /
• v.53 no.4
• /
• pp.306-317
• /
• 2023

Purpose: Biphasic calcium phosphate (BCP), a widely used biomaterial for bone regeneration, contains synthetic hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), the ratio of which can be adjusted to modulate the rate of degradation. The aim of this study was to evaluate the clinical and radiographic benefits of reconstructing peri-implant bone defects with a newly developed BCP consisting of 60% β-TCP and 40% HA compared to demineralized bovine bone mineral (DBBM). Methods: This prospective, multicenter, parallel, single-blind randomized controlled trial was conducted at the periodontology departments of 3 different dental hospitals. Changes in clinical (defect width and height) and radiographic (augmented horizontal bone thickness) parameters were measured between implant surgery with guided bone regeneration (GBR) and re-entry surgery. Postoperative discomfort (severity and duration of pain and swelling) and early soft-tissue wound healing (dehiscence and inflammation) were also assessed. Data were compared between the BCP (test) and DBBM (control) groups using the independent t-test and the χ² test. Results: Of the 53 cases included, 27 were in the test group and 26 were in the control group. After a healing period of 18 weeks, the full and mean resolution of buccal dehiscence defects were 59.3% (n=16) and 71.3% in the test group and 42.3% (n=11) and 57.9% in the control group, respectively. There were no significant differences between the groups in terms of the change in mean horizontal bone augmentation (test group: -0.50±0.66 mm vs. control groups: -0.66±0.83 mm, P=0.133), postoperative discomfort, or early wound healing. No adverse or fatal complications occurred in either group. Conclusions: The GBR procedure with the newly developed BCP showed favorable clinical, radiographic, postoperative discomfort-related, and early wound healing outcomes for peri-implant dehiscence defects that were similar to those for DBBM.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.3
• /
• pp.110-115
• /
• 2023

During the Hg₂Br₂ physical vapor transport process, with increasing the partial pressure of component B, P_B from 40 Torr to 200 Torr, a unicellular convective flow structures move from the crystal growth region to the center region in the vapor phase. The boundary layer flow is dominant for P_B = 40 Torr, and the core region flow is dominant for P_B = 200 Torr. The flow in the vapor phase shows a three-dimensional convective flow structure with a single cell (unicellular) for P_B = 40 Torr and 200 Torr, exhibits an asymmetrical flow with respect to the x, y central axis under the horizontally oriented configuration with an aspect ratio (length-to-width) of 3 and linear conducting walls. The critical temperature difference between the source and crystal region is about 30 K. The total molar flux of Hg₂Br₂ increases with the temperature difference until the total molar flux reaches the critical value. At the critical total molar flux, the total molar flux abruptly decreases.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5A
• /
• pp.729-735
• /
• 2008

For well-constructed concrete, its service life is a long period and it has an enough durability performance. For cracked concrete, however, it is clear that cracks should be a preferential channel for the penetration of aggressive substance such as chloride ions accoding to author's previous researches. Even though crack width can be reduced due to the high reinforcement ratio, the question is to which extend these cracks may jeopardize the durability of cracked concrete. If the size of crack is small, surface treatment system can be considered as one of the best options to extend the service life of concrete structures exposed to marine environment simply in terms of cost effectiveness versus durability performance. Thus, it should be decided to undertake an experimental study to deal with the effect of different types of surface treatment system, which are expected to seal the concrete and the cracks to chloride-induced corrosion in particular. In this study, it is examined the effect of surfaced treated systems such as penetrant, coating, and their combination on chloride penetration through microcracks. Experimental results showed that penetrant can't cure cracks. However, coating and combined treatment can prohibit chloride penetration through cracks upto 0.06 mm, 0.08 mm, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4B
• /
• pp.335-344
• /
• 2006

In this study, sequential mixing model (SMM) was proposed based on the Taylor's theory which can be summarized as the fact that longitudinal advection and transverse diffusion occur independently and then the balance between the longitudinal shear and transverse mixing maintains. The numerical simulation of the model were performed for cases of different mixing time and transverse velocity distribution, and the results were compared with the solutions of 1-D longitudinal dispersion model (1-D LDM) and 2-D advection-dispersion model (2-D ADM). As a result it was confirmed that SMM embodies the Taylor's theory well. By the comparison between SMM and 2-D ADM, the relationship between the mixing time and the transverse diffusion coefficient was evaluated, and thus SMM can integrate 2-D ADM model as well as 1-D LDM model and be an explanatory model which can represents the shear flow dispersion in a visible way. In this study, the predicting equation of the longitudinal dispersion coefficient was developed by fitting the simulation results of SMM to the solution of 1-D LDM. The verification of the proposed equation was performed by the application to the 38 sets of field data. The proposed equation can predict the longitudinal dispersion coefficient within reliable accuracy, especially for the river with small width-to-depth ratio.