• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.135-142
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• 2021

In this work, multi-turn wings and guide plates are installed on recycled aggregate crushing devices to improve existing low recycled aggregate quality. Simulation analysis to evaluate the crushing efficiency of the new device shows enhanced crushing efficiency since the installation of guide plates shreds most of the inputs inside the crushing drum, and the multi-turn wings and guide plates induce rebound and circulation of the aggregate. Through this, the new device was found to be more economical and efficient than the existing recycled aggregate crushing device. Also, the amount of cement paste and mortar attached to the surface of the aggregate was smaller than that of the existing recycled aggregate, and it was found that the mechanical properties and elastic modulus deterioration were reduced. However, the carbonation resistance of concrete was not improved to the level of natural aggregates due to the remaining tiny cement paste and mortar on the surface of the new recycled aggregate. Therefore, it is deemed necessary to further research and experiment such as device improvement or binder development to reduce durability degradation of concrete mixed with new recycled aggregate.

• Journal of agricultural medicine and community health
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• v.48 no.1
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• pp.41-49
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• 2023

Objectives: To obtain audiologic basic data to diagnose the noise induced hearing loss of workers in fisheries. Methods: The charts of the referred fishermen with noise induced hearing loss from November 2022 to February 2023 at a general hospital were retrospectively reviewed. Pure tone audiometry, speech audiometry, auditory brainstem response test and auditory steady state response test were conducted. Results: All of them were men over 60 years of age, and the average duration of exposure to noise was 38.9 ± 10.8 years, and the average symptom duration of hearing loss was 13.4 ± 4.3 years. Although the hearing thresholds in the high frequencies were higher than thresholds in the low frequencies, the audiogram showed a down-sloping pattern without rebound at 8 kHz. 10.5% of the cases had thresholds greater than 75 dB in high frequencies, but 57.9% had thresholds greater than 40 dB in low frequencies. Other hearing test results of fishermen were similar to those of general noise-induced hearing loss. Conclusions: Although the fishermen were exposed to noise for a long time, they recognized hearing loss late. The hearing threshold in lower frequencies of the fishermen was higher than expected. Further studies will be needed to analyze the audiologic characteristics of noise-induced hearing loss of the fishermen after confirming noise exposure by conducting a survey on the working environment, such as the noise level and working hours.

• The Journal of the Convergence on Culture Technology
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• v.9 no.2
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• pp.533-543
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• 2023

This study explores the influence of the COVID-19 pandemic on the Korean art market and contrasts the classic hedonic method of art price prediction with the Artificial Neural Network technique. The empirical analysis of this paper utilizes 14,639 observations of Korean art auction data from 2015 to 2021. There are three types of variables in this study: artist-related, artwork-related, and sales-related. Previous studies have suggested that these three types of variables influence art prices. The empirical findings in this research are in twofold. First, in terms of RMSE and R², the Artificial Neural Network outperforms the hedonic model. Both techniques discover that sales and artwork variables have a greater impact than artist-related attributes. Second, when the primary factors of art price are controlled, Korean art prices are found to fall dramatically in 2020, shortly following the onset of COVID-19, but to rebound in 2021. The main lesson in this study is that the Artificial Neural Network enhances art price prediction and reduces information asymmetry in the Korean art market even in the face of unanticipated turmoil such as the COVID-19 outbreak.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.4 no.2
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• pp.181-190
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• 2001

Purpose: The aim of this study is to investigate the usefulness of intestinal ultrasonography (US) and upper gastrointestinal endoscopy in the early diagnosis of Henoch-Sch$\"{o}$nlein purpura (HSP) with the gastrointestinal (GI) symptoms preceding the emergence of the skin lesion. Methods: The clinical, intestinal US and upper gastrointestinal endoscopic records of 85 patients (88 cases) with GI symptoms relating to HSP presenting between January 1999 and April 2001 were reviewed. Results: 1) GI symptoms were observed in 52 cases (59%) and skin, joint, renal and scrotal manifestations were observed in 88 (100%), 64 (73%), 15 (17%), 3 cases (3%) respectively. 2) Out of 52 cases with GI symptoms, abdominal pain was observed in all cases (100%). Positive stool occult blood, nausea and vomiting, abdominal tenderness, melena or tarry stool, diarrhea, hematemesis, rebound tenderness and rigidity were observed in 28 (50%), 17 (33%), 17 (33%), 12 (23%), 6 (12%), 4 (8%), 1 (2%) and 1 case (2%) respectively in order of frequency. 3) Intestinal US examination was performed in 27 cases with HSP and GI symptoms (52 cases). Out of 27 sonographic examinations 22 showed abnormal findings. Thickening of the duodeno-jejunal wall was observed in 16 cases (73%). Free peritoneal fluid, enlarged mesenteric lymph node, ileus and abnormal gall bladder were seen in 8 (36%), 8 (36%), 4 (18%) and 1 case (5%) respectively. In three cases of HSP without GI symptoms, those changes were absent. 4) In all of five cases with HSP and GI symptoms, endoscopic study showed mucosal edema and multiple hemorrhagic erosions especially at the second portion of the duodenum. Biopsy specimens from the duodenum of 2 cases out of 5 endoscopic examinations showed acute inflammatory infiltrates in the mucosa with hemorrhage. 5) Both intestinal US and endoscopic studies were performed in 4 cases with HSP and GI symptoms simultaneously. Out of 4 those cases, 3 cases showed the thickened duodeno-jejunal wall on the intestinal US, which suggested erosive hemorrhagic duodenitis by endoscopic findings. Conclusion: The typical but nonpathognomonic intestinal US findings including the thickening of the duodeno-jejunal wall and upper gastrointestinal endoscopic findings including hemorrhagicerosive duodenitis, in children with GI symptoms, should be considered a manifestation of HSP, even in the absence of skin lesion.

• Clinical and Experimental Pediatrics
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• v.48 no.1
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• pp.63-67
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• 2005

Purpose : Henoch-$Sch{\ddot{o}}nlein$ purpura(HSP) is a systemic vasculitis, characterized by cutaneous palpable purpura, gastrointestinal(GI) symptoms, arthritis and renal involvement. In general, the prognosis is determined by GI complication as well as the severity of nephritis. In this study, we analyzed the statistical relationship between the GI symptom and other clinical findings for assessing the prognosis, and evaluated abdominal ultrasonographic findings for early diagnosis of this disease with atypical clinical presentation and early detection of serious GI complications. Methods : One hundred seventy seven patients with HSP in the Department of Pediatrics, Wonkwang University Hospital from January 1994 to June 2004, were enrolled. We retrospectively analyzed charts about clinical and abdominal ultrasonographic findings, and classified our patients into two groups(GI-Sx(-), GI-Sx(+)) for statistical analysis. Results : The ratio of female to male is 1.5 : 1. The peak age incidence was five to eight years in 95 cases(53%). The GI symptoms appeared in 117 cases(66%), which include abdominal pain 115 (98 %), tenderness 45(38%), nausea and vomiting 35(30%), bloody stool 10(8.5%), diarrhea four(3.4%), rebound tenderness four(3.4%), and also intussusception and appendicitis were complicated in five and two cases respectively. GI-Sx(+) group had an increased risk of renal involvement and relapse than the GI-Sx(-) group. But there were no relationships about sex and age incidence, or other clinical and laboratory findings between two groups. Ultrasonographic findings in 98 patients with GI symptoms included small bowel thickening in 70 cases(71%) in which duodenum, jejunum and ileum were involved in 71%, 45.7%, 40% respectively, small bowel dilatation in 41 cases(42%), lymph node swelling in 46 cases(47%), and ascites in 25 cases(25.5%). Conclusion : GI symptoms in patients with HSP suggested increased risk of renal involvement and relapse. Abdominal ultrasonography could be helpful in the early diagnosis on atypical clinical presentation and early detection of serious GI complication in these patients.

• Journal of Biomedical Engineering Research
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• v.19 no.6
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• pp.617-622
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• 1998

A cryotherapy system using cold air was developed. The developed system had superior low-temperature characteristics with various flow rates and nozzle sizes, and used R-404A, as a coolant, which has no destructive effects of Ozone layers. Flow rates and the treatment time can be easily altered during the operation. In addition, and alarm system was designed for the overload, overheat, and over-charge of the machine. For clinical applications, skin temperatures, intra-articular temperatures of the knee joint and intra-muscluar temperatures of the gluteal muscles were measured during and after the cryotherapy. After a 5-minute therapy, skin and intra-articular temperatures decreased by $23.3{\pm}4.7 and 4.1 {\pm}1.0^{circ}C$, respectively. A 5-minute cryotherapy was good enough to maintain low intra-articular temperatures for 2-3 hours. Resting intra-muscular temperatures in 2, 4, and 6cm deep in the gluteal muscle were $36.5{\pm}1.2, 36.9{\pm}0.2, 37.1{\pm}0.2^{circ}C$, respectively (p<0.05). Lowest temperatures in 2, 4, and 6cm depth were $35.1{\pm}0.7, 36.2{\pm}0.4, 36.9{\pm}0.3^{circ}C$, respectively (p<0.05). Temperatures after a 2-hour cold air application on the skin and in the muscle in dept도 of 2, 4, and 6cm were $32.2{\pm}1.1, 36.2{\pm}0.5, 36.6{\pm}0.3, 36.9{\pm}0.3^{circ}C$respectively (p<0.05). Temperatures on the skin and in the muscle significantly decreased after 2 hours, compared with before cold air application (p<0.05). The intra-muscular temperature was changed more slowly than the skin temperature, and the deeper the muscle, the lesser temperature changes. The effect of a 5-minute cold air application lasts up to 2 hours, and it seems that the rebound-rise of the temperature dut to the reactive vasodilatation does not occur in the gluteal muscle.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.303-317
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• 1994

This study was designed to measure the changes in the titer of tooth root antibodies accompanying root resorption associated with orthodontic tooth movement in dogs to explore a role of the specific immune response in root resorption during orthodontic tooth movement. Five adult mongrel dogs, 2 years of age, were used in the study. Six lower incisors were extracted as sources of homologous antigen in the dogs. Tooth root antigen preparations were made from a 6M Guanidine-HCl-10% EDTA(pH5.0) extract of these root dentins. Root resorption was elicited by intrusion of six maxillary incisors with 200-250gm intrusive force. In 9th week, resorbing six maxillary anterior teeth were extracted. Serum samples were taken from each dog prior to intrusion and weekly for 11 consecutive weeks. Serum autoantibody titers were determined with an enzyme-linked immunosorbent assay. As controls for antibody specificity, sera which were previously incubated with tooth root antigen as well as sera to an unrelated bacterial antigen (Porphyromonas gingivalis 33277) for 3 hours at 25 were measured in all runs. Root resorption was monitored monthly using occlusal radiographs. And then root resorption patterns were observed with a zoom stereo microscope (Model SZH-121, Olympus optical Co. Ltd.). Incisors did not show clear radiographic evidence of significant and progressive root resorption, but periodontal ligament space had widened. But root resorption was observed on the apical regions of the maxillary incisors with a zoom stereo microscope. Teeth showed the shallow depression generally accompanying deep resorption. These demonstrate a slight tendency for an immediate decrease followed by rebound to levels above the pre-treatment baseline. A peak titer of autoantibody to dentin antigen occurred on day 28, then steadily decreased during the 9th week period as the roots resorbed and then rapidly spiked in animals when the resorbing teeth were extracted. When sera is incubated with tooth root antigen, serum activity in the ELISA was almost absent. This is because serum activity in the ELISA could be removed by absorption of the serum with dog dentin antigen. Serum ELISA activity to the unrelated bacterial antigen remained essentially unchanged in all animals throughout the experimental period. When the time course of changes in autoantibody to homologous tooth root antigen prepatration and unrelated bacterial antigen was compared, no significant differences were found(${\alpha}=0.05$). In general, the overall pattern of changes in autoantibody was similar to the two antigens. These findings suggest the possibility that these immunologic changes precede a significant development of root resorption lesions rather than merely reflecting their presence. Therefore, this suggests that the changes of antibody levels may have some predictive value for root resorption.

• Journal of the Korean Institute of Landscape Architecture
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• v.51 no.4
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• pp.1-15
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• 2023

This research intended to reveal the special characteristics of the vegetation structure and the tendency of change of -landfill slope districts, which are reclaimed land, through an investigationsinto the presently existent vegetation and plant community structure of the World Cup Park landfill slope district. For the analysis of changes in vegetation, this study compared the results of field surveys in 1999, 2003, 2005, 2007, 2008, 2012, 2016, and 2021. For the investigation into the plant community structure, a field investigation was carried out in 2021 with six fixed investigation districts designated in 1999 as subjects. To analyze the change in the plant community structure, the past data on the population, the number of the species, and the species diversity by the layer in 2021 were compared and analyzed in the landfill slope district, which is reclaimed land. The changes of the vegetation distribution and the power had been affected by typhoons (Kompasu). Above the plantation foundation, which had been dry and poor, Salix koreensis, marsh woody plants that had formed the community, decreased greatly. The Robinia pseudoacacia community, after the typhoon in 2010, decreased in the number of species and population. Afterward, it showed a tendency to rebound. Regarding the Ailanthus altissima-Robinia pseudoacacia-Paulownia tomentosa community, the number of the species and the population had shown a change similar to the Robinia pseudoacacia community. The Paulownia tomentosa and the Ailanthus altissima have been culled. The slope was predicted as a Future Robinia pseudoacacia forest. The Salix pseudolasiogyne community has been transitioning to a Robinia pseudoacacia forest. Only some enumeration districts, the Robinia pseudoacacia forests and the Salix pseudolasiogyne, had been growing. However, most had been in been declining. It was predicted that this community will be maintained as a Robinia pseudoacacia forest in the future. As these vegetation communities are the representative vegetation of the landfill slope districts, which is reclaimed land, there is a need to understand the ecosystem changes of the community through continuous monitoring. The results of this research can be utilized as a basic material for the vegetation restoration of reclaimed land.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.101-114
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• 2008

Pressurized grouting is a common technique in geotechnical engineering applications to increase the stiffness and strength of the ground mass and to fill boreholes or void space in a tunnel lining and so on. Recently, the pressurized grouting has been applied to a soil-nailing system which is widely used to improve slope stability. Because interaction between pressurized grouting paste and adjacent ground mass is complicated and difficult to analyze, the soil-nailing design has been empirically performed in most geotechnical applications. The purpose of this study is to analyze the ground behavior induced by pressurized grouting paste with the aid of laboratory model tests. The laboratory tests are carried out for four kinds of granitic residual soils. When injecting pressure is applied to grout, the pressure measured in the adjacent ground initially increases for a while, which behaves in the way of the membrane model. With the lapse of time, the pressure in the adjacent ground decreases down to a value of residual stress because a portion of water in the grouting paste seeps into the adjacent ground. The seepage can be indicated by the fact that the ratio of water/cement in the grouting paste has decreased from a initial value of 50% to around 30% during the test. The reduction of the W/C ratio should cause to harden the grouting paste and increase the stiffness of it, which restricts the rebound of out-moved ground into the original position, and thus increase the in-situ stress by approximately 20% of the injecting pressures. The measured radial deformation of the ground under pressure is in good agreement with the expansion of a cylindrical cavity estimated by the cavity expansion theory. In-situ test revealed that the pullout resistance of a soil nailing with pressurized grouting is about 36% larger than that with regular grouting, caused by grout radius increase, residual stress effect, and/or roughness increase.