• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.306-318
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• 2018

In order to evaluate the seismic capacity of massive vertical type breakwaters which have intensively been deployed along the coast of South Korea over the last two decades, we carry out the preliminary numerical simulation against the PoHang, GyeongJu, Hachinohe 1, Hachinohe 2, Ofunato, and artificial seismic waves based on the measured time series of ground acceleration. Numerical result shows that significant sliding can be resulted in once non-negligible portion of seismic energy is shifted toward the longer period during its propagation process toward the ground surface in a form of shear wave. It is well known that during these propagation process, shear waves due to the seismic activity would be amplified, and non-negligible portion of seismic energy be shifted toward the longer period. Among these, the shift of seismic energy toward the longer period is induced by the viscosity and internal friction intrinsic in the soil. On the other hand, the amplification of shear waves can be attributed to the fact that the shear modulus is getting smaller toward the ground surface following the descending effective stress toward the ground surface. And the weakened intensity of soil as the number of attacking shear waves are accumulated can also contribute these phenomenon (Das, 1993). In this rationale, we constitute the numerical model using the model by Hardin and Drnevich (1972) for the weakened shear modulus as shear waves go on, and shear wave equation, in the numerical integration of which $Newmark-{\beta}$ method and Modified Newton-Raphson method are evoked to take nonlinear stress-strain relationship into account. It is shown that the numerical model proposed in this study could duplicate the well known features of seismic shear waves such as that a great deal of probability mass is shifted toward the larger amplitude and longer period when shear waves propagate toward the ground surface.

• Journal of Food Hygiene and Safety
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• v.36 no.3
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• pp.228-238
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• 2021

The aim of this research was to develop a rapid and easy multi-residue method for determining dimethipin, omethoate, dimethipin, chlorfenvinphos and azinphos-methyl in agricultural products (hulled rice, potato, soybean, mandarin and green pepper). Samples were prepared using QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) and analyzed using gas chromatography-tandem mass spectrometry (GC-MS/MS). Residual pesticides were extracted with 1% acetic acid in acetonitrile followed by addition of anhydrous magnesium sulfate (MgSO₄) and anhydrous sodium acetate. The extracts were cleaned up using MgSO₄, primary secondary amine (PSA) and octadecyl (C₁₈). The linearity of the calibration curves, which waas excellent by matrix-matched standards, ranged from 0.005 mg/kg to 0.3 mg/kg and yielded the coefficients of determination (R²) ≥ 0.9934 for all analytes. Average recoveries spiked at three levels (0.01, 0.1, 0.5 mg/kg) and were in the range of 74.2-119.3%, while standard deviation values were less than 14.6%, which is below the Codex guideline (CODEX CAC/GL 40).

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.617-634
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• 2020

The purpose of this study is to investigate the relationship of between earthquakes and fluctuation of water level in a groundwater well of the active-fault zone and 124 national groundwater monitoring wells in Gyeongju area. The spatial and temporal relationships between the fluctuation of water level and the earthquake were analyzed by the calculation of earthquake effectiveness (ε) and q-factor which are the function of earthquake magnitude and distance from epicenter. Two earthquake events of E1 (April 22, 2019, M 3.8) and E2 (June 11, 2019, M 2.5) show a close relationship with a post-seismic 83 cm decrease and a pre-seismic 76 cm increase in water level at the active fault zone of Dangu-ri, respectively. The spatial analysis of water level fluctuation data in National Groundwater Monitoring Networks caused by earthquake events shows a more distinct response in deep groundwater around fault zones than other area, and a greater change in deep groundwater than shallow groundwater. It's inferred that the decrease and increase in groundwater level are affected by the expansion of fractures and compression of rock mass due to seismic stress, respectively. The effective ranges of ε-value and q-factor of the monitoring well in Dangu-ri were calculated as 2.70E-10~5.60E-10 and 14.4~18.0, respectively.

• Journal of the Korean GEO-environmental Society
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• v.23 no.9
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• pp.33-40
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• 2022

Sedimentation and pH neutralization has been investigated as preteatment of acid contaminate water. The settling and neutralizing process derive more effective degradation efficiency as the pre-treatment process before the removal process of adsorption, volatile, biodegradation, or oxidation. Settling velocity, uniformity coefficient, coefficient of curvature, and grain size index can define in the sedimentation process for characteristics of the soil. The stainless steel sieve has been used to separate each particle size of the dry soil by assembling in order of 4, 10, 20, 40, 80, 100, and 200 mesh sizes. The soil from Gamcheon Port in Busan drops upper side of the sieve and shakes back and forth to separate each different size of the particle. The 1L of Imhoff cone and 200 mL of the mass cylinder were used as settling tanks to calculate settling velocity. Stokes' equation was used to figure out the average density of dry soil with a value from settling velocity. In the results, the average particle density and lowest settling velocity were 1.93 g/cm³ and 0.11 cm/s, respectively. These values can detect the range of settling points of sediment to prevent chemical accidents. In pH neutralization, the initial pH of 2, 3, 4, and 5 of nitric acid and sulfuric acid are used as an acid solution; 0.1, 0.01, and 0.001 M of sodium hydroxide and calcium hydroxide are used as a base solution. The main goal of this experiment is to figure out the volume percentage of the acid solution becomes pH 7. The concentration of 0.001 M of base solution exceeds all the conditions, 0.01 M exceeds partially, and 0.1 M does not exceed 5 v/v% except pH 2. Calcium hydroxide present less volume than sodium hydroxide at pH neutralization both sulfuric and nitric acid.

• Journal of the Korean Orthopaedic Association
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• v.55 no.2
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• pp.169-177
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• 2020

Purpose: To assess the effectiveness of mixed grafts in lumbar posterolateral fusion (PLF) by comparing the bone union rates of an autobone with a bone substitute mixed graft. Materials and Methods: The patients were followed-up for at least two years after PLF and divided into four groups according to the mixed graft retrospectively. Group I was 48 cases using a femoral head allobone. Group II was 38 cases using β-tricalcium phosphate. Group III was 92 cases using biphasic calcium phosphate. Group IV was 38 cases using biphasic calcium phosphate and autologous bone marrow. Union was evaluated by the work up simple radiographs after two years from PLF. Union was defined if the radiographs demonstrated a bilateral continuity in the fusion mass between the cephalad and caudal transverse processes with less than 2° of angular motion and no translation between the vertebrae at the level of fusion on the lateral flexion-extension radiographs. Results: According to simple radiographs after two years from PLF, the rate of union was highest in Group IV using local autobone, biphasic calcium phosphate and autologous bone marrow mixed graft. Conclusion: Biphasic calcium phosphate is an osteoconductive bone substitute that increases the bio-absorbability and mechanical strength. Autologous bone marrow has osteoinductive and osteogenic properties. These features can increase the rate of bone union. Therefore, a local autobone, biphasic calcium phosphate and autologous bone marrow mixed graft can be considered an effective bone graft substitute for lumbar PLF instead of an autobone graft.

• Korean Journal of Plant Resources
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• v.36 no.2
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• pp.181-190
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• 2023

Domestic hop (Humulus lupulus L.) production has been suspended since the early 1990s due to foreign imports, but interest in local production is rising due to the recent craft beer boom in Korea. This study was conducted focusing on the development of growth characteristics and propagation technology for 6 introduced hop cultivars as a basic study for domestic hop production and breeding program. In the hop growth survey conducted in 2021 and 2022, the 5-year-old plants after planting generally showed a tendency to increase the height of strobile setting, strobile size, number and weight of strobile per hill compared to the 4-year-old plants. As a result of the experiment with hop vine cuttings, the average rooting rate of all cultivars was as high as 88% even in only water treatment that were not added with Atonik (Atonik, Arysta, Japan), a rooting agent. There were differences between cultivars in rooting length and rooting rate according to the Atonik treatment method. When checking the survival rate of the rooted cuttings seedlings after transplanting into the soil, it was confirmed that the survival rate of the cuttings in the tissue culture room was significantly lower than that of the cuttings in the greenhouse. However, in transplanting step, cutting plants from culture room condition was strongly inhibited plant growth because of changing environment conditions. As a results of tissue culture, the thidiazuron (TDZ) 1 ㎎/L treatment in the media generated 6 to 9 shoots/explant, while the 6-benzylaminopurine (BAP) 1 ㎎/L treatment generated only 1 to 2 shoots/explant. Therefore, it is more effective to culture by adding TDZ rather than BAP. These results indicated that the development of technology to manage stably after transplanting of cutting or micropropagating plants into potting soil is important for mass propagation of hops.

• Journal of Food Hygiene and Safety
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• v.38 no.4
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• pp.211-216
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• 2023

A total of 100 commercially available olive oil products were analyzed for 179 pesticide residues using gas chromatography-tandem mass spectrometry (GC/MS/MS). The olive oil samples were mixed with organic solvents, centrifuged and frozen to remove fat, and pesticide residues were analyzed using the "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) method. The determination coefficient (R²) of the analysis method used in this study was ≥0.998. The detection limit of the method ranged 0.004-0.006 mg/kg and its quantitative limit ranged 0.012-0.017 mg/kg. The recovery rate (n=5) measured at the level ranging 0.01-0.02, 0.1, and 0.5 mg/kg ranged 66.8-119.5%. The relative standard deviation (RSD) was determined to be ≤5.7%, confirming that this method was suitable for the "Guidelines for Standard Procedures for Preparing Food Test Methods". The results showed that a total of 151 pesticides (including difenoconazole, deltamethrin, oxyfluorfen, kresoxim-methyl, phosmet, pyrimethanil, tebuconazole, and trifloxystrobin) were detected in 64 of the 100 olive oil products. The detection range of these pesticide residues was 0.01-0.30 mg/kg. The percentage acceptable daily intake (%ADI) of the pesticides calculated using ADI and estimated daily intake (EDI) was 0.0001-0.1346, indicating that the detected pesticides were present at safe levels. This study provides basic data for securing the safety of olive oil products by monitoring pesticide residues in commercially available oilve oil products. Collectively, the analysis method used in this study can be used as a method to analyze residual pesticides in edible oils.

• Journal of Food Hygiene and Safety
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• v.39 no.3
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• pp.250-259
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• 2024

In this study, we investigated in pesticide residues and heavy metals in fermented liquor products (wine, beer, makgeolli). Targeted analysis of 400 pesticide residues in the sample was performed using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method, followed by gas chromatography-tandem mass spectrometry (MS/MS) and LC-MS/MS. The contents of heavy metals (Pb, Cd) were determined by ICP-MS using the microwave method. The mercury was measured using a mercury analyzer. From the analysis of 150 cases, 102 (68.0%) cases of fermented liquor were detected, and 35 pesticide residues (including metalaxyl, mandipropamid, azoxystrobin, and fenhexamid) were detected among the 400 pesticide residues tested. Pb, Cd, and Hg were tested in 150 samples. Lead was detected in 73 samples (48.7%), cadmium in 9 samples (6.0%), and mercury in 36 samples (24.0%). Exposure assessment was conducted to determine the safety of the detected pesticide residues and heavy metals. According to this assessment, the pesticide residues and heavy metals showed very low %ADI values (less than 1%).

• Journal of the Korean Applied Science and Technology
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• v.41 no.3
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• pp.813-824
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• 2024

This study was conducted to evaluate the long-term effects of training on the physical development and exercise performance of adolescent weightlifters, aiming to provide effective training and management strategies for improving competitive performance. In order to achieve the objectives of the study, adolescent weightlifters from middle and high schools in Chungcheongnam-do province [male middle school-aged athletes, n=5; female middle school-aged athletes, n=5; male high school-aged athletes, n=12; female high school-aged athletes, n=8] were examined over approximately 10 months of weightlifting-based training to analyse the changes in body composition, physical fitness (muscular strength, muscular endurance, agility, flexibility, dynamic balance, coordination), and isokinetic muscular function (trunk and lower extremity). As a result, it was found that the physical development of middle and high school-aged athletes underwent physical development primarily characterized by an increase in lean body mass. Additionally, back muscle strength and power, which contribute to rapid and efficient force transmission between the upper and lower body, as well as grip strength necessary for controlling the barbell with a stable grip, are significant factors. These aspects were notably enhanced through specialized training and competitive experience for weightlifting performance at the high school level. On the other hand, changes in factors beyond the primary physical attributes contributing to weightlifting performance were limited, suggesting differences in effectiveness likely stemming from the specific composition of training programs or the athletes' experience and skill levels. Collectively, the findings from this study, which evaluates the physical characteristics and exercise abilities of adolescent weightlifters, are expected to contribute to improved competitive performance of weightlifters.

• Journal of Preventive Medicine and Public Health
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• v.3 no.1
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• pp.1-16
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• 1970

The present status of control measures for public health important helminthic infections in Korea was surveyed in 1969 and the following results were obtained. The activities of parasitic examination and Ascaris treatment for the positives which were done during 1966 to 1969 were brought in poor result and could not decrease the infection rate. It is needed to improve or strengthen the activities. The mass treatment activities for paragonimiasis and clonorchiasis in the areas which were designated by the Ministry of Health were carried out during 1965 to 1968 with no good results in decrease of estimated number of the patients. There were too many pharmaceutical companies where many kinds of anthelmintics were produced. It may be better to reduce the number of anthelmintics produced and control the quality. The human feces, the most important source of helminthic infections, was generally not treated in sanitary ways because of the poor sewerage system and no sewage treatment plant in urban areas and insanitary latrines in rural areas. The field soils of 170 specimens were collected from 34 areas out of 55 urban and tourist areas where night soil has been prohibited by a regulation to be used as a fertilizer, and examined for parasites contamination with the result of Ascaris egg detection in 44%. Some kinds of vegetables of 64 specimens each from the supply agents of parasite free vegetables and general markets were collected and examined for parasites contamination with the results of Ascaris egg detection in 25% and 36% respectively. The parasite control activities and the ability of parasitological examination techniques in the health centers of the country were not satisfactory. The budget of the Ministry of Health for the parasite control was very poor. The actual expenditure needed for cellophane thick smear technique was 8 Won per a specimen. As a principle the control of helminthic infections might be led toward breaking the chain of events in the life cycle of the prasites and eliminating environmental and host factors concerned with the infections, and the following methods nay be pointed out. 1) Mass treatment might be done to eliminate human reservoirs of an infection. 2) Animal reservoirs which are related with human infections night be eliminated. 3) The excretes of reservoirs, particularly human feces, should be treated in sanitary ways by the means of sanitary sewerage system and sewage treatment plant in urban areas and sanitary latrines such as waterborne latrine, aqua privy and pit latrine in rural areas. The increase of national economical development and prohibition of the habit of using night soils as a fertilizer might be very important factors to achieve the purpose. 4) The control of vehicles and intermediate hosts might be done by the means of prohibition of soil contamination with parasites, food sanitation, insect control and snail control. 5) The improvement of insanitary attitudes and bad habits which are related with parasitic infections night be done by the means of prohibition of habit of using night soils as a fertilizer, and improving eating habits and personal hygiene. 6) Chemoprophylactic measure and vaccination may be effective to prevent the infections or the development of a parasite to adult in the bodies when the bodies were invaded by parasites. Further studies and development of this kind of measures are needed.