• Journal of Environmental Impact Assessment
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• v.27 no.6
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• pp.595-603
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• 2018

This study was conducted to understand the growth of attached microbial community in small and medium streams of Gyeonggi-do and the removal efficiency of fluoride with changes in growth. The sites monitoring were carried out for 12 weeks at the P1 and P2(P1 is the point where the discharge water flows. P2 is the downstream point of about 2 km flow), and investigated the water quality and the biomass analysis of the attached microbial community. The growth of the attached microbial community increased up to the 7th investigation, and it was observed that detachment phenomenon occurred. Influencing factors about growth of the attached microbial community were flow rate, velocity, and organic material(T-N & T-P). Meanwhile, fluoride content of attached microbial community also tended to increase until the 7th investigation, and decrease from the 8th. It is assumed that fluoride content has also be reduced with the detachment phenomenon of the attached microbial community. It is expected that this will contribute to the evaluation and management of the use of attached microbial community as a means of stream management. The application of techniques using the attached microbial community should include basic investigation of factors that may affect the growth of the attached microbial community and replacement of the attachment plate according to the time of removal.

• Food Science of Animal Resources
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• v.38 no.6
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• pp.1131-1143
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• 2018

This study aimed to investigate the drying yield, meat quality, oxidation stability and sensory properties of Hanwoo beef loin subjected to different dry-aging conditions. A total of 54 Hanwoo beef loins (bone-in, $6^{th}-13^{th}$ ribs) with fat cover at 2 d postmortem were assigned to four groups and hung in a dry-aging room at a controlled temperature ($2^{\circ}C-4^{\circ}C$), humidity (65%-85%) and air velocity (3 m/s). Four treatment conditions were tested; the respective temperature, humidity and treatment duration are as follows: T1, $2^{\circ}C$, 85%, 60 d; T2, $2^{\circ}C$, 65%, $20d+2^{\circ}C$, 75%, $20d+4^{\circ}C$, 85%, 20 d; T3, $2^{\circ}C$, 75%, $20d+4^{\circ}C$, 85%, 40 d; T4, $4^{\circ}C$, 85%, 60 d. The drying yield, total aerobic counts and fat contents increased, whereas the moisture content, meat color (CIE $L^*$, $a^*$, and $b^*$), and Warner-Bratzler shear force values decreased significantly during the aging period for all treatments (p<0.05). The cooking loss (%) did not change significantly until 40 d, and it was significantly higher in T1 and T4 than in T2 and T3 at 60 d (p<0.05). The water-holding capacity, pH and lipid oxidation [thiobarbituric acid reactive substance (TBARS) values] increased during aging (p<0.05). The sensory scores for tenderness, juiciness, flavor, and overall acceptability of dry-aged loin muscles increased as the aging period increased. T2 and T3 had significantly higher sensory scores and T1 had significantly lower scores for tenderness, juiciness, flavor, and overall acceptability at 20, 40, and 60 d for loin muscles (p<0.05).

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.11-22
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• 2019

The objective of this study was to improve the cross-sectional area and height estimation method using stream width. Stream water levels should be calculated together to simulate inundation of agricultural land. However, cross-sectional survey data of small rural rivers are insufficient. The previous study has developed regression equations between the width and the cross-sectional area and between the width and the height of stream cross-section, but can not be applied to a wide range of stream widths. In this study, cross-sectional survey data of 6 streams (Doowol, Chungmi, Jiseok, Gam, Wonpyeong, and Bokha stream) were collected and divided into upstream, midstream and downstream considering the locations of cross-sections. The regression equations were estimated using the complete data. $R^2$ between the stream width and cross-sectional area was 0.96, and $R^2$ between width and height was 0.81. The regression equations were also estimated using divided data for upstream, midstream and downstream considering the locations of cross-sections. The range of $R^2$ between the stream width and cross-sectional area was 0.86 - 0.91, and the range of $R^2$ between width and height was 0.79 ? 0.92. As a result of estimating the cross-sections of 6 rivers using the regression equations, the regression equations considering the locations of cross-sections showed better performance both in the cross-sectional area and height estimation than the regression equations estimated using the complete data. Hydrologic Engineering Center - River Analysis System (HEC-RAS) was used to simulate the flood stage analysis of the estimated and the measured cross-sections for 50-year, 100-year, and 200-year frequency floods. As a result of flood stage analysis, the regression equations considering the locations of cross-sections also showed better performance than the regression equations estimated using the complete data. Future research would be needed to consider the factors affecting the cross-sectional shape such as river slope and average flow velocity. This study can be useful for inundation simulation of agricultural land adjacent to an unmeasured stream.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.460-468
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• 2021

This study investigated the enhanced combustion efficiency of an "air-cooled combustion system" with single F.D. fan, and performed a numerical analysis for the operation and design conditions to increase the combustion efficiency. The combustion efficiency in an actual combustor was compared before and after the structure modification. Numerical analysis for application of a single fan revealed the difficulty of forming a turbulence for circular combustion conditions. This is because the supply ratio of combustion air supplied into 2 flow paths becomes irregular in the combustion furnace due to a change in friction force and pressure in each flow path. Subsequently, two methods of supplying air into the combustion furnace were analyzed numerically to obtain the optimal combustion conditions of an air-cooled combustion system. The first method involved injecting the preheated combustion air after a 180~360 degree rotation from the outer wall, whereas in the second method, the combustion air was injected into the combustion furnace in a tangential direction after primary heat exchange outside the combustion furnace, by applying a rotatable vane structure in the combustion furnace. Results reveal that application of a single F.D. fan to the air injection into a rotatable combustion furnace is desirable for optimization of the combustion conditions for applying a duct structure having a dual cooling wall for the cooling of the outer wall of the combustion furnace, and for maintaining perfect mixing in the combustion furnace. We therefore confirmed enhanced combustion efficiency by comparing the actual combustion efficiency before and after structure modification.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.4
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• pp.223-230
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• 2020

Purpose : The purpose of this study was to examine the effects of tools (i., extracorporeal shock wave therapy, massage gun, and foam roller) on range of motion, muscle tone and pain threshold among patients with hamstring stiffness. Methods : Fourteen participants with hamstrings stiffness were recruited. Interventions were performed 6 times, and each session was for 30 seconds using the three tools. The range of motion, muscle tone, and pain threshold were measured. The order of the use of the three tools was randomly determined. The foam roller was made to move from the bottom of the hip crease to the upper part of the back of the hamstring. Additionally, velocity 5 vibration stimulation was performed on the hamstring using a massage gun. Moreover, vibration stimulation was performed on the hamstring with extracorporeal shock wave therapy 5 minutes, 5 Hz, and 1,500 strokes. The flexibility of the posterior thigh muscle was based on maintaining the knee and hip joints in a 90 ° bend in the supine position. The joint angle of the knee was measured, when the knee was actively extended, at the maximum point where the posterior thigh muscle was stretched. The elasticity of the posterior thigh muscle was measured while the subject was prone and in a relaxed state without any force. Measurements were made at the muscle abdominal area of the semitendinosus muscle of the posterior femur, and the area to be measured was marked with a pen. The measurement of the tenderness threshold of the posterior femur was measured using a tenderness meter(Commander Algometer, J-Tech, USA). The force value at the point at which the pressure sensation change to pain was measured after applying vertical pressure to the posterior femur muscle, which was the halfway point between the ischial tuberosity and the popliteal surface of the subject lying on their stomach. Results : The extracorporeal shock wave therapy increased stiffness and, muscle tone, and caused changes in the pain threshold, whereas the other two tools had no effect on these indices. Conclusion : Extracorporeal shock wave therapy has important effects on range of motion and muscle stiffness and can be used in warmup protocols.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.782-789
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• 2020

The demand for the development of rolling stock technology to maintain the best performance in various climatic environments has increased to expand the overseas market of rolling stock. In this study, international and domestic standards that must be applied to build a harsh climatic environment test system were investigated and compared. The way of improvement for domestic standards is proposed. The wind velocities and temperatures are specified in the UIC, EN, and IEC standards for climatic wind tunnel, and EN 50125-1 provides the velocity test up to 180km/h, the largest wind speed. UIC and EN provide the lowest temperature of -45℃, and IEC 62498-1 provides the highest temperature 55℃. The solar radiation test was specified up to 1200W/m2 in the UIC, EN, and IEC. The IEC, EN, and KS R 9145 provide the water tightness standards, which are different from each other in water capacity, pressure, and methods. The snow test method was not well specified. KRTS-VE-Part 31 provides pressurization test methods. The airtightness standards for high-speed rolling stock are defined and regulated for internal pressure change rate in UIC 660 and 779-11. The domestic standard for the wind tunnel test was not well prepared, and the solar radiation test and snow test do not exist in Korea. Therefore, it is necessary to improve domestic standards to an international level for the climatic wind tunnel test of rolling stock.

• Smart Media Journal
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• v.9 no.4
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• pp.176-186
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• 2020

The size and shape of crops are diverse, and the growing environment is also different. Therefore, when one uses a drone to spray pesticides, the characteristics of each crop must be considered, and flight conditions such as the flight height and forwarding velocity of the drone should be changed. The droplet flow of pesticides is affected by various flight conditions, and a large change occurs in the sprayed area. As a result, an uneven distribution of liquid may be formed at the wake, and the transport efficiency will be decreased as well as there would be a risk of toxic scatter. Therefore, this paper analyzes the degree of distribution of pesticides to the crops through numerical analysis when pesticide is sprayed onto the selected three crops with different characteristics by using agricultural drones with different flight conditions. On the purpose of establishing a guideline for spraying pesticides using a drone in accordance with the characteristics of crops, this paper compares the amount of pesticides distributed in the crops at the wake of nozzle flow using the figure of merit, and the sum of transported liquid rate divided by the root mean square of the probability density function.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.162-176
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• 2022

In Lead-based reactor (LBR) severe accident, the meltdown and migration inside the reactor core will lead to fuel fragment concentration, which may further cause re-criticality and even core disintegration. Accurately predicting the migration and solidification behavior of melt in LBR severe accidents is of prime importance for safety analysis of LBR. In this study, the Moving Particle Semi-implicit (MPS) method is validated and used to simulate the migration and solidification behavior. Two main surface tension models are validated and compared. Meanwhile, the MPS method is validated by the L-plate solidification test. Based on the improved MPS method, the migration and solidification behavior of melt in LBR severe accident was studied furthermore. In the Pb-Bi coolant, the melt flows upward due to density difference. The migration and solidification behavior are greatly affected by the surface tension and viscous resistance varying with enthalpy. The whole movement process can be divided into three stages depending on the change in velocity. The heat transfer of core melt is determined jointly by two heat transfer modes: flow heat transfer and solid conductivity. Generally, the research results indicate that the MPS method has unique advantage in studying the migration and solidification behavior in LBR severe accident.

• Land and Housing Review
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• v.13 no.3
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• pp.93-106
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• 2022

Ventilation plays an important role in controlling indoor air quality. Due to the recent spread of infectious diseases such as COVID-19 and with people spending more time indoors, there's been increased attention on the importance of ventilation performance. In many countries, ventilation is regulated by airflow rates and the number of air changes per hour (ACH). However, airflow rates and ACH alone do not provide an accurate account of actual indoor pollutant removal and ventilation uniformity in a space. This study looked into the ventilation performance of an actual residential unit using several sampling points instead of basing it off of airflow and air change rates. Literature review was used to derive relevant influencing factors and the tracer gas dilution method was used for the field test. The study measured air velocity, age of air, and ventilation efficiency at several locations and compared them to the average value at the center of the test space to determine the differences in ventilation performance at the selected measurement points. The study showed that different sampling locations resulted in different ventilation values. Findings of this study will be used to develop an experimental procedure for evaluating indoor ventilation performance of actual residential spaces.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.41-50
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• 2021

This study investigated the changes in engineering characteristics of sand-tire chip mixtures during repetitive loading. To quantify the changes in the maximum shear modulus according to the tire chip content in the mixtures and the particle size ratio between sand particle and tire chip, the samples were prepared with tire chip content of TC = 0, 10, 20, 40, 60, and 100%, and the particle size ratios SR were also set to be SR = 0.44, 1.27, 1.87, and 4.00. The stress of the prepared sample was applied through a pneumatic cylinder. The experiment was conducted in the order of static loading (= 50 kPa), cyclic loading (= 50-150 kPa), static loading (= 400 kPa) and unloading. The stress applied to tested mixtures was controlled by a pressure panel and a pneumatic valve by using an air compressor. The shear wave velocity was measured during static and cyclic loadings by installing bender elements at the upper and lower caps of the mold. The results demonstrated that the change in maximum shear modulus of all tested materials with varying SR during repetitive loading is the most significant when TC ~ 40%. In addition, the mixture with smaller SR at a given TC shows greater increase in maximum shear modulus during repetitive loading.