본 연구는 무인기로 촬영한 다중분광 영상으로부터 취득한 반사값을 통해 산출된 식생지수로 콩(Glycine max (L.) Merr.)의 경태를 추정하는 머신러닝 회귀모델 개발을 목표로 한다. 연구 대상은 경상남도 밀양시 국립식량과학원 남부작물부 실험포장에서 2022년 6월 20일과 2023년 6월 24일에 파종한 선풍 품종의 콩이며, 관행구와 처리구로 나누어 재배하였다. 생육조사는 2022년 8월 20일과 9월 20일, 2023년 8월 21일과 9월 25일에 수행하였고, 영상은 2022년 8월 22일과 9월 21일, 2023년 8월 22일과 9월 20일에 촬영하였다. 촬영된 영상으로부터 5가지 반사값을 추출하여 9가지 식생지수를 산출하였다. 모델 구축에는 Ridge Regression (RR)과 LASSO Regression (LR), Random Forest Regression (RFR)과 K-Nearest Neighbor Regression (KNR)을 사용하였고, 단계적 변수 선택법을 사용하였다. 훈련과 검증의 비율은 8:2, 7:3, 6:4로 설정하였고, 모델은 R2, RMSE, MAPE로 평가하였다. 단년차 월별 모델의 경우, 8월과 9월 모두 2023년의 모델이 좋은 모델로 선정되었다. 다년차 월별 모델의 경우, 환경적 조건에 편중되어 군집화 현상이 나타나는 경우(8월)와 통계적으로 유의한 차이가 있음에도 불구하고 군집화 현상이 나타나지 않는 경우(9월)가 확인되었다. 따라서 월별 모델에 비해 성능은 낮지만 군집화가 발생하지 않고, 더 많은 샘플 수를 가진 전체 통합 모델을 최적 모델로 선택하였고, Calibration에서 R2=0.916, RMSE=0.683mm, MAPE=5.644%, Validation에서 R2=0.708, RMSE=1.002mm, MAPE=8.957% 의 성능을 나타내었다.

목적 : 동공 직경과 양안시기능이 양안 대비감도에 미치는 영향에 대해 알아보고자 하였다. 방법 : 전신질환 및 안과질환이 없는 성인 남녀 38명을 대상으로 완전 교정 후에 사위도와 조절력, 조절래그, 조절용이성을 측정하였다. 대비감도는 측정 장비(MonCV3, Metrovision, France)를 이용하여 양안으로 정적 대 비감도와 동적 대비감도를 측정하였으며, 공간주파수는 0.8, 1.6, 3.2, 6.4, 12.8, 25.6 cpd에서 측정하였다. 동 공 직경은 조도에 따라 100, 10, 1, 0 cd/m2에서 측정하였다. 결과 : 원거리 사위도는 동적 대비감도 6.4 cpd에서 유의한 상관관계를 보였으며(r=0.373, p=0.043), 외사위도 가 증가할수록 동적 대비감도가 감소될 수 있음을 확인할 수 있었다. 조절 기능은 양안 정적 대비감도와 동적 대비 감도에서 모두 유의한 상관관계를 보이지 않았다. 조도에 따른 동공 직경과 비교하였을 때 양안 정적 대비감도, 동 적 대비감도에서 모두 유의한 상관관계를 보이지 않았으나, 최대 동공 직경과 최소 동공 직경의 차이에서는 정적 대 비감도와 동적 대비감도 모두 1.6 cpd에서 음의 상관관계를 보였다(r=-0.393, p=0.016), (r=-0.367, p=0.046). 따라서 동공 직경의 변화가 큰 경우 낮은 주파수에서 대비감도가 감소될 수 있음을 확인하였다. 결론 : 원거리 사위도가 크거나 명소시와 암소시에서 동공 변화도가 큰 경우 완전 교정하더라도 시력의 질이 떨 어질 수 있고, 야간 선명도가 저하될 수 있다. 임상에서 안질환이 없고, 교정시력이 1.0이 나와도 시력의 만족도가 떨어지는 경우에는 대비감도 검사를 고려해야 될 것으로 사료된다.

Myxomatous mitral valve disease (MMVD) is the most prevalent cardiac disease in dogs worldwide. Left atrial enlargement is a prominent feature associated with an increased risk of congestive heart failure in dogs with MMVD. Left atrial anteroposterior diameter (LAD) has been suggested as a supplementary parameter for evaluating LA size in various species. The purpose of our study was to establish a correlation between the left atrial anteroposterior diameter normalized to body weight (LADn) and N-terminal pro-brain natriuretic peptide (NT-proBNP) in dogs with MMVD and to assess the diagnostic potential of LADn for MMVD. We conducted this study on 35 dogs and categorized them into the control and MMVD groups. The control group consisted of 10 dogs, whereas the MMVD group included 25 dogs classified into stages B1, B2, and C according to the American College of Veterinary Internal Medicine (ACVIM) guidelines. LADn was measured using echocardiography, and NT-proBNP levels were assessed using a fluorescent immunoassay. In conclusion, LADn shows promise as a valuable diagnostic marker of MMVD in dogs. The strong positive correlation between LADn and NT-proBNP levels demonstrates the usefulness of LADn as a clinical index for evaluating cardiac function and disease progression in dogs with MMVD.

This study investigates the effects of canopy fabric material and vent diameter on the deployment performance of sea anchors for fishing operations through field experiments. Three canopy configurations were tested: polyamide (PA), polyester (PES), and a PA – PES alternating combination. Vent diameters of 80 cm and 40 cm were applied to each fabric as controlled structural factors. Deployment performance was evaluated from entrance diameter computed using four evenly spaced water level loggers, and maximum towing tension was recorded with a load cell. Key findings were discovered as follows: PES and the PA – PES mix achieved deployment diameter/ratio and maximum tension comparable to the current PA standard, indicating practical substitutability. PES also exhibited superior stability, showing reduced variability even with the smaller vent (a change in standard deviation ΔSD-1.75 cm). The mixed canopy maintained performance similar to PA. As expected, vent diameter systematically affected geometry and load (80 cm: 187 – 198 kgf vs. 40 cm: 249 – 268 kgf), underscoring the need to pair material selection with appropriate vent sizing. In conclusion, PES and mixed fabrics are viable alternatives to PA, and co-optimization of fabric choice and vent diameter can enhance sea-anchor performance, durability, and operational reliability for fishing operations.

The Magnus airfoil can convert wind energy into kinetic energy, driving the boat forward. The rotating cylinder at the airfoil's leading edge enhances lift and reduces drag, positioning it as a promising technology for boundary layer flow control. This study, based on the NACA0015 airfoil, employs Computational Fluid Dynamics (CFD) to investigate the effect of cylinder diameter on the aerodynamic performance of the Magnus airfoil. The Reynolds number is set to 4×10⁵, with an angle of attack of 18°, a rotational speed ratio of 1.4, and cylinder diameters ranging from 6% to 13% of the airfoil's chord length. Numerical simulations are conducted to analyze and compare the lift and drag characteristics, vorticity distribution, pressure distribution, and flow field structure for varying cylinder diameters. The results show that a high-speed rotating cylinder, when placed at the airfoil’s leading edge, effectively suppresses flow separation on the suction surface, delays boundary layer development, and enhances the overall aerodynamic performance of the airfoil. For the Magnus airfoil studied, the optimal diameter of the rotating cylinder at the leading edge is found to be 12% of the chord length.

산림자원 조사에서 입목의 측정은 조사원이 직접 측정 도구를 사용하여 수행되지만, 측정값의 일관성과 정확성 문제로 인한 오차가 발생할 수 있다. 이러한 문제를 해결하기 위해 최근 LiDAR(Light Detection and Ranging) 기술이 산림자원 조사에 응용되고 있다. 본 연구는 단순림의 산림자원 조사에서 지상 LiDAR 기술의 활용 가능성을 평가하고자 하였다. 연구는 한국의 전주에 위치한 전북대학교 학술림 내의 편백림과 굴참나무 림을 대상으로 수행되었다. 조사원이 측정한 입목의 흉고직경과 수고 측정값을 기준으로, 휴대형 및 고정형 LiDAR 장비를 사용한 측정값을 비교 분석하였다. 결과적으로, 편백 임분의 흉고직경 측정에서는 측정 방법 간 높은 일치도가 나타났으며, 평균의 차이는 유의미하지 않았다. 그러나 수고 측정에서는 낮은 일치도가 관찰되었고, 평균의 차이는 유의미하였다. 특히, 3점 이동 평균 수고에서 휴대형 LiDAR 장비는 수고를 0.3m 과대 측정하였으며, 고정형 LiDAR 장비는 1.2m 과소 측정하였다. 굴참나무 임분의 경우, 흉고직경 측정에서 높은 일치도가 나타났고, 수고 측정에서 도 비교적 높은 일치도를 보였다. 또한, 흉고직경과 수고 모두에서 평균의 차이는 유의미하지 않았다. 이러한 결과는 편백 임분과 굴참나무 임분에서 흉고직경 측정과 굴참나무 임분의 수고 측정에 있어 지상 LiDAR 기술이 높은 정확도를 제공할 수 있음을 시사하지만, 편백 임분의 수고 측정에서는 개선의 여지가 있음을 나타낸다. 본 연구는 지상 LiDAR 기술이 단순림의 산림자원 조사에 활용될 수 있는 초기 단계의 연구로서, 다양한 수종 및 환경 조건에 관한 추가 연구의 필요성을 강조한다.

This study aims to optimize the orifice diameter to reduce pressure hunting in the pilot valves of positioners used in nuclear power plant control systems. Computational Fluid Dynamics (CFD) analysis using ANSYS CFX was conducted to create 3D models with varying orifice diameters (1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm). To enhance the accuracy of the analysis, boundary layer meshing techniques (Inflation) were applied, and the SST k-ω turbulence model was employed. The analysis of pressure variation and pressure hunting over time revealed that larger orifice diameters resulted in reduced pressure hunting, with a 3 mm orifice diameter achieving 0% pressure hunting. Additionally, it was observed that larger orifice radii slightly increased the average outlet pressure. Based on the findings, a 3 mm orifice diameter is recommended to effectively mitigate pressure hunting in pilot valves, contributing to improved system stability in nuclear power plants. Future studies will explore the design of slanted orifices to further analyze fluid flow characteristics.

The recent surge in energy consumption has sharply increased the use of fossil fuels, leading to a steep rise in the concentration of greenhouse gases in the atmosphere. Interest in hydrogen is growing to mitigate the issue of global warming. Currently, hydrogen energy is transported in the form of high-pressure gaseous hydrogen, which has the disadvantages of low safety and energy efficiency. To develop commercial hydrogen vehicles, liquid hydrogen should be utilized. Liquid hydrogen storage tanks have supports between the inner and outer cylinders to bear the weight of the cylinders and the liquid hydrogen. However, research on the design to improve the structural safety of these supports is still insufficient. In this study, through a thermal-structural coupled analysis of liquid hydrogen storage tanks, the model with three supports, which had the lowest maximum effective stress in the outer tank, inner tank, and supports as proposed in the author's previous research, was used to create analysis models based on the diameter of the supports. A structurally safe design for the supports was proposed.

In this study, we examined the effect of orifice diameter on atomization performance such as SMD(Sauter Mean Diameter), MMD(Mass median diameter), particle size distribution, spray distance, and spray angle when water was sprayed through a siphon nozzle. In addition, the behavior characteristics of spray were analyzed using the CFD(Computational Fluid Dynamics) commercial program. In the downstream direction of the flow, the dispersion and diffusion power of the droplets increased, greatly improving atomization performance. The spray spread in the radial direction when the jet velocity of water increased. As a result, atomization performance improved as the jet velocity increased.

In this study, non-destructive technologies that can be applied to evaluate the integrity of valve materials, safety against internal pressure caused by corrosion, and the blocking function of large-diameter water valves during operation without requiring specimen collection or manpower entering the inside of the valve were tested to assess the reliability of the technologies and their suitability for field application. The results showed that the condition of the graphite structure inside the valve body can be evaluated directly through the optical microscope in the field without specimen collection for large-diameter water butterfly valves, and the depth of corrosion inside the valve body can be determined by array ultrasound and the tensile strength can be measured by instrumented indentation test. The reliability of each of these non-destructive techniques is high, and they can be widely used to evaluate the condition of steel or cast iron pipes that are significantly smaller in thickness than valves. Evaluation of blocking function of the valves with mixed gas showed that it can be detected even when a very low flow rate of mixed gas passes through the disk along with the water flow. Finally, as a result of evaluating the field applicability of non-destructive technologies for three old butterfly valves installed in the US industrial water pipeline, it was found that it is possible to check the material and determine the suitability of large-diameter water valves without taking samples, and to determine the corrosion state and mechanical strength. In addition, it was possible to evaluate safety through the measurement results, and it is judged that the evaluation of the blocking function using mixed gas will help strengthen preventive response in the event of an accident.

In this study, the physical properties and fracture characteristics according to the tensile load are evaluated on the materials of the polymeric filler and carbon fiber-based composite sleeve technique. The polymeric filler and the composite sleeve technique are applied to areas where the pipe body thickness is reduced due to corrosion in large-diameter water pipes. First, the tensile strength of the polymeric filler was 161.48~240.43 kgf/cm2, and the tensile strength of the polyurea polymeric filler was relatively higher than that of the epoxy. However, the tensile strength of the polymeric filler is relatively very low compared to ductile cast iron pipes(4,300 kgf/cm2<) or steel pipes(4,100 kgf/cm2). Second, the tensile strength of glass fiber, which is mainly used in composite sleeves, is 3,887.0 kgf/cm2, and that of carbon fiber is up to 5,922.5 kgf/cm2. The tensile strengths of glass and carbon fiber are higher than ductile cast iron pipe or steel pipe. Third, when reinforcing the hemispherical simulated corrosion shape of the ductile cast iron pipe and the steel pipe with a polymeric filler, there was an effect of increasing the ultimate tensile load by 1.04 to 1.06 times, but the ultimate load was 37.7 to 53.7% compared to the ductile cast iron or steel specimen without corrosion damage. It was found that the effect on the reinforcement of the corrosion damaged part was insignificant. Fourth, the composite sleeve using carbon fiber showed an ultimate load of 1.10(0.61T, 1,821.0 kgf) and 1.02(0.60T, 2,290.7 kgf) times higher than the ductile cast iron pipe(1,657.83 kgf) and steel pipe(2,236.8 kgf), respectively. When using a composite sleeve such as fiber, the corrosion damage part of large-diameter water pipes can be reinforced with same level as the original pipe, and the supply stability can be secured through accident prevention.

In this study, as the proportion of aged pipelines increases rapidly, in the event of an accident caused by corrosion and structural deterioration of metal pipes, appropriate overlay welding is applied in the field to partially repair it. The size of the base steel plate and the selection of a stable welding method were evaluated, and possible problems caused by the overlay welding were identified, and improvement measures were proposed. For the test, a new steel pipe coated with epoxy lining on the inner surface and polyethylene on the outer surface was subjected to a tensile test by processing the repaired specimen through overlay welding with a steel plate after artificial cracking, and structural safety was evaluated after repair. Furthermore, the influences of the size of the throat and the size of the steel plate were analyzed. As a result of the tensile test by dividing the repaired steel plate overlay into a constraint and non-constraint conditions, the tensile load was concentrated in the welded part and damage occurred in the welded part. It was found that the maximum load leading to breakage increases as the size of the welding throat increases. In addition, it was found that the resistance to load increased slightly as the size of the overlaid steel plate increased, but the effect was not significant, confirming the need for repair in consideration of the site conditions. As a result of evaluating the damage to the coating material on the back side of the welding, it was confirmed that the coating material on the opposite side of the welding burned black(epoxy) or was greatly deformed by heat(polyethylene). Therefore, it is necessary to secure structural stability through repainting, etc. in order to prevent damage to the coating material on the opposite side during overlay welding.

목적: 20~70대 성인을 대상으로 각막굴절력이 굴절이상과 동공크기에 미치는 영향에 대해서 확인하고자 하였다. 방법 : 안과질환과 각막굴절교정술 경험이 없는 근시안 그룹(831안, 34.55±13.17세, -2.28±1.37 D), 원시 안 그룹(369안, 47.20±12.24세, +1.22±0.72 D)이 본 연구에 참여하였으며, I-Profilerplus를 사용하여 대상안 의 각막굴절력과 동공크기 및 원점굴절도를 측정해 분석하였다. 결과 : 각막굴절력은 근시안 그룹이 원시안 그룹 보다 약 0.35 D 정도 유의하게 컸으며, 근시안과 원시안 및 전체 굴절이상 그룹에서 원점굴절도가 마이너스(-) 방향으로 높을수록 유의하게 증가하였다(p<0.050). 동공크기 는 근시안 그룹이 원시안 그룹에 비하여 약 0.40 mm 정도 유의하게 컸고 근시안과 원시안 및 전체 굴절이상 그 룹 모두에서 원점굴절도가 마이너스(-) 방향으로 높을수록 동공크기가 컸으며(p<0.050), 근시안과 원시안 그룹을 포함하는 전체 굴절이상 그룹에서 각막굴절력이 플러스(+) 방향으로 클수록 동공크기는 유의하게 증가하였다 (p<0.050). 결론 : 각막굴절력은 굴절이상과 동공크기 측정값에 영향을 주는 것을 확인하였으며, 이 연구 결과는 굴절이상 종류에 따른 동공크기 차이를 이해하는데 도움이 되는 기초자료가 될 것으로 생각한다.

Screws are the closest and most familiar mechanical elements of everyday life, and are generally used so widely that there is no machine without screws. Screws are used to make it easier to combine objects with objects, and are also used to transfer large forces from machines. The most influential factor in the coupling of these screws is the effective diameter. If the effective diameter is not accurate, the support cannot be finished or endured, leading to a major accident. The importance of these screws cannot be ignored, so in this study, the effective diameter was measured using the three-wire method, the screw micrometer method, and the projector method, and the one-way factor design method was applied to determine the exact method compared to the KS standard.

The effect of the laser beam diameter on the microstructure and hardness of 17-4 PH stainless steel manufactured via the directed energy deposition process is investigated. The pore size and area fraction are much lower using a laser beam diameter of 1.0 mm compared with those observed using a laser beam diameter of 1.8 mm. Additionally, using a relatively larger beam diameter results in pores in the form of incomplete melting. Martensite and retained austenite are observed under both conditions. A smaller width of the weld track and overlapping area are observed in the sample fabricated with a 1.0 mm beam diameter. This difference appears to be mainly caused by the energy density based on the variation in the beam diameter. The sample prepared with a beam diameter of 1.0 mm had a higher hardness near the substrate than that prepared with a 1.8 mm beam diameter, which may be influenced by the degree of melt mixing between the 17-4 PH metal powder and carbon steel substrate.

In this study, in order to manufacture STS 316L seamless pipes with 18mm, 25mm, and 42mm diameters that can be used for high pressure, we intend to make predictions through design and finite element analysis and produce real objects. It was measured to have the highest hardness value in the deformed part, and it is expected to be due to work hardening. It has been interpreted that plastic deformation does not occur up to 1,000bar for STS 316L seamless pipes with a diameter of 18mm and 25mm, but plastic deformation occurs at 900bar or more in STS 316L seamless pipes with a diameter of 42mm.

본 연구의 목적은 무인기 정사영상 정보를 활용하여 초미세 고해상도 3차원 공간 모델을 구축하고, 구축된 모델을 이용하여 개체목의 수고와 흉고직경을 추정하는 기술을 분석하고자 하였다. 이를 위해 경상북도 봉화군 일대 잣나무 조림지를 대상으로 무인기 정사영상을 촬영하였으며, SfM 기술을 이용해 촬영영상에 대한 3차원 수고 모델을 추출하였다. 유역분류 알고리즘을 이용해 개체목을 선별·추출하였고, 개체목별 수관면적에 따른 흉고직경을 추정하였다. 본 연구 결과에 의하면, 추출된 수고모델과 현장에서 측정한 수고는 평균 제곱근 편차에서 1.492m (R2 = 0.3401) 차이를 보였으며, 오차율이 가장 적은 수고모델 추출 방법은 지형분석지점 사양이 각도 20°, 이격거리 1m, 격자크기 60m 이었다. 개체목 추출율은 75.4% 이었으며, 수고가 높은 우세목의 추출율은 85.2% 이상이었다. 추출된 개체목의 수관면적과 흉고직경의 상관성은 두 변수 사이에 유의 수준(P<0.01)에서 상관관계가 있었으며, 적합도 77.05% 수준에서 수관면적이 커질수록 흉고직경도 증가하는 추세를 확인할 수 있었다.

The purpose of this study was to evaluate the corrosion damage of large diameter metallic pipes buried in reclaimed land due to the corrosion effect by soil, and to propose a method of installing metal pipes in the reclaimed land. The results are as follow. First, the soil of the reclaimed land was gray clay, the soil specific resistance indicating soil corrosiveness was at least 120 Ω-cm, the pH was weakly acidic(5.04 to 5.60), the redox potential was at least 62 mV, the moisture content was at most 48.8%, and chlorine ions and sulfate ions were up to 4,706.1 mg/kg and 420 mg/kg. Therefore, the overall soil corrosivity score was up to 19, and the external corrosion effect seems to be very large. Second, the condition of straight part of pipes was in good condition, but most of KP joints were affected by corrosion at a severe level. The reason for this seems to be that KP joints accelerated corrosion due to stress and crevice corrosion in addition to galvanic corrosion in the same environment. Third, as a result of evaluating correlations of each item that affects the corrosion on the external part, the lower the soil resistivity and redox potential, the greater the effect on the KP joints corrosion, and the moisture content, chloride ion, and sulfate ion, the higher the value, the greater the effect on the corrosion of KP joints. In addition, among soil corrosion items, the coefficient of determination of soil resistivity with corrosion of KP joints was the highest with 0.6439~0.7672. Fourth, when installing metal pipes or other accessories because the soil of the reclaimed land is highly corrosive, it is necessary to apply a corrosion preventive method to extend the life of pipes and prevent leakage accidents caused by corrosion damage to the joint.