• 지구물리와물리탐사
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• 제27권3호
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• pp.171-180
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• 2024

탄성파 자료처리는 탄성파 자료를 분석하여 지구 내부 구조와 특성을 파악하는 기술로, 높은 컴퓨터 연산력이 요구된다. 이러한 도전 과제를 해결하기 위해 머신러닝 기술이 도입되었으며, 잡음 제거, 속도 모델 구축 등 다양한 작업에서 활용되고 있다. 그러나, 대부분의 연구는 특정 탄성파 처리 작업에 집중되어 있어 자료에 내재된 유사한 특징과 구조를 충분히 활용하지 못하는 한계가 있다. 본 연구에서는 BERT (Bidirectional Encoder Representations from Transformers) 기반의 사전학습을 위해 단일 송신원 모음에서 수신기별 시계열 자료('수신기 배열')와 동일 시간에 기록된 수신기 신호('시간 배열')를 입력 자료로 활용하는 방법을 비교하였다. 이를 위해 단층을 포함한 속도 모델에서 생성한 합성 송신원 모음 자료를 이용하여 잡음 제거, 속도 추정, 그리고 단층 확인 작업을 수행하였다. 임의 잡음 제거 작업에서는 수신기 및 시간 배열에서 모두 좋은 성능을 보였으나, 공간적인 분포 파악이 요구되는 속도 추정 및 단층 확인 작업에서는 시간 배열의 결과가 상대적으로 더 우수함을 확인하였다.

• Structural Engineering and Mechanics
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• 제91권3호
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• pp.315-324
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• 2024

An expansive soil in 4970 special railway line in Dangyang City, China, has encountered a series of landslides due to the expansion characteristics of expansive soil over the past 50 years. Thereafter, a sheet-pile retaining structure was adopted to fortify the expansive soil slope after a comprehensive discussion. In order to evaluate the efficacy of engineering measure of sheet-pile retaining structure, the field test was carried out to investigate the lateral pressure and pile bending moment subjected to construction and service conditions, and the local daily rainfall was also recorded. It took more than 500 days to carry out the field investigation, and the general change laws of lateral pressure and pile bending moment versus local daily rainfall were obtained. The results show that the effect of rainfall on the moisture content of backfill behind the wall decreases with depth. The performance of sheet-pile retaining structure is sensitive to the intensity of rainfall. The arching effect is reduced significantly by employing a series of sheet behind piles. The lateral pressure behind the sheet exhibits a single-peak distribution. The turning point of the horizontal swelling pressure distribution is correlated with the self-weight pressure distribution of soil and the variation of soil moisture content. The measured pile bending moment is approximately 44% of the ultimate pile capacity, which indicates that the sheet-pile retaining structure is in a stable service condition with enough safety reserve.

• Geomechanics and Engineering
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• 제38권5호
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• pp.477-486
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• 2024

The process of inspecting and replacing cutting tools in a shield tunnel boring machine (TBM) is called cutterhead intervention (CHI) (Farrokh and Kim 2018). Since CHI is performed by a worker who enters the chamber in TBM, the worker is directly exposed to high water pressure and huge water inflow, especially in areas with high ground water levels, causing health problems for the worker and shortening of available working hours (Kindwall 1990). Ham et al. (2022) proposed a method of reducing the water pressure and water inflow by injecting a grout solution into the ground through the shield TBM chamber, and named it the new face grouting method (NFGM). In this study, the TBM mechanical characteristics including the injection pressure of the grout solution and the cutterhead rotation speed were determined for the best performance of the NFGM. To find the appropriate injection pressure, the water inflow volume according to the injection pressure change was measured by using a water inflow test apparatus. A model torque test apparatus was manufactured to find the appropriate cutterhead rotation speed by investigating the change in the status of the grout solution according to the rotation speed change. In addition, to prove the validity of this study, comprehensive water inflow tests were carried out. The results of the tests showed that the injection pressure equal to overburden pressure + (0.10 ~ 0.15) MPa and the cutterhead rotation speed of 0.8 to 1.0 RPM are the most appropriate. In the actual construction site, it is recommended to select an appropriate value within the proposed range while considering the economic feasibility and workability.

• 드라이브 ㆍ 컨트롤
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• 제21권3호
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• pp.56-69
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• 2024

Tractors are used for farming in harsh terrain such as slopes with slippery fields and steep passages. In these potentially dangerous terrain, steering instability caused by bouncing and sliding can lead to tractor rollover accidents. The center of gravity changes as parts such as engines and transmissions used in existing internal combustion engine tractors are replaced by motors and batteries, and the risk of conduction must be newly considered accordingly. The purpose of this study was to derive the center of gravity of a 55 kW class electric tractor using an electric platform from an existing internal combustion engine tractor, and to numerically investigate the tractor steering instability due to bouncing and sliding. The analysis provides a strong analysis by integrating an elaborate combination of a bouncing model and a sliding model based on Coulomb's theory of friction. Various parameters such as tractor speed, static coefficient of friction, bump length and radius of rotation are carefully analyzed through a series of detailed designs. In particular, the simulation results show that the cornering force is significantly reduced, resulting in unintended trajectory deviations. By considering such complexity, this study aims to secure optimal performance and safety in the challenging terrain within the agricultural landscape by providing valuable insights to improve tractor safety measures.

• 드라이브 ㆍ 컨트롤
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• 제21권3호
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• pp.20-27
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• 2024

This study aimed to evaluate the impact of mechanizing onion harvesting on labor reduction and work efficiency in Shinan Area. The mechanized harvesting system comprised a stem cutter, digging harvester, and collector. The field tests showed that the average residual stem length after using the stem cutter was 13.22±5.01 cm, with a stem cutting ratio of 91.3% and a damage ratio of 0%. The digging harvester achieved a digging ratio of 100% and a damage ratio of 1.2%, while the collector's damage ratio was 4.1%, loss ratio was 2.7%, and debris mixing ratio was 3.2%. The total working capacity of the mechanized system was 2.3 h/10a, significantly reducing 97.2% of labor time compared to manpower. These results indicate that the mechanization of onion harvesting can effectively reduce labor costs and increase work efficiency. Future research should include performance verification in various environments and an economic analysis of the mechanized system.

• Advances in concrete construction
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• 제17권3호
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• pp.127-133
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• 2024

Textile reinforced concrete (TRC) has gained attention as a viable alternative to conventional reinforced concrete due to its improved mechanical properties and design adaptability. Despite significant research into the mechanical properties of TRC, studies regarding the flexural effect of pre-stretching with different numbers of textile reinforcements are currently limited. Therefore, this research focuses on assessing the flexural characteristics of TRC panels with the incorporation of mesh pre-stretching. Additionally, the study compares the flexural behaviour between alkali-resistant (AR) glass fibre TRC and carbon fibre TRC. A three-point bending test was conducted to assess the flexural behaviour of TRC, investigating the impact of the number of textile layers and the application of pre-stretching on flexural strength and post-cracking stiffness. The findings, exhibited by the flexural stress vs. displacement curve, indicate that applying pre-stretching to carbon fibre TRC effectively increases the flexural strength of carbon textiles and enhances post-cracking stiffness. Moreover, the greater the number of carbon textiles, the higher the flexural stress of the specimens, provided the textiles are placed in the tensile zone. Nevertheless, when comparing carbon fibre TRC with AR glass fibre TRC, it is found that the increase in flexural strength is more significant for carbon fibre TRC. Overall, applying pre-stretching to carbon fibre significantly improves the TRC's flexural performance, specifically during the post-cracking stage and in crack distribution. Furthermore, due to the higher elastic modulus and tensile strength of carbon fibre, TRC reinforced with carbon textiles shows greater flexural strength and ductility compared to AR glass fibre TRC.

• Advances in concrete construction
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• 제17권1호
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• pp.13-26
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• 2024

Due to its capacity to address urgent environmental challenges connected to urbanization and stormwater management, pervious concrete, a sustainable and innovative material, has attracted a lot of attention recently. The aim of this study was to find the engineering characteristics of pervious concrete made from recycled aggregate (RA) at various aggregate-to-cement ratios (A/C) and the addition of 5% (by weight of total aggregate) of both natural and recycled fine aggregate to produce a very sustainable concrete product for a variety of applications. The three distinct aggregate-to-cement ratios, 6, 5, and 4, were used to produce pervious concrete using recycled aggregate in the research approach. The ratio of water to cement (w/c) was maintained at 0.3. Pervious concrete was created using single-sized recycled aggregate that passed through a 12.5 mm sieve and was held on a 9.5 mm sieve, as well as natural and recycled sand that passed through a 4 mm sieve. The production of twelve distinct concrete mixtures resulted in the testing of each concrete sample for dry density, abrasion resistance, compressive and splitting tensile strengths, porosity, and water permeability. A statistical method called GLM-ANOVA was also used to assess the characteristics of pervious concrete made using recycled aggregate. According to the experimental results, lowering the aggregate-to-cement ratio enhances the pervious concrete's overall performance. Additionally, a modest amount of fine aggregate boosts mechanical strength while lowering void content and water permeability. However, it was noted that such concretes' mechanical qualities were adversely affected to some extent. The results of this study offer insight into the viability of using recycled aggregates in order to achieve both structural integrity and environmental friendliness, which helps to optimize pervious concrete compositions.

• 대한조선학회논문집
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• 제61권5호
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• pp.389-399
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• 2024

Currently, shipyards are using ship block supports to hold various pre-erection (PE) blocks during ship construction work. The height adjustment method of the ship block support is performed by workers hammering and driving the wedge part, which requires repetitive high-load work. Accordingly, there are concerns about musculoskeletal diseases and safety accidents. To prevent safety accidents and improve work efficiency, this study developed a block support height adjustment device using a hydraulic cylinder. It was designed considering the ease of movement of the block support height adjustment device and the ease of adjusting the height of the block support by workers within the shipyard. Numerical analysis was conducted to confirm the critical points of the structural members of the designed block support height adjustment device and to verify the safety of the stress-based structure. As a result of the analysis, it was confirmed that the stress occurring at the critical point of the structural member was lower than the design allowable stress, making it structurally safe. Afterwards, the block support height adjustment device was redesigned for lightweight, and after verification of structural safety through numerical analysis, a prototype was manufactured and performance evaluation was conducted.

• Advances in concrete construction
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• 제18권1호
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• pp.43-54
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• 2024

According to major part of the energy-intensive manufacture of cement clinker, the cement sector contributes significantly to global CO₂ emissions. Previous experiments that have already been done on the subject of reducing CO₂ emissions and conserving energy during the production of cement clinker typically overlook the possibility of improving aggregate composition as a means of achieving these goals. While process efficiency is the main focus of current techniques, a thorough investigation of how raw material composition can further boost sustainability is lacking. This work presents a novel strategy for enhancing energy efficiency and lowering CO₂ emissions at the same time through aggregate composition optimization. This double gain has the potential to greatly advance cement industry sustainability initiatives. We examined the data set of cement the clinkers. Recycling cement was thought to use as little as 60%-76% of the energy used to produce clinker and emit less carbon dioxide. We proposed an optimal strategy based on the genetic programming with dynamic fuzzy system ensemble and Convolutional Neural networks (GP-DMFSE-CNN) are used to construct prediction models, which are subsequently refined through the application of one-year operation data, focusing attention to a cement clinker production process. To evaluate the suggested solution works in terms of efficiency, employee's satisfaction ratio, prediction rate, and decision make level. As a result, GHRM on EGB demonstrated by the suggested superior performance over other similar models in terms of energy consumption (350 kwh), carbon emission (150 ton), Cement Quality Index (CQI) (90%), and production rate (140 tons).

• 드라이브 ㆍ 컨트롤
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• 제21권4호
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• pp.208-213
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• 2024

The use of drone sprayers in South Korea is on the rise. The pesticides released by these drone sprayers are directed onto crops through the downward airflow created by the drone's rotors, making this airflow a key factor in the effectiveness of the spraying process. The required thrust varies depending on the amount of pesticide carried by the drone, which subsequently affects the intensity of the downward airflow. This study conducted experiments to examine how variations in the intensity of this airflow impact the adhesion of spray particles. Initially, to evaluate differences between nozzle types, two types of nozzles-Air Induction (AI) and XR-were tested to measure the adhesion of spray particles at different load levels. With the AI nozzle, the deposition of spray droplets increased by 25.9% as the load increased by 14.3%. In contrast, the XR nozzle showed a decrease in droplet deposition. Additional experiments using the XR nozzle, divided into three load stages, revealed a similar trend. This behavior is likely due to the increased downward airflow allowing more spray particles to reach the target area, while simultaneously reducing their adhesion because of the intensified downward force. Further research is needed to identify optimal operational strategies that maximize droplet deposition by effectively balancing drift and adhesion.