In the fabrication of curved steel plates for shipbuilding, post line-heating is widely used to induce plastic deformation by applying local heat and controlling residual stress. However, the process is still dependent on skilled labor and empirical methods, making it difficult to ensure consistent quality and precision. To improve the automation and standardization of the post line-heating process, this study aims to investigate the relationship between heating conditions and the resulting deformation behavior of marine structural steel plates. Experiments were conducted on AH36 steel specimens under 24 different heating conditions, including three plate thicknesses (12mm, 16mm, 20mm), two heating speeds, two gas flow ratios, and two torch tip types. Maximum deformation was measured across 15 locations per case. The results showed that thinner plates exhibited greater deformation, and higher heat input—such as slower heating speed and higher gas flow—led to increased deformation. The 800-type torch tip, with a narrower flame focus, also induced larger deformation than the 1000-type. These findings provide fundamental data for optimizing post line-heating parameters and establishing automated correction processes in shipbuilding applications.

This study investigates the deformation behavior of AH32 steel plates under various line heating conditions in the post line-heating process. A total of 24 experimental cases were conducted by varying material thickness (12mm, 16mm, 20mm), heating speed, oxygen and acetylene flow rates, and torch tip size. Deformation was measured at 35 points per specimen, with emphasis on the maximum deformation at the 300mm X-axis location. The deformation results were classified into three groups: high (≥4.0mm), medium (2.0–3.9mm), and low (≤1.0mm). The results confirmed that material thickness had the greatest effect on deformation, followed by heat input parameters such as heating speed and gas flow rate. High deformation occurred under low heating speed and high flow rate conditions, while low deformation was observed in thick plates with fast heating and low flow rates. These findings highlight the importance of controlling heat input and geometric factors for deformation correction. The data acquired from this study can be utilized as a reference for optimizing automated post line-heating processes in shipbuilding.

본 연구는 스탠다드 국화의 종묘 품질 기준을 설정하기 위해 삽수 길이와 굵기가 삽목묘와 절화의 생육에 미치는 영향에 대 해 알아보고 위해 수행되었다. 삽수 길이(3, 5, 7, 9cm)는 발근 및 삽목묘의 지상부 생육 특성에서 유의한 차이를 보이지 않아 품질지표로서 영향이 크지 않은 것으로 나타났다. 반면 삽수의 굵기(1.9, 2.6, 3.3mm)는 굵을수록 발근 이후 삽목묘의 뿌리의 수와 길이가 증가하였다. 또한 정식 후 초기 초장신장률이 높고 개화소요일수가 짧으며 꽃의 직경이 크게 나타나, 삽수의 굵기 는 삽수의 품질을 평가할 수 있는 주요한 형태적 품질지표로 활용될 수 있을 것으로 판단된다. 스탠다드 국화 ‘백강’에서의 삽수의 굵기를 구분하는 규격기준의 범위는 2.0mm 이하, 2.0~2.9mm, 2.9mm 이상 등 세 수준으로 구분 가능하였으며, 삽수 굵기와 생체중 간 높은 상관(r²=0.73)이 확인되어 삽수 평가의 대체 지표로 활용 가능성이 제시되었다. 이상의 결과는 국화 ‘백강’의 우량묘 규격 설정과 품질평가 기준 마련에 기초자 료로 활용될 수 있다.

Background: Muscle thickness (MT) measurement using ultrasound image is emerging as a useful method to assess muscle mass during stretching. Traditionally, range of motion (ROM) measurements assessed by digital inclinometer are considered reliable and valid parameter for monitoring muscle flexibility. The ultrasound-based measurement for MT to monitor muscle flexibility has yet to be validated. Objects: This study aimed to determine whether ultrasound measurement can serve as a valid alternative to a digital inclinometer for assessing muscle flexibility following stretching interventions. Methods: A randomized crossover design study was conducted with 20 healthy young participants. The stretching exercise program was carried out passive static and hold-relax proprioceptive neuromuscular facilitation stretching exercises applied on gastrocnemius-soleus muscle group with 3 times a week for 2 weeks. Data were collected 3 times for pre- and post-tests. Dorsiflexion ROM was measured by a digital inclinometer and the MT of gastrocnemius muscle by the ultrasound. Intraclass correlation coefficient (ICC) analysis for test-retest reliability, Wilcoxon sign rank test for stretching effects, and Spearman’s correlation analysis for determining the concurrent validity of two measurements. Results: ICC values of pre- and post-tests in both ROM and MT measurements were showed good to excellent intra rater reliabilities ranging from 0.782 to 0.968 (p < 0.001). A significant increase in the ROM measurements was observed following the stretching program (p < 0.01), whereas no significant change in the MT measurement was showed. Spearman’s correlations revealed weak relationships between the ROM and MT measurements (r = –0.217 for pre-test, r = –0.259 for post-test, r = –0.282, p < 0.05 for changes). Conclusion: These findings suggest that both the MT and ROM measurements were not compatible for monitoring muscle flexibility following stretching exercises regardless of their good reliabilities. Further investigations may be required to the MT measurement alone to be an alternative method.

Pavement friction under wet conditions is a critical factor affecting driving safety and is determined significantly by water-film thickness (WFT). Although current road geometric design standards incorporate wet-pavement friction coefficients as design parameters, they do not adequately account for the effects of WFT. This study estimates the variation in the coefficient of friction caused by changes in the WFT and applies the results to the calculation of stopping sight distance (SSD) and radius of curvature (RC), which are essential elements in road geometry design. Through this approach, the study identifies the limitations of current standards and proposes potential improvements. WFT was estimated using the Gallaway model, which was previously verified through comparative analysis and experimental validation. The model incorporates key influencing factors such as rainfall intensity, pavement slope, drainage path length, and mean texture depth. Based on the estimated WFT, the longitudinal and lateral friction coefficients were calculated using Gallaway’s SN and Lamm’s models, respectively. Using these friction values, the SSD and RC were evaluated under various pavement and environmental conditions. Furthermore, comparisons with existing design guidelines were performed to assess whether the predicted values satisfy the standards under different conditions. Additionally, areas requiring improvement were identified. The analysis confirmed that WFT increases with rainfall intensity and drainage path length, whereas it decreases as the pavement slope, mean texture depth, and tread depth increase. An increase in the WFT significantly reduces the friction coefficient, which consequently increases the SSD and required RC. In particular, under conditions such as heavy rainfall, worn treads, long drainage paths, and shallow surface textures, the calculated SSD and RC typically exceed the minimum requirements of current road-design standards. By contrast, ensuring sufficient surface texture effectively maintains friction performance and mitigates increases in the SSD and RC. The findings of this study suggest that current road-design standards—based on dry or vaguely defined wet conditions—may not sufficiently address the effects of WFT on pavement friction. A quantitative, WFT-based approach is required for more realistic friction estimations. To enhance safety in rainy conditions, road designs should incorporate structural and material improvements, such as optimizing pavement slopes, reducing the drainage path length, maintaining adequate surface texture and tread depth, and adopting high-performance surfacing materials. Additionally, dynamic speed-management systems during rainfall and preventive maintenance for sections with inferior drainage should be considered to improve driving safety under wet weather conditions.

Background: Core stabilization exercises are widely used to improve trunk stability, balance, and functional movement by enhancing the activation and endurance of deep trunk muscles such as the transversus abdominis (TrA). However, evidence comparing the effects of sling-based unstable surface training and mat-based stable surface training remains limited. Objects: To investigate the effects of mat based core stabilization exercises and sling based unstable surface core stabilization exercises on transversus abdominis thickness and core endurance. Methods: Forty-six healthy adults were randomly assigned to a mat exercise group (MEG, n=23) or a mat with sling exercise group (MSEG, n=23). Both groups performed 30-minute core stabilization exercises twice per week for four weeks. TrA thickness was measured using ultrasonography (SONON 300L), and core endurance was evaluated using the Bourban test for the anterior muscle chain. Results: Both groups showed significant increases in transversus abdominis thickness (MEG: P<.05; MSEG: P<.00) and core endurance (P<.00) after the intervention. However, no statistically significant differences were found between the two groups in post-intervention TrA thickness or Bourban test. Conclusion: Both mat based and sling based core stabilization exercises effectively enhanced TrA thickness and core endurance in healthy adults.

Background: Obesity negatively affects balance and core muscles playing a crucial role in postural stability. However, little is known about the relationship between abdominal muscle thickness and balance in normal weight women. Objectives: This study aimed to investigate the relationship between abdominal muscle thickness and balance ability in normal-weight women in their 20s. Design: Cross-sectional observational study. Methods: Twenty-four healthy normal-weight women participated. Abdominal muscle thickness including the external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) was measured by ultrasonography. Static balance was assessed during the One-leg standing test and Tetrax system, while dynamic balance was assessed using the Y-Balance and single leg triple hop tests. Pearson correlation analysis was conducted to examine the relationship between muscle thickness and balance performance. Results: IO thickness showed a negative correlation with static balance (r=- .42). EO thickness showed a positive correlation with single leg triple hop tests (r=.49-.58) and a negative correlation with posterolateral distance during YBalance test. Conclusion: Our findings suggested that abdominal muscles, specifically the IO and EO, are moderately related to balance performance in normal-weight young women. These findings demonstrated the potential benefit of targeted core strengthening interventions to improve postural stability and functional movement. Further studies involving additional muscles and diverse populations are recommended.

This study establishes a transient CFD and coupled CFD-thermal analysis method for evaluating the insulation performance of a liquid hydrogen control valve system incorporating an MLI-VCS-MLI configuration. Parametric analysis was conducted by varying the thickness of MLI 2 (50–200 mm) to assess its impact on the temperature distribution and heat flux within the valve body and insulation layers. The results indicate that increasing the thickness of MLI 2 significantly reduces heat flux and improves insulation effectiveness, with the highest heat flux occurring at the outermost MLI layer exposed to ambient conditions. These findings provide valuable insights for optimizing insulation design in liquid hydrogen storage and transport systems, contributing to enhanced thermal management and energy efficiency.

Wet pavement friction decreases with an increase in water film thickness (WFT), leading to a significant increase in vehicle crashes. The British pendulum test described in ASTM E303-93 is a method used to measure the pavement friction under wet conditions for the input of geometric design and pavement management systems. The British pendulum number (BPN) under wet conditions varies with WFT. Following the ASTM E303-93 standard procedure, WFT was simulated by spraying water onto the pavement surface. However, the measurement of the BPN did not include specific information regarding the WFT present during testing. To address these issues, WFTs and BPNs are measured using artificial rainfall generated by a rainfall simulator across various intensities, drainage lengths, pavement slopes, and pavement surfaces. This study aims to investigate the influence of the WFT on the BPN for wet pavement friction and provide the WFT corresponding to each BPN measurement for different surface types. The BPNs and WFTs of three test slabs, including diamond grooving and tining surfaces with 16 mm and 25 mm spacing, were measured under wet conditions by spraying water and creating WFTs using a rainfall simulator. Measurements were taken in both longitudinal and transverse directions, considering different rainfall intensities (40 mm/h, 80 mm/h, and 130 mm/h), pavement slopes (2%, 5%, and 10%), and drainage path lengths (1 m, 2 m, 3 m, 4 m, and 5 m). The test results indicated that wet pavement friction decreased as the WFT increased that was influenced by several factors including the pavement slope, mean texture depth, rainfall intensity, and drainage path length. Specifically, the WFT tended to increase with a decrease in the pavement slope and an increase in the mean texture depth, rainfall intensity, and drainage path length. In particular, surface texture played a significant role in the wet friction performance, with diamond-grooved pavements. Among the tested surfaces, the diamond-grooved (longitudinal and transverse) pavements demonstrated a more effective wet friction performance, maintaining higher BPN values across varying WFT levels. Conversely, longitudinally and transversely tined surfaces with 25 mm spacing showed a more significant decrease in BPN, reflecting a higher sensitivity to WFT. In contrast, tined surfaces with 16-mm spacing exhibited a more gradual reduction in friction, likely owing to enhanced drainage and better resistance to water-induced friction loss. Additionally, these results indicated that longitudinal textures demonstrated a more significant reduction in friction with increasing WFT compared with transverse textures. This demonstrated that the texture type, direction, and spacing significantly influenced the friction loss under wet conditions, with diamond grooving offering the best overall performance. This study highlighted the critical role of WFT in pavement friction design, emphasizing the need to consider the WFT for a more accurate assessment of wet pavement friction. The WFT was influenced by factors such as the pavement slope, rainfall intensity, drainage path length, and surface texture. The diamond-grooved pavements demonstrated a more effective wet friction performance, maintaining higher BPN values across varying WFT levels. In contrast, tined surfaces with larger spacings exhibited more significant friction loss, whereas those with smaller spacings showed a more gradual reduction, likely owing to better drainage. In particular, longitudinal textures showed a greater reduction in friction compared with transverse textures. Overall, the texture type, direction, and spacing played crucial roles in wet friction performance, with diamond grooving offering the best results.

목적 : 근시 교정용 (-)렌즈를 대상으로 편심 크기를 변화하면서 동일 직경으로 가공한 렌즈의 가장자리 두께와 무게를 비교하고 분석하고자 하였다. 방법 : 고굴절률(High index, 1.60) 소재의 구면 및 비구면렌즈를 굴절력(-2.00, -4.00, -6.00 D)별로 240개 를 선정하였으며, 굴절력별 편심 크기를 0, 3, 6, 9 mm로 설정하고 동일한 직경의 원형으로 평산각 가공하여 가장 자리 두께와 무게를 비교 분석하였다. 결과 : 편심별 평균 가장자리 두께는 구면렌즈일 때 –2.00 D에서는 편심이 1 mm 증가할 때 가장자리 두께가 0.02 mm 증가하는 것으로 나타났고, –4.00 D는 0.04 mm, –6.00 D는 0.05 mm 증가하는 것으로 나타났으며, 비구면렌즈일 때 –2.00 D에서는 0.02 mm, –4.00 D는 0.03 mm, –6.00 D는 0.04 mm 증가하는 것으로 나타났다. 편심별 평균 무게는 구면렌즈일 때 –2.00 D에서는 편심이 1 mm 증가할 때 무게가 0.05 g 증가하는 것으로 나타 났고, –4.00 D는 0.09 g, –6.00 D는 0.11 g 증가하는 것으로 나타났으며, 비구면렌즈일 때 –2.00 D는 0.04 g, –4.00 D는 0.08 g, –6.00 D는 0.11 g 증가하는 것으로 나타났다. 대상 렌즈의 굴절력별, 편심별 모두에서 굴절력 이 높아질수록 편심 크기가 커질수록 가장자리 두께와 무게가 점점 더 크게 증가하는 것으로 나타났다. 결론 : 동일 굴절력의 근시 교정용 (-)렌즈를 동일 직경으로 가공하였을 때 편심의 크기가 증가하면 가장자리 두께와 무게도 증가하는 것을 확인할 수 있었다.

본 연구에서는 터널부의 환경조건을 고려한 터널 내부 연속철근 콘크리트 포장(CRCP)의 설계 방안을 수립하기 위하여 CRCP 전용 구조해석 프로그램을 이용하여 터널 내부와 토공부의 환경하중을 고려한 수치해석을 수행하였다. 수치해석 모델은 철근비를 0.6%와 0.68%로 고정하고 슬래브의 두께를 26cm, 28cm, 30cm로 변화시켜 구성하였다. 또한, 터널 내외 부의 환경하중과 차륜하중을 적용하여 분석을 수행하였다. 분석 결과, 터널 내외부 모든 경우에서 CRCP의 슬래브 두께 가 증가할수록 균열간격과 균열폭이 증가하게 되며 터널 내부 CRCP는 슬래브 두께를 감소시키더라도 토공부와 유사한 균열간격 및 균열폭이 형성되는 것을 확인하였다. 향후 보다 다양한 조건에서의 수치해석 및 시험시공을 통해 국내 터널 환경에 적합한 터널 내부 CRCP 설계 방안을 마련할 수 있을 것으로 기대된다.

도로 주행 시 차량의 제동거리 확보와 곡선부 주행 안전성은 도로 설계에서 중요한 요소이며, 강우로 인해 형성되는 수 막은 타이어와 노면 간 마찰력을 저하시켜 제동거리를 증가시키고 주행 안전성을 저해하는 요인으로 작용한다. 기존 도 로 설계에서는 습윤 상태에서의 마찰계수를 기준으로 하지만, 측정 방식마다 수막두께 기준이 상이하여 적용에 한계가 있다. 본 연구에서는 RRL 및 Gallaway 수막두께 예측 모델을 활용하여 다양한 도로 및 기상 조건에서의 수막두께를 예 측하고, 실측 실험을 통해 신뢰도가 높은 모델을 선정한 후, Gallaway의 마찰계수 예측식을 적용하여 강우강도, 배수 거 리, 포장 경사, 노면 조직 깊이, 타이어 트레드 깊이에 따른 마찰계수 변화를 분석하였다. 연구 결과, 강우강도가 증가하 고 배수 거리가 길어질수록 수막두께가 증가하면서 마찰계수가 감소하는 경향을 보였으며, 반대로 포장 경사와 노면 조 직 깊이가 증가할 경우 배수 성능이 향상되어 수막두께가 얇아지고 마찰계수가 증가하는 것으로 나타났다. 이러한 마찰 계수 변화는 도로 안전성에 직접적인 영향을 미쳐, 강우가 심한 조건에서는 제동거리가 길어지고 곡선부에서는 더 큰 반 경이 필요해지는 것으로 분석되었다. 특히 설계속도가 높은 구간이나 수막두께가 깊이 형성되는 구간, 타이어 트레드 깊 이가 얕은 경우 현행 도로 설계 기준이 요구하는 정지 시거를 충족하지 못하는 사례가 발생하였으며, 곡선부에서도 동일 한 문제점이 확인되었다. 결과적으로 강우 조건을 반영한 도로 설계 기준의 보완이 필요하며, 배수 성능을 강화하고 마 찰력 저하를 방지할 수 있는 포장 기법을 적용하는 것이 요구된다. 또한, 강우 시 주행 안전성을 확보하기 위해 동적 속 도 제한 시스템 도입 및 유지관리 체계를 강화하고, 강우 조건을 고려한 정지 시거 및 곡선 반경 설계 기준을 마련함으 로써 도로 안전성을 향상시킬 필요가 있다.

최근 콘크리트 타설 중 구조체, 거푸집 및 동바리 사고가 지속적으로 발생하고 있으며, 특히 슬래브 두께가 증가한 비기준층이 존 재하는 다층지지 RC 구조 시스템에서 빈번하게 발생하였다. 양생 온도는 콘크리트의 강도와 강성을 결정하는 주요한 요인이며 이에 따라 시공 하중의 분포가 변화한다. 이 연구에서는 양생 온도에 따른 시공 하중의 분포를 분석하기 위하여 온도와 재령에 따른 적산 온도 이론을 사용하여 등가 재령을 계산하고, 이에 따른 슬래브 콘크리트의 강도 및 강성을 산정하여 시공 하중, 시공 손상 변수의 변 화에 대하여 분석하였다. 시공 하중은 평균 양생 온도가 낮아질 때 초기 재령에서는 소폭 감소하고, 충분한 재령이 지난 후에는 증가 하였다. 시공 손상 변수는 평균 양생 온도가 낮아질 때 크게 증가함을 확인하였다.

목적 : 근시 교정용 비구면렌즈를 대상으로 중심 두께와 굴절률 및 굴절력 그리고 직경이 가장자리 두께와 무게에 어떠한 영향을 미치는지 비교하고 분석하고자 하였다. 방법 : 시중에 판매되고 있는 근시 교정용 렌즈를 굴절률(1.56~1.74)과 굴절력(-3.00~-8.00 D)별로 252개를 대상으로 선정하였다. 굴절률과 굴절력별로 40.00, 50.00 및 60.00 mm 직경 크기로 평산각 가공하여 가장자리 두께와 무게를 측정하여 그 결과를 비교 분석하였다. 결과 : 가장자리 두께는 직경이 1.00 mm 증가하였을 때 0.11 mm 증가하고 굴절력이 –1.00 D 증가하였을 때 0.50 mm 증가하며 굴절률이 한 단계 높아질 때 0.24 mm 감소한 것으로 나타났다. 무게는 직경이 1.00 mm 증가 하였을 때 0.42 g 증가하고 굴절력이 –1.00 D 증가하였을 때 0.75 g 증가하며 굴절률이 한 단계 높아질 때 0.08 g 감소한 것으로 나타났다. 가장자리 두께와 무게와의 인과관계는 직경이 가장 크고, 굴절력, 굴절률, 중심 두께 순으 로 나타났으며 가장자리 두께가 1.00 mm 증가하면 무게는 2.57 g 증가하는 것으로 나타났다. 결론 : 근시안을 비구면렌즈로 교정하고자 할 때, 굴절이상도와 안경렌즈 각 요소와의 관계를 고려하여 안경렌 즈를 선택하면 가장자리 두께 및 무게 감소에 도움이 되리라 사료된다.

The purpose of this study was to optimize the design of asphalt concrete pavements for Jeju Island by considering the regional characteristics of the island. This study employed an MEPDG program to determine the allowable traffic loads for class 4 vehicles by considering the axle loads, climate, and material properties. Samples of basalt asphalt concrete from Jeju were used to measure the dynamic modulus for material property estimation. The climate input was based on 30-year climate data from Jeju. The thicknesses and moduli of the subgrade, subbase, and asphalt layers were incorporated into the design. The regression-analysis program SPSS was used to develop a regression equation for the overlay design, factoring in the modulus and thickness ratios between the existing and overlay asphalt layers. A pavement-thickness design formula tailored to Jeju's characteristics was derived. An equivalent single-axle load factor (ESALF) formula was developed to facilitate traffic-load estimation for different roads, enabling the easy incorporation of varying traffic volumes into the design. The ESALF formula demonstrated a high correlation with the pavement thickness, subgrade conditions, and axle loads, whereas the pavementthickness design formula exhibited strong correlations with the pavement thickness, subgrade state, thickness ratios, and modulus ratios. The use of basalt aggregates in asphalt concrete pavements provides an economically viable and technically sound solution for Jeju. The proposed design methodology not only reduces costs but also enhances pavement performance and road safety. The developed formulas offer flexibility in adjusting designs based on specific traffic conditions, providing optimal pavement solutions for different road categories.

This study aimed to improve the accuracy of road pavement design by comparing and analyzing various statistical and machine-learning techniques for predicting asphalt layer thickness, focusing on regional roads in Pakistan. The explanatory variables selected for this study included the annual average daily traffic (AADT), subbase thickness, and subgrade California bearing ratio (CBR) values from six cities in Pakistan. The statistical prediction models used were multiple linear regression (MLR), support vector regression (SVR), random forest, and XGBoost. The performance of each model was evaluated using the mean absolute percentage error (MAPE) and root-mean-square error (RMSE). The analysis results indicated that the AADT was the most influential variable affecting the asphalt layer thickness. Among the models, the MLR demonstrated the best predictive performance. While XGBoost had a relatively strong performance among the machine-learning techniques, the traditional statistical model, MLR, still outperformed it in certain regions. This study emphasized the need for customized pavement designs that reflect the traffic and environmental conditions specific to regional roads in Pakistan. This finding suggests that future research should incorporate additional variables and data for a more in-depth analysis.