A multi-barrier can be applied for the deep geological disposal of high-level radioactive waste. The multi-barrier comprises an engineered barrier and the natural barrier of the host rock. In the engineered barrier, the bentonite buffer is the key component for the disposal container, and the bentonite buffer thickness is given important consideration when designing the engineered barrier. This study reviewed the safety functions of bentonite buffers. Subsequently, the requirements and factors necessary to determine the thickness of the bentonite buffer, including criteria for radiological safety and the thermal stability of the disposal system, were identified. Additionally, the bentonite buffer thicknesses required for the top, bottom, and side of the disposal container were calculated. A double-layered emplacement method is also proposed for the bentonite buffer to improve disposal efficiency in terms of thermal management. Based on radiological safety and thermal stability analyses, an optimal thickness of 0.36 m was found to be appropriate for the bentonite buffer surrounding the disposal container. The thickness of the bentonite buffer above the disposal container can be determined based on the excavation damaged zone depth. The study findings can be used as a reference when designing deep geological disposal systems.

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.

The rapid urbanization and industrial growth have increased the demand in construction, maintenance, and infrastructure, leading to significant advancements in aerial work vehicle technology. This study focuses on the structural performance of ultra-high-strength steel plates of varying thicknesses used in telescopic booms, which is a critical component of aerial work vehicles. This study aims to address the cost issues associated with the previously used 5mm thick plates by evaluating the structural integrity of thinner plates. Using finite element analysis (FEA), the study analyzes stress and displacement for different thicknesses, specifically targeting the first boom segment, which bears the most load. The results indicate that while 3mm and 3.2mm thick plates are unsuitable due to buckling, the 4mm thick plate meets safety criteria with a safety factor of 2.51 and reduces costs by over 20%. By using 4mm thick ultra-high-strength steel for the first boom segment is cost-effective, providing structural integrity and an applicable solution for aerial work vehicle manufacturers.

인공번식을 통한 야생 재도입은 멸종 가능성이 높은 종을 보존하기 위한 최후의 수단으로 인식되고 있다. 우리나라에서 도 지역 절멸된 따오기를 복원하고자 2008년 중국으로부터 한 쌍을 도입하여 인공증식을 시작하였고, 2019년부터 2023년까지 8회에 걸쳐 290개체가 방사된 상태이다. 유전적인 문제를 제외하면 재도입이 성공하기 위해서는 자연서식처 와 유사한 환경에서 훈련하는 것이 필요하다. 이에 따오기의 생활사에서 휴식 및 교란 회피시 가장 많이 이용하는 횃대의 종류 및 규격을 제안하고자 본 연구를 진행하였다. 방사된 따오기는 자연서식처에서 높이 5m 내외, 가지 굵기 5∼15(9.17±4.94)㎝인 소나무, 곰솔, 상수리나무 등을 가장 많이 이용하고 있었다. 유사한 종류의 횃대를 번식케이지와 관람케이지에 설치하는 것이 야생 적응에 도움이 될 것으로 보인다. 다만, 횃대만으로 서식 환경의 유사성을 확보하기에는 한계가 있기 때문에 먹이터 구조, 둥지 짓는 수목 및 재료 등에 대한 추가적인 연구가 진행되어야 할 필요가 있다.

도심부 도로에서 불투수면적 증가로 인해 발생한 홍수 및 물순환 장애 문제를 해결하기 위해, 투수블록포장이 도입되고 있으며, 물순환 시스템 강화의 필요성에 따라, 투수블록포장은 효과적인 대안으로 주목받고 있다. 투수성 포장의 성능 향상 을 위해서는 교통 하중 지지력을 만족하고, 투수 성능을 동시에 확보해야 하므로 표층뿐만 아니라 하부 투수기층의 설계 기준과 입도 특성에 대한 고려가 필요하다. 그러나, 국내의 경우 설계법이 잘 정립되어 있지 않고, 국외에서는 AASHTO 93 설계법을 구조설계법으로 적용하고 있으며, 투수성 포장재료의 상대강도계수에 대한 연구가 부족하여 다양한 재료에 대 한 설계 적용이 어려운 한계가 존재한다. 이에 본 연구는 투수블록포장 하부 투수기층 골재의 물리적 특성과 입도 기준에 관한 고찰을 통해, 내구성 향상을 위한 설계 요인과 투수 성능 간의 관계 분석 결과를 정리함으로써, 두 방향을 모두 고려하여 효율적인 골재 입도 구성을 도모할 수 있는 적합한 방향성을 정립하는 것을 목표로 한다. 다양한 투수성 포장 설계 조건과 성능에 관한 연구를 다루는 문헌을 수집해 투수 블록포장의 하부구조 단면 설계에 적용할 수 있는 기준 및 연구 방법론을 정리함으로써 실무 연구자들의 국내 연구 활성에 기여하고자 한다

Wet pavement friction decreases due to the increase in water film thickness (WFT), leading to a significant increase in vehicle crashes occurrences. The British Pendulum Test described in ASTM E303-93 is one of the methods used to measure pavement friction in wet conditions for the input of geometric design and pavement management systems. The British Pendulum Number (BPN) in wet conditions varies with WFT. Following ASTM E303-93 standard procedures, water film thickness was simulated by spraying water on the pavement surface. However, the measurement of BPN did not include specific information about the thickness of the water film present during testing. To address these issues, WFTs and BPNs were 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 water film thickness on BPN for wet pavement friction and provide the WFT corresponding to each BPN measurement for different surface types. BPNs of three test slabs, including a smooth surface and tined surfaces with 16 mm and 25 mm spacing, were measured under wet conditions by spraying water, and by creating water film thicknesses using a rainfall simulator. This study demonstrates that the BPNs of non-tined surfaces and longitudinally and transversely tined surfaces with 25mm spacing exhibit a significant decrease with increasing water film thickness, while those with 16mm spacing show a slight decrease. These findings can be attributed to the lower friction observed in both non-tined and longitudinally tined pavements, in contrast to surfaces with transverse tinning.

Background: Core muscles provide important dynamic stabilization of the lumbar spine. The twist sit-up can simultaneously stimulate the external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) muscles. Objectives: The purpose of this study is to investigate the impact of knee angles during twist sit-up exercises and determine the most efficient knee angle for performing this exercise. Design: Cross-sectional study. Methods: The study recruited 30 students from S University regardless of gender. The subjects performed a total of 10 twist sit-ups at five different knee angles (0, 40, 65, 90, and 105 degrees), divided between the ipsilateral and contralateral sides. The thickness of abdominal muscles (EO, IO, and TrA), was measured using ultrasonography on rest position and full contraction position for each angle of knee flexion and compared between angles. Results: There were significant differences in the ipsilateral EO, IO, and TrA muscle thickness at different knee flexion angles (P<0.5). There was a significant difference in the thickness of EO between 0 and 105 degrees and between 40 and 105 degrees (P<0.5), a significant difference in the thickness of IO between 0 and 105 degrees (P<0.5), and a significant difference in the thickness of TrA between 0 and 105 degrees, 40 and 90 degrees, and 65 and 90 degrees (P<0.5). Conclusion: In conclusion, the muscles involved in axial rotation i.e., EO and IO, maximally contract at a knee flexion angle of 105 degrees. Therefore, this may be the most optimal angle to perform twist sit-ups.

PURPOSES : The skid resistance between tires and the pavement surface is an important factor that directly affects driving safety and must be considered when evaluating the road performance. In especially wet conditions, the skid resistance of the pavement surface decreases considerably, increasing the risk of accidents. Moreover, poor drainage can lead to hydroplaning. This study aimed to develop a prediction equation for the roughness coefficient—that is, an index of frictional resistance at the interface of the water flow and surface material—to estimate the thickness of the water film in advance to prevent human and material damage. METHODS : The roughness coefficient can be changed depending on the surface material and can be calculated using Manning's theory. Here, the water level (h), which is included in the cross-sectional area and wetted perimeter calculations, can be used to calculate the roughness coefficient by using the water film thickness measurements generated after simulating specific rainfall conditions. In this study, the pavement slope, drainage path length, and mean texture depth for each concrete surface type (non-tined, and tined surfaces with 25-mm and 16-mm spacings) were used as variables. A water film thickness scale was manufactured and used to measure the water film thickness by placing it vertically on top of the pavement surface along the length of the scale protrusion. Based on the measured water film thickness, the roughness coefficient could be back-calculated by applying Manning's formula. A regression analysis was then performed to develop a prediction equation for the roughness coefficient based on the water film thickness data using the water film thickness, mean texture depth, pavement slope, and drainage path length as independent variables. RESULTS : To calculate the roughness coefficient, the results of the water film thickness measurements using rainfall simulations demonstrated that the water film thickness increased as the rainfall intensity increased under N/T, T25, and T16 conditions. Moreover, the water film thickness decreased owing to the linear increase in drainage capacity as the mean texture depth and pavement slope increased, and the shorter the drainage path length, the faster the drainage, resulting in a low water film thickness. Based on the measured water film thickness data, the roughness coefficient was calculated, and it was evident that the roughness coefficient decreased as the rainfall intensity increased. Moreover, the higher the pavement slope and the shorter the drainage path length, the faster the drainage reduced the water film thickness and increased the roughness coefficient (which is an indicator of the friction resistance). It was also evident that as the mean texture depth increased, the drainage capacity increased, which also reduced the roughness coefficient. CONCLUSIONS : As the roughness coefficient of the concrete road surface changes based on the environmental factors, road geometry, and pavement surface characteristics, we developed a prediction equation for the concrete pavement roughness coefficient that considered these factors. To validate the proposed prediction equation, a sensitivity analysis was conducted using the water film thickness prediction equation from previous studies. Existing models have limitations on the impact of the pavement type and rainfall intensity and can be biased toward underestimation; in contrast, the proposed model demonstrated a high correlation between the calculated and measured values. The water film thickness was calculated based on the road design standards in Korea—in the order of normal, caution, and danger scenarios—by using the proposed concrete pavement roughness coefficient prediction model under rainy weather conditions. Specifically, because the normal and caution stages occur before the manifestation of hydroplaning, it should be possible to prevent damage before it leads to the danger stage if it is predicted and managed in advance.

In this study, a new model using artificial neural networks is proposed to improve the thickness error between the plates, which occurs when the rolling conditions change a lot during the thick rolling. The model was developed by using Python, and the input values are the change in the finish rolling temperature between the plates, the change in target tensile strength, the change in target thickness, and the change in rolling force. The new model is 31.76% better than the existing model based on the standard deviation value of the thickness error. This result is expected to reduce quality costs when applied to online models at actual production sites in the future.

Steel plate shear walls (SPSWs) have been recognized as an effective seismic-force resisting systems due to their excellent strength and stiffness characteristics. The infill steel plate in a SPSW is constrained by a boundary frame consisting of vertical and horizontal structural members. The main purpose of this study was to investigate deformation modes and hysteretic characteristics of steel plate shear walls (SPSWs) to consider the effects of their aspect ratios and width-to-thicness ratios. The finite element model (FEM) was establish in order to simulate cyclic responses of SPSWs which have the two-side clamped boundary condition and made of conventional steel grade. The stress distribution obtained from the FEA results demonstrated that the principal stresses on steel plate with large thickness-to-width ratio were more uniformly distributed along its horizontal cross section due to the formation of multiple struts.

Background: The forward head posture acts as a factor that can cause various neurovascular and musculoskeletal dysfunctions. But searching for a study on quality of life for patient with forward head posture was challenging. Therefore, this study aims to find the factors that most affect the quality of life in patients with forward head posture. Objectives: The purpose of this study was to investigate the correlations between the cranio-vertebral angle (CVA), neck disability index (NDI), pain, and sternocleidomastoid (SCM) thickness of patients with forward head posture and the quality of life of the patients and to figure out important factors that affect the quality of life of the patients with forward head posture. Design: Cress-sectional study. Methods: To measure the CVA, the angle at which the visible protrusion of C7 and the ear bead were connected was measured, and the neck disorder index was evaluated using the Korean version of NDI. The degree of pain of the subject was measured using a visual-analog scale (VAS). The SCM thickness was measured using an ultrasound imaging device, and the quality of life was evaluated using the Korean version of the World Health Organization quality of life questionnaire (WHOQL-BREF). Results: A significant predictive model showing 88% explanatory power for the dependent variable was confirmed, with an appropriate regression equation being found. The factor that most affected patients' quality of life in the forward head posture was confirmed by the SCM thickness. Conclusion: When applying an intervention to improve a patient's quality of life for patient with forward head posture, an intervention method that improves the SCM thickness should be recommended.

Since the decrease of skid resistance of the road surface due to the effects of hydroplaning increases the ratio of vehicle crashes significantly, it is important to predict water film thickness (WFT). Tined is one of the widely used textures for concrete pavements. Since previous WFT models have been developed based on the asphalt pavement texture and broom concrete, it may not give reliable predictions for Water film thickness for tinned concrete. Furthermore, surface flow on tined texture may show hydraulically different characteristics due to the geometric characteristics of tined texture. This study aims to propose a reliable water film thickness prediction model for tined concrete. Three test slabs including a smooth surface, a tined surface with 16mm spacing, and a tined surface with 25mm spacing were prepared. WFTs of the test slab were measured for various conditions such as pavement slope (0-10%), rainfall intensity (0-130mm/h), and drainage path length (0-5m). A statistical model was proposed to predict water film thickness (WFT) as a function of pavement slope, rainfall intensity, drainage path length, and mean texture depth. This model exhibits strong agreement with the experimental test results. The GWNU prediction model consistently provides reliable predictions with the actual WFT for tined concrete pavement. Conversely, the previous equation consistently underestimated the water film thickness, notably on tined surfaces with 16 mm and 25 mm spacing, due to the occurrence of viscous flow along the tined lines.

여름철은 타 계절에 비해 장마와 불안정한 대기 등으로 인하여 빗길 교통사고의 위험성이 크게 증대될 수 있으며, 최근 5년 (2018~2022)간 여름철 빗길 교통사고는 전체 빗길 교통사고의 39%를 차지할 정도로 높은 수준이다. 이러한 빗길 운전은 노면의 배수 불량 및 미끄럼 저항 감소 등으로 인하여 수막현상을 발생시키게 된다. 이에 본 연구에서는 우천 시 도로의 안전성 강화 및 사고 위 험을 최소화하기 위한 요소인 수막두께를 산정하기 위하여 Manning의 평균 유속식을 기반으로 콘크리트 노면의 조도계수 예측 모델을 개발하는 것을 목표로 하였다. 조도계수의 영향인자를 고려하기 위하여 실외 강우 모의 장비를 이용하여 콘크리트를 타설한 뒤 실험 인자로 포장 경사, 배수거리, 강우강도, 노면 조직 특성을 고려하였으며, 이 중 노면 조직 특성은 타이닝 처리를 하지 않은 구간만 고 려한 타 연구의 기존 예측 모델 단점을 보완하기 위하여 16, 25mm 간격의 타이닝 표면 처리한 구간을 추가로 고려하였다. 수막두께 측정은 측정 범위 0.3~5mm의 수막두께 측정 게이지를 제작하여 강우가 모사된 조건에서 배수 거리 1~5m 이내 지점의 노면 조직 상 단과 수면이 접하는 수직 높이를 총 3회 측정하여 평균값을 사용하였다. 실측된 수막두께 데이터베이스를 기반으로 Manning 공식을 이용하여 조도계수를 역산한 결과, 강우강도가 증가함에 따라 조도계수는 감소하였으며, 이는 강우의 증가로 인해 물의 흐름과 콘크리 트 노면 사이의 마찰 저항 감소에 기인한 것으로 판단되었다. 또한 포장 경사가 높고 배수 거리가 짧을수록 배수성이 증가하여 마찰 저항의 지표인 조도계수가 증가하는 것으로 확인되었다. 평균 조직 깊이에 따른 조도계수 영향의 경우, 평균 조직 깊이가 증가할수록 콘크리트 표면에 노출되는 표면적이 증가하여 수막두께가 얕게 생성되고, 얕은 수심으로 인해 물의 흐름 저항이 감소하여 조도계수는 감소하는 것으로 산정되었다. 이후 135개의 데이터를 종합하여 조도계수를 종속변수로 하고 강우강도, 포장경사, 배수거리, 평균 조직 깊이, 수막두께를 독립변수로 하는 회귀분석을 수행하여 조도계수 산정식을 개발하였다.

In this work, the trend in the performance of carbon fiber (CF) and its composite during self-polymerization of polydopamine (PDA) at carbon fiber surface was investigated by varying the self-polymerization time of dopamine in an aqueous solution. Research has shown that the PDA coating elevated the surface roughness and polarity of the inert fiber. The tensile strength of single carbon fiber was significantly improved, especially after 9 h of polydopamine self-polymerization, increasing by 18.64% compared with that of desized carbon fiber. Moreover, the interlaminar shear strength (ILSS) of CF-PDA9-based composites was 35.06% higher than that of desized CF-based composites. This research will provide a deep insight into the thickness and activated ingredients of dopamine oxidation and self-polymerization on interfacial compatibility of carbon fiber/epoxy resin composites.