As high-speed trains operate on both high-speed and conventional lines, wheel-rail interface characteristics have become increasingly important for effective wheel-rail wear management and operational safety. This study compared and analyzed interface characteristics for various combinations of wheels used in high-speed vehicles with various rail configurations, including UIC, KS50, and KS60, to determine the optimal combination. The results were calculated and analyzed for rolling radius differences, equivalent conicity, and wheel-rail contact area characteristics in response to lateral axle displacement. Changes in equivalent conicity and wheel-rail contact area as wear progressed were also analyzed.

In this paper, the structural optimization and experimental validation of lightweight, high stiffness rollers for roll-to-roll(R2R) processing of lithium metal electrodes are presented. Precise dimensional control of electrode thickness below 50㎛ is essential for next-generation high energy density batteries, yet elastic recovery during rolling hinders the achievement of target specifications. To address this challenge, finite element(FE) analysis was employed to determine the optimal rolling gap and roller geometry, and the results were verified through R2R experiments. Simulations indicated that a rolling gap of 153㎛ yielded a final sheet thickness of about 49.6㎛, meeting the design requirement. Experimental results confirmed the validity of the numerical model, with thickness measurements deviating less than ±10% from FE analysis predictions. These findings demonstrate that the proposed roller design not only ensures thickness precision but also improves system efficiency, offering practical guidelines for scalable lithium metal electrode manufacturing.

본 연구는 모의(simulated) 선박 횡요(rolling)가 보행 안정성에 미치는 영향을 하지 관절의 운동학적 관점에서 정량적으로 분석하 여, 선원의 낙상 위험을 이해하기 위한 기초 자료를 제공하고자 하였다. 기존 연구들은 주로 신체 질량 중심(center of mass) 변위와 같은 전신 수준의 거시적 지표를 통해 보행 안정성을 평가하였으나, 실제 낙상과 직결되는 하지 관절의 운동 제어 전략, 특히 최대 관절각(peak joint angle)과 그 변동성(variability)에 대한 분석은 부족했다. 30명의 건강한 성인을 대상으로 0°, 10°, 20°의 횡요 조건에서 보행 실험을 수행 하고, 3차원 동작분석을 통해 고관절, 슬관절, 족관절의 최대 관절각과 그 표준편차를 측정하였다. 횡요각에 따른 각 관절 최대각의 변화 를 분석하기 위하여 일원 반복측정 분산분석을 실시한 결과, 횡요각이 증가함에 따라 안정성 확보를 위한 유의미한 운동학적 보상 전략 (예: 슬관절 및 고관절 굴곡 증가, 족관절 족저굴곡 및 내번 감소)이 관찰되었다. 특히, 모든 하지 관절에서 최대 관절각의 변동성이 횡요 강도에 비례하여 유의하게 증가하였으며, 이는 보행의 일관성이 저하되고 동적 안정성을 유지하기 위한 신경근 제어 부하가 가중됨을 의 미한다. 본 연구 결과는 선박 환경에서의 보행 안정성 평가에 있어 관절 수준의 변동성 분석이 필수적임을 시사하며, 향후 선내 안전 규 정 수립 및 선원 훈련 프로그램 개발에 중요한 과학적 근거를 제공할 수 있을 것으로 기대한다.

본 연구는 Rolling Asymmetric VAR-BEKK-GARCH 모형으로 한·중·일·미 4개 주식 시장 변동성의 비대칭 전이효과를 분석하였다. 연구는 시장 변동성의 정태적인 전이 효과뿐만 아니라 시간가변적인 비대칭 전이효과를 파악하였다. 분석 결과에 따르면, 중국 시장 호황기에는 비대칭 변동성 전이효과의 부호가 대체로 음(-)으로, 시장 불황기나 불안정 시기에는 양(+)의 부호로 나타났다. 또한, 한국, 일본, 미국 등 시장의 충격이 중국 시장 변동성에 대한 영향은 비교적 일관된 방향성을 보이며, 반면에 중국발 충격이 타 시장의 변동성에 미치는 영향은 시간가변적인 특징을 나타냈다. 이는 중국 금융 시장의 동태적 특성을 파악하는 데 유의미한 시사점을 제공할 수 있다.

This study employed a cross-rolling process to fabricate oxide dispersion strengthened (ODS) steel plates and investigated their microstructures and mechanical properties. The 9Cr-1W ODS ferritic steel was fabricated using mechanical alloying and hot isostatic pressing. The hot cross-rolling process produced thick ODS ferritic steel plates with a well-extended rectangular shape. The working direction greatly affected the grain structure and crystal texture of the ODS ferritic steel. Cross-rolled plates showed fine micro-grains with random crystal orientation, while unidirectionally rolled plates exhibited a strong orientation with larger, elongated grains. Transmission electron microscopy revealed a uniform distribution of nano-oxide particles in both rolling methods, with no major differences. Tensile tests of the ODS ferritic steel plates showed that the unidirectional rolled plates had anisotropic elongation, while cross-rolled plates exhibited isotropic behavior with uniform elongation. Cross-rolling produced finer, more uniform grains, reducing anisotropy and improving mechanical properties, making it ideal for manufacturing wide ODS steel components.

Background: Thoracic kyphosis is a condition characterized by an excessive curvature of the thoracic spine, often leading to decreased trunk range of motion and various health complications. Objectives: This study aimed to investigate the effects of a rolling corrector on trunk range of motion (ROM) and thoracic kyphosis angle in individuals with thoracic kyphosis. Design: A randomized controlled trial. Methods: Thirty participants with a thoracic kyphosis angle of 40 degrees or more were randomly assigned to either the rolling corrector group (RCG) or the control group (CG). The RCG used the rolling corrector for 30 minutes per session, five times a week for two weeks, while the CG received no intervention. Trunk ROM and thoracic kyphosis angle were measured before and after the intervention. Results: The RCG showed significant improvements in trunk flexion, extension, lateral flexion, and rotation ROM, as well as in the thoracic kyphosis angle, in within-group comparisons (P<.05). The CG did not exhibit significant changes in any of these variables (P<.05). Significant differences between the RCG and CG were observed in trunk ROM and thoracic kyphosis angle (P<.05). Conclusion: The rolling corrector was effective in improving trunk ROM and reducing the thoracic kyphosis angle in individuals with thoracic kyphosis. These findings suggest that the rolling corrector may be a beneficial intervention for managing thoracic kyphosis.

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.

Hexagonal bolt, nut, fittings, and high-pressure valves with special alloy play an important role in many industrial products, for instance, such as semiconductor facilities, hydrogen stations and fuel cell electric vehicles. The purpose of this study is to predict the reaction force of roller in drawing system. Numerical analysis was conducted to obtain data for designing the turning wheel, which is key parts in drawing system, using the reaction force of roller. As the results, the reaction force of X axis direction was about 9~20 times larger than that of Z axis direction and the reaction force of Y axis direction was negligible. The maximum reaction force of roller was the case of 4 stage and the numerical results in this study could be helped for designing the mechanical parts of variable hexagonal rolling die.

Background: The application of exercise therapy and manual therapy to the thoracic spine is a widely used method of treating neck pain. Nevertheless, studies on the application of foam rollers and vibrating foam rollers to patients with neck pain are lacking. Objectives: To investigated the immediate effects of thoracic spine foam rolling and vibration foam rolling on pain and range of motion (ROM) in patients with chronic neck pain. Design: Randomized crossover trials. Methods: 24 patients with chronic neck pain participated in the study. The study subjects measured pain and ROM. Subjects were divided into vibration foam roller group, foam roller group, and control group. Results: Pain was not significantly different between and within groups (P<.05). There was a significant difference in flexion, extension, left rotation, and right rotation ROM in the vibration foam roller group after intervention (P<.05). There was a significant difference in flexion and extension ROM in the foam roller group after intervention (P<.05). There was a significantly greater increased extension ROM in vibration foam roller and foam roller groups compared with the control group (P<.0167). Conclusion: Thoracic spine foam rolling and vibration foam rolling improve ROM when treating patients with chronic neck pain. Therefore, it is recommended to use it in combination with other treatments

This article suggests the machine learning model, i.e., classifier, for predicting the production quality of free-machining 303-series stainless steel(STS303) small rolling wire rods according to the operating condition of the manufacturing process. For the development of the classifier, manufacturing data for 37 operating variables were collected from the manufacturing execution system(MES) of Company S, and the 12 types of derived variables were generated based on literature review and interviews with field experts. This research was performed with data preprocessing, exploratory data analysis, feature selection, machine learning modeling, and the evaluation of alternative models. In the preprocessing stage, missing values and outliers are removed, and oversampling using SMOTE(Synthetic oversampling technique) to resolve data imbalance. Features are selected by variable importance of LASSO(Least absolute shrinkage and selection operator) regression, extreme gradient boosting(XGBoost), and random forest models. Finally, logistic regression, support vector machine(SVM), random forest, and XGBoost are developed as a classifier to predict the adequate or defective products with new operating conditions. The optimal hyper-parameters for each model are investigated by the grid search and random search methods based on k-fold cross-validation. As a result of the experiment, XGBoost showed relatively high predictive performance compared to other models with an accuracy of 0.9929, specificity of 0.9372, F1-score of 0.9963, and logarithmic loss of 0.0209. The classifier developed in this study is expected to improve productivity by enabling effective management of the manufacturing process for the STS303 small rolling wire rods.

Background: Although it has been reported that both self-myofascial release (SMR) with foam rolling (FR) and active static hamstring stretching (e.g., jackknife stretching) are effective in improving hamstring flexibility, no study has compared the effects of these exercises. Objectives: To compare the effects of SMR with FR and jack-knife stretching on hamstring flexibility. Design: A Randomized controlled trial. Methods: Subjects with hamstring tightness were divided into the SMR with the FR group (n=12) and the jack-knife stretching group (n=12). Subjects groups performed SMR with FR or jack-knife stretching according to group assignment. To identify changes in hamstring flexibility, the finger-to-floor distance (FFD) test, active knee extension (AKE) test, and passive straight leg raising (PSLR) test were performed at pre- and post-exercise. Results: Significant increases occurred in knee extension angle during the AKE test and hip flexion angle during the PSLR test after exercise in both groups (P<.001). Additionally, FFD and anterior pelvic tilt during the FFD test significantly increased (P<.001); however, we observed no significant interaction and main effects for the groups (P>.05). Conclusion: Both SMR with FR and jack-knife stretching are effective in improving hamstring flexibility in subjects with hamstring tightness.

This study suggests a machine learning model for predicting the production quality of free-machining 303-series stainless steel small rolling wire rods according to the manufacturing process's operation condition. The operation condition involves 37 features such as sulfur, manganese, carbon content, rolling time, and rolling temperature. The study procedure includes data preprocessing (integration and refinement), exploratory data analysis, feature selection, machine learning modeling. In the preprocessing stage, missing values and outlier are removed, and variables for the interaction between processes and quality influencing factors identified in existing studies are added. Features are selected by variable importance index of lasso regression, extreme gradient boosting (XGBoost), and random forest models. Finally, logistic regression, support vector machine, random forest, and XGBoost is developed as a classifier to predict good or defective products with new operating condition. The hyper-parameters for each model are optimized using k-fold cross validation. As a result of the experiment, XGBoost showed relatively high predictive performance compared to other models with accuracy of 0.9929, specificity of 0.9372, F1-score of 0.9963 and logarithmic loss of 0.0209. In this study, the quality prediction model is expected to be able to efficiently perform quality management by predicting the production quality of small rolling wire rods in advance.

Background: Vibration stimulation has emerged as a treatment tool to help reduce spasticity during physical therapy. Spasticity includes problems of reduced range of motion (ROM) and stiffness. However, the benefits of vibration rolling (VR) on interventions for stroke patients are unclear. Objectives: This study aimed to investigate the effect of VR intervention on the ankle ROM and ankle stiffness in stroke patients. Design: A randomized crossover study. Methods: Seven stroke patients completed two test sessions (one VR and one non-VR [NVR]) in a randomized order, with 48 hours of rest between each session. Participants completed intervention and its measurements on the same day. The measurements included ankle dorsiflexion and plantarflexion ROM and stiffness of ankle muscles, including the tibialis anterior, medial, and lateral gastrocnemius muscle. Results: After VR, ankle dorsiflexion ROM, lateral gastrocnemius stiffness, and medial gastrocnemius stiffness improved significantly (all P<.05). After NVR, only the lateral gastrocnemius stiffness improved significantly (P<.05). Furthermore, in the cases of changed values for ankle dorsiflexion ROM and lateral gastrocnemius stiffness were compared within groups, VR showed a more significant difference than NVR (P<.05) Conclusion: VR improved ankle ROM and muscle stiffness. Therefore, we suggest that practitioners need to consider VR as an intervention to improve dorsiflexion ROM and gastrocnemius stiffness in stroke patients.

Background: Many trials have been conducted the methods and types of intervention of form rollers, but no research has been done yet that mixes the methods and types of intervention. Objectives: To analyze the effects of myofascial release on the improvement of range of motion (ROM), flexibility, pain pressure threshold, and balance. Design: Randomized controlled trial. Methods: All subjects measured ROM, flexibility, pressure pain threshold, and dynamic balance by pre-test. After pre-test, subjects were randomized that static-vibration foam rolling group (n=12), dynamic-vibration foam rolling group (n=12), general foam rolling group (n=12). For the intervention, 3 sets of 90 seconds were applied to each group, and rest time was set to 60 seconds between sets. In the post-test and follow-up test after 10 minutes, all three groups were measured the ROM, flexibility, pressure pain threshold, and dynamic balance. Results: The results of comparing ROM, flexibility, pressure pain thresholds, dynamic balance ability appeared higher significant difference in the prepost- 10 minutes follow up test in comparison between time in the intragroup (P<.001). As a result of comparing the change of pre-post-10 minutes follow up, static vibration foam rolling showed higher significant difference compared to control groups (P<.001). Conclusion: Through this study, when foam rolling is applied within the same intervention time, static foam rolling can be expected to have a better effect than the existing dynamic foam rolling as well as vibration foam roller can expect better effect than general foam rolling.

A powder-in-sheath rolling method is applied to the fabrication of a carbon nano tube (CNT) reinforced copper composite. A copper tube with outer diameter of 30 mm and wall thickness of 2 mm is used as sheath material. A mixture of pure copper powder and CNTs with a volume content of 3 % is filled in a tube by tap filling and then processed to an 93.3 % reduction using multi-pass rolling after heating for 0.5 h at 400 oC. The specimen is then sintered for 1h at 500 oC. The relative density of the 3 vol%CNT/Cu composite fabricated using powder in sheath rolling is 98 %, while that of the Cu powder compact is 99 %. The microstructure is somewhat heterogeneous in width direction in the composite, but is relatively homogeneous in the Cu powder compact. The hardness distribution is also ununiform in the width direction for the composite. The average hardness of the composites is higher by 8Hv than that of Cu powder compact. The tensile strength of the composite is 280 MPa, which is 20 MPa higher than that of the Cu powder compact. It is concluded that the powder in sheath rolling method is an effective process for fabrication of sound CNT reinforced Cu matrix composites.