영구자석 선형 전동기인 VCM(Voice coil motor)은 직접 구동 방식의 액츄에이터로 기어나 변속장치가 필요 없어 높은 정밀도 를 가지고 구조적인 특성상 기계적 마찰이 적어 소음이 발생하지 않는 장점을 가지고 있다. 아울러 회전운동을 직선 운동으로 변환하기 위한 별도의 장치가 필요하지 않고, 구동부가 가벼워 응답속도가 빠른 특징이 있다. 본 연구에서는 이러한 VCM을 다양한 산업 분야에 적용하기 위한 기초연구로 VCM의 속도제어를 위해 PSO(Pariticle swarm optimization) 기법을 적용하여 제어기의 유용성 평가를 위한 수 치 시뮬레이션을 수행하였다. 제어계는 전류와 속도 제어를 위한 이중 루프로 구성하였고, 각각의 제어 루프에는 PI 제어기를 적용하여 속도 목표치에 추종하는 출력값을 얻기 위한 제어기를 설계하였다. 제어기 파라미터 추정에는 PSO기법을 적용하였고, 제어기의 유용성 을 검증하기 위해 주파수 영역에서의 모델매칭기법을 적용한 제어 기법과의 제어 결과를 비교하였다. 두 가지 제어 기법은 MATLAB을 이용하여 수치 시뮬레이션을 수행했고, 제어 결과는 IAEU(Integral of absolute error units) 평가 지수를 이용하여 비교하였다. 수치 시뮬레 이션 결과 제안한 제어 기법의 유용성을 확인할 수 있었다.

This study compares pure Ni coatings deposited on type 316H stainless steel using high-velocity oxy-fuel (HVOF) and directed energy deposition (DED) processes. Microstructural analysis showed that DED produced more uniform claddings with fewer pores, while HVOF resulted in incomplete melting and cracks. Elemental diffusion of Cr and Fe from the substrate into the cladding was evident in DED samples, especially at higher laser power, but minimal in HVOF due to low heat input. Vickers hardness testing revealed that DED claddings had higher hardness near the interface, which was attributed to solid solution strengthening and reduced porosity. Although HVOF better suppressed diffusion, it exhibited inferior mechanical properties due to internal defects. Overall, the DED process demonstrated superior coating quality and mechanical performance, suggesting its suitability for corrosion-resistant applications requiring both structural integrity and thermal stability, such as molten salt reactors.

Background: Stroke patients commonly suffer from balance impairments that limit functional activities, such as walking difficulties. Robot-assisted gait training is gaining attention as an effective rehabilitation strategy for balance and gait in stroke rehabilitation. Objects: The purpose of this study was to investigate the effects of progressive velocity robot-assisted gait training (PRG) on balance and gait abilities in stroke patients. Methods: All subjects were randomly divided into three groups: PRG (n = 12); comfortable speed robot-assisted gait training (CRG) (n = 12); and control group (n = 16). Subjects in PRG and CRG underwent robot-assisted gait training for 30 minutes, three times a week for six weeks. And the control group performed overground gait training using a treadmill at the same frequency and for the same amount of time as the experimental group. All Subjects were assessed for muscle strength, balance, gait and motor function pre- and post-intervention. Results: The study results showed that all subjects showed significant differences in all measurements post-intervention (p < 0.05). Additionally, PRG was found to significantly improve in Medical Research Council (MRC) and Fugl-Meyer Assessment (FMA) compared to CRG, and CRG showed significant differences compared to the control group in MRC, Berg Balance Scale (BBS) and Timed Up and Go test (TUG) (p < 0.05). PRG exhibited significant differences in all areas in the between-group comparison with the control group (p < 0.05). Conclusion: These results suggest that PRG may be effective strategy to improve balance and gait ability for with stroke.

IIn the context of site response analysis, the use of shear wave velocity (  ) profiles that consider the seismological rock (  ≥ 3,000 m/s) depth is recommended. This study proposes regression analysis and machine learning-based models to predict deep   profiles for a specialized excavated rock site in South Korea. The regression model was developed by modifying mathematical expressions from a previous study and analyzing the correlation between   and model variables to predict deep   beyond 50 m. The machine learning models, designed using tree-based algorithms and a fully connected hierarchical structure, were developed to predict   from 51 m to 300 m at 1 m intervals. These models were validated by comparing them with measured deep   profiles and accurately estimating the trend of deep   variations. The proposed prediction models are expected to improve the accuracy of ground motion predictions for a specialized excavated rock site in Korea.

Strong ground motions at specific sites can cause severe damage to structures. Understanding the influence of site characteristics on the dynamic response of structures is crucial for evaluating their seismic performance and mitigating the potential damage caused by site effects. This study investigates the impact of the average shear wave velocity, as a site characteristic, on the seismic response of low-to-medium-rise reinforced concrete buildings. To explore them, one-dimensional soil column models were generated using shear wave velocity profile from California, and nonlinear site response analyses were performed using bedrock motions. Nonlinear dynamic structural analyses were conducted for reinforced concrete moment-resisting frame models based on the regional information. The effect of shear wave velocity on the structural response and surface ground motions was examined. The results showed that strong ground motions tend to exhibit higher damping on softer soils, reducing their intensity, while on stiffer soils, the ground motion intensity tends to amplify. Consequently, the structural response tended to increase on stiffer soils compared to softer soils.

Spasticity, a frequently encountered symptom in patients with upper motor neuron (UMN) syndrome, poses a significant challenge, negatively affecting function, activity, and social engagement. Despite the acknowledged benefits of exercise in the rehabilitation of UMN syndrome, therapy sessions often trigger an unwelcome increase in muscle stretch reflex activity, resulting in considerable muscle tension despite improvements in function and activity levels. Despite the recognized benefits of exercise in UMN syndrome rehabilitation, there's often an undesirable rise in muscle stretch reflex activity during therapy, leading to considerable muscle tension despite improvements in function and activity levels. The challenge lies in identifying effective strategies that enhance function, activity, and participation while curbing excessive muscle tension caused by heightened stretch reflex activity. Spasticity significantly disrupts the daily lives of affected individuals and presents substantial challenges for caregivers. However, existing methods for measuring and evaluating spasticity have their limitations and are susceptible to errors. This article describes both established and innovative methods utilized for quantitative spasticity assessment and management of spasticity, with the overarching goal of improving the definition of spasticity and identifying assessment techniques suitable for clinical application.

일반적으로 속도 펄스를 가진 지반운동이 속도 펄스가 없는 지반운동에 비하여 구조물에 보다 큰 손상을 줄 수 있다고 알려져 있다. 지진가속도기록으로부터 속도 펄스의 유무의 판정과 이를 정량화하는 연구가 현재 많이 진행되어 오고 있다. 기존 지진기록들을 단 층으로 떨어진 거리를 기준으로 원거리 지진과 근거리 지진으로 구분하였다. 또한, 근거리 지진은 속도 펄스의 유무를 정량화하여 펄 스를 가진 지진과 펄스를 가지지 않은 지진으로 구분하였다. 최종적으로 각 지진그룹별로 40개의 원거리지진, 40개의 속도 펄스를 가 진 근거리 지진과 40개의 속도 펄스를 가지지 않은 근거리 지진을 선정하였으며, 총 120개 지진가속도 기록을 지진취약도 평가를 위 한 지진해석에 사용하였다. 세 그룹의 지진을 이용하여 납-고무받침과 탄성받침을 가진 두 종류의 예제교량에 대한 지진응답을 평가 하여 확률론적 지진요구도 모델을 작성하였다. 확률론적 지진요구도 모델을 이용하여 지진취약도 해석을 수행하여 속도 펄스의 유무 에 따른 지진취약도 영향을 분석하였다. 지진파의 속도 펄스 유무에 따른 지진취약도 곡선의 비교 결과로부터, 속도 펄스를 가진 지진 의 지진취약도가 속도 펄스가 없는 지진의 지진취약도가 약 3배~5배 정도 정도 크게 나타난다. 이는 속도 펄스를 가진 지진의 경우가 그렇지 않은 지진의 경우에 비하여 교량의 손상 피해가 크다는 것을 의미한다.