Exposure to extremely low frequency (ELF) electromagnetic fields (EMFs) from power transmission and distribution facilities has gained increasing attention with rising power demand driven by artificial intelligence (AI). This study proposes a practical EMF measurement method suitable for domestic power facility environments in Korea. Field measurements were conducted on 345 kV and 154 kV overhead transmission lines and 22.9 kV distribution lines based on ICNIRP guidelines and international standards IEC 62110 and IEEE Std 644. Measurements were performed at the maximum sag point at different lateral distances and representative heights. The results show that EMF levels were highest directly beneath the conductors and decreased rapidly with distance, while all measured values remained well below domestic exposure limits.

본 논문에서는 경사기능재료(Functionally Graded Material, FGM) 개념과 위상최적설계 방법을 통해 3차원 경사기능복합재 구조 (Functionally Graded Composite Structure, FGCS)의 설계 방법을 제안한다. 다중 스케일 복합재 구조 설계 시 이방성 재료 물성치의 계 산은 RVE 기반 ML 모듈과 단위 사원수를 활용한 회전 행렬 계산을 통해 수행된다. 또한, 본 연구에서는 다양한 물리적 환경을 설계 에 반영하기 위해 구조물의 강성과 함께 고유진동수를 목적함수로 설정한 다중 목적함수 최적설계를 수행하여 구조물의 최적화 형 상과 성능을 분석한다.

본 연구는 제17차 청소년건강행태조사(2021년) 자료를 활용하여 중학생 27,177명과 고등학생 22,657명을 대상으로 건강행태 요인이 고카페인 음료 섭취 빈도에 미치는 영향을 비교 분석하였다. 카이제곱 검정과 위계적 다중 회귀분석 결과, 고카페인 음료 섭취율은 고등학생(54.8%)이 중학생(42.1%) 보다 높았고, 주 7회 이상 섭취율도 고등학생(7.6%)이 중학생(3.7%)의 약 2배였다. 중학생의 유의한 영향요인은 성적, 경제상태, 음주, 흡연, 신체활동, 스마트폰 사용시간, 피로회복정도, 스트레스, 체형인식이었고(Adj. R²=.060), 고등학생은 경제상태, 음주, 흡연, 신체활동, 앉아서 보낸 시간, 피로회복정 도, 스트레스, 체형인식이었다(Adj. R²=.038). 중학생에서는 성적과 스마트 폰 사용시간이, 고등학생에서는 앉아서 보낸 시간이 유의하여 학교급별 차 이가 확인되었다. 이를 바탕으로 청소년의 고카페인 음료 섭취 예방을 위한 학교급별 맞춤형 보건교육 프로그램 개발과 건강위험행동 통합 예방교육의 필요성을 제언하였다.

This study quantitatively analyzed the target strength (TS) characteristics of the dotted gizzard shad (Konosirus punctatus) across various fork lengths (FL) and frequency conditions. In July 2023, TS measurements were conducted on six size groups (FL: 14.4–23.5 cm) under free-swimming conditions in a seawater acoustic tank at the Fisheries Resources Research Center in Tongyeong, Korea. A scientific echosounder (EK80, SIMRAD) was used to collect TS data at three frequencies: 38, 70, and 120 kHz. The results showed that TS values increased with fork length, and the 120 kHz frequency exhibited the widest distribution range and distinct bi- or multi-modal patterns. The TS–FL relationships for each frequency were as follows: TS38 kHz = 20·log(FL) ‒ 68.41, TS70 kHz = 20·log(FL) ‒ 70.76, and TS120 kHz = 20·log(FL) ‒ 70.90. Unlike traditional tethered measurement methods, this study obtained TS data under free-swimming conditions, providing values more representative of real-world acoustic survey environments. The findings are expected to serve as foundational data for improving the accuracy of monitoring the distribution and biomass estimation of K. punctatus using hydroacoustic methods.

A compact vibratory bowl feeder system is proposed to transport lightweight annular film components. Vibration analysis was conducted to calculate its natural frequencies, and the motion characteristics of the bowl and transported parts were analyzed under resonance excitation at varying supply voltage levels. The natural frequencies of the proposed system were found to be 157Hz, 249Hz, and 505Hz. At these resonance frequencies, significant rotational vibrations occurred, while vertical vibrations were relatively small. Especially at 505Hz, bending of the leaf spring caused large rotational motion of the bowl. The part feeding speed increased linearly with the applied voltage, reaching 4mm/sec at 100V and 18mm/sec at 200V. At 157Hz and 249Hz excitation frequencies, large rotational and vertical vibrations were observed, respectively. Under rotational vibration, the parts moved forward via jumping motion when the bowl's velocity amplitude was relatively large, or via slipping when smaller. Minor backward slipping was also observed. Under vertical vibration, parts exhibited forward jumping motion without back-and-forth slipping.

이 논문은 소비자 설문조사를 통해 여름철 대표 과일인 수박과 참외의 소비자 구매 행태와 구매 빈도에 영향을 미치는 요인을 분석하여 수박·참외 산업의 지속 가능한 발전 방향을 탐구하고자 하였다. 소비자 구매 행태를 분석하고, 구매 빈도에 영향을 미치는 주요 요인을 규명하기 위해 순위형 로짓 분석을 실시하였다. 연구 결과에 따르면 수박은 맛, 외형이 가격보다 더 중요한 요소로 나타나, 고당도 수박 생산, 품종 개선 및 유통 방식 개선의 필요성이 제기되었다. 참외는 맛, 신선도, 외형이 구매시 중요한 요소로 분석되었으며, 고령층 소비자에 비해 젊은층 선호도가 상대적으로 낮아 참외 시장 확대를 위해서는 다양한 소비 계층이 관심을 가질 수 있는 차별화된 판매 전략이 필요하다는 점을 시사하였다.

본 연구는 신속보기 기반 안구운동 과제에서 시선추적 장비의 샘플링 주파수가 시선의 이동 및 고정 지표와 반응 분류 성능에 미치는 영향을 규명하고자 하였다. 고령 성인 30명을 대상으로 정방향과 역방향의 혼합형 신속보기 과 제를 수행하는 동안 기준 주파수인 300Hz로 수집된 시선 데이터를 30∼200Hz 범위로 다운샘플링하여 분석하였다. 조건별 안구운동 주요 지표 분석 결과, 샘플링 주파수가 감소함에 따라 잠복기는 27ms 이상 증가하였고, 이동크기는 2∼3deg, 최대속도는 90∼120deg/s 감소하였다. 시선고정 지속시간은 최대 397ms 증가하였으며, 위치 분산은 정방향에서 약 3배, 역방향에서 최대 10배 증가하였다. 반면, 시표적과의 위치 오차는 큰 변동 없이 유지되었다. 안구운동 반응 분류 성능 비교 결과, 샘플링 주파수 90Hz 이상에서는 정확도 .98, 정밀도 .99, F1 점수 .99, 일치도 계수 .95 이상을 유지하였으나, 60Hz 이하에서는 F1 점수가 .91 이하, 일치도 계수는 .63 이하로 급격히 저하되었다. 본 연구 결과는 신속보기 안구운동 연구에서 시선추적 장비의 샘플링 주파수가 분석 정확도와 신뢰도에 실질적인 영향을 미 친다는 점을 시사하며, 300Hz 기준의 시선 데이터 분석 수준을 안정적으로 유지하기 위해서는 최소 90Hz 이상의 샘플링 주파수 확보가 필요함을 제안한다.

Five novel miniature bipolar radiofrequency (RF) electrode tips with distinct tip geometries (spherical, flat, square, and 45° angled) were developed to enable high-precision tissue ablation. Performance was evaluated on saline-soaked tissue, ex vivo bovine liver, and porcine muscle under consistent RF power settings. All designs produced highly localized lesions only a few millimeters across, confirming precise ablation with minimal damage to surrounding tissue. Tip geometry influenced ablation efficiency: a 45° angled tip created ~5 mm lesions at lower power (highest efficiency), whereas an ultra-fine 1.0 mm tip produced ~1 mm lesions but required higher power. These results indicate that the new bipolar RF electrodes achieve precise, localized tissue ablation with minimal surrounding tissue damage and show promise for precise lesion removal in minimally invasive surgery.

Background: Chronic nonspecific low back pain (CNLBP) is a common musculoskeletal condition among middle-aged adults, often causing physical limitations and reduced quality of life. Transcutaneous electrical nerve stimulation (TENS) is a widely used non-pharmacological method for pain relief and muscle modulation. Objectives: To compare the effects of two high-frequency, high-intensity TENS protocols on pain, muscle tone, and stiffness in individuals with CNLBP. Design: Single-blinded, randomized controlled trial. Methods: Twenty-eight individuals with CNLBP were randomly assigned to an experimental group (EG) or control group (CG). Both received 60 Hz, highintensity TENS twice weekly for four weeks. Pain equivalent current (PEC), visual analogue scale (VAS), pain degree (PD), muscle tone (Hz), and stiffness (N/m) were measured pre- and post-intervention by a blinded assessor. Results: The EG showed significant improvements in all outcomes (P<.05), while the CG showed significant change only in VAS scores. Between-group analysis showed greater reductions in pain and muscle-related variables in the EG. Conclusion: The EG protocol, with individualized intensity adjustments and targeted stimulation sites, was more effective than the CG protocol in improving pain, muscle tone, and stiffness in adults with CNLBP.

Magnetic nanoparticles in nanofluid have a unique ability in that they can be influenced by an external magnetic field, making them a promising heat-exchanging fluid to meet the demands of highly efficient thermal systems. The parametric impact of the magnetic field (static and time-varying) on the heat exchanging rate of Fe3O4 nanoparticles and water-based ferrofluid was investigated in this study. The experimental setup for generating a variable frequency magnetic field and analyzing the thermal behavior of ferrofluid is presented. Temperature data was obtained as heat is transferred from heated water to the ferrofluid used as a coolant. An enhancement of the heat transfer of the magnetic nanofluid was observed when varying the magnetic field frequency, through experimental analysis. The concentration of Fe3O4 nanoparticles in the ferrofluid was varied (0.5 wt%, 1 wt%)to study the impact of nanoparticle loading on heat transfer. An alternative approach for controlling the heat exchange rate in thermal systems is proposed, utilizing the magnetic tunability of the ferrofluid.

Background: Ankle flexibility is important for maintaining proper biomechanical function. Static stretching is used to improve flexibility with minimal risk; however, its effects are often temporary. Transfer of energy capacitive and resistive (TECAR) therapy has the potential to enhance muscle flexibility and circulation through deep heat applications. However, comparative studies evaluating the effectiveness of TECAR therapy and static stretching are lacking. Objects: This study aimed to compare the effects of static stretching therapy (ST) and combined TECAR and static stretching therapy (T-ST) in subjects with gastrocnemius muscle (GCM) tightness. Methods: Twenty-seven participants with bilateral GCM tightness were enrolled. To administer the ST and T-ST, which were each applied to both legs, the participants stood for 15 minutes on a wedge with a 0°–15° incline, with both feet on the wedge during ST and with TECAR therapy in resistive energy transfer mode applied to only one side of the GCM during T-ST. Muscle stiffness (MyotonPRO), dorsiflexion range of motion (DF-ROM), peak torque, and pennation angle (PA) of the GCM were measured before and after the intervention. Normality was confirmed using the Shapiro–Wilk test. Differences between the ST and T-ST leg conditions and between pre- and post-intervention changes in the legs were analyzed using paired t-tests. Results: There were no significant differences in any of the measured variables between the legs before the intervention. ST and T-ST legs showed significant improvements in all measured variables after the intervention (p < 0.05). T-ST legs demonstrated a significantly greater increase in DF and a greater decrease in PA than ST legs (p < 0.05). Conclusion: T-ST outperformed ST in reducing PA and increasing DF-ROM by promoting deep tissue relaxation and stimulating metabolic activity. This may lead to reduced pain and greater flexibility compared to ST. Maintaining an optimal PA ensures efficient force transmission during exercise, as evidenced by the observed increase in peak torque.

Conventional bipolar electrodes (typically with round or flat tips) deliver radiofrequency energy in a broad, continuous manner. Their larger tip size and simple shape cause the applied energy to disperse over a wide area, making precise lesion control difficult and often leading to collateral tissue damage. As a result of these design limitations, traditional electrodes exhibit lower energy efficiency and tend to create lesions that unintentionally extend beyond the target area, with excessive thermal spread to surrounding tissues. In contrast, the five newly developed bipolar electrode designs concentrate energy delivery more effectively and provide improved control over lesion size and shape. These novel electrodes demonstrated higher energy efficiency, produced well-confined lesions, and minimized thermal injury to adjacent tissues, thereby overcoming the major drawbacks of conventional designs.