본 연구는 막 손상을 검지하기 위한 압력손실시험(pressure decay test, PDT)에서 분리막의 초기 상태(virgin state) 의 물성을 고려하여 산정하는 초기설정압력(Ptest, Pmax)에 대한 오차범위를 확인하고자 하였다. 여과 공정을 수행하면서 불가 피하게 발생하는 막오염으로 인하여 변화하는 접촉각을 연속적으로 측정하여 막간차압(transmembrane pressure, TMP)과의 상관관계를 확인한 결과, 막간차압이 0~200 kPa 증가할 때 막 표면에서의 접촉각이 83~41° 범위로 선형 감소하는 결과로 측 정되었다. 물리세척에 의한 회복율이 높은 가역적인 오염구간보다 비가역적인 막오염 구간에서 접촉각의 변화폭이 커지는 것 을 확인할 수 있었다. 이를 통하여 종래 고정된 초기설정압력에서 막의 물성과 막오염도에 따라 적용의 필요성을 확인할 수 있었으며, 막 손상 면적 대비 일정한 압력손실율(pressure decay rate, PDR)을 얻기 위해서 압력손실시험을 수행할 때 막오염의 간접지표인 TMP를 고려하여 동적으로 초기설정압력값을 산정 및 적용해야만 절대적인 수질 보증을 유지할 수 있을 것이다.

This study quantitatively evaluates the effects of embankment height and input excitation frequency on crest settlement—a key damage indicator—for railway embankments founded on liquefiable ground. Dynamic numerical analyses were conducted using FLAC2D, based on the cross-section adopted in a previous 1-g shaking table test. The parametric study considered four embankment heights (0, 2, 4, and 6 m) and three input frequencies (0.8, 2.5, and 5.0 Hz). To simulate liquefaction in the foundation soil, the PM4Sand constitutive model was employed within an effective-stress framework. Model validity was first examined by comparing computed time histories of excess pore-water pressure, acceleration, and settlement with experimental results, and by confirming qualitative agreement with observed settlement trends across different embankment heights. The results show that crest settlement does not increase monotonically with embankment height; instead, it reaches a maximum and then decreases beyond a critical range. The largest settlement occurs when the embankment height is approximately 15~25% of the liquefiable layer thickness. This behavior reflects the competition between increased overburden pressure, which enhances liquefaction resistance beneath the embankment, and amplified lateral spreading, which increases permanent deformation. Although excitation frequency influences settlement, its effect is smaller than that of embankment height.

Background: Firefighter helmets are essential protective gear but add significant weight (average 22 kg for full gear), potentially causing neck muscle fatigue and musculoskeletal disorders. While previous studies have focused on static loads or simple movements, few have analyzed the effect of helmet wear on muscle activity during dynamic, multi-planar movements at different pace. Objects: This study aims to evaluate the effects of wearing a standard Korean firefighter helmet on cervical muscle activity and kinematics during three dynamic head movements (flexion–extension, lateral flexion, and rotation) performed at two different pace. Methods: Twenty-four healthy adults participated in this study. Subjects performed three cervical movements at 45 and 75 rpm guided by a metronome, both with and without a helmet. Kinematics were measured using electromagnetic sensors, and electromyography was recorded from the sternocleidomastoid (SCM), upper trapezius, splenius capitis, and cervical erector spinae (CES). Data were analyzed using repeated measures ANOVA. Results: Helmet wear significantly increased SCM activation during the deceleration phase and CES activation during the acceleration phase (p < 0.05) of neck extension. Higher movement pace (75 bpm) significantly increased peak angular velocity and muscle activation across most tasks compared to the slower pace (45 bpm). However, the interaction between helmet wear and pace was not statistically significant. Conclusion: Wearing a firefighter helmet increases the demand on specific cervical muscles, particularly the SCM and CES, to control head momentum and stability. Movement pace appears to be a more dominant factor in increasing muscle load than helmet weight alone in healthy subjects. These findings contribute to the ergonomic design of future firefighter helmets.

This study proposes a dynamic evaluation framework for diagnosing signal control adequacy using high-resolution Automated Traffic Signal Performance Measures (ATSPM) data. Traditional signal performance assessments have primarily relied on aggregated metrics, such as average delay and volume-to-capacity ratio, which are effective for evaluating overall operational efficiency but insufficient for capturing cycle-level control limitations and temporal variability. Although split failure-based measures, including the Split Failure Ratio (SFR), provide more direct insights into green time adequacy, most existing applications focus on the failure frequency within a fixed analysis period. To address this limitation, this study introduces a Dynamic Operational Strain (DOS) index that extends the split failure into a time-evolving state variable incorporating accumulation and recovery mechanisms. By modeling the recursive evolution of the operational strain, the proposed framework captures how often failures occur and how they persist or dissipate over time. Phase-level DOS measures are subsequently aggregated at the intersection level to derive a priority score reflecting structural control inadequacy. The framework is further applied to classify intersections using DOS–SFR quadrant analysis, enabling the identification of distinct operational patterns, such as persistent oversaturation, localized phase imbalance, intermittent strain accumulation, and stable control conditions. The results demonstrate that intersections with similar SFR values may exhibit substantially different temporal strain structures, highlighting the importance of a dynamic state-based evaluation. The proposed approach provides a diagnostic foundation for data-driven signal re-timing and future adaptive control strategies by shifting the signal performance assessment from static frequency-based measures to dynamic structural adequacy analysis.

기존 비디오 게임은 사전 정의된 스크립트와 정적인 캐릭터 관계 모델로 인해 상호작용 과 몰입감에 한계가 있다. 최근 대규모 언어 모델(LLM)이 대안으로 떠올랐으나, 생성된 서 사와 게임 내부 데이터가 단절되는 문제가 여전히 존재한다. 이에 본 연구는 Unity 엔진, LLM, 게임 서버 플랫폼을 통합하여 캐릭터 데이터가 서사를 생성하고, 그 결과가 다시 데 이터베이스에 반영되는 '순환형 동적 스토리텔링 시스템'을 제안한다. 실험 결과, 캐릭터 성 향에 따른 차별화된 서사 생성 및 관계도의 실시간 DB 동기화를 확인하였다. 본 시스템은 기존 스크립트의 경직성을 극복하고 무한히 확장 가능한 개인화된 게임 경험을 제공한다.

This study examines the dynamic characteristics of an articulated aerial work platform. The platform performs articulated joint motions and telescopic boom extension to access both upper-side and under-structure work areas. The boom system includes two articulated joints with slewing rotation, and the tip section is a multi-stage telescopic boom. Component-level dynamics of three telescopic boom components made of Strenx 960 were compared with the system-level dynamics of the fully assembled vehicle. Natural frequencies and mode shapes up to the second mode were obtained through experimental modal analysis based on frequency response functions (FRFs). For the assembled vehicle, tri-axial acceleration responses were transformed into the frequency domain using FFT, and dominant natural frequencies were identified from the spectra. The results show a clear separation between the two levels. The component-level dynamics appeared in the tens-of-hertz range. In contrast, the dominant system-level natural frequencies were observed in the low-frequency range (near 1 Hz). These findings indicate that the assembled system exhibits dominant dynamics distinct from those of individual boom components. They also highlight the need for system-level considerations when interpreting dynamic performance under practical operating conditions.

이 연구는 충격쇄파 하중에 대한 직립식 방파제의 동적 거동을 정밀히 분석하기 위해 유한요소 기반의 2차원 해석 모델을 구축하 였다. 기존의 단순화된 해석 방법이 지닌 한계를 극복하고자, 유체 요소, 비선형 지반 모델, 접촉 비선형성, 에너지흡수경계요소를 포 함한 정밀한 2차원 수치해석 모델을 구축하였다. 또한, 이론적 파압 공식을 기반으로 충격쇄파 하중의 시간이력을 모델링하여 방파 제의 활동량을 평가하였다. 해석 결과, 비선형 지반 모델은 탄성 지반 대비 더 큰 활동량을 유발하는 것으로 나타났으며, PML (Perfectly Matched Layer)은 고정 경계 조건과 비교했을 때 해석 안정성과 정확성을 크게 향상시키는 것으로 나타났다. 이 연구는 직 립식 방파제 설계 및 안전성 평가를 위한 정밀 동적 해석 기술 개발에 기여하며, 극한 조건에서도 방파제 성능을 예측할 수 있는 기반 을 제공할 것으로 기대된다.

This study investigated the hot deformation behavior and dynamic recrystallization (DRX) characteristics of a coarse-grained Fe-24Mn steel slab using plane strain compression (PSC) tests. Tests were conducted at 900-1,000 °C and strain rates of 0.5-10 s-1. Constitutive equations based on the Zener-Hollomon parameter accurately predicted flow stress ( ). A processing map based on the Dynamic Materials Model (DMM) predicted flow instability at high strain rates (10 s-1) due to a negative strain rate sensitivity exponent. However, electron backscatter diffraction (EBSD) analysis revealed that these regions actually exhibited a fully recrystallized microstructure with low Kernel Average Misorientation (KAM) values, contradicting the DMM prediction. This discrepancy is attributed to adiabatic heating during high-speed deformation, which induces thermal softening and provides the driving force for DRX. Consequently, the region with negative power dissipation efficiency at high strain rates should be reinterpreted not as a failure zone, but as a window for efficient microstructural refinement. The study identifies 950 °C and 10 s-1 as the optimal processing conditions for grain refinement of the as-cast slab.

In this study, vision-based monitoring combined with accelerometer-based measurements was conducted in a large-scale concert hall under crowd loads. First, the dynamic characteristics of the structure were identified from ambient vibrations measured in the absence of crowds. Then, an FE model was established that exhibits dynamic attributes similar to those of the structure. Subsequently, camera footage of crowd motion at a K-pop concert was used to estimate crowd loads, which were then applied to the FE model to assess responses. The acceleration response obtained from the analysis was compared with the measured acceleration and the acceptance criteria of design guidelines, such as AISC DG11. The acceleration predicted by the vision-based estimation was approximately 67% of the estimated value based on peak values and 62% of the measured value based on root mean square (RMS) values. Overall, the vision-based estimation showed a peak response around 10 Hz, while the measurement showed a gradual increase in the frequency range above 10 Hz. This is likely because low-frequency components were underrepresented in the vision-based estimation, resulting in relatively underestimated amplitudes and lower responses in the high-frequency range.

목적: 본 연구는 역동적 신체 활동 상황에서 HMD 기반 가상현실 기기 내부의 온·습도 및 열지수를 실시간 측정하 고, 이러한 환경 변화가 안구건조증과 시각적 불편감에 미치는 영향을 규명하는 데 목적이 있다. 이를 통해 활동형 VR 사용 시 안전성 확보와 열·습도 관리 기반의 최적화된 VR 환경 설계의 근거를 제시하고자 한다. 방법 : 체육계열 대학생 28명을 대상으로 수행되었으며, Oculus Quest2를 이용한 역동적 VR 복싱 콘텐츠 수 행 중 HMD 내부 온도·습도 및 열파지수를 Arduino–DHT11 기반 센서로 2.5초 간격으로 실시간 측정하였다. 참 가자는 안정 상태, 운동 상태, 회복 상태 각 15분씩 총 45분간 실험에 참여하였고, 심박수는 스마트밴드를 통해 목 표 운동 강도 범위(30~50% HRR)로 유지되었다. 안구건조증 평가는 실험 전·후 비침습적 눈물막 파괴시간(NI BUT), Schirmer 검사, OSDI 설문을 통해 객관·주관 지표를 모두 수집하였다. 통계 분석은 대응표본 t-검정과 카이제곱 검정을 사용하였으며 유의수준은 p>0.050로 설정하였다. 결과 : 연구 대상자(평균 23.44세)는 VR 사용 전후 NI BUT과 Schirmer 검사에서 유의한 변화가 나타나지 않았으나(p>0.050), OSDI 점수는 실험 후 유의하게 증가하여 주관적 안구 불편감이 상승한 것으로 확인되었다 (p>0.050). HMD 내부 환경 분석에서는 운동 직후 초기 구간(15~18분)에서 온도, 습도, 열지수의 변화율이 가 장 크게 증가하여(p<0.001) 역동적 신체 활동이 VR 장치 내부 미세환경에 즉각적이고 급격한 변화를 유발함을 보여주었다. 이후 구간에서는 환경 변화 속도가 완만해지며 점차 안정화되는 경향을 보였다. 종합하면, 단기간의 고강도 VR 사용은 내부 열·습도 환경의 급격한 변동과 더불어 사용자의 주관적 시각적 피로 증가와 관련됨을 시사한다. 결론 : 고강도 신체 활동 시 VR HMD 내부의 온·습도 및 열파지수는 급격히 상승하여 열적 불편감과 시각적 피로를 더욱 유발한다. 운동 종료 후에는 빠르게 회복되는 가역적 특성을 보였음으로 이러한 결과는 활동형 VR 사 용 시 휴식·환기 전략의 필요성과 안전성 기반의 HMD 설계 및 사용자 관리 지침 마련의 중요성을 제시한다.

본 연구는 동적 조영증강 MRI 검사 시 조영제의 특성에 대한 기초자료를 제공하고, 이를 통해 신호강도가 최대인 농도 구간을 제시하고자 하였다. 연구방법은 MRI 조영제를 단계적으로 희석한 팬텀을 제작한 다음 영상을 획득하 여, 가돌리늄의 몰 농도에 따른 영상의 신호강도가 어떻게 변화하는지 비교평가 하였다. 연구결과 영상의 신호강도 는, 1000mmol(7.30±0.77) 부터 300mmol(7.39±0.49)까지 평형을 이룬 후 200mmol(26.21±0.33)까지 완만 히 증가하였고 100mmol(140.58±1.52) 부터 급격히 증가하여 20mmol(456.72±1.37)에서 최고치에 이른 다음, 0.0125mmol(17.28±0.79)까지 급격히 감소하였다. 결론적으로 동적 조영증강 MRI에서 가돌리늄 농도가 약 20 mmol 부근으로 희석되는 구간이 신호강도가 최대가 되는 상대적 기준점임을 확인하였으며, 이는 향후 환자 별 혈류 역학을 고려한 개별화된 영상획득 타이밍 최적화 연구의 기초자료로 활용될 수 있을 것이다.

In the present analysis study, an analysis model was developed using ANSYS Workbench to verify the dynamic characteristics of the cabinet and the vibration reduction effect of applying TMD. The analysis modeled a simplified equivalent structure of a nuclear power plant cabinet, and a method was explored to reduce the cabinet's resonant response by installing TMD on top of the cabinet. For the analysis, harmonic loads and SSE seismic waves were input to conduct modal analyses of the cabinet and TMD. The cabinet vibration reduction effect of TMD installation was investigated, as well as the time histories of displacement and acceleration. The analysis results showed that the primary mode of the cabinet had a MPMR of approximately 53.9%, significantly affecting the dynamic behavior of the cabinet compared to other modes. However, a MPMR of approximately 8.9% was also observed in higher-order modes. With TMD installed, the peak response was significantly reduced, the larger curve split into two smaller curves, and the response at the original natural frequency was reduced by up to approximately 60%. The cabinet's time response showed a decrease in displacement/acceleration vibration response as the damping ratio increased. This indicates a narrow bandwidth and peak suppression of the response envelope, and the maximum displacement and acceleration reduction effects were approximately 33.1% and 27%, respectively.

This study investigates the dynamic characteristics of telescopic booms for special-purpose vehicles fabricated with giga-grade ultra-high strength steel (UHSS) plates that have been increasingly adopted in industrial applications. In thin-walled structures such as telescopic booms, dynamic properties – particularly natural frequencies – are critical factors directly related to structural safety. Accordingly, the dynamic characteristics were experimentally measured and analyzed for identically designed booms fabricated using either imported giga-grade steel (Strenx 960) or domestic giga-grade steel (ATOS 980), both of which are widely available in the domestic market. The natural frequencies were identified based on frequency response functions (FRFs), and the corresponding mode shapes were obtained through experimental modal analysis. The results show that the nominal yield and tensile strengths provided by the manufacturers and the measured natural frequencies and mode shapes exhibit highly similar characteristics. These experimental findings confirm that the domestic UHSS exhibits a level of dynamic performance comparable to that of the imported steel of the same grade. Consequently, the results support the feasibility of applying domestic giga-grade UHSS to telescopic boom structures and highlight its potential contribution to material localization and enhanced design competitiveness in the domestic special-purpose vehicle industry.

To improve the seismic performance of a cabinet, a TMD was designed and its dynamic behavior was experimentally investigated as a basic study on vibration reduction. For TMD vibration test, a testing machine base, sliding base and jig were constructed. TMD and base were excited at the same frequency, and their natural frequencies showed a phase difference of approximately 90 degrees. The specifications of the experimental TMD were 20 kg mass, 10% damping ratio, and 7 L of oil. Seismic tests were conducted to investigate the dynamic behavior of the cabinet under earthquakes and the vibration characteristics of the cabinet with and without TMD. Vibration tests were conducted with the cabinet door fully closed, and the acceleration at the top of the cabinet was measured. The maximum acceleration was reduced by approximately 36% when TMD was installed compared to when it was not installed. The experimental results clearly demonstrated the effectiveness of TMD in reducing cabinet vibration.

The molecular dynamic simulation method is usually used to analyse microscopic fluid fields. To use this method in engineering problems with real scales of molecules needs more time and greater computer power than we have now. To overcome these limitations, the expansion method using dimensionless and similarity of physical quantities of molecules is studied and introduced for the engineering scale fluid dynamics.

본 논문에서는 상반회전 추진 프로펠러 이중축계의 회전 동특성을 정밀하게 분석하기 위한 수치해석 방법을 제안하였다. 제안된 해석 기법은 티모쉔코 보 이론 기반의 유한요소법을 이용하여 자이로스코픽 효과와 베어링 감쇠를 포함한 운동방정식을 정식화하였 다. 개발된 해석 코드는 기존 동축 회전체 모델과의 비교를 통해 검증되었으며, 고유진동수와 캠벨선도 결과가 매우 잘 일치함을 확인 하였다. CRP 축계의 시뮬레이션 결과 1차 공진모드에서 내축의 변위가 외축보다 커 축간 충돌 가능성이 높은 것으로 나타났다. 베어 링 강성 증가 시 고유진동수가 상승하여 공진영역을 회피할 수 있었으며, 축 직경 변화는 상대적으로 영향이 작았다. 제안된 해석 기 법은 상반회전 추진 이중축계의 설계 평가 및 진동 안정성 분석에 유용하게 활용될 수 있으며, 향후에는 비선형 베어링 특성 및 유체– 구조 연성효과를 포함한 확장 연구로 발전시킬 수 있을 것이다.

본 연구는 기술 변화와 업무 환경의 불확실성으로 직무복잡성이 증가하는 상황에서, 직무복잡성이 직 무스트레스를 통해 이직의도로 이어지는지, 그리고 비공식학습의 인식된 교육효과가 이 관계에 어떠한 영향을 미치는지를 분석하고자 하였다. 이를 위해 인적자본기업패널(HCCP) Ⅱ WAVE 4차(2023) 자료 중 비공식학습 활동에 참여한 근로자 3,131명을 대상으로 관련 변인을 측정하고, SPSS 25.0과 PROCESS Macro(Model 4, 14)를 활용하여 매개효과와 조절된 매개효과를 검증하였다. 분석 결과, 직무복잡성은 이 직의도에 직접적으로는 부적 영향을 미쳤으나 직무스트레스를 매개로 할 때에는 정적 간접효과를 보여 상반된 경로가 확인되었다. 또한 동료·상사 코칭 및 멘토링, 지식·노하우 공유의 인식된 교육효과는 모두 직무스트레스와 이직의도 간 관계를 유의하게 조절하였으며, 인식된 교육효과가 평균 이상일 때 매개효 과가 강화되는 것으로 나타났다. 이러한 결과는 비공식학습이 직무자원으로 기능하는 동시에 상황적 조 건에 따라 이직의도를 높이는 요인이 될 가능성을 시사한다. 이론적으로는 직무특성과 학습자원의 상호 작용을 통해 직무태도가 형성되는 구조를 확인함으로써 직무요구-자원 모델을 확장하는 데 기여할 수 있으며, 실무적으로는 직무 복잡성과 스트레스 수준을 고려한 비공식학습의 설계 필요성을 제기한다는 점에서 의미를 갖는다.