To characterize the breakdown process, we newly introduce and define a dimensionless number called breakdown zone Reynolds number Reb. Reb represents the relationship between shear frictional resistance and inertial force, equivalent to (Vr /Vs)2. Vr and Vs are rupture and shear wave velocities, respectively. Reb also characterizes the energy budget relationship, seismic energy radiation, and its efficiency. Based on Reb, particle motion can be categorized into two cases: a) Reb≪1 and b) Reb ~1 or Reb>1. For case a), since the inertial force is negligible compared to the shear frictional resistance, the particle motion can be viewed as the response of a linear time-invariant system with the stress drop as an input function, and its impulse response function (IRF) is the second type of modified Bessel function with zeroth order supposing linear phase characteristics. The IRF is quite similar to the regularized Yoffe function. The particle velocity spectrum can be characterized with the approximated spectral attenuation slope in the high frequency range of ∝ω-0.6. The attenuation slope, however, would be changed to ∝ω-1.0 if we consider the pre-slip and phase delay of the response. Then, generic omega-square model can model a finite source’s source time function (STF). On the other hand, case b) shows that IRF has the same form as Brune’s omega-square model, and its STF has steeper spectral attenuation like omega-cube model. This means that the spectral characteristics of STF may change with the rupture velocity. Furthermore, we newly define the ratio of source-controlled fmax to corner frequency f c as Stokes number Sk, a function of Reb and approximately proportional to Reb 3/2. Remarkably, Sk delineates a Reynolds number similarity which is comparable to that of isotropic turbulence. The aggregated results of spectral inversion analysis for more than 130 shallow earthquakes occurring in Japan show that the analyzed fmax/ f c (=Sk) follow the theoretical relationship, and it is also demonstrated that the non-self-similarity parameter ε proposed by Kanamori and Rivera is related to the scale dependence of Reb. Finally, Reb is compared to the inertial number I, a representative dimensionless number governing the behavior of granular suspension as a model for the interaction between fault gouge and pore-pressure in fault core. As a result, Reb is equivalent to I 2 as we consider the differences in length scale and density in each definition. Consequently, I is uniquely linked to Sk by Reb, corresponding to the Stokes number for granular suspension. Hence, it can be asserted that Reb and Sk introduced in this study are representative dimensionless numbers which characterize the whole breakdown process and the behavior of pulverized fault core.

Background: Logistics service workers (LSWs) face significant occupational challenges, with ankle sprains being the second most prevalent work-related musculoskeletal disorder. Foot posture, assessed through the navicular drop test, can significantly influence dynamic balance performance, which is crucial for injury prevention in physically demanding occupational settings. Objects: This study aimed to investigate differences in dynamic balance performance among LSWs with pronated, supinated, and normal foot types using the Y-Balance test (YBT), comparing reach distances across anterior, posteromedial, and posterolateral directions. Methods: A total of 205 LSWs were classified into three groups based on navicular drop measurements: supinated (n = 44), normal (n = 94), and pronated (n = 67) foot types. The YBT was performed on the dominant leg, measuring reach distances in three directions. Participants’ demographic characteristics were recorded, and statistical analyses were conducted using one-way analysis of variance (ANOVA) with Bonferroni correction. Results: Significant differences in YBT performance were observed across all three directions (anterior: p = 0.009, posterolateral: p = 0.015, posteromedial: p = 0.014). The supinated and normal foot groups showed significantly greater reach distances compared to the pronated group (p < 0.026 for anterior direction). In the posterolateral direction, the supinated group demonstrated significantly better performance compared to the pronated group (p = 0.014). Similarly, the posteromedial direction revealed significantly higher reach distances for the supinated group compared to the pronated group (p = 0.012). Conclusion: The study reveals that foot type significantly impacts dynamic balance performance among LSWs. Workers with pronated feet demonstrate reduced balance capabilities, while those with supinated feet show the most superior dynamic balance performance.

국내 도심지에 적용하고 있는 중앙버스정류장의 포장은 주로 아스팔트 포장으로 시공되어 있으나 중차량인 버스의 하 중으로 인해 포장 파손 사례가 증가하여 시민들의 안전에 악영향을 미치고 있으며 유지보수 비용이 매년 증가하고 있다. 서울시에서는 이러한 문제를 해결하기 위해 국내 최초로 중앙버스정류장 신설 구간에 현장타설 방식으로 연속철근 콘크 리트 포장(CRCP)을 시공하였다. 본 연구에서는 이러한 구간의 연속철근 콘크리트 포장에 대한 이동차량 하중에 의한 동 적 거동 특성을 분석하고자 포장 슬래브에 콘크리트 변형률계를 설치하고 덤프트럭을 통과시키며 동적 하중 재하 실험 을 수행하였다. 실험에서는 이동차량의 속도를 다양하게 변화시켜 차량 속도에 따른 포장 슬래브의 동적 거동을 비교 분 석하였으며 이동차량이 CRCP의 여러 위치에서 정지하도록 하여 정지 위치에 따른 거동도 분석하였다. 실험 결과, 차량 이 CRCP를 통행할 경우 차량 속도 및 정지 위치에 따른 포장 슬래브의 동적 변형률은 매우 유사한 것으로 분석되었다.

본 연구에서는 전지구 해양 예측 모델 결과를 동아시아 지역 해양 모델인 ROMS의 초기 및 경계 조건에 적용 한 역학적 규모 축소 모의 실험을 수행하였다. 우선 ROMS 모델의 성능을 AMOR3D, EN4, 정선 관측 자료, 인공위성 영상 및 기존에 발표된 MOHID 모델과 비교하여 검증하였다. 전반적으로 봄과 가을에는 관측 자료와 잘 일치하였으나, 해양 성층화가 강화되는 여름에는 모델 성능이 저하되는 것을 확인하였다. 또한, 동해와 남해보다 황해에서 더 우수한 성능을 보였으며, MOHID 모델보다 아표층 모의 성능이 개선되었다. RCP 4.5 시나리오를 적용하여 2015년부터 2030 년까지 예측한 CM2.1 전지구 해양 모델의 결과를 사용한 역학적 규모 축소 모의를 수행한 결과, 한반도 남서 연안의 저수온 영역, 황해난류의 경로 및 쿠로시오 해류의 사행 등 실제 해양의 다양한 현상이 잘 재현되었다. 또한, 지역 모델은 저해상도 전구 모델보다 평균 수온의 경년 변동 폭이 커지는 것을 확인하였다. 본 연구를 통해 ROMS를 이용한 역학적 규모 축소 결과의 신뢰성이 확인되었으나, 향후 동해 및 남해와 같은 특정 지역의 ROMS 모델의 모의 성능 개 선과 2030년 이후의 장기 시뮬레이션 연구가 추가로 필요할 것으로 보인다.

In this study, a control algorithm was developed to suppress the free vibration amplitude of a cantilever beam with time-varying dynamic characteristics. In other words, since it is assumed that the natural frequency and mode shape of the vibrating structure are not fixed, the system model of the vibrating structure was not used in the control algorithm. A single electromagnet was chosen as the actuator, so the attractive force was applied to only one fixed location in the structure. Through experiments, the proposed control algorithm is proven to effectively suppress the amplitude of vibration even when the dynamic characteristics of the cantilever beam change. Contrary to the usual active vibration control method, the proposed algorithm is just simple and intuitive without complicated mathematics in the modeling and control process. However, the proposed control method is very effective to suppress the vibration even when the dynamic characteristics of the target structure is not exactly known, as is often the case in industries or laboratories.

As digital transformation accelerates, platform business has become a core business model in modern society. Platform business has a network effect where the winner takes all. For this reason, it is crucial for a company's pricing policy to attract as many customers as possible in the early stages of business. Telecommunication service companies are experiencing stagnant growth due to the saturation of the smartphone market and intensifying competition in rates, but the burden of maintaining communication networks is increasing due to the rapid increase in traffic caused by domestic and foreign CSPs. This study aims to understand the dynamic characteristics of the telecommunications market by focusing on pricing policy. To this end, we analyzed how ISPs, CSPs, and consumers react to changes in pricing policy based on the prisoner's dilemma theory. The analysis of the dynamic characteristics of the market was conducted through simulation using the Agent-Based Model.

본 연구는 간 자기공명영상 검사 시 프리모비스트(Gd-EOB-DTPA) 조영제를 사용한 동적 동맥기(dynamic arterial phase)에서 호흡기 운동인공물을 최소화하기 위한 최적의 방법을 연구하였다. 연구는 총 세 집단으로 나누 어 진행되었으며, 첫 번째 집단은 별도의 사전 교육(pre-scan preparation, PSPP) 없이 촬영한 집단, 두 번째 집단은 사전 교육만 시행하고 촬영한 집단, 세 번째 집단은 사전 교육과 검사 중 숨 참기 보조 신호(breath-holding assistance signal, BHAS)를 제공한 집단으로 구성되었다. 각 집단의 촬영 결과를 비교한 결과, 사전 교육과 검사 시 숨 참기 보조 신호를 함께 시행한 집단에서 동적 동맥기 영상의 호흡기 운동인공물이 가장 적었으며, 영상의 품질 도 더 높게 평가되었다. 이러한 결과는 간 MRI 촬영의 동적 동맥 단계 검사에서 사전 교육과 검사 중 숨 참기 보조 신호가 결합한 접근법이 환자의 숨 참기 협조를 강화하여 영상 품질을 개선하고, 정확한 진단에 기여할 수 있음을 시사한다.

이 논문에서는 부유식 구조체의 계류선에 작용하는 장력을 계산함에 있어서 동적 효과를 고려할 수 있는 준동적 계류선 해석 방법 을 제안하였다. 준동적 계류선 해석 방법은 매 시간 단계에서 계류선의 탄성 현수선 해석해에 기반한 정적 장력을 계산한 후, 준동적 장력 계수를 적용해 속도와 가속도에 따른 항력 및 관성력의 영향을 반영하는 방법이다. 제안하는 방법은 정적 탄성 현수선 해석해를 구할 때 계산 효율성을 높이기 위해 응답면 기법을 도입하고, 수평 및 수직 방향의 동적 계수를 결합하여 준동적 장력 계수를 결정하 는 새로운 방법을 제안하였다. 제안된 모델은 계류된 바지선의 운동 해석을 통해 검증하였으며, 다양한 파 조건에서 동적, 준정적, 준 동적 모델을 비교한 결과, 제안된 준동적 모델은 상대적으로 계류선의 동적 효과가 큰 주파수 대역에서 동적 모델과 유사한 장력 응답 을 도출할 수 있음을 확인하였다.

With technological and social development, high-rise atypical buildings have emerged. In order to take into account the structural vulnerability due to their high-rise atypical shape, systems such as vibration control system and seismic isolation can be applied. In this study, dynamic behavior characteristics analysis was conducted based on the location of the seismic isolation system installation of the atypical facade shape Tapered and reverse shell structure models. With the installation of Lead Rubber Bearing(LRB), the maximum story drift ratio showed a decrease, but the maximum absolute acceleration showed a phenomenon in which the response was amplified in the middle and low story. LRB1(base isolation system) is the most effective for simultaneous control of the two dynamic responses, but the 46th floor of ‘Nor’ and’ RS’ and the 41st floor of ‘TA’ are considered the most effective installation location of the seismic isolation system in consideration of the burden of the seismic isolation system and the structure stability.

In this study used Computational Fluid Dynamic analysis to examine NOx reduction in hydrogen combustion, analyzing six conditions with varying air/fuel ratios, temperatures, and concentrations. Results were compared between two combustor shapes and previous experimental data. Findings showed increased air/fuel ratios decreased flame temperature and increased post-combustion O2. NOx emissions peaked at high temperatures and low O2. Numerical results aligned with previous experimental trends, validating the approach. Combustor shape differences, reflecting variations in fuel and air pipes, significantly affected flow rates and combustion positions. This reduced NOx emissions up to a certain air/fuel ratio, but excessive increases diminished this effect. The study highlights the complex relationship between combustor design, operating conditions, and NOx emissions. Further research is needed to optimize NOx reduction by considering pipe numbers and combustion locations. Future studies should explore various combustor geometries, fine-tune air/fuel ratios, and investigate additional parameters influencing NOx formation and reduction in hydrogen combustion systems.

Onboard truck scales can accurately measure payload under static conditions. However, their performance is limited in accounting for dynamic environments encountered during driving, leading to inaccuracies in load estimation under real-world conditions. This study employs TruckCaliber, a dynamic state measurement system, to estimate real-time vehicle loads. Fusion sensor modules were installed on leaf spring suspensions and vehicle frames to collect tilt and IMU data. The system was implemented on a commercial truck, and driving tests were conducted with varying payloads. The analysis focused on curved sections under different dynamic conditions.

This study is about the evaluation for shock-proof performance of the system, elastically support the low accumulator of the naval artillery against underwater explosion, using DDAM. For the evaluation, the shock analysis procedure using DDAM, supported by MSC/NASTRAN, was briefly described. In addition, in order to perform the shock analysis, the elastic support system was modeled as a finite element. The shock analysis of the elastic support system was performed by selecting the analysis frequency range so that reliable results can be obtained. Finally, the shock-proof performance of the system was evaluated by comparing the shock analysis results with the properties of the elastic support system.

In order to overcome the limitations of linear vibration energy harvesters and those using mechanical plucking, magnetic plucking vibration energy harvesters (MVEs) have garnered significant interest. This paper presents parametric studies aimed at proposing design guidelines for MVEs and compares two magnetic force models that describe interactions between two permanent magnets. A mathematical model describing the energy harvester is employed, followed by the introduction of two magnetic force models: an analytic model and an inverse square model. Subsequently, numerical simulations are conducted to investigate dynamic characteristics of MVEs, analyzing results in terms of tip displacement, voltage output, and harvested energy. Parametric studies vary the distance between magnets, the speed of the external magnet, and the beam shape. Results indicate that reducing the distance between magnets enhances energy harvesting effectiveness. An optimal velocity for the external magnet is observed, and studies on beam shape suggest greater energy harvesting when the shape favors deflection.

We investigated dynamic interaction between adjacent magnetic loops in the solar atmosphere, which is a process of volume shrinkage with nonuniform acceleration caused by Lorentz force. When these loops locally have different thermal and dynamic properties, a significant discrepancy between their translational motions driven by means of that force may arise, leading to the dynamic interaction. We use both numerical simulation and analytic model of magnetic piston-driven wave to evaluate how much a single event of the interaction contributes to increasing the temperature in the upper chromosphere. The model shows a possibility that a chromospheric plasma is heated by the single event to have transition region temperature, which is typically several tens of times higher than chromospheric temperature. The model also provides an insight into the formation height of the transition region.

Background: Previous studies have highlighted the beneficial impact of trunk strength training on gross motor muscle function. Additionally, trunk strength training has been shown to enhance upper limb function and balance in children with cerebral palsy. Although numerous studies have explored dynamic and static balance for children with cerebral palsy, none have yet examined the combined application of kinetic link training (KLT) and bird dog exercise (BDE). Objectives: To investigated the effect of cerebral Palsy on the KLT and BDE. Design: A randomized controlled trial. Methods: This study involved 30 children diagnosed with cerebral palsy. They were randomly allocated to two groups: 15 children in the KLT group and 15 in the bird-dog group. During the intervention, four participants dropped out, resulting in 26 subjects for the final analysis (KLT=11, Bird-dog=15). After randomizing the subjects into two groups, we allocated their general characteristics. Prior to starting the intervention, initial measurements were taken using the Romberg test for static balance and the limit of stability (LOS) test for dynamic balance. Each group participated in KLT and BDE for 30 minutes, three times a week for eight weeks, under the supervision of a therapist. Follow-up measurements of static and dynamic balance were taken at the conclusion of the eight-week period. The collected data was analyzed using the SPSS ver. 21.0 program by paired t-test and independent t-test. Results: In the results for static balance, the within-group comparisons indicated a significant reduction in trace length, STD velocity, and velocity postintervention compared to pre-intervention for both the KLT and BDE groups, except for the C90 area (P<.05). Regarding dynamic balance, the withingroup comparisons demonstrated a significant increase in LOS in the forward direction for the BDE group from pre- to post-intervention (P<.05). Similarly, there was a significant increase in LOS in the backward direction for the KLT group from pre- to post-intervention (P<.05). The LOS in both the left and right directions showed significant increases in the BDE group from pre- to post-intervention (P<.05). Conclusion: An eight-week intervention involving KLT and BDE exercises improved both static and dynamic balance in children with cerebral palsy.

Background: Balance is the foundation of performing daily activities, and has been proven to be improved by various compression materials. As a new and never-before-seen means, the floss band improves joint range of motion, increases muscle flexibility, and affects balance. Several studies using the short-term application of a floss band to the ankle have been conducted. However, long-term effects of the floss band on the knee warrant further research. Objectives: This study aims to examine the long-term benefits of strength exercises with a floss band applied to the knee for static and dynamic balance. Design: Quasi-experimental design. Methods: A total of 28 participants (four men and 24 women, aged 20–60 years) with no orthopedic knee conditions were recruited and randomized into two groups, with 14 in the group using the strength exercises with floss bands applied to the knee (the floss band group), and 14 in the group using internal rotation of the tibia during mobilization with movements (MWM; the MWM group). A physical therapist with 10 years of clinical experience applied the intervention 10 times, measuring static and dynamic balance before and after the intervention using the Balance Trainer 4. Independent t-tests and paired t-tests were used for statistical analysis, with a significance level of ⍺=.05. Results: Statistically significant effects for static balance and dynamic balance were observed in the comparison from pre- to post-intervention between the floss band and MWM groups (P<.05). Additionally, a statistically significant effect for dynamic balance was noted in the pre- to post-intervention comparison in the floss band group (P<.05). Conclusion: The strength exercises with floss bands applied to the knee are expected to have a long-term effect on improving dynamic balance.

Due to the complexity of urban area, the city vehicle routing problem has been a difficult problem. The problem has involved factors such as parking availability, road conditions, and traffic congestion, all of which increase transportation costs and delivery times. To resolve this problem, one effective solution can be the use of parcel lockers located near customer sites, where products are stored for customers to pick up. When a vehicle delivers products to a designated parcel locker, customers in the vicinity must pick up their products from that locker. Recently, identifying optimal locations for these parcel lockers has become an important research issue. This paper addresses the parcel locker location problem within the context of urban traffic congestion. By considering dynamic environmental factors, we propose a Markov decision process model to tackle the city vehicle routing problem. To ensure more real situations, we have used optimal paths for distances between two nodes. Numerical results demonstrate the viability of our model and solution strategy.

Concrete structures must maintain their shielding abilities and structural integrity over extended operational periods. Despite the widespread use of dry storage systems for spent nuclear fuel, research on the properties of deteriorated concrete and their impact on structural performance remains limited. To address this significant research gap, static and dynamic material testing was conducted on concrete specimens carefully extracted from the outer wall of the High-flux Advanced Neutron Application ReactOr (HANARO), constructed approximately 30 years ago. Despite its age, the results reveal that the concrete maintains its structural integrity impressively well, with static compression tests indicating an average compressive strength exceeding the original design standards. Further dynamic property testing using advanced high-speed material test equipment supported these findings, showing the consistency of dynamic increase factors with those reported in previous studies. These results highlight the importance of monitoring and assessing concrete structures in nuclear facilities for long-term safety and reliability.

The threat of North Korea's long-range firepower is recognized as a typical asymmetric threat, and South Korea is prioritizing the development of a Korean-style missile defense system to defend against it. To address this, previous research modeled North Korean long-range artillery attacks as a Markov Decision Process (MDP) and used Approximate Dynamic Programming as an algorithm for missile defense, but due to its limitations, there is an intention to apply deep reinforcement learning techniques that incorporate deep learning. In this paper, we aim to develop a missile defense system algorithm by applying a modified DQN with multi-agent-based deep reinforcement learning techniques. Through this, we have researched to ensure an efficient missile defense system can be implemented considering the style of attacks in recent wars, such as how effectively it can respond to enemy missile attacks, and have proven that the results learned through deep reinforcement learning show superior outcomes.

With the birth of ChatGPT, it has had a strong impact on the education industry, and the education association research is also diverse. This study aims to provide reference and new ideas for academic research in the educational field by analyzing the current research status, research hotspots, and research trends of ChatGPT in the field of education, and to provide some suggestions and new initiatives for education regulatory authorities. This study mainly used literature analysis and bibliometric methods to conduct quantitative and statistical analysis on the selected 452 advanced literature. At the same time, with the help of research tools such as CiteSpace 2022, WORDART2024, and XLSX2024, the data of the literature was input to generate visual charts. Through the interpretation of the charts, conclusions were drawn. This study analyzes the main characteristics of the current research situation through the distribution of literature time, disciplinary specialties, research level, and academic journals. Secondly, the distribution of research hotspots is revealed through keyword frequency statistics and keyword co-occurrence analysis. By analyzing the author's research trends and publishing institutions, it aims to explore the development trends in this field. Finally, this study found that the number of publications on the association between ChatGPT and education showed a steady upward trend, with the main disciplines focused on educational theory and computer application technology, and the publication journals concentrated on university sponsored academic journals and Chinese core journals. The research hotspots revolve around artificial intelligence, with strong intersection between hotspots. The research authors have strong independence and weak correlation. But there is strong integration and correlation between research institutions.