Until all vehicles are equipped with autonomous driving technology, there will inevitably be mixed traffic conditions that consist of autonomous vehicles (AVs) and manual vehicles (MVs). Interactions between AVs and MVs have a negative impact on traffic flow. Cloverleaf interchanges (ICs) have a high potential to cause traffic accidents owing to merging and diverging. Analyzing the driving safety of cloverleaf ICs in mixed traffic flows is an essential element of proactive traffic management to prevent accidents. This study proposes a comprehensive simulation approach that integrates driving simulation (DS) and traffic simulation (TS) to effectively analyze vehicle interactions between AVs and MVs. The purpose of this study is to identify hazardous road spots for a freeway cloverleaf IC by integrating DS and TS in mixed traffic flow. The driving behavior data of MVs collected through a DS were used to implement vehicle maneuvering based on an intelligent driver model in the TS. The driving behavior of the AVs was implemented using the VISSIM parameters of the AVs presented in the CoEXist project. Additionally, the market penetration rate of AVs, ranging from 10% to 90% in 10% increments, was considered in the analysis. Deceleration rate to avoid crashes was adopted as the evaluation indicator, and pinpointing hazardous spot technique was used to derive hazardous road spots for the cloverleaf IC. The most hazardous road spot was identified in the deceleration lane where greater speed changes were observed. Hazardous road spots moved downstream within the deceleration lane as traffic volumes increased based on level of service. The number of AVs decelerating stably increased as traffic increased, thereby improving the safety of the deceleration lane. These results can be used to determine the critical point of warning information provision for preventing accidents when introducing AVs.

The seismic performance of lead-rubber bearings (LRBs) is significantly affected by both the axial force and loading rate they experience. Accurate assessment of LRBs’ seismic performance, therefore, requires realistic simulation of these forces and rates, as well as of the response of the isolated structure during seismic events. This study conducted a series of real-time hybrid simulations (RTHS) to evaluate the seismic behavior of LRBs in such conditions. The simulations focused on a two-span continuous bridge isolated by LRBs atop the central pier, exposed to horizontal and vertical ground motions. In the RTHS framework, the LRBs were physically tested in the laboratory, while the remainder of the bridge was numerically modeled. Findings from these simulations indicated that the vertical ground motion had a minimal effect on the lateral response of the bridge when isolated by LRBs.

Being in a stable continental region (SCR) with a limited history of instrumentation, South Korea has not collected sufficient instrumental data for data-driven ground motion models. To address this limitation, we investigated the suitability of the hybrid ground motion simulation method that Graves and Pitarka (2010, 2015) proposed for simulating earthquake ground motions in South Korea. The hybrid ground motion simulation method used in this study relies on region-specific parameters to accurately model phenomena associated with the seismic source and the wave propagation. We initially employed relevant models and parameters available in the literature as a practical approach. We incorporated a three-dimensional velocity model developed by Kim et al. (2017) and a one-dimensional velocity model presented by Kim et al. (2011) to account for the crustal velocity structure of the Korean peninsula. To represent the earthquake source, we utilized Graves and Pitarka’s rupture generator algorithm along with a magnitude-area scaling relationship developed for SCR by Leonard (2014). Additionally, we assumed the stress and attenuation parameters based on studies of regional seismicity. Using the implemented platform, we simulated the 2016 Mw5.57 Gyeongju earthquake and the 2017 Mw5.4 Pohang earthquake. Subsequently, we compared results with recorded accelerations and an empirical ground motion prediction equation at strong motion stations. Our simulations had an overall satisfactory agreement with the recorded ground motions and demonstrated the potential of broadband hybrid ground motion simulation for engineering applications in South Korea. However, limitations remain, such as the underestimation of long-period ground motions during the 2017 Pohang earthquake and the lack of a model to predict the ground motion amplification associated with the near-surface site response accurately. These limitations underscore the importance of careful validation and refinement of region-specific models and parameters for practically implementing the simulation method.

Sequential zone picking is an order picking method designed to enhance warehouse efficiency by dividing the storage area into multiple zones and picking items in a sequential order across these zones. Picked items are often placed in dedicated totes and transported between zones using a conveyor system, which manages the picking flow but can occasionally result in inefficiencies during the process. This study presents a variant of the sequential zone picking system, called a dual-lane zone picking system (DZP), which consists of two parallel conveyor lanes without buffers between consecutive zones. This conveyor configuration allows the picker in each zone to alternate processing between the two lanes, thereby lessening the constraints of tote transitions between zones and improving both system throughput and picker utilization. We design and conduct a series of experiments using a discrete-event simulation model to evaluate the performance of DZPs. The experiment results indicate that DZP surpasses the original single-lane zone picking system by shortening the system’s mean flow time in low flow intensity scenarios and achieving a higher maximum throughput and worker utilization in high flow intensity scenarios. Additionally, we investigate the effects of the number of zones and order batching size on the performance of DZP to gain further insights into the system’s operational control.

A multi-criteria decision-making(MCDM) method allows the decision makers to systematically evaluate the alternatives based on a predefined set of decision criteria. The most commonly used MCDM methods include Analytic Hierarchy Process(AHP), Technique for Order of Preference by Similarity to Ideal Solution(TOPSIS), Weighed Aggregated Sum Product Assessment(WASPAS), Preference Selection Index(PSI), etc. In MCDM Problems, it is common that performance ratings for different criteria are measured by different units. Normalization is thus used to convert performance ratings into commensurable data. There are many normalization techniques that can be used for MCDM problems. Much effort has been made for comparative studies on the suitability of normalization techniques used in MCDM methods. However, most studies present normalization methods suitable for specific MCDM problems based on specific data samples. Therefore, this study proposes the most suitable normalization method for each MCDM method under consideration using extensive data samples. A wide range of MCDM problems with various measurement scales are generated by simulation for comparative study. The experimental results show that vector normalization method is best suited for all MCDM methods considered in this study.

본 연구는 해양에서 선박 운항 시 발생할 수 있는 항행장애물, 특히 부유물과의 충돌 위험성을 예측하기 위해 몬테카를로 시뮬 레이션을 적용한 항행안전 충돌 확률 모델을 개발하는 데 중점을 두고 있다. 항행장애물은 해양에서 선박의 운항을 방해하거나 위험을 초 래할 수 있는 물체로, 선박 사고의 주요 원인 중 하나이다. 연구는 부유물 감김 사고와 관련된 최근 5년간의 해양사고통계 정보와 7년간 사 고 데이터를 분석하여 사고 발생 패턴을 파악하고, 이를 기반으로 위험성 평가 방법론을 검토하였다. 몬테카를로 시뮬레이션을 통해 임의 의 제한된 해상 공간 내에서 표류하는 부유물과 이동 중인 선박이 접촉할 확률을 도출하였으며, 다양한 변수(부유물의 크기, 개수, 속도, 이 동하는 선박의 개수, 선박의 통항 패턴 등)가 충돌 확률에 미치는 영향을 분석하였다. 연구 결과, 표류하는 장애물의 속도보다는 장애물의 크기와 이동하는 선박의 개수에 따라 충돌 확률이 영향을 받음을 확인할 수 있었다. 이 연구는 해양과 선박 데이터 기반 실행 가능한 모델 을 제안하며, 이를 통해 선박 운항의 안전성을 높이고, 사고 예방을 위한 효과적인 관리 방안을 제공하는 것을 목표로 하고 있다.

The MBR process, which uses membrane to separate solids instead of secondary clarifier, has the advantage of maintaining high MLSS (Mixed Liquor Suspended Solids) concentration in bioreactors. In this study, three MBR processes combined with chemical phosphorus removal facility were studied: the phase-isolated MBR process with one recirculation pump, the A2O MBR process with two recirculation pumps, and the MBR process without a oxygen depletion reactor with three recirculation pumps. 116 simulations by EQPS (Effluent Quality Prediction System) were performed, under same design influent characteristics and hydraulic retention time, to see the effects of recirculation ratio changes on effluent water quality. The final effluent limits for total nitrogen and phosphorus were set to as 10 ㎎/L or less and 0.2 ㎎/L or less, respectively. AlCl3 was fed at MBR effluent to make 0.2 ㎎/L of total phosphorus precisely by PI (Proportional-Integral) controller in EQPS. This study showed that the phase isolated MBR process (R1 600%) had the highest nitrogen removal efficiency, with a final effluent T-N concentration of 6.765 mg/L. However, the A2O MBR process (R1 400%, R2 100%) required the lowest AlCl3 flow of 0.742 m3/day, which is approximately 59.1% lower than the average AlCl3 flow of the phase-isolated MBR process. It also produced 4,835 kg/day of sludge, the lowest among the studying MBR processes. It seems that A2O MBR process is the most economic method to treat studying wastewater to meet final effluent nutrient limit targets. However, carbon neutrality must be considered to select the best process to treat studying wastewater and it will be presented later.

Purpose: This study aimed to analyze the reviewers’ evaluations of papers submitted to the Journal of the Korean Society for Simulation in Nursing between 2019 and June 2024. Methods: We analyzed 117 quantitative (69 published and 48 unpublished) and 16 qualitative (11 published and five unpublished) studies. The reviewers’ checklist-based evaluations were analyzed using means and standard deviations. The scope method was used to examine the reviewers’ subjective evaluations. Results: For quantitative studies, the highest average score among published papers was in the “Research Theme” category (3.64±0.73). Contrastingly, the lowest average scores were in the “Discussion” category, with 3.32±0.74 for quantitative studies and 3.23±0.74 for qualitative studies. In rejected papers, the “Discussion” category recorded the lowest scores, at 2.35±0.74 for quantitative studies and 1.92±0.76 for qualitative studies. Conclusion: The results demonstrated the research characteristics of this journal and focus of the review by providing information on the reviewers’ evaluations. Structured scientific research based on these results will contribute to improving the academic quality of journals by reinforcing the openness and systematicity of academic communication.

Purpose: This study aimed to evaluate the effectiveness of low-fidelity simulation and actual human practice on the learning outcomes of a peripheral intravenous injection program for nursing students. Methods: Seventy-two third-year nursing students from a university in Seoul were included and divided into two groups; 38 and 34 in the low-fidelity simulation and human practice groups, respectively. The program was conducted from June 19–20, 2024. Data were analyzed using frequency, percentage, mean, standard deviation, χ²-test, independent t-test, and ANCOVA. Results: Both groups showed significant improvements in venipuncture performance, communication skills, empathy, academic performance, and self-efficacy. However, there were no statistically significant differences in these outcomes between both groups. Additionally, post-program learning satisfaction was similarly high in both groups. Conclusion: Low-fidelity simulation is as effective as actual human practice in achieving comparable learning outcomes in a peripheral intravenous injection program for nursing students. With appropriate instructional design, low-fidelity simulation can be a viable alternative to human practice, providing flexibility and accessibility in nursing education. This study underscores the importance of incorporating additional educational modules that enhance emotional and social skills, such as communication and empathy, tailored to the characteristics of individual learners.

Purpose: This study aimed to identify the need for simulation education to strengthen patient safety competencies in nursing practice field experience and explore and analyze improvements in simulation education. Methods: Data were collected through focus group interviews with 31 participants from four groups of fourth-year nursing students and one group of new nurses from August 7, 2023 to February 11, 2024. Interview data were systematically reviewed by qualitative content analysis. Results: Five major themes were identified; (1) awareness of patient safety competencies among nursing students and new nurses, (2) awareness of patient safety education among nursing students and new nurses, (3) simulation education topics for strengthening patient safety competencies, (4) interfering factors of simulation education for strengthening patient safety competencies, and (5) facilitating factors of simulation education to strengthen patient safety competencies. Accordingly, 15 categories were derived, and the current status of simulation education for patient safety, educational needs, and improvements were reported. Conclusion: This study attempted to reflect on the needs of learners before developing a simulation education program and derive educational content to strengthen patient safety competencies.

Purpose: This single-group pre-post experimental study aimed to develop and apply a simulation-based infection control education program for neonatal intensive care unit (NICU) nurses to verify its effectiveness and provide baseline educational materials to strengthen NICU nurses’ infection control competencies. Methods: The educational program was developed according to the five phases of analysis, design, development, implementation, and evaluation models, with scenarios based on the educational needs of NICU nurses. To verify the program’s effectiveness, a study was conducted on 28 NICU nurses of general and tertiary hospitals. NICU nurses’ infection control knowledge, performance confidence, critical thinking disposition, and satisfaction with the education were surveyed after applying the education program. Results: The simulation-based NICU infection control educational program was effective for NICU nurses’ infection control knowledge (t=−7.35, p < .001), performance confidence (t=−6.30, p < .001), and critical thinking disposition (t=−5.12, p < .001). Conclusions: The infection control educational program can contribute to infection prevention and patient safety by improving the NICU nurses' infection control competencies and be used as a baseline educational material for infection control education.

음이온 교환막(AEM) 수전해용 AEM 소재 개발은 재생 에너지를 활용한 수소 생산 기술을 개선하는 데 중요한 역할을 한다. 이러한 소재를 설계하고 최적화하는 데 분자동역학 전산모사가 유용하게 사용되지만, 전산모사 결과의 정확도 는 사용된 force-field에 크게 의존한다. 본 연구의 목적은 AEM 소재의 구조와 이온 전도 특성을 예측할 때 force-field 선택 이 미치는 영향을 체계적으로 조사하는 것이다. 이를 위해 poly(spirobisindane-co-aryl terphenyl piperidinium) (PSTP) 구조를 모델 시스템으로 선택하고 COMPASS III, pcff, Universal, Dreiding 등 네 가지 주요 force-field를 비교 분석하였다. 각 force-field의 특성과 한계를 평가하기 위해 298~353 K의 온도 범위에서 수화 채널 형태, 물 분자와 수산화 이온의 분포, 수산 화 이온 전도성을 계산하였다. 이를 통해 AEM 소재의 분자동역학 전산모사에 가장 적합한 force-field를 제시하고, 고성능 AEM 소재 개발을 위한 계산 지침을 제공하고자 한다.

PURPOSES : Driving simulations are widely used for safety assessment because they can minimize the time and cost associated with collecting driving behavior data compared to real-world road environments. Simulator-based driving behavior data do not necessarily represent the actual driving behavior data. An evaluation must be performed to determine whether driving simulations accurately reflect road safety conditions. The main objective of this study was to establish a methodology for assessing whether simulation-based driving behavior data represent real-world safety characteristics. METHODS : A 500-m spatial window size and a 100-m moving size were used to aggregate and match the driving behavior indicators and crash data. A correlation analysis was performed to identify statistically significant indicators among the various evaluation metrics correlated with crash frequency on the road. A set of driving behavior evaluation indicators highly correlated with crash frequency was used as inputs for the negative binomial and decision tree models. Negative binomial model results revealed the indicators used to estimate the number of predicted crashes. The decision-tree model results prioritized the driving behavior indicators used to classify high-risk road segments. RESULTS : The indicators derived from the negative binomial model analysis were the standard deviation of the peak-to-peak jerk and the time-varying volatility of the yaw rate. Their importance was ranked first and fifth, respectively, using the proposed decision tree model. Each indicator has a significant importance among all indicators, suggesting that certain indicators can accurately reflect actual road safety. CONCLUSIONS : The proposed indicators are expected to enhance the reliability of driving-simulator-based road safety evaluations.

다중 운집 사고는 주로 도시 내 밀집된 공간에서 발생하며, 보행자의 자유로운 이동이 제한될 때 더욱 위험하다. 이러한 상황에서 군중의 물리적 압력이 더해지면 대형 참사로 이어질 수 있어 예방과 신속한 대응이 필수적이다. 사고 발생 가능성을 최소화하기 위해 서는 실시간으로 군중 밀도를 모니터링하고, 위험 상황을 사전에 경고할 수 있는 예측 시스템 구축이 필요하다. 그러나 현재 사용되는 CCTV 기반 모니터링 시스템은 특정 구역에 국한되며, 설치 및 유지 비용이 높아 광범위한 모니터링에는 한계가 있다. 이에 본 연구 에서는 Cell Transmission Model(CTM)을 기반으로 한 양방향 보행 시뮬레이션 프레임워크를 개발하고, 이를 모바일 통신 데이터로 검증하였다. 연구 과정에서는 먼저 1)단방향 보행 CTM을 구축하고, 2)이를 양방향 보행 CTM으로 확장하여 경계 셀을 재설정하고 유 입량을 조정하는 방식으로 진행했다. 또한, 다중 운집 사고를 구현하기 위해 체류 개념을 추가했다. 검증 단계는 1)대상지 선정, 2)보행 네트워크 구축, 3)시뮬레이션 적용, 4)모바일 통신 데이터와의 비교 검증 순으로 이루어졌다. 대상지는 이태원 참사가 발생했던 이태원 역 부근으로, 20×20m 셀 단위로 보행 네트워크를 구축했다. 시뮬레이션 결과, 모바일 통신 데이터와의 높은 유사도를 보였다. 본 연구 에서 개발한 시뮬레이션은 대규모 행사나 혼잡한 보행 환경에서 군중 밀집을 예측하고, 사고 가능성을 조기에 경고하는 데 활용될 수 있다. 특히, 대형 이벤트나 도시 재난 관리에서 실시간 대응 시스템의 기초 자료로 사용할 수 있다.

The damage to structures during an earthquake can be varied depending on the frequency characteristics of seismic waves and the geological properties of the ground. Therefore, considering such attributes in the design ground motions is crucial. The Korean seismic design standard (KDS 17 10 00) provides design response spectra for various ground classifications. If required for time-domain analysis, ground motion time series can be either selected and adjusted from motions recorded at rock sites in intraplate regions or artificially synthesized. Ground motion time series at soil sites should be obtained from site response analysis. However, in practice, selecting suitable ground motion records is challenging due to the overall lack of large earthquakes in intraplate regions, and artificially synthesized time series often leads to unrealistic responses of structures. As an alternative approach, this study provides a case study of generating ground motion time series based on the hybrid broadband ground motion simulation of selected scenario earthquakes at sites in the Nakdonggang delta region. This research is significant as it provides a novel method for generating ground motion time series that can be used in seismic design and response analysis. For large-magnitude earthquake scenarios close to the epicenter, the simulated response spectra surpassed the 1000-year design response spectra in some specific frequency ranges. Subsequently, the acceleration time series at each location were used as input motions to perform nonlinear 1D site response analysis through the PySeismoSoil Package to account for the site response characteristics at each location. The results of the study revealed a tendency to amplify ground motion in the mid to long-period range in most places within the study area. Additionally, significant amplification in the short-period range was observed in some locations characterized by a thin soil layer and relatively high shear wave velocity soil near the upper bedrock.

We study quasi-spherical, supersonic accretion flows around black holes using high-accuracy numerical simulations. We describe a code, the Lagrangian Total Variation Diminishing (TVD), and a remap routine to address a specific issue in the Advection Dominated Accretion Flow (ADAF) that is, appropriately handling the angular momentum even near the inner boundary. The Lagrangian TVD code is based on an explicit finite difference scheme on mass-volume grids to track fluid particles with time. The consequences are remapped on fixed grids using the explicit Eulerian finitedifference algorithm with a third-order accuracy. Test results show that one can successfully handle flows and resolve shocks within two to three computational cells. Especially, the calculation of a hydrodynamical accretion disk without viscosity around a black hole shows that one can conserve nearly 100% of specific a ngular momentum in one-and twodimensional cylindrical coordinates. Thus, we apply this code to obtain a numerically similar ADAF solution. We perform simulations, including viscosity terms in one-dimensional spherical geometry on the non-uniform grids, to obtain greater quantitative consequences and to save computational time. The error of specific angular momentum in Newtonian potential is less than 1% between r~10rs and r~10 4 rs, where rs is sink size. As Narayan et al. (1997) suggested, the ADAFs in pseudo-Newtonian potential become supersonic flows near the black hole, and the sonic point is rsonic~5.3rg for flow with α =0.3 and  =1 .5. Such simulations indicate that even the ADAF with  =5/3 is differentially rotating, as Ogilvie (1999) indicated. Hence, we conclude that the Lagrangian TVD and remap code treat the role of viscosity more precisely than the other scheme, even near the inner boundary in a rotating accretion flow around a nonrotating black hole.

The main problem of airport noise is the impact of aircraft noise on the residents around the airport. In order to investigate the noise situation of a certain airport in South Korea, this article selects Muan Airport as the research project, selects five measurement points near the airport, takes aircraft takeoff as an example, measures the maximum noise level of each measurement point during each take off, and uses the American Airport Noise Prediction Software (AEDT 3C) to predict the noise of a single aircraft during take off, Calculate the contour area and sound exposure level data for four aircraft models. The results indicate that the average maximum noise level error between the measurement results and the simulation results is within 2dB, and the maximum noise level ranges from 65.1 to 88.1 decibels with the measurement range.