• Title/Summary/Keyword: Computer Simulation

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Analysis of Hydro-Mechanical Coupling Behavior Considering Excavation Damaged Zone in HLW Repository (고준위방사성폐기물 처분장에서의 굴착손상대를 고려한 수리-역학적 복합거동 해석)

  • Jeewon Lee;Minju Kim;Sangki Kwon
    • Explosives and Blasting
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    • v.41 no.3
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    • pp.38-61
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    • 2023
  • An Excavation Damaged Zone(EDZ) caused by blasting impact changes rock properties, in situ stress distribution, etc., and its effects are noticeable at around a radioactive waste repository located at deep underground. In particular, the increase in permeability due to the formation of cracks may significantly increase the amount of groundwater inflow and the possibility of radioactive nuclide outflow. In this study, FLAC2D and FLAC3D were used to analyze the mechanical and thermal behaviors for three categories: a)No EDZ, b)Uniform EDZ, and c)Random EDZ. It was found that the tunnel displacement in the Random EDZ case was 423% higher than that in the No EDZ case and was 16% higher than that in the Uniform EDZ case. Tunnel inflow in the Random EDZ was also 17.3% and 10.8% higher than that in the No EDZ and the Uniform EDZ case, respectively. The permeability around the tunnel was increased by up to 10 times in the corner of the tunnel wall and roof due to the stress redistribution after excavation. From the computer simulation, it was found that the permeability around the tunnel wall was partially increased but the overall tunnel inflow was decreased with increase of stress ratio. Mechanical analysis using FLAC 3D showed similar results. Slight difference between 2D and 3D could be explained with the development of plastic zone during the advance of tunnel excavation in 3D.

Analysis of the effect of improving human thermal environment by road directions and street tree planting patterns in summer (여름철 도로 방향과 가로수 식재 방식에 의한 인간 열환경 개선효과 분석)

  • Jeonghyeon Moon;Yuri Choi;Eunja Choi;Jueun Yang;Sookuk Park
    • Journal of the Korean Association of Geographic Information Studies
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    • v.27 no.2
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    • pp.1-18
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    • 2024
  • This study aimed to identify the optimal street tree planting method to improve the summer thermal environment in Seoul, Republic of Korea. The effects of road direction and street tree planting patterns on urban thermal environments using ENVI-met simulations were analyzed. The 68 scenarios were analyzed based on four road directions and 17 planting patterns. The results showed that tree planting had a reducing air temperature, mean radiant temperature, human thermal sensation (PET and UTCI). The most effective planting pattern among all scenarios was low tree height (6m), wide crown width (9m), high leaf area index (3.0), and narrow planting interval (8m). The largest improvement in the thermal environment was the northern sidewalk of the east-west road. Since this study used computer simulations, the difference from real urban spaces should be considered, and further research is needed through field measurement and consideration of more variables.

Cybersickness and Experience of Viewing VR Contents in Augmented Reality (증강현실에서의 가상현실 콘텐츠 시청 경험과 사이버 멀미)

  • Jiyoung Oh;Minseong Jin;Zion Park;Seyoon Song;Subin Jeon;Yoojung Lee;Haeji Shin;Chai-Youn Kim
    • Science of Emotion and Sensibility
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    • v.26 no.4
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    • pp.103-114
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    • 2023
  • Augmented reality (AR) and virtual reality (VR) differ fundamentally, with AR overlaying computer-generated information onto the real world in a nonimmersive way. Despite extensive research on cybersickness in VR, its occurrence in AR has received less attention (Vovk et al., 2018). This study examines cybersickness and discomfort associated with AR usage, focusing on the impact of content intensity and exposure time. Participants viewed 30-minute racing simulation game clips through AR equipment, varying in racing speed to alter content intensity. Cybersickness was assessed subjectively using the Simulator sickness questionnaire (SSQ; Kennedy et al., 1993). Findings revealed a progressive increase in cybersickness with longer exposure, persisting even after removing the AR equipment. Contrarily, content intensity did not significantly influence cybersickness levels. Analysis of the SSQ subscales revealed higher oculomotor (O) scores compared to nausea (N) and disorientation (D), suggesting that discomfort primarily stemmed from oculomotor strain. The study highlights distinct differences in user experience between AR and VR, specifically in subjective responses.

A study to find the operation conditions to minimize carbon footprint using a simulator(EQPS) (시뮬레이터(EQPS)를 이용한 탄소발자국 최소화 운전 방안에 대한 연구)

  • Jisoo Han;Jeseung Lee;Byonghi Lee
    • Journal of the Korea Organic Resources Recycling Association
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    • v.32 no.2
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    • pp.37-48
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    • 2024
  • Wastewater treatment plants (WWTPs) are obligated to reduce carbon emissions as a part of public sector greenhouse gas (GHG) emission reduction targets. However, Sewage Statistics(2022) shows that CO2 emissions per wastewater treatment volumes have decreased by only 3.03 % compared to 2020, which is far from enough to meet the Nationally Determined Contribution (NDC) targets. This study aimed to find operational conditions of biological reactors that minimize total carbon footprint (CFP). Total CFP considers both direct emissions from biological processes and indirect emissions from energy consumption. A study was conducted using a computer simulation program which is called as EQPS for a 4-stage BNR WWTP. The results showed that total CFP was reduced by 10.97% compared to the design condition when the mixed liquor recirculation (MLR) was set to 100 % of the influent flow. The N2O emission factor (EF) of the target WWTP was calculated to be 0.138-0.199 %, which is significantly lower than the IPCC default value of 1.6 %. This study proposes a method to minimize total CFP in WWTPs by optimizing biological reactor operation and emphasizes the need for further research on N2O emission reduction.

Analysis of The Human Thermal Environment in Jeju's Public Parking Lots in Summer and Suggestion for Its Modification (제주시 공영 주차장 내 여름철 인간 열환경 분석 및 저감 방안 제안)

  • Choi, Yuri;Park, Sookuk
    • Journal of the Korean Institute of Landscape Architecture
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    • v.52 no.3
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    • pp.18-32
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    • 2024
  • This study aims to analyze the summer human thermal environment in Jeju City's outdoor parking lots by measuring microclimate data and comparing pavement and vegetation albedoes and elements through computer simulations. In measured cases, results due to albedo showed no significance, but there was a significant difference between sunny and shaded areas by trees. The sunny area had a PET (physiological equivalent temperature) in the 'very hot' level, while the shaded area exhibited a 2-step lower 'warm' level. UTCI (universal thermal climate index) also showed that the sunny area was in the 'very strong heat stress' level, whereas the shaded area was 1-step lower in the 'strong heat stress' level, confirming the role of trees in reducing incoming solar radiant energy. Simulation results, using the measured albedoes, closely resembled the measured results. Regarding vegetation, scenarios with a wide canopy, high leaf density, and narrow planting spacing were effective in mitigating the human thermal environment, and the differences due to tree height varied across scenarios. The scenario with the lowest PET value was H9W9L3D8 (tree height 9m, canopy width 9m, leaf area index 3.0, planting spacing 8m), indicating a 0.7-step decrease compared to the current landscaping scenario. Thus, it was confirmed that, among landscaping elements, trees have a significant impact on the summer human thermal environment compared to ground pavement.

Bandwidth Adjustment Techniques for MMOG in a Cloud-P2P Hybrid Architecture (클라우드와 P2P 하이브리드 구조의 MMOG를 위한 대역폭 조정 기법)

  • Jin-Hwan Kim
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.24 no.3
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    • pp.55-61
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    • 2024
  • In a hybrid architecture that combines the technological advantages of P2P(peer-to-peer) and cloud computing, it is possible to efficiently supply resources and allocate loads. In other words, by appropriately utilizing the processing power of the players constituting P2P as well as the server in the cloud computing environment, MMOG(Massively Multiplayer Online Game) can be configured that considers the scale of economic cost and service quality. In fact, the computing power and communication bandwidth of servers in the cloud are important demand-based resources. The more it is used when renting, the higher the cost, while the quality of service improves. On the other hand, if the player's processing power is utilized a lot, the quality of service deteriorates relatively while the economic cost decreases. In this paper, a bandwidth adjustment technique between servers and players for MMOG based on this hybrid structure is described. When the number of players running at the same time increases, the players' actions are appropriately distributed to servers and players to effectively utilize the server's computing power and communication volume. Simulation results show that in the MMOG based on cloud and P2P hybrid architecture, the bandwidth of the server is proportionally decreased as the bandwidth directly handled by players is increased.

Functional beamforming for high-resolution ultrasound imaging in the air with random sparse array transducer (고해상도 공기중 초음파 영상을 위한 기능성 빔형성법 적용)

  • Choon-Su Park
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.3
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    • pp.361-367
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    • 2024
  • Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.

Numerical Simulation of Dynamic Response of Seabed and Structure due to the Interaction among Seabed, Composite Breakwater and Irregular Waves (II) (불규칙파-해저지반-혼성방파제의 상호작용에 의한 지반과 구조물의 동적응답에 관한 수치시뮬레이션 (II))

  • Lee, Kwang-Ho;Baek, Dong-Jin;Kim, Do-Sam;Kim, Tae-Hyung;Bae, Ki-Seong
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.26 no.3
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    • pp.174-183
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    • 2014
  • Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (II).

Numerical Simulation of Dynamic Response of Seabed and Structure due to the Interaction among Seabed, Composite Breakwater and Irregular Waves (I) (불규칙파-해저지반-혼성방파제의 상호작용에 의한 지반과 구조물의 동적응답에 관한 수치시뮬레이션 (I))

  • Lee, Kwang-Ho;Baek, Dong-Jin;Kim, Do-Sam;Kim, Tae-Hyung;Bae, Ki-Seong
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.26 no.3
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    • pp.160-173
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    • 2014
  • Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (I).

Performance Analysis of Slave-Side Arbitration Schemes for the Multi-Layer AHB BusMatrix (ML-AHB 버스 매트릭스를 위한 슬레이브 중심 중재 방식의 성능 분석)

  • Hwang, Soo-Yun;Park, Hyeong-Jun;Jhang, Kyoung-Son
    • Journal of KIISE:Computer Systems and Theory
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    • v.34 no.5_6
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    • pp.257-266
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    • 2007
  • In On-Chip bus, the arbitration scheme is one of the critical factors that decide the overall system performance. The arbitration scheme used in traditional shared bus is the master-side arbitration based on the request and grant signals between multiple masters and single arbiter. In the case of the master-side arbitration, only one master and one slave can transfer the data at a time. Therefore the throughput of total bus system and the utilization of resources are decreased in the master-side arbitration. However in the slave-side arbitration, there is an arbiter at each slave port and the master just starts a transaction and waits for the slave response to proceed to the next transfer. Thus, the unit of arbitration can be a transaction or a transfer. Besides the throughput of total bus system and the utilization of resources are increased since the multiple masters can simultaneously perform transfers with independent slaves. In this paper, we implement and analyze the arbitration schemes for the Multi-Layer AHB BusMatrix based on the slave-side arbitration. We implement the slave-side arbitration schemes based on fixed priority, round robin and dynamic priority and accomplish the performance simulation to compare and analyze the performance of each arbitration scheme according to the characteristics of the master and slave. With the performance simulation, we observed that when there are few masters on critical path in a bus system, the arbitration scheme based on dynamic priority shows the maximum performance and in other cases, the arbitration scheme based on round robin shows the highest performance. In addition, the arbitration scheme with transaction based multiplexing shows higher performance than the same arbitration scheme with single transfer based switching in an application with frequent accesses to the long latency devices or memories such as SDRAM. The improvements of the arbitration scheme with transaction based multiplexing are 26%, 42% and 51%, respectively when the latency times of SDRAM are 1, 2 and 3 clock cycles.