• Title/Summary/Keyword: Simulation Test

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Radio transmission link design based on a test bed considering a multi-beam active phase array antenna (다중빔 능동위상배열 안테나를 고려한 테스트베드 기반 Radio 전송링크 설계)

  • Youn, Jong-Taek;Kim, Yongi;Park, Hongjun;Park, Juman
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.25 no.11
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    • pp.1574-1580
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    • 2021
  • This paper designs and presents the results of an air network simulation radio transmission link applied with a multi-beam active phase array antenna simulator in a testbed system for verifying an air network currently underway as a technology development task. Using the Ku band, the Radio transmission link was designed in consideration of the link budget to satisfy the requirements for the system being developed. Considering short-distance links and long-distance links, the required EIRP and G/T performance scales of multi-beam repeaters and mission planes were applied to confirm the minimum and maximum link margins based on Eb/No. In this Radio Transmission Link design, the application analysis results such as rainfall availability are used to effectively establish standards when selecting the operating radius of the multi-beam relay system and related system standards.

Development of DC/DC Converters and Actual Vehicle Simulation Experiment for 150 kW Class Fuel-cell Electric Vehicle (150kW급 수소연료전지 차량용 DC/DC 컨버터 개발 및 실차모사 실험)

  • Kim, Sun-Ju;Jeong, Hyeonju;Choi, Sewan;Cho, Jun-Ho;Jeon, Yujong;Park, Jun-Sung;Yoon, Hye-Sung
    • The Transactions of the Korean Institute of Power Electronics
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    • v.27 no.1
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    • pp.26-32
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    • 2022
  • This paper proposes a power system that includes a 120k W fuel cell DC-DC converter (FDC) and 30 kW bidirectional DC-DC converter (BHDC) for a 150 kW fuel-cell vehicle. With a high DC link voltage of 800 V, the efficiency and power density of the power electronic components are improved. Through the modular design of FDC and BHDC, electric components are shared, resulting in reduced mass production costs. The switching frequency of 30 kHz of full SiC devices and optimal design of coupled inductor reduce the volume, achieving a power density of 8.3 kW/L. Furthermore, a synergetic operation strategy using variable limiter control of FDC and BHDC was proposed to efficiently operate the fuel cell vehicle considering the fuel cell stack efficiency according to the load. Finally, the performance of the prototype was verified by Highway Fuel Economy Driving Schedule testing, EMI test, and the linked operation between FDC and BHDC. The full load efficiencies of the FDC and BHDC prototypes are 98.47% and 98.74%, respectively.

Simulation and Health Risk Evaluation of Indoor Air Quality Changes by Ventilation System in New Apartment (신축아파트 환기방식에 따른 실내공기질 변화와 이에 대한 시뮬레이션 및 건강 위해성 평가)

  • Bao, Wei;Jung, Jaeyoun;Jeong, Insoo
    • Journal of the Korean Institute of Rural Architecture
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    • v.23 no.4
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    • pp.38-45
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    • 2021
  • In this study, air quality conditions were identified and analyzed in real time, at the same time, living habits and ventilation methods were maintained in the daily life of residents, and thus, this present study focuses on the lifestyles of residents. Previous studies showed a difference from this study, focusing on the study on the effects of changes in indoor air quality on human health according to the indoor air quality process test standards of the Ministry of Environment. Formaldehyde concentrations exceeded all ventilation standards, but satisfied the organic standards of the Ministry of Environment when ventilation devices and air purifiers were activated. As such, it was investigated that a large amount of formaldehyde emission in the condo is initially ventilated, but a certain concentration is maintained. The change in PM2.5 concentration according to the ventilation method showed a clear difference. As a result of simulating indoor air flow during natural ventilation, the effects of wind speed and wind direction affect the flow rate of indoor air, and indoor polluted air is stagnant even in the presence of wind and is not completely discharged. When the risk assessment results are averaged on the day of measurement, the trends of change between adults and children are almost equivalent, but the results address that children are more sensitive to risk than adults.

Development and Characterization of an Atmospheric Turbulence Simulator Using Two Rotating Phase Plates

  • Joo, Ji Yong;Han, Seok Gi;Lee, Jun Ho;Rhee, Hyug-Gyo;Huh, Joon;Lee, Kihun;Park, Sang Yeong
    • Current Optics and Photonics
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    • v.6 no.5
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    • pp.445-452
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    • 2022
  • We developed an adaptive optics test bench using an optical simulator and two rotating phase plates that mimicked the atmospheric turbulence at Bohyunsan Observatory. The observatory was reported to have a Fried parameter with a mean value of 85 mm and standard deviation of 13 mm, often expressed as 85 ± 13 mm. First, we fabricated several phase plates to generate realistic atmospheric-like turbulence. Then, we selected a pair from among the fabricated phase plates to emulate the atmospheric turbulence at the site. The result was 83 ± 11 mm. To address dynamic behavior, we emulated the atmospheric disturbance produced by a wind flow of 8.3 m/s by controlling the rotational speed of the phase plates. Finally, we investigated how closely the atmospheric disturbance simulation emulated reality with an investigation of the measurements on the optical table. The verification confirmed that the simulator showed a Fried parameter of 87 ± 15 mm as designed, but a little slower wind velocity (7.5 ± 2.5 m/s) than expected. This was because of the nonlinear motion of the phase plates. In conclusion, we successfully mimicked the atmospheric disturbance of Bohyunsan Observatory with an error of less than 10% in terms of Fried parameter and wind velocity.

The importance of corner sharpness in the BARC test case: A numerical study

  • Chiarini, Alessandro;Quadrio, Maurizio
    • Wind and Structures
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    • v.34 no.1
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    • pp.43-58
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    • 2022
  • The BARC flow is studied via Direct Numerical Simulation at a relatively low turbulent Reynolds number, with focus on the geometrical representation of the leading-edge (LE) corners. The study contributes to further our understanding of the discrepancies between existing numerical and experimental BARC data. In a first part, rounded LE corners with small curvature radii are considered. Results show that a small amount of rounding does not lead to abrupt changes of the mean fields, but that the effects increase with the curvature radius. The shear layer separates from the rounded LE at a lower angle, which reduces the size of the main recirculating region over the cylinder side. In contrast, the longitudinal size of the recirculating region behind the trailing edge (TE) increases, as the TE shear layer is accelerated. The effect of the curvature radii on the turbulent kinetic energy and on its production, dissipation and transport are addressed. The present results should be contrasted with the recent work of Rocchio et al. (2020), who found via implicit Large-Eddy Simulations at larger Reynolds numbers that even a small curvature radius leads to significant changes of the mean flow. In a second part, the LE corners are fully sharp and the exact analytical solution of the Stokes problem in the neighbourhood of the corners is used to locally restore the solution accuracy degraded by the singularity. Changes in the mean flow reveal that the analytical correction leads to streamlines that better follow the corners. The flow separates from the LE with a lower angle, resulting in a slightly smaller recirculating region. The corner-correction approach is valuable in general, and is expected to help developing high-quality numerical simulations at the high Reynolds numbers typical of the experiments with reasonable meshing requirements.

Impact response of a novel flat steel-concrete-corrugated steel panel

  • Lu, Jingyi;Wang, Yonghui;Zhai, Ximei;Zhou, Hongyuan
    • Steel and Composite Structures
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    • v.42 no.2
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    • pp.277-288
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    • 2022
  • A novel flat steel plate-concrete-corrugated steel plate (FS-C-CS) sandwich panel was proposed for resisting impact load. The failure mode, impact force and displacement response of the FS-C-CS panel under impact loading were studied via drop-weight impact tests. The combined global flexure and local indentation deformation mode of the FS-C-CS panel was observed, and three stages of impact process were identified. Moreover, the effects of corrugated plate height and steel plate thickness on the impact responses of the FS-C-CS panels were quantitatively analysed, and the impact resistant performance of the FS-C-CS panel was found to be generally improved on increasing corrugated plate height and thickness in terms of smaller deformation as well as larger impact force and post-peak mean force. The Finite Element (FE) model of the FS-C-CS panel under impact loading was established to predict its dynamic response and further reveal its failure mode and impact energy dissipation mechanism. The numerical results indicated that the concrete core and corrugated steel plate dissipated the majority of impact energy. In addition, employing end plates and high strength bolts as shear connectors could prevent the slip between steel plates and concrete core and assure the full composite action of the FS-C-CS panel.

Design and Implementation of IoT Platform-based Digital Twin Prototype (IoT 플랫폼 기반 디지털 트윈 프로토타입 설계 및 구현)

  • Kim, Jeehyeong;Choi, Wongi;Song, Minhwan;Lee, Sangshin
    • Journal of Broadcast Engineering
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    • v.26 no.4
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    • pp.356-367
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    • 2021
  • With the recent development of IoT and artificial intelligence technology, research and applications for optimization of real-world problems by collecting and analyzing data in real-time have increased in various fields such as manufacturing and smart city. Representatively, the digital twin platform that supports real-time synchronization in both directions with the virtual world digitized from the real world has been drawing attention. In this paper, we define a digital twin concept and propose a digital twin platform prototype that links real objects and predicted results from the virtual world in real-time by utilizing the oneM2M-based IoT platform. In addition, we implement an application that can predict accidents from object collisions in advance with the prototype. By performing predefined test cases, we present that the proposed digital twin platform could predict the crane's motion in advance, detect the collision risk, perform optimal controls, and that it can be applied in the real environment.

Experimental and numerical investigation of closure time during artificial ground freezing with vertical flow

  • Jin, Hyunwoo;Go, Gyu-Hyun;Ryu, Byung Hyun;Lee, Jangguen
    • Geomechanics and Engineering
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    • v.27 no.5
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    • pp.433-445
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    • 2021
  • Artificial ground freezing (AGF) is a commonly used geotechnical support technique that can be applied in any soil type and has low environmental impact. Experimental and numerical investigations have been conducted to optimize AGF for application in diverse scenarios. Precise simulation of groundwater flow is crucial to improving the reliability these investigations' results. Previous experimental research has mostly considered horizontal seepage flow, which does not allow accurate calculation of the groundwater flow velocity due to spatial variation of the piezometric head. This study adopted vertical seepage flow-which can maintain a constant cross-sectional area-to eliminate the limitations of using horizontal seepage flow. The closure time is a measure of the time taken for an impermeable layer to begin to form, this being the time for a frozen soil-ice wall to start forming adjacent to the freeze pipes; this is of great importance to applied AGF. This study reports verification of the reliability of our experimental apparatus and measurement system using only water, because temperature data could be measured while freezing was observed visually. Subsequent experimental AFG tests with saturated sandy soil were also performed. From the experimental results, a method of estimating closure time is proposed using the inflection point in the thermal conductivity difference between pore water and pore ice. It is expected that this estimation method will be highly applicable in the field. A further parametric study assessed factors influencing the closure time using a two-dimensional coupled thermo-hydraulic numerical analysis model that can simulate the AGF of saturated sandy soil considering groundwater flow. It shows that the closure time is affected by factors such as hydraulic gradient, unfrozen permeability, particle thermal conductivity, and freezing temperature. Among these factors, changes in the unfrozen permeability and particle thermal conductivity have less effect on the formation of frozen soil-ice walls when the freezing temperature is sufficiently low.

Adaptive Packet Transmission Interval for Massively Multiplayer Online First-Person Shooter Games

  • Seungmuk, Oh;Yoonsik, Shim
    • Journal of the Korea Society of Computer and Information
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    • v.28 no.2
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    • pp.39-46
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    • 2023
  • We present an efficient packet transmission strategy for massively multiplayer online first-person shooter (MMOFPS) games using movement-adaptive packet transmission interval. The player motion in FPS games shows a wide spectrum of movement variability both in speed and orientation, where there is room for reducing the number of packets to be transmitted to the server depending on the predictability of the character's movement. In this work, the degree of variability (nonlinearity) of the player movements is measured at every packet transmission to calculate the next transmission time, which implements the adaptive transmission frequency according to the amount of movement change. Server-side prediction with a few auxiliary heuristics is performed in concert with the incoming packets to ensure reliability for synchronizing the connected clients. The comparison of our method with the previous fixed-interval transmission scheme is presented by demonstrating them using a test game environment.

Properties of Grout Material for Seawall Using Slags from Steel Making Industry (철강산업부산물을 사용한 방조제용 그라우트 재료 및 그 특성)

  • Ha-Seog, Kim;Kee-Seok, Kim;Bong-Hyun, Baek;Sim-Hoon, Yook
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.4
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    • pp.523-530
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    • 2022
  • The problem in the construction of seawall reinforcing the seawall where there is seawater flow is the outflow of materials. Gravity-type pouring of concrete is difficult to fill the voids smoothly, and the cement of concrete that has not hardened is likely to be dispersed in seawater. This phenomenon not only reduces the reliability of quality after concrete hardening, but can also adversely affect the surrounding environment. Therefore, there is a need for a gel-like injection material that can be injected, In this study, the initial strength and durability improvement effect of seawater immersion were evaluated by using electrofurnace reduction slag and blast furnace slag with acute properties. As a result of the experiment, it was possible to prepare a gel-like injection material having flowability through reaction with silica-based chemical liquid. The flowability of the gel is 105~143 mm depending on the formulation, and the on-site simulation test can fill the voids without external leakage, confirming its on-site applicability.