• Title/Summary/Keyword: numerical stability

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Mathematical Modeling and Simulation for Steady State of a 75-ton Liquid Propellant Rocket Engine (75톤급 액체로켓엔진 정상상태 과정의 수학적 모델링 및 시뮬레이션)

  • Lee, Kyelim;Cha, Jihyoung;Ko, Sangho;Park, Soon-Young;Jung, Eunhwan
    • Journal of Aerospace System Engineering
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    • v.11 no.5
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    • pp.6-12
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    • 2017
  • This paper deals with mathematical modeling of a 75-ton open-cycle Liquid Propellant Rocket Engine (LPRE) and the steady state simulation based on a nominal operating point. Each component of open-cycle LPRE may be classified into seven major categories using thermodynamics and dynamics characteristics. To simplify the simulation model of LPRE in this paper, we used four govern equations with assuming no heat transfer process. We confirmed the mathematical model of LPRE by using the error ratio and comparing the experiment data and simulation data in steady state, and checked the stability with the linearized model. Finally, we demonstrated the simulation model as compared to the transient response of experimental data.

Effect of Kinesiology Taping on Hyolaryngeal Complex Movement in Stroke Patient with Dysphagia

  • Hong, Junyong;Oh, Donghwan;Park, Jisu;Jung, Youngjin
    • Journal of International Academy of Physical Therapy Research
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    • v.11 no.2
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    • pp.2052-2059
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    • 2020
  • Background: Kinesiology taping (KT) is a method that helps immediately increase muscle activation, strength and joint stability by being attached to various skeletal muscles and structures of the body. Objectives: To investigate the effect of KT applied below the hyolaryngeal complex on the movement of the hyolaryngeal complex during swallowing in patients with dysphagia after stroke. Design: One-group, pre-post design. Methods: Twenty individuals with dysphagia after stroke participated in this study. KT was applied to the sternum and both clavicles from the hyolaryngeal complex. We analyzed the motion of the hyolaryngeal complex during swallowing with and placebo KT and KT using the Image-J software with videofluoroscopic swallowing study. In addition, a 0-to-10 numerical rating self-report scale was used to check the required effort and resistance felt during swallowing. Results: KT condition showed that the anterior and superior movement of the hyoid bone during swallowing was significantly lower than placebo KT (P<.05, all). Also, KT condition showed that the anterior and superior movement of the larynx during swallowing was significantly lower than placebo KT (P<.05, all). In result of statistical comparison between KT group and placebo KT group, the KT group showed significantly higher self-report scale score than the placebo KT group in terms of two category; the required effort and resistance felt (P<.05, all). Conclusion: This study demonstrated that KT applied below the hyolaryngeal complex inhibits the anterior and superior movement of hyoid bone and larynx during swallowing of patients with dysphagia after stroke.

Decision Making Process for Wind Barrier Installation Considering Car Accident Risk (차량사고 위험도를 고려한 방풍벽 설치기준)

  • Kim, Dong-Hyun;Lee, Il-Keun;Kwon, Soon-Duck;Jo, Byung-Wan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.1
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    • pp.17-26
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    • 2010
  • This study presents a decision making process for installation of wind barrier which is used to reduce the wind acting on running vehicle on expressway. At the first stage of this study, the lateral deviations of running vehicles under side winds were computed from the commercial softwares, CarSim and TruckSim, and then the critical wind speeds for car accident were evaluated from predefined risk index. To determine whether it is needed to install wind barrier or not, cost and benefit from wind barrier are calculated during lifetime. In obtaining car accidental risk, probabilistic distribution of wind speed, daily traffic volume, mixture ratio in the volume, and duration time for wind speed range are considered. It is recommended to install wind barrier if benefit from the barrier installation exceed construction cost. In the numerical examples, case studies were shown for risk and benefit calculation and main risky regions on Korean highway were all evaluated to identify the number of installation sites.

Flow Analysis of a Engine Manifold with Multiple Injectors Arranged in a Row for Evaluation of Combustion Stability (연소안정성을 평가하기 위한 일렬형 다중 인젝터로 구성된 헤드의 매니폴드 유동해석)

  • Choi, Jiseon;Yu, Isang;Shin, Donghae;Park, Jinsoo;Ko, Youngsung;Kim, Seonjin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.622-627
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    • 2017
  • In this study, the numerical analysis of propellant supply manifold of a sub-scale model combustor with the same combustion and acoustic resonance conditions as the real combustor was carried out. The analysis of the results is based on the shape of the manifold and the number and type of inflow channels. The manifold form of the main propellant was rounded so that the recirculation area was small and easy to manufacture. The liquid oxygen mainfold included a distributor to uniformly supply the flow, and since the kerosene manifold was directly in contact with the flame side, the inflow channel was formed at a radial $360^{\circ}$ so as to minimize the recirculation region. The liquid nitrogen manifold was configured as a radial inflow channel to reduce the velocity difference near the injector.

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Improvements of the CMFD acceleration capability of OpenMOC

  • Wu, Wenbin;Giudicelli, Guillaume;Smith, Kord;Forget, Benoit;Yao, Dong;Yu, Yingrui;Luo, Qi
    • Nuclear Engineering and Technology
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    • v.52 no.10
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    • pp.2162-2172
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    • 2020
  • Due to its computational efficiency and geometrical flexibility, the Method of Characteristics (MOC) has been widely used for light water reactor lattice physics analysis. Usually acceleration methods are necessary for MOC to achieve acceptable convergence on practical reactor physics problems. Among them, Coarse Mesh Finite Difference (CMFD) is very popular and can drastically reduce the number of transport iterations. In OpenMOC, CMFD acceleration was implemented but had the limitation of supporting only a uniform CMFD mesh, which would often lead to splitting MOC source regions, thus creating an unnecessary increase in computation and memory use. In this study, CMFD acceleration with a non-uniform Cartesian mesh is implemented into OpenMOC. We also propose a quadratic fit based CMFD prolongation method in the axial direction to further improve the acceleration when multiple MOC source regions are contained in one CMFD coarse mesh. Numerical results are presented to demonstrate the improvement of the CMFD acceleration capability in OpenMOC in terms of both efficiency and stability.

A Study on the Improvement of Resistance Performance for G/T 4.99ton Class Korean Coastal Fishing Boats (G/T 4.99톤급 한국 연안어선의 저항성능 개선에 관한 연구)

  • Yu, Jin-Won;Lee, Young-Gill;Jee, Hyun-Woo;Park, Ae-Seon;Choi, Young-Chan;Ha, Yoon-Jin;Jeong, Kwang-Leol
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.6
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    • pp.757-762
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    • 2010
  • Korean fishing boats have had appropriate hull forms for the safety, stability and convenience of fishing ability. However, Korean fishermen are recently concerned about the resistance performance and speed of Korean fishing boats, because the prices of fuel oil are gradually risen, also the exhausting of fish resources and the demand of high speed fishing boats are increased. Therefore, the necessity of the study on the improvement of resistance performance for Korean small coastal fishing boats is gradually increased. This study compares the hull form characteristics of Korean fishing boats with those of Japanese fishing boats, and the hull form of a representative Korean fishing boat is modified. From the modification of the hull form parameters for the Korean fishing boat, the improvement of resistance performances is evaluated. Moreover, the increase of resistance performances is also achieved from the modification of local characteristics for the hull form of the Korean fishing boat. A computational method and ship model tests in towing tank are used for the conformations of the improvement of resistance performance.

Numerically Efficient Evaluation of MoM Matrix in Conjunction with the Closed-form Green s Functions in Analysis of Multi-layered Planar Structures (다층 평판구조체 해석시 Closed-form 그린함수와 함께한 모멘트 행렬의 효율적인 수치계산)

  • 이영순;김병철;조영기
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.1
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    • pp.92-98
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    • 2001
  • When analyzing the scatting problem of multi-layered planar structures using closed-form Green's function, one of the main difficulties is that the numerical integrations for the evaluation of diagonal matrix elements converge slowly and are not so stable. Accordingly, even when the integration fur the singularity of type $e^{-jkr}/{\gamma}$, corresponding to the source dipole itself, is performed using such a method, this difficulty persists in the integration corresponding to the finite number of complex images. In order to resolve this difficulty, a new technique based upon the Gaussian quadrature in polar coordinates for the evaluation of the two-dimensional generalized exponential integral is presented. Stability of the algorithm and convergence is discussed. Performance is demonstrated for the example of a microstrip patch antenna.

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Design of the Railbeam Lengths at the Roadbed (철도 레일빔 설계법에 대한 연구)

  • Jung, Hyuksang
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.1
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    • pp.21-28
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    • 2016
  • This paper deals with contents on the estimation of rail beam from the geotechnical engineering aspect. Rail beam is reinforced rail installed on the inside and outside of rail to prevent differential settlement during the construction period of railroad crossing construction. Such rail beam is frequently being installed to ensure stability of existing railroad facilities because of increasing constructions of underground structures crossing railroad in recent. However, there is a difficulty in design due to lack of design standard on rail beam length. Furthermore, derailing accidents are also occurring as a result of rail beam length shortage. Accordingly, this paper presented flow chart based on the classification into soil ground and bedrock ground for the rail beam length estimation. In addition, case study was conducted on rail combination and location through which effective rail combination and location were ensured.

Optimal Location of FACTS Devices Using Adaptive Particle Swarm Optimization Hybrid with Simulated Annealing

  • Ajami, Ali;Aghajani, Gh.;Pourmahmood, M.
    • Journal of Electrical Engineering and Technology
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    • v.5 no.2
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    • pp.179-190
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    • 2010
  • This paper describes a new stochastic heuristic algorithm in engineering problem optimization especially in power system applications. An improved particle swarm optimization (PSO) called adaptive particle swarm optimization (APSO), mixed with simulated annealing (SA), is introduced and referred to as APSO-SA. This algorithm uses a novel PSO algorithm (APSO) to increase the convergence rate and incorporate the ability of SA to avoid being trapped in a local optimum. The APSO-SA algorithm efficiency is verified using some benchmark functions. This paper presents the application of APSO-SA to find the optimal location, type and size of flexible AC transmission system devices. Two types of FACTS devices, the thyristor controlled series capacitor (TCSC) and the static VAR compensator (SVC), are considered. The main objectives of the presented method are increasing the voltage stability index and over load factor, decreasing the cost of investment and total real power losses in the power system. In this regard, two cases are considered: single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC). Using the proposed method, the locations, type and sizes of FACTS devices are obtained to reach the optimal objective function. The APSO-SA is used to solve the above non.linear programming optimization problem for better accuracy and fast convergence and its results are compared with results of conventional PSO. The presented method expands the search space, improves performance and accelerates to the speed convergence, in comparison with the conventional PSO algorithm. The optimization results are compared with the standard PSO method. This comparison confirms the efficiency and validity of the proposed method. The proposed approach is examined and tested on IEEE 14 bus systems by MATLAB software. Numerical results demonstrate that the APSO-SA is fast and has a much lower computational cost.

An Enhanced Reverse-link Traffic Control and its Performance Analysis in cdma2000 1xEV-DO Systems (cdma2000 1xEV-DO 시스템에서 개선된 역방향 트래픽 제어와 성능 분석)

  • Yeo, Woon-Young
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.9A
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    • pp.891-899
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    • 2008
  • The cdma2000 1xEV-DO system controls the data rates of mobile terminals based on a binary overload indicator from the base station and a simple probabilistic model. However, this traffic control scheme has difficulty in controlling the reverse-link traffic load effectively and in guaranteeing a stable operation of the reverse link because each mobile terminal determines the next data rate autonomously. This paper proposes a new trafRc control scheme to improve the system stability, and analyzes the proposed scheme by modeling it as a discrete-time Markov process. The numerical results show that the maximum data rate of the proposed scheme is much higher than that of the conventional one. Moreover, the proposed scheme does not modify the standard physical channel structure, so it is compatible to the existing 1xEV-DO system.