• Title/Summary/Keyword: Nodal

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An Application of Homogenization Theory to the Coarse-Mesh Nodal Calculation of PWRs (PWR 소격격자 Nodal 계산에의 균질화 이론 적용)

  • Myung Hyun Kim;Jonghwa Chang;Kap Suk Moon;Chang Kun Lee
    • Nuclear Engineering and Technology
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    • v.16 no.4
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    • pp.202-216
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    • 1984
  • The success of coarse-mesh nodal solution methods provides strong motivation for finding homogenized parameters which, when used in global nodal calculation, will reproduce exactly all average nodal reaction rates for large nodes. Two approximate theories for finding these ideal parameters, namely, simplified equivalence theory and approximate node equivalence theory, are described herein and then applied to the PWR benchmark problem. Nodal code, ANM, is used for the global calculation as well as for the homogenization calculation. From the comparative analysis, it is recommended that homogenization be carried out only for the unique type of fuel assemblies and for core boundary color-sets. The use of approximate homogenized cross-sections and approximate discontinuity factors predicts nodal powers with maximum error of 0.8% and criticality within 0.1% error relative to the fine-mesh KIDD calculations.

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A Relative for Finite Element Nonlinear Structural Analysis (상대절점좌표를 이용한 비선형 유한요소해석법)

  • Kang, Ki-Rang;Cho, Heui-Je;Bae, Dae-Sung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.788-791
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    • 2005
  • Nodal displacements are referred to the Initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian formulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid fer structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One closed loop structure undergoing large deformations is analyzed to demonstrate the efficiency and validity of the proposed method.

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Nodal Transport Methods Using the Simplified Even-Parity Neutron Transport Equation (단순 우성 중성자 수송방정식을 이용한 노달 수송해법)

  • Noh, Taewan
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.16 no.2
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    • pp.211-221
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    • 2018
  • Nodal transport methods are proposed for solving the simplified even-parity neutron transport (SEP) equation. These new methods are attributed to the success of existing nodal diffusion methods such as the Polynomial Expansion Nodal and the Analytic Function Expansion Nodal Methods, which are known to be very effective for solving the neutron diffusion equation. Numerical results show that the simplified even-parity transport equation is a valid approximation to the transport equation and that the two nodal methods developed in this study also work for the SEP transport equation, without conflict. Since accuracy of methods is easily increased by adding node unknowns, the proposed methods will be effective for coarse mesh calculation and this will also lead to computation efficiency.

Factors Affecting the Production of In Vitro Plants from the Nodal Pieces of Chinese Yam (Dioscorea Opposita Thunb)

  • Shin, Jong-Hee;Kim, Sang-Kuk;Kwon, Jung-Bae;Lee, Bong-Ho;Sohn, Jae-Keun
    • Journal of Plant Biotechnology
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    • v.6 no.2
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    • pp.97-102
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    • 2004
  • This study was carried out to establish The regeneration of healthy seedlings from the nodal segment culture of Chinese yam (Dioscorea opposita cv. Danma), cultivated in Korea. Different explants such as leaves, petioles, roots and nodal pieces, excised from the in vitro grown seedlings of Chinese yam, were cultured on MS medium supplemented with various combinations of growth regulators. All the growth regulators used induced plantlet regeneration from the nodal segments at a high frequency, while there was no induction of shoot or callus from leaf, petiole or root tissues. The medium supplemented with 0.01mg/L NAA, 0.5mg/L BA, 0.5-1.0mg/L kinetin and without plant growth regulator was effective for shoot development of buds from the nodal segment culture. The concentration of BA and NAA was an important factor in the bud induction of buds from the nodal segments of Chinese yam. Nodal segments cultured on the medium containing 1.0mg/L NAA and 0.5-1.0mg/L BA gave the best response to bud formation. The addition of GA$_3$ to the culture medium suppressed shoot induction and growth, while it increased microtuber formation. The shoot growth and microtuber formation were also affected by medium strength and solidity. The MS basal medium containing 1 g/L gelrite was suitable for microtuber formation from the nodal segment of Chinese yam.

Patterns of failure after the reduced volume approach for elective nodal irradiation in nasopharyngeal carcinoma

  • Seol, Ki Ho;Lee, Jeong Eun
    • Radiation Oncology Journal
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    • v.34 no.1
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    • pp.10-17
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    • 2016
  • Purpose: To evaluate the patterns of nodal failure after radiotherapy (RT) with the reduced volume approach for elective neck nodal irradiation (ENI) in nasopharyngeal carcinoma (NPC). Materials and Methods: Fifty-six NPC patients who underwent definitive chemoradiotherapy with the reduced volume approach for ENI were reviewed. The ENI included retropharyngeal and level II lymph nodes, and only encompassed the echelon inferior to the involved level to eliminate the entire neck irradiation. Patients received either moderate hypofractionated intensity-modulated RT for a total of 72.6 Gy (49.5 Gy to elective nodal areas) or a conventional fractionated three-dimensional conformal RT for a total of 68.4-72 Gy (39.6-45 Gy to elective nodal areas). Patterns of failure, locoregional control, and survival were analyzed. Results: The median follow-up was 38 months (range, 3 to 80 months). The out-of-field nodal failure when omitting ENI was none. Three patients developed neck recurrences (one in-field recurrence in the 72.6 Gy irradiated nodal area and two in the elective irradiated region of 39.6 Gy). Overall disease failure at any site developed in 11 patients (19.6%). Among these, there were six local failures (10.7%), three regional failures (5.4%), and five distant metastases (8.9%). The 3-year locoregional control rate was 87.1%, and the distant failure-free rate was 90.4%; disease-free survival and overall survival at 3 years was 80% and 86.8%, respectively. Conclusion: No patient developed nodal failure in the omitted ENI site. Our investigation has demonstrated that the reduced volume approach for ENI appears to be a safe treatment approach in NPC.

Surgical Treatment of Wolff-Parkinson-White Syndrome Combined with AV Nodal Reentrant achycardia in a Patient with Ebstein`s Anomaly - A report of one case - (Ebstein씨 심기형에 동반된 Wolff-Parkinson-White 증후군 및 방실결절 회귀성 빈맥에 대한 수술치험 1례 보고)

  • 장병철
    • Journal of Chest Surgery
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    • v.23 no.1
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    • pp.205-212
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    • 1990
  • A 17 year old female patient with Ebstein`s anomaly received surgical treatment for WPW syndrome and AV nodal reentrant supraventricular tachycardia[SVT] Electrophysiologic study revealed that an anomalous pathway was located in the right posterolateral portion and antegrade dual AV nodal pathway responsible for AV nodal reentrant tachycardia. The patient was underwent surgery on February 18, 1987. Intraoperative mapping was used to define the location of accessory pathway. The accessory pathway was cryoablated through the epicardium. Simultaneously discrete cryoablation around the perinodal area was performed to prevent AV nodal reentrant SVT. The atrialized right ventricle of Ebstein`s anomaly was plicated with 11 pledget mattress sutures under the cardiopulmonary bypass. Two and half years after surgery, the patient has no evidence of WPW syndrome or supraventricular tachycardia.

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Study on the Dynamic Analysis Method using the Modal Coordinates and the Absolute Nodal Coordinates (모드좌표와 절대절점좌표를 혼용한 동역학 해석기법에 관한 연구)

  • Sohn, Jeon-Hyun;Yoo, Wan-Suk
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1730-1735
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    • 2003
  • In this paper, the absolute nodal coordinate formulation was introduced to describe the large deformation problems. And also, the modal coordinates were employed to represent the small elastic deformation. A new hybrid formulation was developed to combine the modal coordinates and the absolute nodal coordinates. A spherical joint and the DOT1 constraint were developed to carry out the numerical simulation of mechanical systems with kinematic joints. A beam example was suggested to show the new formulation. The simulation results using the modal coordinates and the absolute nodal coordinates show a good agreement to the experiments.

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Development of a Consistent General Order Nodal Method for Solving the Three-Dimensional, Multigroup Neutron Diffusion Equation

  • Kim, Hyun-Dae-;Oh, Se-Kee
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • 1993.11a
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    • pp.99-102
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    • 1993
  • A consistent general order nodal method for solving the three-dimensional neutron diffusion equation in (x-y-z) geometry has been derived by using a weighted integral technique and expanding the spatial variable by the Legendre orthogonal series function. The equation set derived can be converted into any order nodal schemes. It forms a compact system for general order of nodal moments. The method utilizes fewer unknown variables in the schemes for iterative-convergence solution than other nodal methods listed in the literatures, and because the method utilizes the analytic solutions of the transverse-integrated one dimensional equations and a consistent approximation for a given spatial variable through all the solution procedures, which renders the use of an approximation for the transverse leakages no longer necessary, we can expect extremely accurate solutions and the solution would converge exactly when the mesh width is decreased or the approximation order is increased.

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Optimum Alignment of Marine Engine Shaftings by the Finite Element Method (有限要素法에 의한 舶用機關軸系裝置의 最適配置에 關한 硏究)

  • Jeon, Hio-Jung;Park, Jin-Gil;Choi, Jae-Sung
    • Journal of Advanced Marine Engineering and Technology
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    • v.2 no.1
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    • pp.3-14
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    • 1978
  • The authors have developed a calculating method of propeller shaft alignment by the finite element method. The propeller shaft is divided into finite elements which can be treated as uniform section bars. For each element, the nodal point equation is derived from the stiffness matrix, the external force vector and the section force vector. Then the overall nodal point equation is derived from the element nodal point equation. The deflection, offset, bending moment and shearing force of each nodal point are calculated from the overall nodal point equation by the digital computer. Reactions and deflections of supporting points of straight shaft are calculated and also the reaction influence number is derived. With the reaction influence number the optimum alignment condition that satisfies all conditions is calculated by the simplex method of linear programming. All results of calculation are compared with those of Det norske Veritas, which has developed a computor program based on the three-moment theorem of the strength of materials. The authors finite element method has shown good results and will be used effectively to design the propeller shaft alignment.

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Development of the Discrete-Ordinates, Nodal Transport Methods Using the Simplified Even-Parity Neutron Transport Equation

  • Noh, Taewan
    • Nuclear Engineering and Technology
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    • v.32 no.6
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    • pp.605-617
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    • 2000
  • Nodal transport methods are studied for the solution of two dimensional discrete-ordinates, simplified even-parity transport equation(SEP) which is known to be an approximation to the true transport equation. The polynomial expansion nodal method(PEN) and the analytic function expansion nodal method(AFEN)which have been developed for the diffusion theory are used for the solution of the discrete-ordinates form of SEP equation. Our study shows that while the PEN method in diffusion theory can directly be converted without complication, the AFEN method requires a theoretical modification due to the nonhomogeneous property of the transport equation. The numerical results show that the proposed two methods work well with the SEP transport equation with higher accuracies compared with the conventional finite difference method.

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