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Boosting the Performance of Python-based Geodynamic Code using the Just-In-Time Compiler (Just-In-Time 컴파일러를 이용한 파이썬 기반 지구동역학 코드 가속화 연구)

  • Park, Sangjin;An, Soojung;So, Byung-Dal
    • Geophysics and Geophysical Exploration
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    • v.24 no.2
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    • pp.35-44
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    • 2021
  • As the execution speed of Python is slower than those of other programming languages (e.g., C, C++, and FORTRAN), Python is not considered to be efficient for writing numerical geodynamic code that requires numerous iterations. Recently, many computational techniques, such as the Just-In-Time (JIT) compiler, have been developed to enhance the calculation speed of Python. Here, we developed two-dimensional (2D) numerical geodynamic code that was optimized for the JIT compiler, based on Python. Our code simulates mantle convection by combining the Particle-In-Cell (PIC) scheme and the finite element method (FEM), which are both commonly used in geodynamic modeling. We benchmarked well-known mantle convection problems to evaluate the reliability of our code, which confirmed that the root mean square velocity and Nusselt number obtained from our numerical modeling were consistent with those of the mantle convection problems. The matrix assembly and PIC processes in our code, when run with the JIT compiler, successfully achieved a speed-up 30× and 258× faster than without the JIT compiler, respectively. Our Python-based FEM-PIC code shows the high potential of Python for geodynamic modeling cases that require complex computations.

Fabrication of Radar Absorbing Shells Made of Hybrid Composites and Evaluation of Radar Cross Section (하이브리드 복합재를 이용한 레이더 흡수 쉘의 제작 및 레이더 단면적 평가)

  • Jung, Woo-Kyun;Ahn, Sung-Hoon;Ahn, Bierng-Chearl;Park, Seoung-Bae;Won, Myung-Shik
    • Composites Research
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    • v.19 no.1
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    • pp.29-35
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    • 2006
  • The avoidance of enemy's radar detection is very important issue in the modem electronic weapon system. Researchers have studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), 'C'-type shell and 'U'-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

A Fundamental Study on the Fracture Mechanism of Steel Plates under Completely Alternating Load (완전교번하중하(完全交番荷重下)에서의 강판(鋼板)의 파괴기구(破壞機構)에 관한 기차적(基磋的) 연구(研究))

  • Chang, Dong Il;Chung, Yeong Wha
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.2 no.3
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    • pp.1-13
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    • 1982
  • Transition process of plastic region. displacements, stresses and strains ahead the flaw tips were analysed by the finite element method on the steel plate with the circular hole and the one with the elliptical hole under completely alternating load (repetition of tensile loading, unloading and compressive loading). As the results, the followings were obtained. Transition process of elastic failure (yielding) region was estimated. From this the tendency was confirmed that the fracture would be initiated from ahead the flaw tip, and propagated along the 45 direction. The fundamental data available in estimating the stress intensity factor that was considered as the core in analysing the fracture mechanism of steel plates were obtained. It was indicated that when unloading after tension the effect of compressive loading, and even the compressive reyield, was occured ahead the flaw tip. Similarly it was indicated that when unloading after compression the effect of tensile loading, and even the tensile reyield, was occured ahead the flaw tip. It was considered that these phenomena were occured because the unloading effect was constrained by the residual strains when unloading. It was considered that the fatigue phenomenon was occured ahead, the flaw tip by repetition of tensile yield, the above compressive reyield, compressive yeild and the above tensile reyield. In addition, the tendency was confirmed that the fracture ahead the flaw tip was occured as the flaw was changed from the circular hole to the elliptical hole and became to be the crack lastly.

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Thermo-mechanical Behavior Characteristic Analysis of B2it(Buried Bump Interconnection Technology) in PCB(Printed Circuit Board) (인쇄회로기판 B2it(Buried Bump Interconnection Technology) 구조의 열적-기계적 거동특성 해석)

  • Cho, Seung-Hyun;Chang, Tae-Eun
    • Journal of the Microelectronics and Packaging Society
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    • v.16 no.2
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    • pp.43-50
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    • 2009
  • Although thin PCBs(Printed Circuit Boards) have recently been required for high density interconnection, high electrical performance, and low manufacturing cost, the utilization of thin PCBs is severely limited by warpage and reliability issues. Warpage of the thin PCB leads to failure in solder-joints and chip. The B2it(Buried Bump Interconnection Technology) for PCB has been developed to achieve a competitive manufacturing price. In this study, chip temperature, package warpage, chip stress and solder-joints stress characteristics of the PCB prepared with B2it process have been calculated using thermo-mechanical coupled analysis by the FEM(Finite Element Method). FEM computation was carried out with the variations in bump shapes and kinds of materials under 1.5W power of chip and constant convection heat transfer. The results show that chip temperature distribution reached more quickly steady-state status with PCB prepared with B2it process than PCB prepared with conventional via interconnection structure. Although B2it structures are effective on low package warpage and chip stress, with high strength bump materials arc disadvantage for low stress of solder-joints. Therefore, it is recommended that optimized bump shapes and materials in PCB design should be considered in terms of reliability characteristics in the packaging level.

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MPI-OpenMP Hybrid Parallelization for Multibody Peridynamic Simulations (다물체 페리다이나믹 해석을 위한 MPI-OpenMP 혼합 병렬화)

  • Lee, Seungwoo;Ha, Youn Doh
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.3
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    • pp.171-178
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    • 2020
  • In this study, we develop MPI-OpenMP hybrid parallelization for multibody peridynamic simulations. Peridynamics is suitable for analyzing complicated dynamic fractures and various discontinuities. However, compared with a conventional finite element method, nonlocal interactions in peridynamics cost more time and memory. In multibody peridynamic analysis, the costs increase due to the additional interactions that occur when computing the nonlocal contact and ghost interlayer models between adjacent bodies. The costs become excessive when further refinement and smaller time steps are required in cases of high-velocity impact fracturing or similar instances. Thus, high computational efficiency and performance can be achieved by parallelization and optimization of multibody peridynamic simulations. The analytical code is developed using an Intel Fortran MPI compiler and OpenMP in NURION of the KISTI HPC center and parallelized through MPI-OpenMP hybrid parallelization. Further parallelization is conducted by hybridizing with OpenMP threads in each MPI process. We also try to minimize communication operations by model-based decomposition of MPI processes. The numerical results for the impact fracturing of multiple bodies show that the computing performance improves significantly with MPI-OpenMP hybrid parallelization.

Nonlinear Analysis of Shear Behavior on Pile-Sand Interface Using Ring Shear Tests (링전단시험을 이용한 말뚝 기초-사질지반 간 인터페이스 거동 분석)

  • Jeong, Sang-Seom;Jung, Hyung-Suh;Whittle, Andrew;Kim, Do-Hyun
    • Journal of the Korean Geotechnical Society
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    • v.37 no.5
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    • pp.5-17
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    • 2021
  • In this study, the shear behavior between pile-sandy soil interface was quantified based on series of rigorous ring shear test results. Ring shearing test was carried out to observe the shear behavior prior to failure and behavior at residual state between most commonly used pile materials - steel and concrete - and Jumunjin sand. The test was set to clarify the shear behavior under various confinement conditions and soil densities. The test results were converted in to representative friction angles for various test materials. Additional numerical analysis was executed to validate the accuracy of the test results. Based on the test results and the numerical validation, it was found that due to the dilative and contractive nature of sand, its interface behavior can be categorized in to two different types : soils with higher densities tend to show peak shear stress and moves on to residual state, while on the other hand, soils with lower densities tend to show bilinear load-transfer curves along the interface. However, the relative density and the confining stress was found to affect the friction angle only in the small train range, and converges as it progresses to large deformation. This study established a large deformation analysis method which can successfully simulate and predict the large deformation behavior such as ring shear tests. Moreover, the friction angle derived from the ring shear test result and verified by numerical analysis can be applied to numerical analysis and actual design of various pile foundations.

Numerical Simulation of Convection-dominated Flow Using SU/PG Scheme (SU/PG 기법을 이용한 이송이 지배적인 흐름 수치모의)

  • Song, Chang Geun;Seo, Il Won
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.3B
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    • pp.175-183
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    • 2012
  • In this study, Galerkin scheme and SU/PG scheme of Petrov-Galerkin family were applied to the shallow water equations and a finite element model for shallow water flow was developed. Numerical simulations were conducted in several flumes with convection-dominated flow condition. Flow simulation of channel with slender structure in the water course revealed that Galerkin and SU/PG schemes showed similar results under very low Fr number and Re number condition. However, when the Fr number increased up to 1.58, Galerkin scheme did not converge while SU/PG scheme produced stable solutions after 5 iterations by Newton-Raphson method. For the transcritical flow simulation in diverging channel, the present model predicted the hydraulic jump accurately in terms of the jump location, the depth slope, and the flow depth after jump, and the numerical results showed good agreements with the hydraulic experiments carried out by Khalifa(1980). In the oblique hydraulic jump simulation, in which convection-dominated supercritical flow (Fr=2.74) evolves, Galerkin scheme blew up just after the first iteration of the initial time step. However, SU/PG scheme captured the boundary of oblique hydraulic jump accurately without numerical oscillation. The maximum errors quantified with exact solutions were less than 0.2% in water depth and velocity calculations, and thereby SU/PG scheme predicted the oblique hydraulic jump phenomena more accurately compared with the previous studies (Levin et al., 2006; Ricchiuto et al., 2007).

A Study on the Measurement of Axial Cracks in the Magnetic Flux Leakage NDT System (자기누설 비파괴 검사 시스템에서 축방향 미소결함 측정에 관한 연구)

  • Kim, Hui-Min;Park, Gwan-Soo;Rho, Yong-Woo;Yoo, Hui-Ryong;Cho, Sung-Ho;Kim, Dong-Kyu;Koo, Sung-Ja
    • Journal of the Korean Magnetics Society
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    • v.22 no.2
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    • pp.49-57
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    • 2012
  • From among the NDT (Non-Destructive Testing) methods, the MFL (Magnetic Flux Leakage) PIG (Pipeline Inspection Gauge) is especially suitable for testing pipelines because the pipeline has high magnetic permeability. MFL PIG showed high performance in detecting the metal loss and corrosions. However, MFL PIG is difficult to detect the crack which occured by exterior-interior pressure difference in pipelines and the shape of crack is very long and narrow. Therefore, the new PIG is needed to be researched and developed for detecting the cracks. The CMFL (Circumferential MF) PIG performs magnetic fields circumferentially and can maximize the magnetic flux leakage at the cracks. In this paper, CMFL PIG is designed and the distribution of the magnetic fields is analyzed by using 3 dimensional nonlinear finite element method (FEM). By Simulating and Measuring the magnetic leakage field, it is possible to detect of axial cracks in the pipeline.

A Study of Tire Curing Bladder shaping by Using Finite Element Method (유한요소법을 이용한 타이머 Curing Bladder Shaping엔 관한 연구)

  • 김천식;김항우
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1992.10a
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    • pp.3-3
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    • 1992
  • 타이어 Curing공정은 공기압 타이어의 제조시 상당히 정교한 단계를 거쳐서 이루어지며, 이는 타이어 설계에 큰 영향을 줄 뿐만아니라, 타이어의 성능에도 관건이 있다. 본 연구에서는 유한요소법을 이용하여 타이어의 molding 공정을 분석하였다. 유한요소해석 프로그램인 MARC가 Cured 타이어 내부의 Curing Bladder 팽창과정해석에 이용되었다. 비압축성 요소로 Curing Bladder를 모형화하였으며, MARC의 접촉문제해석기법(contact option)을 이용하여 Cured 타이어 내부와 Curing Bladder 외부의 접촉부위를 Simulation하였다. 본 연구의 주요 관심내용으로서는 Curing Bladder의 형상변화에 따른 Curing Bladder의 팽창거동해석과, Cured타이어와 Curing Bladder의 접촉부위에서 얻을 수 있는 접촉압력의 비교.검토이다. 타이어 Curing시 타이어와 Bladder의 Contact과정을 해석하여, 아래와 같은 결과를 도출하였다. Bladder의 형상은 Cylinderical 형상 보다는 Toroidal 형태가 접촉압 분포의 균일성 및 크기 측면에 서 우수한 것으로 판단된다. Curing Bladder의 증심선 부위 보다 이에서 약간 떨어진 부위에서 최대 접촉압력이 발생되며, 이는 타이어 내면의 굴곡현상과 깊은 관련이 있윰 것으로 사료된다. 타이어 Bead부의 Carcass 자연평형현상이 유지된 제품을 얻기위해서는, Side-Bead구간의 접촉압력 증가가 필요하며, 이를 위하여는 Bladder 형상이 Cylinderical 보다는 Toroidal 형태가 유리하고, Bead부의 Gage Down, 전체직경의 증가 및 높이의 증가가 유리한 것으로 판단된다. 본 연구 결과를 이용하여, 타이어 Curing과정에서 발생되는 불량제품의 원인파악 및 타이어 설계자가 원하는 제품생산의 불가능한 원인을 파악하는데 도움을 줄 것이다.를 C의 structure와 pointer를 기반으로 하게끔 변경시키고 이에 따르는 제반 변경 사항을 수정 보완하여 프로그램의 분석을 용이하게 하며 기능의 변경 및 추가가 수월하게 하였고 메모리를 동적으로 관리할 수 있게 하였다. 또한 기존의 smpl에 디버깅용 함수 및 설비(facility) 제어용 함수를 추가하여 시뮬레이션 프로그램 작성을 용이하게 하였다. 예를 들면 who_server(), who_queue(), pop_Q(), push_Q(), pop_server(), push_server(), we(), wf(), printfct() 같은 함수들이다. 또한 동시에 발생되는 사건들의 순서를 조종하기 위해, 동시에 발생할 수 있는 각각의 사건에 우선순위를 두어 이 우선 순위에 의하여 사건 리스트(event list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스템에 대한 시뮬레이션 구현과 시스템 분석의 예를 보인다._3$", chain segment, with the activation energy of carriers from the shallow trap with 0.4[eV], in he amorphous regions.의 증발산율은 우기의 기상자료를 이용하여 구한 결과 0.05 - 0.10 mm/hr 의 범위로서 이로 인한 강우손실량은 큰 의미가 없음을 알았다.재발이 나타난 3례의 환자를 제외한 9례 (75%)에서는 현재까지 재발소견을 보이지 않고 있다. 이러한 결과는 다른 보고자들과 유사한 결과를 보이고 있지만 아직까지 증례가 많지 않기 때문에 생존율을 얻

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Evaluation of Tensions and Prediction of Deformations for the Fabric Reinforeced -Earth Walls (섬유 보강토벽체의 인장력 평가 및 변형 예측)

  • Kim, Hong-Taek;Lee, Eun-Su;Song, Byeong-Ung
    • Geotechnical Engineering
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    • v.12 no.4
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    • pp.157-178
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    • 1996
  • Current design methods for reinforced earth structures take no account of the magnitude of the strains induced in the tensile members as these are invariably manufactured from high modulus materials, such as steel, where straits are unlikely to be significant. With fabrics, however, large strains may frequently be induced and it is important to determine these to enable the stability of the structure to be assessed. In the present paper internal design method of analysis relating to the use of fabric reinforcements in reinforced earth structures for both stress and strain considerations is presented. For the internal stability analysis against rupture and pullout of the fabric reinforcements, a strain compatibility analysis procedure that considers the effects of reinforcement stiffness, relative movement between the soil and reinforcements, and compaction-induced stresses as studied by Ehrlich 8l Mitchell is used. I Bowever, the soil-reinforcement interaction is modeled by relating nonlinear elastic soil behavior to nonlinear response of the reinforcement. The soil constitutive model used is a modified vertsion of the hyperbolic soil model and compaction stress model proposed by Duncan et at., and iterative step-loading approach is used to take nonlinear soil behavior into consideration. The effects of seepage pressures are also dealt with in the proposed method of analy For purposes of assessing the strain behavior oi the fabric reinforcements, nonlinear model of hyperbolic form describing the load-extension relation of fabrics is employed. A procedure for specifying the strength characteristics of paraweb polyester fibre multicord, needle punched non-woven geotHxtile and knitted polyester geogrid is also described which may provide a more convenient procedure for incorporating the fablic properties into the prediction of fabric deformations. An attempt to define improvement in bond-linkage at the interconnecting nodes of the fabric reinforced earth stracture due to the confining stress is further made. The proposed method of analysis has been applied to estimate the maximum tensions, deformations and strains of the fabric reinforcements. The results are then compared with those of finite element analysis and experimental tests, and show in general good agreements indicating the effectiveness of the proposed method of analysis. Analytical parametric studies are also carried out to investigate the effects of relative soil-fabric reinforcement stiffness, locked-in stresses, compaction load and seepage pressures on the magnitude and variation of the fabric deformations.

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