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Journal articles on the topic 'DDA simulation'

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Published: 7 July 2024

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1

Ma, Guichen, Hiroyuki Matsuyama, Satoshi Nishiyama, and Yuzo Ohnishi. "Practical studies on rockfall simulation by DDA." Journal of Rock Mechanics and Geotechnical Engineering 3, no. 1 (March 2011): 57–63. http://dx.doi.org/10.3724/sp.j.1235.2011.00057.

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2

Chen, Guangqi, Manchao He, and Fusong Fan. "Rock Burst Analysis Using DDA Numerical Simulation." International Journal of Geomechanics 18, no. 3 (March 2018): 04018001. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0001055.

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3

Fu, Xiaodong, Jingyu Kang, Qian Sheng, Lu Zheng, Wenjie Du, and Haifeng Ding. "Investigation of 2D Seismic DDA Method for Numerical Simulation of Shaking Table Test of Rock Mass Engineering." Mathematics 10, no. 8 (April 17, 2022): 1330. http://dx.doi.org/10.3390/math10081330.

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Since the basic theory of the discontinue deformation analysis (DDA) method was proposed, the DDA open source has gone through a long development process. At present, different kinds of programs have been widely applied in rock mass engineering such as slope, dam, and tunnel. This paper introduces the solution principle of DDA motion equations in detail, as well as the development status of the 2D open-source program. Numerical simulation of shaking table test of rock mass engineering using 2D DDA program is highlighted, and investigations of seismic wave pre-processing and seismic input method are carried out. First, based on the Newmark integration scheme, the integration algorithms of synthetic or measured seismic wave time history, correction function of seismic wave, and DDA simulation are unified. Then, three seismic input methods are implanted in the DDA program, and the applicability of various seismic input methods is discussed. On this basis, using the improved seismic 2D DDA program, a shaking table test of typical rock mass engineering is simulated. Through the comparison between the theoretical/test data and simulation results, the reliability of the improved DDA program in seismic response analysis is verified; the large mass method and the large stiffness method are more suitable for rigid foundation, such as shaking table test; the propagation of the seismic wave presents a significant amplification effect due to the reflection, refraction, and diffraction in the tunnel. The research results provide DDA theory and an open-source program for analyzing the seismic response of rock mass engineering.

4

Gao, Ya Nan, Feng Gao, M. R. Yeung, and Qing Hui Jiang. "Numerical Simulation of Coal Mining Excavation Based on Discontinuous Deformation Analysis." Applied Mechanics and Materials 138-139 (November 2011): 187–92. http://dx.doi.org/10.4028/www.scientific.net/amm.138-139.187.

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The movement and deformation of rock stratum occur when the excavation is carries out during the underground mining process. Rock is a continuous-discontinuous material so the continuum mechanics method may not handle the rock problem well. The discontinuous deformation analysis (DDA) method which discretizes the rock mass to block system can describe the large displacement and deformation of rock blocks, especially the rock stratum collapse. The DDA was employed in this paper to analysis a mining excavation process. The displacement field and stress field of rock stratum was computed. The result shows that the DDA can handle the mining excavation and the rock stratum movement and deformation problem well.

5

Octavia, Karina, Jian-Hong Wu, and Luky Handoko. "Investigating the Stability of the Candi Kelir using DDA." IOP Conference Series: Earth and Environmental Science 1249, no. 1 (October 1, 2023): 012016. http://dx.doi.org/10.1088/1755-1315/1249/1/012016.

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Abstract Candi Kelir, which is a candi in Prambanan, is a historical masonry structures threatened by high potency of earthquake in Indonesia. Investigating the stability of Candi Prambanan is essential for determining the capability to withstand earthquake loads. Discontinuous Deformation Analysis (DDA) has been extensively applied in the disciplines of rock mechanics and rock engineering. Two-dimensional DDA is chosen to simulate the behaviour of Candi Kelir towards earthquake load. Geometry of each block of Candi Kelir is obtained by Close Range Photogrammetry (CRP) method. Simulation of Candi Kelir is conducted using the seismic excitation from the destructive 2006 Yogyakarta Earthquake. The result of the simulation shows the capability of DDA to simulate the behaviour of masonry structure which allows fully detachment of the blocks. During the earthquake, most of the top structures are failing, thus DDA can simulate and generate the result. Wider application of DDA into the historical masonry structure will be helpful to prevent more damage due to earthquakes.

6

Wang, Xiao-Bo, Wen-Jie Xu, Bing-Yin Zhang, and Qi-Cheng Sun. "Particle crushing simulations with improved discontinuous deformation analysis." Engineering Computations 31, no. 7 (September 30, 2014): 1321–41. http://dx.doi.org/10.1108/ec-02-2013-0051.

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Purpose – Rock-fill dams are embankments of compacted free-draining granular earth containing an impervious zone. Earth utilized in such dams often contains a high percentage of large particles – hence the term rock-fill. Mass stability of these dams results from friction and particle interactions rather than through a cementing agent binding the particles together. However, high-stress conditions and prolonged exposure to the elements can severely damage rock-fill. Therefore, understanding and modeling rock-fill breakage is important for dam engineering. The purpose of this paper is to improve discontinuous deformation analysis (DDA) techniques for modeling rock-fill breakage, proving the new method using simulations of spherical particle crushing. Design/methodology/approach – This work models rock-fill as bonded ellipsoid particles, and develops an improved DDA method to model the breakage of particle assemblies. The paper starts by describing the principles of three-dimensional DDA for spherical particles, and then derives the submatrices for normal contact, shear contact, and frictional force. The new algorithm incorporates a bond model with a revised open-close iteration algorithm into the DDA method to simulate particle crushing. To validate the improved DDA method, calculated particle contacts and movements are validated against theoretical results. Finally, this work performs a series of point-loading experimental tests for cement ellipsoid particles of both high and low compression strengths, with the test results compared against the results from corresponding DDA simulations. Findings – In particle crushing tests, the force and displacement show an approximately linear relationship until the crushing point, at which point low compression ellipsoid particles split into several large pieces while the high-compression particles break into many small fragments. The DDA simulation results are in good agreement with the crushing tests, demonstrating the validity of the DDA method for solving particle crushing problems. Although the improved DDA model is applicable to rock-fill particle crushing studies, some issues remain, particularly in increasing calculation efficiency and performing large-scale computations and long real-time simulations. Future research should address these issues. Originality/value – A bond model with a revised open-close iteration algorithm is incorporated into the DDA method. The simulated results shed insight into rock-fill crushing mechanisms, an element of concern in engineering practices.

7

Zhang, Guoxin, Zhengqi Lei, and Heng Cheng. "Shear Creep Simulation of Structural Plane of Rock Mass Based on Discontinuous Deformation Analysis." Mathematical Problems in Engineering 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/1582825.

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Numerical simulations of the creep characteristics of the structural plane of rock mass are very useful. However, most existing simulation methods are based on continuum mechanics and hence are unsuitable in the case of large displacements and deformations. The discontinuous deformation analysis method proposed by Genhua is a discrete one and has a significant advantage when simulating the contacting problem of blocks. In this study, we combined the viscoelastic rheological model of Burgers with the discontinuous deformation analysis (DDA) method. We also derived the recurrence formula for the creep deformation increment with the time step during numerical simulations. Based on the minimum potential energy principle, the general equilibrium equation was derived, and the shear creep deformation in the structural plane was considered. A numerical program was also developed and its effectiveness was confirmed based on the curves obtained by the creep test of the structural plane of a rock mass under different stress levels. Finally, the program was used to analyze the mechanism responsible for the creep features of the structural plane in the case of the toppling deformation of the rock slope. The results showed that the extended DDA method is an effective one.

8

Wang, Li, Rui Xu, Ruohua Liu, Peng Ge, Wei Sun, and Mengjie Tian. "Self-Assembly of NaOL-DDA Mixtures in Aqueous Solution: A Molecular Dynamics Simulation Study." Molecules 26, no. 23 (November 24, 2021): 7117. http://dx.doi.org/10.3390/molecules26237117.

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The self-assembly behaviors of sodium oleate (NaOL), dodecylamine (DDA), and their mixtures in aqueous solution were systematically investigated by large-scale molecular dynamics simulations, respectively. The interaction mechanisms between the surfactants, as well as the surfactants and solvent, were revealed via the radial distribution function (RDF), cluster size, solvent-accessible surface area (SASA), hydrogen bond, and non-bond interaction energy. Results showed that the molecules more easily formed aggregates in mixed systems compared to pure systems, indicating higher surface activity. The SASA values of DDA and NaOL decreased significantly after mixing, indicating a tighter aggregation of the mixed surfactants. The RDF results indicated that DDA and NaOL strongly interacted with each other, especially in the mixed system with a 1:1 molar ratio. Compared to van der Waals interactions, electrostatic interactions between the surfactant molecules were the main contributors to the improved aggregation in the mixed systems. Besides, hydrogen bonds were found between NaOL and DDA in the mixed systems. Therefore, the aggregates in the mixed systems were much more compact in comparison with pure systems, which contributed to the reduction of the repulsive force between same molecules. These findings indicated that the mixed NaOL/DDA surfactants had a great potential in application of mineral flotation.

9

Yan, Xiao Ling, Wang Long Wang, and Nan Xue. "Research and Simulation of an Efficient Circular Interpolation Algorithm." Advanced Materials Research 542-543 (June 2012): 1204–8. http://dx.doi.org/10.4028/www.scientific.net/amr.542-543.1204.

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During the process of conventional DDA circular interpolation, the synthesis feed rate fluctuations often, the machining errors are large also. A new efficient arc interpolation method is proposed in this paper, which uses the principle of DDA circular interpolation, it’s function is optimized and improved, Radius is used as the basis of interpolation feed, the left normalized data and pre-loaded are used also. The simulation result of VB program show that efficient circular interpolation method not only has high efficiency,but also has high accuracy.

10

Ning, Youjun, Xinyang Lv, and Zheng Yang. "DDA Simulation Study on Mechanical Failure of Heterogenous Rock." Geofluids 2021 (November 26, 2021): 1–11. http://dx.doi.org/10.1155/2021/1416560.

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Heterogeneity is an important characteristic that affects the mechanical behavior of rock. In the present work, a statistical rock mesoheterogeneity model based on the Weibull distribution function is introduced into the discontinuous deformation analysis (DDA) method to simulate the mechanical failure of heterogeneous rock, in which the general heterogeneity degree is controlled by a heterogeneity index and the mechanical property of each subblock element is randomly assigned. Brazilian disc and uniaxial compressive rectangular specimens are simulated as examples. Results show that it is more reasonable to consider the heterogeneity of elasticity properties (the elastic modulus and Poisson’s ratio) and strength properties (the tensile strength, cohesion, and friction angle) simultaneously in the heterogeneity model. It is also shown that with a larger heterogeneity index, which means a lower degree of heterogeneity, the reproducibility of the macroscopic response curves of a specimen gets better, while the exact cracking always differs but with less scattered cracks, and the global fracturing failure pattern and mode are weakly influenced by the heterogeneity. Moreover, with the increase in the heterogeneity index, the macroscopic equivalent modulus and strength get larger and approach those of a homogeneous specimen. This work indicates the importance of heterogeneity for rock mechanical behaviors including the macroscopic equivalent response and the fracturing failure. By the subblock DDA method to simulate fracturing realistically, the fracturing failure process of heterogeneous rock can be successfully reproduced, which builds good foundation for the simulation study of heterogeneous rock fracturing in practical problems, e.g., coal and rock fracturing in fluidization mining in the future.

11

Li, Wenzhen, Tao Wang, and Junjiao Wu. "Numerical simulation of air Impact molding using DDA method." International Journal of Cast Metals Research 15, no. 4 (March 2003): 451–56. http://dx.doi.org/10.1080/13640461.2003.11819527.

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12

MA, GUI CHEN, FUMIO KANEKO, SHINZABURO HORI, and MAKOTO NEMOTO. "USE OF DISCONTINUOUS DEFORMATION ANALYSIS TO EVALUATE THE DYNAMIC BEHAVIOR OF SUBMARINE TSUNAMI-GENERATING LANDSLIDES IN THE MARMARA SEA." International Journal of Computational Methods 08, no. 02 (June 2011): 151–70. http://dx.doi.org/10.1142/s0219876211002526.

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This study assessed the relevance of numerical modeling with respect to the mechanical properties of specific rock and investigated the applicability of submarine landslide simulation using discontinuous deformation analysis (DDA). To predict the dynamic behavior of submarine landslides, we developed a way to model a jointed rock mass for the evaluation of rock slope instability and an original DDA approach using an energy loss model that incorporates energy loss caused by collision between blocks and seawater resistance as a viscous force. We applied the developed model to estimate the dynamic behavior of actual submarine landslides. The simulations assessed seawater resistance and energy loss due to collision between blocks, reproducing past events and suggesting the behavior of vulnerable slopes. The results demonstrate that the model can clarify the energy loss caused by slope absorbability and seawater resistance, and that the improved DDA is very useful for submarine land analysis.

13

Lee, Ho Min, Do Guen Yoo, Doosun Kang, Hwandon Jun, and Joong Hoon Kim. "Uncertainty quantification of pressure-driven analysis for water distribution network modeling." Water Supply 16, no. 3 (November 23, 2015): 599–610. http://dx.doi.org/10.2166/ws.2015.168.

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The hydraulic analysis of water distribution networks (WDNs) is divided into two approaches: namely, a demand-driven analysis (DDA) and a pressure-driven analysis (PDA). In the DDA, the basic assumption is that the nodal demand is fully supplied irrespective of the nodal pressure, which is mainly suitable for normal operating conditions. However, in abnormal conditions, such as pipe failures or unexpected increase in demand, the DDA approach may cause unrealistic results, such as negative pressure. To address the shortcomings of DDA, PDA has been considered in a number of studies. For PDA, however, the head-outflow relation (HOR) should be given, which is known to contain a high degree of uncertainty. Here, the DDA-based simulator, EPANET2 was modified to develop a PDA model simulating pressure deficient conditions and a Monte Carlo simulation (MCS) was performed to consider the quantitative uncertainty in HOR. The developed PDA model was applied to two networks (a well-known benchmark system and a real-life WDN) and the results showed that the proposed model is superior to other reported models when dealing with negative pressure under abnormal conditions. In addition, the MCS-based sensitivity analysis presents the ranges of pressure and available discharge, quantifying service reliability of water networks.

14

Li, Yi Nuo, Jun Xiao, Zhen Ya Shen, and Ying Wang. "Discontinuous Deformation Analysis Visualization System Based on VTK." Advanced Materials Research 765-767 (September 2013): 542–46. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.542.

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Discontinuous Deformation Analysis (DDA) is an emerging numerical simulation technology in rock engineering field, which could be used to analyze discontinuous blocks movement. DDA has been widely used in the areas ranging from rock slope stability analysis, underground chamber constructions to earth quake loading predictions. But so far, there is no pre and post processing program for DDA algorithm. In order to make DDA more effectively meet the needs of practical projects, and analyze the computing results more clearly, effectively and conveniently, in this paper, we use an open source VTK (Visualization Toolkit) system to visualize the results of DDA, design and implement a visualization system. We also developed friendly GUI (Graphic User Interface) based on QT. Finally, we demonstrate this tool with two project examples, which will prove that the visualization system is direct, convenient and easy to extension.

15

Nian, Ting-kai, Yan-jun Zhang, Hao Wu, Guang-qi Chen, and Lu Zheng. "Runout simulation of seismic landslides using discontinuous deformation analysis (DDA) with state-dependent shear strength model." Canadian Geotechnical Journal 57, no. 8 (August 2020): 1183–96. http://dx.doi.org/10.1139/cgj-2019-0312.

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The reliable numerical simulation of the landslide process contributes to the establishment of evidence-based disaster mitigation measures in seismically active zones. To achieve this goal, a simple and unified state-dependent shear strength model of discontinuities is presented to describe the shear strength degradation in a seismic landslide process. The proposed model establishes a relationship between the shear strength parameters and the global safety factor of the slope by assuming that the slope instability (or landslide initiation) is accompanied by an instantaneous shear strength degradation of discontinuities. To realize the model numerically, the algorithms for the computation of global safety factor and the modification of shear strength parameters were incorporated into the discontinuous deformation analysis (DDA). Subsequently, the kinematic accuracy of the improved DDA method was validated by comparisons with theoretical solutions for the dynamic sliding of a block on an inclined plane. Numerical simulations of the Daguangbao landslide triggered by the Wenchuan earthquake were performed using the improved DDA method. The results illustrate that the shear strength degradation of discontinuities affect the evolution process, travel distance, and post-failure shape of the seismic landslide significantly.

16

Glukhova, S. A., and M. A. Yurkin. "Scattering of generalized Bessel beams simulated with the discrete dipole approximation." Journal of Physics: Conference Series 2015, no. 1 (November 1, 2021): 012046. http://dx.doi.org/10.1088/1742-6596/2015/1/012046.

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Abstract We consider the simulation of scattering of the high-order vector Bessel beams in the discrete dipole approximation framework (DDA). For this purpose, a new general classification of all existing Bessel beam types was developed based on the superposition of transverse Hertz vector potentials. Next, we implemented these beams in ADDA code – an open-source parallel implementation of the DDA. The code enables easy and efficient simulation of Bessel beams scattering by arbitrary-shaped particles. Moreover, these results pave the way for the following research related to the Bessel beam scattering near a substrate and optical forces.

17

Dong, Zhi Hong, Xiu Li Ding, Ai Qing Wu, and Bo Lu. "Simulation of Whole Movement Process of Muzhuping Landslide with DDA and Prediction of Surge." Advanced Materials Research 989-994 (July 2014): 2254–57. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.2254.

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The surge wave induced by the landslide on reservoir bank is extremely disaster .The prediction of surge height is a difficult problem because the velocity of landslide is hard to obtain. The discontinuous deformation analysis (DDA) is able to simulate landslide movement with real time and acceleration. The whole movement process of Muzhuping landslide in the Qing river reservoir is simulated by DDA method, including startup, accelerating, deceleration and stop, and velocity along time is obtained. Last, empirical formula for computing surge height is discussed.

18

Muranho, João, Ana Ferreira, Joaquim Sousa, Abel Gomes, and Alfeu Sá Marques. "Pressure-Driven Simulation of Water Distribution Networks: Searching for Numerical Stability." Environmental Sciences Proceedings 2, no. 1 (September 4, 2020): 48. http://dx.doi.org/10.3390/environsciproc2020002048.

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EPANET uses a demand-driven approach to compute pressures and flows in the water distribution system. The demand-driven approach (DDA) assumes that the required demand is always fully satisfied no matter the existing pressure. In scenarios of pressure-deficient conditions the DDA results are not accurate, and a pressure-driven approach (PDA) is needed. Frequently, the PDA is accomplished by using equations that compute the available demand/leakage as a function of the current pressure. However, embedding such equations into the solver introduces convergence problems. This paper details the actions taken in WaterNetGen—an EPANET extension—to bring numerical stability to the pressure-driven solver, namely, by smoothing the pressure–demand/leakage relationship and the pump curve.

19

Zhao, Jian, Ming Xiao, Juntao Chen, and Dongdong Li. "Explicit Dynamic DDA Method considering Dynamic Contact Force." Shock and Vibration 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/7431245.

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This paper proposes an explicit dynamic DDA method considering dynamic contact force, which aims at solving the problems of low efficiency of dynamic contact detection and the simulation of dynamic contact force in the conventional DDA method. The mutual contact between blocks can be regarded as the application of point loading on a single block, and the corresponding contact submatrix can be calculated and the simultaneous equations of the block system can be integrated. The central difference method is adopted to deduce the explicit expression of block displacement containing dynamic contact force. With the relationship between displacement and dynamic contact force, contact constraint equations of a block system are obtained to calculate the dynamic contact force and the corresponding block displacement. The accuracy of the explicit dynamic DDA method is verified using two numerical cases. The calculation results show that the new DDA method can be applied in large-scale geotechnical engineering.

20

Moroz, Leonid, Jan L. Cieśliński, Marta Stakhiv, and Volodymyr Maksymovych. "A Comparison of Standard One-Step DDA Circular Interpolators with a New Cheap Two-Step Algorithm." Modelling and Simulation in Engineering 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/916539.

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We present and study existing digital differential analyzer (DDA) algorithms for circle generation, including an improved two-step DDA algorithm which can be implemented solely in terms of elementary shifts, addition, and subtraction.

21

Gao, Yanan, Feng Gao, and Man-chu Ronald Yeung. "A Fractal and Numerical Simulation Coupled Study of Fracture Network during Coal Mining Excavation." Journal of Applied Mathematics 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/158194.

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This paper features a numerical study that is carried out by using discontinuous deformation method (DDA) and fractal geometry. The configurations of rock strata calculated by DDA were imported into a code that is written by using VC++ called “Fractal” to calculate the fractal dimension of the rock strata. As illustrated, a long wall mining case in China was presented. The relationship of the fractal dimension, excavation length, stress, and movement of strata were discussed. The evolution of fractal dimension can be considered as an index of instability or failure. The method proposed in this paper can be employed to predict the period weighting in long wall mining engineering.

22

Potvin, Corey K., Daniel Betten, Louis J. Wicker, Kimberly L. Elmore, and Michael I. Biggerstaff. "3DVAR versus Traditional Dual-Doppler Wind Retrievals of a Simulated Supercell Thunderstorm." Monthly Weather Review 140, no. 11 (November 1, 2012): 3487–94. http://dx.doi.org/10.1175/mwr-d-12-00063.1.

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Abstract Use of the three-dimensional variational data assimilation (3DVAR) framework in dual-Doppler wind analysis (DDA) offers several advantages over traditional techniques. Perhaps the most important is that the errors that result from explicit integration of the mass continuity equation in traditional methods are avoided. In this study, observing system simulation experiments (OSSEs) are used to compare supercell thunderstorm wind retrievals from a 3DVAR DDA technique and three traditional DDA methods. The 3DVAR technique produces better wind retrievals near the top of the storm than the traditional methods in the experiments. This is largely attributed to the occurrence of severe errors aloft in the traditional retrievals whether the continuity equation integration proceeds upward (due to vertically accumulating errors), downward (due to severe boundary condition errors arising from uncertainty in the horizontal divergence field aloft), or in both directions. Smaller, but statistically significant, improvement occurs near the ground using the 3DVAR method. When lack of upper-level observations prevents application of a top boundary condition in the traditional DDA framework, the 3DVAR approach produces better analyses at all levels. These results strongly suggest the 3DVAR DDA framework is generally preferable to traditional formulations.

23

Kartheeswaran, Karpaga Priyaa, Arockia Xavier Annie Rayan, and Geetha Thekkumpurath Varrieth. "Enhanced disease-disease association with information enriched disease representation." Mathematical Biosciences and Engineering 20, no. 5 (2023): 8892–932. http://dx.doi.org/10.3934/mbe.2023391.

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<abstract> <sec><title>Objective</title><p>Quantification of disease-disease association (DDA) enables the understanding of disease relationships for discovering disease progression and finding comorbidity. For effective DDA strength calculation, there is a need to address the main challenge of integration of various biomedical aspects of DDA is to obtain an information rich disease representation. Materials and</p> </sec> <sec><title>Methods</title><p>An enhanced and integrated DDA framework is developed that integrates enriched literature-based with concept-based DDA representation. The literature component of the proposed framework uses PubMed abstracts and consists of improved neural network model that classifies DDAs for an enhanced literature-based DDA representation. Similarly, an ontology-based joint multi-source association embedding model is proposed in the ontology component using Disease Ontology (DO), UMLS, claims insurance, clinical notes etc. Results and</p> </sec> <sec><title>Discussion</title><p>The obtained information rich disease representation is evaluated on different aspects of DDA datasets such as Gene, Variant, Gene Ontology (GO) and a human rated benchmark dataset. The DDA scores calculated using the proposed method achieved a high correlation mainly in gene-based dataset. The quantified scores also shown better correlation of 0.821, when evaluated on human rated 213 disease pairs. In addition, the generated disease representation is proved to have substantial effect on correlation of DDA scores for different categories of disease pairs.</p> </sec> <sec><title>Conclusion</title><p>The enhanced context and semantic DDA framework provides an enriched disease representation, resulting in high correlated results with different DDA datasets. We have also presented the biological interpretation of disease pairs. The developed framework can also be used for deriving the strength of other biomedical associations.</p> </sec> </abstract>

24

Zhang, K. J., B. Da, and Z. J. Ding. "LSP modes of Ag nanocube and dimer studied by DDA simulation." Surface and Interface Analysis 48, no. 11 (August 8, 2016): 1256–62. http://dx.doi.org/10.1002/sia.6081.

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SASAKI, TAKESHI, IKUO HAGIWARA, KASTUJI SASAKI, RYUNOSHIN YOSHINAKA, YUZO OHNISHI, SATISHI NISHIYAMA, and TOMOFUMI KOYAMA. "STABILITY ANALYSES FOR ANCIENT MASONRY STRUCTURES USING DISCONTINUOUS DEFORMATION ANALYSIS AND NUMERICAL MANIFOLD METHOD." International Journal of Computational Methods 08, no. 02 (June 2011): 247–75. http://dx.doi.org/10.1142/s0219876211002575.

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In this paper, the stability including stress distribution of two ancient masonry structures, the pyramid of the Pharaoh Khufu, Egypt and the Pont of Gard, were analyzed using discontinuous deformation analysis (DDA) and numerical manifold method (NMM). For the simulation using NMM, the newly developed four-node isoparametric element was used. The stress distributions/concentration were calculated and compared between the two methods. The calculated results show qualitative agreement with observations. DDA and NMM are applicable to simulate the physical phenomena of masonry structures.

26

Khateb, Fabian, Montree Kumngern, Spyridon Vlassis, Costas Psychalinos, and Tomasz Kulej. "Sub-Volt Fully Balanced Differential Difference Amplifier." Journal of Circuits, Systems and Computers 24, no. 01 (November 10, 2014): 1550005. http://dx.doi.org/10.1142/s021812661550005x.

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This paper presents a new CMOS structure for a fully balanced differential difference amplifier (FB-DDA) designed to operate from a sub-volt supply. This structure employs the bulk-driven quasi-floating-gate (BD-QFG) technique to achieve the capability of an ultra-low voltage operation and an extended input voltage range. The proposed BD-QFG FB-DDA is suitable for ultra-low-voltage low-power applications. The circuit is designed with a single supply of 0.5 V and consumes only 357 nW of power. The proposed circuit was simulated in a 0.18-μm TSMC CMOS technology and the simulation results prove its functionality and attractive parameters. An application example of a state variable filter is also presented to confirm the usefulness of the proposed BD-QFG FB-DDA.

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KHANESHAN, TOHID MORADI, SAEED NAGHAVI, MOJDE NEMATZADE, KHAYROLLAH HADIDI, ADIB ABRISHAMIFAR, and ABDOLLAH KHOEI. "A FAST AND LOW SETTLING ERROR CONTINUOUS-TIME COMMON-MODE FEEDBACK CIRCUIT BASED ON DIFFERENTIAL DIFFERENCE AMPLIFIER." Journal of Circuits, Systems and Computers 23, no. 05 (May 8, 2014): 1450065. http://dx.doi.org/10.1142/s0218126614500650.

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A high-speed and high-accuracy continuous-time common-mode feedback block (CMFB) is presented. To satisfy speed and accuracy requirements, some modifications have been applied on differential difference amplifier (DDA) CMFB circuit. The proposed method is applied to a folded cascode op-amp with power supply of 3.3 V. In order to verify the proposed circuit, simulations are done in 0.35 μm standard CMOS technology. In the worst condition when the output common-mode (CM) voltage is initialized to VCC or GND, only 1.1 ns is required to set the output CM voltage on the desired level. Also in a wide range of input CM voltage variations, the deviation of the output CM voltage from reference voltage is less than 6 mV, so simulation results confirm the expected accuracy and speed while simultaneously the proposed CMFB circuit preserves other characteristics of DDA CMFB circuit such as unity gain frequency, 3-dB bandwidth, phase margin and linearity.

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Chen, Yuening, Kecheng Wang, and Yan Zhuang. "Current state and challenges of ECG amplifiers." Highlights in Science, Engineering and Technology 32 (February 12, 2023): 177–85. http://dx.doi.org/10.54097/hset.v32i.4988.

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This paper describes and compares three amplifiers for ECG recording, namely a four-transistor stage band-pass amplifier, a DDA-based fully differential CMOS instrumentation amplifier and an OTA amplifier using current reuse. The performance metrics of the three amplifiers are listed, their respective advantages are compared, what factors limit their disadvantages are analyzed, the current state of the art and the direction of development of the ECG amplifier are indicated, and suggestions are given for further enhancement of the ECG amp. These amplifier circuits are designed in 0.35 µm CMOS and are verified by layout followed by simulation simulations. The results show that running at 2V dc supply, the quad-transistor stage amplifier and the DDA fully differential amplifier consume 672nW, obtain at least 2uVrms of input reference noise, and obtain greater common mode rejection ratios of 86dB and 83dB, while the OTA amplifier consumes less 320nW, obtains the most 2.05uVrms of input reference noise, and obtains a smaller common-mode rejection ratio of 65dB.

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Liu, Guoyang, and Junjie Li. "Research on the Effect of Tree Barriers on Rockfall Using a Three-Dimensional Discontinuous Deformation Analysis Method." International Journal of Computational Methods 17, no. 08 (May 31, 2019): 1950046. http://dx.doi.org/10.1142/s0219876219500464.

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On rockfall slopes, trees can play a natural and efficient protective role in preventing the occurrence of rockfall disasters. This paper presents a study on the tree barrier effect on rockfall based on a three-dimensional discontinuous deformation analysis (3D DDA) method. The tree barrier effect on rockfall is studied considering the 3D spatial effect of rockfall movement and the 3D spatial distribution of trees. The basic movement forms and collision modes of rockfall related to the tree barrier are classified, and the impact factors of tree arrangements on rockfall are proposed. The contact mechanism employed in the 3D DDA method is illustrated, and the accuracy of the 3D DDA rockfall simulation is verified by comparing with the results obtained from laboratory experiments. Numerical examples are conducted to study the effect of the tree barrier on rockfall, and general laws are derived by analyzing the variation of kinetic energies and motion trajectories of moving blocks. The results show that the 3D DDA method can effectively predict the 3D motion behaviors of rockfall and assess the tree barrier effect. Furthermore, a reasonable arrangement of trees or a combination of protective facilities and trees can prevent or mitigate the rockfall hazards.

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Guo, Pei Xi, and Shao Zhong Lin. "Numerical Simulation by DDA and the Fabrics Analysis of Two Dimensional Experiment on Coarse Granular Material." Applied Mechanics and Materials 170-173 (May 2012): 3621–29. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.3621.

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DDA(Discontinuous Deformation Analysis) was used to study the mechanical characteristics of coarse granular material (CGM). The numerical simulation model was found consulting the two Dimensional test of CGM,and the stress-strain curves obtained by the numerical simulation were basically in agreement with the results of laboratory test. It indicates that the numerical simulation is suitable for the mechanical characteristic research of CGM. In addition,the distribution statistic of several fabric elements about interaction between particles was also presented. Some relation between the stress-strain and fabric element change are found after analysis.

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WU, AIQING, QIGUI YANG, GUISHENG MA, BO LU, and XIAOJUN LI. "STUDY ON THE FORMATION MECHANISM OF TANGJIASHAN LANDSLIDE TRIGGERED BY WENCHUAN EARTHQUAKE USING DDA SIMULATION." International Journal of Computational Methods 08, no. 02 (June 2011): 229–45. http://dx.doi.org/10.1142/s0219876211002563.

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Wenchuan earthquake, Ms 8.0 in magnitude and occurred on May 12, 2008 in Sichuan Province, China, triggered a lot of landslides, rock collapses, debris flow, etc. The Tangjiashan landslide, with its total volume 20.37 million m3, was the biggest and the most notable one for its effects. Based on the field geological investigation and the typical acceleration records of the main shock obtained in the period of the earthquake, numerical simulation of the whole sliding process of Tangjiashan landslide has been carried out by DDA method. It is shown that the Tangjiashan landslide was a high-speed landslide, behaved with nonlinear features in the whole sliding process. The total duration of the landslide was about 30 s while nearly all of their slipping displacements were carried out in the beginning 25 s, with the maximum sliding velocity about 30 m/s, and the average 15–17 m/s in the beginning 25 s. The crash of rock blocks induced a much higher stresses near the middle and lower parts of the landslide, with the maximum value of 6–7 MPa. The dynamic earthquake load caused an incessant deformation of the landslide, resulting in the reduction of mechanical parameters, especially the shear strength on the sliding surface and the ratio of friction coefficient on sliding surface in kinematical and static conditions are no more than 0.35. DDA simulation considering the displacement-based parameter reduction has been developed in the original DDA code, and its results primarily reflect the evolvement process of a landslide under strong seismic loads.

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Lemos de Souza, Michele, Diego Pereira dos Santos, and Paola Corio. "Localized surface plasmon resonance enhanced photocatalysis: an experimental and theoretical mechanistic investigation." RSC Advances 8, no. 50 (2018): 28753–62. http://dx.doi.org/10.1039/c8ra03919d.

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A theoretical (DDA simulation) and experimental (phenol degradation) study has shown the LSPR from Ag and Ag@SiO₂ NPs to contribute to better TiO₂ photocatalytic performances. Au NPs has shown very low contribution, due to its low energy LSPR.

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Yu, Song, Wei Shen Zhu, Hao Zhou, and Dun Fu Zhang. "Analysis of Shear Test for Jointed Rock Sample Using DDA Method." Applied Mechanics and Materials 744-746 (March 2015): 426–31. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.426.

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Based on a shear test for jointed rock sample conducted by former study, a numerical improved method DDARF is carried out to simulate the shear test. The simulation result of shear fracture phenomenon show high compatibility with the model test. Different fracture phenomenon and peak strength value of shear testing are explored in the condition of different colinnear and ladder echelon arrangement of cracks.

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Biazatti, Elisângela Candeias, Gauss Moutinho Cordeiro, and Maria do Carmo Soares de Lima. "The Dual-Dagum family of distributions: Properties, regression and applications to COVID-19 data." Model Assisted Statistics and Applications 17, no. 3 (August 26, 2022): 199–210. http://dx.doi.org/10.3233/mas-221354.

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A new Dual-Dagum-G (DDa-G) family is defined as a good competitor to the Beta-G and Kumaraswamy-G generators, which are widely applied in several areas. Some of its mathematical properties are addressed. We obtain the maximum likelihood estimates, and some simulations prove the consistency of the estimates. The flexibility of this family is shown through a COVID-19 data set. We propose a new regression based on a special distribution of the DDa-G family, and provide a sensitivity analysis by using data from 1,951 COVID-19 patients collected in Curitiba, Brazil.

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Lv, Ruichan, Miao Feng, and Wolfgang Parak. "Up-Conversion Luminescence Properties of Lanthanide-Gold Hybrid Nanoparticles as Analyzed with Discrete Dipole Approximation." Nanomaterials 8, no. 12 (November 29, 2018): 989. http://dx.doi.org/10.3390/nano8120989.

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Up-conversion nanoparticles (UCNP) under near-infrared (NIR) light irradiation have been well investigated in the field of bio-imaging. However, the low up-conversion luminescence (UCL) intensity limits applications. Plasmonic modulation has been proposed as an effective tool to adjust the luminescence intensity and lifetime. In this study discrete dipole approximation (DDA) was explored concerning guiding the design of UCNP@mSiO2-Au structures with enhanced UCL intensity. The extinction effects of gold shells could be changed by adjusting the distance between the UCNPs and the Au NPs by synthesized tunable mesoporous silica (mSiO2) spacers. Enhanced UCL was obtained under 808 nm irradiation. The original theoretical predictions could not be demonstrated to full extend by experimental data, indicating that better models for simulation need to take into account in homogeneities in particle morphologies. Yet, one very certain conclusion resulting from the DDA calculations and experiments is that the absorbance can blue-shift with more Au NPs added and the absorbance can-red shift for samples with enhanced silica sizes in the UCNP@mSiO2-Au structures. Furthermore, when the DDA model is more consistent with the practical structure (dispersed Au NPs instead of Au shell), the theoretical absorbance occurs almost the same as the practical absorbance. All in all, the DDA could fit the extinction effect of Au perfectly and be suitable for guiding how to design the UCNP and Au.

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WU, Jian-Hong, Yuzo OHNISHI, Keiichi MOMMA, and Satoshi NISHIYAMA. "Simulation of Rock Slope Failure with Three-Dimensional Discontinuous Deformation Analysis (3D DDA)." Journal of the Society of Materials Science, Japan 52, no. 5 (2003): 488–93. http://dx.doi.org/10.2472/jsms.52.488.

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Zhang, Rui-qing, Fu-sheng Wei, Cheng-bin Qiao, and Bang-hui Lin. "Numerical simulation for 1975 Haicheng and 1999 Xiuyan earthquake processes by DDA+FEM." Acta Seismologica Sinica 18, no. 2 (March 2005): 171–79. http://dx.doi.org/10.1007/s11589-005-0064-2.

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CHEN, Guangqi, and Chaofan Feng. "Optimizing Lysmer-Kuhlemeyer Boundary Parameters for Different Incident Angles in DDA Seismic Simulation." Japanese Geotechnical Society Special Publication 10, no. 47 (2024): 1775–79. http://dx.doi.org/10.3208/jgssp.v10.os-36-07.

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Li, Yuan, and Nitin Chopra. "Optical properties of nanostructured carbon and gold nanoparticle hybrids." MRS Proceedings 1700 (2014): 79–82. http://dx.doi.org/10.1557/opl.2014.575.

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ABSTRACTWe report simulation of optical properties of hybrid geometry comprised of multilayer graphene shell encapsulated gold nanoparticles loaded with carbon nanotubes. The discrete dipole approximation (DDA) method was employed. The results indicated that the optical properties of encapsulated gold nanoparticles were not suppressed by the carbon material coating. Furthermore, low scattering effects were also observed. The simulation method helped visualize the near-surface normalized electric field, which is directly related to the intensity of hot spots on the surface of these hybrid nanoarchitectures.

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Nian, Ting Kai, Yan Jun Zhang, Lu Zheng, Kai Liu, and Guang Qi Chen. "Failure Process Simulation of Highly Jointed Rock Slope with a Fault." Applied Mechanics and Materials 501-504 (January 2014): 12–15. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.12.

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This paper uses 2D DDA program to simulate the failure process of highly jointed rock slope with a fault. In addition, seismic forces, as a most common triggered factor of landslide, are also simplified simulated by applying an initial velocity to the slope. Based on the simulation results, the weakest discontinuity, fault, determines the slide path of rock blocks; the accumulation of blocks' displacements leads to the overall failure of slope; and the existence of highly developed joints provide the possibility of the accumulation of displacements.

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Lin, Hsueh Chun, Yao Ming Hong, Wen Pei Sung, Ying Chih Chen, and Yao Chiang Kan. "A Risk Evaluation Modeling upon Discontinuous Deformation Analysis and Hydraulic Computation for Aged Dam." Applied Mechanics and Materials 121-126 (October 2011): 4307–14. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.4307.

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This study aims to generate a risk evaluation methodology for the aged dam structure by coupling the micro and macro models created by hydraulic computation and discontinuous deformation analysis (DDA) with numerical manifold method (NMM), respectively. For the macro analysis, DDA+NMM is an energy-convergence algorithm and can be utilized to estimate critical loading based on the potential joints existing within the discontinuous block system. Due to the micro view, the relationship of groundwater level and precipitation can be studied by using hydraulic computation based on the groundwater flow equations. The proposed method presents an evaluation procedure for modeling an aged earth dam with efficient and economic open-source programs. As the result, the simulation can help determining the criterion of risk factors and the prevention strategy.

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Wang, Dan, Zhiqiang Mei, Jiamin Liang, and Jinzhi Liu. "An Improved Channel Estimation Algorithm Based on WD-DDA in OFDM System." Mobile Information Systems 2021 (July 31, 2021): 1–9. http://dx.doi.org/10.1155/2021/6540923.

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Channel estimation is the key technology to ensure reliable transmission in orthogonal frequency division multiplexing (OFDM) system. In order to improve the accuracy of the channel estimation algorithm in a low signal-to-noise ratio (SNR) channel environment, in this paper, we proposed an improved channel estimation algorithm based on the transform domain. The improved algorithm with wavelet denoising (WD) and distance decision analysis (DDA) to perform secondary denoising on the channel estimation algorithm based on the transform domain is proposed. First, after the least-squares (LS) algorithm, WD is used to denoise for the first time, then the DDA is used to further suppress the residual noise in the transform domain, and the important channel taps are screened out. Simulation results show that the proposed algorithm can improve the detection performance of existing channel estimation algorithms based on transform domain in low SNR.

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Yang, M., T. Fukawa, Y. Ohnishi, S. Nishiyama, S. Miki, Y. Hirakawa, and S. Mori. "The application of 3-dimensional dda with a spherical rigid block for rockfall simulation." International Journal of Rock Mechanics and Mining Sciences 41 (May 2004): 611–16. http://dx.doi.org/10.1016/j.ijrmms.2004.03.108.

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Yang, M., T. Fukawa, Y. Ohnishi, S. Nishiyama, S. Miki, Y. Hirakawa, and S. Mori. "The application of three-dimensional DDA with a spherical rigid block to rockfall simulation." International Journal of Rock Mechanics and Mining Sciences 41, no. 3 (April 2004): 476. http://dx.doi.org/10.1016/j.ijrmms.2003.12.147.

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Yao, Shuan, Heng Zhang, Nan Zeng, Hui Ma, Honghui He, and Yuelu Jiang. "Polarization Characterization of Porous Particles Based on DDA Simulation and Multi-Angle Polarization Measurements." Materials 17, no. 8 (April 9, 2024): 1718. http://dx.doi.org/10.3390/ma17081718.

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Porous suspended particles are hazardous to human health due to their strong absorption capacity for toxic substances. A fast, accurate, in situ and high-throughput method to characterize the microporous structure of porous particles has extensive application value. The polarization changes during the light scattering of aerosol particles are highly sensitive to their microstructural properties, such as pore size and porosity. In this study, we propose an overlapping sphere model based on the discrete dipole approximation (DDA) to calculate the polarization scattering characteristics of porous particles. By combining scattering calculations with multi-dimensional polarization indexes measured by a multi-angle polarized scattering vector detection system, we achieve the identification and classification of pore-type components in suspended particles. The maximum deviation based on multiple indexes is less than 0.16% for the proportion analysis of mixed particles. Simultaneously, we develop a quantitative inversion algorithm on pore size and porosity. The inversion results of the three porous polymer particles support the validity and feasibility of our method, where the inversion error of partial particles is less than 4% for pore size and less than 6% for porosity. The study demonstrates the potential of polarization measurements and index systems applied in characterizing the micropore structure of suspended particles.

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Chen, C.-Y., P.-S. Liao, C.-C. Cheng, and G.-F. Jong. "Design and implementation of integrated non-uniform rational B-spline and digital differential analyser interpolators for computerized numerical control servocontrollers." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, no. 9 (September 1, 2007): 1075–87. http://dx.doi.org/10.1243/09544062jmes686.

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The purpose of this article is to propose the design and implement an efficient and open real-time non-uniform rational B-spline (NURBS) interpolator for computerized numerical control (CNC) motion control. The proposed architecture of real-time NURBS interpolator integrates the advantages of digital differential analyser (DDA) and the native NURBS interpolator with the help of the data conversion module. First, the desired compensation positions are generated by NURBS interpolator concerning feedrate and curvature for manufacturing accuracy. A data conversion module is then applied to transform the position commands from float to integer. Using this integral-type position command, the pulse trains can be generated by DDA for the AC servomechanism in position mode. The simulation and experimental results validate that this novel real-time NURBS controller is effective and efficient enough to drive the general servomechanism without changing the control scheme of the traditional AC servomotor.

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Xie, Biting, Xiuli Zhang, Hao Wang, Yuyong Jiao, and Fei Zheng. "Investigations into the Rock Dynamic Response under Blasting Load by an Improved DDA Approach." Advances in Civil Engineering 2021 (February 8, 2021): 1–10. http://dx.doi.org/10.1155/2021/8827022.

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Evaluation of blasting-induced rock damage and fragmentation is very important for safety control of construction in the jointed rock mass. The discontinuous numerical models are commonly applied due to the advantages in modeling fragmentation and treating discontinuities. In this paper, the rock fracturing algorithm and rate dependent strength law are incorporated into the discontinuous deformation analysis (DDA) to study the wave propagation and rock fragmentation phenomena in dynamic problems. By reproducing Hopkinson pressure bar tests under different loading rates, the improved method is validated to be capable of solving dynamic failure problem. Finally, taking the Xiucun tunnel as an example, its failure process under the action of the explosive wave is simulated, and some failure features are captured. In addition, the explosion wave propagation and its induced particle vibration in surrounding rock are studied. The reasonable simulation results indicate that the modified DDA method can effectively model the stress wave propagation and joint growth process in the jointed rock under blasting load.

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Xu, Yunchao, Lianwen Deng, Daitao Kuang, Haipeng Xie, Dongyong Shan, Xiao Wang, Shengxiang Huang, and Heng Luo. "Cu@C core-shell nanoparticles with efficient optical absorption: DDA-based simulation and experimental validation." Results in Physics 16 (March 2020): 102885. http://dx.doi.org/10.1016/j.rinp.2019.102885.

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Wang, Li, Yuehua Hu, Runqing Liu, Jiapeng Liu, and Wei Sun. "Synergistic adsorption of DDA/alcohol mixtures at the air/water interface: A molecular dynamics simulation." Journal of Molecular Liquids 243 (October 2017): 1–8. http://dx.doi.org/10.1016/j.molliq.2017.08.029.

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Do, Trong Nhan, and Jian-Hong Wu. "Simulation of the inclined jointed rock mass behaviors in a mountain tunnel excavation using DDA." Computers and Geotechnics 117 (January 2020): 103249. http://dx.doi.org/10.1016/j.compgeo.2019.103249.

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