Dynamic Diagrams Research Articles

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ УПРУГОПЛАСТИЧЕСКОГО ДИНАМИЧЕСКОГО И СТАТИЧЕСКОГО СЖАТИЯ ПАКЕТОВ МЕТАЛЛИЧЕСКИХ ПЛЕТЕНЫХ СЕТОК

Multilayered packages of metallic woven grids are used for protecting the vessels of explosion chambers and other structures from fragmentation damage and pulsed effects. A grid package is basically formed by stacking up several layers, observing the direction of the wires; that is why such a package can be considered to be a highly-porous deformable structural element with orthotropic properties. Earlier experimental studies made it possible to construct deformation curves for porous packages of woven grids under dynamic and static compression normal to the layer. To find out factors causing differences in dynamic and static deformation curves, normal compression of a symmetric fragment of woven grids under dynamic and static loading modes observed in the experimental studies was numerically modeled. The 3D processes of elastoplastic deformation of a fragment of a woven metallic grid, accounting for contact interaction between the wires, were numerically modeled with the help of computational systems ANSYS and ANSYS LS-DYNA using FEM. The analyzed area consisted of four 3D cylindrical bodies. Compression was applied with a pair of ideally rigid plates, symmetrically approaching each other. The deformational behavior of the wires was described using the model of plasticity with isotropic hardening. To obtain reliable computational results, a static deformation diagram was constructed for the steel the grid was made of. The effect of time limitation of the loading pulse was studied, as well as the effect of the difference in the static and dynamic deformation diagrams of the material of the grid. It is shown that the main effect on the dynamic behavior of the fragment of a porous package of steel grids is caused by the dynamic properties of the wire material, i.e., by the difference between the dynamic and static deformation diagrams. The final duration of the loading pulse and friction between the wires do not have any significant influence for that type of grids.

Use of the Kolsky method for dynamic tests of brittle media

The dynamic test techniques used to obtain the mechanical properties of brittle materials are described. The techniques are based on the fundamental Kolsky method using the Split-Hopkinson Pressure Bar. Dynamic tests are characterized by high intensity and short duration and the influence of inertia on their results should be ruled out which is especially important for brittle media. The prerequisites and assumptions presented methods are described to justify the validity of the obtained data. The methods allow to obtain dynamic deformation diagrams at compression, splitting, indirect tension, shear and triaxial stress state and also to determine the ultimate strength, strain and time properties of brittle materials. The techniques are approved in the tests of ceramic bricks, finegrain concrete and fiber-reinforced concrete.

Numerical analysis of influence of length of the working part of specimen on dynamic diagrams of constructional materials obtained by the Kolsky method

It is known that experiments with intensive dynamic influences and high-speed deformation of specimens under tension are important in the analysis of deformations and strength of structures and their elements. The most reasonable and widely used method for obtaining dynamic stressstrain curves, characteristics of ultimate strength and deformations is the modified Kolsky method. It should be noted a small number of publications on the analysis of the influence of fillets and the length of the working part of the specimen on the most important mechanical characteristics obtained by this method. This work is aimed at increasing knowledge in this area. By numerical and experimental analysis it was established that when the working part of the specimen has a length of 5 mm, then the uniformity and one-dimensionality of the stressed state are seriously violated. When choosing the length of the specimen in the Kolsky method, there are important limitations: the length of the specimen must be much smaller than the length of the loading pulse. Therefore, in this study, two specimen lengths of 10 and 15 mm were analyzed. In this paper, we give experimental and calculated diagrams and their comparison with each other. It was shown, that for the above-mentioned lengths, the homogeneity and one-dimensionality of the stressed state is substantially improved.

Features of excitation reconstruction in flat multielement phased antenna array face using dynamic directional patterns

The study focuses on reconstructing the amplitude-phase distribution of flat multielement passive and active phased antenna arrays with the use of dynamic radiation patterns, measured with electronical scanning without mechanical rotations and antenna movements. The paper describes the measurement settings of dynamic radiation patterns, necessary for reconstructing the amplitude-phase distribution. Findings of the research show that to reconstruct the amplitude-phase distribution according to dynamic radiation diagrams, there is no need for increased computational resources due to the use of Fourier transformation algorithms. After the method was experimentally verified on the specific samples of active phased antenna arrays, its high efficiency was established. The paper gives the examples of reconstructing the amplitude-phase distribution from dynamic radiation patterns in the presence of malfunctions in active phased array antennas.

Dynamics of Two Point Vortices in an External Compressible Shear Flow

This paper is concerned with a system of equations that describes the motion of two point vortices in a flow possessing constant uniform vorticity and perturbed by an acoustic wave. The system is shown to have both regular and chaotic regimes of motion. In addition, simple and chaotic attractors are found in the system. Attention is given to bifurcations of fixed points of a Poincare map which lead to the appearance of these regimes. It is shown that, in the case where the total vortex strength changes, the “reversible pitch-fork” bifurcation is a typical scenario of emergence of asymptotically stable fixed and periodic points. As a result of this bifurcation, a saddle point, a stable and an unstable point of the same period emerge from an elliptic point of some period. By constructing and analyzing charts of dynamical regimes and bifurcation diagrams we show that a cascade of period-doubling bifurcations is a typical scenario of transition to chaos in the system under consideration.

Evidence-based framework for real-time life-cycle management of fatigue-critical details of structures

Ship structures are subjected to repetitive wave loads that can lead to fatigue damage. Accumulation of fatigue damage may eventually result in structural failure. In order to mitigate fatigue hazard to ship structures, timely inspections and maintenance actions must be planned during their life-span. As delays in the process of decision-making could result in the increase of the risk of failure, decision-supportive frameworks working in a real-time fashion are extremely important. In this paper, a life-cycle management framework for fatigue-critical details is proposed on the basis of Dynamic Bayesian Network (DBN) and Influence Diagram (ID). The proposed framework, established based on a stochastic fatigue crack growth model, leverages exact inference and discretisation of continuous random variables to enable real-time Bayesian updating and utility-based decision-making. Compared with previous life-cycle management studies, the new framework is capable of making decisions regarding different inspection techniques and appropriate repair actions in a holistic manner. The relatively simple structure of DBN and ID also makes the proposed framework especially attractive to stakeholders and practitioners, who may have limited knowledge of statistics, Bayesian updating and utility theories.

Stability of a multi-body driveshaft system excited through U-joints

The disk-shaft system is a power transmission system with several industrial applications. The shafts, depending on the mechanism application, can be connected by U-joints through different rotating axes. In spite of the many advantages, these joints transform a constant rotating speed into a variable output one. Therefore, the multi-body system is self-excited that lead to dynamic instability. Here, a driveline system including three elastic shafts, which carry three disks, is considered. The oscillating behavior and resonance phenomenon of this fluctuating mechanism are investigated qualitatively and quantitatively. The angle of joints, damping and stiffness effects are the major topics of the present contribution. Eventually, dynamic stability diagrams are obtained by using a reliable and exact method based on the Floquet theory. It can be found that variations of the first U-joint angle and the intermediate shaft characteristics have greater impact on the machine instability. It is revealed how the stability of the system can be achieved by changing the geometry, shaft damping and stiffness, which should be considered in design and practical applications.

Mesoscale plastic flow instability in a solid under high-rate deformation

Here we consider high-rate deformation in solids in the context of a nonlocal transport theory, present a dynamic stress-strain diagram with elastic and plastic portions defined from a single standpoint, determine the conditions for pulse stress accumulation, and propose a mathematical model of momentum and energy exchange between scales and an instability criterion for transient plastic flow under shock loading. Phe instability criterion for high-rate deformation is verified by the example of shock loading of high-strength 30CrNi4Mo steel.

북한의 항일서사 연구시론

북한문학에 있어서 항일투쟁문학은 김일성의 정통성과 관계되는 부분으로서 중요한 위치를 차지한다. 특히 주체시대에 항일투쟁문학은 문학의 주요 흐름으로 자리 잡았다. 사실 북한의 항일투쟁문학은 해방공간에서부터 시작되어 주체시대에 들어서서 고조를 이루었다. 즉 해방공간에 있어서 "김일성 장군의 노래"는 그 서곡을 이루었고 “백두산”은 ‘영웅서사시’를 형성했다. 주체시대에 있어서는 “불멸의 총서” 해방 전 편 ‘항일투쟁편’을 창작하여 김일성의 항일서사를 전면적이고 체계적으로 진행했다. 본고는 해방공간과 주체시대에 있어서 김일성항일서사를 고찰했다. 즉 해방공간에 있어서 김일성을 건국의 주인공으로서 ‘영웅서사시’와 주체시대에 있어서 유일사상체계를 수립에 있어서 김일성 신격화와 우상화 작업으로서의 ‘영웅서사시’를 고찰했다. 결론적으로 보면 북한에서의 항일서사는 김일성을 둘러싸고 그의 정치적 자본을 얻고 확립하는 문학의 시녀적 성격이 다분하다. 이런 ‘영웅서사시’적 작업을 통하여 김일성은 ‘절세의 애국자’, ‘만고의 빨찌산’, ‘김일성장군’ 및 천출위인, 백전백승의 강철의 영장의 형상이 수립되고 현실적으로 "위대한 수령"으로 군림하고 인민들은 "수령복"을 만끽하는 정치적 역학관계를 형성한다. The anti-Japanese War literature of North Korean literature is consistent with the orthodoxy of Kim Il-sung. Especially in the “Juche Age”, the anti-Japanese War literature was in a dominant position in the whole North Korean literature. The literature began in the liberation war period and reached its peak in the “Juche Age”. Concretely speaking, “Song to General Kim Il-sung” in the liberation war period opened the prologue, “Beakdu Mountain” promoted “heroic narrative poem”, and Immortal Series’ prequel—“anti-Japanese War piece” in “Juche Age” started to elaborate Kim Il-sung’s anti-Japanese struggle history comprehensively and systematically. Given all this, this paper respectively investigates Kim Il-sung’s anti-Japanese struggle history in the liberation war period and “Juche Age”. It refers to the “heroic narrative poem” of the Founding Father Kim Il-sung in the liberation war period and the deific and idolized “heroic narrative poem” of Kim Il-sung in the only established ideological system of “Juche Age”. According to the investigation, the narrative of North Korean anti-Japanese War took Kim Il-sung as the main line and tried to establish his political capital. By means of the “heroic narrative poem”, Kim Il-sung is shaped as “a loyal patriot”, “an immortal guerrilla”, “General Kim Il-sung”, “the great man from above”, “an ever-victorious iron soldier”, and “a great leader”. At the same time, the “heroic narrative poem” delineates the political dynamics diagram that people enjoy “the leader’s blessing”.

Dynamic correlation diagrams for sigmatropic reactions based on orbital phase conservation theory

For sigmatropic reactions, such as [1,3] and [1,5] hydrogen shifts, the Cope and Claisen rearrangements, and the Berson–Nelson rearrangement, no correlation diagrams consistent with the classical electronic formulas have been reported. Here, we report dynamic correlation diagrams for these sigmatropic reactions based on orbital phase conservation theory. The diagrams are consistent with both the selection rules of sigmatropic reactions proposed by Woodward and Hoffmann and classical electronic formulas.

Production Scheduling of Open Pit Metal Mine with Ecological Cost

The ecological costs related to the various optimized production schemes were calculated based on the designed ultimate pit. Moreover, the influence of the ecological costs on the selection of production schemes was discussed. In one designed pit, a series of geologically optimum pushbacks with sufficiently small increment were produced using the floating cone method founded on the principle of the highest metal content. Then all the pushbacks were reordered by the dynamic network diagram. The production scheme with the maximum NPV route was considered as the optimum one. The ecological impacts produced by mining were quantified and the ecological cost calculation models, which contain the direct eco-value loss, the indirect eco-value loss, the eco-restoration cost and the carbon emission cost were proposed. In one big open pit mine case, various production schemes were optimized and the one with maximum NPV was selected without taking into account the eco-costs. The scheme with the maximum comprehensive profit was obtained by calculating the eco-cost of each scheme. The results showed that the best scheme considered with the eco-cost was not the scheme with the maximum NPV. Therefore, the eco-cost presents the effect on the selection of the best production scheme.

Effect of vanadium on dynamic continuous cooling transformation behavior of medium-carbon forging steels

Dynamic continuous cooling transformation (CCT) behavior of medium-carbon forging steels microalloyed with different V contents up to 0.29% was investigated by means of dilatometric measurement, microstructural observation and hardness measurement. The results showed that the dynamic CCT diagrams were similar and the main difference was that the fields of the transformation products were shifted to the right side of the diagrams with the increase of V content, and this effect was more noticeable with an addition of 0.29% V. The Ac1 and Ac3 temperatures showed increasing trends with increasing V content, while the critical cooling rates decreased with increasing V content. The increase of V content resulted in significant increase of hardness and this tendency was enhanced with increasing cooling rate until the formation of acicular ferrite (AF). A promising approach of remarkably improving the toughness of ferritic-pearlitic medium-carbon forging steels with suitable V addition and the introduction of AF without notable penalty on its strength level was suggested.

Process operating performance optimality assessment with coexistence of quantitative and qualitative information

AbstractWhen the process is working normally, process operating performance optimality assessment makes a further judgment on how well the process is running currently. Sustained optimal process operating performance guarantees the greatest economic benefits. However, the operating performance may deteriorate from the optimal status due to the production condition shifts. It is crucial to accomplish operating performance optimality assessment strategies for a deeper understanding of the process status. A Dynamic Causality Diagram (DCD) explicitly and intuitively describes the causal correlations between variables. However, an actual process has both quantitative and qualitative measurements, which makes the conventional DCD imprecise or even invalid. To handle the above problems, a modified DCD is proposed to assess a complicated process with coexistence of quantitative and qualitative information. An operating performance optimality assessing strategy based on the proposed DCD is then established. The proposed method is successfully applied to a gold hydrometallurgy process, and the operating performance optimality assessment result is satisfied.

Towards an Intelligent and Dynamic Geometry Book

The pursuit of an Intelligent and Dynamic Geometry Book should involve the study of how currently developing methodologies and technologies of geometry knowledge representation, management, deduction and discovery can be incorporated effectively into future education. Just as Doron Zeilberger pointed out in the Plane Geometry: An Elementary Textbook By Shalosh B. Ekhad (Circa 2050), a geometry book from the future would be a computer program, in which all the theorems can be automatically discovered (and of course proved) by computer and beautiful illustrations can be automatically generated and dynamically modified. Such a prospect motivates studies on how to represent and manage digitised geometric knowledge on computer. The geometry book of the future (the $$\mathcal {I}$$ nt $$\mathcal {D}$$ yn $$\mathcal {G}$$ eo $$\mathcal {B}$$ ook) should be adaptive, collaborative, visual and intelligent. Adaptive because the contents should adapt itself to the curricula and readers. It will allow collaborative work and its contents would be collaboratively formed using a knowledge base open to contributions. Statements and proofs should be en-lighted by dynamic geometry sketches and diagrams, and the correctness of the proofs should be ensured by computer checking. The book will be intelligent, the reader should be able to ask closed or open questions, and can also for proof hints. The book should also provide interactive exercises with automatic correction. Such a cloud platform, freely available in all standard computational platforms and devices, collaborative, adaptive to each and every user’s profiles, should bring together a whole new generation of mathematical tools with impact in all levels of education. To realise such a book, a network of experts must be built, increasing the connections between several research communities, such as: mathematical knowledge management; computer theorem proving and discovery; education, aggregating expertise in areas such as Proofs in a Learning Context; Interfaces and Searching; Tools Integration; Learning Environments in the Cloud. In this paper the author tries to make the case for such an endeavour.

DBN based failure prognosis method considering the response of protective layers for the complex industrial systems

Abstract In complex industrial systems, operating, regulating, maintenance activities and external incidents take place dynamically and multiple entities in same or different subsystems interact in a complex manner. Most of single faults have multiple propagation paths. Any local slight deviation is able to propagate, spread, accumulate and increase through system fault causal chains. It will finally result in system failure and unplanned outages or even catastrophic accidents. The key issues focus on both of how to reduce the probability of fault occurrence and decrease the loss of fault consequence. The implementation of such requirements can be studied in terms of the determination of the fault root causes, prediction of the possible consequence, and also estimation of the risk and timing of various maintenance activities, which are considered in a failure prognosis scheme. This study proposes a DBN based failure prognosis method for complex system. Not only the interaction between components, but also the influence of the layers of protection in the system is considered when the dynamic failure scenarios are analyzed. Therefore the proposed method considers multiple factors including degradation mechanism, parameter deviation, the response of the layers of protection and also the external environment. With this model, the dynamic influence diagram of the components' degradation trends can be calculated and be used to evaluate the different effects of the layers of protection quantitatively. Some key problems are also explained such as how to determine the new nodes in DBN representing the behavior of protective layers and how to update the CPT in the extended model. In the case study, the proposed method is tested on the flue gas energy recovery system (FGERS) which is widely used in the petrochemical industry to demonstrate its effectiveness. It makes a great help for early warning and optimization of the layers of protection in the complex industrial system.

Modeling of dynamic characteristics of freight car withoptimized parameters of wedge-type shock absorber

Shock absorbers are intended for developing forces providing the elimination or reduction of the amplitude of cars or their parts fluctuations. On the CIS railroads, the wedge-type shock absorber became the most wide-spread in trucks of freight cars. In friction shock absorbers, the friction force arises in vertical and horizontal movements of the absorber wedges rubbing on friction plates fixed on the columns of the truck sidewalls. In the article, the modeling of dynamic characteristics of a freight car with the optimized parameters of the wedge-type shock absorber is performed. The modeling is performed by means of the software complex for studying the problems of dynamics of rail vehicles: “The universal mechanism”. A dynamic and block diagram of the dynamic model of the car platform, as well as of the mathematical model for studying the friction force and interaction of contact power elements, accounting the creep forces in contact by means of the FASTSIM algorithm based on the Kalker linear theory, is developed. The obtained results of modeling of an eight-wheel freight car with modernized frictional wedges show that in the truck modernization it is expedient to provide additional devices, for example a frictional shock absorber in the central step of suspension. The results of the carried out study prove the expediency of using for the upgraded truck of 18-100 model the design of M1816.06.000 SB, M1819.00.000 SB wedges, at this it is recommended to accept rigidity of elastic elements of these wedges equal to 1.1 kN/mm that is a compromise solution for the safe car movement in the empty and loaded modes.

Research of prevalence of schistosomiasis in Hunan province, 1984-2015

Objective: To analyze the prevalence of schistosomiasis in Hunan province, and provide scientific evidence for the control and elimination of schistosomiasis. Methods: The changes of infection rates of Schistosoma (S.) japonicum among residents and cattle in Hunan from 1984 to 2015 were analyzed by using dynamic trend diagram; and the time regression model was used to fit the infection rates of S. japonicum, and predict the recent infection rate. Results: The overall infection rates of S. japonicum in Hunan from 1984 to 2015 showed downward trend (95.29% in residents and 95.16% in cattle). By using the linear regression model, the actual values of infection rates in residents and cattle were all in the 95% confidence intervals of the value predicted; and the prediction showed that the infection rates in the residents and cattle would continue to decrease from 2016 to 2020. Conclusion: The prevalence of schistosomiasis was in decline in Hunan. The regression model has a good effect in the short-term prediction of schistosomiasis prevalence.

Process operating performance optimality assessment and non-optimal cause identification under uncertainties

In his research, a modified Dynamic Causal Diagram (DCD) based process operating performance optimality assessment and non-optimal cause identification method is proposed to handle the online assessment of the complicated chemical processes, where certainties and uncertainties coexist. In addition, the multi-source information usage problem of the traditional DCD is addressed. In the online application, a newly developed scheme is developed, which distinguishes stable performance grade and grades switch transition. For the non-optimal performances, a contribution based root cause identification method is developed, on the framework of the constructed DCD. Finally, the operating performance of a gold hydrometallurgy process is assessed by both the traditional DCD and the modified DCD. The superiority on accuracy and robustness of the modified DCD is demonstrated, and the responsible events for non-optimality is successfully isolated by the proposed contribution based non-optimal cause identification technique.

EFESTS: Educational finite element software for truss structure – Part 3: Geometrically nonlinear static analysis

This article covers the modeling, formulation, solution, and software development of the geometrically nonlinear static finite element method of truss structure. Firstly, we summarize the total Lagrange bar elment formulation, which includes the tangent stiffness matrix and the internal force vector. Secondly, static class diagrams and dynamic sequence diagrams assist students in designing software architecture. Thirdly, the analytical example of the 2-bar truss structure and the numerical example of the 10-bar truss structure are presented to promote students’ understanding of geometrically nonlinear finite element theory and application. Finally, the developed software is free for educational research and can be downloaded from the website: http://mach.jlu.edu.cn/hb_images/xygk/xssz_sz_js.php?id=395 .

Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

DC current induced magnetization reversal and magnetization oscillation was observed in 500nm large size Co90Fe10/Cu/Ni80Fe20 pillars. A perpendicular external field enhanced the coercive field separation between the reference layer (Co90Fe10) and free layer (Ni80Fe20) in the pseudo spin valve, allowing a large window of external magnetic field for exploring the free-layer reversal. A magnetic hybrid structure was achieved for the study of spin torque oscillation by applying a perpendicular field >3kOe. The magnetization precession was manifested in terms of the multiple peaks on the differential resistance curves. Depending on the bias current and applied field, the regions of magnetic switching and magnetization precession on a dynamical stability diagram has been discussed in details. Micromagnetic simulations are shown to be in good agreement with experimental results and provide insight for synchronization of inhomogeneities in large sized device. The ability to manipulate spin-dynamics on large size devices could be proved useful for increasing the output power of the spin-transfer nano-oscillators (STNOs).