•Based on the force method, a modeling method for flexible joined wings under fully intrinsic formulation is proposed.•A mathematical proof for the existence and uniqueness of rotation in orientation ...compatibility condition is given.•By Galerkin...s discretization, the dynamics of joined wing is described by a set of differential-algebraic equations.•According to computing speed and numerical accuracy, the superiority of present method is revealed.•An excessive thrust can lead to the buckling of front wing and the co-existing solutions of joined wing.
The joined-wing aircraft is an alternative configuration compared to general cantilevered configuration because of its superiority. In the present work, an efficient modeling method for flexible joined wing is proposed. The fully intrinsic formulation is applied for the geometrically nonlinear effect and the static indeterminacy of joined wing is addressed based on the force method. To avoid mathematically over-determined problem, an orientation compatibility condition with profound physical meaning is established and subsequently a strict mathematical proof is given for the existence and uniqueness of rotation. By adopting Peters finite inflow theory, the unsteady aerodynamic model for joined wing is built up. The joined-wing aeroelastic model is eventually represented by a set of differential-algebraic equations. Following validation studies show that although the displacements and rotations are excluded, contributing to higher computing speed than the mixed formulation, the numerical accuracy of present method is close to mixed formulation and superior to the incremental method. Finally, the static aeroelastic analysis for a planar joined wing under a thrust force at wingtip is implemented within flutter boundary. Results show that the thrust force can lead to an axial compressive load in front wing and the co-existing solutions are revealed because of the buckling of front wing when the thrust force exceeds a threshold value. Further studies indicate that although either solution path is possible theoretically, the “upward-bending solution” is a more likely practical solution for the planar joined wing.
The paper presents a new four-dimensional hyperchaotic system developed by extension of the generalized diffusionless Lorenz equations. The model is shown to not be equivalent to any hyperchaotic ...system that the authors know of. In particular, the model does not display any equilibria, but can exhibit two-scroll hyperchaos as well as chaotic, quasiperiodic and periodic dynamics. For certain parameter values, coexisting attractors can be observed, e.g. hyperchaotic and periodic attractors. Investigation of the proposed system is performed through a combination of numerical simulation and mathematical analysis in order to obtain time plots, phase portraits, Lyapunov exponents, and Poincaré sections.
Bacterial infectious diseases cause serious harm to human health. At present, antibiotics are the main drugs used in the treatment of bacterial infectious diseases, but the abuse of antibiotics has ...led to the rapid increase in drug-resistant bacteria and to the inability to effectively control infections. Bacteriophages are a kind of virus that infects bacteria and archaea, adopting bacteria as their hosts. The use of bacteriophages as antimicrobial agents in the treatment of bacterial diseases is an alternative to antibiotics. At present, phage therapy (PT) has been used in various fields and has provided a new technology for addressing diseases caused by bacterial infections in humans, animals, and plants. PT uses bacteriophages to infect pathogenic bacteria so to stop bacterial infections and treat and prevent related diseases. However, PT has several limitations, due to a narrow host range, the lysogenic phenomenon, the lack of relevant policies, and the lack of pharmacokinetic data. The development of reasonable strategies to overcome these limitations is essential for the further development of this technology. This review article described the current applications and limitations of PT and summarizes the existing solutions for these limitations. This information will be useful for clinicians, people working in agriculture and industry, and basic researchers.
VIV of flexible structures in 2D uniform flow Kurushina, Victoria; Pavlovskaia, Ekaterina; Wiercigroch, Marian
International journal of engineering science,
20/May , Letnik:
150
Journal Article
Recenzirano
Odprti dostop
•Vortex-induced vibrations of flexible structures in uniform flow are considered.•New two-dimensional wake oscillator model of flexible structure is proposed.•Suite of models is calibrated with the ...existing experimental data.•Complex dynamics resulting in co-existing solutions of the calibrated models are studied.
Display omitted
The paper investigates Vortex-Induced Vibration (VIV) of a horizontal flexible structure with pinned-pinned ends in uniform flow. The fluid – structure interaction is modelled using the wake oscillator approach to describe fluctuations of the fluid forces based on the results, previously reported by Pavlovskaia et al. (2016), Postnikov (2016), and Kurushina et al. (2018). New two-dimensional wake oscillator models are developed in this study employing a number of alternative damping types in the fluid equation. The proposed models are calibrated with the published experimental data by Sanaati and Kato (2012), for VIV of a horizontal flexible structure for the middle cross-section. The calibration is performed with the focus on the maximum of the observed displacement amplitude in the cross-flow direction. One of the models having the Van der Pol – Krenk–Nielsen damping allowed achieving the lowest objective function during the calibration and, hence, was selected for the detailed analysis in 3 and 5 mode approximations. The dynamics of this model is considered in terms of the time histories, changes in the standard deviations of the modal coefficients along the reduced velocity range and frequency response. Also, a comparison with the alternative model versions in terms of the displacements generated at different locations is provided.
In contrast to the previous findings by Kurushina et al. (2018) for VIV of rigid structures, for the flexible structures it was found in this study that both Van der Pol and Rayleigh damping types appear to be applicable for the VIV prediction. A detailed consideration of the 3 mode approximation of the Krenk–Nielsen – Van der Pol model reveals a presence of co-existing solutions in a number of regions of the reduced velocity. They are present in short ranges of reduced velocity in between the lock-in peaks of the in-line displacement coefficient of the first mode. Modulations and co-existing solutions in the in-line modal coefficients make the in-line displacement prediction challenging while the cross-flow displacement amplitudes are described reasonably well by the proposed models.
This chapter contains sections titled: <list style="bulleted" xml:id="l1"> Introduction The business drivers Failure scenarios Existing solutions Protecting the egress – local protection ...solution Conclusion References Further reading Study questions
This chapter contains sections titled:
Function Analysis and Maps for Problem Understanding
Why Use TRIZ Function Analysis?
What Can TRIZ Function Analysis Reveal at a Glance?
Basic Building Blocks ...for Problem Solving – Defining Ideality
For Problem Solving We Need Both the Ideality Audit and the Function Analysis
Function Analysis of the Current System (System We've Got)
Function Analysis for Understanding and Solving Simple Problems
Systems Develop to Deliver Benefits Better – Perfecting Functions to Deliver
Those Benefits
Systems Develop in Response to Changing Needs
Simple Rules of Function Analysis
Function Maps Contain All the System and Relevant Environmental Elements
Problem Solving from the Function Analysis Problem List
Oxford Standard Solutions for Solving Problems Mapped in Function Analysis
Function Analysis at Every Stage and for Every Kind of Difficult Problem
Function Analysis Identifies All Significant Problems
Example of Function Analysis of a Single Item – a Coffee Cup
Function Analysis For Locating and Dealing with the Causes of Problems – Roadside Bombs
Conclusion
Case study: Improving the Opening of the Bitesize Pouch at Mars
Mars Enjoys Immediate Success of New Pouch Packaging Concept
The Pouch Problem
Solving the Pouch Problem with TRIZ
The Winning Idea and the Validation
Patenting the Idea
The Future
Conclusion
Appendix 11.1 – Oxford Standard Solutions These are the Traditional TRIZ 76 Standard
Solutions Re‐Arranged into Three Categories
This chapter contains sections titled:
TRIZ for the Right Functions at the Right Time in the Right Places
Where Do We Start with TRIZ? Which Tools When?
TRIZ is Immediately Useful but Understanding ...Takes Time and Practice
Two Fundamental Areas in Practical Technical Problem Solving
Problem Understanding and Solving Routes and Applying the Ideality Tactics
The influence of humic acid (HA) on the removal of arsenic by FeCl
3
was systematically studied in this paper. Jar tests were performed to investigate the influence on arsenic during FeCl
3
...coagulation of the pH adjusting method, the initial As/Fe ratio, the equilibrium As concentration, and co-occurring anions and cations. Compared with results in HA-free systems, the removal trends of arsenic in HA solutions were quite different. It was found that As(V) removal was higher at low equilibrium concentration, yet the opposite was true for As(III) removal. The presence of HA influenced the effective number of active sites for arsenic removal by FeCl
3
flocculation. In addition, in the presence of HA, the impacts of co-existing solutions on arsenic removal were also different from that of an HA-free system. This study examined the influence of co-occurring anions, such as phosphate, sulfate, and silicate on arsenic removal, depending on their ability to compete for sorption sites and to hinder or facilitate the aggregation of ferric hydroxide flocs. The presence of Ca
2+
or Cd
2+
significantly increased arsenic removal at higher pH. Low concentrations of dissolved HA and high concentrations of colloid affected the adsorption of arsenic onto iron oxide. The influence of HA on the adsorption of arsenic onto iron oxide primarily depended on the relative content of the dissolved and mineral combination states of HA and the interface combination forms.
PDF
