基于奇函数的一类四维四翼混沌系统设计与电路实现

基于奇函数,提出了一类新的四维混沌系统,通过调整该系统的参数,使其在某些平面上形成四翼.对该类系统进行了数值模拟,对其一些基本的动力学行为进行了分析,如平衡点、耗散性和Lyapunov指数.研究了混沌系统的参数敏感性,讨论了系统相图随参数变化所呈现的周期、混沌等状态.设计了一个混动系统的振荡电路,通过MULTISIM得到的相图与数值模拟结果具有良好的一致性.      

Golden Ratio-Based and Tapered Diptera Inspired Wings: Their Design and Fabrication Using Standard MEMS Technology

This work presents our understanding of insect wings, and the design and micromachining of artificial wings with golden ratio-based and tapered veins. The geometric anisotropy of Leading Edge Veins (LEVs) selected by Diptera has a function able to evade impact. As a Diptera example, the elliptic hollow LEVs of cranefly wings are mechanically and aerodynamically significant. In this paper, an artificial wing was designed to be a fractal structure by mimicking cranefly wings and incorporating cross-veins and discal cell. Standard technologies of Microelectromechanical Systems (MEMS) were employed to materialize the design using the selected material. One SU-8 wing sample, light and stiff enough to be comparable to fresh cranefly wings,was presented. The as-prepared SU-8 wings are faithful to real wings not only in weight and vein pattern, but also in flexural stiffness and mass distribution. Thus our method renders possible mimicking with good fidelity of natural wings with complex geometry and morphology.     

Biomechanical aspects of the insect wing: an analysis using the finite element method

Insect wings appear as highly functional and largely optimized mechanical constructions. A series of stabilizing constructional elements have been 'designed' to cope with loading during flight. One such element is the expenditure of material in constructing the wing, i.e. the vein system of the wing and its arrangement. It functions like a zig-zag folding framework which stiffens the wing against aerodynamic bending moments. To quantify the quality of material distribution, models of a dragonfly wing and of a fly wing were calculated using the finite element method (FEM).     

Evolutionary origin of insect wings from ancestral gills

Two hypotheses have been proposed for the origin of insect wings. One holds that wings evolved by modification of limb branches that were already present in multibranched ancestral appendages and probably functioned as gills. The second proposes that wings arose as novel outgrowths of the body wall, not directly related to any pre-existing limbs. If wings derive from dorsal structures of multibranched appendages, we expect that some of their distinctive features will have been built on genetic functions that were already present in the structural progenitors of insect wings, and in homologous structures of other arthropod limbs. We have isolated crustacean homologues of two genes that have wing-specific functions in insects, pdm (nubbin) and apterous. Their expression patterns support the hypothesis that insect wings evolved from gill-like appendages that were already present in the aquatic ancestors of both crustaceans and insects.     

Evaluation of Pile Diameter Effect on Initial Modulus of Subgrade Reaction

This paper presents the results of a study on the effect of pile diameter on the initial modulus of subgrade reaction. A series of ambient and impact vibration tests were performed on four different diameters of cast-in-drilled-hole piles to determine the natural frequencies and damping of the soil-pile systems. The measured natural frequencies were then compared with those estimated from a numerical model. The soil springs in the numerical model were established by implementing two different concepts on initial modulus of subgrade reaction. One is based on Terzaghi’s concept in which the modulus of subgrade reaction is independent of pile diameter. The other was based on recent research suggesting that the initial modulus of subgrade reaction may be linearly proportional to pile diameter. It was found that the measured natural frequencies were in good agreement with the computed ones when the diameter-independent modulus of subgrade reaction was employed. In addition, the test results show that the damping ratio of the system varied with pile diameter from 3% for 0.4-m pile to 25% for 1.2-m pile.     

Numerical Modeling of Bed Evolution in Channel Bends

A two-dimensional numerical model is developed to predict the time variation of bed deformation in alluvial channel bends. In this model, the depth-averaged unsteady water flow equations along with the sediment continuity equation are solved by using the Beam and Warming alternating-direction implicit scheme. Unlike the present models based on Cartesian or cylindrical coordinate systems and steady flow equations, a body-fitted coordinate system and unsteady flow equations are used so that unsteady effects and natural channels may be modeled accurately. The effective stresses associated with the flow equations are modeled by using a constant eddy-viscosity approach. This study is restricted to beds of uniform particles, i.e., armoring and grain-sorting effects are neglected. To verify the model, the computed results are compared with the data measured in 140° and 180° curved laboratory flumes with straight reaches up- and downstream of the bend. The model predictions agree better with the measured data than those obtained by previous numerical models. The model is used to investigate the process of evolution and stability of bed deformation in circular bends.     

Dynamic Analysis of a Composite Cable-Stayed Bridge: Escaleritas Viaduct

This work describes some of the most important results of the experimental and numerical analyses of Escaleritas Viaduct, Spain. Before the inauguration of this composite cable-stayed bridge in 2006, the bridge authority required a dynamic load test identifying, for instance, the natural vibration modes, the dynamic magnification factor, and the maximum vertical acceleration. The dynamic test was accompanied by numerical simulation performed in two different three-dimensional finite-element models, one of them composed of 145,000 shell elements. The correlation of test and analysis data is good and allows several interesting general conclusions to be drawn. It is shown that Escaleritas Viaduct complies with the requirements on the dynamic structural behavior defined in the standards.     

Recurrent Single Delaminated Beam Model for Vibration Analysis of Multidelaminated Beams

Free vibration analysis of a through-width multidelaminated beam is performed in the present study. Multiple delaminations are assumed to spread from the top through the thickness direction of the beam. The natural frequencies of the multidelaminated beams are obtained from a recurrent single delaminated beam (RSDB) model, which is the subsingle delaminated beam from the top surface of a global beam. Each frequency equation for the RSDB with unknown boundary conditions is obtained through continuity conditions. Then this result is updated to the next one. With these sequential operations, the final frequency equation of the multidelaminated beams is obtained for both end boundary conditions of the global beam. The numerical results for the beams are compared with those of finite element analysis to give the reliance on the proposed model and to investigate the effects of the shape, number, and size of multidelaminations on the natural frequency. It was shown that the variations in the natural frequency for the multidelaminated beams were significantly affected by the delamination length.     

Development of Air Vehicle with Active Flapping and Twisting of Wing

This paper addresses mechanisms for active flapping and twisting of robotic wings and assesses flying effectiveness as a function of twist angle. Unlike the flapping motion of bird wings, insects generally make a twisting motion at the root of their wings while flapping, which makes it possible for them to hover in midair. This work includes the development of a Voice Coil Motor (VCM) because a flapping-wing air vehicle should be assembled with a compact actuator to decrease size and weight. A linkage mechanism is proposed to transform the linear motion of the VCM into the flapping and twisting motions of wings. The assembled flapping-wing air vehicle, whose weight is 2.86 g, produces an average positive vertical force proportional to the twist angle. The force saturates because the twist angle is mechanically limited. This work demonstrates the possibility of developing a flapping-wing air vehicle that can hover in midair using a mechanism that actively twists the roots of wings during flapping.     

Planform and Flexibility on Lift Characteristics for Flow over Low-Aspect Ratio Wings

Force measurement and surface oil flow visualization were carried out in wind tunnel to investigate the effects of wing’s planform and flexibility on aerodynamics for flow over low-aspect ratio wings. It is found that the empirical formulas proposed by Polhamus can present remarkably accurate predictions before stall for both rigid and flexible wings. The spiral vortex is responsible for rigid and flexible wing abrupt drop of lift coefficient after stall when the sweep angle is below 35°. The maximum lift coefficient and the stall angle for flexible wings are smaller than those for rigid ones when the sweep angle is below 40°, and the wing flexibility nearly does not influence the aerodynamics as the sweep angle is beyond 40°. Moreover, lift coefficient curves exist hysteresis loop in the following range of sweep angle: 10°–35° for the flexible wings and 5°–50° for the rigid wings. It can be deduced from oil visualization experiment that the sudden disappearance of spiral vortex flow structure may be responsible for the hysteresis.     

Comparison of transesophageal coronary sinus and left anterior descending coronary artery Doppler measurements for the assessment of coronary flow reserve

Genetic variation in correlations among size-related traits of head, thorax, and wings was examined in Drosophila buzzatii, by comparing the pattern of the Phenotypic Correlation Matrix (Rp) between inversion karyotypes of the second chromosome. No similarity in Rp was observed between some karyotypes in a natural population. The pattern of Rp in wild-reared heterokaryotypes, but not in homokaryotypes, was similar to the whole population represented by laboratory-reared flies. While phenotypic correlations in wild-reared flies were found to be larger than in laboratory-reared flies, similarity in the pattern of Rp was very high for one homokaryotype reared in both environments: the relatively homogeneous lab environment and the more variable field environment. While no such a similarity across environments was detected between different karyotypes, the pattern of Rp was similar for a same homokaryotype in different populations. Thus, the lack of karyotypic similarity in Rp is, at least partially, genetic. These results indicate that chromosomal inversions are factors affecting genetic correlations among traits known to be phenotypically correlated with adult fitness components in this species.     

Runout Analysis of Slurry Flows with Bingham Model

In this paper, the Lagrangian finite element method is formulated along with the Bingham model for simulating natural transient slurry flows. The numerical model thus developed is validated with available experimental results. As well, a back-analysis of the dynamic behavior of the 1997 Lai Ping Road landslide in Hong Kong is conducted. Correlating well with field observations, the modeling results are satisfactory in terms of predicting the hazard areas of the debris trail during runout and the debris distribution on deposition fan. The present method is also able to demonstrate the multidirectional sliding features of natural slurry flows. It is noteworthy that the availability of high quality data on site topography is crucial for modeling such a gravity-driven flow. A knowledge of dynamic runout information is useful in estimating landslide mobility, potential hazard areas, and debris impact loads, and in evaluating the effectiveness of counter measures in the debris released area, in relation to downslope property development.     

Suitability of Dynamic Modeling for Flood Forecasting during Ice Jam Release Surge Events

Ice jam release surges present a unique challenge to the flood forecaster, since the surge released when an ice jam fails is highly dynamic in nature and, therefore, traditional hydrologic flood routing techniques are inapplicable. The problem is analogous to the classic dam break scenario and should be amenable to analysis by hydraulic flood routing techniques. However, previous investigations suggest that the influence of ice on the wave propagation and attenuation must also be considered to achieve accurate results. This study explores the applicability of dynamic hydraulic flow modeling techniques to the ice jam surge propagation problem, presenting the results of numerical simulations of the ice jam release event which occurred on the Saint John River upstream of Grand Falls, N.B., in April 1993. The surge propagation analysis was conducted using a one-dimensional finite element implementation of the Saint Venant equations adapted for natural channel geometries. Even neglecting ice effects, the resulting model is successful in terms of reproducing the observed peak stage and the surge propagation speed. Based on these results, it is concluded that accurate channel geometry is a key factor in effectively modeling ice jam release surge events.     

Numerical Analysis of Geomaterials within Theory of Porous Media

It is widely accepted that the mechanical behavior of saturated geomaterials is largely governed by the interaction of the solid skeleton with the fluids present in the pore structure. This interaction is particularly strong in quasi-static and dynamic problems and may lead to the catastrophic loss of strength known as liquefaction, which frequently occurs under earthquake loading. In this work, numerical simulations of saturated granular deposits under transient loads are presented to illustrate the performance of a u-p-U finite-element method formulation and the versatility of the numerical implementation. Closed-form solutions based on both a Biot formulation and modern theories of mixtures are compared with numerical results. In addition, centrifuge experimental results are correlated with numerical simulations. A companion paper presents the details of the theoretical formulation and the numerical implementation within the finite-element method.     

Visual interneurons, sensitive to the size of objects and the direction of their movement in dragonflies of the genus Sympetrum]

Experiments have been made on 4 dragonfly species -- Sympetrum vulgatum, S. flaveolum, S sanguineum, S. danae. A pair of neurons was found in the thoracic ganglia and connectives, which has symmetrical contralateral receptive fields. These neurons are selectively sensitive to swift upward motion of a target of 3--10 degrees in size. This type of response was originally described by Zenkin and Pigarev [1, 2]. The receptive field, 120X25 degrees in size, is oriented horizontally from the medial rim of the eye. The center of sensitivity has the following polar coordinates: 15 degrees laterally from the medial plane and 20 degrees above the equatorial one. The relation of detecting properties of the observed neurones to key stimuli which trigger hunting behaviour is discussed. It is suggested that filtration of single and small optic stimuli by specialized detector neurons results not from the processes in the own receptive field of the neuron, but from the interaction with other neurons which are sensitive to motion of large objects and complex patterns.     

Face Stability Analysis of Circular Tunnels Driven by a Pressurized Shield

The aim of this paper is to determine the face collapse pressure of a circular tunnel driven by a pressurized shield. The analysis is performed in the framework of the kinematical approach of limit analysis theory. It is based on a translational three-dimensional multiblock failure mechanism. The present failure mechanism has a significant advantage with respect to the existing limit analysis mechanisms developed in the case of a frictional soil: it takes into account the entire circular tunnel face and not only an inscribed ellipse to this circular area. This was made possible by the use of a spatial discretization technique. Hence, the three-dimensional failure surface was generated “point by point” instead of simple use of existing standard geometric shapes such as cones or cylinders. The numerical results have shown that a multiblock mechanism composed of three blocks is a good compromise between computation time and results accuracy. The present method significantly improves the best available solutions of the collapse pressure given by other kinematical approaches. Design charts are given in the case of a frictional and cohesive soil for practical use in geotechnical engineering.     

The kleeblattsch?del anomaly in Apert syndrome: intracranial anatomy, surgical correction, and subsequent cranial vault development

We present a case of Apert syndrome in which intracranial anomalies of the cranial base were localized to the lesser wings of the sphenoid and sphenoid ridge. The lesser wings of the sphenoid were displaced superiorly to follow the fused coronal sutures bilaterally, where they met at a single point on the skull vertex. Careful preoperative study of the intracranial anatomy in the kleeblattsch?del anomaly led to a surgical plan for early correction of the anomaly. The present report indicates that an aggressive approach to the correction of the kleeblattsch?del anomaly beginning early in infancy can result in normalization of the trilobar skull configuration. Although this approach can correct the kleeblattsch?del anomaly, 3.5-year follow-up in this patient with Apert syndrome demonstrates progressive turricephaly despite repeated cranial vault remodeling. Although the trilobar skull configuration can be corrected through early surgical intervention, the long-term correction of progressive turricephaly in patients with Apert syndrome remains an unsolved problem.     

In-Plane Free Vibration of Symmetric Cross-Ply Laminated Circular Bars

A parametric study is performed to investigate influences of the opening angles, the slenderness ratios, the material types, the boundary conditions, and the thickness-to-width ratios of the cross section on the in-plane natural frequencies of symmetric cross-ply laminated circular composite beams. Governing equations are obtained based on the classical beam theory. The transfer matrix method is successfully applied to calculate exact natural frequencies with the help of an effective numerical algorithm, which was previously used for isotropic materials. The effects of the shear deformation, the axial deformation, and the rotary inertia are included in the formulation based on the first-order shear deformation theory. The physical system is considered as a continuous system. To verify the present theory, two examples are worked out for straight beams. A quite good agreement is observed with the reported results.     

冲刷深度对海上风电塔地震动力响应的影响分析

基于某海上风电塔进行现场监测、有限元模拟及室内振动台试验研究,考虑桩-土相互作用并对结构进行精细化数值模拟分析,研究了不同冲刷深度下结构自振周期的变化及不同冲刷深度对结构地震动作用下动力响应的影响规律.现场监测结果表明:6#风机结构受海水冲刷严重,与同时期建造的15#风机相比振动幅度明显,说明冲刷深度对结构的影响不可忽略.数值模拟分析表明:冲刷深度主要影响结构高阶振型,使结构自振周期变长,增幅最大达33%.由于冲刷致使土层对高柔性结构约束减弱,结构将产生大的振动进而导致风机停摆;在遭遇7度罕遇地震时,应立即停止发电工作.室内缩尺振动台试验与数值模拟所得结果的变化曲线较为均匀,趋势上较吻合,充分验证了数值模拟的准确性.      

高强深冲冷轧170P1板的试验研究

以高强IF钢(170P1)为研究对象,采用2种不同热轧工艺(常规热轧工艺、铁素体区热轧工艺)及随后相同的冷轧工艺、罩式炉退火及平整工艺进行了工业试制,试制结果表明:采用铁素体区热轧工艺,热轧板预退火及冷轧后,利用罩式炉退火就可保证高强IF钢的r值达2.1,采用这一工艺生产的高强IF钢板在汽车厂生产翼子板等难冲件时合格率可达100%.