Lightweight Design of Mechanical Structures based on Structural Bionic Methodology

With increasing concern over the excessive energy consumption and environment pollution, structural bionics is a viable new tool of lightweight design by mechanical engineers. The structural solutions derived from nature can be successfully transferred into technical construction for maximum structural efficiency from minimal resources. The goal of the study is to develop a standard methodology for bionic mechanical structures with dead-load reduction and performance improvement. Similarity theory and fuzzy assessment method are deployed for selection of analogical samples and analysis based on structure, loading and function similarities. The type spectrum of lightweight design is established for selection convenience and principle extraction, vital to concept designs. Finite element method is used as an effective tool for mechanical performance simulation and comparison. The rapid prototyping, investment casting and Numerical Control (NC) machining are discussed for model fabrication. The static and dynamic test results indicate that the bionic models are lighter but stiffer than the original ones. So by mimicking biological structural principles, the structural bionic design offers a new solution for updating traditional design concepts and achieving maximum structural efficiency.     

The Lightweight Design of Low RCS Pylon Based on Structural Bionics

<正> A concept of Specific Structure Efficiency (SSE) was proposed that can be used in the lightweight effect evaluation ofstructures.The main procedures of bionic structure design were introduced systematically.The parameter relationship betweenhollow stem of plant and the minimum weight was deduced in detail.In order to improve SSE of pylons, the structural characteristicsof hollow stem were investigated and extracted.Bionic pylon was designed based on analogous biological structuralcharacteristics.Using finite element method based simulation, the displacements and stresses in the bionic pylon were comparedwith those of the conventional pylon.Results show that the SSE of bionic pylon is improved obviously.Static, dynamic andelectromagnetism tests were carried out on conventional and bionic pylons.The weight, stress, displacement and Radar CrossSection (RCS) of both pylons were measured.Experimental results illustrate that the SSE of bionic pylon is markedly improvedthat specific strength efficiency and specific stiffness efficiency of bionic pylon are increased by 52.9% and 43.6% respectively.The RCS of bionic pylon is reduced significantly.     

Dynamics Modeling and Simulation of a Bionic Swim Bladder System in Underwater Robotics

While considering that fish could suspend themselves under water and could enhance their mobility by adjusting its swim bladder, we have carried out research on a bionic swim bladder system in underwater robotics, which could amend the underwater robotics' static balance and controllability conditions even if the depth of water changes. First, this paper introduces the bio-swim bladder's structure and function. Second, it works out the dynamic model of the bionic swim bladder, and then it analyses the dynamic characteristic and effect of the bionic swim bladder system with the software Matlab/simulink. Finally, considering about the nonlinear relationship of the parameters in the model, this paper brings forward a dual-speed control method, which could make the effect of the bionic swim bladder non-coupling. The result of the simulation reveals that the bionic swim bladder could change the buoyancy and centroid distribution of the underwater robotics effectively and independently, bringing it into a balance state, under which the control and maneuverability could be enhanced.     

Bionic Leaf Simulating the Thermal Effect of Natural Leaf Transpiration

We proposed a kind of bionic leaf to simulate the thermal effect of leaf transpiration. The bionic leaf was firstly designed to be composed of a green coating, a water holding layer, a Composite Adsorbent （CS） layer and an adsorption-desorption rate controlling layer. A thermophysical model was established for the bionic leaf, and the dynamic simulation results reveal that the water holding layer is not necessary; a CS of high thermal conductivity should be selected as the CS layer; the adsorp- tion-desorption rate controlling layer could be removed due to the low adsorption-desorption rate of the CS; and when CaC12 mass fraction of the CS reaches 40%; the bionic leaf could simulate the dynamic thermal behavior of the natural leaf. Based on the simulation results, we prepared bionic leaves with different CaC12 content. The thermographies of the bionic leaf and the natural leaf were shot using the Infrared Thermal Imager. The measured average radiative temperature difference between the bionic and natural leaves is less than 1.0 ℃.     

Design of Bionic Saw Blade for Corn Stalk Cutting

The serrated incisors of grasshopper [Chondracris rosea rosea （De Geer）] possess an advantageous capacity for cutting plant fiber. Inspired by this special geometrical structure of incisors, bionic saw blade was designed and manufactured. MATLAB software digital image processing technology was used to obtain outer margin profile from stereomicroscope pho- tograph of the serrated incisors. The outer margin profile of incisors was fitted and expressed by six-order polynomial function. To compare the cutting capacity of bionic and traditional saw blades, the internodes of dry corn stalks were cut perpendicularly. Cutting force-deformation characteristics were obtained by universal testing machine. The results of cutting experiments show that the maximum cutting force of bionic saw blade was 128.26 N, which is 15.87% lower than 152.45 N of traditional saw blade; the average cutting force of bionic saw blade was 51.56 N, which is 28.17% less than 71.78 N of traditional saw blade. Meanwhile, the cutting energy consumption of bionic saw blade was 8.95 J, which is 12.85% less than 10.27 J of traditional saw blade. Overall, the bionic saw blade can lead to noticeable reduction of the cutting force and energy. These results will be helpful for designing cutting elements of corn stalk harvesting, biomass size reduction and other processing machinery.     

Myosin V motor proteins: marching stepwise towards a mechanism

Mammalian myosin V motors transport cargo processively along actin filaments. Recent biophysical and structural studies have led to a detailed understanding of the mechanism of myosin V, making it perhaps the best understood cytoskeletal motor. In addition to describing the mechanism, this review will illustrate how "dynamic" single molecule measurements can synergize with "static" protein structural studies to produce amazingly clear information on the workings of a nanometer-scale machine.     

Mechanisms of changes in the human spinal column in response to static and dynamic axial mechanical loading

The purpose of this study was to analyze the characteristics of the reaction of the human spinal column to axial static and dynamic loading. Segments of human column from dorsal vertebra XI to lumber vertebra III were exposed to axial static (20 mm/min) and dynamic (200 and 500 mm/min) loading. The measured variables included the load value, whole segment deformation, deformation of the anterior surfaces of intervertebral disk of Th_XI–Th_XII and dorsal vertebra XII, and acoustic emission signals (indicator of spongy bone microdestruction). It was found that the rate of increase in body deformation is lower than that in the intervertebral disk deformation and that the central parts of the spinal end plate compress greater than the peripheral parts. This difference was larger during static loading than that during dynamic loading. To produce the same deformation of a spinal segment due to dynamic loading as that due to static one, it is necessary to overcome a stronger resistance of a greater number of trabecular bones than that due to static loading. Therefore, it can be concluded that, first, the value of dynamic loading causing the same segment compression should be higher than the value of static loading, and the main practical significance here is that the dynamic strength of the column is markedly higher than the static one; second, spinal hardness during impact is higher than that under the static condition; and, third, the same degree of deformation should result in a larger volume of microdestructions in the case of dynamic loading than that in the case of static loading, which is evidenced by a significant difference in the number of AE signals accumulated prior to fracture. The number of AE signals is 444.2 ± 308.2 and 85.0 ± 36.6 in the case of dynamic and static loading, respectively (p < 0.05 according to Student’s t test).     

Elastic BucMing of Bionic Cylindrical Shells Based on Bamboo

High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.     

Elastic Buckling of Bionic Cylindrical Shells Based on Bamboo

High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years.Biomimicking from nature may offer the potential for lightweight design. In the viewpoint of mechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.     

A Case Study of a Force-myography Controlled Bionic Hand Mitigating Limb Position Effect

Force Myography (FMG),which monitors pressure or radial deformation of a limb,has recently been proposed as a potential alternative for naturally controlling bionic robotic prostheses.This paper presents an exploratory case study aimed at evaluating how FMG behaves when a person with amputation uses a hand prosthetic prototype.One volunteer (transradial amputation) participated in this study,which investigated two experimental cases:static and dynamic.The static case considered forearm muscle contractions in a fixed elbow and shoulder positions whereas the dynamic case included movements of the elbow and shoulder.When considering eleven different hand grips,static data showed an accuracy over 99％,and dynamic data over 86％ (within-trial analysis).The across-trial analysis,that takes into account multiple trials in the same data collection set,showed a meaningful accuracy respectively of 81％ and 75％ only for the reduced six grips setup.While further research is needed to increase these accuracies,the obtained results provided initial evidence that this technology could represent an interesting alternative that is worth exploring for controlling prosthesis.     

Influence of PVD-duplex-treated,Bionic Surface Structures on the Wetting Behavior for Sheet-Bulk Metal Forming Tools

Bionic surface structures,inspired by the flora,were developed for Sheet-Bulk Metal Forming (SBMF) in order to locally control the friction condition by adjusting the wetting behavior.Five bionic structures were micromilled on ASP(R)2023,in annealed as well as hardened and tempered conditions.Subsequently,the structured surfaces were plasma-nitrided and coated with a CrA1N thin film.The influence of the treatment method on the structural geometry was investigated with the aid of a scanning electron microscope and 3D-profilometer.The wetting behaviors of water and deep drawing oil (Berufluid ST6007) on bionic surfaces were evaluated using contact angle measurements.The resulting micro-milled structures exhibit an almost identical shape as their bionic models.However,the roughness of the structured surfaces is influenced by the microstructure.The combination of plasma-nitriding and Physical Vapor Deposition (PVD) leads to an increase in roughness.All bionic structures possess higher contact angles than that of the unstructured surfaces when wetted by water.This can be explained by the fact that the structural elevations block the spreading.When the bionic surfaces are wetted by deep drawing oil,the lubricant spreads in the structural cavities,leading to smaller contact angles.Furthermore,the anisotropy of the structure has an influence on the wetting behavior.     

大孔吸附树脂对家蝇抗菌肽的吸附与分离纯化

通过比较6种不同型号的大孔吸附树脂对家蝇蛋白的吸附解吸特性,发现D101大孔吸附树脂的性能优于其他5种,吸附流速、浓度影响大孔吸附树脂的动态吸附性能。D101大孔吸附树脂对未经诱导的家蝇蛋白的吸附量可达217．18mg／g（以干树脂总量为基准）,洗脱率为76．48％。吸附后的大孔吸附树脂用15％、35％、55％的乙醇溶液阶段洗脱,各洗脱组分的疏水性逐渐增大,蛋白质含量也明显增加。用E.coli、S．aureus和B．subtilis对各洗脱组分进行抑菌活性测定,抑菌活性随洗脱组分的疏水性增加而增大。测得55％乙醇洗脱组分的抑菌活性最大,其中对E.coli的抑菌圈直径达5．8mm。     

Erosion-Resistant Surfaces Inspired by Tamarisk

Tamarisk, a plant that thrives in arid and semi-arid regions, has adapted to blustery conditions by evolving extremely ef- fective and robust anti-erosion surface patterns. However, the details of these unique properties and their structural basis are still unexplored. In this paper, we demonstrate that the tamarisk surface only suffers minor scratches under wind-sand mixture erosion. The results show that the anti-erosion property of bionic sample, inspired by tamarisk surface with different surface morphologies, can be attributed to the flow rotating in the grooves that reduces the particle impact speed. Furthermore, the simulation and experiment on the erosion wear behavior of the bionic samples and bionic centrifugal fan blades show that the bionic surface with V-type groove exhibits the best erosion resistance. The bionic surface on centrifugal fan blades with opti- mum parameters can effectively improve anti-erosion property by 28.97%. This paper show more opportunities for bionic application in improving the anti-erosion performance of moving parts that work under dirt and sand particle environment, such as helicopter rotor blades, airplane propellers, rocket motor nozzles, and pipes that regularly wear out from erosion.     

Relationship between dilemma occurrence and the existence of a weakly dominant strategy in a two-player symmetric game

Defining the dilemma game by the proposition, A game cannot sustain an increase of cooperation strategy in its strategy distribution, we deduced that the substance of a dilemma can be expressed by a productive summation of the static factor and the dynamic factor independently. A static factor is an element of the game's structure that influences a possible dilemma, which relates to a game's structural deviation from a situation where the cooperation strategy can be weakly dominant over other strategies. In contrast, a dynamic factor refers to a strategy distribution's influence on the dilemma by affecting the game dynamics. In a 2x2 game, the existence of a dilemma can be determined only by a static factor. That is, whether or not a dilemma occurs is related only to the structural effect of the game. On the other hand, in a more-than-two-strategies game, both static and dynamic factors determine the occurrence of a dilemma, and the static factor cannot solely explain the occurrence of a dilemma.     

Determination of mechanical properties of human femoral cortical bone by the Hopkinson bar stress technique

The Hopkinson bar stress technique and a universal testing machine (Instron 1125) have been used to investigate the dynamic and static mechanical properties of cortical bone taken from a human femur respectively. We found that the average dynamic Young's modulus value (Ed = 19.9 GPa) to be 23% higher than the average static Young's modulus value (Ed = 16.2 GPa). Furthermore, the Poisson's ratio did not exhibit any significant variation for the two different types of loading. No difference was observed between the values of the dynamic Young's modulus in tension and those found in compression. A comparison was made of the results of this study with those found by other researchers using different techniques, such as ultrasonics, and it was found that they agree well with most of the results of previous studies. Finally, the viscosity for cortical bone found in this study correlates with viscosity reported by Tennyson et al. [Expl Mech. 12, 502-507 (1972)] for ten days post mortem age specimens.     

Study of a Bionic Paddy Impeller Inspired by Buffalo Hoof

Based on the particular geometric characteristics of buffalo hoof, which is capable to walk on the soft soil of paddy-field with low resistance, a bionic blade for paddy field impeller was designed. The test results in soil bin show that the traction ability of the bionic blade for paddy wheel is improved. Compared with the conventional plate blade, the maximum pull force of the bionic blade is increased by 37.8% and the maximum impeller efficiency is 38.3% higher. Computational simulation analysis shows that bionic shape can improve the driving force of the impeller by resisting and reducing the impacts resulted from the sharp velocity change of the discontinuous surface water flow, and the driving torque of the bionic blade may increase as well.     

Loop-length-dependent SVM prediction of domain linkers for high-throughput structural proteomics

The prediction of structural domains in novel protein sequences is becoming of practical importance. One important area of application is the development of computer-aided techniques for identifying, at a low cost, novel protein domain targets for large-scale functional and structural proteomics. Here, we report a loop-length-dependent support vector machine (SVM) prediction of domain linkers, which are loops separating two structural domains. (DLP-SVM is freely available at: http://www.tuat.ac.jp/ approximately domserv/cgi-bin/DLP-SVM.cgi.) We constructed three loop-length-dependent SVM predictors of domain linkers (SVM-All, SVM-Long and SVM-Short), and also built SVM-Joint, which combines the results of SVM-Short and SVM-Long into a single consolidated prediction. The performances of SVM-Joint were, in most aspects, the highest, with a sensitivity of 59.7% and a specificity of 43.6%, which indicated that the specificity and the sensitivity were improved by over 2 and 3% respectively, when loop-length-dependent characteristics were taken into account. Furthermore, the sensitivity and specificity of SVM-Joint were, respectively, 37.6 and 17.4% higher than those of a random guess, and also superior to those of previously reported domain linker predictors. These results indicate that SVMs can be used to predict domain linkers, and that loop-length-dependent characteristics are useful for improving SVM prediction performances.     

Continuous Biosorption of Pb,Cu, and Cd by Phanerochaete chrysosporium in a Packed Column Reactor

The dynamic removal of lead, copper and cadmium in a single component system by Phanerochaete chrysosporium was studied in packed columns. The packed columns consisted of biomass of P. chrysosporium immobilized on polyurethane foam cubes. The performances of packed columns were described through the concept of breakthrough and the values of column parameters predicted as a function of bed depth. The column biosorption data were evaluated in terms of maximum (equilibrium) capacity of the column, the amount of metal loading and the yield of the process. The maximum capacities for lead, copper and cadmium were 70.7, 43.7 and 70.8 mg, respectively, and their yields were 39.2, 40.6 and 41%, respectively. The kinetic and mass transfer aspects of the dynamic removal of the three metals were studied using three mathematical models commonly used to describe the column performance in adsorption processes. Column studies showed good agreement between the experimental data and the simulated breakthrough curves obtained with Adams-Bohart or the Wolborska model and the Clark model. While the initial segment of the breakthrough curve was defined by the Adams-Bohart and Wolborska models, the whole breakthrough curve was well predicted by the Clark model for all the three metals studied.     

Impact of the type of microcarrier and agitation modes on the expansion performances of mesenchymal stem cells derived from umbilical cord

The present study proposed to compare the impact of agitation mode (static, orbital, and mechanical) on the culture of mesenchymal stem cells extracted from the Wharton's jelly of umbilical cords (WJ-MSC), in a clinical grade culture medium, using human platelet lysate and different xeno-free microcarriers. Attachment, expansion, and detachment performances were characterized by a new dedicated tool of microscopic image posttreatment, allowing an in situ cell counting without detachment step. Results showed that performances in static mode were not necessarily representative of those obtained in dynamic mode. Moreover, impacts on nutrient consumptions and metabolite productions were identified, such as a higher glutamine consumption when Cytodex-1 microcarriers were used. The detachment strategy used was relatively efficient for Star-Plus, Plastic-Plus, and Hillex II, but not sufficient for Cytodex-1. Despite Cytodex-1 presented promising attachment and expansion performances, Star-Plus and Plastic-Plus showed a better compromise, respectively, for the orbital and the mechanical agitation modes.     

Do People “Pop Out”?

The human body is a highly familiar and socially very important object. Does this mean that the human body has a special status with respect to visual attention? In the current paper we tested whether people in natural scenes attract attention and “pop out” or, alternatively, are at least searched for more efficiently than targets of another category (machines). Observers in our study searched a visual array for dynamic or static scenes containing humans amidst scenes containing machines and vice versa. The arrays consisted of 2, 4, 6 or 8 scenes arranged in a circular array, with targets being present or absent. Search times increased with set size for dynamic and static human and machine targets, arguing against pop out. However, search for human targets was more efficient than for machine targets as indicated by shallower search slopes for human targets. Eye tracking further revealed that observers made more first fixations to human than to machine targets and that their on-target fixation durations were shorter for human compared to machine targets. In summary, our results suggest that searching for people in natural scenes is more efficient than searching for other categories even though people do not pop out.