Particle Erosion Resistance of Bionic Samples Inspired from Skin Structure of Desert Lizard, Laudakin stoliczkana

In order to improve the particle erosion resistance of engineering surfaces,this paper proposed a bionic sample which is inspired from the skin structure of desert lizard,Laudakin stoliczkana.The bionic sample consists of a hard shell (aluminum) and a soft core (silicone rubber) which form a two-layer composite structure.The sand blast tests indicated that the bionic sample has better particle erosion resistance.In steady erosion period,the weight loss per unit time of the bionic sample is about 10％ smaller than the contrast sample.The anti-erosion mechanism of the bionic sample was studied by single particle impact test.The results show that,after the impact,the kinetic energy of the particle is reduced by 56.5％ on the bionic sample which is higher than that on the contrast sample (31.2％).That means the bionic sample can partly convert the kinetic energy of the particle into the deformation energy of the silicone rubber layer,thus the erosion is reduced.     

Anti-Erosion Function in Animals and its Biomimetic Application

Material failure is usually caused by corrosion, wear and mechanical damage. According to previous researches, erosion wear holds about 8% of regular wear in industrial production. In the present work, a new approach, which adopted the idea of coupling bionics to improve erosion resistance of machine parts, was presented. Simulation by ANSYS/LS-DYNA finite element software was applied to predict the relative erosion severity, and experiment optimum design theory was employed to design experiment scheme. Silica sand of particle size 105 μm–830 μm was used as the erodent. The erosion tests were carried out to validate the simulation results obtained. It is shown that the simulation results are in agreement with those of the experiment. The morphologies of eroded surface were examined by scanning electron microscope, and the possible wear mechanism was discussed.     

Wear Resistance of 3Cr2W8V Rough Surfaces

Three types of rough surface were processed by laser irradiation on the 3Cr2W8V material hot-work die steel surface.The wear experiments with smooth surface and rough surface samples were repeated on the pin-tray wear machine. According to the wear results, we studied the regularity of wear resistance of different rough surface samples. The results indicated that bionic rough surface can improve the wear resistance of the material and the wear resistance can be increased 1 - 2 times, compared with the smooth surface. Also, the wear resistance of the rough surface was affected by laser current and duration of impulse. The bigger the laser current or the impulse duration, the better is the wear resistance. When the distance between the same kind of units which are distributed on the surfaces is changed, the wear resistance changes. The wear resistance of a bionic rough surface on which the grid units were distributed at spacing of 1 mm was the best. And we designed the wear models.     

Rhombomys opimus contribution to the “fertile island” effect of tamarisk mounds in Junggar Basin

Fertile islands are created and maintained by a combination of physical and biologically mediated processes. Plants have been shown to be very important in the formation of fertile islands, and recent research indicates that the activities of burrowing animals have a significant influence on the physiochemical properties of soil that can promote the development of fertile islands. In this paper, we chose tamarisk (Tamarix spp.)??a constructive species that grows in the oasis-desert ecotone, and the great gerbil (Rhombomys opimus)??a widely distributed rodent in Central Asia to study the influence of great gerbils on soil nutrient dynamics in tamarisk mounds. Results indicate that fertile islands exist in tamarisk mounds without burrows of the great gerbil. However, the great gerbil??s burrowing activities promote the fertile island effect in tamarisk mounds: soil nutrients under shrubs with great gerbil activity were significantly higher than inter-mound areas in both surface soil and deep soil from 15 to 50?cm. Available nitrogen in mounds with rodent burrows was over twice as high as in tamarisk mounds without burrows at the same depth. The great gerbil??s burrowing activities promote the concentration of soil nutrients in the tamarisk mounds.     

Thermal Cycling Effect on the Wear Resistance of Bionic Laser Processed Gray Iron

Thermal fatigue and wear both seriously affect the service life of some working parts. Environmental temperature will modify the surface conditions and influences the result of wear. In this research, to come close to working conditions, specimens were tested by a combination of thermal cycles and wear. Different cycles of thermal fatigue was carried out first on the gray iron specimens and subsequently wear test was performed to evaluate the effect of these thermal fatigue cycles. In this case, bionic laser processing was used to enhance the wear performance. The results indicated that bionic laser processing reduces the negative effects from thermal fatigue, such as grain fragmentation and oxidation. Because the initiation and growth of cracks as well as oxidation are suppressed in bionic processed areas. Bionic specimens exhibit high wear resistance compared with the common one. The process described can be considered as an effective method to improve the performance of gray iron in combined thermal fatigue and wear service conditions.     

DEM Numerical Simulation of Abrasive Wear Characteristics of a Bioinspired Ridged Surface

<正> This paper presents numerical investigations into a ridged surface whose design is inspired by the geometry of a Farrer'sscallop.The objective of the performed research is to assess if the proposed Bioinspired Ridged Surface (BRS) can potentiallyimprove wear resistance of soil-engaging components used in agricultural machinery and to validate numerical simulationsperformed using software based on the Discrete Element Method (DEM).The wear performance of the BRS is experimentallydetermined and also compared with a conventional flat surface.Different size of soil particles and relative velocities between theabrasive sand and the testing surfaces are used.Comparative results show that the numerical simulations are in agreement withthe experimental results and support the hypothesis that abrasive wear is greatly reduced by substituting a conventional flatsurface with the BRS.     

Internal Flow Effects on Isotropic Confined Sand-Clay Mixtures

Under the effect of internal flows, a liner can undergo a washing out of particles, which modifies the particle size distribution and affects hydraulic, chemical and mechanical characteristics. This paper discusses the effects of internal flows on sand/kaolin mixture, in terms of rate of erosion and modification of the hydraulic conductivity. A parametric study is conducted with a specific device that consists of three modified triaxial cells. These cells allow isotropically consolidating and confining specimens, they prevent a parasitic flow and survey large deformations of specimen. The tests reveal that suffusion of clay is accompanied by a clogging in the specimen that induces a drop in hydraulic conductivity. For high gradients the erosion of clay is accompanied by the backward erosion of sand and finally the specimen collapses. The erosion rate then depends on the values of the different parameters considered (hydraulic gradient, clay content and filter pore opening size).     

Improvement of Geomechanical Properties of Bio-remediated Aeolian Sand

Aeolian sand is widely distributed in the desert. It is susceptible to wind erosion because it consists of fine particles that lack cohesion between them. Wind erosion of Aeolian sand, dune migration, and dust storms in deserts affect the environment and infrastructure severely. Conventional chemical methods for lessening the effect of wind erosion are environmentally unfriendly. This paper examines Aeolian sand bio-remediated by microbially induced calcite precipitations (MICPs). The geomechanical properties of the Aeolian sand remediated by MICP were tested to explore its behavior as a desert bio-crust. The results indicated that a bio-crust of Aeolian sand with suitable strength required 7 days for formation. The remediated Aeolian sand had an average unconfined compression strength of 0.66 MPa and an average inner friction angle of 36° at a bacterial concentration in the OD₆₀₀ range of 0.5–0.8. These findings indicate that formation of bio-crust could serve as protection against desert erosion. The particle characteristics and the porosity of Aeolian sand play an important role in the formation of the bio-crust. Crust from bio-remediated well-graded, high-porosity soil is stronger than crust from bio-remediated, poorly graded, low-porosity soil, given that both soils have the same bacteria concentration.     

民勤绿洲边缘积沙带的稳定性动态

甘肃河西走廊经过60年的防沙治沙,在绿洲上风向边缘形成了一条流沙堆积带,即积沙带。其中,民勤绿洲上风向边缘的积沙带最高大、最连续。为了揭示积沙带的稳定性动态,在民勤绿洲上风向边缘设置11条观测样线,从2016年11月上旬至2019年4月上旬进行了7次风蚀积沙观测和沙面特征点位移观测。民勤绿洲上风向边缘积沙带按形成方式可分为人工固沙林积沙带、天然灌丛积沙带和乔灌木混交单行林积沙带。结果表明:人工固沙林积沙带风蚀最严重且前移速率最快,天然灌丛积沙带次之;风蚀程度越轻则积沙带前移速率就越慢,草本植物盖度越高沙面风蚀程度就越轻,积沙带前移速率就越慢。草本植物盖度与沙面稳定性二者相辅相成;积沙带迎风坡为风蚀面,而背风坡为积沙面,一蚀一积,维持着积沙带的前移及其动态稳定性。     

Biology Coupling Characteristics of Mole Crickets' Soil-Engaging Components

Mole cricket (Gryllotalpa orientalis) is a typical animal living under ground. The soil-engaging components of mole cricket have the capacity of wear resistance against soil. In this paper, the foreleg, tergum and forewing of mole cricket were chosen as soil-engaging components and were observed by stereomicroscope (SM), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The functions of the components were analyzed from the viewpoints of both entomology and bionics. The factors for function realization were found, and the single effect and coupling effect of these factors were investigated. Results show that the wear resistance characteristic of mole cricket is realized by biology coupling. The research of biology coupling provides a foundation to the technology of bionic coupling.     

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.     

Superhydrophobicity of Bionic Alumina Surfaces Fabricated by Hard Anodizing

Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique.The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa.The water contact angles of the as-anodized bionic samples were measured using a contact angle meter (JC2000A) with the 3 μL water drop at room temperature.The measurement of the wetting property showed that the water contact angle of the unmodified as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time.The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure.The structure is composed of the micro-scaled alumina columns and pores.The height of columns and the depth of pores depend on the anodizing time.The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol (ODT),showing a change in the wettability from hydrophobicity to super-hydrophobicity.This improvement in the wetting property is attributed to the decrease in the surface energy caused by the chemical modification.     

Wear striation direction on primate teeth: a scanning electron microscope examination.

Two experimental methods were used to produce wear striations in one direction on unworn teeth. These include: (1) sliding 22 American Indian (Juntunen site, Michigan; Late Woodland) newly erupted incisors, by hand, across a flat grass surface covered with fine loose sand; and (2) using a unidirectional motor driven mechanical wear machine to draw 56 modern human dental extractions across a flat glass surface covered with silicon carbide powder of different grit sizes. A scanning electron microscope examination of individual wear striation morphology indicates that these wear striations begin with broad pits and have extending grooves that become narrower; characteristics that indicate the motion of wear. Patterns of wear striations on the worn dentitions of American Indians (Juntunen site) and the paleocene primate Phenacolemur pagei show similar characteristics and correspond to the buccal phase of mastication when the mandible is drawn upward, forward and slightly medially into centric occlusion. The data provided by this study can be used to test competing hypotheses concerning the direction of mandibular movement during mastication and food preparation.     

Environmental tolerance of an invasive riparian tree and its potential for continued spread in the southwestern US

Questions: Exotic plant invasion may be aided by facilitation and broad tolerance of environmental conditions, yet these processes are poorly understood in species‐rich ecosystems such as riparian zones. In the southwestern United States (US) two plant species have invaded riparian zones: tamarisk (Tamarix ramosissima, T. chinensis, and their hybrids) and Russian olive (Elaeagnus angustifolia). We addressed the following questions: (1) is Russian olive able to tolerate drier and shadier conditions than cottonwood and tamarisk? (2) Can tamarisk and cottonwood facilitate Russian olive invasion? Location: Arid riparian zones, southwestern US. Methods: We analyzed riparian tree seedling requirements in a controlled experiment, performed empirical field studies, and analyzed stable oxygen isotopes to determine the water sources used by Russian olive. Results: Russian olive survival was significantly higher in dense shade and low moisture conditions than tamarisk and cottonwood. Field observations indicated Russian olive established where flooding cannot occur, and under dense canopies of tamarisk, cottonwood, and Russian olive. Tamarisk and native riparian plant species seedlings cannot establish in these dry, shaded habitats. Russian olive can rely on upper soil water until 15 years of age, before utilizing groundwater. Conclusions: We demonstrate that even though there is little evidence of facilitation by cottonwood and tamarisk, Russian olive is able to tolerate dense shade and low moisture conditions better than tamarisk and cottonwood. There is great potential for continued spread of Russian olive throughout the southwestern US because large areas of suitable habitat exist that are not yet inhabited by this species.     

库布齐沙漠南缘风沙-植被相互作用及其景观效应

干旱区尤其沙漠边缘地区的风沙与植被相互作用对塑造地表景观具有重要意义。选择库布齐沙漠南缘的油蒿灌丛地为研究区,开展了植被调查、风沙流观测和表层沉积物粒度采样测试,分析了顺风向植被盖度、风沙流结构与沉积物特征的沿程变化,探讨了风沙-植被相互作用及其对地表景观格局的影响。结果表明,风沙流与植被相互作用方式的改变使植物生长状况与地表蚀积模式发生变化,进而导致顺风向景观表现出明显的空间异质性。自上风向裸地过渡到均匀分布的新生油蒿和油蒿灌丛再至斑块状分布的灌丛沙堆,植被盖度与覆沙厚度先增大后减小,空气动力学粗糙度沿程不断增加且在过渡时其增幅最大,输沙率与沉积物粒度呈先减小后增大趋势,并在植被盖度与覆沙厚度最大处出现最小值。在沙漠边缘剥蚀高原上,起初适量风沙堆积促进油蒿定植与生长,均匀分布的油蒿灌丛进一步促进沙物质堆积,但当堆积厚度超过油蒿耐沙埋深度时发生退化,灌丛出现斑块状分布且风沙流在丘间地处侵蚀。据此,可理解为剥蚀高原风沙区景观异质性是风沙与植被相互协同与抑制作用的结果。     

碎石覆盖对河流硬质护坡土壤抗侵蚀性及植物生长的影响

针对河流硬质护坡生态修复中的稳定性和水分平衡等技术难点,提出了一种碎石覆盖技术,并通过抗冲刷实验和盆栽实验分析了不同碎石覆盖对土壤抗冲刷能力、保水性能及植物生长的影响.结果表明：粒径为1.5～2 cm的碎石覆盖处理在增强土壤抗冲刷能力、提高土壤保水性能和植物生物量方面效果明显,但覆盖厚度为5 cm和8 cm的碎石覆盖处理在抗冲刷、保水和促进植物生长方面的作用均无明显差异.厚5 cm、粒径为1.5～2 cm的碎石覆盖技术是硬质护坡生态修复中一种经济有效的技术方法.     

Effect of taphonomic processes on dental microwear

Taphonomic processes have the potential to affect microscopic wear on teeth and to modify the wear patterns so as to confound dietary reconstructions based on dental microwear which was formed during the lifetime of an animal. This study describes a series of experiments which were conducted to simulate various taphonomic agents and to record their effect on dental microwear. Three types of experiment were carried out in order to explain anomalous microscopic wear that had been found on the dentition of several hominoid specimens from the 15 M.a. site of Pasalar in Turkey. The effect of two different acids-citric and hydrochloric acid-on dental microwear was investigated. Modification to microscopic wear caused by alkali (carbonatite ash) was examined in the second set of experiments. Lastly, the effect of abrasion by three different size classes of sediment from the site of Pasalar-quartz pebbles (grain size varied from 2,000-11,000 microm), coarse sand (grain size ranged from 500-1,000 microm), and medium-sized sand (grain diameters were between 250 and 500 microm)-was investigated. Results confirm previous findings that the taphonomic modification of dental microwear is readily identifiable and causes the obliteration rather than secondary alteration of microwear features. The experiments show that both citric and hydrochloric acid affect dental microwear but to varying degrees, whereas alkali did not cause any modification of microscopic features. The different size classes of sediment also had different effects on the dental microwear. The largest size sediment (quartz pebbles) polished the enamel and removed finer microwear features. The coarse sand, however, did not have any effect on the microwear. The greatest amount of abrasion was caused by the smallest sediment particles -the medium-sized sand. Several hominoid dental specimens from Pasalar display similar microscopic wear to the two types of acid erosion and the abrasion caused by the medium-sized sands.     

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.     

聚丙烯酰胺(PAM)防治土壤风蚀的研究进展

在我国西北地区,风蚀是造成土地退化的主要影响因素之一.聚丙烯酰胺(PAM)是一种高效的土壤结构改良剂.因其具有特殊的物理化学性质,可以与土壤作用而改善土壤表层结构,近年来一直受到人们的广泛关注.本文介绍了PAM的物理化学性质,详细论述了PAM对土壤风蚀量、起动风速的影响,及PAM在风蚀防治中的不同使用量、使用方法和效果,及其与其他材料的对比,并通过PAM对土壤物理性质的改善进一步分析PAM防治风蚀的机理.综合分析得出,虽然PAM在风蚀防治中存在一些问题,但作为一种固沙剂,它不仅能提高土壤抗风蚀的能力,而且也能改善土壤的物理性状,可为植物生长创造良好的水土条件;提出若在风蚀治理和改良城市环境中将PAM与植物种植相结合,将能大大提高植物的成活率、改善风蚀区的风蚀状况和生态环境工程建设的质量.因此,PAM在防治风蚀方面具有重要的现实意义和广阔的应用前景.     

森林植被对坡面土壤水蚀作用的动力学机理

水力侵蚀是目前世界上分布最广、危害也是最为普遍的一种土壤侵蚀类型。坡面土壤侵蚀主要是由雨滴击溅、坡面径流引起,而森林植被作为陆地上最重要的生态系统以其林冠层、林木茎杆、林地上富集的枯枝落叶层、根系层以及发育疏松而深厚的土壤层截持和蓄储大气降水,发挥着其特有的水文生态功能,从多个角度影响降雨和坡面流的水力特性,在防治土壤侵蚀方面有其不可缺少的意义,然而目前对森林植被防治坡面土壤水蚀机理系统的研究还较少。系统的总结了森林植被各个垂直层次对坡面水蚀作用的动力学机理以及不同学者在此领域所做出的研究成果及此项研究的研究现状,并从以下几个方面指出了林地坡面水蚀作用动力学机理研究中尚存在的问题及发展方向：林冠对降雨重新分配出现林冠截持和干流等现象,降雨雨滴的大小、分布、降落速度和动能等性质发生变化,林冠层通过改变雨滴特性来影响坡面流水力特性,进而改变坡面流对坡面的侵蚀机理;森林植被茎干对径流的分散阻止作用,增大地表径流的阻力系数,茎干绕流现象对坡面土壤侵蚀的作用有正反两方面,林木在一定种植密度内,会使得泥沙起动流速减小,增加坡面侵蚀,因此应合理选择林木的种植密度才能起到减少坡面水蚀的作用;坡面流在枯落物层中流动并穿过枯落物层后下渗进入土壤的过程,类似于水流在多孔介质中的流动,枯落物的物理性质如分解程度、空隙度等的变化,引起水流流动的状态变化复杂,有必要应用渗流理论来深入研究以搞清其流动机理;根系层的存在能逐步改善土壤的内在特性,稳定表土层结构、提高土壤入渗性能使其抗侵蚀能力加强,植物根系层对坡面水蚀作用的研究是一个崭新的领域,需从土力学和植物根系影响土壤力学性质的角度研究土壤的抗侵蚀能力。