Strength criterion for crystalline rocks considering grain size effect and tensile-compressive strength ratio

The macroscopic mechanical properties of rocks are significantly influenced by their microstructure.As a material bonded by mineral grains,the grain morphology of crystalline rock is the primary factor influencing the strength.However,most strength criteria neglect the strength variations caused by different grain characteristics in rocks.Furthermore,the traditional linear criteria tend to overestimate tensile strength and exhibit apex singularity.To address these shortcomings,a piecewise strength criterion that considers the grain size effect has been proposed.A part of an ellipse was employed to construct the envelope of the tensive-shear region on the meridian plane,to accurately reproduce the low tensile-compressive strength ratio.Based on the analysis of experimental data,both linear and exponential modification functions that account for grain size effects were integrated into the proposed criterion.The corresponding finite element algorithm has been implemented.The accuracy and applicability of the proposed criterion were validated by comparing with the experimental data.

Photosynthetic efficiency, cell volume, and elemental stoichiometric ratios in Thalassirosira weissflogii under phosphorus limitation

Nutrient limitation is known to inhibit growth and metabolism and to alter elemental stoichiometric ratios in phytoplankton. In this study, physiological changes in Thalassirosira weissflogii were measured under different dissolved inorganic phosphate (DIP) regimes in semi-continuous cultures to revisit the utility of the Redfield ratio for assessing nutrient limitation. The results showed that cell size increased with decreasing DIP availability. In the P-depleted treatment (f/2-P) the cell size was 1.48 times larger than that in the P-limited (f/100) treatment and 2.67 times larger than that in the P-saturated treatment (f/2 and f/10). The fucoxanthin to chlorophyll a ratio (Fuco/chl a) was relatively stable (about 0.3) in P-saturated cultures and was 10 times higher than that in P-limited and P-depleted cultures. During the experimental period, the photosynthetic efficiency index, ?F/Fm′, was relatively stable at ~0.50 in the P-saturated cultures, but quickly declined with decreasing DIP availability. Although cellular P content showed a significant difference between the P-saturated culture (1.6 pg/cell) and the P-limited culture (0.7 pg/cell), the N/P ratio in T. weissflogii did not show a trend with DIP availability and fluctuated slightly around 25. Our results suggest that cell division in T. weissflogii is not strictly size-gated but is probably regulated by a biochemical, and hence, an elemental stoichiometric ratio threshold, and that deviation of the cellular N/P ratio from the Redfield ratio is not a reliable indicator of algal nutrient stress.

Study on the packed volume and the void ratio of idealized human red blood cells using a ?nite-discrete element method

Numerical simulations are performed to examine the packing behavior of human red blood cells(RBCs). A combined ?nite-discrete element method(FDEM) is utilized, in which the RBCs are modeled as no-friction and no-adhesion solid bodies. The packed volume and the void ratio of a large number of randomly packed RBCs are clari?ed,and the effects of the RBC shape, the mesh size, the cell number, and the container size are investigated. The results show that the packed human RBCs with normal shape have a void ratio of 28.45%, which is slightly higher than that of the ?at or thick cells used in this study. Such information is bene?cial to the further understanding on the geometric features of human RBCs and the research on RBC simulations.

Ratios of Closely Related Elements in Soil and Their Implications

This paper has investigated the ratios of closely related elements such as Mn,Cr,V,Ni,Co,Cu,Pb,Cd,Ba,Sr,La and Ce in the major soils of China,and the factors affecting them,and explored their use as indicators in soil formation,material transport and environmental pollution.Results show that the effect of soil-forming processes on the ratios of closely related elements varied with different elements,and became greater in the sequence of Ce/La <V/Cr≈Ni/Co<Zn/Cu≈Zn/Pb<Zn/Cd<Mn/Cr<Ba/Sr.The magnitude of the variation in the ratios of closely related elements depended on the chemical properties of the elements themselves,on the one hand,and the parent material and climatic conditions on the other.The ratio of Ba/Sr showed a distinct zonality,decreasing gradually in the sequence:cool temperate zone acid soils>grassland soils>desert soils and increasing gradually from the semi-arid subhumid zone soils>the temperate zone neutral soils>the north subtropic zone soils>tropical and subtropical acid soils.

Use of Finite Element Analysis for the Prediction of Driver Fatality Ratio Based on Vehicle Intrusion Ratio in Head-On Collisions

To estimate the aggressivity of vehicles in frontal crashes, national highway traffic safety administration (NHTSA) has introduced the driver fatality ratio, DFR, for different vehicle-to-vehicle categories. The DFR proposed by NHTSA is based on the actual crash statistical data, which makes it difficult to evaluate for other vehicle categories newly introduced to the market, as they do not have sufficient crash statistics. A finite element (FE) methodology is proposed in this study based on computational reconstruction of crashes and some objective measures to predict the relative risk of DFR associated with any vehicle-to-vehicle crash. The suggested objective measures include the ratios of maximum intrusion in the passenger compartments of the vehicles in crash, and the transmitted peak deceleration of the vehicles’ center of gravity, which are identified as the main influencing parameters on occupant injury. The suitability of the proposed method is established for a range of bullet light truck and van (LTV) categories against a small target passenger car with published data by NHTSA. A mathematical relation between the objective measures and DFR is then developed. The methodology is then extended to predict the relative risk of DFR for a crossover category vehicle, a light pick-up truck, and a mid-size car in crash against a small size passenger car. It is observed that the ratio of intrusions produces a reasonable estimate for the DFR, and that it can be utilized in predicting the relative risk of fatality ratios in head-on collisions. The FE methodology proposed in this study can be utilized in design process of a vehicle to reduce the aggressivity of the vehicle and to increase the on-road fleet compatibility in order to reduce the occupant injury out- come.

Germanium/silica ratio and trace element composition of Early Cambrian siliceous rocks in Keping:implications for the siliceous rocks'formation and paleoenvironment interpretations

This study used the germanium/silica(Ge/Si)ratios,together with rare earth elements and other trace elements to infer the siliceous source and sedimentary environment of the siliceous rocks located at the bottom of Yuertusi Formation in Northwestern Tarim Basin,Keping,China.Previous studies have shown that this siliceous rock stratum formed at the edge of the carbonate platform on the continental shelf.Researchers suggest that these siliceous rocks were formed by hydrothermal activity,but some still draw different conclusions.Understanding the silicon source and depositional environment of these siliceous rocks would help us learn the processes of environmental changes and the causes of biological explosions during this period.The value of germanium/silica ratios of these siliceous rocks is from 0.15 to 0.37 pmol/mol and much lower than above 10|imol/mol values in siliceous rocks that are known formed by hydrothermal activity.All samples are rich in HREE,which differ from hydrothermal siliceous rocks that are rich in LREE.Most samples lack hydrothermal related elements.All these features show that the source of these siliceous rocks'siliceous is not hydrothermal flu ids.The samples'Ce/Ce*range from 0.88 to 1,and Th/U ratios range from 0.01 to 0.36.These features suggest these siliceous rocks were formed in an anoxic environment.Considering all the evidence,we conclude that the siliceous rock stratum at the bottom of the Lower Cambrian Yuertusi Formation in northwest Tarim Basin.Keping,was formed in anoxic seawater at the edge of the carbonate platform on the continental shelf.Its silicon source is seawater instead of hydrothermal fluid.

Finite element analysis on the collapse of infill walls with holes and different length-to-height ratios

Wenchuan earthquake damage survey displayed the major structures of buildings suffered only small damages,but it was common that infill walls suffered heavy damages or even collapse. To study the failure forms and collapse mechanism of infill walls in an earthquake,the influence of opening or length-to-height ratio on shake-resisting capability of filling walls was analyzed,and measures to improve the anti-collapse ability of infill walls were put forwaed. The numerical simulations on collapse process in earthquake were carried out by using ABAQUS software. We used 5 single story and single span models. It is revealed that the rigidity and compressive capacity of infill walls are reduced because of the infill walls with holes and the increases of length-to-height ratios. Adding constructional columns and horizontal beams can ensure structural integrity and improve the anti-collapse ability of the wall.

ADAPTIVE EIGENFREQUENCY ANALYSIS BY IMPROVED r-AND h-ADAPTIVE FINITE ELEMENT METHOD BASED ON PERTURBATION AND ELEMENT ENERGY RATIO

A new adaptive technique of r-and h-version for vibration problemsutilizing the matrix per- turbation theory and element energy ratiois proposed. In structural vibration analysis, through the r-conver-gence adaptvie finite element process, mesh optimization can berealized. In the light of the judgement on the changes in themagnitude of the element energy ratio, local refinement can beachieved in the process of h- convergence adaptive finite element sothat more accurate finite element solutions can be obtained with asfew meshes as possible. Many numerical examples are given and theproposed approach is shown to be feasible and effective.

DOUBLE SUBSTITUTE CALIBRATION FOR THE ISOTOPIC RATIO MEASUREMENT AMONG RARE EARTH ELEMENTS

Abstract: Through the application of the method of double substitute calibration using the true isotopic ratios of cerium and europium of our laboratory standards, the atomic weight of ytterbium has been determined as Ac(Yb) 173. 0428(15) on Zσ basis.

The spatial temporal evolution characteristics of the load／unload response ratio（LURR） and its implications for predicting the three elements of earthquakes

The spatial temPOral evolution characteristics of the load/unload response ratio (Y) before strong earthquakes is studied in this paper. The results show that the regions of high value of Y migrate and converge to the impending earthquake epicenter from different directions before the occurrence of the event. Basing on this discovery, it is proposed that the method can be used to predict the three elements of an earthquake. It was applied to predict that an earthquake would occur in the western part of Yunnan Province, southwestern China. The three elements (time, space and magnitude) of the Menglian earthquake with Ms7.3 which occurred on July 12, 1995 in Yunnan Province tallied with our prediction.

Non Degeneration of Fibonacci Series, Pascal’s Elements and Hex Series

Generally Fibonacci series and Lucas series are the same, they converge to golden ratio. After I read Fibonacci series, I thought, is there or are there any series which converges to golden ratio. Because of that I explored the inter relations of Fibonacci series when I was intent on Fibonacci series in my difference parallelogram. In which, I found there is no degeneration on Fibonacci series. In my thought, Pascal triangle seemed like a lower triangular matrix, so I tried to find the inverse for that. In inverse form, there is no change against original form of Pascal elements matrix. One day I played with ring magnets, which forms hexagonal shapes. Number of rings which forms Hexagonal shape gives Hex series. In this paper, I give the general formula for generating various types of Fibonacci series and its non-degeneration, how Pascal elements maintain its identities and which shapes formed by hex numbers by difference and matrices.

Research of Magnesium Alloy Wheel Vibration Performance Based on Finite Element Method

As the automotive industry is increasingly demanding on energy saving and environmental protection,people are taking more attention on the lightweight design and comfort of automobiles.Wheel vibration is one of the most important parts of a vehicle performance.The dynamic characteristics of the vehicle are determined by the modal parameters of the vehicle system.The wheel also has a great influence on the vibration.Based on finite element method,we analyze wheel vibration performance.This research studies the effect of different damping properties on wheel frequency.By comparing of acceleration and speed of the wheel,we can improve the vibration performance of the vehicle.

Tao and Golden Ratio: A Scientific View of Contemporary Acupunctural Principles through Geometry

It is universally accepted that the philosophy of the Tao is the essence that animates the Chinese Cosmogony. Therefore, in last decades I have tried to consolidate its scientific background, looking for solid explanations through Exact Sciences (“Between Heaven and Earth” Scientific Basis of the Action of Shao Yin: Lightning’s Physical-Mathematical Analysis”;“Is Traditional Chinese Medicine Definitely an Exact Science?”;“Euclidean Geometry and Traditional Chinese Medicine: Diving into the Real Origin of the Five Elements”;“Solitons: A Cutting-Edge Scientific Proposal Explaining the Mechanisms of Acupuntural Action”) Currently, research on Chinese medicine leads us—with Dr. Erica Arakaki, collaborator and assistant—to verify through a profound bibliographic review the application of Fibonacci’s Golden Ratio in the constitution of T’ai Ji Tu, adding yet more substance to the hypothesis of Acupuncture and demonstrating how said Chinese Ancient Science is not only an empirical knowledge but a wisdom derived from the most ancient exact science: Geometry.

The Effects of the Particle Size Ratio on the Behaviors of Binary Granular Materials

The particle size ratio(PSR)is an important parameter for binary granular materials,which may aect the microstructure and macro behaviors of granular materials.However,the eect of particle ratio on granular assemblies with dierent arrangements is still unclear.To explore and further clarify the eect of PSR in dierent packing structures,three types of numerical samples with regular,layered,and random packing are designed.Numerical results show that PSR has signi􀀀cant eects on binary granular samples with regular packing.The larger the PSR,the stronger the strength,the larger the modulus,and the smaller the angle between the shear band and the load direction.And a theoretical solution of the peak stress ratio vs.PSR is obtained for regular packing,and the results by DEM are in good agreement with the theoretical solution.Under layered packing,PSR has little eect on peak stress ratio due to similar microstructure obtained with the changing of PSR.The modulus slightly increased with the increase of PSR.Under random packing with small grain content of 50%,PSR has little eect in the range of 0.5–0.9,but in a larger range,larger PSR leads to greater modulus.

不同推进比下螺旋桩在砂土中安装力的离散元研究

螺旋桩作为一种颇具潜力的海上风电基础形式,其安装问题是螺旋桩能否成功应用在海上风电工程中的关键。基于离散元方法,采用PFC^(3D)模拟分析了螺旋桩在不同推进比下安装时的桩身受力情况以及对周围土体的影响。宏观上,研究了螺旋桩在不同推进比下安装时螺旋桩连杆侧壁、连杆端部、螺旋叶片上下表面的受力变化规律;微观上,分析了螺旋桩安装过程中桩周土体孔隙率、配位数及应力变化规律。研究表明:随着推进比的减小,螺旋桩安装时受到的竖向力与扭矩也随之降低,对桩周土体的扰动也更小;螺旋桩在推进比为1时安装与在推进比小于1时安装存在两种不同的安装机制。研究结果对进一步确定螺旋桩在不同推进比下的安装条件具有一定意义。

几何参数对轮缘推进器水动力性能影响的研究

轮缘推进器是近年来发展起来的一种无轴组合式特种推进器。与传统推进器相比,轮缘推进器在水动力设计和性能分析方面存在诸多挑战,水动力性能的研究对轮缘推力器的设计和应用具有重要意义。为了研究几何参数对轮缘推力器水动力性能的影响,本文以7叶轮缘驱动推力器为基本模型,基于面元法原理,利用编译的面元法代码对轮缘推力器在开阔水域的工作状态进行了数值模拟。通过求解每个面元的速度场,计算了水动力性能和叶片表面压力分布。此外,本文选择了几个典型的几何特征,如螺距比和叶片数,通过进行变参数分析,比较了不同几何参数下轮缘推力器的敞水性能。结果表明:本文的相关研究对轮缘推力器的设计和开发具有参考价值。

邢窑六世纪晚期制瓷原料的同位素和微量元素分析

白瓷的出现是我国陶瓷历史上较为重要的技术突破,白瓷的烧制成功为后世青花瓷、彩绘瓷的繁荣奠定了重要基础,被誉为中国古陶瓷工艺发展史中的“第四里程碑”。因此,关于白瓷起源的问题就成为考古界和科技考古界关注的重要学术问题,而邢窑2012年考古发掘出土的北朝晚期窑炉和器物遗存自然成为研究白瓷起源的重要实物资料。本研究利用电感耦合等离子体质谱(ICP-MS)和热电离质谱(TIMS)分析技术,对河北内丘城关服务楼窑址出土的北朝晚期至隋朝初期的早期瓷器样品胎釉原料进行分析,为邢窑早期瓷业的发展演变提供科学依据。结果表明邢窑早期瓷胎的微量元素统计模式明显可以分为两类,说明邢窑早期制瓷存在两种不同的胎料来源。邢窑陶工在开发早期白瓷这一新品种的过程中有意识地选择了一种有别于青瓷的更为优质的原料制胎,这种胎料中与锆石、锐钛矿等杂质赋存密切相关的V、Cr、Ni、Nb、Ta、Zr和Hf等微量元素含量普遍小于青瓷胎。锶(Sr)同位素混合模式分析表明,邢窑早期的大部分样品不符合草木灰配以胎料的制釉方式,应该是采用了草木灰混合其他制釉黏土。同时,早期白瓷釉与青瓷釉的锶同位素特征存在一定差异,说明在制作过程中邢窑陶工为了提高釉面白度对制釉工艺也进行了变革,体现了为创烧早期白瓷而做出的努力。这些结果为科学认知邢窑六世纪晚期制瓷原料的特点和来源提供依据,同时也为破解白瓷起源提供新的科技支撑。

对辊制粒机压辊的有限元分析及优化

对辊制粒机的压辊在工作过程中由于受交变载荷作用寿命往往较短,为改善压辊受力状况,根据对对辊制粒机制粒成型过程的分析以及对压辊受力状况的研究,建立了压辊的力学模型;在此基础上,以某型对辊制粒机为初始模型,通过有限元软件Abaqus探究了压辊表面应力分布情况,并进一步对其长径比及支撑方式进行了优化,结果表明:压辊长径比为1.034时,最大应力比初始模型减小了8.92%,单侧支撑改为双侧支撑可使最大应力减小65.31%,因此这两种优化方式对提高压辊的使用寿命具有重要参考价值。

重组竹内置钢筋后受弯性能有限元分析

重组竹是通过将竹束热压胶合而成的新型工程材料,具有强度高、韧性好以及固碳能力强等优点,为提高重组竹的受弯性能,通过热压工艺在重组竹中内置钢筋形成增强重组竹受弯构件。在四点弯曲试验的基础上,通过ABAQUS有限元模拟研究配筋率及配筋形式对重组竹受弯性能的影响。分析结果表明,与纯重组竹相比,内置钢筋后重组竹的受弯力学性能得到明显提高;当配筋形式相同时,随配筋率的增加,重组竹的承载力及抗弯刚度逐渐提高,与纯重组竹相比,配筋率为1.0%~8.2%的单筋重组竹承载力和抗弯刚度分别提高5.6%~48.36%和10.57%~71.81%;当钢筋直径相同时,重组竹顶部和底部同时配筋的双筋重组竹与重组竹底部配筋的单筋重组竹相比,其承载力及抗弯刚度分别提高21.78%和95.98%。

黄土地基阶梯型截面桩承载模型试验与计算

为研究黄土地基阶梯型截面桩的荷载传递机理,通过室内模型试验与有限元计算,分析阶梯型截面桩竖向静荷载下的桩身轴力、桩侧摩阻力、桩顶沉降和桩身不同深度荷载分担比,并探索了变径比对其工作性能的影响,并对其进行优化设计。结果表明:在相同荷载下,阶梯型截面桩的桩顶沉降明显小于等截面桩,当变径比在0.8~0.9时,沉降控制效果最佳,其材料利用率最高;若二者极限承载力相同时,阶梯型截面桩的最高材料利用率为等截面桩的1.06倍。阶梯型截面桩为摩擦型桩,变截面位置土体对桩体具有支承作用,其变径处底面土体能承担部分桩顶荷载。桩侧能够分担更多桩顶荷载,减轻桩端土体承载,当变径比在0.8~0.9时,侧摩阻力发挥程度更高。在桩体用料相同时,与等截面桩相比,阶梯型截面桩能大幅度提高承载能力。