Influence of Shape and Size of Threshing Frame and Tobacco Grade on Leaf Strip Structure

This paper focused on the influence of the shape and size of threshing frames as well as the grades of tobacco leaves on the structure of threshed leaves.The testing tobacco leaves all came from the hilly ecological region of Nanling and belonged to burnt sweet,alcoholic sweet and scent category.The comprehensive evaluating value S was taken as the test index.Results showed that,without considering the influence of tobacco grade on leaf structure,the shapes of first-stage thresher five-link frames were all hexagons,and the combination with the sizes of 3.5,3.0,3.5,3.0,3.0 inches had the highest evaluating value S of 2.49.For tobacco grade C2FH,the shapes of first-stage thresher five-link frames were also hexagons,and the evaluating value S reached the highest value of 3.40 with sizes of 3.5,3.0,3.5,3.0,3.0 inches.Comprehensive analysis showed that:3.0 inch frame performed better in controlling the percentage of large-sized strips than 3.5 inch frame did;rhombic frames were better than hexagon frames in reducing the breakage rate of tobacco leaves;different shapes or sizes of nonadjacent two-link frames can help to improve the threshing quality.

Growing actin networks regulated by obstacle size and shape

Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.

Size and shape effects on Curie temperature of ferromagnetic nanoparticles

A simplified model was developed to describe the Curie temperature suppression of ferromagnetic nanoparticles. Based on a size and shape dependent model of cohesive energy, the critical temperature variations of ferromagnetic nanoparticles were deduced. It is predicted that the Curie temperature of nanoparticles depends on both size and shape conditions, among which the temperature suppression is strongly influenced by the particle size and the shape effect is comparably minor. The calculation values for freestanding nanoparticles are in good agreement with other theoretical model and the experimental results. The model is also potential for predictions for the nanoparticles embedded in different substrates.

Modeling size-dependent thermo-mechanical behaviors of shape memory polymer Bernoulli-Euler microbeam

The objective of this paper is to model the size-dependent thermo-mechanical behaviors of a shape memory polymer (SMP) microbeam.Size-dependent constitutive equations,which can capture the size effect of the SMP,are proposed based on the modified couple stress theory (MCST).The deformation energy expression of the SMP microbeam is obtained by employing the proposed size-dependent constitutive equation and Bernoulli-Euler beam theory.An SMP microbeam model,which includes the formulations of deflection,strain,curvature,stress and couple stress,is developed by using the principle of minimum potential energy and the separation of variables together.The sizedependent thermo-mechanical and shape memory behaviors of the SMP microbeam and the influence of the Poisson ratio are numerically investigated according to the developed SMP microbeam model.Results show that the size effects of the SMP microbeam are significant when the dimensionless height is small enough.However,they are too slight to be necessarily considered when the dimensionless height is large enough.The bending flexibility and stress level of the SMP microbeam rise with the increasing dimensionless height,while the couple stress level declines with the increasing dimensionless height.The larger the dimensionless height is,the more obvious the viscous property and shape memory effect of the SMP microbeam are.The Poisson ratio has obvious influence on the size-dependent behaviors of the SMP microbeam.The paper provides a theoretical basis and a quantitatively analyzing tool for the design and analysis of SMP micro-structures in the field of biological medicine,microelectronic devices and micro-electro-mechanical system (MEMS) self-assembling.

Coupling effects of void size and void shape on the growth of prolate ellipsoidal microvoid

The combined effects of void size and void shape on the void growth are studied by using the classical spectrum method. An infinite solid containing an isolated prolate spheroidal void is considered to depict the void shape effect and the Fleck-Hutchinson phenomenological strain gradient plasticity theory is employed to capture the size effects. It is found that the combined effects of void size and void shape are mainly controlled by the remote stress triaxiality. Based on this, a new size-dependent void growth model similar to the Rice-Tracey model is proposed and an important conclusion about the size-dependent void growth is drawn： the growth rate of the void with radius smaller than a critical radius rc may be ignored. It is interesting that rc. is a material constant independent of the initial void shape and the remote stress triaxiality.

Size and Shape of Polymer Chain near a Flat Surface

The size and the shape of non-reversal random-walking polymerchains near an impenetrable, non- interacting flat surface areinvestigated by means of Monte Carlo simulation on the simple cubiclattice. It was found that both size and shape are dependent on thenormal-to-surface distance z_0 of the first segment of chain. We findthat the size and shape of chains, characterized by mean squareradius of gyration and mean asphericity parameter respectively, show similar dependence on distance z_0.

A DESCRIPTION METHOD FOR ARBITRARILY SHAPED AND SIZED GRANULES IN 2D IMAGE

An alternative method is proposed in this letter for describing the arbitrary shape and size for granules in 2D image.After image binarization, the edge points on contour are detected, by which the centroid of the shape in question is sought using the moment calculation.Using Principal Component Analysis(PCA), the major and minor diameters are computed.Based on the signature curve-fitting, the first-order derivative is taken so as to seek all the characteristic vertices.By connecting the vertices found, the simplified polygon is formed and utilized for shape and size descriptive purposes.The developed algorithm is run on two given real particle images, and the execution results indicate that the computed parameters can technically well describe the shape and size for the original particles, being able to provide a ready-to-use database for machine vision system to perform related data processing tasks.

Conditions of Incipient Motion of Pebbles Based on Shape and the Equivalent Grain Size

Incipient motion of pebbles is an unsteady and random process,the main influence factors are pebble shape,non-uniformity,location in bed and flow condition.By virtue of the concept of the equivalent grain size,it is shown that d_ηfollows a normal distribution following a regression analysis of measured data.Consid- ering the influence of pebble shape and the relative exposure degree,formula of calculating the incipient veloc- ity for pebbles is deduced based on the equivalent grain size of pebble and the...

Real-Time Characterization of Crystal Shape and Size Distribution Based on Moving Window and 3D Imaging in a Stirred Tank

Crystal shape distribution, i.e. the multidimensional size distribution of crystals, is of great importance to their down-stream processing such as in filtration as well as to the end-use properties including the dissolution rate and bioavailability for crystalline pharmaceuticals. Engineering crystal shape and shape distribution requires knowledge about the growth behavior of different crystal facets under varied operational conditions e.g. supersaturations. Measurement of the facet growth rates and growth kinetics of static crystals in a crystallizer without stirring has been reported previously. Here attention is given to study on real-time characterization of the 3D facet growth behavior of crystals in a stirred tank where crystals are constantly moving and rotating. The measurement technique is stereo imaging and the crystal shape reconstruction is based on a stereo imaging camera model. By reference to a case study on potash alum crystallization, it is demonstrated that the crystal size and shape distributions (CSSD) of moving and rotating potash alum crystals in the solution can be reconstructed. The moving window approach was used to correlate 3D face growth kinetics with supersaturation (in the range 0.04 - 0.12) given by an ATR FTIR probe. It revealed that {100} is the fastest growing face, leading to a rapid reduction of its area, while the {111} face has the slowest growth rate, reflected in its area continuously getting larger.

New Method for Calculating Slit-Shaped Pore Size In Solids from Adsorption Isotherm

Assuming the pores in a porous solid to be slit-shaped,according to the principle of surface chemical thermody-namics,an equation for the calculation of pore size fromthe desorption branch of the isotherm of physical adsorp-tion of nitrogen on the porous solid at liquid nitrogentemperature is derived.The calculation results obtainedby different methods,namely,the classical method,BBmethod and the method of this paper,are compared.Comparison shows that the pore sizes d_T and d_H calculat-ed by the method of this paper and BB method respec-tively are larger than the pore size d_c calculated by theclassical method in the range 0【p/p_s【1;d_T】d_Hatp/p_s【0.71 and d_H】d_T at p/p_s】0.71;The results byBB method and the method of this paper tend to be thesame as that by the classical method while p/p_s ap-proaches 1.

An Experimental Study on the Effect of Foundation Depth, Size and Shape on Subgrade Reaction of Cohessionless Soil

The modulus of subgrade reaction ks depends on several factors such as the size and shape of the foundation as well as the embedment depth of the foundation. The present study is an experimental analysis using plate load test to determine the effect of foundation depth, size as well as the shape on the modulus of subgrade reaction (ks) of cohesionless soils. It was carried out by using nine rigid steel plates with different sizes and shapes (circular, square and retangular). The tests were carried out on cohessionless soil with different relative densities under different applied pressures. The settlement has been measured at the surface of the plate for different depths of footings. The ultimate bearing capacity [qu] has been determined from the stress-settlement relationships. The allowable bearing capacity (qa) was determined by dividing the ultimate bearing capacity (qu) by F.S. = 3.0, after which the corresponding settlement (Sa) has been obtained. However, ks was calculated based on dividing the allowable bearing capacity (qa) by the corresponding settlement (Sa). From the present study it is concluded that the subgrade reaction ks of cohessionless soil increases with increasing foundation depth as well as foundation size. In addition, subgrade reaction ks of cohessionless soil under rectangular footing is higher than that under square and that under circular one with same equivalent area. An empirical formula is presented to calculate the subgrade reaction ks of cohessionless soil under square foundation taking into consideration foundation depth. Fair agreement has been obtained between values of ks from the empirical formula at depth of footing = 0.00 B and Biot (1937) as well as Meyerhof and Baike (1965).

A New Simple Route to ZnS Quantized Particles with Tunable Size and Shape, and Size/Shape-Dependent Optical Properties

With the features of convenience and eco-friendly, the low-temperature solid-state reaction synthesis was successfully developed as a new approach to prepare quantum-sized ZnS nanocrystals. One major achievement is that the size and shape of ZnS nanocrystals can be tuned by adjusting the surfactant and its feed. The UV-Vis absorption spectra of quasispherical and one-dimensional quantum-sized ZnS nanocrystals all showed a blue-shift from the bulk counterpart, indicating large quantum confinement effects of ZnS nanocrystals. These ZnS nanocrystals all showed well-defined excitonic emission features. Contrastive studies on photoluminescence performances indicated that the bandedge emission experienced only the size-dependent quantum confinement effect, while the trap-state emission experienced the size- and shape-dependences. So we can design a purposeful synthesis route to ZnS nanocrystals with target luminescence emission performances.

基于图像识别的叶丝形态表征及其数值模拟

【背景和目的】研究一种叶丝颗粒的粒度和粒形表征方法,表征结果可用于其数值模拟的建模。【方法】采用图像分析技术,确定分散放置在二维平面上的每根叶丝的等面积圆当量径、最大弗雷特(Feret)径、圆形度和纵横比。【结果】(1)利用提出的叶丝颗粒图像采集和处理方法,通过对叶丝样品数据的统计分析,确定叶丝物料粒度和粒形的概率密度分布曲线,实现了长丝、中丝、短丝和碎丝4种长度叶丝物料的颗粒粒度和粒形表征,表征参数可定量的反映不同样品的颗粒尺寸和形状的差异。(2)离散单元法数值模拟结果表明叶丝的粒度和粒形性质对物料堆积高度有重要影响。本文基于实验测量得到的粒度和粒形概率分布曲线,生成了与实际形态分布一致的叶丝颗粒的数值模型,数值模拟结果与实验结果的偏差在1.3%以内。【结论】提出的方法从粒度和粒形对叶丝颗粒进行定量表征,表征结果一方面能反映不同物料的性质差异,另一方面可直接用于建立与实际情况接近的数值模型,从而准确预测不同长度叶丝颗粒的堆积高度。

不同成形方式对WE43镁合金组织和力学性能的影响

采用激光选区熔化成形(SLM)、铸造及挤压方式制备了WE43镁合金试样,通过维氏硬度计、密度测试计、光学显微镜、扫描电镜以及拉伸试验机等设备分析了不同制备方式下WE43镁合金的宏微观组织和力学性能变化规律;设计了基于指数函数的模型对不同成形方式的WE43应力–应变曲线进行统一拟合,为WE43材料未来增材、减材以及等材工艺复合制造复杂零件打下基础。结果表明,SLM成形WE43有明显的各向异性,铸态和挤压态不明显。SLM成形WE43镁合金的强度最高,抗拉强度达到313 MPa,是铸态的183%;挤压态WE43镁合金塑性最好,伸长率达到10.2%,是铸态的232%;此外,SLM态镁合金密度只有1.731 g/cm^(3),仅为挤压态的85.7%和铸态的95.2%。在断裂特性上,SLM态和挤压态为韧性断裂,而铸造态为脆性断裂。在内部存在20μm左右孔洞形缺陷的情况下,SLM成形镁合金依然具有最高的强度,主要原因是SLM成形WE43镁合金平均晶粒尺寸仅为2.6μm,基体内存在大量的稀土相沉淀以及纳米级亚稳相。由此可知,通过进一步的后处理方法焊合SLM态镁合金内部孔洞形缺陷后,材料力学性能可以大幅提高。

基于振动时间序列的威布尔参数检验

为了寻找更适合轴承振动性能的分析方法,将轴承全寿命周期振动时间序列细分为正常运行阶段子序列和故障阶段子序列,以威布尔分布为分析模型,以精度为衡量指标,采用极大似然法、矩量法、图表法,求出3套轴承不同运行阶段的振动加速度概率密度函数,通过比较精度确定最佳参数估计方法。结果表明:极大似然法求得的参数更接近实际情况,矩量法次之,图表法最差。

岬湾海滩沉积物粒度粒形分布及其输运趋势的指示

【目的与方法】粒度和粒形作为沉积物的基本属性,蕴含着输运历史、运动方式和沉积环境等丰富的信息。通过利用动态图像法对海南岛保定湾岬湾海滩52个剖面253组表层沉积物样品的粒度粒形测试,分析探讨了粒度粒形沿岸和横向的空间分布特征,结合粒度趋势分析结果建立了粒形趋势分析模型。【结果】研究表明,保定湾开敞段、过渡段和遮蔽段相同岸段内的球形度在沿岸方向差异不大,横向方向有从陆向海逐渐减小的趋势。不同岸段间沉积物在粒度小于2.5Φ时的球形度,在沿岸方向从开敞段至遮蔽段有逐渐减小的趋势。球形度的增大方向可指示沉积物输运趋势,建立的粒形趋势分析模型具有较高的准确性和优势,可计算任意粒度区间的输运趋势,可与粒度分析方法相结合以达到不同的研究目的。【结论】研究成果可为岬湾海滩的演变机制和稳定性研究提供理论支持。

基于机器视觉的E型卡簧尺寸检测方法

针对传统人工测量方式测量E型卡簧尺寸存在精度低、效率低等问题,提出一种基于机器视觉的E型卡簧尺寸检测方法。首先对灰度图像进行双边滤波,去除噪声;再利用形状匹配并结合先验知识快速准确定位测量区域,同时采用图像金字塔分层搜索策略提高匹配定位效率;然后在测量区域通过亚像素边缘检测方法进行亚像素级的边缘提取,获取出内、外径边缘和开口边缘;最后用迭代重加权最小二乘法拟合圆,用旋转法计算凸多边形之间的最小距离,实现尺寸的测量。试验结果表明,该检测方法测量精度高、测量效率高且稳定性好,满足工业自动化需求。

抛撒装药截面形状对爆炸抛撒过程的影响

针对抛撒装药能量输出方式决定爆炸驱动能力大小,传统的圆截面抛撒装药结构存在爆轰能量周向输出方式单一等问题,通过改变抛撒装药截面形状控制爆轰能量输出方式,研究了圆形、五角星形和花瓣形3种抛撒装药结构对被抛撒介质的爆炸驱动作用大小,抛撒装药结构的比药量均为2%,研究发现:装药爆炸驱动被抛撒介质的能力由其截面积大小决定,受抛撒装药截面形状的影响很小,分析原因主要是非圆截面抛撒装药爆炸产生的冲击波在传播过程中波阵面能量迅速匀化,无法对被抛撒介质产生定向加载效果;在壳体外壁有刻槽的情况下,主射流结构数量与刻槽数量相同,受抛撒装药结构截面形状影响不大。

粒径计算方法对细观混凝土数值建模的影响

采用最小包围盒(MBB)法确定骨料粒径,并与采用等体积球(EVS)法计算的骨料粒径进行比较,分析了这2种粒径计算方法对细观混凝土内部结构的影响.结果表明:采用MBB法计算的骨料粒径与室内试验采用筛分法确定的骨料粒径更为接近;与MBB法相比,EVS法低估了球状、片状和盘状骨料的粒径,且被低估的骨料占比由大到小依次为球状、片状和盘状,EVS法高估了棒状骨料的粒径;粒径计算方法对细观混凝土内部结构的影响因骨料形状类型不同而呈现一定差异性.

陕北白绒山羊角型与生长性状的相关分析

为了研究陕北白绒山羊角型分布规律及角型指标与山羊生长性状的相关性,丰富山羊良种选育的途径,试验对11618只山羊角型数据进行统计和分类,依据羊角特征建立了山羊角的角型分类规则,并对其中3610只陕北白绒山羊的角型指标(角大小、角形状、角弧度、角尖朝向)与生长性状(体长、体高、十字部高、胸深、胸宽、胸围和管围)进行相关性分析和单因素方差分析。结果表明:母羊的中角、拧角、非螺旋角和角尖向侧是优势角型,公羊的大角、非螺旋角和角尖向侧是优势角型。在公羊中,角弧度与胸宽呈极显著正相关(P<0.01),角尖朝向与体高呈显著正相关(P<0.05);在母羊中,4种角型指标均与生长性状存在相关性。母羊的大角对应的体长、十字部高、胸深、胸围、管围、胸宽均极显著高于中角和小角(P<0.01),大角和中角对应的体高也极显著高于小角(P<0.01);拧角对应的体长极显著高于直角(P<0.01);螺旋角对应的体高、十字部高、胸围和胸宽显著或极显著高于非螺旋角(P<0.05或P<0.01);角尖向上对应的体高、十字部高、胸深、胸围极显著高于角尖向侧(P<0.01)。公羊的螺旋角对应的胸宽极显著高于非螺旋角(P<0.01),角尖向侧对应的体高显著高于角尖向上(P<0.05)。在母羊的体高、十字部高、胸宽、胸围和管围等生长性状方面,角大小、角形状、角弧度和角尖朝向之间存在交互作用(P<0.05);在公羊中均没有交互作用。说明陕北白绒山羊角型与生长性状之间存在相关性,角型指标可作为辅助选育指标。