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Chen, Shuangmin, Taijun Liu, Zhenyu Shu, Shiqing Xin, Ying He, and Changhe Tu. "Fast and robust shape diameter function." PLOS ONE 13, no. 1 (January 26, 2018): e0190666. http://dx.doi.org/10.1371/journal.pone.0190666.
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Deja, Mariusz, and Dawid Zielinski. "A pilot study to assess an in-process inspection method for small diameter holes produced by direct metal laser sintering." Rapid Prototyping Journal 26, no. 2 (November 18, 2019): 418–36. http://dx.doi.org/10.1108/rpj-05-2019-0132.
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Purpose The purpose of this study is to evaluate the geometric quality of small diameter holes in parts printed by direct metal laser sintering (DMLS) technology. An in-process optical inspection method is proposed and assessed during a pilot study. The influence of the theoretical hole diameter assumed in a computer-aided design (CAD) system and the sample thickness (hole length) on the hole clearance was analyzed. Design/methodology/approach The samples are made of two different materials: EOS MaragingSteel MS1 and aluminium alloy EOS Aluminium consisted of straight through holes of different diameters and lengths. Dimensional and shape accuracy of the holes were determined with the use of the image processing software and the computer analysis of two-dimensional (2-D) images. The definition of the equivalent hole diameter was proposed to calculate the hole clearance. Feret’s diameters were determined for the evaluation of the shape accuracy. Findings The dependency between the equivalent hole diameter and the theoretical diameter was approximated by the linear function for a specific sample thickness. Additionally, a general empirical model for determining the hole clearance was developed, allowing for calculating the equivalent hole diameter as a function of a sample thickness and a theoretical hole diameter. Practical implications Developed functions can be used by designers for a proper assignment of a hole diameter to achieve the required patency. The relevant procedures and macros based on proposed empirical models can be embedded in CAD systems to support the designing process. Originality/value The analysis of the geometric quality of the holes in parts printed by DMLS was based on the computer analysis of 2-D images. The proposed method of assessing the shape accuracy of straight through holes is relatively cheap, is widely available and can be applied to the features of other shapes produced by three-dimensional printing.
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Jia, Hui, Guo Hua Geng, and Jian Gang Zhang. "Consistent Mesh Segmentation Based on Shape Diameter Function and EM." Advanced Materials Research 1049-1050 (October 2014): 1417–20. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.1417.
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3D model segmentation is a new research focus in the field of computer graphics. The segmentation algorithm of this paper is consistent segmentation which is about a group of 3D model with shape similarity. A volume-based shape-function called the shape diameter function (SDF) is used to on behalf of the characteristics of the model. Gaussian mixture model (GMM) is fitting k Gaussians to the SDF values, and EM algorithm is used to segment 3D models consistently. The experimental results show that this algorithm can effectively segment the 3D models consistently.
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Shapira, Lior, Ariel Shamir, and Daniel Cohen-Or. "Consistent mesh partitioning and skeletonisation using the shape diameter function." Visual Computer 24, no. 4 (January 8, 2008): 249–59. http://dx.doi.org/10.1007/s00371-007-0197-5.
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Kim, Donggeun, Younghwan Son, and Jaesung Park. "Prediction of Settling Velocity of Nonspherical Soil Particles Using Digital Image Processing." Advances in Civil Engineering 2018 (December 9, 2018): 1–8. http://dx.doi.org/10.1155/2018/4647675.
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Digital image processing (DIP) is used to measure shape properties and settling velocity of soil particles. Particles with diameters of 1 to 10 mm are arbitrarily sampled for the test. The size of each particle is also measured by a Vernier caliper for comparison with the classification results using the shape classification table. The digital images were taken with a digital camera (Canon EOS 100d). Shape properties are calculated by image analysis software. Settling velocity of soil particles is calculated by displacement and time difference of images during settling. The fastest settling particles are spherical shaped. Shape factors well explain the difference of settling velocity by a particle shape. In particular, the aspect ratio has a high negative correlation with residual of settling velocity versus mean diameter. Especially, DIP has a higher applicability than classification using the shape classification table because it can measure a number of particles at once. The settling velocity of soil particles is expressed as a function of mean diameter and aspect ratio.
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Vieilledent, Ghislain, Benoît Courbaud, Georges Kunstler, Jean-François Dhôte, and James S. Clark. "Biases in the estimation of size-dependent mortality models: advantages of a semiparametric approach." Canadian Journal of Forest Research 39, no. 8 (August 2009): 1430–43. http://dx.doi.org/10.1139/x09-047.
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Mortality rate is thought to show a U-shape relationship to tree size. This shape could result from a decrease of competition-related mortality as diameter increases, followed by an increase of senescence and disturbance-related mortality for large trees. Modeling mortality rate as a function of diameter is nevertheless difficult, first because this relationship is strongly nonlinear, and second because data can be unbalanced, with few observations for large trees. Parametric functions, which are inflexible and sensitive to the distribution of observations, tend to introduce biases in mortality rate estimates. In this study we use mortality data for Abies alba Mill. and Picea abies (L.) Karst. to demonstrate that mortality rate estimates for extreme diameters were biased when using classical parametric functions. We then propose a semiparametric approach allowing a more flexible relationship between mortality and diameter. We show that the relatively shade-tolerant A. alba has a lower annual mortality rate (2.75%) than P. abies (3.78%) for small trees (DBH <15 cm). Picea abies, supposedly more sensitive to bark beetle attacks and windthrows, had a higher mortality rate (up to 0.46%) than A. alba (up to 0.30%) for large trees (DBH ≥50 cm).
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Ekong, Sylvester A., and Mike O. Osiele. "A Quantum Confinement Study of the Electronic Energy of some Nanocrystalline Silicon Quantum-Dots." International Letters of Chemistry, Physics and Astronomy 63 (January 2016): 106–10. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.63.106.
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We have employed a quantum confinement (QC) model to the study of different shapes of nanocrystalline silicon (nc-Si) quantum dot. Each dots (shapes), although within the limits of an effective diameter of 3nm, exhibits divergence leading to different electronic energy based on the transitions from the quantum selection rule. Also, the graphical representation of the energies from each shape as a function of the effective diameter gives a qualitatively similar spectrum of discrete energies. The results obtained in this work using QC model are in good agreement with experiment and other models in literature.
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Zhao, Man Quan, Yue Qin Liu, and Yong Wen Hu. "An Airflow Field Finite Element Analysis of the Seed Adsorption Hole of Pneumatic Seeder." Applied Mechanics and Materials 117-119 (October 2011): 1810–15. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.1810.
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The seed adsorption disk is an important component of the seed metering device. The differences in size and shape of suction hole on the adsorption disk result in variation of the airflow field formed. A finite element analysis of airflow field for the suction holes of different size and shape was conducted in this paper. The two dimensional simulation of airflow field for different shaped suction hole under the condition of identical bore diameter and air pressure difference reveals that the average airflow velocity inside the different shape of suction holes are the highest one in cylindrical hole and the lowest in tapered hole, the airflow speed at inlet opening of three different suction hole does not vary evidently. Both the result of airflow field two dimensional finite element analysis of different bore diameter suction hole and its proof under the condition of the shape of suction holes and air pressure difference being identical reveal that with the bore diameter being enlarged, the airflow speed inside the suction hole increases in comparison of the airflow speed field for three different suction holes of different bore diameter. To enlarge the bore diameter of suction hole and expand the adsorption surface area of the seed will result in the airflow rate and airflow speed getting higher and the adsorption function on the seed growing stronger.
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Boublík, Tomáš. "Radial Distribution Function in the Hard Sphere Mixtures." Collection of Czechoslovak Chemical Communications 73, no. 3 (2008): 388–400. http://dx.doi.org/10.1135/cccc20080388.
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Equilibrium structures of both homogeneous and heterogeneous systems are, within statistical thermodynamics, characterized by distribution functions. Using the approach proposed recently - based on the determination of the cavity functions for the pair of hard spheres (HS) and the combined body - we studied the effect of different choices of the probe HS (which determines the shape of the combined hard body - enlarged dumbbell) on the prediction of the distribution functions in binary mixtures of HS with the aspect ratio 0.9, ternary mixtures with diameter ratios 1, 0.6 and 0.3, and density profiles of HS mixture with the aspect ratio 2 near a hard wall. It was found that the method, that uses the average geometric functionals determined for the probe HS with individual diameters multiplied by the respective mole fractions yields better results than the approaches based on average probe diameters.
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Kastner, Johann, Richard Kickinger, and Dietmar Salaberger. "High-resolution X-ray computed tomography for 3D microstructure characterization of a cellulose particle filled polymer foam." Journal of Cellular Plastics 47, no. 6 (November 2011): 567–78. http://dx.doi.org/10.1177/0021955x11413659.
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Due to the excellent strength/weight ratio, good energy absorbing ability, superior thermal, and acoustic insulation properties together with reasonable costs, polymer foams are the material of choice for many applications. The incorporation of particulate or fibrous fillers can even improve the properties. In this article, we investigate an open-cell polyurethane foam filled with cellulose particles. This is a new moisture-absorbing wood–plastic composite used for special mattresses. The foam was characterized by high-resolution cone-beam X-ray computed tomography (XCT) with voxel sizes between 0.7 µm3 and 2.2 µm3. The XCT measurements were performed with a tube voltage of 50 kV to obtain enough contrast. The XCT data were processed by various algorithmic steps (e.g., smoothing, thresholding, watershed transformation, erosion, dilation, and feature extraction) to ascertain the three-dimensional open-cell structure together with particle distribution, size, and position. Quantitative data for the cells (mean diameter, shape, volume, and position), for the cellulose particles (mean diameter, shape, volume, and position), for the polymer vertices (shape and position) and for combinations of them (e.g., distance between particles and vertices) were derived from the XCT data. 15.2 cells/mm3, 41 cellulose particles/mm3, and 88.7 polymer vertices/mm3 were found. The average diameter value for the mostly globular cells was found to be 465 µm with a Gaussian-like distribution function. The cellulose particles are globular and elongated and the distribution resembles an exponential function where 95% of the particles have diameters below 60 µm. The particles are situated within the polymer walls and close to the surface. The function for the distance of the particles from the closest vertices corresponds to a Weibull distribution function with a scale parameter of 53 µm and a shape parameter of 1.7.
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Elger, D. F., D. M. Blackketter, R. S. Budwig, and K. H. Johansen. "The Influence of Shape on the Stresses in Model Abdominal Aortic Aneurysms." Journal of Biomechanical Engineering 118, no. 3 (August 1, 1996): 326–32. http://dx.doi.org/10.1115/1.2796014.
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Presence of a small abdominal aortic aneurysm (AAA) often presents a difficult clinical dilemma—a reparative operation with its inherent risks versus monitoring the growth of the aneurysm, with the accompanying risk of rupture. The risk of rupture is conventionally believed to be a function of the AAA bulge diameter. In this work, we hypothesized that the risk of rupture depends on AAA shape. Because rupture is inevitably linked to stress, membrane theory was used to predict the stresses in the walls of an idealized AAA, using a model which was axisymmetric and fusiform, with the ends merged into straight open-ended tubes. When the stresses for many different shapes of model AAAs were examined, a number of conclusions became evident: (i) maximum hoop stress typically exceeded maximum meridional stress by a factor of 2 to 3 (ii) the shape of an AAA had a small effect on the meridional stresses and a rather dramatic effect on the hoop stresses, (iii) maximum stress typically occurred near the inflection point of a curve drawn coincident with the AAA wall, and (iv) the maximum stress was a function—not of the bulge diameter—but of the curvatures (i.e. shape) of the AAA wall. This last result suggested that rupture probability should be based on wall curvatures, not on AAA bulge diameter, Because curvatures are not much harder to measure than bulge diameter, this concept may be useful in a clinical setting in order to improve prediction of the likelihood of AAA rupture.
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Duchateau, E., F. Longuetaud, F. Mothe, C. Ung, D. Auty, and A. Achim. "Modelling knot morphology as a function of external tree and branch attributes." Canadian Journal of Forest Research 43, no. 3 (March 2013): 266–77. http://dx.doi.org/10.1139/cjfr-2012-0365.
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Existing models for describing knot morphology are typically based on polynomial functions with parameters that are often not biologically interpretable. Hence, they are difficult to integrate into tree growth simulators due to the limited possibilities for linking knot shape to external branch and tree characteristics. X-ray computed tomography (CT) images taken along the stems of 16 jack pine (Pinus banksiana Lamb.) trees and 32 black spruce (Picea mariana (Mill.) B.S.P.) trees were used to extract the three-dimensional shape of 3450 and 11 276 knots from each species, respectively. Using a nonlinear approach, we firstly fitted a model of knot geometry adapted from a Weibull function. Separate equations were used to describe both the curvature and the diameter of the knot along its pith. Combining these two equations gave an accurate representation of knot shape using only five parameters. Secondly, to facilitate the integration of the resulting model into a tree growth simulator, we extracted the parameters obtained for each knot and modelled them as functions of external branch and tree characteristics (e.g., branch diameter, insertion angle, position in the stem, tree height, and stem diameter). When fitted to a separate data set, the model residuals of the black spruce knot curvature equation were less than 2.9 mm in any part of the knot profile for 75% of the observations. The corresponding value from the diameter equation was 2.8 mm. In jack pine, these statistics increased to 5.4 mm and 3.2 mm, respectively. Overall, the ability to predict knot attributes from external tree- and branch-level variables has the potential to improve the simulation of internal stem properties.
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Forslund, R. R., and J. M. Paterson. "Nondestructive volume estimates of 11-year-old jack pine and black spruce using the power function volume model." Forestry Chronicle 70, no. 6 (December 1, 1994): 762–67. http://dx.doi.org/10.5558/tfc70762-6.
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Two methods for estimating the total outside-bark stem volume of all trees in young plantations of jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana [Mill.] B.S.P.) were compared. The first method was time-intensive, and required destructive sampling to obtain volume estimates using many paired diameter/height measurements. The second method was nondestructive and required only two field measurements: an outside-bark diameter at either a fixed height (such as breast height) or at a relative height, and the total stem height. The results indicated that total plantation volume estimates to within ±5% can be obtained using the power function model and two stem measurements: a diameter at a relative height of 30% from the base of the stem and total stem height. The power function model offers a good alternative for accurately assessing plantation volume. Key words: black spruce, jack pine, power function volume model, paracone, upper diameters, profile shape, stem volume
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Baldacci, Andrea, Rastislav Kamenický, Adam Riečický, Paolo Cignoni, Roman Ďurikovič, Roberto Scopigno, and Martin Madaras. "GPU-based approaches for shape diameter function computation and its applications focused on skeleton extraction." Computers & Graphics 59 (October 2016): 151–59. http://dx.doi.org/10.1016/j.cag.2016.06.006.
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Wenzel, Michaela, Ilkay N. Celik Gulsoy, Yongqiang Gao, Zihao Teng, Joost Willemse, Martijn Middelkamp, Mariska G. M. van Rosmalen, et al. "Control of septum thickness by the curvature of SepF polymers." Proceedings of the National Academy of Sciences 118, no. 2 (December 21, 2020): e2002635118. http://dx.doi.org/10.1073/pnas.2002635118.
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Gram-positive bacteria divide by forming a thick cross wall. How the thickness of this septal wall is controlled is unknown. In this type of bacteria, the key cell division protein FtsZ is anchored to the cell membrane by two proteins, FtsA and/or SepF. We have isolated SepF homologs from different bacterial species and found that they all polymerize into large protein rings with diameters varying from 19 to 44 nm. Interestingly, these values correlated well with the thickness of their septa. To test whether ring diameter determines septal thickness, we tried to construct different SepF chimeras with the purpose to manipulate the diameter of the SepF protein ring. This was indeed possible and confirmed that the conserved core domain of SepF regulates ring diameter. Importantly, when SepF chimeras with different diameters were expressed in the bacterial hostBacillus subtilis, the thickness of its septa changed accordingly. These results strongly support a model in which septal thickness is controlled by curved molecular clamps formed by SepF polymers attached to the leading edge of nascent septa. This also implies that the intrinsic shape of a protein polymer can function as a mold to shape the cell wall.
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Putranto, Beta. "MODEL DISTRIBUSI DIAMETER LIMA JENIS POHON PADA HUTAN TROPIKA BASAH DI KABUPATEN MAMUJU, SULAWESI BARAT." PERENNIAL 6, no. 1 (January 1, 2010): 44. http://dx.doi.org/10.24259/perennial.v6i1.197.
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The objective of this research is to establish the most suitable tree diameter distribution model for five tree species on tropical rain forest in Mamuju District. This research was conducted on two locations. The 50 square plots were sampled systematically for seedling, sapling, pole and tree measurements of bintangur, jambu-jambu, lada-lada, matoa and nyatoh species. The distance among plots was 50 m. Variables to be measured were stem number of seedlings to trees and tree diameter at breast height (1,3 m) of saplings to trees. About 70% of the data were used to establish the best model, the rest of 30% were used to validate the model. Models to be analyzed were fourth-order semi-logarithmic transformed polynomial function, Weibull density function and monotonic decreasing Weibull function. The results show that the five tree species have a similar diameter distribution pattern. The shape of this distribution is the typical of uneven-aged stand distribution on natural forest, namely reversed J shape. The most suitable model for five species is second-order semi-logarithmic transformed polynomial function. Key words: model, diameter distribution, natural forest, uneven-aged stand.
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Lada, Adveni H. A., Partogi H. Simatupang, and Andi H. Rizal. "Studi Parametrik Pengaruh Variasi Pengekangan Terhadap Nilai Kapasitas dan Daktilitas Penampang Kolom Beton Bertulang Bentuk T." JURNAL FORUM TEKNIK SIPIL (J-ForTekS) 1, no. 1 (April 1, 2021): 35–46. http://dx.doi.org/10.35508/forteks.v1i1.4077.
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Column has a function as a successor of the entire building load for foundation with a cross-sectional shape which generally a square. In its development, the shape of column section has begun to vary, namely the 'L', 'T' and 'Plus (+)' shaped sections. The purpose of this study was to determine the effect of restraint parameters such as diameter of stirrups, distance between stirrups, diameter and configuration of longitudinal reinforcement also concrete quality on the capacity and ductility of T-shaped non-square column using Response-2000, XTRACT and SAP2000 programs to ensure the percentage comparison of the analysis result data is not more than 5%. The results of this study for each type of cross-section, namely each increase in the percentage of concrete quality parameters ranging from 25-35 MPa, the diameter of longitudinal reinforcement and diameter of stirrups will increase the value of capacity and decrease the value of ductility, while for each increase in the percentage of parameters the distance between stirrups will decrease the value of capacity and the ductility value. Meanwhile, the variation of longitudinal reinforcement configuration produces T2-1 section as cross section with the largest capacity value and T1-2 section as cross section with the greatest ductility value.
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Krol, Quirine, and Henning Löwe. "Relating optical and microwave grain metrics of snow: the relevance of grain shape." Cryosphere 10, no. 6 (November 21, 2016): 2847–63. http://dx.doi.org/10.5194/tc-10-2847-2016.
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Abstract. Grain shape is commonly understood as a morphological characteristic of snow that is independent of the optical diameter (or specific surface area) influencing its physical properties. In this study we use tomography images to investigate two objectively defined metrics of grain shape that naturally extend the characterization of snow in terms of the optical diameter. One is the curvature length λ2, related to the third-order term in the expansion of the two-point correlation function, and the other is the second moment μ2 of the chord length distributions. We show that the exponential correlation length, widely used for microwave modeling, can be related to the optical diameter and λ2. Likewise, we show that the absorption enhancement parameter B and the asymmetry factor gG, required for optical modeling, can be related to the optical diameter and μ2. We establish various statistical relations between all size metrics obtained from the two-point correlation function and the chord length distribution. Overall our results suggest that the characterization of grain shape via λ2 or μ2 is virtually equivalent since both capture similar aspects of size dispersity. Our results provide a common ground for the different grain metrics required for optical and microwave modeling of snow.
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Thomas, Tracy A., James A. Kuzman, Brent E. Anderson, Susan M. K. Andersen, Evelyn H. Schlenker, Maurice S. Holder, and A. Martin Gerdes. "Thyroid hormones induce unique and potentially beneficial changes in cardiac myocyte shape in hypertensive rats near heart failure." American Journal of Physiology-Heart and Circulatory Physiology 288, no. 5 (May 2005): H2118—H2122. http://dx.doi.org/10.1152/ajpheart.01000.2004.
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We examined the effects of thyroid hormones (THs) on left ventricular (LV) function and myocyte remodeling in rats with spontaneously hypertensive heart failure (SHHF). SHHF rats were treated with three different TH doses from 20–21 mo of age. In terminal experiments, LV function (as determined by echocardiography and catheterization) and isolated myocyte shape were examined in SHHF rat groups and age-matched Wistar-Furth control animals. Compared with Wistar-Furth rats, the ratio of α- to β-myosin was reduced in untreated SHHF rats. The α-to-β-myosin ratio increased in all TH groups, which suggests a reversal of the fetal gene program. Low-dose TH produced no changes in LV myocyte size or function, but high-dose TH produced signs of hyperthyroidism (e.g., increased heart weight, tachycardia). The chamber diameter-to-wall thickness ratio declined with increasing dose due to reduced chamber diameter and increased wall thickness. This resulted in a 38% reduction in LV systolic wall stress in the middle- and high-dose groups despite sustained hypertension. Isolated myocyte data indicated that chamber remodeling and reduced wall stress were due to a unique alteration in myocyte transverse shape (e.g., reduced major diameter and increased minor diameter). Based on our present understanding of ventricular remodeling and wall stress, we believe these changes are likely beneficial. Results suggest that TH may be an important regulator of myocyte transverse shape in heart disease.
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Qiao, Jinpeng, Kejun Dong, and Chenlong Duan. "DEM Study on the Segregation of a Non-Spherical Intruder in a Vibrated Granular Bed." Processes 9, no. 3 (March 2, 2021): 448. http://dx.doi.org/10.3390/pr9030448.
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The segregation process of a single large intruder in a vibrated bed of small particles has been widely studied, but most previous studies focused on spherical intruders. In this work, the discrete element method was used to study the effects of vibration conditions and intruder shape on the dimensionless ascending velocity (va) of the intruder. The intruder was in a prolate shape with aspect ratio varied but its equivalent diameter fixed. Three equivalent diameters, namely volume-equivalent diameter, surface-area-equivalent diameter, and Sauter diameter, were used. It was found that va increases and then decreases with the rise of the dimensionless vibration amplitude (Ad) and the dimensionless vibration frequency (fd), and va increases with the decrease of the sphericity of the intruder (Φ). Moreover, the porosity variation in the vibrated bed and the granular temperature were analyzed, which can be linked to the change of va. It was further found that va can be uniformly correlated to Ad·fd0.5, while the critical change of the response of va to Ad and fd occurs at Γ = 4.83, where Γ is the vibration intensity. Based on these findings, a piecewise equation was proposed to predict va as a function of Ad, fd, and Φ.
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DENG, JUAN, HUI RAO, and ZHI-YING WEN. "HAUSDORFF MEASURE OF CARTESIAN PRODUCT OF THE TERNARY CANTOR SET." Fractals 20, no. 01 (March 2012): 77–88. http://dx.doi.org/10.1142/s0218348x12500077.
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Computing the Hausdorff measure of C × C, where C is the classical ternary Cantor set, is a long standing difficult problem. It is well-known that for a self-similar set, calculating the Hausdorff measure is equivalent to determining its optimal sets. This paper studies optimal sets of C × C: their diameters, measures, symmetries and the shapes. For this purpose, we introduce several devices: the repulsive principle, a bipartite graph G and a W-function. We show that the diameter of the optimal set B is between 1.2993 and 1.3082. Two symmetry properties of B are proved. Finally, we show that the shape of B is very close to a disk. We conjecture that an optimal set might be a disk.
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Newton, P. F., Y. Lei, and S. Y. Zhang. "A parameter recovery model for estimating black spruce diameter distributions within the context of a stand density management diagram." Forestry Chronicle 80, no. 3 (June 1, 2004): 349–58. http://dx.doi.org/10.5558/tfc80349-3.
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The objectives of this study were to develop and subsequently demonstrate a parameter prediction approach for estimating black spruce (Picea mariana (Mill. ) BSP) diameter frequency distributions within the context of a stand density management diagram (SDMD). The approach consisted of three sequential steps: (1) obtaining maximum likelihood estimates for the location, scale and shape parameters of the Weibull probability density function for 153 empirical diameter frequency distributions; (2) developing and evaluating parameter prediction equations in which the Weibull parameter estimates were expressed as functions of stand-level variables based on step-wise regression and seemingly unrelated regression techniques; and (3) explicitly incorporating the parameter prediction equations into the SDMD modelling framework. The results indicated that the Weibull function was successful in characterizing the diameter distributions within the sample stands: the fitted distributions exhibited no significant (p ≤ 0. 05) differences in relation to their corresponding observed distributions, based on the Kolmogorov-Smirnov test. The parameter prediction equations described 94, 94 and 89% of the variation in the location, scale and shape parameter estimates, respectively. Furthermore, evaluation of the recovered distributions in terms of prediction error indicated minimal biases and acceptable accuracy. As demonstrated, incorporating the parameter prediction equations into an algorithmic version of the SDMD enabled the prediction of the temporal dynamics of the diameter frequency distribution by initial density regime and site quality. Additionally, an executable version of the resultant algorithm with instructions on acquiring it via the Internet is provided. Key words: 3-parameter Weibull probability density function, stepwise and seemingly unrelated regression, predictive error, product value, algorithm, Internet
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Gao, F., L. Zhao, M. C. Boufadel, T. King, B. Robinson, and K. Lee. "CFD simulation of the behavior of droplet rising in water column with the effect of surfactant." International Oil Spill Conference Proceedings 2017, no. 1 (May 1, 2017): 2017289. http://dx.doi.org/10.7901/2169-3358-2017.1.000289.
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Surfactant decreases the oil-water interfacial tension and thus oil droplets breakup into smaller ones and are dispersed into the water column. This paper presents the analysis of surfactant (premixed with oil droplet and bulk separately) on the oil droplet behavior in the water column. We implemented additional equations to account for the oil-water interfacial tension due to the presence of surfactant and those equations were incorporated into FLUENT by using UDF (User Defined Function). The streamlines around the oil droplet show major recirculation both inside and outside the oil droplet. It is noticed that the surfactant concentration is higher at the bottom and edges of oil droplet due to the shear effect. The presence of surfactant affects the deformation process of oil droplets of different diameters: Oil droplet with larger diameter (e.g., 4 mm in diameter) deforms into flat shape and breaks up. Tip-streaming is noticed and the droplet continue to rise up in jelly-fish like shape. However, much smaller droplets (e.g., 20 μm in diameter) only deform into oval shape and do not continue to breakup under the condition of same initial surfactant concentration. The presence of surfactant also deceases the rising speed of oil droplet compared to the terminal velocity of clean oil droplet. The results may be valuable to help us to apply surfactant to oil spill in a more efficient way.
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Vinutha, S. P., V. Suresh, and R. Shubha. "Discriminant Function Analysis of Foramen Magnum Variables in South Indian Population: A Study of Computerised Tomographic Images." Anatomy Research International 2018 (September 26, 2018): 1–8. http://dx.doi.org/10.1155/2018/2056291.
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Background and Objectives. The foramen magnum as a transition area between skull and spine plays an important role as a landmark, because of its close relationship to vital structures such as the brain and spinal cord. Configuration and size of the foramen magnum play an important role for assessing craniovertebral relations. The objectives of the present study are to find out shape and dimensions of foramen magnum in cranial CT scans. All the variables were evaluated by using discriminant function analysis. Materials and Methods. The study sample comprised 200 CT scans (110 males and 90 females) of south Indian origin. The shapes of the foramen magnum were classified into 8 types: oval, egg, round, tetragonal, pentagonal, hexagonal, irregular (A), and irregular (B). The parameters were noted meticulously and the statistical analysis for sex comparison was made by Student’s t-test and was considered significant whenever P≤0.05. To determine the relationships between the studied parameters, Pearson correlation coefficients were calculated. Results. The foramen magnum was classified into 8 types based on shape. Commonest was oval and pentagonal was the least common type. The anteroposterior diameter, transverse diameter, circumference, and area were significantly greater in males than in females (P<0.001). The mean FM index of male CT scans was 85.01 ± 8.67, whereas in case of female CT scans, it was 83.17 ± 7.78. With all the variables in consideration, overall 65% of cranial CT scans were sexed correctly by using multivariate analysis. Conclusion. Several anatomic parameters such as shape and dimensions of FM should be taken into consideration during surgery involving the craniovertebral junction. Also these can be used during forensic and anthropological investigation of unknown individuals for determining gender, ethnicity, and so on. The multivariate analysis is by far the best method for determination of sex of cranium with available resources.
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Thurai, M., G. J. Huang, V. N. Bringi, W. L. Randeu, and M. Schönhuber. "Drop Shapes, Model Comparisons, and Calculations of Polarimetric Radar Parameters in Rain." Journal of Atmospheric and Oceanic Technology 24, no. 6 (June 2007): 1019–32. http://dx.doi.org/10.1175/jtech2051.1.
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Drop shapes derived from a previously conducted artificial rain experiment using a two-dimensional video disdrometer (2DVD) are presented. The experiment involved drops falling over a distance of 80 m to achieve their terminal velocities as well as steady-state oscillations. The previous study analyzed the measured axis ratios (i.e., ratio of maximum vertical to maximum horizontal chord) as a function of equivolumetric spherical drop diameter (Deq) for over 115 000 drops ranging from 1.5 to 9 mm. In this paper, the actual contoured shapes of the drops are reported, taking into account the finite quantization limits of the instrument. The shapes were derived from the fast line-scanning cameras of the 2DVD. The drops were categorized into Deq intervals of 0.25-mm width and the smoothed contours for each drop category were superimposed on each other to obtain their most probable shapes and their variations due to drop oscillations. The most probable shapes show deviation from oblate spheroids for Deq > 4 mm, the larger drops having a more flattened base, in good agreement with the equilibrium (nonoblate) shape model of Beard and Chuang. Deviations were noted from the Beard and Chuang model shapes for diameters larger than 6 mm. However, the 2DVD measurements of the most probable contour shapes are the first to validate the Beard and Chuang model shapes for large drops, and further to demonstrate the differences from the equivalent oblate shapes. The purpose of this paper is to document the differences in radar polarization parameters and the range of error incurred when using the equivalent oblate shapes versus the most probable contoured shapes measured with the 2DVD especially for drop size distributions (DSDs) with large median volume diameters (>2 mm). The measured contours for Deq > 1.5 mm were fitted to a modified conical equation, and scattering calculations were performed to derive the complex scattering amplitudes for forward and backscatter for H and V polarizations primarily at 5.34 GHz (C band) but also at 3 GHz (S band) and 9 GHz (X band). Calculations were also made to derive the relevant dual-polarization radar parameters for measured as well as model-based drop size distributions. When comparing calculations using the contoured shapes against the equivalent oblate spheroid shapes, good agreement was obtained for cases with median volume diameter (D0) less than around 2 mm. Small systematic differences in the differential reflectivity (Zdr) values of up to 0.3 dB were seen for the larger D0 values when using the oblate shapes, which can be primarily attributed to the shape differences in the resonance region, which occurs in the 5.5–7-mm-diameter range at C band. Lesser systematic differences were present in the resonance region at X band (3–4 mm). At S band, the impact of shape differences in the polarimetric parameters were relatively minor for D0 up to 2.5 mm. Unusual DSDs with very large D0 values (>3 mm) (e.g., as can occur along the leading edge of severe convective storms or aloft due localized “big drop” zones) can accentuate the Zdr difference between the contoured shape and the oblate spheroid equivalent, especially at C band. For attenuation-correction schemes based on differential propagation phase, it appears that the equivalent oblate shape approximation is sufficient using a fit to the axis ratios from the 80-m fall experiment given in this paper. For high accuracy in developing algorithms for predicting D0 from Zdr, it is recommended that the fit to the most probable contoured shapes as given in this paper be used especially at C band.
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Yi, Song Lin, Zhi Ming Wang, Xian Zhong Yi, and Wei Chang. "The Fundamental Characteristics on Particle Size Distribution of Drilling Rock-Cuttings." Applied Mechanics and Materials 275-277 (January 2013): 2411–14. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.2411.
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The properties of particle size distribution of rock cuttings and its shape characteristics are the most important parameters to petroleum drilling engineering. The samples of rock drill-cuttings are collected from 7 wells within the depths of 3500 m in Liaohe Oilfield of China. The particle size distribution laws of these rock samples with the average diameter over 74 μm are analyzed. The result shows that the drill cuttings feature obvious sheet shape and the size distribution curve of the particles is mainly related to the formation rocks and drilling bits. While drilling at the well depths of between 0 and 2000m by the cone bits, particle size distribution of drill cuttings has a form of approximately power function, the probability particle diameter being 8.50～9.27 mm. Drilling at the depths of between 2000 and 2800 m by the cone bits, the size distribution of cuttings has a form of nearly function, the probability particle diameter being 3.04～4.67 mm. Drilling at the depths under 2800m by PDC bits, the size distribution has a form of nearly the Rayleigh distribution, the probability rock diameter being 0.91～0.94 mm.
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Mei, Lan, Heng Zhang, Lei Wang, Qi Zhang, and Jianchao Cai. "Fractal analysis of shape factor for matrix-fracture transfer function in fractured reservoirs." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 75 (2020): 47. http://dx.doi.org/10.2516/ogst/2020043.
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As the core function of dual-porosity model in fluids flow simulation of fractured reservoirs, matrix-fracture transfer function is affected by several key parameters, such as shape factor. However, modeling the shape factor based on Euclidean geometry theory is hard to characterize the complexity of pore structures. Microscopic pore structures could be well characterized by fractal geometry theory. In this study, the separation variable method and Bessel function are applied to solve the single-phase fractal pressure diffusion equation, and then the obtained analytical solution is used to deduce one-dimensional, two-dimensional and three-dimensional fractal shape factors. The proposed fractal shape factor can be used to explain the influence of microstructure of matrix on the fluid exchange rate between matrix and fracture, and is verified by numerical simulation. Results of sensitivity analysis indicate that shape factor decreases with tortuosity fractal dimension and characteristic length of matrix, increases with maximum pore diameter of matrix. Furthermore, the proposed fractal shape factor is effective in the condition that tortuosity fractal dimension of matrix is roughly between 1 and 1.25. This study shows that microscopic pore structures have an important effect on fluid transfer between matrix and fracture, which further improves the study on flow characteristics in fractured systems.
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Saputro, Adhi Harmoko, M. Marzuki Mustafa, Aini Hussain, W. Mimi Diyana W. Zaki, Oteh Maskon, and Ika Faizura Mohd Nor. "GLOBAL FEATURE FOR LEFT VENTRICULAR DYSFUNCTION DETECTION BASED ON SHAPE DEFORMATION TRACKING." Biomedical Engineering: Applications, Basis and Communications 27, no. 02 (March 17, 2015): 1550017. http://dx.doi.org/10.4015/s1016237215500179.
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Left ventricular (LV) shape alteration is closely correlated with cardiac disease and LV function. In this paper, we propose a feature to detect LV dysfunction globally by analyzing the LV shape deformation in systolic contraction. The feature is an index that is extracted from geometric measurement of LV shape such as the length of the long axis, the short axis, and the apical diameter. A framework for computing the features is also proposed that consists of shape model construction and motion estimation of myocardial boundary. The LV shape model is extracted from apical 2 and 4 chamber views of 2D echocardiography. The long axis, the short axis, and the apical diameter were redefined according to the LV shape constructed. An optical flow technique was used to estimate the position of the LV boundary in each frame. The classification of the LV dysfunction was performed using linear discriminant analysis (LDA) and neural networks (NNs). The 2D echocardiography dataset collected from routine clinical check-up were used to validate the proposed method by comparing the computation result and cardiac expert diagnose. Classification performance and statistical analysis, which was performed to discriminate between healthy and diseased data, indicated promising results. The global LV features would provide a strong basis for a global LV function diagnosis and a global cardiac pathology assessment.
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Ignaccolo, Massimiliano, Carlo De Michele, and Simone Bianco. "The Droplike Nature of Rain and Its Invariant Statistical Properties." Journal of Hydrometeorology 10, no. 1 (February 1, 2009): 79–95. http://dx.doi.org/10.1175/2008jhm975.1.
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Abstract This study looks for statistically invariant properties of the sequences of inter-drop time intervals and drop diameters. The authors provide evidence that these invariant properties have the following characteristics: 1) large inter-drop time intervals (≳10 s) separate drops of small diameter (≲0.6 mm); 2) the rainfall phenomenon has two phases: a quiescent phase, whose contribution to the total cumulated flux is virtually null, and an active, nonquiescent, phase that is responsible for the bulk of the precipitated volume; 3) the probability density function of inter-drop time intervals has a power-law-scaling regime in the range of ∼1 min and ∼3 h); and 4) once the moving average and moving standard deviation are removed from the sequence of drop diameters, an invariant shape emerges for the probability density function of drop diameters during active phases.
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Giardina, Carmela, Rosalia Ricco, Teresa Lettini, Antonia Gentile, Gabriella Serio, Giuseppe De Benedictis, and V. Pesce Delfino. "Relation between Primary Tumor Shape and Biological Behavior in Breast Cancer." Tumori Journal 75, no. 2 (April 1989): 117–22. http://dx.doi.org/10.1177/030089168907500208.
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The aim of this study was to investigate the biological significance of tumor shape in breast cancer by considering the shape not as a casual event but as an expression of the behavior and natural history of the tumor. The shape was studied by an analytical morphometry procedure and was related to axillary metastases, which up to now are the most meaningful prognostic factors in this disease. Fifty cases of infiltrating breast carcinoma (25 N+ and 25 N-) were investigated. The shape, studied on subgross sections of the tumor, was considered as the result of two components: the subtle contour irregularities and the main distortions of the figure. The procedures used allowed us to distinguish and to parametrize these two components in order to submit them to univariate analysis (Student's t test), a principal components analysis and, finally, a multivariate discriminant analysis (Hotelling test). The utilized analytical procedures by work-station S.A.M. (S.A.M. work station is a product of « Metamorphosis ») consisted of three steps: 1) Extraction of tumor function curve obtained by Kth order polynomials which gives a smoothing effect to the original curve; 2) Evaluation of contour irregularities by Fourier harmonic analysis; 3) Evaluation of shape asymmetry by SAE (shape asymmetry evaluator). We considered also the roundness factors of the original and function curves and finally the maximum tumor diameter. Three parameters relating to contour irregularities (sum and mean value of Fourier harmonic amplitude and percentage of superimposed points) and parameters relating to main distortions of the figure (mean value of SAE) were highly significant (p < 0.001). The roundness factor of the original curve was more significant (p < 0.001) than that of the function curve (p < 0.01) whereas maximum tumor diameter was not significant when tested by Student's t test. Multivariate discriminant analysis allowed 20 % of error to be reached by using 3 parameters relating to the shape analysis and the two roundness factors. By using 8 parameters, including maximum tumor diameter, the percentage error was 16 %. The results obtained, while they stress the usefulness of the employed procedure, reveal that shape of the tumor, together with its dimensions, is an important expression of the biological behavior relating to metastatic spread.
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Cosentino, Federica, Giuseppe M. Raffa, Giovanni Gentile, Valentina Agnese, Diego Bellavia, Michele Pilato, and Salvatore Pasta. "Statistical Shape Analysis of Ascending Thoracic Aortic Aneurysm: Correlation between Shape and Biomechanical Descriptors." Journal of Personalized Medicine 10, no. 2 (April 22, 2020): 28. http://dx.doi.org/10.3390/jpm10020028.
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An ascending thoracic aortic aneurysm (ATAA) is a heterogeneous disease showing different patterns of aortic dilatation and valve morphologies, each with distinct clinical course. This study aimed to explore the aortic morphology and the associations between shape and function in a population of ATAA, while further assessing novel risk models of aortic surgery not based on aortic size. Shape variability of n = 106 patients with ATAA and different valve morphologies (i.e., bicuspid versus tricuspid aortic valve) was estimated by statistical shape analysis (SSA) to compute a mean aortic shape and its deformation. Once the computational atlas was built, principal component analysis (PCA) allowed to reduce the complex ATAA anatomy to a few shape modes, which were correlated to shear stress and aortic strain, as determined by computational analysis. Findings demonstrated that shape modes are associated to specific morphological features of aneurysmal aorta as the vessel tortuosity and local bulging of the ATAA. A predictive model, built with principal shape modes of the ATAA wall, achieved better performance in stratifying surgically operated ATAAs versus monitored ATAAs, with respect to a baseline model using the maximum aortic diameter. Using current imaging resources, this study demonstrated the potential of SSA to investigate the association between shape and function in ATAAs, with the goal of developing a personalized approach for the treatment of the severity of aneurysmal aorta.
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Loewenstein, Edward F., Paul S. Johnson, and Harold E. Garrett. "Age and diameter structure of a managed uneven-aged oak forest." Canadian Journal of Forest Research 30, no. 7 (July 1, 2000): 1060–70. http://dx.doi.org/10.1139/x00-036.
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We studied the age and diameter structure on one section (259 ha) of a 63 000-ha privately owned forest in the Ozark Highlands of Missouri. The forest has been managed using a partial cutting strategy since 1954. Because a majority of the trees predate current management practices, the existing stand structure is a function of not only the current silvicultural system and the dynamics of this ecosystem but also the initial stand conditions. To determine age structure and evaluate the relationship of diameter and age, a random sample of 600 oaks [Formula: see text]4 cm DBH were collected from ten 0.4-ha plots. Based on the test of a binomial proportion, the oak populations on 7 of the 10 plots were deemed uneven aged, two were deemed two aged, and one was even aged. DBH accounted for 40 (red oaks) to 62% (white oaks) of the variation in tree age. Although the overall diameter frequency distribution of oaks formed a reverse-J shape, the age-frequency distribution approximated a normal (bell-shaped) distribution. We show how this apparent inconsistency between diameter and age distributions can be an artifact of a minimum sampling diameter. Such a truncation of the sampled population reduces the observed frequency of trees in the younger age-classes, which in turn results in a bell-shaped rather than a reverse-J-shaped age-frequency distribution. Thus, the lack of a reverse- J-shaped age distribution should not be interpreted as a failure to sustain regeneration in an uneven-aged stand.
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Alves, Luciana F., and Flavio A. M. Santos. "Tree allometry and crown shape of four tree species in Atlantic rain forest, south-east Brazil." Journal of Tropical Ecology 18, no. 2 (March 2002): 245–60. http://dx.doi.org/10.1017/s026646740200216x.
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The allometry of crown shape and trunk diameter with tree height were analysed for four tree species in a tropical lowland rain forest, southeast Brazil. The dimensional relationships of a subcanopy species (Garcinia gardneriana) were contrasted with those of two canopy (Chrysophyllum flexuosum and Swartzia simplex) and one emergent species (Sloanea guianensis). For all trees ≥ 1 cm dbh, we recorded dbh, total height, branching height, crown area, crown width and crown length. Observed allometric relationships indicated interspecific variation in trunk diameter and crown shape with height. All species conformed to the elastic similarity model, except the emergent one that showed thicker trunks and a scaling exponent conforming to the constant stress model. The general allometric function used to describe the overall relationship (all sizes combined) did not specify exceptional variation in crown shape between species of contrasting adult stature (emergent vs. subcanopy species). However, when allometric relationships through ontogeny were considered, different strategies of growth, maintenance and expansion of crown became evident. Crown shapes were much more variable in canopy and emergent species than in the subcanopy one, suggesting that larger-statured species might be more flexible in the relative allocation of energy to height, diameter, and crown growth than smaller-statured ones. Notwithstanding, it is suggested that it is not possible adequately to predict allometric relationships only by adult stature/canopy position. Allometric variation may be also related to size-dependent changes in demographic traits and/or different responses to light availability among tree species.
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Honecker, Julius, Dominik Weidlich, Simone Heisz, Cecilia M. Lindgren, Dimitrios C. Karampinos, Melina Claussnitzer, and Hans Hauner. "A distribution-centered approach for analyzing human adipocyte size estimates and their association with obesity-related traits and mitochondrial function." International Journal of Obesity 45, no. 9 (June 25, 2021): 2108–17. http://dx.doi.org/10.1038/s41366-021-00883-6.
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Abstract Objective Cell diameter, area, and volume are established quantitative measures of adipocyte size. However, these different adipocyte sizing parameters have not yet been directly compared regarding their distributions. Therefore, the study aimed to investigate how these adipocyte size measures differ in their distribution and assessed their correlation with anthropometry and laboratory chemistry. In addition, we were interested to investigate the relationship between fat cell size and adipocyte mitochondrial respiratory chain capacity. Methods Subcutaneous and visceral histology-based adipocyte size estimates from 188 individuals were analyzed by applying a panel of parameters to describe the underlying cell population. Histology-based adipocyte diameter distributions were compared with adipocyte diameter distributions from collagenase digestion. Associations of mean adipocyte size with body mass index (BMI), glucose, HbA1C, blood lipids as well as mature adipocyte mitochondrial respiration were investigated. Results All adipocyte area estimates derived from adipose tissue histology were not normally distributed, but rather characterized by positive skewness. The shape of the size distribution depends on the adipocyte sizing parameter and on the method used to determine adipocyte size. Despite different distribution shapes histology-derived adipocyte area, diameter, volume, and surface area consistently showed positive correlations with BMI. Furthermore, associations between adipocyte sizing parameters and glucose, HbA1C, or HDL specifically in the visceral adipose depot were revealed. Increasing subcutaneous adipocyte diameter was negatively correlated with adipocyte mitochondrial respiration. Conclusions Despite different underlying size distributions, the correlation with obesity-related traits was consistent across adipocyte sizing parameters. Decreased mitochondrial respiratory capacity with increasing subcutaneous adipocyte diameter could display a novel link between adipocyte hypertrophy and adipose tissue function.
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Bubeníčková, Aneta, Jana Simeonovová, Vojtěch Kumbár, Miroslav Jůzl, and Šárka Nedomová. "Mathematical descriptive characteristics of potato tubers’ shape." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 59, no. 6 (2011): 63–68. http://dx.doi.org/10.11118/actaun201159060063.
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Precise modeling of sorting, manipulation, and transport processes of potatoes are conditioned by exact knowledge of tubers shape geometrical characteristics. The paper presents and quantifies some mathematical descriptive characteristics of potatoes. Ten selected varieties of potato tubers were analyzed. The basic dimensions were used for calculation of geometric mean diameter and volume. The maximum/minimum values were in both cases found for the same variety,KarinandVerarespectively. Calculated sphericity ranged from 0.007732 to 0.009803 forKrasaandMarilyn. The contour profiles were calculated by use of descriptive function and satisfying correlation (r2up to 0.9972) between computed and measured values was achieved. Radius of curvature was determined and evaluated in several positions. No statistically significant dependences of differences in curvature radius on neither variety nor position was found.
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Thurai, Merhala, and V. N. Bringi. "Drop Axis Ratios from a 2D Video Disdrometer." Journal of Atmospheric and Oceanic Technology 22, no. 7 (July 1, 2005): 966–78. http://dx.doi.org/10.1175/jtech1767.1.
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Abstract Results from an experiment to measure the drop shapes using a 2D video disdrometer (2DVD) are reported. Under calm conditions, drops were generated from a hose located on a bridge 80 m above ground, this height being sufficient to allow drop oscillations to reach a steady state. The disdrometer data had to be carefully processed so as to eliminate the drops mismatched by the instrument and to remove the system spreading function. The total number of drops analyzed was around 115 000. Their axis ratio distributions were obtained for diameters ranging from 1.5 to 9 mm. The mean axis ratio decreases with increasing drop diameter, in agreement with the upper bound of the Beard and Chuang equilibrium shape model. The inferred mode of oscillation appears to be dominated by the oblate–prolate axisymmetric mode for the diameter range of 1.5 to 9 mm. The mean axis ratio agrees well with two empirically fitted formulas reported in earlier studies. In addition, a linear fit was applied to the data for radar applications relating to rain retrievals from dual-polarization measurements. The 2DVD data taken in moderate stratiform rain were also analyzed in a similar way and the results agree with the artificially generated drop experiment, at least up to 4 mm. No data for larger diameters were available for stratiform precipitation. Finally, the fall velocity was examined in terms of drop diameter. The results closely follow an empirical formula fitted to the Gunn and Kinzer data as well as the Beard and Pruppacher data including a slight decrease in the terminal velocity with a diameter beyond 7 mm.
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Zhang, Xiao Ming, Shu Wen Ding, and Shuang Xi Li. "Tensile Characteristics of Polygonaceae Weed Roots in Slope Collapse Watershed." Advanced Materials Research 690-693 (May 2013): 1792–95. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.1792.
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Root systems, as the reinforced materials, are essential to increase slope stability and mitigate soil erosion. Polygonaceae family weeds are widespread in slope collapse watershed for its rapid growth and hardiness. Some growing around farmlands and ditches affect the farm crop yield. While others growing in slope collapse have medicinal value, revegetation, and root reinforcement effect. The plant height, fresh weight and expansion range of aboveground biomass and roots were measured to research the relationship between the aboveground biomass and the belowground biomass. The relationship between the aboveground biomass fresh weight and root system fresh weight was consistent with linear function. Single root was tested by digital display push-tension meter (SH-100) fixed in vertical electrical machine (SJY-500) to obtain the relationship between tensile force and root diameter. The relationship between tensile force and root diameter conformed to exponential decay function. At last, the relationship between root diameter classes and average tensile force of Polygonaceae family weeds was analyzed. The result showed that the diameters mainly ranged from 0 mm to 2 mm, 87.75% of the total, and the average tensile force increased with the diameter class. At the beginning, the shape of tensile force was a line, then a curved line during pulling, which deformation was nonlinear. It could provide a scientific basis for design of weeder in farmland, and greening, erosion control in slope collapse.
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RUPŠYS, PETRAS, and EDMUNDAS PETRAUSKAS. "QUANTIFYING TREE DIAMETER DISTRIBUTIONS WITH ONE-DIMENSIONAL DIFFUSION PROCESSES." Journal of Biological Systems 18, no. 01 (March 2010): 205–21. http://dx.doi.org/10.1142/s0218339010003263.
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This study presents diffusion processes methodology on tree diameter distribution problem. We use stochastic differential equation methodology to derive a univariate age-dependent probability density function of a tree diameter distribution. The purpose of this paper is to investigate the relationship between the stochastic linear and logistic shape diameter growth models and diameter distribution laws. We establish the probabilistic characteristics of stochastic growth models, such as the univariate transition probability density of tree diameter, the mean and variance of tree diameter. We carry out comparison of proposed continuous time stochastic models on the basis of Hong-Li, Gini, Shapiro-Wilk goodness-of-fit statistics and normal probability plot. Parameter estimations are based on discrete observations over age of trees. To model the tree diameter distribution, as an illustrative experience, a real data set from repeated measurements on a permanent sample plot of pine (Pinus sylvestris) stand in the Kazlu Ruda district at Lithuania is used. The results are implemented in the symbolic computational language MAPLE.
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Yan, Qiu Sheng, Xu Guang Zhou, B. Q. He, and Ling Ye Kong. "A New Grinding Method for Large-Scale Surface of Revolution and Error Analyzing of Its Wheel Dressing." Key Engineering Materials 329 (January 2007): 111–16. http://dx.doi.org/10.4028/www.scientific.net/kem.329.111.
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Large-scale surface such as mould should have low roughness as well as high accuracy of geometry profile. And it is an essential method to reach the accuracy request with grinding process. In this research, due to the variety of geometry profiles, an Arc Envelope Grinding Method (AEGM) is presented, the difficult problem of grinding large-scale revolution surface can be solved. Meanwhile, the grinding wheel dressing and its shape precision are the keys to the precision of revolution surface in the grinding with AEGM. In this paper, the influences of setting error of diamond point dresser, which dress the grinding wheel into an arc section by using numerical control function of NC grinding machine, upon the shape accuracy of plate-shaped grinding are analyzed. It is shown that shape error of the grinding wheel increases with the increases of dresser setting error in diameter direction, radius of tip arc on the grinding wheel, while it reduces with the increase of radius of the grinding wheel, and shape error distributes no uniformly but symmetrically along axial direction.
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Biao, Wang, Xiao Fen Yu, Cong Yu Xu, and Jia Wen Hu. "High Precision Online Measurement Technology to Large Diameter." Applied Mechanics and Materials 303-306 (February 2013): 376–81. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.376.
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Because of the large diameter’s big volume, heavy weight, high thermal capacity and bad measurement environment, the workpiece’s diameter can only be detected in the processing locale. Though the rolling-wheel method can realize the large diameter online measurement, it can not achieve the diameter high precision measurement influenced by rolling-wheel skidding, compression deformation and temperature distribution. Focusing on the above problem, a new multi function rolling-wheel large diameter measurement system is designed. The designed system mainly researches the main error resource’s distinguish and amendment methods, such as the round grating graduator error, rolling-wheel shape error, rolling-wheel compression deformation, skidding of rolling-wheel to measured axis workpiece and its non-uniform temperature etc. The system can obtain the measured axis’s diameter and roundness real time while getting the needed information of error amendment by integrating multi opto-electronic switch, round grating, reference grating, micro-displacement sensor, temperature sensor etc. The system can realize diameter measurement extended uncertainty 5Dμm(D:1m～10m) and roundness measurement extended uncertainty 1.5Dμm.
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Fan, Wenyuan, and Xiaohong Yin. "Bubble formation in shear-thinning fluids: Laser image measurement and a novel correlation for detached volume." Chemical Industry and Chemical Engineering Quarterly 23, no. 3 (2017): 301–9. http://dx.doi.org/10.2298/ciceq151019045f.
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A laser image system has been established to quantify the characteristics of growing bubbles in quiescent shear-thinning fluids. Bubble formation mechanism was investigated by comparing the evolutions of bubble instantaneous shape, volume and surface area in two shear-thinning liquids with those in Newtonian liquid. The effects of solution mass concentration, gas chamber volume and orifice diameter on bubble detachment volume are discussed. By dimensional analysis, a single bubble volume detached within a moderate gas flowrate range was developed as a function of Reynolds number ,Re, Weber number, We, and gas chamber number, Vc, based on the orifice diameter. The results reveal that the generated bubble presents a slim shape due to the shear-thinning effect of the fluid. Bubble detachment volume increases with the solution mass concentration, gas chamber volume and orifice diameter. The results predicted by the present correlation agree better with the experimental data than the previous ones within the range of this paper.
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Xie, Xiong, and Jian Ping Tan. "Simulation Research on Stress – Damage Law of the Blood Cells." Advanced Materials Research 482-484 (February 2012): 776–79. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.776.
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Through simulation analysis of the blood cell by Abques under the function of the different pressures, the change of the cell’s axial diameter and the importance of the effect of external force and double concave shape on the erythrocyte’s deformability are obtained. It lays the foundation for the research artificial organs lubrication.
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Westerhof, Berend E., Ilja Guelen, Wim J. Stok, Karel H. Wesseling, Jos A. E. Spaan, Nico Westerhof, Willem Jan Bos, and Nikos Stergiopulos. "Arterial pressure transfer characteristics: effects of travel time." American Journal of Physiology-Heart and Circulatory Physiology 292, no. 2 (February 2007): H800—H807. http://dx.doi.org/10.1152/ajpheart.00443.2006.
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We investigated the quantitative contribution of all local conduit arterial, blood, and distal load properties to the pressure transfer function from brachial artery to aorta. The model was based on anatomical data, Young's modulus, wall viscosity, blood viscosity, and blood density. A three-element windkessel represented the distal arterial tree. Sensitivity analysis was performed in terms of frequency and magnitude of the peak of the transfer function and in terms of systolic, diastolic, and pulse pressure in the aorta. The root mean square error (RMSE) described the accuracy in wave-shape prediction. The percent change of these variables for a 25% alteration of each of the model parameters was calculated. Vessel length and diameter are found to be the most important parameters determining pressure transfer. Systolic and diastolic pressure changed <3% and RMSE <1.8 mmHg for a 25% change in vessel length and diameter. To investigate how arterial tapering influences the pressure transfer, a single uniform lossless tube was modeled. This simplification introduced only small errors in systolic and diastolic pressures (1% and 0%, respectively), and wave shape was less well described (RMSE, ∼2.1 mmHg). Local (arm) vasodilation affects the transfer function little, because it has limited effect on the reflection coefficient. Since vessel length and diameter translate into travel time, this parameter can describe the transfer accurately. We suggest that with a, preferably, noninvasively measured travel time, an accurate individualized description of pressure transfer can be obtained.
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Bassil, Sarita, Ralph D. Nyland, Christel C. Kern, and Laura S. Kenefic. "Dynamics of the diameter distribution after selection cutting in uneven- and even-aged northern hardwood stands: a long-term evaluation." Canadian Journal of Forest Research 49, no. 12 (December 2019): 1525–39. http://dx.doi.org/10.1139/cjfr-2019-0204.
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Selection cutting is defined as a tool for uneven-aged silviculture. Dependence on diameter distribution by forestry practitioners for identifying stand conditions has led to misuse of selection-like cuttings in even-aged northern hardwood stands. Our study used several long-term data sets to investigate the temporal stability in numbers of trees per diameter class in uneven-aged northern hardwood stands treated with single-tree selection and in 45-year-old second-growth stands treated with selection-like cuttings. We analyzed data from New York, Michigan, and Wisconsin to determine changes through time in number of trees across 2.5 cm diameter classes, shifts in the shape and scale of the three-parameter Weibull function used to describe the diameter distributions, and dynamics of associated stand attributes. Findings showed that single-tree selection cutting created and sustained stable diameter distributions and uniformity of conditions through consecutive entries in uneven-aged stands. By contrast, these characteristics varied through time in the second-growth stands that had been treated with selection-like cuttings. Analysis also showed that the Weibull shape and scale parameters for stands under selection system migrated towards those of the recommended target diameter distribution in the uneven-aged stands. These parameters diverged from the target with repeated use of selection-like cuttings in the second-growth even-aged stands.
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Pogoda, Piotr, Wojciech Ochał, and Stanisław Orzeł. "Performance of Kernel Estimator and Johnson SB Function for Modeling Diameter Distribution of Black Alder (Alnus glutinosa (L.) Gaertn.) Stands." Forests 11, no. 6 (June 3, 2020): 634. http://dx.doi.org/10.3390/f11060634.
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We compare the usefulness of nonparametric and parametric methods of diameter distribution modeling. The nonparametric method was represented by the new tool—kernel estimator of cumulative distribution function with bandwidths of 1 cm (KE1), 2 cm (KE2), and bandwidth obtained automatically (KEA). Johnson SB (JSB) function was used for the parametric method. The data set consisted of 7867 measurements made at breast height in 360 sample plots established in 36 managed black alder (Alnus glutinosa (L.) Gaertn.) stands located in southeastern Poland. The model performance was assessed using leave-one-plot-out cross-validation and goodness-of-fit measures: mean error, root mean squared error, Kolmogorov–Smirnov, and Anderson–Darling statistics. The model based on KE1 revealed a good fit to diameters forming training sets. A poor fit was observed for KEA. Frequency of diameters forming test sets were properly fitted by KEA and poorly by KE1. KEA develops more general models that can be used for the approximation of independent data sets. Models based on KE1 adequately fit local irregularities in diameter frequency, which may be considered as an advantageous in some situations and as a drawback in other conditions due to the risk of model overfitting. The application of the JSB function to training sets resulted in the worst fit among the developed models. The performance of the parametric method used to test sets varied depending on the criterion used. Similar to KEA, the JSB function gives more general models that emphasize the rough shape of the approximated distribution. Site type and stand age do not affect the fit of nonparametric models. The JSB function show slightly better fit in older stands. The differences between the average values of Kolmogorov–Smirnov (KS), Anderson–Darling (AD), and root mean squared error (RMSE) statistics calculated for models developed with test sets were statistically nonsignificant, which indicates the similar usefulness of the investigated methods for modeling diameter distribution.
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Kari, L. "An analytical temperature-dependent collocation model for preloaded rubber cylinders." Journal of Strain Analysis for Engineering Design 37, no. 4 (May 1, 2002): 289–99. http://dx.doi.org/10.1243/030932402760074517.
Full textAbstract:
The non-linear temperature-dependent stiffness of an axially preloaded rubber cylinder is examined by an analytical collocation model, where influences of temperature, cylinder diameter and length, material parameters and prestrain are investigated. The rubber is assumed to be incompressible with the deviatoric response determined by an extended neo-Hookean free energy function, embodying a temperature shift function, being directly proportional to the temperature and to the temperature-dependent rubber density. The model is based on a semi-inverse method where the motion is split into two deformations: the first, a homogeneous temperature expansion, while the second, a preload deformation where material planes parallel to the bonded metal plate in the rubber cylinder are assumed to remain parallel, with the boundary conditions on the free rubber surface satisfied by collocation. The stiffness depends strongly on the preload—particularly for larger diameter-length ratios—and on the temperature covering —60 to + 60° C, where the shift function factor directly proportional to the temperature is found to play the greatest role. Contrary to other semi-inverse models, this model coincides at vanishing preloads with a well-known linear formula while extending the applicable shape factor range to cover shape factors typically found for vibration isolators.
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Bellisario, Denise, Fabrizio Quadrini, and Loredana Santo. "Indentation Recovery of Shape Memory Foams Produced by Solid State Foaming." Key Engineering Materials 611-612 (May 2014): 656–63. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.656.
Full textAbstract:
In this study, solid state foaming was used to produce epoxy foam samples with shape memory properties. Foams were indented at room and high temperature by using flat pins with diameter from 1 to 5 mm. Micro-indentations were performed as well only at room temperature. The indentation marks were measured before and after thermal recovery to evaluate the ability of the material to reach the initial shape. For a better understanding of the overall process, a study was made also to predict the initial precursor density as a function of the compaction parameters. This way, it was also evaluated that the effect of the compaction process is covered by the effect of the foaming step.
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Hartman, Miloslav, Otakar Trnka, Karel Svoboda, and Václav Veselý. "Influence of Particle Shape on the Drag Coefficient for Isometric Particles." Collection of Czechoslovak Chemical Communications 59, no. 12 (1994): 2583–94. http://dx.doi.org/10.1135/cccc19942583.
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A comprehensive correlation has been developed of the drag coefficient for nonspherical isometric particles as a function the Reynolds number and the particle sphericity on the basis of data reported in the literature. The proposed formula covers the Stokes, the transitional and the Newton region. The predictions of the reported correlation have been compared to experimental data measured in this work with the dolomitic materials in respect to their use in calcination and gas cleaning processes with fluidized beds. Approximative explicit formulae have also been reported that make it possible to estimate the terminal free-fall velocity of a given particle or to predict the particle diameter corresponding to a fluid velocity of interest.
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Landis, W., N. Isogai, and J. Vacanti. "Development of Cartilage and Bone During Formation of Phalanges by Tissue Engineering." Microscopy and Microanalysis 5, S2 (August 1999): 378–79. http://dx.doi.org/10.1017/s143192760001521x.
Full textAbstract:
Treatment of human congenital malformations and for loss of tissue or organ function is a serious clinical concern, frequently supported by harvesting autogenous tissue for reconstructive surgery. This paper summarizes an alternate approach through novel tissue engineering methods and describes cell-polymer composites that could be fundamental in developing advances for digit and joint replacement. The work utilizes cells from different sources transplanted on biodegradable polymer matrices to form structures with defined shape, morphological features and composition resembling those of human phalanges and intact joints.Polyglycolic acids (PGA) fibers (Albany International, Mansfield, MA) 15 μm in diameter were used as a mesh support for cell attachment and matrix formation. For cartilage and tendon cells, PGA alone served as a flat surface without specific shape. For bone cells, PGA was copolymerized with poly-L-lactic acid (PLLA) (Polysciences, Warrington, PA) and shaped after a human phalanx molded from cadaveric distal and middle phalangeal bones. Polymers were sterilized with ethylene oxide before use.
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Huet, C., C. Pisselet, B. Mandon-Pepin, P. Monget, and D. Monniaux. "Extracellular matrix regulates ovine granulosa cell survival, proliferation and steroidogenesis: relationships between cell shape and function." Journal of Endocrinology 169, no. 2 (May 1, 2001): 347–60. http://dx.doi.org/10.1677/joe.0.1690347.
Full textAbstract:
The extracellular matrix (ECM), constituting the follicular basal lamina and present also between follicular cells and in the follicular fluid, is believed to regulate granulosa cell (GC) function during follicular development. Ovine GCs isolated from small (1-3 mm in diameter) or large (4-7 mm in diameter) antral follicles were cultured on various pure ECM components (type I collagen, fibronectin, laminin), synthetic substrata enhancing (RGD peptides) or impairing (poly 2-hydroxyethylmethacrylate (poly-hema)) cell adhesion, or in the presence of heparin. The effects of these factors, used alone or in combination with IGF-I and/or FSH, were evaluated in terms of GC spread, survival, proliferation and steroidogenesis. When grown on type I collagen (CI) gel, poly-hema or heparin, GCs from both large and small follicles exhibited a round shape and a low proliferation rate. Compared with non-coated plastic substratum as a control, these ECM or synthetic compounds enhanced estradiol secretion and reduced progesterone secretion by large-follicle GCs. In contrast, GCs from both large and small follicles spread extensively on CI coating, fibronectin, laminin and RGD peptides. Fibronectin and laminin dramatically increased the proliferation rate and enhanced survival of GCs from both origins. Moreover, fibronectin, laminin and RGD peptides reduced estradiol secretion by large-follicle GCs. Unexpectedly, CI coating increased estradiol secretion and reduced progesterone secretion by large-follicle GCs, suggesting that type I collagen was able to maintain estradiol secretion independently of GC shape. Finally, GC responsiveness to IGF-I and FSH, in terms of proliferation and steroidogenesis, was generally maintained when cells were grown on ECM components, RGD peptides and in the presence of heparin. However, when large-follicle GCs were grown as non-adherent clusters (as observed on poly-hema) basal and IGF-I- and/or FSH-stimulated progesterone secretions were totally abolished. Overall, this study shows that GC shape, survival, proliferation and steroidogenesis can be modulated in vitro by pure ECM components in a specific and coordinated manner. It is suggested that, in vivo, fibronectin and laminin would sustain follicular development by enhancing the survival and proliferation of GCs, whereas type I collagen might participate in the maintenance of estradiol secretion in large antral follicles.