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The TC18 titanium alloy as an aviation landing gear material is famous for its high strength and hardenability. However, under the influence of the harsh service environment, its corrosion resistance is relatively poor. WC–12Co ceramic material is one of the most widely used surface strengthening materials, and the coatings are often produced by high velocity oxygen fuel (HVOF) thermal spraying. In the spraying, the deposition state of particles directly affects the quality and strengthening ability of coating. This study combined the correlation of flow field calculation and impact process of particles, and the particle flight characteristics were analyzed in the three‐dimensional HVOF spraying. The change law for temperature and velocity of particles was explored by changing the spraying distance, oxygen/fuel (O/F) ratio, and particle size. Based on the calculation results of flow field, a three‐dimensional random deposition model of WC–12Co multiparticle was established by the coupled Euler–Lagrange method, and the crystal inhomogeneity was introduced by the Voronoi method. Compared the flattening rate and spreading degree of particles deposition, the evolution law of temperature and stress–strain fields for coating and substrate during the deposition was revealed. [ABSTRACT FROM AUTHOR]

Bone cutting is a complicated surgical operation. It is very important to establish a kind of gradient porous bone model in vitro which is close to human bone for the research of bone cutting. Due to the existing bone cutting researches are based on solid bone model, which is quite different from human bone tissue structure. Therefore, Voronoi method was used to establish a gradient porous bone model similar to real bone tissue to simulate the process of bone drilling in this paper. High temperature and large cutting force during bone drilling can cause serious damage to bone tissue. Urgent research on bone drilling parameters is necessary to reduce cutting temperature and cutting force. The finite element analysis (FEA) of Voronoi bone models with different gradients is carried out, and a Voronoi model which is similar to real bone tissue is obtained and verified by combining the cutting experiment of pig bone. Then orthogonal experiments are designed to optimize the cutting parameters of Voronoi bone model. The range method is used to analyze the influence weights of cutting speed, feed speed and tip angle on cutting temperature and cutting force, and the least square method was used to predict the cutting temperature and cutting force, respectively. The gradient porous bone model constructed by Voronoi method was studied in detail in this paper. This study can provide theoretical guidance for clinical bone drilling surgery, and the prediction model of bone drilling has practical significance.

To improve the efficiency of lightweight optimization for stiffened panels, an efficient dynamic sequential lightweight optimization method based on Voronoi is proposed. Above all, the influences of the mesh size of the stiffened panel skin and strings on load-carrying capacity and the buckling modes of the structure are analyzed based on the parametric model. Furthermore, the dynamic mesh partition is realized according to the height-thickness of the web to balance the accuracy and efficiency of post-buckling analysis. Then, a dynamic sequential approximate optimization incorporating an exploration strategy and an exploitation strategy is proposed. Sampling by Voronoi focuses on global space exploration, while sampling by approximate optimal solution focuses on local exploitation. The parallel sampling with both explorative and exploitative performance is realized by dynamic sampling iteration to convergence, which improved the convergence precision and computational efficiency of the algorithm. Ultimately, the proposed algorithm is applied to the lightweight design of stiffened panels, and compared with the traditional sequential approximation optimization method. The results reveal that the proposed method needs fewer initial sample points and less iteration times to achieve higher optimization accuracy, and obtains an optimized structure with a weight reduction of 32.6% compared with the initial design, which indicates that the proposed method is validated for the prospect of engineering applications. [ABSTRACT FROM AUTHOR]

It is shown on the example of the analysis of bulk properties of an aqueous tert-butanol solution that the structure of solution can be better understood using the volumes of their different components. Within molecular dynamics models of solutions, their individual components and volumes can be determined using the Voronoi partition. This is an additional information with respect to the traditional approach where bulk characteristics are calculated from the total solution density. The Voronoi molar volumes of components, components of excess molar volume of the solution, and the apparent alcohol volume are calculated. The nature of the minimum on the apparent volume curve and the association of tert-butanol molecules in water at low concentrations is discussed. [ABSTRACT FROM AUTHOR]

In order to study a new thread rolling forming process from a microscopic perspective, a polycrystalline model was established, based on the crystal plasticity finite element method (CPFEM) and Voronoi polyhedron theory. The fluidity of metals was studied to explain the reason for the concave center. The simulation results show that the strain curve of the representative element can more truly reflect the deformation behavior of the material. The grain orientations after deformation are distributed near the initial orientation. The evolution of each slip system is determined by the initial grain orientations and grain locations. The pole figures obtained from the experiment show high consistency with the pole figures obtained by simulation, which verifies the accuracy of the texture prediction by CPFEM. The experimental results show that thread rolling is more uniform in deformation than ordinary rolling.

Aims: To investigate the relationship of type 2 diabetes duration and myocardial blood flow (MBF) assessed by myocardial CT perfusion.Materials and Methods: We prospectively included 140 patients with type 2 diabetes who underwent dynamic myocardial CT perfusion exam. MBF of the remote myocardium was calculated using the deconvolution technique and the Voronoi method. The relationships of MBF and diabetic duration, diabetic complications, conventional risk factors, coronary calcium, and coronary stenosis were assessed by logistic regression analysis.Results: A weak but significantly negative relationship was present between diabetes duration and MBF (R2 = 0.05, p < 0.01). The average MBF of patients with a duration of >8 years was 13% lower than that of the remaining patients (1.11 ± 0.35 vs 1.28 ± 0.27 ml min-1 g-1, p < 0.01). Duration of one year was associated with a 6% increased risk for low MBF (<1.18 ml min-1 g-1) (odds ratio 1.06, 95% confidence interval 1.01-1.12, p < 0.05). Calcium score was also a significant factor for low MBF (odds ratio 1.08 (per 100 Agatston units), 95% confidence interval 1.01-1.17, p < 0.05).Conclusion: Longer diabetes duration is associated with lower MBF independent of conventional cardiac risk factors or the presence of coronary stenosis. [ABSTRACT FROM AUTHOR]

This paper presents the results of Molecular Dynamics (MD) simulations of Cu60.0Zr32.5Ti7.5 alloy through the open source code LAMMPS. Amorphous samples were produced by quenching the molten metal from 2300 to 300 K. The pair distribution functions of the liquid and solid were calculated. Moreover, the atomic short-range order at 800, 700 and 300 K was obtained by using the Voronoi tesselation method. Cu-centered icosahedral clusters were the prevailing configuration. The tensile stress-strain curve showed that the material present plastic deformation, however, shear bands were not observed in the MD simulation. The evolution of viscosity in temperatures higher than its glass transition temperature was also determined. Furthermore, the fragility of the alloy at glass temperature was evaluated.

We study the spatial distribution of trimethylamine- N -oxide (TMAO) and tert -butyl alcohol (TBA) molecules in aqueous solutions at low concentrations using molecular dynamics simulation, Voronoi-Delaunay method, and statistical cluster analysis. A comparison of these solutions with the systems of randomly distributed hard spheres is carried out. It is shown that TMAO molecules are generally distributed like random spheres. On the contrary, the distribution of TBA substantially differs from the random one, being the result of the self-association process in TBA solutions. Thus, using the methods of statistical geometry and systems of random spheres as a reference system, one can carry out a quantitative characterization of a global structure of a solution to describe general features of the spatial distribution of the solute molecules. [ABSTRACT FROM AUTHOR]

Background Myocardial mass at risk (MMAR) is an important predictor of adverse cardiac events in patients with ischemic heart disease. This study aims to validate the accuracy of MMAR calculated from cardiac computed tomography (CCT) data using the Voronoi-based segmentation algorithm in comparison with actual MMAR measured on ex-vivo swine hearts prepared by injecting a dye into the coronary arteries. Methods Fifteen extracted swine hearts had India ink injected into one of the major coronary arteries. Subsequently, all coronary arteries manually injected with methylcellulose-based iohexiol-370 were imaged by 16-row CT. The ventricles were cross-sectioned perpendicularly to the long axis of the left ventricle (LV). The stained area and the total LV area of individual slices were measured, and actual MMAR was calculated as the ratio of the LV volume with the disc-summation method. CT-based MMAR of each coronary artery was calculated automatically with the Voronoi-based segmentation algorithm. The results were compared using Pearson's correlation coefficient. Results The median value of CT-based MMAR was 50.8% for the left anterior descending artery (LAD), 36.6% for the left circumflex artery (LCX), and 23.0% for the right coronary artery (RCA). Actual MMAR was 49.8% for LAD, 32.2% for LCX, and 25.9% for RCA. CT-based MMAR was significantly related to actual MMAR (r = 0.92, p = 0.02 for LAD; r = 0.96, p = 0.009 for LCX; r = 0.96, p = 0.009 for RCA). Conclusion CT-based MMAR obtained by Voronoi-based segmentation algorithm reliably estimates actual MMAR measured on ex-vivo swine hearts. [ABSTRACT FROM AUTHOR]

To select the best revascularization strategy a correct understanding of the ischemic territory and the coronary anatomy is crucial. Stress myocardial perfusion single photon emission computed tomography (SPECT) is the gold standard to assess ischemia, however, SPECT has important limitations such as lack of coronary anatomical information or false negative results due to balanced ischemia in multi-vessel disease. Angiographic scores are based on anatomical characteristics of coronary arteries but they lack information on the extent of jeopardized myocardium. Cardiac computed tomography (CCT) has the ability to evaluate the coronary anatomy and myocardium in one sequence, which is theoretically the ideal method to assess the myocardial mass at risk (MMAR) for any target lesion located at any point in the coronary tree. In this study we analyzed MMAR of the three main coronary arteries and three major side branches; diagonal (Dx), obtuse marginal (OM), and posterior descending artery (PDA) in 42 patients with normal coronary arteries using an algorithm based on the Voronoi method. The distribution of MMAR among the three main coronary arteries was 44.3 ± 5.6 % for the left anterior descending artery, 28.2 ± 7.3 % for the left circumflex artery, and 26.8 ± 8.6 % for the right coronary artery. MMAR of the three major side branches was 11.3 ± 3.9 % for the Dx, 12.6 ± 5.2 % for the OM and 10.2 ± 3.4 % for the PDA. Intra- and inter-observer analysis showed excellent correlation ( r = 0.97; p < 0.0001 and r = 0.95; p < 0.0001, respectively). In conclusion, CCT-based MMAR assessment is reliable and may offer important information for selection of the optimal revascularization procedure. [ABSTRACT FROM AUTHOR]

In the present paper, we obtain sufficient conditions imposed on the function p(t), under which the Fourier integral of the function f(t) ͧ L(-∞, ∞) is absolutely summable by Voronoi method if the function Φ(t) = f (x + t) + f (x - t) - 2f(x) is of bounded variation on (0; +∞). [ABSTRACT FROM AUTHOR]

Bone cutting is a complicated surgical operation. It is very important to establish a kind of gradient porous bone model in vitro which is close to human bone for the research of bone cutting. Due to the existing bone cutting researches are based on solid bone model, which is quite different from human bone tissue structure. Therefore, Voronoi method was used to establish a gradient porous bone model similar to real bone tissue to simulate the process of bone drilling in this paper. High temperature and large cutting force during bone drilling can cause serious damage to bone tissue. Urgent research on bone drilling parameters is necessary to reduce cutting temperature and cutting force. The finite element analysis (FEA) of Voronoi bone models with different gradients is carried out, and a Voronoi model which is similar to real bone tissue is obtained and verified by combining the cutting experiment of pig bone. Then orthogonal experiments are designed to optimize the cutting parameters of Voronoi bone model. The range method is used to analyze the influence weights of cutting speed, feed speed and tip angle on cutting temperature and cutting force, and the least square method was used to predict the cutting temperature and cutting force, respectively. The gradient porous bone model constructed by Voronoi method was studied in detail in this paper. This study can provide theoretical guidance for clinical bone drilling surgery, and the prediction model of bone drilling has practical significance.

In the study of rock mechanics, the variation of rock mechanical characteristics in high-temperature environments is always a major issue. The discrete element method and Voronoi modeling method were used to study the mechanical characteristics and crack evolution of granite specimens subjected to the high temperature and uniaxial compression test in order to study the internal crack evolution process of granite under the influence of high temperatures. Meanwhile, dependable findings were acquired when compared to experimental outcomes. A modified failure criterion was devised, and a Fish function was built to examine the evolution behavior of tensile and shear cracks during uniaxial compression, in order to better understand the evolution process of micro-cracks in granite specimens. Shear contacts occurred first, and the number of shear cracks reached its maximum value earliest, according to the findings. The number of tensile contacts then rapidly grew, whereas the number of shear cracks steadily declined. Furthermore, it was found that when temperature rises, the number of early tensile cracks grows. This study develops a fracture prediction system for rock engineering in high-temperature conditions. [ABSTRACT FROM AUTHOR]

In order to study a new thread rolling forming process from a microscopic perspective, a polycrystalline model was established, based on the crystal plasticity finite element method (CPFEM) and Voronoi polyhedron theory. The fluidity of metals was studied to explain the reason for the concave center. The simulation results show that the strain curve of the representative element can more truly reflect the deformation behavior of the material. The grain orientations after deformation are distributed near the initial orientation. The evolution of each slip system is determined by the initial grain orientations and grain locations. The pole figures obtained from the experiment show high consistency with the pole figures obtained by simulation, which verifies the accuracy of the texture prediction by CPFEM. The experimental results show that thread rolling is more uniform in deformation than ordinary rolling. [ABSTRACT FROM AUTHOR]