Convex Parts Research Articles

Formation mechanism of the distinctive granular fracture surface in subsurface fracture of Ti6Al4V alloy

The formation mechanism of the granular regions often observed in subsurface fractures of Ti6Al4V alloy was experimentally investigated. To simulate and simplify the phenomenon of crack opening and closure, which is strongly related to fatigue crack propagation and strength properties, uniaxial cyclic compression tests were conducted in air and vacuum using test pieces with rounded surfaces under contact conditions. The results showed ring-like patterns on the parts of the rounded surfaces subjected to cyclic contact regardless of the ambient environmental conditions. However, in the case of vacuum only, fine surface asperities were observed, which were quite similar to those in the subsurface fractures. Microstructural refinement was confirmed by cross-sectional observation of the concave and convex parts. In the refined microstructure, voids and cracks were observed, which were formed during the refinement and adhesion processes. Microstructural refinement and metallic adhesion under compression loading in vacuum are key phenomena for the formation of fine surface asperities. Based on the experimental results, a new model for the formation mechanism of the granular region was proposed. This model can explain the characteristics of the granular region and the properties of subsurface fractures, which occur at lower stress and have longer lifetimes than surface fractures.

Particle Behaviours in Free Surface Flow of Particle Suspensions

In this study, the suspension flows in a Hele-Shaw cell were experimentally examined. We focused on the free surface of suspension in a Hele-Shaw radial flow and discussed the effect of particle behaviors on the change in surface shape. The test fluids used were two kinds of suspension with a different particle size. The volumetric fraction of each fluid was 40 vol.%. In the observation of free surface in the Hele-Shaw flow, it was found that concave and convex parts appeared on the free surface with a time. Furthermore, at the inside region of surface undulation, the occurrence of the particle-induced viscous fingering was confirmed. Measuring velocity profiles inside the viscous fingering using the particle imaging velocimeter (PIV), we found that the velocity in the fingering region became higher than those of entire suspension. The difference between the particle velocity inside fingering and that of entire suspension suggested that the shear flow in the Hele-Shaw cell affected the particle behaviors. Furthermore, since the temporal changes in the fingering shape was different between both fluids, the particle behaviors inside the viscous fingering might relate to the particle migration in the perpendicular direction to flow direction due to the local change in the shear deformation.

Синтаксономическое разнообразие лесных лугов Обь-Инского водораздела в пределах Новосибирской области

Синтаксономическое разнообразие лесных лугов Обь-Инского водораздела в пределах Новосибирской области

Синтаксономия ксеропетрофитной растительности Южного Урала: союз Elytrigion pruiniferae all. nov.

Синтаксономия ксеропетрофитной растительности Южного Урала: союз Elytrigion pruiniferae all. nov.

An optimized passivation mechanism at the copper film recess for achieving efficient planarization of copper chemical mechanical polishing

This article proposed an improvement plan for the slurry to reduce the dishing caused during copper chemical mechanical polishing (CMP) of the interconnect structure. According to the difference in the pressure between the concave and convex parts of the copper film in the high-hardness polishing pad, polishing slurries were designed with a distinct difference in the polishing removal rate under high and low platen pressures to improve their planarization efficiency. 2 wt% GLY (glycine) and 1 wt% H2O2 can provide a chemical dissolution effect, adding 0.1% TAZ (1,2,4-triazole) to slow down the corrosion mainly for the recession, by adjusting the slurry pH to 7. The polishing results showed that the slurry had a high copper removal rate (6772 Å/min) at high pressure (3.0 psi) and a much lower removal rate (3273 Å/min) at low pressure (1.2 psi). The pattern wafer polished with this slurry obtained relatively low dishing. The other comparison groups showed slight differences in copper removal rate at high and low pressure and a deeper dishing of the polished pattern wafer. In this paper, based on the analysis of static dissolution experiments, electrochemical experiments, and XPS experiments of copper films in different slurries, the chemical reaction mechanism of copper films in the solution system of GLY and H2O2 was studied at different pH values. In addition, the inhibition mechanism of TAZ on the copper surface at different slurry pH values was proposed, including the properties of the TAZ molecule adsorption film on the copper surface, the uniformity of the surface coverage, and the thickness of the passivation layer. The results can reflect the polishing results to a certain extent despite some deviations, but it can also be used as a more reasonable argument to explain the optimization scheme of the slurry proposed in this article.

Magnetic Resonance Imaging Segmentation on the Basis of Boundary Tracking Algorithm in Lung Cancer Surgery.

This work was to study the guiding value of magnetic resonance imaging (MRI) based on the target region boundary tracking algorithm in lung cancer surgery. In this study, the traditional boundary tracking algorithm was optimized, and the target neighborhood point boundary tracking method was proposed. The iterative method was used to binarize the lung MRI image, which was applied to the MRI images of 50 lung cancer patients in hospital. The patients were divided into two groups as the progression-free survival (PFS) and overall survival (OS) of surgical treatment group (experimental group, n = 25) and nonsurgical treatment group (control group, n = 25). The experimental group received surgical resection, while the control group received systemic chemotherapy. The results showed that the traditional boundary tracking algorithm needed to manually rejudge whether the concave and convex parts of the image were missing. The target boundary tracking algorithm can effectively avoid the leakage of concave and convex parts and accurately locate the target image contour, fast operation, without manual intervention. The PFS time of the experimental group (325 days) was significantly higher than that of the control group (186 days) (P < 0.05). The OS time of the experimental group (697 days) was significantly higher than that of the control group (428 days) (P < 0.05). Fisher exact probability method was used to test the total survival time of patients in the two groups, and the tumor classification and treatment group had significant influence on the OS time (P < 0.05). The target boundary tracking algorithm in this study can effectively locate the contour of the target image, and the operation speed was fast. Surgical resection of lung cancer can improve the PFS and OS of patients.

Teaching the circle equation using a practical mathematical problem

Practical problem solving is not common in many mathematical classes in Malaysian upper secondary schools. Usually, students receive the mathematical concepts through abstract materials (students cannot see some of them in their daily life). Thus some students believe that ‘mathematics is not necessary for human life’. In this article, the researcher discussed the teaching of the circle equation, using a practical problem about the frontage of some convex and concave parts of buildings. In fact, an arc of a circle is given. Engineers should calculate the radius value of this circle to curve the composite sheets precisely the same as a circle using an engineering machine and frontage of the convex or concave parts of buildings. Engineers use a formula to find the radius of the circle in similar cases of frontage of buildings. Discussion about this practical problem in the classes transfers the concepts of the circle equation to students in better pedagogy and helps them to see an application of the circle equation in the real world. Therefore, this method of teaching provides learners an opportunity to find how mathematical concepts can be used in their everyday life and their future careers.

Probe Standoff Optimization Method for Phased Array Ultrasonic TFM Imaging of Curved Parts.

The reliability of the ultrasonic phased array total focusing method (TFM) imaging of parts with curved geometries depends on many factors, one being the probe standoff. Strong artifacts and resolution loss are introduced by some surface profile and standoff combinations, making it impossible to identify defects. This paper, therefore, introduces a probe standoff optimization method (PSOM) to mitigate such effects. Based on a point spread function analysis, the PSOM algorithm finds the standoff with the lowest main lobe width and side lobe level values. Validation experiments were conducted and the TFM imaging performance compared with the PSOM predictions. The experiments consisted of the inspection of concave and convex parts with amplitudes of 0, 5 and 15 λAl, at 12 standoffs varying from 20 to 130 mm. Three internal side-drilled holes at different depths were used as targets. To investigate how the optimal probe standoff improves the TFM, two metrics were used: the signal-to-artifact ratio (SAR) and the array performance indicator (API). The PSF characteristics predicted by the PSOM agreed with the quality of TFM images. A considerable TFM improvement was demonstrated at the optimal standoff calculated by the PSOM. The API of a convex specimen’s TFM was minimized, and the SAR gained up to 13 dB, while the image of a concave specimen gained up to 33 dB in SAR.

A Coupling between Integral Equations and On-Surface Radiation Conditions for Diffraction Problems by Non Convex Scatterers

The aim of this paper is to introduce an orignal coupling procedure between surface integral equation formulations and on-surface radiation condition (OSRC) methods for solving two-dimensional scattering problems for non convex structures. The key point is that the use of the OSRC introduces a sparse block in the surface operator representation of the wave field while the integral part leads to an improved accuracy of the OSRC method in the non convex part of the scattering structure. The procedure is given for both the Dirichlet and Neumann scattering problems. Some numerical simulations show the improvement induced by the coupling method.

Electrochemical machining of blisk channels with rotations of the cathode and the workpiece

Electrochemical machining (ECM) is a major means of manufacturing blisks. The process consists of two steps: blisk channel machining and blade profile machining. The allowance distribution of the blank after blisk channel machining directly influences the accuracy of machining of the blade profile. Thus, the aim of blisk channel machining is focused to improve the uniformity of the allowance distribution. With this aim, this study proposes a method that combines slow rotations of the cathode and the workpiece during the ECM of blisk channels; A slow rotation of the cathode enables it to adapt to changes in the allowance distribution of the blank profile from the leading edge to the trailing edge, and a slow rotation of the workpiece can render the machining allowance of the concave and convex parts more consistent, thereby reducing the allowance difference of the machined blisk channel. The mathematical models of the relationship between the allowance difference, and the angles of rotation of the cathode and the workpiece were firstly established to obtain strategies to optimize the rotational angles and speeds of the cathode and the workpiece at different feed depths. A simulation was then carried out, and the results showed that the proposed method can improve the uniformity of the allowance distribution. Finally, experiments were conducted to test this method. Compared with the prevalent method, the proposed method reduced the allowance differences in the concave and convex parts by 41.4% and 36.6%, respectively. In conclusion, the proposed method is effective and suitable for processing various types of blisks with twisted blade profiles.

A robust algorithm for global optimization problems

In this paper, a global optimization algorithm namely Kerk and Rohanin’s Trusted Region is used to find the global minimizers by employing an interval technique; with it, the algorithm can find the region where a minimizer is located and will not get trapped in a local one. It is able to find the convex part within the non-convex feasible region. This algorithm has descent property and global convergence. The numerical results have shown the algorithm has an outstanding capability in locating global minimizers.

The Importance of Environmental Factors for the Development of Water Erosion of Soil in Agricultural Land: The Southern Part of Hronská Pahorkatina Hill Land, Slovakia

The water erosion research was carried out in the lowland type of hilly landscape. The aim was to monitor and evaluate the importance of environmental factors (steepness of slope, relief shapes, aspect, slope length, combination slope length (L) and slope (S)—LS factor, types of land use changes) for the development of water erosion. We focused on the identification of areas threatened by erosion by interpreting aerial photographs from several time periods. This was followed by verification of erosion using soil probes. We identified 408.44 ha of areas affected by erosion, and measured the depth of soil and “A” horizons thickness. The environmental factors were modeled in geographical information systems by tools for spatially oriented data. Subsequently, the influence and significance of individual environmental factors were compared, and the probability of erosion was statistically estimated. The decisive factors in the formation of erosive surfaces are the LS factor and the slope. We also consider the factor of the relief shape to be important. The shape did not appear to be very significant as a separately evaluated factor, but all convex parts correlate with the identified erosion surfaces. The susceptibility of erosion related to the aspect of the slopes to the cardinal directions has not been confirmed. Types of land use changes with the most significant relation of erosion were confirmed in areas of strong intensification. We confirmed the importance of factors and land use for the development of erosion processes.

(Invited) Electrodeposition of Si in CsF–CsCl Eutectic Melt

1.Introduction In recent years, the demand for solar cells as a clean energy source has been increasing. Among the various types of solar cells, crystalline Si solar cells dominate the solar cell market due to their high efficiency, excellent stability, and abundant natural resources. However, the major disadvantages of the conventional Si substrate manufacturing method are the low productivity of the Siemens process and the considerable kerf loss in the Si slicing process. As the demand for crystalline Si solar cells continues to grow, there is a strong need to develop alternative manufacturing methods for Si substrates. As a promising method, the direct formation of Si films on inexpensive substrates has been investigated [1]. We have proposed the electrodeposition of Si films from molten KF–KCl which has relatively high fluoride-ion concentration at eutectic composition (KF:KCl = 45:55 mol%, m.p.: 878 K) and high solubility in water [2]. We have already studied the optimum conditions for obtaining adherent, compact, and smooth Si films in molten KF–KCl–K2SiF6 at 923 K [3]. Furthermore, good Si films was obtained from KF–KCl after bubbling SiCl4 as a Si-ion source [4]. In this study, we focused on CsF–CsCl eutectic melt (CsF:CsCl = 50:50 mol%, m.p.: 713 K [5]) as a new electrolyte for Si electrodeposition. Molten CsF–CsCl has lower operable temperature and higher fluoride-ion concentration than molten KF–KCl at the eutectic composition. Moreover, CsF and CsCl have extremely high solubility in water (CsF; 573, CsCl; 191 g per 100 g H2O at 293 K [6]), indicating that the solidified salts can be easily removed. In this study, Si was electrodeposited on Ag plate substrates at 923 K at various Si-ion concentrations and cathodic current densities. The obtained Si films were analyzed by XRD and SEM/EDX to determine the optimum electrodeposition conditions.2. Experimental The experiments were conducted in CsF–CsCl eutectic melt in an Ar glovebox. The experimental temperature was 923 K and Cs2SiF6was used as the Si ions source. Ag plate and Ag flag electrodes were used as the working electrodes. The counter and reference electrodes were Si rods. The potential of the reference electrode was calibrated by Cl2/Cl− potential measured at a glass-like carbon electrode. Samples prepared by galvanostatic electrolysis of Ag plates substrates were analyzed by SEM/EDX after washing with distilled water to remove adhered salts.3. Results and Discussion The electrodeposition was carried out by changing the added amounts of Cs2SiF6 from 0.50 to 3.5 mol%. The cathodic current density was also varied in the range of 25–800 mA cm−2. As typical deposits, Fig. 1 shows SEM images of Si prepared at (a) 600, (b) 100, and (c) 50 mA cm−2 in CsF–CsCl–Cs2SiF6 (2.0 mol%). At a higher current density, Si was nodule-shaped because the concentration gradient of Si(IV) ions increased near the electrode, and Si deposition proceeded preferentially on the convex part close to the bulk molten salt. At medium current densities (e.g., 100 mA cm−2), the electrodeposited Si was film-like and the surface was smooth. Fig. 2 shows a cross-sectional SEM image of the film, indicating the smooth and compact deposit. The thickness is about 20 μm (the theoretical film thickness: 25 μm), indicating a relatively high current efficiency. Furthermore, it was found that the upper current limit to obtain Si with smooth surface is higher at the higher Cs2SiF6 concentration; Si films with smooth surface were obtained even at 600 mA cm−2 in CsF–CsCl–Cs2SiF6 (3.5 mol%). At low current density, Si was film-like, but many humps were observed due to insufficient overvoltage and difficulty in nucleation.AcknowledgementThe present address of Kouji Yasuda is Graduate School of Engineering, Kyoto Univ.

Accelerated Log-Regularized Convolutional Transform Learning and Its Convergence Guarantee.

Convolutional transform learning (CTL), learning filters by minimizing the data fidelity loss function in an unsupervised way, is becoming very pervasive, resulting from keeping the best of both worlds: the benefit of unsupervised learning and the success of the convolutional neural network. There have been growing interests in developing efficient CTL algorithms. However, developing a convergent and accelerated CTL algorithm with accurate representations simultaneously with proper sparsity is an open problem. This article presents a new CTL framework with a log regularizer that can not only obtain accurate representations but also yield strong sparsity. To efficiently address our nonconvex composite optimization, we propose to employ the proximal difference of the convex algorithm (PDCA) which relies on decomposing the nonconvex regularizer into the difference of two convex parts and then optimizes the convex subproblems. Furthermore, we introduce the extrapolation technology to accelerate the algorithm, leading to a fast and efficient CTL algorithm. In particular, we provide a rigorous convergence analysis for the proposed algorithm under the accelerated PDCA. The experimental results demonstrate that the proposed algorithm can converge more stably to desirable solutions with lower approximation error and simultaneously with stronger sparsity and, thus, learn filters efficiently. Meanwhile, the convergence speed is faster than the existing CTL algorithms.

Weight‐based colour constancy using contrast stretching

One of the main issues in colour image processing is changing objects' colour due to colour of illumination source. Colour constancy methods tend to modify overall image colour as if it was captured under natural light illumination. Without colour constancy, the colour would be an unreliable cue to object identity. Till now, many methods in colour constancy domain are presented. They are in two categories; statistical methods and learning-based methods. This paper presents a new statistical weighted algorithm for illuminant estimation. Weights are adjusted to highlight two key factors in the image for illuminant estimation, that is contrast and brightness. The focus was on the convex part of the contrast stretching function to create the weights. Moreover, a novel partitioning mechanism in the colour domain that leads to improvement in efficiency is proposed. The proposed algorithm is evaluated on two benchmark linear image databases according to two evaluation metrics. The experimental results showed that it is competitive to the statistical state of the art methods. In addition to its low computational cost, it has the advantage of improving the efficiency of statistics-based algorithms for dark images and images with low brightness contrast. Moreover, it is robust to camera change types.

Electrochemical machining with independent electrolyte supply at blade leading/trailing edge

The blade is a key component of aero engines. In traditional blade electrochemical machining (ECM) processes, the electrolyte is simultaneously supplied to the concave and convex parts. To improve flow field uniformity at marginal areas of the blade, a new blade flow mode with an independent electrolyte supply at the leading and trailing edges is proposed here. Flow field simulations of the entire blade ECM process are carried out. The results show that in comparison with conventional flow field modes, electrolyte distribution in this new flow field mode is more uniform and the change in velocity is smaller along the flow path. In addition, the size and pressure of the liquid inlets at the leading and trailing edges were optimized, with optimal height and pressure values of 3 mm and 0.9 MPa determined, respectively. The results of experimental investigations proved that the new flow mode proposed here was reasonable, and the surface roughness and contour accuracy of the leading and trailing edges were significantly enhanced.

IMC Growth and Mechanical Properties of Cu/In-48Sn/Cu Solder Joints

The growth and shear properties of intermetallic compound (IMC) in Cu/In-48Sn/Cu solder joints at different bonding times have been studied, and the growth kinetics of interfacial Cu3(In,Sn) phase at different bonding temperatures investigated. The results show that the IMC of the Cu/In-48Sn/Cu joint is composed of Cu6(In,Sn)5 and Cu3(In,Sn) but transforms to Cu3(In,Sn) after 120 min of bonding at 260°C and pressure of 3 MPa. The morphology of the Cu6(In,Sn)5 layer changed from flat to scallop, and the growth rate of Cu3(In,Sn) located directly below the convex part of the Cu6(In,Sn)5 sector was significantly higher than that of Cu3(In,Sn) located directly below the concave part of the Cu6(In,Sn)5 sector. The shear strength of the solder joints first increased then slowly decreased, reaching 21.8 MPa when increasing the bonding time to 60 min. The shear strength of the solder joints was improved by the formation of Cu6(In,Sn)5 and Cu3(In,Sn), and Cu3(In,Sn) phase played a greater role in improving the shear strength of the solder joints than did Cu6(In,Sn)5 phase. The growth kinetics index n of Cu3(In,Sn) was 0.478 to 0.495, and the growth mechanism of Cu3(In,Sn) was controlled by diffusion at bonding temperatures of 250°C to 280°C.

Оценка уровня упрочнения стружки из алюминиевого сплава, предназначенной для последующей обработки давлением

Introduction. It is noted that the chip is an undesirable type of metal scrap, because it has a developed surface, which creates conditions for more intense interaction with the surrounding atmosphere. This creates conditions for oxidation and gas saturation, especially at elevated temperatures typical of remelting processes. Therefore, the process of chip utilizing is considered, bypassing the remelting stage. The aim of the work is to establish the level of work hardening of chips during the processing of aluminum alloys and to predict its effect on the subsequent processing process. Research methods: to assess the deformed state, the finite element method was applied, implemented in the RAPID-2D software package. The sequence of actions included the creation of the initial shape of the deformation region and the configuration of the tool. The mutual displacement of the tool and the deformable material is specified using the corresponding boundary conditions. The deformable medium is a viscous-plastic material with power-law hardening, the physical and mechanical properties correspond to an aluminum-magnesium alloy. Results and discussion: the solution obtained shows that the degree of shear deformation in the chips can reach a value of more than 2. In this case, a higher level of deformation is localized on the side of the convex part of the chip. The comparison of the solution with those obtained earlier by other authors is carried out and its similarity is shown. In the considered solution, the difference in the degree of work-hardening of the chips along its thickness is 36 %. A variant of the sequence of processing the workpiece first by cold deformation, and then by cutting is considered. The field of application of the results of the work is the development of methods for the processing of technogenic formations. Conclusions. During the cutting process, the plastic deformation of the chips reaches significant values. In this paper, the difference in the degree of shear deformation in the chip thickness is established, depending on the proximity of the cut layer to the surface of the cutting tool. It is proposed to take this difference into account at the subsequent stages of chip processing. The presence of the marked inhomogeneity of mechanical properties leads to consequences in the form of an inhomogeneous distribution of the temperature of the beginning of recrystallization during subsequent operations of heat treatment or hot deformation treatment. The principle of additivity of the degree of deformation obtained by the metal at the stage of plastic shaping of the workpiece and the shaping of the chip itself is introduced.

ВИВЧЕННЯ ПРОЦЕСУ ОДНОВІСНОГО РОЗТЯГУ ТРИКОТАЖУ ПЕРЕПЛЕТЕННЯ ЛАСТИК РІЗНИХ РАПОРТІВ

Study of the process of deformation of rib knits, which occurs due to the application of tensile forces in the course direction. Methodology. During the study, methods of theoretical analysis, a camera, a stretching frame, Microsoft Excel software and Autodesk AutoCAD were used. Findings. For producing rib knit samples, a 10th class flat-bed knitting machine PVRK was used. Samples of knitwear were made with repeatable unit patterns of 1x1, 2x2, 3x3, 4x4, 5x5 and 6x6 from bamboo yarn of linear density 29x2 tex, woolen yarn 32x2 tex, half-woolen yarn 31x2 tex and Polyacrylonitrile yarn 32x2 tex. To carry out uniaxial stretching of knitted fabric samples along the line of stitch rows, a stretching frame was used. After fixing the opposite ends of the sample on the needle set of the frame holders, the distance between them gradually increased with an interval of 20 mm. At each stage of stretching, the samples were photographed together with a calibration ruler. Sample photos imported into Autodesk AutoCAD software. After calibration, for each state of stretching of the sample, such characteristics were determined as: the average value of the width of the repeatable unit pattern, the average value of the width of the convex part of the pattern, as well as the visible section of its concave part. The study showed that at the first stages of stretching, there is a mutual displacement of the sections of the pattern, belonging to different layers of knitwear and a decrease in the twisting of the sections of the smooth surface. Further application of the tensile force leads to a more uniform deformation of the ivestigated structural parts of the pattern. Scientific novelty. The change in the geometric characteristics of rib knits with various repeatable units patterns made from various types of raw materials is experimentally determined. Practical value. The characteristics of knitwear, obtained in the course of the study, were used to form a database necessary for the construction of three-dimensional models of rib knits with bamboo, woolen, semi-woolen, and polyacrylonitrile yarns.

A high-output performance mortise and tenon structure triboelectric nanogenerator for human motion sensing

Triboelectric nanogenerator (TENG) can generate renewable energy with huge application potential by converting energy that is inaccessible in the environment into usable electricity. The mortise and tenon structure is the primary structural method of ancient Chinese architecture, furniture, and other appliances. It is a very delicate method of connecting two components by combining the concave and convex parts. This structure can bear a large load and can be integrated into multiple forms. By introducing the traditional Chinese mortise and tenon process in the research, we constructed a kind of mortise and tenon structure triboelectric nanogenerator (MT-TENG) using discarded paper and polypropylene (PP) materials. This new structure can achieve high firmness and spatial division. It is proved that the short-circuit current ( Isc ) output of MT-TENG is 1.7 times higher than that of the grid structure triboelectric nanogenerator (G-TENG) under the same space condition. The influence factors of motion amplitude and frequency on its energy harvesting performance have been investigated in the paper. The MT-TENG device can collect human motion's mechanical energy and detect human hands and feet' motion states. The power generated by the MT-TENG with a size of 3 cm × 3 cm can drive 53 LEDs. This paper provides an innovative mortise and tenon structure that can effectively improve the output performance of TENGs，showing great potential in fields such as wearable electronic devices. • The traditional Chinese mortise and tenon architecture is firstly proposed to build a TENG structure. • The mortise and tenon structure TENG has demonstrated a superior output performance over the grid structure TENG. • The MT-TENG can realize energy supply and sensing of human motion patterns.