Uniformity Degree Research Articles

Effect of VN and TiB2-TiCx Reinforcement on Wear Behavior of Al 7075-Based Composites.

Al 7075 alloy, 15 wt.% VN/7075 composites, and 20 wt.% TiB2-TiCx/7075 composites were prepared by ball milling with subsequent hot-pressing sintering. The microstructure, hardness, and wear properties at room temperature to 200 °C of Al 7075-based composites with different reinforcement phases were discussed. The grain uniformity degree values of 15 wt.% VN/7075 composites and 20 wt.% TiB2-TiCx/7075 composites were 0.25 and 0.13, respectively. The reinforcement phase was uniformly distributed in 15 wt.% VN/7075 composites and 20 wt.% TiB2-TiCx/7075 composites, almost no agglomeration occurred. The order of hardness was 20 wt.% TiB2-TiCx/7075 composites (270.2 HV) > 15 wt.% VN/7075 composites (119.5 HV) > Al 7075 (81.8 HV). At the same temperature, the friction coefficient of 15 wt.% VN/7075 composites was the lowest, while the volume wear rate of 20 wt.% TiB2-TiCx/7075 composites was the lowest. With the increase of temperature, the wear mechanism of Al 7075 changed from spalling wear to oxidation wear and adhesion wear. However, the wear mechanisms of 15 wt.% VN/7075 and 20 wt.% TiB2-TiCx/7075 composites changed from abrasive wear at room temperature to wear mechanism (oxidation wear, abrasive wear, and adhesive wear) at medium and low temperature. Comprehensive wear test results indicated that 20 wt.% TiB2-TiCx/7075 composites had excellent tribological properties at medium and low temperature.

Composition uniformity and large degree of strain relaxation in MBE-grown thick GeSn epitaxial layers, containing 16% Sn

We systematically investigate the compositional uniformity, degree of strain relaxation (DSR), defect structure and surface morphology of GeSn epitaxial layers with 16% Sn, grown by low temperature molecular beam epitaxy (MBE) on Ge-buffered Si(001) substrates. Combining atom probe tomography, reciprocal space mapping, cross-sectional transmission electron microscopy, and atomic force microscopy analyses, we demonstrate that for a layer thickness of , a high DSR (∼70%) can be achieved, while maintaining compositional uniformity at the atomic scale. We find no evidence of Sn clustering in the bulk, or Sn segregation to the surface, for at least this value of . The observed compositional uniformity contrasts the well-established phenomenon of strain-relaxation enhancement of Sn content in chemical vapour deposition (CVD) growth of GeSn. The defect structure leading to strain relaxation in these MBE-grown GeSn epitaxial layers is also distinctly different from that observed in CVD growth of the alloy. We observe the co-existence of highly strain-relaxed and pseudomorphically strained regions in the grown epilayers, tentatively explained by bunching of threading dislocations. Considering that MBE growth of GeSn epitaxial layers, with such high-Sn content and layer thickness, has not been reported before, our results are encouraging for future improvements in design and fabrication of group-IV-based mid-infrared photonic devices.

Quantitative Characterization of Heat Treatment Response in a Single Crystal Nickel-Based Superalloy

To study quantitatively the effect of heat treatment on the microstructure, composition and mechanical property in a new single crystal nickel-based superalloy for industrial gas turbine (IGT) applications, the eutectic fraction, carbide fraction, and the fraction, size, shape and distribution of the γ ́ phase was characterized by quantitative metallographic method, the evolution of chemical composition and hardness between core and inter dendrite was tested through EMPA and nanoindentation. The experimental results indicate that: The eutectic fraction decreases from (0.52±0.08) % to (0.03±0.01) %. The carbides fraction decreases from (0.23±0.04) % to (0.12±0.03) %, and Feret ratio decreases from 3.21±2.54 to 2.14±0.98. The γ ́ fraction increases from (55.66±4.18) % to (73.78±3.24) % in core dendritic region, from (64.82±1.44) % to (70.11±3.10) % in inter dendritic region. The γ ́-size is 406±111(nm) in core dendritic region and 918±384(nm) in inter dendritic region before heat treatment, 359±69(nm) in core dendritic region and 361±57(nm) in inter dendritic region after heat treatment. The γ ́-cuboidal degree is 1.08±0.20 in core dendritic region and 1.14±0.23 in inter dendritic region before heat treatment, 1.08±0.19 in core dendritic region and 1.02±0.14 in inter dendritic region after heat treatment. The solidification segregation coefficient of main segregation elements, such as Re, W, Hf, Ta, Al, and Mo, is closer to 1, with an average decrease of 27% after heat treatment. The hardness and modulus increase in core and inter dendritic, and their inhomogeneity is reduced between cores and inter dendritic. The improvement of properties result from the improvement of size uniformity and cuboidal degree of γ ́, and the reduction of carbides and eutectic through element homogeneity during heat treatment. The solidification segregation coefficient of main segregation elements, such as Re, W, Hf, Ta, Al, and Mo, is closer to 1, with an average decrease of 27% after heat treatment. With the addition of refractory elements, some elements partition to the dendrite core, while other elements tend to accumulate in the interdendritic liquid and then solidify as the interdendritic and eutectic regions during solidification. The hardness and modulus increase in core and inter dendritic, and their inhomogeneity is reduced between cores and inter dendritic. The improvement of properties result from the improvement of size uniformity and cuboidal degree of γ ́, and the reduction of carbides and eutectic through element homogeneity during heat treatment.

Podobnost granulometrijskog sastava agregata za noseće slojeve kolovozne konstrukcije

The assessment of the suitability of the granulometric composition of the crushed stone aggregates (CSA) for an unbound base and subbase layers of pavement, in the Republic of Serbia is done based on the defined gradation bands, uniformity degree (Cu), coefficient of curvature (Cz), percentage of fines and percentage of particles passing a 0.02 mm sieve. On the other hand, standards which define the quality requirements of aggregates and unbound mixtures for road construction SRPS EN 13242 and SRPS EN 13285 introduce a significantly different approach to the assessment of the granulometric composition suitability. Categories are defined. Each category includes a particular boundary band, tolerances on sieves, differences in values passing each sieve. The categories are defined depending on the field of the application. For seven CSA 0/31.5 mm used for the construction of Corridor XI, a comparative analysis of the granulometric composition suitability was performed according to the requirements of the existing Technical Specifications (TS) of PE "Roads of Serbia" (PERS) and the specified SRPS EN standards. The analysed curves satisfy those technical requirements, but vary in categories from the most severe mixtures of the normal granulometric composition of the GA category, to the open mixtures of the GP category. It was concluded that the principle based on the defining allowed tolerances on the sieves and between the sieves, is more suitable for field control of of the granulometric composition and the good granularity of the aggregates. Technical Specifications should be modified to this approach.

Furrow design for improving crop establishment of two-wheel tractor operated strip tillage planters in loam and clay loam soils

Conservation agriculture (CA) based production systems may help in achieving more sustainable intensification of cropping systems that use less labour and energy and have higher profit margins, in addition to soil conservation and environmental impact mitigation advantages. But these objectives can only be achieved when the right mechanization options, including appropriate crop establishment equipment, are in place to assist in timely field operations. An urgent need exists, therefore, to fine tune and re-adjust the existing two-wheel tractor (2WT) operated seed drills, with specific reference to the design of blade and furrow openers, while at the same time considering performance in different soil types and environments. To this end, experiments were conducted during 2013-2014 and 2014-2015 at two BARI Regional Agricultural Research Stations in Jamalpur and Barisal, Bangladesh, on a loam and clay loam soil, respectively, to evaluate five types of furrow opener for strip tillage. Shoe and modified shoe-type furrow openers were tested and compared with three inverted-T furrow openers with rake angles of 75°, 65° and 55°. The newly designed inverted-T furrow openers were narrower than the shoe-type openers; they also had a longer, hollow shanks and provided better options for adjustment to achieve the desired seeding depth and line spacing. Compared to shoe-type openers, better seeding depth, uniformity and higher degree of seed coverage were recorded with use of the inverted-T furrow opener with a 65° rake angle. This resulted in better seed coverage in the furrow, a higher emergence rate index, and the highest emergence percentage of maize and mung bean. Our research findings can be generalized to smallholder production systems on loam and clay loam soils where farmers utilize 2WT operated seed drills for crop establishment in both traditional and conservation agriculture-based planting systems. Keywords: two-wheel tractor, strip tillage planter, inverted-T furrow opener, rake angle, conservation agriculture, emergence percentage DOI: 10.25165/j.ijabe.20211403.5906 Citation: Hoque M A, Hossain M M, Ziauddin A T M, Krupnik T J, Gathala M K. Furrow design for improving crop establishment of two-wheel tractor operated strip tillage planters in loam and clay loam soils. Int J Agric & Biol Eng, 2021; 14(3): 130–139.

Experimental Studies on the Distribution of Air Flows in Air Cooled Steam Condensers

The uniformity degree of the air distribution over the heat-exchange surface of an air cooled condenser (ACC) plays an important role since it determines the efficiency of this surface’s usage. In this paper, this factor at a special stand, where all the main processes of an air flow were simulated, is studied. The typical design of the A-framed ACC was chosen as the basis for the study. Two ACC models differing from one another by the presence of a diffuser after the fan were studied. Each of the models was tested in two versions: with a low-speed electric motor and a high-speed electric motor with a gearbox. In the ACC models, heat transfer surfaces were simulated by a set of flat metal grids with a uniform distribution of square cells. The aerodynamic drag of a set of grids was preliminarily selected so that the Euler criteria were equal for the full-scale object and model. During the tests, the air velocities in front of and behind the grids were measured by traversing, and the velocity fields (isotachs) of the cooling air in these sections were plotted. A condenser with a low-speed electric motor provides the most uniform distribution of cooling air over the heat-exchange surface, while condensers with a high-speed electric motor and gearbox and with a diffuser have significantly greater nonuniformity in the air supply. During the “suction” operation, the flow distribution is more uniform but worse than that for the version with a low-speed electric motor. The effect of the nonuniform velocity field of cooling air on the heat transfer of ACC is estimated. The real condenser module was calculated for various flow and velocity distributions along the tube length. Losses of heat removal due to the nonuniformity of the air flow of the considered circuits can be estimated within 1–3% at a ±50% deviation of the flow rate from the average value.

Algorithm of informative indicators system formation for development of business management tools

The aim of the work is to improve the management decision – making tools based on informative indicators for organizations. To form a system of informative indicators the authors propose using the following methods. These are the assessment of the uniformity degree of empirical data for each indicator, the analysis and elimination of multicollinearity of indicators based on the matrix of paired correlation coefficients, the integrated assessment of the potential of the object of study using a set of indicators. A distinctive feature of this approach was the construction of a potential function that allows you to design a multidimensional object on a geometric plane. In that case, while forming a system of indicators, some indicators will be excluded taking into account their multicollinearity and weights in the potential function. The advantage of the proposed algorithm is using less expert assessments in scientific research.

Tribological properties of carbon fiber toughened SiC prepared by hot pressing sintering

Csf/SiC composites were prepared by hot press sintering to improve the service performance and wear-resistance of SiC. Surface treatment of short carbon fibers was carried out based on air oxidation and liquid oxidation methods. The dispersion and damage of fibers were investigated after surface treatment. There were less particles and some obvious grooves on the surface of carbon fibers treated by concentrated nitric acid (68%) for 90 min. The optimal air oxidation temperature ranged from 420° to 430°C. The best milling time was 48 h for dispersion uniformity and low injury degree. Composites with low(≤ 30 vol%) fiber content were dense, and fibers were evenly distributed in the matrix without agglomeration. The friction coefficients of Csf/SiC composites decreased with increasing fiber content. Specifically, the friction coefficient of Csf/SiC composite with 55 vol% Csf reached to 0.23. The wear rates firstly decreased to the minimum 2.65 × 10−6 mm3/N·m when 30 vol% Csf was added, and then increased with increasing fiber content. To some degree, this study presented an effective way to enhance the service performance and wear-resistance of SiC.

Optimization possibility of beam scanning for electron beam welding: Physics understanding and parameters selection criteria

Scanning electron beam welding (SEBW) is a very important process for welding of thick plates in aerospace, aeronautical and power industries. However, since the invention of this process, the scanning parameters are typically selected through time consuming and costly trial and error. No existing mathematical criterion can be used to select the optimal parameters due to lack of physical understanding of the welding process. In this study, we developed a three-dimensional mathematical model of SEBW capable of modeling the coupled keyhole and weld pool dynamics for the first time, and used it to understand the underlying physics of the welding process and explore the process optimization criterion of circular mode beam scanning by combining welding experiments and modeling. We showed that beam scanning may not always stabilize the keyhole and weld pool, and may not improve the final weld quality of electron beam welding. However, beam scanning can modulate the movement of high temperature positions on keyhole wall, and contribute to a better uniformity of weld pool dynamics behind the keyhole. For circular beam scanning, we proved that low frequency scanning may lead to more welding defects such as porosity, spiking, and spatters because it increases the tendency of keyhole oscillations as compared to the no scanning case. High frequency scanning could stabilize the keyhole to a certain degree and modulate the fluid flow of the weld pool to make it more regular. Additionally, the scanning radius should be neither too small nor too large. Too small radius may lead to more defects, and too large radius can decrease the penetration depth significantly. A dual direction energy uniformity (DDEU) criterion was proposed to select the scanning parameters by considering the energy uniformity degree in the welding direction and the transverse direction. It was demonstrated that process parameters including beam scanning frequency and radius can be successfully optimized using the proposed criterion.

Involutory differentially 4-uniform permutations from known constructions

Substitution boxes (S-boxes) are important components of block ciphers that can cause confusion in cryptosystems. The functions used as S-boxes should have low differential uniformity, high nonlinearity and high algebraic degree. When $$k>3$$ , due to the lack of knowledge about the existence of almost perfect nonlinear permutations over $$\mathbb {F}_{2^{2k}}$$ , which can offer optimal resistance to the differential cryptanalysis, S-boxes are often constructed from differentially 4-uniform permutations. To date, many infinite families of such functions have been constructed. In addition, the lower hardware implementation cost of S-boxes is an important criterion in the design of block ciphers. If the S-box is an involution, which means that the permutation is its own compositional inverse, then the implementation cost for its inverse can be saved. The same hardware circuit can thus be used for both encryption and decryption, which is an advantage in hardware implementation. In this paper, we investigate all of the differentially 4-uniform permutations that are known in the literature and determine whether they can be involutory. We find that some involutory differentially 4-uniform permutations with high nonlinearity and algebraic degree can be given from these known constructions. We also give some partial results and computer experiments to consider the problem of whether a permutation can be affine equivalent to an involution or it will become an involution upon adding an affine function. Some new families of differentially 4-uniform involutions constructed by composing the inverse function and cycles with length 3 are also given. This family of constructions has a high nonlinearity and a maximum algebraic degree.

Microstructural and mechanical responses to various rolling speeds determined in multi-pass break-down rolling of AZ31B alloy

Different rolling operations of as-cast AZ31B alloy were performed under different rolling speed (18 ∼ 72 m min−1) and rolling pass conditions at 400 °C. Microstructural studies, tensile testing and formability evaluation relevant to each rolling operation were investigated. For 1-pass rolling, coarse average grain size (CAGS) region gradually approached the center layer as the rolling speed increased. Moreover, twins, shear bands and coarse-grain structures were the dominant components in the microstructure of plates rolled at 18, 48 and 72 m min−1, respectively, indicating the severe deformation inhomogeneity under the high reduction per pass condition. For 2-pass rolling and 4-pass rolling, dynamic recrystallization was observed to be well and CAGS region has substantially disappeared, indicating the significant improvement in deformation uniformity and further the grain homogenization under the conditions. Microstructure uniformity degree of 2-pass rolled plates did not vary much as the rolling speed varied. On this basis, shear band distribution dominated the deformation behavior during the uniaxial tension of the 2-pass rolled plates. However, microstructure uniformity accompanied by twin distribution played a leading role in stretching the 4-pass rolled plates.

Super Optimal S-boxes Based on Pure Non-linear 3-quasigroups

In this paper, we present an approach to construct cryptographically strong 44-bit S-boxes with pure non-linear 3-quasigroups. PRESENT is a light weight block cipher included in ISO and IEC. The S-box used in PRESENT is optimal in linearity, differential uniformity, branch number and algebraic degree. Our methodology is based on 3-quasigroup operations and it enables someone to get 44-bit S-boxes optimal in all the above four properties that PRESENT S-box has.

A method to calculate differential uniformity for permutations

We introduce a search algorithm to find permutation S-boxes with low differential uniformity, high nonlinearity and high algebraic degree, which play important roles in block ciphers. Inspired by the results of our search algorithm, we propose a method to calculate differential uniformity for permutations. We establish a sufficient condition for differentially 4-uniform permutations based on our method and construct some example classes of differentially 4-uniform permutations.

A force transmission assessment method for thrust system in shield machines based on the relative coefficient in compound ground

Abstract An evaluation method for force transmission in the thrust system of tunneling machines in compound ground was investigated in this study. First, the mechanical model for a pushing system in heterogeneous ground was constructed. Then, the relative coefficient of eccentricity on a conical surface was determined based on the mechanical model. Subsequently, the uniformity degree of force transmission in the thrust system was measured using the relative thrust coefficients of eccentricity. Eventually, the performance of force transmission under various arrangements with an equal number of jacks was discussed in detail by applying the conical model of eccentricity to the thrust mechanism of a tunneling machine used in engineering projects. The 3D parameter models for the thrust system of an earth pressure balance shield machine (diameter: 6.34 m) were established using SolidWorks. In addition, a propelling system with 22 hydraulic cylinders was simulated via the automatic dynamic analysis of mechanical systems (ADAMS). Results of the numerical analysis agree well with those simulated by ADAMS. The results provide a theoretical basis and support for choosing a non-equidistant driving system in a composite stratum.

Differentially 4-Uniform Permutations with the Best Known Nonlinearity from Butterflies

Many block ciphers use permutations defined over the finite field F22k with low differential uniformity, high nonlinearity, and high algebraic degree to provide confusion. Due to the lack of knowledge about the existence of almost perfect nonlinear (APN) permutations over F22k, which have lowest possible differential uniformity, when k > 3, constructions of differentially 4-uniform permutations are usually considered. However, it is also very difficult to construct such permutations together with high nonlinearity; there are very few known families of such functions, which can have the best known nonlinearity and a high algebraic degree. At Crypto’16, Perrin et al. introduced a structure named butterfly, which leads to permutations over F22k with differential uniformity at most 4 and very high algebraic degree when k is odd. It is posed as an open problem in Perrin et al.’s paper and solved by Canteaut et al. that the nonlinearity is equal to 22k−1−2k. In this paper, we extend Perrin et al.’s work and study the functions constructed from butterflies with exponent e = 2i + 1. It turns out that these functions over F22k with odd k have differential uniformity at most 4 and algebraic degree k +1. Moreover, we prove that for any integer i and odd k such that gcd(i, k) = 1, the nonlinearity equality holds, which also gives another solution to the open problem proposed by Perrin et al. This greatly expands the list of differentially 4-uniform permutations with good nonlinearity and hence provides more candidates for the design of block ciphers.

Improved uniform degree of multi-layer interlaminar bonding strength for composite laminate

Due to their high strength-to-weight and stiffness-to-weight ratios, composite materials are widely used in the aerospace industry. As a key factor for the placement process, the compaction force directly affects the product performance by changing the interlaminar bonding strength. Besides the magnitude of the interlaminar bonding strength, the uniformity degree of the bonding strength for each contact interface also affects the overall structural rigidity of laminates. This study is aimed at analyzing and optimizing the compaction force when using a rubber roller to produce a composite product with uniform interlaminar bonding strength. The amount in which the compaction force from a rubber roller on the current layer influences the bonding strength of the layers underneath is investigated, and methods for optimizing the interlaminar bonding strength are developed and experimentally demonstrated.

Self-organization and FORC-based magnetic characterization of ultra-high aspect ratio epitaxial Co nanostrips produced by oblique deposition on an ordered step-bunched silicon surface

Further development of microelectronics requires novel or improved technological approaches for device nanofabrication and functional properties characterization. In this paper, we studied the crystal structure and magnetic properties of epitaxial Co nanostrips with the average width of 32.6, 45.3, and 62.6 nm grown on a step-bunched Si(111)5.55 × 5.55-Cu/Cu surface. Technological conditions, under which the ultra-high aspect ratio (∼104) structurally solid, straight nanostrips of hcp-Co with crystallographic axis [0001] oriented along their long side can be grown, were determined. The dependence of the coercive force on the width of the nanostrips was demonstrated. Magnetization reversal through the transverse domain-wall nucleation and propagation in a Co nanostrip was defined with an analytical approach based on the Stoner–Wohlfarth model. Using the first-order reversal curve method, we analyzed the effect of nanostrip uniformity degree on magnetic behavior and the influence of the magnetostatic interactions on the coercive force of individual nanostrips.

Soft Electrochemical Etching of FTO-Coated Glass for Use in Ni(OH)2-Based Electrochromic Devices

In this paper, we present a method developed for soft electrochemical etching of fluorine-doped tin oxide-coated glass (FTO-coated glass) that consists of FTO treatment with alternating polarity current in a simple electrolyte. The developed method was found to alter morphology and hydrophilicity of FTO. In order to study the influence of soft electrochemical etching on FTO functionally as a substrate for electrochromic films, a Ni(OH)2-based electrochromic film was deposited onto treated FTO. It was discovered that films deposited onto etched substrate had significantly improved uniformity and higher coloration degree than films deposited on untreated FTO.

OPTIMIZATION OF MODIFYING MATERIAL DISTRIBUTION DURING LASER PROCESSING OF THE METAL SURFACE

The improvement of operational properties of metal parts during the laser surface treatment can be obtained by modifying the melt with the prepared nano-sized particles of refractory compounds (carbides, nitrides, and others.). It allowsthe number of crystallization centersto be increased, the structure to be grinded and the uniformity of the solidified metal to be raised. It is known that thermocapillary convection promotes the homogeneous distribution of materials penetrating into the molten metal. It is also known that the presence of surface-active substances in the melt influences the character of convection. There is evidence that the structure of flow in the melt depends on the amount of surface-active substances in the metal. Therefore, the studies were conducted to obtain data on the relationship of characteristics of metal processing by laser and the uniformity degree of modifying additives distribution. Using the numerical modeling the effects of characteristics of pulsing laser action on allocation of modifying particles are estimated at the presence of surface-active substance in metal. With the help of mathematical proposed model the following non-stationary processes are considered: heating and melting of the metal, heat transfer in the melt, fluid motion, nucleation and growth of the solid phase after termination of the pulse. During the numerical realization of the model the heat conduction equation was firstly solved. Upon appearance of molten metal the boundary of the liquid phase was determined. Further the coupled equations of convective heat transfer and motion of an incompressible fluid were solved. After the laser pulse termination, the calculations are continued until the complete solidification of the substrate material is achieved. It was supposed that modifying nano-sized particles under the influence of convective flows penetrate into depth of a melt from its surface. The movement and distribution of particles in a fluid was modeled using markers. The movement of the markers was determined by the local velocity of the melt. According to the results of numerical experiments, the effect of the parameters of pulsed laser action on the nature of the flow and distribution of the particles in the melt were determined. Optimum parametersfor the melting of the metalsubstrate by a laser pulse are proposed for various surface-active substances concentrations.

Construction of Cryptographically Strong S-Boxes Inspired by Bee Waggle Dance

In this paper, we explore a heuristic method called the bee waggle dance to construct cryptographically strong S-boxes. The S-boxes exhibit good cryptographic properties such as high nonlinearity, low differential uniformity and high algebraic degree. The method involves the use of a trinomial power function as the initial S-box. The elements in the S-box are then permuted using the bee waggle dance algorithm. The S-boxes produced using this method are found to compare reasonably well with other existing S-boxes constructed using alternative heuristic methods. To the best of our knowledge, this is the first attempt to construct cryptographically strong S-boxes using the bee waggle dance algorithm.