Recent Advances in Microfluidics-Based Chromatography—A Mini Review

Microfluidics-based liquid chromatography is based on the miniaturization of the different types of liquid chromatography (LC) systems (e.g., affinity, adsorption, size exclusion, ion exchange) on a microchip to perform on-chip separation of different types of analytes. On-chip chromatography finds applications in genomics, proteomics, biomarker discovery, and environmental analysis. Microfluidics-based chromatography has good reproducibility and small sample consumption. However, the on-chip chromatography fabrication techniques are often more challenging to perform than conventional LC column preparation. Different research groups have attempted to develop different techniques to fabricate microfluidics-based LC systems. In this review, we will summarize the recent advances in microfluidics-based chromatography.

Simulation of soil cutting blade wear

The results of a laboratory study of the wear patterns of blades of tillage parts are presented. To substantiate the model of soil-cutting blade wear in laboratory studies. Applied installation, providing rectilinear movement of the sample, one-time interaction of the blade with the particles of abrasive mass, and reproducing chip separation, inherent in most loamy soils. The dependence of the angle of inclination of the occipital chamfer to the bottom of the furrow, the width of the occipital chamfer and blade wear along the length of the sample from the cutting path, taken in studies for the main parameters of wear, were obtained. It was found that with increasing depth of cut, the intensity of wear increases, but when there are irregularities and undulations of the bottom of the furrow, it decreases due to the increase in the cutting path with lower loads due to the alternation of depressions and protrusions at the bottom of the furrow. With increasing hardness of the abrasive mass, the intensity of wear of the blade increases, at the same time the value of the stabilized angle of the occipital chamfer to the bottom of the furrow decreases, due to changes in the wear mechanism. With increasing cutting speed, the intensity of blade wear increases due to increased soil resistance forces and specific energy expended on its deformation and destruction. It was shown that the abrasive model of the soil corresponds to the real loamy soil for the study of wear of cutting elements. The expansion of the characteristics of the soil model peculiar to «nature» is due to the inclusion of additional components, in particular ceresin and vaseline, in the composition of the base "paraffin + quartz particles".

CLASSIFICATION AND ZONING OF RIVERINE TERRITORIES OF SMALL TOWNS ON THE EXAMPLE OF THE BELGOROD REGION

The paper presents an analytical study for comparing different numerical methods used for the modeling of cutting process using finite element method. The aims of this study is to compare capabilities of FE software package (Deform, AdvantEdge, ANSYS Workbench and ABAQUS). The main stages of modeling are discussed, as well as well-known methods and approaches used for their implementation. Main formulations for description of motion of deformable materials are analyzed to Lagrangian approach, Eulerian approach, Arbitrary Lagrangian Eulerian (ALE) approach. Numerical techniques to model chip separation are grouped as geometrical and physical. In this paper two strategies for time integration, implicit and explicit schemes are reviewed. Various models of friction between the chip and the tool are discussed: Amonton-Coulomb's Law, Prandtl's Law and Zorev. In this work, modeling and simulation of cutting process is carried out by FEM software ABAQUS. As a result of modeling, the stress and strain fields for both the workpiece and the tool are presented, as well as the thermal field of the workpiece and the chip. The numerical results obtained are compared with the results have been carried out previously using software ANSYS Workbench. The numerical values of temperatures, stresses and deformations correspond to traditional concepts of the cutting process, as well as experimental data presented in open sources.

A Machining Program Employing a Slip Line Field Modelling Technique Over Other Constitutive Models

Machining involves complex plastic material flow at the chip separation site which makes it difficult to predict forces and other machining outputs to higher accuracy. Modelling is a common technique which facilitates incorporation of analytical and experimentally derived equations to visualize the process and analyses the mechanism. It saves time and machining factors can be optimized without any trial and error method. In this paper, the significance of slip line field model over other constitutive laws in defining the complex regions in machining are thoroughly reviewed and a slip line field model is chosen which incorporates build up edge (BUE) of a larger size than the other previously defined slip line models for machining. The modified model also incorporate a region of shear zone instead of a shear line, takes into account the chip curl effect and conform to the velocity discontinuity and stress equilibrium. The slip line fields are generated using MATLAB and employing Dewhurst-Collin's matrix technique.

Chip Morphology Studies Using Separate Fracture Toughness Values for Chip Separation and Serration in Orthogonal Machining Simulations

It is well known that the chip morphology predictions in machining simulations depend on the separation criteria used for modeling chip formation. In this paper, we propose to use two different criteria for chip separation and serration along with the Johnson-Cook damage model. The threshold value for chip separation is determined from machining experiments using the methodologies discussed in Patel et al. [1]. In addition, two separate damage evolution laws for chip separation and serration are used. Our results indicate that the choice of the evolution law and the threshold values of Gc used for chip separation and serration have a significant effect on chip shape and other field variables such as the equivalent plastic strain, cutting force, temperature, etc.

New Method of Quench Surface Turning

The heating, generated in the process of deformational cutting without chip separation used for phase transformation in steel during lathe machining. Chips are not separated from the workpiece and remain on the surface thus forming a special reinforced structure. The result of processing is a steel surface quenching up to 1 mm deep. The proposed method also makes it possible to obtain hardened surface structures with alternating inclined layers of different hardness. The article presents calculations of heating and cooling rates, types of hardened structures, hardness investigation of hardened steel surfaces.