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The equivalent stress approach allows the comparison of arbitrary multiaxial stress states with a uniaxial one. Based on the concept of the equivalent stress, several strength hypotheses (limit surfaces) were formulated. These hypotheses take into account not only existing information from the tests. They can also describe a experiences and different expectations concerning the material behavior mathematically. Due to the simplicity and clarity, the equivalent stress concept is widely used. Collected experimental data, applications, and know-how make this approach an extremely powerful tool for engineering design. The method can also be easily applied in the case of new materials. As an example, polymethacrylimide (PMI) hard foam ROHACELL 110IG, from manufacturer Evonik Röhm GmbH (Darmstadt), will be in the focus of this study. Modern strength hypotheses are functions of several parameters. The application of these hypotheses requires in addition to tension, compression, and torsion test data further experimental results. Such data are often not reliable or widely scattered. Hence, the adjustment of the parameters of the chosen hypothesis is not unique. Some extrapolations with respect to the hydrostatic stress states can lead to unacceptable results and, therefore, the parameters must be restricted. In this work, several restrictions based on the principles of conservative material description are introduced. They adjust a shape of the limit surface in the principal stress space. These restrictions are geometrically justified. The influence of various restrictions on the limit surface is analyzed. The effectiveness is tested with the help of own measured data. Reliable material descriptions for hard foams will be suggested. [ABSTRACT FROM AUTHOR]

There are many disadvantages affecting the accuracy of surface topography measurement and analysis. One of them are the errors obtained during data processing. Usually surface topographies of car engine parts are studied after form removal. Many algorithms and procedures were developed and suggested. However, the selection of reference plane with accordance to surface topography measurements of cylindrical elements was not fully recognized. In this paper least square fitting methods (cylinder, polynomial) and commercial filters (Gaussian filter, Gaussian regression filter and robust Gaussian regression filter) for areal form removal were compared and proposed. Three types of surfaces: cylinder liners after plateau-honing, plateau-honed cylinder liners with oil pockets created by burnishing techniques and turned piston skirts were analyzed. Distortion of surface topography parameters (from ISO 25178 standard) according to improper selection of reference plane was also taken into consideration. It was assumed that least squares fitted cylinder plane gave better results for both of type cylinder liners according to commonly used algorithm. However, for piston skirt surfaces the obtained results were very similar. For least squares polynomial fittings it was found that applied method for cylinder liners gave usually better robustness for scratches, valleys and dimples occurrence. For piston skirt surfaces better edgefiltering results were obtained. It was also recommended to analyse the Sk parameters for proper selection of reference plane in surface topography measurements. [ABSTRACT FROM AUTHOR]

Fitting algorithms play an important role in the whole measuring cycle in order to derive a measurement result. They involve associating substitute geometry to a point cloud obtained by an instrument. This situation is more difficult in the case of non-linear geometry fitting since iterative method should be used. This article addresses this problem. Three geometries are selected as relevant case studies: circle, sphere and cylinder. This selection is based on their frequent use in real applications; for example, cylinder is a relevant geometry of an assembly feature such as pin-hole relationship, and spherical geometry is often found as reference geometry in high precision artifacts and mechanisms. In this article, the use of Chaos optimization (CO) to improve the initial solution to feed the iterative Levenberg–Marquardt (LM) algorithm to fit non-linear geometries is considered. A previous paper has shown the performance of this combination in improving the fitting of both complete and incomplete geometries. This article focuses on the comparison of the efficiency of different one-dimensional maps of CO. This study shows that, in general, logistic-map function provides the best solution compared to other types of one-dimensional functions. Finally, case studies on hemispheres and industrial cylinders fitting are presented. [ABSTRACT FROM AUTHOR]

This paper describes the experiment of measuring the temperature and cutting force during the drilling of short holes without using cutting lubricants, at constant cutting speed, and at increasing shift . Measurement was performed on steel samples of grade 11 523. During drilling, temperature was monitored by a thermocouple, using the method of two foreign metals. Cutting force was measured by a strain-gauge sensor. The experiment provides a quick orientation in the given issue and points out to the optimisation of cutting conditions. Based on results, it can be stated that the range of temperatures and the size of cutting forces depends on technological conditions, cutting parameters, and mechanical and physical properties of tool and workpiece's material. [ABSTRACT FROM AUTHOR]

This article presents a new method of arc fitting for railway track realignment. The theoretical foundations are presented, along with a detailed algorithm of the iterative computational process. This method is based on solving a set of linearized pseudo-observation equations. The formulas of the functional model of the fitting problem were derived, and a special form of objective function is proposed. An iterative method for optimization of objective functions is described, and an analysis of the functional model is presented. Specific conclusions are presented based on the results of this analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a comprehensive geometric error measurement and identification method for a tilt table equipped in a five-axis machine tool with two turntables using the double ballbar. Three positional errors of the socket, caused by both the volumetric error and linkage error of the tilt table, are measured in the sensitive directions with simple circular paths. A mathematics model is applied to map the relationship between the night results that are from three installation positions of the socket and all the errors of the tilt table. Firstly, all the measured results are applied to establish the average axis that is just with the linkage error of the tilt table using the newly developed circular fitting method, rather than solving the large-scale linear equations. Then, the linkage error is treated as the trend item in the measured results for it keeps constant during the rotation of the tilt table. Hence, the volumetric error is identified by the remaining part of the measured results, which are obtained by subtracting the part caused by the linkage error, using the pseudo invert matrix method. Meanwhile, an error model is established to analyze the influence of the installation errors of the socket and the tool cup. Two simple correction procedures, using a low-cost electron clamp and an easily operated circular path, are developed to eliminate these two installation errors before the ballbar test. Finally, a verification experiment, by comparing the predicted value from the identified errors with the measured results by the ballbar, is carried out to validate the effectiveness and correctness of the proposed method. [ABSTRACT FROM AUTHOR]

High aspect ratio microtools find numerous applications in the production of miniaturized components and structures, e.g., drilling of microholes in ink jet nozzles, air bearings, and biomedical devices. The present study aims to machine microrods using reverse microelectrical discharge machining (R-μEDM) process. These microrods can be used as microtools for drilling microholes. A detailed experimental investigation has been carried out with the help of Taguchi's orthogonal array for understanding the mechanism of the process. The process parameters such as voltage, feed rate, and capacitance are considered to perceive their effect on response measures such as machining time, deviation in length, deviation in average diameter, standard deviation (SD) in diameter, and surface roughness. The optimal process parametric condition of R-μEDM has been determined for desired performance, i.e., obtaining the target length and average diameter of the microrod and ensuring its straightness with minimum time duration. Confirmation experiment has been carried out at the optimum condition and accordingly the results have been presented. Surface morphology of the machined microrod at the optimum condition has also been investigated. Microrod of diameter 170 µm with a high aspect ratio of 18 has been successfully machined using this process. [ABSTRACT FROM PUBLISHER]

In this paper a novel approach is proposed to investigate the characteristics of the plasma channel and material removal in electrochemical discharge machining (ECDM) of glass. For this purpose, a specific pulsed voltage was applied to the ECDM process to perform single discharging on the glass workpiece. In this way, a voltage slightly lower than the critical voltage was applied as the offset voltage. Meanwhile the working voltages above the critical voltage were applied to the process in a specific period of time to produce single sparks. The signatures of the single sparks on the workpiece surface were used to determine the characteristics of the plasma channel. According to the results, the average diameter of 260 µm was achieved for the plasma channel in the glass machining conditions. This paper also reports a thermophysical model for material removal in ECDM process based on the finite element method (FEM) and plasma channel diameter achieved in this study. The amount of the removed material as well as the diameter and depth of the crater, achieved by the FEM, was measured and compared with the experimental outcomes. The results demonstrate the consistency of the proposed model with the experimental observations. [ABSTRACT FROM PUBLISHER]

This paper presents a new approach of tool wear compensation based on “volume removal per discharge” (VRD) in “reverse-micro-electrical-discharge machining.” In this process, a plate with predrilled microhole is used as a tool, the erosion of which limits the fabrication of desired height of microrod(s). Therefore, in order to achieve the dimensional accuracy of this microrod(s), such tool plate wear needs to be compensated. Since this approach is based on the real-time estimation of volume removal from workpiece, which is obtained by multiplying the number of “contributing” pulses with VRD, an accurate estimation of VRD is very much essential for availing correct tool wear compensation. In this work, VRD is estimated by considering two new aspects: the number of actual “contributing” pulses and the variation of VRD with machining depth. These pulses are identified by a “pulse discriminating” system developed in house. The real-time material removal volume from workpiece is then used to estimate the “real-time height” of microrods after considering the over cut and taperness of each microrod. The proposed method is also compared with the normal machining method and “uniform wear method” and found to be more accurate with a negligible error of maximum 1.7%. [ABSTRACT FROM PUBLISHER]

The dominance of the spark eroding process in complex ceramic components has promoted a significant growth analysis in the ceramic composites domain in modern manufacturing industries. The latest developments in ceramic components are concentrated on both the enhancement of the mechanical properties and the machinability of complex 3D parts while using spark EDM. The current (I), pulse on time (Ton), pulse off time (Toff), and dielectric flushing pressure (DP) are considered sparking parameters for the machining of a Si3N4–TiN ceramic composite. These composites find their application in high-temperature environments, viz. metal forming, extrusion dies, turbine blade, and non-ferrous molten metal handling components. Taguchi's orthogonal array (OA), L18, has been used to design the experiments. The optimal machining inputs are determined by the grey relational grade (GRG), which is attained from the grey relation analysis (GRA) for various response characteristics, such as the material removal rate (MRR), tool wear rate (TWR), circularity (CIR), cylindricity (CYL), and perpendicularity (PER). The significant parameters are identified via an analysis of variance (ANOVA). Finally, the optimized process parameters resulting in a higher MRR, lower TWR, lower form tolerance, and decreased orientation tolerance are verified through a confirmation test demonstrating that sparking process responses can be effectively improved. [ABSTRACT FROM PUBLISHER]

This paper investigates the performance analysis and mathematical modeling of a staggered-tooth transverse-flux permanent magnet linear synchronous machine (STTF-PMLSM), which is characterized by simple structure and low flux leakage. Firstly, the structure advantages and operation principle of the STTF-PMLSM are introduced, and a simplified one phase model is established to investigate the performance of the machine in order to save the computation time. Then, the electromagnetic characteristics, including no-load flux linkage, electromotive force (EMF), inductance, detent force and thrust force, are simulated and analyzed in detail. After that, the theoretical analysis of the detent force, thrust force, and power factor are carried out. And the theoretical analysis results are validated with 3-D finite-element method (FEM). Finally, an improved mathematical model of the machine based on d-q rotating coordinate system is proposed, in which inductance harmonics and coupling between d- and q-axis inductance is considered. The results from the proposed mathematical model are in accordance with the results from 3-D FEM, which proves the validity and effectiveness of the proposed mathematical model. This provides a powerful foundation for the control of the machine. [ABSTRACT FROM AUTHOR]

We present a novel approach for feature correspondence and multiple structure discovery in computer vision. In contrast to existing methods, we exploit the fact that point-sets on the same structure usually lie close to each other, thus forming clusters in the image. Given a pair of input images, we initially extract points of interest and extract hierarchical representations by agglomerative clustering. We use the maximum weighted clique problem to find the set of corresponding clusters with maximum number of inliers representing the multiple structures at the correct scales. Our method is parameter-free and only needs two sets of points along with their tentative correspondences, thus being extremely easy to use. We demonstrate the effectiveness of our method in multiple-structure fitting experiments in both publicly available and in-house datasets. As shown in the experiments, our approach finds a higher number of structures containing fewer outliers compared to state-of-the-art methods. [ABSTRACT FROM AUTHOR]

For high-value added products, machining tools' lifespan significantly influences the quantity of procurement in machining process. Preemption of tools from the workpiece while processing is continuing is sometime beneficial to safeguard the product from the damage due to tool failure or its malfunction. Also an early discard of a tool is costly for the manufacturing operation. Therefore an optimal strategy for the tool life is sought here to determine the maximum allowable tool lifespan to preempt from the workpiece and to have an appropriate amount of tool stock in the crib to ascertain the proper running of the production schedule and tool inventory. Therefore, an impact of the machining tool lifespan on the production-inventory policy of the system is investigated in this paper. An integrated lifespan related inventory model for machining tools is developed to meet the responding accurate requirement of procurement and inventory. Two numerical examples are presented to illustrate the integrated model. The results show that the practical lifespan adoption of machining tools has significant impact on the whole quantity of procurement, and eventually influences the coordinating economic decision making. [ABSTRACT FROM AUTHOR]

The clip fitting task is a frequently encountered assembly operation in the car industry. It can cause upper limb pain. During task laboratory simulations, upper limb muscular activity and external force were compared for 4 clip fitting methods: with the bare hand, with an unpowered tool commonly used at a company and with unpowered and powered prototype tools. None of the 4 fitting methods studied induced a lower overall workload than the other three. Muscle activity was lower at the dominant limb when using the unpowered tools and at the non-dominant limb with the bare hand or with the powered tool. Fitting clips with the bare hand required a higher external force than fitting with the three tools. Evaluation of physical workload was different depending on whether external force or muscle activity results were considered. Measuring external force only, as recommended in several standards, is insufficient for evaluating physical workload. [ABSTRACT FROM AUTHOR]

A numerical procedure for constructing the multiaxial viscoelastic model for polymeric packaging material over a wide range of temperature is presented. By using the proposed best-fitting procedure, experimentally measured frequency-domain Young's and shear storage moduli are used to calculate the time-domain bulk and shear relaxation moduli which describe the three-dimensional constitutive behavior of a viscoelastic solid. The numerical procedure incorporates restrictions that ensure that the derived time-domain material function is physics compatible. The proposed procedure was applied to construct the viscoelastic constitutive models of epoxy molding compounds (EMCs), and compared to results obtained by using approximate-formula based direct conversion procedure. It was shown that, without using the proposed procedure, the directly calculated time-dependent Poisson's ratio oscillates significantly in the rubbery regime and is physically inadmissible. To validate the constitutive model constructed by using the proposed procedure, a numerical finite element model that incorporates the viscoelastic constitutive model of the EMC was applied to simulate warpage of an overmolded package under the solder reflow process and compared to experimental shadow Moiré measurements. [ABSTRACT FROM AUTHOR]

The evolution of micro-texture below the machined surface is computationally modeled and experimentally verified. The orientation distribution functions of the grains below the surface were represented in spectral form. The microstructure descriptor coefficients were derived, and their change with respect to the change in the cutting feed rate was computationally calculated and monitored. Micro-texture experimental observations conducted by electron back-scatter diffraction technique verify the modeling outputs. Continuation of changing the process parameter was done by finite element method, and the evolution in texture was investigated by computational modeling. The process path function which correlates micro-texture evolution and cutting feed rate, was obtained by applying the principle of orientation conservation in the Euler space. As a result of the major finding of this work, i.e., derivation of process path functions, the evolution of texture as a function of the material feed rate is numerically determined without any need to texture modeling or finite element analyses. [ABSTRACT FROM AUTHOR]

Many applications, such as surveillance, inspection or search and rescue operations, can be performed with autonomous robots. Our aim is a control of modular autonomous systems in rescue robotics. One of the basic problems with autonomous robotics is the execution part where the control commands (translation and rotational velocities) are produced for mobile bases. Therefore we have focused on this area because there is only a small amount of available path following software for skidsteered mobile robots. Our goal was to develop a velocity controller that could be used for multiple skid-steered mobile bases. We considered differential drive mobile bases such as tracked skid-steering mobile bases. Our approach is based on an arc fitting algorithm, which takes into account the robot constraints and kinematical model. It produces a continuous trajectory where fitting to the given path is adapted based on given parameters. Moreover, we have included orientation angle compensation while the mobile robot is moving and ground inclination compensation. Our rescue robot is described, together with the simulation setup and algorithm implementation. We compared our algorithm to the Hector-based software and curvature velocity approach. The results for the proposed algorithm are shown for the simulation results and the experiment. [ABSTRACT FROM AUTHOR]

Regenerative chatter is an unstable form of self-excited vibration in the machining process, and it is one of the main obstacles which limit the productivity and the surface quality of the component. This paper investigates the effect of 2-D vibration assistance on high frequency regenerative chatter in the micro milling process. External vibration is applied on the workpiece in a range of frequencies and amplitudes using the piezoelectric actuators. The chatter vibration is monitored using the sound pressure signal measured by the microphone. The chatter amplitude with vibration assistance in 1-D (feed or normal direction) and 2-D is studied. The effect of the frequency and amplitude of the vibration assistance on chatter amplitude is analyzed. It is concluded that the vibration assistance is able to effectively attenuate the high frequency chatter by modifying the dynamic chip thickness and adding process damping in the micro milling process. [ABSTRACT FROM AUTHOR]

In this work we present a new approach to damage mechanics in hyperelastic materials and an efficient numerical procedure for modeling the Mullins effect in isochoric, isotropic materials. The formulation is based on the idea that both the virgin loading and the damaged unloading–reloading behavior may be measured, but only the unloading–reloading curve corresponds to hyperelastic behavior. The damaged unloading–reloading curve is the true hyperelastic behavior and may be described by any suitable hyperelastic constitutive model. We employ a spline-based formulation which is known to exactly capture the behavior. The virgin loading curve, which does not correspond to hyperelastic behavior and involves damage evolution is only employed to compute the energy release rate. The procedure does not employ any material parameter (and hence no parameter-fitting procedure) or any explicit damage evolution function. We highlight similarities and differences of the present model with usual damage mechanics models and with pseudo-elasticity. As a result of the detailed computational procedure which simply involves the solution of a nonlinear scalar function, the virgin loading curve and the damaged unloading–reloading curves are exactly captured. The computational algorithm for three-dimensional implicit finite element analysis is also addressed in detail. Examples show that there is no significant increase in computational effort respect to a pure hyperelastic model. [ABSTRACT FROM AUTHOR]

The characteristics of vibrations in microbolometer had significant impact on the performances of its infrared absorption. Due to the complex architectures, leading to the unfavorable connection between the analysis of infrared absorption and vibrations. To solve this issue, a finite element analysis (FEA) method was designed to make better compatible with infrared absorption and vibrations, as well as the resonant frequency analysis was completed. A vanadium oxide (VO2) based microbolometer was designed, and the corresponding three-dimensional (3D) modeling was also built. By vibrations and resonant frequency FEA, mechanics and frequency characteristic were studied. 200 G, 500 G and 1000 G acceleration vibrations were loaded on the 3D model at Z axis, which perpendicular to the bridge-like structure. It shows that under 500 G acceleration vibration, the deformation of the model was small enough to ensure the resonant cavity maintained λ/4 which means a high IR absorption for the microbolometer. The first order modal frequency, the second order modal frequency and the third order modal frequency of the 3D model were also analyzed. Purpose of resonant frequency analyzing of microbolometer was to avoid devices work on this frequency result of failure. Finally, an uncooled infrared focal plane was fabricated, and the experimental data matched the simulation fitting results. Perfect performance in mechanical properties, IR absorption and imaging effect of experimental device indicating a shorter design cycle and low cost potential. The fast, efficient FEA design method enables simulating infrared absorption and vibrations together. [ABSTRACT FROM AUTHOR]

Previous work by the author demonstratedthat a new predictivecorresponding-states viscosity model, based on entity Chapman–Enskogscaling, correlated pure n-alkane component viscositydata with entity scaled residual entropy. With five fitting constants,a 5.2% average absolute relative deviation (AARD) was obtained overthe entire fluid region for a group of 17 n-alkanes,ranging from methane to 1280 Mw linear polyethylene. The work reportedhere demonstrates that this same model and fitting constants predictsfluid viscosity of other molecular classifications over a wide rangeof temperature and pressure. Molecular structure was incorporatedto improve the predictability of the earlier corresponding-statesviscosity model. With the inclusion of molecular structure, an AARDof 6.6% was obtained over the entire fluid region for ten classificationsof nonassociating molecules and a wide range of temperature (60–800K) and pressure (1–46 800 atm). Thus, a predictive corresponding-statesfluid viscosity model for the more general class of nonassociatingmolecules was developed to provide a practical approach to determiningviscosity in process and petroleum engineering applications. [ABSTRACT FROM AUTHOR]

This paper addresses the compensation of cutting process related errors in order to improve the accuracy of manufactured parts. The compensation is a modification of the tool dimension and the tool path using on-machine probing data. A cutting depth distribution-based approach is proposed to calibrate the cutting process according to the on-machine probed error model. This approach is investigated in cases of both rigid and compliant parts. The calibration offset is estimated for the actual cutting conditions with and without a fitting process. In the case study, the offset varies from 12 to 17 μm for down milling at 6000 rpm spindle speed. The impact of the cutting speed is investigated. A rectangular profile was machined with and without compensation in down and up milling mode. The results show that the proposed approach is effective. The error is reduced from a maximum of 25 μm for down milling and 10 μm for up milling to 4 μm in both cases. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of environment protection and energy conservation, we propose to prepare electrical conductive adhesives (ECAs) fitting for UV–thermal dual curing and to investigate the constitution of the ECAs. Based on the determination of the mixture ratio of epoxy resin-44 (E-44) and unsaturated polyester resin (UP), the dosage of 3-Amino-propyl-triethoxy-silane (KH-550), thinner, thermal curing agent, accelerating agent, light-initiator agent, and the conductive filler of the ECAs was determined. The prepared films after UV–thermal dual curing were analyzed by Fourier transform infrared spectrometer and thermogravimetric analyzer to characterize their constitution and thermal properties. The best prescription of ECAs was obtained as follows: the ratio of E-44 and UP is 0.5:1, KH-550 is 6%, thinner is 8%, thermal curing agent is 7.5%, accelerating agent is 7.5%, light-initiator agent is 6%, and the conductive filler is 60%. Under these conditions, the prepared ECAs have cross-linked net structure and good thermal stability. Their properties are applicable as follows: the hardness is 6H; the tensile strength is 95.12 MPa; the volume resistivity is 4.75 Ω cm; the gel content is 93.37%; the water absorption ratio is 5.81%; and the stability is more than 180 days. [ABSTRACT FROM AUTHOR]

Physically-based strain hardening models have become important ingredients in metal forming simulations over the last years, since they allow for the modeling of multi-stage forming processes based on the evolution of physically meaningful internal variables. Although these models are physically-based, there are still many fitting parameters involved which have to be identified from experiments. As a matter of fact, for each physical effect that is included in the model, a separate equation with new fitting parameters is introduced, such that physically-based models tend to contain a large number of fitting parameters. Parameter estimation is often based on the macroscopic response of a specimen which is tested in compression, tension or shear at various strain rates and temperatures. It is not guaranteed that this macroscopic information suffices to estimate parameters in model equations that describe (sub-) microscopic phenomena, since the effect of one parameter on the course of strain hardening can be compensated by other parameters. Since such parameter correlations are hard to detect from the model equations alone, the parameter estimation process may be ill-conditioned, i.e. numerous parameter sets can be found for such models that deliver almost the same minimum value of the error function in the parameter identification process. Given that parameter estimation involves a series of costly experiments, methods are needed that allow for analyzing the identifiability of the model parameters before costly experiments are performed. In this paper, an approach is presented that analyzes model parameter dependencies and quantifies the identifiability of the model parameters. The model considered in this study calculates the flow stress based on the evolution of three dislocation densities and the evolution of deformation twins. The analysis shows that correlations between the model parameters exist and that it is not possible to determine all model parameters based on an experimental set of flow curves in a single curve fitting procedure. An adapted fitting strategy is presented in which fitting is performed step-wise so that in each fitting step, only identifiable parameters are estimated, allowing for successful parameter identification. [ABSTRACT FROM AUTHOR]

In this paper, the weight functions for multiple axial cracks in a coated hollow cylinder have been investigated. The stress intensity factors (SIFs) for two reference loading cases were computed via the finite element method, which was then used to derive the weight functions. Dimensional analysis was carried out to reveal the dependence of dimensionless weight function on various important quantities such as normalized crack depth, crack spacing, and material constants. The results of such parameters dependence were presented in graphical forms and were eventually expressed by an empirical formula through a decoupled fitting method. Comparison was made on the SIF determination by the derived weight function and by other methods in literature, and an excellent agreement was found. The derived weight functions are expected to facilitate SIF calculation for a coated hollow cylinder with multiple axial cracks. [ABSTRACT FROM AUTHOR]

Automated methods for force field parametrization have attracted renewed interest of the community, but the robustness issues associated with the often ill-conditioned nature of parameter optimization have been vastly underappreciated in the recent literature. For this reason, this article offers a detailed description of the origin and nature of these issues. This includes a discussion of the restrained electrostatic potential fit (RESP) charge model, which does contain explicit robustnessenhancing measures albeit not in the context of bonded parameters, and which forms an inspiration for the present work. It is also discussed how all the bonded parameters in a Class I force field can be simultaneously fit using the linear least squares (LLS) procedure, and a novel restraining strategy is presented that overcomes robustness issues in the LLS fitting of bonded parameters while minimally impacting the fitted values of wellbehaved parameters. Two variants of this methodology are then validated through a number of case studies, including the fitting of bond-charge increments, which illustrates the method's potential for robustly solving general LLS problems beyond force field parametrization. [ABSTRACT FROM AUTHOR]

Most of CAD/CAM systems lack fully-automated process planning capabilities and depend on semi-automatic capabilities that necessitate the traditional selection of tools and cutting parameters. This paper attempts to determine proper combinations of cutting tools through the generation of tool paths and optimisation of machining parameters using an example of the CNC milling process. Several machining simulations with different combinations of tool sizes were performed using MasterCAM software. Based on these simulations, substantial variations in tool paths were observed for different tool combinations and as such the optimum tool combination could only be obtained arbitrarily. The tool paths derived from machining simulations were used to optimise machining parameters, that is, cutting speed, feed rate and depth of cut with the objective of minimising production time. In this case, an optimisation model was developed as a nonlinear programming problem and solved using extended LINGO nonlinear software. The results show that the subjectivity when selecting cutting tools can be avoided when appropriate tools are chosen alongside with the generation of a tool path within a CAD/CAM system using optimised machining parameters. As a consequence, CNC machine tools could be effectively utilised and the productivity significantly improved at shorter production time and cost. [ABSTRACT FROM AUTHOR]

Measures to control the spread of COVID-19 have changed the way we shop for food and interact with food environments. This qualitative study explored food shopping practices in the East of England, a large diverse region including coastal, urban and rural settings. In 2020/2021 we interviewed 38 people living in the region and 27 professionals and volunteers providing local support around dietary health. Participants reported disruption to supermarket shopping routines; moving to online shopping; and increased reliance on local stores. COVID-19 has impacted disproportionately upon lower-income households and neighbourhoods. The longer-term implications for dietary health inequalities must be investigated. [ABSTRACT FROM AUTHOR]

In scuffing conditions, the value of the product of the hertzian pressure of contact and the sliding speed generally remains constant. The experimental results reveal that the micro-topography of the contact area has also a determining role in the evolution of the wear and tear and the emergence of severe damages with high scuffing risk The experimental researches and fitting analysis presented in this paper reveals a good validity of the pressure-speed criterion also in the case of the pure slip conditions of experiments. [ABSTRACT FROM AUTHOR]

This paper presents a simulation-based development of a new deburring tool and a CAM-assisted method to deburr intersections of cross-drilled holes. By analyzing and applying derived mathematic equations to construct a three-dimensional view of these contours, a cutting edge specifically aligned to the intersection is developed. The intervention conditions and the synchronization of the tool and numeric control approach require 3-axis machining. This ensures a uniform chamfer along the circumference of the intersection despite the fluctuating cutting conditions. CAM-assisted deburring reveals the exact position of the burr, allowing the deburring tool to adapt to cross-drilled holes of different diameters. [ABSTRACT FROM AUTHOR]

This paper reports on acoustic emission (AE) from electrical discharge machining (EDM) in the context of gap flushing, and demonstrates its sensitivity to gap contamination from both metallic debris and gas bubbles. AE is further shown to relate to the local medium (liquid or gas bubble) through which individual discharges occur, and hence comprise unique and valuable process information on the effectiveness with which material is removed at the scale of a single discharge. This enabling technology is readily implemented for the in-process quantification, monitoring and optimization of flushing, and may constitute the basis for flushing-related adaptive control of EDM. [ABSTRACT FROM AUTHOR]

The variety oriented design problem for rotary production systems is considered. Given the multiple parts to be produced, the problem is to determine the feasible configurations of the machining system with minimum cost. This problem is modelled as a combinatorial optimization problem. Constraints related to the design of machining units as well as to the precedence and compatibility of operations are taken into account. The optimization methods developed to solve the problem are based on its MIP formulation. An industrial example is presented. [ABSTRACT FROM AUTHOR]

Strain distributions in the machined surface and subsurface of OFHC copper workpieces were determined experimentally and through numerical simulations. An experimental setup, comprising a double frame camera and a pulsed laser, was developed to measure the displacement fields using the digital image correlation (DIC) technique; strain distributions were then calculated. A numerical orthogonal cutting model was also developed and applied in order to predict such distributions. Comparison between simulated and measured results enabled an understanding of the fundamental mechanisms of plastic deformation of the machined surface of OFHC copper. [ABSTRACT FROM AUTHOR]

This paper demonstrates the need for and provides an improved fitting of the line parameters when a wide range of frequencies with emphasis on the dc response is the objective. The improved fitting is based on a low-order fitting of a function error for each of the line parameters, that is, the characteristic admittance and propagation function, in the low-frequency range. The function error represents the difference between the analytical evaluation of the line parameters, that is, obtained from a frequency-dependent distributed parameters line model, and their initial rational approximation, for example, given by an electromagnetic transients software tool. The approximated function error, added to the initial rational approximation of the line parameters, provides the enhanced fitted line model. The enhanced fitting improves the dc response of the line and ensures numerical stability in time-domain simulations. This paper applies the proposed fitting approach to the universal line model for time-domain simulations. The simulation results by the enhanced fitting are validated by comparing the results with those obtained from a frequency-domain line model (FDLM). Two case studies are presented to illustrate the proposed fitting approach. [ABSTRACT FROM AUTHOR]

We propose a robust technique called Savitzky-Golay second-derivative (SGSD) fitting for modeling the in situ Raman spectrum of graphitic materials in rock samples such as carbonaceous chondrite meteorites. In contrast to non-derivative techniques, with assumed locally linear or nth-order polynomial fluorescence backgrounds, SGSD produces consistently good fits of spectra with variable background fluorescence of any slowly varying form, without fitting or subtracting the background. In combination with a Monte Carlo technique, SGSD calculates Raman parameters (such as peak width and intensity) with robust uncertainties. To explain why SGSD fitting is more accurate, we compare how different background subtraction techniques model the background fluorescence with the wide and overlapping peaks present in a real Raman spectrum of carbonaceous material. Then, the utility of SGSD is demonstrated with a set of real and simulated data compared to commonly used linear background techniques. Researchers may find the SGSD technique useful if their spectra contain intense background interference with unknown functional form or wide overlapping peaks, and when the uncertainty of the spectral data is not well understood. [ABSTRACT FROM AUTHOR]

The article discusses the structure and length of finite groups such as the derived length and the nilpotency class. Topics include the generalized Fitting series of a group G which is defined by induction and the inverse image of the subgroup F* (G), reducing the Restricted Burnside problem, and automorphisms.