Strain energy density distribution of vertebral body of two motion segment model under combined compression and sagittal bending moment – an in vitro porcine spine biomechanical study

Abstract

The purpose of the current study is to find the strain energy density (SED) distribution of a vertebral body during different compression loadings, combined with sagittal bending moments. The combined flexion and extension, which are generated by applying an eccentric pointed loading on the motion segment, is to mimic different postures of trunk and loading on the spine. Two strain gage rosettes were applied at an anterior site and a posterior site of a vertebral body. The total SED, deviatoric SED and dilatation SED were obtained from the measurements of the two rosettes. Three major phenomena are observed in the current study; first, the anterior site on the vertebra is at higher risk compared to the posterior site on the vertebra when the motion segment is in compression combined with extreme flexion and extension. Second, the SED is minimal when the loading is applied along the trajectories of the spinal canal and joint facets. Third, the major contribution to SED is from the deviatoric SED. The distribution of SED within the vertebral body during different loading conditions can serve as the baseline for treatment to protect the vertebral body from the risk of compression fracture.     

Concept of energy efficient technological system: Machine tool – cutting tool – workpiece

This study deals with the concept of increasing energy efficiency by means of decreasing the energetic losses by using advanced composite machine tool components and interfaces characterized by low friction, and high wear resistance. Moreover, this study provides experimental results of damping property measurements and characteristic time domain curves of the fibre, particle, and sandwich composites, underlining the advantages of such composite types in terms of dynamic loading. Furthermore, it provides an analysis on the usage of thin films (coatings) and energy consumption in terms of cutting conditions. The study analyses the cutting tool geometry and shape of cutting edge that positively affect the cutting forces and chip flow direction, and avoid the energy-intensive restricted cutting effect. Respecting the results of the analyses of mentioned effects contributes to increasing the energy efficiency of the machine tool-cutting tool-workpiece system.     

Simulated Calculations of Strain Induced Precipitation Behaviorin a Nb-Ti-V Steel

On the basis of regular solution sublattice model and classical nucleation and growth theory Strain induced precipitation kinetics in Nb-Ti-V combined treated microalloying Steels has been calcu lated. The calculated precipitation-time-temperature (PTT) diagram is in reasonable agreement with experimental results obtained from isothermal Stress relaxation method.     

Veneering composites – a thermoanalytical examination

Differential thermal analysis and thermal gravimetric analysis were used to characterize veneering composites. Samples weighing 4–20 mg, made from the composite materials Visio-Gem (Espe, Germany), Sinfony (Espe, Germany), Artglass (Kulzer, Germany), Dentacolor (Kulzer, Germany) and Targis (Ivoclar, Liechtenstein), were examined. The samples were subjected to various thermal curing times of between 4 s and 25 min, using the relevant devices of the manufacturers. As a control group, samples of all materials were examined unreacted. In order to avoid post-curing during storage, all samples were subjected, immediately after manufacture, to the appropriate dynamic temperature programme of the thermoanalytical unit at a heating rate of 10 °C min-1. The materials showed specific material characteristics which can, for instance, be used to analyse the curing behaviour of the materials. The position of the glass transition, polymerization and post-polymerization peaks at temperatures between 30 and 100 °C, as well as 150 and 300 °C, and the filler and matrix content, allow the classification of the veneering composites. © 1999 Kluwer Academic Publishers     

Setup-oriented dispatching rules – a survey

This paper provides a survey of dispatching rules that explicitly take into account setup times in their decision making. Rules are classified into the categories of purely setup-oriented, composite and family-based rules, and the most promising rules from the three categories are identified from the literature. These rules are then compared empirically on various job shop problems with sequence-dependent setup times for their performance regarding mean setup time, mean flow time, mean tardiness and proportion of tardy jobs. The setup times are modelled using setup time matrices, and five different types of matrices are applied to assess the influence of this factor on the relative performance of a setup-oriented dispatching rule. Experimental results indicate that the choice of the best rule is often dependent on the setup time matrix structure. While good family-based rules exist for reducing the mean setup time and mean flow time, they are clearly outperformed by effective composite rules for due date-related criteria. Moreover, the better rules all seem to rely on queue information rather than only job attributes.     

Graphene-based materials and structures for energy harvesting with fluids – A review

Graphene and graphene-based systems have recently been recognized as promising platforms for energy harvesting, microelectronic components and energy storage owing to their excellent electrical and thermal conductivity, outstanding mechanical properties, good chemical stability, area adaptability, among other significant properties. Integration of energy harvesting systems relying on the graphene/graphene-based materials in contact with fluids has been emphasized in recent years, as well as their potential impact on electric energy generation for a wide range of applications (e.g. innovative medical devices, advanced electronic systems and highly-efficient transduction systems for renewable energy). This review summarizes, for the first time, major breakthroughs carried out in the scope of energy harvesting exploiting graphene-based material systems (comprising graphene films, graphene grids, graphene membranes, 3D graphene composites and tribological structures) in contact with ionic and non-ionic fluids. Several transduction mechanisms for energy harvesting have been thoroughly analyzed. Energy outputs, materials and structures, substrates, types of fluid, manufacture methodologies, and experimental test methodologies are systematically highlighted in this review. Finally, future research directions and innovative applications of these harvesters are proposed.     

Co(OH)2 nanosheet-decorated graphene–CNT composite for supercapacitors of high energy density

A composite of graphene and carbon nanotubes has been synthesized and characterized for application as supercapacitor electrodes. By coating the nanostructured active material of Co(OH)₂ onto one electrode, the asymmetric supercapacitor has exhibited a high specific capacitance of 310 F g⁻¹, energy density of 172 Wh kg⁻¹ and maximum power density of 198 kW kg⁻¹ in ionic liquid electrolyte EMI-TFSI.     

Effect of tube geometry and ply-angle on energy absorption of a circular glass/epoxy crush tube – A numerical study

The superior specific energy absorption characteristics of long fiber composite structures as compared to aluminum and steel are well established. Due to cost and time involved in testing of composites, it is imperative to develop numerical solution of the crushing phenomenon. The work presented here reports work to better understand the energy absorption characteristics of glass–fiber circular crush tubes. The effect of tube diameter and ply orientation on the energy absorption has been extensively investigated. Numerical results are compared with experiments performed elsewhere and the correlation between the two is encouraging.     

Structure, dielectric, ferroelectric, and energy density properties of (1 − x)BZT–xBCT ceramic capacitors for energy storage applications

We investigate the dielectric, ferroelectric, and energy density properties of Pb-free (1 ? x)BZT–xBCT ceramic capacitors at higher sintering temperature (1600 °C). A significant increase in the dielectric constant, with relatively low loss was observed for the investigated {Ba(Zr_0.2Ti_0.8)O₃}_(1?x ){(Ba_0.7Ca_0.3)TiO₃} _x (x = 0.10, 0.15, 0.20) ceramics; however, electric breakdown was low (~140, 170, 134 kV/cm), and of which room temperature (300 K) charging curve energy density values are largest ~0.88, 0.94, and 0.87 J/cm³ with maximum high dielectric constant values ~7800, 8400, and 5200, respectively. Bulk ceramic BZT–BCT materials have shown interesting energy densities with good energy storage efficiency (~72 %) at high sintering temperature; they might be one of the strong candidates for high energy density capacitor applications in an environmentally protective atmosphere.     

Graphene-reinforced metal matrix nanocomposites – a review

The research works of graphene-reinforced metal matrix composites will be summarised in this paper. Comparatively, much less research works have been undertaken in this field. Graphene has been thought to be an ideal reinforcement material for composites due to its unique two-dimensional structure and outstanding physical and mechanical properties. It is expected to yield structural materials with high specific strength or functional materials with exciting thermal and electrical characteristics. This paper will introduce all kinds of graphene-reinforced metal matrix composites that have been studied. The microstructure and mechanical properties, processing techniques, graphene dispersion, strengthening mechanisms, interfacial reactions between graphene and the metal matrix and future research works in this field will be discussed.     

Nanoparticle-supported catalysts and catalytic reactions – a mini-review

This article reviews recent developments of using nanometer-sized particular matrices for supporting catalysts and catalytic organic reactions. Immobilization of a catalyst onto the surface of an Au or magnetic (e.g. Fe₂O₃) nanoparticle allowed facile separation and recycling of the catalyst out of the reaction mixture. The activity and selectivity of the nanoparticle-supported catalytic species were found to be comparable to those of their parent catalysts in solution or their counterparts immobilized on the solid-phase. In addition, due to the unique surface structure of the nano-host, cooperative catalysis was observed in a dyad of amino acid residues and peptide analogues on the nanoparticle surface. Thereby, immobilization of catalysts on the surface of a nanoparticular matrix will not only facilitate the isolation and recovery of expensive catalysts, but also open a new avenue to regulate their activity and selectivity.     

Selected variants of a Memetic Algorithm for JSP – a comparative study

The article aims to address a research gap concerning the adequate configuration of a Memetic Algorithm adapted to solve the Job-Shop Scheduling Problem. The goal was accomplished by means of conducting a comparative study of 16 variants of a Memetic Algorithm, characterised with different places of hybridisation and local search methods applied. The study involved the solution of eleven instances of JSP and the comparison of the results with the results achieved with an Evolutionary Algorithm lacking the mechanism of hybridisation and selected local search methods. The utilitarian significance of the problem also involved the use of assessment measures intended for both practical applications and research purposes.     

Prediction of molecular weight and density of distillation fractions from gas chromatographic—mass spectrometric detection and multivariate calibration

Brakstad, F., Karstang, T.V., Sørensen, J. Steen, A., 1988. Prediction of molecular weight and density of distillation fractions from gas chromatographic—mass spectrometric detection and multivariate calibration. Chemometrics and Intelligent Laboratory Systems, 3: 321–328.An accurate gas chromatographic method has been developed for the prediction of molecular weight and density of distillation fractions using computerized mass spectrometric detection.Partial least squares regression, which reduces the number of fragment data, is used to quantitatively relate the significant fragmentograms of a distillation fraction to its measured mean molecular weight and density. The final regression models for molecular weight and density give relative standard errors of prediction of 1.0 and 0.3%, respectively.The advantages of this method for the simulated distillation of oils or condensates are discussed.     

Gas pressure dependence of composition in Ta–Ti–N films prepared by pulsed high energy density plasma

Tantalum titanium nitride (Ta–Ti–N) films were deposited on silicon wafer substrates by pulsed high energy density plasma (PHEDP), under different intake gas pressures, ranging from 0.1 to 0.4 MPa. The films were investigated by X-ray photoelectron spectroscopy. Results were analyzed in detail, which reveals that the contents of the metallic elements (Ta and Ti) tend to decrease with pressure, while that of nitrogen increases as expected. With increasing pressure, the films can be denoted as TaTi_3.9N_2.8, TaTi_4.7N_6.0, TaTi_2.2N_8.4 and TaTi_3.1N1_3.5, respectively. The bonding state of tantalum, titanium, as well as nitrogen was fitted and discussed. Our results demonstrate that almost all the titanium bonded with nitrogen. The Ta–N and Ti–N bonds have equal shares under low gas intake pressure, while the Ti–N bonds prevail under high pressure. The preferential sputtering between the coaxial electrodes should be responsible for this phenomenon. Under low nitrogen pressure, the preferential sputtering is quite significant; while it could be neglected under high pressure.     

Specific heat at constant flux density for a low-κ type II superconductor

The specific heat at constant flux densityC _B was measured to study the thermodynamic properties of the mixed state of a type II superconductor at low reduced temperaturet=T/T _c . The sample was a Pb_0.96Tl_0.04 alloy having =0.97. The results are thatC _B increases nearly linearly withB throughout the mixed state, with a discontinuous jump down to the normal state value at the upper critical field. Att<0.21 a small, positive curvature ofC _B versusB is consistent with Eilenberger's calculations. However, this positive curvature is not consistent with fluxoid interaction models for low flux density. These measurements supplement previous measurements fort<0.5 using isothermal calorimetry on the same sample. Taken together, the two experiments indicate that, at a givenT, the incremental entropy per fluxoid is nearly constant for allB. This result forces some interesting empirical relationships among the parameters that characterize the mixed state.On sabbatical leave from South Dakota School of Mines and Technology, Rapid City, South Dakota.     

Onset conditions for a Rayleigh–Taylor instability with step function density profiles

The stability of several density profiles constructed from a linear combination of step functions in a vertically orientated two-dimensional porous medium are considered. A quasi-steady-state approximation is made so that the initial stability of the system can be approximated. Using a similar approach to that of Tan and Homsy (Phys Fluids 29:3549–3556, 1986) a dispersion equation for each density profile is obtained analytically at time zero. Neutral stability curves are then obtained to allow the regions of the parameter space to be divided into stable and unstable regions.     

Biomass feedstock supply chain design – a taxonomic review and a decomposition-based methodology

In this paper, we present a taxonomic review of the literature devoted to the use of operations research approaches for the design and operation of biomass feedstock supply chains (BFSCs). A total of 185 publications that have appeared from 1989 to 2017 are classified based on (1) the embedded optimisation subproblems; (2) the modelling methodologies used for their formulations; and (3) the methods employed for their solution. Our objective of using this classification scheme is to highlight the presence of some useful substructures in a BFSC problem that can, then, be exploited in developing its solution procedure. We illustrate this idea on some generic BFSC problems and present a Dantzig–Wolfe decomposition-based methodology for developing customised approaches to effectively tackle these difficult and large-sized BFSC problems. Finally, we suggest several promising future research directions.     

3D printing for soft robotics – a review

Soft robots have received an increasing attention due to their advantages of high flexibility and safety for human operators but the fabrication is a challenge. Recently, 3D printing has been used as a key technology to fabricate soft robots because of high quality and printing multiple materials at the same time. Functional soft materials are particularly well suited for soft robotics due to a wide range of stimulants and sensitive demonstration of large deformations, high motion complexities and varied multi-functionalities. This review comprises a detailed survey of 3D printing in soft robotics. The development of key 3D printing technologies and new materials along with composites for soft robotic applications is investigated. A brief summary of 3D-printed soft devices suitable for medical to industrial applications is also included. The growing research on both 3D printing and soft robotics needs a summary of the major reported studies and the authors believe that this review article serves the purpose.