In computational biomechanics, two separate types of models have been used predominantly to enhance the understanding of the mechanisms of action of the lumbosacral spine (LSS): Finite element (FE) and musculoskeletal multibody (MB) models. To combine advantages of both models, hybrid FE-MB models are an increasingly used alternative. The aim of this paper is to develop, calibrate, and validate a novel passive hybrid FE-MB open-access simulation model of a ligamentous LSS using ArtiSynth. Based on anatomical data from the Male Visible Human Project, the LSS model is constructed from the L1-S1 rigid vertebrae interconnected with hyperelastic fiber-reinforced FE intervertebral discs, ligaments, and facet joints. A mesh convergence study, sensitivity analyses, and systematic calibration were conducted with the hybrid functional spinal unit (FSU) L4/5. The predicted mechanical responses of the FSU L4/5, the lumbar spine (L1-L5), and the LSS were validated against literature data from in vivo and in vitro measurements and in silico models. Spinal mechanical responses considered when loaded with pure moments and combined loading modes were total and intervertebral range of motions, instantaneous axes and centers of rotation, facet joint contact forces, intradiscal pressures, disc bulges, and stiffnesses. Undesirable correlations with the FE mesh were minimized, the number of crisscrossed collagen fiber rings was reduced to five, and the individual influences of specific anatomical structures were adjusted to in vitro range of motions. Including intervertebral motion couplings for axial rotation and nonlinear stiffening under increasing axial compression, the predicted kinematic and structural mechanics responses were consistent with the comparative data. The results demonstrate that the hybrid simulation model is robust and efficient in reproducing valid mechanical responses to provide a starting point for upcoming optimizations and extensions, such as with active skeletal muscles.

Full metal-ceramic composite beads containing different amounts of niobium and alumina, particularly 100 vol% alumina, 100 vol% niobium, and 95/5 vol% niobium/alumina, were produced by the alginate gelation process. The suspension for bead fabrication contained sodium alginate as gelling agent and was added dropwise into a calcium chloride solution to trigger the consolidation process. After debinding in air, sintering of the composite beads was performed under inert atmosphere. Samples in green and sintered state were analyzed by digital light microscopy and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. Investigations by mercury intrusion porosimetry revealed that pure alumina beads featured smaller pores compared to composite beads, although the open porosities were comparable. The fracture strength was evaluated on single beads. Contrary to the pure alumina, the composite beads showed a clear plastic deformation. Pure niobium beads showed a ductile behavior with very large deformations. XRD analyses revealed the presence of calcium hexaluminate and beta-alumina as minor phases in the alumina beads, while the composite ones contained about 25 wt% of impurities. The impurities comprised NbO arising from the oxidation, and -Nb2C, from the reaction with the residual sodium alginate.

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PurposeAfter a building collapse, people buried alive have to be localized and rescued. This requires the damage site's inspection and surveillance. These tasks are dangerous and challenging due to the area's hard‐to‐reach and hazardous environment. The damage site cannot be actively entered but must be inspected from a safe distance. In this context, mobile robots gain in importance as they can be operated semi‐autonomously or remote‐controlled without exposing the first responders to the risk. The purpose of this paper is to introduce a novel robot.Design/methodology/approachThe novel robot introduced in this paper has a snake‐like build‐up, uses tracks and active flippers for locomotion and negotiates completely structured as well as extremely unstructured and rough terrain. The system's slender, segmented and modular structure is actively articulated by the use of overall 30 degrees‐of‐freedom, which allow the robot's flexible adaptation to a given terrain. System‐terrain‐interaction is detected by the use of an innovative, RFID‐based sensory integrated in the system's tracks.FindingsThe paper presents the mobile robot's basic features, as well as first experimental results for semi‐autonomy and tele‐operation.Originality/valueThe introduced robot stands out due to its high locomotion and mobility capabilities.

This paper presents presents a study on e ciency of Urban Search and Rescue (USAR) missions that has been carried out within the framework of the German research project I-LOV. After three years of development, first field tests have been carried out in 2011 by professionals such as the Rapid Deployment Unit for Salvage Operations Abroad (SEEBA). We present results from evaluating search teams in simulated USAR scenarios equipped with newly developed technical search means and digital data input terminals developed in the I-LOV project. In particular, USAR missions assisted by the "bioradar", a ground-penetrating radar system for the detection of humanoid movements, a semi-active video probe of more than 10 m length for rubble pile exploration, a snake-like rescue robot, and the decision support system FRIEDAA were evaluated and compared with conventional USAR missions. Results of this evaluation indicate that the developed technologies represent an advantages for USAR missions, which are discussed in this paper.

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Large turbine bearings are usually equipped with hydrostatic jacking mechanisms to separate bearing and shaft during transient start-stop procedures. They are turned off once hydrodynamic operation is reached. In some cases, under severe operating conditions, the hydrostatic oil supply is kept running although the rotor already runs in full speed. The supplied amount of jacking oil is very small compared to the regular oil supply. However, experimental data of a large tilting-pad bearing shows that this hybrid operation has a considerable impact on the load carrying capacity in terms of lower pad temperature and larger film thickness. In this paper, a theoretical investigation to analyse the effect of increased load carrying capacity of a large tilting-pad journal bearing in hybrid operation is presented. The increase is driven by three different aspects: 1) hydrostatic pressure component, 2) increase in lubricant viscosity due to the injection of cold oil, 3) decrease of temperature gradients and thus thermal pad deformation. Subject of the approach is a ø500 mm five-pad, rocker-pivot tilting-pad journal bearing in flooded lubrication mode. The experiments are carried out on the Bochum test rig for large turbine bearings. The theoretical analyses are performed with a simulation code solving the Reynolds and energy equations for the oil film and calculating the thermomechanical pad deformations simultaneously. By considering each of the three above aspects separately and in combination, their share of load increase can be assessed individually. Contrary to expectations, the results indicate that the increase is not mostly based on the hydrostatic pressure component. Instead, the advantageously decreased pad deformations make the largest contribution to the increased load carrying capacity while the alteration in viscosity shows the least impact.

Ceramic-matrix and metal-matrix composites have been studied for many years. Traditionally, ceramic-matrix composites consist of ceramic (or carbon) fibers embedded in a ceramic matrix. The role of these fibers is to enhance the fracture toughness of the combined material system while still taking advantage of the inherent high strength and Young's modulus of the ceramic matrix. [1][2][3] On the other hand, metalmatrix composites are made by dispersing a reinforcing material into a metal matrix. [4][5][6][7] The reinforcement usually serves as a structural task, but can be also used to improve physical properties such as wear resistance and thermal conductivity. [8] In general, ceramic-metal composites combine high melting point, hardness and chemical stability of ceramics, and high toughness and ductility of metals. In case of high temperature and wear applications, the combination of ceramics with refractory metals (Nb, Mo, Ta, W, and Re) with melting point above 2000 °C is of high interest. [4][5][6][7][9][10][11][12][13] Such materials are especially attractive for the metallurgical industry, where special functional components are exposed to extreme conditions. Examples are electrodes with nonwetting behavior, [14] ladle sliding gate plates with enhanced thermal shock properties, casting nozzles, or integrated heating elements. Such components with high electrical conductivity can also be applied to replace carbon-bonded parts (e.g., graphite electrodes), in cases where the emission of carbon dioxide should be minimized.Most works report the use of fine-grained powders to produce dense sintered composites with high strength and toughness at the same time. [15] However, dense refractories usually show high shrinkage on sintering, with a pure brittle behavior accompanied by a high susceptibility to cracking and subsequent spalling. To improve the thermal shock resistance, a low Young's modulus and high porosity are beneficial. Recently, the concept of coarse-grained refractory composites based on tantalum-alumina and niobium-alumina was introduced. [16] By combining powder metallurgy with castable technology, low shrinkage values and good mechanical properties up to 1500 °C were obtained. The composites showed plastic deformation behavior between 1300 and 1500 °C. [17] Furthermore, the technology allows to produce large refractory components with low residual stresses. In a novel study, a two-step castable procedure was explored to produce refractory niobium-alumina composites. [18] The first step consisted in the synthesis of composite aggregates, while the second involved the production of coarse-grained refractory castables from the presynthesized composite aggregates. Such a fractal design is required in order to ensure a coherent composition at different aggregate size scales and hence to achieve good electrical