bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reference dosimetry data and modeling challenges for Elekta accelerators based on IROC‐Houston site visit data
Authors: Kerns James R. , Followill David S. , Lowenstein Jessica , Molineu Andrea , Alvarez Paola , Taylor Paige A. , Kry Stephen F. 
Published: March 2018

PurposeReference dosimetry data can provide an independent second check of acquired values when commissioning or validating a treatment planning system (TPS). The Imaging and Radiation Oncology Core at Houston (IROC‐Houston) has measured numerous linear accelerators throughout its existence. The results of those measurements are given here, comparing accelerators and the agreement of measurement versus institutional TPS calculations.MethodsData from IROC‐Houston on‐site reviews from 2000 through 2014 were analyzed for all Elekta accelerators, approximately 50. For each, consistent point dose measurements were conducted for several basic parameters in a water phantom, including percentage depth dose, output factors, small‐field output factors, off‐axis factors, and wedge factors. The results were compared by accelerator type independently for 6, 10, 15, and 18 MV. Distributions of the measurements for each parameter are given, providing the mean and standard deviation. Each accelerator's measurements were also compared to its corresponding TPS calculation from the institution to determine the level of agreement, as well as determining which dosimetric parameters were most often in error.ResultsAccelerators were grouped by head type and reference dosimetric values were compiled. No class of linac had better overall agreement with its TPS, but percentage depth dose and output factors commonly agreed well, while small‐field output factors, off‐axis factors, and wedge factors often disagreed substantially from their TPS calculations.ConclusionReference data has been collected and analyzed for numerous Elekta linacs, which provide an independent way for a physicist to double‐check their own measurements to prevent gross treatment errors. In addition, treatment planning parameters more often in error have been highlighted, providing practical caution for physicists commissioning treatment planning systems for Elekta linacs.
The ultimate intrinsic signal‐to‐noise ratio of loop‐ and dipole‐like current patterns in a realistic human head model
Authors: Pfrommer Andreas , Henning Anke 
Published: March 2018

PurposeThe ultimate intrinsic signal‐to‐noise ratio (UISNR) represents an upper bound for the achievable SNR of any receive coil. To reach this threshold a complete basis set of equivalent surface currents is required. This study systematically investigated to what extent either loop‐ or dipole‐like current patterns are able to reach the UISNR threshold in a realistic human head model between 1.5 T and 11.7 T. Based on this analysis, we derived guidelines for coil designers to choose the best array element at a given field strength. Moreover, we present ideal current patterns yielding the UISNR in a realistic body model.MethodsWe distributed generic current patterns on a cylindrical and helmet‐shaped surface around a realistic human head model. We excited electromagnetic fields in the human head by using eigenfunctions of the spherical and cylindrical Helmholtz operator. The electromagnetic field problem was solved by a fast volume integral equation solver.ResultsAt 7 T and above, adding curl‐free current patterns to divergence‐free current patterns substantially increased the SNR in the human head (locally >20%). This was true for the helmet‐shaped and the cylindrical surface. On the cylindrical surface, dipole‐like current patterns had high SNR performance in central regions at ultra‐high field strength. The UISNR increased superlinearly with B0 in most parts of the cerebrum but only sublinearly in the periphery of the human head.ConclusionThe combination of loop and dipole elements could enhance the SNR performance in the human head at ultra‐high field strength.
Growth of Pacific White Shrimp Litopenaeus vannamei Cultured on Inland Low-Salinity Pond Soils
Authors: Pine Harvey J , Jescovitch Lauren N , Roy Luke A , Boyd Claude E , Davis D Allen , Brown Travis W 
Published: March 2018

Abstract
Low-salinity inland ponds in west Alabama were used to determine whether soil composition and water ionic profiles influenced shrimp growth. Soils from four farms were collected and placed into individual tanks equipped with airlift biofilters and 2.5‰ reconstituted seawater. Pacific white shrimp Litopenaeus vannamei were cultured for 42 d. Growth, survival, water, and sediment ionic profiles were analyzed at the end of the trial. There were no differences in survival among treatments. Shrimp grown on Farm 1 soil had the highest weight gain (4,244%), while shrimp cultured on Farm 3 soil grew the least (3,127%). Water placed in the tanks with Farm 1 soil had a lower calcium concentration (156 mg/L) and higher potassium (58 mg/L) and magnesium (80 mg/L), respectively, than water in the tanks with Farm 3 and Farm 4 soils. Differences were observed in soil pore water for potassium, sodium, exchangeable cations, sand–silt–clay composition, and organic matter. Sand–silt–clay composition indicated that soil from Farm 1 was characterized as sandy clay loam, while soils from Farms 2, 3, and 4 were clay loam. Shrimp growth was higher on sandy clay loam soil.
Effect of Pawpaw Carica papaya Seed Meal on Growth and as a Natural Sex-Reversal Agent for Nile Tilapia
Authors: Ugonna B O , Solomon S G , Olufeagba S O , Okomoda V T 
Published: March 2018

Abstract
This research investigated the use of pawpaw Carica papaya seed meal (PSM) as a natural sex-reversal agent in tilapia production and its effect on growth. Freshly hatched fry of Nile Tilapia Oreochromis niloticus were collected from brooders and randomly distributed (n =50) to 15 aquarium tanks (30 × 30 × 20 cm3). They were fed a commercial diet (35% crude protein) blended with varying levels of PSM (0, 2, 4, 6, and 8 g/kg) for 28 d. Fingerlings were then maintained in outdoor concrete tanks (1 × 1 × 1 m3) and were fed the commercial diet (without the inclusion of PSM) for 140 d. Growth evaluation and sexual phenotype of the fish were recorded during the treatment and recovery periods. The results obtained showed that growth of treated fish was significantly reduced compared to the control group during the treatment period; however, the trend reversed during the recovery period. The optimal PSM inclusion that gave the maximum weight gain (32.65 g) and masculinization percentage (82.19%) was 4.27 g/kg. The female phenotype was not noticed in treatments with inclusion levels greater than 2 g/kg; hence, reproduction was effectively controlled in the treated groups. However, percentages of fish with modified or reduced gonads significantly increased at 4-g/kg and greater PSM inclusion levels. Due to the biodegradable nature of PSM, it could be used as a viable alternative to popular synthetic hormones.
Stable isotope ecology and human palaeodiet in the northern coast of Santa Cruz (Argentine Patagonia)
Authors: Zilio L. , Tessone A. , Hammond H. 
Published: March 2018

AbstractThe aim of this paper is to provide information on the analysis of stable isotopes obtained from bones of marine and terrestrial fauna used as potential food by hunter‐gatherers on the northern coast of Santa Cruz province (Argentine Patagonia). The results from the isotopic ecology are analysed to contribute to dietary interpretations of the human populations who lived in this area. The mean of terrestrial resources is −19.1‰ ± 1.8‰ and 9.2‰ ± 2.6‰ for δ13C and δ15N, respectively. Meanwhile, marine resources recorded a mean of δ13C −12.5‰ ± 1.2‰ and δ15N of 19.4‰ ± 2.4‰. The analysed human samples come from different types of burials dated mainly in the Late Holocene. The δ13C and δ15N isotopic values on human remains suggest the existence of different diets during the Late Holocene, including people who consumed mainly marine, terrestrial, and mixed proteins, with a range between −18‰ to −10.4‰ and 12.4‰ to 23.4‰ for δ13C and δ15N, respectively. Some of these isotopic values, which indicate marine diets, are the highest recorded for Patagonia. The influence of the marine spray on the terrestrial trophic chains is suggested for the Patagonian Atlantic coast, evidenced by higher values in the δ15N of guanacos from the coast in relation to others studied from the hinterland.
Experimental Investigations of Brake Pad Shim Properties
Authors: Schmid Dominik , Gräbner Nils , von Wagner Utz 
Published: March 2018

AbstractThe understanding of NVH problems in brake systems becomes a strongly dominant remit in modern days. Finding solutions is the central task to achieve a calm and smooth system behavior.Brake squeal on automotive disk brakes represents a high frequency noise phenomenon resulting in potential customer complaints. The avoidance of squeal causes high costs in the automotive industry worldwide. One countermeasure for this disruptive noise issue is the application of thin composites named shims bonded to back plates of brake pads. The selection of appropriate shims is according to the state of the art still mainly based on trial and error. Current approaches seem to map the effects of shims on brake squeal insufficiently. To describe the shim behavior in an improved manner, prior experimental investigations have to be carried out, focusing on the identification of modal damping and stiffness values.The contribution shows experimental results of shims firmly bonded to brake pads and rectangular steel plates. Temperature variations and the analysis of nonlinearities like various excitation levels are examined in greater detail. As a result, the general influence of shims is presented and compared to measurements without damping materials. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of complex states for friction‐excited systems
Authors: Stender Merten , Tiedemann Merten , Hoffmann Norbert 
Published: March 2018

AbstractFor many engineering structures the dynamical response during operation is rarely stationary or regular. In fact, many studies on measured data reveal the irregular nature of dynamical system responses, for example in the field of research on brake squeal. Therefore, linear measures, such as amplitude and frequency spectra, cannot characterize the core dynamics contained in an irregular time series. Additionally, linear methods for damping extraction from measured signals tend to lose significance when it comes to irregular responses of self‐ excited systems. This work aims at highlighting the need for quantifiers from nonlinear time series analysis to adequately characterize real‐world vibration data. In a first step a minimal model is studied to relate nonlinear time series quantifiers to internal system states and dissipation considerations. The goal of this research is to develop an understanding for the information contained in time series data concerning dissipation mechanisms of complex friction‐excited systems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control of Human Muscle‐Actuated Motion
Authors: Fehr Joerg , Fuhrer Julian , Gong Lulu , Schiehlen Werner 
Published: March 2018

AbstractThe question how the brain controls locomotion is a highly treated one. This topic is taken up in this study by means of human computational models, simulating the human musculoskeletal system actuated by advanced Hill‐type muscle models. A forward dynamic approach is considered allowing to simulate human motion independently from pre‐measured trajectories and enabling to resemble the control of the central nervous system – the motor command selection. It is suggested that movement paths arise implicitly through optimisation [1,4]. Hence, stimulation patterns passing through activation dynamics are determined by means of constrained optimal control problems with physiologically motivated objective functions. One advantage concerning the implementation within Neweul‐M2 is the possibility to apply well‐elaborated and tested optimisation algorithms available with Matlab to solve optimal control problems, enabling to employ the novel non‐linear model predictive control (NMPC). The introduced framework is applied to treat different biomechanical movement scenarios including reaching scenarios of the arm which are validated against experimental data from [2–4]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Boundary Layer Machine
Authors: Ostermeyer Georg‐Peter , Vietor Thomas , Müller Michael , Inkermann David , Otto Johannes , Lembeck Hendrik 
Published: March 2018

AbstractIn multi‐body systems, friction often occurs as a result of the contact between two bodies. The resulting forces may be desirable or undesirable, depending on the intended function of a technical system. Although a number of different causes of these forces have been worked out, the scientific understanding required for a systematic adjustment of friction towards satisfying given requirements is still incomplete. This makes it difficult for the designer to design an optimal friction contact. This is reflected in a large number of scientific publications in the associated fields. In order to cope with these challenges, a new, holistic approach is required to recognize and describe the general design principles of friction contacts. Based on the understanding of these principles, design guidelines in a design catalog can be formulated to support designers. In further steps, the designer can parametrize the frictional contact based on a catalog of diverse possible solutions. In the future, this tool should help the designer to find a simple, fast, and effective solution. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibration Damping of Flexible Link Robots Using an Eye‐in‐Hand Camera
Authors: Pucher Florian , Gattringer Hubert , Müller Andreas 
Published: March 2018

AbstractDue to their low weight robots with flexible links are ideal candidates for use in dynamically demanding applications. Since the main goal of the robot control is to achieve precise positioning, the damping of oscillations due to low stiffness is imperative. Furthermore classical PD motor position control is insufficient for vibration damping. This paper presents an approach using an eye‐in‐hand camera for vibration damping of an elastic articulated robot with three actuated joints. The idea is to use the position of feature points in the camera image for generating a feedback signal. The image feature position is transformed into the joint space using the image Jacobian. The PD motor control is augmented by a proportional term w.r.t. a virtual arm angle. Experimental results of a comparison with a control concept based on acceleration sensors are presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Motion by variation of the contact force on an inclined plane
Authors: Schorr Philipp , Zeidis Igor , Zimmerman Klaus 
Published: March 2018

AbstractThis paper describes non‐classical locomotion based on the variation of the contact force. The motion of a locomotion system on an inclined plane is considered. The contact force between the locomotion system and the inclined plane can be influenced by the motion of internal masses. Therefore a mechanical model with two internal masses is introduced. The friction between the locomotion system and the environment is described by COULOMB's law. The motion of this locomotion system is investigated and analyzed by using the averaging method of BOGOLJUBOV and MITROPOLSKI. Furthermore the influence of different parameters on the locomotion characteristics like the direction of movement, the stationary velocity and the maximum inclination angle is shown. A prototype based on this locomotion principle is built up for experimental investigations. Additionally, simulations are used to analyze the locomotion system. The experimental values are compared to the theoretically results and confirm the variation of the contact force as an option to enable a controlled locomotion. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biomechanical evaluation of a femoral neck fracture implant using a novel test‐stand
Authors: Mundt Marion , Bettag Sebastian , Bamer Franz , Stoffel Marcus , Knobe Matthias , Markert Bernd 
Published: March 2018

AbstractThe ageing society leads to an increased risk of femoral neck fractures. Besides endoprotheses and established head‐conserving implants, the rotation‐stable screw anchor is used for surgical treatment. In this in vitro study, the influence of cemented versus non‐cemented implants is tested. Therefore, a novel test set‐up is used that is capable of simulating the load during gait cycles. Thereby, the transferability to clinical practise shall be increased. Additionally, time‐series data is recorded to evaluate clinically relevant parameters during the applied cyclical load. The results show that the test set‐up enables deeper insight to the implants behaviour during loading, which is of relevance due to the differences that can be observed between the cemented and non‐cemented implant. Additionally, the results are compared to the literature. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Personalized simulation of a bone–implant–system during a step forward
Authors: Roland Michael , Tjardes Thorsten , Bouillon Bertil , Diebels Stefan 
Published: March 2018

AbstractIn this study, a workflow is presented for a personalized simulation of a bone–implant–system of a fractured tibia during a step forward. The workflow is based on routinely acquired tomographic data, segmentation, material assignment, mesh generation, setup of realistic boundary conditions and a finite element simulation (FEM). In the absence of patient–specific monitoring data, a dataset from the OrthoLoad database is implemented as individualized boundary conditions. This allows a simulation of the bone–implant–system close to reality of patient's step forward. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical analysis of the fracture toughness in phase‐field modelling of adhesive fracture
Authors: Hansen‐Dörr Arne C. , Hennig Paul , Kästner Markus , Weinberg Kerstin 
Published: March 2018

AbstractWe propose and analyse a phase‐field model which allows for adhesive interface failure between two materials by a local reduction of the critical fracture toughness over a given length scale in the vicinity of the interface. A parameter study is carried out which reveals a significant dependence of the cracking behaviour on the ratio between the length scale of the crack phase‐field model and the width of the adhesive interface. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Neural network representation of a phase‐field model for brittle fracture
Authors: Koeppe Arnd , Bamer Franz , Hernandez Padilla Carlos Alberto , Markert Bernd 
Published: March 2018

AbstractPhase‐field models constitute a powerful tool in fracture mechanics. However, the main issues of these types of methods are the selection of the phase‐field model parameters, the numerical requirement of very finely meshed structures, and extremely small integration time steps. The subject of this work is the construction of an artificial neural network representing a finite element model coupled with a phenomenological phase‐field approach for brittle fracture. The approach is demonstrated on a notched plate in 2D. The neural network results and computation time is compared to established phase‐field models. After an initial training process, the neural network is able to predict the response of the complex system in a fraction of the time compared to the non‐local continuum mechanical model. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of Process Parameters on the Interlaminar Fracture Toughness of GF‐PA6‐Tapes
Authors: Schober Michael , Kuboki Takashi , Ameri Ehsan , Hohe Jörg , Peter Gumbsch 
Published: March 2018

AbstractInterlaminar fracture toughness of consolidated, continuous glass fiber reinforced polyamide‐6 tapes, as well as its sensitivity to process parameters are investigated in this study. Therefore, consolidated plaques are manufactured, varying consolidation temperature and pressure, and their delamination behavior in mode I and mode II is analyzed by means of DCB and ENF tests. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The coupling of plasticity with a relaxation‐based approach to damage modeling
Authors: Schwarz Stephan , Junker Philipp , Hackl Klaus 
Published: March 2018

AbstractSince damage occurs in context of high stresses that are also related to the development of plastic strains, it is natural to couple damage and plasticity phenomena to achieve a more realistic model. Hereto, the new damage model presented in [2] was used and enhanced with plasticity and isotropic hardening, as first shown in [1]. Thereby, the damage model is based on a new regularization approach and provides mesh‐independent results. In order to achieve mesh‐independence, damage models usually take into account the non‐local behavior by using a field function that couples the local damage parameter to a non‐local level, in which differences between the local and non‐local parameter as well as the gradient of the non‐local parameter can be penalized [3]. In contrast, the new regularization approach no longer needs a non‐local level at the finite element scale but directly provides mesh‐independent results. Due to the new variational approach, we are also able to improve the calculation times and convergence behavior. Furthermore, the enhancement with plasticity and isotropic hardening allows to investigate the influences between damage and plastic strains to each other as well as the resulting influences to the cracks. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of the Presta process – Transfer of deformation history
Authors: Scherzer Robert , Ihlemann Jörn 
Published: March 2018

AbstractThe Presta joining process is the world's leading manufacturing method for assembled camshafts. It is a multi‐stage forming process separated in different steps. First, the rolling of the shaft creates a local widening of the intended cam seat. Within the subsequent joining process, the cam is forced onto the widened cam seat to form a tight fit. The two substeps are modelled and simulated using FEM. Within the process large local deformations occur, which requires an appropriate material model. The phenomenological material formulation of finite strain viscoplasticity implemented in the introduced simulation model enables the transfer of the deformation history to a new reference configuration. Hence, at the change of simulation models this feature is applied by passing the material model's internal state variables of the rolling step to the initial FE‐mesh of the joining step. This work shows the simulation models of the Presta joining process and gives a detailed insight into the change of the reference configuration. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Co‐rotational extension of the Logarithmic finite element method
Authors: Schröppel Christian , Wackerfuß Jens 
Published: March 2018

AbstractModeling a plane Timoshenko beam, the approximation space of the standalone Logarithmic finite element (LogFE) method provides good approximations for moderate deformations, but deteriorates for large deformations. A co‐rotational extension of the method significantly improves the quality of the approximation for large deformations. However, due to the inability of the extended method to exactly represent low‐order polynomial deformation, the model does not fully converge with mesh refinement, suggesting the use of additional low‐order deformation functions in the co‐rotational update. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)