2,570 research outputs found
3D FEM Simulations of a shape rolling process
A finite element model has been developed for the simulation of the shape rolling of stator\ud
vanes. These simulations should support the design of rolling tools for new vane types. For the time being\ud
only straight vanes (vanes with a constant cross-section over the length) are studied. In that case the rolling\ud
process can be considered stationary and an ALE formulation is suitable to calculate the steady state. Results\ud
of simulations and experiments for a symmetrical straight vane are presente
Crystal-field splittings in CeX (X= N, P, As, Sb, Bi) compounds
The unusual and interesting physical properties of rare earth intemetallic
compounds have their origin in the combination of strongly correlated 4f states
and their hybridization with the conduction electron sea, which gives rise to
their complex low temperature Kondo behavior. In particular, Ce compounds are
very sensitive to the crystalline and chemical environment, as compared to
other rare earth systems. The interaction of the 4f state with the conduction
band plays an important role in the determination of the different magnetic,
structural and transport properties of these systems. Among the cerium
compounds, those of the type CeX, which crystallize in the rock salt structure,
exhibit extremely unusual magnetic properties. By making use of the mixed
LDA-NCA calculation technique we analyse the crystal-field splittings of CeX
compounds (X=N, P, As, Sb, Bi). The obtained ab-initio hybridization functions
are taken as imputs to calculate the crystal-field splittings within NCA (non
crossing approximation) and the tendencies are contrasted with experiments. KEY
WORDS: Highly correlated systems, crystal fields, p-electron.Comment: 8 pages, 2 figure
Neoplastic transformation of mouse C3H 10T1/2 and Syrian hamster embryo cells by heavy ions
C3H 10T1/2 mouse-embryo fibroblasts were used for transformation experiments to study the effectiveness of various heavy ions with energies up to 20 MeV/u and LET values from 170 to 16.000 keV/μm. The transformation frequency per unit absorbed dose decreased with increasing ionization density; at the highest values of LET we found a decrease even of the transformation efficiency per unit fluence. Uranium ions at energies of 5, 9, and 16.3 MeV/u did not induced any transformation.
In additional studies piimary Syrian hamster embryo cells (SHE) were exposed to heavy ions in order to characterize cytological and molecular changes which may be correlated with neoplastic transformation. Growth behaviour, chromosomal status, tumorigenicity in nude mice, and expression of oncogenes of transformed cell lines were examined
A Nonparametric Method for the Derivation of α/β Ratios from the Effect of Fractionated Irradiations
Multifractionation isoeffect data are commonly analysed under the assumption that cell survival determines the observed tissue or tumour response, and that it follows a linear-quadratic dose dependence. The analysis is employed to derive the α/β ratios of the linear-quadratic dose dependence, and different methods have been developed for this purpose. A common method uses the so-called Fe plot. A more complex but also more rigorous method has been introduced by Lam et al. (1979). Their method, which is based on numerical optimization procedures, is generalized and somewhat simplified in the present study. Tumour-regrowth data are used to explain the nonparametric procedure which provides α/β ratios without the need to postulate analytical expressions for the relationship between cell survival and regrowth delay
Adaptive online deployment for resource constrained mobile smart clients
Nowadays mobile devices are more and more used as a platform for applications. Contrary to prior generation handheld devices configured with a predefined set of applications, today leading edge devices provide a platform for flexible and customized application deployment. However, these applications have to deal with the limitations (e.g. CPU speed, memory) of these mobile devices and thus cannot handle complex tasks. In order to cope with the handheld limitations and the ever changing device context (e.g. network connections, remaining battery time, etc.) we present a middleware solution that dynamically offloads parts of the software to the most appropriate server. Without a priori knowledge of the application, the optimal deployment is calculated, that lowers the cpu usage at the mobile client, whilst keeping the used bandwidth minimal. The information needed to calculate this optimum is gathered on the fly from runtime information. Experimental results show that the proposed solution enables effective execution of complex applications in a constrained environment. Moreover, we demonstrate that the overhead from the middleware components is below 2%
Population genetic structure of Sri Lankan backyard chicken flocks: Implication for conservation and genetic improvement programs
Traditional ‘random’ sampling strategy for molecular characterization has revealed low genetic differentiation and weak genetic structure among Asian and African indigenous, non-descript chicken populations although
they carried high within-population phenotypic and molecular genetic diversity. In the present study, 192 backyard
chickens collected following a nearly ‘complete’ sampling strategy for all adult birds within flocks of 75 households in
five villages at two sites in Sri Lanka were genotyped using 20 microsatellite markers. The phenotypes and history of
these birds were also recorded. A link of phenotypic composition and flock size with specific genetic structure of the
backyard chicken populations was explored. The results
suggest that the households who used to keep large flocks
of indigenous backyard chickens of mixed genotypes
should be included in in-situ conservation program to effectively
maintain and sustainably utilize these important
chicken genetic resources
Influence of the pavement surface on the vibrations induced by heavy traffic in road bridges
The irregularity of the pavement surface governs the traffic-induced vibrations in road bridges, but it is either ignored or simulated by means of ideal pavements that differ significantly from real cases. This work presents a detailed dynamic analysis of a heavy truck crossing a 40-m span composite deck bridge using on-site measurements of different existing road profiles, as well as code-based ideal pavements. By activating or deactivating certain spatial frequency bands of the pavement, it is observed that the ranges 0.2 - 1 and 0.02 - 0.2 cycles/m are critical for the comfort of the pedestrians and the vehicle users, respectively. Well maintained roads with low values of the displacement Power Spectral Density (PSD) associated with these spatial frequency ranges could reduce significantly the vibration on the sidewalks and, specially, in the vehicle cabin. Finally, a consistent road categorisation for vibration assessment based on the PSD of the pavement irregularity evaluated at the dominant frequencies is proposed
Agricultural pastures challenge the attractiveness of natural saltmarsh for a migratory goose
Perspectives of End Users on the Potential Use of Trunk Exoskeletons for People With Low-Back Pain:A Focus Group Study
Objective: The objective of this study was to identify criteria to be considered when developing an exoskeleton for low-back pain patients by exploring the perceptions and expectations of potential end users. Background: Psychosocial, psychological, physical load, and personality influence incidence of low-back pain. Body-worn assistive devices that passively support the user’s trunk, that is exoskeletons, can decrease mechanical loading and potentially reduce low-back pain. A user-centered approach improves patient safety and health outcomes, increases user satisfaction, and ensures usability. Still, previous studies have not taken psychological factors and the early involvement of end users into account. Method: We conducted focus group studies with low-back pain patients (n = 4) and health care professionals (n = 8). Focus group sessions were audio-recorded, transcribed, and analyzed, using the general inductive approach. The focus group discussions included trying out an available exoskeleton. Questions were designed to elicit opinions about exoskeletons, desired design specifications, and usability. Results: Important design characteristics were comfort, individual adjustability, independency in taking it on and off, and gradual adjustment of support. Patients raised concerns over loss of muscle strength. Health care professionals mentioned the risk of confirming disability of the user and increasing guarded movement in patients. Conclusion: The focus groups showed that implementation of a trunk exoskeleton to reduce low-back pain requires an adequate implementation strategy, including supervision and behavioral coaching. Application: For health care professionals, the optimal field of application, prevention or rehabilitation, is still under debate. Patients see potential in an exoskeleton to overcome their limitations and expect it to improve their quality of life
Local probing of the field emission stability of vertically aligned multiwalled carbon nanotubes
Metallic cantilever in high vacuum atomic force microscope has been used as
anode for field emission experiments from densely packed vertically aligned
multi-walled carbon nanotubes. The high spatial resolution provided by the
scanning probe technique allowed precise setting of the tip-sample distance in
the submicron region. The dimension of the probe (curvature radius below 50nm)
allowed to measure current contribution from sample areas smaller than 1um^2.
The study of long-term stability evidenced that on these small areas the field
emission current remains stable (within 10% fluctuations) several hours (at
least up to 72 hours) at current intensities between 10-5A and 10-8A.
Improvement of the current stability has been observed after performing
long-time Joule heating conditioning to completely remove possible adsorbates
on the nanotubes.Comment: 15 pages, 7 figure
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