1,259 research outputs found
Properties of 3Y-TZP zirconia ceramics with graphene addition obtained by spark plasma sintering
In this study the influence of graphene addition on the microstructure, phase composition, mechanical, and electrical properties of 3Y-TZP ceramics was investigated. Blends of pure 3Y-TZP and with addition of 1 − 4 vol% graphene were prepared by mixing and milling, and they were consolidated by spark plasma sintering (SPS). Addition of 3 vol% graphene is necessary to overcome the percolation threshold and obtain electrically conductive composites. However, rising the graphene contents obstructs sinterability. Hence, flexural strength, Young's modulus, and hardness decrease with increasing the graphene content, and the fracture resistance reaches an intermediate maximum at 2 vol% graphene. Graphene lamellae are oriented orthogonally to the pressing direction. They evidently provide some energy dissipation by crack deflection. TZP-graphene interfaces are very weak. Thus, crack bridging can be neglected. © 2018 Elsevier Ltd and Techna Group S.r.l.This is the peer-reviewed version of the article: Obradović, N., Kern, F., 2018. Properties of 3Y-TZP zirconia ceramics with graphene addition obtained by spark plasma sintering. Ceramics International 44, 16931–16936. [https://doi.org/10.1016/j.ceramint.2018.06.133
Modelling Emergency Scenarios using Algebraic High Level Net Transformation Systems with Net Patterns
Emergency operations are a good case study for dynamic systems. Their
size and high dynamicity make modelling them a challenging task. Algebraic high
level net transformation systems are a well suited technique for modelling such dynamic
systems. They consist of an algebraic high level net and a set of graph transformation
rules. The net reflects the initial state of the operation and the transformation
rules can be used to adapt this state to reflect the dynamicity of the operation.
The applicability of graph transformation rules depends on the existence of a match
morphism. While designing the algebraic high level net transformation system the
designer has to ensure the existence of the right match morphisms for all reachable
runtime states. This can be a tedious and error prone task for the designer. This
paper uses a case study for modelling emergency operations with algebraic high
level net transformation systems to show how the notion of net patterns can help the
designer to cope with rule applicability
Secondary raw material markets in the C&D sector: Study on user acceptance in southwest Germany
In industrialized countries, regulations demand increasingly higher recycling (RC) rates
and many efforts are undertaken to recycle construction and demolition (C&D) waste
fractions. The C&D sector has indisputable relevance due to the highest mineral waste
fraction, high numbers of employees and turnovers. High-quality RC construction
products can be produced to substitute primary resources and reduce land use.
This empirical study analyses the acceptance of RC materials in Germany particularly
of private awarding authorities in their private construction project(s). In 41 structured
interviews, data is collected and evaluated based on hypotheses.
Qualitative and quantitative analyses show that acceptance problems cannot be stated.
How-ever, medium knowledge and low experience with RC construction materials as
well as communication problems are identified. The respondents have no concerns and
tend to trust in RC construction materials, but this is decreasing with the increased
structural importance of the materials. Surprisingly, quality is the most frequently
mentioned decision criteria in private construction projects, followed by cost. Private
awarding authorities see no increase of their property value by using RC construction
materials. And, the majority is unwilling to pay a premium for RC construction
materials. Higher material quality standards, regular government reviews and financial
support are seen conducive
STABILITY OF POLYNOMIALS UNDER CORRELATED COEFFICIENT PERTURBATIONS.
The robust stability of polynomials with respect to real parameter variations is investigated. The coefficients of the polynomial are assumed to be linear functions of several real parameters. An algorithm to calculate the maximum allowable variations of the parameters so the roots still remain in prescribed regions of the complex plane is presented. Examples are given to illustrate the method
A Combined Digital-Analog Tracker for Terrestrial Applications
A combined Digital-Analog Tracker is suggested to allow maximum efficiency in a solar-electrical energy converter, utilizing a twelve-foot parabolic collector. The analog tracker compares solar beam radiation to ambient (diffuse) light to obtain optimum placement of the collector when the sun is visible. The digital portion of the tracker utilizes a wired program which derives information on solar position from a non-volatile random-access semiconductor memory. This arrangement allows accurate mapping of the sun even when the sun is obscured by atmospheric phenomena which would make mapping impossible
System Modeling and Control of Smart Structures
This paper presents multidisciplinary research and curriculum efforts at the University of Missouri-Rolla in the smart structures area. The primary objective of our project is to integrate research results with curriculum development for the benefit of students in electrical, and mechanical and aerospace engineering and engineering mechanics. The approach to the accomplishment of curriculum objectives is the development of a two-course sequence in the smart structures area with an integrated laboratory. The research portion of the project addresses structural identification and robust control methods for smart structures. A brief summary of the research results and a description of curriculum development in the smart structures area are described in this pape
Real-Time Tracking of Coherent Oscillations of Electrons in a Nanodevice by Photo-assisted Tunnelling
Coherent collective oscillations of electrons excited in metallic
nanostructures (localized surface plasmons) can confine incident light to
atomic scales and enable strong light-matter interactions, which depend
nonlinearly on the local field. Direct sampling of such collective electron
oscillations in real-time is crucial to performing petahertz scale optical
modulation, control, and readout in a quantum nanodevice. Here, we demonstrate
real-time tracking of collective electron oscillations in an Au bowtie
nanoantenna, by recording photo-assisted tunnelling currents generated by such
oscillations in this quantum nanodevice. The collective electron oscillations
show a noninstantaneous response to the driving laser fields with a decay time
of nearly 10 femtoseconds. The temporal evolution of nonlinear electron
oscillations resulting from the coherent nonlinear optical response of the
nanodevice were also traced in real-time. The contributions of linear and
nonlinear electron oscillations in the generated tunnelling currents in the
nanodevice were precisely determined. A coherent control of electron
oscillations in the nanodevice is illustrated directly in the time domain.
Functioning in ambient conditions, the excitation, coherent control, and
read-out of coherent electron oscillations pave the way toward on-chip
light-wave electronics in quantum nanodevices
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