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