40 research outputs found

    The influence of the La3+ content on the mechanical properties of electrooptic transducers based on PLZT type ceramics

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    Modification of the PZT system by the addition La3+ ions has marked beneficial effect on several the basic parameters, such as squerness of the hysteresis loop, decreased coercive filed, increased dielectric constant, maximum coupling coefficients, increased mechanical compliance, decreased Tc temperature, and enhanced optical transparency. The mechanical and electrical properties in lanthanum modified lead zirconate-titanate ceramics of 5/50/50 and 10/50/50 were studied by internal friction Q¥1, dynamic Young modulus E, electric permittivity " and tangent of dielectric loss of angle tan± measurements. The temperature dependences of Q¥1 = f(T) and E = f(T) were determinated in temperature range from 300 K to 600 K. The temperature dependences of " = f(T) and tan± = f(T) were determinated in temperature range from 300 K to 730 K. The values of TC obtained during " and tan± measurements were respectively: 560 K for 5/50/50 and 419 K for 10/50/50

    Contextual factors predicting compliance behavior during the COVID-19 pandemic: A machine learning analysis on survey data from 16 countries

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    Voluntary isolation is one of the most effective methods for individuals to help prevent the transmission of diseases such as COVID-19. Understanding why people leave their homes when advised not to do so and identifying what contextual factors predict this non-compliant behavior is essential for policymakers and public health officials. To provide insight on these factors, we collected data from 42,169 individuals across 16 countries. Participants responded to items inquiring about their socio-cultural environment, such as the adherence of fellow citizens, as well as their mental states, such as their level of loneliness and boredom. We trained random forest models to predict whether someone had left their home during a one-week period during which they were asked to voluntarily isolate themselves. The analyses indicated that overall, an increase in the feeling of being caged leads to an increased probability of leaving home. In addition, an increased feeling of responsibility and an increased fear of getting infected decreased the probability of leaving home. The models predicted compliance behavior with between 54% and 91% accuracy within each country’s sample. In addition, we modeled factors leading to risky behavior in the pandemic context. We observed an increased probability of visiting risky places as both the anticipated number of people and the importance of the activity increased. Conversely, the probability of visiting risky places increased as the perceived putative effectiveness of social distancing decreased. The variance explained in our models predicting risk ranged from < .01 to .54 by country. Together, our findings can inform behavioral interventions to increase adherence to lockdown recommendations in pandemic conditions.info:eu-repo/semantics/publishedVersio

    Non-Standard Errors

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    In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

    Biferroic electro – acoustic ceramics with BiFeO

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    Bismuth ferrite, one of a few multiferroics, has attracted much attention for many decades since 1960. BiFeO3 (BFO) belongs to perovskite class of complex oxides. BFO is one of only a few materials in which (anti)ferromagnetism and ferroelectricity coexis in room temperature. Authors prepared BiFeO3 ceramics by solid state reaction method. The synthesized powders were characterized by X-ray diffraction method. Thermogravimetric and differential thermal analysis were investigated. The microstructure of the BFO ceramics was investigated by means of scanning transmission electron microscopy, and the ferroelectric characteristic of BFO ceramics was demonstrated. BFO is very interesting ceramic material for potential applications in the memory devices, sensors, satellite communications, optical filters and smart devices

    Ceramic bismuth titanate for high – temperature electro-acoustic transducers

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    Bismuth titanate Bi4Ti3O12 (BIT), which belongs to the Aurivillius family, is one of the most interesting compounds among the bismuth-based layered ceramics. BIT is a ferroelectric material with wide applications in the electronic industry, as capacitors, transducers, memory devices and sensors. BIT ceramics materials with m= 3 were prepared by conventional mixed-oxide method by solid-state reaction. Thermal and mass change effects were analyzed in air by thermogravimetric and differential thermal analysis. The crystal structure of Bi4Ti3O12 was examined at room temperature with an X-ray diffraction method using the Rietveld method. Microstructure and chemical composition were analyzed. The investigation of dielectric proprieties of Bi4Ti3O12 ceramics shows that the BIT is ferroelectric with Tc about 675○C. Due to this high transition temperature, BIT ceramics is a good material for high temperature piezoelectric applications

    Processing and some properties of biferroic Bi

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    Bi5Ti3FeO15 (BTF) is an example of bifferoic Aurivillius phase with perovskite layered structure. Materials on the basis BTF are of substantial interest for new types of magnetoelectric device applications. In this review we discuss technology of preparation biferroic ceramic with composition Bi5Ti3FeO15. The ferroelectric layered Bi5Ti3FeO15 (BTF) Aurivillius phases were synthesized by solid-phase synthesis reaction from the conventional mixture of oxides, viz. Bi2O3, Fe2O3, TiO2. Thermal analysis and mass change efect were used to investigate synthesis effects in the stoichiometric mixture of powders. The crystalline structure was checked by X-ray diffraction method at room temperature. Microstructure was investigated by scanning electron microscopy

    Ceramic bismuth titanate for high – temperature electro-acoustic transducers

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