Electrostrictive effect in perovskites and its transducer applications

Properties of new electrostrictive materials for displacive transducers are reviewed including theoretical, material and design studies. Intensive investigation of the electrostrictive effects in ferroelectric and antiferroelectric perovskites have led to some empirical rules: the product of the electrostriction coefficientQ and the Curie-Weiss constantC is constant for all perovskite crystals and theQ value is proportional to the square of the thermal expansion coefficient,α. Consistent with the empirical rules, the relaxor ferroelectric ceramic 0.9 Pb(Mg_1/3Nb_2/3)O₃ −0.1 PbTiO₃ possesses much larger strain with lower hysteresis, aging effects and thermal expansion than that obtained with piezoelectric lead zirconate titanate (PZT). Using a multilayer configuration similar to commercial capacitors, a new mirror control device capable of large strains with high reproducibility, up toΔL/L ∼ 10⁻³, with only 200 V applied has been developed.     

Atom shifts,polarization levels,and curie temperatures in ferroelectric PbZrO3:PbTiO3 solid solutions

New data concerning the atomic shifts and polarization levels in some solid solutions in the Lead Zirconate: Lead Titanate system have been used to re-examine the empirical relations of Abrahams et al. for displacive ferroelectrics. It is shown that the relation between P_s and the homopolar atom shift δz is well followed, with a correlation coefficient of 2.51(7) C/m² ? Å. The second relation between T_c and δz, which is explicable on the Landau-Ginsburg-Devonshire theory if the transitions are near second order appears, however, to require different values of the correlation coefficient in the different ferroelectric structures.     

Temperature dependence of ferrobielastic switching in quartz

Using the piezoelectric effect, the variation of coercive stress with temperature for ferrobielastic switching in synthetic quartz crystals has been measured under unaxial load applied in a direction favoring Dauphiné twinning. It is found that the coercive stress decreases with increasing temperature from about 4×10⁸ Pa at room temperature to less than 10⁷ Pa near 300°C.     

Learning from design experience in an agent-based design system

A learning mechanism based on findings in cognitive science was added to an agent-based computational design system to determine if this mechanism would enable the system to learn from its experiences and transfer useful design knowledge to new problems. Learning and transfer were evaluated by examining how well knowledge learned while solving one problem could be applied to solve the same problem more effectively as well as how well this knowledge could be transferred to new design problems. An existing system, A-Design, was enhanced by giving it the ability to learn and store useful design knowledge so that this knowledge can be used in new design problems. Three electromechanical design problems were used to evaluate this new learning mechanism, and results indicate that this basic, cognitively based, learning mechanism is successful at transferring design knowledge to new problems with a few limitations. This knowledge transfer leads to a more effective design process.     

Materials for High Performance Cymbal Transducers

The effects of materials on the performance of the cymbal-type flextensional transducers were investigated under in-air and water-loaded conditions by finite element analysis (FEA) methods. At the initial stage, FEA and experimental studies were conducted in parallel to gain experience with the FEA models. Later, all calculations were carried out by computational methods: resonance frequencies, projector TVR, receiver FFVS, effective coupling coefficient (k_eff), and mechanical quality factor (Q_m) were calculated. Ceramic and endcap materials have strong effects on the TVR/FFVS performance of cymbal transducers. It is possible to tailor a wide range of flexural resonance frequencies by optimizing the ceramics used as the driver and the metals used as the endcaps.     

Seeded Stage III glass dissolution behavior of a statistically designed glass matrix

The dissolution rate of some glasses accelerates after prolonged time spent at a slow, residual dissolution rate. This phenomenon is referred to as Stage III behavior. The acceleration in glass dissolution rate linked to Stage III behavior is significant and may be the most impactful behavior to long-term performance of glass in a repository. This work is aimed at understanding the effect of glass composition on Stage III behavior to add a level of technical defensibility to glass disposal. To this end, a set of 24 glass compositions were statistically designed, where eight glass components (SiO₂, B₂O₃, Al₂O₃, CaO, Na₂O, SnO₂, ZrO₂, and Others) have been independently varied in order to study the individual effects of each glass component. These glasses have been subjected to static dissolution tests at 90°C in deionized water and then seeded with zeolite Na-P2 28 days into the testing to induce Stage III behavior. The response of the glasses to the zeolite seeds fell into four primary types: (1) no response to seeds; (2) an immediate linear sustained acceleration in the rate; (3) an immediate linear acceleration in the rate followed by a decrease; and (4) a progressive acceleration in the rate that is concurrent with the addition of the seeds. The main glass components observed to influence these behaviors were CaO, Al₂O₃, B₂O₃, and ZrO₂, where (1) CaO influenced which glasses showed a Stage III response to seeds (high CaO: types 2, 3, and 4) or did not respond to seeds (low CaO: type 1), (2) Al₂O₃ and B₂O₃ influenced which glasses showed a sustainable Stage III response (high Al₂O₃: types 2 and 4) versus transitory response (low Al₂O₃ and high B₂O₃: type 3), and (3) ZrO₂ concentration influenced whether glasses showed a linear (high ZrO₂: type 2) versus progressive (low ZrO₂: type 4) response to seeds.     

The Liquidus Temperature of Nuclear Waste Glasses: An International Round-Robin Study

Eight institutions from four countries participated in a round-robin study to determine the precision and bias of a liquidus temperature (T_L) procedure for waste glasses being adopted by ASTM International as ASTM C 1720-11. The participants of the round-robin study were asked to measure three different glasses with one or a combination of the following T_L measurement methods: a gradient temperature (GT) method, a uniform temperature (UT) method, and/or a crystal fraction extrapolation (CF) method. The T_L values reported by different institutions are generally consistent. The precision of T_L measurements with each method was evaluated and is presented herein. The round-robin glasses were all previously studied at Pacific Northwest National Laboratory and included ARG-1 (Glass A), Zr-9 (Glass B), and AmCm2-19 (Glass C), with measured T_L values spanning the temperature range of 960–1240°C. A precision (i.e., standard deviation) for T_L has been obtained from the data, even though the data were not acquired for all three glasses using all three methods from each participating organization. Also, the article provides a brief overview and the importance of the T_L measurement.     

The reliability and validity of the family history method for assessing pathological gambling and gambling involvement.

The family history (FH) method, which involves the use of an informant to gather information about one or more family members, has been used in a number of previous gambling studies. However, no evaluation of the reliability and validity has been conducted on the use of the FH method for assessing pathological gambling (PG) and gambling involvement. The current study examined the test-retest and inter-rater reliability and the validity of the FH method for assessing PG and gambling involvement among a large community-based sample of adult twins (N = 4,764) reporting on their parents, co-twins, and spouses. The test-retest and inter-rater reliabilities of the FH reports of PG were high. Validity of the FH reports of PG was low, primarily because of substantial underestimation of pathology (low sensitivity). The test-retest and inter-rater reliabilities of the FH reports of gambling involvement (ever gambled, ever gambled monthly, and ever gambled weekly) were moderate and the sensitivities were quite high. The results of this study support the use of the FH method for studies of PG and gambling involvement. A number of potential explanations for the low sensitivity of FH reports of PG are elaborated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermomechanical characterization of thermoplastic polyimide–polyurea to improve the chain interaction via internal hydrogen bonds

Recently, we have studied polyimides (PIs) synthesized by incorporating an aromatic diamine monomer with a methylene linker, 4,4′‐methylenebis(2,6‐dimethylaniline), to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to reduce rigidity. In this report, we incorporate a urea linkage into these materials in order to observe the effect of additional hydrogen bonding. The polymers are designed to exhibit thermal properties in between those of conventional aromatic PIs and polymers with wholly aliphatic ether diamine links. Herein, we demonstrate that the addition of 1,6 hexamethylene diisocyanate and the increase of hydrogen bonds at the urea linkage can be used to improve the thermal and mechanical properties of the PI. Furthermore, the imide ring is an important component to maintain the thermal stability characteristics in polyimide–polyurea hybrids. The polymers were characterized by FTIR, thermomechanical and calorimetric analysis, microhardness, and tensile testing. POLYM. ENG. SCI., 59:1948–1959, 2019. © 2019 Society of Plastics Engineers