Article Database

Piezoelectric and Dielectric Properties of PZT–Cement–Aluminum Nano-Composites

Abstract:

Three-phase piezoelectric composites that were comprised of PZT, nano-sized aluminum (18 nm) and Portland cement were prepared via a normal mixing and spreading method. The volume fraction of Al was held constant at 0.02, while the volume fraction of PZT was varied from 0.10 to 0.70. The dielectric constant, tan (δ), and piezoelectric coefficient were experimentally investigated as a function of PZT volume fraction were found to possess higher dielectric constants, than their two-phase counterparts (PZT and Portland cement). A comprehensive age study of the piezoelectric and dielectric properties is presented, where significant reductions in material performance occurred within 2 days of sample preparation, and to a lesser degree after 400 days for piezoelectric properties. Properties of the composites are believed to be influenced by the oxidation of aluminum by the alkaline constituents in the cement matrix, distribution of fillers within the cement matrix and air voids.

POWER (Power Optimization for Wireless Energy Requirements): A MATLAB Based Algorithm for Design of Hybrid Energy Systems

Abstract:

We have expanded and implemented an algorithm for selecting power supplies into a turnkey MATLAB code, “POWER” (power optimization for wireless energy requirements). Our algorithm uses three approaches to system design, specifying either: (1) a single, aggregate power profile; (2) a power system designed to satisfy several power ranges (micro-, milli- and Watt); or (3) a power system designed to be housed within specified spaces within the system. POWER was verified by conducting two case studies on hearing prosthetics: the TICA (LZ 3001) (Baumann group at the Tübingen University) and Amadeus cochlear implant (CI) (WIMS-ERC at the University of Michigan) based on a volume constraint of 2 cm³. The most suitable solution identified by POWER for the TICA device came from Approach 1, wherein one secondary cell provided 26,000 cycles of 16 h operation. POWER identified Approach 2 as the solution for the WIMS-ERC Amadeus CI, which consisted of 1 cell for the microWatt power range and 1 cell for the milliWatt range (4.43 cm³, ∼55% higher than the target volume), and provided 3280 cycles of 16 h operation (including re-charge of the batteries). Future work will be focused on continuously improving our present tool.

Fabrication of Dome-Shaped PZT-Epoxy Actuator Using Modified Solvent and Spin Coating Technique

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An Algorithm for Selection and Design of Hybrid Power Supplies for MEMS with a Case Study of a Micro-Gas Chromatograph System

Abstract:

The Wireless Integrated Microsystems (WIMS)-environmental monitor testbed (EMT) is a multi-component microelectromechanical system (MEMS), incorporating complementary metal oxide semiconductor (CMOS) materials for high-precision circuits used for integrated sensors such as micro-g accelerometers, micro-gyroscopes, and pressure sensors. The WIMS–EMT duty cycle, like many autonomous MEMS systems, has low-power standby periods for sensing, and high-power pulses for R/F transmission and reception. In this paper, we present results of three strategies for providing power to this system, including (1) specification of a single, aggregate power supply, resulting in a single battery electrochemistry and cell size; (2) specification of several power supplies, by a priori division of power sources by power range; and (3) specification of an arbitrary number of power “bundles,” based on available space in the device. The second approach provided the best results of mass (0.032 kg) and volume (0.028 L) among the three approaches. The second and third approaches provided the best battery lifetime results; both systems produced lifetimes in excess of 2E3 h. Future work will incorporate CMOS operational amplifier (op-amp) technologies to accommodate large voltage fluxes in many MEMS devices, and implementation of our approaches into a user-friendly code.

Influence of Al Particle Size and Lead Zirconate Titanate (PZT) Volume Fraction on the Dielectric Properties of PZT-Epoxy-Aluminum Composites

Abstract:

Two-phase PZT-epoxy piezoelectric composites and three phase PZT-epoxy-Al composites were fabricated using a poling voltage of 0.2 kV/mm. The influence of aluminum inclusion size (nano and micron) and (lead zirconate titanate) PZT volume fraction on the dielectric properties of the three phase PZT-epoxy-aluminum composites were experimentally investigated. In general, dielectric and piezoelectric properties of the PZT-epoxy matrix were improved with the addition of aluminum particles. Composites that were comprised of micron scale aluminum inclusions demonstrated higher piezoelectric d₃₃-strain-coefficients, and higher dielectric loss compared to composites that were comprised of nanosize aluminum inclusions. Specifically, composites comprised of micron sized aluminum particles and PZT volume fractions of 20%, 30%, and 40% had dielectric constants equal to 405.7, 661.4, and 727.8 (pC/N), respectively, while composites comprised of nanosize aluminum particles with the same PZT volume fractions, had dielectric constants equal to 233.28, 568.81, and 657.41 (pC/N), respectively. The electromechanical properties of the composites are influenced by several factors: inclusion agglomeration, contact resistance between particles, and air voids. These composites may be useful for several applications: structural health monitoring, energy harvesting, and acoustic liners.

Showtime: Pop Culture’s Impact on Society’s View of the LGBTQ Population

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Popular culture is an influential aspect that shapes society. Popular culture’s impact on society’s view of the LGBTQ population was examined in the context of video media representations. Students at a Mid-Atlantic university (n = 7) were presented with representations of LGBTQ individuals in television media during two focus groups. Participants completed pre-and-post-test qualitative surveys regarding their impact and perceptions. Responses were coded to identify themes of the target populations. Misrepresentations, perpetuated stereotypes, changing perspectives, advocacy, personal connection, differing types of media representation, and lack of representation were themes identified throughout participant responses about the varying popular culture mediums.

Interprofessional Collaboration Among Helping Professions: Experiences with Holistic Client Care

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Exploring the Relationships Among Practitioners’ Consultation Skills, Competence to Counsel Lesbian, Gay, and Bisexual Clients, and Attitudes Toward Transgender People

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Consultation is an intervention that can diffuse expertise in lesbian, gay, bisexual, transgender, and questioning (LGBTQ) issues throughout systems of care. Practitioners (N = 145) were surveyed on their lesbian, gay, and bisexual (LGB) counseling competence, attitudes toward transgender people, and consultation skills. Hierarchical multiple regression analysis identified that consultation competence significantly influenced (p ≤ .01) LGB counseling skills over and above LGB knowledge and awareness, attitudes toward transgender people, and participant demographic characteristics. The domains of LGB competence and attitudes toward transgender people were also significantly correlated within the participant sample. Implications for practice, training, and future research are discussed.

The Value and Importance of International Service Learning Programs: A Model for Human Service Education

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Given our growing globalized society, students are studying abroad at increasing rates. While different formats of study abroad programs exist, there is a surge in the number of short-term international service learning programs. This manuscript defines service learning and discusses the benefits of international service learning programs, specifically for human service students. The manuscript will conclude with a model of a successful study abroad program in San Jose, Costa Rica for undergraduate human service students led by two faculty members.

Inclusion of “Human Service Professional” in the Standard Classification Occupation System

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The human services field has continued to grow, and today, it is considered one of the major social services professions. Despite its establishment, the Standard Occupational Classification (SOC) continues to exclude the term “human service professional” from its classification system. This manuscript encourages advocacy for such inclusion.