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Microstereolithography is capable of producing millimeter-scale polymer parts having micron-scale features. Material properties of the cured polymers can vary depending on build parameters such as exposure. Current techniques for determining the material properties of these polymers are limited to static measurements via micro/nanoindentation, leaving the dynamic response undetermined. The purpose of this paper is to demonstrate a method to measure the dynamic response of additively manufactured parts to infer the dynamic modulus of the material in the ultrasonic range.

Frequency-dependent material parameters, such as the complex Young’s modulus, have been determined for other relaxing materials by measuring the wave speed and attenuation of an ultrasonic pulse traveling through the materials. This work uses laser Doppler velocimetry to measure propagating ultrasonic waves in a solid cylindrical waveguide produced using microstereolithography to determine the frequency-dependent material parameters of the polymer. Because the ultrasonic wavelength is comparable with the part size, a model that accounts for both geometric and viscoelastic dispersive effects is used to determine the material properties using experimental data.

The dynamic modulus in the ultrasonic range of 0.4-1.3 MHz was determined for a microstereolithography part. Results were corroborated by using the same experimental method for an acrylic part with known properties and by evaluating the natural frequency and storage modulus of the same microstereolithography part with a shaker table experiment.

The paper demonstrates a method for determining the dynamic modulus of additively manufactured parts, including relatively small parts fabricated with microstereolithography.

Communications regarding this column should be addressed to Mrs. Cheney, Peabody Library School, Nashville, Tenn. 37203. Mrs. Cheney does not sell the books listed here. They are available through normal trade sources. Mrs. Cheney, being a member of the editorial board of Pierian Press, will not review Pierian Press reference books in this column. Descriptions of Pierian Press reference books will be included elsewhere in this publication.

Purpose – We investigate the impact of overlapping crises of COVID-19 and the George Floyd protests on one major US police department, focusing on staffing and officer proactivity.

Methodology/Approach – The study investigates the impact of the two crises on operational capacity. Using Bayesian interrupted time-series analysis, the authors investigate if officer proactivity levels were adversely impacted in the short and long terms.

Findings – A statewide stay-at-home order (SAHO) was associated with a sharp decline in proactive contacts, but that effect dissipated quickly. However, the Floyd protests were associated with a sharp decline in proactivity, which persisted throughout the study period.

Originality/Value – The findings of this study contribute to ongoing research agendas that seek to understand the impact of dual, overlapping crises on US police departments and the communities they serve. The authors demonstrate a methodological approach capable of disentangling both crises’ effects on police activity levels.

When Trump entered the presidential race in 2015, many white evangelicals turned up their noses at his candidacy. By 2020, Trump had garnered such commitment from white evangelicals that not only did 80% vote for him, but 60% also refused to accept the election results after his loss. How did this transformation occur, and with what lasting results for the evangelical vote and US politics more broadly? This chapter shows that in the “new culture wars” of the Trump era, race has played an even more central and explicit role in religion and politics than it did in the past. Christian nationalism and the intersection of religion and race help explain the strong bond between Trump and many white evangelicals. COVID-19 vaccine refusal and critical race theory bans provide examples of the continuing significance of that bond. These cases demonstrate the likelihood that Trumpian politics will maintain influence over white evangelicals in the near future.

In the common law of the United ¹Kingdom the objective of any award of damages in personal injuries litigation is to achieve as nearly as possible full compensation for the claimant in respect of the injury sustained.² To achieve that objective the court seeks to award such sum as is notionally required to be laid out in the purchase of an annuity which will provide an annual amount equivalent to the loss for the whole period of the loss.³ The basis of the calculation is an assumed annuity. The court makes an assumption about how the award will be invested.⁴ Lord Fraser of Tullybelton in Cookson v. Knowles ⁵ put it thus:The assumed annuity will be made up partly of income on the principal sum awarded, and partly of capital obtained by gradual encroachment of the principal. The income element will be at its largest at the beginning of the period and will tend to decline, while the capital element will tend to increase until the principal is exhausted.The court is not, in fact, concerned with how the award will be spent:How the Plaintiffs will in fact invest their damages is, of course, irrelevant. That is a question for them. It cannot affect the calculation.⁶

Recent research has shown that constrained bistable structures can display negative stiffness behavior and provide extremal vibrational and acoustical absorptive capacity. These bistable structures are therefore compelling candidates for constructing new meta‐materials for noise reduction, anechoic coatings, and backing materials for broadband imaging transducers. To date, demonstrations of these capabilities have been primarily theoretical because the geometry of bistable elements is difficult to construct and refine with conventional manufacturing methods and materials. The purpose of this paper is to leverage the geometric design freedoms provided by selective laser sintering (SLS) technology to design and construct constrained bistable structures with negative stiffness behavior.

A meso‐scale negative stiffness system is designed and fabricated with SLS technology. The system includes a bistable structure in the form of a pre‐compressed/pre‐buckled beam. The dynamic transmissibility of the system is measured, and its behavior is compared to the predictions of analytical models.

Experimental results demonstrate that pre‐compression and pre‐buckling can be used to induce negative stiffness behavior and thereby increase the damping and shift the resonant frequency of an unconstrained beam.

The results support the usefulness of SLS and other additive manufacturing technologies for acoustic and dynamic applications. Specifically, the demonstrated advantages of SLS include the ability to rapidly redesign, functionally 2 prototype, and tune physical models for acoustic and dynamic experimentation. Of significant importance is the ability of SLS to enable consolidation of parts that are traditionally separate, thereby reducing vibrational noise in these systems. In this specific application, SLS enables a proof‐of‐concept comparison of the theoretical and experimental behavior of a meso‐scale negative stiffness system. The demonstrated acoustical and vibrational absorptive capacity of these systems is expected to lead to designs for new structures and materials that offer significantly improved energy absorbing capabilities over a broad range of tunable frequencies without compromising structural stiffness.

Most US activists place a high priority on elections. The default strategy for those seeking policy change is some combination of electoral campaigning and pressure campaigns targeting politicians. Yet policies show a high degree of continuity across recent presidential administrations. Despite substantial differences in rhetoric and legislative agendas, the policies resulting from Republican and Democratic presidencies have stayed within a narrow range, defined by the promotion of corporate profits, the impunity of law enforcement agencies, the defense of imperial prerogatives, and nearly unfettered ecological destruction. Focusing on the Trump and Biden presidencies, I analyze some of the structural barriers that inhibit major policy change. I also explore why the ruling class as a whole has not yet united against parasitic industries like fossil fuels and pharmaceuticals that endanger the interests of other capitalists. I argue that activists must move beyond electoral and legislative approaches by directly disrupting ruling-class interests that have the power to change policy. Only then will we win major progressive reform.

This collection of original papers had its origin in a series of annual meetings of the National Association of Forensic Economics (NAFE) held in Great Britain, Ireland, Italy, and the United States from 2004 to 2008.¹ NAFE sponsored these meetings to explore common research areas in the calculation of damages in personal injury and death litigation in Western Europe and the United States. NAFE was founded in 1986 and is the largest association of economists and other damages experts specializing in the calculation of economic damages in litigation in the United States and Canada. The Journal of Forensic Economics (JFE) is the journal of NAFE and has been the primary outlet of peer-reviewed research in forensic economics over the past 22 years. The field of forensic economics has generated a substantial literature on methodologies and empirical research in the calculation of damages in personal injury, death, employment, and commercial litigation; and the use of that literature in the United States and Canadian courts by economists, Certified Public Accounts (CPAs), and actuaries has become commonplace in the past two decades (Thornton & Ward, 1999).²

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