Research on the school discipline gap reveals growing awareness of the disproportionate impact on students of color; however, dynamics of the racial discipline gap remain underanalyzed. This article uses risk ratios to descriptively establish if ethnic disproportionality in school discipline is present among Asian American and Pacific Islander (AAPI) subgroups. We find that when AAPI data are disaggregated, significant variations in discipline patterns emerge. Pacific Islanders are nearly twice as likely as their White peers to be disciplined when separated from Asian Americans, and all Pacific Islander subgroups are at equal or higher risk for discipline. We also find a discipline gap between ethnic subgroups. Our findings affirm the need to further refine the analyses of race and school discipline.
We seek to advance the topic of large-scale space structures for low-frequency radio interferometry enabled by self-folding shape memory polymers (SMPs). Large-scale space structures, greater than 1 km in diameter, are necessary to unlock the secrets of the cosmological dark ages. Two important considerations in developing such large structures are their ability to deploy to the desired configuration in space and their resilience to harsh space environments, which include UV radiation, atomic oxygen, and thermal cycling under vacuum. These environments lead to long-term degradation and erosion of even the most resilient materials. Degradation of SMPs in space applications has potential to affect both material properties and shape-memory performance. Although a plethora of materials have been evaluated in space conditions, the coupled effects of simultaneous space environments on the properties and shape memory performance of polymers has not been evaluated sufficiently. In this study, we evaluate the effects of relevant space environments on the thermomechanical properties of candidate SMPs using laboratory-based experiments. Representative SMP samples are subjected to UV-Oxygen for varying durations. The effects of these environments on material properties for various amounts of exposure are evaluated using differential scanning calorimetry and dynamic mechanical analysis. Knowledge gained from this study includes how the shape recovery required for in-space deployment is affected by space environments and the resilience of these structures to long-term space exposure. Through improved understanding of the effects of space environments on SMP properties and performance, we can advance the field of low-cost, lightweight, self-deploying space structures.
Self-folding origami utilizes shape memory polymers (SMPs) to enable deployable space structures, such as those intended for large-scale, low-frequency radio interferometry. The size of structure that may be deployed is limited by the capacity of the smart material to do work. Previous studies focused on activation mechanisms and the kinematics of self-folding polymers, but have largely neglected an evaluation of the energy stored in the folding hinge. This paper seeks to characterize the work done by self-folding origami hinges made of pre-strained polystyrene (PSPS) as it deforms due to the shape-memory effect. SMP samples are patterned with black ink hinges and exposed to an infrared (IR) light. The ink absorbs thermal energy from the light, which leads to local heating and shrinking in the hinge region. Activation of the self-folding response, e.g. shrinking, occurs when the material reaches a temperature higher than its glass transition temperature, and a gradient in shrinking causes the sample to fold. The self-folding process is sensitive to physical constraints and changes in energy input into the sample. Thus, we will evaluate the energy stored in the self-folding hinge by measuring the work done under varying thermal stimuli in an array of tests that include universal material shrinkage and single-hinge folds. We evaluate hinge torque based on a dynamic analysis of the motion of the self-folding sheet. Quantification of the capacity of self-folding origami hinges to do work enables the design of deployable space structures by not only considering the activation mechanism and self-folding kinematics, but also accounts for the size of structure that may be deployed.
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