Smoothing with Mixed Model Software

Smoothing methods that use basis functions with penalization can be formulated as fits in a mixed model framework. One of the major benefits is that software for mixed model analysis can be used for smoothing. We illustrate this for several smoothing models such as additive and varying coefficient models for both S-PLUS and SAS software. Code for each of the illustrations is available on the Internet.

OPTIMIZING PROCESS CONDITIONS AND CHARACTERIZING ELASTOMERIC PROPERTIES OF IMMISCIBLE POLYMERS FOR 3D PRINTING APPLICATIONS

Within recent years, 3D printing within the plastics and polymer industries has becoming increasingly prevalent. Also known as additive manufacturing, 3D printing enables the creation of rapid prototypes for short production runs without the need for complex tooling. This allows for runs that are shorter and lower in cost than conventional processes. Polylactic acid (PLA) is a thermoplastic that is widely used in 3D printing for its mechanical properties and low cost. The qualities of PLA however are lacking in the areas of flexibility and toughness which is required in many prototyping scenarios. The solution to this is to incorporate TPU (thermoplastic polyurethane) within the matrix of PLA to address the issue with flexibility. There is another issue that arises with incorporating TPU within the PLA matrix. These materials are immiscible which poses a problem with creating filament within the needed specifications. The goal of this work was to blend PLA and TPU to create a 3D printer filament that exhibits the desirable properties from each material. An additional goal was to optimize the filament diameter to increase compatibility with the feed throat of the 3D printer, which allows for increased consistency of parts. During the extrusion process, parameters such as screw speed, winder settings, and barrel temperatures were adjusted to try and create circular filament within the set specifications of 1.75 mm (+/- 0.05 mm). Both PLA and TPU were extruded at various ratios by weight percentage. Single-screw extrusion was performed on a Yellow Jacket single-screw extruder in processing labs at Pittsburg State University. After processing, filament was analyzed for its thermal, mechanical, and morphological properties. The methods used for thermal analysis were differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and melt flow index rheology. TGA was performed to determine degradation onset of the blends and DSC was performed to determine glass transition temperatures and melting temperatures of the crystalline fractions. Mechanical properties were analyzed via Instron tensile testing. Blends increasing in TPU percentage exhibited a change in strength and flexibility. Morphological analysis was performed via scanning electron microscopy (SEM). Furthermore, the transition between thermoplastic behavior and elastomeric behavior with increasing TPU corporation was studied. In prior studies, glass transition temperatures and filament moduli shifted to values similar to TPU when the blend ratio was above 50% TPU. The filament was successfully produced and exhibited properties intermediate to PLA and TPU. After filament was created successfully via single-screw extruder, filament blends were then created via twin-screw extrusion. This was done in order to determine if processing methods had a significant impact on filament blend properties. Various parameters, such as screw speed, hopper speed, zone temperatures, and winder speed were adjusted to achieve a filament within the desired specifications. Filament extruded via twin-screw extrusion was analyzed for thermal, mechanical, and morphological properties. Twin-screw filament was analyzed by the same thermal and mechanical methods as single-screw filament. The filament produced via twin-screw extrusion was within the specified diameter and was more dimensionally stable than filament produced by single-screw extrusion. Twin-screw extruded filament had less variation in melt pressure than filament produced by single screw extrusion. Thermal stability of filament blends was consistent regardless of processing methods. Mechanical analysis concluded that the modulus of twin-screw filament was slightly lower than single-screw filament. Melt flow index of pellets was significantly higher in single-screw extruded pellet than twin screw extruded pellet. Further work added an additional processing step: injection molding. Thermal, mechanical, and morphological analyses were also performed on specimens produced via injection molding. Injection molded samples were analyzed by the same thermal and mechanical methods as single-screw and twin-screw filament. Impact testing was added, as we were able to produce impact bars in addition to tensile testing dog bones in the injection molder. Finally, we were able to 3D print dog bones using the filament produced by single-screw and twin-screw extrusion. Dog bones were tested for tensile strength after printing and compared to injection molded dog bones

Aquatic biogeochemical eddy covariance fluxes in the presence of waves

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Long, M. H. Aquatic biogeochemical eddy covariance fluxes in the presence of waves. Journal of Geophysical Research: Oceans, 126(2), (2021): e2020JC016637, https://doi.org/10.1029/2020JC016637.The eddy covariance (EC) technique is a powerful tool for measuring atmospheric exchange rates that was recently adapted by biogeochemists to measure aquatic oxygen fluxes. A review of aquatic biogeochemical EC literature revealed that the majority of studies were conducted in shallow waters where waves were likely present, and that waves biased sensor and turbulence measurements. This review identified that larger measurement heights shifted turbulence to lower frequencies, producing a spectral gap between turbulence and wave frequencies. However, some studies sampled too close to the boundary to allow for a spectral turbulence‐wave gap, and a change in how EC measurements are conducted and analyzed is needed to remove wave‐bias. EC fluxes have only been derived from the time‐averaged product of vertical velocity and oxygen, often resulting in wave‐bias. Presented is a new analysis framework for removing wave‐bias by accumulation of cross‐power spectral densities below wave frequencies. This analysis framework also includes new measurement guidelines based on wave period, currents, and measurement heights. This framework is applied to sand, seagrass, and reef environments where traditional EC analysis resulted in wave‐bias of 7.0% ± 9.2% error in biogeochemical (oxygen and H+) fluxes, while more variable and higher error was evident in momentum fluxes (10.5% ± 21.0% error). It is anticipated that this framework will lead to significant changes in how EC measurements are conducted and evaluated, and help overcome the major limitations caused by wave‐sensitive and slow‐response sensors, potentially expanding new chemical tracer applications and more widespread use of the EC technique.This work was supported by the Independent Research & Development Program at WHOI grant 25307and NSF OCE grants 1657727 and 1633951

An on-line velocity flow profiling system using electrical resistance tomography

A system to display velocity profiles of flows through the CPUT FPRC pipe test loop on-line has been developed. An electrical resistance tomography instrument developed at the University of Cape Town is used to generate conductivity profiles through cross sections of the flow in a 057mm pipe at two points, separated by either 50 or 100mm. The two concentration profiles are cross correlated on a pixel-wise basis to produce a velocity profile. The software was developed using C++ and employs a highly modular structure that allows different image reconstruction and cross correlation algorithms to be implemented without substantial changes to the rest of the application. Results showing the speed performance of the system are presented as well as typical velocity profiles from a sliding bed flow regime

Enthusiastic Jew and Lover of Humanity : August Bondi and the Roots of Transnational Freedom during the Long Nineteenth Century

Migration is a decidedly human condition that has influenced the development of all nations. Yet the cultural and demographic impacts upon the United States during the long nineteenth century brought about by the mass movements of peoples from Africa, Europe, and beyond were especially pronounced. Immigrants to North America brought with them more than linguistic and cultural artifacts, however; propelled by intellectual currents in their countries of origin, they often carried with them a sensibility of revolution, radical republican politics, and a moral suasion that they employed as they navigated the political and social realities in their new countries. Many immigrants would come to view America and the New World generally through a prism of their own making, and thus see opportunity to dismantle and remake the world – economically, socially, culturally, and politically – when conditions at home had failed them. Two fundamental events shaped this trans-Atlantic consciousness situated toward revolution during the nineteenth century: the European Revolutions of 1848-51, and an increasingly radical anti-slavery and abolitionist movement in the United States during the lead-up to sectional conflict and the Civil War. Both events sought to upend the established order through political, social, and cultural revolution, and both came to reinforce one another intellectually and strategically. Both revolutions sought to attack the existing systems – monarchy, capital, and the legal institutions that upheld slavery – and replace them, in the spirit of revolutions prior, with more egalitarian and liberal structures. Immigrants were often the main vehicles of this transnational cooperation. When it became clear to freedom fighters on both sides of the Atlantic that moral and political gradualism toward parliamentary, democratic systems of governance, or toward anti-slavery and abolitionist movements, were to be ineffective, they would turn to markedly more radical approaches, and sometimes to violence to enact the changes they sought. This paper investigates these broad trends through the individuals who personally lived them. One such figure, August (Anshl) Mendel Bondi, was a German-speaking, Hungarian Jew who participated in the revolutionary events in Vienna. Upon the restoration of the Hapsburg Monarchy, Bondi would be forced to flee with his family to the United States. Forging a new life in his new home, he would variously spend time in Louisiana and Texas, and work as a waterman on the Mississippi River. Eventually he would settle in Kansas Territory, where he became radicalized and joined Free Soilers in their fight against pro-slavery forces and Missouri border ruffians. Riding with John Brown during the Bleeding Kansas episode would inspire Bondi to a lifetime of freedom fighting; he and his eventual wife, Henrietta Einstein, another German-speaking immigrant from Bavaria, would be pivotal in establishing stops along the Underground Railroad

Mapping the invisible hand: a body model of a phantom limb

After amputation, individuals often have vivid experiences of their absent limb (i.e., a phantom limb). Therefore, one’s conscious image of one’s body cannot depend on peripheral input only (Ramachandran & Hirstein, 1998). However, the origin of phantom sensations is hotly debated. Reports of vivid phantoms in the case of congenital absence of the limb show that memory of former body state is not necessary (Brugger et al., 2000). According to one view, phantoms may reflect innate organization of sensorimotor cortices (Melzack, 1990). Alternatively, phantoms could reflect generalization from viewing other people’s bodies (Brugger et al., 2000), a sensorimotor example of the classic theory that understanding oneself follows from understanding the “generalized other” (Mead, 1934, p. 154). Because phantom limbs cannot be stimulated, sensory testing cannot directly compare visual and somatosensory influences on representations of phantom limbs. Consequently, empirical investigation of phantoms is limited