Diameter Fluctuations Research Articles

Study of Deformation Stability during Semi-Dieless Drawing of Ti-6Al-4V Alloy Wire.

A semi-dieless drawing technology has the advantages of producing a large deformation in a single pass and achieving high-precision dimensions of the finished products. However, instabilities can easily occur in a technique with a large amount of deformation, resulting in its failure. Herein, the deformation behavior of a wire during semi-dieless drawing is studied by finite element simulations. The instability mechanism of the semi-dieless drawing is proposed and validated by experiments. The experiments are conducted under the following conditions: a heating temperature of 950 °C; a distance between the die and heating coil of 20 mm; a feeding speed of 0.25 mm/s; a drawing speed range of 0.38–0.53 mm/s, and a die diameter range of 1.8–2.4 mm. The results show that by increasing the drawing speed or decreasing die diameter, the diameter fluctuation of the dieless drawn wire increases, and the semi-dieless drawing process easily becomes unstable. The diameter of the entering wire shows a fluctuating increasing trend owing to the variation in the drawing speed, which results in the instability during the semi-dieless drawing. The validity of the finite element model is verified by comparing the numerically predicted value and experimentally measured value of the drawn wire diameter.

Model for Acoustic Induced Aluminum Combustion Fluctuations in Solid Rocket Motors

Combustion of aluminum droplets released by the solid propellant is widely used to increase the thrust in solid rocket motors. The combustion dynamics of the released droplet cloud in the unsteady flow is however susceptible to trigger thermoacoustic instabilities. A theoretical analysis is conducted to determine the heat release rate fluctuations produced by the burning droplet cloud for small acoustic disturbances. Two contributions to heat release fluctuations are identified. The first originates from fluctuations of the evaporation rate due to the oscillating flow around the droplets. This leads to local fluctuations of the volumetric rate of heat release within the droplet cloud. The second one originates from the motion of the boundary of the burning droplet cloud at the end of the combustion process. This motion is due to droplet lifetime oscillations leading to an additional source of heat release disturbances. Both contributions to heat release disturbances take place within the acoustic boundary layer along the solid propellant surface. Quasi-steady models for the response of the droplet diameter fluctuations and droplet velocity fluctuations are derived. Combined with a model for the gas velocity fluctuations within the acoustic boundary layer they lead to expressions for the resulting heat release rate disturbances within the droplet cloud and at its boundary. Results are compared to a previous low order model and to numerical flow simulations. It is shown that the new model leads to close agreement with simulations over the entire flow. The derived expressions yield a better understanding on heat release disturbances and can be used to predict the linear stability of a solid rocket motor at reduced computational costs.

Optimization of silica glass capillary and rods drawing process.

Diameter fluctuations of silica glass rods and capillaries, during drawing process have been studied. We investigated an influence of drawing conditions on the quality of capillaries and rods. We fabricated two preforms made from different quality material. Fabricated preforms were used to draw microstructured fibers. Full Text: PDF ReferencesS. Habib et al., "Broadband dispersion compensation of conventional single mode fibers using microstructure optical fibers", Int. J. Lig. Opt. 124, 3851-3855 (2013) CrossRef A. Ziolowicz et al. "Overcoming the capacity crunch: ITU-T G.657.B3 compatible 7-core and 19-core hole-assisted fibers", Proc SPIE 10130, 101300C (2017) CrossRef T.M. Monro et al. "Sensing with microstructured optical fibres", Meas. Sci. Technol. 12, 854-858 (2001) CrossRef G. Statkiewicz-Barabach et al.,"Hydrostatic Pressure and Temperature Measurements Using an In-Line Mach-Zehnder Interferometer Based on a Two-Mode Highly Birefringent Microstructured Fiber", Sensors 2017, 17, 1648 (2017) CrossRef T. Yoon, M. Bajcsy, "Laser-cooled cesium atoms confined with a magic-wavelength dipole trap inside a hollow-core photonic-bandgap fiber", Phys. Rev. A 99, 023415 (2019) CrossRef A.N. Ghosh et al., "Supercontinuum generation in heavy-metal oxide glass based suspended-core photonic crystal fibers", J. Opt. Soc. Am. B 35, 2311-2316 (2018) CrossRef G. Wójcik et al. "Microbending losses in optical fibers with different cross-sections", Proc. SPIE 10830, 108300H (2018) CrossRef F. Xu, Selected topics on optical fiber technology and applications (IntechOpen 2018) CrossRef

Determination of the optimal extrusion temperature of the PMMA optical fibers

The aim of this work was to determine optimal extrusion temperature for polymer optical fibers. For preliminary studies poly(methyl methacrylate) (PMMA) granulate was used. Samples of commercially available PMMA were subjected to four different temperatures in which were kept in oven for three different period of time. To examine the changes in the chemical structure of the polymer, an ATR-FT-IR (Attenuation Total Reflection Fourier Transform Infrared Spectroscopy) was chosen. Full Text: PDF ReferencesK. Peters, "Polymer optical fiber sensors—a review", Smart Mater. Struct. 20, 013002 (2011) CrossRef O. Ziemann, J. Krauser, P.E. Zamzow, W. Daum, "POF Polymer Optical Fibers for Data Communication" (New York, Springer-Verlag Berlin Heidelberg 2002). CrossRef M.A. van Eijkelenborg, M.C.J. Large, A. Argyros, J. Zagari, S. Manos, N.A. Issa, I. Bassett, S. Fleming, R.C. McPhedran, C. Martijn de Sterke, N.A.P. Nicorovici, "Microstructured polymer optical fibre", Opt Express 9, 319 (2001). CrossRef O. Çetinkaya, G. Wojcik, P. Mergo, "Decreasing diameter fluctuation of polymer optical fiber with optimized drawing conditions", Mater Res Express 5, 1 (2018). CrossRef P. Mergo, M. Gil, K. Skorupski, J. Klimek, G. Wójcik, J. Pędzisz, J. Kopec, K. Poruraj, L. Czyzewska, A. Walewski, A. Gorgol, "Low loss poly(methyl methacrylate) useful in polymer optical fibres technology", Phot. Lett. Poland, 5, 170 (2013). CrossRef J. Grdadolnik, "ATR-FTIR Spectroscopy: Its advantages and limitations", Acta Chim Slov. 49, 631 (2002). DirectLink P. Borowski, S. Pasieczna-Patkowska, M. Barczak, K. Pilorz, "Theoretical Determination of the Infrared Spectra of Amorphous Polymers", J Phys Chem A 116, 7424 (2012). CrossRef G. Socrates, "Infrared and Raman Characteristic Group Frequencies Tables and Charts" Third Edition (Baffins Lane Chichester, John Wiley & Sons Ltd 2001). DirectLink W. Schnabel, Polymer Degradation Principles and Practical Applications (Berlin, Akademie-Verlag 1981). DirectLink

Pattern of trunk diameter fluctuations of almond trees in deficit irrigation scheduling during the first seasons

Irrigation needs in mature almond orchards are very high. Although almond trees grow in rainfed conditions, the yield response is very sensitive to irrigation. Continuous monitoring of the water status could be an adequate tool to optimize deficit irrigation. In this sense, trunk diameter fluctuations appeared as a very promising indicator at the beginning of the century, but few data have been published. The aim of this work is to check threshold values of maximum daily shrikage (MDS) and identify possible limitations to their use in commercial orchards. The experiment was performed in a commercial farm in Dos Hermanas (Seville, Spain) during the 2017 season on a 7-years-old orchard (cv Vairo). The irrigation treatments were Control (100% ETc), sustained deficit irrigation (SDI) with a maximum seasonal irrigation of 100 mm and two regulated deficit treatments (RDI). Both RDI treatments (RDI-1 and RDI-2) were scheduled using the signal of maximum daily shrinkage (signal) and the midday stem water potential (SWP). In RDI-1, full irrigation conditions were provided before kernel filling and during postharvest, using the threshold values suggested in the bibliography. During kernel filling, the water stress level was designed to be -1.5 MPa (SWP) and 1.75 (signal). RDI-2 trees were irrigated using the same scheduling as RDI-1, but target water stress values were higher in kernel filling (-2 MPa and 2.75) and with a maximum seasonal amount of water of 100 mm. SWP in Control trees was near the McCutchan and Shackel baseline for most of the season. None of the deficit treatments reached the signal values suggested. Moreover, the signal values were almost equal between treatments, with no water stress effect. The trunk growth rate (TGR) presented clear differences depending on the water status.

Harnessing MSC Osteoprogenitor Subpopulations to Augment Hematopoietic Transplantations

Adjuvant MSC infusions could improve transplantation outcomes via suppression of graft-vs-host reactions and enhancement of HSPC engraftment. However, bone marrow (BM) MSCs are a heterogeneous cell population, particularly when culture expanded to obtain therapeutically relevant cell numbers. A systematic study of expanded subpopulations is hindered by the lack of unique surface markers. In lieu of immunophenotype, we hypothesized and verified that biophysical properties of MSCs can be a useful strategy for isolating unique subpopulations. Here, we will describe a clinically relevant biophysical strategy for deriving different MSC subpopulations and discuss their potential utility in the context of hematopoietic transplantation. Cell diameter, membrane stiffness and nuclear membrane fluctuations are collectively predictive of at least two MSC subpopulations (multipotent and osteoprogenitors). Both MSC subpopulations are distinct in their transcriptome (different signatures of VEGF, IL8, ANG1, etc) and differentiation potential (osteogenic and adipogenic) but no surface marker reliably distinguishes them apart. In functional assays, osteoprogenitor vs multipotent MSCs show stronger capacities for CD34+CD38−HSPC expansion (Day 10: 42.7 ± 6.21 vs 29.1 ± 8.27, n = 5, respectively), but no significant differences (n = 3 biological repeats) in their ability to suppress CD8+T-cell proliferation in mixed lymphocyte reactions. When used as a rescue therapy for lethal irradiation, osteoprogenitors improved survival rates by 30-40% compared to multipotent MSCs. Part of the recovery process was prompted by MSC secretome mediated stimulation of BM tissue repair, including increased cell proliferation, reduced inflammation and the restoration of niche environments. These paracrine effects may be beneficial in fostering favorable post-myeloablative BM environments for donor HSPCs to home, engraft and survive. In murine transplantation models, we observed a higher rate of early engraftment following adjuvant therapy with osteoprogenitors. Week 4 CD45 chimerism in peripheral blood was 2- to 3- fold higher (∼11% vs ∼4%) in the osteoprogenitor treated group compared to the other MSC groups. These results demonstrate heterogeneity in expanded MSCs populations that would lead to inconsistencies in their overall properties. Newer biophysical technologies have the potential for isolating useful subpopulations defined by key quality attributes for specific forms of MSC-therapy; these capabilities may advance MSC-based therapy for regenerative medicine. Here, we demonstrate the augmentation of HSPC transplants in murine models using a biophysically isolated osteogenic MSC subpopulation (osteoprogenitors) which led to the fastest engraftment rates; this may be due to their superior abilities for promoting BM tissue regeneration as well as hematopoietic expansion.

Assessing pain in the postoperative period: Analgesia Nociception IndexTMversus pupillometry

BackgroundPotential methods for objective assessment of postoperative pain include the Analgesia Nociception Index™ (ANI), a real-time index of the parasympathetic tone, the pupillary light reflex (PLR), and the variation coefficient of pupillary diameter (VCPD), a measure of pupillary diameter (PD) fluctuations. Until now, the literature is divided as to their respective accuracy magnitudes for assessing a patient's pain. The VCPD has been demonstrated to strongly correlate with pain in an obstetrical population. However, the pain induced by obstetrical labour is different, given its intermittent nature, than the pain observed during the postoperative period. The aim of the current study was to compare the respective values of these variables at VAS scores ≥4. MethodsAfter approval by the Ethics Committee, 345 patients aged on average 50 (SD 17) yr (range: 18–91 yr) of age were included. The protocols of general anaesthesia and postoperative analgesia were left to the anaesthetist's discretion. Some 40 min after tracheal intubation, VAS, ANI, PD, PLR, and VCPD values were recorded. ResultsVCPD correlates more strongly (r=0.78) with pain as assessed with the VAS than ANI (r=−0.15). PD and PLR are not statistically correlated with VAS. The ability of VCPD to assess the pain of patients (VAS≥4) is strong [area under the curve (AUC): 0.92, confidence interval (CI): 0.89–0.95], and better than for ANI (AUC: 0.39, CI: 0.33–0.45). ConclusionsOur study suggests that VCPD could be a useful tool for monitoring pain in conscious patients during the postoperative period. Clinical trial registrationNCT 03267979.

The characteristics of high-quality Yb:YAG single crystal fibers grown by a LHPG method and the effects of their discoloration.

Single crystal fibers (SCFs), especially ytterbium (Yb) doped crystal fibers, have great potential in the field of high-power lasers. Colorless Yb:YAG single crystal fibers were fabricated using a laser heated pedestal growth (LHPG) method with a diameter fluctuation of less than 2% and a length to diameter ratio greater than 320 : 1. An abnormal color issue exists with respect to Yb:YAG crystals. The origin of coloration was studied via density functional theory, single-crystal X-ray diffraction, XPS and Raman spectroscopy and it was confirmed that the cyan coloration of Yb:YAG crystals is due to oxygen vacancies. Yb:YAG SCFs prepared via the LHPG method could avoid this type of defect due to the large specific surface area and melt convection caused by surface tension. The fundamental properties of the cyan Yb:YAG crystal source rod and colorless Yb:YAG SCFs were systematically investigated. The colorless Yb:YAG SCFs have higher infrared transmittance and thermal conductivity. The distributions of Yb3+ along the radial and axial directions were also measured. Meanwhile we demonstrated the propagation loss and a fiber laser using the colorless Yb:YAG SCFs, obtaining a minimum loss coefficient of 0.008 dB cm−1 and a maximum continuous-wave (CW) output power of 3.62 W. The colorless Yb:YAG SCFs with good thermal conductivity, low propagation loss, wide transparency and uniform ion distribution show promise for acting as the host material in single-mode lasers.

Deficit irrigation in commercial mandarin trees: water relations, yield and quality responses at harvest and after cold storage

Two experiments were conducted on a commercial farm of late ‘Fortune’ mandarin trees in order to know the response of regulated deficit irrigation (RDI), mainly applied during the most harmful ripening stages, on plant water relations, yield and fruit quality at harvest and after cold storage at different temperatures. Control trees were irrigated to satisfy maximum crop evapotranspiration, while RDI-1 and RDI- 2 represented a 20% and 40% reduction, respectively, in the water applied. Total yield and fruit quality at harvest were not significantly affected by either treatment. Late stage II of fruit growth was the most sensitive period to water stress, while deficit irrigation applied during flowering and stage I of fruit growth resulted in a significantly higher number of fruits per tree and an improvement in irrigation water productivity compared with the Control treatment. In both experiments, skin chroma decreased during cold storage, at the same time as titratable acidity fell. Fruit quality (titratable acidity, skin C* and ascorbic and glutamic acids) were more affected by cold storage than by differences between the RDI treatments. The use of trunk diameter fluctuation was useful for restoring the RDI irrigation to levels of the Control at the end of early stage II. From a quality point of view, any difference between treatments found at harvest tended to diminish during the subsequent shelf-life after cold storage. Quality traits (titratable acidity, ascorbic and glutamic acid) could be used as chilling biomarkers.

Significant reduction in propagation loss in electrospun polymer fibers by adopting thermal drawing

Electrospun polymer submicroscale fibers normally have flexible cylindrical waveguide geometries and can be produced with ultra-long and functional materials. Hence, they are promising building blocks for small optical devices. However, the propagation loss in the fibers is still higher than that in submicroscale polymer fibers produced by melt and solution drawing. In this study, thermal drawing of electrospun fibers was found to reduce their propagation loss. Fivefold thermal drawing of as-electrospun polymer fibers significantly reduced their diameters (e.g., from 1.121 μm to 0.497 μm) and propagation loss (e.g., from 16 dB cm−1 to 6.6 dB cm−1 at 521-nm wavelength). Because fluctuations in the fiber diameter significantly reduced after thermal drawing, the propagation loss reduction could be attributed to the reduced fluctuations in addition to the reduced density inhomogeneity in the fibers. These findings pave the way for low-loss electrospun fiber waveguides and their application in small optical devices.

Respiratory fluctuations in pupil diameter are not maintained during cognitive tasks

Pupil diameter fluctuation throughout the respiratory cycle is autonomically controlled in the resting state, as pupils dilate during inspiration and constrict during expiration. Furthermore, pupil size is differentially modulated by cognitive states between task engagement and disengagement. To determine whether respiratory-dependent fluctuations in pupil size are maintained during a cognitive task, we employed healthy human subjects performing a delayed matching-to-sample task with a short delay and measured their pupil sizes and R wave-to-R wave intervals (RRIs). We detected respiratory fluctuations in pupil size and the RRI during the delay period immediately before the discrimination stage of the task. During the discrimination stage, the cognitive state with the higher task engagement yielded more pupil dilation. However, respiratory fluctuations in pupil size were abolished, whereas those in the RRI were still discernible during the discrimination stage. Our results suggest that an alternative control mechanism involving the cognitive state associated with task engagement overrides the respiratory-related autonomic control of pupil diameter.

Pupillary Unrest in Ambient Light and Prediction of Opioid Responsiveness: Case Report on Its Utility in the Management of 2 Patients With Challenging Acute Pain Conditions.

Pupillary unrest in ambient light (PUAL), the normal pattern of pupil diameter fluctuation present in awake humans, has been proposed as a marker of central opioid effect. We report 2 cases in which PUAL identified the appropriate pain management for 2 patients, each with unique, challenging acute pain conditions. In both cases, PUAL accurately predicted opioid responsiveness, suggesting an effective, individualized analgesic approach for both patients.

Decreasing diameter fluctuation of polymer optical fiber with optimized drawing conditions

The diameter fluctuations of poly(methyl methacrylate) based polymer optical fibers, during drawing processes, have been comprehensively studied. In this study, several drawing parameters were selected for investigation; such as drawing tensions, preform diameters, preform feeding speeds, and argon flows. Varied drawing tensions were used to draw fibers, while other parameters were maintained at constant. At a later stage in the process, micro-structured polymer optical fibers were drawn under optimized drawing conditions. Fiber diameter deviations were reduced to 2.2%, when a 0.2 N drawing tension was employed during the drawing process. Higher drawing tensions led to higher diameter fluctuations. The Young’s modulus of fibers drawn with different tensions was also measured. Our results showed that fiber elasticity increased as drawing tensions decreased. The inhomogeneity of fibers was also determined by comparing the deviation of Young’s modulus.

Growth and characterization of Yb:Ho:YAG single crystal fiber

High quality Yb and Ho co-doped Y3Al5O12 single crystal fibers have been successfully grown by the laser heated pedestal growth method of up to 124 mm in length and 450 μm in diameter for the first time. The results of inductively coupled plasma-atomic emission spectrometry analysis, X-ray diffraction and Raman spectroscopy reveal that the lattice structure and doping concentrations of the SCF are the same as that of the bulk. Scanning electron microscopy microphotographs shows that the fibers only have minor diameter fluctuations within 0.5%.

Sleep deprivation increases the costs of attentional effort: Performance, preference and pupil size

Sleep deprivation (SD) consistently degrades performance in tasks requiring sustained attention, resulting in slower and more variable response times that worsen with time-on-task. Loss of motivation to exert effort may exacerbate performance degradation during SD. To test this, we evaluated sustained performance on a vigilance task, combining this with an effort-based decision-making task and pupillometry. Vigilance was tested at rest and after sleep deprivation, under different incentive conditions (1, 5 or 15 cents for fast responses). Subsequently, preference measures were collected from an effort-discounting task, in which a commensurate reward was offered for maintaining attentional performance for different durations (1, 5, 10, 20 or 30 min). Vigilance was impaired during SD, in a manner modulated by reward value. Preference metrics showed that the value of available rewards was discounted by task duration, an effect compounded by SD. Pupillometry revealed that arousal was modulated during SD in a value-based manner, and moment-to-moment fluctuations in pupil diameter were directly predictive of performance. Together, these data demonstrate that attentional performance can be interpreted within a value-based effort allocation framework, such that the perceived cost of attentional effort increases after sleep deprivation.

The relationship of systemic markers of haemostasis with retinal blood vessel responses in cardiovascular disease and/or diabetes

Background Hypercoagulability is a leading factor in diabetes and cardiovascular disease. Retinal vessel responses to flickering light are an important tool for assessing ocular function. We hypothesised a significant relationship between systemic markers of haemostasis and retinal vessel function.Methods Intra-ocular pressure and retinal microcirculation function were measured in 116 patients with diabetes and/or cardiovascular disease using unstimulated and stimulated arterial and venous retinal vessel responses to flickering light. Haemostasis was evaluated by platelet microparticles, soluble P selectin, and five functional markers of fibrin clot formation and lysis, hyperglycaemia by HbA1c.Results Intra-ocular pressure was linked to the rates of clot formation (p = 0.006) and clot dissolution (p = 0.013) whilst central retinal vein equivalent was linked to HbA1c (p = 0.017). In the first of three flickering light cycles only, arterial baseline diameter fluctuation was linked to the lag time to clot formation (p = 0.017), whilst maximum venous dilatation was linked to HbA1c (p = 0.001) and clot density (p = 0.011). HbA1c was linked to venous dilatation amplitude (p = 0.003). There were no significant links between any ocular index and any platelet index.Conclusions In addition to glycaemia, several haemostasis measures, but no measures of platelet activity, are linked to ocular and retinal blood vessel indices in patients with diabetes and/or cardiovascular disease. These associations may have pathophysiological significance.

Anisotropic Thermal and Guest-Induced Responses of an Ultramicroporous Framework with Rigid Linkers.

The interdependent effects of temperature and guest uptake on the structure of the ultramicroporous metal-organic framework [Cu3 (cdm)4 ] (cdm=C(CN)2 (CONH2 )- ) were explored in detail by using in situ neutron scattering and density functional theory calculations. The tetragonal lattice displays an anisotropic thermal response related to a hinged "lattice-fence" mechanism, unusual for this topology, which is facilitated by pivoting of the rigid cdm anion about the Cu nodes. Calculated pore-size metrics clearly illustrate the potential for temperature-mediated adsorption in ultramicroporous frameworks due to thermal fluctuations of the pore diameter near the value of the target guest kinetic diameter, though in [Cu3 (cdm)4 ] this is counteracted by a competing contraction of the pore with increasing temperature as a result of the anisotropic lattice response.

The effects of sediment transport on temporal variation in radiocesium concentrations in very shallow water off the southern coast of Fukushima, Japan

We studied the very shallow coastal water off Iwaki City, Fukushima Prefecture, and investigated: (1) temporal variation in 137Cs concentrations; (2) particle-size distribution of sediments; and (3) the effect on variation by waves, component-fractionated concentration of radiocesium and mineral composition at three sampling stations (Yotsukura, Ena rocky reef and Ena sandy station). There was a decline in 137Cs concentrations in sediment samples at all sampling stations between 425 and 1173 days after the accident. All stations had fluctuations in 137Cs concentrations between 425 and 800 days. At Ena sandy station and Ena rocky reef stations the declines in 137Cs concentrations slowed from about 800 days after the accident. Fluctuations in particle median diameters were seen, as well as in 137Cs concentrations. At Yotsukura, where the fluctuation in median diameter was small, a constant decrease in 137Cs concentrations was observed. We considered that bioturbation may contribute the constant decrease. At Ena sandy station, where the fluctuation of the median diameter was large, the fluctuation in 137Cs concentrations was also large. The movement of sediments was evaluated by the Shields parameter, and results indicated that at any station where the sediment was moved more frequently, the fluctuation in 137Cs concentrations was also large. The highly contaminated small particles moved from our stations due to wave action between 425 and 800 days after the accident. The remaining relatively large particles might contribute to the slowing down in reduction of 137Cs concentrations from 800 days after the accident. However, the 137Cs concentrations in sediments in very shallow water off the southern coast of Fukushima may continue to decline over time.

Sleep deprivation increases the costs of attentional effort: performance, preference and pupil size

Abstract Sleep deprivation (SD) consistently degrades performance in tasks requiring sustained attention, resulting in slower and more variable response times that worsen with time-on-task. Loss of motivation to exert effort may exacerbate performance degradation during SD. To test this, we evaluated sustained performance on a vigilance task, combining this with an effort-based decision-making task and pupillometry. Vigilance was tested at rest and after sleep deprivation, under different incentive conditions (1, 5 or 15 cents for fast responses). Subsequently, preference measures were collected from an effort-discounting task, in which a commensurate reward was offered for maintaining attentional performance for different durations (1, 5, 10, 20 or 30 min). Vigilance was impaired during SD, in a manner modulated by reward value. Preference metrics showed that the value of available rewards was discounted by task duration, an effect compounded by SD. Pupillometry revealed that arousal was modulated during SD in a value-based manner, and moment-to-moment fluctuations in pupil diameter were directly predictive of performance. Together, these data demonstrate that attentional performance can be interpreted within a value-based effort allocation framework, such that the perceived cost of attentional effort increases after sleep deprivation.

Model analysis of feedstock behavior in fused filament fabrication: Enabling rapid materials screening

This research presents a rapid screening process for analyzing the extrudability of polymeric materials for filament extrusion based additive manufacturing (AM) by predicting extrusion failure. This rapid screening process can further suggest optimal Fused Filament Fabrication (FFF) processing conditions for a specific material. Annular backflow and filament buckling, which are the two primary failure modes during extrusion in FFF, are considered in this study. The screening method focuses on model analysis of annular backflow while simultaneously considering a previously developed model for filament buckling and includes the introduction of a non-dimensional number (Flow Identification Number, or FIN) that predicts a material's propensity to backflow based on a rheological analysis and the system geometry. Annular backflow was modeled by calculating velocity profiles and determining the normalized net flow magnitude. The backflow and buckling models were experimentally verified with acrylonitrile butadiene styrene, low density polyethylene, and sodium sulfonated poly(ethylene) glycol. We empirically validated that the FIN was able to accurately predict backflow and that the potential to backflow and, by extension, propensity to fail during extrusion, is most sensitive to fluctuations in filament diameter and the material's shear thinning behavior. Our results demonstrate the importance of printing in the shear thinning regime to reduce the effect of processing conditions on the extrudability of a polymer.