Energy density is often used as a metric to compare components manufactured with Selective Laser Melting (SLM) under different sets of deposition parameters (e.g., laser power, scan speed, layer thickness, etc.). We present a brief review of the current literature on additive manufacturing of 316L stainless steel (SS) related to input parameter scaling relations. From previously published work we identified a range of Volumetric Energy Density (VED) values that should lead to deposition of fully dense parts. In order to corroborate these data, we designed a series of experiments to investigate the reliability of VED as a design parameter by comparing single tracks of 316L SS deposited with variable deposition parameters. Our results show the suitability of VED as a design parameter to describe SLM to be limited to a narrow band of
This study provides insight into the mechanisms that govern morphology in microparticles processed using precipitation by a compressed antisolvent. We explore the time scale of surface tension evolution in jets of miscible fluids injected into critical and near-critical solvents to determine whether the jets atomize into droplets or simply evolve as gaseous plumes. Classical jet breakup length equations, modified with timedependent surface tension, accurately predict observed breakup lengths over a range of liquid miscibilities. Linear jet breakup theory can be applied successfully to near critical conditions. The aerodynamic reduction factor remains constant over a wide range of pressures. However, under miscible conditions, calculations show that surface tension in a 10-cm/s round jet of methylene chloride in carbon dioxide at 8.5 MPa and 35°C approaches 0.01 mN/m in 1 µm. Because this distance is shorter than characteristic breakup lengths, distinct droplets never form. Rather, the jets spread in a fashion characteristic of gaseous jets, whose mixing is well described by the gaseous fluid mixing theory. Presumably, microparticle formation results from gas phase nucleation and growth within the expanding plume, rather than nucleation within discrete liquid droplets.
Exhaled breath condensate (EBC) analysis is a developing field with tremendous promise to advance personalized, non-invasive health diagnostics as new analytical instrumentation platforms and detection methods are developed. Multiple commercially-available and researcher-built experimental samplers are reported in the literature. However, there is very limited information available to determine an effective breath sampling approach, especially regarding the dependence of breath sample metabolomic content on the collection device design and sampling methodology. This lack of an optimal standard procedure results in a range of reported results that are sometimes contradictory. Here, we present a design of a portable human EBC sampler optimized for collection and preservation of the rich metabolomic content of breath. The performance of the engineered device is compared to two commercially available breath collection devices: the RTube™ and TurboDECCS. A number of design and performance parameters are considered, including: condenser temperature stability during sampling, collection efficiency, condenser material choice, and saliva contamination in the collected breath samples. The significance of the biological content of breath samples, collected with each device, is evaluated with a set of mass spectrometry methods and was the primary factor for evaluating device performance. The design includes an adjustable mass-size threshold for aerodynamic filtering of saliva droplets from the breath flow. Engineering an inexpensive device that allows efficient collection of metalomic-rich breath samples is intended to aid further advancement in the field of breath analysis for non-invasive health diagnostic. EBC sampling from human volunteers was performed under UC Davis IRB protocol 63701-3 (09/30/2014-07/07/2017).
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