Local Viscosity Control Printing for High-Throughput Additive Manufacturing of Polymers

Fused deposition modeling's (FDM) throughput is limited by process physics as well as practical considerations favoring single-head polymer extrusion. To expedite the thermoplastic additive manufacturing process, we propose a parallelized material deposition process called local viscosity control (LVC) additive manufacturing. LVC prints an entire layer in one step by selectively modulating the viscosity of polymer feedstock in contact with a heated wire mesh. Layers of molten polymer are contact printed, with the relative motion between the wire mechanism and a build plate allowing wetting and surface tension to transfer selectively heated, lower viscosity regions of polymer to a fixed substrate. Experiments demonstrate the viability of this process using a single cell depositing layered polycarbonate pixels. Theoretical analysis shows this process may offer similar capabilities in resolution to conventional FDM with a significantly higher production rate for commonly available input power

The Tallest Column: On Monetary Value of Stature in Jewish Law

In contrast to the strict requirements of Eruchin pledges found in Leviticus 27:1–8, Damim (monetary) donations are not closely regulated by the Torah and can take many forms. One may not, for example, offer an Erech that corresponds to some fraction of a human being, as Erech donations can be made only on an integer number of persons. To use language that could refer to anything but the entirety of a person renders the Erech attempt failed (Eruchin Chapter 5 Mishna 2). Damim is more flexible as the giver is free to offer almost any value, flexibly comprised. Beyond specifying a donation in the local currency, the Talmud quotes two cases where people offered either their entire value on the slave market, or the more complicated value of a particular body part such as a hand, which requires two evaluations to solve the equation ‘Value of one’s Hand’ = ‘Value of that Person’ – ‘Value of (Person without his Hand).’ A similar situation arises when one offers to contribute the value of his weight in a material. A simple measurement is needed when the entire weight is specified, but if it’s only the weight of a particular limb, the Mishna (Eruchin19a) details an elaborate procedure that involves measuring the volume of the limb through a water displacement exercise, and estimating the density of human flesh using a combination of donkey bone, blood and meat

A three-dimensional self-supporting low loss microwave lens with a negative refractive index

Demonstrations of focusing with metamaterial lenses have predominantly featured two dimensional structures or stacks of planar elements, both limited by losses which hinder realized gain near the focal region. In this study, we present a plano-concave lens built from a 3D self-supporting metamaterial structure featuring a negative refractive index between 10 and 12 GHz. Fabricated using macroscopic layered prototyping, the lens curvature, negative index and low loss contribute to a recognizable focus and free space gains above 13 dB