Comparison of Pulse Shape Discrimination Characteristics in Three Organic Scintillators for a High Resolution Coded-Aperture Neutron Imager

Pulse shape discrimination performances of single stilbene crystal, EJ-299-33 plastic and 6 Li loaded plastic scintillators have been compared. Pulse Gradient Analysis pulse shape discrimination algorithm has been tested for each scintillator sample, assessing their neutron/gamma separation. In this study each scintillator sample was irradiated with a 252Cf neutron source and, a real-time fast digitiser was used to collect the data. The figure-of-merit was utilised to compare the discrimination quality of the tested scintillator samples

Digital Neutron-Gamma Discrimination Performance of Stilbene in Comparison with Plastic Scintillators

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Assessment of research needs for sustainability of unconventional machining processes

AbstractThe use of unconventional machining (UCM) practices is increasing for product manufacture particularly when machining difficult to cut materials and when high precision is required. There is plenty of research conducted on improving sustainability of traditional machining. However, sustainability studies on unconventional/non-traditional machining practices are few. This review aims to determine the current state of the art in sustainability assessment of unconventional machining practices and identify gaps in research. An extensive review was carried out and analysed using a qualitative data analysing software. The analysis shows that only 25 publications directly and indirectly discuss the matter of sustainability of UCM. Out of this almost 70% of publications were recorded after year 2006 showing a clear evidence of uncovered research gap in the field with a growing interest. Despite this trend, evidence on studies which are explicitly dedicated to analyse the sustainability of UCM are rare

Why a Wealth Tax is Definitely Constitutional

Wealth tax reform proposals are playing a major role in the 2020 presidential campaign. However, some opponents of these wealth tax reform proposals have claimed that a wealth tax would be unconstitutional. Other prominent critics have argued that wealth tax reforms are probably unconstitutional, so that, after review by the courts, the “likeliest outcome is that a wealth tax will raise exactly zero dollars.” These claims are wrong. More precisely, these claims are wrong conditioned on wealth tax legislation being carefully drafted so as to ensure its constitutionality. As we will explain in this essay, properly drafted, wealth tax reform legislation is definitely constitutional and thus capable of raising substantial revenues to fund new spending programs. Constitutional scholars disagree about whether a new federal wealth tax would need to be uniform or apportioned in order to be constitutional. We explain how wealth tax legislation could be drafted to ensure its constitutionality regardless of how the Supreme Court ultimately decides on this question. In particular, we explain how Congress could design an apportioned federal wealth tax made equitable through the use of a fiscal equalization program, and could legislate this as a fallback option in case the Supreme Court were to rule against an unapportioned federal wealth tax

Parametric Analysis and Bandwidth Optimisation of Hybrid Linear-exponential Tapered Slot Vivaldi Antennas

This work presents an analysis of the effects of a hybrid linear-exponential tapered slot on the key properties of both the antipodal and co-planar Vivaldi antennas at low frequencies using parametric analysis and Nonlinear Sequential Programming optimisation. It was observed that the hybrid tapered slot can extend the lower frequency limit of the antipodal Vivaldi antenna however with slight deterioration of the gain and E-plane radiation pattern. On the other hand, the optimisation of the hybrid and conventional tapered slot co-planar Vivaldi antennas converged to antennas with the same performance results

Prediction of Turbulent Shear Stresses through Dysfunctional Bileaflet Mechanical Heart Valves using Computational Fluid Dynamics

There are more than 300,000 heart valves implanted annually worldwide with about 50% of them being mechanical valves. The heart valve replacement is often a common treatment for severe valvular disease. However, valves may dysfunction leading to adverse hemodynamic conditions. The current computational study investigated the flow around a bileaflet mechanical heart valve at different leaflet dysfunction levels of 0%, 50%, and 100%, and documented the relevant flow characteristics such as vortical structures and turbulent shear stresses. Studying the flow characteristics through these valves during their normal operation and dysfunction can lead to better understanding of their performance, possibly improved designs, and help identify conditions that may increase the potential risk of blood cell damage. Results suggested that maximum flow velocities increased with dysfunction from 2.05 to 4.49 ms-1 which were accompanied by growing eddies and velocity fluctuations. These fluctuations led to higher turbulent shear stresses from 90 to 800 N.m-2 as dysfunctionality increased. These stress values exceeded the thresholds corresponding to elevated risk of hemolysis and platelet activation. The regions of elevated stresses were concentrated around and downstream of the functional leaflet where high jet velocity and stronger helical structures existed

Signal Noise Filtering Techniques in Radiation Detection Applications for Neutron Gamma Pulse Shape Discrimination

Neutron radiation often occurs as a result of radioactive decay and is accompanied by gamma radiation. This results in a mixed radiation environment comprising photons (gamma rays) and neutrons. Organic liquid scintillators are popularly used to detect both neutrons and gamma rays, where pulse shape analysis determines whether the event was caused by a neutron or a gamma-ray based on the decay characteristics of the pulse. Bespoke fast digitisers are currently widely used with organic liquid scintillators to record the pulse shape as digital samples. Pulse shape has high impact on pulse shape discrimination, especially in low energy region as it is generally difficult to discriminate a neutron event from a gamma-ray event. The quality of the discrimination of detected event is primarily determined by the quality of the pulse shape recreated using digital samples, as the discrimination is based on the characteristics of the pulse. The pulse signal is usually altered by signal noise and, the purpose of this paper is to select the best candidate for signal filtering technique to remove such high frequency noise components. It is important to ensure that the signal filtering technique is not consuming much of the processing power of the system and, it can be easily implemented in a real-time system