Analysis and Wind Tunnel Testing of a Superelastic Slat-Cove Filler for Airframe Noise Reduction

During low speed maneuvers, such as landing and approach, a significant portion of the noise generated by transport aircraft is due to airframe noise. The leading-edge slat is a primary source of airframe noise. Previous work has shown that the slat-cove filler (SCF) is effective at mitigating the noise generated by the slat. The objective of this work was to further the development of a superelastic shape memory alloy (SMA) SCF concept by investigating fluid-structure interaction (FSI) behavior via computational and physical models. Structural optimization of a SCF design for a representative, transport-class airfoil was first conducted considering the SCF response to aerodynamic and slat retraction loads. The objective of the optimization was to minimize the actuation force needed to retract the slat and SCF. A monolithic SMA SCF was found to minimize the actuation force while satisfying constraints, which agreed with findings from prototype testing on the bench-top apparatus. The success of the design optimization motivated further work that sought to determine how the SCF responded in flow using a combination of finite volume fluid models and finite element structural models based on a small-scale wind tunnel model of a conventional multi-element wing configuration with a SCF. Multiple angles of attack and deployment states of high lift devices were considered for computational fluid dynamics (CFD) analysis to gain an initial understanding of the flow around the wing. FSI analysis of the SCF in flow was conducted for multiple load cases using a framework that was compatible with custom material subroutines (for SMA material response). Wind tunnel testing of a physical model of the multi-element wing configuration was used to begin validation of the CFD and FSI models

Inside the Decentralised Casino : A Longitudinal Study of Actual Cryptocurrency Gambling Transactions

Decentralised gambling applications are a new way for people to gamble online. Decentralised gambling applications are distinguished from traditional online casinos in that players use cryptocurrency as a stake. Also, rather than being stored on a single centralised server, decentralised gambling applications are stored on a cryptocurrency's blockchain. Previous work in the player behaviour tracking literature has examined the spending profiles of gamblers on traditional online casinos. However, similar work has not taken place in the decentralised gambling domain. The profile of gamblers on decentralised gambling applications are therefore unknown. This paper explores 2,232,741 transactions from 24,234 unique addresses to three such applications operating atop the Ethereum cryptocurrency network over 583 days. We present spending profiles across these applications, providing the first detailed summary of spending behaviours in this technologically advanced domain. We find that the typical player spends approximately $110 equivalent across a median of 6 bets in a single day, although heavily involved bettors spend approximately$100,000 equivalent over a median of 644 bets across 35 days. Our findings suggest that the average decentralised gambling application player spends less than in other online casinos overall, but that the most heavily involved players in this new domain spend substantially more. This study also demonstrates the use of these applications as a research platform, specifically for large scale longitudinal in-vivo data analysis

Universality and template synthesis of cosmic ray air shower radio emission

Accurate prediction of the radio emission from cosmic ray air showers relies on computationally demanding Monte Carlo simulations such as CoREAS. We aim to expedite this process via a semi-analytical synthesis model while maintaining high accuracy by using simulated radio pulses as templates. We present our key concept for template processing focusing on the development of the particle cascade and its empirical effect on the locally produced radio signal. In this context the universality of the radio emission from small sections of an air shower also becomes important where most previous studies focus on integral quantities observable at far distances.Comment: Proceedings of the 36th ICRC, Madison, USA, PoS(ICRC2019)29

Analysis and Wind Tunnel Testing of a Superelastic Slat-Cove Filler for Airframe Noise Reduction

During low speed maneuvers, such as landing and approach, a significant portion of the noise generated by transport aircraft is due to airframe noise. The leading-edge slat is a primary source of airframe noise. Previous work has shown that the slat-cove filler (SCF) is effective at mitigating the noise generated by the slat. The objective of this work was to further the development of a superelastic shape memory alloy (SMA) SCF concept by investigating fluid-structure interaction (FSI) behavior via computational and physical models. Structural optimization of a SCF design for a representative, transport-class airfoil was first conducted considering the SCF response to aerodynamic and slat retraction loads. The objective of the optimization was to minimize the actuation force needed to retract the slat and SCF. A monolithic SMA SCF was found to minimize the actuation force while satisfying constraints, which agreed with findings from prototype testing on the bench-top apparatus. The success of the design optimization motivated further work that sought to determine how the SCF responded in flow using a combination of finite volume fluid models and finite element structural models based on a small-scale wind tunnel model of a conventional multi-element wing configuration with a SCF. Multiple angles of attack and deployment states of high lift devices were considered for computational fluid dynamics (CFD) analysis to gain an initial understanding of the flow around the wing. FSI analysis of the SCF in flow was conducted for multiple load cases using a framework that was compatible with custom material subroutines (for SMA material response). Wind tunnel testing of a physical model of the multi-element wing configuration was used to begin validation of the CFD and FSI models

Template synthesis approach for radio emission from extensive air showers

We present a novel way to synthesise the radio emission from extensive air showers. It is a hybrid approach which uses a single microscopic Monte-Carlo simulation to generate the radio emission from a shower with a different longitudinal evolution, primary particle type and energy. The method employs semi-analytical relations which only depend on the shower parameters to transform the radio signal in the simulated antennas. We apply this method to vertical air showers with energies ranging from 10$^{17}$eV to 10$^{19}$eV and compare the results with CoREAS using two different metrics. In order to gauge the performance over our simulation set, we subsequently use every shower in the set as a template to synthesise the emission from the other showers. Depending on the scoring metric, template synthesis reconstructs the radio emission with an accuracy of 5 to 10%

Verification of Exhaust Quasineutrality in a Pulsed Cathodic Arc Thruster Testbed

Electric propulsion systems have become more common on-orbit in recent years due to their many benefits[1]. Most flight-rated systems generate thrust by producing an ion beam directed away from the spacecraft, which must then be neutralised to ensure proper spacecraft operation [2]. Despite decades of flight heritage, neutraliser lifetime is one of the more common life-limiting factors for Hall and ion thrusters [2, 3]. Systems currently under development that generate neutral plasma jets do not require a neutraliser, removing failure modes and reducing system complexity [4]. Neumann Space has developed to flight-readiness a pulsed cathodic arc thruster, which does not require a neutraliser. Here we present work done using the inner surface of a steel vacuum chamber as a Faraday cup to capture the exhaust of a pulsed cathodic arc thruster testbed, instrumented to measure charge flow and verify exhaust neutrality

A decision tool for updating Cochrane reviews

This report describes the development and validation of an updating tool to help assess the need and likely benefits of updating a Cochrane review. The report is presented in five sections. Section 1 describes the background and rationale for the updating tool, including information about when and how to update. Section 2 describes the development of the updating tool and the resulting decision tree and checklist. Section 3 presents the results of the in-house and ongoing formal pilot of the tool, while Sections 4 and 5 provide information about the dissemination of the tool and our key conclusions. This project was funded by the Cochrane Opportunities Fund in 2007

Empirically Testing for Indirect Network Externalities in the LCD

This paper examines price data on over 222 LCD televisions to estimate indirect network effects arising from two sources. First, we conjecture that the disconnect between the timing of when broadcasters are required to convert to an only‐digital‐signal world and when television manufacturers are required to have an ATSC digital tuner install on all new televisions has created an indirect network effect whereby television that are backward compatible with the NTSC analog QAM and VSB‐8 systems have short‐run value. Over time, however, we argue that the ATSC digital tuner will become more valuable. The second indirect network effect we estimate stems from the number and types of ports available on LCD televisions. In each case, we find statistically significant evidence for the presence of indirect network effects in the market for LCD televisions

A Scramjet Engine Model Including Effects of Precombustion Shocks and Dissociation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76382/1/AIAA-2008-4619-101.pd