Tortoise: Interactive System Configuration Repair

System configuration languages provide powerful abstractions that simplify managing large-scale, networked systems. Thousands of organizations now use configuration languages, such as Puppet. However, specifications written in configuration languages can have bugs and the shell remains the simplest way to debug a misconfigured system. Unfortunately, it is unsafe to use the shell to fix problems when a system configuration language is in use: a fix applied from the shell may cause the system to drift from the state specified by the configuration language. Thus, despite their advantages, configuration languages force system administrators to give up the simplicity and familiarity of the shell. This paper presents a synthesis-based technique that allows administrators to use configuration languages and the shell in harmony. Administrators can fix errors using the shell and the technique automatically repairs the higher-level specification written in the configuration language. The approach (1) produces repairs that are consistent with the fix made using the shell; (2) produces repairs that are maintainable by minimizing edits made to the original specification; (3) ranks and presents multiple repairs when relevant; and (4) supports all shells the administrator may wish to use. We implement our technique for Puppet, a widely used system configuration language, and evaluate it on a suite of benchmarks under 42 repair scenarios. The top-ranked repair is selected by humans 76% of the time and the human-equivalent repair is ranked 1.31 on average.Comment: Published version in proceedings of IEEE/ACM International Conference on Automated Software Engineering (ASE) 201

Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks

Recent laboratory efforts (Fu et al., 2014) have constrained the remanent magnetizations of chondrules and the magnetic field strengths at which the chondrules were exposed to as they cooled below their Curie points. An outstanding question is whether the inferred paleofields represent the background magnetic field of the solar nebula or were unique to the chondrule-forming environment. We investigate the amplification of the magnetic field above background values for two proposed chondrule formation mechanisms, large-scale nebular shocks and planetary bow shocks. Behind large-scale shocks, the magnetic field parallel to the shock front is amplified by factors $\sim 10-30$, regardless of the magnetic diffusivity. Therefore, chondrules melted in these shocks probably recorded an amplified magnetic field. Behind planetary bow shocks, the field amplification is sensitive to the magnetic diffusivity. We compute the gas properties behind a bow shock around a 3000 km-radius planetary embryo, with and without atmospheres, using hydrodynamics models. We calculate the ionization state of the hot, shocked gas, including thermionic emission from dust, and thermal ionization of gas-phase potassium atoms, and the magnetic diffusivity due to Ohmic dissipation and ambipolar diffusion. We find that the diffusivity is sufficiently large that magnetic fields have already relaxed to background values in the shock downstream where chondrules acquire magnetizations, and that these locations are sufficiently far from the planetary embryos that chondrules should not have recorded a significant putative dynamo field generated on these bodies. We conclude that, if melted in planetary bow shocks, chondrules probably recorded the background nebular field.Comment: 17 pages, 11 figures, accepted for publication in Ap

Evolution and Innerworking of a Car Differential

Create interactive demonstration pieces that display basic concepts of a car differential using visual aids as in the educational video ‘Around the Corner (1937): How differential Steering Works’. Fabricate a custom stand for an open ended car differential. The final design of the car differential will be run by an on/off switch and a motor

The Inconsistent use of ω\omega in the RV Equation

Since the discovery of the first exoplanet orbiting a main-sequence star, astronomers have inferred the orbital properties of planets using stellar radial velocity (RV) measurements. For a star orbited by a single planet, the stellar orbit is a dilation and $180^\circ$ rotation of the planetary orbit. Thus, many of the Keplerian orbital properties of the star are identical to those of the planet. However, there is a notable exception: the argument of periastron, $\omega$, defined as the angle between the periapsis of an orbiting body and its ascending node. The argument of periastron of the star ($\omega_\star$) is $180^\circ$ offset from the argument of periastron of the planet ($\omega_p$). This distinction is important because some derivations of the RV equation use $\omega_\star$, while others use $\omega_p$. This discrepancy arises because commonly used derivations of the RV equation do not adhere to a single coordinate system. As a result, there are inconsistencies in the definitions of the Keplerian orbital parameters in various RV models, leading to values of the ascending node and $\omega$ that are $180^\circ$ offset. For instance, some packages, such as \texttt{RadVel} and \texttt{ExoFast}, report values for $\omega_{\star}$ that are identical to the $\omega_p$ values determined with other packages, such as \texttt{TTVFast} and \texttt{Orvara}, resulting in orbital solutions that differ by $180^\circ$. This discrepancy highlights the need for standardized conventions and definitions in RV modeling, particularly as we enter the era of combining RVs with astrometry.Comment: 5 pages,2 figures, 1 tabl

DIGITAL INNOVATION AND CRAFTSMANSHIP: THE CASE OF C. F. MARTIN & COMPANY

Craftsmanship is a concept often left unaddressed in the IT innovation literature. Further, this literature often fails to consider innovation that involves human labor on the shop floor. With the sheer volume of organizations that operate in craft-based industries, placing a strident focus upon craftsmanship and predominantly innovating on the shop floor, this is particularly concerning. This work therefore examines the influence of considered craftsmanship on the nature and consequences of digital innovation in the guitar manufacturing process at C. F. Martin & Company. We propose a model of innovation that incorporates the concept of the activity system, drawn from the field of activity theory. Individual innovations cause disturbances in actor-tooltask relationships (activity systems). This drives a series of reconfigurations, in an effort to eliminate said disturbances. Preliminary qualitative evidence is provided, supporting the proposed model, in the form of a series of semi-structured interviews