Towards a Systematic Repository of Knowledge About Managing Collaborative Design Conflicts

Increasingly, complex artifacts such as cars, planes and even software are designed using large-scale and often highly distributed collaborative processes. A key factor in the effectiveness of these processes concerns how well conflicts are managed. Better approaches need to be developed and adopted, but the lack of systematization and dissemination of the knowledge in this field has been a big barrier to the cumulativeness of research in this area as well as to incorporating these ideas into design practice. This paper describes a growing repository of conflict management expertise, built as an augmentation of the MIT Process Handbook, that is designed to address these challenges.

Synthesizing Functional Reactive Programs

Functional Reactive Programming (FRP) is a paradigm that has simplified the construction of reactive programs. There are many libraries that implement incarnations of FRP, using abstractions such as Applicative, Monads, and Arrows. However, finding a good control flow, that correctly manages state and switches behaviors at the right times, still poses a major challenge to developers. An attractive alternative is specifying the behavior instead of programming it, as made possible by the recently developed logic: Temporal Stream Logic (TSL). However, it has not been explored so far how Control Flow Models (CFMs), as synthesized from TSL specifications, can be turned into executable code that is compatible with libraries building on FRP. We bridge this gap, by showing that CFMs are indeed a suitable formalism to be turned into Applicative, Monadic, and Arrowized FRP. We demonstrate the effectiveness of our translations on a real-world kitchen timer application, which we translate to a desktop application using the Arrowized FRP library Yampa, a web application using the Monadic threepenny-gui library, and to hardware using the Applicative hardware description language ClaSH.Comment: arXiv admin note: text overlap with arXiv:1712.0024

Star Cluster Formation in Turbulent, Magnetized Dense Clumps with Radiative and Outflow Feedback

We present three Orion simulations of star cluster formation in a 1000 Msun, turbulent molecular cloud clump, including the effects of radiative transfer, protostellar outflows, and magnetic fields. Our simulations all use self-consistent turbulent initial conditions and vary the mean mass-to-flux ratio relative to the critical value over 2, 10, and infinity to gauge the influence of magnetic fields on star cluster formation. We find, in good agreement with previous studies, that magnetic fields of typically observed strengths lower the star formation rate by a factor of 2.4 and reduce the amount of fragmentation by a factor of 2 relative to the zero-field case. We also find that the field increases the characteristic sink particle mass, again by a factor of 2.4. The magnetic field also increases the degree of clustering in our simulations, such that the maximum stellar densities in the strong field case are higher than the others by again a factor of 2. This clustering tends to encourage the formation of multiple systems, which are more common in the rad-MHD runs than the rad-hydro run. The companion frequency in our simulations is consistent with observations of multiplicity in Class I sources, particularly for the strong field case. Finally, we find evidence of primordial mass segregation in our simulations reminiscent of that observed in star clusters like the Orion Nebula Cluster.Comment: 21 pages, 17 figures, accepted by MNRA

The MIT Collaboratorium: Enabling Effective Large-Scale Deliberation for Complex Problems

While current online discussion tools such as email, chat, wikis, and web forums have been enormously successful at enabling unprecedented global knowledge sharing, they face significant limitations from the perspective of enabling effective large-scale deliberation around complex and controversial issues such as climate change. This paper describes the design and rationale of a system, called the Collaboratorium, which was developed to transcend these limitations by supporting large-scale on-line argumentation

Radiation Pressure in Massive Star Formation

Stars with masses of >~ 20 solar masses have short Kelvin times that enable them to reach the main sequence while still accreting from their natal clouds. The resulting nuclear burning produces a huge luminosity and a correspondingly large radiation pressure force on dust grains in the accreting gas. This effect may limit the upper mass of stars that can form by accretion. Indeed, simulations and analytic calculations to date have been unable to resolve the mystery of how stars of 50 solar masses and up form. We present two new ideas to solve the radiation pressure problem. First, we use three-dimensional radiation hydrodynamic adaptive mesh refinement simulations to study the collapse of massive cores. We find that in three dimensions a configuration in which radiation holds up an infalling envelope is Rayleigh-Taylor unstable, leading radiation driven bubbles to collapse and accretion to continue. We also present Monte Carlo radiative transfer calculations showing that the cavities created by protostellar winds provides a valve that allow radiation to escape the accreting envelope, further reducing the ability of radiation pressure to inhibit accretion.Comment: To be appear in "IAU 227: Massive Star Birth: A Crossroads of Astrophysics"; 6 pages, 1 figur