University of Massachusetts Amherst

About: University of Massachusetts Amherst is a education organization based out in Amherst Center, Massachusetts, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 37274 authors who have published 83965 publications receiving 3834996 citations. The organization is also known as: UMass Amherst & Massachusetts State College.

The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-redshift Circumgalactic Medium

Abstract: We analyze the physical conditions of the cool, photoionized (T ∼ 10 4 K) circumgalactic medium (CGM) using the COS-Halos suite of gas column density measurements for 44 gaseous halos within 160 kpc of L ∼ L ∗ galaxies at z ∼ 0.2. These data are well described by simple photoionization models, with the gas highly ionized (nHii/nH 99%) by the extragalactic ultraviolet background. Scaling by estimates for the virial radius, Rvir, we show that the ionization state (tracked by the dimensionless ionization parameter, U) increases with distance from the host galaxy. The ionization parameters imply a decreasing volume density profile nH = (10 −4.2±0.25 )(R/Rvir) −0.8±0.3 . Our derived gas volume densities are several orders of magnitude lower than predictions from standard two-phase models with a cool medium in pressure equilibrium with a hot, coronal medium expected in virialized halos at this mass scale. Applying the ionization corrections to the Hi column densities, we estimate a lower limit to the cool gas mass M cool CGM > 6.5 × 10

Private memoirs of a smart meter

Abstract: Household smart meters that measure power consumption in real-time at fine granularities are the foundation of a future smart electricity grid. However, the widespread deployment of smart meters has serious privacy implications since they inadvertently leak detailed information about household activities. In this paper, we show that even without a priori knowledge of household activities or prior training, it is possible to extract complex usage patterns from smart meter data using off-the-shelf statistical methods. Our analysis uses two months of data from three homes, which we instrumented to log aggregate household power consumption every second. With the data from our small-scale deployment, we demonstrate the potential for power consumption patterns to reveal a range of information, such as how many people are in the home, sleeping routines, eating routines, etc. We then sketch out the design of a privacy-enhancing smart meter architecture that allows an electric utility to achieve its net metering goals without compromising the privacy of its customers.

Professional as Agent: Knowledge Asymmetry in Agency Exchange

Abstract: In this article I examine those business exchanges in which firms hire professional service organizations and give them limited decisionmaking authority to perform knowledge-intensive tasks. I frame such exchanges within agency theory perspective and invoke the extant literature on professions to delineate several attributes that make principal-professional exchanges intrinsically distinct from others. such as owner-manager agency. In doing so. I question and complement same key assumptions in agency theory and also discuss explicitly how the study of principal-professional exchanges helps highlight important considerations not addressed in the mainstream theory. I then present an expanded framework that integrates agency theory and the literature on the professions and present several propositions to outline four types of restraints on potential opportunistic behavior of professional agents; (1) self-control, (2) community control, (3) bureaucratic control, and (4) client control. The article ends with t...