Computer program uses Monte Carlo techniques for statistical system performance analysis

Computer program with Monte Carlo sampling techniques determines the effect of a component part of a unit upon the overall system performance. It utilizes the full statistics of the disturbances and misalignments of each component to provide unbiased results through simulated random sampling

Negative equity does not reduce homeowners' mobility

Some commentators have argued that the housing crisis may harm labor markets because homeowners who owe more than their homes are worth are less likely to move to places that have productive job opportunities. I show that, in the available data, negative equity does not make homeowners less mobile. In fact, homeowners who have negative equity are slightly more likely to move than homeowners who have positive equity. Ferreira, Gyourko, and Tracy's (2010) contrasting result that negative equity reduces mobility arises because they systematically drop some negative-equity homeowners' moves from the data.> some negative-equity homeowners' moves from the data.

Heterogeneous Risk Preferences and the Welfare Cost of Business Cycles

I study the welfare cost of business cycles in a complete-markets economy where some people are more risk averse than others. Relatively more risk-averse people buy insurance against aggregate risk, and relatively less risk-averse people sell insurance. These trades reduce the welfare cost of business cycles for everyone. Indeed, the least risk-averse people benet from business cycles. Moreover, even innitely risk-averse people suer only nite and, in my empirical estimates, very small welfare losses. In other words, when there are complete insurance markets, aggregate uctuations in consumption are essentially irrelevant not just for the average person { the surprising nding of Lucas (1987) { but for everyone in the economy, no matter how risk averse they are. If business cycles matter, it is because they aect productivity or interact with uninsured idiosyncratic risk, not because aggregate risk per se reduces welfare.business cycles; risk aversion; risk sharing; heterogeneity

The lift force on a drop in unbounded plane Poiseuille flow

The lift force on a deformable liquid sphere moving in steady, plane Poiseuille-Stokes flow and subjected to an external body force is calculated. The results are obtained by seeking a solution to Stokes' equations for the motion of the liquids inside and outside the slightly perturbed sphere surface, as expansions valid for small values of the ratio of the Weber number to the Reynolds number. When the ratio of the drop and external fluid viscosities is small, the lift exerted on a neutrally buoyant drop is found to be approximately one-tenth of the magnitude of the force reported by Wohl and Rubinow acting on the same drop in unbounded Poiseuille flow in a tube. The resultant trajectory of the drop is calculated and displayed as a function of the external body force

Monte Carlo Calculations of Neutron Number Spectra and Buildup Factors in Infinite Conical Configurations

A Monte Carlo code simulating neutron transport in infinite cones of water and water-equivalent hydrogen was prepared for an IBM 704 computer. The code was essentially a modification of the point-source, infinite-medium code used in NASA TN D-850. Studies were made of differential neutron number spectra and associated buildup factors for infinite cones having apex half-angles of 15 degrees, 30 degrees, 45 degrees, and 60 degrees. The buildup factors obtained were compared with those for the appropriate infinite medium, which allowed an examination of the effect of solid angle subtended by material on the transport of 6-Mev source neutrons emanating from the cone apex. The variation of number buildup factor with distance for the various cones shows that neutron scattering out of the cones is predominant in the first 30 t o 40 centimeters of material, and that transport beyond this distance is of a similar nature in all the cones

Shield weight optimization using Monte Carlo transport calculations

Outlines are given of the theory used in FASTER-3 Monte Carlo computer program for the transport of neutrons and gamma rays in complex geometries. The code has the additional capability of calculating the minimum weight layered unit shield configuration which will meet a specified dose rate constraint. It includes the treatment of geometric regions bounded by quadratic and quardric surfaces with multiple radiation sources which have a specified space, angle, and energy dependence. The program calculates, using importance sampling, the resulting number and energy fluxes at specified point, surface, and volume detectors. Results are presented for sample problems involving primary neutron and both primary and secondary photon transport in a spherical reactor shield configuration. These results include the optimization of the shield configuration

Sensing the City: Legibility in the Context of Mediated Spatial Terrains

Smartphones, with their “pervasive presence” in contact with our bodies, have come to act as sensory prosthetics that mediate our experience of the city. They activate new possibilities of navigating the urban, such that we can find exactly what we want, rather than what has been placed before us. This article argues that smartphone technologies produce a more fluid engagement with urban space: where space is not so much “given” as “enacted.” In this context, notions of “legibility” take on new algorithmic and virtual forms. Thus, according to Hamilton and colleagues, where “the legible city waited to be read, the transparent city of data waits to be accessed.” Here, stable features dissolve as urban space becomes increasingly fluid and contingent, no longer limited by static patterns of inhabitation. Instead, how we move and where we move shift in accordance with the kinds of urban resources being activated at any given location, at any given moment, and in conjunction with the shifting vicissitudes of the crowd. In this context, the virtual (in its technological definition of cyber-enabled or -enacted space) mediates and activates the virtual (in its philosophical definition pertaining to the capacities of an entity that may or may not be manifested depending on context). The article considers the implications of this novel spatial mediation using an ontological perspective informed by complex adaptive systems theory, which considers forms and objects not as absolutes but rather as contingent entities activated through interactions