background: high density concrete is extensively used for efficient radiation attenuation in radiotherapy rooms and nuclear reactors. over the past eight years, some efficient galena-based concrete samples for shielding x or gamma rays was produced. the goal of this study was to produce a novel high density concrete against neutron and photon radiations using tourmaline and galena. materials an...

background: the characteristics of secondary neutrons in a high energy radiation therapy room were studied using the mcnpx monte carlo (mc) code. materials and methods: two mc models including a model with full description of head components and a simplified model used in previous studies were implemented for mc simulations. results: results showed 4-53% difference between full and with the sim...

The implementation of internal social collaboration technologies confronts corporations with new challenges. Former unidirectional information flows become multidirectional and usercontent driven networks. Prior research describes the successful implementation as a challenging management task with employees’ usage at the center of attention. Consequently, corporations need to select a moderatio...

The Great Moderation refers to the fall in U.S. output growth volatility in the mid-1980s. At the same time, the United States experienced a moderation in inflation and lower average inflation. Using annual data since 1890, we find that an earlier, 1946 moderation in output and consumption growth was comparable to that of 1984. Using quarterly data since 1947, we also isolate the 1969–83 Great ...

The Great Moderation refers to the fall in U.S. output growth volatility in the mid-1980s. At the same time, the United States experienced a moderation in inflation and lower average inflation. Using annual data since 1890, we find that an earlier 1946 moderation in output and consumption growth was comparable to that of 1984. To assess the impact of these moderations, we also isolate the 1969–...

Why did the volatility of U.S. real GDP decline by more than the volatility of final sales with the Great Moderation in the mid-1980s? One possible explanation is that firms shifted their inventory behaviour towards a greater emphasis on production smoothing. In this paper, we investigate the role of inventories in the Great Moderation by estimating an unobserved components model that identifie...

The economy of the United States was markedly less volatile in the past two to three decades than in prior periods. The nation enjoyed long economic expansions in each of the last three decades, interrupted by recessions in 1990-91 and 2001 that were mild by historical standards. While it has proven difficult to conclusively pinpoint the causes of the reduced volatility, candidates include stru...