A Modified Crank-Nicolson Method

In order to obtain a numerical solution to the heat equation using finite differences, either implicit or explicit equations are used to formulate a solution. The advantage in an explicit formulation is its simplicity and minimal computer storage requirements while its disadvantage is its instability. The opposite is true for an implicit formulation such as the Crank-Nicolson method; although it is stable it is more difficult to implement and requires a much larger memory capacity. In this paper we examine the accuracy and stability of a hybrid approach, a modified Crank-Nicolson formulation, that combines the advantageous features of both the implicit and explicit formulations. This hybrid approach results in a 20% reduction in the amount of work required compared to the standard Crank-Nicolson solution if both methods use a special tridiagonal system solver. If Gaussian elimination is used, the modified Crank-Nicolson approach reduces the amount of work by 87%. Regardless of the linear system solver used, the modified Crank-Nicolson approach reduces by 50% the memory requirement of the standard Crank-Nicolson method

Sceloporus jalapae

Number of Pages: 5Integrative BiologyGeological Science

Toronto City Hall and Square

Thesis (M.Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1958.ACCOMPANYING drawings held by MIT Museum.by David Ernest Horne.M.Arch

TakeCARE, a Video Bystander Program to Help Prevent Sexual Violence on College Campuses: Results of Two Randomized, Controlled Trials

Objective: The present research reports on two randomized controlled trials evaluating TakeCARE, a video bystander program designed to help prevent sexual violence on college campuses. Method: In Study 1, students were recruited from psychology courses at two universities. In Study 2, first-year students were recruited from a required course at one university. In both studies, students were randomly assigned to view one of two videos: TakeCARE or a control video on study skills. Just before viewing the videos, students completed measures of bystander behavior toward friends and ratings of self-efficacy for performing such behaviors. The efficacy measure was administered again after the video, and both the bystander behavior measure and the efficacy measure were administered at either one (Study 1) or two (Study 2) months later. Results: In both studies, students who viewed TakeCARE, compared to students who viewed the control video, reported engaging in more bystander behavior toward friends and greater feelings of efficacy for performing such behavior. In Study 1, feelings of efficacy mediated effects of TakeCARE on bystander behavior; this result did not emerge in Study 2. Conclusions: This research demonstrates that TakeCARE, a video bystander program, can positively influence bystander behavior toward friends. Given its potential to be easily distributed to an entire campus community, TakeCARE might be an effective addition to campus efforts to prevent sexual violence

Sceloporus halli

Number of Pages: 3Integrative BiologyGeological Science

A CCIR aeronautical mobile satellite report

Propagation effects in the aeronautical mobile-satellite service differ from those in the fixed-satellite service and other mobile-satellite services because: small antennas are used on aircraft, and the aircraft body may affect the performance of the antenna; high aircraft speeds cause large Doppler spreads; aircraft terminals must accommodate a large dynamic range in transmission and reception; and due to their high speeds, banking maneuvers, and three-dimensional operation, aircraft routinely require exceptionally high integrity of communications, making even short-term propagation effects very important. Data and models specifically required to characterize the path impairments are discussed, which include: tropospheric effects, including gaseous attenuation, cloud and rain attenuation, fog attenuation, refraction and scintillation; surface reflection (multipath) effects; ionospheric effects such as scintillation; and environmental effects (aircraft motion, sea state, land surface type). Aeronautical mobile-satellite systems may operate on a worldwide basis, including propagation paths at low elevation angles. Several measurements of multipath parameters over land and sea were conducted. In some cases, laboratory simulations are used to compare measured data and verify model parameters. The received signals is considered in terms of its possible components: a direct wave subject to atmospheric effects, and a reflected wave, which generally contains mostly a diffuse component

Sceloporus cautus

Number of Pages: 5Integrative BiologyGeological Science

Sceloporus heterolepis

Number of Pages: 3Integrative BiologyGeological Science

Contraction of the geographic range of distribution of snow crab (Chionoecetes opilio) in the eastern Bering Sea: An environmental ratchet?

Over the last three decades the geographic range of distribution of snow crab (Chionoecetes opilio) from the eastern Bering Sea (EBS) has contracted dramatically to the north. An increase in near-bottom temperature (NBT) during 1975–1979 was accompanied by a northward contraction of the cold pool (bound by the 2°C NBT isotherm) that extends over the Middle Domain during the summer. Warming was tracked with a 6-year lag by a contraction to the north of the mature female's range. Snow crab settle and grow to maturity in the Middle Domain. Successful recruitment during cold regimes may result from the occurrence of spring blooms and the stenothermy of early benthic instars. However, recruitment to the mature female population did not expand back to the southern shelf after the mid-1990s, despite some years when NBT was low. Cross-correlation of year-to-year shifts in geographic distribution of cod (Gadus macrocephalus) and immature snow crab during the 1990s suggests that the northward expansions of cod controlled the southern boundary of snow crab’s distribution range. Reestablishment of crab populations in the south may be hindered by cod predation. Also, because spawning females are now located “up-current,” advection of larvae to the south is unlikely. Contraction to the north may not be followed by an expansion back to the south after a change in regime. We refer to this suggested asymmetry as the environmental ratchet hypothesis and discuss it in the context of other conceptual models of the EBS ecosystem.Fil: Orensanz, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ernest, Billy. Universidad de Concepción; ChileFil: Armstrong, David A.. University of Washington; Estados UnidosFil: Stabeno, Phyllis. Pacific Marine Environmental Laboratory; Estados UnidosFil: Livingston, Pat. National Ocean And Atmospheric Administration. Alaska Fisheries Science Center; Estados Unido