Design of an advanced 500-hp helicopter transmission

High contact ratio spar gears planetary, spiral besel gears, bearings, investment-cast planet carrier, and investment cast stainless-steel housings are discussed

Process-dependence of biogenic feedback effects in models of plankton dynamics.

The prospect of human-induced climate change has stimulated research into several biological processes that might affect climate. One such process that has attracted a substantial research effort is the so-called CLAW hypothesis (Charlson et al. 1987). This hypothesis suggests that marine plankton ecosystems may effectively regulate climate by a feedback associated with the production of dimethylsulphide (DMS). Charlson et al. (1987) observed that some of the DMS produced by marine ecosystems is transferred from the ocean to the atmosphere where it is the major source of cloud condensing nuclei (CCN) over the remote oceans. The aerosols resulting from biogenic DMS emissions can have a direct effect on the solar radiative forcing experienced by the Earth through scattering, absorption and reflection and can also lead to increased cloud formation; the CLAW hypothesis proposes that these mechanisms could regulate climate. Charlson et al (1987) argued that an increase in global temperature would lead to increased biogenic DMS emissions from the ocean and result in an increase in scattering, cloud cover and cloud albedo that would increase the proportion of the incoming solar radiation reflected back into space (thus changing the global albedo), and thereby cooling the planet. The objective of this paper is to examine the implications of the climate regulation process proposed by Charlson et al. (1987) for the dynamics of the ecosystems that produce it. Cropp et al. (2007) developed a simple plankton model that incorporated the DMS feedback mechanism and compared its dynamics to the same ecosystem model without the feedback. These simulations revealed that the presence of the feedback generally enhanced the stability of the ecosystem by making it more resilient to perturbation. In this research, we compare the effect of the feedbacks on a similar NPZ ecosystem model that has a greater range of dynamical behaviour than the model used by Cropp et al. (2007). The results of simulations with the new feedback model are compared to the results of Cropp et al. (2007) to elucidate the influence of the model formulation on the effects of the feedback

Filament wound data base development, revision 1

The objective was to update the present Space Shuttle Solid Rocket Booster (SRB) baseline reentry aerodynamic data base and to develop a new reentry data base for the filament wound case SRB along with individual protuberance increments. Lockheed's procedures for performing these tasks are discussed. Free fall of the SRBs after separation from the Space Shuttle Launch Vehicle is completely uncontrolled. However, the SRBs must decelerate to a velocity and attitude that is suitable for parachute deployment. To determine the SRB reentry trajectory parameters, including the rate of deceleration and attitude history during free-fall, engineers at Marshall Space Flight Center are using a six-degree-of-freedom computer program to predict dynamic behavior. Static stability aerodynamic coefficients are part of the information required for input into this computer program. Lockheed analyzed the existing reentry aerodynamic data tape (Data Tape 5) for the current steel case SRB. This analysis resulted in the development of Data Tape 7

Modelling dimethylsulphide production at the Bermuda Atlantic time series (BATS)

Dimethylsulphide (DMS) is produced by upper ocean ecosystems and emitted to the atmosphere where it may have an important role in climate regulation. Several attempts to quantify the role of DMS in climate change have been undertaken in modeling studies. We examine a model of biogenic DMS production and describe its endogenous dynamics and sensitivities. We extend the model to develop a one-dimensional version that more accurately resolves the important processes of the mixed layer in determining the ecosystem dynamics. Comparisons of the results of the one-dimensional model with vertical profiles of DMS in the upper ocean measured at the Bermuda Atlantic Time Series suggest that the model represents the interaction between the biological and physical processes well. Our analysis of the model confirms its veracity and provides insights into the important processes determining DMS concentration in the oceans

Capillary rise in porous fibrous media during liquid immersion

The modified Washburn equation has been further developed in this work, to examine capillary rise in porous media which are being immersed in liquid at a continuous rate. The capillary rise rate and/or properties of the media can be determined by a series of differential equations which govern the processes. The model was applied to oleophillic and oleophobic porous, fibrous media with generally good results, however it was found that the model needed to be fitted separately to the initial rise phase and to the longer-term (near-constant slope) phase. It was also found that a good agreement between the theory and experiment could be found if the porous media was contained inside a glass tube so that inflow could only occur from below and not from the sides of the filter. In order to model the insertion of media without this tube, a combination of a horizontal and a vertical capillary model was needed. The model could not be easily fitted to very thin, oleophillic media, and reasons for this are discussed; one likely reason being the inflow of liquid from the sides of the media. However, good agreement between the model and experiment could be found for equivalent media with an oleophobic coating and the same oil

Pluralistic ignorance concerning alcohol usage among recent high school graduates

Recent high school graduates in a midwestern community estimated their classmates\u27 attitudes toward alcohol use in contrast to their own positions. Attitudes were assessed on three levels: subjective comfort with others\u27 drinking, approval of peer drinking and actual drinking practices. Pluralistic ignorance was found to be a significant factor at all three levels, p \u3c .0005. Respondents reported that they were less comfortable, less approving, and drank less than close friends, lesser still than friends, and far less than peers. These findings provide support for normative education prevention programs that attempt to correct erroneous perceptions about alcohol use and abuse

Modelling the Influence of Filter Structure on Efficiency nd Pressure Drop in Knitted Filters

Fibrous filters are used extensively in a range of applications, including process engineering, automotive filtration and for worker (respiratory) protection. These filters are usually a felted, nonwoven structure of randomly arranged fibres. However, a special class of such filters exists - knitted filters. These filters are advantageous for many applications, as their knitted structure imparts significant mechanical strength. The structure of the fibres in such filters can be described by the classical strophoid equation. There has been relatively little study on the pressure drop and efficiency of such filters. This work has developed a geometric model of a knitted metal filter, by applying the strophoid equation. The geometric model thus allows a range of geometries to be generated, based on the strophoid variables, and also fibre/wire diameter, then the knits layered at a given bulk porosity (packing density), to create a geometry of desired properties. The geometric model outputs can then be coupled with a novel computational fluid dynamics (CFD) model for fibrous filtration (developed by the authors). This then allows, the relationship between the aforementioned structural properties and critical filter properties such as particle capture efficiency and pressure drop to be investigated. This work examined the pressure drop and efficiency of a knitted filter geometry at 3 different packing densities. The CFD results were compared to classical single fibre efficiency theory for conventional fibrous filters. The CFD results showed increased capture efficiency and pressure drop compared to fibrous filter theory

On the elliptic generating region of a tsunami

The surface elevation is calculated for the three-dimensional motion of waves in a fluid of constant depth subject to a given bottom velocity. An example, modeling tsunami generation, with antisymmetric bottom velocity, is considered in detail. The amplitude of the wave front is found to decay much more rapidly than the main wave. The distribution of amplitude with wave number and with angular position is computed for some cases

Using a finite element grid on corner points in flow models

One of the main functions of a multilayer cover liner is to prevent water from infiltrating into mine or other waste thereby preventing the occurrence of ground water pollution. In the past, numerical models have predominantly dealt with vertical infiltration or infiltration into sloping hillsides of infinite extent. The two layer model investigated in this paper has a more realistic shape which is piece-wise linear with a horizontal top, vertical bottom and a sloping section in-between. At the intersection of these segments are corner points where there are changes from sloping flow dynamics to either vertical or horizontal flow dynamics, depending on the corner point. The abrupt change in dynamics at the corner points can cause numerical problems especially when dealing with the boundary condition at the interface of two soils. This paper will deal with the corner point problem at the soil layer interface and, in particular, investigate the use of a finite element grid around the corner points