A finite difference scheme for three-dimensional steady laminar incompressible flow

A finite difference scheme for three-dimensional steady laminar incompressible flows is presented. The Navier-Stokes equations are expressed conservatively in terms of velocity and pressure increments (delta form). First order upwind differences are used for first order partial derivatives of velocity increments resulting in a diagonally dominant matrix system. Central differences are applied to all other terms for second order accuracy. The SIMPLE pressure correction algorithm is used to satisfy the continuity equation. Numerical results are presented for cubic cavity flow problems for Reynolds numbers up to 2000 and are in good agreement with other numerical results

Natural ventilation induced by solar chimneys

Natural-ventilation flow through a two-dimensional but realsized square room is investigated numerically, using a commercial Computational Fluid Dynamics (CFD) software package. The flow is induced by a solar chimney positioned on the room's roof, and it is desired to have this flow passing through the lower part of the room for ventilation purpose. The chimney in turn is in the form of a parallel channel with one plate kept at a uniform temperature that is higher than that of the ambient air (by up to 40°C), while the other plate and all of the room's walls are insulated. Eftects on ventilation flow rate and flow pattern due to a range of changing factors are invcstigated. The factors include temperature of the chimney's heated plate, length and inclination of the chimney, its location and locations of the room's other openings, and the presence of a vertical partition in the room. It is found that all these factors affect either the flow rate or flow pattern, or both. Maximum flow rate is obtained when solar chimney is in a vertical position at a roofs corner, with its heated plate on the room side. On the other hand, flow rate increases with increasing solar plate's temperature and length, as expected, but the manner of the increase varies with relative positions behYcen the chimney and room inlcts

Free-Convection Flow Through a Two-Dimensional Box With Openings on Opposite Walls

Free-convection flow through a two-dimensional rectangular box having openings at opposite corners on the vertical walls is investigated numerically, using a commercial Computational Fluid Dynamics (CFD) software package. Convection is induced when the box's ceiling or its floor is imposed with a temperature that is different to that of the ambient fluid, while all other walls are insulated. The fluid here is air near standard conditions, with a molecular Prandtl number of 0.707. Computation is performed for a range of Rayleigh-number values, up to about 2.7×109. Chien's turbulence model of low-Reynolds-number K-e is used. When convection is induced by a cold roof or a hot floor, higher flow rate and heat transfer occur. However the resultant flow and temperature variation are more confined to the wall regions, while the rest of the box is relatively much less affected. All this is in contrast to when convection is due to a hot roof or a cold floor

How do you pay? The role of incentives at the point-of-sale

This paper uses discrete-choice models to quantify the role of consumer socioeconomic characteristics, payment instrument attributes, and transaction features on the probability of using cash, debit card, or credit card at the point-of-sale. We use the Bank of Canada 2009 Method of Payment Survey, a two-part survey among adult Canadians containing a detailed questionnaire and a three-day shopping diary. We find that cash is still used intensively at low value transactions due to speed, merchant acceptance, and low costs. Debit and credit cards are used more frequently for higher transaction values where safety, record keeping, the ability to delay payment and credit card rewards gain prominence. We present estimates of the elasticity of using a credit card with respect to credit card rewards. Reward elasticities are a key element in understanding the impact of retail payment pricing regulation on consumer payment instrument usage and welfare. JEL Classification: E41, C35, C83credit card rewards, discrete-choice models, Retail payments

Cooling by Free Convection at High Rayleigh Number of Cylinders Positioned Above a Plane

Free convection cooling of isothermal circular cylinders positioned above a horizontal plane is investigated numerically, using a commercial Computational Fluid Dynamics (CFD) software package. Computation is performed for high Rayleigh number, in the range 109 − 1011. Chien’s turbulence model of low-Reynolds-number K-ε is used, with Prandtl number of 0.707, corresponding to air near standard conditions. Influence of the underlying plane on heat transfer from the cylinders' surface is examined. As the gap between the plane and cylinders is narrowed, a pattern can be seen whereby heat transfer reaches a minimum that moves closer to the cylinder surface with higher Rayleigh number. The plane’s thermal condition, adiabatic versus isothermal, produces no significant difference in the heat transfer for the present range of gap ratio, in contrast to laminar case

Tour-based Travel Mode Choice Estimation based on Data Mining and Fuzzy Techniques

This paper extends tour-based mode choice model, which mainly includes individual trip level interactions, to include linked travel modes of consecutive trips of an individual. Travel modes of consecutive trip made by an individual in a household have strong dependency or co-relation because individuals try to maintain their travel modes or use a few combinations of modes for current and subsequent trips. Traditionally, tour based mode choice models involved nested logit models derived from expert knowledge. There are limitations associated with this approach. Logit models assumes i) specific model structure (linear utility model) in advance; and, ii) it holds across an entire historical observations. These assumptions about the predefined model may be representative of reality, however these rules or heuristics for tour based mode choice should ideally be derived from the survey data rather than based on expert knowledge/ judgment. Therefore, in this paper, we propose a novel data-driven methodology to address the issues identified in tour based mode choice. The proposed methodology is tested using the Household Travel Survey (HTS) data of Sydney metropolitan area and its performances are compared with the state-of-the-art approaches in this area

Lower order terms for the moments of symplectic and orthogonal families of LL-functions

We derive formulas for the terms in the conjectured asymptotic expansions of the moments, at the central point, of quadratic Dirichlet $L$-functions, $L(1/2,\chi_d)$, and also of the $L$-functions associated to quadratic twists of an elliptic curve over \Q. In so doing, we are led to study determinants of binomial coefficients of the form $\det (\binom{2k-i-\lambda_{k-i+1}}{2k-2j})$.Comment: 34 pages, 4 table

When an individual’s best friend begins dating someone new: what factors shape how that individual responds?

Powerful emotional responses and conflicts can arise between close friends when one of them begins to romantically see someone new. The addition of a third-party dating partner to an existing friendship is fraught with social consequences and complex negotiations of time (Larson & Richards, 1991; Roth & Parker, 2001). For example, availability for activities once shared by close friends now must be moderated by the amount of time needed to spend with the new partner. This can lead to strong, negative feelings as the friends struggle to make the adjustment and accommodate their friendship\u27s changing status. The emotion of jealousy is focused on within this study. It is an emotion that is aroused when individuals feel threatened in a close relationship (Lazarus, 1991). Within this study, a pool of participants were equally divided among those who are male and female, and those who are straight and non-straight completed various questionnaires assessing their attachment style, feelings of jealousy aroused, the type of relationship they have with their best friend (cross-sex vs. same-sex), and their own relationship status (unattached/single vs. attached/in a relationship). The design of this will allow an exploration of how the combination of all these factors (gender, type of relationship, sexual orientation, attachment style, and relationship status) may influence emotions of jealousy

Development and improvement of artificial diets for larvae of Diabrotica species using multidimensional design space techniques

The western corn rootworm (Coleoptera: Chrysomelidae; Diabrotica virgifera virgifera LeConte) and the northern corn rootworm (Coleoptera: Chrysomelidae; Diabrotica barberi Smith & Lawrence) are highly adaptive insect pests and have developed resistance to most possible management tactics in some regions. Transgenic maize hybrids, the latest control tools, which express insecticidal crystalline toxins from Bacillus thuringiensis (Bt) Berliner, have also faltered due to physiological adaptation of western corn rootworm populations. The United States Environmental Protection Agency has mandated insect resistance management plans for corn rootworms that have been directed toward monitoring the development of resistance to each of the Bt toxins. Toxicity bioassays using artificial diet have proven to be valuable for monitoring resistance to Bt toxins in corn rootworm populations. Currently, several proprietary diet formulations for western corn rootworm larvae that have been developed by each of the maize seed companies are used by industry and public researchers in toxicity bioassays to detect decreases in susceptibility of western corn rootworm populations to Bt proteins. No artificial diet has been developed specifically for northern corn rootworm larvae. Since differences in diet formulations can lead to different results in diet toxicity assays, it is impossible to make diet comparisons between toxicity assays using different artificial diets from individual companies and it may not be possible to determine an accurate picture of the test population's phenotype as it relates to Bt resistance. We report new diet formulations that support improved weight gain, larval development, and survival compared with current diets used in western corn rootworm and northern corn rootworm bioassays. The new formulations were created by using response surface modeling coupled with n-dimensional mixture designs to identify and optimize key ingredients based on integrated evaluation of several life history parameters (i.e., weight, molting, survival) while limiting contamination. The new rootworm formulations supported approximately 97% larval survival and molting and increased larval weight gain after 10 days of feedings compared to other diets used in western corn rootworm and northern corn rootworm bioassays rearing. These new formulations provide a standardized growth medium for western corn rootworm and northern corn rootworm larvae that will facilitate toxicity test comparisons conducted by different working groups and meets all regulatory requirements. We developed an improved diet formulation (WCRMO-1) for western corn rootworm (Chapter 2), which was the optimization of diet ingredients in the only published diet for western corn rootworm larvae. This formulation was also compatible for use with all current Bt proteins targeting western corn rootworm larvae. However, this formulation contains corn root powder, which is not available for purchase, limiting the practical use of the diets. We demonstrated that essential growth factors in corn roots that assist in western corn rootworm growth can be extracted suggesting substituting corn root powder with compounds identified from the extract may be possible (Chapter 3). An improved and accessible diet for western corn rootworm (WCRMO-2) that is comparable with all current diets for western corn rootworm larvae and without corn root powder was created by exploring and characterizing protein ingredients from plant, animal and yeast products (Chapter 4). Lastly, we developed the first artificial diet (NCRMO-1) for northern corn rootworm (Chapter 5) comprised of available ingredients that supports performance of northern corn rootworm larvae better than that of publicly available rootworm formulations.Includes bibliographical reference