Bubble formation at two adjacent submerged orifices in inviscid fluids

A theoretical model has been developed as an extension of single orifice bubble formation to investigate the growth and detachment of vapor/gas bubbles formed at two adjacent submerged orifices in inviscid fluids. The mathematical model treats the two bubbles as an expanding control volume moving to the line of centers above a wall. The movement of the bubbles is obtained by application of force balance acting on the bubble and accounts for surface tension, buoyancy, steam momentum and liquid inertia effects. The liquid inertia effects are determined by applying inviscid and irrotational flow assumptions to allow potential flow theory to calculate the liquid velocity field which then allows the pressure distribution to be calculated. The model is extended to include the mass and energy equations to model the steam bubble formation in sub-cooled water. The theoretical results are compared with the available experimental data of bubble formation during constant mass flow steam bubble formation at two submerged upward facing orifices in sub-cooled water. The model was validated by available experimental data for the growth and detachment processes of two adjacent 1 mm orifices at system pressures of 2 and 3 bars, flow rates of 1.2-4 g/min at sub-cooling of 3.5-35 ºC. The comparisons of theory and experiments indicate that the model successfully predicts the bubbles growth and detachment for the range of conditions studied

GRID PRICING VERSUS AVERAGE PRICING FOR SLAUGHTER CATTLE: AN EMPIRICAL ANALYSIS

The paper compares weekly producer revenue under grid pricing and average dressed weight pricing methods for 2560 cattle over a period of 102 weeks. Regression analysis is applied to identify factors affecting the revenue differential.Livestock Production/Industries,

Carcass Quality Volume and Grid Pricing: An Investigation of Cause and Effect

The relationship between publicly reported weekly grid premiums and discounts for specific carcass characteristics and the percentage of those characteristics reflected in total weekly slaughter volume (i.e., proportional slaughter volume) is investigated. Granger Causality and multi-lag VAR models were used to investigate if grid premiums and discounts were efficiently transmitting market signals to producers with respect to carcass quality attributes. The empirical evidence indicates that there is little evidence to suggest that grid prices are providing efficient price signals to buyers and sellers with respect to market valuation of desirable and undesirable beef carcass characteristics.grid pricing, price discovery, price reporting, slaughter cattle

GRID PRICING FOR FED CATTLE: AN EMPIRICAL ANALYSIS

Weekly grid premium and discount price date for fed cattle have been collected over a 3-year period. The grid price data are combined with carcass data (2590 South Dakota slaughter steers) to investigate the variability in the average weekly carcass premium is affected by changes in packer-determined grid premiums and discounts on a weekly basis. The three-stage recursive model is then estimated using an autoregressive procedure. The results of the empirical analysis indicated that among all grid premiums and discounts, it is the choice-select discount that plays the dominant role in determining weekly changes in the average weekly carcass premium (discount).slaughter cattle, grid pricing, average pricing, value-based-marketing, Marketing,

Price Transparency in the Voluntary Price Reporting System for Live Cattle: Theory and Empirical Evidence

Interregional spatial linkages between South Dakota and Nebraska cash markets for slaughter cattle are investigated. Econometric procedures are used to test whether a thinning market effect or strategic price reporting behavior by packers has degraded market transparency under the voluntary price reporting system. Empirical evidence suggests transparency was not degraded.Demand and Price Analysis,

NAFTA INTRA INDUSTRY TRADE IN AGRICULTURAL FOOD PRODUCTS

The paper focuses on NAFTA's impact on intra-industry and inter-industry trade in agricultural food products. Bilateral trade among U.S., Canada, and Mexico, as well as their trade with the rest of the world during 1990 and 1995 are investigated. U.S. trade patterns for agricultural food products are slowly changing.International Relations/Trade,

The Effect of the Livestock Mandatory Reporting Act on Market Transparency and Grid Price Dispersion

The Livestock Mandatory Reporting Act (MPR) of 1999 was implemented in April 2001. Empirical evidence indicates a significant change in intra-week price dispersion associated with publicly reported fed cattle grid premiums and discounts occurring after MPR implementation. The research objective is to evaluate the effect of increased market transparency resulting from implementation of MPR, on grid intra-week premium and discount dispersion levels. Empirical results suggest that increased transparency is compatible with intra-week dispersion levels increasing. Increased dispersion suggests that during the pre-MPR period weekly premium and discount data may have been drawn from a non-representative sample. From the empirical evidence, it is concluded that reform of the livestock price-reporting system appears to have been necessary in the case of publically reported grid premiums and discounts.fed cattle, grid pricing, market transparency, price dispersion, price volatility, mandatory livestock price reporting, Agricultural and Food Policy, Demand and Price Analysis, Livestock Production/Industries,

Public Price Reporting in the Cash Market for Live Cattle: A Spatial Market Approach

Legislative authorization for the Livestock Mandatory Reporting Act of 1999 was renewed in October of 2006. One of the cited justifications for implementing mandatory reporting was that the voluntary reporting system for the slaughter cattle cash market was unable to provide accurate and timely market information. We extend the spatial market analysis literature by developing a methodology for detecting distortions in spatial relationships across related price series. Using spatially linked regional markets, we compare state-level mandatory price-reporting data to the U.S. Department of Agriculture voluntarily reported state data to determine if the spatial relationship between price-reporting mechanisms was disrupted by market distortions prior to implementation of federal mandatory price reporting. We found no empirical evidence of system failure; therefore, we conclude that market thinning or noncompetitive behavior had not reached the level necessary to disrupt the ability of the voluntary price-reporting system to provide timely and accurate price information.public price reporting, spatial markets, market integration, price transparency, price discovery, livestock markets, Livestock Production/Industries, Marketing,

The Affect of Animal Gender on Fed Cattle Producer Marketing Behavior

Weekly grid market share by volume for slaughter steers is compared to slaughter heifers. Summary statistics indicate average grid market share for steers (42%) is 27% higher than slaughter heifers (33%). The literature indicates that pregnancy and increased dark cutter incidence associated with heifers relative to steers creates additional financial risk when heifers are sold on a grid. Econometric analysis suggests grid market share is less sensitive to change in market conditions for heifers relative to steers. The empirical evidence is consistent with the supposition that marketing heifers is riskier than marketing steers on a grid. Thus sellers need stronger economic incentives to market heifers on a grid relative to steers.grid pricing, fed cattle, animal gender, risk, Livestock Production/Industries, Q00,

Variance Risk Premiums and Predictive Power of Alternative Forward Variances in the Corn Market

We propose a fear index for corn using the variance swap rate synthesized from out-of-the-money call and put options as a measure of implied variance. Previous studies estimate implied variance based on Black (1976) model or forecast variance using the GARCH models. Our implied variance approach, based on variance swap rate, is model independent. We compute the daily 60-day variance risk premiums based on the difference between the realized variance and implied variance for the period from 1987 to 2009. We find negative and time-varying variance risk premiums in the corn market. Our results contrast with Egelkraut, Garcia, and Sherrick (2007), but are in line with the findings of Simon (2002). We conclude that our synthesized implied variance contains superior information about future realized variance relative to the implied variance estimates based on the Black (1976) model and the variance forecasted using the GARCH(1,1) model.Variance Risk Premium, Variance Swap, Model-free Variance, Implied Variance, Realized Variance, Corn VIX