ASSESSING THE COST OF BEEF QUALITY

The number of U.S. fed cattle marketed through a value based or grid marketing system is increasing dramatically. Most grids reward Choice or better quality grades and some pay premiums for red meat yield. The Choice-Select (C-S) price spread increased 55 percent, over $3/cwt between 1989-91 and 1999-01. However, there is a cost associated with pursuing these carcass premiums. This paper examines these tradeoffs both in the feedlot and in a retained ownership scenario. Correlations between carcass and performance traits resulted in economic tradeoffs that change across input costs and quality grade premiums and discounts. Feedlot profitability was largely determined by marbling, carcass weight, and feed efficiency. Carcass weight was most important at a low C-S spread. However, at average C-S spread and higher, marbling became the largest determinate of feedlot profits, and its importance increased with the C-S spread. Carcass weight and feed efficiency influence on feedlot profitability declined at higher C-S spreads. Rib-eye area was the fourth most important variable and declined in importance as marbling increased in importance. There is some indication that cows with lower feed costs also produce the most profitable calf for the feedlot, and vice-versa. The data suggests that cow size and marbling score are negatively correlated. The current trend toward wider C-S spreads and rewarding higher quality grading cattle places greater emphasis on marbling ability of calves. These correlations and results suggest that higher marbling is associated with lower cost cows to maintain.Livestock Production/Industries, Marketing,

Observation of gravity-capillary wave turbulence

We report the observation of the cross-over between gravity and capillary wave turbulence on the surface of mercury. The probability density functions of the turbulent wave height are found to be asymmetric and thus non Gaussian. The surface wave height displays power-law spectra in both regimes. In the capillary region, the exponent is in fair agreement with weak turbulence theory. In the gravity region, it depends on the forcing parameters. This can be related to the finite size of the container. In addition, the scaling of those spectra with the mean energy flux is found in disagreement with weak turbulence theory for both regimes

Observation of intermittency in wave turbulence

We report the observation of intermittency in gravity-capillary wave turbulence on the surface of mercury. We measure the temporal fluctuations of surface wave amplitude at a given location. We show that the shape of the probability density function of the local slope increments of the surface waves strongly changes across the time scales. The related structure functions and the flatness are found to be power laws of the time scale on more than one decade. The exponents of these power laws increase nonlinearly with the order of the structure function. All these observations show the intermittent nature of the increments of the local slope in wave turbulence. We discuss the possible origin of this intermittency.Comment: new version to Phys. Rev. Let

Freely decaying weak turbulence for sea surface gravity waves

We study numerically the generation of power laws in the framework of weak turbulence theory for surface gravity waves in deep water. Starting from a random wave field, we let the system evolve numerically according to the nonlinear Euler equations for gravity waves in infinitely deep water. In agreement with the theory of Zakharov and Filonenko, we find the formation of a power spectrum characterized by a power law of the form of $|{\bf k}|^{-2.5}$.Comment: 4 pages, 3 figure

Ocean response to a hurricane, part II : data tabulations and numerical modeling

Field observations of the ocean's forced stage response to three hurricanes, Norbert (1984), Josephine (1984) and Gloria (1985), are analyzed and presented in a storm-centered coordinate system. All three hurricanes had a non-dimensional speed of O(1) and produced a strongly rightward biased response of the ocean surface mixed layer (SML) transport and current. The maximum layer-averaged SML currents varried from 0.8 m S-1 in response to Josephine, which was a fairly weak hurricane, to 1.7 m S.l in response to Gloria, which was much stronger. In these two cases the current amplitude is set primarly by the strength of the wind stress and its efficiency of coupling with the SML current, and the depth of vertical mixing of the SML. The Norbert case (SML Burger number ≈ 1/2) was also affected by significant pressure-coupling with the thermocline that caused appreciable upwellng by inertial pumping and strong thermocline-depth currents, up to 0.3 m S-l, under the trailing edge of Norbert. The observed SML current has a vertical shear in the direction of the local wind of up to 0.01 S-l. This vertical shear causes the surface current to be larger than the layer-averaged SML current described above by typically 0.2 m S.l.Funding was provided by the Office of Naval Research under grant No. N00014-89-J-I053

Development and Testing of a Power Trough System Using a Structurally-Efficient, High-Performance, Large-Aperture Concentrator with Thin Glass Reflector and Focal Point Rotation

Industrial Solar Technology has assembled a team of experts to develop a large-aperture parabolic trough for the electric power market that moves beyond cost and operating limitations of 1980's designs based on sagged glass reflectors. IST's structurally efficient space frame design will require nearly 50% less material per square meter than a Solel LS-2 concentrator and the new trough will rotate around the focal point. This feature eliminates flexhoses that increase pump power, installation and maintenance costs. IST aims to deliver a concentrator module costing less than $100 per square meter that can produce temperatures up to 400 C. The IST concentrator is ideally suited for application of front surface film reflectors and ensures that US corporations will manufacture major components, except for the high temperature receivers

An Exercise in Forecasting Loop Current and Eddy Frontal Positions in the Gulf of Mexico

As part of a model-evaluation exercise to forecast Loop Current and Loop Current eddy frontal positions in the Gulf of Mexico, the Princeton Regional Ocean Forecast System (PROFS) is tested to forecast 14 4-week periods Aug/25/99- Sep/20/00, during which a powerful eddy, Eddy Juggernaut (Eddy-J) separated from the Loop Current and propagated southwestward. To initialize each forecast, PROFS assimilates satellite sea surface height (SSH) anomaly and temperature (SST) by projecting them into subsurface density using a surface/subsurface correlation that is a function of the satellite SSH anomaly. The closest distances of the forecast fronts from seven fixed stations in the northern Gulf over a 4-week forecast horizon are then compared against frontal observations derived primarily from drifters. Model forecasts beat persistence and the major source of error is found to be due to the initial hindcast fields

Systematic Study of Rogue Wave Probability Distributions in a Fourth-Order Nonlinear Schr\"odinger Equation

Nonlinear instability and refraction by ocean currents are both important mechanisms that go beyond the Rayleigh approximation and may be responsible for the formation of freak waves. In this paper, we quantitatively study nonlinear effects on the evolution of surface gravity waves on the ocean, to explore systematically the effects of various input parameters on the probability of freak wave formation. The fourth-order current-modified nonlinear Schr\"odinger equation (CNLS4) is employed to describe the wave evolution. By solving CNLS4 numerically, we are able to obtain quantitative predictions for the wave height distribution as a function of key environmental conditions such as average steepness, angular spread, and frequency spread of the local sea state. Additionally, we explore the spatial dependence of the wave height distribution, associated with the buildup of nonlinear development.Comment: 10 pages, 11 figures, to appear in Journal of Geophysical Research - Ocean

Field Survey of Parabolic Trough Receiver Thermal Performance: Preprint

This paper describes a technique that uses an infrared camera to evaluate the in-situ thermal performance of parabolic trough receivers at operating solar power plants