Optimization models for the economic design of wind power systems

This paper presents optimization models for the economic design of large scale wind power systems. Two basic models are introduced: (1) Systems without storage—all power generated is fed directly into the existing network, and (2) systems with storage—the systems are operated as part of base load or peak load capacity. The objective of the models is to maximize the total net value of power generated under assumed operating rules and general conditions regarding wind speed and demand variations. The model for wind power systems without storage is developed to determine the total capacity of wind turbines that vary in the values of design parameters such as rotor diameter, tower height, and rated power. The model for systems with storage uses an analytical storage model as a basis of representing storage requirements. The model is designed for the case of little serial correlation in successively measured wind speeds. It is then modified for the case of a low degree of correlation. Separable programming is used as a solution technique in both models and limited computational results, based on available cost estimates and Oklahoma wind and demand data, are presented to illustrate the use of the models. In the first model, separable programming will yield a globally optimal solution for certain types of cost functions used. However, in the second model, the problem structure is such that a global optimum cannot be guaranteed.     

Classical atomistic simulations of surfaces and heterogeneous interfaces with the charge-optimized many body (COMB) potentials

Interest in atomic scale computational simulations of multi-phase systems has grown as our ability to simulate nanometer-sized systems has become commonplace. The recently developed charge optimized many body potential (COMB) potentials have significantly enhanced the atomic-scale simulation of heterogeneous material systems, including chemical reactions at surfaces and the physical properties of interfaces. The COMB formalism, which merges variable charge electrostatic interactions with a classical analytical potential, has the capacity to adaptively model metallic, covalent, ionic and van der Waals bonding in the same simulation cell and dynamically determine the charges according to the local environment. Presented here is the theoretical background and evolution of the COMB potential family. The parameterization of the potential is described for several metals, ceramics, a semiconductor, and hydrocarbons, with the intent that the final parameter sets are consistent among materials. The utility of this approach is illustrated with several examples that explore the structure, stability, and mechanical and thermal properties of metallic systems and metal-ceramic and semi-conductor oxide interfaces, including surfaces and/or interfaces of copper and cuprite, copper and silica, silicon and silica, silicon and hafnia, and copper and zinc oxide. The potential is also applied to the simulation of atomic scale processes such as early stage oxidation of copper surfaces, tensile test of polycrystalline zirconium, and hyper-thermal deposition of ethyl radicals on selected copper surfaces.     

Composition of interfacial layers in complex food emulsions before and after aeration: effect of egg to milk protein ratio

Whipped emulsions were prepared at pilot scale from fresh milk, whole egg, and other ingredients, for example, sugars and stabilizers (starch, polysaccharides). Egg content was varied: 4 recipes were studied differing in their egg to milk protein ratio (0, 0.25, 0.38, and 0.68). Protein and fat contents were kept constant by adjusting the recipes with skim-milk powder and fresh cream. Emulsions were prepared by high-pressure homogenization and whipped on a pilot plant. Particle-size distribution determined by laser-light scattering showed an extensive aggregation of fat globules in both mix and whipped emulsions, regardless of recipe. Amount of protein adsorbed at the oil-water interface and protein composition of adsorbed layer were determined after isolation of fat globules. Protein load is strongly increased by the presence of egg in formula. Values obtained for the whipped emulsions were dramatically lower than those obtained for the mix by a factor of 2 to 3. Sodium dodecyl sulfate-PAGE indicated a preferential adsorption of egg proteins over milk proteins at the oil-water interface, regardless of recipe. This phenomenon was more marked in aerated than in unaerated emulsions, showing evidence for desorption of some milk proteins during whipping. Egg proteins stabilize mainly the fat globule surface and ensure emulsion stability before whipping. Air bubble size distribution in whipped emulsions was measured after 15 d storage. When the egg to milk protein ratio is decreased to 0.25, large air cells appear in whipped emulsions during storage, indicating mousse destabilization. The present work allows linking the protein composition of adsorbed layers at the fat globule surface to mousse formula and mousse stability.     

High and low rigor temperature effects on sheep meat tenderness and ageing

Immediately after electrical stimulation, the paired m. longissimus thoracis et lumborum (LT) of 40 sheep were boned out and wrapped tightly with a polyethylene cling film. One of the paired LT's was chilled in 15°C air to reach a rigor mortis (rigor) temperature of 18°C and the other side was placed in a water bath at 35°C and achieved rigor at this temperature. Wrapping reduced rigor shortening and mimicked meat left on the carcass. After rigor, the meat was aged at 15°C for 0, 8, 26 and 72 h and then frozen. The frozen meat was cooked to 75°C in an 85°C water bath and shear force values obtained from a 1×1 cm cross-section. The shear force values of meat for 18 and 35°C rigor were similar at zero ageing, but as ageing progressed, the 18 rigor meat aged faster and became more tender than meat that went into rigor at 35°C (P<0.001). The mean sarcomere length values of meat samples for 18 and 35°C rigor at each ageing time were significantly different (P<0.001), the samples at 35°C being shorter. When the short sarcomere length values and corresponding shear force values were removed for further data analysis, the shear force values for the 35°C rigor were still significantly greater. Thus the toughness of 35°C meat was not a consequence of muscle shortening and appears to be due to both a faster rate of tenderisation and the meat tenderising to a greater extent at the lower temperature. The cook loss at 35°C rigor (30.5%) was greater than that at 18°C rigor (28.4%) (P<0.01) and the colour Hunter L values were higher at 35°C (P<0.01) compared with 18°C, but there were no significant differences in a or b values.     

Carcinoma of the supraglottic larynx. A review of 221 cases

Between 1962 and 1971, 221 patients (197 men and 24 women) with carcinoma of the supraglottic larynx were treated at our institution. Most of the patients were in the sixth and seventh decades of life. In 89% of the patients, the epiglottis was involved. One hundred ninety patients underwent surgery, 161 for cure initially and 29 for salvage after radiation failure. Definitive surgery included laryngectomy in 117 patients and conservation procedures in 40. Fifty-five patients were treated by radiation for cure. Survival rates after laryngectomy or supraglottic laryngectomy were similar, but radiation therapy carried a poorer prognosis than did definitive surgery. Routine neck dissection was not necessary in all patients with supraglottic carcinoma.     

Behavioral correlates of achievements: A look at high and low achievers.

Examined the relationship of classroom behavior to academic achievement among high and low achieving elementary school children. Classroom behavior of 312 3rd and 4th graders was observed during math and verbal skills instruction and coded in discrete categories using J. A. Cobb's (see record 1972-21857-001) method. Scores from each category were correlated with math and verbal achievement scores for both high and low achievers. Regression equations predicting achievement in each setting were cross-validated in the other setting. Different behaviors were significantly correlated with achievement in each group, and multiple regressions predicting achievement for one group could not be cross-validated in the other group. Results demonstrate that the patterns of behavior stably related to achievement across academic settings may be dissimilar among groups of children in the same setting with different levels of achievement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validation of a microbiological method: the STAR protocol, a five-plate test, for the screening of antibiotic residues in milk.

The results of an in-house laboratory validation of a microbiological method for the screening of antibiotic residues in milk are presented. The sensitivity of this five-plate test, called Screening Test for Antibiotic Residues (STAR), was established by the analysis of milk samples spiked with 66 antibiotics at eight different concentrations. Ten different groups of antibiotics were studied: macrolides, aminoglycosides, cephalosporins, penicillins, quinolones, tetracyclines, sulphonamides, lincosamides, phenicolated and miscellaneous drugs. It was shown that 21 antibiotics were detected by the STAR protocol at or below the maximum residue limit (MRL), and that a further 27 drugs could be detected at levels from the MRL up to four times the MRL. The sensitivity of the STAR protocol was at or below the MRL for three macrolides, one tetracycline, two aminoglycosides, some sulphonamides, half of the beta-lactams, quinolones, lincosamides, trimethoprim and baquiloprim. Moreover, the STAR protocol was at least twice as sensitive as conventional methods for macrolides, quinolones and tetracyclines. The other antibiotics had limits of detection between four and 150 times the MRL. Each plate was preferentially sensitive for one or two families of antibacterials: the plate Bacillus cereus for tetracyclines, the plate Escherichia coli for quinolones, the plate Basillus subtilis for aminoglycosides, the plate Kocuria varians for macrolides, and the plate Bacillus stearothermophilus for sulphonamides and beta-lactams. This method has been used routinely on a day-to-day basis to direct the physicochemical confirmation towards one or two families of antibiotics. Considering the high cost of liquid chromatography coupled with tandem mass spectrometry detection analyses, the reduction of the range of antibiotics to test for confirmation is a significant gain in time and money.     

The passive ALWR approach to assuring containment integrity

Design requirements for the advanced light water reactor (ALWR) have been developed so as to provide high assurance of containment integrity even in the event of a severe accident. The containment integrity requirements are in the form of two design criteria, and associated methodology, which address containment severe accident performance and offsite dose and are specified in the ALWR utility requirements document (URD), a set of detailed design requirements for next generation plants in the US.The containment performance criterion, which is the main focus of this paper, specifies that plant design characteristics and features shall be provided to preclude core damage sequences which could bypass containment and to withstand core damage sequence loads. This containment performance capability, along with the associated dose mitigation capability, provides a technical basis for emergency planning change since there would not be the same need for rapid offsite emergency response that is called for under the existing US emergency planning basis.     

Hydrodynamic hot-electron transport simulation based on the Monte Carlo method

A hydrodynamic hot electron model is used to study electron transport through a submicron N⁺ --- N --- N⁺ GaAs structure. This study is used to investigate improvements which the unique features of this model offer to analysis of devices operating under nonstationary transport conditions. The model is based upon semiclassical “hydrodynamic” conservation equations for the average carrier density, momentum and energy. The general model includes particle relaxation times, momentum relaxation times, energy relaxation times, electron temperature tensors and heat flow vectors as a function of average carrier energy for the Γ, X and L valleys of GaAs. For this study, we utilized a simplified single electron gas version of our model to clearly reveal the impact of the nonstationary terms in the model. Results from both a drift-diffusion model approach and a Monte Carlo analysis are used to show the relative accuracy and facility this new model offers for investigating practical submicron device structures operating under realistic conditions.