NUMERICAL AND EXPERIMENTAL STUDY OF A TWO-STAGE SAVONIUS WIND TURBINE

This article presents a numerical and experimental study of vertical axis wind turbine performance comparison involving a two-stage Savonius rotor with similar parameters. The experimental study is conducted in the aerodynamic tunnel at the Fluid Mechanics Laboratory of the Federal University of Rio Grande do Sul. The aerodynamics rotors are manufactured by 3D prototyping technique. Numerical simulations are performed using the Finite Volumes Method performed by the solution of the Reynolds Averaged Navier-Stokes (RANS) and continuity equations using the SST k-ω turbulence model. The numerical domain is modeled in order to maintain the same characteristics of the experimental model. The mesh quality is evaluated through the GCI (Grid Convergence Index) method. The static and dynamic torque coefficients and the power coefficients are compared. The tests are made without blockage corrections due to the small blockage ratio from 7.5%. Results show that the turbine has a positive static torque coefficient for any rotor angles. The dynamic torque reaches the maximum value for a tip speed ratio (λ) of 0.2 for the experimental and numerical cases. The relative difference between the numerical simulations and the experimental results are between 3.8% and 13.4%

Single-Calf Heifer System Profitability Compared to Other North Dakota Beef Production Systems

Production Economics, Productivity Analysis,

Feasibility of Establishing Small Livestock Slaughter Plants in North Dakota

Agribusiness,

Harmonic behavior of metallic glasses up to the metastable melt

In two amorphous alloys ZrTiCuNiBe and ZrAlNiCu coherent neutron scattering has been measured over five decades in energy, including measurements in the metastable melt of a metallic alloy more than 80 K above Tg. In the vibrational spectra a pronounced "boson" peak is found: Even in crystallized samples the density of states exceeds the Debye ω2 model, and in the amorphous state low-frequency vibrations are further enhanced. The peak position shows no dispersion in q, while intensities are strongly correlated with the static structure factor. Over the full energy range the temperature dependence is strictly harmonic. From high-energy resolution measurements we establish lower bounds for the temperatures at which structural α and fast β relaxation become observable

Economic Feasibility of Utilizing Waste-Water Heat from Coal-Fired Electrical Generating Plants in Commercial Greenhouses in North Dakota

This study provides information on the economic feasibility of establishing commercial greenhouses utilizing waste-water heat in North Dakota.Production Economics, Resource /Energy Economics and Policy,

The new small-angle neutron scattering instrument SANS-1 at MLZ—characterization and first results

AbstractA thorough characterization of the key features of the new small-angle neutron scattering instrument SANS-1 at MLZ, a joint project of Technische Universität München and Helmholtz Zentrum Geesthacht, is presented. Measurements of the neutron beam profile, divergency and flux are given for various positions along the instrument including the sample position, and agree well with Monte Carlo simulations of SANS-1 using the program McStas. Secondly, the polarization option of SANS-1 is characterized for a broad wavelength band. A key feature of SANS-1 is the large accessible Q-range facilitated by the sideways movement of the detector. Particular attention is hence paid to the effects that arise due to large scattering angles on the detector where a standard cos3 solid angle correction is no longer applicable. Finally the performance of the instrument is characterized by a set of standard samples

The association between age at menarche and later risk of gestational diabetes is mediated by insulin resistance.

AIMS: Associations have been reported between age at menarche and the later risk of gestational diabetes. However, it is not known whether these associations reflect differences in insulin sensitivity and/or pancreatic β-cell function in pregnancy. METHODS: We examined this question in women enrolled in the prospective Cambridge Baby Growth Study who recalled their age at menarche in questionnaires during pregnancy. Polynomial logistic and linear regression models were used to relate menarche timing to the risk of gestational diabetes, both unadjusted and adjusted for the Homeostasis Model Assessments of insulin resistance (HOMA IR) and pancreatic β-cell function (HOMA B) at week 28 of pregnancy. RESULTS: Age at menarche showed a U-shaped association with gestational diabetes risk (linear term: p = 9.5 × 10-4; quadratic term: p = 1.0 × 10-3; n = 889; overall model p = 8.1 × 10-3). Age at menarche showed a negative linear association with insulin resistance (HOMA IR: β = -0.13, p = 5.2 × 10-4, n = 771), which explained the relationship between age at menarche and gestational diabetes risk (adjusted linear term going from p = 0.03-0.08; adjusted quadratic term going from p = 0.04-0.08; n = 771). Age at menarche also showed a negative linear association with β-cell function (HOMA B: β = -0.11, p = 2.8 × 10-3, n = 771) but this did not attenuate the relationship between age at menarche and gestational diabetes (adjusted linear term p = 0.02; adjusted quadratic term p = 0.03, n = 771). CONCLUSIONS: These results suggest that the associations between age at menarche and risk of gestational diabetes and raised pregnancy glucose concentrations may be mediated by insulin resistance.Funding for this study has come from the Wellbeing of Women (the Royal College of Obstetricians and Gynaecologists, UK) (RG1644). Other core funding has come from the Medical Research Council (7500001180, G1001995, U106179472), European Union Framework 5 (QLK4-1999-01422), the Mothercare Charitable Foundation (RG54608), Newlife Foundation for Disabled Children (07/20), and the World Cancer Research Fund International (2004/03). In addition, there has been support from National Institute for Health Research Cambridge Biomedical Research Centre. KO is supported by the Medical Research Council (Unit Programme number: MC_UU_12015/2)