Mathisson-Papapetrou equations in metric and gauge theories of gravity in a Lagrangian formulation

We present a simple method to derive the semiclassical equations of motion for a spinning particle in a gravitational field. We investigate the cases of classical, rotating particles (pole-dipole particles), as well as particles with intrinsic spin. We show that, starting with a simple Lagrangian, one can derive equations for the spin evolution and momentum propagation in the framework of metric theories of gravity and in theories based on a Riemann-Cartan geometry (Poincare gauge theory), without explicitly referring to matter current densities (spin and energy-momentum). Our results agree with those derived from the multipole expansion of the current densities by the conventional Papapetrou method and from the WKB analysis for elementary particles.Comment: 28 page

Empowering Students’ Learning Achievement Through Project-Based Learning As Perceived By Electrical Instructors And Students

Purposes of this research were to find out factors empowering electrical students‘ learning achievement through Project-Based Learning (PBL) as perceived by instructors‘ and students‘ opinions. The sample chosen for this study were 247 electrical power instructors at vocational education institutes and 161 electrical students in the 3 rd and 4th year who were studying in the 1st semester of academic year 2006 at Electrical Education Department, Faculty of Industrial Education and Technology, King Mongkut‘s University of Technology Thonburi by using simple random sampling. The instrument used for data collection was 7 rating scales questionnaire. The reliability of the instrument calculated by Cronbach Alpha Coefficient was 0.8185 and 0.9839, respectively. The data were analysed by using mean ( ), Standard Deviation (S.D.) and Analysis of Factors by Principal Component Analysis technique: PCA, orthogonal rotation axis by Varimax Method. The results of the study on factors empowering electrical students‘ learning achievement through Project-Based Learning (PBL) were as follows: both instructors and students agreed on Interesting/Attention(0.799 and 0.885, respectively) while other factors such as Planning(0.722), Sharing Ideas(0.582), Thinking(0.576), Facilitating (0.547), Constructionism (0.540), Scientific Process (0.525), Multiple Intelligence (0.479), and Goal Setting(0.453) were perceived by instructors, and students‘ opinions were on Advising/Guiding(0.863), Thinking(0.661), Goal Setting (0.634), Multiple Intelligence(0.553), Scientific Process(0.528), Assisting(0.524), and Sharing Ideas (0.492), if not more so

Rheological Characteristics of Municipal Thickened Excess Activated Sludge (TEAS): Impacts of pH, Temperature, Solid Concentration and Polymer Dose

Rheological characterization of sludge is known to be an essential tool to optimize flow, mixing and other process parameters in wastewater treatment plants. This study deals with the characterization of thickened excess activated sludge in comparison to raw primary sludge and excess activated sludge. The effects of key parameters (total solid concentration, temperature, and pH) on the rheology and flow behavior of thickened excess activated sludge were studied. The rheological investigations were carried out for total solid concentration range of 0.9–3.7 %w/w, temperature range of 23–55 °C, and pH range of 3.6–10.0. Different rheological model equations were fitted to the experimental data. The model equations with better fitting were used to calculate the yield stress, apparent, zero-rate, infinite-rate viscosities, flow consistency index, and flow index. The decrease in concentration from 3.7 to 3.1 %w/w resulted in a drastic reduction of yield stress from 27.6 to 11.0 Pa, while a further reduction of yield stress to 1.3 Pa was observed as solid concentration was reduced to 1.3 %w/w. The viscosity at higher shear rate (>600 s−1) decreased from 0.05 Pa·s down to 0.008 Pa·s when the total solid concentration was reduced from 3.7 to 0.9 %. Yield stress decreased from 20.1 Pa down to 8.3 Pa for the Bingham plastic model when the temperature was raised from 25 to 55 °C. Activation energy and viscosity also showed decreasing trends with increasing temperature. Yield stress of thickened excess activated sludge increased from a value of 6.0 Pa to 8.3 Pa when the pH was increased from 3.6 to 10.0. The effect of polymer dose on the rheological behavior of the thickening of excess activated sludge was also investigated, and the optimum polymer dosage for enhanced thickener performance was determined to be 1.3 kg/ton DS

The elusive role of soil quality in nutrient cycling: a review

peer-reviewedCycling of nutrients, including nitrogen and phosphorus, is one of the ecosystem services we expect agricultural soils to deliver. Nutrient cycling incorporates the reuse of agricultural, industrial and municipal organic residues that, misleadingly, are often referred to as ‘wastes’. The present review disentangles the processes underlying the cycling of nutrients to better understand which soil properties determine the performance of that function. Four processes are identified (i) the capacity to receive nutrients, (ii) the capacity to make and keep nutrients available to crops, (iii) the capacity to support the uptake of nutrients by crops and (iv) the capacity to support their successful removal in harvested crop. Soil properties matter but it is imperative that, as constituents of ‘soil quality’, they should be evaluated in the context of management options and climate and not as ends in their own right. The effect of a soil property may vary depending on the prevailing climatic and hydrologic conditions and on other soil properties. We recognize that individual soil properties may be enhancing one of the processes underlying the cycling of nutrients but simultaneously weakening others. Competing demands on soil properties are even more obvious when considering other soil functions such as primary production, purification and flow regulation of water, climate modification and habitat provision, as shown by examples. Consequently, evaluations of soil properties and management actions need to be site-specific, taking account of local aspects of their suitability and potential challenges.Horizon 202