Tradeoffs between AC power quality and DC bus ripple for 3-phase 3-wire inverter-connected devices within microgrids

Visions of future power systems contain high penetrations of inverters which are used to convert power from dc (direct current) to ac (alternating current) or vice versa. The behavior of these devices is dependent upon the choice and implementation of the control algorithms. In particular, there is a tradeoff between dc bus ripple and ac power quality. This study examines the tradeoffs. Four control modes are examined. Mathematical derivations are used to predict the key implications of each control mode. Then, an inverter is studied both in simulation and in hardware at the 10 kVA scale, in different microgrid environments of grid impedance and power quality. It is found that voltage-drive mode provides the best ac power quality, but at the expense of high dc bus ripple. Sinusoidal current generation and dual-sequence controllers provide relatively low dc bus ripple and relatively small effects on power quality. High-bandwidth dc bus ripple minimization mode works well in environments of low grid impedance, but is highly unsuitable within higher impedance microgrid environments and/or at low switching frequencies. The findings also suggest that the certification procedures given by G5/4, P29 and IEEE 1547 are potentially not adequate to cover all applications and scenarios

SBMLToolbox: an SBML toolbox for MATLAB users

We present SBMLToolbox, a toolbox that facilitates importing and exporting models represented in the Systems Biology Markup Language (SBML) in and out of the MATLAB environment and provides functionality that enables an experienced user of either SBML or MATLAB to combine the computing power of MATLAB with the portability and exchangeability of an SBML model. SBMLToolbox supports all levels and versions of SBML

Public ubiquitous computing systems:lessons from the e-campus display deployments

In this paper we reflect on our experiences of deploying ubiquitous computing systems in public spaces and present a series of lessons that we feel will be of benefit to researchers planning similar public deployments. We focus on experiences gained from building and deploying three experimental public display systems as part of the e-campus pro ject. However, we believe the lessons are likely to be generally applicable to many different types of public ubicomp deployment

The Crystal Structure of CeNi

X-ray diffraction methods were used to determine the cell constants and structure of CeNi. The unit cell is orthohombic. The spcae group is probably Cmcm with aO=3.77 +/- 0.01, bO=10.46 +/- 0.02, cO=4.37+/- 0.01 A. The cell formula is Ce4Ni4. The observed density if 7.51 grams/cm3 and the calculated density is 7.65 grams/cm3, a deviation of 1.8%

The good and the bad of diabetes mellitus in the critically ill

Diabetes mellitus is increasingly prevalent and associated with significant end organ damage that one may presume to impact upon critical illness. However, Siegelaar and colleagues present data that suggest, excepting those patients admitted to a cardiac intensive care unit, the presence of diabetes mellitus is not associated with increased mortality in critically ill patients. It is not possible to unpick how unmeasured parameters such as glycaemic control, the nature of whether type I or type II, or concomitant drug therapy confound the results. Nevertheless, the results are consistent with many risk-adjustment models used in the critically ill, and clinical practice that tolerates mild hyperglycaemia. Is it even possible that diabetes mellitus is protective

An Analysis of Music Education in the Paul L. Dunbar Elementary School Dallas, Texas

Since music is one of the main facets to a wholesome and happy life, it has been the consensus of the administrators of the Dallas Independent School District to plan a music education program that will enhance the musical growth of the students. It has been realized, that in music education, just in any other phase of education, apprehension and meaning will not be the same to all students because of the differences in maturation and understanding levels. The music education program is not one that is thought of as only to supply music for special occasions, but it is treated as an integral part of the elementary school curriculum. The purpose of this study was: 1. To emphasize the importance music education in the elementary school curriculum 2. To emphasize methods and procedures used in teaching music education on various class levels 3. To emphasize different interests, abilities, and capabilities of class divisions 4. To emphasize musical growth through musical experiences The scope of this research will include the general overview of music education on each grade level in the Dallas School System

Insulin and metabolic substrates during human sepsis

Rusavy and colleagues recently endeavoured to dissect out the metabolic effects of insulin in patients with severe sepsis, in the setting of normoglycaemia. Twenty stable patients were studied 3–7 days after admission using a euglycaemic clamp at two supraphysiological insulin levels. Increased doses of exogenous insulin caused preferential use of glucose as a metabolic substrate, while total energy expenditure remained constant. Consequently, hyperinsulinaemia reduced tissue oxygen demand and catabolism of protein in patients with sepsis; the benefits of these effects are not proven. The effects of insulin at different time points in sepsis were not examined