Switching Flow-Graph nonlinear modeling technique

A unified graphical modeling technique, “Switching Flow-Graph” is developed to study the nonlinear dynamic behavior of pulse-width-modulated (PWM) switching converters. Switching converters are variable structure systems with linear subsystems. Each subsystem can be represented by a flow-graph. The Switching Flow-Graph is obtained by combining the flowgraphs of the subsystems through the use of switching branches. The Switching Flow-Graph model is easy to derive, and it provides a visual representation of a switching converter system. Experiments demonstrate that the Switching Flow-Graph model has very good accuracy

Baseline groundwater chemistry : the Sherwood Sandstone of Devon and Somerset

This report describes the regional geochemistry of groundwater from the Sherwood Sandstone aquifer of Devon and Somerset. In order to assess the likely natural baseline chemistry of the groundwater in the area, information has been gathered from the strategic collection of 21 new groundwater samples, and from collation of existing groundwater, rainfall, mineralogical and geochemical data. The Sherwood Sandstone aquifer results from continental deposition during the early Triassic period. The deposition comprised thick clastic deposits in basins created during the late Permian. There are two distinct units: the Otter Sandstone Formation and the underlying Budleigh Salterton Pebble Beds Formation. These units form the most important aquifer in south-west England. The main chemical properties of the groundwater are determined by rainwater recharge reacting with the aquifer minerals. Of these minerals carbonates are the dominant influence on the water chemistry. While Ca is dominant in groundwaters from both aquifer units, the water types from the two units can be distinguished: the Otter Sandstone Formation aquifer has mainly Ca-HCO3 type waters, with some mixing towards Mg, and the groundwaters in the Budleigh Salterton Pebble Beds Formation aquifer are of Ca-HCO3 type to Na+K-Cl type. There is little variation in the major ion proportion of the groundwaters from the Otter Sandstone Formation, most likely as these represent groundwater in equilibrium with the minerals which give it this character. There is greater variation in the Budleigh Salterton Pebble Beds Formation groundwaters. Besides the difference in groundwater types, the groundwater from the Budleigh Salterton Pebble Beds Formation is more acidic, more oxic, has lower SEC values, and HCO3, Cr, U and Mg concentrations, and higher concentrations of Al, Be, Cd, Cr, Co, Tl and REE than the groundwater from the Otter Sandstone Formation. Human impacts on the water quality are evident. These are mainly visible in the presence of indicator contaminants, such as nitrate. The widespread presence and changes of nitrate concentrations over time indicate the extent to which the unconfined aquifer is influenced by modern farming practices or urban pollution. Concentrations of NO3-N exceeded the current drinking water limit of 11.3 mg L-1 in 25% of the sampled groundwaters, which probably reflects the intensification of agriculture in the study area over the last few decades. Indeed, the dominant land uses of the area are agriculture and grassland. However, recent legislation and the drive towards intelligent farming have meant that in some groundwaters the concentrations of nitrate are decreasing. While many of the groundwaters investigated in this study are of good inorganic quality there are some notable exceptions which contain elevated concentrations of Fe, SO4, Ni, Co and NO3. The distribution of the poor-quality is generally so sporadic that water quality would be difficult to predict prior to drilling a borehole. For many analytes, the 95th percentile of the distributions has been taken as a first approximation of an upper limit of baseline concentrations as this serves to eliminate the most extreme outlier concentrations that likely represent a distinct population

One-cycle control of switching converters

A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-cycle control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects switching errors in one switching cycle. There is no steady-state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with a constant frequency buck converter have demonstrated the robustness of the control method and verified the theoretical predictions. This new control method is very general and applicable to all types of pulse-width-modulated, resonant-based, or soft-switched switching converters for either voltage or current control in continuous or discontinuous conduction mode. Furthermore, it can be used to control any physical variable or abstract signal that is in the form of a switched variable or can be converted to the form of a switched variable

Intraracialized, Anti-Queer Microaggressions Towards Queer Black Men Research Prospectus

Microaggressions are the everyday verbal, nonverbal, and environmental slights, snubs, or insults, whether intentional or unintentional, that communicate hostile, derogatory, or negative messages to target persons based solely upon their marginalized group membership (Sue et al., 2007). As intersectional microaggression research remains understudied (Sterzing et al., 2017), the purpose of this project is to extend the platform by documenting the experiences that Queer Black males experience from microaggressions intraracially in their communities. Through qualitative research and an intersectional framework, I plan to examine the impacts, experiences, and coping methods that Queer Black men encounter from intersectional microaggressions, and additionally code how anti-Queer language is presented within Black vernacular language. Intersectional microaggression research is of high importance because prior research fails to take notice of the microaggressions that intersecting identity individuals encounter (Sterzing et. al., 2017). Although they might be invisible and subtle, microaggressions are truly damaging

Dynamics of one-cycle controlled Ćuk converters

One-cycle control is a nonlinear control method. The flow-graph modeling technique is employed to study the large-signal and small-signal dynamic behavior of one-cycle controlled switching converters. Systematic design method for one-cycle control systems is provided with the Ćuk converter as an example. Physical insight is given which explains how one-cycle control achieves instant control without infinite loop gain. Experimental results demonstrate that a Ćuk converter with one-cycle control reflects the power source perturbation in one-cycle and the average of the diode voltage follows the control reference in one cycle

Secure High DER Penetration Power Distribution Via Autonomously Coordinated Volt/VAR Control

Traditionally voltage control in distribution power system (DPS) is performed through voltage regulating devices (VRDs) including on load tap changers (OLTCs), step voltage regulators (SVRs), and switched capacitor banks (SCBs). The recent IEEE 1547-2018 from March 2018 requires inverter fed distributed energy resources (DERs) to contribute reactive power to support the grid voltage. To accommodate VAR from DERs, well-organized control algorithm is required to use in this mode to avoid grid oscillations and unintended switching operations of VRDs. This paper presents two voltage control strategies (i) static voltage control considering voltage-reactive power mode (IEEE 1547-2018), (ii) dynamic and extensive voltage control with maximum utilization of DER capacity and system stability. Further, effective time-graded control is implemented between VRDs and DER units to reduce the simultaneous and negative operation. The proposed voltage control strategies are tested in a realistic 140-bus southern California distribution power system through extensive time-domain simulation studies. The results show that voltage quality in a distribution system is effectively achieved through the proposed voltage control strategies with a significantly reduction in the number of switching operations of VRDs. In addition, proposed voltage control strategies increase reliability and security of the DPS during unexpected failures

November Snowfall Variability and Trends Around Lake Michigan: Sensitivity to Temperature and Teleconnection Patterns

Using available long-term stations, November climatology of temperature and snowfall since 1950 has been composited for the region near Lake Michigan. Daily data was examined for the available stations to explore the monthly temperature and snowfall, the number of days with snowfall, and snow cover. The characteristics of six sub-region composites were compared using composites around Lake Michigan, respectively. Early season snowfall is much more common in the eastern sub-regions, implying a dominant role of lake-effect snowfall to the overall climatology. The number of days with snowfall is greater in the eastern sub-regions. Western and eastern sub-regions both exhibit a negative correlation between snowfall and temperature. The snowfall is particularly sensitive to the number of near to below freezing days. Teleconnection processes were also examined and a deviation was found with El Niño Novembers as opposed to neutral and La Niña Novembers. A weaker relation to snowfall was seen to the North Atlantic Oscillation (NAO). There is a trend toward less November monthly snowfall and number of days with snow. For some stations in lake-effect prone areas, there are virtually no snowless Novembers in the initial decades, yet three or four out of ten Novembers have been essentially snowless since 1990

Anti-Queer Microaggressions Towards Queer Black Men

Microaggressions are reoccurring derogatory messages that degrade and/ or discredit one’s identity. While invisible and unknown to many, they remain visible and apparent to those impacted by them. The research questions for this project are: (1) What microaggressions do Queer Black men experience within larger society? (2) To contrast with larger society, what microaggressions do Queer Black men experience within Black communities? By conducting focus groups, I will examine the intersectional microaggressions that Queer Black males experience in their own community, as well as document microaggression that they experience in larger society. After conducting my focus groups, I will be adopting Derald Wing Sue’s taxonomy of microaggression themes to translate the underlying messages behind delivered microaggressions. The results in this study will aide in addressing an appeared gap within microaggression literature by, documenting how Queer Black males experience these muted, normalized insults and invalidations in societ

Quantum Bound States in Yang-Mills-Higgs Theory

We give rigorous proofs for the existence of infinitely many (non-BPS) bound states for two linear operators associated with the Yang-Mills-Higgs equations at vanishing Higgs self-coupling and for gauge group SU(2): the operator obtained by linearising the Yang-Mills-Higgs equations around a charge one monopole and the Laplace operator on the Atiyah-Hitchin moduli space of centred charge two monopoles. For the linearised system we use the Riesz-Galerkin approximation to compute upper bounds on the lowest 20 eigenvalues. We discuss the similarities in the spectrum of the linearised system and the Laplace operator, and interpret them in the light of electric-magnetic duality conjectures.Comment: minor corrections implemented; to appear in Communications in Mathematical Physic