Trends in the National Foster Care System

Graduate Textual or Investigativ

Loss Compensation in Time-Dependent Elastic Metamaterials

Materials with properties that are modulated in time are known to display wave phenomena showing energy increasing with time, with the rate mediated by the modulation. Until now there has been no accounting for material dissipation, which clearly counteracts energy growth. This paper provides an exact expression for the amplitude of elastic or acoustic waves propagating in lossy materials with properties that are periodically modulated in time. It is found that these materials can support a special propagation regime in which waves travel at constant amplitude, with temporal modulation compensating for the normal energy dissipation. We derive a general condition under which amplification due to time-dependent properties offsets the material dissipation. This identity relates band-gap properties associated with the temporal modulation and the average of the viscosity coefficient, thereby providing a simple recipe for the design of loss-compensated mechanical metamaterials

A Home of Their Own: Past Policies for Foster Care

For the past fifty years, the states and the National Congress has been attempting to fix problems associated with the Foster Care system. Some of these measures have been successful, while some have not. This raises the question of what effective policy is and what is not. The hypothesis is that a focus on the effective child placement and adoption as well as family reunification will be beneficial policy for the system. This is the question that this study will attempt to answer in order to provide better policies for the problems ailing the system. Through the course of the study, a legislative history was done that looked through bills related to the Foster Care system passed in Virginia, Arizona, and California. These bills were then compared to the data provided by the Children’s Bureau to determine points of correlation. It was found that emphasis on family, on private agencies, and streamlining the adoption process have been successful policies for the states. Conversely focusing on ideology and on small reactionary changes are unsuccessful policies. This study strove to give a roadmap to those looking to improve the system

Preventing Wide Area Blackouts in Transmission Systems: A New Approach for Intentional Controlled Islanding using Power Flow Tracing

A novel method to reduce the impact of wide area blackouts in transmission networks is presented. Millions of customers are affected each year due to blackouts. Splitting a transmission system into smaller islands could significantly reduce the effect of these blackouts. Large blackouts are typically a result of cascading faults which propagate throughout a network where Intentional Controlled Islanding (ICI) has the advantage of containing faults to smaller regions and stop them cascading further. Existing methodologies for ICI are typically calculated offline and will form pre-determined islands which can often lead to excessive splits. This thesis developed an ICI approach based on real time information which will calculate an islanding solution quickly in order to provide a ‘just-in-time’ strategy. The advantage of this method is that the island solution is designed based on the current operating point, but well also be designed for the particular disturbance location and hence will avoid unnecessary islanding. The new method will use a power flow tracing technique to find a boundary around a disturbance which forms the island that will be cut. The tracing method required only power flow information and so, can be computed quite quickly. The action of islanding itself can be a significant disturbance, therefore any islanding solution should aim to add as little stress as possible to the system. While methods which minimise the power imbalance and total power disrupted due to splitting are well documented, there has been little study into the effect islanding would have on voltage. There a new approach to consider the effects that islanding will have on the voltage stability of the system is developed. The ICI method is based on forming an island specific to a disturbance. If the location of a source is known along with information that a blackout is imminent, the methodology will find the best island in which to contain that disturbance. This is a slightly different approach to existing methods which will form islands independent of disturbance location knowledge. An area of influence is found around a node using power flow tracing, which consists of the strongly connected elements to the disturbance. Therefore, low power flows can be disconnected. This area of influence forms the island that will be disconnected, leaving the rest of the system intact. Hence minimising the number of islands formed. Finally the methodology is compared to the existing methods to show that the new tool developed in this thesis can find better solutions and that a new way of thinking about power system ICI can be put forward