Conflict on the mesa: Assessing defensibility of plaza-oriented villages in the Salinas Pueblo Province, New Mexico

Previous archaeological investigations of plaza-oriented villages in the Salinas Pueblo Province investigated the reasons people may have aggregated in these larger towns. The threat of warfare and the need for defense is one possible explanation for the construction of plaza-oriented villages, whose layout is seemingly intended to limit access. This thesis further assesses the defensibility of these sites using Geographic Information Systems (GIS). The use of a GIS approach offers an opportunity to evaluate the potential for line-of-sight communications and inter-visibility between the plaza pueblo villages on Chupadera Mesa, factors which influenced their ability to signal allies and anticipate attack. GIS also offers an opportunity to determine the relative defensibility of the region’s landforms, providing insight into the pueblo inhabitants’ site selection process

A Qualitative Study Toward Understanding Educators’ Perceptions of a Talent Development Program Designed to Address the Underrepresentation of Historically Marginalized Students in Advanced Programming in a Large Virginia School Division

This study extends the limited, existing research on Sunnydale Public School’s (SPS’s) SOAR program. For clarity, SOAR is a talent development (TD) program that aims to not only enhance students’ reasoning and problem-solving abilities but also to remedy the racial/ethnic disproportionality of SPS\u27s gifted and talented program. More specifically, I used interpretive, qualitative methods for this investigation to understand participants’ perceptions of SOAR, in hopes of adding to the talent development knowledge base and informing SOAR policy and practice. Ultimately, participant views converged on several topics (i.e. racial and ethnic disproportionality, brain malleability, multiple intelligences, etc.) and diverged on others (i.e. SOAR’s value). Taking interview and focus group data, SPS documents, past researchers’ findings, my own experiences, and existing literature into account, I arrived at and offer several commendations and recommendations that might benefit SPS’s SOAR program and might be considered alongside other research by districts of similar contexts looking to adopt or improve a TD program

A modelling and simulation of a sensorless control of five-phase PMSM drives using multi-dimension space vector modulation

This paper introduces a new method to track the saturation saliency for position measurement of a five-phase PMSM motor fed by a five-phase inverter through measuring the dynamic current response of the motor line currents due to the IGBT switching actions. The new method uses only the fundamental PWM waveform obtained using the multi-phase space vector pulse width modulation (i.e there is no modification to the operation of the five-phase inverter) similar to the fundamental PWM method proposed for a three-leg inverter. Simulation results are provided to verify the effectiveness of the proposed strategy for saliency tracking of a five-phase PMSM motor driven by five-phase inverter over a wide speed ranges under different load conditions

A SVM-3D Based Encoderless Control of a Fault-Tolerant PMSM Drive

This paper exhibits a novel technique to obtain an encoderless speed control of a permanent magnet synchronous motor (PMSM) in the case of a loss of one phase. The importance of this work is that it presents solutions in order to maintain the operation of the system in various conditions. This will increase the reliability of the whole drive system to meet the safety issues required in some applications. To achieve that, a fault-tolerant inverter modulated through a 3-dimension space vector pulse width modulation technique (3D-SVPWM) is used. Besides that, an algorithm to obtain the exact position of the saturation saliency in the case of a loss of one phase is introduced to achieve a closed-loop field-oriented encoderless speed control and to further enhance the reliability of the whole drive system. This algorithm is based on measuring the transient stator current responses of the motor due to the insulated-gate bipolar transistors (IGBTs) switching actions. Then according to the operating condition (normal or a loss of one phase), the saliency position signals are constructed from the dynamic current responses. Simulation results are provided to demonstrate the effectiveness of the saliency tracking technique under normal and under a loss of one phase conditions. Moreover, the results verify the maximum reliability for the whole drive system that is achieved in this work through a continuous operation of the drive system under a loss of one phase condition and under encoderless speed control

Sensorless Control of a Fault-Tolerant Multi-Level PMSM Drive

This paper presents a new technique to track the saliency position in a permanent magnet synchronous motor (PMSM) post a single phase open-circuit fault. The PMSM is driven by a fault-tolerant multi-level inverter that is utilized to implement a fault-tolerant control strategy to minimize system performance degradation post the fault.The fault-tolerant multi-level inverter is consisting of a number of insulated-gate bipolar transistors (IGBTs). The dynamic current reponses of the PMSM motor due to the switching actions of these IGBTs are used extract the saliency position. This process is not introducing any modification to the operation of the fault-tolerant multil-level inverter as it uses only the fundamental pulse width modulation (PWM) waveform. Moreover,it considers the modifications introduced to the PMSM motor and the multi-level inverter post the fault.Simulation results are provided to verify the effectiveness of the proposed strategy of saliency tracking of a PMSM motor driven by a fault-tolerant four-leg multi-level inverter over a wide range of speeds in the case of a single-phase open circuit fault

Control of 7-phase permanent magnet synchronous motor drive post three failures

The article is introducing a new control technique for the 7-phase permanent magnet synchronous motor (PMSM) drive to enhance its robustness against the failure of phases ‘a’ and ‘c’ in addition to the failure of the encoder occurring simultaneously. The article is firstly developing a new multi-dimension space vector pulse width modulation (SVPWM) technique as a part of the fault-tolerant control technique (FTC) to control the magnitudes and angles of the motor’s current after the failures of phases ‘a’ and ‘c’. Moreover, the paper is developing another FTC to obtain a sensorless operation of the 7-phase motor after the failure in the encoder while the phase ‘a’ and ‘c’ are faulted based on the tracking of the saturation saliency. Simulation results prove that the ripple in the speed post the three failures was maintained to be less than 10 rpm compared to 2 rpm when the 7-phase drive is running without faults. In addition to that, the results demonstrated that the motor responded to instant changes in speeds and loads with a dynamic response very close to that obtained when the 7-phase motor ran under healthy operating conditions

Mathematical analysis of the equivalent impedance at the harmonic frequency for the proposed aircraft power system

The proposals for the `More Electric Aircraft' place a significant, increased demand on the electrical power distribution system. To increase safety and reduce aircraft maintenance times on the ground, there is a greater need to quickly identify and locate electrical faults within the electrical distribution system. The work presented in this study provides the mathematical basis for the use of power system harmonic impedance measurement for identifying and locating faults within power cables. The method is passive - that is, it does not require the injection of any test signals - and can potentially be embedded into a centralised equipment controller to provide intelligent, real time diagnostics. The method monitors the harmonic line-line self-impedance at strategic points in the distribution system; this is obtained by measuring load voltage and current. Faults can be identified and located within a few fundamental cycles, and therefore provides a `backup protection' system which does not require measurement of the line current. It also can provide details of the fault location and could therefore be a significant aid to aircraft maintenance. This study derives the theoretical basis of the scheme and provides simulation results for a proposed aircraft power system to demonstrate the validity of this approach to detect and locate faults within the system