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An achromatic cold-neutron microscope with magnification 4 is demonstrated. The image-forming optics is composed of nested coaxial mirrors of full figures of revolution, so-called Wolter optics. The spatial resolution, field of view, and depth of focus are measured and found consistent with ray-tracing simulations. Methods of increasing the resolution and magnification are discussed, as well as the scientific case for the neutron microscope. In contrast to traditional pinhole-camera neutron imaging, the resolution of the microscope is determined by the mirrors rather than by the collimation of the beam, leading to possible dramatic improvements in the signal rate and resolution., United States. Dept. of Energy (Office of Basic Energy Sciences, Materials Sciences and Engineering under Award No. DE-FG02-09ER46556), United States. Dept. of Energy (Office of Basic Energy Sciences, Materials Sciences and Engineering under Award No. DE-FG02-09ER46557), United States. Dept. of Energy (interagency Agreement No. DE_AI01-01EE50660), National Institute of Standards and Technology (U.S.). Center for Neutron Research, National Institute of Standards and Technology (U.S.). Director’s Office, National Institute of Standards and Technology (U.S.). Radiation and Biomolecular Physics Division

This thesis presents an investigation into the power transmission limitations imposed on a VSC-HVdc converter by ac system strength and ac system impedance characteristics, quantified by the short circuit ratio (SCR). An important result of this study is that the operation of the converter is not only affected by the SCR’s magnitude, but is also significantly affected by the ac system’s impedance angle at the fundamental frequency. As the ac impedance becomes more resistive, the minimum SCR required at the rectifier side increases from that required for ideally inductive ac impedance, but it decreases at the inverter side. The finite megavolt ampere (MVA) limit of the VSC imposes a further limitation on power transfer, requiring an increase in the value of the minimum SCR. This limitation can be mitigated if additional reactive power support is provided at the point-common-connection. A state-space VSC model was developed and validated with a fully detailed non-linear EMT model. The model showed that gains of the phased-locked-loop (PLL), particularly at low SCRs greatly affect the operation of the VSC-HVdc converter and that operation at low SCRs below about 1.6 is difficult. The model also shows that the theoretically calculated power-voltage stability limit is not attainable in practice, but can be approached if the PLL gains are reduced. The thesis shows that as the VSC-HVdc converter is subject to large signal excitation, a good controller design cannot rely on small signal analysis alone. The thesis therefore proposes the application of optimization tools to coordinate the controls of multiple converters in a dc grid. A new method, the "single converter relaxation method", is proposed and validated. The design procedure of control gains selection using the single converter relaxation method for a multi-converter system is developed. A new method for selecting robust control gains to permit operation over a range of operation conditions is presented. The coordi

Primary gyratory crushers are unique pieces of equipment in a mineral processing plant. Unlike most large equipment which aims for steady, controlled power draw, the variable loading on a primary gyratory often shows very high force spikes, which correspond to momentarily higher torque requirements delivered to the electric drive motor. Measured field results showed crushing force spikes can be over 6 times the nominal crushing force, while brief torque spikes measured between the crusher and motor were typically nearly twice the nominal torque. Therefore, special consideration needs to be taken when designing an electric motor to drive a primary gyratory. The need to oversize the drive in order to account for the high load spikes of these crushers is discussed. Some installations have used oversized, derated standard motors in order to force commonality of spares or decrease capital costs. The aim of this paper is to describe the wide ranging and cyclical loads that are seen in the crusher and how proper motor design can be used to minimise downtime and require less amperage for a given torque supply., Primary gyratory crushers are unique pieces of equipment in a mineral processing plant. Unlike most large equipment which aims for steady, controlled power draw, the variable loading on a primary gyratory often shows very high force spikes, which correspond to momentarily higher torque requirements delivered to the electric drive motor. Measured field results showed crushing force spikes can be over 6 times the nominal crushing force, while brief torque spikes measured between the crusher and motor were typically nearly twice the nominal torque. Therefore, special consideration needs to be taken when designing an electric motor to drive a primary gyratory. The need to oversize the drive in order to account for the high load spikes of these crushers is discussed. Some installations have used oversized, derated standard motors in order to force commonality of spares or decrease capital costs. The aim of this paper is to describe the wide ranging and cyclical loads that are seen in the crusher and how proper motor design can be used to minimise downtime and require less amperage for a given torque supply.

This thesis proposes the small signal model for the Interline Power Flow Controller (IPFC). Using this model, the damping performance of the IPFC with different power system configuration is investigated and also compared with the AC Transmission System (FACTS) based controllers such as the Unified Power Flow Controller (UPFC). The IPFC and the UPFC in constant power control mode can be viewed as effectively cutting the connected transmission line. This change on the structure of the network results in a significant change on the small signal stability. This thesis also addresses issues regarding the different levels of models that are required for the investigation of the behavior of FACTS. An effective validation approach that uses a minimum sized demonstration platform is proposed. This platform is small enough for detailed EMTP validation, yet large enough to exhibit the range of transient electrical and electromechanical behavior which is the focus for FACTS devices. To demonstrate the approach, the small signal models of the system embedded with the IPFC and the UPFC are developed respectively. The results obtained from small signal analysis are validated with EMTP-type simulation and show a close agreement.

This TASC publication argues that globalisation not only impacts global flows of trade, finance and investment, it represents a major challenge to both the Irish state and community stakeholders at the most local level.