The 30-cm ion thruster power processor

A power processor unit for powering and controlling the 30 cm Mercury Electron-Bombardment Ion Thruster was designed, fabricated, and tested. The unit uses a unique and highly efficient transistor bridge inverter power stage in its implementation. The system operated from a 200 to 400 V dc input power bus, provides 12 independently controllable and closely regulated dc power outputs, and has an overall power conditioning capacity of 3.5 kW. Protective circuitry was incorporated as an integral part of the design to assure failure-free operation during transient and steady-state load faults. The implemented unit demonstrated an electrical efficiency between 91.5 and 91.9 at its nominal rated load over the 200 to 400 V dc input bus range

Helical Magnetorotational Instability in Magnetized Taylor-Couette Flow

Hollerbach and Rudiger have reported a new type of magnetorotational instability (MRI) in magnetized Taylor-Couette flow in the presence of combined axial and azimuthal magnetic fields. The salient advantage of this "helical'' MRI (HMRI) is that marginal instability occurs at arbitrarily low magnetic Reynolds and Lundquist numbers, suggesting that HMRI might be easier to realize than standard MRI (axial field only). We confirm their results, calculate HMRI growth rates, and show that in the resistive limit, HMRI is a weakly destabilized inertial oscillation propagating in a unique direction along the axis. But we report other features of HMRI that make it less attractive for experiments and for resistive astrophysical disks. Growth rates are small and require large axial currents. More fundamentally, instability of highly resistive flow is peculiar to infinitely long or periodic cylinders: finite cylinders with insulating endcaps are shown to be stable in this limit. Also, keplerian rotation profiles are stable in the resistive limit regardless of axial boundary conditions. Nevertheless, the addition of toroidal field lowers thresholds for instability even in finite cylinders.Comment: 16 pages, 2 figures, 1 table, submitted to PR

Generalized Differentiable Neural Architecture Search with Performance and Stability Improvements

This work introduces improvements to the stability and generalizability of Cyclic DARTS (CDARTS). CDARTS is a Differentiable Architecture Search (DARTS)-based approach to neural architecture search (NAS) that uses a cyclic feedback mechanism to train search and evaluation networks concurrently, thereby optimizing the search process by enforcing that the networks produce similar outputs. However, the dissimilarity between the loss functions used by the evaluation networks during the search and retraining phases results in a search-phase evaluation network, a sub-optimal proxy for the final evaluation network utilized during retraining. ICDARTS, a revised algorithm that reformulates the search phase loss functions to ensure the criteria for training the networks is consistent across both phases, is presented along with a modified process for discretizing the search network\u27s zero operations that allows the retention of these operations in the final evaluation networks. We pair the results of these changes with ablation studies of ICDARTS\u27 algorithm and network template. Multiple methods were then explored for expanding the search space of ICDARTS, including extending its operation set and implementing methods for discretizing its continuous search cells, further improving its discovered networks\u27 performance. In order to balance the flexibility of expanded search spaces with minimal compute costs, both a novel algorithm for incorporating efficient dynamic search spaces into ICDARTS and a multi-objective version of ICDARTS that incorporates an expected latency penalty term into its loss function are introduced. All enhancements to the original search algorithm are verified on two challenging scientific datasets. This work concludes by proposing and examining the preliminary results of a preliminary hierarchical version of ICDARTS that optimizes cell structures and network templates

Regulating Viatical Settlements: Is the Invisible Hand Picking the Pockets of the Terminally Ill?

The newly emerging viatical settlement industry has attracted considerable attention from both insurance regulators and advocates for the terminally ill. In a viatical settlement, a terminally ill person names a viatical settlement company as beneficiary under his life insurance policy in exchange for an immediate lump-sum cash payment of less than face value of the policy. To date, viatical settlement payments to people with AIDS (PWAs) have been disturbingly low as a percentage of the face value of PWA policies. This Note examines the few enacted viatical settlement regulations and the National Association of Insurance Commissioners\u27 model regulations as they particularly relate to PWAs). Acknowledging the importance of viatical settlements as a source of income for financially-strapped PWAs, this Note argues for a regulatory scheme in which PWAs receive greater protections and higher payouts than they receive in the current unregulated market, while still allowing viatical companies a reasonable return commensurate with the actual risks and costs of the viatical business. Part I argues that consumer protection rationales justify licensing and disclosure regulations. Part II explores controversial proposals for minimum payout regulations of viatical settlement providers and concludes that such regulations, if carefully crafted, are warranted. Finally, Part III examines the advent of accelerated benefits provisions in life insurance policies as alternatives to viatical settlements

Free radical processes involving electron transfer or producing [gamma]-lactones

The formation constants of isopropyldichloromercurate and isopropyldiiodomercurate have been calculated to be 8.0 x 10[superscript]-2 and 8.6 dm[superscript]3/mole, respectively, using the variation of [superscript]1H NMR shift as a function of halide ion concentration. The reaction of an equilibrium solution containing approximately 55% isopropyldichlorormercurate with bromotrichloromethane was studied. Evidence is presented that supports the conclusion that the reaction is a free radical chain mechanism of considerable length (initial kinetic chain length \u3e 38,000). The chain propagating step appears to be the reduction of the trichloromethyl radical by the isopropylmercurate. Though dialkylmercurials do not form mercurates with added iodide ion, the presence of iodide ion does significantly increase the production of alkyl bromides (in the reaction with bromotrichloromethane) by reducing the trichloromethyl radical before it can abstract a [beta]-hydrogen from the dialkylmercurial;The reaction of the 1-cyano-1-methylethyl radical with vinyl ethers was studied. In the absence of added electron acceptors, the reaction appears to be controlled by the substituent bound to the oxygen atom and can proceed via electron transfer or by radical abstractions or couplings. In substituent bound to the oxygen atom and can proceed via electron transfer or by radical abstractions or couplings. In the presence of added electron acceptors the reaction proceeds by electron transfer via an inner sphere electron transfer complex;The reaction of free radicals with tert-butyl peroxypent-4-enoate was studied. With alkyl mercurials the reaction gives moderate yields of [gamma]-lactones. With di-tert-butyl-mercury or trialkylphosphites the reaction gives 75-85% yields of the [gamma]-lactone, dihydro-5-(2,2-dimethylpropyl)-2(3H-furanone). Evidence is presented that indicates that the [gamma]-lactones are produced in a free radical chain manner

Tobacco Bed Treatment with Enide 50W

Enide 50W is recommended for trial use on tobacco beds for 1968. The results of treatments with Enide in Kentucky in 1967 have been somewhat variable; therefor e, until additional information is obtained and the tobacco grower becomes more experienced in applying the chemical, it should be used on a trial basis

Enide Recommended for Trial Use on Tobacco Beds

Enide 50W has now been cleared for use on tobacco beds. Treatments with Enide on tobacco beds in mid to late March. at time of seeding have given satisfactory weed control in experimental plots during the past 2 years. No injury or reduction in stand of tobacco plants was observed on plots treated at this time. Reduction in stand of plants did occur in plots treated in late fall. and there are some indications that there may be a reduction in stand from early treatments in February. To insure best results. the chemical should be applied evenly over the treated area. Until additional information is obtained and tobacco growers get more experience with its use, Enide 50W for 1967 is recommended for trial use on only a part of the plant bed

South west Victoria 2012-2050 : are the settlements sustainable?

Over the past few decades coastal cities around the world have grown at an incredible rate. With this growth have come major challenges relating to land use planning, social relationships, economic development, bio diversity and the ecological footprint. The following paper selects three regional coastal towns (Warrnambool, Portland and Port Fairy) situated in the Australian state of Victoria, and addresses the issues of: increasing population and population density, open space requirements, residential density issues, public transport coverage, employment and employment density, a shifting economic climate, environment and climate change, water quality issues and building energy consumption with subsequent C02 emissions. Through a series of simulations the nine issues for each of the three cities will be examined from 2012 through to 2030. The goal is to highlight the current and simulated future impacts of the selected issues and propose solutions that could mitigate those impacts

Stamp Out Chickweed and Henbit from Alfalfa

What are chickweed and henbit? Chickweed and henbit are winter annual weeds that grow during cool weather. The seeds germinate primarily in the fall, and the plants continue to grow and live through the winter. They develop new seeds from April until early summer. Then they die