3,417 research outputs found
Magnesium-zinc reduction is effective in preparation of metals
Uranium, thorium, and plutonium are effectively prepared by magnesium-zinc reduction, using uranium oxides, thorium dioxide, and plutonium dioxide as starting materials. This technique is also useful in performing reduction of metals such as zirconium and titanium
Review of 'Man of the House' and Other New Short Stories from Kenya edited by Emma Dawson.
Review of 'Man of the House' and Other New Short Stories from Kenya edited by Emma Dawson
The hydrological impact of the Parangana Dam on the Mersey River, Tasmania
By diverting the waters of the Mersey River into a neighbouring basin, the Parangana Darn changed the
hydrological character of the downstream river. The flow records of three gauging stations, located at 10, 67 and 88 km below the dam, provide the basis for identifying changes. Intermediate discharges have decreased the most and even at the furthest downstream station are 50% lower than before. The flow extremes, at both ends of the scale, have been less affected, and particularly the less frequent discharges which can be augmented by overspill. Indeed the highest flood on record, with a recurrence interval of over 500 years, occurred in the post-dam period. One-day and 30-day minimum flows are markedly lower downstream of the dam, but below the Dasher, the main tributary of the Mersey, they seem to recover and have almost regained pre-dam levels by the mouth. The entry of unregulated tributaries in the middle section separates a much changed upstream hydrology from a downstream one able to mitigate the worst effects of the dam except at intermediate discharges. In the upstream part, the physical, chemical and biological character of the river could be adversely affected by the altered flow regime, particularly in those reaches immediately below the dam
Streamflow characteristics of northeastern Tasmania: I. regional flood flows
Based on streamflow records from thirteen stations, regional equations are developed which enable the
estimation of mean annual discharge and various flood flows at ungauged sites along rivers in northeastern Tasmania.
The area around Swansea is shown to be hydrologically distinct, at least as far as flood discharges are concerned, and the analysis subsequently focuses on the rest of the region. Despite the wide range of climatic and physiographic conditions there, relationships are highly significant, with drainage area explaining more than 97% of the variation in flood discharge. Rates of change are not only relatively high but increase with flood magnitude, suggesting rapid downstream transmission of flood waters. Network magnitude may be a viable alternative to drainage area as an estimator. Its use has the advantage that the downstream pattern of flow addition can be readily charted for major rivers, as illustrated for the Ringarooma and George
Streamflow characteristics of northeastern Tasmania: II. Hydraulic geometry
Relationships describing the adjustment of water-surface width, mean depth and mean velocity to increasing discharge are calculated for eleven sections in northeastern Tasmania. The at-a-station graphs of two sections display distinct discontinuities related, however, to different causes - sub-bankfull channelization and the attainment of overbank stage. Despite intra-reach and inter-fluvial variations in hydraulic geometry, two types of response seem to be dominant, characterised by a high rate of change of either depth or velocity. Two sections do not fit into this pattern and, significantly, they tend to plot poorly on downstream graphs.
Bankfull discharge probably lies between Q1.11 and Q2 at most sites, so both flows are used as reference discharges in analyses of downstream adjustment at the regional scale. The relations at Ql.ll and Q2 are quite similar and they are within the envelope defined by results from other areas. However, the data base is small and the scatter is large enough to render the velocity-discharge relation non-significant. The main residual from regression is the station on the South Esk at Perth which is used for discharge measurements at higher flows. Nevertheless, the hydraulic geometry equations enable estimates to be made of channel flow properties at ungauged sites within the northeastern river system
Transimpedance Amplifier for Polymer Photodiodes
Dr. Braun’s students in the Polymer Electronics Lab currently have a way to measure the light intensity from their light emitting devices however it consumes an unnecessary amount of space and power. I offer to improve upon the existing transimpedance circuit that Dr. Braun currently uses, reducing the total space occupied by the circuit and the power consumption of the current setup. The transimpedance circuit measures the incidence light intensity from the polymer-based photo detector and outputs an accurate, discrete, and measurable voltage. The current setup however utilizes two 20V wall warts for the positive and negative rails of the transimpedance amplifier. I plan to reduce the two 20V wall warts to a single 12V wall wart. Because of this, difficulty arises from both producing accurate voltage values near the negative rail, or ground, using a single supply, and from measuring the light intensity accurately without additional readings from noise and bias offsets. The current produced from the photo-sensor ranges from pico- to micro- amps, which is a sensitive domain to noise
Higher genus correlators for tensionless strings
It was recently shown in arXiv:2009.11306 that tree-level correlation
functions in tensionless string theory on
match the expected form of
correlation functions in the symmetric orbifold CFT on in the
large limit. This analysis utilized the free-field realization of the
Wess-Zumino-Witten model, along with a surprising
identity directly relating these correlation functions to a branched covering
of the boundary of . In particular, this identity implied the
unusual feature that the string theory correlators localize to points in the
moduli space for which the worldsheet covers the boundary of with
specified branching near the insertion points. In this work we generalize this
analysis past the tree-level approximation, demonstrating its validity to
higher genus worldsheets, and in turn providing strong evidence for this
incarnation of the correspondence at all orders in
perturbation theory.Comment: JHEP versio
The Use of Progressive-Ratio Schedules to Assess Negative Reinforcers
We used a combined multi-element, ABCBC reversal design to examine whether qualities of various negative reinforcers can be assessed under progressive-ratio schedules. Two adults with disabilities participated in this study. We assessed five sounds three times using progressive-ratio schedules to obtain mean break points for each stimulus and ranked negative reinforcers according to their mean break points. We called the stimulus with the highest mean break point the high-quality escape (HQE) stimulus and the stimulus with the lowest break point the low-quality escape (LQE) stimulus and examined responding according to different schedules of reinforcement for each stimulus: FR2, FR4, and FR8 for Jenny and FR1 and FR11 for April. We identified preferred and nonpreferred sounds for both participants.We observed differential responding for both participants between preferred and nonpreferred sounds. We observed differential responding between HQE and LQE stimuli for April but not for Jenny; a larger range in break points was observed for April. These results demonstrate a method to identify preferred and nonpreferred sounds and provide support for the possibility of using progressive-ratio schedules to rank negative reinforcers of various qualities
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