Thermal Conductivity and Volumetric Specific Heat Measurements of an RTV-655/Polyimide Aerogel Compound Under Varying Temperature

The ability to store cryogenic liquids for long duration space missions is essential to future manned space exploration. Boil-off of cryogens due to incident solar radiation leads to self-pressurization of a cryogenic liquid tank. An ideal tank construction material would have low thermal conductivity and would retain its structural integrity through extreme temperatures. In previous research, a small-scale RTV-655/polyimide aerogel cryogenic liquid storage tank was constructed and tested to assess the performance of the compound material. Further development of RTV-655/polyimide aerogel cryogenic tanks for space applications is contigent upon performing computational studies to optimize the tank design and minimize costly experiments. Morever, computational heat transfer models, specifically models simulating conduction heat transfer through the RTV-655/polyimide aerogel compound, are dependent on accurate, measured thermal conductivity and volumetric specific heat values for the RTV-655/polyimide aerogel compound at the temperatures of interest. Thermal conductivity and volumetric specific heat values of the combination of RTV-655 and polyimide aerogel heave not been published at cryogenic temperatures. The transient plane source method was used to measure the thermal conductivity and volumetric psecific heat for RTV-655, polyimide aerogel, and three volume ratios of the compound at 313K, 295K, 253K, and the cryogenic temperature of 85K

Verifying the fully “Laplacianised” posterior Naïve Bayesian approach and more

Mussa and Glen would like to thank Unilever for financial support, whereas Mussa and Mitchell thank the BBSRC for funding this research through grant BB/I00596X/1. Mitchell thanks the Scottish Universities Life Sciences Alliance (SULSA) for financial support.Background In a recent paper, Mussa, Mitchell and Glen (MMG) have mathematically demonstrated that the “Laplacian Corrected Modified Naïve Bayes” (LCMNB) algorithm can be viewed as a variant of the so-called Standard Naïve Bayes (SNB) scheme, whereby the role played by absence of compound features in classifying/assigning the compound to its appropriate class is ignored. MMG have also proffered guidelines regarding the conditions under which this omission may hold. Utilising three data sets, the present paper examines the validity of these guidelines in practice. The paper also extends MMG’s work and introduces a new version of the SNB classifier: “Tapered Naïve Bayes” (TNB). TNB does not discard the role of absence of a feature out of hand, nor does it fully consider its role. Hence, TNB encapsulates both SNB and LCMNB. Results LCMNB, SNB and TNB performed differently on classifying 4,658, 5,031 and 1,149 ligands (all chosen from the ChEMBL Database) distributed over 31 enzymes, 23 membrane receptors, and one ion-channel, four transporters and one transcription factor as their target proteins. When the number of features utilised was equal to or smaller than the “optimal” number of features for a given data set, SNB classifiers systematically gave better classification results than those yielded by LCMNB classifiers. The opposite was true when the number of features employed was markedly larger than the “optimal” number of features for this data set. Nonetheless, these LCMNB performances were worse than the classification performance achieved by SNB when the “optimal” number of features for the data set was utilised. TNB classifiers systematically outperformed both SNB and LCMNB classifiers. Conclusions The classification results obtained in this study concur with the mathematical based guidelines given in MMG’s paper—that is, ignoring the role of absence of a feature out of hand does not necessarily improve classification performance of the SNB approach; if anything, it could make the performance of the SNB method worse. The results obtained also lend support to the rationale, on which the TNB algorithm rests: handled judiciously, taking into account absence of features can enhance (not impair) the discriminatory classification power of the SNB approach.Publisher PDFPeer reviewe

On the interaction of Jupiter's Great Red Spot and zonal jet streams

In this paper, Jupiter's Great Red Spot (GRS) is used to determine properties of the Jovian atmosphere that cannot otherwise be found. These properties include the potential vorticity of the GRS and its neighboring jet streams, the shear imposed on the GRS by the jet streams, and the vertical entropy gradient (i.e., Rossby deformation radius). The cloud cover of the GRS, which is often used to define the GRS's area and aspect ratio, is found to differ significantly from the region of the GRS's potential vorticity anomaly. The westward-going jet stream to the north of the GRS and the eastward-going jet stream to its south are each found to have a large potential vorticity ``jump''. The jumps have opposite sign and as a consequence of their interaction with the GRS, the shear imposed on the GRS is reduced. The east-west to north-south aspect ratio of the GRS's potential vorticity anomaly depends on the ratio of the imposed shear to the strength of the anomaly. The aspect ratio is found to be $\approx$2:1, but without the opposing jumps it would be much greater. The GRS's high-speed collar and quiescent interior require that the potential vorticity in the interior be approximately half that in the collar. No other persistent geophysical vortex has a significant minimum of potential vorticity in its interior and laboratory vortices with such a minimum are unstable.Comment: Manuscript accepted to Journal of the Atmospheric Sciences, March 2007. v2: minor stylistic changes (after journal proof reading

Automatic Construction of Chinese-English Translation Lexicons

The process of constructing translation lexicons from parallel texts (bitexts) can be broken down into three stages: mapping bitext correspondence, counting co-occurrences, and estimating a translation model. State-of-the-art techniques for accomplishing each stage of the process had already been developed, but only for bitexts involving fairly similar languages. Correct and efficient implementation of each stage poses special challenges when the parallel texts involve two very different languages. This report describes our theoretical and empirical investigations into how existing techniques might be extended and applied to Chinese/English bitexts

Green Leaf Grocery - Executive Compensation Case Study

The primary purpose of this teaching case is to aid students in understanding how executive compensation plans are utilized to achieve organizational goals and to then construct their own executive compensation plan for the CEO of Greenleaf Grocery, a fictional retail business based on an actual company. Students have the opportunity to create a comprehensive executive compensation plan using salary, bonuses, stock options, benefits, and other compensation tools.  Additionally, the case provides the opportunity to discuss the use of both short-term and long-term incentive compensation.  The company in this case is poised to undertake an initial public offering of stock and retaining the current CEO is viewed as critical for this next phase.    The case affords the class the opportunity to explore ethical issues in executive compensation as well as other aspects of the organization’s overall compensation structure. &nbsp