Bi-orthogonal Polynomials and the Five parameter Asymmetric Simple Exclusion Process

We apply the bi-moment determinant method to compute a representation of the matrix product algebra -- a quadratic algebra satisfied by the operators $\mathbf{d}$ and $\mathbf{e}$ -- for the five parameter ($\alpha$, $\beta$, $\gamma$, $\delta$ and $q$) Asymmetric Simple Exclusion Process. This method requires an $LDU$ decomposition of the ``bi-moment matrix''. The decomposition defines a new pair of basis vectors sets, the `boundary basis'. This basis is defined by the action of polynomials $\{P_n\}$ and $\{Q_n\}$ on the quantum oscillator basis (and its dual). Theses polynomials are orthogonal to themselves (ie.\ each satisfy a three term recurrence relation) and are orthogonal to each other (with respect to the same linear functional defining the stationary state). Hence termed `bi-orthogonal'. With respect to the boundary basis the bi-moment matrix is diagonal and the representation of the operator $\mathbf{d}+\mathbf{e}$ is tri-diagonal. This tri-diagonal matrix defines another set of orthogonal polynomials very closely related to the the Askey-Wilson polynomials (they have the same moments)

A superfluid helium system for an LST IR experiment

The results are presented of a study program directed toward evaluating the problems associated with cooling an LST instrument to 2 K for a year by using superfluid helium as the cooling means. The results include the parametric analysis of systems using helium only, and systems using helium plus a shield cryogen. A baseline system, using helium only is described. The baseline system is sized for an instrument heat leak of 50 mw. It contains 71 Kg of superfluid helium and has a total, filled weight of 217 Kg. A brief assessment of the technical problems associated with a long life, spaceborne superfluid helium storage system is also made. It is concluded that a one year life, superfluid helium cooling system is feasible, pending experimental verification of a suitable low g vent system

Effect of casing treatment of overall performance of axial-flow transonic fan stage with pressure ratio of 1.75 and tip solidity of 1.5

The effect of a number of casing treatments on the overall performance of a 1.75-pressure-ratio, 423-m/sec-tip-speed fan stage was evaluated. The skewed slot configuration with short-open slots over the midportion of the rotor had a stall margin of 23.5 percent, while the solid casing had a stall margin of 15.0 percent. The skewed slot configuration with long open slots extending ahead of and over portion of rotor displaced the stall line to the lowest flow at all speeds tested. At design speed, the peak efficiency for the long, forward open slots was 1 point less than that for the short midopen slots and 3 points less than that for the solid casing

Evaluation criteria for commercially oriented materials processing in space proposals

An approach and criteria for evaluating NASA funded experiments and demonstrations which have commercial potential were developed. Methods for insuring quick initial screening of commercial proposals are presented. Recommendations are given for modifying the current evaluation approach. New criteria for evaluating commercially orientated materials processing in space (MPS) proposals are introduced. The process for selection of qualified individuals to evaluate the phases of this approach and criteria is considered and guidelines are set for its implementation

Has the housing boom increased mortgage risk?

Adjustable rate mortgages

Auditing the auditors: oversight or overkill?

A growing number of high-profile companies have had to restate their earnings at substantially lower levels to correct the prior use of "aggressive" and even fraudulent accounting practices. Because the companies’ auditors approved the original reports, policymakers have questioned the capacity of public accounting firms to promote fair financial reporting. In response, recent legislation has instituted several reforms, including the creation of the Public Company Accounting Oversight Board, which together with the Securities and Exchange Commission will investigate alleged lapses in accounting practices. But how much oversight is really necessary? Jeffery Gunther and Robert Moore examine recent events in the light of research findings. Based on this analysis, they conclude that market forces have tended, over time, to shape the role of auditors to match or correspond to the needs of investors in monitoring individual companies’ performance. Despite current sentiment to the contrary, substantial government involvement in the business of auditing appears to be needed only when other types of government intervention, such as bank deposit insurance, have already disrupted market-based incentives for effective audits. In the more typical situation, both government and industry policymakers should avoid restrictive measures that unnecessarily increase audit costs, instead taking into account market forces’ successful track record in disciplining ineffective auditors and promoting an effective audit function.>Securities and Exchange Commission ; Accounting

Early warning models in real time

Each quarter, banks file a call report, or Report of Condition and Income, containing hundreds of accounting items pertaining to their financial condition. Because call reports are filed quarterly, whereas banks are typically examined about once every twelve to eighteen months, statistical early warning models using call report data potentially provide a more up-to-date picture of a bank's condition than on-site exams alone. Often neglected, however, is the fact that call report data are subject to revision. We find evidence of a strong relationship between on-site exams and call report revisions. In addition, we evaluate a major class of early warning models using both originally published and revised data to assess whether model accuracy in real time is appreciably lower than accuracy measured using revised data. The findings indicate revised data overstate the accuracy of early warning models. The substantial effect of revisions on the accuracy of early warning models, coupled with the finding of a relationship between revisions and exams, points to a substantial auditing role for on-site exams. More generally, our findings point to the need for care in the use of call report data for research in which the real-time flow of financial information is of some concern.Econometrics ; Banks and banking - Accounting ; Bank supervision

Effects of tip clearance on overall performance of transonic fan stage with and without casing treatment

The overall performance of a transonic fan stage is presented for various tip clearances, with and without casing treatment. The stage was tested with a solid casing, and with open skewed slots and closed skewed slots in the casing over the rotor blade tips. Four nominal nonrotating rotor blade tip clearances from 0.061 to 0.178 centimeter were used. For all three casings, the pressure ratio and efficiency decreased with increasing tip clearance. The stall margin for a given casing also decreased with increasing clearance. At design speed and a given tip clearance, the highest stall margin was obtained with the open-slot casing, and the lowest stall margin was obtained with the solid casing