Signal Detection Techniques for Diagnostic Monitoring of Space Shuttle Main Engine Turbomachinery

An investigation to develop, implement, and evaluate signal analysis techniques for the detection and classification of incipient mechanical failures in turbomachinery is reviewed. A brief description of the Space Shuttle Main Engine (SSME) test/measurement program is presented. Signal analysis techniques available to describe dynamic measurement characteristics are reviewed. Time domain and spectral methods are described, and statistical classification in terms of moments is discussed. Several of these waveform analysis techniques have been implemented on a computer and applied to dynamc signals. A laboratory evaluation of the methods with respect to signal detection capability is described. A unique coherence function (the hyper-coherence) was developed through the course of this investigation, which appears promising as a diagnostic tool. This technique and several other non-linear methods of signal analysis are presented and illustrated by application. Software for application of these techniques has been installed on the signal processing system at the NASA/MSFC Systems Dynamics Laboratory

Mass and Angular momentum of Black Holes in New Massive Gravity

We obtain mass and angular momentum of black holes as conserved charges in three dimensional new massive gravity, after presenting the explicit expression for the potential of the conserved charges. This confirms the expression of those charges obtained in several ways, in particular through AdS/CFT correspondence, and shows us that the first law of black hole thermodynamics is valid in these black holes. We also comment about conserved charges in new type black holes with the emphasis on the AdS/CFT correspondence as guiding principle.Comment: minor corrections, added conclusion, accepted in PR

Signatures of a Deconfined Phase Transition on the Shastry-Sutherland Lattice: Applications to Quantum Critical SrCu2_2(BO3_3)2_2

We study a possible deconfined quantum phase transition in a realistic model of a two-dimensional Shastry-Sutherland quantum magnet, using both numerical and field theoretic techniques. Using the infinite density matrix renormalization group (iDMRG) method, we verify the existence of an intermediate plaquette valence bond solid (pVBS) order, with two fold degeneracy, between the dimer and N\'eel ordered phases. We argue that the quantum phase transition between the N\'eel and pVBS orders may be described by a deconfined quantum critical point (DQCP) with an emergent O(4) symmetry. By analyzing the correlation length spectrum obtained from iDMRG, we provide evidence for the DQCP and emergent O(4) symmetry in the lattice model. Such a phase transition has been reported in the recent pressure tuned experiments in the Shastry-Sutherland lattice material $\mathrm{SrCu_2 (BO_3)_2}$. The non-symmorphic lattice structure of the Shastry-Sutherland compound leads to extinction points in the scattering, where we predict sharp signatures of a DQCP in both the phonon and magnon spectra associated with the spinon continuum. The effect of weak interlayer couplings present in the three dimensional material is also discussed. Our results should help guide the experimental study of DQCP in quantum magnets.Comment: 22 pages, 6 tables, 15 figures; in v2 numerical details added in appendi

Selection Methods of Control Samples: A Comparison of Two Matching Methodologies

To measure abnormal stock returns of a sample of firms in an event study, we often use matching firm adjusted returns where returns of the control firms are subtracted from the raw returns of the sample firms. In most financial studies, the control firms are selected by matching industry and size (the I/S method). That is, for each sample firm, a matching firm with the closest market capitalization within the same 3-digit Standard Industry Classification (SIC) code is selected. In this study, an alternative control firm selection method based on earnings per share (the EPS method) is compared to the traditional method. The EPS method matches each sample firm with a control firm that has the same EPS for a given fiscal year. While the mean matching firm adjusted returns provided by the two methods are close to the expected value of zero, the size of variances of the adjusted returns is somewhat smaller for the I/S method, showing some superiority for the traditional matching method based on industry and size

Chemical Constituents from Calophyllum Inophyllum and Cratoxylum Arborescens and Their Biological Activities

Chemical and biological studies were carried out on two plants, Calophyllum inophyllum (Guttiferae) and Cratoxylum arborescens (Guttiferae). The chemical investigation covered triterpenoids, quinones and xanthones. These compounds were isolated using common chromatographic techniques and were identified using spectroscopic experiments such as NMR, MS, IR and UV. Calophyllum inophyllum (root bark) afforded sitosterol (71) and six other known xanthones which are brasilixanthone (72), inophyllin A (26), inophyllin B (27), 1,3,5-trihydroxy-2-methoxy xanthone (73), caloxanthone A (74) and pyranojacareubin (75). Meanwhile, studies on Cratoxylum arborescens (stem bark) provided one triterpenoid, friedelin (76) together with three others known quinones. These are vismione (77), vismiaquinone (78), and 1,8-dihydroxy-3-methoxy-6-methyl anthraquinone (79).Cytotoxic tests were carried out using CEM-SS cell line and HL-60 cell line. The crude hexane extract of Cratoxylum arborescens B. was found to be inactive to cytotoxic activity. The crude chloroform and methanol extracts of Cratoxylum arborescens B. showed good cytotoxic activity with IC50 values of 16 and 18 μg/ml, respectively. Meanwhile, the crude chloroform extract of the stem bark of Calophyllum inophyllum L. also showed a good cytotoxic activity with an IC50 value of 17 μg/ml. Two pure compounds obtained from Calophyllum inophyllum L., inophylin B (26) and caloxanthone A (74) also showed good activities against the HL-60 cell line with IC50 values of 15 and 29 μg/ml respectively. The antimicrobial activity test was also carried out using four pathogenic bacteria, namely, Methicilin Resistant Staphylococcus aures, Pseudomonas aeruginosa, Staphylococcus typhimurium and Bacillus subtilis. However, most of the crude extracts gave only moderate or weak activity. The larvicidal tests were performed against the larvae of Aedes aegypti using the WHO (1981) standard procedures with slight modifications. The crude hexane, chloroform and methanol extracts of Calophyllum inophyllum and Cratoxylum arborescens were inactive against the larvae of Aedes aegypti. No activity was recorded for the antifungal activity tes

More About the Phase-Synchronized Enhancement Method

A report presents further details regarding the subject matter of "Phase-Synchronized Enhancement Method for Engine Diagnostics" (MFS-26435), NASA Tech Briefs, Vol. 22, No. 1 (January 1998), page 54. To recapitulate: The phase-synchronized enhancement method (PSEM) involves the digital resampling of a quasi-periodic signal in synchronism with the instantaneous phase of one of its spectral components. This resampling transforms the quasi-periodic signal into a periodic one more amenable to analysis. It is particularly useful for diagnosis of a rotating machine through analysis of vibration spectra that include components at the fundamental and harmonics of a slightly fluctuating rotation frequency. The report discusses the machinery-signal-analysis problem, outlines the PSEM algorithms, presents the mathematical basis of the PSEM, and presents examples of application of the PSEM in some computational simulations

Develop advanced nonlinear signal analysis topographical mapping system

As reported in the monthly technical progress report for July 1993, a new signal analysis technique called instantaneous frequency correlation (IFC) for time delay estimation was developed which will be incorporated into the ATMS system. In this report, a different technique for time delay estimation called phase difference time derivative estimator (FDTDE) will be discussed. The FDTDE technique does not replace the IFC method since their application conditions are different. The IFC technique can estimate the time delay between two spectral components of two measurement signals when the center frequency of the components is constant, while the FDTDE method can provide accurate time delay estimation when the frequency of the subject component changes linearly such as during engine startup or shut-down

Conversion-Integration of MSFC Nonlinear Signal Diagnostic Analysis Algorithms for Realtime Execution of MSFC's MPP Prototype System

NASA's advanced propulsion system Small Scale Magnetic Disturbances/Advanced Technology Development (SSME/ATD) has been undergoing extensive flight certification and developmental testing, which involves large numbers of health monitoring measurements. To enhance engine safety and reliability, detailed analysis and evaluation of the measurement signals are mandatory to assess its dynamic characteristics and operational condition. Efficient and reliable signal detection techniques will reduce the risk of catastrophic system failures and expedite the evaluation of both flight and ground test data, and thereby reduce launch turn-around time. During the development of SSME, ASRI participated in the research and development of several advanced non- linear signal diagnostic methods for health monitoring and failure prediction in turbomachinery components. However, due to the intensive computational requirement associated with such advanced analysis tasks, current SSME dynamic data analysis and diagnostic evaluation is performed off-line following flight or ground test with a typical diagnostic turnaround time of one to two days. The objective of MSFC's MPP Prototype System is to eliminate such 'diagnostic lag time' by achieving signal processing and analysis in real-time. Such an on-line diagnostic system can provide sufficient lead time to initiate corrective action and also to enable efficient scheduling of inspection, maintenance and repair activities. The major objective of this project was to convert and implement a number of advanced nonlinear diagnostic DSP algorithms in a format consistent with that required for integration into the Vanderbilt Multigraph Architecture (MGA) Model Based Programming environment. This effort will allow the real-time execution of these algorithms using the MSFC MPP Prototype System. ASRI has completed the software conversion and integration of a sequence of nonlinear signal analysis techniques specified in the SOW for real-time execution on MSFC's MPP Prototype. This report documents and summarizes the results of the contract tasks; provides the complete computer source code; including all FORTRAN/C Utilities; and all other utilities/supporting software libraries that are required for operation

Develop advanced nonlinear signal analysis topographical mapping system

This study will provide timely assessment of SSME component operational status, identify probable causes of malfunction, and indicate feasible engineering solutions. The final result of this program will yield an advanced nonlinear signal analysis topographical mapping system (ATMS) of nonlinear and nonstationary spectral analysis software package integrated with the Compressed SSME TOPO Data Base (CSTDB) on the same platform. This system will allow NASA engineers to retrieve any unique defect signatures and trends associated with different failure modes and anomalous phenomena over the entire SSME test history across turbopump families