Resonance testing of space shuttle thermoacoustic structural specimen

The resonance testing of a structural specimen related to the space shuttle vehicle is described. The specimen consisted of a thin aluminum skin reinforced by hat-section stringers and supported by two ribs or bulkheads of corrugated web. A representative section of the space shuttle thermal protection system was bonded to the outer surface of the skin. The tests were completed by using miniature accelerometers to collect vibration data from locations forming a predetermined mesh over the tiles and base structure. The signals were recorded on FM magnetic tape and subsequently analyzed on a modal analysis system

The LATDYN user's manual

The LATDYN User's Manual presents the capabilities and instructions for the LATDYN (Large Angle Transient DYNamics) computer program. The LATDYN program is a tool for analyzing the controlled or uncontrolled dynamic transient behavior of interconnected deformable multi-body systems which can undergo large angular motions of each body relative other bodies. The program accommodates large structural deformation as well as large rigid body rotations and is applicable, but not limited to, the following areas: (1) development of large flexible space structures; (2) slewing of large space structure components; (3) mechanisms with rigid or elastic components; and (4) robotic manipulations of beam members. Presently the program is limited to two dimensional problems, but in many cases, three dimensional problems can be exactly or approximately reduced to two dimensions. The program uses convected finite elements to affect the large angular motions involved in the analysis. General geometry is permitted. Detailed user input and output specifications are provided and discussed with example runstreams. To date, LATDYN has been configured for CDC/NOS and DEC VAX/VMS machines. All coding is in ANSII-77 FORTRAN. Detailed instructions regarding interfaces with particular computer operating systems and file structures are provided

The Computational Complexity of the Game of Set and its Theoretical Applications

The game of SET is a popular card game in which the objective is to form Sets using cards from a special deck. In this paper we study single- and multi-round variations of this game from the computational complexity point of view and establish interesting connections with other classical computational problems. Specifically, we first show that a natural generalization of the problem of finding a single Set, parameterized by the size of the sought Set is W-hard; our reduction applies also to a natural parameterization of Perfect Multi-Dimensional Matching, a result which may be of independent interest. Second, we observe that a version of the game where one seeks to find the largest possible number of disjoint Sets from a given set of cards is a special case of 3-Set Packing; we establish that this restriction remains NP-complete. Similarly, the version where one seeks to find the smallest number of disjoint Sets that overlap all possible Sets is shown to be NP-complete, through a close connection to the Independent Edge Dominating Set problem. Finally, we study a 2-player version of the game, for which we show a close connection to Arc Kayles, as well as fixed-parameter tractability when parameterized by the number of rounds played

Comorbid Chronic Pain and Depression: Patient Perspectives on Empathy

Clinician empathy is a well-documented component of effective patient/provider communication. Evidence surrounding the association between patient perspectives on clinician empathy and perception of pain management is currently limited, particularly among patients with chronic pain and depression. The aim of this study was to analyze patients’ perspectives on the emergent theme of empathy and describe how patients construct their experiences and expectations surrounding empathic interactions. A secondary analysis of focus group data was designed using grounded theory methodology. Veterans Affairs (VA) and University Primary Care Clinics. Respondents with chronic pain and comorbid depression (N = 18) were 27 to 84 years old (mean 54.8 years), 61% women, 22% black, and 74% white. Study participants highly valued empathy and two types of empathic interactions: empathic listening and empathic action. Patients who provided examples of empathic interactions claimed that others understood, valued, and cared for them. In contrast, patients who perceived a lack of empathy and empathic interactions felt frustrated and uncared for by others (including their physicians) physically and emotionally. Patients with chronic pain and depression claimed that empathy helped them feel understood, believed, taken seriously, and that their needs were met. In demonstrating empathy and engaging in empathic interactions with patients, providers relate better to patients, better understand their life experience, and provide patient-centered care that is meaningful for patients, providers, and the health care systems within which they interact. Future research is needed to purposefully study the effects of empathic interactions on outcomes for patients with chronic pain and comorbid depression

Evaluation of cystatin C for the detection of chronic kidney disease in cats

BackgroundSerum cystatin C (sCysC) and urinary cystatin C (uCysC) are potential biomarkers for early detection of chronic kidney disease (CKD) in cats. An in-depth clinical validation is required. ObjectivesTo evaluate CysC as a marker for CKD in cats and to compare assay performance of the turbidimetric assay (PETIA) with the previously validated nephelometric assay (PENIA). AnimalsNinety cats were included: 49 CKD and 41 healthy cats. MethodsSerum CysC and uCysC concentrations were prospectively evaluated in cats with CKD and healthy cats. Based on plasma exo-iohexol clearance test (PexICT), sCysC was evaluated to distinguish normal, borderline, and low GFR. Sensitivity and specificity to detect PexICT<1.7mL/min/kg were calculated. Serum CysC results of PENIA and PETIA were correlated with GFR. Statistical analysis was performed using general linear modeling. ResultsCats with CKD had significantly higher meanSD sCysC (1.4 +/- 0.5mg/L) (P<.001) and uCysC/urinary creatinine (uCr) (291 +/- 411mg/mol) (P<.001) compared to healthy cats (sCysC 1.0 +/- 0.3 and uCysC/uCr 0.32 +/- 0.97). UCysC was detected in 35/49 CKD cats. R-2 values between GFR and sCysC or sCr were 0.39 and 0.71, respectively (sCysC or sCr=+GFR+epsilon). Sensitivity and specificity were 22 and 100% for sCysC and 83 and 93% for sCr. Serum CysC could not distinguish healthy from CKD cats, nor normal from borderline or low GFR, in contrast with sCr. ConclusionSerum CysC is not a reliable marker of reduced GFR in cats and uCysC could not be detected in all CKD cats

A methodology for the estimation of kappa (κ) for large datasets. Example application to rock sites in the NGA-East database

This report reviews four of the main approaches (two band-limited and two broadband) currently used for estimating the site κ0: the acceleration slope (AS) above the corner frequency, the displacement slope (DS) below the corner frequency, the broadband (BB) fit of the spectrum, and the response spectral shape (RESP) template. Using these four methods, estimates of κ0 for rock sites in Central Eastern North America (CENA) in the shallow crustal dataset from NGAEast are computed for distances less than 100 km. Using all of the data within 100 km, the mean κ0 values are 8 msec for the AS approach and 27 msec for the DS approach. These mean values include negative κ estimates for some sites. If the negative κ values are removed, then the mean values are 25 msec and 42 msec, respectively. Stacking all spectra together led to mean κ0 values of 7 and 29 msec, respectively. Overall, the DS approach yields 2–3 times higher values than the AS, which agrees with previous observations, but the uncertainty of the estimates in each case is large. The AS approach seems consistent for magnitudes down to M3 but not below. There is large within-station variability of κ that may be related to differences in distance, Q, complexity along the path, or particular source characteristics, such as higher or lower stress drop. The station-to-station differences may be due to site-related factors. Because most sites have been assigned Vs30 = 2000 m/sec, it is not possible to correlate variations in κ0 with rock stiffness. Based on the available profile, the individual spectra are corrected for crustal amplification and only affect results below 15 Hz. Since the AS and DS approaches are applied over different frequency ranges, we find that only the DS results are sensitive to the amplification correction. More detailed knowledge of individual near-surface profiles may have effects on AS results, too. Although κ is considered to be caused solely by damping in the shallow crust, measurement techniques often cannot separate the effects of damping and amplification, and yield the net effect of both phenomena. The two broadband approaches, BB and RESP, yield similar results. The mean κ0_BB is 5±0.5 msec across all NEHRP class A sites. The κ0_RESP for the two events examined is 5 and 6 msec. From literature, the average value of κ0 in CENA is 6 ± 2 msec. This typical value is similar to the broadband estimates of this study and to the mean κAS when all available recordings are used along with all flags. When only recordings with down-going FAS slope are selected from the dataset, the mean value of κAS increases by a factor of 2–3. To evaluate the scaling of high-frequency ground motion with κ, we analyze residuals from ground motion prediction equations (GMPEs) versus κ estimates. Using the κ values from the AS approach, the average trend of the ln(PSA) residuals for hard-rock data do not show the expected strong dependence on κ, but when using κ values from the DS approach, there is a stronger correlation of the residuals, i.e., a κ that is more consistent with the commonly used analytically based scaling. The κDS estimates may better reflect the damping in the shallow crust, while the κAS estimates may reflect a net effect of damping and amplification that has not been decoupled. The κDS estimates are higher than the κAS estimates, so the expected effect on the high-frequency ground motion is smaller than that expected for the κAS estimates. An empirical hard-rock site factor model is developed that represents the combined Vs-κ0 site factor relative to a 760 m/sec reference-site condition. At low frequencies ( 10 Hz), the residuals do not show the strong increase in the site factors as seen in the analytical model results. A second hard-rock dataset from British Columbia, Canada, is also used. This BC hard-rock residuals show an increase in the 15–50 Hz range that is consistent with the analytical κ0 scaling for a hard-rock κ0 of about 0.015 sec. The variability of the PSA residuals is also used to evaluate the κ0 scaling for hard-rock sites from analytical modeling. The scatter in existing κ0 values found in literature is disproportionately large compared to the observed variability in high-frequency ground motions. We compared the predicted ground-motion variability based on analytical modeling to the observed variability in our residuals. While the hard-rock sites are more variable at high frequencies due to the additional κ0 variability, this additional variability is much less than the variability predicted by the analytical modeling using the variability from κ0-Vs30 correlations. This is consistent with weaker κ0 scaling compared to that predicted by the analytical modelling seen in the mean residuals

Squeezing Kappa (κ) out of the transportable array: A strategy for using bandlimited data in regions of sparse seismicity

The κ parameter (Anderson and Hough, 1984), and namely its site-specific component (κ0), is important for predicting and simulating high-frequency ground motion. We develop a framework for estimating κ0 and addressing uncertainties under the challenging conditions often imposed in practice: 1. Low seismicity (limited, poor-quality, distant records); 2. Limited-bandwidth data from the Transportable Array (maximum usable frequency 16 Hz); 3. Low magnitudes (ML1.2-3.4) and large uncertainty in stress drop (corner frequency). We cannot resolve stress drop within the bandwidth, so we propose an approach that only requires upper and lower bounds on its regional values to estimate κ0. To address uncertainties, we combine three measurement approaches (acceleration spectrum slope, AS; displacement spectrum slope, DS; broadband spectral fit, BB). We also examine the effect of crustal amplification, and find that neglecting it can affect κ0 by up to 35%. DS estimates greatly exceed AS estimates. We propose a reason behind this bias, related to the residual effect of the corner frequency on κAS and κDS. For our region, we estimate a frequency-independent mean S-wave Q of 900±300 at 9-16 Hz, and an ensemble mean κ0 over all sites of 0.033±0.014 s. This value is similar to the native κ0 of the NGA-West2 ground motion prediction equations, indicating that these do not need to be adjusted for κ0 for use in Southern Arizona. We find that stress drop values in this region may be higher compared to estimates of previous studies, possibly due to trade-offs between stress drop and κ0. For this dataset, the within-approach uncertainty is much larger than the between-approach uncertainty, and it cannot be reduced if the data quality is not improved. The challenges discussed here will be relevant in studies of κ for other regions with band-limited data, e.g., any region where data come primarily from the TA

Statistical modeling of ground motion relations for seismic hazard analysis

We introduce a new approach for ground motion relations (GMR) in the probabilistic seismic hazard analysis (PSHA), being influenced by the extreme value theory of mathematical statistics. Therein, we understand a GMR as a random function. We derive mathematically the principle of area-equivalence; wherein two alternative GMRs have an equivalent influence on the hazard if these GMRs have equivalent area functions. This includes local biases. An interpretation of the difference between these GMRs (an actual and a modeled one) as a random component leads to a general overestimation of residual variance and hazard. Beside this, we discuss important aspects of classical approaches and discover discrepancies with the state of the art of stochastics and statistics (model selection and significance, test of distribution assumptions, extreme value statistics). We criticize especially the assumption of logarithmic normally distributed residuals of maxima like the peak ground acceleration (PGA). The natural distribution of its individual random component (equivalent to exp(epsilon_0) of Joyner and Boore 1993) is the generalized extreme value. We show by numerical researches that the actual distribution can be hidden and a wrong distribution assumption can influence the PSHA negatively as the negligence of area equivalence does. Finally, we suggest an estimation concept for GMRs of PSHA with a regression-free variance estimation of the individual random component. We demonstrate the advantages of event-specific GMRs by analyzing data sets from the PEER strong motion database and estimate event-specific GMRs. Therein, the majority of the best models base on an anisotropic point source approach. The residual variance of logarithmized PGA is significantly smaller than in previous models. We validate the estimations for the event with the largest sample by empirical area functions. etc

Entrainment of randomly coupled oscillator networks by a pacemaker

Entrainment by a pacemaker, representing an element with a higher frequency, is numerically investigated for several classes of random networks which consist of identical phase oscillators. We find that the entrainment frequency window of a network decreases exponentially with its depth, defined as the mean forward distance of the elements from the pacemaker. Effectively, only shallow networks can thus exhibit frequency-locking to the pacemaker. The exponential dependence is also derived analytically as an approximation for large random asymmetric networks.Comment: 4 pages, 3 figures, revtex 4, submitted to Phys. Rev. Let