bluuebunny/crossref_metadata_2025 huggingface dataset:
MODELING OF GAS-DYNAMIC PROCESSES IN THE ELEMENTS OF IMPULSE EJECTOR
Authors: Voropaiev G. O. , Zagumennyi Ia. V. , Rozumnyuk N. V.
Published: September 2021

The paper presents the numerical results on gas-dynamic processes in various elements of the impulse ejector, including pre-chamber, supersonic nozzle and mixing chamber, to determine optimal geometric parameters providing the given flow rate characteristics. At an extra-high pressure of the ejecting gas (>100 bar) it is impossible to create a nozzle design with continuously changing cross-sectional area and limited nozzle length. So, it is necessary to place a pre-chamber between the gas generator and the ejector nozzle for throttling full gas pressure. In order to optimize the pre-chamber parameters in the ejector with discrete holes of the gas generator and the operating pressure in the range of 400÷1000 bar, a series of calculations were performed to determine the pre-chamber parameters, ensuring stable operation of the supersonic annular nozzle at the high pressure of 35÷45 bar and the flow rate of 0.5÷0.6 kg/s. 3D numerical simulation of the gas flow into the pre-chamber through the gas generator holes shows the degree of the flow pattern non-uniformity in the pre-chamber at the ejector nozzle inlet is quite low. This justifies the numerical simulation of gas flow in the ejector in axisymmetric formulation and allows restricting the number of the gas generator holes without inducing significant non-uniformity in the azimuthal direction.
Effect Of Taper Angle On Flow And Stress In Conical Shell Fluid Mixers
Authors: YAVUZ Mustafa Murat
Published: September 2021

Hollow cylindrical flow mixers achieve a homogeneous mixture with less pressure loss and higher momentum. However, the low volume of the mixer due to the hollow creates high pressure effects and mechanical stresses on the mixer. In this study, the stresses formed on the mixer by considering the flow and thermal effects of fluids in a conical cylinder mixer at different temperatures were examined. The effect of taper angle has been studied. In the examinations carried out using the finite element method, a verification study was first made, and solution sensitivity was determined. Water as fluid in standard conditions and common steel properties as cylinder material were used. Plate thickness was chosen to be 1 mm. It seems more appropriate to use a non-conical straight model to achieve thermal equilibrium. The taper angle reduced the velocity of fluid entering the mixer. Stress concentrations were observed at the supports and a lower and decreasing stress distribution was obtained for the conical mixer while it was constant for the straight cylinder in the other regions.
Combination of PCA with SMOTE Oversampling for Classification of High-Dimensional Imbalanced Data
Authors: MULLA Guhdar A. A. , DEMİR Yıldırım , HASSAN Masoud
Published: September 2021

Imbalanced data classification is a common issue in data mining where the classifiers are skewed towards the larger data class. Classification of high-dimensional skewed (imbalanced) data is of great interest to decision-makers as it is more difficult to. The dimension reduction method, a process in which variables are reduced, allows high dimensional datasets to be interpreted more easily with a certain loss. This study, a method combining SMOTE oversampling with principal component analysis is proposed to solve the imbalance problem in high dimensional data. Three classification algorithms consisting of Logistic Regression, K-Nearest Neighbor, Decision Tree methods and two separate datasets were utilized to evaluate the suggested method's efficacy and determine the classifiers' performance. Respectively, raw datasets, converted datasets by PCA, SMOTE and SMOTE+PCA (SMOTE and PCA) methods, were analyzed with the given algorithms. Analyzes were made using WEKA. Analysis results suggest that almost all classification algorithms improve their classification performance using PCA, SOMTE, and SMOTE+PCA methods. However, the SMOTE method gave more efficient results than PCA and PCA+SMOTE methods for data rebalancing. Experimental results also suggest that K-Nearest Neighbor classifier provided higher classification performance compared to other algorithms.
Joint hypocentral determination and the detection of low-velocity anomalies. An example from the Phlegraean Fields earthquakes
Authors: Pujol Jose , Aster Richard
Published: September 2021

Arrival time data from the Phlegraean Fields (Italy) earthquake swarm recorded by the University of Wisconsin array in 1983 to 1984 were reanalyzed using a joint hypocentral determination (JHD) technique. The P- and S-wave station corrections computed as part of the JHD analysis show a circular pattern of central positive values surrounded by negative values whose magnitudes increase with distance from the center of the pattern. This center roughly coincides with the point of the maximum uplift (almost 2 m) associated with the swarm. Corrections range from −0.85 to 0.10 sec for P-wave arrivals and from −1.09 to 0.70 sec for S-wave arrivals. We interpret these patterns of corrections as caused by a localized low-velocity anomaly in the epicentral area, which agrees with the results of a previous 3-D velocity inversion of the same data set. The relocated (JHD) epicenters show less scatter than the epicenters obtained in the velocity inversion, and move more of the seismic activity to the vicinity of the only presently active fumarolic feature. The capability of the JHD technique to detect low-velocity anomalies and at the same time to give reliable locations, particularly epicenters, was verified using synthetic data generated for a 3-D velocity model roughly resembling the model obtained by velocity inversion.
Robust and reliable techniques for epicenter location using time and slowness observations
Authors: Cassidy Frances , Christoffersson Anders , Husebye Eystein S. , Ruud Bent O.
Published: September 2021

The ever-increasing flow of parameterized and waveform data into various kinds of seismological centers cannot be managed properly unless preliminary epicenter locations are available. Here we demonstrate robust and flexible techniques for fast and reliable event location using the P slowness vector, which is easily derived from arrival times and/or waveform data from arrays, networks, and/or single-site three-component stations. Location schemes are tied to 1) azimuth minimization and 2) slowness vector summation on a sphere using slowness from N arbitrarily positioned stations. The advantage of using azimuth alone is that no assumption is needed of phase type, distance range, or structure (travel-time tables). The viability of our location techniques are demonstrated using a variety of P recordings from networks and three-component stations.
The 3 December 1988 Pasadena, California earthquake: Evidence for strike-slip motion on the Raymond fault
Authors: Jones Lucile M. , Sieh Kerry E. , Hauksson Egill , Hutton L. Katherine
Published: September 2021

The Pasadena earthquake (ML = 4.9) occurred on 3 December 1988, at a depth of 16 km. The hypocenters of the earthquake and its aftershocks define a east-northeast striking, steeply northwest-dipping surface that projects up to the active surficial trace of the Raymond fault. One of the nodal planes of the focal mechanism of the earthquake parallels the Raymond fault with left-lateral strike-slip movement on that plane, and is consistent with geomorphic and paleoseismic evidence that the Raymond fault is dominantly a left-lateral strike-slip fault. The existence of a component of sinistral slip along the Raymond fault had been suspected prior to the earthquake, but the northward dip of the fault and the prominent scarp along the western portion of its trace had led most workers to conclude that slip along the fault was dominantly reverse.
Seismic ground-response studies in Olympia, Washington, and vicinity
Authors: King K. W. , Tarr A. C. , Carver D. L. , Williams R. A. , Worley D. M.
Published: September 2021

Relative seismic ground-response characteristics in the cities of Olympia, Lacey, and Tumwater, Washington, were determined from analysis of instrumentally recorded ground motion induced by blasts at an open-pit coal mine near Centralia, Washington. A ground-response function (GRF), defined as the ratio of Fourier spectral amplitudes at an alluvium site to spectral amplitudes on hard rock, is a measure of amplification of seismic waves by localized site conditions. GRF values in three frequency bands (0.5 to 1.0 Hz, 1.0 to 2.0 Hz, and 2.0 to 4.0 Hz) were compared with observed Modified Mercalli (MM) intensities from the 29 April 1965, Puget Sound earthquake and with mapped surficial geologic units. Typically, the GRF values relate well with the surficial geological units.

In addition, MM intensities within the V to VII range appear to be directly related to the frequencies within the 0.5 to 4.0 Hz bandwidth such that MM V intensity sites had a lower GRF value in the 2.0 to 4.0 Hz bandwidth as compared to the 0.5 to 2.0 Hz bandwidth, and the MM VII intensity sites had higher GRF values in the 2.0 to 4.0 Hz bandwidth as compared to the 0.5 to 2.0 Hz bandwidth. The set of GRF values determined for the city of Olympia and its vicinity should be useful in formulating a theoretical relative ground-response model for the southern Puget Sound area.
Two-dimensional elastic pseudo-spectral modeling of wide-aperture seismic array data with application to the Wichita Uplift-Anadarko Basin region of southwestern Oklahoma
Authors: Kang Ik Bum , McMechan George A.
Published: September 2021

Full wave field modeling of wide-aperture data is performed with a pseudospectral implementation of the elastic wave equation. This approach naturally produces three-component stress and two-component particle displacement, velocity, and acceleration seismograms for compressional, shear, and Rayleigh waves. It also has distinct advantages in terms of computational requirements over finite-differencing when data from large-scale structures are to be modeled at high frequencies.

The algorithm is applied to iterative two-dimensional modeling of seismograms from a survey performed in 1985 by The University of Texas at El Paso and The University of Texas at Dallas across the Anadarko basin and the Wichita Mountains in southwestern Oklahoma. The results provide an independent look at details of near-surface structure and reflector configurations. Near-surface (<3 km deep) structure and scattering effects account for a large percentage (>70 per cent) of the energy in the observed seismograms.

The interpretation of the data is consistent with the results of previous studies of these data, but provides considerably more detail. Overall, the P-wave velocities in the Wichita Uplift are more typical of the middle crust than the upper crust (5.3 to 7.1 km/sec). At the surface, the uplift is either exposed as weathered outcrop (5.0 to 5.3 km/sec) or is overlain with sediments of up to 0.4 km in thickness, ranging in velocity from 2.7 to 3.4 km/sec, generally increasing with depth. The core of the uplift is relatively seismically transparent. A very clear, coherent reflection is observed from the Mountain View fault, which dips at ≈40° to the southwest, to at least 12 km depth. Velocities in the Anadarko Basin are typical of sedimentary basins; there is a general increase from ≈2.7 km/sec at the surface to ≈5.9 km/sec at ≈16 km depth, with discontinuous reflections at depths of ≈8, 10, 12, and 16 km.
Statistically optimal event detection using small array data
Authors: Kushnir A. F. , Lapshin V. M. , Pinsky V. I. , Fyen J.
Published: September 2021

A generalization of Capon's maximum-likelihood technique for detection and estimation of seismic signals is introduced. By using a multi-dimensional autoregressive approximation of seismic array noise, we have developed a technique to use Capon's multi-channel filter for on-line processing. Such autoregressive adaptation to the curent noise matrix power spectrum is shown to yield good suppression of mutually correlated array noise processes. As an example, this technique is applied to detection of a small Semipalatinsk underground explosion recorded at the ARCESS array.
Comparison of the direction estimation performance of high-frequency seismic arrays and three-component stations
Authors: Harris David B.
Published: September 2021

This paper presents a theoretical comparison of the backazimuth and velocity estimation performance of arrays and three-component stations in severe noise conditions. Theoretical estimates of performance for low signal-to-noise ratios (SNRs) are validated through simulation. The high SNR limits of array performance are determined through an empirical study of 23 events at a single source location. Theory and simulation indicate a gradual and uniform deterioration in three-component station performance as the SNR is decreased, beginning at relatively high SNR. At very low SNR, the signal is overwhelmed by the noise, and the performance reaches an asymptotic plateau determined by a priori physical limitations on the velocity of incident waves. By contrast, arrays exhibit a sharp transition between a high SNR performance floor determined, presumably, by scattering effects in the signal, and a low SNR plateau. The SNR threshold for the transition in array performance is low enough that a band of SNRs exist for which arrays have usefully small direction and velocity errors, but three-component stations do not.
Estimating azimuth and slowness from three-component and array stations
Authors: Suteau-Henson Anne
Published: September 2021

The capabilities of three-component (3-C) and array stations for estimating azimuth and slowness are compared for short-period P-type phases recorded at the NORESS array. For vertical array data, azimuth and slowness estimates are obtained from broadband frequency-wavenumber (f-k) analysis. For 3-C data, polarization analysis is performed. The data processing is automated, using arrival time and dominant frequency information from the NORESS Bulletin. Independent determinations of azimuth and/or slowness, obtained from locations in the NEIS or regional network bulletins, are used as reference estimates. Over 100 events are analyzed, both teleseismic and regional. They were selected from a variety of distances and azimuths, and cover a wide range of signal-to-noise ratios (SNR).

The capability of 3-C stations for azimuth and slowness estimation critically depends on SNR. For SNR below a threshold of ∼2, the scatter in the estimates is very large for both parameters, and the slowness of teleseismic events tends to be overestimated. Also, the results are site-dependent within the NORESS array. The array measurements obtained with the broadband f-k method are not significantly affected by noise at the levels of SNR considered. For events with sufficient SNR, both methods compare well, and only a slightly better performance is observed with the f-k method.
Coherent processing of regional signals at small seismic arrays
Authors: Der Z. A. , Hirano M. R. , Shumway R. H.
Published: September 2021

Regional arrivals, similarly to short-period teleseismic P waves, have a spectral structure that the Fourier transforms of individual sensors at arrays for events located in limited source regions can be decomposed into source and site spectral factors. This structure has been demonstrated to be valid for Pn and Lg arrivals at NORESS. This property of regional arrivals can be exploited for: (a) Grouping events with respect to relative location; (b) Identifying events with differing source mechanisms; and (c) Finding differences in the source time functions between closely spaced events.

Potentially useful techniques for accomplishing such analyses consist of computing site-averaged interevent coherences, interevent and intersite equalization methods combined with correlation techniques. The advantage of such approaches is that we need not know much about the propagation characteristics (Green's functions) along the paths to an array.
The reflectivity method with polar sampling
Authors: Bourgeois A. , Gutowski P.
Published: September 2021

A modification to the reflectivity method that results in more accurate and efficiently computed theoretical seismograms is introduced. The reflectivity method involves an explosive point source and a radially symmetric earth, and in the temporal frequency domain the displacement field and the complex plane wave reflectivity are, to within a phase factor, Hankel transform pairs in the polar coordinate variables radial offset and wavenumber. This motivates formulation of the time-transformed displacement field into a Fourier-Bessel series over the reflectivity function, and replacement of the traditional method for sampling the plane-wave reflectivity with the proper polar sampling scheme, based on the finite Fourier transform representation for a band-limited signal. Several numerical examples are discussed.
Estimates of velocity structure and source depth using multiple P waves from aftershocks of the 1987 Elmore Ranch and Superstition Hills, California, earthquakes
Authors: Mori Jim
Published: September 2021

Event record sections, which are constructed by plotting seismograms from many closely spaced earthquakes recorded on a few stations, show multiple free-surface reflections (PP, PPP, PPPP) of the P wave in the Imperial Valley, California. The relative timing of these arrivals is used to estimate the strength of the P-wave velocity gradient within the upper 5 km of the sediment layer. Consistent with previous studies, a velocity model with a value of 1.8 km/sec at the surface increasing linearly to 5.8 km/sec at a depth of 5.5 km fits the data well. The relative amplitudes of the P and PP arrivals are used to estimate the source depth for the aftershock distributions of the Elmore Ranch and Superstition Hills main shocks. Although the depth determination has large uncertainties, both the Elmore Ranch and Superstition Hills aftershock sequences appear to have similar depth distribution in the range of 4 to 10 km.
Observations of the transition from linear polarization to complex polarization in short-period compressional waves
Authors: Menke William , Lerner-Lam Arthur
Published: September 2021

We measure the polarization of compressional waves from seismograms of chemical explosion of the Ontario-New York-New England refraction experiment recorded by the seven element ECO array in the New York Adirondack mountains. After careful instrument calibration, a precision of about 5° is achieved in measuring the azimuth of the compressional wave polarization direction. The azimuth of the polarization of the onset of the P wave differs from the geometrical source-receiver azimuth by as much as 20°, possible due to deflection of the first-arriving ray by lateral variation in crustal structure. Shortly after the onset of P, the polarization changes from the linear polarization expected of a compressional wave to become very complex. The time of this transition increases with source-receiver distance, from about 0.4 to 0.5 sec at 50 km distance and 0.7 to 0.8 sec at 150 km distance. The complex polarization may be due to the arrival of strongly scattered waves that have propagated mainly in the shallow crust, which would imply that the upper 1 to 2 km of the crust is particularly heterogeneous.
Behavior of near-source peak horizontal and vertical ground motions over SMART-1 Array, Taiwan
Authors: Niazi M. , Bozorgnia Y.
Published: September 2021

Over 700 accelerograms recorded from 12 earthquakes in northeast Taiwan have been analyzed for investigating the behavior of vertical and horizontal peak and spectral ground motion in the near-source region. Peak horizontal and vertical ground acceleration (PGA), velocity (PGV), and displacement (PGD) in the range of engineering interest have been subjected to a two-step nonlinear regression procedure in terms of magnitude and hypocentral distance.

In comparison with a number of other studies of global PGA observations, our predictions show lower far-field attenuation, lower near-source amplitudes, higher magnitude saturation for the vertical component, lower magnitude saturation for the horizontal component, and higher magnitude scaling.

The 2 / 3 ratio of vertical to horizontal ground motion, commonly used in engineering applications, may be unconservative in the very near-field for high-frequency ground motion. It falls below 1 / 2 at distances greater than 50 km. The same ratio for PGV and PGD tends to increase with distance, the latter at a faster rate. For SMART-1 data the major source of uncertainty appears to be inter-event rather than intra-event randomness. The predominance of the inter-event uncertainty in ground motions near the source is expected to be a characteristic of all dense arrays.
Criticism of some forecasts of the national earthquake prediction evaluation council
Authors: Savage J. C.
Published: September 2021

The Working Group on California Earthquake Probabilities has assigned probabilities for rupture in the interval from 1988 to 2018 to various segments of the San Andreas fault on the basis of the lognormal distribution of recurrence times of characteristic earthquakes postulated by Nishenko and Buland (1987). I question the validity of those probabilities on the basis of three separate arguments: (1) The distributions of recurrence times of the four, best-observed, characteristic-earthquake sequences are each only marginally consistent with the Nishenko - Buland Iognormal distribution. (2) The range of possible 30-year conditional probabilities for many of the fault segments is so great due to uncertainty in the average recurrence time for that segment that the assigned probability is virtually meaningless. (3) The 1988 forecasts not subject to the foregoing objection are those in which there is a low probability of an earthquake in the near future (e.g., only a 5 per cent chance of rupture of the North Coast segment before the year 2049 and of the Carrizo segment before the year 2018). The same reasoning would assign only a 5 per cent chance of rupture before mid-1993 to the southern Santa Cruz Mountains segment, the segment that failed in October 1989. Finally, the forecast of the next Parkfield earthquake (95 per cent probability before 1993.0) by Bakun and Lindh (1985) depends upon an ad hoc explanation of the out-of-sequence 1934 earthquake. A less-contrived forecast would have assigned a conditional probability of about 60 ± 20 per cent to the 1985.0 to 1993.0 interval and 30 ± 15 per cent to the 1990.0 to 1993.0 interval.
Interactive processing to obtain interstation surface-wave dispersion
Authors: Dean E. A. , Keller G. R.
Published: September 2021

A processing scheme for the analysis of surface-wave dispersion is presented. This scheme involves preprocessing seismograms, computing the interstation Green's function, and determining the self-consistent phase and group dispersion with standard errors for one or more events for a two-station path. Time-variable filtering is employed, based on group velocity that is computer-selected by the multiple filter technique and refined by phase matching iteration. The interstation Green's function is frequency filtered to remove spikes from the spectrum. The interstation group velocity, perturbed by standard errors and refined by phase matching, is used to determine phase velocity and its uncertainty. Self-consistency between phase and group velocity is obtained by a simultaneous least-squares method, which ensures the correct functional relation for the two dispersed velocities. The uncertainty in dispersion is computed from the covariance matrix of the simultaneous least-squares solution. The technique is evaluated by comparing the analyzed dispersion for a path along the Andean Cordillera with results employing other techniques.
Inversion of arrival times of microearthquake sources in the North Sea using a 3-D velocity structure and prior information. Part I. Method
Authors: Engell-Sørensen Lisbeth
Published: September 2021

A new method for earthquake source location and velocity structure determination is formulated based on the Bayes theory. The medium is represented by homogeneous layers with plane-dipping interfaces. Inversion of the arrival-time data yields the velocity parameters, the hypocenters, and the origin times of the earthquakes.

A linear combination of model parameters is included in the method, and the determination of the standard deviations of the estimated parameters is elaborated. The possibility of constraining a linear combination of two model parameters are used for the P-to-S velocity ratio. Because the travel time cannot be found analytically, the forward problem is solved numerically, namely, by two-point raytracing.
Damage potential of Loma Prieta ground motions
Authors: Krawinkler Helmut , Nassar Aladdin , Rahnama Mohsen
Published: September 2021

This article focuses on an engineering evaluation of the ground motions recorded during the Loma Prieta earthquake. Regression analysis is employed to evaluate the attenuation characteristics of the elastic and inelastic strength demands imposed by rock and alluvium ground motions on bilinear single degree of freedom (SDOF) systems. Several records are used to illustrate the large seismic demands generated by soft soil ground motions. Strength capacities of modern code-designed structures are compared to the strength demands in order to assess the damage potential of the Loma Prieta ground motions. The Cypress structure is used as an example to illustrate the application of simple demand / capacity concepts for an evaluation of structural performance.
An experimental investigation of retrofitted cripple walls
Authors: Shepherd R. , Delos-Santos E. O.
Published: September 2021

Extensive damage was experienced by wood-frame buildings during the Loma Prieta earthquake. A significant contributory factor was the collapse of cripple walls. This prompted the examination of the behavior of a group of full-scale retrofitted cripple walls subjected to in-plane cyclic loads. The results of investigating seven cripple walls, each 2 ft (0.61 m) high and 16 ft (5 m) long, are presented. Two are control panels, without retrofits. Two are strengthened with 1 by 6 inch (25.4 by 153 mm) braces. Two are retrofitted with 0.5 inch (12.7 mm) plywood and one with a steel strap tie. Stiffness, strength, and damping characteristics are summarized, together with cost aspects. It is shown that relatively cheap and straightforward modifications can substantially eliminate the vulnerability of many existing cripple walls to earthquake shaking.
Site amplification fromS-wave coda in the Long Valley caldera region, California
Authors: Mayeda Kevin , Koyanagi Stuart , Aki Keiiti
Published: September 2021

Following the work of Phillips (1985), we have computed site amplification factors for coda waves at many sites in the Long Valley region in the eastern Sierra Nevada. We computed ratios of coda amplitudes measured at 15 stations in and around Long Valley caldera relative to a granitic site, MMPM, for six frequency bands centered at 1.5, 3.0, 6.0, 9.0, 12.0, and 15.0 Hz. All station sites located within the caldera experienced large ground motion amplification at 1.5 and 3.0 Hz, ranging between five and 17 times that of the reference site. However, at higher frequencies, these same sites exhibited significantly less amplification than the reference granite site. This is attributed to the competing effects of an impedance contrast between the basement rock and caldera fill and very high absorption in the caldera fill at high frequencies. Station MMLM, located on top of a volcanic plug, displayed the largest amplitudes of all the sites studied for frequencies between 9.0 and 15.0 Hz. A dike structure attached to the plug couples the basement rock to the surface. At high frequencies, the resulting large amplitudes at MMLM are not due to amplification resulting from a strong impedance contrast; rather, the absorption under this site is very low, perhaps lower than at the reference site, MMPM. Outside the caldera, another hard-rock site located at Devil's Postpile, MDPM, generally behaved like the reference site for all frequencies. The lowest amplifications observed came from a site outside the caldera, MDCM, located on thin pyroclastic ash deposits overlying granitic basement. This can be attributed to a dominance of absorption over the amplification caused by lower impedance of this layer. Variations among sites on similar surface geology may be due to small local variations in impedance and absorption under and adjacent to the site. The range in the spectral decay parameter, κ, between caldera and rock sites are comparable to results of Anderson and Hough (1984) for sites on alluvium and rock in the San Fernando region. These surprisingly different amplifications support the need for additional site-specific studies. Amplifications determined in this study for the frequency range 1.5 and 3.0 Hz correlate remarkably well with Eaton's (1990) residuals for duration magnitude, FMAG, and amplitude magnitude, XMAG, for the USGS northern California seismic array, further supporting the use of coda waves in determining site-specific amplification.
Near-source effects on regional seismograms: An analysis of the NTS explosions PERA and QUESO
Authors: Taylor Steven R. , Rambo John T. , Swift Robert P.
Published: September 2021

A comparative analysis of two closely spaced Nevada Test Site explosions, PERA and QUESO, is made to study the effects of near-source phenomena on regional-wave excitation. Although the two explosions were of similar size, burial depth, and only separated by 4 km, the 1 to 2 and 6 to 8 Hz regional-wave spectral ratio for QUESO is anomalously low (a factor of 10 smaller than that of PERA). Examination of the regional and close-in spectra for each event shows a remarkable similarity and suggests that QUESO has less low-frequency and more high-frequency energy than PERA. These observations may be caused by a 564 m3, funnel-shaped region filled with unconsolidated sand and a possible void directly above the QUESO detonation point. Close-in observations suggest that this region may have partially decoupled the up-going energy from QUESO, resulting in a reduction of the low-frequency energy. The high-frequency enhancement for QUESO may be due to the rapid loss of energy to nonlinear effects such as greater pore collapse and fracturing in the anomalous region. This resulted in the radiation of more impulsive, shorter-duration waveforms producing a higher corner frequency and less-rapid high-frequency spectral decay for QUESO. For PERA, the loss of energy to a two-wave system occurred more slowly and over a larger volume, resulting in a broader source pulse typical of explosions in porous materials. Comparison of shock radius versus time data suggests that the shock wave was strongly affected in the anomalous zone a few meters above the QUESO device. One-dimensional finite-difference calculations with and without a partial decoupling region within 8 m of the device are consistent with the observations. Although spallation was reduced for QUESO, simulations using a finite spall model indicate that the spall spectral peak should be centered at about 3 to 7 Hz and probably did not significantly contribute to the reduced spectral ratio. The remarkable similarity of the PERA/QUESO spectral ratios taken at distances of 90 m and 400 km suggests that the spectral characteristics of explosions are established in close proximity to the source. Although depth-dependent effects of attenuation acting at small strains may enhance the differences in spectral ratios between NTS explosions and western U.S. earthquakes, these effects are probably secondary to the high-pressure, high strain-rate dynamic material response to the radiated explosion shock wave. These observations point out the importance of up-going energy on the generation of regional phases from explosions. Because of reduced overburden pressures above the detonation point, large nonlinear deformations predominate in this region and appear to affect all of the signals except perhaps the very initial part of the Pn waveform.
Design of a dynamic mock-up bench for testing robotic interventions
Authors: Barbosa Pina Pereira Luana , Veiga Almagro Carlos , Buonocore Luca Rosario , Marín-Prades Raúl , di Castro Mario , Masi Alessandro
Published: September 2021

When a robotic intervention is required in hazardous facilities (e.g. particle accelerators or nuclear plants), it is commonly not possible to test the operation on-site in advance - a considerable challenge since robotic interventions usually require specific tasks for each location -, precluding the team from demonstrating the feasibility of the operation. It becomes mandatory to develop a particular mock-up for each operation, unsuitable for reusing it in future missions. To solve this problem, a general dynamic mock-up bench was designed, allowing to centre the testing of all remote handled tasks and to choose the best set of robots to perform them.
Exoesqueleto híbrido para rehabilitación de las extremidades superiores.
Authors: Contreras-González Aldo-Francisco , Pont-Esteban David , Samper-Escudero José Luis , Cantalejo-Escobar David , Sánchez-Urán Miguel-Ángel , Ferre Manuel
Published: September 2021

The last decades have witnessed a rapid and vast development of robots for physical rehabilitation that allow efficient planning of the rehabilitation process in terms of cost, duration of sessions and availability of the therapist. This project aims to qualitatively evaluate an exoskeleton for upper body rehabilitation. The device presents an approach to the development of a device with the end-effector anchored to the ground that performs the actuation on an exoskeleton coupled to the body of the subject by cables. Experimentation with patients suffering from the supraspinatus tendon is documented by performing a series of movements dictated by a doctor.
Entrenamiento, optimización y validación de una CNN para localización jerárquica mediante imágenes omnidireccionales.
Authors: Cabrera Juan José , Cebollada Sergio , Ballesta Mónica , Jiménez Luis M. , Payá Luis , Reinoso Óscar
Published: September 2021

El objetivo del presente trabajo es abordar la localización de un robot móvil mediante el entrenamiento de una Red Neuronal Convolucional (CNN) de manera que se obtengan unos resultados óptimos. El problema de localización se aborda de forma jerárquica empleando un sistema catadióptrico omnidireccional y se trabaja directamente con las imágenes capturadas sin pasar a panorámicas, ahorrando así el tiempo de cálculo asociado a este proceso. La localización se lleva a cabo en dos pasos y en ambos se emplea la arquitectura de la CNN con diferentes objetivos. Primero se lleva a cabo una localización gruesa que consiste en identificar la estancia en la que se encuentra el robot por medio de la CNN. Después se realiza una localización fina en dicha estancia, en la cual la CNN es empleada para la obtención de descriptores holísticos a partir de las capas intermedias de la red. Estos descriptores globales permiten encontrar la posición donde se encuentra el robot de manera más precisa por medio de una búsqueda del vecino más cercano, comparando el descriptor correspondiente de la imagen test con los descriptores de las imágenes capturadas en la estancia seleccionada en el primer paso. Con el fin de mejorar el desempeño de la red se recurre a un aumento de datos y a una optimización bayesiana de hiperparámetros. Estas técnicas demuestran ser una solución eficiente y robusta para afrontar el problema de localización tal y como se muestra en la sección de experimentos.
Fusión de series temporales de nubes de puntos para su exploración en realidad virtual.
Authors: Punzón Agudo Samuel , Pérez Hernández Emiliano , Merchán Pilar , Salamanca Santiago , Espacio Regalado Alejandro
Published: September 2021

Las nubes de puntos cada vez pueden contener más información, parte de la cual puede ser variable en el tiempo. Por este motivo, es valioso poder generar nubes que contengan la información correspondiente a diferentes instantes de tiempo sin la edundancia de información espacial. De esta forma, se consigue que el procesamiento y la visualización de los datos sea más sencillo, lo que beneficia a sistemas que necesitan que la información que manejen esté optimizada, como son los sistemas de Realidad Virtual. Por lo tanto, se propone una solución que mediante la fusión de las nubes de puntos tomadas en distintos instantes genera una nube resultado con la información óptima. Como prueba de funcionamiento se ha creado una aplicación de Realidad Virtual en la que se permite la exploración y sondeo de la información de la nube.
Análisis de técnicas de aumento de datos y entrenamiento en YOLOv3 para detección de objetos en imágenes RGB y TIR del UMA-SAR Dataset
Authors: Galán-Cuenca Álvaro , Vázquez-Martín Ricardo , Mandow Anthony , Morales Jesús , García-Cerezo Alfonso
Published: September 2021

El uso de imágenes de los espectros visible (RGB) e infrarrojo térmico (TIR) para la detección de objetos puede resultar crucial en aplicaciones donde las condiciones de visibilidad están limitadas, como la robótica para búsqueda y rescate en catástrofes. Para ello resulta beneficioso analizar cómo las técnicas de aprendizaje profundo basadas en redes neuronales convolucionales (CNN) pueden aplicarse a ambas modalidades. En este artículo se analizan diferentes configuraciones y parámetros para el entrenamiento de CNN tanto para imágenes térmicas como para imágenes equivalentes del espectro visible. En concreto, se aborda el problema del sobre-entrenamiento para determinar una configuración eficaz de técnicas de aumento de datos y parada temprana. El caso de estudio se ha realizado con la red de código abierto YOLOv3, pre-entrenada con el dataset RGB COCO y optimizada (o re-entrenada) con el conjunto público de datos UMA-SAR dataset, que incluye pares de imágenes RGB y TIR obtenidas en ejercicios realistas de rescate.
Clasificación y manipulación de basura doméstica utilizando deep-learning
Authors: Puente Santiago , Gil Pablo , Gea Víctor de
Published: September 2021

Este artículo presenta una aplicación de reconocimiento mediante el uso de redes de aprendizaje profundo para llevar a cabo la clasificación de basura en el ámbito doméstico. Así mismo, una vez realizado el reconocimiento se determina su localización, para poder obtener los puntos de agarre para que un brazo robot dotado de una pinza de dedos paralelos pueda hacerlo de manera automática. Se presenta el algoritmo utilizado, así como, los resultados experimentales que permiten comprobar la bondad de la propuesta.
BÜTÜNLEŞİK BİR ÇKKV MODELİ İLE SİGORTA ŞİRKETLERİNİN PİYASA PERFORMANSININ ANALİZİ
Authors: AYDIN Yüksel
Published: September 2021

Bu çalışmanın amacı, bütünleşik SV (Statistical Variance) ve EDAS (Evaluation based on Distance from Average Solution) yöntemlerinden oluşan hibrid bir modelle Borsa İstanbul (BİST)’a kayıtlı hayat dışı sigorta şirketlerinin 2013-2019 dönemine ilişkin piyasa performansını analiz etmektir. Çalışma, pay senetleri BİST’de işlem gören beş sigorta şirketinin verilerini kapsamaktadır. Çalışmada seçilen piyasa değişkenlerinin önem ağırlıklarının belirlenmesinde SV yöntemi, sigorta şirketlerinin performans skorlarının belirlenmesinde ise EDAS yönteminden faydalanılmıştır. SV yönteminden elde edilen sonuçlara göre sigorta şirketlerinin performansı üzerinde etkili olan en önemli kriter 2016 yılı hariç tüm yıllarda piyasa katma değeri kriteridir. Bununla beraber analiz dönemlerde performans üzerinde en etkinsiz kriterin ise Tobin’in Q’su olduğu tespit edilmiştir. Ayrıca EDAS sıralama sonuçlarına göre en yüksek performans skoruna sahip şirket Anadolu Sigorta iken en düşük performans gösteren şirket ise Aksigorta’dır.
Information Services in Evidence Based Medical Education: A Review of Implementation Trends
Authors: Khani Sedigheh , Panahi Sirous , Pirsalehi Ali , Pourabbasi Ata
Published: September 2021

Objective – Evidence based medical education requires supportive information services to facilitate access to the needed educational evidence. Information services designed specifically for evidence based medical education are limited or locally developed for educational units. For librarians to have an opportunity to cooperate efficiently with medical educators in evidence based medical education, they require an empirical prototype for transmission of clinical evidence at the right place and the right time. Therefore, there is a need to recognize types of information services which support evidence based medical education. The purpose of this review is to identify implementation trends of evidence based educational information services.
Methods – We found related studies by implementing search strategies in PubMed, EMBASE, Web of Science, Scopus, LISTA, and Google Scholar with keywords like: evidence based medical education, information services, and library services. We used reference-checking and citation-checking of related articles for completing the process of locating relevant articles. After employing inclusion and exclusion criteria, we selected 11 articles for inclusion in the review and analyzed them using a narrative review technique.
Results – After analyzing the results of the included studies, we identified two elements categorized as program development and five elements categorized as implementation trend. Prerequisites of program and the process of designing were essential parts of program development of information services. Schedule and type of access, how to receive educational-clinical questions, information services types, responding time, and providing evidence based outputs were the elements of the implementation process of educational supported information services. 
Conclusion – Designing an evidence based educational information service strongly depends on the information needs of learners at each educational level. Schedule and type of access to information service, time of responding to the received query, and preparation of evidence based output are essential factors in designing practical educational-developed information services.
May I Borrow a Stapler? Is This All Students Ask at the Service Desk in a University Library?
Authors: Lamøy Liv Inger , Kilvik Astrid
Published: September 2021

Objective – The objective of the study is to increase the knowledge about what questions students ask at the library desk and what the purpose is of their use of the desk. Our focus has been on the physical meetings with the students. The aim is to contribute to the discussion on the future development of the library service desk.  
Methods – We recorded questions asked at the desks to explore how students use the library service desks. The recording, where library staff sorted questions into predefined categories, took place over four weeks between the years 2017–2018.
Results – Our recording showed that 63% of the questions asked at the library service desks were about loan services, document delivery, and access to physical and electronic collections. Practical things such as opening hours, lost and found items, and the location of the group study rooms, accounted for 16% of questions. Questions about information technology (IT) made up 8% of questions. Finally, the results showed that 8% of the questions from the four weeks of counting were counselling and guidance questions, and 2% were about literature lists, reference management, and reference management tools. We found more questions about counselling and guidance in the spring weeks and more practical questions in the fall. We did not find any clear connection between the number of questions and the size of the branch libraries.
Conclusion – By conducting this study, we have learned more about why students use the library desk. Our study shows that students come to the library desk to ask about a lot more than just borrowing staples. The results from the study will inform the development of the library desk service going forward.
Does the READ Scale Work for Chat? A Review of the Literature
Authors: Warner Adrienne , Hurley David A.
Published: September 2021

Objective – This review aims to determine the suitability of the READ Scale for chat service assessment. We investigated how librarians rate chats and their interpretations of the results, and compared these findings to the original purpose of the Scale.
Methods – We performed a systematic search of databases in order to retrieve sources, applied inclusion and exclusion criteria, and read the remaining articles. We synthesized common themes that emerged into a discussion of the use of the READ Scale to assess chat service. Additionally, we compiled READ Scale designations across institutions to allow side-by-side comparisons of ratings of chat interactions.
Results – This review revealed that librarians used a variety of approaches in applying and understanding READ Scale ratings. Determination of staffing levels was often the primary goal. Further, librarians consistently rated chat interactions in the lower two-thirds of the scale, which has implications for service perception and recommendations.
Conclusion – The findings of this review indicated that librarians frequently use READ Scale data to make staffing recommendations, both in terms of numbers of staff providing chat service and level of experience to adequately meet service demand. Evidence suggested, however, that characteristics of the scale itself may lead to a distorted understanding of chat service, skewing designations to the lower end of the scale, and undervaluing the service.