Source Duration Research Articles

Rupture characteristics of major and great (Mw ≥ 7.0) megathrust earthquakes from 1990 to 2015: 2. Depth dependence

AbstractDepth‐varying characteristics of high‐frequency seismic radiation for megathrust earthquakes have been inferred from several recent giant earthquakes and large tsunami earthquakes. To quantify any depth dependence more extensively, we analyzed 114 Mw ≥ 7.0 thrust‐faulting earthquakes with centroid depths from 5 to 55 km on circum‐Pacific megathrusts using teleseismic body wave finite‐fault inversions and source spectrum determinations. Large tsunami earthquakes and some other shallow events at depths less than about 18 km have unusually long source durations, and low values of static stress drop (ΔσE), Vr3ΔσE, and apparent stress, with relatively depleted high‐frequency radiation. Deeper events have no clear global trend with source depth for moment‐normalized centroid time or total duration, static stress drop, moment‐scaled radiated energy, apparent stress, or radiation efficiency. Regional behavior among the 17 sampled subduction zones generally conforms to the global composite. The source spectra have high‐frequency logarithmic spectral decay slopes averaging ~ −1.6. There is relative enrichment in high‐frequency spectral levels with increasing source depth manifested in reduced high‐frequency spectral decay slope. The ratio of high‐frequency (0.3–1 Hz) radiated energy to total energy increases correspondingly. These observations suggest that overall dynamic rupture processes are relatively insensitive to source depth, but varying scale lengths of megathrust heterogeneity may contribute to modest enrichment of high‐frequency seismic radiation for events deeper on the megathrust. A weak correlation of higher estimated average megathrust temperature at 30 km depth with higher spectral decay rate indicates that the depth‐varying pattern may in part result from frictional properties being influenced by temperature variations or by systematic reduction of average attenuation with increasing depth along the megathrust.

Rupture characteristics of major and great (Mw ≥ 7.0) megathrust earthquakes from 1990 to 2015: 1. Source parameter scaling relationships

AbstractSource parameter scaling for major and great thrust‐faulting events on circum‐Pacific megathrusts is examined using uniformly processed finite‐fault inversions and radiated energy estimates for 114Mw ≥ 7.0 earthquakes. To address the limited resolution of source spatial extent and rupture expansion velocity (Vr) from teleseismic observations, the events are subdivided into either group 1 (18 events) having independent constraints onVrfrom prior studies or group 2 (96 events) lacking independentVrconstraints. For group 2, finite‐fault inversions withVr = 2.0, 2.5, and 3.0 km/s are performed. The productVr3ΔσE, with stress drop ΔσEcalculated for the slip distribution in the inverted finite‐fault models, is very stable for each event across the suite of models considered. It has little trend withMw, although there is a baseline shift to low values for large tsunami earthquakes. Source centroid time (Tc) and duration (Td), measured from the finite‐fault moment rate functions vary systematically with the cube root of seismic moment (M0), independent of assumedVr. There is no strong dependence on magnitude orVrfor moment‐scaled radiated energy (ER/M0) or apparent stress (σa). ΔσEaverages ~4 MPa, with direct trade‐off betweenVrand estimated stress drop but little dependence onMw. Similar behavior is found for radiation efficiency (ηR). We useVr3ΔσEandTc/M01/3to explore variation of stress drop,Vrand radiation efficiency, along with finite‐source geometrical factors. Radiation efficiency tends to decrease with average slip for these very large events, and fracture energy increases steadily with slip.

Intra-abdominal Infection

The basic principles of rapid diagnosis, timely physiologic support, and definitive intervention for intra-abdominal infections have remained unchanged over the past century; however, specific management of these conditions has been transformed as a result of numerous advances in technology. This review covers clinical evaluation, investigative studies, options for intervention, early source control and duration of antimicrobial therapy, infections of the upper abdomen, infections of the lower abdomen, other abdominal infections, and special cases. Figures show an algorithm outlining the approach to a suspected upper abdominal infection, abnormal abdominal ultrasounds showing calculi in the gallbladder and confirming the diagnosis of acute acalculous cholecystitis, endoscopic retrograde cholangiopancreatographies showing a distal common bile duct stone in acute pancreatitis, extrinsic compression of the common hepatic duct by a stone in the Hartmann pouch, and endoscopic sphincterotomy for acute biliary decompression in acute obstructive cholangitis, air outlining the gallbladder and bile ducts in emphysematous cholecystitis, abdominal and pelvic CT scans showing pancreatic findings graded by Ranson into five categories, a splenic abscess, an inflamed and thickened appendix with surrounding fat stranding, appendiceal perforation and abscess formation, diverticulitis with a small amount of extraluminal air, left lower quadrant fluid collection consistent with peridiverticular abscess, diffuse inflammation and right upper quadrant extraluminal air, and thickening of the colonic wall with both intramural and extramural air, an algorithm outlining the approach to the patient with a suspected lower abdominal infection, upright chest x-ray and abdominal CT scans of patients with sudden-onset diffuse abdominal pain, and an omental (Graham) patch. Tables list diagnostic indicators of upper abdominal pain and fever, comparison of acute cholecystitis and emphysematous cholecystitis, Hinchey system for classification of perforated diverticulitis, Centers for Disease Control and Prevention (CDC) guidelines for diagnosis of pelvic inflammatory disease, and CDC guidelines for antibiotic treatment of pelvic inflammatory disease. This review contains 16 highly rendered figures, 5 tables, and 238 references

A Quality Assurance (QA) System with a Web Camera for High-dose-rate Brachytherapy

The quality assurance (QA) system that simultaneously quantifies the position and duration of an (192)Ir source (dwell position and time) was developed and the performance of this system was evaluated in high-dose-rate brachytherapy. This QA system has two functions to verify and quantify dwell position and time by using a web camera. The web camera records 30 images per second in a range from 1,425 mm to 1,505 mm. A user verifies the source position from the web camera at real time. The source position and duration were quantified with the movie using in-house software which was applied with a template-matching technique. This QA system allowed verification of the absolute position in real time and quantification of dwell position and time simultaneously. It was evident from the verification of the system that the mean of step size errors was 0.31±0.1 mm and that of dwell time errors 0.1±0.0 s. Absolute position errors can be determined with an accuracy of 1.0 mm at all dwell points in three step sizes and dwell time errors with an accuracy of 0.1% in more than 10.0 s of the planned time. This system is to provide quick verification and quantification of the dwell position and time with high accuracy at various dwell positions without depending on the step size.

Numerical Solution of the Thermophysical Task of Grinding of the Laminated System Consisting of Polymer-Composite Materials

The generated model of the temperature pattern in the lamellate system takes into account the system structure, thermo-physical parameters of the each layer material, and process factors: acting heat source duration and intensity, heat dissipation to the process liquid allowing calculation of maximum cutting modes permitted per a heating temperature for each layer of the system.

Intra-abdominal Infection

The basic principles of rapid diagnosis, timely physiologic support, and definitive intervention for intra-abdominal infections have remained unchanged over the past century; however, specific management of these conditions has been transformed as a result of numerous advances in technology. This review covers clinical evaluation, investigative studies, options for intervention, early source control and duration of antimicrobial therapy, infections of the upper abdomen, infections of the lower abdomen, other abdominal infections, and special cases. Figures show an algorithm outlining the approach to a suspected upper abdominal infection, abnormal abdominal ultrasounds showing calculi in the gallbladder and confirming the diagnosis of acute acalculous cholecystitis, endoscopic retrograde cholangiopancreatographies showing a distal common bile duct stone in acute pancreatitis, extrinsic compression of the common hepatic duct by a stone in the Hartmann pouch, and endoscopic sphincterotomy for acute biliary decompression in acute obstructive cholangitis, air outlining the gallbladder and bile ducts in emphysematous cholecystitis, abdominal and pelvic CT scans showing pancreatic findings graded by Ranson into five categories, a splenic abscess, an inflamed and thickened appendix with surrounding fat stranding, appendiceal perforation and abscess formation, diverticulitis with a small amount of extraluminal air, left lower quadrant fluid collection consistent with peridiverticular abscess, diffuse inflammation and right upper quadrant extraluminal air, and thickening of the colonic wall with both intramural and extramural air, an algorithm outlining the approach to the patient with a suspected lower abdominal infection, upright chest x-ray and abdominal CT scans of patients with sudden-onset diffuse abdominal pain, and an omental (Graham) patch. Tables list diagnostic indicators of upper abdominal pain and fever, comparison of acute cholecystitis and emphysematous cholecystitis, Hinchey system for classification of perforated diverticulitis, Centers for Disease Control and Prevention (CDC) guidelines for diagnosis of pelvic inflammatory disease, and CDC guidelines for antibiotic treatment of pelvic inflammatory disease. This review contains 16 highly rendered figures, 5 tables, and 238 references

Control of hydrogen and carbon impurity inclusion during the growth of GaAsN thin film by atomic layer epitaxy

The effects of growth temperature and nitrogen (N) source duration on N, carbon (C), and hydrogen (H) concentrations in GaAsN layers grown by atomic layer epitaxy (ALE) were investigated to understand the incorporation mechanisms of these atoms. In addition, the effects of the above growth conditions on the self-limiting mechanism (SLM) were investigated. The SLM was in effect at growth temperatures of 500 and 520 °C. The origin of the residual C was not N but other sources. With increasing N source duration, the N and H concentrations increased and saturated. The N incorporation mechanisms were discussed by a simple model considering the absorption and desorption of N atoms on the gallium (Ga)-covered surface. H atoms originating from the N source were incorporated in to the GaAsN layer. According to the ratio of the H concentration to the N concentration, the difference in the incorporation processes of N and H atoms in ALE-grown GaAsN layers was discussed.

Rapid Seismological Quantification of Source Parameters of the 25 April 2015 Nepal Earthquake

ABSTRACT The 25 April 2015 M w 7.9 Nepal earthquake is used to explore rapid seismological quantification methods to determine point-source parameters (seismic moment, focal mechanism, radiated energy, and source duration) and rupture directivity parameters (fault length and rupture velocity). Given real-time access to global seismic data, useful results can be obtained from W -phase, energy estimation, cut-and-paste, and backprojection analyses within 20–30 min of origin time or even faster if regional data were openly available (which is not the case at present for stations in China and India). This information can augment ground-shaking prediction procedures such as ShakeMap, which is currently provided by the U.S. Geological Survey National Earthquake Information Center. For such procedures to achieve their full potential, open access to calibrated high-quality ground-motion recordings at local, regional, and global stations is critical, and this should be embraced internationally.

Inversion for rupture properties based upon 3-D directivity effect and application to deep earthquakes in the Sea of Okhotsk region

Rupture properties, such as rupture direction, length, propagation speed and source duration, provide important insights into earthquake mechanisms. One approach to estimate these properties is to investigate the body-wave duration that depends upon the relative location of the station with respect to the rupture direction. Under the assumption that the propagation is unilateral, the duration can be expressed as a function of the dip and azimuth of the rupture. Examination of duration measurements with respect to both the take-off angle and the azimuth is crucial to obtain robust estimates of rupture parameters, especially for nearly vertical rupture propagation. Moreover, limited data coverage, such as using only teleseismic data, can bias the source duration estimate for dipping ruptures, and this bias can map into estimates of other source properties such as rupture extent and rupture speed. Based upon this framework, we introduce an inversion scheme that uses the duration measurements to obtain four parameters: the source duration, a measure of the rupture extent and speed, and dip and azimuth of the rupture propagation. The method is applied to two deep-focus events in the Sea of Okhotsk region, an Mw 7.7 event that occurred on 2012 August 14 and an Mw 8.3 event from 2013 May 24. The source durations are 26 ± 1 and 37 ± 1 s, and rupture speeds are 49 ± 4 per cent and 26 ± 3 per cent of shear wave speed for the Mw 7.7 and 8.3 events, respectively. The azimuths of the two ruptures are parallel to the trench, but are in opposite directions. The dips of the Mw 7.7 and 8.3 events are constrained to be 48° ± 8° downdip and 19° ± 8° updip, respectively. The fit to the data is significantly poorer for the Mw 8.3 event than the Mw 7.7 event, suggesting that the unilateral rupture may not be a good assumption. The analysis is expanded into a multi-episode model, and a secondary episode is determined for the Mw 8.3 event in the southeast direction. The two-episode model gives a better fit to the data than the unilateral model and is compatible with the back-projection analysis, demonstrating that the rupture propagation of the Mw 8.3 event is complex.

Systematic Changes of Earthquake Rupture with Depth: A Case Study from the 2010Mw 8.8 Maule, Chile, Earthquake Aftershock Sequence

The very shallow part of subduction megathrusts occasionally hosts tsunami earthquakes, with unusually slow rupture propagation. The aftershock sequence of the 2010 Mw 8.8 Maule earthquake, offshore Chile, provides us with the opportunity to study systematic changes in source properties for smaller earthquakes within a single segment of a subduction zone. We invert amplitude spectra for double-couple moment tensors and centroid depths of 71 aftershocks of the Maule earthquake down to magnitudes Mw 4.0. In addition, we also derive average source durations.We find that shallower earthquakes tend to have longer normalized source durations on average, similar to the pattern observed previously for larger magnitude events. This depth dependence is observable for thrust and normal earthquakes. The normalized source durations of normal- faulting earthquakes are at the lower end of those for thrust earthquakes, probably because of the higher stress drops of intraplate earthquakes compared to interplate earthquakes. We suggest from the similarity of the depth dependence of normal and thrust events and between smaller and larger magnitude earthquakes that the depth-dependent variation of rigidity, rather than frictional conditional stability at the plate interface, is primarily responsible for the observed pattern. Tsunami earthquakes probably require both low rigidity and conditionally stable frictional conditions; the presence of longduration moderate-magnitude events is therefore a helpful but not sufficient indicator for areas at risk of tsunami earthquakes.

The mechanism of the deep-focus, Sea of Okhotsk earthquake of May 24, 2013 as inferred from static displacements and broadband seismograms

The seismic moment tensor (SMT) was computed for the source of the deep-focus Sea of Okhotsk earthquake of May 24, 2013 (M w = 8.3) based on two kinds of regional data: (1) coseismic displacements at GNNS stations; and (2) three-component broadband seismograms (in this case we also estimated the depth of the equivalent point source and rupture duration along with the SMT). These computations were done independently for each of the two data sets. In the first of these cases we computed the SMT using simulated static displacements due to elementary dipoles as based on the ak135 spherical earth model. In the second case we used synthetic broadband seismograms as computed for a layered, elastic, isotropic, half-space model. Both of the two inversions were carried out by original methods for calculating the simulated data. The SMT determinations that are based on the two data sets are consistent with each other and with determinations from other publications.

Small size very low frequency earthquakes in the Nankai accretionary prism, following the 2011 Tohoku-Oki earthquake

A large number of shallow low frequency events were recorded after the 2011 Mw 9.0 Tohoku-oki earthquake by the cabled network of broadband ocean bottom seismometers (DONET) deployed in the eastern part of the Nankai trough. This low frequency event activity was intense for the first few days after the great earthquake and gradually decreased. Signals of the events are most clearly visible at the frequency range around 2–8Hz. Some of the events are accompanied by a very long frequency (VLF) signal, which is clearly observed at around 0.02–0.05Hz. The magnitude and source duration estimated by waveform analysis for one of the largest very low frequency earthquakes (VLFEs) was 3.0–3.5 and 17s. This source duration is extremely long compared to ordinary earthquakes of comparable magnitude. These newly detected VLFEs are likely to be normal fault earthquakes located at shallow depths within the accretionary prism, in contrast to the previously reported VLFEs that were explained by a low angle thrusting along the decollement zone. On the other hand, the low frequency events with no clear VLF signal were previously regarded as being low frequency tremors (LFTs). We show that events with and without the VLF signal likely represent the same phenomenon, and the VLF signal is only observed when a large magnitude event occurs near the station. The waveforms of VLFEs are characterized by the coexistence of long source duration and high-frequency radiation of signals, and such features were previously explained by the co-occurrence of shear failure and hydrofractures under the influence of fluid brought into the decollement zone. Our result indicates that the stress state and the mechanical environment, which promote the occurrence of VLFEs, exist not only along the decollement zone but also in the shallower part of the accretionary prism.

Global large deep-focus earthquakes: Source process and cascading failure of shear instability as a unified physical mechanism

We apply a multiple source inversion method to systematically study the source processes of 25 large deep-focus (depth >400 km) earthquakes with Mw > 7.0 from 1994 to 2012, based on waveform modeling of P, pP, SH and sSH wave data. The earthquakes are classified into three categories based on spatial distributions and focal mechanisms of the inferred sub-events: 1) category one, with non-planar distribution and variable focal mechanisms of sub-events, represented by the 1994 Mw 8.2 Bolivia earthquake and the 2013 Mw 8.3 Okhotsk earthquake; 2) category two, with planar distribution but focal mechanisms inconsistent with the plane, including eighteen earthquakes; and 3) category three, with planar distribution and focal mechanisms consistent with the plane, including six earthquakes. We discuss possible physical mechanisms for earthquakes in each category in the context of plane rupture, transformational faulting and shear thermal instability. We suggest that the inferred source processes of large deep-focus earthquakes can be best interpreted by cascading failure of shear thermal instabilities in pre-existing weak zones, with the perturbation of stress generated by a shear instability triggering another and focal mechanisms of the sub-events controlled by orientations of the pre-existing weak zones. The proposed mechanism can also explain the observed great variability of focal mechanisms, the presence of large values of CLVD (Compensated Linear Vector Dipole) and the super-shear rupture of deep-focus earthquakes in the previous studies. In addition, our studies suggest existence of relationships of seismic moment ∼ (source duration)3 and moment ∼ (source dimension)3 in large deep-focus earthquakes.

Estimation of the 2010 Mentawai tsunami earthquake rupture process from joint inversion of teleseismic and strong ground motion data

Joint inversion of teleseismic body-wave data and strong ground motion waveforms was applied to determine the rupture process of the 2010 Mentawai earthquake. To obtain stable solutions, smoothing and non-negative constraints were introduced. A total of 33 teleseismic stations and 5 strong ground motion stations supplied data. The teleseismic and strong ground motion data were separately windowed for 150 s and 250 s and band-pass filtered with frequencies of 0.001–1.0 Hz and 0.005–0.5 Hz, respectively. The finite-fault model was established with length and width of 190 km and 70 km, and the initial seismic source parameters were set by referring to centroid moment tensor (CMT) solutions. Joint inversion results indicate that the focal mechanism of this earthquake is thrust fault type, and the strike, dip, and rake angles are generally in accordance with CMT results. The seismic moment was determined as 5.814 × 1020 Nm (Mw7.8) and source duration was about 102 s, which is greater than those of other earthquakes of similar magnitude. The rupture nucleated near the hypocenter and then propagated along the strike direction to the northwest, with a maximum slip of 3.9 m. Large uncertainties regarding the amount of slip retrieved using different inversion methods still exist; however, the conclusion that the majority of slip occurred far from the islands at very shallow depths was found to be robust. The 2010 Mentawai earthquake was categorized as a tsunami earthquake because of the long rupture duration and the generation of a tsunami much larger than was expected for an earthquake of its magnitude.

Linking shelf delta to deep-marine deposition in reservoir dispersal of the upper Oligocene strata in the Baiyun Sag, the northern South China Sea

Linking shelf delta to deep-marine sediment in the Baiyun Sag (BYS) along the northern South China Sea has led to a great deal of interest, but it remains poorly known. In this paper, we focus on the detailed stratigraphic evaluation and reservoir dispersal of upper Oligocene strata (25.5 to 23.8 Ma, referred to as ZHSQ6), using three-dimensional (3-D) seismic volumes (approximately 2500 km2) calibrated with well-log and core data, to determine internal geometry and sedimentary evolution. Rock velocity estimates from well data show that sedimentary environments may be the most direct controlling factor of wave impedance, reflected polarity and the value of amplitude, which in turn predict the nature of the sedimentary system. Likewise, the analysis of sedimentary sequences reveals that lowstand systems tract and transgressive systems tract consist of inner-shelf deltas. Highstand systems tract, by contrast, contained mid-shelf deltas. A northeast-oriented advantaged longshore current influenced asymmetric sandy ridges with a mixed carbonate–siliciclastic system in the north controlled by paleo-uplift geomorphology. Muddy mass transport deposits (MTDs) and sheet sandstones are both widespread. During falling-stage systems tract, shelf-margin deltas provided coarse grain sediments directly onto the basin floor. Consequently, the volumes of dispersed thick deep-water stacked channels and sand-rich MTDs are significant. The existence of the eastern source clearly increased. Finally, the sediment model for the upper Oligocene Baiyun Sag has been established as an optimal component of source-to-sink systems. This study indicates that sedimentary evolution is controlled by source supply flux and duration, base-level behaviour, topographic gradient and growth faults. Delta front channels and longshore sandy ridges, together with the gully fill, represent the most favourable reservoirs for further hydrocarbon exploration.

Equations generated to predict iodine value of pork carcass back, belly, and jowl fat.

Data from existing literature were used to generate equations to predict finishing pig back, belly, and jowl fat iodine values (IV) and an experiment was conducted to evaluate these equations. The final database included 24, 21, and 29 papers for back, belly, and jowl fat IV, respectively. For experiments that changed dietary fatty acid composition, initial (INT) diets were defined as those fed before the change in diet composition and final (FIN) diets were those fed after. The predictor variables tested were divided into 5 groups: 1) diet fat composition (dietary percent C16:1, C18:1, C18:2, C18:3, EFA, unsaturated fatty acids, and IV product) for both INT and FIN diets, 2) day feeding the INT and FIN diets, 3) ME or NE of the INT and FIN diet, 4) live performance criteria (initial BW, final BW, ADG, ADFI, and G:F), and 5) carcass criteria (HCW and backfat thickness). The PROC MIXED procedure of SAS (SAS Inst., Inc., Cary, NC) was used to develop regression equations. Evaluation of models with significant terms was then conducted based on the Bayesian information criterion. The optimum equations to predict back, belly, and jowl fat IV were backfat IV = 84.83 + (6.87 × INT EFA) - (3.90 × FIN EFA) - (0.12 × INT days) - (1.30 × FIN days) - (0.11 × INT EFA × FIN days) + (0.048 × FIN EFA × INT days) + (0.12 × FIN EFA × FIN days) - (0.0060 × FIN NE) + (0.0005 × FIN NE × FIN days) - (0.26 × backfat depth); belly fat IV = 106.16 + (6.21 × INT EFA) - (1.50 × FIN days) - (0.11 × INT EFA × FIN days) - (0.012 × INT NE) + (0.00069 × INT NE × FIN days) - (0.18 × HCW) - (0.25 × backfat depth); and jowl fat IV = 85.50 + (1.08 × INT EFA) + (0.87 × FIN EFA) - (0.014 × INT days) - (0.050 × FIN days) + (0.038 × INT EFA × INT days) + (0.054 × FIN EFA × FIN days) - (0.0066 × INT NE) + (0.071 × INT BW) - (2.19 × ADFI) - (0.29 × backfat depth). Dietary treatments from the evaluation experiment consisted of a corn-soybean meal control diet with no added fat or a 3 × 3 factorial arrangement with main effects of fat source (4% tallow, 4% soybean oil, or a blend of 2% tallow and 2% soybean oil) and feeding duration (d 0 to 42, 42 to 84, or 0 to 84). The back, belly, and jowl fat IV equations tended to overestimate IV when observed IV were less than approximately 65 g/100 g and underestimate belly fat IV when actual IV are greater than approximately 74 g/100 g or when the fat blend was fed from d 0 to 84 or 42 to 84. Overall, with the exceptions noted, the regression equations were an accurate tool for predicting carcass fat quality based on dietary and pig performance factors.

Thermo-Physical Model of the Lamellate System Grinding

Generated model of the temperature pattern in the lamellate system takes into account system structure, thermo-physical parameters of the each layer material, and process factors: acting heat source duration and intensity, heat dissipation to process liquid, allowing calculating cutting modes, maximum allowed per heating temperature for each layer of the system.

Accelerating the Lagrangian Method for Modeling Transient Particle Transport in Indoor Environments

Computational fluid dynamics (CFD) with the Lagrangian method has been widely used in predicting transient particle transport in indoor environments. The Lagrangian method calculates the trajectories of individual particles on the basis of Newton's law. Statistically speaking, a large number of particles are needed in the calculations in order to ensure accuracy. Traditionally, modelers have conducted an independence test in order to find a reasonable value for this particle number. However, the unguided process of an independence test can be highly time-consuming when no simple method is available for estimating the necessary particle number. Therefore, this investigation developed a method for estimating the necessary particle number in the Lagrangian method. Furthermore, the computing cost of the Lagrangian method is positively associated with the particle number. If this number is too large, the computing cost may not be affordable. Thus, this study proposed the superimposition and time-averaging methods to reduce the necessary particle number. This investigation designed multiple cases to verify the proposed methods. The verification results show that the estimation method can provide the necessary particle number with a reasonable magnitude. Moreover, the superimposition method can reduce the necessary particle number when the particle source duration is relatively long. On the other hand, the time-averaging method can reduce the necessary particle number by up to 30 times. When compared with experimental data, predictions of transient particle transport in indoor environments by the combined Lagrangian, superimposition, and time-averaging method with the estimated particle number are reasonably accurate.Copyright 2015 American Association for Aerosol Research

ESTIMATION OF THE RELEASE TIME OF SOLAR ENERGETIC PARTICLES NEAR THE SUN

This paper investigates the onset time of Solar Energetic Particle (SEP) events with numerical simulations, and analyses the accuracy of the Velocity Dispersion Analysis (VDA) method. Using a 3-dimensional focused transport model, we calculate the fluxes of protons observed in the ecliptic at 1 AU in the energy range between 10 MeV and 80 MeV. In particular, three models are used to describe different SEP sources produced by flare or coronal shock, and the effects of particle perpendicular diffusion in the interplanetary space are also studied. We have the following findings: When the observer is disconnected from the source, the effects of perpendicular diffusion in the interplanetary space and particles propagating in the solar atmosphere have significant influence on the VDA results. As a result, although the VDA method is valid with impulsive source duration, low background, and weak scattering in the interplanetary space or fast diffusion in the solar atmosphere, the method is not valid with gradual source duration, high background, or strong scattering.

New approach for active control of smart structure's vibrations subjected to blast loading using multi actuators and sensors

The blast loadings lead to serious damages in structures so that designers try to reduce these effects by special methods. In comparison with other threats such as earthquake and wind, the blast load has some unique characters, i.e., the applied pressure to the structure, the situation of the blast source and small duration of blast loading. Here, new approach is presented for controlling the structural vibrations arise from the blast loads. The proposed active control method is based on structural dynamics theories in which multi actuators and sensors are utilised. Each actuator force is modelled as an equivalent viscous damper so that several lower vibration modes are damped critically. This subject is achieved by simple mathematical formulation. The proposed method does not depend on the type of dynamic load and it could be applied to control structures with multi degrees of freedom. For numerical verification of proposed method, several criterions such as maximum displacement, maximum kinetic energy and maximum drift are evaluated in five story shear building, subjected to the blast load. This study shows that the proposed method has suitable efficiency for reducing structural vibrations causes from the blast loading.