44,812 research outputs found
Evaluation of the seismic hazard parameters for selected regions of the world: the maximum regional magnitude
No full textParameters of seismic hazard are estimated by the application of the maximum likelihood method. The technique is based on a procedure which utilizes data of different quality, e.g., the ones where the uncertainty in the assessment of the magnitudes is great and those where the magnitudes are computed with great precision. In other words, the data were extracted from both historical (incomplete) and recorded (complete) files. The historical part of the catalogue contains only the strongest events, whereas the complete part can be divided into several subcatalogues each one assumed to be complete above a specified threshold magnitude. Uncertainty in the determination of magnitudes has also been taken into account. The method allow us to estimate the seismic hazard parameters which are the maximum regional magnitude, Mmax , the activity rate, lˆ, of the seismic events and the well known b-value, the slope of the magnitude-frequency relationship. The parameter b, which is interrelated to b (b = bloge), is also obtained. All these parameters are of physical significance. The mean Return Periods, RP, of earthquakes with a certain lower magnitude M ³ m are also determined. The method is applied in some regions of the circum-Pacific belt, which includes various tectonic features, and where catastrophic earthquakes are known from the historical era. The seismic hazard level is also calculated as a function of the form q(Mmax , RP7.5 ) and a relative hazard scale (defined as an index K) is defined for each seismic region. According to this, the investigated regions are classified into five groups of very low, low, intermediate, high and very high seismic hazard levels. This classification is useful for both theoretical and practical reasons and provides a picture of quantitative seismicity.JCR Journalope
Some preliminary results of a worldwide seismicity estimation: a case study of seismic hazard evaluation in South America
No full textGlobal data have been widely used for seismicity and seismic hazard assessment by seismologists. In the present study we evaluate worldwide seismicity in terms of maps of maximum observed magnitude (Mmax), seismic moment (M 0 ) and seismic moment rate (M 0S). The data set used consists of a complete and homogeneous global catalogue of shallow (h £ 60 km) earthquakes of magnitude MS ³ 5.5 for the time period 1894-1992. In order to construct maps of seismicity and seismic hazard the parameters a and b derived from the magnitude-frequency relationship were estimated by both: a) the least squares, and b) the maximum likelihood, methods. The values of a and b were determined considering circles centered at each grid point 1° (of a mesh 1° ´1°) and of varying radius, which starts from 30 km and moves with a step of 10 km. Only a and b values which fulfill some predefined conditions were considered in the further procedure for evaluating the seismic hazard maps. The obtained worldwide M max distribution in general delineates the contours of the plate boundaries. The highest values of M max observed are along the circum-Pacific belt and in the Himalayan area. The subduction plate boundaries are characterized by the largest amount of M 0 , while areas of continental collision are next. The highest values of seismic moment rate (per 1 year and per equal area of 10 000 km 2) are found in the Southern Himalayas. The western coasts of U.S.A., Northwestern Canada and Alaska, the Indian Ocean and the eastern rift of Africa are characterized by high values of M 0 , while most of the Pacific subduction zones have lower values of seismic moment rate. Finally we analyzed the seismic hazard in South America comparing the predicted by the NUVEL1 model convergence slip rate between Nazca and South America plates with the average slip rate due to earthquakes. This consideration allows for distinguishing between zones of high and low coupling along the studied convergence plate boundary.JCR Journalope
Settling of finite-size particles in isotropically forced, homogeneous turbulence: interface-resolved simulations
No full textWe have simulated the gravity-induced settling of finite-size particles in a turbulent background flow which is forced in a statistically-stationary fashion. The simulations are accurately resolving the solid-fluid interface with the aid of an immersed boundary technique [1]. The parameters of the simulation are (apart from background turbulence) identical to those of reference [2], where particle clustering was observed at a Galileo number of 178 and a solid volume fraction of 0.005. In the present case, it is found that a relative turbulence intensity of 0.24 leads to the disappearance of the clusters; as a consequence, the increase in average particle settling velocity found in [2] also vanishes. [1] M. Uhlmann. An immersed boundary method with direct forcing for the simulation of particulate flows. J. Comput. Phys., 209(2):448–476, 2005. [2] M. Uhlmann and T. Doychev. Sedimentation of a dilute suspension of rigid spheres at intermediate Galileo numbers: the effect of clustering upon the particle motion. J. Fluid Mech., 752:310–348, 2014
A probabilistic seismic hazard assessment for Greece and the surrounding region including site-specific considerations
No full textA probabilistic approach was applied to map the seismic hazard in Greece and the surrounding region. The procedure
does not require any specification of seismic sources or/and seismic zones and allows for the use of the
whole seismological record, comprising both historical and instrumental data, available for the region of interest.
The new seismic hazard map prepared for Greece and its vicinity specifies a 10% probability of exceedance
of the given Peak Ground Acceleration (PGA) values for shallow seismicity and intermediate soil conditions for
an exposure time of 50 years. When preparing the map, the new PGA attenuation relation given by Margaris et
al. (2001) was employed. The new map shows a spatial distribution of the seismic hazard that corresponds well
with the features of shallow seismicity within the examined region. It depicts the level of seismic hazard in which
the exceedance of the PGA value of 0.25 g may be expected to occur within limited areas. The highest estimated
levels of seismic hazard inside the territory of Greece are found in the Northern Sporades Islands, where PGA
values in excess of 0.50 g are reached at individual sites, and in the Zante Island in Western Greece, where PGA
values in the range of 0.35 g to 0.40 g are obtained at more numerous localities. High values are also observed
in the sea between the Karpathos and Rhodes islands, near the Island of Amorgos (Cyclades Archipelago) and
in the Southwestern Peloponnesus. The levels of seismic hazard at the sites of seven Greek cities (Athens, Jannena,
Kalamata, Kozani, Larisa, Rhodes and Thessaloniki) were also estimated in terms of probabilities that a
given PGA value will be exceeded at least once during a time interval of 1, 50 and 100 years at those sites. These
probabilities were based on the maximum horizontal PGA values obtained by applying the design earthquake
procedure, and the respective median values obtained were 0.24 g for Athens, 0.28 g for Jannena, 0.30 g for
Kalamata, 0.21 g for Kozani, 0.24 g for Larisa, 0.43 g for Rhodes and 0.35 g for Thessaloniki. The probabilities
of exceedance of the estimated maximum possible PGA value were also calculated for the cities to illustrate the
uncertainty of maximum PGA assessment.PublishedJCR Journalope
Mesophilic-hydrothermal-thermophilic (M-H-T) digestion of green corn straw
No full textMesophilic-hydrothermal (80-160 degrees C, 30 min)-thermophilic (M-H-T) digestion and control tests of mesophilic (M), thermophilic (T), hydrothermal-mesophilic (H-M), and mesophilic-thermophilic digestion (M-T) of green corn straw were conducted for a 20-day fermentation period. The results indicate that M-H-T is an efficient method to improve methane production. A maximum methane yield of 371.74 mL/g volatile solid was obtained by the M (3 days)-H (140 degrees C)-T (17 days) process, which was 20.44%, 16.55%, 31.44%, and 14.31% higher than the yields of the M, T, 140-M, and M-T processes. The enhanced methane production was attributed to (1) the improved hemicellulose degradation and lignin disorganization; (2) prevention of the degradation of soluble sugar, easily hydrolyzed hemicellulose and cellulose into furfural and methylfurfural; and (3) lack of formation of Maillard reaction products during initial hydrothermal treatment. (C) 2015 Elsevier Ltd. All rights reserved
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Evaluation of the seismic hazard parameters for selected regions of the world: the maximum regional magnitude
No full textParameters of seismic hazard are estimated by the application of the maximum likelihood method. The technique is based on a procedure which utilizes data of different quality, e.g., the ones where the uncertainty in the assessment of the magnitudes is great and those where the magnitudes are computed with great precision. In other words, the data were extracted from both historical (incomplete) and recorded (complete) files. The historical part of the catalogue contains only the strongest events, whereas the complete part can be divided into several subcatalogues each one assumed to be complete above a specified threshold magnitude. Uncertainty in the determination of magnitudes has also been taken into account. The method allow us to estimate the seismic hazard parameters which are the maximum regional magnitude, Mmax , the activity rate, l, of the seismic events and the well known b-value, the slope of the magnitude-frequency relationship. The parameter b, which is interrelated to b (b = bloge), is also obtained. All these parameters are of physical significance. The mean Return Periods, RP, of earthquakes with a certain lower magnitude M ³ m are also determined. The method is applied in some regions of the circum-Pacific belt, which includes various tectonic features, and where catastrophic earthquakes are known from the historical era. The seismic hazard level is also calculated as a function of the form q(Mmax , RP7.5 ) and a relative hazard scale (defined as an index K) is defined for each seismic region. According to this, the investigated regions are classified into five groups of very low, low, intermediate, high and very high seismic hazard levels. This classification is useful for both theoretical and practical reasons and provides a picture of quantitative seismicity
Quantitative evaluation of the seismicity in seismogenic sources of the Circum Pacific Rim
No full textΗ σεισμικότητα των σεισμογενών πηγών στις οποίες έχουν χωριστεί η κεντρική και νότια Αμερική, η Ιαπωνία, η Ταϊβάν και οι Φιλιππίνες, μελετάται στην εργασία αυτή από ποσοτική άποψη. Σαν μέτρο σεισμικότητας θεωρήθηκε η μέση περίοδος επανάληψης, Τ , των σεισμών. Οι μέθοδοι που χρησιμοποιήθηκαν ήταν δύο: η μέθοδος της μέσης τιμής και η μέθοδος της πρώτης ασύμπτωτης κατανομής των ακραίων τιμών. Εξετάστηκαν τόσο επιφανειακοί όσο και σεισμοί ενδιαμέσου βάθους των σεισμογενών πηγών. Οι γνωστές παράμετροι a και b της σχέσης της συχνότητας κατανομής των σεισμών υπολογίστηκαν για κάθε σεισμογενή πηγή. Βρέθηκε ότι οι τιμές της μέσης περιόδου επανάληψης σχηματίζουν μεγάλες ζώνες από επικρατούσες τιμές στην κεντρική και νότια Αμερική, ενώ αντίθετα κάτι ανάλογο δεν εμφανίζεται στην άλλη πλευρά του Ειρηνικού και συγκεκριμένα στην Ιαπωνία, στην Ταϊβάν και στις Φιλιππίνες, που πιθανότατα οφείλεται στην διαφορετική τεκτονική συμπεριφορά τους (Tsapanos, 1990).A quantitative measurement of the seismicity is undertaken along the seismogenic sources of the south and central America, as well as of Japan, Taiwan and Philippine islands. The mean return period, Τ , is considered as measure of seismicity. For this purpose the whole process (method of mean value) and the part process (first asymptotic distribution of Gumbel's extreme values) techniques are adopted. The seismicity is evaluated for both shallow and intermediate focal depth shocks which occurred in the examined sources. The a and b values of the magnitude-frequency relationship are estimated for each source. The obtained results show that large welldefine zones of the mean return periods are dominated in the central and south America, while this is not so strong in the areas of Japan, Taiwan and Philippine islands, which probably due to the different tectonic setting of the areas (Tsapanos, 1990)
The maternal immune system during pregnancy and its influence on fetal development
No full textThe maternal immune system plays a critical role in the establishment, maintenance, and completion of a healthy pregnancy. However, the specific mechanisms utilized to achieve these goals are not well understood. Various cells and molecules of the immune system are key players in the development and function of the placenta and the fetus. Effector cells of the immune system act to promote and yet limit placental development. The T helper 1 (Th1)/T helper 2 (Th2) immune shift during pregnancy is well established. A fine balance between proinflammatory and anti-inflammatory influences is required. We herein review the evidence regarding maternal tolerance of fetal tissues and the underlying cell-mediated immune and humoral (hormones and cytokines) mechanisms. We also note the many unanswered questions in our understanding of these mechanisms. In addition, we summarize the clinical manifestations of an altered maternal immune system during pregnancy related to susceptibility to common viral, bacterial, and parasitic infections, as well as to autoimmune diseases.Peer reviewe
Erosie door open taludbekledingen. Samenvattend verslag + Bijlage A t/m D
No full textOpen taludbekledingen die bestaan uit in verband geplaatste betonblokken met gaten, bieden de mogelijkheid vegetatie te doen groeien, waardoor mogelijk een milieuvriendelijke oever kan worden verkregen. In het pioniersstadium van de vegetatie is het evenwel ongewenst dat de gatvulling uitspoelt. Teneinde de relatie tussen waterbeweging en erosie van de gatvulling vast te stellen, is door de Dienst Weg- en Waterbouwkunde van Rijkswaterstaat per brief d.d. 16 maart 1987 (kenmerk WB 570), opdracht verleend aan het Waterloopkundig Laboratorium tot het uitvoeren van onderzoek naar de erosie door open taludbekledingen. Het doel van het onderzoek is het ontwikkelen van ontwerprichtlijnen voor taludbekledingen met gaten die groter zijn dan de zand- of filterkorrels eronder. Hiertoe dient de kritieke waterbeweging bij een oever- of dijkbekleding te worden vastgesteld, waarbij nog toelaatbare erosie is te verwachten. De toelaatbare erosie mag daarbij maximaal gelijk zijn aan de hoeveelheid sediment in de gaten. Filter- of basismateriaal gelegen onder de elementen mag dus niet uitspoelen. Bij oeverbekledingen waar vegetatie een rol moet gaan spelen, is de toelaatbare erosie kleiner, dat wil zeggen in de gaten dient sediment achter te blijven.Steenzettingen - TAW/EN
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