2,809 research outputs found
Removing Love waves from shallow seismic SH-wave data
No full textGeophysical exploration measurements are used to obtain an image of the geological structures of the subsurface, as detailed as possible. To this end, a wavefield is generated by a seismic source. This wavefield propagates through the subsurface, and will partly reflect on boundaries between layers with contrasting properties, and it will partly propagate further into the subsurface. De wavefields that have propagated back to the surface are measured with receivers. When this experiment is repeated several times on different locations, the measured data can be used to obtain the desired image. There are two kinds of seismic waves that can propagate through the subsurface. The ones that are generally used are the pressure waves, or P-waves, where the movement of the particles is parallel to the propagation direction of the wave. The other ones are the shear waves, or S-waves, where the movement of the particles is perpendicular to the propagation direction of the wave. When the particle movement is horizontally polarized (perpendicular to the plane of propagation), this wave type is often decoupled, or in other words, it propagates independently of other wave types. These waves are also called SH-waves. The surface of the Earth behaves as a perfect reflector for SH-waves. This means that all SH-waves that reach the surface will be completely reflected back into the subsurface. When the top layer of the subsurface is thin (smaller than the wavelength of the SH-wave), and when this top layer has a lower wave velocity than deeper layers, then the presence of the surface leads to a kind of surface waves, which were first described by A.E.H. Love, and are therefore called 'Love waves'. Love wave characteristics are: their group velocity is almost equal to the shear wave velocity; since they propagate solely along the surface, they attenuate slowly and are thus often stronger than reflected waves; and they are dispersive. The presence of Love waves deteriorates the quality of the final picture (or seismogram), because they obscure the desired reflections. Existing techniques to remove Love waves from seismic data often perform insufficient, or require certain knowledge about the subsurface. This knowledge is generally not available. Therefore, the ideal method should be one where the measured data alone is sufficient to separate the Love waves from the desired reflection information. The method we describe in this thesis uses the Betti-Rayleigh reciprocity theorem for elastic media. Reciprocity is a mathematical tool to relate two different states to each other. Here, one state is the actual situation, where the medium is bounded by a stress-free surface. The other state is an ideal situation, where there is no surface, and the top layer is extended to infinity. When there is no surface, there are also no surface waves. By applying the reciprocity theorem, we derive an integral equation, from which the Love wave free wavefield can be solved as a function of the data that do contain these surface waves. Other input parameters are the (shear-) wave velocity and the mass density of the top layer, and the source wavelet. When the data are discrete, the integral equation becomes a matrix equation. This can be solved using conventional numerical methods, such as matrix inversion. When the medium is horizontally layered (a so called 1-D medium), the kernel of the matrix equation becomes diagonal in the wave-number domain. Then the matrix equation reduces to a scalar expression. We tested the method on several synthetic datasets. In all cases, the Love waves were completely removed. Even other noise in the form of scattered Love waves was removed, in the cases where it was present. The method also had no problems when the input parameters were chosen wrongly. And when distortions were introduced into the data (distortions like random noise, or the effects of anelastic attenuation), the method still performed well. To test the method on field data, we performed a seismic experiment on the site of the Sofia tunnel (before it was drilled) near Hendrik Ido Ambacht in the Netherlands. The dataset that was the result seemed all right at first. Strong Love waves were indeed present in the data. However, we could not succeed in removing these Love waves with the method. Even worse, the method added noise to the data, to such an extent, that it completely obscured the original data. Although we searched extensively for possible reasons, we were not able to find the exact cause of the bad results. In the final chapter, we made a start to remove the surface waves from coupled P- and SV-wave systems, using the same method as we did for SH-waves. Because P- and SV-waves are coupled, the resulting equations are also coupled. This means that we need all possible source and receiver combinations to remove the surface waves. But it appeared that the equations could be solved independently with regard to the source direction. We validated the theory with an example where we removed the Rayleigh wave from the response of a homogeneousCivil Engineering and Geoscience
Electromagnetic effects in anti-Hermitian media with gain and loss
No full textFunding Information: L.F. was partly supported by DoinQTech, Jane and Aatos Erkko Foundation. L.F. and M.S.M. thank X. Wang, M. Nyman, and B. Zerulla for their invaluable help with numerical simulations. Also, L.F. wishes to acknowledge the support of Carsten Rockstuhl. Publisher Copyright: © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Incorporating both gain and loss into electromagnetic systems provides possibilities to engineer effects in unprecedented ways. Concerning electromagnetic effects in isotropic media that have concurrently electric and magnetic responses, there is, in fact, a degree of freedom to distribute the gain and loss in different effective material parameters. In this paper, we analytically scrutinize wave interactions with those media, and, most importantly, we contemplate the extreme scenario where such media are anti-Hermitian. Considering various conditions for excitation, polarization, and geometry, we uncover important effects and functionalities such as lasing into both surface waves and propagating waves, conversion of evanescent source fields to transmitted propagating waves, full absorption, and enhancing backward to forward scattering ratio. We hope that these findings explicitly show the potential of anti-Hermiticity to be used in optical physics as well as microwave engineering for creating and using unconventional wave phenomena.Peer reviewe
Respiratory and cardiometabolic comorbidities and stages I to III NSCLC survival: a pooled analysis from the international lung cancer consortium
No full textThis study was partially supported by the Public Ministry of Labor Campinas (Research, Prevention, and Education of Occupational Cancer), FINEP-CT-INFRA (02/2010).García-Pardo M., Chang A., Schmid S., Dong M., Brown M.C., Christiani D., Tindel H.A., Brennan P., Chen C., Zhang J., Ryan B.M., Zaridze D., Schabath M.B., Leal L.F., Reis R.M., Tardon A., Fernández-Tardon G., Shete S.S., Andrew A., Brenner H., Xu W., Hung R.J., Liu G
The EJES-3D tool for personalized prescription of exercise in axial spondyloarthritis through multimedia animations: pilot study
No full textFlórez, M.T., Almodóvar, R., García Pérez, F., Rodríguez Cambrón, A.B., Carmona, L., Pérez Manzanero, M.Á., Aboitiz Cantalapiedra, J., Urruticoechea-Arana, A., Rodríguez Lozano, C.J., Castro, C., Fernández-Carballido, C., de Miguel, E., Galíndez, E., Álvarez Vega, J.L., Torre Alonso, J.C., Linares, L.F., Moreno, M., Navarro-Compán, V., Juanola, X., Zarco, P
Exposé Landwinningsvraagstukken
No full textAls algemeen richtslijn is er aangegeven dat bij de opzet van landwinningswerken rekening gehouden moet worden met een tijdperk van ongeveer 40 jaren. Ten einde een nader inzicht in de voor te bereiden werkzaamheden te bekomen, werd er onderzoek verricht en gedeeltelijk in een viertal nota's vastgelegd. De onderzoeken gaan in specifiek over de 'Beplatingsmethode', waarbij slibvangen en beplanting der slikken een voorname rol spelen en de 'Bekleiingsmethode', waarbij getracht wordt sneller tot het doel te komen door inpoldering van een wadgebied en bekleiing ervan met specie uit de ondergrond. Bij het nagaan der mogelijkheden voor de eerstvolgende 40 jaar wordt gestuit op de volgende 7 hoofdvragen van landbouwkundige aard: 1. Is een proefpolder op de Wadden nodig ten einde te onderzoeken welke mening van slib en wadzand de meest wenselijke is? 2. Kan misschien met goedkopere middelen (proefbakken) worden volstaan? Hoe moeten deze worden ingericht? 3. Is het wadzand geschikt om als weidegrond te kunnen dien? Wat is dan de opbrengst per ha.? 4. Kunnen bossen op het Wadzand worden aangelegd? Welke opbrengst? 5. Wat kan met de zogenaamde woelmachine worden bereikt? Deze machine kan vruchtbare klei tot 4 meter diepte beneden maaiveld ophalen en over de oppervlakte spreiden. Kosten per laag van 4 cm dikte bedragen 300 à 400 gulden. 6. Welke resultaten zijn verkregen bij slibbemseting in Westerwolde en Drente? Een ter plaatse gehouden navraag wees uit dat een laag slib van eenige milimeter dikte na 30 jaar nog steeds opmerkelijk resultaten gaf. 7. Welk kavelgrootte is het meest wenselijk? De viertal nota's betreffen: - Verslag werkzaamheden in 1942 op Hollandsch Diep en Maartensgat (door opzichter Molendijk) - Verslag werkzaamheden in 1942 op de Hellegatplaten (door opzcihter Van Eyk) - Programma van onderzoek betreffende plantenonderzoek (door Dr. L.F. Kamps) - Verslag werkzaamheden proefvelden en plantenonderzoek in 1942 (door assisten Van Eerde)Landwinningswerken 194
In vitro regeneration and genetic fidelity of Tigridia pavonia (L.f.) DC.
No full textPlants of Tigridia pavonia (L.f.) DC were regenerated from
twin-scaling explants cultured on Murashige and Skoog and N6 basal
medium. The highest formation of shoots per responding explant was
obtained on N6 medium supplemented with 4.5 µM 2,4-dichlorophenoxy
acetic acid in combination with 2.2 µM benzylaminopurine. Shoots
rooted readily on N6 basal medium supplemented with 1 g l-1 activated
charcoal and 2.6 µM naphtalenacetic acid. The rooted shoots
achieved 100% survival. Inter Simple Sequence Repeat analysis was
carried out to check for possible genetic alterations in plants
obtained after two consecutive subcultures. The results revealed that
the recovered plants did not exhibit any type of polymorphism
Author contributions: L.F
No full textIt is well-known that financial asset returns exhibit fat-tailed distributions and long-term memory. These empirical features are the main objectives of modeling efforts using (i) stochastic processes to quantitatively reproduce these features and (ii) agent-based simulations to understand the underlying microscopic interactions. After reviewing selected empirical and theoretical evidence documenting the behavior of traders, we construct an agent-based model to quantitatively demonstrate that "fat" tails in return distributions arise when traders share similar technical trading strategies and decisions. Extending our behavioral model to a stochastic model, we derive and explain a set of quantitative scaling relations of long-term memory from the empirical behavior of individual market participants. Our analysis provides a behavioral interpretation of the long-term memory of absolute and squared price returns: They are directly linked to the way investors evaluate their investments by applying technical strategies at different investment horizons, and this quantitative relationship is in agreement with empirical findings. Our approach provides a possible behavioral explanation for stochastic models for financial systems in general and provides a method to parameterize such models from market data rather than from statistical fitting. complex systems | power law | scaling laws M odeling price returns has become a central topic in the study of financial markets due to its key role in financial theory and its practical utility. Following models by Engle and Bollerslev (1, 2), many stochastic models have been proposed based on statistical studies of financial data to accurately reproduce price dynamics. In contrast to this stochastic approach, economists and physicists using the tools of statistical mechanics have adopted a bottom-up approach to simulate the same macroscopic regularity of price changes, with a focus on the behavior of individual market participants (3-10). Although the second socalled agent-based approach has provided a qualitative understanding of price mechanisms, it has not yet achieved sufficient quantitative accuracy to be widely accepted by practitioners. Here, we combine the agent-based approach with the stochastic process approach and propose a model based on the empirically proven behavior of individual market participants that quantitatively reproduces fat-tailed return distributions and long-term memory properties (11-14). Empirical and Theoretical Market Behaviors We start by arguing that technical traders (usually agents seeking arbitrage opportunities and make their trading decisions based on price patterns) contribute much more to the dynamics of daily stock prices S t (or log price s t ≡ lnðS t Þ) than fundamentalists (who attempt to determine the fundamental values of stocks). Although fundamentalists hold a majority of the stocks, they trade infrequently (see SI Appendix, Market surveys (16-18) also provide clear evidence of the prevalence of technical analysis. We consider here only technical traders, assuming that fundamentalists contribute only to market noise. Our study is of the empirical data recorded prior to 2006 and ignores the effect of high frequency trading (HFT) that has become significant only in the past 5 y. We propose a behavioral agent-based model that is in agreement with the following empirical evidence: i. Random trading decisions made by agents on a daily basis. n 0 technical traders use different trading strategies, hence their decisions to buy, sell, or hold a position appear to be random. A trading decision is made daily because empirical studies report the lack of intraday trading persistence in empirical trading data (19). Market survey (16) also shows that fund managers put very little emphasis on intraday tradings. We estimate the probability p of having daily trade empirically from trading volumes. ii. Price returns. The price return r t ≡ s t − s t−1 is controlled by the imbalance d t between the demand and the supply of stocks-the difference in the number of buy and sell trades each day. The excess in total demand or supply moves the price up or down, where the largest r t occurs when all traders act in unison, when they all either buy or sell their stocks. We assume this relationship between price change r t and d t to be linear each day, as supported by empirical findings (20, 21). iii. Centralized interaction mechanism of returns on technical strategies. For technical traders, an important input parameter in their strategies is past price movement (22, 23). Consequently, prices and orders reflect a main interaction mechanism between agents. In many agent-based models, the interaction strength between agents need to be adjusted with agent population size (5, 24, 25) or interaction structure (26) to sustain "fat" tails in return distributions. Here we propose a centralized interaction mechanism (price change) among agents so that the strength of interaction grows with agent population and is unaffected by interaction structure. iv. Opinion convergence due to price changes. This is the unique mechanism that distinguishes our model from other models. It specifies the collective behavior of technical traders. Duffy et al. (27) found that agents learn from each other and tend to adopt the strategy that gives the most payoff. Given the price patterns at any point in time, a few most profitable technical strategies dominate the market because every technical trade
Traslación nutrimental e incremento medio anual en teca (Tectona grandis L.f.), en Tabasco, México
No full textNutrient transfer is the amount of nutrients mobilized from senescent leaves to other tree tissues. The objective of this study was to estimate the nutrient transfer and the mean annual increment (MAI) in diameter, height, and volume as affected by chemical fertilization and a green manure (GM) in teak (Tectona grandis L.f.) plantations. In experimental plots, NPK fertilizer treatments were applied at two, three, and four years of age. Using a split-plot design, Crotalaria juncea was established in alleys as GM. Nitrogen transfer (6.75%) was not favored by the GM, but it was by the chemical fertilization treatments. Height showed an MAI of 3.12 m.year⁻¹ at 3.3 years, and it was higher at 4.7 years with GM * 120-60-60 kg.ha⁻¹. The control treatment at 4.7 years showed the lowest diameter and volume MAIs with GM, with significant differences.La traslación nutrimental es la cantidad de nutrientes que son movilizados desde las hojas senescentes a otros tejidos de los árboles. El objetivo de este estudio fue estimar la traslación nutrimental y el incremento medio anual (IMA) en diámetro, altura y volumen por efecto de la fertilización química y un abono verde (AV) en plantaciones de teca (Tectona grandis L.f.). En parcelas experimentales, se aplicaron tratamientos de fertilizante NPK a los dos, tres y cuatro años de edad. Mediante un diseño de parcelas divididas, se estableció Crotalaria juncea en callejones como AV. La traslación nutrimental del N (6.75 %) no fue favorecida por el AV, pero sí por los tratamientos con fertilización química. La altura presentó un IMA de 3.12 m.año-1 a los 3.3 años, y a los 4.7 años fue mayor, con AV * 120-60-60 kg.ha-1. El tratamiento testigo a los 4.7 años mostró los IMA de diámetro y volumen más bajos con AV, presentando diferencias significativas.
In Search of Lost Meaning. Review of the Monograph by Kharayeva L.F., Kuchukova Z.A. “Gender and Ethnogender (on the Material of Kabardian Women’s Prose)”
No full textThe review offered to our readers is devoted to the study of the phenomenon of Kabardian women’s prose, presented in the monograph “Gender and Ethnogender” by L.F. Kharaeva and Z.A. Kuchukova. The author analyzes the monograph from the point of view of its structure, sequence of presentation, relevance to the topic and corpus of chosen literary texts. The undoubted value of the monograph recognizes its theoretical and practical significance, as well as an indisputable novelty. The author recommends this scientific research to be read by all who are interested in issues of gender and its ethnospecificity, gender literature, and the latest Kabardian literature
In vitro regeneration and genetic fidelity of Tigridia pavonia (L.f.) DC.
No full textPlants of Tigridia pavonia (L.f.) DC were regenerated from twin-scaling explants cultured on Murashige and Skoog and N6 basal medium. The highest formation of shoots per responding explant was obtained on N6 medium supplemented with 4.5 µM 2,4-dichlorophenoxy acetic acid in combination with 2.2 µM benzylaminopurine. Shoots rooted readily on N6 basal medium supplemented with 1 g l-1 activated charcoal and 2.6 µM naphtalenacetic acid. The rooted shoots achieved 100% survival. Inter Simple Sequence Repeat analysis was carried out to check for possible genetic alterations in plants obtained after two consecutive subcultures. The results revealed that the recovered plants did not exhibit any type of polymorphism
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