Добірка наукової літератури з теми "Caustic zone"

The shadow optical method of caustics has been applied to the measurement of the bulging out of the surface of aluminum alloy 7075-T6 in the vicinity of a blunt notch in a single edge notch tensile sample after a compression overload and during compression fatigue. The size and shape of the caustic were found to be sensitive functions of the amount of elastic and plastic strain in the vicinity of the notch. Examination of the caustic during application and after release of the overload shows the elastic zone to be larger and more circular than the plastic zone, as predicted. A crack was propagated through the plastic zone using only far-field cyclic compression loading: the crack was self-arresting at the edge of the elasticplastic boundary created by the initial compression overload. The size of the plastic zone as measured by the caustic was found to agree with the maximum length of the crack. The actual surface profile in the vicinity of the notch was measured and its shape was used along with geometrical arguments to develop a model for interpretation of the caustics results. These results indicate that the caustics technique can be used to detect the presence of a plastic zone at the tip of a notch after a compressive overload, and that the size of this zone as measured by caustics is approximately equal to the size as determined by subsequent fatigue crack propagation.

Using an asymptotic approach and an experiment supported by computer simulation, we analyzed processes of restoring structural stability and transitions to new stable states of spiral vortex beams subject to perturbations by curly apertures. Using a tetragonal beam as an example, we considered three perturbation scenarios: 1) asymmetric perturbation, when an opaque screen covers the caustic only on one side of the square, 2) symmetric perturbation, when the curly aperture covers the entire beam except for a narrow caustic region, and 3) symmetric perturbation, when the curly aperture screens only a narrow region of the caustic without affecting the rest of the beam. At the same time, the asymptotic calculation was carried out for all types of polygonal beams. It was shown that if the curly aperture did not destroy the caustic region of the spiral beam, it was able to self-heal in the far diffraction zone. If the perturbation even locally destroyed a part of the caustics, then the perturbed beam passed into a new stable state through chains of creation and annihilation of optical vortices (dislocation reactions).

Focused sonic booms will result from an aircraft accelerating from subsonic to supersonic airspeeds. Sonic boom focusing leads to amplification and phase change of the sonic boom signature and can be modeled by a form of the nonlinear Tricomi equation. This presentation will use the lossy nonlinear Tricomi equation (LNTE) to examine sonic boom focusing for two sample cases. The first case depicts an aircraft with constant rectilinear acceleration at a constant altitude. The second case is slightly more complicated with an aircraft maneuvering at a small climb angle, while accelerating and simultaneously pitching downward. Time-pressure histories at various locations in the illuminated zone above the caustic and in the evanescent zone below the caustic will be provided for each test case.

In allusion to facility corrosion problem in caustic soda industry five types of ni-Cr-cu alloy cast irons were developed. The corrosion rates of ni-Cr-cu alloy cast irons in hot concentrated alkali solution were measured by using self-made dynamic corrosion experiment equipment; the microstructures and surface corrosion morphology of alloy cast irons were observed by means of the optical microscope and SEM; the composition was analyzed using XES. Corrosion resistance mechanism were discussed detailedly. the experimental results showed that ni-Cr-cu cast iron was uniform corrosion macroscopically in the dense caustic soda at high temperature and there was ni, cu enrichment microcosmically. The Ni and Cu enriched in the matrix , which increase in local electrode voltage of the matrix,are advantageous to the improvement of caustic corrosion resistances of that zone. The higher Ni content,the better alkali corrosion resistance performance with high temperature.

The probability of n + 1 intersections of a long needle in the Buffon problem is the eikonal of a Hankel function which is the principal term in the uniform asymptotic expansion in powers of the small distance between the parallel lines. Evaluating this probability using the torus quantization conditions shows that in the physically meaningful region, where a closed convergence of rays covers the caustic circle, the probability is greater than unity. In addition, the method of steepest descent shows that the caustic and reflection indices are more general than the ones given by torus quantization. The distance from the light source to the center of caustic circle corresponds to the length of the needle, and n times the distance between the parallel lines is the radius of the caustic. Unlike diffraction problems, the solution cannot be extended to the shadow zone since the angles become imaginary. In the continuum limit where the distance between the parallels tends to zero, the number of intersections is governed by an arc sine law in which maximum number of intersections, or the maximum chord length in a circle of a given radius, is most probable.

The article describes the methodological approaches to accounting and valuation losses of minerals during open development of deposits with complex mining and geological conditions. As an example, analyzes indicators of losses of minerals during the development phase of plot Kostonaiskogo Chanvinskogo deposits of limestone used for the production of caustic soda. The installed actual level losses exceeding 30% of the total production volume of raw materials. The given reasons of increased losses of limestone in comparison with in the project losses. Installed that with a detailed exploration of the array of limestone was not identified zone karst and zone with high clay content lying in the form of “lived” in zones of high fracturing. In the result of blasting is the mixing of karst explode, clogged areas with pure limestone, its pollution to exceed the allowable values, which leads to loss of balance reserves of minerals during extraction. The article gives recommendations for calculating the level of losses during the when developing complex faces, which are characterized by intermittency breed productive layer of limestone and karst zones.

In the present investigation the particle structure in an AA1200 sheet ingot used for litho applications has been studied. Caustic etching of the as-cast material was seen to result in a zone close to the surface with a different etching response. This zone was identified as what is known as a fir-tree zone or an Altenpohl zone [1,2,3,4]. A variation in particle type over the cross section of the as-cast ingot was seen to follow the differences in etching response. After heat treatment of the material, the fir-tree zones were no longer visible, and the accompanying change in particle structure was studied. Samples from the subsurface regions and from a distance of ~20 cm from the surface has been investigated before and after heat treatment. In the as-cast material, the sample from the surface was dominated by featherlike particles with long strings of particles, identified as AlmFe. While closer to the centre Al3Fe and Al6Fe were seen to be the main phases, however, some AlmFe and probably some α-AlFeSi was also found in this sample. After heat treatment, the particle structure was seen to change, and the surface sample contained mainly Al3Fe in addition to a small amount of AlmFe. The change in particle structure during heat treatment is discussed with reference to the change in etching response.

The computation of the geometrical‐spreading factor and the number of caustics is often considered to be the most fundamental step in computing zero‐order ray solutions for elementary‐wave Green’s functions along a ray that originates at a point source and passes through a 3-D laterally inhomogeneous isotropic medium. Here, a new factorization method is described that establishes both quantities recursively along the ray segments into which the total ray can be subdivided. As a consequence of the proposed method, the point‐source geometrical‐spreading factor and the number of ray caustics along the total ray can be decomposed into (1) point‐source spreading factors of the ray segments and (2) certain Fresnel zone contributions at the ray‐segment connection points. In a so‐called “3-D simple medium,” by which any 3-D laterally inhomogeneous medium can be approximated, the new factorization approach permits a simple computation of both quantities. It thus simplifies and provides new insights into the computation of ray‐theoretical Green’s functions.

Refraction of narrow-band surface waves in coastal areas can result in wave-focal zones where due to interference, wave statistics vary rapidly and on similar length scales as those of individual waves. However such interference patterns, or wave coherence, are not accounted for in conventional stochastic wave models that are based on the energy balance equation or radiative transfer equation. In this work we present a quasi-coherent theory, which is an extension of the radiative transfer equation and quasi-homogeneous theory. We show that this new stochastic modelling approach can resolve rapid variations in wave statistics that occur in the vicinity of a wave caustic. The results compare favourably to those obtained from ensemble averages calculated with a deterministic phase resolving model (SWASH) and, in a focal zone, constitute a significant improvement over those obtained with a conventional stochastic wave model based on an energy balance equation (SWAN).

Das Ziel dieser Arbeit ist es, die Strukturen im äußeren Erdkern zu untersuchen und Rückschlüsse auf die sich daraus ergebenden Konsequenzen für geodynamische Modellvorstellungen zu ziehen. Die Untersuchung der Kernphasenkaustik B mit Hilfe einer kumulierten Amplituden-Entfernungskurve ist Gegenstand des ersten Teils. Dazu werden die absoluten Amplituden der PKP-Phasen im Entfernungsbereich von 142 ° bis 147 ° bestimmt und mit den Amplituden synthetischer Seismogramme verglichen. Als Datenmaterial dienen die Breitbandregistrierungen des Deutschen Seismologischen Re-gionalnetzes (GRSN 1 ) und des Arrays Gräfenberg (GRF). Die verwendeten Wellen-formen werden im WWSSN-SP-Frequenzbereich gefiltert. Als Datenbasis dienen vier Tiefherdbeben der Subduktionszone der Neuen Hebriden (Vanuatu Island) und vier Nuklearexplosionen, die auf dem Mururoa und Fangataufa Atoll im Südpazifik stattgefunden haben. Beide Regionen befinden sich vom Regionalnetz aus gesehen in einer Epizentraldistanz von ungefähr 145 °. Die Verwendung eines homogen instrumentierten Netzes von Detektoren und die Anwendung von Stations- und Magnitudenkorrekturen verringern den Hauptteil der Streuung bei den Amplitudenwerten. Dies gilt auch im Vergleich zu Untersuchungen von langperiodischen Amplituden im Bereich der Kernphasenkaustik (Häge, 1981). Ein weiterer Grund für die geringe Streuung ist die ausschließliche Verwendung von Ereignissen mit kurzer impulsiver Herdzeitfunktion. Erst die geringe Streuung der Amplitudenwerte ermöglicht eine Interpretation der Daten. Die theoretischen Amplitudenkurven der untersuchten Erdmodelle zeigen im Bereich der Kaustik B einen gleichartigen Kurvenverlauf. Bei allen Berechnungen wird ein einheitliches Modell für die Güte der P- und S-Wellen verwendet, das sich aus den Q-Werten der Modelle CIT112 und PREM 2 zusammensetzt. Die mit diesem Q-Modell berechneten Amplituden liegen in geringem Maße oberhalb der gemessenen Amplituden. Dies braucht nicht berücksichtigt zu werden, da die kumulierte Amplituden-Entfernungskurve anhand der Lage des Maximums auf der Entfernungsachse ausgewertet wird. Folglich wird darauf verzichtet, ein alternatives Q-Modell zu entwickeln.
Hinsichtlich der Lage des Kaustikmaximums lassen sich die untersuchten Erdmodelle in zwei Kategorien einteilen. Eine Gruppe besteht aus den Modellen IASP91 und 1066B, deren Maxima bei 144.6 ° und 144.7 ° liegen. Zur zweiten Gruppe von Modellen zählen AK135, PREM und SP6 mit den Maxima bei 145.1 ° und 145.2 ° (SP6). Die gemessene Amplitudenkurve hat ihr Maximum bei 145 °. Alle Entfernungsangaben beziehen sich auf eine Herdtiefe von 200 km. Die Kaustikentfernung für einen Oberflächenherd ist jeweils um 0.454 ° größer als die angegeben Werte. Damit liegen die Maxima der Modelle AK135 und PREM nur 0.1 ° neben dem der gemessenen kumulierten Amplitudenkurve. Daher wird auf die Erstellung eines eigenen Modells verzichtet, da dieses eine unwesentlich verbesserte Amplitudenkurve aufweisen würde. Das Ergebnis der Untersuchung ist die Erstellung einer gemessenen kumulierten Amplituden-Entfernungskurve für die Kaustik B. Die Kurve legt die Position der Kaustik B für kurzperiodische Daten auf ± 0.15 ° fest und bestimmt damit, welche Erdmodelle für die Beschreibung der Amplituden im Entfernungsbereich der Kaustik B besonders geeignet sind. Die Erdmodelle AK135 und PREM, ergänzt durch ein einheitliches Q-Modell, geben den Verlauf der Amplituden am besten wieder. Da die Amplitudenkurven beider Modelle nahe beieinander liegen, sind sie als gleichwertig zu bezeichnen.
Im zweiten Teil der Arbeit wird die Struktur der Übergangszone in den inneren Erdkern anhand des spektralen Abklingens der Phase PKP(BC)diff am Punkt C der Laufzeitkurve untersucht. Der physikalische Prozeß der Beugung ist für die starke Abnahme der Amplituden dieser Phase verantwortlich. Die Diffraktion beeinflußt das Abklingverhalten verschiedener Frequenzanteile des seismischen Signals auf unterschiedliche Weise. Eine Deutung des Verhaltens erfordert die Berechnung von Abklingspektren. Dabei wird die Abschwächung des PKP(BC)diff Signals für acht Frequenzen zwischen 6.4 s und 1.25 Hz ermittelt und als Spektrum dargestellt. Die Form des Abklingspektrums ist charakteristisch für die Beschaffenheit der Geschwindigkeitsstruktur direkt oberhalb der Grenze zum inneren Erdkern (GIK). Die Beben, deren Kernphasen im Regionalnetz als diffraktierte Kernphasen BCdiff registriert werden, liegen in einem Entfernungsbereich jenseits von 150 °. In dieser Distanz befinden sich die Erdbebenherde der Tonga-Fidschi-Subduktionszone, deren Breitbandaufzeichnungen verwendet werden. Die Auswertung unkorrigierter Wellenformen ergibt Abklingspektren, die mit plausiblen Erdmodellen nicht in Einklang zu bringen sind. Aus diesem Grund werden die Daten einer spektralen Stationskorrektur unterzogen, die eigens zu diesem Zweck ermittelt wird. Am Beginn der Auswertung steht eine Prüfung bekannter Erdmodelle mit unterschiedlichen Geschwindigkeitsstrukturen oberhalb der GIK. Zu den untersuchten Modellen zählen PREM, IASP91, AK135Q, PREM2, SP6, OICM2 und eine Variante des PREM. Die Untersuchung ergibt, daß Modelle, die einen verringerten Gradienten oberhalb der GIK aufweisen, eine bessere Übereinstimmung mit den gemessenen Daten zeigen als Modelle ohne diese Übergangszone. Zur Verifikation dieser These wird ein Erdmodell, das keinen verringerten Gradienten oberhalb der GIK besitzt (PREM), durch eine Reihe unterschiedlicher Geschwindigkeitsverläufe in diesem Bereich ergänzt und deren synthetische Seismogramme berechnet. Das Resultat der Untersuchung sind zwei Varianten des PREM, deren Frequenzanalyse eine gute Übereinstimmung mit den Daten zeigt. Das Abklingspektrum des Erdmodells PD47, das in einer 380 km mächtigen Schicht einen negativen Gradienten besitzt, zeigt eine große Ähnlichkeit mit den gemessenen Spektren. Dennoch kann es nicht als realistisches Modell angesehen werden, da der Punkt C in einer zu großen Entfernung liegt. Darüber hinaus müßte die zu kurze Differenzlaufzeit zwischen PKP(AB) und PKP(DF) beziehungsweise PKIKP durch eine größere Änderung der Geschwindigkeitsstruktur im inneren Kern kompensiert werden. Es wird deshalb das Modell PD27a favorisiert, das diese Nachteile nicht aufweist. PD27a besitzt eine Schicht konstanter Geschwindigkeit oberhalb der GIK mit einer Mächtigkeit von 150 km. Die Art des Geschwindigkeitsverlaufs steht im Einklang mit der geodynamischen Modellvorstellung, nach der eine Anreicherung leichter Elemente oberhalb der GIK vorliegt, die als Ursache für die Konvektion im äußeren Erdkern anzusehen ist.
In this thesis the structure of the outer core is investigated with PKP core phases. The knowledge of the physical properties of the earth′s deep interior in this region is important for the understanding of geodynamical processes like the convective flow in the liquid outer core and the differential rotation of the earth′s inner core.
The first part of this thesis describes the investigation of the PKP caustic point B near 145 °. For this purpose a cumulative amplitude distance curve is determined and compared with theoretical amplitude distance curves of different standard earth models. The data are broadband seismograms of the German Regional Seismic Network (GRSN) and the Gräfenberg Array (GRF). In order to measure the absolute amplitudes of the PKP phases, a WWSSN-SP filter is applied to the seismograms. The source regions are located in the South Pacific near Vanuatu Island (4 earthquakes) and on the French atolls Mururoa and Fangataufa (4 explosions). The advantage of a standardized network of seismic stations and the usage of station and magnitude corrections is a reduction of the scatter of the amplitude data. There is even less scatter than in studies with long period amplitude data (Häge, 1981). Another reason for the reduced scattering is the use of events with an impulsive source time function. Only the low scattering of the amplitude values makes it possible to interpret the data. More scattering of the data would have prevented an interpretation. The theoretical amplitude curves are similar in the caustic B distance range. The Q depth distribution for P and S waves used for calculating the synthetic seismograms is a combination of the values of the models CIT112 and PREM. The amplitudes determined with the help of this kind of model are slightly higher than the actually measured amplitudes. However, this needs not be taken into account because the interpretation is based on the position of the caustic peak. Therefore I rejected the computation of an improved Q model.
Regarding the position of the caustic point there are two categories of earth models. The first group consists of the models IASP91 and 1066B with their maxima at 144.6 ° and 144.7 ° respectively. AK135, PREM and SP6 belong to a second group of models with caustic peaks at 145.1 ° and 145.2 ° (SP6). The measured curve has its maximum at 145 °. All distances refer to a source depth of 200 km. For a surface focus the increase in distance is 0.454 °. Therefore the peaks of the models AK135 and PREM are only 0.1 ° beside the maximum of the measured amplitude curve. The main result of this investigation is the amplitude distance curve in the vicinity of the cusp B. The curve determines the position of this point with an accuracy of ± 0.15 ° and points to earth models which would be good for modeling the amplitudes in the distance range of the PKP caustic B. The synthetic seismograms calculated for AK135 and PREM together with a standardized Q model fit the measured amplitude curve equally well.
In the second part of this study the structure of the transition zone to the earth′s inner core is investigated by using the spectral decay of the diffracted wave PKP(BC)diff at point C of the travel time curve. The physical process of diffraction is responsible for the strong reduction in amplitude of this wave. The influence of the diffraction on the seismic signal strongly depends on frequency. The interpretation of this phenomenon requires a calculation of decay spectra. In practice the attenuation of the PKP(BC)diff signal for eight frequencies between 6.4 s and 1.25 Hz are measured and visualized as a decay spectrum. The shape of a spectrum is characteristic of the velocity gradient above the inner core boundary (ICB). Those earthquakes whose core phases are recorded as diffracted core phases BCdiff lie beyond 150 °. In this distance range there are the epicenters of the Tonga-Fiji slab. The broadband waveform data of the earthquakes in this region is used in this study. Decay spectra of waveform data which are not corrected for station site effects are incompatible with standard earth models. Therefore a spectral station correction is applied, which was especially determined for this purpose. The investigation starts with a review of a number of well-known earth models like PREM, IASP91, AK135Q, PREM2, SP6, OICM2 and a version of PREM. All these models have different velocity structures at the ICB. It is shown that models with a reduced velocity gradient above the ICB agree with the data rather than models without such a transition zone. For verification purposes a model without such a reduced gradient (PREM) is completed with different kinds of gradient zones to calculate synthetic seismograms. Two variants of the PREM correspond with the measured decay constants. The decay constants of model PD47 are very close to the measured ones. This model has a 380 km thick negative gradient above the ICB. Nevertheless it is not a realistic model because point C lies in a unrealistic great distance. As a result of the low velocity zone above the inner core there is a differential travel time between the PKP(AB) and the PKP(DF) phase (also PKIKP) which is too short. This would have to be compensated by a correction of the velocities in the inner core. Thus PD27a is the most suitable model which does not have the above mentioned disadvantages. PD27a has a 150 km thick layer of constant velocity above the ICB. This kind of velocity model is compatible with geodynamical theories according to which an enrichment of light elements above the ICB is present and powers the convection in the outer earth core by its buoyancy.

Дисертаційна робота присвячена поглибленому вивченню природи виникнення зони каустики в поліагрегатному підвісі поплавкового гіроскопа, причини формування таких зон в підвісі, їх розвиток у часі і просторі і вплив на виникнення додаткових похибок поплавкового гіроскопа на резонансному рівні хвильового співпадання. Побудовані розрахункові схеми пружної взаємодії проникаючого акустичного випромінювання з поплавковим гіроскопом класу ДУСУ2 надають можливість для поглибленого аналізу причин появи технологічних ризиків експлуатаційних умов внаслідок формування особливостей резонансного типу – за умови великого значення хвильового розміру та незначної величини хвильового розміру. Додатково виявлена небезпека формування ще одного резонансу в підвісі – комбінованого резонансу. Проведені напівнатурні стендові дослідження ДУСУ2-30В та встановлена можливість штучного формування буферної зони для боротьби з негативним впливом проникаючого акустичного випромінювання на прилад. Встановлено наявність в рідинній складовій підвісу гіроскопа окрім циліндричної zone kaustikos ще і плоскої каустики в площині шпангоута корпуса. Експериментально доведена наявність висхідних теплових потоків і температурного стрибка у рідинній частині підвісу гіроскопа, які суттєво змінюють вихідний статичний стан та породжують стохастичний за структурою градієнт тепла, який не взмозі регулюватися тепловим кожухом. Вирішуються комплексні задачі для оборонної галузі: аналізується і окреслюється значення питань маскування та обмеженої примітності деяких типів бойової техніки – окопу для танка у фортифікаційних спорудах відкритого типу, субмарини, літаків палубної авіації.

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Fundação de Amparo a Pesquisa do Estado de São Paulo
In a functional perspective combined to the cognitive perspective of mental spaces, this study focuses on language use as a guidepost to the structure of human conceptual system. the main goal of this research is to verify how grammatical relations are held within the adverbial zone of causalities and, based on that, configure the mental spaces network evoked by these constructions. the specific goals of this project are verifying and analyzing: a) the conceptual connection between the categories of cause and concession; b) the linguistic elements in the construal of the connective and its mental spaces configuration; c) the usage of connectives relative to conceptual domains (content, epistemic, speech act and metalinguistic); d) the usage of tense and mood related to specific connectives and how these categories configure mental spaces; e) the order in these adverbial constructions. based on the list provided by neves (2000), it were selected three adverbial conjunctions in each domain: in the causal domain, já que, uma vez que and visto que; in the concessive domain, ainda que, mesmo que, se bem que. in this study, the corpus came from spoken and written language data available at corpus do português. the analyses considered the following points: (i) the morphosemantic nature of the causal and concessive connectives; (ii) the order of the clauses in the adverbial constructions; (iii) the tense and mood correlations in these constructions; (iv) the presence of traits of (inter)subjectivity in these constructions. these analyses converged on the main hypothesis that the connective used to express causality or concessivity particularizes the relation between adverbial and matrix clause. Regarding specific goals, it was found that: a) the conceptual connection between causality and concessivity lies in more fundamental notions of force dynamics; b) the lexical base of the connectives bears relation to categorial properties of causality and concessivity; c) the connectives show preference for conceptual domains, even though they are pragmatically ambiguous; d) the tense and mood correlations concessive and causal constructions serve to more general functions of signaling epistemic stance and mental spaces embedding; e) the order in these constructions is motived and constrained by the sematic and discursive functions of the adverbial clause. this study revealed that structural complexity in these constructions is a consequence of their semantic and pragmatic complexity with respect to their semantic-pragmatic functions in discourse and with respect to the mental spaces network configuration.
Numa perspectiva funcionalista que se combina à perspectiva cognitivista dos espaços mentais, o estudo se dirige à língua em uso como guia para estrutura do sistema conceptual humano. o objetivo geral desta pesquisa é verificar, dentro da zona adverbial de causalidade-condicionalidade-concessividade, como se manifestam no português brasileiro as relações gramaticais, e, a partir daí, configurar a contraparte da rede dos espaços mentais estabelecida nesse território. os objetivos específicos são verificar e interpretar: a) a ligação conceptual das categorias de causa e concessão; b) a materialidade linguística dos juntivos e sua pré-configuração de espaços mentais; c) o uso dos elementos juntivos nos diferentes domínio conceptuais (conteúdo, epistêmico, atos de fala e metalinguístico); d) o uso dos tempos e modos verbais específicos aos juntivos e a configuração da rede de espaços mentais por eles estabelecida; e) a ordenação dos segmentos nas construções adverbiais e a configuração da rede de espaços mentais por eles estabelecida. a partir da lista de itens juntivos apresentada em neves (2000) foram selecionados três itens juntivos de cada relação: entre os causais se analisaram já que, uma vez que e visto que; entre os concessivos, se analisaram ainda que, mesmo que e se bem que. neste estudo, foram considerados dados de língua escrita e de língua falada coletados no banco de dados do corpus do português. as análises abrangeram os pontos de investigação propostos: (i) a natureza morfossemântica dos itens juntivos causais e dos itens juntivos concessivos; (ii) a ordenação dos segmentos adverbiais em relação aos segmentos nucleares; (iii) a correlação entre tempo e modo dos verbos nessas construções adverbiais; (iv) a presença de traços de (inter)subjetividade nas construções adverbiais de causa e de concessão. o encaminhamento das análises, a partir dos objetivos traçados, convergiu na hipótese central de que o item juntivo utilizado na explicitação das relações adverbiais particulariza a relação entre o segmento nuclear e o segmento adverbial. quanto aos objetivos específicos, verificou-se que: a) a ligação conceptual entre causalidade e concessividade se explica a partir das noções do sistema cognitivo de dinâmica de forças; b) a base lexical dos itens juntivos, ligada às propriedades das categorias de causa e de concessividade; c) esses itens mostraram uma preferência por domínios específicos, ainda que os itens juntivos sejam pragmaticamente ambíguos por ocorrerem nos diversos domínios conceptuais; d) a correlação modo-temporal nas construções causais e concessivas tem as funções mais gerais de tanto marcar a postura epistêmica do falante como de marcar o encaixamento e a hierarquia dos espaços mentais ativados; e) a ordem nas construções causais e concessivas é motivada pela função semântica e pela função pragmática exercidas pelos segmentos adverbiais. O estudo revelou que a complexidade estrutural dessas construções é um reflexo de sua complexidade semântica e pragmática quanto às funções semântico-discursivas que essas construções exercem no discurso e quanto à configuração dos espaços mentais elaborados, construídos e evocados por elas.

The evaporator recycle streams of nuclear waste tanks may contain waste in a chemistry and temperature regime that exceeds the current corrosion control program, which imposes temperature limits to mitigate caustic stress corrosion cracking (CSCC). A review of the recent service history found that two of these A537 carbon steel tanks were operated in highly concentrated hydroxide solution at high temperature. Visual inspections, experimental testing, and a review of the tank service history have shown that CSCC has occurred in uncooled/un-stress relieved tanks of similar construction. Therefore, it appears that the efficacy of stress relief of welding residual stress is the primary corrosion-limiting mechanism. The objective of this experimental program is to test A537 carbon steel small scale welded U-bend specimens and large welded plates (30.48 × 30.38 × 2.54 cm) in a caustic solution with upper bound chemistry (12 M hydroxide and 1 M each of nitrate, nitrite, and aluminate) and temperature (125 °C). These conditions simulate worst-case situations in these nuclear waste tanks. Both as-welded and stress-relieved specimens have been tested. No evidence of stress corrosion cracking was found in the U-bend specimens after 21 days of testing. The large plate test was completed after 12 weeks of immersion in a similar solution at 125 °C except that the aluminate concentration was reduced to 0.3 M. Visual inspection of the plate revealed that stress corrosion cracking had not initiated from the machined crack tips in the weld or in the heat affected zone. NDE ultrasonic testing also confirmed subsurface cracking did not occur. Based on these results, it can be concluded that the environmental condition of these tests was unable to develop stress corrosion cracking within the test periods for the small welded U-bends and for the large plates, which were welded with an identical procedure as used in the construction of the actual nuclear waste tanks in the 1960s. The absence of evidence of stress corrosion cracking and general corrosion in the laboratory-scaled specimens indicate that this type of nuclear waste tank is not susceptible to highly caustic solutions up to 12 M hydroxide at 125 °C when sufficient nitrite inhibitor is present.

This paper investigates wave propagation in two-dimensional nonlinear periodic structures subject to point harmonic forcing. The infinite lattice is modeled as a springmass system consisting of linear and cubic-nonlinear stiffness. The effects of nonlinearity on harmonic wave propagation are analytically predicted using a novel perturbation approach. Response is characterized by group velocity contours (derived from phase-constant contours) functionally dependent on excitation amplitude and the nonlinear stiffness coefficients. Within the pass band there is a frequency band termed the “caustic band” where the response is characterized by the appearance of low amplitude regions or “dead zones.” For a two-dimensional lattice having asymmetric nonlinearity, it is shown that these caustic bands are dependent on the excitation amplitude, unlike in corresponding linear models. The analytical predictions obtained are verified via comparisons to responses generated using a time-domain simulation of a finite two-dimensional nonlinear lattice. Lastly, the study demonstrates amplitude-dependent wave beaming in two-dimensional nonlinear periodic structures.