A fast two-grid and finite section method for a class of integral equations on the real line with application to an acoustic scattering problem in the half-plane

We consider the numerical treatment of second kind integral equations on the real line of the form ∅(s) = ∫_(-∞)^(+∞)▒〖κ(s-t)z(t)ϕ(t)dt,s=R〗 (abbreviated ϕ= ψ+K_z ϕ) in which K ϵ L_1 (R), z ϵ L_∞ (R) and ψ ϵ BC(R), the space of bounded continuous functions on R, are assumed known and ϕ ϵ BC(R) is to be determined. We first derive sharp error estimates for the finite section approximation (reducing the range of integration to [-A, A]) via bounds on (1-K_z )^(-1)as an operator on spaces of weighted continuous functions. Numerical solution by a simple discrete collocation method on a uniform grid on R is then analysed: in the case when z is compactly supported this leads to a coefficient matrix which allows a rapid matrix-vector multiply via the FFT. To utilise this possibility we propose a modified two-grid iteration, a feature of which is that the coarse grid matrix is approximated by a banded matrix, and analyse convergence and computational cost. In cases where z is not compactly supported a combined finite section and two-grid algorithm can be applied and we extend the analysis to this case. As an application we consider acoustic scattering in the half-plane with a Robin or impedance boundary condition which we formulate as a boundary integral equation of the class studied. Our final result is that if z (related to the boundary impedance in the application) takes values in an appropriate compact subset Q of the complex plane, then the difference between ϕ(s)and its finite section approximation computed numerically using the iterative scheme proposed is ≤C_1 [kh log⁡〖(1⁄kh)+(1-Θ)^((-1)⁄2) (kA)^((-1)⁄2) 〗 ] in the interval [-ΘA,ΘA](Θ<1) for kh sufficiently small, where k is the wavenumber and h the grid spacing. Moreover this numerical approximation can be computed in ≤C_2 N log⁡N operations, where N = 2A/h is the number of degrees of freedom. The values of the constants C1 and C2 depend only on the set Q and not on the wavenumber k or the support of z.

On asymptotic behavior at infinity and the finite section method for integral equations on the half-line

e consider integral equations on the half-line of the form and the finite section approximation to x obtained by replacing the infinite limit of integration by the finite limit β. We establish conditions under which, if the finite section method is stable for the original integral equation (i.e. exists and is uniformly bounded in the space of bounded continuous functions for all sufficiently large β), then it is stable also for a perturbed equation in which the kernel k is replaced by k + h. The class of perturbations allowed includes all compact and some non-compact perturbations of the integral operator. Using this result we study the stability and convergence of the finite section method in the space of continuous functions x for which ()()()=−∫∞dttxt,sk)s(x0()syβxβx()sxsp+1 is bounded. With the additional assumption that ()(tskt,sk−≤ where ()()(),qsomefor,sassOskandRLkq11>+∞→=∈− we show that the finite-section method is stable in the weighted space for ,qp≤≤0 provided it is stable on the space of bounded continuous functions. With these results we establish error bounds in weighted spaces for x - xβ and precise information on the asymptotic behaviour at infinity of x. We consider in particular the case when the integral operator is a perturbation of a Wiener-Hopf operator and illustrate this case with a Wiener-Hopf integral equation arising in acoustics.

Tests of non-linearity using LIFFE futures transactions price data

This paper presents and implements a number of tests for non-linear dependence and a test for chaos using transactions prices on three LIFFE futures contracts: the Short Sterling interest rate contract, the Long Gilt government bond contract, and the FTSE 100 stock index futures contract. While previous studies of high frequency futures market data use only those transactions which involve a price change, we use all of the transaction prices on these contracts whether they involve a price change or not. Our results indicate irrefutable evidence of non-linearity in two of the three contracts, although we find no evidence of a chaotic process in any of the series. We are also able to provide some indications of the effect of the duration of the trading day on the degree of non-linearity of the underlying contract. The trading day for the Long Gilt contract was extended in August 1994, and prior to this date there is no evidence of any structure in the return series. However, after the extension of the trading day we do find evidence of a non-linear return structure.

Setting UK standards on the concept of control: an analysis of lobbying behaviour

The present study aims to contribute to an understanding of the complexity of lobbying activities within the accounting standard-setting process in the UK. The paper reports detailed content analysis of submission letters to four related exposure drafts. These preceded two accounting standards that set out the concept of control used to determine the scope of consolidation in the UK, except for reporting under international standards. Regulation on the concept of control provides rich patterns of lobbying behaviour due to its controversial nature and its significance to financial reporting. Our examination is conducted by dividing lobbyists into two categories, corporate and non-corporate, which are hypothesised (and demonstrated) to lobby differently. In order to test the significance of these differences we apply ANOVA techniques and univariate regression analysis. Corporate respondents are found to devote more attention to issues of specific applicability of the concept of control, whereas non-corporate respondents tend to devote more attention to issues of general applicability of this concept. A strong association between the issues raised by corporate respondents and their line of business is revealed. Both categories of lobbyists are found to advance conceptually-based arguments more often than economic consequences-based or combined arguments. However, when economic consequences-based arguments are used, they come exclusively from the corporate category of respondents.

Prebiotics modulate the effects of antibiotics on gut microbial diversity and functioning in vitro

Intestinal bacteria carry out many fundamental roles, such as the fermentation of non-digestible dietary carbohydrates to produce short chain fatty acids (SCFAs), which can affect host energy levels and gut hormone regulation. Understanding how to manage this ecosystem to improve human health is an important but challenging goal. Antibiotics are the front line of defence against pathogens, but in turn they have adverse effects on indigenous microbial diversity and function. Here, we have investigated whether dietary supplementation—another method used to modulate gut composition and function—could be used to ameliorate the side effects of antibiotics. We perturbed gut bacterial communities with gentamicin and ampicillin in anaerobic batch cultures in vitro. Cultures were supplemented with either pectin (a non-fermentable fibre), inulin (a commonly used prebiotic that promotes the growth of beneficial bacteria) or neither. Although antibiotics often negated the beneficial effects of dietary supplementation, in some treatment combinations, notably ampicillin and inulin, dietary supplementation ameliorated the effects of antibiotics. There is therefore potential for using supplements to lessen the adverse effects of antibiotics. Further knowledge of such mechanisms could lead to better therapeutic manipulation of the human gut microbiota.

Joint use of attribute importance rankings and non-attendance data in choice experiments

The joint and alternative uses of attribute non-attendance and importance ranking data within discrete choice experiments are investigated using data from Lebanon examining consumers’ preferences for safety certification in food. We find that both types of information; attribute non-attendance and importance rankings, improve estimates of respondent utility. We introduce a method of integrating both types of information simultaneously and find that this outperforms models where either importance ranking or non-attendance data are used alone. As in previous studies, stated non-attendance of attributes was not found to be consistent with respondents having zero marginal utility for those attributes

An evaluation of three upwinding approximations for numerical modeling the flow in tubular membrane of Newtonian and non-Newtonian fluids

In this paper, the laminar fluid flow of Newtonian and non-Newtonian of aqueous solutions in a tubular membrane is numerically studied. The mathematical formulation, with associated initial and boundary conditions for cylindrical coordinates, comprises the mass conservation, momentum conservation and mass transfer equations. These equations are discretized by using the finite-difference technique on a staggered grid system. Comparisons of the three upwinding schemes for discretization of the non-linear (convective) terms are presented. The effects of several physical parameters on the concentration profile are investigated. The numerical results compare favorably with experimental data and the analytical solutions. (C) 2011 Elsevier Inc. All rights reserved.

Short terms effects of air pollution from biomass burning in mucociliary clearance of Brazilian sugarcane cutters

Nasal mucociliary system is the first line of defense of the upper airways and may be affected acutely by exposure to particulate matter (PM) from biomass burning. Several epidemiologic studies have demonstrated a consistent association between levels of air pollution from biomass burning with increases in hospitalization for respiratory diseases and mortality. To determine the acute effects of exposure to particulate matter from biomass burning in nasal mucociliary transport by saccharin transit time (STT) test, we studied thirty-three non-smokers and twelve light smokers sugarcane cutters in two periods: pre-harvest season and 4 h after harvest at the first day after biomass burning. Lung function, exhaled carbon monoxide (CO), nasal symptoms questionnaire and mucociliary clearance (MC) were assessed. Exhaled CO was increased in smokers compared to non-smokers but did not change significantly after harvest. In contrast, SIT was similar between smokers and non-smokers and decreased significantly after harvest in both groups (p < 0.001). Exposure to PM from biomass burning did not influence nasal symptoms. Our results suggest that acute exposure to particulate matter from sugarcane burned affects mucociliary clearance in smokers and non-smokers workers in the absence of symptoms. (C) 2011 Elsevier Ltd. All rights reserved.

O sindicalismo e a administração publica

A dissertação aqui apresentada versa sobre uma temática nova, quer vista sob a ótica do nascimento do fato sociológico analisado - O Sindicalismo e a Administração Pública quer se considere a quase inexistência de fontes nas quais se possa abeberar, para que fosse possível estabelecer o fio condutor no desenvolvimento do tema. A temática foi analisada em dois planos: primeiro, fêz-se uma apreciação crítica da história do associativismo no Brasil, em sua simbiose com o aspecto social, com o lado econômico e com o lastro jurídico, ao ser analisado o caminho percorrido desde o primeiro clarão do Brasil até os dias presentes. Em segundo estágio, perquiriu-se a questão sindical, no que diz respeito à sua etiologia, o seu despertar mais consciente na década de 80 do nosso século, perpassando pela criação das Centrais Sindicais, ao serem detectados os desvios ideológicos, as contradições, a sua fisiologia em função de sua organização, ideário e ação na direção do que se propõem em nome de seus afiliados. Com efeito, o núcleo do trabalho se cinge à arregimentação do corpo de funcionários públicos com vistas a um eficaz - hoje, ainda muito incipiente - congraçamento, ao se deparar com uma forte resistência institucional, de vez que só a partir da Constituição de 1988, é que se abriu caminho para o direito de associação sindical a esse estamento dos agentes públicos. As disfunções são, aí, analisadas em relação ao despreparo dos Recursos Humanos no exercício de liderança e em confronto com a estrutura institucional anacrônica e de feitio autoritário, para fazer valer, de forma eficaz e efetiva, um bom desempenho da ação sindical, que se deseja genuína, autônoma e autógena, em função dos interesses de classe e a ter em vista a excelência dos serviços públicos; o fenômeno estudado, inversamente, mostra o processamento de uma luta sindical radicada em estrutura antidemocrática, em que o Estado financia os sindicatos e todo o aparelhamento sindical vertical, via contribuição sindical e a considerar que esse lastro sustentador da luta sindical é decalque de uma época de predominância de valores chauvinistas, exaltados no Brasil - e em outros países -, nas décadas de 30 e 40. Ainda foi feito um estudo comparativo com três modelos de sindicalismo, quais sejam: o francês, o alemão e o português. Os dois primeiros por razões de se constituirem em paradigmas de países centrais, tendo em vista que: (1) a França é modelo inspirador das instituições ocidentais, em sede político-jurídico-social, haja vista a sua História prenhe de fatos solapadores do statu quo ante; e (2) a Alemanha, por ter uma classe eficazmente institucionalizada de agentes públicos, tendo tradição araigada desde a burocracia prussiana, o que dá o toque de elevado profissionalismo a esses agentes públicos, os quais contam com uma agremiação sindical que guarda independência com relação ao movimento sindical do trabalhador privado, este, também consolidado em poderosa organização sindical naquele país. Portugal aparece no trabalho como o ascendente cultural do Brasil, o que implica em ser mostrado o nascedouro sindical desse país, dentro do clima cultural em que viveu e vive a península lusitana, e com isso se tenta elucidar o estágio de seu sindicalismo, as suas disfunções e auto funções , as suas semelhanças com o modelo brasileiro, as suas inclinações e natureza. As conclusões aferidas registram alguns aspectos relevantes: 1º) o Brasil nasceu de uma Administração centralizadora, marcada por uma máquina administrativa ineficaz, ineficiente, com a marca do Estato-império e sem a presença da construção concomitante de uma nação que é retardatária no assentar a viga da cidadania, o que levou a delongar a formação dos anseios e do espírito genuinamente autóctones. A repressão ao desenvolvimento das letras foi um entrave à criação de um espírito de povo, com a variante de ser uma maioria inculta, massacrantemente iletrada, em meio a uma pirâmide social em que se registrava apenas uma base desmesurada e um vértice acanhado, sem ter de permeio outras classes sociais que pudessem ser ou vir a ser estratificadas. Na esteira desses elementos, concluiu-se que: 2º) o movimento associativo é uma realidade incipiente e adormecido durante séculos, o que desbordou em uma apatia que só hoje começa a ser sacudida, através dos movimentos associativistas e sindical, este último nascido no meio das fábricas e estendido a algumas capitais de maior relevância política ou de maior peso econômico. o aspecto de maior magnitude para o trabalho foi a sinalização aberta aos servidores públicos para que se sindicalizassem, do que decorreu a conclusão de que essa ação precisa ser tangenciada e carreada a ser um movimento mais autenticamente ligado aos interesses da classe, pois por desvirtuamento contingencial em face da iniciante pouca expressão e inexperiência desse estamento, a ação sindical desses servidores sempre esteve à ilharga do movimento sindical do trabalhador privado, o qual tem outra linha de ação direcionada a interesses mais ligados ao conflito trabalho vs. capital, interesses esses que não se coadunam e nem se identificam com as aspirações e necessidades do funcionalismo público, mesmo que, muitas vezes, a questão do conflito desses agentes tenha uma interface no conjunto da pauta de reivindicação dos trabalhadores privados, ou seja, a questão salarial. O imperativo maior - e esta é a base da recomendação mais substancial - é conduzir a ação dos agentes públicos de forma heterodoxa na direção de se independentizar o movimento sindical desses agentes, a ser impulsionado pelas suas peculiaridades e por sua essencialidade ditada pela sua ontologia de servidores da coisa pública e tendo o público como sua clientela. Este é, em síntese, o caminho aqui trilhado.

Short terms effects of air pollution from biomass burning in mucociliary clearance of Brazilian sugarcane cutters

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Time-periodic perturbation of a Lienard equation with an unbounded homoclinic loop

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Alternative Model of Three-Phase Transmission Line Theory-Based Modal Decomposition

In this paper is shown the development of a transmission line, based on discrete circuit elements that provide responses directly in the time domain and phase. This model is valid for ideally transposed rows represent the phases of each of the small line segments are separated in their modes of propagation and the voltage and current are calculated at the modal field. However, the conversion phase-mode-phase is inserted in the state equations which describe the currents and voltages along the line of which there is no need to know the user of the model representation of the theory in the field lines modal.

Controle on-line para o número de não-conformidades em um ítem inspecionado

The on-line processes control for attributes consists of inspecting a single item at every m produced ones. If the examined item is conforming, the production continues; otherwise, the process stops for adjustment. However, in many practical situations, the interest consist of monitoring the number of non-conformities among the examined items. In this case, if the number of non-conformities is higher than an upper control limit, the process needs to be stopped and some adjustment is required. The contribution of this paper is to propose a control system for the number of nonconforming of the inspected item. Employing properties of an ergodic Markov chain, an expression for the expected cost per item of the control system was obtained and it will be minimized by two parameters: the sampling interval and the upper limit control of the non-conformities of the examined item. Numerical examples illustrate the proposed procedure

Ajuste preventivo versus ajuste corretivo no controle on-line de processo do número de não-conformidades num item inspecionado

In production lines, the entire process is bound to unexpected happenings which may cost losing the production quality. Thus, it means losses to the manufacturer. Identify such causes and remove them is the task of the processing management. The on-line control system consists of periodic inspection of every month produced item. Once any of those items is quali ed as not t, it is admitted that a change in the fraction of the items occurred, and then the process is stopped for adjustments. This work is an extension of Quinino & Ho (2010) and has as objective main to make the monitoramento in a process through the control on-line of quality for the number of non-conformities about the inspected item. The strategy of decision to verify if the process is under control, is directly associated to the limits of the graphic control of non-conformities of the process. A policy of preventive adjustments is incorporated in order to enlarge the conforming fraction of the process. With the help of the R software, a sensibility analysis of the proposed model is done showing in which situations it is most interesting to execute the preventive adjustment

The influence of cervical finish line, internal relief, and cement type on the cervical adaptation of metal crowns

Objective: the aim of this investigation was to evaluate the cervical adaptation of metal crowns under several conditions, namely (1) variations in the cervical finish line of the preparation, (2) application of internal relief inside the crowns, and (3) cementation using different luting materials. Method and Materials: One hundred eighty stainless-steel master dies were prepared simulating full crown preparations: 60 in chamfer (CH), 60 in 135-degree shoulder (OB), and 60 in rounded shoulder (OR). The finish lines were machined at approximate dimensions of a molar tooth preparation (height: 5.5 mm; cervical diameter: 8 mm; occlusal diameter: 6.4 mm; taper degree: 6; and cervical finish line width: 0.8 mm). One hundred eighty corresponding copings with the same finish lines were fabricated. A 30-mu m internal relief was machined 0.5 mm above the cervical finish line in 90 of these copings. The fit of the die and the coping was measured from all specimens (L0) prior to cementation using an optical microscope. After manipulation of the 3 types of cements (zinc phosphate, glass-ionomer, and resin cement), the coping was luted on the corresponding standard master die under 5-kgf loading for 4 minutes. Vertical discrepancy was again measured (L1), and the difference between L1 and L0 indicated the cervical adaptation. Results: Significant influence of the finish line, cement type, and internal relief was observed on the cervical adaptation (P < .001). The CH type of cervical finish line resulted in the best cervical adaptation of the metal crowns regardless of the cement type either with or without internal relief (36.6 +/- 3 to 100.8 +/- 4 mu m) (3-way analysis of variance and Tukey's test, alpha = .05). The use of glass-ionomer cement resulted in the least cervical discrepancy (36.6 +/- 3 to 115 +/- 4 mu m) than those of other cements (45.2 +/- 4 to 130.3 +/- 2 mu m) in all conditions. Conclusion: the best cervical adaptation was achieved with the chamfer type of finish line. The internal relief improved the marginal adaptation significantly, and the glass-ionomer cement led to the best cervical adaptation, followed by zinc phosphate and resin cement.