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Abstract A methodology that utilizes neural network (NN) architecture was developed for predicting P-wave sonic logs. Well logs and fundamental attributes of seismic traces along a 2-D, migrated seismic line from Namorado Reservoir (Campos Basin, Brazil), were used to create and test the method. At a certain well location, P-wave logs and basic attributes of a seismic trace were used as the NN training dataset. The trained system was tested in two well locations. At the first well, the generated sonic log and the basic attributes of the nearest seismic trace were employed for training the NN. Subsequently, the sonic log at a second well was predicted using attributes from seismic traces at the well location as input data to the trained NN. The predicted results are compared with the actual sonic log data acquired at the well. This methodology applied to similar data from Gulf of Mexicoproved to be quite satisfactory. Recursive inversion of seismic trace was utilized for validation and qualification of uncertainties. The result achieved in this research suggests that the application of the proposed methodology when P-wave log information is needed between wells far away from each other leads to acceptable predictions. Introduction Seismic data is not used intensively during well design. The information conveyed by seismic data is normally used for exploration and production purposes. However, the characterization of the overburden can improve very much from an extensive analysis of the seismic data, mainly when used in conjunction with other data such as logs, drilling reports and geological maps. Hidden information in the seismic section should be searched for in order to improve the quality of the drilling operation and, consequently, for thereduction of risks. Traditionally, sonic log data is used to estimate rock properties and pore pressure along a proposed well trajectory. The estimation of sonic log data along a given well trajectory, for drilling planning purposes, is not a straightforward operation and several simplifying assumptions are made. Extensive use of offset wells and a best guess-based sonic log construction are the tools more often used for providing data for well planning. Even though seismic interval velocities have been, more recently, used to predict pore pressure distribution, sonic logs are the source of data preferred by prediction algorithms. The motivation of this paper is to explore the use of seismic data for characterizing the overburden. In the pages to follow, two techniques are explored in order to obtain a rational prediction of sonic logs along planned well location using seismic data. The first technique is based upon the use of genetic algorithm, back propagation neural network scheme, to estimate sonic logs from seismic attributes used as input data to a specially trained neural network. The second technique, used herein for comparison purposes, is based upon seismic trace inversion. The chosen algorithms were obtained from Hampson-Russell Software (Sparse Spike Inversion and Model Based Constrained Inversion) and the NN method was developed in Mathworks MATLAB®.

A back-propagation artificial neural network (ANN) is used in order to predict P-wave sonic logs in well locations where such data are unavailable. Further predictions are also intended to be performed where there are no wells. The data set, to which the methodology was applied, covers a mature oil reservoir, the Namorado sandstone, in Campos Basin, Brazil. Basic seismic attributes were used for training the ANN. In this ongoing project, the construction of a 3-D P-wave velocity distribution over the area of the Namorado reservoir is envisaged. Studies of well bore stability are supposed to be a direct application of the results of the project, since improvement in the knowledge of the geologic features of the subsurface is also expected.

We present a new stable method for interpreting the basement relief of a sedimentary basin which delineates sharp discontinuities in the basement relief and incorporates any law known a priori for the spatial variation of the density contrast. The subsurface region containing the basin is discretized into a grid of juxtaposed elementary prisms whose density contrasts are the parameters to be estimated. It is imposed that any vertical line intersect the basement relief only once and that the mass deficiency be concentrated near the Earth's surface, subject to the observed gravity anomaly being fitted within the experimental errors. In addition, upper and lower bounds on the density contrast of each prism are introduced a priori (one of the bounds being zero) and the method assigns to each elementary prism a density contrast which is close to either bound. The basement relief is, therefore, delineated by the contact between the prisms with null and nonnull estimated density contrasts, the latter occupying the upper part of the discretized region. Thus, the method is stabilized by introducing constraints favoring solutions having the attributes (shared by most sedimentary basins) of being an isolated compact source with lateral borders dipping either vertically or toward the basin center and having horizontal dimensions much greater than its largest vertical dimension. Arbitrary laws of spatial variations of the density contrast, if known a priori, may be incorporated to the problem by assigning suitable values to the nonnull bound of each prism. The proposed method differs from previous stable methods by using no smoothness constraint on the interface to be estimated. As a result, it may be applied not only to intracratonic sag basins where the basement relief is essentially smooth, but also to rift basins whose basements present discontinuities caused by faults. The method's utility in mapping such basements were demonstrated in tests using synthetic data produced by simulated rift basins. The method mapped with good precision a sequence of step faults which are close to each other and present small vertical slips, a feature particularly difficult to detect from gravity data only. The method was also able to map isolated discontinuities with large vertical throw. The method was applied to the gravity data from Reconcavo Basin, Brazil. The results showed close agreement with known geological structures of the basin. It also demonstrated the method's ability to map a sequence of alternating terraces and structural lows, which could not be detected just from the inspection of the gravity anomaly.

Euler deconvolution has been widely used in automatic aeromagnetic interpretations because it requires no knowledge of the source magnetization direction and assumes no particular interpretation model. This rapid inversion method produces stable estimates for the horizontal and vertical positions and respectively) of point sources. Another main advantage of this method is that it does not demand a detailed geologic knowledge of the area. However the two crucial weakenesses of this method are: i) the need of knowing the nature of the magnetic point or line source, that is, the knowledge of the structural index and ii) the presence of an undesirable “spray” of solutions which is obtained when the method is applied in a redundant way by moving the discrete inverse operator around the anomalous area. We present two new criteria for solving these difficulties. The first criterion is aimed at determining It is based on the correlation between the total-field anomaly and the estimates of a baselevel (b) computed at the same locations of the observations and using different This correlation attains a minimum when the correct is assumed. The second criterion selects, from the “spray” of solutions, only the best solutions. We propose that, besides selecting the solutions producing a standard deviation for smaller than a threshold value, only those solutions producing the “best fit” to the known quantities be selected. This additional criterion substantially reduces the “spray” of solutions.

We present a gravity interpretation method for estimating the relief of an arbitrary interface separating two homogeneous media. The upper medium is discretized into rectangular, juxtaposed prisms whose thicknesses represent the depths to the interface and are the parameters to be estimated from the gravity anomaly. To stabilize the inversion, we introduce two kinds of constraints on the depths. The first one requires proximity between the observed and computed depths at isolated points such as those obtained from boreholes (absolute equality constraint). The second one requires that groups of depths approximately follow an established linear relationship among them (relative equality constraint). Both kinds of constraints are imposed in the least-squares sense. This stabilization procedure does not bias the solution either toward an initial approximation, or toward the null solution. The method is applied to synthetic data, producing a good reconstruction of a complex basement consisting of several structural high and lows. It is also applied to real data of Reconcavo Basin, Brazil, leading to a sharper definition of the basement structures as compared with previous gravity interpretations of the area.

Utilizando-se dados topograficos e gravimetricos, pode-se estimar o relevo da interface crostamanto atraves de, pelo menos, duas abordagens independentes. A primeira abordagem (amplamente utilizada) emprega a hipotese de que a regiao em estudo encontra- se isostaticamente compensada (e.g. Banks et aI., 1977). Por outro lado, a segunda abordagem (menos utilizada) efetua previamente a separacao regional-residual do campo gravimetrico total e estima o relevo da interface crosta-manto atraves da inversao da coinponente regional do campo (e.g. Beltrao, 1989). Por ser urn problema mal-posto (cuja solucao e instavel), esta inversao requer a introducao de vinculos para fomecer solucőes estaveis. Um dos vinculos mais utilizados e o da suavidade do relevo da interface crostamanto.

We present theoretical uniqueness, stability, and parameter bias analyses for the simultaneous estimation of: the structural index the horizontal and vertical positions and respectively) of a point magnetic source, and a baselevel b, using Euler’s differential equation. We found that and are independent of the other parameters and can be estimated from the knowledge of the total-field anomaly and its gradients only. On the other hand, and cannot be simultaneously estimated because they are linearly dependent. As a result, to estimate must be either known a priori or independently determined (and vice versa). For a known estimates of and are unique and stable regardless of the value of However, if the vertical (or horizontal) gradient of the observed total field assumes negligible values, the estimation of (or becomes unstable. In contrast, as far as is not too close to zero, estimates of are stable. For equal to zero, estimates of are undetermined.

The interpretation of magnetic anomalies is not a trivial task not only because of the difficulties in allowing for a possible existence of remanent magnetization, but also due to the nonlinear dependence of the magnetic anomaly upon the source geometry. For the sake of simplicity, the magnetization is usually assumed to be induced only while trying to estimate the interpretation model geometry. Alternatively, the spatial orientation of the source may be assumed known in order to estimate the total magnetization. We present a method to simultaneously estimate the total magnetization direction and the spatial orientation of the source. The method is based on the approximation of the anomalous field by the series derived from expansion of the magnetic potential in multipoles, keeping moments up to 2nd order. Because the parameters to be inverted are the source moments, the method has the advantages of being linear and appropriate to interpret anomalies produced by a broad class of sources. This class comprises the finite-volume bodies, homogeneously magnetized in direction, but not necessarily in modulus, and whose spatial distribution of magnetization modulus presents three orthogonal symmetry planes.

To produce meaningful reduced-to-the-pole fields at low magnetic latitudes we combined two procedures. The first one is based on the development, in Taylor’s series, of the theoretical expression of the reduction-to-the-pole filter in the wavenumber domain. By realizing that the filter instability is caused by the huge filter am plitudes (along the magnetization azimuth), which are expressed by the infinite sum of terms close to unity, the stabilizing procedure boils down to truncating the infinite series. The second procedure is the upward continuation operation which attenuates the high wavenumber component ofthe noise and allows, therefore, to design a stabilized filter closer to the theoretical one. Besides, quantitative interpretations of the sources depth based on the filtered field are more reliable as compared with arbitrary low-pass filters.

Gravity inversion is an ill-posed problem because it presents infinite solutions. One efective way to transform it into an well-posed problem is to constrain the solutions with a priori information (about the anomalous density distribution) introduced by a stabilizing functional. In this paper we present a stabilizing functional which incorporates information about symmetry and either overall or directional smoothness in the spatial density distribution. In the case of a linear inverse problem where the parameters to be determined are the densities of several retangular blocks, the proposed functional is the sum of the squared differences between previously established pairs of parameters. The estimator associated with this functional may contribute to stabilize the inversion process if it incorporates information about the density variation in a direction in which the gravity observations have poor resolution particularly in the vertical direction. Let us assume that by inspecting a given gravity profile, we can limit a region R containing the cross-section l? of the anomalous source. To estimate, from the gravity profile, the distribution p(z, z) of density contrasts, we discretize R into M blocks (Figure 1) and estimate them by solving the equation

Since 1970 (1), the fluorescence properties of the acridine derivatives have been utilized to detect the energization state of biological membranes. On the other hand, these compounds have been pointed out as uncoupling agents in chromatophores membranes (2,3), spinach thylakoids (4,5) and submitochondrial particles (6). However, their mechanism of action remains to be fully clarified. The results reported here are the initial part of the study of this action on thylakoid membranes of Anabaena sp. 7119.

The phenomenon of ablation is a process of thermal protection with several applications, mainly, in mechanical and aerospace engineering. Ablative thermal protection is applied using special materials (named ablative materials) externally on the surface of a structure in order to isolate it against thermal effects. The ablative phenomenon is a complex process involving phase changes with partial or total loss of the material. So the position of the boundary is initially unknown. The governing equations of the process form a non-linear system of coupled partial differential equations. The one-dimensional analysis of an ablative process on the plate is performed by using the generalized integral transform technique – GITT for solution of the system of governing equations. By application of this solution technique, the system of partial differential equations is transformed into a system of infinite ordinary differential equations that can be solved after the truncation of that system by numerical techniques codes available. The plate of finite thickness at constant properties is subjected to a time-dependent prescribed radiation heat flux at one face, initially with a uniform temperature T0, and insulated on the other face. After an initial heating period, ablation starts at the heated surface through melting and continuous removal of the plate material. The results of interest are the thickness and the loss rate of the ablative material. The obtained results are compared with available results from other solution techniques in the literature.

The main purpose of this work is the numerical computation of turbulent incompressible fluid flows by a nine-node control volume finite element method (CVFEM) using the methodology of large-eddy simulation.. The domain is discretized using nine nodes finite elements and the equations are integrated into control volumes around the nodes of the finite elements. The Navier?Stokes equations are filtered for simulation of the large scales variables and the sub-grid scales stress appearing due to the filtering process are modeled through the eddy viscosity model of Smagorinsky. The two-dimensional benchmark problem of the lid-driven cavity flow is solved to validate the numerical code and preliminary results for the horizontal and vertical velocity profiles at the centerlines of the cavity and the stream functions are presented and compared with available results from the literature.

A robust magnetic interpretation technique is described. It is based on the minimization of an objective function by a random search algorithm. Instead of just one estimate, this algorithm yields several points in parameter space, all producing objective function values below an assumed noise level. The centroid of the search points is in general a better estimate than each individual search point, especially when data are corrupted by noise. Since no derivatives are employed, even nondifferentiable objective functions, such as the [Formula: see text] norm of residuals, can be used. Computation of parameter covariance matrices and confidence ellipses is possible using simple formulas. The usefulness of R‐ and Q‐mode factor analysis applied to the correlation matrix is demonstrated. The R‐mode factor analysis can be used in parameter variance control, and the Q‐mode factor analysis provides means to find models which are extreme in some sense. The technique was applied to theoretical data and to field data from three different geologic settings. The results show that the algorithm produces accurate estimates of source parameters under different types of geologic constraints. The proposed technique has three main advantages. First, it attacks the multiple minima problem, which is always present in nonlinear inversion. A possible range of acceptable models consistent with a priori geologic information is computed. Second, when the multiple minima are not caused by the inherent ambiguity in potential field data, for example when presence of noise in data is significant or the wrong interpretation model is used, the technique provides parameter estimates which can be more significant than the estimates obtained by most optimization algorithms. Third, it can easily incorporate a priori geologic information, which is always available and should be used to reduce ambiguity. The technique can be applied at any stage of magnetic interpretation. However, its efficiency will depend upon the amount of a priori geologic and geophysical information available.

We have made a theoretical study of the problem of locating and defining a magnetized prism in the vicinity of a drillhole. The study shows that a three‐component borehole magnetometer can be very useful in exploration for deep magnetic targets, which are difficult to intersect by drilling. There are nine parameters to be estimated from the data: the x, y, and z positions of the center of the prism; length, width and depth extent; and the three parameters defining the magnetization vector. The parameters are estimated by minimizing the sum of squared differences between the predicted and observed data. Since the problem is nonlinear, it must be solved iteratively. At each iteration a singular value analysis of the sensitivity matrix is performed, and a particular solution is chosen from a set of minimal length solutions; each solution corresponds to a different rank of the sensitivity matrix. The main difficulty is an ambiguity involving the position parameters and the parameters defining the magnetization vector. In order to minimize this obstacle, a parameter scaling matrix is introduced. The effects of noise, wrong model, probe orientation errors, borehole length, and data density are analyzed. We have found that the position and depth extent of the body can be estimated with reasonable accuracy.

I present a magnetic interpretation method which transforms into a linear problem the nonlinear problem of obtaining the geometric and position parameters of a two‐dimensional vertical, infinite prism. The magnetization, the only linear parameter, becomes nonlinear after the transformation. By assuming a few discrete values over a prescribed interval for the magnetization, I obtain several solutions for the geometric and position parameters. By storing only the extreme solutions, bounds for each parameter are produced. The method was applied to synthetic anomalies due to isolated and interfering sources for which robust alternatives performed better than the least‐squares method. The correlation between the magnetization and the prism width is the most important factor controlling ambiguity of parameters. The horizontal position is the least affected parameter, followed by the depth to the top of the prism. Application to a real anomaly confirmed the results from synthetic data, except for a greater uncertainty in the estimation of the horizontal position. The uncertainty results from the requirement in the present method that the observations be reduced to the pole; an imprecise knowledge of the magnetization direction distorts the position, which is highly correlated with the magnetization inclination. Because the estimation of the position, depth, and width is transformed into a linear problem, the method is simple, fast, and independent of the initial guess. The method might, therefore, be useful in automatic interpretation of basement relief. By producing bounds for each parameter estimate, an analysis of parameter precision and ambiguity is also possible.

We present a new approach to perform any linear transformation of gridded potential field data using the equivalent‐layer principle. It is particularly efficient for processing areas with a large amount of data. An N × N data window is inverted using an M × M equivalent layer, with M greater than N so that the equivalent sources extend beyond the data window. Only the transformed field at the center of the data window is computed by premultiplying the equivalent source matrix by the row of the Green’s matrix (associated with the desired transformation) corresponding to the center of the data window. Since the inversion and the multiplication by the Green’s matrix are independent of the data, they are performed beforehand and just once for given values of N, M, and the depth of the equivalent layer. As a result, a grid operator for the desired transformation is obtained which is applied to the data by a procedure similar to discrete convolution. The application of this procedure in reducing synthetic anomalies to the pole and computing magnetization intensity maps shows that grid operators with N = 7 and M = 15 are sufficient to process large areas containing several interfering sources. The use of a damping factor allows the computation of meaningful maps even for unstable transformations in the presence of noise. Also, an equivalent layer larger than the data window takes into account part of the interfering sources so that a smaller damping factor is employed as compared with other damped inversion methods. Transformations of real data from Xingú River Basin and Amazon Basin, Brazil, demonstrate the contribution of this procedure for improvement of a preliminary geologic interpretation with minimum a priori information.

Traditionally, reduction to the pole has been accomplished either by space‐ or wavenumber‐domain filtering. In the two‐dimensional case, this procedure is stable regardless of the latitude, as long as the source strike is not parallel to the horizontal projection of the geomagnetic field. In the three‐dimensional case, however, reduction‐to‐the‐pole filtering is stable only at high magnetic latitudes. At latitudes lower than 15 degrees, it is of no practical use due to a sharply increasing instability toward the magnetic equator. The three‐dimensional instability of this filtering technique is demonstrated, and the reduction‐to‐the‐pole problem is formulated in the context of a general linear inverse problem. As a result, stable solutions are found by using well‐known stabilizing procedures developed for the inverse linear problem. The distribution of magnetization of an equivalent layer of doublets that reproduces the observed data is computed. The magnetic doublets are parallel to the magnetization direction which is assumed constant throughout the sources. The magnetic field reduced to the pole is then obtained by changing the inclinations of the geomagnetic field and the doublets to 90 degrees and recalculating the total field. The usefulness and limitations of the method at low magnetic latitudes are assessed using theoretical data. The effects of noise and anomaly truncation are also investigated for both high and low latitudes. In all cases, application of the proposed method produced meaningful results regardless of the latitude. The method is applied to field data from two different low‐latitude anomalies. The first anomaly is due to a seamount in the Gulf of Guinea with reversed magnetization. The geomagnetic field at this location is about −23 degrees. The second anomaly is an intrabasement anomaly from Parnaiba Basin, Brazil, where the magnetization is assumed to be induced by a geomagnetic field with −1.4 degree inclination. The results obtained confirm that the proposed method produces stable, meaningful, reduced‐to‐the‐pole maps.

This paper describes an automated, three-dimensional, multibody aeromagnetic interpretation technique, which operates on the total intensity map by means of straightforward operations. The magnetic...

A wastewater treatment pond covered with water hyacinth (Eichhorniacrassipes) was first tested in Bahia in an attempt to treat sewage from an urban area in Salvador, Bahia, Brazil. This pond, which receives a high organic load with an average of 750 kg BOD/ha.day, after a short detention time of as little as 5 days, exhibited a removal rate efficiency of 90.7% of BOD and 96% of suspended solids. The problems related to the operation of this plant and its limitations, mainly regarding removal of nutrients, are discussed.

Introduction The use of insulin analogs for the treatment of type 1 diabetes mellitus (T1DM) is widespread; however, the therapeutic benefits still require further evaluation given their higher costs. The objective of this study was to evaluate the effectiveness and safety of analog insulin glargine compared to recombinant DNA (rDNA) insulin in patients with T1DM in observational studies, building on previous reviews of randomized controlled trials comparing neutral protamine Hagedorn insulin and insulin glargine. Methods A systematic review with a meta-analysis was performed. The review included cohort studies and registries available on PubMed, LILACS, and the Cochrane Central Register of Controlled Trials (CENTRAL), as well as manual and gray literature searches. The meta-analysis was conducted in Review Manager 5.3 software. The primary outcomes were glycated hemoglobin (Hb1Ac), weight gain, and hypoglycemia. Methodological quality was assessed using the Newcastle-Ottawa scale. Results Out of 796 publications, 11 studies were finally included. The meta-analysis favored insulin glargine in HbA1c outcomes (adult patients) and hypoglycemic episodes (P