Direct Estimation Method Research Articles

Non-invasive estimation of central systolic pressure: a comparison between radial artery tonometry and a new direct central blood pressure estimation method (DCBP)

Non-invasive estimation of central systolic pressure: a comparison between radial artery tonometry and a new direct central blood pressure estimation method (DCBP)

Direct estimation of hydraulic parameters relating to steady state groundwater flow

Groundwater as an important, life-sustaining resource for humankind is being threatened by massive over-extraction and wide-spread contamination. Wise development and protection of this crucial resource requires a thorough understanding of groundwater flow in the subsurface. This paper presents a novel direct method to estimate important hydraulic parameters characterizing steady state groundwater flows for confined and unconfined isotropic aquifers. The method is appropriate for application in aquifers where horizontal flow dominates. The governing equations for the direct estimation method are superposed extensions of the well-known Thiem equation governing steady-state radial flow toward a pumping well under confined and unconfined conditions. This new approach has the following advantages over conventional methods: (1) simultaneously provides estimates of both hydraulic conductivity and hydraulic gradient, (2) can be applied using historical data without the need to conduct a pumping test, and (3) is a simple analytical method that can be applied easily. Verification of the direct estimation method is achieved by applying it to hypothetical homogeneous and heterogeneous aquifers simulated by three-dimensional finite element models. The usefulness of the method is also demonstrated with data from an actual field site.

Estimating Steatosis Prevalence in Overweight and Obese Children: Comparison of Bayesian Small Area and Direct Methods

Background Often, there is no access to sufficient sample size to estimate the prevalence using the method of direct estimator in all areas. The aim of this study was to compare small area’s Bayesian method and direct method in estimating the prevalence of steatosis in obese and overweight children. Materials and Methods: In this cross-sectional study, was conducted on 150 overweight and obese children aged 2 to 15 years referred to the Children's digestive clinic of Urmia University of Medical Sciences- Iran, in 2013. After Body mass index (BMI) calculation, children with overweight and obese were assessed in terms of primary tests of obesity screening. Then children with steatosis confirmed by abdominal Ultrasonography, were referred to the laboratory for doing further tests. Steatosis prevalence was estimated by direct and Bayesian method and their efficiency were evaluated using mean-square error Jackknife method. The study data was analyzed using the open BUGS3.1.2 and R2.15.2 software. Results: The findings indicated that estimation of steatosis prevalence in children using Bayesian and direct methods were between 0.3098 to 0.493, and 0.355 to 0.560 respectively, in Health Districts; 0.3098 to 0.502, and 0.355 to 0.550 in Education Districts; 0.321 to 0.582, and 0.357 to 0.615 in age groups; 0.313 to 0.429, and 0.383 to 0.536 in sex groups. In general, according to the results, mean-square error of Bayesian estimation was smaller than direct estimation (P<0.05). Conclusion The study suggests that estimation of prevalence using Bayesian estimation method via the logistic mixed model was more efficient and better than direct estimation method.

Computationally efficient direction finding using polynomial rooting with reduced-order and real-valued computations

The root multiple signal classification (root-MUSIC) algorithm is one of the most important techniques for direction of arrival (DOA) estimation. Using a uniform linear array (ULA) composed of M sensors, this method usually estimates L signal DOAs by finding roots that lie closest to the unit circle of a (2M−1)-order polynomial, where L < M. A novel efficient root-MUSIC-based method for direction estimation is presented, in which the order of polynomial is efficiently reduced to 2L. Compared with the unitary root-MUSIC (U-root-MUSIC) approach which involves real-valued computations only in the subspace decomposition stage, both tasks of subspace decomposition and polynomial rooting are implemented with real-valued computations in the new technique, which hence shows a significant efficiency advantage over most state-of-the-art techniques. Numerical simulations are conducted to verify the correctness and efficiency of the new estimator.

Application of the direct method for cohesive law estimation applied to the strength prediction of double-lap joints

Currently, significant efforts are being made in the design of aircraft and aeronautical applications to reduce weight and improve reliability. Thus, adhesive bonding techniques have been largely employed, which also enables the combined use of steel with lighter materials such as aluminium or high strength composites. Cohesive Zone Models (CZM) are a powerful tool for the design of bonded structures, but they require careful estimation of the cohesive laws for reliable results. This work experimentally evaluates by the J-integral/direct method the tensile and shear CZM laws of three adhesives with distinct ductility. The Double-Cantilever Beam (DCB) and End-Notched Flexure (ENF) specimens were considered to obtain the tensile and shear CZM laws of the adhesives, respectively. After obtaining the tensile and shear CZM laws, triangular, exponential and trapezoidal CZM laws were built to reproduce their behaviour. Validation of these CZM laws was undertaken with a mixed-mode geometry (double-lap joint) considering the same three adhesives and varying overlap lengths (LO). The strength prediction by this technique revealed accurate predictions for a given CZM law shape, depending on the adhesive ductility, although all CZM law shapes were moderately accurate.

Direct method for rotation estimation from spherical images using 3D mesh surfaces with SPHARM representation

Since a large field of view obviously bears important advantages, the use of spherical images is becoming increasingly important in various computer vision and image processing applications. This paper presents a novel rotation estimation approach for spherical images based on 3D mesh representation of gray level intensity. Once the 3D meshes of the underlying spherical images are obtained, the 3D rotation can be estimated directly and efficiently, without feature extraction and matching process. Subsequently, we propose a direct method for 3D object rotation estimation using spherical harmonics representation with SVD decomposition and ICP algorithm for estimation refinement. Experimental results validate our approach and prove its suitability and robustness for rotation estimation. Moreover, it performs well against noisy images, brightness changes, image compression and occlusions. A comparative study of our proposed approach with four similar methods for 3D rotation estimation between spherical images, is realized to prove its effectiveness.

Efficient estimation of quasi-likelihood models using B-splines

We consider a simple yet flexible spline estimation method for quasi-likelihood models. We approximate the unknown function by B-splines and apply the Fisher scoring algorithm to compute the estimates. The spline estimate of the nonparametric component achieves the optimal rate of convergence under the smooth condition, and the estimate of the parametric part is shown to be asymptotically normal even if the variance function is misspecified. The semiparametric efficiency of the model can be established if the variance function is correctly specified. A direct and consistent variance estimation method based on the least-squares estimation is proposed. A simulation study is performed to evaluate the numerical performance of the spline estimate. The methodology is illustrated on a crab study.

Porosity estimation from pre-stack seismic data in gas-hydrate bearing sediments, Krishna-Godavari basin, India

There exist several empirical and statistical methods for estimating porosity from post-stack seismic data. Here we implement and demonstrate a method for direct estimation of porosity from pre-stack seismic data. Rather than solving for acoustic impedance and then mapping those to porosity, we estimate porosity reflectivity. We demonstrate our approach with an application to 2D seismic dataset from Krishna-Godavari basin, which is inverted directly for porosity by simultaneous inversion of angle-stacks. The total porosity estimated from the density log for the depth interval of 1059–1224 m ranges from 49 to 85%. This relationship is used as an input for porosity inversion from the 2D pre-stack seismic data of gas hydrate bearing sediments. Our result images two distinct gas hydrate saturate zones in the porosity image; they are in close agreement with interpretations based on characterization of fractured filled gas hydrate saturation. The porosity along our 2D multichannel seismic section within the time interval of 1450–1615 ms ranges from 50 to 75% within the gas hydrate bearing sediments and unconsolidated sediments below the bottom simulating reflector. The water-bearing silty/clay sediments are characterized by porosity values of about 60–70%. The results demonstrate that the proposed approach is a fast and reliable method for estimating porosity directly from seismic data.

A DIRECT ESTIMATION METHOD FOR THE RUSSELL FLUID FACTOR BASED ON STOCHASTIC SEISMIC INVERSION

AbstractIn this paper we propose Russell fluid factor direct estimation method based on stochastic seismic inversion. It is a Monte Carlo based strategy for non‐linear inversion, which can effectively integrate the high‐frequency information of well‐logging data and have a higher resolution. And the method is formulated in a Bayesian framework. Firstly, we can calculate the Russell fluid factor using well‐logging data and get the a priori information of fluid factor through sequential Gaussian simulation (SGS). Then we construct the likelihood function. Finally, we apply Metropolis algorithm in order to obtain an exhaustive description of the posteriori probability density. In this paper, we use the sequential Gaussian simulation (SGS) in a new implementation way, which can improve the computation speed. According to the numerical calculations, we can conclude that the final results match the model and real well‐logging data well and have a higher resolution. In addition, Russell fluid factor we inverted is a sensitive indicator for reservoir fluid identification.

PMSM Sensorless Control by Injecting HF Pulsating Carrier Signal Into Estimated Fixed-Frequency Rotating Reference Frame

For permanent-magnet synchronous machines (PMSMs) sensorless control, the widely employed high-frequency (HF) pulsating carrier signal injection method is based on tracking the rotor saliency. It may face the problems of long convergence time, potential start-up failure, and limited system stability. Different from the conventional schemes, the proposed strategy is a direct estimation method. In which, a HF pulsating carrier voltage is injected into the estimated fixed-frequency rotating reference frame other than the estimated synchronous reference frame (SRF). With this approach, spatial saliency tracking observer, which is necessary in the conventional sensorless control, is removed to simplify the control structure and improve the system stability. Furthermore, the rotor position information is directly obtained from the response of injected HF pulsating carrier signal, which can avoid potential convergence failure of tracking observer. In addition, the compensation of system delays existing in the proposed sensorless control strategy is deduced to improve the accuracy of rotor position estimation. For magnetic polarity detection, a new method which has the advantages of high signal-to-noise ratio and low vibration is also investigated. Finally, the experimental results on a PMSM indicate that the rotor position with good steady state and dynamic performance can be obtained accurately with the proposed sensorless control strategy.

A direct method for property estimation from analysis of infinite acting production in shale/tight gas reservoirs

Abstract Infinite acting linear flow is a dominant flow regime in many multi-fractured horizontal wells completed in shale/tight gas reservoirs. A well-accepted methodology for analysis of this flow regime in systems without aquifer influence is the square-root of time plot. For reservoirs producing single phase oil, fracture half-length can be estimated from the slope of this plot, provided reservoir permeability is known. However, for gas reservoirs, pseudovariables are required to account for the pressure-dependence of gas properties. For example, the pseudotime function must be used to account for the strong dependence of gas viscosity and compressibility on pressure. As has been previously noted, for tight reservoirs, the pseudotime function must be evaluated at average pressure in the region of influence, which in turn is calculated from the material balance equation. Therefore, the linear flow equation should be coupled with the material balance equation so that fracture half-length can be estimated. This solution methodology is implicit and may require iterative procedures. This paper introduces an explicit solution methodology for estimating fracture half-length. As in the case of implicit solution methodology, the assumptions of no aquifer influence and infinite acting flow are considered. Because of no aquifer support, we can use material balance equation of volumetric reservoirs. We propose an appropriate correlation between viscosity–compressibility product and the material balance equation. This correlation helps to simplify pseudotime calculations and remove the implicit and iterative nature of the previous solution methodology. Accordingly, we have developed simple semi-analytic solutions that provide a methodology for direct estimation of fracture half-length. The solutions were developed for constant rate, constant pressure, and variable pressure/rate production from wells. We used numerical simulation to generate many synthetic production examples with wide ranges in reservoir properties to validate the introduced equations. We further used our approach for analysis of field cases (multi-fractured horizontal wells completed in shale reservoirs) to demonstrate its practical applicability to real data.

A review of sex estimation techniques during examination of skeletal remains in forensic anthropology casework

Sex estimation is considered as one of the essential parameters in forensic anthropology casework, and requires foremost consideration in the examination of skeletal remains. Forensic anthropologists frequently employ morphologic and metric methods for sex estimation of human remains. These methods are still very imperative in identification process in spite of the advent and accomplishment of molecular techniques. A constant boost in the use of imaging techniques in forensic anthropology research has facilitated to derive as well as revise the available population data. These methods however, are less reliable owing to high variance and indistinct landmark details. The present review discusses the reliability and reproducibility of various analytical approaches; morphological, metric, molecular and radiographic methods in sex estimation of skeletal remains. Numerous studies have shown a higher reliability and reproducibility of measurements taken directly on the bones and hence, such direct methods of sex estimation are considered to be more reliable than the other methods. Geometric morphometric (GM) method and Diagnose Sexuelle Probabiliste (DSP) method are emerging as valid methods and widely used techniques in forensic anthropology in terms of accuracy and reliability. Besides, the newer 3D methods are shown to exhibit specific sexual dimorphism patterns not readily revealed by traditional methods. Development of newer and better methodologies for sex estimation as well as re-evaluation of the existing ones will continue in the endeavour of forensic researchers for more accurate results.

Living mulch for weed management in organic vegetable cropping systems under Mediterranean and North European conditions

AbstractThe aim of this study was to investigate the effect of growing in-season agro-ecological service crops as living mulch (LM) with vegetable crops, exploiting their potential to suppress weeds by filling the ecological niches otherwise occupied by weeds. Two field experiments were carried out in Denmark and Italy to compare different LM introduction strategies in organic vegetable cropping systems. In Denmark, leek (Allium porrumL.) was grown with dyers woad (Isatis tinctoriaL.) LM strips, while cauliflower (Brassica oleraceaL. var.botrytis) was intercropped with a broad sowed burr medic (Medicago polimorphaL., var. anglona) in Italy. Two LM times of sowing relative to cash crop transplanting––an early sowing (es LM) and a late sowing (ls LM)––were compared with a control with no LM (no LM). The effects of LM treatment on crop competitiveness, LM smother effect and weed populations were evaluated by direct measurement, visual estimation and competitive index methods. Comparison among hybrid and open pollinated cultivar responses to LM introduction was also performed. Results showed a significant higher cash crop biomass in ls LM than in es LM, with comparable yield to the weeded controls, except for es LM in Italy. Moreover, in the Danish experiment, the LM and weed biomasses were up to 5 times lower in the es LM and ls LM treatments than the weed biomass alone in no LM treatment. Reduction in weed biomass and abundance was observed also in ls LM in the Italian trial. Similarly, the competitive balance (Cb), which quantifies the ability of the cash crop to compete with neighbours, was higher in the es LM (+0.29) and ls LM (+0.72) compared with unweeded no LM control (−0.86) in Denmark. In the Italian experiment, the cauliflower showed more competitive ability against neighbours in ls LM (+0.53) and was a weak competitor in es LM (−1.51). The cash crop had higher competitive ability against LM (Cbc-lm) when sowing was more delayed in both experiments, while, in the Italian trial, the LM was more competitive against weeds (Cblm-w) in ls LM (+1.54) than in es LM (−0.41). The slight differences observed for biomass and competitive ability between the tested cultivars, highlighted similar suitability of both hybrid and open-pollinated cultivars to grow with LM. Our findings suggest the viability of the introduced LM in managing weeds and avoiding a smother effect on the crop, with particular effectiveness with delayed LM sowing.

Investigating practical alternatives to the NRCS-CN method for direct runoff estimation using slope-adjusted curve numbers

The Natural Resources Conservation Service (NRCS) Curve Number (CN) method is generally applied to estimate direct runoff from watersheds. However, its utility in estimating direct runoff in South Korean watersheds is limited due to steep slopes, shallow soil layers, less infiltration losses and sudden peak flow generation. The CN is the primary parameter used in the method and varies with watershed characteristics and measured rainfall runoff data. In this study, we evaluated the performance of NRCS-CN models employing weighted average CNs and watershed slope-adjusted CNs. Furthermore, various combinations of alternatives were investigated to determine the proper watershed average CN. Direct runoff was estimated using different CN approaches and these estimates were compared to the observed values. The results obtained in this study indicated that the slope-adjusted CNs were higher than the NRCS tabulated CNs. Similarly, the Weighted Runoff (WQ) method provided higher runoff estimates than the weighted CN (WCN) method. In conclusion, the runoff estimated using the combination of the WQ method and slope-adjusted CNs showed better agreement with the observed direct runoff compared to other methods.

Direction Estimation for Pedestrian Monitoring System in Smart Cities: An HMM Based Approach

The paper proposes a novel approach for direction estimation of a moving pedestrian as perceived in a 2-D coordinate of field camera. The proposed direction estimation method is intended for pedestrian monitoring in traffic control systems. Apart from traffic control, direction of motion estimation is also very important in accident avoidance system for smart cars, assisted living systems, in occlusion prediction for seamless tracking in visual surveillance, and so on. The proposed video-based direction estimation method exploits the notion of perspective distortion as perceived in monocular vision of 2-D camera co-ordinate. The temporal pattern of change in dimension of pedestrian in a frame sequence is unique for each direction; hence, the dimensional change-based feature is used to estimate the direction of motion; eight discrete directions of motion are considered and the hidden Markov model is used for classification. The experiments are conducted over CASIA Dataset A , CASIA Dataset B , and over a self-acquired dataset: NITR Conscious Walk Dataset . The balanced accuracy of direction estimation for these experiments yields satisfactory results with accuracy indices as 94.58%, 90.87%, and 95.83%, respectively. The experiment also justifies with suitable test conditions about the characteristic features, such as robustness toward improper segmentation, partial occlusion, and changing orientation of head or body during walk of a pedestrian. The proposed method can be used as a standalone system or can be integrated with existing frame-based direction estimation methods for implementing a pedestrian monitoring system.

Constant force grinding control method for unknown curve part based on force/torque information

A method of constant grinding force following unknown curve part based on force/torque information is presented in this paper. A new estimation method of the unknown curve normal direction is proposed based on force and torque information. According to the method, the force control and position control directions of the hybrid force/position control can be estimated. The conventional proportion integration (PI) force control method is tested at first. Since the force PI control parameters are difficult to determine, fuzzy PI control is introduced to optimise the force PI control parameters automatically. According to the experiment result, the method can greatly reduce the contact force fluctuation during grinding wheel contact with part contour, and the contact force during estimating curve surface is in the desired range of ± 2 N. And during grinding procedure, the acting force fluctuation is in the desired range of ± 7 N. [Received 20 April 2015; Revised 17 February 2016; Accepted 23 February 2016]

ひずみゲージとIMUのセンサフュージョンによる筆跡推定

We aim to realize a novel pen based interface system that provides various digital operations for both low-tech and high-tech people. In this paper, we propose a novel sensor fusion method between IMUs (Inertial Measurement Unit) and strain gauges embedded on a pen device. By using strain gauges for obtaining correct direction of pen tip movement during writing, cumulative errors caused by the intrinsic noise/drift of IMU can be corrected. Therefore our proposed sensor fusion method can reconstruct longer handwritten trajectories such as multiple characters including multiple strokes that have not been achieved by conventional methods. This paper provides a pen tip direction estimation method using strain gauges attached on ink cylinder, trajectory reconstruction method using IMUs, and the sensor fusion method of both estimation streams. The algorithms are evaluated by writing experiments conducted by robotic manipulator and human hand.

Study of Vocal Tract Shape Estimation Techniques for Children

Accurate depiction of the vocal tract shape is essential for development of speech training aids for hearing impaired. Speech therapists have concluded from their research that if speech disorders are detected at an early stage then the rectification of those becomes faster and to a great accuracy. In case of adults, the vocal tract shape estimation can be performed by using techniques like X-Ray, MRI or using articulatory analysis by synthesis. Due to certain difficulties present in the methods mentioned like radiation effect and loud sound impulses produced by rapid switching of magnetic field are not considered suitable for children. Thus there is lack of availability of vocal tract shape data for children due to inability to use direct estimation methods for children. So it becomes necessary to carry out comparative study of vocal tract shape estimation techniques of children using indirect vocal tract shape estimation techniques. This paper aims to make available a considerable amount of data to researchers for study towards children's vocal tract shape using implemented techniques.The final objective of research work is to perform a detailed study on techniques available for vocal tract shape estimation, to implement and further compare the covariance and lattice methods for children using MATLAB software. Currently, the vocal tract shape estimation based on autocorrelation method is implemented and the results obtained are presented.

LG-Mod: A Modified Local Gradient (LG) Method to Retrieve SAR Sea Surface Wind Directions in Marine Coastal Areas

This paper describes a novel SAR wind direction estimation method based on the computation of local gradients over quasi-linear and quasi-periodic structures detected by SAR imagery. The method relies upon the standard LG method for the part relevant to the computation of the local gradients. The novelty is that the dominant local wind direction and related accuracy are estimated using results derived from the Directional Statistics. The LG-Mod is validated against in situ coastal wind measurements provided by instrumented buoys with 63 ENVISAT ASAR images. Results show an overall agreement with RMSE values obtained for off-shore areas, but residual effects due to the complex phenomena occurring in the proximity of shoreline may degrade the performance when running in automated mode.

Multi-oriented windowed harmonic phase reconstruction for robust cardiac strain imaging.

The purpose of this paper is to develop a method for direct estimation of the cardiac strain tensor by extending the harmonic phase reconstruction on tagged magnetic resonance images to obtain more precise and robust measurements. The extension relies on the reconstruction of the local phase of the image by means of the windowed Fourier transform and the acquisition of an overdetermined set of stripe orientations in order to avoid the phase interferences from structures outside the myocardium and the instabilities arising from the application of a gradient operator. Results have shown that increasing the number of acquired orientations provides a significant improvement in the reproducibility of the strain measurements and that the acquisition of an extended set of orientations also improves the reproducibility when compared with acquiring repeated samples from a smaller set of orientations. Additionally, biases in local phase estimation when using the original harmonic phase formulation are greatly diminished by the one here proposed. The ideas here presented allow the design of new methods for motion sensitive magnetic resonance imaging, which could simultaneously improve the resolution, robustness and accuracy of motion estimates.