An Improved Equivalent Squint Range Model and Imaging Approach for Sliding Spotlight SAR Based on Highly Elliptical Orbit

As an emerging orbital system with flexibility and brand application prospects, the highly elliptical orbit synthetic aperture radar (HEO SAR) can achieve both a low orbit detailed survey and continuous earth surface observation in high orbit, which could be applied to marine reconnaissance and surveillance. However, due to its large eccentricity, two challenges have been faced in the signal processing of HEO SAR at present. The first challenge is that the traditional equivalent squint range model (ESRM) fails to accurately describe the entire range for the whole orbit period including the perigee, the apogee, and the squint subduction section. The second one is to exploit an efficient HEO SAR imaging algorithm in the squinted case which solves the problem that traditional imaging algorithm fails to achieve the focused imaging processing of HEO SAR during the entire orbit period. In this paper, a novel imaging algorithm for HEO SAR is presented. Firstly, the signal model based on the geometric configuration of the large elliptical orbit is established and the Doppler parameter characteristics of SAR are analyzed. Secondly, due to the particularity of Doppler parameters variation in the whole period of HEO, the equivalent velocity and equivalent squint angle used in MESRM can no longer be applied, a refined fourth-order equivalent squint range model(R4-ESRM) that is suitable for HEO SAR is developed by introducing fourth-order Doppler parameter into Modified ESRM (MESRM), which accurately reconstructs the range history of HEO SAR. Finally, a novel imaging algorithm combining azimuth resampling and time-frequency domain hybrid correlation based on R4-ESRM is derived. Simulation is performed to demonstrate the feasibility and validity of the presented algorithm and range model, showing that it achieves the precise phase compensation and well focusing.

STUDY OF DOPPLER VELOCITY WAVEFORM IN PREGNANCY INDUCED HYPERTENSION PATIENTS AND ITS CORRELATION WITH PERINATAL OUTCOME

Background: Pregnancy induced hypertension( PIH) poses a great risk to the maternal and child health issues. Early diagnosis, assessment of prognosis, and appropriate management at a judicious moment can change its fate in many ways. Objective: To assess the usefulness of Doppler parameters to evaluate PIH and to predict its adverse perinatal outcome. Methodology: 49 pregnant patients were taken after applying criteria and undergone ultrasonography and doppler with follow up subsequently. Results: We found that total 63.26% of patients having abnormal Doppler parameters.Of these all of them had abnormal UA S/D ratio,26.53% had abnormal CPR,46.93% had abnormal UA PI and 48.97% had abnormal UA RI . So in our study most common abnormal Doppler parameter was alteration in UA S/D ratio. Conclusion: Doppler indices from the foetal circulation can reliably predict adverse perinatal outcome in an obstetric patient population with a high prevalence of complications such as pregnancy induced hypertension

The prognostic model for identification of the universe rotation axis upon applying the system of coordinates of a chosen galaxy

This paper describes the theoretical and practical preconditions for identification of the Universe rotation axis using the digital images from ten galaxies and the relative velocities of their movement upon applying a simulation of the parameter <mml:math display="inline"> <mml:mi>z</mml:mi> </mml:math> from the Doppler effect formula and a system of polar coordinates. The value of the Doppler parameter <mml:math display="inline"> <mml:mi>z</mml:mi> </mml:math> shows an approximate relative velocity of the reciprocal movement of two digital images (objects) in respect of the speed of light in vacuum c. The values of the Doppler parameter <mml:math display="inline"> <mml:mi>z</mml:mi> </mml:math> were calculated upon using vectors transformed by pixel intensities of digital images of galaxies cluster and the white solar spectrum. The average values of the Doppler parameter <mml:math display="inline"> <mml:mi>z</mml:mi> </mml:math> were calculated according to the created formula upon applying the expressions of cross-covariance functions of the algebraic sum of the relevant transformed vectors and a single vector. The values of the parameter <mml:math display="inline"> <mml:mi>z</mml:mi> </mml:math> from the Doppler formula enabled calculating the relative velocity of movement of digital images of the galaxies cluster in respect of each other and the relative velocity of movement of the images in respect of the Solar system. The relative velocity of galaxy movement calculated in such a way is a component of the real relative galaxy movement velocity (the velocity of tangential motion in respect of the rotation curve). In addition, the values of the scalar argument <mml:math display="inline"> <mml:mi>β</mml:mi> </mml:math> (the values of the angles between vectors of respective directions of vectors—directions of vectors of galaxies movement in respect of the Solar system and direction of the real galaxies movement vectors) are calculated. In the systems of polar and rectangular coordinates of each galaxy, the values of radii R of galaxies rotation curves (at points of the tangent) and coordinates of their centers were established upon applying the relevant formulas of differential geometry. The calculation data were collected using the software upon applying matlab program package operators.

The predictive value of fetal middle cerebral artery/descending aorta ratio doppler parameter in the evaluation of perinatal results of intrauterine growth restriction

Introduction. Although there are various reasons for intrauterine growth restriction (IUGR), the main cause is inadequate utero- placental and feto-placental circulation. Aim. To determine the predictive values of fetal middle cerebral artery/descending aorta (MCA/DA) Doppler parameter in the evaluation of perinatal outcomes in pregnancies with IUGR. Material and methods. 15 with IUGR and 35 normal newborn, who were born at the 34th gestational week or over included into the study. Doppler ultrasonography (US) measurements were performed. The ratio of pulsatility index/resistive index (PI/ RI) from MCA, umbilical artery (Umb), DA was determined. Neonatal characteristics such as Apgar scores, neonatal intensive care unit (NICU) requirement, weight and sex were also recorded. Results. In the IUGR group, mean MCA/DA RI-PI, MCA/UmB RI-PI were 0.88±0.19, 0.86±0.28, 1.22±0.18 and 1.55±0.39, respectively. In the control group, mean MCA/DA RI-PI, MCA/UmB RI-PI were 1.15±0.13, 1.09±0.41, 1.37±0.35 and 1.82±0.44, respectively. There were statistically significant relationship between MCA/DA PI with cord blood pH value and NICU requirement, age with gravida, parity, MCA/UmB RI, MCA/UmB PI; gravida with age and parity; parity with age, gravida, weight, MCA/DA RI, PI ratios. Conclusion. Intrauterine MCA and DA Doppler US parameters of IUGR can be used safely in predicting perinatal outcomes in pregnancies with IUGR over 34 weeks.

Cloud-by-cloud, multiphase, Bayesian modelling: application to four weak, low-ionization absorbers

ABSTRACT We present a new method aimed at improving the efficiency of component by component ionization modelling of intervening quasar absorption-line systems. We carry out cloud-by-cloud, multiphase modelling making use of cloudy and Bayesian methods to extract physical properties from an ensemble of absorption profiles. Here, as a demonstration of method, we focus on four weak, low-ionization absorbers at low redshift, because they are multiphase but relatively simple to constrain. We place errors on the inferred metallicities and ionization parameters for individual clouds, and show that the values differ from component to component across the absorption profile. Our method requires user input on the number of phases and relies on an optimized transition for each phase, one observed with high resolution and signal-to-noise ratio. The measured Doppler parameter of the optimized transition provides a constraint on the Doppler parameter of H i, thus providing leverage in metallicity measurements even when hydrogen lines are saturated. We present several tests of our methodology, demonstrating that we can recover the input parameters from simulated profiles. We also consider how our model results are affected by which radiative transitions are covered by observations (for example, how many H i transitions) and by uncertainties in the b parameters of optimized transitions. We discuss the successes and limitations of the method, and consider its potential for large statistical studies. This improved methodology will help to establish direct connections between the diverse properties derived from characterizing the absorbers and the multiple physical processes at play in the circumgalactic medium.

Predictive value of uterine artery: peak systolic velocity on the day of trigger for clinical pregnancy rate in infertile women

Background: The purpose of the study is to evaluate the role of uterine artery blood flow parameter measured by uterine artery two-dimensional (2D) power coloured doppler (PCD) ultrasound in predicting fertility outcomes in women undergoing ART treatment.Methods: It is prospective observational study. Total of 60 patients were included of receiving infertility treatment in the age group20-40 years. 20 patients were selected for timed intercourse , 20 patients were selected for intrauterine insemination , 20 patients were selected for invitro fertilization. Transvaginalsonography will be done on the day of trigger by BHCG , UA PSV were measured, and endometrial blood flow will be assessed. Predictivity of pregnancy rate will be looked after by 3 ways: BHCG values , UPT, Gestational sac on USG.Results: In TI/IUI/IVF cycles the Doppler parameter PSV of uterine artery (23.08+/-3.39 vs 20.37-/+5.43) in pregnant vs non-pregnant group did not differ significantly. The mean PSV of UA shows no significant difference women who were became pregnant during treatment and the women who were not became pregnant.Conclusions: With help of Doppler parameter imaging of women undergoing infertility it was found that UA PSV is non-significant to decide the prediction of pregnancy outcome.

Extended Multiple Aperture Mapdrift-Based Doppler Parameter Estimation and Compensation for Very-High-Squint Airborne SAR Imaging

Doppler parameter estimation and compensation (DPEC) is an important technique for airborne SAR imaging due to the unpredictable disturbance of real aircraft trajectory. Traditional DPEC methods can be only applied for broadside, small- or medium-squint geometries, as they at most consider the spatial variance of the second-order Doppler phase. To implement the DPEC in very-high-squint geometries, we propose an extended multiple aperture mapdrift (EMAM) method in this paper for better accuracy. This advantage is achieved by further estimating and compensating the spatial variation of the third-order Doppler phase, i.e., the derivative of the Doppler rate. The main procedures of the EMAM, including the steps of sub-view image generation, sliding-window-based cross-correlation, and image-offset-based Doppler parameter estimation, are derived in detail, followed by the analyses for the EMAM performance. The presented approach is evaluated by both computer simulations and real airborne data.