A generalized scheme to enhance the sensitivity in the measurement of phase difference in an optical interference by measuring the phase of the resultant field is presented. In the proposed scheme, the weak measurement in scalar optical interferometry is achieved by directly accessing the phase of the output state, rather than looking at the centroid shift in the intensity. The spatial confinement or beam-like characteristics for the optical field, an essential criterion for centroid calculation, is not a requirement for the scheme. The ability to uniquely sense and distinguish contributions to the phase difference from individual optical fields; an aspect with potential to improve the measurement accuracy in optical gyroscopes and gravitational wave sensing, is also presented.
A method to generate phase singularities in spectral domain is explained with proper simulation results. This is achieved by the interference of polychromatic fields having Gaussian spectral distribution with slightly different mean wavelengths.
Proper evaluation and detection of uterine contraction is an important treat during gestation period. Uterine contraction happens by the generation of electrical activity from a given myometrial cell to the adjacent cell. There are various methods for monitoring uterine contraction but they lack to distinguish true labour contractions (efficient) from contractions that will not cause delivery (inefficient). One of the most accurate non-invasive technique for monitoring uterine contraction is the uterine electromyogram or Electrohysterogram (EHG). The main aim of this paper is to check whether it is possible to discriminate labour and pregnancy contraction by using 16 electrode database. And also to check bipolar signals give better classification rate than monopolar signals. Result shows that bipolar signal have better performance than monopolar signals.
In the past few decades, extensive research and efforts have been made for developing a phase retrieval iterative algorithm (PRA) for reconstructing a complex object from far-field intensity equivalently from the object autocorrelation. Since most of the existing PRA techniques employ a random initial guess, the reconstruction output sometimes changes in different trials leading to a non-deterministic output. Additionally, the output of such algorithm occasionally either shows non-convergence, needs a longer time to converge, or shows the twin-image problem. Due to these problems, PRA methods are unsuitable for cases where consecutive reconstructed outputs need to be compared. In this Letter, a novel, to the best of our knowledge, method is developed and discussed using edge point referencing (EPR). In the EPR scheme, in addition to illuminating a region of interest (ROI) of the complex object, a small area near the periphery of the complex object within the ROI is illuminated with an additional beam. Such illumination creates an imbalance in the autocorrelation that can be used to improve the initial guess for achieving unique deterministic output free from the aforementioned problems. Furthermore, by introducing the EPR, one can also achieve faster convergence. To support our theory, derivation, simulations, and experiment are performed and presented.
Pregnancy monitoring is the most important challenge during gestation period. Some early deliveries cause mortality and morbidity of the new born babies. Electrohysterogram is the most promising method for monitoring the uterine contraction thus the physiological wellbeing of the foetal and the mother. As it is a non-invasive method there are no side effects and its accuracy for early diagnosis is more. There are different numbers of electrodes used to collect the signals from the mother's abdomen by placing electrodes on the abdomen. Through this paper we are focusing on different researches used for pregnancy monitoring using 16 electrode database. Based on the studies this paper provides different steps in electrohysterogram data processing such as preprocessing, feature extraction, classifiers for classifying pregnancy and labour contraction.
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