Robust Kernel Density Function Estimation

The classical kernel density estimation technique is the commonly used method to estimate the density function. It is now evident that the accuracy of such density function estimation technique is easily affected by outliers. To remedy this problem, Kim and Scott (2008) proposed an Iteratively Re-weighted Least Squares (IRWLS) algorithm for Robust Kernel Density Estimation (RKDE). However, the weakness of IRWLS based estimator is that its computation time is very long. The shortcoming of such RKDE has inspired us to propose new non-iterative and unsupervised based approaches which are faster, more accurate and more flexible. The proposed estimators are based on our newly developed Robust Kernel Weight Function (RKWF) and Robust Density Weight Function (RDWF). The basic idea of RKWF based method is to first define a function which measures the outlying distance of observation. The resultant distances are manipulated to obtain the robust weights. The statement of Chandola et al. (2009) that the normal (clean) data appear in high probability area of stochastic model, while the outliers appear in low probability area of stochastic model, has motivated us to develop RDWF. Based on this notion, we employ the pilot (preliminary) estimate of density function as initial similarity (or distance) measure of observations with the neighbours. The modified similarity measures produce the robust weights to estimate density function robustly. Subsequently, the robust weights are incorporated in the kernel function to formulate the robust density function estimation. An extensive simulation study has been carried out to assess the performance of the RKWF-based estimator and RDWF-based estimator. The RKDE based on RKWF and RDWF perform as good as the classical Kernel Density Estimator (KDE) in outlier free data sets. Nonetheless, their performances are faster, more accurate and more reliable than the IRWLS approach for contaminated data sets. The classical kernel density function estimation approach is widely used in various formula and methods. Unfortunately, many researchers are not aware that the KDE is easily affected by outliers. We have proposed the RKDE which is more efficient and consumes less time. Our work on RKDE or corresponding robust weights has motivated us to develop alternative location and scale estimators. A modification is made to the classical location and scale estimator by incorporating the robust weight and RKDE. To evaluate the efficiency of the proposed method, comprehensive contaminated models are designed and simulated. The accuracy of the proposed new method was compared with the location and scale estimators based on M. Minimum Covariance Determinant (MCD) and Minimum Volume Ellipsoid (MVE) estimator. The simulation study demonstrates that, on the whole, the accuracy of the proposed method is better than the competitor methods. The research also develops two new approaches for outlier and potential outlier detection in unimodal and multimodal distributions. The distance of observations from the center of data set is incorporated in the formulation of the first outlier detection method in unimodal distribution. The second method attempts to define an approach that is useable not only for unimodal distribution but also for multimodal distribution. This approach incorporates robust weights, whereby, high weights and low weights are assigned to normal (clean) and outlying observations, respectively. In this thesis, we also illustrate that the sensitivity of RKDE depends on the setting of the tuning constants of the employed loss function. The results of the study indicate that the proposed methods are capable of labelling normal observation and potential outliers in a data set. Additionally, they are able to assign anomaly scores to normal and outlying observations. Finally this thesis also addresses the estimation of Mutual Information (MI) for mixture distribution which prone to create two distant groups in the data. The formulation of MI involves estimation of density function. Mutual information estimate for bivariate random variables involves the bivariate density estimation. The bivariate density estimation employs the estimate of covariance matrix. The sensitivity of covariance matrix to the presence of outliers has motivated us to substitute it with robust estimate derived from MCD and MVE. The efficiency of the modified mutual information estimate is evaluated based on its accuracy. To do this evaluation, the mixtures of bivariate normal distribution with different percentage of contribution are simulated. Simulation results show that the new formulation of MI increases the accuracy of mutual information estimation

Penta-Modal Imaging Platform with OCT- Guided Dynamic Focusing for Simultaneous Multimodal Imaging

Complex diseases, such as Alzheimer’s disease, are associated with sequences of changes in multiple disease-specific biomarkers. These biomarkers may show dynamic changes at specific stages of disease progression. Thus, testing/monitoring each biomarker may provide insight into specific disease-related processes, which can result in early diagnosis or even development of preventive measures. Obtaining a comprehensive information of biological tissues requires imaging of multiple optical contrasts, which is not typically offered by a single imaging modality. Thus, combining different contrast mechanisms to achieve simultaneous multimodal imaging is desirable. However, this process is highly challenging due to specific optical and hardware requirements for each optical imaging system. The objective of this dissertation is to develop a novel Penta-modal optical imaging system integrating photoacoustic microscopy (PAM), optical coherence tomography (OCT), optical Doppler tomography (ODT), OCT angiography (OCTA) and confocal fluorescence microscopy (CFM) in one platform providing comprehensive structural, functional, and molecular information of living biological tissues. The system can simultaneously image different biomarkers with a large field-of-view (FOV) and high-speed imaging. The large FOV and the high imaging speed is achieved by combining optical and mechanical scanning mechanisms. To compensate for an uneven surface of biological samples, which result in images with non-uniform resolution and low signal to noise ratio (SNR), we further develop a novel OCT-guided surface contour scanning methodology, a technique for adjusting objective lens focus to follow the contour of the sample surface, to provide a uniform spatial resolution and SNR across the region of interest (ROI). The imaging system was tested by imaging phantoms, ex vivo biological samples, and in vivo. The OCT-guided surface contour scanning methodology was utilized for imaging a leaf of purple queen plant, which resulted in a significant contrast improvement of 41% and 38% across a large imaging area for CFM and PAM, respectively. The nuclei and cells walls were also clearly observed in both images. In an in vivo imaging of the Swiss Webster mouse ear, our multimodal imaging system was able to provide images with uniform resolution in an FOV of 10 mm x 10 mm with an imaging time of around 5 minutes. In addition to measuring the blood flow in the mouse ear, the system also successfully imaged mouse ear blood vessels, sebaceous glands, as well as several tissue structures. We further conducted a comparative study of OCTA for rodent retinal imaging by evaluating the performance of three OCTA algorithms, namely the phase variance (PV), improved speckle contrast (ISC), and optical microangiography (OMAG). It was concluded that the OMAG algorithm provided statistically significant higher mean values of BVD and VPI compared to the ISC algorithm (0.27±0.07 vs. 0.24±0.05 for BVD; 0.09±0.04 and 0.08±0.04 for VPI), while no statistically significant difference was observed for VDI and VCI among the algorithms. Results showed that both the ISC and OMAG algorithms are more robust than PV, and they can reveal similar vasculature features. Lastly, we utilized the proposed imaging system to monitor, for the first time, the invasion process of malaria parasites in the mosquito midgut. The system shows a promising potential to detect parasite motion as well as structural changes inside the mosquito midgut. The multimodal imaging system outlined in this dissertation can be useful in a variety of applications thanks to the specific optical contrast offered by each employed modality, including retinal and brain imaging

Development and evaluation of the America On the Move program for university students

2013 Fall.Includes bibliographical references.To view the abstract, please see the full text of the document

A channel matrix rank reduction method using space – time coding in a MIMO system / Jahangir Dadkhah Chimeh

Massive MIMO has an important role in 5G and IoT, however provides hardware problems in the system. To reduce these challenges we introduce a method for channel matrix rank reduction which reduces the computations volume in a m×n MIMO system using space – time coding in this paper. We used this method to 4×2 system to change its rank to 2×2, however it may be used to any desirable higher order m×n Massive MIMO systems

PHISHERS ATTACK ON THE RESEARCHERS FOR FINANCIAL GOALS IN PHARMACEUTICAL AND MEDICAL OPEN ACCESS JOURNALS

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Comparing the effects of lidocaine cream and mefenamic acid on post episiotomy pain

Introduction: A large number of womensuffered from the post episiotomy pain and the common method for pain relief is oral non-steroidal anti-inflammatory drugs. With considering the adverse effects of these drugs, the aim of present study was to compare the effects of lidocaine cream and mefenamic acid capsule on post episiotomy pain. Methods: This clinical trial was carried out in 2011 on 60 women with singleton pregnancy at 38-42 weeks of gestation who underwent episiotomy. Cases were randomly divided into both groups and received lidocaine cream and mefenamic acid capsule. Data were collected by questionnaire and Visual Analogue Scale. Pain intensity was compared with the first complaint of mother and 6, 12 and 24 hours after the delivery in both groups. Data were analyzed by SPSS software (version 16), t-test and paired t-test. P value less than 0.05 was considered significant. Results: With the first complaint of women, the mean of pain intensity was 4.92±1.9 in lidocaine group and 4.90±1.5 in mefenamic acid group that was not significant (p=0.20). Mean intensity of post episiotomy pain in two groups receiving lidocaine cream and mefenamic acid capsule were not significant at hours 6 (3.26±1.3 vs. 3.10±1.6, p=0.05), 12 (2.26±1.7 vs. 2.86±1.4, p=0.36) and 24 (1.46±1.2 vs. 1.49±1.2, p=1) after delivery. Conclusion: The effects of lidocaine cream and mefenamic acid capsule in relief of post episiotomy pain were similar. With considering the side effects of mefenamic acid, lidocaine cream is an appropriate alternative drug in relief of post episiotomy pain

A foucauldian study of space and power in two novels by Nadine Gordimer

This paper aims to study the relation between space and power in Nadine Gordimer’s first novel of the apartheid regime, The Lying Days (1953) and her first novel of the postapartheid era, None to Accompany Me (1994) in the light of Michel Foucault’s theory of space and power. The paper first introduces Gordimer and the concept of apartheid. Then, it states the common engagement of Foucault and Gordimer with the concepts of space and power in their work, the significance of the study and the limitations of the research. After offering the literature review, the researchers discuss Foucault’s theories and his key concept of heterotopias (other spaces) and the relation between his ideas and apartheid. After that, drawing on the theoretical insights of Foucault, the researchers explore how Gordimer’s selected novels display an ongoing and developing understanding of the importance of space as a way of explaining key questions of power, resistance and social organization and reflect on the geopolitics of apartheid and its policies of spatial control in South Africa. The researchers also explore how heterotopias as sites of social struggle and resistance challenge apartheid. The researchers examine space as a technique of control and domination, as well as a means of resistance