Naren Naik | Indian Institute of Technology, Kanpur (original) (raw)

Papers by Naren Naik

Journal of the Indian Institute of Science, Feb 4, 2013

In this study, a perturbation senes solution to the scalar wave equation has been presented, solv... more In this study, a perturbation senes solution to the scalar wave equation has been presented, solving for the total fields propagating through an arbitrary refractive index dlstribution. Results are presented for the case of straight step-index Integrated optics waveguides for modal excitation. Equivalence of the presented solutions to those derived from the Green's function formalism of solving the scalar wave equation for some special cases has been shown.

Journal of the Indian Institute of Science, 2013

2014 Twentieth National Conference on Communications (NCC), 2014

We describe a dual-antenna design for use in radiolocation of remote controlled improvised explos... more We describe a dual-antenna design for use in radiolocation of remote controlled improvised explosive device (IED) triggers in the 136-174 MHz frequency band. Each antenna array consists of 8 dipole-fed corner reflector antennas mounted in a circular array, radiating mainly in azimuth and elevation planes respectively. Received signal from the two arrays are downconverted to baseband using an RF front end and passed onto an FPGA for further processing. The FPGA implements an amplitude comparison algorithm to estimate the direction of arrival of the signal and returns the coordinates (θ, ϕ). We have simulated and studied the error performance of antenna as a function of angle and distance to the antenna.

Imaging and Applied Optics Congress, 2020

We propose the 𝛿-𝑆𝑃𝑁 approximation for the coupled radiative transfer equations modeling fluoresc... more We propose the 𝛿-𝑆𝑃𝑁 approximation for the coupled radiative transfer equations modeling fluorescence with collimated incident beams and present its numerical implementation using the Finite Element Method. The performance of the proposed model is investigated with respect to Monte Carlo simulations and the standard 𝑆𝑃𝑁 approximation over sub-centimeter domains for various optical properties. We find that the 𝛿-𝑆𝑃𝑁 approximation is more accurate than the 𝑆𝑃𝑁 in the near-source region, and provides improved estimates of phase and partial currents, at both excitation and emission wavelengths, over wider range of optical properties. Increasing approximation order improves accuracy of the 𝛿-𝑆𝑃𝑁 model for normally incident beams.

Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet, 2004

Opto-Acoustic Methods and Applications in Biophotonics V, 2021

We propose a “gradient filter” reconstruction scheme for solving the dynamic pharmacokinetic prob... more We propose a “gradient filter” reconstruction scheme for solving the dynamic pharmacokinetic problem using fluorescence-photoacoustic tomography in a shape based framework. The proposed method is validated using cancer mimicking phantoms.

Flow measurement is essential in many process monitoring, instrumentation and control application... more Flow measurement is essential in many process monitoring, instrumentation and control applications in various fields of science and technology. The ultrasonic flowmeters are one of the most popularly used devices for flow measurements. From the inception of first of its kind, enormous advancement has been registered in terms of its wave reflection such as Doppler and transit-time, and mounting to get completely non-invasive and non-intrusive measurements. The ultrasonic flowmeters have been used for various types of flow including sediment laden, viscous and slurry flow in different pipe materials and pipe sizes under fullyand partially-filled conditions. The flowmeters have been developed using both active and passive principles, and have achieved high accuracy using multiple paths. The technological advancements especially in signal processing, electronic circuitry and availability of high precision transducers have given an edge to the researchers and developers of ultrasonic flo...

Supplementary plots for emission wavelength and tabulated error metrics

Diffuse Optical Spectroscopy and Imaging VIII, 2021

We propose a 3D δ -SP3 model based reconstruction scheme for fluorescence optical tomography with... more We propose a 3D δ -SP3 model based reconstruction scheme for fluorescence optical tomography with directed sources. Numerical validations in reflectance-mode demonstrate improvements over existing approaches justifying the use of the proposed scheme.

Lecture Notes in Computer Science, 2002

arXiv: Methodology, 2015

Since the innovation of the ubiquitous Kalman filter more than five decades back it is well known... more Since the innovation of the ubiquitous Kalman filter more than five decades back it is well known that to obtain the best possible estimates the tuning of its statistics X_0X_0X0, P0P_0P_0, Theta\ThetaTheta, RRR and QQQ namely initial state and covariance, unknown parameters, and the measurement and state noise covariances is very crucial. The earlier tweaking and other systematic approaches are reviewed but none has reached a simple and easily implementable approach for any application. The present reference recursive recipe based on multiple filter passes through the data leads to a converged `statistical equilibrium' solution. It utilizes the pre, post, and smoothed state estimates and their corresponding measurements and the actual measurements as well as their covariances to balance the state and measurement equations and form generalized cost functions. The filter covariance at the end of each pass is heuristically scaled up by the number of data points and further trimmed to provide th...

We present first fully-nonlinear 3D SP3 based FOT reconstructions in a shape based framework. We ... more We present first fully-nonlinear 3D SP3 based FOT reconstructions in a shape based framework. We solve for the excitation-wavelength absorption coefficient of anomalies along with their boundaries using a compactly supported parametric level-set shape-representation. Preliminary results obtained with a trust region based iteratively Tikhonov-regularized Gauss-Newton algorithm for tumour mimicking phantoms show good localization and parameter reconstructions. OCIS codes: 100.3190,110.6955

Imaging and Applied Optics 2019 (COSI, IS, MATH, pcAOP), 2019

Pharmacokinetic analysis of optical fluorophore provides physiological information of the abnorma... more Pharmacokinetic analysis of optical fluorophore provides physiological information of the abnormalities in tissue. Compartment modeling of the fluorophore pharmacokinetics quantify the physiological changes in the tissue. We propose a shape based tomographic reconstruction of pharmacokinetic rates, concentrations and volume fractions of the fluorophore using the time varying near infra-red measurements. Radial basis function based parametric levelsets are used to represent the boundary of the spatially varying parameters of interest. A regularized Gauss-Newton filter based scheme is used reconstruct shape, pharmacokinetic rates, volume fractions and concentration parameters. Reconstruction results for tumor mimicking numerical phantom validate our proposed approach.

Fiber-optic probes are imperative for in-vivo diagnosis of cancer. Depending on the access to a d... more Fiber-optic probes are imperative for in-vivo diagnosis of cancer. Depending on the access to a diseased organ and the mutations one aims to sense, the probe designs vary. We carry out a detailed numerical study of the efficacy of the common probe geometries for epithelial cancer characterization based on spatially resolved reflectance data. As per the outcomes of this comparative study, a probe has been manufactured and using Monte Carlo look up table based inversion scheme, the absorption and scattering coefficients of the epithelium mimicking top layer have been recovered from noisy synthetic as well as experimental data.

This report provides a brief historical evolution of the concepts in the Kalman filtering theory ... more This report provides a brief historical evolution of the concepts in the Kalman filtering theory since ancient times to the present. A brief description of the filter equations its aesthetics, beauty, truth, fascinating perspectives and competence are described. For a Kalman filter design to provide optimal estimates tuning of its statistics namely initial state and covariance, unknown parameters, and state and measurement noise covariances is important. The earlier tuning approaches are reviewed. The present approach is a reference recursive recipe based on multiple filter passes through the data without any optimization to reach a `statistical equilibrium' solution. It utilizes the a priori, a posteriori, and smoothed states, their corresponding predicted measurements and the actual measurements help to balance the measurement equation and similarly the state equation to help form a generalized likelihood cost function. The filter covariance at the end of each pass is heuristi...

In the previous paper an adaptive ltering based on a reference recursive recipe was developed and... more In the previous paper an adaptive ltering based on a reference recursive recipe was developed and tested on a simulated dynamics of a spring, mass, and damper with a weak nonlinear spring. In this paper the above recipe is applied to a more involved case of three sets of airplane data which have a larger number of state, measurements, and unknown parameters. Further the ight tests cannot always be conducted in an ideal situation of the process noise and the measurement noises being white and Gaussian as is generally assumed in the Kalman lter. The measurements are not available in general with respect to the center of gravity, possess scale and bias factors which will have to be modelled and estimated as well. The coupling between the longitudinal and lateral motion brings in added diculty but makes the problem more interesting. At times the noisy measurements from the longitudinal and lateral motion are input into the longitudinal states. This leads to the resulting equations becom...