Himadri Sekhar Dutta

Investigation of the electrical switching and rectification characteristics of a single standalone n-type ZnO-nanowire/p-Si junction diode

In this work, n-ZnO-nanowire/p-Si junction diodes have been fabricated and characterized both physically as well as electrically. The measurements are performed on a single standalone nanowire diode for the investigation of electrical transport through the nano-junction. The rectification properties of the single n-ZnO nanowire/p-Si diode have been studied for various input waveforms and frequencies. The diodes exhibit very promising rectification as well as switching behavior with no charge storage effect and consequently, a switching time as small as ∼1 ms has been achieved.

A Simple Approach to Design a Binary Coded Absolute Shaft Encoder

In this paper, an optical type absolute shaft encoder coding pattern is presented. Compared with the conventional binary or gray code pattern resolution (2n), the proposed code exhibits two times more resolution (2n2). Even, to represent high density positional information of rotating object, it is required very less number of tracks. This pattern sequence is based on n-by-2 matrices of binary codes where consecutive two columns of each code represented as high-low order bits. To retrieve the encoded position from these coding patterns, an extra pulse track was added at the outside of coded tracks. Moreover, it was used for providing a synchronized clock pulse into a simple photodetector-based sequential logic circuitry; it is the decoding unit of this encoder. Thus, depending on these synchronized pulses, the proposed encoder is able to provide error free positional information for a high-speed rotating object. Eventually, in order to prove this concept, a prototype is designed and tested, where a satisfactory performance was achieved.

A new contrast enhancement method of retinal images in Diabetic Screening System

A new retinal image contrast enhancement method for Diabetic Screening System is presented here. The proposed method evaluated by comparing the retinal image quality with different contrast enhancement methods which are applied in numerous papers. The proposed method produces better image quality and also preserves the mean brightness of the input images which is very important for medical image analysis. Publicly available datasets like DRIVE, STARE, DIARETDB0, and DIARETDB1 are used for testing purpose. The low contrast noisy retinal images are collected from the Hospital and performance of the proposed contrast enhancement is also measured. The SSIM (Structure Similarity Index Measurement) and AAMBE (Average Absolute Mean Brightness Error) are the important performance measurement parameters applied here to examine the image quality and brightness preserving ability respectively. The average SSIM is reported as 0.82(Std. Dev=0.011) and AAMBE is 0.023(Std. Dev=0.030). The success rate on low contrast noisy retinal image analysis is showing the importance of the proposed method.

Temperature-dependent electrical characteristics of CBD/CBD grown n-ZnO nanowire/p-Si heterojunction diodes

Heterojunction diodes are fabricated using a low-temperature chemical bath deposition of oriented and crystalline ZnO nanowires on a?? ??p-silicon substrate. The electrical transport properties of the heterojunction are investigated at various temperatures by measuring current?voltage (I?V) characteristics in the range of 90?390?K. A thermionic emission (TE) model is used to analyze the transport behavior. The deviation in the experimental value of Richardsons constant for ZnO nanowires is obtained from I?V?T measurement. The temperature dependence of the effective barrier height and ideality factor is attributed to the inhomogeneous barrier height distribution at the n-ZnO NW/p-Si hetero-interface. The TE and barrier inhomogeneity model are simultaneously used to extract the appropriate value of the Richardsons constants in three different temperature regions. Linear fittings for three different temperature regions suggest multiple Gaussian distributions of barrier heights at the junction.

Brightness-preserving fuzzy contrast enhancement scheme for the detection and classification of diabetic retinopathy disease

Abstract. The contrast enhancement of retinal image plays a vital role for the detection of microaneurysms (MAs), which are an early sign of diabetic retinopathy disease. A retinal image contrast enhancement method has been presented to improve the MA detection technique. The success rate on low-contrast noisy retinal image analysis shows the importance of the proposed method. Overall, 587 retinal input images are tested for performance analysis. The average sensitivity and specificity are obtained as 95.94% and 99.21%, respectively. The area under curve is found as 0.932 for the receiver operating characteristics analysis. The classifications of diabetic retinopathy disease are also performed here. The experimental results show that the overall MA detection method performs better than the current state-of-the-art MA detection algorithms.

An Effective Contrast Enhancement Method for Identification of Microaneurysms at Early Stage

ABSTRACT The presence of microaneurysms (MAs) is usually the early sign of diabetic retinopathy (DR) disease. In this study, an effective contrast enhancement scheme has been incorporated with a diabetic screening system to improve the overall quality of MAs identification technique. The proposed scheme is compared with the existing retinal image contrast enhancement methods and a better result is established. Public datasets and also low-contrast noisy images collected from hospitals are used for MAs detection, and satisfactory results are found. The results on low-contrast noisy image diagnosis established the significance of the study. A total of 587 (training = 340, testing = 247) retinal images are examined. The mean sensitivity and specificity are scored as 95.94% and 99.21%, respectively. The value of AUC is 0.932 (SD = 0.013) from the ROC analysis.

A New Approach for Color Distorted Region Removal in Diabetic Retinopathy Detection

Automatic detection of Diabetic Retinopathy (DR) abnormalities in fundus retinal images can assist in early diagnosis and timely treatment of DR, to avoid further deterioration of vision. Many Fundus Retinal images contain color distorted regions originated due to noise, extremely uneven or poor illumination and improper exposure of fundus camera. These regions are required to be removed to avoid poor results for feature extraction and erroneous DR abnormality detections, as they introduce high amount of false positive detections. In this paper, we have proposed a totally automatic method for segmentation and removal of the color distorted regions in retinal fundus images, using modified Valley Emphasized Automatic thresholding method and morphological operations. The proposed algorithm accurately defines the well illuminated color undistorted retinal region inside the input fundus image, from which both the normal and disease features can be successfully detected. The proposed method has yield an average accuracy of more than 95 % when tested over around 700 fundus images from diaretdb0, diaretdb1, STARE, HRFDB and DRIVE databases.

A Survey on the Application of Multi-Objective Optimization Methods in Image Segmentation.

A recent trend in problem formulation in image segmentation is to employ the multi-objective optimization (MOO) methods. The decision-making MOOs are the collection of realistic complex optimization problems, where the objective functions are usually conflicting. Image segmentation is the clustering of pixels applying definite criteria. It is one of the crucial parts in image processing. This chapter provides a comprehensive survey on MOO encompassing image segmentation problems. Here, the segmentation models are categorized by the problem formulation with a relevant optimization scheme. The survey also provides the latest direction and challenges of MOO in image segmentation procedure.

Design and implementation of multibit LFSR on FPGA to generate pseudorandom sequence number

Pseudorandom number generators (PRNGs) are important role in cryptography application. Hardware based random number generators become faster. Field Programming Gate Arrays (FPGA) is one of the most valuable devices in hardware industry. This paper presents multibit linear feedback shift register (LFSR) based PRNGs circuit designed with hardware description languages (HDL). In multibit LFSR system, multiple bits are shift in every clock cycle where a single bit is shift in a conventional LFSR method. This technique is very much applicable in cryptography area. The proposed various bit length multibit LFSR architectures are synthesized using Xilinx ISE 14.7 and Spartan 6 FPGA to target device XC6SLX45. The result analysis indicates that 32-bit length multibit LFSR architecture is better performance than other architectures.

Design & realization of an optical type dual axis inclination sensor

In the field of industrial automation, railways, intelligent platform, machining and other important areas where measurement of inclination of a body with respect to the gravity field plays a crucial role. In this present paper we have demonstrated an optical type dual axis inclination sensor with a precession of 0.6° and a working range of ±70° to fulfill the requirements of the above subjective areas. The sensor elements is made of a semi circular shape wooden block with a proof mass and a specially design imaging plate which are attached to its circumference edge. This fabricated block is clamped with orthogonal surface of a closed housing by a pivot arm which passes through the centre of the block, thus forming a dual axis pendulum structure. Therefore when the sensor is inclined, blocks are experiences deflection due to the gravity field of the earth. The movement of the two blocks is measured optically in two directions utilizing variation of light intensity produced by an imaging plate. The experimental result depicts a satisfactory performance of the sensor having a sensitivity of 40mv/°.