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Optical spectroscopy of Gaia detected protostars with DOT: Can we probe protostellar photospheres?
Optical spectroscopy offers the most direct view of the stellar properties and the accretion indicators. Standard accretion tracers, such as H ? , H ? and Ca II triplet lines, and most photospheric features fall in the optical wavelengths. However, these tracers are not readily observable from deeply embedded protostars because of the large line of sight extinction (Av? 50 100 mag) toward them. In some cases, however, it is possible to observe protostars at optical wavelengths if the outflow cavity is aligned along the line-of-sight that allows observations of the photosphere, or the envelope is very tenuous and thin, such that the extinction is low. In such cases, we not only detect these protostars at optical wavelengths, but also follow up spectroscopically. We have used the HOPS catalog (Furlan et al. in 2016) of protostars in Orion to search for optical counterparts for protostars in the Gaia DR3 survey. Out of the 330 protostars in the HOPS sample, an optical counterpart within 2 ? ? is detected for 62 of the protostars. For 17 out of 62 optically detected protostars, we obtained optical spectra (between 5500 and 8900 using nt Object Spectrograph and Camera (ADFOSC) on the 3.6-m Devasthal Optical Telescope (DOT) and Hanle Faint Object Spectrograph Camera (HFOSC) on 2-m Himalayan Chandra Telescope (HCT). We detect strong photospheric features, such as the TiO bands in the spectra (of 4 protostars), hinting that photospheres can form early in the star-formation process. We further determined the spectral types of protostars, which show photospheres similar to a late M-type. Mass accretion rates derived for the protostars are similar to those found for T-Tauri stars, in the range of 10 - 7 10 - 8M? yr - 1 . 2023, Indian Academy of Sciences. -
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Optical Spectroscopy of Classical Be Stars in The Galaxy
A classical Be (Be hereafter) star is a special type of massive B-type main newlinesequence star surrounded by a geometrically thin, equatorial, gaseous, decretion disc orbiting the central star. Spectra of Be stars show emission lines of different elements. Studying these lines provide an excellent opportunity to understand the geometry and kinematics of the circumstellar newlinedisc and properties of the central star itself. Be stars, thus provide excellent opportunities to study circumstellar discs. However, the disc formation mechanism in Be stars the Be phenomenon is still poorly understood. The present study focuses on studying a large sample of Be stars through newlineoptical spectroscopy and using two national optical telescope facilities. We performed the spectroscopic study of all major emission lines for a sample of 115 feld Be stars in the wavelength range of 3800 - 9000 using the 2.1-m HCT facility at Ladakh. To our knowledge, this is the frst study where near simultaneous spectra covering the whole spectral range of 3800 - 9000 has been studied for over 100 feld Be stars. We, therefore, produce an atlas of emission lines for Be stars which will be a valuable resource for researchers involved in Be star research. We made use of the unprecedented capability of the Gaia mission to re-estimate the extinction parameter (AV ) for these stars. The estimated AV values are used for extinction correction in the analysis of Balmer decrement (D34 and D54) for our program stars. D34 in our sample ranges between 0.1 and 9.0, whereas the corresponding D54 value mostly (and#8776; 70%) ranges between 0.2 and 1.5, clustering somewhere near 0.8 and#8722; 1.0. Our study indicates that Be star discs are generally optically thick in nature in majority of the cases. Through comparative study with the literature, we also noticed that the Hand#945; EW values in Be stars are usually lower than -40 Further from our analysis, it appears that the emission strength of Hand#945;, P14, FeII 5169 and OI 8446 is more in early B-type stars. -
Optical Spectroscopy of Classical Be Stars in Old Open Clusters
We performed the optical spectroscopy of 16 classical Be stars in 11 open clusters older than 100 Myr. Ours is the first spectroscopic study of classical Be stars in open clusters older than 100 Myr. We found that the H? emission strength of most of the stars is less than 40 in agreement with previous studies. Our analysis further suggests that one of the stars, [KW97] 35-12, might be a weak H? emitter in nature, showing H? equivalent width of ?0.5 Interestingly, we also found that the newly detected classical Be star LS III +47 37b might be a component of the possible visual binary system LS III +47 37, where the other companion is also a classical Be star. Hence, the present study indicates the possible detection of a binary Be system. Moreover, it is observed that all 16 stars exhibit a lesser number of emission lines compared to classical Be stars younger than 100 Myr. Furthermore, the spectral type distribution analysis of B-type and classical Be stars for the selected clusters points out that the existence of CBe stars can depend on the spectral type distribution of B-type stars present in these clusters. 2023. National Astronomical Observatories, CAS and IOP Publishing Ltd. -
Optical Resonator-Enhanced Random Lasing using Atomically Thin Aluminium-based Multicomponent Quasicrystals
Photon trapping inside a gain medium using a dispersed two-dimensional (2D) passive scatterer is an impetus to obtain incoherent random lasing (ic-RL) emission due to non-resonant feedback. An optical resonator (OR) can be used to influence such lasing thresholds. Non-noble nanomaterials-based quasicrystals (QCs) are an intriguing research prospect due to their potential surface plasmon resonance (SPR) property and ability to be exfoliated into 2D. In this work, an aluminium-based multicomponent alloy (Al70Co10Fe5Ni10Cu5) has been synthesized via the arc melting method. Thereafter, ultrasonication-based liquid phase exfoliation was used to obtain 2D quasicrystals (2D-QCs). The SPR-induced light scattering properties of synthesized 2D-QCs were exploited to obtain ic-RL from DCM dye gain medium under 532 nm, 10 ns, 10 Hz pulsed laser pumping. The plasmonic field enhancement property of 2D-QCs which enables the gain medium to absorb photons outside its peak absorption band has been demonstrated. The transition from ic-RL to OR-enhanced ic-RL and vice versa in the presence of resonator walls has been achieved by tweaking the device architecture. In this way, the ability of 2D-QCs to be potential passive scatterers and the controllability of lasing thresholds in the presence of an OR has been demonstrated. 2024 Elsevier Ltd -
Optical properties of MnTe2 few-layer quantum dots
Quantum dots (QDs) are gaining attention as a possible emissive material that might be used in flexible optoelectronic and photonic systems. In the present work, the temperature-dependent photoluminescence (TDPL) property of manganese di-telluride (MnTe2) QDs was investigated. The room-temperature PL is attributed to the abrupt breakage of the large-area MnTe2 nanosheets by ultrasonication, which integrates defect-mediated localized trap states inside the electronic bandgap. As a result, deliberately generated defect states ultimately generate such PL emission of QDs. Density functional theory (DFT) results further validate the experimental interpretations of the origin of TDPL. In addition, through an in-situ liquid diffusion approach, the QDs were also integrated into a NaCl matrix. Due to light scattering properties, the hybrid crystals exhibit fluorescence centres at various excitation wavelengths. These results suggest that these MnTe2 QDs can be used as an effective basis for future flexible optoelectronic applications. 2024 Elsevier B.V. -
Optical Properties of Magnetic Quantum Dots
The delta-like dispersion of the density of states (DoS) enable quantum dots (QD) to display optical and electronic properties comparable with those of real atoms. The discrete electronic structure of QDs akin to that of atoms is formed due to the effect of quantum confinement (QCE). In the case of magnetic quantum dots (MQD), the QDs are incorporated with magnetic impurities such as Mn atom, rare earth elements etc., by which the QDs undergo significant changes in optical and electronic properties by lifting their degeneracies (Zeeman effect). The combination of fluorescent and magnetic entities opens up opportunities for synthesizing two-in-one nanocomposites beneficial for multi-functional, multi-targeting, and multi-theranostic tools. Optical properties of QDs consisting of magnetic impurities, such as the absorption coefficient, oscillator strength, and refractive index are discussed in this chapter. 2023 selection and editorial matter, Amin Reza Rajabzadeh, Seshasai Srinivasan, Poushali Das, and Sayan Ganguly. -
Optical design studies for national large optical-IR telescope
A 1012 m class national large optical-IR telescope (NLOT) is envisaged to meet the growing scientific requirements in astronomy and astrophysics. Telescopes of such dimensions can only be made by segmenting the primary mirror, as it eases a more prominent primary mirrors fabrication, transportation, operation, and maintenance process. This paper presents the various optical designs analyzed for NLOT that can be fabricated using the India TMT Optics Fabrication Facility (ITOFF) at the Centre for Research and Education in Science and Technology (CREST) campus. We present the primary mirror segmentation details, its ideal optical performance, and study each designs advantages and technical complexities. Based on the above analysis, we have narrowed it down to an optimal design, and its performance analysis is also discussed. Indian Academy of Sciences 2024. -
Optical characterization of oxadiazoles analogues doped PMMA film for photonic application
In the present study, newly synthesized nitrobenzene derivatives (PBT and PBF) doped poly(methyl methacrylate) films were prepared using spin coating techniques, and their optical properties were analyzed. The absorption spectra of various weight percentages (0.02%, 0.1%, 0.2%, and 0.3%) of nitrobenzene derivative-doped polymer films were recorded using a UVvisible spectrometer. From the absorption spectra, optical properties such as refractive index, band gap energy, extinction coefficient, and dielectric constant were calculated. The effect of doping on the optical properties of PMMA was investigated, with results revealing normal dispersive behavior from the refractive index and extinction coefficient. Atomic force microscopy and scanning electron microscopy images indicated that the synthesized films have a low degree of roughness and a smooth surface. Additionally, the nonlinear optical properties of the PBF-doped polymer film were investigated, and the ? value was determined to be 7.403cm/W. Overall, the findings suggest that PBF-doped polymer films are promising candidates for photonic applications. Indian Association for the Cultivation of Science 2024. -
Optical Character Recognition system with Projection Profile based segmentation and Deep Learning Techniques
Optical character recognition is the solution to convert text from printed or scanned documents into editable data. This project is aimed at building a Optical character recognition system that recognizes digital text. A document is first detected using contour-based detection technique without altering the angle of the image and is segmented into lines, once the lines are segmented the words embedded in them are extracted. This segmentation is done using projection profiling method. Characters are then segmented words with vertical projection profiling from the extracted words. These characters are fed into an image recognition model for recognition. The recognition model is CNN based deep learning model. Modified VGG16 architecture is used here to extract maximum features from the images and then classify them. To train the model a dataset is created from a repository of digital character dataset. The dataset consists of images of 153 font variants. 2022 IEEE. -
Optical Character Recognition (OCR) based Vehicle's License Plate Recognition System Using Python and OpenCV
License Platform Detection is a computer technology that enables us to identify digital images on the platform automatically. Different operations are covered in this system, such as imaging, number pad locations, alphanumeric character truncation and OCR. The final objective of the system is to construct and create efficient image processing procedures and techniques to position a licensing platter on the Open Computer View Library picture. It was used and implemented the K-NN algorithm and python programming language. The technology can be used in different industries such as security, highway speed detection, lighting violations, manuscript documents, automatic charging system, etc. Auto plate recognition is an integrated technology which identifies the auto licence plate. Auto plate auto recognition. Multiple applications include complex safety systems, public spaces, parking and urban traffic control. Automatic Vehicle License Plate Recognition (AVLPR) has undesirable aspects because of many effects, such as light and speed. This work presents an alternative technique to leverage free software for the implementation of AVLPR systems including Python and the Open Computer Vision (openCV). 2021 IEEE. -
Optical and infrared studies of herbig Ae/Be stars
The work makes use of the unprecedented capability of the Gaia mission to study various properties of Herbig Ae/Be stars. We placed the Herbig Ae/Be stars in the Gaia color-magnitude diagram and accurately estimated their age and mass. The mass accretion rate is calculated from Hα line flux measurements of 106 HAeBe stars. The mass accretion rate is found to decay exponentially with the age of Herbig Ae/Be stars. Further, the immediate neighborhood of two Herbig Ae/Be stars, V1787 Ori and IL Cep, are studied using the astrometric and photometric data from the Gaia mission. We discovered a low mass binary companion to V1787 Ori using the analysis of distance and proper motion values from Gaia DR2. The mass ratio of the coeval binary system is found to be 0.23. Such a skewed mass ratio system is rarely identified in Herbig Ae/Be binary systems. The method of identification and characterization of the V1787 Ori wide binary system opens up the possibility of identifying more such systems. The HBe star IL Cep tells a much more complex story. The star is identified with a cluster of low mass stars associated with it. We identified 79 co-moving stars that are coeval to IL Cep, within 2 pc radius, from the analysis of Gaia EDR3 astrometry. The triggered star formation process called the "Rocket effect" caused by a massive star HD 216658 is identified to be the cause of the clustered star formation near IL Cep. The effect of this process is demonstrated for the first time using the proper motion data from Gaia. The immediate neighborhood of Herbig Ae/Be stars is identified as the formation region of long-chain carbon molecules such as Fullerenes and Polycyclic Aromatic Hydrocarbons. -
Optical and Infrared studies of herbig Ae Be stars
The work makes use of the unprecedented capability of the Gaia mission to study various properties of Herbig Ae/Be stars. We placed the Herbig Ae/Be stars in the Gaia color-magnitude diagram and accurately estimated their age and mass. The mass accretion rate is calculated from Hand#945; line newlineflux measurements of 106 HAeBe stars. The mass accretion rate is found to decay exponentially with the age of Herbig Ae/Be stars. Further, the immediate neighborhood of two Herbig Ae/Be stars, V1787 Ori and IL newlineCep, are studied using the astrometric and photometric data from the Gaia mission. We discovered a low mass binary companion to V1787 Ori using the analysis of distance and proper motion values from Gaia DR2. The newlinemass ratio of the coeval binary system is found to be 0.23. Such a skewed mass ratio system is rarely identified in Herbig Ae/Be binary systems. The method of identification and characterization of the V1787 Ori wide binary system opens up the possibility of identifying more such systems. The HBe newlinestar IL Cep tells a much more complex story. The star is identified with a cluster of low mass stars associated with it. We identified 79 co-moving stars that are coeval to IL Cep, within 2 pc radius, from the analysis of newlineGaia EDR3 astrometry. The triggered star formation process called the quotRocket effectquot caused by a massive star HD 216658 is identified to be the cause of the clustered star formation near IL Cep. The effect of this process is demonstrated for the first time using the proper motion data from Gaia. newlineThe immediate neighborhood of Herbig Ae/Be stars is identified as the formation region of long-chain carbon molecules such as Fullerenes and Polycyclic Aromatic Hydrocarbons. -
Optical and Infrared Photometric Study of Pre-Main Sequence Stars in Young Open Cluster NGC 7419 Young Open Cluster NGC 7419
The embryonic stage of development of stars has been a field of astrophysics which still pose many unresolved queries. The problem is largely due to the solitary nature of embryonic stars. Even the largest optical telescopes were not able to reveal many details about such stars as they are formed deep inside molecular cloud thorough which optical wavelength cannot pass through. Forbidding distances to such stars is an added problem. However, recently, this field is slowly turning into observational science. Even though optical radiations fail to reach the destination, longer wavelength infrared (IR) radiations can penetrate through such dusty region. These infrared radiations have been known for decades. But it is only during very recent times that infrared telescopes that have very high sensitivity and resolution came in to scenario. So now the astronomers are able to observe these stellar embryos. Studies about this stage of star formation can help us to solve many questions like how the birth of a star takes place, how these stars accrete matter into it from surroundings, when will this accretion stops, why do some stars have planetary systems around them etc. Current study is an attempt to look for the presence of these embryonic stars in an open cluster using infrared data and to get more details on nature of those stellar embryos. We investigate the properties of young stars and their circumstellar disks in young open cluster NGC 7419. The pre-determined V magnitude and B magnitude of these stars are combined with infrared data from 2MASS J,H, K and 4 band WISE data. The color-color diagrams are made using these 9 bands to identify young stellar objects. The individual SED fitting is done for these identified stars and parameters like their age, mass, temperature, disk radius and disk mass are estimated. These are used to comment on the evolutionary stage of the pre-main sequence stars and their circumstellar disk. Dissertation has been divided into five chapters. Chapter 1 gives a general introduction to the work done. Literatures referred are explained in Chapter 2. Data used in the current study and methodology adopted is described in chapter 3. Current work done on the young stellar objects in cluster NGC 7419 and results obtained from the study are explained in Chapter 4 and Chapter 5 respectively. -
Optical and Electrochromic Properties of CeO2/WO3 Hybrid Thin Films Prepared by Hydrothermal and Sputtering
Innovative chromogenic nanostructures like hybrids but also composite materials can be increased electrochromic efficiency because of their prospective application values in low-power displays, smart windows, electronic papers, and car anti-reflect mirrors. We used a hydrothermal approach to make Cerium oxide Nanorods have various ratios in this report. DC magnetron sputtering procedures cover the generated cerium oxide nanorods of various diameters with a tungsten oxide layer in one step. the surface plasmon effect varies depending on the size of Ce Nanorods, and this phenomenon impacts electrochromic results. the electrochromic performances of CeO2/WO3 nanorods on FTO-coated glass slides are examined using a 0.5 M solution of H2SO4 as the electrolyte in the visible range. These structures produce considerable optical modulation (47 %, 45 %, and 41 % at 700 nm) and coloration efficiency (11.6, 7.57, and 10.84 cm2C-1 at 700 nm). 2022 Seventh Sense Research Group -
Optical and electrical properties of SnS semiconductor crystals grown by physical vapor deposition technique
Tin sulfide (SnS) is a material of interest for use as an absorber in low cost solar cells. Single crystals of SnS were grown by the physical vapor deposition technique. The grown crystals were characterized to evaluate the composition, structure, morphology, electrical and optical properties using appropriate techniques. The composition analysis indicated that the crystals were nearly stoichiometric with Sn-to-S atomic percent ratio of 1.02. Study of their morphology revealed the layered type growth mechanism with low surface roughness. The grown crystals had orthorhombic structure with (0 4 0) orientation. They exhibited an indirect optical band gap of 1.06 eV and direct band gap of 1.21 eV with high absorption coefficient (up to 103 cm-1) above the fundamental absorption edge. The grown crystals were of p-type with an electrical resistivity of 120 ? cm and carrier concentration 1.52015 cm-3. Analysis of optical absorption and diffuse reflectance spectra showed the presence of a wide absorption band in the wavelength range 3001200 nm, which closely matches with a significant part of solar radiation spectrum. The obtained results were discussed to assess the suitability of the SnS crystal for the fabrication of optoelectronic devices. 2011 Elsevier B.V. All rights reserved. -
Oppositional Glowworm Swarm based Vector Quantization Technique for Image Compression in Fiber Optic Communication
In recent times, fiber optic communication networks have become commonly applied for commercial as well as military applications. Fiber optic networks have gained popularity owing to the high data rate. At the same time, the generation of huge quantity of data at a faster rate poses a major challenge in the storing and transmission process. To resolve this issue, data compression approaches have been presented to reduce the quantity of transmitted data and thereby minimizes bandwidth utilization and memory. Vector quantization (VQ) is a commonly employed image compression technique and Linde Buzo Gray (LBG) is used to construct an optimum codebook to compress images. With this motivation, this paper presents a new oppositional glowworm swarm optimization based LBG (OGSO-LBG) technique for image compression in fiber optic communication. The OGSO algorithm involves the integration of oppositional based learning (OBL) concept into the GSO algorithm to boost its convergence rate. The OGSO-LBG algorithm produces the codebook at a faster rate with minimal computation complexity. In order to highlight the enhanced compression performance of the OGSO-LBG technique, a series of experiments were carried out and the results are examined under different dimensions. 2021 IEEE -
Opportunity Recognition, Career Decision-Making, Self-Efficacy and Social Entrepreneurial Intention among Higher Education Students
Building on the entrepreneurship cognition literature, the present research aims to develop a model to examine the direct and indirect effects of opportunity recognition, career decisionmaking and self-efficacy on social entrepreneurial intention. The research adopted a crosssectional design. The research was divided into three distinct studies, each conducted with a specific objective. The data collected for three studies included higher education students newlineacross India. Studies 1 and 2 aimed to develop and validate two scales, namely social entrepreneurial opportunity recognition and social entrepreneurial career decision-making following steps in tool construction. The sample size was 600 for study 1 and 845 for study 2. The social entrepreneurial opportunity recognition scale had 24-items that measures opportunity recognition with six motivating factors as the lower order constructs which are life experiences, social awareness, social inclination, community development, institutional voids, and natural option for a meaningful career. The social entrepreneurial career decision scale had 20 items focusing on the appraisal components in pre-entry social entrepreneurial career decision-making and has four factors, which are relevance, coping potential, knowledge and resources, and normative significance. Study 3 examined the direct and indirect effects of opportunity recognition, career decision-making and self-efficacy on social newlineentrepreneurial intention using a sample of 605 students. The findings show that opportunity recognition influences social entrepreneurial intention and is partially mediated by career decision-making. Furthermore, self-efficacy moderates the mediating role of career decisionmaking between opportunity recognition and intention. This research facilitates a profound understanding of social entrepreneurial cognition and pre-entry decision-making. -
Opportunistic mycoses in COVID-19 patients/survivors: Epidemic inside a pandemic
Being considered minor vexations, fungal infections hinder the life of about 15% of the world population superficially, with rare threats to life in case of invasive sepsis. A significant rise in the intrusive mycoses due to machiavellian fungal species is observed over the years due to increased pathology and fatality in people battling life-threatening diseases. Individuals undergoing therapy with immune suppressive drugs plus recovering from viral infections have shown to develop fungal sepsis as secondary infections while recovering or after. Currently, the whole world is fighting against the fright of Coronavirus disease (COVID-19), and corticosteroids being the primitive therapeutic to combat the COVID-19 inflammation, leads to an immune-compromised state, thereby allowing the not so harmful fungi to violate the immune barrier and flourish in the host. A wide range of fungal co-infection is observed in the survivors and patients of COVID-19. Fungal species of Candida, Aspergillus and Mucorales, are burdening the lives of COVID-19 patients/survivors in the form of Yellow/Green, White and Black fungus. This is the first article of its kind to assemble note on fungal infections seen in the current human health scenario till date and provides a strong message to the clinicians, researchers and physicians around the world non-pathological fungus should not be dismissed as contaminants, they can quell immunocompromised hosts. 2021 -
Opinion mining on newspaper headlines using SVM and NLP
Opinion Mining also known as Sentiment Analysis, is a technique or procedure which uses Natural Language processing (NLP) to classify the outcome from text. There are various NLP tools available which are used for processing text data. Multiple research have been done in opinion mining for online blogs, Twitter, Facebook etc. This paper proposes a new opinion mining technique using Support Vector Machine (SVM) and NLP tools on newspaper headlines. Relative words are generated using Stanford CoreNLP, which is passed to SVM using count vectorizer. On comparing three models using confusion matrix, results indicate that Tf-idf and Linear SVM provides better accuracy for smaller dataset. While for larger dataset, SGD and linear SVM model outperform other models. Copyright 2019 Institute of Advanced Engineering and Science. All rights reserved.