Susmita Biswas - Academia.edu (original) (raw)

Papers by Susmita Biswas

Hot-carrier radiative recombination through phonon confinement in silicon nanocrystals embedded in colloidal xerogel matrix

Journal of Applied Physics

Colloidal suspension of free standing silicon/silicon oxide core/shell nanoparticles has been syn... more Colloidal suspension of free standing silicon/silicon oxide core/shell nanoparticles has been synthesized using a mechanochemical top-down approach. Quasi-mono-dispersed core size distribution of synthesized nanoparticles has been confirmed using different structural, morphological, and optoelectronic characterizations. Raman, continuous wave photoluminescence and time-resolved photoluminescence studies have been performed on synthesized colloidal nanoparticles in ethanol medium. Asymmetric broadening of the Raman peak (red shifted with respect to that of bulk silicon) has been observed. Intensities and positions of photoluminescence emission peaks are prominently dependent on excitation photon energy. Moreover, the photoluminescence decay time varies from sub-nanoseconds to tens of nanoseconds. The decay time also exhibits a strong dependence on the excitation wavelength, while the emission wavelength is kept unaltered. The abovementioned observations indicate the slow relaxation of photo-excited carriers in silicon quantum dots. This particular phenomenon takes place due to phonon mode discretization, which is further responsible for the radiative recombination of hot-carriers and consequent strong visible emission. The enhancement of hot-carrier lifetime in colloidal silicon quantum dots is the key requirement for the active material of the hot-carrier solar cell. Runny texture of the synthesized material inhibits practical device implementation; therefore, the synthesized nanoparticles have been embedded in the silica xerogel matrix. The impression of phonon mode confinement, in silicon quantum dots embedded in a hard matrix, has been observed, resulting in increased hot-carrier lifetime. The enhanced hot-carrier lifetime can lead to the realization of a silicon-based active material for the hot-carrier solar cell.

IAHS Medical Journal

Background: Dengue is a major vector-borne disease that is prevalent in tropical and sub-tropical... more Background: Dengue is a major vector-borne disease that is prevalent in tropical and sub-tropical countries. A hallmark of dengue fever is thrombocytopenia. This study was conducted to evaluate the platelet count in relation to severity and outcome of dengue infection in a cohort of hospitalized children during 2019 dengue outbreak in Bangladesh. Materials and methods: This observational study was carried out in the Department of Pediatrics of Chittagong Medical College Hospital, Chattogram, Bangladesh. One hundred and ninety two consecutive serologically positive dengue cases (Age £ 12 years) admitted from July 2019 to December 2019 were enrolled in the study. Platelet count was done daily from day 3 to 7 days of illness. Results: Overall the mean age was 7.04 (±3.23) years with male preponderance (59.4%). As per the nadir platelet count 53 (27.7%) patients had counts >150,000, 66 patients (34.3%) had count between 100,000 and 150,000, 36 patients (18.7) had count between 50,000...

Estimation of one-dimensional energy density spectrum of surface waves using Genetic Algorithm

2020 International Conference on Computer, Electrical & Communication Engineering (ICCECE), 2020

One-dimensional energy density spectrum was estimated for a grid point in the Indian Ocean (IO) r... more One-dimensional energy density spectrum was estimated for a grid point in the Indian Ocean (IO) region. Empirical orthogonal function (EOF) analysis and genetic algorithm (GA) was applied for the prediction. EOF analysis was implemented separately for the southwest and northeast monsoon months, using a 5-years model generated energy density spectrum data. The first eigenmode accounted for 50.4% and 64% of the total variability of the above parameter for the two seasons respectively. Then GA was applied separately to the time series of the corresponding first principal component, for both the seasons, with a lead time of 06 hours. It was found that the performance of the combined approach was better for the northeast monsoon than the southwest monsoon and the root mean square error (RMSE) of GA forecasted spectra was found to be less when it was calculated with respect to model computed spectra than when it was calculated with respect to buoy observed spectra.

IJCRT1893085 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org 538 THE DE... more IJCRT1893085 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org 538 THE DEVELOPMENT OF LANGUAGE AND COGNITIVE ABILITIES OF HEARING IMPAIRED CHILDREN Sanjoy Dutta Assistant Professor Sundarban B.Ed. College, West Bengal, India Abstract: The purpose of this paper is to analyze the nature and pattern of language development related to different aspects of cognitive abilities of hearing impaired children as well as to classify them according to test scores. A Bengali language test belonging to class VI has been applied to 20 hearing impaired children of class VI standard of Helen Keller Badhir Vidyalaya, Mukundapur, Kolkata. Different aspects of language along with cognitive abilities have been analyzed. The major findings have been found that language development of the class VI students is poor and variable also although their average age is 15.5 years, but comparatively their cognitive abilities in to some extent is not bad. They have lack of sentence construct...

Antibiotics, 2022

There is an increasing focus on researching children admitted to hospital with new variants of CO... more There is an increasing focus on researching children admitted to hospital with new variants of COVID-19, combined with concerns with hyperinflammatory syndromes and the overuse of antimicrobials. Paediatric guidelines have been produced in Bangladesh to improve their care. Consequently, the objective is to document the management of children with COVID-19 among 24 hospitals in Bangladesh. Key outcome measures included the percentage prescribed different antimicrobials, adherence to paediatric guidelines and mortality rates using purposely developed report forms. The majority of 146 admitted children were aged 5 years or under (62.3%) and were boys (58.9%). Reasons for admission included fever, respiratory distress and coughing; 86.3% were prescribed antibiotics, typically parenterally, on the WHO ‘Watch’ list, and empirically (98.4%). There were no differences in antibiotic use whether hospitals followed paediatric guidance or not. There was no prescribing of antimalarials and limit...

Paraquat Poisoning and AKI –A Rare Pediatric Case Report in a Tertiary Care Hospital

Journal of pediatric nephrology, 2021

Paraquat is a widely used synthetic herbicide in agriculture. Ingestion of toxic doses of paraqua... more Paraquat is a widely used synthetic herbicide in agriculture. Ingestion of toxic doses of paraquat can be fatal with life threatening effects on the kidneys, lungs, gastrointestinal tract (GIT), liver, heart, and other organs. There is no specific antidote or effective life saving treatment for paraquat poisoning and its prognosis is very poor worldwide. Here we report a case that presented with acute renal failure, shock, GIT bleeding with oral mucosal ulceration, and pulmonary involvement due to accidental paraquat poi soning and delayed hospitalization after poison ingestion. In spite of partial improvement, the patient expired after two weeks of admission. Therefore, any case of paraquat poisoning must be hospitalized and, if needed, referred to equipped centers as early as possible after poison ingestion

Modeling Earth Systems and Environment, 2020

A wind speed forecasting technique, using deep learning architectures based on long short-term me... more A wind speed forecasting technique, using deep learning architectures based on long short-term memory (LSTM) model and bidirectional long short-term memory (BiLSTM) model is presented in this work. The coastal belts of the Indian peninsula are vulnerable to natural disasters like storm surges and inundations due to cyclones each year. The wind speed is a major parameter for analyzing extreme weather events. Prediction using numerical models is not efficient enough due to the irregular patterns in the data and, thus, deep neural network models involving many layers have been tested. The shallow feed-forward model has also been considered along with deep learning models to estimate future values from past data. The present work employs a comparison study of different models to forecast wind speed time series at two locations in the Bay of Bengal and the Arabian Sea, respectively, having different dynamics and randomness. For training the models, daily wind speed data are considered for the period 2006-2017 and an independent validation set is chosen comprising 2018 wind speed data to check the accuracy. To evaluate forecast efficiency among different network models fitted to given time series, mean square error (MSE) and root mean square error (RMSE) have been computed. Multiple experiments are conducted with different hidden unit values and epoch values to obtain the minimum error. Regression equations generated may be used for forecasting future time series. The BiLSTM model connecting hidden states of opposite directions proved to be most efficient for the wind speed forecasting in different regions.

Materials Today: Proceedings, 2020

A device, supporting negative differential resistance, has been fabricated. Aluminum top contacts... more A device, supporting negative differential resistance, has been fabricated. Aluminum top contacts have been deposited on electrochemically synthesized porous silicon layer on p-type silicon substrate for this purpose. Top-bottom DC current vs. voltage (I-V) characteristics of the fabricated device have been recorded at room temperature under dark condition and injecting photons. Dark I-V characteristics of this device indicate the presence of negative differential resistance (NDR). Similar kind of I-V characteristics has been observed under illumination. At the same time, fabricated device shows photovoltaic effect after injecting photons. This may be due to some series and parallel combination of multiple junctions with photovoltaic nature.

Materials Science in Semiconductor Processing, 2020

Passivation of n-type and p-type monocrystalline CZ Si wafers (both polished and textured) with s... more Passivation of n-type and p-type monocrystalline CZ Si wafers (both polished and textured) with silicon oxide layers prepared by thermal (TO), chemical (CO) and plasma (PO) techniques have been extensively investigated from the measurement of minority carrier lifetime (τ) by transient electrical photoresponse method, density of interface states (N SS) measurement by capacitancevoltage study and silicon oxidation states by X-ray photoelectron spectroscopy (XPS) study of the SiO 2 /Si interface. It has been observed that N SS and τ have an inverse relation but the dependence is not linear. The method (TO, CO or PO) of oxide layer development has been found to play a crucial role to control the passivation of the c-Si wafer surface. It has been observed that the thermally grown oxide layer (TO) is superior among three oxide layers for all the different c-Si surfaces. Very low density of interface states (<5 � 10 11) were found in both p-type and n-type polished wafer passivated with TO layer. Highest lifetimes of 170 μs for n-type polished wafer and 102.74 μs for p-type polished wafer were obtained with TO. The amount of sub oxide formed at the interface of both n-and p-type of wafers during different oxidation process, may have some correlation with N ss which in turn determines the passivation quality of the wafers. Improvement of implied V oc for both polished and textured wafers (n-type and p-type) was found using thermally grown oxide with respect to others.

Chattagram Maa-O-Shishu Hospital Medical College Journal, 2020

Background: Use of automated device with ultrasound guidance in renal biopsy has improved the ade... more Background: Use of automated device with ultrasound guidance in renal biopsy has improved the adequacy and reduced the complication. Chittagong Medical College Hospital (CMCH) is a tertiary teaching hospital where Pediatric Nephrology Department started its journey on 11th December 2013. Since then renal biopsy is going on. Aim of the study is to see the rate of adequacy and complication of renal biopsy along the course of years. Materials and methods: This is a retrospective study carried on 100 consecutive ultrasonography guided percutaneous renal biopsy from lower pole of left native kidney performed by the pediatric nephrologist. All hospitalized children aged up to 12 years admitted since 2014 were included. Spring loaded automated biopsy needle was used in 88% cases and Trucut biopsy needle in 12% cases. Results: Most of the patients were aged between 1 to 10 years with male female ratio 0.9:1. Midazolam was used for sedation in all patients except one who needed general anest...

Applied Physics A, 2020

Passivated emitter rear contact (PERC) solar cell involves upgraded adaptation of technology over... more Passivated emitter rear contact (PERC) solar cell involves upgraded adaptation of technology over the existing silicon waferbased aluminium back surface field (Al-BSF) solar cell. The lower efficiency of Al-BSF is caused by a few drawbacks e.g. higher rear surface recombination and weaker electric field at the rear surface. These technical shortcomings can be mitigated by incorporating field-effect passivation (FEP) layer viz. aluminium oxide (Al 2 O 3) at the rear surface with a capping layer of SiN X on it. Conventionally two new processing steps utilizing two expensive equipments, green laser (532 nm) for laser ablation of the FEP and SiN X capping layer stack at the rear surface and single side etcher for rear side polishing of wafer are used for manufacturing of PERC cells. In this paper, we have shown that instead of these two new expensive processing equipments we can use the IR laser (1024 nm) and RIE etcher, which are commonly available for Al-BSF manufacturing line, for the fabrication of PERC solar cells. Using p-type wafers of rather modest quality (minority carrier lifetime of ≥10 µs) we have demonstrated improvement of the efficiency from 18.71 to 19.62% and enhancements in V OC and J SC from 628 to 646 mV and 38.59 mA/cm 2 to 39.82 mA/cm 2 , respectively. A thorough root-cause analysis has been carried out to optimize the two new approaches within the existing Al-BSF line for the fabrication of PERC solar cell.

Journal of Electromagnetic Waves and Applications, 2020

In this paper, high port isolation in dual feed orthogonally polarized square patch antenna array... more In this paper, high port isolation in dual feed orthogonally polarized square patch antenna array is achieved by the use of Defected Ground Structure (DGS). A simple rectangular-headed cross DGS is implanted in the ground plane underneath the square patch in order to achieve high port isolation between two orthogonal ports at 2.95 GHz. The proposed design offers 58.55 dB port isolation between ports of single element patch and 45 dB that for two-element arrays. The port isolation of microstrip antenna with and without DGS has been studied and the result indicates better port isolation of the array with high cross polarization for two orthogonal polarizations owing to the effect of DGS. Finally, the two-element array is considered for MIMO application and mutual coupling between them is investigated. The simulated results of the proposed antennas are found to be in close agreement with the experimentally measured ones.

Colloids and Surfaces B: Biointerfaces, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Materials Today: Proceedings, 2018

We report synthesis of colloidal suspension of silicon (Si) nanoparticle (NP) with native silicon... more We report synthesis of colloidal suspension of silicon (Si) nanoparticle (NP) with native silicon dioxide (SiO 2) layer by mechanical milling. Different size distribution of Si NPs in the colloid has been obtained by varying the centrifugation time. Width of the particle distribution curve of Si NPs was found to decrease with increasing centrifugation time of the colloidal suspensions, which has been established from the FESEM analysis. The variation of particle size also put its signature in the photoluminescence (PL) properties of the prepared materials.

Paediatrica Indonesiana, 2019

Background The prevalence of childhood overweight and obesity has increased over the last two dec... more Background The prevalence of childhood overweight and obesity has increased over the last two decades due to high caloric intake and decreased physical activity. The dramatic increase in the prevalence of overweight children occurred in conjunction with increasing prevalence of hypertension. Microalbuminuria is an early sign of damage to the kidney and cardiovascular system. Hypertensive, overweight children have an increased chance of microalbuminuria. Objectives To assess the prevalence of overweight, hypertension, and microalbuminuria in urban and rural school going children and contributing risk factors and associations. Methods This cross-sectional study was done in schoolchildren aged 6 to 16 years, from urban and rural areas, in Bangladesh, from September 2015 untill August 2016. Subjects’ weights, heights, and blood pressures (BP) were measured. Overweight and hypertension (HTN) statuses were determined with age-appropriate standardized charts. Subjects were divided into ove...

Applied Surface Science, 2019

Large quantities of free standing quasi mono-disperse silicon nanocrystal/ silicon oxide core-she... more Large quantities of free standing quasi mono-disperse silicon nanocrystal/ silicon oxide core-shell structured particles have been segregated by a cyclic process of sonication and centrifugation of mechanically milled and chemically treated colloidal suspension of silicon powders in ethanol medium. Narrowing of size distribution with the enhancement of centrifugation time has been evidenced from different structural characterisations as well as optical absorption and photoluminescence study. Gradual shifting of photoluminescence peak positions towards higher energy region in samples, prepared through longer centrifugation time, is also detectable with unaided eye when different samples are exposed to laser beam of wavelength ~405 nm. Controlled optoelectronic properties of the final sample achieved after four such cycles indicate a narrow core size distribution centering at 2.15 nm; can also be evidenced from the TEM micrograph.

Journal of Luminescence, 2018

Room temperature time-resolved photoluminescence (TRPL) of colloidal Si nanostructures prepared b... more Room temperature time-resolved photoluminescence (TRPL) of colloidal Si nanostructures prepared by repetitive oxidation-etching-oxidation of mechanically milled silicon, indicate towards phonon confinement in Si nanostructures. The Si nanocrystals have a well-defined Raman peak, which is asymmetrically broadened and red shifted, compared to bulk silicon. The PL intensities exhibit tri-exponential decay characteristics with decay times ranging between pico to nanosecond. For a fixed emission wavelength, the decay time is found to be strongly dependent on excitation wavelength. Steady state luminescence spectra reveal that PL peak positions and intensities are dependent of excitation energy. On the basis of these observations we show that phonon confinement plays a significant role in the non-radiative relaxation of excited carriers at the band edges of nanocrystalline Si core.

Progress In Electromagnetics Research Letters, 2019

In this paper suppression of higher order modes of a microstrip antenna array is investigated. Th... more In this paper suppression of higher order modes of a microstrip antenna array is investigated. The array consists of two radiating elements which are fed by a corporate type microstrip feeding network. The array provides resonance at 5.2 GHz frequency for its fundamental mode (TM 10 mode). Beside this fundamental mode, two harmonics at 10.4 GHz (1st harmonic) and 15.05 GHz (2nd harmonic) and a few sub-harmonics at 7.8 GHz (TM 01), 8.8 GHz (TM 11), and 13.3 GHz (TM 12) are excited. In order to suppress the 1st harmonics, a pair of half wavelength open ended stubs whereas for 2nd harmonic a pair of quarter wavelength open ended stubs are employed. From the simulated results it has been noticed that the 1st and 2nd harmonics are successfully suppressed, and the sub-harmonics are also suppressed. Prototypes of the antenna arrays are fabricated and measured. Measured results have good agreement with simulated ones.

IEEE Transactions on Device and Materials Reliability, 2018

An all Si, p-in device, consisting of nanostructured porous Si layer sandwiched between a p-type ... more An all Si, p-in device, consisting of nanostructured porous Si layer sandwiched between a p-type crystalline Si and an n-type amorphous Si, exhibits current controlled switching. Temperature dependent charge transport characteristics of the device reveal that trapping and detrapping of injected carriers at the interface of nanocrystalline Si core and the oxide shell, through impact excitation, is responsible for the observed switching. The abundance of surface inhomogeneities in the form of sub-oxides and dangling bonds create multiple charge trapping centres which in turn endow the device with switching characteristics. The density of trap states (~10 11 /cm 2) estimated from the detrapping potential is in very good agreement with the trap density obtained directly from C-V measurements.

Applied Materials Today, 2018

Colloidal suspension of nano-dimensional Si-SiO X core-shell has been synthesized by step down me... more Colloidal suspension of nano-dimensional Si-SiO X core-shell has been synthesized by step down mechanical process followed by thermo-chemical treatments. Graphene oxide (GO) has been synthesized by modified hummer's method. A wet chemical in situ co-deposition/reduction technique has been performed in amine rich medium to encapsulate the Si-SiO X core-shell nanostructure by amine functionalized reduced graphene oxide (af-rGO). The presence of silicon nano-crystals and af-rGO in the nanocomposite has been confirmed by Raman, FTIR and XRD studies. Core-shell structure of the nanocomposite has been confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). A simple two terminal device has been fabricated with the synthesized nanocomposite in between two aluminium electrodes on glass substrate. In spite of the symmetric architecture of the device, the current-voltage (I-V) characteristics exhibits an asymmetry in nature, suggesting the formation of rectifying junction at the interfaces. Surface potential mapping has been obtained by Kelvin probe force microscopy (KPFM) to reveal the developed built-in potential at the interfaces. A chemical model has been postulated that assures the formation of dipoles and traps at the respective af-rGO/SiO X and SiO X /Si interfaces. The role of trapped charges has been established by solving Poisson's equation, validated by the trap density estimation from the capacitance-voltage (C-V) curve. This newly developed nano-structure has immense potential in the field of photovoltaics and electronics as a basic building block.