Effective passivation of c-Si by intrinsic a-Si:H layer for hit solar cells

The influence of HF solution etching on surface roughness of c-Si wafer was investigated using AFM. Ultra thin(2-3 nm) intrinsic a-Si:H is necessary to achieve high VOC and Fill factor, as it effectively passivates the defects on the surface of c-Si and increase tunneling probability of minority charge carriers. However, to achieve control over ultra-thin intrinsic a-Si:H layer thickness and passivation properties, the films were deposited by Hot-wire CVD. We used tantalum filament and silane (SiH4) as a precursor gas, where as the deposition parameter such as filament temperature temperature was varied. The deposition rate, Dark and Photoconductivity were measured for all the films. The optimized intrinsic a-Si:H layer was inserted between p typed doped layers and n type c-Si wafers to fabricate HIT solar cells. The Current-Voltage characteristics were studied to understand the passivation effect of intrinsic layer on c-Si surface. The high saturation current density (Jsat > 10–7 A/cm2) and Ideality factor (n > 2) were observed. We achieved the efficiency of 3.28 % with the optimized intrinsic and doped a-Si:H layers using HWCVD technique. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2794

Simulation of brushless direct current machine in ANSOFT Maxwell 3D software environment

Tato práce pojednává o simulaci Brush-less stejnosměrný proud stroj v ANSYS Maxwell - životní prostředí. Stroj je vybrán pro vysoce výkonné elektrického kole jako motor nad (Program OSN pro životní prostředí UNEP) metropolitní jízdního cyklu. Analytická studie sil ovlivňujících stroj spolu s průmyslovými odkazy a literatury vedly k odhadu jmenovitých provozních parametrů. Čtyři modely s 1,500Watt, 380Rpm, 40nm & 48Volt Motor BLDC jsou navrženy a simulovány v modulu RMxprt Maxwell [24 Slot, 36 slot, slot 48, 72 Slot] Tento software umožnil řešení a simulace magneto-statických a přechodových oblastech založené na Maxwellovy rovnice ve 2D a 3D. Řešení sada každého stroje je popsána, a je uvedena v příloze této práce. 2D a 3D analýza odhalí nesrovnalosti ve tvaru vlny vinutí proudů, indukovaných napětí a ztráty 24 Slot a 36 hracích automatů kvůli chybě ve vnitřní konverzní software z 2D na 3D v RMxprt, i polní grafy ukazují abnormálně nízké hustotě magnetického pole ve statoru zubů a vysoký proud ve vinutí velikosti těchto dvou strojů. Mezi 48 a 72 Slot Hrací automaty měly v souladu 2D a 3D křivek vlastnosti, i když překryvy v terénu ukazují, lokalizované horké skvrny magnetické hustoty pole v sekcích statoru. Celkově 72 Automatu nejlépe hodí pro danou aplikaci.This thesis is about the simulation of a Brush-Less Direct Current Machine in the ANSYS - Maxwell Environment. The machine is selected for a high-performance electric-bike as a motor over the UNEP (United Nations Environment Program) metropolitan drive cycle. Analytical study of the forces influencing the machine along with industry references and literature review led to estimation of rated operating parameters. Four models of a 1,500Watt, 380Rpm, 40Nm & 48Volt BLDC Motor are designed and simulated in the RMxprt module of Maxwell [24 Slot, 36 Slot, 48 Slot, 72 Slot] The software enabled solving and simulation of magneto-static and transient fields based on Maxwell's equations in 2D & 3D. The solution set of each machine is described and tabulated in the appendix of this thesis. 2D and 3D analysis reveals inconsistencies in the waveform of winding currents, induced voltages and losses of 24 Slot and 36 Slot Machines due to an error in the internal software conversion from 2D to 3D in RMxprt, also the field plots show abnormally low magnetic field density in stator teeth and high current magnitude in the winding of these two machines. The 48 Slot and 72 Slot machines had consistent 2D and 3D waveform characteristics although field overlays show localized hot spots of magnetic field density in the stator sections. Overall the 72 Slot machine suits best for the given application

Study of Electrical, Optical and Structural Properties of Al- Doped ZnO Thin Films on PEN Substrates

Aluminum-doped zinc oxide (AZO), as one of the most promising transparent conducting oxide (TCO) material, has now been widely used in thin film solar cells. Most of the study of AZO films till date has been done on glass substrates but nowadays there is a growing interest in replacing glass with polymer substrate for the thin-film solar cell technology and many other flexible optoelectronic devices. In this study, AZO thin films were deposited at room temperature by RF magnetron sputtering on flexible substrates from a 3 inch diameter target of 2 wt % Al2O3 in zinc oxide. The effect of RF power on the structural, optical and electrical properties of AZO films was investigated by X-ray Diffraction (XRD), Hall measurement, and UV-visible spectrophotometery. The XRD data indicates a preferential c-axis orientation for all the films. All films exhibit high transmittance ( 85%) in visible region. Films deposited at 60 W power exhibit lowest resistivity of 1.2 10 – 3 Ωcm. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3102

Effect of biosurfactants on Pseudomonas aeruginosa and Staphylococcus aureus biofilms in a BioFlux channel.

Recent studies have indicated that biosurfactants play a role both in maintaining channels between multicellular structures in biofilms and in dispersal of cells from biofilms. A combination of caprylic acid (0.01 % v/v) together with rhamnolipids (0.04 % v/v) was applied to biofilms of Pseudomonas aeruginosa ATCC 15442, Staphylococcus aureus ATCC 9144 and a mixed culture under BioFlux flowthrough conditions and caused disruption of the biofilms. The biofilms were also treated with a combination of rhamnolipids (0.04 % v/v) and sophorolipids (0.01 %). Control treatments with PBS 1× had no apparent effect on biofilm disruption. The Gram-positive bacterium (S. aureus ATCC 9144) was more sensitive than P. aeruginosa ATCC 15442 in terms of disruption and viability as shown by Live/Dead staining. Disruption of biofilms of P. aeruginosa ATCC 15442 was minimal. Oxygen consumption by biofilms, after different treatments with biosurfactants, confirms that sophorolipid on its own is unable to kill/inhibit cells of P. aeruginosa ATCC 15442, and even when used in combination with rhamnolipids, under static conditions, no decrease in the cell viability was observed. Cells in biofilms exposed to mono-rhamnolipids (0.04 % v/v) showed behaviour typical of exposure to bacteriostatic compounds, but when exposed to di-rhamnolipids (0.04 % v/v), they displayed a pattern characteristic of bactericidal compounds

Disruption of Yarrowia lipolytica biofilms by rhamnolipid biosurfactant

BACKGROUND: Yarrowia lipolytica is an ascomycetous dimorphic fungus that exhibits biofilm mode of growth. Earlier work has shown that biosurfactants such as rhamnolipids are efficient dispersants of bacterial biofilms. However, their effectiveness against fungal biofilms (particularly Y. lipolytica) has not been investigated. The aim of this study was to determine the effect of rhamnolipid on a biofilm forming strain of Y. lipolytica. Two chemical surfactants, cetyl-trimethyl ammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) were used as controls for comparison. RESULTS: The methylene blue dye exclusion assay indicated an increase in fungal cell permeability after rhamnolipid treatment. Microtiter plate assay showed that the surfactant coating decreased Y. lipolytica biofilm formation by 50%. Rhamnolipid treatment disrupted pre-formed biofilms in a more effective manner than the other two surfactants. Confocal laser scanning microscopic studies showed that biofilm formation onto glass surfaces was decreased by 67% after sub-minimum inhibitory concentration (sub-MIC) treatment with rhamnolipids. The disruption of biofilms after rhamnolipid treatment was significant (P<0.05) when compared to SDS and CTAB. CONCLUSION: The results indicate a potential application of the biological surfactant to disrupt Y. lipolytica biofilms

Katti-Batti : a digital tool for young adolescents to transgress the limitations of gender socialization through empathy & friendship

The genesis of this project lies in the personal experiences that led me to believe that the culturally learned and perceived gender roles, norms, and expectations limit a person’s health, educational, professional, economic, and social abilities. The work began by finding the evidence connecting the learned, perceived gender roles, norms, and allied cultural expectations to the ability to think freely. The research revealed the limiting effects of gender roles and norms on self-identity, personal belief systems, and a place’s culture. The study further led to uncovering the link between limiting personal belief systems and cultural environment to the lack of openness of a person to receive new knowledge and ideas. This lack of openness was then identified to impair an individual’s decision-making ability, which ultimately negatively affects the ability to self-actualize. Gender Socialization was identified as a fundamental process that leads to the exposure, development, adoption, and conformity to the limiting gender roles, norms, stereotypes, and expectations. Research and expert consultations led to identifying continuous consciousness-raising about gender socialization and stereotype conformity as an efficacious strategy to break the gendered lenses. The early adolescence (12-15 yr.) age group was identified as a window of opportunity to mitigate the effects of gender socialization because of the physical, cognitive, and behavioral changes that occur at this age. In response to this opportunity, initial concept development, prototyping, and testing of a digital tool intended to evoke thought on the topic were accomplished. The tool is designed with the intention to make a complex subject matter accessible and relatable to young adolescents. The goal is to help them reflect on their own biases and gradually become aware of the effects of gender socialization on their choices and decision-making. The emotions of friendship and empathy are used as vehicles to highlight the significance of breaking deeply gendered outlooks

Structure and strain relaxation effects of defects in In<inf>x</inf>Ga<inf>1-x</inf>N epilayers

The formation of trench-defects is observed in 160 nm-thick InxGa1-xN epilayers with x ≤ 0.20, grown on GaN on (0001) sapphire substrates using metalorganic vapour phase epitaxy. The trench-defect density increases with increasing indium content, and high resolution transmission electron microscopy shows an identical structure to those observed previously in InGaN quantum wells, comprising meandering stacking mismatch boundaries connected to an I1-type basal plane stacking fault. These defects do not appear to relieve in-plane compressive strain. Other horizontal sub-interface defects are also observed for these samples and are found to be pre-existing threading dislocations which form half-loops by bending into the basal-plane, and not basal-plane stacking faults, as previously reported by other groups. The origins of these defects are discussed, and are likely to originate from a combination of the small in-plane misorientation of the sapphire substrate and the thermal mismatch strain between the GaN and InGaN layers grown at different temperatures.This work was funded in part by the Cambridge Commonwealth trust and the EPSRC. SKR is funded through the Cambridge-India Partnership Fund and Indian Institute of Technology Bombay via a scholarship. SKR also acknowledges funds from St. John’s College. MAM acknowledges support from the Royal Society through a University Research Fellowship.This is the accepted manuscript version. The final version is available from AIP at http://scitation.aip.org/content/aip/journal/jap/116/10/10.1063/1.4894688

Segregation of in to dislocations in InGaN

Dislocations are one-dimensional topological defects that occur frequently in functional thin film materials and that are known to degrade the performance of InxGa1-xN-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure are expected to occur in and around dislocation cores in InxGa1-xN alloy thin films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films

Generation, Verification, and Attacks on Elliptic Curves and their Applications in Signal Protocol

Elliptic curves (EC) are widely studied due to their mathematical and cryptographic properties. Cryptographers have used the properties of EC to construct elliptic curve cryptosystems (ECC). ECC are based on the assumption of hardness of special instances of the discrete logarithm problem in EC. One of the strong merits of ECC is providing the same cryptographic strength with smaller key size compared to other public key cryptosystems. A 256 bit ECC can provide similar cryptographic strength as a 3072 bit RSA cryptosystem. Due to smaller key sizes, elliptic curves are an attractive option in devices with limited storage capacity. It is therefore essential to understand how to generate these curves, verify their correctness and assure that they are resistant against attacks. The security of an EC cryptosystem is determined by the choice of the curve that is used in that cryptosystem. Over the years, a number of elliptic curves were introduced for cryptographic use. Elliptic curves such as FRP256V1, NIST P-256, Secp256k1 or SM2 curve are widely used in many applications like cryptocurrencies, transport layer protocol and Internet messaging applications. Another type of popular curves are Curve25519 introduced by Dan Bernstein and Curve448 introduced by Mike Hamburg, which are used in an end to end encryption protocol called Signal. This protocol is used in popular messaging applications like WhatsApp, Signal Messenger and Facebook Messenger. Recently, there has been a growing distrust among security researchers against the previously standardized curves. We have seen backdoors in the elliptic curve cryptosystems like the DUAL_EC_DRBG function that was standardized by NIST, and suspicious random seeds that were used in NIST P-curves. We can say that many of the previously standardized curves lack transparency in their generation and verification. We focus on transparent generation and verification of elliptic curves. We generate curves based on NIST standards and propose new standards to generate special types of elliptic curves. We test their resistance against the known attacks that target the ECC. Finally, we demonstrate ECDLP attacks on small curves with weak structure

A Novel Techniques for Classification of Musical Instruments

Musical instrument classification provides a framework for developing and evaluating features for any type of content-based analysis of musical signals. Signal is subjected to wavelet decomposition. A suitable wavelet is selected for decomposition. In our work for decomposition we used Wavelet Packet transform. After the wavelet decomposition, some sub band signals can be analyzed, particular band can be representing the particular characteristics of musical signal. Finally these wavelet features set were formed and then musical instrument will be classified by using suitable machine learning algorithm (classifier). In this paper, the problem of classifying of musical instruments is addressed.  We propose a new musical instrument classification method based on wavelet represents both local and global information by computing wavelet coefficients at different frequency sub bands with different resolutions. Using wavelet packet transform (WPT) along with advanced machine learning techniques, accuracy of music instrument classification has been significantly improved. Keywords: Musical instrument classification, WPT, Feature Extraction Techniques, Machine learning techniques