Micro/Nano Structured Materials for Enhanced Device Performance and Antibacterial Applications

Micro/nanostructured materials have been used extensively for various applications due to their unique chemical, physical, and mechanical properties. In this thesis we report the fabrication and characterization of micro/nanostructured materials with antibacterial properties. Plastics are used in a wide range of medical components such as prosthetics, implants, catheters, and syringes. However, contaminating bacteria can attach to plastic surfaces and grow and form biofilms that lead to healthcare associated infections. The consequences on patients and their families are serious, as infections can extend hospital stays, create long-term disability, increase healthcare costs, and even result in unnecessary deaths. Two strategies for creating antibacterial surfaces are (1) anti-biofouling surfaces that make the bacterial attachment process difficult and (2) bactericidal surfaces that kill bacteria cells that come in proximity of or contact the surface. We demonstrate that a fluorine etch chemistry may be utilized to create lotus leaf-inspired, low surface energy, hierarchical micro-structure/nanofibrils in Polypropylene (PP). Our anti-biofouling PP surfaces exhibit a 99.6% reduction of E. coli cell adhesion compared to untreated PP. We also fabricated bactericidal surfaces consisting of uniform and regular nanostructured arrays. The interest in mechanical bactericidal effect has recently increased, as the bacteria cells grow drug resistance. Nanosphere lithography and combination of reactive ion etching and deep reactive ion etching were utilized to prepare these substrates. The pitch, diameter, taper, and height of the nanostructures are controlled. The bactericidal effect of these structures is investigated and significant enhancement in killing is observed. We also report fabrication of micro/nanostructured materials to improve device performance. Our simulation results show that absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays over a broad range of tilt angles. The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% of the ideal double pass thin film. Incorporation of these structures could improve the efficiency of solar cells

Estimation of Optimum Number of Poles for Random Signal by Yule-Walker Method

The Yule-Walker method is an effective method to estimate the system response or spectrum for random signal. Hence most of the noise and spurious signals are random in nature, so it is very convenient to estimate their spectrum by Yule-Walker method successfully. The Yule-Walker method is an autoregressive process to estimate the poles and errors also based on the number of poles for Wide Sense Stationary (WSS) process as well. Moreover the value of zero will be correspondingly calculated based on the poles in case of all poles model. The main concern of this paper is to analyze the Yule-Walker method and estimate the poles and zero along with the error based on the number of poles for a random signal. Moreover analyze the results to find out the optimum number of poles for least possible error

Biochar benefits green infrastructure: a global meta-analysis and synthesis

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Modeling of Wrong Way Driving Entries and Developing Innovative Approaches for Evaluating the Effectiveness of Advanced Wrong Way Driving Countermeasures

Wrong-way driving (WWD) is a hazardous behavior on interstates, toll roads, and other high-speed limited access facilities. Since WWD crashes are rare, recent researchers have studied WWD events such as WWD 911 calls and WWD citations to understand the overall nature and trend of WWD. It is very difficult to build credible statistical models based solely on crashes due to the small sample size since these are only 3% of all crashes. Modeling of WWD non-crash events can result in more accurate models. A model was developed for Florida limited access facilities to identify roadway factors and traffic characteristics of exit ramp terminals that influence WWD entries. This model indicated that interchange type, intersection angle of exit ramp terminals, presence of tolling at the entrance ramp, presence of channelizing island between the exit ramp lanes, number of lanes on the exit ramp, area (rural or urban), and traffic volumes significantly affect the likelihood of WWD entries at exit ramps. Conventional Wrong Way signs can reduce WWD incidents but can be insufficient in some cases. In areas with many WWD crash and non-crash events, transportation agencies can be proactive by considering the use of countermeasures with advanced technologies to actively warn motorists of WWD violations. To help agencies select the most effective countermeasure, two innovative evaluation of performance approaches were developed so they can be used to evaluate and compare among different advanced WWD countermeasures. These approaches consist of before-after analysis of WWD non-crash events (WWD 911 calls and citations) and turn around rates of wrong way vehicles to self-correct their WWD acts. With this research, transportation agencies can better predict WWD entries at exit ramps; identify suitable locations for possible countermeasures deployment; and improve their current design, signing, and pavement marking practices while still following national and state standards

Content Abuse and Privacy Concerns in Online Social Networks

Online Social Networks (OSNs) have seen an exponential growth over the last decade, with Facebook having more than 1.49 billion monthly active users and Twitter having 135,000 new users signing up every day as of 2015. Users are sharing 70 million photos per day on the Instagram photo-sharing network. Yahoo Answers question-answering community has more than 1 billion posted answers. The meteoric rise in popularity has made OSNs important social platforms for computer-mediated communications and embedded themselves into society’s daily life, with direct consequences to the offline world and activities. OSNs are built on a foundation of trust, where users connect to other users with common interests or overlapping personal trajectories. They leverage real-world social relationships and/or common preferences, and enable users to communicate online by providing them with a variety of interaction mechanisms. This dissertation studies abuse and privacy in online social networks. More specifically, we look at two issues: (1) the content abusers in the community question answering (CQA) social network and, (2) the privacy risks that comes from the default permissive privacy settings of the OSNs. Abusive users have negative consequences for the community and its users, as they decrease the community’s cohesion, performance, and participation. We investigate the reporting of 10 million editorially curated abuse reports from 1.5 million users in Yahoo Answers, one of the oldest, largest, and most popular CQA platforms. We characterize the contribution and position of the content abusers in Yahoo Answers social networks. Based on our empirical observations, we build machine learning models to predict such users. Users not only face the risk of exposing themselves to abusive users or content, but also face leakage risks of their personal information due to weak and permissive default privacy policies. We study the relationship between users’ privacy concerns and their engagement in Yahoo Answers social networks. We find privacy-concerned users have higher qualitative and quantitative contributions, show higher retention, report more abuses, have higher perception on answer quality and have larger social circles. Next, we look at users’ privacy concerns, abusive behavior, and engagement through the lenses of national cultures and discover cross-cultural variations in CQA social networks. However, our study in Yahoo Answers reveals that the majority of users (about 87%) do not change the default privacy policies. Moreover, we find a similar story in a different type of social network (blogging): 92% bloggers’ do not change their default privacy settings. These results on default privacy are consistent with general-purpose social networks (such as Facebook) and warn about the importance of user-protecting default privacy settings. We model and implement default privacy as contextual integrity in OSNs. We present a privacy framework, Aegis, and provide a reference implementation. Aegis models expected privacy as contextual integrity using semantic web tools and focuses on defining default privacy policies. Finally, this dissertation presents a comprehensive overview of the privacy and security attacks in the online social networks projecting them in two directions: attacks that exploit users’ personal information and declared social relationships for unintended purposes; and attacks that are aimed at the OSN service provider itself, by threatening its core business

Frequency combs for spectroscopy and optical metrology

Since their inception, optical frequency combs have created novel avenues for numerous applications such as molecular spectroscopy, atomic clocks, coherent communications, and microwave photonics. The future of frequency combs lies in exploring different comb generation technique, customized for specific applications. This thesis explores the synthesis of novel optical frequency combs in the near infrared wavelength region and the applications of such combs in the field of high-resolution spectroscopy and precise distance measurement. First, the generation of an electro-optic frequency comb with adjustable central wavelength and frequency spacing is experimentally demonstrated. This frequency comb is sourced from a single mode Brillouin fiber laser having an ultra-narrow linewidth that improves the overall phase noise performance of the comb spectral lines. A combined effect of electro-optic modulation, dispersion compensation, and fiber nonlinearity convert the continuous wave laser into a wideband optical frequency comb encompassing the C-band. Next, this frequency comb is used for a high-resolution distance measurement system that operates from the repetition rate modulation of the comb signal. The repetition frequency of the electro-optic comb is adjustable with a high dynamic range. Such broad tunablity of the repetition rate facilitates the measurement of distances with µm level precision. Such a system is also capable of motion tracking thanks to the rapid scan rate of the repetition frequency. Next, the application of electro-optic combs in high-resolution Fourier transform spectroscopy is demonstrated by measuring absorption lines of a chemical sample at 1.55 µm. The pulse train from a frequency comb, subject to a repetition rate modulation, stores the spectral response of a sample when sent to a length imbalanced interferometer. Such a system is equivalent to a dual-comb spectrometer but without the need for a complex phase matching mechanism. Finally, a novel laser resonator is developed for high-resolution dual-comb spectroscopy at 1.9 µm. This resonator supports two counter-propagating laser oscillations sharing a common cavity which relaxes the phase matching requirement for dual-comb spectroscopy. A proof-of-concept experiment demonstrated the measurement of absorption lines of ambient water vapor with a 100 MHz resolution. This approach holds great promise for dual-comb spectroscopy in the mid-infrared region where many chemicals have strong fundamental transitions.Depuis leur tout début, les peignes de fréquences optiques ont pavé la voie à de nombreuses applications tel que la spectroscopie moléculaire, les horloges atomiques, les communications cohérentes ainsi que la photonique appliquée aux micro-ondes. L’avenir des peignes de fréquences se trouve dans l’exploration de différentes techniques de génération de peignes spécialisés pour des applications spécifiques. Cette thèse explore la synthèse de nouveaux peignes de fréquences optiques dans l’infrarouge proche, ainsi que les applications de ces peignes dans le domaine de la spectroscopie à haute résolution et la mesure de distances de haute précision. En premier lieu, la génération d’un peigne de fréquence électro-optique à longueur d’onde centrale ajustable et à espacement de fréquence est démontré expérimentalement. Ce peigne de fréquence provient d’un laser à fibre Brillouin monomode à bande très étroite qui permet d’améliorer la performance globale du bruit de phase des lignes spectrales du peigne. Un effet combiné de la modulation électro-optique, de la compensation de la dispersion et de la non linéarité de la fibre convertit le laser à bande continue à un peigne de fréquence optique large bande englobant la bande C des télécommunications. Par la suite, ce peigne de fréquence est utilisé pour un système de mesure de distance haute résolution qui opère à partir de la modulation du taux de répétition du signal du peigne. La fréquence de répétition du peigne électro-optique est ajustable avec une plage dynamique élevée. Ceci permet de faciliter la mesure de distances avec un niveau de précision de l’ordre du micromètre. Un tel système est également capable de suivre le mouvement grâce au taux de balayage rapide de la fréquence de répétition. En deuxième lieu, l’application d’un peigne électro-optique dans la spectroscopie haute résolution par transformation de Fourier est démontrée par la mesure des lignes d’absorption d’un échantillon chimique à 1.55 µm. Le train d’impulsions d’un peigne à fréquence, sujet à la modulation du taux de répétition, contient la réponse spectrale d’un échantillon lorsqu’envoyé dans un interféromètre à bras asymétriques. Un tel système est équivalent à un spectromètre double-peigne sans le besoin d’un mécanisme d'adaptation de phase complexe. En dernier lieu, un nouveau résonateur laser est développé pour la spectroscopie haute résolution double-peigne à 1.9 µm. Ce résonateur supporte deux oscillations laser contre-propagatrices partageant une cavité commune. Cela permet d’assouplir l'exigence relative à l'adaptation de phase pour la spectroscopie double-peigne. Une preuve de concept a permis de démontrer la mesure des lignes d’absorption de la vapeur d’eau ambiante avec une résolution de 100 MHz. Cette approche s’avère très prometteuse pour la spectroscopie double-peigne dans l’infrarouge moyen où de nombreuses substances chimiques ont de fortes transitions fondamentales

Net-metering and Feed-in-Tariff policies for the optimum billing scheme for future industrial PV systems in Bangladesh

In this paper, the economic sustainability of net billing and feed-in-tariff (all energy buy/sell) method is analyzed in comparison with the current net-metering for the industrial PV systems in Bangladesh. Three billing methods are compared according to plant capacity factor, excess energy transfer, levelized cost of energy (LCOE), net present value (NPV), payback period, and profitability index (PI) for the analysis of optimum billing scheme. The highest plant capacity factor and minimum LCOE are found for the large PV system in Chattogram. Out of three methods, all energy buy/sell exhibits the NPV which is USD 5.85 million and PI of 2.54 at the minimum 4.9 years discounted payback time for the large PV system in Chattogram. The sensitivity analysis of solar irradiation at six other regional areas, bill escalation rate, and discount factor is performed to observe the impact on annual energy production and NPV. For both systems, all three assessed methods are found economically feasible, but the net metering is attained as the least profitable in comparison with net billing and all energy buy/sell schemes. From various analyses, it is found that the adaption of these two schemes in the present guideline can enhance industrial PV production in Bangladesh

SPECKLE NOISE REDUCTION FROM MEDICAL ULTRASOUND IMAGES USING WAVELET THRESHOLDING AND ANISOTROPIC DIFFUSION METHOD

ABSTRACT Medical Images are very often corrupted by various types of noise including speckle noise, salt and pepper noise etc. This corruption of noise is introduced to the original image during image acquisition and transmission. The various image denoising techniques that are proposed from time to time are offering denoising techniques preserving the original image features. The denoising is so important because ultrasound imaging today has gained wide acceptance due to its safety, easy imaging procedure, low cost and adaptability. However the main shortcomings of this process is poor quality of images which is further degraded due to the presence of speckle noise and other types of noise. Hence it has become vital to remove noise while preserving important datails and features of the image. This paper will introduce a unique method to speckle noise filtering using median filters, wavelet and SRAD filters

Analysis Of Performance Data Collected From Two Wrong-Way Driving Advanced Technology Countermeasures And Results Of Countermeasures Stakeholder Surveys

Wrong-way driving (WWD) often leads to severe collisions that cause serious injuries and deaths. Conventional “Wrong Way” signs can reduce WWD events, but can be insufficient in some cases. In areas with many WWD events, transportation agencies can be proactive by considering the use of countermeasures with advanced technologies to actively warn motorists of WWD violations. This paper analyzes recent performance data collected from two types of advanced technology WWD countermeasures implemented in Florida: light-emitting diode (LED) signs in South Florida and rectangular flashing beacon (RFB) signs in Central Florida. The 17 LED sites experienced a 38% reduction in WWD citations and 911 calls after the signs were installed. Images taken by the on-site cameras were examined to see how many vehicles turned around for both the RFB and LED treatment sites. Over 77% of the 170-detected wrong-way vehicles self-corrected their wrong-way movement at the RFB sites (each with two sets of signs and multiple cameras) and 14% self-corrected at the LED sites (each with one set of signs and one camera). Surveys were also conducted regarding these two WWD countermeasures. More than 73% of the 2,052 respondents preferred RFBs over LEDs, mainly due to the double set of RFB signs and their flashing pattern. The performance and survey results show that both the LEDs and RFBs have effectively reduced WWD movements. However, modifications could be made to both countermeasures to improve their detection ability and make wrong-way drivers more likely to turn around