Motion Space Analysis of Smooth Objects in Point Contacts

The present work studies instantaneous motion of smooth planar and spatial objects in unilateral point contacts. The traditional first-order instantaneous kinematic analysis is found insufficient to explain many common physical scenarios. The present work looks beyond the velocity state of motion for a comprehensive understanding through higher-order kinematic analysis of the above system. The methodology proposed herein is a Euclidean space approach to second-order motion space analysis of objects in point contacts. The geometries of the objects are approximated up to second-order in the differential vicinity of the point of contact; meaning, up to curvature at the point of contact. The instantaneous motion is approximated up to second-order kinematics, i.e., up to acceleration state. The basic approach consists of impressing an instantaneous motion upon one object while holding the other fixed which is in a single point contact initially, and observing for one of the following three states: penetration, separation, and persistence of contact between the two objects. These three states are characterized by the interference between the geometries of the objects. Penetration and separation of two curves for rotation about points on the plane is geometrically studied based on the relative configuration of the osculating circles at the point of contact. It is shown that the plane is partitioned into four regions of rotation centers. Partitioning of the plane into motion space regions at a contact provided a geometrical framework compose the motion space for multiple contacts. The applications include second-order form-closure (SFC) and synthesis of kinematic pairs. To explore the consequence of a generic motion, an analytical scheme is formulated using the screw theoretic concepts of twist and twist-derivative. It is shown that the characteristics of second-order motions at a single contact depends only upon the geometric kinematic properties of the motion; meaning, the motion characteristics are time-independent. The geometric conditions for the second-order motion that will be admissible or restrained at a contact are not available in the existing literature on \second-order mobility". The classical Euler-Savary equation for enveloping curves is found to represent the condition which is both necessary and sufficient for the second-order roll-slide motion. An elegant generalized geometric characterization of second-order motions is derived. This is made use for deriving condition of immobilization of, planar mechanisms with up to 2-degrees-of-freedom (d.o.f.), with a single point contact. Illustrative examples of four-bar and 2R-mechanisms are presented. Rapid prototyped model of the four-bar mechanism is fabricated and the SFC theory is verified satisfactorily. Through a novel use of Meusnier's theorem, rotational motion characteristics of planar curves in a point contact is used to determine the patterns and distribution of admissible axes of rotation in space for two surfaces in a single point contact. In the generalized analytical method of motion space analysis, the surfaces are locally represented in Monge's form up to second-order terms and motion is represented using twist and twist-derivative. An analytical framework for the second-order motion space analysis of surfaces with multiple contacts has been developed. Using this procedure, pairs of objects are analyzed for SFC and equivalent lower kinematic pair freedom. Revolute and planar joints with two contacts, prismatic joint with three contacts, SFC of regular concave spherical tetrahedron and regular tetrahedron with four contacts are demonstrated. Although conventional first-order studies demand seven contact points for form-closure, within the context of second-order motion, the present study established that, under special geometric conditions relative immobilization of two smooth objects can be enabled with much fewer contacts. Conditions for immobilization using three and two smooth contacts have been derived. Using contact kinematics equations based on higher-order reciprocity, an instantaneous spatial higher pair to lower pair substitute-connection which is kinematically equivalent up to acceleration analysis for two smooth surfaces in persistent point contact is derived. An illustrative example of a three-link direct-contact mechanism is presented

Mechanisms of Dopaminergic Neurodegeneration in Parkinson's Disease

Parkinson’s disease (PD) is a debilitating movement disorder. The cardinal symptoms of PD are bradykinesia, resting tremors and rigidity. PD is characterized by degeneration of dopaminergic neurons of A9 region, substantia nigra pars compacta (SNpc) and loss of dopaminergic terminals in striatum while the dopaminergic neurons of A10 region, ventral tegmental area (VTA) are relatively protected. Putative mechanisms, such as mitochondrial dysfunction, dysregulation of the ubiquitin proteasome system and increased oxidative stress have been hypothesized to mediate PD pathology. However, precise mechanisms that underlie selective vulnerability of SNpc dopaminergic neurons to degeneration are unknown. The aim of this thesis was to evaluate the pathological mechanisms that may contribute to degeneration of SNpc dopaminergic neurons in PD. Dopaminergic neurons of SNpc are pacemakers and constant calcium entry through L-type calcium channel, Cav1.3 has been reported in these neurons during pacemaking. In addition, these neurons have poor calcium buffering capacity. Together, this leads to dysregulation of calcium homeostasis in the SNpc dopaminergic neurons leading to increased oxidative stress. Gene expression of the full length channel and the variant was investigated in the mouse midbrain and further their presence was verified in mouse SNpc and VTA and also in SNpc and VTA in the MPTP mouse model of PD. Gene expression of Cav1.3 -42 and its variant was also studied in SNpc from autopsy tissue from PD patients and age matched controls. Having studied differential expression of the calcium channels, global changes in gene expression in SNpc from the MPTP mouse model of PD and PD autopsy tissues were next examined. This is the first report of transcriptome profile alterations from SNpc in mouse model and PD tissue performed using RNA-seq. Gene expression profiles were examined from SNpc 1 day post single exposure to MPTP, in which case there is no neuronal death and 14 days after daily MPTP treatment where SNpc has undergone ~50% cell death. Further, RNA- seq was performed to study gene expression alterations in SNpc from human PD patients and age- matched controls. The RNA-seq data was taken through extensive analyses; analysed for differential gene expression, gene-set enrichment analysis, pathway analysis and network analysis. Glutaredoxin 1 (Grx1) is a thiol disulfide oxidoreductase that catalyses the deglutathionylation of proteins and is important for regulation of cellular protein thiol redox homeostasis. Down-regulation of Grx1 has been established to exacerbate neurodegeneration through impairment of cell survival signalling. Previous work from our laboratory has demonstrated that perturbation of protein thiol redox homeostasis through diamide injection into SNpc leads to development of PD pathology and motor deficits. It was therefore investigated if Grx1 down-regulation in vivo, leading to increased glutathionylation and protein thiol oxidation, could result in PD pathology. This work is thus the first study of RNA-seq based transcriptomic profile alterations in SNpc from human PD patients. This work also highlights several differences between mouse model and human PD tissue indicating that the underlying mechanisms of PD pathogenesis differ from mouse to humans in addition to developing a novel model for PD

Development of Photoactive and Photoelectroactive Nanomaterials for Water Remediation

Water pollution has become an environmental catastrophe due to the rapid urbanization. The treatment of dumping of waste chemicals in water bodies has contributed to the increase in pollution. In addition to the pollution caused by waste chemicals, faecal bacteria such as Escherichia, Staphylococcus, Pseudomonas etc., can cause serious health issues. Techniques such as filtration and chlorination provide clean water but are associated with disadvantages such as toxic by-products. Although clean water can be still obtained by these techniques, the development of resistance by microorganisms with such conventional treatments of antibiotics is inevitable and poses a new threat. Various researches have taken place in the past few decades to provide clean drinking water. Photocatalysis is considered to be a promising viable alternative for the existing methods to solve the menace of water pollution. It is an advanced oxidation process where the reactive oxygen species are generated by using nanomaterials that can cause degradation of chemicals and pathogens. Particularly, photocatalysis using semiconductors and their composites have been tested for their use in the destruction of contaminants. Several methods have been used in the synthesis of nanomaterials and the variations in their morphologies have resulted in different applications such as photocatalysis and electrocatalysis. Among all semiconductors, TiO2 has been widely used in this application owing to their non-toxicity and abundance in availability. However, TiO2 can be activated only in the presence of UV light. Therefore, the formation of heterojunctions, doping of metals/no- metals in TiO2 has enabled the activation of TiO2 in the visible region. The former approach has also been studied with ceria and silver salts combination. Besides conventional metal oxides, other transitional metal oxides such as copper oxide and bismuth oxide have also been studied owing to its conducting property and facile growth on substrates respectively for enhanced photocatalysis. All the above tweaking has enabled efficient charge separation, band gap reduction, and prevention of recombination. In this thesis, all the nanomaterials and their composites have been synthesized using simple methods such as solution combustion, hydrothermal, solution co-precipitation, and chemical deposition. The primary aim of this thesis is to synthesize various effective nanomaterials with different morphologies, bandgap engineered nanocomposites, metal or non-metal doped metal oxides for efficient waste water treatment of dyes, antibiotics, phenols, and bacteria. Besides, relying on photocatalytic ability, the photoconductivity and intrinsic conducting properties of nanomaterials were exploited to perform photoelectrocatalysis that enhances the rate of decontamination to several orders than photocatalysis. In addition to focusing on increasing the rate of degradation, the main drawback of photocatalysis which is catalyst retrieval has been overcome using conducting substrates and nanomaterial coated substrates for efficient photocatalytic and photoelectrocatalytic decontamination of waste water. All the structural, morphological, chemical and optical properties were thoroughly studied using various characterization techniques such as XRD, SEM, TEM, XPS, UV-DRS, PL respectively. The rate kinetics of dye, antibiotic and phenol degradation was examined. Experimental data was tested with the proposed model in the case of photoelectrocatalytic degradation. The photocatalysts were also studied for its reusability for many cycles. All the proposed works have analyzed the reason for the enhanced activity by performing scavenger reactions to determine the responsible reactive oxygen species. Thus, this thesis exhibits a thorough understanding of how to design and engineer nanomaterials for photocatalytic and photoelectrocatalytic water remediation. The following are the chapters discussed in this thesis. Chapter 1 discusses the drawbacks associated with the current waste water treatment methods and the possibilities of photocatalysis to replace the existing treatments. The advantages of certain transition metals, conventional methods of synthesis and various other properties of the nanomaterials have been discussed. Chapter 2 explains the synthesis of TiO2 nanobelts using combustion synthesized TiO2 under UV and solar irradiation. The catalyst has been characterized for its structural, morphological, chemical and optical properties. The degradation of anionic and cationic dyes and their activity against E.coli bacteria have been evaluated. The efficiency of this catalyst has been compared with commercial Degussa P25. This study shows the morphological influence of nanomaterials on photocatalytic activity. Chapter 3 describes the synthesis of Ag3PO4 impregnated combustion synthesized TiO2 nanobelts using co-precipitation technique. The activity of this material has been studied under solar light. The catalyst has been characterized for its structural, morphological, chemical and optical properties. Similar to the previous chapter, the degradation of dyes and the antibacterial activity of this catalyst has been compared with commercial Degussa P25. This study explains the importance of morphology and charge carrier facilitation in the case of heterojunction formation. Chapter 4 explains the synthesis of ceria nanoflakes by solution combustion method using ascorbic acid as fuel and PEG assisted sonochemical method. The catalyst has been characterized for its structural, morphological, chemical and optical properties. The effect of silver salts such as AgBr on ceria/Ag3PO4 under visible region for degradation of dyes and antibacterial activity has been evaluated. This work elucidates the effect of band engineering in the charge carrier dynamics between interfaces of components within the catalysts. Chapter 5 elucidates the synthesis of vanadium, nitrogen co doped TiO2 catalysts for the simultaneous degradation of microbes and antibiotics. The primary aim of this work is to understand whether interstitial or substituted doped nitrogen will be effective in the presence of vanadium. The photoactivity of this novel catalyst was studied for its synergistic degradation of antibiotics and bacteria simultaneously towards the prevention of microbial resistance towards antibiotics. Chloramphenicol and E.coli were subjected to photodegradation under visible light. Chapter 6 explains the synthesis of copper oxide based nanomaterial for antibiotic and bacterial degradation by photoelectrocatalysis. In order to enhance the rate of photodegradation, photocatalysis has been upgraded with the application of a potential to photocatalytic systems that possess better charge conducting capability. Highly network like copper oxide has been synthesized using conventional combustion synthesis method and compared with copper oxide nanorods synthesized by hydrothermal method. The rate kinetics of photocatalytic and photoelectrocatalytic degradation of antibiotics has been examined thoroughly and validated based on a cyclic network model. This work demonstrates the synergistic rate enhancing capacity upon combining photocatalysis and electrocatalysis. Chapter 7 discusses the fabrication of Cu/CuO/FTO (fluorine doped tin oxide) based substrates for bacterial degradation. Considering the difficulties in photocatalyst retrieval processes and realizing the importance of electrocatalysis, conducting substrates such as Cu strip, FTO were subjected to antibacterial treatment. Formation of copper oxide onto copper strip during the course of reaction forced us to develop CuO/Cu and CuO/FTO interfaces to examine the photocatalytic and photoelectrocatalytic killing of E.coli. Chapter 8 investigates the fabrication of Bi2O3/Ag based material for photocatalytic and photoelectrocatalytic degradation for phenols and substituted phenols. This work starts with fabrication of Bi2O3 working electrodes by chemical deposition. Photodegradation experiments were conducted under UV irradiation and enhancement of the rate of degradation was observed when the working electrode was deposited with silver nanoparticles via chemical reduction method. Formation of the intermediate Bi(OH)x on Bi2O3 or Bi2O3/Ag has resulted in better hydroxyl radical generation upon excitation. Similarly, surface plasmon resonance due to silver nanoparticles was found to be responsible for augmentation in degradation efficiency of phenol. Chapter 9 briefly summarizes the work and provides future directions. The research work thus attempts to design and engineer photocatalytic nanomaterials that are better than the existing materials and emphasizes the importance towards water remediation

Phase Retrieval and Hilbert Integral Equations – Beyond Minimum-Phase

The Fourier transform (spectrum) of a signal is a complex function and is characterized by the magnitude and phase spectra. Phase retrieval is the reconstruction of the phase spectrum from the measurements of the magnitude spectrum. Such problems are encountered in imaging modalities such as X-ray crystallography, frequency-domain optical coherence tomography (FDOCT), quantitative phase microscopy, digital holography, etc., where only the magnitudes of the wavefront are detected by the sensors. The phase retrieval problem is ill-posed in general, since an in nite number of signals can have the same magnitude spectrum. Typical phase retrieval techniques rely on certain prior knowledge about the signal, such as its support or sparsity, to reconstruct the signal. A classical result in phase retrieval is that minimum-phase signals have log-magnitude and phase spectra that satisfy the Hilbert integral equations, thus facilitating exact phase retrieval. In this thesis, we demonstrate that there exist larger classes of signals beyond minimum-phase signals, for which exact phase retrieval is possible. We generalize Hilbert integral equations to 2-D, and also introduce a variant that we call the composite Hilbert transform in the context of 2-D periodic signals. Our first extension pertains to a particular type of parametric modelling of 2-D signals. While 1-D minimum-phase signals have a parametric representation, in terms of poles and zeros, there exists no such 2-D counterpart. We introduce a new class of parametric 2-D signals that possess the exact phase retrieval property, that is, their magnitude spectrum completely characterizes the signal. Starting from the magnitude spectrum, a sequence of non-linear operations lead us to a sum-of-exponentials signal, from which the parameters are computed employing concepts from high-resolution spectral estimation such as the annihilating filter and algebraically coupled matrix-pencil methods. We demonstrate that, for this new class of signals, our method outperforms existing techniques even in the presence of noise. Our second extension is to continuous-domain signals that lie in a principal shift-invariant space spanned by a known basis. Such signals are characterized by the basis combining coefficients. These signals need not be minimum-phase, but certain conditions on the coefficients lead to exact phase retrieval of the continuous-domain signal. In particular, we introduce the concept of causal, delta dominant (CDD) sequences, and show that such signals are characterized by their magnitude spectra. This condition pertains to the time/spatial-domain description of the signal, in contrast to the minimum-phase condition, which is described in the spectral domain. We show that there exist CDD sequences that are not minimum-phase, and vice versa. However, finite-length CDD sequences are always minimum-phase. Our method reconstructs the signal from the magnitude spectrum up to ma-chine precision. We thus have a class of continuous-domain signals that are neither causal nor minimum phase, and yet allow for exact phase retrieval. The shift-invariant structure is applicable to modelling signals encountered in imaging modalities such as FDOCT. We next present an application of 2-D phase retrieval to continuous-domain CDD signals in the context of quantiative phase microscopy. We develop sufficient conditions on the interfering reference wave for exact phase retrieval from magnitude measurements. In particular, we show that when the reference wave is a plane wave with magnitude greater that the intensity of the object wave, and when the carrier frequency is larger than the band-width of the object wave, we can reconstruct the object wave exactly. We demonstrate high-resolution reconstruction of our method on USAF target images. Our final and perhaps the most unifying contribution is in developing Hilbert integral equations for 2-D first-quadrant signals and in introducing the notion of generalized minimum-phase signals for both 1-D and 2-D signals. For 2-D continuous-domain, first-quadrant signals, we establish partial Hilbert transform relations between the real and imaginary parts of the spectrum. In the context of 2-D discrete-domain signals, we show that the partial Hilbert transform does not suffice and introduce the notion of composite Hilbert transform and establish the integral equations. We then introduce four classes of signals (combinations of 1-D/2-D and continuous/discrete-domain) that we call generalized minimum-phase signals, which satisfy corresponding Hilbert integral equations between log-magnitude and phase spectra, hence facilitating exact phase retrieval. This class of generalized minimum-phase signals subsumes the well known class of minimum-phase signals. We further show that, akin to minimum-phase signals, these signals also have stable inverses, which are also generalized minimum-phase signals

Investigations on Stacked Multilevel Inverter Topologies Using Flying Capacitor and H-Bridge Cells for Induction Motor Drives

Conventional 2-level inverters have been quite popular in industry for drives applications. It used pulse width modulation techniques to generate a voltage waveform with high quality. For achieving this, it had to switch at high frequencies and also the switching is between 0 and Vdc. Also additional LC filters are required before feeding to a motor. 3-phase IM is the work horse of the industry. Several speed control techniques have been established namely the V/f control technique and for high performance, vector control is adopted. An electric drive system comprises of a rectifier, inverter, a motor and a load. each module is a topic by itself. This thesis work discusses the novel inverter topologies to overcome the demerits of a conventional 2-level inverter or even the basic multilevel topologies, for an electric drive. The word ‘multilevel’ itself signifies that inverter can generate more than two levels. The idea was first originated by Nabae, Takahashi and Akagi to bring an additional voltage level so that the waveform becomes a quasi square wave. This additional voltage level brought additional benefits in terms of reduced dv/dt and requirement of low switching frequency. But this was not without any cost. The inverter structure is slightly more complicated than a 2-level and also required more devices. But the advantage it gave was superior enough to such an extent that the above topology (popularly known as NPC) has become quite popular in industry. This topology was later modified to equalize the semiconductor losses among switches by replacing the clamping diodes with controllable switches and such topologies are popularly known as Active NPCs (ANPCs) because of the replacement of diodes with active switches. 3-level flying capacitors were then introduced where the additional voltage level is provided using charged capacitors. But this capacitor voltage has to be maintained at its nominal value during the inverter operation. An additional floating capacitor, which is an electrolytic capacitor is needed for this. Increasing the number of electrolytic capacitors reduces the reliability of the inverter drive since they are the weakest link in any inverters and its count has to be kept to the minimum. By using a H-bridge cell in each of the three phases, three voltage levels can be easily obtained.This is commonly known as Cascaded H-bridge (CHB) multilevel inverter. The above three topologies have been discussed with respect to generation of three pole voltage levels and these topologies are quite suited also. A higher number of voltage levels will reduce the switching frequency even lesser and also the dv/dt. On increasing the number of levels further and further, finally the inverter need not do any PWM switching and just generating the levels is sufficient enough for a good quality waveform and also low dv/dt. But when the above topologies are scaled for more than three voltage levels, all of them suffer serious drawbacks which is briefly discussed below. The diode clamped inverter (known as NPC if it is 3-level), when extended to more than three levels suffers from the neutral point balancing issue and also the count of clamping diodes increase drastically. FC inverters, when extended beyond 3-level, the number of electrolytic capacitors increases and also balancing of these capacitors to their nominal voltages becomes complicated. In the case of multilevel CHB, when extended beyond 3-level, the requirement of isolated DC sources also increases. To generate isolated supplies, phase shifting transformer and 8, 12 or 24 pulse diode rectifier is needed which increases the weight , size and cost of the drive. Therefore its application is limited. In this thesis, the aim is to develop a novel method to develop a multilevel inverter without the drawbacks faced by the basic multilevel topologies when scaled for higher number of voltage levels. This is done through stacking the basic or hybrid combination of these basic multilevel topologies through selector switches. This method is experimentally verified by stacking two 5-level inverters through a 2-level selector switch (whose switching losses can be minimized through soft cycle commutation). This will generate nine levels.Generating 9-levels through scaling the basic topologies is disadvantageous, the comparison table is provided in the thesis. This is true for any higher voltage level generation. Each of the above 5-level inverter is developed through cascading an FC with a capacitor fed H-bridge. The device count can be reduced by making the FC-CHB module common to the selector switches by shifting the selector switches between the DC link and the common FC-CHB module. Doing so, reduces the modular feature of the drive but the device count can be reduced. The FFT plot at different frequencies of operation and the switching losses of the different modules-FC, CHB and the selector switches are also plotted for different frequencies of operation. The next step is to check whether this method can be extended to any number of stackings for generation of more voltage levels. For this, a 49-level inverter is developed in laboratory by stacking three 17-level inverters. Each of the 17-level inverter is developed by cascading an FC with three CHBs. When there are 49 levels in the pole voltage waveform, there is no need to do any regular PWM since the output waveform will be very close to a sine wave even without any PWM switching. The technique used is commonly known in literature as Nearest Level Control (NLC). This method of stacking and cascading has the advantage that the FC and the CHB modules now are of very low voltages and the switching losses can be reduced. The switching losses of the different modules are calculated and plotted for different operating frequencies in the thesis. To reduce the voltages of the modules further, a 6-phase machine has been reconfigured as a 3-phase machine, the advantage being that now the DC link voltage requirement is half of that needed earlier for the same power. This further reduces voltages of the modules by half and this allows the switches to be replaced with MOSFETs, improving the efficiency of the drive. This topology is also experimentally verified for both steady state and transient conditions. So far the research focussed on a 3-phase IM fed through a stacked MLI. It can be observed that a stacked MLI needs as many DC sources as the number of stackings. A 6-phase machine apart from reduced DC link voltage requirement, has other advantages of better fault tolerant capability and better space harmonics. They are serious contenders for applications like ship propulsion, locomotive traction, electric vehicles, more electric aircraft and other high power industrial applications. Using the unique property of a 6-phase machine that its opposite windings always draw equal and opposite current, the neutral point (NP) (formed as a result of stacking two MLIs) voltage can be balanced. It was observed that the net mid point current drawn from the mid point can be made zero in a switching interval. It was later observed that with minimal changes, the mid point current drawn from the NP can be made instantaneously zero and the NP voltage deviation is completely arrested and the topology needs only very low capacity series connected capacitors energized from a single DC link. This topology is also experimentally verified using the stacked 9-level inverter topology discussed above but now for 6-phase application and experimental results are provided in the thesis. Single DC link enables direct back to back conversion and power can be fed back to the mains at any desired power factor. All the experimental verification is done on a DSP (TMS320F28335) and FPGA (Spartan 3 XCS3200) platform. An IM is run using V/f control scheme and the above inverter topologies are used to drive the motor. The IGBTs used are SKM75GB123D for the stacked 9-level inverter in the 3-phase and 6-phase experiments. For the 49-level inverter experiment, MOSFETs-IRF260N were used. Both steady state and transient results ensure that the proposed inverter topologies are suitable for high power applications

Assessment of University Technology Transfer Efficiency in the Context of Medical Device Technologies

Data to understand the inventiveness and technology transfer process for medical devices in India is lacking and majority of medical devices are imported. The presence of a medical school in a university system is expected to enhance healthcare inventiveness. Universities with medical schools have 2.5 times more R&D expenditure and productivity than universities without medical schools. Therefore, the presence or absence of medical schools in universities serves as interesting samples for technology transfer analysis. This thesis focuses on medical device inventiveness and technology transfer office efficiencies of American universities. Three sample sets are used. The first is data from 1242 US universities, of which 734 had medical schools, and their Technology Transfer Office (TTO) productivity from years 1999-2008. The second consisted of 5693 medical device patents filed at USPTO by universities worldwide during years 1999-2008, including US universities. The third consisted of 32 cochlear implant university based patents from 7 primary patent classes in USPTO. Universities involved in medical device research (MDU) and universities not involved in medical device research (NMDU) are compared in our study to understand differences in their technology transfer activities. Initially, Social network analysis is used to understand the interrelatedness of technologies in university based research using patent classes. Degree, betweenness and closeness centrality of 32 cochlear implant patents (out of 345 overall filed patents in USPTO including corporate filings), showed the importance of universities’ R&D contribution to the overall evolution of cochlear implant technology. Dynamics in terms of emergence and disappearance of technologies (represented by US patent classes in years 1977 to 2012), are identified. Our study highlights that universities' research focus within medical device research is confined to few technology classes like surgery, drugs and body treating compositions for therapeutic purposes and image analysis. In these technology areas, universities share of patent holding is found to be more compared to other medical device technologies. Multivariate OLS and binary logistic regressions are used to understand university characteristics that influences amount of patenting by universities. Our study attempts to delineate and highlight university characteristics that may influence amount of patenting in general, i.e., across all technologies and specifically those university characteristics that may influence more patenting in medical device technologies. Our study establishes that university characteristic variables like age, public/private ownership and research productivity influences amount of patenting by universities in general, across all technologies. However, additional university characteristics like presence of medical school and expenditure on legal fees are found influencing amount of patenting in medical device technologies by universities. Data Envelopment Analysis (DEA) is used in our attempt to understand the efficiency of universities in transferring their technologies to industries. Interesting insights are obtained on observing slack obtained during DEA. Our study highlights that some universities may have to reduce their research expenditure in large scales and number of employees working in their technology transfer offices in large scales compared to other universities in order to improve their efficiency in technology transfer process. Our study establishes that in order to improve technology transfer efficiencies, MDUs with higher research expenditure may have to reduce their research expenditure in large volumes compared to universities with lesser research expenditures. However, these MDUs may not be required to greatly reduce their technology transfer employees as compared to universities with lesser research expenditures, in order to improve their technology transfer efficiencies. Moreover, MDUs generating more number of invention disclosures and receiving more faculty awards annually can increase their patenting, licensing and startups in smaller volumes, in order to improve their technology transfer efficiencies, as compared to universities generating lesser invention disclosures and receiving lesser faculty awards, which can increase their patenting and licensing in larger volumes

Studies of "clean" and "disordered" Bilayer Optical Lattice Systems Circumventing the 'fermionic Cooling-problem'

The advancement in the eld of cold-atoms has generated a lot of interest in the condensed matter community. Cold-atom experiments can simulate clean, disor-der/impurity free systems very easily. In these systems, we have a control over various parameters like tuning the interaction between particles by the Feshbach resonance, tuning the hopping between lattice sites by laser intensity and so on. As a result, these systems can be used to mimic various theoretical models, which was hindered because of various experimental limitations. Thus, we have an ex-perimental tool in which we can start with a simple theoretical model and later tune the model experimentally and theoretically to simulate the real materials. This will be helpful in studying the physics of the real materials as we can control interactions as well as the impurities can also be taken care of. But the advance-ment in the eld of cold atoms has seen a roadblock for the fermions in optical lattices. The super uid and anti-ferromagnetic phases has not been achieved for fermions in optical lattices due to the \cooling problem" (entropy issues). In this thesis, we have addressed the issue of the \cooling problem" for fermions in optical lattice systems and studied the system with determinant quantum Monte Carlo technique. We start by giving a general idea of cold-atoms and optical lat-tice potentials, and a brief review of the experimental work going on in the cold-atomic systems. Experimental limitations like \fermionic cooling problem" have been discussed in some detail. Then we proposed a bilayer band-insulator model to circumvent the \entropy problem" and simultaneously increasing the transi-tion temperature for fermions in optical lattices. We have studied the attractive Hubbard model, which is the minimal model for fermions in optical lattices. The techniques that we have used to study the model are mean- eld theory, Gaussian uctuation theory and determinant quantum Monte Carlo numerical technique. . Chapter-1 : provides a general introduction to the ultra-cold atoms, optical lattice and Feshbach resonance. In this chapter we have discussed about cold-atom experiments in optical lattice systems. Here, we have brie y discussed the control over various parameters in the experiments. The goal of these experiments is to realize or mimic many many-body Hamiltonians in experiments, which until now was just a theoretical tool to describe various many-body physics. In the end we give a brief idea for introducing disorder in the cold-atom experiments discuss the limitations of these experiments in realizing the \interesting" super uid and anti-ferromagnetic phases of fermionic Hubbard model in optical lattices. Chapter-2 : gives a brief idea of \Determinant Quantum Monte-Carlo" (DQM C) technique that has been used to study these systems. In this chapter we will discuss the DQM C algorithm and the observables that can be calculated. We will discuss certain limitation of the DQM C algorithm like numerical instability and sign problem. We will brie y discuss how sign problem doesn't occur in the model we studied. Chapter-3 : discusses the way by which we can bypass the \cooling problem" (high entropy state) to get a fermionic super uid state in the cold atom experi-ments. In this chapter we propose a model whose idea hinges on a low-entropy band-insulator state, which can be tuned to super uid state by tuning the on-site attractive interaction by Feshbach resonance. We show through Gaussian uctua-tion theory that the critical temperature achieved is much higher in our model as compared to the single-band Hubbard model. Through detailed variational Monte Carlo calculations, we have shown that the super uid state is indeed the most stable ground state and there is no other competing order. In the end we give a proposal for its realization in the ultra-cold atom optical lattice systems. Chapter-4 : discusses the DQM C study of the model proposed in chapter- 3. Here we have studied the various single-particle properties like momentum distribution, double occupancies which can be easily measured in cold-atom ex-periments. We also studied the pair-pair and the density-density correlations in detail through DQM C algorithm and mapped out the full T U phase diagram. We show that the proposed model doesn't favor the charge density wave for the interaction strengths we are interested in. Chapter-5 : gives a brief idea of the e ect of adding an on-site random disorder in our proposed bilayer-Hubbard model. We study the e ect of random disorder on various single-particle properties which can be easily veri ed in cold-atom ex-periments. We studied the suppression of the pair-pair correlations as we increase the disorder strength in our proposed model. We nd that the critical value of the interaction doesn't change in the weak-disorder limit. We estimated the critical disorder strength needed to destroy the super uid state and argued that the tran-sition from the super uid to Bose-glass phase in presence of disorder lies in the universality class of (d + 1) XY model. In the end, we give a schematic U V phase diagram for our system. Chapter-6 : We studied the bilayer attractive Hubbard model in different lattice geometry, the bilayer honeycomb lattice, both in presence and in absence of the on-site random disorder. We discussed how the pair-pair and density-density cor-relations behave in the presence and absence of disorder. Through the finite-size scaling analysis we see the co-existence of the super fluid and the charge density wave order at half- lling. An in nitesimal disorder destroys the CDW order com-pletely while the super uid phase found to be robust against weak-disorder. We estimated the critical interaction strength, the critical temperature and the critical disorder strength through nite-size scaling, and provide a putative phase diagram for the system considered

Evaporation and Buckling Dynamics of Sessile Droplets Resting on Hydrophobic Substrates

Droplet evaporation is ubiquitous to multitude of applications such as microfluidics, surface patterning and ink-jet printing. In many of the process like food processing tiny concentrations of suspended particles may alter the behavior of an evaporating droplet remarkably, leading to partially viscous and partially elastic dynamical characteristics. This, in turn, may lead to some striking mechanical instabilities, such as buckling and rupture. In this thesis, we provide a comprehensive physical description of the vaporization, self-assembly, agglomeration and buckling kinetics of sessile nanofluid droplet pinned on a hydrophobic substrate in various configurations. We have deciphered five distinct regimes of droplet lifecycle. Regime I-III consists of evaporation induced preferential agglomeration that leads to the formation of unique dome shaped inhomogeneous shell with stratified varying density liquid core. Regime IV involves capillary pressure initiated shell buckling and stress induced shell rupture. Regime V marks rupture induced cavity inception and growth. We provide a regime map explaining the droplet morphology and buckling characteristics for droplets evaporating on various substrates. Specifically, we find that final droplet volume and radius of curvature at buckling onset are universal functions of particle concentration. Furthermore, flow characteristics inside the heated and unheated droplets are investigated and found to be driven by the buoyancy effects. Velocity magnitudes are observed to increase by an order at higher temperatures with self-similar flow profiles. With an increase in the surface temperature, droplets exhibit buckling from multiple sites over a larger sector in the top half of the droplet. In addition, irrespective of the initial nanoparticle concentration and substrate temperature, hydrophobicity and roughness, growth of daughter cavity (subsequent to buckling) inside the droplet is found to be controlled by the solvent evaporation rate from the droplet periphery. The results are of great significance to a plethora of applications like DNA deposition and nanofabrication. In the next part of the thesis, we deploy the droplet in a rectangular channel. The rich physics governing the universality in the underlying dynamics remains grossly elusive. Here, we bring out hitherto unexplored universal features of the evaporation dynamics of a sessile droplet entrapped in a 3D confined fluidic environment. Increment in channel length delays the completion of the evaporation process and leads to unique spatio-temporal evaporation flux and internal flow. We show, through extensive set of experiments and theoretical formulations, that the evaporationtimescale for such a droplet can be represented by a unique function of the initial conditions. Moreover, using same theoretical considerations, we are able to trace and universally merge the volume evolution history of the droplets along with evaporation lifetimes, irrespective of the extent of confinement. These results are explained in the light of increase in vapor concentration inside the channel due to greater accumulation of water vapor on account of increased channel length. We have formulated a theoretical framework which introduces two key parameters namely an enhanced concentration of the vapor field in the vicinity of the confined droplet and a corresponding accumulation lengthscale over which the accumulated vapor relaxes to the ambient concentration. Lastly, we report the effect of confinement on particle agglomeration and buckling dynamics. Compared to unconfined scenario, we report non-intuitive suppression of rupturing beyond a critical confinement. We attribute this to confinement-induced dramatic alteration in the evaporating flux, leading to distinctive spatio-temporal characteristics of the internal flow leading to preferential particle transport and subsequent morphological transitions. We present a regime map quantifying buckling & non-buckling pathways. These results may turn out to be of profound importance towards achieving desired morphological features of a colloidal droplet, by aptly tuning the confinement space, initial particle concentration, as well as the initial droplet volume. These findings may have implications in designing functionalized droplet evaporation devices for emerging engineering and biomedical applications

Design and Development of a Passive Infra-Red-Based Sensor Platform for Outdoor Deployment

This thesis presents the development of a Sensor Tower Platform (STP) comprised of an array of Passive Infra-Red (PIR) sensors along with a classification algorithm that enables the STP to distinguish between human intrusion, animal intrusion and clutter arising from wind-blown vegetative movement in an outdoor environment. The research was motivated by the aim of exploring the potential use of wireless sensor networks (WSNs) as an early-warning system to help mitigate human-wildlife conflicts occurring at the edge of a forest. While PIR sensors are in commonplace use in indoor settings, their use in an outdoor environment is hampered by the fact that they are prone to false alarms arising from wind-blown vegetation. Every PIR sensor is made up of one or more pairs of pyroelectric pixels arranged in a plane, and the orientation of interest in this thesis is one in which this plane is a vertical plane, i.e., a plane perpendicular to the ground plane. The intersection of the Field Of View (FOV) of the PIR sensor with a second vertical plane that lies within the FOV of the PIR sensor, is called the virtual pixel array (VPA). The structure of the VPA corresponding to the plane along which intruder motion takes place determines the form of the signal generated by the PIR sensor. The STP developed in this thesis employs an array of PIR sensors designed so as to result in a VPA that makes it easier to discriminate between human and animal intrusion while keeping to a small level false alarms arising from vegetative motion. The design was carried out in iterative fashion, with each successive iteration separated by a lengthy testing phase. There were a total of 5 design iterations spanning a total period of 14 months. Given the inherent challenges involved in gathering data corresponding to animal intrusion, the testing of the SP was carried out both using real-world data and through simulation. Simulation was carried out by developing a tool that employed animation software to simulate intruder and animal motion as well as some limited models of wind-blown vegetation. More specifically, the simulation tool employed 3-dimensional models of intruder and shrub motion that were developed using the popular animation software Blender. The simulated output signal of the PIR sensor was then generated by calculating the area of the 3-dimensional intruder when projected onto the VPA of the STP. An algorithm for efficiently calculating this to a good degree of approximation was implemented in Open Graphics Library (OpenGL). The simulation tool was useful both for evaluating various competing design alternatives as well as for developing an intuition for the kind of signals the SP would generate without the need for time-consuming and challenging animal-motion data collection. Real-world data corresponding to human motion was gathered on the campus of the Indian Institute of Science (IISc), while animal data was recorded at a dog-trainer facility in Kengeri as well as the Bannerghatta Biological Park, both located in the outskirts of Bengaluru. The array of PIR sensors was designed so as to result in a VPA that had good spatial resolution. The spatial resolution capabilities of the STP permitted distinguishing between human and animal motion with good accuracy based on low-complexity, signal-energy computations. Rejecting false alarms arising from vegetative movement proved to be more challenging. While the inherent spatial resolution of the STP was very helpful, an alternative approach turned out to have much higher accuracy, although it is computationally more intensive. Under this approach, the intruder signal, either human or animal, was modelled as a chirp waveform. When the intruder moves along a circular arc surrounding the STP, the resulting signal is periodic with constant frequency. However, when the intruder moves along a more likely straight-line path, the resultant signal has a strong chirp component. Clutter signals arising from vegetative motion does not exhibit this chirp behavior and an algorithm that exploited this difference turned in a classification accuracy in excess of 97%

Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops

The inhibiting effect of a sharp edge on liquid spreading is well observed during drop interaction with textured surfaces. On groove-textured solid surfaces comprising unidirectional parallel grooves, the edge effect of posts results in the squeezing of drop liquid in the direction perpendicular to the grooves and the stretching of drop liquid along the grooves leading to anisotropy in drop flow, popularly known as wetting anisotropy which has been employed in several engineering applications. A recent study observed that the energy loss incurring at the edges of posts via contact angle hysteresis is primarily responsible for the anisotropic spreading of impacting drops on groove-textured surfaces. The present study aims to elucidate the role of edges on the spreading and receding dynamics of water drops. The experiments of drop impact are carried out on semi-infinite rectangular post comprising a pair of parallel 90-deg edges separated by a distance (post width) comparable to the diameter of impacting drop. The equilibrium shape of drops on the semi-infinite rectangular post is analyzed using open source computational tool Surface Evolver to optimize the ratio of initial droplet diameter to post width. Quantitative measurements of drop impact dynamics on semi-infinite rectangular posts are deduced by analysing high speed videos of impact process captured under three different camera views during experiments. Based on the role of post edges on impacting drops, different regimes of the impacting drops are characterized in terms of drop Weber number and the ratio of diameter of impacting drop to post width. Characteristic features of impact dynamics in each of the regimes are identified and discussed. It is seen that edges play a pivotal role on all stages of impact dynamics regardless of Weber number. Impacts in the regime of completely pinned drops on narrow posts are further analyzed to reveal characteristics of post-spreading oscillations