1,721,008 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Investigating the effects of molarity concentration variation over optical band gap for ZnO based thin film
No full textZinc Oxide (ZnO) is a very promising metal oxide semi conductor for applications in many fields like gas sensors, solar cells, and blue and ultraviolet optoelectronics devices. This thesis deals with the effect of molarity concentration on Zinc Oxide (ZnO) and hence gas sensing thin films which are fabricated by a low cost sol-gel spin coating method. The influence of precursor molarity concentration on structural property of ZnO thin films is characterized by X-ray diffraction (XRD) and Ultra Violet visible (UV-visible) spectroscopy. Sol concentration for ZnO thin film is varied from 0.05M to 1M. The study shows that crystallite sizes (grain sizes) vary with variation of sol concentration. The sol with higher concentration results in the increase in the crystallite size. Optimum sol molarity for the sensitivity of NOx gas comes out to be 0.1M. The highest sensitivity is 80% at optimum temperature 300°C. The minimum response time and minimum recovery time for optimum sol molarity which is 0.1M are 23 seconds and 25 seconds at optimum temperature. The energy band gap also gets affected by sol concentration. As molarity of precursor solution increases energy band gap starts to decrease. At higher solution molarity ZnO thin film starts to acquire the properties of the bulk material and hence energy band gap becomes approximate equal at higher solution molarity. By variation in energy band gap conductivity of material affected. It can be stated from energy band results that conductivity of ZnO thin film increases as energy band gap decreases as we move from lower sol concentration to higher sol concentration
Three Dimensional High Contrast Gratings based Hollow Core Waveguide for Chip Scale Integrated Optical Interconnects
No full textME, ECEDThree dimensional high contrast gratings based hollow core waveguide is a potential
candidate for telecommunication systems which provides a promising platform to realize
integrated optical interconnects. These have been comprehensively studied over the years
due to its diverse applications in the communication systems. With advancement of
technologythese days as we are doing scaling the size of devices and distance between the
devices is reducing which makes interconnects more important in communication system. To
maintain such high speed and small size optical interconnects are required which can play
crucial role to achieve today’s high speed large bandwidth requirementsThe high reflectivity,
high speed and high bandwidth of HCGs based Hollow waveguide is one of the key
component for integrated chip scale optical interconnects.This can be used to guide light and
transmit Tb/s data over the communication link and attracted a lot of attention for next
generation communication network as well as high performance computing applications.SOI
is an ideal platform for the development of passive optical interconnects like Hollow
waveguide. Several key challenges exist in developing the waveguide, including fabrication
difficulties, dispersion and non linearity. Usinghigh contrast gratings, the fabrication
difficulties can be minimized. Dispersion remains to be the most dominant source in the
system of data loss. From the aspects of reflectivity, bandwidth, dispersion and non linearity,
using high contrast gratings in waveguide approach is widely popular. Modified approach
involves the high contrast gratings with high index material surrounded by a low-index
material. The refractive index difference is maintained high that is greater than 2.4 which
provides high reflectivity. Parameters on which reflectivity of waveguide mainly depends are
grating thickness (tg), grating period (Λ), and duty cycle (η). Important design attribute is the
sub wavelength size of gratings
Design of MEMS Based Gas Senor with Inplane Integrated IDT And Micro-Heater
No full textME, ECEDGas sensors are employed to ensure that levels of various harmful (e.g. toxic, flammable, etc.)
gases are within an acceptable range. These monitors are indispensable in industrial facilities
that produce such gases (e.g. oil and natural gas refining), but are also critical for hazardous
conditions in residential and other commercial settings. Hydrogen sensors have obtained
increased interest with the widened application of hydrogen energy in recent years. In this
work, MEMS (Micro-Electro-Mechanical Systems) sensor with interdigitated electrodes have
been designed and simulated. It is observed that micro-heater design parameters imposed
different impacts on the sensor performance. A gas chamber around the device has been
designed and the effects of the hydrogen gas on the sensor device have been studied. In order
to achieve small, robust, low cost and fast hydrogen sensor with high sensitivity, the
designing and its optimization is performed. The effect of the applied voltage on the sensor is
also studied
Energy scavenging using MEMS based power generator
Full text linkME, ECEDOver the past few years, there has been a huge reduction in size and power consumption of MEMS devices like transducers and sensors. These devices are usually designed to run on batteries the replacement of batteries is not practical. The limited lifespan of batteries may
induce costly maintenance, in the case of contaminated areas for instance. Moreover, batteriesdying without warning cause serious problems in safety monitoring applications. That led to a surge of research in the area of energy harvesting. Sustainable power generation may be
achieved in converting ambient energy into electrical energy. Some possible ambient energy sources are, for instance, thermal energy, light energy and mechanical energy. After an extensive survey of potential energy harvesting methods, the conversion of ambient vibrations to electricity was chosen as a method for further research. Since mechanical vibrations exist in most systems,
many works focused on vibration-driven generators. In this field, the electromagnetic induction is well suited for the mechanical to electrical energy conversion. The design of the mechanical
system that transmits the surrounding vibratory energy to the electromagnetic generator is a critical importance.
This thesis presents an optimization of an electromagnetic microgenerator. It describes the theory, design and simulation of an energy converter based on electromagnetic induction. The objectives of this research are designing, improving the performance and operational reliability of electromagnetic microgenerator. These have been achieved by identifying the desirable design
features of the electromagnetic microgenerator. Extensive analytical investigation has been conducted to develop an efficient design of an electromagnetic microgenerator. This thesis deals with the design and simulation of a number of suspension structures to be used for supporting the
moving magnet of an electromagnetic microgenerator. These suspension structures were designed by modeling and finite element method simulation using COMSOL Multiphysics. This helped in understanding the critical aspects of the design at the same time leading to the
determination of the optimum parameters for the structures, such as static deflection
Graphene Based 1-D Photonic Crystal Waveguide for Delay Tuning
No full textMasters of Engineering-ECEA 1-dimensional (1-D) photonic crystal waveguide based on graphene which is
electrically controllable is investigated to achieve slow light having wide bandwidth, low
value of group velocity vg and high value of group index ng. The photonic crystal (PC)
devices have an edge over other materials since they can work on room temperature, on
chip integration is highly suitable, and have low dispersion propagation and wider
bandwidth. Photonic crystal waveguides (PCW) find applications for tuning the delay as
they provide tunable slow light with wide bandwidth
Our proposed structure has a 1-D PCW which is created through a photonic crystal
which is otherwise perfect by introduction of a line defect. The bandgap of the PC
locates some defect states within it by removal of a central slab of air to obtain an
appropriate waveguide design. The light having propagation inside the waveguide has
the constraint that it must move with a frequency which is within the crystal’s bandgap
and it can be made to move along the waveguide. A layer of graphene is inserted in the
1-D PCW to improve the properties of structure further and thus tune the delay by
varying the graphene’s fermi energy level. Graphene’s excellent electrical tuning
properties have various advantages and they are taken into consideration for tuning the
group delay in a PCW. When graphene is not used in the structure, a value of 54.46ps for
group delay is noted which is large enough and that too with a very large applied voltage
of 50V, which is not practically realizable for applications involving tuning of delay on
chip. Whereas when graphene is used in the design i.e. with core and clad; as the voltage
applied to graphene is altered from 1 volt to 4 volts, there is a tuning from 81.1ps to
204.49ps in the group delay value for the structure where core region has graphene on it;
and from 50.45ps to 187.6ps where clad region has graphene applied at 1550nm
wavelength. Thus, a group delay tuning of 123.39 picoseconds and 137.15 picoseconds
is achieved in both the designs respectively which is large enough as compared to 2-D
PCW structures. The slow light which is then achieved has many useful applications in
signal processing and delay scanning in the optical domain
Design Optimization of MEMS Based Piezoelectric Energy Harvester For Low-Frequency Applications
No full textIn recent years, piezoelectric based energy harvester had become major research topic. Piezoelectric materials are excellent transducers in converting vibrational energy into electrical energy, and vibration based piezoelectric generators are seen as an enabling technology for wireless sensor networks, especially in self powered devices. These are mostly made of thin film technology and different configurations as unimorph and bimorph for sensor and actuator applications. In this thesis work, analysis and comparison of two widely used cantilever design in MEMS energy harvesting devices i.e. wide beam structure and narrow beam structure have been done. Aluminum Nitride (AIN) is chosen as a piezoelectric material due to its CMOS and biocompatibility. To study the output of the design, Finite Element Modelling was used. The power density obtained based on the volume of the structure was 14.8 μW/cm3 for the wide beam structure and 0.10 μW/cm3 for narrow beam structure individually. In selecting a device, bandwidth is also a vital parameter. An array of cantilever structure resulted in a bandwidth of 4 Hz for the wide beam structure and 8.1 Hz for narrow beam structure respectively. The conclusion of the results are wide beam structure is preferred to increase power density and a narrow beam for the wide bandwidth. High power density also has a disadvantage which is likely to fail where acceleration is high, as due to increasing stress which they experience
Design of capacitive micromachined ultrasonic transducer for underwater acoustic imaging
No full textME-ECE-ThesisWe introduce Capacitive Micromachined Ultrasonic Transducer (CMUT) for underwater acoustic imaging in order to obtain the high resolution images. CMUT is used because of its several advantages like higher performance, low motional impedance and high quality factor, high bandwidth, less losses. The CMUT consists of a membrane. When AC voltage superimposed with DC voltage is applied across metalized membrane and
substrate, ultrasonic waves are produced. The membrane is attracted towards the bulk by the electrostatic force and induced stress within the membrane resists the attraction. If the biased membrane is exposed to ultrasound, a current is generated due to the capacitance
change under constant bias voltage. The amplitude of this current is a function of the frequency of the incident wave, the bias voltage, and the capacitance of the device. In this report comparative study of CMUT has been done. Objectives have been drawn from the observations and gaps. Simulation results have been achieved using COMSOL multiphysics.Electronics and Communication Engineering, Thapar University, Patial
Verification of Analog and Mixed Signal IPS using SV-UVM Verification Methodology
No full textUVM Based Verification (UVM) is one of the broadly utilized verification methodology to improve the
verifying nature of Analog and Mixed flag IPs Design so as to accelerate the checking procedure. A
confirmation domain to check the functionality of IP by utilizing System Verilog - UVM based approach.
The functionality of Analog IPs was checked by Cadence Incisive and VCS tools. With Incisive and VCS
Simulator, not only check the status of output pins by applying different input pattern but also reduce the
overall debugging effort and shortened debug turnaround time. With the best possible test plan and
verification plan checking the functionality of AMS IPs became simpler. The verification has been done at
pre-silicon stage to make post silicon stage bug free. Because verifying a design at post silicon stage takes
a lot time and costly re-spin process. As time to market has become a crucial factor, a solution must be there
with a verifying IP having both analog and digital block with checking behavior of analog block in a real
manner. Verification of analog blocks have been done in digital environment which make simulation faster
and get better performance. Most frameworks on-chip (SoC) plans today are Mixed signal ones, and all
SoCs will be mixed signal at cutting edge process hubs sooner rather than later. The fundamental objective
of this project is to automate the UVM Environment and make the verification quick and simple
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