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Fault
detection by vibration signal analysis is based on the fact
that every machine component has an inherent capacity to store
energy in certain quantum states which are called modes. When
the machine component is excited by an external force, the
machine takes up the energy and starts vibrating with various
frequencies and their corresponding amplitudes. The resultant
state is a superimposition of all the individual modes of
vibration. Understanding of a mode may be achieved through
the analysis of the response signal in time and frequency
domain. Modern vibration signal analysis is based on frequency
domain analysis using spectrum analyzers which perform the
Fast Fourier Transform (FFT) of the response signals. Any
defect can be recognized as a variation in the signature vibration
of the machine. The paper titled, "Rolling Element Bearing
Fault Detection via Vibration Signal Analysis", by Pratesh
Jayaswal et al., investigates the feasibility of FFT
and band pass analysis for fault detection of rolling element
bearing with multiple faults. It is concluded that the RMS
value of a filtered signal can be a good indicator of the
bearing condition.
Barium
titanate (BaTiO3) nanoparticles have great potential
as a data storage medium that can be read optically and written
electrically, since it is both a ferroelectric and a birefringent.
When used for data storage, their primary advantage is that
they maintain their polarization state after the applied voltage
has been removed and therefore do not require back up memories
or batteries. They can be accessed more quickly and with less
power than many memory devices, which need to push electrons
through a glass barrier. Additionally, they have the potential
for increased miniaturization. The size of the nanoparticles
is a crucial parameter that decides successful miniaturization.
Obtaining high dielectric constant Barium Titanate ceramics
with a high degree of homogeneity and ultra fine grain size
is the dream of anyone aiming to achieve thinner dielectric
layers. Ferroelectric ceramics are widely used in the electronics
industry in a variety of applications such as multilayered
capacitors, transducers and sensors. T K Mandal in the paper
titled, "Structural and Microstructural Evolution in
BaTiO3 Ceramic Nanoparticles", reports the
formation of Barium Titanate nanoparticles at relatively low
temperatures. The nanopowder of about 40 microns size, show
a tetragonal symmetry and interesting properties like high
dielectric constant and low Curie temperatures.
The
Travelling Wave Tube (TWT) is a high-gain, low-noise, wide-bandwidth
microwave amplifier which finds use as a radio frequency amplifier
in microwave equipments. It works on the principle of a continuous
interaction between an electron beam and the microwave signal.
If the velocities of the beam and the wave are nearly the
same, interaction takes place. A helix is used as the delay
line to reduce the signal speeds to that of the beam. The
helical structure however contributes to dispersion due to
which the frequency stability is lost. Vikas Kumar and Vishnu
Srivastava in their paper, "Sensitivity Analysis of a
High Gain Helix TWT Using HFSS", discussed the results
of the sensitivity analysis of dispersion to various helix
parameters. Ansoft HFSS was employed in simulating the helix
TWT and performing the sensitivity analysis. The results discussed
in this paper could be effectively used to control dispersion
in wideband applications.
The
field of antenna engineering is central to all wireless technologies
and plays a central role in the successful deployment of network
systems. Some of the requirements imposed on an antenna are
as follows: it should be relatively cheap and easy to manufacture,
light weight and compact with a low profile but robust and
environment friendly. The microstrip patch antenna fulfills
these requirements. The main drawback with microstrip patch
antennas is that they inherently have very narrow impedance
bandwidth. In the paper, "Design and Development of Slanted
Slot Microstrip Antenna for Multi-Frequency Operation and
Circular Polarization", Satnoor et al., have presented
the design for a slanted slot microwave antenna. The two pair
antenna designed by the team is very simple and uncomplicated
in structure and is found to operate at four bands of frequencies
in the X-band. The authors also report a larger bandwidth
and circular polarization with very small axial ratio value.
This study assumes importance because circular polarization
antennas are more resistant to signal degradation when compared
to linear polarized antennas.
The
importance of biofuels is rapidly increasing with growing
anxiety over depleting crude oil supply, escalating costs
and fast climatic changes. Blending of biodiesel with petro-diesel
has tremendous positive social, ecological and economic impact
on the society. "Emission and Performance Characteristics
of a Single Cylinder Compression Ignition Engine Operating
on Esterified Rice Bran Vegetable Oil and Diesel Fuel",
by Thirupathi Reddy et al., is an experimental study
of the performance of a single cylinder compression ignition
engine when biodiesel is blended with petro diesel in various
proportions. Parameters such as brake power, peak pressure
rise and emissions under varying operating conditions were
measured. Based on the data collected, the authors conclude
that despite having lower thermal efficiency, biodiesel would
be the answer to environmental issues.
This
issue concludes with a short paper titled, "Optimum Modeling
of MEMS Characteristics: An Analytical Solution Approach",
by Shaikh et al., Microelectromechanical systems (MEMS)
is the integration of mechanical elements, sensors, actuators,
and electronics on a common silicon substrate through microfabrication
technology. While the electronic parts are fabricated using
Integrated Circuit (IC) process sequences, the micromechanical
components are fabricated using compatible `micromachining'
processes that selectively etch away parts of the silicon
wafer or add new structural layers to form the mechanical
and electromechanical devices. Due to miniaturization and
the high level of structural complexity of MEMS, the sensor
performance is affected by numerous factors like cross-coupling,
touch-down effect and other parasitic effects. Hence, it is
imperative to perform simulations of the design and performance
evaluation to achieve design optimization. The authors have
used an analytical simulation addressing more specifically,
the issue of touch- down effect.
-
Elizabeth Zacharias
Consulting Editor
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