Abstract: We report on the use of strong external optical
feedback to enhance the modulation response of semiconductor lasers
over a frequency passband around modulation frequencies higher
than 60 GHz. We show that this modulation enhancement is a type of
photon-photon resonance (PPR) of oscillating modes in the external
cavity formed between the laser and the external reflector. The study
is based on a time-delay rate equation model that takes into account
both the strong feedback and multiple reflections in the external
cavity. We examine the harmonic and intermodulation distortions
associated with single and two-tone modulations in the mm-wave
band of the resonant modulation. We show that compared with
solitary lasers modulated around the carrier-photon resonance
frequency, the present mm-wave modulated signal has lower
distortions.
Abstract: Vacuum insulation panel (VIP) is a promising thermal
insulator for buildings, refrigerator, LNG carrier and so on. In general,
it has the thermal conductivity of 2~4 mW/m·K. However, this thermal
conductivity is that measured at the center of VIP. The total effective
thermal conductivity of VIP is larger than this value due to the edge
conduction through the envelope. In this paper, the edge conduction of
VIP is examined theoretically, numerically and experimentally. To
confirm the existence of the edge conduction, numerical analysis is
performed for simple two-dimensional VIP model and a theoretical
model is proposed to calculate the edge conductivity. Also, the edge
conductivity is measured using the vacuum guarded hot plate and the
experiment is validated against numerical analysis. The results show
that the edge conductivity is dependent on the width of panel and
thickness of Al-foil. To reduce the edge conduction, it is recommended
that the VIP should be made as big as possible or made of thin Al film
envelope.
Abstract: A modeling approach for CMOS gates is presented
based on the use of the equivalent inverter. A new model for the
inverter has been developed using a simplified transistor current
model which incorporates the nanoscale effects for the planar
technology. Parametric expressions for the output voltage are
provided as well as the values of the output and supply current to be
compatible with the CCS technology. The model is parametric
according the input signal slew, output load, transistor widths, supply
voltage, temperature and process. The transistor widths of the
equivalent inverter are determined by HSPICE simulations and
parametric expressions are developed for that using a fitting
procedure. Results for the NAND gate shows that the proposed
approach offers sufficient accuracy with an average error in
propagation delay about 5%.
Abstract: This paper evaluates the performance of a multi-lane
four legged modern roundabout operating in Muscat using SIDRA
model. The performance measures include Degree of Saturation
(DOS), average delay, and queue lengths. The geometric and traffic
data were used for model preparation. Gap acceptance parameters,
critical gap and follow up headway, were used for calibration of
SIDRA model. The results from the analysis showed that currently
the roundabout is experiencing delays up to 610 seconds per vehicle
with DOS 1.67 during peak hour. Further, sensitivity analysis for
general and roundabout parameters was performed, amongst lane
width, cruise speed, inscribed diameter, entry radius and entry angle
showed that inscribed diameter is most crucial factor affecting delay
and DOS. Up gradation of roundabout to fully signalized junction
was found as the suitable solution which will serve for future years
with LOS C for design year having DOS of 0.9 with average control
delay of 51.9 seconds per vehicle.
Abstract: The present study involved analysis of certain
characteristics of the perennial ryegrass (Lolium perenne L.)
genotypes collected from the natural flora of Ankara, and explores a
correlation among them. In order to evaluate the plants for breeding
purpose as per Turkey's environmental conditions, the perennial
ryegrass plants were collected from natural pasture of Ankara in 2004
and were utilized for the study. Seeds of the collected plants were
sown in pots and seedlings were prepared in a greenhouse. In 2005,
the seedlings were transplanted at 50 × 50 cm2 intervals in
Randomized Complete Blocks Design in an experimental field. In
2007 and 2008, data were recorded from the observations and
measurements of 568 perennial ryegrasses. The plant characteristics,
which were investigated, included re-growth time in spring, color,
density, growth habit, tendency to form inflorescence, time of
inflorescence, plant height, length of upper internode, spike length,
leaf length, leaf width, leaf area, leaf shape, number of spikelets per
spike, seed yield per spike and 1000 grain weight and the correlation
analyses were made using this data. Correlation coefficients were
estimated between all paired combinations of the studied traits. The
yield components exhibited varying trends of association among
themselves. Seed yield per spike showed significant and positive
association with the number of spikelets per spike, 1000 grain weight,
plant height, length of upper internode, spike length, leaf length, leaf
width, leaf area and color, but significant and negative association
with the growth habit and re-growth time in spring.
Abstract: This paper contains 2 main parts. In the first part of paper we simulated and studied three types of electrode patterns used in various industries for suspension and handling of the semiconductor and glass and we selected the best pattern by evaluating the electrostatic force, which was comb pattern electrode.
In the second part we investigated the parameters affecting the amount of electrostatic force such as the gap between surface and electrode (g), the electrode width (w), the gap between electrodes (t), the surface permittivity and electrode length and methods of improvement of adhesion force by changing these values.
Abstract: Series of laboratory tests were carried out to study the
extent of scour caused by a three-dimensional wall jets exiting from a
square cross-section nozzle and into a non-cohesive sand beds.
Previous observations have indicated that the effect of the tail water
depth was significant for densimetric Froude number greater than ten.
However, the present results indicate that the cut off value could be
lower depending on the value of grain size-to-nozzle width ratio.
Numbers of equations are drawn out for a better scaling of numerous
scour parameters. Also suggested the empirical prediction of scour to
predict the scour centre line profile and plan view of scour profile at
any particular time.
Abstract: An investigation into the effect of countersunk depth,
plate thickness, countersunk angle and plate width on the stress
concentration around countersunk hole is carried out with the help of
finite element analysis. The variation of stress concentration with
respect to these parameters is studied for three types of loading viz.
uniformly distributed load, uniformly varying load and functionally
distributed load. The results of the finite element analysis are
interpreted and some conclusions are drawn. The distribution of
stress concentration around countersunk hole in isotropic plates
simply supported at all the edges is found similar and is independent
of loading. The maximum stress concentration also occurs at a
particular point irrespective of the loading conditions.
Abstract: With advances in solid-state power electronic devices
and microprocessors, various pulse-width-modulation (PWM)
techniques have been developed for industrial applications. This
paper presents the comparison of two different PWM techniques, the
sinusoidal PWM (SPWM) technique and the space-vector PWM
(SVPWM) technique applied to two level VSI for micro grid
applications. These two methods are compared by discussing their
ease of implementation and by analyzing the output harmonic spectra
of various output voltages (line-to-neutral voltages, and line-to-line
voltages) and their total harmonic distortion (THD). The SVPWM
technique in the under-modulation region can increase the
fundamental output voltage by 15.5% over the SPWM technique.
Abstract: The aim of this paper is to propose a novel technique
to guarantee Quality of Service (QoS) in a highly dynamic
environment. The MANET changes its topology dynamically as the
nodes are moved frequently. This will cause link failure between
mobile nodes. MANET cannot ensure reliability without delay. The
relay node is selected based on achieving QoS in previous
transmission. It considers one more factor Connection Existence
Period (CEP) to ensure reliability. CEP is to find out the period
during that connection exists between the nodes. The node with
highest CEP becomes a next relay node. The relay node is selected
dynamically to avoid frequent failure. The bandwidth of each link
changed dynamically based on service rate and request rate. This
paper proposes Active bandwidth setting up algorithm to guarantee
the QoS. The series of results obtained by using the Network
Simulator (NS-2) demonstrate the viability of our proposed
techniques.
Abstract: In MANET, mobile nodes communicate with each
other using the wireless channel where transmission takes place with
significant interference. The wireless medium used in MANET is a
shared resource used by all the nodes available in MANET. Packet
reserving is one important resource management scheme which
controls the allocation of bandwidth among multiple flows through
node cooperation in MANET. This paper proposes packet reserving
and clogging control via Routing Aware Packet Reserving (RAPR)
framework in MANET. It mainly focuses the end-to-end routing
condition with maximal throughput. RAPR is complimentary system
where the packet reserving utilizes local routing information
available in each node. Path setup in RAPR estimates the security
level of the system, and symbolizes the end-to-end routing by
controlling the clogging. RAPR reaches the packet to the destination
with high probability ratio and minimal delay count. The standard
performance measures such as network security level,
communication overhead, end-to-end throughput, resource utilization
efficiency and delay measure are considered in this work. The results
reveals that the proposed packet reservation and clogging control via
Routing Aware Packet Reserving (RAPR) framework performs well
for the above said performance measures compare to the existing
methods.
Abstract: In this paper, we present a comparative assessment of
Space Vector Pulse Width Modulation (SVPWM) and Model
Predictive Control (MPC) for two-level three phase (2L-3P) Voltage
Source Inverter (VSI). VSI with associated system is subjected to
both control techniques and the results are compared.
Matlab/Simulink was used to model, simulate and validate the
control schemes. Findings of this study show that MPC is superior to
SVPWM in terms of total harmonic distortion (THD) and
implementation.
Abstract: This paper presents a hybrid three phase rectifier for
high power factor application. This rectifier is composed by zero
voltage transition (ZVT) and zero current transition (ZCT) boost
converter with three phase diode bridge rectifier, in parallel with a six
pulse three phase pulse width modulation (PWM) controlled rectifier.
The proposed topology is capable of high power factor with DC
output voltage regulation by providing sinusoidal input. Also, it
increases the overall efficiency of the new hybrid rectifier to 94.56%
and the total harmonic distortion of the hybrid structure varies from
0% to 16% at nominal output power. This topology was simulated in
MATLAB/SIMULINK environment and the output waveforms
presented with experimental result.
Abstract: In the present work, the effect of load and sliding
distance on the performance tribology of commercially used
aluminium-silicon engine block and piston was evaluated at ambient
conditions with humidity of 80% under dry sliding conditions using a
pin-on-disc with two different loads of 5N and 20N yielding applied
pressure of 0.30MPa and 1.4MPa, respectively, at sliding velocity of
0.29ms-1 and with varying sliding distance ranging from 260m-
4200m. Factors and conditions that had significant effect were
identified. The results showed that the load and the sliding distance
affect the wear rate of the alloys and the wear rate increased with
increasing load for both the alloys. Wear rate also increases almost
linearly at low loads and increase to a maximum then attain a plateau
with increasing sliding distance. For both applied loads the piston
alloy showed the better performance due to higher Ni and Mg
content. The worn surface and wear debris was characterized by
optical microscope, SEM and EDX analyzer. The worn surface was
characterized by surface with shallow grooves at loads while the
groove width and depth increased as the loads increases. Oxidative
wear was found to be the predominant mechanisms in the dry sliding
of Al-Si alloys at low loads.
Abstract: This paper is about method to produce a stable and
accurate constant output pulse width regardless of the amplitude,
period and pulse width variation of the input signal source. The pulse
generated is usually being used in numerous applications as the
reference input source to other circuits in the system. Therefore, it is
crucial to produce a clean and constant pulse width to make sure the
system is working accurately as expected.
Abstract: In this study, a three dimensional numerical heat
transfer model has been used to simulate the laser structuring of
polymer substrate material in the Three-Dimensional Molded
Interconnect Device (3D MID) which is used in the advanced multifunctional
applications. A finite element method (FEM) transient
thermal analysis is performed using APDL (ANSYS Parametric
Design Language) provided by ANSYS. In this model, the effect of
surface heat source was modeled with Gaussian distribution, also the
effect of the mixed boundary conditions which consist of convection
and radiation heat transfers have been considered in this analysis. The
model provides a full description of the temperature distribution, as
well as calculates the depth and the width of the groove upon material
removal at different set of laser parameters such as laser power and
laser speed. This study also includes the experimental procedure to
study the effect of laser parameters on the depth and width of the
removal groove metal as verification to the modeled results. Good
agreement between the experimental and the model results is
achieved for a wide range of laser powers. It is found that the quality
of the laser structure process is affected by the laser scan speed and
laser power. For a high laser structured quality, it is suggested to use
laser with high speed and moderate to high laser power.
Abstract: Anultra-low power capacitor less low-dropout voltage
regulator with improved transient response using gain enhanced feed
forward path compensation is presented in this paper. It is based on a
cascade of a voltage amplifier and a transconductor stage in the feed
forward path with regular error amplifier to form a composite gainenhanced
feed forward stage. It broadens the gain bandwidth and thus
improves the transient response without substantial increase in power
consumption. The proposed LDO, designed for a maximum output
current of 100 mA in UMC 180 nm, requires a quiescent current of
69 )A. An undershot of 153.79mV for a load current changes from
0mA to 100mA and an overshoot of 196.24mV for current change of
100mA to 0mA. The settling time is approximately 1.1 )s for the
output voltage undershooting case. The load regulation is of 2.77
)V/mA at load current of 100mA. Reference voltage is generated by
using an accurate band gap reference circuit of 0.8V.The costly
features of SOC such as total chip area and power consumption is
drastically reduced by the use of only a total compensation
capacitance of 6pF while consuming power consumption of 0.096
mW.
Abstract: We have studied a method to widen the spectrum
of optical pulses that pass through an InGaAsP waveguide for
application to broadband optical communication. In particular, we
have investigated the competitive effect between spectral broadening
arising from nonlinear refraction (optical Kerr effect) and shrinking
due to two photon absorption in the InGaAsP waveguide with
χ(3) nonlinearity. The shrunk spectrum recovers broadening by
the enhancement effect of the nonlinear refractive index near the
bandgap of InGaAsP with a bandgap wavelength of 1490 nm. The
broadened spectral width at around 1525 nm (196.7 THz) becomes
10.7 times wider than that at around 1560 nm (192.3 THz) without
the enhancement effect, where amplified optical pulses with a pulse
width of ∼ 2 ps and a peak power of 10 W propagate through a
1-cm-long InGaAsP waveguide with a cross-section of 4 (μm)2.
Abstract: A simple multi-wavelength passively Q-switched
Erbium-doped fiber laser (EDFL) is demonstrated using low cost
multi-walled carbon nanotubes (MWCNTs) based saturable absorber
(SA), which is prepared using polyvinyl alcohol (PVA) as a host
polymer. The multi-wavelength operation is achieved based on
nonlinear polarization rotation (NPR) effect by incorporating 50 m
long photonic crystal fiber (PCF) in the ring cavity. The EDFL
produces a stable multi-wavelength comb spectrum for more than 14
lines with a fixed spacing of 0.48 nm. The laser also demonstrates a
stable pulse train with the repetition rate increases from 14.9 kHz to
25.4 kHz as the pump power increases from the threshold power of
69.0 mW to the maximum pump power of 133.8 mW. The minimum
pulse width of 4.4 μs was obtained at the maximum pump power of
133.8 mW while the highest energy of 0.74 nJ was obtained at pump
power of 69.0 mW.
Abstract: There is an increasing demand for broadband services
in Indonesia. Therefore, the answer is the use of Ka-Band which has
some advantages such as wider bandwidth, the higher transmission
speeds, and smaller size of antenna in the ground. However, rain
attenuation is the primary factor in the degradation of signal at the
Kaband. In this paper, the author will determine whether the Ka-band
frequency can be implemented in Indonesia which has high intensity
of rainfall.