Abstract: Cavitation in pumps is known as the formation of
vapor bubbles due to pressure drop and collapsing these bubbles. In
some conditions, it has been observed that the formation of bubbles
occurs at the pressure side of centrifugal pump blades. In this study,
the formation of bubbles at the pressure side of blades has been
investigated. Water is used in this study as the fluid and performance
curves were depicted for different flow rates in an approximately
constant speed. The results show that when a centrifugal pump works
in low flow rates, a secondary flow namely recirculation starts to
begin. In this condition, separation of flow increases which causes
vortex formation and local pressure drop and eventually the
formation of vapor bubbles starts.
Abstract: Relay based communication has gained considerable importance in the recent years. In this paper we find the end-toend statistics of a two hop non-regenerative relay branch, each hop being Nakagami-m faded. Closed form expressions for the probability density functions of the signal envelope at the output of a selection combiner and a maximal ratio combiner at the destination node are also derived and analytical formulations are verified through computer simulation. These density functions are useful in evaluating the system performance in terms of bit error rate and outage probability.
Abstract: At very high speeds, bubbles form in the underwater vehicles because of sharp trailing edges or of places where the local pressure is lower than the vapor pressure. These bubbles are called cavities and the size of the cavities grows as the velocity increases. A properly designed cavitator can induce the formation of a single big cavity all over the vehicle. Such a vehicle travelling in the vaporous cavity is called a supercavitating vehicle and the present research work mainly focuses on the dynamic modeling of such vehicles. Cavitation of the fins is also accounted and the effect of the same on trajectory is well explained. The entire dynamics has been developed using the state space approach and emphasis is given on the effect of size and angle of attack of the cavitator. Control law has been established for the motion of the vehicle using Non-linear Dynamic Inverse (NDI) with cavitator as the control surface.
Abstract: Size based filtration is one of the common methods
employed to isolate circulating tumor cells (CTCs) from whole
blood. It is well known that this method suffers from isolation
efficiency to purity tradeoff. However, this tradeoff is poorly
understood. In this paper, we present the design and manufacturing
of a special rectangular slit filter. The filter was designed to retain
maximal amounts of nucleated cells, while minimizing the pressure
on cells, thereby preserving their morphology. The key parameter,
namely, input pressure, was optimized to retain the maximal number
of tumor cells, whilst maximizing the depletion of normal blood cells
(red and white blood cells and platelets). Our results indicate that for
a slit geometry of 5 × 40 μm on a 13 mm circular membrane with a
fill factor of 21%, a pressure of 6.9 mBar yields the optimum for
maximizing isolation of MCF-7 and depletion of normal blood cells.
Abstract: The plastic flow of metal in the extrusion process is
an important factor in controlling the mechanical properties of the
extruded products. It is, however, difficult to predict the metal flow
in three dimensional extrusions of sections due to the involvement of
re-entrant corners. The present study is to find an upper bound
solution for the extrusion of triangular sectioned through taper dies
from round sectioned billet. A discontinuous kinematically
admissible velocity field (KAVF) is proposed. From the proposed
KAVF, the upper bound solution on non-dimensional extrusion
pressure is determined with respect to the chosen process parameters.
The theoretical results are compared with experimental results to
check the validity of the proposed velocity field. An extrusion setup
is designed and fabricated for the said purpose, and all extrusions are
carried out using circular billets. Experiments are carried out with
commercially available lead at room temperature.
Abstract: Molar excess Volumes, VE ijk and speeds of sound , uijk of 2-pyrrolidinone (i) + benzene or toluene (j) + ethanol (k) ternary mixture have been measured as a function of composition at 308.15 K. The observed speeds of sound data have been utilized to determine excess isentropic compressiblities, ( E S κ )ijk of ternary (i + j + k) mixtures. Molar excess volumes, VE ijk and excess isentropic compressibilities, ( E S κ )ijk data have fitted to the Redlich-Kister equation to calculate ternary adjustable parameters and standard deviations. The Moelywn-Huggins concept (Huggins in Polymer 12: 389-399, 1971) of connectivity between the surfaces of the constituents of binary mixtures has been extended to ternary mixtures (using the concept of a connectivity parameter of third degree of molecules, 3ξ , which inturn depends on its topology) to obtain an expression that describes well the measured VE ijk and ( E S κ )ijk data.
Abstract: En bloc assumes modeling all phases of the orthostatic test with the only one mathematical model, which allows the complex parametric view of orthostatic response. The work presents the implementation of a mathematical model for processing of the measurements of systolic, diastolic blood pressure and heart rate performed on volunteers during orthostatic test. The original assumption of model hypothesis that every postural change means only one Stressor, did not complying with the measurements of physiological circulation factor-time profiles. Results of the identification support the hypothesis that second postural change of orthostatic test causes induced Stressors, with the observation of a physiological regulation mechanism. Maximal demonstrations are on the heart rate and diastolic blood pressure-time profile, minimal are for the measurements of the systolic blood pressure. Presented study gives a new view on orthostatic test with impact on clinical practice.
Abstract: Stresses for the elastic-plastic transition and fully
plastic state have been derived for a thin rotating disc with inclusion
and results have been discussed numerically and depicted graphically.
It has been observed that the rotating disc with inclusion and made of
compressible material requires lesser angular speed to yield at the
internal surface whereas it requires higher percentage increase in
angular speed to become fully plastic as compare to disc made of
incompressible material.
Abstract: To investigates the effect of fiberglass clamping
process improvement on drape simulation prediction. This has
great effect on the mould and the fiber during manufacturing
process. This also, improves the fiber strain, the quality of the
fiber orientation in the area of folding and wrinkles formation
during the press-forming process. Drape simulation software
tool was used to digitalize the process, noting the formation
problems on the contour sensitive part. This was compared
with the real life clamping processes using single and double
frame set-ups to observe the effects. Also, restrains are
introduced by using clips, and the G-clamps with predetermine
revolution to; restrain the fabric deformation during the
forming process.The incorporation of clamping and fabric
restrain deformation improved on the prediction of the
simulation tool. Therefore, for effective forming process,
incorporation of clamping process into the drape simulation
process will assist in the development of fiberglass application
in manufacturing process.
Abstract: Image coding based on clustering provides immediate
access to targeted features of interest in a high quality decoded
image. This approach is useful for intelligent devices, as well as for
multimedia content-based description standards. The result of image
clustering cannot be precise in some positions especially on pixels
with edge information which produce ambiguity among the clusters.
Even with a good enhancement operator based on PDE, the quality of
the decoded image will highly depend on the clustering process. In
this paper, we introduce an ambiguity cluster in image coding to
represent pixels with vagueness properties. The presence of such
cluster allows preserving some details inherent to edges as well for
uncertain pixels. It will also be very useful during the decoding phase
in which an anisotropic diffusion operator, such as Perona-Malik,
enhances the quality of the restored image. This work also offers a
comparative study to demonstrate the effectiveness of a fuzzy
clustering technique in detecting the ambiguity cluster without losing
lot of the essential image information. Several experiments have been
carried out to demonstrate the usefulness of ambiguity concept in
image compression. The coding results and the performance of the
proposed algorithms are discussed in terms of the peak signal-tonoise
ratio and the quantity of ambiguous pixels.
Abstract: In this paper, the feasibility study of using a hybrid
system of ground heat exchangers (GHE) and direct evaporative
cooling system in arid weather condition has been performed. The
model is applied for Yazd and Kerman, two cities with arid weather
condition in Iran. The system composed of three sections: Ground-
Coupled-Circuit (GCC), Direct Evaporative Cooler (DEC) and
Cooling Coil Unite (CCU). The GCC provides the necessary precooling
for DEC. The GCC includes four vertical GHE which are
designed in series configuration. Simulation results show that
hybridization of GCC and DEC could provide comfort condition
whereas DEC alone did not. Based on the results the cooling
effectiveness of a hybrid system is more than unity. Thus, this novel
hybrid system could decrease the air temperature below the ambient
wet-bulb temperature. This environmentally clean and energy
efficient system can be considered as an alternative to the mechanical
vapor compression systems.
Abstract: The sand production problem has led researchers into making various attempts to understand the phenomenon. The generally accepted concept is that the occurrence of sanding is due to the in-situ stress conditions and the induced changes in stress that results in the failure of the reservoir sandstone during hydrocarbon production from wellbores. By using a hypothetical cased (perforated) well, an approach to the problem is presented here by using Finite Element numerical modelling techniques. In addition to the examination of the erosion problem, the influence of certain key parameters is studied in order to ascertain their effect on the failure and subsequent erosion process. The major variables investigated include: drawdown, perforation depth, and the erosion criterion. Also included is the determination of the optimal mud pressure for given operational and reservoir conditions. The improved understanding between parameters enables the choice of optimal values to minimize sanding during oil production.
Abstract: Wireless Sensor Networks (WSN) are emerging
because of the developments in wireless communication technology and miniaturization of the hardware. WSN consists of a large number of low-cost, low-power, multifunctional sensor nodes to monitor physical conditions, such as temperature, sound, vibration, pressure,
motion, etc. The MAC protocol to be used in the sensor networks must be energy efficient and this should aim at conserving the energy during its operation. In this paper, with the focus of analyzing the
MAC protocols used in wireless Adhoc networks to WSN, simulation
experiments were conducted in Global Mobile Simulator
(GloMoSim) software. Number of packets sent by regular nodes, and received by sink node in different deployment strategies, total energy
spent, and the network life time have been chosen as the metric for comparison. From the results of simulation, it is evident that the IEEE 802.11 protocol performs better compared to CSMA and MACA protocols.
Abstract: The proof of concept experiments were conducted to
determine the feasibility of using small amounts of Dissolved
Sulphur (DS) from the gaseous phase to precipitate platinum ions in
chloride media. Two sets of precipitation experiments were
performed in which the source of sulphur atoms was either a
thiosulphate solution (Na2S2O3) or a sulphur dioxide gas (SO2). In
liquid-liquid (L-L) system, complete precipitation of Pt was achieved
at small dosages of Na2S2O3 (0.01 – 1.0 M) in a time interval of 3-5
minutes. On the basis of this result, gas absorption tests were carried
out mainly to achieve sulphur solubility equivalent to 0.018 M. The
idea that huge amounts of precious metals could be recovered
selectively from their dilute solutions by utilizing the waste SO2
streams at low pressure seemed attractive from the economic and
environmental point of views. Therefore, mass transfer characteristics
of SO2 gas associated with reactive absorption across the gas-liquid
(G-L) interface were evaluated under different conditions of pressure
(0.5 – 2 bar), solution temperature ranges from 20 – 50 oC and acid
strength (1 – 4 M, HCl). This paper concludes with information about
selective precipitation of Pt in the presence of cations (Fe2+, Co2+,
and Cr3+) in a CSTR and recommendation to scale up laboratory data
to industrial pilot scale operations.
Abstract: In this paper, a pipelined version of genetic algorithm,
called PLGA, and a corresponding hardware platform are described.
The basic operations of conventional GA (CGA) are made pipelined
using an appropriate selection scheme. The selection operator, used
here, is stochastic in nature and is called SA-selection. This helps
maintaining the basic generational nature of the proposed pipelined
GA (PLGA). A number of benchmark problems are used to compare
the performances of conventional roulette-wheel selection and the
SA-selection. These include unimodal and multimodal functions with
dimensionality varying from very small to very large. It is seen that
the SA-selection scheme is giving comparable performances with
respect to the classical roulette-wheel selection scheme, for all the
instances, when quality of solutions and rate of convergence are considered.
The speedups obtained by PLGA for different benchmarks
are found to be significant. It is shown that a complete hardware
pipeline can be developed using the proposed scheme, if parallel
evaluation of the fitness expression is possible. In this connection
a low-cost but very fast hardware evaluation unit is described.
Results of simulation experiments show that in a pipelined hardware
environment, PLGA will be much faster than CGA. In terms of
efficiency, PLGA is found to outperform parallel GA (PGA) also.
Abstract: Dhaka, the capital city of Bangladesh, is one of the
densely populated cities in the world. Due to rapid urbanization 60%
of its population lives in slum and squatter settlements. The reason
behind this poverty is low economic growth, inequitable distribution
of income, unequal distribution of productive assets, unemployment
and underemployment, high rate of population growth, low level of
human resource development, natural disasters, and limited access to
public services. Along with poverty, creating pressure on urban land,
shelter, plots, open spaces this creates environmental and ecological
degradation. These constraints are mostly resulted from the failures
of the government policies and measures and only Government can
solve this problem. This is now prime time to establish planning and
environmental management policy and sustainable urban
development for the city and for the urban slum dwellers which are
free from eviction, criminals, rent seekers and other miscreants.
Abstract: A new SUZ-4 zeolite membrane with
tetraethlyammonium hydroxide as the template was fabricated on
mullite tube via hydrothermal sol-gel synthesis in a rotating
autoclave reactor. The suitable synthesis condition was SiO2:Al2O3
ratio of 21.2 for 4 days at 155 °C crystallization under autogenous
pressure. The obtained SUZ-4 possessed a high BET surface area of
396.4 m2/g, total pore volume at 2.611 cm3/g, and narrow pore size
distribution with 97 nm mean diameter and 760 nm long of needle
crystal shape. The SUZ-4 layer obtained from seeding crystallization
was thicker than that of without seeds or in situ crystallization.
Abstract: Modeling product configurations needs large amounts of knowledge about technical and marketing restrictions on the product. Previous attempts to automate product configurations concentrate on representations and management of the knowledge for specific domains in fixed and isolated computing environments. Since the knowledge about product configurations is subject to continuous change and hard to express, these attempts often failed to efficiently manage and exchange the knowledge in collaborative product development. In this paper, XML Topic Map (XTM) is introduced to represent and exchange the knowledge about product configurations in collaborative product development. A product configuration model based on XTM along with its merger and inference facilities enables configuration engineers in collaborative product development to manage and exchange their knowledge efficiently. A prototype implementation is also presented to demonstrate the proposed model can be applied to engineering information systems to exchange the product configuration knowledge.
Abstract: Computed tomography and laminography are heavily investigated in a compressive sensing based image reconstruction framework to reduce the dose to the patients as well as to the radiosensitive devices such as multilayer microelectronic circuit boards. Nowadays researchers are actively working on optimizing the compressive sensing based iterative image reconstruction algorithm to obtain better quality images. However, the effects of the sampled data’s properties on reconstructed the image’s quality, particularly in an insufficient sampled data conditions have not been explored in computed laminography. In this paper, we investigated the effects of two data properties i.e. sampling density and data incoherence on the reconstructed image obtained by conventional computed laminography and a recently proposed method called spherical sinusoidal scanning scheme. We have found that in a compressive sensing based image reconstruction framework, the image quality mainly depends upon the data incoherence when the data is uniformly sampled.
Abstract: Digital watermarking is the process of embedding
information into a digital signal which can be used in DRM (digital
rights managements) system. The visible watermark (often called logo)
can indicate the owner of the copyright which can often be seen in the
TV program and protects the copyright in an active way. However,
most of the schemes do not consider the visible watermark removing
process. To solve this problem, a visible watermarking scheme with
embedding and removing process is proposed under the control of a
secure template. The template generates different version of
watermarks which can be seen visually the same for different users.
Users with the right key can completely remove the watermark and
recover the original image while the unauthorized user is prevented to
remove the watermark. Experiment results show that our
watermarking algorithm obtains a good visual quality and is hard to be
removed by the illegally users. Additionally, the authorized users can
completely remove the visible watermark and recover the original
image with a good quality.