Abstract: In this study, direct numerical simulation for the bubble condensation in the subcooled boiling flow was performed. The main goal was to develop the CFD modeling for the bubble condensation and to evaluate the accuracy of the VOF model with the developed CFD modeling. CFD modeling for the bubble condensation was developed by modeling the source terms in the governing equations of VOF model using UDF. In the modeling, the amount of condensation was determined using the interfacial heat transfer coefficient obtained from the bubble velocity, liquid temperature and bubble diameter every time step. To evaluate the VOF model using the CFD modeling for the bubble condensation, CFD simulation results were compared with SNU experimental results such as bubble volume and shape, interfacial area, bubble diameter and bubble velocity. Simulation results predicted well the behavior of the actual condensing bubble. Therefore, it can be concluded that the VOF model using the CFD modeling for the bubble condensation will be a useful computational fluid dynamics tool for analyzing the behavior of the condensing bubble in a wide range of the subcooled boiling flow.
Abstract: An on-line condition monitoring method for transmission line is proposed using electrical circuit theory and IT technology in this paper. It is reasonable that the circuit parameters such as resistance (R), inductance (L), conductance (g) and capacitance (C) of a transmission line expose the electrical conditions and physical state of the line. Those parameters can be calculated from the linear equation composed of voltages and currents measured by synchro-phasor measurement technique at both end of the line. A set of linear voltage drop equations containing four terminal constants (A, B ,C ,D ) are mathematical models of the transmission line circuits. At least two sets of those linear equations are established from different operation condition of the line, they may mathematically yield those circuit parameters of the line. The conditions of line connectivity including state of connecting parts or contacting parts of the switching device may be monitored by resistance variations during operation. The insulation conditions of the line can be monitored by conductance (g) and capacitance(C) measurements. Together with other condition monitoring devices such as partial discharge, sensors and visual sensing device etc.,they may give useful information to monitor out any incipient symptoms of faults. The prototype of hardware system has been developed and tested through laboratory level simulated transmission lines. The test has shown enough evident to put the proposed method to practical uses.
Abstract: Cyprus- offshore aquaculture industry has promising
prospects taking into account that Cyprus is an island. Its production
trend is increasing overtaking bigger countries such Greece and Italy.
However, current mooring systems seem to be under-performing
acting as obstacles for its future development. Furthermore, shallow
coastal waters scarcity due to competing industries dictates future
development to come by moving further from shore exposing fish
farms and subsequently mooring systems to harsher environmental
loadings. It is, therefore, of paramount importance to design mooring
systems based on engineering and scientific principles and leave
behind the present “trial and error" methods. This paper presents the
current state of Cyprus- offshore aquaculture industry and focuses of
its mooring designs by proposing a new methodology for designing
more reliable systems, hence ensuring its future.
Abstract: The paper reports the preparation and photocatalytic
activity of ZnO/SnO2 and SnO2 nanoparticles. These nanoparticles
were synthesized by hydrothermal method. The products were
characterized by X-ray diffraction (XRD) and scanning electron
microscopy (SEM). Their grain sizes are about 50-100 nm. The
photocatalytic activities of these materials were investigated for
congo red removal from aqueous solution under UV light irradiation.
It was shown that the use of ZnO/SnO2 as photocatalyst have better
photocatalytic activity for degradation of congo red than SnO2 or
TiO2 (anatase, particle size: 30nm) alone.
Abstract: Most real world systems express themselves formally
as a set of nonlinear algebraic equations. As applications grow, the
size and complexity of these equations also increase. In this work, we
highlight the key concepts in using the homotopy analysis method
as a methodology used to construct efficient iteration formulas for
nonlinear equations solving. The proposed method is experimentally
characterized according to a set of determined parameters which
affect the systems. The experimental results show the potential and
limitations of the new method and imply directions for future work.
Abstract: The Želazny Most tailing pond is one of the largest
facilities worldwide for waste disposal from the copper mines located
in South-West Poland. A potential failure of the dam would allow
more than 10 million cubic meters of contaminated slurry to flow to
the valley, causing immense environmental problems to the
surrounding area. Thus, the determination of the strength properties
of the dam's soils and their variability is of utmost importance.
An extensive site investigation consisting of more than 480 cone
penetration tests (CPTs) with or without pore water pressure
measurements were conducted within a period of 13 years to study
the mechanical properties of the tailings body. The present work
investigates the point variability of the soil strength parameters
(effective friction angle
Abstract: Transmission network expansion planning (TNEP) is a basic part of power system planning that determines where, when and how many new transmission lines should be added to the network. Up till now, various methods have been presented to solve the static transmission network expansion planning (STNEP) problem. But in all of these methods, lines adequacy rate has not been considered at the end of planning horizon, i.e., expanded network misses adequacy after some times and needs to be expanded again. In this paper, expansion planning has been implemented by merging lines loading parameter in the STNEP and inserting investment cost into the fitness function constraints using genetic algorithm. Expanded network will possess a maximum adequacy to provide load demand and also the transmission lines overloaded later. Finally, adequacy index could be defined and used to compare some designs that have different investment costs and adequacy rates. In this paper, the proposed idea has been tested on the Garvers network. The results show that the network will possess maximum efficiency economically.
Abstract: This paper presents the optimal controller design of
the generator control unit in the aircraft power system. The adaptive
tabu search technique is applied to tune the controller parameters
until the best terminal output voltage of generator is achieved. The
output response from the system with the controllers designed by the
proposed technique is compared with those from the conventional
method. The transient simulations using the commercial software
package show that the controllers designed from the adaptive tabu
search algorithm can provide the better output performance compared
with the result from the classical method. The proposed design
technique is very flexible and useful for electrical aircraft engineers.
Abstract: This paper describes the performance of TCP Vegas
over the wireless IPv6 network. The performance of TCP Vegas is
evaluated using network simulator (ns-2). The simulation experiment
investigates how packet spacing affects the network delay, network
throughput and network efficiency of TCP Vegas. Moreover, we
investigate how the variable FTP packet sizes affect the network
performance. The result of the simulation experiment shows that as
the packet spacing is implements, the network delay is reduces,
network throughput and network efficiency is optimizes. As the FTP
packet sizes increase, the ratio of delay per throughput decreases.
From the result of experiment, we propose the appropriate packet size
in transmitting file transfer protocol application using TCP Vegas
with packet spacing enhancement over wireless IPv6 environment in
ns-2. Additionally, we suggest the appropriate ratio in determining
the appropriate RTT and buffer size in a network.
Abstract: In this paper, an analysis of a target location estimation
system using the best linear unbiased estimator (BLUE) for high
performance radar systems is presented. In synthetic environments,
we are here concerned with three key elements of radar system
modeling, which makes radar systems operates accurately in strategic
situation in virtual ground. Radar Cross Section (RCS) modeling
is used to determine the actual amount of electromagnetic waves
that are reflected from a tactical object. Pattern Propagation Factor
(PPF) is an attenuation coefficient of the radar equation that contains
the reflection from the surface of the earth, the diffraction, the
refraction and scattering by the atmospheric environment. Clutter is
the unwanted echoes of electronic systems. For the data fusion of
output results from radar detection in synthetic environment, BLUE
is used and compared with the mean values of each simulation results.
Simulation results demonstrate the performance of the radar system.
Abstract: Facing the concern of the population to its environment and to climatic change, city planners are now considering the urban climate in their choices of planning. The urban climate, representing different urban morphologies across central Bangkok metropolitan area (BMA), are used to investigates the effects of both the composition and configuration of variables of urban morphology indicators on the summer diurnal range of urban climate, using correlation analyses and multiple linear regressions. Results show first indicate that approximately 92.6% of the variation in the average maximum daytime near-surface air temperature (Ta) was explained jointly by the two composition variables of urban morphology indicators including open space ratio (OSR) and floor area ratio (FAR). It has been possible to determine the membership of sample areas to the local climate zones (LCZs) using these urban morphology descriptors automatically computed with GIS and remote sensed data. Finally result found the temperature differences among zones of large separation, such as the city center could be respectively from 35.48±1.04ºC (Mean±S.D.) warmer than the outskirt of Bangkok on average for maximum daytime near surface temperature to 28.27±0.21ºC for extreme event and, can exceed as 8ºC. A spatially disaggregation of urban thermal responsiveness map would be helpful for several reasons. First, it would localize urban areas concerned by different climate behavior over summer daytime and be a good indicator of urban climate variability. Second, when overlaid with a land cover map, this map may contribute to identify possible urban management strategies to reduce heat wave effects in BMA.
Abstract: Plackett-Burman statistical screening of media
constituents and operational conditions for extracellular lipase
production from isolate Trichoderma viride has been carried out in
submerged fermentation. This statistical design is used in the early
stages of experimentation to screen out unimportant factors from a
large number of possible factors. This design involves screening of
up to 'n-1' variables in just 'n' number of experiments. Regression
coefficients and t-values were calculated by subjecting the
experimental data to statistical analysis using Minitab version 15.
The effects of nine process variables were studied in twelve
experimental trials. Maximum lipase activity of 7.83 μmol /ml /min
was obtained in the 6th trail. Pareto chart illustrates the order of
significance of the variables affecting the lipase production. The
present study concludes that the most significant variables affecting
lipase production were found to be palm oil, yeast extract, K2HPO4,
MgSO4 and CaCl2.
Abstract: Intuitionistic fuzzy sets as proposed by Atanassov,
have gained much attention from past and latter researchers for
applications in various fields. Similarity measures between
intuitionistic fuzzy sets were developed afterwards. However, it does
not cater the conflicting behavior of each element evaluated. We
therefore made some modification to the similarity measure of IFS
by considering conflicting concept to the model. In this paper, we
concentrate on Zhang and Fu-s similarity measures for IFSs and
some examples are given to validate these similarity measures. A
simple modification to Zhang and Fu-s similarity measures of IFSs
was proposed to find the best result according to the use of degree of
indeterminacy. Finally, we mark up with the application to real
decision making problems.
Abstract: While in practice negotiation is always a mix of
cooperation and competition, these two elements correspond to
different approaches of the relationship and also different orientations
in term of strategy, techniques, tactics and arguments employed by
the negotiators with related effects and in the end leading to different
outcomes. The levels of honesty, trust and therefore cooperation are
influenced not only by the uncertainty of the situation, the objectives,
stakes or power but also by the orientation given from the very
beginning of the relationship. When negotiation is reduced to a
confrontation of power, participants rely on coercive measures, using
different kinds of threats or make false promises and bluff in order to
establish a more acceptable balance of power.
Most of the negotiators have a tendency to complain about the
unethical aspects of the tactics used by their counterparts while, as
the same time, they are mostly unaware of the sources of influence of
their own vision and practices. In this article, our intention is to
clarify these sources and try to understand what can lead negotiators
to unethical practices.
Abstract: The effectiveness of consuming a nutrient fortified oat drink on iron, zinc, vitamin A and vitamin C status was assessed among a cohort of school-aged Filipino children. Ultimate study implementation permitted only a within-subject comparison of change in nutritional status after four months of consuming a nutrient fortified oat drink. Thirty-eight anemic children (5-8 years) consumed an oat drink fortified with iron as NaFeEDTA, zinc, vitamin A and vitamin C for 120 days. Height, weight, serum nutrient levels, anemia status and dietary intake were assessed pre and post intervention. Thirty-four anemic children completed the intervention. After 4 months of intervention, prevalence of anemia decreased by 68% and significant improvements in iron and vitamin A status were observed. Results demonstrate the effectiveness of the fortified oat drink in alleviating anemia in young children and highlight the value of fortification programs
Abstract: Generation system reliability assessment is an
important task which can be performed using deterministic or
probabilistic techniques. The probabilistic approaches have
significant advantages over the deterministic methods. However,
more complicated modeling is required by the probabilistic
approaches. Power generation model is a basic requirement for this
assessment. One form of the generation models is the well known
capacity outage probability table (COPT). Different analytical
techniques have been used to construct the COPT. These approaches
require considerable mathematical modeling of the generating units.
The unit-s models are combined to build the COPT which will add
more burdens on the process of creating the COPT. Decimal to
Binary Conversion (DBC) technique is widely and commonly applied
in electronic systems and computing This paper proposes a novel
utilization of the DBC to create the COPT without engaging in
analytical modeling or time consuming simulations. The simple
binary representation , “0 " and “1 " is used to model the states o f
generating units. The proposed technique is proven to be an effective
approach to build the generation model.
Abstract: The present work deals with thermodynamic analysis
of cascade refrigeration system using ozone friendly refrigerants pair
R507A and R23. R507A is azeotropic mixture composed of HFC
refrigerants R125/R143a (50%/50% wt.). R23 is a single component
HFC refrigerant used as replacement to CFC refrigerant R13 in low
temperature applications. These refrigerants have zero ozone
depletion potential and are non-flammable and as R507A an
azeotropic mixture there is no problem of temperature glide. This
study thermodynamically analyzed R507A-R23 cascade refrigeration
system to optimize the design and operating parameters of the
system. The design and operating parameters include: Condensing,
evaporating, subcooling and superheating temperatures in the high
temperature circuit, temperature difference in the cascade heat
exchanger, Condensing, evaporating, subcooling and superheating
temperatures in the low temperature circuit.
Abstract: Operating rooms are important assets for hospitals as
they generate the largest revenue and, at the same time, produce the
largest cost for hospitals. The model presented in this paper helps
make capacity planning decisions on the combination of open
operating rooms (ORs) and estimated overtime to satisfy the
allocated OR time to each specialty. The model combines both
decisions on determining the amount of OR time to open and to
allocate to different surgical specialties. The decisions made are
based on OR costs, overutilization and underutilization costs, and
contribution margins from allocating OR time. The results show the
importance of having a good estimate of specialty usage of OR time
to determine the amount of needed capacity and highlighted the
tradeoff that the OR manager faces between opening more ORs
versus extending the working time of the ORs already in use.
Abstract: This paper mainly proposes an efficient modified
particle swarm optimization (MPSO) method, to identify a slidercrank
mechanism driven by a field-oriented PM synchronous motor.
In system identification, we adopt the MPSO method to find
parameters of the slider-crank mechanism. This new algorithm is
added with “distance" term in the traditional PSO-s fitness function to
avoid converging to a local optimum. It is found that the comparisons
of numerical simulations and experimental results prove that the
MPSO identification method for the slider-crank mechanism is
feasible.
Abstract: To achieve reliable solutions, today-s numerical and
experimental activities need developing more accurate methods and
utilizing expensive facilities, respectfully in microchannels. The analytical
study can be considered as an alternative approach to alleviate
the preceding difficulties. Among the analytical solutions, those with
high robustness and low complexities are certainly more attractive.
The perturbation theory has been used by many researchers to analyze
microflows. In present work, a compressible microflow with constant
heat flux boundary condition is analyzed. The flow is assumed to be
fully developed and steady. The Mach and Reynolds numbers are also
assumed to be very small. For this case, the creeping phenomenon
may have some effect on the velocity profile. To achieve robustness
solution it is assumed that the flow is quasi-isothermal. In this study,
the creeping term which appears in the slip boundary condition
is formulated by different mathematical formulas. The difference
between this work and the previous ones is that the creeping term
is taken into account and presented in non-dimensionalized form.
The results obtained from perturbation theory are presented based
on four non-dimensionalized parameters including the Reynolds,
Mach, Prandtl and Brinkman numbers. The axial velocity, normal
velocity and pressure profiles are obtained. Solutions for velocities
and pressure for two cases with different Br numbers are compared
with each other and the results show that the effect of creeping
phenomenon on the velocity profile becomes more important when
Br number is less than O(ε).