Abstract: The proper selection of the AC-side passive filter
interconnecting the voltage source converter to the power supply is
essential to obtain satisfactory performances of an active power filter
system. The use of the LCL-type filter has the advantage of
eliminating the high frequency switching harmonics in the current
injected into the power supply. This paper is mainly focused on
analyzing the influence of the interface filter parameters on the active
filtering performances. Some design aspects are pointed out. Thus,
the design of the AC interface filter starts from transfer functions by
imposing the filter performance which refers to the significant current
attenuation of the switching harmonics without affecting the
harmonics to be compensated. A Matlab/Simulink model of the entire
active filtering system including a concrete nonlinear load has been
developed to examine the system performances. It is shown that a
gamma LC filter could accomplish the attenuation requirement of the
current provided by converter. Moreover, the existence of an optimal
value of the grid-side inductance which minimizes the total harmonic
distortion factor of the power supply current is pointed out.
Nevertheless, a small converter-side inductance and a damping
resistance in series with the filter capacitance are absolutely needed
in order to keep the ripple and oscillations of the current at the
converter side within acceptable limits. The effect of change in the
LCL-filter parameters is evaluated. It is concluded that good active
filtering performances can be achieved with small values of the
capacitance and converter-side inductance.
Abstract: The basis of this paper is the assumption, that graviton
is a measurable entity of molecular gravitational acceleration and this
is not a hypothetical entity. The adoption of this assumption as an
axiom is tantamount to fully opening the previously locked door to
the boundary theory between laminar and turbulent flows. It leads to
the theorem, that the division of flows of Newtonian (viscous) fluids
into laminar and turbulent is true only, if the fluid is influenced by a
powerful, external force field. The mathematical interpretation of this
theorem, presented in this paper shows, that the boundary between
laminar and turbulent flow can be determined theoretically. This is a
novelty, because thus far the said boundary was determined
empirically only and the reasons for its existence were unknown.
Abstract: The flow field in a centrifugal fan is highly complex
with flow reversal taking place on the suction side of impeller and
diffuser vanes. Generally performance of the centrifugal fan could be
enhanced by judiciously introducing splitter vanes so as to improve
the diffusion process. An extensive numerical whole field analysis on
the effect of splitter vanes placed in discrete regions of suspected
separation points is possible using CFD. This paper examines the
effect of splitter vanes corresponding to various geometrical
locations on the impeller and diffuser. The analysis shows that the
splitter vanes located near the diffuser exit improves the static
pressure recovery across the diffusing domain to a larger extent. Also
it is found that splitter vanes located at the impeller trailing edge and
diffuser leading edge at the mid-span of the circumferential distance
between the blades show a marginal improvement in the static
pressure recovery across the fan. However, splitters provided near to
the suction side of the impeller trailing edge (25% of the
circumferential gap between the impeller blades towards the suction
side), adversely affect the static pressure recovery of the fan.
Abstract: A new class of percolation model in complex networks,
in which nodes are characterized by hidden variables reflecting the
properties of nodes and the occupied probability of each link is
determined by the hidden variables of the end nodes, is studied
in this paper. By the mean field theory, the analytical expressions
for the phase of percolation transition is deduced. It is determined
by the distribution of the hidden variables for the nodes and the
occupied probability between pairs of them. Moreover, the analytical
expressions obtained are checked by means of numerical simulations
on a particular model. Besides, the general model can be applied
to describe and control practical diffusion models, such as disease
diffusion model, scientists cooperation networks, and so on.
Abstract: This interdisciplinary study is an investigation to evaluate user-interfaces in business administration. The study is going to be implemented on two computerized business administration systems with two distinctive user-interfaces, so that differences between the two systems can be determined. Both systems, a commercial and a prototype developed for the purpose of this study, deal with ordering of supplies, tendering procedures, issuing purchase orders, controlling the movement of the stocks against their actual balances on the shelves and editing them on their tabulations. In the second suggested system, modern computer graphics and multimedia issues were taken into consideration to cover the drawbacks of the first system. To highlight differences between the two investigated systems regarding some chosen standard quality criteria, the study employs various statistical techniques and methods to evaluate the users- interaction with both systems. The study variables are divided into two divisions: independent representing the interfaces of the two systems, and dependent embracing efficiency, effectiveness, satisfaction, error rate etc.
Abstract: In this study, the sorption of Malachite green (MG) on Hydrilla verticillata biomass, a submerged aquatic plant, was investigated in a batch system. The effects of operating parameters such as temperature, adsorbent dosage, contact time, adsorbent size, and agitation speed on the sorption of Malachite green were analyzed using response surface methodology (RSM). The proposed quadratic model for central composite design (CCD) fitted very well to the experimental data that it could be used to navigate the design space according to ANOVA results. The optimum sorption conditions were determined as temperature - 43.5oC, adsorbent dosage - 0.26g, contact time - 200min, adsorbent size - 0.205mm (65mesh), and agitation speed - 230rpm. The Langmuir and Freundlich isotherm models were applied to the equilibrium data. The maximum monolayer coverage capacity of Hydrilla verticillata biomass for MG was found to be 91.97 mg/g at an initial pH 8.0 indicating that the optimum sorption initial pH. The external and intra particle diffusion models were also applied to sorption data of Hydrilla verticillata biomass with MG, and it was found that both the external diffusion as well as intra particle diffusion contributes to the actual sorption process. The pseudo-second order kinetic model described the MG sorption process with a good fitting.
Abstract: The aim of this study was to synthesize the single
walled carbon nanotubes (SWCNTs) and determine their hydrogen
storage capacities. SWCNTs were firstly synthesized by chemical
vapor deposition (CVD) of acetylene (C2H2) on a magnesium oxide
(MgO) powder impregnated with an iron nitrate (Fe(NO3)3·9H2O)
solution. The synthesis parameters were selected as: the synthesis
temperature of 800°C, the iron content in the precursor of 5% and the
synthesis time of 30 min. Purification process of SWCNTs was
fulfilled by microwave digestion at three different temperatures (120,
150 and 200 °C), three different acid concentrations (0.5, 1 and 1.5
M) and for three different time intervals (15, 30 and 60 min). Nitric
acid (HNO3) was used in the removal of the metal catalysts. The
hydrogen storage capacities of the purified materials were measured
using volumetric method at the liquid nitrogen temperature and gas
pressure up to 100 bar. The effects of the purification conditions such
as temperature, time and acid concentration on hydrogen adsorption
were investigated.
Abstract: Sol-gel method has been used to fabricate
nanocomposite films on glass substrates composed halloysite clay
mineral and nanocrystalline TiO2. The methodology for the synthesis
involves a simple chemistry method utilized nonionic surfactant
molecule as pore directing agent along with the acetic acid-based solgel
route with the absence of water molecules. The thermal treatment
of composite films at 450oC ensures elimination of organic material
and lead to the formation of TiO2 nanoparticles onto the surface of
the halloysite nanotubes. Microscopy techniques and porosimetry
methods used in order to delineate the structural characteristics of the
materials. The nanocomposite films produced have no cracks and
active anatase crystal phase with small crystallite size were deposited
on halloysite nanotubes. The photocatalytic properties for the new
materials were examined for the decomposition of the Basic Blue 41
azo dye in solution. These, nanotechnology based composite films
show high efficiency for dye’s discoloration in spite of different
halloysite quantities and small amount of halloysite/TiO2 catalyst
immobilized onto glass substrates. Moreover, we examined the
modification of the halloysite/TiO2 films with silver particles in order
to improve the photocatalytic properties of the films. Indeed, the
presence of silver nanoparticles enhances the discoloration rate of the
Basic Blue 41 compared to the efficiencies obtained for unmodified
films.
Abstract: In this study, mechanically alloyed Al 2024 powder is
densified by conventional sintering and by equal channel angular
pressing (ECAP) with and without back pressure. The powder was
encapsulated in an aluminium can for consolidation through ECAP.
The properties obtained in the compacts by conventional sintering
route and by ECAP are compared. The effect of conventional
sintering and ECAP on consolidation behaviour of powder,
microstructure, density and hardness is discussed. Room temperature
back pressure aided ECAP results in nearly full denser (97% of its
theoretical density) compact at room temperature. NanoIndentation
technique was used to determine the modulus of the consolidated
compacts.
Abstract: This paper presents a formalisation of the different existing code mutation techniques (polymorphism and metamorphism) by means of formal grammars. While very few theoretical results are known about the detection complexity of viral mutation techniques, we exhaustively address this critical issue by considering the Chomsky classification of formal grammars. This enables us to determine which family of code mutation techniques are likely to be detected or on the contrary are bound to remain undetected. As an illustration we then present, on a formal basis, a proof-of-concept metamorphic mutation engine denoted PB MOT, whose detection has been proven to be undecidable.
Abstract: This research were investigated, determined, and
analyzed of the climate characteristically change in the provincial
Udon Thani in the period of 60 surrounding years from 1951 to 2010
A.D. that it-s transferred to effects of climatologically data for
determining global warming. Statistically significant were not found
for the 60 years- data (R2
Abstract: The aim of this article is to narrate the utility of novel simulation approach i.e. convolution method to predict blood concentration of drug utilizing dissolution data of salbutamol sulphate microparticulate formulations with different release patterns (1:1, 1:2 and 1:3, drug:polymer). Dissolution apparatus II USP 2007 and 900 ml double distilled water stirrd at 50 rpm was employed for dissolution analysis. From dissolution data, blood drug concentration was determined, and in return predicted blood drug concentration data was used to calculate the pharmacokinetic parameters i.e. Cmax, Tmax, and AUC. Convolution is a good biwaiver technique; however its better utility needs it application in the conditions where biorelevant dissolution media are used.
Abstract: This paper compares planning results of the electricity and water generation inventory up to year 2030 in the State of
Kuwait. Currently, the generation inventory consists of oil and gas fired technologies only. The planning study considers two main cases. The first case, Reference case, examines a generation inventory based on oil and gas fired generation technologies only.
The second case examines the inclusion of renewables as part of the generation inventory under two scenarios. In the first scenario, Ref-RE, renewable build-out is based on optimum economic performance
of overall generation system. Result shows that the optimum installed
renewable capacity with electric energy generation of 11% . In the second scenario, Ref-RE20, the renewable capacity build-out is
forced to provide 20% of electric energy by 2030. The respective energy systems costs of Reference, Ref-RE and Ref-RE20 case
scenarios reach US dollar 24, 10 and 14 billion annually in 2030.
Abstract: 20 years of dentistry was a period of transition from
communist to market economy but Romanian doctors have
insufficient management knowledge. Recently, the need for modern
management has increased due to technologies and superior materials
appearance, as patient-s demands.
Research goal is to increase efficiency by evaluating dental
medical office cost categories in real pricing procedures.
Empirical research is based on guided study that includes
information about the association between categories of cost
perception and therapeutic procedures commonly used in dental
offices.
Due to the obtained results to identify all the labours that make up
a settled procedure costs were determined for each procedure.
Financial evaluation software was created with the main functions:
introducing and maintaining patient records, treatment and
appointments made, procedures cost and monitoring office
productivity.
We believe that the study results can significantly improve the
financial management of dental offices, increasing the effectiveness
and quality of services.
Abstract: A study was conducted to determine the effect of
feeding glycerol on dairy cows performance. Twenty four Holstein
Friesian crossbred (>87.5% Holstein Friesian) lactating dairy cows in
early lactation; averaging 13+2.4 kg of milk, 64+45 days in milk,
55+16 months old and 325+26 kg live weight, were stratified for
milk yield, days in milk, age, stage of lactation and body weight, and
then randomly allocated to three treatment groups. All cows were fed
approximate 8 kg of concentrate together with ad libitum corn silage
and freely access to clean water. Nil or 150 and 300g of glycerol
were supplemented to the cows according to treatment groups. All
cows consumed similar concentrate, corn silage and total DM and
NELP. There were no significant differences in DM intake, CP intake,
NELP intake, milk and milk composition yields. All cows had similar
fat, protein, lactose, solid not fat and total solid percentage. All cows
gain similar live weight. The present study indicated that,
supplementation of glycerol did not enhance milk yield, milk
composition and live weight change.
Abstract: Use of fly ash as a supplementary cementing material
in large volumes can bring both technological and economic benefits
for concrete industry. In this investigation mix proportions for high
volume fly ash concrete were determined at cement replacement
levels of 50%, 55%, 60% and 65% with low calcium fly ash. Flexural
and compressive strengths of different mixes were measured at ages
of 7, 28 and 90 days. Flexural strength of composite section prepared
from pavement quality and lean high volume fly ash concrete was
determined at the age of 28 days. High volume fly ash concrete mixes
exhibited higher rate of strength gain and age factors than
corresponding reference concrete mixes. The optimum cement
replacement level for pavement quality concrete was found to be
60%. The consideration of bond between pavement quality and lean
of high volume fly ash concrete will be beneficial in design of rigid
pavements.
Abstract: Despite the relatively large number of studies that
have examined the use of appeals in advertisements, research on the
use of appeals in green advertisements is still underdeveloped and
needs to be investigated further, as it is definitely a tool for marketers
to create illustrious ads. In this study, content analysis was employed
to examine the nature of green advertising appeals and to match the
appeals with the green advertisements. Two different types of green
print advertisings, product orientation and organizational image
orientation were used. Thirty highly educated participants with
different backgrounds were asked individually to ascertain three
appeals out of thirty-four given appeals found among forty real green
advertisements. To analyze participant responses and to group them
based on common appeals, two-step K-mean clustering is used. The
clustering solution indicates that eye-catching graphics and
imaginative appeals are highly notable in both types of green ads.
Depressed, meaningful and sad appeals are found to be highly used in
organizational image orientation ads, whereas, corporate image,
informative and natural appeals are found to be essential for product
orientation ads.
Abstract: Application of pesticides in the paddy fields has
deleterious effects on non-target organisms including cyanobacteria
which are photosynthesizing and nitrogen fixing micro-organisms
contributing significantly towards soil fertility and crop yield.
Pesticide contamination in the paddy fields has manifested into a
serious global environmental concern. To study the effect of one such
pesticide, three cyanobacterial strains; Anabaena fertilissima,
Aulosira fertilissima and Westiellopsis prolifica were selected for
their stress responses to an Organochlorine insecticide - 6, 7, 8, 9, 10,
10-hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 4, 3-
benzodioxathiepine-3-oxide, with reference to their photosynthesic
pigments-chlorophyll-a and carotenoids as well as accessory
pigments-phycobiliproteins (phycocyanin, allophycocyanin and
phycoerythrin), stress induced biochemical metabolites like
carbohydrates, proteins, amino acids, phenols and enzymes-nitrate
reductase, glutamine synthetase and succinate dehydrogenase. All
the three cyanobacterial strains were adversely affected by the
insecticide doses and inhibition was dose dependent. Reduction in
photosynthetic and accessory pigments, metabolites, nitrogen fixing
and respiratory enzymes of the test organisms were accompanied
with an initial increase in their total protein at lower Organochlorine
doses. On the other hand, increased amount of phenols in all the
insecticide treated concentrations was indicative of stressed activities
of the organisms.
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: 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.