Abstract: We model and simulate the combined effect of fiber
dispersion and frequency chirp of a directly modulated high-speed
laser diode on the figures of merit of a non-amplified 40-Gbps optical
fiber link. We consider both the return to zero (RZ) and non-return to
zero (NRZ) patterns of the pseudorandom modulation bits. The
performance of the fiber communication system is assessed by the
fiber-length limitation due to the fiber dispersion. We study the
influence of replacing standard single-mode fibers by non-zero
dispersion-shifted fibers on the maximum fiber length and evaluate
the associated power penalty. We introduce new dispersion
tolerances for 1-dB power penalty of the RZ and NRZ 40-Gbps
optical fiber links.
Abstract: Taro Scarab beetles (Papuana uninodis, Coleoptera:
Scarabaeidae) inflict severe damage on important root crops and
plants such as Taro or Cocoyam, yam, sweet potatoes, oil palm and
coffee tea plants across Africa and Asia resulting in economic
hardship and starvation in some nations. Scoliid wasps and
Metarhizium anisopliae fungus - bio-control agents; are shown to be
able to control the population of Scarab beetle adults and larvae using
a newly created simulation model based on non-linear ordinary
differential equations that track the populations of the beetle life
cycle stages: egg, larva, pupa, adult and the population of the scoliid
parasitoid wasps, which attack beetle larvae. In spite of the challenge
driven by the longevity of the scarab beetles, the combined effect of
the larval wasps and the fungal bio-control agent is able to control
and drive down the population of both the adult and the beetle eggs
below the environmental carrying capacity within an interval of 120
days, offering the long term prospect of a stable and eco-friendly
environment; where the population of scarab beetles is: regulated by
parasitoid wasps and beneficial soil saprophytes.
Abstract: Collapsible soils go through radical rearrangement of
their particles when triggered by water, stress or/and vibration,
causing loss of volume. This loss of volume in soil as seen in
foundation failures has caused millions of dollars’ worth of damages
to public facilities and infrastructure and so has an adverse effect on
the society and people. Despite these consequences and the several
studies that are available, more research is still required in the study
of soil collapsibility. Discerning the pedogenesis (formation) of soils
and investigating the combined effects of the different geological soil
properties is key to elucidating and quantifying soils collapsibility.
This study presents a novel laboratory testing regime that would be
undertaken on soil samples where the effects of soil type, compactive
variables (moisture content, density, void ratio, degree of saturation)
and loading are analyzed. It is anticipated that results obtained would
be useful in mapping the trend of the combined effect thus the basis
for evaluating soil collapsibility or collapse potentials encountered in
construction with volume loss problems attributed to collapse.
Abstract: In terms of ecology forecast effects of desertification, the purpose of this study is to develop a predictive model of growth and adaptation of species in arid environment and bioclimatic conditions. The impact of climate change and the desertification phenomena is the result of combined effects in magnitude and frequency of these phenomena. Like the data involved in the phytopathogenic process and bacteria growth in arid soil occur in an uncertain environment because of their complexity, it becomes necessary to have a suitable methodology for the analysis of these variables. The basic principles of fuzzy logic those are perfectly suited to this process. As input variables, we consider the physical parameters, soil type, bacteria nature, and plant species concerned. The result output variable is the adaptability of the species expressed by the growth rate or extinction. As a conclusion, we prevent the possible strategies for adaptation, with or without shifting areas of plantation and nature adequate vegetation.
Abstract: The stress-strain relationship of concrete under flexure is one of the essential parameters in assessing ultimate flexural strength capacity of RC beams. Currently, the concrete stress-strain curve in flexure is obtained by incorporating a constant scale-down factor of 0.85 in the uniaxial stress-strain curve. However, it was revealed that strain gradient would improve the maximum concrete stress under flexure and concrete stress-strain curve is strain gradient dependent. Based on the strain-gradient-dependent concrete stress-strain curve, the investigation of the combined effects of strain gradient and concrete strength on flexural strength of RC beams was extended to high strength concrete up to 100 MPa by theoretical analysis. As an extension and application of the authors’ previous study, a new flexural strength design method incorporating the combined effects of strain gradient and concrete strength is developed. A set of equivalent rectangular concrete stress block parameters is proposed and applied to produce a series of design charts showing that the flexural strength of RC beams are improved with strain gradient effect considered.
Abstract: This study investigated the combined effect of cold rolling and heat treatment on the mechanical properties of Al-Ti alloy. Samples of the alloy are cast in metal mould to obtain 0.94-2.19wt% mixes of titanium. These samples are grouped into untreated (as-cast) and those that are cold rolled to fifty percent reduction, homogenized at 5000C and soaked for one hour. The cold rolled and heat treated samples are normalized (RTn) and quench-tempered (RTq-t) at 1000C. All these samples are subjected to tensile, micro-hardness and microstructural evaluation. Results show remarkable improvement in the mechanical properties of the cold rolled and heat treated samples compared to the as-cast. In particular, the RTq-t samples containing titanium in the range of 1.7-2.2% demonstrates improve tensile strength by 24.7%, yield strength, 28%, elastic modulus, 38.3% and micro-hardness, 20.5%. The Al3Ti phase being the most stable precipitate in the α-Al matrix appears to have been responsible for the significant improvement in the alloy’s mechanical properties. It is concluded that quench and temper heat treatment is an effective method of improving the strength-strain ratio of cold rolled Al-.0.9-2.2%Ti alloy.
Abstract: A numerical investigation is performed for non Newtonian fluids flow between two concentric cylinders. The D2Q9 lattice Boltzmann model developed from the Bhatangar-Gross-Krook (LBGK) approximation is used to obtain the flow field for fluids obeying to the power-law model. The inner and outer cylinders rotate in the same and the opposite direction while the end walls are maintained at rest. The combined effects of the Reynolds number (Re) of the inner and outer cylinders, the radius ratio (η) as well as the power-law index (n) on the flow characteristics are analyzed for an annular space of a finite aspect ratio (Γ). Two flow modes are obtained: a primary mode (laminar stable regime) and a secondary mode (laminar unstable regime). The so obtained flow structures are different from one mode to another. The transition critical Reynolds number Rec from the primary to the secondary mode is analyzed for the co-courant and counter-courant flows. This critical value increases as n increases. The prediction of the swirling flow of non Newtonians fluids in axisymmetric geometries is shown in the present work.
Abstract: In this work we study the thermodynamic behavior of some ventilated facades under summer operating conditions in Southern Spain. Under these climatic conditions, indoor comfort implies a high energetic demand due to high temperatures that usually are reached in this season in the considered geographical area.
The aim of this work is to determine if during summer operating conditions in Southern Spain, ventilated façades provide some energy saving compared to the non-ventilated façades and to deduce their behavior patterns in terms of energy efficiency.
The modelization of the air flow in the channel has been performed by using Navier-Stokes equations for thermodynamic flows. Numerical simulations have been carried out with a 2D Finite Element approach.
This way, we analyze the behavior of ventilated façades under different weather conditions as variable wind, variable temperature and different levels of solar irradiation.
CFD computations show the combined effect of the shading of the external wall and the ventilation by the natural convection into the air gap achieve a reduction of the heat load during the summer period. This reduction has been evaluated by comparing the thermodynamic performances of two ventilated and two unventilated façades with the same geometry and thermophysical characteristics.
Abstract: An effective approach for extracting document images from a noisy background is introduced. The entire scheme is divided into three sub- stechniques – the initial preprocessing operations for noise cluster tightening, introduction of a new thresholding method by maximizing the ratio of stan- dard deviations of the combined effect on the image to the sum of weighted classes and finally the image restoration phase by image binarization utiliz- ing the proposed optimum threshold level. The proposed method is found to be efficient compared to the existing schemes in terms of computational complexity as well as speed with better noise rejection.
Abstract: Heat Index describes the combined effect of
temperature and humidity on human body. This combined effect is
causing a serious threat to the health of people because of the
changing climate. With climate change, climate variability and thus
the occurrence of heat waves is likely to increase. Evidence is
emerging from the analysis of long-term climate records of an
increase in the frequency and duration of extreme temperature events
in all over Bangladesh particularly during summer. Summer season
has prolonged while winters have become short in Bangladesh.
Summers have become hotter and thus affecting the lives of the
people engaged in outdoor activities during scorching sun hours. In
2003 around 62 people died due to heat wave across the country. In
this paper Bangladesh is divided in four regions and heat index has
been calculated from 1960 to 2010 in these regions of the country.
The aim of this paper is to identify the spots most vulnerable to heat
strokes and heat waves due to high heat index. The results show
upward trend of heat index in almost all the regions of Bangladesh.
The highest increase in heat index value has been observed in areas
of South-west region and North-west Region. The highest change in
average heat index has been found in Jessore by almost 5.50C.
Abstract: During signal transmission, the combined effect of the
transmitter filter, the transmission medium, and additive white
Gaussian noise (AWGN) are included in the channel which distort
and add noise to the signal. This causes the well defined signal
constellation to spread causing errors in bit detection. A compact pi
neural network with minimum number of nodes is proposed. The
replacement of summation at each node by multiplication results in
more powerful mapping. The resultant pi network is tested on six
different channels.
Abstract: This is a study on numerical simulation of the convection-diffusion transport of a chemical species in steady flow through a small-diameter tube, which is lined with a very thin layer made up of retentive and absorptive materials. The species may be subject to a first-order kinetic reversible phase exchange with the wall material and irreversible absorption into the tube wall. Owing to the velocity shear across the tube section, the chemical species may spread out axially along the tube at a rate much larger than that given by the molecular diffusion; this process is known as dispersion. While the long-time dispersion behavior, well described by the Taylor model, has been extensively studied in the literature, the early development of the dispersion process is by contrast much less investigated. By early development, that means a span of time, after the release of the chemical into the flow, that is shorter than or comparable to the diffusion time scale across the tube section. To understand the early development of the dispersion, the governing equations along with the reactive boundary conditions are solved numerically using the Flux Corrected Transport Algorithm (FCTA). The computation has enabled us to investigate the combined effects on the early development of the dispersion coefficient due to the reversible and irreversible wall reactions. One of the results is shown that the dispersion coefficient may approach its steady-state limit in a short time under the following conditions: (i) a high value of Damkohler number (say Da ≥ 10); (ii) a small but non-zero value of absorption rate (say Γ* ≤ 0.5).
Abstract: One challenging direction of mobile commerce (mcommerce)
that is getting a great deal of attention globally is mobile
financing. The smart-phone and PDA users all around the world are
facing difficulties to become accustomed and trust in m-commerce.
The main rationale can be the slow variation and lack of trust in
mobile payment systems. Mobile payment systems that are in use
need to be more effective and efficient. This paper proposes: the
interface design is not the only factor affecting the m-commerce
adoption and lack of trust; in fact it is the combined effect of
interface usability and trustworthy mobile payment systems, because
it-s the money that the user has to spend at the end of the day, which
the user requires to get transferred securely. The purpose of this
research is to identify the problems regarding the trust and adaption
of m-commerce applications by mobile users and to provide the best
possible solution with respect to human computer interaction (HCI)
principles.
Abstract: This paper reviews recent studies and particularly the
effects of Climate Change in the North Tropical Atlantic by studying
atmospheric conditions that prevailed in 2005 ; Coral Bleaching
HotSpot and Hurricane Katrina. In the aim to better understand and
estimate the impact of the physical phenomenon, i.e. Thermal
Oceanic HotSpot (TOHS), isotopic studies of δ18O and δ13C on
marine animals from Guadeloupe (French Caribbean Island) were
carried out. Recorded measures show Sea Surface Temperature (SST)
up to 35°C in August which is much higher than data recorded by
NOAA satellites 32°C. After having reviewed the process that led to
the creation of Hurricane Katrina which hit New Orleans in August
29, 2005, it will be shown that the climatic conditions in the
Caribbean from August to October 2005 have influenced Katrina
evolution. This TOHS is a combined effect of various phenomenon
which represent an additional factor to estimate future climate
changes.
Abstract: Cooktop burners are widely used nowadays. In
cooktop burner design, nozzle efficiency and greenhouse
gas(GHG) emissions mainly depend on heat transfer from the
premixed flame to the impinging surface. This is a complicated
issue depending on the individual and combined effects of various
input combustion variables. Optimal operating conditions for
sustainable burner design were rarely addressed, especially in the
case of multiple slot-jet burners. Through evaluating the optimal
combination of combustion conditions for a premixed slot-jet
array, this paper develops a practical approach for the sustainable
design of gas cooktop burners. Efficiency, CO and NOx emissions
in respect of an array of slot jets using premixed flames were
analysed. Response surface experimental design were applied to
three controllable factors of the combustion process, viz.
Reynolds number, equivalence ratio and jet-to-vessel distance.
Desirability Function Approach(DFA) is the analytic technique
used for the simultaneous optimization of the efficiency and
emission responses.
Abstract: The present work is concerned with the effect of turning process parameters (cutting speed, feed rate, and depth of cut) and distance from the center of work piece as input variables on the chip micro-hardness as response or output. Three experiments were conducted; they were used to investigate the chip micro-hardness behavior at diameter of work piece for 30[mm], 40[mm], and 50[mm]. Response surface methodology (R.S.M) is used to determine and present the cause and effect of the relationship between true mean response and input control variables influencing the response as a two or three dimensional hyper surface. R.S.M has been used for designing a three factor with five level central composite rotatable factors design in order to construct statistical models capable of accurate prediction of responses. The results obtained showed that the application of R.S.M can predict the effect of machining parameters on chip micro-hardness. The five level factorial designs can be employed easily for developing statistical models to predict chip micro-hardness by controllable machining parameters. Results obtained showed that the combined effect of cutting speed at it?s lower level, feed rate and depth of cut at their higher values, and larger work piece diameter can result increasing chi micro-hardness.
Abstract: Extraction of lactic acid by emulsion liquid membrane technology (ELM) using n-trioctyl amine (TOA) in n-heptane as carrier within the organic membrane along with sodium carbonate as acceptor phase was optimized by using response surface methodology (RSM). A three level Box-Behnken design was employed for experimental design, analysis of the results and to depict the combined effect of five independent variables, vizlactic acid concentration in aqueous phase (cl), sodium carbonate concentration in stripping phase (cs), carrier concentration in membrane phase (ψ), treat ratio, and batch extraction time (τ)
with equal volume of organic and external aqueous phase on lactic acid extraction efficiency. The maximum lactic acid extraction efficiency (ηext) of 98.21%from aqueous phase in a batch reactor using ELM was found at the optimized values for test variables, cl, cs, ψ, and τ as 0.06 [M], 0.18 [M], 4.72 (%,v/v), 1.98 (v/v) and 13.36 min respectively.
Abstract: A two-dimensional numerical simulation of the contribution
of both inertial and aerodynamic forces on the blade loads of
a Vertical-Axis Wind Turbine (VAWT) is presented. After describing
the computational model and the relative validation procedure, a
complete campaign of simulations - based on full RANS unsteady
calculations - is proposed for a three-bladed rotor architecture characterized
by a NACA 0021 airfoil. For each analyzed angular velocity,
the combined effect of pressure and viscous forces acting on every
rotor blade are compared to the corresponding centrifugal forces,
due to the revolution of the turbine, thus achieving a preliminary
estimation of the correlation between overall rotor efficiency and
structural blade loads.
Abstract: An exploratory computational investigation using
RANS & URANS was carried out to understand the aerodynamics
around an isolatedsingle rotating wheel with decreasing ground
proximity. The wheel was initially modeled in free air conditions,
then with decreasing ground proximity and increased yaw angle with
rotational speeds. Three speeds of rotation were applied to the wheel
so that the effect of different angular velocities can be investigated. In
addition to rotation, three different yaw angles were applied to the
rotating wheel in order to understand how these two variables
combined affect the aerodynamic flow field around the wheel.
Abstract: The Muslim faith requires individuals to fast between
the hours of sunrise and sunset during the month of Ramadan. Our
recent work has concentrated on some of the changes that take place
during the daytime when fasting. A questionnaire was developed to
assess subjective estimates of physical, mental and social activities,
and fatigue. Four days were studied: in the weeks before and after
Ramadan (control days) and during the first and last weeks of
Ramadan (experimental days). On each of these four days, this
questionnaire was given several times during the daytime and once
after the fast had been broken and just before individuals retired at
night.
During Ramadan, daytime mental, physical and social activities
all decreased below control values but then increased to abovecontrol
values in the evening. The desires to perform physical and
mental activities showed very similar patterns. That is, individuals
tried to conserve energy during the daytime in preparation for the
evenings when they ate and drank, often with friends. During
Ramadan also, individuals were more fatigued in the daytime and
napped more often than on control days. This extra fatigue probably
reflected decreased sleep, individuals often having risen earlier
(before sunrise, to prepare for fasting) and retired later (to enable
recovery from the fast).
Some physiological measures and objective measures of
performance (including the response to a bout of exercise) have also
been investigated. Urine osmolality fell during the daytime on
control days as subjects drank, but rose in Ramadan to reach values
at sunset indicative of dehydration. Exercise performance was also
compromised, particularly late in the afternoon when the fast had
lasted several hours. Self-chosen exercise work-rates fell and a set
amount of exercise felt more arduous. There were also changes in
heart rate and lactate accumulation in the blood, indicative of greater
cardiovascular and metabolic stress caused by the exercise in
subjects who had been fasting. Daytime fasting in Ramadan produces
widespread effects which probably reflect combined effects of sleep
loss and restrictions to intakes of water and food.