Abstract: The modeling of sound radiation is of fundamental importance for understanding the propagation of acoustic waves and, consequently, develop mechanisms for reducing acoustic noise. The propagation of acoustic waves, are involved in various phenomena such as radiation, absorption, transmission and reflection. The radiation is studied through the linear equation of the acoustic wave that is obtained through the equation for the Conservation of Momentum, equation of State and Continuity. From these equations, is the Helmholtz differential equation that describes the problem of acoustic radiation. In this paper we obtained the solution of the Helmholtz differential equation for an infinite cylinder in a pulsating through free and homogeneous. The analytical solution is implemented and the results are compared with the literature. A numerical formulation for this problem is obtained using the Boundary Element Method (BEM). This method has great power for solving certain acoustical problems in open field, compared to differential methods. BEM reduces the size of the problem, thereby simplifying the input data to be worked and reducing the computational time used.
Abstract: In this paper, two centrifugal model tests (case 1: raft
foundation, case 2: 2x2 piled raft foundation) were conducted in
order to evaluate the effect of ground subsidence on load sharing
among piles and raft and settlement of raft and piled raft
foundations. For each case, two conditions consisting of undrained
(without groundwater pumping) and drained (with groundwater
pumping) conditions were considered. Vertical loads were applied
to the models after the foundations were completely consolidated by
selfweight at 50g. The results show that load sharing by the piles in
piled raft foundation (piled load share) for drained condition
decreases faster than that for undrained condition. Settlement of
both raft and piled raft foundations for drained condition increases
more quickly than that for undrained condition. In addition, the
settlement of raft foundation increases more largely than the
settlement of piled raft foundation for drained condition.
Abstract: The System Identification problem looks for a
suitably parameterized model, representing a given process. The
parameters of the model are adjusted to optimize a performance
function based on error between the given process output and
identified process output. The linear system identification field is
well established with many classical approaches whereas most of
those methods cannot be applied for nonlinear systems. The problem
becomes tougher if the system is completely unknown with only the
output time series is available. It has been reported that the
capability of Artificial Neural Network to approximate all linear and
nonlinear input-output maps makes it predominantly suitable for the
identification of nonlinear systems, where only the output time series
is available. [1][2][4][5]. The work reported here is an attempt to
implement few of the well known algorithms in the context of
modeling of nonlinear systems, and to make a performance
comparison to establish the relative merits and demerits.
Abstract: Ten lactating multiparous Holstein cows were used in
a cross-over design with two dietary treatments and 28-d periods
(with 14 d as an adaptation) to study the effect of restaurant fat on
milk production and composition. Each cow was offered 14.7 kg
DM /d of the basal concentrate diet based on barley and corn (crude
protein = 17.7%, neutral detergent fiber = 23.5%, and acid detergent
fiber = 5.8% of dry matter) with free access to alfalfa. Dietary
treatments were arranged as supplying each cow with 0 (CONTROL)
or 150 g/day (RF) of restaurant fat. Supplemental RF did not
significantly (P > 0.25) affect milk yield, composition, and
composition yields, except for milk fat contents. Milk fat contents
were depressed (P < 0.05) with supplemental RF. Our results indicate
that RF could depress milk fat without affecting milk yield and that
the depression in milk fat in response to RF precedes the depression
in milk yield.
Abstract: One of the purposes of the robust method of
estimation is to reduce the influence of outliers in the data, on the
estimates. The outliers arise from gross errors or contamination from
distributions with long tails. The trimmed mean is a robust estimate.
This means that it is not sensitive to violation of distributional
assumptions of the data. It is called an adaptive estimate when the
trimming proportion is determined from the data rather than being
fixed a “priori-.
The main objective of this study is to find out the robustness
properties of the adaptive trimmed means in terms of efficiency, high
breakdown point and influence function. Specifically, it seeks to find
out the magnitude of the trimming proportion of the adaptive
trimmed mean which will yield efficient and robust estimates of the
parameter for data which follow a modified Weibull distribution with
parameter λ = 1/2 , where the trimming proportion is determined by a
ratio of two trimmed means defined as the tail length. Secondly, the
asymptotic properties of the tail length and the trimmed means are
also investigated. Finally, a comparison is made on the efficiency of
the adaptive trimmed means in terms of the standard deviation for the
trimming proportions and when these were fixed a “priori".
The asymptotic tail lengths defined as the ratio of two trimmed
means and the asymptotic variances were computed by using the
formulas derived. While the values of the standard deviations for the
derived tail lengths for data of size 40 simulated from a Weibull
distribution were computed for 100 iterations using a computer
program written in Pascal language.
The findings of the study revealed that the tail lengths of the
Weibull distribution increase in magnitudes as the trimming
proportions increase, the measure of the tail length and the adaptive
trimmed mean are asymptotically independent as the number of
observations n becomes very large or approaching infinity, the tail
length is asymptotically distributed as the ratio of two independent
normal random variables, and the asymptotic variances decrease as
the trimming proportions increase. The simulation study revealed
empirically that the standard error of the adaptive trimmed mean
using the ratio of tail lengths is relatively smaller for different values
of trimming proportions than its counterpart when the trimming
proportions were fixed a 'priori'.
Abstract: Reliability assessment and risk analysis of rotating
machine rotors in various overload and malfunction situations
present challenge to engineers and operators. In this paper a new
analytical method for evaluation of rotor under large deformation is
addressed. Model is presented in general form to include also
composite rotors. Presented simulation procedure is based on
variational work method and has capability to account for geometric
nonlinearity, large displacement, nonlinear support effect and rotor
contacting other machine components. New shape functions are
presented which capable to predict accurate nonlinear profile of
rotor. The closed form solutions for various operating and
malfunction situations are expressed. Analytical simulation results
are discussed
Abstract: A personal estimate of a health risk may not
correspond to a scientific assessment of the health risk. Hence, there
is a need to investigate perceived health risks in the public. In this
study, a young, educated and healthy group of people from a tertiary
institute were questioned about their health concerns. Ethics
clearance was obtained and data was collected by means of a
questionnaire. 362 students participated in the study. Tobacco use,
heavy alcohol drinking, illicit drugs, unsafe sex and potential
carcinogens were perceived to be the five greatest threats to health in
this cohort. On the other hand natural health products,
unemployment, unmet contraceptive needs, family violence and
homelessness were felt to be the least perceived health risks.
Nutrition-related health risks as well as health risks due to physical
inactivity and obesity were not perceived as major health threats.
Such a study of health perceptions may guide health promotion
campaigns.
Abstract: Radiofrequency (RF) lesioning of nerves have been commonly used to alleviate chronic pain, where RF current preventing transmission of pain signals through the nerve by heating the nerve causing the pain. There are some factors that affect the temperature distribution and the nerve lesion size, one of these factors is the inhomogeneities in the tissue medium. Our objective is to calculate the temperature distribution and the nerve lesion size in an inhomogeneous medium surrounding the RF electrode. A two 3-D finite element models are used to compare the temperature distribution in the homogeneous and inhomogeneous medium. Also the effect of temperature-dependent electric conductivity on maximum temperature and lesion size is observed. Results show that the presence of an inhomogeneous medium around the RF electrode has a valuable effect on the temperature distribution and lesion size. The dependency of electric conductivity on tissue temperature increased lesion size.
Abstract: In Mauritius, much emphasis is put on measures to
combat the high prevalence of non-communicable diseases (NCDs).
Health promotion campaigns for the adoption of healthy behaviors
and screening programs are done regularly by local authorities and
NCD surveys are carried out at intervals. However, the health
behaviors of the poor have not been investigated so far. This study
aims to give an insight on the perceptions of health status and
lifestyle health behaviors of poor people in Mauritius. A crosssectional
study among 83 persons benefiting from social aid in a
selected urban district was carried out. Results showed that 51.8% of
respondents perceived that they had good health status. 57.8% had no
known NCD whilst 25.3% had hypertension, followed by diabetes
(16.9%), asthma (9.6%) and heart disease (7.2%).They had low
smoking (10.8%) and alcohol consumption (6.0%) as well as high
physical activity prevalence (54.2%). These results were significantly
different from the NCD survey carried out in the general population.
Consumption of vegetables in the study was high. Overweight and
obesity trends were however similar to the NCD survey report 2009.
These findings contrast with other international studies showing poor
people having poor perceptions of health status and unhealthy
behavioral choices. Whether these positive health behaviors of poor
people in Mauritius arise out of choice or whether it is because the
alternative behavior is too costly remains to be investigated further.
Abstract: In this paper, the process of obtaining Q and R
matrices for optimal pitch aircraft control system has been described.
Since the innovation of optimal control method, the determination of
Q and R matrices for such system has not been fully specified. The
value of Q and R for optimal pitch aircraft control application, have
been simulated and calculated. The suitable results for Q and R have
been observed through the performance index (PI). If the PI is small
“enough", we would say the Q & R values are suitable for that
certain type of optimal control system. Moreover, for the same value
of PI, we could have different Q and R sets. Due to the rule-free
determination of Q and R matrices, a specific method is brought to
find out the rough value of Q and R referring to rather small value of
PI.
Abstract: When earthquakes strike the city it results in great loss of lives. The present paper talks about a new innovative design system (MegEifel) for buildings which has a mechanism to mitigate deaths in case any earthquake strikes the city. If buildings will be designed according to MegEifel design then the occupants of the building will be safe even when they are in sleep or are doing day wise activities during the time earthquake strikes. The core structure is suggested to be designed on the principle that more deep the foundations are, the harder it is to uproot the structure. The buildings will have an Eifel rod dug deep into earth which will help save lives in tall buildings when earthquake strikes. This design takes a leverage of protective shells to save lives.
Abstract: The problem of wastewater treatment in Egypt is a two-fold problem; the first part concerning the existing rural areas, the second one dealing with new industrial/domestic areas. In Egypt several agricultural projects have been initiated by the government and the private sector as well, in order to change its infrastructure. As a reliable energy source, photovoltaic pumping systems have contributed to supply water for local rural communities worldwide; they can also be implemented to solve the problem “wastewater environment pollution". The solution of this problem can be categorised as recycle process. In addition, because of regional conditions past technologies are being reexamined to select a smallscale treatment system requiring low construction and maintenance costs. This paper gives the design guidelines of a Photovoltaic Small- Scale Wastewater Treatment Plant (PVSSWTP) based on technologies that can be transferred.
Abstract: The machining performance is determined by the
frequency characteristics of the machine-tool structure and the
dynamics of the cutting process. Therefore, the prediction of dynamic
vibration behavior of spindle tool system is of great importance for the
design of a machine tool capable of high-precision and high-speed
machining. The aim of this study is to develop a finite element model
to predict the dynamic characteristics of milling machine tool and
hence evaluate the influence of the preload of the spindle bearings. To
this purpose, a three dimensional spindle bearing model of a high
speed engraving spindle tool was created. In this model, the rolling
interfaces with contact stiffness defined by Harris model were used to
simulate the spindle bearing components. Then a full finite element
model of a vertical milling machine was established by coupling the
spindle tool unit with the machine frame structure. Using this model,
the vibration mode that had a dominant influence on the dynamic
stiffness was determined. The results of the finite element simulations
reveal that spindle bearing with different preloads greatly affect the
dynamic behavior of the spindle tool unit and hence the dynamic
responses of the vertical column milling system. These results were
validated by performing vibration on the individual spindle tool unit
and the milling machine prototype, respectively. We conclude that
preload of the spindle bearings is an important component affecting
the dynamic characteristics and machining performance of the entire
vertical column structure of the milling machine.
Abstract: An upwind difference approximation is used for a singularly perturbed problem in material science. Based on the discrete Green-s function theory, the error estimate in maximum norm is achieved, which is first-order uniformly convergent with respect to the perturbation parameter. The numerical experimental result is verified the valid of the theoretical analysis.
Abstract: This work involved the use of phytoremediation to
remediate an aged soil contaminated with polychlorinated biphenyls
(PCBs). At microcosm scale, tests were prepared using soil samples
that have been collected in an industrial area with a total PCBs
concentration of about 250 μg kg-1. Medicago sativa and Lolium
italicum were the species selected in this study that is used as
“feasibility test" for full scale remediation. The experiment was
carried out with the addition of a mixture of randomly methylatedbeta-
cyclodextrins (RAMEB). At the end of the experiment analysis
of soil samples showed that in general the presence of plants has led
to a higher degradation of most congeners with respect to not
vegetated soil. The two plant species efficiencies were comparable
and improved by RAMEB addition with a final reduction of total
PCBs near to 50%. With increasing the chlorination of the congeners
the removal percentage of PCBs progressively decreased.
Abstract: This paper presents a new hardware interface using a
microcontroller which processes audio music signals to standard
MIDI data. A technique for processing music signals by extracting
note parameters from music signals is described. An algorithm to
convert the voice samples for real-time processing without complex
calculations is proposed. A high frequency microcontroller as the
main processor is deployed to execute the outlined algorithm. The
MIDI data generated is transmitted using the EIA-232 protocol. The
analyses of data generated show the feasibility of using
microcontrollers for real-time MIDI generation hardware interface.
Abstract: This article is devoted to the numerical solution of
large-scale quadratic eigenvalue problems. Such problems arise in
a wide variety of applications, such as the dynamic analysis of
structural mechanical systems, acoustic systems, fluid mechanics,
and signal processing. We first introduce a generalized second-order
Krylov subspace based on a pair of square matrices and two initial
vectors and present a generalized second-order Arnoldi process for
constructing an orthonormal basis of the generalized second-order
Krylov subspace. Then, by using the projection technique and the
refined projection technique, we propose a restarted generalized
second-order Arnoldi method and a restarted refined generalized
second-order Arnoldi method for computing some eigenpairs of largescale
quadratic eigenvalue problems. Some theoretical results are also
presented. Some numerical examples are presented to illustrate the
effectiveness of the proposed methods.
Abstract: This paper presents an overview of the design and
implementation of an online rule-based Expert Systems for Islamic
medication. T his Online Islamic Medication Expert System (OIMES)
focuses on physical illnesses only. Knowledge base of this Expert
System contains exhaustively the types of illness together with their
related cures or treatments/therapies, obtained exclusively from the
Quran and Hadith. Extensive research and study are conducted to
ensure that the Expert System is able to provide the most suitable
treatment with reference to the relevant verses cited in Quran or
Hadith. These verses come together with their related 'actions'
(bodily actions/gestures or some acts) to be performed by the patient
to treat a particular illness/sickness. These verses and the instructions
for the 'actions' are to be displayed unambiguously on the computer
screen. The online platform provides the advantage for patient getting
treatment practically anytime and anywhere as long as the computer
and Internet facility exist. Patient does not need to make appointment
to see an expert for a therapy.
Abstract: By the application of an improved back-propagation
neural network (BPNN), a model of current densities for a solid oxide
fuel cell (SOFC) with 10 layers is established in this study. To build
the learning data of BPNN, Taguchi orthogonal array is applied to
arrange the conditions of operating parameters, which totally 7 factors
act as the inputs of BPNN. Also, the average current densities
achieved by numerical method acts as the outputs of BPNN.
Comparing with the direct solution, the learning errors for all learning
data are smaller than 0.117%, and the predicting errors for 27
forecasting cases are less than 0.231%. The results show that the
presented model effectively builds a mathematical algorithm to predict
performance of a SOFC stack immediately in real time.
Also, the calculating algorithms are applied to proceed with the
optimization of the average current density for a SOFC stack. The
operating performance window of a SOFC stack is found to be
between 41137.11 and 53907.89. Furthermore, an inverse predicting
model of operating parameters of a SOFC stack is developed here by
the calculating algorithms of the improved BPNN, which is proved to
effectively predict operating parameters to achieve a desired
performance output of a SOFC stack.
Abstract: Avalanche release of snow has been modeled in the present studies. Snow is assumed to be represented by semi-solid and the governing equations have been studied from the concept of continuum approach. The dynamical equations have been solved for two different zones [starting zone and track zone] by using appropriate initial and boundary conditions. Effect of density (ρ), Eddy viscosity (η), Slope angle (θ), Slab depth (R) on the flow parameters have been observed in the present studies. Numerical methods have been employed for computing the non linear differential equations. One of the most interesting and fundamental innovation in the present studies is getting initial condition for the computation of velocity by numerical approach. This information of the velocity has obtained through the concept of fracture mechanics applicable to snow. The results on the flow parameters have found to be in qualitative agreement with the published results.