Abstract: This paper presents a generalized formulation for the
problem of buckling optimization of anisotropic, radially graded,
thin-walled, long cylinders subject to external hydrostatic pressure.
The main structure to be analyzed is built of multi-angle fibrous
laminated composite lay-ups having different volume fractions of the
constituent materials within the individual plies. This yield to a
piecewise grading of the material in the radial direction; that is the
physical and mechanical properties of the composite material are
allowed to vary radially. The objective function is measured by
maximizing the critical buckling pressure while preserving the total
structural mass at a constant value equals to that of a baseline
reference design. In the selection of the significant optimization
variables, the fiber volume fractions adjoin the standard design
variables including fiber orientation angles and ply thicknesses. The
mathematical formulation employs the classical lamination theory,
where an analytical solution that accounts for the effective axial and
flexural stiffness separately as well as the inclusion of the coupling
stiffness terms is presented. The proposed model deals with
dimensionless quantities in order to be valid for thin shells having
arbitrary thickness-to-radius ratios. The critical buckling pressure
level curves augmented with the mass equality constraint are given
for several types of cylinders showing the functional dependence of
the constrained objective function on the selected design variables. It
was shown that material grading can have significant contribution to
the whole optimization process in achieving the required structural
designs with enhanced stability limits.
Abstract: This paper investigates and compares performance of
various conventional and fuzzy logic based controllers at generator
locations for oscillation damping. Performance of combination of
conventional and fuzzy logic based controllers also studied by
comparing overshoot on the active power deviation response for a
small disturbance and damping ratio of the critical mode. Fuzzy logic
based controllers can not be modeled in the state space form to get
the eigenvalues and corresponding damping ratios of various modes
of generators and controllers. Hence, a new method based on tracing
envelop of time domain waveform is also presented and used in the
paper for comparing performance of controllers. The paper also
shows that if the fuzzy based controllers designed separately
combining them could not lead to a better performance.
Abstract: This paper addresses the stability of the switched systems with discrete and distributed time delays. By applying Lyapunov functional and function method, we show that, if the norm of system matrices Bi is small enough, the asymptotic stability is always achieved. Finally, a example is provided to verify technically feasibility and operability of the developed results.
Abstract: The stochastic nature of tool life using conventional discrete-wear data from experimental tests usually exists due to many individual and interacting parameters. It is a common practice in batch production to continually use the same tool to machine different parts, using disparate machining parameters. In such an environment, the optimal points at which tools have to be changed, while achieving minimum production cost and maximum production rate within the surface roughness specifications, have not been adequately studied. In the current study, two relevant aspects are investigated using coated and uncoated inserts in turning operations: (i) the accuracy of using machinability information, from fixed parameters testing procedures, when variable parameters situations are emerged, and (ii) the credibility of tool life machinability data from prior discrete testing procedures in a non-stop machining. A novel technique is proposed and verified to normalize the conventional fixed parameters machinability data to suit the cases when parameters have to be changed for the same tool. Also, an experimental investigation has been established to evaluate the error in the tool life assessment when machinability from discrete testing procedures is employed in uninterrupted practical machining.
Abstract: The paper presents a technique suitable in robot
vision applications where it is not possible to establish the object position from one view. Usually, one view pose calculation methods
are based on the correspondence of image features established at a
training step and exactly the same image features extracted at the
execution step, for a different object pose. When such a
correspondence is not feasible because of the lack of specific features
a new method is proposed. In the first step the method computes
from two views the 3D pose of feature points. Subsequently, using a
registration algorithm, the set of 3D feature points extracted at the execution phase is aligned with the set of 3D feature points extracted
at the training phase. The result is a Euclidean transform which have
to be used by robot head for reorientation at execution step.
Abstract: The daily growing use of agents in software environments, because of many reasons such as independence and intelligence is not a secret anymore. One of such environments in which there is a prominent job for the agents would be emarketplaces in which a user is able to give those agents the responsibility of buying and selling, instead of searching the emarketplace himself. Making up a framework which has sufficient attention to the required roles and their relations, is the first step of achieving such e-markets. In this paper, we suggest a framework in order to establish such e-markets and we will continue investigating the roles such as seller or buyer and the relations in JADE environment in details.
Abstract: Recently, as information industry and mobile
communication technology are developing, this study is conducted on
the new concept of intelligent structures and maintenance techniques
that applied wireless sensor network, USN (Ubiquitous Sensor
Network), to social infrastructures such as civil and architectural
structures on the basis of the concept of Ubiquitous Computing that
invisibly provides human life with computing, along with mutually
cooperating, compromising and connecting networks each other by
having computers within all objects around us.
Therefore, the purpose of this study is to investigate the capability
of wireless communication of sensor node embedded in reinforced
concrete structure with a basic experiment on an electric wave
permeability of sensor node by fabricating molding with variables of
concrete thickness and steel bars that are mostly used in constructing
structures to determine the feasibility of application to constructing
structures with USN.
At this time, with putting the pitches of steel bars, the thickness of
concrete placed, and the intensity of RF signal of a
transmitter-receiver as variables and when wireless communication
module was installed inside, the possible communication distance of
plain concrete and the possible communication distance by the pitches
of steel bars was measured in the horizontal and vertical direction
respectively. Besides, for the precise measurement of diminution of an
electric wave, the magnitude of an electric wave in the range of used
frequencies was measured by using Spectrum Analyzer. The
phenomenon of diminution of an electric wave was numerically
analyzed and the effect of the length of wavelength of frequencies was
analyzed by the properties of a frequency band area.
As a result of studying the feasibility of an application to
constructing structures with wireless sensor, in case of plain concrete,
it shows 45cm for the depth of permeability and in case of reinforced
concrete with the pitches of 5cm, it shows 37cm and 45cm for the
pitches of 15cm.
Abstract: The major aim of this paper is to investigate the opposition politics in Africa. The paper also examines the status and the role, the contributions and the weaknesses of opposition1 political parties in Africa, particularly in transitional democracies that emerged in the 1990s. In Africa, many of the opposition parties appear or become active only during an election, and disappear when the election is over. It is found out that most of the opposition parties in Africa are established around the personalities of individuals, lack internal democracy, suffer from inter-party and intra-party conflicts, have severe shortage of finance, and lack strong base and experience. Their weaknesses also include bad organization and weak connection with the popular constituencies. The paper concludes that most of the weaknesses of the African opposition parties emanate from the incumbents- hostile policies, which are mostly aimed at fragmenting and weakening the opposition groups.
Abstract: In order to provide and maintain effective pedagogy for the burgeoning virtual reality community, it is vital to have trained faculty in the institutions of higher education who will teach these courses and be able to make full use of their academic knowledge and expertise. As the number of online courses continues to grow, there is a need for these institutions to establish mentoring programs that will support the novice online instructor. The environment in which this takes place and the factors that ensure its success are critical to the adoption of the new instructional delivery format taught by both seasoned educators and adjunct instructors. Effective one-on-one mentoring promotes a professional, compassionate and collegial faculty who will provide a consistent and rigorous academic program for students online.
Abstract: Chakri Maha Prasart Throne Hall is the important
Audience hall in Grand Palace, Bangkok, Thailand which was
established in the early reign of King Chulalongkorn (King Rama V)
in 1882. The Throne was designed with the distinguished architecture
by significant blending of Western and Thai Traditional styles under
the Thai Social changing in Colony Era and Thai traditional culture.
The western style was represented of modernization and civilization as
the other European countries. In the other hand, Thai traditional
architecture style with national emblem or Royal emblem was shown
the status and power of Thai King as the Thai believes and culture.
Abstract: The expansive nature of soils containing high
amounts of clay minerals can be altered through chemical
stabilization, resulting in a material suitable for construction
purposes. The primary objective of this investigation was to
study the changes induced in the molecular structure of
phosphoric acid stabilized bentonite and lateritic soil using
Nuclear Magnetic Resonance (NMR) and Fourier Transform
Infrared (FTIR) spectroscopy. Based on the obtained data, it
was found that a surface alteration mechanism was the main
reason responsible for the improvement of treated soils.
Furthermore, the results indicated that the Al present in the
octahedral layer of clay minerals were more amenable to
chemical attacks and also partly responsible for the formation
of new products.
Abstract: The scenario of bypass transition is generally described
as follows: the low-frequency disturbances in the free-stream may
generate long stream-wise streaks in the boundary layer, which later
may trigger secondary instability, leading to rapid increase of
high-frequency disturbances. Then possibly turbulent spots emerge,
and through their merging, lead to fully developed turbulence. This
description, however, is insufficient in the sense that it does not
provide the inherent mechanism of transition that during the transition,
a large number of waves with different frequencies and wave numbers
appear almost simultaneously, producing sufficiently large Reynolds
stress, so the mean flow profile can change rapidly from laminar to
turbulent. In this paper, such a mechanism will be figured out from
analyzing DNS data of transition.
Abstract: Dynamic characteristics of a four-lobe journal bearing
of micropolar fluids are presented. Lubricating oil containing
additives and contaminants is modelled as micropolar fluid. The
modified Reynolds equation is obtained using the micropolar
lubrication theory and solving it by using finite difference technique.
The dynamic characteristics in terms of stiffness, damping
coefficients, the critical mass and whirl ratio are determined for
various values of size of material characteristic length and the
coupling number. The results show compared with Newtonian fluids,
that micropolar fluid exhibits better stability.
Abstract: An attractor neural network on the small-world topology
is studied. A learning pattern is presented to the network, then
a stimulus carrying local information is applied to the neurons and
the retrieval of block-like structure is investigated. A synaptic noise
decreases the memory capability. The change of stability from local
to global attractors is shown to depend on the long-range character
of the network connectivity.
Abstract: Availability of high dimensional biological datasets such as from gene expression, proteomic, and metabolic experiments can be leveraged for the diagnosis and prognosis of diseases. Many classification methods in this area have been studied to predict disease states and separate between predefined classes such as patients with a special disease versus healthy controls. However, most of the existing research only focuses on a specific dataset. There is a lack of generic comparison between classifiers, which might provide a guideline for biologists or bioinformaticians to select the proper algorithm for new datasets. In this study, we compare the performance of popular classifiers, which are Support Vector Machine (SVM), Logistic Regression, k-Nearest Neighbor (k-NN), Naive Bayes, Decision Tree, and Random Forest based on mock datasets. We mimic common biological scenarios simulating various proportions of real discriminating biomarkers and different effect sizes thereof. The result shows that SVM performs quite stable and reaches a higher AUC compared to other methods. This may be explained due to the ability of SVM to minimize the probability of error. Moreover, Decision Tree with its good applicability for diagnosis and prognosis shows good performance in our experimental setup. Logistic Regression and Random Forest, however, strongly depend on the ratio of discriminators and perform better when having a higher number of discriminators.
Abstract: Mathematical models can be used to describe the
transmission of disease. Dengue disease is the most significant
mosquito-borne viral disease of human. It now a leading cause of
childhood deaths and hospitalizations in many countries. Variations
in environmental conditions, especially seasonal climatic parameters,
effect to the transmission of dengue viruses the dengue viruses and
their principal mosquito vector, Aedes aegypti. A transmission model
for dengue disease is discussed in this paper. We assume that the
human and vector populations are constant. We showed that the local
stability is completely determined by the threshold parameter, 0 B . If
0 B is less than one, the disease free equilibrium state is stable. If
0 B is more than one, a unique endemic equilibrium state exists and
is stable. The numerical results are shown for the different values of
the transmission probability from vector to human populations.
Abstract: In this paper, computational fluid dynamics (CFD) is utilized to characterize a prototype biolistic delivery system, the biomedical device based on the contoured-shock-tube design (CST), with the aim at investigating shocks induced flow instabilities within the contoured shock tube. The shock/interface interactions, the growth of perturbation at an interface between two fluids of different density are interrogated. The key features of the gas dynamics and gas-particle interaction are discussed
Abstract: Urban road network traffic has become one of the
most studied research topics in the last decades. This is mainly due to
the enlargement of the cities and the growing number of motor
vehicles traveling in this road network. One of the most sensitive
problems is to verify if the network is congestion-free. Another
related problem is the automatic reconfiguration of the network
without building new roads to alleviate congestions. These problems
require an accurate model of the traffic to determine the steady state
of the system. An alternative is to simulate the traffic to see if there
are congestions and when and where they occur. One key issue is to
find an adequate model for road intersections. Once the model
established, either a large scale model is built or the intersection is
represented by its performance measures and simulation for analysis.
In both cases, it is important to seek the queueing model to represent
the road intersection. In this paper, we propose to model the road
intersection as a BCMP queueing network and we compare this
analytical model against a simulation model for validation.
Abstract: The peculiarities of the nanoscale structure-phase
states formed after electroexplosive carburizing and subsequent
electron-beam treatment of technically pure titanium surface in different regimes are established by methods of transmission electron
diffraction microscopy and physical mechanisms are discussed. Electroexplosive carburizing leads to surface layer formation
(40 m thickness) with increased (in 3.5 times) microhardness. It consists of β-titanium, graphite (monocrystals 100-150 nm,
polycrystals 5-10 nm, amorphous particles 3-5nm), TiC (5-10 nm), β-Ti02 (2-20nm). After electron-beam treatment additionally increasing the microhardness the surface layer consists of TiC.
Abstract: In this paper, a nonlinear model predictive swing-up
and stabilizing sliding controller is proposed for an inverted
pendulum-cart system. In the swing up phase, the nonlinear model
predictive control is formulated as a nonlinear programming problem
with energy based objective function. By solving this problem at
each sampling instant, a sequence of control inputs that optimize the
nonlinear objective function subject to various constraints over a
finite horizon are obtained. Then, this control drives the pendulum to
a predefined neighborhood of the upper equilibrium point, at where
sliding mode based model predictive control is used to stabilize the
systems with the specified constraints. It is shown by the simulations
that, due to the way of formulating the problem, short horizon
lengths are sufficient for attaining the swing up goal.