Abstract: The hydrodynamic and thermal lattice Boltzmann
methods are applied to investigate the turbulent convective heat
transfer in the wavy channel flows. In this study, the turbulent
phenomena are modeling by large-eddy simulations with the
Smagorinsky model. As a benchmark, the laminar and turbulent
backward-facing step flows are simulated first. The results give good
agreement with other numerical and experimental data. For wavy
channel flows, the distribution of Nusselt number and the skin-friction
coefficients are calculated to evaluate the heat transfer effect and the
drag force. It indicates that the vortices at the trough would affect the
magnitude of drag and weaken the heat convection effects on the wavy
surface. In turbulent cases, if the amplitude of the wavy boundary is
large enough, the secondary vortices would be generated at troughs
and contribute to the heat convection. Finally, the effects of different
Re on the turbulent transport phenomena are discussed.
Abstract: In this paper an efficient incomplete factorization preconditioner is proposed for the Least Mean Squares (LMS) adaptive filter. The proposed preconditioner is approximated from a priori knowledge of the factors of input correlation matrix with an incomplete strategy, motivated by the sparsity patter of the upper triangular factor in the QRD-RLS algorithm. The convergence properties of IPLMS algorithm are comparable with those of transform domain LMS(TDLMS) algorithm. Simulation results show efficiency and robustness of the proposed algorithm with reduced computational complexity.
Abstract: This research was conducted to develop a correlation
between microstructure of HSLA steel and the mechanical properties
that occur as a result of both laser and mechanical forming processes
of the metal. The technique of forming flat metals by applying laser
beams is a relatively new concept in the manufacturing industry.
However, the effects of laser energy on the stability of metal alloy
phases have not yet been elucidated in terms of phase
transformations and microhardness. In this work, CO2 laser source
was used to irradiate the surface of a flat metal then the
microstructure and microhardness of the metal were studied on the
formed specimen. The extent to which the microstructure changed
depended on the heat inputs of up to 1000 J/cm2 with cooling rates of
about 4.8E+02 K/s. Experimental results revealed that the irradiated
surface of a HSLA steel had transformed to austenitic structure
during the heating process.
Abstract: In this paper, we study the cooperative communications where multiple cognitive radio (CR) transmit-receive pairs competitive maximize their own throughputs. In CR networks, the influences of primary users and the spectrum availability are usually different among CR users. Due to the existence of multiple relay nodes and the different spectrum availability, each CR transmit-receive pair should not only select the relay node but also choose the appropriate channel. For this distributed problem, we propose a game theoretic framework to formulate this problem and we apply a regret-matching learning algorithm which is leading to correlated equilibrium. We further formulate a modified regret-matching learning algorithm which is fully distributed and only use the local information of each CR transmit-receive pair. This modified algorithm is more practical and suitable for the cooperative communications in CR network. Simulation results show the algorithm convergence and the modified learning algorithm can achieve comparable performance to the original regretmatching learning algorithm.
Abstract: The accomplished study is based on the appointment
and identification of ageing effects and according to this absorption
of moisture of aircraft cabin components over the life-cycle. In the
first step of the study ceiling panels from same age and from the
same aircraft cabin have been examined according to weight changes
depending on the position in the aircraft cabin. In the second step of
the study different aged ceiling panels have been examined
concerning deflection, weight changes and the acoustic sound
transmission loss. To prove the assumption of water absorption
within the study and with the theoretical background from literature
and scientific papers, an older test panel was exposed extreme
thermal conditions (humidity and temperature) within a climate
chamber to show that there is a general ingress of water to cabin
components and that this ingress of water leads to the change of
different mechanical properties.
Abstract: The conventional production of biodiesel from crude
palm oil which contains large amounts of free fatty acids in the
presence of a homogeneous base catalyst confronts the problems of
soap formation and very low yield of biodiesel. To overcome these
problems, free fatty acids must be esterified to their esters in the
presence of an acid catalyst prior to alkaline-catalyzed
transesterification. Sulfated metal oxides are a promising group of
catalysts due to their very high acidity. In this research, aluminadoped
sulfated tin oxide (SO4
2-/Al2O3-SnO2) catalysts were prepared
and used for esterification of free fatty acids in crude palm oil in a
batch reactor. The SO4
2-/Al2O3-SnO2 catalysts were prepared from
different Al precursors. The results showed that different Al
precursors gave different activities of the SO4
2-/Al2O3-SnO2 catalysts.
The esterification of free fatty acids in crude palm oil with methanol
in the presence of SO4
2-/Al2O3-SnO2 catalysts followed first-order
kinetics.
Abstract: A two-dimensional moving mesh algorithm is developed to simulate the general motion of two rotating bodies with relative translational motion. The grid includes a background grid and two sets of grids around the moving bodies. With this grid arrangement rotational and translational motions of two bodies are handled separately, with no complications. Inter-grid boundaries are determined based on their distances from two bodies. In this method, the overset concept is applied to hybrid grid, and flow variables are interpolated using a simple stencil. To evaluate this moving mesh algorithm unsteady Euler flow is solved for different cases using dual-time method of Jameson. Numerical results show excellent agreement with experimental data and other numerical results. To demonstrate the capability of present algorithm for accurate solution of flow fields around moving bodies, some benchmark problems have been defined in this paper.
Abstract: This paper presents a critical study about the
application of Neural Networks to ion-exchange process. Ionexchange
is a complex non-linear process involving many factors
influencing the ions uptake mechanisms from the pregnant solution.
The following step includes the elution. Published data presents
empirical isotherm equations with definite shortcomings resulting in
unreliable predictions. Although Neural Network simulation
technique encounters a number of disadvantages including its “black
box", and a limited ability to explicitly identify possible causal
relationships, it has the advantage to implicitly handle complex
nonlinear relationships between dependent and independent
variables. In the present paper, the Neural Network model based on
the back-propagation algorithm Levenberg-Marquardt was developed
using a three layer approach with a tangent sigmoid transfer function
(tansig) at hidden layer with 11 neurons and linear transfer function
(purelin) at out layer. The above mentioned approach has been used
to test the effectiveness in simulating ion exchange processes. The
modeling results showed that there is an excellent agreement between
the experimental data and the predicted values of copper ions
removed from aqueous solutions.
Abstract: The article deals with dividends and their distribution from investors from a theoretical point of view. Some studies try to analyzed the reaction of the market on the dividend announcement and found out the change of dividend policy is associated with abnormal returns around the dividend announcement date. Another researches directly questioned the investors about their dividend preference and beliefs. Investors want the dividend from many reasons (e.g. some of them explain the dividend preference by the existence of transaction cost; investors prefer the dividend today, because there is less risky; the managers have private information about the firm). The most controversial theory of dividend policy was developed by Modigliani and Miller (1961) who demonstrated that in the perfect and complete capital markets the dividend policy is irrelevant and the value of the company is independent of its payout policy. Nevertheless, in the real world the capital markets are imperfect, because of asymmetric information, transaction costs, incomplete contracting possibilities and taxes.
Abstract: Imperfect transmission conditions modeling a thin reactive 2D interphases layer between two dissimilar bonded strips have been extracted. In this paper, the soundness of these transmission conditions for heat conduction problems are examined by the finite element method for a strong temperature-dependent source or sink and non-monotonic temperature distributions around the faces..
Abstract: In this paper the direct kinematic model of a multiple
applications three degrees of freedom industrial manipulator, was
developed using the homogeneous transformation matrices and the
Denavit - Hartenberg parameters, likewise the inverse kinematic
model was developed using the same method, verifying that in the
workload border the inverse kinematic presents considerable errors,
therefore a genetic algorithm was implemented to optimize the model
improving greatly the efficiency of the model.
Abstract: Structural redundancy is an interesting point in
seismic design of structures. Initially, the structural redundancy is
described as indeterminate degree of a system. Although many definitions are presented for redundancy in structures, recently the
definition of structural redundancy has been related to the configuration of structural system and the number of lateral load
transferring directions in the structure. The steel frames with infill walls are general systems in the constructing of usual residential buildings in some countries. It is
obviously declared that the performance of structures will be affected by adding masonry infill walls. In order to investigate the effect of
infill walls on the redundancy of the steel frame which constructed
with masonry walls, the components of redundancy including redundancy variation index, redundancy strength index and
redundancy response modification factor were extracted for the
frames with masonry infills. Several steel frames with typical storey number and various numbers of bays were designed and considered.
The redundancy of frames with and without infill walls was evaluated by proposed method. The results showed the presence of infill causes increase of redundancy.
Abstract: This paper presents a signal analysis process for
improving energy completeness based on the Hilbert-Huang
Transform (HHT). Firstly, the vibration signal of a DC Motor obtained
by employing an accelerometer is the model used to analyze the
signal. Secondly, the intrinsic mode functions (IMFs) and Hilbert
spectrum of the decomposed signal are obtained by applying HHT.
The results of the IMFs constituent and the original signal are
compared and the process of energy loss is discussed. Finally, the
differences between Wavelet Transform (WT) and HHT in analyzing
the signal are compared. The simulated results reveal the analysis
process based on HHT is advantageous for the enhancement of energy
completeness.
Abstract: As the global climate changes, the threat from
landslides and debris flows increases. Learning how a watershed
initiates landslides under abnormal rainfall conditions and predicting
landslide magnitude and frequency distribution is thus important.
Landslides show a power-law distribution in the frequency-area
distribution. The distribution curve shows an exponent gradient 1.0 in
the Sandpile model test. Will the landslide frequency-area statistics
show a distribution similar to the Sandpile model under extreme
rainfall conditions? The purpose of the study is to identify the extreme
rainfall-induced landslide frequency-area distribution in the Laonong
River Basin in southern Taiwan. Results of the analysis show that a
lower gradient of landslide frequency-area distribution could be
attributed to the transportation and deposition of debris flow areas that
are included in the landslide area.
Abstract: Three new algorithms based on minimization of autocorrelation of transmitted symbols and the SLM approach which are computationally less demanding have been proposed. In the first algorithm, autocorrelation of complex data sequence is minimized to a value of 1 that results in reduction of PAPR. Second algorithm generates multiple random sequences from the sequence generated in the first algorithm with same value of autocorrelation i.e. 1. Out of these, the sequence with minimum PAPR is transmitted. Third algorithm is an extension of the second algorithm and requires minimum side information to be transmitted. Multiple sequences are generated by modifying a fixed number of complex numbers in an OFDM data sequence using only one factor. The multiple sequences represent the same data sequence and the one giving minimum PAPR is transmitted. Simulation results for a 256 subcarrier OFDM system show that significant reduction in PAPR is achieved using the proposed algorithms.
Abstract: In this paper, a novel feature-based image
watermarking scheme is proposed. Zernike moments which have
invariance properties are adopted in the scheme. In the proposed
scheme, feature points are first extracted from host image and several
circular patches centered on these points are generated. The patches
are used as carriers of watermark information because they can be
regenerated to locate watermark embedding positions even when
watermarked images are severely distorted. Zernike transform is then
applied to the patches to calculate local Zernike moments. Dither
modulation is adopted to quantize the magnitudes of the Zernike
moments followed by false alarm analysis. Experimental results show
that quality degradation of watermarked image is visually
transparent. The proposed scheme is very robust against image
processing operations and geometric attacks.
Abstract: Current trends in manufacturing are characterized by
production broadening, innovation cycle shortening, and the products
having a new shape, material and functions. The production strategy
focused on time needed change from the traditional functional
production structure to flexible manufacturing cells and lines.
Production by automated manufacturing system (AMS) is one of the
most important manufacturing philosophies in the last years. The
main goals of the project we are involved in lies on building a
laboratory in which will be located a flexible manufacturing system
consisting of at least two production machines with NC control
(milling machines, lathe). These machines will be linked to a
transport system and they will be served by industrial robots. Within
this flexible manufacturing system a station for the quality control
consisting of a camera system and rack warehouse will be also
located. The design, analysis and improvement of this manufacturing
system, specially with a special focus on the communication among
devices constitute the main aims of this paper. The key determining
factors for the manufacturing system design are: the product, the
production volume, the used machines, the disposable manpower, the
disposable infrastructure and the legislative frame for the specific
cases.
Abstract: In this paper optical code-division multiple-access (OCDMA) packet network is considered, which offers inherent security in the access networks. Two types of random access protocols are proposed for packet transmission. In protocol 1, all distinct codes and in protocol 2, distinct codes as well as shifted versions of all these codes are used. O-CDMA network performance using optical orthogonal codes (OOCs) 1-D and two-dimensional (2-D) wavelength/time single-pulse-per-row (W/T SPR) codes are analyzed. The main advantage of using 2-D codes instead of onedimensional (1-D) codes is to reduce the errors due to multiple access interference among different users. In this paper, correlation receiver is considered in the analysis. Using analytical model, we compute and compare packet-success probability for 1-D and 2-D codes in an O-CDMA network and the analysis shows improved performance with 2-D codes as compared to 1-D codes.
Abstract: In this work a new platform for mobile-health systems is
presented. System target application is providing decision support to
rescue corps or military medical personnel in combat areas. Software
architecture relies on a distributed client-server system that manages a
wireless ad-hoc networks hierarchy in which several different types of
client operate. Each client is characterized for different hardware and
software requirements. Lower hierarchy levels rely in a network of
completely custom devices that store clinical information and patient
status and are designed to form an ad-hoc network operating in the
2.4 GHz ISM band and complying with the IEEE 802.15.4 standard
(ZigBee). Medical personnel may interact with such devices, that are
called MICs (Medical Information Carriers), by means of a PDA
(Personal Digital Assistant) or a MDA (Medical Digital Assistant),
and transmit the information stored in their local databases as well as
issue a service request to the upper hierarchy levels by using IEEE
802.11 a/b/g standard (WiFi). The server acts as a repository that
stores both medical evacuation forms and associated events (e.g., a
teleconsulting request). All the actors participating in the diagnostic
or evacuation process may access asynchronously to such repository
and update its content or generate new events. The designed system
pretends to optimise and improve information spreading and flow
among all the system components with the aim of improving both
diagnostic quality and evacuation process.
Abstract: The paper deals with cartographic visualisation of
results of transport accessibility monitoring with the use of a semiautomated
method of unipolar anamorphosis, developed by the
authors in the GIS environment. The method is based on
transformation of distance in the map to values of a geographical
phenomenon. In the case of time accessibility it is based on
transformation of isochrones converted into the form of concentric
circles, taking into account selected topographic and thematic
elements in the map. The method is most suitable for analyses of
accessibility to or from a centre and for modelling its long-term
context.
The paper provides a detailed analysis of the procedures and
functionality of the method, discussing the issues of coordinates,
transformation, scale and visualisation. It also offers a discussion of
possible problems and inaccuracies. A practical application of the
method is illustrated by previous research results by the authors in
the filed of accessibility in Czechia.