International Science Index
Automatic Landmark Selection Based on Feature Clustering for Visual Autonomous Unmanned Aerial Vehicle Navigation
The selection of specific landmarks for an Unmanned
Aerial Vehicles’ Visual Navigation systems based on Automatic
Landmark Recognition has significant influence on the precision of
the system’s estimated position. At the same time, manual selection
of the landmarks does not guarantee a high recognition rate, which
would also result on a poor precision. This work aims to develop an
automatic landmark selection that will take the image of the flight
area and identify the best landmarks to be recognized by the Visual
Navigation Landmark Recognition System. The criterion to select
a landmark is based on features detected by ORB or AKAZE and
edges information on each possible landmark. Results have shown
that disposition of possible landmarks is quite different from the
Total Chromatic Number of Δ-Claw-Free 3-Degenerated Graphs
The total chromatic number χ"(G) of a graph G is the
minimum number of colors needed to color the elements (vertices
and edges) of G such that no incident or adjacent pair of elements
receive the same color Let G be a graph with maximum degree Δ(G).
Considering a total coloring of G and focusing on a vertex with
maximum degree. A vertex with maximum degree needs a color and
all Δ(G) edges incident to this vertex need more Δ(G) + 1 distinct
colors. To color all vertices and all edges of G, it requires at least
Δ(G) + 1 colors. That is, χ"(G) is at least Δ(G) + 1. However,
no one can find a graph G with the total chromatic number which
is greater than Δ(G) + 2. The Total Coloring Conjecture states that
for every graph G, χ"(G) is at most Δ(G) + 2. In this paper, we prove that the Total Coloring Conjectur for a
Δ-claw-free 3-degenerated graph. That is, we prove that the total
chromatic number of every Δ-claw-free 3-degenerated graph is at
most Δ(G) + 2.
An Improved Method to Compute Sparse Graphs for Traveling Salesman Problem
The Traveling salesman problem (TSP) is NP-hard in combinatorial optimization. The research shows the algorithms for TSP on the sparse graphs have the shorter computation time than those for TSP according to the complete graphs. We present an improved iterative algorithm to compute the sparse graphs for TSP by frequency graphs computed with frequency quadrilaterals. The iterative algorithm is enhanced by adjusting two parameters of the algorithm. The computation time of the algorithm is O(CNmaxn2) where C is the iterations, Nmax is the maximum number of frequency quadrilaterals containing each edge and n is the scale of TSP. The experimental results showed the computed sparse graphs generally have less than 5n edges for most of these Euclidean instances. Moreover, the maximum degree and minimum degree of the vertices in the sparse graphs do not have much difference. Thus, the computation time of the methods to resolve the TSP on these sparse graphs will be greatly reduced.
Contrast Enhancement in Digital Images Using an Adaptive Unsharp Masking Method
Captured images may suffer from Gaussian blur due to poor lens focus or camera motion. Unsharp masking is a simple and effective technique to boost the image contrast and to improve digital images suffering from Gaussian blur. The technique is based on sharpening object edges by appending the scaled high-frequency components of the image to the original. The quality of the enhanced image is highly dependent on the characteristics of both the high-frequency components and the scaling/gain factor. Since the quality of an image may not be the same throughout, we propose an adaptive unsharp masking method in this paper. In this method, the gain factor is computed, considering the gradient variations, for individual pixels of the image. Subjective and objective image quality assessments are used to compare the performance of the proposed method both with the classic and the recently developed unsharp masking methods. The experimental results show that the proposed method has a better performance in comparison to the other existing methods.
A Unified Approach for Naval Telecommunication Architectures
We present a chronological evolution for naval telecommunication networks. We distinguish periods: with or without multiplexers, with switch systems, with federative systems, with medium switching, and with medium switching with wireless networks. This highlights the introduction of new layers and technology in the architecture. These architectures are presented using layer models of transmission, in a unified way, which enables us to integrate pre-existing models. A ship of a naval fleet has internal communications (i.e. applications' networks of the edge) and external communications (i.e. the use of the means of transmission between edges). We propose architectures, deduced from the layer model, which are the point of convergence between the networks on board and the HF, UHF radio, and satellite resources. This modelling allows to consider end-to-end naval communications, and in a more global way, that is from the user on board towards the user on shore, including transmission and networks on the shore side. The new architectures need take care of quality of services for end-to-end communications, the more remote control develops a lot and will do so in the future. Naval telecommunications will be more and more complex and will use more and more advanced technologies, it will thus be necessary to establish clear global communication schemes to grant consistency of the architectures. Our latest model has been implemented in a military naval situation, and serves as the basic architecture for the RIFAN2 network.
Studying the Possibility to Weld AA1100 Aluminum Alloy by Friction Stir Spot Welding
Friction stir welding is a modern and an environmentally friendly solid state joining process used to joint relatively lighter family of materials. Recently, friction stir spot welding has been used instead of resistance spot welding which has received considerable attention from the automotive industry. It is environmentally friendly process that eliminated heat and pollution. In this research, friction stir spot welding has been used to study the possibility to weld AA1100 aluminum alloy sheet with 3 mm thickness by overlapping the edges of sheet as lap joint. The process was done using a drilling machine instead of milling machine. Different tool rotational speeds of 760, 1065, 1445, and 2000 RPM have been applied with manual and automatic compression to study their effect on the quality of welded joints. Heat generation, pressure applied, and depth of tool penetration have been measured during the welding process. The result shows that there is a possibility to weld AA1100 sheets; however, there is some surface defect that happened due to insufficient condition of welding. Moreover, the relationship between rotational speed, pressure, heat generation and tool depth penetration was created.
Parametric Study on Dynamic Analysis of Composite Laminated Plate
A laminated plate composite of graphite/epoxy has been analyzed dynamically in the present work by using a quadratic element (8-node diso-parametric), and by depending on 1st order shear deformation theory, every node in this element has 6-degrees of freedom (displacement in x, y, and z axis and twist about x, y, and z axis). The dynamic analysis in the present work covered parametric studies on a composite laminated plate (square plate) to determine its effect on the natural frequency of the plate. The parametric study is represented by set of changes (plate thickness, number of layers, support conditions, layer orientation), and the plates have been simulated by using ANSYS package 12. The boundary conditions considered in this study, at all four edges of the plate, are simply supported and fixed boundary condition. The results obtained from ANSYS program show that the natural frequency for both fixed and simply supported increases with increasing the number of layers, but this increase in the natural frequency for the first five modes will be neglected after 10 layers. And it is observed that the natural frequency of a composite laminated plate will change with the change of ply orientation, the natural frequency increases and it will be at maximum with angle 45 of ply for simply supported laminated plate, and maximum natural frequency will be with cross-ply (0/90) for fixed laminated composite plate. It is also observed that the natural frequency increase is approximately doubled when the thickness is doubled.
From Vertigo to Verticality: An Example of Phenomenological Design in Architecture
Architects commonly attempt a depiction of organic forms when their works are inspired by nature, regardless of the building site. Nevertheless it is also possible to try matching structures with natural scenery, by applying a phenomenological approach in terms of spatial operations, regarding perceptions from nature through architectural aspects such as protection, views, and orientation. This method acknowledges a relationship between place and space, where intentions towards tangible facts then become design statements. Although spaces resulting from such a process may present an effective response to the environment, they can also offer further outcomes beyond the realm of form. The hypothesis is that, in addition to recognising a bond between architecture and nature, it is also plausible to associate such perceptions with the inner ambient of buildings, by analysing features such as daylight. The case study of a single-family house in a rainforest near Valdivia, Chilean Patagonia is presented, with the intention of addressing the above notions through a discussion of the actual effects of inhabiting a place by way of a series of insights, including a revision of diagrams and photographs that assist in understanding the implications of this design practice. In addition, figures based on post-occupancy behaviour and daylighting performance relate both architectural and environmental issues to a decision-making process motivated by the observation of nature.
Parallel 2-Opt Local Search on GPU
To accelerate the solution for large scale traveling
salesman problems (TSP), a parallel 2-opt local search algorithm
with simple implementation based on Graphics Processing Unit
(GPU) is presented and tested in this paper. The parallel scheme is
based on technique of data decomposition by dynamically assigning
multiple K processors on the integral tour to treat K edges’ 2-opt
local optimization simultaneously on independent sub-tours, where
K can be user-defined or have a function relationship with input size
N. We implement this algorithm with doubly linked list on GPU.
The implementation only requires O(N) memory. We compare this
parallel 2-opt local optimization against sequential exhaustive 2-opt
search along integral tour on TSP instances from TSPLIB with more
than 10000 cities.
Investigation of Building Loads Effect on the Stability of Slope
In big cities, construction on sloping land (landslide) is becoming increasingly prevalent due to the unavailability of flat lands. This has created a major challenge for structural engineers with regard to structure design, due to the difficulties encountered during the implementation of projects, both for the structure and the soil. This paper analyses the effect of the number of floors of a building, founded on isolated footing on the stability of the slope using the computer code finite element PLAXIS 2D v. 8.2. The isolated footings of a building in this case were anchored in soil so that the levels of successive isolated footing realize a maximum slope of base of three for two heights, which connects the edges of the nearest footings, according to the Algerian building code DTR-BC 2.331: Shallow foundations. The results show that the embedment of the foundation into the soil reduces the value of the safety factor due to the change of the stress state of the soil by these foundations. The number of floors a building has also influences the safety factor. It has been noticed from this case of study that there is no risk of collapse of slopes for an inclination between 5° and 8°. In the case of slope inclination greater than 10° it has been noticed that the urbanization is prohibited.
Physical Properties and Resistant Starch Content of Rice Flour Residues Hydrolyzed by α-Amylase
Enzymatic modification of rice flour can produce highly functional derivatives use in food industries. This study aimed to evaluate the physical properties and resistant starch content of rice flour residues hydrolyzed by α-amylase. Rice flour hydrolyzed by α-amylase (60 and 300 u/g) for 1, 24 and 48 hours were investigated. Increasing enzyme concentration and hydrolysis time resulted in decreased rice flour residue’s lightness (L*) but increased redness (a*) and yellowness (b*) of rice flour residues. The resistant starch content and peak viscosity increased when hydrolysis time increased. Pasting temperature, trough viscosity, breakdown, final viscosity, setback and peak time of the hydrolyzed flours were not significantly different (p>0.05). The morphology of native flour was smooth without observable pores and polygonal with sharp angles and edges. However, after hydrolysis, granules with a slightly rough and porous surface were observed and a rough and porous surface was increased with increasing hydrolyzed time. The X-ray diffraction patterns of native flour showed A-type configuration, which hydrolyzed flour showed almost 0% crystallinity indicated that both amorphous and crystalline structures of starch were simultaneously hydrolyzed by α-amylase.
Reusing Assessments Tests by Generating Arborescent Test Groups Using a Genetic Algorithm
Using Information and Communication Technologies (ICT) notions in education and three basic processes of education (teaching, learning and assessment) can bring benefits to the pupils and the professional development of teachers. In this matter, we refer to these notions as concepts taken from the informatics area and apply them to the domain of education. These notions refer to genetic algorithms and arborescent structures, used in the specific process of assessment or evaluation. This paper uses these kinds of notions to generate subtrees from a main tree of tests related between them by their degree of difficulty. These subtrees must contain the highest number of connections between the nodes and the lowest number of missing edges (which are subtrees of the main tree) and, in the particular case of the non-existence of a subtree with no missing edges, the subtrees which have the lowest (minimal) number of missing edges between the nodes, where a node is a test and an edge is a direct connection between two tests which differs by one degree of difficulty. The subtrees are represented as sequences. The tests are the same (a number coding a test represents that test in every sequence) and they are reused for each sequence of tests.
A Flute Tracking System for Monitoring the Wear of Cutting Tools in Milling Operations
Monitoring of tool wear in milling operations is essential for achieving the desired dimensional accuracy and surface finish of a machined workpiece. Although there are numerous statistical models and artificial intelligence techniques available for monitoring the wear of cutting tools, these techniques cannot pin point which cutting edge of the tool, or which insert in the case of indexable tooling, is worn or broken. Currently, the task of monitoring the wear on the tool cutting edges is carried out by the operator who performs a manual inspection, causing undesirable stoppages of machine tools and consequently resulting in costs incurred from lost productivity. The present study is concerned with the development of a flute tracking system to segment signals related to each physical flute of a cutter with three flutes used in an end milling operation. The purpose of the system is to monitor the cutting condition for individual flutes separately in order to determine their progressive wear rates and to predict imminent tool failure. The results of this study clearly show that signals associated with each flute can be effectively segmented using the proposed flute tracking system. Furthermore, the results illustrate that by segmenting the sensor signal by flutes it is possible to investigate the wear in each physical cutting edge of the cutting tool. These findings are significant in that they facilitate the online condition monitoring of a cutting tool for each specific flute without the need for operators/engineers to perform manual inspections of the tool.
Analysis of Effects of Magnetic Slot Wedges on Characteristics of Permanent Magnet Synchronous Machine
The influence of slot wedges permeability on the electromagnetic performance of three-phase permanent magnet synchronous machine is investigated in this paper. It is shown that the back-EMF waveform, electromagnetic torque and electromagnetic torque ripple are all significantly affected by slot wedges permeability. The paper presents an accurate analytical subdomain model and confirmed by finite-element analyses.
Edge Detection Using Multi-Agent System: Evaluation on Synthetic and Medical MR Images
Recent developments on multi-agent system have brought a new research field on image processing. Several algorithms are used simultaneously and improved in deferent applications while new methods are investigated. This paper presents a new automatic method for edge detection using several agents and many different actions. The proposed multi-agent system is based on parallel agents that locally perceive their environment, that is to say, pixels and additional environmental information. This environment is built using Vector Field Convolution that attract free agent to the edges. Problems of partial, hidden or edges linking are solved with the cooperation between agents. The presented method was implemented and evaluated using several examples on different synthetic and medical images. The obtained experimental results suggest that this approach confirm the efficiency and accuracy of detected edge.
Malware Beaconing Detection by Mining Large-scale DNS Logs for Targeted Attack Identification
One of the leading problems in Cyber Security today
is the emergence of targeted attacks conducted by adversaries with
access to sophisticated tools. These attacks usually steal senior level
employee system privileges, in order to gain unauthorized access to
confidential knowledge and valuable intellectual property. Malware
used for initial compromise of the systems are sophisticated and
may target zero-day vulnerabilities. In this work we utilize common
behaviour of malware called ”beacon”, which implies that infected
hosts communicate to Command and Control servers at regular
intervals that have relatively small time variations. By analysing
such beacon activity through passive network monitoring, it is
possible to detect potential malware infections. So, we focus on
time gaps as indicators of possible C2 activity in targeted enterprise
networks. We represent DNS log files as a graph, whose vertices
are destination domains and edges are timestamps. Then by using
four periodicity detection algorithms for each pair of internal-external
communications, we check timestamp sequences to identify the
beacon activities. Finally, based on the graph structure, we infer the
existence of other infected hosts and malicious domains enrolled in
the attack activities.
Hamiltonian Related Properties with and without Faults of the Dual-Cube Interconnection Network and Their Variations
In this paper, a thorough review about dual-cubes, DCn,
the related studies and their variations are given. DCn was introduced
to be a network which retains the pleasing properties of hypercube Qn
but has a much smaller diameter. In fact, it is so constructed that the
number of vertices of DCn is equal to the number of vertices of Q2n
+1. However, each vertex in DCn is adjacent to n + 1 neighbors and
so DCn has (n + 1) × 2^2n edges in total, which is roughly half the
number of edges of Q2n+1. In addition, the diameter of any DCn is 2n
+2, which is of the same order of that of Q2n+1. For selfcompleteness,
basic definitions, construction rules and symbols are
provided. We chronicle the results, where eleven significant theorems
are presented, and include some open problems at the end.
A Fast Silhouette Detection Algorithm for Shadow Volumes in Augmented Reality
Real-time shadow generation in virtual environments
and Augmented Reality (AR) was always a hot topic in the last
three decades. Lots of calculation for shadow generation among AR
needs a fast algorithm to overcome this issue and to be capable of
implementing in any real-time rendering. In this paper, a silhouette
detection algorithm is presented to generate shadows for AR systems.
Δ+ algorithm is presented based on extending edges of occluders
to recognize which edges are silhouettes in the case of real-time
rendering. An accurate comparison between the proposed algorithm
and current algorithms in silhouette detection is done to show the
reduction calculation by presented algorithm. The algorithm is tested
in both virtual environments and AR systems. We think that this
algorithm has the potential to be a fundamental algorithm for shadow
generation in all complex environments.
The Effect of Directional Search Using Iterated Functional System for Matching Range and Domain Blocks
The effect of directional search using iterated functional system has been studied on four images taken from databases. The images are portioned successively towards smaller dimension. Presented method provides the faster rate of convergence with respect to processing time in the flat region, but the same has been found to be slower at the border of the images and edges. It has also been revealed that the PSNR is lower at the edges and border portions of the image, and it is found to be higher in the uniform gray region, under the same external illumination and external noise environment.
An Efficient Implementation of High Speed Vedic Multiplier Using Compressors for Image Processing Applications
Digital signal processor, image signal processor and FIR filters have multipliers as an important part of their design. On the basis of Vedic mathematics, Vedic multipliers have come out to be very fast multipliers. One of the image processing applications is edge detection. This research presents a small area and high speed 8 bit Vedic multiplier system comprising of compressor based adders. This results in faster edge detection. This architecture is tested on Xilinx vertex 4 FPGA board and simulations were carried out using the Xilinx synthesis tool. Comparisons are made and this system is found to be smaller in area with high speed (the lesser propagation delay). This compressor based Vedic multiplier is 1.1 times speedier than a typical Vedic multiplier. Also, this Vedic Multiplier is 2 times speedier than a ‘simple’ multiplier.
Complex Network Approach to International Trade of Fossil Fuel
Energy has a prominent role for development of
nations. Countries which have energy resources also have strategic
power in the international trade of energy since it is essential for all
stages of production in the economy. Thus, it is important for
countries to analyze the weaknesses and strength of the system. On
the other side, international trade is one of the fields that are analyzed
as a complex network via network analysis. Complex network is one
of the tools to analyze complex systems with heterogeneous agents
and interaction between them. A complex network consists of nodes
and the interactions between these nodes. Total properties which
emerge as a result of these interactions are distinct from the sum of
small parts (more or less) in complex systems. Thus, standard
approaches to international trade are superficial to analyze these
systems. Network analysis provides a new approach to analyze
international trade as a network. In this network, countries constitute
nodes and trade relations (export or import) constitute edges. It
becomes possible to analyze international trade network in terms of
high degree indicators which are specific to complex networks such
as connectivity, clustering, assortativity/disassortativity, centrality,
etc. In this analysis, international trade of crude oil and coal which
are types of fossil fuel has been analyzed from 2005 to 2014 via
network analysis. First, it has been analyzed in terms of some
topological parameters such as density, transitivity, clustering etc.
Afterwards, fitness to Pareto distribution has been analyzed via
Kolmogorov-Smirnov test. Finally, weighted HITS algorithm has
been applied to the data as a centrality measure to determine the real
prominence of countries in these trade networks. Weighted HITS
algorithm is a strong tool to analyze the network by ranking countries
with regards to prominence of their trade partners. We have
calculated both an export centrality and an import centrality by
applying w-HITS algorithm to the data. As a result, impacts of the
trading countries have been presented in terms of high-degree
Medical Image Edge Detection Based on Neuro-Fuzzy Approach
Edge detection is one of the most important tasks in image processing. Medical image edge detection plays an important role in segmentation and object recognition of the human organs. It refers to the process of identifying and locating sharp discontinuities in medical images. In this paper, a neuro-fuzzy based approach is introduced to detect the edges for noisy medical images. This approach uses desired number of neuro-fuzzy subdetectors with a postprocessor for detecting the edges of medical images. The internal parameters of the approach are optimized by training pattern using artificial images. The performance of the approach is evaluated on different medical images and compared with popular edge detection algorithm. From the experimental results, it is clear that this approach has better performance than those of other competing edge detection algorithms for noisy medical images.
3D Liver Segmentation from CT Images Using a Level Set Method Based on a Shape and Intensity Distribution Prior
Liver segmentation from medical images poses more
challenges than analogous segmentations of other organs. This
contribution introduces a liver segmentation method from a series of
computer tomography images. Overall, we present a novel method for
segmenting liver by coupling density matching with shape priors.
Density matching signifies a tracking method which operates via
maximizing the Bhattacharyya similarity measure between the
photometric distribution from an estimated image region and a model
photometric distribution. Density matching controls the direction of
the evolution process and slows down the evolving contour in regions
with weak edges. The shape prior improves the robustness of density
matching and discourages the evolving contour from exceeding liver’s
boundaries at regions with weak boundaries. The model is
implemented using a modified distance regularized level set (DRLS)
model. The experimental results show that the method achieves a
satisfactory result. By comparing with the original DRLS model, it is
evident that the proposed model herein is more effective in addressing
the over segmentation problem. Finally, we gauge our performance of
our model against matrices comprising of accuracy, sensitivity, and
Spatial Structure of First-Order Voronoi for the Future of Roundabout Cairo since 1867
The Haussmannization plan of Cairo in 1867 formed a
regular network of roundabout spaces, though deteriorated at present.
The method of identifying the spatial structure of roundabout Cairo
for conservation matches the voronoi diagram with the space syntax
through their geometrical property of spatial convexity. In this
initiative, the primary convex hull of first-order voronoi adopts the
integral and control measurements of space syntax on Cairo’s
roundabout generators. The functional essence of royal palaces
optimizes the roundabout structure in terms of spatial measurements
and the symbolic voronoi projection of 'Tahrir Roundabout' over the
Giza Nile and Pyramids. Some roundabouts of major public and
commercial landmarks surround the pole of 'Ezbekia Garden' with a
higher control than integral measurements, which filter the new
spatial structure from the adjacent traditional town. Nevertheless, the
least integral and control measures correspond to the voronoi
contents of pollutant workshops and the plateau of old Cairo Citadel
with the visual compensation of new royal landmarks on top.
Meanwhile, the extended suburbs of infinite voronoi polygons
arrange high control generators of chateaux housing in 'garden city'
environs. The point pattern of roundabouts determines the
geometrical characteristics of voronoi polygons. The measured
lengths of voronoi edges alternate between the zoned short range at
the new poles of Cairo and the distributed structure of longer range.
Nevertheless, the shortest range of generator-vertex geometry
concentrates at 'Ezbekia Garden' where the crossways of vast Cairo
intersect, which maximizes the variety of choice at different spatial
resolutions. However, the symbolic 'Hippodrome' which is the largest
public landmark forms exclusive geometrical measurements, while
structuring a most integrative roundabout to parallel the royal syntax.
Overview of the symbolic convex hull of voronoi with space syntax
interconnects Parisian Cairo with the spatial chronology of scattered
monuments to conceive one universal Cairo structure. Accordingly,
the approached methodology of 'voronoi-syntax' prospects the future
conservation of roundabout Cairo at the inferred city-level concept.
Rapid Expansion Supercritical Solution (RESS) Carbon Dioxide as an Environmental Friendly Method for Ginger Rhizome Solid Oil Particles Formation
Recently, RESS (Rapid Expansion Supercritical Solution) method has been used by researchers to produce fine particles for pharmaceutical drug substances. Since RESS technology acknowledges a lot of benefits compare to conventional method of ginger extraction, it is suggested to use this method to explore particle formation of bioactive compound from powder ginger. The objective of this research is to produce direct solid oil particles formation from ginger rhizome which contains valuable compounds by using RESS-CO2 process. RESS experiments were carried using extraction pressure of 3000, 4000, 5000, 6000 and 7000psi and at different extraction temperature of 40, 45, 50, 55, 60, 65 and 70°C for 40 minutes extraction time and contant flowrate (24ml/min). From the studies conducted, it was found that at extraction pressure 5000psi and temperature 40°C, the smallest particle size obtained was 2.22μm on 99 % reduction from the original size of 370μm.
Fracture Control of the Soda-Lime Glass in Laser Thermal Cleavage
The effects of the contact ball-lens on the soda lime
glass in laser thermal cleavage with a cw Nd-YAG laser were
investigated in this study. A contact ball-lens was adopted to generate
a bending force on the crack formation of the soda-lime glass in the
laser cutting process. The Nd-YAG laser beam (wavelength of 1064
nm) was focused through the ball-lens and transmitted to the soda-lime
glass, which was coated with a carbon film on the surface with a
bending force from a ball-lens to generate a tensile stress state on the
surface cracking. The fracture was controlled by the contact ball-lens
and a straight cutting was tested to demonstrate the feasibility.
Experimental observations on the crack propagation from the leading
edge, main section and trailing edge of the glass sheet were compared
with various mechanical and thermal loadings. Further analyses on the
stress under various laser powers and contact ball loadings were made
to characterize the innovative technology. The results show that the distributions of the side crack at the
leading and trailing edges are mainly dependent on the boundary
condition, contact force, cutting speed and laser power. With the
increase of the mechanical and thermal loadings, the region of the side
cracks might be dramatically reduced with proper selection of the
geometrical constrains. Therefore the application of the contact
ball-lens is a possible way to control the fracture in laser cleavage with
improved cutting qualities.
Finite Element Analysis of the Blanking and Stamping Processes of Nuclear Fuel Spacer Grids
Spacer grid assembly supporting the nuclear fuel rods
is an important concern in the design of structural components of a
Pressurized Water Reactor (PWR). The spacer grid is composed by
springs and dimples which are formed from a strip sheet by means of
blanking and stamping processes. In this paper, the blanking process
and tooling parameters are evaluated by means of a 2D plane-strain
finite element model in order to evaluate the punch load and quality
of the sheared edges of Inconel 718 strips used for nuclear spacer
grids. A 3D finite element model is also proposed to predict the
tooling loads resulting from the stamping process of a preformed
Inconel 718 strip and to analyse the residual stress effects upon the
spring and dimple design geometries of a nuclear spacer grid.
Opponent Color and Curvelet Transform Based Image Retrieval System Using Genetic Algorithm
In order to retrieve images efficiently from a large
database, a unique method integrating color and texture features
using genetic programming has been proposed. Opponent color
histogram which gives shadow, shade, and light intensity invariant
property is employed in the proposed framework for extracting color
features. For texture feature extraction, fast discrete curvelet
transform which captures more orientation information at different
scales is incorporated to represent curved like edges. The recent
scenario in the issues of image retrieval is to reduce the semantic gap
between user’s preference and low level features. To address this
concern, genetic algorithm combined with relevance feedback is
embedded to reduce semantic gap and retrieve user’s preference
images. Extensive and comparative experiments have been conducted
to evaluate proposed framework for content based image retrieval on
two databases, i.e., COIL-100 and Corel-1000. Experimental results
clearly show that the proposed system surpassed other existing
systems in terms of precision and recall. The proposed work achieves
highest performance with average precision of 88.2% on COIL-100
and 76.3% on Corel, the average recall of 69.9% on COIL and 76.3%
on Corel. Thus, the experimental results confirm that the proposed
content based image retrieval system architecture attains better
solution for image retrieval.
Influence of Thermal Damage on the Mechanical Strength of Trimmed CFRP
Carbon Fiber Reinforced Plastics (CFRPs) are widely
used for advanced applications, in particular in aerospace, automotive
and wind energy industries. Once cured to near net shape, CFRP
parts need several finishing operations such as trimming, milling or
drilling in order to accommodate fastening hardware and meeting the
final dimensions. The present research aims to study the effect of the
cutting temperature in trimming on the mechanical strength of high
performance CFRP laminates used for aeronautics applications. The
cutting temperature is of great importance when dealing with
trimming of CFRP. Temperatures higher than the glass-transition
temperature (Tg) of the resin matrix are highly undesirable: they
cause degradation of the matrix in the trimmed edges area, which can
severely affect the mechanical performance of the entire component.
In this study, a 9.50mm diameter CVD diamond coated carbide tool
with six flutes was used to trim 24-plies CFRP laminates. A
300m/min cutting speed and 1140mm/min feed rate were used in the
experiments. The tool was heated prior to trimming using a
blowtorch, for temperatures ranging from 20°C to 300°C. The
temperature at the cutting edge was measured using embedded KType
thermocouples. Samples trimmed for different cutting
temperatures, below and above Tg, were mechanically tested using
three-points bending short-beam loading configurations. New cutting
tools as well as worn cutting tools were utilized for the experiments.
The experiments with the new tools could not prove any correlation
between the length of cut, the cutting temperature and the mechanical
performance. Thus mechanical strength was constant, regardless of
the cutting temperature. However, for worn tools, producing a cutting
temperature rising up to 450°C, thermal damage of the resin was
observed. The mechanical tests showed a reduced mean resistance in
short beam configuration, while the resistance in three point bending
decreases with increase of the cutting temperature.
Dynamic Stability of Axially Moving Viscoelastic Plates under Non-Uniform In-Plane Edge Excitations
This paper investigates the parametric stability of an
axially moving web subjected to non-uniform in-plane edge
excitations on two opposite, simply-supported edges. The web is
modeled as a viscoelastic plate whose constitutive relation obeys the
Kelvin-Voigt model, and the in-plane edge excitations are expressed
as the sum of a static tension and a periodical perturbation. Due to the
in-plane edge excitations, the moving plate may bring about
parametric instability under certain situations. First, the in-plane
stresses of the plate due to the non-uniform edge excitations are
determined by solving the in-plane forced vibration problem. Then,
the dependence on the spatial coordinates in the equation of transverse
motion is eliminated by the generalized Galerkin method, which
results in a set of discretized system equations in time. Finally, the
method of multiple scales is utilized to solve the set of system
equations analytically if the periodical perturbation of the in-plane
edge excitations is much smaller as compared with the static tension of
the plate, from which the stability boundaries of the moving plate are
obtained. Numerical results reveal that only combination resonances
of the summed-type appear under the in-plane edge excitations
considered in this work.