Abstract: In this study, mechanically alloyed Al 2024 powder is
densified by conventional sintering and by equal channel angular
pressing (ECAP) with and without back pressure. The powder was
encapsulated in an aluminium can for consolidation through ECAP.
The properties obtained in the compacts by conventional sintering
route and by ECAP are compared. The effect of conventional
sintering and ECAP on consolidation behaviour of powder,
microstructure, density and hardness is discussed. Room temperature
back pressure aided ECAP results in nearly full denser (97% of its
theoretical density) compact at room temperature. NanoIndentation
technique was used to determine the modulus of the consolidated
compacts.
Abstract: High strength concrete has been used in situations
where it may be exposed to elevated temperatures. Numerous authors
have shown the significant contribution of polypropylene fiber to the
spalling resistance of high strength concrete.
When cement-based composite that reinforced by polypropylene
fibers heated up to 170 °C, polypropylene fibers readily melt and
volatilize, creating additional porosity and small channels in to the
matrix that cause the poor structure and low strength.
This investigation develops on the mechanical properties of mortar
incorporating polypropylene fibers exposed to high temperature.
Also effects of different pozzolans on strength behaviour of samples
at elevated temperature have been studied.
To reach this purpose, the specimens were produced by partial
replacement of cement with finely ground glass, silica fume and rice
husk ash as high reactive pozzolans. The amount of this replacement
was 10% by weight of cement to find the effects of pozzolans as a
partial replacement of cement on the mechanical properties of
mortars. In this way, lots of mixtures with 0%, 0.5%, 1% and 1.5% of
polypropylene fibers were cast and tested for compressive and
flexural strength, accordance to ASTM standard. After that
specimens being heated to temperatures of 300, 600 °C, respectively,
the mechanical properties of heated samples were tested.
Mechanical tests showed significant reduction in compressive
strength which could be due to polypropylene fiber melting. Also
pozzolans improve the mechanical properties of sampels.
Abstract: Due to the legacy of apartheid segregation South Africa remains a divided society where most voters live in politically homogenous social environments. This paper argues that political discussion within one’s social context plays a primary role in shaping political attitudes and vote choice. Using data from the Comparative National Elections Project 2004 and 2009 South African post-election surveys, the paper explores the extent of social context partisan homogeneity in South Africa and finds that voters are not overly embedded in homogenous social contexts. It then demonstrates the consequences of partisan homogeneity on voting behavior. Homogenous social contexts tend to encourage stronger partisan loyalties and fewer defections in vote choice while voters in more heterogeneous contexts show less consistency in their attitudes and behaviour. Finally, the analysis shows how momentous sociopolitical events at the time of a particular election can change the social context, with important consequences for electoral outcomes.
Abstract: A macroscopic constitutive equation is developed for a high-density cellulose insulation material with emphasis on the outof- plane stress relaxation behavior. A hypothesis is proposed where the total stress is additively composed by an out-of-plane visco-elastic isotropic contribution and an in-plane elastic orthotropic response. The theory is validated against out-of-plane stress relaxation, compressive experiments and in-plane tensile hysteresis, respectively. For large scale finite element simulations, the presented model provides a balance between simplicity and capturing the materials constitutive behaviour.
Abstract: This paper discusses a qualitative simulator QRiOM
that uses Qualitative Reasoning (QR) technique, and a process-based
ontology to model, simulate and explain the behaviour of selected
organic reactions. Learning organic reactions requires the application
of domain knowledge at intuitive level, which is difficult to be
programmed using traditional approach. The main objective of
QRiOM is to help learners gain a better understanding of the
fundamental organic reaction concepts, and to improve their
conceptual comprehension on the subject by analyzing the multiple
forms of explanation generated by the software. This paper focuses
on the generation of explanation based on causal theories to explicate
various phenomena in the chemistry subject. QRiOM has been tested
with three classes problems related to organic chemistry, with
encouraging results. This paper also presents the results of
preliminary evaluation of QRiOM that reveal its explanation
capability and usefulness.
Abstract: Implementing Information Technology/ Information
System (IT/IS) is critical for every industry as its potential benefits
have been to motivate many industries including the Malaysian
construction industry to invest in it. To successfully implement IT/IS
has become the major concern for every organisation. Identifying the
critical success factors (CSFs) has become the main agenda for
researchers, academicians and practitioners due to the wide number
of failures reported. This research paper seeks to identify the CSFs
that influence the successful implementation of IT/IS in construction
industry in Malaysia. Limited factors relating to people issue will be
highlighted here to showcase some as it becomes one of the major
contributing factors to the failure. Three (3) organisations have
participated in this study. Semi-structured interviews are employed as
they offer sufficient flexibility to ensure that all relevant factors are
covered. Several key issues contributing to successful
implementations of IT/IS are identified. The results of this study
reveal that top management support, communication, user
involvement, IT staff roles and responsibility, training/skills, leader/
IT Leader, organisation culture, knowledge/ experience, motivation,
awareness, focus and ambition, satisfaction, teamwork/ collaboration,
willingness to change, attitude, commitment, management style,
interest in IT, employee behaviour towards collaborative
environment, trust, interpersonal relationship, personal characteristic
and competencies are significantly associated with the successful
implementations of IT/IS. It is anticipated that this study will create
awareness and contribute to a better understanding amongst
construction industry players and will assist them to successfully
implement IT/IS.
Abstract: In this paper, we study the existence, the boundedness and the asymptotic behavior of the positive solutions of a fuzzy nonlinear difference equations xn+1 = A + k i=0 Bi xn-i , n= 0, 1, · · · . where (xn) is a sequence of positive fuzzy numbers, A,Bi and the initial values x-k, x-k+1, · · · , x0 are positive fuzzy numbers. k ∈ {0, 1, 2, · · ·}.
Abstract: Gurus of the Classical Management School (like
Taylor, Fayol and Ford) had an opinion that work must be delegated
to the individual and the individual has to be instructed, his work
assessed and paid based on individual performance. The theories of
the Human Relations School have changed this mentality regarding
the concept of groups. They came to the conclusion that the influence
of groups greatly affects the behaviour and performance of its
members.
Group theories today are characterized by problem-solving teams
and self-managing groups authorized to make decisions and execute;
professional communities also play an important role during the
operation of knowledge management systems.
In this theoretical research we try to find answers to a question:
what kind of characteristics (professional competencies, personal
features, etc.) a successful team needs to manage a change to operate
a knowledge management system step by step.
Abstract: This article presents a detailed analysis and comparative
performance evaluation of model reference adaptive control systems.
In contrast to classical control theory, adaptive control methods allow
to deal with time-variant processes. Inspired by the works [1] and
[2], two methods based on the MIT rule and Lyapunov rule are
applied to a linear first order system. The system is simulated and
it is investigated how changes to the adaptation gain affect the
system performance. Furthermore, variations in the reference model
parameters, that is changing the desired closed-loop behaviour are
examinded.
Abstract: In this paper an alternative visualisation approach of
the wake behind different vehicle body shapes with simplified and
fully-detailed underbody has been proposed and analysed. This
allows for a more clear distinction among the different wake regions.
This visualisation is based on a transformation of the cartesian
coordinates of a chosen wake plane to polar coordinates, using as
filter velocities lower than the freestream. This transformation
produces a polar wake plot that enables the division and
quantification of the wake in a number of sections. In this paper,
local drag has been used to visualise the drag contribution of the flow
by the different sections. Visually, a balanced wake can be observed
by the concentric behaviour of the polar plots. Alternatively,
integration of the local drag of each degree section as a ratio of the
total local drag yields a quantifiable approach of the wake uniformity,
where different sections contribute equally to the local drag, with the
exception of the wheels.
Abstract: Seismic design may require non-conventional
concept, due to the fact that the stiffness and layout of the structure
have a great effect on the overall structural behaviour, on the seismic
load intensity as well as on the internal force distribution. To find an
economical and optimal structural configuration the key issue is the
optimal design of the lateral load resisting system. This paper focuses
on the optimal design of regular, concentric braced frame (CBF)
multi-storey steel building structures. The optimal configurations are
determined by a numerical method using genetic algorithm approach,
developed by the authors. Aim is to find structural configurations
with minimum structural cost. The design constraints of objective
function are assigned in accordance with Eurocode 3 and Eurocode 8
guidelines. In this paper the results are presented for various building
geometries, different seismic intensities, and levels of energy
dissipation.
Abstract: Fatigue cracking continues to be the main challenges in
improving the performance of bituminous mixture pavements. The
purpose of this paper is to look at some aspects of the effects of fine
aggregate properties on the fatigue behaviour of hot mixture asphalt.
Two types of sand (quarry and mining sand) with two conventional
bitumen (PEN 50/60 & PEN 80/100) and four polymers modified
bitumen PMB (PM1_82, PM1_76, PM2_82 and PM2_76) were used.
Physical, chemical and mechanical tests were performed on the sands
to determine their effect when incorporated with a bituminous
mixture. According to the beam fatigue results, quarry sand that has
more angularity, rougher, higher shear strength and a higher
percentage of Aluminium oxide presented higher resistance to
fatigue. Also a PMB mixture gives better fatigue results than
conventional mixtures, this is due to the PMB having better viscosity
property than that of the conventional bitumen.
Abstract: Modelling techniques for a fluid coupling taken from
published literature have been extended to include the effects of the
filling and emptying of the coupling with oil and the variation in
losses when the coupling is partially full. In the model, the fluid flow
inside the coupling is considered to have two principal velocity
components; one circumferentially about the coupling axis
(centrifugal head) and the other representing the secondary vortex
within the coupling itself (vortex head). The calculation of liquid
mass flow rate circulating between the two halves of the coupling is
based on: the assumption of a linear velocity variation in the
circulating vortex flow; the head differential in the fluid due to the
speed difference between the two shafts; and the losses in the
circulating vortex flow as a result of the impingement of the flow
with the blades in the coupling and friction within the passages
between the blades.
Abstract: This article illustrates a model selection management approach for virtual prototypes in interactive simulations. In those numerical simulations, the virtual prototype and its environment are modelled as a multiagent system, where every entity (prototype,human, etc.) is modelled as an agent. In particular, virtual prototyp ingagents that provide mathematical models of mechanical behaviour inform of computational methods are considered. This work argues that selection of an appropriate model in a changing environment,supported by models? characteristics, can be managed by the deter-mination a priori of specific exploitation and performance measures of virtual prototype models. As different models exist to represent a single phenomenon, it is not always possible to select the best one under all possible circumstances of the environment. Instead the most appropriate shall be selecting according to the use case. The proposed approach consists in identifying relevant metrics or indicators for each group of models (e.g. entity models, global model), formulate their qualification, analyse the performance, and apply the qualification criteria. Then, a model can be selected based on the performance prediction obtained from its qualification. The authors hope that this approach will not only help to inform engineers and researchers about another approach for selecting virtual prototype models, but also assist virtual prototype engineers in the systematic or automatic model selection.
Abstract: We report on the development of a model to
understand why the range of experience with respect to HIV
infection is so diverse, especially with respect to the latency period.
To investigate this, an agent-based approach is used to extract highlevel
behaviour which cannot be described analytically from the set
of interaction rules at the cellular level. A network of independent
matrices mimics the chain of lymph nodes. Dealing with massively
multi-agent systems requires major computational effort. However,
parallelisation methods are a natural consequence and advantage of
the multi-agent approach and, using the MPI library, are here
implemented, tested and optimized. Our current focus is on the
various implementations of the data transfer across the network.
Three communications strategies are proposed and tested, showing
that the most efficient approach is communication based on the
natural lymph-network connectivity.
Abstract: A research program is conducted to evaluate the
mechanical properties of Ultra High Performance Concrete, target
compressive strength at the age of 28 days being more than 150 MPa.
The methodology to develop such mix has been explained. The
material properties, mix design and curing regime are determined.
The material attributes are understood by studying the stress strain
behaviour of UHPC cylinders under uniaxial compressive loading.
The load –crack mouth opening displacement (cmod) of UHPC
beams, flexural strength and fracture energy was evaluated using
third point loading test. Compressive strength and Split tensile
strength results are determined to find out the compressive and tensile
behaviour. Residual strength parameters are presented vividly
explaining the flexural performance, toughness of concrete.Durability
studies were also done to compare the effect of fibre to that of a
control mix For all the studies the Mechanical properties were
evaluated by varying the percentage and aspect ratio of steel fibres
The results reflected that higher aspect ratio and fibre volume
produced drastic changes in the cube strength, cylinder strength, post
peak response, load-cmod, fracture energy flexural strength, split
tensile strength, residual strength and durability. In regards to null
application of UHPC in India, an initiative is undertaken to
comprehend the mechanical behaviour of UHPC, which will be vital
for longer run in commercialization for structural applications.
Abstract: Fracture process in mechanically loaded steel fiber
reinforced high-strength (SFRHSC) concrete is characterized by
fibers bridging the crack providing resistance to its opening.
Structural SFRHSC fracture model was created; material fracture
process was modeled, based on single fiber pull-out laws, which were
determined experimentally (for straight fibers, fibers with end hooks
(Dramix), and corrugated fibers (Tabix)) as well as obtained
numerically ( using FEM simulations). For this purpose experimental
program was realized and pull-out force versus pull-out fiber length
was obtained (for fibers embedded into concrete at different depth
and under different angle). Model predictions were validated by
15x15x60cm prisms 4 point bending tests. Fracture surfaces analysis
was realized for broken prisms with the goal to improve elaborated
model assumptions. Optimal SFRHSC structures were recognized.
Abstract: The Integrated Performance Modelling Environment
(IPME) is a powerful simulation engine for task simulation and
performance analysis. However, it has no high level cognition such
as memory and reasoning for complex simulation. This article
introduces a knowledge representation and reasoning scheme that can
accommodate uncertainty in simulations of military personnel with
IPME. This approach demonstrates how advanced reasoning models
that support similarity-based associative process, rule-based abstract
process, multiple reasoning methods and real-time interaction can be
integrated with conventional task network modelling to provide
greater functionality and flexibility when modelling operator
performance.
Abstract: This paper presents a unified approach based graph
theory and system theory postulates for the modeling and analysis
of Simple open cycle Gas turbine system. In the present paper, the
simple open cycle gas turbine system has been modeled up to its subsystem
level and system variables have been identified to develop the
process subgraphs. The theorems and algorithms of the graph theory
have been used to represent behavioural properties of the system like
rate of heat and work transfers rates, pressure drops and temperature
drops in the involved processes of the system. The processes have
been represented as edges of the process subgraphs and their limits
as the vertices of the process subgraphs. The system across variables
and through variables has been used to develop terminal equations of
the process subgraphs of the system. The set of equations developed
for vertices and edges of network graph are used to solve the system
for its process variables.
Abstract: The present paper proposes high performance nonlinear
force controllers for a servopneumatic real-time fatigue test
machine. A CompactRIO® controller was used, being fully
programmed using LabVIEW language. Fuzzy logic control
algorithms were evaluated to tune the integral and derivative
components in the development of hybrid controllers, namely a FLC
P and a hybrid FLC PID real-time-based controllers. Their
behaviours were described by using state diagrams. The main
contribution is to ensure a smooth transition between control states,
avoiding discrete transitions in controller outputs. Steady-state errors
lower than 1.5 N were reached, without retuning the controllers.
Good results were also obtained for sinusoidal tracking tasks from
1/¤Ç to 8/¤Ç Hz.