Abstract: In the crack growth analysis, the Stress Intensity
Factor (SIF) is a fundamental prerequisite. In the present study, the
mode I stress intensity factor (SIF) of three-dimensional penny-
Shaped crack is obtained in an isotropic elastic cylindrical medium
with arbitrary dimensions under arbitrary loading at the top of the
cylinder, by the semi-analytical method based on the Rayleigh-Ritz
method. This method that is based on minimizing the potential
energy amount of the whole of the system, gives a very close results
to the previous studies. Defining the displacements (elastic fields) by
hypothetical functions in a defined coordinate system is the base of
this research. So for creating the singularity conditions at the tip of
the crack the appropriate terms should be found.
Abstract: The daily increase of organic waste materials resulting
from different activities in the country is one of the main factors for
the pollution of environment. Today, with regard to the low level of
the output of using traditional methods, the high cost of disposal
waste materials and environmental pollutions, the use of modern
methods such as anaerobic digestion for the production of biogas has
been prevailing. The collected biogas from the process of anaerobic
digestion, as a renewable energy source similar to natural gas but
with a less methane and heating value is usable. Today, with the help
of technologies of filtration and proper preparation, access to biogas
with features fully similar to natural gas has become possible. At
present biogas is one of the main sources of supplying electrical and
thermal energy and also an appropriate option to be used in four
stroke engine, diesel engine, sterling engine, gas turbine, gas micro
turbine and fuel cell to produce electricity. The use of biogas for
different reasons which returns to socio-economic and environmental
advantages has been noticed in CHP for the production of energy in
the world. The production of biogas from the technology of anaerobic
digestion and its application in CHP power plants in Iran can not only
supply part of the energy demands in the country, but it can
materialize moving in line with the sustainable development. In this
article, the necessity of the development of CHP plants with biogas
fuels in the country will be dealt based on studies performed from the
economic, environmental and social aspects. Also to prove the
importance of the establishment of these kinds of power plants from
the economic point of view, necessary calculations has been done as
a case study for a CHP power plant with a biogas fuel.
Abstract: This article discusses the questions concerning of creating small packet networks for energy companies with application of high voltage power line carrier equipment (PLC) with functionality of IP traffic transmission. The main idea is to create converged PLC links between substations and dispatching centers where packet data and voice are transmitted in one data flow. The article contents description of basic conception of the network, evaluation of voice traffic transmission parameters, and discussion of header compression techniques in relation to PLC links. The results of exploration show us, that convergent packet PLC links can be very useful in the construction of small packet networks between substations in remote locations, such as deposits or low populated areas.
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: Calcium is a vital second messenger used in signal transduction. Calcium controls secretion, cell movement, muscular contraction, cell differentiation, ciliary beating and so on. Two theories have been used to simplify the system of reaction-diffusion equations of calcium into a single equation. One is excess buffer approximation (EBA) which assumes that mobile buffer is present in excess and cannot be saturated. The other is rapid buffer approximation (RBA), which assumes that calcium binding to buffer is rapid compared to calcium diffusion rate. In the present work, attempt has been made to develop a model for calcium diffusion under excess buffer approximation in neuron cells. This model incorporates the effect of [Na+] influx on [Ca2+] diffusion,variable calcium and sodium sources, sodium-calcium exchange protein, Sarcolemmal Calcium ATPase pump, sodium and calcium channels. The proposed mathematical model leads to a system of partial differential equations which have been solved numerically using Forward Time Centered Space (FTCS) approach. The numerical results have been used to study the relationships among different types of parameters such as buffer concentration, association rate, calcium permeability.
Abstract: The modified Claus process is commonly used in oil
refining and gas processing to recover sulfur and destroy
contaminants formed in upstream processing. A Claus furnace feed
containing a relatively low concentration of H2S may be incapable of
producing a stable flame. Also, incomplete combustion of
hydrocarbons in the feed can lead to deterioration of the catalyst in
the reactors due to soot or carbon deposition. Therefore, special
consideration is necessary to achieve the appropriate overall sulfur
recovery. In this paper, some configurations available to treat lean
acid gas streams are described and the most appropriate ones are
studied to overcome low H2S concentration problems. As a result,
overall sulfur recovery is investigated for feed preheating and hot gas
configurations.
Abstract: Generation system reliability assessment is an
important task which can be performed using deterministic or
probabilistic techniques. The probabilistic approaches have
significant advantages over the deterministic methods. However,
more complicated modeling is required by the probabilistic
approaches. Power generation model is a basic requirement for this
assessment. One form of the generation models is the well known
capacity outage probability table (COPT). Different analytical
techniques have been used to construct the COPT. These approaches
require considerable mathematical modeling of the generating units.
The unit-s models are combined to build the COPT which will add
more burdens on the process of creating the COPT. Decimal to
Binary Conversion (DBC) technique is widely and commonly applied
in electronic systems and computing This paper proposes a novel
utilization of the DBC to create the COPT without engaging in
analytical modeling or time consuming simulations. The simple
binary representation , “0 " and “1 " is used to model the states o f
generating units. The proposed technique is proven to be an effective
approach to build the generation model.
Abstract: The present work deals with thermodynamic analysis
of cascade refrigeration system using ozone friendly refrigerants pair
R507A and R23. R507A is azeotropic mixture composed of HFC
refrigerants R125/R143a (50%/50% wt.). R23 is a single component
HFC refrigerant used as replacement to CFC refrigerant R13 in low
temperature applications. These refrigerants have zero ozone
depletion potential and are non-flammable and as R507A an
azeotropic mixture there is no problem of temperature glide. This
study thermodynamically analyzed R507A-R23 cascade refrigeration
system to optimize the design and operating parameters of the
system. The design and operating parameters include: Condensing,
evaporating, subcooling and superheating temperatures in the high
temperature circuit, temperature difference in the cascade heat
exchanger, Condensing, evaporating, subcooling and superheating
temperatures in the low temperature circuit.
Abstract: The evolution of ICT has changed all sections of society and these changes have been creating an irreversible impact on higher education institutions, which are expected to adopt innovative technologies in their teaching practices. As theorical framework this study select Rogers theory of innovation diffusion which is widely used to illustrate how technologies move from a localized invented to a widespread evolution on organizational practices. Based on descriptive statistical data collected in a European higher education institution three years longitudinal study was conducted for analyzing and discussion the different stages of a LMS adoption process. Results show that ICT integration in higher education is not progressively successful and a linear process and multiple aspects must be taken into account.
Abstract: The use of technology is increasingly adopted to
support flexible learning in Higher Education institutions. The
adoption of more sophisticated technologies offers a broad range of
facilities for communication and resource sharing, thereby creating a
flexible learning environment that facilitates and even encourages
students not to physically attend classes. However this emerging
trend seems to contradict class attendance requirements within
universities, inevitably leading to a dilemma between amending
traditional regulations and creating new policies for the higher
education institutions. This study presents an investigation into
student engagement in a technology enhanced/driven flexible
environment along with its relationship to attainment. We propose an
approach to modelling engagement from different perspectives in
terms of indicators and then consider what impact these indicators
have on student academic performance. We have carried out a case
study on the relation between attendance and attainment in a flexible
environment. Although our preliminary results show attendance is
quantitatively correlated with successful student development and
learning outcomes, our results also indicate there is a cohort that did
not follow such a pattern. Nevertheless the preliminary results could
provide an insight into pilot studies in the wider deployment of new
technology to support flexible learning.
Abstract: The paper presents coupled electromagnetic and
thermal field analysis of busbar system (of rectangular cross-section
geometry) submitted to short circuit conditions. The laboratory model
was validated against both analytical solution and experimental
observations. The considered problem required the computation of
the detailed distribution of the power losses and the heat transfer
modes. In this electromagnetic and thermal analysis, different
definitions of electric busbar heating were considered and compared.
The busbar system is a three phase one and consists of aluminum,
painted aluminum and copper busbar. The solution to the coupled
field problem is obtained using the finite element method and the
QuickField™ program. Experiments have been carried out using two
different approaches and compared with computed results.
Abstract: Many organisations are nowadays interested to adopt
lean manufacturing strategy that would enable them to compete in
this competitive globalisation market. In this respect, it is necessary
to assess the implementation of lean manufacturing in different
organisations so that the important best practices can be identified.
This paper describes the development of key areas which will be
used to assess the adoption and implementation of lean
manufacturing practices. There are some key areas developed to
evaluate and reduce the most optimal projects so as to enhance their
production efficiency and increase the purpose of the economic
benefits of the manufacturing unit.
Lean manufacturing is becoming lean enterprise by treating its
customers and suppliers as partners. This gives the extra edge in
today-s cost and time competitive markets. The organisation is
becoming strong in all the conventional competition points. They are
Price, Quality and Delivery. Lean enterprise owners can deliver high
quality products quickly, with low price.
Abstract: The modified Claus process is the major technology
for the recovery of elemental sulfur from hydrogen sulfide. The
chemical reactions that can occur in the reaction furnace are
numerous and many byproducts such as carbon disulfide and carbon
carbonyl sulfide are produced. These compounds can often contribute
from 20 to 50% of the pollutants and therefore, should be hydrolyzed
in the catalytic converter. The inlet temperature of the first catalytic
reactor should be maintained over than 250 °C, to hydrolyze COS
and CS2. In this paper, the various configurations for the first
converter reheating of sulfur recovery unit are investigated. As a
result, the performance of each method is presented for a typical
clause unit. The results show that the hot gas method seems to be
better than the other methods.
Abstract: Partial combustion of biomass in the gasifier generates producer gas that can be used for heating purposes and as supplementary or sole fuel in internal combustion engines. In this study, the virgin biomass obtained from hingan shell is used as the feedstock for gasifier to generate producer gas. The gasifier-engine system is operated on diesel and on esters of vegetable oil of hingan in liquid fuel mode operation and then on liquid fuel and producer gas combination in dual fuel mode operation. The performance and emission characteristics of the CI engine is analyzed by running the engine in liquid fuel mode operation and in dual fuel mode operation at different load conditions with respect to maximum diesel savings in the dual fuel mode operation. It was observed that specific energy consumption in the dual fuel mode of operation is found to be in the higher side at all load conditions. The brake thermal efficiency of the engine using diesel or hingan oil methyl ester (HOME) is higher than that of dual fuel mode operation. A diesel replacement in the tune of 60% in dual fuel mode is possible with the use of hingan shell producer gas. The emissions parameters such CO, HC, NOx, CO2 and smoke are higher in the case of dual fuel mode of operation as compared to that of liquid fuel mode.
Abstract: Fixed-bed slow pyrolysis experiments of rice husk
have been conducted to determine the effect of pyrolysis
temperature, heating rate, particle size and reactor length on the
pyrolysis product yields. Pyrolysis experiments were performed at
pyrolysis temperature between 400 and 600°C with a constant
heating rate of 60°C/min and particle sizes of 0.60-1.18 mm. The
optimum process conditions for maximum liquid yield from the rice
husk pyrolysis in a fixed bed reactor were also identified. The highest
liquid yield was obtained at a pyrolysis temperature of 500°C,
particle size of
1.18-1.80 mm, with a heating rate of 60°C/min in a 300 mm length
reactor. The obtained yield of, liquid, gas and solid were found be in
the range of 22.57-31.78 %, 27.75-42.26 % and 34.17-42.52 % (all
weight basics) respectively at different pyrolysis conditions. The
results indicate that the effects of pyrolysis temperature and particle
size on the pyrolysis yield are more significant than that of heating
rate and reactor length. The functional groups and chemical
compositions present in the liquid obtained at optimum conditions
were identified by Fourier Transform-Infrared (FT-IR) spectroscopy
and Gas Chromatography/ Mass Spectroscopy (GC/MS) analysis
respectively.
Abstract: Design and land use are closely linked to the
energy efficiency levels for an urban area. The current city
planning practice does not involve an effective land useenergy
evaluation in its 'blueprint' urban plans. The study
proposed an appraisal method that can be embedded in GIS
programs using five planning criteria as how far a planner can
give away from the planning principles (criteria) for the most
energy output s/he can obtain. The case of Balcova, a district
in the Izmir Metropolitan area, is used conformingly for
evaluating the proposed master plan and the geothermal
energy (heating only) use for the concern district.
If the land use design were proposed accordingly at-most
energy efficiency (a 30% obtained), mainly increasing the
density around the geothermal wells and also proposing more
mixed use zones, we could have 17% distortion (infidelity to
the main planning principles) from the original plan. The
proposed method can be an effective tool for planners as
simulation media, of which calculations can be made by GIS
ready tools, to evaluate efficiency levels for different plan
proposals, letting to know how much energy saving causes
how much deviation from the other planning ideals. Lower
energy uses can be possible for different land use proposals
for various policy trials.
Abstract: This paper reviews designs of the built environment
from a sustainability perspective, emphasizing their importance in
achieving ecological and sustainable economic objectives. The built
environment has traditionally resulted in loss of biodiversity,
extinction of some species, climate change, excessive water use, land
degradation, space depletion, waste accumulation, energy
consumption and environmental pollution. Materials used like
plastics, metals, bricks, concrete, cement, natural aggregates, glass
and plaster have wreaked havoc on the earth´s resources, since they
have high levels of embodied energy hence not sustainable.
Additional resources are consumed during use and disposal phases.
Proposed designs for sustainability solutions include: ecological
sanitation and eco-efficiency systems that ensure social, economic,
environmental and technical sustainability. Renewable materials and
energy systems, passive cooling and heating systems and material
and energy reduction, reuse and recycling can improve the sector.
These ideas are intended to inform the field of ecological design of
the built environment.
Abstract: Radial flow reactor was focused for large scale
methanol synthesis and in which the heat transfer type was cross-flow.
The effects of operating conditions including the reactor inlet air
temperature, the heating pipe temperature and the air flow rate on the
cross-flow heat transfer was investigated and the results showed that
the temperature profile of the area in front of the heating pipe was
slightly affected by all the operating conditions. The main area whose
temperature profile was influenced was the area behind the heating
pipe. The heat transfer direction according to the air flow directions. In
order to provide the basis for radial flow reactor design calculation, the
dimensionless number group method was used for data fitting of the
bed effective thermal conductivity and the wall heat transfer
coefficient which was calculated by the mathematical model with the
product of Reynolds number and Prandtl number. The comparison of
experimental data and calculated value showed that the calculated
value fit the experimental data very well and the formulas could be
used for reactor designing calculation.
Abstract: lack of convenience condition is one of the problems
in open spaces in hot and dry regions. Nowadays parks and green
landscapes was designed and constructed without any attention to
convenience condition. If this process continues, Citizens will encounter
with some problems. Harsh climatic condition decreases the
efficiency of people-s activities. However there is hard environment
condition in hot and dry regions, Convenience condition has been
provided in Iranian traditional architecture by using techniques and
methods. In this research at the first step characteristics of Iranian
garden that can effect on creating sustainable spaces were
investigated through observation method. Pleasure space in cities will
be created with using these methods and techniques in future cities.
Furthermore the comparison between Iranian garden and landscape in
today-s cities demonstrate the effectiveness of Iranian garden
characteristics on sustainable spaces. Iranian architects used simple
and available methods for creating open architectural spaces. In
addition desirable conditions were provided with taking in to account
both physically and spiritually. Parks and landscapes in future cities
can be designed and constructed with respect to architectural
techniques that used in Iranian gardens in hot and arid regions.
Abstract: This paper proposes the concept of aerocapture with
aerodynamic-environment-adaptive variable geometry flexible
aeroshell that vehicle deploys. The flexible membrane is composed
of thin-layer film or textile as its aeroshell in order to solve some
problems obstructing realization of aerocapture technique.
Multi-objective optimization study is conducted to investigate
solutions and derive design guidelines. As a result, solutions which
can avoid aerodynamic heating and enlarge the corridor width up
to 10% are obtained successfully, so that the effectiveness of this
concept can be demonstrated. The deformation-use optimum
solution changes its drag coefficient from 1.6 to 1.1, along with the
change in dynamic pressure. Moreover, optimization results show
that deformation-use solution requires the membrane for which
upper temperature limit and strain limit are more than 700 K and
120%, respectively, and elasticity (Young-s modulus) is of order of
106 Pa.