Abstract: In the numerical solution of the forward dynamics of a
multibody system, the positions and velocities of the bodies in the
system are obtained first. With the information of the system state
variables at each time step, the internal and external forces acting on
the system are obtained by appropriate contact force models if the
continuous contact method is used instead of a discrete contact
method. The local deformation of the bodies in contact, represented
by penetration, is used to compute the contact force. The ability and
suitability with current cylindrical contact force models to describe
the contact between bodies with cylindrical geometries with
particular focus on internal contacting geometries involving low
clearances and high loads simultaneously is discussed in this paper.
A comparative assessment of the performance of each model under
analysis for different contact conditions, in particular for very
different penetration and clearance values, is presented. It is
demonstrated that some models represent a rough approximation to
describe the conformal contact between cylindrical geometries
because contact forces are underestimated.
Abstract: The present study is concerned with effect of exciting
boundary layer on increase in heat transfer from flat surfaces. As any
increase in heat transfer between a fluid inside a face and another one
outside of it can cause an increase in some equipment's efficiency, so
at this present we have tried to increase the wall's heat transfer
coefficient by exciting the fluid boundary layer. By a collision
between flow and the placed block at the fluid way, the flow pattern
and the boundary layer stability will change. The flow way inside the
channel is simulated as a 2&3-dimensional channel by Gambit
TM
software.
With studying the achieved results by this simulation for the flow
way inside the channel with a block coordinating with Fluent
TM
software, it's determined that the figure and dimensions of the exciter
are too important for exciting the boundary layer so that any increase
in block dimensions in vertical side against the flow and any
reduction in its dimensions at the flow side can increase the average
heat transfer coefficient from flat surface and increase the flow
pressure loss. Using 2&3-dimensional analysis on exciting the flow at
the flow way inside a channel by cylindrical block at the same time
with the external flow, we came to this conclusion that the heat flux
transferred from the surface, is increased considerably in terms of the
condition without excitation. Also, the k-e turbulence model is used.
Abstract: Supply Chain Management (SCM) is the integration
between manufacturer, transporter and customer in order to form one
seamless chain that allows smooth flow of raw materials, information
and products throughout the entire network that help in minimizing
all related efforts and costs. The main objective of this paper is to
develop a model that can accept a specified number of spare-parts
within the supply chain, simulating its inventory operations
throughout all stages in order to minimize the inventory holding
costs, base-stock, safety-stock, and to find the optimum quantity of
inventory levels, thereby suggesting a way forward to adapt some
factors of Just-In-Time to minimizing the inventory costs throughout
the entire supply chain. The model has been developed using Micro-
Soft Excel & Visual Basic in order to study inventory allocations in
any network of the supply chain. The application and reproducibility
of this model were tested by comparing the actual system that was
implemented in the case study with the results of the developed
model. The findings showed that the total inventory costs of the
developed model are about 50% less than the actual costs of the
inventory items within the case study.
Abstract: Incompressible Navier-Stokes equations are reviewed
in this work. Three-dimensional Navier-Stokes equations are solved
analytically. The Mathematical derivation shows that the solutions
for the zero and constant pressure gradients are similar. Descriptions
of the proposed formulation and validation against two laminar
experiments and three different turbulent flow cases are reported in
this paper. Even though, the analytical solution is derived for nonreacting
flows, it could reproduce trends for cases including
combustion.
Abstract: Nuclear energy sources have been widely used in the
past decades in order to power spacecraft subsystems. Nevertheless,
their use has attracted controversy because of the risk of harmful
material released into the atmosphere if an accident were to occur
during the launch phase of the mission, leading to the general
adoption of photovoltaic systems.
As compared to solar cells, wind turbines have a great advantage
on Mars, as they can continuously produce power both during dust
storms and at night-time: this paper focuses on the potential of a wind
energy conversion system (WECS) considering the atmospheric
conditions on Mars. Wind potential on Martian surface has been
estimated, as well as the average energy requirements of a Martian
probe or surface rover. Finally, the expected daily energy output of
the WECS has been computed on the basis of both the swept area of
the rotor and the equivalent wind speed at the landing site.
Abstract: This paper proposes a methodology for analysis of
the dynamic behavior of a robotic manipulator in continuous
time. Initially this system (nonlinear system) will be decomposed
into linear submodels and analyzed in the context of the Linear
and Parameter Varying (LPV) Systems. The obtained linear
submodels, which represent the local dynamic behavior of the
robotic manipulator in some operating points were grouped in
a Takagi-Sugeno fuzzy structure. The obtained fuzzy model was
analyzed and validated through analog simulation, as universal
approximator of the robotic manipulator.
Abstract: Mapping between local and global coordinates is an
important issue in finite element method, as all calculations are
performed in local coordinates. The concern arises when subparametric
are used, in which the shape functions of the field variable
and the geometry of the element are not the same. This is particularly
the case for C* elements in which the extra degrees of freedoms
added to the nodes make the elements sub-parametric. In the present
work, transformation matrix for C1* (an 8-noded hexahedron
element with 12 degrees of freedom at each node) is obtained using
equivalent C0 elements (with the same number of degrees of
freedom). The convergence rate of 8-noded C1* element is nearly
equal to its equivalent C0 element, while it consumes less CPU time
with respect to the C0 element. The existence of derivative degrees
of freedom at the nodes of C1* element along with excellent
convergence makes it superior compared with it equivalent C0
element.
Abstract: Artificial Immune System is adopted as a Heuristic
Algorithm to solve the combinatorial problems for decades.
Nevertheless, many of these applications took advantage of the benefit
for applications but seldom proposed approaches for enhancing the
efficiency. In this paper, we continue the previous research to develop
a Self-evolving Artificial Immune System II via coordinating the T
and B cell in Immune System and built a block-based artificial
chromosome for speeding up the computation time and better
performance for different complexities of problems. Through the
design of Plasma cell and clonal selection which are relative the
function of the Immune Response. The Immune Response will help
the AIS have the global and local searching ability and preventing
trapped in local optima. From the experimental result, the significant
performance validates the SEAIS II is effective when solving the
permutation flows-hop problems.
Abstract: In this paper, a semi empirical formula is presented based on the experimental results to predict the first pick (maximum force) value in the instantaneous folding force- axial distance diagram of a square column. To achieve this purpose, the maximum value of the folding force was assumed to be a function of the average folding force. Using the experimental results, the maximum value of the force necessary to initiate the first fold in a square column was obtained with respect to the geometrical quantities and material properties. Finally, the results obtained from the semi empirical relation in this paper, were compared to the experimental results which showed a good correlation.
Abstract: The design of technological procedures for
manufacturing certain products demands the definition and
optimization of technological process parameters. Their
determination depends on the model of the process itself and its
complexity. Certain processes do not have an adequate mathematical
model, thus they are modeled using heuristic methods. First part of
this paper presents a state of the art of using soft computing
techniques in manufacturing processes from the perspective of
applicability in modern CAx systems. Methods of artificial
intelligence which can be used for this purpose are analyzed. The
second part of this paper shows some of the developed models of
certain processes, as well as their applicability in the actual
calculation of parameters of some technological processes within the
design system from the viewpoint of productivity.
Abstract: The pipe inspection operation is the difficult detective
performance. Almost applications are mainly relies on a manual
recognition of defective areas that have carried out detection by an
engineer. Therefore, an automation process task becomes a necessary
in order to avoid the cost incurred in such a manual process. An
automated monitoring method to obtain a complete picture of the
sewer condition is proposed in this work. The focus of the research is
the automated identification and classification of discontinuities in
the internal surface of the pipe. The methodology consists of several
processing stages including image segmentation into the potential
defect regions and geometrical characteristic features. Automatic
recognition and classification of pipe defects are carried out by means
of using an artificial neural network technique (ANN) based on
Radial Basic Function (RBF). Experiments in a realistic environment
have been conducted and results are presented.
Abstract: In this study, a nickel film with nano-crystalline grains,
high hardness and smooth surface was electrodeposited using a post
supercritical carbon dioxide (CO2) mixed Watts electrolyte. Although
the hardness was not as high as its Sc-CO2 counterpart, the thin coating
contained significantly less number of nano-sized pinholes. By
measuring the escape concentration of the dissolved CO2 in post
Sc-CO2 mixed electrolyte with the elapsed time, it was believed that
the residue of dissolved CO2 bubbles should closely relate to the
improvement in hardness and surface roughness over its conventional
plating counterpart. Therefore, shortening the duration of
electroplating with the raise of current density up to 0.5 A/cm2 could
effectively retain more post Sc-CO2 mixing effect. This study not only
confirms the roles of dissolved CO2 bubbles in electrolyte but also
provides a potential process to overcome most issues associated with
the cost in building high-pressure chamber for large size products and
continuous plating using supercritical method.
Abstract: This paper describes the experimental efficiency of a
compact organic Rankine cycle (ORC) system with a compact
rotary-vane-type expander. The compact ORC system can be used for
power generation from low-temperature heat sources such as waste
heat from various small-scale heat engines, fuel cells, electric devices,
and solar thermal energy. The purpose of this study is to develop an
ORC system with a low power output of less than 1 kW with a hot
temperature source ranging from 60°C to 100°C and a cold
temperature source ranging from 10°C to 30°C. The power output of
the system is rather less due to limited heat efficiency. Therefore, the
system should have an economically optimal efficiency. In order to
realize such a system, an efficient and low-cost expander is
indispensable. An experimental ORC system was developed using the
rotary-vane-type expander which is one of possible candidates of the
expander. The experimental results revealed the expander
performance for various rotation speeds, expander efficiencies, and
thermal efficiencies. Approximately 30 W of expander power output
with 48% expander efficiency and 4% thermal efficiency with a
temperature difference between the hot and cold sources of 80°C was
achieved.
Abstract: The intention of this study to design the probability optimized sewing sack-s workstation based on ergonomics for productivity improvement and decreasing musculoskeletal disorders. The physical dimensions of two workers were using to design the new workstation. The physical dimensions are (1) sitting height, (2) mid shoulder height sitting, (3) shoulder breadth, (4) knee height, (5) popliteal height, (6) hip breadth and (7) buttock-knee length. The 5th percentile of buttock knee length sitting (51 cm), the 50th percentile of mid shoulder height sitting (62 cm) and the 95th percentile of popliteal height (43 cm) and hip breadth (45 cm) applied to design the workstation for sewing sack-s operator and the others used to adjust the components of this workstation. The risk assessment by RULA before and after using the probability optimized workstation were 7 and 7 scores and REBA scores were 11 and 5, respectively. Body discomfort-abnormal index was used to assess muscle fatigue of operators before adjustment workstation found that neck muscles, arm muscles area, muscles on the back and the lower back muscles fatigue. Therefore, the extension and flexion exercise was applied to relief musculoskeletal stresses. The workers exercised 15 minutes before the beginning and the end of work for 5 days. After that, the capability of flexion and extension muscles- workers were increasing in 3 muscles (arm, leg, and back muscles).
Abstract: Due to today-s turbulent environment, manufacturing resources, particularly in assembly, must be reconfigured frequently. These reconfigurations are caused by various, partly cyclic, influencing factors. Hence, it is important to evaluate the innovation ability - the capability of resources to implement innovations quickly and efficiently without large expense - of manufacturing resources. For this purpose, a new methodology is presented in this article. Within the methodology, design structure matrices and graph theory are used. The results of the methodology include different indices to evaluate the innovation ability of the manufacturing resources. Due to the cyclicity of the influencing factors, the methodology can be used to synchronize the realization of adaptations.
Abstract: Omni directional mobile robots have been popularly
employed in several applications especially in soccer player robots
considered in Robocup competitions. However, Omni directional
navigation system, Omni-vision system and solenoid kicking
mechanism in such mobile robots have not ever been combined. This
situation brings the idea of a robot with no head direction into
existence, a comprehensive Omni directional mobile robot. Such a
robot can respond more quickly and it would be capable for more
sophisticated behaviors with multi-sensor data fusion algorithm for
global localization base on the data fusion. This paper has tried to
focus on the research improvements in the mechanical, electrical and
software design of the robots of team ADRO Iran. The main
improvements are the world model, the new strategy framework,
mechanical structure, Omni-vision sensor for object detection, robot
path planning, active ball handling mechanism and the new kicker
design, , and other subjects related to mobile robot
Abstract: A cognitive collaborative reinforcement learning
algorithm (CCRL) that incorporates an advisor into the learning
process is developed to improve supervised learning. An autonomous
learner is enabled with a self awareness cognitive skill to decide
when to solicit instructions from the advisor. The learner can also
assess the value of advice, and accept or reject it. The method is
evaluated for robotic motion planning using simulation. Tests are
conducted for advisors with skill levels from expert to novice. The
CCRL algorithm and a combined method integrating its logic with
Clouse-s Introspection Approach, outperformed a base-line fully
autonomous learner, and demonstrated robust performance when
dealing with various advisor skill levels, learning to accept advice
received from an expert, while rejecting that of less skilled
collaborators. Although the CCRL algorithm is based on RL, it fits
other machine learning methods, since advisor-s actions are only
added to the outer layer.
Abstract: Delamination between layers in composite materials is a major structural failure. The delamination resistance is quantified by the critical strain energy release rate (SERR). The present investigation deals with the strain energy release rate of two woven fabric composites. Materials used are made of two types of glass fiber (360 gsm and 600 gsm) of plain weave and epoxy as matrix. The fracture behavior is studied using the mode I, double cantilever beam test and the mode II, end notched flexure test, in order to determine the energy required for the initiation and growth of an artificial crack. The delamination energy of these two materials is compared in order to study the effect of weave and reinforcement on mechanical properties. The fracture mechanism is also analyzed by means of scanning electron microscopy (SEM). It is observed that the plain weave fabric composite with lesser strand width has higher inter laminar fracture properties compared to the plain weave fabric composite with more strand width.
Abstract: This paper presents the development of low cost Nano membrane fabrication system. The system is specially designed for anodic aluminum oxide membrane. This system is capable to perform the processes such as anodization and electro-polishing. The designed machine was successfully tested for 'mild anodization' (MA) for 48 hours and 'hard anodization' (HA) for 3 hours at constant 0oC. The system is digitally controlled and guided for temperature maintenance during anodization and electro-polishing. The total cost of the developed machine is 20 times less than the multi-cooling systems available in the market which are generally used for this purpose.
Abstract: Experiments have been performed to investigate the radiation effects on mixed convection heat transfer for thermally developing airflow in vertical ducts with two differentially heated isothermal walls and two adiabatic walls. The investigation covers the Reynolds number Re = 800 to Re = 2900, heat flux varied from 256 W/m2 to 863 W/m2, hot wall temperature ranges from 27°C to 100 °C, aspect ratios 1 & 0.5 and the emissivity of internal walls are 0.05 and 0.85. In the present study, combined flow visualization was conducted to observe the flow patterns. The effect of surface temperature along the walls was studied to investigate the local Nusselt number variation within the duct. The result shows that flow condition and radiation significantly affect the total Nusselt number and tends to reduce the buoyancy condition.