Abstract: This paper presents a numerical investigation of electrically driven flow for enhancing convective heat transfer in a channel flow. This study focuses on the electrode arrangements, number of electrode and electrical voltage on Electrohydrodynamics (EHD) and effect of airflow driven on solid sample surface. The inlet airflow and inlet temperature are 0.35 m/s and 60 oC, respectively. High electrical voltage is tested in the range of 0-30 kV and number of electrode is tested in the range of 1-5. The numerical results show that electric field intensity is depended on electrical voltage and number of electrode. Increasing number of electrodes is increased shear flow, so swirling flow is increased. The swirling flows from aligned and staggered arrangements are affecting within the solid sample. When electrical voltage is increased, temperature distribution and convective heat transfer on the solid sample are significantly increased due to the electric force much stronger.
Abstract: This paper presents a numerical analysis for the dynamic performance of a finite journal bearing lubricated with couple stress fluid taking into account the effect of the deformation of the bearing liner. The modified Reynolds equation has been solved by using finite difference technique. The dynamic characteristics in terms of stiffness coefficients, damping coefficients, critical mass and whirl ratio are evaluated for different values of eccentricity ratio and elastic coefficient for a journal bearing lubricated with a couple stress fluids and a Newtonian fluid. The results show that the dynamic characteristics of journal bearings lubricated with couple stress fluids are improved compared to journal bearings lubricated with Newtonian fluids.
Abstract: Stiffness sensing is an important issue in medical diagnostic, robotics surgery, safe handling, and safe grasping of objects in production lines. Detecting and obtaining the characteristics in dwelling lumps embedded in a soft tissue and safe removing and handling of detected lumps is needed in surgery. Also in industry, grasping and handling an object without damaging in a place where it is not possible to access a human operator is very important. In this paper, a method for object handling is presented. It is based on the use of an intelligent gripper to detect the object stiffness and then setting a programmable force for grasping the object to move it. The main components of this system includes sensors (sensors for measuring force and displacement), electrical (electrical and electronic circuits, tactile data processing and force control system), mechanical (gripper mechanism and driving system for the gripper) and the display unit. The system uses a rotary potentiometer for measuring gripper displacement. A microcontroller using the feedback received by the load cell, mounted on the finger of the gripper, calculates the amount of stiffness, and then commands the gripper motor to apply a certain force on the object. Results of Experiments on some samples with different stiffness show that the gripper works successfully. The gripper can be used in haptic interfaces or robotic systems used for object handling.
Abstract: Shear stresses generate frictional forces thus lead to the reduction of engine performance due to the power losses. This friction can also cause damage to the piston material. Thus, the choice of an optimal material for the piston is necessary to improve the elastohydrodynamical contacts of the piston. In this study, to achieve this objective, an elastohydrodynamical lubrication model that satisfies the best tribological behavior of the piston with the optimum choice of material is developed. Several aluminum alloys composed of different components are studied in this simulation. An application is made on the piston 60 x 120 mm Diesel engine type F8L413 currently mounted on Deutz trucks TB230 by using different aluminum alloys where alloys based on aluminum-silicon have better tribological performance.
Abstract: In nearly all earthquakes of the past century that
resulted in moderate to significant damage, the occurrence of postearthquake
fire ignition (PEFI) has imposed a serious hazard and
caused severe damage, especially in urban areas. In order to reduce
the loss of life and property caused by post-earthquake fires, there is
a crucial need for predictive models to estimate the PEFI risk. The
parameters affecting PEFI risk can be categorized as: 1) factors
influencing fire ignition in normal (non-earthquake) condition,
including floor area, building category, ignitability, type of appliance,
and prevention devices, and 2) earthquake related factors contributing
to the PEFI risk, including building vulnerability and earthquake
characteristics such as intensity, peak ground acceleration, and peak
ground velocity. State-of-the-art statistical PEFI risk models are
solely based on limited available earthquake data, and therefore they
cannot predict the PEFI risk for areas with insufficient earthquake
records since such records are needed in estimating the PEFI model
parameters. In this paper, the correlation between normal condition
ignition risk, peak ground acceleration, and PEFI risk is examined in
an effort to offer a means for predicting post-earthquake ignition
events. An illustrative example is presented to demonstrate how such
correlation can be employed in a seismic area to predict PEFI hazard.
Abstract: The purpose of this study is investigating the influences of logistics performance on organizational performance including both marketing & financial aspects, and showing the financial impacts of selecting the right marketing and logistics priorities in line with their supply chain type, and also giving the practitioners an advance identification of their priorities and participation types of supply chain, and the best combination of their strategies and resources in this regard. We made use of the original model’s questionnaire to gather all expert’s data and also SPSS and AMOS Ver.22 to analyze the gathered data. CFA method was also used to test whether a relationship between observed variables and their underlying latent constructs exists. Supply chain strategy implementation leads to logistics performance improvement, and marketing performance will be affected as well. Logistics service providers should focus on enhancement of supply chain performance, since logistics performance has been considered as a basis of evaluation of supply chain management strategy. Consequently, performance of the organization will be enhanced. This case is the first research made in Iran that analyzes the relationship between Logistics & Organizational performance in Home Appliances and Home Entertainment companies.
Abstract: Recently, Graphene Nanoribbon Field Effect Transistors (GNR FETs) attract a great deal of attention due to their better performance in comparison with conventional devices. In this paper, channel length Modulation (CLM) effect on the electrical characteristics of GNR FETs is analytically studied and modeled. To this end, the special distribution of the electric potential along the channel and current-voltage characteristic of the device is modeled. The obtained results of analytical model are compared to the experimental data of published works. As a result, it is observable that considering the effect of CLM, the current-voltage response of GNR FET is more realistic.
Abstract: Space Radiation has become one of the major factors in successful long duration space exploration. Exposure to space radiation not only can affect the health of astronauts but also can disrupt or damage materials and electronics. Hazards to materials include degradation of properties, such as, modulus, strength, or glass transition temperature. Electronics may experience single event effects, gate rupture, burnout of field effect transistors and noise. Presently aluminum is the major component in most of the space structures due to its lightweight and good structural properties. However, aluminum is ineffective at blocking space radiation. Therefore, most of the past research involved studying at polymers which contain large amounts of hydrogen. Again, these materials are not structural materials and would require large amounts of material to achieve the structural properties needed. One of the materials to alleviate this problem is polymeric composite materials, which has good structural properties and use polymers that contained large amounts of hydrogen. This paper presents steps involved in fabrication of multi-functional hybrid sandwich panels that can provide beneficial radiation shielding as well as structural strength. Multifunctional hybrid sandwich panels were manufactured using vacuum assisted resin transfer molding process and were subjected to radiation treatment. Study indicates that various nanoparticles including Boron Nano powder, Boron Carbide and Gadolinium nanoparticles can be successfully used to block the space radiation without sacrificing the structural integrity.
Abstract: In order to predict and model wrinkling which is caused by out of plane deformation due to compressive loading in the plane of the material during composite prepregs forming, it is necessary to quantitatively understand the relative magnitude of the bending stiffness. This study aims to examine the bending properties of out-of-autoclave (OOA) thermosetting prepreg under vertical cantilever test condition. A direct method for characterizing the bending behavior of composite prepregs was developed. The results from direct measurement were compared with results derived from an image-processing procedure that analyses the captured image during the vertical bending test. A numerical simulation was performed using ABAQUS to confirm the bending stiffness value.
Abstract: One of the main purposes of designing bucklingrestrained
braces is the fact that the entire lateral load is wasted by
the braces, the entire gravitational load is moved to the foundation
through the beams, and the columns can be moved to the foundation.
In other words, braces are designed for bearing lateral load. In the
implementation of the structure, it should be noted that the
implementation of various parts of the structure must be conducted in
such a way that the buckling-restrained braces would not bear the
gravitational load. Moreover, this type of brace has been investigated
under impact loading, and the design goals of designing method
(direct motion) are controlled under impact loading. The results of
dynamic analysis are shown as the relocation charts of the floors and
switch between the floors. Finally, the results are compared with each
other.
Abstract: The power electronic components within Electric Vehicles (EV) need to operate in several important modes. Some modes directly influence safety, while others influence vehicle performance. Given the variety of functions and operational modes required of the power electronics, it needs to meet efficiency requirements to minimize power losses. Another challenge in the control and construction of such systems is the ability to support bidirectional power flow. This paper considers the construction, operation, and feasibility of available converters for electric vehicles with feasible configurations of electrical buses and loads. This paper describes logic and control signals for the converters for different operations conditions based on the efficiency and energy usage bases.
Abstract: We report the design and characterization of ultra high
quality factor filter based on one-dimensional photonic-crystal Thue-
Morse sequence structure. The behavior of aperiodic array of
photonic crystal structure is numerically investigated and we show
that by changing the angle of incident wave, desired wavelengths
could be tuned and a tunable filter is realized. Also it is shown that
high quality factor filter be achieved in the telecommunication
window around 1550 nm, with a device based on Thue-Morse
structure. Simulation results show that the proposed structure has a
quality factor more than 100000 and it is suitable for DWDM
communication applications.
Abstract: In some applications, such as image recognition or
compression, segmentation refers to the process of partitioning a
digital image into multiple segments. Image segmentation is typically
used to locate objects and boundaries (lines, curves, etc.) in images.
Image segmentation is to classify or cluster an image into several
parts (regions) according to the feature of image, for example, the
pixel value or the frequency response. More precisely, image
segmentation is the process of assigning a label to every pixel in an
image such that pixels with the same label share certain visual
characteristics. The result of image segmentation is a set of segments
that collectively cover the entire image, or a set of contours extracted
from the image. Several image segmentation algorithms were
proposed to segment an image before recognition or compression. Up
to now, many image segmentation algorithms exist and be
extensively applied in science and daily life. According to their
segmentation method, we can approximately categorize them into
region-based segmentation, data clustering, and edge-base
segmentation. In this paper, we give a study of several popular image
segmentation algorithms that are available.
Abstract: Passive control methods can be utilized to build
earthquake resistant structures, and also to strengthen the vulnerable
ones. In this paper, we studied the effect of this system in increasing
the ductility and energy dissipation and also modeled the behavior of
this type of eccentric bracing, and compared the hysteresis diagram
of the modeled samples with the laboratory samples. We studied
several samples of frames with vertical shear-links in order to assess
the behavior of this type of eccentric bracing. Each of these samples
was modeled in finite element software ANSYS 9.0, and was
analyzed under the static cyclic loading. It was found that vertical
shear-links have a more stable hysteresis loops. Another analysis
showed that using honeycomb beams as the horizontal beam along
with steel reinforcement has no negative effect on the hysteresis
behavior of the sample.
Abstract: In recent years, honeycomb fiber reinforced plastic
(FRP) sandwich panels have been increasingly used in various
industries. Low weight, low price and high mechanical strength are
the benefits of these structures. However, their mechanical properties
and behavior have not been fully explored. The objective of this
study is to conduct a combined numerical-statistical investigation of
honeycomb FRP sandwich beams subject to torsion load. In this
paper, the effect of geometric parameters of sandwich panel on
maximum shear strain in both face and core and angle of torsion in a
honeycomb FRP sandwich structures in torsion is investigated. The
effect of Parameters including core thickness, face skin thickness,
cell shape, cell size, and cell thickness on mechanical behavior of the
structure were numerically investigated. Main effects of factors were
considered in this paper and regression equations were derived.
Taguchi method was employed as experimental design and an
optimum parameter combination for the maximum structure stiffness
has been obtained. The results showed that cell size and face skin
thickness have the most significant impacts on torsion angle,
maximum shear strain in face and core.
Abstract: The main purpose of this study is static analysis of
two three-degree of freedom parallel mechanisms: 3-RCC and 3-
RRS. Geometry of these mechanisms is expressed and static
equilibrium equations are derived for the whole chains. For these
mechanisms due to the equal number of equations and unknowns, the
solution is as same as 3-RCC mechanism. A mathematical software is
used to solve the equations. In order to prove the results obtained
from solving the equations of mechanisms, the CAD model of these
robots has been simulated and their static is analysed in ADAMS
software. Due to symmetrical geometry of the mechanisms, the force
and external torque acting on the end-effecter have been considered
asymmetric to prove the generality of the solution method. Finally,
the results of both softwares, for both mechanisms are extracted and
compared as graphs. The good achieved comparison between the
results indicates the accuracy of the analysis.
Abstract: The security of cloud services is the concern of cloud
service providers. In this paper, we will mention different
classifications of cloud attacks referred by specialized organizations.
Each agency has its classification of well-defined properties. The
purpose is to present a high-level classification of current research in
cloud computing security. This classification is organized around
attack strategies and corresponding defenses.
Abstract: Water flow management is one of the most important
parts of river engineering. Non-uniformity distribution of rainfall and
various flow demand with unreasonable flow management will be
caused destroyed of river ecosystem. Then, it is very serious to
determine ecosystem flow requirement. In this paper, Flow duration
curve indices method which has hydrological based was used to
evaluate environmental flow in Gharasou River, Ardabil, Iran. Using
flow duration curve, Q90 and Q95 for different return periods were
calculated. Their magnitude were determined as 1-day, 3-day, 7-day
and 30 day. According the second method, hydraulic alteration
indices often had low and medium range. In order to maintain river at
an acceptable ecological condition, minimum daily discharge of
index Q95 is 0.7 m3.s-1.
Abstract: In this paper an isolated wind-diesel hybrid power
system has been considered for reactive power control study having
an induction generator for wind power conversion and synchronous
alternator with automatic voltage regulator (AVR) for diesel unit is
presented. The dynamic voltage stability evaluation is dependent on
small signal analysis considering a Static VAR Compensator (SVC)
and IEEE type -I excitation system. It's shown that the variable
reactive power source like SVC is crucial to meet the varying
demand of reactive power by induction generator and load and to
acquire an excellent voltage regulation of the system with minimum
fluctuations. Integral square error (ISE) criterion can be used to
evaluate the optimum setting of gain parameters. Finally the dynamic
responses of the power systems considered with optimum gain setting
will also be presented.
Abstract: The objective of the Economic Dispatch(ED) Problems
of electric power generation is to schedule the committed generating
units outputs so as to meet the required load demand at minimum
operating cost while satisfying all units and system equality and
inequality constraints. This paper presents a new method of ED
problems utilizing the Max-Min Ant System Optimization.
Historically, traditional optimizations techniques have been used,
such as linear and non-linear programming, but within the past
decade the focus has shifted on the utilization of Evolutionary
Algorithms, as an example Genetic Algorithms, Simulated Annealing
and recently Ant Colony Optimization (ACO). In this paper we
introduce the Max-Min Ant System based version of the Ant System.
This algorithm encourages local searching around the best solution
found in each iteration. To show its efficiency and effectiveness, the
proposed Max-Min Ant System is applied to sample ED problems
composed of 4 generators. Comparison to conventional genetic
algorithms is presented.