
ناصر
رضایی
author
حسین
یکتایی
author
text
article
1998
per
In mobile cellular communication systems, when a mobile station moves out of the coverage
area of serving cell and enters to the coverage area of an adjacent cell, the channel which is used
by without interruption of service. This process which is done without user intervention, is called
Handoff or Handover. Proper decision for handoff and fast execution of it, has considerable effect on
preservation of call quality and reduction of network load.
A well known algorithm for handoff is "Averaging and Hystersis". In choosing averaging
window length and hystersis margin for this algorithm, tradeoff between mean number of
handoffs, delay in handoff and received signal quality must be considered. It is shown that using
more hystersis and less averaging improves signal quality and rreduces sensitivity to variations in the
speed of mobile station. But this method increases sensitivity to variations in the standard deviation
of shadow fading. To reduce this sensitivity, changing hystersis margin proportional to the
standard
deviation
of
shadow
fading
IS
recommended.
Using path loss slope, an algorithm for simultaneous reduction in delay and mean number
of handoffs is peresented. When a mobile station approaches to (recedes from) a base station, the
slope of averaged redeived power is positive (negative). Varying hysteresis margin by this slope,
makes handoff easier(harder) to the base station for which mobile station is approaching (receding). Thus delay and mean number of handoffs reduce simultaneously.
Simulations show that when a mobile station
moves on the cell boundaries, repeated handoffs to the base stations of that cells occur. Care must
be taken to avoid overlap between high traffic streets and cell boundaries, in order to reduce
total number of handoffs in the network.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14538_2d590f2b1194a1093f6acb0a07ccdde1.pdf

رضا
عطارنژاد
author
text
article
1998
per
In geometric nonlinear analysis of space frames, if the displacements are so small that the
change of geometry is negligible, the equilibrium equations in undeformed configuration using
.' '
second order terms of strain statements provides
an
acceptable
approximate
solution
the
to
nonlinear problem.
However
large
displacements
and
finite
III
rotations these equations must be formed with respect to initial configuration using an Updated or Total Lagrangian Formulation.
In nonlinear analysis of space frames in addition to the stiffness matrix that changes at each step,
the transformation mat_ix is changed as well.
In this paper using an updated lagrangin version
the slopedeflection equations are developed in deformed configuration of the member and the.
transformation matrices are
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14539_9fcb5aa1754f5567cda3df9f2b18ea8d.pdf

ایرج محمودزاده
کنی
author
فیروز امامی
فروشانی
author
text
article
1998
per
In this paper, following a description of the damage index resulting from the occurrence of an
earthquake in reinforced concrete structures, the
principal parameters influencing the calculation of
such an index are explained in detail. The relevance of this index and the extent of physical
damage is presented, thereafter.
Afterwards, a new definition for the structure
response coefficient (R) will be presented on the basis of the damage index. For the earthquake
corresponding to the serviceability limit state, a value for the damage index is suggested. In the
end, a sevenstorey reinforced concrete building is studied and the effect of various parameters on
the damage index is discussed.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14540_2deea018e33b81fa06694b7a42b56d83.pdf

محمدصادق
معرفت
author
محمد
رحیمیان
author
عبدالعظیم محمدی
پور
author
تورج خرمی
تاج
author
text
article
1998
per
In this paper, the nature of gas explosion, from
a structural point of view, has been studied. Based
on experimental and theoretical studies, which have been reported by wellknown references,
different _haracteristics
of gas
explosion in
residential buildings and factors influencing it have been discussed. By comparing different methods, a model to predict overpressure of gas explosion has been chosen. Considering geometric
characteristics of Iranian dwellings, on the basis of field investigation, a value for overpressure of gas explosion as much as 25K.N/m2, for masonry and
panelized structures, is recommended.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14541_fc3e85f883c3802d6e3414d586d16707.pdf

اسدالله
نورزاد
author
خسرو
برگی
author
سعید چشمه
کانی
author
text
article
1998
per
Nowadays the tunnels have a main role in daily activites of countries, so the must be designed in a
manner that resist under all static and dynamic loads. In this paper, a deep tunnel in an elastic medium under plane strain condition and
harmonic waves has been studied.
The Boundary Element Method (BEM) in the case of infinite medium is more suitable than
other numerical methods; because the unknown parameters of problem are only on its boundary
and each arbitrary shape of boundary can be modeled easily, furthermore radiation condition
(due to infinite medium) will be satisfied. Hence, the method of analysis is based on Boundary
Element
Method in
unlined
tunnels
and
combinaton of Boundary Element Method and Finite Element Method in lined tunnels.
Results show that stress conentration along the boundary of tunnels due to scattering is about 2 to
3 times greater than the free field stresses imposed by incident wave. As the scattering is due
to the interaction between soil and tunnel, hence this effect should be considered. By parametric
study the effects of types of waves including P and SV waves, the angle of incident wave and the
different shapes of the tunnel are included in this
paper.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14542_0993fe163a0ac49a5b9f653266698fe7.pdf

علی اصغر
حمیدی
author
محمدرضا
خرقانی
author
text
article
1998
per
Drilling mud flow into the well, through the pipe, pipe head and back through the annulus between the bore and pipe is accompanied by
Complicated heat transfer phenomena and
displacement of chips of earth turn off by the
action ot the bit. Considerable amount of heat is
released at the drilling point and earth's
temperature also increases with depth, both of which cause changes in the physical properties of
the mud especially its viscosity. In the return path the mud must carry the soil chips with itself to the ground level. The ability to do this also depends
on the viscosity of the mud, which is a nonNewtonian fluid and the pressure changes in the flow path.
In this study mud viscosity changes due to temperature changes have been studied and by solving the mathematical equations governing the
heat transfer and dynamics of the mud, the transport of the drilling soil chips by the mud has
been investigated.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14543_2c48a763c0d09f6527694bc9ebb15c86.pdf

منوچهر
اولیازاده
author
پرویز
پورقهرمانی
author
text
article
1998
per
Andalusite to its specific due mineral,
refractory properties, plays an important role in steel making industries. There are some andalusite
deposits in the country, on which recently extensive exploration activities have been carried
out. However, beneficiation investigations on these deposits are limited.
In the the results of present paper, benificiation studies, performed on Sartal deposit,
located atsouth of Khorasan province, have been presented. The main goal was to upgrade Sartal
andalusite to, at least, 55% AzI03 and less than 1 % Fez 03 content, which can be sold in the
market.
The raw materials contained 1819% Alz °3, 23% FeZ03, 4% FeO and 61.62% Sial. The
major mineral was amlalusite, while mica, quartz and iron minerals were the main impurities.
The feed material was deslimed at  500 ,urn and then treated by various separation methods.
The results showed that high intensity magnetic separation and then heavy media separation can
upgrade the Sartal and produce a desirable product. Finally, a 11owchart has been suggested, which can be used for economical evaluation.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14544_e08f97d91bbf7c22be78c8800387cb57.pdf

غلامحسین
نوروزی
author
سیدرضا
مهرنیا
author
text
article
1998
per
Sarein region, located in northwest of Iran is
Long known for its geothermal resources.
following a geological and tectonic study, the magnetic field was measured in 16 Km2 of the
area.
Two inportant, geothermal related anomalies were detected at the depth of 150 and 170 m.
The results were closely confirmed by drilling which located the geothermal sourse at the depth
of 180 m.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14545_d8e9453c63724c96514bc5932bcf3ac9.pdf

وحید
اصفهانیان
author
کاظم هجران
فر
author
text
article
1998
per
In this article, a numerical simulation of steady supersonic viscous axisymmetric flow is obtained
using the parabolized NavierStokes equation (PNS). These equaions are solved with implicit
noniterative finite  difference algorithm of the Beam Warming. The parabolized Navier  Stokes
equations (PNS) are obtainted from the steady state of full Navier  Stokes equations (FNS) via
eliminating of the viscous terms in streamwise direction. Stable marching of numerical solution
of PNS equations is achieved in subsonic region of
boundarylayer by the suhlayer and Vigneron approximations. The results for 11at plate blunt cone have been campared with previous numerical and investigations experimental data, which show a good agreement. To demonstrate the ability of developed code, PNSAX flowfield characteristics on the body surface including temperature, pressure, etc. and also aerodynamics coefficients are presented for 11ow over a blunt ogive.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14546_3aefb1446a99966a54c0e0a6593ba6e6.pdf

ناصر
سلطانی
author
وحید متین
فر
author
text
article
1998
per
In this study, the essential equations and parameters for the application of the method of
ret1ected caustics V –notched plates to are reviewed.
Using the equations obtained, ModeI stress intensity factor in the Vnotched plates was
determined by applying the re11ected method of
caustics.
Five models with 45 and 90 degree notches were
tested. All models were made from thin,
transparent sheets of plexiglass of different
thicknesses. The notches were machined
perpendicular to the edge of the plates.
The models were subjected to uniaxial tension.
The image of the generated caustics curve were photographed with a 35 mm camera at different
loading conditions, during the test.
lvleasurment of the photogaphs gave caustic dimensions as
a
function of applied load.
Different thickness and a/w ratios were
considered. The results compared well with
theoretical, experimental (Photoelastic) and numerical methods.
The reliability of the reflected method of caustic for the determination of the stress intensity factor
in Vnotched plates is established.
University College of Engineering
دانشکده فنی
08031026
31
v.
1
no.
1998
https://jfe.ut.ac.ir/article_14547_1b7a500ff322d4bf9887f2f3a307a08b.pdf