Dr. Laith Jawad Aziz
Volume 4, Issue 3 , September 2011, Pages 0-0
Abstract
Due to the importance of the hydraulic structures, sub-surface storage and the building on the problematic soil in Iraq, this work presents the methods for choosing the suitable footing (the behavior of a pile cap embedded into saturated cohesive soil), in other words, the comparison between pile cap ...
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Due to the importance of the hydraulic structures, sub-surface storage and the building on the problematic soil in Iraq, this work presents the methods for choosing the suitable footing (the behavior of a pile cap embedded into saturated cohesive soil), in other words, the comparison between pile cap when it contact with ground surface (pile cap as a raft footing) and it not contact with ground surface ( the resistance of the pile cap is negligible in calculation) such as pile group. The comparisons between two type footings are performed when the soil is very soft (low shear strength) and also when the soil is stiff (high strength).
The stability of two types of footing is analyzed in terms vertical load and the generated displacement by using Plaxis program. The computer program uses a finite element technique to solve the three dimensional problems of variations in the ratio between pile length and cap width (L/B= 0.25, 0.5, 0.75, 1.0, 2.0 and 3.0 ) and to simulate the effects of the different types of cohesive soil which has shear strength equal to (Su=20,30,57.5,112.5 and 150 kPa).
The analysis of the results of the very soft clay soil indicates when the model tests at ratios from (L/B=0.25) to (L/B=2.0), the load – displacement curve for pile group footing is steeper than the curve of the pile raft, this leads to high value of the resistance of the soil for pile group. In other words, the case of pile raft into very soft clay is more dangerous than the pile group. For model tests with (L/B= 3.0), the curves for pile group and pile raft footing are coincided with themselves at any load. The stability of pile raft in soil with ratios from (L/B=0.25) to (L/B=3.0) is high than for pile group embedded into very stiff clay soil.
Volume 4, Issue 3 , September 2011, Pages 0-0
Abstract
The aim of this research is to study the effect of polymeric additives to water on friction coefficient change in a turbulent pipe flow which would cause in reduction of drag resistance.
Experiment is done using the polyacrylamide ( PAM ) as polymeric additive to show the effect of addition of ( ...
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The aim of this research is to study the effect of polymeric additives to water on friction coefficient change in a turbulent pipe flow which would cause in reduction of drag resistance.
Experiment is done using the polyacrylamide ( PAM ) as polymeric additive to show the effect of addition of ( PAM ) with case low concentrations (0.005,0.013 , 0.025%) on the friction factor (λ) . The results show that the addition of (PAM) will reduce (λ) with a range from 6.51 to 37.95% comparable with the friction coefficient (λ) for water before addition in a turbulent flow case.
Also a study of the addition effect of ( PAM ) with different concentrations between ( 0.005 – 0.06% ) on the reduction percent of (λ) is carried out . The results show increasing
the effect of the addition (PAM ) cause in increasing the reduction percent Δλ / λ % with a range of 6.51 to 44.62% . It is found that the peak values called the optimum values)Cp*(of PAM between 0.03&0.042. Increasing the addition of PAM cause in decreasing the effect of reduction percent with concentrations at several Reynolds number as follows:
( Re = 25350 & 0.03%, Re = 28355& 0.033 % , Re=34981&0.038 % , Re=39360 & 0.039% , Re=44985 &0.042%).
K. H. Salih; E. L. Esmail
Volume 4, Issue 3 , September 2011, Pages 168-185
Abstract
A new methodology is developed to design and optimize epicyclic-type automatic transmission gear trains using kinematic nomographs. From such nomographs, the kinematic characteristics of an epicyclic gear mechanism can be expressed in terms of the gear ratios of its gear pairs. The main properties of ...
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A new methodology is developed to design and optimize epicyclic-type automatic transmission gear trains using kinematic nomographs. From such nomographs, the kinematic characteristics of an epicyclic gear mechanism can be expressed in terms of the gear ratios of its gear pairs. The main properties of this methodology are that; from a single nomograph, the angular velocities for all of the coaxial links can be estimated and compared directly without specifying the exact size of each gear, the angular velocities can be arranged in a descending sequence without using complicated techniques, and all of the feasible clutching sequences can be enumerated directly. The optimization procedure to find the optimum gear ratios is applicable to any transmission mechanism composed of two or more fundamental gear entities (FGEs) depending on kinematic and geometric constraints. The reliability of the methodology is established by applying it to the conventionally available three-velocity Simpson gear train for which optimal gear ratios are fully available. The theoretical results are in complete agreement with the practical applications.
Sattar J. Hashim
Volume 4, Issue 3 , September 2011, Pages 186-195
Abstract
This work presents an Analytical model to predict the time to failure of the stress corrosion cracking (SCC) using laboratory experimental data that related stress intensity factor (K) to crack growth rate (V). Current analysis has been implicated on austenitic stainless steel in 42% chloride magnesium ...
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This work presents an Analytical model to predict the time to failure of the stress corrosion cracking (SCC) using laboratory experimental data that related stress intensity factor (K) to crack growth rate (V). Current analysis has been implicated on austenitic stainless steel in 42% chloride magnesium (MgCl2) at 154 oC and the results were in agreement with the experimental recorded data. The present analysis generates very beneficial information about the mechanical and environmental effects on the failure of specific environment and this information is difficult to be obtained from laboratory experiments.
ali abdul mahdi
Volume 4, Issue 3 , September 2011, Pages 196-206
Abstract
It is hoped in this paper to find out the reasons behind the failure in boiler pipes used in Al-Musaib electric power station. Multi types of mechanical and chemical reasons were found behind the failures of these pipes. Two pipes were selected for this analysis (pipe no. 6 in coil 93) and (pipe no. ...
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It is hoped in this paper to find out the reasons behind the failure in boiler pipes used in Al-Musaib electric power station. Multi types of mechanical and chemical reasons were found behind the failures of these pipes. Two pipes were selected for this analysis (pipe no. 6 in coil 93) and (pipe no. 7 in coil 48) were they failed selectively. It was found that these pipes of boiler respectively have failed due to overheating as first reasons. In addition, failures are due to hydrogen damage can be considered in failed pipes that lead to form (Fe2O4) phase. The high sulfur containing fire products are also deposited on the outer surface of the tubes making the condensed water around the cracks acidic. In consequence, the examined pipes of boiler are respectively undergoing pitting corrosion. Un-regularity in thickness of failed tubes where measured and gives an indication about how much they eroded. Microstructural observations of the failed and un-failed show quenched microstructure with small amount of carbides present at the grain boundaries
Mahmoud A .Hassan
Volume 4, Issue 3 , September 2011, Pages 207-214
Abstract
This paper provides some lighting needed for the implementation of the new wave of CAD systems with emphasis on a general application as well as advanced. It is known that a computational approach is used in both design and education so step-by-step examples are introduced. Although the CAD systems are ...
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This paper provides some lighting needed for the implementation of the new wave of CAD systems with emphasis on a general application as well as advanced. It is known that a computational approach is used in both design and education so step-by-step examples are introduced. Although the CAD systems are available but it needs a sound knowledge of many subjects such that: strength of materials and machine design. This work depends on the torsion theory but the input geometry was done inside the SolidWorks environment. The proper use of the CAD tool needs to start from a published case and construct many models in order to reach the final one. The process was done by exporting the geometry to other sophisticated engineering tools: ANSYS The adequacy of the obtained results was obtained by comparing with the theoretical data. Complex cases in both geometry and materials properties like plasticity are presented. Combining these systems with the teaching subjects deepens the engineering knowledge in the design and education.
Rana L. Natoosh
Volume 4, Issue 3 , September 2011, Pages 215-232
Abstract
In this paper, a numerical investigation of steady laminar natural convection in a square enclosure, contain a concentric heated rod and a bundle of four triangular heated cylinders was carried out. Two cases of enclosure inclination angle were studied: case (I) at φ=0o and case (II) at φ=45o. Air ...
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In this paper, a numerical investigation of steady laminar natural convection in a square enclosure, contain a concentric heated rod and a bundle of four triangular heated cylinders was carried out. Two cases of enclosure inclination angle were studied: case (I) at φ=0o and case (II) at φ=45o. Air is filled the enclosure, and the inner heated cylinders are located at equal distance (E) from the enclosure center. A finite element software package (FLEXPDE) is used in the present study to solve the set of non-linear equations governing the process. Solutions are obtained for aspect ratio h/H=0.29, a values of distance E=0.27-0.44 and a range of Rayleigh number 103≤ Ra ≤ 105. The effect of Ra, E and φ were examined. Results are presented by streamlines, isotherms and Nusselt number and they indicates that the Nusselt number is significantly increases with increasing Ra, E and φ. A comparison of the streamlines, isotherms and mean Nusselt number was made with that obtained by other authors, which it reveals a good agreement.
Dhafeer M. AL-Shamkhi; Qahtan A. Abed; Selah M. Salih
Volume 4, Issue 3 , September 2011, Pages 233-247
Abstract
The steady two-dimensional flow of a horizontal heat pipe in vapor region is investigated numerically. For study of heat transfer and fluid flow behaviors of the heat pipe, the governing equations in vapor region have been solved using a finite difference method. The numerical results of heat transfer ...
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The steady two-dimensional flow of a horizontal heat pipe in vapor region is investigated numerically. For study of heat transfer and fluid flow behaviors of the heat pipe, the governing equations in vapor region have been solved using a finite difference method. The numerical results of heat transfer and fluid flow are presented for Reynolds numbers ranging of (Re =4, 10), the Prandtl number taken is (Pr=0.00368), and the pipe dimension is taken to be (L/R =5). The results show that the stream function at the wall increases linearly in the evaporator, decreases linearly in the condenser and is steady in the adiabatic region because of uniform inflow and outflow boundary conditions. Also, it can be seen that as the Reynolds number increases, the pressure distributions shift up without considerable change in their shapes. The numerical analysis have shown that for the low and moderate Reynolds number, the shear stress becomes zero at a point very close to the end of the condenser. For verification of current model, the results of stream function for a heat pipe have been compared with the previous study at the same boundary conditions and a good agreement has been noticed.
Asmaa A. kawi
Volume 4, Issue 3 , September 2011, Pages 248-262
Abstract
Based on three-dimension transient heat diffusion equation a FEM model was developed to simulate coupled thermo-mechanical deformation effects on temperature behavior for four alloys steel during turning process . Alloys used as a workpiece were AISI 1045, AISI 1030, AISI 4340 and AISI 4140, parameters ...
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Based on three-dimension transient heat diffusion equation a FEM model was developed to simulate coupled thermo-mechanical deformation effects on temperature behavior for four alloys steel during turning process . Alloys used as a workpiece were AISI 1045, AISI 1030, AISI 4340 and AISI 4140, parameters such as cutting speed, feed rate were changed to explore their effect on temperature behavior. The results show that Finite element method is a successful technique to perform analysis to estimate cutting temperatures, a possibility of developing temperature forms adequately representing metal cutting temperature as a Polynomial models of third, fourth and fifth degree with time that give steady state temperature and for the four alloys steel used and different operation conditions. All alloys have a sever increasing temperature with increasing feed rate, while it looks less sharp with increasing cutting speed .Also the ratio of the number of nodes have maximum temperature for any operating conditions and any alloy used with respect to the total number of nodes is less than 1%.
Falah A. Abood
Volume 4, Issue 3 , September 2011, Pages 263-273
Abstract
A numerical study is conducted to investigate the natural convection heat transfer in a two cases of the enclosure ,the first case in a square enclosure of aspect ratio AR=1 and the second case in a right-angle trapezoidal enclosure with aspect ratios AR=0.45 and 0.25 .The enclosure was filled with a ...
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A numerical study is conducted to investigate the natural convection heat transfer in a two cases of the enclosure ,the first case in a square enclosure of aspect ratio AR=1 and the second case in a right-angle trapezoidal enclosure with aspect ratios AR=0.45 and 0.25 .The enclosure was filled with a liquid saturated porous media .The bottom wall of the cavity was heated with a sinusoidal temperature distribution θ=0.5(1-cos(2πx)) , the vertical wall was cooled at θ=0 and the other walls were adiabatic. The governing equations were solved numerically using finite element software package (FLEXPDE). Flow and heat transfer characteristics are studied for the range of Rayleigh number (100 ≤ Ra ≤ 1000). Streamlines, isotherms and Nusselt numbers were presented. The obtained results show that the heat transfer coefficient increases with increasing of Rayleigh number and aspect ratio. A comparison of the flow field and isotherm field was made with that obtained by (Yasin et al., 2008), which revealed a good agreement.
Farah Kamil Abd Muslim
Volume 4, Issue 3 , September 2011, Pages 274-291
Abstract
A lot of works have been done by the researchers to solve lot-sizing problems over the past few decades. Many techniques and algorithm have been developed to solve the lot-sizing problems. Basically, most of the algorithms are developed either based on heuristic or mathematical approach. Since Computer-Aided ...
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A lot of works have been done by the researchers to solve lot-sizing problems over the past few decades. Many techniques and algorithm have been developed to solve the lot-sizing problems. Basically, most of the algorithms are developed either based on heuristic or mathematical approach. Since Computer-Aided has been given attention by the researchers in many areas including production planning, therefore in this paper we implement Computer-Aided to solve single level lot-sizing problem. Five models are developed based on five well known heuristic techniques, which are Lot-For-Lot (LFL), Economic Order Quantity (EOQ), Periodic Order Quantity (POQ), Part Period Balancing (PPB) and Wagner-Within algorithm (WW). The planning period involves in the model is 5 period where demand in the periods are varies but deterministic. The model was developed using Visual Basic Version 5 with ACCESS database. Results show that when entering the needed inputs through the user interface, which is general inputs and special inputs, the (CALS) system selects the suitable lot size technique that gave optimum solution and easy application to the lot-sizing problem.
Mohammed A. Hussien
Volume 4, Issue 3 , September 2011, Pages 292-309
Abstract
The performance of a thermosyphon loop in a double – cycle distillation heat pump system, utilizing water as a working fluid and finned tube heat exchangers for evaporator and condenser, has been investigated. A mathematical model is set for the whole system and a simulating program is developed to ...
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The performance of a thermosyphon loop in a double – cycle distillation heat pump system, utilizing water as a working fluid and finned tube heat exchangers for evaporator and condenser, has been investigated. A mathematical model is set for the whole system and a simulating program is developed to simulate the double – cycle processes during the steady – state operation. A complete steam tables subroutine developed and incorporated with the main program to calculate the water and steam properties in the range of (60 – 120)o C and (0.199 – 1.985)bar.
The experimental results show good agreement with the results obtained from the computer program (Quick Basic). During steady – state operation of the system, it found that the thermosyphon loop performance (loop conductance) increase when the working mass flow rate increase and also it increase when the working fluid pressure increase and has a maximum value (493.022 W/m2. K) At working mass flow rate of 5.5 kg/hr, working fluid pressure of 0.8 bar and process fluid pressure of 1.01825 bar.
Dr. Muneer A Ismael
Volume 4, Issue 3 , September 2011, Pages 310-326
Abstract
Natural convection fluid flow and heat transfer of fluid-saturated porous media heated by an internal circular cylinder inside a wavy enclosure is investigated numerically. The 2D enclosure is composed of two isothermal vertical wavy walls and two adiabatic horizontal flat walls. Darcy assumption and ...
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Natural convection fluid flow and heat transfer of fluid-saturated porous media heated by an internal circular cylinder inside a wavy enclosure is investigated numerically. The 2D enclosure is composed of two isothermal vertical wavy walls and two adiabatic horizontal flat walls. Darcy assumption and Boussinesq approximation were relied on in this steady, incompressible study. The governing equations were solved using Galerkin finite element method implemented in FlexPDE software package. The performance of enclosure was evaluated by three non-dimensional parameters namely, the Darcy-modified Rayleigh number Ram (100-1000), the waviness ratio λ (0-0.35), and the position of the inner heated cylinder ξ (0.45-1.05). The results were presented by visualization of the streamline and isothermal contours and by the local and average Nusselt numbers. It was found that the lower the position of the inner cylinder (ξ=0.45) is the largest the values of Nusselt number while the influence of the wall waviness ratio is found to be very small.
Muhammed salah sadiq
Volume 4, Issue 3 , September 2011, Pages 327-339
Abstract
This research studied the adaptive smart antenna system using in cellular phone applications using MATLAB simulation.
In this work, the proposed novel least mean square algorithm (No-LMS) build and studied the results as comparative work with results of two another algorithms called Standard LMS algorithm ...
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This research studied the adaptive smart antenna system using in cellular phone applications using MATLAB simulation.
In this work, the proposed novel least mean square algorithm (No-LMS) build and studied the results as comparative work with results of two another algorithms called Standard LMS algorithm (S-LMS), and normalized LMS algorithm (N-LMS). The computer simulation work results based No-LMS algorithm have better performance refer to obtain the optimum convergence factor (CF) and shows that robustness smart system, good tracking capability, and high adaptation accuracy than the other algorithms.
The smart antenna system that is based on LMS-algorithms for all types (S-LMS),(N-LMS),and (No-LMS) show that this system is affected by the convergence factor, the computer simulation results shows the minimum mean square error (MSE = 0.007) is obtained for the value of convergence factor equal to (0.2). also the smart system is affected by the number of the antennas are used in smart array and number of samples interval, at least three antennas gives the poor steering of array with large MSE value (0.15).
The test of the three algorithms for different values of signal to noise ratio (SNR) show that the (No-LMS) algorithm gives the minimum MSE values compared with the two those obtain from other algorithms.
Abdulhasan Abdullah kadhim
Volume 4, Issue 3 , September 2011, Pages 340-352
Abstract
The aim of this work is to develop a resonant inverter using half bridge inverter configuration which feed power to induction heater during positive and negative cycle of load current. Such system will substitute the using of full bridge configuration, hence a reduction in both cost and complexity. A ...
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The aim of this work is to develop a resonant inverter using half bridge inverter configuration which feed power to induction heater during positive and negative cycle of load current. Such system will substitute the using of full bridge configuration, hence a reduction in both cost and complexity. A full analysis of the proposed circuit using IGBTs at a frequency of 50 kHz, and a power of 1.8 kW is presented. The practical results agree with that of the simulation, and their waveforms are closely similar, so the proposed inverter is completely valid.
Ali K. Ibrahim
Volume 4, Issue 3 , September 2011, Pages 353-363
Abstract
This work included two stages; in the first stage the optimum burning temperature to convert red kaolin clay to metakaolin was investigated. The red kaolin was burnt in a different temperature (800, 850, 900, 950, 1000, and 1050) ºC for one hour. Many tests was carried out on the cement containing (8)% ...
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This work included two stages; in the first stage the optimum burning temperature to convert red kaolin clay to metakaolin was investigated. The red kaolin was burnt in a different temperature (800, 850, 900, 950, 1000, and 1050) ºC for one hour. Many tests was carried out on the cement containing (8)% of calcined kaolin such as normal consistency, setting time, soundness, compressive strength at (3, 7, and 28) days, and pozzolanic activity index at (7, and 28) days. The results show that the optimum burning temperature to convert kaolin clay to metakaolin is (900) ºC.
In the second stage the effect of replacing the red kaolin calcined at (900) ºC at a (5, 8, and 10) % by weight of cement on compressive strength of cement mortar at (3, 7, and 28) days, and compared the results with reference mix. The results shows that the mortars contains red kaolin have compressive strength less than the reference mix at (3, and 7) days, but it shows slightly increasing in the compressive strength at (28) day about (100.8, 102.5, and 103.4) % for the mixes containing (5, 8, and 10) % of red kaolin respectively. The results also showed that the mortar containing (10)% red kaolin gives higher compressive strength compared with the mortar containing (5, and 8)% red kaolin at (28) day.
Hussein Kariem Mohammed; Dr. Amjad H. Albayati
Volume 4, Issue 3 , September 2011, Pages 364-380
Abstract
Asphalt binder, is a thermoplastic liquid, which behaves as an elastic solid at low service temperatures or during rapid loading. At high temperature or slow loading, it behaves as a viscous liquid. This classical dichotomy creates a need to improve the performance of an asphalt binder to minimize the ...
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Asphalt binder, is a thermoplastic liquid, which behaves as an elastic solid at low service temperatures or during rapid loading. At high temperature or slow loading, it behaves as a viscous liquid. This classical dichotomy creates a need to improve the performance of an asphalt binder to minimize the stress cracking that occurs at low temperatures (fatigue) and the plastic deformation at high temperatures (rutting). Use of polymer-modified asphalt binder is one of the solutions to meet the required performance standards for the pavements of today. It appears to be a logical, practical, and economical approach.
In this research an investigation was made to evaluate the influence of asphalt cement modifier on the mechanical properties of asphalt concrete mixtures. The conventional asphalt cement of penetration grade 40-50 was used within this work, modified with styrene butadiene rubber (SBR) at five different modification levels namely 0%, 1%, 3%, 5% and 7% by weight of asphalt cement. Asphalt concrete mixes were prepared at selected optimum asphalt content (4.7%) and then tested to evaluate their mechanical properties which include resilient modulus, permanent deformation and fatigue characteristics in addition to Marshall Properties. The mechanical properties have been evaluated using uniaxial repeated loading and repeated flexural beam tests.
From the experimental results, it can be concluded that the mixes modified with SBR polymer have shown an improved fatigue and permanent deformation characteristics as well as superior elastic properties as a characterized via resilient modulus.
The use of 3 percent SBR has added to local knowledge the ability to produce more durable asphalt concrete mixtures with better serviceability.
Aqeel Salim Raheem
Volume 4, Issue 3 , September 2011, Pages 381-392
Abstract
Optical fiber is a physical medium for optical communication system. It is offer high capacity, very wide band and high data rate. There are two main problems in this physical medium that are dispersion and power loss. The significant restriction in optical fiber system is the dispersion. The dispersion ...
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Optical fiber is a physical medium for optical communication system. It is offer high capacity, very wide band and high data rate. There are two main problems in this physical medium that are dispersion and power loss. The significant restriction in optical fiber system is the dispersion. The dispersion affects the performance of the system and bit error rate. There are two types of dispersion Intermodal and Intramodal. Intermodal occurs in multimode fiber only. Intramodal occur in all type of fiber. The total dispersion in single mode fiber is the sum of material and waveguide dispersion.
In this paper the effect of temperature variations on fiber dispersion is investigated. The temperature variant is a vital factor which plays an effective role on activity of the communication system especially in environmental of Iraq and other Middle East country.
The Sellemeier Coefficients equation is derived for fixed and discrete temperature values. A derivation for this equation to fit continues variation of temperature is done in this paper for optical fiber. Depend on formula of dispersion, Sellemeier Coefficients equation and relation of refractive index at any temperature derivation of propagation constant with normalized frequency for waveguide dispersion is done.
The Temperature effect on total dispersion is modeled for most popular material used in fabrication optical fiber, silica (SiO2), aluminosilicate (Al2SiO5) and vycor glass (96.4%SiO2 ,3% B2O3, 0.5%Al2O3, 0.1% Miscellaneous Traces). Both single mode step index and graded index fibers are considered. The results investigated by using MATLAB and Maple programs.
The refractive index temperature dependence for all three fiber types are fitted in to straight line. The material dispersion and zero material dispersion "λo" wavelengths have approximately linear temperature dependence for all three fiber types. For wide range of increasing temperature [-100◦C to 100◦C] SiO2 and vycor glass fiber has less effect than for Aluminosilicate. The temperature variation shows the step index fiber batter than graded index fiber. The SiO2 is the best one of three fiber types.
