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ALNAHRAIN JOURNAL FOR ENGINEERING SCIENCES

مجلة النهرين للعلوم الهندسية

ISSN: 25219154 / eISSN 25219162
Publisher: Al-Nahrain University
Faculty: Engineering
Language: Arabic and English

This journal is Open Access

About

AlNhrain Journal for Engineering Sciences is a refereed scientific engineering journal published by the College of Engineering, Nahrain University two times per year. The journal publishes the scientific output of researchers from Iraq and abroad in the fields of architectural, chemical, civil, computer, electrical, information technology, laser and optoelectronics, mechanical and medical engineering as well as in related fields. Papers written in Arabic and English are accepted and they are subjected to proper evaluation and accordingly classified as follows:
• Original research papers and papers on novel design, analysis or construction methods of great value to the engineers which include basic and practical results.
• Short communications or short discussions on papers which have already appeared in the journal provided that whose text should not exceed 800 words.

The material of the paper should not violate any intellectual property right of any person or entity and should not contain any subject matter that contravenes any laws and should meet ethical standards applicable to the research discipline.

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Contact info

Editor-in-Chief
College of Engineering Journal
Al-Nahrain University
P.O. Box 64040 , Al-Jadyriah
Baghdad-Iraq.
e-mail: journal.engineering@nahrain-eng.org
jourengnah@gmail.com
Phone: +964 (0) 7817 202 662

Table of content: 2010 volume:13 issue:2

Article
Effect of Conductive Baffles on Natural Convection Heat Transfer in Porous Medium inside Enclosure
تأثير الحواجز الموصلة على انتقال الحرارة بالحمل الطبيعي في وسط مسامي داخل حيز

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Abstract

Two dimensional numerical study of the effect of high thermal conductive baffles on natural convection heat transfer in saturated porous medium inside enclosure. The top and bottom surface of the enclosure are insulated, the two vertical walls of the enclosure have different constant temperature, high conductive thin baffles are attached on the two vertical walls. The governing equations were solved by finite difference method. The results inserted for different value of Rayleigh number and different position’s of the baffles with change in length of baffles, when the baffles attached to the hot and cold walls in distances (0.25,0.75) respectively from bottom surface, also when the baffles attached to the hot and cold walls in distance ( 0.75 , 0.25 ) respectively from bottom surface. The length of baffles in the two cases changed in range ( 0.2 – 0.8 ). For the above cases The Rayleigh number changed in range ( 150 – 750 ). The results are represented by streamlines and isotherm lines to show the behavior of the fluid circulation and temperature distribution. Also some graphics had been obtained which represent the relationship between Nusselt and Rayleigh numbers with the position and length of baffles. The results show that increasing Rayleigh number leads to increase in the Nusselt number for two cases. But in the two cases the increasing in the baffles length results a decreases in Nusselt number.


Article
The Influence of Direction & Solid Loading Ratio on Two Phase Flow Energy
تأثير تغير ألاتجاه ونسبة التحميل على طاقة جريان خليط ثنائي الطور ( غاز –صلب )

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Abstract

This research investigates the influence of solid loading ratio , Reynolds number & angle of flow direction change on minor losses coefficient for two-phase flow type gas-solid through an orifice by manufacturing a special apparatus with solving the equations mathematically . Three different angles of elbow 15 , 30 & 45 deg. was chosen to study this effect on minor losses head and minor losses coefficient for a solid loading ratio range 0 to 1.9 , Reynolds number range 36209 to 78078 . It is found that the minor losses head decrease with increase of mixture velocity and Reynolds number with relationship of elbow angle increasing linearly with solid loading ratio increment . also the minor losses coefficient increasing with minor losses head increment and linearly with mixture velocity , Reynolds number as same as solid loading ratio . fig.(1) shows the apparatus which used in this research

Keywords

two phase flow --- loading


Article
Developed Correlations for Prediction of The Enthalpies of Saturated Vapor – Liquid Coexisting Phases
علاقات مطورة للتنبؤ بالأنثالبيات المشبعة في منطقة البخار والسائل المتاخمة

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Abstract

In this study a new criteria is adopted by the use of Rectilinear Diameter principle to express the saturated vapor and liquid enthalpies at the coexisting phases for pure substances and mixtures, this requires another relation that used to calculate enthalpies of vaporization at the corresponding temperatures. The relationships between saturated vapor enthalpy, saturated liquid enthalpy and pressure are investigated for many pure substances. These investigations show that the saturated vapor and liquid enthalpies cannot be described by pressure as a simple general relation. New simple correlations are developed for pure substances and mixtures. These correlations are based on the principle of Rectilinear Diameter depending on the law of corresponding states, where DH is introduced as a dimensionless term including the average reduced saturated enthalpies. The relations developed are: For Pure Substances For Mixtures The constants A and B are correlated by the following relations: The second relation developed by fitting of literature values using Maximum Likelihood Principle for twenty pure substances out of thirty, and then applying them successfully to the remaining components, which indicates the generality of this correlation. These correlations can be applied successfully up to the critical region. To use this method it requires the values of critical temperature and normal boiling point temperature, and any suitable correlation used to calculate enthalpies of vaporization. The present new method of calculation of saturated enthalpies compares favorably with any equation of state, for example when using Lee – Kesler equation of state. The comparison shows that the accuracy of the proposed method is better than that of Lee and Kesler at the saturation region. This is in addition to the fact that the present correlations are straight forward, easier, and simpler as compared with that of Lee and Kesler method. These correlations can be further developed to be used directly for design purpose of distillation operations, and other processes that involves vaporization, condensation phenomena.


Article
Dynamics and Control of Double-Pipe Heat Exchanger
دراسة ديناميكية المبادل الحراري دو الانبوب المزدوج والسيطرة علية

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Abstract

Experimental investigation was conducted to study the dynamics of double-pipe heat exchanger using step change in flow rate of hot water and observe its effect on the temperature of cold water and it was found that the transfer function can be represented by first order system plus dead time (FOPDT). MATLAB 7.4 simulation and programming was used to show the response of close-loop system using P, PI, PID and fuzzy logic control. The Smith predictor was used to remove the effect of transport delay on the process and it was found that this method greatly improve the response of the system. The stability of the overall closed loop system was proved by using Bod plot diagram.

Keywords


Article
Image Stego Detection using Higher Order Statistics
كشف الصورة المخفية باستخدام الإحصاءات ذات المرتبة العالية

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Abstract

The basic approach taken here works by finding predictable higher-order statistics of “natural” images within a multi-scale decomposition, and then showing that embedded messages alter these statistics. A Fisher linear discriminant analysis is then used to discriminate between untouched and adulterated images. Detection system suggested here is used to detect seven systems these are: hiding in LSB, hiding in palette, hiding in DCT simple level security, and hiding in wavelet simple level security. In addition, highly-secret systems were constructed, i.e. systems that integrate Cryptography with Steganography in both domains, DCT and Wavelet. Moreover, system of hiding in multiwavelet was used with cryptography.


Article
Run-Time Reconfigurable FFT Engine
قابلة لإعادة التشكيل في زمن التنفيذ FFT ماكنة

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Abstract

This paper develops a system level architecture for implementing a cost-efficient, FPGA-based real-time FFT engine. This approach considers both the hardware cost (in terms of FPGA resource requirements), and performance (in terms of throughput). These two dimensions are optimized based on using run time reconfiguration, double buffering technique and the “hardware virtualization” to reuse the available processing components. The system employs sixteen reconfigurable parallel FFT cores. Each core represents a 16 complex point parallel FFT processor, running in continuous real-time FFT engine. The architecture support transform length of 256 complex points, as a demonstrator to the idea design, using fixed-point arithmetic and has been developed using radix-4 architecture. The parallel Booth technique for realizing the complex multiplier (required in the basic butterfly operation) is chosen. That is to save a lot of hardware compared to other techniques. The simulation results that have been performed using VHDL modeling language and ModelSim software shows that the full design can be implemented using single FPGA platform requiring about 50,000 Slices.


Article
Performance Evaluation of Vertical Bell Labs Layered Space Time (Vblast) Algorithms For Mimo System
تقييم الكفاءة لخوارزميات (VBLAST) لأنظمة متعدد الدخل متعدد الخرج

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Abstract

In this paper a possible way of MIMO technique is used to exploit the multipath scattering properly, it is the Spatial Multiplexing, where the parallel streams of data are mixed up in the air but can be recovered at the receiver by using different Vertical Bell Labs Layered Space- Time (VBLAST algorithms like, Zero Forcing (ZF), Minimum Mean Square Error (MMSE), and QR-decomposition decoding methods. This paper focused in performance evaluation between these different algorithms in terms of Bit Error Rate (BER) performance using different modulation schemes (4PSK, 8PSK, 16PSK, and 16QAM), and different numbers of antennas. The results derived have shown that 4PSK has the best performance and 16PSK has the worst for all different types of receiver algorithms, with 16QAM constellation performance better than 16PSK, although they use the same bit rate. The BER performance degrades when the constellation size increases. Also the VBLAST receivers with VBLAST-MMSE perform better than VBLAST-ZF and VBLAST-QR receiver in terms of BER when 2X2 antennas are used. Also, it is noted that with increasing modulation constellation the curves of BER are shifted to right due to the higher data rate that is transmitted. MMSE loses the advantage over ZF that is observed for lower constellations, and VBLAST-QR performs better than lower constellations. Finally it is noticed that the BER performance degrades with increasing the number of antennas.


Article
Genetic-Based Multiresolution Noisy Color Image Segmentation

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Abstract

Segmentation of a color image composed of different kinds of regions can be a hard problem, namely to compute for an exact texture fields and make a decision of the optimum number of segmentation areas in an image when it contains similar and/or unstationary texture fields. A local novel neighborhood-based segmentation approach is proposed. Genetic algorithm is used in the proposed limited segment-pass optimization process. In this pass, an energy function, which is defined based on Markov Random Fields, is minimized. The proposed system uses an adaptive threshold estimation method for image thresholding in the wavelet domain based on the Generalized Gaussian Distribution (GGD) modeling of sub band coefficients. This method called Normal Shrink is computationally more efficient and adaptive because the parameters required for estimating the threshold depend on sub band data energy that used in the pre-stage of segmentation. A quadtree is utilized to implement the fast clustering segments for multiresolution framework analysis, which enables the use of different strategies at different resolution levels, and hence, the computation can be accelerated. The experimental results of the proposed segmentation approach are very encouraging.

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