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The influence of temperature and size on the absorption coefficient of CdSe quantum dots
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Abstract<p>Because of Cadmium selenide quantum dots (CdSe quantum dots) has a tuning energy gap in the visible light range, therefore; it is provided a simple theoretical model for the absorption coefficient of CdSe quantum dots, where the absorption coefficient determines the extent to which the light of a material can penetrate a specific wavelength before it is absorbed. CdSe quantum dots have an energy gap can be controlled through two effects: the temperature and the dot size of them. It is found that; there is an absorption threshold for each directed wavelength, where CdSe quantum dots begin to absorb the visible spectrum at a size of 1.4 nm at room temperature for a directed wavelength 300 nm. It has been observed that; when the wavelength is increasing its absorption threshold is increased. For wavelengths (400, 500, 600) nm, the absorption thresholds for each quantum sizes are (1.8, 2.2. 3.2)nm respectively. On the other hand, a rising of the temperature led to reduces the absorption coefficient value, that at 400 K for all quantum sizes, the absorption coefficient increases >2000cm<sup>−1</sup>(According to the directed wavelength) than it is at 0 K. CdSe quantum dots can be considered as one of the most promising materials because it has a tuning gap for the visible wavelengthsfor different applications, such as light-emitting diodes in different colors of the visible spectrum. It is found that; there is a good agreement between our theoretical calculations and experimental results.</p>
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Publication Date
Mon Sep 30 2002
Journal Name
Iraqi Journal Of Chemical And Petroleum Engineering
The New Synthesis of Potassium-Exchange Zeolite A
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Publication Date
Tue Jun 01 2010
Journal Name
Al-khwarizmi Engineering Journal
Study the Structure Properties of Semiconductor Film Multilayered
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In this research was study the effect of increasing the number of layers of the semiconductor films as PbS on the average grain sizes and illustrate the relationship between the increase in the average grain size and thickness of the membrane, and membrane was prepared using the easy and simple and does not need the complexity of which is that the chemical bath , and from an X-ray diffraction found that the material and the installation of a random cubic and when increasing the number of layers deposited note the emergence of a number of vertices of a substance and PbS at different levels but the level is more severe (200) as well as the value is calculated optical energy gap and found to be not affected by increase thickness and from th

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Publication Date
Fri Sep 30 2022
Journal Name
Journal Of Economics And Administrative Sciences
The Quality of Audit Work Under Expert System
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The research aims to extrapolate the repercussions of the use of expert systems in the work of the external auditor on the quality of audit, as the research problem was that despite the use of these techniques in audit work, there is a problem related to the efficiency and effectiveness of these technological systems used in audit work, the feasibility of their use and the extent of their impact: The quality of the audit process.

The researchers adopted the questionnaire as a tool for collecting study data from a community composed of auditors in auditing offices and companies in Iraq, and the auditors of the Iraqi Federal Financial Supervision Bureau. The number of recovered and valid qu

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Publication Date
Sun Jun 01 2008
Journal Name
Journal Of The College Of Languages (jcl)
The Iraqi Learners' Production Of rp Clipped Vowel
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Within connected speech, RP speakers tend to shorten stressed long vowels end diphthongs in pre. Forties consonants in the same syllable on the basis of complementary Distribution, i.e., the phonological environment decides the influence of the forties plosives and fricatives, as far as they are in find position preceded by stressed long vowels and diphthongs, or particular voiced consonants plus vowels. The Iraqi learners, then, face.

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Publication Date
Sat Feb 27 2021
Journal Name
Journal Of Engineering
Assessing the Marshall Properties of Porous Asphalt Concrete
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Porous asphalt paving is a modern design method that differs from the usual asphalt pavements' traditional designs. The difference is that the design structure of porous pavements allows the free passage of fluids through their layers, which controls or reduces the amount of runoff or water accumulated in the area by allowing the flow of rain and surface runoff.  The cross-structure of this type of paving works as a suitable method for managing rainwater and representing groundwater recharge. The overall benefits of porous asphalt pavements include environmental services and safety features, including controlling the build-up of contaminated metals on the road surface, rainwater management, resistance to slipping ac

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Publication Date
Wed May 10 2023
Journal Name
Journal Of Engineering
Improving the Properties of Gypsum By Using Additives
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Gypsum Plaster is an important building materials, and because of the availabilty of its raw materials. In this research the effect of various additives on the properties of plaster was studied , like Polyvinyl Acetate, Furfural, Fumed Silica at different rate of addition and two types of fibers, Carbon Fiber and Polypropylene Fiber to the plaster at a different volumetric rate. It was found that after analysis of the results the use of Furfural as an additive to plaster by 2.5% is the optimum ratio of addition to that it improved the flexural Strength by 3.18%.
When using Polyvinyl Acetate it was found that the ratio of the additive 2% is the optimum ratio of addition to the plaster, because it improved the value of the flexural stre

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Publication Date
Tue Feb 14 2023
Journal Name
Journal Of Educational And Psychological Researches
Cognitive Balance of Students in the Kindergarten department
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Abstract

Balance is a psychological need and a requirement of importance as the individual seeks to maintain it.  The research problem is summarized in the question: do students in the kindergarten department have a cognitive balance? The research aims to identify the cognitive balance of students in the kindergarten department and to identify if there are differences among students of the four stages according to the cognitive balance. The research community was limited to the students in the kindergarten department at the University of Baghdad / College of Education for Women and Al-Mustansiriya University / College of Basic Education and Iraqi University / College of Education for Women for the academic y

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Publication Date
Thu Jan 01 2015
Journal Name
Al–bahith Al–a'alami
Topics of Iraq in the Arab International Press
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The research entitled "the Iraqi Topics in International Arab Press" is an analytical study of two newspapers: Al-Arab and Al-Hayat published in London from September 1-30, 2013.

      The Arab press is one of the cultural monuments Home stretches for culture and media of Arabs outside the Arab Homeland which made them international press targeting public Arab audience's not civil audiences in a particular country and formulating their contents on this basis taking into account intake affairs and issues that have been national or international.

        Because of this international presence of the Arab press, these newspa

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Publication Date
Wed Jun 29 2022
Journal Name
College Of Islamic Sciences
The Scientific Efforts of Ahmed Mustafa Al-Maraghi
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This conducted research,  (The Scientific Efforts of Ahmed Mustafa Al-Maraghi) deals with Al-Maraghi's life, birth, upbringing, characteristics, title, family and religion secter, as well as his general biography. And his relationship with scholars, his learning and teaching, and the introduction of the Muhammed Abdo School and the College of Dar Al Uloom, and finally the discussion  of his scientific, social and political poin of view, as an interpreter of twentieths century, was  appointed as the president of Al-Azhar and Ifta during the days of the royal era, and he studied at the College of Dar Al-Uloom

 

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Publication Date
Fri Mar 31 2017
Journal Name
Journal Of Engineering
Hydraulic Analysis of the Samarra-Al Tharthar System
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Low incoming discharge upstream of Samarra-Al Tharthar System leads to sediment accumulation and forming islands, especially an island upstream of Al Tharthar Regulator. This island and the sedimentation threaten the stability of the structure and reduce the efficiency of the system. This study aims to hydraulically identify the sedimentation problem mentioned above, to find solutions of how to control the sediment problems, and to develop the capacity of
the system for 500 years return period flood of 15060 m3/s. Surface Water Modeling System (SMS10.1) with two dimensional depth average models (RMA-2) software were used to simulate and analyze the system. The results of analysis showed that the maximum permissible discharge through t

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