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Article
New Algorithm for High Throughput of IEEE 802.11 Distributed Coordination Function

Authors: Sadiq H. Abdulhussain --- Dheyaa J. Kadhim --- Basheera M. Ridha --- Amna M. Abbas
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2018 Volume: 14 Issue: 2 Pages: 27-34
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

The Backoff mechanism is a basic part of a Media Access Control (MAC) protocol which provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multi-point network. Since only one transmitting node uses the channel at any given time, the MAC protocol must suspend other nodes while the media is busy. In order to decide the length of node suspension, a backoff mechanism is installed in the MAC protocol. The choice of backoff mechanism should consider generating backoff timers time, which is uniformly selected from the Contention Window (CW) and allow adequate time for current transmissions to finish and, at the same time, avoid unneeded idle time that leads to redundant delay in the network. Moreover, the backoff mechanism used should decide the suitable action to be taken in case of repeated failures of a node to attain the media. Further, the mechanism decides the action needed after a successful transmission since this action affects the next time backoff is needed [2]. Several back-off schemes will be discussed and a new proposed algorithm has been proposed to achieve high throughput of the IEEE 802.11 DCF.


Article
التآزر البصري الحركي لدى تلامذة صفوف التربية الخاصة واقرانهم العاديين في محافظة بابل

Author: أ.م.د كاظم عبد نور نور رضا عبيس الفنهراوي
Journal: journal of Human Sciences مجلة العلوم الانسانية ISSN: 19922876/25239899 Year: 2018 Volume: 4 Issue: 25 Pages: 1012-1029
Publisher: Babylon University جامعة بابل

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Abstract

This research aimed at identifying the level of visual motor coordination of children in special education classes (CSEC) and their normal peers, and the significant differences between their visual motor coordination levels according to: (A)- their type (CSEC) and normal peers. (B)-their gender (males - females).To achieve these aims, the investigators have constructed a visual motor coordination test and tested its psychometric properties. Then, the test has been applied to a sample of (200) male and female children studying in Hila city schools in Babylon Province- Iraq, (100) of them were (CSEC) and (100) from normal classes. The obtained data was statistically analyzed by (SPSS) package. The findings were: (1) the visual motor coordination level of (CSEC) was low and high among their normal children and (2) there were significant differences at the level (0.05) between the levels of visual motor coordination of the (CSEC) and those of normal classes, in favor of the normal class children, and between males and females in favor of males children.Key words: visual motor coordination, children in special education classes, normal children.

استهدف البحث الحالي تعرف مستوى التآزر البصري الحركي لدى تلامذة صفوف التربية الخاصة واقرانهم العاديين ثم الفروق ذات الدلالة الاحصائية بين مستوى التآزر البصري الحركي لأفراد العينة على وفق: أ- نوع التلامذة (تربية خاصة- عاديين). ب- الجنس (ذكور-اناث). ولتحقيق تلك الأهداف، بُني اختبار التآزر البصري الحركي وأوجدت خصائصه الإحصائية، ثم طبق على عينة مكونة من (200) تلميذٍ وتلميذة من تلامذة صفوف التربية الخاصة واقرانهم العاديين في مدينة الحلة مركز محافظة بابل، (100) منهم من صفوف التربية الخاصة و (100) من التلامذة العاديين. وبعد تحليل النتائج باستعمال الحقيبة الاحصائية (SPSS)، توصلنا الى النتائج الاتية: (1) ان مستوى التآزر البصري الحركي لدى تلامذة صفوف التربية الخاصة كان منخفضاً، ومرتفعاً لدى التلامذة العاديين و(2) ﺇن الفروق بين مستوى التآزر البصري الحركي لدى تلامذة صفوف التربية الخاصة ونظرائهم العاديين دالة إحصائياً عند مستوى دلالة (0.05)، لمصلحة التلامذة العاديين، ولمصلحة الذكور عند مقارنة مستوى أداء أفراد العينة على وفق متغير الجنس (ذكور- اناث).

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