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Rainfall Intensity-Duration-Frequency Relationship for some Regions in Saudi Arabia
No full textIntensity-Duration-Frequency (IDF) relationship of rainfall amount is one of the most commonly used tools in water resources engineering for planning designing, and operation of water resources projects, or for various engineering projects against floods. The objective of this research is therefore, to derive IDF relationship of rainfall for two regions in the kingdom. These relationships are useful in the design of urban drainage works, culverts and other hydraulic structures. Two commonly frequency analysis techniques were used to develop the relationship between the rainfall intensity, storm duration, and return periods from rainfall data for two regions in Saudi Arabia. These techniques are: Gumbel and the Log Pearson Type III distribution. In order to do that, rainfall data was obtained for different durations. A set of curves was plotted using the intensity-duration-frequency data to be the basis of the analysis.
An equation for calculating rainfall intensity for the every region was derived based on the results obtained from the IDF data. The results obtained using Gumbel distribution are slightly higher than the results obtained using the Log Pearson III distribution. In general, the results obtained using the two approaches are very close and have the same trend. Rainfall intensities are drawn from these two methods and the results obtained from that work showed good consistency with what has been done before in some parts of the study area. Further studies are recommended whenever there will be more data to verify the results obtained or updating those IDF curves.Research Center, Faculty of Engineering, King Saud Universit
Comparison of diffusion and chloride ion penetration of high-performance concrete
No full textThis paper reports the results of an investigation of chloride ion penetration and diffusion for high performance concrete. Concrete was prepared incorporating pulverised fuel ash (PFA) and silica fume (SF) with various water-binder ratios. Chloride ion penetration was measured at various ages using rapid chloride permeability test in accordance with ASTM C1202-91. Based on experimentally obtained results, isoresponse contours for chloride permeability were developed showing the interactive and optimized effect between the various parameters investigated. Diffusion coefficient of concrete was determined applying Fick's law of diffusion. The results show that the inclusion of PFA and SF reduced both chloride permeability and chloride concentration of concrete. It was found that rapid chloride permeability values were consistent with diffusion coefficient of concrete
Evaluation and performance of repair materials for rehabilitation of concrete structures
No full textThe most common form of rehabilitation for a deteriorated structure is to remove the deteriorated concrete and replace it with a new material, thus increasing the design life of the structure. Good adhesion of a repair material to concrete is of vital importance in the application and performance of concrete repairs. A major factor that influences the durability of the repair is the bond strength between the new material and the substrate. In this investigation, the most common repair materials, produced by international reputed manufactures, available in the local market were selected from cementitious repair mortars and cementitious polymer modified mortars. The performance of these materials were evaluated in terms of compressive strength, tensile strength, bond strength in tension and bond strength in modulus of rupture. © (2011) Trans Tech Publications
Optimization of an unstructured first-order kinetics model of cyclically operated bioreactors
No full textA procedure for the optimization of an unstructured first-order kinetics model of cyclically operated biological reactors for the biodegradation of a single pollutant is developed using a combination of analytical and numerical tools. Asymptotic analytical profiles for the substrate and biomass for each steady cycle are obtained, which allow the formulation of an analytical design equation that relates the concentration of the pollutant at the end of a steady cycle to all the operating parameters of the bioreactor such as space-time, pollutant feed concentration, filling time, and ratio of minimum to maximum reactor volume. This analytical design equation is used for the systematic construction of practical bifurcation diagrams showing the variations of the pollutant concentration at the end of a cycle with the bioreactor operating parameters. The design equation also allows the formulation of a variety of optimization problems such as the maximization of volumetric efficiency as well as the minimization of the end-of-cycle pollutant concentration. In all cases it is shown that optimal parameter value sets exist. Implications of these results for the optimization of waste-treatment facilities are discussed
A new low sar antenna structure for wireless handset applications
No full textThis paper proposes a new mobile handset antenna structure to reduce the value of the specific absorption rate (SAR). The antenna is based on the PIFA structure and operates at dual-bands of 0.9 GHz and 1.8 GHz. The chassis current is reduced using a metallic shim-layer inserted between the patch and chassis. This shim-layer is connected to the handset chassis through posts whose number and positions are determined using optimization techniques. Sidewalls are attached to increase the gain of the antenna and reduce the radiation towards human head. Simulations in the cheek mode show that the SAR reduction factor (SRF) of the proposed structure averaged over 10-g is more than 75% at 0.9 GHz and 46% at 1.8 GHz. The SRF values obtained using simulations and measurements are found to be better than 51% and 76% at 0.9 GHz and 1.8 GHz, respectively
الترجمات الاستشراقية لمعاني القران الكريم – عرض ونقد وتحليل
No full textيهدف البحث إلى أمرين الأول في بيان ابرز الأخطاء المنهجية في الترجمات الاستشراقية لمعاني القران الكريم على سبيل الإجمال وإيضاح مدى تأثير هذه الأخطاء والثاني تزويد المتخصصين برصد مختصر لأبرز الترجمات الاشتشراقية لمعاني القران الكريم مع أمثلة تطبيقية كيفية توضح وقوع الخلل المنهجي فيها وأسبابه دون توسع واستطراد وقد قسمه إلى مقدمة وفصلين وخاتم
Effect of cement particulates deposition on eco-physiological behaviors of halophytes in the salt marshes of Red Sea, Saudi Arabia
No full textThe effect of cement dust on pigments status was studied for Zygophyllum coccineum, Salsola tetrandra, Cyperus conglomeratus, Limonium axillare and Suaede vermiculata. Measurements were taken for plants very close to early constructed cement factory (Jeddah, Saudi Arabia) about 500 m and other about 4500-5000 m far from the factory. Cement dust was responsible for the mortality of young branches leading to a reduction in the height and cover of the five species. Salsola tetandra and Suaede vermiculata, in particular were the most sensitive to the cement dust. Generally, photosynthetic pigments including chl a, b and carotenoids were negatively correlated with dust deposition, whereas positively correlated with the distance factor. Photosynthetic pigments were declined more with cement accumulation in Salsola tetandra and Limonium axillare than in Zygophyllum coccineum and Suaeda vermiculata, whereas, increased significantly in Cyperus conglomerotus. Both carbohydrates and protein contents were decreased only for leaves of Salsola tetandra and Suaeda vermiculata, whereas, increased significantly for those plants near to the factory and parallel to dust accumulation in the other studied plants. Cement dust pollution greatly affected the photosynthetic pigments of the investigated species. The pH of the cell sap, the metabolism of soluble amino acids and soluble sugars into insoluble reserve substances were all adversely affected
Evaluation of protein and lipid composition of plasma membrane of Zea mays L. in response to relative to copper and cadmium tolerance
No full textThe effect of copper and cadmium on the modification of protein and plasma membrane(P.M.) in maize leaves and roots was studied. In stressed plants for 4 d with 0.25. 1 and 4 mM Cu or Cd the amount of total lipid in the plasma membranes of leaves and roots were decreased. Also, the total sterols in P.M. of the treated roots were decreased whereas, that of the leaves were slightly increased (insignificant) or unchanged in response to heavy metals used. On the other hand, the treatment had no significant effect on total glycolipids. Furthermore, the direct effects of Cu2+ and Cd2+ treatments on the lipid composition of membranes by altering the profile of unsaturated fatty acids have been reported,. After 4 days exposure to Cu2+ and Cd2+ over 50% of the total fatty acids were saturated in plasma membrane of both leaves and roots of Cu2+ and Cd2+ treated plant. SDS-PAGE analysis of protein pattern showed some polypeptide bands were disappeared under Cu2+ and Cd2+ treatments but at different concentrations. The presence of various protein bands which differ in migration position and bands’ intensities, proving the significant effect of both Cu2+ and Cd2+ on the protein content of leaves through induction of new stress protein bands. Taken together, these data strongly indicated that alteration of the protein and plasma membrane lipid composition under the effect of Cu2+ and Cd2+ stresses were mainly due to the reduction in lipid and protein set synthesized during the experimental period or by partial protein and lipid degradation and this is the initial cause of growth reduction under metals treatment in short-term experiments
On-line tuning strategy for PI control algorithms based on simple linear models
No full textOn-line model-based tuning of the parameters of conventional PI control algorithms is considered. This is accomplished to satisfy the requirement of preset performance specifications. The specifications are defined as time-domain response envelopes, which are appealing to the practitioner. The parameter adaptation at each sampling point is accomplished via using a linear relationship between process outputs and PI tuning parameters. Thus the adaptation strategy directly uses the sensitivity of the closed-loop response to the parameters. In this paper, the model used for calculating the sensitivity is a first order model developed by a simple step testing of the plant. Such a model is very common in industrial practice. The efficiency of the method is presented through simulated implementation on two nonlinear reactor examples
المخرجات الرياضية عند عينات من الأنماط الفرعية لاضطراب قصور الانتباه المصحوب بالنشاط الزائد
No full textهدفت الدراسة إلى تقييم فاعلية التعليم المتمازج مقارنة بالاعتيادي على الأبعاد الخمس التالية: تقديم محتوى المادة العلمية، وأسلوب عرضها وتنفيذها، وتنمية مهارات عقلية واجتماعية، وإثارة دافعية الطلبة للتعلم، وتسهيل تعلمهم. من أجل جمع البيانات للإجابة عن أسئلة الدراسة طورت استبانة اشتملت على الأبعاد الخمس المذكورة، وبعد استخراج مؤشرات على ثباتها وصدقها، طبقت على عينة عشوائية مكونة من 191 معلماَ ومعلمة رياضيات في مدارس وزارة التربية والتعليم الاستكشافية.
للإجابة عن أسئلة الدراسة استخرجت المتوسطات الحسابية والانحرافات المعيارية لتقديرات معلمي ومعلمات الرياضيات على كل فقرة من فقرات الاستبانة، وعلى أبعادها الخمس، كذلك استخدم اختبار ت للعينات المترابطة لفحص الفرضيات المتعلقة بتلك الأبعاد، أشارت نتائج الدراسة إلى ارتفاع متوسطات تقديرات معلمي ومعلمات الرياضيات لفاعلية التعليم المتمازج مقارنة بالاعتيادي على الأبعاد الخمس جميعها، كذلك أشارت نتائج اختبار ت للعينات المترابطة إلى وجود فروق ذات دلالة إحصائية في تقديراتهم لفاعلية التعليم المتمازج مقارنة بالاعتيادي على الأبعاد الخمسة ولصالح المتمازج وبحجم أثر بين المتوسط والعالي. وخلصت الدراسة إلى عدد من التوصيات منها عقد دورات للمعلمين في التعامل مع التعليم المتمازج، واستمرار وزارة التربية والتعليم بالسير في تجربة التعليم المتمازج في مدارسها، وإجراء دراسات لبيان أثر أسلوب التعليم المتمازج على تحصيل الطلبة في الرياضيات واتجاهاتهم نحوها