البحث العلمي

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Propagation of Quasi-Vertical Transverse Waves Between Tow Piezothermoelastic Media on the Theory of Lord and Shulman Context under Initial Stresses Influence

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The governing equations for two-dimensional generalized thermoelastic model in piezoelectric media under initial stresses effect by applying suitable conditions are solved. The generalized theories of piezothermoelasticity have been used to investigate the problem. In this model, there are four types of plane waves quasi-vertical transverse (QSV), quasi-longitudinal (QP), thermal wave (T-mode), and potential electric waves (j-mode). The closed-form expressions for the reflection and refraction coefficients for various reflected and refracted waves are obtained. These reflection and refraction coefficients are found to depend upon the angle of incidence of SVwave, thermoelastic, piezoelectric parameters and other material constants. The numerical values of modulus of the reflection and refraction coefficients are presented graphically for different initial stress and thermal relaxation time values.

Material Type: Reading

Author: Fatimah A. Alshaikh

Date created : 3-شعبان-1438

The mathematical modelling for studying the influence of the initial stresses and relaxation times on reflection and refraction waves in piezothermoelastic half-space

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The present paper concentrates on the study of reflection and refraction phenomena of waves in pyroelectric and piezoelectric media under initial stresses and two relaxation times influence by apply suitable conditions. The generalized theories of linear piezo-thermoelasticity have been employed to investigate the problem. In two-dimensional model of transversely isotropic piezothermoelastic medium, there are four types of plane waves quasi-longitudinal (qP), quasitransverse (qSV), thermal wave (T-mode), and potential electric waves (φ-mode) The amplitude ratios of reflection and refraction waves have been obtained. Finally, the results in each case are presented graphically.

Material Type: Reading

Author: Fatimah A Alshaikh

Date created : 1-شعبان-1438

Reflection and refraction of plane quasi-longitudinal waves at an interface of two piezoelectric media under initial stresses

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This paper is devoted to study a problem of reflection and refraction of quasi-longitudinal waves under initial stresses at an interface of two anisotropic piezoelectric media with different properties. One of the two media is aluminum nitride, which is considered the down piezoelectric medium and the above medium is chosen as PZT-5H ceramics. The two piezoelectric media welded are assumed to be anisotropic of a type of a transversely isotropic crystals (hexagonal crystal structure, class 6 mm). The equations of motion and constitutive relations for the piezoelectric media have been written. Suitable boundary conditions are used to obtain the reflection and refraction coefficients. For an incidence of quasi-longitudinal plane waves, four independent-type amplitude ratios of elastic displacement components for plane waves, called quasi-longitudinal (qP) and quasi-shear vertical (qSV) waves, are shown to exist. Also, it is observed that there exist four dependent amplitude ratios of electric potential, which are proportional to the previous four types. Finally, it is found that the coefficients of reflection and refraction are functions of angle of incidence, elastic constants, piezoelectric potential parameters and the initial stresses. Numerical computations and the results obtained are depicted graphically. In the end, a particular case has been reduced from the present study. This investigation is considered important because the initial stresses in such practical problems are inevitable and may result in frequency shift, a change in the velocity of surface waves and controlling the selectivity of a filter compensation of the devices.

Material Type: Reading

Authors: Abo-el-nour N. Abd-alla, Fatimah A. Alsheikh

Date created : 1-شعبان-1438

The Influence of Piezoelectric and Electromagnetic Effects on the Propagation of Rayleigh Surface Waves in Smart Material

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The main aim of the paper is to derive explicit exact secular equations of the Rayleigh surface waves in an anisotropic piezoelectric smart material. A details solutions for variations of displacements and electric fields as a function of distance from the free surface are obtained. First, the governing equations of motion for the piezoelectric media on the basis of a fundamental acoustic tensor are derived. Then, using an appropriate representation of the solution, the frequency equation under suitable mathematical boundary conditions of the wave motion is obtained. Next, the characteristics of surface waves propagating in piezoelectric elastic half-space and their dependence upon the physical parameters are investigated. The real and imaginary parts of complex amplitudes of surface displacements and electrical fields are computed and presented graphically. Furthermore, we verified and computed the results numerically for Barium Titanate material, which is found to be in close agreement with the analytical results. This investigation will be useful in the design and construction of sensors and surface acoustic wave filter devices.

Material Type: Reading

Authors: Abo-El-Nour N Abd-Alla, Fatimah Alshaikh

Date created : 2-شعبان-1438

Influence of Initial Stresses and Piezoelectric Constants on the Propagation Bulk Acoustic Waves in an Anisotropic Smart Material (Aluminum Nitrite)

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The aim of this paper is to illustrate the effect of initial stresses on the propagation of plane waves in a general anisotropic elastic medium. Therefore, an analytical analysis supported by numerical tests to calculate the bulk acoustic wave propagation in Aluminum Nitrite (AlN) as piezoelectric hexagonal elastic material has been presented. In addition, the Christoffel’s equation has been solved and the corresponding eigenvalues and eigenvectors have been obtained. Then, an explicit expressions of the waves propagation with three distinct phase velocities in anisotropic piezoelectric material including the effect of the initial stresses have been derived. The three velocities of bulk acoustic waves (BAW) which are called quasi-longitudinal, quasi-shear vertical and quasi-shear horizontal for Aluminum Nitrite are numerically calculated. The numerical examples are considered to illustrate graphically the effect of initial stresses on the variations of velocities of the BAW versus the angle of the propagation. The velocities of BAW change significantly with initial stresses as well as piezoelectric constants. This research is theoretically useful in signal processing, sound system, wireless communication and for the design of surface acoustic wave (SAW) devices with high performance.

Material Type: Reading

Authors: Abo-el-nour N. Abd-alla, and I. A. Abbas, Fatimah Alshaikh, Idir Mechai

Date created : 2-شعبان-1438

The Effect of the Initial Stresses on the Reflection and Transmission of Plane QuasiVertical Transverse Waves in Piezoelectric Materials

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This study deals with the phenomena of reflection and transmission (refraction) of qSV-waves, for an incident of quasi transverse vertically waves, at a plane interface of two semi-infinite piezoelectric elastic media under the influence of the initial stresses. The relations governing the reflection and transmission coefficients of these reflected waves for various suitable boundary conditions are derived. We have shown analytically that reflection and transmission coefficients of (qP) and (qSV) waves depend upon the angle of incidence, the parameters of electric potential, the material constants of the medium as will as the initial stresses presented in the media. The numerical calculations of the reflection and transmission amplitude ratios for different values of initial stresses have been carried out by computer for different materials as examples and the results are given in the form of graphs. Finally, some of particular cases are considered

Material Type: Reading

Authors: AN Abd-Alla, FA Alsheikh

Date created : 1-شعبان-1438

عمليات العلم

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عمليات العلم هي الاملاحظة - القياس - التصنيف - التفسير - الاستنتاج - الاستنباط - الاستقراء - الاتصال - التنبؤ - وضع الفروض - التجريب

Material Type: Activity/Lab

Author: Dr Loubna AlAjmi

Date created : 8-جمادي الآخرة-1438

البحث العلمي

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خطوات المنهج العلمي في البحث 1- تحديد المشكلة تحديداً دقيقاً 2- جمع المعلومات عن هذه المشكلة 3- وضع الفروض المقترحة لحل المشكل 4- اختبار صحة الفرض 5- التوصل إلى نتائج يمكن تعميمها مراحل إجراء البحث اختيار موضوع البحث: Research topic عنوان البحث: Title خطة البحث : Plan(بروتوكول البحث Protocol) 2- طريقة البحث

Material Type: Lecture

Author: Dr. Nissrein Babiker

Date created : 26-محرم-1440

البحث العلمي: الحدود- الفروض- المصطلحات

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خارطة مفاهيم عن حدود البحث ومصطلحات البحث تتضمن ما يلي: - حدود البحث: § الموضوعية: أي الجوانب التي يتضمنها البحث. § الزمانية: أي المدة التي يغطيها البحث. § المكانية: أي المجال المكاني للبحث. - مصطلحات البحث: 1) المدلول اللغوي. 2) المدلول الاصطلاحي. 3) المدلول الإجرائي.

Material Type: Diagram/Illustration

Author: عبدالعزيز عوض ماطر الروقي

Date created : 8-ربيع الثاني-1440

أدوات البحث العلمي : المقابلة - الملاحظة - الاختبار

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خارطة مفاهيم عن موضوع: أدوات البحث العلمي ( المقابلة - الملاحظة - الاختبار) تتضمن ما يلي: -*المقابلة: المفهوم الخطوات الأنواع المزايا العيوب. * الملاحظة: المفهوم الخطوات الأنواع المزايا العيوب. *الاختبار: المفهوم الخطوات الأنواع جدول المواصفات.

Material Type: Diagram/Illustration

Author: عبدالعزيز عوض ماطر الروقي

Date created : 10-ربيع الثاني-1440

الفصل الثاني: الإطار المفاهيمي والدراسات السابقة

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فاعلية المعامل الافتراضية في تنمية مهارات التفكير البصري لمقرر العلوم لدى طلاب الصف الأول متوسط بمدينة الرياض الفصل الثاني: الإطار المفاهيمي والدراسات السابقة

Material Type: Case Study

Author: عبدالعزيز عوض ماطر الروقي

Date created : 14-ربيع الثاني-1440

أداة البحث: بطاقة الملاحظة "بصورتها الأولية"

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فاعلية المعامل الافتراضية في تنمية مهارات التفكير البصري لمقرر العلوم لدى طلاب الصف الأول متوسط بمدينة الرياض أداة البحث: بطاقة الملاحظة بصورتها الأولية

Material Type: Case Study

Author: عبدالعزيز عوض ماطر الروقي

Date created : 14-ربيع الثاني-1440

أداة البحث: بطاقة الملاحظة بصورتها النهائية

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فاعلية المعامل الافتراضية في تنمية مهارات التفكير البصري لمقرر العلوم لدى طلاب الصف الأول متوسط بمدينة الرياض أداة البحث: بطاقة الملاحظة بصورتها النهائية

Material Type: Case Study

Author: عبدالعزيز عوض ماطر الروقي

Date created : 14-ربيع الثاني-1440