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Register a new userThe oritical study for determination the stiffness factors in ferromagnetic crystal
دراسة نظرية لتحديد عوامل الجسوءة في بلّورة المادة الفيرومغناطيسية ( الحديدية المغنطة )
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Tishreen University ورقة بحثية
Publication date
2014
fields
Physics
and research's language is
العربية
Authors
فرحان ياسين( باحث )
Created by
Shamra Editor
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تم في هذا العمل تحديد عوامل الجسوءة ( ، ، ) في بلّورة مادة فيرومغناطيسية تدخل في حسابات ثوابت تباين المناحي ( Anisotropy) للبلورات المغناطيسية. علاوةً على ذلك, تم تحديد قيم مجالات بين متجهة تمغنط البلورة واتجاه الحقل المغناطيسي المطبق عليها , التي توافق وجود حالات التوازي ، وحالات التوازي المضاد ، وكذلك المجالات المناسبة لعملية القفز المغناطيسي بين الحالتين .
This work studies the determination of stiffness factors , and in ferromagnetic crystal which enter into the calculations of anisotrophic constants of ferromagnetic crystal . However , Value intervals of C3 which coresponds to the existence of parallel states , and antiparallel states between the magnetic crystal vector and applied magnetic field vector . In addition , the suitable intervals for the magnetic jumps between two states have been found
References used
(M.Venkatesan , et. , Anisotropic Ferromognetism in substituted ZnO , Phy. Rew . letters , vol.93 , No 17 , (2004
(Drust, K.D.: Untersuchung der magetischen Eigenschaften und der Ummagnetisierungsprozesse in hartmagentischen Sm ( Co, Cu ,Fe , Zr ) - und Nd-Fe – B- Legierungen . Max - Planck - Institut für Metallforschung ,Stuttgart, (1986
(Drust , K.D. ; Kronmüller , H.: Determination of intrinsic material parameter of Nd2- Fe14-B from magnetic measurements of sintered Nd15-Fe77-B8 magnets . - In : J. Magn . Magn . Mater . 59 ,- 86, (1986
(Givord , D.; Li , H.S. ; Perrir de la Bathie , R. : Magnetic properties of Y2 F14B and Nd2Fe14B single Crystals . - In : Solid state Common . , 51 ,- 857, (1984
(J. Smit and H.P . J. Wign , physical properties at Ferrimagnetic oxides in Relaxien to their technical applications , whrights, lane, Kensinglon , london , W.8. ,(1959
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The aim of this paper is to study spin waves in ferromagnetic with spin (S=1/2) in complex coordinates system, the paper is divided into three sections:
The First section is about finding a transportation system that enables us to study a microsco
pic phenomenon ,its the spin waves in a classical way. The first step in this transportation system lies in finding the suitable wave function in the chosen coordinates, then the Hamiltonian and the Lagrangian then after that the dynamic equations in the general form, and testing the credibility of the system by making sure that it follow the rules of the study.
The Second section is about the use of that system, which is called the Simi classic way of studying the spin waves, and finding the dispersing equations and energetic levels then discussing the resultes from different ways and effects.
The Third section includes 1- Finding the ground state (basic) and the importance of finding the energy of the ground state lies in its direct effect on the system's energy.2- Finding the movement equations connected with time and place (the time-place equations). Its importance lies in two points; the first one is that it enables us to find the variance in the coordinates of the spin according to time. The second point is to know the spread speed of spin waves according to the chosen axle and the connection of the variation of domains (the magnetic sectors) with the spreading of spin waves and its speed
The Syrian steppe occupies an area of about ١٠ millions hectares
representing ٥٥٪ of the country. Due to the relatively high rainfall averages the
steppe is known as one of the best grazing areas in the Arab World. This
picture however has been ch
anged in the recent decades due to the expansion of
rainfed barley cultivation and consequent destruction of the natural shrubby
cover by tillage.
Other reasons leading to land degradation is the steppe overgrazing and
shrub cutting for fuel . High soil erodibility is caused by the week structure and
light texture of the soils of the steppe. As a result wind erosion became a
prevailing process in the steppe. This phenomenon was remarkably accelerated
during the last decade.
Dust, dust storm, sand accumulation on roads, railroads, villages houses,
formation of sand sheets with different thickness and sand hummocks around
shrubs were the main environmental features consequences.
This study aims mainly to determine the temperature distribution
heat transfer enhancement under natural convection experimental,
from three surfaces with industrial roughness created by a special
machine (roughness surfaces) with triangular, trapezoidal, spherical
configuration compared to equivalent smooth surface.
With cross-sectional area.
سطح مخشن
سطح أملس
معامل انتقال الحرارة
Rough surfaces
Smooth surfaces
Enhanced heat transfer
Heat transfer coefficient
Convection heat transfer
Temperature distribution
التوزيع الحراري
التبدد الحراري
التحسن في انتقال الحرارة
انتقال الحرارة بالحمل الطبيعي
تحسين انتقال الحراراة
بروزات
مقاطع
heat dissipation
ribs
configurations
المزيد..
Purpose: Lacunar infarcts is an important stroke subgroup with unique clinical and
pathologic features, but risk factors for lacunar infarcts have been rarely documented. To
address this matter, we studied 65 patients had lacunar infarction at Depa
rtment of
Neurology , Tishreen University Hospital , Lattakia , Syria , and 65 controls during the
period between May 2017 – May 2018 .
Methods: We obtained information concerning risk factor exposure status among the
patients by a structured questionnaire , we recorded age , sex , blood pressure , glucose ,
heart diseases , cigarette smoking , alcohol drinking , physical exercise for patiens and
controls .We do laboratory tests and ECG and echocardiography and CT brain or MRI .
Results: Significantly increasing the risk of lacunar stroke were hypertension
(P-value=0.0001) and (OR=9.9), Current smokers (P-value=0.002) and (OR=5.2), diabetes
(P-value=0.001) and (OR=5.3) , whereas frequent physical exercise was associated with a
significantly decreased risk) P-value=00001( and (OR=2.6). There was no risk of
lacunar stroke associated with heart disease (P-value=0.6) (OR=0.8) , high cholesterol (Pvalue=
1) and (OR=1) , alcohol drinking (P-value=0.7) and (OR=0.8).
Conclusions: Patients with hypertension or diabetes, current smokers, those who
have not heart disease, are at a higher risk of lacunar stroke, whereas those who undertake
regular physical exercise may be at lower risk.
This study aimed to examine students’ attitude and achievement in
relation to their use of Moodle. A Mixture qualitative and quantitative
methods were applied in order to investigate the aims of the study.
Questionnaires and interviews were used f
or collecting data from the
students and the lecturer. Students’ achievement was measured by the grades they obtained in the observed module. Students’ attitudes towards WebCT were measured by using a Likert scale. The data was analysed by using SPSS program. The results of this study showed that the students have positive attitude towards Moodle and they appreciated the flexibility of using it anytime and from anyplace. The module leader valued Moodle as a supporting tool to traditional face-to-face learning but not as an effective tool on students’ learning. The results obtained from the interview and the questionnaire and the quantitative data (tracking system data) can be considered new and promising.
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