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دراسة الموجات المنحرفة والدوامات في البلازما الممغنطة لشريحة في وجود بيتا منخفضة لطاقة الايونات المحددة
No full textThe derivation of reduced nonlinear fluid equations for the description of drift wave turbulence and vortices in low beta confinement, systems with magnetic shear is considered, where the effects associated with trapped particles could be neglected. In the present work, a set of reduced equations governing the slab-type ion temperature gradient driven mode in a shear magnetized plasma with low frequency, is derived which is generalization of the two fluid equations. With the use the model, equations are derived for the drift instabilities from the electrostatic two-fluid equations. The electrical resistivity included in the system that allows the dynamics of both the collisionless ion temperature gradient driven instability and the collisional drift wave instability of plasma. The model equations was used extensively in earlier nonlinear studies and the research developed it as appropriate limits of the model equations derived in the present work, where the effects of sheared velocity flows in the equilibrium plasma. The compressible two fluid equations are considered when fluctuation of magnetic field and electron temperature are ignored. It is also assumed that the mode is localized on a particular magnetic field line, typical frequency and growth rate of the model, which are much smaller than the ion cyclotron frequency. The dispersion relation of the slab-type ion temperature gradient driven mode is obtained for both collisionless and collisional drift waves in sheared magnetic fields of plasma. This illustrates that the strong magnetic shear has a stabilizing effect on the collisionless ion temperature gradient drift instability, which is not shown in collisional drift instability
تسرب الاشعاع المؤين واجراءات الوقاية من الاشعاع في اقسام الاشعة التشخيصية في مستشفيات محافظات غزة الحكومية فلسطين
No full textThe fact of using radiation in medicine has led to major improvements in the diagnostic and treatment of human diseases. However, it carries some risks of health problems. This subject has received a great concern in the recent years. The work is based on measurement of equivalent radiation dose rate in different locations in radio-diagnostic rooms at governmental Gaza governorates hospitals. These include: 19 basic X-ray, 8 fluoroscopy, 3 CT scan and mammography machines. The measurements were carried out by using the radiation survey meter (OD-01), since there is no obvious work have been previously done experimentally. A questionnaire is designed for matching the study needs and 182 radio-diagnostic workers participated in the work in order to obtain an information about their radiation protection measures and practices. The results indicate that the fluoroscopy and CT scan rooms were not efficiently lead lined and the radiation protection is not well organized. The measured values of radiation dose rate at different locations in basic X-ray and mammography rooms are found within a permissible limits for workers and public. However, the recommended distance between the X-ray machine and control panel have not been achieved in some rooms. In addition, the results of questionnaire indicate unsatisfactory practices toward radiation protection issues, where approximately half of participants have negative practices. The participants have reported that 35.2% of personal radiation protection devices are available in radio-diagnostic centers. Also the results revealed very poor of personal radiation exposure monitoring process. Overall, the results represented in this work reflect that majority of participants believe there is no radiation safety officer to provide the service. Therefore, there is a desperate need for rules, regulations and radiation protection act in the field of radiation in medical field. Finally, recommendations in the light of the outcome of study results were given to improve the radiation protection and safety measures
A Model of Drift Waves Modified By Electron Temperature Gradients and ExB Rotation in Cylindrical Magnetized Plasma
Full text linkA general investigation of linear drift-waves phenomena in cylindrically bounded plasmas, immersed in a magnetic field without sheared and curvature, is described by the two-fluid equations, taking into account: (a) electron-temperature oscillation, (b)the radial variation of density and temperature, (c)the radial electric field ; and rotation, as well as (d)the electron motion parallel to the magnetic field lines. For plasmas in which the electron temperature strongly exceeds the ion temperature the problem is reduced to an ordinary complex second- order differential equation describes the radial distribution of the oscillating electric potential. It is shown that the presence of the rotation and the radial gradients in the undisturbed electron temperature leads to an important modification of the theory of drift waves in cylindrical plasma compared with previous models in which these phenomena were disregarded. The theory is applied to an experimental data of helium plasma using Runge-Kutta integration method. Our calculation shows that the temperature variation and the rotation are important in the predictions of drift wave frequency and radial position of the maximum wave amplitude
تقييم مستوى الاشعاع الكهرومغناطيسي المنبعث من محطات الهاتف المحمول في محافظة غزة طبقا للبروتوكول الفلسطيني
No full textThe general objective of this study is to assess the electromagnetic radiation levels emitted from mobile base stations in Gaza Governorate. The mobile base stations distributed all over Gaza Governorate causing a considerable panic to inhabitants from electromagnetic radiation. The studied sites were selected from different regions in the Gaza Governorate, where fifty mobile base stations chosen, adopting a selection criteria of one site for each kilometer. The exposure of electromagnetic radiation levels generated due to these stations were measured and compared with standards of the Palestinian Protocol and some other international standards guidelines like ICNIRP, WHO, IEEE, Egypt and Iraq. A form of observation and questionnaire was designed, based on findings concluded from interviewing experts in this field. The measurements of power density, electric and magnetic field were detected by Narda-550. The results show that all stations are licensed by the EQA, but there is no any warning signs for any existing station. The distance between the antenna and the protective fence is greater than 5m away for 44 stations. The result also illustrates that the maximum value of electromagnetic radiation was which represents 19.3 % of the EQA, ICNIRP, WHO, IEEE, Egypt and Iraq standards. In addition the study shows that electromagnetic radiation levels are much lower than the exposure limit recommended by the international standards and Palestinian protocol. It has been noticed that there is no relationship between the electromagnetic radiation levels and the antenna heights at different distances. The result shows 42% of participants are thought that the wave of radiation means risk and 36% of participants are thought the radiation from mobile stations effect on human health while 52% of participants are assessed the process of government controls to stations weak. The study recommends modifying and upgrading existing protocols, also to raise public awareness and improving the government controls
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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