208 research outputs found

    Nonhyperbolic reflection moveout for orthorhombic media

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    Reflection moveout in azimuthally anisotropic media is not only azimuthally dependent but it is also nonhyperbolic. As a result, the conventional hyperbolic normal moveout (NMO) equation parameterized by the exact NMO (stacking) velocity loses accuracy with increasing offset (i.e., spreadlength). This is true even for a single-homogeneous azimuthally anisotropic layer. The most common azimuthally anisotropic models used to describe fractured media are the horizontal transverse isotropy (HTI) and the orthorhombic (ORT). Here, we introduce an analytic representation for the quartic coefficient of the Taylor’s series expansion of the two-way traveltime for pure mode reflection (i.e., no conversion) in arbitrary anisotropic media with arbitrary strength of anisotropy. In addition, we present an analytic expression for the long-spread (large-offset) nonhyperbolic reflection moveout (NHMO). In this study, special attention is given to Pwave propagation in orthorhombic media with horizontal interfaces. The quartic coefficient, in general, has a relatively simple form, especially for shear wave propagation. The reflection moveout for each shear-wave mode in a homogeneous orthorhombic medium is purely hyperbolic in the direction normal to the polarization. In addition, the nonhyperbolic portion of the moveout for shear-wave propagation reaches its maximum along the polarization direction, and it decreases rapidly away from the direction of polarization. Hence, the anisotropy-induced nonhyperbolic reflection moveout for shear-wave propagation is significant in the vicinity of the polarization directions. In multilayered azimuthally anisotropic media, the NMO (stacking) velocity and the quartic moveout coefficient can be calculated with good accuracy using Dix-type averaging (e.g., the known averaging equations for VTI media). The interval NMO velocities and the interval quartic coefficients, however, are azimuthally dependent. This allows us to extend the nonhyperbolic moveout (NHMO) equation, originally designed for VTI media, to more general horizontally stratified azimuthally anisotropic media. Numerical examples from reflection moveout in orthorhombic media, the focus of this paper, show that this NHMO equation accurately describes the azimuthally-dependent P-wave reflection traveltimes, even on spreadlengths twice as large as the reflector depth. This work provides analytic insight into the behavior of nonhyperbolic moveout, and it has important applications in modeling and inversion of reflection moveout in azimuthally anisotropic media.Massachusetts Institute of Technology. Earth Resources LaboratorySaudi Aramc

    Bis(2,6-diamino­pyridin-1-ium) hexa­aqua­cobalt(II) disulfate dihydrate

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    In the title compound, (C5H8N3)2[Co(H2O)6](SO4)2·2H2O, the complete complex cation is generated by crystallographic inversion symmetry, such that the CoII cation is octa­hedrally coordinated by six water mol­ecules. The organic cation is essentially planar, with a maximum deviation of 0.013 (1) Å. In the crystal structure, the ions and mol­ecules are linked into a pseudo-layered three-dimensional supra­molecular network via O—H⋯O and N—H⋯O hydrogen bonds. Weak inter­molecular π–π inter­actions further stabilize the crystal structure [centroid–centroid distance = 3.5231 (4) Å]

    Teaching Experience based on Service Learning (SL) at the Islamic University in Gaza: the Pros and Obstacles

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    This research aims to evaluate the introduction of the Service Learning (SL) component in three university courses in Islamic University of Gaza. The study focused on the following questions: 1) What are the steps followed to implement teaching that is based on service learning from the perspective of involved faculty members? 2) What are the advantages and the obstacles associate with the implementation of service learning? 3) To what extent was student involvement in this experience beneficial to students' academic, personal, societal and professional domains from their perspectives? The study sample consisted of 101 students, of whom -88- at the bachelor's level. It was distributed as follows: Department of Architecture, Urban Flaming course (16 students), and the Department of Medical Laboratory Sciences, Medical Microbiology course (72 students). The MA students were from the Department of Educational Administration: Educational Management course. Researchers relied on a questionnaire completed by the students, in addition to the interviews conducted with the three (3) faculty members involved in those courses. Results of the analysis showed that teaching based on service learning was successful and has achieved its objectives in various forms. Results exceeded expectations and were ahead of the targets set by the university. It appears through the university has benefited from the experience in a direct way in terms of strengthening the reputation, and in making a positive difference in the lives of the beneficiaries

    Analysis Of Deteriorating Inventory/Production Systems Using ALinearQuadratic Regulator

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    We consider an inventory-production system where items deteriorate at a constant rate. The objective is to develop an optimal production policy that minimizes the cost associated with inventory and production rate. The inventory problem is first modeledas a linear optimal control problem. Then linear quadratic regulator (LQR) technique is applied to the control problem in order to determine the optimal production policy.Examples are solved for three different demand functions. Sensitivity analysis is then conducted to study the effect of changing the cost parameters on the objective function. (C) 1998 Published by Elsevier Science B.V

    Analysis Of Deteriorating Inventory/Production Systems Using ALinearQuadratic Regulator

    Get PDF
    We consider an inventory-production system where items deteriorate at a constant rate. The objective is to develop an optimal production policy that minimizes the cost associated with inventory and production rate. The inventory problem is first modeledas a linear optimal control problem. Then linear quadratic regulator (LQR) technique is applied to the control problem in order to determine the optimal production policy.Examples are solved for three different demand functions. Sensitivity analysis is then conducted to study the effect of changing the cost parameters on the objective function. (C) 1998 Published by Elsevier Science B.V

    Teaching Experience based on Service Learning (SL) at the Islamic University in Gaza: the Pros and Obstacles

    Get PDF
    This research aims to evaluate the introduction of the Service Learning (SL) component in three university courses in Islamic University of Gaza. The study focused on the following questions: 1) What are the steps followed to implement teaching that is based on service learning from the perspective of involved faculty members? 2) What are the advantages and the obstacles associate with the implementation of service learning? 3) To what extent was student involvement in this experience beneficial to students' academic, personal, societal and professional domains from their perspectives? The study sample consisted of 101 students, of whom -88- at the bachelor's level. It was distributed as follows: Department of Architecture, Urban Flaming course (16 students), and the Department of Medical Laboratory Sciences, Medical Microbiology course (72 students). The MA students were from the Department of Educational Administration: Educational Management course. Researchers relied on a questionnaire completed by the students, in addition to the interviews conducted with the three (3) faculty members involved in those courses. Results of the analysis showed that teaching based on service learning was successful and has achieved its objectives in various forms. Results exceeded expectations and were ahead of the targets set by the university. It appears through the university has benefited from the experience in a direct way in terms of strengthening the reputation, and in making a positive difference in the lives of the beneficiaries

    Tetra­guanidinium bis­[citrato(3−)]cuprate(II) dihydrate

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    The asymmetric unit of the title compound, (CH6N3)4[Cu(C6H5O7)2]·2H2O, contains one-half of a centrosymmetric CuII complex anion, two guanidinium cations and a water mol­ecule. The CuII ion, lying on a crystallographic inversion center, is hexa­coordinated with two citrate anions in a distorted octahedral geometry. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, mol­ecules are linked into a three-dimensional framework by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds

    Effectiveness of a community-led shared book reading intervention in Syrian refugee children: a randomised controlled trial.

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    Community-led, shared book reading programs may help improve refugee children's reading abilities and attitudes towards reading. We Love Reading (WLR)-a light-touch, community-led, shared book reading program-was evaluated in a pre-registered, wait-listed, randomised controlled trial (AEARCTR-0006523). 322 Syrian refugee mother-child dyads (children: 4-8-year-olds, 50.0% female) in Jordan were tested at two timepoints, 15 weeks apart. WLR did not significantly affect child literacy or child-reported child attitudes toward reading (ps > 0.05). Mothers did report improved child attitudes toward reading from WLR (p = 0.046, η2 = 0.013). The intervention did not lead to improvements in family relationships (ps > 0.05). WLR may have promise in improving attitudes toward reading in forcibly displaced children but did not affect literacy or child-reported attitudes toward reading; these results provide insight into what changes are needed for effective shared book reading interventions in this population

    Jordanian Women in Academia: Barriers and Motivators in Scientific Research and Promotion

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    The purpose of this study is to evaluate the research output and status of women academics in science fields in Jordan. The rationale is to identify trends as well as challenges to advise policy makers and university administrators on how to promote more involvement of women academics within the university. A survey of two sections was developed. The first section included 36 items that measure demographics and challenges in academic, research, administrative, and family contexts. The second section included questions regarding motivators and barriers to academic research. Participants were prompted to respond per the Likert’s Scale, where the responses were later categorized to a dichotomous variable (e.g., yes/no responses). The tools’ reliability and validity were tested in a pilot study conducted among 36 participants as well as from feedback from experts in the field. A description of the profile of women scientists in Jordan is presented. There was no significant difference between married and unmarried academics and their responses regarding opportunities and challenges faced in research. Additionally, there was no significant difference in responses between those who are married to academics and those married to nonacademics. Furthermore, the t-test showed that those who expressed dissatisfaction with promotion rules in their universities significantly expressed facing more challenges than those satisfied with promotion regulations. This is the first comprehensive study investigating women academics in Jordan in specific and in the Middle East region in general. Whereas previous research in the literature focused on comparing women academics’ progress and achievements with that of men academics, the novelty of this study lies in investigating sub-populations of women academics and identifying factors that affect academic achievement among women themselves. The article also offers suggestions for tailored intervention to improve the professional growth of women scientists in Jordan
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