Conflict and Cooperation Over Transboundary Waters

human development, water, sanitation

Topological Superconductivity without Proximity Effect

Majorana Fermions, strange particles that are their own antiparticles, were predicted in 1937 and have been sought after ever since. In condensed matter they are predicted to exist as vortex core or edge excitations in certain exotic superconductors. These are topological superconductors whose order parameter phase winds non-trivially in momentum space. In recent years, a new and promising route for realizing topological superconductors has opened due to advances in the field of topological insulators. Current proposals are based on semiconductor heterostructures, where spin-orbit coupled bands are split by a band gap or Zeeman field and superconductivity is induced by proximity to a conventional superconductor. Topological superconductivity is obtained in the interface layer. The proposed heterostructures typically include two or three layers of different materials. In the current work we propose a device based on materials with inherent spin-orbit coupling and an intrinsic tendency for superconductivity, eliminating the need for a separate superconducting layer. We study a lattice model that includes spin-orbit coupling as well as on-site and nearest neighbor interaction. Within this model we show that topological superconductivity is possible in certain regions of parameter space. These regions of non-trivial topology can be understood as a nodeless superconductor with d-wave symmetry which, due to the spin-orbit coupling, acquires an extra phase twist of $2\pi$.Comment: 5 Pages, 3 Figure

Middle East water conflicts and directions for conflict resolution:

In looking toward 2020, one of the most severe problems to be faced is an impending shortage of adequate supplies of fresh water essential for drinking and for growing crops. The Middle East, where a few waterways serve large areas of land belonging to a number of nations, is the place where strife over water is most likely to erupt. This paper examines the past how water in the Middle East came to be divided as it is today and looks at possible solutions for alleviating a water crisis and the resulting political tensions.Water resources development Middle East., Water-supply Middle East Management.,

Student Mastery of Engineering with Design Review

Traditional structural engineering pedagogy has consisted of students preparing for class by reading a textbook, followed by a professor giving a lecture, followed by students doing individual homework. Students received feedback in terms of a grade from the professor, and, ideally, the student filed the graded work and possibly reviewed it again before an exam. Following the exam, the professor moved to the next topic and essentially ended any further contact time with the material, resulting in students quickly dumping a good percentage of what was learned. To make matters worse, most faculty would agree that undergraduate students often skip the reading prior to class, and studies have shown that almost half of all students do not pay attention to material presented during a lecture. Thus, it is critical for engineering educators to improve the stagnant method of traditional teaching and learning. Small mistakes in the engineering profession can lead to death or millions of dollars in repair. For the fall 2018 semester, in the Design of Steel and Wood Structures at the United States Military Academy at West Point, Civil Engineering students participated in a cooperative learning technique aimed at improving student learning. These same students tried a different version of this technique in Structural Analysis the prior semester.[1] Prior to submitting individual homework to the instructor for grade, students paired up with a peer within their class hour and checked each other’s work using an instructor provided “Design Review Sheet.” When a student found a mistake, or disagreed with the methodology used by their Design Review partner, the student annotated this on their sheet. The expectation was that when disagreements were discovered between students, they would discuss with each other where the error or misunderstanding existed and subsequently corrected the error prior to submission for grade. This not only required students to explain the work they completed, but it also provided additional contact time with the material. With respect to Engineering Teaching and Learning, Design Review provides the essential cooperative learning characteristic of positive interdependence because individual student learning increases as review partners improved in their Design Review. As a student incentive to complete a thorough review, the quality of review counted for 10% of each assignment. Efforts this iteration were in response to some of the student suggestions following a previous iteration.[1] This iteration, in lieu of students turning in their work in pairs to receive one grade, each student would turn in their individual work and Design Review sheet. This was done to hold all students accountable for the work they completed. In addition, the instructor provided Design Review sheet was modified for clarity and the requirement to write a memorandum summarizing the results of each Design Review was eliminated. This cooperative learning technique was used on six of seven homework assignments during the term and on seven of nine homework assignments in their pre-requisite course. Student feedback was collected from both Likert Scale questions and open-ended questions. This paper will make the case that this pedagogy benefits Engineering Teaching and Learning by: (1) getting engineering students in the practice of what engineers in practice already do (check each other’s work), (2) increasing student learning of course learning objectives through repetition and through observing how others solve problems and present their work, and (3) improving the ability of future engineers to communicate their work clearly and effectively.Cockrell School of Engineerin

Dynamical Friction in a Gas: The Supersonic Case

Any gravitating mass traversing a relatively sparse gas experiences a retarding force created by its disturbance of the surrounding medium. In a previous contribution (Lee & Stahler 2011), we determined this dynamical friction force when the object's velocity was subsonic. We now extend our analysis to the supersonic regime. As before, we consider small perturbations created in the gas far from the gravitating object, and thereby obtain the net influx of linear momentum over a large, bounding surface. Various terms in the perturbation series formally diverge, necessitating an approximate treatment of the flow streamlines. Nevertheless, we are able to derive exactly the force itself. As in the subsonic case, we find that F=Mdot*V, where Mdot is the rate of mass accretion onto the object and V its instantaneous velocity with respect to distant background gas. Our force law holds even when the object is porous (e.g., a galaxy) or is actually expelling mass in a wind. Quantitatively, the force in the supersonic regime is less than that derived analytically by previous researchers, and is also less than was found in numerical simulations through the mid 1990s. We urge simulators to revisit the problem using modern numerical techniques. Assuming our result to be correct, it is applicable to many fields of astrophysics, ranging from exoplanet studies to galactic dynamics.Comment: Accepted to A&A. Comments from the community welcomed. 21 pages, 12 figure