Browsing by Subject "Cooling"
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Item Open Access Cooling quantum gases with entropy localization(Institute of Physics Publishing, 2017) Ünal, F. Nur; Mueller, Erich J.We study the dynamics of entropy in a time dependent potential and explore how disorder influences this entropy flow. We show that disorder can trap entropy at the edge of the atomic cloud enabling a novel cooling method. We demonstrate the feasibility of our cooling technique by analyzing the evolution of entropy in a one-dimensional Fermi lattice gas with a time dependent superlattice potential.Item Open Access Examining the annealing schedules for RNA design algorithm(IEEE, 2016-07) Erhan, H. E.; Sav, Sinem; Kalashnikov, S.; Tsang, H. H.RNA structures are important for many biological processes in the cell. One important function of RNA are as catalytic elements. Ribozymes are RNA sequences that fold to form active structures that catalyze important chemical reactions. The folded structure for these RNA are very important; only specific conformations maintain these active structures, so it is very important for RNA to fold in a specific way. The RNA design problem describes the prediction of an RNA sequence that will fold into a given RNA structure. Solving this problem allows researchers to design RNA; they can decide on what folded secondary structure is required to accomplish a task, and the algorithm will give them a primary sequence to assemble. However, there are far too many possible primary sequence combinations to test sequentially to see if they would fold into the structure. Therefore we must employ heuristics algorithms to attempt to solve this problem. This paper introduces SIMARD, an evolutionary algorithm that uses an optimization technique called simulated annealing to solve the RNA design problem. We analyzes three different cooling schedules for the annealing process: 1) An adaptive cooling schedule, 2) a geometric cooling schedule, and 3) a geometric cooling schedule with warm up. Our results show that an adaptive annealing schedule may not be more effective at minimizing the Hamming distance between the target structure and our folded sequence's structure when compared with geometric schedules. The results also show that warming up in a geometric cooling schedule may be useful for optimizing SIMARD. © 2016 IEEE.Item Open Access Heat transfer through dipolar coupling: Sympathetic cooling without contact(American Physical Society, 2016) Renklioglu, B.; Tanatar, Bilal; Oktel, M. Ö.We consider two parallel layers of dipolar ultracold Fermi gases at different temperatures and calculate the heat transfer between them. The effective interactions describing screening and correlation effects between the dipoles in a single layer are modeled within the Euler-Lagrange Fermi-hypernetted-chain approximation. The random-phase approximation is used for the interactions across the layers. We investigate the amount of transferred power between the layers as a function of the temperature difference. Energy transfer arises due to the long-range dipole-dipole interactions. A simple thermal model is established to investigate the feasibility of using the contactless sympathetic cooling of the ultracold polar atoms and molecules. Our calculations indicate that dipolar heat transfer is effective for typical polar molecule experiments and may be utilized as a cooling process.Item Open Access Non-linear thermoelectricity and cooling effects in metallic constrictions(Institute of Physics Publishing Ltd., 1994) Kulik, I. O.Linear as well as non-linear contributions to the Zeebeck and Peltier coefficients of a metallic film in contact with the equilibrium metal are calculated within a simple model. The non-linear part of the thermoelectric response survives down to a very low temperature which in principle permits thermoelectric cooling at these conditions. Thermal equilibrium in a metallic constriction between dissimilar metals is evaluated in the non-linear current-carrying regime.Item Open Access q-Gaussian trial function in high density Bose-Einstein condensates(Elsevier Science B.V., 2003) Erdemir, E.; Tanatar, BilalWe study the ground-state static properties of Bose-Einstein condensates in the high density regime using a trial wave function of the form of a q-Gaussian. The flexibility afforded by a q-Gaussian trial function yields very accurate ground-state energies for large number of particles. The resulting condensate wave function profiles are also in good agreement in the high density regime. Comparing our results with those of numerical calculations we provide information on the possible limitations of the q-Gaussian trial functions.