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Light Controlled Optical Aharonov-Bohm Oscillations in a Single Quantum Ring
Kim, Heedae,Park, Seongho,Okuyama, Rin,Kyhm, Kwangseuk,Eto, Mikio,Taylor, Robert A.,Nogues, Gilles,Dang, Le Si,Potemski, Marek,Je, Koochul,Kim, Jongsu,Kyhm, Jihoon,Song, Jindong American Chemical Society 2018 NANO LETTERS Vol.18 No.10
<P>We found that optical Aharonov-Bohm oscillations in a single GaAs/GaAlAs quantum ring can be controlled by excitation intensity. With a weak excitation intensity of 1.2 kW cm<SUP>-2</SUP>, the optical Aharonov-Bohm oscillation period of biexcitons was observed to be half that of excitons in accordance with the period expected for a two-exciton Wigner molecule. When the excitation intensity is increased by an order of magnitude (12 kW cm<SUP>-2</SUP>), a gradual deviation of the Wigner molecule condition occurs with decreased oscillation periods and diamagnetic coefficients for both excitons and biexcitons along with a spectral shift. These results suggest that the effective orbit radii and rim widths of electrons and holes in a single quantum ring can be modified by light intensity via photoexcited carriers, which are possibly trapped at interface defects resulting in a local electric field.</P> [FIG OMISSION]</BR>
Kim, Hee Dae,Okuyama, Rin,Kyhm, Kwangseuk,Eto, Mikio,Taylor, Robert A.,Nicolet, Aurelien L.,Potemski, Marek,Nogues, Gilles,Dang, Le Si,Je, Ku-Chul,Kim, Jongsu,Kyhm, Ji-Hoon,Yoen, Kyu Hyoek,Lee, Eun Hy American Chemical Society 2016 Nano letters Vol.16 No.1
<P>The Aharonov-Bohm effect in ring structures in the presence of electronic correlation and disorder is an open issue. We report novel oscillations of a strongly correlated exciton pair, similar to a Wigner molecule, in a single nanoquantum ring, where the emission energy changes abruptly at the transition magnetic field with a fractional oscillation period compared to that of the exciton, a so-called fractional optical Aharonov-Bohm oscillation. We have also observed modulated optical Aharonov-Bohm oscillations of an electron-hole pair and an anticrossing of the photoluminescence spectrum at the transition magnetic field, which are associated with disorder effects such as localization, built-in electric field, and impurities.</P>
The structural performance of arches made of few vossoirs with dry-joints
Ernest Bernat-Maso,Lluís Gil,Jordi Marcé-Nogué 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.6
This work approaches the structural performance of masonry arches that have a small ratio between number of vossoirs and span length. The aim of this research is to compare and validate three different methods of analysis (funicular limit analysis F.L.A., kinematic limit analysis K.L.A. and plane stress Finite Element Analysis F.E.A.) with an experimental campaign. 18 failure tests with arches of different shapes and boundary conditions have been performed. The basic failure mechanism was the formation of enough hinges in the geometry. Nevertheless, in few cases, sliding between vossoirs also played a relevant influence. Moreover, few arches didn’t reach the collapse. The FLA and KLA didn't find a solution close to the experimental values for some of the tests. The low number of vossoirs and joints become a drawback for an agreement between kinematic mechanism, equilibrium of forces and geometry constraints. FLA finds a lower bound whereas KLA finds an upper bound of the ultimate load of the arch. FEA is the most reliable and robust method and it can reproduce most of the mechanism and ultimate loads. However, special care is required in the definition of boundary conditions for FEA analysis. Scientific justification of the more suitability of numerical methods in front of classic methods at calculating arches with a few vossoirs is the main original contribution of the paper.
EFFICIENCY SENSITIVITY ANALYSIS OF A HYDROSTATIC TRANSMISSION FOR AN OFF-ROAD MULTIPLE AXLE VEHICLE
M. COMELLAS,J. PIJUAN,X. POTAU,M. NOGUÉS,J. ROCA 한국자동차공학회 2013 International journal of automotive technology Vol.14 No.1
There is a large variety of multiple driven axle vehicles. Some of the most common are the 3-axle rigid vehicles and the 4-axle articulated vehicles, which can in some cases have different steering mechanisms, adaptive suspension, etc. This last kind of vehicles usually have very complex transmission configurations. Moreover, the required torques in each of the wheels can be very different, especially when the vehicle is working in rough terrains. The aim of this work is to study and model the driveline of this kind of vehicles, when using a hydrostatic transmission, from the performance and efficiency point of view, by analysing the influence of the operating conditions in the transmission efficiency. A global model is used to quantify the power flow in each of the transmission elements and the overall performance of the entire vehicle driveline, given the operating conditions thereof. A sensitivity analysis has also been done showing the influence of vehicle speed, rolling resistance, terrain slope and hydraulic motors displacement in the overall transmission efficiency. The interest of this work is also to make a contribution to the literature in the field of global modelling of drivelines under variable operating conditions and its application to ATVs. One important aspect is the influence of different actuation requirements that occur in different wheels at the same time. The results show that the overall performance of the transmission is highly dependent on operating conditions, on the selected transmission configuration and on the used components.
The structural performance of arches made of few vossoirs with dry-joints
Bernat-Maso, Ernest,Gil, Lluis,Marce-Nogue, Jordi Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.6
This work approaches the structural performance of masonry arches that have a small ratio between number of vossoirs and span length. The aim of this research is to compare and validate three different methods of analysis (funicular limit analysis F.L.A., kinematic limit analysis K.L.A. and plane stress Finite Element Analysis F.E.A.) with an experimental campaign. 18 failure tests with arches of different shapes and boundary conditions have been performed. The basic failure mechanism was the formation of enough hinges in the geometry. Nevertheless, in few cases, sliding between vossoirs also played a relevant influence. Moreover, few arches didn't reach the collapse. The FLA and KLA didn't find a solution close to the experimental values for some of the tests. The low number of vossoirs and joints become a drawback for an agreement between kinematic mechanism, equilibrium of forces and geometry constraints. FLA finds a lower bound whereas KLA finds an upper bound of the ultimate load of the arch. FEA is the most reliable and robust method and it can reproduce most of the mechanism and ultimate loads. However, special care is required in the definition of boundary conditions for FEA analysis. Scientific justification of the more suitability of numerical methods in front of classic methods at calculating arches with a few vossoirs is the main original contribution of the paper.