583 research outputs found
Turbulent skin-friction drag reduction by travelling waves induced by spanwise Lorentz force
No full textThe streamwise and spanwise travelling waves induced by spanwise Lorentz force are studied for skin-friction drag reduction in a turbulent channel. The streamwise travelling wave by spanwise Lorentz force on drag reduction is compared to the with the spanwise wall motion. The drag reduction map shows a drag reduction region and a drag increase region, depending on a time scale . For spanwise travelling wave, a large drag reduction appears at large oscillation frequencies and small spanwise wave numbers, while all stationary wave cases give a drag increase. When the wave travels at an oblique angle to the streamwise mean flow, the optimal drag reduction appears in backward travelling wave case. Generally, the backward streamwise travelling wave is found to be most efficient in drag reduction among all oblique travelling waves. Spanwise oscillation, forward streamwise travelling, spanwise travelling and backward streamwise travelling wave cases share a similar drag reduction mechanism: first, the spanwise motion directly breaks the near wall quasi-streamwise vortices structure array \cite{Jeong_etal1997}, which results in the shortening of streamwise streaks; second, the spanwise velocity layer maintains the asymmetry of the positive and negative quasi-streamwise vortices, which leads to a sustained drag reduction
The Ontology of the Causal Basis of Man : To the Theory of Time
No full textIn 2014, Amirbegov Y.M.'s monograph titled "Mechanics of Thinking" or "Ontological Basis of the Subject" was published, which dealt with a philosophical question: the relationship of matter with consciousness and time of our being. But since the monograph duplicated the thesis conceived by the author and did not go beyond the material presented in it, on the advice of the consultant the author of the monograph is preparing its second edition in an expanded version with a new title: " Ontology of Causal Basis of Man", attracting his mentor, the author of "The Theory of Time or Principle of Formation of Matter Forms" Amirbegov M.R., as a co-author of this book,
Adhering to the opinion that matter between past and future temporal conti-nuity of eternity is reduced to nothing and in reality there remains only a causeless "Nothing", the authors of this book from a clean sheet, but with baggage of knowledge about objective forms of being and causeless reality with its possibili-ties, build an unparalleled theoretical model of human integrity, answering the question: what does a man, his sensorium, consciousness, his thinking apparatus and thought itself, why and how? The authors submit this book to the judgment of the reader
The Ontology of the Causal Basis of Man : To the Theory of Time
No full textIn 2014, Amirbegov Y.M.'s monograph titled "Mechanics of Thinking" or "Ontological Basis of the Subject" was published, which dealt with a philosophical question: the relationship of matter with consciousness and time of our being. But since the monograph duplicated the thesis conceived by the author and did not go beyond the material presented in it, on the advice of the consultant the author of the monograph is preparing its second edition in an expanded version with a new title: " Ontology of Causal Basis of Man", attracting his mentor, the author of "The Theory of Time or Principle of Formation of Matter Forms" Amirbegov M.R., as a co-author of this book,
Adhering to the opinion that matter between past and future temporal conti-nuity of eternity is reduced to nothing and in reality there remains only a causeless "Nothing", the authors of this book from a clean sheet, but with baggage of knowledge about objective forms of being and causeless reality with its possibili-ties, build an unparalleled theoretical model of human integrity, answering the question: what does a man, his sensorium, consciousness, his thinking apparatus and thought itself, why and how? The authors submit this book to the judgment of the reader
On quantum entanglement, measurement and decoherence in nanosystems
No full textThis thesis discusses the interplay between entanglement, measurement and decoherence in quantum nanosystems.Theoretical Physics - Kavli Institute of Nanoscience DelftApplied Science
Ultimate performance of GRP-laminates under in-plane biaxial loading
No full textCivil Engineering and Geoscience
Quantum transport in strongly interacting one-dimensional nanostructures
No full textIn this thesis we study quantum transport in several one-dimensional systems with strong electronic interactions. The first chapter contains an introduction to the concepts treated throughout this thesis, such as the Aharonov-Bohm effect, the Kondo effect, the Fano effect and quantum state transfer. It also includes a brief historical introduction to these phenomena. The next three chapters discuss electronic transport in strongly interacting systems with a focus on the transport produced by the Kondo effect. The final chapter deals with spin quantum state transfer, where we analytically address the idea of having a one-dimensional spin chain as a quantum data bus in a quantum computer. In chapter 2 we model a system of coupled donors to explain experimental data of conductance, and use this model to investigate coherence and correlation effects. The two donors are strongly coupled to two leads in a parallel configuration embedded in a nano-wire field effect transistor. We then model the system as an Aharonov-Bohm ring with a strongly interacting quantum dot in each arm, and calculate the conductance in the middle of the Coulomb diamond when the system is in the Kondo regime. In the experimental data, interference was observed when a magnetic field was applied [Fig. 2.3(a)]. This interference shows a dependence on the Aharonov-Bohm phase picked up by electrons traversing the structure. This means that donors can be coupled coherently through a many-body state (the Kondo state). Calculations show the non-monotonic behavior of the conductance that was seen in the experimental data [Fig. 2.4(a)]. The conductance decreases since the Kondo effect is destroyed by the magnetic field, and at the same time an oscillatory behavior appears due to the magnetic phase picked up by the electrons going through the parallel structure. Our results improve the general understanding of possible interference effects in an atomic system, especially in the regime where strong interactions take over. Non-symmetric conductance resonances were observed in the data used in chapter 2 when the transport regime of one of the quantum dots changes from Coulomb blockade to sequential tunneling. We model this situation in chapter 3 and arrive at an analytical expression of conductance which we rewrite as a Fano equation. We demonstrate that the strongly interacting quantum dot creates a Kondo scattering channel which serves as a continuum and interferes with the resonant quantum dot, hence producing a non-symmetric Fano like shape in the conductance. Simulations were done using experimental parameters and good agreement with the data is found [Fig. 3.3]. Furthermore, we predict that even if the interacting channel is fully in the Kondo regime, we can use the magnetic flux to diminish its contribution by lowering the characteristic Kondo temperature (Kondo state broadening), producing an alteration in the electron’s path preference. The next challenge consisted of modeling a strongly-interacting chain of atoms, and study the impact of disorder on the Kondo conductance. In chapter 4 we model the energy levels of the quantum dots to be in the middle of the Coulomb blockade region without disorder. Transport calculations of the atomic chains show that in the weak disorder regime conductance drops with increasing disorder, which is surprising and not expected as the disorder is screened by the pinning of the Kondo state at the Fermi level. We demonstrate that the cause of this decrease is an induced non-screened disorder due to the local distribution of Kondo temperatures along the chain. We also show that weak disorder increases the Kondo temperature of a chain without disorder. We propose two experimental scanning tunneling microscopy setups where the impact of local Kondo temperatures can be observed [Fig. 4.5]. It has been reported that quantum state transfer (QST) can be achieved in a Heisenberg spin chain consisting of three spins. Then it might also be possible to achieve QST in longer spin chains if they can be modeled by an effective three-spin system during the complete quantum state transfer. This idea is formally discussed in chapter 5. We propose simple protocols to achieve quantum state transfer across a spin bus with high accuracy. We propose an effective toy model and apply our findings to a spin chain with a sender and a receiver qubit. We find that within the scope of the effective model the control of only the couplings of the spin bus to the sender and receiver qubits yield high fidelity. We also find an interesting high fidelity region that cannot be described by the effective toy model, and predict the high fidelities to be a consequence of a time-independent first excited state energy. We apply the socalled superadiabatic formalism, which makes the evolution 100% adiabatic, and find fidelities that are equal to one. We derive an approximate Hamiltonian containing parameters that correspond to physical (experimental) knobs, and demonstrate that this Hamiltonian improves the fidelity in both of the treated protocols [Fig. 5.9].Quantum NanoscienceApplied Science
Machine-learning-based calving prediction from activity, lying, and ruminating behaviors in dairy cattle
No full textThe objective of this study was to use automated activity, lying, and rumination monitors to characterize prepartum behavior and predict calving in dairy cattle. Data were collected from 20 primiparous and 33 multiparous Holstein dairy cattle from September 2011 to May 2013 at the University of Kentucky Coldstream Dairy. The HR Tag (SCR Engineers Ltd., Netanya, Israel) automatically collected neck activity and rumination data in 2-h increments. The IceQube (IceRobotics Ltd., South Queensferry, United Kingdom) automatically collected number of steps, lying time, standing time, number of transitions from standing to lying (ly-. ing bouts), and total motion, summed in 15-min increments. IceQube data were summed in 2-h increments to match HR Tag data. All behavioral data were collected for 14 d before the predicted calving date. Retrospective data analysis was performed using mixed linear models to examine behavioral changes by day in the 14 d before calving. Bihourly behavioral differences from baseline values over the 14 d before calving were also evaluated using mixed linear models. Changes in daily rumination time, total motion, lying time, and lying bouts occurred in the 14 d before calving. In the bihourly analysis, extreme values for all behaviors occurred in the final 24 h, indicating that the monitored behaviors may be useful in calving prediction. To determine whether technologies were useful at predicting calving, random forest, linear discriminant analysis, and neural network machine -learning techniques were constructed and implemented using R version 3.1.0 (R Foundation for Statistical Computing, Vienna, Austria). These methods were used on variables from each technology and all combined variables from both technologies. A neural network analysis that combined variables from both technologies at the daily level yielded 100.0% sen-sitivity and 86.8% specificity. A neural network analysis that combined variables from both technologies in bihourly increments was used to identify 2-h periods in the 8 h before calving with 82.8% sensitivity and 80.4% specificity. Changes in behavior and machine-learning alerts indicate that commercially marketed behavioral monitors may have calving prediction potential
Qubits quantum state transfer through coupled single mode resonators
No full textQuantum Nanoscience - Theoretical PhysicsApplied Science
Interplay of Charge Current and Spin in Nanostructures
No full textControlling magnetization on short time scales and/or small dimensions is a hot topic in the field of spintronics, owing to its fundamental physics and its applications for information technology. The most straightforward way to control magnetization is by using an external magnetic field. However, because of the technical limitation in using a magnetic field at smaller sizes and larger amplitudes, alternatives have been investigated such as using currents or light to control the magnetization. In this thesis, we study the interplay of current and spin in nanostructures. The charge current, in the work of this thesis, is generated by shining circularly polarized light on conducting rings, or by applying a voltage to magnetic wires. We use the Lagrangian multiplier method to obtain the Hamiltonian of the system in the presence of the current quantum mechanically. In the first part of the thesis, we study the effect of the current on the magnetization of a system. We demonstrate that circular current has the potential to generate or change the magnetization in certain systems, when the spin orbit interaction is present. Moreover, we study the current-induced motion of pinned domain walls, by only using energy considerations. The second part of this thesis focuses on an opposite effect, viz. the conductance controlled by the spin orbit interaction in an array of rings, an effect known as Aharonov effect. We demonstrate that the oscillations for arrays of rings with different average radii are in good agreement with the experimental as well as the theoretical results obtained for a single mode ring strongly coupled to the leads. We suggest experiments to distinguish between these fundamentally different theoretical models.Kavli Institute of Nanoscience DelftApplied Science
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