71 research outputs found
Determination of air and hydrofoil pressure coefficient by laser doppler anemometry
Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles
Diagnostic Systems as Basis for Technological Improvement
AbstractHereunder the ways of technical diagnostics in metal manufacturing and peculiarities of challenges which are faced in technical diagnostics are given. The matters of the ways of technical diagnostics, which are required to be solved in near future, are described in the article. Solutions of problems concerning diagnostics of condition of an edge tool, using real-time vibration analysis, are provided. The article says about affect of bearings of spindle units on three-dimensional distribution of vibration parameters. An example concerning a spindle unit that induces auto vibration, which produce a false diagnosis regarding the condition of the edge tool, is given
Synthesis and Optimization of Reversible Circuits - A Survey
Reversible logic circuits have been historically motivated by theoretical
research in low-power electronics as well as practical improvement of
bit-manipulation transforms in cryptography and computer graphics. Recently,
reversible circuits have attracted interest as components of quantum
algorithms, as well as in photonic and nano-computing technologies where some
switching devices offer no signal gain. Research in generating reversible logic
distinguishes between circuit synthesis, post-synthesis optimization, and
technology mapping. In this survey, we review algorithmic paradigms ---
search-based, cycle-based, transformation-based, and BDD-based --- as well as
specific algorithms for reversible synthesis, both exact and heuristic. We
conclude the survey by outlining key open challenges in synthesis of reversible
and quantum logic, as well as most common misconceptions.Comment: 34 pages, 15 figures, 2 table
Effect of quantum confinement and influence of extra charge on the electric field gradient in ZnO
By means of electron-nuclear double resonance (ENDOR), it is shown that the Al impurity, which acts as a shallow donor in ZnO, leads to a significant reduction of the electric field gradient in ZnO single crystals. In ZnO quantum dots, however, the gradient on the Al sites remains virtually unchanged. When the Zn 2+ ion is substituted by Mn 2+ in a ZnO single crystal, the electric field gradient slightly increases (by about 20%). Therefore, the Mn 2+ ions can be used as probes to monitor the electric field gradients in ZnO crystals. © 2012 Pleiades Publishing, Ltd
Simulating chemistry efficiently on fault-tolerant quantum computers
Quantum computers can in principle simulate quantum physics exponentially
faster than their classical counterparts, but some technical hurdles remain.
Here we consider methods to make proposed chemical simulation algorithms
computationally fast on fault-tolerant quantum computers in the circuit model.
Fault tolerance constrains the choice of available gates, so that arbitrary
gates required for a simulation algorithm must be constructed from sequences of
fundamental operations. We examine techniques for constructing arbitrary gates
which perform substantially faster than circuits based on the conventional
Solovay-Kitaev algorithm [C.M. Dawson and M.A. Nielsen, \emph{Quantum Inf.
Comput.}, \textbf{6}:81, 2006]. For a given approximation error ,
arbitrary single-qubit gates can be produced fault-tolerantly and using a
limited set of gates in time which is or ; with sufficient parallel preparation of ancillas, constant average
depth is possible using a method we call programmable ancilla rotations.
Moreover, we construct and analyze efficient implementations of first- and
second-quantized simulation algorithms using the fault-tolerant arbitrary gates
and other techniques, such as implementing various subroutines in constant
time. A specific example we analyze is the ground-state energy calculation for
Lithium hydride.Comment: 33 pages, 18 figure
Conditional Disclosure of Secrets: Amplification, Closure, Amortization, Lower-bounds, and Separations
In the \emph{conditional disclosure of secrets} problem (Gertner et al., J. Comput. Syst. Sci., 2000) Alice and Bob, who hold inputs and respectively, wish to release a common secret to Carol (who knows both and ) if only if the input satisfies some predefined predicate . Alice and Bob are allowed to send a single message to Carol which may depend on their inputs and some joint randomness and the goal is to minimize the communication complexity while providing information-theoretic security.
Following Gay, Kerenidis, and Wee (Crypto 2015), we study the communication complexity of CDS protocols and derive the following positive and negative results.
1. *Closure* A CDS for can be turned into a CDS for its complement with only a minor blow-up in complexity. More generally, for a (possibly non-monotone) predicate , we obtain a CDS for whose cost is essentially linear in the formula size of and polynomial in the CDS complexity of .
2. *Amplification* It is possible to reduce the privacy and correctness error of a CDS from constant to with a multiplicative overhead of . Moreover, this overhead can be amortized over -bit secrets.
3. *Amortization* Every predicate over -bit inputs admits a CDS for multi-bit secrets whose amortized communication complexity per secret bit grows linearly with the input length for sufficiently long secrets. In contrast, the best known upper-bound for single-bit secrets is exponential in .
4. *Lower-bounds* There exists a (non-explicit) predicate over -bit inputs for which any perfect (single-bit) CDS requires communication of at least . This is an exponential improvement over the previously known lower-bound.
5. *Separations* There exists an (explicit) predicate whose CDS complexity is exponentially smaller than its randomized communication complexity. This matches a lower-bound of Gay et. al., and, combined with another result of theirs, yields an exponential separation between the communication complexity of linear CDS and non-linear CDS. This is the first provable gap between the communication complexity of linear CDS (which captures most known protocols) and non-linear CDS
Quantum Multicollision-Finding Algorithm
The current paper presents a new quantum algorithm for finding multicollisions, often denoted by -collisions, where an -collision for a function is a set of distinct inputs having the same output value. Although it is fundamental in cryptography, the problem of finding multicollisions has not received much attention \emph{in a quantum setting}. The tight bound of quantum query complexity for finding -collisions of random functions has been revealed to be , where is the size of a codomain. However, neither the lower nor upper bound is known for -collisions. The paper first integrates the results from existing research to derive several new observations, e.g.~-collisions can be generated only with quantum queries for a small constant . Then a new quantum algorithm is proposed, which finds an -collision of any function that has a domain size times larger than the codomain size. A rigorous proof is given to guarantee that the expected number of quantum queries is for a small constant , which matches the tight bound of for and improves the known bounds, say, the above simple bound of
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