3,218 research outputs found
DCCII-Based Novel Lossless Grounded Inductance Simulators With No Element Matching Constrains
In 1996, the differential current conveyor (DCCII) was introduced as a versatile active element with current differencing capability. Therefore, in this study, the usefulness of the DCCII is shown on six novel lossless grounded inductance simulator circuits. Proposed circuits simultaneously employ minimum number of elements, i.e. single DCCII, one capacitor, and two resistors. No passive element matching restriction is needed and all solutions are electronically tunable in case that one of resistors is replaced by MOSFET-based voltage-controlled resistor. The internal structure of the active element has been implemented using the TSMC 0.25 um SCN025 CMOS process BSIM3v3.1 parameters. Firstly, the performance of the selected inductor simulator is evaluated and subsequently verified in the design of 5th-order high-pass ladder and 2nd-order frequency filters. In addition, experimental results using commercially available AD844/ADs are given to verify the theoretical analysis and SPICE simulations
Realization of Resistorless Lossless Positive and Negative Grounded Inductor Simulators Using Single ZC-CCCITA
This paper is in continuation with the very recent work of Prasad et al. [14], wherein new realizations of grounded and floating positive inductor simulator using current differencing transconductance amplifier (CDTA) are reported. The focus of the paper is to provide alternate realizations of lossless, both positive and negative inductor simulators (PIS and NIS) in grounded form using z-copy current-controlled current inverting transconductance amplifier (ZC-CCCITA), which can be considered as a derivative of CDTA, wherein the current differencing unit (CDU) is reduced to a current-controlled current inverting unit. We demonstrate that only a single ZC-CCCITA and one grounded capacitor are sufficient to realize grounded lossless PIS or NIS. The proposed circuits are resistorless whose parameters can be controlled through the bias currents. The workability of the proposed PIS is validated by SPICE simulations on three RLC prototypes
Experimental Demonstration of Continuous Variable Cloning with Phase-Conjugate Inputs
We report the experimental demonstration of continuous variable cloning of
phase conjugate coherent states as proposed by Cerf and Iblisdir (Phys. Rev.
Lett. 87, 247903 (2001)). In contrast to the proposal of Cerf and Iblisdir, the
cloning transformation is accomplished using only linear optical components,
homodyne detection and feedforward. Three clones are succesfully produced with
fidelities about 89%.Comment: 5 page
2+1 KdV(N) Equations
We present some nonlinear partial differential equations in 2+1-dimensions
derived from the KdV Equation and its symmetries. We show that all these
equations have the same 3-soliton structures. The only difference in these
solutions are the dispersion relations. We also showed that they pass the
Painlev\'e test.Comment: 15 page
Integrable discrete systems on R and related dispersionless systems
The general framework for integrable discrete systems on R in particular
containing lattice soliton systems and their q-deformed analogues is presented.
The concept of regular grain structures on R, generated by discrete
one-parameter groups of diffeomorphisms, through which one can define algebras
of shift operators is introduced. Two integrable hierarchies of discrete chains
together with bi-Hamiltonian structures are constructed. Their continuous limit
and the inverse problem based on the deformation quantization scheme are
considered.Comment: 19 page
Universal optical amplification without nonlinearity
We propose and experimentally realize a new scheme for universal
phase-insensitive optical amplification. The presented scheme relies only on
linear optics and homodyne detection, thus circumventing the need for nonlinear
interaction between a pump field and the signal field. The amplifier
demonstrates near optimal quantum noise limited performance for a wide range of
amplification factors.Comment: 5 pages, 4 figure
Why Levallois? A Morphometric Comparison of Experimental âPreferentialâ Levallois Flakes versus Debitage Flakes
Background
Middle Palaeolithic stone artefacts referred to as âLevalloisâ have caused considerable debate regarding issues of technological predetermination, cognition and linguistic capacities in extinct hominins. Their association with both Neanderthals and early modern humans has, in particular, fuelled such debate. Yet, controversy exists regarding the extent of âpredeterminationâ and âstandardizationâ in so-called âpreferential Levallois flakesâ (PLFs).
Methodology/Principal Findings
Using an experimental and morphometric approach, we assess the degree of standardization in PLFs compared to the flakes produced during their manufacture. PLFs possess specific properties that unite them robustly as a group or âcategoryâ of flake. The properties that do so, relate most strongly to relative flake thicknesses across their surface area. PLFs also exhibit significantly less variability than the flakes generated during their production. Again, this is most evident in flake thickness variables. A further aim of our study was to assess whether the particular PLF attributes identified during our analyses can be related to current knowledge regarding flake functionality and utility.
Conclusions/Significance
PLFs are standardized in such a manner that they may be considered âpredeterminedâ with regard to a specific set of properties that distinguishes them statistically from a majority of other flakes. Moreover, their attributes can be linked to factors that, based on current knowledge, are desirable features in flake tools (e.g. durability, capacity for retouch, and reduction of torque). As such, our results support the hypothesis that the lengthy, multi-phase, and hierarchically organized process of Levallois reduction was a deliberate, engineered strategy orientated toward specific goals. In turn, our results support suggestions that Levallois knapping relied on a cognitive capacity for long-term working memory. This is consistent with recent evidence suggesting that cognitive distinctions between later Pleistocene hominins such as the Neanderthals and anatomically modern humans were not as sharp as some scholars have previously suggested
Godel-type Metrics in Various Dimensions II: Inclusion of a Dilaton Field
This is the continuation of an earlier work where Godel-type metrics were
defined and used for producing new solutions in various dimensions. Here a
simplifying technical assumption is relaxed which, among other things,
basically amounts to introducing a dilaton field to the models considered. It
is explicitly shown that the conformally transformed Godel-type metrics can be
used in solving a rather general class of Einstein-Maxwell-dilaton-3-form field
theories in D >= 6 dimensions. All field equations can be reduced to a simple
"Maxwell equation" in the relevant (D-1)-dimensional Riemannian background due
to a neat construction that relates the matter fields. These tools are then
used in obtaining exact solutions to the bosonic parts of various supergravity
theories. It is shown that there is a wide range of suitable backgrounds that
can be used in producing solutions. For the specific case of (D-1)-dimensional
trivially flat Riemannian backgrounds, the D-dimensional generalizations of the
well known Majumdar-Papapetrou metrics of general relativity arise naturally.Comment: REVTeX4, 17 pp., no figures, a few clarifying remarks added and
grammatical errors correcte
Closed timelike curves and geodesics of Godel-type metrics
It is shown explicitly that when the characteristic vector field that defines
a Godel-type metric is also a Killing vector, there always exist closed
timelike or null curves in spacetimes described by such a metric. For these
geometries, the geodesic curves are also shown to be characterized by a lower
dimensional Lorentz force equation for a charged point particle in the relevant
Riemannian background. Moreover, two explicit examples are given for which
timelike and null geodesics can never be closed.Comment: REVTeX 4, 12 pages, no figures; the Introduction has been rewritten,
some minor mistakes corrected, many references adde
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