7,283 research outputs found
Ultrahigh dielectric constant of thin films obtained by electrostatic force microscopy and artificial neural networks
Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.A detailed analysis of the electrostatic interaction between an electrostatic force microscope tip and a thin film is presented. By using artificial neural networks, an equivalent semiinfinite sample has been described as an excellent approximation to characterize the whole thin film sample. A useful analytical expression has been also developed. In the case of very small thin film thicknesses (around 1 nm), the electric response of the material differs even for very high dielectric constants. This effect can be very important for thin materials where the finite size effect can be described by an ultrahigh thin filmdielectric constant.This work was supported by TIN2010-196079. G.M.S. acknowledges support from the Spanish Ramón y Cajal Program
\u3ci\u3eOn the Sacred Disease\u3c/i\u3e: The Historical Significance of Hippocratic Humanism, Rationality and Scientific Procedure
Although many of the Hippocratic Corpus\u27 anatomical, physiological and pathological doctrines have since been superseded, the premise of On the Sacred Disease - that disease is of a physical origin - stimulated the rise of rational, secular, and systematic medicine over magico-religious healing and the recognition of medicine as a true techne, or science. Before the time of Hippocrates, \u27pre-scientific\u27 Western medicine was predominantly magico-religious or characterized by magic-based appeals to supernatural beings. In On the Sacred Disease, however, Hippocrates attributes disease to both internal and external factors. Further holding that prognosis should be based on thorough examination, Hippocrates required highly detailed and meticulous clinical observations of his patients. After extensive studying of the work of Hippocrates, second century practitioner Galen argued in On Medical Experience that truth can be obtained only by means of reason in conjunction with experience, because expectation founded on reason alone is likely to be fruitless and misleading. As such, through its contributions to medical practicum and the scientific method, Hippocrates\u27 On the Sacred Disease remains as relevant in contemporary Westem society as it was over two millennia ago on the-Greek island of Cos
A Note on Charles Williams’ \u3ci\u3eThe Place of the Lion\u3c/i\u3e
Considers why Williams refers to a non-existent Gnostic tradition in a conversation between Anthony and Mr. Richardson. Is this mere error or purposeful
Nonlinear envelope equation for broadband optical pulses in quadratic media
We derive a nonlinear envelope equation to describe the propagation of
broadband optical pulses in second order nonlinear materials. The equation is
first order in the propagation coordinate and is valid for arbitrarily wide
pulse bandwidth. Our approach goes beyond the usual coupled wave description of
phenomena and provides an accurate modelling of the evolution of
ultra-broadband pulses also when the separation into different coupled
frequency components is not possible or not profitable
Intellectual Capacities of Chronic Alcoholics
It is the purpose of this paper to present the results of an investigation of the mental capacities of a group of forty chronic hospitalised male alcoholics, and to describe the special mental abilities and deficiencies that were uncovered by the use of the Wechsler-Bellevue Intelligence Scale
Constructive Multiuser Interference in Symbol Level Precoding for the MISO Downlink Channel
This paper investigates the problem of interference among the simultaneous
multiuser transmissions in the downlink of multiple antennas systems. Using
symbol level precoding, a new approach towards the multiuser interference is
discussed along this paper. The concept of exploiting the interference between
the spatial multiuser transmissions by jointly utilizing the data information
(DI) and channel state information (CSI), in order to design symbol-level
precoders, is proposed. In this direction, the interference among the data
streams is transformed under certain conditions to useful signal that can
improve the signal to interference noise ratio (SINR) of the downlink
transmissions. We propose a maximum ratio transmission (MRT) based algorithm
that jointly exploits DI and CSI to glean the benefits from constructive
multiuser interference. Subsequently, a relation between the constructive
interference downlink transmission and physical layer multicasting is
established. In this context, novel constructive interference precoding
techniques that tackle the transmit power minimization (min power) with
individual SINR constraints at each user's receivers is proposed. Furthermore,
fairness through maximizing the weighted minimum SINR (max min SINR) of the
users is addressed by finding the link between the min power and max min SINR
problems. Moreover, heuristic precoding techniques are proposed to tackle the
weighted sum rate problem. Finally, extensive numerical results show that the
proposed schemes outperform other state of the art techniques.Comment: Submitted to IEEE Transactions on Signal Processin
Symbol Based Precoding in The Downlink of Cognitive MISO Channels
This paper proposes symbol level precoding in the downlink of a MISO
cognitive system. The new scheme tries to jointly utilize the data and channel
information to design a precoding that minimizes the transmit power at a
cognitive base station (CBS); without violating the interference temperature
constraint imposed by the primary system. In this framework, the data
information is handled at symbol level which enables the characterization the
intra-user interference among the cognitive users as an additional source of
useful energy that should be exploited. A relation between the constructive
multiuser transmissions and physical-layer multicast system is established.
Extensive simulations are performed to validate the proposed technique and
compare it with conventional techniques.Comment: CROWNCOM 201
Non-linear frequency and amplitude modulation of a nano-contact spin torque oscillator
We study the current controlled modulation of a nano-contact spin torque
oscillator. Three principally different cases of frequency non-linearity
( being zero, positive, and negative) are investigated.
Standard non-linear frequency modulation theory is able to accurately describe
the frequency shifts during modulation. However, the power of the modulated
sidebands only agrees with calculations based on a recent theory of combined
non-linear frequency and amplitude modulation.Comment: 4 pages, 4 figure
Intelligent search for distributed information sources using heterogeneous neural networks
As the number and diversity of distributed information sources on the Internet exponentially increase, various search services are developed to help the users to locate relevant information. But they still exist some drawbacks such as the difficulty of mathematically modeling retrieval process, the lack of adaptivity and the indiscrimination of search. This paper shows how heteroge-neous neural networks can be used in the design of an intelligent distributed in-formation retrieval (DIR) system. In particular, three typical neural network models - Kohoren's SOFM Network, Hopfield Network, and Feed Forward Network with Back Propagation algorithm are introduced to overcome the above drawbacks in current research of DIR by using their unique properties. This preliminary investigation suggests that Neural Networks are useful tools for intelligent search for distributed information sources
Infinite non-causality in active cancellation of random noise
Active cancellation of broadband random noise requires the detection of the
incoming noise with some time advance. In an duct for example this advance must
be larger than the delays in the secondary path from the control source to the
error sensor. In this paper it is shown that, in some cases, the advance
required for perfect noise cancellation is theoretically infinite because the
inverse of the secondary path, which is required for control, can include an
infinite non-causal response. This is shown to be the result of two mechanisms:
in the single-channel case (one control source and one error sensor), this can
arise because of strong echoes in the control path. In the multi-channel case
this can arise even in free field simply because of an unfortunate placing of
sensors and actuators. In the present paper optimal feedforward control is
derived through analytical and numerical computations, in the time and
frequency domains. It is shown that, in practice, the advance required for
significant noise attenuation can be much larger than the secondary path
delays. Practical rules are also suggested in order to prevent infinite
non-causality from appearing
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