207 research outputs found
Efficient Synthesis of Room Acoustics via Scattering Delay Networks
An acoustic reverberator consisting of a network of delay lines connected via
scattering junctions is proposed. All parameters of the reverberator are
derived from physical properties of the enclosure it simulates. It allows for
simulation of unequal and frequency-dependent wall absorption, as well as
directional sources and microphones. The reverberator renders the first-order
reflections exactly, while making progressively coarser approximations of
higher-order reflections. The rate of energy decay is close to that obtained
with the image method (IM) and consistent with the predictions of Sabine and
Eyring equations. The time evolution of the normalized echo density, which was
previously shown to be correlated with the perceived texture of reverberation,
is also close to that of IM. However, its computational complexity is one to
two orders of magnitude lower, comparable to the computational complexity of a
feedback delay network (FDN), and its memory requirements are negligible
The effect of lipophilicity on the antibacterial activity of some 1-benzylbenzimidazole derivatives
In the present paper, the antibacterial activity of some 1-benzylbenzimidazole derivatives were evaluated against the Gram-negative bacteria Escherichia coli. The minimum inhibitory concentration was determined for all the compounds. Quantitative structure–activity relationship (QSAR) was employed to study the effect of the lipophilicity parameters (log P) on the inhibitory activity. Log P values for the target compounds were experimentally determined by the “shake-flask” method and calculated by using eight different software products. Multiple linear regression was used to correlate the log P values and antibacterial activity of the studied benzimidazole derivatives. The results are discussed based on statistical data. The most acceptable QSAR models for the prediction of the antibacterial activity of the investigated series of benzimidazoles were developed. High agreement between the experimental and predicted inhibitory values was obtained. The results of this study indicate that the lipophilicity parameter has a significant effect on the antibacterial activity of this class of compounds, which simplifies the design of new biologically active molecules
The influence of heat input on the toughness and fracture mechanism of surface weld metal
© 2018 The Authors. Surface welding is a way to extend the exploitation life of damaged parts and constructions and the heat input has a major influence on the weldment properties. In this paper is shown the influence of the heat input on the toughness and the fracture mechanism of the surface welded joint. Surface welding of high carbon steel with self shielded wire was conducted with three different heat inputs (6kJ/cm, 10 kJ/cm and 16 kJ/cm). Total impact energy, crack initiation and crack propagation energy were estimated at room temperature, -20 o C and -40 o C. Fracture analysis of fractured surfaces was also conducted and it has been found that increasing of heat input leads to an increase of share of transgranular brittle fracture, what is in complete accordance with the obtained energy values. Based on all obtained results, the optimum value of heat input for welding procedure applied was defined
Application of semidefinite programming to maximize the spectral gap produced by node removal
The smallest positive eigenvalue of the Laplacian of a network is called the
spectral gap and characterizes various dynamics on networks. We propose
mathematical programming methods to maximize the spectral gap of a given
network by removing a fixed number of nodes. We formulate relaxed versions of
the original problem using semidefinite programming and apply them to example
networks.Comment: 1 figure. Short paper presented in CompleNet, Berlin, March 13-15
(2013
Identification and Characterization of Potential Discharge Areas for Radionuclide Transport by Groundwater from a Nuclear Waste Repository in Sweden
Altérations athéroscléreuses de l’artère dentaire inférieure en corrélation avec celles de la bifurcation carotidienne et de l’aorte abdominale
50 corpses from adults aged 20 to 75 have been used in order to study the atherosclerotic lesions occurring in typical regions (bifurcation of the common carotid artery and the abdominal aorta) and their relationship to atherosclerotic changes in the inferior alveolar artery. Histological analysis revealed that atherosclerotic alterations of the inferior alveolar artery may appear sometimes earlier than it would be expected on the ground of age. Intima cell proliferation and thickening of elastic elements in the middle layer of the arterial wall, the first signs of atherosclerosis, were found already at the beginning of the third decade of life when the signs of this process in the typical regions were not yet evident. Atherosclerosis affects essentially the functional capacity of the inferior alveolar artery. The development of atherosclerosis in the wall of this artery favours an hypovascularization of the mandible, which must be of certain importance in every operative procedure in oral surgery, especially in those inducing a severe and long traumatism in bone and soft tissues, such as dental implantations.Cette étude, faite sur 50 cadavres (de 20 à 75 ans) concerne les altérations athéroscléreuses de l’artère dentaire inférieure et leurs rapports avec les altérations athéroscléreuses dans les territoires typiques (bifurcation carotidienne et aorte abdominale). L’examen histologique a fait apparaître que les altérations athéroscléreuses de l’artère dentaire inférieure peuvent être relativement plus évidentes et précoces que l’on ne s’y attendrait compte tenu de l’âge. Une prolifération cellulaire de l’intima et un épaississement de la lame élastique moyenne dans la paroi artérielle, premiers signes de l’athérosclérose, peuvent apparaître dès30 ans, alors que l’on ne trouve pas encore d’altérations de ce type dans les territoires typiques. L’athérosclérose a une influence cruciale sur la capacité fonctionnelle de l’artère dentaire inférieure puisque celle-ci chemine dans le canal osseux, qui empêche sa dilatation. Le développement de l’athérosclérose dans la paroi de cette artère favorise une hypovascularisation de la mandibule, ce qui a une importance certaine lors de toute intervention en chirurgie orale, surtout lorsqu’elle entraîne un traumatisme grave et prolongée de l’os et des parties molles, comme c’est le cas lors de l’insertion d’implants dentaires
Anatomie chirurgicale de la glande sublinguale
Because of its position, the sublingual gland is clinically important especially in the events of injuries and infections in the anterior part of the sublingual region.The morphology and relationships of this gland were studied by dissection methods applied on 80 fresh or formaldehyde fixed preparations of the mouth floor and of the tongue, which were partly (31 preparations) taken out together with the mandible.As for the shape of the gland, three main types were found: 1° the cuneiform type which was the most frequent (71 %), 2° the pyramidal type which was less frequent (16%) and the fusiform type (13%) which comprised the cases of a very elongated gland (up to 65 mm).The space in which the gland lied had four walls. Its internal wall consisted of the mylohyoid muscle and it comprised the hyoglossus muscle as well when the gland was very elongated. The inferior wall consisted of the mylohyoid muscle and sometimes it comprised also a narrow part of the superior surface of the geniohyoglossus muscle. An osseous depression on the internal side of the mandible represented the external wall of the sublingual gland space. The superior wall is clinically the most significant. It consists of the sublingual mucosa and a sublingual fold. This wall represents a main surgical access to the gland. In edentulous mandibles this mucous fold may be at the level of the upper mandibular border which may hinder the use of the lower dental prosthesis.La morphologie et les rapports de la glande sublinguale ont été étudiés par 80 dissections du plancher de la bouche et de la langue.Trois types différents de glandes ont été définis du point de vue forme: le type cunéiforme (71%), le type pyramidal (16%) et le type fusiforme (13%).La loge de la glande sublinguale possède quatre parois: deux (parois inférieure et interne) de nature musculaire, une (paroi externe) de nature osseuse et une (paroi supérieure) de nature muqueuse
Spectral Simplicity of Apparent Complexity, Part I: The Nondiagonalizable Metadynamics of Prediction
Virtually all questions that one can ask about the behavioral and structural
complexity of a stochastic process reduce to a linear algebraic framing of a
time evolution governed by an appropriate hidden-Markov process generator. Each
type of question---correlation, predictability, predictive cost, observer
synchronization, and the like---induces a distinct generator class. Answers are
then functions of the class-appropriate transition dynamic. Unfortunately,
these dynamics are generically nonnormal, nondiagonalizable, singular, and so
on. Tractably analyzing these dynamics relies on adapting the recently
introduced meromorphic functional calculus, which specifies the spectral
decomposition of functions of nondiagonalizable linear operators, even when the
function poles and zeros coincide with the operator's spectrum. Along the way,
we establish special properties of the projection operators that demonstrate
how they capture the organization of subprocesses within a complex system.
Circumventing the spurious infinities of alternative calculi, this leads in the
sequel, Part II, to the first closed-form expressions for complexity measures,
couched either in terms of the Drazin inverse (negative-one power of a singular
operator) or the eigenvalues and projection operators of the appropriate
transition dynamic.Comment: 24 pages, 3 figures, 4 tables; current version always at
http://csc.ucdavis.edu/~cmg/compmech/pubs/sdscpt1.ht
Performance Modeling of Fresnel-Based CPV Systems: Effects of Deformations under Real Operation Conditions
Getting a lower energy cost has always been a challenge for concentrated photovoltaic. The FK concentrator enhances the performance (efficiency, acceptance angle and manufacturing tolerances) of the conventional CPV system based on a Fresnel primary stage and a secondary lens, while keeping its simplicity and potentially low‐cost manufacturing. At the same time F‐XTP (Fresnel lens+reflective prism), at the first glance has better cost potential but significantly higher sensitivity to manufacturing errors. This work presents comparison of these two approaches applied to two main technologies of Fresnel lens production (PMMA and Silicone on Glass) and effect of standard deformations that occur under real operation condition
Importance of Itinerancy and Quantum Fluctuations for the Magnetism in Iron Pnictides
By applying density functional theory, we find strong evidence for an
itinerant nature of magnetism in two families of iron pnictides. Furthermore,
by employing dynamical mean field theory with continuous time quantum Monte
Carlo as an impurity solver, we observe that the antiferromagnetic metal with
small magnetic moment naturally arises out of coupling between unfrustrated and
frustrated bands. Our results point to a possible scenario for magnetism in
iron pnictides where magnetism originates from a strong instability at the
momentum vector (, , ) while it is reduced by quantum
fluctuations due to the coupling between weakly and strongly frustrated bands.Comment: 4 pages, 4 figure
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