Accurate and efficient evaluation of bit error rate for dynamic directional modulation for standard modulation schemes

Directional modulation (DM) has been proposed as a technique to enhance physical layer security of wireless transmissions. In DM, the improvement of security is achieved by increasing the transmitted power in such a way that the bit error rate (BER) is degraded in the observation angles out of the desired secure direction. The performance of DM in terms of BER is typically evaluated by transmitting a stream of symbols for every observation angle, but this approach can be time consuming. In this communication, we propose an approach to evaluate, accurately and efficiently, the BER of dynamic DM (DDM) for standard modulation schemes. Several DDM configurations will be tested to illustrate the benefits and limitations of the evaluation method. The proposed approach is also used to present a non-iterative DDM synthesis with restrictions in the BER response

LEAN maintenance model based on change management allowing the reduction of delays in the production line of textile SMEs in Peru

This article examines the problem of production line delays in a textile small- and medium-sized enterprise (SME) that produces polyester fibre from recycled bottles, based on orders. Factors that have resulted in production line delays include prolonged unscheduled maintenance time, and preparations and adjustments prior to operating the equipment. To address the problem, a model was developed applying lean manufacturing tools through change management, with the aim of increasing equipment availability and useful life. To validate the model, a pilot was developed to determine how the increase in equipment availability helps reduce delays in the production line, which eventually improves completion of customer orders

Transient quantum evolution of 2D electrons under photoexcitation of a deep center

We have considered the ballistic propagation of the 2D electron Wigner distribution, which is excited by an ultrashort optical pulse from a short-range impurity into the first quantized subband of a selectively-doped heterostructure with high mobility. Transient ionization of a deep local state into a continuum conduction c-band state is described. Since the quantum nature of the photoexcitation, the Wigner distribution over 2D plane appears to be an alternating-sign function. Due to a negative contribution to the Wigner function, the mean values (concentration, energy, and flow) demonstrate an oscillating transient evolution in contrast to the diffusive classical regime of propagation.Comment: 8 pages, 6 figures, pape

Arteriovenous uterine malformation: case report

The case of a 49-year-old patient is reported, with a particular history of obstetric risk, who presented with severe transvaginal hemorrhage, was performed doppler arteriography and ultrasound, finding data suggestive of arteriovenous uterine malformation, surgery was decided due to heavy menstrual bleeding with anemia, the pathology report shows characteristics of an arteriovenous uterine malformation

Theoretical study of incoherent phi photoproduction on a deuteron target

We study the photoproduction of phi mesons in deuteron, paying attention to the modification of the cross section from bound protons to the free ones with the aim of comparing with recent results at LEPS. For this purpose we take into account Fermi motion in single scattering and rescattering of the phi to account for phi absorption on a second nucleon as well as the rescattering of the proton. We find that the contribution of the double scattering is much smaller than the typical cross section of gamma p to phi p in free space, which implies a very small screening of the phi production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligible compared to the cross section of gamma p to phi p in free space, and leads to a moderate reduction of the phi photoproduction cross section on a deuteron at forward angles if LEPS set up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden by phase space in the free case. In particular, we find that for momentum transferred squared close to the maximum value, the Fermi motion changes drastically the shape of d sigma / dt, to the point that the ratio of this cross section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem the most indicated to find effects of a possible phi absorption in the deuteron. This reaction is studied theoretically as a function of t and the effect of the experimental angular cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction.Comment: 17 pages, 16 figure

The spinorial geometry of supersymmetric backgrounds

We propose a new method to solve the Killing spinor equations of eleven-dimensional supergravity based on a description of spinors in terms of forms and on the Spin(1,10) gauge symmetry of the supercovariant derivative. We give the canonical form of Killing spinors for N=2 backgrounds provided that one of the spinors represents the orbit of Spin(1,10) with stability subgroup SU(5). We directly solve the Killing spinor equations of N=1 and some N=2, N=3 and N=4 backgrounds. In the N=2 case, we investigate backgrounds with SU(5) and SU(4) invariant Killing spinors and compute the associated spacetime forms. We find that N=2 backgrounds with SU(5) invariant Killing spinors admit a timelike Killing vector and that the space transverse to the orbits of this vector field is a Hermitian manifold with an SU(5)-structure. Furthermore, N=2 backgrounds with SU(4) invariant Killing spinors admit two Killing vectors, one timelike and one spacelike. The space transverse to the orbits of the former is an almost Hermitian manifold with an SU(4)-structure and the latter leaves the almost complex structure invariant. We explore the canonical form of Killing spinors for backgrounds with extended, N>2, supersymmetry. We investigate a class of N=3 and N=4 backgrounds with SU(4) invariant spinors. We find that in both cases the space transverse to a timelike vector field is a Hermitian manifold equipped with an SU(4)-structure and admits two holomorphic Killing vector fields. We also present an application to M-theory Calabi-Yau compactifications with fluxes to one-dimension.Comment: Latex, 54 pages, v2: clarifications made and references added. v3: minor changes. v4: minor change

Finance, foreign (direct) investment, and the Dutch disease: the case of Colombia

In recent years Colombia has grown relatively rapidly, but it has been a biased growth. The energy sector (the locomotora minero-energetica, to use the rhetorical expression of President Juan Manuel Santos) grew much faster than the rest of the economy, while the manufacturing sector registered a negative rate of growth. These are classic symptoms of the well-known ‘Dutch disease’, but our purpose here is not to establish whether the Dutch disease exists or not, but rather to shed some light on the financial viability of several, simultaneous dynamics: (i) the existence of a traditional Dutch Disease being due to a large increase in mining exports and a significant exchange rate appreciation; (ii) a massive increase in foreign direct investment (FDI), particularly in the mining sector; (iii) a rather passive monetary policy, aimed at increasing purchasing power via exchange rate appreciation; (iv) more recently, a large distribution of dividends from Colombia to the rest of the world and the accumulation of mounting financial liabilities. The paper will show that these dynamics constitute a potential danger for the stability of the Colombian economy. Some policy recommendations are also discussed

VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory

VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l. in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design, construction techniques and data acquisition system of the HAWC observatory. HAWC is an air-shower array currently under construction at the same site of VAMOS with the purpose to study the TeV sky. The VAMOS setup included six water Cherenkov detectors and two different data acquisition systems. It was in operation between October 2011 and May 2012 with an average live time of 30%. Besides the scientific verification purposes, the eight months of data were used to obtain the results presented in this paper: the detector response to the Forbush decrease of March 2012, and the analysis of possible emission, at energies above 30 GeV, for long gamma-ray bursts GRB111016B and GRB120328B.Comment: Accepted for pubblication in Astroparticle Physics Journal (20 pages, 10 figures). Corresponding authors: A.Marinelli and D.Zaboro