Adaptive MBER space-time DFE assisted multiuser detection for SDMA systems

In this contribution we propose a space-time decision feedback equalization (ST-DFE) assisted multiuser detection (MUD) scheme for multiple antenna aided space division multiple access systems. A minimum bit error rate (MBER) design is invoked for the MUD, which is shown to be capable of improving the achievable bit error rate performance over that of the minimum mean square error (MMSE) design. An adaptive MBER ST-DFE-MUD is proposed using the least bit error rate algorithm, which is demonstrated to consistently outperform the least mean square (LMS) algorithm, while achieving a lower computational complexity than the LMS algorithm for the binary signalling scheme. Simulation results demonstrate that theMBER ST-DFE-MUD is more robust to channel estimation errors as well as to error propagation imposed by decision feedback errors, compared to the MMSE ST-DFE-MUD

Minimum Bit-Error Rate Design for Space-Time Equalisation-Based Multiuser Detection

A novel minimum bit-error rate (MBER) space–time equalization (STE)-based multiuser detector (MUD) is proposed for multiple-receive-antenna-assisted space-division multiple-access systems. It is shown that the MBER-STE-aided MUD significantly outperforms the standard minimum mean-square error design in terms of the achievable bit-error rate (BER). Adaptive implementations of the MBER STE are considered, and both the block-data-based and sample-by-sample adaptive MBER algorithms are proposed. The latter, referred to as the least BER (LBER) algorithm, is compared with the most popular adaptive algorithm, known as the least mean square (LMS) algorithm. It is shown that in case of binary phase-shift keying, the computational complexity of the LBER-STE is about half of that required by the classic LMS-STE. Simulation results demonstrate that the LBER algorithm performs consistently better than the classic LMS algorithm, both in terms of its convergence speed and steady-state BER performance. Index Terms—Adaptive algorithm, minimum bit-error rate (MBER), multiuser detection (MUD), space–time processing

Following the relaxation dynamics of photoexcited aniline in the 273-266 nm region using time-resolved photoelectron imaging

Scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES) have been used to investigate the growth morphology of ultra-thin Pb films on the Ni3Al(111) face at room temperature. A previous study [K. Miśków and A. Krupski Appl Surf Sci 273, 2013, 554] using low-energy electron diffraction (LEED) and real time Auger intensity recording has demonstrated that an initial two-dimensional growth of the first Pb monolayer thick ‘wetting layer’ takes place. With further deposition and for T = 300 K, flat three atomic-layer-high islands are grown. Above 350 K, the Stranski–Krastanov growth mode was observed. In the current study, the analysis of STM measurements indicate and confirm that for coverage θ = 1.0 ML two-dimensional growth of the first Pb monolayer took place. Above θ > 1.0 ML, a three-dimensional growth of the Pb islands was observed with a strongly preferred atomic-scale ‘magic height (N),’ hexagonal shape and flat-tops. At coverage θ = 3.5 ML, only islands containing N = 3, 5, 7 and 11 atomic layers of Pb are observed. At the higher coverage θ = 5.5 ML, three types of regular hexagonal islands with side lengths of 25, 30 and 45 nm are observed. Furthermore, three different island adsorption configurations rotated by 10° ± 1° and 30° ± 6° with respect to each other were observed. After an annealing at T = 400 K of 5.5 ML of lead deposited at RT on the Ni3Al(111) the morphology of the surface changes. Post-anneal, islands of Pb are observed above the ‘wetting layer’ with an estimated average size and diameter of 768 ± 291 nm2 and 38.17 ± 6.56 nm and constant uniform height of two atomic layers (N = 2)

Speech and Gesture in Classroom Interaction: A Case Study of Angola and Portugal

Una de las principales razones por la cual los seres humanos usan el lenguaje es para comunicarse. Sus comunicaciones, sin embargo, no se realizan  de forma mecánica o robótica. Suele haber una sinergia entre el acto de habla y ciertas partes del cuerpo. En la medida que se producen enunciados hablados, se mueven estas partes corporales produciendo así acciones que son visibles, denominadas ‘acciones corporales visibles’. Estas acciones corporales visibles suelen ejecutarse con distintas partes del cuerpo. Se utiliza el término ‘gestos’ para referirse al movimiento de los miembros superiores del cuerpo. Estos gestos están vinculados más directamente con el habla. Sin importar su edad, nacionalidad, cultura, antecedentes o etnia, los seres humanos, cuando hablan, hacen gestos de forma natural y ubicua. Estos movimientos revelan mucho de sus pensamientos, objetivos, creencias e intereses, entre otros. A la luz de lo anteriormente mencionado, esta investigación pretende comparar descriptivamente el habla y el gesto en dos contextos distintos con dos métodos didácticos diferentes (Angola y Portugal). Se revisan unos metrajes de video de los contextos de interacción —con estudiantes adolescentes y profesores— y se lleva a cabo un análisis descriptivo comparativo general. Por medio del software ELAN, se efectúa un microanálisis de 30 segundos de cada uno de los contextos de interacción. Se presentan algunas conclusiones basadas en el estudio realizado

The Meaning of Collaborative Research

Summary This article examines the prospects for inter?country collaborative research between academic institutions of greatly varying experience and resources, and notes the case for unilateral action by research institutes in poor countries which have suffered the domination of rich and powerful foreign research interests. Some criteria are suggested for assessing the readiness of research institutions in any part of the world to cooperate effectively. The question is left open as to whether we possess or are likely to acquire the capacity to collaborate successfully across barriers of history and contemporary events. Resume Signification de la recherche en collaboration Cet article examine les perspectives relatives à la recherche inter?pays impliquant la collaboration d'institutions académiques ayant une expérience et des ressources extrémement variées, et il cite l'argument en faveur de l'action unilatérale par des instituts de recherche dans les pays pauvres qui ont subi la domination d'intérêts de recherche étrangers riches et puissants. Plusieurs critères sont suggérés pour déterminer si les institutions de recherche en n'importe quel coin du monde sont prêtes à collaborer efficacement. Il n'est pas donné de réponse à la question de savoir si nous avons ou sommes susceptibles d'acquérir l'aptitude à collaborer efficacement malgré les barrières de l'histoire et des événements contemporaines. Resumen El significado de la investigación colaborativa En el artículo se examinan las perspectivas para la investigación colaborativa entre países, a través de las instituciones académicas de experiencia y recursos muy variables, y pone de relieve la oportunidad de adoptar una acción unilateral por parte de institutos de investigación en países pobres que han sufrido el dominio de intereses de investigación extranjera potentes y ricos. Se sugieren ciertos criterios para evaluar la preparación de las instituciones de investigación en cualquier parte del mundo con objeto de cooperar de manera eficaz. Queda por saber si poseemos o es probable que consigamos adquirir la capacidad de colaborar con éxito a través de barreras históricas y acontecimientos contemporáneos

Fast iterative solvers for geomechanics in a commercial FE code

There is a pressing need to improve the feasibility of three-dimensional finite element (FE) methods applied to many problems in civil engineering. This is particularly the case for static analyses in geotechnical engineering: ideally, models would be 3D, follow the actual geometry, use non-linear material formulations and allow simulation of construction sequences, and all of this with a reasonable degree of accuracy. One major obstacle to improvements in this regard is the difficulty in solving of the set of (linearised) algebraic equations which arises from a typical discretisation approach. Very large systems become cumbersome for direct techniques to solve economically. This paper describes the incorporation of iterative (rather than direct) solution techniques, developed through University research, into commercial FE software for geotechnics

Ultrafast molecular dynamics of model biological systems

Femtosecond time resolved photoelectron imaging spectroscopy equipment was designed, constructed, and used to reveal the non-adiabatic dynamics of model biological systems. Indole and phenol derivatives were studied as models for eumelanin, a pigment found in humans designed to protect the body from ultraviolet radiation. The photo-dynamics of these molecules was studied after excitation with ultraviolet radiation, with particular emphasis on the effect that the hydroxyl groups have on the p * dissociative state. It was found that adding a hydroxyl group onto indole to create 5-hydroxyindole had little significant effect on the photodynamics at the excitation wavelengths studied. Adding a second hydroxyl group to phenol had a strongly marked effect only when the hydroxyl groups were in close proximity to each other, in which case it dramatically increased the relaxation rate. An ultrafast optical system, imaging photoelectron spectrometer, and software to control the hardware, and collect and analyse photoelectron data were successfully implemented and used to collect and analyse data. This system will be of use for many more years and will be the basis of much future research.Engineering and Physical Sciences Research Council (EPSRC