Reception Mechanism Research Articles

Stable Throughput Region of the Two-User Broadcast Channel

In this paper, we consider the two-user broadcast channel and we characterize its stable throughput region. We start the analysis by providing the stability region for the general case without any specific considerations on transmission and reception mechanisms. We also provide conditions for the stable throughput region to be convex. Subsequently, we study the case where the transmitter uses superposition coding and we consider two special cases for the receivers. The first one is when both receivers treat interference as noise. The second is when the user with a better channel uses successive decoding and the other receiver treats interference as noise.

Energy-Efficient Resource Scheduling Within DRX Cycles for LTE-A Networks With Carrier Aggregation

For the future-generation wireless communications, the carrier aggregation (CA) of third generation partnership project (3GPP) long-term evolution-advanced (LTE-A) is one of the most promising technologies, which can support significant high data rates over wide frequency bandwidths for various real-time services/applications. To reduce the energy consumption, the LTE-A standard defines the discontinuous reception (DRX) mechanism that allows user equipments (UEs) to turn off radio interfaces when no data is expected to be received. However, how to allocate resource optimally within the DRX cycle for UEs with the CA technology is still an open issue. In this paper, we address the resource scheduling with CA within the DRX cycle, with an objective that maximizes the spectrum utilization while minimizes UE wake-up time. We formulate this problem and propose an energy-efficient iterative heuristic. Our scheme consists of two phases; the first phase determines the scheduling order of component carriers (CCs) to improve the resource efficiency, whereas the second phase minimizes UEs’ unnecessary wake-up periods by optimizing their resource intervals from different CCs. Extensive simulation results show that our scheduling achieves better performance than the existing schemes.

Exploring Flexibility of DRX in LTE/LTE-A: Design of Dynamic and Adjustable DRX

Only two types of sleep cycles with two fixed sleep periods are defined in the standard of the discontinuous reception (DRX) mechanism in LTE/LTE-A. Explicitly, such a DRX mechanism is simple but lacks flexibility. To provide flexibility, two types of dynamic and adjustable DRX (DADRX) mechanisms are proposed and investigated in this paper. The first type of DADRX extends the number of types of sleep cycles through adding different pairs of sleep cycles with different sleep periods gradually. As for the second type of DADRX, it fixes the total number of types of sleep cycles like the first-type DADRX but further employs a set of level expanding probabilities to control probabilistically the possible pairs of sleep cycles that can be reached. To enable the analytical calculation, performance metrics for the proposed DADRX mechanisms are acquired, including average response delay and average long-term power consumption. Via both analytical and simulation approaches, we investigate the dynamics of performance for the proposed DADRX mechanisms extensively. We successfully show that these two proposed mechanisms can exhibit much more flexibility than the closely related mechanisms in the literature.

Розробка та розрахунок кінематичної схеми механізму для одержання короткого льоноволокна

Розробка та розрахунок кінематичної схеми механізму для одержання короткого льоноволокна

Influence of leading-edge curvature on excited unsteady cross-flow vortices in three-dimensional boundary-layer

Three-dimensional boundary-layer receptivity is the first stage of the laminar-turbulent transition in a three-dimensional boundary layer, and also a key issue for predicting and controlling the laminar-turbulent transition in the three-dimensional boundary layer. At a high turbulence level, the three-dimensional boundary-layer instability in the transition is caused mainly by the unsteady cross-flow vortices. And the leading-edge curvature has a significant influence on three-dimensional boundary-layer receptivity. In view of this, the direct numerical simulation is utilized in this paper to study the mechanism of receptivity to exciting unsteady cross-flow vortices in the three-dimensional (swept-plate) boundary layer with various elliptic leading edges. In order to solve the Navier-Stokes equation numerically, a modified fourth-order Runge-Kutta scheme is introduced for discretization in time; high-order compact finite difference schemes are utilized for discretization in the x-and y-direction; and Fourier transform is used in the z-direction. The pressure Helmholtz equation is solved by a fourth-order iterative scheme. Additionally, the numerical calculation is performed in the curvilinear coordinate system via Jaccobi transform. And the elliptic equation technique is used to gene-rate the body-fitted mesh. The effect of leading-edge curvature on the propagation speed and direction, distribution and receptivity coefficient of the excited unsteady cross-flow vortex wave packet, and the amplitude, dispersion relation and growth rate of the extracted unsteady cross-flow vortex are revealed. In addition, the inner link among the receptivity to unsteady cross-flow vortex, intensity, and direction of free-stream turbulence is established. Furthermore, the receptivity to anisotropic free-stream turbulence is also analyzed in detail. The numerical results indicate that the more intense receptivity to the unsteady cross-flow vortex wave packets is triggered with a smaller leading-edge curvature; whereas, the less intense receptivity is triggered with a greater leading-edge curvature. The receptivity to the unsteady cross-flow vortex wave packets in different curvatures are also found to vary with the angle of free-stream turbulence. Moreover, the anisotropic degree of free-stream turbulence can affect the excitation of the unsteady cross-flow vortex obviously. Through the above study, a further step can be taken to understand the prediction and control of laminar-turbulent transition in the three-dimensional boundary layer and also improve the theory of the hydrodynamic stability.

A Boundary-Layer Receptivity Mechanism Excited by the Interaction Between Free-Stream Turbulence and the Three-Dimensional Localized Wall Roughness

A Boundary-Layer Receptivity Mechanism Excited by the Interaction Between Free-Stream Turbulence and the Three-Dimensional Localized Wall Roughness

Analysis of Signal Reception Mechanism of Sky Wave Long-distance Maritime Communication

Based on the principle of high frequency radio propagation, the signal reception mechanism of sky wave communication over oceans is investigated. Due to long distance signal transmission, the energy loss is inevitable, especially in the space and on the sea surface. Firstly, we establish the space propagation loss model by the ionospheric absorption, the free space propagation characteristics and other extra loss. Referring to the reflection principle of smooth ground and the Kirchhoff approximation, the energy loss models of the calm sea surface and the turbulent sea surface are obtained respectively. Then, through combining the space propagation loss model and the sea surface propagation loss models, we give out a formula of receiving point field strength. According to the signal to noise ratio, we summarize a complete and concise sky wave maritime communication calculation process, through which multi hops number of the receivable sky wave signal can be calculated accurately. The experimental results show the effectiveness.

“Mi casa es esta pieza”: migración femenina y precariedad habitacional en la Ciudad de Buenos Aires

El objetivo de este artí­culo es analizar, por un lado, el escenario migratorio de nueve mujeres y sus familias tomando en consideración las motivaciones de la migración y el proceso de desplazamiento desde sus lugares de origen hacia la Ciudad de Buenos Aires y, por otro lado, el proceso de integración en la sociedad receptora desde su residencia en hoteles-pensión de la ciudad capital. Esta modalidad del hábitat popular urbano, junto con los conventillos, inquilinatos, villas miseria, asentamientos y casas tomadas pone de relieve la precariedad habitacional de la ciudad. Se realizaron entrevistas en profundidad y observaciones participantes en los hoteles-pensión.Uno de los resultados obtenidos es que la ausencia de propuestas integradoras de polí­tica habitacional dirigidas a los sectores populares, sobre todo migrantes internos y de paí­ses limí­trofes, incide en la falta de acceso a la vivienda digna. En este sentido, el Estado se desentiende en cuanto a polí­ticas habitacionales destinadas a la integración. Las mujeres migrantes entrevistadas han sido seducidas y atraí­das por los beneficios que otorga la gran ciudad y simultáneamente abandonadas por el Estado, pues los mecanismos de recepción y albergue son sumamente escasos. No sólo se les niega el derecho a la ciudad sino también se las despoja del derecho a una vivienda digna y se las “condena” a vivir en viviendas precarias o en los márgenes de la ciudad.

Systematic study of distributed excitation of unsteady Görtler modes by freestream vortices

The paper is devoted to experimental investigation of an efficient mechanism of distributed excitation of nonstationary Görtler vortices in a boundary layer on concave wall due to scattering of three-dimensional, streamwise oriented freestream vortices on natural two-dimensional base-flow nonuniformity associated with the boundary layer growth. The investigations are performed in a broad range of disturbance frequencies and spanwise wavenumbers. The measurements have shown that the distributed receptivity mechanism is able to modify significantly the disturbance growth rates. This mechanism is found to be able to compete successfully with the linear instability mechanism. It is found that at relatively low frequencies and not too large freestream disturbance amplitudes, the Görtler modes’ development is dominated basically by the corresponding linear instability mechanism. Meanwhile, this mechanism becomes weaker with growth of frequency and, simultaneously, the distributed receptivity mechanism gets stronger. This leads to enhancement of role of the latter in amplification of Görtler instability modes, and at high frequencies the role of the distributed receptivity mechanism becomes very important and often even decisive one. Based on deep processing of the experimental data, quantitative values of the distributed linear receptivity coefficients are obtained for the case of excitation of unsteady Görtler modes and estimated for the case of steady Görtler vortices by means of extrapolation to the zero frequency. A complementary experiment devoted to investigation of the problem of linear unsteady Görtler instability is performed for the particular conditions of the distributed receptivity experiments. All main stability characteristics are obtained and compared with calculated ones. In general, the experimental information presented in this paper can be used for verification of various instability and vortex receptivitytheories.

A política de acolhimento de refugiados - considerações sobre o caso Português

Resumo A eclosão de conflitos armados e civis no Médio Oriente, bem como a expansão do autoproclamado Estado Islâmico provocou um fluxo considerável de refugiados com destino ao espaço comunitário europeu, sendo a maior vaga migratória desde a II Guerra Mundial. A atratividade do espaço europeu, associado às políticas de acolhimento, constitui o ponto de partida para esta análise que incide sobre os mecanismos de acolhimento registados pelo Estado Português. Através de um estudo iminentemente exploratório e recorrendo ao método de análise descritiva, optámos por analisar as estratégias de acolhimento, bem como os dados existentes sobre os processos em vigor em Portugal, considerando igualmente uma visão comparativa com os demais Estados-membros da União Europeia.

A Batch Packet Server (BPS) Based Discontinuous Reception Mechanism for Energy Saving

LTE/LTE-A systems have specified a discontinuous reception (DRX) mechanism for battery energy saving of user equipment (UE). Until now, most analytical works have been on the DRX mechanism based on a single packet server. However, a single packet server typically yields low performance in energy saving under high arrival rates. On the other hand, practical LTE/LTE-A systems can allocate a variable size of resource for UE at one service time. To reflect the variable size of resource allocation and analyze the exact DRX mechanism under high arrival rates, we first model the DRX mechanism based on a batch server with varying buffer thresholds and server capacities. We also investigate the effect of system parameters such as buffer threshold, server capacity, DRX cycle, and inactivity timer in terms of delay and sleep ratio. Then, we find the optimal system parameter values of the batch packet server based DRX mechanism while satisfying the given delay requirements and maximizing the sleep ratio simultaneously. Finally, we show that the batch packet server yields the longer sleep ratio from 0.6 to 0.9 at high arrival rates, compared to a single packet server.

QoS Support Analysis of LTE Device Using Four State Markov Model Based DRX with OTSC for Power Efficient Bearer Services

The battery endurance of the user equipment device is enhanced by using discontinuous reception mechanism (DRX) in the long term evolution (LTE) networks. Configuring the DRX parameters for the pow...

Pupillary light reflex, receptive field mechanism and correction for retinal position for the assessment of visual discomfort

Light sources causing annoyance or pain produce discomfort glare. Traditional glare metrics fail for non-uniform luminaires. As an alternative, visual discomfort is determined by a model incorporating the centre–surround receptive field mechanism, the pupillary light reflex and a correction for retinal position. The pupil area, controlled by the pupillary light reflex, regulates the retinal illuminance. A centre–surround receptive field, described by a difference of Gaussians, represents the visual signal. A correction according to the Guth position index accounts for the reduction in brightness perception when a light source is moved away from the line of sight. The model is analysed with a forced choice paired comparison experiment involving 17 non-uniform rear projected stimuli with different spatial frequencies and luminance steps. A coefficient of determination of 0.68 between the subjective assessment and the model is obtained. A paired comparison office luminaire experiment and a magnitude estimation experiment involving diffusor luminaires validate the model resulting in a coefficient of determination of 0.86 and 0.81, respectively. By including the pupillary light reflex, receptive field mechanism and a correction for retinal position, the more physiologically justified model is a promising alternative to current, often empirical, glare metrics, especially for non-uniform luminaires.

INFLUENCE OF DYNAMIC MAGNETIZATION TO IMPROVE THE EFFICIENCY OF ELECTROMAGNETIC-ACOUSTIC TRANSFORMATION WITH WAVEGUIDE CONTROL RODS

The disadvantage of the electromagnetic-acoustic (EMA) method receiving ultrasonic waves are low efficiency. The traditional way to enhance its effectiveness is increase the bias field. The aim of the study was research the way to improve the efficiency of the EMA transformation, using a time-varying bias field.The researches held with the help of a specially designed installation that allows the magnetization to be performed by a constant and alternating magnetic field (dynamic bias), synchronously with the passage of the received pulse. The object of the study were rods made of different grades of steel with a diameter of 4–6 mm, in which the symmetrical zero mode S0 of the rod wave was excited by the EMA method (in the frequency range of about 40 kHz). A comparative analysis of the amplitudes and form pulses of multiple reflections during static and dynamic reversal of magnetization and with a full cycle of magnetization reversal conducted.The result of the efficiency measurements EMA reception during static and dynamic bias found a significant (up to 5 times) increase in the signal amplitude on the receiving transducer. Taking into account that the main contribution to the excitation mechanism and the reception mechanism made the magnetostrictive effect on low frecuncy, it can assumed that using a dynamic bias field is impacting significant on the effective mobility of magnetic domains (that is changes the dynamic magnetic susceptibility of the material). It is established that it is possible to monitor steel at lower values of the bias field, and, consequently, to reduce the mass dimensions of the magnetic system.Thus, in the course of the researchers found of effect of dynamic bias and effect of dynamic bias increase acoustic pulse amplitude of the signal of the received EMA method. Using this method will improve the quality EMA testing by creating more efficient EMA transducer. Taking into account that the value of the detected effect depends significantly on the steel grade, we can assume its possible application in the methods of express analysis, estimation of structural and stressed states.

Energy harvesting discontinuous reception (DRX) mechanism in wireless powered cellular networks

The energy harvesting paradigm enables the design of new wireless powered cellular networks (WPCNs) for the Internet-of-Things (IoT). In a WPCN, if the harvested energy is larger than the consumed energy, an IoT device may utilise the surplus harvested energy to extend the battery lifetime or to enhance the performance. Otherwise, a power saving mechanism is utilised as in traditional wireless cellular networks. In long-term evolution (LTE) systems, the discontinuous reception (DRX) mechanism has been adopted to save the power consumption of user equipments (UEs). However, the wakeup delay increases as the amount of the saved energy increases, and the optimisation for the DRX mechanism is required. In this study, the authors propose a novel energy harvesting DRX (EH-DRX) mechanism to minimise the wakeup delay in WPCNs. In the authors' proposed EH-DRX mechanism, an IoT device utilises the harvested energy to minimise the wakeup delay. Then they provide an optimisation algorithm to allocate the DRX parameters by utilising the harvesting capability of IoT devices. The optimisation algorithm is based on the analytical model for the proposed EH-DRX mechanism. Analysis and simulations indicate that the proposed EH-DRX mechanism reduces the wakeup delay compared to the traditional DRX mechanisms.

Cytoneme-mediated cell-cell contacts for Hedgehog reception.

Morphogens regulate tissue patterning through their distribution in concentration gradients. Emerging research establishes a role for specialized signalling filopodia, or cytonemes, in morphogen dispersion and signalling. Previously we demonstrated that Hedgehog (Hh) morphogen is transported via vesicles along cytonemes emanating from signal-producing cells to form a gradient in Drosophila epithelia. However, the mechanisms for signal reception and transfer are still undefined. Here, we demonstrate that cytonemes protruding from Hh-receiving cells contribute to Hh gradient formation. The canonical Hh receptor Patched is localized in these cellular protrusions and Hh reception takes place in membrane contact sites between Hh-sending and Hh-receiving cytonemes. These two sets of cytonemes have similar dynamics and both fall in two different dynamic behaviours. Furthermore, both the Hh co-receptor Interference hedgehog (Ihog) and the glypicans are critical for this cell-cell cytoneme mediated interaction. These findings suggest that the described contact sites might facilitate morphogen presentation and reception.

On Timing Reacquisition and Enhanced Primary Synchronization Signal (ePSS) Design for Energy Efficient 3GPP LTE MTC

Machine Type Communications (MTC) is one of the major drivers for the future growth of the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE)/LTE-Advanced (LTE-A) standards. A primary challenge associated with MTC using LTE/LTE-A is to cater to varied requirements of the User Equipment (UE) like coverage enhancement, low complexity, low power consumption, etc. The current LTE/LTE-A standards incorporate the Discontinuous Reception (DRX) mechanism for reduced energy consumption where the UE wakes up periodically to check for a paging message from the base-station. On each wake-up occasion, the UE has to decode the paging information, which requires accurate timing resynchronization. In the case of the MTC UEs, especially when the devices are deployed in low coverage areas, the resynchronization consumes a significant amount of time which increases the ON time of the UE leading to higher energy consumption. In this paper, we introduce the Enhanced Primary Synchronization Signal (ePSS) within the LTE/LTE-A standardization framework and propose a novel DRX mechanism which uses our ePSS for faster resynchronization and reduced energy consumption. We demonstrate that our mechanisms are more energy efficient than the legacy DRX mechanism for the MTC UEs with coverage enhancement.

Arte en la encrucijada. La recepción de la obra del pintor griego Dimitri Perdikidis (1922-1989) en España

En el marco del arte contemporáneo de la segunda mitad del siglo XX, son fundamentales los mecanismos de asimilación y recepción de la obra de aquellos artistas que vivieron, de manera permanente o durante largos períodos de tiempo, como extranjeros en un país distinto al propio. Un caso de especial interés es el de los artistas griegos y en concreto el del pintor Dimitri Perdikidis (1922-1989) que vivió entre 1953 y 1985 en Madrid. El artículo se propone analizar algunos de los aspectos del proceso de integración de su obra en el contexto artístico español teniendo en cuenta su recepción por parte de la crítica.

Hybrid Directional Discontinuous Reception (HD-DRX) for 5G Communication

For mmWave directional air interface expected in 5G communications, current discontinuous reception (DRX) mechanisms would be inadequate. Beam searching, for alignment of beams at User Equipment (UE) and 5G base station (NR nodeB), cannot be avoided in directional communication. We propose to exploit dual connectivity of UE, to both LTE eNB and NR nodeB, for effective 5G DRX. We present a novel hybrid directional-DRX (HD-DRX) mechanism, where beam searching is performed only when necessary. Probabilistic estimate of power saving and delay is conducted by capturing various states of UE through a semi-Markov process. Our numerical analysis achieves 13% improvement in power saving for HD-DRX compared with directional-DRX. We validate our numerical analysis with simulation studies on real traffic trace.

Mechanism of three-dimensional boundary-layer receptivity

Boundary-layer receptivity is always a hot issue in laminar-turbulent transition. Most actual laminar-turbulent transitions belong to three-dimensional flows. An infinite back-swept flat-plate boundary layer is a typical three-dimensional flow. Study of its receptivity is important both in theory and applications. In this paper, a freestream turbulence model is established. A modified fourth-order Runge-Kutta scheme is used for time marching, and compact finite difference schemes are used for space discretization. On these bases, whether unsteady cross-flow vortices can be excited in the three-dimensional boundary layer (the infinite back-swept flat-plate boundary layer) by free-stream turbulence is studied numerically. If so, effects of the level and the direction of free-stream turbulence on the three-dimensional boundary-layer receptivity are further studied. Differences of the three-dimensional boundary-layer receptivity are then discussed by considering the non-parallel effect, influence of the leading-edge stagnation point of the flat plate, and variation of the back-swept angle separately. Intensive studies on the three-dimensional boundary-layer receptivity will benefit the development of the hydrodynamic stability theory, and provide a theoretical basis for prediction and control of laminar-turbulent transition.