1,721,154 research outputs found
Dynamic implementation of function-oriented selective and adaptive assembly in small-lot production
No full textThe increasing trend towards high-variety, complex assembled products combined with the growing attention to sustainable manufacturing call for novel methods to reduce defects in small-lot productions. Selective assembly may improve assembled product quality, but the inherent rigidity of the underlying assembly strategy bounds its industrial applications. The paper presents a methodology to dynamically implement selective and adaptive assembly of complex products. Based on cyber-physical system capabilities, the assembly components are dynamically selected to match evolving quality requirements of the assembled product. The method is validated in a real opto-electronics industry case, showing significant benefits in quality and production logistics performance
Turkey's response to sex trafficking of migrant women : is it efficient enough?
Full text linkHuman trafficking for sexual exploitation is a serious problem affecting especially women and children. Turkey has been particularly affected by sex trafficking because of the large numbers of female migrants that it receives. This article aims to critically assess the effectiveness of Turkey's current policies against sex trafficking using a feminist theoretical perspective with a particular focus on migrant women. To this end, the scope of the problem in Turkey, the supply and demand sides of sex trafficking, and the existing policies are discussed. Sex trafficking is examined at the intersection of Turkey's migration and prostitution regimes. It is argued that Turkey's response to sex trafficking has been inefficient because it currently focuses only on the economic supply side of the problem, ignoring the patriarchal demand side of it. The article concludes with a discussion of policy recommendations for Turkey that could help reduce sex trafficking in this country. © 2016 The Authors. International Migration © 2016 IO
Cell-Free Massive MIMO with Large-Scale Fading Decoding and Dynamic Cooperation Clustering
No full textThis paper considers the uplink of user-centric cell-free massive MIMO (multiple-input multiple-output) systems. We utilize the user-centric dynamic cooperation clustering (DCC) framework and derive the achievable spectral efficiency with two-layer decoding that is divided between the access points and the central processing unit (CPU). This decoding method is also known as large-scale fading decoding (LSFD). The fronthaul signaling load is analyzed and a nearly optimal second-layer decoding scheme at the CPU is proposed to reduce the fronthaul requirements compared to the optimal scheme. We also revisit the joint optimization of LSFD weights and uplink power control and show that the corresponding max-min fair optimization problem can be solved optimally via an efficient fixed-point algorithm. We provide simulations that bring new insights into the cell-free massive MIMO implementation
A Primer on Near-Field Beamforming for Arrays and Reconfigurable Intelligent Surfaces
No full textWireless communication systems have almost exclusively operated in the far-field of antennas and antenna arrays, which is conventionally characterized by having propagation distances beyond the Fraunhofer distance. This is natural since the Fraunhofer distance is normally only a few wavelengths. With the advent of active arrays and passive reconfigurable intelligent surfaces (RIS) that are physically large, it is plausible that the transmitter or receiver is located in between the Fraunhofer distance of the individual array/surface elements and the Fraunhofer distance of the entire array. An RIS then can be configured to reflect the incident waveform towards a point in the radiative near-field of the surface, resulting in a beam with finite depth, or as a conventional angular beam with infinity focus, which only results in amplification in the far-field. To understand when these different options are viable, an accurate characterization of the near-field behaviors is necessary. In this paper, we revisit the motivation and approximations behind the Fraunhofer distance and show that it is not the right metric for determining when near-field focusing is possible. We obtain the distance range where finite-depth beamforming is possible and the distance where the beamforming gain tapers off
Foundations of user-centric cell-free massive MIMO
No full textImagine a coverage area where each mobile device is communicating with a preferred set of wireless access points (among many) that are selected based on its needs and cooperate to jointly serve it, instead of creating autonomous cells. This effectively leads to a user-centric post-cellular network architecture, which can resolve many of the interference issues and service-quality variations that appear in cellular networks. This concept is called User-centric Cell-free Massive MIMO (multiple-input multiple-output) and has its roots in the intersection between three technology components: Massive MIMO, coordinated multipoint processing, and ultra-dense networks. The main challenge is to achieve the benefits of cell-free operation in a practically feasible way, with computational complexity and fronthaul requirements that are scalable to enable massively large networks with many mobile devices. This monograph covers the foundations of User-centric Cell-free Massive MIMO, starting from the motivation and mathematical definition. It continues by describing the state-of-the-art signal processing algorithms for channel estimation, uplink data reception, and downlink data transmission with either centralized or distributed implementation. The achievable spectral efficiency is mathematically derived and evaluated numerically using a running example that exposes the impact of various system parameters and algorithmic choices. The fundamental tradeoffs between communication performance, computational complexity, and fronthaul signaling requirements are thoroughly analyzed. Finally, the basic algorithms for pilot assignment, dynamic cooperation cluster formation, and power optimization are provided, while open problems related to these and other resource allocation problems are reviewed. All the numerical examples can be reproduced using the accompanying Matlab code
The Social Organisation of Migrant Smugglers in Turkey: Roles and Functions
No full textWOS: 000407244300007Thousands of irregular migrants and refugees are transported from conflict areas and/or underdeveloped countries to wealthy Western states. These transfers are usually facilitated and arranged by migrant smuggling organisations. This paper reflects part of a comprehensive research project on irregular migration and migrant smuggling in Turkey and examines the structure and networks of smugglers operating in Turkey. Based on face-to-face interviews with smugglers (N = 54), it aims to shed light on migrant smugglers, smuggling structures and their organisations in Turkey. The findings suggest that the migrant smuggling business is composed of networks established at the local, national and international levels. These are structured on an ad hoc basis and are often adaptable to any changes and opportunities that may arise
Channel Modeling and Channel Estimation for Holographic Massive MIMO With Planar Arrays
No full textIn a realistic wireless environment, the multi-antenna channel usually exhibits spatially correlated fading. This is more emphasized when a large number of antennas is densely deployed, known as holographic massive MIMO (multiple-input multiple-output). In the first part of this letter, we develop a channel model for holographic massive MIMO by considering both non-isotropic scattering and directive antennas. With a large number of antennas, it is difficult to obtain full knowledge of the spatial correlation matrix. In this case, channel estimation is conventionally done using the least-squares (LS) estimator that requires no prior information of the channel statistics or array geometry. In the second part of this letter, we propose a novel channel estimation scheme that exploits the array geometry to identify a subspace of reduced rank that covers the eigenspace of any spatial correlation matrix. The proposed estimator outperforms the LS estimator, without using any user-specific channel statistics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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