5G Mobile Communications

This book provides a comprehensive overview of the emerging technologies for next-generation 5G mobile communications, with insights into the long-term future of 5G. Written by international leading experts on the subject, this contributed volume covers a wide range of technologies, research results, and networking methods. Key enabling technologies for 5G systems include, but are not limited to, millimeter-wave communications, massive MIMO technology and non-orthogonal multiple access. 5G will herald an even greater rise in the prominence of mobile access based upon both human-centric and machine-centric networks. Compared with existing 4G communications systems, unprecedented numbers of smart and heterogeneous wireless devices will be accessing future 5G mobile systems. As a result, a new paradigm shift is required to deal with challenges on explosively growing requirements in mobile data traffic volume (1000x), number of connected devices (10–100x), typical end-user data rate (10–100x), and device/network lifetime (10x). Achieving these ambitious goals calls for revolutionary candidate technologies in future 5G mobile systems. Designed for researchers and professionals involved with networks and communication systems, 5G Mobile Communications is a straightforward, easy-to-read analysis of the possibilities of 5G systems

Isopropyl 3,4-dihy­droxy­benzoate

In the crystal structure of the title compound, C10H12O4, O—H⋯O hydrogen bonds incorporating R 2 2(10) and R 2 2(14) motifs link mol­ecules into chains along [10]. An intra­molecular O—H⋯O hydrogen bond is also observed

IMAP: Intrinsically Motivated Adversarial Policy

Reinforcement learning agents are susceptible to evasion attacks during deployment. In single-agent environments, these attacks can occur through imperceptible perturbations injected into the inputs of the victim policy network. In multi-agent environments, an attacker can manipulate an adversarial opponent to influence the victim policy's observations indirectly. While adversarial policies offer a promising technique to craft such attacks, current methods are either sample-inefficient due to poor exploration strategies or require extra surrogate model training under the black-box assumption. To address these challenges, in this paper, we propose Intrinsically Motivated Adversarial Policy (IMAP) for efficient black-box adversarial policy learning in both single- and multi-agent environments. We formulate four types of adversarial intrinsic regularizers -- maximizing the adversarial state coverage, policy coverage, risk, or divergence -- to discover potential vulnerabilities of the victim policy in a principled way. We also present a novel Bias-Reduction (BR) method to boost IMAP further. Our experiments validate the effectiveness of the four types of adversarial intrinsic regularizers and BR in enhancing black-box adversarial policy learning across a variety of environments. Our IMAP successfully evades two types of defense methods, adversarial training and robust regularizer, decreasing the performance of the state-of-the-art robust WocaR-PPO agents by 34%-54% across four single-agent tasks. IMAP also achieves a state-of-the-art attacking success rate of 83.91% in the multi-agent game YouShallNotPass

1-Butyl-3-(1-naphthyl­meth­yl)benzimidazolium hemi{di-μ-iodido-bis­[diiodidomercurate(II)]} dimethyl sulfoxide monosolvate

In the title compound, (C22H23N2)[Hg2I6]0.5·(CH3)2SO, the 1-butyl-3-(1-naphthyl­meth­yl)benzimidazolium anion lies across a centre of inversion. The dihedral angle between the benzimidazolium and naphthalene ring systems is 81.9 (3)°. In the crystal structure, π–π stacking inter­actions are observed between the imidazolium ring and the unsubstituted benzene ring of the naphthalene ring system, with a centroid–centroid separation of 3.510 (5) Å. In the centrosymmetric anion, the Hg(II) atoms are in a distorted tetrahedral coordination. The dimethyl sulfoxide solvent mol­ecule is disordered over two sites with occupancies of 0.615 (9) and 0.385 (9)

Taking Teaching out of the Equation with Technology

In this creative non-fiction essay, the authors share experiences from a morning visitwith preservice mathematics teachers at a local high school. Through a series of vignettes, theauthors share positive and negative encounters with technology as they pose rich questions tostudents (and their teacher) in a remedial algebra classroom and observe the use of classroommanagement software (CMS) with the same students