Interference Modeling And Control In Wireless Networks

With the successful commercialization of IEEE802.11 standard, wireless networks have become a tight-knit of our daily life. As wireless networks are increasingly applied to real- time and mission-critical tasks, how to ensuring real-time, reliable data delivery emerges as an important problem. However, wireless communication is subject to various dynamics and uncertainties due to the broadcast nature of wireless signal. In particular, co-channel interfer- ence not only reduces the reliability and throughput of wireless networks, it also increases the variability and uncertainty in data communication [64, 80, 77]. A basis of interference control is the interference model which \emph{predicts} whether a set of concurrent transmissions may interfere with one another. Two commonly used models, the \textit{SINR model} and the \textit{radio-K model}, are thoroughly studied in our work. To address the limitations of those models, we propose the physical-ratio-K(PRK) interference model as a reliablility-oriented instantiation of the ratio-K model, where the link-specific choice of K adapts to network and environmental conditions as well as application QoS requirements to ensure certain minimum reliability of every link. On the other hand, the interference among the transmissions, limits the number of con- current transmissions. We formulate the concept of \emph{interference budget} that, given a set of scheduled transmissions in a time slot, characterizes the additional interference power that can be tolerated by all the receivers without violating the application requirement on link reliability. We propose the scheduling algorithm \emph{iOrder} that optimizes link ordering by considering both interference budget and queue length in scheduling. Through both simulation and real-world experiments, we observe that optimizing link ordering can improve the performance of existing algorithms by a significant. Based on the strong preliminary research result on interference modeling and control, we will extend our method into distributed protocol designs. One future work will focus on imple- menting the \textit{PRK model} in a distributed protocols. We will also explore the benefits of using multiple channels in the interference control

Three Essays On Insurance Asset Management

The insurance industry manages a large amount of financial assets. In recent years, a growing number of investment companies are providing insurance asset management solutions, and the use of external asset management by the insurance industry is increasing over time. Therefore, understanding insurance asset management is important for academics and practitioners in both insurance and general finance. In the first essay, we investigate industrial portfolio tilt (referred to as “industry bias”) in the U.S. property liability insurers’ comstock portfolios. We find that U.S. property-liability insurers exhibit a negative industry bias by tilting their portfolios away from their own industry. We examine the nature of the industry bias and find that property-liability insurers have asymmetric information in investing in industrially close stocks but that their underwriting risk drives their portfolio tilt away from these stocks. Therefore, the property-liability insurers’ negative industry bias is driven by hedging in spite of information advantages. In the second essay, we investigate the betting-against-beta strategy in the presence of leverage in the U.S. property-liability insurance industry and empirically test whether these institutional investors’ leverage is an important determinant of their portfolio beta choice. Through empirical analysis, we find that property-liability insurers’ portfolio beta is not negatively related to their leverage, implying that these institutional investors do not bet against beta. In addition, we explore its explanation using a holdings-based calendar-time portfolio approach and find that these institutional investors’ low-beta portfolio does not outperform their high-beta portfolio. Overall, our results suggest that betting-against-beta strategy does not exist. In the third essay, we investigate the relation between cash holdings and market concentration in the U.S. property-liability insurance industry. We leverage the highly disaggregated nature of insurer statutory data to construct a refined market concentration measure, market space weighted concentration, which more accurately reflects an insurer’s state-line market space. Through our empirical analysis, we provide evidence in support of the predation risk theory. Specifically, insurers exposed to higher market concentration tend to hold more cash, and their cash is used to support future growth by reducing predation risk

Hungary Higher Education Quality Assurance System

Higher education quality assurance system has drawn much attention since 1980s. Most countries are committed to build the higher education quality assurance system to meet international standards. Under such an international trend, Hungary also actively promotes higher education reform, and established Hungarian Accreditation Committee and in order to ensure the quality of higher education

catena-Poly[[aqua­(dipyrido[3,2-a:2′,3′-c]phenazine-κ2 N 4,N 5)zinc(II)]-μ-pyrazine-2,3-dicarboxyl­ato-κ3 N 1,O 2:O 3]

In the title compound, [Zn(C6H2N2O4)(C18H10N4)(H2O)]n or [Zn(PZDC)(DPPZ)(H2O)]n (where DPPZ is dipyrido[3,2-a:2′,3′-c]phenazine and H2PZDC is pyrazine-2,3-dicarboxylic acid), the Zn atom is six-coordinated in a slightly distorted octa­hedral coordination geometry by three N atoms from one DPPZ ligand and one PZDC2− dianion, three O atoms from two different PZDC2− ligands and one water mol­ecule. Each PZDC2− dianion serves as a spacer, connecting adjacent metal atoms into a polymeric chain structure parallel to the b axis. The chain motif is consolidated into a three-dimensional supra­molecular network by O—H⋯O and O—H⋯N hydrogen bonds and π–π aromatic stacking inter­actions involving adjacent DPPZ ligands and PZDC2− dianions with centroid–centroid separations of 3.522 (6) and 3.732 (8) Å, respectively

Play as You Like: Timbre-enhanced Multi-modal Music Style Transfer

Style transfer of polyphonic music recordings is a challenging task when considering the modeling of diverse, imaginative, and reasonable music pieces in the style different from their original one. To achieve this, learning stable multi-modal representations for both domain-variant (i.e., style) and domain-invariant (i.e., content) information of music in an unsupervised manner is critical. In this paper, we propose an unsupervised music style transfer method without the need for parallel data. Besides, to characterize the multi-modal distribution of music pieces, we employ the Multi-modal Unsupervised Image-to-Image Translation (MUNIT) framework in the proposed system. This allows one to generate diverse outputs from the learned latent distributions representing contents and styles. Moreover, to better capture the granularity of sound, such as the perceptual dimensions of timbre and the nuance in instrument-specific performance, cognitively plausible features including mel-frequency cepstral coefficients (MFCC), spectral difference, and spectral envelope, are combined with the widely-used mel-spectrogram into a timber-enhanced multi-channel input representation. The Relativistic average Generative Adversarial Networks (RaGAN) is also utilized to achieve fast convergence and high stability. We conduct experiments on bilateral style transfer tasks among three different genres, namely piano solo, guitar solo, and string quartet. Results demonstrate the advantages of the proposed method in music style transfer with improved sound quality and in allowing users to manipulate the output

Synthesis Of Open-Shell Iron Oxide-Polyelectrolyte-Silica Nanocomposite For Water Treatment Application

A open shell structure of silica-polyelectrolyte-iron oxide nanocomposite is synthesized via layer-by-layer assembly. Here, silica colloid is synthesized by Stöber process and iron oxide nanoparticles (IONPs) is synthesized by co-precipitation method. The successful assembly of silica, polyelectrolyte and IONPs into unified nanocomposite was monitored with dynamic light scattering (DLS) and electrophoretic mobility. The core-shell morphology of the nanocomposite was confirmed under the examination of Transmission Electron Microscope (TEM). The final structure showed good colloidal stability up to 10 hours under the monitoring of DLS. The nanocomposite was more magnetically responsive than the bare IONPs with shorten collection time after their exposure to low magnetic field gradient. The interfacial phenomena, which is the conformation of the particles-polymeric structure was monitored by Quartz Crystal Microbalance with Dissipation (QCM-D). The loosely bound and flexible nature of polyelectrolyte promoted larger IONPs deposited amount compared to the bare silica surface without a pre-adsorbed polyelectrolyte. Increasing the initial IONPs concentration (20 to 500 ppm) suppressed the polyelectrolyte layer, giving rise to a stiffer particles-polymeric structure. By increasing the solution ionic strength (0.1 to 100 mM) within critical coagulation concentration up to 50 mM NaCl (obtained by DLS and Derjaguin-Landau-Verwey-Overbeek theory), the particles-polymeric structure became more flexible, leading to the greater amount of deposited IONPs. The open shell structure of the nanocomposite was varied with different polyelectrolyte hierarchy, nature and architecture. From DLS, QCM-D, TEM and AFM (Atomic Force Microscope), it was observed that the deposition of greater amount of IONPs and pollutants molecules into polymeric network was attributed by: (1) the flexible structure conserved by the single layer rather than multilayers of polyelectrolyte, (2) the more extended structure constructed by higher molecular weight than the lower molecular weight of polyelectrolyte, and (3) the branched chain compared to linear chain of polyelectrolyte. Mean field and scaling approximations showed that the protruding side chains of branched PEI contributed to the thicker adsorbed layer (16.14 nm) with more ramified structure compared to linear PDDA (0.19 nm). By taking cationic Methylene Blue, anionic Methyl Orange dyes and Amoxicillin antibiotic as the model system, the performance of nanocomposite can be compared with the silica, silica-polyelectrolyte and bare IONPs. With the ability to facilitate Fenton and Fenton-like reaction with the presence of hydrogen peroxide, nanocomposite achieved highest pollutant removal efficiency among the synthesized nanoparticles. The easiness of magnetic recollection enabled nanocomposite to be recycled for subsequent pollutant removal runs. Nanocomposite retained high pollutant removal efficiency for total 5 recycled runs without significant dissolution of the IONPs from the nanocomposite. The pollutant removal process by nanocomposite can be well illustrated using Langmuir isotherm and pseudo-second-order kinetic model