Statistical analysis and hybrid modeling of high-frequency underwater acoustic channels affected by wind-driven surface waves.

High frequency is a solution to high data-rate underwater acoustic communications. Extensive studies have been conducted on high-frequency (>40 kHz) acoustic channels, which are strongly susceptible to surface waves. The corresponding channel statistics related to acoustic communications, however, still deserve systematic investigation.

Impacts of channel fluctuations on least-squares channel estimation in underwater acoustic communications.

The time-varying multipath introduces major distortions to transmissions in the underwater acoustic communication channel. Channel estimation is often used as one of the central steps to address such distortions in high-rate communication receivers. The focus of this paper is to quantify the impacts of the channel fluctuations on the performance of the least-squares channel estimator.

Design and Evaluation of an Acoustic Modem for a Small Autonomous Unmanned Vehicle.

Design of underwater acoustic (UWA) modems for compact-sized, underwater platforms such as autonomous underwater vehicles (AUVs) is challenging because of the practical requirement to keep an engineering balance between the performance and the system overhead. Considering this type of mobile communication scenario, Doppler spread as well as the multipath draws substantial attention in implementing the system's design and engineering. Specifically, for a small AUV, the large computational complexity of real-time resampling for the classic Doppler correction poses significant difficulty for the limited capability of the low-cost processor.

Interaction between toll-like receptor 4 (TLR4) gene and alcohol drinking on Parkinson's disease risk in Chinese Han population.

The aim of this study was to investigate the association of several single nucleotide polymorphisms (SNPs) within Toll-like receptor 4 (TLR4) gene, additional SNP- SNP and gene- alcohol drinking interaction with Parkinson's disease (PD) risk. Generalized multifactor dimensionality reduction (GMDR) was used to screen the best interaction combination among 4 SNPs within TLR4 gene and alcohol drinking. Logistic regression was performed to calculate the ORs (95%CI) for association between 4 SNPs within TLR4 gene, additional gene- alcohol drinking interaction and PD risk.

Distributed compressed sensing based channel estimation for underwater acoustic multiband transmissions.

Distributed compressed sensing techniques are applied to enhance sparse channel estimation performance in underwater acoustic multiband systems. The core idea is to use receptions from multiple sub-bands to enhance the detection of channel tap positions. A known variant of the orthogonal matching pursuit (OMP) algorithm based on the distributed compressed sensing principle is simultaneous orthogonal matching pursuit (SOMP).

Underwater acoustic channel characteristics and communication performance at 85 kHz.

A high frequency acoustic experiment was conducted in the northern portion of the Gulf of Mexico in August 2016 to examine the operating range, data rates, and performance of acoustic communication systems at the carrier frequency of 85 kHz. The received signal-to-noise ratios, channel coherence, and impulse responses were reported between two 85 kHz transducers and a five-element hydrophone array over multiple ranges up to 1500 m. Channel estimation based decision feedback equalizers (DFEs) were applied to process the communication measurements.

Arrival-time fluctuations of coherent reflections from surface gravity water waves.

Arrival time fluctuations of coherent reflections from surface gravity waves are examined. A two-dimensional ray model with an evolving rough sea surface is used to explain the mechanism and formation of the deterministic striation patterns due to the surface reflection. Arrival time predictions from the ray model match qualitatively well with the measurements from bidirectional acoustic transmissions in a water depth of 100 m.

Three-dimensional mapping of evolving internal waves during the Shallow Water 2006 experiment.

Detailed knowledge of sound speed profiles and the sound speed profile's spatial and temporal variability resulting from internal waves (IWs) are indispensable to investigating significant acoustic field fluctuations in shallow water. A strategy to obtain a time-varying, three-dimensional (3D) IW temperature field is presented. It uses two types of simultaneous measurements: dense observations from a farm of thermistor strings and IW surface expressions from a ship-based radar.

Impact of HIV/sexually transmitted infection testing on risky sexual behaviors among men who have sex with men in Langfang, China.

Background: Men who have sex with men (MSM) in China remain at high risk for HIV infection, the proportion of reported HIV/AIDS cases that occurred among MSM rose greatly from 2005 to 2011. HIV testing and counseling is a critical HIV prevention strategy among HIV related high-risk population, including MSM in China. This article aimed to assess the association between receiving HIV testing and high-risk sexual behaviors among MSM in Langfang, Hebei Province, China.

Coherent reflection from surface gravity water waves during reciprocal acoustic transmissions.

During a recent experiment in Kauai, Hawaii, reciprocal transmissions were conducted between two acoustic transceivers mounted on the seafloor at a depth of 100 m. The passage of moving surface wave crests was shown to generate focused and intense coherent acoustic returns, which had increasing or decreasing delay depending on the direction of propagation relative to the direction of surface wave crests. It is shown that a rough surface two-dimensional parabolic equation model with an evolving sea surface can produce qualitative agreement with data for the dynamic surface returns.

Time reversal acoustic communication for multiband transmission.

In this letter, multiband acoustic communication is proposed to access a relatively wide frequency band. The entire frequency band is divided into multiple separated sub-bands, each of which is several kilohertz in width. Time reversal decision feedback equalizers are used to compensate for inter-symbol interference at each sub-band.

Time reversal multiple-input/multiple-output acoustic communication enhanced by parallel interference cancellation.

Multiple-input/multiple-output (MIMO) techniques can lead to significant improvements of underwater acoustic communication capabilities. In this paper, receivers based on time reversal processing are developed for high frequency underwater MIMO channels. Time reversal followed by a single channel decision feedback equalizer, aided by frequent channel updates, is used to compensate for the time-varying inter-symbol interference.

Delay and Doppler spreads in underwater acoustic particle velocity channels.

Signal processing and communication in acoustic particle velocity channels using vector sensors are of interest in the underwater medium. Due to the presence of multiple propagation paths, a mobile receiver collects the signal with different delays and Doppler shifts. This introduces certain delay and Doppler spreads in particle velocity channels.

A clinical risk score for the prediction of very late stent thrombosis in drug eluting stent patients.

Aims: Very late stent thrombosis (VLST; >1 year) is an infrequent but potentially serious complication, whose risk factors have not been fully elucidated. This investigation sought to develop a clinically useful risk stratification score for VLST following drug eluting stent (DES) placement.

Methods And Results: A Cox proportional hazards multivariate model of VLST was developed based on follow-up into a second year of patients enrolled in the ARRIVE registries, utilising readily available baseline clinical and angiographic characteristics.

Impact of source depth on coherent underwater acoustic communications.

A recent paper [Song et al., J. Acoust.

Drug-eluting stent thrombosis in routine clinical practice: two-year outcomes and predictors from the TAXUS ARRIVE registries.

Background: Stent thrombosis (ST) is an uncommon but serious complication of drug-eluting and bare metal stents. To assess drug-eluting stent ST in contemporary practice, we analyzed 2-year data from the 7492-patient ARRIVE registry.

Methods And Results: Patients were enrolled at the initiation of percutaneous coronary intervention with no inclusion/exclusion criteria beyond use of the paclitaxel-eluting TAXUS stent.

Effect of reflected and refracted signals on coherent underwater acoustic communication: results from the Kauai experiment (KauaiEx 2003).

The performance of a communications equalizer is quantified in terms of the number of acoustic paths that are treated as usable signal. The analysis uses acoustical and oceanographic data collected off the Hawaiian Island of Kauai. Communication signals were measured on an eight-element vertical array at two different ranges, 1 and 2 km, and processed using an equalizer based on passive time-reversal signal processing.

[Survey on AIDS/STD risk behaviors and prevalence among men who have sex with men in Langfang, Hebei].

Objective: To understand the demographic and HIV risk behaviors, HIV and syphilis infection among men who have sex with men (MSM) in Langfang, Hebei.

Methods: 106 completed questionnaires were collected from 118 participants, who were recruited from MSM pubs and internet from October to November, 2007. Data on homosexual and heterosexual relationships as well as sexual behaviors were collected by face-to-face interview.

A clinical risk score for prediction of stent thrombosis.

The aim was to develop a clinically useful patient risk score predictive for stent thrombosis (ST). Using readily available baseline clinical and angiographic characteristics, a Cox proportional hazards multivariate model was used to identify significant (p <0.10) predictors of ST through 1 year in 2,487 patients receiving a TAXUS Express (Boston Scientific Corp.

Impact of ocean variability on coherent underwater acoustic communications during the Kauai [corrected] experiment (KauaiEx).

During the July 2003 acoustic communications experiment conducted in 100 m deep water off the western side of Kauai, Hawaii, a 10 s binary phase shift keying signal with a symbol rate of 4 kilosymbol/s was transmitted every 30 min for 27 h from a bottom moored source at 12 kHz center frequency to a 16 element vertical array spanning the water column at about 3 km range. The communications signals are demodulated by time reversal multichannel combining followed by a single channel decision feedback equalizer using two subsets of array elements whose channel characteristics appear distinct: (1) top 10 and (2) bottom 4 elements. Due to rapid channel variations, continuous channel updates along with Doppler tracking are required prior to time reversal combining.

3-(m-Tol-yloxy)phthalonitrile.

In the mol-ecule of the title compound, C(15)H(10)N(2)O, the dihedral angle between the two benzene rings is 65.49 (9)°.

3-(2-Nitro-phen-oxy)phthalonitrile.

In the title compound, C(14)H(7)N(3)O(3), the dihedral angle between the two arene units is 62.57 (12)°.