Physics-based characterization of soft marine sediments using vector sensors

In a 2007 experiment conducted in the northern North Sea, observations of a low-frequency seismo-acoustic wave field with a linear horizontal array of vector sensors located on the seafloor revealed a strong, narrow peak around 38 Hz in the power spectra and a presence of multi-mode horizontally and vertically polarized interface waves with phase speeds between 45 and 350 m/s. Dispersion curves of the interface waves exhibit piece-wise linear dependences between the logarithm of phase speed and logarithm of frequency with distinct slopes at large and small phase speeds, which suggests a seabed with a power-law shear speed dependence in two distinct sediment layers. The power spectrum peak is interpreted as a manifestation of a seismo-acoustic resonance. A simple geoacoustic model with a few free parameters is derived that quantitatively reproduces the key features of the observations. This article's approach to the inverse problem is guided by a theoretical analysis of interface wave dispersion and resonance reflection of compressional waves in soft marine sediments containing two or more layers of different composition. Combining data from various channels of the vector sensors is critical for separating waves of different polarizations and helps to identify various arrivals, check consistency of inversions, and evaluate sediment density

Информационные технологии для бизнес -анализа в коммерческой организации

В работе рассмотрены основные концепции бизнес-анализа. Особое внимание уделено аналитической платформе Dedukto

Federated Meta Learning Enhanced Acoustic Radio Cooperative Framework for Ocean of Things Underwater Acoustic Communications

Sixth-generation wireless communication (6G) will be an integrated architecture of "space, air, ground and sea". One of the most difficult part of this architecture is the underwater information acquisition which need to transmitt information cross the interface between water and air.In this senario, ocean of things (OoT) will play an important role, because it can serve as a hub connecting Internet of things (IoT) and Internet of underwater things (IoUT). OoT device not only can collect data through underwater methods, but also can utilize radio frequence over the air. For underwater communications, underwater acoustic communications (UWA COMMs) is the most effective way for OoT devices to exchange information, but it is always tormented by doppler shift and synchronization errors. In this paper, in order to overcome UWA tough conditions, a deep neural networks based receiver for underwater acoustic chirp communication, called C-DNN, is proposed. Moreover, to improve the performance of DL-model and solve the problem of model generalization, we also proposed a novel federated meta learning (FML) enhanced acoustic radio cooperative (ARC) framework, dubbed ARC/FML, to do transfer. Particularly, tractable expressions are derived for the convergence rate of FML in a wireless setting, accounting for effects from both scheduling ratio, local epoch and the data amount on a single node.From our analysis and simulation results, it is shown that, the proposed C-DNN can provide a better BER performance and lower complexity than classical matched filter (MF) in underwater acoustic communications scenario. The ARC/FML framework has good convergence under a variety of channels than federated learning (FL). In summary, the proposed ARC/FML for OoT is a promising scheme for information exchange across water and air

The impact of SARS-Cov-2 infection on the periocular injection pain and hypersensitive reaction to botulinum toxin type A: results from clinical questionnaires

BackgroundThe COVID-19 pandemic has brought about significant changes in the medical field, yet the use of botulinum toxin type A has remained uninterrupted. Plastic surgeons must carefully consider the timing of administering botulinum toxin type A to patients who have recovered from COVID-19.MethodsA questionnaire survey was conducted among patients who had contracted and recovered from SARS-CoV-2 within a month. The survey aimed to investigate various indicators in patients who had received botulinum toxin A injections at the same site before and after their infection, including pain scores and allergic reactions and the occurrence of complications.ResultsThe pain scores of patients who contracted SARS-CoV-2 infection between 14-21 days post-infection exhibited significant variation from previous injections. However, patients who contracted the infection between 22-28 days post-infection did not exhibit significant variation from previous injections. Furthermore, the incidence of allergic reactions and complications following botulinum toxin injection within one month after contracting the infection did not significantly differ from that observed prior to infection.ConclusionAdministering botulinum toxin type A three weeks after COVID-19 recovery is a justifiable and comparatively secure approach

Methylation levels at IGF2 and GNAS DMRs in infants born to preeclamptic pregnancies

BACKGROUND: Offspring of pregnancy complicated with preeclampsia are at high risk for hypertension, stroke and possibly obesity. The mechanisms behind the association of intrauterine exposure to preeclampsia and high risk of health problems in the later life remain largely unknown. The aims of the current investigation were to determine the changes in DNA methylation at IGF2 and GNAS DMR in offspring of preeclamptic pregnancy and to explore the possible mechanisms underlying the association between maternal preeclampsia and high risk for health problems in the later life of their offspring. RESULTS: Umbilical cord blood was taken from infants born to women of preeclampsia (n=56), gestational hypertension (n=23) and normal pregnancy (n=81). DNA methylation levels of IGF2 and GNAS DMR were determined by Massarray quantitative methylation analysis. Methylation levels at IGF2 DMR were significantly lower in preeclampsia than normal pregnancy. The average methylation level at IGF2 DMR was significantly correlated with preeclampsia even after birth weight, maternal age, gestational age at delivery and fetal gender were adjusted. The difference in methylation level was not significantly different between mild and severe preeclampsia. The methylation level at GNAS DMR was not significantly correlated with birth weight, maternal age, gestational age at delivery, fetal gender, preeclampsia or gestational hypertension. CONCLUSIONS: We concluded preeclampsia induced a decrease in methylation level at IGF 2 DMR, and this might be among the mechanisms behind the association between intrauterine exposure to preeclampsia and high risk for metabolic diseases in the later life of the infants

Experimental Assessment of Different Receiver Structures for Underwater Acoustic Communications over Multipath Channels

Underwater communication channels are often complicated, and in particular multipath propagation may cause intersymbol interference (ISI). This paper addresses how to remove ISI, and evaluates the performance of three different receiver structures and their implementations. Using real data collected in a high-frequency (10–14 kHz) field experiment, the receiver structures are evaluated by off-line data processing. The three structures are multichannel decision feedback equalizer (DFE), passive time reversal receiver (passive-phase conjugation (PPC) with a single channel DFE), and the joint PPC with multichannel DFE. In sparse channels, dominant arrivals represent the channel information, and the matching pursuit (MP) algorithm which exploits the channel sparseness has been investigated for PPC processing. In the assessment, it is found that: (1) it is advantageous to obtain spatial gain using the adaptive multichannel combining scheme; and (2) the MP algorithm improves the performance of communications using PPC processing

Time Diversity Passive Time Reversal for Underwater Acoustic Communications

Underwater acoustic signal propagation is greatly affected by source-receiver motion, surface variations, and water column variabilities, which make the underwater acoustic communications very challenging. A passive time reversal (pTR) system is widely used for underwater communication systems due to its focusing property, which minimizes the time spreading of the underwater channel. The performance of the pTR system degrades when the underwater channel varies rapidly. During the experiment in TrondheimFjord on September 22, 2016, some environmental variations are observed which resulted in channel variations and the performance of the pTR system degraded. A time diversity pTR system is proposed and it uses the time diversity of the channel to compensate for the channel variations. The proposed system is tested at two receiver positions and it provides 2-3-dB gain in terms of mean square error in the presence of rapid channel variations

Blind deconvolution based equalizer for underwater acoustic communications

Reliable and efficient underwater acoustic communications are challenging problems because of complex underwater channel properties. With the recent advancements in underwater technologies, there is a need for a robust underwater communication system which can endure high data rate and optimize the use of resources like bandwidth and time. In this work, a blind deconvolution based equalizer is proposed, which uses the received signal to compute the channel impulse response estimates and equalizes the received signal using these channel impulse response estimates. The performance of the proposed system is tested with both simulated and real data. The real data were obtained during an experiment in September 2017 in TrondheimFjord. In the case of real data, the difference in performance in terms of mean square error between the proposed equalizer and the probe-based channel estimation equalizer is only 0.68 dB. This suggests that the proposed blind deconvolution technique can provide good channel estimates to equalize the underwater channel effects. In addition to that, it can save the resources allocated for the probe signal estimation