Impact of channel statistics and correlation on underwater acoustic communication systems

Several statistical properties of underwater acoustic channels gathered from experiment data are analyzed. The baseband channel impulse response (CIR) is estimated using a time domain least squares technique with a sliding window applied to the probing sequences. From the CIR estimation, the probability distribution functions (PDFs) of the magnitude, real part, imaginary part, and phase of the CIR are calculated. Gamma, Rayleigh, and compound k distributions are fitted to the magnitude PDF and the fitness of the distributions are calculated with a two-sample Kolmogorov-Smirnov test. Other statistics such as the autocorrelation function, coherence time, and scattering function are evaluated. The results show that the underwater acoustics channels are worse than the Rayleigh fading commonly seen as the worst case radio channel. Furthermore, the spatial and intertap correlation matrices of multiple input multiple output (MIMO) systems are estimated using experimental data. It is shown that underwater acoustic MIMO channels exhibit high spatial and temporal correlation. The bit error rate (BER) of the receiver using Frequency-domain turbo equalization is also evaluated in different channel correlation setups, demonstrating strong effects of the spatial-temporal correlation function on the performance --Abstract, page iv

Low pressure and plasma enhanced chemical vapor deposition of molybdenum oxide films

Thin films of molybdenum oxides were produced on silicon substrates from Mo(CO)[subscript]6 and O[subscript]2 using both a low pressure and plasma enhanced chemical vapor deposition (LPCVD and PECVD). The substrates were heated using a SiC coated graphite susceptor which was inductively coupled to a 200-450 kHz radio-frequency (RF) generator and using a Macor resistive heater. The process variables investigated were temperature, 250-530°C; pressure, 100-1014 mtorr; Mo(CO)[subscript]6 flow rate, 0.56-6.7 mg/min; O[subscript]2 flow rate, 5-15 sccm; H[subscript]2O flow rate of 0.0-0.53 sccm; and RF current, 22-34 amps;Thermodynamic equilibrium calculations were conducted on the system using a computer program, Solgasmix-PV. The calculations indicated that [alpha]-MoO[subscript]3 was the most stable phase for all deposition conditions. [alpha]-MoO[subscript]3 films formed under LPCVD conditions at temperatures greater than 350°C and pressures of 300 mtorr or more depending upon the reactor geometry and the heater used during deposition. The [alpha]-MoO[subscript]3 films were oriented and had a columnar or platelet structure. At lower temperatures under LPCVD conditions reduced molybdenum oxides, MoO[subscript]2 and Mo[subscript]4O[subscript]11, were produced. A quadratic model was developed of the formation of LPCVD [alpha]-MoO[subscript]3 as a function of temperature and pressure. The film uniformity and composition were strongly influenced by transport processes;At high RF currents, the RF generator created an inductively coupled Ar-O[subscript]2 plasma in the system when using the Macor heater. Films deposited under PECVD conditions were oriented [alpha]-MoO[subscript]3; the PECVD films had lower deposition rates and were produced at lower temperatures than LPCVD [alpha]-MoO[subscript]3 films. The deposits contained little carbon (\u3c1%). A model of the [alpha]-MoO[subscript]3 formation as a function of the process variables was developed using experimental design and regression analysis. The model indicated that the process variables act synergistically on the [alpha]-MoO[subscript]3 formation. The films were characterized using profilometry, x-ray diffraction and x-ray photoelectron, Fourier transform infrared, Auger and laser Raman spectroscopy

Child welfare policy and practice on children's exposure to domestic violence

There are emerging movements in several countries to improve policy and practice to protect children from exposure to domestic violence. These movements have resulted in the collection of new data on EDV and the design and implementation of new child welfare policies and practices. To assist with the development of child welfare practice, this article summarizes current knowledge on the prevalence of EDV, and on child welfare services policies and practices that may hold promise for reducing the frequency and impact of EDV on children. We focus on Australia, Canada, and the United States, as these countries share a similar socio-legal context, a long history of enacting and expanding legislation about reporting of maltreatment, debates regarding the application of reporting laws to EDV, and new child welfare practices that show promise for responding more effectively to EDV

Influential Article Review - Evaluation of Spillover Effects on Nigeria's Sovereign Bond Yields

This paper examines finance. We present insights from a highly influential paper. Here are the highlights from this paper: This study examines the spillover effects of U.S. monetary policy normalization on Nigeria 10-Year Treasury bond yield between 2011 and 2017, using the vector error correction model approach. Our results reveal that domestic factors, such as exchange rate and inflation, rather than the U.S. 10-Year sovereign bond yield, are the key drivers of Nigeria 10-Year bond yield. Additionally, the spillover effect from the U.S. monetary policy was amplified by oil price shocks and changes in Nigeria’s monetary policy rates. Our counterfactual analysis confirms the findings. For our overseas readers, we then present the insights from this paper in Spanish, French, Portuguese, and German

LoCoH: nonparameteric kernel methods for constructing home ranges and utilization distributions.

Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: "fixed sphere-of-influence," or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an "adaptive sphere-of-influence," or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original "fixed-number-of-points," or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu)

Using new and innovative technologies to assess clinical stage in early intervention youth mental health services: Evaluation study

Background: Globally there is increasing recognition that new strategies are required to reduce disability due to common mental health problems. As 75% of mental health and substance use disorders emerge during the teenage or early adulthood years, these strategies need to be readily accessible to young people. When considering how to provide such services at scale, new and innovative technologies show promise in augmenting traditional clinic-based services. Objective: The aim of this study was to test new and innovative technologies to assess clinical stage in early intervention youth mental health services using a prototypic online system known as the Mental Health eClinic (MHeC). Methods: The online assessment within the MHeC was compared directly against traditional clinician assessment within 2 Sydney-based youth-specific mental health services (headspace Camperdown and headspace Campbelltown). A total of 204 young people were recruited to the study. Eligible participants completed both face-to-face and online assessments, which were randomly allocated and counterbalanced at a 1-to-3 ratio. These assessments were (1) a traditional 45- to 60-minute headspace face-to-face assessment performed by a Youth Access Clinician and (2) an approximate 60-minute online assessment (including a self-report Web-based survey, immediate dashboard of results, and a video visit with a clinician). All assessments were completed within a 2-week timeframe from initial presentation. Results: Of the 72 participants who completed the study, 71% (51/72) were female and the mean age was 20.4 years (aged 16 to 25 years); 68% (49/72) of participants were recruited from headspace Camperdown and the remaining 32% (23/72) from headspace Campbelltown. Interrater agreement of participants’ stage, as determined after face-to-face assessment or online assessment, demonstrated fair agreement (kappa=.39, P\u3c.001) with concordance in 68% of cases (49/72). Among the discordant cases, those who were allocated to a higher stage by online raters were more likely to report a past history of mental health disorders (P=.001), previous suicide planning (P=.002), and current cannabis misuse (P=.03) compared to those allocated to a lower stage. Conclusions: The MHeC presents a new and innovative method for determining key clinical service parameters. It has the potential to be adapted to varied settings in which young people are connected with traditional clinical services and assist in providing the right care at the right tim

Task-irrelevant auditory metre shapes visuomotor sequential learning

The ability to learn and reproduce sequences is fundamental to every-day life, and deficits in sequential learning are associated with developmental disorders such as specific language impairment. Individual differences in sequential learning are usually investigated using the serial reaction time task (SRTT), wherein a participant responds to a series of regularly timed, seemingly random visual cues that in fact follow a repeating deterministic structure. Although manipulating inter-cue interval timing has been shown to adversely affect sequential learning, the role of metre (the patterning of salience across time) remains unexplored within the regularly timed, visual SRTT. The current experiment consists of an SRTT adapted to include task-irrelevant auditory rhythms conferring a sense of metre. We predicted that (1) participants’ (n = 41) reaction times would reflect the auditory metric structure; (2) that disrupting the correspondence between the learned visual sequence and auditory metre would impede performance; and (3) that individual differences in sensitivity to rhythm would predict the magnitude of these effects. Altering the relationship via a phase shift between the trained visual sequence and auditory metre slowed reaction times. Sensitivity to rhythm was predictive of reaction times over all. In an exploratory analysis, we, moreover, found that approximately half of participants made systematically different responses to visual cues on the basis of the cues’ position within the auditory metre. We demonstrate the influence of auditory temporal structures on visuomotor sequential learning in a widely used task where metre and timing are rarely considered. The current results indicate sensitivity to metre as a possible latent factor underpinning individual differences in SRTT performance