Per-channel Basis Research Articles

Assessment of inland flood hazard sensitivity to hydrological intensification in coastal watersheds

IntroductionIntensification of the hydrologic cycle induced by climate variability and landscape modification is expected to increase the frequency of extreme flood events. Multi-jurisdictional approaches to manage inland flood risks at watershed scales demand the ability to objectively assess not only future flood potentials, but to also set priorities based upon multiple factors such as the stream channels most sensitive to hydrologic stress.MethodsThis study presents a method to estimate flood hazard sensitivities to increasing stormwater runoff due to hydrologic intensification (e.g., urbanization, climate effects) on local and watershed scales. The method is demonstrated in the low-gradient inland watershed regions of southwestern coastal Louisiana, USA. Utilizing highly detailed numerical models from the Federal Emergency Management Agency (FEMA), absolute and relative flood sensitivities were calculated for 45 flood-prone stream channels in the Lafayette, LA region. Channel sensitivities to flood hazards induced by changes in the 10-yr (10% annual exceedance probability) flood flows were quantified by analysis of 485 scenarios developed using a downward counterfactual scaling strategy.Results and discussionRelying entirely upon publicly available numerical models and input datasets, the study revealed key information about the relationship between estimable hydraulic characteristics (e.g., conveyance, resistance, and flow) and absolute and relative flood hazard sensitivity measures on a per-channel basis. Information from the subset of detailed numerical models was efficiently leveraged to provide a regional map of relative flood sensitivities. The methodology is robust and can be applied in very general settings to address the concern of hydrologic intensification in practical flood risk management applications.

Noise Efficient Integrated Amplifier Designs for Biomedical Applications

The recording of neural signals with small monolithically integrated amplifiers is of high interest in research as well as in commercial applications, where it is common to acquire 100 or more channels in parallel. This paper reviews the recent developments in low-noise biomedical amplifier design based on CMOS technology, including lateral bipolar devices. Seven major circuit topology categories are identified and analyzed on a per-channel basis in terms of their noise-efficiency factor (NEF), input-referred absolute noise, current consumption, and area. A historical trend towards lower NEF is observed whilst absolute noise power and current consumption exhibit a widespread over more than five orders of magnitude. The performance of lateral bipolar transistors as amplifier input devices is examined by transistor-level simulations and measurements from five different prototype designs fabricated in 180 nm and 350 nm CMOS technology. The lowest measured noise floor is 9.9 nV/√Hz with a 10 µA bias current, which results in a NEF of 1.2.

Strip sensor performance in prototype modules built for ATLAS ITk

ATLAS experiment is preparing an upgrade of its detector for High-Luminosity LHC (HL-LHC) operation. The upgrade involves installation of the new all-silicon Inner Tracker (ITk). In the context of the ITk preparations, more than 80 strip modules were built with prototype barrel sensors. They were tested with electrical readout on a per-channel basis. In general, an excellent performance was observed, consistent with previous ASIC-level and sensor-level tests. However, the lessons learned included two phenomena important for the future phases of the project. First was the need to store and test the modules in a dry environment due to humidity sensitivity of the sensors. The second was an observation of high noise regions for 2 modules.The high noise regions were tested further in several ways, including monitoring the performance as a function of time and bias voltage. Additionally, direct sensor-level tests were performed on the affected channels. The inter-strip resistance and bias resistance tests showed low values, indicating a temporary loss of the inter-strip isolation. A subsequent recovery of the noise performance was observed. We present the test details, an analysis of how the inter-strip isolation affects the module noise, and the relationship with sensor-level quality control tests.

Coupled 3D neutronics/thermal hydraulics modeling of the SAFARI-1 MTR

The purpose of this study was to develop a coupled accurate multi-physics model of the SAFARI-1 Material Testing Reactor (MTR), a facility that is used for both research and the production of medical isotopes. The model was developed as part of the SAFARI-1 benchmarking project as a cooperative effort between the Pennsylvania State University (PSU) and the South African Nuclear Energy Corporation (Necsa). It was created using a multi-physics coupling of state of the art nuclear reactor simulation tools, consisting of a neutronics code and a thermal hydraulics code.The neutronics tool used was the PSU code NEM, and the results from this component were verified using the Necsa neutronics code OSCAR-4, which is utilized for SAFARI-1 core design and fuel management. On average, the multiplication factors of the neutronics models agreed to within 5pcm and the radial assembly-averaged powers agreed to within 0.2%.The thermal hydraulics tool used was the PSU version of COBRA-TF (CTF) sub-channel code, and the results of this component were verified against another thermal hydraulics code, the RELAP5-3D system code, used at Necsa for thermal–hydraulics analysis of SAFARI-1. Although only assembly-averaged results from RELAP5-3D were available, they fell within the range of values for the corresponding assemblies in the comprehensive CTF solution. This comparison allows for the first time to perform a quantification of steady-state errors for a low-powered MTR with an advanced thermal–hydraulic code such as CTF on a per-channel basis as compared to simpler and coarser-mesh RELAP5-3D modeling. Additionally, a new cross section representation was used to ensure that the thermal hydraulic feedback effects on the core neutronics were captured as accurately as possible. This cross section representation was applied to SAFARI-1 core calculations for the first time in this work. Such implementation helps to quantify the effect of detailed modeling of thermal–hydraulics feedback effects on neutronics results in multi-physics simulations.The outcome of the study is the intended coupled neutronics/thermal–hydraulics model of the SAFARI-1 reactor.

Using channel-specific statistical models to detect reverberation in cochlear implant stimuli

Reverberation is especially detrimental for cochlear implant listeners; thus, mitigating its effects has the potential to provide significant improvements to cochlear implant communication. Efforts to model and correct for reverberation in acoustic listening scenarios can be quite complex, requiring estimation of the room transfer function and localization of the source and receiver. However, due to the limited resolution associated with cochlear implant stimulation, simpler processing for reverberation detection and mitigation may be possible for cochlear implants. This study models speech stimuli in a cochlear implant on a per-channel basis both in quiet and in reverberation, and assesses the efficacy of these models for detecting the presence of reverberation. This study was able to successfully detect reverberation in cochlear implant pulse trains, and the results appear to be robust to varying room conditions and cochlear implant stimulation parameters. Reverberant signals were detected 100% of the time for a long reverberation time of 1.2 s and 86% of the time for a shorter reverberation time of 0.5 s.

Using channel-specific models to detect and remove reverberation in cochlear implants

Reverberation results in the smearing of both harmonic and temporal elements of speech through self-masking (masking within an individual phoneme) and overlap-masking (masking of one phoneme by a preceding phoneme). Self-masking is responsible for flattening formant transitions, while overlap-masking results in the masking of low-energy consonants by higher-energy vowels. Reverberation effects, especially the flattening of formant transitions, are especially detrimental to cochlear implant listeners because they already have access to only limited spectral and temporal information (Kokkinakis and Loizou, 2011). Efforts to model and correct for reverberation in acoustic listening scenarios can be quite complex, requiring estimation of the room transfer function and localization of the source and receiver. However, due to the limited resolution associated with cochlear implant stimulation, simpler processing for reverberation detection and mitigation may be possible. This study models speech stimuli in a cochlear implant on a per-channel basis both in quiet and in reverberation, where reverberation is characterized by different reverberation times, room dimensions, and source locations. The efficacy of these models for detecting the presence of reverberation and subsequently removing its effects from speech stimuli is assessed. [This work was funded by the National Institutes of Health (NIDCD), R01-DC-007994-04.]

Per‐channel basis normalization methods for flow cytometry data

Between-sample variation in high-throughput flow cytometry data poses a significant challenge for analysis of large-scale data sets, such as those derived from multicenter clinical trials. It is often hard to match biologically relevant cell populations across samples because of technical variation in sample acquisition and instrumentation differences. Thus, normalization of data is a critical step before analysis, particularly in large-scale data sets from clinical trials, where group-specific differences may be subtle and patient-to-patient variation common. We have developed two normalization methods that remove technical between-sample variation by aligning prominent features (landmarks) in the raw data on a per-channel basis. These algorithms were tested on two independent flow cytometry data sets by comparing manually gated data, either individually for each sample or using static gating templates, before and after normalization. Our results show a marked improvement in the overlap between manual and static gating when the data are normalized, thereby facilitating the use of automated analyses on large flow cytometry data sets. Such automated analyses are essential for high-throughput flow cytometry.

A Tale of Two Reports

Conclusions in the 2006 annual video competition report released by the Federal Communications Commission undercut the rationale for additional regulation of cable providers. Although the data used in the report is 30 months out-of-date, it illustrates a steady trend of increasing competition among video service providers and increasing sources of diverse information and video programming.The most important finding of the recently released Thirteenth Annual Video Competition Report is the continuation of trends discussed in previous reports: cable competition is growing, consumer choice of diverse sources of video programming and information is increasing and cable operators are offering an ever-increasing array of video and non-video services. These results undermine the arguments for both increased regulation and sustaining the current level of regulation of cable in two ways. First, the report indicates even as of June 2006, cable penetration is unlikely to have surpassed 70% of the market, the threshold in which cable would be open to further regulation. Second, the report reveals that as of that date, the vertical integration of video programming and distribution channels was decreasing, and the video market was successfully providing consumers with a diversity of information sources, including new distribution methods, such as the Internet. Especially lamentable is the 14 month delay in the release of the report, keeping vital statistics about the video marketplace out of the hands of both Congress and consumers. Had the FCC been up to date with its annual video competition reports, it might have discovered that the answer to [the perceived twin problems of] cable pricing and the inability of consumers to buy programming on a per-channel basis - are already being addressed through technological innovation and market forces without the expenditure of a single full time equivalent federal employee man or woman hour.

A Shuttered Neural Probe With On-Chip Flowmeters for Chronic In Vivo Drug Delivery

This paper describes the development of shutters, fluidic ribbon cables, and flowmeters for use on bulk-micromachined neural probes. The resulting devices permit electrical recording, stimulation, and chemical drug delivery in the central nervous system at the cellular level. Dielectric shutters reduce unintended drug delivery by a factor of about 25 compared with an open orifice, while silicon fluidic cables are 1.5 times more flexible than the 70 mum-ID polyimide tubing previously used. A pulsed thermal flowmeter integrated on the probe allows verification of drug delivery on a per-channel basis with a resolution of 150 pL/s. Thermal time constants are about 60 mus, allowing multiple measurements within one delivery pulse while restricting any tissue heating to negligible levels. Finally, test structures have shown the process compatibility of on-chip thermopneumatic microvalves and micropumps. The fabrication of these fluidic structures (microchannels, shutters, cables, valves, and pumps) requires only two masks in addition to the eight normally used for passive probes, providing important new capabilities for use in neurophysiological research and neural prostheses

Focus on Data Acquisition

Focus on Data Acquisition

Superposition of chirped fibre Bragg grating for third-order dispersion compensation over 32 WDM channels

Multiple superposition of fibre Bragg gratings was used to fabricate a dispersion compensator that operates over 32 WDM channels. The channel spacing is 100 GHz and the total operation bandwidth is 25 nm. The dispersion was adjusted on a per-channel basis allowing for a compensation up to the third order.

User-space protocols deliver high performance to applications on a low-cost Gb/s LAN

Two important questions in high-speed networking are firstly, how to provide Gbit/s networking at low cost and secondly, how to provide a flexible low-level network interface so that applications can control their data from the instant it arrives. We describe some work that addresses both of these questions. The Jetstream Gbit/s LAN is an experimental, low-cost network interface that provides the services required by delay-sensitive traffic as well as meeting the performance needs of current applications. Jetstream is a combination of traditional shared-medium LAN technology and more recent ATM cell- and switch-based technology. Jetstream frames contain a channel identifier so that the network driver can immediately associate an incoming frame with its application. We have developed such a driver that enables applications to control how their data should be managed without the need to first move the data into the application's address space. Consequently, applications can elect to read just a part of a frame and then instruct the driver to move the remainder directly to its destination. Individual channels can elect to receive frames that have failed their CRC, while applications can specify frame-drop policies on a per-channel basis. Measured results show that both kernel- and user-space protocols can achieve very good throughput: applications using both TCP and our own reliable byte-stream protocol have demonstrated throughputs in excess of 200 Mbit/s. The benefits of running protocols in user-space are well known- the drawback has often been a severe penalty in the performance achieved. In this paper we show that it is possible to have the best of both worlds.

A Per-Channel, Memory-Oriented Transmultiplexer with Logarithmic Processing

This paper describes a memory-oriented design for a digital transmultiplexer which performs conversion between TDM and FDM on a per-channel basis. The processor uses FIR bandpass filters which also perform interpolation (TDM-to-FDM) and decimation (FDM-to-TDM). Hardware efficiency is obtained by implementing the FIR filters in a logarithmic mode, wherein multiplication becomes addition. Conversions to and from the logarithmic format are done in ROM look-up tables. ROM's are also used to store the filter coefficients. Signal samples are stored in RAM's. This paper describes the architecture of the transmultiplexer and presents simulation results. A TTL laboratory implementation and performance results are presented.