Auxiliary Channels Research Articles

Matched filter analysis of burst waveform injections

Hardware injections provide us with a crucial tool for proving that we understand the response and performance of the LIGO detectors. Since we have complete knowledge of the injected waveform and detailed measurements of the detector response function, we are able to predict and confirm the instrument response. During the S5 science run of LIGO, various burst-type waveforms are being injected. We have analyzed the first seven months of these injections, using optimal matched filters derived from the injection waveforms. We have confirmed that most of the responses follow the predictions and have measured the accuracy of the estimated arrival time. In addition, we examined transients identified by the KleineWelle algorithm in auxiliary data channels at the time of hardware injections. Through this study, we could recognize couplings between auxiliary channels and the gravitational wave channels and assess the safety of the use of auxiliary channels as vetoes for gravitation wave candidates.

Data quality studies for burst analysis of Virgo data acquired during Weekly Science Runs

Virgo started collecting science data during weekends in order to not interfere with commissioning activities. The goal of Weekly Science Runs is to ease the transition between commissioning periods and data taking periods, in addition to providing data sets exploiting the stationary behavior of the detector. The detection of gravitational wave (GW) bursts emitted by core collapse of supernovae is one of the most difficult tasks for the GW community due to the fact that there are uncertainties in the exact shape of the waveforms, as we do not have complete models. A major task for this kind of detection effort is the cleaning of the event triggers found by the detection pipelines, namely the removal of accidental transient signals due to noise source events. In order to clean our data from false GW events, we need to define a strategy for data quality cut and veto of auxiliary and environmental monitoring channels. In this paper we report on the analysis we performed on data acquired during Weekly Science Runs to explore and define the data quality cut and veto studies for burst analysis.

Preliminary results from the hierarchical glitch pipeline

This paper reports on the preliminary results obtained from the hierarchical glitch classification pipeline on LIGO data. The pipeline that has been under construction for the past year is now complete and end-to-end tested. It is ready to generate analysis results on a daily basis. The details of the pipeline, the classification algorithms employed and the results obtained with one days analysis on the gravitational wave and several auxiliary and environmental channels from all three LIGO detectors are discussed.

Analysis of gravitational wave bursts in TAMA300 data using an ALF filter

We analysed the TAMA300 data in time domain using the ALF filter. Two kinds of vetoes were implemented in order to reduce fake events. One is the method based on the time scale of burst gravitational wave (GW) signals. The other is the veto using one of the auxiliary monitor channels of the interferometer operation. The analysed data were DataTaking9 data of the TAMA300 taken from 28th November 2003 to 10th January 2004. Finally, we did not find any evidence of the detection of gravitational wave events, and obtained an upper limit rate of 0.55 (events/day) with a confidence level 90% at the level of 10−17hrss GW amplitude for a 1304 Hz sine-Gaussian signal.

Null-Steering LMS Dual-Polarised Adaptive Antenna Arrays for GPS

The implementation of a null-steering antenna array using dual polarised patch antennas is considered. Several optimality criterion for adjusting the array weights are discussed. The most effective criteria minimises the output power of the array subject to maintaining a right hand circular polarisation (RHCP) response on the reference antenna. An unconstrained form of this criteria is derived, in which the reference channel is the RHCP output of the reference antenna and the LHCP output of the reference antenna is included as one of the auxiliary channels. An FPGA implementation of the LMS algorithm is then described. To prevent weight vector drift a variant of the circular leakage LMS algorithm was used. The implementation details of a simplified circular leakage algorithm more suited to an FPGA implementation are presented. This simplified leakage algorithm was shown to have a similar steady state weight vector as the full algorithm.

Scaled-Out Multilayer Gas−Liquid Microreactor with Integrated Velocimetry Sensors

We describe the design and flow distribution of a scaled-out gas−liquid silicon-based microreactor that consists of three vertically stacked reaction layers each containing 20 reaction channels. The reaction channels are operated in parallel from single feeds of gas and liquid with a liquid throughput of 80 mL/h. Gas and liquid are introduced to the device through single inlet ports, flow vertically to the reaction layers, and are controllably distributed to the horizontal reaction channels through gas and liquid auxiliary channels that present pressure drops significantly larger than that across the reaction channels. The product mixture flows out of the device through a single outlet port. Flow visualization by pulsed-laser fluorescence imaging reveals that the flow regime is uniform across the top layer. By integrating waveguided optical multiphase flow sensors, slug-flow properties are measured across the reaction channels on the top and middle layers; comparable slug frequencies and slug velocities a...

Gravitational wave burst vetoes in the LIGO S2 and S3 data analyses

The LIGO detectors collected about four months of data in 2003–2004 during two science runs, S2 and S3. Several environmental and auxiliary channels that monitor the instruments' physical environment and overall interferometric operation were analysed in order to establish the quality of the data as well as the presence of transients of non-astrophysical origin. This analysis allowed a better understanding of the noise character of the instruments and the establishment of correlations between transients in these channels and the one recording the gravitational wave strain. In this way, vetoes for spurious burst events were identified. We present the methodology we followed in this analysis and the results from the S2 and S3 veto analysis within the context of the search for gravitational wave bursts.

Development of a High‐Performance Boiling Heat Exchanger by Improved Liquid Supply to Narrow Channels

A two-phase flow loop is a promising method for application to thermal management systems for large-scale space platforms handling large amounts of energy. Boiling heat transfer reduces the size and weight of cold plates. The transportation of latent heat reduces the mass flow rate of working fluid and pump power. To develop compact heat exchangers for the removal of waste heat from electronic devices with high heat generation density, experiments on a method to increase the critical heat flux for a narrow heated channel between parallel heated and unheated plates were conducted. Fine grooves are machined on the heating surface in a transverse direction to the flow and liquid is supplied underneath flattened bubbles by the capillary pressure difference from auxiliary liquid channels separated by porous metal plates from the main heated channel. The critical heat flux values for the present heated channel structure are more than twice those for a flat surface at gap sizes 2 mm and 0.7 mm. The validity of the present structure with auxiliary liquid channels is confirmed by experiments in which the liquid supply to the grooves is interrupted. The increment in the critical heat flux compared to those for a flat surface takes a maximum value at a certain flow rate of liquid supply to the heated channel. The increment is expected to become larger when the length of the heated channel is increased and/or the gravity level is reduced.

C124 給液促進機構を持つ狭あい流路構造による限界熱流束の増大

To develop compact space heat exchangers, experiments on the increase of CHF for narrow heated ducts between parallel plates are conducted. Fine grooves are machined on the surface of heat transfer side, and liquid is supplied underneath flattened bubbles by capillary pressure from auxiliary liquid channels separated from the main channel by porous metal plates. With this structure, values of CHF for the heating surface are increased up to twice as much as those without the structure. Effect of inlet liquid velocity on CHF values is also investigated. At an optimum flow rate, values of CHF take the maximum for a given liquid subcooling. Teh increase in CHF values is expected to become much higher when the duct is elongated and/or gravity level is reduced.

Endoscope washers – a protocol for their use

A protocol for the disinfection of gastroduodenoscopes, retrograde cholangiopancreatography endoscopes and colonoscopes using endoscope washers is described. The process recommends initial manual washing with a disinfectant containing didecyldimethylammonium chloride, surfactants and enzymes, a second washing in the endoscope washer using a detergent associated with a bacteriostatic, fungistatic substance (benzoisothiazolone) and finally the use of a 2% glutaraldehyde product buffered at pH6. After treatment with 2% Steranios added to the washer, less than 1 micro-organism/ml liquid was found in the following units: 83% of the colonoscopes, 83% of the oesophagogastroduodenoscopes, 83% of the main channels of the retrograde cholangiopancreatography endoscopes and 75% of the auxiliary channels of the latter instruments. In 14% of the colonoscopes, 42% of the gastroduodenoscopes, 42% of the main and 50% of auxiliary channels in the retrograde cholangiopancreatography endoscopes there were no signs of microbial growth in the wash liquid. The results obtained indicated that this protocol allowed adequate disinfection of the endoscope channels, structurally the most difficult part of the instrument to disinfect. Emphasis is given to the degree by which instrument contamination can increase during overnight storage, suggesting that endoscopes need to be submitted to further disinfection after overnight storage. Moreover, the water flowing into the washers can also cause instrument recontamination, particularly during the final rinses. Therefore, to better safeguard the health of patients undergoing endoscopy, special care must be taken to maintain the filters and disinfect the washers themselves, no matter how effective the disinfection protocol used may be.

Endoscope washers – a protocol for their use

A protocol for the disinfection of gastroduodenoscopes, retrograde cholangiopancreatography endoscopes and colonoscopes using endoscope washers is described. The process recommends initial manual washing with a disinfectant containing didecyldimethylammonium chloride, surfactants and enzymes, a second washing in the endoscope washer using a detergent associated with a bacteriostatic, fungistatic substance (benzoisothiazolone) and finally the use of a 2% glutaraldehyde product buffered at pH6. After treatment with 2% Steranios added to the washer, less than 1 micro-organism/ml liquid was found in the following units: 83% of the colonoscopes, 83% of the oesophagogastroduodenoscopes, 83% of the main channels of the retrograde cholangiopancreatography endoscopes and 75% of the auxiliary channels of the latter instruments. In 14% of the colonoscopes, 42% of the gastroduodenoscopes, 42% of the main and 50% of auxiliary channels in the retrograde cholangiopancreatography endoscopes there were no signs of microbial growth in the wash liquid. The results obtained indicated that this protocol allowed adequate disinfection of the endoscope channels, structurally the most difficult part of the instrument to disinfect. Emphasis is given to the degree by which instrument contamination can increase during overnight storage, suggesting that endoscopes need to be submitted to further disinfection after overnight storage. Moreover, the water flowing into the washers can also cause instrument recontamination, particularly during the final rinses. Therefore, to better safeguard the health of patients undergoing endoscopy, special care must be taken to maintain the filters and disinfect the washers themselves, no matter how effective the disinfection protocol used may be.

Performance of corrected adaptive monopulse estimation

The shape of sum and difference beams can be severely distorted if nulls in jammer directions are formed. In a previous paper a correction formula was developed that can be applied to monopulse estimation with subarray output adaptive arrays as well as to generalised sidelobe canceller (GSLC) configurations. The present paper derives the probability density function for such monopulse estimators with given adaptive beams for Rayleigh targets and jammers. With this both mean and variance can be easily calculated. For nonfluctuating targets and gaussian jammers formulas for the mean and variance are given which have to be evaluated numerically. These results can be used to analyse the performance of different corrected adaptive monopulse schemes. In particular it is demonstrated how the bias and variance of the monopulse estimates depend on jammer location, SNR, type and number of subarrays or auxiliary channels for the GSLC.

Asymptotic S/N results for an adaptive polyspectral canceller using sample matrix inversion

An adaptive polyspectral canceller configuration is defined, whereby auxiliary canceller channels are formed using distinct monomial expressions of the auxiliary sensor channels. If noises in the auxiliary canceller channels are correlated with the noise in a main channel, then improvement in output signal-to-noise (S/N) power ratio is possible by cancelling in linear fashion the correlated auxiliary canceller channels with the main channel. The convergence performance of the polyspectral canceller is analyzed. A simple expression is derived for the asymptotic S/N efficiency of the adaptive polyspectral canceller as a function of the number of independent input sample vectors used to calculate the adaptive canceller weights and other canceller/noise model parameters. It is shown by simulation for low-order polyspectral cancellers of a specific form with Gaussian inputs that this asymptotic expression is a good approximation of the actual S/N efficiency for a moderate number of input sample vectors. However, for moderate-to-high order polyspectral cancellers, the asymptotic expression is a poor indicator of performance. >

Convergence rate of an SMI canceler in nonstationary noise

Convergence results for the sample matrix inversion (SMI) canceler algorithm in nonstationary noise are presented. Exact results are given for the convergence rate of the average output noise power residue of the canceler normalized to the quiescent average output noise power residue for a two-input canceler (one auxiliary), and lower and upper bounds are derived for cancelers with two or more inputs under the assumption that there is no internal noise. These bounds are a function of the number of independent samples processed per channel (main and auxiliary), the number of auxiliary input channels, and the external noise environment. The external noise environment is modeled as a single interfering source that is conditionally Gaussian, with a power level specified at each sampling time instant. Furthermore, this model is generalized in the sense that a joint probability distribution function is defined for the power levels over a canceler processing batch. This leads to the capability of modeling and evaluating the SMI canceler in a variety of nonstationary single interference scenarios. >

Development of anastomosing channels in south-central Indiana

Numerous streams in south-central Indiana, tributary to the Ohio River, exhibit anastomosed channel patterns. The anastomosing patterns are characterized by a primary channel and one or more auxiliary channels (anabranches) that are often abandoned or receive flow only during flood. Development of the anastomosed pattern involves avulsion and proceeds in a sequential manner where: (1) aggradation significantly reduces channel depth, (2) overbank flow occurs more frequently as channel capacity is reduced, (3) floodplain deposits are incised by sediment-deficient overbank flow producing a new channel (gully) having a lower gradient and elevation than the primary channel, and (4) the gully created by overbank flow extends upstream and captures the drainage system converting the previous trunk channel into an anabranch. Avulsion is typically associated with aggrading fluvial systems, but the investigated streams are undergoing an episode of degradation. Avulsion occurs because of localized deposition along concave-up channel segments. The concave-up channel reaches are spatially controlled by the occurrence of non-resistant strata that separate beds of resistant sandstone. Thus, the location of avulsion and anastomosing channels is predetermined by the lithology and stratigraphy of the underlying bedrock.

Cancellation of specular and diffuse jammer multipath using a hybrid adaptive array

It has been demonstrated that specular or diffuse jammer multipath can be canceled to a desired level by using an adaptive array that combines bandwidth partitioning with tapped delay lines. Such hybrid systems are studied. In particular, the author studies an ideal two-element array that uses bandwidth partitioning in both the main and auxiliary channels, with an Mth-order adaptive finite impulse response filter in each subband of the auxiliary. The ability of this system to cancel specular moderately diffuse and diffuse multipath is studied. The combinations of bandwidth partitioning and filter order that can achieve a specified jammer cancellation level are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Adaptive array transient sidelobe levels and remedies

The transient sidelobe level of a sidelobe canceler (SLC) is a function of the external noise environment, the number of adaptive auxiliary antennas, the adaptive algorithm used, auxiliary antenna gain margins, and the number of samples used to calculate the adaptive weights. An analytical result for the adaptive sidelobe level is formulated for the case when the adaptive algorithm is the open-loop, sampled matrix inversion (SMI) algorithm. The result is independent of whether concurrent or nonconcurrent data processing is used in the SMI algorithm's implementation. It is shown that the transient sidelobe level is eigenvalue dependent and increases proportionally to the gain margin of the auxiliary antenna elements with respect to the quiescent main antenna sidelobe level. Techniques that reduce this transient sidelobe level are discussed, and it is theoretically shown that injection independent noise into the auxiliary channels significantly reduces the transient sidelobe level. It is demonstrated that using this same technique reduces the SMI noise power residue settling time. >

Performance of a modified feedback loop adaptive array with TVRO satellite signals

Performance of an experimental adaptive antenna array system is evaluated using television receive-only (TVRO) satellite signals. The experimental system is a sidelobe canceller with two auxiliary channels. Modified feedback loops are used to enhance the suppression of weak interfering signals. The modified feedback loops used two spatially separated antennas, each with an individual amplifier for each auxiliary channel. Thus, the experimental system uses five antenna elements. Instead of using five separate antennas, a reflector antenna with multiple feeds is used to receive signals from various TVRO satellites. The details of the earth station are given. It is shown that the experimental system can null up to two signals originating from interfering TVRO satellites while receiving the signals from a desired TVRO satellite.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Algorithmic, architectural, and beam pattern issues of sidelobe cancellation

Various important issues concerning the sidelobe cancellation (SLC) approach for suppressing sidelobe interference signals in radar are investigated. The concepts are presented in a tutorial manner and include: formulating the calculation of the complex weights for the auxiliary channels as an exact least-squares (LS) problem; computing the LS weights using orthogonal transformation for improved numerical accuracy; and mapping orthogonalization-based algorithms onto systolic arrays. The problem of excessive degrees of freedom (EDOF) associated with utilizing too many auxiliary elements when a relatively small number of jammers are present, is also considered. A divisionless orthogonalization-based algorithm is presented for the computation of the auxiliary weights. Many of these issues have previously been either implicitly stated or only individually addressed in various sources by a number of researchers. Besides showing simulation results and the divisionless procedure for obtaining the final auxiliary weights, a major consideration was to present all of the aforementioned concepts in a coherent and unified framework.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Single- and double-mode gas trigatron: main-gap and trigger-gap interactions

In the past, it has been presumed that the main-gap breakdown in a trigatron is caused by a precursor spark channel occurring either at the trigger gap or between a trigger electrode and oppositely located main electrode. Based on the detailed analysis of voltage and current waveforms at the trigger gaps of single- and double-mode gas trigatrons, the authors have proposed an interaction between the main gap and the trigger gap under favourable conditions. This interaction gives rise to two or more auxiliary spark channels which develop between different over-volted electrode pairs in a predictable manner. The enhanced UV illumination and electric field distortion as a result of these multiple auxiliary arcs lead to the development of a streamer breakdown between the main electrodes.