Instrumental Errors Research Articles

Stochastic Linearization of the Bearing in Adaptive Antenna Arrays with Coarse Space-Time Statistics

We analyze the construction of a system for processing space-time signals in a radio system that takes into account technical limitations in the measurement of the bearing. A desired efficiency can be achieved by using simplified processing procedures with stochastic controlled bearing interpolation. For implementation, we use processing based on truncated (low-element) managed apertures of antenna arrays and coarse (“binary”) robust signal statistics. We propose an alternative approach that involves applying the Monte Carlo method with feedback in the process of digital processing: we implement randomization and incremental stochastic control for the phase center position by sequentially activating a small number of elements during the accumulation and averaging of rough samples of the input signal. We also present quantitative results of reducing instrumental errors in bearing measurement.

COMPUTER MODELING OF ACCURACY CHARACTERISTICS OF STRAPDOWN INERTIAL NAVIGATION SYSTEM

Context. The problem of correction for operation of strapdown inertial navigation system used for unmanned aerial vehicle is urgent because of further increased requirements to autonomous flight in blackout zones. The object of the study was to simulate the accuracy characteristics of strapdown inertial navigation system based on known (or given) instrument errors of its sensors. Objective. The goal of the work is to develop a mathematical and computer model of the strapdown inertial navigation system and estimate its accuracy characteristics based on given values of sensor errors. Method. The mathematical and computer models of the strapdown inertial navigation system based on slow, medium and fast cycles are developed. For the simulation of accuracy characteristics, the strapdown inertial navigation system is represented as a set of dynamic and kinematic equations in local tangent plane coordinate system with the Earth’s model taking into account components of gravity acceleration. The models of sensors are developed based on characteristics of low-cost microelectromechanical sensors used onboard. Data fusion algorithms were previously considered and include modified Kalman filter or, for some cases, complimentary filter by compensation scheme, but not considered here in details. Direction cosine matrix for strapdown inertial navigation system algorithms is found by Poisson’s method. Results. The developed models have been realized and simulated in MATLAB+Simulink. Initial parameters (errors of the primary information sensors and the flight conditions) during simulation have been varied: medium, high and low latitudes; direction of flight (along and across the meridian; on and against the direction of rotation of the Earth). Conclusions. The developed models and their simulations have been compared with actual testing results of strapdown gyrovertical СБКВ-П2А and confirmed the validity. It allow us to recommend them for use in designing strapdown inertial navigation system of unmanned aerial vehicle, as well as for experimental study of innovative data fusion algorithms for integrated satellite and inertial navigation system.

SOFTWARE METHODS FOR INCREASING THE RELIABILITY OF AERODROME QUASI-DOPPLER AUTOMATIC RADIO DIRECTION FINDERS

Objectives To develop software methods that can improve the reliability of airfield quasi-Doppler automatic direction finders (ADFs).Method. Mathematical models and algorithms of software fault recovery of aerodrome quasi-Doppler automatic radio direction finders were developed. It is proposed to change the structure of aerodrome quasi-Doppler automatic radio direction finders.Results. Methods and algorithms for software improvement of the reliability of airfield quasi-Doppler automatic direction finders are proposed. A novel structural organisation of airfield quasi-Doppler automatic radio direction finders is given. New software methods are proposed for ensuring ADF operability in the event of a failure of the antenna system vibrators, both with the use of phase relations from any two pairs of orthogonally arranged ring antenna vibrators and with the use of the combinatorial method. The proposed organisational ADF scheme allows the average operating time per failure of one direction-finding channel to be increased by 4.4 times.Conclusion. The developed methods for ensuring ADF operability in the event of a failure of antenna system vibrators enable a simultaneous calculation of the azimuth and angle of position on the radio emission source. The use of the proposed method increases the potential reliability of airfield quasi-Doppler automatic direction finders without any hardware costs, as well as ensuring the adequacy of the calculated instrumental error values of airfield quasi-Doppler automatic direction finders relative to the real ones.

The impact of atmospheric dispersion in the performance of high-resolution spectrographs

ABSTRACT Differential atmospheric dispersion is a wavelength-dependent effect introduced by the atmosphere. It is one of the instrumental errors that can affect the position of the target as perceived on the sky and its flux distribution. This effect will affect the results of astronomical observations if not corrected by an atmospheric dispersion corrector (ADC). In high-resolution spectrographs, in order to reach a radial velocity (RV) precision of 10 cm s−1, an ADC is expected to return residuals at only a few tens of milliarcseconds (mas). In fact, current state-of-the-art spectrograph conservatively require this level of residuals, although no work has been done to quantify the impact of atmospheric dispersion. In this work, we test the effect of atmospheric dispersion on astronomical observations in general, and in particular on RV precision degradation and flux losses. Our scientific objective was to quantify the amount of residuals needed to fulfil the requirements set on an ADC during the design phase. We found that up to a dispersion of 100 mas, the effect on the RV is negligible. However, on the flux losses, such a dispersion can create a loss of ∼2 per cent at 380 nm, a significant value when efficiency is critical. The requirements set on ADC residuals should take into consideration the atmospheric conditions where the ADC will function, and also all the aspects related with not only the RV precision requirements but also the guiding camera used, the tolerances on the flux loss, and the different melt data of the chosen glasses.

Methods of secondary information transformation for the evaluating of object’s spatial orientation

Problem statement. Today, systems in which it is necessary to evaluate the parameters of the spatial orientation of objects are widely used . Examples of such systems are computer systems (CS) for drilling control during geological exploration, seismic hazard prediction systems, diagnostic systems in nuclear energy, and others. Such an assessment is carried out, as a rule, by the software and hardware components of the spatial orientation assessment (SHCSOA) included in specialized CSs and are intended for primary and secondary transformation of information. In this case, the bias of the orientation estimation determines the efficiency of the use of the CS. A number of SHCSOA works in difficult conditions, characterized by the presence of vibration and magnetic anomalies, instability of the temperature, etc., with severe restrictions on the size of the primary sensors (PS). An analysis of the existing PAKOPOs showed that the need to ensure the orientation estimation is sufficient for the needs of the practice leads to an increase in the resource of the CS as a whole, which significantly narrows their scope. This gives rise to a contradiction between the efficiency and resource intensity of SHCSOA and specialized CSs. Purpose. To resolve this contradiction, this paper proposes methods for the secondary conversion of measurement information, which can provide a given bias and increase the efficiency of assessing the spatial orientation of objects. Conclusion. By mathematical modeling of the PS, as well as by preliminary determination of the instrumental errors of the PS and the parameters of the external magnetic anomalies, methods of secondary processing of information are proposed that can significantly reduce the bias in the estimation of the spatial orientation of objects using SHCSOA as part of specialized CS.

Perspectives On Blood-Based Point-Of-Care Diagnostics.

BackgroundPoint of Care (POC) diagnostics are an essential component of modern medicine and are employed in a variety of clinical disciplines to improve patient outcomes and provider efficiency. Despite these benefits, there are aspects of POC testing which may still hold room for improvement. In the present study, a group of healthcare professionals familiar with different facets of blood-based POC testing provided their perspectives on the benefits and challenges of POC testing within their respective fields.Materials and methodsThe study was conducted from April to June 2019, in Colorado, United States of America. Five healthcare professionals, each working in a distinct field (anesthesiology, nursing, emergency medicine, trauma surgery, and POC management) were interviewed. Results from each of the interviews were transcribed as qualitative perspectives on POC diagnostics.DiscussionThe general consensus among participants in this study is that POC testing is tremendously beneficial, providing rapid test results, increased access to diagnostics, and improvements in hospital efficiency. However, significant challenges remain in blood-based POC diagnostics, particularly in maintaining sample quality, due to the fact that devices used for sample acquisition and handling are not designed for POC. This raises the possibility for interferents like hemolysis to occur, which may alter diagnostic results. Errors in POC diagnostics, whether due to sample, operator, or instrument error, may cause providers to lose confidence in the test. This lack of confidence can lead to duplicate testing and delayed patient diagnoses.ConclusionThe perspectives presented in this study suggest there is a significant need for improvement in the pre-analytical phase of POC testing, and that current practice employs specimen collection technology not designed for POC. Therefore, one hypothesis is that the introduction of a collection device designed specifically for POC could reduce pre-analytical errors, standardize sample quality, improve efficiency, and further benefit patient care.

The POLARBEAR Fourier transform spectrometer calibrator and spectroscopic characterization of the POLARBEAR instrument.

We describe the Fourier Transform Spectrometer (FTS) used for in-field testing of the POLARBEAR receiver, an experiment located in the Atacama Desert of Chile which measures the cosmic microwave background (CMB) polarization. The POLARBEAR-FTS (PB-FTS) is a Martin-Puplett interferometer designed to couple to the Huan Tran Telescope (HTT) on which the POLARBEAR receiver is installed. The PB-FTS measured the spectral response of the POLARBEAR receiver with signal-to-noise ratio >20 for ∼69% of the focal plane detectors due to three features: a high throughput of 15.1 sr cm2, optimized optical coupling to the POLARBEAR optics using a custom designed output parabolic mirror, and a continuously modulated output polarizer. The PB-FTS parabolic mirror is designed to mimic the shape of the 2.5 m-diameter HTT primary reflector, which allows for optimum optical coupling to the POLARBEAR receiver, reducing aberrations and systematics. One polarizing grid is placed at the output of the PB-FTS and modulated via continuous rotation. This modulation allows for decomposition of the signal into different harmonics that can be used to probe potentially pernicious sources of systematic error in a polarization-sensitive instrument. The high throughput and continuous output polarizer modulation features are unique compared to other FTS calibrators used in the CMB field. In-field characterization of the POLARBEAR receiver was accomplished using the PB-FTS in April 2014. We discuss the design, construction, and operation of the PB-FTS and present the spectral characterization of the POLARBEAR receiver. We introduce future applications for the PB-FTS in the next-generation CMB experiment, the Simons Array.

Metrology of nerve-similar sensing systems in anthropomorphic robots and living organisms

The features of metrological support of nerve-similar sensor measuring systems with the use of neural networks are considered. It is established that the metrological verification of such measuring systems, by analogy with living organisms, is possible by comparing their responses, invariant to the external unstable environment. It is shown that from the standpoint of classical metrology, instrumental, methodical, static, dynamic, systematic and random errors of nerve-like sensory measurement systems with neural network results are reduced to two types – methodical and systematic errors of neural network training. It is proved that without using of reference calibration tools for embedded sensors, it is possible to experimentally evaluate systematic and random errors in the presence of several similar measurement systems by multiple pairwise comparisons of their responses, and the obtained systematic error can be introduced in the form of a metrological correction in the results of responses.

Simulation of fiber optic sensors of electrical quantities based on Bragg gratings with instrumental errors correction

The principle and an example of simulating a network high-sensitivity sensor of electrical quantities based on fiber Bragg gratings interlinked with a sensor-actuator structure, and a method for instrumental errors correction are described.

On the surface energy balance closure at different temporal scales

Measurements of the surface energy fluxes (turbulent and radiative) and other ancillary atmospheric/soil parameters made in the Columbia River Basin (Oregon) in an area of complex terrain during a 10-month long portion of the second Wind Forecast Improvement Project (WFIP 2) field campaign are used to study the surface energy budget (SEB) and surface fluxes over different temporal scales. This study analyzes and discusses SEB closure based on half-hourly, daily, monthly, seasonal, and sub-annual (~10-month) temporal averages. The data were collected over all four seasons for different states of the underlying ground surface (dry, wet, and frozen). Our half-hourly direct measurements of energy balance show that the sum of the turbulent sensible and latent heat fluxes systematically underestimate positive net radiation by around 20–30% during daytime and overestimate negative net radiation at night. This imbalance of the surface energy budget is comparable to other terrestrial sites. However, on average, the residual energy imbalance is significantly reduced at daily, weekly, and monthly averaging timescales, and moreover, the SEB can be closed for this site within reasonable limits on seasonal and sub-annual timescales (311-day averaging for the entire field campaign dataset). Increasing the averaging time to daily and longer time intervals substantially reduces the ground heat flux and storage terms, because energy locally entering the soil, air column, and vegetation in the morning is released in the afternoon and evening. Averaging on daily to sub-annual timescales also reduces random instrumental measurement errors and other uncertainties as well as smooths out a hysteresis effect (phase lag) in the SEB relationship between different components. This study shows that SEB closure is better for dry soils compared to wet soils and the statistical dependence of the turbulent fluxes and net radiation for freezing soil surfaces appears weak, if not non-existent, apparently due to lack of the latent heat of fusion term in the traditional SEB equation.

Northern Ireland's longstanding record wind gust is almost certainly incorrect

Abstract Online onlyAccurate assessment of record extreme wind gusts is important for building design standards and for industries such as insurance and forestry. Here, we show that the current record wind gust for Northern Ireland – 108kn (56ms−1) recorded at Kilkeel on 12 January 1974 – is almost certainly incorrect and may have arisen from an instrumental error or a power surge. We deduce this from direct anemograph inspection and from a variety of indirect supporting evidence. We recommend that other longstanding UK record wind gusts should also be independently re‐examined to assess their veracity.

Estimation of clock errors in underwater acoustic instruments

All underwater acoustic sensors require accurate on-board clocks for subsequent data analysis and interpretation. Unfortunately, most clock oscillators change their frequency over time, which occurs due to environmental changes, aging, and other factors. Typically, clock errors are accounted for by referencing the instrument clock to a known accurate clock (such as GPS) before and after the deployment and applying a correction during data post-processing. This method, however, does not accurately estimate clock errors during a specific experimental event. A method to estimate clock performance during the specific event of interest has been developed. It is shown that advanced signal processing techniques can be used to accurately reconstruct the motion of the acoustic source, which, in turn, can improve the accuracy of the acoustic receivers deployed on the seafloor in the deep ocean. A small subset of data collected on the last day of the Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June–July 2013 is analyzed for the demonstration of these techniques. [Work supported by the MITRE Corporation’s R&D Program.]

Long rotation period main-sequence stars from Kepler SAP light curves

ABSTRACT Stellar rotation plays a key role in stellar activity. The rotation period could be detected through light curve variations caused by star-spots. Kepler provides two types of light curves: one is the Pre-search Data Conditioning (PDC) light curves, and the other is the Simple Aperture Photometer (SAP) light curves. Compared with the PDC light curves, the SAP light curves keep the long-term trend, relatively suitable for searches of long-period signals. However, SAP data are inflicted by some artefacts such as quarterly rolls and instrumental errors, making it difficult to find the physical periods in the SAP light curves. We explore a systematic approach based on the light curve pre-processing, period detection, and candidate selection. We also develop a simulated light curve test to estimate our detection limits for the SAP-like LCs. After applying our method to the raw SAP light curves, we found more than 1000 main-sequence stars with periods longer than 30 d; 165 are newly discovered. Considering the potential flaw of the SAP, we also inspect the newly found objects with photometry methods, and most of our periodical signals are confirmed.

Slitless Solar Imaging Spectroscopy

Abstract Spectrometers provide our most detailed diagnostics of the solar coronal plasma, and spectral data is routinely used to measure the temperature, density, and flow velocity in coronal features. However, spectrographs suffer from a limited instantaneous field of view (IFOV). Conversely, imaging instruments can provide a relatively large IFOV, but extreme-ultraviolet (EUV) multilayer imaging offers very limited spectral resolution. In this paper, we suggest an instrument concept that combines the large IFOV of an imager with the diagnostic capability of a spectrograph, develop a new parametric model to describe the instrument, and evaluate a new method for “deconvolving” the data from such an instrument. To demonstrate the operating principle of this new slitless spectroscopy instrument, actual spectroscopic raster data from the Hinode/EUV Imaging Spectrometer (EIS) spectrometer is used. We assume that observations in multiple spectral orders are obtained, and then use a new inverse problem method to infer the spectral properties. Unlike previous methods, physical constraints and regularization derived from prior knowledge can be naturally incorporated as part of the solution process. We find that the fidelity of the solution is vastly improved compared to previous methods. The errors are typically only a few km s−1 over a large IFOV, with a width of a few hundred pixels and an arbitrarily large height. These errors are not much larger than the errors in current slit spectroscopic instruments with limited IFOV. A further benefit is that the performance of candidate instruments can be optimized for specific scientific objectives. We demonstrate this by deriving optimum values for the spectral dispersion and signal-to-noise ratio.

Specific Features of Application of Current and Voltage Transducers When Calculating Eletrical Network Unbalance

Purpose of research. The purpose of this article is to consider the main features of the application of current and voltage transducers determining the electrical network unbalance factor. Also, an important issue is the value of measuring instruments inaccuracy, at which there is no impact on the unbalance factor determining. Methods. The article describes classifications of main current and voltage transducers. An example of the implementation of one of the voltage transducer and analog-to-digital converter variants is shown. The essence of the process of balancing is explained, various unbalance factors are considered, explanatory formulae are provided. The main requirements for current and voltage measurement circuits and for computational signal processing are mentioned. In particular, such important points as determining the phase angle, determining the network parameters and consideration of the influence of measurement errors on the determination of the unbalance factor are studied. The issur of determining the phase angle is considered and the need for its determination is indicated. It is explained that when determining the network parameters, high precision of measurement is required. Results. The impact of the instrumental error of measurements on the determination of the unbalance factor is considered, and instruments rating below which an error may occur while finding the unbalance factor is determined. When determining the instrument rating at which an unacceptable error occurs, a probabilistic model of power distribution of a three-phase network is mentioned; a graphical description of this model is given. Determining the sets of unbalance factors before balancing, after balancing and after balancing taking into account the error, is provided. It is mentioned that in determining these sets, weights are used as increasing and decreasing factors for the terms included in the set. The factor showing the percentage of the decrease of unbalance changes due to the effect of the error is introduced. The dependence of this factor on the measurement error is considered. Conclusion. A conclusion on the value of the error which does not impact the determination of the unbalance factor is provided.

Investigations beyond standard operating procedure on internal standard response.

Internal standard response is routinely monitored in regulated studies to accept or reject individual samples with outlier results due to potential sample processing or instrumentation errors, and processes are typically governed by standard operating procedures. However, acceptance or rejection of individual samples is not always sufficient. Internal standard response trends and substantial systemic differences between spiked and incurred samples using a method with an otherwise stable internal standard response should be investigated. Investigations may range from informal evaluations to detailed studies with formal investigation reports. Atypical internal standard response can be an indicator of systemic problems with a bioanalytical method and modification to allow for a relatively stable internal standard response across an analytical run may be essential.

Detection and characterization of estradiol (E2) and unconjugated estriol (uE3) immunoassay interference due to anti-bovine alkaline phosphatase (ALP) antibodies

ObjectivesCompetitive immunoenyzmatic assays for estradiol (E2) and unconjugated estriol (uE3) on UniCel DxI 800 Access immunoassay systems (Beckman Coulter) utilize bovine alkaline phosphatase (ALP) for amplification. In these assays, rare ‘IND’ error flags indicate that a relative light unit (RLU) raw result is past the high or low end of the calibration curve but cannot be differentiated from an instrument error or analytical interference. The present studies were conducted to establish a protocol to identify analytical interference and to characterize its mechanism when present. Design and methodsMatrix and recovery studies were conducted to establish a protocol for interference identification. Spiking experiments with inactivated calf intestinal ALP were performed to determine whether interference could be blocked. Commercial anti-ALP antibodies (Abs) were spiked into human serum to model assay interference. Three E2 immunoassays which do not include ALP as a reagent component (cobas e602, Roche; Centaur XP, Siemens; ARCHITECT i2000SR, Abbott) were tested for comparative purposes. Results1:2 dilution of specimen into Access Sample Diluent A (Beckman) differentiated IND error flags due to true low results (e.g. less than the analytical measurement range; AMR) from those due to assay interference. Interferences were reduced by pre-incubation with inactivated ALP and could be replicated by spiking with commercial anti-ALP Abs. ConclusionsPatient anti-bovine ALP Abs can cause interference on DxI 800 E2 and uE3 assays. This model can be used to investigate interference risk with other ALP-dependent assays.

Development and Students’ Perception on Teaching Aids of Photoelectric Effect Experiment Using Leds

The photoelectric effect experiment generally uses a very sophisticated and expensive apparatus. Some high schools and even universities in Indonesia cannot afford to conduct this experiment because of the high price of the apparatus. The purpose of this study was to develop a user-friendly, and cost-effective teaching aids which can be used to demonstrate the concepts of modern physics related to the photoelectric effect. The stages of this study employed the Four-D model, namely define, design, develop, and disseminate. Based on experts and practitioner evaluation, the developed teaching aids and practicum devices of photoelectric effect experiment were found to be valid and reliable. The results of the experiment by using this developed teaching aids of the photoelectric effect showed that there is a linear relationship between the stopping potential and the frequency of light emitted by the LED. These results are consistent with Millikan's experimental results, the first physicist who succeed in proving Einstein's hypothesis of the photoelectric effect, that in the photoelectric effect the stopping potential does not depend on the intensity of light but depends only on the frequency of light. In this study, the Planck’s constant value obtained is 6.408x10-34 J.s. Although this value is slightly smaller than the accepted value of Planck's constant that is 6.626x10-34 J.s, it is good enough considering the instrumental error occurred during the measurement of current and voltage. Furthermore, the students’ perception of the developed teaching aids and practicum devices of the photoelectric effects experiment are 74.9% (good) and 80.2% (very good), respectively. This indicates that the photoelectric effect experiment teaching aids and practicum devices that have been developed can be used to demonstrate and prove the concepts of modern physics related to the photoelectric phenomena correctly.Keywords: Teaching Aids, Photoelectric Effect, Students’ Perception

Hybrid IRBM-BPNN Approach for Error Parameter Estimation of SINS on Aircraft.

To realize the error parameter estimation of strap-down inertial navigation system (SINS) and improve the navigation accuracy for aircraft, a hybrid improved restricted Boltzmann machine BP neural network (IRBM-BPNN) approach, which combines restricted Boltzmann machine (RBM) and BP neural network (BPNN), is proposed to forecast the inertial measurement unit (IMU) instrument errors and initial alignment errors of SINS. Firstly, the error generation mechanism of SINS is analyzed, and initial alignment error model and IMU instrument error model are established. Secondly, an unsupervised RBM method is introduced to initialize BPNN to improve the forecast performance of the neural network. The RBM-BPNN model is constructed through the information fusion of SINS/GPS/CNS integrated navigation system by using the sum of position deviation, the sum of velocity deviation and the sum of attitude deviation as the inputs and by using the error parameters of SINS as the outputs. The RBM-BPNN structure is improved to enhance its forecast accuracy, and the pulse signal is increased as the input of the neural network. Finally, we conduct simulation experiments to forecast and compensate the error parameters of the proposed IRBM-BPNN method. Simulation results show that the artificial neural network method is feasible and effective in forecasting SINS error parameters, and the forecast accuracy of SINS error parameters can be effectively improved by combining RBM and BPNN methods and improving the neural network structure. The proposed IRBM-BPNN method has the optimal forecast accuracy of SINS error parameters and navigation accuracy of aircraft compared with the radial basis function neural network method and BPNN method.

Challenges in relative sea-level change assessment highlighted through a case study: The central coast of Atlantic Patagonia

There are areas in the world where our understanding of past sea-level changes is less robust than in others. This is partly due to the difficulty past investigators had adopting i) high-resolution elevation measurement techniques (largely available only in the last decade) and ii) standardized methodological approaches to reconstruct past relative sea levels starting from field measurements. The central coast of Atlantic Patagonia (Argentina), preserves a unique succession of coastal landforms, which scientific investigations suggest to have been formed discontinuously since at least marine isotope stage 11 up to the Holocene. Patagonian coastal deposits (in particular raised beach ridges, marine terraces and river mouth terraces) and erosional landforms (slope angles, marine notches) were studied in the past with the aim of reconstructing relative sea-level changes and provide geological evidence to constrain geophysically based models for an area affected by significant vertical displacement due to isostatic adjustment and possibly by tectonic uplift. So far, there is no general agreement about the interpretation of Patagonia landforms and deposits in terms of sea-level index points. This is certainly a gap within a planetary scale overview of sea-level change and represents an obstacle for the construction of a sound model of glacial isostatic adjustment for the area. In this paper we critically analyse previous works on sea-level change along the central coast of Atlantic Patagonia and highlight the major sources of uncertainty, including choices about calculating past relative sea levels from the elevation of indicators and the vertical datum used. We also provide a comparison between different vertical datums (tidal, gravimetric and geodetic) at a real site (Puerto Deseado) where Differential Global Positioning System measurements were performed by our team in 2016, and address the problem from a trans-disciplinary point of view. In order to obtain accurate sea-level change estimates in the area, we suggest the use of a large spectrum of sea-level markers with well-defined indicative meanings and the adoption of specific technical choices capable of minimizing instrumental errors.