Continuous Calibration Research Articles

Selection and Characterization of Glaciers on the Tibetan Plateau as Potential Pseudoinvariant Calibration Sites

Vicarious calibration using pseudoinvariant calibration sites (PICS) has become increasingly popular, as it is the most cost-effective method for on-orbit calibration of space-borne optical sensors. Glaciers on the Tibetan Plateau (TP) are located at more than 4500 m above sea level. These snow targets, exhibiting much brighter reflectance and less affected by aerosol and water vapor than desert targets, can help to reduce the uncertainties associated with vicarious calibration. In contrast to polar snow, the TP is not limited by polar night, thus ensuring continuous calibration monitoring. This study investigated the potential role of TP glaciers as PICS for the first time. To accomplish this, the coefficient of variation (CV) was applied to characterize the spatial uniformity and temporal stability of five relatively larger and flatter TP glaciers based on several independent Landsat Thematic Mapper and Operational Land Imager datasets over 20 years. The criteria of CV < 3% (both spatial and temporal) through Landsat visible and near-infrared channels were used to identify potential PICS across the candidate glaciers. Finally, three snow PICS with areas of at least 7.2 km2 and two snow PICS with areas of 1.2–2.1 km2 were identified. The area of the snow PICS is smaller in autumn and winter due to the snow cover. The feasibility of using these sites for long-term calibration monitoring of satellite sensors is also discussed. Results indicate that although the snow PICS exhibits stronger BRDF than the invariant desert target, the MODIS calibration trends detected from snow PICS are comparable to those from the desert target.

Two-dimensional Finite Element Model of Breast Cancer Cell Motion Through a Microfluidic Channel.

A two-dimensional model for red blood cell motion is adapted to consider the dynamics of breast cancer cells in a microfluidic channel. Adjusting parameters to make the membrane stiffer, as is the case with breast cancer cells compared with red blood cells, allows the model to produce reasonable estimates of breast cancer cell trajectories through the channel. In addition, the model produces estimates of quantities not as easily obtained from experiment such as velocity and stress field information throughout the fluid and on the cell membrane. This includes locations of maximum stress along the membrane wall. A sensitivity analysis shows that the model is capable of producing useful insights into various systems involving breast cancer cells. Current results suggest that dynamics taking place when cells are near other objects are most sensitive to membrane and cytoplasm elasticity, dynamics taking place when cells are not near other objects are most sensitive to cytoplasm viscosity, and dynamics are significantly affected by low membrane bending elasticity. These results suggest that continued calibration and application of this model can yield useful predictions in other similar systems.

Permanent densification of silica glass for pressure calibration between 9 and 20 GPa at ambient temperature

ABSTRACTPermanent density increase of silica glass was used to calibrate pressure generation delivered by cupped sintered diamond anvils (‘dimple anvils’) [Haberl B, Molaison JJ, Neuefeind JC, et al. Simple modified Bridgman anvil design for high pressure synthesis and neutron scattering. High Press. Res. submitted] within the Paris-Edinburgh press between approximately 9 and 20 GPa. Raman spectral changes of recovered silica glass with increased density were used to determine the maximum pressure reached by following an established calibration curve [Deschamps T, Kassir-Bodon A, Sonneville C, et al. Permanent densification of compressed silica glass: a Raman-density calibration curve. J. Phys. Condens. Matter. 2013;25:025402]. The monotonic Raman shift of the Main Band spectral region (∼200–700 cm−1) of silica glass recovered from 9 to 20 GPa allows for continuous pressure calibration and is applicable to all presses that operate within this pressure range. Radial & axial Raman profiles were conducted to determine the pressure distribution within the sample chamber. This technique has been verified by in situ resistance measurements of the insulator-to-metal phase transition of ZnS near 15 GPa.

The Industrial Temperature Measurement System Based on the Uncooled IRFPA Detector

Most of the non-contact temperature measuring devices in the market are mainly based on dot infrared thermometers. The single machine operated instruments can only meet the requirements of temperature measurement for local temperature points, and can not feedback the temperature information and temperature direction of the whole temperature field in real time. Under the condition of low temperature, for the Commonly non-contact temperature measurement system, the reaction is not sensitive, can not keep up with the temperature change, Continuous calibration and debugging are needed in the case of changing ambient temperature, resulting in a great waste of personnel and time. In the aspect of infrared detector, the operating wavelength of the traditional infrared CCD is 0.4-1.1μm, affected by the cut-off wavelength, the error of infrared CCD is very large in industrial low temperature measurement. The operating wavelength of uncooled focal plane array infrared camera is generally between 8-14μm, which temperature measurement accuracy can reach 0.01°C under the optimum working environment. The UL01011 is most commonly used as the core photo detector in the uncooled focal plane uncooled micro-bolometer array infrared camera, we used it as the experimental photoelectric detector, Experiments showed that this method could achieve better results in practice.

Response of the TDR sensor to moisture under different types of management of a typical Latosol in the Cerrado

The technique of Time Domain Reflectometry (TDR) is important in the evaluation of soil moisture due to being an instantaneous method, which is non-destructive, precise and little dependent on environmental factors. However, researchers have emphasised the need for continuous specific calibration for each soil-management situation. The aim of this work therefore, was to evaluate the response of a portable TDR sensor to soil moisture in a Dystroferric Red Latosol in the Cerrado, under three different systems of soil management and at three different depths in the soil profile. To do this, TDR equipment consisting of two rods, each 0.12 m in length, was used for instantaneous measurement of the volumetric water content of the soil. The depths of 0-0.12, 0.12-0.24 and 0.24-0.36 m were evaluated under three different systems: no-tillage (NT), crop-livestock integration (CLI) and conventional planting (CONV). The response of the TDR sensor varied for both the type of management and for depth. After statistical regression analysis of the data, the values for moisture as a function of the response period of the sensor, and the correlation between moisture by TDR and moisture by the gravimetric method, were highly representative. This demonstrated that the apparatus under evaluation proved to be effective in measuring soil moisture at each depth and under each management system in the specific Latosol under analysis, displaying statistical differences between the treatments.

Characteristics of Si and SiC detectors at registration of Xe ions

The results of an investigation of silicon (Si) and silicon carbide (SiC) detectors when irradiated with a beam of Xenon (Xe) ions are presented. The irradiation was carried out at the IC-100 cyclotron, JINR, Dubna. The effect of the Pulse Height Defect (PHD) in registering Xe ions with energies 165, 82 and 45 MeV is shown to be twice as large for SiC detectors as that for Si detectors. It is also shown that degradation of SiC detectors irradiated with heavy Xe ions occurs at doses an order of magnitude greater than for Si detectors. The measurement method described, including continuous detector calibration by alpha-particles, makes it possible to simultaneously control the characteristics of detectors during irradiation and determine the energy of a beam of ions.

Prevalence of Seismic Rate Anomalies Preceding Volcanic Eruptions in Alaska

Seismic rate increases often precede eruptions at volcanoes worldwide. However, many eruptions occur without such precursors, limiting their usefulness for forecasting in some cases. Additionally, identifying seismic rate increases near volcanoes with high levels of background seismicity is non-trivial and many periods of elevated seismicity occur without ensuing eruptions. Although these issues are commonly known, efforts to quantify them are limited. In this study, we consistently apply a common statistical tool, the -statistic, to seismically monitored eruptions in Alaska of various styles to determine the overall prevalence of seismic rate anomalies immediately preceding eruptions. We find that 6 out of 14 (43%) Volcanic Explosivity Index (VEI) ≥2 eruptions have statistically significant precursory seismic rate increases. Of these 6 eruptions, 4 of them occur at volcanoes with relatively felsic compositions, repose periods greater than 10 years, and VEI ≥ 3. Overall, our results confirm that seismic rate increases are common prior to larger eruptions at long dormant, ‘closed-system’ volcanoes, but uncommon preceding smaller eruptions at more frequently active, ‘open-system’ volcanoes with more mafic magmas. We also explore the rate of other anomalies not precursory to eruptions and investigate their origins. Some of these non-eruptive anomalies can be explained by aftershocks of regional seismic events, magmatic activity that did not lead to eruption, or unrest at other nearby volcanoes within our search radius. Some open-system volcanoes have high non-eruptive anomaly rates and low pre-eruptive anomaly rates and are thus not amenable to forecasting with this method. In this study, we find that 26% of anomalies lead to eruption, while 74% do not. With continued calibration at more volcanoes, the statistical tool that we apply may be used more broadly to analyze future periods of seismic unrest at other volcanoes, properly placing such episodes into the context of the long-term background rate. These results and this tool may be useful for informing future eruption forecasts around the world.

A fully integrated and high precision 350 mV amplitude regulated LVDS transmitter compensating PVT variations

A low cost solution and high precision output amplitude regulation for Low-Voltage Differential Signaling (LVDS) driver targeted for TIA/EIA-644-A standard is reported. The proposed architecture has high tolerance towards internal resistors variations by adapting continuous calibration of output amplitude through a negative-feedback loop. It eliminates the requirements of high precision or expensive external resistor or post-fabrication calibration. Fabricated in 0.13-μm CMOS with a supply voltage of 3.3 V, the prototype exhibits regulated 700 mV output amplitude which is able to compensate for process, voltage and temperature (PVT) variations.

Solution to the Problem of Calibration of Low-Cost Air Quality Measurement Sensors in Networks.

We provide a simple, remote, continuous calibration technique suitable for application in a hierarchical network featuring a few well-maintained, high-quality instruments ("proxies") and a larger number of low-cost devices. The ideas are grounded in a clear definition of the purpose of a low-cost network, defined here as providing reliable information on air quality at small spatiotemporal scales. The technique assumes linearity of the sensor signal. It derives running slope and offset estimates by matching mean and standard deviations of the sensor data to values derived from proxies over the same time. The idea is extremely simple: choose an appropriate proxy and an averaging-time that is sufficiently long to remove the influence of short-term fluctuations but sufficiently short that it preserves the regular diurnal variations. The use of running statistical measures rather than cross-correlation of sites means that the method is robust against periods of missing data. Ideas are first developed using simulated data and then demonstrated using field data, at hourly and 1 min time-scales, from a real network of low-cost semiconductor-based sensors. Despite the almost naïve simplicity of the method, it was robust for both drift detection and calibration correction applications. We discuss the use of generally available geographic and environmental data as well as microscale land-use regression as means to enhance the proxy estimates and to generalize the ideas to other pollutants with high spatial variability, such as nitrogen dioxide and particulates. These improvements can also be used to minimize the required number of proxy sites.

Advancement of analytical modes in a multichannel, microfluidic droplet-based sample chopper employing phase-locked detection.

In this work, we expand upon our recently developed droplet-based sample chopping concepts by introducing a multiplexed fluidic micro-chopper device (μChopper). Six aqueous input channels were integrated with a single oil input, and each of these seven channels was controlled by a pneumatic valve for automated sampling through software control. This improved design, while maintaining high precision in valve-based droplet generation at bandwidths of 0.03 to 0.05 Hz, enabled a variety of analytical modes to be employed on-chip compared to previous devices limited to sample/reference alternations. The device was analytically validated for real-time, continuous calibration with a single sample and five standards; multiplexed analysis during calibration using a mixed mode; and standard addition through spiking of six sample droplets with varying amounts of standard. Finally, the standard addition mode was applied to protein quantification in human serum samples using on-chip, homogeneous fluorescence immunoassays. Ultimately, with only ~1.2 μL of total analyzed solution volume- representing 100-fold and 75-fold reductions in reagent and serum volumes, respectively-we were able to generate full, six-point standard addition curves in only 1.5 min, and results correlated well with those from standard plate-reader equipment. This work thus exploited microfluidic valves for both their automation and droplet phase-locking capabilities, resulting in a micro-analytical tool capable of complex analytical interrogation modes on sub-microliter sample volumes while also leveraging drastic noise rejection via lock-in detection. The multichannel μChopper device should prove particularly useful in analyzing precious biological samples or for dynamic analyses at small volume scales.

A K-Band Backscatter Fiducial for Continuous Calibration in Coherent Millimeter-Wave Imaging

We present a modulated ultrawideband backscatter calibration target (fiducial) intended for group delay calibration in large-aperture multitransceiver millimeter-wave imagers. The fiducial is designed to resemble a modulated point scatterer across the K-band (17.5–26.5 GHz). Multiple such fiducials may be used to mitigate thermal and mechanical drift across multiple transceivers comprising the imager. This approach allows tracking and removing both time-varying amplitude and phase drift in the RF hardware and associated cables. Backscatter modulation of the fiducial allows the system to separate the fiducial from the imaged scene and clutter in the environment. We show that the −10 dB beamwidth of the proposed fiducial is approximately 84° along the azimuth plane and 60° along the elevation plane. A proof of concept group delay calibration experiment is presented for a K-band laboratory setup, where a single fiducial and a metal plate target are placed in a scene together. After the backscatter-based calibration, the measured range error of the metal plate at a two-way slant distance of 70.54 cm is reduced to only 1.06 mm (0.15% position error).

Links between Gestures and Multisensory Processing: Individual Differences Suggest a Compensation Mechanism.

Speech-associated gestures represent an important communication modality. However, individual differences in the production and perception of gestures are not well understood so far. We hypothesized that the perception of multisensory action consequences might play a crucial role. Verbal communication involves continuous calibration of audio–visual information produced by the speakers. The effective production and perception of gestures supporting this process could depend on the given capacities to perceive multisensory information accurately. We explored the association between the production and perception of gestures and the monitoring of multisensory action consequences in a sample of 31 participants. We applied a recently introduced gesture scale to assess self-reported gesture production and perception in everyday life situations. In the perceptual experiment, we presented unimodal (visual) and bimodal (visual and auditory) sensory outcomes with various delays after a self-initiated (active) or externally generated (passive) button press. Participants had to report whether they detected a delay between the button press and the visual stimulus. We derived psychometric functions for each condition and determined points of subjective equality, reflecting detection thresholds for delays. Results support a robust link between gesture scores and detection thresholds. Individuals with higher detection thresholds (lower performance) reported more frequent gesture production and perception and furthermore profited more from multisensory information in the experimental task. We propose that our findings indicate a compensational function of multisensory processing as a basis for individual differences in both action outcome monitoring and gesture production and perception in everyday life situations.

A distance transform for continuous parameterization of discrete geologic facies for subsurface flow model calibration

AbstractConstruction of predictive subsurface flow models involves subjective interpretation and interpolation of spatially limited data, often using imperfect modeling assumptions. Hence, the process can introduce significant uncertainty and bias in predicting the flow and transport behavior of these systems. In particular, the uncertainty in the facies distribution in complex geologic environments, such as alluvial/fluvial channels, can be consequential for forecasting the dynamic response of these systems to perturbations due to pumping and development activities. Conventional model calibration techniques that are designed to update continuous model parameters cannot be used to estimate discrete parameters from flow and pressure data. We present a distance transform approach for converting discrete facies models to continuous parameters that can be updated using continuous model calibration methods. Distance transforms are widely used in discrete image processing, where the discrete values in each pixel are replaced with their distance (i.e., a continuous variable) to the nearest boundary cell. After updating the continuous distance maps during model calibration, a back transformation is applied to retrieve the updated facies maps. To preserve large‐scale facies connectivity, truncated singular value decomposition (SVD) parametrization may be used to represent the distance maps with low‐rank parameters. A variant of the ensemble smoother, ES‐MDA is used to update the continuous parameters of the inversion (either distance maps or their SVD coefficients if used). The distance transform method addresses an important problem in facies model calibration where model updating can result in losing facies connectivity and discreteness.

Continuous and fast calibration of the CMS experiment: design of the automated workflows and operational experience

The exploitation of the full physics potential of the LHC experiments requires fast and efficient processing of the largest possible dataset with the most refined understanding of the detector conditions. To face this challenge, the CMS collaboration has setup an infrastructure for the continuous unattended computation of the alignment and calibration constants, allowing for a refined knowledge of the most time-critical parameters already a few hours after the data have been saved to disk. This is the prompt calibration framework which, since the beginning of the LHC Run-I, enables the analysis and the High Level Trigger of the experiment to consume the most up-to-date conditions optimizing the performance of the physics objects. In the Run-II this setup has been further expanded to include even more complex calibration algorithms requiring higher statistics to reach the needed precision. This imposed the introduction of a new paradigm in the creation of the calibration datasets for unattended workflows and opened the door to a further step in performance. The paper reviews the design of these automated calibration workflows, the operational experience in the Run-II and the monitoring infrastructure developed to ensure the reliability of the service.

Performance Evaluation of Passive Haptic Feedback for Tactile HMI Design in CAVEs.

This article presents a comparison of different haptic systems, which are designed to simulate flat Human Machine Interfaces (HMIs) like touchscreens in virtual environments (VEs) such as CAVEs, and their respective performance. We compare a tangible passive transparent slate to a classic tablet and a sensory substitution system. These systems were tested during a controlled experiment. The performance and impressions from 20 subjects were collected to understand more about the modalities in the given context. The results show that the preferences of the subjects are strongly related to the use-cases and needs. In terms of performance, passive haptics proved to be significantly useful, acting as a space reference and a real-time continuous calibration system, allowing subjects to have lower execution durations and relative errors. Sensory substitution induced perception drifts during the experiment, causing significant performance disparities, demonstrating the low robustness of perception when spatial cues are insufficiently available. Our findings offer a better understanding on the nature of perception drifts and the need of strong multisensory spatial markers for such use-cases in CAVEs. The importance of a relevant haptic modality specifically designed to match a precise use-case is also emphasized.

Accuracy enhancement of MEMS accelerometer by determining its nonlinear coefficients using centrifuge test

In order to increase accuracy of inertial navigation system, it is necessary to calibrate inertial measurement unit (IMU). In some applications, acceleration applied to accelerometer is larger than its linear operation area, thus input-output relationship deviates from linear form. Main purpose of this paper is to estimate coefficients of nonlinear terms in input-output relationship of accelerometer to increase its measurement accuracy. A centrifuge device is used to generate high acceleration levels as calibration reference. In this paper, linear and nonlinear coefficients of a low cost MEMS accelerometer (x axis) are estimated using continuous calibration method (using earth gravity vector (0–1g)) and centrifuge test (accelerations between 0 and 16g generated by the centrifuge). In addition, adequacy of the nonlinear model is evaluated. The well-known F test is used to compare linear and nonlinear models. Also, errors of linear and nonlinear models are compared using Mean Square Error (MSE). Experimental results showed that nonlinear model has improved measurement accuracy about 11.7%.

9‐5L: Late‐News Paper: 6Gb/s Ultra Definition Display Interface (UDDI) for Large‐size 8K Displays

A 6Gb/s per lane ultra‐definition display interface (UDDI) system is presented to reduce the production cost and to improve the form‐factor of Quad‐UHD TV panels. The receiver (RX) is implemented in a 0.18um Source IC process. The transmitter (TX) is fabricated in a low‐leakage 65nm process for integration with a Timing Controller (TCON) ASIC. The analog front‐end of the receiver is equipped with a continuous‐time linear equalizer and a 5‐tap decision feedback equalizer. Continuous calibration and adaptation engines in the receiver ensure reliable communication over an extended operation period. The transmitter employs 3‐tap pre‐emphasis for channel equalization and a dual‐VCO LC PLL for low jitter transmission. System link layer employs a low‐overhead error correction code to protect video data against random errors and to limit worst‐case run‐length. The system also deploys scrambling to reduce EMI. Noise‐free video quality was achieved at 6Gb/s over 65” display Source PCBs and at 4Gb/s over 105” display Source PCBs. The UDDI system improves the highest existing intra‐panel interface speed by nearly a factor of 2.

Continuous Online Item Calibration: Parameter Recovery and Item Utilization.

Parameter recovery and item utilization were investigated for different designs for online test item calibration. The design was adaptive in a double sense: it assumed both adaptive testing of examinees from an operational pool of previously calibrated items and adaptive assignment of field-test items to the examinees. Four criteria of optimality for the assignment of the field-test items were used, each of them based on the information in the posterior distributions of the examinee's ability parameter during adaptive testing as well as the sequentially updated posterior distributions of the field-test item parameters. In addition, different stopping rules based on target values for the posterior standard deviations of the field-test parameters and the size of the calibration sample were used. The impact of each of the criteria and stopping rules on the statistical efficiency of the estimates of the field-test parameters and on the time spent by the items in the calibration procedure was investigated. Recommendations as to the practical use of the designs are given.

Feedback traps for virtual potentials.

Feedback traps are tools for trapping and manipulating single charged objects, such as molecules in solution. An alternative to optical tweezers and other single-molecule techniques, they use feedback to counteract the Brownian motion of a molecule of interest. The trap first acquires information about a molecule's position and then applies an electric feedback force to move the molecule. Since electric forces are stronger than optical forces at small scales, feedback traps are the best way to trap single molecules without 'touching' them (e.g. by putting them in a small box or attaching them to a tether). Feedback traps can do more than trap molecules: they can also subject a target object to forces that are calculated to be the gradient of a desired potential function U(x). If the feedback loop is fast enough, it creates a virtual potential whose dynamics will be very close to those of a particle in an actual potential U(x). But because the dynamics are entirely a result of the feedback loop-absent the feedback, there is only an object diffusing in a fluid-we are free to specify and then manipulate in time an arbitrary potential U(x,t). Here, we review recent applications of feedback traps to studies on the fundamental connections between information and thermodynamics, a topic where feedback plays an even more fundamental role. We discuss how recursive maximum-likelihood techniques allow continuous calibration, to compensate for drifts in experiments that last for days. We consider ways to estimate work and heat, using them to measure fluctuating energies to a precision of ±0.03 kT over these long experiments. Finally, we compare work and heat measurements of the costs of information erasure, the Landauer limit of kT ln 2 per bit of information erased. We argue that, when you want to know the average heat transferred to a bath in a long protocol, you should measure instead the average work and then infer the heat using the first law of thermodynamics.This article is part of the themed issue 'Horizons of cybernetical physics'.

Real-Time Production Surveillance and Optimization in a Mature Subsea Asset

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 181103, “Real-Time Production Surveillance and Optimization at a Mature Subsea Asset,” by Xiang Ma, Zachary Borden, Paul Porto, Damian Burch, Nancy Huang, Paul Benkendorfer, Lynne Bouquet, Peng Xu, Cassandra Swanberg, Lynne Hoefer, Daniel F. Barber, and Tom C. Ryan, ExxonMobil, prepared for the 2016 SPE Intelligent Energy Conference and Exhibition, Aberdeen, 6–8 September. The paper has not been peer reviewed. A real-time production-surveillance and -optimization system has been developed to integrate available surveillance data with the objective of driving routine production optimization. The system aims to streamline data capture, automate data quality assurance, integrate high- and low-frequency data to extract maximum value, optimize the design and analysis of commingled well tests, and provide real-time multiphase well-rate estimates for continuous well-performance evaluation. Introduction The technology was piloted in an offshore field consisting of stacked deepwater channel deposits developed with five individual subsea drill centers, 15 active oil producers, one gas injector, and five water injectors. Equipment is controlled remotely, and produced fluids are routed to surface by two 8-in. risers from each drill center. Produced gas is treated for use as fuel gas on the surface and for gas lift by reinjecting into each production well. All wells were originally deployed with a full suite of instrumentation, as well as valve-status sensors for each well flowline and riser. The three-phase separators on the surface use orifice plate meters for rate measurement. The approach taken was to integrate real-time data and physical models for real-time production surveillance and optimization. The deployed system uses software that incorporates in-house-developed techniques for continuous model tuning. First, a complete integrated production model (IPM) of the production system was built, spanning reservoir inflow and wells on the one hand and flowlines, risers, and topsides on the other. The IPM is embedded in a field management software platform that houses several standard work flows as well as proprietary algorithms. Calculation results and real-time data are visualized with a visualization application. As with other digital-oilfield applications, the key is continuous calibration of the physical models when field producing conditions change. The standard solution within the chosen field- management software relies on calibrating the well models with single-producing-well tests. However, most of the subsea wells in the asset have lost the ability to flow alone, and only commingled well tests are available. Operators thus resort to a test-by-difference protocol to obtain periodic well rates for allocation, which introduces significant errors when test conditions deviate largely from production conditions. To overcome this issue, a customized commingled well-test-analysis (CWTA) work flow was developed to analyze multisegment commingled well tests simultaneously.