Immersion Probes Research Articles

Time-series forecasting for ships maneuvering in waves via recurrent-type neural networks

The prediction capability of recurrent-type neural networks is investigated for real-time short-term prediction (nowcasting) of ship motions in high sea state. Specifically, the performance of recurrent neural networks, long short-term memory, and gated recurrent units models are assessed and compared using a data set coming from computational fluid dynamics simulations of a self-propelled destroyer-type vessel in stern-quartering sea state 7. Time-series of incident wave, ship motions, rudder angle, as well as immersion probes, are used as variables for a nowcasting problem. The objective is to obtain about 20 s ahead prediction. Overall, the three methods provide promising and comparable results.

RECURRENT-TYPE NEURAL NETWORKS FOR REAL-TIME SHORT-TERM PREDICTION OF SHIP MOTIONS IN HIGH SEA STATE

The prediction capability of recurrent-type neural networks is investigated for real-time short-term prediction (nowcasting) of ship motions in high sea state. Specifically, the performance of recurrent neural networks, long-short term memory, and gated recurrent units models are assessed and compared using a data set coming from computational fluid dynamics simulations of a self-propelled destroyer-type vessel in stern-quartering sea state 7. Time series of incident wave, ship motions, rudder angle, as well as immersion probes, are used as variables for a nowcasting problem. The objective is to obtain about 20 s ahead prediction. Overall, the three methods provide promising and comparable results.

Calibration model transfer in mid-infrared process analysis with in situ attenuated total reflectance immersion probes.

Process applications of mid-infrared (MIR) spectrometry may involve replacement of the spectrometer and/or measurement probe, which generally requires a calibration transfer method to maintain the accuracy of analysis. In this study, direct standardisation (DS), piecewise direct standardisation (PDS) and spectral space transformation (SST) were compared for analysis of ternary mixtures of acetone, ethanol and ethyl acetate. Three calibration transfer examples were considered: changing the spectrometer, multiplexing two probes to a spectrometer, and changing the diameter of the attenuated total reflectance (ATR) probe (as might be required when scaling up from lab to process analysis). In each case, DS, PDS and SST improved the accuracy of prediction for the test samples, analysed on a secondary spectrometer-probe combination, using a calibration model developed on the primary system. When the probe diameter was changed, a scaling step was incorporated into SST to compensate for the change in absorbance caused by the difference in ATR crystal size. SST had some advantages over DS and PDS: DS was sensitive to the choice of standardisation samples, and PDS required optimisation of the window size parameter (which also required an extra standardisation sample). SST only required a single parameter to be chosen: the number of principal components, which can be set equal to the number of standardisation samples when a low number of standards (n < 7) are used, which is preferred to minimise the time required to transfer the calibration model.

Spatial-temporal characteristics of temperature fluctuations of turbulent fluid flow and velocity measurements based on them

The paper describes the temperature cross-correlation velocimetry method applied to flows of water or liquid metal. The technique allows us to measure temperature waveforms and averaged longitudinal velocity in a flow simultaneously. This approach is a simple and reliable method for measuring the velocity in flows of opaque coolants. At the same flow parameters, liquids of different origins provide non-similar spatial-temporal characteristics having a different impact on the applicability of the temperature correlation method. This work is devoted to the development of practical methods allowing to form a set of specific recommendations on the application of the technique of temperature correlation velocimetry and to determine the metrological characteristics of the technique in various conditions. Calibration was carried out using water and mercury as a model liquid. Used experimental facility and measuring system are described, accompanied by a detailed description of the developed temperature-correlation sensor. Measuring directly from within a flow is made possible by a unique micro thermocouple immersion probes technique. Data obtained are presented as fields of temperature and intensity of temperature fluctuations. Autocorrelation and cross-correlation functions are compared and analysed for two studied fluids under identical conditions.

Application of Raman spectroscopy to real-time monitoring of CO2 capture at PACT pilot plant; Part 1: Plant operational data

Process analyzers for in-situ monitoring give advantages over the traditional analytical methods such as their fast response, multi-chemical information from a single measurement unit, minimal errors in sample handing and ability to use for process control. This study discusses the suitability of Raman spectroscopy as a process analytical tool for in-situ monitoring of CO2 capture using aqueous monoethanolamine (MEA) solution by presenting its performance during a 3-day test campaign at PACT pilot plant in Sheffield, UK. Two Raman immersion probes were installed on lean and rich streams for real time measurements. A multivariate regression model was used to determine the CO2 loading. The plant performance is described in detail by comparing the CO2 loading in each solvent stream at different process conditions. The study shows that the predicted CO2 loading recorded an acceptable agreement with the offline measurements. The findings from this study suggest that Raman Spectroscopy has the capability to follow changes in process variables and can be employed for real time monitoring and control of the CO2 capture process. In addition, these predictions can be used to optimize process parameters; to generate data to use as inputs for thermodynamic models, plant design and scale-up scenarios.

Probeless non-invasive near-infrared spectroscopic bioprocess monitoring using microspectrometer technology

Real-time measurements and adjustments of critical process parameters are essential for the precise control of fermentation processes and thus for increasing both quality and yield of the desired product. However, the measurement of some crucial process parameters such as biomass, product, and product precursor concentrations usually requires time-consuming offline laboratory analysis. In this work, we demonstrate the in-line monitoring of biomass, penicillin (PEN), and phenoxyacetic acid (POX) in a Penicilliumchrysogenum fed-batch fermentation process using low-cost microspectrometer technology operating in the near-infrared (NIR). In particular, NIR reflection spectra were taken directly through the glass wall of the bioreactor, which eliminates the need for an expensive NIR immersion probe. Furthermore, the risk of contaminations in the reactor is significantly reduced, as no direct contact with the investigated medium is required. NIR spectra were acquired using two sensor modules covering the spectral ranges 1350–1650 nm and 1550–1950 nm. Based on offline reference analytics, partial least squares (PLS) regression models were established for biomass, PEN, and POX either using data from both sensors separately or jointly. The established PLS models were tested on an independent validation fed-batch experiment. Root mean squared errors of prediction (RMSEP) were 1.61 g/L, 1.66 g/L, and 0.67 g/L for biomass, PEN, and POX, respectively, which can be considered an acceptable accuracy comparable with previously published results using standard process spectrometers with immersion probes. Altogether, the presented results underpin the potential of low-cost microspectrometer technology in real-time bioprocess monitoring applications.Graphical abstract

Hydrolysis of acetic anhydride: In situ, real-time monitoring using NIR and UV–Vis spectroscopy

Hydrolysis of acetic anhydride is a fast and very exothermic reaction that has been studied with different analytical techniques to account for the reaction progress. This work presents the real-time monitoring of the hydrolysis of acetic anhydride using in situ NIR and UV–Vis spectroscopy, under non-isothermal and non-adiabatic conditions. The experimental apparatus consists of a reaction vessel equipped with a magnetic stirrer, NIR and UV–Vis immersion probes and a thermocouple. Two multivariate models are proposed to account for the conversion of acetic anhydride as a function of time, one for NIR and other for UV–Vis. The calibration data were generated by calorimetry. The external validation permits the assessment of the adherence of the model to data not used for calibration. The results show that both models can be useful to monitor this hydrolysis, employing a simple and intuitive apparatus.

Comparison of two immersion probes coupled with visible/near infrared spectroscopy to assess the must infection at the grape receiving area

The aim of this work was to investigate the applicability of visible/near infrared (vis/NIR) spectroscopy comparing two immersion probes to evaluate the phytosanitary status of must at the grape receiving area to support wineries for an objective quantification of grape infection level.The experimentation was conducted on white and red varieties (Vitis vinifera L.), employing grapes naturally infected with the major wine grape diseases. A total of 159 musts were product and analysed by using a vis/NIR spectrophotometer coupled with two kind of immersion probes: a reflectance probe and a transmittance one. Classification analysis (Partial Least Squares – Discriminant Analysis, PLS-DA) was performed on musts spectra to test the performance of the spectrophotometer, combined with the two probes, to classify healthy and infected samples.Considering three different spectral range analysed (430–1000 nm; 1000–1650 nm; 430–1650 nm), the results obtained from PLS-DA models, in cross-validation, gave values of correctly classified samples (accuracy, %) between 52.5% and 90.4%, and ranged from 68.4% to 84.3% for reflectance and transmittance probes respectively.The optical system was tested in controlled laboratory conditions, simulating the desirable final use of device. A future real scale application could be envisaged inside the analysis tank at the grape receiving area, after setting the operative conditions to perform the measurements directly coupled with the traditional and common quality analysis (soluble solid content and acidity) performed on grape musts sampled at the grape consignment.

Implementation of NIR technology for at-line rapid detection of sunflower oil adulterated with mineral oil

Three experimental setups, based on near infrared technology (NIR), were tested for rapid “at-line” assessment of sunflower oil adulteration by mineral oil. Experimental setups included a commercial portable NIR, coupled to both reflexion (S1) and immersion probes (S2), and a prototype of a multichannel Quasi Imaging Visible NIR spectrometer (QIVN) coupled to an immersion probe (S3). Independent calibration and validation samples sets were prepared with mineral oils (MOs) content up to 10% (w/w), and calibrations were developed using partial least square (PLS) regressions. Root mean square error of prediction (RMSEP) ranges from 0.23 to 1.26% (w/w) MOs, depending on the NIR setup.The best performances were obtained with S1, which provides satisfactory calibrations, and low number of false positives starting from levels of mineral oil around 1%. S3 still provides acceptable calibrations, and could be practically used to detect mineral oil at concentrations higher than 2.5% (w/w) MOs.

Seasonal activity and unpredicted polar front migration of northern New Zealand Common Diving Petrels (Pelecanoides urinatrix)

ABSTRACTThe Common Diving Petrel (Pelecanoides urinatrix) is an abundant seabird species within New Zealand waters. Breeding in this species occurs from late July through to December and adults are thought to remain in New Zealand waters during non-breeding months. Yet no studies of the spatial ecology of the species within New Zealand have been undertaken to confirm this. We used geolocation loggers with seawater immersion probes to characterise the year-round distribution and activity of P. urinatrix from two colonies (Kauwahaia Island and Burgess Island) in northern New Zealand. Adult birds exhibited extended pre-laying occupation of breeding sites (~95 days) and throughout breeding remained within 300 km of their colony. Burgess Island birds returned near nightly to their burrows throughout the breeding season. During non-breeding birds made a rapid and unpredicted migration south-east to the Antarctic polar front (covering 3000–5000 km in 3–13 days) and exhibited a dramatic shift in behaviour by spending 95% of their time on (and under) the water surface. Given its already high wing loading, it appears that the primary moult reduced flight efficiency during this time. But by targeting highly productive oceanic regions, and the improved foraging opportunities therein, P. urinatrix may offset this reduced flight capacity.

Innovative Method to Authenticate Copper Canisters Used for Spent Nuclear Fuel Based on the Ultrasonic Investigation of the Friction Stir Weld

Sweden is planning to store nuclear spent fuel in long-term geological repositories. Copper canisters with a ductile iron insert will preserve the fuel for thousands of years at a depth of about 500 m in Swedish bedrock. The International Atomic Energy Agency (IAEA) and Euratom safeguards inspectorates have to maintain the continuity of knowledge (CoK) during transport and deposition of canisters from the encapsulation plant to the final repository. The aim of this paper is then oriented to provide such CoK for canisters by an identification and authentication based on ultrasound. This paper describes an authentication method oriented to prevent falsification of copper canisters. According to the ultrasonic investigation of the friction stir welding process of the copper lid onto the cylindrical tube, the ultrasonic response of the remaining gap partially filled during the welding is used as a unique pattern for authentication. The analysis of various measurements made on angular sections of copper lids friction stir welded onto the tube revealed the feasibility of acquisition of a valuable signal from the reflection of the internal gap. Following the observations on this data set, a possible technical design is detailed, where the identification and authentication methods can be combined with immersion probes.

Monte Carlo uncertainty assessment of ultrasonic beam parameters from immersion transducers used to non-destructive testing

The uncertainty of ultrasonic beam parameters from non-destructive testing immersion probes was evaluated using the Guide to the expression of uncertainty in measurement (GUM) uncertainty framework and Monte Carlo Method simulation. The calculated parameters such as focal distance, focal length, focal widths and beam divergence were determined according to EN 12668-2. The typical system configuration used during the mapping acquisition comprises a personal computer connected to an oscilloscope, a signal generator, axes movement controllers, and a water bath. The positioning system allows moving the transducer (or hydrophone) in the water bath. To integrate all system components, a program was developed to allow controlling all the axes, acquire waterborne signals, and calculate essential parameters to assess and calibrate US transducers. All parameters were calculated directly from the raster scans of axial and transversal beam profiles, except beam divergence. Hence, the positioning system resolution and the step size are principal source of uncertainty. Monte Carlo Method simulations were performed by another program that generates pseudo-random samples for the distributions of the involved quantities. In all cases, there were found statistical differences between Monte Carlo and GUM methods.

Measuring mutual solubility in the H2O–CO2 system up to 200 bar and 100 °C by in situ Raman spectroscopy

The solubility control in the H2O–CO2 system under high pressure is of prime interest in numerous geochemical systems from hydrothermal fluids to CO2 geological storage. However, the number of experimental data is scarce in the range of interest of geological storage, especially in the CO2-rich phase. A new experimental device was built to measure mutual solubility in the CO2–H2O system without sampling by coupling a batch reactor with Raman immersion probes. The system was first calibrated by measuring the solubility of CO2 in water at 100°C. The results were provided with an accuracy of a few % between 40bar and 200bar and in agreement with other published experimental data sets and models. The linear correlation between Raman peak intensity and CO2 solubility in the aqueous phase was then used to provide new experimental data of CO2 solubility in water at 65°C from 3bar to 200bar. The Raman data of the CO2-rich phase or supercritical phase are compared to a thermodynamic models and the few experimental data available in literature to provide a new data set of H2O–CO2 mutual solubility at 100°C and up to 200bar.

Development of a Near-Infrared/Mid-Infrared Dual-Region Spectrometer for Online Process Analysis

A near-infrared (NIR) and mid-infrared (mid-IR) dual-region spectrometer having two immersion probes, a transmission probe for NIR, and an attenuated total reflection (ATR) probe for mid-IR has been developed for highly reliable process monitoring and deep process understanding. This spectrometer facilitates sequential acquisition of both NIR (10,000-4000 cm(-1)) and mid-IR (5000-1200 cm(-1)) spectra by switching the light path leading to the probes without the need for probe replacement. The use of a single light source and a single beam splitter enables achievement of a permanent alignment of the optical system and sequential data acquisition. The transmission NIR and ATR mid-IR probes designed and developed in the present study facilitate the acquisition of NIR/mid-IR spectra with optimized absorption intensities in both regions by simply placing the probes into a sample solution. The performance of the developed spectrometer was demonstrated in monitoring the ethanol fermentation process. NIR/mid-IR spectra of the fermentation solution with multiplicative scatter correction (MSC) represent the relative changes in the concentrations of glucose and ethanol in both regions. Principal component analysis (PCA) was performed on the MSC-treated spectra in the regions 6300-5650 cm(-1), 4850-4300 cm(-1), and 3500-2880 cm(-1) to detect the end-point of the fermentation as an example of process monitoring. For all the regions, the score plot of the first principal component (PC) indicates that the fermentation progresses with the fermentation time and stops after 210 minutes and thus the end-point of the fermentation exists at around 210 minutes. The loading plot indicates that all of the first PCs are the relative changes in the concentrations of glucose and ethanol. This result reveals that the same chemical changes are observed in both transmission NIR and ATR mid-IR spectra. Multiple and simultaneous analysis was also performed, and intensity change in light scattering relating the growth of yeasts was monitored by the NIR spectra.

Ultrasonic immersion probes characterization for use in nondestructive testing according to EN 12668-2:2001

Ultrasound is often used as a Non-Destructive Testing (NDT) technique to analyze components and structures to detect internal and surface flaws. To guarantee reliable measurements, it is necessary to calibrate instruments and properly assess related uncertainties. An important device of an ultrasonic instrument system is its probe, which characterization should be performed according to EN 12668-2. Concerning immersion probes beam profile, the parameters to be assessed are beam divergence, focal distance, width, and zone length. Such parameters are determined by scanning a reflector or a hydrophone throughout the transducer beam. Within the present work, a methodology developed at Inmetro's Laboratory of Ultrasound to evaluate relevant beam parameters is presented, based on hydrophone scan. Water bath and positioning system to move the hydrophone were used to perform the scan. Studied probes were excited by a signal generator, and the waterborne signals were detected by the hydrophone and acquired using an oscilloscope. A user-friendly virtual instrument was developed in LabVIEW to automate the system. The initial tests were performed using 1 and 2.25 MHz-ultrasonic unfocused probes (Ø 1.27 cm), and results were consistent with the manufacturer's specifications. Moreover, expanded uncertainties were lower than 6% for all parameters under consideration.

Monitoring and classification of wastewater quality using supervised pattern recognition techniques and deterministic resolution of molecular absorption spectra based on multiwavelength UV spectra deconvolution

A field flow approach for the in situ monitoring of wastewater quality is developed and assessed in this work, based on a combination of methods employing deconvolution of molecular absorption spectra and in situ/on-line analysis of wastewater effluent of various origin. The approach involves in situ immersion probes to monitor basic physicochemical parameters followed by UV spectrum deconvolution in order to provide a rapid estimate of organic matter, suspended solids and nitrate and on-line analysis of phosphates in a fully automated setup. The collected data are then treated with a series of supervised pattern recognition techniques in order to classify wastewater effluent according to their origin in three major categories namely municipal, industrial and hospital. The results suggest that the method affords a good approximation of realistic concentrations, as determined by reference methods, while it affords a good classification among various wastewater effluents of different origin. In that manner, the method enables a rapid inference of treated wastewater quality and a robust assessment of treatment process state, especially with regards to violations of effluent quality parameters.

Reaction Monitoring of Heterogeneously Catalyzed Hydrogenation of Imines by Coupled ATR‐FTIR, UV/Vis, and Raman Spectroscopy

AbstractCoupled ATR‐FTIR, UV/Vis, and Raman spectroscopy has been introduced for the monitoring of liquid phase hydrogenation reactions under elevated H2 pressure by implementation of spectroscopic immersion probes into a modified autoclave reactor. The setup was successfully tested for the heterogeneously catalyzed hydrogenation of several imine substrates under H2 pressures up to 20 bar. The conversion of the imines could be analyzed by Raman spectroscopy and the product formation was observable by attenuated total reflectance FTIR spectroscopy (ATR‐FTIR), which illustrates the benefits of coupling complementary spectroscopic methods. Separate spectroscopic investigations show that imines intensively interact with the phosphoric acid ester that is used as catalyst modifier, indicated by a shift of the original ν(CN) band of the imine to higher wavenumbers. UV/Vis spectroscopic investigations reveal a distinct shift of the absorption edge to a higher wavelength. Furthermore, the formation of adsorbates on the surface of used Pt/Al2O3 catalysts, resulting mainly from adsorbed imine, was detected by FTIR spectroscopic analysis. The potential of UV/Vis spectroscopy in transmission mode for analyzing the organic components was tested. Due to its high sensitivity at low concentrations this method offers an additional possibility for a quantitative in situ analysis of the reaction progress in real time.

Quantitative monitoring of an activated sludge reactor using on-line UV-visible and near-infrared spectroscopy

The performance of an activated sludge reactor can be significantly enhanced through use of continuous and real-time process-state monitoring, which avoids the need to sample for off-line analysis and to use chemicals. Despite the complexity associated with wastewater treatment systems, spectroscopic methods coupled with chemometric tools have been shown to be powerful tools for bioprocess monitoring and control. Once implemented and optimized, these methods are fast, nondestructive, user friendly, and most importantly, they can be implemented in situ, permitting rapid inference of the process state at any moment. In this work, UV-visible and NIR spectroscopy were used to monitor an activated sludge reactor using in situ immersion probes connected to the respective analyzers by optical fibers. During the monitoring period, disturbances to the biological system were induced to test the ability of each spectroscopic method to detect the changes in the system. Calibration models based on partial least squares (PLS) regression were developed for three key process parameters, namely chemical oxygen demand (COD), nitrate concentration (N-NO(3)(-)), and total suspended solids (TSS). For NIR, the best results were achieved for TSS, with a relative error of 14.1% and a correlation coefficient of 0.91. The UV-visible technique gave similar results for the three parameters: an error of approximately 25% and correlation coefficients of approximately 0.82 for COD and TSS and 0.87 for N-NO(3)(-) . The results obtained demonstrate that both techniques are suitable for consideration as alternative methods for monitoring and controlling wastewater treatment processes, presenting clear advantages when compared with the reference methods for wastewater treatment process qualification.

Combined 50- and 20-MHz Frequency Ultrasound Imaging in Intermediate Uveitis

To evaluate the information provided by multifrequency ultrasound examination in patients with intermediate uveitis. Prospective observational case series. High-resolution ultrasonography with 50- and 20-MHz frequency immersion probes was performed in seven eyes of five young patients with clinical diagnosis of intermediate uveitis. Exudative material over the inferior pars plana and peripheral retina (snowbank) was found in all eyes with 50- and 20-MHz probe, although resolution of the latter was poorer. The 50-MHz imaging was superior for visualization of angle structures and details of pars planitis; the anterior vitreous involvement and cyclitic bands were better shown with the 20-MHz probe, which could also evidence cystoid macular edema. Ultrasound examination with both 50- and 20-MHz frequency probes can detect the typical snowbank in intermediate uveitis and be useful in eyes with small pupil, dense vitreitis, or both, especially before pars plana vitrectomy or cataract surgery.

In Situ Measurement of Steady-State Hydrogen Concentrations during a Hydrogenation Reaction in a Gas-Inducing Stirred Slurry Reactor

A new instrument, the Fugatron, is presented that was developed to make in situ measurements of dissolved hydrogen concentrations in laboratory reactors. The principle of measurement is based on a probe with a tip that consists of a small porous metal substrate coated with a dense layer of fluoropolymer. The probe is exposed to the liquid phase and is internally purged by a constant flow of carrier gas. Driven by the hydrogen concentration gradient between the external and internal side of the composite layer, the hydrogen molecules permeate into the carrier gas stream. The concentration of the permeate in the carrier gas stream is measured by a gas analyzer. The analyzer signal is proportional to the partial pressure of dissolved gas. The steady-state concentration of dissolved hydrogen in the liquid is calculated from the analyzer signal by using solubility data. Calibration methods are described for immersion probes used for in situ measurements in reactors which are operated in batch or continuous mode as well as for flow-through probes used for liquid stream analysis. The sensitivity of the instrument and the reliability of the measurements were tested in different solutions as a function of temperature and pressure. The hydrogenation of an alkyne with a suspended palladium catalyst was chosen as a model reaction for in situ measurements. The hydrogenation experiments were carried out in a 0.5-L stirred-tank reactor with a turbine stirrer in a semibatch mode. Initial hydrogen uptake rates and dissolved hydrogen concentrations during this model reaction were measured as a function of the amount of catalyst in the liquid. The solubility of hydrogen in the pure liquid was determined by a gas absorption measurement at reaction conditions. From these measurements, the volumetric liquid-side mass transfer coefficient kLa at the gas−liquid interface was calculated as a function of catalyst loading. In addition, the kLa value was also determined in the absence of solid particles by the dynamic pressure drop method. Discrepancies that may result from calculating steady-state dissolved hydrogen concentrations using kLa values obtained from measurements conducted either in pure liquids or in liquids that contain suspended catalyst particles are discussed and illustrated by these measurements. The new method allows direct measurement of the concentrations of dissolved gases during a reaction, which can be a decisive factor for the rate as well as for the selectivity of a process. Estimations of the gas concentrations via reaction rate data and cumbersome determinations of kLa values are, therefore, no longer necessary.