Multi-output soft sensor with a multivariate filter that predicts errors applied to an industrial reactive distillation process. - In: Mathematics, ISSN 2227-7390, Bd. 9 (2021), 16, 1947, S. 1-14
The paper deals with the problem of developing a multi-output soft sensor for the industrial reactive distillation process of methyl tert-butyl ether production. Unlike the existing soft sensor approaches, this paper proposes using a soft sensor with filters to predict model errors, which are then taken into account as corrections in the final predictions of outputs. The decomposition of the problem of optimal estimation of time delays is proposed for each input of the soft sensor. Using the proposed approach to predict the concentrations of methyl sec-butyl ether, methanol, and the sum of dimers and trimers of isobutylene in the output product in a reactive distillation column was shown to improve the results by 32%, 67%, and 9.5%, respectively.
https://doi.org/10.3390/math9161947
Comparison of semirigorous and empirical models derived using data quality assessment methods. - In: Minerals, ISSN 2075-163X, Bd. 11 (2021), 9, 954, insges. 19 S.
With the increase in available data and the stricter control requirements for mineral processes, the development of automated methods for data processing and model creation are becoming increasingly important. In this paper, the application of data quality assessment methods for the development of semirigorous and empirical models of a primary milling circuit in a platinum concentrator plant is investigated to determine their validity and how best to handle multivariate input data. The data set used consists of both routine operating data and planned step tests. Applying the data quality assessment method to this data set, it was seen that selecting the appropriate subset of variables for multivariate assessment was difficult. However, it was shown that it was possible to identify regions of sufficient value for modeling. Using the identified data, it was possible to fit empirical linear models and a semirigorous nonlinear model. As expected, models obtained from the routine operating data were, in general, worse than those obtained from the planned step tests. However, using the models obtained from routine operating data as the initial seed models for the automated advanced process control methods would be extremely helpful. Therefore, it can be concluded that the data quality assessment method was able to extract and identify regions sufficient and acceptable for modeling.
https://doi.org/10.3390/min11090954
Challenges for nanotechnology. - In: Encyclopedia, ISSN 2673-8392, Bd. 1 (2021), 3, S. 618-631
The term "Nanotechnology" describes a large field of scientific and technical activities dealing with objects and technical components with small dimensions. Typically, bodies that are in-at least-two dimensions smaller than 0.1 [my]m are regarded as "nanobjects". By this definition, a lot of advanced materials, as well as the advanced electronic devices, are objects of nanotechnology. In addition, many aspects of molecular biotechnology as well as macromolecular and supermolecular chemistry and nanoparticle techniques are summarized under "nanotechnology". Despite this size-oriented definition, nanotechnology is dealing with physics and chemistry as well as with the realization of technical functions in the area between very small bodies and single particles and molecules. This includes the shift from classical physics into the quantum world of small molecules and low numbers or single elementary particles. Besides the already established fields of nanotechnology, there is a big expectation about technical progress and solution to essential economic, medical, and ecological problems by means of nanotechnology. Nanotechnology can only meet these expectations if fundamental progress behind the recent state of the art can be achieved. Therefore, very important challenges for nanotechnology are discussed here.
https://doi.org/10.3390/encyclopedia1030051
Matrix pencil method for vital sign detection from signals acquired by microwave sensors. - In: Sensors, ISSN 1424-8220, Bd. 21 (2021), 17, 5735, insges. 24 S.
Microwave sensors have recently been introduced as high-temporal resolution sensors, which could be used in the contactless monitoring of artery pulsation and breathing. However, accurate and efficient signal processing methods are still required. In this paper, the matrix pencil method (MPM), as an efficient method with good frequency resolution, is applied to back-reflected microwave signals to extract vital signs. It is shown that decomposing of the signal to its damping exponentials fulfilled by MPM gives the opportunity to separate signals, e.g., breathing and heartbeat, with high precision. A publicly online dataset (GUARDIAN), obtained by a continuous wave microwave sensor, is applied to evaluate the performance of MPM. Two methods of bandpass filtering (BPF) and variational mode decomposition (VMD) are also implemented. In addition to the GUARDIAN dataset, these methods are also applied to signals acquired by an ultra-wideband (UWB) sensor. It is concluded that when the vital sign is sufficiently strong and pure, all methods, e.g., MPM, VMD, and BPF, are appropriate for vital sign monitoring. However, in noisy cases, MPM has better performance. Therefore, for non-contact microwave vital sign monitoring, which is usually subject to noisy situations, MPM is a powerful method.
https://doi.org/10.3390/s21175735
Numerical and experimental investigation of a semi-active vibration control system by means of vibration energy conversion. - In: Energies, ISSN 1996-1073, Bd. 14 (2021), 16, 5177, S. 1-19
A vibration control concept based on vibration energy conversion and storage with respect to a serial-stiffness-switch system (4S) has previously been proposed. Here, we first present a rotational electromagnetic serial-stiffness-switch system as a novel practical vibration control system for experimental validation of the concept and, furthermore, an improved control strategy for higher vibration suppression performance is also proposed. The system consists of two spring-switch elements in series, where a parallel switch can block a spring. As an alternating mechanical switch, the experimental system uses two electromagnets with a shared armature. By connecting the armature to the rotating load or the base, the electromagnets decide which of the two spiral springs is blocked, while the other is active. A switching law based on the rotation velocity of the payload is used. Modelling and building of the experimental system were carried out. The corresponding experiment and simulation were executed and they matched well. These results prove that our serial-stiffness-switch system is capable of converting vibration energy and realizing vibration reduction under a forced harmonic disturbance. The effects of disturbance frequency, disturbance amplitude and sampling frequency on the system performance are shown as well. A position feedback control-based switching law is further put forward and experimentally verified to improve the repositioning accuracy of the disturbed system.
https://doi.org/10.3390/en14165177
Non-exponential 1H and 2H NMR relaxation and self-diffusion in asphaltene-maltene solutions. - In: Molecules, ISSN 1420-3049, Bd. 26 (2021), 17, 5218, insges. 35 S.
Im Titel sind "1" und "2" hochgestellt
The distribution of NMR relaxation times and diffusion coefficients in crude oils results from the vast number of different chemical species. In addition, the presence of asphaltenes provides different relaxation environments for the maltenes, generated by steric hindrance in the asphaltene aggregates and possibly by the spatial distribution of radicals. Since the dynamics of the maltenes is further modified by the interactions between maltenes and asphaltenes, these interactions - either through steric hindrances or promoted by aromatic-aromatic interactions - are of particular interest. Here, we aim at investigating the interaction between individual protonic and deuterated maltene species of different molecular size and aromaticity and the asphaltene macroaggregates by comparing the maltenes’ NMR relaxation (T1 and T2) and translational diffusion (D) properties in the absence and presence of the asphaltene in model solutions. The ratio of the average transverse and longitudinal relaxation rates, describing the non-exponential relaxation of the maltenes in the presence of the asphaltene, and its variation with respect to the asphaltene-free solutions are discussed. The relaxation experiments reveal an apparent slowing down of the maltenes’ dynamics in the presence of asphaltenes, which differs between the individual maltenes. While for single-chained alkylbenzenes, a plateau of the relaxation rate ratio was found for long aliphatic chains, no impact of the maltenes’ aromaticity on the maltene-asphaltene interaction was unambiguously found. In contrast, the reduced diffusion coefficients of the maltenes in presence of the asphaltenes differ little and are attributed to the overall increased viscosity.
https://doi.org/10.3390/molecules26175218
Experimental approach to determine the impact of the droplet transfer mode on the degradation of fused tungsten carbides during GMAW. - In: International journal of refractory metals & hard materials, ISSN 0263-4368, Bd. 101 (2021), 105692
The application of fused tungsten carbides (FTCs) in nickel-based alloys is important for improving the wear resistance of tooling equipment in the mining industry. However, FTCs are thermally unstable and will dilute under excessive energy input during welding. The parameters affecting dilution in this context are diverse and not yet completely understood. To date, the existing scientific literature focuses on the impact of the melt bead characteristics to explain the degradation during gas metal arc welding (GMAW). The degradation-promoting influence of the droplet transfer mode has not yet been considered. A methodology was developed to experimentally quantify the dependence of the degradation kinetics of FTCs on the droplet transfer mode. The established experimental model demonstrated that the globular transfer mode leads to increased degradation of FTCs in comparison to that of the short-arc mode, which can be attributed to the higher process power and hence higher droplet temperature. In this context, the quantifiable impact of the droplet transfer mode was determined.
https://doi.org/10.1016/j.ijrmhm.2021.105692
Foreword to the special issue on "Tip- and laser-based 3D nanofabrication in extended macroscopic working areas". - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 131
https://doi.org/10.1007/s41871-021-00113-7
Optimal design of on-scalp electromagnetic sensor arrays for brain source localisation. - In: Human brain mapping, ISSN 1097-0193, Bd. 42 (2021), 15, S. 4869-4879
Optically pumped magnetometers (OPMs) are quickly widening the scopes of noninvasive neurophysiological imaging. The possibility of placing these magnetic field sensors on the scalp allows not only to acquire signals from people in movement, but also to reduce the distance between the sensors and the brain, with a consequent gain in the signal-to-noise ratio. These advantages make the technique particularly attractive to characterise sources of brain activity in demanding populations, such as children and patients with epilepsy. However, the technology is currently in an early stage, presenting new design challenges around the optimal sensor arrangement and their complementarity with other techniques as electroencephalography (EEG). In this article, we present an optimal array design strategy focussed on minimising the brain source localisation error. The methodology is based on the Cramér-Rao bound, which provides lower error bounds on the estimation of source parameters regardless of the algorithm used. We utilise this framework to compare whole head OPM arrays with commercially available electro/magnetoencephalography (E/MEG) systems for localising brain signal generators. In addition, we study the complementarity between EEG and OPM-based MEG, and design optimal whole head systems based on OPMs only and a combination of OPMs and EEG electrodes for characterising deep and superficial sources alike. Finally, we show the usefulness of the approach to find the nearly optimal sensor positions minimising the estimation error bound in a given cortical region when a limited number of OPMs are available. This is of special interest for maximising the performance of small scale systems to ad hoc neurophysiological experiments, a common situation arising in most OPM labs.
https://doi.org/10.1002/hbm.25586
In-situ evaluation of the pitch of a reflective-type scale grating by using a mode-locked femtosecond laser. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 17, 8028, S. 1-16
Major modifications are made to the setup and signal processing of the method of in-situ measurement of the pitch of a diffraction grating based on the angles of diffraction of the diffracted optical frequency comb laser emanated from the grating. In the method, the improvement of the uncertainty of in-situ pitch measurement can be expected since every mode in the diffracted optical frequency comb laser can be utilized. Instead of employing a Fabry-Pérot etalon for the separation of the neighboring modes in the group of the diffracted laser beams, the weight-of-mass method is introduced in the method to detect the light wavelength in the Littrow configuration. An attempt is also made to reduce the influence of the non-uniform spectrum of the optical comb laser employed in the setup through normalization operation. In addition, an optical alignment technique with the employment of a retroreflector is introduced for the precise alignment of optical components in the setup. Furthermore, a mathematical model of the pitch measurement by the proposed method is established, and theoretical analysis on the uncertainty of pitch measurement is carried out based on the guide to the expression of uncertainty in measurement (GUM).
https://doi.org/10.3390/app11178028