Universal Calibration Method Research Articles

A universal calibration method for eliminating topography-dependent current in conductive AFM and its application in nanoscale imaging

A universal calibration method for eliminating topography-dependent current in conductive AFM and its application in nanoscale imaging

The Universal Calibration for Structure- and Solvent-Independent Molar Mass Determinations of Polymers Using Diffusion-Ordered Spectroscopy.

It will be shown how diffusion-ordered spectroscopy (DOSY) can produce a universal calibration of molar mass dependences of polymers compared to size exclusion chromatography (SEC) or recently published DOSY methods. Whereas SEC can deliver only structure-independent universal calibrations for a particular solvent, DOSY was used for creating solvent-independent calibrations for a certain polymer. Now, we can demonstrate a universal calibration method that generates both a structure- and solvent-independent molar mass calibration. Only one mathematical function describes the structure- and solvent-independent calibrations for DOSY by implementing the Mark-Houwink approach. The derived equation is tested on polystyrene (PS), poly(ethylene oxide), and poly(methyl methacrylate) of different molar masses and in different solvents. Altogether, 94 diffusion coefficients representing 16 molar mass calibrations of the diffusion coefficients in 10 different solvents could be perfectly matched to one universal calibration function with an average deviation of just 2.5%. It was also found that the Mark-Houwink parameters calculated by DOSY are very close to the SEC data. In any case, this new approach is a very useful tool for the determination of molar masses and new Mark-Houwink parameters via DOSY.

Electrochemical Determination of Tert-Butylhydroquinone (TBHQ) in Edible Oil by Differential Pulse Voltammetry (DPV) at Modified Screen-Printed Carbon Electrodes (SPCEs) with a Three-Dimensional Standard Curved Surface Method

Reliable quantitative analysis using electrochemical sensors remains a challenge due to the differences in the effective area after surface modification of the electrodes, resulting in poor precision of the signals between electrodes. Herein, a novel quantitative approach called standard curved surface for the electrochemical detection is reported which does not require identical electrodes, high modification, or the use of internal standards that may cause calibration interferences. The technique is based upon the principle that the current is linearly correlated with the electroactive area of the electrodes. By introducing the electroactive area as a new variable into the standard curve, a three-dimensional standard curved surface was obtained to correct for differences among electrodes, thereby improving the accuracy of electrochemical detection. Furthermore, it was applied to the determination of tert-butylhydroquinone (TBHQ) in edible oil. Compared with the traditional standard curve, the reported method reduced the relative standard deviation values from 13.22% to 4.01%. The current response was linear with the concentration of TBHQ between 5 × 10−6 and 1.25 × 10−3 mol/L. The limit of detection was 1.07 × 10−6 mol/L and the spike recovery was from 90.44% to 112.09%. Therefore, a universal calibration method has been reported with expected additional applications for electrochemical sensors.

Universal calibration for a ring camera array based on a rotational target.

Panoramic dynamic and static measurements of objects in the application of vision measurement are difficult due to the constraints of a camera field of view and multicamera calibration technology. This paper proposes a universal global calibration method for ring multicamera systems based on rotating target and multi-view vision technology. This method uses a rotating target to establish the relationship between ring multi-camera arrays, retrieves the coordinates of the target corners from the fields of view of different cameras, and combines them with the rotation angle to complete the coordinate unification of the system. The unification of coordinates is unaffected by the overlapping fields of view between cameras, and the number of cameras can be configured arbitrarily. The calibration accuracy, validity, and precision of the proposed method are verified through reprojection error, dynamic tensile test, and 3D reconstruction.

Application of a Universal Calibration Method for True Molar Mass Determination of Fluoro-Derivatized Technical Lignins by Size-Exclusion Chromatography

The determination of the true molar mass distribution (MMD) of lignin is highly important to understand the physicochemical characteristics for lignin-based value-added applications. It is imperative to develop a universal method to quantify accurate MMD of lignin using size exclusion chromatography (SEC), as the conventional method with polymer standards provides irregular MMD results. This work aims to evaluate the MMD of five lignin samples (Protobind 1000, Organosolv, Indulin, Pine Kraft and Eucalyptus Kraft) in THF. Different derivatization methods (acetylation, fluorobenzylation and fluorobenzoylation) were performed. FTIR and 19F NMR analyses were used to follow derivatization. The MMDs of derivatized and underivatized lignins were determined by the conventional method and compared with the universal calibration method developed using intrinsic viscosity. The 19F NMR spectra provided the information to quantify the degree of substitution of lignin hydroxyl groups, to calculate the true molar mass of the derivatives of lignin monomers. The obtained MMDs values for all the derivatized lignin by universal calibration were found to be three to five times higher than that of the conventional calibration. The polydispersity values obtained with the acetylation method were higher than the fluoro-derivatives. The results demonstrated that fluoro-derivatization is an appropriate method to apply to higher molar mass technical lignins and lacks solubility and aggregation issues.

Universal Calibration Method for Line Structured Light Galvanometer Scanning System

Universal Calibration Method for Line Structured Light Galvanometer Scanning System

Designing an interactive molecular autoburette for quantification approach of pharmaceuticals by MCR-ALS

Chemical devices as molecular level devices can be used instead of physical ones, and change an environmental parameter (pH, temperature, etc.) inside a reaction chamber in a controlled way without interfering with the progression of the studied reaction. Here, we modeled pH-modulated automatic spectrophotometric titration in the reaction vessel based on a model-based analysis. Proper simulation of this system, relying on the kinetic or intertwined equilibrium-kinetic reaction, enable us to design an experimental direction for its use as a molecular autoburette. Universal calibration method was applied due to the advantages provided by a molecular autoburette. The multivariate curve resolution coupled to alternating least-squares under non-negativity, correspondence and trilinearity constraints was used to analyze the molecular spectrophotometric auto titration data. The proposed method was used to determine acetaminophen and some vitamins, as a model analyte, in different pharmaceutical forms. The process is remarkably fast for professionals and easy for beginners.

A universal method for the calibration of swing-scanning line structured light measurement system

As a non-contact, low cost and efficient method for three dimensional (3D) measurements, the swing-scanning line structured light measurement system has a more compact structure than the linear scanning system. In measuring process, the laser line projector is driven by a step motor with the laser plane intersecting the object sequentially. To obtain the intersection profiles, the corresponding laser plane equations need to be real-time calculated. Moreover, the laser plane can be an arbitrary relative position with the swing axis due to the mount error of laser projector. These would make the calibration model and the solution rather difficult. To address these problems, a universal calibration method is proposed which bridges the swing angle and the coefficients of laser plane with a constant mapping matrix directly. This matrix is determined by use of several (three at least) specific laser planes. The whole calibration process can be achieved by one freely moved checkerboard and is very convenient to use. Several experiments are carried out to validate the proposed method including the measurement of the planar surface, the steps and the sculptured surface.

A Universal Calibration Method for Electronic Nose Based on Projection on to Convex Sets

The drift of electronic nose (e-nose) sensors is the most challenging problem. An effective calibration method for e-nose is proposed in this article, which is based on projection on to convex sets (POCS) and extreme learning machine (ELM) method, including an automatic sampling platform and an e-nose sensor calibration model. It realizes a unified and universal calibration for both recognition and regression application to solve the electronic nose drift problem under long-term working conditions. Isopropanol and acetone gases that respond to most sensors were chosen as training gases for the model. Experiments show the effectiveness of the proposed e-nose calibration method.

Research on Threshold Characteristics of Telemetry Receive Channel

This article first explains the nature of the threshold effect. Combining various shipborne telemetry channels with regard to the threshold input signal-to-noise ratio, which is the most widely used channel test link for detection, a unified and universal calibration method is proposed: modulation calibration and carrier signal-to-noise calibration According to the different background noise of the channel, it is divided into two ways: radio-frequency wired and wireless. The detailed, theoretical, and highly operable test procedures and steps are given. Finally, the dual-mode loop circuit is implemented. The dynamic tracking of the carrier can significantly reduce the threshold effect.

A study of multibody modeling and calibration method for FMVSS 208 rollover test

Finite element simulation technology has been widely used in vehicle safety research. However, compared with other vehicle collision accidents, finite element model (FEM) used for passive safety research of rollover cannot be accepted generally due to its relatively long computation time. Aimed at the issue, this article proposes a kind of multibody modeling method based on FEM and test results. First, taking an example of the minivan, vehicle body is divided into suspension system, deformable upper body, and rigid lower body, and each part is constructed using MADYMO (a multibody dynamic software). Detailed modeling steps of each part are provided. Second, the upper body of model is corrected by static pressure test on vehicle top conducted in accordance with FMVSS 216, and the correspondence of output response of acceleration of B-pillar and centroid angular velocity between simulation model and FMVSS 208 rollover test is evaluated by ISO/TS 18571. The quantitative correspondence score is taken as optimization objective to calibrate uncertain parameter of MADYMO model. Finally, the correctness of MADYMO model and effectiveness of model calibration method are verified after comparison with test results of FMVSS 208. The result verifies that multibody vehicle rollover model created with this method can provide simulation with relatively high accuracy and present key deformation of vehicle body, meanwhile saving massive calculation time, which provides reliable simulation model for passenger damage research and vehicle safety performance optimization in subsequent process. The proposed method is general and universal modeling and calibration method, suitable for other vehicle.

DEM Calibration Approach: Random Forest

A lot of researchers are developing new DEM parameters calibration approaches based on an experiment plan or the use of learning algorithms. This research is aimed at improving iterative algorithms frequently used for calibration. The big time consumption as a main problem of iterative algorithms is questioned. It is proposed to use Random forest algorithm to determine DEM parameters impact on the measured bulk responses. Measured responses are the parameters obtained by image processing using a technical vision system. As a result of 200 experiments processing, DEM parameters impact values on each bulk response were generated and presented as histograms. Obtained results were interpreted on the basis of the bulk material behavior and its physical properties. There is a discussion on the possibility of developing a universal DEM parameters calibration method based on the iterative algorithm.

Star sensor installation error calibration in stellar-inertial navigation system with a regularized backpropagation neural network

The star sensor is the attitude reference in a stellar-inertial navigation system. It is essential to acquire the star sensor installation error, which has a great influence on the system navigation performance. However, traditional methods have a poor tolerance for a large range of installation errors, especially when the system works under a separate installation mode. In this paper a novel calibration method, using a regularized backpropagation (BP) neural network, is proposed. With a specially designed calibration procedure, the neural network is structured with BP and the regularization is improved. The network training is conducted for parameter solidification. The calibration can be achieved without formula derivation and numerical calculation under both small and large installation errors. In the experiment, the calibration accuracy is about 5 arcsec under small installation errors and about 20 arcsec under large installation errors, which is much better than a Kalman filter. The proposed method has the potential to be a universal star sensor calibration method under integrative installation mode or separated installation mode with large installation error.

Transmission and division of total optical depth method: A universal calibration method for Sun photometric measurements

AbstractSun photometric measurements, which provide accurate and timely information on atmospheric components such as aerosols, clouds, and gases are important to climate research. For regions with heavy and variable aerosol loading, the traditional Langley plot method cannot be applied for Sun photometric instrument calibration, as almost no suitable prolonged periods with stable atmosphere and low‐aerosol loading occurs. An improved calibration method, namely, the transmission and division of total optical depth method, is proposed in this study. Atmospheric total optical depth variation information obtained via other methods is transmitted, and period groups with similar atmospheric extinction effects are selected for Langley regression. This method is validated through calibration of a multifilter rotating shadowband radiometer under heavy aerosol‐loading conditions. The obtained aerosol optical depth (AOD) compares well with the interpolated AOD from a Cimel Sun‐sky radiometer.

Broadening of polymer chromatographic signals: Analysis, quantification and correction through effective diffusion coefficients

Average molecular weights and polydispersity indexes are some of the most important parameters considered in the polymer characterization. Usually, gel permeation chromatography (GPC) and multi angle light scattering (MALS) are used for this determination, but GPC values are overestimated due to the dispersion introduced by the column separation. Several procedures were proposed to correct such effect usually involving more complex calibration processes.In this work, a new method of calculation has been considered including diffusion effects. An equation for the concentration profile due to diffusion effects along the GPC column was considered to be a Fickian function and polystyrene narrow standards were used to determine effective diffusion coefficients. The molecular weight distribution function of mono and poly disperse polymers was interpreted as a sum of several Fickian functions representing a sample formed by only few kind of polymer chains with specific molecular weight and diffusion coefficient.Proposed model accurately fit the concentration profile along the whole elution time range as checked by the computed standard deviation. Molecular weights obtained by this new method are similar to those obtained by MALS or traditional GPC while polydispersity index values are intermediate between those obtained by the traditional GPC combined to Universal Calibration method and the MALS method.Values for Pearson and Lin coefficients shows improvement in the correlation of polydispersity index values determined by GPC and MALS methods when diffusion coefficients and new methods are used.

Absolute molecular weight determination of hypromellose acetate succinate by size exclusion chromatography: Use of a multi angle laser light scattering detector and a mixed solvent

Molecular weight distribution is an important quality attribute for hypromellose acetate succinate (HPMCAS), a pharmaceutical excipient used in spray-dried dispersions. Our previous study showed that neither relative nor universal calibration method of size exclusion chromatography (SEC) works for HPMCAS polymers. We here report our effort to develop a SEC method using a mass sensitive multi angle laser light scattering detector (MALLS) to determine molecular weight distributions of HPMCAS polymers. A solvent screen study reveals that a mixed solvent (60:40%, v/v 50 mM NaH 2PO 4 with 0.1 M NaNO 3 buffer: acetonitrile, pH* 8.0) is the best for HPMCAS-LF and MF sub-classes. Use of a mixed solvent creates a challenging condition for the method that uses refractive index detector. Therefore, we thoroughly evaluated the method performance and robustness. The mean weight average molecular weight of a polyethylene oxide standard has a 95% confidence interval of (28,443–28,793) g/mol vs. 28,700 g/mol from the Certificate of Analysis. The relative standard deviations of average molecular weights for all polymers are 3–6%. These results and the Design of Experiments study demonstrate that the method is accurate and robust.

Universal calculation formula and calibration method in Fourier transform profilometry

We propose a universal calculation formula of Fourier transform profilometry and give a strict theoretical analysis about the phase-height mapping relation. As the request on the experimental setup of the universal calculation formula is unconfined, the projector and the camera can be located arbitrarily to get better fringe information, which makes the operation flexible. The phase-height calibration method under the universal condition is proposed, which can avoid measuring the system parameters directly. It makes the system easy to manipulate and improves the measurement velocity. A computer simulation and experiment are conducted to verify its validity. The calculation formula and calibration method have been applied to measure an object of 22.00 mm maximal height. The relative error of the measurement result is only 0.59%. The experimental results prove that the three-dimensional shape of tested objects can be reconstructed exactly by using the calculation formula and calibration method, and the system has better universality.

Pyrometric temperature measurement of ceramic thermal shock samples

The determination of critical failure parameters during thermal shock requires a time and space resolved temperature measurement of the sample. High frequency pyrometry is a suitable technique for such a measurement task, which usually requires the knowledge of the optical properties of the investigated material. Another challenge is the infrared transparency of materials to be checked in the wavelength range of the pyrometer. The thermal shock disks are very thin, due to the need of homogeneous temperature distribution and to maintain a two-dimensional problem. To allow a pyrometric temperature measurement a universal calibration method for high frequency infrared cameras has been developed. Pyrometry in various media was demanded, as well as the estimation of optical properties (reflection, transmittance and emission) for the selected ceramics to be tested.

Evaluation of kinetics parameters for poly( l-lactic acid) hydrolysis under high-pressure steam

In order to evaluate more precise kinetics parameters: rate constant k and E a values for poly( l-lactic acid) hydrolysis, the reaction was carried out under high-pressure steam in a temperature range of 100–130 °C. Molecular weights of hydrolyzates were calculated by the universal calibration method without being influenced by any weight loss. The changes in molecular weight could be successfully explained according to the auto-catalytic hydrolysis mechanism, clearly indicating the critical point. Resulting k and E a values were estimated as 8.4 × 10 −5–7.2 × 10 −4 s −1 and 87.2 kJ mol −1 with high R 2 values, respectively. Moreover, to determine the deviation of the parameter values, influences of four factors on the measurements and calculation: (1) use of number-average molecular weight value alone, (2) use of relative molecular weight based on polystyrene standards, (3) weight loss during the hydrolysis, and (4) selection of reaction mechanism were evaluated quantitatively.

Characterization of Styrene Copolymers Using Size-Exclusion Chromatography with On-line FT-IR Viscometer Detectors

Size-exclusion chromatography (SEC) provides a rapid method for determining molar mass distributions of macromolecules. In this article, we demonstrate the method of SEC coupled with an on-line Fourier-transform infrared (FT-IR) detector and an on-line differential viscometer developed for copolymer characterization. Using a chemometric technique to analyze the FT-IR spectra allows for determining copolymer concentration and composition. The combination of the FT-IR concentration detector and the viscometer allows the universal calibration method to be used for measuring copolymer molar mass. Molar mass distribution and compositional distribution are described and the method's application demonstrated using several types of styrene copolymers.