2d-CUSUM for the detection of tendencies inherent in noisy bivariate data

Noisy analytical data dependent on 2 different variables (bivariate data) can be evaluated by an extended (2-dimensional) CUSUM-algorithm. Even at very high random fluctuations this 2d-CUSUM allows to detect long-term instationarities even from short series of measurements. The model of 2d-CUSUM as well as examples (distribution analysis, time-series analysis, treatment of calibration functions) are shown in this paper.Dedicated to Professor Dr. R. Geyer (Naumburg/Saale) on the occasion of his 80th birthday on April 14, 1994     

Dielectric and depolarization thermocurrent study of the γ relaxation in polyethylene isophthalamide

The depolarization thermocurrents (DTC) from polyethylene isophthalamide are studied below the glass-transition temperature. The “entire” DTC spectrum is analyzed in terms of a continuous distribution of relaxation times; the corresponding distribution function is very close to that which fits data deduced from bridge measurements. The complex DTC spectrum can be experimentally resolved into single relaxation time processes. The analysis of each “elementary” DTC peak yields dielectric dispersion and relaxation time which allow one to calculate the frequency variation of the complex dielectric constant. The corresponding Cole–Cole plot is in good agreement with that deduced from studies of the “unresolved” γ relaxation.     

Use of data from environmental sampling for IAEA safeguards. Case study: uranium with near-natural 235U abundance

Environmental sampling (ES) is one of the measures applied in international nuclear safeguards. The detection capability of safeguards ES relies on a combination of highly sensitive analytical techniques and resourceful data evaluation. The evaluation process is dynamic, employing a variety of tools, information and analytical results. While the presence of uranium or plutonium may be a significant finding in itself, high quality isotopic measurements are essential to associate the material with a specific nuclear activity. This is illustrated in cases where the uranium detected appears to be “natural” or “near-natural”, but in fact can be identified with various nuclear processes.     

A real‐time Mooney‐viscosity prediction model of the mixed rubber based on the Independent Component Regression‐Gaussian Process algorithm

With the rapid development of rubber industry, it becomes more and more important to improve the performance of the quality control system of rubber mixing process. Unfortunately, the large measurement time delay of Mooney viscosity, one of the most important quality parameters of mixed rubber, badly blocks the further development of the issue. The independent component regression‐Gaussian process (ICR‐GP) algorithm is used to solve such typical nonlinear “black‐box” regression problem for the first time to predict Mooney viscosity. In the ICR‐GP method, the non‐Gaussian information is extracted by the independent component regression method firstly, and then the residual Gaussian information is extracted by the Gaussian process method. Meanwhile, both the linear and nonlinear relationships between the input and output variables can be extracted through the ICR‐GP method. With the fact that there is no need to optimize parameters, the ICR‐GP method is especially suitable for “black‐box” regression problems. The highest prediction accuracy was achieved at M = 0.8765 (the root mean square error), which was high enough considering the measuring accuracy (M = ±0.5) of the Mooney viscometer. It is by using the online‐measured rheological parameters as the input variables that the measurement time delay of Mooney viscosity could be dramatically decreased from about 240 to 2 min. Consequently, such Mooney‐viscosity prediction model is very helpful for the development of the rubber mixing process, especially of the emerging one‐step rubber mixing technique. The practical applications performed on the rubber mixing process in a large‐scale tire factory strongly proved the outstanding regression performance of this ICR‐GP Mooney‐viscosity prediction model. Copyright © 2012 John Wiley & Sons, Ltd.     

On new approaches in nonlinear dynamics of complex systems

An approach is introduced that tries to make sense of interaction of physical processes characterized by strongly different space and especially time scales. Slow processes can be assumed as “rules” that govern fast processes, but it's argued that some feedback must exist. Some new models are also introduced. The first is extension of K. Sneppen SOC model of solid body – vapor interface depinning. The second is model of a toy “physical” Universe with evolving “physical laws”. The last one imitates evolution of animal population with slowly evolving instincts.     

Some remarks on mechanism and kinetics of the coulometric variant of the Karl-Fischer titration reaction

The quasi-lattice model for quaternary reciprocal systems of molten salts, previously developed for association processes in mixed solvents, has been modified to apply to an association process involving a “mixed ligand” in a pure salt as solvent. The association energies, determined from e.m.f. measurements in the range 620–720 K, for the association of silver(I) with chloride-bromide mixtures in molten sodium nitrate, are in satisfactory agreement with the predictions of the model. The very small, but significant, discrepancies between calculated and experimental association energy values show the same trend as those previously found for the mixed solvent systems.     

“Demonstration” vs. “designation” of measurement competence: the need to link accreditation to metrology

Formal acceptance of the results of chemical laboratories is increasingly organized through a) accreditation of measuring laboratories nationally and b) mutual recognition of accreditation internationally (through formal Multilateral Recognition Agreements, MRAs). However, real comparability of results of measurements is realized by using common (internationally agreed) measurement scales which make these results traceable to this scale, i.e. “traceable” to the same (internationally agreed) value of the unit of that scale. In addition, the criterion against which the evaluation is done, should be “external” to the measurement laboratories which are being evaluated. This is realized in IRMM’s International Measurement Evaluation Programme (IMEP) where evaluation is performed against values which are anchored using “metrology”, the science of measurement with its own rules, which offers a sound foundation for measurement in all scientific disciplines. It is argued in this paper that the demonstration of measurement capability against values on such scales provides a result-oriented rather than a procedure-oriented evaluation. Thus, competence can be “demonstrated” rather than just “designated” and this can be shown to both customers and regulators. It inspires more confidence.     

The frost model and perturbation theory

Symmetry-adapted double perturbation theory is applied to the Frost model. Even when used only through zero-order in the correcting ”internal“ perturbation it gives values of average electric polarizabilities in fair agreement with experiment. If the model is extended by employing clliptical gaussians rather than spherical ones, the anisotropy of the molecular polarizability can be determined.     

Mechanism of formation of shish kebab structures

To describe the characteristic crystalline structure of polyolefins, Pennings first proposed a model consisting of a combination of an extended chain crystal (a “shish”) and folded chain crystals (“kebabs”). In Pennings' model the “shish” forms first during a crystallization process under stress and then later the “kebabs” overgrow this “shish” structure epitaxially. Because we had some doubts about such a mechanism, we undertook a series of experimental studies on linear polyethylene, particularly in regard to the crystallization process from a solution under shear. Our conclusion is that the crystals grow first by a screw dislocation mechanism, like whiskers, and then later these are deformed by the shear stress to form the shish kebab structures.     

Scaling in nonstationary voltammetry representations

Despite the widespread use of voltammetry for a range of chemical, biological, environmental, and industrial applications, there is still a lack of understanding regarding the functionality between the applied voltage and the resulting patterns in the current response. This is due to the highly nonlinear relation between the applied voltage and the nonstationary current response, which casts a direct association nonintuitive. In this Article, we focus on large-amplitude/high-frequency ac voltammetry, a technique that has shown to offer increased voltammetric detail compared to alternative methods, to study heterogeneous electrochemical reaction-diffusion cases using a nonstationary time-series analysis, the Hilbert transform, and symmetry considerations. We show that application of this signal processing technique minimizes the significant capacitance contribution associated with rapid voltammetric measurements. From a series of numerical simulations conducted for different voltage excitation parameters as well as kinetic, thermodynamic, and mass transport parameters, a number of scaling laws arise that are related to the underlying parameters/dynamics of the process. Under certain conditions, these observations allow the determination of all underlying parameters very rapidly, experiment duration typically相似文献   

Application of the Solvatic Model for Prediction of Retention in RP-LC for Multi-Step Gradient Profiles

Application of the solvatic retention model of reversed-phase liquid chromatography was studied to predict retention of phenylisothiocyanate derivatives of amino acids from structural formulae and stationary and mobile phase properties. The gradient elution mode with methanol and acetonitrile aqueous mobile phases was used. It was shown that practically acceptable prediction or retention time values can be achieved after the first approximation step when experimental data of one run are used. The zero approximation level predictions—from structural formulae, column and mobile phase properties can be used as a “first guess” method from which further optimization can begin.

     

Automation of Structure Analysis. Part II. Automation of the Evaluation

The extent to which it is possible to automate the determination of a structure from the data collected with automatic measuring equipment is discussed. The development of the automatic evaluation is synchronous with that of digital computer program.—Even the simple calculation of structure factors from the intensities (i.e. the analysis of the geometrical and physical intensity factors) takes several weeks when the many thousand reflections are processed “manually”, i.e. with a desk calculator. A large electronic computer, on the other hand, executes these calculations in a few seconds. Nevertheless, even the largest computers available at present are too small for many of the complex steps in the calculation and for the quantity of data involved. Evaluation methods which, owing to long computing times, can at present only be tested on relatively simple structures will become more attractive with the advent of machines with computing times in the nanosecond range. For corrigendum see DOI: 10.1002/anie.196605112     

Erythemal UV Radiation on Days with Low UV Index Values—an Analysis of Data from the German Solar UV Monitoring Network over a Ten‐year Period

According to the World Health Organization and partner organizations, no protection against ultraviolet (UV) radiation is required on days with “low” values (i.e., values <3) of the Global Solar Ultraviolet Index (UVI). Erythemal irradiance (E_er) data of such days were analyzed to evaluate this claim. Measurements from 9 stations of the German solar UV monitoring network from 2007 to 2016 yielded 14,431 daily E_er time series of low UVI days. Erythemal doses for certain fixed time intervals—acquired from measurements on horizontal planes—were compared with the average minimal erythemal dose (MED) of skin phototype II. Doses from days with rounded UVI values of 0 were insufficient to induce erythema and even on days with rounded UVI values of 1 doses exceeding 1 MED of skin type II could only be acquired under very specific circumstances of prolonged exposure. Conversely, sun exposure on days with rounded UVI values of 2 can indeed provide doses sufficient to induce erythema in skin type II after two hours around noon. In conclusion, our analyses do not support the claim of harmlessness currently associated with the entire low UVI exposure category in public guidance on interpretation of the UVI.     

Zeta-potential measurements of OTS-covered silica samples

We have carried out zeta-potential measurements on two different OTS (octadecyl-trichlorosilane)-covered silicas (fused silica, quartz 0001) prepared under identical conditions. Streaming current measurements on the fused silica supported OTS sample indicate a well reproducible IEP of 3.5. The major part of the study focused on the quartz 0001 supported sample with an IEP lower than that of the fused silica support and in agreement with that found in a spectroscopic study. The IEP in water (on addition of HCl) was found at around pH 3, and appeared to shift to lower values in three subsequent measurements. A final measurement after a separate series in KCl media gave the same IEP as obtained in the very first measurement, suggesting that the experiments did not significantly change the interfacial properties despite a large number of experiments. In one series of measurements care was taken to exclude any cations other than protons from the measurements, such that protons are the only counter-ions to the negative net charge. While our IEPs with the quartz support agree well with recent estimates from sum frequency generation (SFG) investigations, none of the zeta-potential vs pH curves would mimic a pattern experimentally observed in the amplitude of the “ice-like” water band between pH 3.5 and 5 in that SFG study. Furthermore, our results do not indicate any significant chloride-ion adsorption in KCl systems, but instead the shift of the IEP with increasing KCl to higher pH values rather indicates specific effects of potassium ions. Under conditions more relevant to the spectroscopic study (i.e. in absence of potassium) no specific pattern reminiscent of the SFG results was found. When tested it was found that surface conductivity was negligible.     

Stability conditions for the solutions of the hartree-fock equations. VII. Stability of some closed-shell nonalternant systems

The instabilities of the solutions to the Hartree-Fock equations for the nonalternants in the pentalene, heptalene, etc., series and in the azulene, etc., series are examined. The systems are found to have symmetry-adapted solutions which are unstable for values of the core integral β close to the standard (spectroscopic) value; for example, the pentalene solution is unstable with β equal to 75% of its standard value. The “broken” symmetry solutions although exhibiting only a very slightly lower energy (0.01 eV) may exhibit dramatically different values for other properties, e.g., 30% changes in bond orders. The off-diagonal charge-density wave (CDW ) appearing in the “broken” symmetry solutions at the onset of instability is amplified as the cooperative phenomena dominate, until in the “fully correlated” limit, the linked-ethylenic (bond alternating) structure is obtained.     

Auswahl,Vergleich und Bewertung optimaler Arbeitsbedingungen für die quantitative Mehrkomponenten-Analyse

Calibration and analytical measurements in spectrometric multicomponent analysis can be solved by linear algebra supposing the observed values being a homogenous linear function of the expected quantities. The increase of precision is one of the most important problems for the analyst. Using two-dimensional overdetermined systems of equations precision can be extended up to the outer limits. In calibration procedures both the number of calibration samples and wavelengths should be higher than the minimum, in analysis the overdetermination in the number of wavelengths is sufficient. Two alternative ways in producing the amount of overdetermination by “repetitive and additive measurements” respectively, are discussed on the basis of information theory. The metric functional term “sensitivity” can be derived from the matrix of the system. There exists an statistical correlation between this term and the precision of analysis. A stepwise maximisation procedure of the sensitivity in the system to be solved is used as a criterion of decision.