peter holstein - Academia.edu (original) (raw)

Papers by peter holstein

Acta Polymerica

Three types of drawn PP fibres have been investigated by nuclear magnetic relaxation methods. The... more Three types of drawn PP fibres have been investigated by nuclear magnetic relaxation methods. The two minima observed in both the temperature dependence of T1 and T2eff are related to the well known β‐and α‐processes, respectively. The results of the experiments show that in particular the crystalline regions are influenced by drawing.

Hydrological Sciences Journal-journal Des Sciences Hydrologiques, Jan 20, 2023

Elsevier eBooks, 1998

This chapter discusses nuclear magnetic resonance (NMR) techniques that are particularly appropri... more This chapter discusses nuclear magnetic resonance (NMR) techniques that are particularly appropriate for solid fluoropolymers, different classes of these materials, and homopolymers. A special characteristic of fluoropolymers for NMR is the incorporation of the 19 F nucleus, which is in many ways particularly suitable for study and can act as a unique probe to examine the chemical microstructure, domain structure, and mobility at the molecular level for these materials. However, some special techniques are frequently required for the best results from 19 F NMR of solid polymers. Most NMR work on fluoropolymers not containing hydrogen has concentrated on poly(tetrafluoroethylene) (PTFE) because of its high commercial importance. PTFE is a very unusual solid material in the sense that its bonds are among the strongest known while its weak ones are among the weakest of such interactions. Among polymers, poly(vinylidene fluoride) (PVDF) exhibits some peculiarities arising mainly from the extremely strong piezoelectricity and pyroelectricity. These outstanding electric properties make PVDF suitable for a variety of applications. Parallel to the large number of papers in the scientific and engineering literature presenting the complexity of the properties and their potential for application, several attempts have been made to obtain relevant information from wideline NMR spectra.

Denkmal und Energie 2020, 2019

Akustische Verfahren zeichnen sich dadurch aus, dass sie fur vielfaltige Einsatzgebiete modifizie... more Akustische Verfahren zeichnen sich dadurch aus, dass sie fur vielfaltige Einsatzgebiete modifiziert werden konnen. Sowohl Luft als auch andere Materialien kommen als Ubertragungswege aber auch als Untersuchungsziele infrage. Das Spektrum der Methoden reicht dabei vom horbaren bis in den Ultraschallbereich.

Denkmal und Energie 2018, 2017

In der Industrie werden akustische Verfahren zu Dichtheitsprufung seit langerer Zeit erfolgreich ... more In der Industrie werden akustische Verfahren zu Dichtheitsprufung seit langerer Zeit erfolgreich eingesetzt. Beispiele sind die Lecksuche in Druckluftleitungen, die Dichtheitsprufung von Vakuumanlagen, LKW-Bremssystemen, Fahrzeugkabinen, und Frachtraumen von Schiffen. Die Aufzahlung liese sich erweitern.

Progress in colloid and polymer science, 1989

Solid state NMR is used to study molecular motion and orientational distribution in thin films of... more Solid state NMR is used to study molecular motion and orientational distribution in thin films of PVDF and PA 11 which are of particular interest in technical application. The variation of angle between the static magnetic B 0-field and preferred directions given by drawing and poling, respectively, leads to characteristic angular dependencies of the effective transverse relaxation time T 2eff. This allows one to obtain information on the effect of external mechanical and electrical fields on c- and b-axies distribution. A good c-axes alignment could be reached by drawing. The tendency for b-axes to orient towards the direction of the applied electric field is evident. This effect is stable over a longer period of time but can be reversed at high temperatures. The results of first in-situ measurements are given showing the the b-axes alignment in electric fields up to 2 MV cm−1 can be “switched” periodically).

Progress in Colloid & Polymer Science

In this paper, solid-state NMR investigations of polyamide 11 (PA 11) films are presented. This p... more In this paper, solid-state NMR investigations of polyamide 11 (PA 11) films are presented. This polymer is semicrystalline and can exist in various crystalline polymorphs. Polymaide 11 shows interesting electric properties. The piezo- and pyroelectric effects of this polar polymer are comparable with those of polyvinylidenfluoride (PVDF). Multiple pulse 1H-NMR and 13C CP/MAS NMR measurements are used to investigate the influence of the preparation conditions (thermal, mechanical, electric effects) on the morphology of PA 11. Various preparation procedures provde film material with predominantly a — and γ crystallites, respectively. The 13C NMR spectra and IR measurements support the assumption of the co-esistence of various crystalline polymorphs. The chemical shift patterns are different for the various crystalline modifications. Separated 13C NMR spectra are recorded for the crystalline and amorphous parts of the films. Orientation effects due to the mechanical strechting and the poling in electric fields are reflected in the results of the 1H NMR multiple pulse investigations.

&lt;p&gt;The Brazilian semiarid region covers about 1 million km&amp;#178... more &lt;p&gt;The Brazilian semiarid region covers about 1 million km&amp;#178; and is characterised by irregular rainfall and high potential evaporation (above 2000 mm per year of water loss). To overcome the lack of water, the population depends on man-made reservoirs, which are the main source of water during the dry season (8 months of the year). In the federal state of Cear&amp;#225; there is on average one dam every 5 km, totalling more than 20,000. It is, therefore, noteworthy how the accurate estimation of evaporation would improve the management of scarce water resources. Moreover, climate change scenarios predict impacts on water availability in this region and better accuracy in evaporation assessments are fundamental to foster such simulations, which itself works at an intra-day time resolution. We suggest the most precise measurements possible, close to the lake and preferably on top of the water body. We used between October-December 2019 two direct measurement sensors in floating pans on the reservoir. A newly developed one based on the echo sounder principle and a standard differential pressure meter. Both show that at the reservoir more than 6 mm evaporate per day on average in the dry period. Uncertainty analyses for a single measurement show good performance of the acoustic sensor (&amp;#177; 0.11 mm) compared to the standard sensor (&amp;#177; 0.6 mm), sensitive enough to record the daily course of evaporation. The field measurements show 3.7% of uncertainty comparing the acoustic sensor with the standard pressuremeter. The minimum number of measurements with the acoustic sensor to obtain such uncertainty is 307. In this case, for 1h step, the uncertainty is 1.1%. The wave movement caused by wind influences the quality and frequency of the measurement. These results serve as a basis for future approaches to assess spatial variation of evaporation and wind on the lake. This might highlight the minimal number of instruments needed to solve the issue of spatial variability of evaporation.&lt;/p&gt;

Solid State Nuclear Magnetic Resonance, 1998

Solid state NMR techniques have been developed to investigate dynamic molecular effects e.g., mol... more Solid state NMR techniques have been developed to investigate dynamic molecular effects e.g., molecular reorienta-. Ž. tions due to simultaneously applied external electric fields on electrically sensitive materials such as liquid crystals LC , Ž. liquid crystalline polymers LCP and polymeric electrets. Such effects can be observed only on relatively thin systems Ž. 10-200 mm. That means that many scans are necessary to achieve a sufficiently high signal-to-noise-ratio in the spectra Ž. 500-1000 scans. If the material is also magnetically sensitive, the electric field can be used to orient molecules in a starting orientational state and by switching-off the voltage to access fast reorientation processes in the magnetic field B. 0 Until now, the behaviour of orientable molecular systems under the influence of electric fields has been investigated by Ž. means of a more or less quasistatic approach LCP: 100 V, electrets: 1 kV in equilibrium states. The achievable time resolution depends on the desired signal-to-noise-ratio. For the case of proton NMR this means a time resolution of about 10 min. However, very often switching processes occur on a much shorter time scale. Using conventional techniques it is Ž. impossible to observe fast ca. 100 ms electrically or magnetically induced reorientation processes. In this work, we present a concept to overcome the problems outlined above and to extend the area of our current in situ NMR investigations on thin electrically-switched or poled polymeric layers. The basic idea is to include synchronized electric pulses during the NMR experiment using the preparation andror mixing periods of a 1D or 2D pulse sequence for the application of an orienting Ž. field electric or magnetic and to use the reversibility of the molecular switching phenomenon to achieve a sufficient signal-to-noise-ratio. The techniques extend the range of possible investigations from about 100 ms to approximately T for 1 Ž. correlated spectra and to longer times of applied fields for uncorrelated spectra. Results are shown for a nematic LC and a nematic polymer having a similar side chain. q 1998 Elsevier Science B.V.

The invention relates to a method for acoustic measurement of exit speeds and / or outlet flow ra... more The invention relates to a method for acoustic measurement of exit speeds and / or outlet flow rates of gases and / or liquids. The invention further relates to a device for implementing this method and a sensor for acoustic measurement of exit speeds and / or outlet flow rates of gases and / or liquids.

Die Aufgabenstellungen zum messtechnischen Einsatz signalverarbeitender Systeme zeichnen sich dur... more Die Aufgabenstellungen zum messtechnischen Einsatz signalverarbeitender Systeme zeichnen sich durch eine Reihe von Tendenzen aus, die erhöhte Anforderungen an Systeme, Entwicklungsumgebungen und Bearbeiter stellen. Solche Merkmale sind z. B. zunehmende Verteiltheit, Heterogenität, Komplexität und abnehmende verfügbare Entwicklungszeit Der plattformunabhängigen Beschreibbarkeit des Gesamtsystems kommt dabei eine entscheidende Rolle zu, ermöglicht sie einerseits die Wiederverwendung bewährter Lösungen und Teillösungen, anderseits die vereinfachte Migration auf neue Plattformen. Ansatz zur deklarativen Beschreibung Die Anforderungen an signalverarbeitende Strukturen auf verscheidenen Ebenen werden immer komplexer. Das betrifft sowohl Abläufe auf real-time-Ebene als auch die Anbindung hochkomplexer algorithmischer Werkzeuge. Modular strukturierte Arbeitsebenen und wiederverwendbare Techniken erleichtern sowohl Programmierbarkeit als auch Pflegbarkeit solcher Lösungen. Besonders aussicht...

Denkmal und Energie 2021, 2021

Der Blower-Door-Test zählt zu den traditionellen und leistungsstarken Verfahren bei der Bewertung... more Der Blower-Door-Test zählt zu den traditionellen und leistungsstarken Verfahren bei der Bewertung der energetischen Dichtheit von Räumen und Gebäuden. In den letzten Jahren kamen zunehmend andere Verfahren wie Thermografie und auf Ultraschall basierende und andere akustische Methoden zum Einsatz. Die Verfahren haben jeweils ihre spezifischen Vor-und Nachteile. Im Beitrag werden die Methoden bezüglich ihres Aufwandes und ihrer Aussagemöglichkeiten verglichen. Insbesondere werden die Verfahren bezüglich ihres Einsatzes an Bestandsgebäuden untersucht. Die Verfahren benötigen unterschiedlich vorbereitete Objekte, bei denen ein physikalischer Gradient erzeugt wird. Beim Blower-Door-Test ist ein Überdruck erforderlich, bei den akustischen Verfahren wird eine geeignete Schallquelle benötigt. Dies ermöglicht auch komplementäre Untersuchungen und Aussagen.

Piezokomposite werden seit uber 20 Jahren beim Bau von Ultraschallwandlern fur die zerstorungsfre... more Piezokomposite werden seit uber 20 Jahren beim Bau von Ultraschallwandlern fur die zerstorungsfreie Materialprufung eingesetzt. Gegenuber den klassischen keramischen oder kristallinen Materialien zeichnen sie sich durch sehr gute akustische Eigenschaften, hohe Adaptierbarkeit und ein gutes Preis-Leistungs-Verhaltnis aus. Auch in der Technischen Diagnose und der Materialprufung spielen akustische Methoden eine immer grosere Rolle. Bei Reibungsprozessen, Rissentstehungen, bei Bruchvorgangen oder auch bei Kavitationsvorgangen, wird oft Schall bei relativ hohen Frequenzen erzeugt, welcher mit Schallemissionssensoren aufgenommen werden kann. Die Bewertung der Ergebnisse ist oft jedoch dadurch erschwert, dass die Sensoren uber nichtlineare Kennlinien verfugen und deshalb vor allem parameterbasierte Auswerteverfahren zur Anwendung kommen. Vorgestellt werden neue Prufkopfe und Sensoren auf der Basis von Piezokompositschwingern sowie einige Anwendungsbeispiele (Monitoring von Pumpen, an Brem...