Search results for "HYSTERESIS"

Influence of the pressure head sequence on the soil hydraulic conductivity determined with tension infiltrometer

2005

An increasing and a decreasing sequence of pressure head, h0, values were applied with the tension infiltrometer (TI) to determine the corresponding hydraulic conductivity, K0. The pressure head sequence is expected to influence the K0 results given the hysteretic nature of the hydraulic conductivity relationship. The objective of this study was to evaluate the influence of the selected pressure head sequence on the hydraulic conductivity of a sandy loam soil measured by a multipotential TI experiment. Twenty experiments were carried out by applying h0 values varying between -150 and +5 mm (site A). The h0 values ranged from -150 to -10 mm in another 20 spots (site B). Both wetting and dryi…

Pressure-induced hysteresis in the high spin \leftrightarrow low spin transition in bis(2,4-bis(pyridin-2-yl)thiazole) iron(II) tetrafluoroborate

2008

Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz)2](BF4)2 have been carried out under hydrostatic pressures up to 9.13 kbar in the 5–300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS ↔ LS transition with T1/2 = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T1/2 and a slight decrease in the residual high spin fraction at low T . Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T1/2 the surpris…

Non-Linear Hysteretic Instability in Rotating Machinery

2013

Downsizing of robust Fe-triazole@SiO2 spin-crossover nanoparticles with ultrathin shells

2019

A chemical protocol to design robust hybrid [Fe(Htrz)2(trz)](BF4)@SiO2 nanoparticles (NPs) with sizes as small as 28 nm and ultrathin silica shells below 3 nm has been developed. These NPs present a characteristic abrupt spin transition with a subsequent decrease in the width of the thermal hysteresis upon reducing the NP size.

Spin-crossover nanocrystals with magnetic, optical, and structural bistability near room temperature.

2008

Creep Modeling with Time-Dependent Damping Parameters in Piezoelectric Actuators

2019

This paper develops a creep model based on the Kelvin-Voigt model with time varying damping parameters. In the piezoelectric actuators, the creep phenomenon is an important issue in precise positioning applications as well as the hysteresis property. It is well-known that the creep effect can be represented by a series connection of a number of Kelvin-Voigt elements as a viscoelastic model. In the motion for the continuous stepwise positioning, however, the creep shape is different for each response. Since the phenomenon can be captured as temporal creep relaxation, time-dependent damping parameters are introduced to improve the reproducibility of the creep for the various motion. On the ot…

Field-Induced Hysteresis and Quantum Tunneling of the Magnetization in a Mononuclear Manganese(III) Complex

2013

International audience

Magnetic hysteresis up to 80 kelvin in a dysprosium metallocene single-molecule magnet

2018

Breaking through the nitrogen ceiling Single-molecule magnets could prove useful in miniaturizing a wide variety of devices. However, their application has been severely hindered by the need to cool them to extremely low temperature using liquid helium. Guo et al. now report a dysprosium compound that manifests magnetic hysteresis at temperatures up to 80 kelvin. The principles applied to tuning the ligands in this complex could point the way toward future architectures with even higher temperature performance. Science , this issue p. 1400

Magnetic phase transition and magnetic bistability in oxamato-based CoIICuII bimetallic MOF thin films

2019

Abstract Thin films of an anionic oxamato-bridged cobalt(II)–copper(II) 3D MOF have been growth at 120 °C in DMSO through a one-pot reaction from Co(NO3)2·6H2O and (Me4N)2[Cu(2,6-Et2pa)2]·6H2O (2,6-Et2pa = N-2,6-diethylphenyloxamate) over Si(111) surfaces functionalized with carboxylic acid terminating groups. These heterobimetallic CoII2CuII3 MOF thin films (2) of about ten nanometers thickness show a ferrimagnetically ordered phase below ca. 10 K with a relatively large magnetic hysteresis similar to that of the bulk material of formula (Me4N)2[Co2Cu3(2,6-Et2pa)6]·5H2O (1).

The First 1,3,4‐Oxadiazole Based Dinuclear Iron(II) Complexes Showing Spin Crossover Behavior with Hysteresis

2015

Three new dinuclear complexes [FeII2(μ-L)2]X4 (L is the bis-tridentate ligand 2,5-bis{[(2-pyridylmethyl)amino]methyl}-1,3,4-oxadiazole and X = ClO4–, BF4– and CF3SO3–) have been synthesized and fully characterized by single-crystal X-ray diffraction, Mossbauer spectroscopy and magnetic susceptibility measurements. Upon cooling, a trapped [high-spin–low-spin] state of the iron(II) centres is detected. Depending on the counterion, a pronounced thermal hysteresis is found. In one case, it was possible to observe a space group change that accompanies the spin transition. This is the first system showing spin crossover based on an oxadiazole ligand.