scholarly journals Water in Mesoporous Confinement: Glass-To-Liquid Transition or Freezing of Molecular Reorientation Dynamics?

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3563
Author(s):  
Schranz ◽  
Soprunyuk
Keyword(s):  
Porous Silica ◽  
Mechanical Analysis ◽  
Mechanical Relaxation ◽  
Molecular Reorientation ◽  
Work Related ◽  
The Core ◽  
Liquid Transition ◽  
Relaxation Measurements ◽  
Reorientation Dynamics ◽  
Lower Temperature

The first mechanical relaxation measurements (f = 400 Hz) of water confined in micro-porous silica were performed more than 40 years ago. The authors reported a so called “capillary transition” (here denoted as P3) of water in the core of the pores and a second one at a lower temperature, which they called the “adsorbate transition” (P1 in present work) related to water near the surface of the pores. The capillary transition was identified with the freezing of water in the centre of the pores. However, even 40 years later, the origin of the adsorbate transition is not yet clear. One study relates it to the liquid-to-glass transition of the supercooled water in the pores, and another study to the freezing of the proton reorientations at the lattice defects. The present work shows the data from extensive dynamic mechanical analysis (DMA) measurements (f = 0.1 Hz–70 Hz) of water confined in mesoporous silica (d = 2.5, 5 and 10 nm), which are in favour of a liquid-to-glass scenario.

Numerical Experiments of Coolant Mixing in a Lower Plenum of PWR Under Asymmetric Thermal- Hydraulics Conditions

2006 ◽  
Author(s):  
Masanori Ohtani ◽  
Akito Kozuru ◽  
Yasuyuki Kashimoto ◽  
Mitsuto Montani ◽  
Koutaro Takeda ◽  
...  
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Turbulent Mixing ◽  
Numerical Experiments ◽  
Time Dependent ◽  
Inlet Temperature ◽  
Velocity Fluctuations ◽  
The Core ◽  
State Calculation ◽  
Lower Temperature

Asymmetric thermal-hydraulic conditions among primary loops during a postulated steam line break (SLB) induce a non-uniform temperature distribution at a core inlet. When coolant of lower temperature intrudes into a part of core, it leads to a reactivity insertion and a local power increase. Therefore, an appropriate model for the core inlet temperature distribution is required for a realistic SLB analysis. In this study, numerical experiments were conducted to examine the core inlet temperature distribution under the asymmetric thermal-hydraulic coolant conditions among primary loops. 3D steady-state calculations were carried out for Japanese standard Pressurized Water Reactor (PWR) such as 2, 3, 4 loop types and an advanced PWR. Since the flow in a reactor vessel involves time-dependent velocity fluctuations due to a high Reynolds number condition and a complicated geometry of flow path, the turbulent mixing might be enhanced. Hence, the turbulent thermal diffusivity for the steady-state calculation was examined based on experimental results and another transient calculation. As a result, it was confirmed that (1) the turbulent mixing in a downcomer and a lower plenum were enhanced due to time-dependent velocity fluctuations and therefore the turbulent thermal diffusivity for steady-state calculation was specified to be greater, (2) the core inlet temperature distribution predicted by a steady-state calculation reasonably agreed with a experimental data, (3) the patterns of core inlet temperature distribution were comprehended to be dependent on the plant type, i.e. the number of primary loop and (4) under a low flow rate condition, the coolant of lower temperature appeared on the opposite side of the affected loop due to the effect of a natural convection.

New Economy Careers Demand Adaptive Mental Models and Resources

2014 ◽  
Author(s):  
Annelies E. M. van Vianen ◽  
Ute-Christine Klehe
Keyword(s):  
Labor Market ◽  
Mental Models ◽  
Recent Literature ◽  
New Economy ◽  
Future Research ◽  
Career Transitions ◽  
Work Related ◽  
The Core ◽  
Identity Threats ◽  
And Coping

Volatile economic and labor market circumstances have significant effects on the development of people’s work careers; thus recent literature on careers has started to take into account the reality of increasingly unpredictable, nonlinear, and inherently uncertain careers. In this chapter we argue that careers in the new economy require, first, that people learn to cope with identity threats; second, that they need to change their mental models of careers; and third, that they must develop the resources to adapt to more frequent and unpredictable career transitions. Specifically we address three themes that we consider at the core of adaptation to nonlinear careers: people’s work-related identities, their conceptualization of career success, and their adaptability resources. We build a model called “identity and coping during career transitions” (ICCT), which integrates theories on identity, careers, and adaptability and could serve as an agenda for future research. Finally, we provide some guidelines for practitioners and organizations.

Differences in the viscoelastic properties between earlywood and latewood in the growth rings of Chinese fir as analyzed by dynamic mechanical analysis (DMA) in the temperature range between −120°C and 120°C

Holzforschung ◽  
2019 ◽  
Vol 73 (3) ◽  
pp. 241-250 ◽  
Author(s):  
Anxin Li ◽  
Jiali Jiang ◽  
Jianxiong Lu
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Microfibril Angle ◽  
Mechanical Analysis ◽  
Chinese Fir ◽  
Individual Growth ◽  
Tree Age ◽  
Dry Density ◽  
Mechanical Relaxation ◽  
Growth Rings ◽  
Dynamic Mechanical

AbstractTo clarify the viscoelasticity of earlywood (EW) and latewood (LW) within different growth rings of Chinese fir, the following data were determined: absolute dry density, percentage of tracheid cell wall, microfibril angle (MFA), modulus of elasticity (MOE), storage modulus (E′) and loss modulus (E″) within the 3rdand 6thgrowth rings (in heartwood, hW) and the 14thand 18thgrowth rings (in sapwood, sW). The E′ and E″ data were obtained by dynamic mechanical analysis (DMA) between −120°C and 120°C, at a heating rate of 1°C min−1at the frequencies of 1, 2, 5 and 10 Hz under a dynamic load amplitude of 10 μm. All measured data were different between EW and LW. In the same growth ring, LW had a greater MOE and larger E′ than those of EW due to the higher density of LW. The MOE and E′ increased for both EW and LW with increasing tree age. The variation of MFA in different growth rings of EW influenced the MOE and E′. Both density and the MFA affected the MOE and E′ in LW. The profiles of E″ plots vs. DMA temperature reveal two maxima around −12°C (β mechanical relaxation process, βMRP) and 12°C (αMRP). The LW-MRP maxima are higher than those of EW, but in both cases increased with tree age. No frequency dependence was seen for the αMRP, whereas the loss peak temperature (LPT) of the βMRP increased with increasing frequency of DMA. Almost no difference in αLPT was observed between the four EW growth rings, and their βLPTs were similar. The LW-αLPT was almost the same in the four growth rings, but the hW-βLPT was higher than that of sW. In addition, the apparent activation energy (ΔH) of the hW-βMRP was greater than that of sW in both EW and LW, and the EW data>LW data in individual growth rings. These differences can be explained tentatively that hW and EW contain more extractives than sW and LW, and the deposited of extractives limit the motion of molecular segments within the cell walls.

scholarly journals Dynamic Mechanical Relaxation in LaCe-Based Metallic Glasses: Influence of the Chemical Composition

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1013 ◽  
Author(s):  
Minna Liu ◽  
Jichao Qiao ◽  
Qi Hao ◽  
Yinghong Chen ◽  
Yao Yao ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Metallic Glasses ◽  
Physical Aging ◽  
Enthalpy Of Mixing ◽  
Mechanical Analysis ◽  
Mechanical Relaxation ◽  
Atomic Mobility ◽  
Dynamic Mechanical ◽  
Β Relaxation

The mechanical relaxation behavior of the (La0.5Ce0.5)65Al10(CoxCu1−x)25 at% (x = 0, 0.2, 0.4, 0.6, and 0.8) metallic glasses was probed by dynamic mechanical analysis. The intensity of the secondary β relaxation increases along with the Co/Cu ratio, as has been reported in metallic glasses where the enthalpy of mixing for all pairs of atoms is negative. Furthermore, the intensity of the secondary β relaxation decreases after physical aging below the glass transition temperature, which is probably due to the reduction of the atomic mobility induced by physical aging.

Influence of Cobalt Addition on Microstructure and Damping Properties of Cu-Al-Ni Shape Memory Alloys

2020 ◽  
Vol 1010 ◽  
pp. 34-39
Author(s):  
Ying Ci Wee ◽  
Hamidreza Ghandvar ◽  
Tuty Asma Abu Bakar ◽  
Esah Hamzah
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Elastic Anisotropy ◽  
Mechanical Analysis ◽  
Damping Capacity ◽  
Damping Properties ◽  
Additional Element ◽  
Lower Temperature ◽  
Co Addition ◽  
High Degree

Copper-based shape memory alloys (SMAs) gaining attention due to their high damping properties during martensitic transformation and effective in energy dissipation which is applicable to damping application. However, copper-based SMAs such as the ternary Cu-Al-Ni are not easily deformed in the lower temperature martensitic phase which can be attributed to brittleness induced by coarse grain size, high degree of order and elastic anisotropy. Hence, this study aims to improve the properties of Cu-Al-Ni SMAs by addition of fourth alloying element. In this research, Cu-Al-Ni alloys with the addition of the fourth additional element, cobalt were prepared by casting. Microstructure characteristics of Cu-Al-Ni SMAs with and without Co addition were investigated via scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Damping capacity was determined by dynamic mechanical analysis (DMA). It was found that the alloy with 0.7wt% of Co addition showed the best improvement on the damping properties.

Molecular Reorientation in Liquid Methanol

1991 ◽  
Vol 46 (1-2) ◽  
pp. 89-94 ◽  
Author(s):  
R. Ludwig ◽  
D. S. Gill ◽  
M. D. Zeidler
Keyword(s):  
Nmr Relaxation ◽  
Quadrupole Coupling Constant ◽  
Dipolar Interaction ◽  
Proton Relaxation ◽  
Coupling Constant ◽  
Relaxation Rates ◽  
Molecular Reorientation ◽  
Quadrupole Coupling ◽  
Relaxation Measurements ◽  
Recent Computer

AbstractOxygen-17 enriched methanol CD317OH was synthesized and 1H as well as 17O nmr relaxation rates were measured in the temperature range 180-310 K. By varying the 17O-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time of the OH bond was determined. These results are compared to recent computer simulation data. Additional deuteron relaxation measurements on CH3OD yielded the quadrupole coupling constant which increases with falling temperature. The 17O quadrupole coupling constant shows a similar trend with temperature but not as pronounced.

Removal Method of Core Shaft of Primary Mirror

2013 ◽  
Vol 552 ◽  
pp. 221-226
Author(s):  
Qi Rui Xu ◽  
Fan Wu
Keyword(s):  
Mechanical Analysis ◽  
Primary Mirror ◽  
Supporting Structure ◽  
Removal Method ◽  
The Core ◽  
Large Aperture

The structure of core shaft combined with mercury belt is widely used as the primary mirror supporting structure of 1 meter class and 2 meter class large aperture telescope currently. In order to reduce the structure jitter of primary mirror, the fitting clearance between core shaft and shaft sleeve is very small, so clamping stagnation occurs during installation and disassembling process of core shaft. The removal method of clamping stagnation of core shaft is introduced. Mechanical analysis of core shaft and primary mirror is applied to make sure that the primary mirror is safe. Some tools are designed specially, and the process and the attention points to remove core shaft are introduced. In this way, the clamping stagnation of core shaft can be removed easily. The core shaft of 1 m class primary mirror was removed by the method and the primary mirror was excellent without damage.

Photoinduced molecular reorientation dynamics in confined domains of Langmuir monolayers

2005 ◽  
Vol 122 (24) ◽  
pp. 244722 ◽  
Author(s):  
Joaquim Crusats ◽  
Rosa Albalat ◽  
Josep Claret ◽  
Jordi Ignés-Mullol ◽  
Ramon Reigada ◽  
...  
Keyword(s):  
Langmuir Monolayers ◽  
Molecular Reorientation ◽  
Reorientation Dynamics ◽  
Confined Domains
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