scholarly journals Пики термодесорбции водорода: моделирование и интерпретация

2021 ◽  
Vol 91 (2) ◽  
pp. 222
Author(s):  
Ю.В. Заика ◽  
Е.К. Костикова ◽  
Ю.С. Нечаев
Keyword(s):  
Parametric Identification ◽  
Binding Energies ◽  
Limiting Factors ◽  
Dynamics Model ◽  
Dynamic Boundary Conditions ◽  
Heating Rates ◽  
Degree Of Dominance ◽  
Analytical Criterion ◽  
Component Spectrum ◽  
Activation Energy Of Desorption

Various models of hydrogen thermal desorption peaks are analyzed. The dynamics model of the volume-averaged concentration with a continuum parameter allows integrally taking into account the degree of dominance of the limiting factors (diffusion and recombination of atoms into molecules during desorption). An analytical criterion for peaks symmetry is proposed in the context of comparison with the method of decomposing the component spectrum into the sum of Gaussian. Modifications of the Kissinger method for estimating the activation energy of desorption in experiments with several heating rates and procedures for solving the inverse problem of parametric identification of a unimodal peak using only one heating rate are presented. A comparative with a diffusion model with dynamic boundary conditions is performed. It is shown that the cause of local peaks can be not only capture with different binding energies but also the dynamics of interaction of bulk and surface processes, change in the surface structure during heating.

scholarly journals SEARCH FOR POSSIBLE WAY OF PRODUCING SUPER-HEAVY ELEMENTS: DYNAMIC STUDY ON DAMPED REACTIONS OF 244Pu+244Pu, 238U+238U and 197Au+197Au

2005 ◽  
Vol 20 (34) ◽  
pp. 2619-2627 ◽  
Author(s):  
NING WANG ◽  
ZHUXIA LI ◽  
XIZHEN WU ◽  
ENGUANG ZHAO
Keyword(s):  
Molecular Dynamics ◽  
Time Scale ◽  
Incident Energy ◽  
Composite System ◽  
Binding Energies ◽  
Decay Process ◽  
Heavy Elements ◽  
Quantum Molecular Dynamics ◽  
Dynamics Model ◽  
Production Probability

By using the Improved Quantum Molecular Dynamics model, the 244 Pu +244 Pu , 238 U +238 U and 197 Au +197 Au reactions at the energy range of E c.m. =800 MeV to 2000 MeV are studied. We find that the production probability of superheavy fragments (SHFs) with Z≥114 for the 244 Pu +244 Pu reaction is much higher compared with that for the 238 U +238 U reaction and no product of SHF is found for the 197 Au +197 Au . The production probability of SHFs strongly depends on the incident energy and a narrowly peaked energy dependence of production probability is found. The decay mechanism of the composite system of projectile and target is studied and the time scale of decay process is explored. The binding energies and the shapes of SHFs are studied. The binding energies of SHFs are broadly distributed and the shapes of SHFs are strongly deformed.

Evaluation of Effective Nucleon-Nucleon Potential and Description of α-Cluster Type Nuclei in Restricted Dynamics Approach

1997 ◽  
Vol 06 (03) ◽  
pp. 341-390 ◽  
Author(s):  
J. Tambergs ◽  
J. Ruža ◽  
T. Krasta ◽  
J. A. Castilho Alcarás ◽  
O. Katkevičius
Keyword(s):  
Transition Probabilities ◽  
Electric Quadrupole ◽  
Nucleon Nucleon ◽  
Binding Energies ◽  
Dynamics Model ◽  
Nucleon Interaction ◽  
Nucleon System ◽  
Nucleon Potential ◽  
Cluster Type ◽  
Nucleon Nucleon Interaction

The application of the Restricted Dynamics Approach in nuclear theory, based on the approximate solution of many-particle Schrödinger equation, which accounts for all conservation laws in many-nucleon system, is discussed. The Strictly Restricted Dynamics Model is used for the evaluation of binding energies, level schemes, E2 and M1 transition probabilities as well as the electric quadrupole and magnetic dipole momenta of light α-cluster type nuclei in the region 4 ≤ A ≤ 40. The parameters of effective nucleon-nucleon interaction potential are evaluated from the ground state binding energies of doubly magic nuclei 4 He , 16 O and 40 Ca .

scholarly journals The role of the Heisenberg principle in constrained molecular dynamics model

2019 ◽  
Vol 28 (06) ◽  
pp. 1950039
Author(s):  
K. Wang ◽  
A. Bonasera ◽  
H. Zheng ◽  
G. Q. Zhang ◽  
Y. G. Ma ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Pauli Principle ◽  
Binding Energies ◽  
Light Nuclei ◽  
Scattering Data ◽  
Collision Term ◽  
Dynamics Model ◽  
Heisenberg Principle ◽  
The One

We implement the Heisenberg principle into the Constrained Molecular Dynamics model with a similar approach to the Pauli principle using the one-body occupation probability [Formula: see text]. Results of the modified and the original model with comparisons to data are given. The binding energies and the radii of light nuclei obtained with the modified model are more consistent with the experimental data than the original one. The collision term and the density distribution are tested through a comparison to p+[Formula: see text]C elastic scattering data. Some simulations for fragmentation and superheavy nuclei production are also discussed.

Binding energies and radii of α-cluster-type nuclei from calculations based on the strictly restricted dynamics model

2002 ◽  
Vol 65 (4) ◽  
pp. 720-724
Author(s):  
T. Krasta ◽  
J. Ruža ◽  
J. Tambergs ◽  
O. Katkevičius ◽  
J. A. Castilho Alcarás
Keyword(s):  
Binding Energies ◽  
Dynamics Model ◽  
Cluster Type

Effects of sterilization modes on the mechanical strengths of plaster of paris implants

1989 ◽  
Vol 47 ◽  
pp. 890-891
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
T. Devine ◽  
J. Hanker
Keyword(s):  
Gamma Radiation ◽  
Calcium Sulfate ◽  
Significant Loss ◽  
Potassium Sulfate ◽  
Limiting Factors ◽  
Radiation Sterilization ◽  
Plaster Of Paris ◽  
Hardness Tester ◽  
Dry Heat ◽  
Calcium Sulfate Hemihydrate

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σo were then calculated: where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4 and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4 in both compressive and tensile strength (Table 1).

Mosaic Mapping: A Means of Tiling Images to Shorten Acquisition Speed for Lower - Magnification SEM Images and Wavelength Dispersive Spectrometers (WDS) X-Ray Maps

1996 ◽  
Vol 54 ◽  
pp. 438-439
Author(s):  
J.D. Geller ◽  
C.R. Herrington
Keyword(s):  
Limiting Factors ◽  
X Rays ◽  
Angular Range ◽  
Acceptance Angle ◽  
Sem Images ◽  
Worst Case ◽  
X Ray ◽  
Focusing Distance ◽  
Layered Crystals ◽  
Working Distance

The minimum magnification for which an image can be acquired is determined by the design and implementation of the electron optical column and the scanning and display electronics. It is also a function of the working distance and, possibly, the accelerating voltage. For secondary and backscattered electron images there are usually no other limiting factors. However, for x-ray maps there are further considerations. The energy-dispersive x-ray spectrometers (EDS) have a much larger solid angle of detection that for WDS. They also do not suffer from Bragg’s Law focusing effects which limit the angular range and focusing distance from the diffracting crystal. In practical terms EDS maps can be acquired at the lowest magnification of the SEM, assuming the collimator does not cutoff the x-ray signal. For WDS the focusing properties of the crystal limits the angular range of acceptance of the incident x-radiation. The range is dependent upon the 2d spacing of the crystal, with the acceptance angle increasing with 2d spacing. The natural line width of the x-ray also plays a role. For the metal layered crystals used to diffract soft x-rays, such as Be - O, the minimum magnification is approximately 100X. In the worst case, for the LEF crystal which diffracts Ti - Zn, ˜1000X is the minimum.

Comparing fast inductive tempering and conventional tempering: Effects on microstructure and mechanical properties

2018 ◽  
Vol 115 (4) ◽  
pp. 407 ◽  
Author(s):  
Annika Eggbauer Vieweg ◽  
Gerald Ressel ◽  
Peter Raninger ◽  
Petri Prevedel ◽  
Stefan Marsoner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Energy ◽  
Charpy Impact ◽  
Heat Treating ◽  
Processing Route ◽  
High Heating Rate ◽  
Heating Rates ◽  
High Heating ◽  
Tempering Treatment ◽  
Carbide Distribution

Induction heating processes are of rising interest within the heat treating industry. Using inductive tempering, a lot of production time can be saved compared to a conventional tempering treatment. However, it is not completely understood how fast inductive processes influence the quenched and tempered microstructure and the corresponding mechanical properties. The aim of this work is to highlight differences between inductive and conventional tempering processes and to suggest a possible processing route which results in optimized microstructures, as well as desirable mechanical properties. Therefore, the present work evaluates the influencing factors of high heating rates to tempering temperatures on the microstructure as well as hardness and Charpy impact energy. To this end, after quenching a 50CrMo4 steel three different induction tempering processes are carried out and the resulting properties are subsequently compared to a conventional tempering process. The results indicate that notch impact energy raises with increasing heating rates to tempering when realizing the same hardness of the samples. The positive effect of high heating rate on toughness is traced back to smaller carbide sizes, as well as smaller carbide spacing and more uniform carbide distribution over the sample.

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