-
Study on the Use of Silicon Drift Detector to Get Information on Light Emitted by Luminescent Materials
Issue:
Volume 7, Issue 2, March 2019
Pages:
34-42
Received:
23 January 2019
Accepted:
5 March 2019
Published:
21 March 2019
Abstract: Energy dispersive X-Ray detectors are among the most common tools installed on scanning electron microscopes and, as they are sensitive to light, they can be used to get panchromatic cathodoluminescence information. This article presents practical considerations about the parameters to choose to obtain a good cathodoluminescence signal on a silicon drift detector. Probe current is the most important but other parameters of electron microscope and energy dispersive X-Ray detector are also explored. Filament brightness, if not fixed, influences the number of electrons incident on the sample and modifies cathodoluminescence response. Beam voltage and working distance must be adapted to the sample and to the electron microscope geometry. Acquisition and shaping times are important parameters for spectrum quality: the high sensitivity of silicon drift detector to light allows the use of low acquisition times and high shaping times. As cathodoluminescent materials are mostly high band gap materials, charge effects can influence their response and the size of the acquisition area must be carefully chosen. The influence of all these parameters is studied through two scintillating materials. Some examples of application are described to show the potential of this method. They include localization of luminescent particles, a demonstration of the effect of strong electron beam on a needle of material and the characterization of light emitted by a structural defect in a scintillator material.
Abstract: Energy dispersive X-Ray detectors are among the most common tools installed on scanning electron microscopes and, as they are sensitive to light, they can be used to get panchromatic cathodoluminescence information. This article presents practical considerations about the parameters to choose to obtain a good cathodoluminescence signal on a silicon...
Show More
-
The Realization of “College Physics” Teaching for Non-Physics Major Students
Issue:
Volume 7, Issue 2, March 2019
Pages:
43-47
Received:
14 February 2019
Accepted:
30 March 2019
Published:
11 May 2019
Abstract: Physics is an exciting, living, discipline that continually moves in new directions. College Physics is a very important course for scientists and engineers. According to the study of Physics teaching experience, authors believe that the goal of studying Physics for non-physics major students is the application of Physics. Using the thinking fashion, research method and knowledge of Physics enhances student’s science accomplishment, innovation ability, obtaining knowledge in other fields and scientific literacy. In Physics learning, students obtain the ability of raising the question, analyzing and solving the question, and therefore which has a significant influence in their major or profession in future. Do not teach non-Physics major students with the pure professional teaching mode of Physics. Physics course should be combined with the specialty of students; also the contents of physics course should be kept in a basic system. The culture in physics, such as philosophy, is very important in the study of special knowledge of physics. Physics teachers should pay attention to teaching and scientific research, and promote each other. Teacher should cultivate students' ability of thinking and expression, and train students in scientific thinking, etc.
Abstract: Physics is an exciting, living, discipline that continually moves in new directions. College Physics is a very important course for scientists and engineers. According to the study of Physics teaching experience, authors believe that the goal of studying Physics for non-physics major students is the application of Physics. Using the thinking fashio...
Show More
-
Discussion on the Principle and Reliability Improvement of AC Magnetic Flux Leakage Detection of Steel Rod
Issue:
Volume 7, Issue 2, March 2019
Pages:
48-54
Received:
13 March 2019
Accepted:
7 May 2019
Published:
4 June 2019
Abstract: In this paper, the principle of ac magnetic flux leakage (referred to as MFL) detection is presented by analyzing the formation of ac magnetic flux leakage and how it is collected. It is found that ac excitation frequency is a very important equipment parameter for ac magnetic flux leakage detection of steel rod. High-frequency current not only stabilizes the penetration depth of ac magnetic field under the rod surface and leakage magnetic field of defects, but also improves the ability to detect defects and adapts to higher detection speed. It is concluded that the lift-off effect is the fundamental reason affecting the reliability of MFL detection of steel rod, and there is an inherent signal amplitude deviation from the irremovable probe bouncing on the surface of steel rod. Then, the factors that aggravate the lift-off effect are analyzed synthetically, and the corresponding countermeasures are put forward. It provides an effective basis for improving the test reliability and reasonably controls the quality risk of the rod.
Abstract: In this paper, the principle of ac magnetic flux leakage (referred to as MFL) detection is presented by analyzing the formation of ac magnetic flux leakage and how it is collected. It is found that ac excitation frequency is a very important equipment parameter for ac magnetic flux leakage detection of steel rod. High-frequency current not only sta...
Show More
-
Simplified Fokker-Plank Equation Treatment of Finite-temperature Spin-torque Problems
Issue:
Volume 7, Issue 2, March 2019
Pages:
55-60
Received:
11 January 2019
Accepted:
23 May 2019
Published:
12 June 2019
Abstract: A Legendre function expansion method is proposed to solve the simplified Fokker-Plank equation to study the dynamics of a macrospin under spin-torque-driven magnetic reversal at finite temperature. The first and second eigenvalues (λτ0)1 and (λτ0)2 as functions of I/Ic and Hk are obtained, in agreement with the previous results using the Taylor series expansion method. The Legendre function expansion method compared with the Taylor series expansion method has faster convergence properties and clear physical means. Besides, it is found that in some case, especially the second eigenvalue (λτ0)2 can become complex, that means that the probability density P not only decays with time, but also oscillates with time.
Abstract: A Legendre function expansion method is proposed to solve the simplified Fokker-Plank equation to study the dynamics of a macrospin under spin-torque-driven magnetic reversal at finite temperature. The first and second eigenvalues (λτ0)1 and (λτ0)2 as functions of I/Ic and Hk are obtained, in agreement with the previous results using the Taylor ser...
Show More
-
Genodynamics: A New Biophysical Approach to Modeling Adaptation in Human Populations
Tshela Elizabeth Mason,
James Lindesay,
Georgia Mae Dunston
Issue:
Volume 7, Issue 2, March 2019
Pages:
61-67
Received:
3 March 2019
Accepted:
9 May 2019
Published:
13 June 2019
Abstract: Using genodynamics, the Howard University biophysics research and interdisciplinary development group transforms genomic sequence data into genomic energy measures to explore the science of genome variation in population diversity and human biology. Genodynamics utilizes the statistical distribution of single nucleotide polymorphism (SNP) data from the Haplotype Map project to mathematically model whole genome-environment interactions in human adaptation to environmental stressors/stimuli by functionally parameterizing the interplay between the biophysical and environmental factors in a quantifiable manner. Our double-blind computer program flagged smooth mathematical function relationships between allelic energies of two SNPs in intron one of the egl-9 family hypoxia inducible factor 1 (EGLN1) and the environmental parameter averaged ancestral annual ultraviolet radiation exposure. EGLN1 is a gene on chromosome 1 known to play an essential role in the regulation of the hypoxia inducible factor pathway. We have demonstrated that our genodynamics approach can quantify, through adaptive forces, the effects that environmental stressors/stimuli have had on patterns of common variation in the human genome and by doing so offer an alternative means of investigating the implications of SNP information dynamics on natural selection in human populations.
Abstract: Using genodynamics, the Howard University biophysics research and interdisciplinary development group transforms genomic sequence data into genomic energy measures to explore the science of genome variation in population diversity and human biology. Genodynamics utilizes the statistical distribution of single nucleotide polymorphism (SNP) data from...
Show More
