Pub Date : 2018-09-15DOI: 10.11648/J.AJMP.20180704.14
Yashu Swami, Sanjeev Rai
A strange relationship of gate leakage current and threshold voltage variation for nano MOSFETs is analyzed using factual strategy and subsequently a physical model is proffered. The gate leakage current increments with the threshold voltage before it diminishes at higher threshold voltage in nanoscale devices. This inconsistent behavior of gate leakage current with threshold voltage variations is precisely clarified in the manuscript through the concept of accord between two contrary operations: threshold voltage roll-off impact and gate leakage current reliance on surface potential. The tunneling gate leakage current density diminishes with threshold voltage over surface potential. However, the threshold voltage roll-off impact causes higher threshold voltage for larger channel length devices. The net gate leakage current is adjusted by these two contrary functions of threshold voltage. In addition, the rate of accretion of the gate leakage current with threshold voltage variation is also analyzed. The impact of the increase in the power supply voltage on the rate of accretion of the gate leakage current vs. threshold voltage curve is also explored. Thorough methodical TCAD simulations are accomplished to validate the proffered models. Both the experimental outcomes, TCAD simulations and physics based models are implemented to uncover and clarify the threshold voltage gate leakage relationship, particularly for nano MOSFETs. The proposed notion is not currently captured in conventional gate leakage nano device models, hence the proffered physical models may be utilized in progression of reliable and trustworthy TCAD simulation tools for nano devices.
{"title":"Modeling and Characterization of Inconsistent Behavior of Gate Leakage Current with Threshold Voltage for Nano MOSFETs","authors":"Yashu Swami, Sanjeev Rai","doi":"10.11648/J.AJMP.20180704.14","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180704.14","url":null,"abstract":"A strange relationship of gate leakage current and threshold voltage variation for nano MOSFETs is analyzed using factual strategy and subsequently a physical model is proffered. The gate leakage current increments with the threshold voltage before it diminishes at higher threshold voltage in nanoscale devices. This inconsistent behavior of gate leakage current with threshold voltage variations is precisely clarified in the manuscript through the concept of accord between two contrary operations: threshold voltage roll-off impact and gate leakage current reliance on surface potential. The tunneling gate leakage current density diminishes with threshold voltage over surface potential. However, the threshold voltage roll-off impact causes higher threshold voltage for larger channel length devices. The net gate leakage current is adjusted by these two contrary functions of threshold voltage. In addition, the rate of accretion of the gate leakage current with threshold voltage variation is also analyzed. The impact of the increase in the power supply voltage on the rate of accretion of the gate leakage current vs. threshold voltage curve is also explored. Thorough methodical TCAD simulations are accomplished to validate the proffered models. Both the experimental outcomes, TCAD simulations and physics based models are implemented to uncover and clarify the threshold voltage gate leakage relationship, particularly for nano MOSFETs. The proposed notion is not currently captured in conventional gate leakage nano device models, hence the proffered physical models may be utilized in progression of reliable and trustworthy TCAD simulation tools for nano devices.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"17 1","pages":"166"},"PeriodicalIF":0.0,"publicationDate":"2018-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81835216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-08-08DOI: 10.11648/J.AJMP.20180704.13
H. V. Cong
In various degenerate donor-silicon systems, taking into account the effects of donor size and heavy doping and using an effective autocorrelation function for the potential fluctuations expressed in terms of the Heisenberg uncertainty relation and also an expression for the Gaussian average of , a ≥ 1 being the kinetic energy of the electron, calculated by the Kane integration method (KIM), we investigated the density of states, the optical absorption coefficient and the electrical conductivity, noting that this average expression calculated by the KIM was found to be equivalent to that obtained by the Feynman path-integral method. Then, those results were expressed in terms of for total electron energy , vanished at the conduction-band edge: , and for exhibited their exponential tails, going to zero as , and presenting the maxima, in good accordance with an asymptotic form for exponential conduction-band tail obtained by Halperin and Lax, using the minimum counting methods. Further, in degenerate d-Si systems at low temperatures, using an expression for the average of , p ≥ 3/2, calculated using the Fermi-Dirac distribution function, we determined the mobility, electrical conductivity, resistivity, Hall factor, Hall coefficient, Hall mobility, thermal conductivity, diffusion coefficient, absolute thermoelectric power, Thomson coefficient, Peltier coefficient, Seebeck thermoelectric potential, and finally dimensionless figure of merit, which were also compared with experimental and theoretical results, suggesting a satisfactory description given for our obtained results.
{"title":"Effects of Donor Size and Heavy Doping on Optical, Electrical and Thermoelectric Properties of Various Degenerate Donor-Silicon Systems at Low Temperatures","authors":"H. V. Cong","doi":"10.11648/J.AJMP.20180704.13","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180704.13","url":null,"abstract":"In various degenerate donor-silicon systems, taking into account the effects of donor size and heavy doping and using an effective autocorrelation function for the potential fluctuations expressed in terms of the Heisenberg uncertainty relation and also an expression for the Gaussian average of , a ≥ 1 being the kinetic energy of the electron, calculated by the Kane integration method (KIM), we investigated the density of states, the optical absorption coefficient and the electrical conductivity, noting that this average expression calculated by the KIM was found to be equivalent to that obtained by the Feynman path-integral method. Then, those results were expressed in terms of for total electron energy , vanished at the conduction-band edge: , and for exhibited their exponential tails, going to zero as , and presenting the maxima, in good accordance with an asymptotic form for exponential conduction-band tail obtained by Halperin and Lax, using the minimum counting methods. Further, in degenerate d-Si systems at low temperatures, using an expression for the average of , p ≥ 3/2, calculated using the Fermi-Dirac distribution function, we determined the mobility, electrical conductivity, resistivity, Hall factor, Hall coefficient, Hall mobility, thermal conductivity, diffusion coefficient, absolute thermoelectric power, Thomson coefficient, Peltier coefficient, Seebeck thermoelectric potential, and finally dimensionless figure of merit, which were also compared with experimental and theoretical results, suggesting a satisfactory description given for our obtained results.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"2015 1","pages":"136"},"PeriodicalIF":0.0,"publicationDate":"2018-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78929753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-07-13DOI: 10.11648/J.AJMP.20180704.11
Pei-Lin You
Large-scale Bose-Einstein condensation (BEC) of cesium atoms has been observed (T=343K). The technical bottleneck of BEC is very small trapping volume (10-8cm3), which made the number of condensed atoms still stagnant (less than 107), much smaller than normal condensation (more than 1013), large-scale BEC has never been observed. In BEC experiment, scientists have applied magnetic field (used to trap atoms) and laser (used to cool atoms), but never considered applying electric field, because they think that all kinds of atoms are non-polar atoms. The breakthrough of the bottleneck lies in the application of electric field. In theory, despite 6s and 6p states of cesium are not degenerate, but Cs may be polar atom doesn't conflict with quantum mechanics because it is hydrogen-like atom. When an electric field was applied, Cs atoms become dipoles, therefore large-scale BEC can be observed. BEC experiment of cesium has been redone. From the entropy S=0, critical voltage Vc=78V. When V 0; when V > Vc, S Vc, almost all Cs atoms (bosons) are in exactly the same state，according to Feynman, “the quantum physics is the same thing as the classical physics”, so our classical theory can explain BEC experiment satisfactorily. Ultra-low temperature is to make Bose gas phase transition, we used critical voltage to achieve phase transition, ultra-low temperature is no longer necessary. Five innovative formulas were first reported in the history of physics, the publication of this article marking mankind will enter a new era of polar atoms.
观察到铯原子的大规模玻色-爱因斯坦凝聚(BEC) (T=343K)。BEC的技术瓶颈是非常小的俘获体积(10-8cm3)，这使得凝聚态原子的数量仍然停滞不前(小于107)，远小于正常凝聚态原子的数量(大于1013)，大规模的BEC从未被观测到。在BEC实验中，科学家们已经应用了磁场(用于捕获原子)和激光(用于冷却原子)，但从未考虑过应用电场，因为他们认为各种原子都是非极性原子。突破瓶颈的关键在于电场的应用。理论上，尽管铯的6s态和6p态都不是简并态，但Cs可能是极性原子，这与量子力学并不冲突，因为它是类氢原子。当施加电场时，Cs原子变成偶极子，因此可以观察到大规模的BEC。重新进行了铯的BEC实验。由熵S=0，临界电压Vc=78V。当V 0;当V > Vc, S Vc时，几乎所有的Cs原子(玻色子)都处于完全相同的状态，按照费曼的说法，“量子物理与经典物理是一回事”，所以我们的经典理论可以很好地解释BEC实验。超低温是为了使玻色气相转变，我们用临界电压来实现相变，超低温就不再需要了。五个创新公式在物理学史上首次被报道，这篇文章的发表标志着人类将进入一个极性原子的新时代。
{"title":"Large-Scale Bose-Einstein Condensation in an Atomic Gas by Applying an Electric Field","authors":"Pei-Lin You","doi":"10.11648/J.AJMP.20180704.11","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180704.11","url":null,"abstract":"Large-scale Bose-Einstein condensation (BEC) of cesium atoms has been observed (T=343K). The technical bottleneck of BEC is very small trapping volume (10-8cm3), which made the number of condensed atoms still stagnant (less than 107), much smaller than normal condensation (more than 1013), large-scale BEC has never been observed. In BEC experiment, scientists have applied magnetic field (used to trap atoms) and laser (used to cool atoms), but never considered applying electric field, because they think that all kinds of atoms are non-polar atoms. The breakthrough of the bottleneck lies in the application of electric field. In theory, despite 6s and 6p states of cesium are not degenerate, but Cs may be polar atom doesn't conflict with quantum mechanics because it is hydrogen-like atom. When an electric field was applied, Cs atoms become dipoles, therefore large-scale BEC can be observed. BEC experiment of cesium has been redone. From the entropy S=0, critical voltage Vc=78V. When V 0; when V > Vc, S Vc, almost all Cs atoms (bosons) are in exactly the same state，according to Feynman, “the quantum physics is the same thing as the classical physics”, so our classical theory can explain BEC experiment satisfactorily. Ultra-low temperature is to make Bose gas phase transition, we used critical voltage to achieve phase transition, ultra-low temperature is no longer necessary. Five innovative formulas were first reported in the history of physics, the publication of this article marking mankind will enter a new era of polar atoms.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"473 1","pages":"121"},"PeriodicalIF":0.0,"publicationDate":"2018-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77138062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-07-07DOI: 10.11648/J.AJMP.20180703.12
E. Kuvaldin
A relative method is proposed for measuring the coefficient of retro reflective light intensity CRLI through specific coefficient of retro reflective Luminance CRL and area of controlled product. In contrast to the adopted absolute measurement method, by measuring the ratio of light intensity of retro reflective sample to illuminance on it, it is proposed to measure reflectance of retro reflective sample in a small solid angle with calculation CRLI. The proposed method allows using the same testing unit and instruments for measuring CRLI, which are used to measure the CRL road signs and road markings. That permits to significantly reduce measurement error.
{"title":"Relative Method of Measuring Coefficient of Luminous Intensity of Retro Reflective Devices","authors":"E. Kuvaldin","doi":"10.11648/J.AJMP.20180703.12","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180703.12","url":null,"abstract":"A relative method is proposed for measuring the coefficient of retro reflective light intensity CRLI through specific coefficient of retro reflective Luminance CRL and area of controlled product. In contrast to the adopted absolute measurement method, by measuring the ratio of light intensity of retro reflective sample to illuminance on it, it is proposed to measure reflectance of retro reflective sample in a small solid angle with calculation CRLI. The proposed method allows using the same testing unit and instruments for measuring CRLI, which are used to measure the CRL road signs and road markings. That permits to significantly reduce measurement error.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"65 1","pages":"116"},"PeriodicalIF":0.0,"publicationDate":"2018-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73571677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-29DOI: 10.11648/J.AJMP.20180703.11
Zhou Shuwen
In order to unite gravitational field with other fields, we must find the common material foundation of the gravitation theory and quantum theory. For the end, I propose the duality framework of the universe. The universe is composed of continuous universal continuum and separate p net; Universal energy Eu and various special energies Es that transform into one another at high frequency; Basic forces that dominate the universe are the universal compressive force and quantum dispersive force. The above duality framework, can explain naturally the wave-particle duality, probabilistic nature, uncertainty relation and quantum entanglement; no using Einstein’s theory, can obtain the mass-energy relation, Einstein’s equations, Friedmann’s equation and the proportions of dark energy, dark matter and ordinary matter; includes, links and foreruns both the gravitation theory and quantum theory; is their common material foundation to give their unified harmonious image; and can solve the puzzlers about the singularity, non-locality, uncertainty of energy, et al . Daring predictions: The electromagnetic wave must have an adjoint strain wave. The gravitational wave must have an adjoint wave of matching field. It is in the wrong direction to find the particle of the “dark matter”.
{"title":"Common Material Foundation of Gravitation Theory and Quantum Theory","authors":"Zhou Shuwen","doi":"10.11648/J.AJMP.20180703.11","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180703.11","url":null,"abstract":"In order to unite gravitational field with other fields, we must find the common material foundation of the gravitation theory and quantum theory. For the end, I propose the duality framework of the universe. The universe is composed of continuous universal continuum and separate p net; Universal energy Eu and various special energies Es that transform into one another at high frequency; Basic forces that dominate the universe are the universal compressive force and quantum dispersive force. The above duality framework, can explain naturally the wave-particle duality, probabilistic nature, uncertainty relation and quantum entanglement; no using Einstein’s theory, can obtain the mass-energy relation, Einstein’s equations, Friedmann’s equation and the proportions of dark energy, dark matter and ordinary matter; includes, links and foreruns both the gravitation theory and quantum theory; is their common material foundation to give their unified harmonious image; and can solve the puzzlers about the singularity, non-locality, uncertainty of energy, et al . Daring predictions: The electromagnetic wave must have an adjoint strain wave. The gravitational wave must have an adjoint wave of matching field. It is in the wrong direction to find the particle of the “dark matter”.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"11 1","pages":"103"},"PeriodicalIF":0.0,"publicationDate":"2018-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82385325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.11648/J.AJMP.20200904.11
B. Gao
An algebraical superposition technic for trasformation from z domain to time domain is presented. The establishing model process is: starting the inverse z transforms integral formula, and in its region of convergence based on thelsquocomplex function integralrsquothe inverse z transform integral is represented by 2k-1 term series. When the transform function on iterm series along integral circle are conjugated complex number distribution,the bidirectional series sum on k[-K,K] term series can be expressed by a monomial trigonomial function series sum on k[0,K],in which the members are easy calculation and sum. In the paper the solution process and main points are presented.nbsp The application examples are shown,the resules are supported to the algebraical superposition technic.The technic can be used to solve the problem which are difficult to be solved by presented method#65288such as Partial Fraction Exparation method,etc#65289.
{"title":"The Algebraical Superposition Technic for Transformation from S Domain to Time Domain","authors":"B. Gao","doi":"10.11648/J.AJMP.20200904.11","DOIUrl":"https://doi.org/10.11648/J.AJMP.20200904.11","url":null,"abstract":"An algebraical superposition technic for trasformation from z domain to time domain is presented. The establishing model process is: starting the inverse z transforms integral formula, and in its region of convergence based on thelsquocomplex function integralrsquothe inverse z transform integral is represented by 2k-1 term series. When the transform function on iterm series along integral circle are conjugated complex number distribution,the bidirectional series sum on k[-K,K] term series can be expressed by a monomial trigonomial function series sum on k[0,K],in which the members are easy calculation and sum. In the paper the solution process and main points are presented.nbsp The application examples are shown,the resules are supported to the algebraical superposition technic.The technic can be used to solve the problem which are difficult to be solved by presented method#65288such as Partial Fraction Exparation method,etc#65289.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91260472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-05DOI: 10.11648/J.AJMP.20180702.14
Osama A. Marzouk
This work presents a multidisciplinary mathematical model, as a set of coupled governing equations and auxiliary relations describing the fluid-flow, thermal, and electric fields of partially-ionized plasma with low magnetic Reynolds numbers. The model is generic enough to handle three-dimensionality, Hall effect, compressibility, and variability of fluid, thermal, and electric properties of the plasma. The model can be of interest to computational modelers aiming to build a solver that quantitatively assesses direct extraction of electric energy from a plasma flow. Three different approaches are proposed to solve numerically for the electric fields with different levels of tolerance toward possible numerical instability encountered at a large Hall parameter, where the effective conductivity tensor loses diagonal dominance and becomes close to singular. A submodel for calculating the local electric properties of the plasma is presented in detail and is applied to demonstrate the effect of different factors on the electric conductivity, including the fuel’s carbon/hydrogen ratio and the alkaline seed element that acts as the ionizing species. An analytical expression for the collision cross-section for argon is developed, such that this noble gas can be included as one of the gaseous species comprising the plasma.
{"title":"Multi-Physics Mathematical Model of Weakly-Ionized Plasma Flows","authors":"Osama A. Marzouk","doi":"10.11648/J.AJMP.20180702.14","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180702.14","url":null,"abstract":"This work presents a multidisciplinary mathematical model, as a set of coupled governing equations and auxiliary relations describing the fluid-flow, thermal, and electric fields of partially-ionized plasma with low magnetic Reynolds numbers. The model is generic enough to handle three-dimensionality, Hall effect, compressibility, and variability of fluid, thermal, and electric properties of the plasma. The model can be of interest to computational modelers aiming to build a solver that quantitatively assesses direct extraction of electric energy from a plasma flow. Three different approaches are proposed to solve numerically for the electric fields with different levels of tolerance toward possible numerical instability encountered at a large Hall parameter, where the effective conductivity tensor loses diagonal dominance and becomes close to singular. A submodel for calculating the local electric properties of the plasma is presented in detail and is applied to demonstrate the effect of different factors on the electric conductivity, including the fuel’s carbon/hydrogen ratio and the alkaline seed element that acts as the ionizing species. An analytical expression for the collision cross-section for argon is developed, such that this noble gas can be included as one of the gaseous species comprising the plasma.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"9 1","pages":"87"},"PeriodicalIF":0.0,"publicationDate":"2018-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90163705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-23DOI: 10.11648/J.AJMP.20180702.13
Ngargoto Ngarmoundou, El Hadji Oumar Gueye, M. Barka, A. Beye
A simple method for characterizing the flow curve of a polymer solution (PEO) in shear in Couette geometry is developed. It consists in considering a priori the fluid in Newtonian flow with the assumptions related to the influence of the rheological and geometrical parameters, then to evaluate the shearing speed characteristic of this partially and/or totally sheared material. The results obtained by the numerical simulations in 2D and in 3D in this flow configuration allow to find a heterogeneity of rheological behavior related to the properties of the fluid on the one hand and on the other hand, to size the Couette geometry while fixing explicitly the experimental conditions according to whether the fluid is Newtonian or not Newtonian.
{"title":"Geometrical and Experimental Conditions for the Homogeneous and Inhomogeneous Flows of the Polyethylene Oxide Solution in the Cylinder of Couette","authors":"Ngargoto Ngarmoundou, El Hadji Oumar Gueye, M. Barka, A. Beye","doi":"10.11648/J.AJMP.20180702.13","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180702.13","url":null,"abstract":"A simple method for characterizing the flow curve of a polymer solution (PEO) in shear in Couette geometry is developed. It consists in considering a priori the fluid in Newtonian flow with the assumptions related to the influence of the rheological and geometrical parameters, then to evaluate the shearing speed characteristic of this partially and/or totally sheared material. The results obtained by the numerical simulations in 2D and in 3D in this flow configuration allow to find a heterogeneity of rheological behavior related to the properties of the fluid on the one hand and on the other hand, to size the Couette geometry while fixing explicitly the experimental conditions according to whether the fluid is Newtonian or not Newtonian.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"20 1","pages":"75"},"PeriodicalIF":0.0,"publicationDate":"2018-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90404625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-18DOI: 10.11648/J.AJMP.20180702.12
M. Fähnle, Michael Haag, C. Illg, B. Y. Mueller, W. Weng, T. Tsatsoulis, Haonan Huang, J. Briones, N. Teeny, Lifa Zhang, T. Kuhn
When a magnetic film is excited by a femtosecond laser pulse, either with THz or with optical frequencies, then there is at least a partial demagnetization within a few hundred femtoseconds, followed by a remagnetization to the original state on a bit longer time scale. This phenomenon is caused by a complex interaction of light with quantum matter. This paper gives a review of the present knowledge of the underlying physics. It discusses first the situation of a direct change of the magnetization by its interaction with the electromagnetic wave of the laser pulse, which appears during THz laser pulses with small field amplitudes. Then it considers the situation of an indirect change which appears after THz laser pulses with large field amplitudes and after optical laser pulses. In these cases the laser photons primarily excite electrons, with subsequent modifications of their spin-angular momenta by spin-flip scatterings of these electrons at quasiparticles, either at other electrons or at phonons or at magnons. The contributions of these various spin-flip scatterings to demagnetization are investigated. Then the transfer of angular momentum from the electronic spin system to the lattice during ultrafast demagnetization is discussed by describing the lattice vibrations in terms of magnetoelastic spin-phonon modes. Finally, the effect of electronic correlations in the sense of the density-matrix theory is investigated.
{"title":"Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter","authors":"M. Fähnle, Michael Haag, C. Illg, B. Y. Mueller, W. Weng, T. Tsatsoulis, Haonan Huang, J. Briones, N. Teeny, Lifa Zhang, T. Kuhn","doi":"10.11648/J.AJMP.20180702.12","DOIUrl":"https://doi.org/10.11648/J.AJMP.20180702.12","url":null,"abstract":"When a magnetic film is excited by a femtosecond laser pulse, either with THz or with optical frequencies, then there is at least a partial demagnetization within a few hundred femtoseconds, followed by a remagnetization to the original state on a bit longer time scale. This phenomenon is caused by a complex interaction of light with quantum matter. This paper gives a review of the present knowledge of the underlying physics. It discusses first the situation of a direct change of the magnetization by its interaction with the electromagnetic wave of the laser pulse, which appears during THz laser pulses with small field amplitudes. Then it considers the situation of an indirect change which appears after THz laser pulses with large field amplitudes and after optical laser pulses. In these cases the laser photons primarily excite electrons, with subsequent modifications of their spin-angular momenta by spin-flip scatterings of these electrons at quasiparticles, either at other electrons or at phonons or at magnons. The contributions of these various spin-flip scatterings to demagnetization are investigated. Then the transfer of angular momentum from the electronic spin system to the lattice during ultrafast demagnetization is discussed by describing the lattice vibrations in terms of magnetoelastic spin-phonon modes. Finally, the effect of electronic correlations in the sense of the density-matrix theory is investigated.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"271 1","pages":"68-74"},"PeriodicalIF":0.0,"publicationDate":"2018-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78440019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-17DOI: 10.11648/j.ajmp.20180702.11
H. Ibrahim, N. Yakubu
This work is on measurement of automobile performance on Nigerian roads using the method of fuel economy. The current located area is the road linking Maiduguri city to Bama town all in Bono State, Nigeria. The emphasis is made on performance of automobile in relation to fuel consumption with fuel economy. Road safety enhancement is also highlighted. Two particular methods (by two groups of physicists) were first identified for measurement of automobile performance. For reasons of accuracy, one of them was decided for the current study area covering a distance of sixty-six kilometers (66 km). Three samples of vehicles namely, Golf II, Hiace II and 505 Peugeot Station Wagon were chosen because the 1985 models were found to be commoner. Conditions of the road affected the results. Further, when global averages of the samples were analyzed, except for small deviation, the method verified well. Other useful parameters associated with fuel consumption and fuel economy were also determined. This study particularly finds that the average fuel economy, average energetic performance of both Golf II and 505 Peugeot Station Wagon is equivalent but higher than that of Hiace II.
{"title":"Energy Performance Evaluation for Three Selected Common Commercial Vehicles Based on Fuel Economy","authors":"H. Ibrahim, N. Yakubu","doi":"10.11648/j.ajmp.20180702.11","DOIUrl":"https://doi.org/10.11648/j.ajmp.20180702.11","url":null,"abstract":"This work is on measurement of automobile performance on Nigerian roads using the method of fuel economy. The current located area is the road linking Maiduguri city to Bama town all in Bono State, Nigeria. The emphasis is made on performance of automobile in relation to fuel consumption with fuel economy. Road safety enhancement is also highlighted. Two particular methods (by two groups of physicists) were first identified for measurement of automobile performance. For reasons of accuracy, one of them was decided for the current study area covering a distance of sixty-six kilometers (66 km). Three samples of vehicles namely, Golf II, Hiace II and 505 Peugeot Station Wagon were chosen because the 1985 models were found to be commoner. Conditions of the road affected the results. Further, when global averages of the samples were analyzed, except for small deviation, the method verified well. Other useful parameters associated with fuel consumption and fuel economy were also determined. This study particularly finds that the average fuel economy, average energetic performance of both Golf II and 505 Peugeot Station Wagon is equivalent but higher than that of Hiace II.","PeriodicalId":7717,"journal":{"name":"American Journal of Modern Physics","volume":"8 1","pages":"62"},"PeriodicalIF":0.0,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90810321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：