Oct 21

I didn’t know graphene is so newly discovered!

Ok, it’s my ignorance. History time ! Year: 2004 Location: The University of Manchester Nobel Physics: 2010

Here is the whole story and information from ‘the home of graphene‘, Manchester.

Scotch Tape

Sep 01

Science policy is giving rise to open science or a new form of capitalism?

Here is a provocative paper recently published. I will add my thoughts when I’m done with reading.

 

http://journals.sagepub.com/doi/abs/10.1177/0306312718772086

Aug 29

Notes from iPlasmaNano 2018

It was a really dense conference. Mostly, the professors gave talks about the latest updates of their research. The discussions were at high level. I tried to keep my eyes open to follow almost every talk 🙂 But, it’s worth it 🙂 Here are the topics attracting my attention.

 

 

Nano particle synthesis: https://scholar.google.com/citations?user=ni1mqkEAAAAJ&hl=en

–>in-situ FTIR:plasma-nano particle interaction

Graphite (anode–>mix with catalyst), BN nanotube synthesis by arc: https://scholar.google.com/citations?user=-PkzDBQAAAAJ&hl=en

–>B mix with metal (Ni, Co)

Computational plasma: http://faculty.ucmerced.edu/vayyaswamy/research.html

–>plasmaFOAM, Ti=Tg+((m_i/3k_b)mu_i^2E^2), non-Maxwellian ion number density 10^19 #/m^3

–>sheath oscillation: in low pressure-stochastic heating (can’t apply LFA,local field approx), in high pressure-ohmic heating

Space charge limited emission: https://aip.scitation.org/doi/10.1063/1.5004654

–>in high pressure-Matt-Gurney, in low pressure-Child-Langmuir, further Schrödinger

–>Rougher surfaces have lower breakdown voltage

Social impact: https://www.linkedin.com/in/sung-jin-park-b2a5b510/

Plasma-surface interactions: https://www.researchgate.net/profile/Carles_Corbella

Hall thruster, BN self heating, catalyst with carbon nanotube: https://www.researchgate.net/profile/Carles_Corbella 

Tensile stress btw atoms, quantum dots with thermomechanical stress: https://scholar.google.com/citations?user=wSJ6cxcAAAAJ&hl=en

–>larger atoms are collected in one dot

10kW, IEDF affects selectivity: https://scholar.google.com/citations?user=cRanOQUAAAAJ&hl=en

–>by lowering Q-factor under mismatch, more lossy matching –>e energy increases, equilvalent circuit mdelling by M.Kushner

Plasma-based tuning, lower resonance freq–sheath diminishes  https://scholar.google.com/citations?user=Qjw1ACoAAAAJ&hl=en

–>negative permittivity (meta material) — more number of electrons, conductivity increases

–>DC abnormal glow: i increases, res freq decreases

–>applied freq<< plasma freq (sqrt (e^2 n_e / m Epsilon_0))

–>alpha discharge –> walls are protected by ion bombardment

Double negative meta material (Epsilon<0, Mu<0): https://scholar.google.com/citations?user=LknRjyEAAAAJ&hl=en

–>1 W, low pressure, dielectric resonator

RF manipulations: https://scholar.google.com/citations?user=PKxNAt0AAAAJ&hl=en

–>tuning number of electrons (n_e), Epsilon(V)=1-n_e/(w^2+v_m^2) where v_m^2=collision resonance freq which is a func of pressure

–>define ‘effective secondary emission coefficient’, i increases, cathode sheath diminishes for gamma mode of RF disch–>it is like DC with switching polarity (AC?)

–>P_noise / delta f = 4kT_e / (1+w^2/v_m^2) , power noise, in metal just  P_noise / delta f = 4kT_e but as noise reduces, conductivity decreases.

–>if purpose is to produce high number of electrons, HV, high pulsing rate –>low Te, high n_e

–>Add H2O vapor to reduce T_e

–>pd – 0.0001 Torr cm , field ionization, 20 ps ignition time (e time of flight) n_e – 10^10 cm^-3

CNT growth on substrates, energy storage applications, super capacitor: https://scholar.google.com/citations?user=N2yMgt8AAAAJ&hl=en https://engineering.ucsb.edu/~mjgordon/research/index.html

In-situ plasma catalysis: https://www.research.manchester.ac.uk/portal/en/researchers/chris-hardacre(c10c2a33-9679-4501-b20f-272a2460b25c)/publications.html

–>NOx with HC, CO2 selectivity increased with Al2O3+Pd

–>Temp in plasma 100 C (?)

–>plasma jet in DRIFT, plastic dome,

–>EXAFS data

–>SEI: 2.637 kJ/L

Carbon arc discharge: http://pdml.tamu.edu/

–>600 Torr, 2mm, e, He, C+, C*,C2…

–>55-60 A, low ablation-low deposit if anode diameter is decreased

–>T_e-1 eV

Laser produced plasma: http://www.inrs.ca/mohamed-chaker?f=publications

–>0.8 THz

–>VO2 for microsatellites

Jul 25

Chemical bonds simulated with quantum computers!

“Quantum chemistry is the science of understanding the complicated bonds and reactions of molecules using quantum mechanics. The ‘moving parts’ of anything but the most-simple chemical processes are beyond the capacity of the biggest and fastest supercomputers. By modelling and understanding these processes using quantum computers, scientists expect to unlock lower-energy pathways for chemical reactions, allowing the design of new catalysts. This will have huge implications for industries, such as the production of fertilizers.”

If you spend a little time with chemical reactions and bonds, you should notice that we’re just saying reactants turn into some products. The intermediate mechanism is tried to be explained by collision theory and density functional theory. There are many other interpretations in the literature, but there are millions of different possibilities for the reaction paths which are all simplified to understand the process. I wish I can comprehend more about quantum chemistry because after all, the microscopic behaviors are driving a reaction resulting in macroscopic properties. For now, simulations are valuable tool to observe the possible pathways and quantum computing is a promising approach for quantum chemistry.

World-first quantum computer simulation of chemical bonds using trapped ions

 

 

Jul 22

Acceleration with stars

His idea is that an advanced civilization could build a sphere that emits waste radiation in a specific direction. This radiation would accelerate the sphere—and the star it contains—in the opposite direction.”

I’m not sure about the process of building a sphere around ‘stars’, but the idea is very exciting. However, comparing the whole universe, how many stars should be covered with spheres? 100, 1000, 100000000 ?! I don’t think the only possibility to use this idea is just for the stars lost in the horizon. The expelled radiation can give enough thrust to spacecrafts, only if that radiation is collected and transmitted to the busters. Agh! We’re so little for the universe!

An advanced civilization could resist the accelerating expansion of the universe

 

Jul 19

Family tree :)

Here is my collage of powerpuffs with acrylic paints. This is a gift for my family 🙂 I’ve used this website: https://powerpuffyourself.com/#!/en

Jul 19

Stabilizing fusion plasmas

Sawtooth swings—up-and-down ripples found in everything from stock prices on Wall Street to ocean waves—occur periodically in the temperature and density of the plasma that fuels fusion reactions in doughnut-shaped facilities called tokamaks. These swings can sometimes combine with other instabilities in the plasma to produce a perfect storm that halts the reactions. However, some plasmas are free of sawtooth gyrations thanks to a mechanism that has long puzzled physicists.”

For the large scale fusion plasmas, it seems like a real challenge!

No more zigzags: Scientists uncover mechanism that stabilizes fusion plasmas

Jul 15

Surface-bound hydrogen: diffusion > desorption

Wait! What? “The first step in hydrogen storage is chemisorption, wherein gaseous H2 collides with Pd and adsorbs (sticks) to the surface. Secondly, the chemisorbed H atoms diffuse into the sub-surface, several nanometers deep.”

Why gold-palladium alloys are better than palladium for hydrogen storage

Jul 14

Improvizing a history

If you’re willing to listen some Turkish music, here we go! This song means a lot to me but also it is hard to explain. To me, it is about the changes happening without our intervention or will. I’ve played this song many times so I have tons of versions of the same song.

Soft version:

Hard version:

Jul 14

Review: UNIQUE SOLUTIONS TO BOUNDARY VALUE PROBLEMS IN THE COLD PLASMA MODEL

In this article, Otway provides a solution to the closed Dirichlet problem which is a mixed eliptic-hyperbolic equation. This type of equations are encountered in electromagnetic wave propagation in cold plasmas. The equation in the model for electromagnetic wave propagation in zero-temperature plasma is:

(x-y^2)u_{xx}+u_{yy}+\kappa u_{x}=0

where u(x,y) is twice-continuously differentiable function. This is a homogeneous closed Dirichlet problem with D-star-shaped domains. To determine the boundary conditions, a geometric or physical analogy is considered to solve the equation. The boundary arcs are good approximations to produce an appropriate vector field. Although this approach is introduced by Lupo and Payne, the results of this study generalize the starlike boundary conditions to elliptic-hyperbolic boundary value problems. Before this study, the closed Dirichlet problems are considered as ill-posed. However, the author describes a novel method to solve the problem by presenting a unique weak solution with suitable weight function. The weight function is determined as y=x^2 and it reduces to y=0 when uniqueness is eliminated. Physically, it refers to a heating point in the plasma satisfying the equation itself.

image credit: Visual Mathematics – Math in Art – Works in Progress (Geometry and Topology)

The unstable heating on plasmas creates anisotropy for electromagnetic waves. The field potential in inhomogeneous regions can be represented as Equation 1. By reducing the number of hybrid waves in the plasma, an unstable heating solution can be obtained with kappa=0. The function domain Omega is defined as open, bounded and connected. The boundary condition is decided as:

u(x,y)=0 for all (x,y) in Omega.

In the study, it is shown that there is a solution to a closed Dirichlet problem by proving the existence of L^2 solutions where L is differential operator, such that:

Lu=[K(x,y)u_x]_x+u_{yy}=f(x,y)

where K(x,y)=x-y^2. The advantage of this approach is that a homogeneous equation with singularity is converted into an inhomogeneous equation by avoiding trivial solutions with known f(x,y).

For the weak solution, the problem is simplified by ignoring kappa. The general solution can be obtained by defining u=(u_1(x,y),u_2(x,y)). For this strong solution, K(x,y)=x-sigma(y) is chosen.

(Lu)_1=[x-\sigma(y)]u_{1x}+u_{2y}+\kappa_1u_1+\kappa_2u_2  and  (Lu)_2=u_{1y}-u_{2x}

where kappa_1 and kappa_2 are constants. The reduced forms of these equations imply Cinquini-Cibrario equation which presents applicable models for atmospheric and space plasmas.

The article is well-explained in terms of the clarity of the mathematical methods; however, the author failed to recognize the physical phenomena, described here as the wave propagation in the plasma. The article could include precisely the temperature level interested and the pressure dependence of plasma waves. The derivation is conducted at zero temperature by neglecting fluid properties. The Maxwell equations are derived for the electric displacement vector. Still, those who are interested in solving elliptic-hyperbolic equations would benefit from this article by approaching to the closed Dirichlet problems with different boundary conditions.

*Latex format will be updated.

References:

Otway, Thomas H.,2010, Unique solutions to boundary value problems in the cold plasma model, SIAM Journal on Applied Mathematics, 42(6): 3045-3053.

Lupo, D. and Payne, K.R., 2003. Critical exponents for semilinear equations of mixed elliptic‐hyperbolic and degenerate types. Communications on pure and applied mathematics, 56(3), pp.403-424.

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