Journal of Mathematical and Fundamental Sciences
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Solusi Model Aliran Gas Dalam Pipa pada Kondisi Line Packing Menggunakan Skema Richtmyer
Get PDFLine packing is a process storing gas in pipeline by increasing inlet gas flow rate while outlet gas flow rate is kept constant. This difference of gas flow rate causes the gas flow in pipeline being transient. Line packing process is intended to guarantee gas supply when trouble occurs. In this paper, a transient model with boundary condition is solved numerically using Richtmyer scheme, because stability analysis showed that Richtmyer scheme is better than other explicit schemes. In the case presented, it is shown that Richtmyer scheme sufficiently agrees with the real data in gas pipeline transmission, which is in many cases unsteady-state
Excitation Mechanism in Laser-Induced Plasma at Atmospheric Air Pressure
Get PDFA special interferometric technique has been devised on the basis of rainbow refractometry without the use of an additional and delicate amplitude-splitting setup. This new technique was used for the characterization of plasma induced by a Q-switched Nd-YAG laser on zinc samples under atmospheric air pressure. An unmistakable signal of the density jump was detected simultaneously with the observation of the emission front signal. It was proved that the emission front and the front of the shock wave coincided and moved together with time at the initial stage of the secondary plasma expansion. However, at a later stage, the emission front began to separate from and left behind the shock wave front propagating in the surrounding air. With the use of zinc sample, the experimental results showed that the separation of the emission front and shock wave front took place at about 4 mm above sample surface for laser energy of 26 mJ. It was also found that the separation time increased by increasing the power density which further supported shock wave model. Analysis of the data of the shock front movement along with the emission characteristics has led us to the conclusion that models other than the shock wave model, such as the gas breakdown model, should be excluded, at least for a zinc sample, as not satisfactorily explaining the excitation process in the secondary plasma generated at atmospheric air pressure of 760 Torr
SEM-EDX Analysis of Laser Surface Alloying on Aluminum
Get PDFMicrostructure and chemical composition changes on the alloyed aluminum surface were investigated using SEM-EDX analysis. A Q-switched Nd:YAg laser was focused to induce breakdown and plasma formation. The high plasma temperature and the shock wave pressure were responsible for speeding up the laser surface alloying process. The rapid heat and cooling process introduced a non-equilibrium condition causing changes in the microstructure as well as the chemical composition of the alloyed aluminum surface. The remelted layer and molten pools were realized after the aluminum received a power density greater than 5 x 108 Wcm-2. The chemical composition change confirms that the convection process had taken place during the alloying process
Development of an Inversion Method for Low Velocity Medium
Get PDFThe main problem with the inversion of a low velocity medium is the application of an appropriate ray tracing method after choosing a suitable model parameterization. Block parameterization is not suitable, because it is not capable of representing the velocity model well. A large amount of blocks with a small grid size are needed to express the model well, but in that case, a ray coverage problem will be encountered. A knot-point parameterization model is better suited than a block model, because it can express the velocity model well, while the number of variables is much smaller. Ray calculation using the pseudo-bending method is not appropriate for the velocity model because of an instability problem at high velocity gradients. The crucial problem of this method involves the initial ray-path that is optimized in order to obtain the "true" ray, but does not satisfy the Fermat principle. These problems can be solved by applying the eikonal-solver method, because this can handle high-velocity gradients and does not need an initial ray path. Using a suitable model parameterization and appropriate ray tracing method, the inversion can obtain good results that fit the desired output. Applying a block model and the pseudo-bending method will not produce the desired output
Characteristics of Earthquake-Generated Tsunamis in Indonesia Based on Source Parameter Analysis
No full textWe have characterized 27 earthquake-generated tsunamis from 1991 to 2012 in Indonesia, based on source parameter analysis. This includes the focal mechanism derived by W phase inversion analysis, the ratio (Θ) between the seismic energy (E) and the seismic moment (Mo), the moment magnitude (Mw), the rupture duration (To) and the distance of the hypocenter to the trench. Most of the earthquakes (24 events) were tsunamigenic earthquakes with various fault types, a shallow focal depth (12 km ≤ D ≤ 77.8 km), a small to large magnitude (6.6 ≤ Mw ≤ 9.0), a low ratio of seismic energy to seismic moment (-5.8 < Θ < -4.9), a short to long rupture duration (27 s ≤ To ≤ 257 s), a small to large tsunami height (0.1 m ≤ H ≤ 50.9 m) and a short to long distance from the hypocenter to the trench (10 km < HT ≤ 230 km). Three tsunami earthquakes were characterized by a thrust fault mechanism, a very shallow depth (D ≤ 20 km), a moderate magnitude (7.5 ≤ Mw ≤ 7.8), a very low ratio of seismic energy to seismic moment (Θ ≤ -5.8), a long rupture duration (99 s ≤ To ≤ 135 s), a large tsunami height (7.4 m ≤ H ≤ 14 m) and a short distance from the hypocenter to the trench (HT ≤ 20 km)
Photoemission Studies of Si Quantum Dots with Ge Core: Dots formation, Intermixing at Si-clad/Ge-core interface and Quantum Confinement Effect
Get PDFSpherical Si nanocrystallites with Ge core (~20nm in average dot diameter) have been prepared by controlling selective growth conditions of low-pressure chemical vapor deposition (LPCVD) on ultrathin SiO2 using alternately pure SiH4 and 5% GeH4 diluted with He. XPS results confirm the highly selective growth of Ge on the pregrown Si dots and subsequently complete coverage by Si selective growth on Ge/Si dots. Compositional mixing and the crystallinity of Si dots with Ge core as a function of annealing temperature in the range of 550-800oC has been evaluated by XPS analysis and confirms the diffusion of Ge atoms from Ge core towards the Si clad accompanied by formation of GeOx at the Si clad surface. The first subband energy at the valence band of Si dot with Ge core has been measured as an energy shift at the top of the valence band density of state using XPS. The systematic shift of the valence band maximum towards higher binding energy with progressive deposition in the dot formation indicate the charging effect of dots and SiO2 layer by photoemission during measurements
Electronic Transport Parameter of Carbon Nanotube MetalSemiconductor OnTube Heterojunction
Get PDFCarbon Nanotubes research is one of the top five hot research topics in physics since 2006 because of its unique properties and functionalities, which leads to widerange applications. One of the most interesting potential applications is in term of nanoelectronic device. Carbon nanotubes heterojunction has been modeled, which was built from two different carbon nanotubes, that one is metallic and the other one is semiconducting. There are two different carbon nanotubes metalsemiconductor heterojunction. The first one is built from CNT(10,10) as metallic carbon nanotube and CNT (17,0) as semiconductor carbon nanotube. The other one is built from CNT (5,5) as metallic carbon nanotube and CNT (8,0). All of the semiconducting carbon nanotubes are assumed to be a pyridinelike Ndoped. Those two heterojunctions are different in term of their structural shape and diameter. It has been calculated their charge distribution and potential profile, which would be useful for the simulation of their electronic transport properties. The calculations are performed by using selfconsistent method to solve NonHomogeneous Poisson's Equation with aid of Universal Density of States calculation method for Carbon Nanotubes. The calculations are done by varying the doping fraction of the semiconductor carbon nanotubes The electron tunneling transmission coefficient, for low energy region, also has been calculated by using WentzelKramerBrillouin (WKB) approximation. From the calculation results, it is obtained that the charge distribution as well as the potential profile of this device is doping fraction dependent
Partial Internal Control Recovery on 1-D Klein-Gordon Systems
Get PDFIn this exposition, a technique to recover internal control on a distributed parameter system is reported. The system is described by 1-D Klein- Gordon partial differential equation with a time-varying parameter. We would like to recover the internal control applied to the system if we know some limited information about the output. We use a method called sentinel method to recover the internal control. It involves some construction of a linear functional, and we show that this construction relates closely to the exact controllability problem
On Tight Euclidean 6-Designs: An Experimental Result
Get PDFA finite set n X ⊆ â„n with a weight function w: X → â„ > 0 is called Euclidean t-design in â„ > 0 (supported by p concentric spheres) if the following condition holds:           1 i p i i i S x X w X f d w f S ï³ ï€½    x x  x x for any polynomial f(x) ∈ Polâ„ > 0 of degree at most t. Here Si â„n is a sphere of radius ri ≥ 0, Xi=X ∩ S, and σi(x) is an O(n) -invariant measure on Si such that |Si|=rin-1|Sn-1>|, with |Si| is the surface area of Si and |Sn-1|is a surface area of the unit sphere in â„n. Recently, Bajnok [1] constructed tight Euclidean t-designs in the plane (n=2) for arbitrary t and p . In this paper we show that for case t=6 and p=2 , tight Euclidean 6-designs constructed by Bajnok is the unique configuration in â„œn, for 2 ≤ n ≤ 8
Effect of Aluminium Content in Aluminium Pillared Montmorillonite on Its Surface Acidity Properties
Get PDFAluminium pillared montmorillonites from Indonesian natural montmorillonite has been prepared using Al13 Keggin ion pillaring precursor in varied concentrations. Herein we studied their characterization and catalysis application for esterification reaction. X-ray diffraction (XRD), energy dispersive x-ray analysis (EDX), and BET gas sorption analysis were employed to characterize the prepared materials besides the characterization on surface acidity by pyridine and n-butylammine adsorptions and FTIR analysis. The result showed that significant improvement on physicochemical character data was obtained by a pillarization process. Such a process also provided improvements on catalytic activities in esterification reactions. The effect of aluminium content on material characters was discussed in this paper. It was observed from the catalytic activity tests that pillared montmorillonite samples demonstrated higher activity in esterification reaction relative to the raw montmorillonite. It was found that surface profile of materials consist of specific surface area, pore volume and Lewis acidity were significantly affect the catalyst activity