Engineering topics

Suprijadi

Publications and source records attributed to Suprijadi.

10 records

DOE OSTI2016

Study on efficiency of time computation in x-ray imaging simulation base on Monte Carlo algorithm using graphics processing unit

Monte Carlo (MC) is one of the powerful techniques for simulation in x-ray imaging. MC method can simulate the radiation transport within matter with high accuracy and provides a natural way to simulate radiation transport in complex systems. One of the codes based on MC algorithm that are widely used for radiographic images simulation is MC-GPU, a codes developed by Andrea Basal. This study was aimed to investigate the time computation of x-ray imaging simulation in GPU (Graphics Processing Unit) compared to a standard CPU (Central Processing Unit). Furthermore, the effect of physical parameters to the quality of radiographic images and the comparison of image quality resulted from simulation in the GPU and CPU are evaluated in this paper. The simulations were run in CPU which was simulated in serial condition, and in two GPU with 384 cores and 2304 cores. In simulation using GPU, each cores calculates one photon, so, a large number of photon were calculated simultaneously. Results show that the time simulations on GPU were significantly accelerated compared to CPU. The simulations on the 2304 core of GPU were performed about 64 -114 times faster than on CPU, while the simulation on the 384 core of GPU were performed about 20 – 31 times faster than in a single core of CPU. Another result shows that optimum quality of images from the simulation was gained at the history start from 10{sup 8} and the energy from 60 Kev to 90 Kev. Analyzed by statistical approach, the quality of GPU and CPU images are relatively the same.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2016

The study of electronic structure and properties of silicene for gas sensor application

In this study, we investigated the adsorption of gas molecules (H{sub 2}S, CO) on pristine silicene using first principles calculation. The structure, electronic properties, and adsorption energy of H{sub 2}S,CO/silicene are discussed thoroughly. We found that the pristine silicenewith low buckling structure is the most stable as compared with planar and high buckling structures. Silicene was able to detect a gas molecule which can be observed according tothe density of states analysis. Though a gas molecule adsorbed weakly, the electronic properties of the low buckling pristine silicene changed from semi-metal (zero band gap) to semiconductor. The adsorption energy of H{sub 2}S and CO on silicene is 0.075 eV and 0.06 eV, respectively.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Hydrogen concentration and electric field dependent on electronic properties of germanene

Electronic properties of the pristine/hydrogenated germanene are investigated by means of first principles calculations. Our calculation shows interesting results where the electronic properties of the hydrogenated germanene exhibit semiconductor with a direct band gap. It is interesting because pristine germanene (germanium analogue to graphene) has semi-metal properties with zero band gap. We also obtained that the band gap of hydrogenated germanene was influenced by the hydrogen (H) concentration, it is decreasing non-linearly as the H concentration decreased. As 100 percent concentration of H applied on top and bottom layer of germanene, the band gap is 1.41 eV. The pairing of the p{sub z}-orbital of Ge with the s-orbital of H gave contribution to the band gap of hydrogenated germanene. External electrical field is also can be applied to open the band gap. The band gap increasing linearly when the external electrical field increased on pristine germanene. The external electrical field no longer effect the band gap when it applied to the hydrogenated germanene.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Monte Carlo study of double exchange interaction in manganese oxide

In this paper we study the magnetoresistance properties attributed by double exchange (DE) interaction in manganese oxide by Monte Carlo simulation. We construct a model based on mixed-valence Mn{sup 3+} and Mn{sup 4+} on the general system of Re{sub 2/3}Ae{sub 1/3}MnO{sub 3} in two dimensional system. The conduction mechanism is based on probability of e{sub g} electrons hopping from Mn{sup 3+} to Mn{sup 4+}. The resistivity dependence on temperature and the external magnetic field are presented and the validity with related experimental results are discussed. We use the resistivity power law to fit our data on metallic region and basic activated behavior on insulator region. On metallic region, we found our result agree well with the quantum theory of DE interaction. From general arguments, we found our simulation agree qualitatively with experimental results.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

Study of hydrogenated silicene: The initialization model of hydrogenation on planar, low buckled and high buckled structures of silicene

We study the hydrogenation structures possessed by silicene i.e. planar (PL), low buckled (LB) and high buckled (HB). On those structures we found the hydrogenation process occurs with some particular notes. Hydrogen stable position on the silicene surface is determined by its initial configuration. We only considered the fully hydrogenated case with the formula unit (SiH){sub n} for all of these structures. Physical and electronic structure shift after the process are compared with hydrogenated graphene. Moreover, we observed a chemical process in the presence of hydrogen on the PL structure by nudged elastic band (NEB) which illustrates how hydrogen has a significant impact to the force barrier of the PL that changing it from its original structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

First-principles calculations on electronic properties of single-walled carbon nanotubes for H{sub 2}S gas sensor

In this research, we performed first-principles calculations by means of density functional theory (DFT) to investigate the interaction of H{sub 2}S gas on the surface of single-walled carbon nanotubes (SWNTs). In order to understand the effect of chirality to the electronic structure of SWNTs/H{sub 2}S, the pristine SWNTs was varied to become SWNTs (5,0), (6,0), (7,0), (8,0), (9,0), and (10,0). From the calculation we found that after H{sub 2}S adsorbed on surface of SWNTs, the electronic properties of system changes from semiconductor to metal but not vice versa. It was only SWNTs (5,0), (7,0), (8,0), and (10,0) occuring the changing on its electronic properties behavior, others were remain similar with its initial behavior. In the degassing process, metal return to semiconductor behavior, which is an indication that SWNTs is a good gas sensors, responsive and reversible.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2015

Study on transport properties of silicene monolayer under external field using NEGF method

We investigate the current-voltage (I-V) characteristics of a pristine monolayer silicene using non-equilibrium Green function (NEGF) method combining with density functional theory (DFT). This method succeeded in showing the relationship of I and V on silicene corresponding to the electronic characteristics such as density of states. The external field perpendicular to the silicene monolayer affects in increasing of the current. Under 0.2 eV external field, the current reaches the maximum peak at Vb = 0.3 eV with the increase is about 60% from what it is in zero external field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Developing stereo image based robot control system

Application of image processing is developed in various field and purposes. In the last decade, image based system increase rapidly with the increasing of hardware and microprocessor performance. Many fields of science and technology were used this methods especially in medicine and instrumentation. New technique on stereovision to give a 3-dimension image or movie is very interesting, but not many applications in control system. Stereo image has pixel disparity information that is not existed in single image. In this research, we proposed a new method in wheel robot control system using stereovision. The result shows robot automatically moves based on stereovision captures.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Ab initio study of semiconductor atoms impurities in zigzag edge (10,0) carbon nanotubes

The substitutional impurities in zigzag edge (10,0) carbon nanotubes have been studied by using first principles calculations. Silicon (Si), gallium (Ga), and arsenic (As) atom have been chosen as semiconductor based-atom for replacing carbon atoms in CNT’s surface. The silicon atom changes the energy gap of pristine zigzag (10,0) CNT, it is 0.19 eV more narrow than that of pristine CNT. Geometrically, the silicon atom creates sp{sup 3} bond with three adjacent carbon atoms, where the tetrahedral form of its sp{sup 3} bond is consisted of free unoccupied state. The silicon atom does not induce magnetism to zigzag CNT. Due to gallium (Ga) and arsenic (As) atom substitution, the zigzag CNT becomes metallic and has magnetic moment of 1 µ{sub B}. The valance and conduction band are crossed each other, then the energy gap is vanished. The electronic properties of GaAs-doped CNT are dominantly affected by gallium atom and its magnetic properties are dominantly affected by arsenic atom. These results prove that the CNT with desired properties can be obtained with substitutional impurities without any giving structural defect.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Simulation of the 2-dimensional Drude’s model using molecular dynamics method

In this paper, we reported the results of the simulation of the electronic conduction in solids. The simulation is based on the Drude’s models by applying molecular dynamics (MD) method, which uses the fifth-order predictor-corrector algorithm. A formula of the electrical conductivity as a function of lattice length and ion diameter τ(L, d) cand be obtained empirically based on the simulation results.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗