1,617 research outputs found
Modelling of Krakatoa Tsunami Wave Propagation and Community Engagement Based on SWOT Analysis in Southern Lampung, Indonesia
The eruption of Krakatoa which occurred on the 22 December 2018 caused an avalanche from the Gunung Anak Krakatau (GAK) body into the sea, causing a tsunami in the Sunda Strait. The tsunami affected Lampung (Sumatra) and Banten (Java) provinces in Indonesia. Based on the field observations made by Takabatake et al. (2019) in the southern part of Lampung, it was identified that there were severely damaged areas in Lampung; i.e. East Way Muli, Central Way Muli, and Kunjir villages. A numerical model was developed to simulate past and future tsunami wave propagation scenarios. In addition, the strategic planning technique of SWOT analysis was carried out in order to make recommendations for the resilience of local coastal communities for future tsunami events in Southern Lampung
Mekanisme Pelindian PT, Pd dan Rh dari Limbah Katalis Otomotif dalam Sistem Larutan Naclo-hcl-h
MEKANISME PELINDIAN Pt, Pd DAN Rh DARI LIMBAH KATALIS OTOMOTIF DALAM SISTEM LARUTAN NaClO-HCl-H2O2. Kelompok Logam Platinum, KLP (Platinum Group Metals, PGM) merupakan logam mulia penting dalam aplikasi berbagai industri. Oleh karena itu proses daur ulang (recycling) dan perolehan kembali (recovery) logam ini dari sumber sekunder menjadi penting akibat keterbatasan cadangan logam mulia dari cadangan primer (bijih). Untuk memperoleh kembali KLP ini, proses hidrometalurgi berupa pelindian (leaching) dipandang sangat handal. Kajian ini dilakukan untuk mendaur ulang dan memperoleh kembali KLP, seperti platinum (Pt) paladium (Pd) dan rhodium (Rh) dari limbah produksi konverter katalis dengan proses pelindian menggunakan campuran larutan NaClO-HCl-H2O2. Cuplikan limbah konverter katalis, yang sebelumnya telah di giling dan direduksi dengan gas hidrogen, dilindi dengan campuran larutan NaClO-HCl- H2O2 pada 338 K selama 3 jam. Pengaruh beberapa parameter pelindian diamati pula selama proses. Dari pengujian dihasilkan kondisi optimum pelindian Pt, Pd dan Rh pada konsentrasi 3 %(vol) NaClO, 5 M HCl dan penambahan 1 %( vol) H2O2. Perolehan kembali Pt, Pd dan Rh setelah 3 jam pelindian secara berurutan adalah 88%, 99% dan 77%. Mekanisme reaksi pelindian akan dibahas dalam publikasi ini dengan mengamati kinetika reaksinya. Diamati dari hasil pengujian dan perhitungan bahwa mekanisme reaksi pelindian KPL dalam campuran larutan NaClO-HCl-H2O2 adalah mekanisme yang dikontrol oleh difusi (diffusion controlled mechanism)
Electronic Properties of Topological Materials: Optical Excitations in Moebius Conjugated Polymers
Electronic structures and optical excitations in Moebius conjugated polymers
are studied theoretically. Periodic and Moebius boundary conditions are applied
to the tight binding model of poly(para-phenylene), taking exciton effects into
account. We discuss that oligomers with a few structural units are more
effective than polymers for observations of effects of discrete wave numbers
that are shifted by the change in boundary condition. Next, calculations of
optical absorption spectra are reported. Certain components of optical
absorption for an electric field perpendicular to the polymer axis mix with
absorption spectra for an electric field parallel to the polymer axis.
Therefore, the polarization dependences of an electric field of light enable us
to detect whether conjugated polymers have the Moebius boundary.Comment: 10 pages, 6 figures, to be published in J. Phys. Soc. Jpn., Vol. 74
No. 2 (February, 2005), Letter sectio
Quantum dislocations: the fate of multiple vacancies in two dimensional solid 4He
Defects are believed to play a fundamental role in the supersolid state of
4He. We have studied solid 4He in two dimensions (2D) as function of the number
of vacancies n_v, up to 30, inserted in the initial configuration at rho =
0.0765 A^-2, close to the melting density, with the exact zero temperature
Shadow Path Integral Ground State method. The crystalline order is found to be
stable also in presence of many vacancies and we observe two completely
different regimes. For small n_v, up to about 6, vacancies form a bound state
and cause a decrease of the crystalline order. At larger n_v, the formation
energy of an extra vacancy at fixed density decreases by one order of magnitude
to about 0.6 K. In the equilibrated state it is no more possible to recognize
vacancies because they mainly transform into quantum dislocations and
crystalline order is found almost independent on how many vacancies have been
inserted in the initial configuration. The one--body density matrix in this
latter regime shows a non decaying large distance tail: dislocations, that in
2D are point defects, turn out to be mobile, their number is fluctuating, and
they are able to induce exchanges of particles across the system mainly
triggered by the dislocation cores. These results indicate that the notion of
incommensurate versus commensurate state loses meaning for solid 4He in 2D,
because the number of lattice sites becomes ill defined when the system is not
commensurate. Crystalline order is found to be stable also in 3D in presence of
up to 100 vacancies
Simple choreographies of the planar Newtonian -body Problem
In the -body problem, a simple choreography is a periodic solution, where
all masses chase each other on a single loop. In this paper we prove that for
the planar Newtonian -body problem with equal masses, , there are
at least different main simple choreographies. This
confirms a conjecture given by Chenciner and etc. in \cite{CGMS02}.Comment: 31pages, 6 figures. Refinements in notations and proof
On the existence of supersolid helium-4 monolayer films
Extensive Monte Carlo simulations of helium-4 monolayer films adsorbed on
weak substrates have been carried out, aimed at ascertaining the possible
occurrence of a quasi-two-dimensional supersolid phase. Only crystalline films
not registered with underlying substrates are considered. Numerical results
yield strong evidence that helium-4 will not form a supersolid film on {any}
substrate strong enough to stabilize a crystalline layer. On weaker substrates,
continuous growth of a liquid film takes place
Improving surface acousto-optical interaction by high aspect ratio electrodes
International audienceThe acousto-optical interaction of an optical wave confined inside a waveguide and a surface acoustic wave launched by an interdigital transducer (IDT) at the surface of a piezoelectric material is considered. The IDT with high aspect ratio electrodes supports several acoustic modes that are strongly confined to the surface, causing a significant increase in the strain underneath the surface. A finite element method is employed to model the surface acoustic waves generated by a finite length IDT with 12 electrode pairs and subsequently to study their interaction with an optical wave propagating in a waveguide buried in the lithium niobate substrate supporting the electrodes. The interaction can be increased up to 600 times using these new types of surface acoustic waves as compared to using a conventional IDT with thin electrodes. This result could find applications in improved acousto-optical integrated modulators
Binary Tree Approach to Scaling in Unimodal Maps
Ge, Rusjan, and Zweifel (J. Stat. Phys. 59, 1265 (1990)) introduced a binary
tree which represents all the periodic windows in the chaotic regime of
iterated one-dimensional unimodal maps. We consider the scaling behavior in a
modified tree which takes into account the self-similarity of the window
structure. A non-universal geometric convergence of the associated superstable
parameter values towards a Misiurewicz point is observed for almost all binary
sequences with periodic tails. There are an infinite number of exceptional
sequences, however, which lead to superexponential scaling. The origin of such
sequences is explained.Comment: 25 pages, plain Te
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