Simulasi Penanganan Potensi Aliran Debris di Gunung Sago (Studi Kasus di Batang Lakin, Kecamatan Lareh Sago Halaban, Kabupaten Lima Puluh Kota)

The regions in foothills of Sago mountain are flood-prone area due to debris flow. As occurred on March 22, 2010, there has been a catastrophic overflow of debris flow from Sago mountain. The disaster resulted in severe damage around the rivers downstream Sago mountains, including Batang Lakin river. This research study debris flow potential and how to mitigate it in Batang Lakin river, West Sumatra. Analysis of potential debris flow hazard of Batang Lakin river and alternative debris mitigation is simulated using the debris flow simulator Kanako 2D version 2.051. Simulation is important for verifying effect of controlling flow of debris prior to construction work carried out. Rain data input was calculated based on fifty years time period and one hundred years time period Research findings show that at Batang Lakin river, debris flow occurred and overflowing river channel. Alternative countermeasure chosen is sabo dam. For fifty years period when debris flow peak discharge of 59.50 m3/second required 2 units of sabo dams (closed type) with positions at Sta 0 +200 (Sabo height 6 m) and at Sta 0 +450 (Sabo height 4 m). For one hundred years period when debris flow peak discharge of 62.66 m3/second required 2 units of sabo dams (closed type) with positions at Sta 0 +200 (Sabo height 6 m) and at Sta 0 +450 (Sabo height 5 m) to prevent overflow of debris flow to the settlement. Thus, the right efforts to control debris flow on Batang Lakin is the sabo dam

The Topology of Branching Universes

The purpose of this paper is to survey the possible topologies of branching space-times, and, in particular, to refute the popular notion in the literature that a branching space-time requires a non-Hausdorff topology

Phantom stars and topology change

In this work, we consider time-dependent dark energy star models, with an evolving parameter $\omega$ crossing the phantom divide, $\omega=-1$. Once in the phantom regime, the null energy condition is violated, which physically implies that the negative radial pressure exceeds the energy density. Therefore, an enormous negative pressure in the center may, in principle, imply a topology change, consequently opening up a tunnel and converting the dark energy star into a wormhole. The criteria for this topology change are discussed, in particular, we consider the Morse Index analysis and a Casimir energy approach involving quasi-local energy difference calculations that may reflect or measure the occurrence of a topology change. We denote these exotic geometries consisting of dark energy stars (in the phantom regime) and phantom wormholes as phantom stars. The final product of this topological change, namely, phantom wormholes, have far-reaching physical and cosmological implications, as in addition to being used for interstellar shortcuts, an absurdly advanced civilization may manipulate these geometries to induce closed timelike curves, consequently violating causality.Comment: 19 pages, 13 figures. V2: Extended version of the paper accepted for publication in Physical Review

Long term stable integration of a maximally sliced Schwarzschild black hole using a smooth lattice method

We will present results of a numerical integration of a maximally sliced Schwarzschild black hole using a smooth lattice method. The results show no signs of any instability forming during the evolutions to t=1000m. The principle features of our method are i) the use of a lattice to record the geometry, ii) the use of local Riemann normal coordinates to apply the 1+1 ADM equations to the lattice and iii) the use of the Bianchi identities to assist in the computation of the curvatures. No other special techniques are used. The evolution is unconstrained and the ADM equations are used in their standard form.Comment: 47 pages including 26 figures, plain TeX, also available at http://www.maths.monash.edu.au/~leo/preprint

Topology Change and Causal Continuity

The result that, for a scalar quantum field propagating on a ``trousers'' topology in 1+1 dimensions, the crotch singularity is a source for an infinite burst of energy has been used to argue against the occurrence of topology change in quantum gravity. We draw attention to a conjecture due to Sorkin that it may be the particular type of topology change involved in the trousers transition that is problematic and that other topology changes may not cause the same difficulties. The conjecture links the singular behaviour to the existence of ``causal discontinuities'' in the spacetime and relies on a classification of topology changes using Morse theory. We investigate various topology changing transitions, including the pair production of black holes and of topological geons, in the light of these ideas.Comment: Latex, 28 pages, 10 figures, small changes in text (one figure removed), conclusions remain unchanged. Accepted for publication in Physical Review

Event horizons and apparent horizons in spherically symmetric geometries

Spherical configurations that are very massive must be surrounded by apparent horizons. These in turn, when placed outside a collapsing body, must propagate outward with a velocity equal to the velocity of radially outgoing photons. That proves, within the framework of (1+3) formalism and without resorting to the Birkhoff theorem, that apparent horizons coincide with event horizons.Comment: 5 pages, plainte

Scanning Tunneling Microscope-Induced Luminescence Spectroscopy on Semiconductor Heterostructures

Scanning tunneling microscope (STM)-induced luminescence is explored as a technique for the characterization of semiconductor quantum wells and quantum wire heterostructures. By injecting minority carriers into the cleaved cross section of these structures, luminescence excitation on a nanometer scale is demonstrated. Using spectrally resolved STM-induced luminescence for the tip placed at various positions across the cleaved heterostructure, it is possible to obtain local spectroscopic information on closely spaced quantum structures

If You’re Going Through Hell, Keep Going: Nonlinear Effects of Financial Liberalization in Transition Economies

Copyright © Taylor & Francis Group, LLC. Did increasing the level and pace of financial liberalization during transition expose countries to crises? And if a crisis did strike, did liberalization do more harm or good? Using a database of 28 transition economies over 22 years, this article examines these questions across a host of economic outcomes, including savings and the size of the private sector. The results provide evidence that, while liberalization may initially increase the probability of a crisis, the prospect of a crisis drops dramatically at higher levels of financial openness. Moreover, the benefits of liberalization across several metrics outweigh the risks of these intermediate stages

Egorov's theorem for transversally elliptic operators on foliated manifolds and noncommutative geodesic flow

The main result of the paper is Egorov's theorem for transversally elliptic operators on compact foliated manifolds. This theorem is applied to describe the noncommutative geodesic flow in noncommutative geometry of Riemannian foliations.Comment: 23 pages, no figures. Completely revised and improved version of dg-ga/970301