Dynamic effective mass of granular media

We develop the concept of frequency dependent effective mass, M(omega), of jammed granular materials which occupy a rigid cavity to a filling fraction of 48%, the remaining volume being air of normal room condition or controlled humidity. The dominant features of M(omega) provide signatures of the dissipation of acoustic modes, elasticity and aging effects in the granular medium. We perform humidity controlled experiments and interpret the data in terms of a continuum model and a "trap" model of thermally activated capillary bridges at the contact points. The results suggest that attenuation in the granular materials is influenced significantly by the kinetics of capillary condensation between the asperities at the contacts.Comment: 4 pages, 3 figure

Multilevel ensemble transform particle filtering

This paper extends the multilevel Monte Carlo variance reduction technique to nonlinear filtering. In particular, multilevel Monte Carlo is applied to a certain variant of the particle filter, the ensemble transform particle filter (EPTF). A key aspect is the use of optimal transport methods to re-establish correlation between coarse and fine ensembles after resampling; this controls the variance of the estimator. Numerical examples present a proof of concept of the effectiveness of the proposed method, demonstrating significant computational cost reductions (relative to the single-level ETPF counterpart) in the propagation of ensembles

KINERJA LALU LINTAS PERSIMPANGAN LENGAN EMPAT BERSIGNAL (STUDI KASUS: PERSIMPANGAN JALAN WALANDA MARAMIS MANADO)

Permasalahan kemacetan dan antrian di kota Manado pada umumnya terjadi pada persimpangan. Salah satu persimpangan di Kota Manado yang mengalami permasalahan tersebut adalah simpang bersinyal Area Patung Maria Walanda Maramis.Penelitian ini dilakukan untuk menganalisa persimpangan bersignal tersebut dengan metode Manual Kapasitas Jalan Indonesia (MKJI 1997), maka perlu ditinjau karakteristik dan komposisi lalu lintasnya sehingga bisa dihitung tingkat kejenuhan dan tingkat layanan dari masing-masing pendekat pada persimpangan, serta besarnya tundaan yang terjadi. Data-data yang digunakan untuk analisa didapatkan dengan cara pengumpulan data primer dan pengumpulan data sekunder sesuai dengan kebutuhan penelitian. Analisis data dimulai dengan penentuan kondisi lapangan, arus lalu lintas, kapasitas dan derajat kejenuhan, dan perilaku lalu lintas.Nilai Derajat Kejenuhan (DS) maksimum untuk masing-masing pendekat yaitu pendekat Paal II sebesar 0,763 pendekat Pasar Kanaka sebesar 0,656, pendekat Tikala sebesar 0,700, dan pendekat Pusat Kota sebesar 0,720. Kinerja lalu lintas/Level Of Service (LOS) didapatkan dengan melihat nilai Tundaan Rata-rata. Dari hasil analisa didapat tundaan rata-rata persimpangan yaitu 67,12 det/kend sehingga didapat Level of Service yaitu LOS E.Kata Kunci : kapasitas, Level of Service, tundaan

Aniline hydrogenolysis on nickel: effects of surface hydrogen and surface structure

Fluorescence yield near-edge spectroscopy (FYNES) above the carbon K edge and temperature programmed reaction spectroscopy (TPRS) have been used as the methods for characterizing the reactivity and structure of adsorbed aniline and aniline derived species on the Ni(100) and Ni(111) surfaces over an extended range of temperatures and hydrogen pressures. The Ni(100) surface shows appreciably higher hydrogenolysis activity towards adsorbed aniline than the Ni(111) surface. Hydrogenolysis of aniline on the Ni(100) surface results in benzene formation at 470 K, both in reactive hydrogen atmospheres and in vacuum. External hydrogen significantly enhances the hydrogenolysis activity for aniline on the Ni(100) surface. Based on spectroscopic evidence, we believe that the dominant aniline hydrogenolysis reaction is preceded by partial hydrogenation of the aromatic ring of aniline in the presence of 0.001 Torr of external hydrogen on the (100) surface. In contrast, very little adsorbed aniline undergoes hydrogen induced C-N bond activation on the Ni(111) surface for hydrogen pressures as high as 10 −7 Torr below 500 K. Thermal dehydrogenation of aniline dominates with increasing temperature on the Ni(111) surface, resulting in the formation of a previously observed polymeric layer which is stable up to 820 K. Aniline is adsorbed at a smaller angle relative to the Ni(111) surface than the Ni(100) surface at temperatures below the hydrogenolysis temperature. We believe that the proximity and strong π-interaction between the aromatic ring of the aniline and the surface is one major factor which controls the competition between dehydrogenation and hydrogen addition. In this case the result is a substantial enhancement of aniline dehydrogenation relative to hydrogenation on the Ni(111) surface.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44251/1/10562_2004_Article_BF00806886.pd

Fluorescence Yield Near Edge Spectroscopy (FYNES) of benzene adsorbed in Na-Y zeolite

Benzene adsorbed in sodium-Y zeolite has been investigated using Fluorescence Yield Near Edge Spectroscopy (FYNES). These studies demonstrate that FYNES measurements are feasible as a direct probe of the local electronic structure of hydrocarbons adsorbed in and on insulating, microporous practical catalysts. The distribution of π energy levels for adsorbed benzene was not significantly altered as compared to the condensed phase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44256/1/10562_2004_Article_BF00764058.pd

On Robustness of Discrete Time Optimal Filters

A new result on stability of an optimal nonlinear filter for a Markov chain with respect to small perturbations on every step is established. An exponential recurrence of the signal is assumed

Maximum Likelihood Estimator for Hidden Markov Models in continuous time

The paper studies large sample asymptotic properties of the Maximum Likelihood Estimator (MLE) for the parameter of a continuous time Markov chain, observed in white noise. Using the method of weak convergence of likelihoods due to I.Ibragimov and R.Khasminskii, consistency, asymptotic normality and convergence of moments are established for MLE under certain strong ergodicity conditions of the chain.Comment: Warning: due to a flaw in the publishing process, some of the references in the published version of the article are confuse

Why Effective Medium Theory Fails in Granular Materials

Experimentally it is known that the bulk modulus, K, and shear modulus, \mu, of a granular assembly of elastic spheres increase with pressure, p, faster than the p^1/3 law predicted by effective medium theory (EMT) based on Hertz-Mindlin contact forces. To understand the origin of these discrepancies, we perform numerical simulations of granular aggregates under compression. We show that EMT can describe the moduli pressure dependence if one includes the increasing number of grain-grain contacts with p. Most important, the affine assumption (which underlies EMT), is found to be valid for K(p) but breakdown seriously for \mu(p). This explains why the experimental and numerical values of \mu(p) are much smaller than the EMT predictions.Comment: 4 pages, 5 figures, http://polymer.bu.edu/~hmaks