Effect of Paste-Aggregate Bond Strength on Behavior of Concrete

This is the published version.Coarse aggregate was coated with a thin layer of polystyrene to reduce paste-aggregate bond strength. The resulting concrete was compared to concrete containing uncoated control aggregate for strength, stiffness, and type and amount of microcracking. Large changes in interfacial paste-aggregate bond strength caused only small changes in compressive strength, stiffness, and microcracking

Different mechanics of snap-trapping in the two closely related carnivorous plants Dionaea muscipula and Aldrovanda vesiculosa

The carnivorous aquatic Waterwheel Plant (Aldrovanda vesiculosa L.) and the closely related terrestrial Venus Flytrap (Dionaea muscipula SOL. EX J. ELLIS) both feature elaborate snap-traps, which shut after reception of an external mechanical stimulus by prey animals. Traditionally, Aldrovanda is considered as a miniature, aquatic Dionaea, an assumption which was already established by Charles Darwin. However, videos of snapping traps from both species suggest completely different closure mechanisms. Indeed, the well-described snapping mechanism in Dionaea comprises abrupt curvature inversion of the two trap lobes, while the closing movement in Aldrovanda involves deformation of the trap midrib but not of the lobes, which do not change curvature. In this paper, we present the first detailed mechanical models for these plants, which are based on the theory of thin solid membranes and explain this difference by showing that the fast snapping of Aldrovanda is due to kinematic amplification of the bending deformation of the midrib, while that of Dionaea unambiguously relies on the buckling instability that affects the two lobes.Comment: accepted in Physical Review

The Relationship Between Financial Ratios and Stock Prices of Telecommunication Companies of Indonesian Stock Exchange Telecommunication Sub Sector Indices

For companies to obtain additional funding or capital, one alternative in mind is through the capital markets. The capital market is a means that brings sellers and buyers of securities. The place an offer to sell these securities held is by an official body called the stock exchange. Through securities trading, the public is attracted to generate funds in this case the investor to develop the economy in which the fund is capital that the company needs to expand its business. People are given the opportunity to own and profit. Stock price is a very important factor on capital market activity, and should be considered by investors in making investment because the stock price indicates the issuer achievement, because the stock price in line with the performance of the issuer. Stock price also shows the value of a company. And, it can be also said that the higher the price of the stock, the higher the value of the company and vice versa. Therefore, any company that issued the shares very concerned about its stock price. Through the company's financial statements, investor can obtain data on financial ratios and analyze it in order for them to determine whether they would predict the changes on stock price or not.Telecommunication industry is a promising industry to invest. This study is on the telecommunication industry of the Indonesian stock exchange telecommunication sub sector. The study resulted on recommendation for investors to invest in PT Telkom Indonesia because it was found that through financial ratios alone is beneficial and greatly affect the stock price especially on net profit margin (r = 0.987) and return on asset (r = 0.961). For PT. IndosatTbk and PT. Inovisi InfracomTbk the results is, there is no significant relationship of financial ratios on its stock price

Kerr black hole lensing for generic observers in the strong deflection limit

We generalize our previous work on gravitational lensing by a Kerr black hole in the strong deflection limit, removing the restriction to observers on the equatorial plane. Starting from the Schwarzschild solution and adding corrections up to the second order in the black hole spin, we perform a complete analytical study of the lens equation for relativistic images created by photons passing very close to a Kerr black hole. We find out that, to the lowest order, all observables (including shape and shift of the black hole shadow, caustic drift and size, images position and magnification) depend on the projection of the spin on a plane orthogonal to the line of sight. In order to break the degeneracy between the black hole spin and its inclination relative to the observer, it is necessary to push the expansion to higher orders. In terms of future VLBI observations, this implies that very accurate measures are needed to determine these two parameters separately.Comment: 17 pages, 4 figures, one section added, to appear on Physical Review

When Darwin Met Einstein: Gravitational Lens Inversion with Genetic Algorithms

Gravitational lensing can magnify a distant source, revealing structural detail which is normally unresolvable. Recovering this detail through an inversion of the influence of gravitational lensing, however, requires optimisation of not only lens parameters, but also of the surface brightness distribution of the source. This paper outlines a new approach to this inversion, utilising genetic algorithms to reconstruct the source profile. In this initial study, the effects of image degradation due to instrumental and atmospheric effects are neglected and it is assumed that the lens model is accurately known, but the genetic algorithm approach can be incorporated into more general optimisation techniques, allowing the optimisation of both the parameters for a lensing model and the surface brightness of the source.Comment: 9 pages, to appear in PAS