Experimental determination of material damping using vibration analyzer

Structural damping is an important dynamic characteristic of engineering materials that helps to damp vibrations by reducing their amplitudes. In this investigation, an experimental method is illustrated to determine the damping characteristics of engineering materials using a dual channel Fast Fourier Transform (FFT) analyzer. A portable Compaq III computer which houses the analyzer, is used to collect the dynamic responses of three metal rods. Time-domain information is analyzed to obtain the logarithmic decrement of their damping. The damping coefficients are then compared to determine the variation of damping from material to material. The variations of damping from one point to another of the same material, due to a fixed point excitation, and the variable damping at a fixed point due to excitation at different points, are also demonstrated

WTO ACCESSION: WHAT’S IN IT FOR RUSSIA?

Prospects for Russia’s membership in the WTO now look better than any point since accession negotiations began almost a decade ago. Good progress with economic and legal reforms within Russia has left the country’s economy better prepared for membership. Nevertheless, the economy still suffers from various weaknesses including, but not limited to, pervasive subsidies for different sectors, lack of liberalization and foreign participation especially in the service sector, inefficiency in custom administration, lack of enforcement of intellectual property rights, etc. For all their sensitivity, the negotiations on the import tariff levels and access to the service sectors are the least of the problems. Much more difficult will be non-tariff barriers and the general trade-related legislative framework. Resolving the remaining weaknesses would be a complex process. However, given the importance of WTOrelated measures for the overall domestic structural reform, any delay in accession would be at least marginally negative for investor perceptions of country risk.http://deepblue.lib.umich.edu/bitstream/2027.42/39981/3/wp595.pd

Comparing the usability of doodle and Mikon images to be used as authenticators in graphical authentication systems

Recognition-based graphical authentication systems rely on the recognition of authenticator images by legitimate users for authentication. This paper presents the results of a study that compared doodle images and Mikon images as authenticators in recognition based graphical authentication systems taking various usability dimensions into account. The results of the usability evaluation, with 20 participants, demonstrated that users preferred Mikon to doodle images as authenticators in recognition based graphical authentication mechanisms. Furthermore, participants found it difficult to recognize doodle images during authentication as well as associate them with something meaningful. Our findings also show the need to consider the security offered by the images, especially their predictability

An experiment on the use of disposable plastics as a reinforcement in concrete beams

Illustrated here is the concept of reinforced concrete structures by the use of computer simulation and an inexpensive hands-on design experiment. The students in our construction management program use disposable plastic as a reinforcement to demonstrate their understanding of reinforced concrete and prestressed concrete beams. The plastics used for such an experiment vary from plastic bottles to steel reinforced auto tires. This experiment will show the extent to which plastic reinforcement increases the strength of a concrete beam. The procedure of using such throw-away plastics in an experiment to explain the interaction between the reinforcement material and concrete, and a comparison of the test results for using different types of waste plastics are discussed. A computer analysis to simulate the structural response is used to compare the test results and to understand the analytical background of reinforced concrete design. This interaction of using computers to analyze structures and to relate the output results with real experimentation is found to be a very useful method for teaching a math-based analytical subject to our non-engineering students

The Impact of Financial Reform on Private Savings in Bangladesh

Private savings, Financial reform, Bangladesh, Time series analysis

Do asymmetric terms of trade shocks affect private savings in a transition economy?

This paper examines whether terms of trade shocks have an asymmetric effect on private savings in transition economies. A simple three-period framework is developed to show that, in the presence of binding credit constraints in bad states of nature, savings rates can be sensitive to favorable movements in the permanent component of the terms of trade. This result contrasts with the prediction of the conventional consumption-smoothing model. Empirical analysis with a dynamic panel model further confirms that while favorable movements in the permanent component of the terms of trade have an asymmetric effect on private savings, the magnitude of the effect is relatively small. The results are robust for alternative estimators, determinants, and country groupings.transition, private savings, terms of trade

PRIVATE SAVINGS IN TRANSITION ECONOMIES: ARE THERE TERMS OF TRADE SHOCKS?

The paper examines the impact of terms of trade shocks on private savings in the transition economies after accounting for the effect of other determinants. Economic agents in the transition economies are subject to tight credit constraints which are more pronounced during bad state of nature. Thus, adverse shocks to commodity prices in the world market can force them to reduce savings by a larger amount than they would otherwise have. Empirical analysis using a dynamic panel model and data from twenty one transition economies confirm that most of the determinants of savings identified in the literature also apply to the transition economies. Favorable movements in both the permanent and transitory components of the terms of trade have a significant positive impact on private savings with transitory movements having a larger impact than the permanent component. This reflects the lack of access to foreign borrowing that many of the transition economies have faced during the last decade. Although the impact of terms of trade shocks are found to be asymmetric, the magnitude of the impact appears to be small. The results are robust for alternative estimators, determinants, and country groupings.transition, private savings, terms of trade

External Debt and Growth in Developing Countries: A Sensitivity and Causal Analysis

external debt, growth, sensitivity analysis, causality

Do asymmetric terms of trade shocks affect private savings in a transition economy?

This paper examines whether terms of trade shocks have an asymmetric effect on private savings in transition economies. A simple three-period framework is developed to show that, in the presence of binding credit constraints in bad states of nature, savings rates can be sensitive to favorable movements in the permanent component of the terms of trade. This result contrasts with the prediction of the conventional consumption-smoothing model. Empirical analysis with a dynamic panel model further confirms that while favorable movements in the permanent component of the terms of trade have an asymmetric effect on private savings, the magnitude of the effect is relatively small. The results are robust for alternative estimators, determinants, and country groupings.transition; private savings; terms of trade

Multi-centered D1-D5 solutions at finite B-moduli

We study the fate of two-centered D1-D5 systems on T^4 away from the singular supergravity point in the moduli space. We do this by considering a background D1-D5 black hole with a self-dual B-field moduli turned on and treating the second center in the probe limit in this background. We find that in general marginal bound states at zero moduli become metastable at finite B-moduli, demonstrating a breaking of supersymmetry. However, we also find evidence that when the charges of both centers are comparable, the effects of supersymmetry breaking become negligible. We show that this effect is independent of string coupling and thus it should be possible to reproduce this in the CFT at weak coupling. We comment on the implications for the fuzzball proposal.Comment: 19 pages + appendices, 14 figures; v2: added important remark in example in introduction, rewrote first paragraph in sect 3.2 for clarity, other misc. small edits; as accepted for publication in JHE