Abstract

We consider the problem of reliable message transmission between two synchronous players connected by n wires, some t< n 2 of which may be faulty. We show how to get reliability “for free”—reliable transmission of b bits involves a total communication of only O (b) bits, when b is large enough. We also construct an efficient Perfectly Secure Message Transmission Protocol.

Abstract

We provide a complete characterization of directed networks in which probabilistic reliable communication is possible. We also outline a round optimal protocol for the same.

Abstract

We consider perfect verifiable secret sharing (VSS) in a synchronous network of n processors (players) where a designated player called the dealer wishes to distribute a secret s among the players in a way that no t of them obtain any information, but any t + 1 players obtain full information about the secret. The round complexity of a VSS protocol is defined as the number of rounds performed in the sharing phase. Gennaro, Ishai, Kushilevitz and Rabin showed that three rounds are necessary and sufficient when n > 3t. Sufficiency, however, was only demonstrated by means of an inefficient (i.e., exponential-time) protocol, and the construction of an efficient three-round protocol was left as an open problem. In this paper, we present an efficient three-round protocol for VSS. The solution is based on a three-round solution of so-called weak verifiable secret sharing (WSS), for which we also prove that three rounds is a lower bound. Furthermore, we also demonstrate that one round is sufficient for WSS when n > 4t, and that VSS can be achieved in 1 + ε amortized rounds (for any ε > 0 ) when n>3t.

Abstract

When an active bedrock fault ruptures, the movement along the fault propagates through the overlying soil and produces zones of intense shear. If the fault movement propagates upto or near the ground surface, the damage to constructed facilities due to faulting, in conjunction with that induced by strong ground motion, can be significant. This paper contributes to the understanding of the response of soil deposits to the underlying bedrock fault displacement. In the conventional attenuation relationship, peak ground acceleration shows maximum value at the closest distance from the fault. However, in the real observations, sometimes it is found that the damage near to the surface fault is not maximum, instead it is high little away from the surface rupture zone. To understand the above-mentioned response of soil deposits, we attempted to develop a new application to Applied Element Method (AEM) by modeling the fault rupture zone. In this, we study the behavior of dip-slip faults. The effect of the slip velocity on the ground motion is studied first and then the attenuation of PGA in the near fault zone is studied. Effect of the material properties is also discussed.

Abstract

Earthquake, now everyone is familiar with this word. We have clearly witnessed during the recent Sumatra, Indonesia earthquake (M 9.0) the amount of damage an earthquake can cause to the society. Had this earthquake occurred on land, it would have easily damaged few hundreds of kilometers and the damage estimates would have been unimaginable. Earthquakes are not new to our country. We have had the long history of earthquake occurrences. Some of the major earthquakes of the world occurred in our country and neighborhood areas. During past 15 years also we have witnessed 6 moderate earthquakes: Bihar-Nepal border (M6.4) in 1988, Uttarkashi, Uttaranchal (M6.6) in 1991, Latur, Maharastra (M6.3) in 1993, Jabalpur, Madhya Pradesh (M6.0) in 1997, Chamoli, Uttaranchal (M6.8) in 1999 and Bhuj, Gujarat (M6.9) in 20011). These earthquakes caused around 40,000 casualties (see Table 1) and innumerable property loss. These events occurred with a time gap of 2 ~ 3 years. Are we ready to face another event? Even with the current level of understanding, it is very difficult to predict the occurrence time and exact location of next earthquake. The only way to ensure the safety is to get prepared.

Abstract

Natural disasters like earthquake, landslide, flood, drought, cyclone, forest fire, volcanic eruption are quite common in different parts of the globe. These natural disasters lead to the loss of life, property damage and socio-economic disruption. Earthquakes are one of the worst among the natural disasters. Seismic zonation map given in IS 1893:2002 shows that India is highly vulnerable for earthquake and over 60% of India is prone to moderate to major earthquakes. During past century, India has witnessed more than 650 earthquakes of magnitude greater than 5 and during past 15 years, 6 earthquakes of magnitude over 6. From recent earthquakes, it is very well understood that lack of awareness is one of the contributing factors for huge casualty losses. In order to increase the awareness about the effects of earthquakes among professionals involved in construction, it is necessary to make them understand the concepts of structural dynamics and earthquake engineering. For this, we have developed a software tool called Interactive Structural Dynamics Learning Kit (ISDLK) for explaining structural dynamics in a simple manner. For convenience in explaining the concepts, we divided the tool into six modules. Each module contains few experiments with good G.U.I. In these modules, user can input the value and he/she can find the desired results with explanation using graphical diagram. At the end of sixth module, user can understand the complete dynamic behavior of a structure. ISDLK aims to help students, architects and design professional in understanding structural dynamics.

Abstract

India has witnessed 6 earthquakes during past 15 years causing around 40,000 casualties and immense property loss. More than 90% of these casualties are due to collapse of buildings and they occurred within very short period of time after the earthquake. Hence, for reducing casualty losses and subsequent consequences due to earthquake, it is very important to study the response of structures due to seismic excitations. For studying the response of the structures and consequent issues after the earthquake disaster, information technology can play a major role. This paper contributes to understand the importance of information technology in earthquake disaster mitigation.

Abstract

India has witnessed 6 earthquakes during past 15 years causing around 40,000 casualties and immense property loss. More than 90% of these casualties are due to collapse of buildings and they occurred within very short period of time after the earthquake. Hence, for reducing casualty losses and subsequent consequences due to earthquake, it is very important to study the response of structures due to seismic excitations. This paper contributes to understand the importance of concrete constructions in earthquake disaster mitigation. Paper first discusses the effects of earthquakes of past in general and gives a brief summary of 26th Jan, Bhuj earthquake. Shortcomings observed in constructions during authors visit to Bhuj are highlighted. Finally the recommendations for concrete constructions are given.

Abstract

This article aims to understandthe response of soil deposits underlying bedrock fault displacement in three dimensions. When an active bedrock fault ruptures movement along the fault propagates through the overlying soil and produces zones of intense shear. Hence it is important to study the sruface behaviour based on fault characteristics. Hence we attempted to develop application of applied element method by modelling the fault rupure zone. In this article we have modelled the fault rupture problem in three dimensions. First a simple model is used to illustrate absorption of the bedrock deformation by the overlying soin in elastic case. In the later part nonlinear analysis is carried out to study the complex failure propogation in three dimensions. Influence of mechanical propertices of the material is also discussed.

Abstract

The earthquake-resistant design methodology in most existing codes of practice is based on ensuring no collapse” during the most severe event expected at the given site while most of the input energy is dissipated through inelastic deformations. Evolution of the performance-based design over the last decade has seen a few performance levels added up to this so that the structure remains functional even after a moderately strong event. This methodology however overlooks the possibility that in case of multiple earthquake events expected during the design life of the structure the structure may get gradually damaged and that it may not be feasible to carry out repairs in the structure after every damaging event. As a result, the structure may collapse earlier than expected and perhaps during an event of moderate intensity. To address such a concern a new spectrum, called as design force ratio spectrum is proposed in this paper. DFR spectrum gives the ratio by which the design yield force level of a conventionally-designed single degree of freedom structure should be raised such that the damage caused by all earthquake events expected to occur during its lifetime is limited to a specified level. A numerical study is carried out for a hypothetical seismic region by following a simple procedure based on several assumptions and DFR spectra are obtained for elastic-perfectly plastic oscillators when the return periods of earthquakes follow exponential distribution over the entire range of magnitudes.