Pinakpani Pal

PARSHA-256 – A New Parallelizable Hash Function and a Multithreaded Implementation

In this paper, we design a new hash function PARSHA-256. PARSHA-256 uses the compression function of SHA-256 along with the Sarkar-Schellenberg composition principle. As a consequence, PARSHA-256 is collision resistant if the compression function of SHA-256 is collision resistant. On the other hand, PARSHA-256 can be implemented using a binary tree of processors, resulting in a significant speed-up over SHA-256. We also show that PARSHA-256 can be efficiently implemented through concurrent programming on a single processor machine using a multithreaded approach. Experimental results on P4 running Linux show that for long messages the multithreaded implementation is faster than SHA-256.

Sodar image segmentation by fuzzy c -means

Sodar facsimile records provide meteorological information of the atmospheric boundary layer (ABL). Segmentation of sodar image (digitised sodar record) is vital for subsequent interpretation of ABL structure. The problem of segmentation is presented here as classification problem. Fuzzy c-means classification algorithm has been adopted for segmentation purpose using a set of four feature vectors calculated over a mask such that they characterise the nature of local grey value distribution. The classified images are also compared to another segmentation technique. The results presented prove the definite merits of the proposed technique.

Estimation of atmospheric boundary layer using Kalman filter technique

Sodar provides round-the-clock information about the atmospheric boundary layer (ABL). However, computer-based extraction of relevant ABL information from sodar data calls for techniques of image processing to remove the inherent noise. Kalman filter is employed as an alternative methodology to extract the ABL. Thus, it becomes possible to bypass the time-consuming image processing steps, making it faster for real time interpretation of atmospheric conditions from ABL. The technique compares well with the performance of the image processing technique.

Continuous detection of atmospheric patterns from SODAR signals

Abstract One major aspect of atmospheric pattern analysis from SODAR signals is to identify the pattern of the atmospheric boundary layer (ABL). In the present work, we attempt continuous detection of ABL patterns by shifting the region of interest on which the pattern analysis is done. On-line SODAR signal is treated as image and through analysis of the imagery certain features are extracted in the form of a degree of confidence associated with them. An inferencing network is fed with these confidence values and the possibility of each pattern is computed by a belief revision process. The whole exercise is repeated from time to time by sliding over the time scale. By doing this it is possible to monitor how the possibility of each pattern changes with time. This provides an idea about the break points where the SODAR pattern changes its nature. A study of the randomness of the possibility of the patterns is also useful in monitoring turbulent situations in the lower atmosphere.

Boundary extraction of sodar images

Abstract Sound radars provide valuable information on the characteristic patterns of atmospheric boundary layer (ABL). The ABLs are, however, often corrupted and broken due to various noises present in the sodar imageries. This often leads to wrong interpretation of the image. Standard image-processing techniques do not seem to remove these noises adequately. In our present work, we offer a preprocessing scheme that enables detection of continuous boundaries for the ABL and other regions of interest. The method adopted here is a two-step filtering approach specially designed to take into account the subtleties of sodar images and their characteristic patterns so that a continuous ABL contour can be obtained. Boundaries of other significant information regions are also demarcated. These contour lines can then be used in determining various features necessary for interpretation of the sodar imageries.

ADAPTIVE DESIGN FOR ESTIMATION OF MIXING HEIGHTS FROM SODAR BASED MEASUREMENTS

Accurate estimation of mixing height is important, since it is an important parameter for lower atmospheric studies involving aerosol monitoring and pollutant dispersal models. Sodar happens to be one of the best instruments for monitoring the mixing height. But it suffers from the drawback of acoustic noise, which makes the measurement inaccurate. Conventional Kalman filter has been used to estimate atmospheric boundary layer by filtering the measurement noise involved in sodar data. But there are certain limitations of the accuracy available from conventional Kalman filter which may be overcome by proper adaptive design. The present work develops an adaptive scheme for estimation of mixing heights. It considers the selection of a proper meteorological system model from a bank of system models. Diurnal and seasonal changes in measurement noise statistics of the acoustic radar is taken into account by designing a fuzzy logic based adaptive scheme.

A Novel Scheme for Abatement of Privacy Concern by Controlling the Reachability in Online Social Network

Online social networks (OSNs) play a significant role to exchange the gamut of information from user oriented personal information to global marketing. Due to the pervasiveness of OSNs, the security and privacy control of information creates a threat. Nowadays the OSN is a platform of socializing which allows its users to take part in information spreading among its friend circle. The user-popularity grows linearly or exponentially depending upon how the users are connected to their friends as well as visibility-settings (like friends, friend-of-friend, public) of each. In many cases the users instead of the intended target discloses information to a wider audience being unaware of the data sharing and information flow policies through the social networks. To address this issue, we propose a dynamic model for social network based on the edge property of friendof relation using semantic web tools. Experiments conducted with a dataset, which is a snapshot of Facebook, show that it provides good blocking quality and privacy using the trust values of friend to tune the default settings.

Resolving authorization conflicts by ontology views for controlled access to a digital library

– This paper provides a new Digital Library architecture that supports polyhierarchic ontology structure where a child concept representing an interdisciplinary subject area can have multiple parent concepts. The paper further proposes an access control mechanism for controlled access to different concepts by different users depending on the authorizations available to each such user. The proposed model thus provides a better knowledge representation and faster searching possibility of documents for modern Digital Libraries with controlled access to the system. , – Since the proposed Digital Library Architecture considers polyhierarchy, the underlying hierarchical structure becomes a Directed Acyclic Graph instead of a tree. A new access control model has been developed for such a polyhierarchic ontology structure. It has been shown that such model may give rise to undecidability problem. A client specific view generation mechanism has been developed to solve the problem. , – The paper has three major contributions. First, it provides better knowledge representation for present-day digital libraries, as new interdisciplinary subject areas are getting introduced. Concepts representing interdisciplinary subject areas will have multiple parents, and consequently, the library ontology introduces a new set of nodes representing document classes. This concept also provides faster search mechanism. Secondly, a new access control model has been introduced for the ontology structure where a user gets authorizations to access a concept node only if its credential supports it. Lastly, a client-based view generation algorithm has been developed so that a client’s access remains limited to its view and avoids any possibility of undecidability in authorization specification. , – The proposed model, in its present form, supports only read and browse facilities. It would later be extended for addition and update of documents. Moreover, the paper explains the model in a single user environment. It will be augmented later to consider simultaneous access from multiple users. , – The paper emphasizes the need for changing the present digital library ontology to a polyhierarchic structure to provide proper representation of knowledge related to the concepts covering interdisciplinary subject areas. Possible implementation strategies have also been mentioned. This design method can also be extended for other semantic web applications. , – This paper offers a new knowledge management strategy to cover the gradual proliferation of interdisciplinary subject areas along with a suitable access control model for a digital library ontology. This methodology can also be extended for other semantic web applications.

Intermediate Monitoring, Sample Size Reassessment, and Multi-Treatment Optimal Response-Adaptive Designs for Phase III Clinical Trials with More Than One Constraint

Optimal response-adaptive designs in Phase III clinical trial set up are becoming more and more current interest. In the present article, an optimal response-adaptive design is introduced for more than two treatments at hand. We minimize an objective function subject to more than one inequality constraints. For this purpose, we propose an extensive computer search algorithm. The proposed procedure is illustrated with extensive numerical computation and simulations. Some real data set is used to illustrate the proposed methodology.

SPEAR: design of a secured peer-to-peer architecture

In a Peer-to-Peer (P2P) system, a large number of nodes are pooled together to share their resources, information and services. Here all nodes are considered to be peers and so they should be at the same level with no hierarchy, like clients or servers. An ideal P2P system is supposed to be dynamic, where a node can join or leave the network any time. Exploiting this idea, many systems have already been developed for different application areas. A major concern of a P2P system is the searching of proper resources among different autonomous peers. Two well known P2P systems, Napster and Gnutella, have shown two different approaches. Napster [1] provides a central indexing facility where any search process has to go through the machine that provides the central index. On the other hand, Gnutella [2] is an absolutely open P2P environment where searching is done by flooding and it uses IP for its underlying network service. Kaaza [3] provides a service that may be viewed as a hybrid of Gnutella and Napster. It has nodes distributed in two layers. Some nodes, called super nodes or Super-Peers, act as indexing servers for other nodes. Searching across Super-Peers may be done in Gnutella style. Nodes, other than super-peers, are known as ordinary peers One ordinary peer is connected to only one Super-Peer. So, each super-peer is connected to many ordinary peers where the super-peer provides the indexing service to its ordinary peers. An ordinary peer, on the other hand, reports to its Super-Peer the resources that it likes to share in the P2P environment. While the communication between a Super-Peer and its ordinary peers may be done in the Napster style, communication among Super-Peers is supposed to adopt the Guntella protocol. In order to make efficient search in a P2P environment, many good search protocols have already been proposed. Development of an efficient P2P architecture is also an interesting area of study. A recent review paper [9] has made a summary of all these research efforts. Security is another important area of investigation in a P2P environment. [9] and [5] have listed the essential security requirements in a P2P environment. These requirements may be divided into two groups. While the first group includes secure storage, access control, identity management and authentication, the second group deals with secure routing, provisions of anonymity and resilience against denial of service. Individual nodes handle the security requirements in the first group. However, the second set of requirements can be met only by considering the entire network with all the nodes and their interconnections. So the required security measures must be embedded in the network architecture and in the different protocols of peer-to-peer communication. SPEAR is a research effort that ventures to design a secured peer-to-peer architecture. It aspires to provide two-way anonymity, resilience against denial of service and network stability against withdrawal of nodes. Subsequent sections discuss the salient features of the project.