This paper presents a comprehensive survey of QE techniques in IR. Core techniques, employed data sources, and methodologies used in the process of query expansion are discussed. The output study highlights four main steps concerned with expanding queries: steps related to preprocessing of data sources and term extraction, calculation of weights and ranking of terms, selection of terms, and finally expansion. The most important findings are that only effective text normalization and removal of stopwords provide a real platform for performing QE. The introduction of contextually relevant terms significantly enhanced relevance feedback and thesaurus-based WordNet expansion techniques. They have been shown to significantly improve retrieval effectiveness as has been realized from various experiments conducted over years now. It also uses the manual query expansion techniques and discusses several automated ways in order to improve retrieval effectiveness. This work, by reviewing the related literature and methodologies, gives an overview of how the techniques of query expansion have been evolving with time and achieved better results in IR systems. The survey offers a valuable resource for researchers and practitioners in information retrieval, shedding light on the advancements, challenges, and future directions in query expansion research.

Underwater Wireless Sensor Networks (UWSNs) explore aquatic environment to facilitate various underwater surveillance applications. However, UWSN unique features also impose new challenges such as limited bandwidth, huge propagation delay, mobile nature of nodes and high error rates. UWSNs deployment in unattended environment further exacerbates their vulnerabilities to the attacks. These challenges make security solutions proposed for Wireless Sensor Network (WSN) impractical to be applicable for UWSN. This paper analyzes the problem of security and mobility in UWSN and proposes Cluster based Key management Protocol (CKP), a new key management protocol for hierarchical networks where sensor nodes form cluster around more capable nodes. CKP also proposes a new communication architecture that handles mobility efficiently and minimizes the impact of a node compromisation to itself. CKP provides confidentiality, authentication, integrity and freshness. The performance evaluation demonstrates that the CKP is energy and storage-efficient. Further, we investigate the survivability and the security of the CKP against various security threats in order to evaluate its effectiveness.

Investigations in hydrologic sciences are bounded because most of existing water surveillance methods are manual. Such systems are incapable to gather information at spatial and temporal level due to location constraints. In this paper, we present a new communication architecture for Underwater Wireless Sensor Network (UWSN) based on acoustic communication. However, unique challenges offered by underwater environment are main hindrance in deployment of UWSN in real life applications. So, we discuss various communication methodologies to figure out which one suits best to the requirements of UWSN. Our simulation results illustrate change in data transmission rate, energy consumption and transmission time w.r.t transmission range and number of nodes in network. Results prove that multi-hop communication offer high transmission rate, large bandwidth. Moreover, multi-hop communication is much more energy and time efficient than direct communication.

Increased employment of WSN (Wireless Sensor Network) in real life applications and their hostile and remote locations accelerate demand of security in WSN. Publicly accessible wireless communication channel also makes WSN vulnerable to numerous security attacks. Scarcity of resources acquaints new sort of challenges and difficulties during implementation of effective security mechanisms. In this paper, we evaluate and compare performance of three different security mechanisms (ECRKS, CKP and AP scheme). ECRKS (Energy-efficient, Connected, Resilient Key pre-distribution Scheme) is based upon multi hop communication architecture specifically designed for homogeneous WSN. Clustering based protocols, AP (Asymmetric pre-distribution) scheme and CKP (Clustering based Key management Protocol) are proposed for heterogeneous WSN. All the above mentioned schemes are simulated in MATLAB to evaluate their effectiveness and suitability for WSN. Simulation result shows that CKP outperforms other two schemes in terms of transmission distance, memory burden, energy dissipation and resilience.

In this paper four fiber-loop-buffer based photonic packet switched architectures are compared. It is done in terms of their packet loss probability and their optical cost under various load conditions for the random traffic model. The recirculating type delay lines are used for the storage of packets to resolve the contention. The architectures use semiconductor optical amplifiers(SOAs) and tunable wavelength converters(TWCs) in the recirculating loop buffer. The architectures have advantage of simultaneous Read/Write and, wavelength reallocation using TWCs in the recirculating loop buffer. Therefore, it improves the switch performance over the architectures using SOAs in the loop buffer. The cost of the various architectures is evaluated by considering FCC (fiber-to-chip coupling) and the WSU (wavelength speed up factor) model.