181,073 research outputs found
Medium access control, error control and routing in underwater acoustic networks: a discussion on protocol design and implementation
No full textThe journey of underwater communication which began from Leonardo’s era took four and a half centuries to find practical applications for military purposes during World War II. However, over the last three decades, underwater acoustic communications witnessed a massive development due to the advancements in the design of underwater communicating
peripherals and their supporting protocols. Successively, doors are opened for a wide range of applications to employ in the underwater environment, such as oceanography, pollution
monitoring, offshore exploration, disaster prevention, navigation assistance, monitoring, coastal patrol and surveillance. Different applications may have different characteristics and hence, may require different network architectures. For instance, routing protocols designed for unpartitioned multi-hop networks are not suitable for Delay-Tolerant Networks. Furthermore, single-hop networks do not need routing protocols at all. Therefore, before
developing a protocol one must study the network architecture properly and design it accordingly.
There are several other factors which should also be considered with the network architecture while designing an efficient protocol for underwater networks, such as long propagation delay, limited bandwidth, limited battery power, high bit error rate of the channel and several other adverse properties of the channel, such as, multi-path, fading and refractive behaviors. Moreover, the environment also has an impact on the performance of the protocols designed for underwater networks. Even temperature changes in a single day have an impact on the performance of the protocols. A good protocol designed for any network should consider some or all of these characteristics to achieve better performance.
In this thesis, we first discuss the impact of the environment on the performance of MAC and routing protocols. From our investigation, we discover that even temperature changes within a day may affect the sound speed profile and hence, the channel changes and the protocol performance vary. After that we discuss several protocols which are specifically designed for underwater acoustic networks to serve different purposes and for different network architectures. Underwater Selective Repeat (USR) is an error control protocol designed to assure reliable data transmission in the MAC layer. One may suspect that employing an error control technique over a channel which already suffers from long propagation delays is a burden. However, USR utilizes long propagation by transmitting multiple packets in a single RTT using an interlacing technique. After USR, a routing protocol for surveillance networks is discussed where some sensors are laid down at the bottom of the sea and some sinks are placed outside the area. If a sensor detects an asset within its detection range, it announces the presence of intruders by transmitting packets to the sinks. It may happen
that the discovered asset is an enemy ship or an enemy submarine which creates noise to jam the network. Therefore, in surveillance networks, it is necessary that the protocols have
jamming resistance capabilities. Moreover, since the network supports multiple sinks with similar anycast address, we propose a Jamming Resistance multi-path Multi-Sink Routing
Protocol (MSRP) using a source routing technique. However, the problem of source routing is that it suffers from large overhead (every packet includes the whole path information) with
respect to other routing techniques, and also suffers from the unidirectional link problem. Therefore, another routing protocol based on a distance vector technique, called Multi-path
Routing with Limited Cross-Path Interference (L-CROP) protocol is proposed, which employs a neighbor-aware multi-path discovery algorithm to support low interference multiple paths
between each source-destination pair. Following that, another routing protocol is discussed for next generation coastal patrol and surveillance network, called Underwater Delay-Tolerant
Network (UDTN) routing where some AUVs carry out the patrolling work of a given area and report to a shore based control-center. Since the area to be patrolled is large, AUVs
experience intermittent connectivity. In our proposed protocol, two nodes that understand to be in contact with each other calculate and divide their contact duration equally so that
every node gets a fair share of the contact duration to exchange data. Moreover, a probabilistic spray technique is employed to restrict the number of packet transmissions and for error correction a modified version of USR is employed.
In the appendix, we discuss a framework which was designed by our research group to realize underwater communication through simulation which is used in most of the simulations in this thesis, called DESERT Underwater (short for DEsign, Simulate, Emulate and Realize Test-beds for Underwater network protocols). It is an underwater extension of the
NS-Miracle simulator to support the design and implementation of underwater network protocols. Its creation assists the researchers in to utilizing the same codes designed for the
simulator to employ in actual hardware devices and test in the real underwater scenario
Ulnar collateral ligament injuries of the thumb- An overview of the injury and treatment
No full textAppropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
RELATIONSHIP BETWEEN RESONANT LEADERSHIP PERCEPTION AND ORGANIZATIONAL CITIZENSHIP BEHAVIOR AMONG ISFAHAN AZAD UNIVERSITY STAFFS
No full textPurpose: This study aimed at specifying the relationship between resonant leadership perception and organizational citizenship behavior among Isfahan Azad University staffs and was conducted through a correlational descriptive method.
Methodology: Research population was all the staffs of Isfahan Azad University, 375 individuals, among whom 189 individuals were accidentally selected based on Cochran sample mass according to their units or departments of work. Instruments used for this study are; Wagner (2010) questionnaire of Resonant leadership, Alonen (2008) questionnaire of organizational trust, and questionnaire of organizational citizenship behavior of Poudsakov (1990). Cronbach's Alpha computed the stability of these questionnaires as 0.79, 0.82, and 0.80 for resonant leadership, organizational trust and organizational citizenship behavior, respectively.
Main Findings: Data analysis shows that there is no meaningful relation between resonant leadership perception and organizational citizenship behavior (OCB). (r=0.096). But a meaningful relationship exists between organizational trust (r=0.189), side trust (r=0.153), vertical trust (r=0.229), institutional trust (r= 0.189) and organizational citizenship behavior.
Implications: Results of this study can help education administrator to understand organizational citizenship behavior among Isfahan Azad University staff’s activity.
Originality: This study is first of its kind in researching relationship between resonant leadership perception and organizational citizenship behavior among Isfahan Azad University, Iran staffs.</jats:p
RELATIONSHIP BETWEEN RESONANT LEADERSHIP PERCEPTION AND ORGANIZATIONAL CITIZENSHIP BEHAVIOR AMONG ISFAHAN AZAD UNIVERSITY STAFFS
No full textPurpose: This study aimed at specifying the relationship between resonant leadership perception and organizational citizenship behavior among Isfahan Azad University staffs and was conducted through a correlational descriptive method.
Methodology: Research population was all the staffs of Isfahan Azad University, 375 individuals, among whom 189 individuals were accidentally selected based on Cochran sample mass according to their units or departments of work. Instruments used for this study are; Wagner (2010) questionnaire of Resonant leadership, Alonen (2008) questionnaire of organizational trust, and questionnaire of organizational citizenship behavior of Poudsakov (1990). Cronbach's Alpha computed the stability of these questionnaires as 0.79, 0.82, and 0.80 for resonant leadership, organizational trust and organizational citizenship behavior, respectively.
Main Findings: Data analysis shows that there is no meaningful relation between resonant leadership perception and organizational citizenship behavior (OCB). (r=0.096). But a meaningful relationship exists between organizational trust (r=0.189), side trust (r=0.153), vertical trust (r=0.229), institutional trust (r= 0.189) and organizational citizenship behavior.
Implications: Results of this study can help education administrator to understand organizational citizenship behavior among Isfahan Azad University staff’s activity.
Originality: This study is first of its kind in researching relationship between resonant leadership perception and organizational citizenship behavior among Isfahan Azad University, Iran staffs
Super-Efficiency and Sensitivity Analysis Based on Input-Oriented DEA-R
No full textThis paper suggests a method of finding super-efficiency
scores and modification of input-oriented models for sensitivity
analysis of decision making units. First, by using DEA-R (ratiobased
DEA) models in the input orientation, the models of superefficiency
and also models of super-efficiency modification are suggested.
Second, the worst-case scenarios are considered where the
efficiency of the test DMU is deteriorating while the efficiencies
of the other DMUs are improving. Then, by combining these two
ideas, a model is suggested which increases the super-efficiency
score and modifies the change ranges in order to preserve the performance
class. In the end, the super-efficiency and change interval
of efficient decision making units for 23 branches of Zone 1 of the
Islamic Azad University are calculate
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
On the paper “Symmetry analysis of wave equation on sphere” by H. Azad and M.T. Mustafa
No full textAbstractUsing the scalar curvature of the product manifold S2×R and the complete group classification of nonlinear Poisson equation on (pseudo) Riemannian manifolds, we extend the previous results on symmetry analysis of homogeneous wave equation obtained by H. Azad and M.T. Mustafa [H. Azad, M.T. Mustafa, Symmetry analysis of wave equation on sphere, J. Math. Anal. Appl. 333 (2007) 1180–1188] to nonlinear Klein–Gordon equations on the two-dimensional sphere
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Social power and information technology implementation: a contentious framing lens
No full textResearch on the organizational implementation of information technology (IT) and social power has favoured explanations based on issues of resource power and process power at the expense of matters of meaning power. As a result, although the existence and importance of meaning power is acknowledged, its distinctive practices and enacted outcomes remain relatively under-theorized and under-explored by IT researchers. This paper focused on unpacking the practices and outcomes associated with the exercise of meaning power within the IT implementation process. Our aim was to analyze the practices employed to construct meaning and enact a collective 'definition of the situation'. We focused on framing and utilizing the signature matrix technique to represent and analyze the exercise of meaning power in practice. The paper developed and illustrated this conceptual framework using a case study of a conflictual IT implementation in a challenging public sector environment. We concluded by pointing out the situated nature of meaning power practices and the enacted outcomes. Our research extends the literature on IT and social power by offering an analytical framework distinctly suited to the analysis and deeper understanding of the meaning power properties. © 2010 Blackwell Publishing Ltd.Avgerou C, 2007, MIS QUART, V31, P295; Azad B, 2009, GOV INFORM Q, V26, P5, DOI 10.1016-j.giq.2008.08.005; Barrett M., 2006, J APPL BEHAV SCI, V42, P6, DOI 10.1177-0021886305285299; Bateson G., 1972, STEPS ECOLOGY MIND; Berger P. L., 1966, SOCIAL CONSTRUCTION; Bijker W. E., 1997, BICYCLES BAKELITES B; Boudreau MC, 2005, ORGAN SCI, V16, P3, DOI 10.1287-orsc.1040.0103; Bourdieu P., 1970, REPROD ED SOC CULTUR; Bradshaw-Camball P, 1991, ORGAN SCI, V2, P379, DOI 10.1287-orsc.2.4.379; Creed D, 2002, ORGAN SCI, V13, P475; Creed D. W. E., 2002, ORGAN RES METHODS, V5, P34; Davidson E., 2006, J APPL BEHAV SCI, V42, P23, DOI DOI 10.1177-0021886305285126; Davidson EJ, 2002, MIS QUART, V26, P329, DOI 10.2307-4132312; Dougherty D, 1996, ACAD MANAGE J, V39, P1120, DOI 10.2307-256994; Dowell G, 2002, ADV STRAT M, V19, P97; EISENHARDT KM, 1989, ACAD MANAGE REV, V14, P532, DOI 10.2307-258557; ENTMAN RM, 1993, J COMMUN, V43, P51, DOI 10.1111-j.1460-2466.1993.tb01304.x; Evered R., 1981, ACAD MANAGE REV, V6, P385, DOI DOI 10.2307-257374; Faraj S, 2004, INFORM TECHNOLOGY PE, V17, P186, DOI 10.1108-09593840410542501; Gamson W., 1983, EVALUATING WELFARE S, P397; GAMSON WA, 1989, AM J SOCIOL, V95, P1, DOI 10.1086-229213; Gitlin Todd, 1980, WHOLE WORLD IS WATCH; Goffman E., 1974, FRAME ANAL ESSAY ORG; HARDY C, 1985, J MANAGE STUD, V22, P384, DOI 10.1111-j.1467-6486.1985.tb00004.x; Hardy C., 1996, BRIT J MANAGE, V7, P3; Hargrave TJ, 2006, ACAD MANAGE REV, V31, P864; Howcroft D, 2006, INFORM SYST J, V16, P215, DOI 10.1111-j.1365-2575.2006.00216.x; Jasperson J, 2002, MIS QUART, V26, P397, DOI 10.2307-4132315; Lin A, 2005, EUR J INFORM SYST, V14, P49, DOI 10.1057-palgrave.ejis.3000521; MARKUS ML, 1987, COMMUN ACM, V30, P498, DOI 10.1145-214762.214764; MARKUS ML, 1983, COMMUN ACM, V26, P430, DOI 10.1145-358141.358148; Markuss M. L., 2004, J INF TECHNOL, V19, P3; Nidumolu SR, 1996, MIS QUART, V20, P197, DOI 10.2307-249478; ORLIKOWSKI WJ, 1994, ACM T INFORM SYST, V12, P174, DOI 10.1145-196734.196745; Pettigrew A.M., 1973, POLITICS ORG DECISIO; Pfeffer J., 1981, POWER ORG; Sillince JAA, 1997, INFORM SYST RES, V8, P368, DOI 10.1287-isre.8.4.368; Silva L., 2003, J ASSOC INF SYST, V4, P294; Benford RD, 2000, ANNU REV SOCIOL, V26, P611, DOI 10.1146-annurev.soc.26.1.611; Swan J, 2005, HUM RELAT, V58, P913, DOI 10.1177-0018726705057811; Thomas W. I., 1928, SOCIAL PSYCHOL SYMBO, P154; *UN DEV PROGR, 2005, RBAS MIC BEST PRACT; WILLCOCKS L, 2003, SOCIAL THEORY PHILOS, P238; *WORLD BANK, 1994, MEM PRES REV ENH TEC; *WORLD BANK, 2003, MEM REC PRES SUPPL L; Yin R. K., 2003, CASE STUDY RES DESIG86
- …
