Traffic placement policies for a multi-band network

Recently protocols were introduced that enable the integration of synchronous traffic (voice or video) and asynchronous traffic (data) and extend the size of local area networks without loss in speed or capacity. One of these is DRAMA, a multiband protocol based on broadband technology. It provides dynamic allocation of bandwidth among clusters of nodes in the total network. A number of traffic placement policies for such networks are proposed and evaluated. Metrics used for performance evaluation include average network access delay, degree of fairness of access among the nodes, and network throughput. The feasibility of the DRAMA protocol is established through simulation studies. DRAMA provides effective integration of synchronous and asychronous traffic due to its ability to separate traffic types. Under the suggested traffic placement policies, the DRAMA protocol is shown to handle diverse loads, mixes of traffic types, and numbers of nodes, as well as modifications to the network structure and momentary traffic overloads

A New Feather Mite Species of the Genus \u3ci\u3eTrouessartia\u3c/i\u3e Canestrini (Acariformes: Trouessartiidae) from the Northern Rough-winged Swallow \u3ci\u3eStelgidopteryx serripennis\u3c/i\u3e (Passeriformes: Hirundinidae) in Pennsylvania

A new feather mite species, Trouessartia stelgidopteryx sp. n. (Astigmata: Trouessartiidae), is described from the Northern rough-winged swallow Stelgidopteryx serripennis Newton (Passeriformes: Hirundinidae) in Pennsylvania, USA. The new species is close to the minutipes species group and differs from its representatives and all other known species of the genus Trouessartia in having a unique combination of features in males: the opisthosomal lobes are much longer than wide, they are separated by a large semi-ovate terminal cleft, and their lobar apices bear semi-ovate terminal lamellae with a smooth margin

Extremely high data-rate, reliable network systems research

Significant progress was made over the year in the four focus areas of this research group: gigabit protocols, extensions of metropolitan protocols, parallel protocols, and distributed simulations. Two activities, a network management tool and the Carrier Sensed Multiple Access Collision Detection (CSMA/CD) protocol, have developed to the point that a patent is being applied for in the next year; a tool set for distributed simulation using the language SIMSCRIPT also has commercial potential and is to be further refined. The year's results for each of these areas are summarized and next year's activities are described

A Flexible System for Simulating Aeronautical Telecommunication Network

At Old Dominion University, we have built Aeronautical Telecommunication Network (ATN) Simulator with NASA being the fund provider. It provides a means to evaluate the impact of modified router scheduling algorithms on the network efficiency, to perform capacity studies on various network topologies and to monitor and study various aspects of ATN through graphical user interface (GUI). In this paper we describe briefly about the proposed ATN model and our abstraction of this model. Later we describe our simulator architecture highlighting some of the design specifications, scheduling algorithms and user interface. At the end, we have provided the results of performance studies on this simulator

Scalable parallel communications

Coarse-grain parallelism in networking (that is, the use of multiple protocol processors running replicated software sending over several physical channels) can be used to provide gigabit communications for a single application. Since parallel network performance is highly dependent on real issues such as hardware properties (e.g., memory speeds and cache hit rates), operating system overhead (e.g., interrupt handling), and protocol performance (e.g., effect of timeouts), we have performed detailed simulations studies of both a bus-based multiprocessor workstation node (based on the Sun Galaxy MP multiprocessor) and a distributed-memory parallel computer node (based on the Touchstone DELTA) to evaluate the behavior of coarse-grain parallelism. Our results indicate: (1) coarse-grain parallelism can deliver multiple 100 Mbps with currently available hardware platforms and existing networking protocols (such as Transmission Control Protocol/Internet Protocol (TCP/IP) and parallel Fiber Distributed Data Interface (FDDI) rings); (2) scale-up is near linear in n, the number of protocol processors, and channels (for small n and up to a few hundred Mbps); and (3) since these results are based on existing hardware without specialized devices (except perhaps for some simple modifications of the FDDI boards), this is a low cost solution to providing multiple 100 Mbps on current machines. In addition, from both the performance analysis and the properties of these architectures, we conclude: (1) multiple processors providing identical services and the use of space division multiplexing for the physical channels can provide better reliability than monolithic approaches (it also provides graceful degradation and low-cost load balancing); (2) coarse-grain parallelism supports running several transport protocols in parallel to provide different types of service (for example, one TCP handles small messages for many users, other TCP's running in parallel provide high bandwidth service to a single application); and (3) coarse grain parallelism will be able to incorporate many future improvements from related work (e.g., reduced data movement, fast TCP, fine-grain parallelism) also with near linear speed-ups

Marine Leeches of the Eastern United States and the Gulf of Mexico with a Key to the Species

Unlike the Eurasian marine leeches (Johansson, 1896; Selensky, 1915; Herter, 1935; Vasileyev, 1939; Knight-Jones, 1961; Sawyer, 1970; Soós, 1965), those from North America comprise an unusually neglected group, due primarily to the bewildering taxonomy of the members. Most early descriptions were brief, ambiguous, and concerned only with superficial characters. Some of the nominal species reported from the eastern United States and Canada are unrecognizable today, thus perpetuating nomenclatural confusion. We attempt to analyze critically the marine leeches from Newfoundland to Texas, with emphasis on those of the southern states from Virginia to Mississippi. An illustrated dichotomous key and a diagnosis for each species is presented. A synonymy, a list of hosts, the geographical distribution, and biological observations accompany the diagnoses. The poorly known Pacific marine leeches (Moore & Meyer, 1951; Moore, 1952a) will be deferred to another study. We found 14 valid species in the Atlantic Ocean and in the Gulf of Mexico from Newfoundland to Texas. Fortunately, the internal anatomy of most is now well known: Ozobranchus branchiatus (Menzies, 1791); O. margoi (Apathy, 1890); Stibarobdella macrothela (Schmarda, 1861); Branchellion torpedinis Savigny, 1822; Trachelobdella lubrica (Grube, 1840); Oxytonostoma typica Malm, 1863; Branchellion ravenelii (Girard, 1850); Trachelobdella rugosa Moore, 1898; Calliobdella vivida (Verrill, 1872); Platybdella buccalis Nigrelli, 1946; Malmiana nuda Richardson, 1970; Myzobdella lugubris Leidy, 1851; Austrobdella rapax (Verrill, 1873); and a new species provisionally assigned to Malmiana Strand, 1942. The first six are also European or cosmopolitan species. Trachelobdella lubrica, Oxytonostoma typical, and the undescribed species of Malmiana are new to the region under study. Trachelobdella rugosa, Austrobdella rapax, and Platybdella buccalis are reported for the first time since their original descriptions. In addition the following important synonyms are presented for the first time: Calliobdella vivida synonymous with C. carolinensis of Sawyer & Chamberlain (1972) and C. nodulifera of Threlfall (1969); Myzobdella lugubris synonymous with Illinobdella alba, I. elongata, I. richardsoni, and I. moorei of Meyer (1940), Ichthyobdella rapax of Wass (1972) and Cystobranchus virginicus of Paperna and Zwerner (1974); and the undescribed Malmiana species synonymous with Piscicola funduli of Causey (1953). Piscicola zebra Moore, 1898, is species inquirendae

A depolarization and attenuation experiment using the COMSTAR and CTS satellites

Monthly statistical data are presented on ground rainfall rate and attenuation of satellite downlinks at 11.7 GHz, 19.04 GHz, and 28.56 GHz and on cross-polarization isolation at 11.7 GHz. Regression equations for relating isolation to attenuation, attenuation to rain rate, and attenuation at one frequency to attenuation at another frequency are also included. Longer-term statistics are also presented and discussed

Multi-study analysis of learning culture, human capital and operational performance in supply chain management: The moderating role of workforce level

Purpose – The purpose of this study is to empirically evaluate the relationship between learning culture, workforce level, human capital and operational performance in two diverse supply chain populations, aircraft maintenance and logistics readiness. Design/methodology/approach – Drawing upon competence-based view of the firm and human capital theory, this paper analyzes data from two studies. Findings – The results provide support for the hypothesized model. Workforce level moderates the relationship between learning culture and human capital, and human capital partially mediates the relationship between learning culture and operational performance. Research limitations/implications – The findings have implications for behavioral supply chain management research and implications for educating and training the supply chain management workforce. While the populations represent a diverse set of logistics functions and responsibilities, the participants are all military members, which may limit generalizability. Practical implications – This study should help leaders understand the importance of learning culture and the perceived differences in its effect on human capital based upon workforce level. Originality/value – This research is among the first to investigate the role of workforce level and answers a multitude of calls for research into the human side of supply chain management