A mechanized proof of loop freedom of the (untimed) AODV routing protocol

The Ad hoc On-demand Distance Vector (AODV) routing protocol allows the nodes in a Mobile Ad hoc Network (MANET) or a Wireless Mesh Network (WMN) to know where to forward data packets. Such a protocol is 'loop free' if it never leads to routing decisions that forward packets in circles. This paper describes the mechanization of an existing pen-and-paper proof of loop freedom of AODV in the interactive theorem prover Isabelle/HOL. The mechanization relies on a novel compositional approach for lifting invariants to networks of nodes. We exploit the mechanization to analyse several improvements of AODV and show that Isabelle/HOL can re-establish most proof obligations automatically and identify exactly the steps that are no longer valid.Comment: The Isabelle/HOL source files, and a full proof document, are available in the Archive of Formal Proofs, at http://afp.sourceforge.net/entries/AODV.shtm

Mechanizing a Process Algebra for Network Protocols

This paper presents the mechanization of a process algebra for Mobile Ad hoc Networks and Wireless Mesh Networks, and the development of a compositional framework for proving invariant properties. Mechanizing the core process algebra in Isabelle/HOL is relatively standard, but its layered structure necessitates special treatment. The control states of reactive processes, such as nodes in a network, are modelled by terms of the process algebra. We propose a technique based on these terms to streamline proofs of inductive invariance. This is not sufficient, however, to state and prove invariants that relate states across multiple processes (entire networks). To this end, we propose a novel compositional technique for lifting global invariants stated at the level of individual nodes to networks of nodes.Comment: This paper is an extended version of arXiv:1407.3519. The Isabelle/HOL source files, and a full proof document, are available in the Archive of Formal Proofs, at http://afp.sourceforge.net/entries/AWN.shtm

Currents, Fronts and Fine Structure in the Marginal Ice Zone of the Chukchi Sea

The article of record as published may be found at https://doi.org/10.1017/S0032247400021975Project MIZPAC (Marginal Ice Zone Pacific) was initiated in 1971 by the Arctic Submarine Laboratory, San Diego, California, to further the US Navy's understanding of problems associated with operating submarines under ice-covered oceans. Oceanographers from the Naval Postgraduate School took part in six summer cruises to the marginal sea ice zone (MIZ) of the shallow Chukchi Sea between 1971 and 1978 (Fig 1), providing the first detailed observations of the temperature-salinity structure within this dynamically active zone. Strong horizontal gradients of temperature and salinity marking boundaries between water masses (fronts), are widespread and well developed (Paquette and Bourke 1981). Where water masses intrude upon each other large-scale temperature inversions (anomalous increases in temperature with depth) often appear. Termed fine structure, these temperature anomalies include some of the largest observed anywhere in the world's oceans, sometimes exceeding 2°C over vertical distances of 5–10 m (Paquette and Bourke 1979). This article describes some of the fronts and fine structures observed in the Chukchi Sea, and shows how they develop within the general patterns of sea ice and circulation

Atlantic water on the Chukchi Shelf

An anomalously warm saline layer in the bottom of the shallow Chukchi Sea in August 1975 is believed due to a surge which drove water from the Atlantic Layer of the Arctic Ocean up onto the shelf. Two earlier occurrences of this kind of water in the Chukchi Sea have been identified in historical data.Submitted to: Director, Arctic Submarine Laboratory Naval Undersea Center, San Diego, CA.http://archive.org/details/atlanticwateronc00bourProject Order No. 00010N

USNS BARTLETT Cruise to the Greenland Sea in September 1989: Data Report

As a component of the Greenland Sea Project, a hydrographic cruise was conducted on board the USNS BARTLETT during September 1989 in the southern Greenland Sea to characterize the water mass structure and circulation features of the Jan Mayen Current (JMC). A total of 48 high-quality CTD stations were occupied to depths of 1000 m; five stations extended to 3000 m or more. Five north-south tending transects permitted tracking of the JMC by its low temperature (< 0°C) , low salinity near-surface core. The JMC could also be well defined from its warm, saline intermediate water properties. Deep stations made in the trough of the Jan Mayen Fracture Zone suggest that the interchange of deep and bottom water from the Greenland and Norwegian Seas via this trough is a slow diffusive process and not an active advective feature as previously thought.Arctic Submarine Laboratory, Naval Ocean Systems Center, San Diego, CA.http://archive.org/details/usnsbartlettcrui00bourO&MN, Direct Fundin

Development of an Arctic Low Frequency Ambient Noise Model

LONG TERM GOALS: To develop a low frequency Arctic ambient noise model to predict extreme (loud /quiet) noise events due the presence or absence of storms.Award No. N0001497WR3009

Filamentary Accretion Flows in the Embedded Serpens South Protocluster

One puzzle in understanding how stars form in clusters is the source of mass -- is all of the mass in place before the first stars are born, or is there an extended period when the cluster accretes material which can continuously fuel the star formation process? We use a multi-line spectral survey of the southern filament associated with the Serpens South embedded cluster-forming region in order to determine if mass is accreting from the filament onto the cluster, and whether the accretion rate is significant. Our analysis suggests that material is flowing along the filament's long axis at a rate of ~30Msol/Myr (inferred from the N2H+ velocity gradient along the filament), and radially contracting onto the filament at ~130Msol/Myr (inferred from HNC self-absorption). These accretion rates are sufficient to supply mass to the central cluster at a similar rate to the current star formation rate in the cluster. Filamentary accretion flows may therefore be very important in the ongoing evolution of this cluster.Comment: 19 pages, 8 figures, 2 tables; accepted for publication in Ap

A study of the seasonal variation in temperature and salinity along the Oregon - Northern California coast

This study examines the seasonal variability in temperature and salinity of the nearshore waters off Oregon and Northern California. Specifically, temperature and salinity variations during summer and winter were ana1yzed from data gathered at shore stations along the coast and from hydrographic data collected within 25 nautical miles of shore. At each of five shore stations a modal cell technique was used to establish the temperature-salinity characteristics of the "normal" water type existing at each station during summer and winter. A classification scheme was employed to determine what local processes were influential in altering the "normal" T-S characteristics at each station. In summer mixing with Columbia River plume water was found to be the major modifying process along the Northern Oregon coast. Off Central and Southern Oregon local heating and mixing with water from the shelf/slope region were found to be most influential. In winter dilution due to precipitation and subsequent runoff is the major modifying factor along the entire coast except off Northern Oregon where mixing with shelf/slope waters is slightly more influential. The temperature and salinity structure of the near surface waters (< 200 meters) was examined for four latitudinal zones off the Oregon- Northern California coast. Within each zone profiles were constructed at 5, 15, and 25 nautical miles offshore. Surface waters are warmer and more saline in summer than in winter. Surface temperatures increase seaward in both seasons. Surface salinities increase seaward only during winter; in summer the increase is shoreward. Offshore gradients of temperature and salinity are one to two orders of magnitude greater than longshore gradients. A strong thermocline to 30 meters and a strong halocline to 75 meters is present in summer. In winter the water is isothermal to 50 meters while a strong halocline is present to 100 meters. Below these levels temperatures and salinities continue to slowly decrease and increase, respectively, until at 200 meters they become constant throughout the study area. Variability with distance from shore is significant only in summer and is constrained to the upper 150 meters of the water column

The Spitzer c2d Survey of Nearby Dense Cores. V. Discovery of a VeLLO in the "Starless" Dense Core L328

This paper reports the discovery of a Very Low Luminosity Object (VeLLO) in the "starless" dense core L328, using the Spitzer Space Telescope and ground based observations from near-infrared to millimeter wavelengths. The Spitzer 8 micron image indicates that L328 consists of three subcores of which the smallest one may harbor a source, L328-IRS while two other subcores remain starless. L328-IRS is a Class 0 protostar according to its bolometric temperature (44 K) and the high fraction ~72 % of its luminosity emitted at sub-millimeter wavelengths. Its inferred "internal luminosity" (0.04 - 0.06 Lsun) using a radiative transfer model under the most plausible assumption of its distance as 200 pc is much fainter than for a typical protostar, and even fainter than other VeLLOs studied previously. Note, however, that its inferred luminosity may be uncertain by a factor of 2-3 if we consider two extreme values of the distance of L328-IRS (125 or 310 pc). Low angular resolution observations of CO do not show any clear evidence of a molecular outflow activity. But broad line widths toward L328, and Spitzer and near-infrared images showing nebulosity possibly tracing an outflow cavity, strongly suggest the existence of outflow activity. Provided that an envelope of at most ~0.1 Msunis the only mass accretion reservoir for L328-IRS, and the star formation efficiency is close to the canonical value ~30%, L328-IRS has not yet accreted more than 0.05 Msun. At the assumed distance of 200 pc, L328-IRS is destined to be a brown dwarf.Comment: 29 pages, 8 figures, 1 table, to be published in Astrophysical Journa