Compositional Verification of a Communication Protocol for a Remotely Operated Vehicle

This paper presents the specification and verification in the Prototype Verification System (PVS) of a protocol intended to facilitate communication in an experimental remotely operated vehicle used by NASA researchers. The protocol is defined as a stack-layered com- position of simpler protocols. It can be seen as the vertical composition of protocol layers, where each layer performs input and output message processing, and the horizontal composition of different processes concurrently inhabiting the same layer, where each process satisfies a distinct requirement. It is formally proven that the protocol components satisfy certain delivery guarantees. Compositional techniques are used to prove these guarantees also hold in the composed system. Although the protocol itself is not novel, the methodology employed in its verification extends existing techniques by automating the tedious and usually cumbersome part of the proof, thereby making the iterative design process of protocols feasible

Computing infrastructure issues in distributed communications systems : a survey of operating system transport system architectures

The performance of distributed applications (such as file transfer, remote login, tele-conferencing, full-motion video, and scientific visualization) is influenced by several factors that interact in complex ways. In particular, application performance is significantly affected both by communication infrastructure factors and computing infrastructure factors. Several communication infrastructure factors include channel speed, bit-error rate, and congestion at intermediate switching nodes. Computing infrastructure factors include (among other things) both protocol processing activities (such as connection management, flow control, error detection, and retransmission) and general operating system factors (such as memory latency, CPU speed, interrupt and context switching overhead, process architecture, and message buffering). Due to a several orders of magnitude increase in network channel speed and an increase in application diversity, performance bottlenecks are shifting from the network factors to the transport system factors.This paper defines an abstraction called an "Operating System Transport System Architecture" (OSTSA) that is used to classify the major components and services in the computing infrastructure. End-to-end network protocols such as TCP, TP4, VMTP, XTP, and Delta-t typically run on general-purpose computers, where they utilize various operating system resources such as processors, virtual memory, and network controllers. The OSTSA provides services that integrate these resources to support distributed applications running on local and wide area networks.A taxonomy is presented to evaluate OSTSAs in terms of their support for protocol processing activities. We use this taxonomy to compare and contrast five general-purpose commercial and experimental operating systems including System V UNIX, BSD UNIX, the x-kernel, Choices, and Xinu

Spatio-temporal influence of tundra snow properties on Ku-band (17.2 GHz) backscatter

During the 2010/11 boreal winter, a distributed set of backscatter measurements was collected using a ground-based Ku-band (17.2 GHz) scatterometer system at 26 open tundra sites. A standard snow-sampling procedure was completed after each scan to evaluate local variability in snow layering, depth, density and water equivalent (SWE) within the scatterometer field of view. The shallow depths and large basal depth hoar encountered presented an opportunity to evaluate backscatter under a set of previously untested conditions. Strong Ku-band response was found with increasing snow depth and snow water equivalent (SWE). In particular, co-polarized vertical backscatter increased by 0.82 dB for every 1 cm increase in SWE (R2 = 0.62). While the result indicated strong potential for Ku-band retrieval of shallow snow properties, it did not characterize the influence of sub-scan variability. An enhanced snow-sampling procedure was introduced to generate detailed characterizations of stratigraphy within the scatterometer field of view using near-infrared photography along the length of a 5m trench. Changes in snow properties along the trench were used to discuss variations in the collocated backscatter response. A pair of contrasting observation sites was used to highlight uncertainties in backscatter response related to short length scale spatial variability in the observed tundra environment

Audio-visual Rhetoric: Visualizing the Pattern Language of Film

Audio-visual Rhetoric is a knowledge domain for designers in theory and practice that is valid for all communicative actions through media that aim for persuasion. Within this domain, we introduce a framework for media analysis. We developed an Audio-Visual Pattern (AVP) language for film that is visualized within a notation system. This system shows auditory and visual parameters in order to reveal film’s rhetorical structure. We discuss related theories from pattern language and rhetoric and apply the AVP method to analyze 10 commercials. Keywords: Pattern Language, Film Analysis, Rhetoric, Emotion, Persuasion, Design Research</p

Vertical distributions of non-methane hydrocarbons and halocarbons in the lower troposphere over northeast China

Vertical distributions of air pollutants are crucial for understanding the key processes of atmospheric transport and for evaluating chemical transport models. In this paper, we present measurements of non-methane hydrocarbons (NMHCs) and halocarbons obtained from an intensive aircraft study over northeast (NE) China in summer 2007. Most compounds exhibited a typical negative profile of decreasing mixing ratios with increasing altitude, although the gradients differed with different species. Three regional plumes with enhanced VOC mixing ratios were discerned and characterized. An aged plume transported from the northern part of the densely populated North China Plain (NCP; i.e. Beijing-Tianjin area) showed relatively higher levels of HCFC-22, 1,2-dichloroethane (1,2-DCE) and toluene. In comparison, the plume originating from Korea had higher abundances of CFC-12, tetrachloroethene (C2Cl4) and methyl chloride (CH3Cl), while regional air masses from NE China contained more abundant light alkanes. By comparing these results with the earlier PEM-West B (1994) and TRACE-P (2001) aircraft measurements, continuing declining trends were derived for methyl chloroform (CH3CCl3), tetrachloromethane (CCl4) and C2Cl4 over the greater China-northwestern Pacific region, indicating the accomplishment of China in reducing these compounds under the Montreal protocol. However, the study also provided evidence for the continuing emissions of several halocarbons in China in 2007, such as CFCs (mainly from materials in stock) and HCFCs. © 2011 Elsevier Ltd

Waist-to-height ratio is independently related to whole and central body fat, regardless of the waist circumference measurement protocol, in non-alcoholic fatty liver disease patients

This is the peer reviewed version of the following article: Pimenta N.M., Cortez-Pinto H., Melo X., Silva-Nunes J., Sardinha L.B. & Santa-Clara H. (2017) Waist-to-height ratio is independently related to whole and central body fat, regardless of the waist circumference measurement protocol, in non-alcoholic fatty liver disease patients. J Hum Nutr Diet. 30, 185–192, which has been published in final form atdoi: 10.1111/jhn.12410. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Background: Waist-to-height ratio (WHtR) has been reported as a prefer-able risk related body fat (BF) marker, although no standardised waistcircumference measurement protocol (WCmp) has been proposed. Thepresent study aimed to investigate whether the use of a different WCmpaffects the strength of relationship between WHtR and both whole andcentral BF in non-alcoholic fatty liver disease (NAFLD) patients.Methods: BF was assessed with dual energy X-ray absorptiometry (DXA) in28 NAFLD patients [19 males, mean (SD) 51 (13) years and nine females,47 (13) years]. All subjects also underwent anthropometric evaluationincluding height and waist circumference (WC) measurement using fourdifferent WCmp (WC1, minimal waist; WC2, iliac crest; WC3, mid-distancebetween iliac crest and lowest rib; WC4, at the umbilicus) and WHtR wascalculated using each WC measurements (WHtR1, WHtR2, WHtR3 andWHtR4, respectively). Partial correlations were conducted to assess the rela-tion of WHtR and DXA assessed BF.Results: All WHtR were particularly correlated with central BF, includingabdominal BF (r = 0.80, r = 0.84, r = 0.84 and r = 0.78, respectively, forWHtR1, WHtR2, WHtR3 and WHtR4) and central abdominal BF (r = 0.72,r = 0.77, r = 0.76 and r = 0.71, respectively, for WHtR1, WHtR2, WHtR3and WHtR4), after controlling for age, sex and body mass index. There wereno differences between the correlation coefficients obtained between allstudied WHtR and each whole and central BF variable.Conclusions: Waist-to-height ratio was found a suitable BF marker in thepresent sample of NAFLD patients and the strength of the relationshipbetween WHtR and both whole and central BF was not altered by usingdifferent WCmp in the present sample of NAFLD patients.FUNDING SOURCES The first author of this paper was supported by a research grant (PhD scholarship) from the Foundation for Science and Technology (FCT), Ministry of Education and Science of Portugal (grant: SFRH/ BD/ 70515/ 2010). The present study was funded by: the Centre for the Study of Human Performance, Portuguese Foundation for Science and Technology, Lisbon, Portugal.info:eu-repo/semantics/publishedVersio