Life Cycles of \u3ci\u3eLeuctra Duplicata\u3c/i\u3e and \u3ci\u3eOstrocerca Prolongata\u3c/i\u3e in an Intermittent Streamlet in Quebec (Plecoptera: Leuctridae and Nemouridae)

Large populations of Ostrocerca prolongata and Leuctra duplicata developed in a small intermittent stream in the foothills of the Laurentian Highlands of Quebec. Both species were univoltine in 1974-1975. Ostrocerca prolongata started emerging in mid-to late May. followed by L. duplicata about 2 weeks later. The emergence periods lasted 3-4 weeks with similar patterns in both sexes. Ostrocerca prolongata laid its eggs before the stream dried up in early July. while L. duplicata oviposited just afterward. The eggs of both species did not hatch before October when flow had resumed; the prolonged incubation was due to a diapause in Ostrocerca, but to a depressed development rate in Leuctra. Nymphal growth continued through winter and accelerated considerably in May in both populations. Despite much overlap in timings of the life cycles and in size-frequency distributions of the nymphs. there appeared to be little competition between the two species. probably due to differing food habits

Waveshaping electronic circuit

Circuit provides output signal with sinusoidal function in response to bipolar transition of input signal. Instantaneous transition shapes into linear rate of change and linear rate of change shapes into sinusoidal rate of change. Circuit contains only active components; therefore, compatibility with integrated circuit techniques is assured

Input gate circuit converted for use as linear amplifier

Commercially available integrated circuit that is marketed as a digital computer input gate circuit was converted to a linear amplifier in a microphone circuit that has high input impedance, low output impedance, low cost, and is small enough to fit on a standard printed circuit card

Tire/wheel concept

A tire and wheel assembly is disclosed in which a low profile pneumatic tire (having sidewalls which deflect inwardly under load) and a wheel (having a rim featuring a narrow central channel and extended rim flanges) form the combination. The extended rim flanges support the tire sidewalls under static and dynamic loading conditions to produce a combination particularly suited to aircraft applications

The role of voice technology in advanced helicopter cockpits

The status of voice output and voice recognition technology in relation to helicopter cockpit applications is described. The maturing of this technology provides many opportunities for new approaches to crew workload reduction. The helicopter operating environment, potential application areas, and the impact on advanced cockpit design are discussed

MUSE CSP: An Extension to the Constraint Satisfaction Problem

This paper describes an extension to the constraint satisfaction problem (CSP) called MUSE CSP (MUltiply SEgmented Constraint Satisfaction Problem). This extension is especially useful for those problems which segment into multiple sets of partially shared variables. Such problems arise naturally in signal processing applications including computer vision, speech processing, and handwriting recognition. For these applications, it is often difficult to segment the data in only one way given the low-level information utilized by the segmentation algorithms. MUSE CSP can be used to compactly represent several similar instances of the constraint satisfaction problem. If multiple instances of a CSP have some common variables which have the same domains and constraints, then they can be combined into a single instance of a MUSE CSP, reducing the work required to apply the constraints. We introduce the concepts of MUSE node consistency, MUSE arc consistency, and MUSE path consistency. We then demonstrate how MUSE CSP can be used to compactly represent lexically ambiguous sentences and the multiple sentence hypotheses that are often generated by speech recognition algorithms so that grammar constraints can be used to provide parses for all syntactically correct sentences. Algorithms for MUSE arc and path consistency are provided. Finally, we discuss how to create a MUSE CSP from a set of CSPs which are labeled to indicate when the same variable is shared by more than a single CSP.Comment: See http://www.jair.org/ for any accompanying file

A method for the measurement of hydrodynamic oil films using ultrasonic reflection

The measurement of the thickness of an oil film in a lubricated component is essential information for performance monitoring and control. In this work, a new method for oil film thickness measurement, based on the reflection of ultrasound, is evaluated for use in fluid film journal bearing applications. An ultrasonic wave will be partially reflected when it strikes a thin layer between two solid media. The proportion of the wave reflected depends on the thickness of the layer and its acoustic properties. A simple quasi-static spring model shows how the reflection depends on the stiffness of the layer alone. This method has been first evaluated using flat plates separated by a film of oil, and then used in the measurement of oil films in a hydrodynamic journal bearing. A transducer is mounted on the outside of the journal and a pulse propagated through the shell. The pulse is reflected back at the oil film and received by the same transducer. The amplitude of the reflected wave is processed in the frequency domain. The spring model is then used to determine the oil film stiffness that can be readily converted to film thickness. Whilst the reflected amplitude of the wave is dependent on the frequency component, the measured film thickness is not; this indicates that the quasi-static assumption holds. Measurements of the lubricant film generated in a simple journal bearing have been taken over a range of loads and speeds. The results are compared with predictions from classical hydrodynamic lubrication theory. The technique has also been used to measure oil film thickness during transient loading events. The response time is rapid and film thickness variation due to step changes in load and oil feed pressure can be clearly observed

Exact Random Walk Distributions using Noncommutative Geometry

Using the results obtained by the non commutative geometry techniques applied to the Harper equation, we derive the areas distribution of random walks of length $N$ on a two-dimensional square lattice for large $N$, taking into account finite size contributions.Comment: Latex, 3 pages, 1 figure, to be published in J. Phys. A : Math. Ge

Effets de travaux de curage sur la faune benthique d'un cours d'eau d'une région agricole du Québec

Une étude quantitative et qualitative du benthos du Ruisseau des Anges (Comté de Montcalm, Québec), un bassin à vocation agricole, réalisée de 1986 à 1988, a permis d'évaluer les effets d'un curage effectué en 1987.L'échantillonnage couvrait les zones d'amont destinées être curés, ainsi que des sites en aval des travaux et des sites témoins. Les cours d'eau y sont enrichis, principalement en azote, et le benthos s'avère dominé par les Oligochètes Tubificidae. Mémo la station-témoin, située dans une zone plus boisée, contient une faune appauvrie, bien que plus diversifiée, dominée par les Diptères Chironomidae, les Mollusques Sphaeriidae, les Coléoptères Elmidae et les Mégaloptères Sialidae, groupes résistants à la pollution. Le curage a éliminé les accumulations de boues organiques, ainsi que les plantes aquatiques qui les retenaient, et favorisé la colonisation du milieu par les Diptères Chironomidae. Cependant, dès l'automne suivant (1988), l'envasement avait repris et les Tubificidae avaient recouvré leur position de dominance, particulièrement dans les stations d'amont, sans toutefois atteindre les densités de 1986. Les bénéfices du curage sur le benthos ont été de faible importance et de courte durée, dans la mesure où l'envasement et la pollution organique maintiennent des conditions de dégradation en absence de mesures efficaces de contrôle de l'érosion. L'utilisation de plusieurs indices biotiques pour décrire l'état des cours d'eau illustre la difficulté de leur application à des cours d'eau de plaine.A quantitative and qualitative study of the benthos of Ruisseau des Anges (Montcalm County, Quebec), in an agricultural area, in 1986 to 1988 was undertaken to evaluate the effects of ditching operations in 1987.Sampling included upstream zones where the ditching occurred, downstream stations, and control areas. All streams were enriched, particularly in nitrogen, and their benthic fauna was dominated by Tubificidae (Oligochaeta). Even the control area had a reduced fauna dominated by Chironomidae (Diptera), Sphaeriidae (Mollusca), Elmidae (Coleoptera) and Sialidae (Megaloptera), all resistant to pollution. The ditching operations eliminated the accumulated mud and destroyed the vegetation winch choked the streams. This allowed a colonization by Chironomidae. However, by the fall of 1988 much silting had occurred and the Tubificidae reestablished, though not in the high densities of 1986. Any improvement of the benthic fauna was marginal and shortlived, as silting and organic pollution restored the degradated conditions in the absence of erosion control. The use of several biotic indices to assess stream conditions showed that these are often unsatisfactory in lowland streams

A new approach for the measurement of film thickness in liquid face seals

Face seals operate by allowing a small volume of the sealed fluid to escape and form a thin film between the contacting parts. The thickness of this film must be optimized to ensure that the faces are separated, yet the leakage is minimized. In this work the liquid film is measured using a novel ultrasonic approach with a view to developing a condition monitoring tool. The trials were performed in two stages. Initially tests were based on a lab simulation, where it was possible to compare the ultrasonic film thickness measurements with optical interference methods and capacitance methods. A direct correlation was seen between ultrasonic measurements and capacitance. Where ultrasonic and optical methods overlap, good correlation is observed; however, the optical method will not record film thickness above 0.72 m. A second set of trials was carried out, where the film thickness was monitored inside a seal test apparatus. Film thickness was successfully recorded as speed and load were varied. The results showed that while stationary the film thickness varied noticeably with load. When rotating, however, the oil film remained relatively stable around 2 m. During the normal operation of the seal, both sudden speed and load changes were applied in order to initiate a seal failure. During these events, the measured film thickness was seen to drop dramatically down to 0.2 m. This demonstrated the ability of the technique to predict failure in a face seal and therefore its aptitude for condition monitoring