Considering Cable Stretch in Logging Applications

This paper considers three methods for calculating the un-stretched length of a cable with significant self weight when the final static equilibrium conditions are known. The first method uses an average line tension and Hooke’s Law to estimate the un-stretched length. The second method uses a Lagrangian co-ordinate and Hooke’s Law to form an exact equation for the un-stretched length, given the assumption that the cable is linear elastic and the change in length is due to elastic stretch. The third method uses a Lagrangian coordinate; however, construction stretch is included in addition to elastic stretch. The results of this paper indicate the average tension is a suitable surrogate for a tension function that is a function of position when considering elongation to be the result of elastic stretch. When construction stretch is considered, the average tension method also performed well for cables with tensions less than one-third the minimum breaking strength

Noise suppression in inverse weak value based phase detection

We examine the effect of different sources of technical noise on inverse weak value-based precision phase measurements. We find that this type of measurement is similarly robust to technical noise as related experiments in the weak value regime. In particular, the measurements considered here are robust to additive Gaussian white noise and angular jitter noise commonly encountered in optical experiments. Additionally, we show the same techniques used for precision phase measurement can be used with the same technical advantages for optical frequency measurements.Comment: 6 pages, 4 figure

Power-recycled weak-value-based metrology

We improve the precision of the interferometric weak-value-based beam deflection measurement by introducing a power recycling mirror, creating a resonant cavity. This results in \emph{all} the light exiting to the detector with a large deflection, thus eliminating the inefficiency of the rare postselection. The signal-to-noise ratio of the deflection is itself magnified by the weak value. We discuss ways to realize this proposal, using a transverse beam filter and different cavity designs.Comment: 5 pages, 1 figur

Noise Suppression in Inverse Weak Value-Based Phase Detection

We examine the effect of different sources of technical noise on inverse weak value-based precision phase measurements. We find that this type of measurement is similarly robust to technical noise as related experiments in the weak value regime. In particular, the measurements considered here are robust to additive Gaussian white noise and angular jitter noise commonly encountered in optical experiments. Additionally, we show the same techniques used for precision phase measurement can be used with the same technical advantages for optical frequency measurements

Load Sharing in Gravel Decked Log Stringer Bridges

Log bridges are an economical alternative to steel and concrete structures for temporary crossings; however, reduced availability of large logs for stringers and the advancing age of existing log bridges increases the importance of structural analysis. Load sharing between the stringers is complicated and can result from load spread due to the gravel deck, cable lashing, and mechanical interlocking and friction between the stringers. This paper describes the development of a finite element model (FEM) for gravel decked log stringer bridges that includes elements capable of transferring vertical loads between the stringers. The FEM was used to interpret load deflection data from two in-situ bridges. The results of this paper suggest the segments of lashing that pass under one stringer and over an adjacent stringer contribute to load sharing between the stringers; however, care must be taken to ensure that the pattern of lashing supports the stringers directly loaded by the live loads

Skyline Tensile Forces in Cable Logging: Field Observations vs. Software Calculations

Skyline tensile forces have been shown to frequently exceed the recommended safety limits during ordinary cable logging operations. Several models for skyline engineering analyses have been proposed. Although skyline tensile forces assume a dynamic behaviour, practical solutions are based on a static approach without consideration of the dynamic nature of the cable systems. The aim of this study was to compare field data of skyline tensile forces with the static calculations derived by dedicated available software such as SkylineXL. To overcome the limitation of static calculation, this work also aimed to simulate the actual response of the tensile fluctuations measured in the real environment by mean of a finite element model (FEM). Field observations of skyline tensile forces included 103 work cycles, recorded over four different cable lines in standing skyline configuration. Payload estimations, carriages positions, and time study of the logging operations were also collected in the field. The ground profiles and the cable line geometries were analysed using digital elevation models. The field data were then used to simulate the work cycles in SkylineXL. The dynamic response of six fully-suspended loads in a single-span cable line was also simulated by a dedicated FEM built through ANSYS ®. The observed data and the software calculations were then compared. SkylineXL resulted particularly reliable in the prediction of the actual tensile forces, with RMSE ranging between 7.5 and 13.5 KN, linked to an average CV(RMSE) of 7.24%. The reliability in predicting the peak tensile forces was lower, reporting CV(RMSE) of 10.12%, but still not likely resulting in a safety or performance problem. If properly set-up and used, thus, SkylineXL could be considered appropriate for operational and practical purposes. This work, however, showed that finite element models could be successfully used for detailed analysis and simulation of the skyline tensile forces, including the dynamic oscillations due to the motion of the carriage and payload along the cable line. Further developments of this technique could also lead to the physical simulation and analysis of the log-to-ground interaction and the investigation of the breakout force during lateral skidding

Quantifying habitat selection and variability in habitat suitability for juvenile white sharks

While adult white sharks (Carcharodon carcharias) are apex predators with a circumglobal distribution, juvenile white sharks (JWS) feed primarily on bottom dwelling fishes and tend to be coastally associated. Despite the assumedly easier access to juveniles compared to large, migratory adults, limited information is available on the movements, environments, and distributions of individuals during this life stage. To quantify movement and understand their distribution in the southern California Bight, JWS were captured and fitted with dorsal fin-mounted satellite transmitters (SPOT tags; n = 18). Nine individuals crossed the U.S. border into Baja California, Mexico. Individuals used shallow habitats (134.96 +/- 191.1 m) close to shore (7.16 +/- 5.65 km). A generalized linear model with a binomial distribution was used to predict the presence of individuals based on several environmental predictors from these areas. Juveniles were found to select shallow habitats (\u3c 1000 m deep) close to land (\u3c 30 km of the shoreline) in waters ranging from 14 to 24 degrees C. Southern California was found to be suitable eight months of the year, while coastal habitats in Baja California were suitable year-round. The model predicted seasonal movement with sharks moving from southern California to Baja California during winter. Additionally, habitat distribution changed inter annually with sharks having a more northerly distribution during years with a higher Pacific Decadal Oscillation index, suggesting sharks may forego their annual fall migrations to Baja California, Mexico, during El Nino years. Model predictions aligned with fishery-dependent catch data, with a greater number of sharks being captured during periods and/or areas of increased habitat suitability. Thus, habitat models could be useful for predicting the presence of JWS in other areas, and can be used as a tool for potentially reducing fishery interactions during seasons and locations where there is increased susceptibility of incidental catch

Ecology of the Ocean Sunfish, Mola mola, in the southern California Current System

The common ocean sunfish, Mola mola, occupies a unique position in the eastern Pacific Ocean and the California Current Large Marine Ecosystem (CCLME) as the world\u27s heaviest, most fecund bony fish, and one of the most abundant gelativores. M. mola frequently occur as bycatch in fisheries worldwide and comprise the greatest portion of the bycatch in California\u27s large-mesh drift gillnet fishery. In this first long-term tagging study of any ocean sunfish species in the eastern Pacific, 15 M. mola (99 cm to 200 cm total length) were tagged in the southern California Bight (SCB) between 2003 and 2010 using 14 satellite pop-off archival tags (PATs) and one Fastloc Mk10 GPS tag. Ten tags provided positional data for a cumulative dataset of 349 tracking days during the months of july through March. Thirteen tags provided temperature and depth data. All M. mola remained within similar to 300 km of the coast, and nearly all exhibited seasonal movement between the SCB and adjacent waters off northern and central Baja California, Mexico. No tagged individuals were tracked north of the SCB. Tag depth data showed diel vertical migration and occasional deep (\u3e500 m) dives. Data from the Fastloc GPS tag allowed close examination of the relationship between the movements of the largest tagged ocean sunfish (2 m TL) and fine-scale oceanographic features. Near-instantaneous satellite sea surface temperature images showed this individual associated with upwelling fronts along its migration path, which exceeded 800 km and ranged from 6 to 128 km from the coast. Tag depth data showed active use of the water column within the frontal zones. Synthetic aperture radar (SAR) images demonstrated that surface slicks, which often indicate convergent circulation, coincided with this type of front. Zooplankton tows in the southern region of tracking off central Baja California, Mexico revealed dense populations of salps toward the warm side of these fronts. Satellite tag and ecosystem data suggest that bio-physical interactions in coastal upwelling fronts create favorable foraging habitat. (C) 2015 The Authors. Published by Elsevier B.V

Correction to: Assessment of cable tensile forces in active winch-assist harvesting using an anchor machine configuration

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Bridging disciplines to advance elasmobranch conservation: applications of physiological ecology

A strength of physiological ecology is its incorporation of aspects of both species\u27 ecology and physiology; this holistic approach is needed to address current and future anthropogenic stressors affecting elasmobranch fishes that range from overexploitation to the effects of climate change. For example, physiology is one of several key determinants of an organism\u27s ecological niche (along with evolutionary constraints and ecological interactions). The fundamental role of physiology in niche determination led to the development of the field of physiological ecology. This approach considers physiological mechanisms in the context of the environment to understand mechanistic variations that beget ecological trends. Physiological ecology, as an integrative discipline, has recently experienced a resurgence with respect to conservation applications, largely in conjunction with technological advances that extended physiological work from the lab into the natural world. This is of critical importance for species such as elasmobranchs (sharks, skates and rays), which are an especially understudied and threatened group of vertebrates. In 2017, at the American Elasmobranch Society meeting in Austin, Texas, the symposium entitled \u27Applications of Physiological Ecology in Elasmobranch Research\u27 provided a platform for researchers to showcase work in which ecological questions were examined through a physiological lens. Here, we highlight the research presented at this symposium, which emphasized the strength of linking physiological tools with ecological questions. We also demonstrate the applicability of using physiological ecology research as a method to approach conservation issues, and advocate for a more available framework whereby results are more easily accessible for their implementation into management practices