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Landing
Terms modified by Landing Selected AbstractsRANDOM PENALTIES AND RENEWABLE RESOURCES: A MECHANISM TO REACH OPTIMAL LANDINGS IN FISHERIESNATURAL RESOURCE MODELING, Issue 3 2009FRANK JENSEN Abstract Recent literature considers illegal landings a moral hazard problem that arises because individual landings are unobservable. The literature proposes incentive schemes to solve the information problem. However, most of the proposed schemes raise huge information requirements and social budget balance is not secured. In this paper, we suggest a random penalty mechanism that reduces the information requirements and secures budget balance in the case of a given number of licensed vessels. In the random penalty mechanism, aggregate landings are measured through stock sizes and the natural growth function. If aggregate landings are below optimal landings, each fisherman receives a subsidy. If aggregate catches are above optimal landings, the mechanism works such that either the fisherman is randomly selected and pays a fine or the fisherman is not selected and receives a subsidy. The fine and subsidy can be designed such that budget balance is secured. Provided risk aversion is sufficiently large and the fine is high enough, the random penalty mechanism will generate optimal individual landings. The budget balance combined with risk aversion drives the result for this advanced tax/subsidy system that does not exhaust the resource rents. The budget balance creates interdependence between fishermen that secure optimality. [source] Venezuela in the Eye of the Hurricane: Landing an Analysis of the Bolivarian RevolutionJOURNAL OF LATIN AMERICAN & CARIBBEAN ANTHROPOLOGY, Issue 1 2006Cristóbal Valencia RamírezArticle first published online: 28 JUN 200 Lower-class politics is rudimentary and dense; it takes place in the neighborhood, in the community, in places of production. Rarely is it granted the "honor" of being called "politics" by the canonic texts; instead, it is referred to as daily life, conversation, gossip, rumor or local conflict. [Gilly 2005:39] [source] TO DIVE OR NOT TO DIVE: SCUBA VERSUS ROV SAMPLING OF MACROALGAE AT 30M DEPTHJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Spalding, H. L. Moss Landing Marine Laboratories, 8272 Moss Landing, Rd., Moss Landing, CA 95039 USA Remotely Operated Vehicles (ROVs) and enriched air Nitrox SCUBA diving have recently become available to researchers for studying the deep-water environment. Each use a different technique for collecting macroalgal abundance data: ROVs use collections and high-resolution digital video which can be quantified using an integrative laser and computer imagery program (high tech), while divers often count the densities of individuals and use a point contact method for sampling percent (%) cover in situ (low tech). While the types of data collected by both techniques are the same, the effects of the different sampling methods on data resolution are unknown. As part of a larger study on deep-water macroalgae in central California, I compared the abundance of common macroalgae (% cover of macroalgal groups and individuals/m2) collected by divers and the ROV Ventana at a depth of 30m at 3 locations in central California. Generally, there were no significant differences between diver and ROV data in the % cover of coralline Rhodophyta, non-coralline Rhodophyta, and Pleurophycus gardneri/m2. The use of a laser-calibrated computer imagery program and an ROV with user-controlled lighting greatly decreased lab analysis time, and a method for sampling macroalgal layers with the ROV was developed. Thus, ROVs with high-resolution digital video and supplemental macroalgal collections can be used to quantify deep-water algae as accurately as in situ divers, but without the limited dive time, depth limits, and physical demands of the latter. [source] Ecospace utilization in early Phanerozoic deep-marine environments: deep bioturbation in the Blakely Sandstone (Middle Ordovician), Arkansas, USALETHAIA, Issue 2 2003PATRICK J. ORR Ichnofabric analysis of alternating light and dark-coloured mudstone layers in the Blakely Sandstone (Middle Ordovician) at Crystal Springs Landing, Lake Ouachita (west of Hot Springs, western Arkansas, USA) reveals two equilibrium palaeoichnocoenoses. The first was emplaced under variable, but low, oxygen levels during deposition of the dark-coloured layers; small diameter transition layer burrows overprint a mixed layer ichnofabric. The transition layer infauna was tiered with abundant Chondrites representing the deeper of two shallow tiers. Light-coloured layers accumulated during prolonged intervals in which the sediments were oxygenated to a greater extent and depth. Preservation of a mixed layer ichnofabric within them is the result of limited, but deep (up to at least 400 mm), reworking subsequently in the transition layer by an equilibrium community. These transition layer trace fossils are not tiered. If representative of oxygenated sediment columns in Ordovician deep-marine environments, an extensive volume of infaunal ecospace was colonized (in this case by deposit feeders); its more efficient use subsequently, including vertical partitioning of the infaunal community into specific environmental niches (tiering), could have accommodated increases in diversity and community complexity. Changes over time in the maximum depth to which sediments were bioturbated, alone, would therefore be a poor measure of the extent of ecospace utilization. [source] Documenting Loss of Large Trophy Fish from the Florida Keys with Historical PhotographsCONSERVATION BIOLOGY, Issue 3 2009LOREN McCLENACHAN arrecifes de coral; ecología histórica; directrices cambiantes; peces de arrecife; sobrepesca Abstract:,A loss of large vertebrates has occurred in aquatic and terrestrial ecosystems, but data to measure long-term population changes are sparse. Historical photographs provide visual and quantitative evidence of changes in mean individual size and species composition for groups of marine fish that have been targeted by sport fishing. I measured such trends for 13 groups of recreationally caught "trophy" reef fish with photographs taken in Key West, Florida, from 1956 to 2007. The mean fish size declined from an estimated 19.9 kg (SE 1.5) to 2.3 kg (SE 0.3), and there was a major shift in species composition. Landings from 1956 to 1960 were dominated by large groupers (Epinephelus spp.), and other large predatory fish were commonly caught, including sharks with an average length of just <2 m. In contrast, landings in 2007 were composed of small snappers (Lutjanus spp. and Ocyurus chrysurus) with an average length of 34.4 cm (SE 0.62), and the average length of sharks declined by more than 50% over 50 years. Major declines in the size of fish caught were not reflected in the price of fishing trips, so customers paid the same amount for a less-valuable product. Historical photographs provide a window into a more pristine coral reef ecosystem that existed a half a century ago and lend support to current observations that unfished reef communities are able to support large numbers of large-bodied fish. Resumen:,Una pérdida de vertebrados mayores ha ocurrido en ecosistemas acuáticos y terrestres, pero los datos para medir los cambios poblaciones a largo plazo son escasos. Las fotografías históricas proporcionan evidencia visual y cuantitativa de cambios en el tamaño individual promedio y de la composición de especies en grupos de peces marinos que han sido blanco de la pesca deportiva. Medí esas tendencias en 13 grupos de peces de arrecife capturados recreativamente como "trofeos" mediante fotografías tomadas en Key West, Florida, desde 1956 a 2007. El peso promedio de los peces declinó de unos 19.9 kg (ES 1.5) a 2.3 kg (ES 0.3), y hubo un cambio mayor en la composición de especies. Las capturas entre 1956 y 1960 estuvieron dominadas por meros (Epinephelus spp.) grandes, y otros peces depredadores eran capturados comúnmente, incluyendo tiburones con una longitud promedio de poco menos de 2m. En contraste, las capturas en 2007 fueron compuestas de pargos (Lutjanus spp. y Ocyurus chrysurus) pequeños con una longitud promedio de 34.4 cm (ES 0.62), y la longitud promedio de los tiburones declinó más de 50% en 50 años. La gran declinación en el tamaño de los peces capturados no se reflejó en los precios de los viajes de pesca, así que los clientes pagaron la misma cantidad por un producto menos valioso. Las fotografías históricas proporcionan una visión de un ecosistema arrecifal coralino prístino que existió hace medio siglo y proporcionan soporte a los comentarios actuales de que las comunidades arrecifales no explotadas son capaces de soportar numerosos peces de talla grande. [source] Landings, logbooks and observer surveys: improving the protocols for sampling commercial fisheriesFISH AND FISHERIES, Issue 2 2007A J R Cotter Abstract The sampling of commercial marine fisheries for management purposes often displays a key weakness in the form of poor documentation of the scientific basis of sampling and estimation, the assumptions made, and the practical constraints. This paper reviews systematically the theoretical and practical options that can remedy this situation and recommends that decisions be archived in regularly updated ,Sampling Approach and Modifications' (SAM) documents. Defining the target population, the observable population (usually a subset of the target), and the assumed links between them is important, along with the distinction between design- and model-based sampling approaches. Fleet-targeted and stock-targeted sampling strategies are contrasted, the latter being much harder to implement. Sampling protocols aimed at estimating quantities of fish landed and discarded, length,frequency distributions, length-related variables such as age, weight and maturity, and ratio variables such as catch per unit of effort and the proportions of discards are discussed, together with the raising of estimates to fleet and/or stock levels. The ideas are summarized in the specific contexts of landings sampling, logbook schemes and sea-going observer surveys. SAMs are commended for enhancing the scientific value of fishery sampling, and for encouraging methodological discussions among users and producers of the data. [source] Did lack of spawners cause the collapse of the European eel, Anguilla anguilla?FISHERIES MANAGEMENT & ECOLOGY, Issue 6 2003W. Dekker Abstract Since the 1980s, a 90% decline in recruitment of European eel, Anguilla anguilla (L.), has occurred across most of Europe. Whether the continental stock has equally declined is uncertain. This study compiles available landings statistics since the beginning of the 20th century and identifies trends over time and space, using a statistical model that takes varying levels of reporting into account. Landings in the pre-1940s reached over 40 000 tonnes yr,1, declined during World War II, rose to a peak of 40 000 tonnes yr,1 in the 1960s (coincident with a peak in re-stocking) and dropped to an all time low of <20 000 tonnes yr,1 in the 1990s. The decline in recruitment since the early 1980s was preceded by a decline in landings two or more decades earlier, indicating a decline of the continental stock. Considering the continental stock and the spawning stock must have declined in parallel, insufficient spawning stock biomass might have caused the recruitment collapse currently observed. [source] Trends in NE Atlantic landings (southern Portugal): identifying the relative importance of fisheries and environmental variablesFISHERIES OCEANOGRAPHY, Issue 3 2005KARIM ERZINI Abstract Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to identify trends and explore the relationships between the response variables (annual landings of 12 species) and explanatory variables [sea surface temperature, rainfall, an upwelling index, Guadiana river (south-east Portugal) flow, the North Atlantic oscillation, the number of licensed fishing vessels and the number of commercial fishermen]. Landings were more highly correlated with non-lagged environmental variables and in particular with Guadiana river flow. Both techniques gave coherent results, with the most important trend being a steady decline over time. A DFA model with two explanatory variables (Guadiana river flow and number of fishermen) and three common trends (smoothing functions over time) gave good fits to 10 of the 12 species. Results of other models indicated that river flow is the more important explanatory variable in this model. Changes in the mean flow and discharge regime of the Guadiana river resulting from the construction of the Alqueva dam, completed in 2002, are therefore likely to have a significant and deleterious impact on Algarve fisheries landings. [source] The role of olfactory stimuli in the location of weakened hosts by twig-infesting Pityophthorus spp.ECOLOGICAL ENTOMOLOGY, Issue 1 2001Pierluigi Bonello Summary 1. Senescing, shade-suppressed, or broken branches of Monterey pine Pinus radiata are infested by twig beetles in the genus Pityophthorus (Coleoptera: Scolytidae). The studies reported here tested whether twig beetles can discriminate between healthy and pitch canker-diseased branches, whether diseased branch tips produce more ethylene than undamaged controls, and whether ethylene and other volatiles, produced by the plant in response to tissue damage, are utilised by twig beetles in host location. 2. Significantly greater numbers of twig beetles were reared from pitch canker-symptomatic than from pitch canker-asymptomatic branches of Monterey pine collected in the field. 3. Needles of Monterey pine branches inoculated with the pitch canker fungal pathogen Fusarium circinatum produced significantly higher levels of ethylene than needles of control branches, and this was evident just prior to, and during, symptom expression. 4. In trapping studies in which pheromone production was prevented, there was no evidence of attraction of twig beetles to a source of ethylene alone, to cut host branches, or to cut branches treated with the ethylene-releasing compound, ethephon. The results suggest that twig beetles identify weakened branches after landing. [source] China and the UK EconomyECONOMIC OUTLOOK, Issue 5 2004Article first published online: 29 OCT 200 China's boom has been a major pillar of the global economic recovery from early 2002 onwards. However, earlier this year fears that the economic boom was threatening to run out of control prompted the Chinese authorities to implement a number of targeted measures to try to restrain activity in the most overheated sectors. This article by Simon Knapp discusses both how much the UK has benefited from the China boom and how much it might be affected if the Chinese slowdown now becomes a hard landing. It argues that emerging Asia, Japan and raw materials producers have been the principal beneficiaries of the China boom, while the UK's gains have been small, because exports to the whole of Asia only account for 9% of the total. Equally, looking forward, the UK, and the UK's two major trading partners, the US and Eurozone, would only be relatively lightly affected if Chinese growth decelerated rapidly, as they would be helped by offsets such as lower oil prices and a lower interest rate profile. However, the current evidence suggests that the Chinese economy is slowing down in broadly the way the government wants, with the greatest deceleration in the previously overheated sectors but relatively little impact on the export and consumer sectors. An abrupt halt in bank lending could, however, still pose a significant downside risk. [source] UK Assessment , What would be the impact of a US hard landing?ECONOMIC OUTLOOK, Issue 2 2001Article first published online: 9 OCT 200 [source] Companion planting , behaviour of the cabbage root fly on host plants and non-host plantsENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2005Kate Morley Abstract Six-hundred individual female cabbage root flies (Delia radicum L.) (Diptera: Anthomyiidae) were each observed for 20 min under laboratory conditions to record how they behaved after landing on a host or a non-host plant. Fly movements were recorded on host plants [cabbage ,Brassica oleracea var. capitata (Cruciferae)] and non-host plants [clover ,Trifolium subterraneum L. (Papilionaceae)] surrounded by bare soil and on cabbage surrounded by clover. The most frequently observed behaviours made by the flies were (1) hops/spiral flights and (2) walks/runs. In the bare soil situation, the 50 individual flies observed in each treatment made 66 hops/spiral flights on the cabbage and 94 on the clover. When the two plants were tested together the movements were not additive as, instead of the expected 160 hops/spiral flights in the mixed plant treatment, the flies made 210 hops/spiral flights when they landed initially on cabbage but only 130 when they landed initially on clover. Few of the flies that landed initially on clover moved onto the host plant, even though the host plant was only a few centimetres away. The duration of the individual walks and runs made by the cabbage root flies were similar on both the host and non-host plants. The only differences were the numbers of walks/runs made and the time the flies remained inactive. On the host plants, the females made four walks/runs, each of about 12 s duration, interspersed by rest periods that totalled 1.5 min. In contrast, on the non-host plants the females made 10 walks/runs, each of about 9 s duration, interspersed by rest periods that totalled 7 min. Therefore, after landing on a plant, the flies, on average, left the host plant after 2.25 min and the non-host plant after 8.5 min. Our conclusion is that the protracted time spent on the non-host plants is the mechanism that disrupts insects from finding host plants in diverse plantings. Hence, the flies were arrested by non-host plants rather than being repelled or deterred as suggested in earlier studies. [source] Repellent efficacy of wood vinegar against Culex pipiens pallens and Aedes togoi (Diptera: Culicidae) under laboratory and semi-field conditionsENTOMOLOGICAL RESEARCH, Issue 2 2010Martha W. KIARIE-MAKARA Abstract The repellent efficacy of wood vinegar was assessed against mosquitoes under laboratory conditions at 1, 5, 10, 20, 40, 60 and 80% concentrations. The study evaluated whether wood vinegar is able to repel Culex pipiens pallens Coquillet and Aedes togoi (Theobald) from the human body and if so at what concentrations. The tests were conducted using the arm-in-cage method in 80 × 40 × 40 cm screened mosquito cages. The data were analyzed and compared with those of N,N-Diethyl-3-methylbenzamide (deet) at 10.3% concentration. The results showed that wood vinegar provided mosquito repellence of varying degree depending on the concentration used. The observed repellence averaged from as low as 39.6% at 5.0% concentration to as high as 100% at 80% concentration against Ae. togoi. Repellence against Cx. pipiens pallens was high being 90.3% at 20% concentration, 92.2% at 40% concentration, 93.9% at 60% concentration and 100% at 80% concentration. The duration of protection time tests showed that the 40% and 60% concentrations of the wood vinegar give protection from landing of Ae. togoi for a period of up to 7 h, though the lower concentration gave lower protection after the first five hours. The results indicated that wood vinegar has mosquito repellent characteristics that tend to vary with the concentration used and the species of mosquitoes. Wood vinegar in this case was very effective in repelling Cx. pipiens pallens, even at lower concentrations while higher concentrations were required to repel Ae. togoi. [source] The risk of a horse-and-rider partnership falling on the crosscountry phase of eventing competitionsEQUINE VETERINARY JOURNAL, Issue 2 2006J. K. Murray Summary Reasons for performing study: Fatalities resulting from horse falls occurring during the cross-country phase of eventing competitions initiated epidemiological investigation of the risk factors associated with horse falls. Objectives: To identify variables that increased or decreased the risk of a horse fall during the cross-country phase of an eventing competition. Methods: Data were collected from randomly selected British Eventing competitions held in Great Britain during 2001 and 2002. Data were obtained for 173 cases (jumping efforts resulting in a fall of the horse-and-rider partnership) and 503 matched controls (jumping efforts not resulting in a fall). The risk of falling was modelled using conditional logistic regression. Results: An increased risk of a horse fall was associated with jumping into or out of water; taking off from good-to-soft, soft or heavy ground; fences with a drop landing; nonangled fences with a spread ,2 m; and angled fences. Other risk factors included riders who knew that they were in the lead within the competition before the cross-country phase; an inappropriate speed of approach to the fence (too fast or too slow); horse-and-rider partnerships that had not incurred refusals at earlier fences; and riders who received cross-country tuition. Conclusions: This study has identified modifiable course- and fence-level risk factors for horse falls during the cross-country phase of eventing competitions. The risk of horse and rider injury at eventing competitions should be reduced by 3 simple measures; maintaining good to firm take-off surfaces at fences, reducing the base spread of fences to <2 m and reducing the use of fences at which horses are required to jump into or out of water. Risk reduction arising from course and fence modification needs to be confirmed by intervention studies. Potential relevance: Knowledge of factors that increase or decrease the risk of a horse fall can be used by UK governing bodies of the sport to reduce the risk of horse falls on the cross-country phase of eventing competitions, and reduce the risk of horse and rider injuries and fatalities. As one in 3 horses that fall injure themselves and one in 100 horse falls results in fatality to the horse, we suggest that immediate consideration is given to these recommendations. [source] Joint moments in the distal forelimbs of jumping horses during landingEQUINE VETERINARY JOURNAL, Issue 4 2001L. S. MEERSHOEK Summary Tendon injuries are an important problem in athletic horses and are probably caused by excessive loading of the tendons during demanding activities. As a first step towards understanding these injuries, the tendon loading was quantified during jump landings. Kinematics and ground reaction forces were collected from the leading and trailing forelimbs of 6 experienced jumping horses. Joint moments were calculated using inverse dynamic analysis. It was found that the variation of movement and loading patterns was small, both within and between horses. The peak flexor joint moments in the coffin and fetlock joints were larger in the trailing limb (,0.62 and ,2.44 Nm/kg bwt, respectively) than in the leading limb (,0.44 and ,1.93 Nm/kg bwt, respectively) and exceeded literature values for trot by 82 and 45%. Additionally, there was an extensor coffin joint moment in the first half of the stance phase of the leading limb (peak value 0.26 ± 0.18 Nm/kg bwt). From these results, it was concluded that the loading of the flexor tendons during landing was higher in the trailing than in the leading limb and that there was an unexpected loading of the extensor tendon in the leading limb. [source] The artisanal fishery fleet of the lower AmazonFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2008V. J. ISAAC Abstract, The present study analyses temporal trends in the characteristics of the artisanal fleet landing at ports in the city of Santarém (lower Amazon) from 1993 to 2003. A total of 2714 boats visited the city, accounting for more than 76 000 landings. Of these, 1952 were fishing boats; the others were buyer boats, specialised in the purchase of fish in rural areas for resale in Santarém. The activity involves more than 13 000 fishermen. Fishing boats are made of wood, are on average 11 m long and powered by a 20 hp outboard motor. Boats operate with an average of six to seven fishermen, spending 6 days per trip and catching between 300 and 800 kg of fish. Most variability in yield can be explained by the ice consumed (70%), the number of fishermen trip,1 (19%), fuel consumed (4%) and days spent fishing (3%). The yield changed according to the size, origin and type of boat. Fishing boats coming from more distant locations, in the state of Amazonas, performed better than those from Santarém. Total yield declined slightly during the study period. Mean age of fishing boats and fishing power is increasing. Consumption of ice and fuel by trip, number of fishermen trip,1 and mean days fishing showed positive trends. Financial subsidies from governmental agencies are criticised. Fleet performance and management options are discussed. [source] Haemorrhage into a popliteal cyst: an unusual complication of haemophilia AHAEMOPHILIA, Issue 5 2002V. Rodriguez Summary. ,A 7½-year-old boy with severe haemophilia A had increasing discomfort and pain in his left knee after sledding on ice and landing on his knees. Left knee pain persisted for days despite recombinant factor VIII replacement. Imaging studies showed that by day 10 a popliteal cyst had ruptured, with diffusion of blood into the calf muscles. This case illustrates another possible bleeding complication in patients with a bleeding disorder and a popliteal cyst. [source] Crinkling Ultralong Nanotubes: Crinkling Ultralong Carbon Nanotubes into Serpentines by a Controlled Landing Process (Adv. Mater.ADVANCED MATERIALS, Issue 41 200941/2009) A rational approach to crinkling ultralong CNTs into serpentine geometries by controlling their landing on a quartz substrate is demonstrated by Jin Zhang and co-workers on p. 4158. Using this method, the length, density, and number of parallel CNT segments in the serpentine CNTs were significantly increased. When incorporated into ultrahigh-current devices, the performance of the devices could be improved by increasing the number of parallel segments in the serpentine CNT arrays. [source] Crinkling Ultralong Carbon Nanotubes into Serpentines by a Controlled Landing ProcessADVANCED MATERIALS, Issue 41 2009Yagang Yao Serpentine carbon nanotubes (CNTs) are successfully synthesized by controlling the landing of ultralong CNTs on a quartz surface. Several experimental parameters are investigated and the growth mechanism is further clarified (see figure). It is demonstrated that the high on/off ratio of single CNTs is maintained when serpentine CNTs are used to produce ultrahigh-current CNT-based devices. [source] Comparative activity pattern during foraging of four albatross speciesIBIS, Issue 1 2002Henri Weimerskirch The activity patterns of foraging Yellow-nosed Diomedea chlororhynchos, Sooty Phoebetria fusca, Black-browed D. melanophris impavida and Grey-headed Albatross D. chrysostoma were compared using loggers recording the timing of landing and take-offs, as well as the duration of bouts in flight or on the water, and the overall time spent in flight. The four species spent a similar proportion of their foraging time in flight (56,65%). During the day they were mostly flying (77,85% of the daylight period) whereas at night they were mainly (61,71%) sitting on the water. The amount of time spent in flight during the daytime foraging period was related to the amount of time spent sitting on the water at night. Differences between species occurred in the duration of bouts in flight and on the water as well as in the frequency of landings and in the time elapsed between successive landings. Yellow-nosed Albatrosses were more active than the other species, with more frequent short bouts in flight and more frequent successive landings at short intervals. Sooty Albatrosses landed or took-off less often than the other species and were more active just before dusk. Black-browed and Grey-headed Albatrosses were more active at night, especially the first part of the night and far from the colonies. Their trips consisted of a commuting part and a foraging part. Black-browed Albatrosses landed more often during the foraging than the commuting part, suggesting that they were not searching when travelling. The study suggests that there is no fundamental difference between the overall activity budgets of the four species although they show distinctive diet, morphology and life history traits. The differences observed between the four species were related mainly to differences in foraging technique. Comparison with the Wandering Albatross, the only species for which data were available previously, suggest that this larger species might differ completely in foraging technique from the smaller albatrosses. [source] Flight control of a rotary wing UAV using backsteppingINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 6 2010Bilal Ahmed Abstract This paper presents a novel application of backstepping controller for autonomous landing of a rotary wing UAV (RUAV). This application, which holds good for the full flight envelope control, is an extension of a backstepping algorithm for general rigid body velocity control. The nonlinear RUAV model used in this paper includes the flapping and servo dynamics. The backstepping-based controller takes advantage of the ,decoupling' of the translation and rotation dynamics of the rigid body, resulting in a two-step procedure to obtain the RUAV control inputs. The first step is to compute desired thrusts and flapping angles to achieve the commanded position and the second step is to compute control inputs, which achieve the desired thrusts and flapping angles. This paper presents a detailed analysis of the inclusion of a flapping angle correction term in control. The performance of the proposed algorithm is tested using a high-fidelity RUAV simulation model. The RUAV simulation model is based on miniature rotorcraft parameters. The closed-loop response of the rotorcraft indicates that the desired position is achieved after a short transient. The Eagle RUAV control inputs, obtained using high-fidelity simulation results, clearly demonstrate that this algorithm can be implemented on practical RUAVs. Copyright © 2009 John Wiley & Sons, Ltd. [source] A backstepping controller for path-tracking of an underactuated autonomous airshipINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 4 2009José Raul Azinheira Abstract In this paper we propose a nonlinear control approach for the path-tracking of an autonomous underactuated airship. A backstepping controller is designed from the airship nonlinear dynamic model including wind disturbances, and further enhanced to consider actuators saturation. Control implementation issues related to airship underactuation are also addressed, namely control allocation and an attitude reference shaping to obtain a faster error correction with smoother input requests. The results obtained demonstrate the capacity of an underactuated unmanned airship to execute a realistic mission including vertical take-off and landing, stabilization and path-tracking, in the presence of wind disturbances, with a single robust control law. Copyright © 2008 John Wiley & Sons, Ltd. [source] Transformation of the pectoral girdle in the evolutionary origin of frogs: insights from the primitive anuran DiscoglossusJOURNAL OF ANATOMY, Issue 1 2006Pavla Havelková Abstract Using cleared-and-stained whole mounts and computer-aided three-dimensional reconstructions made from serial histological sections, we studied the development of the pectoral girdle in Discoglossus pictus, an extant member of an ancient frog lineage, represented for example by Eodiscoglossus from the Middle Jurassic to Early Cretaceous periods in Europe. Basic developmental features were compared with those of extinct Temnospondyli, considered to be the most probable anuran ancestors, and with Triadobatrachus, an early Triassic proanuran. In the endochondral girdle, the separate scapula and coracoid of Discoglossus and other anurans (completed by suprascapular and procoracoid cartilages) evolved from the compact scapulocoracoid of temnospondyls by paedomorphosis. In parallel, the dermal ossifications of the girdle were reduced to a small clavicle and cleithrum. The overall reduction in ossification of the anuran pectoral girdle supports the hypothesis of a paedomorphic origin for Anura. The almost simultaneous appearance of dermal and endochondral ossifications may be explained by the accumulation of developmental events during a short, distinct metamorphosis (which did not occur in neotenic temnospondyls living permanently in water). The sternal elements seem to be neomorphs for the most part, which help to cushion the shock of landing in jumping anurans but which also evolved as functional substitutes (insertion area for the pectoralis muscles) of the temnospondyl interclavicle. [source] The role of prey size and abundance in the geographical distribution of spider socialityJOURNAL OF ANIMAL ECOLOGY, Issue 5 2007KIMBERLY S. POWERS Summary 1Social species in the spider genus Anelosimus predominate in lowland tropical rainforests, while congeneric subsocial species occur at higher elevations or higher latitudes. 2We conducted a comparative study to determine whether differences in total biomass, insect size or both have been responsible for this pattern. 3We found that larger average insect size, rather than greater overall biomass per se, is a key characteristic of lowland tropical habitats correlating with greater sociality. 4Social species occupied environments with insects several times larger than the spiders, while subsocial species nearing dispersal occupied environments with smaller insects in either high or low overall biomass. 5Similarly, in subsocial spider colonies, individuals lived communally at a time when they were younger and therefore smaller than the average insect landing on their webs. 6We thus suggest that the availability of large insects may be a critical factor restricting social species to their lowland tropical habitats. [source] The seasonal abundance of blowflies infesting drying fish in south-west IndiaJOURNAL OF APPLIED ECOLOGY, Issue 2 2001R. Wall Summary 1Blowfly infestation of sun-drying fish is a major economic problem in many developing countries of Asia, Africa and the Pacific. To consider the ecology of infestation, adult and larval blowfly populations were monitored between 27 October 1997 and 27 April 1999 at a fish landing and drying site, approximately 5 km north of Calicut, in Kerala state on the coast of south-west India. 2During the 548-day sampling period, a total of 96 953 adult Diptera was collected from 16 sticky targets, placed inside and outside eight fish-storage sheds. Of these, 91 912 (95%) were Chrysomya megacephala, 3719 (4%) were other Calliphoridae and 1322 (1%) were other species, largely Sarcophagidae. 3The population of C. megacephala showed pronounced seasonal fluctuations in response to climate, particularly relative humidity. Significantly shorter-frequency fluctuations within fish-processing sheds were also evident, the periodicity of which corresponded approximately to C. megacephala generation cycles. Spatial variation in C. megacephala abundance was evident within the site, higher populations occurring closest to the beach and numbers declining with distance inland. 4The pattern of drying fish infestation by C. megacephala broadly followed changes in the density of adult flies and the seasonal change in weather, with peaks during the monsoon and troughs in the dry hot periods. High relative humidity played a significant but secondary role in increasing infestation. 5Quantification of the relationship between larval infestation and percentage fish loss suggests that, given the infestation levels observed, between 10% and 60% post-harvest wet weight losses would be expected in the monsoon period, depending on the species of fish landed. 6The study emphasizes the importance of developing a clear understanding of the basic ecology and spatial and temporal dynamics of an insect pest, prior to the design or implementation of any pest management programme. [source] CONOPS and autonomy recommendations for VTOL small unmanned aerial system based on Hurricane Katrina operationsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8 2009Kevin S. Pratt This field study examines vertical takeoff and landing (VTOL) small unmanned aerial system (SUAS) operations conducted as part of an 8-day structural inspection task following Hurricane Katrina in 2005. From the observations of the 32 flights spread over 12 missions, four key findings are identified for concept of operations (CONOPS) and the next level of artificial intelligence for rotary-wing SUASs operating in cluttered urban environments. These findings are (1) the minimum useful standoff distance from inspected structures is 2,5 m, (2) omnidirectional sensor capabilities are needed for obstacle avoidance, (3) global positioning system waypoint navigation is unnecessary, and (4) these operations require three operators for one SUAS. Based on the findings and other observations, a crewing organization and flight operations protocol for SUASs are proposed. Needed directions in research and development are also discussed. These recommendations are expected to contribute to the design of platforms, sensors, and artificial intelligence as well as facilitate the acceptance of SUASs in the workplace. © 2009 Wiley Periodicals, Inc. [source] Vision-aided inertial navigation for pin-point landing using observations of mapped landmarksJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2007Nikolas Trawny In this paper we describe an extended Kalman filter algorithm for estimating the pose and velocity of a spacecraft during entry, descent, and landing. The proposed estimator combines measurements of rotational velocity and acceleration from an inertial measurement unit (IMU) with observations of a priori mapped landmarks, such as craters or other visual features, that exist on the surface of a planet. The tight coupling of inertial sensory information with visual cues results in accurate, robust state estimates available at a high bandwidth. The dimensions of the landing uncertainty ellipses achieved by the proposed algorithm are three orders of magnitude smaller than those possible when relying exclusively on IMU integration. Extensive experimental and simulation results are presented, which demonstrate the applicability of the algorithm on real-world data and analyze the dependence of its accuracy on several system design parameters. © 2007 Wiley Periodicals, Inc. [source] A review of host finding behaviour in the parasitic sea louse, Lepeophtheirus salmonis (Caligidae: Copepoda)JOURNAL OF FISH DISEASES, Issue 1 2009A J Mordue (Luntz) Abstract Ectoparasitic sea lice are the most important parasite problem to date for the salmon farming industry in the northern and southern hemispheres. An understanding of host location in the specialist species, Lepeophtheirus salmonis, the most important louse species in the North Atlantic, is now being realized using behavioural in vitro and in vivo bioassays coupled with chemical analysis of fish conditioned waters. Both physical and chemical cues are important in host location. Responses of sea lice to physical cues such as light and salinity may enable them to gather in areas where host fish are likely to be found. Mechanoreception is an important sensory modality in host location and acts by switching on specific behaviours that enable landing on a fish. Chemoreception plays a defining role in host location and recognition. The detection of host kairomones switches on ,host search' behavioural patterns and also induces landing responses whereas non-host kairomones fail to induce attraction or significant landing behaviour. Semiochemicals derived from salmon and also non-host fish have been identified, and may prove useful for the development of integrated pest management strategies, by the introduction of odour traps for monitoring lice numbers, and by the use of stimulo-deterrent diversionary (push:pull) strategies in their control. [source] Gender differences in hip adduction motion and torque during a single-leg agility maneuverJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2006Timothy E. Hewett Abstract The purpose of this study was to identify gender differences in hip motion and kinetics during a single leg bidirectional deceleration maneuver. The rationale for the development of this maneuver was to test dynamic hip control during the deceleration of three different types of single-leg landings. The hypothesis was that female athletes would display increased hip adduction angles and moments during the maneuver compared to male athletes. Thirty-six collegiate soccer players (19 female, 17 male) volunteered to participate. Subjects were instructed to start the maneuver balancing on one foot, to hop through an agility-speed ladder on the same leg "up two boxes, back one, and then up one and hold it." Hip kinematics and kinetics during all three landings were examined. Females demonstrated significantly greater hip adduction angles at initial contact during all three landings and greater maximal hip adduction during landings 1 and 2 compared to male athletes. Females also exhibited significantly increased external hip adduction moments during landing 1, however, no differences were found between genders during landings 2 and 3. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:416,421, 2006 [source] Nonweight-bearing anterior knee laxity is related to anterior tibial translation during transition from nonweight bearing to weight bearingJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2006Sandra J. Shultz Abstract We examined the relationship between anterior knee laxity (AKL), evaluated while the knee was nonweight bearing, and anterior translation of the tibia relative to the femur (ATT), evaluated when the knee transitioned from nonweight-bearing to weight-bearing conditions in response to an applied compressive load at the foot. Twenty subjects with normal knees (10 M, 10 F; 25.2,±,4.1 years, 169.8,±,11.5 cm, 71.6,±,16.9 kg) underwent measurements of AKL and ATT of the right knee on 2 days. AKL was measured at 133N with the KT-2000Ô. ATT was measured with the Vermont Knee Laxity Device and electromagnetic position sensors attached to the patella and the anteromedial aspect of the proximal tibia. Three trials for each measure were averaged and analyzed. Measurement consistency was high for both AKL (ICC,=,0.97; SEM,=,0.44 mm) and ATT (ICC,=,0.88; SEM,=,0.84 mm). Linear regression revealed that AKL predicted 35.5% of the variance in ATT (p,=,0.006), with a prediction equation of YATT,=,3.20,+,0.543(XAKL). Our findings suggest that increased AKL is associated with increased ATT as the knee transitions from nonweight-bearing to weight-bearing conditions. The potential for increased knee joint laxity to disrupt normal knee biomechanics during activities such as landing from a jump, or the foot strike phase of gait deserves further study. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:516,523, 2006 [source] | ||||||||||||||||||||||||||||||||||||||||||||||