4,788 research outputs found
Global wave-induced loads in abnormal waves: comparison between experimental results and classification society rules
No full textIt is important to assess the consequences of ship encounters with abnormal waves due to the perceived dangers of such encounters. A starting point for this is the assessment of global loads, with a focus on examining how the design rules fare with respect to loads induced by abnormal wave encounters. This paper presents the results of an experimental investigation into the global wave induced loads experienced in a range of abnormal sea states. Results are obtained for a segmented, flexible backbone model of a typical naval frigate. Abnormal wave encounters result in a significant increase in the global wave-induced loads compared to the equivalent random sea, with slamming becoming considerably more severe. Through comparisons with the experimental measurements it is concluded that the design rules which allow for an extreme wave encounter provide a reasonable safety margin for the global loads in abnormal waves, although discrepancies occur towards the aft of the vessel. Further investigation of the amount and conditions in which the design rules may be exceeded by an abnormal wave encounter is require
The influence of forward speed on ship motions in abnormal waves: experimental measurements and numerical predictions
No full textShip encounters with abnormal waves are increasingly well documented and it is therefore important to be able to model such encounters in order to assess the risks involved and whether there is a requirement for more stringent design rules.This paper presents the results of an experimental investigation into the influence of abnormal waves on a vessel travelling with forward speed in irregular seas. The vessel studied in this case is a naval frigate travelling at a range of speeds. To put the motions measured in abnormal waves into context comparisons are made to those in random seas with a variety of significant wave heights, both non-severe and severe. A further objective is to compare experimental measurements with motion predictions from both a two-dimensional linear strip theory and a three-dimensional partly nonlinear seakeeping model.Results demonstrate that abnormal waves may not necessarily be the worst conditions that a ship can encounter. However, accelerations derived from the rigid body motions appear to be in excess of rules values. This has implications for design due to the unexpected nature of abnormal wave occurrence and the consequent likelihood of encountering such a wave at a higher speed (hence in a more severe operating condition) than a random sea of an equivalent height.The three-dimensional partly nonlinear model demonstrates improved agreement with experimental measurements of rigid body motions, compared to the two-dimensional strip theory. It is therefore considered to have greater potential as a design tool for abnormal wave encounters. Further validation with a wide range of sea states and vessel types is required.<br/
A comparison of abnormal wave generation techniques for experimental modelling of abnormal wave-vessel interactions
No full textThe ability to model abnormal waves in an accurate and repeatable manner is important in order to achieve the objective of assessing vessel response in such conditions.Although techniques for the practical generation of abnormal waves are readily available in literature, no comparison of their suitability to modelling abnormal waves experimentally is available. The purpose of this paper is to provide such a comparison. Identified techniques are the NewWave, constrained NewWave and optimised sea, all based on sea spectra. A particular focus is the usefulness of each technique for modelling a travelling vessel encountering an abnormal wave. Experimental results are presented for each model compared to linear and second order wave theories, and the quality of results is assessed using an uncertainty analysis. Results demonstrate the constrained NewWave is highly repeatable, but suffers from discrepancies in the time domain when compared to predicted profiles. In order to generate a known wave profile, the NewWave or optimisation techniques appear the most suitable. Of these, NewWave should be used if only the local (abnormal) wave profile is required. To model a realistic scenario including the response history of a vessel, the optimised sea should be applied.<br/
Nesophrosyne ogradyi Bennett, sp. nov.
No full text<i>Nesophrosyne ogradyi</i> Bennett sp. nov. <p>(Fig. 8 a–g)</p> <p> <b>Diagnosis.</b> Length: male = 4.17mm, female = 5.65mm. A paler species than <i>N. broussaisiai</i>. Clavus entirely pale or with three spots, with a central round saddle mark flanked by lateral pale marks (Fig. 8 a). Pronotum posterior 1/2 pale. Genitalia matching species group description (Fig. 8 b–g). Endemic to East Maui, Haleakalā windward face.</p> <p> <b>Distribution.</b> USA: Hawaiian Islands, Maui, Haleakalā windward face,> 910m, wet forest (Fig. 3)</p> <p> <b> Measurements. <i>Body length</i></b> : Male (n=10) = 4.17mm (4.00mm– 4.30mm); Female (n=10) = 5.65mm (5.50mm – 5.80mm). <i>Genitalia</i> (n=5): Pygofer = 0.57mm (0.56mm – 0.58mm); Style = 0.47mm (0.46mm – 0.48mm); Connective = 0.27mm (0.26mm – 0.28mm); Aedeagus lateral length = 0.31mm (0.30mm – 0.33mm); Aedeagus posterior height = 0.16mm (0.15mm – 0.17mm).</p> <p> <b> Material examined. <i>Type Material</i></b> : Holotype: 1 male, Hawaiian Islands, East Maui, Waikamoi Forest Reserve, Heed Trail, N20 o 48.638 W156 o 14.509, Elevation: 1310m, 31July2009. Host Plant: <i>Broussaisia arguta</i>. Coll. G.M. Bennett, P.M. O’Grady, K.M. Magnacca. Deposited in the BPBM, Honolulu, Hawai’i. Type #: 17305. <i>Additional Material</i>: 13 males, 17 females, Hawaiian Islands, East Maui, Makawao Forest Preserve, N20 o 48.638 W156 o 14.509, Elevation: 1310m, 31July2007, 6Aug2007, 6June2009. Host Plant: <i>Broussaisia arguta</i>. Coll. G.M. Bennett. Deposited in the BPBM, Honolulu, Hawai’i. 2 males, 2 females, Hawaiian, Islands, East Maui, Waikamoi Forest Reserve, N20 o 48.397 W156 o 15.295, Elevation: 1300m, 1June2009. Host Plant: <i>Broussaisia arguta</i>. Coll. G.M. Bennett. P.M. O’Grady, K.M. Magnacca. Deposited in the BPBM, Honolulu, Hawai’i. 5 males, Hawaiian Islands, Maui, Haleakalā, Pu’u O Kakai, TNCH, Waikamoi Preserve, N20o 48’00” W156o 14’44”, Elevation: 1500m, 16May2003. Host Plant: <i>Broussaisia arguta</i>. Coll: D.A. Polhemus. Deposited in D.A. Polhemus’s personal collection at the Smithsonian, Washington D.C.</p> <p> <b>Etymology.</b> This species is named after Dr. Patrick O’Grady (Hawaiian Dipterologist) for his invaluable contributions to this project and for his positive scientific mentorship of G.M. Bennett.</p> <p> <b>Discussion.</b> <i>Nesophrosyne ogradyi</i> represents a lighter form than <i>N. broussaisiai</i>. External morphology is nearly identical to <i>N. kaupoi</i>. <i>Nesophrosyne kaupoi</i> is distinguishable from <i>N. ogradyi</i> by its absent apical processes.</p>Published as part of <i>Bennett, Gordon M & O'Grady, Patrick M, 2011, Review of the native Hawaiian leafhopper genus Nesophrosyne (Hemiptera: Cicadellidae: Deltocephalinae) with description of eight new species associated with Broussaisia arguta (Hydrangeaceae), pp. 1-25 in Zootaxa 2805</i> on page 17, DOI: <a href="http://zenodo.org/record/207804">10.5281/zenodo.207804</a>
The influence of abnormal waves on global wave-induced loads
No full textAbnormal wave encounters can result in significant damage to, or loss of, a vessel. There is a need to identify the risks to a vessel when encountering abnormal waves, from a structural viewpoint. This paper approaches this need, by carrying out an experimental investigation of rigid body motions and global wave-induced loads experienced by a ship in abnormal waves and using the findings to validate a two-dimensional linear hydroelasticity model. Experiments were conducted using a segmented, flexible backbone model in regular and irregular (random and abnormal) sea states, at forward speed. Abnormal sea states were generated using a previously developed optimisation technique. Measurements were made of symmetric motions and the vertical bending moment at various locations along the ship. The influence of slamming on the severity of abnormal wave encounters is discussed
Nesophrosyne broussaisiai Bennett, sp. nov.
No full text<i>Nesophrosyne broussaisiai</i> Bennett sp. nov. <p>(Fig. 7 a)</p> <p> <b>Diagnosis.</b> Length: male = 4.22mm, female = 5.21mm. A dark species, with three conspicuous pale spots on clavus. Clavus with a central round pale saddle mark, anteriorally flanked by lateral symmetrical pale marks, sometimes showing as clear patches along clavus (see Fig. 7 a); darkest forms with only a central saddle mark. Crown and pronotum with posterior pale bands. Genitalia matching species group description (see Fig. 8 b–g). Endemic to West Maui.</p> <p> <b>Distribution.</b> USA: Hawaiian Islands, Maui, West Mauna Kahalawai, Pu’u Kukui, ~ 1220m, wet forest (Fig. 3).</p> <p> <b> Measurements. <i>Body length</i></b> (n=5): Male (n=5) = 4.22mm (4.15mm – 4.30mm); Female (n=8) = 5.21mm (5.10mm – 5.40mm). <i>Genitalia</i> (n=5): Pygofer = 0.57mm (0.55mm – 0.59mm); Style = 0.47mm (0.46mm – 0.48mm); Connective = 0.28mm (0.27mm – 0.29mm); Aedeagus lateral length = 0.35mm (0.34mm – 0.37mm); Aedeagus posterior height = 0.15mm (0.14mm – 0.16mm).</p> <p> <b>Material examined.</b> <i>Type Material</i>: Holotype: 1 male, Hawaiian Islands, West Maui, Mauna Kahalawai, Pu’u Kukui, Boardwalk Trail, N20 o 56.078 W156 o 36.985, Elevation: 1220m, 23Nov2009. Host Plant: <i>Broussaisia arguta</i>. Coll. G.M. Bennett, K. Magnacca, P.M. O’Grady. Deposited in the BPBM, Honolulu, Hawai’i. Type #: 17304. <i>Additional Material</i>: 12 males, 11 females, Hawaiian Islands, West Maui, Mauna Kahalawai, Pu’u Kukui, Boardwalk Trail, N20 o 56.078 W156 o 36.985, Elevation: 1220m, Elevation: 940m, 23Nov2009, 7Aug2007, Coll. G.M. Bennett, K. Magnacca, P.M. O’Grady. Deposited in the BPBM, Honolulu, Hawai’i. 1 female, Hawaiian Islands, West Maui, Wet Forest below Nakalalua, Pu’u Kukuii Trail, 1220m, 26May2004. N20o 54’58” W156o 35’37”, Coll: DA Polhemus. Deposited in D.A. Polhemus’s personal collection at the Smithsonian, Washington D.C.</p> <p> <b>Etymology.</b> The name chosen for this species refers to the host plant genus name it occurs on, <i>Broussaisia</i>.</p> <p> <b>Discussion.</b> This species is nearly indistinguishable from the East Maui sibling species. Morphologically, the only character that distinguishes <i>N. broussaisiai</i> is the variable color pattern on the clavus, which is generally darker.</p>Published as part of <i>Bennett, Gordon M & O'Grady, Patrick M, 2011, Review of the native Hawaiian leafhopper genus Nesophrosyne (Hemiptera: Cicadellidae: Deltocephalinae) with description of eight new species associated with Broussaisia arguta (Hydrangeaceae), pp. 1-25 in Zootaxa 2805</i> on pages 16-17, DOI: <a href="http://zenodo.org/record/207804">10.5281/zenodo.207804</a>
Electrically generated indistinguishable and entangled photon pairs
No full textWe present measurements on electrically generated photons from a quantum dot in an LED structure, showing high entanglement fidelity and two-photon interference visibility, both necessary requirements for scalable quantum communication and logic
A wireless sensor network for measuring ship responses in abnormal waves
No full textThe responses of a ship to abnormal waves are of considerable importance due to the severe nature of such wave-ship encounters. To fully investigate the influence of abnormal waves on ship design, experimental investigations need to include both the directional aspect of abnormal waves and the forward speed of the vessel.This paper presents the development of a novel wireless sensor network as an alternative to conventional towing tank methods for recording rigid body motions, accelerations and distortions in regular and irregular waves, including the influence of abnormal waves. Key advantages of such sensors are that they are lightweight, capable of providing a large range of information from an individual test, and are a simple method that allows the measurement of responses of a model in directional seas (either a wave basin or open water) without the limitation of a shore-based acquisition system.Use of the wireless sensor network is validated in towing tank experiments via regular wave seakeeping tests, and tests in random and abnormal waves. Results show good agreement with conventional acquisition methods, although some improvement in the method of obtaining heave is desirable. In addition, a discussion is included of the influence of abnormal waves on ship responses.Overall the wireless sensor network shows significant potential for obtaining responses a ship in a range of sea states. There is good agreement with responses measured using conventional techniques and levels of uncertainty are low, in general less than 5%. The integration of additional hardware such as synchronised video provides a useful tool for visualising wave encounters
Measurement of ship hydroelastic response using multiple wireless sensor nodes
No full textA measurement system is required for the assessment of the structural and kinematic response of a free-running model, either at model or full scale. Tethered and optical measurements systems used in towing tanks and wave basins are unsuited to this application. A system of wireless sensor nodes with synchronised video capability has been developed which allows rigid body motions and three-axis accelerations to be obtained by a single nine degree of freedom sensor node whilst the structural deformation of the hull girder can be obtained from a minimum of three nodes in parallel. The system performance was assessed in a controlled towing tank environment in comparison to a tethered system, using three nodes mounted on a flexible, four segment model hull. Measurements from the wireless system were comparable to the tethered results with the same degree of accuracy. Further tests showed a single node to produce comparable measurements to an optical system. The additional synchronised video capability allows a visual image of an extreme wave encounter to be correlated to the magnitude of the responses experienced. Practical advantages of the wireless system demonstrate its viability for acquiring high quality model data; further development should allow its application to full scale
Nesophrosyne makaihe Bennett, sp. nov.
No full text<i>Nesophrosyne makaihe</i> Bennett sp. nov. <p>(Fig. 5 a–g)</p> <p> <b>Diagnosis.</b> Length: male = 3.74mm, female = 4.97mm. A dark species, with a prominent saddle mark resembling a spear point, pointed anterad. Crown produced and bluntly rounded. Pygofer with a pointed apex at 2/3 height from base. Aedeagus with long apical processes, recurving anterolaterally 1/4 length of aedeagal arms. Endemic to O’ahu, Wai’anae Mountain Range.</p> <p> <b> Description. <i>Dorsum</i></b> : Dark species with prominent pale-yellow markings, extending from clavus through mesonotum (Fig. 5 a). Crown and pronotum dark; lighter forms with pale light brown blotches between ocelli. Mesonotum mesially pale; mesonotal triangles dark, extending to lateral margins. Scutellum pale. Forewing predominantly dark with cells and veins obfuscate in dark pigmentation; costal cells along posterior half clear, divided by a darkly pigmented R1 vein; outer anteapical cells present, triangular. Clavus with large conspicuous saddle mark, widest at base and tapering anteriorally, resembling a spear point.</p> <p> <i>Venter</i>: Face with well-formed grill pattern on clypeus, divided by central dark latitudinal line, posterior half entirely dark; clypellus, lorum, and gena dark. Abdominal segments predominately dark with thin pale line along each posterior margin; pleurites partially dark on anterior half. Legs almost entirely pale; hind femora dark anteroventrad; hind tarsal segments dark at joints.</p> <p> <i>Genitalia</i>: Pygofer (Fig. 5 b) produced and pointed, rising at 2/3 height from base; ventral lobe produced with long flat edge, angled posteroventrad, giving rise sharply to apex; posterior-dorsal edge rising form apex rounded; posterior edge flat; 11 macrosete. Aedeagus (Fig. 5 c,f,g) with aedeagal arms widely splayed, rising above central apodeme; gonopore preapical; apical processes long approximately 1/4 length of aedeagus, distad of gonopore, tapering before hooking anterolaterally. Style (Fig. 5 e) large; posterior processes short; preapical lobe flat and angular with microsete. Connective (Fig. 5 d) short; posterior edge notched; anterior appendages splayed widely.</p> <p> <b>Distribution.</b> USA: Hawaiian Islands, O’ahu, Western Wai’anae Mountain Range, ~ 1220m, wet forest</p> <p> <b> Measurements. <i>Body length</i></b> (n=8): Male (n=8) = 3.74mm (3.60mm – 3.90mm); Female (n=10) = 4.97mm (4.80mm – 5.10mm). <i>Genitalia</i> (n=6): Pygofer = 0.48mm (0.47mm – 0.50mm); Style = 0.38mm (0.37mm – 0.39mm); Connective = 0.28mm (0.27mm – 0.29mm); Aedeagus lateral length = 0.26mm (0.24mm – 0.27mm); Aedeagus posterior height = 0.25mm (0.23mm – 0.27mm).</p> <p> <b> Material examined. <i>Type material</i></b> : Holotype: 1 male, Hawaiian Islands, O’ahu, Wai’anae Mountains, Mt. Ka’ala, Summit Bog Boardwalk, N21 o 30.504, W158 o 0 8.865, Elevation: 1210m, 29Aug2009. Host Plant: <i>Broussaisia arguta.</i> Coll. G.M. Bennett, K. Magnacca, and D.A. Polhemus. Deposited in the BPBM, Honolulu, Hawai’i. Type #: 17302. <i>Additional material</i>: 22 males, 12 females, Hawaiian Islands, O’ahu, Wai’anae Mountains, Mt. Ka’ala, Summit Bog Boardwalk, N21 o 30.504, W158 o 0 8.865, Elevation: 1210m, 26May2007, 27July2009, and 29Aug2009. Host Plant: <i>Broussaisia arguta</i>. Coll. G.M. Bennett, K. Magnacca, and D.A. Polhemus. Deposited in the BPBM, Honolulu, Hawai’i. 21 males, 7 females, Hawaiian Islands, O’ahu, Wai’anae Mountains, Mt. Ka’ala, Summit Bog Boardwalk, N21o 40’40” W158o 08’48”, Elevation: 1220m, 6May2000. Host Plant: <i>Broussaisia arguta</i>. Coll. D.A. Polhemus. Deposited in D.A. Polhemus’s personal collection at the Smithsonian, Washington D.C.</p> <p> <b>Etymology.</b> <i>Makaihe</i> is a Hawaiian phrase for spear tip: <i>Maka</i> is the noun for point or tip of blade, and <i>Ihe</i> is the noun for spear. The name was chosen to describe the resemblance of the claval saddle mark to that of a spear point.</p> <p> <b>Discussion.</b> A single species is described for the <i>Nesophrosyne</i> occurring on <i>Broussaisia arguta</i> on O’ahu. Three specimens of a morphologically similar population from the Ko’olau Range on East O’ahu were examined (provided by D. Polhemus). The male specimens are dorsally paler than the <i>N. makaihe</i> (West O’ahu); the genitalia were not examined due to limited sample size. Eastern O’ahu populations may represent a potential sibling species system as seen on Maui and Hawai’i (Fig. 3). Due to the difficulty of collecting species from <i>B. arguta</i> on the eastern side of O’ahu, we are unable to make an adequate comparison of the two populations here.</p> <p> Phylogenetic evidence places <i>N. makaihe</i> in a clade with the <i>kanawao</i> species group, with low support. <i>Nesophrosyne makaihe</i> is placed sister to a clade associated with the host plant genus <i>Myrsine</i> (Myrsinaceae), containing two species found on East Maui and Hawai’i island (COII % divergence avg. = 16.03%). Both taxa occur in high elevation (~ 914.4m) rainforest.</p> <p> Further gene and taxonomic sampling are required to resolve this relationship. <i>Nesophrosyne makaihe</i> ’s internal genitalia is considerably different, further confusing inference of relationships to other species associated with <i>B. arguta</i>.</p> <p> <i>Nesophrosyne magnaccai</i> Bennett <b>sp. nov.</b> (Fig. 6 a–g)</p> <p> <b>Diagnosis.</b> Length: male = 4.7mm, female = 5.60mm. Brown species with conspicuous dark colored veins; without saddle mark or pale colored claval veins. Crown produced, bluntly rounded. Pygofer appearing triangular, with sharply produced apex rising at mid-length. Aedeagal arms widely splayed, appearing relatively compressed in ventral view; gonopore preapical, with apical processes recurving anterolaterad 1/5 length of aedeagal arms. Endemic to Moloka’i.</p> <p> <b> Description. <i>Dorsum</i></b> Brownish species with forewing veins conspicuous (Fig. 6 a). Crown predominately dark with thin pale line extending along posterior margin, triangular pale region emerging at apex. Pronotum almost entirely dark except for lateral edges, which are marked with two lateral pale spots on margins. Mesonotum dark. Scutellum central region variably dark, lateral margins pale. Forewing veins dark and conspicuous, including clavus; cells clear tinged with brown; central anteapical cell infused with dark pigmentation at ends; discal cells dark; lacking any pale coloration common in <i>Nesophrosyne</i>; outer anteapical cell present, triangular.</p> <p> <i>Venter</i>: Face with clypeus, clypellus, lorum dark; gena dark with lateral margins pale. Abdominal segments almost entirely dark with thin pale line along each posterior margin; pleurites dark with posterior edge variably pale. Forelegs pale, base of sete dark; middle femora and tibia dark at joints; hind femora and tibia mostly dark with pale macrosete.</p> <p> <i>Genitalia</i>: Pygofer (Fig. 6 b) triangular, sharply produced at mid-height from base; dorsal and ventral edges narrowing straight to apex; ventral lobe produced; 11 macrosete. Aedeagus (Fig. 6 f,c,g) comparatively compressed in posterior view, rising nearly above of central apodeme; aedeagal arms splayed widely; gonopore preapical; apical processes extending just above gonopore, hooking approximately 1/5 the length of aedeagal arms. Style (Fig. 6 e) preapical lobe sloping, forming an oblique angular edge, with microsete. Connective (Fig. 6 d) with posterior edge notched and wider than anterior arms; anterior arms thick, moderately splayed.</p> <p> <b>Distribution.</b> USA: Hawaiian Islands, Moloka’i Eastern Mountain Range,> 1340m, wet forest.</p> <p> <b> Measurements. <i>Body length</i></b> (n=4): Male (n=4) = 4.70mm (4.46mm – 4.80mm); Female (n=1) = 5.60mm. <i>Genitalia</i> (n=3): Pygofer = 0.60mm (0.59mm – 0.62mm); Style = 0.46mm (0.45mm – 0.47mm); Connective = 0.32mm (0.32mm – 0.33mm); Aedeagus lateral length = 0.39mm (0.38mm – 0.39mm); Aedeagus posterior height = 0.13mm (0.13mm – 0.14mm).</p> <p> <b> Material examined. <i>Type material</i></b> : Holotype: 1 male, Hawaiian Islands, Moloka’i, Kamakou Preserve, Pu’u Kolekole, N21 o 0 6.436 W156 o 54.141, Elevation: 1340m, 19Feb2007. Host Plant: <i>Broussaisia arguta</i>. Coll. K. Magnacca. Deposited in the BPBM, Honolulu, Hawai’i. Type #: 17303. <i>Additional material</i>: 3 males, 1 female, same as holotype. Deposited in the BPBM, Honolulu, Hawai’i.</p> <p> <b>Etymology.</b> This species is named after its collector Dr. Karl Magnacca (Hawaiian Entomologist, University of Hawai’i, Hilo) for his contributions to this project and for his extensive, and helpful guidance in the field.</p> <p> <b>Discussion.</b> A single <i>Nesophrosyne</i> species associated with <i>Broussaisia arguta</i> is described from Moloka’i. Similarly to <i>N. heopoko</i>, the Moloka’i species is morphologically distinct from the other species described here. Current phylogenetic evidence provides weak support for an independent shift to <i>B. arguta</i>. <i>N. magnaccai</i> is placed sister to <i>N. sp.4</i> and <i>N. oblique</i> (data not shown), which are associated with the host plant genera <i>Lobelia</i> (Campanulaceae) and <i>Myrsine</i> (Myrsinaceae), respectively. Both sister taxa occur in on East Maui in high elevation (~ 914.4m) rainforest. COII percent divergence between <i>N. magnaccai</i> and <i>N. sp.4</i> avg. = 15.68%, and <i>N. magnaccai</i> and <i>N. obliqua</i> = 15.67%.</p>Published as part of <i>Bennett, Gordon M & O'Grady, Patrick M, 2011, Review of the native Hawaiian leafhopper genus Nesophrosyne (Hemiptera: Cicadellidae: Deltocephalinae) with description of eight new species associated with Broussaisia arguta (Hydrangeaceae), pp. 1-25 in Zootaxa 2805</i> on pages 11-14, DOI: <a href="http://zenodo.org/record/207804">10.5281/zenodo.207804</a>
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