Ship Masts Research Articles

A Study on the Mast Structure Vibration Limits considering the Operating Time of Naval Ships

The mast structure of a naval ship has a lot of expensive equipment attached and is easily exposed to strong vibration due to its structural characteristics, so it is necessary to manage vibrations well to prevent equipment failure and increase operating time. Since September 2015, the Navy has been managing the vibration of the ship's mast structure with a separate tolerance standard from the local vibration, but this standard is set at 1/2 of the vibration limits for mast-mounted equipment without any engineering basis. So the establishment of new vibration limits based on the operating conditions of naval ships is required. In this study, the mast structure vibration limits were reviewed considering the actual operating time of naval ships, and the results were compared with the standards of major overseas classification societies and the actual measurements of a ship that had mast structure vibration problems.

Multi-Band Array Antenna Sharing a Common Aperture with Heterogeneous Array Elements

This paper proposes a multi-band array antenna that shares a common aperture with heterogenous array elements. The multi-band array antenna includes one printed dipole antenna for the S-band and 3 × 3 array E-shaped patch antennas for the X-band. The current directions of the printed dipole and E-shaped antenna are orthogonal to each other, which properly diminishes the mutual coupling interference. To decrease the mutual coupling interference among the X-band components, we placed cavities using multiple vias surrounding the X-band components. To check the validity of the proposed design, the unit-cell was expanded to a 12 × 12 X-band array configuration, and then the beam steering properties were examined. The proposed antenna’s average gains are 5.2 dBi in the S-band and 5.2 dBi in the X-band. The bore-sight gain of the extended array configuration on the ship mast is 35.6 dBi. The results confirm that the proposed design is suitable for MFR applications even in a shared aperture.

Tie Rod-Equivalent Non-Linear Constitutive Law for Uniformly Loaded Cables.

Cables are typically used in engineering applications as tensile members. Relevant examples are the main cables of suspension bridges, the stays of cable-stayed bridges, the load-bearing and stabilizing cables of tensile structures, the anchor cables of floating mooring structures, the guy-ropes for ship masts, towers, and wind turbines, the copper cables of electrical power lines. Since cables are characterized by non-linear behavior, analysis of cable structures often requires advanced techniques, like non-linear FEM, able to consider geometric non-linearity. Nevertheless, a traditional simplified approach consists in replacing the cable with an equivalent tie rod, characterized by a suitable non-linear constitutive law. Currently used equivalent constitutive laws have been derived by Dischinger, Ernst and Irvine. Since the equivalence is restricted to taut cables, characterized by small sag to chord ratios, these traditional formulae are not appropriate for uniformly loaded sagging cables: the main cables of suspension bridges are a particularly emblematic case. Despite some recent attempts to find more refined solutions, the problem is still open, since closed form solutions of general validity are not available. In the paper, general analytical formulae of the non-linear constitutive law of the equivalent tie rod are proposed, distinguishing two relevant cases, according as the length of the cable can vary or not. The expressions, derived by applying the general form of the theorem of virtual work, can be applied independently on the material, on the sag to chord ratio, on the load intensity and on the stress level, so allowing the replacement of the whole cable with a single equivalent tie rod. The expressions are critically discussed referring to a wide parametric study also in comparison with the existing formulae, stressing the influence of the most relevant parameters.

Effect of NACA0012 Airfoil Pitching Oscillation on Flow Past a Cylinder

The flow past a cylinder is a classical problem in flow physics. In a certain range of Reynolds number, there will be Karman vortex street phenomenon in the wake of a cylinder, which will greatly increase the pressure drag of the cylinder. By controlling the vortex shedding phenomenon, drag reduction of the cylinder could be effectively realized. In this paper, a NACA0012 airfoil with pitching oscillation is placed downstream of the cylinder. Based on the tight coupling method, kinematics equations and Navier–Stokes equations in the arbitrary Lagrangian–Eulerian form are solved. Firstly, the effect of airfoil oscillation period and the distance between airfoil leading edge and cylinder center (x/D) are studied respectively, especially considering the aspects of vortex shedding and drag reduction effect. Besides, the vortex interaction in the flow field around the airfoil and cylinder is analyzed in detail. It is found that the NACA0012 airfoil with pitching oscillation can change the period of vortex shedding. Moreover, it can also increase the drag reduction rate to as high as 50.5%, which presents a certain application prospect in the engineering drag reduction field, e.g., for launch vehicles, ship masts, submarine pipelines, etc.

Analysis of coupling characteristics of coaxial line parallel to lightning current channel

Base on the analysis of the coaxial coupling theory, the experimental model of the coaxial cable short-range coupling lightning electromagnetic pulse is established to study the problem of coaxial cable short-range coupling lightning electromagnetic pulse on the ship mast and high tower. The combination wave generator is used to simulate the 8/20 μs lightning current waveform, and the metal bar with the length of 1 m and diameter of 0.016 m is used to simulate the lightning channel as the radiation source. The length of the coaxial cable and the distance from the radiation source are changed for the test. The conclusion is as follows: when the coaxial cable is coupled with lightning wave in a short distance, the voltage waveform of cable terminal is still double exponential wave, with strong damping oscillation at 0.1 ∼0.4 μs. When the cable terminal is open circuit or connected with matching resistance, the rising time is shorter, about 1 μs; when the cable terminal shielding layer is grounded, the rising time is longer, about 10 μs. The peak voltage and energy coupled to the coaxial cable at short distance are positively correlated with the cable length, and inversely correlated with the distance from the radiation source. The energy that the cable is coupled to mainly comes from the low-frequency part, and there are multiple energy peaks below 100 Hz. Using fitting curve and experimental data, when the coaxial cable terminal is open circuit, the lightning current reaches 30 kA, the cable length is 30 m, and the distance from the lightning channel is 0.15 m, the peak value of the voltage coupled to the cable terminal is 66 V. It has certain guiding significance and value in the practical application of electromagnetic pulse protection.

Bridge condition monitoring using fixed moving principal component analysis

This paper proposes a data-driven damage detection method based on fixed moving principal component analysis (FMPCA) to analyze structural dynamic responses and monitor the bridge operational condition and the damage occurrence. The damage indices based on principal components (PCs) and eigenvalues can be calculated continuously by applying a fixed moving window. The length of the moving window is determined by using a new criterion based on the convergent spectrum of cumulative contribution ratio. Numerical simulations and experimental tests in the laboratory on beam bridge models subjected to stochastic loads are conducted to investigate the accuracy and effectiveness of the proposed approach. Both simulation and experimental results indicate that using the FMPCA can well analyze the dynamic vibration data to detect damage or abnormal vibration behavior during the operational condition. It can be used to accurately monitor the time instant of damage occurrence, which is very important in long-term monitoring of civil engineering structures. The proposed method is successfully applied to analyze the data recorded during an incident that a real large-scale suspension bridge was slightly scraped by the mast of a sand ship, which further verifies the effectiveness and feasibility of this method in engineering applications. The results also indicate that the bridge was not damaged after the incident but presented a short time abnormal vibration behavior owing to the impact of the ship mast.

On Learning to Enjoy Housman

On Learning to Enjoy Housman Stephen Kampa (bio) If I let myself slip into a rainy, brown-and-gray reverie, I can summon to mind even now the illustration that accompanied Longfellow's "The Wreck of the Hesperus" in my tenth-grade English textbook. It was a reproduction of J. M. W. Turner's The Shipwreck, and to the eye of a teenager raised on kung fu movies, it was a little short on action. Sure, Turner included nervous tangles of white on the wave-tops to suggest the waters' dangers, and more than one lifeboat passenger perches inches from overboard, but there isn't even any lightning. As for the Longfellow poem, it immediately became my benchmark for boredom. What ought to have been a suspenseful, even macabre, narrative—I mean, there is a kid frozen to a ship's mast by the end—instead sounded ponderous and fusty. No syntactic prude out-prudes a tenth-grader facing the lines: "Last night, the moon had a golden ring, And to-night no moon we see!"The skipper, he blew a whiff from his pipe, And a scornful laugh laughed he. No moon we see? A scornful laugh laughed he? Boring, this is. It would be hard to pinpoint when all that changed. During my sophomore year, I had a superb creative writing teacher, one who later ended up being my 11th-grade English teacher and who was instrumental in bringing me around to poetry, but specific memories—and especially the chronology of them—remain jumbled. When did that Stetson professor come dazzle us with his reading of e. e. cummings during a guest lecture? When did I first read and reread Seamus [End Page 538] Heaney's "Blackberry-Picking" and feel that I had understood it as a series of implications as much as a series of sentences? And when did I first feel viscerally struck by the force of self-recognition in a poem? When it happened, the poet who made me feel I had seen an aspect of myself in poetry was nearly as fusty as Longfellow: it was A. E. Housman, whom I am sure I must have read around the same time I read "The Wreck of the Hesperus"—perhaps "To an Athlete Dying Young" or "Terence, this is stupid stuff"? Those anthology pieces were not what hit a nerve, however; it was a Housman B-side that knocked me off my feet. Shake hands, we shall never be friends, all's over; I only vex you the more I try.All's wrong that ever I've done or said,And nought to help it in this dull head: Shake hands, here's luck, good-bye. But if you come to a road where danger Or guilt or anguish or shame's to share,Be good to the lad who loves you trueAnd the soul that was born to die for you, And whistle and I'll be there. I grant that "I only vex you the more I try" still sometimes holds true, but I confess I am now embarrassed ever to have experienced this poem as a revelation. True, the loose iambic movement (there are too few anapests really to call it an anapestic meter) nicely reinforces the casual tone of the first stanza, which almost revels in the absolute frustration of seeming never to get things right ("All's wrong," the speaker says, and "nought to help it"—really, it has become an all-and-nothing situation); and true, the first and last lines of the first stanza balance the abruptness and gravity of the moment with an offhand casualness that betrays the speaker's deep grief; but the turn in the second stanza brings me waves of shame, almost a shipwreck's worth. I cannot dispute that in the phrase "the lad who loves you true," true as an adverb has a long pedigree—in the OED, there are ample attestations [End Page 539] to this with citations from the illustrious Barnaby Googe and one H. Crompton ("Once I did love, and loved true"), who upon further examination is Hugh Crompton, a poet also so illustrious that a...

Modal Analysis of Ship’s Mast Structure using Effective Mass Participation Factor

Background/Objectives: Each structure tends to vibrate at particular frequencies, called resonant or natural frequencies. When a structure is excited by dynamic load with frequency coinciding one of its natural frequencies the structure experiences stresses and large displacements. In this paper effective mass participation factor criterion is used to solve the vibration problem in the ship mast. Methods/Statistical Analysis: The effective mass participation factor provides a measure of the energy contained within each resonant mode. Vibration problem originated when one of the antenna at top of mast was replaced by a new antenna with greater mass at same location. The overall mast structure started vibrating because of the resonance of natural frequencies of the mast structure with natural frequencies of rotary equipment. Findings: It caused interruption in sensitivity of equipment installed on the mast structure. Instead of fabricating the new mast structure, some alteration has been carried out on the basis of results obtained from modal analysis. Application/Improvements: The study is very effective to overcome the vibration problems in ship mast.

Numerical Simulation of the Wind Load on the Mast at Different Wind Angles

The wind load acted on ship mast at different wind angles of large Reynolds number is numerically simulated in this paper. CFX software was used to analyze the trend of constant and fluctuating forces that the mast surface suffered at different Reynolds numbers.The vortex shedding strength of the wind load around the mast was also analyzed according to the trend of Strouhal number varing with the simulated Reynolds numbers. The results show that the wind angle has an important impact on the lift, drag, and vertical force of the mast. The vertical force of the inclined side wall on the mast can not be ignored,and the angle of direction wind has great impact on the Strouhal number at different Reynolds numbers.

초음파 풍향 풍속계 데이터 로거 시스템의 구현

선박 통신은 1993년 ISO에서 국제 표준 규격인 RS-422통신을 이용하며, 마이크로컨트롤러들 간의 통신을 위해 설계된 시리얼 네트워크 통신 방식을 사용하였으나, 최근 NMEA2000 표준화가 진행됨에 따라 점차 빠르게 Ethernet 기반 통신 환경으로 대체 되어질 전망이다. 선박에서 사용되어지고 있는 주요 계측 장비들은 점차 범용성과 편의성을 가지는 최신 장치들을 이용해 이를 관리하게 되어짐에 따라 선박 내 다양한 곳에서 이를 활용하여 제어 및 관리 시스템들이 구현되어지고 있는 실정이다. 풍향 풍속계는 선박의 마스트 끝이나 풍력 단지 가장 높은 곳에 일반적으로 설치되어 풍향과 풍속을 계측하는 장비로써, 국제해사기구(IMO : International Maritime Organization)의 규정에 따라 필수 장비로 선박에 탑재되고 있는 장비이다. 본 논문에서는 초음파 풍향 풍속 시스템을 처리하기 위해 기존에는 별도 제어 콘솔, 데이터 로거(data-logger), 인디케이터(Indicator) 등의 제어 처리를 위한 기반 장비들이 필요하였던 시스템을 사용자 환경에 따른 PC NETWORK를 이용하여 풍향 풍속 자료 처리시스템을 구현하였다. 또한, 초음파 풍향 풍속 자료 처리 시스템을 구현하기 위한 요소 기술을 기능별 함수로 나타내었으며, NMEA 2000 표준 인증에서도 별도의 운용 콘솔 없이 풍향 풍속 자료의 처리를 위한 자료 처리 운용시스템의 기능들을 구현하고자 하였다. Until now ship communication micro serial network communication method is designed for the communication between the controller and the RS-422 communication on the international standard ISO 1993, but gradually progresses NMEA 2000 standardized fast Ethernet-based communications environments expected to be replaced. In addition, the ship's main instrumentation equipment versatility with ease gradually to control devices by monitoring and controlling are. Wind anemometer, ship mast end, where the highest wind farms typically install a separate console boxes, data loggers, indicators was required in order to manage them, to maintain them, to go through the procedures and cumbersome data update firmware were Therefore, in this paper, using the PC network, ultrasonic wind speed data processing system for implementing functional was expressed as a function of the technology elements, NMEA 2000 standard certified in separate operating console without the features of the data loggers, indicators, implementation by ultrasonic wind data processing system was implemented to minimize the maintenance cost of the operating system.

함정 마스트 장착 레이더용 회전 중형 안테나의 외부 형상 설계

To satisfy the operational requirements of surveillance radar and the operational concept of a ship combat system, an active-array-type antenna was designed using solid-state transmitters and receivers. The arrangement of the constituent electronic components of the antenna system, considerably large in size, and therefore, the antenna needs to be housed in a box. The rotational antenna system installed on a ship mast is installed in a sealed housing to protect the interior equipment from environmental conditions. The outer shape of the housing is that the antenna should be capable of rotating normally despite strong winds. Furthermore, in recent times, designs with low radar cross section (RCS) have attracted attention from the viewpoint of improving the stealth of the ship. In this light, four types of models are proposed for the outer shape design of the antenna system, and they are investigated from the viewpoint of low RCS design as well as wind load.

AirDyn: an instrumented model-scale helicopter for measuring unsteady aerodynamic loading in airwakes

This paper describes the design, calibration and application of an instrument that measures the effects of unsteady air flow (airwake) on a helicopter in flight. The instrument is a 1/54th-scale model helicopter that is mounted on a six-component dynamic force balance to measure the forces and moments that an airwake imposes onto the helicopter; it is therefore an ‘Airwake Dynamometer’ to which we have given the name AirDyn. The AirDyn has been designed, in particular, to measure the effect of a ship airwake on a helicopter translating over the ship's landing deck. The AirDyn, which has been implemented in a water tunnel, in preference to a wind tunnel, senses the integrated effect of a turbulent airwake on the helicopter, and the resulting unsteady forces and moments are an indication of the workload the pilot would need to exert to counteract these effects in a real helicopter. Binocular sensing elements and semiconductor strain gauges have been adopted to achieve high sensitivity and relatively high stiffness. The compact strain gauge balance is fitted into the helicopter fuselage, and protective coatings and a flexible bellows are used to seal the balance and protect it from the water. The coefficient matrix of the AirDyn has been obtained by static calibrations, while impulse excitation tests have confirmed that its frequency response is suitable for the measurements of unsteady loads. The application of the instrument is illustrated by using it to quantify the effect that a bulky ship mast has on the airwake and thus on a helicopter as it lands onto a simplified ship in a scaled 50 knot headwind.

Notice

Notice D. S. Martin (bio) Do we ever stop to notice the rightness of organic designsthe broad-leafed maples that grab every raindrop they canevery ray of light so light that they're almost weightlessextending as far as possible beyond the branches' reachproviding a place for us to escape the heat & for mosses& mushrooms to flourish on the forest floor?Is it coincidence that their fibres are so fittingfor a builder's needs for fuelthat their roots prevent soil from washing away& they breathe out what we need to breathe in? Do we notice the efficiency of man-made thingsthe strength of intersecting lines right angleswithin a window frame dividing four panes of glasstelephone pole after telephone pole stretching acrossthe prairie a ship's mast rising above the seathat practical recurring patternbuilders use when framing a house?Do you think as I do of its significancebeyond that of structural design& notice heaven wink at the coincidence? [End Page 126] D. S. Martin D.S. Martin is a Canadian poet whose work has appeared in Canadian Literature, Christianity & Literature, The Dalhousie Review and Queen's Quarterly. His most recent poetry collection, Poiema (Wipf & Stock, 2008) received an award from The Word Guild in 2009. ds_martin@yahoo.com Copyright © 2011 The Johns Hopkins University Press

Review: Another City: Urban Life and Urban Spaces in the New American Republic by Dell Upton

Dell Upton . Another City: Urban Life and Urban Spaces in the New American Republic . New Haven: Yale University Press, 2008, 395 pp., 20 color and 144 b/w illus. $45 (cloth), ISBN 9780300124880 In this postmetropolitan age, with most cities in the United States still grappling with the infrastructural, economic, and social problems of the postindustrial, postfordist transition, it is well worth considering what those cities were like before mass industrialization; before, that is, the creative destruction, immigration, wealth, and poverty that industry brought to the city. Those cities of the United States' relatively new republic were primarily mercantile in nature, and their wealth was garnered from the ships that plied our shores, taking away the grains, hides, timber, cotton, and other natural resources that the United States was supplying to the world, and bringing back goods of all kinds to be consumed. Compared to industrial cities, these mercantile cities were relatively small in area and in population; on the eve of the Civil War, the largest city-New York-contained just over 800,000 people. Ship masts ruled their skylines, and economic activity clustered around their docks, wharves, and warehouses; these were cities that looked as rough and tumble as the mercantile economy that created them. But, as Dell Upton's insightful book tells us, we would be missing the mark by a wide margin if we focused only on the purely functional aspects of mercantile cities in the United States. Cities like Philadelphia and New Orleans, the foci of Upton's book, were rimmed by wharves and docks, …

Motets in Amber, and: Migration

Motets in Amber, and: Migration Rebecca Dunham (bio) Motets in Amber Bring to me the two hot fingers.Forehead and temple, they flashover a cornfield's rows,anesthetized and curared, alldried stalks choppedyellow sharp, stunted knives. I'll convulse beneath the storm,my body rubbed byits woolen cloth to somethingrich and new. Amber-bright,I gown myself and go forthfrocked in feather, straw, and leaf. * If the past shines like a fixedstar reflected in the deepest well;if its spring muddies his chillfeet, all wet and wildering; Thalesof Miletus will fall, felled bya wild thirst down earth's pitch tube. * Amber: literally, burn stone. Orin Arabic, straw robber. Duskybirds hang like a handfulof ash thrown into air. Electric:borrowed from the Greekelektron, amber. Out our car's [End Page 118] window, I watch Illinois pour by,power lines lashed to richsoil. Moored as if by a wound'sstitched thread, its black cord. * The frog's dead muscles twitch,kindled by jolts from Luigi Galvani'selectrostatic machine, provingThales of Miletus right: there isno difference between the livingand the dead. Our nerves fire and seek; what connects us burnsfilament-bright, incandesces.Resinous and vitreous in our glassyvacuum, still we spark, chargedtungsten coiling. Why do I notdie? Because there is no difference. * My son traps fireflies in glassjars, a constellationto light his room, to flashlike semaphores across his sleep. Nothing ends, or everything, if,thunderbolt, you leave your cloud. In daylight, their dullamber bodies clickagainst the jar's clear neck. * [End Page 119] Lamprey-like, lightning writhes,June 1752, key knottedto a silk string, a continual streamthe size of a Crow Quill, the bellsring and ring, plasma and kite,a slick flash, a continued, dense,white stream whereby the whole staircasewas enlightened as by sunshine,filling Leyden jars, the violetcorona of a ship's mast and rigging,a blur no man can handfast. * Injured, my body exudes itsamber globules. Syrupy, sappedplanets fed to earth's soil,its blue loam, a resin fossiled lapidary fine. Only to be liftedon ocean's current, eel, torch, whiplash,its long muscled arm, and foamits way ashore. Set me aflame.Aburn. Apine. [End Page 120] Migration Two shoals of geese flylow, mixing amid the carscrossing Cedar River. Snowsieves down and dark-necked,the birds honk likelong-married couplesquarreling over which wayto go. I steer fromthe place I was to the placethat I am going. Migration:from the lost adjective*migros, or moving.Etymology explains meto myself far better thanpsychology. To my doctor,I don't even try to explain,I never do. The birdssort things out and headtheir separate ways, backon course. Of course, Iknow what I am: lost, homeless,each abandoned selfrosaried and strung throughits vacant core. All nightthis bothers me. Onepoint-bird must be wrong. [End Page 121] Rebecca Dunham Rebecca Dunham's first book of poetry, The Miniature Room, won the T. S. Eliot Prize for Poetry and was published by Truman State University Press. She has received an NEA fellowship and her poems have appeared or are forthcoming in FIELD, Iowa Review, and Antioch Review, among others. Copyright © 2010 University of Nebraska Press

Semi-active control of ship mast vibrations using magneto-rheological dampers

On marine vessels, delicate instruments such as navigation radars are normally mounted on ship masts. However the vibrations at the top of mast where the radar is mounted often cause serious deterioration in radar-tracking resolution. The most serious problem is caused by the rotational vibrations at the top of mast that may be due to wind loading, inertial loading from ship rolling and base excitations induced by the running propeller. This paper presents a method of semi-active vibration control using magneto-rheological (MR) dampers to reduce the rotational vibration of the mast. In the study, the classical optimal control algorithm, the independent modal space control algorithm and the double input - single output fuzzy control algorithm are employed for the vibration control. As the phenomenological model of an MR damper is highly nonlinear, which is difficult to analyse, a back- propagation neural network is trained to emulate the inverse dynamic characteristics of the MR damper in the analysis. The trained neural network gives the required voltage for each MR damper based on the displacement, velocity and control force of the MR damper quickly. Numerical simulations show that the proposed control methods can effectively suppress the rotational vibrations at the top of mast.

Page 2

Page 2 ?: "am deeply proud to add my name to the masthead of this publication. Few publications have -mastheads as illustriously peopled as ABR's. Our masthead reveals much about the identity of the publication as well as about the level of excellence with which it is affiliated. It is clearly noted on our masthead that "ABR is published by its editors." This means that ABÄ's editors are charged with recommending books for review, suggesting and soliciting reviewers , assisting in the editorial development of the reviews, and voting on whether reviews should be accepted for publication. Our editors are charged with working collectively in the operation ofthis publication. Its quality is a function of their unique talents and expertise, and of the time and commitment they generously donate. None of our editors are paid for their efforts. Their compensation is the continued publication of ABR in a manner consistent with its mission—a mission which remains as important today as when it was chartered nearly thirty years ago. I am grateful to all of our editors for their commitment to this publication and for the goodwill efforts they expend on its behalf. The esteemed place that ABR holds in the literary world is due to their efforts. On behalf of ABR's readership, I thank our editors for the care and work they have volunteered to the publication over the years. You will notice that changes to the masthead have been inaugurated in this issue. They are primarily reorganizational, but still important. Their aim is to clarify the editorial responsibilities at ABR. Just as the flags that fly on top of a ship's mast announce the identity of the ship, ABR's masthead reveals to its readership much about its identity and history. It is my hope that our revamped masthead will allow you to appreciate more clearly our history and understand more transparently our present. Jeffrey R. Di Leo Publisher and Editor Victoria, Texas Rants & Raves letter to the editors THE IMAGINARY POETS I am writing in response to Bill Porter's review of my edited volume. The Imaginary Poets (ABR 27.6), not to quibble but to note inaccuracies and infelicities. I do so on behalf of the volume's contributors , and to offer some necessary information omitted from Mr. Porter's considerations. The gist of Mr. Porter's criticism of the volume seems to be his belief that the contributors have appropriated the suffering of Holocaust victims. To this end, he comments, "half of the book might have been redacted and renamed The Imaginary Holocaust Survivors." I'm not sure what book he's speaking of: only four of the twenty-two entries in the volume feature imaginary victims of World War II, one of whom survives in hiding; none are sent to a concentration camp, and one turns out to have been a Nazi, perhaps. While such hyperbole (or bad math, as even a rounded-up four does not equal eleven) may well suit Mr. Porter's assessment of the volume, his inaccurate measure willfully misrepresents the contents of 7"Ae Imaginary Poets. Perhaps, too, the project itself has been misconstrued, for Mr. Porter omits the long and well-respected history of imagined authorship— not to mention of the dramatic monologue—and what such an endeavor offers its creator. To infer as Mr. Porter does that an act of imagination appropriates the suffering of others, when no claim to authenticity has been made, misses the mark entirely; the entries in The Imaginary Poets detail imagined lives, not the "sincere" feelings of real poets writing in the first person. I share Mr. Porter's aversion to such acts of appropriation, of course, and to what he perceives to be the current "reign of the bedroom confessional" (although such a statement smacks of more hyperbole, and of a Puritanical sort); but what Mr, Porter misses as well is the fact that such an aversion to mock-sincerity makes possible this volume. Revisionist history? Biographical criticism? "Creative" nonfiction? Confessional poetry? The Imaginary Poets calls into question a numberofother serious literary subjects, none of which Mr. Porter chooses to discuss. Sadly, too, the poetics wholly miss his gaze, as...

Dorsal fin in the white shark, Carcharodon carcharias: A dynamic stabilizer for fast swimming

Transverse sections of the skin in the dorsal fin of the white shark, Carcharodon carcharias, tiger shark, Galeocerdo cuvier, and spotted raggedtooth shark, Carcharias taurus, show large numbers of dermal fiber bundles, which extend from the body into the fin. The bundles are tightly grouped together in staggered formation (not arranged in a straight line or in rows). This arrangement of dermal fibers gives tensile strength without impeding fiber movement. Tangential sections indicate that the fibers in all three species are strained and lie at angles in excess of 60 degrees . Of the three species investigated the dermal fibers in C. carcharias are the most densely concentrated and extend furthest distally along the dorsal fin. The overall results indicate that the dorsal fin of C. carcharias functions as a dynamic stabilizer and that the dermal fibers are crucial to this role. The fibers work like riggings that stabilize a ship's mast. During fast swimming, when the problems of yaw and roll are greatest, hydrostatic pressure within the shark increases and the fibers around the body, including in the dorsal fin, become taut, thereby stiffening the fin. During slow swimming and feeding the hydrostatic pressure is reduced, the fibers are slackened, and the muscles are able to exert greater bending forces on the fin via the radials and ceratotrichia. In C. carcharias there is a trade-off for greater stiffness of the dorsal fin against flexibility.

A ship's mast discovered during excavation of the Roman port at Olbia, Sardinia

A ship's mast discovered during excavation of the Roman port at Olbia, Sardinia

The Ship's Mast. The legacy of the Macassan presence in northern Australia

A ship's mast with flags attached stands anchored to the ground in a cleared area near the centre of a number of Yolngu (Aboriginal) communities in north-east Arnhem Land. The mast is, I argue, the most significant and enduring legacy of contact with Macassanl trepangers from Sulawesi, who ventured onto the northern Australian coast from at least 1700 until the early years of this century. Drawing on Taussig's ( 1993) text 'Mimesis and Alterity,' and more recently Merlan's (1998) examination of the mimetic quality of the Aboriginal social agenda, I discuss the ways in which lessons from the Arnhem Land mast are of political import for contemporary Arnhem Landers pursuing self-determination. I also examine the proposition that the revelation of sacred Dreaming law by Aborigines, in particular those narratives incorporating representations of non-Aborigines, is a strategy being pursued by Yolngu in order to advance the reconciliation process in Australia.