CSM玻璃钢复合型断裂的有限元分析

对切短玻璃纤维毡增强聚脂层板的复合型断裂进行了有限元分析。采用八节点四边形等参元的正规型式计算应力分布与损伤区扩展;而用坍塌(collapsed)三角形四分之一点(quarter-point)奇异元计算应力强度因子K_Ⅰ与K_Ⅱ。 用节点位移约束与释放技术计算了裂纹扩展过程。对决定应力强度因子K_Ⅰ与K_Ⅱ的三种方法进行了对比。对施加于裂纹顶点节点约束条件的影响进行了评价。最后基于实验测得的断裂载荷与临界裂纹长度,估算了材料在这种受力条件下的复合型临界应力强度因子K_(ⅠC)和K_(ⅡC)。

Numerical investigation of dynamic stall of an oscillating aerofoil

The flow structure around an NACA 0012 aerofoil oscillating in pitch around the quarter-chord is numerically investigated by solving the two-dimensional compressible N-S equations using a special matrix-splitting scheme. This scheme is of second-order accuracy in time and space and is computationally more efficient than the conventional flux-splitting scheme. A 'rigid' C-grid with 149 x 51 points is used for the computation of unsteady flow. The freestream Mach number varies from 0.2 to 0.6 and the Reynolds number from 5000 to 20,000. The reduced frequency equals 0.25-0.5. The basic flow structure of dynamic stall is described and the Reynolds number effect on dynamic stall is briefly discussed. The influence of the compressibility on dynamic stall is analysed in detail. Numerical results show that there is a significant influence of the compressibility on the formation and convection of the dynamic stall vortex. There is a certain influence of the Reynolds number on the flow structure. The average convection velocity of the dynamic stall vortex is approximately 0.348 times the freestream velocity.

Quince años de investigaciones histórico-arqueológicas en torno a Getaria

Homenaje a Jesús Altuna

The Annual Economic Survey of Federal Gulf Shrimp Permit Holders: Report on the Design, Implementation, and Descriptive Results for 2006

This technical memorandum documents the design, implementation, data preparation, and descriptive results for the 2006 Annual Economic Survey of Federal Gulf Shrimp Permit Holders. The data collection was designed by the NOAA Fisheries Southeast Fisheries Science Center Social Science Research Group to track the financial and economic status and performance by vessels holding a federal moratorium permit for harvesting shrimp in the Gulf of Mexico. A two page, self-administered mail survey collected total annual costs broken out into seven categories and auxiliary economic data. In May 2007, 580 vessels were randomly selected, stratified by state, from a preliminary population of 1,709 vessels with federal permits to shrimp in offshore waters of the Gulf of Mexico. The survey was implemented during the rest of 2007. After many reminder and verification phone calls, 509 surveys were deemed complete, for an ineligibility-adjusted response rate of 90.7%. The linking of each individual vessel’s cost data to its revenue data from a different data collection was imperfect, and hence the final number of observations used in the analyses is 484. Based on various measures and tests of validity throughout the technical memorandum, the quality of the data is high. The results are presented in a standardized table format, linking vessel characteristics and operations to simple balance sheet, cash flow, and income statements. In the text, results are discussed for the total fleet, the Gulf shrimp fleet, the active Gulf shrimp fleet, and the inactive Gulf shrimp fleet. Additional results for shrimp vessels grouped by state, by vessel characteristics, by landings volume, and by ownership structure are available in the appendices. The general conclusion of this report is that the financial and economic situation is bleak for the average vessels in most of the categories that were evaluated. With few exceptions, cash flow for the average vessel is positive while the net revenue from operations and the “profit” are negative. With negative net revenue from operations, the economic return for average shrimp vessels is less than zero. Only with the help of government payments does the average owner just about break even. In the short-term, this will discourage any new investments in the industry. The financial situation in 2006, especially if it endures over multiple years, also is economically unsustainable for the average established business. Vessels in the active and inactive Gulf shrimp fleet are, on average, 69 feet long, weigh 105 gross tons, are powered by 505 hp motor(s), and are 23 years old. Three-quarters of the vessels have steel hulls and 59% use a freezer for refrigeration. The average market value of these vessels was $175,149 in 2006, about a hundred-thousand dollars less than the average original purchase price. The outstanding loans averaged $91,955, leading to an average owner equity of $83,194. Based on the sample, 85% of the federally permitted Gulf shrimp fleet was actively shrimping in 2006. Of these 386 active Gulf shrimp vessels, just under half (46%) were owner-operated. On average, these vessels burned 52,931 gallons of fuel, landed 101,268 pounds of shrimp, and received $2.47 per pound of shrimp. Non-shrimp landings added less than 1% to cash flow, indicating that the federal Gulf shrimp fishery is very specialized. The average total cash outflow was $243,415 of which $108,775 was due to fuel expenses alone. The expenses for hired crew and captains were on average $54,866 which indicates the importance of the industry as a source of wage income. The resulting average net cash flow is $16,225 but has a large standard deviation. For the population of active Gulf shrimp vessels we can state with 95% certainty that the average net cash flow was between $9,500 and $23,000 in 2006. The median net cash flow was $11,843. Based on the income statement for active Gulf shrimp vessels, the average fixed costs accounted for just under a quarter of operating expenses (23.1%), labor costs for just over a quarter (25.3%), and the non-labor variable costs for just over half (51.6%). The fuel costs alone accounted for 42.9% of total operating expenses in 2006. It should be noted that the labor cost category in the income statement includes both the actual cash payments to hired labor and an estimate of the opportunity cost of owner-operators’ time spent as captain. The average labor contribution (as captain) of an owner-operator is estimated at about $19,800. The average net revenue from operations is negative $7,429, and is statistically different and less than zero in spite of a large standard deviation. The economic return to Gulf shrimping is negative 4%. Including non-operating activities, foremost an average government payment of $13,662, leads to an average loss before taxes of $907 for the vessel owners. The confidence interval of this value straddles zero, so we cannot reject, with 95% certainty, that the population average is zero. The average inactive Gulf shrimp vessel is generally of a smaller scale than the average active vessel. Inactive vessels are physically smaller, are valued much lower, and are less dependent on loans. Fixed costs account for nearly three quarters of the total operating expenses of $11,926, and only 6% of these vessels have hull insurance. With an average net cash flow of negative $7,537, the inactive Gulf shrimp fleet has a major liquidity problem. On average, net revenue from operations is negative $11,396, which amounts to a negative 15% economic return, and owners lose $9,381 on their vessels before taxes. To sustain such losses and especially to survive the negative cash flow, many of the owners must be subsidizing their shrimp vessels with the help of other income or wealth sources or are drawing down their equity. Active Gulf shrimp vessels in all states but Texas exhibited negative returns. The Alabama and Mississippi fleets have the highest assets (vessel values), on average, yet they generate zero cash flow and negative $32,224 net revenue from operations. Due to their high (loan) leverage ratio the negative 11% economic return is amplified into a negative 21% return on equity. In contrast, for Texas vessels, which actually have the highest leverage ratio among the states, a 1% economic return is amplified into a 13% return on equity. From a financial perspective, the average Florida and Louisiana vessels conform roughly to the overall average of the active Gulf shrimp fleet. It should be noted that these results are averages and hence hide the variation that clearly exists within all fleets and all categories. Although the financial situation for the average vessel is bleak, some vessels are profitable. (PDF contains 101 pages)

Benthic sampling program in Biscayne Bay, 1981-1982

The Biscayne Bay Benthic Sampling Program was divided into two phases. In Phase I, sixty sampling stations were established in Biscayne Bay (including Dumfoundling Bay and Card Sound) representing diverse habitats. The stations were visited in the wet season (late fall of 1981) and in the dry season (midwinter of 1982). At each station certain abiotic conditions were measured or estimated. These included depth, sources of freshwater inflow and pollution, bottom characteristics, current direction and speed, surface and bottom temperature, salinity and dissolved oxygen, and water clarity was estimated with a secchi disk. Seagrass blades and macroalgae were counted in a 0.1-m2 grid placed so as to best represent the bottom community within a 50-foot radius. Underwater 35-mm photographs were made of the bottom using flash apparatus. Benthic samples were collected using a petite Ponar dredge. These samples were washed through a 5-mm mesh screen, fixed in formalin in the field, and later sorted and identified by experts to a pre-agreed taxonomic level. During the wet season sampling period, a nonquantitative one-meter wide trawl was made of the epibenthic community. These samples were also washed, fixed, sorted and identified. During the dry season sampling period, sediment cores were collected at each station not located on bare rock. These cores were analyzed for sediment size and organic composition by personnel of the University of Miami. Data resulting from the sampling were entered into a computer. These data were subjected to cluster analyses, Shannon-Weaver diversity analysis, multiple regression analysis of variance and covariance, and factor analysis. In Phase II of the program, fifteen stations were selected from among the sixty of Phase I. These stations were sampled quarterly. At each quarter, five Petite Ponar dredge samples were collected from each station. As in Phase I, observations and measurements, including seagrass blade counts, were made at each station. In Phase II, polychaete specimens collected were given to a separate contractor for analysis to the species level. These analyses included mean, standard deviation, coefficient of dispersion, percent of total, and numeric rank for each organism in each station as well as number of species, Shannon-Weaver taxa diversity, and dominance (the compliment of Simpson's Index) for each station. Multiple regression analysis of variance and covariance, and factor analysis were applied to the data to determine effect of abiotic factors measured at each station. (PDF contains 96 pages)

Morphometric comparisons among yellowfin tuna, Neothunnus macropterus, from the Eastern Tropical Pacific Ocean

ENGLISH: The fishery for yellowfin tuna in the Eastern Tropical Pacific Ocean extends from Southern California to Northern Peru and offshore to a distance of several hundred miles. Sound management of this resource is dependent on knowledge of the relationships among stocks of the many fishing regions within this oceanic area of about one and one quarter million square miles. Godsil (1948), Godsil and Greenhood (1951), Schaefer (1952, ]955) and Royce (1953) have previously examined the morphometry of the yellowfin tuna of the Pacific Ocean and, although these studies were helpful in delineating the major yellowfin stocks of this region, they were of limited value in examining possible sub-divisions f the population fished off the West Coast of the Americas. The importance of this problem and the increase in fishing effort, in recent years, in the new areas off Peru, suggested a re-examination of selected body measurements from fish taken in the various areas of the Eastern Tropical Pacific Ocean, including the more recently exploited grounds off Peru. SPANISH: La pesquería de atún aleta amarilla en el Océano Pacífico Oriental Tropical se extiende desde la California del Sur hasta la región septentrional del Perú, y mar afuera en una extensión de varios cientos de millas. La acertada administración de este recurso depende del conocimiento de las relaciones entre los stocks de las muchas regiones de pesca que se encuentran dentro de esta área oceánica, cuya dimensión es de alrededor de un millón y cuarto de millas cuadradas. Godsil (1948), Godsil y Greenhood (1951), Schaefer (1952, 1955) y Royce (1953) han examinado la morfología del atún aleta amarilla del Océano Pacífico, y a pesar de que los estudios de estos científicos contribuyeron a delinear los más importantes stocks de dicha especie en esta región, han sido, sin embargo, de un valor limitado para el examen de posibles subdivisiones de la población explotada por la pesca frente a la costa occidental de las Américas. La importancia de este problema y el aumento en el esfuerzo de pesca, en años recientes, en las nuevas áreas frente al Perú, han hecho pensar en una revisión de las medidas anatómicas seleccionadas en pescados que se han obtenido en las diversas áreas del Océano Pacífico Oriental Tropical, incluyendo las localidades más recientemente explotadas a la altura de la tierra peruana.

A study of measures of population density and of concentration of fishing effort in the fishery for yellowfin tuna, Neothunnus macropterus, in the Eastern Tropical Pacific Ocean, from 1951 to 1956

ENGLISH: This study shows how the catch and effort statistics, from 1951 to 1956, of the fishery for yellowfin tuna, Neothunnus macropterus, in the Eastern Tropical Pacific Ocean, have been used to compute: (i) two indices of average population density; (ii) an index of concentration of effort on areas of greatest density of available yellowfin. These three indices were then used to determine: (i) quarterly and annual variation in each of them; (ii) the relationship between the two indices of density; (iii) the relationship of each of the indices to the number of exploited one-degree rectangles. To remove extreme sampling variation at low levels of effort, the data from all one-degree rectangles subjected to less than five logged days' fishing in a quarter were eliminated, and the computations were repeated for comparison with those of the original data. SPANISH: Este estudio da a conocer cómo las estadísticas sobre la pesca y el esfuerzo de pesca de la pesquería del atún aleta amarilla, Neothunnus macropterus, en el Océano Pacífico Oriental Tropical, durante 1951 a 1956, han servido para computar: (i) dos índices del promedio de la densidad de la población; (ií) un índice de la concentración del esfuerzo en las áreas de mayor densidad de atún aleta amarilla disponible. Estos tres índices han sido luego usados para determinar: (i) la variación trimestral y anual en cada uno de ellos; (ií) la relación entre los dos índices de densidad; (iii) la relación de cada uno de los índices con el número de rectángulos de un grado explotados. Para evitar la extrema variación del muestreo a bajos niveles de esfuerzo, se eliminaron los datos de todos los rectángulos de un grado sujetos a menos de cinco días de actividad pesquera durante un trimestre según los registros de los cuadernos de bitácora, y las computaciones se repitieron para compararlas con las de los datos originales.

Estimation of year class abundance and mortality of yellowfin tuna in the Eastern Tropical Pacific

ENGLISH: Age composition of catch, and growth rate, of yellowfin tuna have been estimated by Hennemuth (1961a) and Davidoff (1963). The relative abundance and instantaneous total mortality rate of yellowfin tuna during 1954-1959 have been estimated by Hennenmuth (1961b). It is now possible to extend this work, because more data are available; these include data for 1951-1954, which were previously not available, and data for 1960-1962, which were collected subsequent to Hennemuth's (1961b) publication. In that publication, Hennemuth estimated the total instantaneous mortality rate (Z) during the entire time period a year class is present in the fishery following full recruitment. However, this method may lead to biased estimates of abundance, and hence mortality rates, because of both seasonal migrations into or out of specific fishing areas and possible seasonal differences in availability or vulnerability of the fish to the fishing gear. Schaefer, Chatwin and Broadhead (1961) and Joseph etl al. (1964) have indicated that seasonal migrations of yellowfin occur. A method of estimating mortality rates which is not biased by seasonal movements would be of value in computations of population dynamics. The method of analysis outlined and used in the present paper may obviate this bias by comparing the abundance of an individual yellowfin year class, following its period of maximum abundance, in an individual area during a specific quarter of the year with its abundance in the same area one year later. The method was suggested by Gulland (1955) and used by Chapman, Holt and Allen (1963) in assessing Antarctic whale stocks. This method, and the results of its use with data for yellowfin caught in the eastern tropical Pacific from 1951-1962 are described in this paper. SPANISH: La composición de edad de la captura, y la tasa de crecimiento del atún aleta amarilla, han sido estimadas por Hennemuth (1961a) y Davidoff (1963). Hennemuth (1961b), estimó la abundancia relativa y la tasa de mortalidad total instantánea del atún aleta amarilla durante 1954-1959. Se puede ampliar ahora, este trabajo, porque se dispone de más datos; éstos incluyen datos de 1951 1954, de los cuales no se disponía antes, y datos de 1960-1962 que fueron recolectados después de la publicación de Hennemuth (1961b). En esa obra, Hennemuth estimó la tasa de mortalidad total instantánea (Z) durante todo el período de tiempo en el cual una clase anual está presente en la pesquería, consecutiva al reclutamiento total. Sin embargo, este método puede conducir a estimaciones con bias (inclinación viciada) de abundancia, y de aquí las tasas de mortalidad, debidas tanto a migraciones estacionales dentro o fuera de las áreas determinadas de pesca, como a posibles diferencias estacionales en la disponibilidad y vulnerabilidad de los peces al equipo de pesca. Schaefer, Chatwin y Broadhead (1961) y Joseph et al. (1964) han indicado que ocurren migraciones estacionales de atún aleta amarilla. Un método para estimar las tasas de mortalidad el cual no tuviera bias debido a los movimientos estacionales, sería de valor en los cómputos de la dinámica de las poblaciones. El método de análisis delineado y usado en el presente estudio puede evitar este bias al comparar la abundancia de una clase anual individual de atún aleta amarilla, subsecuente a su período de abundancia máxima en un área individual, durante un trimestre específico del año, con su abundancia en la misma área un año más tarde. Este método fue sugerido por Gulland (1955) y empleado por Chapman, Holt y Allen (1963) en la declaración de los stocks de la ballena antártica. Este método y los resultados de su uso, en combinación con los datos del atún aleta amarilla capturado en el Pacífico oriental tropical desde 1951-1962, son descritos en este estudio.

Taxonomic and ecological survey of the flora of Calvert County, Maryland

Resulted from a occasional field trips on the Patuxent River, 1964-1968. Taxonomy and ecology survey following the quarter method (Cottam and Curtis, 1956) Includes: Literature review: Forests, soils, ecology; Materials and Methods: location, criteria, map of Calvert county; Results: descriptive, species of trees sampled; soils, ecology; discussion: vegetational, soils, ecology; Summary; Climate; Physical features of Calvert County; Botanical descriptions; Tables, Current checklist of vascular plants; selective bibliography

Size composition, growth and sexual maturity of bigeye tuna, Thunnus obesus (Lowe), from the Japanese long-line fishery in the Eastern Pacific Ocean

Size composition data of bigeye tuna taken from the eastern tropical Pacific Ocean by Japanese Prefectural experimental training vessels from 1958 to 1964 are examined. A gradient of increasing fish size from east to west is noted. Males increase in ratio over females for the entire range of lengths examined, and beyond 170 cm comprise more than 75 per cent of the total. The first semester of the year is important as a bigeye spawning season. A general relationship between sexual maturity and thermal structure of the water is discussed. At the end of their 12th quarter of life bigeye are about 114 cm long, by the 16th quarter, 137 cm and at the end of 20 quarters, about 153 cm. The long-line fishery in the eastern Pacific has had a marked effect on the size composition of the stocks of bigeye, but whether the fishing has driven the stocks below a point which could afford a maximum sustainable yield could not be determined. (PDF contains 55 pages.)

Geographical distribution of yellowfin tuna and skipjack catches in the Eastern Pacific Ocean, by quarters of the year, 1963-1966

ENGLISH: Logbook records of tuna vessels fishing in the eastern Pacific Ocean were used to prepare charts showing the distribution of yellowfin and skipjack tuna catches by 1-degree area, by quarter of the year, and by gear for the years 1963-1966. Recent changes in the geographical distribution of yellowfin catches are illustrated. The size composition of the U. S. tuna fleet is given, and recent changes are discussed. SPANISH: Los registros de los cuadernos de bitácora de los barcos atuneros que pescan en el Océano Pacifico oriental, se emplearon para preparar los gráficos que indican la distribuci6n de las capturas de atún aleta amarilla y de barrilete por área de 1 grado, por trimestre del ano y por aparejo de pesca para los anos de 1963-1966. Se ilustran los cambios recientes en la distribucion geográfica de las capturas de atún aleta amarilla. Se da la composición de tamaño de la flota atunera de los E. U. y se discuten los cambios recientes. (PDF contains 76 pages.)

Geographical catch distribution of yellowfin and skipjack tuna in the Eastern Pacific Ocean, 1967-1970, and fleet and total catch statistics, 1962-1970

ENGLISH: Logbook records of tuna vessels fishing in the eastern Pacific Ocean were used to prepare charts showing the distribution of yellowfin tuna and skipjack catches by i-degree area, by quarter of the year, and by gear, for the years 1967-1970. Recent changes in the geographical distribution of yellowfin catch are illustrated. Also given are annual catch statistics and the composition of the international tuna fishing fleets which operated in the Commission's Yellowfin Regulatory Area each year, 1962-1970. SPANISH: Los registros de los cuadernos de bitácora de los barcos pesqueros de atún en el Océano Pacífico oriental se usaron para preparar gráficos que presentan para los años de 1967-1970, la distribución de captura del atún aleta amarilla y barrilete por área de 1 grado, trimestre del año y, por las artes. Se ilustran los recientes cambios en la distribución geográfica de la captura del atún aleta amarilla. Se presentan también las estadísticas de captura anual y la composición de la flota internacional de pesca, que explota cada año el Area Reglamentaria de la Comisión, 1962-1970. (PDF contains 95 pages.)

Geographical distribution of yellowfin and skipjack tuna catches in the Eastern Pacific Ocean, and fleet and total catch statistics, 1971-1974

ENGLISH: Logbook records of purse seiners and baitboats fishing for yellowfin and skipjack tunas in the eastern Pacific Ocean were used to prepare charts showing the distribution of catches by l-degree area and quarter of the year for each gear and regulation status, for the years 1971-1974. Changes in geographical distribution of the catch over the four-year period are discernible. Information on annual catch statistics and fleet composition by country is presented. SPANISH: Los registros de bitácora de los cerqueros y clíperes (barcos de carnada) que pescan atún aleta amarilla y barrilete en el Océano Pacífico oriental se emplearon para preparar los diagramas en los que se indica la distribución de las capturas por área de 1 grado y trimestre, correspondiente a cada arte y condición reglamentaria en los años de 1971 a 1974. Se pueden distinguir los cambios en la distribución geográfica de la captura durante el período de cuatro años. Se presenta la información por país sobre las estadísticas de la captura anual y la composicón de la flota. (PDF contains 116 pages.)

Die deutsche Fischerei auf den "ozeanischen" Rotbarsch (Sebastes mentella) von 1995 bis 1998

Recently, the German redfish fishery displayed a pronounced seasonal pattern in geographic effort distribution and depth. The second and third quarters were the main season when 80 % of the effort was exerted. During the second quarter, the fleet activities were concentrated in international waters close to the Icelandic Exclusive Economic Zone (EEZ), fishing at depths exceeding 600 m. In contrast, the catches in the third quarter were taken mainly inside the Greenland EEZ at depths around 300 m. From 1995 to 1998, the annual effort ranged from 14 000 to 18 000 trawling hours, without a trend. This effort yielded about 18 000 to 21 000 t (international catch > 100 000 t) annually. Since 1996, the catch rate (CPUE) decreased during the main season. The decrease in CPUE should be interpreted as the first reaction of the stock to increased exploitation. The fish size also varied seasonally and peaked during the second quarter at depths exceeding 600 m. Here, males were bigger than females and both sexes were equally frequent. The increase of fish size with increasing depth did not contribute to the hypothesis of two separate pelagic redfish stocks above and below 500 m. In contrast, the close relation between fish size and depth point to the so-called “deeper-bigger phenomenon” which was found in numerous fish stocks. Very few redfish in the catches were immature.

Geographical distribution of yellowfin and skipjack tuna catches in the Eastern Pacific Ocean, and fleet and total catch statistics, 1975-1978

ENGLISH: Logbook records of purse seiners and baitboats fishing for yellowfin and skipjack tunas in the eastern Pacific Ocean were used to prepare charts showing the distribution of catches by one-degree area and quarter of the year for each gear and regulation status, for the years 1975-1978. Changes in geographical distribution of the catch over the four-year period are described. Information on annual catch statistics and fleet composition by country is presented. SPANISH: Se emplearon los registros de bitácora de las embarcaciones cerqueras y de carnada que pescan atún aleta amarilla y barrilete en el Océano Pacífico oriental, para preparar los diagramas que indican la distribución de captura por zonas de un grado y trimestres del año de cada arte y condición de las reglamentaciones, en los años de 19'75 a 1978. Se describen los cambios de la distribución geográfica de la captura durante un período de cuatro Se presenta la información, por país, de las estadísticas de captura y de la composición de la flota. (PDF contains 120 pages.)