Einfluss des Tag-Nacht-Verhaltens von Fischen auf das Ergebnis hydroakustischer Messungen

Echo integration is an established method for stock estimation. However, this method is not free of errors like every other measuring method. Especially the variation between day and night behaviour of fish may lead to large measuring errors. A new method is represented detecting such systematic errors, exemplified by investigations during the international hydroacoustic survey on the spring spawning herring in the Norwegian Sea. For this method all measured sA-values are sorted by starting time of the measuring unit distance. In order to reduce random influences a moving average over five time intervals is computed. When displaying these values in a diagram makes it is very easy to detect systematic errors based on the differences in day-night behaviour. For both species, herring and blue whiting, stock estimations are calculated based on the measured sA-values and the results of the analysed trawl catches. The influence of the differnt day and night behaviour of herring on the results of its biomass estimation is rather low. For blue whiting the measured values were about three time higher during day time than during night time. The result of this investigation should initiate a change of the evaluation procedure for stock estimation based on hydroacoustic measurements.

随机缺陷对蜂窝结构动态行为影响的有限元分析

通过对胞壁随机移除的蜂窝结构动态变形过程的有限元模拟，分析了随机缺陷对蜂窝结构变形模式的影响，得到蜂窝结构在两个加载方向上的变形模式图及不同模式间转换的临界速度. 对含缺陷蜂窝结构平台应力的研究发现，当变形模式为过渡模式或动态模式时结构平台应力与冲击速度的平方成线性关系. 相同密度下，低缺陷蜂窝结构的平台应力在由过渡模式向动态模式转变的临界速度附近高于规则蜂窝结构，较高的随机缺陷则使蜂窝结构的平台应力在由准静态模式向过渡模式转变的临界速度附近显著下降.

Nuevo sistema de propulsión naval

143 p.

准定常强激波反射马赫杆突出变形准则的探讨

分析了滑移线延长线与楔面交点附近的流动特点,研究了准定常强激波反射中马赫杆的变形,建立了马赫杆突出变形消失的过渡准则,并用激波极曲线方法进行了求解.对马赫杆的变形过程进行了描述,研究了比热比、马赫数的变化对马赫杆突出变形消失条件的影响,并对突出变形消失区域与终点双马赫反射区域进行了比较.结果表明:马赫杆突出变形的消失是低比热比介质中出现的一种激波反射现象.马赫杆突出变形的消失,导致出现一种新的无射流、直马赫杆的双马赫反射结构.

"Talla 38"

Capítulo 6 del libro: Guisasola, Jenaro ; Garmendia, Mikel (eds.) "Aprendizaje basado en problemas, proyectos y casos: diseño e implementación de experiencias en la universidad" (ISBN: 978-84-9860-959-2)

Evolución y progreso de las asociaciones de desarrollo rural en Gipuzkoa, un modelo necesitado de mayor autonomía y apoyo institucional

[ES] Tras dos décadas dedicadas a la promoción de los espacios rurales las Asociaciones de Desarrollo Rural de Gipuzkoa se han convertido en el vehículo prioritario para el progreso de este tipo de espacios. Su trayectoria ha estado marcada por toda una sucesión de programas con objetivos diversos y directrices políticas y presupuestarias diferentes. Como consecuencia se ha creado un modelo de dinamización rural centrado en la comarca y caracterizado por la diversidad de acciones que aborda y por su capacidad para incorporar nuevos campos, por su alto grado de implicación en la coordinación, ejecución e incluso gestión de servicios y por su capacidad de incorporar actores al desarrollo de los espacios rurales. A pesar de lo acertado del modelo éste aún tiene asignaturas pendientes, especialmente su dependencia de la decisiones políticas que en cada momento se toman y como consecuencia su falta de autonomía, la excesiva ligazón que aún presenta con el que fue el objeto inicial de estas Asociaciones, la realización de infraestructuras y especialmente el estrépito fracaso que ha tenido su pretensión de incorporar a otras instituciones y departamentos además de los propiamente agrarios.

Two-phase flow and pool boiling heat transfer in microgravity

Researches on two-phase flow and pool boiling heat transfer in microgravity, which included groundbased tests, flight experiments, and theoretical analyses, were conducted in the National Microgravity Laboratory/CAS. A semi-theoretical Weber number model was proposed to predict the slug-to-annular flow transition of two-phase gas–liquid flows in microgravity, while the influence of the initial bubble size on the bubble-to-slug flow transition was investigated numerically using the Monte Carlo method. Two-phase flow pattern maps in microgravity were obtained in the experiments both aboard the Russian space station Mir and aboard IL-76 reduced gravity airplane. Mini-scale modeling was also used to simulate the behavior of microgravity two-phase flow on the ground. Pressure drops of two-phase flow in microgravity were also measured experimentally and correlated successfully based on its characteristics. Two space experiments on pool boiling phenomena in microgravity were performed aboard the Chinese recoverable satellites. Steady pool boiling of R113 on a thin wire with a temperature-controlled heating method was studied aboard RS-22, while quasi-steady pool boiling of FC-72 on a plate was studied aboard SJ-8. Ground-based experiments were also performed both in normal gravity and in short-term microgravity in the drop tower Beijing. Only slight enhancement of heat transfer was observed in the wire case, while enhancement in low heat flux and deterioration in high heat flux were observed in the plate case. Lateral motions of vapor bubbles were observed before their departure in microgravity. The relationship between bubble behavior and heat transfer on plate was analyzed. A semi-theoretical model was also proposed for predicting the bubble departure diameter during pool boiling on wires. The results obtained here are intended to become a powerful aid for further investigation in the present discipline and development of two-phase systems for space applications.

A review paper on Integrated Aquaculture Benefits Project at Federal College of Forestry, Ibadan

This paper highlights some of the practices involved in integrated aquaculture such as poultry-cum-fish, pig-cum-fish, sheep and goat-cum-fish and grasscutter-cum-fish. Also the role of fisheries in alleviating protein deficiency was reviewed. Successful research findings on these practices in aquaculture at the Federal College of Forestry, Jericho, Ibadan (Nigeria) will eventually lead to alleviating protein deficiency of the inhabitants of the largest city in West African thus alleviating poverty in the nation

钙质砂的胶结性及对力学性质影响的实验研究

对南海钙质砂进行了三轴实验研究, 重点针对不同胶结情况下的力学性质,如不同胶结材料和含量的变化对强度和应力应变特性的影响等.研究表明,钙质砂具有与陆源砂不同的性质,它的内摩擦角高达48°,远大于一般陆源砂的35°左右;在低围压下钙质砂表现出剪胀性,但随围压增加剪胀性降低;利用硅酸盐水泥作为胶结材料效果较好;随着水泥含量的增加,钙质砂试样的强度增加.

Storage potential and utilization of tilapia mince

Production of mince from Tilapia using a combination of physical and chemical methods was found to improve the storage life of the mince in the deep freezer. Though the chemical composition of the mince was slightly affected, the mince was microbiologically stable throughout the five weeks frozen storage. Fish cakes prepared traditionally from tilapia minces were more acceptable than oven dried cakes. Production of fish cakes form tilapia will improve utilization of this species in areas where small size tilapia are regarded as fish of low economic value

THE FORMATION MECHANISM OF THE VITRIFIED SLAG IN A PLASMA ARC REACTOR FOR HAZARDOUS WASTE TREATMENT

Various hazardous wastes with additives have been vitrified to investigate the formation mechanism of the glassy slag by a 30 kW DC plasma-arc reactor developed by the Institute of Mechanics, Chinese Academy of Sciences. The average temperature in the reaction area is controlled at 1500°C. The chemical compositions of three sorts of fly ashes are analyzed by XRF (X-Ray Fluorescence). Fly ashes with vitrifying additives can be vitrified to form glassy slag, which show that the ratio of the whole oxygen ions to the whole network former ions in glass (R) is appropriate in the range of 2~3 to form durable vitrified slag. In this experiment, the arc power is controlled below 5 kW to inhibit waste evaporation. To enhance the effects of heat transfer to wastes, ferrous powder has been added into the graphite crucible, which aggregates as ingot below the molten silicate after vitrification. The slag fails to form glass if the quenching rate is less than 1 K/min. Therefore, the slag will break into small chips due to the sharp quenching rate, which is more than 100 K/sec.

Fisheries statistics of Kainji Lake, northern Nigeria, Nov. 1994 - Dec. 1998

Results are presented for the first 4 years data (1994-1998) of the Kainji Lake catch assessment survey, collected and analysed by the Nigerian-German Kainji Lake Fisheries Promotion Project. The following areas are covered: Methodology and alterations of the original sampling concept; Frame survey results - factors relating to the CAS; Catch assessment survey results - general; Gill net fishery; Drift net fishery; Beach seine fishery; Cast net fishery; Longline fishery; Trap fishery; and, Catch statistics from fisherwomen. (PDF contains 143 pages)

Effects of some environmental factors on the fecundity of Tilapia species (Family Cichlidae) in Kigera Reservoir, New Bussa

The effects of some environmental factors on the fecundity of Tilapia species (Family Cichilidae) was carried out at the Kigera dam. Four Tilapia species caught were Tilapia zilli, Hemichromis fasciatus, Sarotherodon galilaeus and Oreochromis niloticus while the environmental factors considered were water temperature, Dissolved Oxygen, pH value, level of rainfall and rate of sunshine and range of time. 43 fish comprising of 25 male with (58.1%) and 18 females having (41.9%) were studied with 74.42% been sexually matured. Both high levels of rainfall and dissolved oxygen favoured fecundity. The spawning peak occurred in (July), environmental factors monitored indicated that dissolved oxygen ranges from 3.7 to 4.45mg/lit rainfall ranges from (34.90mm to 237.80mm) sunshine ranges from (5hrs-8hrs) and pH ranges from (7.35-7.45). The spawning of these species in their natural or hatchery condition is therefore best achieved during the peak of raining season

Analyse des Fluchtverhaltens von Fischen auf Schiffsgeräusche mit hydroakustischen Methoden

Investigations on the avoidance reactions of pelagic schooling fish (herring and sprat) released by an approaching fishery vessel were carried out during the 378th cruise of FRC "Solea" from 25 September to 3 October 1995 in the Arkona Sea, southern Baltic. An echosounder system EK 500/BI500 with a 38 kHz transducer mounted on a towed body as weIl as a 120 kHz hull mounted transducer were used. Fish densities were measured synchronously as well as under the ship as at a laterally distances from the ship by the transducer of the towed body. By these means the variation of fish densities up to a certain distance from the ship is possible. The advantage of using an echo integrating system for these measurements is, that it works also for not schooling fish and under conditions where schooling fish disperse (e.g. at night).