An assessment of the efficiency of three active fish capture methods and a study of roach / bream hybrids on the Crossens drainage system near Southport.

An assessment of three methods of fish capture, to establish the best fishing method which reflects the best range of sizes and species of fish in a given area. The methods used were trawl netting, electrofishing, and seine netting which were assessed on the Crossens drainage system near Southport. The report also includes a study of roach / bream hybrids that were found at the site, which focuses on their distinguishing features and compared with the features of roach and bream.

Measurement errors in body size of sea scallops (Placopecten magellanicus) and their effect on stock assessment models

Body-size measurement errors are usually ignored in stock assessments, but may be important when body-size data (e.g., from visual sur veys) are imprecise. We used experiments and models to quantify measurement errors and their effects on assessment models for sea scallops (Placopecten magellanicus). Errors in size data obscured modes from strong year classes and increased frequency and size of the largest and smallest sizes, potentially biasing growth, mortality, and biomass estimates. Modeling techniques for errors in age data proved useful for errors in size data. In terms of a goodness of model fit to the assessment data, it was more important to accommodate variance than bias. Models that accommodated size errors fitted size data substantially better. We recommend experimental quantification of errors along with a modeling approach that accommodates measurement errors because a direct algebraic approach was not robust and because error parameters were diff icult to estimate in our assessment model. The importance of measurement errors depends on many factors and should be evaluated on a case by case basis.

Comparison of Standard Length, Fork Length, and Total Length for Measuring West Coast Marine Fishes

Measurements of adult marine fishes on the U.S. west coast are usually made using one of three methods: standard length, fork length, or total length. Each method has advantages and disadvantages. In this paper we attempt to determine whether one method is faster and/or more reliable than the other methods. We found that all three methods were comparable. There was no appreciable difference in the time it took to measure fish using the different methods. Fork length had the most reproducible results; however, it had the highest level of bias between researchers. We therefore suggest that selection of measurement type be based on what other researchers have used for the species under study. The best improvement in measurement reliability probably occurs by adequate training of personnel and not type of measurement used.

TWO TUTORIAL EXAMPLES OF MULTIVARIABLE CONTROL SYSTEM DESIGN.

Two tutorial examples are presented which illustrate different methods of designing practical multivariable control systems using frequency-domain techniques. In the first case eigenvector alignment techniques are used to manipulate and shape the generalized Nyquist diagrams, while in the second case LQG theory in conjunction with singular value plots is employed. In both cases the designs are carried out on a modern computer-aided control-system design package.

Improved chemical methods for extraction of fin rays from shark fins

A survey was undertaken of methods available for the extraction of fin rays from shark fins. The development of new, quicker and easier methods of processing is presented.

Fibre optics monitoring of clay cuttings and embankments along London's ring motorway

Although a wide range of techniques exist for slope monitoring, the task of monitoring slopes is sometimes complicated by the extensive nature and unpredictability of slope movements. The Brillouin optical time-domain reflectometer (BOTDR) is a distributed optical fiber strain measurement technology utilising Brillouin scattering. This method measures continuous strain along a standard optical fibre over a distance up to 10 km and hence has potential to detect deformations and diagnose problems along large sections of slopes and embankments. This paper reports the demonstration of BOTDR method for monitoring surface ground movements of clay cuttings and embankments along London's ring M25 motorway. A field trial investigating varying methods of onsite fibre optic installations was conducted. The surrounding ground was artificially moved by excavating a 3 m deep trench perpendicular to the instrumented sections. Results obtained from onsite installations after slope movement demonstrate a half-pipe covered fibre optic installed on wide (200mm) Tensar ™SS20 geogrid gives the most consistent recorded strain change profile. Initial conclusions suggest this method best represents induced ground motion at the surface and hence is recommended for implementation in future sitework. Copyright ASCE 2008.

Impacts of fishing gears, fishing methods and fishing effort in the fisheries of Lake Victoria and proposals for management

The initial subsistence fisheries of Lake Victoria were dominated by two indigenous tilapiines, Oreochromis esculentus (Graham 1929) and Oreochromis variabilis Boulenger 1906, exploited with simple fishing crafts and gears that had little impact on the fish stocks (Jackson 1971). Commercial fisheries, targeting the tilapia fishery, started at the beginning of the 20th Centurywhen cotton flax gillnets were first introduced in 1905 into the Nyanza Gulf in Kenya. Gillnets were quickly adopted around the whole lake and consequently, the native methods of fishing soon died out (Jackson 1971). Following the introduction of gillnets, fishing boats and their propulsion methods were also improved. These improvements in fishing capacity coincided with development of urban centres and increasing human population around the lake, which increased the demand for fishery products. To satisfy the increasing demand, fishing effort increased greatly during the 20th century, despite the decline of catch per unit of effort (CPUE) (Jackson 1971; Ogutu-Ohwayo 1990). The initial catch rates of 127mm (5 inch) mesh size gill nets in the tilapia-based fishery, in 1905, was in the range of 50 to 100 fish per gillnet of approximately 50 m in length. However, twenty years later, the catch rates of gillnets of the same mesh size had declined to about six fish per net and gillnets of smaller mesh sizes, which had better catch rates, had been introduced suggesting overfishing (Worthington and Worthington, 1933).

Experimental investigation of stratified combustion: Application of laser diagnostic techniques

In order to better understand the stratified combustion, the propagation of flame through stratified mixture field in laminar and turbulent flow conditions has been studied by using combined PIV/PLIF techniques. A great emphasis was placed on developing methods to improve the accuracy of local measurements of flame propagation. In particular, a new PIV approach has been developed to measure the local fresh gas velocity near preheat zone of flame front. To improve the resolution of measurement, the shape of interrogation window has been continuously modified based on the local flame topology and gas expansion effect. Statistical analysis of conditioned local measurements by the local equivalence ratio of flames allows the characterization of the properties of flame propagation subjected to the mixture stratification in laminar and turbulent flows, especially the highlight of the memory effect.

Micro-measurement and monitoring system for ageing underground infrastructure (Underground M3)

Advances in the development of computer vision, miniature Micro-Electro-Mechanical Systems (MEMS) and Wireless Sensor Network (WSN) offer intriguing possibilities that can radically alter the paradigms underlying existing methods of condition assessment and monitoring of ageing civil engineering infrastructure. This paper describes some of the outcomes of the European Science Foundation project "Micro-Measurement and Monitoring System for Ageing Underground Infrastructures (Underground M3)". The main aim of the project was to develop a system that uses a tiered approach to monitor the degree and rate of tunnel deterioration. The system comprises of (1) Tier 1: Micro-detection using advances in computer vision and (2) Tier 2: Micro-monitoring and communication using advances in MEMS and WSN. These potentially low-cost technologies will be able to reduce costs associated with end-of-life structures, which is essential to the viability of rehabilitation, repair and reuse. The paper describes the actual deployment and testing of these innovative monitoring tools in tunnels of London Underground, Prague Metro and Barcelona Metro. © 2012 Taylor & Francis Group.

A critical analysis of loudness calculation methods

The physical meaning and methods of determining loudness were reviewed Loudness is a psychoacoustic metric which closely corresponds to the perceived intensity of a sound stimulus. It can be determined by graphical procedures, numerical methods, or by commercial software. These methods typically require the consideration of the 1/3 octave band spectrum of the sound of interest. The sounds considered in this paper are a 1 kHz tone and pink noise. The loudness of these sounds was calculated in eight ways using different combinations of input data and calculation methods. All the methods considered are based on Zwicker loudness. It was determined that, of the combinations considered, only the commercial software dBSonic and the loudness calculation procedure detailed in DIN 45631 using 1/3 octave band levels filtered using ANSI S1.11-1986 gave the correct values of loudness for a 1 kHz tone. Comparing the results between the sources also demonstrated the difference between sound pressure level and loudness. It was apparent that the calculation and filtering methods must be considered together, as a given calculation will produce different results for different 1/3 octave band input. In the literature reviewed, no reference provided a guide to the selection of the type of filtering that should be used in conjunction with the loudness computation method.

Continuous weak measurement and feedback control of a solid-state charge qubit: A physical unravelling of non-Lindblad master equation

Conventional quantum trajectory theory developed in quantum optics is largely based on the physical unravelling of a Lindblad-type master equation, which constitutes the theoretical basis of continuous quantum measurement and feedback control. In this work, in the context of continuous quantum measurement and feedback control of a solid-state charge qubit, we present a physical unravelling scheme of a non-Lindblad-type master equation. Self-consistency and numerical efficiency are well demonstrated. In particular, the control effect is manifested in the detector noise spectrum, and the effect of measurement voltage is discussed.

Quantum measurement of an electron in a disordered potential: Delocalization versus measurement voltages

Quantum point contact (QPC), one of the typical mesoscopic transport devices, has been suggested to be an efficient detector for quantum measurement. In the context of two-state charge qubit, our previous studies showed that the QPC's measurement back-action cannot be described by the conventional Lindblad quantum master equation. In this work, we study the measurement problem of a multistate system, say, an electron in disordered potential, subject to the quantum measurement of the mesoscopic detector QPC. The effect of measurement back-action and the detector's readout current are analyzed, where particular attention is focused on some new features and the underlying physics associated with the measurement-induced delocalization versus the measurement voltages.

Method for measurement of lattice parameter of cubic GaN layers on GaAs (001)

An extended technique derived from triple-axis diffraction setup was proposed to measure lattice parameters of cubic GaN(c-GaN) films. The fully relaxed lattice parameters of c-GaN are determined to be 4.5036+0.0004 Angstrom, which is closer to the values of a hypothetical perfect crystal. The speculated zero setting correction (Deltatheta) is very slight and within the range of the accuracy of measurement. Additionally, we applied this method to analyze strain of four different kinds of c-GaN samples. It is found that in-plane strain caused by large lattice mismatch and thermal expansion coefficients mismatch directly influence the epilayer growth at high temperatures, indicating that the relaxation of tensile strain after thermal annealing helps to improve the crystalline quality of c-GaN films and optical properties. (C) 2003 Elsevier Science B.V. All rights reserved.

Low-temperature (10 K) infrared measurement of interstitial oxygen in heavily antimony-doped silicon via wafer thinning

A new technique is reported for the rapid determination of interstitial oxygen in heavily Sb-doped silicon. This technique includes wafer thinning and low-temperature 10 K infrared measurement on highly thinned wafers. The fine structure of the interstitial oxygen absorption band around 1136 cm(-1) is obtained. Our results show that this method efficiently reduces free-carrier absorption interference, allowing a high reliability of measurement, and can be used at resistivities down to 1 x 10(-2) Omega cm for heavily Sb-doped silicon.