Developments in the application of multibeam sonar backscatter for seafloor habitat mapping

Human impacts on the seafloor environment have reached unprecedented levels. To facilitate ocean management and mitigate these impacts, there is a need to improve our understanding of seabed habitats. Recent developments in acoustic survey techniques, in particular multibeam echosounders (MBES), have revolutionised the way we are able to image, map and understand benthic ecosystems. Using MBES, it is now cost-effective to image large areas of the seafloor, and such surveys provide baseline data from which thematic maps of the seabed environment, including maps of benthic habitat, can be derived and interpreted in conjunction with in situ ground-truthing data. This paper provides an overview of recent developments in the application of MBES for seafloor habitat studies, with a focus on the use of backscatter data for surficial geology and habitat mapping. In March 2006, a MBES backscatter workshop brought together a number of international research teams/groups working on novel methods for interpretive/classification routines for segmentation of the backscatter into acoustic classes with the potential to facilitate the delineation of seabed geological and habitat characteristics. This paper introduces the common data set used as part of the workshop, sets out the research context in which the different studies were conducted, and outlines the main themes of the papers presented in Section 6.     

The use of multibeam backscatter angular response for marine sediment characterisation by comparison with shallow electromagnetic conductivity

In this empirically-driven research, multibeam backscatter angular response analysis is presented, together with shallow electromagnetic data and groundtruthing, to examine its suitability as a proxy for sediment characterisation. Backscatter angular curves extracted from Kongsberg EM1002 sonar (95–98 kHz), acquired in the Malin Basin to the northwest of Ireland, have been selected as a case study. Standard angular backscatter features and newly derived curvature features are examined and cross compared. Exhaustive statistical analysis has been performed on the data to elucidate the complex relationship between multibeam backscatter and sediment properties. Subtle subsurface sediment property gradients across the basin identified by the conductivity system are also captured by the newly derived backscatter features. The results reveal that Near-range backscatter is better suited for subsurface sediment characterisation in soft, fine-grained sediments than far-range. Furthermore, the analysis has constrained the optimum interval for such characterisation to in-between 4° and 16° for the parameters of this study. A number of shape features (slope, first derivative, second derivative and Fourier-smoothed least-squares-fitted curvature) have been examined, and their suitability discussed, in terms of sediment characterisation and, in particular, as potential proxies for delineating the boundary between sand- or silt-dominated sediment facies. Nonetheless, curvature features are found to be independent from average angular backscatter response, but outperform both first and second derivatives when correlating with conductivity in the central part of this case-study with fine-grained homogeneous sediments.     

Neural network classification of multibeam backscatter and bathymetry data from Stanton Bank (Area IV)

The paper presents an approach to automated seabed classification that incorporates spatially coincident bathymetric and backscatter data collected in multibeam surveys. The classification algorithm is a self-organising artificial neural network that can be used as a rapid classifier of grids of bathymetry (and attributes such as slope and roughness) and backscatter strength (and textures), or in a mode that uses both datasets at beam level to construct high spatial resolution classifications that preserve angular information in the backscatter. The latter mode requires processing of backscatter angular responses in a manner consistent with the essential physics of acoustic scattering from the seafloor.     

Numerical investigation of ultrasound reflection and backscatter measurements in cancellous bone on various receiving areas

In this study, new ultrasound reflection and backscatter measurements in cancellous bone using a membrane-type hydrophone are proposed. A membrane hydrophone made of a piezoelectric polymer film mounted on an annular frame allows an incident ultrasound wave to pass through its aperture because it has no backing material. Therefore, in measurements using the membrane hydrophone, the receiving area could be located independently from the transmitting area. In addition, the size and shape of the receiving area, which corresponded to those of the electrode deposited on the piezoelectric film, could be arranged in various ways. To investigate the validity of the proposed measurements, before bench-top experiments, the reflected and backscattered waves from cancellous bone were numerically simulated using a finite-difference time-domain method. The reflection and backscatter parameters were measured on various receiving areas, and their correlation coefficients with the structural parameters in the cancellous bone were derived. The simulated results suggested that appropriate receiving areas for the reflection and backscatter measurements could exist and that the proposed measurements could be more effective for evaluating bone properties than conventional measurements.     

Comparison of four methods for processing data on exponential decay

Multiphoton resonant ionization in the case of a doubly degenerate intermediate bound state is studied. In the Keldysh-Feisal-Reiss approach, expressions for the energy and angular photoelectron distributions and the quasi-classical formula for the total rate of resonant ionization are obtained. It is shown that the ionization rate may be both higher and lower than the ionization rate in the usual case depending on the relationship between parameters. A situation with a strongly suppressed probability of resonant ionization is possible. In the near-threshold region, the angular dependence of the probability of photoelectron escape is shown to be weaker in comparison with the case of ionization via a nondegenerate level.     

Comparison of wire and fiber optics data transfer systems for large military aircraft

Methods for comparing the life-cycle cost of fiber optics and wire data transfer systems on large military aircraft are established. Using the B-1 as an example, the applicability of fiber optics to avionics/electrical systems on large aircraft is identified. Conceptual fiber optics data transfer systems are described. The present wire and the conceptual fiber optics designs form a basis for computerized lifecycle cost comparisons. Sensitivity analyses and cost trade-offs to determine cost drivers in the application of fiber optics are described. Results show that significant cost benefits can be gained by the implementation of fiber optics in newly designed data transfer subsystems having data rates in excess of 2-3 Mbits/sec.     

High power lasers for processing of materials - a comparison of available systems

Lasers are being used increasingly for specialized engineering applications such as the drilling and scribing of ceramics, and the profile cutting, welding and surface heat-treatment (hardening, alloying and splat-quenching) of metals. The most important characteristics of lasers used for these materials- processing applications (in particular argon-ion, Nd-YAG, and CO₂) are reviewed, with special emphasis on the importance of the electrical efficiency of such systems. The article concludes with a summary of the current status of industrial multi-kilowatt CO₂ lasers, which are of particular interest for metal-working applications.     

椭圆偏振法数据处理软件设计

以C^ Builder 6．0为开发工具,成功设计和编制了一套椭偏法数据处理软件．它具有求解透明膜厚度、折射率和金属复折射率以及绘制(n,d)～(Ψ,△)列线图的功能,求解膜厚和折射率精度分别达到0．01nn、和0001．实验表明该软件的求解结果是准确和可靠的．     

密立根油滴实验数据处理方法的分析与改进

介绍了目前常用的几种密立根油滴实验数据处理的方法,并对其中一种方法进行了改进,使其更加科学,更加符合实验教学实际．     

Digital holographic cameras and data processing for remote monitoring and measurements of mechanical parts

Fast growing technology and requirements for testing of different types of materials and devices require new methods and systems for investigation of their parameters. Among the quantities of high interest are shape, deformation, roughness, local materials constants, displacement, and strain fields of elements under load. In the paper, we present novel solutions for digital holographic cameras, which allow for remote monitoring and measurement of the above mentioned quantities at small mechanical objects or at restricted areas of interest at big structures. The systems have compact design, “black box” measurement approach, and allows for fast and accurate measurements performed directly at the element and often in outdoor environment. The principles of digital and optoelectronic reconstruction and phase manipulation are described together with the exemplary measurement results obtained by means of the cameras presented.     

振动线数据采集和数据处理方案设计与验证

振动线理论提供了一种高精度准直方法,将振动线理论应用于共架磁铁准直,可大大提高共架磁铁间的准直精度。介绍了应用振动线准直共架磁铁的实施方案,从总体方案出发,以振动线理论为依据提出了一种振动线系统数据采集和数据处理设计方案,并对传感器工作点对准、导线电流测量、数据采集设备选取、磁感应强度计算、磁场中心计算等关键问题进行分析,给出了解决方案。最后通过实验验证了方案的可行性以及系统的测量精度。     

Refractive power mapping of progressive power lenses using Talbot interferometry and digital image processing

A method of refractive power mapping of a lens is presented which is based on Talbot interferometry and utilizes a digital image processor. By adding a digital image processing system, fast measurement of a lens power distribution is feasible. A test lens is placed in front of two collinearly arranged gratings. The light passing through the test lens produces a shifted Talbot image of the first grating on the second grating and generates moiré fringes. Given the inclination angle of moiré fringes, the refractive power of the lens can be calculated. The calculation is performed using a digital image processor. This method is effective in finding the refractive power distribution of progressive power lenses.     

三维声波测井探测特性分析与处理技术应用

三维声波测井技术是近年来测井领域的重要进展,由于其集成了井孔轴向、径向和周向的三维信息探测能力,因而在各种复杂油气藏勘探开发中具有广阔的应用前景.从井孔声波探测的基本原理入手,对三维声波测井在井孔径向和周向的探测特性进行了研究.并且在传统资料处理方法的基础上,研发了适合三维声波测井的各向异性快速反演技术、径向速度层析反...     

Comparison of experimental stopping power data for MeV protons,deutrons and alpha particles

Stopping power data for MeV light ions published by groups from Nara University and from Risö are compared. The results of the two groups agree within the stated accuracies for deutrons and alphas, while the Nara results are systematically lower for protons. Based on the failure of the Nara group to obtain the same stopping power for protons and deutrons of the same velocity, and on comparisons with other published data, it is concluded that the Nara proton results are systematically too low.     

Overview: Effect of High Pressure on Enzymes Related to Food Quality - Kinetics as a Basis for Process Engineering

In the last decade, high pressure technology received a major interest in food processing/preservation since it offers some advantages especially in retaining food quality attributes ( i.e. colour, flavour and nutritional value). In the framework of defining HACCP guidelines or 'Novel Food' regulation, and also from an engineering point of view, kinetics of pressure process impact on safety and quality aspects of foods are indispensable. In this context, quantitative kinetic studies of the combined pressure and temperature effect on several food related aspects such as food quality related enzymes, pathogenic/spoilage microorganisms, nutritional and sensorial quality characteristics are required. Moreover, from an engineering point of view, such kinetic data are of major importance for evaluation of process uniformity, for process validation and process optimisation.     

Comparison of the performance of different tools for fast simulation of ultrasound data

Simulation of ultrasound data is often performed for developing new ultrasound data processing techniques. The spatial impulse response method (as implemented in FieldII) has typically been used as the gold standard due to its excellent accuracy in the linear domain. When scatterer numbers become significant and when 3D volumetric data sets need to be computed, calculation time can become an issue however. In order to solve this problem, two alternative methods have recently been proposed both of which are based on the principle of convolving a set of point scatterers with a point spread function. “FUSK” operates in the frequency domain while “COLE” runs in the spatio-temporal domain. The aim of this study was to directly contrast both methodologies in terms of accuracy and processing speed using FieldII as a reference.     

用高亮度LED和简便数据处理方法测定椭圆偏振光的椭圆曲线

通过建立椭圆偏振光在β方向上的光振动大小与检偏器在β+90°方向时光电检测器所测光强之间的关系式,以高亮度LED为光源,可简便地测定椭圆偏振光的椭圆曲线.