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1 – 10 of 11Zhenzhen Shang, Wendong Zhang, Guojun Zhang, Xiaoyong Zhang, Lansheng Zhang and Renxin Wang
The problem of port and starboard ambiguity will exist when only utilize the vector or scalar parameters. Meanwhile, the amplitude-phase error between the vector and scalar can…
Abstract
Purpose
The problem of port and starboard ambiguity will exist when only utilize the vector or scalar parameters. Meanwhile, the amplitude-phase error between the vector and scalar can also cause this problem. In this paper, a compound MEMS vector hydrophone which contains cilia vector microstructure and piezoelectric ceramic tube has been presented to solve the problem. Compared with traditional MEMS vector hydrophone, the compound MEMS vector hydrophone can realize the measurement of sound pressure and vibration velocity simultaneously.
Design/methodology/approach
A compound MEMS vector hydrophone has been presented. The unipolar directivity of the combined signal which combine the acoustic pressure and vibration velocity is used to achieve the direction of arrival (DOA). This paper introduced the working principle and the target detection mechanism of the compound vector hydrophone. The amplitude and phase error are analyzed and corrected in the standing wave tube. After that, the authors use beam-forming algorithm to estimate the DOA.
Findings
The experimental results in the standing wave tube and the external field verified the vector hydrophone's directional accuracy up to 1 and 5 degrees, respectively.
Practical implications
The research of compound vector hydrophone plays an important role in marine acoustic exploration and engineering applications.
Originality/value
This research provides a basis for MEMS hydrophone directivity theory. The compound vector hydrophone has been applied in the underwater location, with a huge market potential in underwater detection systems.
Details
Keywords
Zhenzhen Shang, Libo Yang, Wendong Zhang, Guojun Zhang, Xiaoyong Zhang, Hairong Kou, Junbing Shi and Xin Xue
This paper aims to solve the problem that strong noise interference seriously affects the direction of arrival (DOA) estimation in complex underwater acoustic environment. In this…
Abstract
Purpose
This paper aims to solve the problem that strong noise interference seriously affects the direction of arrival (DOA) estimation in complex underwater acoustic environment. In this paper, a combined noise reduction algorithm and micro-electro-mechanical system (MEMS) vector hydrophone DOA estimation algorithm based on singular value decomposition (SVD), variational mode decomposition (VMD) and wavelet threshold denoising (WTD) is proposed.
Design/methodology/approach
Firstly, the parameters of VMD are determined by SVD, and the VMD method can decompose the signal into multiple intrinsic mode functions (IMFs). Secondly, the effective IMF component is determined according to the correlation coefficient criterion and the IMF less than the threshold is processed by WTD. Then, reconstruction is carried out to achieve the purpose of denoising and calibration baseline drift. Finally, DOA estimation is achieved by the combined directional algorithm of preprocessed signal.
Findings
Simulation and field experiments results show that the algorithm has good noise reduction and baseline drift correction effects for nonstationary underwater signals, and high-precision azimuth estimation is realized.
Originality/value
This research provides the basis for MEMS hydrophone detection and positioning and has great engineering significance in underwater detection system.
Details
Keywords
AN encouraging degree of reliability has been achieved with the prototype Skyvan which to date has flown in excess of 200 hours in development and demonstration. The initial 30…
Abstract
AN encouraging degree of reliability has been achieved with the prototype Skyvan which to date has flown in excess of 200 hours in development and demonstration. The initial 30 hours were completed in the Mk. 1 piston engined configuration and consisted solely of handling and development flying; the aircraft was then grounded and re‐engined with the Turbomeca Astazou II since when, some 175 hours have been flown in 230 flights, as the Mark 1 A. A reliability assessment of this latter period shows that, using technical delays as the criterion, the aircraft has achieved a 98 per cent flight regularity, and the premature removal rate of system components has been commendably low for development flying.
The purpose of the present work is to develop a unified mathematical theory of the steady and disturbed motion of a helicopter with particular emphasis on the dynamical aspects of…
Abstract
The purpose of the present work is to develop a unified mathematical theory of the steady and disturbed motion of a helicopter with particular emphasis on the dynamical aspects of the problem. The helicopter is assumed to undergo arbitrary small disturbances in velocity and angular velocity from a steady rectilinear flight condition, and the rotor forces are calculated as generalized functions of the initial and disturbed velocities. A high degree of accuracy is maintained both in the retention, where necessary, of products of small quantities and in the retention of high powers of µ in the solution of the trim equations. The steady motion of the helicopter is discussed at length as a preliminary to a study of its dynamic stability. Part I deals with the general features underlying helicopter motion. The importance is emphasized of a three‐dimensional approach to the problem, and it is shown that a complete description of steady rectilinear motion demands the use of fifteen equations in eighteen parameters, the solution of which presents no real difficulty. A start is made on the analysis of rotor blade motion, and the geometrical aspects are discussed by means of a system of rotating vectors.
THE art of navigating any mobile craft depends essentially on being able to determine the position of that craft with relation to a fixed point or points; the position may either…
Abstract
THE art of navigating any mobile craft depends essentially on being able to determine the position of that craft with relation to a fixed point or points; the position may either be obtained in the form of a bearing on, and a distance from, any known fixed point, or of simultaneous bearings from two or more fixed points, which bearings are laid off on a chart and denote, by their intersection, the position of the craft at the time.
In order to provide information for flutter and dynamic stress calculations on an aircraft a knowledge of the normal modes of vibration is required. In the following paper a…
Abstract
In order to provide information for flutter and dynamic stress calculations on an aircraft a knowledge of the normal modes of vibration is required. In the following paper a matrix method, due to Dr Traill‐Nash, is extended and used to obtain a general expression for the complete aircraft normal modes, and is applicable to most aircraft configurations. The method is considered to be eminently suitable for use with modern digital electronic computational equipment. Methods arc discussed vthcrcby the degrees of freedom may be economized without significant loss of accuracy. By restriction of the degrees of freedom allowed, important subsidiary cases arc drawn from the general expressions, allowing standard matrix solutions suitable for normal oflicc routine.
The purpose of this paper is to explore Thomas Pynchon's novel Against the Day as a symptomatology of organization and examine the (un)easy relationship between the novel and…
Abstract
Purpose
The purpose of this paper is to explore Thomas Pynchon's novel Against the Day as a symptomatology of organization and examine the (un)easy relationship between the novel and organization.
Design/methodology/approach
The novel is explored through three interrelated readings: first, the novel is considered as a representation of the gruesome nature of capitalist ordering; Second, the novel's textual strategies are examined to consider its co‐implication and knotting into the very logic of organization it abhors; Third, the novel is read as a search for other spaces haunting the broken machine of capitalist organizing.
Findings
The paper shows how Pynchon's writing and critique of capitalist organizing occupies an indeterminate space characterised by the ambivalence of ambivalence, where deciding upon its final meaning is a reductivist strategy ill suited to this complex text. Instead the novel functions through a complex process of displacement and emplacement.
Originality/value
Theoretically, the paper extends further the understanding of the relationship between literature and organization, challenging reductivist readings of this relationship to explore how the novel simultaneously emplaces and displaces the reader so that critique, as well as convention, are thoroughly unsettled.
Details
Keywords
THERE HAS never been more than one good reason for the founding of the European Economic Community — the Common Market, as it has come to be called. That was to extend the…
Abstract
THERE HAS never been more than one good reason for the founding of the European Economic Community — the Common Market, as it has come to be called. That was to extend the boundaries of each member nation to encompass them all.
The Aviation Division of the Dunlop Co. Ltd. (Engineering Group) is to install Dynex power units, designed and built by Applied Power (U.K.) Ltd., in the latest design of…
Abstract
The Aviation Division of the Dunlop Co. Ltd. (Engineering Group) is to install Dynex power units, designed and built by Applied Power (U.K.) Ltd., in the latest design of hydraulic production test rigs at the Division's Coventry factory. The company is completely re‐equipping its production test facilities by providing every rig with the higher pressures and flows which future trends in fluid technology will demand, and to ensure that each testing station is capable of handling service fluids currently in use, including kerosene, DTD 585, Skydrol, Lockheed 22 and Oronite.