Showing papers by "Harbin Engineering University published in 1998"
TL;DR: An electrode modified with a polybasic lanthanide heteropoly tungstate/molybdate complex, denoted as Nd(SiMo7W4)(2)-PPy, exhibits three couples of two-electron redox waves in pH 1-5 buffer solutions.
44 citations
TL;DR: In this article, a white light fiber optic interferometer was used to sense strain in a fiber embedded in a specimen concrete beam and a calibration procedure was developed by which the optical signals were converted into displacements.
Abstract: The development of a fibre optic sensor for embedding in cementitious composites and the measurement of displacements associated with the opening of microcracks are described. The sensor can be employed as a transducer for the measurement of crack-tip opening displacements during fracture tests. A white light fibre optic interferometer was used to sense strain in a fibre embedded in a specimen concrete beam. A direct relationship between the fibre deformation and the optical path variation of the fibre sensor has been obtained. A calibration procedure was developed by which the optical signals were converted into displacements. The sensor was employed in a series of fracture tests and the experiments involved embedment of the optical fibre in concrete beams. Specimens were centre-edge-notched and the fibre optic sensor of the gauge length L was embedded at the tip of the notch. This arrangement allowed for the direct measurement of displacements associated with the opening of microcracks at the crack tip. Experimental results are presented and crack-tip opening displacement (CTOD) results are compared with crack-opening displacements (CODs) measured by conventional transducers at the crack mouth.
39 citations
TL;DR: In this article, a simple model is developed for evaluating the interaction between the surrounding matrix and a length of optical fiber embedded in it, in which a sensitivity coefficient K(L) is used to describe the percentage of strain applied to the composite actually transferred to the fiber.
Abstract: A simple model is developed for evaluating the interaction between the surrounding matrix and a length of optical fiber embedded in it. The analysis has been performed for nominal uniform pull-stress applied to the matrix, in which a sensitivity coefficient K(L) is used to describe the percentage of strain applied to the composite actually transferred to the fiber. The theoretical results have shown that the sensitivity coefficient of the fiber-optic strain sensor depends on the embedded length of the optical fiber and the material properties of the fiber coating.The general trend of increasing the sensitivity coefficient with increasing action length has been confirmed by the experimental results. The distributions of interfacial shearing stress between matrix and coating and coating and glass fiber are given. Experiments have been performed using a white-light fiber-optic interferometer.
39 citations
TL;DR: An intelligent CAD system for a multilayer electromagnetic absorber design that includes a functional virtual reality design for all kinds of electromagnetic absorbers is discussed and a number of canonical results are presented.
23 citations
TL;DR: In this article, an interferometric fiber-optic temperature sensing system employing a light emitting diode (LED) as the broadband optical source and a single mode fiber coil which was fabricated in a definite length as the sensor head is described.
Abstract: An interferometric fibre-optic temperature sensing system employing a light emitting diode (LED) as the broadband optical source and a single mode fibre coil which was fabricated in a definite length as the sensor head is described. A reference fibre line transmitting back and forth along the same path as the sensing transmitting fibre is used, so the change caused by the environmental temperature fluctuation of the fibre path can automatically be compensated. The sensitivity of the sensing system can be easily improved by using the long length of the sensing fibre. The experiment results of the sensing gauge length versus the sensitivity are given. Two typical wavelengths (1300 and 1550 nm). LED sources are used, it is shown that the sensitivity of the system between the two wavelengths is different. The experimental curve of the resolution characteristic of the system related to the length of sensing fibre coil is also discussed.
18 citations
TL;DR: In this article, a novel two-dimensional intensity-type optical fiber reflective sensor is presented, which can automatically compensate for variations in light source intensity and changes in the reflectivity of the measuring target.
16 citations
15 Apr 1998
TL;DR: In this paper, a method incorporating a fuzzy logic inference with an artificial neural network is presented to establish a controller to control an autonomous underwater vehicle (AUV) to avoid obstacles.
Abstract: If an underwater vehicle is to be completely autonomous, it must have the ability to avoid obstacles to safely operate. A new method incorporating a fuzzy logic inference with an artificial neural network is presented. The method is used to establish a controller to control an autonomous underwater vehicle (AUV) to avoid obstacles. It not only exerts some expertise, but also endows the controller with adaptability. As a result, the AUV is provided with the ability of obstacle avoidance at the beginning, which greatly shortens the time of network learning. On the other hand, the controller can adjust itself to the variations of oceanic environment. Results of simulation using a five degrees of freedom nonlinear manoeuvring mathematical model of the vehicle show that the proposed method can be efficiently applied to obstacle avoidance of an AUV in complex and unknown oceanic environment.
13 citations
15 Apr 1998
TL;DR: In this paper, the authors address the problem of how to extract the target's size/shape features from a sequence of 2D acoustic images acquired by a forward looking sonar (SeaBat 6012).
Abstract: Underwater target recognition techniques are very important for an autonomous underwater vehicle (AUV) to complete its missions such as relocation of lost targets, removal of toxic wastes and mine counter measures, etc. In this paper we address the problem of how to extract the target's size/shape features from a sequence of 2D acoustic images acquired by a forward looking sonar (SeaBat 6012). We make use of image processing techniques and the near field acoustic scattering principle of underwater target to estimate the two-dimensional position and size/shape of a nearby target. These features are very useful for an AUV to design its obstacle avoidance or recognition strategies. Some experimental and analytical results about these features are provided to demonstrate the feasibility of these methods.
12 citations
12 Oct 1998
TL;DR: In this article, the chaotic characteristics of noise signals radiated from ships using power spectrum analysis, singular spectrum analysis and Lyapunov exponents and correlation dimension were investigated and it was proved that there exist chaotic characteristic in this type of signal.
Abstract: It is very important to study the dynamic properties of underwater acoustic signals for improving the performance of underwater acoustic systems. This paper studies the chaotic characteristics of noise signals radiated from ships using power spectrum analysis, singular spectrum analysis, Lyapunov exponents and correlation dimension. All studies proved that there exist chaotic characteristic in this type of signal. Experiments showed that the fractal dimensions of different signal sources are different. It would be very useful to be able to classify this type of signal. As a byproduct, a method for estimating Lyapunov exponents based on the idea of system identification is presented in this paper.
10 citations
TL;DR: In this article, a novel fiber-optic interference method called fiberoptic Moire interferometry has been developed and demonstrated, based on the special relative positions and the polarization directions of three HiBi fiber ends.
10 citations
TL;DR: In this paper, a high pressure window bomb was used for the combustion chamber and a modulating disk was used to induce the pressure oscillation above the combustion bomb, which was controlled easily with selecting the rotating velocity of the disk.
TL;DR: In this paper, a differential demodulation fiber optic strain sensing system adapted to the needs of complex materials or smart structures monitoring is presented, which can automatically compensate for temperature-induced variations in the refractive index and thermal expansion of the silica fibres.
Abstract: A differential demodulation fibre optic strain sensing system adapted to the needs of complex materials or smart structures monitoring is presented. It is based on low-coherence interferometry in standard single mode fibres and has the advantage that it can automatically compensate for temperature-induced variations in the refractive index and thermal expansion of the silica fibres.
12 Oct 1998
TL;DR: In this article, a time-of-arrival location and tracking method for a maneuvering target is discussed, which uses nonlinear weighted least square (WLS) estimation and a self-adapting Kalman filter based on the acceleration time correlation model.
Abstract: A time-of-arrival location and tracking method for a maneuvering target is discussed in this paper. The rapid location and tracking of a target in two-dimensional space is realized by using nonlinear weighted least square (WLS) estimation and a self-adapting Kalman filter based on the acceleration time correlation model. Computer simulations indicate that this method is very efficient. The algorithm is of great importance to the practicability of passive location and tracking systems.
TL;DR: A comparative study of the finite element analysis of the local stresses in a ship structural detail has been carried out by the members of Technical Committee II.1 of ISSC ’97 as mentioned in this paper.
11 Oct 1998
TL;DR: The simulator presented in the paper can not only accomplish the navigation and manoeuvring training under various conditions, but also coordinate its activities with the C/sup 3/I system carrying on the tactical practice in docked state all-sidedly and systematically.
Abstract: The simulator presented in the paper can not only accomplish the navigation and manoeuvring training under various conditions, but also coordinate its activities with the C/sup 3/I system carrying on the tactical practice in docked state all-sidedly and systematically. The simulator can perform a six-freedom motion under soft-platform environment and generate various navigation information. It can also simulate the influence caused by damage leading to water rushing into submarine underneath deep water in order to study the emergency measures. The paper introduces the hardware and software design and realization of the simulator function.
TL;DR: Reflection-induced phase retardance inside bulk optic-material current sensors makes the state of polarization of the light change, which reduces the immunity of the sensors against electromagnetic interference, and these effects are analyzed theoretically for the first time, to the knowledge.
Abstract: Reflection-induced phase retardance inside bulk optic-material current sensors makes the state of polarization of the light change, which reduces the immunity of the sensors against electromagnetic interference. These effects are analyzed theoretically for the first time, to our knowledge. A comparison between the theoretical analysis and the experimental results are given.
25 Sep 1998
TL;DR: In this paper, the output probability density functions of generalized open-closing (GOC) and generalizedcbs-opening (GCO) filters under the different input distributions such as uniform, Gaussian and biexponential distributions, and calculate their digital features (expectations and variances).
Abstract: In this paper, we present the output probability density functions of generalized open-closing (GOC) and generalizedcbs-opening (GCO) filters under the different input distributions such as uniform, Gaussian and biexponential distributions,and calculate their digital features (expectations and variances). Then, we apply these filters to restore an image corrupted by impulsive noise and further test their efficiency in noise-suppressing and detail-preserving characteristics. The simulation results show that the GOC and GCO filters have good performances.Key words: Morphological filters, Nonlinear filtering, Statistical properties, Image processing i.INTRODUCTION Morphological filters are nonlinear signal transformations that locally modify geometric features of signals. In recentyears, morphological filters have been successfully applied to the many fields of image analysis and processing includingbiomedical image processing, automated industrial inspection, shape recognition and image restoration ect.111.
15 Apr 1998
TL;DR: An integrated simulator used in the research and development of autonomous underwater vehicles (AUV) is introduced, constructed using the SGI workstation connected to other computers via Ethernet to develop the software of the intelligent control system for AUV.
Abstract: An integrated simulator, which is used in the research and development of autonomous underwater vehicles (AUV), is introduced. It is constructed using the SGI workstation connected to other computers via Ethernet. This simulator can display the scene of the underwater virtual world, describe the motions of the underwater vehicle, and simulate a number of sensors. We use this simulator to develop the software of the intelligent control system for AUV, and study the dynamics of the underwater vehicle, pattern recognition, etc. The use of the simulator can greatly reduce the time and money spent in AUV development and risks in future sea test.
15 Apr 1998
TL;DR: A novel underwater interfacing system, which adopts "catching" manipulators to assist in interfacing, is introduced in this paper.
Abstract: A novel underwater interfacing system, which adopts "catching" manipulators to assist in interfacing, is introduced in this paper. The overall description of the system, including the basic working principle, interfacing apparatus' degrees of freedom and system's configuration, are given. The kinematics and statics of the interfacing apparatus are analyzed, and the automatic interfacing strategy is presented.
TL;DR: In this paper, the rotational angle and translation distance of the robot is divided into seven and four grades respectively and the length of the path that the robot covers before collision with obstacle is taken as fitness.
Abstract: The local path planning of mobile robots can be regarded as finding a mapping from perception space to action space. Genetic algorithm is used to search optimal mapping in this paper so as to improve the obstacle avoidance ability of the robot. In this paper, the rotational angle and translation distance of the robot is divided into seven and four grades respectively. In addition, the length of the path that the robot covers before collision with obstacle is taken as fitness. The robot can learn to carry out local path planning through selection, crossover and mutation in genetic algorithm. The simulation results are given at the and of this paper.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the thermal emission of a disc body of gray semitransparent material is analyzed with considering the influences of the characteristic optical thickness, the dimensionless radius, the refractive index of the material and the reflecting characteristics of the flank surface.
Abstract: By introducing the concept of radiosity intensity to diffuse surfaces, the ray tracing method is improved to analyze the thermal emission of a disc body of gray semitransparent material. The two plane surfaces of the disc body are both specularly reflecting, and the flank surface is either diffusely reflecting or specularly reflecting. The apparent thermal emission from one plane surface is investigated with considering the influences of the characteristic optical thickness, the dimensionless radius, the refractive index of the material and the reflecting characteristics of the flank surface. The directional and hemispherical emissions show considerable differences under different reflecting characteristics of the flank surface. Moreover, in some cases, the emission not only varies with the viewing direction but also with the apparent emitting position on the plane surface. Some interesting results are presented and discussed.
15 Apr 1998
TL;DR: In this paper, the authors present a technique for automatically estimating the sea current and finding the optimal heading through neural network motion control, which can estimate the direction of the current with little error.
Abstract: For an autonomous underwater vehicle (AUV), sea current is an unknown varying parameter which can not be given before operation and which may impose significant influence on the performance of an AUV. Furthermore, it is difficult to measure the sea current from a moving or suspending AUV. This paper presents a technique for automatically estimating the sea current and finding the optimal heading through neural network motion control. By using a model reference neural network controller, the velocity vector of the vehicle can be oriented to point to the goal position. Meanwhile the heading of the vehicle turns to the angle where the lateral resistance approaches to zero. When the vehicle reaches the goal point, the heading is approximately opposite to the direction of the current. Thus, the AUV can estimate the direction of the current with little error.
15 Apr 1998
TL;DR: In this article, a cycloidal propeller was used for underwater vehicle control in six dimensions and it was shown that the vehicle can be controlled in 6 dimensions and that it is easier to keep vehicle's positions and azimuth by setting three cycloid propellers on it so its maneuverability is improved.
Abstract: Underwater vehicles with cycloidal propellers are a new invention. It is shown that the vehicle can be controlled in six dimensions and it is easier to keep vehicle's positions and azimuth by setting three cycloidal propellers on it. So its maneuverability is improved. First, a formula is set up based on the experimental results of the cycloidal propeller's pitch ratio varied from 0.2 /spl pi/ to 0.75 /spl pi/ and steering angle from -90 to +90 degrees. The experiments of that cycloidal propeller were made in Harbin Engineering University Towing Tank. Using these experimental results, a simulating calculation is also carried out and is compared with that of the vehicle controlled by other kind of propellers.
15 Apr 1998
TL;DR: An intelligent underwater vehicle is introduced and the architecture of the control system, especially the mission execution module, is described, where an artificial neural network is used to deal with the nonlinear dynamics of underwater vehicle and the unpredictable disturbances.
Abstract: This paper introduces an intelligent underwater vehicle and describes the architecture of the control system, especially the mission execution module. An artificial neural network is used to deal with the nonlinear dynamics of underwater vehicle and the unpredictable disturbances. Performances of the system on motion control, autonomous navigation and obstacle avoidance were tested by a series of experiments in a lake. The results show that the performance of the system was stable and reliable.
TL;DR: In this article, a theoretical analysis model of fiber-optic sliding sensor is presented for robot hands or intelligent mechanical clamping apparatuses, where a sliding ball has been used as sliding transfer device of the sensor in the center of the in side sliding ball, a 4-face-prismoid reflective mirror has been fixed with the sliding ball to determine the 2D rotation angles.
Abstract: A theoretical analysis model of fiber-optic sliding sensor is presented The sliding sensor is designed for robot hands or intelligent mechanical clamping apparatuses In the sliding sensor designing, a sliding ball has been used as sliding transfer device of the sensor In the center of the in side sliding ball, a 4-face-prismoid reflective mirror has been fixed with the ball to determine the 2D rotation angles, and the angles were measured by a five-fiber-optic probe The theoretical characteristic functions of the sliding sensor are deduced and simulated
TL;DR: In this article, the long and short fatigue crack growth (FCG) behavior of 12CrNi3MoV and 10CrNi5MoV (S2) steel was investigated at cathodic protection in 3.5% NaCl solution and artificial seawater.
Abstract: The long and short fatigue crack growth (FCG) behavior of 12CrNi3MoV (S1) and 10CrNi5MoV (S2) steel was investigated at cathodic protection in 3.5% NaCl solution and artificial seawater. The results indicate that long and short FCG show different behavior at cathodic protection. Short FCG is apparently hindered at appropriate cathodic protection potential (−900 mV SCE) and accelerated at over-protection potential (−1200 mV SCE). Cathodic protection increases long FCG rate, and the more negative the cathodic protection potential, the greater the long FCG rate. At the same amplitude of stress intensity (ΔK), short FCG rate is greater than the long one and their difference becomes less at cathodic protection. The FCG rate in 3.5% NaCl solution is greater than in artifitial seawater. The FCG rate of S2 steel is bigger then that of S1 steel. The FCG rate of weld bond of S2 steel is lower than that of parent metal and weld beam. In above cases, the anode dissolution, the wedging of corrosion products or deposit and hydrogen embrittlement in long and hort crack tip are also discussed.