Showing papers by "Harbin Institute of Technology published in 1988"

An Experimental Investigation Into the Reasons of Reducing Secondary Flow Losses by Using Leaned Blades in Rectangular Turbine Cascades With Incidence Angle

Abstract: Up to now the reasons of reducing the secondary flow losses by using leaned blades, especially in the case of great incidence angle, have been little concerned with in published references. The experimental results in this paper have shown that the decisive factor reducing secondary flow losses in turbine stator cascades is the static pressure gradient along the blade height inside the cascade channel near the suction surface, especially in the rear part of it, because the negative pressure gradient in the hub region and the positive one in the tip region are beneficial for the boundary layer in both the regions to be sucked into the main stream region, consequently, the accumulation and the separation of the boundary layer have been weakened in both regions. Moreover, the effectiveness of applying the positively or negatively leaned blades is increased with the increase of a incidence angle, in the hub or the tip regions respectively.© 1988 ASME

Airgap permeance of vernier-type, doubly-slotted magnetic structures

Abstract: A series of design curves for airgap permeance of vernier-type, doubly-slotted magnetic structures is presented in the paper. Permeance data are obtained from numerical field solutions. Reducing the number of governing geometric parameters makes it possible to express the airgap permeance in as convenient a manner as in equal-pitch-type structures. By using the Fourier expansion method, and these design curves, the airgap permeance per stator pole can be easily determined at any specified tooth misaligned position of a vernier motor.

An Experimental Investigation Into the Influence of Blade Leaning on the Losses Downstream of Annular Cascades With a Small Diameter-Height Ratio

Abstract: Five types of cascades with different leaned blades have been tested in a low speed annular cascade tunnel. The experimental results show that by using positively leaned blades the hub wall boundary layer in cascade passage can be sucked into main stream zone, and the amount of low energy gas getting into downstream of the cascade is reduced obviously, so that the energy losses downstream is decreased considerably.Copyright © 1988 by ASME

Group Direction Difference Chain Codes For The Representation Of The Border

Abstract: In this paper, a new method of the group direction difference chain code representation is presented which can be used to represent the curves or shape borders, and also can be used for the features extraction of shape borders. The idea of this method is to construct a chain codes based on the Freeman chain codes whose values represent the average changes in direction along the boundary of an any shape. For the sake of overcoming the noise in Freeman chain codes, in this paper the concept of direction smoothing is proposed, and a transform from Freeman chain codes to the direction smoothing chain codes is developed. Finally, the method and algorithm for obtaining the group direction difference chain codes are presented.

A Rule Based Image Segmentation System (RBISS)

Abstract: Based on the comprehensive utilization of the conventional techniques this paper presents a Rule-Based Expert System for Image Segmentation. Under the Control of various rules, this System can segment the images of many kinds and the complicate image which includes many image areas of various kinds by using corresponding segmentation algorithms. Therefore, this image segmentation system can be used in many cases of application.

A Three Dimensional Fuzzy Intelligent Controller

Abstract: A new three-dimensional Fuzzy Intelligent Controller (FIC), combining a three-dimensional fuzzy controller with a human intelligent integrat controller, is proposed in this paper. The simulation results indicate that the performance index of the FIC is better than that of a general fuzzy controller or of a conventional PID controller. This controller has been applied in a paper making control system and valuable results have been obtained.

Effect of temperature and humidity on electrical breakdown characteristics of low-density polyethylene film for the various stressing modes

Abstract: The effects of temperature and humidity on the electric strength of low-density polyethylene (LDPE) film for various stressing modes were studied experimentally. As the temperature exceeds the glass-transition temperature of the polymer, the temperature dependence of the impulse electric strength follows the free volume breakdown theory. If the breakdown process is greatly controlled by space charge, the application of free volume breakdown theory is limited. In addition, it is shown that the water molecule acts either as acceptor or as plasticizer, thus exerting a complicated influence on the dielectric breakdown in the polymers. It is also shown that the higher the direct prestressing, the more charges injected in deeper traps as the temperature rises but does not exceed 70 degrees C, because the space charge in deeper traps disappears only partly or slightly; the recovery of the normalized impulse breakdown strength of the dry specimen becomes slow and even vanishes. These findings are confirmed by thermally stimulated current measurements. >

A New Variational Finite Element Computation for the Aerodynamic Inverse Problem in Turbines With Long Blades

Abstract: In this paper a new finite element computation for the aerodynamic inverse problem in turbines with long blades is proposed. The influences of blade thickness, blade force, and other factors on aerodynamic parameters may be taken into account. The computational results are compared with those of the finite difference method in noncurvilinear coordinates. They indicate that this method has an appropriate accuracy, good suitability to the complex boundaries, and good convergence. This new finite element computation is a good method for aerodynamic design in turbines with long blades. By use of this method the influence of the various design factors (curved and leaned blades, blade thickness, etc.) on the distributions of the aerodynamic parameters can be studied.

An accurate method for recognition of printed Chinese characters

Abstract: An accurate method for recognition of printed Chinese characters is proposed. An improved peripheral method and the Walsh transform of both horizontal and vertical projection functions of a Chinese character are used for feature extraction. Study shows that this method has the advantages of fast processing speed, accurate recognition rate, and strong resistance to noise. >

An investigation of radiation damage in a cured epoxy resin system using regression experiment design

Abstract: A regression experimental design was used to study gamma-irradiation damage to cured epoxy resin system. The three factors chosen as control variables were dose rate, dose period, and the ratio of hardener to resin. The percentage moisture absorption by weight and the glass transition temperature were used as indicators of material degradation. Only 15 sets of measurements were required to obtain the regression equation. The results showed that for this resin system the dose required to produce a given state of degradation is dependent on both dose rate and hardener concentration. >

A dynamic target recognition system

Abstract: A dynamic target recognition system is described which uses blackboard structure to organize the knowledge of images targets, background objects, and procedures An optical matcher is used to find a suitable knowledge source during the process This system can quickly recognize an incomplete image target >

The ALFALFA Entomology Pest Identification System

Abstract: Rule groups with preconditions, postconditions, and termination conditions were added to the ADVISE Meta-Expert System. Multiple, varying goals are also an attribute of the new rule groups. By treating the data collection process as separating from the rule inference engine, techniques for enhanced data acquisition were developed using semantic networks to describe relations among variables and to restructure value sets for variables dynamically. Having thus extended the ADVISE tools, an automated key to alfalfa field pest identification was selected as a test application and found to be particularly well suited by the new features. A need for disjunctive (“OR”) constructs in the right hand side of rules is discussed, and directions for future applications are given.

Improvement of six-port precision using linear space concept

Abstract: A method using the linear space concept to improve six-port precision is presented. The method uses the constrained equation to describe the true power in six-port measurement systems under the assumption that system constants calibrated are precise. The theoretical analysis, geometric interpretation and computer simulation all prove the method to be effective as long as the second-order derivate of the constrained equation is not large. Experimental results for a coaxial six-port measurement system agree with the simulated results. >

Thermally stimulated current study on polyimide film

Abstract: The authors have observed two peaks in TSC (thermally stimulated current) spectra of Du Pont polyimide film. The low-temperature peak in the range of 50-70 degrees C is ascribed to dipole depolarization of unimidized polyamic acid in the film. The high-temperature peak in the range of 160-180 degrees C, in agreement with the authors' experimental results, is attributed to depolarization of ionic space charge generated by ionization of unimidized polyamic acid, ionic impurities, and water and then bound into Frohlich's two-potential well. >

The self-calibration of six-port in the presence of noise

Abstract: The concept of middle constants, which are all functions of system constants only, is introduced. A self-calibration method in which system constants are calculated from middle constants is proposed. A linear least-square recursive-identification formula is derived to self-calibrate middle constants in the presence of noise. This formula convergers if the noise follows a normal probability distribution. A method to realize the large-sample condition is also suggested. This method might be able to trace the slow shift of system constants. >

Calculation of the Flow Along the S1 Stream Surface With Inviscid-Viscous Interaction Method

Abstract: As an extension of the author’s previous work, this paper proposes a mixed iterative method for calculating the interactions of boundary layer with inviscid flow on S1 stream surface. It is shown from the comparison with experimental results that the iteration method given in this paper has a high calculation accuracy. In addition, the rate equation of the entrainment coefficient adapted for the turbulent boundary layer in the S1 stream surface has been established in this paper. The predicted results show that taking this equation as the supplemental equation for solving the turbulent boundary layer on cascade blades can improve the accuracy of calculation of the turbulent boundary layer on cascade blades.Copyright © 1988 by ASME

Laser Holographic Inspection Of Solder Joints On Printed Circuit Board (PCB)

Abstract: The principle of inspecting solder joints by holographic interferometric technique is introduced. The criterion of discriminating the flaws is suggested. The results are given and testified by metallographical sectioning.

New Compensation Method For The Control Systems Of Industrial Robots

Abstract: The increased demand on robotic manipulator performance leads to the use of advanced control structures. A new model reference adaptive control system for the industrial robot is presented in this paper. We first develop a compensation method to make the practical system behave like a time invariant system, then use the Linear adaptive theories to synthesize the compensated system. The control scheme doesn't need special sensors and has simple structure, it presents a new approach for improving today's robot control systems.

A Knowledge Based List Recognition And Understanding System (KBLRUS)

Abstract: This paper introduces a knowledge based list recognition and understanding system. It is capable of classifying the list of various types, recognizing the characters in the items of a list and finally constructing a symbolic description of a list. The problems which have to be solved in the development of this system are divided into three parts. . Analysis of a list image skeleton . Recognition of lists . Construction of a list symbolic description A blackboard model of problem solving is adopted in the development of this system which realize a hierarchical control strategy. This system consists of five parts,Know-ledge Base System, Control System, Dynamic Data Station (or Blackboard), Processing Modules and I/O System. Now, the system is still under development. The first researches which we have done have achieved a satisfactory results.

Axisymmetric Elastodynamic Response from a Penny-Shaped Interface Crack in Layered Composites

Abstract: This paper is concerned with the scattering of time harmonic longitudinal wave by a penny-shaped interface crack in layered composites. By Hankel and Abel integral transform, the problem is reduced to a set of singular integral equations which are treated numerically by Jacobi polynomials. The improper integrals in the equations are delt with by contour integral technique so that the accuracy of numerically computing is guaranteed. As an example, the scattering surface displacement field of elastic wave by a penny-shaped interface crack in a layered half space has been investigated in far field case. The theoretical results show that the surface displacements are composed of Rayleigh-Like-Mode waves predominantly. The scattered amplitudes for the first two modes are plotted versus the incident frequency, and it is observed that the multi-resonances occur in a frequency range.