Showing papers by "Harbin Institute of Technology published in 1993"

Solutions of the equation AV+BW=VF and their application to eigenstructure assignment in linear systems

Abstract: Two new simple, complete, analytical, and restriction-free solutions with complete and explicit freedom of the matrix equation AV+BW=VF are proposed. Here (AB) is known and is controllable, and F is in the Jordan form with arbitrary given eigenvalues. Based on the proposed solutions of this matrix equation, a complete parametric approach for eigenstructure assignment in linear systems via state feedback is proposed, and two new algorithms are presented. The proposed solutions of the matrix equation and the eigenstructure assignment result are generalizations of some previous results and are simpler and more effective. >

A theoretical analysis of the effect of crystallographic orientation on chip formation in micromachining

Abstract: The effect of crystallographic orientation on the shear zone formation in micromachining has been analysed with a single crystal cutting model. Based on the minimum shear strength criterion, a range of shear angle values is found to exist. The most likely shear plane is the one that has the most negative texture softening factor among the ones with the same minimum shear strength. Theoretical findings for the shear angle and cutting force variations compare well with published experimental data. The significance of the microplasticity analysis to the understanding of chip formation in micromachining is discussed.

Analysis of the compensation mechanism of a fiber-optic displacement sensor

Abstract: This paper describes the evaluation of a fiber-optic displacement sensor that is compensated for variations in light-source intensity as well as for losses in the fibers. On the basis of the intensity distribution function of the output optical field formed by the source fiber end, the compensation mechanism of the twin-receiving-fiber displacement sensor is analyzed. It is shown theoretically that the ratio of the outputs of a pair of detecting fibers is independent of the light-source intensity and losses in the fiber system. Results are presented that confirm this.

Expansion of det(A+B) and robustness analysis of uncertain state space systems

Abstract: In this note, an expansion for the determinant of the sum of two matrices, det(A+B), is given. A robustness analysis approach for state space systems with uncertain parameters is investigated by using Kharitonov's theorem. Some useful results are obtained. Several illustrative examples are given. >

Effects of Leaning and Curving of Blades With High Turning Angles on the Aerodynamic Characteristics of Turbine Rectangular Cascades

Abstract: To intensively understand the effects of the origination and development of centralized vortices on the aerodynamic characteristics of turbine rectangular cascades with high turning angles, an experiments with 5-hole micro spherical probes, accompanied by color helium bubble flow display, were carried out. The measurement planes are arranged as 3 before, 6 in and 1 after, the cascade. The experiments reveal that the origination and development of horseshoe vortices and passage vortices as well as the interaction of the latters almost dominate the whole flow field of traditional linear cascades. Lean linear cascades favor the horseshoe vortices and passage vortices in the acute angle zone, and impede those in the obtuse angle zone. So it is a logical result to adopt the negatively curved blades, whose pressure surfaces and both endwalls compose both obtuse angles respectively, to improve the cascade aerodynamic characteristics.Copyright © 1993 by ASME

The experimental investigations on the compressor cascades with leaned and curved blade

Abstract: This paper presents the results of the experimental investigations on the effects of leaned and curved blade of plane axial compressor cascade. The ink trace method has been used for the surface flow visualization. The five-hole probe measurements are performed at the cascade exit 12.5 percent chord downstream, and the static pressure distributions are measured on the endwalls and blade surfaces.Copyright © 1993 by ASME

Enhancement of the exponential gain coefficient as a result of the light-fanning effect in thin doped LiNbO 3 crystals

Abstract: The enhancement of the exponential gain coefficient of two-beam coupling in several thin samples of doped LiNbO3 crystals is reported. The mechanism is analyzed by light crawling that originates from the light-fanning effect. Some experimental results to support the explanation are presented.

Effect of pre-quenching on martensite-bainitic microstructure and mechanical properties of GCr15 bearing steel

Abstract: In order to improve the strength and toughness of steel GCr15 (52100), the effect of different amounts of pre-transformed martensite on the kinetics of isothermal bainitic transformation and the strength and toughness of martensite-bainitic (MB) duplex microstructure has been studied by using pre-quenching after conventional 850°C heating to different temperatures (220, 200, 180°C) below Ms and then isothermal treatment at 240°C. The experimental results show that the accelerating effect of pre-quenched martensite on isothermal bainitic transformation principally depends upon the pre-quenching temperature (the amount of pre-quenched martensite). The MB duplex microstructure with 33% pre-transformed martensite has the optimum combination of strength and toughness.

Deformation and restoration behaviour of ferrite-austenite two-phase structures

Abstract: Pure iron and four low carbon steels with different carbon contents were compressed in a ferrite-austenite two-phase range at strain rates of 0.002, 0.02, 0.2 and 2 s−1. The experimental results show that dynamic recovery occurs in the ferrite (F) phase, and dynamic recrystallization of austenite (A) nucleates through the grain boundary bulging mechanism where there were A-A boundaries before deformation and proceeds through the formation and subsequent movement of new A-A boundaries at F-A phase boundaries in the case where no A-A boundaries existed before deformation. The shape of the true stress-true strain (σ-e) curves is affected by both the volume fractions and the morphologies of the constituents. The peak stress of the σ-e curve of two-phase structures responds to the strain rate in the same way as that of single-phase structures. The peak stress and the stable state stress on σ-e curves of two-phase structures are higher than those calculated from the linear law of mixtures owing to the existence of F-A boundaries.

Self-pumped phase conjugation of 18°-cut Ce-doped KNSBN crystal at 632.8 nm

Abstract: We report the self-pumped phase conjugation of an 18°-cut Ce-doped (KyNa1−y)2m(SrxBa1−x)1−m Nb2O6 crystal at a 632.8-nm He–Ne laser wavelength. A maximum phase-conjugation reflectivity of 84.3% has been measured. In addition, its incident angular response and time response are measured.

Time-dependent tetragonal to monoclinic transition in hot-pressed zirconia stabilized with 2 mol% yttria

Abstract: The kinetics of isothermal transformation from tetragonal (T) to monoclinic (M) structure in zirconia stabilized with 2 mol% yttria was systematically studied using thermal expansion analysis, electron probe microanalysis, X-ray diffractometry and transmission electron microscopy. Results showed that tetragonal phase obtained from rapid cooling transforms isothermally to monoclinic phase during holding at 200–400‡C for 4 h. The time-temperature-transformation (TTT) curve has a characteristic C-shape, with 300‡C as the “nose” temperature. A small amount of M phase can be detected when the holding temperature is not in the preceding temperature range. The isothermal transformation kinetics can be expressed in terms of the Johnson-Mehl-Avrami equation in which the nucleation and growth of new phase are both functions of time with the activation energy determined to be 28.67 KJ mol−1. The metastability of T phase is associated with cooling rate, stabilizer content, as well as grain size.In situ observation of M phase propagation induced by the electron beam reveals the T → M transition to be diffusion controlled.

Distortion of two-pion interferometry by multipion correlations

Abstract: Multipion correlations arising from the symmetrization of the [ital n]-pion wave function affect the extracted information from two-pion correlation measurements. The influence of multipion correlations on a sample of like-pion pairs can be expressed as a multipion correlation factor, the distribution of which offers good sensitivity to the multipion correlation effect. Analyses of the multipion correlation factor for two Bevalac streamer chamber data samples of 2.1[ital A] GeV Ne+Pb and 1.8[ital A] GeV Ar+Pb collisions show that the multipion correlation effect in the former sample is greater than in the latter. This result mainly arises from the fact that the pion source for Ne projectiles is smaller than for Ar projectiles. The residual correlations in the reference sample are related to the multipion correlation factor in multipion events, which can be expressed as a residual correlation factor. The influence of multipion correlations on two-pion interferometry analyses arises from the ratio of the residual correlation factor to the multipion correlation factor.

The Study of Hydrostatic Lubrication of the Slipper in a High-Pressure Plunger Pump

Abstract: The lubrication condition between the slipper and the oblique plate of a high pressure pump affects its operating life. One of the studies in this paper is to analyze the oil film pressure distribution and load characteristics, considering the pressure-viscosity effect of the lubricant and the pressure-elasticity effect of the lubricating surface. In addition, a laser holographic photoelastic experimental verification is proposed. Another aspect of the study concerns the investigation of the dynamic stiffness properties of the oil film and its experimental verification. The conclusions obtained here provide a new theoretical basis for the design and parameter selection of a J high pressure plunger pump.

Closed-Loop Control of Weld Penetration Using Front-Face Vision Sensing:

Abstract: Feedback control of weld penetration based on a front-face sensor is a challenging problem in the field of welding. A novel vision-based approach is proposed in this paper for full penetration control of the gas tungsten arc welding (GT AW). Owing to the relationship between the front-face weld geometry and back-face weld width (representation of the full penetration state), which has been reported earlier by the present authors, it is possible to use the front-face geometry as feedback of full penetration. Based on the dynamic modelling and the analysis of accepted adaptive control algorithms, an adaptive predictive decoupling controller is developed. Simulations and experiments under a variety of welding conditions have been conducted to verify the effectiveness of the proposed approach and controller.

Mechanical properties of Al2O3 and Al2O3 + ZrO2 ceramics reinforced by SiC whiskers

Abstract: The effect of the SiC whisker content on the mechanical properties of Al2O3 and Al2O3 + 20 vol% ZrO2 (2 mol% Y2O3) ceramic composites has been investigated. It is shown that the strength and fracture toughness of the composites are increased by the addition of 0–30 vol% SiC whiskers with only one exception that 30 vol% SiC whisker leads to a decrease in the flexure strength. The addition of 20 vol% ZrO2 (2 mol% Y2O3) significantly improves the mechanical properties of the Al2O3 + SiC whisker (SiCw) composites and the t-m phase transformation of ZrO2 is enhanced by the residual stresses caused by the thermal incompatibility between the SiCw and the matrix. The toughening effect of both SiC whiskers and the t-m phase transformation of ZrO2 (2 mol% Y2O3) is shown to be additive, but the addition of ZrO2 decreases the strengthening effect of the SiC whiskers.

High-order stimulated electronic Raman scattering from lithium vapor

Abstract: An intense radiation at 395.0 nm has been observed when lithium vapor is optically pumped in a heat pipe with a pulsed dye laser whose output wavelength is tuned near the Li 2s–4s two-photon resonance transition. The radiation is emitted in the direction along the pump laser beam. It is proposed that the 395.0 nm radiation is mainly generated through three-photon excitation and one-Raman-photon scattering followed by two-cascade (spontaneous) emission. The overall reaction mechanism can be described by a parametric six-wave mixing process. The quantum efficiency of the observed process is estimated to be of the order of 2 × 10−6.

The transient regime of a multiwavelength pyrometer

Abstract: The transient operation of a new multiwavelength pyrometer based on a dispersing prism and a Si photodiode array is presented. After calibration, transient tests were performed using a tungsten strip lamp, supplied by a current pulse of 0.3-s duration. Measurements were carried out with a data acquisition system consisting of a FET multiplexer, a DVM (14 bit, 100 kHz), and a buffer memory (64 kbytes). Pyrometer signals are processed off-line, and temperature vs time is displayed. With the present arrangement, temperature measurements at 20 wavelengths may be performed with 200μs resolution. Faster measurements are possible with a reduced number of channels.