Showing papers by "Harbin Institute of Technology published in 1985"

Ferrite recrystallization and austenite formation in cold-rolled intercritically annealed steel

Abstract: The recrystallization of ferrite and austenite formation during intercritical annealing were studied in a 0.08C-1.45Mn-0.21Si steel by light and transmission electron microscopy. Normalized specimens were cold rolled 25 and 50 pct and annealed between 650 °C and 760 °C. Recrystallization of the 50 pct deformed ferrite was complete within 30 seconds at 760 °C. Austenite formation initiated concurrently with the ferrite recrystallization and continued beyond complete recrystallization of the ferrite matrix. The recrystallization of the deformed ferrite and the spheroidization of the cementite in the deformed pearlite strongly influence the formation and distribution of austenite produced by intercritical annealing. Austenite forms first at the grain boundaries of unrecrystallized and elongated ferrite grains and the spheroidized cementite colonies associated with ferrite grain boundaries. Spheroidized cementite particles dispersed within recrystallized ferrite grains by deformation and annealing phenomena were the sites for later austenite formation.

Effect of Slotting in Pm Electric Machines

Abstract: The effect of sinttinq in permanent magnet electric machines differs from that in wound field ones. An analytically extended field model for slotted permanent magnet machines is presented in this paper. By using the model, the Carter's coefficient for permanent magnet machines can be easily deduced from the Carter's classical formula. The closed-form solution to the problem at hand is exact and much simpler than that of previously approximate methods.

The Contribution of Vessel Volume Change and Blood Resistivity Change to the Electrical Impedance Pulse

Abstract: An impedance pulse, recorded noninvasively, has contributions due to both the change in blood volume of the arteries and to the change in the blood resistivity. Other researchers have tried to quantify the relative contributions and have either underestimated or overestimated the contributions since they did not simulate the physiological conditions. We have used an in vitro flow circulation system to more closely simulate the physiological conditions and quantify the two contributions. We find that the blood resistivity change contribution is strong enough (21.5 percent of the arterial volume change contribution) to change the morphology of the impedance pulse. There is, however, a phase difference between the two contributions. As a result of this, the blood resistivity change contribution to the height of the impedance pulse will be less than 5.5 percent.

Emissivities of diffuse cavities. 4: Isothermal and nonisothermal cylindro-inner-cones.

Abstract: A precise calculation is presented of the local hemispherical effective emissivities of isothermal and nonisothermal diffuse cylindro-inner-cone cavities. For those cases where shadowing occurs, it is shown how to obtain exact analytical expressions for the angle factors involving incomplete circular bands and conical frustums by application of the Stokes theorem and contour integration. The effective emissivities of the cone and adjacent part of the cylinder are lower than predicted by previously published approximate calculations by from 1 to 5 × 10−4, amounts significant in metrological applications. The effective emissivities of nonisothermal cavities change with wavelength and depend on the details of the temperature distribution.

Air Gap Field for Pm Electric Machines

Abstract: The air gap field distribution in permanent magnet electric machines differs from that in wound field ones. In order to analyse the influence of magnet and air gap geometry on the shape of the air gap field in PM machines, an analytical method, which is much more economic and efficient than the numerical ones, is proposed in this paper. By using the method of Fourier expansion, a great set of curves for the air gap field characteristic coefficients in PM machines can be obtained. These design curves are necessary in simplified performance calculations for both AC and DC PM machines.

Influence of cerium and mischmetal on the hardness and brightness of AlMgSi alloys

Abstract: The effect of small amounts of cerium and mischmetal on the maximum reflectance and hardness of an Al-1%Mg-0.5%Si alloy was investigated with an automatic spectrophotometer and a Brinell tester. The measurements show that mischmetal concentrations of up to 0.1–0.3 wt.% give rise to an appreciable increase in the surface brightness. The increase in hardness is also most pronounced for small addition of rare-earth metals.

Emission line redshift distribution of QSOs

Abstract: This paper is the second one of a series of papers on the redshift distribution of QSOs. In this paper, we shall study the influence of the selection effect in the identification of emission lines on the redshift distribution of QSOs more thoroughly than the previous paper (Zhouet al., 1983). If we assume that the QSO's redshift is cosmological, adopt the standard model, and consider the selection effect due to the redshift identification, the limiting apparent magnitude in the observation and the evolutionary effect of QSOs, we can compute the emission line redshift distribution for the so-called optically selected QSOs discovered by objective prism, grating prism technique alone, the QSOs discovered by positional methods or by colour technique and for whole QSOs, respectively (see Figures 6, 11, 12). The results of computation agree with the observations very well, especially for optically selected QSOs; the computational distribution has almost the same shape with the observational one. For this kind of the QSOs the computational distribution may give the positions and heights of all these observed peaks. The correlation coefficient γ between the calculated and observed distributions is larger than 0.95. It shows that (a) the peaks and dips in the redshift distribution of QSOs are mainly caused by the selection effect in the redshift identification, and (b) the redshift of QSOs is cosmological.

Relationship between solidification thermal parameters and dendrite arm spacing and ultimate tensile strength in AlCuMm alloys

Abstract: The relationship between thermal parameters, dendrite arm spacing (DAS) and ultimate tensile strength (UTS) in AlCuMm alloy plate castings was analysed statistically. Freezing index and gradient acceleration parameters are two suitable parameters for the control of the DAS in this alloy. A nearly linear relation was found between DAS and UTS, as follows: UTS = 33.61 — 0.16 DAS , with a correlation coefficient of 0.814. Thus, UTS can be calculated from the experimental data of DAS.

An Investigation of Microstructure and Properties of a Thermo-mechanically Treated High Strength Al-Zn-Mg-Cu Alloy

Abstract: The mechanical properties of thermomechanically treated LC4 aluminum alloy (equivalent to 7075 in ASTM) were tested. The microstructural characteristics of the alloy was studied with optical microscopy, replica and thin foil TEM and SEM fractography. The results show that a proper themomechanical treatment (TMT) can improve the tensile strength and decrease the tendency of intergranular fracture of the alloy, (but has no apparent effect on fatigue properties). This relates to the high density of tangled dislocations, well-distributed precipitates, the elimination of precipitate free zone (PEZ) and the formation of discontinuous intergranular precipitates.

On associative recognition of isolated Chinese word

Abstract: This paper presents a new method of recognition of isolated Chinese word. Here a local feature of an input utterence to be compared with an appropriate part of every reference template.Depending on the result of local comparision(pretest), the system associates the input utterance with a sebset of recognition vocabulary, which is less than the vocabulary(set) always. Then the input utterence to be compared with the contents of the subset only, not with all templates in the vocabulary. Because the linear shift matching and a tenth of utterance length is used for ocal comparasion, the computation quantity of this stage isn't comparable to that one for word matching by dynamic programing, therefore the new method of recognition can save much time for DP matcaing. An important problem discussed here is how to establish a subset system, which can provide a subset with appropriate size and contents for every word in the recognition vocabulary. Especially, it must be easy to establish when a vocablary or a speaker is changed. In our investigation a special algorithm was used to make the system experienced in given vocabulary and speaker automaticlly. It was based on statistics of intra-word and inter-word local distance of each word in given vocabulary nd for given speaker. A number of repetation of utterence for the vocabulary is necessary for experince mentioned above. The recognition accuracy provided by the new method was equal to that one provided by typical method using word emplates directly, it was 98.33% for the best score and 94.72% for the worst. But the time-consumption of the associative method was fourth-thirth as much as it was taken by the typical method.

Effect of Cold Rolling and Intercritical Annealing on Microstructure and Deformation of Mn-Si-C Steel

Abstract: The microstructures and deformation behavior of normalized and normalized and cold rolled 1.45 Mn-0.21 Si-0.08 C steel subjected to intercritical annealing between 717 and 835°C were evaluated and compared. All specimens developed multiple stages of strain hardening, with more pronounced second stages characteristic of specimens annealed at the lower temperatures. Specimens with initially cold rolled structures prior to intercritical annealing exhibit lower yield strengths, higher strain hardening rates at high strains, and higher uniform elongations than do identically treated specimens with initially normalized structures. The improved deformation behavior of the initially cold rolled specimens is attributed to the fine ferritic grain size and dispersions of fine martensite particles which develop when the cold rolled steels are intercritically annealed.

Influence of Room Temperature Deformation on Mechanical Properties of A Dual-Phase Steel

Abstract: The influence of room temperature deformation on mechanical properties of the dual-phase 14MnNi was studied. Experimental results indicate that the combination of strength and ductility of the steel with strip regions of martensite is much better than that with island regions of maretnsite. The increase in volume fraction of ferrite leads to a considerable decrease of toughness of the steel in both quenched and cold deformed state. Cold deformation remarkably improves the tensile strength but decreases the impact toughness of the steel. The toughening effect of texture has been found in which the higher the intensity of (111) texture developed, the less the decrease in toughness will be. The impact cracks initiate at M/F interface and pass through the ferrite matrix in deformed and non-deformed specimens.

Analysis of Field Harmonics of Pole-Changing Pumped Storage Machines in View of Distribution Factor

Abstract: The rotor poles in conventional pumped storage machines are with different sizes and unequal distribution. It contains both Integral and fractional harmonics. A synthetic distribution factor of poles are introduced in this paper to evaluate the effects of construction parameters on harmonics (such as the positions, dimensions and the turn ratio of large and small poles and the length of air gap). A unified formula for calculating integral and fractional harmonics are derived also. The results, which were checked with the FEM for typical rotor models of pole-changing pumped storage machines, show that the method introduced in this paper can be used not only to calculate the magnitude of harmonics but also to propose a method to suppress some undesired harmonics.

On the structure of solutions of linear partial differential equation $$\sum\limits_{i + j \leqslant n} {a_{ij} p^i q^j \varphi } = 0$$ with two independent variables and constant coefficients

Abstract: this paper is a continuation of [1]. In this paper, the solutions of the more general linear partial differential equation $$\sum\limits_{i + j \leqslant n} {a_{ij} p^i q^j \varphi } = 0$$ with two independent variables and constant coefficients are discussed in detail. The general solution which can be used in the approximation to the conditions of the definite solution of the practical problems is presented. To illustrate the use of the results obtained in this paper, some practical examples in mechanics are given.

Comparison Between Single Shield with Damping Winding and Two-Shield Damping System for Superconducting Generators

Abstract: This paper makes a comparison of damping performance between two types of damping/shielding systems for superconducting generators. The first of these, used in the HIT/DOE machine employs a discrete winding plus a shield. The second is the more traditional double shield system. The method of analysis used in the paper employs the Laplace Transform of the operational impedances.