NKK jointly with Asahi Glass Co., Ltd. have developed a Hot Blast Control Valve (HBCV) which can control the flow rate at each tuyere. 19 HBCVs out of 38 tuyeres were installed in Keihin No. 2 BF in 1986. Through various test operations, innovative technologies for blast furnace operation have been developed. This paper reports the circumferential balance control of stock line levels.
(1)At the proper block with closed HBCVs, the coke consumption amount at the tuyere decreases, however the burden descending rate at the throat becomes faster. Applying these phenomena, it is Possible to control the circumferential balance of SL levels.
(2)The simple stand-alone method, where the HBCVs at the block with higher SL level are closed based on the average SL levels during the past definite period of time, had sometimes put into disorder, and it was impossible to continue a stable control of SL levels.
(3) For further stable control, Successive Alleviative Integration (SAINT) method has been developed, taking account of their interferences of each HBCV opening, dead time and integral action of changes in valve opening.
(4)The test operation in Keihin No. 2 BF showed that it is extremely effective for the improvement of furnace conditions and decrease of Si content in hot metal to control the circumferential balance of SL levels on the SAINT method.

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It is important to decide the arrangement of PID controller with multivariable control system.
Therefore, this paper describes the selection method of the effective combination between the controlled variables and manipulating variables.

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There are many difficult requirements imposed on block triangulation when it is applied on a practical basis. The main problem with aerial analytical triangulation is the error occurence and the necessity of reconstructing the block model. Because a certain number of operational errors always occur, the system of block triangulation is evaluated by the way it corrects such errors with certainly while at the same time reducing total working time.
The authors of this paper have solved the problem by introducing the concept of block to block triangulation. With this concept, operational errors are kept in local and the volume of errors needing correction is minimized in total.
Requirements for computerr use on practical basis are as follows: -
1. The error check method
2. The saving of computer costs (using only core memory-300 kc)
To satisfy these requirements we have developed two concepts:
1. The concept of block to block triangulation
2. The reduction method on divided linear equation
The system which the authors of this paper have developed has a cost/performance ratio level that is nearly comparable to the usual strip type solution method.

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It is well known that if one places a pendulum with an iron bob in the neighborhood of a coil fed from the main, one observes that the pendulum attains its stationary oscillation. It seems that there is no necessity of a rational ratio between the frequency of the pendulum which is close to its proper one and the frequency of the main which is very high compared with that of the pendulum.
In this paper, this phenomenon, first treated by J. Bêthenod, is studied analytically and it is concluded that the dissipated energy of the pendulum is supplied from the main by some retarded action of the electromagnetic force of the coil.
The method of analysis can be applied to a class of electromechanical phenomena in which the mechanical system is maintained in oscillation at a frequency of or near its proper one at the expense of the energy supplied from the electrical system. Further, an electromechanical rotator based on the same principle as the Bêthenod's pendulum was devised and the experiment of which seems to support the validity of the analysis.
Finally, the case in which the electrical system is a series ferroresonant circuit is discussed and it is pointed out that the energy of the pendulum is supplied by the oscillation hysteresis of the nonlinear circuit. As an application of this phenomenon, an electric master clock without electric contact was devised.

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In this paper, a fracture model for polycrystalline ceramics is proposed. In the model, it is assumed that fracture toughness along a crack front has a distribution and that the fracture toughness for the macro-material is the mean value of those. It follows from the model that the probability distribution of fracture toughness for polycrystalline ceramics with a crack of the same configuration can be approximated by a normal distribution and that the coefficient of variation of fracture toughness for polycrystalline ceramics with a crack of the similar figure is inversely proportional to the root of the crack front length. In order to examine the theoretical results, indentation fracture tests of alumina ceramics are carried out. The experimental results agree with the theoretical results.

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Abnormal vibration of a single ball bearing subjected to an axial load was studied. The primary purpose of this study was to elucidate the mechanism of generation of the abnormal vibration. Therefore, we examined the following points: the system of the abnormal vibration, the excitation acting upon the system, and the relationship between the abnormal vibration and the lubricant properties. From the experimental results, the analytical results and related considerations, it is clear that the abnormal vibration is a forced self excited vibration in the angular direction of the outer ring of the ball bearing having a nonlinear spring property.

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Given in this paper are the control systems with adaptable indexes in the phase space, a development of the subject of previous paper. The results obtained are as follows:
1) Basic equation of the control system with adaptable indexes has same property in the phase space as one of conventional control systems.
2) Pontriagin's maximum principle can be applied to the control system with adaptable indexes.
3) General method is discussed to determine the region which contains necessary conditions for the optimum control system with adaptable indexes.
4) Concept of the control system with adaptable indexes is useful for unified consideration of approximation problems.

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When a layer of fluid is heated uniformly from below, a convection occurs in a regular cellular pattern for the values of the Rayleigh number in excess of a critical value. A perturbation method is presented here to determine the form and amplitude of this steady convection. The essential point is to expand functions describing the field (velocity and temperature) in a power series of a parameter ε, while the Rayleigh number is put as a product of its critical value times (1+ε²). A set of inhomogeneous equations thus obtained can be solved by the perturbation method used in non-linear oscillation problems. In the two-dimensional case the slope of heat transport curve steepens abruptly at the critical Rayleigr number. As another example which can be dealt with in this way, a convection in a sphere is studied. This is an extention of Chandrasekhar's linearized stability theory.

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When a small induction motor with ball bearings is running under no load, an abnormal axial vibration of the rotating shaft often occurs. This vibration was studied in order to elucidate the generating mechanism. The test motor was operated at constant temperature, and the rotating shaft speed was varied by changing the frequency of an inverter. The vibration was measured by an eddy current type gap sensor, and was analyzed by an FFT analyzer. From the experimental results and related considerations, the vibratory system and the exciting force and self-exciting force that act upon the system were examined. It is clear that the abnormal vibration is a forced self-excited vibration of the vibratory system with an axial nonlinear spring due to ball bearings.

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Nonlinear forced oscillations in a cold electron plasma are treated in Lagrangean form, and exact equations for the density and the velocity are derived. In the absence of the forcing term, we have Konyukov's result but not Amer's and Amer's error is shown. According to the Coddington and Levinson's method, the existence conditions of the periodic solut on of these equations are given.
As a typical example of the forcing term, the case of F=-m (νv+βv³) +C sin ωt is treated and for β=0, we find that the density tend to n₀ as, t→∞, while in the velocity there remains only the forced oscillation.Also, for β≠0we have essintially the same result, and the density converges to n₀ and the periodic solution of the velocity corres-ponds to the forced oscillation.

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A ship, which is directionally unstable on straight course, can turn against the rudder in a certain range of rather small rudder angle. This singular phenomenon was first pointed out by P. Contensou.
The present writer discusses this phenomenon mathematically by assuming that the resistance derivatives are linear functions of the curvature of ship's path. He assumes, for simplicity, that C_Yβ=C_Yβ₀ (1+kΩ), and descrives the motion of ship by nonlinear differential equations. Then the stability of the steady turning of an unstable ship can be tested topologically on a phase plane.

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  The die cast process is useful for producing parts with smooth surface, high dimensional precision, and complicated shapes. However, with increasing importance placed on energy-saving in recent years, energy-saving has also become an important theme in the die casting process. During the die casting process, molten metal is injected at high velocity and pressure into a mold die cavity to prevent casting defects such as porosity, cold shut, flow line, etc. For this reason, die casting machines require considerable energy using several hydraulic pressure pumps and accumulators. On the other hand, melting furnaces have poor energy efficiency of about 20% due to large energy loss through radiant heat from the furnace surface and exhaust fumes.
  To promote energy-saving in the die casting process, we developed the “hybrid die casting machine with servo and hydraulic mechanism” to enhance energy efficiency. By using this technology, we have successfully reduced energy consumption to 1/6 of that of our previous die casting process.

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This paper deals with methods of reconstructing, in the stochastic sense, the state of continuous-time dynamical systems with unknown initial conditions and subjected to random inputs. By extending to the stochastic systems the concept of n-observability with a deterministic system, the unknown stochastic states are reconstructed from the statistical knowledge of the system output during a finite time interval provided that the observation system is a scalar.
The technique of the determination of minimal, optimal observation time points is described by paying particular attention to the n-observability in the stochastic sense and the relation between sample and population qualities such as mean and covariance.
Two cases for the state reconstruction are treated such that the confidence intervals of the states are constructed (1) by using only the variances of the outputs at oprimal observation time points and (2) by using the variances and correlation function of the outputs.
In order to clarify the proposed technique for the state reconstruction a numerical example is given and the relations between the confidence intervals and the observation methods are discussed in detail.

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