Industrial products usually involve initial failure type components. It is most important to remove initial failure products by screening after aging. Considering constant delivery products with a long average life time, both initial failure type and the repair system, we shall find that soon after initial delivery the number repaired exceeds the number produced. We call this point the maintenance deffect point". To solve this problem, it is effective to remove initial failure products by screening after aging. The aging effect is calculated under the assumption that failure occurs according to the Weibull distribution. In the case where aging time is normalized by using time, the effect becomes similar to the effect calculated under the assumption of the non-repair system. In this case, the total cost consists of failure cost and aging cost. By using the aging effect to calculate failure cost, we find that the aging time for minimum total cost in a macroscopic view is almost independent of both the shape parameter m and the accelerating factor α. It does depend, however, on the cost ratio, which is the ratio of the aging cost limit to the repair cost limit at no aging. This result is useful in programming both aging space and electric power for aging at the time of plant construction. This programming results in highly reliable products.

A recognition method of printed Thai characters by local information of contours is described. In the method, Freeman chain code and directional differences of contour tracing of characters are utilized for eliminating contour noises and extracting concavities and convexities of characters. Each arc is then segmented by points at which the arc bends. Several local features of arcs are extracted, and are used to detect a pair of the most similar arcs between a model and an input character. Finally, the similarity between each arc pair and the similarity between characters are calculated. Further, a model making, in which a single model is generated for each category by making use of feature values of characters belonging to the same category, is described. By applying the method to 69 categories (345 data) of 5050 dots of Thai characters rotated with five kinds of arbitrary angles, a very high recognition rate has been obtained.

A new procedure to derive low-sensitivity second-order digital filters is presented. This procedure is simple compared to other existing methods. First, a denominator polynomial of a filter transfer function is characterized in terms of ω₀ and ω_b, which are defined as a center angular frequency and a 3 dB bandwidth of a bandpass filter, respectively. On the other hand, the denominator polynomial is also expressed as a general form including multiplier coefficients and some integer parameters corresponding to existent degrees of freedom. Then the sensitivities of cos ω₀ and tan with respect to a multiplier coefficient, which are referred to as frequency sensitivities, are calculated. The integer parameters are determined so that the frequency sensitivities are reduced for small ω₀ and ω_b. This procedure yields several forms of transfer functions including those of well-known low-sensitivity circuits. One of them is new and the corresponding circuit structures are also given. In addition to its low sensitivity, the new filter has a useful feature; ω₀ and ω_b are determined independently by each of two multiplier coefficients.

An iteration procedure for exactly determining the capacity is proposed for a discrete menoryless channel in both cases with and without restriction to input probability distributions. Optimality conditions for obtaining the capacity reveal themselves to be the same for both cases. As a geometrical structure inherent in the channel, a simplex spanned by all the input probability distributions is introduced. When this is combined with the Newton method for computation, an iteration procedure for the capacity can be completed.

A steady-state convective diffusion problem is analyzed using a mixed boundary element method with both of constant and linear elements in three dimensions. The usefulness of the present method is shown as compared with a boundary element method with only constant elements.

Scattering problem of an electromagnetic beam wave by rectangular grooves on a perfect conductor is rigorously analyzed. The numerical examples of the far field patterns are presented for some parameters such as the number and the depth of grooves.

A technique is described to compensate the difference between lateral magnifications in ellipso-interferometry with tilted image plane by using an optical fiber bundle having an obliquely cut and polished end. A major limitation of this technique also presented.

The method of improvement on the polarization property of a turnstile spherical array antenna is proposed and its numerical results are discussed. It is found that the spherical array becomes capable of scanning its beam up to large angle with circular polarization through the improvement.