Hirofumi Sanada

Quality improvement technique for JPEG images with fractal image coding

This paper proposes a quality improvement technique for JPEG images by using fractal image coding. JPEG coding is a commonly used standard method of compressing images. However, in its decoded images, quantization noise is sometimes visible in high frequency regions, such as the edges of objects. Hence, in order for the JPEG coding to become a more powerful image-coding method, the JPEG image quality must be improved. Therefore, our method solves this problem by adding the obtained codes by the fractal image coding to improve the image quality. Some simulation results verify that the proposed method achieved higher coding-performance than the traditional JPEG coding.

Practical band estimation for periodic superlattices by using semi-infinite periodic model

In this paper, we propose a practical band estimation method for periodic superlattices by using semi-infinite periodic model, which is located in the middle of finite periodic model and infinite periodic model. According to the model proposed, we can estimate not only band structures but also ripples in passbands for periodic superlattices with simple calculation by applying image parameters in circuit theory. This model may be useful for energy filter designing, since the ripples in passbands are the essential information related with energy filter abilities.

Regularity in difference in transmission characteristics for Gaussian superlattices and periodic superlattices

It is known that periodic superlattices have minibands in their transmission characteristics. Gaussian superlattices show flat pass-bands similar to the minibands. This paper shows that some regularity can be found in the difference in the transmission characteristics of both superlattices. According to the regularity found, it is possible to estimate the transmission characteristics of Gaussian superlattices without calculating them from those of periodic superlattices.

Real-Passband Estimation for Modulated Superlattices Based on Circuit Theory

This paper presents that Gaussian superlattices modulated layer thickness form a band structure, which consists of real-passbands, quasi-passbands and stopbands, same as those modulated potential height unlike the periodic superlattices. This paper shows a close relation between the band structure of Gaussian superlattices modulated layer thickness and that of periodic superlattices. According to the relation, the real-passbands of the former can be estimated with simple calculation from the latter effectively evaluated by applying image parameters in circuit theory

Transmission-line filter synthesis using genetic algorithms

Summary form only given. We present a new method for designing transmission-line filters with shunt-connected open circuit stubs. This method is based on a genetic algorithm and can effectively be applied to various filter design problems without increasing the computational complexity. Conventional methods of designing and implementing transmission-line filters begin with lumped-element prototype filters. As a result, transmission-line filters must be created using transmission-line sections of the same electrical length. If this limitation could be avoided, however, it might be possible to design transmission-line filters with better characteristics than those of conventional filters. To evaluate the proposed method, several different types of filters were synthesized according to the proposed method.