Large-scale parallel corpora are essential for training high-quality machine translation systems; however, such corpora are not freely available for many language translation pairs. Previously, training data has been augmented by pseudo-parallel corpora obtained by using machine translation models to translate monolingual corpora into the source language. However, in low-resource language pairs, in which only low-accurate machine translation systems can be used, translation quality degrades when a pseudo-parallel corpus is naively used. To improve machine translation performance with low-resource language pairs, we propose a method to effectively expand the training data via filtering the pseudo-parallel corpus using quality estimation based on sentence-level round-trip translation. For experiments with three language pairs that utilized small, medium, and large size parallel corpora, BLEU scores significantly improved for low-resource language pairs. Additionally, the effects of iterative bootstrapping on translation performance quality is investigated; resultingly, it is confirmed that bootstrapping can further improve the translation performance.

What differentiates biological tissues from one another, thereby allowing their accomplishment of a physiological function, is their organization at supracellular and cellular levels. We developed general dielectric models for Cantorian (or treelike) fractal networks of transmission lines that mimic supracellular organization in numerous biological tissues and tissue surfaces, and which are compatible with both in vitro and in vivo measuring techniques. By varying a set of adjustable physical and geometrical parameters pertaining to the structure, we could numerically reproduce a variety of dielectric dispersion curves-most of them of a composite type-that suitably described experimental data from relatively organized biological tissues. We therefore conclude that the well-documented non-Debye dielectric behavior of biological structures reflects their self-similar architecture.

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