Let A be any nonrecursive set. For each k 0, we show that there are functions (k + 1)-truth-table reducible to A that are not k-weak-truth-table reducible to A; and we show that there are functions (k + 1)-Turing reducible to A that are not k-Turing reducible to A. Intuitively, this means that k + 1 queries to a nonrecursive oracle are strictly more useful than k queries to the same oracle (for...

We present proper motions of 59 stars of the ROSAT All-Sky Survey (RASS) located in direction of the Chamaeleon star forming region (SFR) in the magnitude range B=5.1 17 mag. Proper motions of the fainter stars were newly derived utilizing survey Schmidt plates from the GSC II plate archive and from a set of special plates taken with the ESO Schmidt telescope. The vector point diagram (VPD) ind...

Ferroresonance is a non-linear phenomenon and very dynamic in the power quality problems. This phenomenon should be carefully analyzed so that preventive measures could be taken before its appearance and prevent injury and damage to electrical power appliances. Ferroresonance is seen more in the middle-voltage networks with supplying unloaded or slightly loaded transformers by cables. The mater...

In this paper, a combined neural network and an evolutionary programming scheme is proposed to improve the quality of wound core distribution transformers in an industrial environment by exploiting information derived from both the construction and transformer design phase. In particular, the neural network architecture is responsible for predicting transformer iron losses prior to their assemb...

The stress response in Drosophila melanogaster reveals sex differences in behavior, similar to what has been observed in mammals. However, unlike mammals, the sex determination pathway in Drosophila is well established, making this an ideal system to identify factors involved in the modulation of sex-specific responses to stress. In this study, we show that the Drosophila fat body, which has be...

In this study, a disk-shaped piezoelectric transformer was fabricated using lead-free (K,Na)NbO(3)-based ceramics with high mechanical quality factor. The transformer can operate in the fundamental or the third radial vibration mode. The transformer is poled along the thickness direction. The top surface is covered by ring/dot silver electrodes separated by an annular gap which serve as the inp...

Geomagnetically Induced Currents (GIC) are supposed to be a threat to power transformers worldwide. Recent surveys show correlation between solar storm activities, the cause of GIC, and transformers failing within a relatively short time period. The scope of this contribution is to create and investigate a laboratory setup emulating GIC effects by injecting DC currents into a three phase power ...

Reliability of a power system is considerably influenced by its equipments. Power transformers are one of the most critical and expensive equipments of a power system and their proper functions are vital for the substations and utilities. Therefore, reliability model of power transformer is very important in the risk assessment of the engineering systems. This model shows the characteristics an...

This paper proposes an industrial solution (equipment) for lightning and surge protection of distribution transformers. The proposed protection equipment has been installed at 100 distribution transformers (sample) of the Public Power Corporation (PPC) of Greece. The article estimates the future transformer failures, considering two different cases: (a) transformer without the proposed protecti...

The delta primary transposed zigzag secondary (DTz) transformer has been designed and used to reduce the bad impacts of the harmonic in the distribution power system. The DTz transformer is constructed with delta connection in primary winding and the three transposed windings at the different core legs of secondary winding. The harmonic reduction method of the DTz transformer applies two basic ...