Recurrent Neural Networks with Backtrack-points and Negative Reinforcement Applied to Cost-based Abduction

Abduction is the process of proceeding from data describing a set of observations or events, to a set of hypotheses which best explains or accounts for the data. Cost-based abduction (CBA) is an AI formalism in which evidence to be explained is treated as a goal to be proven, proofs have costs based on how much needs to be assumed to complete the proof, and the set of assumptions needed to complete the least-cost proof are taken as the best explanation for the given evidence. In this paper, we present two techniques for improving the performance of high order recurrent networks (HORN) applied to cost-based abduction. In the backtrack-points technique, we use heuristics to recognize early that the network trajectory is moving in the wrong direction; we then restore the network state to a previously stored point, and apply heuristic perturbations to nudge the network trajectory in a different direction. In the negative reinforcement technique, we add hyperedges to the network to reduce the attractiveness of local minima. We apply these techniques to a suite of six large CBA instances, systematically generated to be difficult

Magnetization of three Nubia Sandstone formations from Central Western Desert of Egypt

A total of 198 oriented cores (from 16 sites) have been sampled from three Cretaceous Nubia sandstone formations distributed around the Kharga–Dakhla and Dakhla–Uwainat roads in the Western Desert for paleomagnetic studies. Two of these formations are of the Early Cretaceous (the Six Hills, Abu Ballas formations) and the third one is of the Late Cretaceous (Maghrabi formation). The studied rocks are subjected to rock magnetic measurements as well as demagnetization treatment. Rock magnetic experiments reveal that the presence of hematite is the main magnetic mineral in the three formations. Therefore, present study relies mostly on thermal demagnetization. Two magnetic components have been isolated from the studied rocks. The first component has been isolated from the Six Hills and Abu Ballas formations and is carried by hematite with D = 347.1°, I = 41.6° with α95 = 7.8° and the corresponding pole lies at lat. = 78.2° N and long. = 294.1° E. The second component has been isolated from the Maghrabi formation and is carried also by hematite with D = 22.7°, I = 28.4° with α95 = 9.9° and pole position lies at lat. = 66.3° N and long. = 140.6° E. The first magnetic component obtained from the two older formations is considered primary, as the corresponding pole reflects the age when compared with the previously obtained Cretaceous poles for North Africa. On other hand, the second pole obtained from the Maghrabi formation (the younger) is inconsistent with the Cretaceous pole positions for North Africa, but falls closer to the Eocene pole indicating that the rocks of this formation could have suffered remagnetization during the late Eocene time

1st paleomagnetic investigation of Nubia Sandstone at Kalabsha, south Western Desert of Egypt

Two profiles have been sampled from the Nubia Sandstone at Aswan, south Western Desert: the 1st profile has been taken from Abu Aggag Formation and the 2nd one was from Sabaya Formation (23.25 °N, 32.75 °E). 136 oriented cores (from 9 sites) have been sampled. Abu Aggag Formation is of Late Cretaceous (Turonian) and Sabaya Formation is of early Cretaceous (Albian–Cenomanian). The studied rocks are subjected to rock magnetic measurements as well as demagnetization treatment. It has been found that hematite is the main magnetic mineral in both formations. Four profile sections from Abu Aggag Formation, yielded a magnetic component with D = 352.7°, I = 36.6° with α95 = 5.2° and the corresponding pole lies at Lat. = 82.8 °N and Long. = 283.1 °E. Five profile sections from Sabaya Formation, yielded a magnetic component with D = 348.6°, I = 33.3° with α95 = 5.8° and the corresponding pole lies at Lat. = 78.3 °N and Long. = 280.4 °E. The obtained paleopole for the two formations lies at Lat. = 80.5 °N and Long. = 281.7 °E. The obtaind magnetic components are considered primary and the corresponding paleopole reflects the age of Nubia Sandstone when compared with the previously obtained Cretaceous poles for Egypt