Microstructure and mechanical properties of Al-Mg2Si composite fabricated in-situ by vibrating cooling slope

An innovative semisolid technique termed as vibrating cooling slope (VCS) has been applied to producing in-situ Al-25%Mg₂Si (mass fraction) composite. The molten Al-16.5Mg-9.4%Si (mass fraction) alloy with 100 °C superheat was poured on the surface of an inclined copper plate (set at 45° inclined angle) while it was vibrated at a frequency of 40 Hz and an amplitude of 400 μm. After travelling the length of 40 cm on the slope, the resultant semisolid alloy was cast into a steel mold. For the purpose of comparison, reference composite samples were made by gravity casting (GC) and conventionally still cooling slope casting (CS) methods using the same alloy under identical conditions. The samples were hot extruded at 500 °C. It was concluded that the size of Mg₂Si particles was decreased by about 50% and 70% for the CS and VCS produced samples respectively when compared to that of the GC produced sample. Despite of their higher porosity contents, both the as-cast and hot-extruded VCS processed samples exhibited higher hardness, shear yield stress (SYS) and ultimate shear strength (USS) values as compared with their GC produced counterparts. These results were attributed to the refined and modified microstructure obtained via this newly developed technique.     

Investigation of lanthanum and Si/Al ratio effect on the HZSM-5 catalyst efficiency for production of Olefin from Methanol

The effect of lanthanum and Si/Al ratio on catalytic performance of HZSM-5 in methanol to olefin process is investigated in this paper. The catalyst with bases of HZSM-5 is modified using the lanthanum by a wet impregnation producer. The Box-Behnken method, experimental design is used to evaluate effects of lanthanum parameters, Si/Al ratio, temperature and the effect of the interaction between them in methanol to olefin process for production of ethylene and propylene. Finally, the obtained results show the highest yield of ethylene is achieved for high load lanthanum catalyst, low Si/Al ratio and high temperature.     

Optimal parallel scheduling of M-way join queries

The problem of computing multirelation (M-way) join queries on uniprocessor architectures has been considered by many researchers in the past. This paper lays the necessary foundation for work involving optimization of M-way joins in parallel architectures. We explain the inadequacies of previous uniprocessor strategies and describe a more suitable formulation based on the concept of matching in graph theory to approach the problem in a parallel environment. It has been shown that the problem of optimizing M-way joins is an NP-hard problem and hence we would expect that in a parallel processing environment the search space of possible solutions (join schedules) would be enormous, especially when a variable number of processors are considered. Our strategy seeks to reduce the region to search by partitioning the search space according to the number of available processors. Based on this a significant portion of the search space, which will produce non-optimal join schedules, may be ignored.     

Feature Extraction Based on Speech Attractors in the Reconstructed Phase Space for Automatic Speech Recognition Systems

In this paper, a feature extraction (FE) method is proposed that is comparable to the traditional FE methods used in automatic speech recognition systems. Unlike the conventional spectral‐based FE methods, the proposed method evaluates the similarities between an embedded speech signal and a set of predefined speech attractor models in the reconstructed phase space (RPS) domain. In the first step, a set of Gaussian mixture models is trained to represent the speech attractors in the RPS. Next, for a new input speech frame, a posterior‐probability‐based feature vector is evaluated, which represents the similarity between the embedded frame and the learned speech attractors. We conduct experiments for a speech recognition task utilizing a toolkit based on hidden Markov models, over FARSDAT, a well‐known Persian speech corpus. Through the proposed FE method, we gain 3.11% absolute phoneme error rate improvement in comparison to the baseline system, which exploits the mel‐frequency cepstral coefficient FE method.     

Investigation of ex-vessel core catcher for SBO accident in VVER-1000/V528 containment using MELCOR code

Nuclear Science and Techniques - An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator (linac) to accommodate the new development of compact,...     

On the probability of facing random breakdowns: a measure of networks’ vulnerability

In this paper, we study the vulnerability of networks in the case of random removal of individual nodes. To achieve this goal, a network reliability measure, the probability of messages facing malfunctions, has been proposed. The benefit of this measure is its capability of applying in a wide range of graphs. Moreover, it is well suited to human activities and foraging patterns of some sorts of animals, as they try to make an alternative path in the case of facing failures. We examine the most prominent communication networks such as meshes and tori; further, CAN, Chord, Petersen, PRU, and Hypergrid, which are well suited for P2P networks, have been investigated. In order to gain a better understanding of the studied networks’ vulnerability and easier evaluation of the proposed measure, an ant colony-based communication protocol has been presented. Experimental results verify the correctness of the proposed measure.