Modified Hamiltonian chain: A graph theoretic approach to group technology

Graph theory can be effectively applied to the group technology configuration problem (GTCP). Earlier attempts were made to use graph theoretic algorithms, e.g. minimal spanning tree (MST), tree search, and branch & bound to solve the group technology (GT) problem. The proposed algorithm is based on modified Hamiltonian chain (MHC) and consists of two stages. Stage I forms the graph from the machine part incidence matrix. Stage II generates a modified Hamiltonian chain which is a subgraph of the main graph developed in Stage I, and it gives machine sequence and part sequence directly. Dummy edges are considered in MHC for better accessibility in order to arrive at a block diagonal solution to the problem. This paper presents a simple approach by designing a MHC in the graph theoretic method to solve the group technology configuration problem. Results obtained from testing the method are compared with the other well-known methods and found to be satisfactory.     

Understanding the mechanical reinforcement of uniformly dispersed multiwalled carbon nanotubes in alumino-borosilicate glass ceramic

The improvement of mechanical properties of carbon nanotube–reinforced polycrystalline ceramic or glass matrix composites was limited in earlier studies by the difficulties in producing a good dispersion of carbon nanotubes. Additionally, a proper understanding of the reinforcing mechanisms, if any, affecting the mechanical properties of ceramics containing carbon nanotubes is still lacking. We report here the effects of a good dispersion of as much as 10 wt.% multiwalled carbon nanotubes (MWCNTs) on the mechanical properties of dense alumino-borosilicate glass ceramics (ABS) prepared by an ultrasonication-assisted sol–gel technique followed by hot pressing (950 °C; 2 h; Ar atmosphere). The fracture toughness and flexural strength of the nanocomposites increased with increasing MWCNT content up to 10 wt.%. The ABS–10 wt.% MWCNT nanocomposite possessed nearly double the strength of the unreinforced ABS, accompanied by ～150% improvement in fracture toughness. However, a further increase in MWCNT content to 15 wt.% resulted in a modest deterioration of the mechanical properties due to agglomeration of the MWCNTs. The carbon nanotubes have been observed to bridge crack openings of the order of ～100 nm and the experimental evidence, along with theoretical analysis, showed that crack bridging provided the major contribution towards the improvement in fracture toughness. Debonding between the MWCNTs and the matrix appeared to occur in the matrix, away from the actual interface. However, the absence of significant pull-out of broken sections of the MWCNTs during fracture, due to failure of the bridging CNTs being predominantly at the crack plane, indicates that further toughening may be available if this mechanism can be activated.     

DESIGNING OPEN SYSTEMS WITH CASE

Abstract

CASE technology is now advanced enough for use in the design of open systems for distributed computing. Open systems can be accessed for operations by other systems through standard interfaces. This article includes a step-by-step approach for designing an open system architecture using CASE.     

Two-stage procedures for selecting the best exponential population when the scale parameters are unknown and unequal

In this paper, we discuss two-stage procedures for selecting the largest location parameter among k (≥ 2) negative exponential populations having unknown and unequal scale parameters. We compare this new two-stage procedure for k = 2 with that of Mukhopadhyay (1984), and Mukhopadhyay's (1984) procedure comes out as the inferior one. To facilitate this comparison, we need a specialized table (Table I) for the Studentized smaller Chi-squares, and we provide with an exact method to do just that. The Table I is also very useful for another related problem discussed in Mukhopadhyay and Hamdy (1963). In the end, we present a limited simulation study about the moderate sample-size performances of the two-stage procedures in Mukhopadhyay (1984), and Mukhopadhyay and Hamdy (1983) for k = 2. However, for a general k (≥ 3), our newly developed two-stage procedures as developed here are the only ones known to us at this time.     

Preparation of single crystal films of magnetic bubble materials—rare earth yttrium iron gallium garnets by liquid phase epitaxy and their physical properties

The liquid phase epitaxial growth of rare earth-substituted magnetic garnet films suitable for magnetic bubble domain application by both vertical and horizontal dipping using PbO and B₂O₃ as flux is reported. The dependence of various parameters on lead incorporation in the films present as inhomogeneity has been studied.     

Blockchain-based multimedia content distribution with the assured system update mechanism

Multimedia Tools and Applications - Advancement in Internet technology is providing the exponential growth to the multimedia industry, which handles digital content broadcast and distribution over...     

Diagnosis of delay-deadline failures in real time discrete event models

In this paper a method for fault detection and diagnosis (FDD) of real time systems has been developed. A modeling framework termed as real time discrete event system (RTDES) model is presented and a mechanism for FDD of the same has been developed. The use of RTDES framework for FDD is an extension of the works reported in the discrete event system (DES) literature, which are based on finite state machines (FSM). FDD of RTDES models are suited for real time systems because of their capability of representing timing faults leading to failures in terms of erroneous delays and deadlines, which FSM-based ones cannot address. The concept of measurement restriction of variables is introduced for RTDES and the consequent equivalence of states and indistinguishability of transitions have been characterized. Faults are modeled in terms of an unmeasurable condition variable in the state map. Diagnosability is defined and the procedure of constructing a diagnoser is provided. A checkable property of the diagnoser is shown to be a necessary and sufficient condition for diagnosability. The methodology is illustrated with an example of a hydraulic cylinder.