A genetic algorithm for facility layout

Facility layout is an important aspect of designing any manufacturing setup. However, the problem of finding optimal layouts is hard and deterministic techniques are not computationally feasible. In this work a genetic algorithm is presented for obtaining efficient layouts. The different aspects involved in the design of efficient genetic algorithms are discussed in detail. It is shown that the population maintained by the genetic algorithm for facility layout should consist of feasible solutions only. A new efficient crossover operator is developed. Experimental results obtained with the proposed algorithm on test problems taken from the literature are promising.     

Towards an integrated evaluation of flexible automation investments

This paper presents a decision-support-system (DSS) structure for flexible automation investments. It takes into account: (1) a comprehensive investment context for multimachine systems; (2) developments in modelling flexibility in economic evaluation; and (3) an integrated physical/financial design and evaluation, for capitalizing on recent developments in DSS technologies and automated decision/risk-analysis tools.     

YTTRIUM ALUMINATE CERAMIC FIBERS VIA PRE-CERAMIC POLYMER AND SOL-GEL ROUTES

ABSTRACT

Yttrium aluminum garnet (YAG - Y₃Al₅O₁₂) fibers have been prepared by dry spinning solutions of yttrium and aluminum carboxylate polymers (precursor route) and by dry spinning aqueous oxide sols (sol-gel route). Fibers from aqueous diphasic gels are prepared by mixing a colloidal alumina sol containing 50-nm hydrous alumina with a colloidal yttria sol containing 10-nm yttrium oxide, using polyvinylpyrrolidone as a spinning aid. Fibers by the precursor route are made from spinnable THF solutions of yttrium isobutyrate and aluminum isobutyrate or from aqueous solutions of polymeric aluminum formate and yttrium acetate.

The isobutyrate materials decompose between 200-400^°C to an amorphous residue. Crystallization occurs abruptly between 875°C and 900^°C, forming the YAG phase directly. The formate-acetate also decomposes to amorphous residues, which form YAG at 900^°C. In the diphasic gel, YAG forms gradually between 1000 and 1200^°C, with intermediate products YAP (YalO₃ perovskite) and/or YAM (Y₄Al₂O₉ monoclinic). At 1500^°C, single phase YAG is obtained as pore-free fibers with 500 nm grains.     

SHELF LIFE OF SPRAY-DRIED MILK FORMULATIONS SUPPLEMENTED WITH N-3 FATTY ACIDS

Studies were carried out to assess the shelf life of spray‐dried milk formulation containing linseed oil (LSO) or fish oil (FO) as a source of n‐3 polyunsaturated fatty acids (PUFA) in comparison with a milk formulation containing groundnut oil (GNO) stored at 4, 27 and 37C in tin cans for a period of up to 6 months. Total protein, fat, carbohydrate, moisture and solubility index of formulations stored for 6 months were comparable with fresh samples. The fresh samples containing LSO contained 20% ∝ linolenic acid (LNA). At the end of 6 months, the ∝ LNA levels were found to be 18.4, 18.0 and 16.2% in samples stored at 4, 27 and 37C, respectively. The fresh samples containing FO had 2.4% eicosapentaenoic acid (EPA). At the end of 6 months, the EPA levels were found to be 2.2, 2.0 and 1.6% in samples stored at 4, 27 and 37C, respectively. The docosahexaenoic acid (DHA) level in the freshly prepared sample containing FO was 2.1%. At the end of 6 months, the DHA levels were found to be 1.7, 1.6 and 1.3% in samples stored at 4, 27 and 37C, respectively. The whiteness of the formulation containing GNO, LSO or FO remained unaltered for a period of 5 months, but dropped marginally when n‐3 PUFA‐containing formulations were stored at 37C for 6 months. Acceptability scores of formulations were similar for 5 months storage but declined significantly in the FO formulation at the end of 6 months of storage. All n‐3 PUFA‐enriched milk formulations were stable and accepted well for up to 5 months when stored at different temperatures.     

PHYSICAL and THERMAL PROPERTIES of GORGON NUT

Bulk density, true density, angle of repose, coefficient of friction on metal surfaces, specific heat, thermal diffusivity and conductivity of gorgon nut were determined using standard techniques for different sizes of nuts at moisture contents and temperatures ranging from 15 to 60% (dry basis) and 25 to 55C, respectively. the physical properties varied quadratically with moisture content. Specific heat increased with moisture and temperature but decreased with the size of the nut; whereas, the thermal diffusivity showed a reverse trend. Thermal conductivity increased with moisture content but did not follow any trend with temperature within the range of the study. the physical and thermal properties data at various moisture contents and temperatures were used to develop equations for different sizes of gorgon nuts.     

Alkali Tungstates: Stability Relations in the Systems A2O WO3-WO3

Phase relations in the systems alkali monotungstate-tungsten trioxide were investigated in the range 600° to 1100°C.In the Li system, compounds with an A₂O/WO³ ratio of 1:2 and 1:4 are stable and melt incongruently at 745° and 805°C, respectively. In the Na system, the 1:2 compound melts congruently at 746°C, whereas the other 2 sodium tungstates (1:4 and 1:6) melt incongruently at 835° and 913°C, respectively. The K system includes compounds of 1:2, 1:3, 1:4, and 1:6 which melt incongruently at 684°, 842°, 912°, and 964°C, respectively. Eutectic points between the 1:l and 1:2 compounds in these respective systems are at 692°C and 56 mol%WO³, 622°C and 56.3 mol% WO³, and 633°C and 63 mol%WO³. In the Rb and Cs systems, the 1:2 and 1:3 compounds form complete solid-solution series, and their melting temperatures increase with increasing WO³ content, respectively, from 690° to 868°C and from 732° to 902°C. The 1:6 compounds are also stable in these systems and melt incongruently at 1040° and 1046°C, respectively.     

A review on front end conversion in ocean wave energy converters

Harvesting the energy from ocean waves is one of the greatest attractions for energy engineers and scientists. Till date, plenty of methods have been adopted to harvest the energy from the ocean waves. However, due to technological and economical complexity, it is intricate to involve the majority of these energy harvesters in the real ocean environment. Effective utilization and sustainability of any wave energy harvester depend upon its adaptability in the irregular seasonal waves, situation capability in maximum energy extraction and finally fulfilling the economic barriers. In this paper, the front end energy conversions are reviewed in detail which is positioned in the first stage of the wave energy converter among other stages such as power take off (PTO) and electrical energy conversion. If the recent development of these front end energy conversion is well known then developing wave energy converter with economic and commercial viability is possible. The aim of this review is to provide information on front end energy conversion of a point absorber and emphasize the strategies and calamity to be considered in designing such kinds of devices to improve the energy harvesting competence. This will be useful to the engineers for speeding up the development of a matured point absorbing type wave energy converter.     

A new universal gate for low power SoC applications

This paper formulates a new design technique for an area and energy efficient Universal NAND gate. The proposed robust three transistors (3T) based NAND gate is just as effective for dynamic power control in CMOS VLSI circuits for System on Chip (SoC) applications. The 3T NAND gate is intuitively momentous and lead to better performance measures in terms of dynamic power, reduced area and high speed while maintaining comparable performance than the other available NAND gate logic structures. Simulation tests were performed by employing standard Berkeley Predictive Technology Model (BPTM) 22 nm, 45 nm and 90 nm process technologies. The experiment and simulation results show that, the proposed 3T NAND gate effectively outperforms the basic CMOS NAND gate with excellent driving capability and signal integrity with exact output logic levels.     

Effect of Crystallites on Subcritical Crack Growth and Strain-Rate Sensitivity of Strength of Cordierite Glass-Ceramics

A study was conducted of the subcritical crack growth in a series of cordierite glass-ceramics, including the original glass, by means of the double-torsion method and measurement of the strain-rate sensitivity of the strength of specimens with controlled indentation cracks subjected to biaxial flexure. The double-torsion data showed that the same rate of crack growth required a stress intensity factor for the fully crystallized glass-ceramic about 3 times higher than for the original glass, accompanied by a simultaneous increase in the stress intensity exponent ( N ). The suppression in the rate of crack growth in the crystallized material at any value of stress intensity factor was attributed to enhanced crack deflection around the crystallites. Limited observations suggested that the increase in N on crystallite formation may be due to a greater degree of crack deflection at the lower crack velocities than at the higher velocities. For strength specimens of the as-received and crystallized glass with large surface flaws, the N values obtained by the strain-rate measurements and the double-torsion test showed good agreement. However, for the fully crystallized material with surface flaws too small to interact significantly with the coarser crystallites, the N value for the strain-rate data was well below the value for the double-torsion method. Indentation-fracture data of the double-torsion specimens confirmed the existence of crack-size dependent fracture toughness. Limited fracture toughness data coupled with SEM fractography indicated that with increasing crystallite size toughening occurs by crack deflection as well as by microcrack toughening counteracted by fracture through the crystallites.