Shop-floor scheduling at shipbuilding yards using the multiple intelligent agent system

The intelligent agent system has become a typical approach to research distributed artificial intelligence and distributed problem solving. However, despite its various technical advantages, the distribution and expansion of the intelligent agent system approach has been limited because existing methodologies rely on specialized applications and therefore require intensive investment to develop new systems. In an attempt to conquer these difficulties, a standardized methodology to construct intelligent agent systems is proposed. This approach deviates from current agent system approaches of repeatedly constructing new and customized expert systems. Specifically, it provides an economical method for developing intelligent agent systems by investigating the possibility of standardizing message communication protocols in linguistics speech-act theory and by supplementing traditional algorithmic systems with intelligent segments using, among others, expert system tools. To verify effectiveness, the shop-floor scheduling system of a large-scale shipbuilding yard has been redesigned, developed, and tested using this approach. This shop-floor scheduling system requires the scheduling of when and where to process block construction under various constraints. It is a difficult four-dimensional time and space allocation problem involving traditional NP-complete search spaces. The tested intelligent agent system proposes an innovative method for reducing the search space into three levels: the algorithm level, the agent intelligence level, and the level of cooperation among agents. It also provides methods for solving deadlock occurrence and non-uniformity problems resulting from parallel processing. Test results demonstrate applicability and economy, among other technical advantages.     

INHIBITION STUDIES ON BURDOCK POLYPHENYL OXIDASE (PPO) ACTIVITY

The inhibitory effect of 4-hexylresorcinol (HR), ascorbic acid (AA), citric acid (CA), and bisulfites on polyphenol oxidase (PPO) of burdock roots was studied. HR was an effective inhibitor at low concentrations used in this study for crude PPO from root slices. A binary mixture of HR and AA at 1.0% concentration for 5 min achieved more than 90% inhibition of crude PPO. AA also showed high antibrowning activity for the purified PPO comparable to that of bisulfites, whereas its activity was much lower than that of HR in the crude extract. The inhibitory effect of the combined use of inhibitors was overall in the decreasing order of HR+AA, HR+CA and AA+CA, irrespective of the crude PPO or the purified PPO from burdock slices.     

OVER-EXPRESSION OF PROLINE-LINKED ANTIOXIDANT PATHWAY AND MODULATION OF PHENOLIC METABOLITES IN LONG LIFE SPAN CLONAL LINE OF ORIGANUM VULGARE IN RESPONSE TO ULTRAVIOLET RADIATION

Tissue culture-generated shoot-based clonal lines of oregano that have a short and long life span during in vitro culture were investigated to determine the role of proline-linked pentose phosphate pathway in modulating phenolic response following ultraviolet (UV) exposure. This novel reductant cycling pathway for energy and oxidative pentose phosphate pathway (PPP) is more efficient in long life span O-17 clonal line in response to UV and this supported antioxidant response. UV treatment stimulated rosmarinic acid and associated antioxidant enzyme response in O-17 clonal line compared with short life span O-3 clonal line. Additionally, O-17 clonal line had higher glucose-6-phosphate dehydrogenase and guaicol peroxidase activity in response to UV exposure compared with O-3 clonal line, indicating stimulation of anabolic pathway supporting PPP during UV treatment. The stimulation of proline dehydrogenase (PDH) activity in O-17 clonal line in response to UV indicated a switch to PDH-linked energy pathway via proline oxidation.

PRACTICAL APPLICATIONS

This oregano clonal model of ultraviolet (UV)-induced oxidative stress management has implications for designing dietary phytochemicals to manage oxidation-linked disease in humans. Further, the correlation between UV-linked inducibility of phenolic-linked antioxidant enzyme response through proline-linked pentose phosphate pathway and life span of in vitro shoot cultures of specific oregano clonal lines can be a good model for aging studies. The metabolic response link to aging and protective phytochemicals can be investigated in oregano tissue cultures, and phenolic extracts from various responding clonal lines could be explored in other eukaryotic aging models.     

Interface characterization of Al/Cu 2-ply composites under various loading conditions

The effects of reduction ratio during roll bonding on the microstructural evolution at interface and subsequent mechanical properties of roll-bonded Al/Cu 2-ply sheets were investigated. The interface microstructures for several Al/Cu 2-ply sheets fabricated under different reduction ratios between 30% and 65% were verified by transmission electron microscopy (TEM). Taking the difference of interface microstructure into consideration, 3-point bending and peel tests were performed for obtaining flexural and bonding strengths for Al/Cu 2-ply sheets. The effect of the quantified areas of metallurgical bonding at interfaces on the bonding strength was also discussed. The results show that both the bonding and flexural strengths for Al/Cu 2-ply sheets are reduced by decreasing the reduction ratio during the roll bonding process, which is strongly correlated with the interface microstructure. This was especially verified by observing the interface delamination from the 3-point bent samples.     

Friction stir butt welding of A5052-O aluminum alloy plates

Friction stir butt welding (FSW) between A5052-O aluminum alloy plates with a thickness of 2 mm was performed.The rotation speeds of the welding tool were 2000 and 3000 r/min,respectively.The traverse speed was ranged from 100 mm/min to 900 mm/min.The defect-free welds with the very smooth surface morphology were successfully obtained,except for at the welding condition of 3000 r/min and 100 mm/min.The onion ring structure was observed in the friction-stir-welded zone (SZ) at the condition of 2000 r/min and 100 mm/min.For all the welding conditions,the grain size of the SZ was smaller than that of the base metal,and was decreased with the decrease of the tool rotation speed and with the increase of the tool traverse speed.The stir zone exhibited higher average hardness than the base metal.The decrease of the tool rotation speed and the increase of the tool traverse speed resulted in the increase in the average hardness of the SZ.The tensile strength of the FSWed plates was similar to that of the base metal,except for at the welding condition of 3000 r/min and 100 mm/min.The total elongation of the FSWed plates was lower than that of the base metal.     

Effects of Cr interlayer on mechanical and tribological properties of Cr-Al-Si-N nanocomposite coating

Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ~50 N is observed for the coating containing Cr interlayer of 60 nm as compared ~ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.     

Performance improvement using time delays in multivariable controller design

A new controller for linear multivariable ordinary systems is suggested in which distributed delays are included in the feedback loop. A general design approach to obtain this type of controller is suggested. It is shown that the resulting closed-loop system is asymptotically stable under some sufficient conditions. Sufficient conditions are derived under which the disturbance attenuation, the robustness against parameter variations, and the time-delay stability margins are improved by the proposed controller. The state feedback tracking controller and the dual-state observer are obtained by modification of the proposed controller.     

STRESS CONTROLLED FERROELECTRIC (BA0.5Sr0.5)TiO3 THIN FILMS PREPARED ON GD2O3/SRTiO3(001) BY A PULSED LASER DEPOSITION

ABSTRACT

Stress controlled epitaxial ferroelectric Ba_0.5Sr_0.5TiO₃ (BST) films have been deposited on Gd₂O₃/SrTiO₃ by pulsed laser deposition with oxygen background pressure of 200 mTorr at the deposition temperature of 750°C. In order to control the stress in BST films, oxygen pressures for Gd₂O₃ buffer layers have been varied from 0.1 to 100 mTorr, while that of BST films have been fixed at 200 mTorr. It has been found that the lattice parameters of the BST films deposited on Gd₂O₃ were changed. Furthermore, microwave properties of co-planar waveguide (CPW) fabricated on BST films were investigated by a HP 8510C vector network analyzer from 1–20 GHz. Large dielectric tunabilities were observed from the CPW's fabricated on BST films deposited on Gd₂O₃ layers deposited at low and high oxygen pressures, 0.1 and 100 mTorr, respectively.     

The relationship between sensitisation and small punch test behaviour in a high-nitrogen austenitic stainless steel at cryogenic temperatures

Austenitic stainless components used in nuclear fusion reactors must be capable of maintaining reasonable mechanical properties to thermal ageing caused by welding and in‐service. Recently, high‐nitrogen (High‐N) austenitic stainless steels (SS) are receiving increased attention because of their strength advantages, but they have been found to be susceptible to dichromium nitride (Cr₂N) precipitation during thermal exposure at 823–1073 K. The susceptibility to sensitisation at thermal ageing temperature for high‐N austenitic SS is examined using the single‐loop electrochemical potentiokinetic reactivation (EPR) test. High‐N SS were found to be susceptible to sensitisation caused by grain boundary precipitation of Cr₂N, with the degree of sensitisation increasing systematically with ageing time and temperature. In particular, it was found that the precipitates, which effected sensitisation, were changed from carbides (M₂₃C₆) to nitrides (Cr₂N) with increasing ageing time and temperature. The deterioration of mechanical properties associated with thermal ageing in high‐N SS was investigated by a small punch (SP) test using miniature specimens at cryogenic temperatures. Results indicated that the degradation of mechanical properties in this alloy was caused by a decrease of cohesive strength resulting from carbides (Cr₂₃C₆) and nitrides (Cr₂N) precipitated in grain boundaries.