A mathematical model and a heuristic approach for periodic material delivery in lean production environment

One of the important design elements for a good production system is material handling. In cases where it is not well-designed, it can be the bottleneck in the system. Moreover, it can cause a lot of wastes such as waiting time, idle time, and excessive transportation and cost. In this study, material handling in lean-based production environments is taken into account. Depending on the lean structure of the production systems such as being pull-based, smooth, and repetitive, delivering the materials to the stations periodically becomes important. At this point, milk-run trains are highly used in real applications since they enable the handling of required amount of materials on a planned basis. With this study, it is aimed to develop a specific model for milk-run trains which travel periodically in the production environment on a predefined route in equal cycle times with the aim of minimizing work-in-process and transportation costs. Since the milk-run trains having equal cycle times start their tours at the same time intervals, it becomes simple to manage them. For this reason, they are used in lean production systems where level scheduling is performed. The developed model is based on mixed-integer linear programming, and since it is difficult to find the optimum solution due to the combinatorial structure of the problem, a novel heuristic approach is developed. A numerical example is provided so as to show the applicability of the mathematical model and the heuristic approach.     

Synthesis of copper-based bulk metallic glasses in the ternary Cu–Mg–Ca system

This paper reports the discovery of novel copper-based bulk metallic glasses free of group IV transition metals (Zr, Hf and Ti) in the Ca–Cu–Mg ternary system. Alloys of compositions ranging from Cu-33–55 at.%, Mg-18–36 at.% and Ca-18–36 at.%, located far from eutectic reactions, were found to exhibit high glass-forming ability (up to 8 mm using conventional copper mold casting), high hardness (up to 328H_V) and low densities (2.9–4.0 g/cm³).     

Clinical evaluation of the ASTY colorimetric microdilution panel for antifungal susceptibility testing

A method using a commercially prepared colorimetric microdilution panel (ASTY; Kyokuto Pharmaceutical Industrial Co., Ltd.) was compared in four different laboratories with the National Committee for Clinical Laboratory Standards (NCCLS) reference microdilution method by testing 802 clinical isolates of Candida spp. (C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. krusei, C. lusitaniae, C. guilliermondii, C. lipolytica, C. rugosa, and C. zeylanoides) against amphotericin B, 5-fluorocytosine (5FC), fluconazole, and itraconazole. Reference MIC endpoints were established after 48 h of incubation, and ASTY endpoints were established after 24 and 48 h of incubation. ASTY endpoints were determined to be the time at which the color of the first well changed from red (indicating growth) to purple (indicating growth inhibition) or blue (indicating no growth). Excellent agreement (within 2 dilutions) between the reference and colorimetric MICs was observed. Overall agreement was 93% at 24 h and 96% at 48 h. Agreement ranged from 90% with itraconazole and 5FC to 96% with amphotericin B at 24 h and from 92% with itraconazole to 99% with amphotericin B and 5FC at 48 h. The ASTY colorimetric microdilution panel method appears to be comparable to the NCCLS reference method for testing the susceptibilities of Candida spp. to a variety of antifungal agents.     

Rare manifestations of the ovarian hyperstimulation syndrome: a report of two cases

Eosinophilic ulcer of the oral mucosa (EUOM) is an uncommon lesion that usually affects the tongue. The lesion is benign and self-limiting, develops rapidly and usually disappears after several weeks without treatment. Microscopically, it contains a diffuse polymorphous cell infiltrate composed mainly of eosinophils. The cause of EUOM is unknown, but the condition has been attributed to trauma. We now describe a case of EUOM on the lateral surface of the tongue with recurrence on its dorsal surface 3 years later. The occurrence of multiple lesions, whether at the same time or subsequently as reported here, makes a purely traumatic origin rather unlikely and suggests that there may be a predisposition of some patients to develop EUOM. Eosinophilic ulcer of the oral mucosa (EUOM) is an uncommon lesion that is very rarely reported in the dermatological literature. It usually affects the tongue and presents clinically as an ulcer with elevated and indurated borders. Recognition is important because it often mimicks tongue cancer; however, the lesion is benign and self-limiting, develops rapidly and usually disappears after several weeks without treatment. Usually the ulcer occurs in a single episode, but the possibility of recurrence at other sites has been poorly emphasized.     

Nonlinear free bending vibrations of plates

A general solution for the Helmholtz differential equations is obtained in the complex domain and applied to the nonlinear, free, bending vibrations of plates. The analysis is based on the decoupled nonlinear von Karman field equations by Berger assumption for the large deformations of plates. The decoupled differential equation in terms of the deflection function is a fourth order Helmholtz differential equation. Its solution, called the dynamic deflection function, is obtained in the complex domain by means of newly defined first and second kind and modified Bessel functions. The dynamic deflection function can be applied to any plates having any shape and any boundary condition under any arbitrary dynamic loads. For plates with smooth boundary, the parameters of the dynamic deflection function are determined from the boundary conditions of the plates and the initial conditions of the vibrations. The analyses of plates with piece-wise smooth boundaries are obtained on the mapped planes. The nonlinear, free vibration of circular plates are investigated by the dynamic deflection function. The effect of stretching on the natural circular frequencies are illustrated.     

Oil Content,Oil Yield and Fatty Acid Profile of Groundnut Germplasm in Mediterranean Climates

A high amount of good-quality vegetable oil in seeds has an overwhelming contribution to the groundnut (Arachis hypogaea L.) cultivation throughout the world. In order to take into account great variation in oil characteristics in Arachis subspecies and botanical varieties, 256 groundnut genotypes including ICRISAT’s mini core collection were investigated. Significant variability in oil content (31.7–57.0%) was detected among groundnut genotypes. Oil yield varied from 9.5 to 179.3 kg da^?1 with the average being 67.7 kg da^?1. Significant genotypic differences were also observed for all the fatty acids studied. Oleic and linoleic acids accounted for the major fraction with mean values of 45.3 and 32.1% in the ranges of 35.3–60.9% and 16.1–43.6%, respectively. Significant negative correlation was observed between oleic and linoleic acid. In the present investigation, desirable values were obtained for oil traits which would be useful to develop nutritional and health-beneficial cultivars.     

Thermal stabilization of an active alumina and effect of dopants on the surface area

The -AI₂O₃ transformation of a monolithic active alumina has been increased from 1200 to 1380 C through structural incorporation of silica. This shift is significant since -Al₂O₃ transformation determines the limits of the usefulness of these materials as catalysts and catalyst carriers. The thermal stabilization effect is optimized at around 6% silica doping. At elevated temperatures, the material containing no silica rapidly loses surface area, primarily by -Al₂O₃ transformation, whereas the material containing excess silica loses surface area by classical sintering.     

Zirconium oxides formed by hydrolytic condensation of alkoxides and parameters that affect their morphology

When zirconium oxides are formed via hydrolytic condensation of zirconium alkoxides, the particle size and morphology of the resultant zirconia is strongly affected by certain parameters during the condensation. These parameters include: the type of alkyl group in the alkoxide, water/alkoxide ratio, molecular separation of species, and the reaction temperature. The particle size and the morphology in turn affect the sintering behaviour and crystalline transformation of ZrO₂, In this work the parameters that affect the formation of ZrO₂ from zirconium alkoxides are investigated. It has been shown that the alkyl groups and molecular separations during the hydrolytic polycondensation have particular significance in the modification of monoclinic tetragonal transformation of the resultant ZrO₂. Tetragonal phase can also be stabilized by copolymerization of ZrO₂ with SiO₂ producing tough ceramic materials.     

Maximizing lifetime of event-unobservable wireless sensor networks

In wireless sensor networks (WSNs) contextual information such as the information regarding whether, when, and where the data is collected cannot be protected using only traditional measures (e.g., encryption). Contextual information can be protected against global eavesdroppers by periodic packet transmission combined with dummy traffic filtering at proxy nodes. In this paper, through a Linear Programming (LP) framework, we analyze lifetime limits of WSNs preserving event-unobservability with different proxy assignment methodologies. We show that to maximize the network lifetime data flow should pass through multiple proxies that are organized as a general directed graph rather than as a tree.     

Force-torque based on-line tool wear estimation system for CNC milling of Inconel 718 using neural networks

In a modern machining system, tool condition monitoring systems are needed to get higher quality production and to prevent the downtime of machine tools due to catastrophic tool failures. Also, in precision machining processes surface quality of the manufactured part can be related to the conditions of the cutting tools. This increases industrial interest for in-process tool condition monitoring (TCM) systems. TCM supported modern unmanned manufacturing process is an integrated system composed of sensors, signal processing interface and intelligent decision making strategies. This study includes key considerations for development of an online TCM system for milling of Inconel 718 superalloy. An effective and efficient strategy based on artificial neural networks (ANN) is presented to estimate tool flank wear. ANN based decision making model was trained by using real time acquired three axis (F_x, F_y, F_z) cutting force and torque (M_z) signals and also with cutting conditions and time. The presented ANN model demonstrated a very good statistical performance with a high correlation and extremely low error ratio between the actual and predicted values of flank wear.