A comparison of sintering techniques using different particle sized β-SiAlON powders

In the present study sintering behavior and mechanical properties of β-SiAlON ceramics were investigated using different sintering techniques (gas pressured sintering (GPS), pressureless sintering and spark plasma sintering (SPS)) and different particle sized powders (with D_BET 216 and 130 nm). After sintering of the microstructure and phase characterization were carried out using a scanning electron microscope (SEM) and the X-ray diffraction (XRD) method, respectively. All the samples, prepared using fine powder, were sintered at lower temperatures than samples prepared by conventional powder, by two sintering techniques (GPS and pressureless). Additionally, the results showed that cooling rates had an important effect on the formation and the amount of intermediate phase in the sample. As a result, it was shown that the particle size of starting raw materials, the amount of additive, the sintering temperature and the technique had a significant effect on the microstructure and mechanical properties of the SiAlON samples.     

Optical wireless localization

In this paper, we explore the possibility of using directionality of free-space-optical (a.k.a. optical wireless) communications for solving the 3-D localization problem in ad-hoc networking environments. Range-based localization methods either require a higher node density (i.e., at least three other localized neighbors must exist) than required for assuring connectedness or a high-accuracy power-intensive ranging device such as a sonar or laser range finder which exceeds the form factor and power capabilities of a typical ad-hoc node. Our approach exploits the readily available directionality information provided by a physical layer using optical wireless and uses a limited number of GPS-enabled nodes, requiring a very low node density (2-connectedness, independent of the dimension of space) and no ranging technique. We investigate the extent and accuracy of localization with respect to varying node designs (e.g., increased number of transceivers with better directionality) and density of GPS-enabled and ordinary nodes as well as messaging overhead per re-localization. Although denser deployments are desirable for higher accuracy, our method still works well with sparse networks with little message overhead and small number of anchor nodes (as little as 2). We also present a proof-of-concept prototype of our FSO-based localization techniques and show the validity of our approach even with three transceivers per node.     

Clinoptilolite-rich mineral as a novel carrier for the active constituents present in Ginkgo biloba leaf extract

The possible use of clinoptilolite-rich mineral as a novel carrier for the active constituents present in Ginkgo biloba leaf extract solutions was investigated. The flavonoid aglycone constituents were found to be selectively adsorbed on the clinoptilolite surface. The antioxidant activity determinations of the extract solutions were performed by the Trolox Equivalent Antioxidant Capacity (TEAC) assay. The antioxidant activity measurements performed for the Ginkgo leaf extract solutions showed decreasing antioxidant activities due to adsorption. The decrease in antioxidant activity was attributed to the adsorption of phenolic constituents on the clinoptilolite surface.     

Percutaneous treatment of an orbital hydatid cyst: a new therapeutic approach

PURPOSE: To describe the percutaneous treatment of an orbital hydatid cyst as an alternative approach to conventional surgery. METHODS: In a 21-year-old man with diplopia and right proptosis, radiologic studies disclosed a 25 x 25 x 20-mm purely cystic mass in the right retrobulbar area. Based on the presumptive diagnosis of hydatid cyst, the cyst was treated percutaneously under ultrasonographic guidance with aspiration, 15% hypertonic saline injection, and reaspiration without any complication. RESULTS: A substantial decrease in the size of the cyst was observed in the 3 months after treatment. Nine months after treatment, the shrunken cyst had a volume of only 0.5 ml, and the patient was asymptomatic. Twenty-one months after the procedure, the findings were consistent with those at 9 months of follow-up. CONCLUSION: Percutaneous treatment of orbital hydatid cysts, which is more satisfactory to both the patient and the physician, may be a safe and effective alternative to surgical extirpation.     

Technological and economic comparison of the usage of beech and alder wood in plywood and laminated veneer lumber manufacturing

In this study, the economic and technological benefits of the usage of alder wood instead of beech wood as a raw material in plywood and laminated veneer lumber (LVL) manufacturing were compared, besides the conservation of national forest resources. For this aim, some technological properties of plywood and LVL panels manufactured from beech and alder logs were determined, and then compared with the values indicated in related standards. According to the results of this study, mechanical strength values of beech plywood and LVL panels were higher than those of alder panels. Bending strength mean values of plywood panels were higher than the limit values indicated in DIN 68705-3 and DIN 68792. Shear strength mean values obtained for the plywood panels manufactured from alder logs were above the limit value (1.0 N/mm²) indicated in EN 314-2 standard. Mechanical strength values of beech LVL panels were also higher than those of alder LVL panels. When the annual increments of beech and alder trees in 1 ha and the time they need to reach suitable diameters for the manufacturing rotary cut veneers were taken into consideration, it was calculated that alder trees allow 3.82 times additional physical harvesting than beech trees.     

A new algorithm and multi-response Taguchi method to solve line balancing problem in an automotive industry

One of the most important issues in an assembly line balancing problem is to control a flow of production and manufacturing to provide continuous flow to balance the production line. For this purpose, a line balancing problem was considered for a special assembly line in an automotive factory. A new algorithm was required to deal with balancing an assembly line which consisted of the same job which must be performed by more than one worker at the same time. In this way, the new algorithm was expected to be effective in such a case that jobs were simultaneously completed in a parallel way. In order to measure effectiveness of the proposed algorithm, performance criteria were identified as total number of assembly station, total number of workers, and line productivity. As a result of the application of the proposed algorithm with taking into consideration factors such as cycle time, an allowable number of workers in an assembly station, and an allowable idle time of a worker, alternative solutions were determined in order to measure these criteria. However, these alternative solutions do not give any information about which of the solutions provide not only minimization of the number of assembly station and number of workers on the line but also maximize the line productivity at the same time. Hereby, a multi-response Taguchi method was applied in order to investigate levels of factors which directly affected system performance criteria.     

Balancing and scheduling of flexible mixed model assembly lines with parallel stations

In this paper, we study flexible mixed model assembly lines with serially connected stages where stages may have one or more parallel stations. Station parallelism in flexible mixed model assembly lines improves system reliability and enables rapid adaptability to customer demand fluctuations. However, in order to effectively manage such lines under real-world conditions, there is a need to extend traditional assembly line management methods. This study extends the current research by simultaneously considering the problems of task assignment and model scheduling on parallel stations. Furthermore, scheduling of assigned tasks on each station is considered. We formulate the problem context first as a mixed integer programming model and then develop a decomposition scheme for large scale applications. Finally, we compare the performance of the proposed model and decomposition scheme using various size test instances.     

Encrustation Prevention in PVC Reactors

Poly(vinyl chloride) is one of the world's most important bulk thermoplastics. Approximately 15 million tons are produced annually. About 80% of this is made by the suspension process. Suspension polymerization of vinyl chloride is almost invariably accompanied by the formation of scale on the internal surfaces of the polymerization reactor, including moving surfaces such as those of the impeller. The formation of scale, or deposits of PVC, on the internal surfaces of reactors has always been a problem in the manufacture of PVC because of reduced heat transfer, large alteration of the agitation regime present in the reactor, and broken-off scale fragments that block transfer systems and contaminate the product. Therefore scale must be cleaned periodically. Until the early 1970s these deposits were removed manually; PVC workers were exposed to high levels of VCM and considerable production time was lost. The introduction of large reactors in 1975 made it practical to mechanize the cleaning. High-pressure water sprays are employed for this purpose. However, such devices remove only the slightly adherent sandy deposits. For strongly attached deposits, a thorough manual cleaning is necessary after a series of polymerization batches. Manual cleaning requires extensive safety measures to protect the workers from VCM vapor inside the reactor. In addition, such cleaning is costly and undesirable. In more recent years, methods have been developed to suppress or inhibit the formation of scale on the reactor walls. Proposed solutions in this field are sparese. The patient literature claims many chemical treatments to resuce reactor fouling. Many PVC producers have developed effective buildup-suppressant treatments, which significantly reduce the need for reactior cleaning. They vary from treatments to render the reactor wall hydrophilic and reduce the adsorption of VCM (e.g., application of a sulfonic acid polymer to the reactor surface [1]) to systems containing polymerization inhibitors and radical traps (e.g., organic dyes and phenolic resins). The most successful of these probably work by a combination of both mechanisms. In this paper the soultions are reviewed brifly and emphasis is given to suspension polymerization where the initiator is monomer soluble.