Process of extrusion in the unit of special design

Extrusion of paste materials is a means of processing powder materials to a granulated form. A powder material is mixed with a liquid and transformed to the form of paste. The paste has to have the appropriate flow properties to be able to be extruded. This is very important especially in the area of reduction between the barrel and die. There is the place where the paste has to deform itself and to flow into the holes of die that have a smaller cross section than is in the barrel. It is the zone where the rheology properties of paste and its speed have the biggest influence on the extrusion pressure. It can even happen that the paste can be dewatered under the pressure gradient in this place. If the rotor with blades is situated in this zone it has a positive influence on the process of extrusion. This element has an influence on the rate of shear strain and decreasing of the apparent viscosity with a following drop in the extrusion pressure. This paper describes research of the process of extrusion in equipment with separated drives of the screw and a rotor that is placed in the input zone in the hole of matrix. First influence of the operating speeds of screw and rotor on extrusion pressure is studied here, then it is compared with the torque that is needed for the drive of the rotor. According to the results it is evident that the extrusion pressure increases with the accrual of the speed of flowing paste and decreases with the increase of the rotors operating speed. The influence of flowing paste on the torque is complicated. There is an interval where the torque goes up and then an interval in which the torque decreases. The results of experiments confirmed that the rotor has a positive influence on the process of extrusion.We would like to thank the Grant Agency of the Slovak Republic for supporting our research work performed in the frame of Grant Project No.1/8092/01.     

The effect of mixing on reactor performance: an application of perturbation technique

The effect of local mixing on the performance of a reactor system is derived by the perturbation technique. It is found that the sign of the inner product of the adjoint vector λ and the acceleration vector ? is the only indicator as to whether or not local mixing at a certain point of a reaction path is desirable. A complex reaction system with competing side reactions of different order is treated as an example. The possibility of applying the results in this work to the selection of the optimal type of reactor is also discussed.     

Ultrasonic techniques for imaging and measurements in molten aluminum

In order to achieve net shape forming, processing of aluminum (Al) in the molten state is often necessary. However, few sensors and techniques have been reported in the literature due to difficulties associated with molten Al, such as high temperature, corrosiveness, and opaqueness. In this paper, development of ultrasonic techniques for imaging and measurements in molten Al using buffer rods operated at 10 MHz is presented. The probing end of the buffer rod, having a flat surface or an ultrasonic lens, was immersed into molten Al while the other end with an ultrasonic transducer was air-cooled to room temperature. An ultrasonic image of a character "N", engraved on a stainless steel plate immersed in molten Al, and its corrosion have been observed at 780 degrees C using the focused probe in ultrasonic pulse-echo mode. Because cleanliness of molten Al is crucial for part manufacturing and recycling in Al processing, inclusion detection experiments also were carried out using the nonfocused probe in pitch-catch and pulse-echo modes. Backscattered ultrasonic signals from manually added silicon carbide particles, with an average diameter of 50 microm, in molten Al have been successfully observed at 780 degrees C. For optimal image quality, the spatial resolution of the focused probe was crucial, and the high signal-to-noise ratio of the nonfocused probe was the prime factor responsible for the inclusion detection sensitivity using backscattered ultrasonic signals. In addition, it was found that ultrasound could provide an alternative method for evaluating the degree of wetting between a solid material and a molten metal. Our experimental results showed that there was no ultrasonic coupling at the interface between an alumina rod and molten Al up to 1000 degrees C; therefore, no wetting existed at this interface. Also because ultrasonic velocity in alumina is temperature dependent, this rod proved to be able to be used as an in-line temperature monitoring sensor under 1000 degrees C in molten Al.     

Hydrophobic Chromophores in Aqueous Micellar Solution Showing Large Two‐Photon Absorption Cross Sections

A series of new hydrophobic two‐photon absorbing (2PA) chromophores with varied electron‐donating groups in quasi‐linear and multibranched structures are synthesized to correlate their structure/photophysical property relationships. The feasibility of using these large two‐photon absorption cross‐sectional (δ, expressed in GM = 1 × 10^–50 cm⁴ s photon^–1 molecule^–1) materials in aqueous solution is also explored. All four hydrophobic 2PA materials can be encapsulated into micelles generated by dispersing an amphiphilic block copolymer, poly(methacrylic acid)‐block‐polystyrene (PMAA‐b‐PS), into water. The micellar nanostructures are characterized using dynamic light scattering, atomic force microscopy, and transmission electron microscopy. After these dyes are incorporated into micelles, they exhibit strong fluorescence in water. It is found that the quantum yield and δ values of these chromophores are strongly dependent on the diameters of the micelles, concentrations of the PMAA‐b‐PS, and molecular structures of the 2PA chromophores. One of the compounds that has a strong triarylamino donor and a multibranched structure exhibits a large δ value of 2790 GM and high quantum yield (0.56) in micelle‐containing water. Although this value is smaller than the original value of 5300 GM in toluene, it is still substantially larger than the values of most water‐soluble 2PA materials, which have δ values of less than 100 GM.     

A location‐aware peer‐to‐peer overlay network

This work describes a novel location‐aware, self‐organizing, fault‐tolerant peer‐to‐peer (P2P) overlay network, referred to as Laptop. Network locality‐aware considerations are a very important metric for designing a P2P overlay network. Several network proximity schemes have been proposed to enhance the routing efficiency of existing DHT‐based overlay networks. However, these schemes have some drawbacks such as high overlay network and routing table maintenance overhead, or not being completely self‐organizing. As a result, they may result in poor scalability as the number of nodes in the system grows. Laptop constructs a location‐aware overlay network without pre‐determined landmarks and adopts a routing cache scheme to avoid maintaining the routing table periodically. In addition, Laptop significantly reduces the overlay maintenance overhead by making each node maintain only the connectivity between parent and itself. Mathematical analysis and simulations are conducted to evaluate the efficiency, scalability, and robustness of Laptop. Our mathematical analysis shows that the routing path length is bounded by log_d N, and the joining and leaving overhead is bounded by d log_d N, where N is the number of nodes in the system, and d is the maximum degree of each node on the overlay tree. Our simulation results show that the average latency stretch is 1.6 and the average routing path length is only about three in 10 000 Laptop nodes, and the maximum degree of a node is bounded by 32. Copyright © 2006 John Wiley & Sons, Ltd.     

Versioned linking of semantic enrichment of legal documents

Regulations affect every aspect of our lives. Compliance with the regulations impacts citizens and businesses similarly: they have to find their rights and obligations in the complex legal environment. The situation is more complex when languages and time versions of regulations should be considered. To propose a solution to these demands, we present a semantic enrichment approach which aims at (1) decreasing the ambiguousness of legal texts, (2) increasing the probability of finding the relevant legal materials, and (3) utilizing the application of legal reasoners. Our approach is also implemented both as a service for citizens and businesses and as a modeling environment for legal drafters. To evaluate the usefulness of the approach, a case study was carried out in a large organization and applied to corporate regulations and Hungarian laws. The results suggest this approach can support the previous aims.     

A continuous ultrasound‐assisted packed‐bed bioreactor for the lipase‐catalyzed synthesis of caffeic acid phenethyl ester

BACKGROUND: The focus of this paper is the ultrasound‐assisted synthesis of caffeic acid phenethyl ester (CAPE) from caffeic acid and phenyl ethanol in a continuous packed‐bed bioreactor. Immobilized Novozym^® 435 (from Candida antarctica) is used as the catalyst. A three‐level–three‐factor Box–Behnken design and a response surface methodology (RSM) are employed to evaluate the effects of temperature, flow rate, and ultrasonic power on the percentage molar conversion of CAPE. RESULTS: Based on ridge max analysis, it is concluded that the optimum condition for synthesis is reaction temperature 72.66 °C, flow rate 0.046 mL min^?1, and ultrasonic power 1.64 W cm^?2. The expected molar conversion value is 97.84%. An experiment performed under these optimal conditions resulted in a molar conversion of 92.11 ± 0.75%. The enzyme in the bioreactor was found to be stable for at least 6 days. CONCLUSIONS: The lipase‐catalyzed synthesis of CAPE by an ultrasound‐assisted packed‐bed bioreactor uses mild reaction conditions. Enzymatic synthesis of CAPE is suitable for use in the nutraceutical and food production industries. Copyright © 2011 Society of Chemical Industry     

Plasticized properties of poly (lactic acid) and triacetine blends

Systematically investigations of the plasticizing effects of triacetine (TAc) on crystallization, chain mobility, microstructure, and tensile properties of the Poly (lactic acid)/triacetine (PLA/TAc) blends are reported. A new transition hump was observed on the tan δ curve of PLA_xTAc_y specimens at temperatures ranging from ?80 to ?20°C. Thermal, wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis properties of PLA and PLA_xTAc_y series specimens suggest that PLA and PLA_xTAc_y series specimens can hardly crystallize by cooling the melt in room temperature. However, significant recrystallization of α form PLA crystals was found during the annealing processes of PLA_xTAc_y series specimens. Some “less perfect” β form PLA crystals were found as the TAc contents of PLA_xTAc_y specimens reach 30 wt %. Further morphological analysis show that the inherent brittle deformation behavior of the PLA specimen was successfully transformed into relatively ductile fracture behavior after blending sufficient but optimum amounts of TAc in PLA resins. Possible reasons accounting for this interesting recrystallization, thermal, microstructure and tensile properties of PLA_xTAc_y specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Optimization of Dynamic Hardware Reconfigurations

Recent generations of Field Programmable Gate Arrays (FPGA) allow the dynamic reconfiguration of cells on the chip during run-time. For a given problem consisting of a set of tasks with computation requirements modeled by rectangles of cells, several optimization problems such as finding the array of minimal size to accomplish the tasks within a given time limit are considered. Existing approaches based on ILP formulations to solve these problems as multi-dimensional packing problems turn out not to be applicable for problem sizes of interest. Here, a breakthrough is achieved in solving these problems to optimality by using the new notion of packing classes. It allows a significant reduction of the search space such that problems of the above type may be solved exactly using a special branch-and-bound technique. We validate the usefulness of our method by providing computational results.     

Flow and thermal characteristics of cationic dyeable nylon 6/cationic dyeable poly(ethylene terephthalate) polyblended polymers and filaments

Cationic dyeable nylon 6 (CD‐N6) and cationic dyeable poly(ethylene terephthalate) (CD‐PET) polymers were extruded (in the proportions of 75/25, 50/50, 25/75) from one melt twin‐screw extruders to prepare three CD‐N6/CD‐PET polyblended polymers and then spin filaments. The molar ratio of 5‐sodium sulfonate dimethyl isophthalate (5‐SSDMI) for CD‐N6 and CD‐PET polymers were 2.01% and 2.04%, respectively. This study investigated the flow and thermal characteristics of CD‐N6/CD‐PET polyblended polymers and filaments using gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), potentiometer, a rheometer, the density gradient, wide‐angle X‐ray diffraction (WAXD), and extension stress–strain measurement. Flow behavior of CD‐N6/CD‐PET polyblended polymers exhibited negative‐deviation blends (NDB), and the 50/50 blend of CD‐N6/CD‐PET showed a minimum value of the melt viscosity. Experimental results of the DSC indicated CD‐N6 and CD‐PET molecules formed an immiscible system. Particularly, a double endothermic peak was observed from CD‐N6, CD‐PET and their polyblended filaments. The tenacity of CD‐N6/CD‐PET polyblended filaments decreased initially and then increased as the CD‐PET content increased. Crystallinities and densities of CD‐N6/CD‐PET polyblended filaments were the linear relation with the blend ratio. The miscibility parameter μ values of CD‐N6/CD‐PET all samples were less than zero. It indicated the electrostatic repulsion was evident between CD‐N6 and CD‐PET molecules. From the experimental data, the CD‐N6 and CD‐PET polymers were identified to be immiscible. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2049–2056, 2007