Effect of an obstacle during processing on the weld line of injection‐molded glassy polystyrene: Microhardness study

The microhardness (H) technique is used to characterize the quality of the weld line in injection‐molded glassy polystyrene by means of a cylindrical obstacle. In particular, the effect of the indentation location (closer or further from the obstacle edge parallel to the injection direction and across the weld line), both on the surface and in the bulk, was examined. Only for surface measurements close to the obstacle (up to 10 mm) a well‐pronounced decrease in H (～30%), followed by a sharp increase in a narrow distance (0.20–0.25 mm), was observed. For the bulk measurements on the same location a slight decrease in H was detected. Additional H measurements made up to 60 mm from the obstacle for both cases showed that the weld line remains undetectable. The results obtained reveal that the presence of a cylindrical obstacle causes the formation of a weld line on and near the surface only at distances not exceeding the obstacle diameter. At larger distances, because of the effective mutual interdiffusion of polymer chains, the two parallel fronts coming from the two sides of the obstacle developed a homogeneous material without any weld line according to the microhardness test. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3362–3367, 2004     

Effects of ZnO nano particles on thermal stabilization of polymers

It was reported that a nanocrystal ZnO had a thermal stabilizing effect for branched low‐density polyethylene (BLDPE). In this study, the thermal stabilizing effect of the nanocrystal ZnO was studied in more detail in comparison to a conventional, micron‐size ZnO using several polymers and a common antioxidant. The experimental results in this investigation suggest that the nanocrystal ZnO particles have different surface properties from micron‐size particles because of their extremely small size, and the particular surface properties are responsible for the thermal stabilizing effect. Polym. Eng. Sci. 44:1702–1706, 2004. © 2004 Society of Plastics Engineers.     

Design optimization of extruded preform for hydroforming processes based on ideal forming design theory

The conventional practice to predict preform shapes in hydroformimg processes based on finite-element analysis and/or experiment is an iterative procedure and requires many trials. In this paper, a computationally efficient direct design method, which effectively improves the design procedure, was introduced. The direct design method based on ideal forming theory, which was successfully applied for the design of flat blanks for stamping processes, was extended for the design of non-flat preform for tube hydroforming processes. A preform optimization methodology for non-flat blank solutions was proposed based on the penalty constraint method for the cross-sectional shape and length of a tube. The hybrid membrane/shell method was employed to capture thickness effect while maintaining membrane formulation in the ideal forming theory. Several classes of examples were analyzed to verify the current formulation.     

Athabasca油砂沥青焦化蜡油中富氮组分的分离与表征

油砂沥青焦化蜡油的加氢处理是比较困难的,为了选择合适的加工流程和操作条件,有必要对油砂沥青及其焦化蜡油的分子结构有更全面的认识。本研究尝试分离和鉴别焦化蜡油中对加氢过程不利的组分。研究发现,焦化蜡油中主要的富氮组分是较小分子的戊烷不溶物,或者是更小分子、极性较强的己烷不溶物。组分的结构信息表明它们是由胶质分子裂化反应后形成的。吡咯类化合物是主要的氮化物类型,其次是吡啶类化合物。这两类氮化物都对加氢过程不利,如吡咯类化合物容易聚合产生胶质和沉淀,堵塞过滤器和其它设施;而吡啶类物质能直接导致加氢催化剂失活。     

A spatiotemporal neural network for recognizing partially occludedobjects

In this paper, a spatiotemporal neural network for partially occluded object recognition is presented. The system consists of two major components: a feature extraction process and a spatiotemporal modular neural network. The former is made up of a sequence of preprocessing techniques including thresholding, boundary extraction, Gaussian filtering, and a split-and-merge algorithm to generate features that will represent the objects to be recognized. These acquired features are invariant to rotation, translation, and scaling and can serve as input to the spatiotemporal network that utilizes the concept of tap delay to account for spatial correlation between consecutive input features. A shape perceiver is designed into the network to extract continued parts of an object as well as to enable the inclusion of each object's unique characteristics into the system. Traditional neural network approaches for recognizing partially occluded objects have encountered significant problems because of the incomplete boundaries of the objects. In our approach, by creatively installing tap delays, the system can escape this limitation. Experimental results show that the proposed system can produce satisfactory results in efficiently and effectively recognizing partially occluded objects. Furthermore, intrinsic to this system is the ease by which it can be realized through parallel implementation, thus minimizing the tremendous time spent in matching object contours stored in a model database, as is the case in conventional recognition systems     

Manipulation of xenogeneic skin and/or renal graft survival in the rat-mouse concordant combination by portal vein pretransplant transfusion

In cell culture, human osteoblasts and the osteosarcoma cell line MG-63 express annexins I, II, IV, V and VI. Small proportions of annexins IV and V are lost from MG-63 cells into the culture medium in a sedimentable form. however, the bulk of these annexins is intracellular. In non-confluent cells 3 days after passaging, annexin IV and annexin V are strongly present throughout the nucleus and are also present in the cytoplasm. On elevation of the intracellular calcium concentration with the lonophore ionomycin, the intranuclear pools of annexin IV in 38 +/- 4% of cells and annexin V in 70 +/- 5% of cells show relocation to the nuclear membrane within 40 s. Extracellular ATP, which causes a transient increase in the cytosolic free calcium concentration by acting at P2-purinoceptors, also causes relocation of the intranuclear pool of annexin IV in 22 +/- 4% of cells and of annexin V in 38 +/- 8% of cells. After stimulation no significant reversal of the relocation is observed. Elevation of intracellular calcium with ionophore and ATP also causes relocation of the cytoplasmic pools of annexins IV and V. The results support a role for annexins at cellular membranes in response to elevation of cytosolic calcium levels.     

A new instantaneous torque control of PM synchronous motor forhigh-performance direct-drive applications

A new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal flux distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results demonstrate the effectiveness of the proposed control     

Effects of the Use of Pore Formers on Performance of an Anode Supported Solid Oxide Fuel Cell

The effects of amount of pore former used to produce porosity in the anode of an anode supported planar solid oxide fuel cell were examined. The pore-forming material utilized was rice starch. The reduction rate of the anode material was measured by Thermogravimetric analysis to qualitatively characterize the gas transport within the porous anode materials. Fuel cells with varying amounts of porosity produced by using rice starch as a pore former were tested. The performance of the fuel cell was the greatest with an optimum amount of pore former used to create porosity in the anode. This optimum is believed to be related to a trade off between increasing gas diffusion to the active three-phase boundary region of the anode and the loss of performance because of the replacement of active three-phase boundary regions of the anode with porosity.     

Design of Scalable Continuous Media Servers

Multimedia applications place high demands for quality-of-service (QoS), performance, and reliability on systems. These stringent requirements make design of cost-effective and scalable systems difficult. Therefore efficient adaptive and dynamic resource management techniques in conjunction with data placement techniques can be of great help in improving performance, scalability, and reliability of such systems. This is the focus of our paper.     

Effects of molding conditions on the electromagnetic interference performance of conductive ABS parts

Polymers filled with conducting fibers to prevent electromagnetic interference (EMI) performance have recently received great attention due to the requirements of 3C (computer, communication, and consumer electronics) products. In the present article, the effect of fiber content and processing parameters, including melt temperature, mold temperature, and injection velocity, on the electromagnetic interference shielding effectiveness (SE) in injection molded ABS polymer composites filled with conductive stainless steel fiber (SSF) was investigated. The influence of fiber orientation and distribution resulting from fiber content and molding conditions on EMI performance was also examined. It was found from measured results that fiber content plays a significant role in influencing part EMI SE performance. SE value can reach the highest values of approximately 40 dB and 60 dB at 1000 MHz frequency for fiber content 7 wt % and 14 wt %, respectively, under the best choice of molding conditions. Higher melt and mold temperature would increase shielding effectiveness due to a more uniform and random fiber orientation. However, higher injection velocity leading to highly‐orientated and less uniform distribution of fiber reduces shielding effectiveness. Among all molding parameters, melt temperature affects SE performance most significantly. Its influence slightly decreases as fiber content increases. Injection speed plays a secondary importance in affecting SE values, and its influence increases as fiber content increases. Upon examination of fiber distribution via optical microscope and subsequent image analysis, it was found that the fiber becomes more densely and random distributed toward the last melt‐filled region, whereas fiber exhibits less concentration around the middle way of the flow path. This can be attributed to the combined effects of fountain flow, frozen layer thickness, and gapwise melt front velocity. The results indicate that molding conditions, instead of fiber content alone, are very important on the SE performance for injection molded SSF filled ABS composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1072–1080, 2005