On the linear friction welding process of aluminum alloys: Experimental insights through process monitoring

Linear friction welding is a solid-state joining process for non-axisymmetric components in which joining of materials is obtained through the relative motion of two components under pressure. In the process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and eventually bonding conditions. A dedicated fixture was equipped with sensors for the in-process acquisition of variables regarding kinematics, dynamics and temperature levels. The results of an experimental campaign aimed to weld AA6082-T6 aluminum alloy parts are presented and a process window is identified for the used alloy.     

The use of acrylated fatty acid methyl esters as styrene replacements in triglyceride‐based thermosetting polymers

Resins containing plant oil‐based cross‐linkers were studied with two reactive diluents: a styrene and an acrylated fatty acid methyl ester‐based (AFAME) monomer. Acrylated epoxidized soybean oil and maleinated castor oil monoglyceride were bio‐based cross‐linkers used. The viscosity and mechanical properties of the resulting polymers were measured and analyzed. Both bio‐based cross‐linkers prepared using the modified AFAME as diluent had a fairly high viscosity, so blends of AFAME and styrene were needed to meet the viscosity requirements established by the composite industry (<1000 cP at room temperature). In addition, the glass transition temperature (T_g) and stiffness of bio‐based cross‐linker/AFAME polymers were significantly lower than the resin/styrene polymers. Ternary blends of maleinated castor oil monoglyceride with AFAME and styrene improved the mechanical properties to acceptable comparable values (storage modulus at 30°C ～ 1200 MPa and T_g ～ 100°C). The addition of 5 wt% of chemically modified lignin led to an improvement in the mechanical properties of the polymeric matrix but caused an increase in the viscosity. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Partitioning of Carboxylic Acid between Oil and Water Phases. Experimental,Correlation, and Prediction

Partition coefficients for the carboxylic acids (A) acetic and formic acids between oil and water were measured, correlated, and predicted. The experiments were conducted by equilibrating the systems, soybean oil (SO)–H₂O–A and fatty acid methyl ester (FAME)–H₂O–A, at 40 °C employing different compositions. The partition coefficients were correlated using the UNIQUAC model and, also, predicted by calculating the activity coefficients of the carboxylic acid in the two phases using a group contribution method, the UNIFAC equation. Agreement of experimental partition coefficients values with those estimated by UNIFAC are fair. Other experimental data from literature were also correlated and are discussed.     

Detection of incipient object slippage by skin-like sensing andneural network processing

Detection of incipient slippage is of great importance in robotics for the control of grasping and manipulation tasks. Together with fine-form reconstruction and primitive recognition, it has to be the main feature of an artificial tactile system. The system presented here is based on a neural network used to detect incipient slippage and on a skin-like sensor sensible to normal and shear stresses. Normal and shear stresses components inside the sensor are the input data of the neural net. An important feature of the system is that the a priori knowledge of the friction coefficient between the sensor and the object being manipulated is not needed. To validate the method we worked on both simulated and experimental data. In the first case, the finite element method is used to solve the direct problem of elastic contact in its full nonlinearity by resorting to the lowest number of approximations regarding the real problem. Simulation has shown that the network learns and is robust to noise. Then an experimental test was carried out. Experimental results show that, in a simple case, the method is able to detect the insipiency of slippage between an object and the sensor.     

Effective bandwidth optimization for noncoherent full-response CPMsystems

The optimization of the baseband pulse shape for full response CPM signals, when a noncoherent lowest complexity receiver is used, is carried out. The effective bandwidth is chosen as the objective of the optimization. In order to obtain the minimum error probability for high signal-to-noise ratio, orthogonal signaling is taken into consideration. A closed form for the optimum pulse shape, the value of the optimum modulation index and of the optimum effective bandwidth is determined. The power spectral density and the fractional out-of-band power have been compared with some phase functions considered in the literature     

Electrochemical determination of pharmaceuticals in spiked water samples

The electrochemical behaviour of acidic and neutral pharmaceutical active compounds (PhACs) was studied by cyclic voltammetry and pulse voltammetric techniques on mercury, carbon nanotube paste, carbon paste and gold electrodes. The best results, in terms of sensitivity, linearity range and detection limits, were obtained by differential pulse voltammetry (DPV) for ofloxacin (LOD 5.2 microM), differential pulse polarography (DPP) for clofibric acid (LOD 4.7 microM) and normal pulse voltammetry (NPV) for diclofenac (LOD 0.8 microM) and propranolol (LOD 0.5 microM). An enrichment step of approximately two orders of magnitude was performed by a solid-phase extraction procedure (SPE) in order to concentrate the samples. The developed method was optimized and tested on spiked river water samples.     

Communications satellites: orbiting into the 90s

Engineering advances in satellite communications are discussed. These include sophisticated switchboards, narrow beams, source coding for higher capacity, larger networks, and the use of higher and lower frequency bands and lower orbits. One of the most popular new 14/11-14/12 GHz commercial services has been time-division multiplexing of multiple carriers operating at low to medium bit rates. Multiple-carrier, low-burst-rate TDMA (time-division multiple access), in which several TDMA carriers are shared among ground terminals, is widely used with very small-aperture terminals (VSAT) on the customer's premises. NASA's (US National Aeronautic and Space Administration) ACTS and Italy's Italsat both plan to use signal regeneration at 30/20 GHz. Onboard switching and multiplexing will not only minimize noise and boost power, but also trim the cost of the entire satellite network     

Network Control for Multibeam TDMA and SS/TDMA

This paper concentrates on the control of individual burst transmissions of traffic and reference stations in TDMA and SS/ TDMA networks. In a TDMA system, the principal task of a TDMA terminal is to transmit each burst at the proper time to assure that, at the satellite, the burst resides in its assigned location in the TDMA frame. The composite of assigned positions for all bursts in the TDMA frame, or frames if more than one transponder is involved, is called the burst time plan. The paper discusses a specific concept of control used by a station to acquire and synchronize its burst transmission to assigned time slot(s) in the TDMA frame. The concept is applied to single-beam (global or regional) and muitibeam systems. The method used controls the instant of traffic burst transmission by introducing a time delay at each station which causes the round-trip propagation time between the satellite and all earth stations to be equal for burst position control purposes. This time delay is simple to implement in the TDMA terminal's timing circuitry and does not require the storage of traffic to accomplish it. It is also shown that the control method leads to a simple means for accomplishing synchronous burst time plan changes throughout the network. The functions of the reference stations needed to accomplish the burst time plan control are defined and explained. The discussion extends to SS/TDMA, and explains how the satellite switch state time plan change can be synchronized to the overall network burst time plan change.     

Effect of isomaltodextrin on dough rheology and bread quality

Isomaltodextrin (IMD) is a novel highly branched α-glucan ingredient that has potential applications in foods as a promising source of dietary fibre. In this study, we assessed the incorporation of IMD in baked products and its effect on dough rheology and physico-textural characteristics of wheat breads. IMD was added to wheat flour to reach the US FDA level of ‘good’ source of fibre (10% IMD). Use of the straight-dough method with IMD and regular dough mixing time (8 min) resulted in less elastic doughs and resulting breads displayed lower cohesiveness, springiness and chewiness compared to the control bread. A modified straight-dough method, with longer mixing time (36 min) and adjusted water level (70%), and a sponge-and-dough method were used to allow gluten structure to more fully hydrate and develop. With IMD addition, the modified straight-dough (36 min dough mixing time) and sponge-and-dough methods yielded enhanced dough elasticity compared to the original straight-dough method. Breadmaking methods were identified (improved straight-dough and sponge-and-dough) whereby IMD could be added at a 'good source' of fibre level with loaf appearance and texture similar to breads without IMD.     

High‐quality instant sorghum porridge flours for the West African market using continuous processor cooking

The overall goal of this study was to develop high quality, pregelatinised sorghum flours for instant thin and thick porridges, foods that are commonly consumed in the West Africa Sahel. Use of a continuous processor, a high shear/low pressure mixer, with feed sorghum flour moisture content of 30% to 35% and a screw temperature fixed at 168 °C gave instant sorghum flours with stable and creamy thin and thick porridge textures. Water activity of 0.22–0.35 for instant flours was within an acceptable range for dried commercial cereal foods. Molecular weight distributions of starch molecules showed significant fragmentation in instant flours that likely contributed to their smoother and creamy texture, and rheometry showed stronger gels and lower viscosity for the instant thick and thin porridges, respectively. In sensory testing performed in Niger at four locations, instant flour thin and thick porridges scored better than the control prepared locally from the same flour.