Fundamentals of the incremental tube forming process

The manufacture of bent tubes made of high-strength materials requires high bending loads, which lead to large springback and eventually distortion of the cross-section. The incremental tube forming process allows significant reduction of the bending moment. This is achieved by combining the continuous bending process with an incremental tube spinning process. The paper describes an analytical model to predict the bending moment reduction as a function of the superposed spinning process parameters. Experimental results are provided to validate the theoretical results. This model allows the design and optimization of the incremental tube forming process with low springback.     

Wood pellets production costs and energy consumption under different framework conditions in Northeast Argentina

The development of cleaner and renewable energy sources are needed in order to reduce dependency and global warming. Wood pellets are a clean renewable fuel and has been considered as one of the substitutes for fossil fuels. In Argentina, large quantities of sawmill residues are still unused and wood pellets production could be seen as both, as an environmental solution and an extra economical benefit. The general aim of this study was to determine the wood pellets production costs and energy consumption under different framework conditions in northeast Argentina. The specific costs of wood pellets for the different scenarios showed relative lower costs comparing to the ones reported in other studies, ranging from 35 to 47 €/Mg_pellets. Raw material costs represented the main cost factor in the calculation of the total pellets production costs. A lower specific production cost was observed when 50% of the raw material input was wood shavings. The specific electricity consumption per metric ton of pellet was lower in scenarios with higher production rate. Lower heat energy consumption was observed in scenarios that have a mixed raw material input. The most promising framework condition for Northeast Argentina, in terms of costs effectiveness and energy consumption could be acquired with production rates of 6 Mg/h with sawdust and wood shavings as raw material. However, simultaneous increment of the electricity by 50% and raw material price by 100% may increase the specific costs up to 50%.     

Stochastic correlative learning algorithms

This paper addresses stochastic correlative learning as the basis for a broadly defined class of statistical learning algorithms known collectively as the algorithm of pattern extraction (ALOPEX) family. Starting with the neurobiologically motivated Hebb's rule, the two conventional forms of the ALOPEX algorithm are derived, followed by a modified variant designed to improve the convergence speed. We next describe two more elaborate versions of the ALOPEX algorithm, which incorporate particle filtering that exemplifies a form of Monte Carlo simulation, to exchange computational complexity for an improved convergence and tracking behavior. In support of the different forms of the ALOPEX algorithm developed herein, we present three different experiments using synthetic and real-life data on binocular fusion of stereo images, on-line prediction, and system identification.     

Rapid application design and testing of Web usability

The rapid application design and testing (RAD-T) process greatly advances time-driven development of Web applications without sacrificing usability. Our GUI-based toolset, in conjunction with an extension of HTML, provides for early usability testing at the onset of Web specification and design activities     

亚周期脉冲光束的严格解

基于复点源模型给出了单周期与亚周期脉冲光束的严格表达式,它是麦克斯韦方程组的严格解,可以用来描述聚焦的脉宽小于一个光学周期的任意偏振脉冲光束.该表达式包含了时域中的"戈维-相位"、"自蓝移"、和脉冲翼的"自啁啾"等载波-包络近似表达式中没有的新现象.     

Laplace Plane Analysis of Transient Impedance Between Acupuncture Points Li-4 and Li-12

AC impedance between two acupuncture points (Li-4 and Li-12) and two pairs of anatomically similar points with the same separation was studied via Laplace plane analysis of the time domain current response to a predetermined voltage perturbation. The series resistance between the two acupuncture points was found to be significantly lower than between either pair of control points. The characteristic impedance of an equivalent transmission line was lower and the signal propagation velocity higher for the acupuncture point system as compared to both controls.     

Use of acetyl chloride/methanol for assumed selective methylation of plasma nonesterified fatty acids results in significant methylation of esterified fatty acids

The albumin-bound nonesterified fatty acid pool in plasma, which represents a very small percentage of total plasma fatty acids, has previously been quantitated by a variety of methods. In the present study we determined that the nonesterified fatty acid concentrations in the plasma, quantitated by a popular method using acetyl chloride and methanol which is reported to be specific for methylation of nonesterified fatty acids in the presence of esterified fatty acids (i.e., without prior isolation of the plasma non-esterified fatty acids), were significantly overestimated due to cleavage and methylation of esterified fatty acids. Quantitation of the contaminating fatty acid from the esterified pool demonstrated that the amount of fatty acid cleaved from the esterified pool was enough to exceed the entire mass of nonesterified fatty acids. As an established method for comparison, we isolated nonesterified fatty acids from the plasma by thin-layer chromatography prior to methylation, using a number of simple precautions to limit oxidation. By performing all thin-layer chromatography steps in an atmosphere of nitrogen and by including fatty acid standards in the plasma with 0,1, 2 or 4 double bounds, we were able to accurately and reproducibly determine the concentration of nonesterified fatty acids in the plasma, including arachidonate. We demonstrated that no oxidation occurred in the thin-layer chromatographic isolation of homonesterified fatty acids and that the coefficients of variation for repeat measurements of the same sample were <11% using our reference method. Our data indicate that the use of acetyl chloride and methanol for assumed selective methylation of plasma nonesterified fatty acids results in significant methylation of esterified fatty acids.     

Regiospecific analysis of triacylglycerols using allyl magnesium bromide

A method for the regiospecific analysis of triacylglycerols (TAG), using the Grignard reagent allyl magnesium bromide (AMB) to partially deacylate TAG, is described. 1,3-Distearoyl-2-oleoyl-glycerol (SOS) and 1,3-didecanoyl-2-palmitoyl-glycerol (CPC) were reacted with AMB. From the resulting mixture, the four different classes of partial acylglycerols and TAG were isolated, and the mole ratios between stearic acid and oleic acid, or decanoic acid and palmitic acid, respectively, were determined in each fraction. Different approaches of calculating the composition of the fatty acids in positionssn-1(3) andsn-2 of the original TAG were compared. For thesn-2 position, the best estimate was the direct determination of the fatty acid composition of 2-monoacylglycerol (MAG). Mole percentages of stearic acid and decanoic acid in thesn-1(sn-3) positions of SOS and CPC, respectively, were most accurately estimated from the fatty acid compositions of TAG and 2-MAG according to the formula: 1.5×TAG−0.5×2-MAG. Using AMB and the present method of calculation, the results obtained were more accurate and showed smaller standard derivations than those obtained using other common deacylating agents, such as ethyl magnesium bromide or pancreatic lipase.