A scheme to randomly generate surface dust points for the 3D complex variable boundary element method (CVBEM)

A scheme to randomly generate dust points on the surface of a three-dimensional (3D) object is proposed. This scheme will potentially eliminate the bias of a density of points which are approximately equally spaced on the surface, as well as eliminate possible weighting requirements for areas of higher density. This method has the potential to reduce computational effort, as fewer points might be required to define the surface area. The global trial function vector can be assigned to these dust points and then entered into the complex variable boundary element method (CVBEM) commercial code. This scheme can be applied to each piece of a system that is comprised of a connected multiple geometry. A noticeable benefit of this approach is that the same problem can be studied several times, using a new random distribution of surface points each time. The smallest error can then be determined and that run selected. The Mathematica code used to generate the scheme is attached as an appendix.     

AV通信产业面临的全球性机遇

我今天很高兴能来到这里与你们一起讨论关于AV通信产业所面临的全球性机遇以及中国AV通信产业如何随着世界市场共同成长的问题。从某种意义上讲，我们所面临的机遇是无限的，因为对于政府、商务、教育和几乎其他所有机构的未来通信基础构造而言，AV通信将是极其关键的。     

Railgun performance with a two-stage light-gas gun injector

Results obtained with the HELEOS (hypervelocity experimental launcher for equation of state) railgun, which uses a two-stage light-gas gun (2SLGG) as an injector, are presented. The high-velocity 2SLGG injector preaccelerates projectiles up to ~7 km/s. The high injection velocity reduces the exposure duration of the railgun barrel to the passing high temperature plasma armature, thereby reducing the ablation and subsequent armature growth. The 2SLGG also provides a column of cool, high-pressure hydrogen gas to insulate the rails behind the projectile, thereby eliminating restrike. A means to form an armature behind the injected projectile has been developed. In preliminary tests, the third-stage railgun has successfully increased the projectile velocity by 1.35 km/s. Extensive diagnostics have been used to determine the behavior of the armature and track the launcher's performance. Insome cases, velocity increases in the railgun section have been achieved, which are in close agreement with theoretical predictions, whereas in other experiments deviations from theoretical have been observed. The reasons for and implications of these results are addressed. Recent tests are reported     

Formation of hydrophilic starch coatings on polyethylene films

Thin starch coatings were deposited onto polyethylene (PE) film surfaces when PE films were immersed in 1% jet cooked starch solutions and the hot solutions were allowed to cool. Normal cornstarch, waxy cornstarch, high amylose cornstarch, and solvent‐extracted normal cornstarch (to remove native lipid) were used in these experiments. Amounts of adsorbed starch varied from about 0.03–0.05 mg per cm² of PE, and these starch coatings imparted hydrophilic properties to film surfaces, as evidenced by contact angle measurements. Although starch could be removed by gently rubbing water‐wet PE surfaces, air‐dried coatings were more firmly attached, and did not separate from the PE surface when films were bent or flexed. SEM images of starch‐coated film surfaces showed that starch was deposited as particles less than 1 μm in diameter, and also as aggregates of these submicron particles. Despite the fact that some starch samples contained only very small amounts of amylose and native lipid, surface‐deposited starch in all experiments contained 90–100% amylose; and exhibited the same V_h X‐ray diffraction pattern, indicative of helical inclusion complex formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1781–1788, 2002; DOI 10.1002/app.10589     

Characterization of a nylon 6/poly(methyl acrylate) copolymer produced by radiation grafting

Acrylic acid has been grafted onto nylon 6 by the mutual γ-irradiation technique. Methods are described for removing poly(acrylic acid) homopolymer and ungrfted nylon, the latter involving intermediate conversion to the calcium ionomer. The pure graft copolymer in its methylated form, viz., nylon 6/poly(methyl acrylate), NY/PMA, was characterized by light scattering in mixed solvents to yield the true molecular weight (3.2 × 10⁶) as well as the molecular weights M_PMA(domain) and M_NY(domain) of the PMA and NY portions, respectively. The molecular weight M_PMA of the grafts was measured after hydrolysis of the backbone, and the molecular weight M_NY of the backbone was determined via a previously devised indirect procedure. Comparisons of M_PMA(domain) with M_PMA and of M_NY(domain) with M_NY gave ? 7 nylon chains and ? 17 poly(methyl acrylate) chains per copolymer molecule. Chain transfer and bimolecular terminatin during grafting are proposed as probable contributory factors to the branched structure of the copolymer.     

Gas-Liquid chromatography of fatty derivatives. I. Separation of homologous series ofa-olefins,n-hydrocarbons,n-nitriles,and n-alcohols

Summary Gas-liquid chromatography has been shown to be applicable to the analysis of several fatty derivatives. The difficulties inherent in conventional separation schemes such as liquid-liquid chromatography, fractional distillation, and crystallization can be overcome through the use of gas-liquid chromatography. It becomes the preferred procedure for several reasons: a) fractions are more nearly pure, b) analysis time is a fraction of the time required for conventional separations, c) operational procedures are simple and highly reproducible, d) sample size requirements are low, e) the cost per unit analysis is low. These factors suggest that gas-liquid chromatography is highly useful as an analytical tool in fat research. In many cases the determination of chainlength distribution has already become a routine function. There remain areas in which gas-liquid chromatography has not been completely successful. Until very recently the separation of fatty methyl esters of similar chain length and varying degrees of unsaturation has been time-consuming and tedious. Several new partitioning agents hold out great promise in the separation of the isomeric C₁₈ fatty acids. More selective partitioning agents and refined techniques undoubtedly will equally improve the resolution of unsaturated alcohols and other unsaturated fatty derivatives. Presented at annual meeting, American Oil Chemists' Society, Memphis, Tenn., April 21–23, 1958. Technical Paper No. 160, Archer-Daniels-Midland Company.     

2009 CAV award announcement

The 2009 CAV (Computer-Aided Verification) award was presented to seven individuals who made major advances in creating high-performance Boolean satisfiability solvers. This annual award recognizes a specific fundamental contribution or series of outstanding contributions to the CAV field.