Effects of Compression and Filler Particle Coating on the Electrical Conductivity of Thermoplastic Elastomer Composites

Elastomeric polymers can be filled with metallic micro- or nanoparticles to obtain electrical conductivity, in which the conductivity is largely determined by the intrinsic conductivity of and contact resistance between the particles. Electrons will flow through the material effectively when the percolation threshold for near-neighbor contacts is exceeded and sufficiently close contacts between the filler particles are realized for electron tunneling to occur. Silver-coated glass microparticles of two types (fibers and spheres) were used as fillers in a thermoplastic elastomer composite based on styrene–ethylene–butylene–styrene copolymer, and the direct-current (DC) resistance and radiofrequency impedance were significantly reduced by coating the filler particles with octadecylmercaptan. Not only was the resistance reduced but also the atypical positive piezoresistivity effect observed in these elastomers was strongly reduced, such that resistivity values below 0.01 Ω cm were obtained for compression ratios up to 20%. In the DC measurements, an additional decrease of resistivity was obtained by inclusion of π-extended aromatic compounds, such as diphenylhexatriene. Some qualitative theories are presented to illuminate the possible mechanisms of action of these surface coatings on the piezoresistivity.     

Provably-Secure Time-Bound Hierarchical Key Assignment Schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class can compute the keys of all classes lower down in the hierarchy, according to temporal constraints.     

Finite multidimensional behaviors

We study finitely generated and finite systems defined by linear partial difference equations with constant coefficients in a Noetherian ring. The two notions coincide for finite rings, and we show that all finite systems exhibit certain periodicity properties. For the particular case of systems over the ring of integers modulo m?>?1, which is important in coding theory, a method is given for determining the number of trajectories, using Gr?bner basis techniques.     

Very fast accurate square-root algorithm for use with gradient edge operators

Commonly used gradient edge operators such as the Sobel, Prewitt and Roberts operators all required a square root operation; this is, however, computationally intensive and, consequently, simple but very inaccurate approximations are often used instead. The author describes a new square root algorithm specifically designed for use with these edge operators. The result is a very simple, fast and extremely accurate algorithm.<>     

A mathematical morphology approach to Euclidean distancetransformation

A distance transformation technique for a binary digital image using a gray-scale mathematical morphology approach is presented. Applying well-developed decomposition properties of mathematical morphology, one can significantly reduce the tremendous cost of global operations to that of small neighborhood operations suitable for parallel pipelined computers. First, the distance transformation using mathematical morphology is developed. Then several approximations of the Euclidean distance are discussed. The decomposition of the Euclidean distance structuring element is presented. The decomposition technique employs a set of 3 by 3 gray scale morphological erosions with suitable weighted structuring elements and combines the outputs using the minimum operator. Real-valued distance transformations are considered during the processes and the result is approximated to the closest integer in the final output image.     

用开关稳压控制器产生快速脉冲

模拟步进功能的快速上升沿脉冲源可以完成很多有用的实验室测量工作,包括确定同轴电缆上升时间特性,以及用时域反射方法找到电缆故障点。例如,在估算一个10英尺～20英尺长RG-58/U电缆的上升时间时,就需要1ns～2ns的边沿跃升时间。Agilent公司(www．agilent．com)的HP8012B是一个在很多电子实验室中都有使用的,可以承受大量工作负荷的脉冲发生器,它提供具有5 ns上升时间的脉冲,这足以用于许多应用场合,但不适合用于确定电缆特性。     

Effect of release rate and ratio of (Z)-11-hexadecen-1-ol from synthetic pheromone blends on trap capture ofHeliothis subflexa (Lepidoptera: Noctuidae)

Response of maleHeliothis subflexa to pheromone-baited traps containing blends of tetradecanal, (Z)-9-tetradecanal, hexadecanal, (Z)-7-hexadecenal, (Z)-9-hexadecenal, (Z)-11-hexadecenal, hexadecan-1-ol acetate, (Z)-7-hexadecen-1-ol acetate, (Z)-9-hexadecen-1-ol acetate, (Z)-11-hexadecen-1-ol acetate, (Z)-9-hexadecen-1-ol, and (Z)-11-hexadecen-1-ol was evaluated. Analysis of trap capture data indicated that (Z)-11-hexadecen-1-ol was a critical component of the pheromone blend. It was determined from emission rate data and measurements of the ratio of pheromone components emitted from rubber septa tested that a significant increase in trap capture of maleH. subflexa occurred when the blends investigated released the alcohol in a narrow range relative to the total amount of pheromone emitted. The optimum range of release ratio of the alcohol for the capture of males in sticky traps was determined to be 0.9–3.5% of the pheromone blend. This release ratio range was reduced to 0.9–1.6% when bucket traps were used.     

Rewarming from immersion hypothermia: a comparison of three techniques

Analysis of measurements from the tali of 21 individual fossil primates from Africa shows that the specimens fall into five clearly defined groups. Accordingly, these specimens have been included as groups along with extant species in a subsequent canonical analysis thus allowing the fossils to play their part in the determination of the canonical separations. The results of this procedure show that the five fossil groups lie in a part of the canonical space not occupied by any extant African primate. Their positions are between the envelope of Asiatic apes (Hylobates and Pongo) and the envelope of African forms near the edge which contains Pan and Papio. One fossil group is so similar to Hylobates that its talus may have functioned in locomotion in a parallel manner. Others lie near to Pongo in directions proceeding towards Pan and Papio and it is possible that this similarity may indicate remnants of morphological adaptation for climbing in these fossils. At the same time, however, individual specimens are closer to one or another of the extant groups and this considerable spread suggests that the locomotor adaptations as evidenced by talar morphology, of the primate fauna in Africa, may have been very different from those of the present day. This would not the inconsistent with the different habitats, floras and non-primate faunas that may have characterized the East African scene at these earlier times. Particular fossils from Olduvai and Kromdraai that are supposed to be australopithecine and therefore bipeds, are confirmed (Oxnard, '72; Lisowski et al., '74) as being totally different from man in their talar morphology and essentially rather similar to the majority of the other fossil tali examined.     

A copulatory system in the hypothalamus and tegmentum of the domestic chick

A tract in the chick is described that runs from the posterior nucleus paraventricularis magnocellularis (PVM) through the lateral hypothalamus to a small area of the anterior tegmentum, which is adjacent to the ventral tegmental area. Bilateral lesions of the posterior PVM or of the PVM tract or of its tegmental destination abolish the facilitation of copulation in male chicks by testosterone. The effect is specific in that the facilitation of attack is either unaffected or only slightly depressed by such lesions, while being itself specifically depressed by other hypothalamic lesions. No other hypothalamic tracts were found that were necessary for the facilitation of copulation. An equivalent copulatory system probably exists in the mammal, with a more diffuse distribution in the preoptic area but with similar connections back to the tegmentum.