Basic longitudinal texture and fracturing process in thermoset polymers

The “basic longitudinal texture”, which is present everywhere on the fracture surfaces of glassy thermosets and is the finest texture observed on such surfaces, consists of low ridges and shallow grooves that are aligned parallel with the direction of crack propagation. The periodicity of the basic longitudinal texture, i.e., the average lateral separation between the ridges (or grooves), has been found to be characteristic of materials. This and other properties were measured for a series of rigid epoxy specimens made from diglycidyl ether of bisphenol-A and methylhexahydrophthalic anhydride. For the series of epoxies studied, the glass transition temperatures varied from 76 to 143 °C, the room temperature Young's modulus varied from 2.29 to 2.97 G Pa, the room temperature yield stress in compression varied from 99 to 128 M Pa, the room temperature Knoop hardness numbers varied from 133.5 to 163.5, the rubbery modulus at 200'C varied from 12.8 to 21.6 MPa, and the periodicity of the basic longitudinal texture varied from 205 to 368 nm. Only properties of the liquid state, namely glass transition temperature and the rubbery modulus, correlated well with periodicity of the basic longitudinal texture. This suggests that the basic longitudinal texture is the remnant left on the fracture surfaces of a liquid state that must have developed during fracture. This suggests in turn that liquefaction is an intrinsic part of the brittle fracture of polymer network glasses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44718/1/10853_2005_Article_BF01197652.pd

The toughness of epoxy-poly(butylene terephthalate) blends

Blends containing 5% poly(butylene terephthalate) (PBT) in an anhydride-cured epoxy with three different PBT morphologies were studied. The three morphologies were a dispersion of spherulites, a structureless gel and a gel with spherulites. The average fracture toughnesses, K Ic , and fracture energies, G Ic , for those morphologies were 0.83, 2.3 and 1.8 MPa m 1/2 and 240, 2000 and 1150 J m −2 , respectively. These values should be compared with the values of 0.72 MPa m 1/2 and 180 J m −2 , respectively, for the cured epoxy without PBT. The elastic moduli and yield strengths in compression for all three blend morphologies remained essentially unchanged from those of the cured epoxy without PBT, namely, 2.9 GPa for the modulus and 115 MPa for the yield strength. The fracture surfaces of the cured spherulitic dispersion blends indicate the absorption of fracture energy by crack bifurcation induced by the spherulites. The fracture surfaces of the cured structureless gel blends indicate that fracture energy was absorbed by matrix and PBT plastic deformation and by spontaneous crack bifurcation. But phase transformation of the PBT and anelastic strain of the matrix below the fracture surfaces may account for most of the large fracture energy of the cured structureless gel blends.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44733/1/10853_2004_Article_BF00366876.pd

Klasifikace kontur rukou s využitím množiny přirozených charakteristic: velká komparativní studie.

Biometrics is a standalone scientific discipline which enjoys more and more attention of many researchers. The provision of the general security plays a key role in many modern branches. In the presented paper a person identification task is solved using the shape of a human hand, and also the hand contour classification algorithm based on an evolutionary estimator is also. The proposed methodology provides the comparison of the identified person with a set of model contours. The examination of the proposed method was performed with use of a database which contains 940 images of the scanned hands from 94 persons, including 10 images from every person. Totally 88360 combinations of the input images. The proposed evolutionary estimator uses an EPSDE algorithm, which is derived from a differential evolution algorithm which was proposed at the end of the 90’s. The model of the hand contour of every person is represented by only one image, which has movable finger contours in the classification process regarding the knuckle positions of the hand. Thanks to that, it is not necessary to use the pegs to hold the individual fingers in correct positions. The hand can be both placed on a support desk or can be freely hung in the air. All results obtained at classification time with use of the presented evolutionary estimator provide accuracy of approximately 98%.Biometrika jakožto samostatná vědní disciplína se v posledních letech těší stále větší a větší oblibě. Zabezpečování bezpečnosti s využitím biometrických metod patří dnes mezi velmi žádané oblasti. V předkládaném článku je řešena úloha identifikace osob s využitím kontury lidské ruky. Pro klasifikaci je současně využit pokročilý evoluční optimalizátor. Navržený algoritmus porovnává množinu identifikovaných osob s množinou tzv. modelových kontur. Jedna kontura od každé osoby je uvažována jako modelová. Testování probíhalo na databázi o velikosti 940 snímků od 94 osob, 10 snímků od každé osoby. Celkem 88360 kombinací vstupních obrazů. Navržený evoluční estimátor využívá algoritmus EPSDE, což je derivát algoritmu diferenciální evoluce, který byl publikovaný v polovině 90. let. Model kontury ruky každé osoby je reprezentován jen jedním jediným obrazem, který má ale pohyblivé všechny prsty. Palec má 2 klouby. Díky tomuto uspořádání není nutné využívat stavící kolíky při snímkování rukou. Ruka může být položena na projekční desce nebo volně viset ve vzduchu ve vhodné poloze. Maximální dosažená přesnost při experimentech byla cca 98 procent