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  • 1
    Electronic Resource
    Electronic Resource
    Identification of archaeogastropod larvae from a hydrothermal vent community (1996)
    Springer
    Marine biology 124 (1996), S. 551-560 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dispersal is essential in order that endemic species living in ephemeral, patchy vent environments may persist over evolutionary time. Quantitative field studies of larval dispersal, however, require specieslevel identification of the larval forms because each individual must be distinguished from related vent species, and from non-vent species living in the surrounding deep-sea environment. Methods for culturing these larvae to an identifiable stage have not yet been developed. To solve the larval identification problem for the archaeogastropod molluscs (a prominent component of vent communities), we used a scanning electron microscope (SEM) to image shells of larvae collected in the water column near vents along the East Pacific Rise (9°40′ to 9°50′N; 104°W). Larval shell size, shape and ornamentation were compared to protoconchs retained in juvenile or adult shells of identified species, and used to assign five larval groups unequivocally to species (Cyathermia naticoides Warén and Bouchet, 1989; Neomphalus fretterae McLean, 1981; Clypeosectus delectus McLean, 1989; Rhynchopelta concentrica McLean, 1989; and Lirapex granularis Warén and Bouchet, 1989) and seven groups tentatively to species or genus [Lepetodrilus spp. (three groups); Gorgoleptis sp; Peltospira ?operculata McLean, 1989; and ?Melanodrymia sp. (two groups)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351036
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  • 2
    Electronic Resource
    Electronic Resource
    Exact Algorithm for the Surrogate Dual of an Integer Programming Problem: Subgradient Method Approach (1998)
    Springer
    Journal of optimization theory and applications 96 (1998), S. 363-375 
    Details
    ISSN: 1573-2878
    Keywords: Integer programming ; surrogate dual ; nondifferentiable optimization ; subgradient method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract One of the critical issues in the effective use of surrogate relaxation for an integer programming problem is how to solve the surrogate dual within a reasonable amount of computational time. In this paper, we present an exact and efficient algorithm for solving the surrogate dual of an integer programming problem. Our algorithm follows the approach which Sarin et al. (Ref. 8) introduced in their surrogate dual multiplier search algorithms. The algorithms of Sarin et al. adopt an ad-hoc stopping rule in solving subproblems and cannot guarantee the optimality of the solutions obtained. Our work shows that this heuristic nature can actually be eliminated. Convergence proof for our algorithm is provided. Computational results show the practical applicability of our algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022622231801
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  • 3
    Electronic Resource
    Electronic Resource
    On the generality of discontinuous fatigue crack growth in glassy polymers (1977)
    Springer
    Journal of materials science 12 (1977), S. 531-542 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fatigue fracture surface characteristics of five commercially available amorphous polymers [poly(methylmethacrylate) (PMMA), polycarbonate (PC), poly(vinyl chloride) (PVC), polystyrene (PS), and polysulphone (PSF)] as well as bulk-polymerized PMMA prepared over a wide range of molecular weights were studied to determine if common mechanisms of fatigue crack propagation prevail among these glassy polymers. In those polymers with viscosity-average molecular weight ¯M v≲2×105, the macroscopic appearance of the fracture surface showed the presence of a highly reflective mirror-like region which formed at low values of stress intensity and high cyclic test frequencies (∼100 Hz). The microscopic appearance of this region revealed that many parallel bands exist oriented perpendicular to the direction of crack growth and that the bands increase in size with ΔK. In all instances, the crack front advanced discontinuously in increments equal to the band width after remaining stationary for hundreds of fatigue cycles. Electron fractographic studies verified the discontinuous nature of crack extension through a craze which developed continuously with the load fluctuations. By equating the band size to the Dugdale plastic zone dimension ahead of the crack, a relatively constant yield strength was inferred which agreed well with reported craze stress values for each material. At higher stress intensity levels in all polymers and all values of ¯M v, another series of parallel bands were observed. These were also oriented perpendicular to the direction of crack growth and likewise increased in size with the range in stress intensity factor, ΔK. Each band corresponded to the incremental advance of the crack during one load cycle, indicating these markings to be classical fatigue striations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540278
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of molecular weight distribution on fatigue crack propagation in poly(methyl methacrylate) (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 145-150 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is well established that both molecular weight (M) and its distribution (MD) affect many polymer properties such as mechanical behavior. Thus studies have shown that fatigue life is enhanced by increases in M. Research here has shown that with notched specimens fatigue crack propagation (FCP) rates are dramatically decreased by increasing M, even when the M is high enough that the static fraeture energy has essentially reached its asymptotic limit. In this study, specimens of poly(methyl methacrylate) containing either high- or low-M tails were prepared and characterized. The earlier finding that FCP rates are inversely related to average M was confirmed, but specific effects of M distribution were observed. At constant Mn, a low-M tail had little effect on FCP resistance, while a high-M tail improved FCP resistance of polymers whose average M was too low for effective entanglements. Thus with high-M tails, it was possible to test specimens whose average M's were too low to permit machining. It is proposed that the effects noted are due to relative stabilization or destabilization of crazes ahead of the crack.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190218
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  • 5
    Electronic Resource
    Electronic Resource
    Fatigue crack propagation in poly(methyl methacrylate): Effect of molecular weight and internal plasticization (1977)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 194-203 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In spite of the importance of fatigue behavior in engineering plastics, relatively few fundamental studies have been made of the effects of polymer structure, molecular weight, composition, and morphology on fatigue crack propagation (FCP). As, part of a broad program for the study of such effects, the role of molecular weight and internal plasticization has been studied in poly(methyl methacrylate) (PMMA) which had been specially prepared and characterized with respect to molecular weight, dynamic mechanical behavior, and, in some cases, stress-strain response. As expected, values of fracture toughness, Kc, varied considerably as the molecular weight was rai ed, from 0.7 MPa, √m at Mv = 1.0 × 105 to 1.1 at Mv, = 4.8 × 106. However, a specific effect of fatigue was noted: over the same range of Kc, values of FCP rate decreased by two orders of magnitude as molecular weight was; increased. It is proposed that this high sensitivity is due to differences in the degree of chain disentanglement effected by the cyclic loading, with consequent differences in the strength of the craze preceding the crack. With PMMA plasticized internally with a low level (10 percent) of n-butyl acrylate (nBA), the FCP rate and Kc, were similar to those of controls, with very high rates shown. At higher nBA levels (up to 30 percent), the sensitivity of FCP rate to stress intensity factor range decreased considerably, Kc, increased by 30 percent and the pre-exponential constant in the growth rate law increased. Plasticization weakens the polymer but at high degrees leads to enough hysteretic heating to induce local creep and crack blunting.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760170308
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  • 6
    Electronic Resource
    Electronic Resource
    Tensile, impact and fatigue behavior of an amine-cured epoxy resin (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 1093-1100 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Although crosslinked networks are commonly used as adhesives and composite matrixes, structure-property relationships are not as well established as with thermoplastics. For this reason, an extensive study was begun to systematically examine effects of stoichiometry, morphology, and distribution of crosslink density on viscoelastic behavior and ultimate properties. The system selected was based on a bisphenol-A-type epoxy cured with methylene dianiline. This paper describes and discusses results obtained for resins in which the amine/epoxy ratio ranged between 0.7 and 2.2. In agreement with reports by others, the tensile strength, modulus, and ultimate elongation were relatively insensitive to stoichiometry but did not show slight maxima or minima when the amine was somewhat in excess. Impact strengths, tensile energies-to-break and fracture toughness were, in contrast, quite sensitive, though the patterns of each differed significantly. Both fracture toughness and the stress intensity factor required to drive the crack at a given rate varied directly with the amine/epoxy ratio, as did estimates of the characteristic flaw size. Fatigue striations were observed on the fracture surfaces and corresponded to the incremental advance of the crack in one loading cycle.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760181410
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  • 7
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    On the generality of discontinuous fatigue crack growth in glassy polymers (1977)
    Springer
    Details
    Publication Date: 1977-03-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 8
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    The 2003-2004 multisite photometric campaign for the {beta} Cephei and eclipsing star 16 (EN) Lacertae with an appendix on 2 Andromedae, the variable comparison star (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-26
    Description: A multisite photometric campaign for the β Cephei and eclipsing variable 16 Lacertae is reported. 749 h of high-quality differential photoelectric Strömgren, Johnson and Geneva time series photometry were obtained with 10 telescopes during 185 nights. After removing the pulsation contribution, an attempt was made to solve the resulting eclipse light curve by means of the computer program ebop . Although a unique solution was not obtained, the range of solutions could be constrained by comparing computed positions of the secondary component in the Hertzsprung–Russell diagram with evolutionary tracks. For three high-amplitude pulsation modes, the uvy and the Geneva UBG amplitude ratios are derived and compared with the theoretical ones for spherical-harmonic degrees ≤ 4. The highest degree, = 4, is shown to be incompatible with the observations. One mode is found to be radial, one is = 1, while in the remaining case = 2 or 3. The present multisite observations are combined with the archival photometry in order to investigate the long-term variation of the amplitudes and phases of the three high-amplitude pulsation modes. The radial mode shows a non-sinusoidal variation on a time-scale of 73 yr. The = 1 mode is a triplet with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and 29.1 yr. The amplitude and phase of the = 2 or 3 mode vary on time-scales of 380.5 d and 43 yr. The light variation of 2 And, one of the comparison stars, is discussed in the appendix.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Apsidal motions of 90 eccentric binary systems in the Small Magellanic Cloud (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: We examined light curves of 1138 stars brighter than 18.0 mag in the I band and less than a mean magnitude error of 0.1 mag in the V band from the Optical Gravitational Lensing Experiment (OGLE)-III eclipsing binary catalogue, and found 90 new binary systems exhibiting apsidal motion. In this study, the samples of apsidal motion stars in the Small Magellanic Cloud (SMC) were increased by a factor of about 3.0 than previously known. In order to determine the period of the apsidal motion for the binaries, we analysed in detail both the light curves and eclipse timings using the MACHO (MAssive Compact Halo Objects) and OGLE photometric data base. For the eclipse timing diagrams of the systems, new times of minimum light were derived from the full light curve combined at intervals of one year from the survey data. The new 90 binaries have apsidal motion periods in the range of 12–897 yr. An additional short-term oscillation was detected in four systems (OGLE-SMC-ECL-1634, 1947, 3035, and 4946), which most likely arises from the existence of a third body orbiting each eclipsing binary. Since the systems presented here are based on homogeneous data and have been analysed in the same way, they are suitable for further statistical analysis.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    KIC 6220497: a new Algol-type eclipsing binary with multiperiodic pulsations (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-30
    Description: We present both binarity and pulsation of KIC 6220497 from the Kepler observations. The light curve synthesis shows that the eclipsing system is a semidetached Algol with parameters of q = 0.243 ± 0.001, i = 77.3 ± 0.3 deg, and T = 3372 ± 58 K, in which the detached primary component fills its Roche lobe by ~87 per cent. A multiple frequency analysis of the eclipse-subtracted light residuals reveals 33 frequencies in the range of 0.75–20.22 d –1 with amplitudes between 0.27 and 4.56 mmag. Among these, four are pulsation frequencies in fundamental ( f 1 , f 5 ) and p ( f 2 , f 7 ) modes, and six are orbital frequency ( f 8 , f 31 ) and its harmonics ( f 6 , f 11 , f 20 , f 24 ), which can be attributed to tidally excited modes. For the pulsation frequencies, the pulsation constants of 0.16–0.33 d and the period ratios of P pul / P orb = 0.042–0.089 indicate that the primary component is a Sct pulsating star and, thus, KIC 6220497 is an oscillating eclipsing Algol (oEA) star. The dominant pulsation period of 0.117 4051 ± 0.000 0004 d is significantly longer than that expected from empirical relations that link the pulsation period with the orbital period. The surface gravity of log g 1 = 3.78 ± 0.03 is clearly smaller than those of the other oEA stars with similar orbital periods. The pulsation period and the surface gravity of the pulsating primary demonstrate that KIC 6220497 would be the more evolved eclipsing binary, compared with normal oEA stars.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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