Error correction method and apparatus for electronic timepieces

A method and apparatus for correcting errors in an electronic digital timepiece that includes an oscillator which has a 2 in. frequency output, an n-stage frequency divider for reducing the oscillator output frequency to a time keeping frequency, and means for displaying the count of the time keeping frequency. In first and second embodiments of the invention the timepiece is synchronized with a time standard at the beginning of the period of time T. In the first embodiment of the invention the timepiece user observes E (the difference between the time standard and the timepiece time at the end of the period T) and then operates a switch to correct the time of the timepiece and to obtain a count for E. In the second embodiment of the invention, the user operates a switch at the beginning of T and at the end of T and a count for E is obtained electronically

Unitary ambiguity in the extraction of the E2/M1 ratio for the γN↔Δ\gamma N\leftrightarrow\Delta transition

The resonant electric quadrupole amplitude in the transition $\gamma N\leftrightarrow\Delta(1232)$ is of great interest for the understanding of baryon structure. Various dynamical models have been developed to extract it from the corresponding photoproduction multipole of pions on nucleons. It is shown that once such a model is specified, a whole class of unitarily equivalent models can be constructed, all of them providing exactly the same fit to the experimental data. However, they may predict quite different resonant amplitudes. Therefore, the extraction of the E2/M1($\gamma N\leftrightarrow\Delta$) ratio (bare or dressed) which is based on a dynamical model using a largely phenomenological $\pi N$ interaction is not unique.Comment: 10 pages revtex including 4 postscript figure

Reflexivity of the translation-dilation algebras on L^2(R)

The hyperbolic algebra A_h, studied recently by Katavolos and Power, is the weak star closed operator algebra on L^2(R) generated by H^\infty(R), as multiplication operators, and by the dilation operators V_t, t \geq 0, given by V_t f(x) = e^{t/2} f(e^t x). We show that A_h is a reflexive operator algebra and that the four dimensional manifold Lat A_h (with the natural topology) is the reflexive hull of a natural two dimensional subspace.Comment: 10 pages, no figures To appear in the International Journal of Mathematic

Measurement and analysis of critical crack tip processes during fatigue crack growth

The mechanics of fatigue crack growth under constant-amplitudes and variable-amplitude loading were examined. Critical loading histories involving relatively simple overload and overload/underload cycles were studied to provide a basic understanding of the underlying physical processes controlling crack growth. The material used for this study was 7091-T7E69, a powder metallurgy aluminum alloy. Local crack-tip parameters were measured at various times before, during, and after the overloads, these include crack-tip opening loads and displacements, and crack-tip strain fields. The latter were useed, in combination with the materials cyclic and monotonic stress-strain properties, to compute crack-tip residual stresses. The experimental results are also compared with analytical predictions obtained using the FAST-2 computer code. The sensitivity of the analytical model to constant-amplitude fatigue crack growth rate properties and to through-thickness constrain are studied

Ultrasonic locating devices for central venous cannulation: meta-analysis

OBJECTIVES: To assess the evidence for the clinical effectiveness of ultrasound guided central venous cannulation. DATA SOURCES: 15 electronic bibliographic databases, covering biomedical, science, social science, health economics, and grey literature. DESIGN: Systematic review and meta-analysis of randomised controlled trials. POPULATIONS: Patients scheduled for central venous access. INTERVENTION REVIEWED: Guidance using real time two dimensional ultrasonography or Doppler needles and probes compared with the anatomical landmark method of cannulation. DATA EXTRACTION: Risk of failed catheter placement (primary outcome), risk of complications from placement, risk of failure on first attempt at placement, number of attempts to successful catheterisation, and time (seconds) to successful catheterisation. DATA SYNTHESIS: 18 trials (1646 participants) were identified. Compared with the landmark method, real time two dimensional ultrasound guidance for cannulating the internal jugular vein in adults was associated with a significantly lower failure rate both overall (relative risk 0.14, 95% confidence interval 0.06 to 0.33) and on the first attempt (0.59, 0.39 to 0.88). Limited evidence favoured two dimensional ultrasound guidance for subclavian vein and femoral vein procedures in adults (0.14, 0.04 to 0.57 and 0.29, 0.07 to 1.21, respectively). Three studies in infants confirmed a higher success rate with two dimensional ultrasonography for internal jugular procedures (0.15, 0.03 to 0.64). Doppler guided cannulation of the internal jugular vein in adults was more successful than the landmark method (0.39, 0.17 to 0.92), but the landmark method was more successful for subclavian vein procedures (1.48, 1.03 to 2.14). No significant difference was found between these techniques for cannulation of the internal jugular vein in infants. An indirect comparison of relative risks suggested that two dimensional ultrasonography would be more successful than Doppler guidance for subclavian vein procedures in adults (0.09, 0.02 to 0.38). CONCLUSIONS: Evidence supports the use of two dimensional ultrasonography for central venous cannulation

The eta-photon transition form factor

The eta-photon transition form factor is evaluated in a formalism based on a phenomenological description at low values of the photon virtuality, and a QCD-based description at high photon virtualities, matching at a scale $Q_{0}^{2}$. The high photon virtuality description makes use of a Distribution Amplitude calculated in the Nambu-Jona-Lasinio model with Pauli-Villars regularization at the matching scale $Q_{0}^{2}$, and QCD evolution from $Q_{0}^{2}$ to higher values of $Q^{2}$. A good description of the available data is obtained. The analysis indicates that the recent data from the BaBar collaboration on pion and eta transition form factor can be well reproduced, if a small contribution of twist three at the matching scale $Q_{0}^{2}$ is included.Comment: 14 pages, 3 figures, revised version, minor corrections, references added, conclusions unchanged. Accepted for publication in Phys. Rev.

Auger electron intensity variations in oxygen-exposed large grain polycrystalline silver

Auger electron spectroscopic studies of the grains in oxygen-charged polycrystal-line silver show significant intensity variations as a function of crystallographic orientation. These intensity variations were observed by studies of the Auger images and line scans of the different grains (randomly selected) for each silver transition energy. The results can be attributed to the diffraction of the ejected Auger electrons and interpreted by corresponding changes in the electron mean-free path for inelastic scattering and by oxygen atom accumulation in the subsurface. The subsurface (second layer) octahedral sites increased in size because of surface relaxation and serve as a stable reservoir for the dissolved oxygen

Shrink-Fit Stress Systems in Built Crankshafts

Among applications of the well-known practice of shrink-fitting, the assembly of large marine crankshafts from relatively small forgings is perhaps the most outstanding example, having regard to the stringent operating conditions in which the component must function satisfactorily. Variations in shrink-fitting practice and failures attributable to slipping of the grip have directed attention to the lack of information on crankshaft assemblies and instigated an investigation, the results of which are presented in this thesis. A major part of the investigation comprises a survey of published literature relevant to the subject. It has been found that little is yet known about stress or grip conditions at the shrink-fit, and that the rules for sizes and proportions have evidently no theoretical foundation. The scope of the survey has therefore been extended to include work on all types of interference fits, from v/hich it is evident that, while a useful amount of empirical data on factors affecting grip strength exists, treatment of interface pressure and stress has been limited to the application of elastic thick cylinder theory. With a view to analysing stress conditions in assemblies overstrained by fit allowances which cause permanent enlargement of the hollow element, a part of the survey is devoted to examining work on thick cylinders subjected to internal fluid pressure. A number of features of shrink-fitting, such as prevention of free axial shrinkage, overstrain of the hollow element, and the influence of temperature on the elastic constants of the material, have been analysed as part of the theoretical work of the present investigation. On the basis of certain reasonable assumptions, a solution for the stress in a representative crank web shape has been obtained, using Relaxation Methods of analysis. Stress concentration and radial stiffness values, which correlate the complex shape to the rotationally-symmetrical, follow readily from the solution. The experimental investigations comprise tests on rings-and-plugs, on model crank webs, and on large crank webs removed from a vessel which had been scrapped. The results indicate that prevention of free axial shrinkage does, in fact, occur to a marked degree. Furthermore, the presence of axial grip has been detected in large crank webs which had suffered extensive cold-working due to pulsating bending actions during service. Model experiments have demonstrated the influence of surface finish on the grip strength to be quite unimportant. Friction values in the large crankshaft, on the mating surfaces of which tool-marks were clearly visible, were comparable with those in model webs with near-perfect honed surfaces. Interface pressure and stress values predicted from theoretical considerations were in sound agreement with values measured by electrical strain gauges and inferred from deformations. A list of design formulae and data, and recommendations for improvements to shrink-fitting practice, based on the results of the investigation, are presented

Problems with Extraction of the Nucleon to Delta(1232) Photonic Amplitudes

We investigate the model dependence and the importance of choice of database in extracting the {\it physical} nucleon-Delta(1232) electromagnetic transition amplitudes, of interest to QCD and baryon structure, from the pion photoproduction observables. The model dependence is found to be much smaller than the range of values obtained when different datasets are fitted. In addition, some inconsistencies in the current database are discovered, and their affect on the extracted transition amplitudes is discussed.Comment: Revtex, 2 figs., submitted to PR