[en] The problem of cumulative beam break up in a periodic linac for a general impedance is discussed, with the effects of acceleration included. The transverse equations of motion for a set of identical point like bunches moving along the length of the linac are cast into a simple form using a smooth approximation. This results in a working formula that is used to analyze beam breakup. Explicit expressions for the transverse motion in the case of a single resonance impedance are found using saddle point integration. This is done first with no external focusing, and again in the strong focusing limit

[en] We address one key source of the known discrepancies between theory and experiment in poroelasticity, i.e., the fact that Gassmann's equations for the bulk and shear moduli predict that the shear modulus is independent of the saturating fluid properties, whereas it is observed on the contrary that at high enough frequencies the shear modulus can in fact depend on the fluid's elastic properties in many porous materials. One clue to understanding this behavior comes from effective medium theory, which shows that the shear modulus does depend on the fluid properties in many circumstances. In comparison to values predicted by effective medium theory, Gassmann's equations predict different, smaller values for both the effective bulk and shear moduli of porous media. Sorting through these apparent (but not actual) disagreements among theory and theory, and theory and experiment is the main thrust of the paper

[en] SSI-FEBEM is a computer program for dynamic soil-structure (or structure-soil-structure) interaction analysis in the frequency domain. The program SAP IV (FEM) and the program SSI 2D/3D (BEM) have been integrated into a new program, which allows a coupling of finite and boundary elements. It is applicable to two- and three-dimensional problems. In this manual, the theoretical concept for both FEM and BEM, as used in the program, are briefly introduced. Details of the coupling of FE and BE, are also discussed. However, emphasis is directed towards the use of the computer program concerning data input and output. Finally, several examples on soil-structure interaction (SSI) and structure-soil-structure interaction (SSSI), together with their data are presented. (orig.)

[en] We study the intensity-dependent behavior of laser-induced vibrational quasi-energy (VQE) resonance structure and photodissociation rates of H₂⁺ molecular ions in intense laser fields and report a novel new high-intensity phenomenon. At strong fields, the vibrational levels are shifted and broadened and break into several separate VQE resonance groups. Distortion of the internuclear potential by the fields leads to the formation of various (field-dressed) adiabatic potential wells near multiphoton resonances which can support long-lived resonance states. The most striking finding is that high-lying VQE resonance states can in fact become more stabilized and longer lived at higher laser intensities, a phenomenon which may be termed as open-quotes bond hardening.close quotes Time-dependent calculations confirm the laser-induced stabilization reveals that molecular population may be trapped simultaneously in different potential wells, at different internuclear separations

[en] We discuss an alternative approach to the detection of solar neutrinos using a coarsely segmented detector based on inverse-beta decay onto ¹⁶⁰Gd or ¹⁷⁶Yb. While it is known that similar approaches, already discussed in the literature, can in principle provide low-threshold, real-time energy spectroscopy with intrinsic background rejection features, the concepts presented here make this scheme possible with lower background and current technology

[en] Compressional (P) and shear (S) wave velocities have been measured for two synthetic polycrystalline specimens of pyrope-majorite garnets (Py60Mj40 and Py50Mj50) by ultrasonic interferometry to 8 GPa and 1000 K, in a DIA-type cubic anvil high pressure apparatus (SAM-85) interfaced with synchrotron X-radiation and X-ray imaging. Elastic bulk (KS) and shear (G) moduli data obtained at the end of the cooling cycles were fitted to functions of Eulerian strain to third order yielding pressure derivatives of the elastic moduli (?KS/?P)T = 4.3 (3); (?G/?P)T = 1.5 (1) for Py60Mj40 garnet and (?KS/?P)T = 4.4 (1); (?G/?P)T = 1.3 (1) for Py50Mj40 garnet. Both (?KS/?P)T and (?G/?P)T are identical for the two garnet compositions and are also consistent with Brillouin scattering data for polycrystalline Py50Mj50. Moreover, the new pressure derivatives of the elastic moduli are equal within experimental uncertainties to those of end-member pyrope garnet from ultrasonic studies.

[en] The higher requirements for beam injection stability at the APS storage ring (SR) demand improvement of pulsed power supplies for the septum magnets. The new specification for the current repeatability is 1/2000. The upgrade will be performed in two stages. In the first stage we will implement a new voltage regulation circuit in the power supply with a new timing sequence that will provide better voltage regulation performance. A common design is made for all of the septum magnet power supplies (SMPSs) at the APS. The new regulation module has already been tested on both thin and thick SMPSs. The test shows that the achieved voltage regulation is much better than 1/2000. Combined with a current feedback loop, it can provide a shot-to-shot current repeatability better than 1/2000. The second phase of the upgrade will develop the current feedback loop and control algorithm. This paper will describe the design and test results for the first phase only.

[en] The energy-level alignment at metal/organic interfaces has traditionally been studied using ultraviolet photoelectron spectroscopy (UPS) in ultra-high vacuum (UHV). However, since most devices are fabricated in high vacuum (HV), these studies do not accurately reflect the interfaces in real devices. We demonstrate, using UPS measurements of samples prepared in HV and UHV and current-voltage measurements of devices prepared in HV, that the small amounts of residual gases that are adsorbed on the surface of clean Cu, Ag, and Au (i.e., the noble metals) in HV can significantly alter the energy-level alignment at metal/organic interfaces.

[en] The US Nuclear Regulatory Commission (USNRC) has undertaken a program to assess the integrity of control rod drive mechanism nozzles in existing plants that are not immediately replacing their reactor pressure vessel heads. This paper summarizes some of the efforts undertaken on behalf of the USNRC for the development of circumferential crack-driving force solutions to be used in probabilistic determinations of the time from detectable leakage to failure. Detailed three-dimensional elastic-plastic finite element analyses of these nozzles were conducted to determine the effects of operating conditions, tube-to-head interference fit, tube yield strength, and nozzle-to-head angle on the crack-driving force. Three major observations to date are: - Conducting simple tube-only analyses can severely overpredict the actual crack-driving force in the control rod drive mechanism nozzles. - The crack-driving force is a strong function of the nozzle yield strength, nozzle-to-head angle, interference fit, and weld residual stress; and; - In many cases, when the crack is made to be perpendicular to the wall of the nozzle, the operating conditions and residual stresses appear to create some crack closure along the crack faces, suggesting that cracks in service will grow at an angle through the thickness

[en] Hydrogen and oxygen stable isotope compositions in soil waters have been widely used to investigate hydrologic cycles, particularly for understanding plant water usage. However, most studies of soil water isotopes have traditionally ignored the importance of O-horizon that may potentially influence the accurate evaluation of hydrologic processes, especially in alpine regions where O-horizon are thick due to low temperatures. Therefore, we investigated the isotopic differences (via mean effect size, lnRR) of waters from O-horizon and 0–10 cm soil layer in grasslands and woodlands of Western Sichuan alpine regions and evaluated the influences of climatic and biotic factors on observed differences. The results indicated that the δ2H and δ18O of O-horizon water were significantly higher than those of the 0–10 cm soil layer in grasslands, but these differences were not significant in woodlands. The influence of climatic factors on lnRR was limited relative to biotic factors, and the influence of climate contrasted with expectations based on evaporation principles. Rather, above ground biomass (AGB) was the most important factor associated with lnRR and it was significantly correlated with lnRR between and within soil waters from two vegetation types. Consequently, the observed differences were mainly related to vegetation conditions that influence microclimates within canopies. Therefore, investigations of hydrological processes may inaccurately estimate their influences when not separately considering the high stable isotopes values of O-horizon in grasslands of alpine regions with thin soil layers. In particular, the influence of O-horizon should especially be considered when AGB was lower than 100 t/hm2 not only in grassland but also in other vegetation types.