Designing double-gap linear accelerators for a wide mass range

For applications like ion implantation, rf linacs using double-gap structures with external resonators can be used because they are practical at low frequencies. However, since the two gaps associated with a given resonator cannot be individually phased, it is not obvious how to build a linac that can efficiently accelerate particles having different mass/charge ratios. This paper describes the beam dynamics of double-gap rf linacs and shows how to maximize the range of mass/charge ratios. The theory also tells one how to rescale a linac tune (i.e., reset the voltages and phases) so that a new particle, having a different mass or charge, will behave similarly to the original particle

Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model

An analytical nonadiabatic approach has been developed to study the dimerization gap and the optical absorption coefficient of the Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum phonons. By investigating quantitatively the effects of quantum phonon fluctuations on the gap order and the optical responses in this system, we show that the dimerization gap is much more reduced by the quantum lattice fluctuations than the optical absorption coefficient is. The calculated optical absorption coefficient and the density of states do not have the inverse-square-root singularity, but have a peak above the gap edge and there exist a significant tail below the peak. The peak of optical absorption spectrum is not directly corresponding to the dimerized gap. Our results of the optical absorption coefficient agree well with those of the experiments in both the shape and the peak position of the optical absorption spectrum.Comment: 14 pages, 7 figures. to be published in PR

Optimal Design of Single-Layer and Multi-Layer Air-Core Inductors Considering Uncertainty Factors

Air-core inductors are key components in power converters and measurement equipment. To optimally design inductors, their self-resonant frequency (SRF) as a result of inherent stray capacitance should be accurately estimated. This paper presents optimal design procedures for air-core inductors, considering constraints such as SRF and inductor volume. To this end, a methodology is proposed to estimate the variability of stray capacitances, accounting for various uncertainty factors. Specifically, for single-layer air-core inductors, an empirical expression is adopted and experimentally verified to provide better predictions compared to the commonly used physical-based approach. For multi-layer air-core inductors, an enhanced analytical approach based on the energy-conservation method is proposed, which considers the impact of five influence factors. Two key factors (the proximity effect and the variation of turn length) are investigated by FEM simulations and incorporated into the enhanced models. The other three factors (the effective permittivity of the wire insulation coating, the winding tightness, and the electric field path assumption) are taken into account as uncertainty factors, leading to statistical estimates of the stray capacitance and SRF. Finally, two samples are fabricated for single- and multi-layer air-core inductors, which agree well with the design specifications, proving the effectiveness of the proposed design methodology

FIRST SEARCHES FOR OPTICAL COUNTERPARTS TO GRAVITATIONAL-WAVE CANDIDATE EVENTS

During the LIGO and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type

Wavelet Sparse Approximate Inverse Preconditioners

. We show how to use wavelet compression ideas to improve the performance of approximate inverse preconditioners. Our main idea is to first transform the inverse of the coefficient matrix into a wavelet basis, before applying standard approximate inverse techniques. In this process, smoothness in the entries of A \Gamma1 are converted into small wavelet coefficients, thus allowing a more efficient approximate inverse approximation. We shall justify theoretically and numerically that our approach is effective for matrices with smooth inverses. AMS subject classification: 65F10, 65F35, 65F50, 65Y05, 65Y20. Key words: Preconditioning, Approximate inverses, Sparse matrices, Wavelet. 1 Introduction. Consider solving the linear systems: Ax = b; (1.1) where A is large and sparse. There is an increasing interest in using sparse approximate inverse preconditioners for Krylov subspace iterative methods to solve (1.1). On one hand, it possesses a conceptually straightforward parallel Sup..

ANN-based automatic contingency selection for electric power system

Automatic contingency selection aims to quickly predict the impact of a set of next contingencies on an electric power system without actually performing a full ac load flow. Artificial neural network methods have been employed to overcome the masking effects or slow execution associated with existing methods. However, the large number of input features for the ANN limits its applications to large power systems. In this paper, a novel feature selection method, named the Weak Nodes method, based on a heuristic approach is proposed for an ANN-based automatic contingency selection for electric power system, especially for the voltage ranking problem. Pre-contingency state variables of weak nodes in the power system are adopted as input features for the ANN. The method is tested on the 77 busbar NGC derived network by Counter-propagation Method and it is proved that it reduces the input features for ANN dramatically without losing ranking accuracy

Role of non-receptor protein tyrosine kinases in spermatid transport during spermatogenesis

Non-receptor protein tyrosine kinases are cytoplasmic kinases that activate proteins by phosphorylating tyrosine residues, which in turn affect multiple functions in eukaryotic cells. Herein, we focus on the role of non-receptor protein tyrosine kinases, most notably, FAK, c-Yes and c-Src, in the transport of spermatids across the seminiferous epithelium during spermatogenesis. Since spermatids, which are formed from spermatocytes via meiosis, are immotile haploid cells, they must be transported by Sertoli cells across the seminiferous epithelium during the epithelial cycle of spermatogenesis. Without the timely transport of spermatids across the epithelium, the release of sperms at spermiation fails to occur, leading to infertility. Thus, the molecular event pertinent to spermatid transport is crucial to spermatogenesis. We provide a critical discussion based on recent findings in this review. We also provide a hypothetical model on spermatid transport, and the role of non-receptor protein tyrosine kinases in this event. We also highlight areas of research that deserve attention by investigators in the field

New insights into FAK function and regulation during spermatogenesis

Germ cell transport across the seminiferous epithelium during the epithelial cycle is crucial to spermatogenesis, although molecular mechanism(s) that regulate these events remain unknown. Studies have shown that spatiotemporal expression of crucial regulatory proteins during the epithelial cycle represents an efficient and physiologically important mechanism to regulate spermatogenesis without involving de novo synthesis of proteins and/or expression of genes. Herein, we critically review the role of focal adhesion kinase (FAK) in coordinating the transport of spermatids and preleptotene spermatocytes across the epithelium and the blood-testis barrier (BTB), respectively, along the apical ectoplasmic specialization (ES) – blood-testis barrier – basement membrane (BM) functional axis during spermatogenesis. In the testis, p-FAK-Tyr397 and p-FAKTyr407 are spatiotemporally expressed during the epithelial cycle at the actin-rich anchoring junction known as ES, regulating cell adhesion at the Sertolispermatid (apical ES) and Sertoli cell-cell (basal ES) interface. Phosphorylated forms of FAK exert their effects by regulating the homeostasis of F-actin at the ES, mediated via their effects on actin polymerization so that microfilaments are efficiently re-organized, such as from their “bundled” to “de-bundled/branched” configuration and vice versa during the epithelial cycle to facilitate the transport of: (i) spermatids across the epithelium, and (ii) preleptotene spermatocytes across the BTB. In summary, p-FAK-Tyr407 and p-FAK-Tyr397 are important regulators of spermatogenesis which serve as molecular switches that turn “on” and “off” adhesion function at the apical ES and the basal ES/BTB, mediated via their spatiotemporal expression during the epithelial cycle. A hypothetical model depicting the role of these two molecular switches is also proposed