Sliderule-like property of Wigner's little groups and cyclic S-matrices for multilayer optics

It is noted that two-by-two S-matrices in multilayer optics can be represented by the Sp(2) group whose algebraic property is the same as the group of Lorentz transformations applicable to two space-like and one time-like dimensions. It is noted also that Wigner's little groups have a sliderule-like property which allows us to perform multiplications by additions. It is shown that these two mathematical properties lead to a cyclic representation of the S-matrix for multilayer optics, as in the case of ABCD matrices for laser cavities. It is therefore possible to write the N-layer S-matrix as a multiplication of the N single-layer S-matrices resulting in the same mathematical expression with one of the parameters multiplied by N. In addition, it is noted, as in the case of lens optics, multilayer optics can serve as an analogue computer for the contraction of Wigner's little groups for internal space-time symmetries of relativistic particles.Comment: RevTex 13 pages, Secs. IV and V revised and expande

The submuscular sliding plate technique for acetabular posterior wall fractures extending to the acetabular roof

AbstractThere is extension of the Kocher-Langenbeck approach using trochanteric osteotomy for posterior wall fracture extending to acetabular roof, but it exposes to complications such as nonunion, breakage, and heterotopic ossification. The current study introduces a submuscular sliding plate technique. We retrospectively analyzed 13 patients treated with this technique. It is based on conventional method for posterior wall fracture. After reduction of roof fragment with direct visualization, a pre-contoured plate was passed through a submuscular tunnel under the gluteus medius and minimus. A small split incision was performed on the muscles, and screws were inserted with a triple trocar complex safely under fluoroscopic imaging. All patients had fracture union without complications. X-rays results showed anatomical reduction in 10 cases and imperfect reduction in 3 cases. Our results were satisfactory, particularly without heterotopic ossifications despite no prophylactic regimen of NSAID was applied and no neurological complications, so we believe that this technique is a good option for posterior wall fractures extending to the acetabular roof

Rest-to-Rest Slew Maneuver of Three-Axis Rotational Flexible Spacecraft

The article of record as published may be found at http://dx.doi.org/10.3182/20080706-5-KR-1001.02040This paper presents a slew maneuver control design of three-axis rotational flexible spacecraft. The focus of the work is to investigate the nonlinear effect of the three axis maneuver for a flexible spacecraft when a vibration suppression technique for linear systems such as input shaping is used in the control design. A simple method of slewing three-axis rotational spacecraft using input shaping is proposed and the proposed technique is implemented on an experimental three-axis spacecraft simulator. This paper presents a slew maneuver control design of three-axis rotational flexible spacecraft. The focus of the work is to investigate the nonlinear effect of the three axis maneuver for a flexible spacecraft when a vibration suppression technique for linear systems such as input shaping is used in the control design. A simple method of slewing three-axis rotational spacecraft using input shaping is proposed and the proposed technique is implemented on an experimental three-axis spacecraft simulator. This paper presents a slew maneuver control design of three-axis rotational flexible spacecraft. The focus of the work is to investigate the nonlinear effect of the three axis maneuver for a flexible spacecraft when a vibration suppression technique for linear systems such as input shaping is used in the control design. A simple method of slewing three-axis rotational spacecraft using input shaping is proposed and the proposed technique is implemented on an experimental three-axis spacecraft simulator. This paper presents a slew maneuver control design of three-axis rotational flexible spacecraft. The focus of the work is to investigate the nonlinear effect of the three axis maneuver for a flexible spacecraft when a vibration suppression technique for linear systems such as input shaping is used in the control design. A simple method of slewing three-axis rotational spacecraft using input shaping is proposed and the proposed technique is implemented on an experimental three-axis spacecraft simulator

Penalized Orthogonal-Components Regression for Large p Small n Data

We propose a penalized orthogonal-components regression (POCRE) for large p small n data. Orthogonal components are sequentially constructed to maximize, upon standardization, their correlation to the response residuals. A new penalization framework, implemented via empirical Bayes thresholding, is presented to effectively identify sparse predictors of each component. POCRE is computationally efficient owing to its sequential construction of leading sparse principal components. In addition, such construction offers other properties such as grouping highly correlated predictors and allowing for collinear or nearly collinear predictors. With multivariate responses, POCRE can construct common components and thus build up latent-variable models for large p small n data.Comment: 12 page

Optical Beam Jitter Control for NPS HEL Beam Control Testbed

In this paper, an optical beam jitter control method for the Naval Postgraduate School HEL beam control testbed is presented. Additional hardware is developed and integrated on the testbed to realize the strap-down IRU jitter compensation architectures. Feedforward control design of the strap-down IRU design is studied and tested on the testbed. An adaptive filtering method for narrow-field-of-view video tracker jitter correction is also presented. In this paper, an optical beam jitter control method for the Naval Postgraduate School HEL beam control testbed is presented. Additional hardware is developed and integrated on the testbed to realize the strap-down IRU jitter compensation architectures. Feedforward control design of the strap-down IRU design is studied and tested on the testbed. An adaptive filtering method for narrow-field-of-view video tracker jitter correction is also presented

On the growth of the Bergman kernel near an infinite-type point

We study diagonal estimates for the Bergman kernels of certain model domains in $\mathbb{C}^2$ near boundary points that are of infinite type. To do so, we need a mild structural condition on the defining functions of interest that facilitates optimal upper and lower bounds. This is a mild condition; unlike earlier studies of this sort, we are able to make estimates for non-convex pseudoconvex domains as well. This condition quantifies, in some sense, how flat a domain is at an infinite-type boundary point. In this scheme of quantification, the model domains considered below range -- roughly speaking -- from being ``mildly infinite-type'' to very flat at the infinite-type points.Comment: Significant revisions made; simpler estimates; very mild strengthening of the hypotheses on Theorem 1.2 to get much stronger conclusions than in ver.1. To appear in Math. An

Molecular dynamics simulations of oxide memristors: thermal effects

We have extended our recent molecular-dynamic simulations of memristors to include the effect of thermal inhomogeneities on mobile ionic species appearing during operation of the device. Simulations show a competition between an attractive short-ranged interaction between oxygen vacancies and an enhanced local temperature in creating/destroying the conducting oxygen channels. Such a competition would strongly affect the performance of the memristive devices.Comment: submit/0169777; 6 pages, 4 figure

Absorption cross section in the topologically massive gravity at the critical point

The absorption cross section for the the warped AdS$_3$ black hole background shows that it is larger than the area even if the s-wave limit is considered. It raises some question whether the deviation from the areal cross section is due to the warped configuration of the geometry or the rotating coordinate system, where these two effects are mixed up in the warped AdS$_3$ black hole. So, we study the low-frequency scattering dynamics of propagating scalar fields under the warped AdS$_3$ background at the critical point which reduces to the BTZ black hole in the rotating frame without the warped factor, which shows that the deformation effect at the critical point does not appear.Comment: 12 pages, LaTe

Granular clustering in a hydrodynamic simulation

We present a numerical simulation of a granular material using hydrodynamic equations. We show that, in the absence of external forces, such a system phase-separates into high density and low density regions. We show that this separation is dependent on the inelasticity of collisions, and comment on the mechanism for this clustering behavior. Our results are compatible with the granular clustering seen in experiments and molecular dynamic simulations of inelastic hard disks.Comment: 4 pages, 5 figure

High-resolution Ce 3d-edge resonant photoemission study of CeNi_2

Resonant photoemission (RPES) at the Ce 3d -> 4f threshold has been performed for alpha-like compound CeNi_2 with extremely high energy resolution (full width at half maximum < 0.2 eV) to obtain bulk-sensitive 4f spectral weight. The on-resonance spectrum shows a sharp resolution-limited peak near the Fermi energy which can be assigned to the tail of the Kondo resonance. However, the spin-orbit side band around 0.3 eV binding energy corresponding to the f_{7/2} peak is washed out, in contrast to the RPES spectrum at the Ce 3d -> 4f RPES threshold. This is interpreted as due to the different surface sensitivity, and the bulk-sensitive Ce 3d -> 4f RPES spectra are found to be consistent with other electron spectroscopy and low energy properties for alpha-like Ce-transition metal compounds, thus resolves controversy on the interpretation of Ce compound photoemission. The 4f spectral weight over the whole valence band can also be fitted fairly well with the Gunnarsson-Schoenhammer calculation of the single impurity Anderson model, although the detailed features show some dependence on the hybridization band shape and (possibly) Ce 5d emissions.Comment: 4 pages, 3 figur