Wind Tunnel Modeling of Jack Rabbit II Mock Urban Environment Gas Concentration Measurements

The 2015 Jack Rabbit (JR) II field trials were conducted to improve understanding of the denser-than-air dispersion of chlorine in an urban environment. The field study involved five large-scale, outdoor release trials of chlorine in a mock urban environment (MUE) at Dugway Proving Ground (DPG). Various instrumentation was deployed, including JazTM Ultraviolet-Visible (UV-Vis) point sensors capable of measuring gas-phase chlorine concentration throughout the mock urban array. The Chemical Hazards Research Center (CHRC) was tasked by the Chemical Security Analysis Center (CSAC) with the Mock Urban Wind Tunnel (MUWT) program to study the 2015 JR II Trials at wind tunnel scale. A 50:1 physical model of the 2015 JR II Trials was developed. After the establishment of proper wind profile and source characterization, the physical model was prepared for model concentration measurements at Jaz locations in the scaled MUE. Seven concentration-measurement studies (Tests A–G) involving either JR II Trial 2 or Trial 4 conditions were conducted. Each test used either a fast-response nondispersive infrared detector (Cambustion NDIR500) or flame ionization detector (Cambustion HFR400 FID) to obtain concentration measurements with carbon dioxide or methane as a chlorine cloud “tracer,” respectively. Two methods for achieving similarity were used: Froude (Tests A, B, and G) and Richardson (Tests C–F) number similarity. Froude similarity required that the source-gas density in the full-scale experiment (e.g., JR II) be identical to the source-gas density in the wind tunnel model. Achieving near source-gas density equivalence required the use of sulfur hexafluoride (a high molecular weight species) in tunnel source-gas mixtures. Richardson similarity relaxed the density-match requirement; wind tunnel source-gas densities (“high-density case” and “low-density case”) were less than full-scale source-gas densities, but a lower wind speed and increased scaled release duration were required to compensate for density deviations. Tests A–T4NFr and B–T2NFr involved releases of a 1.787 g/L simulant gas mixture under (50:1) JR II Trial 4 and Trial 2 conditions, respectively. Tests C–T2FRi(H) (high-density case) and D–T2FRi(L) (low-density case) utilized Richardson similarity to compare with Test B–T2NFr and investigate the reliability of the Richardson similarity approach for different deviations in the release gas density. Likewise, Tests E–T2FRi(H) (high-density case) and F–T2FRi(L) (low-density case) utilized Richardson similarity to model (50:1) JR II Trial 2 Jaz profiles and investigate the reliability of the Richardson similarity approach. Test G was an extension of physical model capabilities and involved simulated releases of a 1.440 g/L simulant gas mixture under JR II Trial 4 atmospheric conditions. Results from Tests A–G were transformed to field scale and compared with each other and JR II concentration-time profiles. Comparison studies showed that the physical model was capable of reproducing field-scale (JR II) and wind tunnel (validation) experiments. Similar durations of exposure and cloud times of arrival and departure confirmed that model gas cloud dynamics throughout the physical model were scaled correctly. The validity of Richardson number scaling was verified as well as the method to scale measured concentrations between gases of different molecular weights

Alignment in total knee arthroplasty : what’s in a name?

Dissatisfaction following total knee arthroplasty is a well-documented phenomenon. Although many factors have been implicated, including modifiable and nonmodifiable patient factors, emphasis over the past decade has been on implant alignment and stability as both a cause of, and a solution to, this problem. Several alignment targets have evolved with a proliferation of techniques following the introduction of computer and robotic-assisted surgery. Mechanical alignment targets may achieve mechanically-sound alignment while ignoring the soft tissue envelope; kinematic alignment respects the soft tissue envelope while ignoring the mechanical environment. Functional alignment is proposed as a hybrid technique to allow mechanically-sound, soft tissue-friendly alignment targets to be identified and achieved

Improved Performance of Analog and Digital Acousto-Optic Modulation with Feedback under Profiled Beam Propagation for Secure Communication using Chaos

Using intensity feedback, the closed-loop behavior of an acousto-optic hybrid device under profiled beam propagation has been recently shown to exhibit wider chaotic bands potentially leading to an increase in both the dynamic range and sensitivity to key parameters that characterize the encryption. In this work, a detailed examination is carried out vis-à-vis the robustness of the encryption/decryption process relative to parameter mismatch for both analog and pulse code modulation signals, and bit error rate (BER) curves are used to examine the impact of additive white noise. The simulations with profiled input beams are shown to produce a stronger encryption key (i.e., much lower parametric tolerance thresholds) relative to simulations with uniform plane wave input beams. In each case, it is shown that the tolerance for key parameters drops by factors ranging from 10 to 20 times below those for uniform plane wave propagation. Results are shown to be at consistently lower tolerances for secure transmission of analog and digital signals using parameter tolerance measures, as well as BER performance measures for digital signals. These results hold out the promise for considerably greater information transmission security for such a system

A generalized Lefschetz number for local Nielsen fixed point theory

AbstractLet X be a connected, finite dimensional, locally compact polyhedron. Let f:U→X be a compactly fixed map defined on an open, connected subset U of X, and let H be any normal subgroup of π1(X). We seek information about NH(f), the local H-Nielsen number of f. It is a lower bound for min{|Fix g|: g≃f}, where the homotopies must be admissible.Let NH(f; f̃, ĩ) denote the well-known sum Σα∈Wi(NαH[α], where i(NαH) is the local fixed point index of an H-Nielsen class, [α] is the Reidemeister orbit associated with that class and W is a set of representatives of the Reidemeister orbits. Then NH(f) is the number of terms of NH(f;f̃,ĩ) with nonzero coefficient. We call NH(f;f̃,ĩ) a Nielsen-Reidemeister chain, and we prove that for certain subsets of U, N H(f; f̃, ĩ) splits into the sum of the Nielsen-Reidemeister chains for the subsets.We define the local generalized H-Lefschetz number LH(f; f̃, ĩ) in terms of a globally defined trace. We prove that, for X a connected, triangulable n-manifold with n⩾3, LH(f;f̃, ĩ) = NH(f; f̃, ĩ). Thus, LH(f; f̃, ĩ) can provide a means to compute NH(f). Also, for H = 1, a generalization of the converse of the Lefschetz fixed point theorem holds

Numerical Analysis of First-order Acousto-optic Bragg Diffraction of Profiled Optical Beams using Open-loop Transfer Functions

In standard acousto-optic Bragg analysis, the incident light and sound beams are assumed to be uniform plane waves (with constant profiles) leading to the results based on standard weak interaction theory. As a follow-up to earlier work dealing with nonuniform incident optical beams, we revisit the problem of Bragg diffraction under nonuniform profiles, and include Gaussian, third-order Hermite–Gaussian, and zeroth-order Bessel profiles in our investigation, along with a few others. The first-order diffracted beam is examined (using a transfer function formalism based on angular spectra) under several parametric limits [such as the Klein–Cook parameter Q, the effective profile width, and the optical phase-shift parameter (α^ 0) in the sound cell]. Wherever feasible, the numerical results are compared with analytic theory. The scattered first-order profile output versus the optical phase-shift appears to maintain behavior similar to the known first-order characteristics (sin2 in intensity) encountered for the uniform incident beam case. It is observed, however, that such conformity exists seemingly only at relatively small values of Q (typically about 20 to 50). At higher Qs, on the other hand (where one would otherwise expect behavior closer to standard Bragg theory based on large Qs), it is found that the first-order intensity deviates substantially from the expected sin2- (or related) pattern. This deviation actually becomes more severe at even higher Qs. Additionally, the output profiles at higher Qs are also found to be distorted relative to the incident profiles. These results, though anomalous, are nevertheless generally compatible with earlier studies. Based on the transfer function theory, it is also known that for very large optical phase shifts (i.e., when α^ 0 goes to infinity), the scattered first-order output for a Gaussian profile undergoes an axial (spatial) shift past the output plane of the sound cell. This predicted result is corroborated in our numerical simulation for both the Gaussian and third-order Hermite–Gaussian profiles, but not the zeroth-order Bessel or Airy profiles. These results provide both confirmation of some expected behavior for profiled beam scattering (including likely affirmation of the well-known and unique diffractionless properties of certain Bessel beams), but also some insight into unexpected and anomalous photon-phonon interaction behavior

Secure Transmission of Static and Dynamic Images via Chaotic Encryption in Acousto-optic Hybrid Feedback with Profiled Light Beams

Secure information encryption via acousto-optic (AO) chaos with profiled optical beams indicates substantially better performance in terms of system robustness. This paper examines encryption of static and time-varying (video) images onto AO chaotic carriers using Gaussian-profile beams with diffracted data numerically generated using transfer functions. The use of profiled beams leads to considerable improvement in the encrypted signal. While static image encryption exhibits parameter tolerances within about ±10% for uniform optical beams, profiled beams reduce the tolerance to less than 1%, thereby vastly improving both the overall security of the transmitted information as well as the quality of the image retrieval

Secure Transmission and Retrieval of Images in Conjunction with Steganography using Chaos in Nonlinear Acousto-optic Feedback

Digital images are encrypted onto a chaotic carrier in a Bragg cell under hybrid nonlinear feedback and secure data is embedded into the system via steganography. System robustness (with and without channel noise) is analyzed vis-a-vis information security

Information Encryption, Transmission, and Retrieval via Chaotic Modulation in a Hybrid Acousto-optic Bragg Cell under Profiled Beam Illumination

In recent work, the propagation of a profiled optical beam through an open-loop acousto-optic Bragg cell was examined using a transfer function formalism. The device was also studied under closed-loop via intensity feedback, and shown to exhibit more extended chaotic band responses, thereby potentially increasing the dynamic range and parameter sensitivities of any applied signal and the device operation respectively. In this paper, simple low- to mid-RF signals (periodic waveforms and low BW audio) are transmitted through the closed-loop system and the resulting encryption and recovery at the receiver are examined especially from the perspective of overall robustness of the system

Numerical Examination of Acousto-optic Bragg Interactions for Profiled Lightwaves Using a Transfer Function Formalism

Classically, acousto-optic (AO) interactions comprise scattering of photons by energetic phonons into higher and lower orders. Standard weak interaction theory describes diffraction in the Bragg regime as the propagation of a uniform plane wave of light through a uniform plane wave of sound, resulting in the well-known first- and zeroth-order diffraction. Our preliminary investigation of the nature of wave diffraction and photon scattering from a Bragg cell under intensity feedback with profiled light beams indicates that the diffracted (upshifted photon) light continues to maintain the expected (uniform plane wave) behavior versus the optical phase shift in the cell within a small range of the Q-parameter, and at larger Qs, begins to deviate. Additionally, we observe the asymptotic axial shift of the beam center as predicted by the transfer function formalism