All-fiber fused directional coupler for highly efficient spatial mode conversion

We model and demonstrate a simple mode selective all-fiber coupler capable of exciting specific higher order modes in two- and few-mode fibres with high efficiency and purity. The coupler is based on inter-modally phase-matching the propagation constants in each arm of the asymmetric fused coupler, formed by dissimilar fibres. At a specific coupler diameter, the launched fundamental LP01 mode is coupled into the higher order mode (LP11, LP21, LP02) in the other arm, over a broadband wavelength range around 1550 nm. Unlike other techniques, the demonstrated coupler is composed of a multimode fiber that is weakly fused with a phase matched conventional single mode telecom fiber (SMF-28). The beating between the supermodes at the coupler waist produces a periodic power transfer between the two arms, and therefore, by monitoring the beating while tapering, it is possible to obtain optimum selection for the desired mode. High coupling efficiencies in excess of 90% for all the higher order modes were recorded over 100 nm spectral range, while insertion losses remain as low as 0.5 dB. Coupling efficiency can be further enhanced by performing slow tapering at high temperature, in order to precisely control the coupler cross-section geometry

Final Design Report for an Automatic Diffraction Grating

The Automatic Diffraction Grating project explored using said technology to measure the angular separation between binary stars. This system would be a dramatic improvement from the current, fixed and manually adjusted diffraction gratings in use, increasing the capability of observatories to conduct autonomous studies of binary systems. Ideally, realizing such a system would be accomplished using a simple design and off the shelf parts, so that the project could easily replicated. The design of this system was approached with a broad look at the possible mechanisms that could be used to effectively construct an Automatic Diffraction Grating, as well as extensive testing on the effectiveness of these systems. After a functional design and prototype system was developed, it was determined that while an Automatic Diffraction Grating system is feasible, achieving a precision design would require custom, precision machined parts

Sample Size for Biosimilar Trials: In Defense of Synthesis

Biosimilars are biological products similar to, but not the same as, the innovator products. Both the European Medicines Agency and the Food and Drug Administration have released detailed guidance on the development of biosimilars. This guidance requires the pivotal phase 3 clinical study to have an equivalence design, which means that the study objective is to demonstrate that one treatment is neither "worse than" nor "better than" the other by some clinically unimportant" amount. The most critical and controversial step in designing such a study is the choice of equivalence margin, as this determines the conclusion of the study. In this paper, we outline the methodology for determining an equivalence margin and, through case studies on biosimilar trastuzumab (HERCEPTIN ) and biosimilar bevacizumab (AVASTIN), explain the challenges of applying this in practice and why the synthesis method should be given greater consideration by regulatory authorities and biosimilar developers

Echo statistics associated with discrete scatterers: A tutorial on physics-based methods

Author Posting. © Acoustical Society of America, 2018. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America, 144(6), (2018): 3124-3171. doi: 10.1121/1.5052255.When a beam emitted from an active monostatic sensor system sweeps across a volume, the echoes from scatterers present will fluctuate from ping to ping due to various interference phenomena and statistical processes. Observations of these fluctuations can be used, in combination with models, to infer properties of the scatterers such as numerical density. Modeling the fluctuations can also help predict system performance and associated uncertainties in expected echoes. This tutorial focuses on “physics-based statistics,” which is a predictive form of modeling the fluctuations. The modeling is based principally on the physics of the scattering by individual scatterers, addition of echoes from randomized multiple scatterers, system effects involving the beampattern and signal type, and signal theory including matched filter processing. Some consideration is also given to environment-specific effects such as the presence of boundaries and heterogeneities in the medium. Although the modeling was inspired by applications of sonar in the field of underwater acoustics, the material is presented in a general form, and involving only scalar fields. Therefore, it is broadly applicable to other areas such as medical ultrasound, non-destructive acoustic testing, in-air acoustics, as well as radar and lasers.The content of this work is based on research conducted in the past from years of support from the U.S. Office of Naval Research and the Woods Hole Oceanographic Institution, Woods Hole, MA. Writing of the manuscript by W.-J.L. was also supported by the Science and Engineering Enrichment and Development Postdoctoral Fellowship from the Applied Physics Laboratory, University of Washington, WA. The authors are grateful to Dr. Benjamin A. Jones of the Naval Postgraduate School, Monterey, CA for his thoughtful suggestions on an early draft of the manuscript. The authors are also grateful to the reviewer for the in-depth and constructive recommendations. W.-J.L. and K.B. contributed equally to this work.2019-06-0

A Virtual Reality–Supported Intervention for Pulmonary Rehabilitation of Patients With Chronic Obstructive Pulmonary Disease: Mixed Methods Study

Background: Uptake of traditional pulmonary rehabilitation classes from Chronic Obstructive Pulmonary Disease (COPD) patients is poor due to personal factors preventing accessibility to the venue. Therefore, there is a need for innovative methods of pulmonary rehabilitation and Virtual Reality (VR) could be the promising technology for COPD patients to access services remotely. Objectives: This study aims to investigate whether VR improves COPD patient’s compliance with pulmonary rehabilitation, particularly vulnerable patient group (MRC four or five), and whether VR provides a credible alternative to traditional pulmonary rehabilitation programmes. Methods: Eight-week patient trial using an innovative VR pulmonary rehabilitation programme. Purposive sample of ten COPD patients graded MRC four or five registered at a selected healthcare centre and a hospital in Cumbria, UK. Qualitative (focus groups and interviews) data were collected and to further support the qualitative findings, quantitative data (self-report patient surveys) were also gathered before and after the eight-week trial. The five self-report surveys included the Patient Activation Measure (PAM), Generalized Anxiety Disorder (GAD-7), Patient Health Questionnaire (PHQ-9), Short Physical Performance Battery (SPPB), and the Edmonton Frail Scale (EFS). Results: Using thematic analysis for the qualitative data, eleven themes emerged specific to delivering pulmonary rehabilitation using VR. The quantitative data further supports the qualitative findings by revealing significant improvements in all physical measures. Conclusion: Overall, this study demonstrates how remotely supervised VR-based pulmonary rehabilitation could help to overcome current issues and limitations associated with providing this service to COPD patients at scal

Orientation dependence of broadband acoustic backscattering from live squid

Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 4461-4475, doi:10.1121/1.3701876.A controlled laboratory experiment of broadband acoustic backscattering from live squid (Loligo pealeii) was conducted using linear chirp signals (60–103 kHz) with data collected over the full 360° of orientation in the lateral plane, in <1° increments. The acoustic measurements were compared with an analytical prolate spheroid model and a three-dimensional numerical model with randomized squid shape, both based on the distorted-wave Born approximation formulation. The data were consistent with the hypothesized fluid-like scattering properties of squid. The contributions from the front and back interfaces of the squid were found to dominate the scattering at normal incidence, while the arms had a significant effect at other angles. The three-dimensional numerical model predictions out-performed the prolate spheroid model over a wide range of orientations. The predictions were found to be sensitive to the shape parameters, including the arms and the fins. Accurate predictions require setting these shape parameters to best describe the most probable squid shape for different applications. The understanding developed here serves as a basis for the accurate interpretation of in situ acoustic scattering measurements of squid.Funding for this research was provided by the Taiwan Merit Scholarship (NSC-095-SAF-I-564-021-TMS) and the Academic Program Office at WHOI

Modified Linear Theory Aircraft Design Tools and Sonic Boom Minimization Strategy Applied to Signature Freezing via F-function Lobe Balancing

Commercial supersonic travel has strong business potential; however, in order for the Federal Aviation Administration to lift its ban on supersonic flight overland, designers must reduce aircraft sonic boom strength to an acceptable level. An efficient methodology and associated tools for designing aircraft for minimized sonic booms are presented. The computer-based preliminary design tool, RapidF, based on modified linear theory, enables quick assessment of an aircraft's sonic boom with run times less than 30 seconds on a desktop computer. A unique feature of RapidF is that it tracks where on the aircraft each segment of the of the sonic boom came from, enabling precise modifications, speeding the design process. Sonic booms from RapidF are compared to flight test data, showing that it is capability of predicting a sonic boom duration, overpressure, and interior shock locations. After the preliminary design is complete, scaled flight tests should be conducted to validate the low boom design. When conducting such tests, it is insufficient to just scale the length; thus, equations to scale the weight and propagation distance are derived. Using RapidF, a conceptual supersonic business jet design is presented that uses F-function lobe balancing to create a frozen sonic boom using lifting surfaces. The leading shock is reduced from 1.4 to 0.83 psf, and the trailing shock from 1.2 to 0.87 psf, 41% and 28% reductions respectfully. By changing the incidence angle of the surfaces, different sonic boom shapes can be created, and allowing the lobes to be re-balanced for new flight conditions. Computational fluid dynamics is conducted to validate the sonic boom predictions. Off-design analysis is presented that varies weight, altitude, Mach number, and propagation angle, demonstrating that lobe-balance is robust. Finally, the Perceived Level of Loudness metric is analyzed, resulting in a modified design that incorporates other boom minimization techniques to further reduce the sonic boom

A study of electronic commerce and tourism : e-commerce system evaluation and consumer behaviour in the e-business environment

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Probing the A1 to L10 Transformation in FeCuPt Using the First Order Reversal Curve Method

The A1- L10 phase transformation has been investigated in (001) FeCuPt thin films prepared by atomic-scale multilayer sputtering and rapid thermal annealing (RTA). Traditional x-ray diffraction is not always applicable in generating a true order parameter, due to non-ideal crystallinity of the A1 phase. Using the first-order reversal curve (FORC) method, the A1 and L10 phases are deconvoluted into two distinct features in the FORC distribution, whose relative intensities change with the RTA temperature. The L10 ordering takes place via a nucleation-and-growth mode. A magnetization-based phase fraction is extracted, providing a quantitative measure of the L10 phase homogeneity.Comment: 17 pages, 5 figures, 4 page supplementary material (4 figures