Planar Detonation Wave Initiation in Large-Aspect-Ratio Channels

In this study, two initiator designs are presented that are able to form planar detonations with low input energy in large-aspect-ratio channels over distances corresponding to only a few channel heights. The initiators use a single spark and an array of small channels to shape the detonation wave. The first design, referred to as the static initiator, is simple to construct as it consists of straight channels which connect at right angles. However, it is only able to create planar waves using mixtures that can reliably detonate in its small-width channels. An improved design, referred to as the dynamic initiator, is capable of detonating insensitive mixtures using an oxyacetylene gas slug injected into the initiator shortly before ignition, but is more complex to construct. The two versions are presented next, including an overview of their design and operation. Design drawings of each initiator are available elsewhere [7]. Finally, photographs and pressure traces of the resulting planar waves generated by each device are shown

Analytical Model for the Impulse of Single-Cycle Pulse Detonation Tube

An analytical model for the impulse of a single-cycle pulse detonation tube has been developed and validated against experimental data. The model is based on the pressure history at the thrust surface of the detonation tube. The pressure history is modeled by a constant pressure portion, followed by a decay due to gas expansion out of the tube. The duration and amplitude of the constant pressure portion is determined by analyzing the gasdynamics of the self-similar flow behind a steadily moving detonation wave within the tube. The gas expansion process is modeled using dimensional analysis and empirical observations. The model predictions are validated against direct experimental measurements in terms of impulse per unit volume, specific impulse, and thrust. Comparisons are given with estimates of the specific impulse based on numerical simulations. Impulse per unit volume and specific impulse calculations are carried out for a wide range of fuel–oxygen–nitrogen mixtures (including aviation fuels) of varying initial pressure, equivalence ratio, and nitrogen dilution. The effect of the initial temperature is also investigated. The trends observed are explained using a simple scaling analysis showing the dependency of the impulse on initial conditions and energy release in the mixture

Improved AURA k-Nearest Neighbour approach

The k-Nearest Neighbour (kNN) approach is a widely-used technique for pattern classification. Ranked distance measurements to a known sample set determine the classification of unknown samples. Though effective, kNN, like most classification methods does not scale well with increased sample size. This is due to their being a relationship between the unknown query and every other sample in the data space. In order to make this operation scalable, we apply AURA to the kNN problem. AURA is a highly-scalable associative-memory based binary neural-network intended for high-speed approximate search and match operations on large unstructured datasets. Previous work has seen AURA methods applied to this problem as a scalable, but approximate kNN classifier. This paper continues this work by using AURA in conjunction with kernel-based input vectors, in order to create a fast scalable kNN classifier, whilst improving recall accuracy to levels similar to standard kNN implementations

Arthroscopic transosseous rotator cuff repair: A prospective study on cost savings, surgical time, and outcomes

Objectives: Health expenditures in the United States are outpacing national income, and affordability has become a major policy issue. Over 500,000 rotator cuff repairs (RCR) are performed annually in the United States making RCR a potential source of cost savings. Arthroscopic trans-osseous equivalent (TOE) repair using a double row of anchors has shown superior biomechanical strength compared to other techniques, but at a higher cost. The arthroscopic transosseous (TO) repair is a novel technique allowing arthroscopic rotator cuff repair to be performed without suture anchors. Arthroscopic TO repair may be a means to provide similarly excellent patient outcomes while lowering the cost of care. The primary purpose is to compare the price differential and time of surgery for an arthroscopic rotator cuff repair using anchorless TO repair verses an anchor trans-osseous equivalent (TOE) repair. A secondary purpose of the study was to evaluate outcomes at 6 months postoperatively. Methods: A prospective, case-controlled study evaluating arthroscopic rotator cuff repair using two techniques was performed. The study group consisting of 21 patients undergoing TO repair was compared to a control group consisting of 22 patients undergoing TOE repair. The groups were controlled for size of tear, biceps treatment, acromioplasty, distal clavicle excision, and labral pathology. The primary outcome measures were surgical time as well as total cost of implants and equipment for each surgery, determined by an independent third party, Atlanticare Hospital. Secondary outcomes were changes in the SST, VAS, and SANE scores. Results: Mean total surgical implant/equipment cost per procedure for TOE repair was $2348.03 (SD 490.30) and for TO repair was$1204.97 (SD 330.69; p\u3c0.0001). Mean cut to close time for TOE repair was 85 minutes (95% CI is 77-90) verses 74 (95% CI = 71-98) for TO repair. A log rank test revealed no difference in time (p =0.95). A linear regression model was developed to evaluate the change in SST, VAS, and SANE scores from pre-op to 6 months follow-up. Our study was underpowered but no difference in outcome was observed. Conclusion: Arthroscopic TO rotator cuff repair is a cost savings and time neutral technique compared to TOE repair. A mean of $1100 can be saved in surgical cost per case. In a country that performs over 500,000 RCRs annually, utilizing a TO repair technique can provide substantial cost savings to the healthcare system. © The Author(s) 2015

China’s Blue Soft Power

On 3 September 2014, almost six years since Chinese warships first entered the Gulf of Aden to fulfill antipiracy duties, China Central Television (CCTV)–8 aired the first episode of “In the Gulf of Aden” (舰在亚丁湾). The multidozen-episode program, designed to “ignite raging patriotism” (燃起熊 熊爱国心), given evening prime-time status, and attracting a popular audience with a star-studded cast, explores in dramatic fashion Beijing’s experience fighting modern piracy

No Substitute for Experience

The twenty-sixth of December 2012 marked an important date in Chinese military history—the fourth anniversary of China\u27s furthest and most extensive naval operations to date, the ongoing antipiracy deployments in the Gulf of Aden. In the first-ever simultaneous three-fleet public display, China\u27s North Sea Fleet, East Sea Fleet, and South Sea Fleet all held open day activities. The guided-missile destroyers Qingdao, Guangzhou, and Shenzhen and guided-missile frigate Zhoushan, together with their associated helicopters and personnel, were visited by more than eight thousand people from all sectors of the society at the port cities after which they are named.https://digital-commons.usnwc.edu/cmsi-red-books/1009/thumbnail.jp