163 research outputs found
The cross-section of Asia-Pacific mortality dynamics: Implications for longevity risk sharing
We study the dynamics of longevity risk across a subset of cou ntries in the Asia-Pacific (APAC) region. We use hand-collected and existing data on age-spec ific mortality rates from emerging and developed economies, to understand how secular changes in mortality vary within and across APAC countries. We use our results to identify cross-hedging opportunities among longevity risk exposures in the APAC region. We also introduce k -forward contracts, which offer natural risk sharing opportunities to hedgers in different countries. We consider the example of Korea and Japan as a case stud
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Effect of clocking on compressor noise generation
The effect of stator clocking on the acoustic noise generation characteristics in an axial high-pressure compressor is analysed. A realistic geometry with one-and-a-half stages is assessed using high fidelity and low-order numerical methods for different clocking positions at approach operating conditions.
The compressor efficiency and the acoustic noise emission is found to vary insignificantly between the simulated clocking configurations. Nonetheless, the pressure distribution is altered significantly right upstream of the inlet guide vanes. Although the cut-on modes exhibit at least 10 dB higher amplitudes, the cut-off modes contribute decisively to the wave pattern in the near field. Optimal acoustic liner design can expand on the differently evolving interference pattern of acoustic waves at discrete frequencies.
The low-order model is found to predict the directionality of the acoustic waves and the cut-on criteria for the individual modes in excellent agreement with the high fidelity simulations. However, the phase cannot be estimated due to the simplicity of the low-order formulation.The authors wish to express their sincere gratitude to Rolls-Royce plc for the permission to publish this paper, which partly developed through the Rolls-Royce plc and Innovate UK Aerospace Technology Institute funded research programme, ACAPELLA
The evolution of the double-horse chariots from the bronze age to the Hellenistic times
Light chariots with spoked wheels were developed initially in Syria or Northern Mesopotamia at about the beginning of the 2nd millennium B.C. and quickly propagated all over Middle East. The two-wheeled horsedrawn chariot was one of the most important inventions in history. It gave humanity its first concept of personal transport, and for two thousand years it was the key technology of war. Information on chariots of Mesopotamia, Egypt, the Mycenaean and Archaic Greece, China, and Europe, with light and flexible spoked wheels from extant findings of ancient chariots, stone reliefs, and vase paintings is used for a design study of the dual chariot and its evolution in the centuries. Design reconstruction of the dual chariot found in Anyang China is incorporated herewith to prove that its development contains the seeds of a primitive design activity
The evolution of the double-horse chariots from the bronze age to the Hellenistic times
Light chariots with spoked wheels were developed initially in Syria or Northern Mesopotamia at about the beginning of the 2nd millennium B.C. and quickly propagated all over Middle East. The two-wheeled horsedrawn chariot was one of the most important inventions in history. It gave humanity its first concept of personal transport, and for two thousand years it was the key technology of war. Information on chariots of Mesopotamia, Egypt, the Mycenaean and Archaic Greece, China, and Europe, with light and flexible spoked wheels from extant findings of ancient chariots, stone reliefs, and vase paintings is used for a design study of the dual chariot and its evolution in the centuries. Design reconstruction of the dual chariot found in Anyang China is incorporated herewith to prove that its development contains the seeds of a primitive design activity
A Partitioning Methodology for Accelerating Applications in Hybrid Reconfigurable Platforms *
Abstrac
The Impact of Dance-Specific Neuromuscular Conditioning and Injury Prevention Training on Motor Control, Stability, Balance, Function and Injury in Professional Ballet Dancers: A Mixed-Methods Quasi-Experimental Study
# Background
Professional ballet dancers suffer high injury rates and are less likely than other athletes to specifically train to improve muscular strength, coordination, agility, speed and motor control because of heavy training demands, aesthetic appearances and financial barriers.
# Hypothesis/Purpose
The purpose of this study was to examine the effects of a supplemental conditioning program on professional and pre-professional contemporary ballet dancers. The authors hypothesized that those participating in a training program would reduce injury rate by improving their motor control, stability, balance and physical function. The authors aimed to observe the feasibility and qualitative phenomena related to a conditioning program from the dancer’s perspective.
# Study Design
A mixed-methods study; within subject quasi-experimental design and qualitative interviews.
# Methods
Six professional classical and contemporary ballet dancers completed the five-week conditioning and injury prevention training program. Non-parametric analysis of baseline, posttest and four-month follow-up physical performance measures, subjective outcomes, and qualitative follow-up interviews, were reported.
# Results
Significant post-test improvements included: The Dance Functional Outcome Survey (Z= -2.2, *p*= 0.04), composite Modified Star Excursion Balance Test (Z= -2.2, *p*= 0.03 bilaterally), Single Leg Hop for Distance (Z= -2.02, *p*= 0.04), and Upper Extremity Closed Kinetic Chain Test (Z=-2.03, *p*= 0.04). Significant changes from baseline to the four-month follow up remained for: (1) Dance Functional Outcome Survey (Z= -2.2, *p*= 0.03), (2) Single Leg Hop for Distance (Z= -2.2, *p*= 0.03), and (3) Modified Star Excursion Balance Test composite maximum reach for the left lower extremity (Z= -2.2, *p*= 0.03).
# Conclusion
Completing a conditioning and prevention program for professional ballet dancers was related to improved function, balance, hop distance/stability and upper extremity stability. Dancers found the program beneficial, identified barriers to participation, and elucidated factors making the program feasible and successful. More research is necessary to determine the effect of such programs on injury incidence.
# Level of evidence
3
Simultaneous 13N-Ammonia and gadolinium first-pass myocardial perfusion with quantitative hybrid PET-MR imaging: a phantom and clinical feasibility study
Background
Positron emission tomography (PET) is the non-invasive reference standard for myocardial blood flow (MBF) quantification. Hybrid PET-MR allows simultaneous PET and cardiac magnetic resonance (CMR) acquisition under identical experimental and physiological conditions. This study aimed to determine feasibility of simultaneous 13N-Ammonia PET and dynamic contrast-enhanced CMR MBF quantification in phantoms and healthy volunteers.
Methods
Images were acquired using a 3T hybrid PET-MR scanner. Phantom study: MBF was simulated at different physiological perfusion rates and a protocol for simultaneous PET-MR perfusion imaging was developed. Volunteer study: five healthy volunteers underwent adenosine stress. 13N-Ammonia and gadolinium were administered simultaneously. PET list mode data was reconstructed using ordered subset expectation maximisation. CMR MBF was quantified using Fermi function-constrained deconvolution of arterial input function and myocardial signal. PET MBF was obtained using a one-tissue compartment model and image-derived input function.
Results
Phantom study: PET and CMR MBF measurements demonstrated high repeatability with intraclass coefficients 0.98 and 0.99, respectively. There was high correlation between PET and CMR MBF (r = 0.98, p < 0.001) and good agreement (bias − 0.85 mL/g/min; 95% limits of agreement 0.29 to − 1.98). Volunteer study: Mean global stress MBF for CMR and PET were 2.58 ± 0.11 and 2.60 ± 0.47 mL/g/min respectively. On a per territory basis, there was moderate correlation (r = 0.63, p = 0.03) and agreement (bias − 0.34 mL/g/min; 95% limits of agreement 0.49 to − 1.18).
Conclusion
Simultaneous MBF quantification using hybrid PET-MR imaging is feasible with high test repeatability and good to moderate agreement between PET and CMR. Future studies in coronary artery disease patients may allow cross-validation of techniques
Concentrating Solar Thermal Technologies – Status, Cost and Research Trends
This article presents an overview of the status of CST technologies, their cost, and their future trends. The information regarding the trends in CST technologies is based on the informed opinion of the authors, many of which have decades of experience in the CST field in academia and industry. Thus, it does not pretend to be an exhaustive list of all lines of research and commercial innovations being explored around the world, but a summary of the lines of research that the institutions and groups that the authors belong to are explorin
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