Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 69.98K | Year: 2007
Most UUV payload systems require high navigational accuracy for target localization. Once the vehicle dives from the surface, it is dependent upon a velocity log to maintain navigational accuracy. Thus, DVL bottom lock range effectively limits the water depth in which target localization missions can be prosecuted. The team proposes to pair a 150 kHz DVL with a 600 kHz DVL. The performance of this dual frequency sensor will be less dependent on water column properties because the low frequency transducer will provide sufficient performance margin at high altitudes while the high frequency transducer will provide measurement accuracy at low altitudes that is sufficient for synthetic aperture sonars. The resulting DVL sensor will be ideal for integration with existing inertial navigation systems (e.g. Kearfott, IxSea). The team shall implement a sensor fusion algorithm that augments the DVL velocity estimates with data from the inertial measurement sensors (accelerometers and rate gyros) to produce a more accurate velocity estimate than is possible with the DVL alone. Additionally, auto-tuning algorithms that will reduce configuration requirements for the field operator will be investigated. High fidelity simulation of acoustics, vehicle dynamics, and the operating environment will be integral to the design process.
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 70.00K | Year: 2008
The proposed Glider design concept is based on quantitative tradeoffs between cost and performance. Existing glider technology has been analyzed, and two significant design details have led to a simplified design that will result in a compact, less expensive glider and a simplified delivery/launching mechanism. Using its high fidelity simulation and design tools, VCT has gained important new insights into glider design for performance. This has led to tradeoffs among wing parameters, vertical fin size, Ycg shift and rudder deflection for optimizing turn performance. Combining these discoveries has led to the design of the proposed wingless glider that can achieve equal or better turn performance of the legacy winged gliders. Legacy gliders use a weight-shift method pitch, roll and heading control. This increases the internal complexity of the system as it requires the weight to be mobile, and also increases the size of the pressure housing, effectively increasing the gliders size, weight, buoyancy required, and ultimately, cost. The low-cost expendable glider we are proposing would use a lift-up mast to transmit information. The mast is raised using the same actuator that operates the variable buoyancy engine, but at an extended stroke position.
Padma S.,AIIMS |
Archives of Medical Science | Year: 2010
The NINDS trial demonstrated for the first time the effectiveness of intravenous thrombolysis in improving outcome after acute ischemic stroke. The absolute benefit of this intervention was 11-13% greater chance of being normal or near normal (MRS ≤ 1) at 3 months. However, if patients with severe stroke were considered (NIHSS ≥ 20), the absolute benefit dropped to 5-6%, indicating that IV thrombolysis may not be as effective for large vessel occlusion. This observation was further supported by TCD studies that clearly demonstrated that large artery occlusions had a recanalization rate of 13-18% with IV rt-PA. Intra-arterial thrombolysis achieves recanalization rates of 60-70%. Since tissue viability is clearly important, it is time to stop defining rigid time windows and if there is a large penumbra (20-50%) and the occlusion is in a large artery, there exists a logic and a growing evidence to consider either bridge therapy or direct intra-arterial therapy. Copyright © 2010 Termedia & Banach. Source
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011
Many end stage renal disease (ESRD) patients suffer from anemia due to insufficient endogenous production of erythropoietin (EPO). The discovery of recombinant human EPO (rHuEPO) over 30 years ago has shifted the treatment of anemia for patients on dialysis from blood transfusions to rHuEPO therapy. Many anemia management protocols (AMPs) used by clinicians comprise a set of experience-based rules for weekly-to-monthly titration of rHuEPO doses based on hemoglobin (Hgb) measurements. In order to facilitate the design of an AMP based on formal control design methods, we present a physiologically-relevant erythropoiesis model, and show that its nonlinear dynamics can be approximated using a static nonlinearity, a step that greatly simplifies AMP design. We demonstrate applicability of our results using clinical data. Source
Melby M.K.,University of Delaware |
Melby M.K.,National Institute of Health and Nutrition |
Sievert L.L.,UMASS |
Anderson D.,Queensland University of Technology |
Maturitas | Year: 2011
This paper reviews the methods used in cross-cultural studies of menopausal symptoms with the goal of formulating recommendations to facilitate comparisons of menopausal symptoms across cultures. It provides an overview of existing approaches and serves to introduce four separate reviews of vasomotor, psychological, somatic, and sexual symptoms at midlife. Building on an earlier review of cross-cultural studies of menopause covering time periods until 2004, these reviews are based on searches of Medline, PsycINFO, CINAHL and Google Scholar for English-language articles published from 2004 to 2010 using the terms "cross cultural comparison" and "menopause." Two major criteria were used: a study had to include more than one culture, country, or ethnic group and to have asked about actual menopausal symptom experience. We found considerable variation across studies in age ranges, symptom lists, reference period for symptom recall, variables included in multivariate analyses, and the measurement of factors (e.g., menopausal status and hormonal factors, demographic, anthropometric, mental/physical health, and lifestyle measures) that influence vasomotor, psychological, somatic and sexual symptoms. Based on these reviews, we make recommendations for future research regarding age range, symptom lists, reference/recall periods, and measurement of menopausal status. Recommendations specific to the cross-cultural study of vasomotor, psychological, somatic, and sexual symptoms are found in the four reviews that follow this introduction. © 2011 Elsevier Ireland Ltd. All rights reserved. Source