1,991 research outputs found
Effect of alloy chemistry and exposure conditions on the oxidation of titanium
Multiwall is a new thermal protection system concept for advanced space transportation vehicles. The system consists of discrete panels made up of multiple layers of foil gage metal. Titanium is the proposed candidate metal for multiwall panels in the reentry temperature range up to 675 C. Oxidation and embrittlement are the principal concerns related to the use of Ti in heat shield applications. The results of a broad study on the oxidation kinetics of several titanium alloys subjected to different exposure conditions are described. The alloys include commercially pure titanium, Ti-6Al-4V, and Ti-6Al-2Sn-4Zr-2Mo. Oxidation studies were performed on these alloys exposed at 704 C in 5-760 torr air pressure and 0 to 50% relative humidity. The resulting weight gains were correlated with oxide thickness and substrate contamination. The contamination depth and weight gains due to solid solutioning were obtained from microhardness depth profiles and hardness versus weight percent oxygen calibration data
Development of a ROT22 - DATAMAP interface
This report (Contract NAS2-10331- Mod 10), outlines the development and validation of an interface between the three-dimensional transonic analysis program ROT22 and the Data from Aeromechanics Test and Analytics-Management and Analysis Package (DATAMAP). After development of the interface, the validation is carried out as follows. First, the DATAMAP program is used to analyze a portion of the Tip Aerodynamics and Acoustics Test (TAAT) data. Specifically, records 2872 and 2873 are analyzed at an azimuth of 90 deg, and record 2806 is analyzed at 60 deg. Trim conditions for these flight conditions are then calculated using the Bell performance prediction program ARAM45. Equivalent shaft, pitch, and twist angles are calculated from ARAM45 results and used as input to the ROT22 program. The interface uses the ROT22 results and creates DATAMAP information files from which the surface pressure contours and sectional pressure coefficients are plotted. Twist angles input to ROT22 program are then iteratively modified in the tip region until the computed pressure coefficients closely match the measurements. In all cases studied, the location of the shock is well predicted. However, the negative pressure coefficients were underpredicted. This could be accounted for by blade vortex interaction effects
Re-equilibration after quenches in athermal martensites:Conversion-delays for vapour to liquid domain-wall phases
Entropy barriers and ageing states appear in martensitic
structural-transition models, slowly re-equilibrating after temperature
quenches, under Monte Carlo dynamics. Concepts from protein folding and ageing
harmonic oscillators turn out to be useful in understanding these
nonequilibrium evolutions. We show how the athermal, non-activated delay time
for seeded parent-phase austenite to convert to product-phase martensite,
arises from an identified entropy barrier in Fourier space. In an ageing state
of low Monte Carlo acceptances, the strain structure factor makes
constant-energy searches for rare pathways, to enter a Brillouin zone `golf
hole' enclosing negative energy states, and to suddenly release entropically
trapped stresses. In this context, a stress-dependent effective temperature can
be defined, that re-equilibrates to the quenched bath temperature.Comment: 11 pages, 12 figures. Under process with Phys. Rev. B (2015
Surface pressure measurements at two tips of a model helicopter rotor in hover
Surface pressures were measured near the tip of a hovering single-bladed model helicopter rotor with two tip shapes. The rotor had a constant-chord, untwisted blade with a square, flat tip which could be modified to a body-of-revolution tip. Pressure measurements were made on the blade surface along the chordwise direction at six radial stations outboard of the 94 percent blade radius. Data for each blade tip configuration were taken at blade collective pitch angles of 0, 6.18 and 11.4 degrees at a Reynolds number of 736,000 and a Mach number of 0.25 both based on tip speed. Chordwise pressure distributions and constant surface pressure contours are presented and discussed
A Qualitative Study on the Feasibility and Benefits of Foot Hygiene Measures Practiced by Patients with Brugian Filariasis
Disability alleviation is an important component of Global
Programme for Elimination of Lymphatic Filariasis'. In Brugia malayi
infection the disability is largely due to acute attacks of
adenolymphangitis (ADL), which frequently prevent patients from
attending their normal activities, causing much suffering and
economic loss. The foot care programme has been shown to reduce
the frequency and severity of these episodes. In the present study
we used semi-structured interviews to evaluate the impact of the
foot care in 127 patients with brugian filariasis. They were previously
trained in this procedure and were advised to practice it regularly,
unsupervised. All except one could recollect the various components
of foot hygiene and were practicing it regularly. They were aware of
the factors causing ADL attacks and were able to avoid them. Majority
(95.2%) expressed their happiness with the relief provided by foot
care, which prevented or reduced the ADL episodes. The motivation
was such that they transmitted this knowledge to others suffering in
the community and even physically helped them to carry out foot
care. This study fully endorses the advocacy of foot care programme
as an easy to carry out, effective, sustainable and economically
feasible ,procedure to prevent acute ADL attacks
Forecasting Stock Time-Series using Data Approximation and Pattern Sequence Similarity
Time series analysis is the process of building a model using statistical
techniques to represent characteristics of time series data. Processing and
forecasting huge time series data is a challenging task. This paper presents
Approximation and Prediction of Stock Time-series data (APST), which is a two
step approach to predict the direction of change of stock price indices. First,
performs data approximation by using the technique called Multilevel Segment
Mean (MSM). In second phase, prediction is performed for the approximated data
using Euclidian distance and Nearest-Neighbour technique. The computational
cost of data approximation is O(n ni) and computational cost of prediction task
is O(m |NN|). Thus, the accuracy and the time required for prediction in the
proposed method is comparatively efficient than the existing Label Based
Forecasting (LBF) method [1].Comment: 11 page
Nutritional evaluation of an indigenous low cost protein food
A study of supplementary feeding was conducted on children with a protein food (edible fish powder in the form of 'chutney') for 35 days and the effect assessed periodically. The most noticeable effect was gain in weight and mid arm circumference in children. 35% children showed a weight gain of 1 kg, 27% 0.5 kg, 21% 1.5 kg and 2.5% 2.5 kg. 48% children registered an increase in their mid-arm circumference by 0.5 cm, 16% 1 cm and 2.5% 1.5 cm. 10% children did not gain weight. However, these children had intercurrent infections like measles, whooping cough and asthma
IOBR: Interoperable bee-hive routing in a heterogeneous multi-radio network
WiMAX and WiFi are the two proliferating wireless technologies with different physical and Media Access Control (MAC) layers. Today, WiFi radio is present in almost all the devices, and most of the devices are equipped with WiMAX radio. Both these technologies can be utilized, if the devices are equipped with both of them, to improve the performance. To cope up with the scenario, a method for routing in a heterogeneous infrastructure based mesh network is proposed. The heterogeneous network consists of a coordinator node and a subscriber node. In this paper, we assume that the coordinator nodes are equipped with both WiMAX and WiFi radios, whereas, the subscriber nodes need not have WiMAX radio. The protocol used for routing data is based on the bee-hive algorithm, in which the entire network is divided into foraging zones/regions. We propose a technique in which the intra-foraging zone communication happens through WiFi and the nodes across the foraging zone communicate via the coordinator using WiMAX. It is observed through simulations that our technique improves the overall network performance by making use of both the radios efficiently
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