ASTROP2 users manual: A program for aeroelastic stability analysis of propfans

A user's manual is presented for the aeroelastic stability and response of propulsion systems computer program called ASTROP2. The ASTROP2 code preforms aeroelastic stability analysis of rotating propfan blades. This analysis uses a two-dimensional, unsteady cascade aerodynamics model and a three-dimensional, normal-mode structural model. Analytical stability results from this code are compared with published experimental results of a rotating composite advanced turboprop model and of nonrotating metallic wing model

Keeping the dream alive: Managing the Space Station Program, 1982 to 1986

The management is described and analyzed of the formative years of the NASA Space Station Program (1982 to 1986), beginning with the successful initiative for program approval by Administrator James M. Beggs through to the decision to bring program management to Reston, Virginia. Emphasis is on internal management issues related to the implementation of the various phases of the program. Themes examined are the problem of bringing programmatic and institutional interests together and focusing them to forward the program; centralized versus decentralized control of the program; how the history of NASA and of the individual installations affected the decisions made; and the pressure from those outside NASA. The four sections are: (1) the decision to build the space station, (2) the design of the management experiment, (3) the experiment comes to life, and (4) the decision reversal

Analytical flutter investigation of a composite propfan model

A theoretical model and an associated computer program for predicting subsonic bending-torsion flutter in propfans are presented. The model is based on two-dimensional unsteady cascade strip theory and three-dimensional steady and unsteady lifting surface aerodynamic theory in conjunction with a finite element structural model for the blade. The analytical results compare well with published experimental data. Additional parametric studies are also presented illustrating the effects on flutter speed of steady aeroelastic deformations, blade setting angle, rotational speed, number of blades, structural damping, and number of modes

Stellar Mixing and the Primordial Lithium Abundance

We compare the properties of recent samples of the lithium abundances in halo stars to one another and to the predictions of theoretical models including rotational mixing, and we examine the data for trends with metal abundance. We find from a KS test that in the absence of any correction for chemical evolution, the Ryan, Norris, & Beers (1999} sample is fully consistent with mild rotational mixing induced depletion and, therefore, with an initial lithium abundance higher than the observed value. Tests for outliers depend sensitively on the threshold for defining their presence, but we find a 10$--$45% probability that the RNB sample is drawn from the rotationally mixed models with a 0.2 dex median depletion (with lower probabilities corresponding to higher depletion factors). When chemical evolution trends (Li/H versus Fe/H) are treated in the linear plane we find that the dispersion in the RNB sample is not explained by chemical evolution; the inferred bounds on lithium depletion from rotational mixing are similar to those derived from models without chemical evolution. We find that differences in the equivalent width measurements are primarily responsible for different observational conclusions concerning the lithium dispersion in halo stars. The standard Big Bang Nucleosynthesis predicted lithium abundance which corresponds to the deuterium abundance inferred from observations of high-redshift, low-metallicity QSO absorbers requires halo star lithium depletion in an amount consistent with that from our models of rotational mixing, but inconsistent with no depletion.Comment: 39 pages, 9 figures; submitted Ap

Damage Assessment in Concrete Structures using PZT patches

Piezoelectric based PZT smart sensors offer significant potential for continuously monitoring the development and progression of internal damage in concrete structures. PZT-based damage sensors consisting of piezo-electric patches, which are bonded to the surface of a concrete structure can be developed for assessing the damage progression of concrete members. The primary challenge in developing a PZT-based sensor lies in developing a methodology to infer about the level of damage in the material from measurement. Changes in the resonant behavior in the measured electrical conductance obtained from electro-mechanical (EM) response of a PZT bonded to a concrete substrate is investigated for increasing levels of damage. The sensitivity of EM impedance- based measurements to level of damage in concrete is reported. Incipient damage in the form of microcracks in the concrete substrate produces a change in the electrical conductance signature associated with the resonant peaks. Changes in the conductance resonant signature from EM conductance measurement are detected before visible signs of cracking. The root mean square deviation of the conductance signature at resonant peaks is shown to accurately reflect the level of damage in the substrate. The findings presented here provide a basis for developing a sensing methodology using PZT patches for continuous monitoring of concrete structures

PZT Sensor Arrays for Integrated Damage Monitoring in Concrete Structures

The broad objective of the work reported here is to provide a fundamental basis for the use of Lead Zirconate Titanate (PZT) patches in damage detection of concrete structures. Damage initiation in concrete structures starts with distributed microcracks, which eventually localize to form cracks. By the time surface manifestation in the form of visible cracking appears there may be significant degradation of the capacity of the structure. Early detection of damage, before visible signs appear on the surface of the structure is essential to initiate early intervention, which can effectively increase the service life of structures. Development of monitoring methodologies involves understanding the underlying phenomena and providing a physical basis for interpreting the observed changes in the parameters which are sensed. PZT is a piezoelectric material, which has a coupled constitutive relationship. In the case of the PZT patches bonded to a concrete structure, any sensing strategy requires developing an understanding of the coupled electromechanical (EM) response of the PZT-concrete system. The challenges associated with the use of PZT patches for damage monitoring in a concrete substrate include providing the following: a clear understanding of the fundamental response of the PZT patch when bonded to a concrete substrate; interpretation of the coupled response of the PZT patch under load induced damage; and development of an efficient, continuous monitoring methodology to sense a large area of the concrete substrate. Due to a lack of a fundamental basis, the use of PZT patches in concrete structures often involves inferring the measured response using model-based procedures. The work outlined in this thesis addresses the key issue of developing the theoretical basis and providing an experimental validation for PZT-based damage monitoring methodology for concrete structures. A fundamental understanding of response of the PZT patch when bonded to concrete substrate is developed. The outcome of the work is an integrated local and distributed sensing methodology for concrete structures by combining the electromechanical impedance and stress wave propagation methods using an array of bonded PZT patches. The work presented in this thesis is focused on using PZT patches bonded to a concrete substrate. A fundamental understanding of the coupled electromechanical behaviour of a PZT patch under an applied electrical excitation in an electrical impedance (EI) measurement, is developed. The influence of the substrate size and its material properties on the frequency dependent EI response of a PZT patch is investigated using concrete substrates of different sizes. The dynamic response of a PZT patch is shown to consist of resonance modes of the PZT patch with superimposed structural response. The resonance behaviour of the PZT patch is shown to be influenced by the material properties of the substrate. The size dependence in the EI response of a PZT patch bonded to a concrete substrate is produced by the dynamic behaviour of the structure. The size of the local zone of the concrete material substrate in the vicinity of the bonded PZT patch, which influences the frequency dependent EI response of the PZT patch is identified. For each resonant mode, a local zone of influence, which is free from the influence of boundary is identified. The dynamic response of the PZT resonant mode is influenced by the elastic material properties and damping within the zone of influence. The structural effects of the concrete substrate produced by the finite size of the specimen are separated from the material effects produced by the material properties and the material damping in the coupled EM response of the bonded PZT patch. The influence of size of the concrete substrate on the coupled impedance response of the PZT is identified with peaks of structural resonance, which are superimposed on the resonant peaks of the bonded PZT patch The EI response of the PZT patch when bonded to concrete for detecting load-induced damage from distributed microcrack to localized cracks within the zone of influence of the PZT patch is investigated. Using an approach which combines an understanding of the coupled EM constitutive behaviour of PZT with experimental validation, a methodology is developed to decouple the effects of stress and damage in the substrate on the coupled EM response of a PZT patch. The features in the EI signature of a bonded PZT patch associated with stress and damage are identified. An increasing level of distributed damage in the concrete substrate produces a decrease in the magnitude and the frequency of the resonant peak of the bonded PZT patch. The substrate stress produces a counter acting effect in the EI spectrum of the bonded PZT patch. A measurement procedure for the use of bonded PZT patches for continuous monitoring of stress-induced damage in the form of distributed microcracks in a structure under loading is developed. An integrated methodology for damage monitoring in concrete structures is developed by combining the EI method for local sensing and the stress wave propagation-based method in a distributed sensing mode. An array of surface mounted PZT sensors are deployed on a concrete beam. The EI measurements from individual PZT sensors are used for detecting damage within the local zone of influence. PZT sensor pairs are used as actuators and sensors for distributed monitoring using stress wave propagation. A stress-induced crack is introduced in a controlled manner. It is detected very accurately from the full-field displacement measurement obtained using digital image correlation. The crack opening profile in concrete produced by the fracture is established from the surface displacement measurements. From the measurements of bonded PZTs, the localized crack is detected in the zone of influence by EI. The change in compliance of the material medium due to a localized crack is small and it is reflected in the smaller change in the measured EI when compared to distributed damage. Stress wave based measurements sensitively detect crack openings on the order of 10m. The material discontinuity produced by a closed crack, after removal of the stress is also detected. A damage matrix is developed for stress wave based method which is independent of transmission path to assess the severity of damage produced by the crack in a concrete structure

Factors influencing development of trans urethral resection of prostate (TURP) syndrome in benign prostatic hyperplasia patients with various co morbid medical illness: a prospective study

Background: The aim of this prospective study is to analyse the factors influencing development of trans urethral resection of prostate (TURP) syndrome in benign Prostatic hyperplasia patients with various co morbid medical illness in Thanjavur Medical College Hospital, from February 2015 to January 2017.Methods: This prospective study was done among 38 benign hyperplasia prostate patients with various co morbid medical illness underwent TURP. Pre-operative and post-operative serum sodium levels correlated with signs and symptoms developed in various prostate gland sizes, resection times and volume of irrigation fluids.Results: Sodium level has gone down to 14 meq/L, gone up to 2 meq/L post-operatively. Major fluctuations in serum sodium was seen in prostate size more than 50 grams, resection time more than 40 mints, irrigant volume more than 24 litres. Mean sodium decrease was increased when gland size was increased, resection time was increased, irrigant volume was increased.Conclusions: In renal insufficiency patients, it is safe to complete the procedure within 40 minutes and restrict irrigant volume 15 litres, in coronary artery disease patients it is safe to restrict irrigant fluid volume less than 20 litres. In Diabetes Mellitus patients, it is safe to restrict irrigant fluid volume less than 24 litres. In hypertensive patients, it is safe to restrict the resection time less than 45 minutes. In patients with Diabetes and hypertension, it is safe to restrict the resection time less than 40 minutes and irrigant fluid less than 20 litres

A study on peroneus longus autograft for anterior cruciate ligament reconstruction

Background: To compare the clinical outcome and donor site morbidity of ACL reconstruction with Peroneus longus tendon autografts in patients with isolated ACL injury.Methods: This was a prospective study that included patients who underwent ACL reconstruction using Peroneus longus tendon autograft. Results were assessed via physical examination. Donor site morbidity of the foot and ankle after tendon harvesting was assessed using Medical Research Council (MRC) grading of ankle and foot movements.  Post-operative knee function was evaluated by the International Knee Documentation Committee (IKDC) scoring.Results: In this study sample of 25 patients, the ankle functions at the donor site are grossly preserved in almost all the patients, which was elucidated by grading the power of foot eversion. Post operatively knee function (IKDC scoring) were rated as normal in 92% (23 cases).Conclusions: Peroneus longus is an appropriate autograft source for ACL reconstruction in view of ease of harvest, adequate size, cosmetically appealing, considering excellent post-operative knee scores. And removing the Peroneus longus tendon has no effect on gait parameters and does not lead to instability of the ankle. So, it can be used as an autogenous graft in orthopaedic surgeries

Damage Assessment in Concrete Structures using PZT patches

Piezoelectric based PZT smart sensors offer significant \ud potential for continuously monitoring the development and \ud progression of internal damage in concrete structures. \ud PZT-based damage sensors consisting of piezo-electric \ud patches, which are bonded to the surface of a concrete \ud structure can be developed for assessing the damage \ud progression of concrete members. The primary challenge \ud in developing a PZT-based sensor lies in developing a \ud methodology to infer about the level of damage in the \ud material from measurement. Changes in the resonant \ud behavior in the measured electrical conductance obtained \ud from electro-mechanical (EM) response of a PZT bonded \ud to a concrete substrate is investigated for increasing \ud levels of damage. The sensitivity of EM impedance- \ud based measurements to level of damage in concrete is \ud reported. Incipient damage in the form of microcracks in \ud the concrete substrate produces a change in the electrical \ud conductance signature associated with the resonant \ud peaks. Changes in the conductance resonant signature \ud from EM conductance measurement are detected before \ud visible signs of cracking. The root mean square deviation \ud of the conductance signature at resonant peaks is shown \ud to accurately reflect the level of damage in the substrate. \ud The findings presented here provide a basis for developing \ud a sensing methodology using PZT patches for continuous \ud monitoring of concrete structures