Effect of fillers and fire retardant compounds on hydroxy terminated polybutadiene based insulators

A series of polyurethane compositions have been formulated using hydroxy-terminated polybutadiene as polymeric binder and carbon black as a major filler. Various binder-to-filler ratios of the formulations were evaluated to get calendered sheets. The formulations have been characterised for pot-life and rollability and the calendered sheets for mechanical and thermal properties, bUm rate, glass transition temperature, shore hardness and density . The different fillers tried were varieties of carbon black as a major filler; metal oxides, silicates and organic compounds; and fire retardants, such as zinc borate, sodium metaborate, ammonium dihydrogen phosphate and antimony trioxide. The structure and morphology of the fillers have been correlated with the properties. The optimised composition has been evaluated in an end-burning motor, as an insulator for case-bonded application, using a typical composite propellant. The results of interface bonding between the propellant and the insulator have also been presented

Synergistic Hypergolic Ignition of Amino End Group in Monomers and Polymers

A few monomers, oligomers and polymers with amino end groups have been discovered to undergo synergistic ignition with red fuming nitric acid (RFNA) when mixed with large quantities of magnesium powder. Aluminium powder under similar conditions does not ignite the mixture while powders of Zn, Co and Cu cause the ignition. Amongst the polymers used in the experiment commercially available nylon 6 is the most important which may be used as a binder for rocket propellant fuel grains, hypergolic with RFNA. Degree of polymerisation or the chain length of the polymers does not drastically affect the synergistic ignition of the polymer mixture with magnesium powder but high molecular weight and fully aromatised polymers like Kevlar and Nomex fail to ignite under similar conditions. Based upon the earlier work of the authors, explanations for the phenomena oberved have been provided in terms of creation of hot spots leading to ignition at the amino end groups

A study to assess effectiveness of video assisted teaching programme on gastro intestinal tract assessment among student nurses of tertiary care hospital: a statistical approach

Background: The gastro intestinal is important system in the human body. Many times it is found that its uneasy for student nurses to check the patient. So, there is need to improve the available learning programmes regarding gastro intestinal tract assessment.So, it was necessary to conduct this study for educating student nurses regarding the gastro intestinal tract assessment to improve their knowledge. The objectives of this study were to assess the knowledge of student nurses regarding gastro-intestinal tract assessment and to evaluate the effectiveness of video assisted teaching programme on knowledge regarding gastro intestinal tract assessment.Methods: Material and methods used for the study is the evaluative approach; one group pre test, post test design was used. Study was conducted on sample of 70 student nurses by using convenient sampling technique. The data were collected by structured questionnaire. The data were analyzed using descriptive and inferential statistics.Results: The mean knowledge score of student nurses during the pre-test was 39.89% where as it had raised up to 72% during the post-test regarding gastro intestinal tract assessment as effectiveness of video assisted teaching programme. Therefore, the difference assessed was 32.11% between pre-test and post-test.Conclusions: There was significant difference between the pre-test knowledge level and post-test knowledge level of student nurses on gastro intestinal tract assessment. Hence health education programs and on-going teaching both can further improve the knowledge of student nurses

The Changing Relationship between Surface Temperatures and Indian Monsoon Rainfall with the Phase of ESI Tendency

Effective Strength Index (ESI) is the relative strength of NAO and SO. ESI tendency is the algebraic difference between April-ESI and January-ESI and it represents the simultaneous evolution of NAO and SO from winter to spring. During positive (negative) phase of ESI tendency, NAO restores positive (negative) phase and SO restores negative (positive) phase before the beginning of summer season. Thus during contrasting phases (positive and negative) of ESI tendency, the evolution of NAO and SO is out of phase. In this paper we have studied the spatial and temporal variability of winter-time temperature field over Europe, Arabian Sea and Bay of Bengal during contrasting phases of ESI tendency. The study reveals that during positive (negative) ESI tendency, smaller (larger) region of Europe is showing significant winter-time cooling (warming) at surface. The relationship between winter-time surface temperature over above regions and Indian summer monsoon rainfall (ISMR) also shows spatial and temporal variability. The probable explanation for this change in the relationship is discussed in the paper. Two sets of temperature parameters for two different phases of ESI tendency are found out. Multiple regression equations are developed for the prediction of ISMR in each phase of ESI tendency. The performance of these equations is also discussed in this paper

Effect of Additives on Liner Properties of Case-bonded Composite Propellants

A thin layer of liner is applied to ensure a good bond between the insulator and the propellant in case-bonded rocket motors. It also acts as a protective shield for the insulatorby providing a limited fire protection effect. Liner compositions should preferably be based on the same binder system used in the propellant formulations. As the liner has to hold the propellant and the insulator without debond under all the environmental conditions, it plays a key role in predicted performance of a rocket motor. Hence, studies were carried out to improve the liner properties using various hydroxyl compounds, such as butanediol, cardanol, trimethylol propane, pyrogallol, etc as additives. Butanediol and phloroglucinol combination gave the best results in terms of mechanical properties and interface properties for the liner compositions. The effect of filler content on the liner properties was also studied. The results showed that higher filler content does not affect interface properties. Considering the fire retardancy effect and reinforcement of antimony trioxide (S£203), the formulation containing higher Sb2O3 was selected. The studies on pot life/castable life of liner showed that propellant could be cast up to 6 days after liner coating, without adversely affecting the bonding and the bond strength

The Computational Power of Optimization in Online Learning

We consider the fundamental problem of prediction with expert advice where the experts are "optimizable": there is a black-box optimization oracle that can be used to compute, in constant time, the leading expert in retrospect at any point in time. In this setting, we give a novel online algorithm that attains vanishing regret with respect to $N$ experts in total $\widetilde{O}(\sqrt{N})$ computation time. We also give a lower bound showing that this running time cannot be improved (up to log factors) in the oracle model, thereby exhibiting a quadratic speedup as compared to the standard, oracle-free setting where the required time for vanishing regret is $\widetilde{\Theta}(N)$. These results demonstrate an exponential gap between the power of optimization in online learning and its power in statistical learning: in the latter, an optimization oracle---i.e., an efficient empirical risk minimizer---allows to learn a finite hypothesis class of size $N$ in time $O(\log{N})$. We also study the implications of our results to learning in repeated zero-sum games, in a setting where the players have access to oracles that compute, in constant time, their best-response to any mixed strategy of their opponent. We show that the runtime required for approximating the minimax value of the game in this setting is $\widetilde{\Theta}(\sqrt{N})$, yielding again a quadratic improvement upon the oracle-free setting, where $\widetilde{\Theta}(N)$ is known to be tight

Development of 3 DOF Kinematics

In today’s society, robots are used in various areas especially in those where high precision is required. Robots have improved life standards and we are upgrading their performances in order to make our lives easier and more comfortable. Many applications in the field of medicine and industry use different kind of motor-based systems such as robots because of their wide-range of sufficient characteristics like the fact that they can be used as constant power devices with accurate positioning and fast response. This project describes implementation of the proposed control of the stepper motor and robotic arm by development of suitable transfer function. In this work a motorized robot arm with a 3 degree of freedom is designed. For this design control algorithm will be developed using MATLAB software which is widely used in controlling application

Filled Ethylene-propylene Diene Terpolymer Elastomer as ThermalInsulator for Case-bonded Solid Rocket Motors

Ethylene-propylene diene terpolymer (EPDM)-based insulation system is being globallyused for case-bonded solid rocket motors. A study was undertaken using EPDM as base polymer,blended with hypalon and liquid EPDM and filled with fibrous and non-fibrous fillers. Theseformulations were evaluated as rocket motor insulation system. The basic objective of the studywas to develop an insulation system based on EPDM for case-bonded applications. A series ofrocket motor insulator compositions based on EPDM, filled with particulate and fibrous fillerslike precipitated silica, fumed silica, aramid, and carbon fibres have been studied for mechanical,rheological, thermal, and interface properties. Compositions based on particulate fillers wereoptimised for the filler content. Comparatively, fumed silica was found to be superior as fillerin terms of mechanical and interface properties. Addition of fibrous filler (5 parts) improved thepeel strength, and reduced the thermal conductivity and erosion rate. All the compositions wereevaluated for sulphur and peroxide curing. Superior mechanical properties were achieved forsulphur-cured products, whereas peroxide-cured products exhibited an excellent ageing resistance.Rocket motors were insulated with optimised composition and propellant cast, and the motorswere evaluated by conducting static test in end-burning mode.Defence Science Journal, 2008, 58(1), pp.94-102, DOI : http://dx.doi.org/10.14429/dsj.58.162

Polyurethane Based Inhibition for High Flame Temperature Nitramine Based Composite Modified Double Base propellant

The findings for polypropylene glycol (PPG) and hydroxyl-terminated polybutadiene (HTPB)-based inhibition systems are reported. These findings established that the inhibition system comprising HTPB-IPDI-IDP binder and Sb/sub 2/O/sub 3/-C black filler is most suitable for advanced nitramine-based composite modified double-base propellants in terms of mechanical properties and processibility. The promising composition was characterised for glass-transition behaviour and propellant-inhibition bond strength. Propellant grains inhibited with selected formulations were subjected to static evaluation at extreme temperatures and limited aging studies to obtain data of practical value

HAND HYGIENE AND HEALTH: AN EPIDEMIOLOGICAL STUDY OF STUDENTS IN AMRAVATI

Hands may be the most important means by which enteric pathogens are transmitted. Skin hygiene particularly of the hands, has been accepted as a primary mechanism to control the spread of infectious agents. Therefore the present study was undertaken to evaluate the number and type of enteric bacterial pathogens associated with hands. A total of 160 hands swab samples of 80 students of KG, PS, SS, UG, and PG were analyzed. Pathogens were isolated from hands includes Escherichia coli (22%), Pseudomonas aeruginosa (12%), Staphylococcus aureus (15%), Proteus mirabilis (11%), Citrobacter freundii (10%), Enterobacter aerogenes (8%), Streptococcus sp. (7%), Klebsiella sp. (6%), Micrococcus sp. (5%) and Salmonella typhi (4%). The prevalence of the bacterial pathogens was high in students of K.G. and primary than those in secondary schools and colleges. The data indicated that the hands of the female were more contaminated than male and the left hand was more contaminated than the right hand. Thus, the potential risk factors for transmission of enteric pathogens through hands should be investigated in order to improve the general health of the students