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

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

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

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

Area Under Curve UV Spectrophotometric Method for Determination of an Opioid Analgesic in Bulk

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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

Detection of dengue-4 virus in pune, western india after an absence of 30 years - its association with two severe cases

<p>Abstract</p> <p>Background</p> <p>Difference in severity of dengue outbreaks has been related to virus serotype, genotype and clades within genotypes. Till the 1980 s, India and Sri Lanka reported low number of dengue hemorrhagic fever (DHF) cases despite circulation of all four serotypes of dengue virus (DENV). Since the 1990 s the occurrence of DHF has increased. The increase has been attributed to changes in virus lineage especially with regard to DENV-2 and DENV-3. DENV-1 has been associated with dengue fever (DF) outbreaks and DENV-4 reports have been rare. The emergence of DENV-4 was reported recently in 2003 in Delhi and in 2007 in Hyderabad. The last report of DENV-4 from Maharashtra was in 1975 from Amalner.</p> <p>Results</p> <p>We report on the detection of DENV-4 in Pune, Maharashtra after an absence of almost 30 years. Two cases were detected in 2009-10, serotyped by multiplex reverse transcriptase polymerase chain reaction (RT-PCR). Both the cases were recorded as severe dengue (Category 3) requiring intensive care unit (ICU) level of treatment. Depending on the hemagglutination inhibiting (HI) antibody titres the 2009 case was characterized as a primary infection and the 2010 case as a secondary infection. Both the cases presented plasma leakage and neither showed any kind of haemorrhage. The 2009 case survived while the 2010 case was fatal. An isolate was obtained from the 2009 case. Based on envelope (E) gene sequence analysis, the virus belonged to genotype I of DENV-4, and clustered with isolates from India and Sri Lanka and was distant from the isolates from Thailand. The nucleotide and amino acid diversity of the E gene of the Indian isolates increased from 1996 to 2007 to 2009 in context of the E gene sequences of other isolates belonging to genotype I.</p> <p>Conclusion</p> <p>The increasing diversity in the circulating DENV-4 calls for close monitoring of the DENV-4 serotype.</p

Outcomes of resection for rectal cancer in India: The impact of the double stapling technique

BACKGROUND: The introduction of circular staplers into colorectal surgery has revolutionized anastomotic techniques stretching the limits of sphincter preservation. Data on the double-stapling technique (DST) has been widely published in the West where the incidence of colorectal cancer is high. However studies using this technique and their results, in the Indian scenario, as well as the rest of Asia, have been few and far between. AIM: To evaluate the feasibility of the DST in Indian patients with low rectal cancers and assess its impact on anastomotic leak rates, covering colostomy rates, level of resection and morbidity in patients undergoing low anterior resection (LAR). METHODS: A comparative analysis was performed between retrospectively acquired data on 78 patients (mean age 53.2 ± 13.5 years) undergoing LAR with the single-stapling technique (SST) (between January 1999 and December 2001) and prospective data acquired on 138 LARs (mean age 50.3 ± 13.9 years) performed using the DST (between January 2003 – December 2005). RESULTS: A total of 77 out of 78 patients in the SST group had Astler Coller B and C disease while the number was 132/138 in the DST group. The mean distance of the tumor from anal verge was 7.6 cm (2.5–15 cm) and 8.0 cm (4–15 cm) in the DST and SST groups, respectively. In the DST group, there were 5 (3.6%) anastomotic failures and 62 (45%) covering stomas compared to 7 (8.9%) anastomotic failures and 51 (65.4%) covering stomas in the SST group. The anastomotic leak rate, though objectively lower in the DST group, did not attain statistical significance (p = 0.12). Covering stoma rates were significantly lower in DST group (p = 0.006). There was 1 death in the DST group due to cardiac causes (unrelated to the anastomosis) and no mortality in the SST group. The LAR and abdominoperineal resection (APR) rates were 40% and 60%, respectively, during 1999–2001. In 2005, these rates were 55% and 45%, respectively. CONCLUSION: This study, perhaps the first from India, demonstrates the feasibility of the DST in a country where the incidence of colorectal cancer is increasing. Since the age at presentation is at least a decade younger than the Western world, consideration of sphincter preservation assumes greater significance. The observed improvement of surgical outcomes with DST needs further studies to significantly prove these findings in a population where the tumors at presentation are predominantly Astler Coller Stage B and C

Estimation of Metformin Hydrochloride in Bulk and Formulation by UV - Spectroscopic Area Under Curve Method

The current work is carried out for estimation of Metformin Hydrochloride&nbsp;&nbsp; by using area under curve (AUC) method using UV-visible spectrophotometer. For this purpose the wavelength range 221-241 nm was selected. Distilled water was used as a solvent throughout the work. Linearity was observed in concentration range 5-25 µg/ml (R2= 0.994) for the method. The present method was found to be simple and linear which can be used for routine quality control analysis for spectrophotometric estimation of Metformin hydrochloride in bulk. Keywords: Metformin Hydrochloride, Area under curve, Antidiabetic, λmax