Stress Corrosion Cracking of Ring Type Joint of Reactor Pipeline of a Hydrocracker Unit

Failure of a ring type joint (RTJ) of reactor pipeline of a hydrocracker unit has been reported. Cracks were noticed on the flange as well as the ring gasket of the RTJ during inspection following a periodic shutdown of the unit. These components of the RTJ were manufactured from stabilized grades of austenitic stainless steel, namely, type 321 and 347, respectively. Study showed that the failure of the RTJ components occurred by transgranular stress corrosion cracking. It was further established that formation of polythionic acid due to presence of H₂S in the process gas and H₂O in the system was responsible for initiation of SCC in RTJ components. Detailed metallurgical investigation was carried out to identify the probable causes that could have been responsible for formation of polythionic acid in the process gas.     

Microstructural study: an aid to determination of failure mechanism in nickel base superalloy blades

Cast nickel base superalloys are extensively used for high temperature gas turbine blade applications. The elevated temperature properties in these alloys are optimized through engineered microstructure, which is a combination of (a) γ-solid solution of Ni with elements such as W, Mo, Cr, Ta, Re etc, (b) γ′ precipitates, and (c) dispersed carbides. Over the years, the demand for high engine efficiency has resulted in the development of new generation superalloys with improved elevated temperature properties, especially creep resistance. These superalloys are highly alloyed with solid-solution strengthening elements and hence, impose greater technological challenges in fabrication. Due to high alloy contents, these alloys are prone to formation of detrimental phases such as the topologically close packed (TCP) phases. These phases may appear in the microstructure during the blade fabrication stages or precipitate out during exposure to high temperature and stress. In addition, the γ′ precipitates can change in morphology, shape and size during applications resulting in deterioration in high temperature mechanical properties, in general. These unfavorable microstructural changes often lead to premature failure in gas turbine engines. While analyzing these failures, the microstructural study provides important information in identifying whether the blades had faulty microstructure to start with or the abnormalities observed have resulted during exposure to service conditions. This in turn can be related to engine operating conditions. In the present paper, this has been demonstrated through analysis of two service failure cases wherein the high pressure turbine blades had failed in flight leading to aircraft accidents.     

Query processing over incomplete autonomous databases: query rewriting using learned data dependencies

Incompleteness due to missing attribute values (aka “null values”) is very common in autonomous web databases, on which user accesses are usually supported through mediators. Traditional query processing techniques that focus on the strict soundness of answer tuples often ignore tuples with critical missing attributes, even if they wind up being relevant to a user query. Ideally we would like the mediator to retrieve such possibleanswers and gauge their relevance by accessing their likelihood of being pertinent answers to the query. The autonomous nature of web databases poses several challenges in realizing this objective. Such challenges include the restricted access privileges imposed on the data, the limited support for query patterns, and the bounded pool of database and network resources in the web environment. We introduce a novel query rewriting and optimization framework QPIAD that tackles these challenges. Our technique involves reformulating the user query based on mined correlations among the database attributes. The reformulated queries are aimed at retrieving the relevant possibleanswers in addition to the certain answers. QPIAD is able to gauge the relevance of such queries allowing tradeoffs in reducing the costs of database query processing and answer transmission. To support this framework, we develop methods for mining attribute correlations (in terms of Approximate Functional Dependencies), value distributions (in the form of Naïve Bayes Classifiers), and selectivity estimates. We present empirical studies to demonstrate that our approach is able to effectively retrieve relevant possibleanswers with high precision, high recall, and manageable cost.     

Attacks and Remedies in Collaborative Recommendation

Collaborative-filtering recommender systems are an electronic extension of everyday social recommendation behavior: people share opinions and decide whether or not to act on the basis of what they hear. Collaborative filtering lets you scale such interactions to groups of thousands or even millions. Publicly accessible user-adaptive systems such as collaborative recommender systems introduce security issues that must be solved if users are to perceive these systems as objective, unbiased, and accurate.     

Measurement of changes in viscosity in polymers with gamma-ray dose using a differential viscometer

Although some works on changes in viscosity of liquids with gamma-ray dose have been made near the “gel point”, very little works have been done below this point. Changes in viscosities of different-grade silicone fluids below gel point have been measured using a differential viscometer developed in our laboratory, capable of measuring change in viscosities of two liquids directly. Preliminary results on viscosity changes when irradiated with energetic alpha particles will also be reported.     

Xenon molecular laser in the vacuum ultraviolet

Vacuum ultraviolet emission from high-pressure Xe gas under excitation by a pulsed electron beam has been investigated. When cavity mirrors were provided, significant line narrowing and a thousandfold increase in spectral intensity occurred at 1730 ± 10 Å. This was accompanied by severe mirror burning and provides strong evidence that an associative molecular Xe laser has been achieved.     

Tack and Green Strength of Blends of Bromobutyl and EPDM Rubbers. I. Unfilled Gum Blends

Polymer blends are gaining importance in recent years because they provide a compromise of properties. In this paper, tack and green strength of several blends of EPDM and bromobutyl rubbers (BIIR) have been studied over a wide range of temperaures, contact times and rates.

Tack increases with increase in contact time and with increase in contact temperature up to 47°C for a particular blend. At a much higher temperature the tack strength falls gradually. Green strength increases with increase in bromobutyl content and decreases with temperature. Tack index, a ratio of tack strength divided by the cohesive strength under the same geometry, decreases slowly with the test temperature. At a 50:50 ratio of BIIR:EPDM, the two rubbers form an interpenetrating network as observed under the phase contrast microscope.     

Fragment docking to S100 proteins reveals a wide diversity of weak interaction sites

The S100 protein family is a highly conserved group of Ca(2+)-binding proteins that belong to the EF-hand type and are considered potential drug targets. In the present study we focused our attention on two members of the family: S100A13 and S100B; the former is involved in the nonclassical protein release of two proangiogenic polypeptides FGF-1 and IL-1alpha that are involved in inflammatory processes, whereas S100B is known to interact with the C-terminal domain of the intracellular tumor suppressor p53 and promote cancer development. We screened, using waterLOGSY NMR experiments, 430 molecules of a generic fragment library and we identified different hits for each protein. The subset of fragments interacting with S100B has very few members in common with the subset interacting with S100A13. From the (15)N-HSQC NMR spectra of the proteins in the presence of those hits the chemical shift differences Deltadelta(HN) were calculated, and the main regions of surface interaction were identified. A relatively large variety of interaction regions for various ligands were identified for the two proteins, including known or suggested protein-protein interaction sites.     

A secure image encryption scheme based on three different chaotic maps

Multimedia Tools and Applications - In the current decade, chaos based image encryption has distinctly captured a remarkable position in multimedia data security. In this paper, a hybrid chaos...