Activated-TIG Welding of Different Steels: Influence of Various Flux and Shielding Gas

In tungsten inert gas (TIG) welding, a low depth of penetration (DOP) is achieved during single pass. To achieve the required DOP, the speed of welding should be reduced; thus productivity reduces significantly. In this work, influence of 14 different oxide-, chloride-, and fluoride-based fluxes are evaluated on DOP and width-to-penetration ratio during flux-activated TIG (ATIG) welding of low alloy steel (AISI 4340), austenitic (AISI 304 and AISI 316) and duplex (Duplex 2205) stainless steels. The effect of welding current and three different shielding gas compositions is also studied during ATIG for these workpieces. Arc and weld metal pool behaviors are captured in order to study the physical behavior of the process. Results revealed that oxide-based fluxes like SiO₂, MoO₃, MoS₂, CrO₃, and TiO₂ increases DOP significantly and in many cases through penetration (penetration reaches beyond plate thickness) is achieved. There is a noteworthy enhancement in penetration because of the addition of H₂ in shielding gas. Addition of helium also helps to increase DOP. Arc behavior reveals the constriction of arc column during activated TIG welding, and positive surface tension-induced flow in centripetal (inward) direction is observed.     

Materials response to high pressures

There are many fascinating areas of research related to the response of materials at high static and dynamic pressures. The experimental range of compression achievable in the condensed state under pressure is much larger than the range of expansion achievable before melting by variation of temperature. The advances in the experimental techniques have been matched by the developments in the first principles theories and in computational resources. Studies of equation of state and of phase transitions in materials have helped to increase our basic understanding of the condensed state of matter, with possible applications in many fields, including nuclear technology. The current status of high pressure research is briefly reviewed, taking examples mainly from the work of our group at Trombay.     

Technology and the Decentralization of Information Systems

More than 100 IS executives discuss their organizations' plans to decentralize information systems and the larger role decentralization will play in their systems architecture. This changing architecture reflects a changing role for IT, which will be increasingly more responsible for setting enterprisewide standards and supporting business strategies.     

Effects of leadership style and anonymity on group potency and effectiveness in a group decision support system environment.

A longitudinal laboratory experiment was conducted to evaluate the effects of leadership style (transactional vs transformational) and anonymity level (identified vs anonymous) on group potency and effectiveness of 36 undergraduate student work groups performing a creativity task using a Group Decision Support System (GDSS). GDSS are interactive networks of computers for generating solutions to unstructured problems. Results indicated that GDSS anonymity amplified the positive effect of transformational leadership on group potency relative to transactional leadership in the group writing session of the task. GDSS anonymity also increased the effect of transformational leadership relative to transactional leadership on group effectiveness. Implications for practice and future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extending shelf life of chapatti by partial baking and frozen storage

The effect of conventional and partial baking and storage at two different temperatures (ambient and −18 °C) on the texture of wheat flour chapatties was evaluated using tensile deformation and the extent of retrogradation was studied using DSC. The extensibility of the conventionally baked chapatti decreased by 58.7% and 20.15%, respectively after storage of 24 h at ambient and frozen temperature. The partially baked chapatti showed a much lower decrease of 3.7% and 0.01% in extensibility when stored under the same conditions. Chapatties, both conventionally and partially baked stored at ambient temperature showed higher retrogradation enthalpy than their counterparts kept at −18 °C. Extended frozen storage of the chapattis from partially baked chapatti resulted in a progressive increase in the extensibility whereas the extensibility of the conventionally baked chapatties was not affected. Lowest water absorption index of 4.60 was observed in partially baked chapatti stored for 24 h at ambient temperature indicating that maximum retrogradation (4.19 J/g) had taken place. Frozen partially baked chapatties after thawing and rebaking exhibited texture equivalent to that of conventionally baked chapatties therefore they could be considered a better option than frozen conventionally baked chapatties for retarding staling.     

A coupled and interactive influence of operational parameters for optimizing power output of cleaner energy production systems under uncertain conditions

The mechanisms in proton‐exchange membrane fuel cells (PEMFCs) cannot be explicitly represented by a mathematical function because the PEMFC system is multi‐dimensional and complex and represents uncertainty in operation variables, which cannot be modeled by experiments or by trial‐and‐error approach. Therefore, this work proposes to study the coupled and interactive influence of stack current (SC), stack temperature (ST), oxygen excess ratio (OER), hydrogen excess ratio (HER), and inlet air humidity (IAH) for optimizing the power output of PEMFC. The data obtained from the experiments have been inserted into architecture of automated neural‐network search, which automates the selection of error function, activation function, uncertainties in inputs and number of hidden neurons in formulation of a robust and accurate model for power density as a function of five operational variables. Among the operational variables, the correlation coefficient between the SC and the output power is the highest, followed by OER, and the ST. However, for HER and IAH, the power output follows negative nonlinear relation. The optimization converged at 130^th iteration results in maximum power output of 3410 W for an optimum value of SC (51A), ST (59°C), OER (3:2), HER (1:10), and IAH (0.8).     

Design and analysis of all-optical up- and down-wavelength converter based on FWM of SOA-MZI for 60 Gbps RZ data signal

In this paper, the design and analysis of the all-optical up- and down-wavelength converter based on four-wave mixing (FWM) effect of semiconductor optical amplifier Mach–Zehnder interferometer (SOA-MZI) have been presented. The return-to-zero (RZ) modulated data signal at a bit rate of 60 Gbps has been evaluated for error-free operation to show the feasibility of proposed system at different pump wavelength. The converted signal power and quality factor are investigated as the function of variable signal power and pump power. The optimized operating input signal power of ?5 dBm with Q-factor of \(\sim \)28 dB for RZ modulated signal by using SOA-MZI structure with enhanced FWM effect. The important contribution of these investigations that it is possible to expand the optical network with limited available channel bandwidth by utilizing the wavelength converter and gives an approach to implement wavelength converter for future hybrid optical access networks.     

Colorimetric detection of nucleic acid signature of shiga toxin producing Escherichia coli using gold nanoparticles

Enterohemorrhagic E. coil (EHEC) serotype O157:H7 is one of the major pathogens, responsible for the severe disease outbreaks. EHEC causes diseases in humans through production of shiga-like toxin leading to bloody diarrhea. The toxin is encoded by stx2 gene in E. coli. The current methodology for detection of EHEC relies on fluorogenic-substrate based culture media or nucleic acid amplification based Real-Time Polymerase Chain Reaction assays that are either time consuming or need expensive instrumentation. In this study, the optical properties of gold nanoparticles (GNPs) have been exploited for detection of nucleic acid of Escherichia coli O157:H7. The stx2 gene representing EHEC signature has been targeted using the gold nanoparticle probes. Gold nanoparticles (GNPs) of 20 +/- 0.2 nm were synthesised by citrate reduction method and characterised by spectroscopy and transmission electron microscopy. The GNPs were functionalised with 19 and 22 bp of thiolated single stranded DNA complementary to target highly conserved 149 bp region of stx2 gene. Transmission Electron Microscopy revealed the hybridization, aggregation and reduction in the interparticle distances of the GNP probes in the presence of target DNA. The aggregation and the spectral shift in the plasmon band observed with 10(6) copies of target DNA indicates feasibility of a simple and quick colorimetric 'spot and read' test in contrast to amplification based detection methods.