The corrosion of some superalloys in contact with coal chars in coal gasifier atmospheres

Six alloys, 310 stainless steel, Hastelloy X, Inconel 671, Incoloy 800, Haynes 188, and FeCrAlY (GE1541 and MA956), were corroded in two chars at 1600° and 1800°F. The chars, FMC and Husky, contained 2.7% and 0.9% sulfur, respectively. Various parameters were investigated, including char size, cover gas, char quantity, char replenishment period, gas composition, and the use of coatings. The corrosion process was strictly sulfidation when the char was replenished every 24 hr or less. The kinetics of reaction were nearly linear with time. The reaction resulted in thick external sulfide scales with extensive internal sulfidation in the substrate. The kinetics and reactionproduct morphologies suggested that diffusion through the sulfide scale played a minor role, and that an interfacial reaction was the rate-controlling step, A mathematical model was developed which supported this hypothesis.The reaction rates showed a relatively minor role on alloy composition, depending upon whether the alloys were tested singularly or in combination with others. Inconel 671, the best alloy in CGA environments, consistently corroded the most rapidly of the chromia-former types regardless of char sulfur content or of the temperature. Type 310 stainless was marginally better than Inconel 671. Incoloy 800 was intermediate, whereas, Haynes 188 and Hastelloy X exhibited the best corrosion resistance. The FeCrAlY alloys reacted very rapidly in the absence of preoxidation treatments. All alloys corroded in char at least 1000 times more rapidly than in the CGA (MPCITTRI) environment. None of the alloys will be acceptable for use in contact with char unless coatings are applied.     

Coupled circuit–field formulation for analysis of parallel operation of converters with interphase transformer

This paper deals with the coupled circuit–field analysis of an interphase transformer (IPT) required for two three-pulse controlled converters operating in parallel for the typical low voltage high current electrolysis application. Two-dimensional nonlinear transient finite element (FE) model of the IPT is coupled with external power electronic circuit comprised of switching thyristors. Output current is maintained constant at 6000 A by implementing current feedback control system. The resulting system of transient nonlinear equations is solved by backward Euler and Newton–Raphson methods, and analyzed under balanced, unbalanced and short circuit conditions. The results obtained from short circuit condition are verified with experimental results and design values, making them helpful for design purpose.     

Preparation of highly conductive p-type μc-Si:H window layer using lower concentration of hydrogen in the rf glow discharge plasma

Boron doped p-type hydrogenated microcrystalline silicon (μc-Si:H) films have been prepared by radio-frequency glow discharge method. Highly conductive p-type μc-Si:H films can be obtained even with lower concentration of hydrogen in the rf glow discharge plasma if chamber pressure is low. Effects of increase in hydrogen (H₂) flow rate and chamber pressure have been studied. The structural properties of the films have been studied by X-ray diffractometry. The electrical and optical characterization have been done by dark conductivity, Hall measurements and optical absorption measurements respectively. Film with conductivity 0.1(Ω-cm)⁻¹ with band gap 2.1 eV has been obtained.     

Choice of selective coating for flat plate collectors

A simplified method is presented for the comparison of thermal performance of two similarly fabricated flat plate collectors having absorbers coated with coatings of known solar absorptance and emittance with close values. It essentially determines the insolation value at which the two collectors have the same thermal performance. Curves have been presented which can be directly utilized by the designer for selecting the coating having better thermal performance.     

Permeability of silicone polymers to ammonia and hydrogen sulfide

Permeability coefficients, P?, for NH₃ AND H₂S in 11 different types of silicone membranes were measured in the temperature range from 10.0 to 55.0°C and at pressures up to 115 psig (～ 7.8 atm). The values of P? for NH₃ and H₂S in different silicone polymers decrease considerably as the bulkiness of the functional groups in the side and backbone chains of these polymers increases. the substitution of Si? O bonds with stifer Si? C bonds in the backbone chains also results in a considerable decrease in gas permeability. the values of P? for NH₃ and H₂S increse exponentially with incresing δp, the pressure difference across the membrancs. The temperature dependence of NH₃ and H₂S varies greatly: P? can increase, decrease, or pass through a minimum with increasing temperature, depending on the nature of the silicone polymer. The temperature dependence of P? is also affected in some cases by Δp. The permeability behavior of silicone polymers to NH₃ and H₂S is compared with that to other penetrant gases, and the factors which might affect this behavior are discussed.     

Neuronal high-affinity glutamate transport in the rat central nervous system

EAAC1 is a neuronal and epithelial high affinity glutamate transporter previously cloned from rabbit intestine. Here we report the isolation of EAAC 1 from rat brain* and its expression in the central nervous system based on in situ hybridization. Strong signals were detected in brain, spinal cord and retina. Expression of EAAC1 was particularly strong in pyramidal cells of the cerebral cortex, pyramidal cells of the hippocampus, mitral cells of the olfactory bulb, various thalamic nuclei and cells of certain retinal layers. EAAC1 was also expressed in non-glutamatergic neurons such as GABAergic cerebellar Purkinje cells and alpha-motor neurons of the spinal cord. We propose that EAAC1 is not only involved in the sequestration of glutamate at glutamatergic synapses and in protecting neurons from glutamate excitotoxicity, but also in the cellular metabolism involving glutamate.     

Labeling of MR brain images using Boolean neural network

Presents a knowledge-based approach for labeling two-dimensional (2-D) magnetic resonance (MR) brain images using the Boolean neural network (BNN), which has binary inputs and outputs, integer weights, fast learning and classification, and guaranteed convergence. The approach consists of two components: a BNN clustering algorithm and a constraint satisfying Boolean neural network (CSBNN) labeling procedure. The BNN clustering algorithm is developed to initially segment an image into a number of regions. Then the segmented regions are labeled with the CSBNN, which is a modified version of BNN. The CSBNN uses a knowledge base that contains information on image-feature space and tissue models as constraints. The method is tested using sets of MR brain images. The regions of the different brain tissues are satisfactorily segmented and labeled. A comparison with the Hopfield neural network and the traditional simulated annealing method for image labeling is provided. The comparison results show that the CSBNN approach offers a fast, feasible, and reliable alternative to the existing techniques for medical image labeling.     

Per-packet rate adaptation for wireless video

Streaming video over error-prone wireless channels is a challenge as the dynamic network conditions and slow adaptation to channel degradations may affect the quality of the streamed video. Unequal error protection (UEP) can potentially address this issue by considering the importance of each video packet and its impact on the quality of reconstructed video. This paper proposes a cross-layer UEP solution for wireless video streaming over IEEE 802.11 networks. Video packets are prioritized based on the relative importance of the video packet. UEP is achieved by adapting the link layer parameters on a per-packet basis, using inherent forward error correction and adaptive modulation capabilities of the 802.11n network. Experimental results revealed that the proposed solution achieves comparable performance to the state-of-the-art methods at a lower complexity.     

The protein tyrosine phosphatase SHP-2 is expressed in glial and neuronal progenitor cells, postmitotic neurons and reactive astrocytes

In this study we examined the distribution and developmental profile of the src homology 2 (SH2) domain-containing protein tyrosine phosphatase SHP-2 in the mouse brain. We found that SHP-2 is present in both mitotically active and postmitotic cells in the forebrains of embryonic day 12 (E12) mice. In a developmental study extending from embryonic day 12 to adulthood, Western blotting analysis demonstrated equivalent levels of SHP-2 protein at all of the ages examined. Expression of SHP-2 paralleled the level of enzymatic activity at the different developmental periods. In the adult brain SHP-2 was restricted to diverse classes of neurons, while the majority of glial cells did not express detectable levels of protein. However, reactive astrocytes in response to an ischemic brain injury showed SHP-2 immunolabelling. Our data suggest that SHP-2 may play a role in pathways of neuronal and glial progenitor cells, in a broad spectrum of neuronal responses in the adult brain and in the gliotic response to the injury.