Electrochemical characterization of Cu dissolution and chemical mechanical polishing in ammonium hydroxide–hydrogen peroxide based slurries

Chemical mechanical polishing (CMP) of copper in ammonium hydroxide based slurry in the presence of hydrogen peroxide was investigated. The polishing trend was found to be similar to that exhibited by other slurries containing hydrogen peroxide and various complexing agents used for Cu CMP. When the hydrogen peroxide concentration is increased, the polish rate increases, reaches a maximum and then decreases. The location and the magnitude of the maximum depend on the ammonium hydroxide concentration. The dissolution of copper in the NH₄OH–hydrogen peroxide solution was probed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) experiments. Electrical equivalent circuit (EEC) and reaction mechanism analysis (RMA) were employed to determine the mechanistic reaction pathway of Cu dissolution in NH₄OH–hydrogen peroxide system. Based on the RMA analysis, a four step catalytic mechanism with two adsorbed intermediate species is proposed.     

Broadcasting in multi-radio multi-channel wireless networks using simplicial complexes

We consider the broadcasting problem in multi-radio multi-channel ad hoc networks. The objective is to minimize the total cost of the network-wide broadcast, where the cost can be of any form that is summable over all the transmissions (e.g., the transmission and reception energy, the price for accessing a specific channel). Our technical approach is based on a simplicial complex model that allows us to capture the broadcast nature of the wireless medium and the heterogeneity across radios and channels. Specifically, we show that broadcasting in multi-radio multi-channel ad hoc networks can be formulated as a minimum spanning problem in simplicial complexes. We establish the NP-completeness of the minimum spanning problem and propose two approximation algorithms with order-optimal performance guarantee. The first approximation algorithm converts the minimum spanning problem in simplical complexes to a minimum connected set cover (MCSC) problem. The second algorithm converts it to a node-weighted Steiner tree problem under the classic graph model. These two algorithms offer tradeoffs between performance and time-complexity. In a broader context, this work appears to be the first that studies the minimum spanning problem in simplicial complexes and weighted MCSC problem.     

Reaction products of ammonium nitrate phosphate fertilizers of varying water-soluble phosphorus content in different Indian soils

Studies were undertaken on the isolation and identification of reaction products of ammonium nitrate phosphate (ANP) fertilizers containing 30, 50 and 70 per cent water-soluble phosphorus (WSP) of total phosphorus in representative soils of the vertisol, oxisol, alfisol, entisol, mollisol and aridisol groups of India. ANP fertilizers were applied in solid form to soil, and reaction products formed at and around the site of ANP fertilizer placement were identified after six weeks incubation in moist soils by X-ray diffraction technique. DCPD (dicalcium phosphate dihydrate- CaHPO₄ · 2H₂O) was the major reaction product of ANP fertilizers containing 30 and 50 per cent WSP in vertisol, entisol, aridisol, mollisol, oxisol and alfisol, and of ANP containing 70 per cent WSP in vertisol, entisol, alfisol, aridisol and mollisol. DCP (dicalcium phosphate-CaHPO₄) was detected with ANP of 30 and 50 per cent WSP in the vertisol, alfisol, entisol, mollisol and aridisol groups of soils. In addition to DCPD, FePO₄ · 2H₂O (metastrengite) and AlPO₄ · 2H₂ O-monoclinic (metavariscite) were formed in alfisol and oxisol soils with ANP of 30 and 50 per cent WSP. FePO₄ · 2H₂O and AlPO₄ · 2H₂O (metavariscite) were identified in alfisol and oxisol soils while AlPO₄ · 2H₂O-orthorhombic (variscite) was formed in alfisol soils with ANP of 70 per cent WSP.     

Perceived exertion associated with breathing hyperoxic mixtures during submaximal work

The effect of an enriched inspired oxygen concentration on perceived exertion (RPE) was investigated while running at two submaximal treadmill loads. Twelve males (VO2 max = 49.3 ml/kg-min) worked at 50% and 80% VO2 max, breathing either air or 80% O2-20% N2 in random order using a single blind technique. Subjects were evaluated while running for 10 min and during a 20 min recovery. Heart rate (HR), ventilation (VE), respiration rate (RR), tidal volume (VT) and RPE were measured before, during and after work. Blood lactate was measured 1 min after work. Oxygen concentration did not statistically affect HR, VE, RR or VT during exercise or recovery. At both loads, RPE at the end of exercise was significantly reduced breathing the hyperoxic mixture. At 50% VO2 max, mean RPE decreased from 11.2 breathing room air to 9.6 breathing 80% O2 and, 80% VO2 max, from 13.8 to 11.7 (P less than 0.01). Blood lactates were significantly reduced breathing 80% O2; from 23.4 mg to 13.3 at 50% VO2 max and from 55.5 to 36.5 at 80% VO2 max (P less than 0.01). The RPE correlated with lactate (r=0.64) at the end of work. Results indicate that during moderate and heavy work RPE is significantly affected by the inspired O2 concentration and there is a significant relationship between RPE and blood lactate.     

Effects of postmortem storage time on color and mitochondria in beef

To assess the effects of aging time (0, 15, 30, and 45 d) and temperature (0 or 5 °C) on beef mitochondria and steak color, vacuum packaged longissimus (n = 15) and cardiac muscles were assigned to 1 of 6 temperature × time combinations. As time increased, initial red color intensity increased whereas both mitochondrial oxygen consumption and color stability decreased. The decrease in mitochondrial oxygen consumption associated with longer aging times will increase initial color intensity. However, this improvement in color development will be negated by the decreased color stability that results from the effects of storage on mitochondria.     

Society of Gastroenterology Nurses and Associates, Inc. (SGNA) Endoscopic Disinfectant Survey results compared with control group

Disinfectant surveys from responding members of the American Society of Postanesthesia Nurses were divided into two groups based on whether or not they considered themselves to be exposed to disinfectants in their work environment. Their survey responses were then compared with those obtained previously from members of the Society of Gastroenterology Nurses and Associates, Inc., who were regularly exposed to 2% alkaline glutaraldehyde in the work setting. There were significant differences among the groups in the percentage of respondents who reported having headaches, eye irritations, respiratory problems, shortness of breath, rashes, memory loss, mood swings, and fatigue. These findings support the association of these complaints with 2% alkaline glutaraldehyde exposure. In contrast, there were no significant differences among the groups in the percentage of respondents who reported having asthma, rhinitis, chest pain, nausea, diarrhea, muscle/joint pain, visual disturbances, or dermatitis.     

Nanofabrication with metallopolymers ‐ recent developments and future perspectives

Synthetic polymers containing metals and metal centers have experienced rapid growth in the last two decades. Metal‐containing polymers have an unprecedented role to play in modern high‐tech applications including nanomanufacturing, sensing, separation and catalysis. Advancement in synthetic strategies for macromolecules has enabled the synthesis of novel, exotic and use‐inspired metallopolymers. Using state‐of‐the‐art design strategies, it is now possible to perform targeted synthesis of macromolecules with varied complexity that contain a range of metal centers either in the backbone or in the side chains of the organic moiety. The presence of an inorganic element (metals and metal centers) in organic moieties has led to a number of new physicochemical properties while implementing novel functionality to the polymer matrix. This review covers nanotechnology influenced by distinctive features of metal‐containing macromolecular systems, particularly in developing flexible, functional materials. © 2013 Society of Chemical Industry     

Stress analysis & life prediction of a cryogenic rocket engine thrust chamber considering low cycle fatigue, creep and thermal ratchetting

The paper deals with stress analysis, cyclic and creep life prediction of a cryogenic rocket engine thrust chamber, being used in one of the satellite launch vehicles of ISRO. The thrust chamber is of double walled construction wherein high conductivity copper alloy is used for the inner wall and stainless steel for the outer. Regenerative cooling of the chamber is achieved by passing the fuel through rectangular coolant passages milled on outer surface of the inner wall. The inner and outer walls are bonded together by brazing at high temperature. Failure of a double walled chamber occurs due to thinning of the inner wall and bulging into the chamber due to three mechanisms viz. (i) low cycle fatigue (ii) thermal ratchetting and (iii) creep. To capture the structural behaviour of the chamber in a complete sequence of operation of the engine, axisymmetric modeling and cyclic stress analysis is carried out using the ANSYS finite element analysis software package. High temperature mechanical properties, low cycle fatigue and creep properties of copper are characterised. Results of creep tests conducted at various temperatures are utilized for evaluating creep constants of Norton secondary creep model available in ANSYS. Analysis is performed in a seven load step sequence simulating one complete hot test of the engine. Life prediction is done using the cumulative damage accumulation methodology, considering the above three damage mechanisms. Allowable number of hot runs permissible is then arrived at after assigning suitable factors of safety for each damage mode.     

Dynamic Load Flow Technique for Power System Simulators

This paper presents a dynamic load flow technique for power system simulators. The approach presented can be applied to a system when there is a net accelerating or decelerating power in the system. It possesses all the attractive features and basic structure of the normal fast decoupled method, and it does not depend on the selected reference bus. The modifications to the standard fast decoupled power flow algorithm are derived, and power system simulator implementation considerations are discussed. The algorithm has been tested on standard IEEE test cases and on a metropolitan utility 559 bus model. A numerical example of the above algorithm on the 559 test case is presented which demonstrates convergence characteristics and computation requirements of the proposed algorithm. These results are compared with those of normal fast decoupled load flow.     

Data envelopment analysis for weight derivation and aggregation in the analytic hierarchy process

Data envelopment analysis (DEA) is proposed in this paper to generate local weights of alternatives from pair-wise comparison judgment matrices used in the analytic hierarchy process (AHP). The underlying assumption behind the approach is explained, and some salient features are explored. It is proved that DEA correctly estimates the true weights when applied to a consistent matrix formed using a known set of weights. DEA is further proposed to aggregate the local weights of alternatives in terms of different criteria to compute final weights. It is proved further that the proposed approach, called DEAHP in this paper, does not suffer from rank reversal when an irrelevant alternative(s) is added or removed.