Performance enhancement in coal fired thermal power plants. Part IV: overall system

This paper provides an analysis of the overall performance of 22 coal‐fired power plants. The net overall efficiency is in the range 19·23–30·69%. The effects of ash in coal, contaminants in feed water, leakage, incondensables, etc., have been quantified. Ways of minimizing secondary oil consumption have been provided. The techniques for performance improvement, low cost as well as capital intensive, have been described. The role of overhauling the plant and associated opportunities for performance improvement are also discussed. It is concluded that achieving a high annual plant load factor (PLF) will bring about all round improvement in the unit performance. Unless the pressing problems of high ash in coal, inadequate contaminant control and leakage/ingress are solved, mere repowering by equipment of higher efficiency may not yield the desired results. Design margins of 10–20% are essential for both repowered and new units. In the long term, it is economical to de‐commission all units below 210 MW and only three sizes need be retained: 210, 500 and 1000 MW. Automation of the DM water plant provides maximum economic advantage. Considerable opportunity exists for energy conservation through introduction of information technology and variable frequency drives in all units. Copyright © 1999 John Wiley & Sons, Ltd.     

Crystallinity,conductivity, and magnetic properties of PVDF‐Fe3O4 composite films

The formation of Fe₃O₄ nanoparticles by hydrothermal process has been studied. X‐ray Diffraction measurements were carried out to distinguish between the phases formed during the synthesis. Using the synthesized Fe₃O₄ nanoparticles, poly(vinyledene fluoride)‐Fe₃O₄ composite films were prepared by spin coating method. Scanning electron microscopy of the composite films showed the presence of Fe₃O₄ nanoparticles in the form of aggregates on the surface and inside of the porous polymer matrix. Differential Scanning calorimetry revealed that the crystallinity of PVDF decreased with the addition of Fe₃O₄. The conductitivity of the composite films was strongly influenced by the Fe₃O₄ content; conductivity increased with increase in Fe₃O₄ content. Vibration sample magnetometry results revealed the ferromagnetic behavior of the synthesized iron oxide nanoparticles with a Ms value of 74.50 emu/g. Also the presence of Fe₃O₄ nanoparticles rendered the composite films magnetic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermodynamic Basis for Glass Formation in Cu-Zr Rich Ternary Systems and Their Synthesis by Mechanical Alloying

Topological factors such as mismatch entropy and configurational entropy, along with thermodynamic entity such as enthalpy of chemical mixing, are found to control glass formation in metallic systems. Taking both these factors into consideration, a parameter called P _HS was proposed to correlate glass forming ability successfully in the Cu-Zr-Ti system. The parameter P _HS (=?H _chem × ?S _σ /k _B ) is a product of enthalpy of chemical mixing and mismatch entropy. Our study indicates that the more negative is the P_HS value within the configurational entropy (?S _config/R) range of 0.9 to 1.0, the higher is the stability of glassy phase resulting in a larger diameter of bulk metallic glass rods. Observed theoretical predictions are supported by experimental results in which the compositions with high negative P _HS resulted in easy amorphous phase formation in comparison with less negative P _HS compositions by mechanical alloying. This criterion was extended to Cu-Zr-Al and Cu-Zr-Ag systems as well, thus establishing a strong correlation between P _HS and the glass forming ability of alloys. The role of size effect, probability of atomic arrangements, and heat of formation among constituent elements in obtaining a larger dimension bulk metallic glasses was addressed in this study.     

The Significance of the Aesthetic in Postmodern Architectural Theory

Recent postmodern suspicion of truth, objectivity, and rationality has radically transformed our understanding of architecture and its relationship to politics. In this paper, I draw upon Hilary Putnam (1981), Nelson Goodman (1968), and Satya Mohanty (1997), who propose a sophisticated account of objectivity by reexamining the "hard" sciences, and by interpreting them as complex social practices. Building upon these writers, I argue that our subjective experiences of architecture are rational. As an alternative to both modern essentialism and postmodern skepticism, this paper defends a theory of objectivity that explains the relationship of architecture to political power without abandoning rational thought.     

Microstructures using RF sputtered PSG film as a sacrificial layer in surface micromachining

In this paper, we explore RF magnetron sputtered Phosphor-silicate-glass (PSG) film as a sacrificial layer in surface micromachining technology. For this purpose, a 76 mm diameter target of phosphorus-doped silicon dioxide was prepared by conventional solid-state reaction route using P₂O₅ and SiO₂ powders. The PSG films were prepared in a RF (13·56 MHz) magnetron sputtering system at 300 watt RF power, 20 mTorr pressure and 45 mm target-to-substrate spacing without external substrate heating. Microstructures of sputtered silicon dioxide film were fabricated using sputtered PSG film as sacrificial layer in surface micromachining process.     

Screw-theoretic analysis framework for cooperative payload transport by mobile manipulator collectives

In recent times, there has been considerable interest in creating and deploying modular cooperating collectives of robots. Interest in such cooperative systems typically arises when certain tasks are either too complex to be performed by a single agent or when there are distinct benefits that accrue by cooperation of many simple robotic modules. However, the nature of both the individual modules as well as their interactions can affect the overall system performance. In this paper, we examine this aspect in the context of cooperative payload transport by robot collectives wherein the physical nature of the interactions between the various modules creates a tight coupling within the system. We leverage the rich theoretical background of analysis of constrained mechanical systems to provide a systematic framework for formulation and evaluation of system-level performance on the basis of the individual-module characteristics. The composite multi-degree-of-freedom (DOF) wheeled vehicle, formed by supporting a common payload on the end-effectors of multiple individual mobile manipulator modules, is treated as an in-parallel system with articulated serial-chain arms. The system-level model, constructed from the twist- and wrench-based models of the attached serial chains, can then be systematically analyzed for performance (in terms of mobility and disturbance rejection). A two-module composite system example is used throughout the paper to highlight various aspects of methodical system model formulation, effects of selection of active, passive or locked articulations on system performance, and experimental validation on a hardware prototype test bed.