Impeller Repair Techniques For Centrifugal Compressors.

LecturePg. 91-106Successfully repairing centrifugal compressor impellers requires careful consideration and planning. The selection of techniques for inspection, material, and welding procedures are determined by numerous factors. Original design and manufacturing techniques, the nature of a failure, and environmental or process concerns all play a role. The relevant issues are addressed that may assist the user's maintenance personnel in formulating an overall strategy to extend the service life of their impellers through the selection of adequate repair procedures

Making subaltern shikaris: histories of the hunted in colonial central India

Academic histories of hunting or shikar in India have almost entirely focused on the sports hunting of British colonists and Indian royalty. This article attempts to balance this elite bias by focusing on the meaning of shikar in the construction of the Gond ‘tribal’ identity in late nineteenth and early twentieth-century colonial central India. Coining the term ‘subaltern shikaris’ to refer to the class of poor, rural hunters, typically ignored in this historiography, the article explores how the British managed to use hunting as a means of state penetration into central India’s forest interior, where they came to regard their Gond forest-dwelling subjects as essentially and eternally primitive hunting tribes. Subaltern shikaris were employed by elite sportsmen and were also paid to hunt in the colonial regime’s vermin eradication programme, which targeted tigers, wolves, bears and other species identified by the state as ‘dangerous beasts’. When offered economic incentives, forest dwellers usually willingly participated in new modes of hunting, even as impact on wildlife rapidly accelerated and became unsustainable. Yet as non-indigenous approaches to nature became normative, there was sometimes also resistance from Gond communities. As overkill accelerated, this led to exclusion of local peoples from natural resources, to their increasing incorporation into dominant political and economic systems, and to the eventual collapse of hunting as a livelihood. All of this raises the question: To what extent were subaltern subjects, like wildlife, ‘the hunted’ in colonial India

Selection Mechanisms Underlying High Impact Biomedical Research - A Qualitative Analysis and Causal Model

BACKGROUND: Although scientific innovation has been a long-standing topic of interest for historians, philosophers and cognitive scientists, few studies in biomedical research have examined from researchers' perspectives how high impact publications are developed and why they are consistently produced by a small group of researchers. Our objective was therefore to interview a group of researchers with a track record of high impact publications to explore what mechanism they believe contribute to the generation of high impact publications. METHODOLOGY/PRINCIPAL FINDINGS: Researchers were located in universities all over the globe and interviews were conducted by phone. All interviews were transcribed using standard qualitative methods. A Grounded Theory approach was used to code each transcript, later aggregating concept and categories into overarching explanation model. The model was then translated into a System Dynamics mathematical model to represent its structure and behavior. Five emerging themes were found in our study. First, researchers used heuristics or rules of thumb that came naturally to them. Second, these heuristics were reinforced by positive feedback from their peers and mentors. Third, good communication skills allowed researchers to provide feedback to their peers, thus closing a positive feedback loop. Fourth, researchers exhibited a number of psychological attributes such as curiosity or open-mindedness that constantly motivated them, even when faced with discouraging situations. Fifth, the system is dominated by randomness and serendipity and is far from a linear and predictable environment. Some researchers, however, took advantage of this randomness by incorporating mechanisms that would allow them to benefit from random findings. The aggregation of these themes into a policy model represented the overall expected behavior of publications and their impact achieved by high impact researchers. CONCLUSIONS: The proposed selection mechanism provides insights that can be translated into research coaching programs as well as research policy models to optimize the introduction of high impact research at a broad scale among institutional and governmental agencies

Charting Evolution’s Trajectory: Using Molluscan Eye Diversity to Understand Parallel and Convergent Evolution

For over 100 years, molluscan eyes have been used as an example of convergent evolution and, more recently, as a textbook example of stepwise evolution of a complex lens eye via natural selection. Yet, little is known about the underlying mechanisms that create the eye and generate different morphologies. Assessing molluscan eye diversity and understanding how this diversity came about will be important to developing meaningful interpretations of evolutionary processes. This paper provides an introduction to the myriad of eye types found in molluscs, focusing on some of the more unusual structures. We discuss how molluscan eyes can be applied to the study of evolution by examining patterns of convergent and parallel evolution and provide several examples, including the putative convergence of the camera-type eyes of cephalopods and vertebrates

The similarity of life across the universe

Is the hypothesis correct that if life exists elsewhere in the universe, it would have forms and structures unlike anything we could imagine? From the subatomic level in cellular energy acquisition to the assembly and even behavior of organisms at the scale of populations, life on Earth exhibits characteristics that suggest it is a universal norm for life at all levels of hierarchy. These patterns emerge from physical and biochemical limitations. Their potentially universal nature is supported by recent data on the astrophysical abundance and availability of carbon compounds and water. Within these constraints, biochemical and biological variation is certainly possible, but it is limited. If life exists elsewhere, life on Earth, rather than being a contingent product of one specific experiment in biological evolution, is likely to reflect common patterns for the assembly of living matter

Final report on LDRD project 52722 : radiation hardened optoelectronic components for space-based applications.

This report describes the research accomplishments achieved under the LDRD Project 'Radiation Hardened Optoelectronic Components for Space-Based Applications.' The aim of this LDRD has been to investigate the radiation hardness of vertical-cavity surface-emitting lasers (VCSELs) and photodiodes by looking at both the effects of total dose and of single-event upsets on the electrical and optical characteristics of VCSELs and photodiodes. These investigations were intended to provide guidance for the eventual integration of radiation hardened VCSELs and photodiodes with rad-hard driver and receiver electronics from an external vendor for space applications. During this one-year project, we have fabricated GaAs-based VCSELs and photodiodes, investigated ionization-induced transient effects due to high-energy protons, and measured the degradation of performance from both high-energy protons and neutrons

Why Did Memetics Fail? Comparative Case Study

Although the theory of memetics appeared highly promising at the beginning, it is no longer considered a scientific theory among contemporary evolutionary scholars. This study aims to compare the genealogy of memetics with the historically more successful gene-culture coevolution theory. This comparison is made in order to determine the constraints that emerged during the internal development of the memetics theory that could bias memeticists to work on the ontology of meme units as opposed to hypotheses testing, which was adopted by the gene-culture scholars. I trace this problem back to the diachronic development of memetics to its origin in the gene-centered anti-group-selectionist argument of George C. Williams and Richard Dawkins. The strict adoption of this argument predisposed memeticists with the a priori idea that there is no evolution without discrete units of selection, which in turn, made them dependent on the principal separation of biological and memetic fitness. This separation thus prevented memeticists from accepting an adaptationist view of culture which, on the contrary, allowed gene-culture theorists to attract more scientists to test the hypotheses, creating the historical success of the gene-culture coevolution theory