229 research outputs found
Shams al-dim al-Sakhawi as a historian of the 9th/15th century : with an edition of that section of his chronicles (Wajiz al-kalam) covering the period 800-849 / 1397-1445
No full textAlthough a prolific writer of history, Sakhawi is, primarily, a
traditionist. As such, accuracy both in utterance and writing would,
by the very nature of his training, be his first objective.
Modern writers appear to have neglected the importance of his
contribution to the understanding of the history of his century.
accept for a few articles, comparatively little has been written. It
is, therefore, strange that such a mine of information as Sakhawi's
writing presents has remained so long in oblivion.
In this thesis an attempt has been made to evaluate that contribution
together with an edition of part of his work.
The study has been divided into three sections, the first dealing
with Sakhawi’s life and times. This part of the study is based largely
on his autobiography which was written but a few months before he died.
During research no reference was discovered to this most informative
work.
The section falls into three chapters, the first of which endeavours
to show the political and educational aspects of Cairo during the early
part of Sakhawi's lifetime. Cairo was his native city and, as such,
made great impact on his early life.
In the second chapter the position of his family, his Shaykhs, the
academic journeys he made, his residence in Hijaz and the last phase of
his life are portrayed.
The third chapter deals with his activities as an adult, his reputation
as a traditionist together with a survey of his works as presented in
his autobiography.
In the second part, the study deals exclusively with Sakhawi as
a historian of the 9th/15th century. This part also is divided into
two chapters, the first of which considers the following aspects: -
I Sakawi's works on the century;
II His motives, methods and literary style and
III His treatment of the history of the century.
The second chapter collates Sakhawi's methods of selecting his
information and the painstaking efforts he made to verify them, together
with his historical achievements, while the last two topics endeavour to
evaluate his task as a historian in that century.
Section three presents the hitherto unedited part of Wajiz al-Kalam...
which deals with the history of the 9th/15th century. This section
also falls into the three divisions of preface, text and annotations.
The last divides again into two groups one of which deals with the
textual variants mentioned in the footnotes and the other attempts to
deal with the interpretation of most of the idiom, colloquial expressions
and the names of places and personalities mentioned in the supplement to
the text
Corresponding author and mailing address:
No full textThe author is grateful to the organizers and participants of the ‘Reward and decision making in cortico-basal-ganglia networks ’ meeting for much stimulating discussion and feedback, and to Rui Costa, Nathaniel Daw, Peter Dayan, Daphna Joel and Geoffrey Schoenbaum for helpful comments on the manuscript
Field Measurements of Flame Scanners in a Gas-Fired Boiler under Controlled Operation Charges
No full textPaper from the AFRC 2017 conference titled Field Measurements of Flame Scanners in a Gas-Fired Boiler under Controlled Operation ChargesReal-time monitoring of coal-fired utility boiler flames has been in active commercial implementation for at least two decades. One such system - Flame Doctor® - relies on numerical analysis and pattern matching of flickering dynamics as measured by visible-IR flame scanners installed on each burner. This diagnosis system can monitor up to hundreds of burners in large furnaces and allow operators to optimize the unit for combustion efficiency and emissions. Field experience has shown that significant improvements in emissions performance can be achieved with changes to just a small number of burners, and the ability to monitor all flames, especially where visual access is not possible, is of great utility for plant operation.; We have begun adapting the successful Flame Doctor paradigm to gas-fired furnaces and process heater systems. As a first step, we present here analysis of field data acquired from a six-burner gas-fired furnace firing natural gas. A portable Flame Doctor system monitored the output of custom visible-UV flame scanners, and the furnace operating parameters were varied through a series of controlled experiments. We show how the statistical changes in the furnace flame response show promise for a gas-fired flame-monitoring system which would be applicable from single-burner process heaters to large, multi-burner furnaces
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Characterizing and modeling combustion of mild-gasification chars in pressurized fluidized beds
No full textOak Ridge National Laboratory (ORNL) is supported by the Morgantown Energy Technology Center (METC) of the Department of Energy (DOE) under FWP-FEAA310 to characterize the fuel properties of liquid and char coproducts from the mild gasification of coal, Because most of the energy content of coals subjected to mild gasification is retained in the byproduct char, efficient and cost-effective utilization of the char is essential in insuring that candidate gasification processes are commercially viable. One potential use for char of particular interest to DOE is pressurized fluidized bed combustion (PFBC). PFBC is of particular interest because it has the potential for 10 to 30 percent greater overall energy efficiency than atmospheric fluidized bed combustion (AFBC), While bench-scale tools and analytical procedures for characterizing fuels for AFBC have been recently demonstrated, no such tools have been reliably demonstrated for PFBC. This report summarizes the results of joint research collaboration between ORNL and B&W that has been directed at modifying the previously developed AFBC fuel characterization procedures to be applicable for mild-gasification chars and PFBC conditions. The specific objectives were to: (1) characterize the combustion reactivity of a selected set of candidate mild- gasification chars at PFB conditions; (2) compare the measured char characteristics with those of more conventional PFBC fuels; (3) modify an AFBC computer code previously developed by B&W and ORNL for the Electric Power Research Institute (EPRI) to predict PFBC performance; and (4) apply the modified code and measured char combustion characteristics to make performance predictions for the candidate chars relative to more conventional fuels
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Characterizing and modeling combustion of mild-gasification chars in pressurized fluidized beds
No full textPerformance estimates for the UCC2, IGTP1, and IGTP2 chars were made for a typical utility PFBC boiler having nominal characteristics similar to those of the American Electric Power 75 MW(e) Tidd PFBC demonstration facility. Table 2 summarizes the assumed boiler operating conditions input to the PFBC simulation code. Input fuel parameters for the chars and reference fuels were determined from their standard ASTM analyses (Table 1) and the results of the bench-scale characterization tests at B W's Alliance Research Center. The required characterization information for the reference fuels was available from the B W data base, and the combustion reactivity information for the mild-gasification chars was generated in the pressurized bench-scale reactor as described earlier. Note that the combustion reactivity parameters for Beulah lignite are those previously measured at low-pressure conditions. It was necessary to use the previous values as the new parameters could not be accurately measured in the pressurized bench-scale facility. Based on very limited measurements of particle size attrition in paste-type feed systems, it was assumed that all of the fuels (including the chars) would have a very small (essentially negligible) degree of attrition in the feed system. Char devolatilization parameters were assumed to be equal to those of anthracite because of the very low levels of volatiles present in UCC2, IGTP1, and IGTP2. Major fuel input parameters and higher heating values are summarized in Table 3
Characterizing and modeling combustion of mild-gasification chars in pressurized fluidized beds
No full textIdentifying Sources of Thermoacoustic Vibrations in Industrial Furnaces and Boilers
No full textPaper from the AFRC 2018 conference titled Identifying Sources of Thermoacoustic Vibrations in Industrial Furnaces and BoilersIndustrial gas-fired boilers, furnaces and heaters occasionally suffer low-frequency vibrations generated by dynamic feedback between the burner (or burners) and acoustic modes in adjacent cavities in the main combustion chamber or ductwork. Feedback occurs when pressure pulses associated with acoustic resonances propagate to the burner so that they are in phase with combustion rate fluctuations. When the combustion and acoustic fluctuations become sufficiently phase-synchronized, normal sources of dissipation are insufficient to damp the combined pressure waves, and they can become sufficiently amplified to reduce thermal efficiency, increase emissions, and even cause structural damage. In the literature, such oscillations are referred to as thermoacoustic oscillations or ‘rumble\u27, and their basic physics have been the subject of numerous investigations for well over a century. Although it occurs relatively infrequently, rumble poses a significant challenge because it is difficult to predict, diagnose, and resolve. The underlying relationships involved are sufficiently complex that it is possible for two apparently identical boilers or furnaces to exhibit completely different rumble tendencies. In this study, we review common sources of rumble and how nonlinear signal analyses, such as bivariate mutual information and transfer entropy, can be used to locate both its sources and impact in boilers, furnaces and heaters
Author Deborah Heffernan of Bridgton describes how secret plans to have a Queen
No full textAuthor Deborah Heffernan of Bridgton describes how secret plans to have a Queen Anne bonnet-top high boy built for her husband Jack Heffernan turned into a community affair, while yet remaining a secret. The actual design and construction of the high boy fell on Bob Dunning, with the help cabinetmaker Greg Marston. Others involved on the project included Mary and Don Johnson and their sons Tom and Eric. With descriptive details of elements included in the highboy
Opportunities for the next generation of optical boiler diagnostics
No full textPaper from the AFRC 2015 conference titled Opportunities for the next generation of optical boiler diagnosticsInefficient boiler operation and control are responsible for wasting large amounts of fuel and releasing excess greenhouse gases (CO2 and N2O) and pollutants (CO, NOx). This is especially true in the United States where more than 80% of the energy used across all sectors is generated by fossil-fuels combustion. It is now recognized that continuous monitoring and control of both individual burners and groups of burners in boilers is essential to meet and sustain ever more stringent greenhouse and pollutant emission limits. This has become especially true as incremental improvements in burner performance have become disproportionately more difficult, and variations in fuel properties due to the widespread practice of fuel blending require frequent adjustment in burner settings to maintain optimum performance. One approach for advanced optical burner monitoring has been pioneered and successfully implemented commercially on coal-fired utility boilers by The Babcock & Wilcox Company. The Flame Doctor® system statistically characterizes dynamic information in the flicker signals captured by optical flame scanners to assess (and potentially adjust) the performance of individual burners or ensembles of burners (e.g., by mill group). While the value of this technology has been demonstrated repeatedly for over 12 years, it is inherently limited because conventional flame-scanner systems have been designed to meet very specific safety objectives and were never intended to be used for burner performance monitoring. In this work, we describe the current state of the art for burner diagnostics as embodied in the Flame Doctor system. Next, we present the theoretical basis for a new generation of advanced optical flame monitoring technology that could go well beyond the capabilities of current flame-scanner-based systems. We expect that the need for such capabilities will increase substantially as boiler fuel sources and needs for tighter emissions and efficiency controls continue to grow
Thermoacoustic Vibrations in Industrial Furnaces and Boilers
No full textPaper from the AFRC 2017 conference titled Thermoacoustic Vibrations in Industrial Furnaces and BoilersIndustrial boilers and furnaces occasionally suffer low-frequency vibrations generated by a dynamic feedback process between the burner (or burners) and acoustic modes in adjacent gas-filled cavities in the main combustion chamber or connecting ductwork. This occurs when pressure pulses associated with acoustic resonances propagate to the burner so that they are in phase with combustion rate fluctuations caused by turbulence and reaction dynamics. When these pressure pulses become sufficiently phase-synchronized with fluctuations in heat release from the flame, the forces that normally dissipate the pressure waves are overwhelmed and an amplifying feedback loop is created. In the literature, such oscillations are referred to as thermoacoustic oscillations or ‘rumble,\u27 and their basic physics have been the subject of numerous investigations for well over a century. Unfortunately, rumble amplitudes can be large enough to negatively impact thermal efficiency and emissions, and the associated mechanical vibrations they cause can even lead to structural damage. The potential for rumble poses a significant challenge to combustion engineers because it is often very difficult to predict and can be associated with a large number of design and operating factors such as fuel quality, burner swirl and staging, induction and draft fan characteristics, ducting design and combustion cavity shape. The underlying relationships involved are sufficiently complex that it is possible for two apparently identical boilers or furnaces to exhibit completely different rumble tendencies. In this study, we review the published information currently available about the causes and suppression of burner rumble and suggest possible opportunities for improving its prediction, diagnosis, and active control
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