Electron sources: Past, present, and future

1993 ◽  
Vol 51 ◽  
pp. 764-765
Author(s):  
David C Joy
Keyword(s):  
Glass Tube ◽  
Source Size ◽  
Electron Gun ◽  
Operating Parameters ◽  
Operational Parameters ◽  
Electron Sources ◽  
Difficult Decision ◽  
Probe Size ◽  
Wide Range ◽  
Overall Performance

The electron source is the most important component of the Scanning electron microscope (SEM) since it is this which will determine the overall performance of the machine. The gun performance can be described in terms of quantities such as its brightness, its source size, its energy spread, and its stability and, depending on the chosen application, any of these factors may be the most significant one. The task of the electron gun in an SEM is, in fact, particularly difficult because of the very wide range of operational parameters that may be required e.g a variation in probe size of from a few angstroms to a few microns, and a probe current which may go from less than a pico-amp to more than a microamp. This wide range of operating parameters makes the choice of the optimum source for scanning microscopy a difficult decision.Historically, the first step up from the sealed glass tube ‘cathode ray generator’ was the simple, diode, tungsten thermionic emitter.

scholarly journals Electron Sources: Past, Present, and Future

1994 ◽  
Vol 2 (4) ◽  
pp. 7-8
Author(s):  
David C. Joy
Keyword(s):  
Source Size ◽  
Electron Gun ◽  
Operating Parameters ◽  
Operational Parameters ◽  
Electron Sources ◽  
Difficult Decision ◽  
Probe Size ◽  
Wide Range ◽  
Overall Performance ◽  
Scanning Electron

The electron source is the most important component of the Scanning Electron Microscope (SEM) since it is this which will determine the overall performance of the machine. The gun performance can be described in terms of quantities such as its brightness, its source size, its energy spread, and its stability and, depending on the chosen application, any of these factors may be the most significant one. The task of the electron gun in a SEM is, in fact, particularly difficult because of the very wide range of operational parameters that may be required, e.g. a variation in probe size of from a few angstroms to a few microns, and a probe current which may go from less than a pico-amp. to more than a microamp. This wide range of operating parameters makes the choice of the optimum source for scanning microscopy a difficult decision.

Managing operating performance at an ophthalmology clinic

2019 ◽  
Vol 25 (12) ◽  
pp. 1-13
Author(s):  
Harshal Lowalekar ◽  
N Ravichandran
Keyword(s):  
Waiting Times ◽  
Operating Performance ◽  
Central India ◽  
Throughput Capacity ◽  
Operating Parameters ◽  
Operational Parameters ◽  
Scheduling System ◽  
Simulation Based ◽  
System Improvement ◽  
Overall Performance

This article documents the experience of addressing improvements in the operational parameters of an ophthalmology clinic in central India. Shortcomings in the operating parameters of throughput, capacity use and patient waiting times required the immediate attention of senior management. Based on elementary data analysis, the present study advocates a scheduling system that improves all three of these operating parameters. Several administrative options to improve the overall performance of the system were identified. For a deeper understanding of the design issues, a simulation-based model was developed. The results of the simulation model were used to prioritise action areas that needed system improvement.

Thermoacoustic Stability Analysis of a Full-Annular Lean Combustor for Heavy-Duty Applications

2021 ◽  
Author(s):  
Daniele Pampaloni ◽  
Antonio Andreini ◽  
Alessandro Marini ◽  
Giovanni Riccio ◽  
Gianni Ceccherini
Keyword(s):  
Stability Analysis ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Numerical Procedure ◽  
Pollutant Emissions ◽  
Computational Time ◽  
Heavy Duty ◽  
Operational Parameters ◽  
3D Fem ◽  
Wide Range

Abstract Thermoacoustic characterization of gas turbine combustion systems is of primary importance for successful development of gas turbine technology, to meet the stringent targets on pollutant emissions. In this context, it becomes more and more necessary to develop reliable tools to be used in the industrial design process. The dynamics of a lean-premixed full-annular combustor for heavy-duty applications has been numerically studied in this work. The well-established CFD-SI method has been used to investigate the flame response varying operational parameters such as the flame temperature (global equivalence ratio) and the fuel split between premixed and pilot fuel injections: such a wide range experimental characterization represents an opportunity to validate the employed numerical methods and to give a deeper insight into the flame dynamics. URANS simulations have been performed, due to their affordable computational costs from the industrial perspective, after validating their accuracy through the comparison against LES results. Furthermore, an approach where the pilot and the premixed flame responses are analyzed separately is proposed, exploiting the independence of their evolution. The calculated FTFs have been implemented in a 3D FEM model of the chamber, in order to perform linear stability analysis and to validate the numerical approach. A boundary condition for rotational periodicity based on Bloch-Wave theory has been implemented into the Helmholtz solver and validated against full-annular chamber simulations, allowing a significant reduction in computational time. The reliability of the numerical procedure has been assessed through the comparison against full-annular experimental results.

scholarly journals Development of the PGT 25 High Efficiency Gas Turbine: Part 2 — Aerodynamic Design and Performance

1984 ◽  
Author(s):  
E. Benvenuti ◽  
B. Innocenti ◽  
R. Modi
Keyword(s):  
Gas Turbine ◽  
High Efficiency ◽  
Performance Testing ◽  
Operating Conditions ◽  
Aerodynamic Design ◽  
Direct Drive ◽  
Gas Generator ◽  
Full Load ◽  
Wide Range ◽  
Overall Performance

This paper outlines parameter selection criteria and major procedures used in the PGT 25 gas turbine power spool aerodynamic design; significant results of the shop full-load tests are also illustrated with reference to both overall performance and internal flow-field measurements. A major aero-design objective was established as that of achieving the highest overall performance levels possible with the matching to latest generation aero-derivative gas generators; therefore, high efficiencies were set as a target both for the design point and for a wide range of operating conditions, to optimize the turbine’s uses in mechanical drive applications. Furthermore, the design was developed to reach the performance targets in conjunction with the availability of a nominal shaft speed optimized for the direct drive of pipeline booster centrifugal compressors. The results of the full-load performance testing of the first unit, equipped with a General Electric LM 2500/30 gas generator, showed full attainment of the design objectives; a maximum overall thermal efficiency exceeding 37% at nominal rating and a wide operating flexibility with regard to both efficiency and power were demonstrated.

Optimization of injection parameters for ethanol blends of plastic oil in VCR engine using RSM and ANN

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Datta Bharadwaz Yellapragada ◽  
Govinda Rao Budda ◽  
Kavya Vadavelli
Keyword(s):  
Compression Ratio ◽  
Fuel Injection ◽  
Injection Pressure ◽  
Operating Parameters ◽  
Injection Timing ◽  
Oxides Of Nitrogen ◽  
Operational Parameters ◽  
Content Type ◽  
Injection Parameters ◽  
Ethanol Blends

Purpose The present work aims at improving the performance of the engine using optimized fuel injection strategies and operating parameters for plastic oil ethanol blends. To optimize and predict the engine injection and operational parameters, response surface methodology (RSM) and artificial neural networks (ANN) are used respectively. Design/methodology/approach The engine operating parameters such as load, compression ratio, injection timing and the injection pressure are taken as inputs whereas brake thermal efficiency (BTHE), brake-specific fuel consumption (BSFC), carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and smoke emissions are treated as outputs. The experiments are designed according to the design of experiments, and optimization is carried out to find the optimum operational and injection parameters for plastic oil ethanol blends in the engine. Findings Optimum operational parameters of the engine when fuelled with plastic oil and ethanol blends are obtained at 8 kg of load, injection pressure of 257 bar, injection timing of 17° before top dead center and blend of 15%. The engine performance parameters obtained at optimum engine running conditions are BTHE 32.5%, BSFC 0.24 kg/kW.h, CO 0.057%, HC 10 ppm, NOx 324.13 ppm and smoke 79.1%. The values predicted from ANN are found to be more close to experimental values when compared with the values of RSM. Originality/value In the present work, a comparative analysis is carried out on the prediction capabilities of ANN and RSM for variable compression ratio engine fuelled with ethanol blends of plastic oil. The error of prediction for ANN is less than 5% for all the responses such as BTHE, BSFC, CO and NOx except for HC emission which is 12.8%.

Diagnosis of hydrous ethanol combustion in a spark-ignition engine

2020 ◽  
Vol 235 (1) ◽  
pp. 245-259
Author(s):  
Caio H Rufino ◽  
Waldyr LR Gallo ◽  
Janito V Ferreira
Keyword(s):  
Engine Speed ◽  
Combustion Characteristics ◽  
Spark Ignition Engine ◽  
Ignition Timing ◽  
Operational Parameters ◽  
Fuel Ratio ◽  
Combustion Duration ◽  
Wide Range ◽  
Hydrous Ethanol ◽  
The Relationship

By evaluating combustion duration and flame development, it is possible to evaluate the effects of utilizing a new type of fuel. This allows for optimization of the operational parameters such as the ignition timing, air–fuel ratio, and throttle opening with respect to efficiency, knock, emissions, and performance. In this work, the combustion of a Brazilian hydrous ethanol fuel was evaluated in a commercial flexfuel engine. Investigations were conducted by performing a heat release analysis of the experimental data and providing combustion characteristics. The experimental design comprised of variations in engine speed, load, ignition timing, and air–fuel ratio under lean condition. The results indicated the relationship between the engine parameters and combustion characteristics under a wide range of operational conditions, and identified the relationship between the physical characteristics of the fuels and their combustion in the commercial engine. For high engine speed, lean combustion presented a similar duration to the stoichiometric combustion duration. When comparing the combustion characteristics obtained for the hydrous ethanol with gasoline combustion, the main differences noted were reduced sensitivity to detonation and a shorter duration of combustion, although the temperature at the start of combustion was lower for ethanol. In addition to shorter combustion duration, ethanol presented a lower value for the Wiebe exponent. The results obtained from the combustion duration values and Wiebe function parameters enable the composition of a set of data required for a simplified combustion simulation.

Programmed Temperature Gas Chromatography (PTGC) and Microcoulometric Detection of Chlorinated Insecticides

1963 ◽  
Vol 46 (2) ◽  
pp. 198-204
Author(s):  
Jerry Burke
Keyword(s):  
Gas Chromatography ◽  
Detection System ◽  
Operating Parameters ◽  
Gas Chromatograph ◽  
Relative Retention ◽  
Wide Range ◽  
Isothermal Gas

Abstract Commercial models of a programmed temperature gas chromatograph and microcoulometric detection system were combined to study programmed temperature gas chromatography (PTGC) of chlorinated insecticides. PTGC permitted the analysis of samples containing materials whose volatilities cover a wide range. PTGC produced better chromatograms and was faster than isothermal gas chromatography. PTGC did not achieve separations which were not possible by isothermal gas chromatography. Operating parameters for a PTGC residue screening operation were determined. Relative retention times at these conditions are given for 22 pesticides. Other advantages of the PTGC instrumentation are noted.

scholarly journals Spark Plasma Sintering of Ceramics: From Modeling to Practice

Ceramics ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 476-493
Author(s):  
Michael Stuer ◽  
Paul Bowen ◽  
Zhe Zhao
Keyword(s):  
Spark Plasma Sintering ◽  
Ceramic Materials ◽  
Model Material ◽  
Operational Parameters ◽  
Key Factors ◽  
Engineering Approach ◽  
Plasma Sintering ◽  
Wide Range ◽  
Spark Plasma ◽  
Industrial Settings

Summarizing the work of nearly a decade of research on spark plasma sintering (SPS), a review is given on the specificities and key factors to be considered in SPS of ceramic materials, based on the authors’ own research. Alumina is used primarily as a model material throughout the review. Intrinsic inhomogeneities linked to SPS and operational parameters, which depend on the generation of atomistic scale defects, are discussed in detail to explain regularly observed inhomogeneities reported in literature. Adopting an engineering approach to overcome these inherent issues, a successful processing path is laid out towards the mastering of SPS in a wide range of research and industrial settings.

Hierarchical Engineering Model of the Human Body

2016 ◽  
Author(s):  
Somayajulu D. Karamchetty
Keyword(s):  
Human Body ◽  
Hierarchical Modeling ◽  
Control Volume ◽  
The Body ◽  
Whole Body ◽  
Operational Parameters ◽  
Sufficient Detail ◽  
Wide Range ◽  
Level Model ◽  
Complex Engineering

Engineers and scientists are able to understand and analyze the behavior of complex engineering systems in a wide range of critical technologies through hierarchical modeling followed by simulation of the model operation. This process results in a high fidelity integrated model as each level in the hierarchy is modeled in sufficient detail. The overall objective of this effort is to develop a sophisticated hierarchical model of the human body, followed by simulation of the model operation. In this initial research phase, the feasibility of the concept is explored and a framework for the model is described. A six-level model consisting of the whole body as a system, system of systems, organs, tissues, cells, and molecules is proposed and described. This paper explains that the human body is amenable to such hierarchical modeling and describes the benefits that can be achieved. The systems in the body deal with numerous processes: electrical, chemical, biochemical, energy conversion, transportation, pumping, sensing, communications, and so on. Control volume models for the organs in the body capture the mass and energy balance and chemical reactions. Tissue can be represented similar to structural components made of various biomaterials. Cells can be represented as a manufacturing and maintenance workforce assisted by molecular reactions. Following the representation of a healthy body, simulation runs by inserting faults and/or deficiencies in the operational parameters into the model could reveal the causes for specific diseases and illnesses. Such modeling and simulation will benefit medical, pharmaceutical, nutritional specialists, and engineers in designing, developing, and delivering products and services to enable humans to lead healthy lives.

scholarly journals Designing Multifunctional Protective PVC Electrospun Fibers with Tunable Properties

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2086
Author(s):  
Pedro J. Rivero ◽  
Iker Rosagaray ◽  
Juan P. Fuertes ◽  
José F. Palacio ◽  
Rafael J. Rodríguez
Keyword(s):  
Fiber Diameter ◽  
Electrospinning Process ◽  
Operating Parameters ◽  
Electrospun Fibers ◽  
Polymeric Precursor ◽  
Operational Parameters ◽  
Electrospinning Technique ◽  
Coating Morphology ◽  
Hydrophobic Nature ◽  
First Time

In this work, the electrospinning technique is used for the fabrication of electrospun functional fibers with desired properties in order to show a superhydrophobic behavior. With the aim to obtain a coating with the best properties, a design of experiments (DoE) has been performed by controlling several inputs operating parameters, such as applied voltage, flow rate, and precursor polymeric concentration. In this work, the reference substrate to be coated is the aluminum alloy (60661T6), whereas the polymeric precursor is the polyvinyl chloride (PVC) which presents an intrinsic hydrophobic nature. Finally, in order to evaluate the coating morphology for the better performance, the following parameters—such as fiber diameter, surface roughness (Ra, Rq), optical properties, corrosion behavior, and wettability—have been deeply analyzed. To sum up, this is the first time that DoE has been used for the optimization of superhydrophobic or anticorrosive surfaces by using PVC precursor for the prediction of an adequate surface morphology as a function of the input operational parameters derived from electrospinning process with the aim to validate better performance.

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