Further studies of the role of radiative ignition in the propagation of large explosions

1987 ◽  
Vol 409 (1836) ◽  
pp. 1-20 ◽  
Keyword(s):  
Combustion Products ◽  
Theoretical Modelling ◽  
Combustion Properties ◽  
Radiation Induced ◽  
Path Lengths ◽  
Basic Hypothesis ◽  
Definition Of ◽  
Explosive Composition ◽  
Radiance Distribution ◽  
Gas Volume

Following previous work demonstrating that the anomalously high rates of propagation of unconfined vapour cloud explosions could be caused, or aggravated, by radiation-induced multi-point ignition due to small fibrous particles ahead of the main flame front, the investigation is extended towards more practical criteria. Ignition lag measurements are carried out in various hydrocarbons, at different relative velocities between particle and mixture, in a radiation flux that is varied in magnitude, direction and range of wavelengths. An image furnace with a tungsten filament as source is used as an alternative to a CO 2 laser, to obtain a closer approximation to radiation from combustion products. Measurements on particles of clean insulating and cotton wool are complemented by more ‘practical’ dusts collected from, for example, vacuum cleaners and shelves. The spectral absorption of various particles is compared with the radiance distribution due to various path lengths of combustion products, and the effect of coating clean particles with lamp black (to simulate the effect of dirt) is assessed. The basic hypothesis is reassessed in terms of a more detailed theoretical model that allows for slip between particle and gas velocity, radiation from secondary ignition centres and a definition of flame speed based on the rate of product gas volume generation. It is found that the susceptibility of various hydrocarbons and mixtures to this type of ignition accords with other combustion properties such as ignition temperatures and burning velocities. While the absorp­tive properties of certain particles and the propensity of others to emit inert blanketing vapour renders them less effective in producing ignition in the laboratory, all particles become hazardous when blackened by dirt and particularly, when subjected to previous exposure to radiation while not surrounded by a mixture of explosive composition. Theoretical modelling confirms that flame speeds of the order required to account for the damage observed in practice are generated by this mechanism and that this result applies for surprisingly low concentrations of hazardous particles. Thus, given the facility with which agglomerates of fibres are raised in suspension and the likelihood of their presence in numbers sufficient for this mechanism, the hazard warning implied by the previous work is reinforced.

scholarly journals Study of the influence of temperature on the parameters of natural fuel gas

2021 ◽  
Vol 36 ◽  
pp. 52-60
Author(s):  
V. Konovaliuk ◽  
Yu. Yu. Franchuk
Keyword(s):  
Natural Gas ◽  
Combustion Products ◽  
Heat Of Combustion ◽  
Fuel Gas ◽  
Energy Value ◽  
Normative Documents ◽  
Influence Of Temperature On ◽  
Wobbe Index ◽  
Definition Of ◽  
Gas Volume

Differences in normative documents on the definition of "standard conditions" and parameters at which the heat of combustion of natural gas is determined are analyzed. When determining the energy value of natural gas in European countries, different values of the final temperature of combustion products, values of higher or lower heat of combustion are used. This causes a deviation of up to 19 % of the values of the heat of combustion of natural gas of the same composition, depending on the standard conditions established in a particular country. The dynamics of temperature change in some sections of the network and its influence on the determination of gas volumes were studied on the example of the urban-type settlement of Yampil, Khmelnytsky region. On the basis of actual values of the basic gas parameters in characteristic pointss of the settlement network, influence of ambient temperature on the basic parameters of the gas is investigated. Graphical dependences of gas density, Wobbe index, and gas volume on temperature are constructed. Based on the calculations, it was determined that when the temperature changes in the range from 0 to 40 °C, the volume of gas increases by 0.34 m3 per 1 °C. The density decreases by 0.002 kg/m3 per 1 °C. The maximum value of the Wobbe index is reached at temperatures of 10 and 25 °C. The same volume of gas can have different energy value, as it directly depends on the composition and percentage of the components of the gas mixture. There are special metters, which analyze the gas components. But they are installed only at large consumers. The presence of a corrector for temperature and pressure at the gas metering unit allows to increase the reliability of metering, but does not completely solves the problem. The amount of gas measured by the meters must be brought to standard conditions and converted into units of energy.

scholarly journals Aerosol-based antimicrobial photoinactivation in the lungs: an action spectrum study

2021 ◽  
Author(s):  
Chiara Treghini ◽  
Alfonso Dell’Accio ◽  
Franco Fusi ◽  
Giovanni Romano
Keyword(s):  
Light Source ◽  
A Priori ◽  
Action Spectrum ◽  
Multidrug Resistant ◽  
Theoretical Modelling ◽  
Resistant Bacteria ◽  
Lung Infections ◽  
Killing Action ◽  
Definition Of

AbstractChronic lung infections are among the most diffused human infections, being often associated with multidrug-resistant bacteria. In this framework, the European project “Light4Lungs” aims at synthesizing and testing an inhalable light source to control lung infections by antimicrobial photoinactivation (aPDI), addressing endogenous photosensitizers only (porphyrins) in the representative case of S. aureus and P. aeruginosa. In the search for the best emission characteristics for the aerosolized light source, this work defines and calculates the photo-killing action spectrum for lung aPDI in the exemplary case of cystic fibrosis. This was obtained by applying a semi-theoretical modelling with Monte Carlo simulations, according to previously published methodology related to stomach infections and applied to the infected trachea, bronchi, bronchioles and alveoli. In each of these regions, the two low and high oxygen concentration cases were considered to account for the variability of in vivo conditions, together with the presence of endogenous porphyrins and other relevant absorbers/diffusers inside the illuminated biofilm/mucous layer. Furthermore, an a priori method to obtain the “best illumination wavelengths” was defined, starting from maximizing porphyrin and light absorption at any depth. The obtained action spectrum is peaked at 394 nm and mostly follows porphyrin extinction coefficient behavior. This is confirmed by the results from the best illumination wavelengths, which reinforces the robustness of our approach. These results can offer important indications for the synthesis of the aerosolized light source and definition of its most effective emission spectrum, suggesting a flexible platform to be considered in further applications.

scholarly journals The evolving definition of salivary gland stem cells

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Cecilia Rocchi ◽  
Lara Barazzuol ◽  
Rob P. Coppes
Keyword(s):  
Stem Cells ◽  
Salivary Gland ◽  
Adult Stem Cell ◽  
Cell Types ◽  
Research Field ◽  
New Therapeutic Approaches ◽  
Recent Developments ◽  
Radiation Induced ◽  
Definition Of

AbstractDysfunction of the salivary gland and irreversible hyposalivation are the main side effects of radiotherapy treatment for head and neck cancer leading to a drastic decrease of the quality of life of the patients. Approaches aimed at regenerating damaged salivary glands have been proposed as means to provide long-term restoration of tissue function in the affected patients. In studies to elucidate salivary gland regenerative mechanisms, more and more evidence suggests that salivary gland stem/progenitor cell behavior, like many other adult tissues, does not follow that of the hard-wired professional stem cells of the hematopoietic system. In this review, we provide evidence showing that several cell types within the salivary gland epithelium can serve as stem/progenitor-like cells. While these cell populations seem to function mostly as lineage-restricted progenitors during homeostasis, we indicate that upon damage specific plasticity mechanisms might be activated to take part in regeneration of the tissue. In light of these insights, we provide an overview of how recent developments in the adult stem cell research field are changing our thinking of the definition of salivary gland stem cells and their potential plasticity upon damage. These new perspectives may have important implications on the development of new therapeutic approaches to rescue radiation-induced hyposalivation.

scholarly journals Editorial: changing views on Empire and Imperialism

2004 ◽  
Vol 12 (3) ◽  
pp. 267-271 ◽  
Author(s):  
H. L. WESSELING
Keyword(s):  
World Order ◽  
The Other ◽  
The Bible ◽  
Global Power ◽  
The New Testament ◽  
New Form ◽  
Political Philosopher ◽  
Basic Hypothesis ◽  
Definition Of ◽  
Antonio Negri

Words can be confusing and titles can be misleading, particularly if titles consist of one simple word. Two titles suffice to illustrate this phenomenon. In 2000, a book appeared with the title Empire and in 2002 another book appeared with exactly the same title. In the first Empire, Michael Hardt, an American literary theorist, and Antonio Negri, an Italian political philosopher, argued that although classical imperialism is over, Empire is alive and well, albeit in a new form. For them ‘Empire’ means the following: ‘Our basic hypothesis is that sovereignty has taken a new form, composed of a series of national and supranational organisms united under a single logic of rule. This new global form of sovereignty is what we call Empire.’ This is a rather special definition of Empire because what one usually has in mind when using that word is something very different. It is the Empire that the other book, written by the British historian Niall Ferguson, is about. This book describes, as the subtitle indicates, The Rise and Demise of the British World Order. But it is also about something more, as is apparent from the rest of the subtitle: and the Lessons for Global Power. These lessons are intended for the rulers of the Empire of today, the Americans. While the first Empire is the Bible for anti-globalists, Ferguson's book can be considered as the New Testament of the advocates of America's imperial ambitions.

scholarly journals Experimental and numerical research of the influence of thrust vector control on the missile aerodynamics by cold and hot jet simulations

2020 ◽  
Vol 48 (4) ◽  
pp. 770-778
Author(s):  
Goran Ocokoljić ◽  
Boško Rašuo ◽  
Dijana Damljanović ◽  
Saša Živković
Keyword(s):  
Vector Control ◽  
Three Dimensional ◽  
Combustion Products ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Cfd Model ◽  
Thrust Vector Control ◽  
Thrust Vector ◽  
And Performance ◽  
Definition Of

The flow field phenomena that occur as a result of thrust vector control (TVC) system activity on a missile with lateral jets are very complex and influence all other components of the missile. Influence is more significant when TVC is generating commands, when jets are asymmetrically directed. The main goal of these study was to determine the influence of of the hot rocket motor's combustion products on the basis of the CFD model proven with the cold-jet simulation. Based on obtained experimental aerodynamic coefficients for the cold-jet simulation the preliminary aerodynamic CFD model was designed. Three-dimensional Reynolds averaged Navier-Stokes numerical aerodynamic and hot-jet simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. The study resulted in the definition of a methodology for the investigation of the jet reaction effects in a wind tunnel. A method for determining of the TVC system interference on the aerodynamic characteristics, as a basic prerequisite for structural, stability and performance analysis, was proposed. Mutual verification and validation process was carried out through experiment and proper application of the commercial CFD software code for calculation aerodynamic effects of the hot gases lateral jets on the performance of a guided missile. Experimental and computational results of the pitching moment coefficients are presented and agreed well with.

Combustion Properties of Spray Flames of Canola Methyl Ester and Diesel Blends

2011 ◽  
Author(s):  
Cristian Aldana ◽  
Ramkumar N. Parthasarathy ◽  
Subramanyam R. Gollahalli
Keyword(s):  
Methyl Ester ◽  
Flame Temperature ◽  
Combustion Products ◽  
Phase Reaction ◽  
Fuel Blend ◽  
Fuel Blends ◽  
No Formation ◽  
Spray Flames ◽  
Combustion Properties ◽  
No Emissions

Canola methyl ester (CME) is a biofuel that is produced by the transesterification of canola oil; it is renewable, carbon-neutral and low in sulfur content. The objective of this study was to document the combustion characteristics of spray flames of CME and No 2 diesel (petroleum fuel) blends. Three blends with 25%, 50% and 75% volume concentration of CME were studied. The fuel was atomized and mixed with air in a heated environment at a supply equivalence ratio of 0.62. Measurements of global CO and NO emissions, inflame temperature and in-flame concentrations of combustion products were made. The near-injector homogeneous gas-phase reaction zone increased in size with the addition of CME. The global CO and NO emissions decreased with the increase in CME content in the fuel blend. The in-flame NO concentration profiles and flame temperature profiles followed similar trends, suggesting that the thermal mechanism of NO formation was dominant in these flames.

scholarly journals Modelling optimal behavioural strategies in structured populations using a novel theoretical framework

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Andrew Morozov ◽  
Oleg A. Kuzenkov ◽  
Elena G. Arashkevich
Keyword(s):  
Developmental Stages ◽  
Fitness Function ◽  
Natural Populations ◽  
Theoretical Framework ◽  
Structured Populations ◽  
Theoretical Modelling ◽  
Structured Population Model ◽  
Definition Of ◽  
Evolutionary Fitness ◽  
Behavioural Strategies

Abstract Understanding complex behavioural patterns of organisms observed in nature can be facilitated using mathematical modelling. The conventional paradigm in animal behavior modelling consists of maximisation of some evolutionary fitness function. However, the definition of fitness of an organism or population is generally subjective, and using different criteria can lead us to contradictory model predictions regarding optimal behaviour. Moreover, structuring of natural populations in terms of individual size or developmental stage creates an extra challenge for theoretical modelling. Here we revisit and formalise the definition of evolutionary fitness to describe long-term selection of strategies in deterministic self-replicating systems for generic modelling settings which involve an arbitrary function space of inherited strategies. Then we show how optimal behavioural strategies can be obtained for different developmental stages in a generic von-Foerster stage-structured population model with an arbitrary mortality term. We implement our theoretical framework to explore patterns of optimal diel vertical migration (DVM) of two dominant zooplankton species in the north-eastern Black Sea. We parameterise the model using 7 years of empirical data from 2007-2014 and show that the observed DVM can be explained as the result of a trade-off between depth-dependent metabolic costs for grazers, anoxia zones, available food, and visual predation.

scholarly journals A Compact Dual-Band Printed Antenna Design for LTE Operation in Handheld Device Applications

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Ding-Bing Lin ◽  
Jui-Hung Chou ◽  
Son-On Fu ◽  
Hsueh-Jyh Li
Keyword(s):  
Reflection Coefficient ◽  
Frequency Band ◽  
Ground Plane ◽  
Low Frequency ◽  
Dual Band ◽  
Handheld Devices ◽  
Printed Antenna ◽  
Handheld Device ◽  
Path Lengths ◽  
Definition Of

A novel internal printed antenna suitable for triple long-term evolution (LTE) bands for handheld devices is presented. The operating bandwidths of the design are LTE700 (698~800 MHz), LTE2300 (2300~2400 MHz), and LTE2500 (2500~2690 MHz). Through the use of a C-shape broadside coupled feed structure, full operation in the lower band is achieved. The antenna itself uses two unequal path lengths to produce a low frequency band with two resonant modes. The required bandwidth is then adjusted using a couple feed, and finally placed over a ground plane via another C-type coupling element in order to enhance the two low-frequency matches. In the definition of the −6 dB reflection coefficient, the bandwidth of two basic modes in the low frequency band is 0.689~0.8 GHz. We adopt the definition of the −10 dB reflection coefficient for the high frequency mode, and its working frequency bands are shown to be 2.3~2.72 GHz. The antenna size is only 40 × 12 × 0.8 mm3with a ground plane of 98 × 40 mm2.

To Definition of Toxic Potency of Combustion Products of Combustible Materials in Compartment

2011 ◽  
Vol 20 (4) ◽  
pp. 4-13 ◽  
Author(s):  
S.V. Puzach ◽  
◽  
V.G. Puzach ◽  
V.M. Doan ◽  
◽  
...  
Keyword(s):  
Combustion Products ◽  
Definition Of ◽  
Combustible Materials
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