Direct Blast Research Articles

The critical tube diameter and critical energy for direct initiation of detonation in C2H2/N2O/Ar mixtures

In this study, the dynamic detonation parameters, namely, the critical tube diameter and critical energy for direct initiation, of C2H2/N2O/Ar mixtures were measured at various initial conditions. Using chemical kinetics with the Konnov mechanism and experimental measured data, a simple correlation to evaluate the critical tube diameter of C2H2/N2O/Ar detonation is developed, given by dc=594.8φ0.623(1-XAr)0.2176(p/po)-0.0246ΔI which is applicable for stoichiometric mixtures with initial pressures ranging from 50 to 130kPa, equivalence ratios from 0.625 to 2.5 and stoichiometric mixtures with maximum percentage of argon dilution up to 50% at the atmospheric pressure. By combining this correlation function with a theoretical model based on a simple work done concept, the critical energy for direct blast initiation can be predicted; and the theoretical predictions are found to be in good agreement with the critical energy measured experimentally. To assess the detonation sensitivity, the critical energy results for direct initiation of detonation in C2H2/N2O/Ar mixtures are compared with those in H2/N2O/Ar mixtures [Zhang et al., Int. J. Hydrogen Energy 39 (2011) 5707–5716]. The results indicate that C2H2/N2O/Ar is more sensitive than H2/N2O/Ar at the same initial conditions. This is also supported qualitatively by the chemical kinetic calculation which shows that the ZND induction length scale for C2H2/N2O/Ar is relatively smaller than that of H2/N2O/Ar mixture. Lastly, the effect of the oxidizer on the detonation sensitivity is studied by comparing the critical energy between C2H2/N2O/Ar and C2H2/O2/Ar mixture. It is found that a higher energy is required to successfully initiate a spherical detonation in C2H2/N2O/Ar than in C2H2/O2/Ar mixtures and equivalently, the results agree qualitatively with the ZND induction length analysis.

Enhancement of Acoustic Field Aberration for Underwater Forward Detection with Experimental Verification

When an object crosses the source-receiver line, a weak acoustic field aberration is produced. However, it is often overwhelmed by the fluctuation of direct blast. A principal component analysis of stable portion of beam output on vertical receiver array is proposed to enhance the field aberration for forward detection. A lake experiment utilized a vertical receiver array spanning the water column was conducted. A 10 kHz pulse was transmitted successively, and the field aberration caused by the forward scattering of the crossing object was observed. The beam output waveform at the horizontal direction is processed with the proposed method, and the field aberration about 10dB above the background acoustic field is achieved, while the maximum aberration is only about 2dB above the background field before processing.

Brick Chimney in Complex Environment Demolished by Accurate Directional Blasting

High and thin brick chimney in complex environment was successfully demolished by directional blasting. By accurate orientation by theodolite, symmetry directional opening window, used small cut length, lower cut position, appropriate cut height and rational blasting parameters, the chimney dumped accurately according to design direction and eliminate the recoil phenomenon effectively when it down. Sandbags wall putting on ground for reduce the impact of the vibration effect; strictly coverage of the incision position can stop the flying rock effectively.

Acoustic forward scattering by a moving object and its range estimation in littoral experiment

When an object crosses the source-receiver line, the sound field aberration can be caused by the forward scattering. However, the aberration is difficult to be seen because of the direct blast overwhelming. An experiment was conducted in littoral environment with several hydrophones deployed at different depths. A repeated wideband LFM pulse is transmitted and data is processed with correlation. The experimental results show that the sound field aberration takes minimum values if the object is located mid-point along the source-receiver line, whereas it attains its maximum if the object is close to the source or receiver. The total field is either enhanced or suppressed if the object crosses different Fresnel zones. In addition, the duration of shadow-induced aberration is dependent on the width of the first Fresnel zone, which is longest at the mid-point of the source-receiver line. Furthermore, a range estimation scheme is proposed. The scheme uses two-point field aberrations of the stable arrival caused by forward scattering of moving object. The ranges of intruder are estimated with a prior knowledge of the moving speed, which agree well with the measurements.

Colonizing the Caribbean: is the GAARlandia land‐bridge hypothesis gaining a foothold?

Colonizing the Caribbean: is the GAARlandia land‐bridge hypothesis gaining a foothold?

Measurement of effective blast energy for direct initiation of spherical gaseous detonations from high-voltage spark discharge

In this study, effective energy from spark discharge for direct blast initiation of spherical gaseous detonations is investigated. In the experiment, direct initiation of detonation is achieved via a spark discharge from a high-voltage and low-inductance capacitor bank and the spark energy is estimated from the analysis of the current output. To determine the blast wave energy from the powerful spark, the time-of-arrival of the blast wave in air is measured at different radii using a piezoelectric pressure transducer. Good agreement is found in the scaled blast trajectories, i.e., scaled time c o·t/R o where c o is the ambient sound speed, as a function of blast radius R s/R o between the numerical simulation of a spherical blast wave from a point energy source and the experimental results where the explosion length scale R o is computed using the equivalent spark energy from the first 1/4 current discharge cycle. Alternatively, by fitting the experimental trajectories data, the blast energy estimated from the numerical simulation appears also in good agreement with that obtained experimentally using the 1/4 cycle criterion. Using the 1/4 cycle of spark discharge for the effective energy, direct initiation experiments of spherical gaseous detonations are carried out to determine the critical initiation energy in C2H2–2.5O2 mixtures with 70 and 0% argon dilution. The experimental results obtained from the 1/4 cycle of spark discharge agree well with the prediction from two initiation models, namely, the Lee’s surface energy model and a simplified work done model. The main source of discrepancy in the comparison can be explained by the uncertainty of cell size measurement which is needed for both the semi-empirical models.

Brain Injuries from Blast

Traumatic brain injury (TBI) from blast produces a number of conundrums. This review focuses on five fundamental questions including: (1) What are the physical correlates for blast TBI in humans? (2) Why is there limited evidence of traditional pulmonary injury from blast in current military field epidemiology? (3) What are the primary blast brain injury mechanisms in humans? (4) If TBI can present with clinical symptoms similar to those of Post-Traumatic Stress Disorder (PTSD), how do we clinically differentiate blast TBI from PTSD and other psychiatric conditions? (5) How do we scale experimental animal models to human response? The preponderance of the evidence from a combination of clinical practice and experimental models suggests that blast TBI from direct blast exposure occurs on the modern battlefield. Progress has been made in establishing injury risk functions in terms of blast overpressure time histories, and there is strong experimental evidence in animal models that mild brain injuries occur at blast intensities that are similar to the pulmonary injury threshold. Enhanced thoracic protection from ballistic protective body armor likely plays a role in the occurrence of blast TBI by preventing lung injuries at blast intensities that could cause TBI. Principal areas of uncertainty include the need for a more comprehensive injury assessment for mild blast injuries in humans, an improved understanding of blast TBI pathophysiology of blast TBI in animal models and humans, the relationship between clinical manifestations of PTSD and mild TBI from blunt or blast trauma including possible synergistic effects, and scaling between animals models and human exposure to blasts in wartime and terrorist attacks. Experimental methodologies, including location of the animal model relative to the shock or blast source, should be carefully designed to provide a realistic blast experiment with conditions comparable to blasts on humans. If traditional blast scaling is appropriate between species, many reported rodent blast TBI experiments using air shock tubes have blast overpressure conditions that are similar to human long-duration nuclear blasts, not high explosive blasts.

New Technology of Efficient Blasting Rock for Large Section Rock Roadway Drivage in Deep Shaft with Complicated Conditions

Based on the different failure mechanism for shallow and deep rock mass, combined with the test result of ground stress and difficulties of blasting rock in Xinwen mining area, used mines rock mass mechanics and modern blasting theory and actively carried out technical reform, the new forming control technology of directional fracture blasting and control technology of multi-directional fusion blasting and efficient blasting technology of compound cut had been adopted, which produced a set of new efficient blasting rock technology for large section rock roadway drivage in deep shaft with complicated conditions. The engineering practice application results showed that the new efficient blasting rock technology could decrease the numbers of shot holes and explosive material consumption, enhance drivage efficiency and circulation footage, ameliorate integral forming quality of roadway and realize maximum month drilling footage at 146 m, the research achievements can provide reference for deep roadway drivage construction in other mining areas with similar conditions.

High-low-blasting technology and its application in methane dynamic disaster prevention

The gas cooperative control model combined local pressure-relief with regional pressure-relief was established, based on the theory of multi-parameters cooperative. For the status of high gas contents, high in-situ stress and low-permeability of Ji-15 seam of No.12 coal mine in Pingmei Group. The law of detonation wave propagation and ground-stress change distribution were simulated by means of the finite element analysis software. The technology of high-low-blasting, composed of high blasting(deep crossing hole controlled hydraulic blasting) and low blasting (special roadway deep hole controlled blasting) were developed. The research shows that around control hole produce maximum tension fracture failure, and result in directional and controlled blasting, when the distance between control hole and blasting hole is 1.2 m. The theory makes blasting force and hydraulic force advantage superimpose, which raises the effect of pressure relief and permeability enhancements compared with general blasting. High blasting influence radius and low blasting influence radius superimposed with each other, that prevents methane dynamic disaster. The result of type approval test shows that the technology can increase gas permeability as high as 22.7∼36.2 ratio, decrease gas pressure from 2.85 MPa to 0.30 MPa, increase drilling influence radius to about 9 m. The technology realizes regional overall permeability improvement, that provides a new technical measure for methane dynamic disaster prevention.

Primary succession trajectories on pumice at Mount St. Helens, Washington

AbstractQuestionsDoes vegetation become less variable over time? Do floristic trajectories converge during succession? Can either allogenic (external) or autogenic (internal) factors predict species patterns during succession?LocationPumice Plain of Mount St. Helens (46.23449°N; 122.15929°W, 1230 m a.s.l.), which was sterilized in 1980 by a direct volcanic blast, then buried in pumice.MethodsWe monitored a grid of 200 100‐m2 contiguous plots annually (1989–2010) and classified the 2010 data into five community types (CTs). We characterized plots using external (e.g. distance from relict sites) and internal (e.g. moisture) factors and clustered plots by position and habitat factors to assess trajectories. We used redundancy analysis (RDA) to assess relationships between vegetation and these variables over time. Mantel tests, similarity changes and detrended correspondence analysis (DCA) were used to evaluate successional trends.ResultsFive CTs were weakly related to habitats at this scale. Over time, vegetation became more homogeneous and successional trajectories of plots clustered by position and habitat factors became more similar or developed in parallel. The succession rate slowed fitfully as persistent species became dominant, while Lupinus fluctuated. Mantel tests indicated that relationships between species and environment were maximized using only autogenic factors. RDA found that autogenic factors were stronger than allogenic ones, while explained variance did not increase after 1992 and factor correlations to species stabilized by 1996.ConclusionsThe strength of links between vegetation and environment were weak at this scale, yet explained variation stabilized early in succession. As substantial vegetative variation persisted and convergence was far from complete due to weak links to habitat factors, habitat variation and stochastic establishment should be considered by vegetation managers.

Rodent Model of Direct Cranial Blast Injury

Traumatic brain injury resulting from an explosive blast is one of the most serious wounds suffered by warfighters, yet the effects of explosive blast overpressure directly impacting the head are poorly understood. We developed a rodent model of direct cranial blast injury (dcBI), in which a blast overpressure could be delivered exclusively to the head, precluding indirect brain injury via thoracic transmission of the blast wave. We constructed and validated a Cranium Only Blast Injury Apparatus (COBIA) to deliver blast overpressures generated by detonating .22 caliber cartridges of smokeless powder. Blast waveforms generated by COBIA replicated those recorded within armored vehicles penetrated by munitions. Lethal dcBI (LD(50) ∼ 515 kPa) was associated with: (1) apparent brainstem failure, characterized by immediate opisthotonus and apnea leading to cardiac arrest that could not be overcome by cardiopulmonary resuscitation; (2) widespread subarachnoid hemorrhages without cortical contusions or intracerebral or intraventricular hemorrhages; and (3) no pulmonary abnormalities. Sub-lethal dcBI was associated with: (1) apnea lasting up to 15 sec, with transient abnormalities in oxygen saturation; (2) very few delayed deaths; (3) subarachnoid hemorrhages, especially in the path of the blast wave; (4) abnormal immunolabeling for IgG, cleaved caspase-3, and β-amyloid precursor protein (β-APP), and staining for Fluoro-Jade C, all in deep brain regions away from the subarachnoid hemorrhages, but in the path of the blast wave; and (5) abnormalities on the accelerating Rotarod that persisted for the 1 week period of observation. We conclude that exposure of the head alone to severe explosive blast predisposes to significant neurological dysfunction.

Scattering in a Pekeris waveguide from a rough bottom using a two-way coupled mode approach

Scattering from a rough ocean bottom is described numerically with a two-way coupled-mode formalism that contains scattering effects to all orders and provides an exact solution to the wave equation. Both scattered field and direct blast components are computed within the formalism framework. A comparison of the scattered component solution from the coupled mode with the Born approximation (BA) solution for scattering from a rough bottom Pekeris waveguide shows that the BA predicts correctly the scattered field levels but not detailed structure. The transition from direct blast to scattered field dominance is identified in the total field time series.

Scattering in a Pekeris waveguide from a rough bottom using a two-way coupled mode approach.

Scattering from a rough surface is described numerically with a two-way coupled-mode formalism that contains scattering effects to all orders and provides, in principle, an exact solution to the wave equation. Both scattered field and direct blast components are computed within the framework of the formalism. In contrast to finite elements, each modal component can be calculated separately. A comparison between the scattered component from the coupled mode and Born approximation solutions is presented for scattering from a rough bottom Pekeris waveguide. Total field time series are constructed, and the transition from direct blast to scattered field dominance is identified. For a Gaussian source pulse, the frequency band needed to resolve the scattered component is shown to be much less than is required to resolve the direct blast. Convergence tests to validate the accuracy of the solution are discussed. The importance of the nonlinear contributions to the scattering is identified. The usual method of time averaging the solution produces lower intensity levels than those obtained from the envelope of the time series.

Critical energy for direct initiation of spherical detonations in H 2/N 2O/Ar mixtures

Although the detonation phenomenon in hydrogen–nitrous oxide mixtures is a significant issue for nuclear waste storage facilities and development of propulsion materials, very limited amount of critical energy data for direct initiation – which provides a direct measure of detonability or sensitivity of an explosive mixture − is available in literature. In this study, the critical energies for direct blast initiation of spherical detonations in hydrogen–nitrous oxide–Ar mixtures obtained from laboratory experiments and theoretical predictions at different initial conditions (i.e., different initial pressure, equivalence ratio and amount of argon dilution) are reported. In the experiments, direct initiation is achieved via a spark discharge from a high voltage and low inductance capacitor and the initiation energy is estimated accordingly from the current output. Characteristic detonation cell sizes of hydrogen–nitrous oxide–Ar mixtures are estimated from chemical kinetics using a recently updated reaction mechanism. A correlation expression is developed as a function of initial pressure, argon dilution and equivalence ratio, which is fitted to provide good estimation of the experimental measured data. The direct link between cell size and critical energy for direct blast initiation is then analyzed. Good agreement is found between experimental results and theoretical predictions, which make use of the cell size estimation correlation and the semi-empirical surface energy model. The effects of the initial pressure, equivalence ratio and the amount of Ar dilution on the critical initiation energy H 2–N 2O–Ar mixtures are investigated. By comparing the critical energies with those of H 2–O 2–Ar mixtures, it is shown that H 2–N 2O mixtures are more detonation sensitive with smaller initiation energies than H 2–O 2 mixtures at the same initial pressure, equivalence ratio and amount of argon dilution, except for higher diluted condition with amount of argon in the mixture above 20%. Attempt is made to explain the critical energy variation and comparison between the two H 2–N 2O–Ar and H 2–O 2–Ar mixtures from the induction length analysis and detonation instability consideration.

E0020 Compound heterozygous novel splicing mutation D202sp and missence mutation G272D on KCNQ1 caused Jervel and Lange-Nielsen syndrome in a Chinese family

BackgroundLong QT syndrome (LQTS) is an inherited cardiac disorder characterised by QT interval prolongation on ECG, ventricular arrhythmias and sudden death. Two forms have been identified: autosomal dominant Romamo-Ward syndrome...

Direct blast initiation of spherical gaseous detonations in highly argon diluted mixtures

In this study, direct initiation of spherical detonations in highly argon diluted mixtures is investigated. Direct initiation is achieved via a high voltage capacitor spark discharge and the critical energy is estimated from the analysis of the current output. Stoichiometric acetylene–oxygen mixtures highly diluted with 70% argon is used in the experiment. Previous investigations have suggested that detonations in mixtures that are highly diluted with argon have been shown to be “stable” in that the reaction zone is at least piecewise laminar described by the ZND model and cellular instabilities play a minor role on the detonation propagation. For the acetylene–oxygen mixture that is highly diluted with argon, the experimental results show that the critical energy where the detonation is “stable” is in good agreement with the Zel’dovich criterion of the cubic dependence on the ZND reaction length, which can be readily determined using the chemical kinetic data of the reaction. The experimental results are also compared with those estimated using Lee’s surface energy model where empirical data on detonation cell sizes are required. Good agreement is found between the experimental measurement and theoretical model prediction, where the breakdown of the 13 λ relationship for critical tube diameter – and hence a different propagation and initiation mechanism – is elucidated in highly argon diluted mixtures and this appears to indicate that cellular instabilities do not have a prominent effect on the initiation process of a stable detonation.

Defoliation negatively affects plant growth and the ectomycorrhizal community of Pinus pinaster in Spain

In this work, by artificially reproducing severe (75%) and moderate (25%) defoliation on maritime pines Pinus pinaster in NW Spain, we investigated, under natural conditions, the consequences of foliage loss on reproduction, abundance, diversity and richness of the fungal symbionts growing belowground and aboveground. The effect of defoliation on tree growth was also assessed. Mature needles were clipped during April 2007 and 2008. Root samples were collected in June-July 2007 and 2008. Collection of sporocarps was performed weekly from April 2007 to April 2009. Taxonomic identity of ectomycorrhizal fungi was assessed by using the internal transcribed spacer (ITS) regions of rDNA through the polymerase chain reaction (PCR) method, subsequent direct sequencing and BLAST search. Ectomycorrhizal colonization was significantly reduced (from 54 to 42%) in 2008 by 75% defoliation, accompanied with a decline in species richness and diversity. On the other hand, sporocarp abundance, richness and diversity were not affected by foliage loss. Some ECM fungal symbionts, which are assumed to have a higher carbon cost according to the morphotypes structure, were reduced due to severe (75%) defoliation. Furthermore, 75% foliage loss consistently depressed tree growth, which in turn affected the ectomycorrhizal growth pattern. Defoliation impact on ECM symbionts largely depends on the percentage of foliage removal and on the number of defoliation bouts. Severe defoliation (75%) in the short term (2 years) changed the composition of the ECM community likely because root biomass would be adjusted to lower levels in parallel with the depletion of the aboveground plant biomass, which probably promoted the competition among mycorrhizal types for host resources. The persistence of fungal biomass in mycorrhizal roots would be crucial for nutrient up-take and recovery from defoliation stress of the host plants.

Process Analysis of the Effective Utilization of Molten Slag Heat by Direct Blast Furnace Cement Production System

This paper principally presents a process analysis of the production systems of blast furnace cement (BFC) based on exergy analysis and its carbon dioxide emission. The analysis was first carried out by using exergy balances of actual operating data in the cement industry. The results revealed that a large sum of net exergy losses was found on the conventional BFC production; this was contrary to the preliminary expectations. In the BFC production, the recovery of the thermal exergy of the molten slag should reduce the total exergy losses by up to 20%. In contrast, the emission of CO2–488.2 kg/ton–in BFC production was ower than 797.5 kg/ton emission in portland cement production; this was because portland cement consumes more carbonaceous fuels such as coal. In conclusion, to reduce exergy loss, save energy and minimize CO2 emission, it is imperative that the BFC production process should be improved with the recovery of the thermal exergy of the molten slag, e.g. the direct mixing of raw material of limestone with molten slag is an innovative and attractive solution because limestone can be easily decomposed by sensible heat of the molten slag. This means thermal combination of portland cement and BFC for the effective use of waste heat, in which waste heat in the conventional BFC process is recovered and used for limestone decomposition in the clinker production to produce BFC.

Validation study on numerical simulation of RC response to close-in blast with a fully coupled model

The characteristic response of a structure to blast load may be divided into two distinctive phases, namely the direct blast response during which the shock wave effect and localized damage take place, and the post-blast phase whereby progressive collapse may occur. A reliable post-blast analysis depends on a sound understanding of the direct blast effect. Because of the complex loading environment and the stress wave effects, the analysis on the direct effect often necessitates a high fidelity numerical model with coupled fluid (air) and solid subdomains. In such a modelling framework, an appropriate representation of the blast load and the high nonlinearity of the material response is a key to a reliable outcome. This paper presents a series of calibration study on these two important modelling considerations in a coupled Eulerian-Lagrangian framework using a hydrocode. The calibration of the simulated blast load is carried out for both free air and internal explosions. The simulation of the extreme dynamic response of concrete components is achieved using an advanced concrete damage model in conjunction with an element erosion scheme. Validation simulations are conducted for two representative scenarios; one involves a concrete slab under internal blast, and the other with a RC column under air blast, with a particular focus on the simulation sensitivity to the mesh size and the erosion criterion.

Murrah Building Bombing Revisited: A Qualitative Assessment of Blast Damage and Collapse Patterns

On April 19, 1995, a truck loaded with an ammonium nitrate and fuel oil bomb caused collapse of fully half of the total floor area of the nine-story, reinforced concrete Murrah Federal Building in Oklahoma City. The extent of the collapse, which extended well beyond the zone of direct structural blast damage, prompted studies of progressive/disproportionate collapse and development of new design guidelines for important buildings. While there is no question that the collapse was the result of the loss of only four columns, there is a common belief that direct blast effects destroyed three of those columns. Firsthand observation of debris, collapse patterns, damage patterns, and thousands of photographs taken during search and rescue activities at the building suggest the possibility that only one column was destroyed by direct blast effects, while the other three buckled due to loss of lateral support provided by beams and floor diaphragms that were destroyed by the blast. While the distinction may be subtle, it has significant implications for the design of tougher buildings. Specific lessons include ductile detailing, the necessity of maintaining the integrity of a three-dimensional frame, and explicit consideration of structural fuses to protect critical elements.