Time-Lapse Monitoring of Daily Velocity Changes in Binchuan, Southwestern China, Using Large-Volume Air-Gun Source Array Data

Temporal changes of seismic velocities in the Earth’s crust can be induced by stress perturbations or material damage from reasons such as strong ground motion, volcanic activities, and atmospheric effects. However, monitoring the temporal changes remains challenging, because most of them generally exist in small travel-time differences of seismic data. Here, we present an excellent case of daily variations of the subsurface structure detected using a large-volume air-gun source array of one-month experiment in Binchuan, Yunnan, southwestern China. The seismic data were recorded by 12 stations within ∼10 km away from the source and used to detect velocity change in the crust using the deconvolution method and sliding window cross-correlation method, which can eliminate the “intercept” error when cutting the air-gun signals and get the real subsurface variations. Furthermore, the multichannel singular spectral analysis method is used to separate the daily change (∼1 cycle per day) from the “long-period” change (<1 cycle per day) or noise. The result suggests that the daily velocity changes at the two nearest stations, 53277 (offset ∼700 m) and 53278 (offset ∼2.3 km), are well correlated with air temperature variation with a time lag of 5.0 ± 1.5 hr, which reflects that the velocity variations at the subsurface are likely attributed to thermoelastic strain. In contrast, both daily and long-period velocity changes at distant stations correlate better with the varying air pressure than the temperature, indicating that the velocity variations at deeper depth are dominated by the elastic loading of air pressure. Our results demonstrate that the air-gun source is a powerful tool to detect the velocity variation of the shallow crust media.

The Wolfspar experience with low-frequency seismic source field data: Motivation, processing, and implications

The promise of fully automatic full-waveform inversion (FWI) — a (seismic) data-driven velocity model building process — has proven elusive in complex geologic settings, with impactful examples using field data unavailable until recently. In 2015, success with FWI at the Atlantis Field in the U.S. Gulf of Mexico demonstrated that semiautomatic velocity model building is possible, but it also raised the question of what more might be possible if seismic data tailor-made for FWI were available (e.g., with increased source-receiver offsets and bespoke low-frequency seismic sources). Motivated by the initial value case for FWI in settings such as the Gulf of Mexico, beginning in 2007 and continuing into 2021 BP designed, built, and field tested Wolfspar, an ultralow-frequency seismic source designed to produce seismic data tailor-made for FWI. A 3D field trial of Wolfspar was conducted over the Mad Dog Field in the Gulf of Mexico in 2017–2018. Low-frequency source (LFS) data were shot on a sparse grid (280 m inline, 2 to 4 km crossline) and recorded into ocean-bottom nodes simultaneously with air gun sources shooting on a conventional dense grid (50 m inline, 50 m crossline). Using the LFS data with FWI to improve the velocity model for imaging produced only incremental uplift in the subsalt image of the reservoir, albeit with image improvements at depths greater than 25,000 ft (approximately 7620 m). To better understand this, reprocessing and further analyses were conducted. We found that (1) the LFS achieved its design signal-to-noise ratio (S/N) goals over its frequency range; (2) the wave-extrapolation and imaging operators built into FWI and migration are very effective at suppressing low-frequency noise, so that densely sampled air gun data with a low S/N can still produce useable model updates with low frequencies; and (3) data density becomes less important at wider offsets. These results may have significant implications for future acquisition designs with low-frequency seismic sources going forward.

Penetrating Brain Trauma due to Air Gun Shot – a Case Report

Cases of severe injuries caused by air guns are really uncommon, but they can lead to a fatal outcome. Usually, these injuries occur in children due to their not fully developed skull bones or in adults through less resistant and thin regions of the cranium. Most of them are accidental events, followed by low percentage of suicidal attempts. In this paper, we present the case of a 68-year-old man suffering from severe depression, with self-inflicted air gun injury to the head. The patient was admitted to the hospital in a coma with a Glasgow Coma Scale (GCS) score of 8, with severe penetrating head injury manifested with brain contusion and intraventricular bleeding seen at the CT examination. Metal particles from the projectile were seen inside the brain. The entry wound had inverted margins, abraded collar and skin defect. The additional neurological examination of the patient showed symptoms of increased intracranial pressure. The treatment started with the air gun wound care. Craniotomy surgery was also done and bone fragments around the entry wound were successfully extracted with subsequent debridement and duraplasty. The patient was treated with new-generation combined antibiotics for preventing inflammatory complications. On the nineteenth day, the patient was discharged with mild hemiparesis on the left side and with GCS score of 15. Air-gun traumatic cases with head injury or with injury to other parts of the body are often mistaken for firearm accidents, because air guns are seriously underestimated devices. Nevertheless, they could lead to severe health consequences and severe disability. This case highlights the necessity of strict monitoring of air guns by the responsible government institutions which should apply the same regulations in controlling these weapons as they implement in controlling the firearm guns. Presence of severe depression, mental illnesses, and neoplasms are risk factors for committing suicide with this type of weapons and the control over the air weapons in this group of people should be stricter.

Analysis of Film Forming Law and Characteristics for an Air Static Spray with a Variable Position of the Plane

In order to accurately establish the film thickness distribution model of a static spraying plane with air gun displacement, the film forming law and characteristics of the static spraying plane with air gun displacement were analyzed. The spray simulation model was established by the Euler–Euler method, and the spray process and film forming condition were calculated. The numerical simulation results show that oblique spraying has a large influence on the near-surface liquid velocity. With the increase in the spray angle, the droplets at the edge of the torch diffuse to the inclined direction, and the uniformity of the coating distribution becomes worse. Spraying height has a large influence on droplet trajectory. The coating thickness decreased significantly with the increase in spraying height, and the coating diffused in the air increased. With the increase in spraying height, the more obvious the droplet diffusion at the edge of the torch, the worse the uniformity quality of the coating. In order to ensure better spraying quality, the spraying height and angle should be controlled within a reasonable range at the same time. Spraying experiments verified the film forming law and characteristics of static spraying with gun displacement.

Accidentally lodged airgun pellet in maxilla during childhood play retrieved surgically after a decade

Non-powder firearm-related injuries to the head and neck carry the potential risk of significant morbidity and mortality. Such penetrating injuries tend to be under-reported and trivialised especially in children. Air gun pellet injury may cause damage to both soft tissue and bone. Some metals, when embedded in body tissue, can evoke a foreign body reaction or release toxins over time. It therefore becomes imperative to retrieve these pellets. We present one such case of accidental lodgement of airgun pellet in the right maxilla of a 12-year-old boy during childhood play with an airgun which went unnoticed at that time and was surgically retrieved after a decade. The patient had not suffered from any neurosensory deficit.

De-bubbling Seismic Data using a Generalized Neural Network

Estimating the far-field source signature has always been an important part of seismic processing. However, estimating the source signature from an air gun array is difficult because of the complex interaction between the air bubble oscillations from each air gun, the state of the sea surface, variations in air pressure, the air guns geometry, etc. Removing the bubble noise is important since proper seismic imaging requires a zero-phased, spiky wavelet. De-bubbling has conventionally been done by deconvolution using an (assumed) known source signature. Several methods to estimate the signature and de-bubble the data have been implemented, for instance, source modeling or using near-field hydrophone measurements. We describe an alternative approach using a convolutional neural network for de-bubbling. The network is trained on real data containing a large range of source signatures to make the network robust and adaptive to signature variations. If the signature in the test data is equal to one of the signatures used in the training, the network performs well. Also, if the signature changes in the middle of a sail line, the network can adapt to this change. Moreover, we investigate the network’s sensitivity to changing geology within a survey and on two different surveys on the Norwegian Continental Shelf. If the test data are from similar geology as the training data, the network performs better than if not. Even when applied to a different part of the Norwegian Continental Shelf, the network is still able to remove most of the bubble noise.

On the Free Recovery Bending Shape Memory Effect in Powder Metallurgy FeMnSiCrNi

This paper presents the results of an original experimental study on the training capacity of a powder metallurgy (PM) FeMnSiCrNi shape memory alloy (SMA). The specimens were sintered under protective atmosphere from blended elemental powders, 50 vol.%. of alloy particles being mechanically alloyed. Lamellar specimens, hot rolled to 1 mm thickness, were bent against cylindrical calibres with five decreasing radii, to induce cold shapes with higher and higher deformation degree, as compared to the straight hot shape. During the training procedure, bent specimens were heated with a hot air gun, and developed free-recovery shape memory effect (SME) and partially deflected, by reducing their curvature. The first set of experiments involved fastening the specimens at one end, heating it and monitoring free end’s displacement by means of cinematographic analysis. Within the second set of experiments, both cold and hot shapes were recorded and digitalized and their chord’s length (b) and circle segment height (a) were measured and the radius was determined as R = a/2 + b2/8a for the cold (Rc) and hot shapes (Rh). Finally, the shape recovery degree was calculated for the nth calibre as Δrecn = (Rhn-Rrn)/(Rhn-1-Rrn) and the variation of Δrecn with calibre’s radius was discussed.

PECULIARITIES OF MORPHOLOGICAL CHANGES IN BRAIN STRUCTURES OF RATS UNDER CONDITIONS OF MODEL TRAUMATIC BRAIN INJURY

Experimental animal models of traumatic brain injury (TBI) were created to study themorpho-functional features of the disease and to fill the therapeutic window betweenpreclinical trials and the introduction of drugs into the clinical medical practice.The aim of the work – to study the morphological changes in the brain structures ofrats under conditions of model TBI.Material and methods. The experiments were performed on white male rats weighing160-190 g. The experimental model of TBI in rats under conditions of propofolanesthesia (60 mg/kg) was caused by the action of a stream of carbon dioxide underpressure, which was created using a gas cylinder air gun. For histological examination,the brain was fixed with 10% neutral formalin, dehydrated in alcohols in increasingconcentrations, and immersed in paraffin. Sections were stained with hematoxylinand eosin, toluidine blue. The microscopy of histological specimens was performedusing a light microscope OLIMPUS BX 41 using magnifications of 40, 100, 200 and400 times. The morphological research studied the structural changes of neurons inthe sensorimotor zone of the cerebral cortex, the hippocampal structures of the CA1zone and the condition of blood vessels in two groups of animals: Group II - rats withsimulated trauma.Results. In animals with model TBI, there was a predominance of the number ofdegenerating pyramidal neurons over those preserved in the sensorimotor zone ofthe cortex of the large hemispheres and in the CA1 zone of the hippocampus. In thesensorimotor zone of the cortex of the large hemispheres, the death of neurons wasmanifested by morphological signs of karyopyknosis, karyorexis and cytopicnosiswith the phenomena of cytolysis. Only single preserved neurons were visualized in thepyramidal layer; most cells are represented by pyknotic cells; 3) in the hippocampusof animals with TBI, the cytolytic type of nerve cell death was mainly observed. Themorphological signs of cytolysis indicate deep damage to all neurocyte structures.Conclusions. The morphological basis of the remodeling of brain structures in traumaticbrain injury is: reduction in the number of normochromic neurons in experimentalanimals, formation of a significant number of hypochromic neurons, formation ofhyperchromic neurons with pronounced signs of tigrolysis, hemodynamic disorderswith pericellular and perivascular edema.