Gun Source Research Articles

Radiation-Induced Hydrogel for Water Treatment.

Along with serving as drug delivery sensors and flexible devices, hydrogels are playing pioneering roles in water purification. Both chemical and radiation methods can produce hydrogels, with the latter method gaining preference for its pure adducts. The water treatment process entails the removal of heavy and toxic metals (above the threshold amount), dyes, and solid wastes from industrial effluents, seawater, and groundwater, as well as sterilization for microorganism destruction. This review analyzed the different types of hydrogels produced by applying various radiations for water treatment. Particularly, we examined the hydrogels created through the application of varying levels of gamma and electron beam radiation from the electron gun and Co-60 sources. Moreover, we discuss the optimized radiation doses, the compositions (monomers and polymers) of raw materials required for hydrogel preparation, and their performance in water purification. We present and predict the current state and future possibilities of radiation-induced hydrogels. We explain and compare the superiority of one radiation method over other radiation methods (UV-visible, X-ray, microwave, etc.) based on water treatment.

Analysis of factors affecting the performance of air gun source under shallow water conditions: Insights from the non-ideal gas air gun wavelet model

Optimized design of high-resolution air gun sources is crucial with the exploration of oil and gas resources moving toward the middle-deep reservoir in the Bohai Sea. To this end, the absorption and attenuation law of seismic waves in the stratum of the Bohai Sea was analyzed. It was clarified that expanding the low frequency based on retaining the high frequency was the focus of optimized design of air gun array. Then the air gun wavelets in the shallow sea environment were simulated based on the non-ideal gas air gun wavelet model. The emphasis is put on several key aspects: the influence law of array sinking depth, towed-streamer sinking depth, single air gun spacing, subarray spacing, and air gun volume on the performance of wavelets. Finally, array parameters for shallow sea environments were optimized based on simulation results. The resulting optimized array wavelet in this work is able to provide significant improvements in energy, spectrum quality, and directional response. Moreover, the imaging effect of the acquired data can be improved to a large degree using the optimized array wavelet, which indicates that an optimized array with the consideration of multiple factors is more suitable for the exploration of the middle-deep reservoir.

(Invited) Advances in XPS Analysis of Battery Materials

Energy storage (batteries, capacitors) and conversion (solar cells) systems are increasing demand for vehicles, mobile electronics, and other areas as alternatives to fossil fuels.These systems are complex and multi-component with many materials and interfaces that are difficult to handle and characterize. To optimize materials properties and improve battery lifetimes, there is a pressing need for physicochemical characterization approaches with air-free handling capabilities, high spatial resolution, the ability to analyze buried interfaces without damaging the chemistry, and the need to bridge the gap by in situ and operando surface analysis.Developments in X-ray Photoelectron Spectrometers (XPS) open up new capabilities to address these challenges. In this talk, I will discuss how we can overcome obstacles in analyzing battery materials using: Inert environment transfer vessel: This allows for handling battery materials in an air-free environment, which is essential for preventing oxidation and other degradation reactions.Microprobe X-ray source with <5 µm spatial resolution: This provides high spatial resolution for analyzing small areas of interest, such as SEI, dendrites and other features.Hard X-ray source and cluster ion gun source: These allow for the analysis of buried interfaces not accessible by conventional soft X-ray XPS.In situ energy gap measurements: These allow for the study of the changes in the electronic structure of battery materials as they are cycled, which can provide insights into the mechanisms of charge storage and discharge.Operando XPS experiments: These allow for the study of the changes in the surface structure of battery materials as they are operating, which can provide insights into the factors that affect their performance. Figure 1

Trends and Sources of Crime Guns in California: 2010-2021.

Firearm-related interpersonal violence is a leading cause of death and injury in cities across the United States, and understanding the movement of firearms from on-the-books sales to criminal end-user is critical to the formulation of gun violence prevention policy. In this study, we assemble a unique dataset that combines records for over 380,000 crime guns recovered by law enforcement in California (2010-2021), and more than 126,000 guns reported stolen, linked to in-state legal handgun transactions (1996-2021), to describe local and statewide crime gun trends and investigate several potentially important sources of guns to criminals, including privately manufactured firearms (PMFs), theft, and "dirty" dealers. We document a dramatic increase over the decade in firearms recovered shortly after purchase (7% were recovered within a year in 2010, up to 33% in 2021). This corresponds with a substantial rise in handgun purchasing over the decade, suggesting some fraction of newly and legally acquired firearms are likely diverted from the legal market for criminal use. We document the rapid growth of PMFs over the past 2-3 years and find theft plays some, though possibly diminishing, role as a crime gun source. Finally, we find evidence that some retailers contribute disproportionately to the supply of crime guns, though there appear to be fewer problematic dealers now than there were a decade ago. Overall, our study points to temporal shifts in the dynamics of criminal firearms commerce as well as significant city variation in the channels by which criminals acquire crime guns.

Characteristics of the far-field source signature and its ghost effect of a marine single air gun

The estimation of the air gun source signature is a crucial topic in marine seismic. Typical approaches such as numerical modelling or near-field measurement-based inversion normally work in practice, but suffer from lack of knowledge on the varying sea surface reflection coefficient, the signature directional consistency and the dynamically changed source geometry. For better understanding of the above uncertainties, real far-field air gun source signatures were acquired. A customized approach combined with sparse f-k transformation and adaptive subtraction is applied to deblend the source signature from the sea-floor reflections. Characteristic of the ghost notch distribution and bubble oscillation period indicate an overall good match to the simulated results, except the latter part due to the unexpected air-leakage. Amplitude decay with incidence-angle increase is observed, indicating that the point-source spherical theory for directional signature estimation may be questionable. The sea-surface reflection coefficient appears time-variant and frequency-dependent which challenges the assumption of flat sea surface in signature estimation. An innovative notional source inversion workflow is adapted to the frequency-dependent reflection coefficient. The notional signature inversed through the adapted approach results in less ghost residuals and weaker spectral notch effect comparing with the normal inversion result, i.e., based on a constant reflection coefficient.

Design and construction of a compact, high-repetition-rate ultrafast electron diffraction instrument.

We present the design and performance of a compact ultrafast electron diffraction instrument. The diffractometer provides a means of examining time-resolved ultrafast dynamical properties of solids. The system's utilization is discussed in terms of instrument parameters and diffraction data from selected condensed matter samples. The difractometer's performance is highlighted in terms of detection sensitivity, instrumental temporal resolution, and the electron beam transverse coherence length. Following specific details of the construction, we present a practical discussion of parameters such as repetition rate and provide advice on general construction approaches for laboratory-based, keV ultrafast electron diffractometers. In addition, design guidance for constructing a compact electron gun source that is well-suited for studying diffraction from hard condensed matter is given. A unique data acquisition scheme, utilizing high laser repetition rates, is presented.

Study on air gun wavelet characteristics under different source and towed-streamer sinking depths in the Bohai sea

It is important to optimize air gun source design when exploring resources in the Bohai Sea. To date, the majority of related research has focused on the optimal design of array combinations, while research on sources and towed-streamer sinking depths is very limited. In this work, air gun wavelet numerical models were established based on nonideal gas conditions. Then, the wavelet morphologies and spectral characteristics of a single air gun were studied according to the sound wave propagation path under shallow sea conditions. A method for evaluating source performance using wavelets considering the towed-streamer ghost wave was proposed. Finally, 64 simulation experiments considering source and towed-streamer sinking depths were carried out, focusing on analyzing the wavelet and its spectral characteristics under different working conditions. The simulation results verify the reliability of the proposed method and show that this work has important guiding significance for the optimal design and quality evaluation of air gun sources in the Bohai Sea.

Electron beam-induced etching of SiO2, Si3N4, and poly-Si assisted by CF4/O2 remote plasma

Electron-stimulated etching of surfaces functionalized by remote plasma is a flexible and novel approach for material removal. In comparison with plasma dry etching, which uses the ion-neutral synergistic effect to control material etching, electron beam-induced etching (EBIE) uses an electron-neutral synergistic effect. This approach appears promising for the reduction of plasma-induced damage (PID), including atomic displacement and lateral straggling, along with the potential for greater control and lateral resolution. One challenge for EBIE is the limited selection of chemical precursor molecules that can be used to produce functionalized materials suitable for etching under electron beam irradiation. In this work, we studied a new experimental approach that utilizes a remote plasma source to functionalize substrate surfaces in conjunction with electron beam irradiation by an electron flood gun. Etching rates (ERs) of SiO2, Si3N4, and poly-Si are reported in a broad survey of processing conditions. The parametric dependence of the ER of these Si-based materials on the operating parameters of the flood gun and the remote plasma source is evaluated. We also identified the processing parameters that enable the realization of material selective removal, i.e., the etching selectivity of Si3N4 over SiO2 and poly-Si over SiO2. Additionally, surface characterization of etched materials is used to clarify the effects of the co-introduction of particle fluxes from the remote plasma and flood gun sources on surface chemistry.

Privately manufactured firearms, newly purchased firearms, and the rise of urban gun violence

Gun violence in many U.S. cities increased dramatically after the commencement of the COVID-19 pandemic. Surges in criminal access to untraceable privately manufactured firearms and new guns purchased from licensed dealers have been suggested as risk factors associated with the pandemic increase in gun violence. Official data on 4593 guns recovered in Oakland, California between 2017 and 2021 that were submitted to ATF for subsequent tracing are analyzed to determine whether the sources of crime guns changed and whether privately manufactured firearms and fast time-to-crime traced guns were more likely to be used in violent crime during this time period. Descriptive statistics are used to summarize the characteristics of firearms recovered during the study period and the results of ATF tracing. Logistic regression models are then used to assess systematic differences between firearms recovered during the pre-pandemic years as compared to firearms recovered during the pandemic years, and determine whether certain firearms are more likely to be recovered in violent crime. These analyses estimated large increases during the pandemic in the odds that recovered firearms were privately manufactured and recently purchased. Recovered privately manufactured firearms were also more likely to be associated with violent crimes. These findings support recent efforts to regulate privately manufactured firearms and continued efforts to reduce the illegal diversion of firearms from lawful commerce.

Research on combined processing techniques of air gun and sparker source towed streamer seismic data

Research on combined processing techniques of air gun and sparker source towed streamer seismic data

Facial characteristics of air gun array wavelets in the time and frequency domain under real conditions

How to determine the wavelet of air gun source and how to improve the performance of air gun source have gradually become two important topics in the field of air gun. The existing performance evaluation system of air gun array can only evaluate the performance of air gun from a single point of view, and can not characterize the change of three-dimensional acoustic field produced by air gun array. We first use the Van der Waals air gun wavelet model to simulate the three-dimensional air gun spatial wave field under real conditions. The experimental and modeled data are in good agreement at different pressure amplitudes and frequencies. Then, based on the three-dimensional spatial acoustic field simulated by the model, we proposed a facial characteristics to evaluate the time domain and frequency domain characteristics of the three-dimensional acoustic field. In this air gun wavelet evaluation system, we extend the evaluation parameters such as zero peak, peak-to-peak amplitude, bubble period and main bubble ratio from single wavelet to acoustic field, from one dimension to three dimension. By introducing the instantaneous property of wavelet, we can observe the amplitude, phase and frequency of the far-field wavelet from different angles. The experimental results show that the proposed air gun wavelet evaluation system can evaluate the spatial wave field from any Angle with multiple parameters, and effectively guide the optimization of the structure of the air gun array.

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.

Seismic Anisotropy Within an Active Fluid Flow Structure: Scanner Pockmark, North Sea

Understanding sub-seabed fluid flow mechanisms is important for determining their significance for ocean chemistry and to define fluid pathways above sub-seafloor CO2storage reservoirs. Many active seabed fluid flow structures are associated with seismic chimneys or pipes, but the processes linking structures at depth with the seabed are poorly understood. We use seismic anisotropy techniques applied to ocean bottom seismometer (OBS) data, together with seismic reflection profiles and core data, to determine the nature of fluid pathways in the top tens of meters of marine sediments beneath the Scanner pockmark in the North Sea. The Scanner pockmark is 22 m deep, 900 m × 450 m wide and is actively venting methane. It lies above a chimney imaged on seismic reflection data down to ∼1 km depth. We investigate azimuthal anisotropy within the Scanner pockmark and at a nearby reference site in relatively undisturbed sediments, using the PS converted (C-) waves from a GI gun source, recorded by the OBS network. Shear-wave splitting is observed on an OBS located within the pockmark, and on another OBS nearby, whereas no such splitting is observed on 23 other instruments, positioned both around the pockmark, and at an undisturbed reference site. The OBSs that show anisotropy have radial and transverse components imaging a shallow phase (55–65 ms TWT after the seabed) consistent with PS conversion at 4–5 m depth. Azimuth stacks of the transverse component show amplitude nulls at 70° and 160°N, marking the symmetry axes of anisotropy and indicating potential fracture orientations. Hydraulic connection with underlying, over pressured gas charged sediment has caused gas conduits to open, either perpendicular to the regional minimum horizontal stress at 150–160 N or aligned with a local stress gradient at 50–60 N. This study reports the first observation of very shallow anisotropy associated with active methane venting.

A Modeling Comparison of the Potential Effects on Marine Mammals from Sounds Produced by Marine Vibroseis and Air Gun Seismic Sources

Concerns about the potential environmental impacts of geophysical surveys using air gun sources, coupled with advances in geophysical surveying technology and data processing, are driving research and development of commercially viable alternative technologies such as marine vibroseis (MV). MV systems produce controllable acoustic signals through volume displacement of water using a vibrating plate or shell. MV sources generally produce lower acoustic pressure and reduced bandwidth (spectral content) compared to air gun sources, but to be effective sources for geophysical surveys they typically produce longer duration signals with short inter-signal periods. Few studies have evaluated the potential effects of MV system use on marine fauna. In this desktop study, potential acoustic exposure of marine mammals was estimated for MV and air gun arrays by modeling the source signal, sound propagation, and animal movement in representative survey scenarios. In the scenarios, few marine mammals could be expected to be exposed to potentially injurious sound levels for either source type, but fewer were predicted for MV arrays than air gun arrays. The estimated number of marine mammals exposed to sound levels associated with behavioral disturbance depended on the selection of evaluation criteria. More behavioral disturbance was predicted for MV arrays compared to air gun arrays using a single threshold sound pressure level (SPL), while the opposite result was found when using frequency-weighted sound fields and a multiple-step, probabilistic, threshold function.

Underground Gun Markets and the Flow of Illegal Guns into the Bronx and Brooklyn: A Mixed Methods Analysis

New York City (NYC) has experienced large reductions in violent crime over the last two decades, but gun-related violence continues to pose a threat to public safety. Despite strong gun laws, high-risk individuals in NYC neighborhoods are unfortunately still able to access and misuse firearms. This research analyzes NYC's underground gun market by closely examining the flow of guns into the two boroughs where gun violence and crime gun recoveries are most prevalent: the Bronx and Brooklyn. A mixed methods approach is utilized that consists of an assessment of firearms trace data and in-depth interviews with individuals considered to be at high risk for involvement in gun violence. Findings suggest that guns recovered in the Bronx and Brooklyn were significantly more likely to originate in states with less restrictive gun laws and more likely to have changed ownership in unregulated transactions relative to guns recovered elsewhere in NYC. Interviews revealed three primary avenues for illegal guns reaching Bronx and Brooklyn neighborhoods: high-volume gun brokers, middlemen, and individuals who make episodic low-level acquisitions from straw purchasers in other states. No subjects identified theft as a meaningful source of crime guns.

The influence of firearms trafficking on gunshot injuries in a co-offending network.

Individuals at the greatest risk of gunshot victimization are often prohibited from legally acquiring guns in the U.S. due to prior felony convictions or other disqualifications. Prohibited persons often rely on others - such as friends, family members, fellow gang members, and gun brokers - to acquire firearms. This study examines whether the sources of guns recovered from high-risk individuals differ relative to the sources of guns recovered more generally in a major U.S. city, and whether illegally-diverted guns are associated with increased gunshot victimization risk. Using official data, we recreate the co-offending network of individuals in Boston who were arrested or contacted by the police with at least one other person between 2007 and 2014. Firearms trace data are then used to develop measures of the shortest distance between individuals and firearms in their immediate network. Results suggest guns with markers of illegal diversion are more likely to be recovered in the highest risk sector of the network and that the probability of gunshot victimization increases with decreased distance to an individual linked to firearms with markers of illegal trafficking.

Internal Structure of the Oceanic Lithosphere at a Melt‐Starved Ultraslow‐Spreading Mid‐Ocean Ridge: Insights From 2‐D Seismic Data

AbstractExtensive outcrops of serpentinized peridotite in melt‐starved spreading corridors of the ultraslow easternmost Southwest Indian Ridge are hypothesized to be due to slip on successive long‐offset normal faults that alternate polarity (flip‐flop detachment faults). We investigate the nature of the oceanic crust which forms under these conditions, using seismic reflection data acquired during the SISMOSMOOTH 2014 cruise. Using 3‐D binning, the seismic profiles were binned elastically, while three of the profiles shot closely were merged into one to take advantage of the larger air gun source volume. Using a poststack imaging sequence, we observe several types of reflectors at crustal and infracrustal depths, in the axial valley and off‐axis. Correlating our seismic observations with Residual Mantle Bouguer gravity anomalies and seafloor observations, we find that our results are explicable in the framework of the flip‐flop hypothesis of detachment faulting. Reflectors imaged down to 5 km into the basement and interpreted as due to damaged zones outlining the detachment faults dip 50° at the early stages, while at late stages after developing offsets &gt;10 km, they dip 25°. Other reflectors observed in the crust are interpreted as moderate offset (&lt;200 m) normal faults accommodating deformation and alteration in the hanging wall and channeling the sparse melt to the seafloor. We interpret these and other observed seismic reflectors in the frame of a two‐phase evolutionary sequence over the lifetime of two successive flip‐flop detachment faults: exhumation, footwall flexure, damage, serpentinization, and incipient magmatism in the footwall of one detachment fault; followed by further tectonic damage, alteration, and incipient magmatism in the hanging wall of the next detachment fault.

Gun Source and Muzzle Head Detection

There is a surging need across the world for protection against gun violence. There are three main areas that we have identified as challenging in research that tries to curb gun violence: temporal location of gunshots, gun type prediction and gun source (shooter) detection. Our task is gun source detection and muzzle head detection, where the muzzle head is the round opening of the firing end of the gun. We would like to locate the muzzle head of the gun in the video visually, and identify who has fired the shot. In our formulation, we turn the problem of muzzle head detection into two sub-problems of human object detection and gun smoke detection. Our assumption is that the muzzle head typically lies between the gun smoke caused by the shot and the shooter. We have interesting results both in bounding the shooter as well as detecting the gun smoke. In our experiments, we are successful in detecting the muzzle head by detecting the gun smoke and the shooter.

Comparison of Propagation Models for the Characterization of Sound Pressure Fields

This paper aimed at comparing different propagation models for the calculation of sound pressure fields in the ocean as well as sound exposure levels. The chosen models are freely available and commonly used by the general underwater acoustics community when sound propagation losses need to be predicted in an ocean environment. The models used were Ocean Acoustics and Seismic Exploration Synthesis (OASES), RAM, Bellhop, and Kraken, which are all based on different approximations of the wave equation. The comparison exercise was carried out by calculating propagation loss, sound pressure waveforms, and sound exposure levels produced by a modeled air gun source. Calculations were performed for a simple range-independent problem of a Pekeris waveguide and produced insights into applicability of each model with regards to near- and far-fields, as well as low and high frequencies for example. Two of the models, RAM and Bellhop, which are suitable to range-dependent problems, were also used to solve a slightly complex case having a sloping bottom. It is hoped that the results presented here will be particularly useful to those who need to use propagation models for marine environmental and bioacoustics studies.

Effects of the Rough Sea Surface on the Signature of a Single Air Gun

The calculation of air gun source signatures gives insight into applications such as air gun array design, deghosting and the impact of sound on marine life. Single air gun source signatures were calculated from the numerical solution of a set of differential equations based on different branches of physics. Some characteristic parameters of air guns were obtained from the Svein Vaage broadband air gun data set (SVBAD) measurements to calibrate the model. The comparison between measured and modeled air gun signals helps to investigate the accuracy of air gun source models. The modeled air gun signatures compared well with measurements from the SVBAD for the case of a calm sea surface of sea state 2 or less. The source ghost signal modeled for a rough sea surface showed amplitude and phase changes, affecting the ghost notches, which may explain discrepancies between the SVBAD measurements and modeled air gun signals at frequencies above 150 Hz.