External Background Research Articles

Charged and rotating multi-black holes in an external gravitational field

We construct analytical and regular solutions in four-dimensional General Relativity which represent multi-black hole systems immersed in external gravitational field configurations. The external field background is composed by an infinite multipolar expansion, which allows to regularise the conical singularities of an array of collinear static black holes. A stationary rotating generalisation is achieved by adding independent angular momenta and NUT parameters to each source of the binary configuration. Moreover, a charged extension of the binary black hole system at equilibrium is generated. Finally, we show that the binary Majumdar–Papapetrou solution is consistently recovered in the vanishing external field limit. All of these solutions reach an equilibrium state due to the external gravitational field only, avoiding in this way the presence of any string or strut defect.

Background knowledge in ontology matching: A survey

Ontology matching is an integral part for establishing semantic interoperability. One of the main challenges within the ontology matching operation is semantic heterogeneity, i.e. modeling differences between the two ontologies that are to be integrated. The semantics within most ontologies or schemas are, however, typically incomplete because they are designed within a certain context which is not explicitly modeled. Therefore, external background knowledge plays a major role in the task of (semi-) automated ontology and schema matching. In this survey, we introduce the reader to the general ontology matching problem. We review the background knowledge sources as well as the approaches applied to make use of external knowledge. Our survey covers all ontology matching systems that have been presented within the years 2004–2021 at a well-known ontology matching competition together with systematically selected publications in the research field. We present a classification system for external background knowledge, concept linking strategies, as well as for background knowledge exploitation approaches. We provide extensive examples and classify all ontology matching systems under review in a resource/strategy matrix obtained by coalescing the two classification systems. Lastly, we outline interesting and yet underexplored research directions of applying external knowledge within the ontology matching process.

Occupational Exposure to Silica Nanoparticles: Evaluation of Emission Fingerprints by Laboratory Simulations

Silica nanoparticles (SiO2 NPs), due to their chemical-physical properties, are among the most widely produced nanomaterials (NMs) in the world, and therefore used in a wide range of industries. Such widespread use, however, draws attention to the health of workers during the production of such NMs and the need for techniques to assess occupational exposure. In the present study, laboratory simulation techniques were used to reproduce a critical work activity in a controlled environment in order to identify emission profiles useful for studying exposure during NM handling in the workplace. Weighing activity inside a glove box isolated from the external environment background and any pollutants was simulated. Real-time instrumentation was used to calculate the concentration, size distribution and surface area of the particles generated during the simulation, and time-integrated instrumentation was used to collect dust for off-line analysis.

Background shielding by dense samples in low-level gamma spectrometry

In low activity gamma spectrometric measurements of large, dense samples, the bulk sample material shields the HPGe crystal from external background sources. If not accounted for in studies that utilise background-subtraction methods, this effect may result in systematic errors in the sample activity and detection limit estimation. We introduce a Monte Carlo based method to minimise the impact of this effect on sample gamma spectra. It is validated using simulated detector backgrounds and applied to a measurement of low-activity Gd2SO43⋅8H2O. One main prerequisite for the correct application of this method is to know in advance the nuclides which contribute to the detector background spectrum and their spatial distribution. With a thorough understanding of the detector backgrounds, the method improves the accuracy of sensitive low-background measurements of low-activity samples. Even without knowing the background sources and their distribution, conservative results may still be presented that account for the potential systematic errors introduced by this background shielding effect.

KRYSTAL: Knowledge graph-based framework for tactical attack discovery in audit data

Attack graph-based methods are a promising approach towards discovering attacks and various techniques have been proposed recently. A key limitation, however, is that approaches developed so far are monolithic in their architecture and heterogeneous in their internal models. The inflexible custom data models of existing prototypes and the implementation of rules in code rather than declarative languages on the one hand make it difficult to combine, extend, and reuse techniques, and on the other hand hinder reuse of security knowledge – including detection rules and threat intelligence. KRYSTAL tackles these challenges by providing a knowledge graph-based, modular framework for threat detection, attack graph and scenario reconstruction, and analysis based on RDF as a standard model for knowledge representation. This approach provides query options that facilitate contextualization over internal and external background knowledge, as well as the integration of multiple detection techniques, including tag propagation, attack signatures, and graph queries. We implemented our framework in an openly available prototype and demonstrate its applicability on multiple scenarios of the DARPA Transparent Computing dataset. Our evaluation shows that the combination of different threat detection techniques within our framework improved detection capabilities. Furthermore, we find that RDF provenance graphs are scalable and can efficiently support a variety of threat detection techniques.

Intercomparisons of methods for extracting the internal climate variability from the observed records over the Indo‐Pacific sector

AbstractA careful isolation of the externally forced component (EFC) and the internal climate variability (ICV) embedded in the observed records as well as the climate simulations is critical to investigate an actual response to the external radiative forcing and/or background dynamics in the ICV. Employing three different methods, we evaluate the EFCs contained in the observed sea surface temperature (SST) and sea level pressure (SLP) fields in the Indo‐Pacific region. After removing these EFCs, we obtain the respective ICVs as the remaining anomalies. The remaining SST and SLP anomalies are then evaluated on decadal time scales in a combined empirical orthogonal function (EOF) analysis of different spatial portions: the tropical Pacific, the Indian Ocean and the whole Indo‐Pacific region. After making statistical intercomparisons of the spatial patterns and associated time series of the EOF analyses, we found that the EFCs of the individual grid point values (GPVs) were appropriately estimated by regressing onto the multi‐model ensemble global mean surface temperature (GMSTMME) and were less well approximated by the conventional linear trend and the multi‐model ensemble mean of the simulated GPVs. The regressed SST anomalies of the individual historical simulations onto the GMSTMME were much larger than the observed anomalies, illustrating that the ICV‐to‐EFC variance ratio is a performance‐improvement indicator of climate models.

A Reel-to-Reel Scanning Hall Probe Microscope for Characterizing Long REBCO Conductor in Magnetic Fields Up to 5 Tesla

We have developed and routinely used a reel-to-reel (R2R) scanning Hall-probe microscopy (SHPM) system to characterize REBCO conductors developed at the University of Houston. By mapping the screening-current-induced field of a magnetized REBCO conductor, the SHPM system enables 2-dimensional imaging of critical current density (<i>J</i>_c) distribution in a contact-free, non-destructive approach. Most existing SHPM systems investigate the magnetized REBCO conductors at remnant state without external background field. However, because of the inhomogeneity in the distribution of nanoscale artificial pinning centers in advanced REBCO conductors, there is a demand for reel-to-reel in-field examination over long conductor lengths. We have been developing a new R2R SHPM, capable of measuring the <i>J</i>_c profile of long REBCO conductors at the temperature of 63.5&#x2013;77 K and in an applied field up to 5 T. With optimal data acquisition and processing techniques, we overcame the challenge of measuring weak screening-current-field signals in a strong background field. R2R <i>J</i>_c mapping has been performed on long REBCO conductors with a spatial resolution as low as 0.15 mm² and a longitudinal scanning speed comparable with our existing system. Our previous study revealed a good correlation between the REBCO conductors&#x2019; 65-K in-field <i>J</i>_c and their <i>J</i>_c over a wide span of temperatures and fields. Using this correlation, the in-field R2R SHPM will serve not only as a means of quality control, but also provide insight into high-field performance of advanced REBCO conductors at low temperatures.

Spontaneous symmetry breakings in the singlet scalar Yukawa model within the auxiliary field method

The aim of this work is to investigate the occurrence of two different spontaneous symmetry breakings at two levels of the description of fermion-scalar field model, by means of a set of gap equations and with a background field effective action. For that, we consider the Yukawa model, as a toy model for interactions between nonmassive fermions intermediated by a self-interacting real scalar field. This model has at stake two symmetries at the classical level that, as we know, might be spontaneously or dynamically broken with mass generation for the particles. The auxiliary field method is considered and it produces coupled renormalized gap equations. The effective action is then written with quantum contributions by the external background field method. We brought to light how the renormalization procedure affects the physical gaps, investigate its properties, and discuss the connection between the auxiliary fields not only to define composite states but also to compute the effective action.

Spinor Field Singular Functions in QED with Strong External Backgrounds

We construct and study singular functions in strong-field $QED$ with two external electromagnetic fields that represent principally different types of external backgrounds, the first one belongs to the class of so-called $t$-potential electric steps (electric-like fields that are switched on and off at initial and final time instants), and the second one belongs to the class of so-called $x$-potential electric steps (time-independent electric-like fields of constant direction that are concentrated in a restricted spatial area). As the first background ($T$-constant electric field) is chosen an uniform electric field which acts during a finite time interval $T$ , whereas as the second background ($L$-constant electric field) is chosen a constant electric field confined between two capacitor plates separated by a large distance $L$. For the both cases we find \textrm{in}- and \textrm{out}-solutions of the Dirac equation in terms of light cone variables. With the help of these solutions, we construct Fock-Schwinger proper-time integral representations for all the singular functions that provide nonperturbative (with respect to the external backgrounds) calculations of any transition amplitudes and mean values of any physical quantities. Considering calculations in the $T$-constant field and in the $L$-constant field as different regularizations of the corresponding calculations in the constant uniform electric field, we have demonstrated their equivalence for sufficiently large $T$ and $L$.

Dynamical fixed points in holography

Typically, an interactive system evolves towards thermal equilibrium, with hydrodynamics representing a universal framework for its late-time dynamics. Classification of the dynamical fixed points (DFPs) of a driven Quantum Field Theory (with time dependent coupling constants, masses, external background fields, etc.) is unknown. We use holographic framework to analyze such fixed points in one example of strongly coupled gauge theory, driven by homogeneous and isotropic expansion of the background metric — equivalently, a late-time dynamics of the corresponding QFT in Friedmann-Lemaitre­Robertson-Walker Universe. We identify DFPs that are perturbatively stable, and those that are perturbatively unstable, computing the spectrum of the quasinormal modes in the corresponding holographic dual. We further demonstrate that a stable DFP can be unstable non-perturbatively, and explain the role of the entanglement entropy density as a litmus test for a non-perturbative stability. Finally, we demonstrated that a driven evolution might not have a fixed point at all: the entanglement entropy density of a system can grow without bounds.

A Study of the Effect of Sound Therapy in People with Mild Tinnitus

Purpose: Tinnitus refers to the maladaptive perception of sound in the absence of external sounds. Sound therapy is a representative rehabilitation option that has been used to relieve the adverse effects of tinnitus. It helps to reduce the discomfort caused by tinnitus by providing various external background noises to those suffering from tinnitus. The purpose of this study was to identify the effects of sound therapy on tinnitus relief in people with mild tinnitus.Methods: Twelve participants with mild tinnitus participated in this study. Sound therapy was performed for 3 months using a customized mobile phone application. Broadband noise was used as the sound therapy stimulus. The level of stimulus was set to the level of the mixing point. The Korean version of the Tinnitus Primary Function Questionnaire (K-TPFQ) score, Visual Analogue Scale (VAS) score, and tinnitus loudness level were recorded as outcome measurements at baseline and 3 months.Results: There were no significant differences in the K-TPFQ and VAS scores and tinnitus loudness level between the baseline and 3-month follow-up session.Conclusion: The results of this study showed that sound therapy alone for 3 months does not provide significant tinnitus relief in participants with mild tinnitus. Therefore, considering only sound therapy for rehabilitation in people with mild tinnitus might not be ideal for providing relief.

The emission properties, structure and stability of ionic liquid menisci undergoing electrically assisted ion evaporation

The properties and structure of electrically stressed ionic liquid menisci experiencing ion evaporation are simulated using an electrohydrodynamic model with field-enhanced thermionic emission in steady state for an axially symmetric geometry. Solutions are explored as a function of the external background field, meniscus dimension, hydraulic impedance and liquid temperature. Statically stable solutions for emitting menisci are found to be constrained to a set of conditions: a minimum hydraulic impedance, a maximum current output and a narrow range of background fields that maximizes at menisci sizes of 0.5–3 ${\rm \mu}{\rm m}$ in radius. Static stability is lost when the electric field adjacent to the electrode that holds the meniscus corresponds to an electric pressure that exceeds twice the surface tension stress of a sphere of the same size as the meniscus. Preliminary investigations suggest this limit to be universal, therefore, independent of most ionic liquid properties, reservoir pressure, hydraulic impedance or temperature and could explain the experimentally observed bifurcation of a steady ion source into two or more emission sites. Ohmic heating near the emission region increases the liquid temperature, which is found to be important to accurately describe stability boundaries. Temperature increase does not affect the current output when the hydraulic impedance is constant. This phenomenon is thought to be due to an improved interface charge relaxation enhanced by the higher electrical conductivity. Dissipated ohmic energy is mostly conducted to the electrode wall. The higher thermal diffusivity of the wall versus the liquid, allows the ion source to run in steady state without heating.

The SHADES neutron detection array

The detection of neutrons in low energy astrophysics poses two main problems: low cross section measurement requires high detection efficiency and ideally, beam-induced and external neutron backgrounds should be identified through an energy sensitive detector. In recent years, capture-gated neutron spectroscopy has found new opportunities to grow through new materials and better availability of modern data acquisition systems. In this work we will present the design, expected capabilities and preliminary characterization of the hybrid neutron detector array SHADES. Its purpose is the first direct measurement of the reaction 22Ne(α, n)25Mg in the Gamow window for s-process nucleosynthesis with LUNA-MV in the deep underground environment of the LNGS.

Discussion on the Change of Nationalism in German Gymnastics in the 19th Century: Focusing on Two Nationalists

PURPOSE This study examined the process and cause of change in nationalism in German gymnastics in the 19th century.METHODS The study used a literature study method and analyzed data from previous studies. Eleven articles related to the research topic were chosen for domestic research data by searching RISS for "German gymnastics," "Turnen," and "German nationalism." Overseas research data involved seven articles related to this study and were found by searching for "German gymnastics" and "Turnen" in Google Scholar.RESULTS First, German nationalism was originally divided into liberal nationalism and nationalistic nationalism, resulting in nationalistic nationalism after German reunification. Second, Jahn as a liberal nationalist and Spiess as a nationalist attempted to spread their ideas through German gymnastics. Finally, German gymnastics change from Jahn's liberal nationalism to Spiess' nationalistic nationalism was inevitable due to German gymnastics' external background and inherent limitations.CONCLUSIONS This study illustrated the process and cause of the change in the nationalistic characteristics of German gymnastics in the 19th century. Various historical cases that have not yet received attention but are worthy of investigation must be studied.

ОПТОЕЛЕКТРОННИЙ АПАРАТНО-ПРОГРАМНИЙ МОНОМОДУЛЬНИЙ ДАТЧИК МЕТЕОРОЛОГІЧНОЇ ДАЛЬНОСТІ ВИДИМОСТІ ТА ПРОЗОРОСТІ АТМОСФЕРИ З АВТОМАТИЧНОЮ КОРЕКЦІЄЮ ВПЛИВУ ЗОВНІШНЬОГО ЗАБРУДНЕННЯ ОПТИЧНИХ СИСТЕМ

A model sample of a monomodular hardware-software optoelectronic sensor of k-factor, meteorological range of visibility and atmosphere transparency with high technical and operational characteristics of small -sized execution is developed and created. The combination in the algorithm of functioning of the developed hardware-software methods of sensor creation provided increase of accuracy and invariance of results of measurement concerning external background illumination and self-testing with automatic correction of pollution effect of optical windows of the sensor. Continuous monitoring of the degree of contamination of optical windows provides an opportunity in case of detection of exceeding the permissible level of pollution to provide the operator with information about the need for preventive work. The proposed method of automatic correction of contamination of optical windows either completely eliminates or significantly increases the time interval of their mechanical cleaning operations, which reduces labour costs for maintenance of the sensor. The analysis of technical capabilities of the nodes of the model sample of the sensor allowed to estimate its basic meteorological parameters: the k-factor – (0.17÷1.11∙10-4) m-1, the meteorological visibility – (18÷27∙103 ) m and the atmosphere transparency per 1 km of the layer – (0÷0.895). The developed meteorological sensor can be used as a basic remote-controlled instrument for measuring meteorological parameters of the state of the atmosphere at the hydrometeorological stations of the country, mobile meteorological stations, stationary meteorological stations of road and air services to ensure guaranteed safety of workers.

Vacuum instability due to the creation of neutral fermion with anomalous magnetic moment by magnetic-field inhomogeneities

We study neutral fermions pair creation with anomalous magnetic moment from the vacuum by time-independent magnetic-field inhomogeneity as an external background. We show that the problem is technically reduced to the problem of charged-particle creation by an electric step, for which the nonperturbative formulation of strong-field QED is used. We consider a magnetic step given by an analytic function and whose inhomogeneity may vary from a “gradual” to a “sharp” field configuration. We obtain corresponding exact solutions of the Dirac-Pauli equation with this field and calculate pertinent quantities characterizing vacuum instability, such as the differential mean number and flux density of pairs created from the vacuum, vacuum fluxes of energy and magnetic moment. We show that the vacuum flux in one direction is formed from fluxes of particles and antiparticles of equal intensity and with the same magnetic moments parallel to the external field. Backreaction to the vacuum fluxes leads to a smoothing of the magnetic-field inhomogeneity. We also estimate critical magnetic field intensities, near which the phenomenon could be observed.

Pneumoconiosis computer aided diagnosis system based on X-rays and deep learning

PurposeThe objective of this study is to construct a computer aided diagnosis system for normal people and pneumoconiosis using X-raysand deep learning algorithms.Materials and methods1760 anonymous digital X-ray images of real patients between January 2017 and June 2020 were collected for this experiment. In order to concentrate the feature extraction ability of the model more on the lung region and restrain the influence of external background factors, a two-stage pipeline from coarse to fine was established. First, the U-Net model was used to extract the lung regions on each sides of the collection images. Second, the ResNet-34 model with transfer learning strategy was implemented to learn the image features extracted in the lung region to achieve accurate classification of pneumoconiosis patients and normal people.ResultsAmong the 1760 cases collected, the accuracy and the area under curve of the classification model were 92.46% and 89% respectively.ConclusionThe successful application of deep learning in the diagnosis of pneumoconiosis further demonstrates the potential of medical artificial intelligence and proves the effectiveness of our proposed algorithm. However, when we further classified pneumoconiosis patients and normal subjects into four categories, we found that the overall accuracy decreased to 70.1%. We will use the CT modality in future studies to provide more details of lung regions.

Black hole induced false vacuum decay from first principles

We provide a method to calculate the rate of false vacuum decay induced by a black hole. The method uses complex tunneling solutions and consistently takes into account the structure of different quantum vacua in the black hole metric via boundary conditions. The latter are connected to the asymptotic behavior of the time-ordered Green’s function in the corresponding vacua. We illustrate the technique on a two-dimensional toy model of a scalar field with inverted Liouville potential in an external background of a dilaton black hole. We analytically derive the exponential suppression of tunneling from the Boulware, Hartle-Hawking and Unruh vacua and show that they are parametrically different. The Unruh vacuum decay rate is exponentially smaller than the decay rate of the Hartle-Hawking state, though both rates become unsuppressed at high enough black hole temperature. We interpret the vanishing suppression of the Unruh vacuum decay at high temperature as an artifact of the two-dimensional model and discuss why this result can be modified in the realistic case of black holes in four dimensions.

Epistemology of Prison Interpretation: Analysis of Hamka and Sayyid Qutb’s Political Thoughts

This article reviews the epistemology of the works of interpretation generated from prison rooms. Hamka and Qutb have similarities in their life struggles. Their presence in prison greatly influences the pattern of their phenomenal works in the field of interpretation, Al-Azhar and Fi Zilal al-Qur'an. The objective of writing this article is to make a typification through a hermeneutic-philosophy-based approach. From the analysis carried out, we find a conclusion that each character, even though both are in prison, both have differences and similarities in the character of the work produced. This can be seen from his interpretation of the verses concerning politics. A comparative analysis shows that three domains characterize the prison interpretation of the two: first, the interpretation is generated from a strong psychosocial aspect of the author's affection; second, the interpretation contains more explanations that are building a system of action; Third, the difference in interests in writing commentaries is caused by the external and internal background of the writer's life.

Calculation of the Effective Energy Release Centerʼs Position of Inorganic Scintillation Detectors for Calibration at Small “Source–Detector” Distances

Inorganic scintillation detectors are widely used to measure of dose rate in the environment due to their high sensitivity to photon radiation. A distinctive feature when using such detectors is the need to take into account of the position of the effective energy release center. This peculiarity is actual when using measuring instruments with inorganic scintillation detectors as working standards during calibration at short “source–detector” distances in conditions of low-background shield or using a facility with protection from external gamma radiation background in the dose rate range from 0.03 to 0.3 μSv/h (μGy/h). The purpose of this work was to calculate the position of the effective energy release center of NaI(Tl) scintillation detectors and to take it into account when working at short “source–detector” distances.An original method of determining the position of the effective energy release center when irradiating the side and end surfaces of inorganic scintillation detector with parallel gamma radiation flux and point gamma radiation sources at small “source–detector” distances using Monte Carlo methods is proposed. The results of calculations of the position of the effective energy release center of NaI(Tl) based detectors of “popular” sizes for the cases of parallel gamma radiation flux and point sources of gamma radiation at small “source–detector” distances are presented. The functional dependences of the position of the effective energy release center of NaI(Tl) based detectors on the distance to the point gamma radiation sources and the energy of gamma radiation sources are presented.As a result of the study it was found that for scintillation NaI(Tl) detectors of medium size (for example, Ø25×40 mm or Ø40×40 mm) the point gamma radiation source located at a distance of 1 m or more, creates a radiation field which does not differ in characteristics from the radiation field created by a parallel flux of gamma radiation. It is shown that approaching the point gamma radiation source to the surface of scintillation detector leads to displacement of the position of the effective energy release center to the surface of the detector.