Holes In Clusters Research Articles

Key Technologies for Volume Fracturing of Yingxiongling Shale Oil in the Qaidam Basi

Abstract The Yingxiongling shale oil in the Qaidam Basin is the preferred choice for Qinghai Oilfield to enter the field of unconventional oil and gas resources, and volume fracturing is the core technology for shale oil exploration and development. Through the analysis of the geological and engineering characteristics of the Yingxiongling shale oil, it is found that there are difficulties in volume fracturing of the Yingxiongling shale oil, such as frequent changes in vertical mechanical properties and limited vertical control range; large stress differences, making it difficult to form complex artificial fractures; difficulty in opening multiple clusters of perforation holes; high water shortage in the plateau, high mineralization of the formation backflow fluid, and difficulty in reusing the backflow fluid. By iteratively modeling three-dimensional geomechanics, a high-resolution three-dimensional geomechanical model is established to guide the optimization of volume fracturing schemes. Through the integration of geological and engineering selection and clustering, three-stage active control technology for cracks, and the dual temporary plugging process of boreholes and cracks, the targeted and complex degree of artificial crack transformation can be improved. Through the study of high salinity fracturing fluid system, it has been found that high salinity backflow fluid can replace slick water and alleviate the demand for fresh water in volume fracturing. The article analyzes the difficulties of shale oil volume fracturing and studies the formation of an effective set of key techniques for volume fracturing, achieving the goal of improving the degree and effectiveness of transformation, and providing support for the exploration and development of the Yingxiongling shale oil in the Qaidam Basin.

Supermassive black hole formation via collisions in black hole clusters

More than 300 supermassive black holes have been detected at redshifts larger than six, and they are abundant in the centers of local galaxies. Their formation mechanisms, however, are still rather unconstrained. A possible origin of these supermassive black holes could be mergers in dense black hole clusters, forming as a result of mass segregation within nuclear star clusters at the center of galaxies. In this study, we present the first systematic investigation of the evolution of such black hole clusters in which the effect of an external potential is taken into account. Such a potential could be the result of gas inflows into the central region; for example, as a result of galaxy mergers. We show here that the efficiency of the formation of a massive central object is mostly regulated by the ratio of cluster velocity dispersion divided by the speed of light, potentially reaching efficiencies of 0.05–0.08 in realistic systems. Our results show that this scenario is potentially feasible and may provide black hole seeds of at least 103 M⊙. We conclude that the formation of seed black holes via this channel should be taken into account in statistical assessments of the black hole population.

Contamination in Trypophobia: investigating the role of disgust

ABSTRACT Trypophobia is a relatively common aversion to clusters of holes. There is no consensus yet on which emotions are involved in Trypophobia nor in its functional utility. This report investigates the role of disgust using contamination tasks in two studies, which contrast people with an aversion to trypophobic stimuli to those without. In Study 1, participants reported their emotional reactions to imagined contamination of trypophobic images. In Study 2, participants evaluated physically present trypophobic, disgust, fear, and control stimuli. The capacity of these stimuli to contaminate other objects was established using a chain of contagion task. Across both studies, contamination was present, however, only those with an aversion to trypophobic stimuli evidenced contamination on the chain of contagion task, a hallmark of disgust responding. Elevated levels were not only reported for disgust, but also alongside fear/anxiety. Participant reports suggest an underlying disease avoidance mechanism in Trypophobia, with trypophobic participants demonstrating an exaggerated response to such stimuli involving disgust and fear/anxiety, which is also seen in small animal phobia, BII, and C-OCD. Implications, particularly for treatment are discussed.

Clustering of primordial black holes from quantum diffusion during inflation

We study how large fluctuations are spatially correlated in the presence of quantum diffusion during inflation. This is done by computing real-space correlation functions in the stochastic-δ N formalism. We first derive an exact description of physical distances as measured by a local observer at the end of inflation, improving on previous works. Our approach is based on recursive algorithmic methods that consistently include volume-weighting effects. We then propose a “large-volume” approximation under which calculations can be done using first-passage time analysis only, and from which a new formula for the power spectrum in stochastic inflation is derived. We then study the full two-point statistics of the curvature perturbation. Due to the presence of exponential tails, we find that the joint distribution of large fluctuations is of the form P(ζ R 1, ζ R 2) = F(R 1,R 2, r) P(ζ R 1)P( ζ R 2), where ζ R 1 and ζ R 2 denote the curvature perturbation coarse-grained at radii R 1 and R 2, around two spatial points distant by r. This implies that, on the tail, the reduced correlation function, defined as P(ζ R 1 > ζc, ζ R 2 > ζc)/[P(ζ R 1 > ζc) P(ζ R 2 > ζc)]-1, is independent of the threshold value ζc. This contrasts with Gaussian statistics where the same quantity strongly decays with ζc, and shows the existence of a universal clustering profile for all structures forming in the exponential tails. Structures forming in the intermediate (i.e. not yet exponential) tails may feature different, model-dependent behaviours.

Investigation of the dynamics of interaction of a cluster of primordial black holes with stellar cluster

In this paper, we revise dynamical constraint on primordial black hole (PBH) abundance following the effect of their interaction with stellar cluster in dwarf galaxy Eridanus II in case of PBH clustering. We consider scattering of stars on PBH cluster as a whole, dynamical friction of stars inside cluster and finally we are taking into account tidal forces’ effects due to the finite size of PBH cluster. We obtain the rate of change of kinetic energy of the stars and PBHs to make conclusion about constraints on clusters.

Effects of cluster size on trypophobic discomfort in children aged 4–9 years

It has been reported that strong discomfort associated with clusters of circles and holes (trypophobia), including lotus pod seeds, manifests in individuals as young as 4 or 5 years old. This study investigated how the size and number of circles within clusters affected discomfort levels in adults and in children aged 4–9 years. In Experiment 1, we confirmed that the remote experimental procedure could evoke discomfort when participants were presented with cluster images. The findings reveal that children as young as 4 or 5 years old consistently experienced discomfort when rating trypophobic images, even printed images rated in real time during video calls. In Experiment 2, we explored the impact of cluster size, considering both the size and number of circles, in a remote experiment. The results indicate that discomfort tended to increase with cluster size in both children and adults, with the effect becoming more pronounced with age.

The steady state of intermediate-mass black holes near a supermassive black hole

Aims. Our aim is to investigate the properties of a cluster of intermediate-mass black holes (IMBHs) surrounding a supermassive black hole (SMBH). Methods. We simulated clusters of equal-mass IMBHs (mIMBH = 103 M⊙) initialised in a shell between 0.15 ≤ r [pc] ≤ 0.25 centred about a SMBH. We explored the influence of the cluster population and SMBH on the merger rate, the ejection rate, and the escape velocity. For MSMBH = 4 × 106 M⊙, we used both a Newtonian and post-Newtonian formalism, going up to the 2.5th order and including cross terms. We ran 40 and 60 simulations per cluster population for either formalism, respectively. For the other two SMBH masses (MSMBH = 4 × 105 M⊙ and MSMBH = 4 × 107 M⊙), we modelled the system only taking into account relativistic effects. In the case of MSMBH = 4 × 105 M⊙, 30 simulations were run per population. For MSMBH = 4 × 107 M⊙ we ran ten simulations per population. The simulations ended once a black hole escaped the cluster, a merger occured, or the system evolved until 100 Myr. Results. The post-Newtonian formalism accelerates the loss rate of IMBHs compared to the Newtonian formalism. Ejections occur more often for lighter SMBHs while more massive ones increase the rate of mergers. Although relativistic effects allow for circularisation, all merging binaries have e ≳ 0.97 when measured 1 − 2 kyr before the merging event. The strongest gravitational wave signals are often sourced by IMBH-SMBH binaries that eventually merge. Strong signals were suppressed during our Newtonian calculations since, here, the IMBH typically stalls in the vicinity of the SMBH, before being generally ejected via the slingshot mechanism or experiencing a head-on collision. Weaker and more frequent signals are expected from gravitational wave radiation emitted in a flyby. In our post-Newtonian calculations, 30/406 (7.4%) of the gravitational wave events capable of being observed with LISA and μAres were detected as gravitational wave capture binaries with the remaining being in-cluster mergers. Throughout our investigation, no IMBH-IMBH binaries were detected.

Theoretical analysis and engineering application of controllable shock wave technology for enhancing coalbed methane in soft and low-permeability coal seams

Coalbed methane (CBM) is a significant factor in triggering coal and gas outburst disaster, while also serving as a clean fuel. With the increasing depth of mining operations, coal seams that exhibit high levels of gas content and low permeability have become increasingly prevalent. While controllable shockwave (CSW) technology has proven effective in enhancing CBM in laboratory settings, there is a lack of reports on its field applications in soft and low-permeability coal seams. This study establishes the governing equations for stress waves induced by CSW. Laplace numerical inversion was employed to analyse the dynamic response of the coal seam during CSW antireflection. Additionally, quantitative calculations were performed for the crushed zone, fracture zone, and effective CSW influence range, which guided the selection of field test parameters. The results of the field test unveiled a substantial improvement in the gas permeability coefficient, the average rate of pure methane flowrate, and the mean gas flowrate within a 10 m radius of the antireflection borehole. These enhancements were notable, showing increases of 3 times, 13.72 times, and 11.48 times, respectively. Furthermore, the field test performed on the CSW antireflection gas extraction hole cluster demonstrated a noticeable improvement in CBM extraction. After antireflection, the maximum peak gas concentration and maximum peak pure methane flow reached 71.2% and 2.59 m3/min, respectively. These findings will offer valuable guidance for the application of CSW antireflection technology in soft and low-permeability coal seams.

Trypophobia, skin disease, and the visual discomfort of natural textures

In the last decade, the behavioral sciences have described the phenomenon of trypophobia, which is the discomfort felt by some individuals when viewing images containing clusters of bumps or holes. One evolutionary hypothesis for this phenomenon is that this visual discomfort represents an adaptation which helps organisms avoid skin disease and/or ectoparasites. Even though trypophobic imagery and disease imagery are both examples of visual textures, to date there has been no comparison of the visual discomfort elicited by these two specific kinds of textures within the larger context of the visual comfort elicited by natural texture imagery more generally. In the present study, we administered the Trypophobia Questionnaire (TQ) and recorded the visual comfort ratings elicited by a large set of standard natural texture images, including several trypophobic and skin disease images. In two independent samples, we found that while all observers find skin diseases uncomfortable to view, only those scoring high on the TQ rated trypophobic imagery equally uncomfortable. Comparable effects were observed using both standard ANOVA procedures as well as linear mixed effects modeling. Comparing the ratings of both high-TQ and low-TQ participants to the standard textures, we find remarkably consistent rank-order preferences, with the most unpleasant textures (as rated by both groups) exhibiting qualitative similarities to trypophobic imagery. However, we also find that low-level image statistics which have been previously shown to affect visual comfort are poor predictors of the visual comfort elicited by natural textures, including trypophobic and disease imagery. Our results suggest that a full understanding of the visual comfort elicited by natural textures, including those arising from skin disease, will ultimately depend upon a better understanding of cortical areas specialized for the perception of surface and material properties, and how these visual regions interact with emotional brain areas to evoke appropriate behavioral responses, like disgust.

The social learning account of trypophobia.

Trypophobia is the condition in which individuals report a range of negative emotions when viewing clusters of small holes. Since the phenomenon was first described in the peer-reviewed literature a decade ago, 49 papers have appeared together with hundreds of news articles. There has also been much discussion on various Internet forums, including medical and health-related websites. In the present article, we examine the degree to which the phenomenon is caused by a form of social learning, specifically, its ubiquitous social media presence. We also examined its prevalence among the broad population. In Experiment 1 (n = 2,558), we assessed whether younger people and females (i.e., greater social media users) are more sensitive to trypophobic stimuli, as predicted by the social media hypothesis. In Experiment 2 (n = 283), we examined whether sensitivity to trypophobic stimuli and rates of trypophobia is greater in people who are aware of the condition's existence, as opposed to those who have never heard of the phenomenon. In line with the social media theory, results showed that younger people and females are indeed more susceptible to trypophobia. However, 24% of trypophobic individuals have never heard of the condition. Overall, these data suggest that both social learning and non-social learning contribute to trypophobia. We also find that the prevalence of trypophobia is approximately 10%.

Is trypophobia real?

Approximately 10-18% of the adult population experience some form of anxiety when viewing clusters of small holes. 'Trypophobia' has been the subject of much discussion within the peer-reviewed literature, news outlets, health-related websites and social media. However, there is some scepticism surrounding the phenomenon. It is often stated that the condition is not recognised by the American Psychiatric Association, and not listed as a phobia in the DSM-5. It has also been claimed that trypophobia is no more than a particularly successful internet meme. In this editorial, I argue that such criticisms are misplaced. There is, for instance, no list of phobias in the DSM-5; only criteria that determine phobia classification. Using these criteria, as well as personal testimonials, trypophobia is clearly a phobia. Furthermore, the meme hypothesis cannot account for the fact that the phenomenon existed long before the internet.

Generalized black hole clustering algorithm

The Black Hole Clustering (BHC) algorithm is a density-based partitional clustering method inspired by the Density-based Spatial Clustering of Applications with Noise (DBSCAN). It does not require the number of clusters nor the computation of the pair-wise distance matrix between the data points, making it faster than DBSCAN. Also, it only needs one parameter that is intuitively easier to set than the epsilon parameter of DBSCAN. However, BHC needs the allocation of the so-called black holes that have to be linearly independent, making the algorithm in its current version suitable only for two or three-dimensional data sets. In this paper, we propose a generalized version of the black hole clustering algorithm (GBHC) by introducing a novel black hole allocation procedure for higher-dimensional data spaces. Furthermore, the proposed method is data-independent, so we have to run it once to obtain the black hole positions for all finite-dimensional metric spaces. We performed extensive computational experiments to compare GBHC with DBSCAN. The results show that both algorithms obtain comparable clustering solutions. GBHC, however, outperforms DBSCAN in computational complexity and explainability.

Clustering of primordial black holes from QCD axion bubbles

We study the clustering of primordial black holes (PBHs) and axion miniclusters produced in the model proposed to explain the LIGO/Virgo events or the seeds of the supermassive black holes (SMBHs) in ref. [1]. It is found that this model predicts large isocurvature perturbations due to the clustering of PBHs and axion miniclusters, from which we obtain stringent constraints on the model parameters. Specifically, for the axion decay constant fa = 1016 GeV, which potentially accounts for the seeds of the SMBHs, the PBH fraction in dark matter should be f PBH ≲ 7 × 10-10. Assuming that the mass of PBHs increases by more than a factor of 𝒪(10) due to accretion, this is consistent with the observed abundance of SMBHs. On the other hand, for fa = 1017 GeV required to produce PBHs of masses detected in the LIGO/Virgo, the PBH fraction should be f PBH ≲ 6 × 10-8, which may be too small to explain the LIGO/Virgo events, although there is a significant uncertainty in calculating the merger rate in the presence of clustering.

From Independent to Related: Voltage Ramp Rate Effects on Self-Healing Scaling in Metallized Polypropylene Film Capacitors

Metallized polypropylene film capacitors (MPPFCs) are well-suited for high-frequency and high-electric-field applications, such as electric vehicles, aerospace, and pulsed power systems, due to their self-healing (SH) properties. However, the SH process is affected by operating conditions such as voltage level and ramp rate. It is not well understood whether the SH mechanism is consistent across various operating conditions, which may lead to inaccurate assessments of MPPFC reliability. This paper explores the effect of the DC voltage ramp rates on the SH performance of MPPFC. A more specific classification of SH processes under a high electrical field: independent SH (ISH) and related SH (RSH, composed of two or more sub-SHs). Additionally, the SH process of MPPFCs can be characterized using multiple Weibull subpopulation distributions for various voltage ramp rates. At slow ramp rates (<500 V/s), both ISH and RSH processes are present in the MPPFC, whereas at rapid ramp rates (≥500 V/s), the SH process is mainly dominated by ISH. Moreover, the cumulative SH energy of the MPPFC at the 30 V/s ramp rate is about 10 times that of the 900 V/s ramp rate. The ISH at the 900 V/s ramp rate causes several point-like damaged regions on the metalized PP film (~0.06% decrease in capacitance). In comparison, the RSH at the 30 V/s ramp rates induces clusters of holes across multiple layers in the MPPFC (~9.85% decrease in capacitance), implying that the MPPFC has overreached its expected lifetime.

Excessive fear of clusters of holes, its interaction with stressful life events and the association with anxiety and depressive symptoms: large epidemiological study of young people in Hong Kong.

Excessive and persistent fear of clusters of holes, also known as trypophobia, has been suggested to reflect cortical hyperexcitability and may be associated with mental health risks. No study, however, has yet examined these associations in representative epidemiological samples. To examine the prevalence of trypophobia in a population-representative youth sample, its association with mental health and functioning, and its interaction with external stress. A total of 2065 young people were consecutively recruited from a household-based epidemiological youth mental health study in Hong Kong. Trypophobia, symptoms of anxiety, depression and stress, and exposure to personal stressors were assessed. Logistic regression was used to assess the relationships between trypophobia and mental health. Potential additive and interaction effects of trypophobia and high stress exposure on mental health were also tested. The prevalence of trypophobia was 17.6%. Trypophobia was significantly associated with severe symptoms of anxiety (odds ratio (OR) = 1.83, 95% CI = 1.32-2.53), depression (OR = 1.78, 95% CI = 1.24-2.56) and stress (OR = 1.68, 95% CI = 1.11-2.53), even when accounting for sociodemographic factors, personal and family psychiatric history, resilience and stress exposure. Dose-response relationships were observed, and trypophobia significantly potentiated the effects of stress exposure on symptom outcomes, particularly for depressive symptoms. Those with trypophobia also showed significantly poorer functioning across domains and poorer health-related quality of life. Screening for trypophobia in young people may facilitate early risk detection and intervention, particularly among those with recent stress exposure. Nevertheless, the generally small effect sizes suggest that other factors have more prominent roles in determining recent mental health outcomes in population-based samples; these should be explored in future work.

Large N two-dimensional Yang–Mills fields for the spectral behavior of Brownian particles and relativistic many-body systems

This work explores the spectral behavior of interacting many-body systems — gravitating dust solutions (galaxy formations and black hole clusters) and Brownian fluids. The eigenvalue dynamics of these systems are then represented by the two-dimensional Yang–Mills field (i.e. spectral projection). The interacting particles in the many-body systems are associated with random matrices of dimensions, N. The Painlevé II dynamical system is shown to surface at large N ([Formula: see text]); when the mentioned Yang–Mills field is configured in a specific way. Critical phenomena (Douglas–Kazakov phase transition) of the interacting many-body systems at large N were attained via the spectral projection of the mentioned physical systems. In addition, the existence of instantons (spectral Dirac monopoles) in the strong coupling phase was shown during phase transition.

On black hole surface gravity

We analyze the properties of the black hole surface gravity by using an alternative approach based upon the use of light surfaces that are represented by certain characteristic frequencies. To this end, we rewrite the Kerr line element in terms of the characteristic frequencies, which allows us to obtain copies of the Kerr geometries (black hole–clusters) as the parameters vary. In particular, we replace the spin parameter a=J/M with the corresponding characteristic frequencies so that the line element describes only black holes. This new representation is particularly adapted to analyze how the surface gravity behaves as the black hole passes from one state to another. It turns out that the spins a={sqrt{3}}/{2} M and a=1/sqrt{2} M for black holes and a/M=sqrt{9/8} for naked singularities are of particular relevance for the analysis of the surface gravity properties.

Gravitational Waves from the Merger of Two Primordial Black Hole Clusters

The orbital evolution of a binary system consisting of two primordial black hole clusters is investigated. Such clusters are predicted in some theoretical models with broken symmetry in the inflation Lagrangian. A cluster consists of the most massive central black hole surrounded by many smaller black holes. Similar to single primordial black holes, clusters can form gravitationally bounded pairs and merge during their orbital evolution. The replacement of single black holes by such clusters significantly changes the entire merger process and the final rate of gravitational wave bursts in some parameter ranges (with sufficiently large cluster radii). A new important factor is the tidal gravitational interaction of the clusters. It leads to an additional dissipation of the orbital energy, which is transferred into the internal energy of the clusters or carried away by black holes flying out of the clusters. Comparison with the data of gravitational-wave telescopes allows one to constrain the fractions of primordial black holes in clusters, depending on their mass and compactness. Even the primordial black hole fraction in the composition of dark matter ≃1 turns out to be compatible with LIGO/Virgo observational data, if the black holes are in clusters.

Did JWST observe imprints of axion miniclusters or primordial black holes?

The James Webb Space Telescope has detected surprisingly luminous early galaxies that indicate a tension with the $\Lambda$CDM. Motivated by scenarios including axion miniclusters or primordial black holes, we consider power-law modifications of the matter power spectrum. We show that the tension could be resolved if dark matter consists of $2\times 10^{-18}{\rm eV}$ axions or if a fraction $f_{\rm PBH} > 0.005$ of dark matter is composed of compact heavy $4\times 10^6 M_\odot (f_{\rm PBH}/0.005)^{-1}$ structures such as primordial black hole clusters. However, in both cases, the star formation efficiency needs to be significantly enhanced.

Ruling Out Initially Clustered Primordial Black Holes as Dark Matter.

Combining constraints from microlensing and Lyman-α forest, we provide a simple argument to show that large spatial clustering of stellar-mass primordial black holes at the time of formation, such as the one induced by the presence of large non-Gaussianities, is ruled out. Therefore, it is not possible to evade existing constraints preventing stellar-mass primordial black holes from being a dominant constituent of the dark matter by boosting their initial clustering.