Local Breaking Research Articles

Failure Process of Rock Strata Due to Multi-seam Coal Mining: Insights from Physical Modelling

With an increasing number of multi-seam mining projects, the problem of strata movement caused by multi-seam mining has attracted increasing attention. Previous studies have shown that the rock failure mechanism for multi-seam mining is obviously different from single-seam mining. When a lower coal seam is being mined, two issues are apparent: the activation that the upper goaf will suffer and the difference in the break mechanism of the stratum between single-seam and multi-seam mining. The research regarding these two issues is still inadequate. In this paper, a physical model experiment was used to simulate the full longwall mining process of multiple seams. Then, the failure mechanics of the stratum and the influence of mining the lower coal seam on the activation of the upper goaf are discussed under the condition that the upper coal seam has been fully mined. The results show that a part of the fracture zone that formed by mining the upper coal seam will be converted into a caving zone when the lower coal seam is mined. In multi-seam mining, the cracks in the overlying fractured rock mass will widen and propagate upward. During the process of mining the lower coal seam, the interburden rock mass presents a typical plate bending failure, and the break location is greatly affected by the distribution of the periodic weighting in the upper coal seam mining. Multi-seam mining will cause the surface subsidence trough produced by upper coal mining to move towards the end of the mining panel. The mechanism of rock stratum movement revealed by the test has a certain practical guidance for the control of roof pressure in multi-seam mining and the subsidence of surface.

GDSL-domain proteins have key roles in suberin polymerization and degradation.

Plant roots acquire nutrients and water, while managing interactions with the soil microbiota. Their endodermis provides an extracellular diffusion barrier via a network of lignified cell walls, called Casparian strips, supported by subsequent formation of suberin lamellae. Whereas lignification is thought to be irreversible, suberin lamellae display plasticity, which is crucial for root adaptative responses in the plant. Despite suberin being a major plant polymer, fundamental aspects of its biosynthesis and turnover have remained obscure. Plants shape their root system via lateral root formation, an auxin-induced process requiring local breaking and re-sealing of endodermal lignin and suberin barriers. Here, we show that differentiated endodermal cells have a specific, auxin-mediated transcriptional response, dominated by cell wall remodelling genes. We identified two sets of auxin-regulated GDSL-lipases. One is required for suberin synthesis, while the other can drive suberin degradation. These enzymes constitute novel core players of suberisation, driving root suberin plasticity.

Deep-sea turbulence evolution observed by multiple closely spaced instruments

Turbulent mixing in the deep ocean is not well understood. The breaking of internal waves on sloped seafloor topography can generate deep-sea turbulence. However, it is difficult to measure turbulence comprehensively due to its multi-scale processes, in addition to flow–flow and flow–topography interactions. Dense, high-resolution spatiotemporal coverage of observations may help shed light on turbulence evolution. Here, we present turbulence observations from four broadband ocean bottom seismometers (OBSs) and a 200-m vertical thermistor string (T-string) in a footprint of 1 × 1 km to characterize turbulence induced by internal waves at a depth of 3000 m on a Pacific continental slope. Correlating the OBS-calculated time derivative of kinetic energy and the T-string-calculated turbulent kinetic energy dissipation rate, we propose that the OBS-detected signals were induced by near-seafloor turbulence. Strong disturbances were detected during a typhoon period, suggesting large-scale inertial waves breaking with upslope transport speeds of 0.2–0.5 m s−1. Disturbances were mostly excited on the downslope side of the array where the internal waves from the Pacific Ocean broke initially and the turbulence oscillated between < 1 km small-scale ridges. Such small-scale topography caused varying turbulence-induced signals due to localized waves breaking. Arrayed OBSs can provide complementary observations to characterize deep-sea turbulence.

Multifactor analysis of delayed absorption of subretinal fluid after scleral buckling surgery

BackgroundThe purpose of this study is to assess the absorption of subretinal fluid (SRF) after scleral buckling (SB) surgery for the treatment of rhegmatogenous retinal detachment (RRD). We also examined related factors that may affect the delayed absorption of SRF.MethodsThis retrospective study included patients who underwent successful SB surgery for the treatment of macula-off RRD and in which the retina was reattached after the surgery. The patients were categorized according to gender, duration, age, the number, and location of retinal breaks. Subfoveal choroidal thickness (SFCT), height of subretinal fluid (SRFH), and the choriocapillaris flow density (CCFD) within 3 × 3 mm macular fovea were included. Delayed absorption was determined by the SRF that remained unabsorbed for 3 months after the procedure. The endpoint was determined when the SRF could no longer be observed.ResultsA total of 62 patients (63 eyes) were enrolled. In 35 eyes (56.45%) SRF was completely absorbed and in 28 (43.55%) eyes delayed absorption of SRF in macular areas was observed at 3 months after surgery. A young age (< 35 years), inferior retinal breaks were associated with good outcomes by applying multivariable analysis on the rate of SRF absorption after SB instead of gender, the number of breaks, and duration (p < 0.05). CCFD was significantly different between the SRF group and the non-SRF group after SB (0.66 ± 0.04% vs 0.63 ± 0.05%, P < 0.05). SRFH showed a moderate positive correlation with SFCT (rs = 0.462, p = 0.000), however, using binary logistic regression analysis it was determined that SFCT was not related to the absorption of the SRF.ConclusionsThe absorption of SRF after SB may be correlated with choriocapillaris flow density. Age and location of breaks are significant factors affecting the absorption of SRF. The duration of disease is an uncertain factor due to several subjective reasons.

Breaking-Wave Induced Transient Pore Pressure in a Sandy Seabed: Flume Modeling and Observations

Previous studies on wave-induced pore pressure in a porous seabed mainly focused on non-breaking regular waves, e.g., Airy linear waves or Stokes non-linear waves. In this study, breaking-wave induced pore pressure response in a sandy seabed was physically simulated with a large wave flume. The breaking-wave was generated by superimposing a series of longer waves onto the foregoing shorter waves at a specified location. Water surface elevations and the corresponding pore pressure in the process of wave breaking were measured simultaneously at three typical locations, i.e., at the rear, just at, and in front of the wave breaking location. Based on test results, characterization parameters are proposed for the wave surface elevations and the corresponding pore-pressures. Flume observations indicate that the wave height was greatly diminished during wave breaking, which further affected the pore-pressure responses. Moreover, the measured values of the characteristic time parameters for the breaking-wave induced pore-pressure are larger than those for the free surface elevation of breaking-waves. Under the action of incipient-breaking or broken waves, the measured values of the amplitude of transient pore-pressures are generally smaller than the predicted results with the analytical solution by Yamamoto et al. (1978) for non-breaking regular waves with equivalent values of characteristic wave height and wave period.

Breaking Location of Internal Solitary Waves Over a Sloping Seabed

AbstractWe present a semi‐analytical model for predicting the breaking location of internal solitary waves (ISWs) over a sloping seabed. Our conceptual model is based on laboratory experiments, performed in a wave tank, that reproduce the ISW breaking mechanisms and show how the steepening of the trailing edge leads to verticalization of the wave profile during the shoaling phase. We derive the location of ISWs breaking, that is, the wave verticalization point, through two‐layer, interfacial theoretical models and conservation of wave mass. We apply our model to the case of tidally forced ISWs that are generated in the Strait of Messina (Central Mediterranean Sea), where northward traveling ISWs are expected to refract and break over the frontal slope of Capo Vaticano. Our application is then assessed through numerical investigations, which allow to consider realistic field conditions in terms of water column stratification and geometrical setting. Our results, and the expected ISW‐induced bed shear stress, suggest a link between the predicted breaking locations and the occurrence of sediment resuspension over that specific portion of the slope.

Predictive Factors for Long-Term Postoperative Visual Outcome in Patients with Macula-Off Rhegmatogenous Retinal Detachment Treated with Vitrectomy

Purpose: The purpose of this prospective study was to evaluate potential predictive factors of long-term postoperative outcomes in patients with macula-off rhegmatogenous retinal detachment (RRD) treated with pars plana vitrectomy (PPV). Methods: Participants in this study were 86 patients diagnosed with macula-off RRD, who underwent PPV. Demographic characteristics and preoperative characteristics of RRD were recorded, while best corrected visual acuity (BCVA) was measured preoperatively and at specific postoperative time points (6 weeks and 6, 12, and 24 months). In addition, spectral domain-optical coherence tomography (SD-OCT) characteristics at postoperative week 6 were assessed as potential factors affecting the long-term postoperative visual outcome 24 months after PPV for RRD. Results: Increasing age, duration of RD of more than 1 week, presence of proliferative vitreoretinopathy, increasing central retinal thickness, ellipsoid zone disruption, and external limiting membrane disruption were significantly associated with a worse BVCA. BCVA was not associated with gender, lens status, the location of breaks, the gas tamponade agent used in PPV, the presence of subretinal fluid, and intraretinal fluid. Conclusions: It is important to determine predictive factors for visual outcomes in order to inform patients about their prognosis and help in the decision-making process for patient management.

Pressure wave behavior and its effects on structure under In-box LOCA in a helium-cooled lead lithium blanket of hydrogen fusion reactors

The helium-cooled lead lithium (PbLi) blanket is considered as one of the candidate blanket concepts selected for the hydrogen fusion DEMO reactors and beyond, which has the advantages of simple structure, strong heat removal capacity and high tritium breeding ratio. However, due to the harsh environment such as high-energy neutron irradiation, high thermal load and great pressure gradient, there is a high possibility that one or some of the thousands of coolant channels will break in the breeding zone, which is so-called In-box Loss of Coolant Accident (In-box LOCA). When the accident occurs, the high pressure helium will rapidly inject into the lead lithium flow channel, generating a complex two-phase flow and great pressure shock effect, which may cause the peak pressure to exceed the design limit and threaten the integrity of the blanket structure. Therefore, it is of great significance to perform the transient analysis of in-box LOCA to improve the safety of the blanket and avoid the leakage of radioactive materials. In this paper, a two-way coupling model for fluid-solid interaction was established based on the ANSYS Workbench, and the model were validated through the experimental data obtained by injecting the high pressure helium gas into liquid lithium lead. Then the validated model was applied to the transient pressure wave propagation analysis and structural stress analysis of the Dual-Functional Lithium Lead (DFLL) blanket in order to explore the integrity of blanket structure under In-box LOCA. In addition, the effects of break location on pressure and structural stress was also investigated through six cases. The study found that the transient pressure in the DFLL blanket gone through three stages in any case: step rise, oscillate, and flatten out. Pressure peaks occurred during oscillations and their values were strongly dependent on the break location. The closer to the inlet/outlet, the higher the peak pressure was. The maximum pressure reached more than twice of the inlet pressure (up to ~16 MPa). As a result, the structural stress in some local areas has exceeded the allowable limits, and the corresponding suggestions for improvement have also been put forward. This study can provide guidance for safety design, operation and accident mitigation measures of helium-cooled lead lithium blankets.

CAP1400 passive core cooling integral testing and application in code validation

CAP1400 is an advanced passive nuclear power plant. In order to support its safety analysis required by the authority, a new integral test facility, ACME, is founded. A series of SBLOCA tests are performed to validate CAP1400 technology. In this paper, some test data are shown to explain several important phenomena (cold leg stratification, accumulator nitrogen injection, downcomer asymmetric temperature distribution, and break size effect) observed in the tests. Among these phenomena, the earlier occurrence of cold leg stratification is caused by coolant pumps’ specific structure. The nitrogen injected by ACCs is found to delay the recovery of CMT injection flow. The downcomer asymmetric temperature profile is resulted from DVI injection. Tests are also compared to discover the effect of break sizes and locations. Afterwards, a modified version of RELAP5/MOD3 is validated by the test data. The results show that the modified code can be used for CAP1400 SBLOCA analysis.

Co‐location of the Downdip End of Seismic Coupling and the Continental Shelf Break

AbstractAlong subduction margins, the morphology of the near shore domain records the combined action of erosion from ocean waves and permanent tectonic deformation from the convergence of plates. We observe that at subduction margins around the globe, the edge of continental shelves tends to be located above the downdip end of seismic coupling on the megathrust. Coastlines lie farther landward at variable distances. This observation stems from a compilation of well‐resolved coseismic and interseismic coupling data sets. The permanent interseismic uplift component of the total tectonic deformation can explain the localization of the shelf break. It contributes a short wave‐length gradient in vertical deformation on top of the structural and isostatic deformation of the margin. This places a hinge line between seaward subsidence and landward uplift above the downdip end of high coupling. Landward of the hinge line, rocks are uplifted in the domain of wave‐base erosion and a shelf is maintained by the competition of rock uplift and wave erosion. Wave erosion then sets the coastline back from the tectonically meaningful shelf break. We combine a wave erosion model with an elastic deformation model to illustrate how the downdip end of high coupling pins the location of the shelf break. In areas where the shelf is wide, onshore geodetic constraints on seismic coupling are limited and could be advantageously complemented by considering the location of the shelf break. Subduction margin morphology integrates hundreds of seismic cycles and could inform the persistence of seismic coupling patterns through time.

Energy stability and electronic properties of carbon nanotorus at a localized breaking of interatomic bonds: computer modeling

This paper is devoted to the study of the dynamic processes that occur in the carbon nanotorus during localized breaking of interatomic bonds, and to the analysis of the influence of these processes on the electronic properties of carbon nanotorus. The object of research is a carbon nanotorus with chirality indices (13, 0) with a diameter of 20 nm and a thickness of 1 nm obtained as a result of defect-free folding of a zigzag carbon nanotube of appropriate geometric dimensions into a ring. The behavior of the nanotorus is modeled by the molecular dynamics method using a modified Brenner potential to describe the interaction between atoms. It is shown that over time, the nanotorus straightens into a nanotube, while maintaining energy stability. It is found that the process of nanotorus straightening is accompanied by the appearance of deformation wave-like bends propagating at a speed of 200 m/s along the atomic network of the structure. These bends lead to deformation of the nanotorus and numerous local breaks in the bonds between atoms. However, broken bonds are restored within a few femtoseconds before the structure relaxes in energy, therefore, in general, the atomic framework of the nanotorus remains defect-free after rectification. The results of calculating the distribution of the density of electronic states (DOS) of a nanotorus by the self-consistent charge density functional tight-binding (SCC-DFTB) quantum method showed that at the moment of localized breaking of interatomic bonds around the circumference of the tubular framework, the nanotorus loses its semiconductor properties, becoming a gapless conductor. The discovered physical phenomenon explains the process of nanotorus formation during synthesis accompanied by multiple ruptures of the nanotori and reverse closure of the nanotubes into the nanotori.

Process of local government fragmentation in Croatia: From a big-bang to a status quo

Abstract The paper explores and explains the fragmentation process in Croatian local government during the transition period from 1990 onwards. Special focus is given to the emergence of new municipalities (municipal splits/secessions) that occurred after the new two-tier local government system was established in 1993. Excessive fragmentation of territorial structure at the beginning of the 1990s was a systematic and centrally driven reform that was meant to break with the inherited local government model and break up its territorial structure as radically as possible. While the initial overhaul in 1993 was mostly the result of conscious policy implemented in a top-down manner, subsequent municipal splits were mostly the outcome of local initiatives and lobbying, and were predominantly shaped by local, primarily economic factors, whereas political and cultural factors were of secondary importance. The national institutional context, including criteria and procedural rules for splits, were quite liberal during this whole period, with a moderate tightening-up trajectory. The number of municipalities finally stabilised in 2006, since when there have been no more splits.

Growth path of industrial clusters embedded in global value chain from the perspective of knowledge transfer: A fuzzy game approach

How local industrial clusters break through the lock-in status of low end of value chains and realize industrial upgrading in the development process of embedded global value chain is the central topic of current industrial development research. To explore how industrial clusters achieve the enhancement of their innovation capability and value chains when they are embedded in the global value chain, from the perspective of knowledge transfer and according to the differences in the knowledge levels of the local industrial clusters, three fuzzy game models of knowledge transfer paths were constructed, and the model of the realization mechanism of knowledge transfer and its stability condition was analyzed, which make clear the path of cluster growth under different embedding modes. Results show that although the mode of embedding and the path of knowledge transfer is different, the local industrial clusters can obtain external knowledge transfer by embedding in the global value chain; the knowledge transformation ability of local industrial clusters is the determining factor that the knowledge transfer can smoothly achieve and become stable. The conclusion also shows that the feasibility of the cross-sectional growth of industrial clusters by actively embed the global value chain and acquiring external knowledge transfer if the industrial clusters want to enhance their technology accumulation, their innovation ability, and their position in the global value chain.

RELAP5 Foresight Thermal-Hydraulic Analysis of Hypothesis Passive Safety Injection System under LOCA for an Existing NPP in China

Qinshan nuclear power plant is the first large Chinese-designed nuclear power station based on pressurized water reactor, and the second generation main stream active safety injection system is adopted for Qinshan nuclear power plant. In this paper, a novel passive safety injection system (PSIS) has been proposed for ocean-based Qinshan Phase One nuclear power plant to replace the original active one. The PSIS contains high-pressure, medium-pressure, and lower-pressure safety injection systems, and a two-stage automatic depressurization system. To evaluate the system performance, small-break LOCA has been investigated using RELAP5. Various break sizes and locations including 2-inch, 10-inch cold leg break, and double-ended direct vessel injection line break were analyzed. Key safety parameters such as safe injection mass flow rates, coolant level of the core, system pressure, and fuel cladding temperature were monitored during the accident process. The results illustrate that the performance of the safety injection system can guarantee the effective core cooling and submerged under different LOCA even with only half of the safety injection system, which can fulfill the single failure criteria. The thermal-hydraulic analysis for the Qinshan passive safety injection system is significant to master the related technologies for Chinese engineer and develop the Chinese-designed third-generation nuclear power plants, and the PSIS can guarantee the reactor submerged under LOCA even plus the station block out accident.

Rectification of AC Electric Current at the Edge of 2D Electron Gas

Driving a 2D electron gas by AC electric field leads to a DC electric current flowing along the edge of the system. The effect is caused by the local breaking of space inversion symmetry at the edge. The current is generated in a narrow stripe determined by the screening length of the AC electric field and the mean free path of carriers. The developed microscopic theory of the effect shows that the excitation spectrum of the edge current and even the current direction depend on the mechanism of electron scattering. In an external magnetic field, the excitation spectrum of the current features the cyclotron resonance.

Vector mesons spectrum in a medium with a chiral imbalance induced by the vacuum of fermions

The properties of the light vector mesons in the presence of local parity breaking medium with a chiral imbalance are considered in the vector-meson dominance model. Applying the finite lowest-order radiatively induced local effective Lagrangian, initially developed for the QED, for the vector ρ and ω mesons, we obtained the mass spectrum as a function of momentum and chiral chemical potential μ5. We showed that in addition to the Chern–Simons term, splitting the transverse polarisations of the mesons, there is another radiatively induced contribution that becomes important at momentum and μ 5 around a few hundred MeV.

Testing and dating structural changes in copula-based dependence measures

This paper is concerned with testing and dating structural breaks in the dependence structure of multivariate time series. We consider a cumulative sum (CUSUM) type test for constant copula-based dependence measures, such as Spearman's rank correlation and quantile dependencies. The asymptotic null distribution is not known in closed form and critical values are estimated by an i.i.d. bootstrap procedure. We analyze size and power properties in a simulation study under different dependence measure settings, such as skewed and fat-tailed distributions. To date breakpoints and to decide whether two estimated break locations belong to the same break event, we propose a pivot confidence interval procedure. Finally, we apply the test to the historical data of 10 large financial firms during the last financial crisis from 2002 to mid-2013.

An automated model-based approach to repair test suites of evolving web applications

Capture–Replay tools are widely used for the automated testing of web applications The scripts written for these Capture–Replay tools are strongly coupled with the web elements of web applications. These test scripts are sensitive to changes in web elements and require repairs as the web pages evolve. In this paper, we propose an automated model-based approach to repair the Capture–Replay test scripts that are broken due to such changes. Our approach repairs the test scripts that may be broken due to the breakages (e.g., broken locators, missing web elements) reported in the existing test breakage taxonomy. Our approach is based on a DOM-based strategy and is independent of the underlying Capture–Replay tool. We developed a tool to demonstrate the applicability of the approach. We perform an empirical study on seven subject applications. The results show that the approach successfully repairs the broken test scripts while maintaining the same DOM coverage and fault-finding capability. We also evaluate the usefulness of the repaired test scripts according to the opinion of professional testers. We conduct an experiment to compare our approach with the state-of-the-art DOM-based test repair approach, WATER. The comparison results show that our approach repairs more test breakages than WATER.

DNA Damage-Induced Nucleosome Depletion Enhances Homology Search Independently of Local Break Movement

To determine whether double-strand break (DSB) mobility enhances the physical search for an ectopic template during homology-directed repair (HDR), we tested the effects of factors that control chromatin dynamics, including cohesin loading and kinetochore anchoring. The former but not the latter is altered in response to DSBs. Loss of the nonhistone high-mobility group protein Nhp6 reduces histone occupancy and increases chromatin movement, decompaction, and ectopic HDR. The loss of nucleosome remodeler INO80-C did the opposite. To see whether enhanced HDR depends on DSB mobility or the global chromatin response, we tested the ubiquitin ligase mutant uls1Δ, which selectively impairs local but not global movement in response to a DSB. Strand invasion occurs in uls1Δ cells with wild-type kinetics, arguing that global histone depletion rather than DSB movement is rate limiting for HDR. Impaired break movement in uls1Δ correlates with elevated MRX and cohesin loading, despite normal resection and checkpoint activation.

Properties of breaking irregular waves over slopes

The present study numerically investigates the breaking and spectral characteristics and geometric properties of breaking irregular waves over slopes for different incident waves. The growth of wave non-linearity and wave energy redistribution during shoaling and breaking process are observed to be major factors in determining the free surface elevation skewness and spectral bandwidth. In general, the variation of the breaker indices with the surf similarity parameter is found to be mainly governed by the type of wave breakers. The wave breaker type further depends on the seabed slope, incident wave parameters and water depth at the location of wave breaking. The study further explores the geometric properties for both spilling and plunging irregular wave breakers. The wave deformation due to wave-seabed interaction plays a major role in affecting the breaker shapes. Every individual breaking wave in the irregular wave train possesses different wave profiles and breaker characteristics. In order to study these parameters in a probabilistic way, the statistics of the breaker characteristics and the breaker shape parameters are investigated. The lognormal distribution is noticed to be the most suitable fit for the wave crest steepness and asymmetry factors. This study is performed using the open-source computational fluid dynamics (CFD) based numerical model. The numerical model is validated for a submerged bar under breaking irregular waves and the numerical results are compared with experimental data. The transformations of the free surface elevation due to wave shoaling, wave breaking and wave decomposition are explored.