Discontinuous Characteristics Research Articles

Characteristics of Interplanetary Discontinuities in the Inner Heliosphere Revealed by Parker Solar Probe

Abstract We present a statistical analysis for the characteristics and spatial evolution of the interplanetary discontinuities (IDs) in the solar wind, from 0.13–0.9 au, by using the Parker Solar Probe measurements on Orbits 4 and 5. We collected 3948 IDs, including 2511 rotational discontinuities (RDs) and 557 tangential discontinuities (TDs), with the remnant unidentified. The statistical results show that (1) the ID occurrence rate decreases from 200 events per day at 0.13 au to 1 event per day at 0.9 au, following a spatial scaling of r −2.00, (2) the RD to TD ratio decreases quickly with the heliocentric distance, from 8 at r < 0.3 au to 1 at r > 0.4 au, (3) the magnetic field tends to rotate across the IDs, 45° for TDs and 30° for RDs, in the pristine solar wind within 0.3 au, (4) a special subgroup of RDs exists within 0.3 au, characterized by small field rotation angles and parallel or antiparallel propagations to the background magnetic fields, (5) the TD thicknesses normalized by local ion inertial lengths (d i ) show no clear spatial scaling and generally range from 5–35 d i and the normalized RD thicknesses follow an r −1.09 spatial scaling, and (6) the outward (antisunward) propagating RDs predominate in all RDs, with the propagation speeds in the plasma rest frame proportional to r −1.03. This work could improve our understanding of the ID characteristics and evolution and shed light on the study of the turbulent environment in the pristine solar wind.

Comprehensive identification of statistical homogeneity of fractured rock masses for a candidate HLW repository site, China

Determining the statistically homogeneous regions is important for engineering geological modeling and promoting systematic research on regional rock mass characteristics and rock engineering designs. This study proposes a comprehensive framework considering multiple discontinuity geometry parameters (e.g., orientation, trace length, density, and cluster characteristics.) to distinguish statistical homogeneity of fractured rock masses. First, based on the equal-area plot method (Schmidt net), the quantitative judgment ability of the Miller method for determining the similarity between two discontinuity orientation populations was improved by optimizing block network division scheme and blank area merging principle. Then, considering the distribution characteristics of discontinuity in rock mass space and the variation features of discontinuity at different geographical locations, a three-dimensional fracture network model, established using the discontinuity geometry parameters obtained from field investigation, was combined with the fractal dimension method (called the network fractal dimension method; NFD) to further evaluate the statistical homogeneity of fractured rock mass. The proposed approaches were subsequently applied to the identification of the statistical homogeneity of several typical granite fracture outcrops in the Beishan area, which is a candidate site for high-level radioactive waste (HLW) repository of China. The case study reveals that the optimized Miller method is more flexible and applicable than the conventional orientation-based methods, especially in dealing with the complex situation of the coexistence of gentle dip angle and steep dip angle as well as clustering characteristics of discontinuity. The NFD method was used to unify the influence of the main discontinuity characteristic parameters for a logical and unbiased evaluation of the statistical homogeneity. The comprehensive framework developed herein integrates the advantages of the two methods and reduces the interference of subjective evaluation. Therefore, it can be employed to efficiently determine the statistical homogeneity of rock masses at different locations at a large scale without concern over the deviation caused by different directions and size of the compared areas.

Dominant Weathering Profile Assessment of Kebo-Butak Volcanic Rocks in Gedangsari and Ngawen area, Yogyakarta, Indonesia

The Gedangsari and Ngawen area is predominantly composed of volcanic and volcaniclastic sequencesdistributed east – west direction of the northern parts of Southern Mountain. The massive tectonism as well as tropical climatein this region have been producing weathering profiles in varying thickness which inevitably affects thegeotechnical properties. This study aims to assess the dominant weathering profileof the lower part of Kebo-Butak Formation as well as evaluating the distribution of the discontinuity. In order to know the dominant weathering profile and discontinuity evaluation, this study utilizes a total of 26 panels from five stations investigated through a geotechnical data acquisition including the geological condition, weathering zones, joint distribution, and discontinuity characteristics. The result shows four types of dominant weathering profiles in lower part of Kebo-Butak Formation called as dominant weathering profile A, B, C, and D. Profile A, B, C consisted of a relatively identical weathering degree pattern of fresh, slightly, moderately, completely weathered zone with the variation of thicknesses. However, the weathering degree in profile D reached the residual soil degree controlled by more intensive joints. The fine-grained sedimentary rocks also tends to have smaller spacing, shorter persistence, and higher weathering degree of discontinuities as compared to coarse-grained sedimentary rocks.

Numerical investigation of Strouhal number discontinuity and flow characteristics around single rectangular cylinder at low aspect ratios and Reynolds numbers

Numerical investigation of Strouhal number discontinuity and flow characteristics around single rectangular cylinder at low aspect ratios and Reynolds numbers

A composite element solution of convection-conduction heat transfer in fractured rock mass

A reliable and efficient numerical model is required for predictions of convection-conduction behavior in fractured rock mass to obtain a better understanding of heat transfer processes within it. This study presents a composite element formulation that addresses the problem of heat transfer via fluid flow in fractured rock mass. The three-dimensional convection-conduction equation is converted to an equivalent variational principle, and the governing equations of the rock sub-elements and fracture segments are subsequently deduced based on the composite element method (CEM). The developed CEM algorithm takes into account the heat transfer inside the fracture fluid and inside the rock matrix, respectively, as well as the heat exchange between the fracture fluid and the adjacent rock blocks. The CEM model allows for the simulation of the discontinuous characteristics of temperature across the fractures via a simplified computational mesh that is generated without restrictions, and the fractures are explicitly and automatically embedded into the mapped composite element via the CEM pre-process program. The composite element contains fracture segments exhibiting arbitrary shapes, the temperatures of fractures are interpolated from their corresponding mapped nodal temperatures of rock sub-elements delimited by the fractures, and, therefore, the temperature of the fracture is not necessarily continuous. The performance of the developed CEM algorithm is verified by comparisons with analytical solutions, a case study of lab experiments and numerical results, which demonstrate the validity and advantages of the composite element solution.

Lithological and stress anisotropy control large-scale seismic velocity variations in tight carbonates

Our knowledge of subsurface structures often derives from seismic velocities that are measured during seismic acquisition surveys. These velocities can greatly change due to lithological, fracture frequencies and/or effective pressure/temperature variations. However, the influence of such intrinsic lithological properties and environmental conditions at the large scale is poorly understood due to the lack of comprehensive datasets. Here, we analyze 43 borehole-derived velocity datasets of 3 end-member tight carbonate sequences from Central Italy, including massive pure limestone (Calcare Massiccio, CM), thick-layered (20–50 cm) pure limestone (Maiolica, MA), and thin-layered (2–20 cm) marly limestone (Calcareous Scaglia, CS). Our results show that the main rock parameters and environmental conditions driving large scale velocity variations are bedding and paleostresses, while mineralogical composition and current tectonic stress also play a role. For each of the 3 end-members, measured VP values vary differently with depth, as the thin-layered CS units show a clear increase in Vp, while velocity slightly increases and remains constant for the thick-layered MA and massive CM units, respectively. Such observations show that velocities are affected by specific characteristics of lithological discontinuities, such as the thickness of bedding. Counterintuitively, larger Vp values were recorded in the deformed mountain range than in the undeformed foreland suggesting that higher paleo-stresses increase velocity values by enhancing diagenesis and healing of discontinuities. Our results thus demonstrate that large scale velocity variations are strictly related to variation of lithological properties and to the geological and tectonic history of an area. We suggest that such lithological and environmental controls should be taken into account when developing velocity and mechanical models for tectonically active regions of the Mediterranean Area, where earthquakes mostly nucleate and propagate through carbonate formations, and for resource exploration in fractured carbonate reservoirs.

RETRACTED ARTICLE: Seismic stability analysis of arch dam abutment based on full structural surface yield method

This paper proposes an improved dynamic stability analysis for abutment of dam (IDSAM) by combining interface boundary element with partitioned finite element (PFE-IBE). The total yield of the control area is taken as the instability criterion, and the area is made up of contact point pairs controlling the structural surface. The full structural surface yield state of the structural surface of the dam abutment rock mass was taken into account. The strength reduction coefficient corresponding to the full structural surface yield was taken as the safety factor of dam abutment stability. In this way, the damage of the structural surface can be reflected more accurately and intuitively, eliminating the impact of human factors on the valuation of the safety factor. Three calculation methods are used to evaluate the abutment stability of the Shapai Arch Dam, including pseudo-static method, the combination between finite element method and rigid body limit equilibrium method, and the proposed IDSAM. The comparison of results shows that the dam abutment safety factor obtained by IDSAM (left 2.4, right 3.0) ranges between those obtained by pseudo-static method (left 2.116, right 2.945) and finite element rigid body limit equilibrium method (left 2.429, right 3.182). Hence, the safety factor acquired by our method is rational. Considering the nonlinear characteristics of rock mass discontinuity, IDSAM reflects the operating state of the arch dam, shedding new light on the evaluation of aseismatic safety.

Progressive Failure Analysis of Slope Water Damage Based on Improved Green-Ampt Infiltration Model

In order to get the law of rainwater infiltration and the law of progressive water damage, the slope of Tianshang bridge foundation in Yunnan Province of China is taken as the engineering basis. The site investigation of the damaged slope is carried out. The traditional Green-Ampt model is improved by considering the ponding effect of dynamic water flow on the slope surface. Based on the variation characteristics of wetting front obtained by the improved infiltration model, the progressive failure process of slope with continuous infiltration is simulated by FLAC3D software. The results show that the water damage of Tianshang bridge slope is mainly caused by the slope absorbing a lot of rainwater in a short time, which has obvious time discontinuity characteristics in time, and shows obvious multi-layer progressive failure characteristics in failure space. The wetting front characteristics obtained by the improved Green-Ampt infiltration model are more consistent with the engineering practice. The water accumulation effect of surface water gradually weakens with the increase of the wet front depth. The slope failure develops gradually from the toe to the top and from shallow to deep. The intermittent failure characteristics provide surplus time for the engineering treatment, the gravel soil slope should be treated after a small-scale water damage occurs.

공압 계측을 통한 상용차량 ABS 용 압력 제어 밸브 모델링 및 On/Off 제어 전략

This paper reports on the modeling of a pneumatic brake system and valve control strategies for commercial vehicles with an ABS (Anti-lock Brake System). A PCV (Pressure Control Valve), consisting of two solenoid valves and two diaphragm valves, is a key part of a pneumatic ABS. To examine the pneumatic ABS, a PCV model that could accurately represent the dynamics of the air flowing through the PCV components was developed. The dynamic compressible airflow equations, which can describe the flow through an orifice, were adopted to describe the directional motion of the dynamic airflow, as commanded by the driver and modified by the PCV to facilitate the ABS activity. The discharge coefficient as a function of the pressure ratio was obtained experimentally. The PCV model was verified through pneumatic measurements of the relay valve and brake chamber. The verification results demonstrated that the simulation data were in agreement with those obtained experimentally. Furthermore, the PCV model was integrated with a whole vehicle model in Trucksim to conduct ABS simulation studies. The investigated system involved both the continuous wheel dynamics and inherent discontinuous characteristics of the PCV Two on/off valve control strategies based on the pressure and switching surface were introduced to regulate the slip ratio and analyzed via simulations. In addition, the switching-surface-based control strategy was evaluated through a hardware-in-loop experimental setup. The experimental results demonstrated that the implemented control strategy is effective even under uncertainties in the pneumatic ABS.

Thorough Analysis of the Phase Diagram for the Bell–Lavis Model: An Entropic Simulational Study

In this work, we investigate the Bell-Lavis model using entropic simulations for several values of the energy parameters. The $T\times\mu$ phase diagram and the ground state configurations are analyzed thoroughly. Besides, we examine the particle density and specific heat behavior for different values of the chemical potential $\mu$ as functions of temperature. We also obtain configurations that maximize the canonical probability for several values of chemical potential and temperature, enabling the identification of the low density ($LDL$) and high-density liquid ($HDL$) phases, among others, in the critical regions. We found a second-order phase transition from the $LDL-HDL_0$ to $LDL-HDL$ coexistence in the range of $0<\mu<1.05503$. In the $1.05503<\mu<1.48024$ range, the transition between the $LDL-HDL_0$ and $LDL-HDL_0-empty$ coexistence presents discontinuous and continuous transitions characteristics. Finally, for $1.48024<\mu<1.5$, the phase transition between $LDL$ and $empty$ phases is of first-order.

In-process Measurement and Geometric Error Fusion Control of Discontinuous Surface Based on Bayesian Theory

For workpieces with discontinuous surface characteristics such as shafts with keyways, obtaining continuous and valid measurement data is essential for assessing machining quality. In this paper, a Bayesian approach based on prior knowledge is proposed to evaluate the geometric characteristics of the discontinuous surface. Effective measurement data for discontinues surface is supplemented by accurate Bayesian parameter estimation. By using the supplemented data, the dimensional error and roundness error can be calculated. Using the in-process measurement method, the process progress can be adjusted in time according to the error value to realize the fusion control of dimension and roundness. Experimental investigations for machining multi-keyway shaft are carried out based on the proposed method. The results show that grinding workpieces with discontinuous surface by using the in-process measurement method based on Bayesian theory can significantly improve product quality and efficiency.

Characterizing the performance of eddy current probes using photoinductive field-mapping: a numerical approach

Nondestructive evaluation (NDE) method has been applied to analyze the configura- tions of coil probes and the characteristics of discontinuities in the few years, especially the ef- fects of probe tilt are paid attention to gradually. However, the probe tilt has been recognized as the one reason of producing noise in eddy current testing (ECT), such as the flaw manual scan- ning or the manufacture of probes with the irregular orientation coil. The inability to calibrate the tilt coil of probe makes it impossible to accurately inspect the surface cracks. Based on the above, we should found the applicable method to examine the structures of probe and demonstrate that it has the feasibility on investigating of probe with tilted coil. The photoinductive (PI) method is a novel inspection technique for detecting surface cracks. This paper shows how the PI technique can be utilized to analyze the effects of tilted coil of probe. The numerical multiphysics simula- tions of the PI imaging was performed with two dimensional finite element method (2D FEM) to characterize the variations of magnetic field and probe's impedance on a conductive metal foil. As anticipated, the proposed model shows that the PI imaging signals can reveal the construction of the probe. The FEM simulation results of tilted coils are showed and discussed. The effects of PI signals with different excited frequencies of the coil are also examined and analyzed. The simulation results demonstrate that not only the PI method is appropriate for investigating the structures of probe, but also how the tilt probe can affect the reliability of an eddy current in- spection.

A state-of-the-art review of automated extraction of rock mass discontinuity characteristics using three-dimensional surface models

In the last two decades, significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional (3D) models. This provides several methodologies for acquiring discontinuity measurements from 3D models, such as point clouds generated using laser scanning or photogrammetry. However, even with numerous automated and semi-automated methods presented in the literature, there is not one single method that can automatically characterize discontinuities accurately in a minimum of time. In this paper, we critically review all the existing methods proposed in the literature for the extraction of discontinuity characteristics such as joint sets and orientations, persistence, joint spacing, roughness and block size using point clouds, digital elevation maps, or meshes. As a result of this review, we identify the strengths and drawbacks of each method used for extracting those characteristics. We found that the approaches based on voxels and region growing are superior in extracting joint planes from 3D point clouds. Normal tensor voting with trace growth algorithm is a robust method for measuring joint trace length from 3D meshes. Spacing is estimated by calculating the perpendicular distance between joint planes. Several independent roughness indices are presented to quantify roughness from 3D surface models, but there is a need to incorporate these indices into automated methodologies. There is a lack of efficient algorithms for direct computation of block size from 3D rock mass surface models. • Review of automatic and semi-automatic methods for discontinuity characterization. • Focused on joint sets, orientation, persistence, spacing, roughness and block size. • Strengths and limitations of methods are discussed from a practical perspective. • Computation time, number of parameters, accuracy, and robustness are discussed. • Region growing was found fast and accurate for joint detection from LiDAR data.

Dynamics of a discontinuous coupled electro-mechanical system oscillator with strong irrational nonlinearities and with two outputs

The dynamics of the nonlinear electromechanical device, consisting of a mechanical part with two outputs and an electrical part which acts as the server is strongly investigated in the present work. The mechanical part consists of two nonlinear oscillators with strong irrational nonlinearities having smooth or discontinuous characteristics, where nonlinearity is just due to the inclination of springs, the geometric configuration, which are both elastically coupled. While the electrical part is the Rayleigh equation. By using the Lagrangian formulation, the model equations are established and used to investigate the equilibrium points and their stabilities. Nest by using the multiple time scales method, the analytical solutions are found both for the case of large amplitude and the weak amplitude, leading to interesting bifurcation sets of the equilibria by varying the control parameters, the inclination angles and driven frequency. Finally, numerical investigations of the exact equation of the system are used to justify the validity of analytical results and to find new phenomena such as chaotic impulses, chaotic bursting and the train of kink signal generations.

Model experiment of large superstructures’ influence on hull girder ultimate strength for cruise ships

Cruise ships have large and long superstructures, which are almost extending the whole ship length with discontinuous characteristics, such as side shell recess and many window openings. The superstructure effectiveness on hull girder longitudinal strength is a complicated but unavoidable issue in ship design stage. This paper has carried out a collapse experiment of steel model with superstructures, which is designed based on one actual cruise ship. Critical factors including initial imperfections and welding residual stress used in nonlinear FE analysis have been validated by the experiment results. Then, the superstructure effectiveness is analyzed to revise the increment-iterative to be applicable for ultimate strength evaluation for cruise ships. At last the combination action of bending moment and shear force is studied, and a new combination formula is proposed. The conclusions in this paper will be useful for ship design, rules amendment and safety assessment for cruise ships.

The Scale Effect of Coarse-Grained Materials by Triaxial Test Simulation

The scale effect is an unavoidable problem in the laboratory test of coarse-grained materials. By combining the self-developed cellular automaton program with laboratory experiments, a method of simulating the triaxial test of coarse-grained materials was proposed in this paper, and a triaxial test numerical specimen that can characterize the discontinuous, nonuniform, and heterogeneous characteristics of bulk geotechnical materials was established. The parallel grading method was adopted to create six grading curves for numerical simulation based on one in situ grading curve. The failure process and the scale effect on the strength and deformation of coarse-grained materials were analyzed and discussed. The results showed that under the same confining pressure, the peak stress and initial deformation modulus E i increased with the increase of the maximum particle size d max , while the degree of shear shrinkage and Poisson’s ration υ decreased. As the confining pressure increased, the scale effect of coarse-grained materials would be magnified. If particle breakage and migration were assumed to be neglected, the internal friction angle φ and d max would be roughly proportional, the cohesive force c fluctuated with the increase of d max , and the empirical relations between d max and c and φ were established, respectively, which provides a reference for estimating the actual shear strength parameters of coarse-grained materials on-site. The research results can provide a way of thinking for the study of the scale effect of coarse-grained materials and also have certain reference significance for inferring the strength parameters of the original-graded coarse-grained materials.

Fracture Mechanism of Unstable Rock With Double-Crack Control Discontinuity Subjected to High Earthquake Intensities

Unstable rock in the limestone area has typical characteristics of quasimasonry structure and control discontinuity, where the failure essence is the fracture propagation under loads. The unstable rock control discontinuity in the limestone zone was analyzed, and the geological model for a doublecrack unstable rock mass was obtained according to the theory of geomorphologic evolution. The mechanical model and fracture mechanical model for the complex control discontinuity were constructed. Based on the rock weight, the fissure water pressure and the earthquake load, the formula of the fracture stability coefficient was obtained under the maximum circumferential stress criterion. The fracture stability coefficient expression for the unstable rock is rational according to the verifying case analysis. The fracture stability coefficient corresponding to each intensity decreases with the crack length ratio. Under earthquake intensities Ⅷ and Ⅸ, the unstable rock will collapse; the stability of the unstable rock is liable to the coupling effects of the crack length ratio of the main control discontinuity and the earthquake intensity. The critical crack length ratio decreases with the earthquake intensity. Under earthquake intensity Ⅶ, the theoretical value of the critical crack length ratio is 25.8%, which is slightly less than the actual value of 27.7%, and on the slightly safer side. The fracture stability coefficient expression has good applicability. The research results provide an important theoretical support for the treatment of such unstable rock masses.

Acquired long bone defects classifications: Literature review (Part II – long bone defects around the joint)

Introduction: In recent years, multiple classifications of long bone defects around the joint (LBDAJ) have been proposed. However, there is no universal clinical classification of LBDAJ to date. Through comprehensive literature review, we aim to identify the criteria that may be used to develop a future universal classification of LBDAJ. Materials and Methods: We performed a comprehensive review of the literature to identify all articles describing classification systems of LBDAJ in both native and prosthetic joints. Two reviewers searched the following electronic databases independently: The Cochrane Bone, Joint and Muscle Trauma Group, MEDLINE, and eLibrary. Studies investigating bone defects around the joint reporting a classification or any criteria to classify bone defects were included in this review. All studies not related to bone articular surfaces were excluded. Results: A total of 15 classifications for LBDAJ in the preserved joint were. Most systems considered the size of bone defect as a key criterion for clinical decision-making. A total of 31 classifications for periprosthetic bone defects related to hip, knee and shoulder arthroplasty were identified. The following criteria were used by different authors to classify periprosthetic bone defects: Location (n = 22), size (n = 20), containment (n = 9), discontinuity (n = 6), shape or geometrical characteristics of the defect (n = 4), fracture (n = 2), and deformity. Conclusion: Despite the large variety of the existing classifications of bone defects around the joint, there is no classification that could be considered universal. For the development of a future universal classification, defect location, size, and containment are likely to be the main factors to consider as important.

Characteristics of discontinuities in Heifangtai landslide area in Gansu, China

Loesses are widely distributed all over the world, especially in China. Meanwhile, long-term agricultural irrigation and extreme climate changes have led to frequent geological disasters in the Heifangtai area of Lanzhou, Gansu, China. Of these, landslides are one of the most frequent types of disasters that are harmful to humans and the environment. A landslide is closely related to the lithology, structure, and groundwater of the site and consists of a combination of structure units divided by discontinuities, such as faults, joints, and fissures. Therefore, geological surveys, engineering drilling, and trenching are typically used to identify the stratum lithology, structure, and groundwater in order to visually display underground information within a limited depth range. However, these methods have disadvantages. In particular, geological surveys can only describe geological phenomena on the surface, while the cost of drilling and trenching may be high, along with the inefficiency of exploration. In this research, the integrated geophysical exploration method was used to analyze the hidden joints, cracks, and other discontinuities and geophysical features of the discontinuities. The results were verified by trench exploration, and large amounts of underground information were obtained, especially the spread and distribution of discontinuities in landslide areas. Such information can be effectively used for carrying out and providing meaningful experiences and lessons in future comprehensive geophysical processing and interpretations related to the prediction and evaluation of landslides.

Study on the dynamic response of dip bedded rock slope using discontinuous deformation analysis (DDA) and shaking table tests

AbstractStability prediction for bedded rock slopes under seismic loading is very important for landslide hazard assessment. To clarify the dynamic behaviors and damage mechanism of dip bedded slope, shaking table tests and its prototype simulation analyses were performed. Shaking table tests were conducted to analysis the acceleration dynamic response firstly and then the discontinuous deformation analysis (DDA) method was used to reproduce the test results, and study the influence of vertical earthquake on the dynamic response of dip bedded rock slope. Both the two methods results reveal that the amplification coefficients increase with increasing acceleration amplitude under sinusoidal waves shaking condition, and show an increased trend with the relation height. With Wenchaun waves loading, the discontinuous characteristics between the test model and numerical model are consistent, the dynamic responses of the slope tops are strong, and it is easy to be destroyed. Compare the failure mechanism of the slope between shaking table test and numerical method, the damage areas both the numerical model and test model are the nearly identical, and the failure modes of two models are mainly the cracking sliding failure. Moreover, with horizontal and vertical earthquake loading, the acceleration response on the numerical slope top is strong, and the maximum peak acceleration amplification factors are at the leading and rear edges of the slope top. In overall, the dynamic response of the slope surface is more significant than that inside the slope. However, with an increase of amplitude, acceleration responses are different with different directional loading, the acceleration response with horizontal loading is stronger than with vertical loading.