Discontinuous Structure Research Articles

Fracture behavior analysis of X80 pipelines welded joints with unequal wall thickness

Pipeline transportation is one of the main methods for transporting oil and natural gas worldwide. The structural safety of welded joints of large diameter pipes with cracks and unequal wall thickness has become a research focus due to discontinuous geometrical structure and cracks in weld seams. In this paper, the tensile experiment and analysis of specimens with unequal wall thickness across welding seam based on the digital image correlation technology are carried out. Moreover, the influence of transition length and transition form on fracture behavior of welded joints of unequal wall thickness pipeline is obtained. In addition, a three-dimensional finite element model of welded joint of unequal wall thickness pipe with oblique line transition form and circular arc transition form is established. and the accuracy of the full-scale pipeline finite element model modeling method is verified by small-scale experiment data. On this basis, the influence of geometrical parameters of the transition section and wall thickness ratio, pipe diameter, and weld strength matching coefficient on the crack driving force of welded joints with unequal wall thickness is obtained. From the perspective of strain-based design, a method for obtaining the minimum transition length section and avoiding girth weld fracture is proposed. The research results guide the design and safety evaluation of welded joints with unequal wall thickness.

Multimodal Self-sustainable Autonomous Locomotions of Light-driven Seifert Ribbon Actuators based on Liquid Crystal Elastomers.

Multimodal self-sustainable autonomous locomotions integrated into one individual system, are high-level intelligent behavioral characteristics of living organisms and are the scientific hotspot of bionic soft actuators. Here, we report a light-fueled soft actuator with multimodal self-sustainable movements based on a Seifert ribbon bounded by a Hopf link. The Seifert ribbon actuator can self-sense the illumination area adjustment, and the actuation component becomes either a discontinuous strip-like structure or a continuous toroidal structure, which can realize adaptive switches between self-sustained oscillatory and rotary motions. The two motion modes are applied to the self-oscillatory piezoelectric generation and self-rotational work multiplication of cargo transport, respectively. The unique smartness of Seifert surface topology advances the level of actuation intelligence with broad implications for the adaptability, multifunctionality, and autonomy of soft robots.

Seismic Performance of Frame Structure with Hysteretic Intermediate Discontinuity

The introduction of an intermediate discontinuity in frame structures is commonly named inter-storey isolation. Inter-storey isolation is an effective technique for the seismic protection of new or existing frame structures. The devices that are used to perform the discontinuity, mainly of the structural stiffness, are placed at a higher storey level of the structure and not at the base level. In the latter years, this technique has gained increasing interest because, especially for existing buildings, it is cheaper and technically easier to implement than base isolation. In this paper, the attention is focused on the effects on a frame structure of an intermediate elasto-plastic discontinuity that can be described by a Bouc-Wen model. The frame structure with the intermediate discontinuity is modelled with a 3-DOF reduced model. Its dynamical behaviour is investigated by considering both harmonic and seismic external excitation. The results are summarized in gain maps aimed at finding the parameters that optimize the seismic behaviour of the structure.

DNALI1 interacts with the MEIG1/PACRG complex within the manchette and is required for proper sperm flagellum assembly in mice.

The manchette is a transient and unique structure present in elongating spermatids and required for proper differentiation of the germ cells during spermatogenesis. Previous work indicated that the MEIG1/PACRG complex locates in the manchette and is involved in the transport of cargos, such as SPAG16L, to build the sperm flagellum. Here, using co-immunoprecipitation and pull-down approaches in various cell systems, we established that DNALI1, an axonemal component originally cloned from Chlamydomonas reinhardtii, recruits and stabilizes PACRG and we confirm in vivo, the co-localization of DNALI1 and PACRG in the manchette by immunofluorescence of elongating murine spermatids. We next generated mice with a specific deficiency of DNALI1 in male germ cells, and observed a dramatic reduction of the sperm cells, which results in male infertility. In addition, we observed that the majority of the sperm cells exhibited abnormal morphology including misshapen heads, bent tails, enlarged midpiece, discontinuous accessory structure, emphasizing the importance of DNALI1 in sperm differentiation. Examination of testis histology confirmed impaired spermiogenesis in the mutant mice. Importantly, while testicular levels of MEIG1, PACRG, and SPAG16L proteins were unchanged in the Dnali1 mutant mice, their localization within the manchette was greatly affected, indicating that DNALI1 is required for the formation of the MEIG1/PACRG complex within the manchette. Interestingly, in contrast to MEIG1 and PACRG-deficient mice, the DNALI1-deficient mice also showed impaired sperm spermiation/individualization, suggesting additional functions beyond its involvement in the manchette structure. Overall, our work identifies DNALI1 as a protein required for sperm development.

Real-time spatial quantification of gastric acid diffusion in whey protein gels with different NaCl concentrations by wide-field fluorescence microscopy

Gastric acid diffusion and penetration constitute an essential process in the structural breakdown and enzymatic hydrolysis of solid food during digestion. This study aimed to quantify the real-time diffusion and spatial distribution of gastric acids in whey protein isolate (WPI) gels in the presence of 0–0.05 M NaCl during simulated digestion using a wide-field fluorescence microscope. For all the gels regardless of NaCl concentration, the outer surface rapidly developed a near-saturated layer, resulting in a higher normalized gastric acid concentration in the outer layer than in the inner layer. The pH decrease was more significant for the gels at a higher NaCl concentration (i.e., 0.05 M) due to the formation of a more discontinuous and looser network structure that would facilitate acid diffusion into the gel matrix and decrease the gel buffering capacity. Consistently, the effective diffusion coefficient (DA) estimated via the Fick diffusion model was 6.19 × 10−10 m2/s for 0.05 M WPI-RITC gels, significantly higher than 0.015 M (4.46 × 10−10 m2/s) and 0 M (3.54 × 10−10 m2/s) gels. The present study has provided a quantitative understanding of the diffusion process and spatial distribution of gastric acids within the WPI gel matrix in real-time during in vitro gastric digestion as influenced by NaCl concentration.

Biomimetic Design and Topology Optimization of Discontinuous Carbon Fiber-Reinforced Composite Lattice Structures

The ever-increasing requirements for structural performance drive the research and development of lighter, stronger, tougher, and multifunctional composite materials, especially, the lattice structures, heterogeneities, or hybrid compositions have attracted great interest from the materials research community. If it is pushed to the extreme, these concepts can consist of highly controlled lattice structures subject to biomimetic material design and topology optimization (TO). However, the strong coupling among the composition and the topology of the porous microstructure hinders the conventional trial-and-error approaches. In this work, discontinuous carbon fiber-reinforced polymer matrix composite materials were adopted for structural design. A three-dimensional (3D) periodic lattice block inspired by cuttlefish bone combined with computer modeling-based topology optimization was proposed. Through computer modeling, complex 3D periodic lattice blocks with various porosities were topologically optimized and realized, and the mechanical properties of the topology-optimized lattice structures were characterized by computer modeling. The results of this work were compared with other similar designs and experiments to validate the effectiveness of the proposed method. The proposed approach provides a design tool for more affordable and higher-performance structural materials.

Mechanical, microstructural and fracture studies on inconel 825–SS316L functionally graded wall fabricated by wire arc additive manufacturing

This paper presents a novel method that uses the cold metal transfer based wire arc additive manufacturing process to fabricate functionally graded Inconel 825–SS316L walls. The optical micrograph of Inconel 825 exhibits continuous and discontinuous dendritic structures. The SS316L region comprises 5% of δ-ferrite in primary austenitic (γ) dendrites which was confirmed by the Creq/Nieq ratio of 1.305. The functionally graded interface reveals a partially mixed zone with a transition from the elongated dendrites to fine equiaxed dendrites. The tensile properties of the fabricated wall were determined at room temperature using specimens extracted from Inconel 825, SS316L, and the interface regions. The morphology of the tensile tested specimens revealed significant plastic deformation, indicating ductile failure. The fracture toughness of the wall was experimentally investigated by employing the crack tip opening displacement (CTOD) test. The fracture morphology exhibited a ductile mode of fracture with striations perpendicular to the direction of crack development. Elemental mapping revealed that there was no evidence of elemental segregation on the fractured surfaces, and the elements were uniformly dispersed. The CTOD measures 0.853 mm, 0.873 mm on the Inconel 825 side and the SS316L side respectively. The test results confirm that both the Inconel 825 and SS316L sides have good fracture toughness.

A study of mesh influence on extended finite element cracked plate and finite element plate bending

The object of this study is a refining mesh effect on discontinuous structures response. This paper presents a study of mesh influence between cracked and non-cracked plates using extended finite element and standard finite element method, respectively. For the first case, the plate is stressed on one side, in which cracked zone displacements are given for different mesh refinements. The second case study is bending orthotropic and isotropic plates under uniform rectangular impulsive load, in which mesh influence on the structural response is presented. The numerical modelization is done using an isoperimetric quadrilateral element. On one hand, the stiffness linear matrix of a cracked plate is evaluated numerically by adding an enriched shape function to the standard shape function to be able to model discontinuity numerically. On the other hand, for the case of the non-cracked plate, the use of the finite element method with standard shape function is well suited to the numerical design of stiffness and mass matrix. The essence of this study is to show the mesh effect on cracked and non-craked plate response, which is a first step that allows to go even further on monoitoring of our crack evolution.It is a very useful field as any structure in our daily life is subject to a discontinuity (crack) which we must be able to control in order to evoid a future structure collapse.

English Discontinuous Structures

This paper examines the possibility of inserting linguistic elements
 in unusual positions. The outcome of such insertion has come to be
 known as a discontinuous structure. Learners of English as a foreign
 language are warned against the use of such structures in their speech or
 writing. However, in several cases the insertion of a word or a clause
 within a constituent or between constituents becomes obligatory or
 stylistically preferable. One striking example is the use of adverbials
 between the main verb of a sentence and its direct object when the object
 of the sentence is long or heavy.

Structures of longitudinal-torsional shock waves and special discontinuities in nonlinearly viscoelastic media with dispersion

Structures of longitudinal-torsional shock waves and special discontinuities in nonlinearly viscoelastic media with dispersion

Simulation of High Breakdown Voltage, Improved Current Collapse Suppression, and Enhanced Frequency Response AlGaN/GaN HEMT Using A Double Floating Field Plate

In this paper, DC, transient, and RF performances among AlGaN/GaN HEMTs with a no field plate structure (basic), a conventional gate field plate structure (GFP), and a double floating field plate structure (2FFP) were studied by utilizing SILVACO ATLAS 2D device technology computer-aided design (TCAD). The peak electric fields under the gate in drain-side can be alleviated effectively in 2FFP devices, compared with basic and GFP devices, which promotes the breakdown voltage (BV) and suppresses the current collapse phenomenon. As a result, the ON-resistance increase caused by the current collapse phenomena is dramatically suppressed in 2FFP ~19.9% compared with GFP ~49.8% when a 1 ms duration pre-stress was applied with Vds = 300 V in the OFF-state. Because of the discontinuous FP structure, more electric field peaks appear at the edge of the FFP stacks, which leads to a higher BV of ~454.4 V compared to the GFP ~394.3 V and the basic devices ~57.6 V. Moreover, the 2FFP structure performs lower a parasitic capacitance of Cgs = 1.03 pF and Cgd = 0.13 pF than those of the GFP structure (i.e., Cgs = 1.89 pF and Cgd = 0.18 pF). Lower parasitic capacitances lead to a much higher cut-off frequency (ft) of 46 GHz and a maximum oscillation frequency (fmax) of 130 GHz than those of the GFP structure (i.e., ft = 27 GHz and fmax = 93 GHz). These results illustrate the superiority of the 2FFP structure for RF GaN HEMT and open up enormous opportunities for integrated RF GaN devices.

FLIE: First-Look Enabled Inspect-Explore Autonomy Toward Visual Inspection of Unknown Distributed and Discontinuous Structures

In this article, the problem of an online autonomous aerial inspection, specifically for discontinuous and distributed objects is presented. The proposed approach imposes view culling and photogrammetric constraints based on a geometrically modelled three-dimensional view pyramid, a view cone to filter surfaces by desired observation angle, a framework-integrated passive collision-avoidance scheme with the object under inspection, and a dynamically enveloping bounding-box region to map the visited surfaces. Furthermore, the proposed inspect-explore framework is validated for the case of an unknown environment with no prior knowledge of the object model under inspection. The overall inspection scheme is based on the novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">First-Look</i> approach, enabling the UAV to progressively adapt its inspection path to match the profile of the structure autonomously. The implemented exploration strategy imposes a tiered policy enabling the UAV to search, identify and navigate towards the structure for inspection. The presented work utilizes a unified architecture of the aforementioned inspect-explore framework to improve situational awareness in a previously unknown environment by enabling the UAV to explore its surrounding space and identify structures to execute closer inspection tasks. Extended simulations to evaluate the efficacy of the proposed inspect-explore framework are presented with multiple structure scenarios.

Ore-containing data of lyalyagun mineralized zone of malguzar mountains

An analysis of the Malguzar Mountains allows us to note that Silurian formations (sandstones, gravestones, shale) are ore-bearing here, crumpled into folds, which are complicated by a series of faults with a northwest strike. These structures are rectilinear; their zone is characterized by the presence of small discontinuous structures and areas of swelling. Within the Lyalyagun zone, the localization sites of mineralized zones of gold mineralization were identified based on established direct and indirect cosmogeological features.

Multi-scale machining damages of CFRP circular cell honeycomb during end face machining

CFRP circular cell honeycomb is becoming increasingly important in aerospace due to its low density, high specific stiffness, impact resistance and microwave absorption performance. However, high-quality machining of CFRP circular cell honeycomb still represents a significant challenge due to its anisotropic, heterogeneity and discontinuous characteristics. This paper is presented to summarize the machining damage and analyze its cause. In this paper, the exit angle and MRR are defined to describe the effect of discontinuous structure on material removal process, the machining damage of CFRP circular cell honeycomb is classified based on the morphology and scale, the end face machining experiments are carried out to study the effect of machining method (milling and grinding), geometry of tools, exit angle and MRR on damage. The results show that milling produces larger tearing and less burr than grinding. The exit angle influences the curvature radius of fiber that determines fiber fracturing significantly, and side face burr occurs as exit angle and curvature radius of fiber increases. The MRR is larger in cut in and cut out stage of circular cell, tearing and delamination occurs respectively, but the chamfer or fillet of the grinding wheel tetrad material removal process and strength the stiffness of machining area, damage was suppressed. Considering the frequency and the size of damage may occur systematically, grinding wheel with chamfer or fillet is recommended to process CFRP circular cell honeycomb.

Research on impact reduction of flexible boundary particle damping honeycomb plate based on discrete element multi body dynamics coupling

&lt;abstract&gt; &lt;p&gt;The exposed platform is the main component of precision instruments such as pyrotechnic separation devices and load adapters, and its dynamic response characteristics are a key factor affecting the stability of aircraft. When the pyrotechnic separation device explodes, the exposed platform will be subjected to high-frequency, transient and high-order pyrotechnic impacts. High order pyrotechnic impacts can easily cause damage to sensitive components in onboard equipment, resulting in incalculable losses. Filling the honeycomb core cavity inside the exposed platform with a flexible boundary particle damper can effectively attenuate the pyrotechnic impact load after experiencing a large number of discontinuous structures. A numerical model of a flexible boundary particle damper and an exposed platform honeycomb panel was established through the coupling of discrete element and multi body dynamics. The effects of particle material, particle size, filling rate and flexible boundary film thickness on the impact reduction performance of the flexible boundary particle damper were analyzed, and the optimal characteristic parameters of the flexible boundary particle damper were obtained. The impact test was conducted on the honeycomb panel of the exposed platform using a light gas gun impact experiment, verifying the impact reduction effect of the flexible boundary particle damper and the accuracy of the numerical model. Finally, a pyrotechnic impact experiment was conducted on the exposed platform honeycomb panel with the optimal parameter flexible boundary particle damper. The experimental results showed that the impact reduction effect of the flexible boundary particle damper with this parameter reached 55.52%.&lt;/p&gt; &lt;/abstract&gt;

Application of GIS technologies for engineering geodynamic zoning of mountain territories

The lack in practise of applying special engineering-tectonic studies in the course of standard engineering surveys does not allow us to fully take into account the features of engineering-geological conditions of mountainous territories.In the work for the section of the Black Sea coast from Gelendzhik to Tuapse, which is part of the Afipsko-Defanovskaya orographic stage, a detailed study of discontinuous structures was carried out using cartographic constructions. The use of the GIS technology tool made it possible to carry out an overlay analysis of maps of morphometric indicators, as well as to draw up a diagram of tectonic blocks. The results showed good convergence with the data obtained earlier on a smaller scale. This provided the basis for zoning the territory according to the degree of favorability of engineering and tectonic conditions with the involvement of morphometric and tectonic features. The study of this territory was conducted for the first time and contributes to the clarification of its neotectonic structure, expanding the scope of application of structural and geomorphological methods based on GIS technologies in engineering and geological research.

Diffraction separation and imaging using ensemble empirical mode decomposition and multichannel singular spectrum analysis

AbstractSeismic diffracted wavefield has substantial potential for high‐resolution subsurface imaging of discontinuous geological structures; however, they are often masked by higher amplitude reflection, thus requiring separation. According to the low‐rank nature of a seismic wavefield, the diffracted wavefield can be extracted using the rank‐reduction method. The traditional low‐rank diffraction separation suffers from a threshold selection problem, especially for field data. To improve threshold accuracy, we propose a method in the common‐offset or poststack domains based on the f–x ensemble empirical mode decomposition and multichannel singular spectrum analysis. We demonstrate that such decomposition allows the determination of the diffraction threshold according to the difference between the singular values of the data before and after it. Synthetic and field data examples prove that the decomposition can effectively predict and suppress the horizontal reflected signal, while attenuating the energy of the dipping reflected signal. The following multichannel singular spectrum analysis suppresses the dipping reflection and separates the diffraction according to the precise threshold obtained earlier. The proposed method effectively improves the accuracy of the diffraction threshold selection, enhances diffraction and attenuates reflection, resulting in an enhanced image of small‐scale geological structures.

Discontinuous grammar as a foreign language

In order to achieve deep natural language understanding, syntactic constituent parsing is a vital step, highly demanded by many artificial intelligence systems to process both text and speech. One of the most recent proposals is the use of standard sequence-to-sequence models to perform constituent parsing as a machine translation task, instead of applying task-specific parsers. While they show a competitive performance, these text-to-parse transducers are still lagging behind classic techniques in terms of accuracy, coverage and speed. To close the gap, we here extend the framework of sequence-to-sequence models for constituent parsing, not only by providing a more powerful neural architecture for improving their performance, but also by enlarging their coverage to handle the most complex syntactic phenomena: discontinuous structures. To that end, we design several novel linearizations that can fully produce discontinuities and, for the first time, we test a sequence-to-sequence model on the main discontinuous benchmarks, obtaining competitive results on par with task-specific discontinuous constituent parsers and achieving state-of-the-art scores on the (discontinuous) English Penn Treebank.

First validation of GEDI canopy heights in African savannas

Savannas have complex, discontinuous woody vegetation structures that vary greatly in vertical and spatial arrangement and change due to climatic, ecological and management impacts. While airborne laser scanning (ALS) data have provided detailed information on vertical vegetation structure and is widely used in ecological studies, it is lacking in availability and repeat frequency. Although the Global Ecosystem Dynamics Investigation (GEDI) waveform Light Detection and Ranging (LiDAR) sensor and algorithms were optimized for measuring dense forests, it was anticipated that GEDI metrics could provide useful characterization of lower stature, sparse savannas structures. This study provided the first baseline validation of Version 2 GEDI (L2A) relative height 98 (RH98) by comparing the on-orbit GEDI-RH98orb to the simulated GEDI-RH98sim derived from ALS data across diverse savanna vegetation. It furthermore determined the influence of various factors on error, e.g. algorithm setting group (SGs), beam type, day vs. night, beam sensitivity, and vegetation phenology. After applying quality flags, 22,813 GEDI footprints were analyzed across 11 sites. SGs 4–6 that are aimed at dense forests had much larger errors than SGs 1–3. The phenological conditions at the time of GEDI data acquisition had a very large influence on the error of RH98orb. During leaf-on conditions for savanna vegetation with RH98sim < 15 m, RH98orb was very accurate with R2 = 0.61, mean bias = −0.55 m, %bias = −11.1%, RMSE = 1.64 m and %RMSE = 29.8%. In leaf-off conditions where RH98sim < 15 m, RH98orb was less accurate with R2 = 0.43, mean bias = −1.47 m, %bias = −26.5%, RMSE = 2.03 m and %RMSE = 40.9%. During leaf-off conditions, the GEDI LiDAR signal at the start of the waveform may be weaker as it interacts with denuded branches and may be truncated as noise, leading to a large negative height bias. Therefore, assessments of deciduous vegetation structures should be conducted during leaf-on periods. In leaf-on conditions, GEDI's RH98orb was very accurate between canopy heights of 3 and 7 m, with a mean bias of −0.79 m (−10%). The bias of RH98orb was not influenced by canopy cover. Due to the GEDI LiDAR pulse width of 15.6 ns, the GEDI-RH98 data product cannot reliably estimate canopy heights of shrubs below 2.34 m and will require more complex deconvolution of the waveform. GEDI's RH98 accurately estimates the canopy height of trees between 3 and 15 m allowing assessment of canopy heights over vast savanna areas.

Three age ranges of Cenozoic basaltic rocks from Lower Silesia (SW Poland) based on 40Ar/39Ar step-heating data

The precise ages of Cenozoic basaltic rocks from 20 localities (24 samples) in south-western Poland were studied by means of the 40Ar/39Ar isotope method. Three phases of volcanic activity were identified in this area. The older, Ruphelian phase took place 31–29 Ma ago and the younger, Aquitanian phase occurred 22–21 Ma ago. Significantly younger ages (4.8–4.6 Ma: Zanclean phase) were obtained for the basalts cropping out in the vicinity of Lądek Zdrój only. Most of the analyzed basalts from the Ruphelian phase are classified as nephelinites. They occur in the area of Lausitz Masif, south of Sudetic Marginal Fault and in the Opole Depression. The volcanic rocks from the Aquitanian phase crop out in the wide area north of the Sudetic Marginal Fault. They are composed of alkali basalts. The youngest phase is represented by the basanites only. The deep discontinuous tectonic structures intersecting the areas of volcanic activity in SW Poland, parallel or oblique to the tectonic stress directions previously reconstructed for the Oligocene and Miocene in the Bohemian Massif, were most probably reactivated by an extension approximately parallel or slightly oblique to them, thus opening pathways for the migration of basaltic magma in the Sudetes and their foreland.