Discontinuous Line Research Articles

Utilizing laser scribing for graphene ablation

We present the investigation of graphene ablation by laser scribing from a LightScribe DVD. In laser scribed graphene (LSG) samples, laser scribed holes (LSHs) were observed as dark features filled with residuals from copper etching. The LSHs tend to form a series of discontinuous lines aligning to laser scribed traces on the disk. The calculated fluence of laser scribing was about 93 and 124 mJ/cm2 for a pulse train and a single pulse, respectively. These fluences are in the range of fluence threshold of graphene ablation by femtosecond laser and are much higher than that of cw laser. From characterizations and electrical measurements, evidence of extended defects in graphene from LSHs in LSG was observed. From testing of graphene-based gas sensors, we can see that the response of LSG to ethanol is almost 100 times higher than that of graphene. This work provides a low-cost, facile method of graphene ablation by utilizing laser scribing. By improving sample preparation, our method could be applied to patterning graphene into microstrips, which have applications in novel devices such as THz sources and gas sensors.

Processing Algorithm of Irregular Table Image in Tobacco Package Based on Dual-coding Difference of Gaussians Method

Objectives: Currently, in a large number of print-out report documents from tobacco package, there exist irregular phenomena such as discontinuous vertical lines, misplaced frame lines and multi-page tables. Thus, the existing table recognition algorithm cannot be adopted to perform digital identification. In order to solve this problem, this paper proposes a table image processing algorithm based on the dual-coding difference of Gaussians iterative clustering. Firstly, the method of local regional sub-block is used to the skew correction threshold to conduct image correction. Secondly, the corrected images are coded by rows and columns, and 2D image features are transformed into 1D image features. Thirdly, the Gaussian differenced operation is adopted to obtain effective characteristic matrices that are stable and easily distinguishable. Then the iterative clustering analysis is performed to obtain the feature values of effective frame lines. Fourthly, after finishing the tasks, such as the table positioning, inner structure reconstruction, and text information identification, the dichotomy judgmentsof the integrity of multi-page tablesare realized according to the local pixel features. Finally, the text information inside the local regions and the reconstructed regions are merged, and the digital reproduction of the multi-page tables is realized. To validate the effectiveness of the proposed algorithm, an experiment in the sample set containing 12,840 table images with different resolutionsis carried out. The average detection accuracies of table positioning, table cell reconstructionand multi-page incompleteness are 98.95%, 99.80%, and 95.85%, respectively. The experimental results show that the proposed algorithm is simple and effective, and can accomplish the digital reproduction of irregular tables.

Near-field electrospinning polycaprolactone microfibers to mimic arteriole-capillary-venule structure.

The ability to create three-dimensional (3D) cell-incorporated constructs for tissue engineering has progressed tremendously. One of the major challenges that limit the clinical applications of tissue engineering is the inability to form sufficient vascularization of capillary vessels in the 3D constructs. The lack of a functional capillary network for supplying nutrients and oxygen leads to poor cell viability. This paper presents the near-field electrospinning (ES) technique to fabricate a branched microfiber structure that mimics the morphology of capillaries. Polycaprolactone solution was electrospun onto a sloped collector that resulted in morphological and geometric variation of the fibers. With proper control over the solution viscosity and the electrospinning voltage, a single fiber was scattered into a branched fiber network and then converged back to a single fiber on the collector. The obtained fibers have a diameter of less than 100microns at the two ends with coiled and branched fibers of less than 10 microns that mimics the arteriole-capillary-venule structure. The formation of such a structure in the near-field ES strongly depends on the solution viscosity. Low viscosity solutions form beads and discontinuous lines thus cannot be used to achieve the desired structure. The branching of PCL fiber occurs due to an electrohydrodynamic instability. The transition from the straight large fiber to smaller coiled/branched fibers is not instantaneous and stretches over a horizontal region of 1.5cm. The current work shows the feasibility of electrospinning the stem-branch-stem fibrous structure by adopting a valley-shaped collector with potentials for tissue engineering applications.

Satellite Observation of Spatio-temporal Variations in Nitrogen Dioxide over West Africa and Implications for Regional Air Quality.

Background.Nitrogen dioxide (NO2) is known to affect human health, causing heart and cardiovascular diseases, and it has been shown that locations with long term NO2 pollution recorded a high number of fatalities due to the COVID-19 pandemic. There are no ground stations monitoring emissions of NO2 over West Africa. The present study aimed to use satellite observations to examine pollutant trends over this region.Objective.To examine the trend of NO2 over the entire West Africa sub region in relationship to contributions to environmental emissions using satellite-derived data. This enables the assessment of West Africa regional air pollution hot spots in relationship to enhancing atmospheric factors. The results from this study will also be useful guidance for setting air quality standards for air pollution controls to minimize health hazards.Methods.The present study examined thirteen years of average monthly values of nitrogen dioxide (NO2) to determine the spatio-temporal variation of this pollutant over West Africa. Satellite data for NO2 between 2005 and 2017 were used to determine the variation in pollution levels over West Africa. Correlations between NO2 and meteorological variables (wind speed, rainfall and air temperature) were obtained to explain the influence of West African weather on the region's pollution accumulation.Results.The present study observed that NO2 concentrations varied from place to place and from season to season. Nitrogen dioxide concentrations during the dry season were higher (sometimes 200% higher) than values observed in the wet season which ranged between 0.5 and 6×1015 molec/cm2. Nitrogen dioxide north-south oscillation during the course of a year is largely controlled by the inter-tropical discontinuity (ITD) zone as high concentrations of NO2 are found in the vicinity of the ITD where wind speeds and horizontal vorticity approaches zero. Correlation analysis between NO2 and some atmospheric variables indicated NO2 concentrations are well influenced by atmospheric variables showing bipolar signals depending on the season. An increasing trend of NO2 was also found over selected cities of the region. This indicated that regional air quality is gradually deteriorating.Conclusions.The implications of worsening regional air quality were examined in the light of the prevailing COVID-19 pandemic. The dominant atmospheric factor determining pollution episodes in the region is the inter-tropical discontinuity line which marks the meeting point between the two wind regimes over the region. Densely populated areas are characteristically prone to elevated pollution and have experienced high fatalities during the COVID-19 pandemic.Competing Interests.The authors declare no competing financial interests.

Investigation and Improvements of UWB Microstrip Delay Lines

Microstrip ultra-wide band (UWB) delay lines consisting of a novel periodically loaded transmission line (PLTL) are presented, along with discontinuous structured guard lines (DSGLs). The distinctive advantage of the proposed approach is that the far-end crosstalk (FEXT) between the adjacent lines is effectively suppressed comparing to the conventional circuits. Afterward, the crosstalk of connected adjacent lines is effectively suppressed by modifying the DSGLs, since the current distributions are different from the separated adjacent lines. Subsequently, the strong reflection points are eliminated, which seriously deteriorate the performances in amplitude and group delay. Moreover, the serpentine delay line (SDL) and serpentine meandered delay line (SMDL) are studied, respectively, using the conventional microstrip (CMS) and the proposed PLTL with DSGLs. As a result, the SMDL pattern is also demonstrated useful to suppress the near-end crosstalk (NEXT) between the adjacent second-level curves, which in turn reduce the fluctuations in the group delay. In addition, the PLTL SMDL with DSGLs consequently have the superiority of suppressing the NEXT and FEXT simultaneously. Further simulations and measurements indicate that the performances of the PLTL SMDL with DSGLs lines are superior to the conventional method in a UWB range of dc to 25 GHz, including amplitude and group delay flatness, along with high time delay efficiency due to the slow wave property.

Limit Cycles of Planar Piecewise Differential Systems with Linear Hamiltonian Saddles

We provide the maximum number of limit cycles for continuous and discontinuous planar piecewise differential systems formed by linear Hamiltonian saddles and separated either by one or two parallel straight lines. We show that when these piecewise differential systems are either continuous or discontinuous and are separated by one straight line, or are continuous and are separated by two parallel straight lines, they do not have limit cycles. On the other hand, when these systems are discontinuous and separated by two parallel straight lines, we prove that the maximum number of limit cycles that they can have is one and that this maximum is reached by providing an example of such a system with one limit cycle. When the line of discontinuity of the piecewise differential system is formed by one straight line, the symmetry of the problem allows to take this straight line without loss of generality as the line x=0. Similarly, when the line of discontinuity of the piecewise differential system is formed by two parallel straight lines due to the symmetry of the problem, we can assume without loss of generality that these two straight lines are x=±1.

Metamorphosis of discontinuity lines and rectification of magnetic flux avalanches in the presence of noncentrosymmetric pinning forces

Considering a noncentrosymmetric pinning texture composed of a square array of triangular holes, the magnetic flux penetration and expulsion are investigated experimentally and theoretically. A direct visualization of the magnetic landscape obtained using a magneto-optical technique on a Nb film is complemented by a multiscale numerical modeling. This combined approach allows the magnetic flux dynamics to be identified from the single flux quantum limit up to the macroscopic electromagnetic response. Within the theoretical framework provided by time-dependent Ginzburg-Landau simulations, an estimation of the in-plane current anisotropy is obtained and its dependence with the radius of the curvature of hole vertices is addressed. These simulations show that current crowding plays an important role in channeling the flux motion, favoring hole-to-hole flux hopping rather than promoting interstitial flux displacement in between the holes. The resulting anisotropy of the critical current density gives rise to a distinct pattern of discontinuity lines for increasing and decreasing applied magnetic fields, in sharp contrast to the invariable patterns reported for centrosymmetric pinning potentials. This observation is partially accounted for by the rectification effect, as demonstrated by finite-element modeling. At low temperatures, where magnetic field penetration is dominated by thermomagnetic instabilities, highly directional magnetic flux avalanches with a fingerlike shape are observed to propagate along the easy axis of the pinning potential. This morphology is reproduced by numerical simulations. Our findings demonstrate that anisotropic pinning landscapes and, in particular, ratchet potentials produce subtle modifications to the critical state field profile that are reflected in the distribution of discontinuity lines.

Singularities in one-dimensional Euler flows

In this paper, a system of one-dimensional gas dynamics equations is considered. This system is a particular case of Jacobi type systems and has a natural representation in terms of 2-forms on 0-jet space. We use this observation to find a new class of multivalued solutions for an arbitrary thermodynamic state model and discuss singularities of their projections to the space of independent variables for the case of an ideal gas. Caustics and discontinuity lines are found.

Rich dynamics of a Filippov avian-only influenza model with a nonsmooth separation line

Depopulation of birds has been authenticated to be an effective measure in controlling avian influenza transmission. In this work, we establish a Filippov avian-only model incorporating a threshold policy control. We choose the index—the maximum between the infected threshold level I_{T} and the product of the number of susceptible birds S and a ratio threshold value ξ—to decide on whether to trigger the control measures or not, which then leads to a discontinuous separation line and two pieces of sliding-mode domains. Meanwhile, one more sliding-mode domain gives birth to more complex dynamics. We investigate the global dynamical behavior of the Filippov model, including the real and/or virtual equilibria and the two sliding modes and their dynamics. The solutions will eventually stabilize at the real endemic equilibrium of the subsystem or the pseudoequilibria on the two sliding modes due to different threshold values. Therefore an effective and efficient threshold policy is essential to control the influenza by driving the number of infected birds below a certain level or at a previously given level.

Pencil Drawing Generation Algorithm Based on GMED

The automatic generation of pencil drawings from natural images has been a hot spot in the field of nonphotorealistic rendering in recent years and has attracted the attention of many scholars. Aiming at the characteristics of single line drawings generated by the existing pencil drawing algorithm and stiff lines, this paper proposes a new edge generation Gradlent Morphological Edge Detector (GMED) algorithm, which uses the generated edge convolution to generate pencil line drawings, making stylized pictures more natural. First, the gradient map of the input image is extracted according to the feature of the tone rate of change around the line at the boundary. Second, to make up for the shortcomings of too thin and discontinuous lines in the gradient map, morphological operations are performed on the gradient map and convolved to generate a hand-drawn pencil line drawing. Finally, texture filling and tone mapping are performed, and the resulting line drawing is fused to obtain the final pencil drawing effect. Compared with the existing pencil drawing algorithm, the proposed GMED edge generation method is applied to the line drawing generation process to generate a hand-drawn style, fine and concise line drawing, and the texture simulation process is simple and efficient, combined with histogram matching. In the process, a more suitable GML method is used, so that the final pencil drawing not only has natural lines but also colors closer to the input image.

Description of Hemicycliophora cardamomi sp. n. (Nematoda: Hemicycliophoridae) associated with Amomum longiligulare T.L. Wu and a web-based key for the identification of Hemicycliophora spp.

During a survey of plant diseases in the Central Highlands of Vietnam, a new plant-parasitic nematode, Hemicycliophora cardamomi sp. n., was discovered in the growing areas of Amomum longiligulare, a valuable medicinal plant with high economical value. The new species is characterized by a cuticular sheath loosely fitting body; a labial region continuous to the body contour bearing 3 annuli; a lateral field frequently marked by a discontinuous single line with indistinct additional short lines in some parts along the body; a modified vulval lip with an anterior lip c. 4 annuli long; and a post-vulval body tapering to a pointed tail tip with an abrupt constriction at the last third of the post-vulval body. Morphology and molecular characterizations of D2-D3 expansion segment of 28S rRNA, ITS, and COI mtDNA gene regions clearly distinguish the new species from all other 133 known species. This study also provides a newly developed web-based key for the identification of Hemicycliophora spp. in order to accelerate the identification process, to minimize the increasing error load associated with larger datasets, and to avoid any dependence on a single starting entry. This key includes both an existing Bray-Curtis similarity measure and a newly developed similarity formula.

A sphere packing model for shear bands in dense soils

The rhombic sphere packing can be used to model the biaxial test on granular soils in a very simple way. According to the angle of assemblage, the packing is dilatant or contractive. Correspondingly, overall stresses are transmitted as chains of forces or oblique forces of contact. The connection of the soil stress-strain behaviour and the packing void ratio is achieved by mapping both of the plots. The mapping shows that dense soils are dilatant and loose soils are contractive, separated by the critical state. It also shows that the bifurcation point and the peak strength are features only of dense soils. The band of strain localization is analysed in the elastic regime, and its inclination is found maximizing the intensity of the mobilized stress ratio. The stresses within the shear band are obtained by assuming a partially coaxial packing rotated to reach the full plastic state. The equilibrium of the overall stress at the line of discontinuity reveals a relationship between the peak friction angle and the coefficient of lateral pressure at rest. As long as these parameters are obtained independently of each other, they allow the validation of the theory.

Minor surface displacement caused by the Kumamoto earthquake detected by DInSAR

The LC-InSAR map by DInSAR showed a large number of ‘phase discontinuous lines' at locations other than the main trace of the surface rapture caused by the Kumamoto earthquakes. On the Line of this ‘phase discontinuous line', many places where minute surface displacement was observed were found. Most of the ‘phase discontinuity lines' are thought to represent minor surface displacements caused by the Kumamoto earthquake. It is considered that such a minor displacement was difficult to find out only by the field survey after the earthquake because the displacement was too small. It was confirmed that the LC-InSAR map is effective for detecting minute surface displacement.

Следы от обработки дерева и кости на вулканическом кремне палеовулкана Дунда-Ага: предварительные экспериментальные данные

Abstract: The article is a description of an experiment on planing the raw and dry wood, as well as boiled bone, which was carried out by flakes from volcanic flint from the raw material source of the Dunda-Aga paleovolcano, located in the Aginsky Buryat district of the Transbaikal region. In its course, changes in the working edge of the tools were monitored using binocular and metallographic microscopes, as well as photographic recording of these results using digital cameras and Helicon Focus v. 5.3. During the experiment, it was possible to identify a tendency for the formation of macro and micro wear of the surface of the working edge of objects, depending on the material processed by planing. It was found that on volcanic flint, in places of the most intense contact with a hard surface to be treated, micropolishing in individual microsections is formed already within the first 30 minutes of operation. Then these areas expand and close along the length of the working edge. Over time, tools that work dry wood show a fine micro-polish line, while wet wood forms a more discontinuous line of different widths. Bone processing showed the strongest modification of the tool. After an hour of work, it became dull due to intense rounding, and after two hours it almost completely lost its effectiveness. The results of this experiment clarify the dynamics of the formation of macro and micro wear on tools made of volcanic flint when processing dry and damp wood, as well as bone. Keywords: microwear analysis, petroarcheology, the sources of raw materials, Stone Age, Transbaikalia, Dunda-Aga paleovolcano, volcanic flint Acknowledgements: The work was supported by a grant from the Transbaikal State University No. 292‑ГР.

Ibn al-Mukhayem: esclusione e soggettività dei rifugiati palestinesi in Cisgiordania

‘The camp’ is a heterogeneity of forms of housing/confinement located in extremely various contexts and managed by dissimilar institutions. The refugee camps are a characteristic place of modernity and impure, exceeding the national order of things. The camp and its inhabitants are a chimera, living matter that escapes the representation of the real as rational: in fluid becoming, crossed by the bodies that shape it but a place where one lives in a state of liminality for uncertain time. The central question posed by the text revolves around the living conditions of the refugee camp in relation to the 'outside'. Through a comparative ethnography I will try to trace some lines of continuity and discontinuity between the 'inside' and the 'outside' of the space of a refugee camp in the West Bank, in relation to the existential conditions linked to land, expropriation, and living within which the possibilities of discourses, identities, techniques, knowledge and forms of politics are articulated and intersect.

An approximate method for solving Wiener-Hopf matrix equations in problems of applied mechanics

Method of successive approximations for the solution of the Wiener---Hopf functional equations system is offered. The method uses the presentation of matrix coefficient of the system as a sum of two matrices, where the first matrix assumes the exact factorization, and the second matrix --- matrix-perturbation --- is much smaller than the first matrix in the domain of system definition. Solution of the system is sought in the form of expansions in powers of the matrix-perturbation. At each step of the approximation the solution of the system is carried out by means of the Wiener---Hopf method using factorization of the main component of the matrix coefficient. The example of the use of method is considered for the solution of the problem about the calculation of the pre-fracture zone parameters in connecting material near the tip of the interfacial crack outcoming from the angular point of the broken interface of two different materials. The zone is modeled by the discontinuity line of displacement, on which the stresses meet the Mises---Hill failure criterion. It is shown that under certain conditions, already in the first approximation, the method allows to obtain solutions with permissible accuracy.

Improvement in the weldability of molybdenum alloy by pre-welding solid carburising

Molybdenum (Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry; however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone (FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo2C, and some free C atoms, and MoC and MoOxCy phases were also present. The distribution of Mo2C directly influenced the bonding strength of the grain boundaries. As Mo2C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo, it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo2C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoOxCy phase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.

A modified cutting line in the single-door cervical laminoplasty via a computed tomography-based morphological study of the subaxial cervical spine

ObjectiveTo modify the conventional methods of grooving and direction during the single-door cervical laminoplasty (SDCL) in the subaxial cervical spine. MethodsThe distance between the left and the right lamina-lateral mass junction at the upper, middle, and lower levels of each segment (DLL-U, DLL-M, DLL-L), angle between the posterior edge of the vertebral body and the lamina (AVL) and thickness of lamina (TL) were measured in the transverse plane. The parameters of preoperative computed tomography scans of 200 patients who had undergone SDCL were measured. The patients were divided into male and female groups and developmental canal stenosis (DCS) and non-DCS (NDCS) groups. ResultsDLL-M gradually increased from the cranial to the caudal except for C7, and DLL-L > DLL-M > DLL-U in each vertebra. AVL increased from C3 to C7, TL decreased from C3 to C5 and increased from C5 to C7, with both parameters showing no significant differences between the left and right sides. AVL of the DCS group was less than that of the NDCS group (P < 0.01). ConclusionsIn the SDCL, the ideal surgical trough should be several discontinuous lines sloping from top to bottom, rather than a straight line. The abduction angle during drilling should gradually increase from C3 to C7 in the SDCL averaging 40 degrees. This method mentioned above improves the efficiency of the operation with less blood loss as an extended cut into the lateral mass is avoided.

Evolution of vortices created by conical diffraction in biaxial crystals versus orbital angular momentum

Light states evolution versus their fractional orbital angular momentum (OAM) has been analyzed in the conical diffraction process occurring through biaxial crystals. Experimental results are provided by a non-degenerate cascade of KGd(WO$_2$)$_4$ and Bi$_2$ZnOB$_2$O$_6$ biaxial crystals. The continuous $0\to 1\to 2$ $\hbar$/photon increasing of the fractional OAM in passing through integer values was operated with the help of the spin-orbit coupling in the Bi$_2$ZnOB$_2$O$_6$ crystal. The phase of the state light and its vortices were visualized by interference patterns with a reference beam. The evolution of the fractional OAM value is accompanied by a continuous evolution of pairs of vortices with opposite signs and linked by a $-\pi/+\pi$ discontinuous phase line. The phase pattern evolution around half-integer OAM is observed to be continuous. In other cases, the evolution can be interrupted by the breaking of a $-\pi/+\pi$ discontinuous phase line and a new pair of vortices with opposite charges is born.

Semi-analytical analysis of vibrations induced by a mass traversing a beam supported by a finite depth foundation with simplified shear resistance

In this paper the new semi-analytical solution for the moving mass problem on massless foundation, published by the author of this paper, is extended to account for inertial foundation modelled by a continuous homogeneous finite depth foundation with simplified shear resistance. Derivations are presented for infinite as well as finite homogeneous beams. Mode expansion method is used to solve the problem on finite beams, thus vibration modes, the corresponding orthogonality condition, reengagement of coupled equations to ensure significant calculation time savings are derived. Methods of integral transforms and contour integration are exploited to obtain the solution on infinite beams. Resulting vibrations are derived as a sum of the steady and unsteady harmonic vibrations and a transient contribution. The unsteady harmonic vibration is proven to be a useful indicator of unstable behaviour through the mass induced frequencies. Besides frequency lines also discontinuity lines are determined and their influence on the proximity of harmonic and full solutions is discussed. Even if the differences between these two versions are larger than for the massless foundation, it is shown that the harmonic solution provides a very good estimate of the full solution (in several cases perfect match is achieved) with the advantage to be obtainable by a simple evaluation of the derived closed-form results. Like for the massless foundation, also here, vibrations on infinite beams can be obtained on long finite beams with eliminated effect of its supports. All mentioned approaches are also validated by the finite element method.