Vertical Stroke Research Articles

Initiation of Downward Positive Leader Beneath the Negative Leader Channel

AbstractDue to the weak radiation generated by positive leaders, our understanding of how positive leaders are initiated and reach the ground remains limited. This study investigated positive cloud‐to‐ground (CG) lightning induced after the long intracloud lightning based on high‐speed video and fast antenna mapping results. Below the cloud base in the field of view, re‐breakdowns of decayed negative branches occurred consecutively beneath the horizontal negative channel in the form of bidirectional leaders. These bidirectional leaders advanced along the same channel, and eventually, the third reached the ground, generating a positive return stroke (RS) with a peak current of 157 kA. Following the RS, new negative discharges emerge adjacent to the vertical return stroke channel, persisting and propagating to form a continuing current (CC) lasting over 200 milliseconds.

Physical Modeling of Tsunamis Generated by Submarine Volcanic Eruptions

AbstractSubmarine volcanic eruptions can induce major local and regional tsunami hazards through varied source mechanisms. Large‐scale experiments of tsunamis generated by submarine volcanic eruptions are conducted to study the cylindrical wave generation and propagation in a three‐dimensional wave basin. A unique volcanic tsunami generator (VTG) was deployed at the bottom of the wave basin to generate volcanic tsunamis with repeatable and controlled source parameters. The physical modeling is based on the generalized Froude number defined with the VTG velocity and the near source water depth. The pneumatically driven vertical stroke motion generates leading elevation waves in the wave basin. The tsunami waves generated by the VTG are measured with a wave gauge array. The wave maker performance is characterized by the dimensionless leading wave amplitudes and periods. The experimental data show the variations of the leading wave amplitude, period, and celerity along the radial propagation distance. The generated cylindrical waves belong to the weakly nonlinear wave regime in the near field with decaying wave amplitude along radial propagation. The attenuation rate of the leading wave exceeds the range from the linear wave theory in runs with higher Froude numbers. The dimensionless leading wave period increases with the dimensionless propagation distance due to the dispersion relation. Empirical equations for the characteristic wave parameters such as amplitudes and periods are derived. The experimental results contribute to the understanding of volcanic tsunami generation processes and may serve rapid volcanic tsunami hazard assessments as well as the advancement and validation of numerical models.

Multi-planar injection lap riveting

This paper is focused on multi-planar hybrid busbars made from copper and aluminum for electric energy distribution systems. The objective is to provide an overview of its assembly by injection lap riveting in multidirectional tools and to compare the electrical performance of its joints against that of conventional (in-plane) busbars.The injected lap riveted joints require a dovetail ring hole and a countersunk hole to be first machined in the overlapped copper and aluminum sheets and then to inject the semi-tubular rivets by compression through the lined-up holes in order to fix the sheets in position. In this work, the injection of the semi-tubular rivets was carried out in a laboratory multidirectional tool set that converts the vertical press stroke into two-orthogonal horizontal movements by means of cam slide units consisting of compression punch holders and sliding wedge actuators attached to the upper bolster.Experimental results obtained for a multi-planar, three-conductor, rake-shaped elbow of a hybrid busbar system allow concluding that while the required compression force is proportional to the number of injected lap riveted joints, the electrical performance is non-proportional due to changes in the distribution of electric current density. Numerical simulation with finite elements gives support to the discussion and allows readers to recognize the pitfalls of designing busbar joints exclusively based on mechanical requirements.

Active smelling in the American cockroach.

Motion plays an essential role in sensory acquisition. From changing the position in which information can be acquired to fine scale probing and active sensing, animals actively control the way they interact with the environment. In olfaction, movement impacts the time and location of odour sampling as well as the flow of odour molecules around the olfactory organs. Employing a detailed spatiotemporal analysis, we investigate how the insect antennae interact with the olfactory environment in a species with a well studied olfactory system - the American cockroach. Cockroaches were tested in a wind-tunnel setup during the presentation of odours with different attractivity levels: colony extract, butanol and linalool. Our analysis revealed significant changes in antennal kinematics when odours are presented, including a shift towards the stream position, an increase in vertical movement and high-frequency local oscillations. Nevertheless, the antennal shifting occurred predominantly in a single antenna while the overall range covered by both antennae was maintained throughout. These findings hold true for both static and moving stimuli and are more pronounced for attractive odours. Furthermore, we find that upon odour encounter, there is an increased occurrence of high-frequency antennal sweeps and vertical strokes, which are shown to impact the olfactory environment's statistics directly. Our study lays out a tractable system for exploring the tight coupling between sensing and movement, in which antennal sweeps, in parallel to mammalian sniffing, are actively involved in facilitating odour capture and transport, generating odour intermittency in environments with low air movement where cockroaches dwell.

Impact of Various Remineralizing Agents on Artificial White Spot Lesion on Primary Teeth-A Comparative Study.

The aim of the current research was to assess the effectiveness of different remineralizing substances on artificial white spot lesions on deciduous teeth. 45 deciduous teeth without dental caries constituted the study group for this in vitro research. A 3 mm by 3 mm window of enamel was uncovered at the occluso-gingival midpoint of the coronal labial surface; an acid-resistant nail varnish was coated alongside the uncovered enamel surface of all specimens, employing vertical strokes. Demineralization was executed for the tenure of 72 hours at 37°C temperature in an incubator. The forty-five specimens, fifteen in each group, were assigned to the investigational groups plus a control group as: Group A: Control, Group B: Calcium sucrose phosphate (CaSP), Group C: Casein phosphopeptide-amorphous calcium phosphate-fluoride (CPP-ACPF). Microhardness tester was employed for testing the microhardness of the enamel surface using a Vickers diamond indenter laden with twenty-five milligrams for approximately ten seconds. Vickers hardness number (VHN) calculations for the microhardness were performed at baseline and on the fourteenth day. The CPP-ACPF group exhibited greater mean microhardness value at 236.14 ± 2.12, in pursuit by CaSP group with a score of 231.98 ± 3.16 and then the control group at 220.22 ± 5.08. An extremely statistically significant difference was seen amid the groups. The current research arrived at a conclusion that both the remineralizing substances were certainly efficient in handling early dental caries, and additionally, casein phosphopeptide-amorphous calcium phosphate-fluoride (CPP-ACPF) was found highly efficient as a remineralizing substance, in pursuit by calcium sucrose phosphate (CaSP).

Characterization of the Fracture Forming Limits by Radial Extrusion

This paper introduces a new formability test based on double-action radial extrusion to characterize material formability in the three-dimensional to plane-stress material flow transitions that are found in bulk metal-formed parts. The presentation draws from a multidirectional tool, which was designed to convert the vertical press stroke into horizontal movement of the compression punches towards each other, aspects of experimental strain determination, fractography, and finite element analysis. Results show that three-dimensional to plane-stress material flow transitions at the radially extruded flanges lead to different modes of fracture (by tension and by shear) that may or may not be preceded by necking, such as in sheet metal forming. The new formability test also reveals adequate characteristics to characterize the failure limits of very ductile wrought and additively manufactured metallic materials, which cannot be easily determined by conventional upset compression tests, and to facilitate the identification of the instant of cracking and of the corresponding fracture strains by combination of the force vs. time evolutions with the in-plane strains obtained from digital image correlation.

Physical modeling of spikes during the volcanic tsunami generation

Tsunamis generated by underwater volcanic eruptions are physically modeled in a large three-dimensional wave basin. A unique pneumatic volcanic tsunami generator (VTG) was deployed at the bottom of the wave basin to generate volcanic tsunamis with repeatable source parameters under controlled physical conditions. The volcanic Froude number defined with the VTG eruption velocity and water depth allows to physically model real-world events from slow mud-volcanoes to explosive eruptions. The VTG generates radial N-waves with prescribed vertical stroke motions in the wave basin. Initial three-dimensional water surfaces are reconstructed for the daylighting scenarios. Smooth dome shapes are observed during the submarine volcanic eruption and tsunami wave generation, which is followed by a trough formation at the source. A concentric vertical spike is observed for a specific range of water depths, which is generated by superposition of an inward propagating circular bore on top of the wave generator. The spike can be clustered with different ranges of a dimensionless VTG parameter. With an increasing dimensionless parameter, the spike pattern transitions through three distinct categories: smooth spike, rough spike, and splash spike. The dimensionless spike height and the dimensionless vertical velocity of the spike tip are dependent on the dimensionless VTG parameters. The maximum values of the dimensionless spike height and spike tip velocity are observed in the rough spike regime among all tested experimental scenarios.

A Brief Discussion of the Writing Characteristics in the Transition from Seal Script to Clerical Script

In this paper, we analyze the process of seal script clerical transformation through time, and summarize four characteristics of the process of seal script clerical transformation: turning curves into straightness; turning turns into folds, changing horizontal and vertical strokes, changing the direction of strokes, and the creation of " wave limb".

Analytical Formulae and Applications of Vertical Dynamic Responses for Railway Vehicles

To effectively improve the estimated level of railway vehicles’ vertical dynamic responses and provide a more suitable reference for the selection of its secondary suspension damping parameter, this paper has derived the root mean square values analytical formulae of the car body vertical acceleration, the secondary suspension vertical stroke, and the axle box vertical action force for railway vehicles under the random excitation of the track closer to the actual track characteristics. The correctness of the analytical formulae is verified by testing a real vehicle. Then, according to the analytical formulae derived, an analytical design method of the optimal damping ratio for the secondary suspension system is constructed based on the multi-objective programming and single-objective interval constraint analysis, which can be used to find the best trade-off for conflicting performance indices, such as ride comfort, running smoothness, and running safety, and the influences of the system parameters on the optimal damping ratio are analysed. This research can effectively characterize the vertical vibration response of railway vehicles and provide an effective reference for the initial design of the railway vehicle secondary suspension damping parameter.

Exact Expressions for Lightning Electromagnetic Fields: Application to the Rusck Field-to-Transmission Line Coupling Model

An exact analytical expression for the electric field of the return stroke as excited by a propagating step current source is derived in this paper. This expression could be advantageously used to evaluate the disturbances caused by lightning on overhead lines. There are three equivalent procedures to evaluate the voltages induced by lightning on power lines, namely, the Agrawal–Price–Gurbaxani model, the Taylor–Satterwhite–Harrison model, and the Rachidi model. In the case of a vertical return stroke channel, the coupling model developed by Rusck becomes identical to these three coupling models. Due to its simplicity, the Rusck model is frequently used by engineers to study the effects of lightning on power distribution and transmission lines. In order to reduce the time involved in the electromagnetic field calculation, the Rusck model is incorporated with an analytical expression for the electromagnetic fields of the return stroke excited by a propagating step current pulse. Our research work shows that the Rusck expression can be used to calculate the peak values of lightning induced voltages to an accuracy of about 10%. However, the use of this analytical expression to calculate the time derivatives of lightning induced voltages may result in errors as large as 50%. The derived expression in this paper can be used to correct for this inaccuracy. We also provide an exact expression for the electric field at any given point in space when the propagating current is an impulse function. This expression can be combined with the convolution integral to obtain the electric field corresponding to waveforms similar to measured return stroke currents.

الخط العربي نشأته و تطوره في العصر العثماني

The first calligraphy style developed during the end of the 7th century. Called Kufic, it was named for the city of Kufa in southern Iraq and was based on early 3rd- or 4th-century Arabic scripts. It was the first calligraphy used for the Quran, though it wasn't easy to use when writing long texts. It had angular letters with short vertical strokes and long horizontal strokes. Over time, many other calligraphic styles developed in the Muslim world. Some were used for specific purposes. Some were highly decorative. Others were easy to read, which made them appropriate for books and documents.The other script included Naskh or Naskhi, a script that developed in the 10th century that was easily readable with small balanced letters made from curving, fluid lines. Naskh eventually replaced Kufic as the script of choice for the Quran.

Razvoj i istraživanje pečata za sečenje valjanog materijala sa diferenciranom stegom

The work aims to develop and research a stamp with a differentiated clamp of a rolled stock for cutting by shear. A new stamp design with a differentiated clamp of the rolled stock has been developed. In terms of their technical and economic indicators, these stamps meet or exceed the modern samples of similar punch tools. At the same time, in the process of vertical cutting, a constant position of the rolled stock axis is ensured. The transmission of force to the clamp through the rolled stock is excluded. The stamp design ensures its sufficiently high rigidity and relatively small overall dimensions. Based on the analysis of the mathematical model of a stamp with a differentiated clamp, the effective angles of force transmission to the clamp and the cutting of the rolled stock between the stamp parts have been established. The resulting model was used to optimize the angles of force transfer to the clamp, and the cutting rolled stock, respecting the force from the side of a buffer and the minimum required press force. At the same time, the vertical stroke of the moving parts is reduced, the overall dimensions of the stamp are decreased, and the buffer also has a minimum size. To reduce the required force of the press, it is necessary to reduce the value of a frictional slipping coefficient by using antifriction materials on contact surfaces and ensuring good lubrication conditions. The results of the conducted experiments confirm the adequacy of the mathematical model. The value of the required force on the press slide available from experiments is slightly higher than the values obtained by the developed analytical model. The results of the stamp implementation show that: the stamps are efficient and reliable in exploitation; the quality of the cutoff workpieces corresponds to the quality indicators of the workpieces cut on similar modern equipment.

Association between cervical abrasion, oral hygiene practices and buccolingual dimension of tooth surfaces: A cross-sectional study

Background:Cervical abrasion is a multifactorial process due to the use of abrasive dentifrices along with improper brushing patterns. An extensive lesion may cause loss of structural integrity of tooth and esthetically unacceptable. The purpose of the study was to assess the prevalence of cervical abrasion with age, gender, and oral hygiene practices among workers in a spinning mill, Kerala. The study also aimed to identify the buccolingual measurements of each abraded tooth using the Community Abrasion Index of Treatment Needs (CAITN) probe.Materials and Methods:A cross-sectional study where 366 subjects (257 males and 109 females) above 20 years of age were selected using a random sampling technique. Data was collected from the assessment form comprising demographic data and oral hygiene practices of the subjects. Clinical examination for abrasion and buccolingual measurements of abraded tooth recorded using CAITN probe. The statistical analysis was done using SPSS 26.0. for calculating descriptive statistics, Chi-square test, and binary logistic regression.Results:The overall prevalence of abrasion was 37.2% and 97.7% of subjects with abrasion had sensitive teeth and were statistically significant. Age, gender (males) and combined horizontal and vertical method of brushing technique were strongly associated with the cervical lesion (P < 0.001). Binary logistic regression analysis showed that age group, gender, combined horizontal and vertical method of brushing, and presence of sensitive tooth was associated with the abrasion.Conclusion:It is concluded that the severity of the abrasion is an age-related phenomenon associated with combined horizontal and vertical strokes of brushing and is common among the male population. Dentinal hypersensitivity is also more prevalent with cervical abrasion. The novel CAITN probe can be used as an effective tool to assess the cervical abrasion and its treatment needs.

Aerodynamic investigation on shifted-back vertical stroke plane of flapping wing in forward flight

In order to properly understand aerodynamic characteristics in a flapping wing in forward flight, additional aerodynamic parameters apart from those in hover—an inclined stroke plane, a shifted-back stroke plane, and an advance ratio—must be comprehended in advance. This paper deals with the aerodynamic characteristics of a flapping wing in a shifted-back vertical stroke plane in freestream. A scaled-up robotic arm in a water towing tank was used to collect time-varying forces of a model flapping wing, and a semi-empirical quasi-steady aerodynamic model, which can decompose the forces into steady, quasi-steady, and unsteady components, was used to estimate the forces of the model flapping wing. It was found that the shifted-back stroke plane left a part of freestream as a non-perpendicular component, giving rise to a time-course change in the aerodynamic forces during the stroke. This also brought out two quasi-steady components (rotational and added-mass forces) apart from the steady one, even the wing moved with a constant stroke velocity. The aerodynamic model underestimated the actual forces of the model flapping wing even it can cover the increasingly distributed angle of attack of the vertical stroke plane with a blade element theory. The locations of the centers of pressure suggested a greater pressure gradient and an elongated leading-edge vortex along a wingspan than that of the estimation, which may explain the higher actual force in forward flight.

Model sub-ionospheric ELF – VLF pulses

The propagation of natural wide-band pulsed radio signals in the spherical Earth – ionosphere cavity is numerically simulated. The frequency band considered is 1–10,000 Hz. We address the TM waves originated from a vertical lightning stroke of the Bruce and Golde, Williams, or Jones model. Major data are based on the Williams’ lightning model. The upper boundary of the cavity is horizontally stratified and the conductivity of each stratum depends on its altitude. We apply several models of vertical conductivity profile, and all of them adequately describe the global electromagnetic (Schumann) resonance. The electromagnetic fields are expanded into a series of normal waves (modes). The frequency dependence of the complex propagation constant of each mode is found by using the full wave solution in the form of Riccati equation. The roots of this equation are found by iterations. Various source–observer distances are used in the waveguides with different height conductivity profiles. The Fourier transform of complex spectra provides the time domain realizations of the wide-band pulsed signals. The results of different model profiles are compared and their correspondence to the known observational data is demonstrated. Computations show that the model pulses similar to either tweek or to slow tail atmospherics. They acquire the form of slow tail atmospherics when the conventional night or day conductivity profiles are used. In this case, a train of VLF oscillations precedes a typical Q-burst. The delay of Q-burst from the VLF precursor grows in proportion to the source – observer distance. The tweek atmospheric emerges combined with the Q-burst when the mesosphere conductivity profile has a section of rapid conductivity increase by 4–5 orders of magnitude in the altitude interval of a few kilometers around 90 km.

Impact of vertical succussion strokes vs. vortex potentization on droplet evaporation patterns obtained from Iscador Quercus 3x potency

Background Pharmaceutical processing of homeopathic potencies consists of consecutively performed dilution and succussion steps. While the dilution steps are well defined, the manner of performing the succussions varies broadly among potency producers. Aims To study the impact of potentization consisting in the performance of vertical succussion strokes vs. vortex-like flow on droplet evaporation patterns obtained from Iscador Quercus 3x (ISCQ 3x). Methodology ISCQ 3x was prepared in three following variants: potentized for 2.5 min (i) by application of mechanically performed vertical strokes, or (ii) hand-made vortex-like flows; or (iii) only diluted and not-succussed control. Droplet evaporation method was performed as described in (1); in short: droplets of the three ISCQ 3x variants were evaporated on microscope slides (56 droplets of each variant distributed on four slides were evaporated in one experimental repetition). The experimental setup robustness was monitored by means of positive systematic control experiments, where on all 12 slides droplets of the ISCQ 3x variant potentized by the application of strokes were evaporated. The experiments were repeated five times. The resulting droplet residues were photographed in magnification 100x; the patterns were analyzed by means of the Image J software for their grey level distribution and textural and fractal parameters. Results and discussion All three ISCQ 3x variants could be significantly differentiated regarding some textural and fractal parameters; most parameters differentiated between the variant potentized by means of vertical strokes and the control and vortex-potentized variants. Fractal and textural parameters ranked the samples differently. Control experiments showed a reasonable experimental setup robustness. Conclusion The potentization by performing mechanical strokes vs. hand-made vortex-like flows influenced some phenomenological aspects of droplet evaporation patterns. This might indicate that some changes occurred on substance level as consequence of the mechanical impact. Further studies are necessary in this field.

Rule-based perspective rectification for Chinese text in natural scene images

Recognizing text with large perspective deformation is challenging, especially when the orientation of the text is arbitrary. A rule-based method is proposed in this paper to recover the fronto-parallel image for Chinese text in natural scenes. It relies on the fact that there are many horizontal and vertical strokes in Chinese text and they are accurately or approximately perpendicular to each other in non-italic type. A homography is utilized to describe the relationship between the scene text and its image. Horizontal and vertical strokes are extracted and selected to construct perspective quadrilaterals and the expected rectangles for calculating the homography. Experiments show that the proposed method could rectify the perspective deformation of Chinese text in any orientation effectively and it outperforms the state-of-the-art perspective rectification method based on vanishing point detection.

A-Comparative evaluation of root surface roughness after the use of gracey curettes and piezo-surgery-driven root planning tip on root surface: An in-vitro study

Introduction and Objective: The ideal instrument for initial periodontal therapy should enable the removal of all extraneous substances from the root surfaces without any iatrogenic effects. Because of that the objective of this study is to analyses and to compare the root surface roughness after using Gracey curettes, and a piezosurgery driven root planning tip, using SEM scanning electron microscopy. Aim: The aim of this study was to compare root surface characteristics following root planing with hand- instrument and piezo surgery driven root planning tip instruments. Material and Methods: A2 mm, 2 mm interproximal root area of 20 teeth (n = 40 surfaces) was evaluated by scanning electron microscopy (·50 to ·1000 magnification). Teeth were randomly assigned to the following two groups: Gracey curettes with 20 vertical strokes; and a piezosurgery ultrasonic scaler in mode ROOT with a power of two. In each case the evaluation for root surface roughness before and after root planing and surface roughness using the Index ‘t’ test ‘p’ value was measured. Result: SEM microscopy reviled, the mean preoperative surface roughness was 3.587 with a standard deviation of 0. 466. The samples were root planed by curettes (Gracey) and the mean post-operative surface roughness was 2.364 with a standard deviation of 0.345. The results show that there was average surface roughness reduction in group A, following root planing by curette instrument, with ‘t’ value of 6.670 and ‘p’ value of =0.0000129. The ‘p’ value was more than 0 .01. Conclusions:Out of the two instruments, namely Gracey curette, and piezosurgery driven root planning tip, were effective in mechanical debridement of the root surface. The results favored the use of piezo surgery root planning tip to achieve a smooth, clean root surface; however, the use of piezo surgery instrument tip was more time consuming, which might limit its use in clinical practice. Further clinical studies are needed. Ke

The Energy, Momentum, and Peak Power Radiated by Negative Lightning Return Strokes

Electromagnetic radiation fields generated by return strokes transport both energy and momentum from the return stroke to outer space. The momentum transported by the radiation field has only a vertical or z component due to azimuthal symmetry (cylindrical symmetry) associated with a vertical return stroke. In this paper, the energy, momentum, and peak power radiated by return strokes as a function of the return stroke current, return stroke speed, and the zero-crossing time of the radiation fields are studied. The results obtained by numerical simulations for the energy, vertical momentum, and the peak power radiated by lightning return strokes (all parameters normalized by dividing them by the square of the radiation field peak at 100 km) are the following: A typical first return stroke generating a radiation field having a 50 μs zero-crossing time will dissipate field normalized energy of about (1.7–2.5) × 103 J/(V/m)2 and field-normalized vertical momentum of approximately (2.3–3.1) × 10−6 Kg m/s/(V/m)2. A radiation field with a zero-crossing time of 70 μs will dissipate about (2.6–3.4) × 103 J/(V/m)2 in field-normalized energy and (3.2–4.3) × 10−6 Kg m/s/(V/m)2 in field-normalized vertical momentum. The results show that, for a given peak radiation field, the radiated energy and momentum increase with increasing zero-crossing time of the radiation field. The normalized peak power generated by a first return stroke radiation field is about 1.2 × 108 W/(V/m)2 and the peak power is generated within about 5–6 μs from the beginning of the return stroke. Conversely, a typical subsequent return stroke generating a radiation field having a 40 μs zero-crossing time will dissipate field-normalized energy of about (6–9) × 102 J/(V/m)2 and field-normalized vertical momentum of approximately (7.5–11) × 10−7 Kg m/s/(V/m)2. The field-normalized peak power generated by a subsequent return stroke radiation field is about 1.26 × 108 W/(V/m)2 and the peak power is generated within about 0.7–0.8 μs from the beginning of the return stroke. In addition to these parameters, the possible upper bounds for the energy and momentum radiated by return strokes are also presented.

Use of mandibular guidance prosthesis with the buccal guide flange in hemimandibulectomy patient

Hemi-mandibulectomy causes the remaining segment of the mandible to deviate towards the resected side, this is due to the loss of soft and hard tissues on the resected side. Immediate surgical reconstruction will improve the prognosis of the rehabilitation procedures. This case report presents a patient with hemimandibulectomy defect on the left side was discussed. The patient was able to bring the mandible in proper occlusal relationship with the maxilla but was not able to maintain it for masticatory purposes. Therefore he was rehabilitated by a mandibular guide flange. Rehabilitation of the defect by mandibular guide flange will help in maintaining a proper occlusal relationship of the mandible for improved vertical stroke and chewing efficacy. Keywords: Hemimandibulectomy, Mandibular guide flange, Mandibular resection, Prosthesis, Reconstruction.