Sequence Of Strokes Research Articles

Analysis of serve and first shot sequences in U-12 and U-14 tennis players

Stroke sequence analysis in junior tennis helps identify patterns of play and could help improve the performance of players in formative stages. The purpose of the study was to analyze the sequences of serve and third shot (serve +1) in elite youth tennis, in the men's U-12 and U-14 categories. The direction of the serve, the position of the players when executing the third stroke and the direction in which they send the ball were evaluated. It was found that U-12 players have less effectiveness in second serves. The location of the shots varies depending on the category and the situation of the game. The importance of training service sequences and first shots to improve performance in junior tennis is highlighted.

ViSTec: Video Modeling for Sports Technique Recognition and Tactical Analysis

The immense popularity of racket sports has fueled substantial demand in tactical analysis with broadcast videos. However, existing manual methods require laborious annotation, and recent attempts leveraging video perception models are limited to low-level annotations like ball trajectories, overlooking tactics that necessitate an understanding of stroke techniques. State-of-the-art action segmentation models also struggle with technique recognition due to frequent occlusions and motion-induced blurring in racket sports videos. To address these challenges, We propose ViSTec, a Video-based Sports Technique recognition model inspired by human cognition that synergizes sparse visual data with rich contextual insights. Our approach integrates a graph to explicitly model strategic knowledge in stroke sequences and enhance technique recognition with contextual inductive bias. A two-stage action perception model is jointly trained to align with the contextual knowledge in the graph. Experiments demonstrate that our method outperforms existing models by a significant margin. Case studies with experts from the Chinese national table tennis team validate our model's capacity to automate analysis for technical actions and tactical strategies. More details are available at: https://ViSTec2024.github.io/.

Transformer-based stroke relation encoding for online handwriting and sketches

Stroke classification for online handwriting and sketches, aimed at grouping strokes into different semantic categories, has drawn considerable attention due to its wide applications. This task is challenging since individual strokes look similar and are easily confused with each other. The key is to consider both the individual strokes and the contextual information jointly for making prediction. Previous methods are insufficient in modeling and exploiting complex contextual information of strokes. To overcome this limitation, we propose a Transformer-based model for Online Handwriting and Sketches (T-OHS), with novel relation encoding schemes to take advantage of temporal and spatial information in stroke sequence. Particularly, we introduce a coarse-to-fine hierarchical encoding approach based on the polar coordinate system for precisely modeling spatial relations between strokes. Experiments on three types of handwriting data, including online handwritten documents, diagrams, and sketches, demonstrate that our method is universal and provides state-of-the-art performance.

Polarity Asymmetries in Rocket‐Triggered Lightning

AbstractThe dissonant development of positive and negative lightning leaders is a central question in atmospheric electricity. It is also the likely root cause of other reported asymmetries between positive and negative lightning flashes, including the ones regarding: stroke multiplicity, recoil activity, leader velocities, and emission of energetic radiation. In an effort to contrast lightning leaders of different polarities, we highlight the staggering differences between two rocket‐triggered lightning flashes. The flash beginning with upward positive leaders exhibits an initial continuous current stage followed by multiple sequences of dart leaders and return strokes. On the other, in its opposite‐polarity counterpart, the upward development of negative leaders is by itself the entire flash. As a result, the flash with negative leaders is faster, briefer, transfers less charge to the ground, has lower currents, and smaller spatial extent. We conclude by presenting a discussion on the three fundamental leader propagation modes.

Docubox Dragon

ABSTRACT Strokes are the sequence, in which writing strokes are placed on the paper. To analyze whether documents such as wills, letters, contracts, and bank books are genuine or not. The present study of Docubox Dragon was used for observation and examination of the exemplar by handling and operator convenience to fulfill the increasing demands for a quick and efficient investigation of travel documents, banknotes, and security printed matter, not only in the field but also in the laboratory. The sequences of strokes in the exemplars were primarily observed using stereomicroscope and the forged exemplars were further examined using Docubox Dragon. It was observed that stereomicroscope was used for preliminary examination whereas through Docubox Dragon detailed and evident results were obtained using various light sources and filters.

Implementation of a Fusion Classification Model for Efficient Pen-Holding Posture Detection

Pen-holding postures (PHPs) can significantly affect the speed and quality of writing, and incorrect postures can lead to health problems. This paper presents and experimentally implements a methodology for quickly recognizing and correcting poor writing postures using a digital dot matrix pen. The method first extracts basic handwriting information, including page number, handwriting coordinates, movement trajectory, pen tip pressure, stroke sequence, and pen handling time. This information is then used to generate writing features that are fed into our proposed fusion classification model, which combines a simple parameter-free attention module for convolutional neural networks (CNNs) called NetworkSimAM, CNNs, and an extension of the well-known long short-term memory (LTSM) called Mogrifier LSTM or MLSTM. Finally, the method ends with a classification step (Softmax) to recognize the type of PHP. The implemented method achieves significant results through receiver operating characteristic (ROC) curves and loss functions, including a recognition accuracy of 72%, which is, for example, higher than that of the single-stroke model (i.e., TabNet incorporating SimAM). The obtained results show that a promising solution is provided for accurate and efficient PHP recognition and has the potential to improve writing speed and quality while reducing health problems induced by incorrect postures.

An omnidirectional approach to touch-based continuous authentication

This paper focuses on how touch interactions on smartphones can provide a continuous user authentication service through behaviour captured by a touchscreen. While efforts are made to advance touch-based behavioural authentication, researchers often focus on gathering data, tuning classifiers, and enhancing performance by evaluating touch interactions in a sequence rather than independently. However, such systems only work by providing data representing distinct behavioural traits. The typical approach separates behaviour into touch directions and creates multiple user profiles. This work presents an omnidirectional approach which outperforms the traditional method independent of the touch direction - depending on optimal behavioural features and a balanced training set. Thus, we evaluate five behavioural feature sets using the conventional approach against our direction-agnostic method while testing several classifiers, including an Extra-Tree and Gradient Boosting Classifier, which is often overlooked. Results show that in comparison with the traditional, an Extra-Trees classifier and the proposed approach are superior when combining strokes. However, the performance depends on the applied feature set. We find that the TouchAlytics feature set outperforms others when using our approach when combining three or more strokes. Finally, we highlight the importance of reporting the mean area under the curve and equal error rate for single-stroke performance and varying the sequence of strokes separately.

Examination of sequence of strokes by optical method

The sequence in which the writing strokes have been executed on a paper is known as sequence of strokes. Examining the sequence of strokes can help in determining the relative age of ink which is required in various cases related to document examination including examination of wills, cheques, statements, receipts, agreements etc. The current study is focused on examining the sequence of strokes executed with a ball point pen. Video Spectral Comparator 8000 (VSC8000) has been used for the current examination. The test samples and the actual questioned documents were examined under VSC8000. It was observed that depending on the pressure through which the strokes have been executed, identification of sequence of two or more intersecting writing strokes was possible.

Sketch-Segformer: Transformer-Based Segmentation for Figurative and Creative Sketches.

Sketch is a well-researched topic in the vision community by now. Sketch semantic segmentation in particular, serves as a fundamental step towards finer-level sketch interpretation. Recent works use various means of extracting discriminative features from sketches and have achieved considerable improvements on segmentation accuracy. Common approaches for this include attending to the sketch-image as a whole, its stroke-level representation or the sequence information embedded in it. However, they mostly focus on only a part of such multi-facet information. In this paper, we for the first time demonstrate that there is complementary information to be explored across all these three facets of sketch data, and that segmentation performance consequently benefits as a result of such exploration of sketch-specific information. Specifically, we propose the Sketch-Segformer, a transformer-based framework for sketch semantic segmentation that inherently treats sketches as stroke sequences other than pixel-maps. In particular, Sketch-Segformer introduces two types of self-attention modules having similar structures that work with different receptive fields (i.e., whole sketch or individual stroke). The order embedding is then further synergized with spatial embeddings learned from the entire sketch as well as localized stroke-level information. Extensive experiments show that our sketch-specific design is not only able to obtain state-of-the-art performance on traditional figurative sketches (such as SPG, SketchSeg-150K datasets), but also performs well on creative sketches that do not conform to conventional object semantics (CreativeSketch dataset) thanks for our usage of multi-facet sketch information. Ablation studies, visualizations, and invariance tests further justifies our design choice and the effectiveness of Sketch-Segformer. Codes are available at https://github.com/PRIS-CV/Sketch-SF.

Characteristics of dart leader and attempted leader in a triggered lightning

• Intuitive high-speed camera images exhibit clear attempted leaders and dart leaders, along with an analysis of development features and electric field characteristics, which makes up for the deficiency that other observation methods are easy to confuse the leader types. • A dart leader in a dart leader-return stroke sequence is considered similar to attempted leaders based on two-dimensional speed, light variation along the channel, and time intervals. • Dart leaders and attempted leaders are thought to be able to convert to each other which is related to the carried amount of charge. Attempted leaders (ALs) are a kind of downward leaders which unsuccessfully initiate a following return stroke in natural cloud-to-ground lightning and artificially triggered lightning. The relationship between ALs and dart leaders (DLs) is a topic of great concern. Some reported cases of ALs were difficult to identify. A negative artificially triggered lightning case was reported, including five dart leader-return stroke (DL-RS) sequences and two ALs in intuitively visual images. In this case, the two-dimensional (2D) speed of two ALs had an average of 0.46 × 10 7 m/s. The sum and maximum brightness of two ALs both increased initially and then slid down. The maximum brightness either descended from the beginning or remained for a while and then went down. Compared with DLs, the upper part of AL channels became obviously faint. Interestingly, the DL in the 4th DL-RS sequence performed like ALs. On the contrary, AL1 was similar to DLs in the early stage of development. DLs and ALs are considered to convert to each other. DLs convert to ALs when there is not enough negative charge for carrying from the cloud to the leader channel. Once the carrying charge is abundant, ALs convert to DLs as a result of initiating return strokes.

КОЛЕБАНИЯ КРУГОВОЙ ТРЕХСЛОЙНОЙ СТУПЕНЧАТОЙ ПЛАСТИНЫ ПРИ УДАРНОМ ПЕРИОДИЧЕСКОМ ВОЗДЕЙСТВИИ

Forced oscillations of a three-layer circular plate with step-variable thickness of the outer layers are analyzed. The deformation of the plate is described with the zig-zag theory. In thin border layers of plate Kirchhoff’s hypotheses are valid. In a relatively thick in thickness medium layer Timoshenko’s hypothesis on the straightness and incompressibility of the deformed normal is fulfilled. The equations of motion are derived from Hamilton’s variational principle. A special case of exposure is considered: periodic sequence of strokes with constant intensity. The problem is reduced to finding three required functions in each section, deflection, shear and radial displacement of the median plane of the filler. The solution is presented as a sum of quasi-static and dynamic components of the unknown displacements. Numerical results of the obtained solution are presented. The influence of the impact stress on the oscillatory character is analyzed.

Teaching Method Design of Tennis Baseline Stroke Technique Relying on Neural Network Learning Algorithm

Tennis is an important sporting event. In China, the number of people who study and participate in tennis can be said to be quite large, but there are not many people who insist on playing tennis in the end. Some coaches and tennis groups have come up with a number of different teaching styles in order to keep tennis players going. Its main features are as follows: To cultivate students’ interest in learning, the sequence of strokes in tennis is used for teaching. Although tennis has no special requirements for the physical condition of the athlete, tennis is a relatively difficult sport to master. What is lacking at present is more effective and simpler teaching methods, so training should be carried out in a targeted manner in the tennis baseline stroke technique. In order to make the tennis baseline stroke teaching more intuitive and easy to learn, this paper applies the neural network learning algorithm to the research and analysis of the tennis baseline stroke technique and proposes the core technology of the tennis baseline stroke technique. On this basis, the key techniques of tennis baseline stroke technique are discussed. Based on this, a basic model based on deep convolutional neural network is proposed. The experimental results show that the forehand scores of the three throwing methods in the experimental group are 6.47 and 7.28, respectively, which is better than the control group. The three throwing methods are self-throwing, close throwing, and long throwing. It shows that the teaching method in this paper can greatly improve the students’ tennis baseline hitting skills.

PENGGUNAAN APLIKASI LINE-DICTIONARY UNTUK MENINGKATKAN KEMAMPUAN SISWA DALAM MENGUASAI URUTAN PENULISAN GORESAN HURUF MANDARIN

Chinese is one of the most popular languages in the world. Chinese language is famous for its letters which are often called Hanzi. In learning Chinese, apart from how to pronounce it, you also learn how to write it. Therefore, the author uses the Line-Dictionary application to help students learn Hanzi, especially how to write it well. The purpose of the study was to find out how the Line-Dictionary app uses in teaching stroke sequences to students, the effects of using the LineDictionary app in studying stroke sequences, and how students respond to the use of the Line-Dictionary app. Authors use quantitative methods through written tests to collect data, as well as qualitative methods by distributing questionnaires to determine students' responses to the use of the Line-Dictionary app. Based on the resultsof the data analysis, showed that the error rate of writing mandarin letters in students was reduced by 24%. This can be seen in the average pre-test error rate of 68%, while in post-test by 44%. The student's response to the use of the Line-Dictionary app in studying the stroke sequence of Mandarin letters was excellent.

Free2CAD

CAD modeling, despite being the industry-standard, remains restricted to usage by skilled practitioners due to two key barriers. First, the user must be able to mentally parse a final shape into a valid sequence of supported CAD commands; and second, the user must be sufficiently conversant with CAD software packages to be able to execute the corresponding CAD commands. As a step towards addressing both these challenges, we present Free2CAD wherein the user can simply sketch the final shape and our system parses the input strokes into a sequence of commands expressed in a simplified CAD language. When executed, these commands reproduce the sketched object. Technically, we cast sketch-based CAD modeling as a sequence-to-sequence translation problem, for which we leverage the powerful Transformers neural network architecture. Given the sequence of pen strokes as input, we introduce the new task of grouping strokes that correspond to individual CAD operations. We combine stroke grouping with geometric fitting of the operation parameters, such that intermediate groups are geometrically corrected before being reused, as context, for subsequent steps in the sequence inference. Although trained on synthetically-generated data, we demonstrate that Free2CAD generalizes to sketches created from real-world CAD models as well as to sketches drawn by novice users. Code and data are at https://github.com/Enigma-li/Free2CAD.

Working memory for sequences of verbal stimuli: The impact of stimulus type and presentation mode

Previous studies have shown that the use of a static or dynamic mode of presenting a non-verbal series (a sequence of strokes that make up a broken line, like an open polygonal chain), as well as varying the retention time of this information in working memory, can affect the accuracy and temporal characteristics of the sequence reproduction. The present study aims to investigate the effects of the presentation mode and the retention time on the memorization and reproduction of a sequence of verbal items. For this purpose, adult subjects were asked to memorize and reproduce sequences of letters and digits which were visually presented either simultaneously (statically) or sequentially (dynamically). The response delay time (500 or 3000 ms) and the length of the sequences (from 3 to 5 elements) were varied. As dependent variables, the accuracy of stimulus reproduction and the reaction time were computed. It turned out that the memorization of verbal sequences depended on the presentation mode (static or dynamic), and the static mode seemed to lead to a more complete representation of the memorized sequences. It was shown that the sequences of letters and digits are memorized differently. It is assumed that, unlike sequences of letters, sequences of digits are stored in working memory not as a sequence of individual elements but as shorter sequences of larger chunks or even as a whole. In contrast to the situation of reproducing a broken line, in the case of reproducing verbal sequences, no significant change in the reaction time was revealed when the time of information retention in working memory was varied

Optimizing low-Reynolds-number predation via optimal control and reinforcement learning

We seek the best stroke sequences of a finite-size swimming predator chasing a non-motile point or finite-size prey at low Reynolds number. We use optimal control to seek the globally optimal solutions for the former and reinforcement learning (RL) for general situations. The predator is represented by a squirmer model that can translate forward and laterally, rotate and generate a stresslet flow. We identify the predator's best squirming sequences to achieve the time-optimal (TO) and efficiency-optimal (EO) predation. For a point prey, the TO squirmer executing translational motions favours a two-fold$L$-shaped trajectory that enables it to exploit the disturbance flow for accelerated predation; using a stresslet mode expedites significantly the EO predation, allowing the predator to catch the prey faster yet with lower energy consumption and higher predatory efficiency; the predator can harness its stresslet disturbance flow to suck the prey towards itself; compared to a translating predator, its compeer combining translation and rotation is less time-efficient, and the latter occasionally achieves the TO predation via retreating in order to advance. We also adopt RL to reproduce the globally optimal predatory strategy of chasing a point prey, qualitatively capturing the crucial two-fold attribute of a TO path. Using a numerically emulated RL environment, we explore the dependence of the optimal predatory path on the size of prey. Our results might provide useful information that help in the design of synthetic microswimmers such asin vivomedical microrobots capable of capturing and approaching objects in viscous flows.

Experimental Measurement and Markov Chain Modelling of Stroke Order Intuition

As a feature of Chinese characters, stroke order plays an important role in Chinese character education, Chinese character recognition and handwriting identification. However, in recent years, the research on stroke order is limited to elaboration and supplementation of existing stroke order and stroke order rules. There is no special research that focuses on the principle behind stroke order. To quantify the internal regularity of stroke order, we start with the stroke order intuition in the actual writing. Because stroke order has individual differences, we select a group of students with small differences as testers. In this paper, we design an algorithm to generate random strokes and collect the timing data during testers copying strokes. After pre-processing the collected data, a Markov chain is introduced to model stroke order intuition, which can divide the stroke sequences into three states. And then we classify them into three situations according to the stroke distribution. Next, we compare them with some well-known stroke order rules. The results show that the probability distribution of strokes in different situations is not always consistent with the empirical rules, as well as the relations between them.

The Effect of Visual Mnemonics and the Presentation of Character Pairs on Learning Visually Similar Characters for Chinese-As-Second-Language Learners.

This study investigates the effects of visual mnemonics and the methods of presenting learning materials on learning visually similar characters for Chinese-as-second-language (CSL) learners. In supporting CSL learners to build robust orthographic representations in Chinese, addressing the challenges of visual similarity of characters (e.g., 理 and 埋) is an important issue. Based on prior research on perceptual learning, we tested three strategies that differ in the extent to which they promote interrelated attention to the form and meaning of characters: (1) Stroke Sequence, a form-emphasis strategy, (2) Key-images, a form + meaning strategy utilizing visual code, (3) Pithy Formulas with Key-images, a form + meaning strategy combining visual and verbal codes. A pretest–posttest equivalent-group design was adopted. The independent variables were the learning strategy, the method of presenting character pairs (visually similar vs. dissimilar), and testing time. The dependent variables were learners’ proportions of accurate responses to reading and writing Chinese characters through a posttest (immediately performed after learning) and a delayed posttest (1 week after learning); a learner experience survey was also administered to investigate learners’ opinions on each strategy. Sixty-six non-beginning learners of Chinese participated; they were randomly assigned to one of the two groups in which participants learned ten characters via the three strategies, respectively, differing between whether the characters were presented in similar pairs or dissimilar pairs. Data were analyzed via three-way ANCOVAs. The Pithy Formulas with Key-images and the Key-images generally yielded higher writing accuracy than Stroke Sequence immediately after learning. Notably, the advantage of the Pithy Formulas with Key-images (verbal and visual) over the Key-images (visual) on writing was specific to the participants that learned with visually similar pairs rather than those that learned with dissimilar pairs. All strategies were effective for reading, yet learners’ experience ratings favored the two form + meaning strategies over the strategy that focused primarily on form. Suggestions for future research and pedagogical implications on learning visually similar characters were offered.

The initial radius of lightning return stroke channel and its relation with discharge intensity

The initial radius of the return stroke is one of the important parameters reflecting lightning discharge intensity. Based on spectral diagnosis and electrostatic approximation of the vertically descending leader model, the lightning channel temperature, line charge density, and electrostatic energy of seven dart leader–return stroke sequences were estimated. Finally, the initial radii of the return strokes were obtained. We analyzed the relationship between the initial radii and the corresponding discharge parameters. The initial radius is found to have a good linear correlation with each of the following quantities: the line charge density of the dart leader, the total intensity of ionic lines in the spectra, and the optical radius. It is also inversely proportional to the leader duration. These correlations confirm that the initial radius is closely related to discharge intensity, and that the charge stored in the leader channel directly determines the initial radius and discharge intensity of the return stroke.

Multichannel pulse high-current driver of magnetic actuator

Magnetic linear actuators have a wide range of applications. Their main advantage is the ease with which they can be controlled by regulating the current. However, high electrical power is required for obtaining a large continuous force, acceleration, and stroke from a device with small dimensions. In this study, we developed a comprehensive open-source system consisting of simple movable iron magnetic actuators, a four-channel controller, and dedicated software. The graphical user interface facilitates the designing of the sequence of piston strokes, including the start time, duration of movement, and force for each stroke separately. The controller generates a high current of pulses, which allows achieving a high force, acceleration, and stroke from small-sized coils while maintaining a relatively safe voltage. The system was originally designed as a reagent syringe driver to control the rapid mixing process used for studying the kinetics of enzymatic reactions. However, this driver may also be applied in various other scientific as well as nonscientific applications.