Comparison of Conventional Double-Helical and Curvilinear Cylindrical Gear Drives in Terms of Transmission Errors and Stress

Curvilinear cylindrical gear drives are similar to double-helical gear drives as they can avoid the axial thrust during the meshing process. Whether curvilinear cylindrical gear drives are better than double-helical gear drives is a problem to be solved. In this paper, a new gear-generating method for curvilinear gears is proposed based on the theory of gearing. Two different single-side face-milling cutters are used for the generation of concave and convex tooth surfaces, respectively. The curvilinear gear sets being generated have line contact in the meshing process. For the sake of comparison, the double-helical gear sets involved in the comparison study are also a kind of gear sets with line contact. This article includes the following: (1) Comparison of transmission errors and stresses of two types of gear sets with the same contact ratio; (2) Derivation of tooth surface equations, transmission error analysis, and finite element analysis; (3) Four numerical examples which show the advantages and disadvantages of curvilinear cylindrical gear drives

Design, Meshing Characteristics and Stress Analysis of Cylindrical Gears with Curvilinear Tooth Profile

Curvilinear tooth gears are commonly produced on a face milling cutter and a hob cutter. However, this paper proposes a kind of curvilinear tooth gear which is processed by a parallel linkage with a single blade cutter. For the purpose of identifying the meshing and contact characteristics of curvilinear tooth gears, the paper covers the following: (i) equations of tooth surfaces are deduced from the meshing theory, and a parameterized geometric model is developed by applying computer graphics; (ii) an investigation into meshing characteristics for an ideal assembly condition is performed, and an instantaneous contact curve is obtained from the developed tooth contact algorithm; (iii) based on the application of the finite element method, the evolution of contact and bending stresses during the cycle of meshing and between different arc radii of the curvilinear tooth is illustrated by numerical examples. The result shows that curvilinear tooth gear drives possess a higher contact ratio, severe contact stresses on the top edge of the tooth, and lower contact and bending stresses between appropriate arc radii, hence they may replace spur gears in the future

Effect of correlated oxide electrodes on disorder pinning and thermal roughening of ferroelectric domain walls in epitaxial PbZr\u3csub\u3e0.2\u3c/sub\u3eTi\u3csub\u3e0.8\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e thin films

We report the competing effects of disorder pinning and thermal roughening on ferroelectric domain walls as a function of temperature in epitaxial PbZr0.2Ti0.8O3 thin films deposited on (001) SrTiO3 substrates buffered by three types of correlated oxide electrodes, La0.67Sr0.33MnO3, LaNiO3, and SrIrO3. Piezoresponse force microscopy studies show that the 50-nm PbZr0.2Ti0.8O3 films are uniformly polarized in the as-grown states, with the patterned domain structures persisting above 700 °C. For all three types of films, the domain wall roughness is dominated by two-dimensional (2D) random bond disorder at room temperature, and transitions to 1D thermal roughening upon heating. The roughness exponent ζ increases progressively from 0.3 to 0.5 within a temperature window that depends on the bottom conducting oxide type, from which we extracted the distribution of disorder pinning energy. We discuss the possible origins of the disorder pinning and the effect of the correlated oxide electrodes on the energy landscape of DW motion

Design of an Automatic Defect Identification Method Based ECPT for Pneumatic Pressure Equipment

In this paper, in order to achieve automatic defect identification for pneumatic pressure equipment, an improved feature extraction algorithm eddy current pulsed thermography (ECPT) is presented. The presented feature extraction algorithm contains four elements: data block selection; variable step search; relation value classification; and between-class distance decision function. The data block selection and variable step search are integrated to decrease the redundant computations in the automatic defect identification. The goal of the classification and between-class distance calculation is to select the typical features of thermographic sequence. The main image information can be extracted by the method precisely and efficiently. Experimental results are provided to demonstrate the capabilities and benefits (i.e., reducing the processing time) of the proposed algorithm in automatic defect identification

DAGKT: Difficulty and Attempts Boosted Graph-based Knowledge Tracing

In the field of intelligent education, knowledge tracing (KT) has attracted increasing attention, which estimates and traces students' mastery of knowledge concepts to provide high-quality education. In KT, there are natural graph structures among questions and knowledge concepts so some studies explored the application of graph neural networks (GNNs) to improve the performance of the KT models which have not used graph structure. However, most of them ignored both the questions' difficulties and students' attempts at questions. Actually, questions with the same knowledge concepts have different difficulties, and students' different attempts also represent different knowledge mastery. In this paper, we propose a difficulty and attempts boosted graph-based KT (DAGKT), using rich information from students' records. Moreover, a novel method is designed to establish the question similarity relationship inspired by the F1 score. Extensive experiments on three real-world datasets demonstrate the effectiveness of the proposed DAGKT.Comment: 12 pages, 3figures, conference:ICONI

DRONES FOR IMPROVING TRAFFIC SAFETY IN RITI COMMUNITIES IN WASHINGTON STATE

Transportation and traffic safety is a primary concern in Rural, Isolated, Tribal, or Indigenous (RITI) communities in Washington (WA) State. Parallel to this, while emerging technologies (e.g., connected/autonomous vehicles, drones) have been developed and tested in addressing traffic safety issues, they are often not widely shared in RITI communities for various reasons. Compared with other technological advances, drone technologies have been rapidly improved and can be flexibly applied to multiple fields, including engineering, agriculture and disaster managements. The goal of this study is to explore and synthesize the opportunities, challenges and scenarios that drone technologies can assist to resolve traffic safety related issues and concerns in RITI communities. Through the outreach activities with the outer Pacific Coast in WA state, it is found that the principal concern within these communities are disaster management and mitigation since they are facing the threat of coastal erosion, earthquake and tsunami. Thus, the emergency management and hazard mitigation becomes the major way to further explore drone applications in the selected communities. To achieve this, we reviewed the current state of the drone technologies, conducted surveys from National Guard and coastal communities in WA, including City of Westport, South Beach Region, Grays Harbor County, Shoalwater Bay Tribe, and Quinault Indian Nation, to better understand their current needs, challenges and issues. Ultimately, recommendations of drone applications under specific scenarios are provided based upon the integration of drone technologies with community safety needs.TABLE OF CONTENTS Disclaimer....................................................................................................................................................... i Technical Report Documentation Page ........................................................................................................ ii SI* (Modern Metric) Conversion Factors ..................................................................................................... iii List of Figures ................................................................................................................................................ v List of Tables ................................................................................................................................................ vi Executive Summary ....................................................................................................................................... 1 CHAPTER 1. Introduction .......................................................................................................................... 2 1.1. General Background ...................................................................................................................... 2 1.2. Problem Statement ....................................................................................................................... 3 CHAPTER 2. Literature review of drone technology and Application ....................................................... 5 2.1. State of the Art Drone Technologies............................................................................................. 5 2.2. Practice of drones in Washington State ........................................................................................ 6 CHAPTER 3. Outreach activities ................................................................................................................ 7 3.1. Community Engagement for Coastal Resilience Studio ................................................................ 8 3.1.1. Westport/South Beach Workshop – 11/2018 (27) ............................................................. 10 3.2. WA National Guard Workshop – 6/2019 .................................................................................... 11 CHAPTER 4. Online survey ...................................................................................................................... 14 CHAPTER 5. results and recommendationS ............................................................................................ 15 5.1. Outreach Activity Findings .......................................................................................................... 15 5.1.1. Transportation and Traffic Safety in Westport ................................................................... 15 5.1.2. Learning from WA National Guard Workshop .................................................................... 17 5.2. Online Survey Results.................................................................................................................. 18 5.3. Recommendation of drone applications .................................................................................... 18 CHAPTER 6. conclusion and future study ............................................................................................... 24 Reference .................................................................................................................................................... 25 Appendix A: UAV (Drones) technologies ...................................................................................................... 1 Appendix B: Workshop report for Westport Coastal Resilience................................................................... 1 Appendix C: Online Survey ............................................................................................................................ 1 Appendix D: Executive Summary of Westport Costal Resilience Report ...................................................... 1 Appendix E: Transportation Chapter of Westport Costal Resilience Report ................................................

Indications of magnetic coupling effects in spin cross-over molecular thin films

Room temperature isothermal reversible spin crossover switching of [Fe(H2B(pz)2)2(bipy)] thin films is demonstrated. The magnetic oxide substrate locks the [Fe{H2B(pz)2}2(bipy)] largely in a low spin state. With an X-ray fluence, excitation to a high spin state occurs, while relaxation back to low spin state is aided by alternating the substrate magnetization. Includes supplementary materials

Boundedness in a quasilinear two-species chemotaxis system with consumption of chemoattractant

This paper deals with a two-species chemotaxis system \begin{equation*} \begin{cases} u_t=\nabla\cdot(D_1(u)\nabla u)-\nabla\cdot(u\chi_1(w)\nabla w)+\mu_1 u(1-u-a_1v),\quad &x\in \Omega,\quad t>0,\\ v_t=\nabla\cdot(D_2(v)\nabla v)-\nabla\cdot(v\chi_2(w)\nabla w)+\mu_2 v(1-a_2u-v),\quad &x\in \Omega,\quad t>0,\\ w_t=\Delta w-(\alpha u+\beta v)w,\quad &x\in\Omega,\quad t>0, \end{cases} \end{equation*} where $\Omega\subset \mathbb{R}^n$ ($n\geq 1$) is a bounded domain with smooth boundary $\partial\Omega$; ${\chi}_i (i=1,2)$ are chemotactic functions satisfying ${\chi}'_i\geq0$; the parameters $\mu_1, \mu_2>0, a_1, a_2>0$ and $\alpha, \beta>0$, the initial data $(u_0,v_0)\in (C^0(\overline{\Omega}))^2$ and $w_0\in W^{1,\infty}(\Omega)$ are non-negative. Based on the maximal Sobolev regularity, it is shown that this system possesses a unique global bounded classical solution provided that the logistic growth coefficients $\mu_1$ and $\mu_2$ are sufficiently large

Design of Hypervelocity-Impact Damage Evaluation Technique Based on Bayesian Classifier of Transient Temperature Attributes

With the rapid increasement of space debris on earth orbit, the hypervelocity-impact (HVI) of space debris can cause some serious damages to the spacecraft, which can affect the operation security and reliability of spacecraft. Therefore, the damage detection of the spacecrafts has become an urgent problem to be solved. In this paper, a method is proposed to detect the damage of spacecraft. Firstly, a variable-interval method is proposed to extract the effective information from the infrared image sequence. Secondly, in order to mine the physical meaning of the thermal image sequence, five attributes are used to construct a feature space. After that, a Naive Bayesian classifier is established to mine the information of different damaged areas. Then, a maximum interclass distance function is used choose the representative of each class. Finally, in order to visualize damaged areas, the Canny operator is used to extract the edge of the damage. In the experiment, ground tests are used to simulate hypervelocity impacts in space. Historical data of natural damaged material and artificial damaged material are used to build different classifiers. After that, the effective of classifiers is illustrated by accuracy, F-score and AUC. Then, two different types of materials are detected by proposed method, Independent Component Analysis (ICA) and Fuzzy C-means (FCM). The results show that the proposed method is more accurate than other methods