Layer Adhesion Test of Additively Manufactured Pins: A Shear Test

Additive Manufacturing (AM) became a popular engineering solution not only for Rapid Prototyping (RP) as a part of product development but as an effective solution for producing complex geometries as fully functional components. Even the modern engineering tools, such as the different simulation software, have a shape optimization solution especially for parts created by AM. To extend the application of these methods in this work, the failure properties of the 3D-printed parts have been investigated via shear test measurements. The layer adhesion can be calculated based on the results, which can be used later for further numerical modeling. In conclusion, it can be stated that the layer formation and the structure of the infill have a great influence on the mechanical properties. The layers formed following the conventional zig-zag infill style show a random failure, and the layers created via extruded concentric circles show more predictable load resistance.

Evidences of Colletotrichum fructicola Causing Anthracnose on Passiflora edulis Sims in China

Passion fruit (Passiflora edulis) is a tropical and subtropical plant that is widely cultivated in China due to its high nutritional value, unique flavor and medicinal properties. In August 2020, typical anthracnose symptoms with light brown and water-soaked lesions on Passiflora edulis Sims were observed, which result in severe economic losses. The incidence of this disease was approximately 30%. The pathogens from the infected fruit were isolated and purified by the method of tissue isolation. Morphological observations showed that the colony of isolate BXG-2 was gray to celadon and grew in concentric circles. The orange conidia appeared in the center after 14 days of incubation. The pathogenicity was verified by Koch’s postulates. The internal transcribed spacer (ITS), chitin synthase (CHS-1), actin (ACT), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were amplified by relevant PCR programs. The multi-gene (ITS, GAPDH, ACT, CHS-1) phylogeny analysis confirmed that isolate BXG-2 belongs to Colletotrichum fructicola. The inhibitory effect of six synthetic fungicides on the mycelial growth of the pathogen was investigated, among which difenoconazole 10% WG showed the best inhibitory effect against C. fructicola with an EC50 value of 0.5579 mg·L−1. This is the first report of anthracnose on Passiflora edulis Sims caused by Colletotrichum fructicola in China.

A Lopsided Outer Solar System?

Axisymmetric disks of eccentric orbits in near-Keplerian potentials are unstable and undergo exponential growth in inclination. Recently, Zderic et al. showed that an idealized disk then saturates to a lopsided mode. Here we show, using N-body simulations, that this apsidal clustering also occurs in a primordial Scattered Disk in the outer solar system, which includes the orbit-averaged gravitational influence of the giant planets. We explain the dynamics using Lynden-Bell's mechanism for bar formation in galaxies. We also show surface density and line-of-sight velocity plots at different times during the instability, highlighting the formation of concentric circles and spiral arms in velocity space.

The Emergence of an “Intersecting Circle” in Kachru’s Three Concentric Circles of World Englishes: A Case of Ethno-linguistic Neutrality in Central Nigeria

There is evidence that contemporary Nigeria is drifting towards a society of monolingual English users a component of which could be defined as lacking in ethno-linguistic identity. This trend is found among a generation of young Nigerian urban dwellers (between the age bracket of (12 and 25) who can neither communicate in their parents’ native language(s) nor indeed in any other Nigerian indigenous language; their only medium of communication is English. Although based on their childhood exposure to the English language and their relative competence in it, English can be described as their ‘‘mother tongue’’ but the fact that they are not native speakers given the socio-geographical circumstances of their birth excludes them from Kachru’s (1988) Inner Circle classification of native speakers. Consequently, these Nigerians are left without a clearly defined ethno-linguistic affiliation. This paper interrogates this emerging sociolinguistic phenomenon in especially Central Nigeria, with the aim of stimulating scholarly consciousness on the ethno-linguistic identity of this category of Nigerians, and its implications for English usage among them. The submission of the paper is that another circle, “the intersecting circle”, be created for them since they bestride both the inner circle in having English as their “mother tongue” and yet they are not native speakers of the language

Scattering in the Poincaré Disk and in the Poincaré Upper Half-Plane

We investigate the scattering of a plane wave in the hyperbolic plane. We formulate the problem in terms of the Lippmann-Schwinger equation and solve it exactly for barriers modeled as Dirac delta functions running along: (i) N−horizontal lines in the Poincaré upper half-plane; (ii) N− concentric circles centered at the origin; and, (iii) a hypercircle in the Poincaré disk.

O ENSINO DA HISTÓRIA E DA GEOGRAFIA:

O ensino dos estudos sociais nos anos iniciais do ensino fundamental é a temática deste artigo. Por que ensinamos estudos sociais, história e geografia, nos anos iniciais da educação básica da forma como ensinamos? Que fundamentos psicológicos e pedagógicos dão lastro à tradição curricular de ensino dos estudos sociais (história e geografia) dispostos em círculos concêntricos? O objetivo é fustigar a tradição consolidada em torno da forma como ensinamos os conhecimentos dos estudos sociais nos anos iniciais do ensino fundamental da educação básica. Apesar da reflexão se originar de constatações do mundo prático, trata-se de um ensaio teórico. A linguagem é o horizonte de onde abordamos o objeto. Trata-se de dizer e interpretar o mundo e as coisas, dialogando com as diferentes tradições epistemológicas, contudo demarcando um olhar crítico e reflexivo sobre a problemática. Após uma breve apresentação das questões epistemológicas implicadas nos círculos concêntricos, a reflexão que segue se estrutura em dois movimentos: o primeiro discute a concepção naturalista de desenvolvimento psicológico humano da modernidade a partir do pensamento de Comenius e o segundo reflete sobre as implicações pedagógicas dessa concepção de desenvolvimento para a educação. Palavras-chave Estudos sociais, Círculos concêntricos, Fundamentos psicológicos e pedagógicos. TEACHING HISTORY AND GEOGRAPHY: psychological and pedagogical assumptions of concentric circles Abstract The teaching of social studies in the initial years of elementary education is the theme of this article. Why do we choose certain ways of teaching social studies, history and geography in the early years of basic education? What psychological and pedagogical foundations give weight to the curricular tradition of teaching social studies (history and geography) arranged in concentric circles? The aim of this essay is to question the consolidated tradition concerning the way we teach social studies in the initial years of elementary education. Although this discussion comes from the findings of the practical world, it is a theoretical reflection. The language is the horizon from which we approach the object. It is about telling and interpreting the world and things, dialoguing with different epistemological traditions, however demarcating a critical and reflective view on the problem. After a brief presentation of the epistemological issues involved in the concentric circles, the reflection that follows is structured in two movements: the first one discusses the naturalistic conception of human psychological development of modernity, according to Comenius’ ideas; and the second one reflects on the pedagogical implications of such conception for educational development. Keywords Social studies, Concentric circles, Psychological and pedagogical foundations.

A novel method quantifying caries following orthodontic treatment

This retrospective pilot study used a newly developed evaluation tool to assess the prevalence and incidence of White Spot Lesions (WSL) before and after multibracket appliance (MB) therapy. Digital photographs of 121 adolescent patients (63 ♂, 58 ♀) with metal brackets were analyzed retrospectively before and after MB therapy. The labial surfaces of anterior teeth, canine teeth, and premolars in the upper (UJ) and lower jaws (LJ) were evaluated using the Enamel Decalcification Index (EDI) by Banks and Richmond (Eur J Orthod, 16(1):19–25, 1994, levels 0–3) and a specially developed digitally scaled graticule with concentric circles to quantify the extent of WSL (in %). The statistical data analysis was based on crosstabulations and logistic regression. Before MB, 69.4% of the patients presented at least one WSL and 97.5% after, an increase of 28.1%. Before MB, 18.4% of the tooth surfaces (TS) showed an EDI level of 1–3. After MB, 51.8% of the TS featured WSL. 18.2% of the TS showed a WSL to the extent of ≥ 20–100% before and 52.3% after MB. The incidence in the UJ (71–79%) as well as the LJ (64–76%) was highest for the first and second premolars and lowest for LJ incisors (22–35%). The probability for developing a new distal WSL is higher than developing gingival, mesial or occlusal WSL. Labial MB therapy drastically increases the risk of developing WSL. We verified a concise quantification of the extent of labial WSL with the evaluation index.

Influence of the beam oscillation parameters on the porosity of electron beam freeform fabricated titanium alloy SPT-2

The effect of electron beam oscillation on the formation of metal during electron beam freeform fabrication has received practically no attention. Nevertheless, it is a variable technological tool that allows to significantly influence the formation of metal during EBFFF process, including the probability of defects formation. The effect of the focus current, the form, and the frequency of the beam oscillation on the formation of pores in single beads by method of electron beam freeform fabrication of the titanium alloy SPT-2 on the substrate of the alloy VT6 was investigated. The porosity of the obtained beads was studied using x-ray images. It was found that too deep an arrangement of the focal plane relative to the substrate surface leads to excessive pore formation. Reducing the oscillation frequency from 1000 Hz to 100 Hz made it possible to completely get rid of the pores in the metal. The use of a spiral-shaped oscillation made it possible to reduce the probability of pore formation in comparison with an oscillation in the form of concentric circles.

Conic tangents based high precision extraction method of concentric circle centers and its application in camera parameters calibration

A high-precision camera intrinsic parameters calibration method based on concentric circles was proposed. Different from Zhang’s method, its feature points are the centers of concentric circles. First, the collinearity of the projection of the center of concentric circles and the centers of two ellipses which are imaged from the concentric circles was proved. Subsequently, a straight line passing through the center of concentric circles was determined with four tangent lines of concentric circles. Finally, the projection of the center of concentric circles was extracted with the intersection of the straight line and the line determined by the two ellipse centers. Simulation and physical experiments are carried out to analyze the factors affecting the accuracy of circle center coordinate extraction and the results show that the accuracy of the proposed method is higher. On this basis, several key parameters of the calibration target design are determined through simulation experiments and then the calibration target is printed to calibrate a binocular system. The results show that the total reprojection error of the left camera is reduced by 17.66% and that of the right camera is reduced by 21.58% compared with those of Zhang’s method. Therefore, the proposed calibration method has higher accuracy.