scholarly journals Experimental Study for the Stripping of PTFE Coatings on Al-Mg Substrates Using Dry Abrasive Materials

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 799
Author(s):  
Guillermo Guerrero-Vaca ◽  
David Carrizo-Tejero ◽  
Óscar Rodríguez-Alabanda ◽  
Pablo E. Romero ◽  
Esther Molero
Keyword(s):  
Walnut Shell ◽  
Glass Microspheres ◽  
Sem Images ◽  
Environmental Controls ◽  
Different Types ◽  
One Step ◽  
The One ◽  
Almost All ◽  
The Cost ◽  
Substrate Hardness

Polytetrafluoroethylene (PTFE) coatings are used in many applications and processing industries. With their use, they wear out and lose properties and must be replaced by new ones if the cost of the element so advises. There are different stripping techniques, but almost all of them are very difficult and require strict environmental controls. It is a challenge to approach the process through efficient and more sustainable techniques. In the present work, we have studied the stripping of PTFE coatings by projection with abrasives (1 step) as an alternative to carbonization + sandblasting procedures (2 steps). For this purpose, different types of abrasives have been selected: brown corundum, white corundum, glass microspheres, plastic particles, and a walnut shell. The tests were performed at pressures from 0.4 to 0.6 MPa on PTFE-coated aluminium substrates of EN AW-5182 H111 alloy. Stripping rates, surface roughness, and substrate hardness have been studied. Scanning electron microscopy (SEM) images of sandblasted specimens have also been obtained. All abrasives improved mechanical and surface properties in one-step vs. two-step processes. The abrasives of plastic and glass microspheres are the most appropriate for the one-step process, which increases the hardness and roughness level Ra in the substrate. Corundum abrasives enable the highest stripping rates.

scholarly journals Analysis of the Influence of Fibers on the Formability of Metal Blanks in Manufacturing Processes for Fiber Metal Laminates

2019 ◽  
Vol 3 (1) ◽  
pp. 2 ◽  
Author(s):  
Thomas Mennecart ◽  
Soeren Gies ◽  
Noomane Ben Khalifa ◽  
A. Erman Tekkaya
Keyword(s):  
Contact Forces ◽  
Starting Time ◽  
Fiber Metal Laminate ◽  
Metal Sheets ◽  
Different Types ◽  
One Step ◽  
Fiber Metal ◽  
The One ◽  
Metal Blank

In the one-step manufacturing process for fiber metal laminate parts, the so-called in situ hybridization process, the fabrics are interacting with metal blanks. During deep drawing, the liquid matrix is injected between the metal sheets through the woven fiber layers. The metal blanks can be in contact with dry or with infiltrated fibers. The formability of the blanks is influenced by the variation of the starting time of injection. The reason for that is that, due to high contact forces, the fibers are able to deform the metal surface locally, so that movement and the strain of the blanks is inhibited. To investigate the influence of different fibers on the formability of metals, Nakazima tests are performed. In these tests, two metal blanks are formed with an interlayer of fibers. The results are compared with the formability of two blanks without any interlayer. It is shown that in with fibers between sheets, the formability decreases compared to the formability of two metal blanks without interlayers. Based on a simplified numerical model for different types of fibers, the interactions of the fibers with the metal blank are analyzed. It could be shown that the friction due to contact has more influence than the friction due to the form fit caused by the imprints.

scholarly journals Absorbing boundary conditions for wave‐equation migration

Geophysics ◽  
1980 ◽  
Vol 45 (5) ◽  
pp. 895-904 ◽  
Author(s):  
Robert W. Clayton ◽  
Björn Engquist
Keyword(s):  
Wave Equation ◽  
Boundary Conditions ◽  
Final Section ◽  
Absorbing Boundary Conditions ◽  
Absorbing Boundary ◽  
Seismic Section ◽  
Difference Wave ◽  
Different Types ◽  
Almost All ◽  
The Cost

The standard boundary conditions used at the sides of a seismic section in wave‐equation migration generate artificial reflections. These reflections from the edges of the computational grid appear as artifacts in the final section. Padding the section with zero traces on either side adds to the cost of migration and simply delays the inevitable reflections. We develop stable absorbing boundary conditions that annihilate almost all of the artificial reflections. This is demonstrated analytically and with synthetic examples. The absorbing boundary conditions presented can be used with any of the different types of finite‐difference wave‐equation migration, at essentially no extra cost.

scholarly journals A PPMAP analysis of the filamentary structures in Ophiuchus L1688 and L1689

2021 ◽  
Author(s):  
A D P Howard ◽  
A P Whitworth ◽  
M J Griffin ◽  
K A Marsh ◽  
M W L Smith
Keyword(s):  
B Stars ◽  
Mapping Algorithm ◽  
Dust Temperature ◽  
Different Types ◽  
Prestellar Cores ◽  
Different Temperatures ◽  
The One ◽  
Additional Support ◽  
Almost All ◽  
Rule Out

Abstract We use the PPMAP (Point Process MAPping) algorithm to re-analyse the Herschel and SCUBA-2 observations of the L1688 and L1689 sub-regions of the Ophiuchus molecular cloud. PPMAP delivers maps with high resolution (here 14″, corresponding to ∼0.01 pc at ∼140 pc), by using the observations at their native resolutions. PPMAP also delivers more accurate dust optical depths, by distinguishing dust of different types and at different temperatures. The filaments and prestellar cores almost all lie in regions with $N_{\rm H_2}\gtrsim 7\times 10^{21}\, {\rm cm}^{-2}$ (corresponding to $A_{_{\rm V}}\gtrsim 7$). The dust temperature, T, tends to be correlated with the dust opacity index, β, with low T and low β tend concentrated in the interiors of filaments. The one exception to this tendency is a section of filament in L1688 that falls – in projection – between the two B stars, S1 and HD147889; here T and β are relatively high, and there is compelling evidence that feedback from these two stars has heated and compressed the filament. Filament fwhms are typically in the range 0.10 pc to 0.15 pc. Most filaments have line densities in the range $25\, {\rm M_{_\odot }\, pc^{-1}}$ to $65\, {\rm M_{_\odot }\, pc^{-1}}$. If their only support is thermal gas pressure, and the gas is at the canonical temperature of 10 K, the filaments are highly supercritical. However, there is some evidence from ammonia observations that the gas is significantly warmer than this, and we cannot rule out the possibility of additional support from turbulence and/or magnetic fields. On the basis of their spatial distribution, we argue that most of the starless cores are likely to disperse (rather than evolving to become prestellar).

scholarly journals Exteriorização de material cirúrgico em luz esofageana / Exteriorization of surgical material in esophagus lumen

2021 ◽  
Vol 66 (1u) ◽  
pp. 1
Author(s):  
Guilherme Henrique Freire Costa ◽  
Vitor Doria Ricardo ◽  
Jean Lucas Benatti ◽  
Juliana Lucena Queiroz ◽  
Danilo Gagliardi ◽  
...  
Keyword(s):  
Back Pain ◽  
Obstructive Uropathy ◽  
Laparoscopic Technique ◽  
Low Back ◽  
Review Of Literature ◽  
Retrocaval Ureter ◽  
Lower Back ◽  
Different Types ◽  
One Step ◽  
The One

Introdução: O ureter retrocava é uma malformação congênita rara que pode ser causa de uropatia obstrutiva com sintomas inespecíficos como dor lombar e complicações como ureterolitíase e pielonefrite, que normalmente aparecem entre a terceira e a quarta décadas de vida, e exige tratamento cirúrgico na maior parte dos casos. Objetivo: Apresentar um caso de ureter retrocava associado a ureterolitíase e uma revisão da literatura a respeito das técnicas cirúrgicas para sua correção. Relato de caso: Os autores apresentam um caso de ureterolitíase e ureter retrocava, diagnosticado por tomografia computadorizada, em um paciente masculino de 43 anos com dor lombar direita, corrigido através de técnica laparoscópica transperitoneal. Conclusão: A correção cirúrgica laparoscópica do ureter retrocava tem se mostrado benéfica em diversos aspectos quando comparada ao acesso aberto e uma abordagem que ainda não havia sido publicada é a correção do ureter retrocava associado a ureterolitíase num mesmo tempo cirúrgico.Palavras chave: Ureter retrocava, Hidronefrose, Ureterolitíase, Anomalia urogenital, LaparoscopiaABSTRACTIntroduction: The retrocaval ureter is a rare congenital malformation which may cause obstructive uropathy with nonspecific symptoms such as low back pain and complications as ureterolithiasis and pyelonephritis, which usually appear between the third and fourth decades of life, and requires surgical treatment in most cases. Objective: To present a case of ureterolithiasis and retrocaval ureter and a review of literature, regarding the different types of access for his surgery. Case Report: The authors present a case of ureterolithiasis and retrocaval ureter diagnosed by computed tomography in a 43-year-old male patient with right lower back pain, corrected using a transperitoneal laparoscopic technique. Conclusion: Laparoscopic surgical correction of the retrocaval ureter has shown to be beneficial in several aspects when compared to open access, and one that has not been previously reported is the one-step resolution of the association with ureterolithiasis.Keywords: Retrocaval ureter, Hydronephrosis, Ureterothiasis, Urogenital abnormalities, Laparoscopy

A novel crease-resistant and hydrophobic dual-function foam coating for silk fabric by the one-step method

2019 ◽  
Vol 90 (13-14) ◽  
pp. 1495-1506
Author(s):  
Fangqing Ge ◽  
Jinju Zhang ◽  
Jingyan Liu ◽  
Liang Fei ◽  
Chaoxia Wang
Keyword(s):  
Foam Stability ◽  
Dual Function ◽  
Silk Fabric ◽  
Step Method ◽  
Sem Images ◽  
Foaming Agent ◽  
Hydrophobic Agent ◽  
One Step ◽  
The One ◽  
Fabric Surface

A dual-function silk fabric possessing crease-resistance and hydrophobicity is obtained by one-step foam finishing. A system with a high foaming ratio, containing hydrophobic reagent, crease-resistant agent, and foaming agent, is achieved by optimizing the hydrophobic agent. The results show the foamability and foam stability of finishing solution are enhanced slightly with the increase of the foaming agent dosage. The hydrophobicity and crease-resistance of the treated silk fabric are significantly improved. The contact angle of the treated silk fabric is increased to 132.6 ± 0.7° with the hydrophobic agent addition; meanwhile, the crease recovery angle was improved from 212.5 to 230.3° compared with the silk treated by crease-resistant agent, resulting from the cross-linking reaction of hydroxyls between the hydrophobic agent and silk fabric. SEM images reveal that the surface roughness of the finished silk fabric exhibits an obvious enhancement, indicating a film is formed by the resin curing on the fabric surface, which also explains why the crease-resistance and hydrophobicity of silk fabric are improved. The tearing strength retention ratio is increased 160% after the one-bath finishing of crease-resistant reagent and hydrophobic agent, and the breaking strength of the silk fabric is well maintained. The one-step foam finishing is a facile and energy-saving technology to endow the silk fabric with crease-resistance and hydrophobicity dual-function.

scholarly journals Role Substitution in Preschoolers’ Play with DifferentTypes of Materials for Pretend Play

2021 ◽  
Vol 17 (1) ◽  
pp. 67-74
Author(s):  
I.A. Ryabkova ◽  
E.G. Sheina
Keyword(s):  
Pretend Play ◽  
Free Play ◽  
Different Types ◽  
Real Objects ◽  
The One ◽  
Almost All ◽  
Gender Specific ◽  
Different Levels

This paper is devoted to the observation of preschoolers’ free play with different types of materials for pretend play. It is shown that role substitution varies in play with different materials. When children played with play costumes (role markers), many of them renamed themselves; however, the roles were similar in character and strictly related to the proposed costumes. Also, children rarely performed their role through actions. Playing with character toys turned out to be gender specific. Boys rarely played a role, preferring a director's position. Girls’ play was of different levels of complexity, their roles were complementary to their toys and original in character. When children played with toys that imitate real objects (cups, swords, irons and so on), they were less likely to rename themselves, the roles were rather similar; however, almost all children acted from inside their roles. The most balanced environment for pretend play was the one with open-ended materials: many children renamed themselves, and the roles were original (in fact, originality was the highest with this type of materials), many children performed the role through play actions (this was especially true for older preschoolers). The exception were 6-year-old children who, despite renaming themselves, did not perform any play actions in this environment.

scholarly journals Preparation Methods and Challenges of Hybrid Nanofluids: A Review

2020 ◽  
Vol 78 (2) ◽  
pp. 56-66
Author(s):  
Wajiha Tasnim Urmi ◽  
A.S Shafiqah ◽  
Md Mustafizur Rahman ◽  
Kumaran Kadirgama ◽  
Md Abdul Maleque
Keyword(s):  
Rapid Development ◽  
Step Method ◽  
Preparation Methods ◽  
One Step ◽  
High Production ◽  
Hybrid Nanofluids ◽  
High Production Cost ◽  
The One ◽  
The Cost ◽  
Transfer Properties

The recent studies on nanotechnology have reported rapid development of nanofluids in various aspects due to the enhanced thermophysical and heat transfer properties of nanofluids. This paper reviews the preparation methods and some challenging issues of hybrid nanofluids during the Preparation of hybrid nanofluids. One-step and two-step are mainly the preparation methods of hybrid nanofluids. Compared to the one-step method, the two-step method is a widely used technique for preparing nanofluids due to its simplicity, whereas this technique has a complexity of achieving stability of hybrid nanofluids. On the contrary, the one-step is very flexible for achieving uniformity of nanofluids with comparatively high production cost. Some researchers followed various techniques such as surfactant addition, surface treatment, and pH modification for preparing a durable nanofluid. However, these methods also have their limitation, such as degrading the thermal attributes of hybrid nanofluids. So, future studies need to address these challenges along with the cost analysis during preparing the hybrid nanofluids.

scholarly journals Tratamento laparoscópico de cálculo ureteral em ureter retrocava / Laparoscopic treatment of ureteral stone in retrocaval ureter

2021 ◽  
Vol 66 (1u) ◽  
pp. 1
Author(s):  
Robson Cristian Virgilio ◽  
Fernanda Monteiro Orellana ◽  
Luiz Felipe De Melo Pereira Leitão ◽  
Tiago Granucci Guirro ◽  
Rafael Freitas de Andrade Neri ◽  
...  
Keyword(s):  
Back Pain ◽  
Obstructive Uropathy ◽  
Laparoscopic Technique ◽  
Low Back ◽  
Review Of Literature ◽  
Retrocaval Ureter ◽  
Lower Back ◽  
Different Types ◽  
One Step ◽  
The One

Introdução: O ureter retrocava é uma malformação congênita rara que pode ser causa de uropatia obstrutiva com sintomas inespecíficos como dor lombar e complicações como ureterolitíase e pielonefrite, que normalmente aparecem entre a terceira e a quarta décadas de vida, e exige tratamento cirúrgico na maior parte dos casos. Objetivo: Apresentar um caso de ureter retrocava associado a ureterolitíase e uma revisão da literatura a respeito das técnicas cirúrgicas para sua correção. Relato de caso: Os autores apresentam um caso de ureterolitíase e ureter retrocava, diagnosticado por tomografia computadorizada, em um paciente masculino de 43 anos com dor lombar direita, corrigido através de técnica laparoscópica transperitoneal. Conclusão: A correção cirúrgica laparoscópica do ureter retrocava tem se mostrado benéfica em diversos aspectos quando comparada ao acesso aberto e uma abordagem que ainda não havia sido publicada é a correção do ureter retrocava associado a ureterolitíase num mesmo tempo cirúrgico. Palavras chave: Ureter retrocava, Hidronefrose, Ureterolitíase, Anomalia urogenital, Laparoscopia ABSTRACT:Introduction: The retrocaval ureter is a rare congenital malformation which may cause obstructive uropathy with nonspecific symptoms such as low back pain and complications as ureterolithiasis and pyelonephritis, which usually appear between the third and fourth decades of life, and requires surgical treatment in most cases. Objective: To present a case of ureterolithiasis and retrocaval ureter and a review of literature, regarding the different types of access for his surgery. Case Report: The authors present a case of ureterolithiasis and retrocaval ureter diagnosed by computed tomography in a 43-year-old male patient with right lower back pain, corrected using a transperitoneal laparoscopic technique. Conclusion: Laparoscopic surgical correction of the retrocaval ureter has shown to be beneficial in several aspects when compared to open access, and one that has not been previously reported is the one-step resolution of the association with ureterolithiasis.Keywords: Retrocaval ureter, Hydronephrosis, Ureterothiasis, Urogenital abnormalities, Laparoscopy

scholarly journals VAZÃO IDEAL DE GOTEJADORES PARA A CULTURA DO PIMENTÃO EM DIFERENTES TIPOS DE SOLO

Irriga ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 121
Author(s):  
Allan Cunha Barros ◽  
TALES PEREIRA DOs SANTOS ◽  
ANTENOR OLIVEIRA AGUIAR NETTO
Keyword(s):  
Irrigation System ◽  
Management Strategies ◽  
Sweet Pepper ◽  
Application Time ◽  
Ideal Flow ◽  
Irrigation Design ◽  
Different Types ◽  
Almost All ◽  
The Cost ◽  
The Ideal

VAZÃO IDEAL DE GOTEJADORES PARA A CULTURA DO PIMENTÃO EM DIFERENTES TIPOS DE SOLO  ALLAN CUNHA Barros¹; TALES PEREIRA DOS SANTOS² E ANTENOR DE OLIVEIRA AGUIAR NETTO³  [1] Engenheiro Agrônomo. Prof. Doutor UFAL, Campus Arapiraca, AL,  [email protected]² Engenheiro Agrônomo, formado na UFAL. [email protected]³ Engenheiro Agrônomo. Prof. Doutor, UFS, São Cristóvão, SE, [email protected]  1 RESUMO O processo de projetar um sistema de irrigação passa, primeiramente, pela escolha da vazão do gotejador, que por sua vez influencia a porcentagem de área molhada (PAM). Comercialmente existem muitas vazões de gotejadores e sua escolha poderá influenciar o manejo e o custo do sistema de irrigação. Objetivou-se com este trabalho determinar a vazão ideal de gotejadores para a cultura do pimentão (Capsicum annun) em diferentes tipos de solo. O projeto foi desenvolvido em parceria entre as Universidades Federais de Sergipe e Alagoas. Os tratamentos foram baseados no tipo de solo (Latossolo, Argissolo e Cambissolo) x vazões de emissores (24 vazões) de diferentes marcas comerciais x no tempo de aplicação de água (1, 2, 4 e 7 horas), na cultura do pimentão. Foram realizadas simulações das dimensões dos bulbos superficiais em planilha eletrônica, utilizando as equações de Maia et al. (2010). Considerou-se vazão ideal as que possuíam PAM entre 33 a 70%.  Para o Argissolo e o Cambissolo quase todas as vazões atenderam ao critério, nos tempos de irrigação de 1 e 2 hora. Já para o Latossolo o tempo de aplicação mais indicado com as vazões observadas foi de 2 horas. As vazões próximas a 1,5 L h-¹ tendem a ser mais indicadas para a cultura do pimentão. Palavra-chave: Modelagem, faixa molhada, bulbo úmido, dimensionamento de irrigação.  A. C. Barros, T. P. DOS SANTOS, A. O. AGUIAR NETTOFLOW DRIPPERS IDEAL FOR CULTURE OF PEPPER (Capsicum ANNUN) IN DIFFERENT TYPES OF SOIL  2 ABSTRACT The process of designing an irrigation system, firstly, passes by the choice of the dripper flow, which depends on the percentage of wetted volume (PW). Commercially, there are many flows of drippers and its choice may influence management strategies and the cost of the irrigation system. So, the aim of this study was to estimate the ideal flow drippers for sweet pepper (Capsicum annun) in different types of soil. The project was developed in partnership with the Federal University of Sergipe and Alagoas. The treatments were based on the type of soil (Oxisol, Argisol and Cambisol) vs emitters flow (24 flows) by different brands vs water application time (1, 2, 4 and 7 hours) in pepper. Simulations were made with the dimensions of the superficial bulbs in a spreadsheet, by using the equations of Maia et al. (2010). The ideal flow was considered when the PW was found between 33-70%. For Argisol and Cambisol, almost all flows met the criteria, at irrigation times of 1 and 2 hours. As for the Latossol the most suitable application times studied with the flow were 2 hours. Overall flows next to 1.5L.h-¹ tend to be more suitable for the bell pepper crop. Keywords: Modeling, wet track, wet bulb, irrigation design.

Types of refractive errors and methods for their diagnosis

2020 ◽  
pp. 30-36
Author(s):  
Olga Lemzyakova
Keyword(s):  
Optical System ◽  
Contact Lenses ◽  
Vision Impairment ◽  
Refractive Errors ◽  
Vision Correction ◽  
Light Rays ◽  
Different Types ◽  
Almost All ◽  
Degrees Of Severity ◽  
The Brain

Refraction of the eye means its ability to bend (refract) light in its own optical system. In a normal state, which is called emmetropia, light rays passing through the optical system of the eye focus on the retina, from where the impulse is transmitted to the visual cortex of the brain and is analyzed there. A person sees equally well both in the distance and near in this situation. However, very often, refractive errors develop as a result of various types of influences. Myopia, or short-sightedness, occurs when the light rays are focused in front of the retina as a result of passing through the optical system of the eye. In this case, a person will clearly distinguish close objects and have difficulties in seeing distant objects. On the opposite side is development of farsightedness (hypermetropia), in which the focusing of light rays occurs behind the retina — such a person sees distant objects clearly, but outlines of closer objects are out of focus. Near vision impairment in old age is a natural process called presbyopia, it develops due to the lens thickening. Both myopia and hypermetropia can have different degrees of severity. The variant, when different refractive errors are observed in different eyes, is called anisometropia. In the same case, if different types of refraction are observed in the same eye, it is astigmatism, and most often it is a congenital pathology. Almost all of the above mentioned refractive errors require correction with spectacles or use of contact lenses. Recently, people are increasingly resorting to the methods of surgical vision correction.

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