scholarly journals Modelling and thermal simulation of absorber-free quasi-simultaneous laser welding of transparent plastics

2020 ◽  
Vol 64 (11) ◽  
pp. 1939-1946
Author(s):  
Nam-Phong Nguyen ◽  
Stefan Behrens ◽  
Maximilian Brosda ◽  
Alexander Olowinsky ◽  
Arnold Gillner
Keyword(s):  
Laser Wavelength ◽  
Single Step ◽  
Fibre Laser ◽  
Biotechnological Applications ◽  
Laser Transmission Welding ◽  
Emit Radiation ◽  
Radiation Sources ◽  
Plastics Processing ◽  
Plastic Components

Abstract The growing demands on the quality of plastic components and the trend towards miniaturisation are posing a great challenge on plastics processing technology. As many complex components can no longer be manufactured in a single step, joining processes such as laser transmission welding are gaining in importance. In classic laser transmission welding, the joining partners have different optical properties. The upper joining partner is transparent in the laser wavelength range, whilst the lower partner is absorbent due to the addition of absorber materials. In medical and biotechnological applications, the addition of absorber materials is often undesirable due to strict biocompatibility requirements. If, on the other hand, radiation sources are used which emit radiation in the area of the natural absorption of the plastic (λ = 1600–2000 nm), untreated transparent plastics can also be welded. In this work, a theoretical model will be presented to calculate the temperature distribution and progression during quasi-simultaneous welding using a thulium fibre laser (λ = 1940 nm). A sensitivity analysis is carried out to investigate the influence of different parameters on the heat affected zone (HAZ). The simulated HAZ is then compared with the HAZ from the experimental work.

Formation of laser-induced periodic surface structures on different materials: fundamentals, properties and applications

2020 ◽  
Vol 9 (1-2) ◽  
pp. 11-39 ◽  
Author(s):  
Stephan Gräf
Keyword(s):  
Friction And Wear ◽  
Review Paper ◽  
Laser Wavelength ◽  
Single Step ◽  
Surface Structures ◽  
Direct Writing ◽  
Periodic Surface ◽  
Experimental Approaches ◽  
Ordered Nanostructures ◽  
Physical Background

AbstractThe use of ultra-short pulsed lasers enables the fabrication of laser-induced periodic surface structures (LIPSS) on various materials following a single-step, direct-writing technique. These specific, well-ordered nanostructures with periodicities in the order of the utilised laser wavelength facilitate the engineering of surfaces with functional properties. This review paper discusses the physical background of LIPSS formation on substrates with different material properties. Using the examples of structural colours, specific wetting states and the reduction of friction and wear, this work presents experimental approaches that allow to deliberately influence the LIPSS formation process and thus tailor the surface properties. Finally, the review concludes with some future developments and perspectives related to forthcoming applications of LIPSS-based surfaces are discussed.

Understanding Smart City Solutions in Turkish Cities From the Perspective of Sustainability

2018 ◽  
pp. 236-266
Author(s):  
H. Filiz Alkan Meshur
Keyword(s):  
Information And Communication Technologies ◽  
Smart City ◽  
Social Life ◽  
Communication Technologies ◽  
Global Scale ◽  
Single Step ◽  
Information And Communication ◽  
General Practices ◽  
Urban Problems

The purpose of this chapter is to analyze the concept of smart city and its potential solutions to correct urban problems. Smart city practices and solutions have been investigated through the lens of a sustainable perspective. As the general practices in the global scale were examined, particular focus has been directed to smart city practices in Turkey and applicable suggestions have been developed. A number of cities in Turkey rank the lowest in the list of livable cities index. Consequential to the rapidly rising population ratios, the quality of provided services declines; economic and social life in cities are adversely affected and brand images of cities are deteriorated. With the implementation of smart city practices, such problems could be corrected, and these cities could gain competitive advantage over their rivals. The key component of this smart administration is to most effectively utilize information and communication technologies during each single step of this process.

scholarly journals Selected Issues Concerning Degradation of Material in the Production of Injection Molded Plastic Components

2016 ◽  
Vol 10 (3) ◽  
pp. 173-180
Author(s):  
Marek Jałbrzykowski
Keyword(s):  
Thermal Characteristics ◽  
Test Results ◽  
Base Materials ◽  
Plastic Materials ◽  
Technological Quality ◽  
Injection Molded ◽  
Plastic Components ◽  
Injection Molded Plastic ◽  
Selection Of

Abstract This paper presents the problem of thermal degradation of thermoplastic materials processed using the injection method. Attention was paid to the issue of the optimal selection of a dye for modifying the base materials. For the selected materials and dyes, derivatograph tests were performed in order to assess their thermal characteristics and breakdown kinetics. Additionally, tribological tests and microscope observations of selected samples were performed. The obtained test results suggest a diverse level of thermal processes in the analyzed materials. This is crucial for the appropriate selection of dyes for plastic materials. As it turned out, the tribological properties of materials can also influence the technological quality of the injected alloy.

Research on Electrical Discharge Machining for Injection Mold of Automotive Connector

2012 ◽  
Vol 522 ◽  
pp. 17-20
Author(s):  
Wei Min Pan ◽  
Ke Ke Shi ◽  
Xian Qing Lei
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
Tool Electrode ◽  
Injection Mold ◽  
Workpiece Material ◽  
Electrode Tool ◽  
Mating Surface ◽  
Plastic Components

Electrical discharge machining (EDM) processing is generally applied on the area of molding plastic component or mating surface required high accuracy. The areas determine the quality of the plastic components. The principle of EDM is based on the material vaporization of high potential difference across the workpiece and Tool electrode. Tool electrode and workpieces are discontiguous when the EDM processes. Because there is no mechanical contact, Hardness and strength of the workpiece material have minimal effect on the material removal rate .The application of EDM technology on injection mold of automotive connector is focused on in this paper. Processing of the complex cores is researched. The design and processing of the tool electrode have been completed in the meantime.

Variables in the radiation-attenuation of helminth larvae: the effect of differences in quality of radiation

Parasitology ◽  
1966 ◽  
Vol 56 (4) ◽  
pp. 651-656 ◽  
Author(s):  
T. Kassai ◽  
B. Fitzpatrick ◽  
W. Mulligan
Keyword(s):  
Agricultural Research ◽  
Dose Range ◽  
X Rays ◽  
British Council ◽  
Agricultural Research Council ◽  
Radiation Sources ◽  
Γ Rays ◽  
Low Radiation Doses ◽  
Total Worm Burden

A comparison has been made of the attenuating effect on N. brasiliensis larvae of X-rays (HVL, 8 mm Al) and γ-rays from 60Co over the range 10–80 kr. In the dose range where attenuation was manifested as a decrease in total worm burden the γ-rays had an RBE (relative biological effect) of 0-7 relative to the X-rays as unity.Because of the enhancement of infectivity occurring at low radiation doses, attenuation in this region is better assessed in terms of alteration to the sex-ratio of the parasite rather than effect on total population.This work was supported by grants from the Agricultural Research Council and the Horse Race Betting Levy Board, and was carried out during the tenure by one of the authors (T. Kassai) of a British Council exchange scholarship.Thanks are due to Dr T. Martin Young and Mr J. S. Orr of the Radiotherapy Department, Western Infirmary, Glasgow, for access to radiation sources and helpful advice.

Experimental Determination of the Focal Length of a Laser Beam from the Output Nozzle of a Laser Cutting Head

2017 ◽  
Vol 756 ◽  
pp. 71-79
Author(s):  
Martin Lachman ◽  
Jiří Šafka
Keyword(s):  
Laser Beam ◽  
Laser Cutting ◽  
Focal Point ◽  
Focal Length ◽  
Cutting Speed ◽  
Vital Role ◽  
Fibre Laser ◽  
Cutting Head ◽  
Industrial Operations

Laser technologies are considered to be unconventional technologies. Laser cutting is one of the most popular industrial operations that use a laser beam. Fibre lasers are most commonly used for cutting metallic materials. The aim of this paper is to experimentally demonstrate a procedure for determining the focal length of a laser beam from the output of the cutting head of a JK400FL fibre laser. Along with other factors, the correct position of the focal point of a laser beam cutting materials, plays a vital role in the quality of the cut and also in determining the cutting speed. It is possible to use a higher cutting speed of the laser machine, without compromising the quality of the cut.

scholarly journals Gamma Shielding Experiment Simulation utilizing MCNPX Code

2021 ◽  
Vol 12 (2) ◽  
pp. 11-21
Author(s):  
Shafiqul Islam Faisal ◽  
Abi Muttaquin Bin Jalal Bayar
Keyword(s):  
Gamma Ray ◽  
Cost Effective ◽  
Radiation Shielding ◽  
Engineering Science ◽  
Gamma Source ◽  
Mcnpx Code ◽  
Radiation Sources ◽  
Absorbing Materials ◽  
Code Version

Experimental investigation requires materials, radiation sources, and test arrangements with a high monetary financial plan. Furthermore, radiation exposure involves people during the experiment. On the contrary, the simulation technique for examining radiation interactions is radio-logically safer, less timeconsuming, cost-effective, and applicable for all desired radiation sources. Through 48.86 mCi 662 keV Caesium-137 gamma-ray source; shielding experiment as well as simulation of it with MCNPX were performed for three shielding materials Lead, Copper, and Aluminum. These materials were placed in front of the gamma source and the emergent radiation was counted in a Geiger- Muller detector to understand the attenuation quality of these materials to each other. These courses of action were simulated utilizing the MCNPX code version 2.7.0 and the results likewise gave and looked at that of the experiment. There are huge similarities of shielding behavior between MCNPX simulation and experiments for the three absorbing materials. The modeled geometry of this MCNPX simulation could be used for future approaches of new designs and structures of radiation shielding, especially where no analogous experimental data exist Journal of Engineering Science 12(2), 2021, 11-21

scholarly journals Micro-Machining of Diamond, Sapphire and Fused Silica Glass Using a Pulsed Nano-Second Nd:YVO4 Laser

Optics ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 169-183
Author(s):  
David G. Waugh ◽  
Chris D. Walton
Keyword(s):  
Silica Glass ◽  
Surface Engineering ◽  
Laser System ◽  
Laser Wavelength ◽  
Fused Silica ◽  
Threshold Fluence ◽  
Diode Pumped ◽  
Properties Of Materials ◽  
Fused Silica Glass

Optically transparent materials are being found in an ever-increasing array of technological applications within industries, such as automotive and communications. These industries are beginning to realize the importance of implementing surface engineering techniques to enhance the surface properties of materials. On account of the importance of surface engineering, this paper details the use of a relatively inexpensive diode-pumped solid state (DPSS) Nd:YVO4 laser to modify the surfaces of fused silica glass, diamond, and sapphire on a micrometre scale. Using threshold fluence analysis, it was identified that, for this particular laser system, the threshold fluence for diamond and sapphire ranged between 10 Jcm−2 and 35 Jcm−2 for a laser wavelength of 355 nm, dependent on the cumulative effects arising from the number of incident pulses. Through optical microscopy and scanning electron microscopy, it was found that the quality of processing resulting from the Nd:YVO4 laser varied with each of the materials. For fused silica glass, considerable cracking and deformation occurred. For sapphire, good quality features were produced, albeit with the formation of debris, indicating the requirement for post-processing to remove the observed debris. The diamond material gave rise to the best quality results, with extremely well defined micrometre features and minimal debris formation, comparative to alternative techniques such as femtosecond laser surface engineering.

scholarly journals State-of-the-art augmented NLP transformer models for direct and single-step retrosynthesis

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Igor V. Tetko ◽  
Pavel Karpov ◽  
Ruud Van Deursen ◽  
Guillaume Godin
Keyword(s):  
Language Processing ◽  
Data Augmentation ◽  
Search Algorithm ◽  
Single Step ◽  
Test Dataset ◽  
Reaction Prediction ◽  
Direct Reactions ◽  
Appearance Frequency ◽  
Target Data

Abstract We investigated the effect of different training scenarios on predicting the (retro)synthesis of chemical compounds using text-like representation of chemical reactions (SMILES) and Natural Language Processing (NLP) neural network Transformer architecture. We showed that data augmentation, which is a powerful method used in image processing, eliminated the effect of data memorization by neural networks and improved their performance for prediction of new sequences. This effect was observed when augmentation was used simultaneously for input and the target data simultaneously. The top-5 accuracy was 84.8% for the prediction of the largest fragment (thus identifying principal transformation for classical retro-synthesis) for the USPTO-50k test dataset, and was achieved by a combination of SMILES augmentation and a beam search algorithm. The same approach provided significantly better results for the prediction of direct reactions from the single-step USPTO-MIT test set. Our model achieved 90.6% top-1 and 96.1% top-5 accuracy for its challenging mixed set and 97% top-5 accuracy for the USPTO-MIT separated set. It also significantly improved results for USPTO-full set single-step retrosynthesis for both top-1 and top-10 accuracies. The appearance frequency of the most abundantly generated SMILES was well correlated with the prediction outcome and can be used as a measure of the quality of reaction prediction.

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