scholarly journals Present Status in Polymeric Mouthguards. A Future Area for Additive Manufacturing?

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1490 ◽  
Author(s):  
Ana M. Sousa ◽  
Ana C. Pinho ◽  
Ana Messias ◽  
Ana P. Piedade
Keyword(s):  
Additive Manufacturing ◽  
Impact Energy ◽  
Present Status ◽  
Material Characterization ◽  
Control Parameters ◽  
Contact Sports ◽  
Different Types ◽  
Manufacturing Techniques ◽  
The Impact ◽  
The Ideal

Athletes from contact sports are more prone to orofacial injuries because of the exposure to possible shocks and collisions derived from physical proximity. The use of protector polymeric mouthguards proved to be useful in the prevention of the described injuries. There are different types of mouthguards with varying ranges of protection and prices, but they are all made from polymers and share the same propose: to absorb and dissipate the impact energy resulting from the shocks. As they are used inside the mouth, they should not impair breathing and speaking nor compromise the comfort of the athlete. However, the ideal mouthguard is yet to be created. The choice of the most appropriate polymeric material and the standard required properties have not yet been reported. Regardless of the numerous studies in this field, normalized control parameters for both material characterization and mouthguard fabrication are absent. This paper aims to present a review of the current types of available mouthguards and their properties/characteristics. Moreover, a detailed description of the most common polymers for the fabrication of mouthguards, together with the manufacturing techniques, are discussed.

Warpage Behaviors of System-in-Packages on a Substrate Strip

2018 ◽  
Vol 2018 (1) ◽  
pp. 000344-000348
Author(s):  
Eric Ouyang ◽  
Billy Ahn ◽  
SeonMo Gu ◽  
Jim Hsu ◽  
Yonghyuk Jeong ◽  
...  
Keyword(s):  
Material Characterization ◽  
Epoxy Resins ◽  
Curing Process ◽  
Molding Compound ◽  
Advanced Material ◽  
Curing Reaction ◽  
Different Types ◽  
The Impact ◽  
Compound Materials ◽  
Kinetics Of

Abstract In this paper, the impact of two different types of warpage, strip warpage and system-in-packages (SiP) module warpage, are considered and studied, both experimentally and numerically. An advanced material characterization method is also conducted to study the curing reaction and Pressure-Volume-Temperature-Cure (PVTC) kinetics of the packages. The curing reaction of epoxy resins, as a function of temperature and activation energies, is experimentally determined. During the curing process, the viscosity of epoxy resins change with temperature and conversion rate. The Castro-Macosko model is adopted to describe the rheological properties of epoxy resins. Experimentally, we have prepared substrate strip samples with different component density and molding compound materials. Each substrate strip contains eighteen system-in-packages. The warpages of all substrate strips and all the system-in-package modules were measured, compared, and correlated.

scholarly journals Analyzing COVID-19 Challenges in Bangladesh

2020 ◽  
Author(s):  
Jayasree Nath ◽  
Abdullah Fahim Chowdhury ◽  
Amit Kumar Nath
Keyword(s):  
South Asian ◽  
Present Status ◽  
Health Sector ◽  
Economic Modelling ◽  
Proper Treatment ◽  
Treatment Facility ◽  
Socioeconomic Condition ◽  
The Poor ◽  
Different Types ◽  
The Impact

Bangladesh is a developing country. The effect of the covid-19 pandemic in Bangladesh is enormous. A research conducted by South Asian network of Economic Modelling predicted that the pandemic could double the poverty. But it is not that only the socioeconomic condition is dropping in Bangladesh, the impact of COVID-19 pandemic is manifold. The poor condition of Bangladesh's health sector has also been exposed due to the pandemic. People are not getting proper treatment due to lack of isolation beds, oxygen, ICU etc. The health sector of Bangladesh is not much developed and now with this pandemic it has become impossible to provide treatment facility for all the patients. Education sector, which is the backbone of a country,has also been greatly affected by the pandemic. We know that different types of cultural occasions are an inherited tradition of Bangladesh, COVID-19 have not even spared these traditions, all the cultural programes and festivals have been cancelled due to this pandemic.In this paper, our aim is to present the present status of all these sectors.

scholarly journals Fatigue Cracking of Additively Manufactured Materials—Process and Material Perspectives

2020 ◽  
Vol 10 (16) ◽  
pp. 5556
Author(s):  
Torsten Fischer ◽  
Bernd Kuhn ◽  
Detlef Rieck ◽  
Axel Schulz ◽  
Ralf Trieglaff ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Fatigue Strength ◽  
Process Control ◽  
High Performance ◽  
Chemical Engineering ◽  
Fatigue Cracking ◽  
Metal Powders ◽  
Wide Range ◽  
Manufacturing Techniques ◽  
The Impact

Strong efforts are made internationally to optimize the process control of laser additive manufacturing processes. For this purpose, advanced detectors and monitoring software are being developed to control the quality of production. However, commercial suppliers of metal powders and part manufacturers are essentially focused on well-established materials. This article demonstrates the potential of optimized process control. Furthermore, we outline the development of a new high temperature structural steel, tailored to best utilize the advantages of additive manufacturing techniques. In this context, the impact of production-induced porosity on fatigue strength of austenitic 316L is presented. Additionally, we discuss the first conceptual results of a novel ferritic steel, named HiperFer (High Performance Ferrite), which was designed for increased fatigue strength. This ferritic, Laves phase-strengthened, stainless steel could be used for a wide range of structural components in power and (petro)chemical engineering at maximum temperatures ranging from about 580 to 650 °C. This material benefits from in situ heat treatment and counteracts process-related defects by “reactive” crack obstruction mechanisms, hampering both crack initiation and crack propagation. In this way, increased fatigue resistance and safety can be achieved.

scholarly journals An algorithm for topology optimization of gear reducer housing elements

2019 ◽  
Vol 287 ◽  
pp. 01020
Author(s):  
Stoyan D. Slavov ◽  
Mariya Iv. Konsulova-Bakalova
Keyword(s):  
Topology Optimization ◽  
3D Model ◽  
Optimization Methods ◽  
Design Stage ◽  
Control Parameters ◽  
Optimization Software ◽  
Optimization Control ◽  
Different Types ◽  
Definition Of ◽  
The Impact

In recent years, topology optimization methods are becoming more widely used in many engineering fields, and they are already being successfully integrated at the design stage of the different types of products. An active field of research in this area is the definition of appropriate constraints in topology optimization models in order to facilitate the production of the optimized objects. An algorithm for topology optimization of housing elements from gear reducers by using the capabilities of CAD-CAE topology optimization software is presented in the current work. The purposed algorithm is taking into account the resulting loads during operation of the reducer, the geometrical and manufacturing constraints of the production process of these housing elements. Obtained results from conducted Taguchi experimental study to investigate the impact of some topology optimization control parameters over optimized 3D-model also are shown and discussed. Conclusions on the applicability of the algorithm have been made.

scholarly journals Laser Metal Wire drop-by-drop Deposition: a material and dilution investigation

2021 ◽  
Vol 1135 (1) ◽  
pp. 012001
Author(s):  
Adrien Da Silva ◽  
Keivan Amiri Kasvayee ◽  
Jan Frostevarg ◽  
Jan Zachrisson ◽  
Alexander F.H. Kaplan
Keyword(s):  
Additive Manufacturing ◽  
Cross Sections ◽  
Material Properties ◽  
Material Characterization ◽  
Power Efficiency ◽  
Power Input ◽  
Metal Wire ◽  
Inconel 625 ◽  
Advantages And Disadvantages ◽  
Manufacturing Techniques

Abstract Additive Manufacturing has become a field of high interest in the industry, mostly due to its strong freedom of design and its flexibility. Numerous Additive Manufacturing techniques exist and present different advantages and disadvantages. The technique investigated in this research is a drop-by-drop deposition alternative to Laser Metal Wire Deposition. This technique is expected to induce a better control over the power input in the material, resulting in a better power efficiency and tailorable material properties. The aim of this research is to investigate selected material properties of the structures produced with the drop-by-drop deposition technique. Multi-drops structures were deposited from 316L, Inconel 625 (NW6625) and AlSi5 (AW4043) wires. Two drop deposition methods were investigated: (i) a contactless recoil pressure driven detachment for 316L and Inconel 625, (ii) a contact-based surface tension driven detachment for AlSi5. A material characterization including optical microscopy, EDS and hardness measurements was performed in transverse and longitudinal cross-sections. The microstructure of the deposited material, the dilution with the substrate and the heat affected zone were analysed. The contactless detachment showed a higher dilution than the contact-based technique due to the laser irradiating the substrate between two drop detachments, which melts the substrate that then mixes with the deposited drops.

Product Family Redesign Using Additive Manufacturing

2018 ◽  
Author(s):  
Sangjin Jung ◽  
Timothy W. Simpson
Keyword(s):  
Additive Manufacturing ◽  
Product Family ◽  
Integrated Approach ◽  
Design Structure Matrix ◽  
Platform Architecture ◽  
Design Structure ◽  
Market Requirements ◽  
Different Types ◽  
The Impact

In this study we investigate how we can effectively redesign a product family using additive manufacturing (AM). Specifically, we propose an integrated approach to product family redesign using platform metrics for a product family that uses AM. The proposed approach can help identify what to platform and how to platform with AM. We employ a variety metric to measure the amount of redesign for each component, a commonality metric to capture different types of commonality, and Design Structure Matrix (DSM) to analyze a platform architecture. After integrating these metrics, we can optimize balancing the tradeoffs between commonality and differentiation of components. Components that offer little variety for the market can be made common and part of the platform while components that must be varied to achieve market requirements should not be platformed and may be easily customized with AM. In order to facilitate customization of AM components, we can evaluate redesign of platform interfaces to help embed flexibility and modularity into the product family. To investigate the impact of the integrated approach, we apply the proposed approach to a family of Unmanned Aerial Vehicles (UAVs) as a case study. The results show the proposed approach can be effectively employed to identify ways to redesign the UAV family to improve the balance of commonality and variety of future product offerings.

scholarly journals Design and manufacturing of shin pads with multi-material additive manufactured features for football players: A comparison with commercial shin pads

2018 ◽  
Vol 233 (1) ◽  
pp. 160-169 ◽  
Author(s):  
Aitor Cazón-Martín ◽  
Macarena Iturrizaga-Campelo ◽  
Luis Matey-Muñoz ◽  
María Isabel Rodríguez-Ferradas ◽  
Paz Morer-Camo ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Football Players ◽  
Novel Approach ◽  
Transmitted Force ◽  
Design And Manufacturing ◽  
Impact Acceleration ◽  
Manufacturing Techniques ◽  
Traditional Manufacturing ◽  
Design And Manufacture ◽  
The Impact

Shin pads are part of the mandatory equipment footballers must wear so as to prevent lesions. Most players wear commercially available shin pads made from a variety of common materials (polypropylene or polyethylene) and high-resistance materials (glass fibre, carbon fibre or Kevlar) using traditional manufacturing techniques. Additive manufacturing was used years ago to deliver customised rigid shin pads, but they did not offer any significant advantage in terms of materials or design compared to traditional shin pads. This project analyses a novel approach to the design and manufacture of shin pads for football players that combines existing digitisation tools, lattice structures and a multi-material additive manufacturing device. A total of 24 different additive manufacturing geometries were evaluated using a customised rig where a 1-kg impactor was released from several heights (100–400 mm). The impact acceleration, the transmitted force to the leg and penetration were calculated. Results were compared against two commercially available shin pads. Results show that two of the additive manufacturing specimens tested at the highest drop height had lower impact accelerations than commercial shin pads. They had an acceleration reduction between 42% and 68% with respect to the commercial shin pads. Regarding the penetration, the improvement achieved with additive manufacturing specimens ranged from 13% to 32%, while the attenuation and the contact times were similar.

Quota Women Are Threatening to Men

2017 ◽  
Vol 76 (3) ◽  
pp. 107-116 ◽  
Author(s):  
Klea Faniko ◽  
Till Burckhardt ◽  
Oriane Sarrasin ◽  
Fabio Lorenzi-Cioldi ◽  
Siri Øyslebø Sørensen ◽  
...  
Keyword(s):  
Decision Making ◽  
Organizational Performance ◽  
Gender Stereotypes ◽  
Perceived Threat ◽  
Preferential Treatment ◽  
Public Sector Employees ◽  
Different Types ◽  
Low Levels ◽  
Women In Decision Making ◽  
The Impact

Abstract. Two studies carried out among Albanian public-sector employees examined the impact of different types of affirmative action policies (AAPs) on (counter)stereotypical perceptions of women in decision-making positions. Study 1 (N = 178) revealed that participants – especially women – perceived women in decision-making positions as more masculine (i.e., agentic) than feminine (i.e., communal). Study 2 (N = 239) showed that different types of AA had different effects on the attribution of gender stereotypes to AAP beneficiaries: Women benefiting from a quota policy were perceived as being more communal than agentic, while those benefiting from weak preferential treatment were perceived as being more agentic than communal. Furthermore, we examined how the belief that AAPs threaten men’s access to decision-making positions influenced the attribution of these traits to AAP beneficiaries. The results showed that men who reported high levels of perceived threat, as compared to men who reported low levels of perceived threat, attributed more communal than agentic traits to the beneficiaries of quotas. These findings suggest that AAPs may have created a backlash against its beneficiaries by emphasizing gender-stereotypical or counterstereotypical traits. Thus, the framing of AAPs, for instance, as a matter of enhancing organizational performance, in the process of policy making and implementation, may be a crucial tool to countering potential backlash.

Methods for Restricting Maximum Exposure Rate in Computerized Adaptative Testing

Methodology ◽  
2007 ◽  
Vol 3 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Juan Ramon Barrada ◽  
Julio Olea ◽  
Vicente Ponsoda
Keyword(s):  
Measurement Accuracy ◽  
Computerized Adaptive Testing ◽  
Computation Time ◽  
Adaptive Testing ◽  
Exposure Rate ◽  
Control Parameters ◽  
The Impact ◽  
Two Alternatives ◽  
Selection Of ◽  
Maximum Exposure

Abstract. The Sympson-Hetter (1985) method provides a means of controlling maximum exposure rate of items in Computerized Adaptive Testing. Through a series of simulations, control parameters are set that mark the probability of administration of an item on being selected. This method presents two main problems: it requires a long computation time for calculating the parameters and the maximum exposure rate is slightly above the fixed limit. Van der Linden (2003) presented two alternatives which appear to solve both of the problems. The impact of these methods in the measurement accuracy has not been tested yet. We show how these methods over-restrict the exposure of some highly discriminating items and, thus, the accuracy is decreased. It also shown that, when the desired maximum exposure rate is near the minimum possible value, these methods offer an empirical maximum exposure rate clearly above the goal. A new method, based on the initial estimation of the probability of administration and the probability of selection of the items with the restricted method ( Revuelta & Ponsoda, 1998 ), is presented in this paper. It can be used with the Sympson-Hetter method and with the two van der Linden's methods. This option, when used with Sympson-Hetter, speeds the convergence of the control parameters without decreasing the accuracy.

Status, Impact, and Factor Determining Rural Non-farm Economy of India: A Review

2020 ◽  
pp. 68-76
Keyword(s):  
Rural Areas ◽  
Present Status ◽  
Economic Activity ◽  
Rural Livelihoods ◽  
Pivotal Role ◽  
Inclusive Development ◽  
Farm Sector ◽  
Income Inequalities ◽  
Review Study ◽  
The Impact

The rural non-farm sector (RNFS) involves a spectrum of economic activity in rural areas and encompasses all rural productive entities other than farm holdings. It has the potential to play a pivotal role in holistic and inclusive development of India’s rural areas by increasing the employment and wages of rural labour, which can reduce income inequalities. The review was carried out in order to explain the present status of RNFE state wise as well as overall to get a comprehensive view on the topic. The review study also focuses to disaggregate RNFE on the basis of gender, size of landholding and castes. Literature depicting the impact of RNFE on rural livelihoods especially in employment and poverty and factors determining it also been compiled to get an overall idea on the study.

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