scholarly journals Three-Dimensional Printed PLA and PLA/PHA Dumbbell-Shaped Specimens: Material Defects and Their Impact on Degradation Behavior

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2005 ◽  
Author(s):  
Joanna Rydz ◽  
Jakub Włodarczyk ◽  
Jennifer Gonzalez Ausejo ◽  
Marta Musioł ◽  
Wanda Sikorska ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Hydrolytic Degradation ◽  
Processing Parameters ◽  
Polymer Materials ◽  
Original Research ◽  
Polymer Properties ◽  
Subsequent Behavior ◽  
And Behavior ◽  
The Impact ◽  
Printing Direction

The use of (bio)degradable polymers, especially in medical applications, requires a proper understanding of their properties and behavior in various environments. Structural elements made of such polymers may be exposed to changing environmental conditions, which may cause defects. That is why it is so important to determine the effect of processing conditions on polymer properties and also their subsequent behavior during degradation. This paper presents original research on a specimen’s damage during 70 days of hydrolytic degradation. During a standard hydrolytic degradation study of polylactide and polylactide/polyhydroxyalkanoate dumbbell-shaped specimens obtained by 3D printing with two different processing build directions, exhibited unexpected shrinkage phenomena in the last degradation series, representing approximately 50% of the length of the specimens irrespective of the printing direction. Therefore, the continuation of previous ex-ante research of advanced polymer materials is presented to identify any possible defects before they arise and to minimize the potential failures of novel polymer products during their use and also during degradation. Studies on the impact of a specific processing method, i.e., processing parameters and conditions, on the properties expressed in molar mass and thermal properties changes of specimens obtained by three-dimensional printing from polyester-based filaments, and in particular on the occurrence of unexpected shrinkage phenomena after post-processing heat treatment, are presented.

scholarly journals Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Hamid Ait Said ◽  
Hassan Noukrati ◽  
Hicham Ben Youcef ◽  
Ayoub Bayoussef ◽  
Hassane Oudadesse ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Compressive Strength ◽  
Mechanical Strength ◽  
Bone Repair ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Composite Effect ◽  
Solid Liquid ◽  
The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

scholarly journals Forensic Engineering of Advanced Polymeric Materials—Part VII: Degradation of Biopolymer Welded Joints

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1167
Author(s):  
W. Sikorska ◽  
M. Zięba ◽  
M. Musioł ◽  
M. Kowalczuk ◽  
H. Janeczek ◽  
...  
Keyword(s):  
Degradation Products ◽  
Bond Cleavage ◽  
Hydrolytic Degradation ◽  
Welding Process ◽  
Polymeric Materials ◽  
Polymer Materials ◽  
Scanning Calorimetry ◽  
Forensic Engineering ◽  
The Impact ◽  
Welding Processes

Welding technology may be considered as a promising processing method for the formation of packaging products from biopolymers. However, the welding processes used can change the properties of the polymer materials, especially in the region of the weld. In this contribution, the impact of the welding process on the structure and properties of biopolymer welds and their ability to undergo hydrolytic degradation will be discussed. Samples for the study were made from polylactide (PLA) and poly(3-hydroxyalkanoate) (PHA) biopolymers which were welded using two methods: ultrasonic and heated tool welding. Differential scanning calorimetry (DSC) analysis showed slight changes in the thermal properties of the samples resulting from the processing and welding method used. The results of hydrolytic degradation indicated that welds of selected biopolymers started to degrade faster than unwelded parts of the samples. The structure of degradation products at the molecular level was confirmed using mass spectrometry. It was found that hydrolysis of the PLA and PHA welds occurs via the random ester bond cleavage and leads to the formation of PLA and PHA oligomers terminated by hydroxyl and carboxyl end groups, similarly to as previously observed for unwelded PLA and PHA-based materials.

APPLICATION OF ELASTIC MATERIALS IN PROTECTION FROM STRONG IMPACTS

2004 ◽  
Vol 18 (14) ◽  
pp. 1977-1990
Author(s):  
MASKOVIC D. LJILJANA ◽  
MOHORA EMILIJAN ◽  
TOSIC S. BRATISLAV ◽  
VUJOVIC R. RATKO
Keyword(s):  
Elastic Material ◽  
Short Pulse ◽  
Three Dimensional ◽  
Polymer Materials ◽  
Elastic Materials ◽  
One Dimensional ◽  
Spherical Surfaces ◽  
The Impact ◽  
Theoretical Results ◽  
Good Agreement

The analysis of the behavior of elastic material subject to strong short pulse impact has shown that only one-dimensional structures support the impact without destruction. Compact two- and three-dimensional structures are destroyed during the impact along circular lines and spherical surfaces. For that reason, web-like shields are proposed for the protection of man and equipment. Polymer materials are most suitable for the production of web-like shields since they are made of fibers and highly stress resistant. Theoretical results are experimentally tested and the good agreement with theory was found.

scholarly journals MAP-IT: A Practical Tool for Planning Complex Behavior Modification Interventions

2017 ◽  
Vol 18 (5) ◽  
pp. 696-705 ◽  
Author(s):  
Sylvia Hansen ◽  
Martina Kanning ◽  
Romy Lauer ◽  
Jürgen M. Steinacker ◽  
Wolfgang Schlicht
Keyword(s):  
Complex Interventions ◽  
Noncommunicable Diseases ◽  
Original Research ◽  
Evidence Based ◽  
Time Saving ◽  
Effective Interventions ◽  
The Matrix ◽  
And Behavior ◽  
Multicomponent Interventions ◽  
The Impact

Health research often aims to prevent noncommunicable diseases and to improve individual and public health by discovering intervention strategies that are effective in changing behavior and/or environments that are detrimental to one’s health. Ideally, findings from original research support practitioners in planning and implementing effective interventions. Unfortunately, interventions often fail to overcome the translational block between science and practice. They often ignore theoretical knowledge, overlook empirical evidence, and underrate the impact of the environment. Accordingly, sustainable changes in individual behavior and/or the environment are difficult to achieve. Developing theory-driven and evidence-based interventions in the real world is a complex task. Existing implementation frameworks and theories often do not meet the needs of health practitioners. The purpose of this article is to synthesize existing frameworks and to provide a tool, the Matrix Assisting Practitioner’s Intervention Planning Tool (MAP-IT), that links research to practice and helps practitioners to design multicomponent interventions. In this article, we use physical activity of older adults as an example to explain the rationale of MAP-IT. In MAP-IT, individual as well as environmental mechanisms are listed and behavior change techniques are linked to these mechanisms and to intervention components. MAP-IT is theory-driven and evidence-based. It is time-saving and helpful for practitioners when planning complex interventions.

Multi-Layer Computational Modeling of Selective Laser Sintering Processes

2014 ◽  
Author(s):  
Daniel Moser ◽  
Scott Fish ◽  
Joseph Beaman ◽  
Jayathi Murthy
Keyword(s):  
Selective Laser Sintering ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Laser Sintering ◽  
Incomplete Fusion ◽  
Temperature History ◽  
Powder Layer ◽  
Large Temperature ◽  
Powder Bed ◽  
The Impact

Selective laser sintering (SLS) is an additive manufacturing technique able to rapidly create parts directly from a CAD model using a laser to selectively fuse successive layers of powder. However, defects can arise in SLS parts due to incomplete fusion of the powder layers or thermal stresses introduced by large temperature gradients during the part build. Accurate models of the SLS process are needed to ensure that high quality parts are produced and to allow new materials and designs to be used without requiring extensive experimentation. Most existing models of the SLS process are very narrowly focused, predicting the temperature history of a single powder layer after a single laser pass or examining the impact of a few processing parameters on the properties of the produced part. A model capable of predicting a complete temperature history during an entire part build does not yet exist. Therefore, a new thermal model able to simulate multiple powder layers is proposed. A transient, three-dimensional, finite volume model is developed and implemented in ANSYS Fluent. A domain of cells representing multiple layers of an SLS build is initialized, some with the properties of air and some with the properties of powder, depending on cell location. A Gaussian heat source representing the laser is applied to the top layer of powder cells. The center of the Gaussian is varied with time along an established path to simulate the motion of the laser along the powder bed. At all times the three-dimensional heat equation is solved to produce a temperature profile of the powder bed. When the laser completes a full scan of the powder layer, the air cells directly above the powder layer are re-initialized as powder cells and re-set to an initial temperature, representing the addition of a new powder layer. The process is repeated for each new layer. Temperature history results from the model are validated against experimental data available in the literature and good agreement is obtained. As the model accounts for multiple powder layers, it can be used to simulate an entire part build and predict the impact of any of the SLS processing parameters on part quality and thus enable better control and optimization of the SLS process.

The Impact of COVID-19 Quarantine on Children‘s Behaviors and Language

2020 ◽  
Vol 11 (SPL1) ◽  
pp. 796-806
Author(s):  
Sana M Kamal ◽  
Ali Al-Samydai ◽  
Rudaina Othman Yousif ◽  
Talal Aburjai
Keyword(s):  
Social Relations ◽  
Child Psychology ◽  
Simple Random Sample ◽  
Community Pharmacies ◽  
The World ◽  
Female Children ◽  
And Behavior ◽  
The Impact ◽  
Pharmaceutical Interventions

COVID-19 pandemic has spread across the world, which considered a relative of the severe acute respiratory syndrome (SARS), with possibility of transmission from animals to human and effect each of health and economic. Several preventative strategies and non-pharmaceutical interventions have been used to slow down the spread of COVID-19. The questionnaire contained 36 questions regarding the impact of COVID-19 quarantine on children`s behaviors and language have been distributed online (Google form). Data collected after asking parents about their children behavior during quarantine, among the survey completers (n=469), 42.3% were female children, and 57.7 were male children. Results showed that quarantine has an impact on children`s behaviors and language, where stress and isolationism has a higher effect, while social relations had no impact. The majority of the respondents (75.0%) had confidence that community pharmacies can play an important role in helping families in protection their children`s behaviors and language as they made the highest contact with pharmacists during quarantine. One of the main recommendations that could be applied to help parents protection and improvement their children`s behaviors and language in quarantine condition base on simple random sample opinion is increasing the role of community pharmacies inpatient counseling and especially towards children after giving courses to pharmacists in child psychology and behavior. This could be helpful to family to protect their children, from any changing in them behaviors and language in such conditions in the future if the world reface such the same problem.

THE IMPACT OF "PUBLIC CULTURE" ON YOUTH SPIRITUALITY

2020 ◽  
Vol 3 (1) ◽  
pp. 130-135
Author(s):  
Mukhiddin Tursunmuratov ◽  
Keyword(s):  
Popular Culture ◽  
Young People ◽  
Public Culture ◽  
And Behavior ◽  
The Impact

This article provides a detailed description and explanation of the term "popular culture". It also analyzes a number of aspects of "popular culture" that are becoming more widespread today, their role and influence in the formation of the minds and behavior of young people, and draws the necessary conclusions. Most importantly, it also describes ways to protect young people from threats in the form of "popular culture" that negatively affect their morale.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

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