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Journal articles on the topic "Free-to-pla"
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da Rocha Lindner, Gabriela, Najeh Maissar Khalil, and Rubiana Mara Mainardes. "Resveratrol-Loaded Polymeric Nanoparticles: Validation of an HPLC-PDA Method to Determine the Drug Entrapment and Evaluation of Its Antioxidant Activity." Scientific World Journal 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/506083.
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Poly(lactic acid) (PLA) and PLA-poly(ethylene glycol) (PLA-PEG) nanoparticles containing resveratrol (RVT) were developed, and their antioxidant activity was evaluated. An analytical method using high performance liquid chromatography (HPLC)/photodiode array (PDA) detection was also developed and validated for RVT determination in nanoparticles. The mobile phase consisted of methanol : water (51 : 49, v/v) flowed at 0.9 mL/min, and the PDA detector was set at wavelength of 306 nm. The mean diameter of the nanoparticles varied between 180 and 220 nm, and the encapsulation efficiency of RVT ranged from 60% to 88%. The nanoparticles containing RVT were evaluated for their ability to scavenge the radical (2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) (ABTS•+). The profile obtained from the PLA nanoparticles containing RVT demonstrated that after 24 h, there was almost no increase in antioxidant activity, which was lower than that of the free RVT and RVT-loaded PLA-PEG nanoparticles. For PLA-PEG nanoparticles, the radical-scavenging activity of RVT was shown to increase with time, and after 48 h, it was similar to that observed with free RVT.
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Dunaj, Paweł, Stefan Berczyński, Karol Miądlicki, Izabela Irska, and Beata Niesterowicz. "Increasing Damping of Thin-Walled Structures Using Additively Manufactured Vibration Eliminators." Materials 13, no. 9 (May 3, 2020): 2125. http://dx.doi.org/10.3390/ma13092125.
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The paper presents a new way to conduct passive elimination of vibrations consisting of covering elements of structures with low dynamic stiffness with polylactide (PLA). The PLA cover was created in 3D printing technology. The PLA cover was connected with the structure by means of a press connection. Appropriate arrangement of the PLA cover allows us to significantly increase the dissipation properties of the structure. The paper presents parametric analyses of the influence of the thickness of the cover and its distribution on the increase of the dissipation properties of the structure. Both analyses were carried out using finite element models (FEM). The effectiveness of the proposed method of increasing damping and the accuracy of the developed FEM models was verified by experimental studies. As a result, it has been proven that the developed FEM model of a free-free steel beam covered with polylactide enables the mapping of resonance frequencies at a level not exceeding 0.6% of relative error. Therefore, on its basis, it is possible to determine the parameters of the PLA cover. Comparing a free-free steel beam without cover with its PLA-covered counterpart, a reduction in the amplitude levels of the receptance function was achieved by up to 90%. The solution was validated for a steel frame for which a 37% decrease in the amplitude of the receptance function was obtained.
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Li, Fenfen, Caili Zhang, Yunxuan Weng, Xiaoqian Diao, Yingxin Zhou, and Xinyu Song. "Enhancement of Gas Barrier Properties of Graphene Oxide/Poly (Lactic Acid) Films Using a Solvent-free Method." Materials 13, no. 13 (July 6, 2020): 3024. http://dx.doi.org/10.3390/ma13133024.
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Graphene oxide(GO)/polylactic acid (PLA) nanocomposite, prepared using a solvent-free melt mixing processing, is investigated as a potential oxygen barrier packaging film in this work. In order to disperse GO homogeneously in PLA matrix, hydrophobic silane coupling agent, i.e., γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), is used to modify the graphene oxide sheets. The modified GO is able to be well bonded to the PLA due to the formation of covalent bonds between the epoxy groups of KH560 and the carboxyl and hydroxyl terminal groups of PLA. Furthermore, the thermal stability of GO is enhanced due to the long alkyl side chain of KH560, which could also increase the crystallinity of PLA. As a result, the crystallinity of PLA is significantly improved because of the linear KH560 chains, which can act as nucleating agents to improve the crystallization. The KH560-GO helps to reduce the O2 permeability of KH560-GO/PLA composite films via a dual-action mechanism: (1) providing physical barrier due to their native barrier properties, and (2) by resulting in higher degree of crystallinity. The as-prepared KH560-GO0.75/PLA is able to exhibit ca. 33% and ca. 13% decrease in the PO2 than the neat PLA and GO0.75/PLA film, respectively. Finally, the mechanical properties and impact fractured surfaces indicate that the increase in the tensile strength and elongation at break value of KH560-GO/PLA are due to the strong interfacial adhesion and the strong bonding between the epoxy group of KH560-GO and hydroxyl and carboxyl acid terminal groups of PLA matrix.
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Mohammad, Nor Nisa Balqis, Agus Arsad, Abdul Razak Rahmat, Mohammad Shukor Talib, and Mohd Shaiful Zaidi Mat Desa. "Influence of Compatibilizer on Mechanical Properties of Polylactic Acid/Natural Rubber Blends." Applied Mechanics and Materials 554 (June 2014): 81–85. http://dx.doi.org/10.4028/www.scientific.net/amm.554.81.
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Derived from renewable resources, Poly (lactic) acid (PLA) exhibits good mechanical properties comparable with conventional polyolefins. However, major obstacle in PLA which may limit its application is due to brittleness. Thus, PLA requires toughening to overcome the weakness. In this study, PLA was blended with different ratio of natural rubber (0 to 20 wt.%) through melt blending in a twin screw extruder. The results of tensile strength and Young’s modulus of PLA/NR blends were decreased. In order to enhance the blend performance, PLA grafted maleic anhydride (PLA-g-MA) was used as compatibilizer. The preparation of PLA-g-MA was carried out using internal mixer by free radical melt grafting reaction followed by Fourier Transform Infrared Spectroscopy (FTIR) analysis to confirm the grafting reaction. To investigate the compatibilization effect on the mechanical properties of PLA/NR blends, PLA-g-MA was added to the blends at various compositions (1 – 10 phr). Mechanical properties increased markedly compared to the virgin PLA/NR blends and FTIR result confirmed grafting reaction occurred between MA and PLA.
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Chitrattha, Sasiprapa, and Thawatchai Phaechamud. "Modifying Poly(L-Lactic Acid) Matrix Film Properties with High Loaded Poly(Ethylene Glycol)." Key Engineering Materials 545 (March 2013): 57–62. http://dx.doi.org/10.4028/www.scientific.net/kem.545.57.
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Poly(L-lactic acid) (PLA) is a biodegradable and bioabsorbable polymer which has many potential uses. However, PLA shows the poor toughness, slow degradation rate and relatively hydrophobic.Poly(ethylene glycol) (PEG) is widely used as a plasticizer and of great interest because it presents outstanding properties, e.g. solubility in water and also in some organic solvents, lack of toxicity and absence of antigenicity and immunogenicity, which are essential for biomedical applications. The aim of this study was to investigate the ability of high amount PEG 400 to improve the characteristics of PLA matrix film. PLA matrix films were prepared using a solvent casting method and their various properties were investigated. Mechanical properties were determined with texture analyzer. Contact angle and surface free energy were measured using the goniometer. From the mechanical properties evaluated (tensile strength (TS) and elongation at break (E)), all plasticized PLA films exhibited the softer behavior and the plasticized PLA films with150 % PEG 400 indicated the higher % elongation at break than pure PLA, significantly. The contact angle and surface free energy values indicated that PEG 400 could improve the wettability of solventsand also increase % water sorption and % weight loss with as dose dependent.Surprisingly, SEM photographs revealed more porous structure as the higher amount PEG 400 was incorporated in PLA film. This porous structure and density of developed plasticized PLA film could be modified with temperature change technique. Parameters affecting the 3-D porous plasticized PLA matrix were revealed in this study. The optimum condition for producing the continuous 3-D porous plasticized PLA matrix was obtained. This porous topography in PLA matrix film will be applied further as material in tissue engineering and drug delivery systems.
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Chitrattha, Sasiprapa, and Thawatchai Phaechamud. "Film Properties of Poly(lactic Acid) Comprising N-Methyl-2-Pyrrolidone." Advanced Materials Research 528 (June 2012): 140–43. http://dx.doi.org/10.4028/www.scientific.net/amr.528.140.
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Poly (lactic acid) (PLA) has many potential uses, for example as packaging, textiles, biomedical fields, including suture, bone fixation material, drug delivery microsphere, and tissue engineering. However, PLA shows the poor toughness, slow degradation rate and relatively hydrophobic. The aim of this study was to investigate the ability of N-methyl-2-pyrrolidone (NMP) to improve the characteristics of PLA film. PLA films were prepared using a solvent casting method and their various properties were investigated. From tensile strength (TS), elongation at break (E) and young’s modulus (ε) determinations, the incorporated PLA films exhibited the softer behavior than plain PLA film. On the other hand, from the contact angle and surface free energy values, the PLA films incorporated with NMP could improve the wettability of solvents and also increased % water sorption (WS) and % weight loss (WL) than PLA films with NMP dose dependent. However SEM photographs revealed the more rather rough and cracked surface as the higher amount of NMP was incorporated in PLA film.
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Tateishi, Ikki, Mai Furukawa, Hideyuki Katsumata, and Satoshi Kaneco. "Development of Heavy Metal-Free Photocatalytic RhB Decomposition System Using a Biodegradable Plastic Substrate." ChemEngineering 5, no. 1 (March 3, 2021): 11. http://dx.doi.org/10.3390/chemengineering5010011.
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The heavy-metal-free photocatalytic system, in which carbon nitride is coated on polylactic acid (PLA) as biodegradable plastic through a simple dip coating method, was used for dye decomposition under visible light irradiation. Solvent selection, solvent concentration, and the number of coatings for dip coating were investigated to optimize the conditions for loading carbon nitride on PLA. Carbon nitride cannot be coated on PLA in water, but it can be strongly coated by decomposing the surface of PLA with ethanol or chlorobenzene to promote physical adsorption and activate surface. The number of dip coatings also affected the photocatalytic decomposition ability. The photocatalytic system was able to decompose the dye continuously in the flow method, and dye (rhodamine B) was decomposed by about 50% at a residence time of 12 min (flow rate 0.350 mL/min) for 30 h.
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Miao, Junming, Feng Lin, Ning Huang, and Yan Teng. "Improving Anti-Inflammatory Effect of Luteolin with Nano-Micelles in the Bacteria-Induced Lung Infection." Journal of Biomedical Nanotechnology 17, no. 6 (June 1, 2021): 1229–41. http://dx.doi.org/10.1166/jbn.2021.3101.
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The effective therapy for lung infectious diseases became more and more difficult since the severe antibiotic resistance of pathogenic microorganisms, it is urgent to develop new antimicrobial agents. Luteolin has been reported to play a crucial part in host immune responses. However, the clinical use of luteolin is impeded due to its hydrophobicity and low oral bioavailability. In this study, we formulated luteolin-loaded Methoxy poly(ethylene glycol)-poly(lactide) micelles (luteolin/MPEG-PLA), to improve the bioavailability of luteolin in lung infectious diseases. The results showed that luteolin/MPEG-PLA treatment could reduce the adhesion of Klebsiella pneumoniae (K. pneumoniae) to lung epithelial cells and enhance the germicidal ability of macrophages against K. pneumoniae compared to untreated group. Meanwhile, luteolin/MPEG-PLA showed stronger adhesion resistance of epithelial cells and germicidal ability of macrophages compared with free luteolin. In vivo study, luteolin/MPEG-PLA administration significantly promoted the clearance of bacteria and reduced inflammatory infiltration of lung tissue in K. pneumoniae induced lung infectious mice model. Further studies showed that treatment with luteolin/MPEG-PLA reduced the mRNA expression of LPS-induced inflammatory cytokines and chemokines in macrophages significantly. In general, luteolin/MPEG-PLA can enhance the anti-bacterial ability of lung epithelial cells and macrophages, and has a stronger therapeutic effect than free luteolin in bacterial-induced lung infection. Luteolin/MPEG-PLA may be an excellent potential drug for bacterial-induced lung infectious diseases treatment.
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Vadas, Dániel, Dávid Kmetykó, György Marosi, and Katalin Bocz. "Application of Melt-Blown Poly(lactic acid) Fibres in Self-Reinforced Composites." Polymers 10, no. 7 (July 12, 2018): 766. http://dx.doi.org/10.3390/polym10070766.
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The aim of our research was to produce poly(lactic acid) (PLA) fibres with diameters in the micrometer size range, serving as the reinforcing phase in self-reinforced (SR) PLA composites. Nonwoven PLA mats were manufactured by solvent-free melt-blowing technology. Three types of PLA differing in d-lactide content were processed with a productivity as high as 36 g/h. The crystallinity of the PLA microfibres was enhanced by thermal annealing. A 2–3-fold increase in the degree of crystallinity was obtained, as measured by differential scanning calorimetry (DSC). Fibre diameters between 2–14 µm were revealed by scanning electron microscopy (SEM). Static tensile tests were performed on the nonwoven mats, showing the reduced moduli of the annealed fibres due the amorphous relaxation. The PLA mats were processed via the hot compaction technique and formed into SR–PLA composites. The morphological and mechanical properties of the obtained microstructural composites were comprehensively studied. Composites prepared from annealed, thermally more stable PLA nonwoven mats showed superior mechanical properties; the tensile strength improved by 47% due to the higher residual fibre content.
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Chang, Jing, Zhe Yang, Junfeng Li, Yufen Jin, Yihang Gao, Yanwen Sun, Hainan Li, and Ting Yu. "Preparation and In Vitro and In Vivo Antitumor Effects of VEGF Targeting Micelles." Technology in Cancer Research & Treatment 19 (January 1, 2020): 153303382095702. http://dx.doi.org/10.1177/1533033820957022.
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Background: Doxorubicin (DOX) has antitumor effects mediated by cell viability inhibition and by inducing cellular apoptosis. However, it has limited use in clinical applications due to various factors such as hydrophobicity, dose-dependent toxicity effects on normal tissues, short cycle retention time, and low targeting ability. This study aims at enhancing hydrophilicity of DOX to restrict its toxic effects to within or around the tumor sites and also to improve its targeting ability to enhance antitumor efficiency. Methods: Micelles composed of biodegradable poly (ethylene glycol)-poly (lactic acid) copolymers (PEG-PLA) were employed to deliver DOX via a self-assembly method and were coupled to VEGF antibodies. The morphology, size, and physical stability of PEG-PLA-DOX targeting VEGF micelles (VEGF-PEG-PLA-DOX micelles) were assessed. Then, the release ability of DOX from these micelles was monitored, and their drug loading capacity was calculated. MTT assay revealed the in vitro antitumor effect of VEGF-PEG-PLA-DOX micelles. Moreover, ROS release was measured to evaluate apoptotic effects of these nanoparticle micelles. In vivo therapeutic efficiencies of VEGF-PEG-PLA-DOX micelles on a lung cancer nude mouse model was evaluated. Results: DOX-loaded micelles were obtained with a drug loading capacity of 12.2% and were monodisperse with 220 nm average diameter and a controlled in vitro DOX release for extended periods. In addition, VEGF-PEG-PLA-DOX micelles displayed a larger cell viability inhibitory effect as measured via MTT assays and greater cell apoptosis induction through in vitro ROS levels compared with PEG-PLA-DOX micelles or free DOX. Furthermore, VEGF-PEG-PLA-DOX micelles could improve in vivo antitumor effects of DOX by reducing tumor volume and weight. Conclusions: VEGF-PEG-PLA-DOX micelles displayed a larger anti-tumor effect both in in vitro A549 cells and in an in vivo lung cancer nude mouse model compared with PEG-PLA-DOX micelles or free DOX, and hence they have potential clinical applications in human lung cancer therapy.
Dissertations / Theses on the topic "Free-to-pla"
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OLIVEIRA, Ruy Guilherme Silva Gomes de. "Aplicação de Meta-modelos à Monetização de Jogos Free-to-Play." Universidade Federal do Maranhão, 2017. http://tedebc.ufma.br:8080/jspui/handle/tede/1325.
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The recent emergence of Free-to-Play games, also known as Freemium games, has considerably changed the way games are made. The definition of monetization strategies is now part of the process of making games. Choosing which strategy to adopt among the various ones and understanding how they work could be an arduous task. When analysing the market, to realize that popular games use similar strategies is not difficult, which demonstrates that the reuse of strategies is common among developers. Although there are catalogs of popular monetization strategies used by Free-to-Play games in the literature, little attention has been given to formalize the description of those strategies, leaving openings for misunderstandings and making the reuse harder. For that reason, a meta-model of Free-to-Play games monetization that allows the representation of Free-toPlay games monetization strategies based on a set of popular strategies is proposed. That meta-model, called Meta-F2P, was elaborated from the investigation of the most rentable Free-to-Play games for mobile devices. Besides that, case studies were used to validate and refine the accuracy, expressiveness and extensibility of that meta-model. Based on the results obtained, the applicability of the meta-model in the process of making games and the advantages and disadvantages of the use of case studies in the concept of meta-models are analyzed.
A recente ascensão dos jogos Free-to-Play, também conhecidos como Freemium, provocou mudanças consideráveis na forma como os jogos são produzidos. A elaboração de estratégias de monetização passou a fazer parte do processo de desenvolvimento. Escolher qual estratégias adotar dentre as diversas existentes e entender o seu funcionamento pode tornar esta uma tarefa árdua. Ao se analisar o mercado não é difícil perceber que os jogos mais rentáveis abordam estratégias de monetização similares, demonstrando que reuso de estratégias é uma abordagem adotada por diversos desenvolvedores. Embora existam na literatura catálogos de estratégias de monetização populares em jogos Free-to-Play, pouca atenção tem sido dada no intuito de formalizar a descrição das estratégias, dando margem para interpretações errôneas e dificultando o reuso. Assim propõe-se um meta-modelo que permite representar as estratégias de monetização de jogos Free-to-Play a partir de um conjunto de estratégias populares. O meta-modelo denominado Meta-F2P foi elaborado a partir da análise de jogos Free-to-Play para dispositivos móveis mais rentáveis. Além disso, utilizou-se estudos de caso para a validação e o refinamento da exatidão, expressividade e extensibilidade do meta-modelo. A partir dos resultados obtidos analisa-se a aplicabilidade do meta-modelo no processo de design de jogos e as vantagens e desvantagens da aplicação de estudos de caso na elaboração de meta-modelos.
Conference papers on the topic "Free-to-pla"
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Wang, Xiaoxi, Wei Li, and Vipin Kumar. "Solvent Free Fabrication of Biodegradable Porous Polymers." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59553.
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Biodegradable porous polymers with interconnected pores of sub-micrometers to a few hundred micrometers find many applications in emerging technology areas such as tissue engineering, controlled drug delivery, and biochemical sensors. However, most of the current fabrication processes involve organic solvents and chemical blowing agents that may cause environmental concerns and leave residues harmful to biological cells. This paper presents a solvent free fabrication approach for biodegradable porous polymers. Ultrasound cavitation is introduced after the solid state foaming process to produce open cell structures. The material used in this study is polylactic acid (PLA). It belongs to a family of biodegradable polymers that can be used for tissue engineering scaffolds. In order to identify suitable conditions to apply ultrasound, a saturation and foaming study is conducted for the PLA-CO2 gas polymer system. The effects of various process variables are discussed.
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Mahmoud, Abdelrahman, Mohammed Naser, Mahmoud Abdelrasool, Khalid Jama, Mohamed Hussein, Asma Abdulkareem, Peter Kasak, and Anton Popelka. "Development of PLA Fibers as an Antimicrobial Agent with Enhanced Infection Resistance using Electrospinning/Plasma Technology." In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0079.
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Humans are vulnerable and easily prone to all kind of injuries, diseases, and traumas that can be damaging to their tissues (including its building unit, cells), bones, or even organs. Therefore, they would need assistance in healing or re-growing once again. Medical scaffolds have emerged over the past decades as one of the most important concepts in the tissue-engineering field as they enable and aide the re-growth of tissues and their successors. An optimal medical scaffold should be addressing the following factors: biocompatibility, biodegradability, mechanical properties, scaffold architecture/porosity, precise three-dimensional shape and manufacturing technology. There are several materials utilized in the fabrication of medical scaffolds, but one of the most extensively studied polymers is polylactic acid (PLA). PLA is biodegradable thermoplastic aliphatic polyester that is derived from naturally produced lactic acid. PLA is characterized with its excellent mechanical properties, biodegradability, promising eco-friendly, and excellent biocompatibility. PLA can be fabricated into nanofibers for medical scaffolds used through many techniques; electrospinning is one of the widely used methods for such fabrication. Electrospinning is a favorable technique because in the preparation of scaffolds, some parameters such as fiber dimensions, morphology, and porosity are easily controlled. A problem that is associated with medical scaffolds, such as inflammation and infection, was reported in many cases resulting in a degradation of tissues. Therefore, a surface modification was thought of as a needed solution which mostly focuses on an incorporation of extra functionalities responsible for the surface free energy increase (wettability). Therefore, plasma technique was a favorable solution for the surface treatment and modification. Plasma treatment enables the formation of free radicals. These radicals can be easily utilized for grafting process. Subsequently, ascorbic acid (ASA) could be incorporated as anti-inflammatory and anti-infection agent on the plasma pretreated surface of scaffolds.
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Woldemariam, Yoseph, Martin Garcia, Tris Utschig, and Ayse Tekes. "Design, Development and Implementation of Vibratory Mechanisms to Be Utilized in Dynamics and Vibrations Courses." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10235.
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Abstract There is still a demand for novel laboratory equipment designs that are to be utilized in undergraduate level machine dynamics, mechanical vibrations, control theory and their related labs. Since the turn-key systems preferred in most undergraduate labs are expensive and require wide lab space, 3D printed portable, small scale and cost-effective vibrational lab equipment are designed to study the fundamentals of free and forced vibrations. Four laboratory equipment designs are proposed in this study to demonstrate the fundamentals of vibration such as free vibration, forced vibration, modeling, base excitation and vibration isolation. The first device is a vibration isolator and resonator mechanism incorporating large deflecting fixed-free flexible links and composed of primary and secondary masses and a linear actuator, the second mechanism is a compliant parallel arm consisted of flexible beams, mass and a support, third mechanism is a translational vibratory mechanism comprised of slider carts, 3D printed springs, rods and bearings and the final mechanism is the model of driver seat consisted of DC motor, driver and driven wheels and a mass. Main parts of each apparatus are built by 3D printing using either PLA or PETG filament. Learning outcomes and the methods of implementing each device to the course and their associated laboratories are provided.
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Kumstát, Michal, Martin Sebera, and Michal Vičar. "The Effects Of Commercially Available Energy Drink On Cognitive Performance." In 12th International Conference on Kinanthropology. Brno: Masaryk University Press, 2020. http://dx.doi.org/10.5817/cz.muni.p210-9631-2020-7.
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Energy drinks are frequently purported as a non-alcoholic beverage food commodity to im-prove cognitive function and concentration and as such is marketed especially on vulnerable populations such as professional drivers, students, managers. We aimed to explore the acute dose-effect of commercially available multi-ingredient beverage on cognitive performance. Twenty adult university students, caffeine-deprived received two 500 ml non-alcoholic, glucose-free, multi-herbal extract drinks differing in ingredients dose: DRINK100, threefold higher concentration dosage (DRINK300) and ingredients-free, flavored-matched placebo (PLA) in a double-blind, three-way cross over, randomized order, separated by a 7-day wash-out period. Cognitive functions, autonomous nervous system activity, and specific mental performance were assessed. Drinks were consumed in the late evening (20 p.m.). Standardized psychomotor vigilance task (PVT) to detect reaction time, lapses and the total score and spectral analysis of heart rate variability (software-driven, standing/lying down with ~300 beats recorded in each position, relative change in total power score be-tween consecutive measurements was used) took place immediately prior and 60, 120 and 180 min post-drink consumption (post-drink). Thirty minutes of the cognitively demanding task (continuous manual text transcription) was commenced immediately and in 90, and 150 min post-drink. Total word counts were used in assessing mental performance chang-es. The ecologically valid methodology was used to mimic typical students time of drink consumption. During the 60min post-drink, the level of alertness decreased independently of the drink category, however, DRINK300 increased correct: lapsus ratio in 120 min and this remained elevated until the end of testing. No significant effect of DRINK100 over PLA on vigilance was present. DRINK300 led to an increase in autonomic nervous system activity after drink admin-istration in 60–90 minutes post-drink with a clear decline observed in PLA. This corresponds with a significant increase in the number of words transcripted in the corresponding time in DRINK300, however, not sustained in 180 min post-drink. We demonstrate an acute and transitional dose-effect of multi-herbal caffeine-containing non-energetic beverage on cognitive and autonomous nervous system performance. The effect appears to be evident immediately ( < 30 min) post-drink. A beverage containing guar-ana equivalent to 120 mg of caffeine reduce cognitive performance impairment and this is sustained over ~180 min.
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Heras Segura, Mariona, Kumar Vikram Singh, and Fazeel Khan. "Free and Forced Vibration Characteristics of Axially Graded Multifunctional Viscoelastic Beams." In ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3966.
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Variable performance characteristics in a multifunctional structure may be achieved by identifying suitable material candidates, and spatially varying, or grading, their material properties along the structures. Additive manufacturing (e.g. 3D printing) offers various possibilities to fabricate/manufacture such graded structures. The material properties of multifunctional composite structures, such as beams or plates, are often graded along their thickness (laminate/sandwich) or distributed in a material matrix (fibers/nanoparticles). In recent years, it has been demonstrated that by tailoring the materials in other directions (axially/radially), superior mechanical behavior and structural stability can be realized. In this research, the modeling and analyses of axially graded polymeric beams to maximize their vibration performance for a large bandwidth of frequencies and damping is presented. Polymeric materials have frequency and temperature dependent viscoelastic properties (complex modulus, glass transition temperature etc.) which can be leveraged for different applications. The goal is to spatially combine these materials such that desired longitudinal vibration characteristics (natural frequencies, damping and modes) can be achieved. To this end, the modeling for the free and forced vibration of beams with spatially varying properties, is carried out by a piecewise uniform continuous model. The spectral characteristics (natural frequency, damping ratios, and frequency response functions) of the axially graded beams are computed by solving associated transcendental eigenvalues problems. The parametric studies included the grading of polymers which are regularly used for additive manufacturing, such as ABS, PLA, etc. These results demonstrate that the response of the system can be manipulated by axial grading and optimal design/fabrication (3D printing) of multifunctional smart structures may be developed for vibration control applications.
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Yamada, Akira, Fuminori Niikura, and Koji Ikuta. "Three-Dimensional Microfabrication System for Biodegradable Microdevices With High-Resolution and Bio-Applicability." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82154.
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Biodegradable polymers are employed in medicine and its further application is expected with eagerness. But the lack of an appropriate processing method retards the progress. To overcome this problem, we have developped a novel three-dimensional microfabrication system. The system design allows us the processing of the free three-dimensional micro-level forms by stacking up melted polymers from the nozzle. Different from the conventional method, we adopted a batch process to supply materials in order to eliminate the prior process that required toxic solvents. In addition, it is possible to handle almost all biodegradable thermoplastic resins by adopting this system. A single layer from the piled-up layers of extruded lines was observed to evaluate the resolution. The lateral and depth resolutions attained are 40 μm and 45 μm, respectively. Biodegradable polymers enable three-dimensional microstructures such as micro-pipes, micro-bends, and micro-coil springs to be manufactured in less than 15 min. The biocompatibility of the newly fabricated structure was evaluated using a cell line (PC12). For this purpose, a small vessel, with a transparent base, was fabricated using PLA and cells were cultivated in it. The results were then compared with the results obtained using the standard method. The mechanical strength of our microstructures was evaluated using a tensile strength test. The tensile strength of the microstructure was lower than the one obtained from the conventional method, but has enough strength for fabrication of medical devices. Our system renders it possible to produce toxic-free, as well as transparent and leakage-free devices. Our system is expected to have potential applications in optimum design and fabrication of implantable devices, especially in tissue engineering.
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Jerkovic, Boris, Abram Rowell, Nathan Ellis, and Ayse Tekes. "Design, Modeling and Development of a Compliant Dual Resonator-Isolator." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10299.
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Abstract This paper investigates the construction, instrumentation, and dynamical modeling of a coupled three degrees of freedom compliant parallel arm mechanism. The compliant parallel arm, whose complete construction is carried out using 3D printing of polylactide (PLA) filaments, is a folded beam type mechanism, which is comprised of one primary and two secondary masses connected to two large deflecting beams. Dynamical model of the complete mechanism is obtained using Elastica Theory, where the large deflecting beams are considered as fixed-free cantilever beams subjected to a vertical tip load. Nonlinear load deflection curve, which is derived from the solutions of elliptical integrals, is approximated by a high-order polynomial function. Finally, the dynamics of the complete mechanism is derived using a classical lumped mass-spring-damper second order system. A linear actuator, PCB triaxial accelerometers, two laser displacement sensors and Arduino are utilized to gather acceleration and position information of each mass to identify the parameters of the lumped second order model using the offline Elastica Theory-based approach and polynomial fitting method. Numerical and experimental results verify the effectiveness of the proposed parameter identification schemes. Since system is nonlinear, state feedback linearization approach is adapted to linearize system equations at all operating points to control the trajectory of primary mass using a PID controller.
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Heras Segura, Mariona, Kumar Vikram Singh, and Fazeel Khan. "Vibration Performance of Axially Graded Polymeric Viscoelastic Beams." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-12214.
Full textAbstract:
Abstract Structures having a non-homogenous axial distribution of geometrical and material parameters have shown marked improvements in their load carrying capacity, bucking and vibration characteristics. Viscoelastic polymeric materials inherently offer a combination of stiffness and damping which are dependent on frequency and temperature. Therefore, the vibration and dynamic behavior of such engineering structures can be manipulated by grading polymeric viscoelastic materials in a structure. In this research, the transverse vibration performance of an axially graded polymeric beam is considered through systematic modeling and optimization study. A piecewise continuous model has been developed for axially graded beams and their free vibration and frequency response characteristics were analyzed for different combination and grading schemes of polymeric materials. By spatially distributing the range of polymeric materials along the span, spectral characteristics (natural frequencies, modal damping) of graded beams are obtained. Numerical simulations are carried out with axially graded beams made of materials (PLA, ABS, Nylon and TPU) which are easily available for 3D printing. Their spectral characteristics were analyzed and it is demonstrated that frequency and damping characteristics can be manipulated with a prescribed axial distribution of viscoelastic materials. Hence they can be the basis for optimal structural design to achieve a desired dynamic performance.
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Jahangir, Md Naim, Jeremy Cleeman, and Rajiv Malhotra. "Enhancing Conductivity in 3D Bulk-Embedded Electronics." In ASME 2020 15th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/msec2020-8361.
Full textAbstract:
Abstract Integrating nanoparticle (NP)-based electrically conductive elements inside additive manufactured parts has a high potential for next-generation smart structures. We investigate, a novel technique in which mixed silver nanowires (NW) and nanospheres (NS) are printed as interconnects and sintered using out-of-chamber Intense Pulsed Light (IPL) sintering inside 3D printed thermally sensitive Acrylonitrile Butadiene Styrene (ABS) and Polylactide (PLA) polymer structures. The inclusion of NWs with the typically used NSs is found to realize dual advantages of no thermal damage of the polymers and a that is much lesser resistivity than the state-of-the-art (13.1 μΩ-cm) only 8X higher than bulk silver. Resistivity decreases with a greater percentage of NW content. On the contrary, the NS-only sample didn’t show any conductivity even after IPL sintering because the wavy feature of 3D printed surface didn’t allow NSs to bond. Even though a greater reduction of resistivity is achieved due to IPL, sintering temperature was below 97°C and maximum sintering time reported is 0.75 seconds which cumulatively resulted in damage-free substrates. When dynamic resistivity is analyzed during polymer overprinting on interconnects, four different resistance trends are seen and explained here. Surprisingly, overprinting on the post-IPL interconnect to fully embed the interconnect inside the structure causes a further resistivity reduction to 11.8 μΩ-cm as well.
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Tekes, Ayse, Kevin Van Der Horn, Zach Marr, and Chong Tian. "Dynamics, Vibrations and Control Lab Equipment Design." In ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-8913.
Full textAbstract:
Take home lab equipment and hands-on learning tools are still in demand for control theory and vibrations courses. The existing equipment are extremely expensive and require wide lab space. The aim of this research is to build vibratory mechanical system that is compact, modular and small scale so that each student can work on their setup and take it home if necessary. For this purpose, in this study, a semi-compliant mechanism is designed to be utilized in systems control and vibrations courses which would enhance the understanding of students by using experimental demonstration of the theoretical systems. The superiorities of the design over commercially available equipment are their low cost and simplicity. A parallel arm mechanism consisting of several flexible links that can be attached at different points on the slider is designed, finite element analysis (FEA) is performed in Solidworks, and the flexible beams are 3D printed using polyactic acid (PLA) and Polyethylene terephthalate glycol-modified (PETG) filaments. Different configurations of the mechanism are explored by changing the number of flexible beams attached to the slider. The mathematical model of the proposed mechanism can be represented by a single mass and multiple springs in parallel. Since mass is a known property, the equivalent stiffness can be experimentally found from the frequency analysis of free response. For this purpose, a PCB model tri-axial accelerometer is attached to the slider and the equations of motion are derived from the analysis of frequency characteristics of the complaint dual arm mechanism for each configuration. System properties including the equivalent friction are obtained from the acceleration vs time data using logarithmic decrement. The forced response is studied by attaching a load to the mass through a pulley system. The load deflection curve is obtained experimentally from LabVIEW. Since the system parameters are obtained from the free response, Matlab Simulink model outputs for the same initial displacement and force input are verified with the experimental data.