Pengaruh Fraksi Volume Serat terhadap Sifat-sifat Tarik Komposit Diperkuat Unidirectional Serat Tebu dengan Matrik Poliester

Sugar cane fiber has not optimallybeen used as reinforcement of compositematerial. So far, bagasse has been used as  firewood-substitute, raw material for papers, and brake lining. The purpose of this study is to investigate the effect of fiber volume fraction, Vf, on tensile strength of unidirectional sugar cane fiber/polyester composites. The material being used was sugar cane fiber, 268 SHCP BQTN  polyester resin and catalyst . Fibers were soaked in alkali (NaOH) 5% for 2 hours in order to remove their impurities. Composite panels were made with a printing press and the volume fractions of the fiber were 0%, 10%, 20%, 30% and 40%. Prior to being cut into specimens, the panels were subsequenlypost-cured at a temperature of 60 0C for 4 hours. Tensile testing wa carried out according to theASTM D638 standard, and fracture area photo macrographs of selected sampleswere analysed in order to find out the characteristics of fracture. It was found out that increasing the fiber volume fraction resulted in thedecrease of tesilestrength and strain,butincrease of the modulus of elasticity . The highest average tensile strength and strain was obtained at Vf = 0% (31.44 MPa and 9,11%), and a tensile modulus of elasticity was at Vf = 20% of 426.92 MPa. The observations on the photo macrographs showed thatcomposite fracture predominantly occuredspecimens withVf = 30%, and single fracture combined withfiber pull-out was identified for those ofVf = 0%, 10%, 20% and 40%

FeetBack – Redirecting touch sensation from a prosthetic hand to the human foot

Introduction: Adding sensory feedback to myoelectric prosthetic hands was shown to enhance the user experience in terms of controllability and device embodiment. Often this is realized non-invasively by adding devices, such as actuators or electrodes, within the prosthetic shaft to deliver the desired feedback. However, adding a feedback system in the socket adds more weight, steals valuable space, and may interfere with myoelectric signals. To circumvent said drawbacks we tested for the first time if force feedback from a prosthetic hand could be redirected to another similarly sensitive part of the body: the foot. Methods: We developed a vibrotactile insole that vibrates depending on the sensed force on the prosthetic fingers. This self-controlled clinical pilot trial included four experienced users of myoelectric prostheses. The participants solved two types of tasks with the artificial hands: 1) sorting objects depending on their plasticity with the feedback insole but without audio-visual feedback, and 2) manipulating fragile, heavy, and delicate objects with and without the feedback insole. The sorting task was evaluated with Goodman-Kruskal’s gamma for ranked correlation. The manipulation tasks were assessed by the success rate. Results: The results from the sorting task with vibrotactile feedback showed a substantial positive effect. The success rates for manipulation tasks with fragile and heavy objects were high under both conditions (feedback on or off, respectively). The manipulation task with delicate objects revealed inferior success with feedback in three of four participants. Conclusion: We introduced a novel approach to touch sensation in myoelectric prostheses. The results for the sorting task and the manipulation tasks diverged. This is likely linked to the availability of various feedback sources. Our results for redirected feedback to the feet fall in line with previous similar studies that applied feedback to the residual arm

Let’s Enjoy an Evening on the Couch? A Daily Life Investigation of Shared Problematic Behaviors in Three Couple Studies

Symptom-system fit theory proposes that problematic behaviors are maintained by the social system (e.g., the couple relationship) in which they occur because they help promote positive relationship functioning in the short-term. Across three daily life studies, we examined whether mixed-gender couples reported more positive relationship functioning on days in which they engaged in more shared problematic behaviors. In two studies (Study 1: 82 couples who smoke; Study 2: 117 couples who are inactive), days of more shared problematic behavior were accompanied by higher daily closeness and relationship satisfaction. A third study with 79 couples post-stroke investigating unhealthy eating failed to provide evidence for symptom-system fit. In exploratory lagged analyses, we found more support for prior-day problematic behavior being associated with next-day daily relationship functioning than vice-versa. Together, findings point to the importance of a systems perspective when studying interpersonal dynamics that might be involved in the maintenance of problematic behaviors

An interdisciplinary approach towards improved understanding of soil deformation during compaction

International audienceSoil compaction not only reduces available pore volume in which fluids are stored, but it alters the arrangement of soil constituents and pore geometry, thereby adversely impacting fluid transport and a range of soil ecological functions. Quantitative understanding of stress transmission and deformation processes in arable soils remains limited. Yet such knowledge is essential for better predictions of effects of soil management practices such as agricultural field traffic on soil functioning. Concepts and theory used in agricultural soil mechanics (soil compaction and soil tillage) are often adopted from conventional soil mechanics (e.g. foundation engineering). However, in contrast with standard geotechnical applications, undesired stresses applied by agricultural tyres/tracks are highly dynamic and last for very short times. Moreover, arable soils are typically unsaturated and contain important secondary structures (e.g. aggregates), factors important for affecting their soil mechanical behaviour. Mechanical processes in porous media are not only of concern in soil mechanics, but also in other fields including geophysics and granular material science. Despite similarity of basic mechanical processes, theoretical frameworks often differ and reflect disciplinary focus. We review concepts from different but complementary fields concerned with porous media mechanics and highlight opportunities for synergistic advances in understanding deformation and compaction of arable soils. We highlight the important role of technological advances in non-destructive measurement methods at pore (X-ray tomography) and soil profile (seismic) scales that not only offer new insights into soil architecture and enable visualization of soil deformation, but are becoming instrumental in the development and validation of new soil compaction models. The integration of concepts underlying dynamic processes that modify soil pore spaces and bulk properties will improve the understanding of how soil management affect vital soil mechanical, hydraulic and ecological functions supporting plant growth

Ionisation and dissociation of cometary gaseous organic molecules by solar wind particles I: Formic Acid

In order to simulate the effects of energetic charged particles present in the solar wind colliding with the cometary gaseous formic acid molecule (HCOOH), laboratory experiments have been performed. The absolute ionisation and dissociation cross sections for this molecule interacting with solar wind particles were measured employing fast electrons in the energy range of 0.5 to 2 keV and energetic protons with energies varying from 0.128 to 2 MeV. Despite the fact that both projectiles lead to a very similar fragmentation pattern, differences in the relative intensities of the fragments were observed. Formic acid survives about 4-5 times more to the proton beam than to the energetic electron collision.The minimum momentum transfer in the electron impact case was estimated to be 3-38% larger than the minimum momentum transfer observed with the equivelocity protons. The UV photodissociation rates and half-lives for HCOOH are roughly closer to the values obtained with energetic electrons. It is consequently important to take electron impact data into account when developing chemical models to simulate the interplanetary conditions.Comment: 11 pages, 7 figures, 5 tables, Accepted to be published in MNRA