1,413 research outputs found

    When companies have ties to politicians or military officials

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    Entrepreneurs want to reduce uncertainty and shape environments to their advantage. To do so, they sometimes collaborate with government leaders to gain valuable information, resources, and favourable legislation

    Performance comparison of thin-film composite forward osmosis membranes

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    Forward osmosis (FO) is an emerging low-energy technology. Much effort was given on developing a new membrane material and engineering membrane structure to improve the performance of FO membranes. The performances of two newly developed polyamide-based thin-film composite (TFC) FO membranes were tested and compared with the commercially available cellulose triacetate (CTA) FO membrane. The intrinsic properties of the two TFC FO membranes determined in RO experiments indicate superior performance of the membranes. When tested in FO experiments, TFC membranes delivered consistent results, confirming their outstanding permeability and selectivity properties. The study shows that future studies on membrane fouling will be necessary to have a better understanding of membrane performance and to further optimize membrane properties. © 2013 Copyright Balaban Desalination Publications

    Forward osmosis membranes and processes: A comprehensive review of research trends and future outlook

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    Recently, Forward Osmosis (FO) desalination process has been widely investigated as a potential technology that could minimize the drawbacks of traditional desalination processes. To review the past, current, and future research scope of the FO desalination process, a statistical analysis that gives insights on the FO topics of interest is needed to assist researchers in the development of the FO technology. The main objective of this work is to conduct a survey highlighting the general and specific research trends in FO technology topics. The level of research interest is quantified based on the number of publications in each area collected from Science Direct and Scopus databases from 1999 to 2020. This survey indicated an increasing number of publications on the FO processes and membranes technology. The topics of interest are fouling phenomenon, draw solutions, membrane fabrication and modification. Some potential research areas highlighted in this review to help researchers to further advance the FO technology. This review reveals that recycling the draw solution and energy consumption are the most important research areas that have shown growth in the number of publications over the last eight years. An increase of publications was also found in the treatment of the organic matter over the last decade. To further promote FO process in industry, developing FO membranes, optimizing the energy consumption, and establishing an effective recovery system are the most essential topics. Thus, the interest in this process is expected to be continued in the future

    Molecular dynamics simulation of boundary lubrication

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    Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaves 116-121).by Shon W. Yim.M.S

    Dynamics of sliding mechanisms in nanoscale friction

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references.Nanotribology is the study of friction and wear at the nanoscale, with relevance to such applications as micromechanical systems (MEMS) and thin, hard coatings. For these systems, classical laws of friction are inappropriate due to the small dimensions of the sliding elements and the lack of excessive plastic deformation. This thesis presents a theoretical investigation of friction at the sliding interface by Molecular Dynamics (MD) simulations of ideal Lennard-Jones solids. The effect of the interfacial structure on the frictional behavior is investigated by simulating a variety of interface configurations: commensurate, noncommensurate (or grain boundary), and amorphous. The effect of adhesion on the frictional behavior is also explored through a parametric study. For the commensurate interface, the degree of adhesion determines whether sliding occurs in the frictional or "frictionless" regime; the former is distinguishable by the presence of jump phenomena, the principal mechanism of friction in the MD model. The Sigma-5 [100](310) symmetric tilt grain boundary exhibits three distinct sliding regimes which are, in the order of increasing adhesion, frictionless sliding, frictional sliding, and sliding coupled with grain boundary migration. Twist grain boundaries of the (111) plane exhibit frictionless sliding for all degrees of adhesion. Among the structures simulated, the grain boundary systems have the lowest friction due to the intrinsic misorientation at the sliding interface. In the amorphous system, sliding occurs by a series of random local slips due to the individual atomic motion associated with the disordered structure.(cont.) Increasing the adhesion leads to the initiation of a shear-induced crystallization process followed by an extremely rapid growth of the crystalline cluster. Friction in the amorphous system increases with adhesion only up to a certain limit due to the onset of bulk deformation. Similar trends have been observed in AFM measurements of the friction of thin, hard coatings.by Shon W. Yim.Ph.D

    The Impact Of Stuttering On Quality Of Life Of Children And Adolescents.

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    Understanding the experience of people who stutter, both in and out treatment, will lead to improved outcomes. To investigate how stuttering affects the quality of life of children and adolescents who stutter. The Overall Assessment of the Speaker's Experience of Stuttering--School-Age (OASES-S) was used to assess the impact of stuttering and the Fluency Profile Protocol was used to stuttering severity. These age groups do experience moderate negative impact as measured by the OASES-S. The results showed a tendency toward a positive correlation between severity and the impact of stuttering on quality of life. A better understanding of the impact of stuttering in these age groups provides a needed guide for the development of stuttering treatments and treatment outcomes research.22567-

    Chemically Cross-Linked Graphene Oxide as a Selective Layer on Electrospun Polyvinyl Alcohol Nanofiber Membrane for Nanofiltration Application.

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    Graphene oxide (GO) nanosheets were utilized as a selective layer on a highly porous polyvinyl alcohol (PVA) nanofiber support via a pressure-assisted self-assembly technique to synthesize composite nanofiltration membranes. The GO layer was rendered stable by cross-linking the nanosheets (GO-to-GO) and by linking them onto the support surface (GO-to-PVA) using glutaraldehyde (GA). The amounts of GO and GA deposited on the PVA substrate were varied to determine the optimum nanofiltration membrane both in terms of water flux and salt rejection performances. The successful GA cross-linking of GO interlayers and GO-PVA via acetalization was confirmed by FTIR and XPS analyses, which corroborated with other characterization results from contact angle and zeta potential measurements. Morphologies of the most effective membrane (CGOPVA-50) featured a defect-free GA cross-linked GO layer with a thickness of ~67 nm. The best solute rejections of the CGOPVA-50 membrane were 91.01% for Na2SO4 (20 mM), 98.12% for Eosin Y (10 mg/L), 76.92% for Methylene blue (10 mg/L), and 49.62% for NaCl (20 mM). These findings may provide one of the promising approaches in synthesizing mechanically stable GO-based thin-film composite membranes that are effective for solute separation via nanofiltration

    Dynamics of an electron in finite and infinite one dimensional systems in presence of electric field

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    We study,numerically, the dynamical behavior of an electron in a two site nonlinear system driven by dc and ac electric field separately. We also study, numerically, the effect of electric field on single static impurity and antidimeric dynamical impurity in an infinite 1D chain to find the strength of the impurities. Analytical arguments for this system have also been given.Comment: File Latex, 8 Figures available on reques

    Development of wirelessly-powered, extracranial brain activator (ECBA) in a large animal model for the future non-invasive human neuromodulation

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    As transcranial electrical stimulation (tES) is an emerging and promising technique for neuromodulation, we developed a novel device; wirelessly-powered, extracranial brain activator (ECBA), which is mounted subcutaneously, and its neuromodulation effect was investigated. The oscillatory changes in electrocorticography (EcoG) were analyzed from two types of stimulation. Two weeks prior to the recording experiment, we underwent surgery for implantation of subdural strips and ECBA module over centroparietal regions of anesthetized beagles. Low-frequency stimulation (LFS) and subsequent high-frequency stimulation (HFS) protocols (600 pulses respectively) were applied. Then, the power changes before and after each stimulation in five different bands were compared. A significantly larger voltage difference with subcutaneous than transcutaneous stimulation measured at EcoG channels indicated a substantial current attenuation between the skin and skull. Compared with the baseline, all subjects showed consistently decreased delta power and increased gamma power after HFS. LFS also induced a similar, but opposite, pattern of power change in four beagles. The results from this study indicate that LFS and HFS with our novel ECBA can consistently and effectively modulate neural activity of the cortex, inducing neural inhibition and facilitation functions, respectively. Future studies are necessary to further ensuring a consistent efficacy and long-term safety.11Ysciescopu

    Integrating mobile-phone based assessment for psychosis into people\u27s everyday lives and clinical care: a qualitative study

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    Background: Over the past decade policy makers have emphasised the importance of healthcare technology in the management of long-term conditions. Mobile-phone based assessment may be one method of facilitating clinically- and cost-effective intervention, and increasing the autonomy and independence of service users. Recently, text-message and smartphone interfaces have been developed for the real-time assessment of symptoms in individuals with schizophrenia. Little is currently understood about patients\u27 perceptions of these systems, and how they might be implemented into their everyday routine and clinical care. Method: 24 community based individuals with non-affective psychosis completed a randomised repeated-measure cross-over design study, where they filled in self-report questions about their symptoms via text-messages on their own phone, or via a purpose designed software application for Android smartphones, for six days. Qualitative interviews were conducted in order to explore participants\u27 perceptions and experiences of the devices, and thematic analysis was used to analyse the data. Results: Three themes emerged from the data: i) the appeal of usability and familiarity, ii) acceptability, validity and integration into domestic routines, and iii) perceived impact on clinical care. Although participants generally found the technology non-stigmatising and well integrated into their everyday activities, the repetitiveness of the questions was identified as a likely barrier to long-term adoption. Potential benefits to the quality of care received were seen in terms of assisting clinicians, faster and more efficient data exchange, and aiding patient-clinician communication. However, patients often failed to see the relevance of the systems to their personal situations, and emphasised the threat to the person centred element of their care. Conclusions: The feedback presented in this paper suggests that patients are conscious of the benefits that mobile-phone based assessment could bring to clinical care, and that the technology can be successfully integrated into everyday routine. However, it also suggests that it is important to demonstrate to patients the personal, as well as theoretical, benefits of the technology. In the future it will be important to establish whether clinical practitioners are able to use this technology as part of a personalised mental health regime
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