60 research outputs found
Arbitrating Traffic Contention for Power Saving with Multiple PSM Clients
Data transmission over WiFi quickly drains the batteries of mobile devices. Although the IEEE 802.11 standards provide power save mode (PSM) to help mobile devices conserve energy, PSM fails to bring expected benefits in many real scenarios. In particular, when multiple PSM mobile devices associate to a single access point (AP), PSM does not work well under transmission contention. Optimizing power saving of multiple PSM clients is a challenging task, because each PSM client expects to complete data transmission early so that it can turn to low power mode. In this paper, we define an energy conserving model to describe the general PSM traffic contention problem. We prove that the optimization of energy saving for multiple PSM clients under constraint is an NPcomplete problem. Following this direction, we propose a solution called harmonious power saving mechanism (HPSM) to address one specific case, in which multiple PSM clients associate to a single AP. In HPSM, we first use a basic sociological concept to define the richness of a PSM client based on the link resource it consumes. Then, we separate these poor PSM clients from rich PSM clients in terms of link resource consumption and favor the former to save power when they face PSM transmission contention. We implement prototypes of HPSM based on the open source projects Mad-wifi and NS-2. Our evaluations show that HPSM can help the poor PSM clients effectively save power while only slightly degrading the rich PSM clients\u27 performance in comparison with the existing PSM solutions
Automated Interactive Visualization on Abstract Concepts in Computer Science
The paper presents CSVisFrame, a framework formaking visualizations, which solves the understanding difficultyon learning abstract concepts in computer science including datastructures and algorithms. With the framework, instructors anddevelopers can develop all varieties of interactive visualizations,with which students can learn and understand abstract conceptsin computer science more easily.CSVisFrame has been applied to both offline and onlinecomputer courses. Students from Sichuan Normal Universityhave enjoyed visualizations based on CSVisFrame in their AlgorithmDesign and Analysis course, and thousands of students ofJisuanke have benefitted from online CSVisFrame-based visualizedcomputer science courses. The effectiveness of CSVisFramebasedvisualizations has been demonstrated by our sample survey,which shows that visualizations are widely accepted, and almostall students can achieve a better learning. CSVisFrame is opensourced1,and demonstrations based on CSVisFrame are free2
A practical graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>)based fluorescence sensor for the competitive detection of trithiocyanuric acid and mercury ions
[EN] A fluorescent sensor for the detection of trithiocyanuric acid (TCA) and Hg was developed based on competitive interactions: non-covalent stacking between g-CN and TCA vs coordinative interaction between TCA and Hg. Electrostatic simulations were used to evaluate the interactions and help describe the detection mechanism. Moreover, normalized 2D fluorescence contour plots have been used to understand the fluorescence phenomenon. When TCA was added into a g-CN nanosheet solution free of Hg, TCA interacted with g-CN nanosheets via hydrogen bonding and π-π interactions, resulting in fluorescence quenching of the g-CN nanosheets. However, upon the addition of Hg, the fluorescence of the TCA-g-CN nanosheet hybrid system was restored, due to coordination of Hg with TCA through the S atoms, breaking the TCA-g-CN stacking interaction. Our results provide a new approach for the design of multifunctional nanosensors suitable for the detection of environmental pollutants.The present work is supported by the National Natural Science Foundation of China (No. 21607044), the Natural Science Foundation of Hebei Province (No. B2017502069) and the Fundamental Research Funds for the Central Universities (No. 2018MS113). All data sup-porting this study are provided as supplementary information accom-panying this paper. T.D.J. wishes to thank the Royal Society for a Wolfson Research Merit Award
Amphiphilic engineering of reduced graphene oxides using a carbon nitride coating for superior removal of organic pollutants from wastewater
Amphiphilic carbon nitride (g-C3N4) was decorated onto reduced graphene oxide (rGO) to obtain rGO-g-C3N4 composites as excellent adsorbents for the removal of aromatic organic compounds from industrial wastewater. The as obtained rGO-g-C3N4 composites are effective adsorbents for organic compounds due to the amphiphilic g-C3N4. We propose a new adsorption model using an amphiphilic additive which can enhance the water accessibility and hydrophobic interactions between rGO with organic compounds in aqueous media. Where, even water-soluble organic molecules like rhodamine B (RhB) have a high adsorption capability for the rGO-g-C3N4 (520 mg g−1). Molecular dynamics simulations were used to investigate the interactions between RhB and rGO-g-C3N4 and indicated that amphiphilic g-C3N4 accelerates the adsorption process. In addition, the amphipathic adsorption approach is enhanced as the salinity of water increases, which can offer great operational flexibility and versatility. This research demonstrates that the highly efficient interactions between aromatic organic molecules and amphiphilic carbon-based nanomaterials can be used for practical applications.</p
Self-Assembled Materials Incorporating Functional Porphyrins and Carbon Nanoplatforms as Building Blocks for Photovoltaic Energy Applications.
As a primary goal, this review highlights the role of supramolecular interactions in the assembly of new sustainable materials incorporating functional porphyrins and carbon nanoplatforms as building blocks for photovoltaics advancements
Ampere-hour-scale soft-package potassium-ion hybrid capacitors enabling 6-minute fast-charging
Extreme fast charging of Ampere-hour (Ah)-scale electrochemical energy storage devices targeting charging times of less than 10 minutes are desired to increase widespread adoption. However, this metric is difficult to achieve in conventional Li-ion batteries due to their inherent reaction mechanism and safety hazards at high current densities. In this work, we report 1 Ah soft-package potassium-ion hybrid supercapacitors (PIHCs), which combine the merits of high-energy density of battery-type negative electrodes and high-power density of capacitor-type positive electrodes. The PIHC consists of a defect-rich, high specific surface area N-doped carbon nanotube-based positive electrode, MnO quantum dots inlaid spacing-expanded carbon nanotube-based negative electrode, carbonate-based non-aqueous electrolyte, and a binder- and current collector-free cell design. Through the optimization of the cell configuration, electrodes, and electrolyte, the full cells (1 Ah) exhibit a cell voltage up to 4.8 V, high full-cell level specific energy of 140 Wh kg-1 (based on the whole mass of device) with a full charge of 6 minutes. An 88% capacity retention after 200 cycles at 10 C (10 A) and a voltage retention of 99% at 25 ± 1 °C are also demonstrated
Interactions between an aryl thioacetate-functionalized Zn(II) porphyrin and graphene oxide
The surface modification of graphene oxide (GO) is carried out via the supramolecular functionalization route using a Zn(II)-porphyrin which is soluble in common organic solvents on basis of long alkyl chains present at the exocyclic positions. This acts as a dispersing agent and decorates the surface of the graphene oxide uniformly, giving rise to a new nanohybrid denoted Zn(II)-porphyrin@GO. The resulting Zn(II)-porphyrin@GO nanohybrid forms a stable dispersion in ethanol (as characterized by several different spectroscopic techniques such as UV–vis, Fourier transform infrared, Raman). The morphology of Zn(II)-porphyrin@GO nanohybrid is investigated by atomic force microscopy (AFM) and transmission electron microscope (TEM)/selected area electron diffraction. Both TEM and AFM measurements indicate that the Zn(II)-porphyrin self-assemble onto the surface of graphene oxide sheets. Steady-state and time-resolved fluorescence emission studies in the dispersed phase, and as a thin film, point toward the strongly quenched fluorescence emission and lifetime decay, suggesting that energy transfer occurs from the singlet excited state of Zn(II)-porphyrin unit to GO sheets
STUDY ON ANTICANCER EFFECT OF SYNTHETIC BIOGENIC SOURCE OF GERMACRENE A
Objective: Based on obtaining germacrene A, which is the analogue of synthetic β-elemene, by means of synthetic biology,this experiment aims to explore the anti-tumor effect of germacrene A.
Results: After administration, the volume of T24 cells was significantly reduced. The shape of the T24 cells gradually changed from wedge-shaped and polygonal to round, and the T24 cells soon fell off, atrophied and disintegrated. After Tet blue staining, a large number of T24 cells after administration were observed to be dead; It was found by means of MTT assay that T24 cells were inhibited to varying degrees by the effects of different concentrations of germacrene A.
Conclusion: The above experimental results show that the synthetic biological source of germacrene A has obvious inhibitory effect on bladder cancer T24 cells, and this effect has obvious time and concentration dependence.
Keywords:Germacrene A; Synthetic drugs; Antitumor; β-elemen
MOF-Derived Robust and Synergetic Acid Sites Inducing C-N Bond Disruption for Energy-Efficient CO<sub>2</sub>Desorption
Amine-based scrubbing technique is recognized as a promising method of capturing CO2 to alleviate climate change. However, the less stability and poor acidity of solid acid catalysts (SACs) limit their potential to further improve amine regeneration activity and reduce the energy penalty. To address these challenges, here, we introduce two-dimensional (2D) cobalt-nitrogen-doped carbon nanoflakes (Co-N-C NSs) driven by a layered metal-organic framework that work as SACs. The designed 2D Co-N-C SACs can exhibit promising stability, superhydrophilic surface, and acidity. Such 2D structure also contains well-confined Co-N4 Lewis acid sites and -OH Brønsted acid sites to have a synergetic effect on C-N bond disruption and significantly increase CO2 desorption rate by 281% and reduce the reaction temperatures to 88 °C, minimizing water evaporation by 20.3% and subsequent regeneration energy penalty by 71.7% compared to the noncatalysis.</p
- …