Drexel University

About: Drexel University is a education organization based out in Philadelphia, Pennsylvania, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 26770 authors who have published 51438 publications receiving 1949443 citations. The organization is also known as: Drexel & Drexel Institute.

MXene-Bonded Activated Carbon as a Flexible Electrode for High-Performance Supercapacitors

Abstract: We report a strategy to employ two-dimensional Ti3C2Tx MXene as a flexible, conductive, and electrochemically active binder for one-step fabrication of MXene-bonded activated carbon as a flexible electrode for supercapacitors in an organic electrolyte. In this electrode, the activated carbon particles are encapsulated between the MXene layers, eliminating the need for insulative polymer binders. MXene plays a multifunctional role in the electrode, including as a binder, a flexible backbone, a conductive additive, and an additional active material. The synergetic effect of MXene and activated carbon constructs a three-dimensional conductive network and enlarges the distance between the MXene layers, greatly enhancing the electrode capacitance and rate capability. As a result, the flexible MXene-bonded activated carbon electrode exhibits a high capacitance of 126 F g–1 at 0.1 A g–1 and a retention of 57.9% at 100 A g–1 in an organic electrolyte, which is required for developing high-performance, flexible su...

MoS2 Nanosheets Vertically Aligned on Carbon Paper: A Freestanding Electrode for Highly Reversible Sodium Ion Batteries

Abstract: The development of sodium-ion batteries for large-scale applications requires the synthesis of electrode materials with high capacity, high initial Coulombic efficiency (ICE), high rate performance, long cycle life, and low cost. A rational design of freestanding anode materials is reported for sodium-ion batteries, consisting of molybdenum disulfide (MoS2) nanosheets aligned vertically on carbon paper derived from paper towel. The hierarchical structure enables sufficient electrode/electrolyte interaction and fast electron transportation. Meanwhile, the unique architecture can minimize the excessive interface between carbon and electrolyte, enabling high ICE. The as-prepared MoS2@carbon paper composites as freestanding electrodes for sodium-ion batteries can liberate the traditional electrode manufacturing procedure, thereby reducing the cost of sodium-ion batteries. The freestanding MoS2@carbon paper electrode exhibits a high reversible capacity, high ICE, good cycling performance, and excellent rate capability. By exploiting in situ Raman spectroscopy, the reversibility of the phase transition from 2H-MoS2 to 1T-MoS2 is observed during the sodium-ion intercalation/deintercalation process. This work is expected to inspire the development of advanced electrode materials for high-performance sodium-ion batteries.

fNIRS Study of Walking and Walking While Talking in Young and Old Individuals

Abstract: Background. Evidence suggests that gait is influenced by higher order cognitive and cortical control mechanisms. However, less is known about the functional correlates of cortical control of gait. Methods. Using functional near-infrared spectroscopy, the current study was designed to evaluate whether increased activations in the prefrontal cortex (PFC) were detected in walking while talking (WWT) compared with normal pace walking (NW) in 11 young and 11 old participants. Specifically, the following two hypotheses were evaluated: (a ) Activation in the PFC would be increased in WWT compared with NW. (b) The increase in activation in the PFC during WWT as compared with NW would be greater in young than in old participants. Results. Separate linear mixed effects models with age as the two-level between-subject factor, walking condition (NW vs WWT) as the two-level repeated within-subject factor, and HbO2 levels in each of the 16 functional near-infrared spectroscopy channels as the dependent measure revealed significant task effects in 14 channels, indicating a robust bi lateral increased activation in the PFC in WWT compared with NW. Furthermore, the group-by-task interaction was significant in 11 channels with young participants showing greater WWT-related increase in HbO2 levels compared with the old participants.

Scalable salt-templated synthesis of two-dimensional transition metal oxides

Abstract: Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm(-3) in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications.

Transmission Capacity of Wireless Ad Hoc Networks With Successive Interference Cancellation

Abstract: The transmission capacity (TC) of a wireless ad hoc network is defined as the maximum spatial intensity of successful transmissions such that the outage probability does not exceed some specified threshold. This work studies the improvement in TC obtainable with successive interference cancellation (SIC), an important receiver technique that has been shown to achieve the capacity of several classes of multiuser channels, but has not been carefully evaluated in the context of ad hoc wireless networks. This paper develops closed-form upper bounds and easily computable lower bounds for the TC of ad hoc networks with SIC receivers, for both perfect and imperfect SIC. The analysis applies to any multiuser receiver that cancels the K strongest interfering signals by a factor z isin [0, 1]. In addition to providing the first closed-form capacity results for SIC in ad hoc networks, design-relevant insights are made possible. In particular, it is shown that SIC should be used with direct sequence spread spectrum. Also, any imperfections in the interference cancellation rapidly degrade its usefulness. More encouragingly, only a few - often just one - interfering nodes need to be canceled in order to get the vast majority of the available performance gain.