NAND flash reliability (both endurance and retention) degrades with the scaling of NAND flash memory technology and the introduction of multilevel cell (MLC) and triplelevel cell (TLC) technologies. ...As a result, stronger error correction code (ECC) methods are required in the solid-state drive application, especially for MLC and TLC flash memory devices. Modeling of the threshold voltage (Vt) distribution in the NAND flash memory can make the ECC simulations more effective and efficient. In this paper, we show a semiphysical and Monte Carlo method to generate a reallike V t distribution by mimicking the NAND flash programming and data retention (DR) processes. Probability distributions used in the Monte Carlo method are obtained by the measurements of the NAND devices and data interpolation or extrapolation. Simulations by this model can obtain reallike V t distribution for any given Program/Erase cycle and DR time. Excellent results have been obtained and confirmed by comparing the simulations with the measured data from 16-nm NAND flash devices.
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•Adsorption behaviors of ibuprofen and naproxen by UiO-66 and UiO-66-NH2.•Adsorption mechanisms of ibuprofen and naproxen were revealed by DFT calculation.•π-π EDA, H-bonding, LAB ...complexing, and anion-π interaction were involved.•The binding energies followed the order of π-π > hydrogen bonding > LAB > anion-π.
Ibuprofen (IBP) and naproxen (NAP), two typical anti-inflammatory drugs, were frequently detected in natural waters. Therefore, their adsorption to various materials has drawn great interests. However, the adsorption mechanisms of IBP and NAP at a molecular level were not well-known. This study investigated the adsorption of IBP and NAP by two types of metal organic frameworks (MOFs), UiO-66 and UiO-66-NH2, and the adsorption mechanisms were revealed at macro and micro molecule levels based on experiments and density functional theory (DFT) calculations. Greater adsorption of IBP onto MOFs was observed compared with NAP, which is incurred by its higher binding energies with adsorbents than NAP as revealed by DFT calculations. Four mechanisms, including π-π EDA interaction, Lewis acid/base complexing (LAB), hydrogen bonding, and anion-π interaction, were simultaneously involved in the adsorption of IBP/NAP by MOFs. The binding energies followed the order of π-π > hydrogen bonding > LAB > anion-π. The decreasing adsorption of IBP and NAP with rising pH was induced by the facilitated aggregation of MOFs at pH < pHpzc and the electrostatic repulsion between IBP/NAP and MOFs at pH > pHpzc. Direct competition for adsorption sites accounted for the competitive adsorption between IBP and NAP, and the extra type of binding site (amino group) and less amount of adsorption sites induced the less competition between IBP and NAP onto UiO-66-NH2 compared with UiO-66. This study, at a molecular level, provides adsorption mechanisms of acidic pharmaceuticals with MOFs.
In this work, carbon polyhedron and carbon nanotube hybrids (HCN) have been synthesized by employing ZIF-67 as precursor for electrochemical supercapacitor and capacitive deionization (CDI). ...Basically, uniform polyhedral nanocrystals of ZIF-67 were firstly fabricated, and then they were directly subjected to chemical vapor deposition for growing carbon nanotubes. It is found that the as-fabricated HCN electrode exhibits remarkable electrochemical performance, i.e. the highest capacitance of 343 F g−1 at the scan rate of 10 mV s−1 and excellent rate capability. This is due to that HCN can provide rich space and short ion diffusion path. Moreover, the HCN electrodes shows superior CDI performance, i.e. the electrosorption capacity reached as high as 7.08 mg g−1 and the adsorption rate of 0.03958 mg g−1·min−1.
Membrane capacitive deionization (MCDI) integrates the advantages of capacitive deionization (CDI) and ion-exchange membrane technology and has shown great potential to improve the desalting ...efficiency. MCDI works based on the same working principle of CDI. In addition, ion-exchange membranes are introduced in front of the electrodes so that the charged ions can be selectively passed through the membrane layer and are subsequently adsorbed by the oppositely charged electrodes without interference of co-ions and therefore improve the salt removal efficiency as well as strengthen the regeneration. In this research, electrodes made from single walled carbon nanotubes (SWCNTs) were used together with cation- and anion-exchange membranes. The correlation between solution concentration and conductivity was calibrated prior to the experiment. Through bench scale batch mode desalination experiments, a salt removal efficiency of as high as 97% was achieved with initial conductivity of 110μs/cm and electrical voltage of 1.2V. This efficiency is much higher than the corresponding CDI without membrane whose salt removal efficiency is only about 60%. Further, the obtained adsorption rate constant as a result of adsorption kinetics clearly demonstrated that the ion-exchange membrane can help to achieve a faster ion transfer rate in the electrosorption process due to low co-ions expulsion effect.
The environmental risks of antibiotics have attracted increasing research attention, but their environmental behaviors remain unclear. In this study, functionalized carbon nanotubes (CNTs), namely, ...hydroxylized (MH), carboxylized (MC), graphitized multi-walled CNTs (MG) and single-walled CNTs (SW) were used as adsorbents and ciprofloxacin (CIP) as an adsorbate to investigate the effect of pH and temperature on sorption and desorption processes. Sorption isotherms of CIP were fitted well by Freundlich and Dubinin-Ashtakhov models. Highly nonlinear isotherms of CIP were observed, indicating the highly heterogeneous site energy distribution on CNTs. At all pHs, SW had the highest sorption for CIP due to its largest surface area among all CNTs. Sorption distinction between MH and MC was explained by π-π electron donor-acceptor interactions. For SW, CIP sorption was thermodynamically favorable and endothermic associated with an entropy driven process, while the reverse process occurred for MC and MG. The rearrangement of CNTs bundles/aggregates and covalent bond formation may be responsible for CIP desorption hysteresis on CNTs. Desorption of antibiotics from CNTs may lead to potential exposure, particularly under changing environmental conditions such as temperature and pH.
Lithium‐sulfur batteries (LSBs) have been regarded as a competitive candidate for next‐generation electrochemical energy‐storage technologies due to their merits in energy density. The sluggish redox ...kinetics of the electrochemistry and the high solubility of polysulfides during cycling result in insufficient sulfur utilization, severe polarization, and poor cyclic stability. Herein, sulfiphilic few‐layered MoSe2 nanoflakes decorated rGO (MoSe2@rGO) hybrid has been synthesized through a facile hydrothermal method and for the first time, is used as a conceptually new‐style sulfur host for LSBs. Specifically, MoSe2@rGO not only strongly interacts with polysulfides but also dynamically strengthens polysulfide redox reactions. The polarization problem is effectively alleviated by relying on the sulfiphilic MoSe2. Moreover, MoSe2@rGO is demonstrated to be beneficial for the fast nucleation and uniform deposition of Li2S, contributing to the high discharge capacity and good cyclic stability. A high initial capacity of 1608 mAh g−1 at 0.1 C, a slow decay rate of 0.042% per loop at 0.25 C, and a high reversible capacity of 870 mAh g−1 with areal sulfur loading of 4.2 mg cm−2 at 0.3 C are obtained. The concept of introducing sulfiphilic transition‐metal selenides into the LSBs system can stimulate engineering of novel architectures with enhanced properties for various energy‐storage devices.
A sulfiphilic few‐layered MoSe2 nanoflakes decorated rGO (MoSe2@rGO) hybrid is synthesized through a facile hydrothermal method and displays good prospects as an excellent sulfur scaffold for lithium‐sulfur batteries. Benefiting from the sulfiphilic MoSe2, this nanocomposite sulfur cathode indicates excellent cycle life and delivers promising areal capacities with high‐mass‐loading electrodes.
We herein demonstrate the unusual effectiveness of two strategies in combination to enhance photoelectrochemical water splitting. First, the work function adjustment via molybdenum (Mo) doping ...significantly reduces the interfacial energy loss and increases the open-circuit photovoltage of bismuth vanadate (BiVO
) photoelectrochemical cells. Second, the creation and optimization of the heterojunction of boron (B) doping carbon nitride (C
N
) and Mo doping BiVO
to enforce directional charge transfer, accomplished by work function adjustment via B doping for C
N
, substantially boost the charge separation of photo-generated electron-hole pairs at the B-C
N
and Mo-BiVO
interface. The synergy between the above efforts have significantly reduced the onset potential, and enhanced charge separation and optical properties of the BiVO
-based photoanode, culminating in achieving a record applied bias photon-to-current efficiency of 2.67% at 0.54 V vs. the reversible hydrogen electrode. This work sheds light on designing and fabricating the semiconductor structures for the next-generation photoelectrodes.
Herein, we demonstrate a simple strategy to boost the photocatalytic performance of BiOI by introducing oxygen defects into the BiOI. The oxygen-deficient BiOI exhibits superior photocatalytic ...performance for the degradation of formaldehyde gas. The enhancement of photocatalytic activity is due to the enhanced separation and migration efficiency of photogenerated electrons and holes.
Vertical nystagmus is a common neuro-ophthalmic sign in vestibular medicine. Vertical nystagmus not only reflects the functional state of vertical semicircular canal but also reflects the effect of ...otoliths. Medical experts can take nystagmus symptoms as the key factor to determine the cause of dizziness. Traditional observation (visual observation conducted by medical experts) may be biased subjectively. Visual examination also requires medical experts to have enough experience to make an accurate diagnosis. With the development of science and technology, the detection system for nystagmus can be realized by using artificial intelligence technology. In this paper, a vertical nystagmus recognition method is proposed based on deep learning. This method is mainly composed of a dilated convolution layer module, a depthwise separable convolution module, a convolution attention module, a Bilstm-GRU module, etc. The average recognition accuracy of the proposed method is 91%. Using the same training dataset and test set, the recognition accuracy of this method for vertical nystagmus was 2% higher than other methods.
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