Decoupled energy‐law preserving numerical schemes for the Cahn–Hilliard–Darcy system

We study two novel decoupled energy‐law preserving and mass‐conservative numerical schemes for solving the Cahn‐Hilliard‐Darcy system which models two‐phase flow in porous medium or in a Hele–Shaw cell. In the first scheme, the velocity in the Cahn–Hilliard equation is treated explicitly so that the Darcy equation is completely decoupled from the Cahn–Hilliard equation. In the second scheme, an intermediate velocity is used in the Cahn–Hilliard equation which allows for the decoupling. We show that the first scheme preserves a discrete energy law with a time‐step constraint, while the second scheme satisfies an energy law without any constraint and is unconditionally stable. Ample numerical experiments are performed to gauge the efficiency and robustness of our scheme. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 936–954, 2016     

Synthesis of Co-Ni oxide microflowers as a superior anode for hybrid supercapacitors with ultralong cycle life

Li-ion hybrid capacitors (LIHCs), composing of a lithium-ion battery (LIB) type anode and a supercapacitor (SC) type cathode, gained worldwide popularity due to harmonious integrating the virtues of high energy density of LIBs with high power density of SCs. Herein, nanoflakes composed microflower-like Co-Ni oxide (CoNiO) was successfully synthesized by a simple co-precipitation method. The atomic ratio of as-synthesized CoNiO is determined to be 1:3 through XRD and XPS analytical method. As a typical battery-type material, CoNiO and capacitor-type activated polyanilinederived carbon (APDC) were used to assemble LIHCs as the anode and cathode materials, respectively. As a result, when an optimized mass ratio of CoNiO and APDC was 1:2, CoNiO//APDC LIHC could deliver a maximum energy density of 143 Wh kg^-1 at a working voltage of 1-4 V. It is worth mentioning that the LIHC also exhibits excellent cycle stability with the capacitance retention of 78.2% after 15,000 cycles at a current density of 0.5 A g^-1.     

A simple and accurate method for measuring program/erase speed in a memory capacitor structure

With the merits of a simple process and a short fabrication period, the capacitor structure provides a convenient way to evaluate memory characteristics of charge trap memory devices. However, the slow minority carrier generation in a capacitor often makes an underestimation of the program/erase speed. In this paper, illumination around a memory capacitor is proposed to enhance the generation of minority carriers so that an accurate measurement of the program/erase speed can be achieved. From the dependence of the inversion capacitance on frequency, a time constant is extracted to quantitatively characterize the formation of the inversion layer. Experimental results show that under a high enough illumination, this time constant is greatly reduced and the measured minority carrier-related program/erase speed is in agreement with the reported value in a transistor structure.     

Efficiency at high spinning frequencies of heteronuclear decoupling methods designed to quench rotary resonance

The performance of two recently developed heteronuclear decoupling schemes designed to quench rotary resonance, phase-inverted supercycled sequence for attenuation of rotary resonance (PISSARRO) and high-phase two-pulse phase modulation (high-phase TPPM), are probed at high spinning frequencies. High-phase TPPM may be useful at the n=1 rotary resonance condition while PISSARRO permits efficient decoupling over a broad commonly used range of rf amplitudes, even at very high spinning frequencies. New insights into the response of spin systems to both decoupling schemes have been gained. High-phase TPPM is sensitive to the offsets of remote protons, their chemical shift anisotropies, and the relative orientations of the heteronuclear dipolar and proton chemical shift tensors. Since PISSARRO is virtually immune against such effects, the method is especially suited for very high magnetic fields.     

旋转椭球形电容器的电容与静电能

采取一种新的方法求解得出了旋转椭球形电容器的电容和静电能.     

Chemically Modified Ordered Mesoporous Carbon/Polyaniline Composites for Electrochemical Capacitors

Chemically modified ordered mesoporous carbon CMK-3 materials were prepared by means of an easy wet-oxidative method in 2 mol/L nitric acid aqueous solution. A large amount of oxygen-containing functional groups were introduced onto the CMK-3 surface. Modified CMK-3(m-CMK-3) and aniline monomer were polymerized via an in situ chemical oxidative polymerization method. Morphological characterizations of m-CMK-3/PANI (polyaniline) composites were carried out via field emission scanning electron microscopy(SEM)...     

不同不耦合系数下花岗岩爆破损伤特性的离散元模拟

为研究径向装药不耦合系数对花岗岩爆破损伤程度的影响,在考虑爆炸冲击波和爆生气体共同作用的基础上,提出了一种"动"、"静"荷载混合施加的PFC爆破模拟方法,采用该方法分别进行了6种不耦合系数下花岗岩爆破过程的数值模拟。模拟结果显示,随着装药不耦合系数的增大,花岗岩爆破损伤程度先增强后减弱。耦合装药下,爆生裂纹数量为9367;不耦合系数为1.2时,裂纹数量增加至最多,为24975;不耦合系数为2.0时,裂纹数量减少为292。对比耦合装药和不耦合系数为1.4时的花岗岩损伤模式发现,爆生气体的准静态压力对爆生裂纹的扩展具有重要作用。根据不同不耦合系数下的爆生裂纹数量,建立了不耦合系数大于或等于1.2时的岩石爆破损伤程度预测模型,拟合度达0.9808。该预测模型对爆破施工设计等工作具有一定的参考意义。     

Lead‐enhanced gas‐phase stability of multiply charged EDTA anions: a combined experimental and theoretical study

Besides their fundamental importance, multiply charged anions (MCAs) are considered as promising molecular capacitors for which their intrinsic stabilities are of great significance. Herein, the gas‐phase stabilities of ethylenediaminetetraacetic acid (EDTA) anions (i.e. [EDTA‐nH]^n?, n = 1–4) and their Pb(II) complexes (i.e. [EDTA + Pb‐nH]^(2‐n)?, n = 3, 4) have been investigated using an approach that combines extractive electrospray ionization mass spectrometry (EESI‐MS) measurements, Car–Parrinello molecular dynamics simulations and density functional theory/Tao–Perdew–Staroverov–Scuseria calculations. The EESI‐MS data showed that the doubly charged EDTA anions in the form of [EDTA‐2H]^2? and [EDTA + Pb‐4H]^2? were much more abundantly observed than the singly charged species such as [EDTA‐H]^? and [EDTA + Pb‐3H]^?, respectively. The calculation results indicated that [EDTA‐2H]^2? and [EDTA + Pb‐4H]^2? anions were thermodynamically more stable than the [EDTA‐H]^? and [EDTA + Pb‐3H]^? species in the gas phase, respectively. The [EDTA + Pb‐3H]^? anions preferred five‐coordinated structure, whereas [EDTA + Pb‐4H]^2? anions formed either five‐coordinated or six‐coordinated structures. The calculations further revealed that significant electron clouds drifting from the ligand EDTA to the metal Pb(II) ions and the large distances between the carboxylic groups reduced the Coulomb repulsion among the excess electrons of these MCAs. Our data demonstrated that EESI‐MS combined with theoretic calculations were able to provide a deep insight into the fundamental behavior of stability of MCAs in the gas phase and, thus, might be useful tools for studying MCAs for potential molecular capacitors. Copyright © 2012 John Wiley & Sons, Ltd.     

Substrate temperature influenced physical properties of silicon MOS devices with TiO2 gate dielectric

DC reactive magnetron sputtering technique was employed for deposition of titanium dioxide (TiO₂) films. The films were formed on Corning glass and p‐Si (100) substrates by sputtering of titanium target in an oxygen partial pressure of 6×10^?2 Pa and at different substrate temperatures in the range 303 – 673 K. The films formed at 303 K were X‐ray amorphous whereas those deposited at substrate temperatures ≥ 473 K were transformed into polycrystalline nature with anatase phase of TiO₂. Fourier transform infrared spectroscopic studies confirmed the presence of characteristic bonding configuration of TiO₂. The surface morphology of the films was significantly influenced by the substrate temperature. MOS capacitor with Al/TiO₂/p‐Si sandwich structure was fabricated and performed current–voltage and capacitance–voltage characteristics. At an applied gate voltage of 1.5 V, the leakage current density of the device decreased from 1.8 × 10^?6 to 5.4 × 10^?8 A/cm² with the increase of substrate temperature from 303 to 673 K. The electrical conduction in the MOS structure was more predominant with Schottky emission and Fowler‐Nordheim conduction. The dielectric constant (at 1 MHz) of the films increased from 6 to 20 with increase of substrate temperature. The optical band gap of the films increased from 3.50 to 3.56 eV and refractive index from 2.20 to 2.37 with the increase of substrate temperature from 303 to 673 K. Copyright © 2012 John Wiley & Sons, Ltd.