2D Laminar Membranes for Selective Water and Ion Transport

Selective water and ion transport are essential in fields related to the environment, resources, energy, and more. Membranes, especially those constituted by 2D materials, are promising to control mass transport within nano‐ and sub‐nanoscales. When stacked together, the ultrathin nanosheets of these materials can build up laminar membranes with an ordered layer‐like structure. Numerous channels are thereby created among layers for fast and selective mass transport, which arouses huge research and application interests. This Review aims to present the latest theoretical and experimental advances of 2D laminar membranes for selective water and ion transport, covering three fundamental aspects. Starting with a concise introduction to the materials and assembly for laminar membranes, it then mainly focuses on systematically discussing the transport‐controlling effects caused by intrinsic membrane structure and extrinsic influences. The relation between these effects and current membrane selective performance as well as future membrane designs is then elucidated. The most urgent challenges and corresponding opportunities that emerge around 2D laminar membranes are highlighted thereafter.     

A Game Changer: Functional Nano/Micromaterials for Smart Rechargeable Batteries

The imperative to electrify the transport sector in the past few decades has put millions of electric vehicles on the road worldwide with an extended mile range from critical technological breakthroughs in developing the rechargeable energy storage systems, which also covers electronic devices and smart grid applications. However, the available energy density of prevailing systems in the market (i.e., batteries) is reaching its boundaries due to the limited choice of electrochemical reactions that necessarily depend on the thermodynamics and kinetics of the components (e.g., cathode, anode, electrolyte, separator, and current collectors). Reaching the high energy density of batteries exploits new redox chemistry such as sensitive metal anodes, insulating and highly dissolving sulfur cathodes, etc., thus requiring novel designs of various multiscale functional materials to address the corresponding issues. Here, the recent achievements on the designs of smart functional materials for emerging problems in the whole range of systems are discussed: i) interfacial control/kinetic regulation of Li–S battery; ii) self‐healing‐driven structural stability in the electrode and electrolyte; iii) ion‐sieving functional membranes for selective scavenging capability; and iv) functional materials to ensure battery safety.     

Bioresorbable Wireless Sensors as Temporary Implants for In Vivo Measurements of Pressure

Pressures at targeted locations inside the human body serve as critically important diagnostic parameters for monitoring various types of serious or even potentially fatal medical conditions including intracranial, intra‐abdominal, and pulmonary hypertension, as well as compartment syndromes. Implantable commercial sensors provide satisfactory accuracy and stability in measurements of pressure, yet surgical removal is required after recovery of the patient to avoid infections and other risks associated with long‐term implantation. Sensors that dissolve in biofluids (or, equivalently, bioabsorb or bioresorb) avoid the need for such surgeries, yet current designs involve either hard‐wired connections and/or fail to provide quantitative measurements over clinically relevant lifetimes. Here, a bioresorbable, wireless pressure sensor based on passive inductor‐capacitor resonance circuits in layouts and with sets of materials that overcome these drawbacks is reported. Specifically, optimized designs offer sensitivity as high as ≈200 kHz mmHg^?1 and resolution as low as 1 mmHg. Encapsulation approaches that use membranes of Si₃N₄ and edge seals of natural wax support stable operation in vivo for up to 4 days. The bioresorbable pressure sensing technology reported here may serve as an important solution to temporary, real‐time monitoring of internal pressure for various medical conditions.     

Modeling, design and fabrication of a freestanding nanoporous membrane

Nanoporous membranes are widely researched on many application fronts. One challenge for nanoporous membrane research is to provide mechanically stable designs due to inherently weak strength from diminished dimensions. We present a mathematical model that predicts the deflection behavior and strength of nanoporous membranes. Based on these mathematic predictions, we fabricated a nanoporous membrane based on a hierarchical design using microfabrication techniques. Direct force measurement with an atomic force microscope shows that the model accurately predicts the deflection behavior of the fabricated nanoporous membrane.     

Minimum Stored Energy High-Field MRI Superconducting Magnets

A globally optimum minimum stored energy optimization strategy is implemented to design actively shielded superconducting magnet configurations used in high-field applications. The current density map is first obtained and used as a foundation for the magnet configurations by placing coils at current density local extremities. Optimized current density maps based on the stored energy formulation along with final magnet arrangements are provided to illustrate the findings. In this work, the focus was on compact superconducting magnets as measured by physical size and system footprint for given magnetic field properties inside the imaging region. The process of obtaining the current density maps proposed here over the given magnet domain, where superconducting coils are laid out, suggests that peak current densities occur around the perimeter of the domain, where in the most compact designs, with the domain length less than 1 m, the current direction alternates amongst adjacent coils. To reduce the peak magnetic field to acceptable levels on the superconductors in high-field designs, the size of the magnet domain is made larger, to the extent that the current densities no longer alternate between coils.      

Inductor design for high-power applications with broad-spectrumexcitation

The design of high-power inductors for applications with broad current spectrum excitation is a challenging task. The resonant inductor of a resonant DC-link inverter (RDCLI) is one such example. The inductor current consists of a resonant current component, a DC component, which supplies the active power to the load and a modulation component, which depends on the modulation strategy. In addition, the frequency and amplitude of the dominant current components change with operating point. Conventional inductor designs for single-frequency excitation do not perform well in broad-spectrum applications. In order to improve these designs, the impact of broad current spectrums on winding design, core selection, power density, and thermal-handling capability must be investigated. In this paper, alternate inductor topologies, which better address the above issues, are proposed and investigated     

一种基于BLDC电机的矢量控制电路设计

以CKS 32为主控芯片,研制了一种基于直流无刷电机(BLDC)的控制系统。该系统主要功能模块包括三相驱动系统、电流采样系统、保护系统和电源系统。传统采集三相电流的方式是三电阻采样和霍尔传感器采样,为进一步节省成本,提出一种基于MOS管内阻采样三相电流的方法。测试结果表明,该设计方案具有良好的性能。     

Sensors for electromagnetic pulse measurements both inside and away from nuclear source regions

For measuring transient electromagnetic fields and related quantities, one needs accurate broadband sensors with simple transfer functions. The various sensor designs developed to achieve this in an optimal manner are summarized. Such sensors are designed for use either in a "free space" environment (such as in an EMP simulator or on a system under test in such a simulator) or in a nuclear source region that includes local source current and perhaps conductivity. There are now numerous designs which have been iterated for improvements over the last decade.     

Atom‐Thick Membranes for Water Purification and Blue Energy Harvesting

Membrane‐based processes, namely, water purification and harvesting of osmotic power deriving from the difference in salinity between seawater and freshwater are two strategic research fields holding great promise for overcoming critical global issues such as the world growing energy demand, climate change, and access to clean water. Ultrathin membranes based on 2D materials (2DMs) are particularly suitable for highly selective separation of ions and effective generation of blue energy because of their unique physicochemical properties and novel transport mechanisms occurring at the nano‐ and sub‐nanometer length scale. However, due to the relatively high costs of fabrication compared to traditional porous membrane materials, their technological transfer toward large‐scale applications still remains a great challenge. Herein, the authors present an overview of the current state‐of‐the‐art in the development of ultrathin membranes based on 2DMs for osmotic power generation and water purification. The authors discuss several synthetic routes to produce atomically thin membranes with controlled porosity and describe in detail their performance, with a particular emphasis on pressure‐retarded osmosis and reversed electrodialysis methods. In the last section, an outlook and current limitations as well as viable future developments in the field of 2DM membranes are provided.     

Microstrip patch designs that do not excite surface waves

Two variations of a circular microstrip patch design are presented which excite very little surface wave power. Both of the designs are based on the principle that a ring of magnetic current in a substrate (which models the patches) will not excite the dominant TM₀ surface wave if the radius of the ring is a particular critical value. Numerical results for radiation efficiency and radiated field strength from a ring of magnetic current are shown to verify this basic design principle. The proposed patch designs are chosen to have a radius equal to this critical value, while maintaining resonance at the design frequency. The designs excite very little surface-wave power, and thus have smoother radiation patterns when mounted on finite-size ground planes, due to reduced surface-wave diffraction. They also have reduced mutual coupling, due to the reduced surface-wave excitation. Measured results for radiation patterns and field strength within the substrate are presented to verify the theoretical concepts     

Comparison of contact designs for improved stability of broad areasemiconductor lasers

Patterned electrode designs are used to control optical mode shape in high-power semiconductor lasers by localizing current injection. In this letter, we present comparison of current density profiles in the active layer achieved by different contact designs. Single-voltage digitated contact, distributed regular and random Gaussian contact configurations are studied using numerical solutions of semiconductor device equations that govern electrostatic potential and carrier concentrations in three spatial dimensions. The results of our calculations indicate that lateral current profile is influenced by the contact shape in the transverse direction and the thickness of the junction on the contact side     

Review of planarization and reliability aspects of future interconnect materials

Device linewidths are shrinking resulting in more stringent requirements on choice of materials, processes and designs. Current generation of memory and microprocessor designs use tungsten as the main interconnect material with aluminum being utilized in lines. It is being proposed at the current time that copper and aluminum will be likely candidates for the future interconnect structures. Although both metals are equally suitable as the next generation interconnect, there still exist certain material issues relating to deposition, electromigration/reliability, and planarization that need to be addressed.     

交流电能表检定装置的自动检定程序

设计和介绍了一款应用程序。程序可以实现对国内某一种型号的交流电能表检定装置进行自动检定,并可以对检定数据进行查询、修改、打印等操作     

CMOS tunable linear current divider

A CMOS current divider is proposed which can handle an input current as large as the bias current, i.e. the modulation depth can be 100%;. The performance of the circuit is nearly independent of transistor characteristics. Therefore the circuit is well applicable for designs in modern submicron processes. The measured divider can be tuned over more than a factor of 2     

Electromigration: the time bomb in deep-submicron ICs

Electromigration results from the movement of metal ions as current flows through power wires in integrated circuits, causing voids and hillocks in the wires. The voids increase resistance or even cause opens in the wires, while hillocks can cause shorts to adjacent wires. This paper describes how electromigration is a ticking time bomb in IC designs, which can trigger a system failure at some undefined future time. The phenomenon is particularly likely to afflict the thin, tightly spaced power-distribution lines of deep-submicron designs     

光接收机前端等效输入噪声电流谱密度与噪声系数间的关系

根据光接收机前端等效电路模型,建立了噪声系数与等效输入噪声电流谱密度的关系.提出通过测量光接收机前端电路噪声系数间接获得等效输入噪声电流谱密度的方法.155Mb/s高阻结构光接收机前置放大器的电路仿真与计算验证了推导公式的正确性.最后给出在芯片测试实例.     

Edge leakage control in platinum-silicide Schottky-barrier diodesused for infrared detection

Platinum silicide (PtSi) on p-silicon Schottky-barrier focal plane arrays (FPAs) are strong candidates for infrared (IR) detection up to a wavelength of about 5 μm. However, an inherently low quantum efficiency (about 1% at 4 μm) makes it important to maximize the fill factor or the area of the array that is IR-sensitive. Current designs use an n^- guard ring around the PtSi diodes to suppress edge leakage. This is effective, but the guard-ring overlap can significantly reduce the sensitive area of the diode. An aluminium plate that is already used as a photon reflector above the diode in current designs can be positively biased as a field plate to create a surface depletion layer around the diode periphery. This produces leakage current suppression equivalent to the guard ring without giving up IR-sensitive diode area     

Carrier scattering approach to the origins of dark current in mid and far-infrared (terahertz) quantum-well intersubband photodetectors(QWLPs)

A carrier scattering approach is taken in an analysis of the affect on the dark current of extending the operating wavelength of conventional bound to continuum quantum-well intersubband photodetectors. It is found that both the sequential tunneling and the thermionic emission contributions to the dark current increase as the wavelength of the detector is extended from the mid- to far-infrared. Dark current designs rules are derived     

Dynamically Gas‐Phase Switchable Super(de)wetting States by Reversible Amphiphilic Functionalization: A Powerful Approach for Smart Fluid Gating Membranes

In nature, cellular membranes perform critical functions such as endocytosis and exocytosis through smart fluid gating processes mediated by nonspecific amphiphilic interactions. Despite considerable progress, artificial fluid gating membranes still rely on laborious stimuli‐responsive mechanisms and triggering systems. In this study, a room temperature gas‐phase approach is presented for dynamically switching a porous material from a superhydrophobic to a superhydrophilic wetting state and back. This is realized by the reversible attachment of bipolar amphiphiles, which promote surface wetting. Application of this reversible amphiphilic functionalization to an impermeable nanofibrous membrane induces a temporary state of superhydrophilicity resulting in its pressure‐less permeation. This mechanism allows for rapid smart fluid gating processes that can be triggered at room temperature by variations in the environment of the membrane. Owing to the universal adsorption of volatile amphiphiles on surfaces, this approach is applicable to a broad range of materials and geometries enabling facile fabrication of valve‐less flow systems, fluid‐erasable microfluidic arrays, and sophisticated microfluidic designs.     

光接收机前端等效输入噪声电流谱密度与噪声系数间的关系

根据光接收机前端等效电路模型,建立了噪声系数与等效输入噪声电流谱密度的关系.提出通过测量光接收机前端电路噪声系数间接获得等效输入噪声电流谱密度的方法.155Mb/s高阻结构光接收机前置放大器的电路仿真与计算验证了推导公式的正确性.最后给出在芯片测试实例.