Environmentally Adaptive Polymer Hydrogels: Maintaining Wet-Soft Features in Extreme Conditions

Hydrogels have been widely explored to adapt to different application circumstances. As typical wet-soft materials, the high-water content of hydrogels is beneficial to their wide biomedical applications. Moreover, hydrogels have been displaying considerable application potential in some high-tech areas, like brain-computer interface, intelligent actuator, flexible sensor, etc. However, traditional hydrogel is susceptive to freezing below zero, dehydration, performance swelling-induced deformation, and suffers from mechanical damage in extremely mechanical environments, which result in the loss of wet-soft peculiarities (e.g., flexibility, structure integrity, transparency), greatly limiting their applications. Therefore, reducing the freezing point, improving the dehydration/solution resistance, and designing mechanical adaptability are effective strategies to endow hydrogels with the extreme environmental adaptability, thus broadening their application fields. This review systematically summarizes research advances of environmentally adaptive hydrogels (EAHs), comprising anti-freezing, dehydration-resistant, acid/base/swelling deformation-resistant, and mechanical environment adaptive hydrogels (MEAHs). Firstly, fabrication methods are presented, including the deep eutectic solvent/ionic liquid substituent, the addition of salts, organogel, polymer network modification, and double network (DN) complex/nanocomposite strategy, etc. Meanwhile, the features of different approaches are overviewed. The mechanisms, properties, and applications (e.g., intelligent actuator, wound dressing, flexible sensor) of EAHs are demonstrated. Finally, the issues and future perspectives for EAHs’ researches are demonstrated.     

Hydrometeor classification system using dual-polarization radar measurements: model improvements and in situ verification

A hydrometeor classification system based on a fuzzy logic technique using dual-polarization radar measurements of precipitation is presented. In this study, five dual-polarization radar measurements (namely horizontal reflectivity, differential reflectivity, specific differential phase, correlation coefficient, and linear depolarization ratio) and altitude relating to environmental melting layer are used as input variables of the system. The hydrometeor classification system chooses one of nine different hydrometeor categories as output. The system presented in this paper is a further development of an existing hydrometeor classification system model developed at Colorado State University (CSU). The hydrometeor classification system is evaluated by comparing inferred results from the CSU CHILL Facility dual-polarization radar measurements with the in situ sample data collected by the T-28 aircraft during the Severe Thunderstorm Electrification and Precipitation Study.     

Fabrication of the flexible pentacene thin-film transistors on 304 and 430 stainless steel (SS) substrate

Flexible organic thin-film transistors (OTFT) were fabricated on 304 and 430 stainless steel (SS) substrate with aluminum oxide as a gate insulator and pentacene as an organic semiconductor. Chemical mechanical polishing (CMP) process was used to study the effect of the SS roughens on the dielectric properties of the gate insulator and OTFT characteristics. The surface roughness was decreased from 33.8 nm for 304 SS and 19.5 nm for 430 SS down to ～2.5 nm. The leakage current of the metal–insulator–metal (MIM) structure (Au/Al₂O₃/SS) was reduced with polishing. Mobility and on/off ratio of pentacene TFT with bare SS showed a wide range of values between 0.005 and 0.36 cm²/Vs and between 10³ and 10⁵ depending on the location in the substrate. Pentacene TFTs on polished SS showed an improved performance with a mobility of 0.24–0.42 cm²/Vs regardless of the location in the substrate and on/off ratio of ～10⁵. With self assembled monolayer formation of octadecyltrichlorosilane (OTS) on insulator surface, mobility and on/off ratio of pentacene TFT on polished SS was improved up to 0.85cm²/Vs and ～10⁶. I–V characteristics of pentacene TFT with OTS treated Al₂O₃/304 SS was also obtained in the bent state with a bending diameter (D) of 24, 45 or 70 mm and it was confirmed that the device performed well both in the linear regime and the saturation regime.     

Plasmonic Light Beaming Manipulation and its Detection Using Holographic Microscopy

Plasmonic off axis beaming and focusing of light by the use of asymmetric or non-periodic dielectric gratings around a metallic slit are experimentally demonstrated. The far-field probing was done by holographic microscopy. While the conventional near-field microscopes can probe only near-fields, our four-step phase-shift interferometer provides an efficient way of probing and reconstructing light paths coming out from the plasmonic devices. We hope our experimental work contributes to the practical applications of plasmonics such as optical interconnection and optical data storage.      

ECG measurement on a chair without conductive contact

For the purpose of long-term, everyday electrocardiogram (ECG) monitoring, we present a convenient method of ECG measurement without direct conductive contact with the skin while subjects sat on a chair wearing normal clothes. Measurements were made using electrodes attached to the back of a chair, high-input-impedance amplifiers mounted on the electrodes, and a large ground-plane placed on the chair seat. ECGs were obtained by the presented method for several types of clothing and compared to ECGs obtained from conventional measurement using Ag-AgCl electrodes. Motion artifacts caused by usual desk works were investigated. This study shows the feasibility of the method for long-term, convenient, everyday use.     

Designing training sequences for carrier frequency estimation in frequency-selective channels

A procedure for selecting a training sequence (TS) is developed for frequency estimation in frequency-selective channels. An expression for the unconditional Crame/spl acute/r-Rao bound (UCRB) is obtained by averaging the CRB for frequency estimation over the probability density function of Gaussian random channels. In addition, a necessary and sufficient condition for minimizing the UCRB is derived. Based on these results, a procedure for selecting a TS is developed. Through a computer search, binary TSs up to length 24 are found and tabulated. It is observed that periodic TSs tend to be selected when the TS length is twice the channel duration. Simulation results demonstrate that the proposed TSs can enhance the performance of the maximum likelihood (ML) frequency estimate.     

共面转换液晶显示器中获得对比度高于1:600的新技术

薄膜晶体管液晶电视(TFT-LCD TV)因为具有薄、轻、紧凑和可随意放置的特点，已经占据了大部分电视机市场。除了这些物理特性以外，最重要的特性是已具有了良好像质的对比度。为了将对比度提高到1：600以上，对偏振片膜、背光源板、滤色片树脂、电极锥角和摩擦条件等都进行了研究。优化的背光板组合，光滑的电极锥角和摩擦方法的控制是提高对比度的主要控制因素。应用新开发的滤色片树脂，对获得高对比度最为有效。     

A One‐Kilobit PQR‐CMOS Smart Pixel Array

The photonic quantum ring (PQR) laser is a three dimensional whispering gallery (WG) mode laser and has anomalous quantum wire properties, such as microampere to nanoampere range threshold currents and √T‐dependent thermal red shifts. We observed uniform bottom emissions from a 1‐kb smart pixel chip of a 32×32 InGaAs PQR laser array flip‐chip bonded to a 0.35 µm CMOS‐based PQR laser driver. The PQR‐CMOS smart pixel array, now operating at 30 MHz, will be improved to the GHz frequency range through device and circuit optimization.     

Model-based disturbance attenuation for CNC machining centers incutting process

A disturbance attenuation method in a control system, called the model-based disturbance attenuator (MBDA), is proposed, and its properties are studied. The MBDA makes the plant performs similarly to the nominal plant, as much as possible, using a compensator. Then, a controller is designed based on the nominal plant. It is shown that the MBDA is extremely robust with respect to large variations of load inertia. The MBDA is implemented in a position control system of a computer numerical control (CNC) machining center, where the velocity control system is composed of a servo-pack (PI controller), a servo motor, and a load. The MBDA attenuates external disturbances significantly in the cutting process containing high-frequency components, as well as the frictional forces containing large DC component. Several other controllers are also implemented in a position control system of a CNC machining center in a similar way as the MBDA, and the experimental results are compared with one another     

Roles of wave impedance and refractive index in photonic crystalswith magnetic and dielectric properties

We investigated the roles of wave impedance and refractive index in photonic crystals by means of analytical expressions for edges frequencies of a photonic bandgap (PBG) in a one-dimensional photonic crystal with magnetic and dielectric properties. The analytical expressions were derived when the optical thicknesses of layers are the same. The wave impedance governs the formation of PBG's and the intensity of defect modes. Meanwhile, the position of PBG's and the creation of defect modes are related to the refractive index