Impedance matching by series condensers for power receivers of in vivo robotic capsules

An impedance matching technique using series condensers for the power receivers of in vivo robotic capsules is proposed. The power delivery function of the condenser ratio and its optimal ratio are derived. Experimental results validate the derived function.     

Regulated Breathing Effect of Silicon Negative Electrode for Dramatically Enhanced Performance of Li‐Ion Battery

Si is an attractive negative electrode material for lithium ion batteries due to its high specific capacity (≈3600 mAh g^–1). However, the huge volume swelling and shrinking during cycling, which mimics a breathing effect at the material/electrode/cell level, leads to several coupled issues including fracture of Si particles, unstable solid electrolyte interphase, and low Coulombic efficiency. In this work, the regulation of the breathing effect is reported by using Si–C yolk–shell nanocomposite which has been well‐developed by other researchers. The focus is on understanding how the nanoscaled materials design impacts the mechanical and electrochemical response at electrode level. For the first time, it is possible to observe one order of magnitude of reduction on breathing effect at the electrode level during cycling: the electrode thickness variation reduced down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials. The Si–C yolk–shell nanocomposite electrode exhibits excellent capacity retention and high cycle efficiency. In situ transmission electron microscopy and finite element simulations consistently reveals that the dramatically enhanced performance is associated with the regulated breathing of the Si in the new composite, therefore the suppression of the overall electrode expansion.     

DNA/Tannic Acid Hybrid Gel Exhibiting Biodegradability,Extensibility, Tissue Adhesiveness,and Hemostatic Ability

DNA has emerged as a novel material in many areas of materials science due to its programmability. Especially, DNA hydrogels have been studied to incorporate new functions into gels. To date, only a few methods have been developed for fabricating DNA hydrogels, such as the use of complementary sequences or covalent bond. Herein, it is demonstrated that one of the most well‐known plant‐derived polyphenols, tannic acid (TA), can form a DNA hydrogel which is named TNA hydrogel ( T A + D NA ). TA plays a role as a “molecular glue” by a new mode of action reversibly connecting between phosphodiester bonds, which is different from the crosslinking utilizing complementary sequences. TA intrinsically degrades due to ester bonds connecting between pyrogallol groups, causing a degradable DNA hydrogel. Furthermore, TNA gel is multifunctional in that the gel is extensible upon pulling and adhesive to tissues because of the rich polyphenol groups in TA (ten phenols per TA). Unexpectedly, TNA gel exhibits superior in vivo hemostatic ability that can be useful for biomedical applications. This new DNA hydrogel preparation method represents a new technique for fabricating a large amount of DNA‐based hemostatic hydrogel without chemically modifying DNA or requiring the crosslinking by complementary sequences.     

Microstructure Evolution of Concentration Gradient Li[Ni0.75Co0.10Mn0.15]O2 Cathode for Lithium‐Ion Batteries

Detailed analysis of the microstructural changes during lithiation of a full‐concentration‐gradient (FCG) cathode with an average composition of Li[Ni_0.75Co_0.10Mn_0.15]O₂ is performed starting from its hydroxide precursor, FCG [Ni_0.75Co_0.10Mn_0.15](OH)₂ prior to lithiation. Transmission electron microscopy (TEM) reveals that a unique rod‐shaped primary particle morphology and radial crystallographic texture are present in the prelithiation stage. In addition, TEM detected a two‐phase structure consisting of MnOOH and Ni(OH)₂, and crystallographic twins of MnOOH on the Mn‐rich precursor surface. The formation of numerous twins is driven by the lattice mismatch between MnOOH and Ni(OH)₂. Furthermore, the twins persist in the lithiated cathode; however, their density decrease with increasing lithiation temperature. Cation disordering, which influences cathode performance, is observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles lead to the deterioration of electrochemical properties. The twins in the FCG cathode precursor may promote the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor.     

In situ high-resolution transmission electron microscopy of photocatalytic reactions by excited electrons in ionic liquid

A transmission electron microscope (TEM) sample for observing photocatalysis in a liquid was prepared by using N,N,N-trimetyl-N-propylammonium-bis(trifluoromethanesulfonyl)imide. The ionic liquid (IL) was used as a reaction solvent. Tetrachloroauric acid was dissolved in the IL as gold ion species. Rutile particles were added in the solution as a photocatalyst. The low vapor pressure of the IL enables a diffusing system in high vacuum of TEM. Rutile particles were UV irradiated in that liquid phase. After 3 h UV irradiation, a gold particle of 8 nm diameter was grown on the TiO2 surface. Photonucleation of Au/TiO2 system was discussed from the high-resolution TEM images.     

Evaluation of 1/f Noise Characteristics for Si‐Based Infrared Detection Materials

Silicon antimony films are studied as resistors for uncooled microbolometers. We present the fabrication of silicon films and their alloy films using sputtering and plasma‐enhanced chemical vapor deposition. The sputtered silicon antimony films show a low 1/f noise level compared to plasma‐enhanced chemical vapor deposition (PECVD)‐deposited amorphous silicon due to their very fine nanostructure. Material parameter K is controlled using the sputtering conditions to obtain a low 1/f noise. The calculation for specific detectivity assuming similar properties of silicon antimony and PECVD amorphous silicon shows that silicon antimony film demonstrates an outstanding value compared with PECVD Si film.     

Community-based diffusion scheme using Markov chain and spectral clustering for mobile social networks

Wireless Networks - With the increase in the number of mobile devices such as tablets and smart watches, mobile social networks (MSNs) provide great opportunities for people to exchange...     

Novel concepts for reliability technology

We begin by examining the diverse connotations of the term quality. The desirable shape traced by the failure rate of the entire life of a good product, which might be called a hockey-stick line rather than a bathtub curve, is introduced. From the hockey-stick line and the definition of reliability, we extract two measurements. The terms r-reliability (failure rate) and durability (product life) are then explained. The conceptual analysis of failure mechanics explains that reliability technology pertains to the design area.The desirable shape of the failure-rate curve of electronic items, the hockey-stick line, clarifies that mean time to failure (MTTF) as the inverse of failure rate can be regarded as nominal life. We then discuss the BX life which is different from the MTTF, and reliability relationships between components and the set product. We recommend reshaped definitions of r-reliability and durability.We clarify the procedure to improve reliability and to identify the failure mode in order to find for right solutions and recommend a generalized life-stress failure model.     

Compensation of RF impairment in multi-band receiver based on RF sub-sampling

This paper is studied about multi-band receiver using sub-sampling and time division multiplexing (TDM) techniques. Software defined radio (SDR) has a goal that places the analog to digital converter (ADC) as near the antenna as possible. But current technique actually cannot process ADC about radio frequency (RF) band signals. So one method is being studied that samples RF band signals to intermediate frequency (IF) band. As one of the ways, sub-sampling technique can convert signals from RF band to IF band without oscillator. If sub-sampling technique is used, over 2 bands can convert signals from RF band to IF band. However, due to the filter performance in RF band, it is possible that interference is generated between signals that are converted to low frequency band. And the problem degrades performance. In this paper, we propose one method that uses TDM technique as a solution to avoid interference between signals. By processing TDM and sub-sampling at the same time, the method can get signals without large changes from the conventional structures.     

High‐Performance Piezoelectric,Pyroelectric, and Triboelectric Nanogenerators Based on P(VDF‐TrFE) with Controlled Crystallinity and Dipole Alignment

Poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)), as a ferroelectric polymer, offers great promise for energy harvesting for flexible and wearable applications. Here, this paper shows that the choice of solvent used to dissolve the polymer significantly influences its properties in terms of energy harvesting. Indeed, the P(VDF‐TrFE) prepared using a high dipole moment solvent has higher piezoelectric and pyroelectric coefficients and triboelectric property. Such improvements are the result of higher crystallinity and better dipole alignment of the polymer prepared using a higher dipole moment solvent. Finite element method simulations confirm that the higher dipole moment results in higher piezoelectric, pyroelectric, and triboelectric potential distributions. Furthermore, P(VDF‐TrFE)‐based piezoelectric, pyroelectric, and triboelectric nanogenerators (NGs) experimentally validate that the higher dipole moment solvent significantly enhances the power output performance of the NGs; the improvement is about 24% and 82% in output voltage and current, respectively, for piezoelectric NG; about 40% and 35% in output voltage and current, respectively, for pyroelectric NG; and about 65% and 75% in output voltage and current for triboelectric NG. In brief, the approach of using a high dipole moment solvent is very promising for high output P(VDF‐TrFE)‐based wearable NGs.