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In this work, we fabricated an ITO/WOX/TaN memristor device by reactive sputtering to investigate resistive switching and conduct analog resistive switching to implement artificial synaptic devices. The device showed good pulse endurance (104 cycles), a high on/off ratio (>10), and long retention (>104 s) at room temperature. The conduction mechanism could be explained by Schottky emission conduction. Further, the resistive switching characteristics were performed by additional pulse-signal-based experiments for more practical operation. Lastly, the potentiation/depression characteristics were examined for 10 cycles. The results thus indicate that the WOX-based devices are appropriate candidates for synaptic devices as well as next-generation nonvolatile memory. [ABSTRACT FROM AUTHOR]

The ferroelectric characteristics of a metal-ferroelectric-metal (MFM) ferroelectric tunneling junction (FTJ) capacitor device are investigated herein. The device consists of an aluminum-doped hafnium oxide (HAO) insulator sandwiched between tungsten (W) and titanium nitride (TiN) metal electrodes. Rapid thermal annealing (RTA) is performed for 20 s under a nitrogen atmosphere at temperatures of 750 °C, 800 °C, and 850 °C to find that ferroelectricity with a large remanent polarization (Pr) of 41.28 μC cm−2 can be obtained at the optimum annealing temperature of 800 °C. The presence of ferroelectricity is confirmed by polarization-switching positive-up–negative-down (PUND) measurements and by the hysteric polarization–voltage (P–V) loop. All devices exhibit excellent reliability, with an endurance of up to ∼106 cycles and long retention characteristics. In addition, the interfacial paraelectric capacitance (Ci) values of the three HAO FTJs are investigated via pulse-switching measurements. The results indicate that the HAO film annealed at 800 °C for 20 s exhibits an excellent tunneling electro-resistance (TER) ratio of 186% and this is attributed to the extra paraelectric layer formed between the ferroelectric layer and the bottom electrode. The detailed findings of this study are expected to assist in the development of hafnium oxide-based ferroelectric non-volatile memory applications. [ABSTRACT FROM AUTHOR]

In this work, we evaluate the resistive switching (RS) and synaptic characteristics of a fully transparent resistive random-access memory (T-RRAM) device based on indium-tin-oxide (ITO) electrodes. Here, we fabricated ITO/WOX/ITO capacitor structure and incorporated DC-sputtered WOX as the switching layer between the two ITO electrodes. The device shows approximately 77% (including the glass substrate) of optical transmittance in visible light and exhibits reliable bipolar switching behavior. The current-voltage (I–V) curve is divided into two types: partial and full curves affected by the magnitude of the positive voltage during the reset process. In the partial curve, we confirmed that the retention could be maintained for more than 104 s and the endurance for more than 300 cycles could be stably secured. The switching mechanism based on the formation/rupture of the filament is further explained through the extra oxygen vacancies provided by the ITO electrodes. Finally, we examined the responsive potentiation and depression to check the synaptic characteristics of the device. We believe that the transparent WOX-based RRAM could be a milestone for neuromorphic devices as well as future non-volatile transparent memory. [ABSTRACT FROM AUTHOR]

This paper presents an optical see-through head-mounted display (OST-HMD) that can provide a highly immersive augmented reality (AR) environment. Because visibility of objects is degraded by external light and because projection optics cannot represent black color, the reality of AR content is reduced. To solve this problem, we adopted an additional transparent display to adjust the transmittance of exterior light. This adjustment is achieved using a guest–host liquid crystal (GHLC) to provide transparency in the initial state and opacity when voltage is applied. To verify the display's usefulness, we measured ambient contrast ratio (ACR) and color gamut under various ambient light conditions after attaching the GHLC panel to the existing OST-HMD (Microsoft HoloLens). Under typical office illumination, use of the GHLC panel increased the ACR by 4.67 times, and the color gamut by 2.87 times compared to the OST-HMD without it. Under high illumination the panel increased the ACR by 1.54 times and the color gamut by 16.16 times. The proposed method significantly improved the ambient contrast ratio and color expression, and yielded a flexible way to customize existing OST-HMDs by adding a detachable display. [ABSTRACT FROM AUTHOR]

This paper presents a channel estimation scheme using a new jammed pilot detection algorithm for orthogonal frequency-division multiplexing (OFDM) systems under narrow-band jamming (NBJ). The jammed pilot subcarrier can be detected and excised by using the proposed algorithm after least squares estimation. The average mean square error (mse) on one OFDM symbol both under a jammed and a removed pilot subcarrier are derived analytically. Moreover, the symbol error rate (SER) performance for the channel estimation scheme using the proposed algorithm is evaluated by simulation. From the results, we can show that the channel estimator with the proposed algorithm improves the mse and SER performances at a low signal-to-jamming ratio. Index Terms--Channel estimation, least squares (LS), linear interpolation, narrow-band jamming (NBJ), orthogonal frequency-division multiplexing (OFDM) systems.

In time-varying fading channels, orthogonal frequency division multiplexing systems suffer severe performance degradation caused by interchannel interference (ICI). We utilize this ICI as a source of diversity by using a new ICI-cancellation algorithm and Wiener filter. The proposed algorithm can support joint Doppler-frequency diversity gain. In addition, both the computational complexity and total detection time are reduced. Index Terms--Hybrid interference cancellation (HIC), joint Doppler-frequency diversity, orthogonal frequency division multiplexing (OFDM), parallel interference cancellation (PIC), successive interference cancellation, Wiener filter (WF).

Leucine‐rich repeat kinase 2 (LRRK2) is considered a promising therapeutic target for Parkinson's disease, Crohn's disease, and cancer. Despite considerable research, none of these inhibitors are available for clinical application. Herein, we designed and synthesized novel thienopyrimidine derivatives by a bioisosteric replacement and investigated their structure–activity relationships. Thieno[3,2‐d]pyrimidine derivative 22 showed the most potent inhibitory activity and inhibited both wild‐type and G2019S mutant LRRK2 with IC50 values of 30 and 14 nM, respectively. [ABSTRACT FROM AUTHOR]