Implementation of mmWave long-range backhaul for UAV-BS

Uncrewed aerial vehicles (UAVs) have become a vital element in nonterrestrial networks, especially with respect to 5G communication systems and beyond. The use of UAVs in support of 4G/5G base station (uncrewed aerial vehicle base station [UAV-BS]) has proven to be a practical solution for extending cellular network services to areas where conventional infrastructures are unavailable. In this study, we introduce a UAV-BS system that utilizes a high-capacity wireless backhaul operating in millimeter-wave frequency bands. This system can achieve a maximum throughput of 1.3 Gbps while delivering data at a rate of 300 Mbps, even at distances of 10 km. We also present the details of our testbed implementation alongside the performance results obtained from field tests.     

Tetraphenylimidazole‐Based Excited‐State Intramolecular Proton‐Transfer Molecules for Highly Efficient Blue Electroluminescence

Aiming for highly efficient blue electroluminescence, we have designed and synthesized a novel class of tetraphenylimidazole‐ based excited‐state intramolecular proton‐transfer (ESIPT) molecules with covalently linked charge‐transporting functional groups (carbazole‐ and oxadiazole‐functionalized hydroxyl‐substituted tetraphenylimidazole (HPI), i.e., HPI‐Cbz and HPI‐Oxd, respectively). High T_g (ca. 130 °C) amorphous films of HPI‐Cbz and HPI‐Oxd showed intense and ideal blue‐light emission (λ_max = 462 and 468 nm, Φ_PL = 0.44 and 0.38) with a large Stokes shift of over 160 nm and a narrow full width at half‐maximum of less than 65 nm. Organic light‐emitting devices using HPI‐Cbz and HPI‐Oxd as the emitting layer generated an efficient blue electroluminescence (EL) emission peaking at around 460 nm with excellent CIE coordinates of (x, y) = (0.15, 0.11). A maximum external quantum efficiency of 2.94%, and a maximum brightness of 1 229 cd m⁻² at 100 mA cm⁻², as well as a low turn‐on voltage of 4.8 V were achieved in this work.     

啤酒色泽研究进展

人类对颜色的感觉是一个微妙而复杂的过程,色彩能引起人们多样的情感和心理效应。啤酒能否让消费者喜欢,啤酒色泽起着很重要的作用。该文对啤酒色泽的形成机理,影响啤酒色泽形成的因素、改进啤酒色泽的工艺措施以及啤酒色度测定方法等方面进行了综述,以期为新品种啤酒的研究开发提供帮助。     

Priority Based Error Correction Code (ECC) for the Embedded SRAM Memories in H.264 System

With aggressive supply voltage scaling, SRAM bit-cell failures in the embedded memory of the H.264 system result in significant degradation to video quality. Error Correction Coding (ECC) has been widely used in the embedded memories in order to correct these failures, however, the conventional ECC approach does not consider the differences in the importance of the data stored in the memory. This paper presents a priority based ECC (PB-ECC) approach, where the more important higher order bits (HOBs) are protected with higher priority than the less important lower order bits (LOBs) since the human visual system is less sensitive to LOB errors. The mathematical analysis regarding the error correction capability of the PB-ECC scheme and its resulting peak signal-to-noise ratio(PSNR) degradation in H.264 system are also presented to help the designers to determine the bit-allocation of the higher and lower priority segments of the embedded memory. We designed and implemented three PB-ECC cases (Hamming only, BCH only, and Hybrid PB-ECC) using 90 nm CMOS technology. With the supply voltage at 900 mV or below, the experiment results delivers up to 6.0 dB PSNR improvement with a smaller circuit area compared to the conventional ECC approach.     

Polymer solar cells fabricated with 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene and alkyl-substituted thiophene-3-carboxylate-containing conjugated polymers: Effect of alkyl side-chain in thiophene-3-carboxylate monomer on the device performance

Four alkyl-substituted thiophene-3-carboxylate containing donor–acceptor (D–A) copolymers were designed, synthesized, and characterized. Thiophene-3-carboxylate was used as a weak electron acceptor unit in the copolymers to provide a deeper highest occupied molecular orbital (HOMO) level for obtaining a higher open-circuit voltage in polymer solar cells (PSCs). The resulting bulk heterojunction PSCs, made of the copolymers and [6,6]-phenyl-C71-butyric acid methyl ester (PC₇₁BM), exhibited different short circuit currents (J_SCs) and open-circuit voltages (V_OCs), depending on the length of alkyl side-chain in the thiophene-3-carboxylate unit. Among all fabricated photovoltaic (PV) devices, PC2:PC₇₁BM (1:1 wt. ratio) showed the highest efficiency with the highest J_SC of 10.5 mA/cm². Although PC5:PC₇₁BM (1:1) displayed the highest V_OC of 0.93 V, the device efficiency was observed to be poor, which is due to poor nanophase segregation. This comparison shows that the side-chain of thiophene carboxylate in these copolymers plays a very important role in the device efficiency.