Conspectus Electrochemical synthesis of organic compounds has emerged as an attractive and environmentally benign alternative to conventional approaches for oxidation and reduction of organic ...compounds that utilizes electric current instead of chemical oxidants and reductants. As such, many useful transformations have been developed, including the Kolbe reaction, the Simons fluorination process, the Monsanto adiponitrile process, and the Shono oxidation, to name a few. Electrochemical C–H functionalization represents one of the most promising reaction types among many electrochemical transformations, since this process avoids prefunctionalization of substrates and provides novel retrosynthetic disconnections. However, site-selective anodic oxidation of C–H bonds is still a fundamental challenge due to the high oxidation potentials of C–H bonds compared to organic solvents and common functional groups. To overcome this issue, indirect electrolysis via the action of a mediator (a redox catalyst) is regularly employed, by which the selectivity can be controlled following reaction of said mediator with the substrate. Since the redox potentials of transition metal complexes can be easily tuned by modification of the ligand, the synergistic use of electrochemistry and transition metal catalysis to achieve site-selective C–H functionalization is an attractive strategy. In this Account, we summarize and contextualize our recent efforts toward transition metal-catalyzed electrochemical C–H functionalization proximal to a suitable directing group. We have developed C–H oxygenation, acylation, alkylation, and halogenation reactions in which a Pd(II) species is oxidized to a Pd(III) or Pd(IV) intermediate by anodic oxidation, followed by reductive elimination to form the corresponding C–O, C–C, and C–X bonds. Importantly, improved monofunctionalization selectivity is achieved in the Pd-catalyzed C(sp3)–H oxygenation compared to conventional approaches using PhI(OAc)2 as the chemical oxidant. Physical separators are sometimes used to prevent the electrochemical deposition of Pd black on the cathode resulting from reduction of high valent Pd species. We skirted this issue through the development a Cu-catalyzed electrochemical C(sp2)–H amination using n-Bu4NI as a redox cocatalyst in an undivided cell. In addition, we developed Ir-catalyzed electrochemical vinylic C–H functionalization of acrylic acids with alkynes in an undivided cell, affording various substituted α-pyrones in good to excellent yield. More importantly, chemical oxidants, including Ag2CO3, Cu(OAc)2, and PhI(OAc)2, resulted in much lower yields in the absence of electrical current under otherwise identical conditions. As elaborated below, progress in the area of electrochemical transition metal-catalyzed synthesis provides an effective platform for environmentally friendly and sustainable selective chemical transformations.
RGB-D Salient Object Detection (RGB-D SOD) aims at detecting remarkable objects by complementary information from RGB images and depth cues. Although many outstanding prior arts have been proposed ...for RGB-D SOD, most of them focus on performance enhancement, while lacking concern about practical deployment on mobile devices. In this paper, we propose mobile asymmetric dual-stream networks (MoADNet) for real-time and lightweight RGB-D SOD. First, inspired by the intrinsic discrepancy between RGB and depth modalities, we observe that depth maps can be represented by fewer channels than RGB images. Thus, we design asymmetric dual-stream encoders based on MobileNetV3. Second, we develop an inverted bottleneck cross-modality fusion (IBCMF) module to fuse multimodality features, which adopts an inverted bottleneck structure to compensate for the information loss in the lightweight backbones. Third, we present an adaptive atrous spatial pyramid (A2SP) module to speed up the inference, while maintaining the performance by appropriately selecting multiscale features in the decoder. Extensive experiments are conducted to compare our method with 15 state-of-the-art approaches. Our MoADNet obtains competitive results on five benchmark datasets under four evaluation metrics. For efficiency analysis, the proposed method significantly outperforms other baselines by a large margin. The MoADNet only contains 5.03 M parameters and runs 80 FPS when testing a <inline-formula> <tex-math notation="LaTeX">256\times 256 </tex-math></inline-formula> image on a single NVIDIA 2080Ti GPU.
α-Pyridones and α-pyrones are ubiquitous structural motifs found in natural products and biologically active small molecules. Here, we report an Rh-catalyzed electrochemical vinylic C-H annulation of ...acrylamides with alkynes, affording cyclic products in good to excellent yield. Divergent syntheses of α-pyridones and cyclic imidates are accomplished by employing N-phenyl acrylamides and N-tosyl acrylamides as substrates, respectively. Additionally, excellent regioselectivities are achieved when using unsymmetrical alkynes. This electrochemical process is environmentally benign compared to traditional transition metal-catalyzed C-H annulations because it avoids the use of stoichiometric metal oxidants. DFT calculations elucidated the reaction mechanism and origins of substituent-controlled chemoselectivity. The sequential C-H activation and alkyne insertion under rhodium catalysis leads to the seven-membered ring vinyl-rhodium intermediate. This intermediate undergoes either the classic neutral concerted reductive elimination to produce α-pyridones, or the ionic stepwise pathway to produce cyclic imidates.
Two novel nitrogen‐doped, hexa‐peri‐hexabenzocoronene (HBC)‐based nanographenes (NGs) 1 and 2 bearing an azepine and an azocine at the fjord region, respectively, were synthesized and characterized. ...Notably, structure 1 was synthesized by Diels–Alder reaction of cyclic alkene and tetrachlorothiophene‐S,S‐dioxide, followed by Suzuki–Miyaura cross‐coupling and Scholl‐type reactions, which represents a modified strategy to construct NGs. The azo‐heptagon‐embedded NG 1 leads to a saddle shape, and the azo‐octagon‐embedded NG 2 exhibits a distorted saddle‐helix conformation with the largest torsion angle recorded so far in 5helicenes. As a result, the different structural topographies for NGs 1 and 2 lead to significant changes in the optical properties including UV absorption and fluorescent emission. Additionally, the 8π‐heterocycles azepine and azocine in the NGs 1 and 2 exhibited obvious antiaromatic properties.
Two nitrogen‐doped nanographenes bearing an azepine ring and an azocine ring, respectively, were synthesized and saddle‐shaped and saddle‐helix structures were obtained. Notably, two synthetic routes were adopted for the synthesis, the azepine‐embedded polyaromatic was prepared by using cyclic alkene and tetrachlorothiophene‐S,S‐dioxide instead of typical alkyne and tetraphenylcyclopenta‐2,4‐dien‐1‐one.
An LLC series-resonant converter has many unique characteristics and improvements over pulsewidth-modulation topologies. However, many output capacitors are needed in parallel to satisfy an output ...voltage ripple and a rated ripple current of the capacitors. This paper deals with a novel two-phase interleaved LLC resonant converter using a phase of the resonant capacitor. The proposed converter satisfies low output-voltage ripple requirement and meets the rated ripple of output capacitor's current with few output capacitors. The operation and features are considered in detail, and a prototype with a 12-V-100-A output is investigated.
In order to explore the driver's multiple prediction effects of flux changes (MPEFC) on traffic flow on a curved road, parameters of the weighted flow gradient of multiple lattices ahead are ...introduced to characterize the MPEFC effect on a curved road. On this basis, combined with the characteristics of a curved road, a lattice model considering the drive's MPEFC effects is proposed under the V2X environment. The stability criterion is obtained. Through the reduced perturbation method, the density wave equation and its solution used to describe the propagation law of traffic congestion near the critical point are derived. The results show that the stability of traffic flow on a curved road increases along with the increase in radian, and that considering the MPEFC effects simultaneously has a significant stabilizing effect for traffic flow on a curved road. It is also discovered that under the V2X environment, the traffic flow is optimally stabilized by considering the information of just two lattices ahead.
Synergistic use of electrochemistry and organometallic catalysis has emerged as a powerful tool for site-selective C–H functionalization, yet this type of transformation has thus far mainly been ...limited to arene C–H functionalization. Herein, we report the development of electrochemical vinylic C–H functionalization of acrylic acids with alkynes. In this reaction an iridium catalyst enables C–H/O–H functionalization for alkyne annulation, affording α-pyrones with good to excellent yields in an undivided cell. Preliminary mechanistic studies show that anodic oxidation is crucial for releasing the product and regeneration of an Ir(III) intermediate from a diene-Ir(I) complex, which is a coordinatively saturated, 18-electron complex. Importantly, common chemical oxidants such as Ag(I) or Cu(II) did not give significant amounts of the desired product in the absence of electrical current under otherwise identical conditions.
An edge computing system is a distributed computing framework that provides execution resources such as computation and storage for applications involving networking close to the end nodes. An ...unmanned aerial vehicle (UAV)-aided edge computing system can provide a flexible configuration for mobile ground nodes (MGN). However, edge computing systems still require higher guaranteed reliability for computational task completion and more efficient energy management before their widespread usage. To solve these problems, we propose an energy efficient UAV-based edge computing system with energy harvesting capability. In this system, the MGN makes requests for computing service from multiple UAVs, and geographically proximate UAVs determine whether or not to conduct the data processing in a distributed manner. To minimize the energy consumption of UAVs while maintaining a guaranteed level of reliability for task completion, we propose a stochastic game model with constraints for our proposed system. We apply a best response algorithm to obtain a multi-policy constrained Nash equilibrium. The results show that our system can achieve an improved life cycle compared to the individual computing scheme while maintaining a sufficient successful complete computation probability.
Document forgery is a significant issue in Korea, with around ten thousand cases reported every year. Analyzing paper plays a crucial role in examining questionable documents such as marketable ...securities and contracts, which can aid in solving criminal cases of document forgery. Paper analysis can also provide essential insights in other types of criminal cases, serving as an important clue for solving cases such as the source of a blackmail letter. The papermaking process generates distinct forming fabric marks and formations, which are critical features for paper classification. These characteristics are observable under transmitted light and are created by the forming fabric pattern and the distribution of pulp fibers, respectively. In this study, we propose a novel approach for paper identification based on hybrid features. This method combines texture features extracted from images converted using the gray-level co-occurrence matrix (GLCM) approach and a convolutional neural network (CNN), with another set of features extracted by the CNN using the same images as input. We applied the proposed method to classification tasks for seven major paper brands available in the Korean market, achieving an accuracy of 97.66%. The results confirm the applicability of this method for visually inspecting paper products and demonstrate its potential for assisting in solving criminal cases involving document forgery.
To better understand the efficacy of intravitreal dexamethasone implant (Ozurdex) versus antivascular endothelial growth factor (anti-VEGF) treatment in patients with diabetic macular edema (DME). A ...systematic review and meta-analysis. The study included randomized control trials (RCTs) and non-randomized control trials (Non-RCTs) before December 2021 that compare the efficacy of Ozurdex-related therapyand anti-VEGF therapy. We searched PubMed, Cochrane Library, and EMBASE. The quality of the included studies was assessed carefully. 30 studies were included. Regarding BCVA change, the overall result revealed no significant differences between Ozurdex and anti-VEGF therapies in patients with nonresistant DME, but Ozurdex group had significantly more VA improvement than anti-VEGF therapies in patients with resistant DME (MD 0.12, 95% CI 0.02-0.21). In terms of central retinal thickness (CRT) decrease, there was a significant difference between Ozurdex therapy and anti-VEGF therapy in patients with nonresistant DME (MD 48.10, 95% CI 19.06-77.13) and resistant DME (MD 65.37, 95% CI 3.62-127.13). Overall, Ozurdex therapy resulted in significantly greater VA improvement and CRT decrease than anti-VEGF therapy in resistant DME patients. Ozurdex therapy was not inferior to anti-VEGF therapy in patients with nonresistant DME.
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