North China has undergone a severe drying trend since the 1950s, but whether this trend is natural variability or anthropogenic change remains unknown due to the short data length. This study extends ...the analysis of dry–wet changes in north China to 1900–2010 on the basis of self-calibrated Palmer drought severity index (PDSI) data. The ensemble empirical mode decomposition method is used to detect multidecadal variability. A transition from significant wetting to significant drying is detected around 1959/60. Approximately 70% of the drying trend during 1960–90 originates from 50–70-yr multidecadal variability related to Pacific decadal oscillation (PDO) phase changes. The PDSI in north China is significantly negatively correlated with the PDO index, particularly at the 50–70-yr time scale, and is also stable during 1900–2010. Composite differences between two positive PDO phases (1922–45 and 1977–2002) and one negative PDO phase (1946–76) for summer exhibit an anomalous Pacific–Japan/East Asian–Pacific patternlike teleconnection, which may develop locally in response to the PDO-associated warm sea surface temperature anomalies in the tropical Indo-Pacific Ocean and meridionally extends from the tropical western Pacific to north China along the East Asian coast. North China is dominated by an anomalous high pressure system at mid–low levels and an anticyclone at 850 hPa, which are favorable for dry conditions. In addition, a weakened land–sea thermal contrast in East Asia from a negative to a positive PDO phase also plays a role in the dry conditions in north China by weakening the East Asian summer monsoon.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Over the past two decades, the development and application of ynamide chemistry have received more and more attention. Ynamides have proven to be versatile reagents for organic synthesis, and have ...been widely applied to the rapid assembly of a diverse range of structurally complex N-containing molecules, especially the valuable N-heterocycles. In comparison with the well-established transition metal-catalyzed reactions of ynamides, metal-free ynamide transformations have relatively seldom been exploited. Recently, Brønsted acid-mediated reactions of ynamides represent significant advances in ynamide chemistry. This review summarizes the latest trends and developments of Brønsted acid-mediated reactions of ynamides, including cycloaddition, cyclization, intramolecular alkoxylation-initiated rearrangement, oxygen atom transfer reactions and hydro-heteroatom addition reactions.
This review summarizes the latest trends and developments of Brønsted acid-mediated reactions of ynamides, including cycloaddition, cyclization and so on.
Rate capability as well as power performance of lithium ion batteries (LiBs) is becoming more and more important, especially as the application targets of LiBs move from mobile devices to ...transportation, such as EVs and HEVs. In this research, we report porous graphene sponge additives for both anode and cathode materials for better rate performance. The charge capacity retention improved from 56% to 77% at 6C and from 7% to 45% at 10C with 0.5 wt% added to the anode, while the discharge capacity retention at the 6C rate improved from 43% to 76% and the 10C rate discharge improved from 16% to 40% with the same amount of MG added to the cathode. The cyclability at high rate was also improved with the MG additive. Moreover, preparation of the MG was facile, cost-effective, and compatible with commercially available active materials. These results demonstrate the suitability of MG for use with LiB additives to ensure better rate capability and high rate cyclability.
A Simple Modification of ESPRIT Qian, Cheng
IEEE signal processing letters,
08/2018, Letnik:
25, Številka:
8
Journal Article
Recenzirano
In this letter, a manifold reconstruction based ESPRIT algorithm is devised for direction-of-arrival (DOA) estimation. Unlike the standard ESPRIT approach, the proposed method employs two smaller ...overlapping subarrays to construct the rotational invariance equation, which is then used to recover the array manifold matrix. This way, the DOA estimation can be split into K single-source DOA estimation problems, where each DOA is estimated by minimizing a nonlinear least squares fitting criterion that is solved via a computationally efficient Newton's method. Numerical results are included to validate the effectiveness of the proposed algorithm.
A practical and efficient propargylboration of ketones is presented using general allenylboronic acid pinacol esters (allenyl‐Bpins) without a catalyst. This reaction is triggered by in‐situ ...activation of stable allenyl‐Bpins through the sequential addition of 1.25 equiv. of nBuLi and the prerequisite 2.0 equiv. of TFAA. Under the optimized reaction conditions, the versatile trisubstituted allenyl‐Bpins react with various ketones smoothly to afford a wide range of tert‐homopropargyl alcohols bearing vicinal stereocenters in high yields with good to excellent diastereoselectivities. Furthermore, propargylboration of ketones with chiral trisubstituted allenyl‐Bpins allows for the asymmetric synthesis of chiral tert‐homopropargyl alcohols with a full chirality transfer.
Tertiary homopropargyl alcohols bearing vicinal stereocenters can be obtained through catalyst‐free propargylboration of ketones with general allenyl‐Bpins. The key factor for the success is enhancing the reactivity of the Bpin unit in‐situ by sequentially adding 1.25 equiv. of nBuLi and 2.0 equiv. of TFAA. Additionally, propargylboration of ketones with chiral trisubstituted allenyl‐Bpins enables the asymmetric synthesis of enantiomerically enriched tert‐homopropargyl alcohols with complete chirality transfer.
The increasing demand of customized production results in huge challenges to the traditional manufacturing systems. In order to allocate resources timely according to the production requirements and ...to reduce disturbances, a framework for the future intelligent shopfloor is proposed in this paper. The framework consists of three primary models, namely the model of smart machine agent, the self-organizing model, and the self-adaptive model. A cyber-physical system for manufacturing shopfloor based on the multiagent technology is developed to realize the above-mentioned function models. Gray relational analysis and the hierarchy conflict resolution methods were applied to achieve the self-organizing and self-adaptive capabilities, thereby improving the reconfigurability and responsiveness of the shopfloor. A prototype system is developed, which has the adequate flexibility and robustness to configure resources and to deal with disturbances effectively. This research provides a feasible method for designing an autonomous factory with exception-handling capabilities.
Abstract
Quantification of the contribution of atmospheric circulation to damaging extreme weather and climate events and the attribution of extreme events in the context of climate change has been ...gaining worldwide interest. Attribution analysis helps us to better understand the risks associated with the effects of climate change on extreme events. However, the contribution of atmospheric circulation, as well as the influence of climate change, to the record-breaking precipitation event in the middle and lower reaches of the Yangtze River and the concurrent record-breaking hot event in South China during the Meiyu period (June–July) in 2020 are still unclear. In this study, we use flow analogues to estimate how much the atmospheric circulation can explain these two extreme events and the influence of climate change. The results show that the atmospheric circulation explains 70.73% and 43.61% of the extreme precipitation event and the concurrent hot event, respectively. Compared with past climate, the occurrence risk of an event reaching or exceeding the 2020 Meiyu amount under similar atmospheric circulation conditions increased by 5.1 times under the present climate, 80% of which can be attributed to climate change. In addition, hot events similar to the 2020 event cannot occur under past climate, while those reaching or exceeding a one standard deviation threshold increased from 0.58% under past climate conditions to 68.83% under the present climate, 99% of which can be attributed to climate change. These results are beneficial for the understanding and prediction of extreme events in the context of climate change in this region.
Rechargeable aprotic lithium (Li)–O2 batteries with high theoretical energy densities are regarded as promising next‐generation energy storage devices and have attracted considerable interest ...recently. However, these batteries still suffer from many critical issues, such as low capacity, poor cycle life, and low round‐trip efficiency, rendering the practical application of these batteries rather sluggish. Cathode catalysts with high oxygen reduction reaction (ORR) and evolution reaction activities are of particular importance for addressing these issues and consequently promoting the application of Li–O2 batteries. Thus, the rational design and preparation of the catalysts with high ORR activity, good electronic conductivity, and decent chemical/electrochemical stability are still challenging. In this Review, the strategies are outlined including the rational selection of catalytic species, the introduction of a 3D porous structure, the formation of functional composites, and the heteroatom doping which succeeded in the design of high‐performance cathode catalysts for stable Li–O2 batteries. Perspectives on enhancing the overall electrochemical performance of Li–O2 batteries based on the optimization of the properties and reliability of each part of the battery are also made. This Review sheds some new light on the design of highly active cathode catalysts and the development of high‐performance lithium–O2 batteries.
Cathode catalysts play an essential role in determining the electrochemical performance of Li–O2 batteries. Strategies in the design and preparation of efficient cathode catalysts for Li–O2 batteries are summarized, and perspectives on improving the overall performance of Li–O2 batteries are presented.
Nanoemulsions are finding increasing utilization in the food and beverage industries for certain applications because of their unique physicochemical and functional properties: high encapsulation ...efficiency; low turbidity; high bioavailability; high physical stability. In this study, we examined the impact of system composition and homogenization conditions on the formation of nanoemulsions using a high-pressure homogenizer (microfluidizer). The mean particle diameter decreased with increasing homogenization pressure and number of passes, with a linear log–log relationship between mean particle diameter and homogenization pressure. The minimum droplet diameter that could be produced after 6 passes at 14kbar depended strongly on emulsifier type and concentration: SDS<Tween 20<β-lactoglobulin<sodium caseinate. Small-molecule surfactants formed smaller droplets than proteins, which was attributed to their ability to rapidly adsorb to the droplet surfaces during homogenization. The impact of phase viscosity was examined by using different octadecane-to-corn oil ratios in the oil phase and different glycerol-to-water ratios in the aqueous phase. The minimum droplet size achievable decreased as the ratio of disperse phase to continuous phase viscosities (ηD/ηC) decreased for SDS-stabilized emulsions, but was relatively independent of ηD/ηC for β-lactoglobulin-stabilized emulsions. At low viscosity ratios, much smaller mean droplet diameters could be achieved for SDS (d∼60nm) than for β-lactoglobulin (d∼150nm). The information reported in this study will facilitate the rational design of food-grade nanoemulsions using high-pressure homogenization methods.
Schematic drawing of the formation of nano of oil-in-water emulsions. Display omitted
A coordinated balance between the positive and negative regulation of pattern-recognition receptor (PRR)-initiated innate inflammatory responses is required to ensure the most favorable outcome for ...the host. Post-translational modifications (PTMs) of innate sensors and downstream signaling molecules influence their activity and function by inducing their covalent linkage to new functional groups. PTMs including phosphorylation and polyubiquitination have been shown to potently regulate innate inflammatory responses through the activation, cellular translocation, and interaction of innate receptors, adaptors, and downstream signaling molecules in response to infectious and dangerous signals. Other PTMs such as methylation, acetylation, SUMOylation, and succinylation are increasingly implicated in the regulation of innate immunity and inflammation. In this review, we focus on the roles of PTMs in controlling PRR-triggered innate immunity and inflammatory responses. The emerging roles of PTMs in the pathogenesis and potential treatment of infectious and inflammatory immune diseases are also discussed.
Post-translational modifications (PTMs) of innate sensors and downstream signaling molecules influence their activity and function, and this regulation is crucial to maintain host immunity. Cao and colleagues discuss the emerging roles of PTMs in the pathogenesis and potential treatment of infectious and inflammatory immune diseases.
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